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Poster Session II

4:30 pm – 6:30 pm, Wednesday October 15 Session DW5 COEX, Lobby E
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A study on the Low-Temperature etching mechanism of ONO layer components using NF3/H2 plasma

Poster 48
Presenter: Taemin Kim (UNIST)
Authors: Youngmin Sunwoo (Ulsan National Institute of Science and Technology), Paul Seo (Graduate School of Semiconductor Materials and Devices, Ulsan National Institute of Science and Technology (UNIST)), Hongsik Jeong (Ulsan National Institute of Science and Technology), Byungjo Kim (Ulsan National Institute of Science and Technology)

The cryogenic etching process is gaining attention as a next-generation technology for channel hole fabrication in 3D NAND flash memory, due to its advantage in forming high aspect ratio (HAR) structures compared to conventional RIE. Prior studies have shown that HF acts as a key etchant at low temperatures, where its enhanced physical adsorption enables HAR etching.

In this study, we examined the etching behavior of SiO2 and SiN (the main layers of the ONO stack in 3D NAND) using an NF3/H2 plasma under cryogenic conditions. QDB simulations, OES, and QMS analyses confirmed that increasing H2 flow enhances HF generation in plasma.

Under HF dominant conditions, FT-IR analysis showed that SiN forms stable ammonium fluorosilicate such as (NH4)2SiF6 at low temperatures, evidenced by NH peaks. The accumulation of these (NH4)2SiF6 on the surface suppressed the etch rate. In contrast, although NH peaks were also observed on SiO2. QMS results showed low NH4F formation, indicating limited (NH4)2SiF6 generation. Instead, the physical adsorption of HF and H2O played a key role in enhancing the etch reaction, increasing the etch rate.

This study provides insight into SiO2 and SiN etching mechanisms in NF3/H2 cryogenic plasma and supports process optimization for HAR etching in 3D NAND.

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