Patterning optical and X-ray masks for integrated circuit fabrication

Claim 1

A method of lithographic patterning of integrated circuit chip process mask plates and mask membranes comprising the steps of: applying a thin layer of metal over a mask substrate; covering the layer of metal with a layer of negative electron resist; delineating the peripheral boundaries of the desired mask geometry using a direct-write spot electron beam; said electron beam serving to expose the resist in the peripheral boundaries delineated by said electron beam; developing and etching the mask substrate to remove all but the peripheral metallic boundaries from the mask substrate; coating the mask substrate and the metal boundaries thereon with a positive electron resist; raster scanning the mask substrate with a low exposure level intensity beam until a peripheral boundary is detected, the detection then serving to increase the beam intensity ten or more times so as to expose the high intensity raster scanned positive resist; said scanning and high intensity exposure continuing until the mating peripheral boundary is detected, the latter detection then serving to rapidly decrease the beam intensity to its former low exposure-level intensity; developing the substrate to remove the positive electron resist subjected to the increased exposure-level beam intensity; depositing a layer of metal over the entire mask substrate; and lifting-off the remaining positive electron resist and the metal covering the same so that only the peripheral metal boundaries and the metal layer between the boundaries remain on the mask substrate, said detection having an intrinsic delay so that the increase and decrease in beam intensity occurs a short predetermined time after a boundary has been encountered.

Claim 2

A method of lithographic patterning of integrated circuit chip process mask plates and mask membranes comprising the steps of: applying a thin layer of metal over a mask substrate; covering the layer of metal with a layer of negative electron resist; delineating the peripheral boundaries of the desired mask geometry using a direct-write spot electron beam; said electron beam serving to expose the resist in the peripheral boundaries delineated by said electron beam; developing and etching the mask substrate to remove all but the peripheral metallic boundaries from the mask substrate; coating the mask substrate and the metal boundaries thereon with a positive electron resist; raster scanning the mask substrate with a low exposure level intensity beam until a peripheral boundary is detected, the detection then serving to increase the beam intensity ten or more times so as to expose the high intensity raster scanned positive resist; said scanning and high intensity exposure continuing until the mating peripheral boundary is detected, the latter detection then serving to rapidly decrease the beam intensity to its former low exposure-level intensity; developing the substrate to remove the positive electron resist subjected to the increased exposure-level beam intensity; depositing a layer of metal over the entire mask substrate; and lifting-off the remaining positive electron resist and the metal covering the same so that only the peripheral metal boundaries and the metal layer between the boundaries remain on the mask substrate, said detection having an intrinsic delay so that the increase and decrease in beam intensity occurs a short predetermined time after a boundary has been encountered.