Comparison of the structural properties of a-C:H films prepared by pulsed and continuous RF

Abstract

Hydrogenated amorphous carbon (a-C:H) films were grown on silicon substrates by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) with the RF power of 100 W. The structural properties of a-C:H films prepared using the RF on in continuous-wave (CW) and pulsed-wave (PW) modes were compared. The pulse frequency of 1 Hz and a duty cycle of 10% were used for PW mode. The deposition time for CW and PW modes were set as 3 and 30 minutes, respectively. A mixture of argon and acetylene (1:10) was used as a precursor gas and carbon source, respectively. Raman spectroscopy was used to characterize I_D/I_G. Near edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to identify sp² content, while the X-ray photoelectron spectroscopy (XPS) was used to analyze  sp³ content. The X-ray reflectivity (XRR) was used to evaluate the density, roughness, and thickness of the films. The experimental results show that the a-C:H film prepared using the RF on in PW mode gives the ratio of I_D/I_G, sp², and sp² contents of 0.76, 59.3%, and 33.2 %, respectively, with the thickness and density of 53.0 nm and 2.1 g/cm³, respectively. While the RF on in CW mode gives the ratio of I_D/I_G, sp², and sp² contents of 0.57, 62.5%, and 29.5 %, respectively, with the thickness and density of 54.5 nm and 2.0 g/cm³, respectively. Therefore, with the same RF power and RF on time, the a-C:H film prepared using PW mode gives the structural properties better than using CW mode.