An Extreme Surface Proximity Push for Embedded SiGe in pMOSFETs Featuring Self-Aligned Silicon Reflow

Abstract

This letter proposes a novel process to modulate the distance, or proximity, between the tip of embedded silicongermanium (e-SiGe) and the channel region in pMOSFETs. Traditionally, sophisticated etching treatment is adopted in a spacer structure; however, process-induced variation in the e-SiGe proximity may lead to serious variation in pMOSFET performance. In this letter, an extremely close proximity is achieved using selfaligned silicon reflow (SASR) in hydrogen ambient. As opposed to conventional approaches which have e-SiGe proximity determined by spacer width, the tip of e-SiGe with SASR can be positioned flush with the gate edge, as corroborated by both the TEM analyses and TCAD simulation. A significant improvement in pMOSFET performance is also measured.