Study On Preparation Technology And Properties Of High Quality TaC Coating On Graphite

As a third-generation semiconductor material with excellent performance,SiC single crystal occupies a pivotal position in semiconductor and related fields.In order to improve the quality and yield of SiC single crystal products,in addition to the need for a suitable single crystal growth process,due to its single crystal growth temperature is as high as 2400℃ or more,and there are extremely stringent requirements for the cleanliness of the process equipment,especially the graphite trays necessary for the growth of SiC single crystals and the graphite crucibles in the SiC single crystal growth furnace.The impurity content introduced by these graphite parts to the SiC single crystal needs to be controlled below the ppm level,so A high temperature and anti-pollution coating must be prepared on the surface of these graphite parts,otherwise the graphite will easily lead to contamination of the SiC single crystal due to the weak bond force between the crystal layers and the impurities contained therein.As a transition metal carbide with excellent performance,TaC has a melting point of up to 3880℃,and has stable physical and chemical properties at high temperature.It does not react with SiC and graphite,and has good thermal matching with graphite.So it is an ideal anti-pollution coating material for the graphite parts required for the above-mentioned SiC single crystal growth.The main purpose of this paper is to study the process and coating properties of TaC coatings prepared on the surface of graphite substrates.In this paper,TaCl₅-C₃H₆-H₂-Ar reaction system was used to prepare TaC coating on graphite surface by chemical vapor deposition（CVD）.Finally,the best TaC deposition process was obtained:the deposition temperature was 1350℃,the deposition pressure was 1700 Pa,the flow ratio of H₂ to C₃H₆ was 7.50,and TaCl₅ was slightly excessive.The quality of the TaC coating prepared under this process condition is the best:the coating is smooth and dense,with a preferred orientation of（200）crystal plane.The effect of oxygen plasma-treated graphite substrates on TaC-coated samples was also investigated.Firstly,the effect of oxygen plasma treatment time on graphite substrates was discussed,and two kinds of graphite flakes,both oxygen plasma treated and untreated,were used to deposit TaC coatings using the optimal process described above.Finally,the deposition rate,composition,morphology and properties of the obtained samples are characterized,tested and analyzed.The research results show that the best oxygen plasma treatment time is 10 min,and the TaC coating prepared from the oxygen plasma treated graphite sheet has a higher deposition rate of 1.02μm/h,a higher hardness of 18.61 Gpa,and a higher elastic modulus of 291.45 GPa,the oxidation resistance has also been improved,but its thermal shock resistance has deteriorated.