Study On Preparation Of Large Nano-crystalline Diamond Film In A MPCVD Device

Due to its excellent physical and chemical properties, diamond has a very broad development prospects. Chemical vapor deposition is also thought highly of because it can make synthetic diamond with properties that are similar to the nature ones. Microwave plasma vapor deposition attracts a lot of attention because of electrodeless discharge and highly concentrated plasma. The key factor that limit the domestic researches’ breakthrough is the fabrication and the mastery of the relvant parameters. In this paper, we investigated the relationship between the various process parameters and the quality/uniformity and other indicators by using our self-made 10 k W MPCVD device, and summarized some of the actual optimal parameters and suggestions for industrialized production.The influence of process parameters on the deposition was systematic studied by our advanced 10kW-MPCVD device, and the improvements was found reasonable. The influence of microwave power and pressure on the substrate temperature was found by the comparison of different temperature distribution. Basing on this a comparison was made and found that the increase of either methane concentration or microwave power can effectively improve the deposition rate of the film, and a great leap is on concentration of 1% or substrate temperature 850℃. By this theory, the uniform diamond film with large area of more than 100 mm in diameter was finally obtained.The influence of the auxiliary gas in deposition was studied. The results show that the introduction of oxygen may develop both the quality and the deposition rate, the carbon dioxide can greatly improve the deposition speed, but will affect the uniformity of surface, while small amount of nitrogen can inhibit the growth of grain and obviously promote secondary nucleation in our selective parameter.Comparing the effects of different concentrations of nitrogen/oxygen mixture systematically, the comprehensive influence was found decided by higher concentration, that is to say, more oxygen leads to oxygen style, and more nitrogen shows nitrogen style. By appropriate parameters nano-crystalline diamond film with large area and certain uniformity was finally obtained. A method for rapid qualitative detection by using of the square resistance meter was used to exam the uniformity and the improvable parts was found that the accuracy may be affected by the substrate, the combination and the thickness of the film.