W and WC layers deposition by shielded inductively coupled plasma source

Abstract

Tungsten and carbon tungsten films have been deposited by a plasma enhanced chemical vapor deposition (PECVD) technique. The plasma-assisted deposition was performed by inductively coupled plasma source (ICP). A Faraday shield was arranged within the plasma chamber to prevent electrically conductive film deposition on the dielectric chamber wall that would screen the electromagnetic field. External electrical parameters and ion densities of the shielded inductive plasma source are measured and compared to classical ICPs source characteristics. Tungsten deposition has been performed from WF6 diluted in argon and hydrogen. A deposition rate of 5 μm/h was obtained. Hardness measurements show that the tungsten hardness can be increased from 5 to 20 GPA by biasing the substrate. WC films were deposited by adding methane or acetylene to the WF6/H2 mixture. The hardness of the WC films depends strongly on the methane or acetylene flow rate, i.e., on the film carbon content. The WC hardness has been correlated to the crystallographic structure. The first hardness maximum peak corresponds to a solid solution of carbon in the tungsten. Correlation between the deposition parameters, such as the gas composition, dc bias and coating properties has been investigated by means of AES, XRD, and nanoindentation analysis.