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This book provides readers with an overview of the design, fabrication, simulation, and reliability of nanoscale semiconductor devices, MEMS, and sensors, as they serve for realizing the next-generation internet of things. The authors focus on how the nanoscale structures interact with the electrical and/or optical performance, how to find optimal solutions to achieve the best outcome, how these apparatus can be designed via models and simulations, how to improve reliability, and what are the possible challenges and roadblocks moving forward.





Chapter 1. High-k Dielectric for Nanoscale MOS Devices

The continuous shrinking of device dimensions in order to follow Moore’s Law makes SiO2 almost meets its physical limit in thickness, hence gate insulators with higher dielectric constant (high-k) to maintain sufficient capacitance are necessary for MOS devices. Promising candidates such as Hf-based high-k material have already been applied commercially, and La2O3, Ta2O5, ZrO2, etc. have been paid much attention in recent years. On the other hand, replacing Si with Ge or III-V compound semiconductors including GaAs, InGaAs, GaN, etc. to further increase carrier mobility is another trend to meet the requirements of future CMOS technology. However, unlike the stable SiO2 and the excellent SiO2/Si interface, challenges including (1) thermodynamic and kinetic stability, (2) high-k/substrate and high-k/metal gate interface engineering, (3) mobility degradation and threshold voltage shift in high-k dielectrics on Si, Ge or III-V compounds still remain. Therefore, based on the mechanism and current progress of high-k materials, a review of the current status and challenges in high-k dielectrics applied in MOS devices is made in this chapter. Section 1.1 gives a brief introduction of the background of this area. Section 1.2 introduces the basic mechanism and properties of high-k materials. Section 1.3 compares different high-k dielectric deposition methods. While Sects. 1.4 and 1.5 focus on the applications of promising candidates of high-k dielectrics (Hf-, rare earth-, and perovskite-based) in varieties of MOS devices.
Ling-Xuan Qian

Chapter 2. Challenge of High Performance Bandgap Reference Design in Nanoscale CMOS Technology

To design a high performance bandgap reference circuit in nanoscale CMOS technology becomes a great challenge. Many negative effects of nanoscale CMOS technology in high performance bandgap reference design are discussed in this chapter. A bandgap reference circuit design with both voltage output and current output is presented also. In this design, low threshold voltage MOSfet have been utilized in this design to ensure the circuit at suitable DC operation points under extreme low temperature. Operational transconductance amplifier (OTA) has been used to achieve high DC power supply rejection rate (PSRR). Two opposite temperature coefficient resistors have been connected in series to obtain a one-order temperature independent resistor which also achieves a weak curvature compensation effect for reference voltage’s generation. This bandgap reference is implemented in a 65 nm CMOS technology, occupies 0.75 × 0. 67 mm including bond pads, Measured results show that this circuit can operate at supply voltage from 1.1 to 1.3 V, and the temperature coefficient of voltage output is 30 ppm/°C with 60 dB PSRR (DC, 30°C), and the temperature coefficient of current output is 52 ppm/°C with 70 dB PSRR (DC, 30°C), among −55°C to 125°C without any trimming or calibration.
Zhang Jun-an, Li Guangjun, Zhang Rui-tao, Yang Yu-jun, Li Xi, Yan Bo, Fu Dong-bing, Luo Pu

Chapter 3. Metal Oxide Semiconductor Thin-Film Transistors: Device Physics and Compact Modeling

Metal oxide semiconductor thin-film transistors (TFTs) have been recognized as the most promising technology in the field of flexible electronics and flat-panel displays because of their high mobility, low-temperature fabrication process, and spatial uniformity of device characteristics. In this chapter, we review the development and operating principles of the metal oxide semiconductor TFTs, as well as the compact-modeling framework. For both the non-degenerate and degenerate conductions, the core compact models, including the analysis of surface potential and drain current, are discussed and compared. To enhance the computational efficiency of the calculations, an explicit and closed-form scheme for the surface potential solution is developed by including both exponential deep and tail states. The resulting DC and surface potential models give accurate descriptions with single-piece formulas, which are suitable for CAD applications. The numerical simulation and experimental results are also included in order to assess the validity of the models introduced.
Wanling Deng, Jielin Fang, Xixiong Wei, Fei Yu

