HF-Last Wet Clean in Combination with a Low Temperature GeH<sub>4</sub>-Assisted HCl <i>In Situ</i> Clean Prior to Si<sub>0.8</sub>Ge<sub>0.2</sub>-on-Si Epitaxial Growth

Epitaxial growth requires a clean starting surface for the growth of a high-quality crystalline layer. For epitaxy on Si, an HF-last wet clean followed by an in-situ high-temperature hydrogen bake is the reference pre-epi clean sequence to obtain an oxygen-free surface [1, 2]. The temperature required to remove all residual oxygen also makes the surface atoms mobile, resulting in reflow. The high temperatures used during the H 2 -bake can also result in intolerable doping profile changes. A lower temperature pre-epi clean sequence is required to avoid this reflow, especially when moving away from Si. In addition the high temperatures needed during a H 2 -bake would result in the relaxation of high mobility channels, e.g. strained Si 1-x Ge x or III-V materials [3]. Several low temperatures pre-epi cleaning solutions have been proposed in the past, e.g. GeH 4 -assisted H 2 -bake [4] or more recently, a GeH 4 -assisted HCl clean [5]. In this study we looked at the interaction between HF-last wet clean and the in-situ GeH 4 -assisted HCl clean prior to Si 0.8 Ge 0.2 -on-Si epitaxy.