Dual-Tone Development
Dual-tone development, such as Fujifilm's double development process, is similar to the dual-tone photoresist technique above in that it doubles features without additional exposure. Instead the photoresist is developed twice; the first time by conventional developer which removes the high exposure dose areas, the second time by a different organic solvent which removes the unexposed or lowest exposure dose areas. This leaves the intermediate dose areas (normally defining the two feature edges) standing. A key challenge is to not only show successful positive and negative tone development process windows, but also to ensure the windows overlap sufficiently. Up to now, the successful overlap has only been shown in simulations rather than experimentally.
Read more about this topic: Multiple Patterning
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