Dual-mask etch of dual-poly gate in cmos processing

Abstract

The invented method involves separately etching the P and N gate features in a dual-poly gate using dual masks, thereby permitting the etching recipes to be tuned to the differentially responsive P and N materials that form the gate. The method involves a) providing a polysilicon layer of a first type over a first region of a semiconductor substrate; b) providing a polysilicon layer of a second type over a second region of the semiconductor substrate; c) depositing a metallic layer overlying the polysilicon layers in the first and second regions; d) depositing an anti-reflective layer overlying the metallic layer in the first and second regions; e) selectively etching the dielectric hard-mask multi-layer film to form a patterned outer hard-mask multi-layer; f) forming a first photoresist pattern overlying the patterned outer hard-mask multi-layer in the first region; g) first etching the metallic layer and the polysilicon layer of the second type to form a stacked gate structure in the second region; h) forming a second photoresist pattern overlying the patterned outer hard-mask multi-layer in the second region; and i) second etching the metallic layer and the polysilicon layer of the first type to form a stacked gate structure in the first region. Preferably, the first photoresist pattern and the second photoresist pattern define a nominal boundary therebetween, with the patterns having a predefined gap therebetween in a region around the boundary. Alternatively, the dual-mask technique is used on a non-hardmask dual-poly film stack and the top dielectric multi-layer film is replaced by an anti-reflection coating (ARC) film.