Analysis of microstructure and surface morphology of a-C:H films deposited on a trench target

Abstract

The bipolar-type plasma-based ion implantation and deposition (bipolar PBII&D) is beneficial in coating a hydrogenated amorphous carbon film (a-C:H film) on a 3-dimensional coating target. In this study, a trench (pitch: 20 mm, aspect ratio: 1.0) was prepared as a coating target and evaluated the microstructure and surface morphologies of a-C:H films. Although the a-C:H films were coated successfully in all trench surfaces, the sidewall surface showed quite different properties as compared to that of coated on the top or bottom surface. It is because of the conformal ion sheath cannot be formed around the sidewall surface, which in turn leads to the decrease of incidence ion flux to the sidewall. The structural properties and surface morphology are investigated using scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). From the Raman measurements of a-C:H films on the sidewall surface, it is observed that the Raman G-peak position shifts to a higher wave number. The Full Width at Half Maximum of G-peak (FWHM(G)) decreases to a smaller value compared to those of the films on the top and bottom surfaces. These results indicate that the structure of a-C:H films on the sidewall surface is graphitized compared to those on top and bottom surfaces, which results in the reduction of hardness.