Experimental Study On Cutting Polycrystalline Silicon Using Micro-Abrasive Water Jet

At present, large-scale integrated circuits are in the rapid development. Silicon materialas the most important semiconductor material is widely used in integrated circuits. Howevercutting of the wafer highlights technical problems such as low machining efficiency, surfaceintegrity, high processing costs and processing injury which seriously hampered thelarge-scale use of silicon in the IC industry.Micro abrasive water jet （Micro Abrasive Water Jet, MAWJ） technology was defined thejet beam diameter in microns or submicrons. The Micro abrasive water jet technology is onthe basis of improvement, innovation and development of traditional abrasive water jet. Microabrasive water jet was used to cut polycrystal silicon in this article. Polysilicon cuttingexperimental model is established based on the experimental data. The relationship betweenthe cutting force, material damage layer and the cutting conditions developed during thecutting process. Micro-abrasive jet cutting parameters on the processing capacity andprocessing quality in the different cutting conditions are analyzed.The theoretical formula of the speed of the water jet, flow and other basic jet parametersand micro abrasive water jet cutting theoretical basis wasstuded on the basic equations offulid mechanics, energy conservation law and momentum theorem and other basic theory inthis paper. The theoretical model of micro-Abrasive Water Jet Cutting polysilicon isestablished.Simulation of the impact of the the nozzle contour structure of the abrasive track andspeed is carried out using the Fluent software DPM （Discrete Phase Model） model. Analysisof the impact of micro abrasive water jet cutting polysilicon process parameters on theprocessing capacity of the material and processing quality were studied according to theexisting laboratory equipment and select the optimal nozzle structure for micro-abrasive waterjet cutting experiments. It was showed that as the jet pressure increases, the velocity of the jetimpact force and the kinetic energy of the abrasive increases, a deeper level of material isdamaged, the cutting depth was a linear relationship between the increased roughness value ofthe cutting section is significantly reduced. However, as the optimal target distance rangewithin the jet target groups increases, the energy of the jet will spread and then micro abrasivewater jet will be driven along the axis of the jet. Therefore the roughness of cutting crosssection of the polysilicon decreased. When abrasive exceed the optimum value of the cuttingjet target, the machining depth will decrease rapidly and the surface roughness will graduallyincreased. The smaller the moving velocity of the nozzle, the longer the micro abrasive waterjets impact the material, the deeper of thecutting depth. The greater of the moving speed ofthe nozzle, repeated shock reduces the number of cutting depth of processing, the material being cut in a unit time will be significantly reduced. When the moving speed of the nozzle isincreased to a certain value, the reduction in machining depth becomes obvious, and willeventually stabilize at a cutting depth. The roughness of the cross section after cutting,however, increases with jet moving speed increases。 The cutting depth is linearly increasedwith the abrasive flow rate. As the abrasive flow rate has been increased, the depth of cut willbecome slow increase, roughness sectional does not reduce significantly.Orthogonal experiment method of micro-abrasive water jet cutting the polysilicon andrange analysis were carried out. The analysis results show that the most obvious effect is thejet pressure, followed by the target distance. The optimal results of moving speed of5mm/min,the nozzle standoff distance of3mm, the jet pressure of230MPa, the abrasive flow rate of95.8g/min for the optimum combination are obtained based on the level of the experimentalparameters. The Cutting roughness range analysis showed that the jet pressure is the mostobvious role, followed by the abrasive flow and the moving speed of the nozzle. Finallyoptimal results is at the jet pressure of230MPa, jet target distance of7mm, the nozzle movingspeed of10mm/min, and the abrasive flow rate of95.8g/min for the optimum combination oflevels.By using the Matlab language and multiple regression analysis, A prediction model forthe cutting depth and cutting cross-section roughness in micro-abrasive water jet cuttingpolysilicon material. Cutting depth of processing specific prediction model H:H=4.609×10^-4P^1.8814S^-0.1684V^-0.2015Q_m^0.1759;cutting cross-section surface roughnessprediction model Ra: Ra=2.008×10⁸P^-3.1430S^-0.011V^0.016Q_m^0.1438...