SOI LIGBT抗闩锁效应的研究与进展

概述了绝缘层上硅横向绝缘栅双极晶体管(SOI LIGBT)抗闩锁结构的改进历程,介绍了从早期改进的p阱深p+欧姆接触SOI LIGBT结构到后来的中间阴极SOI LIGBT、埋栅SOILIGBT、双沟道SOI LIGBT、槽栅阳极短路射频SOI LIGBT等改进结构;阐述了一些结构在抗闩锁方面的改善情况,总结指出抑制闩锁效应发生的根本出发点是通过降低p基区电阻的阻值或减小流过p基区电阻的电流来削弱或者切断寄生双极晶体管之间的正反馈耦合。     

基于TSPC的4/5双模前置分频器设计

针对无线传感网络对射频电路高速、低功耗方面日益增长的性能要求,设计了一款用于高频锁相环中的高速、低功耗4/5双模前置分频器。在分析真单相时钟(TSPC)电路工作原理的基础上,指出了该电路结构存在的两个主要缺点,并结合器件工艺和物理给出了相应的版图优化解决方法。然后,采用SMIC 0.18μm标准CMOS工艺,设计了一款基于这种改进后的真单相时钟电路的集成4/5双模前置分频器。在版图优化设计后利用Cadence Spectre进行了后仿真验证,结果表明,在直流电源电压1.8 V时,该4/5双模前置分频器的最高工作频率可达到3.4 GHz,总功耗仅有0.80 mW。该4/5双模前置分频器的最低输入幅值为0.2 V时,工作频率范围为20 MHz~2.5 GHz,能够满足面向无线传感网络应用的锁相环(PLL)的高速、低功耗性能要求。     

TiC/n型4H-SiC欧姆接触的低温退火研究

利用电子回旋共振(ECR)氢等离子体处理n型4H-SiC(0.5～1.5×1019cm-3)表面,采用溅射法制备碳化钛(TiC)电极,并在低温(<800℃)条件下退火。直线传输线模型(TLM)测试结果表明,TiC电极无需退火即可与SiC形成欧姆接触,采用ECR氢等离子体处理能明显降低比接触电阻,并在600℃退火时获得了最小的比接触电阻2.45×10-6Ω.cm2;当退火温度超过600℃时,欧姆接触性能开始退化,但是比接触电阻仍然低于未经氢等离子体处理的样品,说明ECR氢等离子体处理对防止高温欧姆接触性能劣化仍有明显的效果。利用X射线衍射(XRD)分析了不同退火温度下TiC/SiC界面的物相组成,揭示了电学特性与微观结构的关系。     

SiO2/4H-SiC(0001)界面过渡区的ADXPS研究

采用角依赖X射线光电子谱技术(ADXPS)对高温氧化SiO2/4H-SiC(0001)界面过渡区的组成、成分分布等进行了研究.通过控制1%浓度HF酸刻蚀氧化膜的时间,制备出超薄膜(1～1.5nm)样品,同时借助标准物对照分析,提高了谱峰分解的可靠性.结果显示,高温氧化形成的SiO2/4H-SiC(0001)界面,同时存在着Si1+,Si2+,Si33+3种低值氧化物,变角分析表明,一个分层模型适合于描述该过渡区的成分分布.建立了过渡区的原子级模型并计算了氧化膜厚度.结合过渡区各成分含量的变化及电容-电压(C-V)测试分析,揭示了过渡区成分与界面态的直接关系.     

用XPS法研究SiO_2/4H-SiC界面的组成

利用X射线光电子谱(XPS)研究了高温氧化形成的SiO2/4H-SiC界面的化学组成.获取低浓度HF酸刻蚀速度基础上制备出超薄氧化膜(1～1.5 nm)样品,并借助标准物对照法辅助谱峰分析.结果表明,高温氧化SiO2/4H-SiC界面,类石墨碳较多,除Si1 成分外,还存在Si2 和Si3 两种低值氧化物.三种工艺处理后界面成分含量的对比,指出界面成分可通过合理工艺有效控制,以C-V测试曲线印证了界面成分减少对电学特性的改善.     

