The chemical vapor deposition process can be divided into three important stages: the reaction gas diffuses to the substrate surface, the reaction gas is adsorbed on the substrate surface, the chemical reaction takes place on the substrate surface to form solid deposits, and the generated gaseous by-products leave the substrate surface. The most common chemical vapor deposition reactions are: Thermal decomposition reaction Chemical synthesis reaction and chemical transport reaction. Usually, TiC or TiN is deposited by feeding TiCl into the reaction chamber at 850~1100 ℃ four ，H two ，CH four And other gases, through chemical reaction, form a coating on the surface of the substrate. The development of chemical vapor deposition is inseparable from its own characteristics, which are as follows.
1) Various types of deposits: metal films, non-metallic films, multi-component alloy films, and ceramic or compound layers can be deposited as required.
2) CVD reaction is carried out under normal pressure or low vacuum, and the coating has good diffraction property. It can be evenly coated on surfaces with complex shapes or deep and fine holes of workpiece.
3) The thin film coating with high purity, good compactness, low residual stress and good crystallization can be obtained. Due to the mutual diffusion of reaction gas, reaction product and matrix, a film with good adhesion can be obtained, which is very important for surface enhanced films such as surface passivation, corrosion resistance and wear resistance.
4) Because the temperature of film growth is much lower than the melting point of the film material, a film with high purity and complete crystallization can be obtained, which is necessary for some semiconductor films.
5) The chemical composition, morphology, crystal structure and grain size of the coating can be effectively controlled by adjusting the deposition parameters.
6) The equipment is simple and easy to operate and maintain.
7) The reaction temperature is too high, generally 850~1100 ℃. Many matrix materials can not withstand the high temperature of CVD. Plasma or laser assisted technology can reduce the deposition temperature.
There are many chemical vapor deposition methods, such as atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), ultrahigh vacuum CVD (UHVCVD), laser CVD (LCVD), metal organic CVD (MOCVD), Plasma enhanced chemical vapor deposition (PECVD), etc.