Chapter 4. AC Random Telegraph Noise (AC RTN) in Nanoscale MOS Devices

Metal oxide semiconductor thin-film transistors (TFTs) have been recognized as the most promising technology in the field of flexible electronics and flat-panel displays because of their high mobility, low-temperature fabrication process, and spatial uniformity of device characteristics. In this chapter, we review the development and operating principles of the metal oxide semiconductor TFTs, as well as the compact-modeling framework. For both the non-degenerate and degenerate conductions, the core compact models, including the analysis of surface potential and drain current, are discussed and compared. To enhance the computational efficiency of the calculations, an explicit and closed-form scheme for the surface potential solution is developed by including both exponential deep and tail states. The resulting DC and surface potential models give accurate descriptions with single-piece formulas, which are suitable for CAD applications. The numerical simulation and experimental results are also included in order to assess the validity of the models introduced.
Jibin Zou, Shaofeng Guo, Ru Huang, Runsheng Wang

Chapter 5. Passivation and Characterization in High-k/III–V Interfaces

III–V compound semiconductors are regarded as promising candidates to replace silicon channel for future metal-oxide-semiconductor field effect transistors (MOSFETs) because of their high mobility. However, compared with Si-MOSFETs, lack of high quality high-k gate stack hampers the development of III–Vs MOSFETs. Therefore, for high-k/III–Vs, interface passivation and characterization become very important to realize high-performance devices.
In this chapter, after a brief review about the background and the history of III–V MOSFETs, we select several typical high-k/III–V stacks, such as high-k/InP, high-k/GaSb, high-k/GaAs, to illustrate the impacts and mechanism of various passivation methods on them. Moreover, some effective electrical and optical characterization methods for high-k/III–V system are also introduced and discussed.
Shengkai Wang, Honggang Liu

Chapter 6. Low Trigger Voltage and High Turn-On Speed SCR for ESD Protection in Nanometer Technology

As CMOS technology scales down to the nanometer technology, the thickness of the gate oxide becomes thinner and thinner, the breakdown voltage of the gate oxide reduces largely. It is imperative to reduce the trigger voltage and improve the turn-on speed of the SCR for ESD protection. In order to reduce the trigger voltage, a novel gate-coupled silicon-controlled rectifier (GCSCR) device is proposed without using an external trigger circuit. In the GCSCR structure, there is a parasitic RC sub-network which can provide a potential to make the SCR turn on. The trigger voltage of the GCSCR is lower than that of the conventional SCR device to effectively protect the interior CMOS circuits. The simulation and experimental results show that the trigger voltage of the GCSCR can be adjusted by changing the sizes of the device layout parameters and the ESD robustness of the GCSCR is same as the conventional LVTSCR. For improving the turn-on speed of the SCR, a new SCR with the variation lateral base doping (VLBD) structure (VSCR) is proposed for electrostatic discharge (ESD) protection. Through theoretical analysis, the turn-on speed of the SCR was determined mainly by the base transit time of the parasitic p-n-p and n-p-n transistors of the SCR. The VLBD structure can reduce the base transit time of the bipolar transistors to improve the turn-on speed of the SCR. The experimental and simulation results show that the turn-on time of the SCR with the VLBD structure (VSCR) is 12% less than that of the MLSCR with the traditional uniform base doping without adding extra process masks and increasing the chip area.
Jizhi Liu, Zhiwei Liu, Fei Hou, Hui Cheng, Liu Zhao, Rui Tian

Chapter 7. Silicon-Based Junctionless MOSFETs: Device Physics, Performance Boosters and Variations

