27 December 1996 Exposure of the OCG895i resist at the visible 413-nm Kr-ion line in a laser maskwriter
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Can the i-line resist OCG895i, normally exposed with UV radiation from an i-line (365 nm) mercury discharge or an argonion laser (364 nm), be exposed with the visible 407 and 413 nm lines of the krypton-ion laser. If so, with what quality? Visible radiation is desirable since it simplifies the optical design, and makes the system more reliable and easily serviceable. Simulations with PROLITH/2 show the lithographic performance to be equal or even slightly better at the longer wavelengths. Optical theory gives that at equal resolution there is a marginal loss in depth of focus (12%) at 413 compared to 364 nm. However, this is compensated for by the better optical design of the optical system —in particular the better corrected field curvature — made possible by the much wider range of glasses available in the visible. In a practical context there results no resolution penalty from using 413 nm exposure. Experimental reticle exposures with 413 nm and NA = 0.42 using a large-area writer for micro-tip FED lX masks confirm the viability of the 895i in the visible. Furthermore, the good image decay properties at 364 nm are retained at 413 nm.
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Torbjoern Sandstrom, Torbjoern Sandstrom, Peter Henriksson, Peter Henriksson, } "Exposure of the OCG895i resist at the visible 413-nm Kr-ion line in a laser maskwriter", Proc. SPIE 2884, 16th Annual BACUS Symposium on Photomask Technology and Management, (27 December 1996); doi: 10.1117/12.262845; https://doi.org/10.1117/12.262845

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