main-content

## Über dieses Buch

This volume contains full proceedings of the Fourth International Conference on Secondary Ion Mass Spectrometry (SIMS-IV), held in the Minoo-Kanko Hotel, Osaka, Japan, from November 13th to 19th, 1983. Coordinated by a local or­ ganizing committee under the auspices of the international organizing com­ mittee, it followed earlier conferences held in MUnster (1977), Stanford (1979), and Budapest (1981). The conference was attended by about 250 participants from 18 countries, and 130 papers including 24 invited ones were presented. Reflecting the rap­ idly expanding activities in the SIMS field, informative papers were pre­ sented containing up-to-date information on SIMS and various related fields. The proceedings focussed upon six main issues: (1) Fundamentals of sput­ tering and secondary ion formation. (2) Recent progress in instrumentation, including submicron SIMS and image processing. (3) SIMS combined with other surface analysis techniques. (4) Outstanding SIMS-related analytical methods such as laser-microprobe SIMS, sputtered neutral mass spectrometry, mass spectrometry of sputtered neutrals by multi-photon resonance ionization, and accelerator-based SIMS. (5) Organic SIMS and FAB which has recently become a rapidly expanding technique in pharmacy, biotechnology, etc. (6) Appl ica­ tions of SIMS to various fields such as metallurgy, geology, and biology, including depth profiling of semiconductors, and analysis of inorganic mate­ rials. As a venue for the exchange of ideas and information concerning all the above issues, the conference proved a great success.

## Inhaltsverzeichnis

### Fundamentals of Sputtering

From a user’s point of view, one would wish that a secondary-ion-mass-spectroscopic (SIMS) signal [1,2] S be given by S=YP, where Y is a sputter yield and P an ionization probability. As we all know, things are more complex. As a next step, one could write schematically (1) $$S\left( {x,y} \right) = \smallint dz Y\left( {x;y,z} \right) P\left( {y,z} \right) ,$$ where x stands for a set of bombardment parameters (ion type, energy, angle of incidence etc.), y for the detected signal (mass, charge, energy etc. of the emitted ion), and z for all those parameters that may influence the ionization probability without being specified in the measured signal. The existence of the latter class of parameter (the original site of the emitted ion, the physical and chemical state of the surroundings of the point of emission, etc.) causes S to be a convolution rather than a product and makes it questionable to draw conclusions from a SIMS signal on the sputter process [3], despite increasing knowledge of the ionization mechanism [4]. This is true at least when P is small (≪1). Therefore, studies of the sputter process have to rely predominantly on other than SIMS measurements.

P. Sigmund

### Sputtered Atom Yields and Ionization Probabilities of Binary Alloys Under O 2 + Bombardment

It is well known that oxygen primary ion beam enhances and stabilizes the yield of the secondary sample ions. But the role of oxygen ion in the process of secondary ion emission is not yet fully understood. In a previous paper(1) the authors reported the surface structure, sputtered atom yields and secondary ion mass spectra of pure metals under 02+bombardment. The authors have now extended this study to series Cr-Fe,Mn-Fe, Mn-Co,Fe-Co,Fe-Ni,Co-Ni and Ni-Cu binary alloys. Accumulation of these fundamental data is indispensable for elucidating the effect of oxygen ion on sputtering and establishing the method of quantitative interpretation of mass spectra.

K. Tsunoyama, T. Suzuki

### Sputtering and Secondary Ion Yields of Ti-Al Alloys Subjected to Oxygen Ion Bombardment

A principal approach to the fundamental understanding of SIMS process requires the accumulation of reliable data. Recently, we determined the yields of sputtering and secondary ion emission of pure metals under oxygen ion bombardment, and found some factors governing fundamental phenomena of SIMS[1].

K. Inoue, Y. Taga, K. Satta

### Outermost Surface Composition of Au-Cu Alloys Under Ion Bombardment of Different Current Densities of Ar+ Ions

Since the interacion of sputtered atoms with the outermost atomic layer of the alloy sample plays the most important role in the ionization and neutralization process, the exact knowledge of the surface composition of the outermost atomic layer under ion bombardment is needed. With respect to the surface composition of alloy samples under Ar+ ion bombardment, it is now well recognized that the ion-enhanced subsurface re-distribution results in a marked enrichment of constituent atoms of lower surface binding energy at the outermost atomic layer[l,2,3]. Furthermore, it has recently been suggested that the composition of the outermost atomic layer of Au-Cu alloys may change for different current densities of ion beam in the range below several tens of µA/cm2 [5],which corresponds to the current densities in usual SIMS measurement. If so, the outermost atomic layer leads to the change of secondary ion yield. The present work, therefore, aimed at examining whether or not such a density effect exists in usual operating conditions of SIMS. For this, surface composition of the outermost atomic layer of Ar-43at%Cu alloys was measured by ion scattering spectroscopy with the mixed He+ and Ar+ ions(mixed ion beam ISS).

H. J. Kang, R. Shimizu

### Secondary Dimer Ion Emission Probability in Sputtering Cu-Ni Alloy

For a quantitative determination of composition and local order structure of alloy surfaces using SIMS, relative intensities among various cluster ions and their influences by matrix effects have been analysed. Dimer formation yield is considered to reflect, to some degree, the atomic arrangement of surroundings, from the standpoint of either model that the dimer leaves the surface as an intact species or as a recombination product of monomers. In this paper, a systematic study of homo- and hetero-dimer emission yields is presented with our particular interests in the possible alloying effect and the concentration dependence of the yields. The secondary ion sampling depth of the sputtering technique is also discussed in comparison between AES and SIMS results.

F. Honda, K. Nakajima, Y. Fukuda

### Empirical Formula for Sputtering Yield and Z2 Dependence of Its Q Values

Preliminary estimations of sputtering yields for various ion-atom combinations are very important for SIMS and PWI problems. Recently, Yamamura et al.[1] have proposed the empirical formula for sputtering yield at normal incidence. Their formula includes two adjustable parameters, which correspond to Sigmund α and the threshold energy of sputtering. These two parameters were determined by the least square method so as to fit their formula to experimental data. The best-fit values of α show the interesting Z2 dependence and they factorized α into two parts, i.e., α = Q(Z2) αII , where αII is the average value of best-fit α’s. The main purpose of this note is to investigate this Z2 dependence of Q value from the viewpoint of nuclear stopping power of low-energy recoil atom.

Y. Yamamura, S. Nakagawa, S. Enoki

### Molecular Dynamics Computer Simulation Study of the Damage Produced in Metal Target Surfaces During Ion Bombardment

Molecular dynamics simulations now study the damage created in metal surfaces by bombarding ions [1–5]. The computer model used in atom ejection studies [6] has been extended to cool and recrystallize the target. The target’s response is physically plausible, and its final configuration is consistent with transmission electron microscope (TEM) studies of ion-bombarded target surfaces. Here the chief emphasis will be placed on effects which influence the outcome of a SIMS experiment.

D. E. Harrison, W. A. Mason, R. P. Webb

### Simulation of Ion Sputtering Process on the Binary Alloy

The composition of the alloy sputtered with low energy ions changes very much by the effect of the preferential sputtering, segregation of the constituent atoms to the surface and the ion-enhanced diffusion [1–7]. The simulation of the sputtering including the segregation and the ion enhanced diffusion with computer has advantage in order to understand the sputtering mechanism of the alloys.

T. Koshikawa, T. Ikuta, R. S. Li

### Secondary Ion Emission from Si Subjected to Oxygen Ion Bombardment

In practical SIMS ,O2+ ion beam is generally used as primary species. However there have been little systematic and reliable data on the yields of spattering and secondary ion emission from a material subjected to 02+ ion bombardment[1,2,3,4,5].On the other hand,an understanding of secondary ion emission mechanism requires the measurements of secondary ion yields and energy distribution [6,7,8]. In this paper,we describe the results of secondary ion emission from Si under O2+ ion bombardment.

T. Ohwaki, Y. Taga, K. Satta

### Surface Structure of Oxidized Metals Bombarded by Incident Ions

On the metal surface bombarded by incident ions, there is recognized the irregular pattern by TSUNOYAMA (1), that is called a cone. The cone affects inexplicably on the precision of ion mass spectrometry. However, the mechanism of cone growth is not well revealed. To clarify this, the experiment using 42%Ni-Fe alloy has been carried out in the ion mass analyzer.

Y. Sekimoto, Y. Igarashi, T. Kawata

### The Effect of Energetic Electrons on the Secondary Ion Emission

There have been two main mechanisms proposed for ionization processes in SIMS; they are the electronic excitation by atomic collisions [1] and the atom-surface resonant electron tunneling [2,3]. A direct evidence of the electron tunneling has recently been reported [4], and its delicate experiment was a rather academic task, adjusting the relative position between the Fermi-level and vacuum level (or changing the work function of sample surface). In the present work, we have tried to perform the experiments under conventional conditions which could meet the requirement for traditional utilities of SIMS.

Zhu Ang-Ru, Wu Xe-Ling

### Influence of Alkali Metals on the Negative Secondary Ion Emission from Silicon

The utility of ion implantation to investigate the influence of reactive ions on the secondary ion emission has been demonstrated by COLLIGON and KIRIAKIDES [1] in the case of copper matrix material.

W. Frentrup, M. Griepentrog, H. Klose, G. Kreysch, U. Mueller-Jahreis

### Secondary Ion Emission Peculiarities at Metal Interfaces

Specific physical and chemical states of interfaces are known to affect substantially the parameters of emission processes. Therefore it is of interest to investigate peculiarities of such a surface-sensitive phenomenon as the secondary ion emission (SIE) on the boundary of different metal phases. The present work deals with the study of thin metal film - metal substrate interfaces.

M. A. Vasilyev, S. P. Chenakin

### Intensities and Energy Spectra of Secondary Ions Sputtered from Fe-Al Alloys by Ar+ Ion Bombardment in Ultrahigh Vacuum

The main mechanism responsible for the emission of singly charged ions from ion-sputtered solid samples is known as the “surface excitation”, that is the electronic excitation of the outgoing particle during its separation from the target [1–3]. At a given velocity, such a process is governed by the electronic structure of the surface near the ejection point, and therefore is very sensitive to the local environment [4,5] . However the surface excitation model cannot explain the emission of multiply charged ions from light elements. In fact, to account for secondary ion emission from light metals, JOYES [6] early proposed a collisional mechanism where ionization results from Auger decay of collision-induced L-shell excitations and which is well supported by the observation of Auger electrons under ion bombardment [7].

R.-L. Inglebert, J.-F. Hennequin

### CF 3 + : An Alternative Primary Beam Source for the Sensitive Detection of Electropositive Elements in SIMS

Traditionally O2+ has been used as the primary projectile for the sensitive detection of electropositive elements. Excellent secondary ion yields have been obtained particularly for those elements which can be completely oxidized and form strong ionic bonds with oxygen. Secondary ion yields, however, may decrease by several orders of magnitude for those elements (e.g., Cu, Ni, Zn, Ag) which are not forming strong ionic bonds under 02+ bombardment. One would expect that for these elementu, secondary ion yields may increase dramatically if bombarded with fluorine containing primary ions.

