Patterning of membrane masks for projection e-beam lithography

A process for high-resolution patterning of the membrane-type masks used in the SCALPEL(1) (SCattering with Angular Limitation in Projection Electron-beam Lithography) lithography system is described. SCALPEL is a 4x projection electron beam lithography tool with the potential to extend commercial lithographic capability well into the deep sub-micron range: the recently-completed SCALPEL proof-of-concept (SPOC) system has printed 0.08 mu m lines in thick resist on Si. The details of the patterning process we currently employ and metrology results from the first series of masks are presented here. The SPOC mask blank(2) consists of a segmented W-coated SiN (Si-rich) membrane, fabricated on a 4'' Si wafer. The blank is patterned with 45 different test chips using a vector-scanned e-beam lithography tool. Metrology is performed on completed masks, and results from measurements of line-edge roughness, CD linearity, and pattern uniformity are presented. We examine the need for proximity effect correction of the pattern data, and compare the effect of correction on pattern data file size for a variety of mask technologies.