Impact of low-energy ions on plasma deposition of cubic boron nitride

Plasma deposition of cubic boron nitride (cBN) films under low-energy (a few eV to ~ 40 eV) ion impact with the chemistry of fluorine is studied in terms of ion energy, ion flux, and ion to boron flux ratio onto the substrate. The ion energy and the ion to boron flux ratio are determined from the sheath potential and the ratio of incident ion flux to net deposited boron flux, respectively. For negative substrate biases where a mixture of turbostratic and amorphous BN phases only or no deposit is formed, both the ion energy and the ion to boron flux ratio are high. For positive substrate biases where cBN phase is formed, the ion energy and the ion to boron flux ratio are in the range of a few eV to 35 eV and 100 to 130, respectively. The results indicate that the impact of positive ions with high ion to boron flux ratios makes a substantial contribution to the formation of cBN phase, while that of negative ions and electrons makes only a minor contribution.