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

Charge to breakdown Q
BD
has been used to evaluate the quality of thin gate oxides for some time. It is well known that the Q
BD
of 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
Q_{BD} \propto \exp (-A(T)t)
where t is annealing time, T is annealing temperature, and A is the "rate constant" for the Q
BD
degradation. 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 Q
BD
during short annealing time which may be related to the relaxation of built-in stress induced during the oxidation process.