分子を操り、ナノ構造を作る。そして、利用する。
Research in the Hayakawa Laboratory focuses on the development of functional materials based on polymer synthesis techniques. Among various research themes, particular emphasis is placed on utilizing the self-assembly of block copolymers for the development of ultrafine processing technologies and porous materials. By actively leveraging relatively weak intermolecular interactions, such as hydrogen bonding, coordination bonding, van der Waals forces, and hydrophilic-hydrophobic interactions, it is possible to create precise nanostructures with controlled molecular arrangement and orientation, crystalline-liquid crystal structures, and phase-separated structures on the nanoscale. By maximizing the inherent potential of molecules to self-assemble, the lab engages in everything from molecular structure design and precision polymerization to controlling higher-order structures, successfully developing tailor-made materials unparalleled in other fields.
If you feel that the explanation above is honestly difficult to understand, don’t worry! Don’t overthink it! Once you see the fascinating process of a compound you designed and synthesized self-assembling right before your eyes, you’ll immediately be captivated by the allure of self-assembled materials. Let’s conduct research together!
Research 1. Synthesis of High-χ Block Copolymers and Next-Generation Lithography
The miniaturization and enhanced functionality of electronic devices such as computers and smartphones rely on the progress of semiconductor microlithography (lithography) technologies. Therefore, advancing new lithographic techniques capable of high-resolution (high-definition) and ultrafine processing is crucial for the development of organic polymeric materials. However, current mainstream lithography methods are approaching the limits of resolution due to cost and technical constraints.
Recently, a novel lithography technique that utilizes the self-assembly of high molecular weight block copolymers to create periodic structures has gained attention. This technique, called “block copolymer lithography,” has a significant connection to improving semiconductor microlithography. Block copolymers consist of polymers with structurally distinct blocks at each end. These polymers can self-assemble into nanoscale periodic structures (domains) corresponding to the size of polymer chains, typically in the range of 10 to 50 nm. This phenomenon is known as microphase separation.
Microphase separation results in various morphologies such as sphere, hexagonally packed cylinder, and lamellar structures. These distinctive features of block copolymers are being applied in creating fine patterns on semiconductor substrates, forming ultrafine patterns at the single-nanometer scale. By combining block copolymers designed and synthesized in-house with lithography techniques, we are pursuing the creation of ultra-high-resolution circuit patterns for the next generation.
Research 2. Development of Insulating, High-Thermal-Conductivity Epoxy Adhesives
With the increasing performance of electronic devices, efficiently dissipating excessive heat generated in mounted components has become a critical challenge. However, the electrically insulating materials used to bond substrates to semiconductors inside devices, such as epoxy resins, have extremely low thermal conductivities (0.1–0.2 W/m·K), creating a bottleneck in heat dissipation.
To address this issue, we are conducting research aimed at developing high-thermal-conductivity epoxy resins by introducing mesogenic structures into the epoxy resin backbone, thereby imparting liquid crystallinity to the material.
Research 3. Creation of Porous Materials Utilizing Microphase Separation of Block Copolymers
Research 4. Development of Low Dielectric Loss Materials
Research 5. Materials Informatics Utilizing Deep Learning and Robotics
Materials informatics, which advances materials research from the perspective of data science, is gaining attention as a methodology for creating new materials. At its core are computational techniques, including artificial intelligence (AI), which are used to predict and propose materials, as well as robotic systems to control experimental processes. To achieve chemical research with AI robots that possess the rich knowledge, advanced decision-making skills, and refined techniques of veteran scientists, large-scale language models (foundation models), deep learning, and autonomously constructed automated experimental equipment are being integrated. This enables the construction of systems from scratch for applications such as polymer synthesis.
生成AIの化学研究への適用可能性検証 東工大が実験の効率化や成功確率の向上へ
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Materials for Future Nanolithography
Polyhedral Oligomeric Silsesquioxane (POSS)-containing Block Copolymers (BCPs)
It is important to develop lithographic materials and techniques for future devises of which size scale becomes ever smaller. However, conventional lithographic processes become increasingly more difficult and expensive, especially at a minimum feature size of less than 22 nm. Thus, it is crucial to develop innovative routes to circumvent both cost and manufacturing issues. In recent years, BCP lithography has emerged as an attractive alternative to drive down the feature size. BCPs can spontaneously self-assemble into dense, periodic array of nanostructures such as spheres, cylinders, and lamellae with feature sizes less than 50 nm.
