Low-temperature deposition of SiNx, SiOxNy, and SiOx films from plasma discharge of SiH4 for polycarbonate glazing applications

To improve the abrasion resistance of polycarbonate, which can be used as a replacement for glass, SiNx, SiOxNy, and SiOx thin films were deposited at low temperatures using a slot antenna electron cyclotron resonance (SLAN ECR) plasma source. The SLAN ECR plasma source has a high ionization rate even at low pressure and can thus rapidly deposit films with good mechanical properties at low temperatures. When SiH4 gas is used as the Si precursor, the deposition rates of thin films can exceed 100 nm/min at 6.65 Pa. As the N2 or O2 flow decreases, the deposition rate is decreased, but the hardness H and elastic modulus E of the films gradually increases. The maximum hardness values of the prepared SiNx, SiOxNy, and SiOx films are 16.8, 14.9, and 11.4 GPa, respectively. The H/E and H3/E2 values of such films are associated with abrasion resistance. However, the correlation between the H/E and H3/E2 values and the abrasion resistances of our films is not strong. It is shown by annealing and abrasion experiments that the porosities of these films are more closely related than the H/E and H3/E2 values to their abrasion resistances. When a hyper-thermal neutral beam (HNB) is used at low pressures, denser films are deposited. The hardness values of these films are also significantly higher.