Research On Mechanics Of Abrasive And Its Impact On Surface Roughness In Fam Slicing Silicon Crystal Using Wiresaw

Wiresaw is widely perceived as the technology for future, capable of meeting among IC, PV and LED industry's requirements for producing wafers from large diameter ingots and thin wafers. It needs reseachers to underatand and study the technology comprehensively. Although many research have been done a lot of work, the study focused on mechnial behaviors of abrasive are still not understood very well.Based on quasi-static indentation fracture mechnical model, the model on mechanics behavior of the abrasive in a full contact between the wire and ingot during rolling-indenting process is established. In the modeling process, a single grain of rolling-indenting model is first estabilshed, and then the mechanics behavior of abrasive in working area between the wire and ingot is analyzed. The abrasives between the wire and ingot are divided into engaged grits and engaged grits for each instant sawing in working area. The model not only consider the abrasive distrubtion along the wire in axial and radial direction, but also take minimum indenting times to make the material removal into account. Moreover, the relationship between the average force and cutting parameters, including wire speed, table speed, wrie tension, abrasive size, slurry concentration and cutting length, is concluded. Finally, Simulation on the average normal force, tangential force of single grit and number of engaged grits for each instant with cutting parameters have been done. On the basis of this, a model of three-body abrasion for hard-brittle materials on predicting the surface roughness Rz which is determined by the normal force is introduced, so that the relationship between the surface roughness and cutting parameters is derived. The experiment is also implemented to contrast with the pedicted Rz value, which proved to be consistent with the pedicted. Besides, the reason of the deviation between them is analyzed. Finally, Process Optimization experiments on surface roughness Rz of sliced silicon wafers is carried out in different levels component by orthogonal experiment, Uses range analysis method to find the influence extent of different factors on wafer quality. In a certain extent produces the optimal process parameters which can be guidance to the application of wire saw in FAM. The main conclusion as follows: (1) The number of engaged grits for each instant sawing in working area increases with the increasing of wire speed, wire tension and slurry concentration, while decreases with the increasing of table speed, abrasive size and slicing length. With the decreasing of number of engaged girts for each instant sawing, the average force for single abrasive increases.(2) Wire tension plays a decisive role on number of engaged grits for each instant sawing, while abrasvie size largely determines the average force for a single one. The average force exerted on silicon ingot by single grit is so low that the ingot can not be voluminously fractured. The main material removal mechanism of wiresaw is Hertzian Fracture.(3) The surface roughness Rz decreases with the increasing of wire speed, wire tension and slurry concentration, while increases with the increasing of the table speed, abrasive size and diameter of silicon ingot.(4) Orthogonal Experiment results show that the descending order of the impact on different parameters is abrasive size, slurry concentration, wire tension, table speed, wire speed. The optimum component parameters to surface roughness include that wire speed is 12m/s, speed table is 0.4mm/min, wire tesion is 16N, SiC grain size is F800, slurry concentration is 60%.