Optimization of Imperfect Morphology for Selective Epitaxial Sige Growth

With advanced devices continuously scaling down, embedded SiGe in source and drain regions has been demonstrated to improve p-MOSFET device performance through hole mobility enhancement. However, as germanium and in-situ boron concentrations are required to increase simultaneously, the pattern loading effect of selective epitaxial growth of SiGe:B in recess sigma structure is enhanced after processes. Compared with logical areas, the SRAM areas show the imperfect morphology of SiGe:B growth, which becomes the major killer of the yield. In this paper, we investigate the effect of annealed SiN films as hard-mask layer and films of various thicknesses on the formation of SiGe growth in recess sigma structure. The formation mechanism of the imperfect morphology is analyzed, and the selective epitaxial SiGe growth is optimized to improve electrical properties.