A comparative study of hot-carrier instabilities in p- and n-type poly gate MOSFETs

The effects of p-type poly-Si gates on the hot-carrier instability of 7-nm oxides are investigated using uniform hot-electron injection from a buried junction injector (BJI) and channel-hot-carrier stress. From BJI experiments, electron trapping (instead of oxide trap generation) and interface state generation are shown to be the major effects of hot-electron injection. Electron trapping and interface state generation are found to be similar in p- and n-type poly-Si gated n-MOSFETs. From the results on channel-hot-carrier stress on surface-channel n- and p-channel MOSFETs, it was also found that the channel-hot-carrier instabilities of p- and n-type poly-Si gated MOSFETs are comparable. These results indicate that electron trapping, instead of oxide trap generation, becomes a major concern when the oxide thickness is scaled down, and p-type poly-Si gate can be used in scaled CMOS technologies without degrading the hot-carrier induced oxide instability.