Research On Single Crystal Osmium Oxide Lapping And Polishing Processing Technology

Theβ-Ga₂O₃ is a semiconducting material with excellent physicochemical properties such as ultra-wide band gap,high breakdown field strength,and deep ultraviolet wavelength transmittance,which has broad application prospects in the field of high-frequency,high-efficiency,high-power microelectronic devices and high voltage equipment.Theβ-Ga₂O₃ processing technology includes crystal growth,slicing,lapping,polishing,etc.In particular,lapping and polishing processing are the key processing steps that determine the wafer surface processing quality.Due to its own cleavage properties,defects such as cleavage cracks,cleavage tongues,and cleave pits are easy to occur during the traditional lapping process,and it is difficult to remove during the later polishing process,which seriously affects the surface quality of wafers and restricts their popularization and application.The main research contents of this article are as follows:（1）A lapping pad for the viscoelasticβ-Ga₂O₃ was prepared.Based on the deformation theory of the viscoelastic material,a lapping pad for the viscoelasticβ-Ga₂O₃ was prepared and its composition was determined through experimental studies.The results show that:The elastic layer is a cloth base,and the lapping layer is composed of 5%-10%diamond fine powder,25%-40%resin glue,30%-40%water-soluble grinding aid and deionized water.（2）The influence of the prepared viscoelastic lapping pad on the lapping effect of theβ-Ga₂O₃ was studied.A comparative experiment was conducted on the lapping of theβ-Ga₂O₃ by using sandpaper,a tin plate,and a prepared lapping pad.The results show that:When the lapping pressure is 50g/cm² and the rotation speed is 120rpm,using a tin plate and sandpaper,the number of abrasive grains participating in the effective removal is large,and the abrasive grains rapidly cut into the wafer surface instantaneously to cause stress concentration,and the material removal rate and surface roughness are large.The wafer surface produces a large number of cleavage tongues.When the viscoelastic lapping pad is being ground,the viscoelastic lapping pad has a certain ability to wrap the abrasive particles,so that the number of abrasive grains participating in effective grinding is reduced,and part of the mechanical energy can be converted into elastic energy to be taken out of the processing area to reduce the vibrations and impacts of grinding,which prevent the abrasive particles cutting into the crystal surface too quickly and deeply.The surface roughness of the wafer is small and cleavage is weak,but the material removal rate is low.In this experiment,the traditional method of lapping and viscoelastic lapping was used to ensure the lapping efficiency and the wafer surface quality after lapping.（3）The effects of different types of polishing pads on the polishing effect of theβ-Ga₂O₃ were studied.Politex,Suba600 and LP57 polishing pad were used to perform chemical mechanical polishing experiments on the polished wafers.The results showed that:When the polishing pressure is 60 g/cm²,the rotation speed of the polishing plate is 50 rpm,the rotation speed of the wafer is 30 rpm,and the flow rate of the polishing liquid is 20 ml/min,the NS-24 silica sol with a pH value of 10 was used for polishing,the material removal rate of the Suba600 polishing pad was the largest at 30.8 nm/min,but after the polishing,the surface of theβ-Ga₂O₃ had significant pits;The material removal rate of the LP57 polishing pad is 22.6 nm/min,which is larger than 16.4 nm/min of the Politex polishing pad.Although Politex and LP57 polishing pad polished the surface morphology of the wafers are good,the surface roughness Ra of LP57 after polishing reaches sub-nanometer accuracy of 0.48nm,which satisfies the polishing processing requirements of theβ-Ga₂O₃.