Illumination spot profile correction in digital holographic microscopy for overlay metrology

Manashee Adhikary; Tamar van Gardingen-Cromwijk; Jo de Wit; Stefan M. Witte; Johannes F. de Boer; Arie den Boef

doi:10.1117/1.JMM.22.2.024001

5 June 2023 Illumination spot profile correction in digital holographic microscopy for overlay metrology

Manashee Adhikary, Tamar van Gardingen-Cromwijk, Jo de Wit, Stefan M. Witte, Johannes F. de Boer, Arie den Boef

Author Affiliations +

Journal of Micro/Nanopatterning, Materials, and Metrology, Vol. 22, Issue 2, 024001 (June 2023). https://doi.org/10.1117/1.JMM.22.2.024001

Abstract

Background

Precise, accurate, and fast overlay (OV) metrology is an important step in semiconductor device manufacturing. With the increasing demand for better OV over a larger range of different process layers, the optics used in OV metrology tools become more complex, bulky, and expensive. OV, which is to be measured with sub-nanometer precision, is susceptible to many small imperfections in the measurement system.

Aim

We present a dark-field digital holographic microscope (DHM) that measures the complex field of the OV targets using simple optics, followed by computational algorithms to correct for hardware imperfections. With the setup, we aim to correct the effects of the absolute intensity of the illumination beam as well as the spatial profile.

Approach

The spatial profiles of two oblique illumination beams for diffraction based OV metrology are calibrated using large gratings as calibration targets using DHM, and thereafter OV target images are corrected by the calibrated illumination spot profiles.

Results

OVs are calculated for test targets with known OV values, and illumination spot correction removes errors originating from intensity imbalance and intensity variation.

Conclusion

We present an optical OV measurement method that is more robust against non-uniform illumination beams using simple calibration steps.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Citation Download Citation

Manashee Adhikary, Tamar van Gardingen-Cromwijk, Jo de Wit, Stefan M. Witte, Johannes F. de Boer, and Arie den Boef "Illumination spot profile correction in digital holographic microscopy for overlay metrology," Journal of Micro/Nanopatterning, Materials, and Metrology 22(2), 024001 (5 June 2023). https://doi.org/10.1117/1.JMM.22.2.024001

Received: 3 March 2023; Accepted: 15 May 2023; Published: 5 June 2023

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