W. Reuter

### Hydrogen Ion Bombardment in Secondary Ion Mass Spectrometry

Secondary ion mass spectrometry (SIMS) has been successfully used for fundamental and applied studies of solid surfaces. Thus it is important to know regularities in the secondary ion emission (SIE) induced by the primary beams of inert or chemically active elements [1]. The SIE intensity was found to depend not only on the surface sputtering processes (the intensity rises with the atomic number of the bombarding ion) but also on the ionization efficiency of the sputtered atoms (the efficiency is strongly dependent on the physico-chemical state of target surface and experimental conditions). Analytical capabilities of SIMS might be improved by the use of light ions producing low sputtering and causing minimum surface erosion.

V. T. Cherepin, A. A. Kosyachkov, I. N. Makeeva

### Electron Tunneling and the Emission of Secondary Ions from Silicon Surfaces

It has been observed in many systems that lowering of the work function Ф of the sample surface enhances the formation of negative secondary ions [1, 2] while suppressing the formation of positive ions [3]. A model based on the tunneling of electrons between the surface and the sputtered atom has been proposed [3,4,5] to explain these results. According to the model, the work-function dependence of the ionization probability should be independent of how the work-function change ΔФ is being induced, provided that the external atom used to induce ΔФ does not affect the chemical state of the target atoms. We have tested this prediction by studying the emission of secondary ions from Si(111) surfaces using Cs and Li overlayers to induce changes in Ф. These systems are chosen because the adsorption of Cs and Li does not change the chemical state of the surface Si atoms in any appreciable way.

Ming L. Yu

### Detection of Sputtered Neutrals by Multiphoton Resonance Ionization

Recently, we have demonstrated the selective ionization of atoms sputtered from solids by Multiphoton Resonance Ionization (MPRI) [1,2]. Three salient features of MPRI coupled to ion beam methods make it attractive as an analytical tool. First, the technique can be applied to all elements but He and Ne. Next, MPRI can be made selective to a single element by appropriate choice of the excitation wavelength, eliminating the need for a high resolution mass spectrometer. Both ground and excited state atoms can be examined. Finally, MPRI is extremely sensitive, i.e., with adequate photon fluxes every atom in the laser beam can be ionized [3]. As a consequence of this high sensitivity, the flux of ejected neutral species can be monitored under low dose bombardment conditions. Thus, MPRI of sputtered neutrals should be applicable to problems of structural and chemical analysis, as well as trace level determinations.

F. M. Kimock, J. P. Baxter, D. L. Pappas, P. H. Kobrin, N. Winograd

### The Energy Dependence of the Ionisation Coefficient in SIMS

If the process of secondary ion formation is viewed as one in which the secondary ion is formed amongst the sputtered flux from the surface and then survives the outgoing trajectory to be analysed, we can write the yield in the energy range E to E + dE, and angle range θ to θ + dθ as (1) $${{\rm{Y}}^ + }\left( {{\rm{E,}}\theta } \right){\rm{dEd}}\theta = {\rm{N}}\left( {{\rm{E,}}\theta } \right){{\rm{R}}^ + }\left( {{\rm{E,}}\theta } \right){\rm{P}}\left( {{\rm{E,}}\theta } \right){\rm{dEd}}\theta$$ where ⇅(E,θ) is the sputtered atom fluxR+(E,θ) is the probability of ionisation in the ejection processP(E,θ) is the probability of surviving the outgoing trajectory in an ionised state.

R. F. Garrett, R. J. MacDonald, D. J. O’Connor

### Accurate Measurement of Energy Distribution Curves of Secondary Ions by UHV-IMMA

The UHV-IMMA [1] developed at ULVAC Laboratory has excellent capability to measure energy distribution of secondary ions. As shown in Figure 1, hemispherical electrostatic ion energy analyser (IEA) with central orbit radius of 1.5 cm has been designed and normal incidence of primary ion beam on the sample surface and extraction of secondary ion beam normal to the sample surface have been made possible.

O. Tsukakoshi, K. Komatsu, S. Komiya

### Energy Distribution of Positive Secondary Ions from Pure Elements and Amorphous Alloys

As it is well-known,one of the most serious problem of the quantitation of SIMS is that the secondary ion yield of the elements varies strongly with matrix and concentration. This problem has been studied by numerous authors; usually, however,they did not analyze the influence of the energy distribution of the secondary ions on this effect. The works dealing with the influence of the matrix on the energy spectra in detail also used polycrystal-line, multiphase alloys. Therefore, the yields were mean values of the differently emitting surface sites [1,2]. To eliminate this imperfection of multicomponent targets, reliably homogeneous and isotrope materials, amorphous alloys ( metallic glasses ) were used.

M. Riedel, H. Düsterhöft

### Energy Distribution of Secondary Ions Emitted from Silicate Minerals

One of the approaches to clarify the emission mechanism of secondary ions is to study the kinetic energy distribution (ED). THOMPSON [1] proposed that the most probable energy Em is near Eb/2, where Eb is the binding energy for metal targets. SIGMUND [2] discussed the nature of the binding energy and proposed to take sublimation energy as Eb for metals and cohesive energy per atom for covalent crystals. SCHROEER [3] deduced a formula for the ionization efficiency of sputtered atoms from metals based on a quantum mechanical model. Using the Schroeer result, GRIES and RUEDENAUER [4] obtained an expression for the ED of secondary ions which leads to Em=0.768Eb for metals.

J. Okano, H. Nishimura

### A Retarding-Accelerating Energy Analyser for SIMS

It is well known that secondary ion energy spectra can give us much interesting information. As a very high energy resolution is not needed for most cases, the retarding-accelerating energy analyser (derived from the Staib type energy analyser[1]) for quadrupole based SIMS is very useful because of its ion acceptance from a large target surface and a large emitting angle. Unfortunately, knowledge of this analyser is very meager[2] in spite of its being widely used in some modern instruments[3][4][5].

Cha Liang-Zhen, Xue Zu-Qing, Zheng Zhao-Jia, Tong Yu-Qing, Wu Yong-Qing

### Current Status of Sputtered Ion Emission Models

Significant progress appears to have been made in recent years in understanding the sputtered ion emission process. Theoretical efforts have followed two diverse paths. One approach assumes a highly simplified model of a metal surface; the ionization probability of a moving atom near the surface can now be calculated analytically. Given this capability, one then attempts to extend the model to real surfaces without losing the attractive simplicity of the analytical treatment. The second approach attempts to deal directly with the complexities of real surfaces, in particular those of complex materials. Here, the possibility of analytical solution appears remote, but the goal of the work is to construct appropriate potential energy diagrams, and thereby to indicate in a general way the form that an analytical approach would have to take. In parallel with these theoretical developments there have been advances in experimental technique. Studies on clean metal surfaces have reached the point where direct, and successful, comparisons with theoretical predictions can be made. On complex, oxyqenated surfaces, techniques are now available which allow quantification of the surface oxygen content, and correlation with ionization probability of the sputtered species. From such studies an idea of the form of the potential energy diagram appropriate for sputtered ion emission is beginning to emerge, and it is apparent that simple one-dimensional potential energy diagrams will not be adequate.

P. Williams

### LTE Quantification of SIMS of Ni-Cr Alloy

The quantitative correction of secondary ion intensities to elemental concentrations utilizing the Saha-Eggert equation was tried with a calibration sample of Ni-Cr alloy containing Ti , Fe, Cu and Zr. Some simplifications and improvements in the procedure as well as searches for bombarding conditions were made to get higher accuracy, and the relative deviation in concentration could be smaller than 20% for all constituent elements.

S. Tamaki, H. Matsuda

### Simplified IMISR Method with Computer Data Acquisition

The calibrational methods for SIMS use external (MISR(1, 2)) or internal (SAA (3, 4)) standards. The IMISR (Implantation Modificated Matrix Ion Species Ratio) method proposed by us (5) is a combination of these approaches and allows the quantification depth profiles of inhomogeneous samples. Using computer data processing the IMISR quantification can now be performed in five simple steps: 1. implantation of a “standard”, 2. depth profiling of the unknown, 3. depth profiling of the “standard” samples, 4. calibration, 5. (computer) data evaluation.

J. Giber, A. Solydom, D. Marton, I. Barsony

### Relative Sensitivity Factor of Compound Semiconductor by SIMS

The relative sensitivity factor (RSF) is generally used for quantitative analysis of elements by SIMS CID. Usually, the RSF has been discussed in connection with trace elements in standard samples. The RSF of major components has been seldom studied. In this paper, we consider the RSF in relation to the major components, namely, croup III and group V elements in the III-V semiconductors, where characteristics such as ionicity of the compound semiconductor are relatively well known.

K. Kusao, K. Tsukamoto, Y. Yoshioka, F. Konishi

### Quantitative Ion Probe Analysis of Oxidized Surface Using N 2 + Primary Ions

The Ion Microprobe Mass Analyser (IMMA) has been widely used for surface and high sensitivity analysis of various materials. For quantitative analysis of homogeneous materials, the calibration curve method is effective using reference samples [1][2]. On the other hand, quantitative methods for surface oxide layers have not been established, because the existence of oxygen significantly enhances secondary ion intensities [1]. In addition available reference samples can not be obtained.

J. Murayama, N. Usuki, N. Fujino

### Oxygen Effect on Secondary Ion Yield in Oxygen-Doped Silicon

SIMS quantification is complicated by the fact that ion yields of a given element are not matrix-independent (the SIMS matrix effect). When oxygen-ion bombardment is employed, the surface oxygen concentration is considered to be an important factor in determining ion yield. Some workers have attempted to explain the matrix effect in terms of the surface oxygen concentration [1,2]. However, no simple theory has been verified that can predict ion yield variations for a given element sputtered from different matrices [3,4]. The purpose of our study was to obtain fundamental information about the oxygen effect using oxygen-doped silicon for SIMS quantification.

Y. Homma, H. Tanaka, Y. Ishii

### The Role of Standards in Secondary Ion Mass Spectrometry

In the evolution of a basis for quantitative compositional analysis in an instrumental technique, the development of standards plays a critical role. For techniques which utilize a primary beam of radiation to excite secondary radiation which is characteristic of the sample composition, the measured signal intensity i for a constituent x is a complex function of C, the atomic concentration, specimen parameters (that is, matrix effects M), and instrument parameters I: (1) $${\rm{i = f}}\left( {{\rm{C,M,I}}} \right).$$ If the interactions of the primary and secondary radiation with the sample and the secondary radiation with the measuring instrument can be accurately described, then i could be measured and C calculated directly. Unfortunately, it is rare in any of the instrumental analysis techniques to obtain such complete characterization of the matrix and instrumental factors, and this is particularly true for secondary ion mass spectrometry (SIMS). In SIMS the secondary ion signals are strongly affected by the electronic character of the matrix [1], by modifications of the matrix due to implantation of the primary ions [2], by adsorbed atoms on the sample surface [3], and in crystalline samples, by effects of crystal orientation [4]. To complicate further this situation, the collection, transmission, and detection efficiencies of the mass spectrometer are not uniform with mass and may be difficult to measure or calculate accurately.

D. E. Newbury, D. Simons

### SIMS Quantitative Analysis of Impurities in GaAs Using Multi-Element-Doped GaAs

As SIMS has a very high sensitivity, it is useful for analyzing low concentrations of impurities in GaAs [1]. Usually, ion-implanted samples are used as standards for SIMS quantitative analysis. However, secondary ion yields of various impurities in GaAs have not been investigated, because for GaAs, there are no standard samples having certified values such as with NBS standard samples.