In this chapter, we provide a review on the junctionless transistors which are promising nanoscale devices in terms of controlled doping fluctuations. We introduce a physics-based analytical model to describe the transistors’ characteristics in all the operation regions through which their device physics are clearly illustrated. Based on that, several performance boosters with geometry engineering are described to enhance the performance of junctionless transistors. Nonetheless, junctionless transistors are still subject to certain variations even with limited doping fluctuations. We discuss about the cross section and line edge roughness as two main variation sources and also explain one possible solution using the charge plasma concept to further suppress the variations.
Xinnan Lin, Haijun Lou, Ying Xiao, Wenbo Wan, Lining Zhang, Mansun Chan



Chapter 8. Effect of Nanoscale Structure on Reliability of Nano Devices and Sensors

Steeper subthreshold slope and lower off-state current accessible by Tunnel FET offers great potentials in low power electronics applications. In this chapter, to enhance to a major roadblock of TFET i.e. the lower on-state current, hetero gate dielectric (HD) engineering has been amalgamated onto cylindrical gate all around GAA TFET. The reliability issues of both the devices i.e. GAA TFET and HD GAA TFET have been discussed. To study the reliability issues, at first, the effect of interface traps charge density, which are common during the pre and post-fabrication process, has been studied followed by the effect of temperature on the performance of Tunnel FET has been examined. The impact of trap density and the temperature affectability has been examined on the electrical, analog and high-frequency parameters of tunnel FET such as transfer characteristics, nonlocal Band to band tunneling rate of electrons, electric field, ambipolar current, parasitic capacitances, cut off frequency and maximum oscillation frequency. Results show that TFET exhibits weak temperature dependence for high gate bias owing to the weak dependence of band to band tunneling mechanism on temperature and for lower gate bias, the temperature dependence is large. Moreover it was analyzed that, amalgamating HD engineering scheme onto GAA TFET, along with higher ION also provides better immunity against interface trap charges in comparison with GAA TFET.
Jaya Madan, Rishu Chaujar

Chapter 9. MEMS/NEMS-Enabled Vibrational Energy Harvesting for Self-Powered and Wearable Electronics

Recent advance in internet of things (IoT) and low-power electronic devices has accelerated the implementation of smart materials and technologies for cheap, portable and sustainable energy sources. Energy harvesting systems as self-sustained power sources are capable of capturing and transforming unused ambient energy into the electrical energy. Such energy harvesters provide an alternative to conventional electrochemical battery and could pave the way for actualizing of self-autonomous devices and intelligent monitoring activities. Micro/Nano power generators capable of converting biomechanical energy to electricity with highly efficient energy conversion materials and smart structures could yield breakthrough in self-powered and wearable electronic device evolutions. This chapter looks into MEMS/NEMS-enabled vibrational energy harvesters that are able to convert kinetic energy to electricity for self-power and wearable applications. Recent advances and challenges in MEMS/NEMS-enabled vibration-to-electricity conversion mechanisms including electromagnetic, piezoelectric, electrostatic, triboelectric and magnetostrictive are reviewed and discussed.
Kai Tao, Jin Wu, Ajay Giri Prakash Kottapalli, Sun Woh Lye, Jianmin Miao

