Post tungsten etch back anneal, to improve aluminum step coverage

摘要

A process has been developed in which an aluminum based, interconnect structure overlies a tungsten plug structure, in a small diameter contact hole. The tungsten plug is formed via RIE removal of unwanted tungsten, from areas other then the contact hole using a halogen containing etchant, and using a RIE overetch cycle that created an unwanted crevice in the center of the tungsten plug. A post RIE anneal, in a nitrogen ambient removes moisture from surrounding dielectric layers and also forms a protective, nitrogen containing tungsten layer, filling the crevice in the tungsten plug. The filling of the crevice allows a planar overlying aluminum based, interconnect structure to be obtained.