The effects of substrate bias on phase stability and properties of sputter-deposited tungsten carbide

Abstract

The effects of substrate bias on phase formation and physical properties of rf magnetron sputter-deposited tungsten carbide films have been investigated in this work. Films were deposited at 275 °C using bias levels ranging from 0 to −150 V and at room temperature and −160 V. At low bias levels, the films were primarily composed of the WC 1− x /W 2(C,O) phases, both of which have the B1 structure, and the fraction of the hexagonal W 2C phase increased with bias level. The increased substrate bias levels also correlated with a reduction in oxygen content, suggesting that reducing oxygen content promotes formation of the W 2C phase. However, the film deposited at room temperature and −160 V bias had an oxygen content of only 3%, yet did not form the W 2C phase, indicating a minimum level of thermal activation is also required to form W 2C. Increasing the bias voltage also resulting in increases in film hardness, modulus and compressive residual stress, while reducing resistivity.