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1988 | Buch

The Physics and Technology of Amorphous SiO2

herausgegeben von: Roderick A. B. Devine

Verlag: Springer US

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SUCHEN

Über dieses Buch

The contents of this volume represent most of the papers presented either orally or as posters at the international conference held in Les rd th Arcs, Savoie, from June 29 to July 3 1987. The declared objective of the conference was to bring together specialists working in various fields, both academic and applied, to examine the state of our under­ standing of the physics of amorphous sioz from the point of view of its structure, defects (both intrinsic and extrinsic), its ability to trans­ port current and to trap charges, its sensitivity to irradiation, etc. For this reason, the proceedings is divided, as was the conference schedule, into a number of sections starting from a rather academic viewpoint of the internal structure of idealized Si0 and progressing 2 towards subjects of increasing technological importance such as charge transport and trapping and breakdown in thin films. The proceedings terminates with a section on novel applications of amorphous SiOz and in particular, buried oxide layers formed by ion implantation. Although every effort was made at the conference to ensure that each presentation occured in its most obvious session, in editing the proceedings we have taken the liberty of changing the order where it seems that a paper was in fact more appropriate to an alternative section. In any event, because of the natural overlap of subjects, many papers could have been suitably placed in several different sections.

Inhaltsverzeichnis

Frontmatter

Structure: Theory and Experiment

Current Models for Amorphous SiO2

I discuss central questions of glass structure and define four ranges of order in an amorphous solid: short, intermediate, long and global. These concepts are used to catalog all of the elements of order in the Zachariasen-Warren model for a-SiO2, in preparation for a later deduction of the logically possible improvements in that model. Six existing approximate forms of the ZW model are discussed using the language developed in the paper. This provides a fundamental background regarding structure for the rest of the papers in this volume.

Frank L. Galeener
Structural Similarities and Dissimilarities Between SiO2 and H2O

To date the atomistic structure of a crystalline substance can be determined with high accuracy. Due to lack of long-range order (distances r > 10Å) and the rather low degree of intermediate-range order (5Å ≲ r ≲10Å), the structure of amorphous substances can only be determined with considerably lower precision. For example, in crystalline SiO2 the bond lengths d(Si-O) and the bond angles ≮ O-Si-0 and ≮ Si-O-Si can be determined with standard deviations of approximately 0.003Å, 0.2° and 0.2° respectively, and the bond topology can be precisely given. In contrast, for amorphous silica corresponding values for the standard deviations of bond lengths and angles are considerably higher and only speculations can be made about the ratio between the numbers of rings containing 3, 4, 5, 6, etc.. Si atoms. Therefore, in order to derive reliable information on the intermediate range order of an amorphous phase this phase should be studied not only by diffraction (X-ray, neutron) and spectroscopic (IR, Raman, NMR etc.) methods but these results should also be compared in light of the structural knowledge of the crystalline phases of the same composition and, if possible, of crystal chemically related compounds. In the case of amorphous SiO2, the structures of the crystalline silica polymorphs and of the various crystalline phases having H2O frameworks should be considered.

Friedrich Liebau
Geometrical Methods in the Theory of Glassses

In some branches of physics one can observe a surplus of theoretical models coexisting with the dramatic lack of experimental data. The physics of glass is in an opposite situation: the enormous and rich variety of experimental results goes along with an absence of a consistent theory. We rely, in this domain, on some hints or analogies, no more. Somehow the two natural paths which should lead to the theory of glass, namely the theory of liquids and the solid state physics (up to now almost a synonym for the theory of the crystalline state) both come to a dead end or a kind of a no man’s land before penetrating into the territory on which the theory of glass should be found.

Richard Kerner
Low Lying Excitations in Silica

Neutron scattering measurements in vitreous silica show soft vibrational modes and structural relaxations with the same eignenvector, namely relative rotation of connected SiO4 tetrahedra. The results imply a common origin of soft vibrations, relaxations and tunneling states.

U. Buchenau
New Methods of IR Spectroscopic Investigation of Amorphous Insulating Films

The infrared (IR) spectroscopy of very thin insulating films on semiconductors has some perspective for the non-destructive analysis of corresponding microelectronic systems. Therefore, the derivation of IR optical equations for insulating films (on semiconductors) of decreasing thickness is of increasing importance. On the basis of the FRESNEL theory we derive relations for the determination of the reflection (R), transmission (T), and attenuated total reflection (ATR) of such films from their dielectric functions taking into account oblique incidence of polarized light. In this way we find a theoretical explanation for the detection and identification of transverse and longitudinal optical phonons by means of oblique incidence of IR light, realized within different experimental modes (R, T, ART). Furthermore, this framework leads to a theoretical basis for the ATR spectroscopy of very thin films as well as to a very effective method of determination of the IR optical (dielectric) functions of the film from corresponding experimental spectra, wich is based on the inversion of the optical relations mentioned above. Finally, it will be shown that the theory developed is in quantitative agreement with corresponding measurements performed for SiO2 and Al2O3 on silicon.

Klaus Hübner, Ulf Teschner
Vibrational Studies of Amorphous SiO2

There have been many studies of the vibrational structure of SiO2 glass, using infrared, Raman, neutron and other spectroscopies. Over the past few years, we have used vibrational spectroscopy, especially Raman scattering, to investigate glassy silicas prepared in a variety of ways or subjected to different treatments. Some of our work is summarized here, and the results are discussed in the light of recent models for the structure and dynamics of vitreous SiO2.

Paul McMillan
Raman Spectra of SiO2 Fibers at High Tensile Strain

Raman spectra were obtained for SiO2 fibers of 125 μm diameter at tensile strains ranging form 0 to 3.5.%. The spectrum only for the main peak at 440 cm-1 decreased its height with increase in the tensile strain. All the Raman spectra observed were decomposed into their Gaussian components, which are then assigned to normal vibration modes of either SiO4 or Si2O molecules. It is concluded that the stress-induced change in the Raman spectrum near 440 cm-1 is principally due to a change in the tetrahedral angle of the SiO4 molecules constituting silica networks and not to either a Si-0 bond stretching or a Si-0-Si bond angle broadening.

Hiroshi Kobayashi, Kazuhiro Ema
A Comparison of the Structure of a-SiO2 Prepared by Different Routes

Three different silica samples, Heraeus Suprasil I, silica prepared from colloidal silica gel and silica produced by hydrolysis were investigated using Magic Angle Spinning (MAS) 29Si and 1H NMR. Silica produced via the two low temperature routes contained a significant number of Si-OH linkages giving rise to Si03 (OH) and SiO2(OH)2 as well as Si04 tetrahedra. After heating to 950°C for the hydrolysis prepared sample and 1200°C for the sol-gel material most of the OH was removed and the silicon environment becomes similar to that in melt formed material.

