Laser annealing of amorphous germanium on silicon-germanium source/drain for strain and performance enhancement in pMOSFETs

Abstract

We report the first demonstration of a novel germanium-enrichment process for forming a silicon-germanium (SiGe) source/drain (S/D) stressor with a high Ge content. The 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 a significant increase in the peak Ge content. Various laser fluences were investigated for the laser annealing process. The process is then successfully integrated in a device fabrication flow, forming strained silicon-on-insulator p-channel field-effect transistors (p-FETs) with a high Ge content in SiGe S/D. A drive current enhancement of ∼12% was achieved with this process, as compared to a strained p-FET with Si0.8Ge0.2 p-FETs. The IDsat enhancement, primarily attributed to strain-induced mobility improvement, is found to increase with decreasing gate lengths. © 2008 IEEE.