Physical techniques for silicon layer analysis

This paper reviews the application of physical techniques (SIMS, RBS, XPS, AES, XRD, Raman and FTIR spectroscopies and AFM) for the characterisation of layers, structures and processes in Si technology. The principles of the techniques are given, and their use for the analysis of Si related structures and processes is discussed. Structural features related to the device and system performances are considered. These include features related to amorphous, polycrystalline and single crystal layers, as grain size and crystal orientation, disorder, defects, strain, composition,…, as well as the quality and nature of surfaces and interfaces in Si related layers (Si, SiGe and ternary related alloys, SiC, dielectric layers, silicides…). Examples taken from the current research in these areas are presented.     

Double-crystal X-ray diffraction analysis of low-temperature ion implanted silicon

Silicon wafers implanted at room temperature and liquid nitrogen temperatures and annealed at 750°C are analyzed by transmission electron microscopy (TEM) and double-crystal X-ray diffractometry (DCD). TEM evidences a buried layer of perfect dislocation loops in the room-temperature—implanted sample and a perfect crystal for the case of liquid-nitrogen—temperature implant. DCD reveals a buried strained layer and a thin deformed surface region for both cases. The deep strain distributions are related to residual damage beneath the original amorphous layer, whereas the surface defects are due to an impurity coming from outside.     

Levitation of a micromachined rotor for application in a rotatinggyroscope

The design of a micromachined rotating gyroscope is described, incorporating an electromagnetically levitated aluminium rotor. The coil design for levitation produces good lateral stability. A 400 μm diameter, 12 μm thick rotor is levitated to a height of 30 μm     

Visitor-based application analysis methodology for early design space exploration

Applications and architectures for embedded systems are becoming more and more complex. It is difficult to analyze complex embedded applications at early stages of the design flow without generic automated tools and methodologies. Consequently, application analysis under the real input conditions is becoming more and more important. Existing application analysis methodologies mainly focus on a single design objective. A general purpose application analysis methodology is required to satisfy multiple objectives of early design space exploration. This article proposes a general purpose application analysis methodology based on a visitor design pattern. High level source specifications are transformed into a trace tree representation by dynamic analysis. Trace tree representation is analyzed by using a visitor design pattern to get run-time characteristics of the application. Among other outcomes, application characterization and average inherited parallelism are key concerns in this article. Experimental results with MPEG-2 video decoder shows viability of the proposed methodology.     

工业级FPGA空间应用器件封装可靠性分析

分析了工业级和宇航级FPGA(Field Programmable Gate Array)在封装结构上的差别。用Ansysworkbench有限元软件对热循环、随机振动和外力载荷下封装的变形和应力以及焊点的塑性应变进行了仿真。依据剪切塑性应变变化范围预测了焊点热疲劳寿命。结果表明,FCBGA(Flip-Chip Ball Grid Array)封装内部倒装芯片焊点可靠性低于CCGA(Ceramic Column Grid Array)封装,其外部焊点的热疲劳寿命、随机振动等效应力均优于CCGA封装;在外力载荷下,其热疲劳寿命下降速率也明显小于CCGA封装。     

Compensating commutation-angle domain disturbances with application to waveform optimization for piezo stepper actuators

Piezo stepper actuators are very promising for nanopositioning systems due to their high resolution, high stiffness, fast response, and the ability to position a mover over an infinite stroke by means of motion reminiscent of walking. The aim of this paper is to enhance the waveforms for actuating piezo steppers, by actively compensating for repetitive disturbances that are introduced by the walking behavior. A compensation method is developed to compensate for disturbances in the stepping domain, since disturbances may vary in the time domain if the velocity changes. The results from this procedure are exploited to determine an optimal waveform for the working range of the actuator. A significant improvement in performance is achieved after applying this waveform to a piezo stepper actuator.     

Performance analysis of space time block coding techniques for indoor optical wireless systems

Indoor optical wireless systems provide an attractive alternative for realizing next generation Wireless Local Area Networks (WLANs). In this paper, the performance of diffuse optical wireless systems, employing Space Time Block Coding (STBC) techniques, is numerically investigated, accurately taking into account, the indoor channel impulse response and the characteristics of ambient light and thermal noises at the receiver. Discrete Multitone modulation (DMT) is used to mitigate the effect of intersymbol interference due to the channel?s impulse response. The performance of STBC systems, employing two transmit elements, is compared against Single Input/ Single Output (SISO) and Maximum Ratio Combining (MRC) systems operating with the same total optical transmitter power. It is shown that STBC techniques can be used to increase the capacity of diffuse optical wireless systems, improve their coverage and decrease the required optical power at the transmitter. These results demonstrate the usefulness of Multiple Input Multiple Output (MIMO) techniques in the realization of optical WLANs.     

