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Spectral Interferometry for TSV Metrology in Chiplet Technology

April 2024 @ SPIE
Authored by: Stefan Schoeche, Daniel Schmidt, Junwon Han, Shahid Butt, Katherine Sieg, Marjorie Cheng, Aron Cepler, Shaked Dror, Jacob Ofek, Ilya Osherov, and Igor Turovetsc IBM Research, 257 Fuller Road, Albany, NY 12203, USA Nova Measuring Instruments Inc., 3342 Gateway Blvd, Fremont, CA 94538, USA Nova Ltd., 5 David Fikes St., Rehovot, 7632805, Israel

Comprehensive through-silicon-via (TSV) characterization, including grind side measurements, is critical to ensure device reliability in chiplet technology. Here we report on TSV metrology using spectral interferometry (SI), which is used to
acquire absolute phase information of polarized and broad-band light interacting with a sample. This phase information can be translated into the optical path length of the partial beams traveling within the structure. We utilize the spatial
separation of peaks related to light reflected from the top surface and the surface of interest to directly measure the TSV depth after reactive ion etching as well as the reveal height on the grind side, without modeling and even in the presence
of multilayers or surrounding patterning. Polarization-dependent SI measurements enable the quantification of asymmetry at the bottom of the TSVs not visible in top-down CD measurements. SI is robust and fast and unveils novel information in TSV metrology not accessible with established in-line metrology techniques.
Keywords: Through-Silicon-Vias, Spectral Interferometry, Metrology