Preparation Of 6H-SiC Single Crystal Substrate Dry Chemical Mechanical Polishing Powder

As a third-generation semiconductor material,Si C has the advantages of wide forbidden band,high electron saturation drift rate,high thermal conductivity and low on-resistance,and is widely used in semiconductor lighting,integrated circuits and new energy vehicles.The traditional chemical mechanical polishing technology can ensure the application requirements of Si C single crystal substrate surface,but there are problems such as high cost of polishing solution and pollution of the environment if the polishing solution composition is not handled properly.Therefore,this paper proposes a dry chemical mechanical polishing powder polishing technology,replacing the polishing solution with a lower cost and relatively convenient recycling polishing powder,and further improving the chemical mechanical polishing technology through the exploration and research of dry chemical mechanical polishing powder.First,the composition of the dry chemical mechanical polishing powder formulation is determined;then,the polishing powder formulation is optimized;then,based on the optimal formulation,the physical and chemical properties of the polishing powder and the mode of action of the polishing powder in the polishing process are studied and the mechanism of action of the polishing powder is explained;Finally,the process parameters are optimized and the application of the dry chemical mechanical polishing powder is carried out on quartz glass and 304 stainless steel as the processed objects.Finally,the process parameters are optimized and the application of the dry chemical mechanical polishing powder is carried out on quartz glass and 304 stainless steel.The main work is as follows:(1)In order to determine the composition of the chemical mechanical polishing powder,a literature search was carried out to first determine the composition of the formulation.Firstly,the best oxidizing agent was selected by experimental comparison and the mechanism of action of some of the oxidizing agents was investigated using XRD and FESEM.Finally,potassium permanganate was identified as the oxidizing agent in the polishing powder formulation.A comprehensive comparison of the effects of diamond,silicon carbide,alumina and silica abrasives in the polishing powder formulation showed that the use of alumina abrasives in the polishing powder formulation was the most cost effective.The orthogonal tests showed that the abrasives had a significant effect on the material removal rate and that there was an interaction between the solid lubricant and the abrasives.The addition of catalysts,solid lubricants,dispersants and surfactants to the formulation did not significantly improve the material removal rate and the test results showed that the addition of these components reduced the material removal rate.(2)The results show that the highest material removal rate is achieved with a 1:1 ratio of oxidizer to abrasive in a total of 6 g.The maximum removal rate was achieved when only the oxidizer and abrasive were present in the formulation,and the surface roughness of the polished material was minimum.(3)The physical and chemical properties and polishing performance of the polishing powder were investigated.The results show that the polishing powder has the highest material removal rate when polishing6H-Si C single crystal substrates at a temperature of 200 °C,and the material removal rate decreases significantly at 250 °C.The polishing powder is soluble in acid and alkali solutions.A polishing powder formulation using 1 μm alumina as abrasive can polish the surface roughness of 6H-Si C single crystal substrates to around 1 nm.The mode of action of the polishing powder was investigated and the results show that the components of the polishing powder are not uniformly dispersed,but rather agglomerated into blocks in three-dimensional space,with the abrasive and oxidizing agent adsorbing each other to form agglomerates.The material removal rate is mainly influenced by the effective area of contact between the oxidant and the surface of the 6H-Si C single crystal substrate,independent of the initial particle size of the oxidant.The only real polishing effect of the formulation is the layer in close contact with the 6H-Si C single crystal substrate,while the rest of the components that are not in contact have almost no effect.The process parameters were optimized with a final pressure setting of 3 psi,a disc speed of 60 r/min and a polishing head speed slightly greater than or equal to the disc speed.The polishing powder was also found to have good polishing performance on quartz glass and 304 stainless steel by comparison with the test.