Patent ID: 6919150

Claim:
A mask assembly for use in electron beam lithography, wherein said mask assembly is formed by a method comprising the steps of: forming a support structure that comprises a substrate that includes an initial plurality of windows; filling the initial plurality of windows with a temporary fill material; forming an additional plurality of windows in portions of said substrate which do not contain the temporary fill material; filling the additional plurality of windows in the substrate with a temporary fill material; forming over the filled-windowed substrate a mask structure which includes a supporting membrane which permits transmission of electrons therethrough and a patterned mask layer overlying the supporting membrane; and essentially completely removing the temporary fill material, whereby a mask assembly is produced which comprises a windowed substrate containing a plurality of open windows, with a supporting membrane which transmits electrons directly overlying, parallel to, and supported by a major surface of said windowed substrate, and a patterned mask layer directly overlying the support membrane, wherein said mask assembly width and length dimensions are each several inches on a side.