Properties of SiCN Films Deposited by Plasma Enhanced CVD: Effects of RF Power

Abstract

Silicon carbonitride (SiCN) thin films were deposited on Si(100) substrates using plasma-enhanced chemical vapor deposition (PECVD) at a substrate temperature of 500℃. The films were synthesized using a gas mixture of SiH₄, CH₄, and N₂ with flow rates of 1, 16, and 83 sccm, respectively. The effect of RF power (50-150 W) on the film properties was systematically investigated. The deposition rate increased from 14.5 nm/min at 50 W to 43.3 nm/min at 150 W, with a reduced growth rate acceleration above 100 W. X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS) and hydrogen forward scattering (HFS) analyses revealed that the films contained Si (35-39 at.%), C (24-27 at.%), N (33 at.%), and H (23 at.%). X-ray diffraction (XRD) measurements indicated an amorphous structure of the deposited films. The optical properties showed that the band gap decreased from 3.2 to 2.3 eV and the refractive index decreased from 2.1 to 2.0 with increasing RF power. Nanoindentation measurements demonstrated that the maximum hardness of 30 GPa was achieved at 75 W RF power, which is attributed to the optimum balance between Si-N and Si-C bonds. The obtained a-SiCN:H films exhibited properties suitable for applications in semiconductor devices as insulating and protective layers, as well as for optical coatings and hard protective coatings for tools.