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Fabrication and evaluation of a grayscale mask for x-ray lithography using MEMS technology

[+] Author Affiliations
Harutaka Mekaru, Takayuki Takano

National Institute of Advanced Industrial Science and Technology (AIST), Advanced Manufacturing Research Institute, 1-2-1, Namiki, Tsukuba, Ibaraki 305-8564, Japan

Koichi Awazu

National Institute of Advanced Industrial Science and Technology (AIST), Center for Applied Near Field Optics Research, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8562, Japan

Masaharu Takahashi, Ryutaro Maeda

National Institute of Advanced Industrial Science and Technology (AIST), Advanced Manufacturing Research Institute, 1-2-1, Namiki, Tsukuba, Ibaraki 305-8564, Japan

J. Micro/Nanolith. MEMS MOEMS. 7(1), 013009 (March 14, 2008). doi:10.1117/1.2894817
History: Received June 15, 2007; Revised November 21, 2007; Accepted November 27, 2007; Published March 14, 2008
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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 3-D 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 150mAh, and the subsequent resist development was done by a GG developer at room temperature for 16h. 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.

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© 2008 Society of Photo-Optical Instrumentation Engineers

Citation

Harutaka Mekaru ; Takayuki Takano ; Koichi Awazu ; Masaharu Takahashi and Ryutaro Maeda
"Fabrication and evaluation of a grayscale mask for x-ray lithography using MEMS technology", J. Micro/Nanolith. MEMS MOEMS. 7(1), 013009 (March 14, 2008). ; http://dx.doi.org/10.1117/1.2894817


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