Model-less analysis method for characterizing overlay in EUV lithography

Roel Gronheid; Zhen Zhang; Woong Jae Chung; Fatima Anis; Franz Zach; Holger Bald; Boris Habets

doi:10.1117/12.2617746

26 May 2022 Model-less analysis method for characterizing overlay in EUV lithography

Roel Gronheid, Zhen Zhang, Woong Jae Chung, Fatima Anis, Franz Zach, Holger Bald, Boris Habets

Proceedings Volume 12053, Metrology, Inspection, and Process Control XXXVI; 120530Y (2022) https://doi.org/10.1117/12.2617746
Event: SPIE Advanced Lithography + Patterning, 2022, San Jose, California, United States

Abstract

Modern overlay metrology instruments have evolved into systems that provide large amounts of data points (up to 4 overlay targets/sec). Traditionally, this data has been analyzed using models that are based on physically expected parameters. They are typically derived from translation, rotation and magnification (both symmetric and asymmetric) at reticle and wafer level. The resulting coefficients of these models can be directly fed into the scanner to correct overlay errors. As overlay requirements have become more stringent, higher order corrections have been enabled, ultimately leading to corrections-per-exposure (CPE) where no model is used at wafer level. Instead, a different correction at reticle level is allowed for each field. Although this approach has been extremely successful for overlay control purposes, it is increasingly difficult to interpret the resulting models and appreciate the underlying root causes for the overlay corrections as well as for the overlay residuals. This is especially true for new lithographic technologies where all contributors to overlay errors may not be fully characterized yet. In order to gain more insight into the root causes of these overlay errors, we have proposed a model-less overlay analysis technique [1]. In this paper we will apply this method to understand the impact of wafer stack on overlay through wafer heating in EUV lithography. Wafer heating-induced overlay signature is a typical example where the conventional overlay models cannot properly describe the wafer signature and only CPE models can be used to adequately correct. By comparing the signatures of highly reflective (resulting in little wafer heating) with highly absorbing (resulting in more wafer heating) wafer stacks, more insight is gained into the factors that contribute to the overlay corrections.

Conference Presentation

Citation Download Citation

Roel Gronheid, Zhen Zhang, Woong Jae Chung, Fatima Anis, Franz Zach, Holger Bald, and Boris Habets "Model-less analysis method for characterizing overlay in EUV lithography", Proc. SPIE 12053, Metrology, Inspection, and Process Control XXXVI, 120530Y (26 May 2022); https://doi.org/10.1117/12.2617746

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