Study On The Effect Of Photo Acid Generator And Photolithography Process On The Performance Of KrF Photoresist

Photoresists,also known as photoresists,are photosensitive protective films on the substrates of manufactured semiconductor devices with etch resistance properties.In this thesis,the effects of different structures of Photo Acid Generator(PAG),other raw materials in photoresist formulation,and lithography process on the performance of KrF photoresist are investigated as follows :(1)Effect of different photogenic acid agents on the performance of photoresistsThe solubility,thermal stability,and UV absorption of ionic sulfonium salt PAGs were compared with those of nonionic PAGs to select three PAGs suitable for use in KrF photoresists,and the selected three PAGs were formulated into a photoresist with a target thickness of 500 nm.The effects of the three PAGs on the basic properties of the photoresist,such as viscosity,film thickness,sensitivity,contrast,transmittance and solubility,were investigated.The results showed that the PAGs with different structures had no significant effects on the viscosity and film thickness of the photoresists;the acid yield,acid diffusion length and photoresist solubility values of PAG-2were higher than those of the other two PAGs,so the sensitivity of the photoresists formulated with PAG-2 was higher,but also the contrast and process window values of the photoresists formulated with PAG-2 were smaller;the best contrast value among the three photoresists was that of PAG-3 The best contrast value among the three photoresists is PAG-3,but the sensitivity of the photoresist is poor because of the low acid production;compared to PAG-1,which has moderate acid production,the sensitivity and contrast of the photoresist are better,and the process window value is the best.(2)The influence of formulation process on the properties of photoresistChanging the use of PAG types in the photoresist formulation through the photoresist basic performance data can not be clear which PAG use the best effect,so change the concentration of PAG in the formulation,combined with the photoresist simulation graph,to obtain experimental results: the use of PAG in the photoresist is not the more the better,PAG concentration is too low resulting in low sensitivity of the photoresist;PAG concentration is too high will lead to low photoresist transmission rate.Combined with the simulations of photoresists,it is found that PAG-2 has too low photoresist process window value due to strong acid production,and the quality of photoresist morphology is too poor compared with that of PAG-2,and changing the concentration value in the formulation does not improve the problem;while PAG-1 has moderate acid production,and the process window value of photoresist and photoresist morphology are both good,and a suitable concentration value is obtained in the experimental formulation;PAG-3 has the worst photoresist sensitivity due to too low acid production,and increasing the concentration value in the formulation will lead to low photoresist sensitivity.PAG-3 has the worst photoresist sensitivity because the acid production is too low,and increasing the concentration value in the formulation decreases the photoresist transmittance,so the quality of photoresist morphology is affected.Therefore,the ionic sulfonium salts of PAG-1 were determined to be used in the photoresist formulation.Because the purpose of using alkaline additives is to neutralize the excess acid produced by PAG,only PAG can be determined to experimentally investigate alkaline additives,change the type and concentration of alkaline additives in photoresist formulations,and determine the use of alkaline additives through the effects of photoresist transmittance,sensitivity,contrast,and solubility;because the solubility of PAG and alkaline additives in photoresist requires the type of solvent Experiments were conducted.The experimental results show that: different structures of the same type of amine additives on the photoresist sensitivity,contrast,solubility is not obvious,the strong alkaline A-1 formulated photoresist better transmittance,through the photoresist simulation morphology found that the three structures of amine additives on the photoresist morphology is not significant;comprehensive selection of strong alkaline additives A-1 concentration change,the experimental results prove that the additive concentration of high The experimental results show that the higher concentration of the additive has higher contrast,and the best photoresist simulation shape is determined by combining the photoresist simulation pattern with the use of the amine additive A-1,solvent PGMEA and PGME mixture.The final experiments determined that the raw materials for the photoresist formulation were ionic sulfonium salts of PAG-1,amine additive A-1,and the mixture of solvent PGMEA and PGME.(3)Effect of photolithography process on the morphology of photoresistAfter determining the photoresist formulation,the lithography process conditions were adjusted,and the effect of energy,focal length and baking temperature on the photoresist morphology was observed by observing the photoresist side electron microscope scan.And it was verified that the actual lithography process could correspond to the simulation graph results,and the accuracy of the photoresist simulation data was verified.Finally,the applicable film thickness range and resolution range of photoresist under the determined photoresist formulation and lithography process conditions were examined.The experimental results are as follows: the photoresist formulated with hydroxy styrene resin,ionic sulfoniμm salt PAG-1,amine additive A-1,PGMEA,PGME and other additives was baked at 120 ℃ and 60 s before and110 ℃ and 90 s after,and the best morphology of the photoresist was obtained,and the best exposure dose value of the photoresist was about 40 m J/cm2 with a focal depth of 0.6 μm;Photoresist film thicknesses are available in the range of 300 nm-700 nm,with resolutions of 120 nm-200 nm.