New concept of specification for mask flatness

Masamitsu Itoh; Soichi Inoue; Katsuya Okumura; Tsuneyuki Hagiwara; Jiro Moriya

doi:10.1117/12.476957

1 August 2002 New concept of specification for mask flatness

Masamitsu Itoh, Soichi Inoue, Katsuya Okumura, Tsuneyuki Hagiwara, Jiro Moriya

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

Abstract

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.

Citation Download Citation

Masamitsu Itoh, Soichi Inoue, Katsuya Okumura, Tsuneyuki Hagiwara, and Jiro Moriya "New concept of specification for mask flatness", Proc. SPIE 4754, Photomask and Next-Generation Lithography Mask Technology IX, (1 August 2002); https://doi.org/10.1117/12.476957

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