An application of sparse matrix techniques to frequency analysis of linear circuits

An implementation of Gaussian reduction of complex matrices by sparse matrix techniques is presented. The computer program described has been specifically tailored to perform frequency analysis of linear circuits within an on-line circuit-design programming system.     

Comparative analysis of parameter extraction techniques for AlGaN/GaN HEMT on silicon/sapphire substrate

We report a comparative study of artificial neural network (ANN) model and small signal model (SSM) based on extracted parameters. ANN model training is done using Levenberg-Marquardt back propagation algorithm, whereas SSM is formed by extracting circuit parameters from measured S-parameters of GaN HEMT on Silicon and Sapphire. It has been found that, for the GaN HEMT parameter extraction, it takes 85 hidden layer neurons to produce the output with higher accuracy. The optimized test and training error/performance are found to be 1.12 × 10^− 8/0.97 and 1 × 10^− 8/0.99, respectively.     

Characterization of TiAl alloy films for potential application in MEMS bimorph actuators

In this letter, we demonstrate the feasibility of applying TiAl alloy film for the fabrication of bimorph actuators. The TiAl alloy films were prepared by thermal annealing at 400°C of Ti/Al multilayers, which were deposited by DC magnetron sputtering from Ti and Al targets. The microstructure and surface morphology of TiAl alloy films were analyzed by X-ray diffraction and scanning electron microscopy, which showed that TiAl alloy film is formed in the mixed phases of TiAl₃ and Ti₃₆Al₆₄, depending on the deposition conditions. The resistivity of TiAl film is about 9 μΩ cm, and the stress is about 200 MPa. Our nano-indentation measurements showed that the Young's modulus and hardness of TiAl alloy films are 175 and 6.5 GPa, respectively, which are larger than that of Al and comparable to Si. We have successfully fabricated the bimorph actuators based on the TiAl alloy films and our test cantilevers up to 500 μm long showed very straight with tip bending as small as ±5 μm, indicating negligible stress gradient in TiAl film. Our preliminary testing results indicated that TiAl alloy film has potential application for bimorph actuators.     

用代码分析技术对ATE应用程序的自动分析

在不少过程化的IC ATE测试应用程序中,测试的数据条件往往与测试算法紧密耦合,使得程序平台转换的工作严重依赖人工的阅读理解.文中提出了一种新途径,将软件反向工程领域中基于概念的源代码分析技术引入到测试程序的转换工作中,对于某种过程化C语言测试程序,在一定程度上实现测试条件等信息的自动提取.     

Quantitative analysis and evaluation of bilateral control schemes applied to electro-hydrostatic actuators

A bilateral teleoperator allows operators to use a master manipulator to interact with the environment via a slave manipulator. It can be used in remote, hazardous or inaccessible situations. Although numerous bilateral teleoperation studies have been conducted on electrical actuators, research on hydraulic actuators, especially research on electro-hydrostatic actuators (EHAs), a class of pump-controlled systems, is currently limited. In bilateral teleoperation, one issue concerns how to tune the controller parameters with regard to stability and transparency in the presence of uncertainty. In this paper, an approach based on quantitative feedback theory (QFT) that provides guidance on controller parameter selection during the bilateral teleoperation of EHAs is introduced. Parametric uncertainties in dynamics of human operators, master manipulators and environments are described in templates to compute bounds quantitatively, and trade-offs between stability and transparency are visualized. Four commonly used bilateral control schemes are exemplified using this method: force reflection (FR), position error (PE), shared compliant control (SCC) and force reflection with passivity (FRP). The bilateral controllers are tuned through simulations and are validated through contact experiments involving both soft and hard environments. Given its simple structure and excellent level of transparency, FR is found to be the most suitable scheme of the four for teleoperations of EHAs.     

