Interplay of voltage and temperature acceleration of oxide breakdown for ultra-thin gate oxides

In this work, we resolved several seemingly conflicting experimental observations regarding temperature dependence of oxide breakdown in the context of change of voltage acceleration factors with reducing voltages. It is found that voltage acceleration factor is temperature dependent at a fixed voltage while voltage acceleration factors are temperature independent at a fixed T-BD. We unequivocally demonstrated that strong temperature dependence of time(charge)to-breakdown, T-BD(Q(BD)), observed on ultra-thin gate oxides (<5 nm) is not a thickness effect as previously suggested. It is a consequence of two experimental facts: (1) voltage-dependent voltage acceleration and (2) temperature-in dependent voltage acceleration at a fixed T-BD window. For the first time, time-to-breakdown at low temperature of -50 degreesC is reported. It is found that Weibull slopes are insensitive to temperature variations using accurate area-scaling method. The stress-induced leakage current (SILC) was used as a measure of defect-generation rate and critical defect density to investigate its correlation with the directly measured breakdown data, Q(BD)(T-BD). The comprehensive and statistical measurements of SILC at breakdown as a function of temperature are presented in detail for the first time. Based on these results, we conclude that SILC-based measurements cannot adequately explain the temperature dependence of oxide breakdown. Finally, we provide a global picture for time-to-breakdown in voltage and temperature domains constructed from two important empirical relations based on comprehensive experimental database. (C) 2002 Published by Elsevier Science Ltd.