Characteristics of SiO2-like thin film deposited by atmospheric-pressure PECVD using HMDS/O-2/Ar

SiO2-like thin films were deposited at low temperatures (<50 degrees C) by atmospheric-pressure plasma-enhanced chemical vapor deposition using a pin-to-plate-type dielectric barrier discharge with a gas mixture containing hexamethyldisilazane (HMDS)/Ar/O-2. The deposition rate increased with increasing concentration of HMDS in the gas mixture. However, a powdery film with Si-OH bonding, high roughness, and low transmittance was obtained, which was attributed to the enhanced homogeneous reaction with increasing HMDS. The increase in 02 flow rate at a fixed HMDS flow rate increased the reaction rate of the remaining HMDS on the substrate surface, which resulted in an increase in deposition rate until the remaining HMDS had completely reacted. An increase in the oxygen flow rate also increased the surface roughness and decreased the optical transmittance slightly, possibly due to the formation of small SiO2 particles in the gas phase during the dissociation of the gas mixture under high-oxygen-percentage conditions. At the optimum condition of HMDS (15 sccm)/O-2 (300 sccm)/Ar (2 slm), smooth SiO2-like thin films with a transmittance >95% could be obtained with a deposition rate of approximately 21 nm/min. (C) 2007 The Electrochemical Society.