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Unique Spectral Interferometry solutions for complex High AspectRatio 3D NAND structures

April 2024 @ SPIE
Authored by: Jaesuk Yoona, Jongmin Parka, Minjung Shina, and Dongchul Ihma, Oshrat Bismuthb, Smadar Ferberb, Jacob Ofekb, Igor Turovetsb, Isaac Kim, aFlash Process Development Team MI, Samsung R&D Center, Hwaseong, Korea, NOVA Ltd, Rehovot, Israel, Nova Measuring Instruments Korea Ltd., Gyeonggi-do, Korea.

We have demonstrated the unique capabilities of spectral interferometry (SI) with vertical traveling scatterometry
algorithms (VTS) to solve 3D NAND challenges by measuring complex layer thicknesses of the multideck 3D
structures directly from the VTS signals, without modeling, with Cell Over Periphery (COP) underlayer filtering.
Multiple examples are presented in the paper, including the measurement of the thin and thick layers of memory
structures above the complex logic arrays and the remaining thickness of the fully processed Si wafer from the back
side after thinning.
In addition, VTS and AI enable direct profiling of the deep through-type cell metal contacts in the areas with
nonperiodic staircases and significant lateral variations under the measurement spot.
Keywords: OCD, Spectral Interferometry, Spectral Reflectometry, 3D NAND, HAR, contact hole profiles, staircases,
and non-periodical targets.