Mushroom-Free Selective Epitaxial Growth of Si, SiGe and SiGe:B Raised Sources and Drains on FD-SOI MOSFETs

Heavily chlorinated chemistries deliver the selectivity (versus Si₃N₄ sidewall spacers) which is required to grow Si or SiGe(:B) raised sources and drains (RSDs) on each side of n-type and p-type fully depleted-silicon on insulator MOSFETs. We are however faced with the formation of mushrooms that use as seeds the poly-Si layers sitting on top of unprotected gates (by for instance a SiO₂ hard mask). Those mushrooms will hamper ion implantation close to the channel (and merge for dense devices such as Static Random Access Memory cells), as illustrated in Figure 1 for 23 nm thick Si raised sources and drains grown at 750°C, 20 Torr with SiH₂Cl₂ + HCl (J. Cryst. Growth 280, 530 (2005)).