We have successfully synthesized polystyrene(PS)-b-polymethylmethacrylate (PMMA) block copolymer that is precious with controlled molecular weight, PDI and composition ratio by living anionic polymerization method using large-scale apparatus. In addition, the influence of PDI, composition ratio and composition distribution for micro phase separation about PS-b-PMMA block copolymer is investigated. The results show that PDI is the major factor for defect, while composition ratio and composition distribution has influence for morphology. As PDI increase 1.06 to 1.13, also defects are increased a lot. As composition ratio of PS increase 51% to 60%, micro phase separation structure was changed from lamella to gyroid. Moreover, we surmised that these properties have a boundary of influence towards micro phase separation. Therefore, is necessary to control these properties by living anionic polymerization in order to use DSA materials in semiconductor process.
Directed self-assembly (DSA) of block copolymers (BCPs) is a lithographic technique that is expected to be mutually complimentary with ArF immersion lithography, EUV lithography, electron beam direct writing, or nanoimprint for sub-15 nm line patterning and sub-20 nm contact hole patterning. Defect mitigation is the primary challenge behind the use of DSA lithography in practical applications in advanced semiconductor device manufacturing. Therefore, resolve this issue, defect dynamics needs to be clarified using in-situ measurements of self-assembling processes of BCPs in conjunction with modeling approaches.
In this work, the evolution of a surface morphology in self-assembling processes of BCPs during annealing was investigated using in-situ atomic force microscope (AFM).5 A JPK NanoWizard ULTRA Speed AFM (JPK Instruments AG) under AC mode (lock-in phase signal image) was employed to carry out in-situ measurements of self-assembling of symmetrical polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) thin films with a thickness of 40 nm, and a domain spacing 30 nm domain spacing (L0) of 30 nm on a 5 nm thick neutral layer (PS-r-PMMA) during the thermal annealing process starting from a disordered as-cast state. The COOrdinated Line epitaxy (COOL) process was applied to provide DSA line multiplication patterns as hybrid guide patterns which act as chemical and physical epitaxy process.
The in-situ observation approach of the surface morphology during micro-phase separation process revealed the defect generation and rectification processes in DSA thin films. A combination of the time development data in the in-situ AFM and grazing-incidence small-angle X-ray scattering (GI-SAXS) will also be discussed to develop a kinetic modeling for predicting dynamical changes in the three-dimensional nanostructures.
We have successfully synthesized various and over wide range molecular weight block copolymers (BCPs): these are polystyrene(PS)-polymethylmethacrylate(PMMA) as general components and poly(4-trimethylsilylstyrene)(PTMSS)- poly(4-hydroxystyrene)(PHS) system as very strong segregated components (high chi) and multiblock type of those copolymers which form the microphase-separated structure pattern using living anionic polymerizing method by which the size of polymer can be precisely controlled. In addition, we were able to observe alternating lamellar and cylinder structures which were formed by our various BCPs using small angle X-ray scattering (SAXS). Moreover, we have successfully developed new apparatus for high volume manufacturing including our original technologies such as purification of monomer, improvement of wetted surface, and mechanical technology for high vacuum. And we have successfully synthesized all the BCPs with narrow molecular weight distribution (PDI <1.1) with large-scale apparatus.
In this study, we have successfully synthesized polystyrene-b-poly(4-hydroxystyrene) (SH) with molecular weight of 14k and with narrow molecular weight distribution by living anionic polymerization, and the obtained SH diblock copolymer has formed the definite alternative lamellar structure with the half pitch of 10.4nm. In order to achieve narrow half pitch pattern, diblock copolymer (XY) with stronger segregated polymer components with high chi (X and Y) was used, and it was confirmed that the high-chi XY diblock copolymer having molecular weight of 6k showed the clear lamellar structure with the half pitch of 5.5nm. Furthermore syntheses of multiblock copolymers with high chi such as YXY (where X is Si contained polymer) triblock and XYXY (where XYXY is Si contained high χ polymer) tetrablock copolymers were attempted to achieve the narrower half pitch pattern less than 5 nm, and the multiblock copolymers with aimed molecular weight and narrow molecular weight distribution have been successfully obtained. From the highchi multiblock copolymers, it was confirmed that the formation of the definite microphase-separated structure with the half pitch of 4.8nm was observed by TEM and SAXS measurements. Moreover we have developed a large-scale living anionic polymerization apparatus for the preparation of well-defined block copolymers scaled over 3kg.