Construction Of Non-chemically Amplified Photoresist System Based On O-nitrobenzyl Carbonate And Their Performance Study

Since the 21st century,chips have deeply impacted various aspects of human life.With the acceleration of China’s technological development,the demand for chips has been growing,even surpassing that of oil.Chip manufacturing is one of the industries that China urgently needs to break through,involving processes such as lithography,ion implantation,etching,and packaging,where the importance of lithography technology is self-evident.Chemically amplified resists（CARs）have undergone rapid development since their establishment.However,as chip designs reach feature sizes below 20 nm,CARs suffer from severe line edge roughness（LER）caused by acid diffusion.Therefore,researchers have begun to explore non-chemically amplified resists（n-CARs）.This dissertation discusses the synthesis of various non-chemically amplified photoresists through several techniques such as click polymerization,RAFT polymerization and post-modification.The preliminary investigation into their properties has been conducted,and the design approach for non-chemically amplified photoresists has been summarized.The specific research content includes:（1）Preparation of thin-film negative photoresistsA new photosensitive molecule,Dinitrobenzyl carbonate（DNBC）,was designed and synthesized,and its photodegradation and recombination behavior was determined through NMR,UV-vis,and HPLC-MS analysis.Linear polymers LP1-LP4 with main chain repeating units of DNBC were prepared by click polymerization.To study the photochemical behavior of the polymers,data were collected from NMR,UV,and GPC over time.The results indicated that the polymers underwent degradation and subsequent recombination under UV irradiation.Through this photochemical process,these polymers were used as negative photoresists to create micro-patterns.By observing the solubility of several groups of polymers in different solvents,the polymer LP2（M_n=1.2 KDa）with the best solubility was directly used as a resin material to form a film and undergo photolithography.A low-resolution micro-pattern with a thickness of approximately 100 nm was formed after a photolithography time of 12 minutes and a development time of 90 seconds.Additionally,polymer LP3 was prepared by introducing benzaldehyde into the polymer branching structure,and amine-functionalized molecules were clicked onto the patterned surface.Low-resolution fluorescent patterns were obtained through confocal fluorescence microscopy.（2）Preparation of high-resolution thin film negative photoresistsA series of hyperbranched polymers HBP1-HBP4 with repeating units of DNBC were prepared by click polymerization.To monitor the changes in the structure of the polymers under different irradiation times,data were collected from UV-vis and FTIR spectroscopy over time.The results indicated that the polymers underwent degradation and subsequent recombination under UV irradiation.By observing the solubility of several groups of polymers in different solvents,the hyperbranched polymers exhibited better solubility than linear polymers.Polymer HBP4（M_n=1.3 KDa）was directly used as a resin material to form a film and undergo photolithography,which resulted in a high-resolution micro-pattern with a thickness of approximately 200 nm after a photolithography time of 12 minutes and a development time of 90 seconds.（3）Preparation of high-resolution thick film negative photoresistPoly（bromomethyl methyl acrylate）（p BMEA）and poly（glycidyl methacrylate）（p GMA）were prepared by RAFT polymerization.A novel post-polymerization modification method was developed based on the efficient reaction between the active end groups of p BMEA and phenolic hydroxyl groups.Phenol,1-hydroxynaphthalene,azophenol（Azo-OH）and5-hydroxy-2-nitrobenzyl alcohols were grafted onto the polymeric side chains of p BMEA to obtain grafted polymers（GP1,GP2,GP3 and GP4）,with a grafting rate of nearly 100%.An amphiphilic block copolymer p（BMEA）-b-p（m PEG）was prepared by RAFT polymerization,and Azo-OH was grafted onto the block copolymer using the new post-polymerization modification method to prepare the photoresponsive polymer p（BMEA-Azo）-b-p（m PEG）.Under UV irradiation,the micelles of the modified amphiphilic block copolymer p（BMEA-Azo）-b-p（m PEG）were decomposed,which proved that the functional molecules grafted onto the side chains of p BMEA can still express functional properties.p（GMA-N₃）can be obtained by the post-polymerization modification method.GP4,p GMA,and p（GMA-N₃）were used as film-forming resins,and corresponding crosslinking agents DPC,DNBC amine derivative C2,and DNBC alkyne derivative C1 were selected to construct the DNBC structure in the branching chain.The polymer solubility was regulated by methyl methacrylate（MMA）,and the solubility performance of polymers with different degrees of crosslinking in different solvents was observed.Finally,p（GMA-co-MMA）was used as the resin material and C2 was used as the crosslinking agent for film formation and photolithography.High-resolution micro-patterns with a film thickness of about 1μm can be obtained under the conditions of a photolithography time of 12 min and a developing time of90 seconds.（4）Preparation of Lift-off photoresistTwo reactive polymers（RP1 and RP2）were prepared by RAFT polymerization.RP1 has a dimethylamine group as the active end group,and RP2 has a benzaldehyde group as the active end group.In addition,this study also used post-modification methods to prepare grafted polymer GP5 with the ene group as the active end group.Based on the photo-cleavage behavior of o-nitrobenzyl ester,RP1,RP2,and GP5 can be used as positive photoresists with corresponding crosslinking agents.However,there are problems such as low crosslinking efficiency,complex synthesis steps,and difficulty in choosing crosslinking systems.To solve this problem,p（GMA-N₃）was used as the film-forming resin,and C3 was used as the crosslinking agent.The solubility performance of polymers with different degrees of crosslinking in different solvents was observed.Finally,p GMA was used as the resin material,and C4 was used as the crosslinking agent for film formation and photolithography.High-resolution micro-patterns with a film thickness of about 1μm can be obtained under the conditions of a photolithography time of 12 min and a developing time of 90 s.In addition,using p GMA as the lower layer and p（GMA-co-MMA）as the resin material,C2 as the crosslinking agent for the upper layer,and a photolithography time of 12 min,a flood exposure time of 20 min,and a developing time of 90 s,an undercut structure can be obtained with a film thickness of 2μm.