Synergistic Mechanism Of UV Photocatalysis-Fenton Reaction CMP For Single-crystal SiC

With the rapid development of 5G wireless communication technology and intelligent electric vehicle technology,higher and higher requirements are put forward for the developing and manufacturing of semiconductor devices.As the third generation semicondu-ctor material with excellent performance,single-crystal silicon carbide（SiC）has been widely used in the fields of high-power LED lighting,aviation optical mirror,automotive electronics,5G communication,and other fields.When single-crystal SiC wafer is used for IC substrate,the surface is required to be super smooth,free of scratch defects and damage,and the surface roughness is less than Ra0.5 nm（10μm×10μm）.However,due to the high hardness,brittleness and chemical stability of single crystal SiC,it is extremely difficult to flatten the surface of single-crystal SiC substrate and power devices with high efficiency,which is very difficult to ensure high precision and high efficiency,which tremendously limits the application and development of SiC substrate and its power devices.In this study,based on hydroxyl radicals（?OH）can be produced by both UV photocatalysis reaction and Fenton reaction,it is proposed utilizing the synergistic effect of these two groups to significantly improve the concentration of?OH,to improve the CMP polishing efficiency of single-crystal SiC,and to realize the high efficiency and non-damage ultra-smooth surface flattening of the substrate.Firstly,the formation rate and concentration of hydroxyl radicals（?OH）produced by UV photocatalysis-Fenton reaction were quantitatively measured by degradation of methyl orange,and the ORP value of the reaction solution was measured.It was proved that the reaction rate of the UV photocatalysis-Fenton reaction was faster than the single UV photocatalysis reaction and Fenton reaction,and the oxidation performance of polishing slurry was stronger.Through the detected corrosion voltage,friction coefficient,surface elements and morphology of SiC under the action of UV photocatalysis-Fenton reaction confirmed the effectiveness of the synergistic effect of the two reactions action on the surface of SiC.The feasibility of polishing single-crystal SiC by UV photocatalysis-Fenton reaction was verified by polishing experiments.The results show that the oxidability of the slurry is stronger,the corrosion layer on the SiC surface is thicker and the polishing material removal rate is higher under the action of UV photocatalysis-Fenton.Secondly,the UV photocatalysis-Fenton polishing reaction system of single-crystal SiC was optimized.The effects of different Fenton reagent components,solid iron catalyst,different illumination methods,and electron capture agents on the polishing of single-crystal SiC were investigated.The results show that the polishing effect is better by using solid phase Fenton reagent,Fe₃O₄ catalyst,light polishing pad,and H₂O₂ electron capture agent.Thirdly,the influence of mechanical and chemical factors on the single-crystal SiC UV photocatalysis-Fenton CMP process was investigated.The results show that the polishing effect of nanodiamond abrasive is better than other abrasives;the larger the particle size and polishing pressure are,the deeper the abrasive is pressed into the wafer,the higher the material removal rate is,but too much will cause scratches and increase the surface roughness.Under acidic conditions,increasing the concentration of TiO₂ and light intensity can enhance the chemical reaction and improve the material removal efficiency.The optimum CMP technology obtained by single factor experiment is 15 g/L of 200 nm diamond abrasive,0.04 MPa polishing pressure,12 g/L TiO₂ concentration,p H value 3,and1000 m W/cm² light intensity.After polishing single crystal SiC for 1 h,the surface roughness of Ra 0.249 nm is obtained.Finally,for the synergistic material removal behavior of single-crystal SiC polished by UV photocatalysis-Fenton reaction,the contribution of pure mechanical action,UV photocatalysis reaction,Fenton reaction,and their synergistic effects to the polishing materials removal was studied.The synergism mechanism of UV photocatalysis-Fenton polishing single-crystal SiC was revealed by experiments and analysis.The material removal influence mechanism of UV photocatalysis-Fenton polishing single crystal SiC was analyzed by mathematical relationship model.