Study On The Preparation Of High-purity SiC Powder For The Growth Of The Third-generation Semiconductor SiC Single Crystal

As a typical third-generation semiconductor material,SiC single crystal material is gradually becoming mainstream in the field of semiconductor materials due to its excellent performance.The current method for preparing SiC single crystals is mainly the physical vapor phase transport(PVT)method,and SiC powder is the raw material for growing SiC single crystals by the PVT method.To improve the quality of SiC single crystals,in addition to the need for a suitable single crystal growth process,the raw material of SiC powder used for growing single crystals is also very important,and its purity and other physical parameters will directly affect the quality of SiC single crystals,which in turn affects the performance of SiC devices.Therefore,the preparation of high-purity SiC powder is the key to the growth of high-quality SiC single crystals by the PVT method.The improved self-propagation high-temperature synthesis method is to maintain the reaction between carbon powder and silicon powder by increasing the reaction temperature and continuous heating.This method is relatively simple to operate,the synthesis parameters are easy to control.Theoretically,it is a low-cost powder synthesis method suitable for large-scale production.In this paper,SiC powder was synthesized from high purity C powder and Si powder by improved self-propagating high temperature synthesis method,and the SiC powder was purified.Firstly,the effects of parameters such as synthesis temperature,synthesis gas pressure,synthesis time,and Si/C molar ratio on the phase composition,morphology,and particle size of SiC powder were systematically investigated,and then the preliminary synthesized SiC powder was purified.The effects of decarburization time,decarburization temperature,ball mill crushing,and high-temperature decarburization on SiC powder on the purity of SiC powder were studied in the purification process.Experimental results show: increasing the reaction temperature,extending the holding time,and decreasing the synthesis pressure are beneficial to the synthesis of SiC powder;the higher temperature,the longer time,the lower pressure,and the larger Si/C molar ratio,the larger the particle size of the synthesized SiC;increasing the Si/C molar ratio could reduce the remaining C in the product,and when the Si/C molar ratio reached 1.05:1,no excess C appeared in the powder;the synthesis pressure affects the product morphology,which is mainly granular at 0.01 k Pa,while the products synthesized at other pressures show both whisker and granular morphology.The results also show that the optimum decarburization process parameters are850 ℃ and 2 h.The high decarburization temperature will lead to the oxidation of SiC.It is also found that since some of the C is wrapped by SiC,the ball milling and crushing of SiC powder is beneficial to the removal of C impurities.after the SiC powder is decarburized at high temperature,the ICP-MS results show that the impurity content in the SiC powder decreases significantly,and at the same time,high temperature promotes the transformation of the SiC crystal from 3C-SiC to 6H-SiC,and the grains also assume a hexagonal shape.