Investigation of the Two-Way Injection Slurry-Supply Method for the Cu CMP Process

Round 1

Reviewer 1 Report

The communication entitled “Investigation of the Two-way Injection Slurry Supply Method for Cu CMP Process” focus on use of copper chemical mechanical planarization process was investigated.

Comments:

1. The article does not indicate the novelty of this approach. Authors should clearly indicate the advantages of this method.

2. Can other metals be used besides Cu coupon wafers? What are the advantages of this choice?

3. How was pH controlled? 

4. Figures 1 and 2 are difficult to read. These data should have been presented in the form of a table with values.

 

As a result, I will recommend the publication of this manuscript after minor revision.

Author Response

1. The article does not indicate the novelty of this approach. Authors should clearly indicate the advantages of this method.

Thank you for your comment. The following sentence has been added to the introduction.

In previous articles, a method of supplying one slurry using multiple nozzles was used. In addition, there are many studies to reduce slurry consumption, not to prevent CMP performance degradation. But in this study, CMP performance was confirmed when the slurry was supplied through an on-plate mixing method in which slurry excluding H₂O₂ and H₂O₂ were separately supplied. Through this method, decomposition of H₂O₂ in the slurry can be minimized to prevent degradation of the CMP performance.

2. Can other metals be used besides Cu coupon wafers? What are the advantages of this choice?

This method can be used when hydrogen peroxide is used as an additive in the CMP slurry of another metal CMP process. The reason why Cu wafers were selected is that Cu was widely used in metal lines. So, we determined that Cu which can be a general metal in CMP process.

3. How was pH controlled?

pH was controlled by KOH solution to pH 10. Also, as a pH detector, AT-710M (Kyoto Electronics Manufacturing Co.,LTD.) was used.

4. Figures 1 and 2 are difficult to read. These data should have been presented in the form of a table with values.

 Thank you for your comments. We will add the table to manuscript.

Flow rate (ml/min)	MRR (Å/min)	pH
Reference	3105.4	9.78
100 / 50	2969.99	9.76
75 / 75	3010.31	9.72
50 / 100	3313.02	9.76

Table 1. MRR and pH of reference and two-way injection with position; slurry- H₂O₂

Flow rate (ml/min)	MRR (Å/min)	pH
Reference	3105.4	9.78
100 / 50	2931.78	9.82
75 / 75	3276.01	9.81
50 / 100	3301.85	9.83

Table 2. MRR and pH of reference and two-way injection with position; H₂O₂-slurry

Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript reported the “Investigation of the Two-way Injection Slurry Supply Method for Cu CMP Process”. This work reports a two-way slurry supply method was investigated as a method to prevent degradation of Cu slurry. Nevertheless, it still leaves something to be desired in terms of testing. Some issues should be addressed before possible publication as follows:

1.       Some English and formatting errors in the manuscript should be corrected.

In the full text, the pre-crown is missing before "two-way slurry".

There is no space in the middle of "40 %".

2.       The introduction is too short, and the background section is not detailed.

3.       Some related works maybe are useful for support and background, such as Nano-Micro Lett 14 (2022) 6, ACS Energy Lett. 2023, 8, 457.

4.       There are too few diagrams in the main text, suggest adding two more to make the article more scientific.

5.       A photo to prove the difference between the improved method and the original method can reflect the excellence of the method more deeply.

6.       The test means are monotonous, and it is suggested to add other test means to support the superiority of the method.

7.       The conclusion section has little data and no corresponding outlook is drawn.

Author Response

Reviewer 2

This manuscript reported the “Investigation of the Two-way Injection Slurry Supply Method for Cu CMP Process”. This work reports a two-way slurry supply method was investigated as a method to prevent degradation of Cu slurry. Nevertheless, it still leaves something to be desired in terms of testing. Some issues should be addressed before possible publication as follows:

 

1. Some English and formatting errors in the manuscript should be corrected.

 

In the full text, the pre-crown is missing before "two-way slurry".

 

There is no space in the middle of "40 %".

 

Answer)

Thank you for your comments. We have revised what you said in the full text.

 

2. The introduction is too short, and the background section is not detailed.

 

Answer)

Thank you for your comment.

In the introduction part, we added or revised contents of the H₂O₂ degradation and two-way injection method.

