Constant bias-temperature and constant charge-temperature agings for silicon oxide films of MOS devices

Abstract

Effects of the conventional constant bias-temperature aging and newly reported constant charge-temperature aging on the silicon oxide films of MOS devices are theoretically and experimentally compared. Under the positive field condition, it is found that the movement of mobile ionic charges is different between these agings. In constant bias-temperature aging there appears an increasing peak electric fieldE _P at the SiO₂-Si interface and a constant gate voltageV _G during aging, while in constant charge-temperature aging there appears a constantE _p and a decreasingV _G .The time dependencies of the flatband voltageV _FB for both cases are consistent with the experimental results. Under the negative field condition, the trapping of the holes from Si into SiO₂ is important. It is found that the variation of the electric fieldE _i at the SiO₂-Si interface depends strongly on the aging method. An aging with constantE _i excludes the field variation effect during annealing, and can be achieved by the successive charge-temperature technique. Experimental results of these agings are given for comparison.