Selective deposition of amorphous silicon for formation of nickel silicide with smooth interface on N-doped substrate

Abstract

A nickel silicide layer is formed on a semiconductor device having a crystalline silicon source/drain region doped with arsenic. Arsenic is doped into the crystalline silicon, by implantation, for example, so that the concentration of arsenic is slightly below the surface of the silicon. Annealing restores the crystalline structure of the silicon after implantation of the arsenic. Amorphous silicon is selectively deposited over the source/drain regions and over the top of the gate electrode. Nickel is deposited over the entire semiconductor device and a second anneal reacts the nickel with the amorphous silicon. The second anneal is timed so that the nickel reacts with the amorphous silicon, and does not substantially react with the silicon source/drain regions containing arsenic. Preventing the nickel from substantially reacting with the silicon source/drain regions containing arsenic provides a smooth interface between the resulting nickel silicide and the silicon source/drain regions doped with arsenic.

Dependencies are inferred from the claim text.