Two lithographic processes for phase-shift mask manufacturing have been investigated in which the pattern of a Cr layer and the pattern of a phase-shifter layer of a spin-on- glass (SOG) are delineated by a laser writer or an E-beam writer. Masks both of a shifter-on-chrome stmcture and of a chrome-on-shifter structur were fabricated. Five different processes were chosen by combination of the writers and the structures. The accuracy of alignment between the Cr layer and the SOG layer was measured for the mask fabricated by each of them. An alignment accuracy of less than 70nm was obtained when an Etec WW6000 laser writer was used with proper offset-correction. The side wall angle of the SOG pattern was 85±5° in laser lithography and 80° in EB lithography. For EB lithography an additional conductive layer either under the shifter layer or on the resist layer is indispensable to avoid the charging-up effect. Among the three transparent conductive materials evaluated, Indium Tin Oxide, Sn02, and DNP’s proprietary, only Sn02 showed acceptable practical properties, necessary also as an etch- stop, including sufficient durabilities against both sulfuric acid and dry-etch plasma. The optical transmittance of its 10 nm thick film on a quartz substrate at i-line wavelength is acceptable (88 %) although that at KrF excimer-laser wavelength is poor (64 %). The two commercial conductive polymers, TQV and ESPACER 100, were found to work well. Advantages and disadvantages of the two processes are discussed

Date Published: 1 June 1992
PDF: 14 pages
Proc. SPIE 1674, Optical/Laser Microlithography V, (1 June 1992); doi: 10.1117/12.130322

Published in SPIE Proceedings Vol. 1674:
Optical/Laser Microlithography V
John D. Cuthbert, Editor(s)