Effectiveness of Si thin buffer layer for selective SiGe epitaxial growth in recessed source and drain for pMOS

Locally strained Si technology using embedded SiGe has been used to improve pMOSFET device performance through hole mobility enhancement. Embedded SiGe is achieved by selectively growing epitaxial SiGe film in recessed Si pMOSFET source and drain areas. Prior to selective SiGe epi growth, a thin layer of Si seed was employed to help nucleate following low-temperature selective SiGe epitaxial film in recessed source and drain areas. In combination with pre-epi wet clean and low-temperature chemical bake, use of Si seed resulted in improved SiGe film morphology and micro-loading effect, and further improved device performance.