Role of hydrogen anneal in thin gate oxide for multi-metal-layer CMOS process

This work investigated the impact of H/sub 2/ gas in the final annealing cycle of a 5-metal-layer CMOS process and its effect on MOS device behavior in the presence of Al/Ti metallization. The role of H/sub 2/ was evaluated with transistor electrical testing and with gate-oxide stressing, namely, bias-temperature and hot-carrier injection. Both electrical testing and stressing data showed no difference in device behavior when different external H/sub 2/% was used. However, some differences in PMOSFET bias-temp were observed when the annealing cycle was totally eliminated. Moreover, some differences were observed for devices with different metal coverage. This paper details the results and proposes a model to explain the observations.