Precise measurement of thin-film thickness in 3D-NAND device with CD-SEM

Machine learning (ML) is proposed as a method to predict threshold voltage (Vt) distribution by read disturbance in the unselected strings of three-dimensional NAND Flash Memory (3D NAND). We extracted the Vt distribution after each read cycles in 3D NAND considering the process variation using Technology Computer-Aided Design (TCAD) simulation. The neural network (NN) was developed and was trained to have a small error rate. Through a test process, predicted Vt by ML was in good agreement with TCAD simulation data. In rapidly developed technology, the prediction by ML-based on the NN can be a powerful tool in terms of consuming less time. Also, ML can be applied to predict other conditions and reliability issues.

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“…Dev) values of the device parameters. 28,29) The values shown in Table I are applied to each device parameters of 1200 unselected strings.…”

Section: Simulation Structure and ML Methodsmentioning

confidence: 99%

Machine learning method to predict threshold voltage distribution by read disturbance in 3D NAND Flash Memories

Park

Lee

Shin

2020

Jpn. J. Appl. Phys.

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“…The large thermo-mechanical stress can be mitigated by proper CMP (Chemical Mechanical Planarization) process. In a study of a CMP process resulting in VIA shape that is slightly protruding on the top wafer and slightly dishing in the bottom wafer, thus allowing for necessary wafer to wafer overlay bonding tolerance, better overall resistivity and yield were achieved [4] .…”

Section: X-tackingmentioning

confidence: 99%

Metrology Challenges in 3D NAND Flash Technical Development and Manufacturing

Zhang¹,

Xu²,

Wang³

et al. 2019

Journal of Microelectronic Manufacturing

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3D NAND technical development and manufacturing face many challenges to scale down their devices, and metrology stands out as much more difficult at each turn. Unlike planar NAND, 3D NAND has a three-dimensional vertical structure with high-aspect ratio. Obviously top-down images is not enough for process control, instead inner structure control becomes much more important than before, e.g. channel hole profiles. Besides, multi-layers, special materials and YMTC unique X-Tacking technology also bring other metrology challenges: high wafer bow, stress induced overlay, opaque film measurement. Technical development can adopt some destructive methodology (TEM, etch-back SEM), while manufacturing can only use nondestructive method. These drive some new metrology development, including X-Ray, mass measure and Mid-IR spectroscopy. As 3D NAND suppliers move to >150 layers devices, the existing metrology tools will be pushed to the limits. Still, the metrology must innovate.

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“…We propose a CD-SEM as a suitable tool for the thickness measurement of a vertical film. 27,28) It seems possible for the top-down observation tool in principle. However, sufficiently high precision (∼0.1 nm) would be challenging.…”

Section: D Nand Ono (Oxide Nitride Oxide) Thickness Measurementsmentioning

confidence: 99%

“…The technique was already discussed in a previous publication. [29][30][31] Here we apply this approach in order to reconstruct a 3D NAND memory hole. As shown in Fig.…”

Section: D Qualification Of 3d Nand Memory Holementioning

confidence: 99%

Electron beam metrology for advanced technology nodes

Lorusso

Horiguchi

Bömmels

et al. 2019

Jpn. J. Appl. Phys.

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The critical dimension scanning electron microscope (CD-SEM) is one of the main tools used to estimate critical dimension (CD) in semiconductor manufacturing nowadays, but, as all metrology tools, it will face considerable challenges to keep up with the requirements of the future technology nodes. The root causes of these challenges are not uniquely related to the shrinking CD values, as one might expect, but to the increase in complexity of the devices in of morphology and chemical composition as well. In fact, complicated three-dimensional device architectures, high aspect ratio features, and wide variety of materials are some of the unavoidable characteristics of the future metrology nodes. In this paper, we report on the development of advanced CD-SEM metrology at imec on a variety of device platforms and processes, for both logics and memories. The large variety of results reported here a clear indication of the on-going creative effort needed to ensure that the critical potential of CD-SEM metrology tools is fully enabled for the 5 nm node and beyond.

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Precise measurement of thin-film thickness in 3D-NAND device with CD-SEM

Cited by 8 publications

References 9 publications

Machine learning method to predict threshold voltage distribution by read disturbance in 3D NAND Flash Memories

Machine learning method to predict threshold voltage distribution by read disturbance in 3D NAND Flash Memories

Metrology Challenges in 3D NAND Flash Technical Development and Manufacturing

Electron beam metrology for advanced technology nodes

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