R. Aujla, R. Dupree, I. Farnan, D. Holland
NMR Studies of Neutron-Irradiated Crystalline and Vitreous Silica

Some results of a 29Si NMR study of neutron-irradiated crystalline and vitreous SiO2 are reported. The spin-lattice relaxation time is found to change markedly with increasing neutron dose. Pronounced changes are also observed in the shape and position of the magic-angle spinning NMR lineshape. The shift in peak position for the metamict state is associated with a decrease in oxygen bond angle, and this is related to the densificaction of the glass observed upon neutron irradiation.

S. L. Chan, L. F. Gladden, S. R. Elliott

Intrinsic and Extrinsic Defects: Theory

Electronic Structure of Defects in Amorphous SiO2

The electronic structure, local bonding and reactions of the principal intrinsic point defects and some impurities (H2O, H, B, N, Ga, Ge, P, As) in amorphous silicon dioxide are reviewed.

J. Robertson
Electron and Hole Traps Related to A π-Bonded Oxygen Vacancy Center in SiO2

An oxygen vacancy is one of the most fundamental defects in SiO2. It influences many physical properties of silicon dioxide, e.g. charge trapping. Therefore a detailed knowledge of microscopy and chemical bonding of this defect is essential in understanding the physics of many problems in SiO2.

Ireneusz Strzalkowski
Theory of Oxygen-Vacancy Defects in Silicon Dioxide

Large, asymmetric atomic relaxations are important features of oxygen-vacancy-related defects in silicon dioxide. To investigate these defects we have adapted the MIND0/3 and MOPN semiempirical molecular structure methods. In several cases (the E1′, E2′, and E4′ centers) the defect is paramagnetic and its primary characteristic is a single sp3 electron localized on one Si and oriented towards or away from the O vacancy. Different atomic relaxations and charge states, along with the presence or absence of atomic H, distinguish these defects from one another. One important type of relaxation appears to be the displacement of a Si into a “back-bonds” interstitial position.

W. Beall Fowler, Jayanta K. Rudra, Arthur H. Edwards, Frank J. Feigl
Total Energy Calculations for Intrinsic Defects in Amorphous SiO2

The semi-empirical methods MINDO/3 and MOPN are used to calculate the total energies of various intrinsic defect configurations. We find that the positively charged trivalent silicon site gains about 1 eV by overcoordination and that the effective correlation energy of the trivalent silicon defect is positive. The creation energy of valence alternation pairs and like-atom bonds is also calculated.

J. Robertson
Boron Impurity Centers in SiO2 a Tight Binding Consideration

Boron is a common dopant in silicon technology, its implantation is frequently used in MOS VLSI circuit fabrication. In this way some atoms can be located in the SiO2. An interesting question is how boron can be incorporated into the SiO2 network and whether the presence of implanted boron can create electron and/or hole trapping centers.

Mariusz Marczewski, Ireneusz Strzalkowski, Jacek Baranowski

Intrinsic and Extrinsic Defects: Experiment

Intrinsic and Extrinsic Point Defects in a-SiO2

Point defects in amorphous silicon dioxide (a-SiO2) can be considered as any local deviations from the “perfect” glass structure, which for the sake of discussion will be taken to be a continuous random network of Si (0½)4 tetrahedra joined at the corners. Thus, for example, a vacancy-interstitial pair defined on such an otherwise perfect network would be the analogue of a Frenkel pair in crystalline solid. Since in our ideal glass each silicon has four bonds to neighboring atoms while each oxygen has but two, Frenkel pairs involving oxygen atoms (fig. 1a) would seem more probable than those involving silicons. Other possibilities include over or under-coordinated atoms, substitutional or interstitial impurities, or bonds between like atoms. Note in fig. 1a that a neutral oxygen vacancy is tantamount to a Si-Si homo bond.

David L. Griscom
Self-Trapped Excitons in Amorphous and Crystalline SiO2

Properties of the self-trapped excitons in amorphous and crystalline SiO2 studied through transient volume and optical absorption change and luminescence are compared. It is emphasized that local lattice relaxation induced upon electronic excitation in crystalline and amorphous materials is similar except that the time decay of the self-trapped excitons in the amorphous is non-exponential. Based on the fact that the self-trapped exciton in crystalline SiO2 is a close vacancy-interstitial pair, we propose a new mechanism for the luminescence in amorphous SiO2 exhibiting a non-exponential time decay.

Noriaki Itoh, Katsumi Tanimura, Chihiro Itoh
Identification of Native Defects in a-SiO2

One of the most powerful experimental tools for the identification of defects in solids is electron paramagnetic resonance (EPR). In a-SiO2, however, the defects are diamagnetic in their ground state, and are therefore invisible to EPR. Because of this, researchers interested in the structure of defects in SiO2 have had to rely on the use of ionizing or heavy particle radiation (γ, e-, n, X,..) in order to generate paramagnetic defects which can then be detected by EPR1. While these studies have been very fruitful, and the question of the mechanism by which defects are generated in a glass by the influence of high-energy radiation is an interesting and important one2, they leave open a fundamental question. Namely, since ionizing radiation may create additional structural defects in the glass, either by direct knock-ons or by a radiolytic process such as a recombination-assisted reaction, one gains little or no information about the native defects present before irradiation. The identity and properties of these native defects in a-SiO2 are important both for technological reasons, and because they help us to understand the nature of glasses in general.

J. H. Stathis
UV and VUV Optical Absorption due to Intrinsic and Laser Induced Defects in Synthetic Silica Glasses

We examined twelve kinds of synthetic silica glasses prepared by various methods, such as flame hydrolysis plasma-CVD, CVD-soot remelting and sol-processes. Each synthetic method and preparation process could berelated to particular intrinsic defects in the glasses such as hydroxyl groups, peroxy-linkages and oxygen-deficient defects. It was found that excess absorption near the band edge was caused in each case by the dominant intrinsic defects. The E’ center induced by ArF laser irradiation in the glasses containing oxygen-deficient defects was found quite stable at room temperature, whilst for glasses containing other dominant defects, it was unstable. The irradiation effects on the 7.6 and 5.0 eV absorption bands strongly suggest that these bands originate from oxygen-deficient defect.

