Influence of oxygen on the growth of cubic boron nitride thin films by plasma-enhanced chemical vapour deposition

Cubic boron nitride thin films were deposited on siliconsubstrates by low-pressure inductively coupled plasma-enhancedchemical vapour deposition. It was found that the introduction ofO₂ into the deposition system suppresses both nucleation andgrowth of cubic boron nitride. At a B₂H₆ concentration of2.5% during film deposition, the critical O₂ concentrationallowed for the nucleation of cubic boron nitride was found to beless than 1.4%, while that for the growth of cubic boron nitridewas higher than 2.1%. Moreover, the infrared absorption peakobserved at around 1230--1280~cm^-1, frequently detected forcubic boron nitride films prepared using non-ultrahigh vacuumsystems, appears to be due to the absorption of boron oxide, acontaminant formed as a result of the oxygen impurity. Therefore,the existence of trace oxygen contamination in boron nitride filmscan be evaluated qualitatively by this infrared absorption peak.