Research On The Influence Of Sapphire Substrate Polishing Accuracy On Its Graphic Processing

Light-emitting diode(LED)is an electronic component of electroluminescence,which is widely used in the fields of backlight,special lighting and large screen display.LED chip is the core component of LED products,and sapphire is the main substrate material for the chip.The quality of sapphire substrate processing directly affects the performance and life of LED chips.In order to improve the combination of Ga N epitaxial layer and sapphire substrate and improve the brightness of LED lamp,it is usually necessary to perform graphic processing on the surface of sapphire substrate.As the last step of sapphire substrate preparation,polishing quality has an important influence on the subsequent graphical processing of sapphire substrate.Based on this topic,the influence of sapphire substrate polishing precision parameters on its graphical processing is studied.The effect of polishing process parameters on the polishing quality of sapphire substrate was studied by polishing experiments.Then the sapphire substrate graphical processing experiment was carried out to analyze the influence of sapphire substrate polishing quality parameters on its graphical processing.Finally,by establishing a random forest prediction model,the correlation between the polishing accuracy of sapphire substrate and the processing quality of graphical substrate is analyzed,and the correctness of the prediction model is verified by the mass production experimental data.The main research work of this paper is as follows:(1)The CMP polishing process of sapphire substrate was carried out,and the effects of polishing time,polishing speed and polishing pressure on material removal rate,surface roughness and surface shape accuracy were investigated.The material removal rate increases with the increase of polishing time,polishing speed and polishing pressure,while the surface roughness decreases with the increase of polishing time,polishing speed and polishing pressure.The surface accuracy of substrate(Bow,Warp,TTV and LTV)decreases rapidly with the increase of polishing time,and finally tends to be stable.Polishing pressure and polishing speed have little effect on substrate surface accuracy.(2)The graphical processing experiment of sapphire substrate was carried out,and the influence of polishing accuracy parameters of sapphire substrate on the processing quality of graphical substrate was analyzed.The surface accuracy of sapphire substrate has an important influence on the uniformity of the coating.When the surface accuracy of the substrate is poor,the thickness uniformity of the coating becomes worse,and the uniformity of etching becomes worse,thus affecting the dimensional accuracy of the etching pattern.The substrate surface roughness and surface defects(scratches,pits,etc.)affect the combination of photoresist and substrate surface,and surface defects may even cause the loss of microstructure.(3)Based on the random forest algorithm,the prediction model of the quality of the graphical sapphire substrate was established,and the relationship between the polishing quality parameters of the sapphire substrate and the graphical processing quality was analyzed.The processing quality of sapphire graphical substrate is predicted by this model.The prediction accuracy of microstructure depth level is 92%,the prediction accuracy of reflectivity level is 95%,and the prediction accuracy of reflectivity STD level is 59%.It is proved that the prediction model can be used to predict and analyze the quality of sapphire substrate graphical processing.