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Research On Chemical Mechanical Polishing Mechanism Of UV-assisted Silicon Carbide

Posted on:2021-03-28Degree:MasterType:Thesis
Country:ChinaCandidate:Y XiaFull Text:PDF
GTID:2428330611473109Subject:Mechanical engineering
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With the rapid development of optoelectronic technology and microelectronic technology,electronic components are gradually developing towards extreme working environments such as high temperature resistance,high voltage resistance,radiation resistance,high frequency,and high power.Therefore,the third-generation semiconductor materials represented by silicon carbide have broad development prospects in power electronics,optoelectronic devices,semiconductor LED lighting,new energy vehicles,5G communication technology and other fields.Because the surface quality of silicon carbide affects the quality of the epitaxial layer and the device performance,it is particularly critical to obtain an atomically smooth and damage-free Si C substrate surface.However,the high hardness and significant chemical inertness of SiC have brought great difficulties to achieve atomically smooth and damage-free surface.The photo-Fenton reaction system was used to chemical mechanical polishing the Si surface of 6H-Si C wafer.The effects of Fenton reagent components(pH value,H2O2concentrations,and Fe2+concentrations)and ultraviolet light power on the polishing effect were studied from the perspective of chemical influence factors.The study found that as the pH values,H2O2 concentrations,and Fe2+concentrations increased,the material removal rate?MRR?of the SiC wafer increased firstly and then decreased,and the surface roughness decreased firstly and then increased.As the power of ultraviolet light increasing,the MRR gradually increased.Under the conditions of pH3,H2O2 concentration of 4wt%,Fe2+concentration of 0.4 mmol/L and ultraviolet light power of 32 W,the 6H-SiC wafer has the highest polishing efficiency and the best surface quality.The effects of polishing process parameters?polishing pressure,speed of polishing disc,and polishing slurry flow rate?on the material removal rate and surface quality of 6H-SiC wafer were studied from the perspective of polishing process.It was found that under the process parameters of polishing pressure of 8 kg?5.6 psi?,polishing disc rotation speed of 120rpm,polishing fluid flow rate of 90 ml/min,the 6H-Si C wafer has the best polishing effects,and an ultra-smooth surface with a surface roughness of Ra0.158nm was obtained.By measuring the particle size distribution of the abrasive particles in the polishing slurry,measuring the Zeta potential of the abrasive particles,and measuring the ultraviolet-visible spectrum,the mechanism of the abrasive particles dispersion stability and ultraviolet light on the chemical mechanical polishing effect of 6H-SiC wafer Si surface was analyzed.The results show that the pH values affects the electrostatic repulsion between the abrasive particles and the dispersion stability of the abrasive particles,thereby affecting the MRR and surface quality of the 6H-SiC wafer.Compared with the polishing slurry using the Fenton reaction system,the amount of hydroxyl radica produced in the polishing slurry using the photo-Fenton reaction system is larger,indicating that ultraviolet light can increase the amount of hydroxyl radica in the reaction system,thereby promoting the surface oxidation of SiC wafer,increasing the MRR of 6H-SiC and improving its surface quality.The effects of pH values,H2O2 concentrations,Fe2+concentrations,and ultraviolet light power on the surface film formation characteristics of 6H-SiC wafers were studied by electrochemical experiments.The study shows that with the increase of pH values,H2O2concentrations and Fe2+concentrations,the corrosion potential of 6H-SiC wafers increases firstly and then decreases,and the corrosion current density decreases firstly and then increases,indicating that the thickness of the oxide film on the surface of 6H-SiC wafers increases firstly and then decreases;increasing the ultraviolet light power,the corrosion potential gradually increases,and the corrosion current density continues to decreases,indicating that the thickness of the oxide layer on the surface of 6H-SiC increases with the increase of ultraviolet light power.The larger the thickness of the oxide layer,the easier it is to be mechanically removed.The higher the material removal rate of the 6H-SiC wafer,the better the surface quality,which verifies the accuracy of the polishing experiments.Finally,the processing mechanism of the SiC wafer is analyzed,the relationship between the mechanical and chemical effects is analyzed from the dynamic process,and the material removal model of the SiC wafer surface is analyzed.Based on the theory of contact mechanics,discuss the different contact deformation forms and material removal model analysis between wafers,abrasive particles and polishing pads.The effect of surface oxide layer on CMP of Si C wafer was analyzed by the chemical action of polishing solution on SiC.
Keywords/Search Tags:silicon carbide(SiC), photo-Fenton reaction, chemical mechanical polishing, hydroxyl radical, electrochemistr
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