Radial microstructural nonuniformity of boron nitride films deposited on a wafer scale substrate by unbalanced magnetron sputtering

Abstract

The nonuniform deposition behavior of boron nitride (BN) films, which is governed by the natural gradient of plasma density, was examined by investigating their microstructure and phase formation. The BN films were deposited on a 10 cm diameter, negatively self-biased Si wafer via unbalanced magnetron sputtering. At a bias voltage of −160 V, where only a turbostratic BN (tBN) film formed, the (0002) hexagonal BN laminates composing the film were aligned normal to the substrate. However, their degree of alignment tended to decrease as their distance from the substrate center increased. At a bias voltage of −220 V, a cubic BN film formed at the center of the substrate, while a tBN film formed on the periphery. These two deposition behaviors were attributed to the bombarding ion flux gradient inherent in the plasma used in sputtering.