Run-time correction of proximity effects in raster scan pattern generator systems
✍ Scribed by L. Veneklasen; U. Hofmann; L. Johnson; V. Boegli; R. Innes
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 936 KB
- Volume
- 46
- Category
- Article
- ISSN
- 0167-9317
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✦ Synopsis
In a raster scan lithography system, it is possible to correct proximity effects while the pattern is being exposed. This technique will be called run-time proximity correction. It is quite different from conventional methods that preprocess pattern data before exposure. It is a user transparent part of an exposure strategy whose throughput does not depend on the density, complexity, or randomness of the pattern. Coverage parameters are calculated, accounting for short-range aerial-image edge resolution and forward scattering effects which distort the shape of features, as well as backscattering effects which shift exposure levels with pattern density. These parameters are used to modify pixel doses according to precalculated and preloaded algorithms that equalize the exposure of all edges. This paper formulates the physical and mathematical basis for the technique, describes one of many possible correction algorithms, and explains how rasterized data is dose modulated in real time using digital signal processors and lookup table memory.