Influence of Common Source and Word Line Electrodes on Program Operation in SuperFlash Memory

Round 1

Reviewer 1 Report

The comments to authors:

1. In Section 2, what is the fixed value of V_WLto simulate the impact of Common Source Electrode ?
2. For thementioned numerical simulations in Section 2, which are suitable for the latest technology node, the current node or the past nodes? Please specify the adopted value.
3. In Section 3, what is the fixed value of V_CSto simulate the impact of Word Line Electrode ?
4. Check and revise the Figure 11.
5. Check the typos and grammatical errors in the manuscript. For example, the sentence ‘the literature model defined for previous nodes do not always apply’ should be ‘‘the literature model defined for previous nodes is not always applied’ and so on.

Author Response

1. In Section 2, what is the fixed value of VWL to simulate the impact of Common Source Electrode ?

- We would like to thank the Reviewer for outlining our oversight. That V_WL value is now specified (line121).

2. For the mentioned numerical simulations in Section 2, which are suitable for the latest technology node, the current node or the past nodes? Please specify the adopted value.

- In lines 114-117 a focus on additional effects, caused by technology scaling, has been appended.

3. In Section 3, what is the fixed value of VCS to simulate the impact of Word Line Electrode ?

- We would like to thank the Reviewer for outlining our oversight. That VCS value is now specified (line121).

4. Check and revise the Figure 11.

- We would like to thank the Reviewer for bringing up this point. The old Figure 11 is now Figure 12 (since another figure has been added to answer to Reviewer 3). It has been revised and the layout has been modified.

5. Check the typos and grammatical errors in the manuscript. For example, the sentence ‘the literature model defined for previous nodes do not always apply’ should be ‘‘the literature model defined for previous nodes is not always applied’ and so on.

- We would like to thank the reviewer for highlighting the typo, which has been corrected (line 13).

Reviewer 2 Report

Please shorten the conclusion.

Author Response

1. Please shorten the conclusion.

- We wish to thank the Reviewer for the kind consideration. Following this suggestion, we shortened the Conclusion.

Reviewer 3 Report

The Authors consider ESF3 memory cell with respect to the influence of potentials of Common Source and Word Line electrodes on the performance of such a cell. In general, the results presented in the paper seem correct, but some fragments require improvement.

 

Detailed remarks:

 

1. I think the manuscript requires some ordering by introducing the Methods section and clearly stating what the Authors are going to do. As a part of this, Lines 88-101 could be included in that section. I think also the models found in literature, e.g. eq. (1a), (1b) and similar should be placed in that section to show the reader the current state of art. On the other hand, the proposed models given by equations (4) and so on should be put in the next section like Results or Discussion to clearly indicate the contribution of the research.

 

2. Consider adding a figure with an ESF memory cell and potentials placed as in table 1. It certainly would make it easier to imagine the expected E field values.

 

3. Line 129: total electric field is not EH + EV, but a square root of EH^2 +EV^2.

 

4. There is certain lack of order in units.

4a) In figure 3b you use A/μm which suggests the total current is obtained by multiplication of the channel width. In Figure 3c you use C, so the multiplication is not necessary here. I do not say this is wrong, but can be unclear.

 

4b) Equation (4) seems wrong for me, because y has a unit of length so you cannot just calculate e^-y; rather e^-y/d should be used, where d is a specific length so y/d is non-dimensional. Therefore the results obtained with this equation should be verified, in particular: equation (6) and related description.

 

4c) coefficients like k1, alpha and so on should be given units (e.g. in Fig. 6).

 

5. It is not clear for me how equations (5a) and (5b) were obtained. I see they are for fit the results given in Fig. 6a, but how were the results obtained? Was it a simulation based on eq. (4)? Then it would require using (5a) and (5b). Could you please describe it more clearly?

 

6. Line 261: according to Table 2, EH decreases and Ev increases with VWL.

 

7. Line 405-406: “excellent agreement between the analytical model and the numerical values was found”. This is not clear for me. Weren’t the numerical values obtained via analytical model?

 

8. The conclusions could be improved. For example, they contain repetitions (lines 409-419 are repetitions of former results).

 

9. Language: correct some evident typos/language errors, e.g.:

- Line 13: “model…do not always apply”,

- Line 314: “theoverall”

- Line 401: “…model are...”

 

10. Minor remarks:

- Line 74: what are “noticeable x, y coordinates”?

- Line 94 and Table 1: VBL should be IBL, rather.

- Line 231: “extremes” → “limits”,

- Line 244, Figure 6b: “Eye Guide”?

- Figure 6 caption: Line 252: “charge” → “charge density”

- I think notation |Ev| should be used instead of abs(EV), and similarly for abs(EH) and so on.

- Figure 11: check the layout.

Author Response

Detailed remarks:

1) I think the manuscript requires some ordering by introducing the Methods section and clearly stating what the Authors are going to do. As a part of this, Lines 88-101 could be included in that section. I think also the models found in literature, e.g. eq. (1a), (1b) and similar should be placed in that section to show the reader the current state of art. On the other hand, the proposed models given by equations (4) and so on should be put in the next section like Results or Discussion to clearly indicate the contribution of the research.

