Investigation of quasi-breakdown mechanism through post-quasi-breakdown thermal annealing

Abstract

Quasi-breakdown (QB) in thin gate oxide (45 A) is studied using post-QB thermal annealing and bipolar current stressing. It has been observed that there exist at least two different stages within quasi-breakdown differentiated by their electrical recoverability. Post-QB thermal annealing on oxides stressed to electrically recoverable QB stage shows significant recovery and reduction in the gate leakage current. When stressed to electrically unrecoverable QB stage however, no reduction in the gate leakage current can be observed by thermal annealing. Using low current stressing and post-QB thermal annealing, it is observed that the QB leakage current comprises of two components: an initial leakage current at the onset of QB (QB(threshold)) and an additional stress-induced QB leak-age current due to post-QB stressing. Carrier separation measurement on post-QB thermal annealed oxides shows that electrons are responsible for the QB(threshold) current while holes are mainly responsible for the stress-induced QB leakage current.