Selective NiGe wet etch for transistors with Ge body and/or Ge source/drain extensions

摘要

The wet etch stage of the salicide process normally used to fabricate polysilicon and silicon-based semiconductor transistors may not be appropriate for germanium-based transistors because the wet etch chemicals at such temperatures will dissolve the germanium leaving no source, gate, or drain for the transistor. In embodiments of the invention, nickel is blanket deposited over the source, drain, and gate regions of the germanium-based transistor, annealed to cause the nickel to react with the germanium, and wet etched to remove un-reacted nickel from dielectric regions (e.g., shallow trench isolation (STI) regions) but leave NiGe in the source, gate, and drain regions. The wet etch is a mild oxidizing solution at room temperature.