A Study Of TFT-LCD Critical Dimension Control

In recent years,with the continuous development of information technology,the social demand for display technology is also growing.TFT LCD(thin film transistor liquid crystal display)has become the absolute mainstream in the market due to its advantages of light weight,cost and life.Liquid crystal panel industry in China has developed rapidly in the past decade,and the large generation line is basically produced with a-Si(amorphous silicon)technology as the carrier.Due to the low electron mobility of a-Si,a larger metal linewidth is needed for signal transmission,with weak points with low opening rate and brightness ratio.In order to meet the requirements of larger size,higher brightness and flexible display,COA(color filter)is born.On array array substrate color filter technology).In the via lithography process of coa process,the array via hole needs to be opened in CF open,and the film thickness of CF color resistance 3?m forms a depression in CF open area,which causes the actual photoresist thickness in the exposure area of array via to be thicker than the design value,affects the production beat and productivity,and deteriorates the CD(critical dimension characteristic linewidth)uniformity of via process.Therefore,this paper analyzes the steps of via photolithography in COA process,including cleaning unit,photoresist coating,vacuum drying,pre baking,exposure process,development process,and so on,and analyzes one by one through experiments.1.Photoresist thickness study : reducing the photoresist film thickness to 1.8?m can effectively reduce the dose(exposure energy)by about 4mj.2.Pre baking temperature study: via adjusting the pre baking temperature,the ratio of via CD / temperature is about-0.21?m /10 ?.3.Exposure energy study: the exposure energy is in the range of CD 5.4-6.6?m,showing a linear relationship with CD,and the coefficient of change is 0.075?m /mj.4.Study on the developer concentration: the developer concentration has the most significant contribution to the change of CD.Raising the developer concentration from 2.38% to 2.42% can reduce the exposure machine dose by 21 MJ.The final improvement condition is to increase the development concentration to 2.42% and increase the economic benefit by 1.07 million / month.For the improvement of CD uniformity,this paper studies the improvement of the best focus of the exposure machine,analyzes the focus dynamic measurement and compensation and its shortcomings when the exposure machine is exposed,and proposes a comprehensive measurement and correction scheme for chuck's flatness.Furthermore,the exposure focus was optimized manually.Through the above two methods,the overall variance of CD was improved from 0.287 to 0.194.The research in this paper provides a strong basis for the industry to adjust via CD and improve the capacity,and provides a new adjustment idea and equipment management method for improving CD uniformity from the perspective of exposure machine.