The Photopolymer Science and Technology Award No.141100, the Outstanding Achievement Award 2014, was presented to Hiroo Kinoshita (University of Hyogo) for his outstanding achievements in photopolymer science and technology, involving “Technology Development of Extreme Ultraviolet Lithography (EUVL) for Semiconductors”.

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The Photopolymer Science and Technology Award No. 142100, the Best Paper Award 2014, was presented to Hirokazu Kato, Yuriko Seino, Hiroki Yonemitsu, Hironobu Sato, Masahiro Kanno, Katsutoshi Kobayashi, Ayako Kawanishi, Tsubasa Imamura, Mitsuhiro Omura, Naofumi Nakamura, Tsukasa Azuma (Toshiba Corporation) for their outstanding contribution published in the Journal of Photopolymer Science and Technology, 26, (2013) 21-26, entitled “Electrical Via Chain Yield for DSA Contact Hole Shrink Process”.

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The development of extreme ultraviolet (EUV) lithography has been pursued toward the 11 nm node. With the reduction in feature size, the stochastic effect becomes an essential problem in the lithography used for the high-throughput production of semiconductor devices. In this study, the relationships between stochastic phenomena [line edge roughness (LER) and stochastic defect generation] and optical contrast were investigated using a Monte Carlo simulation on the basis of the reaction mechanisms of chemically amplified EUV resists. Optical contrast did not affect the protected unit fluctuation at the boundary between lines and spaces. However, the protected unit fluctuation at the centers of lines and spaces increased with decreasing optical contrast. The stochastic defect generation is basically affected more by the optical contrast degradation than LER.

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We have studied the self-assembly of PS-PMMA block copolymers by means of SCFT simulations in elongated templates and established commensurability windows for the formation of single rows of two and three cylindrical VIAs. Our results indicate that VIAS with increasing CD form inside templates of increasing dimensions. The VIAs are symmetrically arranged inside the template and the resulting hole-to-hole distances range from 24 nm to 34 nm for template lengths between 80 nm and 140 nm. We emphasize that the present work assumed perfect templates; future studies will examine VIA positioning within templates with line edge roughness. While encouraging for both CD and placement aspects, our results nonetheless indicate low defect formation energies leading to defect densities well above the targets of the lithography community. The development of novel strategies, including alternative polymer architectures, to reduce defectivity is thus critical for the success of DSA in VIA lithography and contact multiplication.

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In 2002, the simulation software system for high functional polymeric material OCTA is released. OCTA is the general purpose simulator and each multi-scale-level simulation can be easily done. Recently, we have applied our OCTA system to the problems of lithography. In this paper we discuss the applicability of OCTA system to the simulations for lithography. Two kinds of applicability are discussed. One is the development and the rinse process simulations, and another is the directed self assembly simulation. In the former study, LER can be discussed using OCTA simulation. In the latter study, many kinds of coarse-grained models can be applicable for the DSA simulation using OCTA. These wide applicability are discussed in this paper.

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We have investigated the process margin for fabrication of line/space directed self-assembled (DSA) patterns using a simulation method based on self-consistent field theory. We studied three systems, namely, chemoepitaxial DSA using lamellar-forming block copolymers (BCPs), graphoepitaxial DSA using lamellar-forming BCPs, and graphoepitaxial DSA using cylindrical BCPs. In the case of the chemoepitaxial DSA, both the subtle change of the wetting condition and the topography of the prepattern surface were found to strongly affect the process margin of the pinning layer width. In the case of the graphoepitaxial DSA using cylindrical BCPs, both the pattern pitch and CD of the forming DSA cylindrical patterns were found to intensely depend on both the trench width and the film thickness of the BCPs.

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To conclude, linear block copolymers are promising materials for DSA in cylindrical templates. However, for contact multiplication in extended and rounded templates, low defect formation energies and correspondingly high defect levels are anticipated for AB diblocks. In contrast, A2B-type miktoarm copolymers show potential for achieving the required defectivity threshold. Future work will include computational studies of miktoarm copolymers with n > 2 such as A₃B and A₄B, and confinement in rows of many cylinders beyond two.

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A novel method for the direct analysis of photoresist pattern was developed on the basis of Pyrolysis-GC/MS combined with micro-GPC. Firstly, a new sampling technique allowed us to collect the surface and the core of the photoresist pattern separately. Moreover, μGPC and Py-GC/MS analyses provide the information for the distribution of resist ingredient inside resist pattern, which includes original polymer, reacted polymer, and photo acid generator through the ArF patterning process. This novel analytical method can provide remarkably helpful information about identifying proper control knobs for lithographic performance of ArF resist and for next generation lithography.

