Instrument Development for Spectroscopic Ellipsometry and Diffractometry in the EUV

Published

April 24, 2024

Author(s)

Stephanie Moffitt, Bryan Barnes, Thomas A. Germer, Steven Grantham, Eric Shirley, Martin Sohn, Daniel Sunday, Charles S. Tarrio

Abstract

Semiconductor devices are noted for ever-decreasing dimensions but now are also becoming more complex. While scanning probe microscopy can still resolve the smallest features, it does not have the throughput for high-volume characterization of full wafers. Instead, optical scatterometry, operating at wavelengths in the visible and deep ultraviolet (DUV), has the throughput needed for process control. State-of-the-art visible and ultraviolet scatterometry should be acceptable through at least 2026, but five years from now, no known optical solutions exist for metrology1. We are currently developing a new scatterometry tool that will utilize the extreme ultraviolet (EUV). Shorter wavelength, higher energy photons will enable both the improved spatial resolution and elemental sensitivity needed to extend optics-based high-volume characterization of patterned wafers for the foreseeable future. The instrument will include two different types of measurements, spectroscopic ellipsometry and diffractometry. The first measurement will require the development of all-reflective optics to enable ellipsometry in the 150 nm to 50 nm wavelength range. All materials are strongly absorbing in this wavelength range, meaning that the technique will be surface sensitive, measuring only the top few nm of samples. The second measurement will concentrate on the 50 nm to 10 nm wavelength range. These shorter wavelengths will allow deeper penetration into samples as well as measurements above and below atomic absorption edges. The latter will enhance our ability to determine the dimensions of a specific material within multi-material samples, which reduces ambiguities in feature dimensions. Initial development will be done at the Synchrotron Ultraviolet Radiation Facility (SURF III), an electron storage ring on the campus of the National Institute of Standards and Technology (NIST). The tool will then be attached to a laser-based high-harmonic-generation (HHG) source that is compact enough to be installed in a NIST laboratory and potentially within a fab facility.

Proceedings Title

International Conference on Frontiers of Characterization and Metrology for Nanoelectronics

Conference Dates

April 15-18, 2024

Conference Location

Monterey, CA, US

Conference Title

Inational Conference on Frontiers of Characterization and Metrology for Nanoelectronics

Pub Type

Conferences

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Keywords

Scatterometry, Ellipsometry, Diffractometry, Extreme ultraviolet, Process control, Optical critical dimension

Citation

Moffitt, S. , Barnes, B. , Germer, T. , Grantham, S. , Shirley, E. , Sohn, M. , Sunday, D. and Tarrio, C. (2024), Instrument Development for Spectroscopic Ellipsometry and Diffractometry in the EUV, International Conference on Frontiers of Characterization and Metrology for Nanoelectronics, Monterey, CA, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=957261 (Accessed December 22, 2024)