Chemical Vapor Deposition and Etch for Seamless W Gapfill

A novel tungsten (W) chemical vapor deposition and etch process was developed for improved W gapfill in via structures. While conventional conformal W deposition processes typically lead to void or seam formation, mostly resulting from excessive W surface roughness generated by a large W grain size, this new process provides a pathway towards eliminating voids and creating seamless W gapfill. A TaN/Ti/TiN metal liner stack and a thin conformal W layer were deposited into via features with an approximate width of 40 nm, and subsequently a W etch process was developed to allow modification of the shape and profile of the deposited W layer. Under certain W etch process conditions a tapered W layer was thus formed, which acted as a starting surface for an additional conformal W deposition process. Structural analysis by transmission electron microscopy revealed void-free W gapfill as a result of this sequential W deposition/W etch/W deposition process.