Host: The Japan Society of Vacuum and Surface Science
Name : Annual Meeting of the Japan Society of Vacuum and Surface Science 2023
Location : [in Japanese]
Date : October 31, 2023 - November 02, 2023
Metal pattern formation by vacuum deposition is an important process from basic research to industrial mass production. Selective metal deposition utilizing desorption of metal atoms from organic surfaces is a promising method for forming metal patterns by maskless vacuum deposition. Maskless vapor deposition for metal pattern preparation is possible by changing the glass transition temperature (Tg) due to photoisomerization of photochromic diarylethene (DAE) [1,2]. The core phenomenon of selective metal deposition is metal atom desorption from the low Tg surface near room temperature. Metal atoms including Mg, Mn, and Pb desorb and the metal film is not formed on the colorless DAE surface. However, selective metal deposition of DAE could not be attained for such metal species having a high melting-point and low intrinsic-vapor-pressure as Ag, Cu, and Cr [3].
In this work, we demonstrate the formation of metal patterns by maskless deposition for various metal species using vacuum-depositable and printable perfluoropolyether (PFPE)-based materials [4]. A simple fluorinated alkyl chain film (a), which is silane-oupled to a glass substrate, exhibited low surface energy, but did not exhibit good desorption property of metal atoms. PFPE film (b), in which an ether moiety was incorporated in the alkyl chain, exhibits good metal atom desorption due to its low surface energy and surface molecular flexibility. It was found, furthermore, that the highest metal desorption property was attained for PFPE polymerized film (c) because of its large surface softness.
We adopted the antifouling/mold-release agent KY-1901 (Shin-Etsu Chemical Co., Ltd.) as a PFPE material, which can be used for both vacuum deposition and printing. Since this PFPE material was supplied as a solution, it was dropped into an evaporation boat and then annealed at 120°C for 1 hour to evaporate the solvent before being placed in a vacuum chamber as an evaporation source. In the PFPE film with a thickness of about 10 nm, a metal film was formed when the deposition amount of Ag and Cr was large. On the other hand, a 30-nm-thick PFPE film showed good desorption properties. PFPE-patterns were prepared on a glass substrate by vacuum deposition with a shadow mask and then metal evaporation was carried out without a shadow mask, resulting metal pattern formation for a variety of metal species including Ag, Cu, Cr, and Ni (d). This method provides complementary patterns for direct metal patterning using a shadow mask, including the pattern with isolated non-metallized areas. Even in the case of PFPE pattern formation by printing method, metal pattern formation was possible by maskless metal deposition. The resolution of the metal pattern obtained by this method depends on the fineness of the original PFPE pattern.
This method enables metal pattern formation by maskless vacuum deposition for various metals with high melting points and low intrinsic vapor pressures and can be applied to electrode pattern formation in electronics and other applications.
[1] T. Tsujioka, et al., J. Am. Chem. Soc., 130, 10740 (2008).
[2] T. Tsujioka, Chem. Rec., 16, 231 (2016).
[3] T. Tsujioka, S. Matsumoto, J. Mater. Chem. C, 6, 9786 (2018).
[4] T. Tsujioka, H. Kusaka, Adv. Mater. Interfaces, 9, 2201096 (2022).
