Characteristics of aluminum substitution technology for self-aligned full metal gate nMOSFETs

We investigated self-aligned metal gate MOSFETs that feature an ideal low-resistance aluminum gate using aluminum substitution technology (AST). This technology can be used to fabricate metal gate MOSFETs with submicrometer gate lengths and 1.8-nm-thick gate insulators processed at 350 degrees C. We found that AST is especially suitable for MOSFET with short gate lengths, because the aluminum substitution is accelerated under gate lengths of 0.1-mu m. We will explain the aluminum substitution phenomenon based on the counter diffusion between aluminum and silicon and the capillary effect. We will also show the electric properties of full metal gate nMOSFET produced using AST with a 60-nm gate length.