Improvement of Sige Relaxation by a New Clamping Film Deposition Process Method

SiGe has been widely used as stressors in source/drain (S/D) regions of Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) to enhance the carrier mobility of channel. However, relaxation of SiGe films led to less strain and the increase of hole mobility can not achieve expectations. In this paper, a method to prevent SiGe relaxation is provided. The method, which we call clamping film deposition process (CFD), consists of two parts: the common germanium concentration gradient down step is used to eliminate the lattice constant mismatch between films, while the low temperature silicon film deposition is used to eliminate the thermal mismatch between SiGe and silicon cap. The CFD can completely solve the problem of SiGe relaxation. Compared to common SiGe film deposition, the device performance is greatly improved ($\sim 8$%) by this process, pattern wafer yield is baseline level. And this method is compatible with more advanced GAA process.