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Proceedings Paper

Mask CD relationship to temperature at the time backscatter is received
Author(s): Harold Zable; Tom Kronmiller; Ryan Pearman; Bill Guthrie; Nagesh Shirali; Yukihiro Masuda; Takashi Kamikubo; Noriaki Nakayamada; Aki Fujimura
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Paper Abstract

Mask writers need to be able to write sub-50nm features accurately. Nano-imprint lithography (NIL) masters need to create sub-20nm line and space (L:S) patterns reliably. Increasingly slower resists are deployed, but mask write times need to remain reasonable. The leading edge EBM-9500 offers 1200A/cm2 current density to shoot variable shaped beam (VSB) to write the masks.

Last year, thermal effect correction (TEC) was introduced by NuFlare in the EBM-95001. It is a GPU-accelerated inline correction for the effect that the temperature of the resist has on CD. For example, a 100nm CD may print at 102nm where that area was at a comparably high temperature at the time of the shot. Since thermal effect is a temporal effect, the simulated temperature of the surface of the mask is dynamically updated for the effect of each shot in order to accurately predict the cumulative effect that is the temperature at the location of the shot at the time of the shot and therefore its impact on CD. The shot dose is changed to reverse the effects of the temperature change.

This paper for the first time reveals an enhancement to this thermal model and a simulator for it. It turns out that the temperature at the time each location receives backscatter from other shots also make a difference to the CD. The effect is secondary, but still measurable for some resists and substrates. Results of a test-chip study will be presented.

The computation required for the backscatter effect is substantial. It has been demonstrated that this calculation can be performed fast enough to be inline with the EBM-9500 with a reasonable-sized computing platform. Run-time results and the computing architecture will be presented.

Paper Details

Date Published: 13 July 2017
PDF: 8 pages
Proc. SPIE 10454, Photomask Japan 2017: XXIV Symposium on Photomask and Next-Generation Lithography Mask Technology, 104540C (13 July 2017);
Show Author Affiliations
Harold Zable, D2S, Inc. (United States)
Tom Kronmiller, D2S, Inc. (United States)
Ryan Pearman, D2S, Inc. (United States)
Bill Guthrie, D2S, Inc. (United States)
Nagesh Shirali, D2S, Inc. (United States)
Yukihiro Masuda, D2S, Inc. (United States)
Takashi Kamikubo, NuFlare Technology, Inc. (Japan)
Noriaki Nakayamada, NuFlare Technology, Inc. (Japan)
Aki Fujimura, D2S, Inc. (United States)

Published in SPIE Proceedings Vol. 10454:
Photomask Japan 2017: XXIV Symposium on Photomask and Next-Generation Lithography Mask Technology
Kiwamu Takehisa, Editor(s)

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