Diffusion barrier properties of tungsten nitride films grown by atomic layer deposition from bis(<i>tert</i>-butylimido)bis(dimethylamido)tungsten and ammonia

Abstract

Highly uniform, smooth, and conformal coatings of tungsten nitride (WN) were synthesized by atomic layer deposition (ALD) from vapors of bis(tert-butylimido)bis(dimethylamido)tungsten and ammonia. The films are shiny, silver colored, and electrically conducting. The films were amorphous as deposited. 100% step coverage was obtained inside holes with aspect ratios greater than 40:1. WN films as thin as 1.5 nm proved to be good barriers to diffusion of copper for temperatures up to 600 °C. Annealing for 30 min at temperatures above 725 °C converted the WN to pure, polycrystalline tungsten metal. ALD of copper onto the surface of the WN produced strongly adherent copper films that could be used as “seed” layers for chemical vapor deposition or electrodeposition of thicker copper coatings.