2017 PST Awardees
The Outstanding Achievement Award
The Photopolymer Science and Technology Award No.171100
Paul F. Nealey
The University of Chicago
The Photopolymer Science and Technology Award No. 171100, the Outstanding Achievement Award 2017, was presented to Prof. Paul F. Nealey (The University of Chicago) for his outstanding achievements in photopolymer science and technology, “Pioneering Contribution in Directed Self-Assembly (DSA) Technologies using Lithographically Defined Nano-Patterns.”
Prof. Paul F. Nealey is currently the Brady W. Dougan Family Professor in Molecular Engineering at the Institute for Molecular Engineering of the University of Chicago, and a Senior Scientist at Argonne National laboratory. His research interests include nanofabrication techniques based on the advanced lithography and directed self-assembly, dimension dependent material properties of nanoscopic macromolecular systems, and quantitative three-dimensional characterization of the structure of soft materials. He is a fellow of the American Physical Society, and has received the National Science Foundation Career Award, the Camille Dreyfus Teacher-Scholar Award, the Nanoscale Science and Engineering Forum Award from the American Institute of Chemical Engineers, the Arthur K. Doolittle Award from the American Chemical Society, the 2015 Intel Outstanding Researcher Award in Patterning, and the 2016 Semiconductor Industry Association—Semiconductor Research Corporation University Researcher Award. He was also the Founding Director of the National Science Foundation-funded Nanoscale Science and Engineering Center in Templated Synthesis and Assembly at the Nanoscale.
Directed self-assembly (DSA) is one of the most promising strategies for the cost-effective high-volume manufacturing at nanoscale. Over the past decades, top-down manufacturing techniques have been developed with such remarkable efficiency that it is now possible to engineer complex systems of heterogeneous materials at the scale of a few ten nanometers to support the every growing market for semiconductor devices.
However, further evolution of these techniques is faced with difficult challenges not only in feasibility of implementation at 10 -nm scale and below, but also in prohibitively high-capital-equipment costs.
On the other hand, materials that self-assemble spontaneously can form nanostructures down to the molecular scale. The materials which can self-assemble with adequate perfection in the pre-defined structure can be used to create structures in the devices. DSA refers to the integration of self-assembling materials with the traditional manufacturing processes of devices.
Prof. Paul F. Nealey is a pioneer of DSA strategies, materials, processes, and applications, and this work has contributed substantially to the progress of photopolymer science technology. His group proposed the methods of DSA of block copolymer films on lithographically defined chemically nano-patterned surfaces. The methods are an emerging technology to impact sub-10 nm lithography and the manufacture of the integrated circuits and magnetic storage media.
Block copolymer materials self-assemble to form densely packed features with highly uniform dimensions and shapes in ordered arrays at the scale of 3 to 50 nm. Chemical pre-patterns are defined using traditional lithographic materials and processes such as 193 nm immersion or electron beam lithography at the scale of 20 to 40 nm. By directing the assembly of block copolymer films on the chemical pre-patterns, the overall resolution of the lithographic process can be increased by three to four-fold or more.
Going beyond laboratory scale demonstrations and development of materials and processes, Prof. Nealey has played a leading role in elucidating fundamental and technological understanding to enable DSA to meet the stringent constraints of the manufacturing: perfection, processing latitude, and integration of the technology with existing infrastructure, and device design for use with DSA patterns.
Prof. Nealey has published more than 300 papers overall, and his important research results in DSA have been presented at the annual Conference of Photopolymer Science and Technology and more than 12 papers have been published in the Journal of Photopolymer Science and Technology.
The contribution above greatly influenced the society of DSA research. Many scientists and engineers are continuing the research of DSA for patterning application in industry with the influence of his achievements. With these achievements, The Outstanding Achievement Award 2017 was presented to Prof. Paul F. Nealey.
The Best Paper Award 2017
The Photopolymer Science and Technology Award 172100
Kenji Yoshimotoa,b, Akihisa Yoshidab, Masahiro Ohshimac, Takashi Taniguchic, Katsuyoshi Koderac, Yoshihiro Nakac, Hideki Kanaic, Sachiko Kobayashic, Simon Maedac, Phubes Jiravanichsakulc, Katsutoshi Kobayashic, Hisako Aoyamac
aCenter for the Promotion of Interdisciplinary Education and Research, Kyoto University
bDepartment of Chemical Engineering, Graduate School of Engineering, Kyoto University
cToshiba Corporation
The Photopolymer Science and Technology Award No. 172100, the Best Paper Award 2017, was presented to Kenji Yoshimotoa,b, Akihisa Yoshidab, Masahiro Ohshimab, Takashi Taniguchib, Katsuyoshi Koderac, Yoshihiro Nakac, Hideki Kanaic, Sachiko Kobayashic, Simon Maedac, Phubes Jiravanichsakulc, Katsutoshi Kobayashic, Hisako Aoyamac (aCenter for the Promotion of Interdisciplinary Education and Research, Kyoto University, bDepartment of Chemical Engineering, Graduate School of Engineering, Kyoto University, cToshiba Corporation) for their outstanding contribution published in Journal of Photopolymer Science and Technology, 29, (2016) 709-715, entitled “Direct Self-Assembly for Non-Periodic Designs” and Journal of Photopolymer Science and Technology, 26, (2013) 809-816, entitled “Large-Scale Simulations of Directed Self-Assembly with Simplified Model.”
