Titanium polycide stabilization with a porous barrier

Abstract

A 'porous barrier' is formed without formation of a discrete barrier layer by enriching grain boundaries of a body of polysilicon with nitrogen to inhibit thermal mobility of silicon species therealong. In a polycide gate/interconnect structure, the reduced mobility of silicon suppresses agglomeration of silicon in a metal silicide layer formed thereon. Since silicon agglomeration is a precursor of a polycide inversion phenomenon, polycide inversion which can pierce an underlying oxide and cause device failure is effectively avoided. The increased thermal stability of polycide structures and other structures including a body of polysilicon thus increases the heat budget that can be withstood by the structure and increases the manufacturing process window imposed by the presence of polysilicon which can be exploited in other processes such as annealing to develop a low resistance phase of refractory metal silicide included in the polycide structure, drive-in annealing for formation of source/drain regions of field effect transistors and the like.