Research On Nano Scratching And Chip Processing Performance Of Single Crystal Silicon

Single crystal silicon is a semiconductor material with excellent performance.It is widely used in the fabrication of integrated circuit(IC),micro/nanoscale devices and micro structures.Although single crystal silicon is a typical anisotropic brittle material,it exhibits plastic behavior in precision machining and the material is removed in ductile region.The key to obtain high-quality precision machined surfaces of brittle materials is the material removed in ductile region.Based on the research of single crystal silicon nano scratching,by controlling the crack damage in the slicing process,the precision slicing process can be realized with low or no crack damage on the surface of single crystal silicon substrate wafer.In this paper,theoretical analysis and experimental research on nano indentation and scratching of single crystal silicon are carried out.The influence of cutting tool structure on micro and nano scratching is represented by the typical scratching direction of Berkovich indenter.The residual scratch depth and material removal rate of typical scratching direction of Berkovich indenter are investigated.Based on the research results of nano indentation and scratching,a method for determining the slicing process parameters of single crystal silicon is established.The research work is of great significance to the development of single crystal silicon micro structure precision machining and diamond wire saw precision slicing technology.The micro and nano classical contact theories and its applicable conditions are comprehensive analyzed and clarified.The tip microstructure and the indentation normal contact area of Berkovich indenter are analyzed.A simplified method for calculating the normal contact area of indentation of Berkovich indenter is proposed.The equivalent contact model between Berkovich indenter and specimen is established.The Tabor number of adhesive contact between Berkovich indenter and single crystal silicon is calculated.A method for calculating the adhesion force of Berkovich indenter under the condition of indentation and scratching contact is presented.The contact problem of Berkovich indenter along three typical scratching directions is analyzed.The formulas for calculating the normal and tangential contact area of the Berkovich indenter in three typical scratching directions and the change rule of the contact area with the contact depth of scratching are obtained.The nano indentation experiments on the polished single crystal silicon(100)surface are finished.The normal loads are increased by 2mN from 2mN to 48mN.The mechanical properties,load-depth curve and indentation morphology of single crystal silicon are obtained.The variation of elastic contact stiffness with normal load in the nano indentation contact between Berkovich indenter and single crystal silicon is revealed.The maximum indented depth and residual indentation depth of Berkovich indenter under different normal loads are extracted from the experimental data.The theoretical models of acting force,the indented depth,comprehensive elastic deformation size,and residual indentation depth during the load indenting process of Berkovich indenter are established.The calculation results of the indented depth and residual indentation depth of Berkovich indenter are basically in well agreement with the experimental results of nano indentation.The theoretical models of scratching force acting on Berkovich indenter along three typical scratching directions are established.The scratching experiments of single crystal silicon under varying normal loads along the direction ?=0°are carried out using Berkovich indenter.Using the drastic change of tangential force as the criterion,the critical normal load and critical residual scratch depth for brittle-ductile transition determining rule in single crystal silicon scratched by Berkovich indenter are established.The scratching experiments of single crystal silicon under the constant normal loads along the direction ?=0°and ?=60°are carried out using Berkovich indenter,and the residual scratch depth and scratch morphology of single crystal silicon scratched by Berkovich indenter are measured.The elastic deformation,residual scratch depth and material removal rate of scratching single crystal silicon by Berkovich indenter are calculated.The calculation results of residual scratch depth are in good agreement with the experimental results.The effects of normal load and scratching direction on the residual scratch depth and material removal rate of single crystal silicon scratching with Berkovich indenter are investigated.The resin bonded diamond wire saw with base wire diameter of 60?m and abrasive of D50 as 8.01 ?m is developed,and the experiments of slicing single crystal silicon are carried out.The protrusion height,the position distribution and cutting edge shape of diamond abrasives are analyzed.Considering the random distribution of diamond abrasive position on the wire saw surface,the simplified three-dimensional topography model of resin bondeb diamond wire saw is established.The relationship between the circumferential position of a single diamond abrasive on the surface of a diamond wire saw and the abrasive scratching depth in slicing process is analyzed.Based on the critical cutting depth of ductile-brittle transition obtained from the experiments of Berkovich indenter scratching single crystal silicon,the relationship between circumferential abrasive ductile domain scratching and feed rate of diamond wire saw is analyzed.The specific feed rate calculation model of diamond wire saw slicing process is established.To take the diamond abrasives which in a certain circumference of resin bonded diamond wire saw in ductile domain scratching as a precondition,the determining method of single crystal silicon slicing process parameters is established.