Ge outdiffusion effect on flicker noise in strained-Si nMOSFETs

The flicker noise characteristics of strained-Si nMOSFETs are significantly dependent on the gate oxide formation. At high temperature (900 °C) thermal oxidation, the Si interstitials at the Si/oxide interface were injected into the underneath Si-SiGe heterojunction, and enhanced the Ge outdiffusion into the Si/oxide interface. The Ge atoms at Si/oxide interface act as trap centers, and the strained-Si nMOSFET with thermal gate oxide yields a much larger flicker noise than the control Si device. The Ge outdiffusion is suppressed for the device with the low temperature (700 °C) tetraethylorthosilicate gate oxide. The capacitance-voltage measurements of the strained-Si devices with thermal oxide also show that the Si/oxide interface trap density increases and the Si-SiGe heterojunction is smeared out due to the Ge outdiffusion.