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29 July 2004 Active membrane masks for improved overlay performance in proximity lithography
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Membrane masks are thin (2 micron x 35 mm x 35 mm) structures that carry the master exposure patterns in proximity (X-ray) lithography. With the continuous drive to the printing of ever-finer features in microelectronics, the reduction of mask-wafer overlay positioning errors by passive rigid body positioning and passive stress control in the mask becomes impractical due to nano and sub-micron scale elastic deformations in the membrane mask. This paper describes the design, mechanics and performance of a system for actively stretching a membrane mask in-plane to control overlay distortion. The method uses thermoelectric heating/cooling elements placed on the mask perimeter. The thermoelectric elements cause controlled thermoelastic deformations in the supporting wafer, which in turn corrects distortions in the membrane mask. Silicon carbide masks are the focus of this study, but the method is believed to be applicable to other mask materials, such as diamond. Experimental and numerical results will be presented, as well as a discussion of the design issues and related design decisions.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Dryver R. Huston, James Plumpton, Brian Esser, and Gerald A. Sullivan "Active membrane masks for improved overlay performance in proximity lithography", Proc. SPIE 5388, Smart Structures and Materials 2004: Industrial and Commercial Applications of Smart Structures Technologies, (29 July 2004);


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