Deposition of Amorphous Carbon Thin Films by Pulsed RF Plasma CVD

Abstract

Amorphous carbon thin films are deposited by RF pulsed plasma chemical vapor deposition (CVD) on Si wafers at 15°C. The depositions are carried out using a mixture of methane and hydrogen by changing DC self-bias voltage from -100 to -400 V. The morphologies of the deposited films are observed by atomic force microscopy (AFM). The structure and the properties of the deposited films are analyzed by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). With an increase in the DC self-bias voltage value to -400V, a needle-like surface morphology forms, which indicates that clusters of sp2-coordinated carbon atoms originate in the film and their amount increases. Raman and XPS spectra are analyzed in more details by deconvolution using the Gaussian and Lorentz curve fitting. Raman and XPS analyses showed that diamond-like films with highest sp3 are formed at -300 V while at higher DC self-bias voltage (>-400 V), films with a little decrease of sp3 contents are formed due to high ion bombardment.