• We wish to thank the Reviewer for the suggestions. As recommended, sections have been re-arranged in order to improve the clarity of the paper and to highlight the research contribution: a section Methods and a section Results have been introduced including the contents as suggested by the Reviewer. As a consequence, new lines (112-127) have been added for readability purposes.

2) Consider adding a figure with an ESF memory cell and potentials placed as in table 1. It certainly would make it easier to imagine the expected E field values.

• Again, we agree with the Reviewer and, following this suggestion, added a new Figure (Fig. 2 of the revised version).

3) Line 129: total electric field is not EH + EV, but a square root of EH^2 +EV^2.

• We apologize for the mistake and thank the Reviewer for outlining it.  The definition of total electric field has been corrected (line 143).

 

There is certain lack of order in units.

4a) In figure 3b you use A/μm which suggests the total current is obtained by multiplication of the channel width. In Figure 3c you use C, so the multiplication is not necessary here. I do not say this is wrong, but can be unclear.

• That’s correct, now Amperes have been used in place of Amperes per micrometer both in Fig. 4b and Fig. 8b.

4b) Equation (4) seems wrong for me, because y has a unit of length so you cannot just calculate e-y; rather e-y/d should be used, where d is a specific length so y/d is non-dimensional. Therefore the results obtained with this equation should be verified, in particular: equation (6) and related description.

• We apologize and would like to thank the reviewer for pointing out this mistake, which of course led to a measurement unit mismatch in equation 6. A reference length (d_ref) has been added in the exponential argument of equation 4 (properly commented in the text). As a consequence, the reference length also appears in equation 6, so the results in the following figures have been changed accordingly.

4c) coefficients like k1, alpha and so on should be given units (e.g. in Fig. 6).

• Yes, we agree with the Reviewer. Measurement units have been explicated in Fig. 7a.

5) It is not clear for me how equations (5a) and (5b) were obtained. I see they are for fit the results given in Fig. 6a, but how were the results obtained? Was it a simulation based on eq. (4)? Then it would require using (5a) and (5b). Could you please describe it more clearly?

• We would like to thank the reviewer for highlighting such an ambiguity. Ns and dFG were actually derived from direct inspection of carrier concentration values provided by TCAD simulations in x=xFG. In particular, ns and dFG dependencies on VWL were obtained, respectively, by probing carrier concentration values at the Si/SiO2 interface and by examining carrier concentration behavior as a function of y. Finally, equations (5a) and (5b) were brought about by curve fitting. All these considerations about the deduction of equations (5a) and (5b) have been added in lines 233-238.

 

6) Line 261: according to Table 2, EH decreases and Ev increases with VWL.

• We would like to thank the reviewer for highlighting this mistake. The sentence has been corrected (line 275) with the actual dependency of both EH and EV on VWL.

 

7) Line 405-406: “excellent agreement between the analytical model and the numerical values was found”. This is not clear for me. Weren’t the numerical values obtained via analytical model?

• We would like to thank the reviewer for pointing out this lack of clarity. As previously reported at point 5), ns and dFG were obtained by directly extracting carrier concentrations from TCAD simulations. The same can be said about charge, which could be derived from charge mapping of the structure. In line 259 we pointed out that the values of charge were extracted by numerical simulations.

8) The conclusions could be improved. For example, they contain repetitions (lines 409-419 are repetitions of former results).

• We would like to thank the reviewer for this constructive criticism. Conclusions have been revised and shortened in order to improve the manuscript readability.  

 

Language: correct some evident typos/language errors, e.g.:

- Line 13: “model…do not always apply”,

• “Model do not always apply” has been replaced by “model is not always suitable” (line 13)

- Line 314: “theoverall”

• This typo has been corrected (line 332).

- Line 401: “…model are...”

• That line of the section Conclusion has been cut.

 

Minor remarks:

- Line 74: what are “noticeable x, y coordinates”?

• This description has been replaced by “adopted frame of reference definition”

- Line 94 and Table 1: VBL should be IBL, rather.

• VBL has been replaced by IBL in both line 95 and Tab. 1

- Line 231: “extremes” → “limits”,

• The error has been corrected (line 248)

- Line 244, Figure 6b: “Eye Guide”?

• “Linear fitting” has been used in place of “eye guide” in line both line 261 and Fig. 7b.

- Figure 6 caption: Line 252: “charge” → “charge density”

• That is correct, now we used charge per unit width. In fact, Fig. 7b (old Fig.6) displays channel charge per unit width as a function of VWL. The term has been corrected in line 269, together with the replacement of “surface charge” with “surface electron density” in line 267.

- I think notation |Ev| should be used instead of abs(EV), and similarly for abs(EH) and so on.

• | |notation has been used instead of abs() in Fig. 3a, Fig. 4c, Fig. 5, Fig. 8c, Fig. 10a, Fig. 10b and Fig. 13a.

- Figure 11: check the layout.

• Layout of that Figure (now Figure 12) has been changed by equalizing fonts of both Fig. 12a and Fig. 12b.