Influence of substrate bias on the microstructure and internal stress in Cu films deposited by filtered cathodic vacuum arc

Abstract

Copper films were deposited by a novel off-plane double bend filtered cathodic vacuum arc technique at ambient temperatures. X-ray diffraction (XRD) and atomic force microscopy (AFM) are used to characterize the film’s structure and surface morphology. The substrate bending method was used to study the internal stress. The influence of substrate bias on the surface morphology, grain size, crystalline structure, and internal stress was systematically studied. XRD results indicate that all the deposited Cu films exhibit face-centered cubic-type (fcc) crystallite structure with (111) preferred orientation growth. The increase of substrate bias results in the improvement of (111) preferred orientation. At the substrate bias of 0 V, the deposited films are composed of nano-sized columnar grains, which contribute to the tensile stress in the deposited films. The grain size and surface roughness increase gradually with increasing substrate bias up to −200 V. Further increase of substrate bias results in the drastic decrease of grain size and surface roughness due to self-sputtering. The internal stress in the deposited films is also strongly dependent on the substrate bias. The increase of substrate bias results in the decrease of tensile stress in the deposited films, and the transition of tensile to compressive stress at the substrate bias of −300 V. Further increase of substrate bias results in the linear increase of compressive stress in the deposited films. At the substrate bias of −300 V, dense and stress-free Cu films can be obtained.