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

Abstract In this study, amorphous silicon carbonitride (SiC x N y ) films were fabricated by radio frequency (RF) chemical vapor deposition (PECVD) using a single silazane precursor and a low power density (0.15 W/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 SiC x N y 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. SiC x N y films deposited using MTSCP involving Si C 3 N rings formed Si N and Si (CH 2 ) 3 crosslinked structures at T s  ≤ 100 °C, and were then changed to predominantly Si CH 2 N Si crosslinked structures at T s  > 300 °C, leading to a wide range of optical band gap from 5.2 to 3.7 eV. Compared to DVTMDS-deposited SiC x N y 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 (CH 2 ) 2 bridge in SiC x N y films T s  ≤ 200 °C, resulting in excellent optical transmittance. The transmittance in the visible wavelengths of 400 °C-deposited SiC x N y film using DVTMDS still showed 85%. Also, tunable refractive index between 1.44 and 2.10 were obtained for SiC x N y films deposited at T s  ≤ 400 °C.