센서학회지 (Journal of Sensor Science and Technology)

  • 제28권4호
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  • Pages.251-255
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  • 2019
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  • 1225-5475(pISSN)
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  • 2093-7563(eISSN)
한국센서학회 (The Korean Sensors Society)
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Two step lithography와 나노 실리카 코팅을 이용한 초발수 필름 제작

Fabrication of Superhydrophobic Film with Uniform Structures Using Two Step Lithography and Nanosilica Coating

  • Yu, Chaerin (School of Mechanical Engineering, Chonnam National Unversity) ;
  • Lee, Dong-Weon (School of Mechanical Engineering, Chonnam National Unversity)
  • 투고 : 2019.06.11
  • 심사 : 2019.07.25
  • 발행 : 2019.07.31
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초록

We propose a two-step lithography process to minimize edge-bead issues caused by thick photoresist (PR) coating. In the conventional PR process, the edge bead can be efficiently removed by applying an edge-bead removal (EBR) process while rotating the silicon wafer at a high speed. However, applying conventional EBR to the production of desired PR mold with unique negative patterns cannot be used because a lower rpm of spin coating and a lower temperature in the soft bake process are required. To overcome this problem, a two-step lithography process was developed in this study and applied to the fabrication of a polydimethylsiloxane (PDMS) film having super-hydrophobic characteristics. Following UV exposure with a first photomask, the exposed part of the silicon wafer was selectively removed by applying a PR developer while rotating at a low rpm. Then, unique PR mold structures were prepared by employing an additional under-exposure process with a second mask, and the mold patterns were transferred to the PDMS. Results showed that the fabricated PDMS film based on the two-step lithography process reduced the height difference from 23% to 5%. In addition, the water contact angle was greatly improved by spraying of hydrophobic nanosilica on the dual-scaled PDMS surface.

키워드

HSSHBT_2019_v28n4_251_f0001.png 이미지

Fig. 1. Schematic diagram of fabricating superhydrophobic PDMS film.

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Fig. 2. Multi-coated thick PR with removed EB.

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Fig. 3. Improved contact angle after nanosilica coating.

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Fig. 4. Mushroom structures height compared with and without EB in PR mold.

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Fig. 5. Fabricated PDMS film with EB, showing different mushroom structures.

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Fig. 6. Fabricated PDMS film without EB, showing uniform mushroom structures.

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Fig. 7. Optical images of water droplets on the PDMS substrates ; (a) Before nanosilica coating (partial wetting), (b) After nanosilica coating (non-wetting).

HSSHBT_2019_v28n4_251_f0008.png 이미지

Fig. 8. Transmittance of superhydrophobic PDMS film.

참고문헌

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