S. Kurosawa, Y. Homma, T. Tanaka, M. Yamawaki

### SIMS Quantitative Analysis of Gallium in Silicon by Using Ion-Implanted Samples for Standards

Ion-implanted samples are generally used as SIMS impurity analysis standard materials for semiconductor devices. However, che accuracy of the calibration has not been so clear. The impurity concentration is generally determined by using the Relative Sensitivity Factor, RSF value. RSF value is determined from the relation between the ion implantation dose and the integrated value of secondary ion signals. There are various error factors in this calibration method. One of them is che accuracy of the ion dose. Another one is the error related to depth profiling. Errors due to depth profiling are mainly 1) lack of accuracy of the depth measurement, 2) non-uniform sputtering, 3) the variation of secondary ion yield and 4) cascade mixing and radiation-enhanced diffusion. The depth measurement error can be decreased to a very small value by careful experiment. However, other errors have originated in SIMS fundamental phenomena and not easily decreased. In this reporc these errors are investigated in detail for gallium in silicon.

H. Yamaguchi, Y. Honma, J. Kashiwakura, K. Koike

### Ion Gun Systems for Submicron SIMS

The possibility of submicron scanning ion microscopy was demonstrated long ago [1, 2], Its potential use for SIMS applications has been the subject of theoretical and experimental investigations in a number of laboratories [3–12]. With the growing importance of submicron devices this instrumentation will surely have a future.

H. Liebl

### Submicron Ion Probes

An increased interest in developing focused ion beams has arisen in recent years. This was motivated by a great success of liquid metal ion (LMI) source technology. Primary experiments with this type of source originated in the 1960’s. Mahoney et al.[1] used a capillary emitter to obtain ion emissions of cesium, although their purpose was in an ion thruster. For a similar purpose Bailey[2] built an ion emitter which is thought to be an original model of the present LMI sources. Evans and Hendricks[3] used an alloy type LMI source of Ga-In as an ion source for mass spectrometry. Krohn and Ringo[4] built a focusing system, using an electrostatic einzel lens with a Ga source. Prewett and Jefferies[5] developed ion sources consisting of a capillary and a needle, which are almost the same configuration as that of Bailey’s. Seliger et al.[7] originally realized an ion probe of less than 1 micron in diameter, using a Ga ion source made by Clampitt’s group. Emission characteristics of LMI sources were intensively studied by Swanson et al.[8].

N. Anazawa, R. Aihara

### Optimization of High Brightness Cs Ion Source and Ion Optics for UHV-IMMA

An ultra - high vacuum ion microprobe mass analyser (UHV-IMMA) aimed at hydrogen detection and microanalysis of semiconductor devices has been developed [1] at ULVAC. A schematic diagram of the UHV-IMMA is shown in Fig. 1. A cesium ion beam extracted from the surface ionization type ion source is focused by the stigmatic focusing sector type mass analyser onto the image aperture. The image aperture (300 μm in diam.) determines the initial spot size and acts as an orifice for effective differential pumping. The ion beam passing through the image aperture is focused onto the sample surface by both of the symmetrical einzel lens (the 1st lens) and the asymmetrical lens (the 2nd lens). Two octupole deflectors used for raster scanning are located between these lenses to minimize the deflection-induced aberration and are operated so as to make the primary ion beam always pass through the center of the second lens. The secondary ions ejected from the sample surface travel in the spherical electrostatic ion energy analyser (IEA) and the quadrupole mass spectrometer (QMS). The number of secondary ions is counted by a high rate pulse counting system.

K. Komatsu, O. Tsukakoshi, T. Katagawa, S. Komiya

### A New Type Surface Ionization Source with an Additional Mode of Electrohydrodynamic Ionization for SIMS

The secondary ion mass spectrometry(SIMS) is widely used as a powerful technique for surface analysis. Although SIMS shows a very high sensitivity for many elements by using positive or negative ion emissions from the specimen(l), its spatial resolution is limited mainly by the source size of the ion gun with such a type as the duoplasmatron or the surface ionization with a porous W flat emitter. Thus, we developed a new type ion source with a small source size which can be used in two modes, either surface ionization or electrohydrodynamic(EHD).

T. Okutani, M. Fukuda, T. Noda, H. Tamura, H. Watanabe

### A Study on Argon Ion Gun in SIMS

In order to use SIMS for static state, sweeping and composition profiling analysis on specimen, an ion source of electron impact ionization type with beam-forming electrode [1,2] is investigated, besides the potential distribution in the ion source and ion trajectories in the exit system are calculated using numerical method. The results show that this ion source is capable to produce a beam with small initial energy spread and high ion yield, then a small ion beam spot could be obtained by means of suitable ion optical system and filter.

Wang Jian-Hua, Li You-Zhe, Chen Pi-Jin, Long Zhi-Qiao, Ho Xiao-Fang, Zhang Quan-Zhen, Zhang Zhen-Xiang

### Liquid Metal Ion Sources for Scanning SIMS

Liquid metal ion sources (LMIS) were introduced in the field of microanalysis by SIMONS et al. [1] who demonstrated that the high ion currents which can be extracted from a single liquid metal tip can be usefully applied for high sensitivity compositional analysis of liquefied metal alloys. KROHN and RINGO [2] were the first to suggest the use of a finely focused liquid metal ion beam as the primary beam in a scanning ion microprobe. Somewhat later, true submicron scanning ion beam columns of high current density (1 A/cm2 50nm diameter) were developed for applications in ion lithography, microfabrication and maskless ion implantation [3], [4], The first demonstration of the feasibility of a submicron primary ion beam in SIMS was given by PREWETT et al. [5], Obviously, submicron lateral resolution was the main driving force behind the introduction of the LMIS in SIMS. There are. however, a number of reasons why the LMIS could be a useful alternative to the routinely used gaseous primary ion beams. In addition, some unexpected properties of LMIS beams have emerged which, if judiciously exploited, could also be useful in microanalysis (see Table 1).

F. G. Ruedenauer

### SIMS with Very High Spatial Resolution Using Liquid Metal Ion Sources

The practical lateral spatial resolution of scanned ion microprobes has been limited until recently to ≳ 1μm by the relatively low brightness and large source size of duoplasmatron ion sources [1]. During the last decade liquid metal field-ion sources (LMFIS) have been developed with much higher brightness (~106 A/cm2.sr) and small source size (<100nm) [2,3] : it was recognised early on that these sources were potentially very suitable for ion probes with sub-micron resolution [1, 31. SELIGER and coworkers [4] showed that probe diameters of less than 100nm at 55keV were possible using gallium ion.

A. R. Waugh, A. R. Bayly, K. Anderson

### Development of High Performance Ion Microanalyzer

The ion microanalyzer (IMA) is the only surface analyzer which enables high sensitivity analysis of both surface and depth profile of various materials. Recently the IMA has been extensively utilized for quality control of diverse materials. Along with this, high sensitivity has been in increasing demand. The Model IMA-3 developed by Hitachi has realized an exceptionally high sensitivity, excellent resolution and ultrahigh vacuum owing to use of new ideas and technology.

E. Izumi, Y. Kato, M. Yano, Y. Arima, H. Tamura

### MIQ-156 MARK II A Highly Advanced and Versatile Quadrupole SIMS Instrument, with Dual Primary Ion Source

Analytical work based on SIMS is greatly improved using primary beams of reactive gases. Matrix effects are reduced, ion yield are enhanced and relative peak intensities are more representative of the atomic surface concentration (1 to 6). This affords the use of different ion species and separate ion sources. We use a duoplasmatron to produce Ar+ , N2+ and O2+ ions combined to a commercial cesium ion source (7). Aim of our development is to check the feasibility of a dual line configuration, so that both sources can be run simultaneously and the beam switched in a matter of minutes.

F. Simondet, P. Staib

### Development of Shielded Ion Microprobe Analyser for Irradiated Fast Reactor Fuel and Material Examination

A shielded ion microprobe analyser(SIMA) has been developed for the mass spectral analysis of bulky highly activated mixed oxide fuels and their components. Radiation shielding of the instrument ensures the radiation dose rate less than 0.52[C/kg.h](2.0[mR/h]) at the outer surface of the SIMA for 185[GBq](5.0[Ci]) of Co-60 source. The analyses have been carried out with urania-plutonia fuels, B4C control rods and stainless steel fuel claddings irradiated in Japanese Experimental Fast Reactor “JOYO”. The isotopic compositions and the distributions of U and Pu, and the fission products’ behaviour in the fuel, boron and lithium characteristics in the control rods and the chemical information at inner and outer surfaces of the cladding can be obtained very accurately and quickly. We found no serious problems in function of the instrument and in reliability working with the shielding capability in comparison with the conventional one.

Y. Enokido, M. Mizuno, S. Yamanouchi, K. Kohno, T. Itaki

### Parameters Influencing Ion Intensities for Quadrupole SIMS Instruments

It is well known that quadrupole mass spectrometers can be operated in various resolution modes, for example, constant ΔM or constant M/ΔM. This property is easy to understand theoretically from the stability diagram and from the equation for the scan line: (1) $${\rm{U = \alpha V}} \pm {\rm{\gamma }}$$ and the equation for the resolution: (2) $$\frac{{\rm{M}}}{{\Delta {\rm{M}}}} = \frac{{\rm{C}}}{{0.16784 - {\rm{U/V}}}}.$$ In these equations U and V are the d.c. and a.c. potentials aoplied to the electrodes, α and γ are constants determined by adjustments on the guadrupole control and C is a constant that depends on peak shape. From these equations and the fact that V is proportional to M,it can be seen that if α = 0.16784 and K ≠ 0 ΔM will be constant. Also if K = 0 and α ≠ 0.16784 M/ΔM will be constant.

M. Kotera, D. B. Wittry

### Isotopic Measurements at High Mass Resolution by Electrostatic Peak Switching

Precise measurement of isotope abundance ratios is usually obtained by a sequential scanning of the appropriate section of the mass spectrum in front of the selection slit of a spectrometer. When secondary ion emission is used, the existence of cluster ions makes it necessary to resort to high mass resolution. So, a precise and reliable peak switching system is required.

G. Slodzian, J. C. Lorin, R. Dennebouy, A. Havette

### Laser Microprobe Mass Spectrometry

The use of lasers as an ionization source for solid samples is nearly as old as the laser itself. The first papers in this field were published in 1963 [1]. Since then there has been a growing interest as well as a proliferation of publications on this subject, to the extent that a recent bibliography listed nearly 1000 references [2]. The reasons for this increase in popularity are twofold. First, commercial instruments that use lasers as a microprobe have become available in the last five years. Second, the laser is one of a class of “soft” ionization sources that have become popular in organic mass spectrometry for the analysis of nonvolatile and thermally labile materials. The laser is unique as a means of ionizing solids because the ionization mechanism can be altered by simply changing the power density in the focal spot.

