Atomic force microscopy study of the microroughness of SiC thin films

Abstract

An atomic force microscopy study of the microroughness of SiC thin films deposited by both plasma-enhanced chemical vapour deposition (PECVD) and laser ablation deposition (LAD) techniques was conducted. PECVD films present the characteristic Zone I structure type, with hill-like domed columns separated by grooves. Both the size of the domes and the depth of the grooves were found to increase with the film thickness as it is varied from 0.5 μm to 2.0 μm. This morphology is consistent with theoretical models describing the equation of motion of the surface profile during the film growth. In contrast, LAD films are made of a few protrusions embedded in an otherwise structureless surface. This morphology is most probably due to the large surface diffusion length of Si and C atoms, arising as a consequence of their high kinetic energy in the LAD process (0.9 and 14 eV, respectively). The mean roughness values are R a = 2.2 nm and R a = 0.58 nm for 2 μm thick SiC films deposited by PECVD and LAD techniques, respectively. The microroughness of both types of films did not show any significant variation upon thermal annealing of films up to 850 °C, and fulfils well the microroughness criterion of membrane materials needed for X-ray mask technology.