Polarity dependence of charge trapping in poly-silicon gate HfO/sub 2/ MOSFETs

Polarity dependence of charge trapping in poly-Si gate HfO/sub 2/ MOSFETs has been systematically studied. It is shown that both the stress-induced threshold voltage shift (/spl Delta/V/sub th/) and the transconductance degradation (/spl Delta/G/sub m/) are worse in nMOSFETs than in pMOSFETs. For substrate injection in nMOSFETs, electron trapping occurs at the n-poly/HfO/sub 2/ interface and/or in bulk HfO/sub 2/, whereas for gate injection in pMOSFETs hole trapping near the Si substrate is observed. These results strongly suggest the poly-Si/HfO/sub 2/ interface should play an important role in hot carrier induced degradation in HfO/sub 2/ gated nMOSFETs.