基于SoPC的自感知运动图像采集系统设计

设计一种基于SoPC技术的自感知运动图像采集系统.该系统通过在FPGA芯片上配置采集控制电路和动态检测电路,可以实时捕捉外界场景运动变化,实现无人值守情况下有选择地采集并保存数据.由于主要控制电路集成在一个FPGA芯片上,该系统具有体积小,功耗低,设计灵活,可扩展性好等优点.     

Ozone oxidation of 4H-SiC and flat-band voltage stability of SiC MOS capacitors

We investigate the effect of ozone (O₃) oxidation of silicon carbide (SiC) on the flat-band voltage (V_fb) stability of SiC metal-oxide-semiconductor (MOS) capacitors. The SiC MOS capacitors are produced by O₃ oxidation, and their V_fb stability under frequency variation, temperature variation, and bias temperature stress are evaluated. Secondary ion mass spectroscopy (SIMS), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) indicate that O₃ oxidation can adjust the element distribution near SiC/SiO₂ interface, improve SiC/SiO₂ interface morphology, and inhibit the formation of near-interface defects, respectively. In addition, we elaborate the underlying mechanism through which O₃ oxidation improves the V_fb stability of SiC MOS capacitors by using the measurement results and O₃ oxidation kinetics.     

Effects of wet-ROA on shallow interface traps of n-type 4H-SiC MOS capacitors

The effects of wet re-oxidation annealing （wet-ROA） on the shallow interface traps of n-type 4H-SiC metal oxide-semiconductor （MOS） capacitors were investigated by Gray-Brown method and angle-dependent X- ray photoelectron spectroscopy technique. The results present the energy distribution of the density of interface traps （Dit） from 0 to 0.2 eV below SiC conduction band edge （Ec） of the sample with wet-ROA for the first time, and indicate that wet-ROA could reduce the Dit in this energy range by more than 60%. The reduction in Dit is attributed to the reaction between the introduced oxygen and the SiOxCy species, which results in C release and SiOxCy transformation into higher oxidation states, thus reducing the SiOxCy content and the SiOxCy interface transition region thickness.     

石墨烯过渡层对金属/SiC接触肖特基势垒调控的第一性原理研究

由于SiC禁带宽度大,在金属/SiC接触界面难以形成较低的势垒,制备良好的欧姆接触是目前SiC器件研制中的关键技术难题,因此,研究如何降低金属/SiC接触界面的肖特基势垒高度(SBH)非常重要.本文基于密度泛函理论的第一性原理赝势平面波方法,结合平均静电势和局域态密度计算方法,研究了石墨烯作为过渡层对不同金属(Ag,Ti,Cu,Pd,Ni,Pt)/SiC接触的SBH的影响.计算结果表明,单层石墨烯可使金属/SiC接触的SBH降低;当石墨烯为2层时,SBH进一步降低且Ni,Ti接触体系的SBH呈现负值,说明接触界面形成了良好的欧姆接触;当石墨烯层数继续增加,SBH不再有明显变化.通过分析接触界面的差分电荷密度以及局域态密度,SBH降低的机理可能主要是石墨烯C原子饱和了SiC表面的悬挂键并降低了金属诱生能隙态对界面的影响,并且接触界面的石墨烯及其与金属相互作用形成的混合相具有较低的功函数.此外,SiC/石墨烯界面形成的电偶极层也可能有助于势垒降低.     

Passivation of carbon dimer defects in amorphous SiO_2/4H–SiC(0001) interface:A first-principles study

An amorphous SiO_2/4 H–Si C(0001) interface model with carbon dimer defects is established based on density functional theory of the first-principle plane wave pseudopotential method.The structures of carbon dimer defects after passivation by H_2 and NO molecules are established,and the interface states before and after passivation are calculated by the Heyd–Scuseria–Ernzerhof(HSE06) hybrid functional scheme.Calculation results indicate that H_2 can be adsorbed on the O_2–C = C–O_2 defect and the carbon–carbon double bond is converted into a single bond.However,H_2 cannot be adsorbed on the O_2–(C = C) –O_2 defect.The NO molecules can be bonded by N and C atoms to transform the carbon–carbon double bonds,thereby passivating the two defects.This study shows that the mechanism for the passivation of Si O_2/4 H–SiC(0001) interface carbon dimer defects is to convert the carbon–carbon double bonds into carbon dimers.Moreover,some intermediate structures that can be introduced into the interface state in the band gap should be avoided.