Research On Technology Of Low Subsurface Damage In Ultra-Precision Machining Of Single Crystal Silicon

With the development of semiconductor industry,the demand of silicon wafer with high quality surface and damage-free subsurface is increasing.In order to obtain high quality semiconductor silicon substrate,single crystal silicon rod needs a series of processes such as cutting,grinding and polishing cloud meet the requirements of integrated circuit.With aim of exploring the influence of process parameters on the surface quality and subsurface damage depth of mono-crystalline silicon during grinding and polishing.In this paper,the experiments of mono-crystal silicon diamond grinding wheel grinding,loose abrasive grinding and CMP are carried out.The depth of sub-surface defects in rough grinding and fine grinding under different grinding modes is detected by the method of magnetorheological polishing spots.Based on the scratch experiment of mono-crystal silicon,the depth of sub-surface cracks is predicted.The SSD depth of mono-crystal silicon in the machining processes is systematically studied,a guideline is proposed to minimize subsurface damage in the grinding process of silicon wafers.The time needed to remove the depth of sub surface defects is reduced.The main contents of this paper are as follows:(1)The magnetorheological polishing spot method has been successfully applied to detect the depth of sub-surface defects caused by grinding of mono-crystalline silicon,Compared with other methods,this method will not introduce new damage and reduce the defect detection time.The influence of material anisotropy is fully considered in the detection process.(2)Through the grinding experiments of diamond grinding wheel in different process parameters along the direction of<100>and<110>of mono-crystalline silicon,the effects of grinding wheel size,feed speed,grinding wheel linear speed and cutting depth on the depth of sub surface defects are clarified,and the grinding direction and process parameters for the lower value of sub-surface defect depth under the processing mode with feed direction are obtained.(3)The effect of process parameters on the depth of subsurface in the process of bulk grinding is investigated,and the influence of crystal orientation on the depth of sub surface defects is compared in<100>,<110>,so as to guide the process of loose abrasive grinding in the processing of an-isotropic materials to obtain high-quality surface and sub surface.(4)The CMP of the ground surface was carried out.The limit value of machining and the time required to remove subsurface defects under different particle size and process parameters were explored,and obtained the most suitable process parameters with the high removal efficiency and smooth surface.