The 3D NAND sample with high aspect ratio (HAR) etched by plasma was investigated. By controlling the plasma etching parameters, a relatively high etch rate could be obtained. Moreover, with appropriately controlling the etch time, we could etch top region of HAR sample with expected number of layers, which could help us to completely analyze the high aspect ratio sample with TEM cross-section analysis, especially for the middle region of 3D NAND.

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