【公開日：2025.06.10】【最終更新日：2025.05.21】
課題データ / Project Data
課題番号 / Project Issue Number
24UT1260
利用課題名 / Title
Microchannel device for trapping electrons on superfluid 4He
利用した実施機関 / Support Institute
東京大学 / Tokyo Univ.
機関外・機関内の利用 / External or Internal Use
外部利用/External Use
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）加工・デバイスプロセス/Nanofabrication（副 / Sub）計測・分析/Advanced Characterization
【重要技術領域 / Important Technology Area】（主 / Main）量子・電子制御により革新的な機能を発現するマテリアル/Materials using quantum and electronic control to perform innovative functions（副 / Sub）-
キーワード / Keywords
量子効果/ Quantum effect,電子顕微鏡/ Electronic microscope,膜加工・エッチング/ Film processing/etching
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
Morais Natalia
所属名 / Affiliation
Okinawa Institute of Science and Technology (OIST) Graduate University, Quantum Dynamics Unit
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）-
利用した主な設備 / Equipment Used in This Project
UT-600：汎用ICPエッチング装置
UT-855：高精細電子顕微鏡
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
This study investigates the effectiveness of different oxygen plasma etching recipes using inductively coupled plasma reactive ion etching (ICP-RIE) to remove hard-baked photoresist (PR) in a multilayer microfabrication stack. Despite variations in ICP, bias power, and etching durations ranging from 5 to 15 minutes, none of the tested conditions completely removed the approximately 1.6 µm-thick PR. These results indicate limitations of the tested oxygen plasma parameters for PR removal in the presence of a gold metal mask, suggesting the need for either alternative process conditions or complementary cleaning steps.
実験 / Experimental
The substrate consisted of a 300 µm-thick silicon wafer with a 500 nm thermal SiO2 layer. The patterned structures consist of a 50 nm gold bottom and top layer, separated with 1.6 μm hard-baked photoresist. The top gold layer also acts as hard mask for ICP etching, defining features down to 4 µm in size, and the bottom gold layer as an etch stop layer. ICP-RIE etching was performed using ULVAC CE-300I (three recipes):- Recipe A: Antenna Power 50 W / Bias 50 W / Time: 11 min- Recipe B: Antenna Power 200 W / Bias 50 W / Time: 5 min- Recipe C: Antenna Power 50 W / Bias 30 W / Time: 11 min- All with: O2 flow: 10 sccm, Pressure: 1.33 Pa (10 mTorr), Samples were 15 mm × 15 mm and 10 mm × 10 mm chips, and care was taken to avoid over-etching the gold layer, which was essential for electrical contact. The SEM photographs of sample surface after ICP-RIE etching with three recipes are shown in Fig. 1, 2 and 3.
結果と考察 / Results and Discussion
None of the ICP O2 plasma recipes tested led to complete removal of the hard-baked PR layer. This included both long-duration, lower-power recipes (e.g., 50 W/50 W for 11–15 minutes) and short-duration, high-ICP power recipes (e.g., 200 W/50 W for 5 minutes). The resistance of the PR to the etching process is attributed to its significant thickness (～1.6 µm) and cross-linkage due to hard baking. The results suggest that:- Increasing ICP power alone (e.g., to 200 W) does not ensure full PR removal within short etch times.- Moderate power over longer times is insufficient under these gas flow and pressure conditions.- There may be additional effects from surface passivation due to etch by-products or limited ion energy for deeper PR removal. Further investigation is required to optimize the PR removal without compromising the underlying gold layer integrity.
図・表・数式 / Figures, Tables and Equations
Fig.1 ICP etching P = 1.33 Pa (=10 mTorr), O2 flow = 10 sccm, Antenna power (ICP) = 50 W, ICP bias = 50 W, Time 11 min
Fig.2 ICP etching, P = 1.33 Pa (=10 mTorr), O2 flow = 10 sccm, Antenna power (ICP) = 50 W, ICP bias = 30 W, Time 11 min
Fig3 ICP etching, P = 1.33 Pa (=10 mTorr), O2 flow = 10 sccm, Antenna power (ICP) = 200 W, ICP bias = 50 W, Time 5 min
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
This work is supported by the internal grant from the Okinawa Institute of Science and Technology (OIST) Graduate University and the Grant-in-Aid for Scientific Research (Grant No. 23H01795 and 23K26488) KAKENHI MEXT
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件