Chapter 10. The Application of Graphene in Biosensors

Graphene sparks great interest to develop and extend its applications with its excellent mechanical, electrical, chemical, physical properties. Especially, its higher sensitivity and stronger selectivity presents exciting and bright prospects for biomedical detection applications. From 2008, piles of teams set foot to study graphene applications in biosensors and significant progress has been made. Here we will introduce the applications of graphene in the measurements of biological molecules and microorganism, which facilitates the diagnosis of related diseases, such as diabetes, coronary heart disease, arteriosclerosis and especially cancer.
This chapter is composed of five sections. In the first section, we introduce the synthesis properties of graphene, which enables readers to gain a better understanding of the synthesis and properties of graphene and the advantages of graphene for biosensing. The second section mainly depicts photoluminescence and Raman imaging, electrochemical sensors for enzymatic bio-sensing, DNA sensing, and immune-sensing, which can be applied in optical imaging methods. In the third section, the biological quantification of cancer biomarkers and cells will be discussed. Particularly electrochemical methods like voltammetry and amperometry will be the focus in the content. Due to the properties, for example, simplicity, high sensitivity and low-cost, they are generally adopted transducing techniques for the development of graphene, which based sensors for bio-sensing. The fourth section will describe the Luminescence Sensors in cancer detection applications. The detection method of other biomarkers will be presented in the fifth section, including glucose, hydrogen peroxide, L-Cysteine, dopamine, lysozyme etc. In the final section, in order to reach the necessary standards for the early detection of biomarkers by providing reliable information concerning the patient disease stage, the graphene based biosensors must be established and used, which is the major challenge.
Ting Li, Zebin Li, Jinhao Zhou, Boan Pan, Xiao Xiao, Zhaojia Guo, Lanhui Wu, Yuanfu Chen

Chapter 11. Modelling and Optimization of Inertial Sensor-Accelerometer

This book chapter presents the modelling and optimization details of a Micromachined (MEMS) dual-axis accelerometer. After providing detailed review of existing and proposed applications of these inertial sensors, the chapter introduces various present-day accelerometers available in the literature. The major challenges faced by the accelerometer sensors designs are minimization of the device foot print, noise floor, and cross-axis sensitivity. As dual axis accelerometers are designed to work in both x- and y- (in-plane) directions, they became prone to cross-coupling between the in-plane and the out of the plane (Z-axis) direction. This is due to the structural design that makes them sensitive to other cross-axis acceleration. In most of the design mode-cross-coupling occurs with Z-direction. Moreover, low stiffness in Z-axis causes the proof-mass to sag due to gravity. The present design is modelled according to the Inertial Measurement Unit (IMU) platform of GlobalFoundries. The designed accelerometer consist of a square proof mass suspended using crab leg springs. Primary focus is given to have high differential capacitance sensitivity in small foot print of 1.5 × 1.5 mm. Also, to reduce cross-axis sensitivity and to reduce mode coupling between in-plane modes and Z-axis mode. Simulation results show that the differential capacitive sensitivity of 59 fF/g. The device achieves a mode separation of 10 kHz between the in-plane and out-of-the plane modes. The average cross-axis sensitivity in XY is 1.33% and cross-axis sensitivity due to Z-axis acceleration is zero.
Zakriya Mohammed, Waqas Amin Gill, Mahmoud Rasras

Chapter 12. Graphene for Future High-Performance Gas Sensing

The emerging 2D materials such as graphene (Gr) has attracted widespread attention in chemical sensing due to its unique structural and electronic properties such as high conductivity, large surface areas and high sensitivity to electrical perturbations from gas molecules. This book chapter discusses and summarizes recent advancement of Gr-based gas sensors from basic principles to applications. The performance of Gr-based gas sensors can be optimized from several aspects, such as chemical composition, structures and defects, which are discussed systematically in this chapter. The technical barriers that limit their practical application and an outlook of Gr in next-generation gas sensors is presented.
Jin Wu, Kai Tao, Jianmin Miao, Leslie K. Norford

