Pressure dependence of the negative bias voltage for stabilization of cubic boron nitride thin films deposited by sputtering

Thin films of boron nitride were deposited by unbalanced magnetron sputtering at pressures between 0.065 and 1.32 Pa in order to study the effects of pressure and negative substrate bias on the energy of the bombarding plasma ions and subsequent stabilization of the cubic phase. It was found that the threshold bias voltage for nucleation of films with a high percentage of the cubic phase increases with the product of the pressure and sheath thickness. This trend is explained in terms of the changes in the average energy of the particles bombarding the growing film produced by pressure-dependent charge-exchange collisions in the plasma/substrate sheath. This energy modification process has predictable consequences in complex deposition processes. (C) 1998 American Institute of Physics. [S0003-6951(98)02920-9].