Signal-to-noise ratio evaluation for the nanometer-scale patterned defect inspection using dark-field microscopy with tailored polarization illumination

Akinori Ohkubo; Janghwi Lee; Hyungu Kim; Jiyoung Chu; Sungho Jang; Sangwoo Bae; Wondon Joo

doi:10.1117/12.2567116

20 August 2020 Signal-to-noise ratio evaluation for the nanometer-scale patterned defect inspection using dark-field microscopy with tailored polarization illumination

Akinori Ohkubo, Janghwi Lee, Hyungu Kim, Jiyoung Chu, Sungho Jang, Sangwoo Bae, Wondon Joo

Author Affiliations +

Proceedings Volume 11485, Reflection, Scattering, and Diffraction from Surfaces VII; 114850N (2020) https://doi.org/10.1117/12.2567116
Event: SPIE Optical Engineering + Applications, 2020, Online Only

Conference Poster

Abstract

Advances in the semiconductor industry have led the wafer inspection technology to the limit of nanometer-scale defect detection, which is far beyond the diffraction limit. In this regime, the signal-to-noise ratio (SNR) is the figure-of-merit to determine whether the optical system can detect a single nanometer-scale defect. In this paper, we investigated the SNR properties of various line defects using the dark-field inspection with tailored polarized illumination by simulation and experiment. Conventional crossed Nicols configuration with linear polarized illumination and crossed analyzer can minimize background scattering noise and maximize line defect signal only for a specific kind of line defect such as gap or bridge due to strong polarization dependence on a line and space (L/S) pattern. The nulling elliptically polarized illumination is optimized to suppress background scattering noise moderately and maintain defect signal intensity at the same time. We confirmed SNR improvement for both 10 nm open and bridge defects on 40 nm line and space silicon pattern with 40 nm depth. There was a good agreement between our simulation results and experimental results. We experimentally confirmed SNR ~ 4 for both line gap and bridge defect detection on 40 nm L/S patterned wafer with the fixed nulling illumination.

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Akinori Ohkubo, Janghwi Lee, Hyungu Kim, Jiyoung Chu, Sungho Jang, Sangwoo Bae, and Wondon Joo "Signal-to-noise ratio evaluation for the nanometer-scale patterned defect inspection using dark-field microscopy with tailored polarization illumination", Proc. SPIE 11485, Reflection, Scattering, and Diffraction from Surfaces VII, 114850N (20 August 2020); https://doi.org/10.1117/12.2567116

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