Recently, attenuated phase-shifting masks (att-PSMs) with advanced illumination technology of a modified beam illumination (MBI) become a pioneer to expand applications of i-line and KrF lithography. This technology can enhance a depth of focus even for a dense pattern layout by eliminating an undesirable secondary peak intensity which is found in att-PSMs with a normal illumination. In order to extract appropriate performance of att-PSMs with the MBI, a new systematic evaluation method using exposure-defocus and mask fabrication latitude (EDM) methodology in which all sorts of process parameters can be considered is proposed for setting att-PSM specifications. Mask transmittance and biasing are the parameters that essentially contribute to the optimum att-PSM characteristics. In this paper, first the evaluation flow using EDM methodology is explained in detail. Next, feasible ranges of mask transmittance and bias are discussed. Finally, it is shown that the mask line width uniformity significantly affects lithography performance with the att-PSMs and mask specifications of transmittance and bias.

Date Published: 8 December 1995
PDF: 12 pages
Proc. SPIE 2621, 15th Annual BACUS Symposium on Photomask Technology and Management, (8 December 1995); doi: 10.1117/12.228198

Published in SPIE Proceedings Vol. 2621:
15th Annual BACUS Symposium on Photomask Technology and Management
Gilbert V. Shelden; James N. Wiley, Editor(s)