On the Polarity Dependence of Oxide Breakdown in MOS-Devices with N+ and P+ Polysilicon Gate

In this paper the influence of polarity and polysilicon gate doping type on time-to- breakdown (tBD) and charge-to-breakdown (QBD) is investigated. The anode hole injection model is used in order to describe the field dependence of tBD and QBD. For n-type gate (positive and negative gate voltage) and p-type gate at positive gate voltage no significant difference is found: tBD and QBD data can be well explained with the same model parameters. In the case of p-type gate with negative polarity ( gate injection) a significant difference is observed: at the same oxide field tBD is larger while QBD is lower. The larger tBD is explained by the occurrence of valence band injection from the p-type gate. One possible reason for the lower QBD is believed to be the higher hole generation coefficient for valence band injection.