Fabrication and Microstructure Study of SiC Thin Film by PECVD Based on Single-source Gas

In recent years, silicon carbide (SiC) thin films are regarded as very important target materials in laser inertial confinement fusion (ICF) physical experiments due to their excellent physical and chemical properties. In order to meet the requirements of ICF physical experiment, many harsh conditions were put forward for SiC thin films, such as good surface morphology, low roughness, high density and fast deposition rate. Up to now, in order to study and improve the structure and properties of SiC thin films, a lot of researches were carried out by using different preparation processes. Among them, the preparation method of SiC thin films grown by single-source gas has the advantages of safety, reliability, simplicity and convenience, and avoiding the introduction of unnecessary impurities. Therefore, in order to reduce experimental errors and improve film quality, a single-source gas with stable chemical properties can be used to grow SiC thin films. In addition, the plasma enhanced chemical vapor deposition (PECVD) can be used to deposit crystalline or amorphous SiC thin films at lower temperature, with higher deposition rate and lower internal stress. The PECVD method based on a single-source gas was expected to produce SiC thin films that meet the requirements of ICF experiment, but few related studies were reported. In this work, SiC thin films used for ICF physical experiments were deposited on single-side polished n-type silicon (100) wafer by PECVD method with using the tetramethylsilane (TMS) as the single precursor gas and hydrogen (H₂) as the carrier gas with different working pressures. The surface morphology, microstructure, surface roughness, mass density, deposition rate, chemical elemental composition and bonding state of SiC thin films were mainly analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), precision electronic balance, surface profilometer, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR), respectively. In the condition that deposition parameters keep unchanged, the influence of the working pressure on the microstructure and properties of the SiC thin films was systematically investigated. The dominant factors which affect the surface roughness, chemical composition, mass density and deposition rate of SiC thin films were discussed. It is observed that the composition of SiC thin films is closely related to the working pressure. With the increase of working pressure, the content of Si in SiC thin films decreases. With the increase of working pressure, the deposition rate firstly increases and then decreases, and the density first decreases and then increases. Compared with other deposition processes, the surface roughness of SiC thin films prepared by using a single-source gas is very low (1.25-1.85 nm), and the surface roughness increases first and then decreases with the increase of working pressure. This work may lay a foundation for preparation of high quality SiC spherical shell used in the ICF experiments.