Study On The Removal Mechanism Of Photocatalyst Assisted Polishing Silicon Carbide Material

In some power devices,the substrate material needs to guarantee some basic properties,such as a wide energy band gap,excellent thermal conductivity,high breakdown electric field,and good chemical stability.Therefore,as the third generation semiconductor material,single crystal silicon carbide(4H-SiC)has received a high degree of attention,and is widely used in the electronic field of high pressure,high temperature,high power,high frequency and so on.These areas have extremely high requirements on the surface quality of silicon carbide.The existing silicon carbide polishing methods,such as mechanical grinding,chemical mechanical polishing,electrochemical mechanical polishing,and plasma assisted polishing,etc.These processing methods have low surface material removal rates.There are defects such as scratches on the surface after processing.Basing on these shortcomings,this paper proposes a new method of polishing silicon carbide,ultraviolet photocatalyst assists polishing silicon carbide,this method is the use of mechanical and chemical synergy to the silicon carbide surface efficient and non-damaging material removal.Molecular dynamics and reactive molecular dynamics simulations are used to simulate the polishing of silicon carbide.The effect of mechanical and chemical mutual promotion during the polishing process is observed from the atomic level.Part of the simulation is verified by the photocatalytic assisted polishing silicon carbide test.(1)Based on the principle of molecular dynamics,the effects of parameters of diamond abrasive grain polishing silicon carbide are simulated by lammps molecular dynamics simulation software.The research shows that: first,under the conditions of the same pressing speed,scratching speed and abrasive,scratching different surfaces,the scratch quality of the Si surface is better than that of the c surface.Different abrasives scratch the Si surface of the silicon carbide workpiece.The effect of diamond abrasive particles is better than that of silicon dioxide.Silica can only disturb the surface atoms,proving the hardness relationship: diamond is greater than silicon carbide and greater than silicon dioxide.The abrasive grains scratch the Si surface of the silicon carbide workpiece at different depression depths.The greater the depth of the scratch,the higher the temperature and the higher the potential energy.The more resistance the abrasive grains are subjected to,the greater the abrasive particle’s cutting force.Mechanical scratching increases the potential energy of the workpiece,and the increase in potential energy can promote chemical reactions.(2)Based on the principle of chemical action assisted mechanical action,the atomic molecular removal mechanism of diamond abrasive grain polishing silicon carbide in hydroxyl radical aqueous solution is studied by Reactive Molecular Dynamics Simulation(ReaxFF MD).Studies have shown that: first,hydroxyl radicals and water molecules are adsorbed on the surface of silicon carbide,and then immersed in the surface of silicon carbide and form bonds with Si atoms and C atoms to achieve oxidation of the silicon carbide matrix.Under the mechanical action of abrasive grains,the Si atoms of the workpiece are mainly removed in the form of SiO,SiO2 or Si chain,and the C atoms of the workpiece are mainly removed in the form of CO and CO2.The effect of polishing pressure on the removal process is more obvious than the polishing speed.The greater the polishing pressure,the more atoms are adsorbed on the surface of the workpiece,and the more atoms are removed from the workpiece;the polishing rate is too large,and the reaction time between the substrate and the solution is shortened,resulting in a small amount of atoms removed from the workpiece.The chemical reaction produces low hardness silicon dioxide and other products on the surface of silicon carbide,which facilitates the mechanical action to remove the surface material of the workpiece.(3)The photocatalytic assists polishing of silicon carbide is used to verify the simulation,and XPS is used to analyze the surface.The results show that there are Si-C,Si-CO,Si-O,CO and C=O etc.The accuracy of the simulation.