Growth of c-axis oriented AlN thin films on titanium alloy substrate by middle frequency magnetron sputtering

Abstract

A two-step deposition process was developed to deposit highly c-axis oriented AlN thin films on titanium alloy substrates by middle-frequency magnetron sputtering. Smooth AlN seed layer was first prepared on rough titanium alloy substrate at the first step. Then, c-axis oriented AlN films with small grain size were deposited at the second step. The effects of the growth time at the first and second step on the microstructure and the c-axis orientation of the AlN films were studied. It was found that the c-axis orientation of the AlN films is strongly dependent on the film thickness at the first step and the substrate temperature at the second step. With optimal process conditions, the full-width at half-maximum of the AlN (0002) peak rocking curve decreased to a minimum of 4.1° and the root-mean-square surface roughness of the prepared AlN films was 4.3 nm. The prepared AlN films have potential applications in piezoelectric microelectromechanical-systems and surface acoustic wave devices.