H. Imai, K. Arai, T. Saito, S. Ichimura, H. Nonaka, J. P. Vigouroux, H. Imagawa, H. Hosono, Y. Abe
Incommensurate Phase of Quartz: Microscopic Origin and Interaction with Defects

Silicon dioxide is well known for its extensive polymorphism1: in addition to about 20 crystalline phases, it is also easily obtained in an amorphous state which is a prototype of glass structure. With the exception of Stishovite, these phases consist of three dimensional frameworks of corner sharing SiO4 tetrahedra, giving structures with different topological connections. Furthermore the low pressure phases (quartz, cristobalite, tridymite) present displacive transitions produced by small displacements of the SiO4 tetrahedra, without breaking any atomic bond. In this way quartz at 846 K transforms from the low temperature α phase of trigonal symmetry to the high temperature β phase of hexagonal symmetry. Although this transition has been studied for nearly a century, it was only in 1980 that Bachheimer discovered that the α-β transition was not direct2 but occured through a new intermediate phase, later characterized as an incommensurate (inc) phase3. In an inc structure some property (atomic position, electronic or spin density …) is modulated with a period λ which is not commensurate with the lattice period a. In a diffraction experiment satellite peaks are observed in addition to the usual lattice reflections. Indeed in the inc phase of quartz satellites have been observed by diffraction experiments with neutrons3, X rays4 and electrons5: satellites are observed along the 6 equivalent <100> directions of the hexagonal reciprocal lattice at a small distance q ≃ 0.03 a * from the Bragg peaks.

G. Dolino
Gamma-Ray Induced 2 eV Optical Absorption Band in Pure-Silica Core Fibers

The mechanism of optical absorption near 2 eV induced by γ-irradiation in pure silica glass has been studied by many workers1–6. It appears that non-bridging oxygen hole centers (NBOHC), which were revealed by Friebele et al. through the study of electron spin resonance (ESR) spectra1, are the most probable factor causing the optical absorption2–5. However, it is also clear that the 2 eV band cannot be ascribed to only one kind of defect center, because, as the OH-group content of the sample increases, the peak wavelength shifts from 630 nm to 600 nm3,5 and the oscillator strength decreases3. Friebele et al. thus assumed that the 2 eV band is caused mainly by NBOHC in high-OH silica (i.e., silica which contains a high amount of OH groups) and by a non-paramagnetic center such as ≡ Si:- in low-OH silica3. Contrary to the above assumption, the present authors thought that the difference in the 2 eV band induced in high-OH silica and in low-OH silica is caused by hydrogen bonds between the NBOHC and an OH group near the NBOHC, and that the 2 eV band in both low- and high-OH silica is caused only by NBOHC2. In this paper, experimental results are presented followed by discussion of the model derived from these results.

Kaya Nagasawa, Yoshimichi Ohki, Yoshimasa Hama
On the Decay of X-Ray Induced Luminescence of SiO2

A radiation induced luminescence in crystalline and glassy SiO2 has been widely studied1,2 but, only few investigations of its afterglow behaviour have been reported3,4,5. This paper is dedicated to the study of the influence of usual and different added impurities on the x-ray induced luminescence and especially on it’s afterglow in crystalline and glassy SiO2.

I. Godmanis, W. Hohenau
On the Role of O 2 - in the Luminescence of Amorphous and Crystalline SiO2

The study of defects in the various forms of SiO2 has been greatly assisted by the use of optical methods. However, few conclusive assignments have been made of the known absorption or emission bands to particular defects. This is partly due to the difficulties in correlating the data obtained using different techniques.

M. Guzzi, M. Martini, F. Pio, G. Spinolo, A. Vedda
Transformation of Radiation Induced Defect Centers as a Probe of Molecular Diffusion in a-SiO2

An important cause of ionizing radiation induced degradation in MOS integrated circuit devices is the buildup of trapped positive charge in gate and field oxides1. Recent electron paramagnetic resonance (EPR) studies2 have identified virtually all trapping sites in the oxides as E′ centers (paramagnetic bridging oxygen vacancies). The formation of these vacancies during irradiation by energetic photons or electrons is predominantly by ionization processes3, i.e., bond rearrangements after electron-electron collisions, rather than displacements from electron-atom collisions.

R. L. Pfeffer
Observation of the Neutral Oxygen Vacancy in Silicon Dioxide

We have studied electron-trapping defects in SiO2 films incorporated into Metal-Oxide-Silicon capacitors. The film consisted of SiO2 sputtered onto the native oxide formed on silicon. A process of direct band-to-trap tunneling of electrons into defects within the oxide film was isolated. This trap filling process, and the reverse emptying process, were analyzed using the assumptions that the trapping defects had a fixed spatial location and an extended energy level distribution. For a trap located at the sputtered SiO2/native SiO2 interface, we found a trap depth of 4 eV and a trap relaxation of 1 eV upon capture of an electron. These experimental results are consistent with theoretical calculations for the formation of a neutral oxygen vacancy in quartz by the addition of an electron to a positively-charged oxygen vacancy (that is, to an E1′ center). We therefore may have obtained the first direct experimental evidence for a neutral oxygen vacancy in SiO2.

M. E. Zvanut, F. J. Feigl, W. B. Fowler, J. K. Rudra
New Insight Into the Structure of SiO2 Glass from a Point Defect Study

Formation of defect centers in pure silica glass (a-SiO2) depends greatly on the manufacturing process of the glass. Non-bridging oxygen hole centers (NBOHC: ≡Si-0•) are dominantly created by γ-ray irradiation in high OH-group content (≥ 700 ppm) silica made by the direct glass deposition process1. In low OH-group content silica made by the plasma or soot method, oxygen content in the glass strongly affects the defect formation2,3; drawing induced peroxy radicals, drawing induced NBOHC, ≥-ray induced peroxy radicals and the 1.52 μm band induced by hydrogen treatment are created in oxygen-rich silica, but the 5 eV (245 nm) band and drawing induced E′ center (≡Si•) are created in oxygen-deficient silica. Based on these experimental results, the authors proposed2 the defect in the form of ≡Si-Si≡ as a model of the oxygen deficiency. In the present paper, further experimental evidence which supports the authors’ model and its proof by numerical calculation are presented. The structure of glass is also discussed.

K. Nagasawa, H. Mizuno, Y. Yamasaka, R. Tohmon, Y. Ohki, Y. Hama
Hydrogen Bonds Between Peroxy Radicals and Hydrogen Molecules in SiO2 Glass

Optical fibers are one of the most important components supporting communication systems in these modern days. Many studies have been devoted to clarifying the mechanism of loss increment caused by hydrogen-diffusion which affects adversely the long-term reliability of optical communication systems. In addition to the absorption band at 1.24 μm caused by hydrogen molecules1 and the one spreading from 1.39 to 1.4l μm caused by OH groups2, the absorption bands at 1.42, 1.45 and 1.52 μm are known to be related to hydrogen3,6. Among them, the absorption at 1.52 μm is important because it influences the transparency at 1.55 μm where single-mode fibers are operated. In this paper, the cause of this absorption is discussed.

