N型LDMOS器件在关态雪崩击穿条件下的退化

针对功率开关管在未箝位电感性开关转换时会反复发生雪崩击穿,引起器件参数退化的问题,对一种20 V N型横向双扩散MOS器件(NLDMOS)在关态雪崩击穿条件下导通电阻的退化进行研究.通过恒定电流脉冲应力测试、TCAD（technology computer aided design）仿真和电荷泵测试,分析研究导通电阻退化发生的区域及退化的微观机理,并针对实验结果提出2种退化机制：(1) NLDMOS漂移区中的空穴注入效应,这种机制会在器件表面产生镜像负电荷,造成开态导通电阻Ron的减少；(2)漂移区中的表面态增加效应,这种机制会造成载流子迁移率的下降,引起Ron的增加.这2种机制都随着雪崩击穿电流的增加而增强.

Off-state avalanche breakdown induced degradation in NLDMOS devices

Degradation behaviors of 20 V NLDMOS operated under off-state avalanche breakdown condition were presented to study the reliability issue caused by repeatedly avalanche breakdown of the N-type lateral double diffusion MOS transistor（NLDMOS）under unclamped inductive switching. The on-resistance degradation region and micro-mechanism were investigated by the analysis of constant current pulse stress tests, technology computer-aided design (TCAD) simulation and charge pumping measurements. Two different degradation mechanisms are identified: (1) The positive oxide trapped charge accumulation effect in the N-type drift region induces the mirrored negative charges in the device surface, so the on-resistance decreases;(2)The surface states formation effect reduces the channel electron mobility, so the on resistance increases. The both mechanisms are enhanced with the increasing avalanche breakdown current.