Influence Of Resin And Photolithography Process On 248 Nm Photolithography

Photoresist as the key material of chip preparation has been monopolized by foreign enterprises for a long time.In order to realize the localization of photoresist and get rid of the unfavorable situation of being controlled by others,it is necessary to improve the quality of raw materials,have sufficient formulations and lithography verification experiments.As the core component of photoresist formulation,film-forming resin,its molecular weight design,stable batch control and stable synthesis process play an important role in realizing the localization of resin.In this paper,polyparahydroxystyrene polymers with different molecular weights were synthesized and prepared by free radical polymerization in a 2L jacketed reactor.The influence of the process on the performance of the photoresist is optimized,and the limit resolution can reach 1 μm and the aspect ratio can reach 5 under the condition of 5 μm thickness and 1:1 line/space.The main work of this paper is as follows:(1)Preparation of polymers for photoresist and evaluation of lithographic propertiesThe effects of initiator dosage,reaction temperature,time,and solid content of the system on the molecular weight of the polymer were investigated.The results show that the solid content and the amount of initiator can effectively adjust the molecular weight of the polymer;prolonging the reaction time and increasing the reaction temperature can improve the conversion rate of the reaction;changing the heating process of the reaction can achieve the stability of the molecular weight and molecular weight distribution between batches.Different molecular weight polymers synthesized in experiments are used as film-forming resins to prepare photoresist.As the molecular weight of the film-forming resin used increases,the development and dissolution rate of the photoresist slows down,the contrast becomes better,the acid diffusion length decreases,and the edge roughness decreases.It is improved,the lithography pattern is closer to the rectangle,the limit resolution is improved,and the process window range is increased,but the sensitivity will be worse.(2)The effect of formulation process on the properties of photoresistThe resin with a molecular weight of 20621g/mol is selected and applied to the photoresist.From the solid content,photoacid(PAG)content,alkaline neutralizer(Base)content,solvent type,use of oligomer additives,and filtering methods in the formula.In terms of selection,etc.,the influence of formulation process on lithography performance was studied.The results show that: using 3% PAG,3% Base,adding a certain proportion of oligomer additives,PGMEA: PGME = 7: 3 mixed solvent to prepare 32.5% solid-containing photoresist,after circulating through the capsule filter Photolithography process,the obtained pattern has better appearance,higher sensitivity and contrast.(3)The effect of photolithography process on the properties of photoresistOn the basis of formula optimization,the effects of lithography conditions such as pre-bake conditions,post-bake temperature,exposure dose,and focus value on photoresist properties were studied.After experiments,the optimum lithography conditions for photoresist with a thickness of 5μm were established: pre-bake 140°C for 90 s,post-bake 130°C for 90 s,and the focus value is 2μm.Less thickness loss,no topography problem.Under these lithography conditions,the limit resolution can reach 1 μm,and the aspect ratio can reach 5.