Controllable Preparation And Polishing Mechanism Of Cerium Oxide Micro/Nano Rods

With the development of very large scale integrated circuits,the surface of single crystal silicon is required to have nano-scale surface precision and sub-nanometer surface roughness,while ensuring no damage to the surface,which makes wafer polishing technology a hot spot in the micro/nano manufacturing industry.Cerium oxide has been widely concerned with its advantages of high polishing speed,high smoothness and long service life.Spherical micron cerium oxide has the best polishing quality but low polishing efficiency;Octahedral cerium oxide has low polishing quality but high polishing efficiency.In this paper,the particle size is controlled by adjusting the preparation parameters of cerium oxide,so as to achieve the purpose of both polishing efficiency and polishing quality.The main work of this paper is as follows:?1?Using sodium citrate and lanthanum nitrate hexahydrate,sodium hydroxide and zinc acetate as experimental materials,Under the condition of low temperature hydrothermal conditions,the diameter-to-length ratio of cerium oxide micro/nano rods was controlled by adjusting the molar amount of zinc acetate capping agent Zn?CH₃COO?₂.XRD analysis showed that the precursor prepared by hydrothermal method was unset.After calcination at 300? for 10 hours,the nanorod precursor was converted into a cubic fluorite structure.It was confirmed that as the molar amount of zinc acetate increased,the rod-shaped nano cerium oxide diameter ratio increased.Electron irradiation can also cause the amorphous precursor to transform into a crystal.?2?The contact pressure distribution model of rod-shaped micro-nano-cerium oxide and single crystal silicon with different aspect ratios was established by finite element software.The contact form of the CeO₂ nanorod with the silicon single crystal is line contact.The results of three-dimensional finite element analysis showed that the contact compressive stress of silicon monocrystalline substrate presented a downward trend with the change of the length of CeO₂ nanorods,and the strain variable first decreased,then slowly increased and then decreased.Therefore,it was concluded that the removal rate of cerium oxide was unstable with the increase of the length.With the increase of the diameter of the CeO₂ nanorods,the contact compressive stress on the silicon monocrystalline showed a decrease first,then a slow increase,and then a decline.The contact strain showed a decrease first,then a slow increase,and then a decline.Therefore,it can be concluded that the removal rate of cerium oxide is not stable with the growth of its length.?3?The polishing liquid was prepared by using the prepared micro-nano cerium oxide with different diameter-to-length ratio as the abrasive,and the single crystal silicon wafer was mechanically polished to characterize the surface quality of the single crystal silicon.The results show that with the increase of the length-to-length ratio,the scratches on the surface of the silicon wafer after mechanical polishing are gradually deepened,which indicates that the wear mechanism of silicon single crystal surface is changed from single grinding wear to the form of mainly grinding wear,supplemented by slight plough cutting wear.The polishing quality decreases gradually and the polishing efficiency increases.