Chapter 13. Nanoporous Palladium Films Based Resistive Hydrogen Sensors

Hydrogen sensing technology is significant in many circumstances, such as in the synthesis process of ammonia and methanol, leak detection during shuttle launches and fuel cells. Palladium (Pd) has been widely used in hydrogen sensors for its noteworthy ability to absorb a large quantity of H2 and its high selective response to H2. Pd based resistive H2 sensors have attracted much attention due to their simple device structure and fabrication process. In this chapter, nanoporous Pd films have been demonstrated for hydrogen sensors using anodic aluminum oxide (AAO) template as substrate. Nanoporous Pd films based on AAOs were found to have a quick and reversible response due to their enhanced absorption and desorption of hydrogen compared with dense Pd films that usually have very slow response. The performance of hydrogen sensors depending on different post-deposition annealing temperatures of Pd films has been investigated. A response time as short as 30 s at 1% hydrogen concentration with an anneal temperature of 200°C has been obtained. Then, the sensing performance of hydrogen sensors based on nanoporous Pd supported by AAOs was enhanced by pore-widening treatment of AAO using phosphoric acid (H3PO4) as etching solution. It is demonstrated that different concentrations of H3PO4 and different pore-widening time lead to different pore-diameters of AAO, resulting in different performance of hydrogen sensors. The optimized hydrogen sensor shows a fast response time of 19 s at hydrogen concentration of 1% and a detection range of H2 concentration from 0.1% to 2% by pore-widening treatment with a time of 30 min and 5% H3PO4 concentration. A novel carbon nanotubes and Pd nanocomposite thin films was introduced for hydrogen sensors, which exhibits very fast response speed with a response time of 8 s at 2% hydrogen gas.
Shuanghong Wu, Han Zhou, Mengmeng Hao, Zhi Chen

Nanostructured Oxide


Chapter 14. Microstructure of the Nanostructured Oxide Composite Thin Films and Its Functional Properties

In this manuscript, the nanocomposite oxide film and its functional properties are discussed. The microstructure and the interfacial coupling effect play key roles in determining the functional properties. Thus, recent experimental research progresses in the growth mechanism and the microstructure of the nanocomposite oxide film are presented, with a focus on ferromagnetic (FM), ferroelectric (FE), supperconductor, dielectric and conductor (CD) nanocomposite oxide thin films. In this part, the growth mechanism has been the major part of this chapter, and is devoted to the relationship between the microstructure and the physical properties.
Xingkun Ning

Chapter 15. Fabrication and Characterizations of Bi2Te3 Based Topological Insulator Nanomaterials

In this manuscript, recent experimental research progresses in topological insulators Bi2Se3 and Bi2Te3 based nanostructures are presented, with a focus on nanoflakes, nanoplates, nanosheets, nanowires, and thin films of Bi2Te3 based topological insulator materials. Among the various synthesis methods, the chemical vapor deposition (CVD) method is described here as an example for the synthesis of topological insulator nanomaterials. The Raman spectroscopy and electrical transport characterizations are discussed on a few different types of topological insulators, such as binary/ternary/quaternary compound and elementally-doped nanostructures and films.
Z. H. Wang, Xuan P. A. Gao, Z. D. Zhang

Other Nanoscale Devices


Chapter 16. Micro/Nanoscale Optical Devices for Hyperspectral Imaging System

Hyperspectral imaging (HSI) technique has successfully combined 2D images and spectral analysis for sensing and inspection functions and thus has a wide range of perspective applications. However, traditional HSI system using stand-alone dispersive optics or filters features with complex system structure, large devices and high cost. With development of microfabrication technology and materials, currently, compact microspectrometer integrated with spectral modulating optics and photodetectors have shown great potential in providing fast, reliable, robust and high performance hyperspectral imaging and spectroscopy system, which has drawn great attention in both academic researches and industry. Therefore, current research status of such devices are reviewed in this chapter in terms of novel structure design, fabrication techniques applied.
Li Li, Chengjun Huang, Haiying Zhang

Chapter 17. Fabrication and Physical Properties of Nanoscale Spin Devices Based on Organic Semiconductors

Fabrication and physical properties of organic spin devices were introduced. The shadow masks were generally used to form a cross junction in stacking structure devices because the chemical solvent for cleaning would pollute organic semiconductor layers if an etching technique was used. Interface coupling between molecular layer and ferromagnetic metal plays important roles in determining spin injection/detection efficiency of traditionally organic spin devices and constructing molecular spin memory devices. Both giant magnetoresistance and tunneling magnetoresistance effects were discussed to understand spin conserved electron transport behaviors in organic semiconductors. The configuration and composition of molecules contributes greatly to improve the performance in spin based devices.
Xianmin Zhang
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