Comprehensive low-frequency and RF noise characteristics in strained-Si NMOSFETs

Abstract

Due to the mobility enhancement of strained-Si channels, the strained-Si MOSFET has reportedly a great improvement in DC characteristics. The improvement in the cut-off frequency ( f/sub T/) of strained-Si devices is demonstrated in this work. The strained-Si device has the same flicker noise (1/f) as the control Si device as long as no threading dislocation exists in the channel and the thermal budget is properly controlled. The large defect density in the relaxed SiGe buffer layers shows no effect on the flicker noise. The threading dislocation penetrating into the strained-Si channel and Ge outdiffusion can degrade the flicker noise of strained-Si NMOSFETs. A thicker strained-Si channel layer can reduce the roughness scattering from the underlying strained Si/relaxed SiGe heterojunction, and yields a higher mobility, higher f/sub T/, and lower noise figures, as compared to the thin strained-Si channel.