Strain Engineering for Enhanced P-channel Field Effect Transistor Performance

Abstract

This thesis work focuses on strain engineering for p-channel transistors. A new process technology for increasing strain and performance level in a p-channel field effect transistor by increasing Germanium content in SiGe source/drain (S/D) was demonstrated. This process involves laser-induced local melting and intermixing of a Ge layer with an underlying Si0.8Ge0.2 S/D region, leading to a graded SiGe S/D stressor with significant increase in the peak Ge content. A drive current enhancement was achieved with this process.Furthermore, a new device structure employing a reverse embedded Silicon-Carbon (Si:C) stressor under the transistor channel is also investigated. Process concerns and issues are addressed.Incorporation of Sn was investigated to relief the undesirable tensile strain caused by supersaturated boron doping in S/D. This Sn strain compensation implant was also found to enhance boronb s thermal stability, and improves the retention of highly-activated and metastable boron through a local strain compensation effect.