Study On Photolithography Technology Based On New Block Copolymer Directed Self-assembly (BCPs-DSA)

Over the past 50 years,lithography technology has been one of the core technologies to promote the design of advanced integrated circuits and the updating of their devices.The emergence of new types of integrated circuits in each generation is always marked by lithography technology to achieve smaller feature sizes.Semiconductor integrated circuit technology has been developing rapidly along the speed predicted by Moore's law.Its strategic core is to reduce the key dimensions of semiconductor devices through technological innovation.Lithography technology is the key to realize the strategy of device miniaturization,but the cost and process complexity of lithography are also increasing day by day in the process of development.At present,industry,academia and many other scientific research institutes have adopted 193 nm/EUV lithography,combined with immersion lithography technology and double?multiple?pattern exposure technology.193nm/EUV lithography technology has extended semiconductor technology nodes to 3220,16,14,10 and even 7 nm,and has continued to promote research and development of 5/3 nm.Conventional lithography technology has almost reached its physical limit.However,the high cost of process research and development,the complexity of process,the physical limitations of lithography itself and the design defects of many photoresist materials restrict the further development of the existing lithography technology.Industry,academia and other research institutes are in urgent need of a solution that can take into account both accuracy and cost,especially in the face of the limitations and shortcomings in promoting the graphical fabrication of smaller and smaller nano-size.International Semiconductor Technology Blueprint?ITRS?proposed in 2013,the next generation lithography technology solutions are mainly EUV,NIL,Maskless Lithography and block copolymer directed self-assembly?DSA?.By March 2016,the latest report changed ITRS to IRDS?International Devices and Systems Technology Blueprint?,focusing not on how to continue to improve speed and efficiency,but on how to make the chip development more in line with the needs of smartphones,wearable devices and data center exchange.In the2017 IRDS lithography roadmap,its mission is to predict?15 years?manufacturing pattern technology?HVM?;identify challenges and obstacles to key patterns;provide challenging advice to more Moore;and provide available parameter roadmaps for the industry.In recent years,all of the above need to be applied to high-performance memory chips in-depth research and rapid application of chip demand development in all walks of life.Compared with multi-patterning,the cost of EUV technology is more advantageous for small batch parts,but most applications of EUV still bring high costs.Among them,block copolymer directed self-assembly of Block Copolymer Lithography is short for DSA,which uses block copolymer which is made of two monomers with different chemical properties as raw materials.Under"non-field"conditions?thermal annealing,solvent annealing,mechanical force,hydrogen bond driving,hydrophilic/hydrophobic interaction driving,surface tension driving,etc.?and"field"conditions?electric field driving,magnetic field driving,etc.?,the patterns are divided into nano-scale graphs,and then induced into regular nanowire arrays,nanopore arrays and nanosphere arrays by certain methods.Thus,etching templates are formed to fabricate nanostructures and related semiconductor devices.DSA has the advantages of low cost,high resolution,high yield and large-scale application without light source,mask and complex process conditions compared with other related technologies.It has attracted wide attention in the semiconductor industry,including IBM,Intel,JSR,Dow Chemistry,IMEC,IMEICAS,Fudan University and many other well-known international and domestic companies and research institutes which corresponding and fruitful research has been carried out on this technology.The related research of block copolymer directed self-assembly lithography?BCPs-DSA?was carried out based on the research platform of Institute of Microelectronics of Chinese Academy of Sciences,and mainly in charge of DSA project.Under the"no-field"conditions,the synthesis of new block copolymers?PS-b-PC?,the research and development of self-assembly technology of films,the innovative research of vertical phase separation without neutral layer,the research of directed self-assembly technology,the development of pattern transfer technology and the research of self-assembly to directed self-assembly under the"field"conditions were systematically studied.Some key problems and challenges were solved.A set of block copolymer directional self-assembly lithography baseline process compatible with existing CMOS and FinFET processes was established.The main contents are as follows:1.A new type of high-?,low molecular weight styrene-b-polycarbonate block copolymer?PS-b-PC?has been successfully synthesized.It contains active-NH-groups in the polymer skeleton between PS block and PC block.Vertical phase separation has been successfully experimented on the substrate without neutral layer under"non-field"conditions.2.Study on self-assembly process and phase separation characteristics of block copolymer?PS-b-PC?films:The properties of vertical self-assembly of PS-b-PC block copolymer with periodic sub-20?16.8nm?in thin films were studied.The key process conditions of self-assembly were optimized,including substrate treatment,film thickness of block copolymer,degradation temperature and time.Finally,a set of self-assembly process schemes with the advantages of low defect density and high yield were established,which provided experimental basis and process window for the subsequent development of directional self-assembly lithography technology.3.PS-b-PC also studies and achieves vertical phase separation on different substrates?Si,SiO₂ and Si₃N₄?under the condition that block copolymers have no neutral layer.4.Through K-layout,different nano-scale layouts are designed,and the required layouts are finally realized on silicon substrates.Especially,the research on PS-b-PC induced directional self-assembly pattern was carried out on the side wall of the substrate,and the rule of the number and shape of PS-b-PC lines changing with the increase of groove width was found,and the theoretical model was established.The block molecule in the film near the side wall of the layout pulls toward the side wall area,which will cause the change of the block composition in the area near the side wall.The change of the block composition causes the change of the shape of the figure size.This effect gradually weakens with the increase of the distance,thus forming a gradually changing structure with the increase of the line width value.This structure reaches stability when the groove width increases to a certain extent.In the middle of the groove,a periodic nanostructure pattern with uniform line size will appear.5.Graphics transfer technology research and development:Through experimental optimization and process improvement,block copolymers are established to realize vertical pattern transfer without neutral layer.A new pattern transfer technology combining Atomic Layer Deposition?ALD?and Hard Mask is also established.Al₂O₃ is used to enhance block etching resistance of PC,and Hard Mask is used to reduce defect density.The problem of low selectivity and weak etching resistance of ultrathin block copolymer films was solved.The etching transfer pattern of 16.8 nm nanowire structure was realized on silicon substrates,and a set of directional self-assembly pattern transfer process for block copolymers with size of 20nm and below was established.6.The effect of electric field and magnetic field on the self-assembly and directional self-assembly behavior of PS-b-PC was studied.It was found that PS-b-PC had the best phase separation results when its film thickness was 34 nm and there was no neutral layer on the silicon wafer,i.e.when the micro-phase separation period of PS-b-PC was 2 times?2.0L₀?,and the applied electric field intensity was 4 kV/mm and the time was half an hour.The results of phase separation under other conditions are not ideal.The magnetic field intensity?Tesla?range set by another"field"scheme?0.5T-1.0T?makes PS-b-PC sample phase separation preliminary.