Influence of inner shell electron on material processing by soft X-ray free electron laser

• Project/Area Number: 20K12494
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 80040:Quantum beam science-related
• Research Institution: The University of Tokyo
• Principal Investigator: Sakaue Kazuyuki 東京大学, 大学院工学系研究科(工学部), 准教授 (80546333)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Project Status: Completed (Fiscal Year 2022)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2022: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000); Fiscal Year 2021: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2020: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
• Keywords: 軟X線レーザー / レーザー加工 / 光・物質相互作用 / 極端紫外レーザー / 自由電子レーザー / 内殻電子

Outline of Research at the Start

半導体産業にけん引され、レーザーによる物質の加工は微細化の一途をたどっている。本研究では、従来より微細な直接レーザー加工を可能とする、軟X線(波長30nm以下)レーザーによる加工に取り組む。そのでも特徴的な物質中の内殻電子の加工における寄与・物理を明らかにすることで、将来のレーザー微細加工に向けた土壌を形成する。

Outline of Final Research Achievements

In this project, we worked on processing using a soft x-ray laser, which enables direct laser processing more precisely than conventional lasers. Since the photon energy of the laser light is 10 times higher than that of conventional laser light, the physical process of the processing was investigated. Laser direct micro-processing on the sub-micrometer scale was achieved on various targets such as silicon, sapphire, and diamond. As a processing mechanism, it was confirmed that the effect of absorption by inner-shell electrons determines the structure of the material after laser irradiation and that the processing mechanism on the material surface differs depending on the relationship between the photoionization energy and the binding energy. These achievements open up soft X-ray processing as a new laser processing.

Academic Significance and Societal Importance of the Research Achievements

本研究課題における上記の成果は、軟X線レーザーによる加工の原理をすべて理解するにはもちろん至らないものの、その一部を明らかにした。従来のレーザーでは到達困難なサブマイクロメートルスケールの直接微細加工を実現し、見出した軟X線レーザー加工のユニークな特徴は、今後より微細化が進むレーザー加工技術開発において、重要な知見となる。これらの成果より次世代のレーザー直接微細加工の基盤を確立することができたといえる。今後もこの基盤を活用し、軟X線レーザーによる加工のメカニズムに関する研究や特徴的な加工の抽出に取り組んでいく。

Research Products

• [Journal Article] Independent contribution of optical attenuation length in ultrafast laser-induced structural change (2021)
  • Author(s): Tatsunori Shibuya, Kazuyuki Sakaue, Hiroshi Ogawa, Daisuke Satoh, Thanh-Hung Dinh, Masahiko Ishino, Masahito Tanaka, Masakazu Washio, Takeshi Higashiguchi, Masaharu Nishikino, Akira Kon, Yuya Kubota, Yuichi Inubushi, Shigeki Owada, Yohei Kobayashi, and Ryunosuke Kuroda
  • Journal Title: Optics Express, pp. 33121-33133 (2021.9). Volume: Vol. 29(21) Issue: 21 Pages: 33121-33133
  • DOI: 10.1364/oe.432130
  • Peer Reviewed / Open Access
• [Journal Article] Ablation threshold and crater morphology of amorphous and crystalline SiO2 glass for extreme ultraviolet femtosecond pulses (2020)
  • Author(s): Shibuya T.、Sakaue K.、Ogawa H.、Dinh T.-H.、Satoh D.、Terasawa E.、Washio M.、Tanaka M.、Higashiguchi T.、Ishino M.、Kubota Y.、Inubushi Y.、Owada S.、Nishikino M.、Kobayashi Y.、Kuroda R.
  • Journal Title: Japanese Journal of Applied Physics Volume: 59 Issue: 12 Pages: 122004-122004
  • DOI: 10.35848/1347-4065/abc85a
  • Peer Reviewed
• [Journal Article] Surface processing of PMMA and metal nano-particle resist by sub-micrometer focusing of coherent extreme ultraviolet high-order harmonics pulses (2020)
  • Author(s): Sakaue Kazuyuki、Motoyama Hiroto、Hayashi Ryosuke、Iwasaki Atsushi、Mimura Hidekazu、Yamanouchi Kaoru、Shibuya Tatsunori、Ishino Masahiko、Dinh Thanh-Hung、Ogawa Hiroshi、Higashiguchi Takeshi、Nishikino Masaharu、Kuroda Ryunosuke
  • Journal Title: Optics Letters Volume: 45 Issue: 10 Pages: 2926-2926
  • DOI: 10.1364/ol.392695
  • Peer Reviewed / Open Access