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Non-integral depth measurement of high-aspect-ratio multi-layer microstructures using numerical-aperture shaped beams.

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Bibliographic Details
Title: Non-integral depth measurement of high-aspect-ratio multi-layer microstructures using numerical-aperture shaped beams.
Authors: Chein, Wei-Hsin1 (AUTHOR), Yang, Fu-Sheng1 (AUTHOR), Thakur, Komal1 (AUTHOR), Wu, Guo-Wei1 (AUTHOR), Chen, Liang-Chia1 (AUTHOR) lchen@ntu.edu.tw
Source: Optics & Lasers in Engineering. Jul2023, Vol. 166, pN.PAG-N.PAG. 1p.
Subjects: Bathymetry, Reflectometry, Numerical apertures, Microstructure, Signal-to-noise ratio
Abstract: • A new optical metrology technique for accurate depth measurement of individual high-aspect-ratio (HAR) multi-layer microstructures with high spatial resolution and signal-to-noise ratio (SNR) • The development is vital to semiconductor manufacturing and inline automated optical inspection (AOI). • A 28-fold improvement in SNR for measuring large-depth structures was achieved. This work presents a new optical metrology technique for accurate depth measurement of individual high-aspect-ratio (HAR) multi-layer microstructures with high spatial resolution and signal-to-noise ratio (SNR). To resolve the limitations of existing optical metrology techniques, light shaping with high light efficiency is optimized using numerical-aperture controlled laser beams. Experimental tests evidenced a 28-fold improvement in SNR for measuring large-depth structures when compared with measurements obtained using traditional broadband incoherent illumination. More importantly, instead of integral measurement characteristics currently limited by conventional spectral reflectometry or scatterometry, non-integral depth measurement of an individual microstructure from densely spaced microstructures such as through-silicon vias (TSV) and redistribution layers (RDL) can be realized using the developed optical measuring system with desired numerical aperture and field of view achieved simultaneously. As demonstrated by the measurement of a single submicron structure with linewidth as small as 0.6 µm and an aspect ratio of 5, the precision of depth measurement can be kept within a few nanometers. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:• A new optical metrology technique for accurate depth measurement of individual high-aspect-ratio (HAR) multi-layer microstructures with high spatial resolution and signal-to-noise ratio (SNR) • The development is vital to semiconductor manufacturing and inline automated optical inspection (AOI). • A 28-fold improvement in SNR for measuring large-depth structures was achieved. This work presents a new optical metrology technique for accurate depth measurement of individual high-aspect-ratio (HAR) multi-layer microstructures with high spatial resolution and signal-to-noise ratio (SNR). To resolve the limitations of existing optical metrology techniques, light shaping with high light efficiency is optimized using numerical-aperture controlled laser beams. Experimental tests evidenced a 28-fold improvement in SNR for measuring large-depth structures when compared with measurements obtained using traditional broadband incoherent illumination. More importantly, instead of integral measurement characteristics currently limited by conventional spectral reflectometry or scatterometry, non-integral depth measurement of an individual microstructure from densely spaced microstructures such as through-silicon vias (TSV) and redistribution layers (RDL) can be realized using the developed optical measuring system with desired numerical aperture and field of view achieved simultaneously. As demonstrated by the measurement of a single submicron structure with linewidth as small as 0.6 µm and an aspect ratio of 5, the precision of depth measurement can be kept within a few nanometers. [ABSTRACT FROM AUTHOR]
ISSN:01438166
DOI:10.1016/j.optlaseng.2023.107563