Simulation And Experimental Research On Ultrasonic Electrochemical Anodization Of SiC Single Crystal

SiC single crystal having excellent thermal and electrical properties,is typical of third-generation power semiconductor device material.In order to obtain SiC single crystal semiconductor materials without scratches and sub-surface damage,the excellent performance of SiC single crystal semiconductor materials should be fully utilized to meet the needs of SiC semiconductor materials in various fields.This article proposes a new polishing technology-electrochemistry anodic oxidation and mechanical polishing.This article takes SiC single crystal semiconductor materials as the research object.From a microscopic point of view,the mechanism of SiC single crystal electrochemical anodic oxidation and polishing is studied,and a new method combining surface modification and mechanical polishing is proposed to treat SiC single crystals.The wafer is processed.SiC single crystal electrochemical anodic oxidation polishing is divided into two steps:First,anodic oxidation,the SiC single crystal is electrochemically anodized by external power supply to modify its surface to generate a loose SiO2 oxide layer.Second,grinding and polishing,the SiO2 oxide modified layer is removed by mechanical polishing process,and the SiO2 oxide film is easily removed by an abrasive less than SiC,such as CeO2,to finally achieve the requirements of no scratches and sub-surface damage.Aiming at the anodization process in the electrochemical mechanical polishing of SiC single wafers,simulation of SiC single crystal electrochemical anodizing electric field by COMSOL Multiphysics simulation software.Solve and analyze the electric field distribution,film formation process,and current density distribution during the electrochemical anodization of single crystal SiC.The influence of applied voltage,anodic oxidation time,and current density changes on the formation rate of SiO2 oxide film and the thickness of SiO2 oxide film are discussed and studied.Based on the simulation process conditions,a single sheet is built.The SiC single crystal ultrasonic electrochemical anodization and polishing test platform was designed for the SiC single crystal ultrasonic electrochemical anodization test system and the polishing experiment design;finally,based on the simulation results and the single crystal SiC ultrasonic electrochemical anodization and polishing test platform,Carry out SiC single crystal ultrasonic electrochemical anodic oxidation test.The test process corresponds to the simulation analysis.The same anodization parameters are used for the test.After the electrochemical anodization test,the SiC sample is tested.The test results of SiC single crystal electrochemical anodic oxidation test are compared with simulation analysis.The conclusion is that the simulation results are consistent with the change trend of the SiC electrochemical anodization test results.The same voltage,SiO2 oxide film is thickened to increase with time,the boundary layer thickness at the surface of the SiC sample also becomes thick as time increases;At the same time,SiO2 oxide film becomes thicker with increasing voltage,SiC test sample film thickness at the boundary surface can also be thickened with increasing voltage.It is concluded that the simulation method of SiC electrochemical anodization process in this paper is correct,and it can be used as an auxiliary method for mechanism research and experimental research in the process of SiC electrochemical anodization and polishing.The results of the SiC single crystal polishing test were analyzed,and the comparison study was carried out on the SiC single crystal polishing test with or without ultrasound assistance.The results show that the longer the electrochemical anodization time of the SiC sample,the greater the voltage and the ultrasonic frequency during the electrochemical anodization of the SiC sample,the greater the material removal rate of the SiC sample.However,it does not mean that the longer the anodizing time,the higher the voltage,and the higher the ultrasonic frequency,the better the surface quality of the SiC sample after polishing.According to the measurement results,the maximum surface roughness of the SiC sample is 22.5nm,the minimum is 3.9nm,and the average is 12.5nm.The surface quality of the SiC sample has been effectively improved,indicating that the SiC single crystal electrochemical anodic oxidation polishing method is an effective polishing technique.Comprehensive analysis shows that when the voltage E=350V,the time t=250s,and the ultrasonic frequency is 20KHz,the polishing effect is the best.