Insertion of nanocrystalline diamond film and the addition of hydrogen gas during deposition for adhesion improvement of cubic boron nitride thin film deposited by unbalanced magnetron sputtering method

Abstract

Cubic boron nitride (c-BN) thick film growth was attempted by the addition of hydrogen for residual stress reduction and by using a nanocrystalline diamond (NCD) buffer layer for stabilizing the turbostratic boron nitride interfacial layer. The c-BN films were deposited by the unbalanced magnetron sputtering method. Thin (100μm) Si strips (3×40mm2) were used as substrates. A boron nitride target was used, which was connected to a radio frequency power supply at 400W. High frequency power connected to a substrate holder was used for self-biasing of −40V. The deposition pressure was 0.27Pa with a flow of Ar (18sccm)–N2 (2sccm) mixed gas. Hydrogen gas of 2sccm was added to the Ar–N2 mixed gas. The effect of the addition time of the hydrogen to the Ar–N2 gas during deposition was investigated and found to be critical to the occurrence of the delamination of the c-BN film on the NCD buffer layer. As the addition of the hydrogen was delayed, the delamination started later. C-BN film of 3μm thickness adherent to the substrate was obtained.