Study On Micro-Material Removal Mechanism For Optical Glass Chemical Mechanical Polishing

Since the 21st century,the demand of space technology and energy technology has led to a rapid increase in the demand for large optical components in optical systems of weapons equipment.The performance requirements,processing requirements and efficiency requirements of optical components have been greatly improved.The most widely used ultra-precision machining method of the optical component,Chemical Mechanical Polishing?CMP?,faces serious challenges.How to minimize the production cost and improve the surface accuracy,surface quality and processing efficiency of optical components has become an important issue to be solved in the optical manufacturing industry.CMP uses chemical-mechanical synergy to polish and flatten the workpiece material during processing.The coupling of many physical and chemical factors in the process and the uncertainty of parameter influence make the quantitative analysis of CMP process difficult.At present,the research on mechanism is still lacking.The existing CMP process research is somewhat independent of the behind-the-scenes mechanism,most of which are empirical single-factor variable experiments or orthogonal experiments.The process experiments are time-consuming,causing great difficulties for coping with many process requirements.The existing CMP models are divided into different scales with their limitations.It is difficult to link the micro-material removal process with the process research.At the same time,the surface scratching characteristics,etching characteristics and surface hydroxylation characteristics of different SiO₂ materials need further study.There are few reports on the asperity contact characteristics,contact point distribution characteristics and multi-asperity material removal process on the surface of the polishing pad.In this paper,the CMP process of optical glass is studied based on the roughness peak scale.And the scratching characteristics,etching characteristics and surface hydroxylation characteristics of the glass surface are studied.Moreover the transition from single roughness peak to multi-asperity contact and removal features are studied.The main research contents of this paper are as follows:?1?A single POM ball scratching experiment method based on asperity scale was proposed.The feasibility of the single POM ball scratch test method is verified by comparing the contact state of the polishing pad/workpiece with the contact state of the POM/workpiece,analyzing the characteristics between the POM ball and the workpiece and comparing the removal rate of quartz and K9 glass under single ball scratching and macroscopic CMP test.The theoretical calculation shows the way of the glass being removed during the single POM ball scratching process.The experimental method has certain advantages for the study of material removal and surface properties in the contact points under the asperity scale.?2?The surface properties of different SiO₂ materials were studied by single POM ball scratching test method and etching method.The effects of external load on the removal of different SiO₂ materials,the etching rate and surface morphology of different SiO₂ materials during etching,the hydroxylation characteristics of the K9 glass surface and the influence of load on hydration were summarized.?3?Based on the analysis method of probability and statistics,the calculation method for material removal of random distribution polishing pad asperities was proposed.The average spacing of the randomly distributed polishing pads asperities was obtained by analytical calculation and was verified by numerical method.Moreover,the mechanical action of single asperity and the chemical action of the CMP process were further calculated to obtain the material removal of random distribution polishing pad asperities.Furthermore,the effect of different parameters on the material removal rate was investigated.