D. S. Simons

### Metastable Molecular Ion Emission from Semiconductor Surfaces Under N2 Laser Irradiation

The ion emission from solid surfaces under intense laser irradiation was observed for the first time by F. BRECH and L. CROSS.[1] In spite of numerous investigations of this phenomenon during the past 20 years, the microscopic mechanism of ion emission has not been analyzed well enough, partly due to the lack of time-resolving experiments for identifying bonding/ionic states of emitted particles and for measuring their kinetic energies. Our previous investigation on laser-induced ion-cluster emission from graphite surfaces shows the presence of such unstable ionic states which may be observed only in the time scale of a few micro-seconds.[2]

A. Kasuya, Y. Nishina

### Laser-Induced Sputtering from CdS and GaAs

The laser-induced sputtering from semiconductors not only involves basic problems about lattice dynamics and chemical reactions in dense electron-hole (e-h) plasmas, but also gives important clues to wide applications in the laser-controlled bulk and surface processes. Time of flight (TOF) spectra of emitted particles have been used as a measure of the surface temperature during the laser annealing of Si by fitting a Maxwellian distribution function (1). For the compound semiconductors, however, TOF spectra of the neutral particles showed a velocity distribution apparently deviated from the Maxwellian one(2). Three possible mechanisms have appeared for the dynamics of atoms in pulsed laser-irradiated semiconductors. Those are (1) vaporization of molten phase(1), (2) instability of e-h plasma and concomitant phase transition(3), and (3) non-radiative relaxation as a result of two hole localization in e-h plasma(2). While these are rather concerned with the neutral particle ejection, knowledge about the relation of ions and neutrals is still scarce. CdS and GaAs are very interesting semiconductors from the view-point of practical use and basic problems of optical properties. We will employ here a dynamic mass spectroscopic method with a pulsed laser and discuss the emission of ions and neutrals.

H. Fukano, A. Namiki, Y. Yasuda, T. Nakamura, T. Noda

### SIMS at Higher Energies

The IsoTrace (Isotope and Rare Atom Counting Equipment) facility is based on a small tandem electrostatic accelerator (General Ionex Corporation 3 MV Tandetron). When fully commissioned the laboratory will offer a wide range of analytical strategies for SIMS at higher energy. Three ion sources are currently being tested. Two of these employ wide ( 0.25–1.0 mm), high current (tens of μA) beams of Cs+ or I- for ultrasensitive (sub-ppb) analysis of bulk samples and the third, when adapted to sputtering mode in 1984, will be part of an ion microprobe attachment for ppm-ppb trace element and isotopic work.

A. E. Litherland, J. C. Rucklidge, G. C. Wilson, W. E. Kieser, L. R. Kilius, R. P. Beukens

### The Radiocarbon Measurement with the Tandem Accelerator at Nagoya University

The Tandetron accelerator mass spectrometer manufactured by General Ionex Corporation in the USA was installed at Nagoya University to measure the low-abundance isotopes in natural samples. In the installation, the apparatus was especially assembled to measure the radiocarbon abundance.

T. Nakamura, H. Yamashita, N. Nakai, T. Sakase, S. Sato, A. Sakai

### Image Processing SIMS

One of the potentially most useful capabilities of SIMS, which has been somewhat underutilized in the past, is imaging. The ability to quantitatively map the distribution of elements on the micron scale with high sensitivity and isotopic discrimination is unique to SIMS. This capability is a powerful tool for investigation of the solid state, where properties correlate not only with chemical composition, but also with the degree of chemical heterogeneity. SIMS images give information on both the composition and morphology of the sample. To date, SIMS imaging has been mostly used in a qualitative manner to solve problems. With the advent of digital image processing techniques, more quantitative information can be extracted from image data, which in turn will improve the problem-solving capabilities of SIMS.

G. H. Morrison, M. G. Moran

### Evaluation of Metal Interaction by Color Display SIMS Technique

The SIMS method is available to obtain the one-dimensional depth profile of elements and two-dimensional map of elements. However, metals used for manufacturing semiconductor devices can interact three-dimensionally to cause complex distribution of elements. And it is necessary to know the exact distribution of elements for obtaining highly reliable devices. This report describes the results of investigation on metal interaction observed by color display SIMS technique.

Y. Mashiko, K. Tsutsumi, H. Koyama, S. Kawazu

### A Comparison of Camera-Based and Quantized Detectors for Image Processing on an Ion Microscope

Secondary ion mass spectrometry (SIMS)/ion microanalysis of materials surfaces is capable of detecting all the elements in the periodic table and provides the highest elemental detection sensitivity of all existing microanalytical techniques[l]. SIMS/ion microanalysis performed on the CAMECA IMS-3f Ion Microanalyser not only provides these elemental detection capabilities but also produces mass-selected ion images of the secondary ions formed during the sputtering process. These secondary ion images are produced by combining specialized secondary ion extraction and focusing ion optics with a stigmatic focusing mass spectrometer. The ion images are observed by converting the ion intensity into visible light through the use of a microchannel plate (MCP)/fluorescent screen image intensifier. Although the ion optics of the CAMECA IMS-3f are capable of resolving the lateral distribution of secondary ion emission down to a lateral resolution of ~0.3μm, the ion images produced on the standard imaging detector contain only a qualitative measure of the secondary ion signal intensity. The incorporation of a quantitative image detector (i.e. a detector which quantitates the ion intensity in the image) would provide a means of extending the microanalysis capabilities of the IMS-3f into areas such as three-dimensional depth profiling, multi-area, multi-element analysis and quantitative and lateral distribution analysis.

R. W. Odom, D. H. Wayne, C. A. Evans

### Automation of an Ion Microprobe Mass Analyzer

Many reports have been published for the automatic control of SIMS instruments, but most of them are based on rather expensive systems. The present paper describes a more economical system for an Applied Research Laboratories’ Ion Microprobe Mass Analyzer.

T. Suzuki, K. Tsunoyama

### Ultra-High Vacuum SIMS: A Pilgrim’s Journey Through History

Many people no doubt remember that Secondary Ion Mass Spectrometry (SIMS) contributed a great deal to the early days of the space age by playing a major role in the microanalysis of lunar rocks returned from the Apollo missions of the United States. By successfully using either argon or oxygen as the primary ion species, many applications focussed on the identification of oxides and other chemical states. SIMS has also been widely used to analyze ferrous and non-ferrous alloys required by heavy industry, in a period roughly starting around 1964. In these instances, a primary argon ion beam has been enhanced with a small oxygen jet or the actual primary beam used oxygen ions. In all of these techniques mentioned so far, the SIMS technique could be carried out without the need for an ultra-high vacuum (UHV) environment.

S. Komiya

### Single Crystal Surface Structure Studies with Static SIMS

When Benninghoven demonstrated the high surface sensitivity of SIMS and introduced static SIMS 14 years ago it was natural to ask the question: If static SIMS can be used to determine the composition of the surface, can it not also be used to determine the arrangement of its constituents, that is the atomic structure of the surface? We embarked on an attempt to answer this question 12 years ago and came to a conditional “no” a few years later. The “no” was conditional in the sense that SIMS gave no structural information which could not be obtained easier and/or more accurately using other methods for surface structure analysis. This answer and the supporting experimental results were never published so that it is not surprising that the discussion of the question is still continuing, stimulated in part by computer experiments of oxygen on (Cu(100) [1,2]),in part by the claim that the bonding site of CO on metal surfaces can be determined by SIMS [3] • The CO controversy (for references see [4,5]) is not very relevant from the point of view of practical surface structure analysis because the information extractable from SIMS is inferior to that obtainable with other methods and will, therefore, not be discussed here for lack of space.

E. Bauer, S. Prigge

### Ion Dose Effect in Thin Film Formation on Nb(100)

The growth of metal films under the influence of ion bombardment has attracted considerable interest recently in connection with ion beam deposition. In ion beam deposition condensation and surface damage are not separable. Such a separation is, however, possible if the metal is thermally evaporated in small doses and bombarded in between doses with ions whose nature, energy and angle of incidence can be chosen freely. The secondary ions produced by these ions can simultaneously be used to characterize the film. We have studied the initial growth of Cu and Pd on Nb(100) in this manner. These two systems differ fundamentally in that Pb alloys with Nb while Cu does not. A comparison of the two systems should, therefore, give some insight into the influence of alloyibility on the ion beam influence.

T. Koshikawa, S. Prigge, E. Bauer

### A Low-Energy SIMS Investigation on Thermal Diffusion on Vapor-Deposited Nickel on Copper Substrate

Diffusion coefficients of metallic atoms at an interface have been determined by chemical methods radio isotope methods and recently by XPS methods. These measuring methods are not enough to analyze diffusion behavior of metallic atoms in angstrom range for their depth resolution. In comparison with these methods, SIMS with low primary ion energy and ion current density provides high depth resolution of 5 — 20 Å for metallic copper, nickel and their alloys [1] and therefore it is the most powerful method for getting information of angstrom range at solid surface region.

H. Yamamoto, T. Kikuchi, K. Furuya

### SIMS Combined with Other Methods of Surface Analysis

Like all methods of surface analysis, SIMS provides only fragmentary information and therefore profits by combination with complementary techniques. Comparable results can only be obtained if these additional methods are applied to the same surface simultaneously or sequentially in one UHV system.

Otto Ganschow

### Combined SIMS and Electron Spectroscopy Investigation of the Chemical State of Some Ion-Implanted Transition Metals and Steels

Several transition metal substrates and steel specimens were ion-implanted with various species including nitrogen, chromium, and titanium at doses from 1016 to 1018 atoms/cm2. The purpose of the implantation study was to modify the surfaces of the materials in order to improve their resistance to wear, fatigue, and corrosion [1,2].

W. M. Bone, T. M. Barlak, I. L. Singer, R. A. Jeffries, R. J. Colton

### SIMS-Auger Analysis of Organic Films on Gallium Arsenide

Gallium arsenide is proposed as a suitable substance to prepare photo-electrodes which effectively convert photon energy to chemical energy through photo-assisted electrode reactions. However, the semiconductor,having band gap below 2 eV,is easily corroded by the electrolyte when exposed to light[1]. To develop a protective organic film on the electrode surface it is recommended for the purpose to make the surface anti-corrosive , but material of low surface energy such as GaAs is difficult to cover uniformly with organic polymer film thin enough to allow electrons to be exchanged between electrode surface and electrolyte.

### SIMS and AES Studies of Ni-Zn Alloys

Ni-Zn alloy is one of good corrosion resistant materials [1]. Since the alloy with low Ni composition has several times resistance to corrosion in comparison with Zn, the electrodeposited alloys on steel sheets are being used for automobiles [2]. Preferential sputtering and oxygen-induced enhancement of ion formation are important problems in applications of SIMS to studies of alloys. The former leads to enrichment of one constituent of binary alloys. The latter has two factors, changes in the surface composition and the electronic structures of atoms on oxygen incorporation . Ion yield of a constituent for binary alloys depends upon the surface composition, the ionization probability, and the sputter yield if experimental conditions are kept constant. Therefore, SIMS measurements combined with AES are required in order to characterize alloy surfaces.

Y. Fukuda

### The Application of SIMS and Other Surface Techniques to the Study of Antimony-Doped Tin Oxide Surfaces

Surface studies of real catalyst surfaces are exceedingly difficult because the surfaces usually contain many elements, small concentrations of certain species may determine the catalytic behavior of the surface, the spatial distribution of the species is highly inhomogeneous and the active surfaces are often smaller than the probe dimensions and may not be directly accessible for surface studies. Nevertheless, much progress is being made in characterizing model catalysts using ultrahigh vacuum surface techniques such as electron spectroscopy for chemical analysis (ESCA), ultraviolet photoemission spectroscopy (UPS), Auger electron spectroscopy (AES), electron stimulated desorption (ESD), secondary ion mass spectrometry (SIMS) and many others. The model catalytic surface usually is prepared on a planar substrate which is convenient for surface analysis.

G. B. Hoflund, P. H. Holloway, W. H. Hocking

### Silver Catalyst for Partial Oxidation of Methanol. Reaction Path and Catalyst Poisoning by Iron. A Combined SIMS, TDMS, AES, XPS and ISS Study

Formaldehyde formation from methanol on silver catalysts is a well-known technical process, but only parts of the elementary steps of this reaction are known. In previous work /1/ we have shown that the characteristics of the silver-oxygen adsorption system play an important role in this catalytic reaction. We therefore investigated in detail the adsorption and reaction kinetics of both oxygen and methanol on silver by combined SIMS, TDMS, AES, XPS, and ISS. For reasons of brevity, only SIMS and TDMS results will be presented here. The experiments were performed in a combined surface analytical and microreactor instrument, which has been described in full detail elsewhere /2/.

