SiGe SOI p-MOSFET在高频、高速、低功耗、抗辐射方面具有极大的优势。但二氧化硅埋层较低的热导率以及SiGe材料较低的热稳定性,使器件内部自加热效应的减弱或消除成为提高器件温度特性的关键因素。对应变SiGe SOI p-MOSFET温度特性机理进行研究,给出了三种缓解MOS-FET器件内部自加热效应的结构,并对其效果进行对比分析。结果表明:DSOI结构不适宜于低压全耗尽型SOI器件;Si3N4-DSOI结构对自加热的改善幅度较小;Si3N4埋层结构效果最好,尤其在低温领域改善更为明显。
This paper analyses the reverse recovery characteristics and mechanism of SiGeC p-i-n diodes. Based on the integrated systems engineering （ISE） data, the critical physical models of SiGeC diodes are proposed. Based on heterojunction band gap engineering, the softness factor increases over six times, reverse recovery time is over 30% short and there is a 20% decrease in peak reverse recovery current for SiGeC diodes with 20% of germanium and 0.5% of carbon, compared to Si diodes. Those advantages of SiGeC p-i-n diodes are more obvious at high temperature. Compared to lifetime control, SiCeC technique is more suitable for improving diode properties and the tradeoff between reverse recovery time and forward voltage drop can be easily achieved in SiGeC diodes. Furthermore, the high thermal-stability of SiGeC diodes reduces the costs of further process steps and offers more freedoms to device design.
A novel structure of ideal ohmic contact p^＋ （SiGeC）-n^- -n^＋ diodes with three-step graded doping concentration in the base region is presented, and the changing doping concentration gradient is also optimized. Using MEDICI, the physical parameter models applicable for SiGeC/Si heterojunction power diodes are given. The simulation results indicate that the diodes with graded doping concentration in the base region not only have the merit of fast and soft reverse recovery but also double reverse blocking voltage,and their forward conducting voltage has dropped to some extent,compared to the diodes with constant doping concentration in the base region. The new structure achieves a good trade-off in Qs-Vf-Ir ,and its combination of properties is superior to ideal ohmic contact diodes and conventional diodes.