K. Nagasawa, Y. Yokomachi, R. Tohmon, Y. Ohki, Y. Hama
ESR Studies of Paramagnetic Defects formed in Amorphous SiO2 by High Energy Heavy Ions

High energy heavy ions in insulators induce the formation of defects which have been studied by track etching methods and small angle X-ray scattering1-3. These previous studies have shown that the formation of defects is linked to electronic energy losses. However, the processes which result in lattice defects following such interactions are not well understood. In order to characterize the defects formed and their lattice environment, we studied amorphous SiO2 (dry Tetrasil SE) irradiated by heavy ions using Electron Spin Resonance (ESR). The paramagnetic defects formed in this material by γ-ray, X-ray and electron irradiation have already been extensively studied4–7. After such irradiation, two major types of defects have been observed: the E1′ center8 (hole trapped by an oxygen vacancy) and the oxygen hole center 9 (or OHC, associated with a peroxy radical). The density of defects observed was closely related to the total energy deposited in the sample. We previously showed 10 that high energy heavy ions also induce the formation of E1′ centers and OHC’s. However, the ion irradiated samples present specific characteristics, which are linked to the very high density of energy deposited near the path of heavy ions11. We present here a study of the dependence of the defects on the residual energy, the atomic number and the fluence of the incident ions. We show that, in contrast to γ-ray irradiations, the total energy deposited is not the single parameter controlling the formation of paramagnetic defects by high energy heavy ions.

E. Dooryhee, Y. Langevin, J. Borg, J. P. Duraud, E. Balanzat
On the Radiation Induced Coloration of SiO2

The radiation induced absorption spectra of crystalline and glassy SiO2 generally consist of broad overlapping A (450–650 nm), B (290–350 nm) and C (200–250 nm) bands1. Their relative intensities and distinct spectral positions slightly change in different types of crystalline and glassy SiO22. The absorption in the A band is attributed to the aluminium hole (Al/e+) and the C band region to E′ type defect centers3,4. Contrary to this is, the nature of the color centers forming the B band, is not determined. A more effective detection of this band in short time experiments as during stationary absorption measurements could indicate an unstable character of corresponding color centers in SiO25.

W. Hohenau, I. Godmanis
Effects of Processing on Radiation Damage Thresholds in Silica Glasses

We report experimental evidence linking near-surface radiation damage mechanisms to identifiable variations in the manufacturing process of silica glasses. We have bombarded a well-characterized set of Suprasil and Spectrosil glasses with ions and electrons under ultrahigh vacuum conditions. Relative yields of atoms and molecules desorbed from the sample glasses were obtained from the characteristic optical spectra; the time dependence of the bulk luminescence arising from electronic excitations in the near-surface bulk was also monitored. Comparison of these data with other work suggest a correlation between radiation damage susceptibility and the OH content of the fused silica.

R. F. Haglund Jr., D. L. Kinser, H. Mogul, N. H. Tolk, P. W. Wang, R. A. Weeks
The Structure of Defects in Doped SiO2

The common silicon dopants B, P and As tend to be incorporated in SiO2 as network formers, i.e. they will attempt to occupy Si sites in the glassy oxide structure. The present study deals with dopants introduced by ion implantation. Since the amount of oxygen is not sufficient to fulfill the bonding requirements of silicon and the dopant the implantation process leaves an oxygen deficient system. Annealing in an O2-free ambiant will restore the bonding in the network but will not affect this deficiency. The latter is only possible by an O2 treatment. Consequently, the oxide will have a different defect structure in the two cases. In the present paper we will review data on diffusion, XPS, IR absorption and electron trapping studies supporting this model.

M. Offenberg, P. J. Grunthaner, D. D. Krut, P. Balk
Electrical and Optical Characteristics of Vanadium Doped Amorphous Silicon Dioxide Films Prepared by CVD

Previous experiments on pure and vanadium (V) doped amorphous silicon dioxide (a-SiO2) films prepared by r.f. sputtering have shown that both the V-doped and undoped films can be switched reproducibly between two stable states of widely differing conductivity by field stressing the films1,2. Similar experiments using chromium, colbalt or titanium doping have also resulted in significant changes in the electrical properties of the oxide, but in these cases the material was less stable, even when annealed, with instabilities present at low to moderate fields. The behaviour of such materials is of great interest from both pure and applied aspects, but greater control over preparation is desirable. In the present paper we report the electrical and optical properties of V-doped a-SiO2 films prepared by CVD and compare them with the previous results on sputtered films.

K. V. Krishna, J. J. Delima, A. J. Snell, A. E. Owen

Interfaces

Theory of Dangling Orbital Defects at the <111> Si/SiO2 Interface

We review the experimental and theoretical pictures of the dangling orbital defects at the <111> Si/SiO2 interface. We show that recent theory agrees in detail with the observed hyperfine and super hyperfine. Also, the estimated level positions obtained from cluster calculations imply that the dangling orbital on the <111> interface is a normal, positive U defect. This is at variance with recent local-density Green’s-function calculations on the dangling orbital in crystalline silicon, that predict that the dangling orbital is a negative U defect. We discuss possible sources of the discrepancy. Finally, calculations on the recently proposed model for the Pb defect involving a three-fold coordinated oxygen atom yield general disagreement with spin resonance data, as well as with electrical measurements. Hence, the original, simple model of a trivalent silicon atom continues to be strongly preferred.

Arthur H. Edwards
Structure and Hyperfine Interaction of Si3≡ Si• Defect Clusters

The Pb center located at the Si(111)/SiO2 interface1,2 and the D-center in a-Si and a-Si:H3–5 each have g-tensors whose isotropic part g ~ 2.0055. A value of g = 2.0055 ± 0.0005 is considered to be diagnostic of radicals with the schematic structure Si3 ≡ Si•, in which the trivalent defect atom is bonded into the bulk material through three Si nearest neighbors. When the nearest neighbors are not all Si atoms (e.g., the E′ center in silica, O3≡ Si•) characteristically different ESR signatures are obtained. The similarity of the Pb and D-center g-factors suggests that the two defects might resemble each other closely not only in their schematic structures, but also in their detailed physical conformation and electronic structure.

Michael Cook, C. T. White
On the Relationship Between Thermal Growth and Thickness Inhomogeneities in Very Thin SiO2 Films

Roughness on the atomic scale at the Si-SiO2 interface caused by thickness inhomogeneities of the oxide film in MOS structures has been found to have strong influence on the electrical characteristics of IC devices when dimensions are scaled down1–4. Thus, there is need for a deeper physical and mathematical understanding of local thickness inhomogeneities in thin oxide layers.

