This letter proposes a novel process to modulate the distance, or proximity, between the tip of embedded silicon-germanium (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 self-aligned 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.
Lin, D. W., Liang, C. C., Chen, M-J., & Wu, C-C. (2010). An Extreme Surface Proximity Push for Embedded SiGe in pMOSFETs Featuring Self-Aligned Silicon Reflow. IEEE Electron Device Letters, 924-926. https://doi.org/10.1109/LED.2010.2056350