R. Jede, E. Manske, L. D. An, O. Ganschow, U. Kaiser, L. Wiedmann, A. Benninghoven

### Behavior of Inorganic Materials on Catalysts Used for Coal Liquefaction

MoO3-Al2O3 catalysts developed so far were rapidly deactivated by the deposition of metal elements, originated from coal, on the catalyst during hydroliquefaction of coal [1,2]. The clarification of the behavior of the metal elements on the catalyst is needed to establish practical methods for the lessening of catalyst deactivation by metal deposition.

H. Shimada, Y. Kobayashi, M. Kurita, T. Sato, Y. Yoshimura, A. Nishijima

### Quantitative Investigation of As Segregation at the SiO2/Si Interface by SIMS and RBS

Dynamic segregation of dopants at the SiO2/Si-interface during thermal oxidation is of major interest for process development and modelling in silicon integration circuit technology. The dopant concentrations of interest extend over a wide concentration range, hardly accessible with methods other than SIMS.

H. Frenzel, J. L. Maul, P. Eichinger, E. Frenzel, K. Haberger, H. Ryssel

### Low Energy Oxygen Ion Implantation and Ion-Bombardment Induced Oxidation of Silicon, Studied by SIMS, AES, and XPS

The influence of oxygen ion bombardment and oxygen exposure on secondary ion emission of silicon surfaces seems to be the subject most extensively studied in SIMS literature, but only little is known about the kinetics of oxygen uptake and oxygen depth profiles for low energy oblique incidence primary bombardment. In the present paper we give a preliminary account of our combined method investigations of secondary ion emission of silicon under oxygen load.

P. Sander, U. Kaiser, O. Ganschow, R. Jede, L. Wiedmann, A. Benninghoven

### The Effects of Ion Beam Sputtering on the Chemical State of Metal Oxide Surfaces

For the studies of the surface properties of solids and the measurement of the depth profile of an element, ion beam sputtering has been used generally in combination with various methods for surface analysis, e.g. secondary ion mass spectrometry(SIMS). However, it has not been investigated experimentally about the interrelations of the sputtering and the changes of surface states.[1]

K. Hara, T. Itoh

### Combined Spectrometer with the Techniques of SIMS, ISS, AES and XPS

In order to realize “in situ observation” of a specimen using several surface analytical techniques, one usually needs to arrange several excitation sources, analyzers and detectors around the specimen. Furthermore, to pursue the best performance of each technique, it is essential to install the above devices as close to the specimen as possible. However, it is difficult to arrange them close to the specimen, because the size of the devices is fairly large. Model ASIX-1000, a combined surface analytical instrument developed by us, gives a solution to the problem by separating the main body into two portions connected with each other. One is for the micro-area analysis by SIMS (Secondary ion mass spectrometry), ISS (Ion scattering spectrometry) and AES (Auger electron spectrometry), and the other is for the macro-area analysis by XPS (X-ray photoelectron spectrometry). A specimen can be transferred between both portions in the same vacuum chamber.

Y. Kodama, S. Sumitomo, I. Kato, M. Jinno, H. Yamauchi

### The Use of SIMS for Semiconductor Processing Technology: The Influence of Oxygen at Depth Profiling

Secondary ion mass spectrometry (SIMS) is one of the most powerful characterization methods in semiconductor processing technology. In SIMS, the presence of oxygen has been found to influence the intensities of the secondary ions emitted by the material under study, and therefore it is important to take the effect of oxygen into consideration. The following experimental facts are known. 1) The intensity of the secondary ion emitted from the surface or the interface of multilayer samples increases abnormally in the presence of oxygen (oxide). 2) When O2+ or 0- is used as primary ion beam, it is difficult to determine fully the identity of the upper most surface layer (~200A), because the concentration of oxygen implanted in the surface increases continuously.

F. Konishi, Y. Yoshioka, K. Kusao

### Photon Radiation Annealing of Ion-Implanted Silicon

Transient annealing of ion-implanted semiconductors has recently recieved considerable attention. Photon beam radiation from a graphite heater, a halogen lamp or an arc lamp is utilized for transient annealing for a few seconds[1,2,3]. One of the advantages of rapid annealing is the possibility of activation of implanted dopants without their redistribution. This is desirable for making shallow junctions which are required in high density and high speed VLSI and the three-dimensional IC’s. In this paper, we present the characteristics of rapid annealing of ion-implanted silicon by using photon beam radiation from a graphite heater. Activation and redistribution of dopants were studied by the measurements of sheet resistance and the secondary ion mass spectroscopy (SIMS). Recovery of crystallinity and the secondary defects in the ion-implanted layer were observed by transmission electron microscopy (TEM).

T. Isu, K. Sugahara, Y. Akasaka

### Quantification of Silicon Wafer Cleaning Using Secondary Ion Mass Spectroscopy

The basic surface cleanliness requirements for Si-based semiconductor technology have become an increasingly more difficult analytical problem as the density of active elements on integrated circuits has increased. No longer is a relative “sea” of Si present to soak up and disperse contaminants left from one processing step so they will not affect subsequent steps. The basic sensitivity of Auger electron spectroscopy (AES) and electron spectroscopy for chemical analysis (ESCA) has been stretched to the limit for a number of elements [1] and therefore a study of the application of SIMS to this problem was undertaken. This study concentrates on the analysis of the s contaminants in the native oxide left on Si wafers after most cleaning processes and the quantitation of the impurity elements found in this layer.

B. F. Phillips, Ch. A. Peterson

### SIMS Study of Surface Contamination Due to Ion Implantation

Silicon surface contamination due to ion implantation was found by using secondary ion mass spectroscopy (SIMS). Silicon wafers were prepared by keeping their surface condition as identical as possible. Only minimal, necessary different process steps were received by the samples. All experimental data were analyzed on a comparative basis. Effect of incident ion mass on sputtering phenomena of the target material is discussed.

A. C. Yen, A. F. Puttlitz, W. A. Rausch

### Quantitative Analysis of Amorphous Silicon Nitride Using SIMS

Plasma silicon nitride film has been widely applied to a passivation layer of photo-electric devices. Since its physical and electrical properties are strongly dependent on a variety of deposition parameters, it is important to evaluate the film composition to control the deposition process. From this point of view, we utilized SIMS for the quantitative estimation of nitrogen in silicon nitride using Ar+ primary ion beam. Results are compared with those obtained by XPS.

T. Shima, M. Koyama

### The Contribution of SIMS to the Characterization of III-V Compounds

For several years, secondary ion mass spectrometry (SIMS) has been very successfully applied in the electronics industry to the characterization of semiconductor materials. It contributes in particular to the improvement of the III-V materials used in the new electronics industry for microwave and opto-electronic devices. A number of interesting published works provide evidence for this.

A. M. Huber, G. Morillot, A. Friederich

### Effects of Donor Impurities on the Redistribution of Mn Acceptors in In1−xGaxAs

The ditribution of impurities introduced during epitaxial growth or by ion implantation and impurity redistribution during subsequent annealing are of great importance due to their relevance to device fabrication [1–4]. Secondary Ion Mass Spectrometry (SIMS) has been used to study the redistribution of dopant level Mn in In1-XGaXAs. A variety of Ge donor and Mn acceptor doped layers and structures were incorporated during MBE growth of InGaAs layers on InP substrates at 500°C. Portions of each layer were annealed at temperatures of 650°C and 700°C for 4 hours.

Ch. J. Hitzman, E. Silberg, T. Y. Chang, E. A. Caridi

### Residual Donor Impurities in Undoped LEC SI-GaAs Crystals

Undoped liquid encapsulated Czochralski (LEC) semi-insulating (SI) GaAs is a promising substrate for GaAs IC’s . However, high electrical uniformity across a wafer has not yet been attained. The SI mechanism is explained by the compensation of shallow levels with deep levels (1, 2). In order to improve the electrical uniformity, distribution measurements of these levels are required in the first place. However, most studies done so far were limited to the deep levels and little is known about the shallow levels. In this study, SIMS measurements have been carried out to obtain the distribution of residual shallow donor impurities such as Si, S, Se and Te in several wafers. We describe the correlation between the impurity distribution and dislocation density, and a possible origin of resistivity inhomogeneity.

K. Kuramoto, M. Nakajima, T. Kikuta, F. Orito, H. Emori, K. Ishida

### Quantitative Depth Profile Analysis by Secondary Neutral Mass Spectrometry (SNMS)

Concentration depth profiles at or below a solid surface are mostly determined by combining a surface sensitive analytical technique with controlled sputter removal of the sample. When electron spectroscopic techniques as AES or XPS are employed, the analytical signals refer to the mostly drastically changed surface stoichiometry during the sputtering attack [1], Mass spectrometric techniques as Secondary Ion or Secondary Neutral Mass Spectrometry, SIMS or SNMS, monitoring the ejected particle flux, are less sensitive to such misleading influences, at least for quasi-stationary conditions, i.e. for slowly varying concentration profiles. With SIMS, the true concentration profiles are often veiled by matrix effects. Such effects, as well as the high selectivity of SIMS, are circumvented by SNMS where, contrary to the secondary ion formation, the emission and the ionization process of an analyzed particle are decoupled. Thus, the ionization probability $${\rm{\alpha }}_{\rm{X}}^{\rm{O}}$$ for an ejected neutral species X becomes a constant of the SNMS apparatus [2,3] and is no longer a function of the chemical environment at the emission site.

H. Oechsner

### Practical Limitations in Depth Profiling of Low Energy Implants into Amorphised and Crystalline Silicon

As lateral dimensions in semiconductor devices shrink, so must the depth dimensions, requiring accurate analysis of impurity concentrations with ever increasing depth resolution [1–2]. Measurement of impurity dopant profiles by secondary ion mass spectrometry is complicated by the presence of physical and instrumental effects which result in measured secondary ion intensity distributions with depth which deviate from the original concentration variation with depth [3–5]. These effects are assessed, particularly in the case of some instrumental effects, using low energy ion implants.

J. D. Brown, W. H. Robinson, F. R. Shepherd, S. Dzoiba

### Depth Profiling of Dopant Distribution in Small Area Transistors

The analysis of semiconductor devices in research and development has to deal with: Narrow structures (up to few micrometers),Thin layers from 0.01 to 10 micrometers,Low concentrations of doping elements. The SIMS technique has been extensively used for depth profiling of dopant distribution in large analyzed areas. In this paper,some examples of depth profiles obtained in transistors as small as 4 micrometers across will be shown.

H. N. Migeon, A. E. Morgan

### Comparison of Oxygen and Indium Primary Ion Beams for SIMS-Depth Profiling

Liquid metal ion sources (LMIS) have recently received increased attention as a possible alternative to conventional primary ion sources in scanning SIMS. The main hope in the introduction of LMIS primary ion guns lies in the implementation of a true submicron scanning ion microprobe with an expected spatial resolution limit below 100 nm [1], [2]. While good progress has been made towards this particular goal [3],[2], very little has been reported C23 on the use of LMIS guns in depth profiling. Here, we want to report on a comparison of depth profiling capabilities using oxygen and In primary beams from a duoplasmatron and a LMIS respectively.

