Preparation Of Non-spherical Silica Abrasives And Their CMP Characteristics And Mechanism

Sapphire and zirconia ceramics materials have broad application prospects and significant economic benefits in the advanced electronics manufacturing industry.The sharp increase in the demand for electronic devices poses a huge challenge to the ultra-precision processing efficiency and surface quality of materials.At present,chemical mechanical polishing(CMP)is a recognized surface finishing technology that can provide the global planarization of workpieces,which becomes one of the most promising methods in the field of ultra-precision processing.The abrasive is the implementer and transmitter of mechanical and chemical effects,and is an important factor affecting the CMP performance of workpieces.Silica has good dispersibility,stability and high polishing accuracy,but traditional silica has a regular spherical structure,low hardness,and low polishing rate,which hinders the further expansion of the application range of materials.Therefore,the preparation of non-spherical silica abrasives and the research on the CMP characteristics of sapphire and zirconia ceramics help to achieve the goal of meeting the needs of industrialization,which plays a key role in the development and progress of the advanced electronics manufacturing industry.Taking non-spherical(petal shaped,dumbbell shaped,chain shaped)silica abrasives as the research object,the synthesis process and CMP characteristics of non-spherical silica abrasives are analyzed through scanning electron microscopy(SEM),particle size and potential analyzer,CMP experiment,surface profiler,X-ray photoelectron spectroscopy(XPS),etc.The polishing mechanism of non-spherical silica is explored by the combination of theoretical analysis and experimental research.The specific research contents and results are as follows:(1)Petal shaped silica abrasives are prepared by the cation induction method,and the synthesis process and CMP characteristics are analyzed by SEM,electric potential,conductivity,CMP experiment and XPS.The results show that the generation of petal shaped silica abrasives is attributable to the reduction of the electrostatic interaction between the particles.The silica particles are stuck together by the cation inducer to form a petal shaped structure and form new-Si-O-M-O-Si-chemical bonds(M is Ni,La,Cr)at the joints of the particles.The petal shaped silica abrasives have a larger coefficient of friction and a stronger mechanical effect.In sapphire CMP,the material removal rate of petal shaped silica abrasives prepared by the induction method of nickel ion,lanthanum ion,and chromium ion is 116%,200%and 135%higher than that of the corresponding spherical silica abrasives,respectively.Petal shaped silica abrasives can undergo tribochemical reactions on the surface of sapphire,and the aluminum element exists in the form of Al₂O₃,Al₂SiO₅,AlOOH and Al₂NiO₄(or AlLaO₃,or AlCrO₃).(2)In order to improve the stability of non-spherical silica abrasives,dumbbell shaped silica abrasives are prepared by the oxo acid salt anion induction method,and the synthesis process and CMP characteristics are analyzed by SEM,conductivity,CMP experiment and XPS.The results show that the formation of dumbbell shaped silica is ascribed to the hydroxyl groups contained in the anion hydrolyzed can undergo dehydration condensation reactions with the surface hydroxyl groups of silica particles,and form-Si-O-X-O-Si-chemical bonds(X is W,Al).Compared with spherical silica,the friction coefficient and mechanical effects of dumbbell shaped silica are increased.In zirconia ceramic CMP,the material removal rate of dumbbell shaped silica abrasives prepared by the aluminate and tungstate anion induction method is 39%and 240%higher than that of the corresponding spherical silica abrasives,respectively.Dumbbell shaped silica and zirconia ceramics can undergo tribochemical reactions,and the zirconium element exists in the form of ZrO₂,ZrSi O₄and ZrW_xSi₂O_y(or ZrAl₂Si₂O₉).(3)One-dimensional self-assembled chain shaped silica abrasives are prepared by the polymer template method,and the synthesis process and CMP characteristics are analyzed by SEM,infrared spectroscopy,contact angle analysis,CMP experiment and XPS.The results show that the formation of chain shaped silica mainly utilizes the chain shaped structure and guiding effect of PEG template to form new-Si-O-Si-bonds at the joints of the particles.And as the molecular weight of PEG increases,the chain length and aggregation degree of chain shaped silica increase.Chain shaped silica shows good CMP performance for sapphire and zirconia ceramics,and can have tribochemical reactions with sapphire.Aluminum exists in the form of Al₂SiO₅,AlOOH and Al₂O₃.In the fine spectrum of Al 2p,the proportion of the fitting peak area of Al₂O₃is significantly increased,which indicates the mechanical effect of chain shaped silica is significantly enhanced.(4)The CMP mechanism of non-spherical silica is explored through the combination of theoretical analysis and experimental research.The results show that there is a greater adhesion between the non-spherical silica and the surface of the workpiece,which can increase the number of particles participating in the CMP process.The feasibility of the tribochemical reaction between the non-spherical silica and the workpiece is discussed from the perspective of thermodynamics and kinetics,and the apparent activation energy of the tribochemical reaction is calculated.The finite element simulation analysis shows that non-spherical silica is sliding motion on the surface of the workpiece with rotating motion,which will produce a higher friction temperature.This can provide a foundation and guarantee for the progress of the tribochemical reaction and the enhancement of the mechanical effect.The increase in temperature provides energy for the breaking of the Zr-O bonds,which increases the tribochemical reaction rate and produces a silicate film on the surface,where the main element composition is Zr,Y,O,Si,C shown by XPS.The formation of the surface film is conducive to the progress of mechanical effect,where the material removal rate increases and the surface is gradually flattened.