X. Aymerich, J. Suñé, F. Campabadal, Y. Placencia
The Pb Center at the Si-SiO2 Precipitate Interfaces in Buried Oxide Materials: 29Si Hyperfine Interactions and Linewidths

Electron Spin Resonance (ESR) has recently been very successfully applied to the problem of thermal oxide — Si interfaces1–3. That work resulted in the identification of the Pb center as the primary fast interface trap and the determination that its basic structure is a trivalent Si atom at the Si-SiO2 interface. In addition to the technological motivations, there is also fundamental interest in this defect, which is at the interface between a crystalline solid and an amorphous one, and, therefore, might be expected to have features characteristic of defects in both types of materials. The detailed ESR study of the structure of this defect is inhibited by the small fraction of interfacial atoms in a typical Si-SiO2 structure. It has recently been shown that the principal paramagnetic defect observed in silicon on insulator materials formed by oxygen implantation is a Pb center at the interface between Si and SiO2 precipitates in the Si film over the buried oxide layer4–6. The total precipitate surface area can be much greater than the simple surface area of an Si-SiO2 structure. This increased number of “interfacial” atoms affords the opportunity to conduct more detailed ESR studies of the Pb center than readily possible with Si-thermal oxide structures. In addition these interfaces are formed in a significantly different manner than the thermal oxide interfaces and a comparison of the Pb centers formed in the two manners may offer insights into their formation.

W. E. Carlos
Metastabile and Multiply-Charged Individual Defects at the Si:SiO2 Interface

In small-area silicon metal-oxide-semiconductor field-effect transistors (MOSFETs), the fluctuating occupancy of individual Si:SiO2 interface states generates Random Telegraph Signals (RTSs) in the drain current. We have observed a new class of RTS which exhibits anomalous behaviour. We demonstrate that these signals are due to individual interface states which can exist in two or more charge-equivalent metastable states. We present results on a single defect which exhibits two-electron capture, metastability and negative-U-like behaviour.

M. J. Kirton, M. J. Uren, S. Collins
The Influence of Disorder on the Si2p XPS Lineshape at the Si — SiO2 Interface

The origins of X ray photoelectron spectroscopy Si2p core level lineshapes and lineshifts in thermally grown SiO2 on Si are discussed. It is demonstrated that photoelectron lineshapes are related to bridging bond angle distributions through convolutions which result in linewidths being substantially narrower than initially expected. We conclude, by comparison with experiment, that broadening effects are present in SiO2 Si2p experimental spectra which mask the intrinsic linewidth expected from bond angle distribution arguments.

R. A. B. Devine, J. Arndt
Si — SiO2 Interfaces — a Hrtem Study

A High Resolution Transmission Electron Microscopy (HRTEM) study of the Si — SiO2 interfaces is reported here. The study has been carried out on the thermal oxidation of (a). Si and (b). Ge implanted Si. Evolution of the Si-SiO2 interface with oxide thickness and the presence of small amounts of Ge, i.e., one mono-layer at the interface and its influence on the oxidation kinetics is discussed.

N. M. Ravindra, D. Fathy, O. W. Holland, J. Narayan
Electrical and Interface Properties of MOS Structures of Getter Treated Silicon

Electrical and micro-structural properties of Metal-Oxide-Semiconductor (MOS) capacitors fabricated utilizing silicon wafers, treated differently for gettering of impurities, is reported in this study. The treatment of silicon wafers for gettering purposes, considered here, essentially involves (i) back side argon ion implantation at doses of 2.5 × 1015 cm-2 and 5.0 × 1015 cm-2, at energies of 195 and 350 keV respectively, and (ii) back side polysilicon deposition. The results of these measurements have been compared with those of ungettered silicon. Results indicate that some improvement has been attained in minority carrier lifetimes and maximum breakdown voltages in MOS capacitors fabricated particularly using back side argon ion implanted silicon.

N. M. Ravindra, Patrick Smith, J. Narayan
Influence of Different Preparation Methods on Interfacial (SiO2/Si) Parameters of Very Thin SiO2 Layers

Very thin Silicon dioxide layers (thickness less than 100 Ä) have a growing importance for the VLSI integrated circuits. Indeed they are used in EEPROM (memories) and in a variety of bistable devices (as the MISS for example). Besides they could be used as intermediate dielectric tunnel layers serving to enhance injection in Schottky contacts for bipolar circuit applications.

Georges Pananakakis, Panagiota Morfouli, Georges Kamarinos

Oxidation, Oxynitrides and Deposited Films

Thermal Oxidation of Silicon

Thermal oxidation of silicon results in the formation of a non-crystalline (nc) SiO2 film through which the oxidizing species, oxygen or OH, diffuses. A key feature of nc-SiO2 is the wide range of Si-O-Si bond angles (120°-l80°) associated with a very small variation (≈0.1 eV) in the Si-O bond energy. The Si substrate influences the structure of the oxide by affecting the short-range-order (SRO) of the (newly formed) oxide at the interface. Thus the structure of the as-grown oxide resembles that of some high density polymorph of SiO2; this effect is labelled quasi-expitaxy. As further growth occurs at the interface, pushing away the previously grown oxide, the structure then relaxes to more closely resemble that of vitreous SiO2. This relaxation process is similar to that which occurs after pressure compaction of vitreous SiO2, as indicated by measurements of the changes in the index of refraction and density of the oxide. This process is essentially a pseudo-polymorphic transformation of the oxide structure in the course of which the SRO of the oxide mimics that of various crystalline SiO2 polymorphs and results in substantial accomodation of the large volume expansion (≈126 %) associated with the transfer of Si atoms from the substrate to the oxide. This transformation differs from viscous flow, which has often been used to account for the relaxation of stress in the oxide, primarily in that it does not require the breaking of bonds, as does the viscous flow model. We point out several difficulties of the viscous flow model in explaining experimental observations.Because the transformation does not involve breaking bonds, in dry oxides some remnants of the originial quasi-epitaxial layer remain in the oxide in the form of intrinsic structural channels which are oriented preferentially normal to the interface. Because transport of O2 molecules along these channels is easier than through the bulk of the oxide, they affect the oxidation kinetics of the Si. Hence, the oxidation kinetics in dry O2 is described in terms of two transport processes; one which describes the normal random-walk interactive diffusion through the oxide and depends on the oxide thickness, and one which describes a non-interactive oxygen transport through the structural channels and which is relatively independent of the thickness of the oxide. The random-walk diffusion is associated with a limited exchange process between O2 molecules in solubility sites and network O atoms. This interaction has been observed by 18O tracer experiments as affecting mostly the outer surface region of the Sil6O2 films. Such a model for the oxidation kinetics and mechanism produces very good agreement with experimental growth rate data over a wide range of oxide thicknesses without assuming any special mechanism for the initial “fast growth” regime and/or the oxygen exchange process.