J. D. Brown, M. J. Higatsberger, F. G. Ruedenauer, W. Steiger

### Application of Computer-Controlled SIMS to Depth Profiling of Impurities Implanted in Silicon with High Dose of B+or BF2 + Ions

Recently, TANIGAKI and co-workers have developed an electronic data processing system for an ion microprobe mass analyzer (ARL-IMMA) interfaced with a personal computer, that is to say an “automatic depth profiler” [1]. In this system, conversion of secondary ion intensity to atomic concentration and of sputtering time to depth scale can be easily carried out by setting two main parameters, viz. the measured conversion coefficient and the sputtering rate.

T. Tanigaki, S. Kawado, K. Nishiyama

### Improvements in the Routine Depth Profiling of Doping Elements

In the SIMS depth profiling of doping elements, crater-edge and surrounding influences may still limit the dynamic range [1] , despite the impressing progress that has been achieved in the past [2,3] . In addition, profile deviations may sometimes be caused by residual contamination spots in the crater area.

R. v. Criegern, I. Weitzel, J. Fottner

### Aspects of SIMS Evaluation of Tracer Diffusion and Its Isotope Effect

Tracer techniques are still the dominant experimental approach to the microscopic mechanisms of atomic transport /1/. In today’s “state of the art”, however, in order to extract reliable new information from diffusion measurements one requires a precision considerably above that furnished by conventional instrumentation a decade ago. During recent years, the technique of SIMS has proven its particular usefulness in this freld /2,3/. The tasks include the delineation of very slight curvatures in the Arrhenius plot of diffusion /4,5/. Even higher requirements apply in measurements of the isotope effect of diffusion /1,3/, potentially a very powerful technique for pinpointing atomic mechanisms of diffusion /6,7/. With increasing sophistication of such applications, however, several particular artifacts of SIMS have emerged as non-negligible obstacles. The present paper attempts to discuss the following factors in the evaluation, from in-depth profiles, of diffusion coefficients and particularly of their isotope mass dependence: a)Counting dead-timeb)Assignment of correct time coordinate at each peak countc)Geometry of diffusion profiled)Determination of effective position of specimen surface, x=0 in the profile.

H. Odelius, U. Södervall

### High-Performance Depth Profiling with a Quadrupole-Based SIMS Instrument

Because of its good depth resolution and high sensitivity, SIMS is ideally suited for determining the depth distribution of sample constituents in the 0.1–10 μm depth range. The accuracy of measured depth distributions is generally limited by instrumental distortions [1]. A primary goal in SIMS instrument development, therefore, has been to eliminate such distortions by careful instrument design. The most recent advance in this direction is the Physical Electronics Model 6300 SIMS system. In this paper, the design and operation of this system is briefly described. An example of a depth profile of a B implant in Si is presented that demonstrates the performance of the instrument.

D. G. Welkie, R. L. Gerlach

### Depth Profiling of Evaporated Se-Te Films with SIMS

The Se-based photoconductor is widely used in photoconductive printing. Depth profiling of elements of major components and also low concentration dopants and impurities is desirable to understand the photoconductive behavior of the materials. However, until recently, use of SIMS on chalcogen photocon-ductors has been minimal because of the charging problem encountered in the measurement.

F. Soeda, K. Okuno, A. Ishitani, M. Nagano, T. Iijima

### Depth Profiling of Heat-Treated Mo Films on SiO2/Si Substrates

An Mo film deposited on an SiO2 surface is composed of columnar grains. Heat treatment causes grain growth and results in an increase in surface roughness [1] . As a result, Mo film sputtering features are different from pre-annealed Mo films.

K. Fujinaga, I. Kawashima

### SIMS Depth Profiling of Shallow As Implants in Si and SiO2

The usefulness of SIMS as a process tool in integrated circuits has been investigated. As a testcase shallow As implants (4–40 keV) in Si and SiO2 are measured and the range parameters (projected range, range straggling, skewness and kurtosis) are derived [1]. It is shown that the measurements of these shallow profiles are extremely sensitive to disturbing effects such as collisional mixing and/or radiation enhanced diffusion. The effect of the primary energy and of the primary mass on the measured profiles is discussed in terms of these two mechanisms. It is found that very low primary energies are mandatory for measuring shallow profiles without disturbing effects. However,a lower limit for oxygen bombardment of SiO2 is encountered below which the sensitivity drops over orders of magnitude.

W. Vandervorst, H. Maes, R. De Keersmaecker

### Depth Profiling by SIMS to Minimize Charging Effects

So far, some trials (1)–(5) to obtain the depth profiling of impurities in insulators by SIMS have been carried out. However, they have not always been appropriate in view of accuracy because of the charging. The charging made the shape of the secondary ion energy distribution curve broaden and shift. For example, the distribution curve of 28Si+ secondary ion in SiO2 layer of 0.6 μm thickness on Si substrate varies with the sputtering time ( t1→ t4 ), as shown in Fig. 1. The energy shift was about +100 eV at the beginning of the sputtering and decreased as the sputtering time passed by t4. On the other hand, the intensity of the secondary ion increased with the reduction of the energy shift, as shown in Fig. 2. Therefore,

H. Mutoh, M. Ikeda

### Quantitative Depth Profiling of B and P in Borophosphosilicate Glass

Borophosphosilicate glass (BPSG) is used in the semiconductor industry for two purposes: (1) as a top passivation layer on electronic devices and (2) as an intermetal dielectric (typically between aluminum and polysilicon) [1,2]. The advantages of BPSG over undoped Si02 is its ability to reflow within device-compatible temperature ranges [3,4] and its formation of better aluminum contact step coverage [5]. In addition, the presence of phosphorus in the passivation layer serves to getter impurities and minimizes the penetration of alkali metals into the device [6]. Although these advantages are significant, the high P concentration in BPSG, coupled with its high porosity and hygroscopicity (related to P contents), is a major cause of corrosion of aluminum runs in devices [7,8]. As a consequence, it is necessary to have a thin phosphorus free glass layer between the BPSG and A1.

P. K. Chu

### Investigation of Gas Phase Ions with a Quadrupole SIMS Instrument

SIMS instruments using a quadrupole mass spectrometer are usually provided with an electrostatic spectrometer in order to avoid degradation of the mass resolution due to energetic sputtered ions. In such an instrument, it is possible to study the energy distribution of sputtered ions by keeping the potentials applied to the electrostatic analyzer and to the extraction electrode constant and varying the specimen voltage. This approach was used by WHATLEY and WITTRY [1] to study the energy distribution of positive ions from group III and group VI elements in III-V semiconductors.

M. Kotera, D. B. Wittry

### Organic Secondary Ion Mass Spectrometry

Organic SIMS is based on the primarily unexpected fact that sputtering of even involatile and thermally labile organic molecules results in-the formation of parent-like secondary ions, as (M+H)+ and (M-H)-, e.g. [1–3]. In addition, characteristic fragment ions are generated.

A. Benninghoven

### Characteristics of Molecular Secondary Ion Mass Spectrometry

Secondary ion mass spectrometry(SIMS) has been widely used for elementary analysis of solids. Since Benninghoven applied SIMS to analysis of amino acids in 1976[1], various large bio-organic compounds have been investigated using SIMS[2,3]. Introduction of the glycerol matrix by Barber et al. [4] prompted great progress in use of SIMS for such large bio-organic compounds[5,6]. They put a sample on a metal surface together with two or three μg of glycerol and hit it with a fast neutral argon beam. They called this technique fast atom bombardment(FAB). At first, it was thought that ion bombardment could not be used because of surface charging. However, it was found that an analogous spectrum could be obtained by SIMS using charged particle bombard-ment[7,8]. It is now widely admitted that the same physical phenomenon occurs with both ion and neutral fast atom bombardment.

H. Kambara

### Mechanisms of Organic Molecule Ejection in SIMS and FABMS Experiments

A classical dynamics model is used to investigate nuclear motion in solids due to bombardment by energetic atoms and ions. Of interest are the mechanisms of ejection and cluster formation of molecular species where we have predicted intact ejection of benzene-C6H6, pyridine-C5H5N, napthalene-C10H8, bipheny1-C12H10 and coronene-C24H12. The results presented here show that the energy distributions of the parent molecular species, e.g., benzene, are narrower than those of atomic species, even though the ejection processes in both cases arise from energetic nuclear collisions. The bonding geometry also influences the ejection yield and angular distribution. The specific case of π-bonded and σ-bonded pyridine on a metal surface is discussed with comparisons between the calculated results and experimental data. These calculations provide a means of interpreting SIMS, FABMS and possibly even PDMS experimental data.

B. J. Garrison

### Comparison of the Laser Mass Spectra and SIMS Spectra of Amino Acids

Particle-induced mass spectrometry encompasses a number of mass spectral techniques: SIMS,LMS,FABMS, and PDMS. The similarities of quasimolecular and fragment ions detected for organic compounds indicate that the secondary ionization processes occurring in the “selvedge” are similar. Gain or loss of protons, ion-attachment reactions, and unimolecular dissociations generally are the same, even though the primary particles (photon, ion, or neutral) interacting with the organic material are dissimilar. A comparison of the mass spectral results among the techniques should help to elucidate the relative degrees of energy transfer from the particle to the organic material, in the primary process of particle-material interaction. The present communication is part of an overall comparison being carried out in our laboratory.

C. D. Parker, D. M. Hercules

### Laser Desorption Mass Spectrometry of Complex Biomolecules at High Laser Power Density

The laser microprobe mass analyzer LAMMA® 500 originally designed for the extremely sensitive tracing of elements and molecules in microsamples and tissue obviously comprises soft ionization characteristics allowing the mass spectrometric analysis of ther-molabile, non-volatile high-molecular-weight biomolecules [1] . The possibilities and limitations of getting information on molecular weight and chemical structure are demonstrated with the aid of positive and negative ion LD mass spectra of two free lipid A samples isolated from Proteusmirabilis bacteria which were grown at different temperatures. Furthermore, a model of the laser-induced desorption process from organic solids is derived based on the experimental experience with LAMMA 500 applied to a large number of chemically different compounds and on the influence of laser power density and sample conditions (geometry, compactness).

B. Lindner, U. Seydel

### Organic SIMS Studies with a Hollow Anode Ion Source

Fast atom bombardment (FAB), a new ionization technique, has been applied to many areas in organic SIMS. Neutral ion sources such as the saddle field neutral source [1] and fast atom capillaritron [2] have been used as primary neutral beam sources for this technique. Since a hollow anode ion source yields good results for ion beam thinning application, we expect that it will have good characteristics as a neutral beam source.

Y. Naito, K. Tanaka, T. Sueyoshi

### An Apparatus for Studying Liquid Matrix Assisted Organic Secondary Ion Processes

FAB is a form of organic secondary ion mass spectrometry (SIMS) in which the primary beam is neutral and the sample is dissolved in a liquid matrix during bombardment. The success of FAB is now generally attributed to the use of the liquid sample matrix and not, as earlier claimed, the neutral charge state of the primary beam. Continued development of FAB mass spectrometry or, more generally, liquid matrix assisted SIMS requires investigation of the processes of secondary ion emission from liquid sample matrices.

