Threshold voltage instability of MOS field effect transistors

Abstract

This paper presents the results of accelerated life tests performed on p-channel enhancement mode MOSFETs, the test conditions being storage at 140°C, with and without gate bias. It is observed that with positive gate bias, | V T | drifts upwards, and with negative gate bias also, the | V T | drift is upwards at least after a hundred hours. In the latter case, the augmentation of positive ion density in the oxide regions near the oxide-semiconductor interface is postulated, and the results presented are explained in terms of this postulation.