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Laser bandwidth and other sources of focus blur in lithography

[+] Author Affiliations
Timothy Brunner

IBM Semiconductor Research and Development Center, Zip 40E, 2070 Route 52, Hopewell Junction, New York 12533

Daniel Corliss

IBM Semiconductor Research and Development Center, Zip 40E, 2070 Route 52, Hopewell Junction, New York 12533

Shahid Butt

IBM Semiconductor Research and Development Center, Zip 40E, 2070 Route 52, Hopewell Junction, New York 12533

Timothy Wiltshire

IBM Semiconductor Research and Development Center, Zip 40E, 2070 Route 52, Hopewell Junction, New York 12533

Christopher P. Ausschnitt

IBM Semiconductor Research and Development Center, Zip 40E, 2070 Route 52, Hopewell Junction, New York 12533

Mark Smith

KLA-Tencor, Finle Division, 8834 N. Capital of Texas HW, Suite 301, Austin, Texas 78759

J. Micro/Nanolith. MEMS MOEMS. 5(4), 043003 (November 20, 2006). doi:10.1117/1.2396926
History: Received February 27, 2006; Revised August 25, 2006; Accepted August 29, 2006; Published November 20, 2006
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It is well known that the refractive optics used in today’s exposure tools are highly chromatic, meaning that small wavelength shifts will cause large focus shifts. Even a line-narrowed excimer laser has a large enough range of wavelengths that we can no longer think of an infinitely thin image plane. The concept of “focus blur” can be generalized to encompass the effect of laser bandwidth chromatic aberrations, vertical stage vibrations, and stage tilts, which cause the focus to change during the scan. We introduce a new parameter called mean absolute defocus that can characterize the focus blur and is shown to correlate with the lithographic effects. Focus blur can be incorporated into simulation models, in a manner similar to the way that stage vibration is modeled. New simulation results illustrate the impact of focus blur on modern lithographic processes. Process stability and machine-to-machine matching issues are discussed.

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© 2006 Society of Photo-Optical Instrumentation Engineers

Citation

Timothy Brunner ; Daniel Corliss ; Shahid Butt ; Timothy Wiltshire ; Christopher P. Ausschnitt, et al.
"Laser bandwidth and other sources of focus blur in lithography", J. Micro/Nanolith. MEMS MOEMS. 5(4), 043003 (November 20, 2006). ; http://dx.doi.org/10.1117/1.2396926


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