The ideal BCP for nanolithography applications exhibits (1) one highly etch-resistant block, (2) high repulsive interaction, and (3) thermal stability at ambient temperature. In order to satisfy these criteria, we are focusing on designing and fabricating POSS-containing BCPs. The high density of silicon in the POSS provides extremely high etch contrast between the constituent organic block when treated in an oxygen plasma, which is advantageous for high-aspect-ratio pattern transfer into underlying materials. Also POSS shows high repulsive interaction between constituent organic polymer, which is important to smallest attainable self-assembled structure. Compared to other silicon-containing polymer such as silicones, POSS-containing polymers are extremely thermally robust, which is crucial property for uniformly cast onto the substrate and keep the ideal morphology at ambient temperature.
We have succeed living anionic polymerization of a series of POSS-sustituted methacrylates (PMAPOSSs) and block copolymererization with organic polymers such as polystyrene (PS) and poly(methyl methacrylate) (PMMA). Obtained POSS-containing BCPs have shown extremely long-range-ordered structure, of which size is down to 10 nm. We have also demonstrated directed self-assembly (DSA) of POSS-containing BCPs on chemically patterned templates to arbitrary align the self-assembled structure. A combination of density multiplication system and thermal annealing gave perfectly aligned hexagonally arranged spheres over an area of around 6Tera-dots/inch2. This result would change the future lithographic processes as introduced on .
Our next challenge for these POSS-based BCPs is to reduce the POSS-cotaining polymer/organic polymer interface roughness in order to reduce the line-edge roughness (LER) of the nanopattern. Currently we are investigating the interface structure using synchrotron X-ray scattering analyses to understand correlation between molecular structure and interface structure. We are now refining the molecular structure based on the fundamental understanding of POSS-containing BCPs.
Block copolymer lithography
Polyhedral Oligomeric Silsesquioxane (POSS)
13nm ordered nanostructure of BCP containing POSS
POSS-based Liquid Crystalline Molecules for Sub-10nm Structure Patterns
In addition to BCP lithography, we are attempting "molecular" lithography by utilizing POSS-based liquid crystalline molecules. Self-assembled structure formed by BCPs usually have a size range between 10~50 nm while the one formed by liquid crystalline molecules have a size of sub-10nm. Also single molecular weight of the liquid crystalline molecules would be advantageous for long-range ordering of the self-assembled structure.
Currently we are in collaboration with companies to develop double-decker-shaped silsesquioxane (DDSQ) molecules, and POSS molecules with long alkyl chains. Obtained molecules showed extremely high resolution pattern derived from silicone-containing part and alkyl chain part. Our next challenge is applying these molecules to directed-self-assembly in order to perfectly ordering on the substrate such as silicon wafer.
Molecular lithography material
高熱伝導性エポキシ樹脂の開発
電子機器の高性能化に伴い、実装部品において発生する過剰な熱を効率良く取り除くことが非常に大きな課題として掲げられています。しかしながら機器内部で基板と半導体を接着する電気絶縁材料には、エポキシ樹脂が用いられており、その熱伝導率が0.1 - 0.2 W/m･K と非常に低いために熱放散のボトルネックとなっています。そこで私たちはこの問題を解決するために、エポキシ樹脂前駆体にメソゲン骨格を導入し、液晶性を付与することで高熱伝導性を示すエポキシ樹脂を開発することを目的として研究を行っています。
この研究における最終的な目標は成型加工性に優れ、高熱伝導性を示すエポキシ樹脂を開発することですが、樹脂中に形成される高次構造と熱伝導性の相関や、熱伝導性を制御するための方法について基礎的な知見を得ることは科学的・技術的な視点からも非常に重要です。
これまでに、私達は種々のメソゲン骨格を有するエポキシ樹脂を合成してきており、非対称型のメソゲン骨格を導入するとエポキシ樹脂前駆体の融点を大きく下げられることを見出しました。またエポキシ樹脂中にスメクチックB相のような高規則性を有する液晶相を形成させることが、高熱伝導性樹脂を得る上で重要であるといった知見も得られました。
エポキシモノマーの分子設計
エポキシ樹脂の熱伝導率