Best depth of focus on 22-nm logic wafers with less shot count

Aki Fujimura; David Kim; Tadashi Komagata; Yasutoshi Nakagawa; Vikram Tolani; Tom Cecil

doi:10.1117/12.866413

26 May 2010 Best depth of focus on 22-nm logic wafers with less shot count

Aki Fujimura, David Kim, Tadashi Komagata, Yasutoshi Nakagawa, Vikram Tolani, Tom Cecil

Proceedings Volume 7748, Photomask and Next-Generation Lithography Mask Technology XVII; 77480V (2010) https://doi.org/10.1117/12.866413
Event: Photomask and NGL Mask Technology XVII, 2010, Yokohama, Japan

Abstract

The contact layer for the 22 nm logic node faces many technological hurdles. Even using techniques such as multiple-exposure patterning and 193 nm immersion, it will be difficult to achieve the depth of focus and CD uniformity required for 22 nm production. Such difficulties can be mitigated by recent advances in Inverse Lithography Technology (ILT). For example, circular main features combined with complex curvilinear assist features can provide superior CD uniformity with the required depth of focus, particularly for isolated contacts. However, such a solution can lead to long mask write times, because the curvilinear shapes necessitate a higher shot count induced by inefficient data fracturing, even without considering the circular main features. The current approach is to Manhattanize the curvilinear features resulting in a nearly equivalent image quality on the wafer; but a further reduction in mask write times could help lower costs. This paper describes a novel mask-writing method that uses a production e-beam mask writer to write main features as circles, with curvilinear assist features, while reducing shot count compared to traditional Manhattanized masks. As a result the new method makes manufacturing of ideal ILT-type masks feasible from a technical as well as from an economic standpoint. Resist-exposed SEM images are presented that validate the new method.

Citation Download Citation

Aki Fujimura, David Kim, Tadashi Komagata, Yasutoshi Nakagawa, Vikram Tolani, and Tom Cecil "Best depth of focus on 22-nm logic wafers with less shot count", Proc. SPIE 7748, Photomask and Next-Generation Lithography Mask Technology XVII, 77480V (26 May 2010); https://doi.org/10.1117/12.866413

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