This technique also eliminates the need for fluorocarbon gases, which have significant global warming potentials.

After more than a decade of research and development, Tokyo Electron Miyagi Ltd. has introduced an innovative semiconductor etching method that achieves etch rates up to five times faster than conventional processes. Now, a collaborative research team from ºÚÁϳԹÏÍø and the company has examined the underlying etching mechanisms responsible for this enhanced performance.

This new method employs plasma etching with hydrogen fluoride (HF) at very low temperatures. In contrast to conventional fluorocarbon etching gases, which have high global warming potentials (GWPs), HF has a substantially lower GWP.

The study demonstrated that this process significantly reduces processing time and enhances energy efficiency, particularly for etching complex three-dimensional (3D) structures in advanced devices, such as gate-all-around (GAA) transistors and 3D NAND flash memory chips. The findings were published in the .

Semiconductor etching is an essential chip-manufacturing process that selectively removes material from a wafer surface to form precise circuit patterns. Reactive ion etching technologies have played a pivotal role in wafer fabrication through synergistic reactions between chemical gases and ions.

However, ongoing miniaturization of semiconductor devices poses substantial challenges for etching techniques, especially in delivering chemical species deep into complex 3D structures with high aspect ratios, where the depth is much greater than the width. These difficulties have led to a considerable decrease in “etching throughput,” the amount of etching work done in a particular period of time.

To address these challenges, a ºÚÁϳԹÏÍø research team, led by Professors and of the , collaborated with , a manufacturer of plasma etching equipment, to verify that this new etching process mechanism significantly enhances throughput.

Previous studies have indicated that cooling the substrate to ultra-low temperatures substantially increases etch rates in silicon-based materials, such as silicon dioxide (SiOâ‚‚) films. Furthermore, it has been suggested that co-absorption of HF and the etching reaction product, water (Hâ‚‚O), significantly enhances surface reactions at very low temperatures.

“However, precise synergistic interactions between HF ions, surface-adsorbed HF and Hâ‚‚O, and the material surface being etched for cryogenic plasma etching remain unclear,” stated Professor Hsiao. “Therefore, we assessed the performance of etching SiOâ‚‚ films using HF plasma at very low temperatures.”

The researchers cooled the semiconductor substrate to −60°C and then exposed it to an HF plasma. They observed that both HF and H₂O adsorbed onto the SiO₂ surface and found that H₂O acts as a catalyst, reducing the etching activation barrier to nearly zero.

The study also demonstrated that increasing ion irradiation energy promotes the generation of Hâ‚‚O, which subsequently adsorbs onto the surface, accelerating a self-catalytic cycle that attracts HF. Interestingly, this process, referred to as an ion-enhanced surface autocatalytic reaction, resulted in an exponential increase in the film etching rate per unit of ion energy.

The study confirmed that this new process achieves an etching throughput for SiOâ‚‚ films approximately 100 times greater than that attained under conventional room-temperature and low-ion-energy conditions.

“Furthermore, the use of HF plasma instead of conventional fluorocarbon gases, which typically exhibit high global warming potentials, eliminates the carbon footprint associated with the etching process,” stated Professor Hsiao.

“Through this industry collaboration, we are advancing verification in an environment similar to actual manufacturing equipment. We aim to apply this process to semiconductor manufacturing lines and extend its use to broader production processes.”

Paper information:

Shih-Nan Hsiao, Yusuke Imai, Makoto Sekine, Ryutaro Suda, Yuki Iijima, Yoshihide Kihara, Kenji Ishikawas, and Masaru Hori (2025). Revolutionizing reactive ion etching: ion-enhanced surface autocatalytic reactions enabling ultra-high throughput using cryogenic hydrogen-fluoride plasma. Chemical Engineering Journal.
DOI:

Expert contact:

Shih-Nan Hsiao
Center for Low-temperature Plasma Sciences
Email: hsiao.shih.nan.t8@f.mail.nagoya-u.ac.jp

Media contact:

Naomi Inoue
International Communications Office, ºÚÁϳԹÏÍø
Email: icomm_research@t.mail.nagoya-u.ac.jp

Top image:

Synergy of ion-enhanced and surface adsorbed HF/H₂O for etching
(Credit: Shih-Nan Hsiao)

Event supported by GCoM Japan secretariat at ºÚÁϳԹÏÍø

The Global Covenant of Mayors for Climate and Energy (GCoM) awarded badges to eight municipalities in Japan during a ceremony on September 23, 2025. The event was held at the European Union (EU) Pavilion at Expo 2025 in Osaka, under the auspices of the Japan-EU Green Alliance. ºÚÁϳԹÏÍø serves as the secretariat for the Japanese branch of the organization, GCoM Japan.

The ceremony was attended by leaders of the eight municipalities that were awarded a badge for compliance (Kamishihoro and Yoichi in Hokkaido; Tomiya in Miyagi Prefecture; Yamagata in Gifu Prefecture; Okazaki, Ichinomiya, and Obu in Aichi Prefecture; and Sakaide in Kagawa Prefecture), as well as representatives from the delegation of the European Union to Japan. The badge for compliance is awarded to municipalities that have been officially recognized by the global secretariat in Brussels as having completed all three stages of both the climate change mitigation measures (inventory assessment, target setting, and planning) and adaptation measures (risk and vulnerability assessment, target setting, and planning).

At the beginning of the ceremony, ºÚÁϳԹÏÍø Associate Professor Feifan Xu and Designated Professor Noriko Sugiyama, the Secretariat for GCoM Japan, gave an explanation about the purpose of the ceremony.

Jean-Eric Paquet, Ambassador of the EU to Japan, then spoke about the urgency of climate change measures, emphasizing the importance of municipalities continuing to take the lead role. Additionally, Naoko Hamashima, Director of the Office for Regional Decarbonization Policy at the Ministry of the Environment, expressed her hope that municipalities would promote the creation of “regional circular and ecological spheres” together with the people living in their communities.

At the main event of the day, the badge conferral ceremony, Ambassador Paquet presented the badges of compliance to the leaders of the municipalities. The awardees took to the stage and introduced the climate policies that their regions are focusing on, such as the “leading decarbonization regions” initiative, and expressed their determination to make use of this network to further accelerate their efforts.

In addition, Margot Roose, a Deputy Mayor of Tallinn, Estonia, spoke about her experience of when Tallinn was selected as the European Green Capital in 2023, and Professor Albert Edman from the Swedish National Research Institute (RISE) delivered a speech on green transformation in European cities.

At the end of the ceremony, Andreas Roettger, Head of the Asia-Pacific Regional Team in the EU Service for Foreign Policy Instruments, and ºÚÁϳԹÏÍø Professor Hiroki Tanikawa, Dean of the Graduate School of Environmental Studies, where the GCoM Japan office is located, stated that they would continue to support the creation of sustainable and resilient communities in collaboration with local governments and civil society.