Study On The Influence Of Photoresist Concentration In Developer On Critical Dimention

In semiconductor and display industry,one of the main manufacturing methods is to make electronic circuits on silicon semiconductors or glass substrates.Photolithography is the key technology to define the pattern,and the main processes include coating,exposure and development.During exposure,the coated photoresist is catalysted to occur series of chemical reactions,which finally change its original chemical properties.After the development,the exposed area will be neutralized and the unexposed area is left to complete the pettern definition.The common goal of the above processes is to reduce the critical dimension of the defined pattern.This paper focuses on the effect of the photoresist concentration in the developer on critical dimension.The research content and the results obtained are as follows:(1)The characteristic of recycled liquid in photolithography process was studied.The relationship between photoresist concentration and absorbance in the developer was researched.The reaction mechanism of the photoresist in the developer was analysised systematically.The results show that photoresist can reduce the surface free energy of the developer.With the increasing of the photoresist concentration,the developing ability of developer can be enhanced.(2)The influence of the pattern density of the mask on the critical dimension was studied.The results show that the high density pattern outside the covered area greatly affects the critical dimension of the low density pattern.The pattern density is proportional to the critical dimension,and the critical dimension can be reduced by decreasing the pattern density.(3)The reliability of the critical dimension testing equipment was studied.The results show that the reliability and stability of the testing equipment are within the range of error.The influences of softbake time,softbake temperature,developer time,vacuum dry time and photoresist concentration in developer on critical dimension were researched.The results show that the photoresist concentration in developer is the key factor influencing the critical dimension.(4)The influence of the photoresist concentration on the critical dimension was studied.The results show that the relationship between the photoresist concentration and the critical dimension is linear in the range of 0.16 abs to 0.21 abs.The relationship follows the quadratic function within the range of 0.05 abs to 0.13 abs.The optimal photoresist concentration was estimated to be around 0.092 abs.Based on above findings,the standard deviation of the critical dimension can be reduced from 0.12 to 0.073,and the critical dimension can be decreased to 81.3%.Above results proved valuable reference for design and fabrication of products with smaller critical dimension.