Mr. David E. Godfrey Profile

David E. Godfrey

Senior Applications Engineer

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Publications (2)

Proceedings Article | 26 June 2003 Paper

Evaluating scanner lens spherical aberration using scatterometer

Changan Wang, Gary Zhang, Colin Tan, Chris Atkinson, Mark Boehm, Jay Brown, David Godfrey, Michael Littau, Christopher Raymond

Proceedings Volume 5040, (2003) https://doi.org/10.1117/12.485437

KEYWORDS: Monochromatic aberrations, Spherical lenses, Scanners, Critical dimension metrology, Optical lithography, Semiconducting wafers, Phase measurement, Scatter measurement, Scanning electron microscopy, Distortion

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Proceedings Article | 26 June 2003 Paper

Illumination pupil fill measurement and analysis and its application in scanner V-H bias characterization for 130-nm node and beyond

Gary Zhang, Changan Wang, Colin Tan, John Ilzhoefer, Chris Atkinson, Stephen Renwick, Steve Slonaker, David Godfrey, Catherine Fruga

Proceedings Volume 5040, (2003) https://doi.org/10.1117/12.485352

KEYWORDS: Scanners, Fiber optic illuminators, Critical dimension metrology, Semiconducting wafers, Metrology, Monochromatic aberrations, Printing, Data modeling, Reticles, Calibration

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A detailed characterization of across chip line width variation (ACLV) has been carried out on the latest Nikon scanners with a combination of advanced metrology techniques in Texas Instruments, including scatterometer-based image field and CD fingerprinting, lens aberrations measurement using a Litel in-situ interferometer, and illumination source imaging with a pin-hole camera. This paper describes the application of the above techniques in our investigation of the root causes for pattern CD bias between vertical and horizontal features. Illumination source radiance distribution is found sometimes to have a significant impact on V-H bias and the final overall ACLV on production wafers. Examples are given to demonstrate a comprehensive methodology that is used to quantitatively break down the overall CD errors and correlate them back to the basic optical and imaging components. It is shown through pupil-gram analysis that the ellipticity in partial coherence is typically within 1+/-1% for conventional illuminations settings on the advanced Nikon scanners while the uneven radiance distribution across the source plays a major role in V-H pattern CD bias. For scanners with low and uniform lens coma aberrations, the V-H bias after removing the contribution from image field errors is found to follow a linear relationship with the source radiance non-uniformity described also in terms of ellipticity. It is shown that radiance ellipticity is a bigger concern for off-axis illuminators. Tighter design rules patterned with off-axis illumination are more vulnerable to source radiance non-uniformity as well as lens aberrations. Illuminator induced V-H bias across the slit is compared to the signature caused by lens aberrations specifically uneven x,y-coma. Implications to exposure tool specification, control, and matching are further explored through experiments and lithography simulation for the current 130nm production and the future technology nodes in development.

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