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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.

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A Flexible Deep Learning Based Approach for SEM Image Denoising

Aפרןך 2024 @ SPIE
Authored by: Jun Chen, Xinheng Jiang, Keisuke Goto, Takashi Tsutsumi, Yasutaka Toyoda Hitachi High-tech Corp.,

In the field of semiconductor manufacturing, Scanning Electron Microscope (SEM) is employed for critical dimension (CD) measurements, overlay measurements, and defect inspections to ensure the quality and reliability of semiconductor devices. Nevertheless, SEM images inherently carry a significant level of noise, leading to inaccurate metrology and false defect inspections. Therefore, it is crucial to develop denoising techniques. One widely used method is frame averaging, which reduces cumulative noise by averaging multiple scans. While increasing scan times enhances SEM image quality, it comes with drawbacks such as surface charging, pattern shrinkage, and reduced throughput. Deep learning (DL) techniques, including supervised and unsupervised approaches, have shown remarkable progress in the field of SEM image denoising. However, supervised methods are notably affected by phenomena such as pattern shrinkage and surface charging, which occur during the capture of reference images. On the other hand, unsupervised methods are typically more effective with lower noise levels. In this paper, we introduced a flexible DL method for denoising SEM images that operates without the requirement for paired data. To demonstrate its effectiveness, we analyzed and evaluated its performance in two metrology tasks. Experimental results validated the efficacy of our method in reducing noise, demonstrating its applicability to both ADI and AEI.

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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

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Spectral Interferometry for Fully Integrated Device Metrology

September 2023 @ SPIE
Authored by: Authored by: Daniel SchmidtiD ,a,* Manasa Medikonda,a Michael Rizzolo,a Claire Silvestre,a Julien Frougier,a Andrew Greene,a Mary Breton,a Aron Cepler,b Jacob Ofek,c Itzik Kaplan,c Roy Koret,c and Igor Turovetsc

A spectral interferometry technique called vertical travelling scatterometry (VTS) is introduced, demonstrated, and discussed. VTS utilizes unique information from spectral interferometry and enables solutions for applications that are infeasible with traditional scatterometry approaches. The technique allows for data filtering related to spectral information from buried layers, which can then be ignored in the optical model. Therefore, using VTS, selective analyses of the topmost part of an arbitrarily complex stack are possible within a single metrology step. This methodology helps to overcome geometrical complexities and allows for focusing on parameters of interest through dramatically simplified optical modeling. Such model simplifications are specifically desired for back-end-of-line applications. Three examples are monitored discussed: (i) the critical dimensions (CDs) of a first metal level on top of nanosheet gate-all-around transistor structures, (ii) the thickness of an interlayer dielectric above embedded memory in the active area, and (iii) the CDs of trenches on top of tall stacks in the micrometer range comprising many layered dielectrics. It was found that, in all three cases, data filtering through VTS allowed for a simple optical model capable of delivering parameters of interest. The validity and accuracy of the VTS solution results were confirmed by extensive reference metrology obtained by traditional scatterometry, scanning electron microscopy, and transmission electron microscopy. Furthermore, it was shown that machine learning models trained with VTS filtered data can converge to a robust solution with a smaller dataset compared with models training with traditional scatterometry data. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 International License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. [DOI: 10.1117/1.JMM.22.3.031203] –

spectral interferometry; vertical travelling scatterometry; scatterometry; optical critical dimension; spectral reflectometry.