Sapphire Substrate Surface Shape Features To The Influence Of Annealing Process

LED is widely used in the automoblies,cellular phone,televisions and lighting fields.Sapphire as the most widely used substrate material,its manufacturing process directly affects the level of LED product performance and cost. Sapphire substrate is made of ingot,via slicing,double side lapping,edge bevelling,annealing,cu-polishing,CMP and other process,wherein the annealing has an important impact on substrate surface shape accuracy.In current manufacturing process about 60% losses arise from substrate surface shape accuracy oversize. Therefore,researching the effect of annealing on sapphire substrate surface shape accuracys is of vital importance.Combining with the practiccal production status in internship factory,I detected the sapphire substrate surface shape features in the paper, based on theoretical and experimental aspects to analyse the changing rules of surface shape accuracys between different types sapphire substrate in annealing process. Meanwhile,from the point of lapping and polishing,the annealing process of various surface shape types sapphire substrate were optimized and concluded the following conclusions:(1) By detecting the surface shape features of lapping substrate,we found that the surface shape of substrate has two main types.The surface shape of one type likes saddle were defined as A type,which has 1/3 in total,the warp distribution ranges from15~25μm;Another type in surface shape likes concentric circles were defined as B type,which has 2/3 in total,the warp distribution ranges from 5~15μm.(2) Based on Stoney theory,we calculated the stress condition of two types substrate,the results show that the stress range of A type is 124~207Mpa before annealing,the stress range of B type is 10~31Mpa before annealing.(3) We analyzed the displacement of lapping substrate after annealing on account of Ansys software and calculated the variation of warp and bow.Finally results show that the axial displacement is about-2~1.8μm, the variation of warp ranges from0.9~3.5μm,bow ranges from 0~3.5μm.(4) In terms of the annealing process in the factory,we reserached the surface shape accuracy changing rule in the same annealing process and found that annealing nearly has no impact on Ttv and Tir,however,has an active impact on Warp and Bowof sapphire substrate.(5) By studying the annealing process between A type and B type of lapping and polishing substrate,we concluded that both A type lapping substrate and B type lapping substrate have the same optimum process,which is annealed at 1400 ℃ and holding 4 hours; At the same time,the optimum process of A type polishing substrate is annealed at 1600℃ and holding 6 hours, unlike A type,the the optimum process of B type polishing substrate is annealed at 1400℃ and holding 2 hours.