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We have done SCFT simulations to investigate the directed self-assembly on CH pitch division. The structural change by the thickness L_z of oval prepattern reveals that perpendicular cylinders are favored when Lz is not commensurate with the distance between cylinders L₀. In this case linear rows of cylinders are along major radius for narrow ovals, and wider ovals tend to pack additional rows of cylinders in a staggered hexagonal arrangement. Sweeping from neutral to PMMA attractive substrates causes a transition from cylinders that penetrate completely through the film, to cylinders that terminate in nearly spherical caps. Thus a neutral substrate would be favorable in order to get cylinders that penetrate completely through the film.

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A simple analysis of aerial image quality reveals that negative tone imaging is superior to positive tone for small dimension contacts and trenches. Negative Tone Development (NTD) of positive chemically amplified (de-protecting) photoresist is currently the favored method for realizing such images on the wafer. One of the challenges for these materials is prediction of cross-section shape. Cross-section shape is often critical in leading-edge lithography processes where resist thinning or top loss can lead to pattern failure during the etch process.
There are two important effects that make prediction of cross-section shape more difficult for NTD materials. First, NTD materials typically do not have the develop contrast of positive tone develop (PTD) systems. NTD often has a larger minimum (unexposed) develop rate, and a smaller maximum (fully exposed) develop rate. Second, photoresist typically shrinks after post-exposure bake in regions where de-protection is high. For PTD, these regions dissolve, and the features are formed by the protected areas which do not show shrinkage. The opposite is true for NTD, where the regions with the largest amount of shrinkage form the features on the wafer.
We demonstrate a photoresist model that incorporates resist shrinkage following the elasticity theory described by Flory-volume loss due to de-protection leads to a stress in the photoresist, and the material deforms in a way that minimizes the free energy of the system. We show that this model, combined with accurate dissolution rate measurements, can accurately predict cross-section shape for isolated and dense trenches formed with an example NTD material.

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The effectiveness of condensable gas, used as ambience, in UV nanoimprint lithography has been demonstrated. Bubble defect problem, which is inherent in UV nanoimprint under non vacuum ambience, can be solved by PFP condensable gas. UV nanoimprint lithography using PFP was validated for 45 nm pattern fabrication under thin residual layer conditions, which are required for UV nanoimprint used as UV nanoimprint lithography. PFP reduces the viscosity and demolding force of UV curable resins. These properties are helpful in increasing the throughput and reliability of UV nanoimprint. PFP occasionally produces large shrinkages, and degrades pattern quality depending on UV curable resin. These drawbacks can be mitigated by selecting UV curable monomers with a low PFP absorption. In the end, we have demonstrated the satisfied LER and LWR values requested in 22 nm node NAND flash memories and 20,000 repeated imprints with a single mold by UV nanoimprint using PFP.

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In this study, Cu/polyimide multilayer interconnections (dual-damascene) approach based on a UV-assisted thermal nanoimprint technique at every lithography process was demonstrated aiming at developing a low-cost fabrication process for high-density interconnections in polyimide. The dual-damascene process can be simplified by nanoimprint using a multi-tiered mold, and realize fine interconnections using a soluble polyimide block copolymer with a high formability and low shrinkage during a polyimide patterning process. Three-layered Cu/polyimide structures with a minimum wire-width of 5 μm were fabricated in the polyimide by performing subsequent Cu electroplating and chemical mechanical polishing (CMP). The feasibility of the process was thus verified. The electric resistances values of the fabricated three-layered interconnections measured by a four-terminal method showed linear increase as a function of the number of interconnection vias. Heat resistance test at 260 °C which corresponded to reflow soldering process was also evaluated; less than 1.2%-increasing ratio of electric resistance was obtained in the case of 3-cycle heating.

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We examined the release property of HSQ pattern fabricated by RT nanoimprinting using PDMS soft mold. The water contact angle of HSQ was increased by RT-nanoimprinting with baking process. It was found that the improvement of release property was caused by PDMS adhesion onto HSQ. In addition, PDMS adhesion onto HSQ was also occurred in thermal and UV nanoimprintings using PDMS soft mold. As a result, it was confirmed that the HSQ pattern fabricated by RT-nanoimprinting with baking process can be used as the replica mold without ASL coating process. We have been further studying about durability of the replica HSQ mold fabricated by RT-nanoimprinting with baking process.

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Backside lithography with a moving mask UV exposure technique is proposed. A novel moving-mask exposure apparatus was developed and evaluated both experimentally and through exposure simulations. The backside exposure using this technique was validated and is capable of producing tapered microstructures of thick photoresist for molding. The shape of the structure can be modified by the trajectory of the stage movement. It was confirmed that the shape of the processed structure could be successfully predicted using the proposed simulation method.

