Investigation of structural properties of high-rate deposited SiNx films prepared at low temperatures (100-300 °C) by atmospheric-pressure plasma CVD

We have investigated the structural properties of silicon nitride (SiNx) films deposited at low temperatures (100-300 degrees C with very high rates (>50 nm/s) in atmospheric-pressure He/H-2/SiH4/NH3 plasma excited by a 150 MHz very high-frequency (VHF) power using a cylindrical rotary electrode. For this purpose, SiNx films are prepared on Si(001) wafers varying NH3/SiH4 ratio, H-2 concentration in the plasma and substrate temperature (T-sub). Infrared absorption spectroscopy is used to analyze the bonding configurations of Si, N and H atoms in the films. It is shown that by decreasing NH3/SiH4 ratio or increasing H-2 concentration, Si-N and Si-H bond densities increase, while N-H bond density decreases. A reasonably good-quality film showing a BHF etching rate of 28 nm/min and a refractive index of 1.81 is obtained at T-sub = 300 degrees C despite the very high deposition rate of 166 nm/s. However, it is found that the decrease in T-sub causes the deterioration of film quality. Further surface excitation by increasing VHF power and/or H-2 concentration together with the optimization of other deposition parameters will be needed to form high-quality SiNx films with high rates at lower temperatures (T-sub <= 100 degrees C). (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim