The effects of certain process variables on the grain size, grain type, and microhardness of vapor-dt(osited tungsten were established, and the near-optimum parameters and the efficacy of the vapor deposition process were determined. No significant change in the grain size or microstructure resulted from ultrasonic vibration of the substrate during deposition, from variations in the hydrogen (h2) to tungsten hexafluoride (wf6) ratio, or from small increases in reaction chamber pressure. Near-optimum conditions were continuous deposition at atmospheric pressure, a deposition rate of 2 mils thickness per square inch of substrate area per hour, a temperature of 550 deg. C, and a hydrogen to wf6 ratio of 4:1. The addition, individually, of about 2 vol-pct of butane, 24 vol-pct of carbon dioxide, or 4 vol-pct of propane to the hydrogen and wf6 mixture produced deposits with the finest grain size for each gas. A corresponding increase in microhardness accompanied the decrease in grain size. The addition of these gases did not alter the columnar microstructure found in vapor-deposited tungsten.
Electrodeposition and Surface Treatment, Elsevier Sequoia S.a., Lausanne, Switzerland, 1973/74