A New Quasi 2-Dimensional Analytical Approach to Predicting Ring Junction Voltage,Edge Peak Fields and Optimal Spacing of Planar Junction with Single Floating Field Limiting Ring Structure

WT8.BZ]A new quasi 2-dimensional analytical approach to predicting the ring voltage,edge peak fields and optimal spacing of the planar junction with a single floating field limiting ring structure has been proposed,based on the cylindrical symmetric solution and the critical field concept.The effects of the spacing and reverse voltage on the ring junction voltage and edge peak field profiles have been analyzed.The optimal spacing and the maximum breakdown voltage of the structure have also been obtained.The analytical results are in excellent agreement with that obtained from the 2-D device simulator,MEDICI and the reported result,which proves the presented model valid.

A Novel Polysilicon and Oxide Sandwich Deep Trench with Field Limiting Ring for RF Power Transistors

A vertical sandwich deep trench with a field limiting ring is proposed to improve the breakdown voltage of power devices and high voltage devices.Simulation result shows that nearly 100% breakdown voltage of the plane junction can be realized.

A novel thin drift region device with field limiting rings in substrate

A novel thin drift region device with heavily doped N＋ rings embedded in the substrate is reported, which is called the field limiting rings in substrate lateral double-diffused MOS transistor （SFLR LDMOS）. In the SFLR LDMOS, the peak of the electric field at the main junction is reduced due to the transfer of the voltage from the main junction to other field limiting ring junctions, so the vertical electric field is improved significantly. A model of the breakdown voltage is developed, from which optimal spacing is obtained. The numerical results indicate that the breakdown voltage of the device proposed is increased by 76% in comparison to that of the conventional LDMOS.

Experimental and numerical analyses of high voltage 4H-SiC junction barrier Schottky rectifiers with linearly graded field limiting ring

This paper describes the successful fabrication of 4H-SiC junction barrier Schottky （JBS） rectifiers with a linearly graded field limiting ring （LG-FLR）. Linearly variable ring spacings for the FLR termination are applied to improve the blocking voltage by reducing the peak surface electric field at the edge termination region, which acts like a variable lateral doping profile resulting in a gradual field distribution. The experimental results demonstrate a breakdown voltage of 5 kV at the reverse leakage current density of 2 mA/cm2 （about 80% of the theoretical value）. Detailed numerical simulations show that the proposed termination structure provides a uniform electric field profile compared to the conventional FLR termi- nation, which is responsible for 45% improvement in the reverse blocking voltage despite a 3.7% longer total termination length.

Generating femtosecond coherent X-ray pulses in a diffractionlimited storage ring with the echo-enabled harmonic generation scheme

To study ultrafast processes at the sub-picosecond level, novel methods based on coherent harmonic generation technologies have been proposed to generate ultrashort radiation pulses in existing ring-based light sources. Using the High Energy Photon Source as an example, we numerically test the feasibility of implementing one coherent harmonic generation technology, i.e.,the echo-enabled harmonic generation(EEHG) scheme, in a diffraction-limited storage ring(DLSR). Two different EEHG element layouts are considered, and the effect of the EEHG process on the electron beam quality is also analyzed. Studies suggest that soft X-ray pulses, with pulse lengths of a few femtoseconds and peak powers of up to1 MW, can be generated by using the EEHG scheme, while causing little perturbation to the regular operation of a DLSR.

合肥先进光源储存环超导纵向梯度弯铁样机研制

介绍了合肥先进光源储存环超导纵向梯度弯铁样机的研制工作,基于已发展的一种磁体结构参数优化方法,综合考虑磁场空间分布需求和超导线圈工作负载,完成了磁铁结构的设计和优化。为了验证磁体设计方案,应用一种矩形铌钛线材和DT4C电工纯铁材料,研制了一台纵向长度0.30 m、磁极间隙46 mm的磁体样机。并搭建了一套简易低温测试装置,对该磁体进行了励磁特性测量,经过10余次失超,测得磁体最大工作电流大于275 A。磁体纵向磁场分布测量结果表明,该磁体在约196 A工作电流下,纵向磁场积分值达到0.4 T·m,峰值磁场约4.5 T。测试结果与理论设计结果基本一致,表明该种超导磁体的设计是可行的。

一种沟槽-场限环复合终端结构的设计

为了改善硅功率器件击穿电压性能以及改善IGBT电流的流动方向,提出了一种沟槽-场限环复合终端结构。分别在主结处引入浮空多晶硅沟槽,在场限环的左侧引入带介质的沟槽,沟槽右侧与场限环左侧横向扩展界面刚好交接。结果表明,这一结构改善了IGBT主结电流丝分布,将一部分电流路径改为纵向流动,改变了碰撞电离路径,在提高主结电势的同时也提高器件终端结构的可靠性;带介质槽的场限环结构进一步缩短了终端长度,其横纵耗尽比为3.79,较传统设计的场限环结构横纵耗尽比减少了1.48%,硅片利用率提高,进而减小芯片面积,节约制造成本。此方法在场限环终端设计中非常有效。

