Exposing a semiconductor wafer using two different spectral...

Photocopying – Projection printing and copying cameras – Focus or magnification control

Reexamination Certificate

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C355S052000

Reexamination Certificate

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11116439

ABSTRACT:
A semiconductor wafer is exposed with a pattern from a mask or reticle in an exposure tool. The exposure tool has an adjustable lens system and a light source, which is tunable in wavelength. A first exposure is performed with a tuned first wavelength and a first setting of the lenses. Prior to performing a second exposure onto the same wafer and into the same resist layer, the wavelength of the light source is varied to a second wavelength in order to mimic a focus offset. A resulting image shift at the slit edges of the scanning system due to chromatic aberration is then corrected for by setting the lens system in dependence of the difference between the tuned first and second wavelength. Having tuned second wavelength of the light source and having set the lens system, the second exposure is performed. A continuous adjustment of the lens system based upon a continuously varying light source wavelength can be accomplished.

REFERENCES:
patent: 6831731 (2004-12-01), Omura et al.
patent: 2002/0048288 (2002-04-01), Kroyan et al.
patent: 2002/0163733 (2002-11-01), Takahashi
patent: 2004/0059444 (2004-03-01), Tsukakoshi
patent: 2005/0128452 (2005-06-01), Matsumoto
Fukuda H. et al., “Improvement of defocus tolerance in a half-micron optical lithograph by the focus latitude enhancement exposure method: simulation and experiment”, J. Vac Sci. Technol. B7 (4) Jul./Aug. 1989, pp. 667-674.
Lalovic I, et al., “Depth of focus enhancement by wavelength modulation: can we RELAX and improve focus latitude?” Interface 2003, Proceedings 40thInterface Symposium Conference—San Diego, Sep. 21-23, 2003.
Slonaker S., “TAO: Technology for Aberration Optimization”, Proceedings of SPIE, vol. 5754-190, 2005 (to be publixhed)//Litho Vision conference 2004-Feb. 22, 2004.

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