PECVD silicon nitrides with low hydrogen content

Abstract

Abstract Dielectric thin films are important materials in sensor technology, particularly in the case of silicon nitride which presents many useful properties including mechanical hardness and high chemical resistance. Unfortunately, the low-temperature, plasma-enhanced, chemical-vapour deposition (PECVD) used to avoid damage to the substrate, often results in a low density material of poor stability. We report on the preparation of silicon nitride thin films by low frequency PECVD (50 kHz) at moderate temperatures (350 °C), with the reactive gases diluted by helium. As the thermal stability of the silicon nitride depends on the nature and the energy of the chemical bonds, we propose preparation conditions that maintain a very low level for the weak SiH bond and high SiN bond densities. Our results relate to the influence of some preparation parameters on the composition of the material, and the resulting properties such as density, chemical resistance, and thermal stability.