既有砌体结构摩擦滑移隔震加固工程有限元分析

摩擦滑移隔震技术具有成本经济、设计简洁等优点,广泛应用于各类隔震建筑中。基于摩擦滑移的隔震原理,结合既有砌体结构的特征,设计出新型摩擦滑移装置,并将其应用于既有结构加固设计中。结合工程实例,通过建立3组不同连接方式的多层砌体结构模型,对比基础不同连接形式在罕遇地震下的加速度、基底剪力及位移反应。试验结果表明:摩擦滑移隔震装置的设置能够大大降低结构的地震响应。设置限位型的摩擦滑移连接也能起良好的隔震效果,限位装置的增加能够有效地减小底部滑移量,满足工程使用的要求。根据工程实例,对摩擦滑移隔震的“双基础圈梁”装置的具体构造,以及在加固设计中的平面布置及关键部位的构造等进行说明,为摩擦滑移技术在加固设计中的应用与进一步优化提供思路。

Generation of two-color polarization-adjustable radiation pulses for storage ring light source

To date, two-color pulses are widely used in pump–probe experiments. For a ring-based light source, the power of the spontaneous radiation fluctuates randomly in the longitudinal direction. It is difficult to produce twocolor double pulses by optical methods. In this paper, we introduce a method based on the echo-enabled harmonic generation scheme that generates two-color pulses in a storage ring light source. By adopting crossed undulators and a phase shifter, the polarization of the two-color pulses can be easily switched. A numerical simulation based on a diffraction-limited storage ring, the Hefei Advanced Light Source, suggests that the time delay and spectral separation of the two pulses can be adjusted linearly by changing the pulse duration and chirp parameters of the seed laser. A circular polarization degree above 80% could be achieved.

Different radial growth responses to climate warming by two dominant tree species at their upper altitudinal limit on Changbai Mountain

We analyzed the influence of climate change over the past 50 years on the radial growth of two tree species: Korean pine (Pinus koraiensis) and Yezo spruce (Picea jezoensis), located on Changbai Mountain, Northeast China, using a dendrochronology approach to understand factors that limit the altitude for tree species. Elevated temperatures increased the radial growth of Korean pine and decreased that of Yezo spruce. The positive response of tree growth to hydrothermal conditions was the key reason that the upper limit of elevation of Korean pine followed the temperature fluctuation pattern. Increased temperatures and precipitation and longer growing seasons accelerated Korean pine growth. As the temperature increased, correlations between Korean pine ring-width chronology and precipitation changed from negative to positive. In Yezo spruce, increasing monthly temperatures and inadequate precipitation during the middle and late parts of the growing season led to narrow growth rings, whereas decreasing monthly temperatures and sufficient precipitation during the late growing season promoted growth. Rising temperatures and adequate precipitation increases Korean pine growth, possibly elevating the upper range limit in altitude for this species. In contrast, Yezo spruce growth is negatively affected by warming temperatures and limited precipitation. Under future temperature increases and precipitation fluctuations, the upper limit altitude of Korean pine can reasonably be expected to shift upward and Yezo spruce downward.

具有多场限环结构的SiC LDMOS击穿特性研究

场限环终端结构因能够显著提高击穿电压而被广泛应用于半导体功率器件。基于数值模拟软件建立了具有多场限环结构的SiC LDMOS仿真模型。分别仿真场限环各项参数和漂移区掺杂浓度与击穿电压的关系。提取器件击穿时的表面电场,从表面电场分布均匀程度和峰值电场两方面分析击穿原理。研究结果表明,当漂移区掺杂浓度一定时,击穿电压随场限环数量、结深和掺杂浓度的增大而先增大后减小;当场限环参数一定时,击穿电压随漂移区掺杂浓度的增大而先增大后减小;经验证在相同条件下,线性环间距设计的LDMOS击穿特性优于等环间距设计,且漂移区掺杂浓度越高,环掺杂浓度和环结深越小,失效场限环数量越多。

10 kV P沟道SiC IGBT终端结构优化设计与实现

提出采用五区多重场限环FRM-FLRs(five-region multistep field limiting rings)终端设计并流片,研制10 kV P沟道碳化硅绝缘栅双极晶体管SiC IGBT(silicon carbide insulated gate bipolar transistor)终端。通过Silvaco TCAD软件仿真,对比研究传统等间距场限环ES-FLRs(equally spaced field limiting rings)终端和五区多重场限环终端对器件击穿特性的影响。仿真结果表明,五区多重场限环终端具有更均衡的近表面电场分布,减缓电场集中,优化空间电荷区横向扩展,且击穿电压可达到14.5 kV,而等间距场限环终端击穿电压仅为7.5 kV。同时,分别对五区多重场限环终端,以及采用此终端结构的P沟道SiC IGBT进行流片验证。测试结果表明,五区多重场限环终端可以实现12.2 kV的击穿电压;P沟道SiC IGBT的击穿电压达到10 kV时,漏电流小于300 nA,并且栅源电压为-20 V,集电极正向电流为-10 A时,器件的正向导通压降为-8 V。