D. F. Barofsky, J. H. Murphy, A. M. Ilias, E. Barofsky

### Comparison of Three Source Geometries for Cs+ Liquid SIMS

In the typical liquid SIMS (LSIMS) geometry, the primary beam direction is fixed at 90° to that of the secondary ion beam, and the secondary signal is optimized by varying the target plane angle. Best results are often obtained at an incident angle of 60° [1]. It can be argued that this large angle improves secondary ion efficiency because a greater portion of the incident ion energy is deposited close to the target surface where it can more effectively cause secondary ion ejection [2]. However, the complementary extraction angle for the secondary ions must then be small and ambiguity exists as to the most effective independent combination of incident and secondary ion beam angles [3]. It has been suggested that the greater efficiency of high-mass ion production using the plasma desorption technique may be partly due to the similarity in direction of the primary and secondary beams [4]. Thus some of the momentum of the primary beam assists in extracting the sample ion from the target matrix. These considerations motivated us to try alternate LSIMS source configurations that could permit sampling of ions ejected close to the direction of the primary beam. The small size of the cesium ion gun used for LSIMS [5,6] provided a flexibility of orientation not generally available to FAB and other types of ion sources.

W. Aberth, R. Reginato, A. L. Burlingame

### Study of Metastable Ions from Molecular Species Produced by Molecular Secondary Ion Mass Spectrometry

Molecular secondary ion mass spectrometry has been successfully used for structural elucidation of bio-organic compounds[l–3]. A serious drawback for such structural studies is the observation of interfering peaks due to impurities. One solution to this problem is the investigation of daughter ions.

H. Kambara, Y. Ogawa, S. Seki

### Monte Carlo Simulation of an Ion Sputtering Process of Polymer Materials

Recently, the surface analysis of polymer materials has been becoming more and more important in industry. SIMS is expected to become a powerful tool for characterization of polymer surfaces. Several authors [1–5] have discussed the potential of SIMS in the field. However, understanding of sputtering mechanism of polymers is far from a satisfactory level. In this paper, we have examined sputtered surfaces with XPX and interpreted the observed spectra with a simple calculation based on Monte Carlo simulation.

T. Takahagi, K. Okuno, S. Tomita, A. Ishitani

### Depth Profiling of Polymer Blends and Optical Fiber with the Aid of SIMS

In inhomogeneous polymer blends we cannot expect a homogeneous distribution of each component along the direction vertical to the free surface. Even in homogeneous polymer blends the distribution might be affected by the surface energy. This leads to the importance of the establishment of a depth profiling method. For polymer blends, AKIYAMA(1) has classified characterization methods into three categories: morphological, chemicophysical, and thermodynamic. They have been appreciated as useful methods. Besides these methods, the present authors would like to propose an application of the secondary ion mass spectrometry (SIMS) as a useful method for characterizing polymer blends, especially for depth profiling.

R. Chûjô, T. Nishi, Y. Sumi, T. Adachi, H. Naitoh, H. Fenzel

### Application of SIMS Technique to Organic Polymers

SIMS has started to be used to study organic polymers [1, 2] and biological specimens [3] because of its potential capabilities such as high sensitivity and good lateral and depth resolution [4]. Three major fields of SIMS application to polymers are 1) identification of chemical structure [1, 2], 2) analysis of low concentration inorganic elements and, hopefully, 3) analysis of organic materials in polymer matrix, among which the first one has mainly been pursued up to now by analyzing a characteristic mass fragmentation pattern from a polymer.

K. Okuno, S. Tomita, A. Ishitani

### Analysis of Molecular Species of Organic Compounds Dispersed in Polymer Layer Using LDMS and SIMS

Many important contributions have been recently made, to our knowledge, to the analysis of organic compounds using LDMS or SIMS. Most of these works have been carried out on specific samples such as thin layer compounds deposited on a metal surface [1]. Recently, characteristic secondary ions (SI) of various kinds of practical polymer films were shown by Briggs [2, 3]. In his paper, the importance of surface potential stabilization attained by selecting the optimum parameters for primary ions and electron flood was emphasized to obtain finger print SI mass spectra of individual polymers.

K. Kurosaki, A. Toba, M. Yasutake, T. Adachi, H. J. Heinen

### Cesium Ion Liquid Matrix Secondary Ion Mass Spectrometry and Its Impact on the Characterization of Free Labile Biological Substances

The early foundations of organic mass spectrometry evolved with the requirement and constraint that the sample or a suitable chemical derivative thereof be volatilized without thermal degradation prior to ionization and internal energy deposition into either the ambient ion source chamber vacuum or the injection port of a gas chromatograph/mass spectrometer, both usually held in the order of 200 + 50°. However, in this past decade, the inventions of new types of ion sources and techniques which obviate the requirement of sample volatilization prior to ionization per se have been occurring at a seemingly accelerating pace since the description of the first breakthrough in 1969 (viz., field desorption) and subsequently plasma desorption, laser desorption, secondary ion and thermospray techniques [1]. The steady successes, particularly using the techniques of field desorption and plasma desorption, have made sustained pioneering contributions in the characterization of previously intractable polar and labile biological substances and have set the stage for intimate mass spectrometric participation in studies of higher molecular weight biological and synthetic polymeric substances [2, 3]. Judging from the sometimes similar nature of the mass spectra observed, all of these new ionization/“desorption” techniques have attributes in common. However, their diversity (including their associated instruments’ ion optical properties, detectors, and computers) has quickly led to the ability to analyze directly the majority of compound types previously inaccessible by mass spectrometric techniques, including the polyfunctional polar, chemically and/or thermally labile biological substances, their salts, organometallic complexes, modified biopolymers, etc. [1, 2].

A. L. Burlingame

### A New Time-of-Flight Instrument for SIMS and Its Application to Organic Compounds

For the e/m-analysis of secondary ions, different types of mass spectrometers with considerable differences concerning their mass range, their transmission and their dynamic range, have been applied. An important aspect which determines the choice of an appropriate mass analyzer in SIMS is the quantity of sample material that is available. It determines the total number of secondary ions that can be produced. This may be an extremely low number, if e.g. in static SIMS, only a fraction of one monolayer in the bombarded target area of some 0.01 cm2 is allowed to be sputtered during an experiment [1].

P. Steffens, E. Niehuis, T. Friese, D. Greifendorf, A. Benninghoven

### Analysis of CsI and Peptide Mixture by Molecular SIMS

Two significant results obtained by the SIMS technique are reported. One is the analysis of CsI and cluster ions of [(CsI)nCs]+ up to n=350 (m/z=90,000). The other is the analysis of human hemoglobin. Mass spectra of tryptic peptides of globin α, β, γ and δ chains were investigated, and a new technique which determines the site and type of amino acid mutation of variants (digital printing method) was developed.

I. Katakuse, I. Ichihara, H. Nakabushi, T. Matsuo, T. Sakurai, H. Matsuda

### Sequencing of Peptides by SIMS from the C or N Terminus

A novel method has been developed to sequence proteins and peptides from either the C or N terminus using secondary ion mass spectrometry (SIMS) [1]. Unlike other mass spectrometric methods, fragmentation during ionization or desorption in the mass spectrometer is not relied upon. Instead, this method is based on observations by Cooks and coworkers [2] that the emission of ‘preformed ions’ is greatly enhanced over that of non-charged species. If a peptide is labeled at either the N or C terminus with a charged moiety and randomly cleaved with acid or enzymes, only the products with the charged grouping are observed in the SIMS spectrum of the mixture. The sensitivity for some peptides is in the picomole range.

D. A. Kidwell, M. M. Ross, R. J. Colton

### Secondary Ion Mass Spectra of Triterpenoidal Oligoglycoside

Mass spectrometric behavior of triterpenoidal oligoglycosides isolated from Panax ginseng C. A. Meyer have been investigated and the structures of four new triterpenoidal glycosides (MG-Rb,, MG-Rb2, MG-Rc, and MG-Rd) were determined using secondary ion mass spectrometry.

Y. Ikenishi, K. Iwatani, Y. Nakagawa, I. Kitagawa

### Structural Characterization of Naturally Occurring Oligosaccharides by Matrix-Assisted Molecular Secondary Ion Mass Spectrometry

Normally, a glycerol matrix is essential in sputtered ion mass spectrometry such as fast atom bombardment (FAB) and molecular secondary ion mass spectrometry (SIMS) [1]. Recently, we have successfully applied an amine matrix, diethanolamine (DEA) and triethanolamine (TEA), instead of glycerol for the determination of molecular weight of neutral oligosaccharides by molecular SIMS [2]. When DEA was used, a stable molecular adduct ion species, the [M+DEAH]+ ion, was formed as the sole ion derived from a neutral saccharide molecule and no fragment ions were detected. Moreover, the [M+DEAH]+ ion scarcely decomposed even under collisionally activated dissociation (CAD) conditions.

M. Suzuki, K.-I. Harada, A. Tatematsu, H. Kambara

### Characteristics of Peptide Fragmentation Patterns in Molecular Secondary Ion (SI) Mass Spectra

Molecular Secondary Ion Mass Spectrometry (SIMS) has successfully provided molecular weights and structural information on various kinds of nonvolatile and labile bio-organic compounds [1–4]. Many studies on peptides have also attempted to interpret the fragmentation mechanism or amino acid sequence by analysis of the fragmentation patterns in SI or Fast Atom Bombardment (FAB) mass spectra [5–8].

S. Seki, H. Kambara

### Detection of Hydrogen in Steel Using SIMS

Hydrogen in steel causes various defects such as delayed fracture of high strength steel, delayed cracking of weldment, blistering of mild steel used in sour environment and UST defects in hot rolled plates. A number of studies [1] – [5] have been made to clarify the initiation and propagation processes of the hydrogen embrittlement ; however, the details of the microscopic process have not been revealed because the microscopic detection of hydrogen in steel was not successful.

T. Ohtsubo, K. Suzuki

### Surface Analysis Applied to Cold Rolled Steel Sheets

Just as observed for other materials, the surface properties of steel sheets are to day of increasing importance for many applications; it is particularly true for cold-rolled steel sheets as used in automotive industry for car body making, because surface properties may have a significant impact in fabrication operation such as finishing treatments where they affect the corrosion resistance of painted panels (1). A few years ago, substantial evidence was given that surface carbon pollution observed in some cases on temper-rolled steel sheets was the main contaminant responsible for corrosion performance of painted steel panels (2, 3, 4, 5). For such reasons steel industry carries out large research programs devoted not just to defining the different sources of surface pollutions but really to developing a deeper understanding of the steel processing - steel properties relationships (6).

V. Leroy, J. P. Servais, B. Chatelain

### Effects of Atmosphere Upon SIMS Analysis of Oxygen Isotopes in Oxides and Accurate Determination of Tracer Diffusivity of Oxygen

SIMS has been extensively applied to evaluating the tracer diffusivities of oxygen for many metal oxides[l–3]. This is based on the view that the oxygen isotope ratio in oxides is safely represented by the SIMS-peak intensity of the isotope without significant deviation. However, we have found that residual oxygen in the gas phase plays an interfering role in the SIMS analysis of oxygen isotope concentration, the effects of which are strongly dependent on the nature of bond between oxygen and metal atoms. This fact might lead to an unfavorable influence on determining the tracer diffusivities of oxygen, since the previous method using the gas-oxide exchange reaction requires the absolute values of oxygen concentration in bulk and at surface.

