High-density silicon nitride deposited at low substrate temperature with high deposition rate using hot wire chemical vapour deposition

For application as barrier coatings in (opto-)electronic devices, it is important to deposit transparent silicon nitride (SiNx) films with high mass density at low substrate temperatures. By using hot wire chemical vapour deposition (HWCVD) we were able to deposit transparent SiNx coatings at temperatures below 230 °C. As determined with elastic recoil detection (ERD), these films have a density of 2.8 g/cm3, which is only slightly lower than the density of 3.0 g/cm3 obtained for samples deposited at 450 °C. The low 16BHF etch-rates of 18 nm/min and 7 nm/min, respectively, confirm the high compactness of the films. An interesting feature of these films is that the composition at which a maximum in mass density is obtained changes from slightly Si-rich towards stoichiometric when lowering the substrate temperature. The deposition rate of these high-density films is 3 nm/s. Moreover, these high-density films have very low absorption for the visible wavelength region, which enables the use in optical devices. Since this high transparency is obtained in combination with the high mass density and a high deposition rate (3 nm/s), we conclude that these HWCVD deposited SiNx films have great potential for application in barrier coatings.