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We have systematically investigated the effects of strain on the gate oxide reliability, using biaxially strained Si MOSFETs, to elucidate their physical origins. It was found that the time-dependent dielectric breakdown reliability was significantly improved in strained Si nMOSFETs but was slightly degraded in strained Si pMOSFETs. These observations could be well explained by the strain-induced modulation of the gate current, resulting from band-structure modulation in the channels. It was also found that negative bias temperature instability was degraded in the strained Si pMOSFETs. This fact was attributable to the strain-induced enhancement of hole tunneling probability and hole wave function penetration into Si-H bonding states near the MOS interface, which could enhance Si-H bond breaking.
Date of Publication: Nov. 2008