Light-diffraction-based overlay measurement

Joerg Bischoff; Robert Brunner; Joachim J. Bauer; Ulrich Haak

doi:10.1117/12.436745

22 August 2001 Light-diffraction-based overlay measurement

Joerg Bischoff, Robert Brunner, Joachim J. Bauer, Ulrich Haak

Proceedings Volume 4344, Metrology, Inspection, and Process Control for Microlithography XV; (2001) https://doi.org/10.1117/12.436745
Event: 26th Annual International Symposium on Microlithography, 2001, Santa Clara, CA, United States

Abstract

Optical overlay measurement methods are very effective since they are rapid and non-destructive. Imaging techniques need sophisticated image processing and suffer from the wave- optical resolution drawback. Presently, leading edge devices are offered with 5 though 10 nm measuring accuracy. In this paper a method is proposed that relies on the diffraction of a probing laser beam at a periodic reference pattern. This special pattern is implemented in the circuit layout. After the resist patterning of the second of two consecutive layers, the diffraction at the resulting net grating is measured. If an appropriate grating design is chosen, the misalignment error can be directly extracted from the diffraction efficiency. In order to obtain a strong diffraction signal and thus a sufficient signal-to- noise ratio optimum grating designs have been computed by means of rigorous diffraction modeling. Experimental results supported by rigorous modeling suggest that this technique could have the potential to meet next generation overlay accuracy requirements.

Citation Download Citation

Joerg Bischoff, Robert Brunner, Joachim J. Bauer, and Ulrich Haak "Light-diffraction-based overlay measurement", Proc. SPIE 4344, Metrology, Inspection, and Process Control for Microlithography XV, (22 August 2001); https://doi.org/10.1117/12.436745

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