Nano-mechanism Of Ultra-precision Machining Of Defected Single-crystal Silicon Workpieces

Monocrystalline silicon(Si)is widely used in microelectronics industry because of its excellent physical and mechanical properties.However,due to its high hardness and brittleness,monocrystalline silicon always contains a series of defects such as cracks and inclusions.These defects have a great influence on the processing performance and service performance of materials.With the miniaturization of electronic devices,the precision requirement of silicon wafer has reached the nanometer scale.In such a small scale,even small defects in the processing process will have a huge impact on the performance of the Si wafer,and the material removal mechanism and defect evolution mechanism are also very different from those in the macro scale.Therefore,the research on the nano mechanism in the defective monocrystalline silicon during ultra precision machining will help to improve the surface quality of the workpiece,prevent the premature failure of the workpiece,and then improve the performance of the monocrystalline silicon workpiece.A three-dimensional molecular dynamics model of monocrystalline silicon with nanoindentation cracks was established to simulate the evolution of different cracks under the same indentation conditions.The influence of nanoindentation process on crack evolution and the influence of crack closure mode on test parameters and indentation results were investigated.In addition,the corresponding theoretical calculation model is established,the stress at the crack tip is analyzed combined with the theoretical calculation,and the evolution trend and internal mechanism of different cracks are revealed.Through three-dimensional molecular dynamics simulation and theoretical analysis,the evolution process of nano cracks in single crystal silicon during three-body polishing was studied.The evolution difference of cracks with different dip angles and the effect of initial temperature on the crack evolution were investigated.Two different ways of crack closure were found,and the influence of crack evolution on polishing process was analyzed.The relationship between crack inclination angle and evolution mode was revealed,and the influence of initial temperature on crack evolution was also revealed.The evolution of silicon carbide(Si C)inclusions in monocrystalline silicon during grinding was studied by molecular dynamics simulation.The evolution of inclusions with different diameters and positions in grinding process is compared,and the influence of the diameter and position of inclusions on the evolution of inclusions and grinding process is summarized.Although it is difficult to remove a large number of inclusions in the grinding process,the inclusions will have a significant impact on the diamond-like structure,temperature,potential energy,average grinding force and other physical parameters of the workpiece.In this paper,the nanoindentation model and ultra precision polishing model of monocrystalline silicon with cracks are established,as well as the corresponding theoretical calculation model.In addition,a molecular dynamics model of grinding process of single crystal silicon containing Si C inclusions is established.The influence of crack and inclusion defects on the ultra precision machining process of single crystal silicon was studied in nano scale.The research results can provide guidance for the selection and optimization of material design phase,and achieve the purpose of improving the performance of the workpiece.