A low temperature gate oxide process for n-channel SiGe modulation doped field effect transistors

Abstract

The implementation of a novel low temperature gate oxide to a n-channel SiGe modulation doped field effect transistor (MODFET) fabrication process is investigated. The approach is based on the thermal oxidation rate of sputtered a-Si being twice as high compared to c-Si, thus enabling self-aligned nm control in oxide growth at reduced temperatures (600 °C). The electrical characterization of metal-oxide-semiconductor (MOS)-gated MODFETs was used to check the device quality of the silicondioxide. The transconductance varies with the oxide thickness according to the expectations. Device modeling studies show how drawbacks (e.g., of a negative threshold voltage) can be eliminated to yield a practical high-performance MOS-gated SiGe MODFET with a largely improved gate swing.