Achieving the low stress and defects of diamond film by introduction of SiNx dielectric layer

Abstract

The epitaxial growth of diamond films with minimal deformation, stress and high density on heterogeneous substrates has consistently represented a significant challenge in the utilisation of diamond film materials in thermal diffusers, high-precision optical components and other domains. In this study, a SiNx dielectric layer was prepared on a (100) oriented monocrystalline silicon substrate by low-pressure chemical vapor deposition (LPCVD). The pH dependence of solid $\zeta$ potential on Si and SiNx surfaces was investigated. The $\zeta$ potential of the ethanol-based nanodiamond colloid was controlled using electrostatic seeding technology, resulting in denser diamond seed adsorption and lower surface roughness on the SiNx nanocoating. Subsequently, high-quality diamond films were successfully prepared on both Si and Si/SiNx substrates using microwave plasma chemical vapor deposition (MPCVD). The N content in the film was quantitatively analysed through Ultraviolet-visible-near-infrared (UV–Vis-NIR) absorption spectrum of the free-standing diamond film. This analysis revealed a potential relationship between the consistency of the nucleation layer and the abundance of N impurities. The test results of the white light interference three-dimensional profiler demonstrate that the warpage of the diamond film is significantly reduced following the introduction of the SiNx dielectric layer. The warpage displacement vector component in the direction perpendicular to the film is reduced by 22.63 %, and the overall stress (calculated by the Stoney formula) is reduced by 21.43 %. This indicates that the SiNx dielectric layer effectively alleviates the stress mismatch.