pMOS器件NBTI界面电荷引起耦合的数值模拟分析

Numerical Simulation of the Coupling of NBTI Interface Traps in pMOSFETs

从二维模拟pMOS器件得到沟道空穴浓度和栅氧化层电场,用于计算负栅压偏置温度不稳定性NBTI(Negative bias temperature instability)效应的界面电荷的产生,是分析研究NBTI可靠性问题的一种有效方法。首先对器件栅氧化层/硅界面的耦合作用进行模拟,通过大量的计算和已有的实验比对分析得出:当NBTI效应界面电荷产生时,栅氧化层电场是增加了,但并没有使界面电荷继续增多,是沟道空穴浓度的降低决定了界面电荷有所减少(界面耦合作用);当界面电荷的产生超过1012/cm2时,界面的这种耦合作用非常明显,可以被实验测出;界面耦合作用使NBTI退化减小,是一种新的退化饱和机制,类似于"硬饱和",但是不会出现强烈的时间幂指数变化。

Without any assumptions, the channel hole concentration and the gate oxide layer electric field are got from the 2D simulation of pMOSFETs, and used to calculate the interface charge generation of Negative Bias Temperature Instability （NBTI）. This is an effective method to study NBTI reliability. First all, gate oxide/silicon interface coupling is simulated and com- pared with the existing experimental data. The analysis results show that when the interface charge of NBTI is generated, the gate oxide layer electric field will be increased, but will not make the interface charge continuously increase, the interface charge will be decreased because the channel hole concentration is reduced （the interface coupling）. When the interface charge is generated more than 1012/cm2, the interface coupling is very obvious and could be measured. The interface coupling effect to reduce NBTI degradation is a kind of new degradation saturation mechanism, similar to the ＂hard saturation＂, but the strong time power index changes will not appear.