Mechanisms And Experimental Study Of Ultra-smooth Surface Processing By Electrically Assisted Photo-induced Colloidal Jet

The development of the semiconductor industry has seriously affected the development of the national economy and society,with the first generation of semiconductors as the representative of silicon materials in integrated circuits and other aspects have made great achievements,the third generation of semiconductors as the representative of silicon carbide because of its excellent performance in smart grid,5G communication and other aspects are widely used.Therefore,the surface finishing processing of silicon and silicon carbide semiconductor materials has put forward new requirements,the surface roughness needs to reach the nanometer level,the traditional finishing surface processing method has been unable to meet the processing requirements,so an ultra-precision processing method is needed for its surface processing.Nanoparticle colloidal jet processing as a surface ultra-precision processing method,its basic principle is the interfacial reaction between nanoparticles and the surface of the workpiece,and then the removal of the atoms of the interfacial reaction between nanoparticles and the surface of the workpiece through shear action,so that the surface of the material is ultra-smooth and without damage,so nanoparticle colloidal jet processing is a nanoscale processing method.In order to improve the material removal rate introducing UV photocatalysis to improve the interfacial reaction between nanoparticles and workpiece surface atoms,due to the compounding rate of photogenerated carriers affects the intermediate active body hydroxyl of the interfacial reaction,this paper introduces electric field and investigates the effect of electric assistance on photoinduced colloidal jet processing by a combination of theoretical simulation analysis and experimental verification as follows:(1)Introduction of several theories of material removal by electrically assisted photo-induced colloidal jet processing and energy exchange between binding energy,workpiece surface energy and kinetic energy of nanoscale processing atoms;analysis of the effect of binding energy and workpiece surface energy on atomic instability at the workpiece surface and the relationship between binding energy and Fermi energy,workpiece surface energy and bond breaking work.The force analysis of nanoparticles in the colloidal jet field is performed to obtain a material removal model for electrically assisted photo-induced colloidal jet processing.(2)The adsorption process of nanoparticles on different surface structures of silicon and silicon carbide workpieces and several theories of atom removal from the workpiece surface were analyzed by first-nature principle simulation.A model of titanium dioxide clusters and different surface structures of silicon and silicon carbide were established;the adsorption of titanium dioxide clusters with different surface structures of single-crystal silicon without electric field assistance and the adsorption of titanium dioxide clusters with different surface structures of silicon carbide with the assistance of 30 V applied electric field were analyzed respectively;by calculating the adsorption energy and bonding residence,it can be seen that the "convex surface The adsorption energy and bonding residence were calculated to show that the"convex" target atoms have a high adsorption rate,followed by the "flat" target atoms,and the "concave" target atoms have a low adsorption rate.When the nanoclusters are desorbed,the "convex" target atoms are the first to be removed,the "planar" target atoms are the second,and the "concave" target atoms are the lowest.(3)The electric field distribution on different surface structures of the workpiece was studied based on the computational fluid dynamics method.According to the surface roughness of the workpiece,two structure combination models were developed to analyze the current density distribution on the "convex","flat" and"concave" surfaces of the workpiece at different voltages,different injection distances,different machining pressures and differ ent surface profiles,respectively."The results show that the highest current density is found on the "convex" side of the workpiece,followed by the "flat" side and the "concave" side,regardless of the conditions.The current density is the smallest.When the voltage is different,the higher the voltage,the higher the current density in the center of the surface of the workpiece,when the injection distance is different,the current density in the center of the surface of the workpiece is the best at 1 mm,and the current density on the surface of the workpiece does not change with different processing pressure.The current density of "concave surface" is the highest and the current density of "concave surface" is the lowest.(4)The experimental platform of electrically assisted photo-induced colloidal jet processing was set up for the adsorption and processing experiments to verify the above simulation results.The adsorption effect of nanoparticles on the workpiece surface was characterized by SEM images,and the results showed that the adsorption of nanoparticles on the smooth surface of Si C workpiece was significantly more than that on the light-induced condition only.In the adsorption process of different surface structures of the workpiece,the number of nanoparticles adsorbed on the "convex" surface is the highest and the number of nanoparticles adsorbed on the "flat" surface is the lowest.The results showed that the surface roughness of Si C and Si workpieces were reduced to different degrees and the surface quality of the workpieces was significantly improved when both Si C and Si workpieces were processed under electrically assisted photoinduced conditions.