Characterization of Epitaxial Si:C:P and Si:P Layers for Source/Drain Formation in Advanced Bulk FinFETs

Uniaxial stressors have received much interest over the last few years as a method to enhance carrier mobility and, hence, drive current with minimal modification to the structure of the transistor. However, the shift in device design to complex structures with multiple crystallographic orientations like advanced bulk-FinFETs has significantly complicated the incorporation of mobility enhancing stressors. For the n-FinFET in particular, it turns out that the crystal quality and growth rate of Si:P and Si:C:P films can be strongly dependent upon the crystallographic orientation of the starting surface. Both for raised and recessed epi we find that formation of (111) facets and twin defects occurs already after a limited growth on the fin. Besides the growth on raised and recessed fins, we also discuss the resistivity increase in Si: C: P layers as a function of carbon content and demonstrate that laser annealed Si: P films with high phosphorus content (e.g. 4% or higher) can be considered as potential alternatives to Si:C:P with a lower resistivity for the same strain.