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Proceedings Paper

Effect of electrostatic chucking on EUVL mask flatness
Author(s): Andrew R. Mikkelson; Roxann L. Engelstad; Edward G. Lovell; Lutz Aschke; Frauke Rueggeberg; Frank Sobel
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Paper Abstract

The International Technology Roadmap for Semiconductors for Extreme Ultraviolet Lithography (EUVL) places strict requirements on the quality and flatness of the substrate and patterned mask. The SEMI EUVL Mask Substrate Standard (SEMI P37) specifies that the substrate frontside and backside nonflatness be no more than 50 nm peak-to-valley (p-v). Recent technological advances in polishing and finishing techniques have placed the 50 nm p-v specification within reach. A key ingredient in the development of EUVL is understanding and characterizing the clamping ability of the electrostatic chuck and the resulting effect on the flatness of the chucked mask. By implementing the shape of a representative EUVL mask surface into a numerical model, the effect of electrostatic chucking on the shape of the mask was determined. Legendre polynomials have been identified as an effective and efficient means of representing EUVL mask surface shapes. Finite element (FE) models have been developed to utilize the Legendre coefficients as input data to define the surfaces of an EUVL mask. The FE models were then used to determine the clamping response of the mask. In particular, the maximum mask-to-chuck gap within the Flatness Quality Area and over the entire mask has been tracked as a function of clamping pressure for representative EUVL surfaces. One of the important parameters in this study was the chuck's mechanical stiffness (comprised of the thickness and modulus). The flatness of the EUVL mask also depends on the intrinsic stress and thickness of the multilayer and backside layers. The results in this paper show that the recent advances in EUVL substrate polishing have resulted in masks that can be chucked relatively flat.

Paper Details

Date Published: 2 June 2004
PDF: 9 pages
Proc. SPIE 5504, 20th European Conference on Mask Technology for Integrated Circuits and Microcomponents, (2 June 2004); doi: 10.1117/12.568014
Show Author Affiliations
Andrew R. Mikkelson, Univ. of Wisconsin/Madison (United States)
Roxann L. Engelstad, Univ. of Wisconsin/Madison (United States)
Edward G. Lovell, Univ. of Wisconsin/Madison (United States)
Lutz Aschke, Schott Lithotec AG (Germany)
Frauke Rueggeberg, Schott Lithotec AG (Germany)
Frank Sobel, Schott Lithotec AG (Germany)

Published in SPIE Proceedings Vol. 5504:
20th European Conference on Mask Technology for Integrated Circuits and Microcomponents
Uwe F. W. Behringer, Editor(s)

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