Bi/In bimetallic thermal resists for microfabrication, photomasks, and micromachining applications

Glenn H. Chapman; Richard Yuqiang Tu; Marinko V. Sarunic

doi:10.1117/12.474201

24 July 2002 Bi/In bimetallic thermal resists for microfabrication, photomasks, and micromachining applications

Glenn H. Chapman, Richard Yuqiang Tu, Marinko V. Sarunic

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Proceedings Volume 4690, Advances in Resist Technology and Processing XIX; (2002) https://doi.org/10.1117/12.474201
Event: SPIE's 27th Annual International Symposium on Microlithography, 2002, Santa Clara, California, United States

Abstract

Bilayer Bi/In thin films form thermal resists with many new microfabrication and micromachining applications due to their changed physical, chemical and optical characteristics after the laser exposures. Wavelength invariance has been shown from the results of both experiment and Airy Summation optical modeling. The modeling projects bimetallic resist sensitivity to be nearly constant at about ~7 mJ/cm² from 248 to 13.4 nm and is still very sensitive at 1 nm in X-ray range. Two kinds of acid solutions were effective in developing the exposed films by removing the unexposed area. Both nitric acid mixture (HNO₃:CH₃COOH:H₂O=1:3:6) and hydrochloride acid mixture (HCl:H₂O₂:H₂O=1:1:48) give etching selectivity of exposed to unexposed area of larger than 60:1. The etch rate of unexposed area is about 2.6 nm/sec. The Bi/In resist can be stripped away by an RCA2 clean. Bi/In resist was successfully used as a mask layer for KOH anisotropic silicon etching process. Due to the unusual conductive property of its exposed and developed films, Bi/In has demonstrated that it can be used as a direct laser write electroplating resist material. Copper and nickel plating was carried out on developed Bi/In layers on various substrates such as Si wafers, glass slides, wet-oxidized wafers. Large optical transmission changes (OD>3.5 before exposure and OD<0.3 after exposure at I-line) indicate that Bi/In can be used as a direct-write photomask material.

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Glenn H. Chapman, Richard Yuqiang Tu, and Marinko V. Sarunic "Bi/In bimetallic thermal resists for microfabrication, photomasks, and micromachining applications", Proc. SPIE 4690, Advances in Resist Technology and Processing XIX, (24 July 2002); https://doi.org/10.1117/12.474201

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