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Proceedings Paper

Plasmonic lithography modeling and measurement of near-field distribution of plasmonic nano-aperture
Author(s): Yongwoo Kim; Seok Kim; Howon Jung; Jinhee Jang; Jae Yong Lee; Jae Won Hahn
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Paper Abstract

In plasmonic nano lithography, a photoresist responds to the localized electric field which decays evanescently in the direction of depth. A simple analytic model is suggested to predict profiles of exposed and finally developed pattern with a finite contrast of photoresist. In this model, the developing process is revisited by accounting the variation of dissolution rate with respect to expose dose distribution. We introduce the concept of nominal developing thickness (NDT) to determine the optimized developing process fitting to the isointensity profile. Based on this model, we obtained three dimensional distribution of near-field of bowtie shaped plasmonic nano aperture in a metal film from the near-field lithography pattern profile. For the near-field exposure, we fabricated a nano aperture in a aluminum metal film which is coated on the contact probe tip. By illuminating 405 nm diode laser source, the positive type photoresist is exposed by the localized electric field produced by nano aperture. The exposed photoresist is developed by the TMAH based solution with a optimum NDT, which leads the developing march encounters the isoexposure contour at threshold dose. From the measurement of developed pattern profile with a atomic force microscope (AFM), the three-dimensional isoexposure (or iso-intensity) surface at the very near region from the exit plane of an aperture (depth: 5 ~ 50 nm) is profiled. Using the threshold dose of photoresist and exposure time, the absolute intensity level is also measured. The experimental results are quantitatively compared with the calculation of FDTD (finite- difference time-domain) method. Concerning with the error in exposure time and threshold dose value, the error in measurement of profile and intensity are less than 6% and 1%, respectively. We expect the lithography model described in this presentation allows more elaborated expectation of developed pattern profile. Furthermore, a methodology of mapping is useful for the quantitative analysis of near-field distribution of nano-scale optical devices.

Paper Details

Date Published: 21 March 2012
PDF: 8 pages
Proc. SPIE 8323, Alternative Lithographic Technologies IV, 832320 (21 March 2012); doi: 10.1117/12.916237
Show Author Affiliations
Yongwoo Kim, Yonsei Univ. (Korea, Republic of)
Seok Kim, Yonsei Univ. (Korea, Republic of)
Howon Jung, Yonsei Univ. (Korea, Republic of)
Jinhee Jang, Yonsei Univ. (Korea, Republic of)
Jae Yong Lee, Korea Research Institute of Standards and Science (Korea, Republic of)
Jae Won Hahn, Yonsei Univ. (Korea, Republic of)

Published in SPIE Proceedings Vol. 8323:
Alternative Lithographic Technologies IV
William M. Tong, Editor(s)

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