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Proceedings Paper

Systematic error reduction: non-tilted reference beam method for long trace profiler
Author(s): Shinan Qian; Kun Qian; Yiling Hong; Liusi Sheng; Tonglin Ho; Peter Takacs
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Paper Abstract

Systematic error in the Long Trace Profiler (LTP) has become the major error source as measurement accuracy enters the nanoradian and nanometer regime. Great efforts have been made to reduce the systematic error at a number of synchrotron radiation laboratories around the world. Generally, the LTP reference beam has to be tilted away from the optical axis in order to avoid fringe overlap between the sample and reference beams. However, a tilted reference beam will result in considerable systematic error due to optical system imperfections, which is difficult to correct. Six methods of implementing a non-tilted reference beam in the LTP are introduced: 1) application of an external precision angle device to measure and remove slide pitch error without a reference beam, 2) independent slide pitch test by use of not tilted reference beam, 3) non-tilted reference test combined with tilted sample, 4) penta-prism scanning mode without a reference beam correction, 5) non-tilted reference using a second optical head, and 6) alternate switching of data acquisition between the sample and reference beams. With a non-tilted reference method, the measurement accuracy can be improved significantly. Some measurement results are presented. Systematic error in the sample beam arm is not addressed in this paper and should be treated separately.

Paper Details

Date Published: 2 October 2007
PDF: 7 pages
Proc. SPIE 6704, Advances in Metrology for X-Ray and EUV Optics II, 67040I (2 October 2007); doi: 10.1117/12.740440
Show Author Affiliations
Shinan Qian, Brookhaven National Lab. (United States)
Kun Qian, Brookhaven National Lab. (United States)
Yiling Hong, National Synchrotron Radiation Lab. (China)
Liusi Sheng, National Synchrotron Radiation Lab. (China)
Tonglin Ho, National Synchrotron Radiation Lab. (China)
Peter Takacs, Brookhaven National Lab. (United States)

Published in SPIE Proceedings Vol. 6704:
Advances in Metrology for X-Ray and EUV Optics II
Lahsen Assoufid; Peter Z. Takacs; Masaru Ohtsuka, Editor(s)

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