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Proceedings Paper

Modeling of secondary radiation damage in LIGA PMMA resist exposure
Author(s): Aili Ting
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Paper Abstract

Secondary radiation during LIGA PMMA resist exposure adversely affects feature definition, sidewall taper and overall sidewall offset. Additionally, it can degrade the resist adjacent to the substrate, leading to the loss of free-standing features through undercutting during resist development or through mechanical failure of the degraded material. The source of this radiation includes photoelectrons, Auger electrons, fluorescence photons, etc. Sandia’s Integrated Tiger Series (ITS), a coupled electron/photon Monte Carlo transport code, was used to compute dose profiles within 1 to 2 microns of the absorber edge and near the interface of the resist with a metallized substrate. The difficulty of sub-micron resolution requirement was overcome by solving a few local problems having carefully designed micron-scale geometries. The results indicate a 2-μm dose transition region near the absorber edge resulting from PMMA’s photoelectrons. This region leads to sidewall offset and to tapered sidewalls following resist development. The results also show a dose boundary layer of around 1 μm near the substrate interface due to electrons emitted from the substrate metallization layer. The maximum dose at the resist bottom under the absorber can be very high and can lead to feature loss during development. This model was also used to investigate those resist doses resulting from multi-layer substrate.

Paper Details

Date Published: 15 January 2003
PDF: 11 pages
Proc. SPIE 4979, Micromachining and Microfabrication Process Technology VIII, (15 January 2003); doi: 10.1117/12.478237
Show Author Affiliations
Aili Ting, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 4979:
Micromachining and Microfabrication Process Technology VIII
John A. Yasaitis; Mary Ann Perez-Maher; Jean Michel Karam, Editor(s)

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