Investigation of Program Efficiency Overshoot in 3D Vertical Channel NAND Flash with Randomly Distributed Traps
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Published:2023-04-24
Issue:9
Volume:13
Page:1451
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ISSN:2079-4991
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Container-title:Nanomaterials
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language:en
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Short-container-title:Nanomaterials
Author:
Park Chanyang1ORCID, Yoon Jun-Sik1ORCID, Nam Kihoon1ORCID, Jang Hyundong1ORCID, Park Minsang2ORCID, Baek Rock-Hyun1ORCID
Affiliation:
1. Department of Electrical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea 2. SK hynix Inc., Icheon 17336, Republic of Korea
Abstract
The incremental step pulse programming slope (ISPP) with random variation was investigated by measuring numerous three−dimensional (3D) NAND flash memory cells with a vertical nanowire channel. We stored multiple bits in a cell with the ISPP scheme and read each cell pulse by pulse. The excessive tunneling from the channel to the storage layer determines the program efficiency overshoot. Then, a broadening of the threshold voltage distribution was observed due to the abnormal program cells. To analyze the randomly varying abnormal program behavior itself, we distinguished between the read variation and over−programming in measurements. Using a 3D Monte−Carlo simulation, which is a probabilistic approach to solve randomness, we clarified the physical origins of over−programming that strongly influence the abnormal program cells in program step voltage, and randomly distributed the trap site in the nitride of a nanoscale 3D NAND string. These causes have concurrent effects, but we divided and analyzed them quantitatively. Our results reveal the origins of the variation and the overshoot in the ISPP, widening the threshold voltage distribution with traps randomly located at the nanoscale. The findings can enhance understanding of random over−programming and help mitigate the most problematic programming obstacles for multiple−bit techniques.
Funder
POSTECH the National Research Foundation of Korea Institute of Information & communications Technology Planning & Evaluation the Ministry of Trade, Industry & Energy
Subject
General Materials Science,General Chemical Engineering
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