Optical properties of plasma-enhanced chemical vapor deposited SiCxNy films by using silazane precursors

Abstract

In this study, amorphous silicon carbonitride (SiCxNy) films were fabricated by radio frequency (RF) chemical vapor deposition (PECVD) using a single silazane precursor and a low power density (0.15W/cm(3)) for better compositional control. The effects of the precursor chemical structure (C/Si ratio, C-Si-N structure, and vinyl groups) and deposition temperature (T-s) on the chemical structure and optical properties of SiCxNy films were examined using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Specifically, two new single precursors; namely, n-methyl-aza-2,2,4-trimethylsilacyclopentane (MTSCP) and 1,3-divinyl-1,1,3,3-tetramethyl-disilazane (DVTMDS) were studied and compared. SiCxNy films deposited using MTSCP involving Si-C-3-N rings formed Si-N and Si-(CH2)(3)-crosslinked structures at T-s <= 100 degrees C, and were then changed to predominantly Si-CH2-N-Si crosslinked structures at Ts > 300 degrees C, leading to a wide range of optical band gap from 5.2 to 3.7 eV. Compared to DVTMDS-deposited SiCxNy films, their relatively higher percentage of Si-C-N structure accounted for the lower optical band gap and reduced transmission. DVTMDS with di-vinyl groups readily formed a Si-(CH2)(2)-bridge in SiCxNy films Ts <= 200 degrees C, resulting in excellent optical transmittance. The transmittance in the visible wavelengths of 400 degrees C-deposited SiCxNy film using DVTMDS still showed 85%. Also, tunable refractive index between 1.44 and 2.10 were obtained for SiCxNy films deposited at T-s <= 400 degrees C. (c) 2017 Elsevier B.V. All rights reserved.