Research On 3-step Lithography Technology Of Thin Film Transistor Liquid Crystal Display

After nearly 30 years of development,thin film transistor liquid crystal display(TFT-LCD)industry has been expanding in scale and deepening in technology maturity.Especially in the past 10 years,China's LCD industry has developed rapidly.With Beijing Jingdong,Shanghai Tianma and Shenzhen Huaxing Photoelectric Panel Company,G4.5-G11 LCD Panel Production Lines have been put into operation one after another.With the development of LCD industry,the number of lithography processes of thin film transistors has also been reduced from 7 to 5,and the manufacturing cost has been greatly reduced.In 2010,with the application of half tone and gray tone technology,the number of lithography turns from five to four.At present,four photolithography technologies are still the mainstream technologies in various panel factories.At the same time,three photolithography technologies have become the main research and development topics of major panel factories.However,due to the difficulty and low yield of three lithographys,there are still many problems to be solved before mass production.In this paper,three common three-channel lithography technology methods are analyzed,including ITO lift off,Contact hole filling and three-stage mask.The key technologies of ITO lift off technology are studied,including Negative PR under cut method,Double layer PR under cut method and PR/PV under cut method.On this basis,we independently developed a new ITO lift off technology,named Photoresist Cashmere Technology.The principle of photoresist cashmere technology is to use plasma to treat the surface of photoresist,and grow a layer of velvet on the surface of photoresist.This layer of velvet has a large surface area,which is conducive to ITO deposition on it.This combination of photoresistive fluffy objects and ITO metals will form a large number of cracks at their interface,which will reduce the difficulty of ITO and photoresistive peeling in subsequent processes.This method overcomes the problem of unclean ITO and photoresist stripping in traditional three-channel lithography technology,solves the problem of pipeline blockage of stripping equipment caused by too large stripping particles in three-channel lithography technology,and greatly improves the possibility of mass production of three-channel lithography technology.A new three-channel lithography process is developed by studying the three-channel lithography technology of photoresist velvet making,which includes dry lithography velvet making process,film forming process and yellow light process.Optimum parameters and technological window of photoresist wool making process,key parameters and technological window of yellow photoresist process,optimum parameters and technological window of photoresist ashing process of Dry Etch process were obtained through experimental research.Finally,the world's first 28-inch TFT substrate and LCD module were fabricated with a new three-channel lithography technology.At the same time,several patents related to three-channel lithography technology were produced.The three-channel lithography technology greatly reduces the production cost of TFT LCD,and solves the problem of photoresist stripping which is difficult to overcome by other three-channel lithography technology,which greatly improves the production possibility of three-channel lithography TFT technology and contributes to the subsequent development of China's LCD industry.