Communication Journal of Photopolymer Science and Technology Volume 35, Number 4 (2022) － Ⓒ2022SPST 371 374 371 Investigation of Pressure Dependence in Photoresist Ashing Process using Microwave Excited Water Vapor Plasma Khant Nyar Paing 1* , Takeshi Aizawa 1 , Hiroto Nishioka 2 , Masashi Yamamoto 2 , Tasuku Sakurai 1 , Bat-Orgil Erdenezaya 1 , Yusuke Kayamori 1 , Yusuke Nakano 1 , Yasunori Tanaka 1 , and Tatsuo Ishijima 1 1 Electrical Engineering and Computer Science, Graduate School of Natural Science & Technology, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan 2 Department of Electrical and Computer Engineering, National Institute of Technology Kagawa College, Chokushi-cho, Takamatsu, Kagawa 761-8058, Japan *khantnyarpaing@stu.kanazawa-u.ac.jp, ishijima@ec.t.kanazawa-u.ac.jp Microwave-excited water plasma asher (WPA) is our laboratory's new technology for the photoresist (PR) ashing process in semiconductor manufacturing which uses water vapor as process gas. It has the potential to solve many problems of conventional PR ashing technologies including high temperature, oxidation of metal structure, low ashing rate for ion-implanted PR, and high costs of chemicals. In this study, the pressure dependence of various aspects of plasma in water plasma asher, including light emission area, emission intensity, and substrate temperature was investigated. The ashing rate of the novolak PR film on the silicon wafer at the various condition of process pressure was also investigated. Average emission intensity and emission area of plasma significantly increased as process pressure in the chamber were decreased, and they were the highest when the process pressure was 0.3 kPa. The average ashing rate of PR film was only 0.42 μm/min when process pressure was 2.14 kPa, and it gradually increased as process pressure was decreased. It is also found that the ashing rate was improved after reducing the temperature of the water. The ashing rate when using air-rich condition of plasma was observed to be higher than when only water vapor is used as process gas. Keywords: Microwave-excited plasma, Semiconductor, Photoresist, Pressure, Ashing rate, Water vapor, H-shaped antenna 1. Introduction In modern life, semiconductor products are used in all fields such as automobiles, smartphones, medical devices, and industrial robots. With the development of AI and 5G technology, the trend toward multi-functionalization of these products will accelerate and the types of semiconductor devices will also diversify. Photoresist (PR), a photosensitive polymer material, is used as a mask in the lithography process in semiconductor device manufacturing. Removal of PR is an important step in the semiconductor manufacturing process. Conventional technologies for PR removal are (1) Chemical treatment using SPM solution (H2SO4 + H2O2) [1] and (2) Oxygen plasma treatment [2–4]. Chemical treatment method uses dangerous, costly, and toxic chemicals that are environmentally damaging. It is necessary to continue flowing the chemical solution because the instance of mixing sulfuric acid and hydrogen peroxide is the most effective in removing PR. Oxygen plasma treatment increases the temperature of the substrate to 250- 300 0 C. It can cause damage to the substrate and deterioration of the metal interconnects on the substrate due to oxidation. When ashing PR with ion implantation, the PR can be blown off by an Received Accepted March 31, 2022 June 20, 2022