Research On Synchronous Modification Mechanism And CMP Removal Of RB-SiC Surface

As the rapid development of space application technologies such as space lidar systems and high-precision space telescopes,reactive sintered silicon carbide(RB-SiC)has attracted extensive attention and research as an ideal space mirror material.However,due to the extremely high hardness of the RB-SiC ceramic material,and the internal structure of the RB-SiC ceramic material is composed of different two-pHase properties,it is difficult to manufacture large-scale mirrors by its processing technology.Chemical mechanical polishing(CMP)has the advantage of improving the polishing efficiency of RB-SiC mirrors,and the polished workpiece has better surface quality.Processing RB-SiC by CMP technology is one of the ideas to solve its difficult processing problem.Chemical mechanical polishing(CMP)technology is the use of chemical and mechanical synergy to remove the workpiece.In the study of RB-SiC chemical mechanical polishing process,it is necessary to explore the mechanism and effect of the Fenton oxidation system on the simultaneous modification of sintered SiC surface.The chemical oxidation modification model was used to study the effect of different parameters of the Fenton system oxidizing solution on the simultaneous oxidation of RB-SiC.A polishing removal model was established,and the contact pressure of the lower surface of the workpiece under different polishing process parameters was studied by simulation.A chemical-mechanical synergistic experiment was established to study the effects of various parameter changes on material removal rate and surface quality,and the optimal CMP condition parameters of RB-SiC were obtained.The main research contents of this paper are as follows:(1)Analyze the influence of chemical composition on the thickness of RB-SiC modified layer in the polishing solution.In this paper,the surface two-way diffusion principle and the classical Deal-Grove oxidation model were used to establish the Si pHase and SiC in FB-SiC in the Fenton oxidation system.Modified model,calculation of modification rate,analysis and modification principle,theoretically explore different oxidation parameters such as catalyst type,oxidant concentration,temperature,solution pH,RB-SiC modified layer thickness,oxidation rate,oxide surface morpHology Impact.(2)The mechanism of surface modification of RB-SiC surface was studied experimentally.The Fenton oxidation system modified RB-SiC experiment was carried out to analyze the effect of the oxidation parameter change on the hydroxyl radical concentration in the Fenton reaction.Then,the Fenton reaction-based method was used to perform surface synchronous oxidation of RB-SiC by evaluating RB-.The thickness of the oxidation reaction layer on the surface of SiC is used to judge the oxidation reaction speed,and the single oxidation and single crystal SiC are used for uniform oxidation to investigate the influence of catalyst type,oxidant concentration,polishing solution pH and oxidation temperature on the simultaneous oxidation of RB-SiC.Based on the principle of thin film mechanics,the variation of hardness of the modified oxide layer with thickness was investigated.(3)The contact stress during the removal process was studied by simulation.In the CMP process,along with the chemical modification process is a mechanical polishing process,in which the change of contact stress directly affects the surface removal rate of the material and the surface quality after processing.Based on the direct contact between RB-SiC workpiece and polishing pad,the chemical mechanical polishing model of RB-SiC workpiece was established by Comsol finite element analysis software.The different polishing pressure,polishing pad thickness and polishing pad elastic modulus were analyzed during polishing.The distribution of contact stress on the surface of the workpiece under Poisson's ratio and the uneven distribution of stress on the surface of the workpiece.(4)RB-SiC material removal experiment.On the basis of chemical and mechanical effects,the barrel was subjected to experimental research on the material removal rate under the synergistic effect of material modification and mechanical removal,and compared with the pure chemical effect and pure mechanical action.The crossexperiment was designed to study the effects of polishing pressure,polishing pad type and different properties of the abrasive particles used in the polishing solution on CMP of RB-SiC workpieces.According to the results,the polishing process parameters and the composition of the polishing solution were optimized to obtain RB-SiC high material removal.The optimum CMP polishing parameters for the rate.