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

SiCxNy films deposited using MTSCP involving SiC3N rings formed SiN and Si(CH2)3 crosslinked structures at Ts ≤ 100 °C, and were then changed to predominantly SiCH2NSi crosslinked structures at Ts > 300 °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 SiCN 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 °C, resulting in excellent optical transmittance. The transmittance in the visible wavelengths of 400 °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 Ts ≤ 400 °C.