Nitride based sidewall spaces for submicron mosfets

Abstract

A transistor and a method for making a transistor are described. A silicon gate conductor is patterned over a gate dielectric upon a silicon substrate. Dopant impurity distributions self-aligned to the gate conductor may be introduced. Silicon nitride (“nitride”) spacers are formed adjacent to opposed sidewall surfaces of the gate conductor. Oxide caps are formed covering exposed outer surfaces of the nitride spacers. The oxide caps prevent dissociation of the nitride spacers during a subsequent pre-amorphization implant. A preclean is subsequently used to remove oxides from the surfaces of the gate conductor and semiconductor substrate. The preclean may also remove the oxide caps, but does not attack the nitride spacers. A salicide process is used to form low-resistance gate, source, and drain silicides. The presence of nitrogen in the nitride spacers is believed to help prevent dopant outdiffusion from adjacent silicon, prevent silicide bridging across spacers, and increase resistance of the spacers to oxide etchants.