Solution growth of silicon from liquid tin for application to photovoltaic solar cells

Thick epitaxial front junctions offer some interesting potential advantages for photovoltaic solar cell fabrication. An optimization model was developed which predicts open circuit voltages of 0.75 V and AM1 efficiency of 25% (before correction for reflection and grid losses and substrate recombination). For concentrator cell application, sheet resistances of 10 Ω² with open circuit voltages near 0.7 V are predicted. Experimental realization of these predictions requires an epitaxial deposition technology capable of producing layers 10–50 μm thick with minority carrier lifetimes ～ 10 μs. Solution growth of silicon from liquid tin at 900°C was evaluated because lifetimes greater than 1 μ s have been reported using this method, and because it is a low-temperature technology which should not degrade the high substrate lifetimes also required for high-efficiency cells. Lifetimes were measured using Quantitative Electron Beam Induced Conductivity (QEBIC). The best lifetimes obtained were 1 μ s, which would produce a photovoltaic cell comparable to, but not significantly better than, that obtained with present shallow-junction technology.     

Design of M-G modal space sliding mode control for lower limb exoskeleton robot driven by electrical actuators

Lower limb exoskeleton robot (LLER) can help patients with lower limb paralysis to carry out effective rehabilitation training. However, LLER is a kind of nonlinear system with the strong dynamic coupling between joints and the parameter perturbation following different poses of the robot. They will damage the control performance in the process of trajectory tracking. To solve these problems, a novel control strategy, Mass-Gravity modal space sliding mode control (M-GMSSMC), is proposed. The objective for this paper is to develop a novel decoupling control framework for an electrical actuators driven LLER to track a predefined gait trajectory. The controller design aims to improve trajectory tracking accuracy, reduce dynamic coupling between hip joint and knee joint and weaken the chattering phenomenon of the sliding mode controller. The decoupling condition and the robust stability condition are analyzed in this work. Experimental results validate the correctness of the presented conclusions and show the effectiveness of the proposed M-GMSSMC.     

A compact model for NBTI degradation and recovery under use-profile variations and its application to aging analysis of digital integrated circuits

We present an aging analysis which considers variations in chip environment and workload as they are caused by dynamic voltage or frequency scaling, power-down modes, etc. Therefore, we developed a model for NBTI degradation and recovery based on trapping/detrapping. Our model accurately describes the relaxation during detrapping, the quasi-permanent degradation and shows good agreement with measurements from a 65 nm technology. The aging analysis utilizes this model to consider variations in environment and workload. Results show that our analysis can be used for system-level design decisions and reduces substantially estimated degradation.     

A comparison of measurement techniques for determining phosphorus densities in semiconductor silicon

Phosphorus densities in semiconductor silicon slices cut from 14 single crystal ingots have been determined by two electrical and two analytical techniques. Hall effect measurements were made on specimens from all ingots, and junction capacitance-voltage measurements were made on specimens with densities up to about 5 × 10¹⁷ cm⁻³. Neutron activation analysis was used to measure phosphorus densities from 5 × 10¹⁵} to 5 x 10¹⁹} cm⁻³, and a photometric technique was used for densities greater than 10¹⁷ cm⁻³. A systematic discrepancy of about 15% between the photometric and neutron activation data is indicative of the interlaboratory agreement that might be realized in practice with these techniques. This work was conducted as part of the Semiconductor Technology Program at NBS and was supported by the Defense Advanced Research Projects Agency (Order 2397). Not subject to copyright.     

The application of coherent optical techniques to wide-band networks

The successful demonstration of optical heterodyne and homodyne techniques for point to point transmission links has led to an examination of their use in the context of wide-band systems. The high receiver sensitivity and frequency tuning ability potentially provide a means for accessing a significant part of the 50 000-GHz bandwidth provided by single-mode fiber. The possibilities for new network structures based on combinations of space, wavelength, and time switching are presented here, together with the concept of transparent networks which are not dependent on a particular modulation format or information rate.     

A new formulation of fringing capacitance and its application to the control of parallel-plate electrostatic micro actuators

Though the effect of fringing field in electrostatic parallel-plate actuators is a well-understood phenomenon, the existing formulations often result in complicated mathematical models from which it is difficult to determine the deflection of the moving plate for given voltages and hence, they are not suitable for accurate actuation control. This work presents a new formulation for tackling the fringing field, in which the effect of fringing field is modeled as a variable serial capacitor. Based on this model, a robust control scheme is constructed using the theory of input-to-state stabilization (ISS) and backstepping state feedback design. This method allows loosening the stringent requirements on modeling accuracy without compromising the performance. The stability and the performance of the system using this control scheme are demonstrated through both stability analysis and numerical simulation.     

Flash-lamp annealing of ion-implanted silicon and its application to solar cells

Xe-lamps were used to anneal p+-implanted silicon. The redistribution of implanted dopants does not occur by flash annealing. The substrate-orientation dependence of electrical activity of implanted dopants between