Research On Damage Revolution In Grinding Of Monocrystalline Silicon By MD Simulation

As a kind of important semiconductor material,monocrystalline silicon is widely used in the manufacturing of large scale integrated circuits(IC).The quality of silicon surface after processing has a great influence on the service performance and life of the devices.However,it is inevitable to cause surface and subsurface damage in the process of machining silicon.In order to take action to control damage for a better machining quality,it is significant to understand how the damage in the machining process emerges.Grinding process is an important part in the machining of monocrystalline silicon,which has a great effect in the machining quality.At present,there has been no explicit explanation for the change and formation of damage in grinding monocrystalline silicon.Moreover,it is hard to observe the structure change during the processing by experimental research.In this study,molecular dynamic simulation(MD)has been applied to investigate the grinding process of monocrystalline silicon.Firstly,large scale simulation model for single grain scratching of monocrystalline silicon is established.The change of stress,structure and temperature in the typical region and phase transformation is studied.The effect of parameters,such as crystal orientation and the radius of grain on the machining process is also analyzed.Secondly,multiple grains scratching simulation is carried out to research the change of stress and structure under the combined action of two grains and the effect of distance between two grains.At last,multiple scratching simulation is completed to understand the change and control of damage in the multiple scratching.At the same time,as a comparison,the nanoindentation experiment is carried out.The reason for the gap between simulation and experiment and the improvement are discussed.In the single grain scratching simulation,the stress state in the region in front of the grain and region below the grain is studied.The structure change under the stress is analyzed by coordination number(CN).The stress state of research regions under different radii is compared and it explains the reason why the damage is smaller with a smaller radius of grain from the point of view of stress.In the multiple grains scratching simulation,the stress and temperature of the middle region of grains and the structure change and the distribution of damage are studied.A smaller distance between two grains leads to larger stress and temperature of the middle region.However,a lager distance produces a higher bulge in the machined surface,which makes the flatness of the surface worse.The machined surface is composed of the amorphous phase of silicon.Its hardness and elastic modulus have decreased compared with the ideal surface,which will influence the subsequent machining.There is a gap between the data gained by simulation and nanoindentation.In order to make the simulation closer to the reality,the simulation scale needs to be enlarged.The existed damage layer can be reduced stably without new damage structures generating through multiple scratching with an appropriate re-scratching depth to control the damage.