Formation of high resistivity phases of nickel silicide at small area.

Nickel silicide phases of Ni3Si2 on n+ and NiSi2 on p+ active area or poly gate with high resistivity are formed in small silicide area. The conditions for these phase formations are the same as NiSi formation in large silicide area. These high resistivity phases deteriorate sheet resistance uniformity of nickel silicide. The formation of these phases strongly depends on silicide area rather than the silicide width. The formation of these high resistivity phases at small area must be related to interface energy increase by boundary area. Tensile or compressive stress from implanted impurities, silicide formation and STI might affect the formation of NiSi2 or Ni3Si2, respectively.