Effects of discharge power for magnetron sputter deposition of boron carbide films on tilted substrates

Abstract

High-rate growth of B4C films with low residual stress and nodular defect density remains a challenge. Here, we use a 75-mm-diameter full-face erosion magnetron source operated in the direct-current mode and systematically study how changing the deposition rate, controlled by adjusting the average plasma discharge power in a wide range of 100–2000 W, affects the microstructure and key properties of B4C films deposited on tilted planar substrates with tilt angles in the range of 0°–90°. Results show that the deposition rate close-to-linearly increases with increasing discharge power, peaking at 9 μm/h for 2000 W, with no evidence of gas rarefaction effects. All films are x-ray amorphous and columnar. In the oblique angle deposition regime, the column tilt angle increases with increasing discharge power, attributed to higher adatom mobility. The size and density of nodular defects decrease and oxygen content and porosity increase with increasing substrate tilt at constant discharge power. With increasing discharge power above 500 W for constant film thickness, the nodule density increases, while the average nodule diameter remains constant, suggesting increased nucleation and constant growth of nodular defects. All films have relatively low residual stress of <0.4 GPa. However, residual stress exhibits a complex dependence on both discharge power and substrate tilt, attributed to the impact of these parameters on the film microstructure.