Comparison of interface trap measurements in high field stressed MOS transistors

Abstract

The effects of high field stress on interface trap densities (Dit in MOS transistors are compared using three methods: charge-pumping, subthreshold swing and 1/f noise. The experimental MOS devices subjected to high field stress originated from two wafer lots processed with different concentrations of copper in the buffered oxide etchant. For the charge-pumping and subthreshold methods, no dependency is found on stress current polarity, wafer lot or transistor type (n- or p-channel). These two methods yield similar Dit values. For the 1/f noise method, no dependency is found on current polarity or wafer lot. However, the noise in the n-channel devices increases by several orders of magnitude as compared to the p-channel devices. A large discrepancy is found between Dit calculated from 1/f noise when compared to charge-pumping/subthreshold swing results for n-channel transistors. For p-channel transistors, the 1/f Dit results are in much better agreement with the results of the other two methods.