Study On The Surface/subsurface Characteristic Of PV Polycrystalline Silicon Sawn By Electroplated Diamond Wire Saw

The electroplated diamond wire sawing technology is the mainstream processing method for cutting PV polycrystalline silicon ingots.It has a lot of advantages such as smaller kerf loss,higher cutting efficiency and accuracy,shallower subsurface damage layer,environment friendly and so on,compared with free abrasive wire sawing technology.In the processing of fabricating solar cells with the polycrystalline silicon wafers.,the wafers’surface needs to be textured to reduce the surface’s reflectivity.However,there are many smooth areas on the wafers surface cut by electroplated diamond wire sawing,which are covered by an amorphous silicon layer.This layer of amorphous silicon has the characteristics of acid corrosion resistance,which makes it impossible for the traditional high-efficiency acid texturization to carry out effective texturing,the industry had to use only a high-cost and low-efficiency"black silicon" technology to texturing.In this paper,the numerical simulation was developed during the process of electroplated diamond wire sawing,and the cracks nucleated and propagated during single abrasive scratching are studied.At the same time,the roughness and damage layer of silicon wafer cut under different processing parameters is studied experimentally.The research work has a guiding role for getting the surface,which cut by electroplated diamond wire sawing technology,to meet the requirement of acid etch texturization.The main research work of this paper is as follows:(1)The numerical simulation model of with electroplated diamond wire sawing process was established,the cutting depth of abrasives at different positions on the saw wire was analyzed under different processing parameters or wire parameters,the material removal modes and removal volume of abrasives in different cutting depths were studied,and the number of abrasives removed by brittle and plastic modes and their distribution on the saw wire were counted.The change of workpiece surface morphology with different processing parameters was verified by experiments.(2)The stress field distribution model under the abrasive tip in the process of single abrasive scratching was established,and the change of nucleation position and propagation direction of radial crack under two different material removal modes,ductile mode and brittle mode,were analyzed,the prediction results were compared with the experiments done by relevant scholars.The change of propagation direction of median crack with the half angle of abrasive tip was studied,and the prediction results were also compared with the experimental data,the correctness of the model was verified.The median-radial crack system in indentation process was extended,and a new median-radial crack system in scratching process was proposed.Finally,the median crack deflection angle of polycrystalline silicon was predicted in scratching process.(3)The prediction model of surface roughness and sub-surface damage layer of polycrystalline silicon wafer cut by electroplated diamond wire saw was established.The slicing experiments of polycrystalline silicon wafer were carried out at different feed speeds and wire speeds.The surface roughness of the wafers was measured by roughness measuring instrument.The depth of sub-surface damage layer of the wafers was observed and measured by cross-section microscopy method.The validity of the model is verified by comparing the prediction results and measure results.