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SiO₂ nanoline with extremely high aspect ratio could be fabricated by the edge lithography, however, such a high aspect nanoline was fragile. Since nanotrench pattern was stronger than nanoline pattern, a new process was developed for obtaining the Si nanotrench from the SiO₂ nanoline in order to obtain a strong nanoimprint mold. A resist nanotrench pattern is fabricated by using only the resist coating and the resist etching. The process is much simpler than the lift-off process. The Si wafer is etched by the modified Bosch process. The fabricated Si trench width and depth are 35nm and 260nm, respectively. The Si trench pattern is replicated to polystyrene (PS) film on a silicon wafer by thermal nanoimprint lithography. The PS nanoline, whose width and height are 28 nm and 360 nm, is successfully fabricated.

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Ormostamp^TM (Microresist technology GmbH) is a UV curable Silica based organic hybrid material and can be for hard substrates like e.g. quartz plates. In this report, fabrication of the 1-st and 2-nd generation replica mold from the Ormostamp^TM to Ormostamp^TM is addressed. Around 40nm lines with 20nm spaces are fairly transferred.

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We demonstrated the fabrication process of chemically patterned templates by UV and thermal nanoimprintings for DSA and carried out microphase separation of PS-b-PMMA on the templates. The microdomain structure of PS-b-PMMA was occurred and it was influenced by chemical pattern. The results indicate that nanoimprint process is a useful method to fabricate the chemical pattern.

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We demonstrated the localized abrasion resistance test by AFM to examine the ASL deterioration induced by local friction. It was found that the contamination may attach to the ASL formed using FAS-13 due to leaving in air, because the adhesion and frictional forces increased when we measured about 2 days after from ASL forming. Although the localized abrasion resistance test was carried out for about 1 week, the contamination due to experimental conditions were not avoided, which might be caused the random behaviors of adhesion and frictional forces. However, we proved from these results that the localized abrasion resistance test by AFM was one of the useful evaluation methods to examine the ASL deterioration induced by local friction. We will further study ALS deterioration deeply by AFM with an optimized experimental condition.

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In recent years, the reduction in pattern size is driving the rapid adoption of nanoimprint lithography (NIL). Since nanoimprinting is contact printing, high separation forces might damage the master and/or the imprint tool, either of which degrades pattern quality. One of the biggest concerns in NIL utilization is the mold-release characteristic of the master and the resin. Although Optool DSX (DAIKIN Ind. Ltd.) is a defacto standard as mold anti-sticking reagent, there is a problem with its UV-NIL durability. Accordingly, we focused on developing new fluorinated low molecular weight compounds to enhance the mold-release characteristic of the resist. This paper reports that resists containing these fluorinated compounds offer improved durability as anti-stick layers for quartz molds even under repeated UV-NIL exposure.

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Quantitative evaluation of template release energy is reported for UV nanoimprint resists containing various kinds of fluorinated segregation agents. The template release energy is evaluated based on fracture mechanics for various types of UV curable resists in which a fluorinated segregation agent is dissolved. The template release energy is effectively reduced. The higher molecular weight agent containing a hydrophilic group effectively reduces the energy by 5/6^th. The defect ratio in nanoimprint lithography is also examined. The result shows that the defect ratio is effectively reduced by the use of fluorinated segregation agents.

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We evaluated the effect of DSN4034 (fluorosurfactant) to carry out ASL free UV nanoimprinting. The water contact angle of C-TGC-02 (UV nanoimprint resin) with DSN4034 decreased with increase in additive amount of DSN4034. We assumed that this phenomenon was caused by large amount of PEO chain and OH group in DSN4034. However, it is necessary to investigate the phenomenon by X-ray photoelectron spectroscopy and atomic force microscopy. When both the mold and the substrate were the equivalent hydrophilic surface treated by O₂ RIE, the resin was peeled from the substrate. By putting the difference of interface between the mold and the substrate, we succeeded ASL free UV nanoimprinting.

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We here designed a new hybrid resist for UV-NIL based on the thiol-yne photopolymerization. The hybrid resist is comprised of bifunctional polyhedral oligomeric silsesquioxane containing octyl and mercaptopropyl groups (POSS-OA-SH) and difunctional alkyne. The obtained hybrid resists possess numerous desirable characteristics for UV-NIL, such as great coating ability, high thermal stability, low surface-energy, low bulk volumetric shrinkage (0.8~4.8%), and excellent oxygen-etch resistance. Because of the click reaction characteristics of thiol-yne photopolymerization, the hybrid resists can be photo-cured within seconds under UV exposure at room temperature. Finally, through the double-layer resist approach for pattern transfer onto silicon substrate, the transfer pattern with the height of about 3 times more than that of the original NIL pattern can be obtained due to excellent oxygen-etch resistance of the etch barrier material. These results provide the thiol-yne hybrid resists as an alternative for UV-NIL.

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