【公開日：2024.07.25】【最終更新日：2024.07.12】
課題データ / Project Data
課題番号 / Project Issue Number
23UT1053
利用課題名 / Title
クヌッセン力計測のための表面微細構造の作製
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
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
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）次世代ナノスケールマテリアル/Next-generation nanoscale materials（副 / Sub）-
キーワード / Keywords
ナノ構造表面、クヌードセン力,光学顕微鏡/ Optical microscope,リソグラフィ/ Lithography,電子線リソグラフィ/ EB lithography,膜加工・エッチング/ Film processing/etching,ダイシング/ Dicing
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)
杵淵 郁也
所属名 / Affiliation
東京大学大学院工学系研究科機械工学専攻
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
Clint John Otic,佐藤 康平
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-606：汎用平行平板RIE装置
UT-906：ブレードダイサー
UT-500：高速大面積電子線描画装置
UT-850：形状・膜厚・電気特性評価装置群
UT-800：クリーンドラフト潤沢超純水付
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 explores Knudsen forces, which arise from temperature variations around micro/nano-structures [1]. This phenomenon has potential for energy conversion systems which can harness Knudsen forces to extract work from heat. Through theoretical analysis and numerical simulations, we investigate the optimum parameters (length scale, shape of the surface micro-structure, etc.,) that can induce enough Knudsen force for directed motion. Crucially, we fabricate a sample with specific surface microstructures and conduct experimental analysis to verify the feasibility of the system.
実験 / Experimental
To fabricate surface micro/nano-structures, initially, silicon (Si) wafer samples are diced into 20mmx20mm sizes. Subsequently, electron beam lithography was applied to generate parallel line patterns exposed on the surface. Next, reactive ion etching (RIE) using the SAMCO RIE-10NR system was employed for dry etching. To induce Knudsen forces for directed motion, the micro/nano-structures must possess an asymmetric shape [1]. We determined a "tilted ridge" configuration as the optimal shape for this purpose [2]. Fabricating micro/nano-scale tilted ridges involves tilting the sample beyond 30 degrees during the etching process [2]. Additionally, to ensure structural tilt, a metallic shield must be positioned over the sample [3]. In our setup, the sample rests on an aluminum wedge block (inclined 45 degrees), with another aluminum wedge block (inclined 45 degrees) serving as the shield structure (see Fig. 1). Consequently, sufficient space for the etching process, accommodating both blocks and ensuring gas flow, is necessary, justifying the choice of the RIE-10NR system.
We used the following recipe for the dry etching: CH4 flow rate = 50sccm, power = 100W, pressure = 5Pa, duration = 10min.
結果と考察 / Results and Discussion
The surface micro/nano-structures produced by the dry-etching process were examined using scanning electron microscopy (SEM). Figure 1 displays SEM images capturing surface structures at various locations on the etched Si sample. These images reveal variations in structure geometry based on location. Near the upper edge of the Si sample (labeled (1)), the surface structure appears ridge-like but lacks tilt. This absence of tilt is attributed to the unshielded region near the upper edge, where etching occurs perpendicular to the inclined surface (see Ref. [3]). Conversely, at locations away from the upper edge (labeled (2) and (3)), tilted structures are observed, albeit with differing geometries. Notably, the close proximity of electron beam resists leads to the formation of "saw-tooth" structures instead of the intended tilted ridges. Consequently, to address these observations, we plan to optimize process conditions, including the etching recipe and the geometry of the aluminum block. Additionally, adjustments to the thickness of the electron beam resist will be made based on these findings.
図・表・数式 / Figures, Tables and Equations
Fig. 1. Experimental set-up for reactive ion etching, and the resulting microstructures at various locations.
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
[1] C. J. C. Otic and S. Yonemura, Micromachines 13, 871(2022).
[2] R. L. Agapov et al., Nanoscale 6, 9293-9299 (2014).
[3] S. Choi et al., IEICE Electronics Express 10, 1-8 (2013).
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