固体激光工艺

采用1.06或1.33微米运转的Nd:YAG振荡放大器装置可达到激光系统有不同波长和每个脉冲有高的能量的要求。本文提出了1.06微米的抑制振荡而取得1.33微米振荡方法。加热问题的解决就能提高激光振荡器的每个脉冲的能量。实现此目的一种方法是对闪光灯输出进行光谱滤光。本文提出了1.33微米运转的Nd:YAG振荡器所采用的各种滤光片所取得的实验结果。而使用激光放大器则能进一步提高每个脉冲的能量。对圆形和高斯形截面光束都作了放大器对激光脉冲影响的研究。这种研究包括了放大器的饱和、输出脉冲形状变形和输出强度分布变形的各种影响。把分析结果与1.06微米运转的实验Nd:YAG放大器作了比较。     

高精度三维微结构微细电火花加工系统研究

针对微细电火花加工技术的特点,开发、研制了高精度三维微结构加工的细电火花设备,主要介绍了该装置的结构和数字比例、积分和微分(PID)结合双向静差补偿的控制方法,实现放电间隙与放电状态的自适应调节,并利用该装置进行了平台性能的试验研究,试验结果表明该加工技术响应时间快、平稳、超低速和超高分辨率、加工效率较高,可实现平台在100 mm行程内达到亚微米级精度,最低速度为0.1μm/s,闭环最小步进量为100nm,可满足微细电火花加工的要求。     

基于CAN总线的分布式无CPU型电力电子装置参数检测模块的研制

本文介绍了一种基于现场CAN总线的无CPU型分布式电力电子参数监测节点的设计与工程应用。并对系统的整体结构、硬件配置和工作模式作了详细的说明。实验表明，该装置具有结构简单、可靠性高的特点，有着广阔的应用前景。     

熔锥型光纤耦合器折射率传感特性研究

构建了熔锥型光纤耦合器微米量级下的波导结构模型。利用光束传播法对光功率在熔锥型光纤耦合器模型中的分布变化进行了数值模拟,分析得到了在不同折射率环境下耦合器输出光谱响应图的变化规律。依据微米量级光纤倏逝场耦合模理论,搭建基于熔锥型光纤耦合器结构模型的传感实验系统,研究了其透射光谱与外界蔗糖溶液折射率的变化关系。理论模拟和实验结果表明,当外界环境溶液折射率在1.3330～1.4000范围内变化时,传感结构透射光谱的漂移与折射率变化呈现良好的线性关系,响应灵敏度能够达到2272.7569 nm/RIU。该折射率传感结构测量范围宽,响应速度快,结构紧凑,传感光路搭建操作简单。     

空间衍射望远镜自展开结构设计

为了满足空间探测对衍射望远镜的发展需求,针对某衍射光学系统设计了一种空间可展开衍射望远镜。首先,根据Serrurier桁架原理及优化设计理论确定了文中所用展开结构的形式及几何尺寸,并针对某衍射光学系统设计了一种新型自展开结构;其次,建立了该展开结构的有限元模型并分析了其展开后的特性;最后,搭建了原理样机并对其进行了实验研究。实验结果表明:该展开结构的展开距离为2.9 m,展开后的重复精度误差小于2 mm,偏心小于0.3 mm,倾角小于0.2,且可通过促动器将其展开精度调整至微米级,能够满足空间衍射望远镜自展开机构的结构简单、质量轻、稳定可靠、精度高等要求。     

用于测量激光烧蚀下靶材获得冲量的方法

强激光与固体靶物质相互作用产生的等离子体膨胀对靶有强烈的反冲作用,这就是激光等离子体推进的基本思想。固体靶获得冲量大小的测量在研究冲量传递效率过程中有重要作用。采用一种悬摆法和光电测速法相结合的测量方法对激光等离子体膨胀时靶摆动的周期、角速度进行了实验测量,结合测试装置的几何结构和流体力学理论得到了有空气阻力影响下靶的摆动方程,并将实验测量的靶摆动周期与由摆动方程计算的结果进行了比较,两者之间的相对误差小于0．5％,即这一摆动方程能较精确地描述靶的摆动过程,采用此摆动方程和实验测量的靶摆动角速度求得了靶的冲量。理论和实验研究结果表明该测试方法具有结构简单、操作方便、测量精确度高等特点。     

一种新型薄腔法-珀干涉测速系统研究

本文所关注的激光干涉测速技术主要用于测试在冲击波或爆轰波作用下各种材料样品的自由面速度随时间变化的过程,介绍了基于光学谐振腔的选频特性利用薄腔法-珀干涉仪直接测量高速飞片所引起的多普勒频移从而获得其速度信息的设想,并根据此设想构建薄腔法-珀干涉测速系统的技术路线。最后描述了利用该项测试技术实际测量金属箔电爆炸驱动的Kapton膜飞片速度的实验并对实验结果进行了分析。与其它激光测速装置相比,该干涉仪具有体积小、结构简单紧凑和成本低的特点。     

