Titanium silicide/germanide formation on submicron features for high mobility SiGe channel field effect transistors

Abstract

The formation of self-aligned Ti(Si_(1−x)Ge_(x))₂ on submicron lines is described. The silicide/germanide is formed by reacting sputtered Ti with epitaxially grown Si_(1−x)Ge_(x) of composition and thickness relevant to high mobility Si_(1−x)Ge_(x) channel field effect transistors. Ti(Si_(1−x)Ge_(x))₂ formation on narrow lines was carried out on phosphorous doped material, because of the well known difficulties of forming silicide on heavily n-doped silicon. A companion set of boron doped blanket films was also processed. The results show that the process temperature required for the minimization of silicide/germanide sheet resistance is reduced as compared to silicide formation on Si alone. However, the silicide/germanide films agglomerate with increased high temperature processing more easily than pure silicide. The thermal stability is degraded more for films with higher Ge content and is a strong function of dopant type. Silicide/germanide formation on phosphorous doped Si_(1−x)Ge_(x) layers with x = 10% have a line width dependence similar to silicide formation. Formation on phosphorous doped Si_(1−x)Ge_(x) layers with x = 27% display an inverse line width dependence, with higher overall sheet resistance. Formation of silicide/germanide on blanket films of boron doped Si_(1−x)Ge_(x) with x = 27% behaved similar to the formation of silicide on silicon.