A. G. Revesz, B. J. Mrstik, H. L. Hughes
A Framework for Incorporating Memory Effects of Structural Relaxation in Models for Thermal Oxidation of Silicon

Thermal oxidation of silicon occurs as a result of the transport of oxidizing species through the existing oxide to react with silicon at the Si-SiO2 interface and form SiO2. The resulting SiO2 films are similar to silica glass in their index of refraction, density and other properties, although there are subtle but important differences in their structures. In the present work, we summarize and discuss the physical ingredients necessary for a quantitative understanding of time-dependent structural relaxations of the oxide. For glasses formed by quenching from the melt, the time-dependent recovery of a nonequilibrium structure to its equilibrium state has been widely documented by measurement of quantities such as specific volume, index of refraction, enthalpy, and others1,2 These exhibit nonlinearity with respect to the magnitude of departure from equilibrium, asymmetry with respect to the sign of the departure and memory effects which are sensitive to the thermal and annealing history. Such phenomena are also to be expected in thermally grown silicon dioxide layers. Indeed, measurements have indicated that the density of SiO2 can be a time-dependent quantity which eventually relaxes toward a final value3. Such structural changes are expected to modify the oxide growth process. For instance, it has been shown in vitreous silica and other glasses that the diffusion of inert gasses is dependent upon the thermal history of the specimen4.

R. W. Rendell, K. L. Ngai
Analysis of Stress Relaxation and Growth Kinetics for Two-Step Thermal Oxidation of Silicon

Thermal oxidation of silicon has been the subject of much research. The anomalous initial regime of dry oxidation is still a key point for the understanding of the oxidation process. This phenomenon has been studied by many workers1–5 and, in particular, has been attributed to the existence of stress during growth6,7.

Gérard Ghibaudo
Photo-Induced Oxidation Processes in Silicon

We review in this paper the different ways which have been explored to photo-induce oxidation of silicon using CW and pulsed lasers of different wavelengths working both in solid and liquid phase regimes. The specific influence of visible and ultraviolet intense light sources on the oxidation processes will be detailed with special attention to the non thermal effects suggested to be present when using UV photons of high energy (> 3.5 eV).

E. Fogarassy
Growth and Structure of Argon Laser Grown SiO2

The use of intense beams of photons from 193 nm to 10.6 μ to oxidise single crystal silicon (c-Si) in dry oxygen (O2) has been widely studied using lasers and incoherent light sources1. Depending upon the precise wavelength of the radiation used, thermal and/or non-thermal reactions can be initiated. Here we review the results of a recent experiment with visible radiation, which indicates that the induced reaction is thermally dominated, and that there is an additional wavelength dependent component to the overall mechanism2. We also present new results of a study by infrared spectrometry of the bonding nature of the films grown by this method.

Francesca Micheli, Ian W. Boyd
Transport Properties of Plasma Enhanced CVD Silicon Oxynitride Films

Up to now, few transport property measurements have been made on low temperature deposited Silicon Oxide or Silicon Oxynitride Films. In SiO2 prepared by RF sputtering and annealed at 570 K, the current was not measurable at 300 K for low electrical field, but subsequently presented linear Ln J versus E1/2. For electric field E between 6xl05 V cm-1 and 1.2 106 V cm-1 1, 2, ionic Na+ transport with an activation energy of 1.1 eV has been observed above 470 K2. For plasma Enhanced Chemical Vapor Deposited (PECVD) low temperature Silicon Oxide/Oxynitride, in spite of considerable work on composition and mechanical properties3, 4, 5, the electrical properties at low field remain unknown. Silicon rich-Silicon dioxide has been studied with the dynamic ramp I-V technique for fields above 5 106 V cm-1i.e. currents above 10-10 Amp corresponding to Fowler Nordheim characteristics before breakdown occurs6. Recently7,8,9 electrical quality improvement was obtained when a large dilution with of He and low deposition rate were used in the PECVD technique, but transport properties at low and intermediate electric field were not published.

Yves Cros, Jean Christophe Rostaing
Characteristics of SiO2 and SiOXNY, Obtained by Rapid Thermal Processes

Thin gate oxides of 30–150 Å are currently grown in a rapid thermal processing machine. Oxidation kinetics have been studied in the temperature range of 1000°-1250°C for an oxidation time of 5 to 60 s. An activation energy EA of 1.4 eV has been obtained. Rapid thermal nitridation of a 96 Å SiO2 film has been performed at a temperature of 1150°C for a nitridation time up to 150 s. The electrical characteristics of MOS capacitors were compared to those of MIS and an average breakdown field of 14.6 MV/cm has been obtained. The evolution of the stoichiometry of Nitrogen profiles has been studied for various nitridation times and will be discussed.

N. Chan Tung, Y. Cartini, R. Pantel, J. L. Buevoz
Evidence for Oxygen Bubbles in Fluorine Doped Amorphous Silicon Dioxide Thin Films

The superstoichiometry (x from 2.0 to 2.5) observed by R.B.S. in P.E.C.V.D. fluorine doped silicon dioxide thin films deposited at 300°C was correlated with the density of bonded oxygen detected by IR absorption spectroscopy. These results were interpreted in terms of structurally inhomogeneous Si Ox HY Fz films consisting in an a-Si:O:H:F phase and oxygen bubbles accomodated by a SiO2 tissue. This description is further supported by SEM, which shows sample blistering and bubble explosion upon annealing at 800°C.

A. G. Dias, E. Bustarret, R. C. da Silva
Low Temperature P.E.C.V.D. Silicon Rich Silicon Dioxide Films Doped with Fluorine

The production of new silicon rich silicon dioxide films doped with fluorine, deposited by PECVD at low substrate temperatures is reported. Films deposited with substrate temperatures lower than 200°C exhibit a multiphase structure consisting of Si microcrystallites (60 Å-100 Å) embedded in an amorphous insulating tissue, whereas in films produced with substrate temperatures between 200°C and 300°C this microcrystalline phase is replaced by an a~Si:0:H:F zone and oxygen bubbles.

A. G. Dias, L. Guimarães, M. Brunel

Transport, Trapping and Breakdown

High Field Transport in SiO2

For a great many years, the transport of electrons in amorphous silicon dioxide has been of interest to the electronics community. This interest stems from the importance of this material as an insulator for microelectronics. Primarily, silicon dioxide has been studied for its structure and conductivity, as well as breakdown strength, due to the high voltages applied across the thin layers found in gate oxides of MOS devices. For VLSI, and the new ULSI, fields in the insulator are expected to be on the order of a few MV/cm, and thus relatively close to electrical breakdown.