三相全控桥式整流电路实验装置的研制

介绍了开发三相全控桥式整流电路实验装置的背景;叙述了TC787芯片的内部结构、工作原理、特点及芯片的各个管脚的功能;详细介绍了该实验装置的触发电路的设计思路、设计结果和工作原理;介绍了该实验装置的主电路部分的结构和特点。该实验装置性能可靠,符合本科生实验要求。     

高精度激光准直及其可能应用

我们对三点法点光源的稳定性和光束传输的影响因素作了实验研究,制成一台21米长、精度为±0.6～0.8微米(或±3～4×10~(-8))的激光准直实验装置。利用这台装置,测出了人造断层的潮汐变化,小潮期间,24小时水平位移最大变幅不超过11微米。分析了用于地震预报、测定大坝变形和调整粒子加速器的可能性,讨论了广义相对论时空弯曲对准直光束的影响。     

日本研究一系列超大规模集成电路用的生产技术

<正> 日本超大规模集成电路技术研究组合共同研究所最近研究了可能实现亚微米图形的高速电子束扫描装置与电子束掩模制造装置,并研究了在实现1兆位存贮器中能发挥作用的新结构“SHC RAM”(迭式高电容随机存取存贮器),其中关于“SNC RAM”在2月份召开的美国国际固体电路会议上已发表。上述的电子束扫描装置是在该所1978年研制的光栅扫描方式基础上改进而成的,采用绕过没有图形的部分进行扫描的可变成形束方式,这样扫描速度就大大提高了。用过去的方式扫描100毫米见方的片子和掩模需要180分钟,而用该方式12分钟就可完成,而且由于电子束系统采用可变束方式,能进行最小线宽0.5微米(束斑0.125微米)的描画,     

Measurement and analysis of hot-carrier-stress effect on NMOSFET's using substrate current characterization

Short-channel NMOSFET degradation is explored by measuring the effect of hot-carrier stress on the substrate and drain currents, with normal and reverse polarities applied. The degradation mechanism can be explained as being, under most conditions, the trapping of electrons in the gate oxide near the stressed drain. This mechanism can explain results which have previously been attributed to trapped holes in the oxide. Two-dimensional simulation of the device characteristics, with the degradation modeled as localized electrons in the oxide, supports this conclusion.     

The external switching of intrinsic optically bistable devices by incoherent illumination

We report the observation of external switching of an intrinsic optically bistable device by incoherent illumination. The InSb etalons used in this study were switched by a photographic flashlamp both from off to on resonance and, under different conditions, from on to off resonsance. It has been demonstrated experimentally that switching can be initiated as a result of either an electronic or a thermal effect. The parameters that determine which mechanism dominates in a particular instance are discussed. The results should have general application to a variety of materials of device interest.     

Failure mechanisms of IGBTs under short-circuit and clampedinductive switching stress

The application of insulated gate bipolar transistors (IGBTs) in high-power converters subjects them to high-transient electrical stress such as short-circuit switching and turn-off under clamped inductive load (CIL). Robustness of IGBTs under high-stress conditions is an important requirement. Due to package limitations and thermal parameters of the semiconductor, significant self-heating occurs under conditions of high-power dissipation, eventually leading to thermal breakdown of the device. The presence of a parasitic thyristor also affects the robustness of the device. In order to develop optimized IGBTs that can withstand high-circuit stress, it is important to first understand the mechanism of device failure under various stress conditions. In this paper, failure mechanisms during short-circuit and clamped inductive switching stress are investigated for latchup-free as well as latchup-prone punchthrough IGBTs. It is shown that short-circuit and clamped inductive switching cannot be considered equivalent in the evaluation of a device safe operating area (SOA). The location of thermal failure of latchup-free punchthrough IGBTs is shown to be different for the two switching stresses     

SiO_2/SiC界面对4H-SiC n-MOSFET反型沟道电子迁移率的影响

提出了一种基于器件物理的4 H- Si C n- MOSFET反型沟道电子迁移率模型.该模型包括了界面态、晶格、杂质以及表面粗糙等散射机制的影响,其中界面态散射机制考虑了载流子的屏蔽效应.利用此模型,研究了界面态、表面粗糙度等因素对迁移率的影响,模拟结果表明界面态和表面粗糙度是影响沟道电子迁移率的主要因素.其中,界面态密度决定了沟道电子迁移率的最大值,而表面粗糙散射则制约着高场下的电子迁移率.该模型能较好地应用于器件模拟.     

