Herstellung einer Phasenverschiebungsphotomaske mit unterbrochenen Bereichen

摘要

A method and apparatus for photolithographically fabricating features on a very large scale integrated circuit wafer by use of a phase shift mask defining discrete regions. This overcomes the problems of intensity nulls at the junction of regions formed by portions of the mask having opposite phase. The mask includes a transition region defining three phases which are assigned to pixels in the transition region, such that the phase assignment of the pixels is synthesized from an algorithm taking into account optical resolution and depth of focus. Each pixel is assigned one of three discrete phases, which thereby creates a transition region simulating a ramp between the two regions of opposite phases, such that intensity variation of the optical image corresponding to the transition region is minimized.