Time-dependent degradation of thin gate oxide under post-oxidation high-temperature anneal

Charge to breakdown QBDhas been used to evaluate the quality of thin gate oxides for some time. It is well known that the QBDof a thin oxide degrades with subsequent high-temperature thermal cycles. This paper reports on the time-dependent degradation of an 80-Å gate oxide at various post-oxidation annealing temperatures. An empirical relation was obtained as where t is annealing time, T is annealing temperature, and A is the "rate constant" for the QBDdegradation. An Arrhenius plot of A versus 1/T yields an activation energy in the range of 6-7 eV. Also reported is the observation of an increase in QBDduring short annealing time which may be related to the relaxation of built-in stress induced during the oxidation process.