Inhibited Channel Potential of 3D NAND Flash Memory String According to Transient Time

Round 1

Reviewer 1 Report

This paper presents an interesting study about a challenge with 3D NAND flash memory. Results are presented as a phenomenon observed and the authors try to explain the reason for this phenomenon.

1)  I understand that the channel potential for NLSB was analyzed according to the transient time and Vth value change of adjacent cells. However, the authors did not emphasize on the importance of this analysis and how it will make the 3D NAND Flash memory better.
2) There is no reference 20?
3) I feel that there are a lot of unnecessary self citation. Also, the reference list can be reduced. It is not a survey paper.
4) Why did the authors choose analysis based on t = 0s, 30ms, 100ms, 300ms and 1s. Also how does this study hold or shift during much longer time when the NAND is used.

In Summary. This is an interesting paper with a lot of potentials. Results from the study are interesting but need further verification. I am also not too confident in the explanation given for the observed phenomenon.  Lastly, emphasis should be made on the importance of this study to future 3D NAND developments.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

In this communication, the authors analyze the effect of channel potential in 3D NAND flash memories by means of TCAD simulations. The authors demonstrate that the transient decrease of the potential can result in program disturbance. Even though technically sound and well-written, the contribution is rather marginal but it can be of interest to some readers of the Applied Sciences. Just a minor note is that the reference [20] is missing.

- The main question addressed is a transient analysis of NAND flash memories during a programming operation and the impact of NLSB on the adjacent bit cells. The analysis is performed in terms of TCAD simulation.

- The topic is original and relevant, but the contribution is rather marginal.

- The authors come from a well-known research group whose focus is on NAND flash memories. The presented results are in line with their previous publications, e.g., [30], but the contribution just presents the simulation which makes it incremental.

- The simulation methodology is fine. The measurement results are absent, however, it is non-trivial to confirm the analyzed effect by real measurements on the memory prototype.

- I have not published before any papers in the Applied Sciences nor I did the review for the journal before. Hence I cannot really judge if the novelty level of the manuscript is sufficient and whether it meets the criteria. The paper is technically sound, but is written by the students. An example of this is that even in the abstract there is a specific WL8 which stands for word line 8. This is specific for the actual authors simulation, and it should not be really connected to the 8th word line  (it could be 4, 10, 14 or any other).

Author Response

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Reviewer 3 Report

The overall idea of the paper (applsci-2211477) entitled “Inhibited Channel Potential of 3D NAND Flash Memory String according to Transient Time” by Taeyoung Cho et al. is clear and the logic is reasonable. I find the framework of the topic interesting and being worth of investigation which can serve nicely the Flash community, but the paper cannot be published in the current version. The detailed comments and suggestions are listed as follows:

Point 1: Both language and readability of this paper should be checked by a native speaker. Specifically, several sentences are long and hard to read/understand.  Although, the authors are invited to check the following lines, I propose here some examples but there are more in fact:

-         Line 24, Page 1: in the memory semiconductor market>>>in the semiconductor-based memory market

-         Line 48, Page 2: Figure 1a shows the 3D NAND flash memory structure used>> Figure 1a shows the 3D NAND flash memory structure used her.

-       Table 1: Value of Doping (Arsenic/Boron) 1×10e20/cm3 / 1×10e18/cm3 >>>1×10²⁰/cm3 / 1×10¹⁸/cm3

-        Line 48-53: to rephrase

-        Figure 3(a): X-Axis the unit is (micron)

-        Line 58, Page 3: and gate spacing >>>, gate spacing

-        Line 84, Page 4: Figure 3 was confirmed that>>> Figure 3 confirms that

-        Line 83-97: page 3: to rephrase

-        Line 118-119: (Caption of Figure 5) graph of electron concentration according to…  >>> Electron concentration electron profiles for various …

-         Line 120: Figure 5 is graph of>>to rephrase

-         Line 123-124: the electron concentration in WL7, WL9 channel increase over time.>>>the electron concentration in WL7 and WL9 channels increase over time.

-        And others…

Some additional points that authors should take into account to improve their manuscript:

Point 2: The Keywords must be revised.

Point 3: The use of abbreviations in the entire of this manuscript must be checked.

Point 4: I would consider improving the introduction of this submission. The authors are invited to present other interventions in relation to the subject of this submission.

Point 5: In the introduction, the novelty and the interest of this work must be focused on. Please introduce a brief motivation and justify the innovativeness of this study, by this way; the readers can easily understand the significance of this work.

Point 6: In general, the presentation and quality of all figures requires a deep improvement throughout the submission.

Point 7: in the whole manuscript what do you mean by (Speed) and why do you use it instead of rate term?

Point 8 (On Figure (3-d)): Can you justify the second point at about 10 ms on P3 curve? What happens in the interval 300 ms-1s?

Point 9 (Figure 5): Please check the magnitude of electron concentration on the Y-axis.

Point 10: I noticed many repetition of the (NLSB) mechanism through the submission. The authors are invited to present it adequately in the introduction only.

Point 11: In the Structure of the proposed 3D NAND flash memory section; the authors are invited to propose a helpful figure of the general architecture of NAND flash memory with a conceptual view of a vertical channel 3D NAND with the main elements such as SSL, WLs, DSL and BL with necessary discussion.

Point 12: To be honest, the interest of the paper is not given by the authors; the authors are advised to give more discussions and explanations on the results.

Point 13: Lots of intermediate conclusions are missing in the entire of this manuscript.

Point 14: From the viewpoint of NAND Flash devices performance, why they use silicon polycrystalline material in the conduction channel in their proposed 3D NAND flash memory?

Point 15: I want to discuss with the authors how the results reported in this study can be used to improve and to achieve the optimal performance and storage capabilities of 3D NAND Flash devices?

Point 16: Conclusion must be revised and re-written. More significant conclusions of this study should be mentioned in the conclusion section. Pay attention to the order of different intermediates conclusions.

Point 17: I have detected inappropriate self-citations by authors (8 references of Myounggon Kang): [1-3], [6], [9], [17, 18] and [30]. The authors are advised to reduce the number of self-reference in this submission.

Point 18: Some references are relatively out-of-date. This section should be update with citation of new papers.

-       Please add Ref 20,

-       Please check the date the date of publication of the following references:

-      Ref 3: 27 October 2011 instead of January 2012

-      Ref 5: 11 August 2009 instead of 2008

-     The authors are advised to check others references

Based on the above comments, I recommend major revision.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The author's response to all my questions is satisfactory

Author Response

Thank you for giving us a good comment. We can also reflect the good advice you gave us, so our paper has improved in completion.

Reviewer 3 Report

Dear editor,

The Submission (applsci-2211477) entitled “Inhibited Channel Potential of 3D NAND Flash Memory String according to Transient Time” by Taeyoung Cho et al. has been improved and the revision is clearly presented. I think most of my suggestions and comments have been addressed with necessary discussion. In my opinion this paper is worth to be published in Applied Science (MDPI) journal.

In the following lines, I give two more comments:

Comment 1:

Both the fluency, grammatical and style of this manuscript should be checked by a native speaker.

Comment 2:

- Figure 3(a)>>>X-Axis the unit is (micron)

-  Caption of Figure 5>>> Electron concentration profiles for various …

Author Response

Please see the attachment.

Author Response File: Author Response.docx