1 August 2002 New concept of specification for mask flatness
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Proceedings Volume 4754, Photomask and Next-Generation Lithography Mask Technology IX; (2002) https://doi.org/10.1117/12.476957
Event: Photomask and Next Generation Lithography Mask Technology IX, 2002, Yokohama, Japan
The shrinkage of semiconductor devices creates demand for micronization in the photolithographic process. As a result, problems are arising in photolithography in the semiconductor manufacturing process. Focus latitude in photolithography becomes smaller as micronization advances and therefore the flatness of the mask can no longer be ignored. In this work, we clarified what the specification of mask flatness should be from the standpoint of its warpage in vacuum chucking of an exposure tool. A two-dimensional approach was applied for the prediction of mask surface after chucking. The approach is simple analytical calculation distinguishing between x-direction and y-direction. Warpage of mask surface after chucking has two modes depending on the directions. One is leverage caused by interaction of mask surface and chucking stage. Another one is warpage along chucking stage surface. The prediction shows good agreement with the actual surface of chucked mask. From this study, a new concept of the specification for mask blank flatness was proposed, taking warpage in vacuum chuck into consideration in the prediction. The proposed specification certainly can exclude masks that show large deformation after chucking even though with good free-standing flatness.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Masamitsu Itoh, Masamitsu Itoh, Soichi Inoue, Soichi Inoue, Katsuya Okumura, Katsuya Okumura, Tsuneyuki Hagiwara, Tsuneyuki Hagiwara, Jiro Moriya, Jiro Moriya, } "New concept of specification for mask flatness", Proc. SPIE 4754, Photomask and Next-Generation Lithography Mask Technology IX, (1 August 2002); doi: 10.1117/12.476957; https://doi.org/10.1117/12.476957

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