D. K. Ferry
Hot Electrons in SiO2: Ballistic and Steady-State Transport

One of the strongest impacts of the Very-Large-Scale-Integration (VLSI) on fundamental physics we have been witnessing in recent years is the revival of activities aimed to better understand the properties of electron transport in crystals. For many years the basic “semiconductor equations” (that is: the standard “Drift-Diffusion” coupled to the Poisson equation) have helped engineers to design semiconductor devices which have changed our lives in quite a remarkable way. Only in the past decade or so, with the shrinkage of the device dimensions towards a scale approaching the mean-free-path (or even De Broglie wavelength) of electrons in semiconductors, have we begun feeling the need for more realistic solutions of the Boltzmann-transport-equation (BTE). Hence, the present “golden age” of Monte Carlo simulations, of the “hot-electron”, “high-field” problem, of the efforts to reach fully coupled an self-consistent Poisson-Schrödinger-Monte Carlo description of small devices which we see flooding the scientific literature today.

M. V. Fischetti, D. J. DiMaria
Electronic Charge Transport in Thin SiO2 Films

Some observations concerning the Fowler Nordheim conduction of electrons in SiO2 are reviewed. The substrate hole currents accompanying the tunneling currents possibly originate from photon stimulated emission. Coulomb repulsion between adjacent sites inhibits trapping in the dielectric and realistic trapping kinetics have to account for this, as has been illustrated for high field and for avalanche injection.It has been shown that small electron fluences of ≤ 10-6C/cm2 are able to change the effective barrier height of the electrode-dielectric interface. The changes are attributed to the generation of interface traps.The degradation of the dielectric by further injection is described in terms of the generation of low-ohmic paths which can explain a number of phenomena not previously understood.

D. R. Wolters, A. T. A. Zegers-van Duynhoven
The Role of Hole Traps in the Degradation of Thermally Grown SiO2 Layers

Due to the high fields present in small-geometry metal-oxide-semiconductor (MOS) transistors charge injection into the gate oxide can readily occur leading to serious reliability problems related to the degradation of the SiO2 layer and of the Si/SiO2 interface. It is therefore extremely important to have a thorough understanding of the degradation mechanisms occurring upon charge injection.

M. M. Heyns, R. F. De Keersmaecker
The Influence of High Temperature Nitrogen Annealing on the Electrical Properties of Plasma Nitrided Oxides

The effect of nitrogen gas annealing on intrinsic electrical properties of thin plasma nitrided oxide films is studied. It is shown that nitridation related trap densities and other electrical properties have been considerably improved after a high temperature (1 000°C, 1 hour) nitrogen annealing.

J. Camargo da Costa, M. El-Sayed
High-Field Positive-Charge Generation and its Relation to Breakdown in a-SiO2

This paper reviews and discusses the issues of how electrically active defects are created in thermally grown SiO2 during high-field stressing of MOS structures and their relation to dielectric breakdown. Positive charge, appearing in various electrical stress experiments, has been observed in early research. It is now clear that depending on the field strength, its duration, and oxide properties that positive charge, negative charge, fast interface states, slow states, amphoteric states, and creation of electron traps may all occur and furthermore they may be interrelated. The term “positive charge”, therefore, is somewhat misleading as it does not convey the whole meaning of the phenomena expected to occur in the oxide under high-field injection. To avoid more confusion, however, I will use it throughout in the loose sense of lumping all the defects together.

Zeev A. Weinberg
Breakdown Mechanisms of Thermally Grown
Silicon Dioxide at High Electric Fields

Mechanisms of high field electrical breakdown have been widely investigated in recent years in thermally grown silicon dioxide films at fields larger than 7 MV/cm. We find for oxide films thicker than 10 nm that constant voltage and constant current tests produce breakdown by different mechanisms. Specifically, the fast breakdowns of constant voltage tests can be explained by the IIR (Impact ionization-recombination) breakdown model by the growth of positive charge at the cathode at fields larger than a critical field, Fr. The slow breakdowns in constant current tests cannot be explained by the IIR mode, since growth of electron trapping during a test keeps the critical field increasing. It appears that breakdown in constant current tests may be explained as due to the effects of the generation of a very large density of trap states at the injection barrier. The density of trap states generated may grow to 1019/cm3. Such change in the oxide may produce current instability by diverse processes: barrier lowering, resonant tunneling, or transition of the oxide from an insulating to a conducting state. The mechanism of these breakdown processes has not yet been identified. Breakdown by effects of defect generation present novel models of insulator breakdown, and it is of interest to explore their range of validity for SiO2 and also for other insulators.

N. Klein
Field Dependence of Time-To-Breakdown Distribution of Thin Oxides

The accurate prediction of thin insulator reliability is of significant importance to the development of MOS VLSI technologies. In most reliability studies1,5, the time-to-failure tbd and/or the total injected charge prior to breakdown Qbd are measured under high field stresses typically greater than or equal to 8 MV/cm. These data are then extrapolated down to normal operating fields to give a prediction of device wear-out. The important assumptions of this procedure are: a) the phenomena that take place at high fields and eventually lead to oxide failure also occur at the operating field and b) no additional failure mechanisms exist at low fields. These assumptions have been used routinely but never been proven to be valid to our knowledge.

P. Olivo, Thao N. Nguyen, B. Ricco

Radiation Effects

Radiation Effects in MOS VLSI Structures

Ionizing radiation is known to cause changes in the electrical properties of MOS devices1. Radiation effects in various oxide structures such as gate and field oxides have been previously studied2,3. As MOS technology now progresses to smaller feature sizes-one micron and less-new types of oxide regions have been added to VLSI circuits for device isolation and improved reliability. These new VLSI oxide structures, in turn, introduce new radiation-induced failure modes limiting circuit functionality and performance.

H. L. Hughes
Relationship Between Hole Trapping and Interface
State Generation in the Si/SiO2 System

We have discovered a general relationship between the distance from the interface at which holes are trapped, and the subsequent generation of interface states. With photon assisted tunneling it has been previously established that there are two types of trapped holes near the Si/SiO2 interface after high-field stress (Fowler-Nordheim tunneling) and radiation damage. These types are distinguished by their location and behavior upon electron capture. The first type (“near-interfacial trapped holes”) are located between 20 and 70 Å from the interface and completely disappear upon electron capture. The second type (“interfacial trapped holes”) lie within about 15 Å of the interface, and immediately become interface states when they capture an electron. The experiments show that these two types of interface states are not independent, but rather holes are first trapped in the near-interfacial sites, and then are converted to interfacial trapped holes by thermal energy or very high fields.

S. J. Wang, J. M. Sung, S. A. Lyon
Radiation-Induced Conductivity of Thin Silicon Dioxide Films on Silicon

The use of electron and X-ray lithography in the production of semiconductor devices poses some problems related to the study of changes arising in dielectric films on the surface of semiconductors due to their interaction with ionizing radiation1. Of special interest in this respect is silicon dioxide which is most commonly used in microelectronics. Some aspects of radiation induced positive charge formation in silicon dioxide are well understood2–4. However, some aspects of charge transport in silicon dioxide films of MOS structures due to irradiation of the gate are still poorly studied.

