Stencil masks for electron projection lithography (EPL) require peculiar patterns as perforations in a thin membrane. The stencil pattern accuracy of a conventional mask with 1-mm subfields and a new geometry mask with 4-mm subfields was evaluated and compared. No significant influence of the mask geometry on most of critical dimension (CD) specifications was observed. The stencil patterns in both geometry masks had vertical sidewalls ~ 90° with angle range less than 0.3° and CD uniformity of ~12 nm (3σ) across the mask. CD linearity is also similar for both geometry masks. On the other hand, enlarging the membrane windows considerably increased CD deterioration and image placement (IP) distortion within individual membranes. A practical 4 mm-window mask requires solution to this issue. The stencil pattern accuracy is, however, acceptable level for not only the 1 mm-window mask but also the 4 mm-window mask at current EPL development status. According to the evaluation of the stencil pattern accuracy, pattern specification of the EPL mask for 45-nm node would be achieved with further process optimization despite of its peculiarity in pattern structure.

Date Published: 28 June 2005
PDF: 8 pages
Proc. SPIE 5853, Photomask and Next-Generation Lithography Mask Technology XII, (28 June 2005); doi: 10.1117/12.617279

Published in SPIE Proceedings Vol. 5853:
Photomask and Next-Generation Lithography Mask Technology XII
Masanori Komuro, Editor(s)