Microstructural properties of plasma-enhanced chemical vapor deposited WNx films using WF6–H2–N2 precursor system

Abstract

A WF 6 –H 2 –N 2 precursor system was used for plasma-enhanced chemical vapor deposition (PECVD) of WN x films. We examined the microstructural changes of the WN x films depending on N 2 /H 2 flow-rate ratio and post-annealing (600–800 °C for 1 h). As the N 2 /H 2 flow rate was increased from 0 to 1.5, as-deposited WN x films exhibited various different crystalline states, such as nanocrystalline and/or amorphous structure comprising W, WN, and W 2 N phases, a fine W 2 N granular structure embedded in an amorphous matrix, and a crystalline structure of β-W 2 N phase. After post-annealing above 600 °C, crystalline recovery with phase separation to β-W 2 N and α-W was observed from the WN x films deposited at an optimized deposition condition (flow-rate ratio = 0.25). From this PECVD method, an excellent step coverage of ∼90% was obtained from the WN x films at a contact diameter of 0.4 μm and an aspect ratio of 3.5.