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Nanophotonic identification of defects buried in three-dimensional NAND flash memory devices


Advances in nanophotonics and plasmonics have led to the creation of a variety of innovative optical components and devices. However, the development of powerful practical applications has so far been limited. Here we show that subsurface defects in three-dimensional NAND flash memory devices can be identified by exploiting the inherent hyperbolic metamaterial structure of the devices and associated nanophotonic interactions, such as the epsilon-near-zero effect and hyperbolic Bloch mode formation. By incorporating a hyperspectral imaging scheme into an industrial optical inspection tool, we experimentally demonstrate that a diffraction-assisted volume-plasmonic resonance provides a robust mechanism for identifying subsurface defects at a depth that is around ten times deeper than the conventional optical skin depth limit. Further spectral analysis in the longer-wavelength infrared region shows clear hyperbolic guided-mode-resonance signatures that would potentially allow defect identification over the entire device depth and on the scale of multiple micrometres.

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Fig. 1: Three-dimensional NAND flash memory architecture and optical defect-inspection system.
Fig. 2: Optical properties of tungsten and a W–SiO2 layer stack.
Fig. 3: Spectral response of a 3D NAND flash memory structure and resonant enhancement of the optical field penetration.
Fig. 4: Inspection test results on a 12-inch wafer specimen.
Fig. 5: FTIR measurement and predicted optical field penetration.


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This work was supported by the i-TAP (Innovative-Technology Advancement Program) of SK hynix Inc. We thank S. J. Moon and G. Ahn for providing us with the FTIR spectrum analyser and associated discussions.

Author information




J.W.Y., S.-M.M., and S.H.S. conceived the original concept and initiated the work. S.M.M., Y.K., J.H., O.-J.K., and K.K. performed the optical inspection and FIB-SEM analysis. J.W.Y. and S.H.S. established the theoretical ground of the concept and performed the FTIR analysis. G.P.K., S.-M.M., and J.W.Y. performed the numerical analyses. All authors discussed the results. J.W.Y., S.H.S., and S.-M.M. wrote the manuscript. J.W.Y. and S.-M.M. contributed equally to this work.

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Correspondence to Jae Woong Yoon, Seong-Min Ma or Seok Ho Song.

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The authors declare no competing financial interests.

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Yoon, J.W., Ma, SM., Kim, G.P. et al. Nanophotonic identification of defects buried in three-dimensional NAND flash memory devices. Nat Electron 1, 60–67 (2018).

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