衍射极限储存环束流注入物理方案的设计及模拟

衍射极限储存环(DLSR)作为第四代同步辐射光源,正得到世界各国的大力发展和建设。如何在尽量减小对存储束流扰动情况下,高效率地将束流注入到储存环中,是衍射极限储存环设计与运行中的重要课题之一。传统的局部凸轨注入法有着很长的历史,应用广泛且技术成熟,但是传统凸轨注入法会对存储束流造成扰动,且衍射极限储存环的动力学孔径较小,这给传统凸轨注入法的应用带来了困难。为了解决这些问题,改进了一些传统的离轴注入法,提出并发展了一些在轴的注入方法。合肥先进光源(HALF)是规划建设中的衍射极限储存环光源,基于HALF储存环的物理设计方案,设计并应用了几种离轴或在轴的注入方案,通过粒子跟踪和模拟的方法验证了它们的可行性并研究了注入效率等物理问题,并对模拟结果进行了讨论和总结。

多重场限环型终端结构的优化设计

开展了硅基金属氧化物场效应晶体管用多重场限环型终端结构的优化设计工作。研究了体区注入剂量、场限环宽度、主结宽度对击穿电压的影响规律,并对其机理进行了分析。通过仿真获得了器件内部的电场、电势和碰撞电离率分布。通过逐步优化获得了最终结构和工艺参数,体区注入剂量为1.3×10^(13)cm^(-3),场限环宽度为1.5μm,主结宽度为11μm,对应终端击穿电压为106 V。实验开版流片获得的器件击穿电压为105.6 V,良率达到98.65%。

纯水系统平面O形密封圈密封性能仿真分析

针对纯水系统平面O形密封存在的失效问题,从平面密封结构出发,研究了影响密封间隙大小的主要因素,给出了介质压力和螺栓预紧力与结合面间隙的关系,并以某纯水支架卸载式三通块的平面密封为例,基于ABAQUS建立了平面O形密封的有限元仿真模型,分析了密封间隙和介质压力对密封主应力、接触应力及剪切应力等密封性能的影响规律。仿真结果表明:当平面O形密封的螺栓负载力大于预紧力时,将会在结合面产生间隙,且间隙随预紧力和工作压力的增大而变大;平面O形密封的等效主应力、上下接触应力随结合面间隙的增大而减小;密封间隙处的剪切应力大于材料的抗剪强度是出现间隙咬伤的主要原因,且间隙越大极限挤出压力越小,密封越容易被挤出而损坏。

衍射极限储存环物理设计研究进展

总结了国内外在衍射极限储存环(DLSR)物理设计方面的研究进展。为了在合理的周长范围内实现超低束流发射度,DLSR线性束流光学设计普遍采用紧凑型多二极铁消色散结构。在非线性动力学优化中,通常采用相移控制技术、解析和数值优化技术减小由色品六极铁导致的强非线性效应。DLSR束流接受度较小,主要考虑脉冲多极铁偏轴注入和快速冲击磁铁在轴注入两种注入方案。束流集体效应(尤其是束流内部散射和托歇克散射效应)随发射度降低而增强,需要采用束长拉伸、横向反馈等方法提高DLSR中束流的稳定性。

程序温控仪中PID参数自整定算法

提出了一种适合于程序温控仪使用的ＰＩＤ参数自整定算法，介绍了该算法原理和软件设计，并将此算法应用于实际的控制系统中，取得了良好的控制效果。

一种新型高压功率器件终端技术

为了改善高压功率器件的击穿电压、节省芯片面积,提出一种P-场限环结合P+补偿结构、同时与金属偏移场板技术相结合的高压终端技术。采用TCAD(ISE)对该技术进行模拟,结果表明,该技术具有比较好的面积优化和击穿电压优化特性。

单场限环结构的表面电场分布及环间距的优化

基于横向扩散与纵向扩散构成的冶金结边界为椭圆形这一特点,讨论单场限环结构表面电场强度的分布,给出表面电场强度、主结及环结分担电压的解析表达式。在纵向结深和掺杂浓度一定的条件下,根据临界电场击穿理论,讨论环间距的优化设计方法。单场限环结构主结环结间表面电场强度的绝对值曲线近似呈抛物线,最大电场位于主结处。随着环间距的增大,最大电场变大;随着横向扩散深度的增大,最大电场变小。环右侧最大电场也出现在结处,随着环间距和横向扩散深度的增加,最大电场均减小。在场限环结构中,当主结和环结在表面处的最大电场强度均等于临界电场强度时,击穿电压达到最大值,此时所对应的环间距为最佳环间距。

场限环结构电压和边界峰值电场分布及环间距优化

采用与平面结物理机理最接近的圆柱坐标对称解进行分析 ,提出了平面结场限环结构的电压分布和边界峰值电场的解析理论。以单场限环为例 ,给出了场限环结构极为简单的各电压和边界峰值电场表达式。讨论了不同环间距和反偏电压对场限环电压的影响 ,并用流行的 2 -D半导体器件模拟工具 MEDICI对解析计算进行了验证。根据临界电场击穿近似 ,讨论了环间距的优化设计并给出了优化环间距表达式。在一定结深和掺杂浓度时 。