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Proceedings Paper

Video-based alignment system for x-ray lithography
Author(s): R. Emmett Hughlett; Keith A. Cooper
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Paper Abstract

The fundamental aspects and implementation of the SUSS ALX alignment system for x-ray lithography are described. This paper details the algorithm, the logic behind the alignment target design, and the real-world overlay results achieved. The system reliably achieves an overlay accuracy of 150 nanometers at 3(sigma) being the norm. Focus repeatability is +/- 0.2 microns, including zero level. Alignment calculations are performed in less than 200 msecs. Focus finding is complete in 400 msec. The ALX is a three-camera video system imaging specified mask and wafer alignment patterns to perform coarse alignment of mask and wafer to the imaging field of view, fine alignment of mask to wafer, and automatic focus. The illumination is brightfield, white light. As an auxiliary function, the ALX is used to set planarity and gap of the mask and wafer, by means of fast autofocus. This allows for completely passive (non-contact) gap setting. Both alignment and autofocus on a high SNR image profiling technique for image preprocessing and data compression, here termed 'summed projection.' This vital operation is performed in hardware in true real-time (frame rate). An optical edge detection signal processing algorithm is applied to extract position information from the compressed video input signal.

Paper Details

Date Published: 1 August 1991
PDF: 11 pages
Proc. SPIE 1465, Electron-Beam, X-Ray, and Ion-Beam Submicrometer Lithographies for Manufacturing, (1 August 1991); doi: 10.1117/12.47347
Show Author Affiliations
R. Emmett Hughlett, Karl Suss America, Inc. (United States)
Keith A. Cooper, Karl Suss America, Inc. (United States)


Published in SPIE Proceedings Vol. 1465:
Electron-Beam, X-Ray, and Ion-Beam Submicrometer Lithographies for Manufacturing
Martin C. Peckerar, Editor(s)

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