K. Sato, Y. Inoue, M. Ohno, H. Igarashi, M. Someno

### Tracer Diffusion Coefficient of Oxide Ions in LaFeO3 by SIMS Measurement

Oxygen has no radioactive isotope suitable for use as a tracer in diffusion experiments. Therefore, the gas-solid isotopic exchange technique using the stable isotope 18O has been used for the measurements of the tracer diffusion coefficients of oxide ions in oxide materials. So far, the gas phase analysis has been mainly adopted, in which the decrease of the 180 concentration in the atmosphere is measured. In this method, the numerical analysis of the data is very complicated when the surface reaction rate is low [1]. Moreover, a painstaking and highly skillful experiment must be performed, especially for the compounds with low oxide ion diffusivity [2]. The depth profile measurement has an advantage that the diffusion profile in solids is directly determined. It is also easily applied for the compounds with low oxide ion diffusivity, because the penetration length in the order of micrometer is adequate for this method.

T. Ishigaki, S. Yamauchi, K. Fueki, H. Naitoh, T. Adachi

### A Study by Low Energy SIMS of Chromium Behavior in an Oxide Film of Low-Chromium Steel

Chromium has an important role for passivation of metal surfaces. Many researchers have studied the composition and structure of oxide film on the surface of various kinds of iron-chromium alloys by means of XPS [1], AES [2, 3], ISS [4] and SIMS [5]. These surface analyzing methods afford to give information on the topmost surfaces. Tjong et al. [3] have studied the alloys (Cr; 3, 9, 12 and 18%) and found the bulk compositions of these alloys may bring significant changes of growth rate of oxide on them. Buczek et al. [2] also reported that the thickness of oxide was reduced as chromium content in an alloy increased.

S. Yamaguchi, T. Kikuchi, K. Furuya

### FAB-SIMS Study for Analysis of Insulators

For the SIMS analysis of insulators, sample surface charging caused by primary ion bombardment should be prevented by, e.g., irradiation with electrons. The charging takes place by primary ion adhering on the sample surface and by emission of secondary electrons or secondary ions from the sample surface. Primary ion adherence and secondary electron emission are more significant in the charging than secondary ion emission, because the quantity of emitted secondary ions is very small, compared with secondary electrons and primary ions.

K. Nagai, H. Kuwano

### Geological Applications of SIMS

In geology, SIMS is applied mainly to trace element and isotopic analysis rather than surface analysis or depth profiling. Good spatial resolution is desirable, hence the instruments used are generally of the ion probe type, with primary beam focussed to a few μm. The image-forming type of instrument (ion microscope) can also be used, in which case a small part of the image may be selected for ‘spot’ analysis. Molecular interferences necessitate high mass resolution in many geological applications, hence double-focussing magnetic-sector mass spectrometers are favoured in preference to the simpler quadrupole type.

S. J. B. Reed

### Mineral/Groundmass Partitioning for Chrome Spinel in Boninite

Mineral/magma partition coefficients are important factors for understanding magma genesis. ONUMA et al. [1] have proposed a diagram of partition coefficient (PC) vs. ionic radius (IR) which has a potential ability for elucidating how major and trace elements are distributed between minerals and magma. The PC of an element is under a strong control of the crystal structure, so that each cation position in the crystal structure gives rise to a parobola-shaped peak on the PC-IR diagram [l, 2]. The parabolic dependence is predicted on the basis of simple isotropic balk strain theory [3J or ionic lattice strain theory [4!]. Recently YURIMOTO and SUENO [5] have developed a new method for obtaining a set of coherent data for major and trace elements partitioning from the micro-area in rocks by secondary ion mass spectrometry (SIMS). They found the PC for anions was also under control of the crystal structure for olivine- and plagioclase-groundmass systems. The PC-IR diagrams are well established for major rock forming minerals [e.g. 2]. However, PC’s are least available for spinel which is an important phase in oceanic basalt and boninite.

H. Yurimoto, S. Sueno

### Quantitative SIMS Analysis of Metastable Plagioclase in Boggild Intergrowth

Quantitative SIMS data can be obtained either by using working curve methods based both on combined secondary ion microprobe and electron microprobe analyses [1, 2] or using various methods of purifying of each isotopic peak [3]. Although almost all SIMS studies on geological samples are made on natural and synthesized crystals and glasses, few applications to metastable minerals showing exsolved microstructure are found mainly because of difficulty in explanation of inhomogeneity of the surface and the formation process.

Y. Miura, T. Tomisaka

### SIMS Study on Ion Impact Desorption of Water from Silica Gel

Previous studies on the radiation chemical reactions of CO-H2 mixture [1], CH4 [2], and CO-H2O mixture [3] in the presence of various solid catalysts revealed that some insulators such as silica gel and alumina exhibit catalytic activity for the reactions under electron beam irradiation. Although such activity of insulators has been ascribed to transfer of radiation energy from insulators to gases adsorbed on their surfaces, the mechanism of energy transfer is not well understood at present. In order to shed some light on the mechanism, we have initiated the studies of fundamental processes which take place at gas/solid interfaces when energetic electrons or ions impinge on the surfaces of solids, especially insulators, covered with gases, using a combined surface analysis system of AES/SIMS. This paper describes the results on Ar+ ion impact desorption of water from silica gel as studied by SIMS.

S. Nagai, Y. Shimizu

### Molecular Ion Suppression in the Secondary Ion Mass Spectra of Minerals

The application of SIMS as a practical analytical tool has been severely restricted by molecular ion interferences in the spectrum. The principle advantages of SIMS, specifically high sensitivity for a wide range of elements, low inherent backgrounds and large dynamic range, are often lost in a sea of molecular species. The large number of major and trace elements, and thus considerable spectral complexity, has made mineral analysis one of the more difficult challenges for this form of spectrometry.

J. B. Metson, G. M. Bancroft, N. S. Mclntyre, W. J. Chauvin

### Self-Diffusion of Silicon and Oxygen in Silicate Melts: An Experimental Study

The rate of diffusive transport of Si and O in silicate melts is important not only in understanding kinetics of magmatic processes but also in studying the structure of silicate melts. The coefficients of self-diffusion of Si and O were determined experimentally in two simple silicate melts of geologic interest: jadeite composition; NaAlSi2O6, and diopside composition, CaMgSi2O. These melts were selected because they represent: (1) contrasting degrees of polymerization, i.e., jadeite melt is highly polymerized, whereas diopside melt is de-polymerized [1], (2) extremes in the spectrum of viscosities, i.e., jadeite melt at the high viscosity end and diopside melt at the low viscosity end [2], and (3) contrasting behavior in terms of their pressure-induced variations in viscosities, i.e., jadeite melt shows a decrease of viscosity with increasing pressure [3], whereas diopside melt shows an increase of viscosity with increasing pressure [2].

N. Shimizu, I. Kushiro

### Quantitative Analysis of Metallic Ions Associated with Fluid Inclusion

The authors developed previously a new technique of the analysis of fluid inclusion in mineral of the size less than 100 μm and also reported some results in mineral samples taken from several ore deposits[1]. The inclusion fluid is frozen by cooling, to avoid rapid evaporation of the liquid under vacuum at the time when the ion beam breaks the wall of the inclusion. Since Na ion is a major constituent in almost all inclusions, the intensity of each ion is compared to that of Na. the relative intensity is used to estimate the content of each ion using the relative intensities obtained from the synthesized aqueous solution containing each element at different concentrations.

T. Sato, Y. Omori, M. Nambu

### SIMS Measurement of Magnesium Isotopic Ratios in Primitive Meteorites

Much information about the origin of the primordial solar nebula has been acquired by the investigation of primitive meteorites including the discovery of 16O excess by CLAYTON et al. [1], 26Mg excess originated from the in situ decay of now-extinct 26A1 (half life = 7.2 × 106 y) by GRAY and COMPSTON [2] and 24Mg excess by NISHIMURA and OKANO [3]. These were obtained by the investigations of the Allende and other primitive meteorites. Based on the data, the primordial solar nebula is thought to contain two or more components from different sources.

H. Nishimura, J. Okano

### Sensitivity and Quantitation of SIMS as Applied to Biomineralizations

Quantitative applications of SIMS to tooth and bone hard tissue, first reported a decade ago /1/, have during recent years established efficient routines and gathered new momentum /2–4/. However, although exploratory studies have been made elsewhere, practically all hitherto published work in this field has been performed in Sweden. The reason is probably to be found in the particular artifacts encountered and in the consequent costs of routine development.

A. Lodding, H. Odelius, L. G. Petersson

### SIMS in Biology and Medicine

I thank the Organizing Committee for inviting me to talk on SIMS in the biological sciences. I would also like to thank the many colleagues who have been crucial in developing SIMS of biological materials to its current and evolving state. I have a heavy debt of gratitude to my laboratory and collaborators who have made my work possible [1, 2].

M. S. Burns

### Cell Cultures: An Alternative in Biological Ion Microscopy

Most of the applications of ion microscopy to biological systems to date have involved the examination of thin tissue sections. Inherent in this approach has been the problem of redistribution of ions during sample preparation [1, 2]. An alternate approach which deserves exploration is the analysis of cell cultures. It has long been known that the study of cells growing and dividing in culture (in vitro) reveals many of the basic properties of cells, whose study is more difficult within the organisms. The use of tissue culture cells over thin sections in elemental distribution studies using ion microscopy provides several advantages. The cultured cells can be attached directly on the substrates typically used in SIMS analysis without showing any evidence of toxicity. This eliminates the need for tissue dissection before fixation, thereby limiting redistribution of diffusible elements (Na, K, Ca, etc.). The thickness of the cultured cells is less than 0.1 mm, so that their actual physiological and morphological states can be preserved relatively well by quick freezing [3].

S. Chandra, C. H. Morrison

### Secondary Ion Emission Microanalysis Applied to the Uranium Detection in Aquatic Organisms

The presence of toxic elements, such as radionuclides, in the aquatic environment and their bioaccumulation within the organisms has increased the need of sensitive and accurate methods to detect them. Uranium was shown to occur in France, in rivers and in the polluted coastal areas of the Channel and the North Sea where various industrial wastes are released (such as U-containing phosphogypsum and TiO2). Uranium is a heavy metal which consists of 3 isotopes: 238 U (99,3%),235 U (0,7%) and 234 U (0,006% , allα emitters, chemotoxic and radiotoxic. Fishes, crustaceans and molluscs were collected from these polluted sites. Sample preparation was made by two methods: 1. fixation in Carnoy liquid, embedding in paraffin, sectioning at 7 μm, deposit on gold specimen holder and removal of paraffin; 2. cryofixation, cryosectioning and deposit on gold specimen holder. Microanalyses were performed with a CAMECA IMS 300 instrument, equipped with an electrostatic deflector. Table 1 indicates the 13 investigated species collected from 12 stations of the Channel and the North Sea.

C. Chassard-Bouchaud

### Tissue Microlocalization of Isotopes by Ion Microscopy and by Microautoradiography

Micro-Auto-Radiography (MAR) is a method used in biological research for the microlocalization of elements in a tissue section. The spatial resolution is often of the order of 0.5 μm and the sensitivity may be extremely high. In this paper we shall compare the sensitivity of this method with Ion Microscopy (I.M), an other method of microlocalization with a similar spatial resolution.

P. Galle

### An Empirical Approach to Quantitative Analysis of Biological Samples by Secondary Ion Mass Spectrometry (SIMS)

It appears that secondary ion mass spectrometry plays an important part in biological fields. This paper discusses the elimination of the charge accumulated under the primary ion beam at the surface of non-conductive samples. It also discusses spectral interferences with molecular and their fragment ion spectra, and quantitative SIMS analysis using concentration of an implanted primary ion species as an internal standard element.

H. Tamura, J. Tadano, H. Okano

### Backmatter

Weitere Informationen