Thermal atomic layer deposition of tungsten carbide films from WCl6 and AlMe3

Abstract

The atomic layer deposition (ALD) of tungsten carbide films is described with a thermal process employing WCl6 and AlMe3 as precursors. WCl6 has not been previously reported as an ALD precursor. Furthermore, WCl6 has favorable precursor characteristics and advantages over the widely used WF6, which is corrosive and toxic. The process displays an ALD window between 275 and 350 °C and a high growth rate of 1.5–1.8 Å/cycle within the ALD window. High purity tungsten carbide films with low Al and Cl contaminants were deposited at 300 °C. Film resistivities decreased with increasing growth temperature, reaching a minimum value of 1500 μΩ cm at 375 °C. The as-deposited films are amorphous, which could indicate superior performance as a Cu diffusion barrier over previously studied polycrystalline tungsten carbide barrier layers.