Method for reducing pattern deformation and photoresist poisoning in semiconductor device fabrication

Abstract

A hardmask stack is comprised of alternating layers of doped amorphous carbon and undoped amorphous carbon. The undoped amorphous carbon layers serve as buffer layers that constrain the effects of compressive stress within the doped amorphous carbon layers to prevent delamination. The stack is provided with a top capping layer. The layer beneath the capping layer is preferably undoped amorphous carbon to reduce photoresist poisoning. An alternative hardmask stack is comprised of alternating layers of capping material and amorphous carbon. The amorphous carbon layers may be doped or undoped. The capping material layers serve as buffer layers that constrain the effects of compressive stress within the amorphous carbon layers to prevent delamination. The top layer of the stack is formed of a capping material. The layer beneath the top layer is preferably undoped amorphous carbon to reduce photoresist poisoning. The lowest layer of the hardmask stack is preferably amorphous carbon to facilitate easy removal of the hardmask stack from underlying materials by an ashing process.