700V高压LDMOS器件瞬态失效机理研究

详细分析了700V横向双扩散金属氧化物半导体(LDMOS)器件瞬态失效机理的特性。研究表明触发器件寄生晶体管开启的失效功率不仅与器件内部温度有关,同时也与电场分布有关。器件温度影响寄生阱电阻和衬底电流的大小,而电场分布影响器件内部碰撞电离。器件温度与电场分布均与栅脉冲参数有密切关系。为了阐述栅脉冲参数对器件温度的影响,模拟仿真了器件的热响应曲线。     

异质栅单Halo沟道SOI中隐埋层对器件特性的影响

研究异质栅单Halo沟道SOI MOS器件的隐埋层中二维效应对器件特性,如电势分布、阈值电压等的影响,仿真结果表明,隐埋层中的二维效应会引起更明显的SCE及DIBL效应.在考虑隐埋层二维效应的基础上,提出了一个新的二维阈值电压模型,能较好地吻合二维器件数值模拟软件Medici的仿真结果.     

关于VDMOSFET二次击穿现象的分析和研究

在PDP驱动电路中的高压功率器件大量采用了VDMOS器件,由二次击穿引起的器件损坏不容忽视。本文讨论了双极晶体管和功率晶体管VDMOS二次击穿的现象,着重分析了功率晶体管VDMOS二次击穿的原因,并提出了改善其二次击穿现象的最佳设计参数及最优准则：基于寄生晶体管基区结深和浓度优化的方法。同时用器件仿真软件MEDICI模拟了各参数对功率晶体管VDNMOS二次击穿的影响。给出了仿真结果。     

体硅、SOI和SiCMOS器件高温特性的研究

首先介绍了体硅 MOS器件在 2 5～ 30 0℃范围高温特性的实测结果和分析 ,进而给出了薄膜 SOI MOS器件在上述温度范围的高温特性模拟结果和分析 ,最后介绍了国际有关报道的Si C MOS器件在 2 2～ 4 50℃范围的高温特性。在上述研究的基础上 ,提出了体硅、SOI和 Si C MOS器件各自所适用的温度范围和应用前景     

沟道宽度对MOSFET高功率微波效应的影响

关于高功率微波(HPM)对半导体器件影响的研究往往采用二维仿真模型,而器件宽度作为第三个维度,对仿真结果的影响并没有得以足够的重视。通过Sentaurus TCAD软件对器件的三维模型进行模拟仿真,重点研究了器件宽度在高功率微波注入条件下对于器件电击穿和热积累的影响。研究结果表明,随着器件宽度的增加,标志着二次击穿开始发生的"快回"电压Vt1会明显降低,因此在HPM注入下,较大宽度的器件将有更多的时间处于击穿区域;同时,高功率微波引起热集聚效应在大沟道宽度器件中将更加显著,其内部的峰值温度大于沟道宽度较小的器件。提出了一种新型的轻掺杂漏极结构,能够改善器件内部沿宽度方向上的热扩散条件,减小器件内部的峰值温度,并可提高器件的Vt1,进而提高器件在HPM下的稳定性。     

超晶格雪崩光电二极管的结构优化及性能研究

基于碰撞离化理论研究了异质材料超晶格结构对载流子离化率的作用,设计得到In0.53Ga0.47As/In0.52Al0.48As超晶格结构的雪崩光电二极管。通过分析不同结构参数对器件性能的影响,得到了低隧道电流、高倍增因子的超晶格结构雪崩层,根据电场分布方程模拟了器件二维电场分布对电荷层厚度及掺杂的依赖关系,并优化了吸收层的结构参数。对优化得到的器件结构进行仿真并实际制作了探测器件,进行光电特性测试,与同结构普通雪崩光电二极管相比,超晶格雪崩光电二极管具有更强的光电流响应,在12.5~20 V的雪崩倍增区,超晶格雪崩光电二极管在具备高倍增因子的同时具有较低的暗电流,提高了器件的信噪比。     

线性掺杂缓冲层结构VDMOSFET抗单粒子烧毁的仿真研究

通过引入缓冲层可以提高器件的二次击穿电压,进而提高器件发生单粒子烧毁的阈值电压。本文提出采用线性掺杂缓冲层结构。通过准静态雪崩仿真和重离子入射仿真发现,优化线性缓冲层是必要的,对于固定厚度的缓冲层,具有线性掺杂缓冲层结构的器件发生单粒子烧毁时的内部电场强度明显小于优化后的恒定掺杂缓冲层结构的器件。二次击穿电压与寄生晶体管的开启电流明显比具有优化后的恒定掺杂缓冲层结构的器件高。因此,线性掺杂缓冲层结构的器件在抗单粒子烧毁方面更有优势。     

短沟道GaAs功率MESFET器件的二维有限差分数值模拟

本文系统叙述了用于分析短沟道GaAs MESFET器件特性的二维稳态数值模拟通用软件。模拟中首次考虑了GaAs器件内部杂质的非均匀分布及短沟道效应,以使求解符合实际;为了加快模拟收敛速度及精度,采用改进的有限差分算法对短沟道GaAs MESFET功率器件进行了模拟计算,取得了与实验相一致的结果。本通用软件具有自动网格划分,自由格式输入及模块化结构等特点,可方便、准确地描述GaAs MESFET内部的物理图象,预测器件在不同偏置下的特性。     

电场偏置对MOS器件电离辐射效应的影响

研究了外加电场对MOS器件电离辐射效应的影响.采用10 keV X射线对MOS器件在正/反电场偏置条件下进行总剂量辐射,分析了MOS器件辐射前后阈值电压的漂移量.实验结果表明,正偏情况下MOS器件的阈值电压漂移量远大于反偏情况下MOS器件的阈值电压漂移量.基于一维连续性方程,在考虑电子-空穴对的复合/逃逸率、电子及空穴的捕获横截面与外加电场关系的基础上,模拟了辐射诱生栅氧化层内陷阱电荷与辐射总剂量之间的关系,分析了陷阱电荷对MOS器件阈值电压的影响,仿真结果与实验数据吻合良好.     

VVMOS功率晶体管的负阻击穿

VVMOS晶体管是一种开有V形槽的垂直沟道高频功率MOS场效应器件,它的一个主要优点是与其它MOS器件一样不会发生二次击穿,然而近来一些作者报道MOS器件有负阻击穿效应,而这种负阻击穿效应也会引起二次击穿,导致器件烧毁。我们在测量自制的VVMOS晶体管时,也观察到了负阻击穿,经过研究,提出了纵向寄生npn双极晶体管的VVMOS晶体管负阻击穿模型,在此基础上还提出了几种抑制负阻击穿效应的方法,在采用了这些方法后,负阻击穿效应被减弱,甚至被消除,从而证实了所提出的VVMOS晶体管负阻击穿模型。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.