• H₂O₂ tends to decompose easily, especially in high temperature, sunlight or high pH conditions. Over time, decomposed H₂O₂ in the slurry can change the pH of the slurry. A change in pH can change in the ionic state of glycine, which act as a chelating agent.
• In the other articles, a method of supplying one slurry using multiple nozzles was used. In addition, there are many studies to reduce slurry consumption, not to prevent CMP performance degradation. But in this study, CMP performance was confirmed when the slurry was supplied through an on-plate mixing method in which slurry excluding H₂O₂ and H₂O₂ were separately supplied. Through this method, decomposition of H₂O₂ in the slurry can be minimized to prevent degradation of the CMP performance.

 

 

 

 

3. Some related works maybe are useful for support and background, such as Nano-Micro Lett 14 (2022) 6, ACS Energy Lett. 2023, 8, 457.

 

Answer)

Thank you for recommending the article. Based on the article, the part related to H₂O₂ was added to the introduction.

However, in many fields, including CMP, problems arise due to decomposition or generation of H₂O₂.

 

4. There are too few diagrams in the main text, suggest adding two more to make the article more scientific.

 

Answer)

Thank you for your comment.

We are currently studying the effects of process conditions and injection positions. Changing the position, CMP target film or other process condition. Also, studying the decomposition of H₂O₂ in more detail. We plan to publish this as an article later.

 

5. A photo to prove the difference between the improved method and the original method can reflect the excellence of the method more deeply.

 

Answer)

Thank you for your comment. We added the schematic and photo in the manuscript to easily compare the slurry injection method.

 

 

6. The test means are monotonous, and it is suggested to add other test means to support the superiority of the method.

 

Answer)

Thank you for your comment.

As mentioned in answer 4, we test more complex and detailed in a future article as the changing the position, CMP target film or other process condition. In addition, we plan to test  the effect of  decomposition of H2O2 in CMP process more detail, explain the advantages compared to the CMP efficiency when two-way injection is used in various condition.

 

7. The conclusion section has little data and no corresponding outlook is drawn.

 

Answer)

Thank you for your comment. So we added following content in the conclusion.

1. The average MRR difference is about 163.13 Å/min, which is a small difference of about 5%.
2. In addition, since the two-way injection method is a study on CMP performance different from previous papers related to slurry consumption, it can be suggested as a different method of slurry injection.

 

Author Response File: Author Response.docx

Reviewer 3 Report

Authors investigated the effect of a two-way injection method during a copper chemical mechanical planarization process. Compared to the conventional method, the two-way injection method has unique advantage, so the two-way injection slurry supply method can be considered as an alternative to the general injection method that can prevent slurry degradation. Therefore, this work is recommended to be published in this journal after minor modification.

1. The abbreviation CMP should be explained in detail in abstract.

2. The material characterization should be added to confirm the difference between two-way injection method and conventional method.

3. More experimental data should be provided, for example, reproducibility, stability, availability effectivity etc.  

Author Response

1. The abbreviation CMP should be explained in detail in abstract.

Thank you for your comment. We add the abbreviation of CMP in abstract.

The effect of a two-way injection method during a copper chemical mechanical planarization (CMP) process was investigated. The two-way slurry injection method has the advantage of not only preventing degradation of the slurry but also shortening the process time because the mixing process of slurry and H₂O₂ is not required. Compared to the conventional method, the two-way injection method has an equivalent level of less than 9% in material removal rate. In particular, when injecting near the center of the pad, the influence according to the positions and flow rates of the two nozzles is also insignificant, so it deserves to be studied as a slurry supply method.

2. The material characterization should be added to confirm the difference between two-way injection method and conventional method.

Thank you for your comments. The following sentences were added in introduction part.

H₂O₂ tends to decompose easily, especially in high temperature, sunlight or high pH conditions. Over time, decomposed H₂O₂ in the slurry can change the pH of the slurry. A change in pH can change in the ionic state of glycine, which act as a chelating agent.[1]

 

3. More experimental data should be provided, for example, reproducibility, stability, availability effectivity etc.

Thank you for your advice. In this experiment, we tested at least three times for each condition, and error bars were added to each figure. Therefore, there is reliability of the experimental results such as reproducibility and stability.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

accept.