Directed self-assembly (DSA) is considered as a candidate for future patterning technology for semiconductor manufacturing. The DSA utilizes the phase separation of block copolymers and provides further resolution enhancement by the use of chemically and physically pre-patterned surface. The major challenge of the DSA is to realize defect-free manufacturing process. During the annealing process, some self-assembled block copolymers get stuck into the meta-stable structures and remain as defects. In the last few years, the defect level has been significantly improved (e.g., < 1 defect/cm2), whereas it still needs to be reduced by a few orders of magnitude to satisfy with the manufacturing requirements.
Simulation can be a useful and powerful tool to predict the morphology of the self-assembled block copolymers and to optimize the DSA process. Among various techniques, the self-consistent field theory (SCFT) and the Monte Carlo (MC) simulations have provided many useful insights into the DSA defects. The resulting morphologies from the SCFT and MC simulations have a reasonable agreement with the experimental data. In addition, both methods can be used to estimate the free energy of the DSA defects and to find the transition path between defective and perfect states (for example). Note, however, that the SCFT and MC methods are based on the thermodynamics and that they are in principle not suitable for the dynamic simulations.
In 2013, Dr. Yoshimoto and Dr. Taniguchi have published a paper in the Journal of Photopolymer Science and Technology (JPST) where they applied the Ohta-Kawasaki (OK) model to the large-scale dynamic simulations of the DSA processes. In the simulations, the density fields of different blocks were evolved by numerically solving the time-dependent Ginzburg-Landau equations. By using the parallel computing, they successfully observed the time evolution of DSA defects over a much larger area than the other segment-based simulations. It was interesting that relatively large DSA defects were formed at the initial stage of phase separation and gradually diminished by thermal fluctuations.
In 2016, Dr. Yoshimoto and his coworkers have reported an application of the OK model to the new DSA process for generating the periodic and non-periodic patterns at one step. In this study, they determined the values of interactive parameters between surface and block copolymers from the calibration to some experimental data. The simulated morphologies qualitatively agreed with those in the SEM images. They also demonstrated how the design of pre-patterned surface would impact on the formation of complicated defects in the three dimensions.
The simulations with the OK model have already been used by semiconductor industry, due to the advantage of simplicity, speed and scalability to large systems. The major challenge of the OK model is accuracy and predictability. In principle, the OK model is valid only for relatively weak segregation and it becomes inaccurate for strongly segregated block copolymers. Recently, new phase-field model has been proposed, where all coefficients in the OK free energy formula were treated as fitting parameters to the SCFT. The defect morphology and free energy simulated by the phase-filed model had a good agreement with the SCFT results. Such approach can be extended to various large-scale DSA simulations, e.g., hotspot analysis over a large area, materials and process optimizations, and screening of DSA design rules.
As described above, the authors have not only initiated research on large-scale simulations of the DSA defects using the simplified model but also demonstrated the model extensibility to the real DSA processes. These interesting research results were presented at the Annual Conference of Photopolymer Science and Technology in 2013 and 2016, and published in the JPST.
The Best Paper Award 2017
The Photopolymer Science and Technology Award 172200
Kyohei Nakano, Yujiao Chen, Kaori Suzuki and Keisuke Tajima
The Center for Emergent Matter Science (CEMS), RIKEN
The Photopolymer Science and Technology Award No. 172200, the Best Paper Award 2017, was presented to Kyohei Nakano, Yujiao Chen, Kaori Suzuki and Keisuke Tajima (The Center for Emergent Matter Science (CEMS), RIKEN) for their outstanding contribution published in Journal of Photopolymer Science and Technology, 29, (2016) 533–536, entitled “Modification of Donor/Acceptor Interface for Efficient Organic Photovoltaics”.
The power conversion efficiency of organic solar cells (OSCs) has now reached 11%, as a result of intensive efforts on the synthesis of new materials, understanding of device physics, and optimization of device fabrication processes. One of the largest breakthroughs in OSCs is the invention of bulk-heterojunction (BHJ) structure that is a random mixture of donor and acceptor materials. The donor (D) and acceptor (A) materials form large area of the interface, leading to the high efficiency as the photo-electro conversion only occurs at the D/A interface. It is thus highly important to control and to evaluate the interface, which is, however, very tough because of the randomness of the interface. This limits the investigation of the relationship between the interfacial properties and the device performances.
An effective way to investigate the D/A interface properties is to utilize a bilayer structure, sometimes called planer-heterojuntion (PHJ) structure. However, it has been very difficult to construct the bilayer structure with solution processes. Recently, the authors have developed a new processing method to fabricate the bilayer structure, which is called “contact film transfer method”. This technique enables us to realize solution-processed bilayer structures with well-defined D/A interfaces being suitable for the investigation of interfacial properties.
This Communication reports a new methodology for the solution of the trade-off issue between the current and voltage together with a brief overview of their recent works utilizing OSCs with the bilayer structure. They first found that the introduction of an insulating material (CYTOP) as the interlayer between the donor and acceptor layers can enhance the voltage, but it decreased the current. They then found that a charge/energy cascade layer (a semiconducting polymer with suitable electronic structures), which do not intermix with the donor and acceptor layers, could be an ideal interfacial structure for the efficient OSCs, resulting in the improvement of the current and voltage at the same time. Although these great findings are obtained using the bilayer system as a model system, the methodology could be expanded to the BHJ system if the interface is more precisely controlled by progress in processing techniques in the future.
These results were also presented at the Annual Conference of Photopolymer Science and Technology in 2016. In addition, more recently, a follow-up paper investigating deeply the charge/energy cascade layer and the extensive review paper about bilayer OSCs were published by the same group. The results presented in this Communication will provide new important insights into the solution of the issue of the trade-off between the current and voltage, and hence deserves the Photopolymer Science and Technology Award.