The Deposition of Cubic Boron Nitride Fillms by Ion Beam Assisted Sputter Deposition

The relationship between film properties and assisting ion beam parameters such as the ion-to-atom arrival ratio, the mean energy transfer or the mean momentum transfer to a depositing atom has been established with a new method. We have made use of a focused assisting ion beam which generates zones of locally varying current densities on the film surface. By mapping these and the deposition rate, and measuring film properties as function of surface coordinates, we can determine their relationship from few samples. The: advantage is that the number of deposition runs can considerably be reduced, and errors can be avoided which may originate from slightly different deposition conditions (pressure, temperature, gas flow etc.) in different deposition runs.

This method has been applied to establish the relationship between the cubic phase formation of a boron nitride film and various assisting beam parameters. The BN films were characterized by transmission FTIR spectroscopy. The spectra were evaluated by fitting the absorption lines to Gaussian functions. The experiments show that the momentum transferred to a depositing atom is the relevant control parameter for the formation of the cubic phase and that a threshold exists at 250 (eV.amu)^1/2 above which the cubic phase is synthesized in accordance with results obtained by Kester and Messier. Below this threshold a small fraction of c-BN was also observed.