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Proceedings Paper

Optical Lithography For Half-Micron And Sub-Half-Micron Resolution
Author(s): F. A. Vollenbroek; M. J. H. J. Geomini
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Paper Abstract

The lithographic requirements for half-micron and sub-half-micron design rules are discussed in terms of the resolution capability of 436 nm, 365 nm and 248 nm reduction steppers, the depth of focus, bulk and reflection effects and the impact of using advanced single-layer resist systems instead of conventional positive photoresists. Using the simulation model SLIM (Simulation of Latent Image Manipulations) the distribution of the product of photolysis in the latent image is calculated as resulting from patternwise exposures and resolution enhancing procedures as Image Reversal (ImRe) and Built In Mask (BIM). On the basis of the concentrations and gradients arising from patterning with 365 nm in a 1.5 μm thick resist layer it is shown that, using an i-line lens with 0.42 NA, the patterning of 0.5 μm lines and spaces will be possible. For sub-half-micron dimensions a shorter wavelength (e.g. 248 nm) is required to ensure a sufficient image contrast. A difficulty that arises at this wavelength is that novolak-based photoresists exhibit a very low transparency, thus hampering the penetration of UV-light in the resist layer. It is shown that, in order to image these resists in the positive mode either the absorptivity of the resin or the thickness of the resist layer has to be reduced considerably. Alternatively a 'top-imaging' procedure, as for instance BIM and DESIRE could be used. In this case a penetration depth of the imaging UV-light of 0.3 μm may be sufficient. An additional advantage of these procedures is that both the problem of limited focus depth and the detrimental effects caused by reflection of UV-light at the substrate are alleviated.

Paper Details

Date Published: 1 January 1988
PDF: 10 pages
Proc. SPIE 0920, Advances in Resist Technology and Processing V, (1 January 1988); doi: 10.1117/12.968343
Show Author Affiliations
F. A. Vollenbroek, Philips Research Laboratories (The Netherlands)
M. J. H. J. Geomini, Philips Research Laboratories (The Netherlands)

Published in SPIE Proceedings Vol. 0920:
Advances in Resist Technology and Processing V
Scott A. MacDonald, Editor(s)

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