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Journal of Micro/Nanolithography, MEMS, and MOEMS

Fabrication and evaluation of a grayscale mask for x-ray lithography using MEMS technology
Author(s): Harutaka Mekaru; Takayuki Takano; Koichi Awazu; Masaharu Takahashi; Ryutaro Maeda
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Paper Abstract

We propose a new fabrication method of an x-ray grayscale mask using micro-electro-mechanical-systems (MEMS) technologies, and also report on successful fabrication of three-dimensional (3D) microstructures on a polymethylmethacrylate (PMMA)sheet by using only a single x-ray exposure. We showed that silicon can be diagonally etched by optimizing the etching condition in a reactive-ion-etching (RIE) process. It is well known that the absorbers of an x-ray mask can be made into 3D shapes. Here, we describe how this process can be extended to fabricate an x-ray grayscale mask by using a tapered-trench-etching technique. With such a mask, we carried out experiments on x-ray lithography (XRL) using a beam line BL-4 in the synchrotron radiation facility TERAS of National Institute of Advanced Industrial Science and Technology (AIST). The dose energy used for the exposure was 150 mA·h, and the subsequent resist development was done by a GG developer at room temperature for 16 h. The sidewalls in the upper part of the PMMA resist structure were inclined and rounded. In particular, the shape of the PMMA resist structure of the lines with 20-μm width (also referred as 20-μm lines) could be processed to achieve a halberd-like shape. Thus, the effectiveness of the grayscale mask in adjusting to the varying thicknesses of absorber was confirmed by XRL experiments. Moreover, we showed that the final shape of PMMA resist structures after XRL was predictable by calculations.

Paper Details

PDF: 9 pages
J. Micro/Nanolith. 7(1) 013009 doi: 0.1117/1.2894817
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 7, Issue 1, January 2008
Show Author Affiliations
Harutaka Mekaru, National Institute of Advanced Industrial Science and Technology (Japan)
Takayuki Takano, National Institute of Advanced Industrial Science and Technology (Japan)
Koichi Awazu, National Institute of Advanced Industrial Science and Technology (Japan)
Masaharu Takahashi, National Institute of Advanced Industrial Science and Technology (Japan)
Ryutaro Maeda, National Institute of Advanced Industrial Science and Technology (Japan)


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