V. A. Gurtov, A. I. Nazarov
Interface Degradation in Short-Channel MOSFETs
Comparison Between the Effects of Radiation and Hot Carrier Injection

The degradation in performance of short-channel MOSFETs induced by ionizing radiation is a crucial problem for space applications. According to the radiation type, dose and energy, various defects are formed at the interface, in the oxide and in the substrate. This defect generation is almost homogeneous along the channel and is, therefore, different from the damage induced by hot carrier injection into the gate oxide. Indeed, the aging of short-channel devices after electrical stress consists in the progressive formation of a greatly localized defective region close to the drain.

H. Haddara, S. Cristoloveanu, B. Boukriss, A. Chovet, P. Jarron

Buried Dielectric Layers and Novel Applications

Synthesis of Buried Dielectric Layers in Silicon by Ion Implantation

Some of the ideas presented here are expanded from a review of the synthesis of SiO2 by ion implantation written for the second radiation effects in insulators conference1. Since 1983 there have been many developments confirming (and a few contradicting) the theses and hypotheses contained therein. One major development has been the upsurge in interest in synthesis of buried layers of the nitrides and carbides of silicon and so these have been included here. This paper is an attempt to address the fundamental processes that occur when silicon is implanted with high doses of carbon, nitrogen and oxygen.

Ian H. Wilson
Electrical Properties of Simox Material and Devices

The interest in Silicon On Insulator (SOI) structures as advanced substrates for integrated circuits has been generated by the inability of standard bulk Si processing to overcome some major VLSI limitations (parasitic capacitances affecting speed and power, intolerance to radiation effects, poor lateral isolation, etc.). Several technological approaches are under very active and competitive research: silicon hetero-epitaxy on various insulators (sapphire, zirconia), silicon deposition and subsequent recrystallization (laser, lamp, electron beam, etc.), oxidation of porous silicon, wafer bonding and, finally, deep implantation of insulator-forming ions into silicon (SIMOX). In spite of its relatively recent development SIMOX is now in a privileged position. The silicon overlayer is indeed a wafer scale monocrystal of high quality and offers the best perspective for microelectronics.

Sorin Cristoloveanu
Formation Mechanisms and Structures of Thin Buried Layers of SiO2 Fabricated Using Ion Beam Synthesis

The effects of variations in the implanted dose Φ1 and the annealing temperature TA during the formation of buried layers of SiO2 produced by ion beam synthesis (IBS) are discussed. It is found that when specimens implanted with oxygen doses below 0,3 x 10l80+cm-2 are annealed at 1405°C for 30 minutes a buried layer consisting of two discontinuous rows of SiO2 precipitates is produced. For higher doses these two layers coalesce to give a single continuous layer of SiO2. The interfacial irregularity of this layer is found to decrease with increasing dose such that for doses of ≧ 1.8 x 10l80+cm-2 the interfaces are almost planar. Studies of these higher dose specimens annealed in the temperature range 1280–1300°C for times of 2–20 hours show that the crystal quality of the silicon overlay improves with increasing temperature and time. The oxygen concentration in the silicon overlayer also appears to increase with annealing time and mechanisms are proposed to explain the observed phenomena.

R. J. Chater, J. A. Kilner, C. D. Marsh, G. R. Booker, J. R. Davis, G. K. Celler, K. J. Reeson, P. L. F. Hemment
Low-Temperature ESR Study of SIMOX Structures

X- and K-band ESR data are presented of a SIMOX structure fabricated by implanting [001] n-type c-Si with 1.7 x10180+cm-2 at an energy of 170 keV. The report focusses on three signals. A first one, with g ≃ 2.070 is due to interstitial Fe impurities probably introduced as a result of 0+ implantation. A second anisotropic signal of $$\textup{g}(\overline{B}||\;\;[001]\;;\;4.3\;\;\textup{K}) = 1.99963$$ reveals the presence of P piling up; c-Si regions of effective P concentration ∼ 1.2 xl019cm-3 are present in the bulk of the SIMOX sample. A third isotropic signal of g = 1.9983 is tentatively identified as a thermal donor. The observations are discussed in the light of the formation of internal Si/SiO2 structures.

A. Stesmans, G. Van Gorp
Defects in Silicon-on-Insulator Structures Formed by O+ Implantation: Their Dependence on Implantation Temperature

EPR measurements have been made on silicon-on-silicon dioxide samples produced by implanting n type (100) silicon wafers with a dose of 1.4 × 1018 0+cm-2 using 200 keV l60+ ions and an implantation temperature of 250, 350, 450 and 600°C The EPR spectra reveal the presence of E1′, Pbo and amorphous silicon centres. The dependence of the concentrations of these defects on implantation and annealing temperatures is reported.

T. J. Ennis, R. C. Barklie, K. Reeson, P. L. F. Hemment
Interface Properties and Recombination Mechanisms in Simox Structures

In this paper, we present new methods and results related to the characterization of silicon on insulator material fabricated by deep oxygen implantation (SIMOX). The minority carrier lifetime as well as the surface recombination velocity are obtained using depletion-mode MOSFETs. This is done by monitoring the drain current while the gate is being pulsed into deep depletion.

T. Elewa, H. Haddara, S. Cristoloveanu
Porous Silica Sol-Gel Coatings for Nd: Glass High-Power Pulsed Laser Uses

A method of forming a laser damage resistant antireflective (AR) coating on fused silica, borosilicate and phosphate glasses, and even onto KDP crystals has been used. The single-layer porous coating is applied by dip or spin from a specific silica colloidal suspension in ethanol. This sol-gel coating deposit is processed at room temperature and requires no subsequent treatment. The coated surfaces work near 100 % transmittance and exhibit laser-induced damage thresholds, measured with 1.06 μm, 1-ns pulses, two to three times greater than levels of widely used PVD (Physical Vapor Deposition) silica-titania multilayer1, anti-reflection films.

Hervé Floch, Jean-Jacques Priotton, Ian Malvil Thomas
Vacuum Re-Emission of Positrons from a-SiO2 Layers

A study of vacuum re-emission of positrons from high electric field stressed a-SiO2 layers is proposed. Measurements of positron re-emission energies and efficiencies would be of interest in understanding positron transport at high electric fields as well as offering the possibility of producing intense (up to 109e+/sec) positron beams in the laboratory.

R. I. Simpson, C. D. Beling, M. Charlton
Backmatter
Metadaten
Titel
The Physics and Technology of Amorphous SiO2
herausgegeben von
Roderick A. B. Devine
Copyright-Jahr
1988
Verlag
Springer US
Electronic ISBN
978-1-4613-1031-0
Print ISBN
978-1-4612-8301-0
DOI
https://doi.org/10.1007/978-1-4613-1031-0