Fabrication by tri-level electron beam lithography of X-ray masks with 50nm linewidths, and replication by X-ray nanolithography

A process has been developed to produce x-ray nanolithography masks containing fine linewidth patterns generated by scanning-electron-beam lithography. This technology allows researchers to combine the high resolution, arbitrary-pattern-generation capability of electron-beam lithography with the parallel replication, high contrast, and large process-latitude of x-ray nanolithography. A tri-level structure was used which consisted of PMMA as the electron-sensitive material, titanium as the middle, masking layer, and polymide as the buffer layer on top of a gold plating base. After electron-beam exposure and development, the pattern is transfered to the Ti layer by CCl2F2 RIE, and then a polyimide mold is produced by O2 RIE. Gold is then electroplated into this mold to form the x-ray absorber. X-ray masks with 100nm-period gratings and electronic device patterns of ≈ 100nm linewidths were fabricated by this process and replicated. © 1987.