Air break for improved silicide formation with composite caps

Abstract

Disclosed is a structure and method for tuning silicide stress and, particularly, for developing a tensile silicide region on a gate conductor of an n-FET in order to optimize n-FET performance. More particularly, a first metal layer-protective cap layer-second metal layer stack is formed on an n-FET structure. However, prior to the deposition of the second metal layer, the protective layer is exposed to air. This air break step alters the adhesion between the protective cap layer and the second metal layer and thereby, effects the stress imparted upon the first metal layer during silicide formation. The result is a more tensile silicide that is optimal for n-FET performance. Additionally, the method allows such a tensile silicide region to be formed using a relatively thin first metal layer-protective cap layer-second metal layer stack, and particularly, a relatively thin second metal layer, to minimize mechanical energy build up at the junctions between the gate conductor and the sidewall spacers to avoid silicon bridging.