Patterning optical and X-ray masks for integrated circuit fabrication

摘要

A layer of metal is deposited on a mask substrate and then covered with a layer of negative electron resist. A delineation of the peripheral boundaries of the desired mask geometry is carried out by means of a direct-write electron beam. After development and etching, the peripherally defined metal boundaries are all that remain on the substrate. The substrate is then covered with a positive electron resist. The mask is, next, raster scanned with a low intensity beam until a boundary is detected and then the beam intensity is increased significantly to a level sufficient to expose the positive resist. The scan and exposure continue until the mating peripheral boundary is detected and then the beam is rapidly decreased in intensity to its former low detection level. The positive resist subjected to the exposure level beam intensity is removed and a layer of metal is evaporated over the entire mask substrate. A lift-off operation leaves only the metal boundaries and the metal fill-in areas inside of the boundaries.