A methodology for accelerated testing by mechanical actuation of MEMS devices

In order to fully understand the reliability issues around MEMS device a means of carrying out accelerated testing is required. This research investigated the use of mechanical means to actuate MEMS membranes so that lifetime estimates could be obtained. A Talysurf measurement system was adapted to allow a MEMS membrane to be cycled by moving it with a stylus. This cycling was continued until the membrane failed according to the definitions provided by the device manufacturer. This experiment was repeated with different forces and this allowed standard life testing techniques to be used to produce a prediction of lifetime under normal use conditions. The lifetime predicted was of the order of 30 million cycles and was in keeping with the expectations of the device manufacturer for this geometry and materials. This demonstrated that the acceleration technique is a valid way to accelerate the device type and so can provide a method for predicting lifetimes for other devices. Such a prediction will be useful in Understanding the reliability of MEMS devices in actual usage.     

New phase modulation technique based on spatial soliton switching

A phase modulation technique able to increase the transmission capacity of an optical channel is presented. It is based on spatial soliton switching properties. The modulator device accepts as inputs two streams of amplitude modulated pulses and generates an output stream of phase modulated pulses whose phase values depends on the different input combinations, coding properly the input streams and increasing the transmission capacity of the optical channel that carries this information. The modulator device can be properly cascaded, generating a unique stream of pulses capable of carrying the information of a certain number of input channels. A proper demodulator device is also presented. It is capable of accepting as input a phase modulated stream of pulses, generating as outputs the original amplitude modulated pulse streams     

Power and energy limitations of bipolar transistors imposed by thermal-mode and current-mode second-breakdown mechanisms

Two distinct second-breakdown modes observed in bipolar power transistors are described. Experimental results obtained on a number of power-transistor types are presented and interpreted. The conditions under which each of these second-breakdown modes occurs, as evidenced by a very sudden collapse in voltage, are shown to be the result of the application of relatively high voltage and current to the device. Thermal-mode breakdown, the classical mechanism, is shown to be related to the total energy absorbed by the device; the primary parameters are voltage, current, and duration of application of these. Current-mode breakdown, which occurs essentially at the instant that critical current and voltage levels are achieved, is shown to be primarily related to the instantaneous power the device is forced to handle. The validity of the term current mode is established by the contention that, although the voltage collapse is caused by the presence of an excessive field, the mechanism is actually induced by the forcing of very high currents through the device under bias conditions that produce a local critically high current density.     

Novel failure mode of chip corrosion at automotive HALL sensor devices under multiple stress conditions

Semiconductor devices used in automotive applications undergo numerous stress situations depending on their particular application. Corrosion, as one main crucial failure mechanisms, can affect the lifetime of electronic components on system, device or even die level. In this paper, a novel corrosion mechanism on HALL sensor devices is investigated and clarified. This corrosion is only occurring under complex conditions like layout aspects, ionic impurities combined with humidity penetration and thermo-mechanical strain due to packaging and additional mechanical load from further over moulding. It is shown how advanced physical and chemical analysis can be combined with finite element simulation to ascertain a chemical degradation running on silicon, silicon dioxide and metallisation level to derive the complete chemical reaction mechanism for the observed corrosion defects. To verify the new failure mode, experiments to recreate this type of corrosion were carried out. Finally, conclusions are drawn on how failure modes can be prevented and how the robustness of the HALL devices under harsh environments can be increased.     

Temperature study of the dielectric polarization effects of capacitive RF MEMS switches

This paper investigates both theoretically and experimentally the dielectric charging effects of capacitive RF microelectromechanical system switches with silicon nitride as dielectric layer. Dielectric charging caused by charge injection under voltage stress was observed. The amphoteric nature of traps and its effect on the switch operation were confirmed under both positive and negative control voltages. It has been confirmed that charging is a complicated process, which can be better described through the stretched exponential relaxation. This mechanism is thermally activated with an activation energy being calculated from the temperature dependence of the capacitance transient response. The charging mechanism, which is responsible for the pull-out voltage and the device failure, is also responsible for the temperature-induced shift of the capacitance minimum bias.     

一种虚拟路由冗余协议负载均衡技术实现机制

标准VRRP（虚拟路由器冗余协议）解决在配置默认网关环境下消除网络单点故障问题,其协议自身不够灵活,即虚拟路由器中只有主设备进行流量转发,其他备用设备均作为备份不进行流量转发,无法负载分担,不能最大程度提高带宽和设备利用率。针对该局限,在此基于与某公司的合作项目,论述了一种虚拟路由冗余协议负载均衡实现机制,在标准VRRP协议分析研究基础上引入虚拟转发器和转发状态机,实现一个虚拟IP对应多个虚拟MAC的机制,无需配置多个备份组就能同时实现路由冗余备份和流量负载均衡,使局域网内用户能够通过每台虚拟转发器与外界通信,极大地提高资源利用率,最后以实验验证了设计可行性。