PUPIL PLANE FILTER FOR EUV LITHOGRAPHY
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Jul-23
Placing a phase and or amplitude filter in the pupil plane of an optical projection lithography sys- tem has been shown to increase resolution and depth of focus1,2,3,4. The pupil filter sharpens the image intensity slope at the wafer by modifying the spatial frequency spectrum of the image. The pupil plane of a projection imaging system contains a spatial frequency spectrum of the image. A filter in this plane can tailor the spatial frequency spectrum to sharpen the image.