Properties of Si_xN_y thin film deposited by plasma enhanced chemical vapor deposition at low temperature using SiH₄/NH₃/Ar as diffusion barrier film

Si_xN_y thin films were deposited by PECVD using SiH₄/NH₃/Ar gases and by biasing the substrate at - 50 V as a function of the ratio of R (R = NH₃/(NH₃ + SiH₄)) at a low temperature (< 80 °C), and their properties as the thin film diffusion barrier were investigated. When R was lower than 0.4, the deposited Si_xN_y film showed low optical transmittance and high surface roughness due to the Si-H bonding in the deposited film. When R is higher than 0.6, the deposited Si_xN_y film was transparent, however, possibly due to the N-H bonding in the film, the film became porous and surface roughness was again increased. When R = 0.4, an optically transparent and smooth film could be obtained. When the WVTR was measured with a multilayer film composed of Si_xN_y (R = 0.4) and parylene on PES substrate, PES (200 μm)/parylene (1.2 μm)/Si_xN_y SixNy(120 nm)/parylene (1.2 μm) showed the WVTR lower than the detection limit of 0.01 g/(m² day).