Atomic Layer Deposition of Insulating AlF₃/Polyimide Nanolaminate Films

Round 1

Reviewer 1 Report

This work demonstrates possibility to deposit inorganic/organic AlF3/polyimide nanolaminated stacks by ALD/MLD. The structural, dielectric and electrical properties of the stacks have been studied from the view point of their application as interlayer dielectric in ICs. Although the results obtained reveal that the deposited stacks do not meet the requirements for low enough permittivity (low-k) the work is interesting and useful. The results are comprehensively described. There are some issues, which need to be clarified.

1. In the Introduction it is not clear what is the motivation for using AlF3/PI stacks; which properties are expected to be better than those of single-layer counterparts?
2. The chemical composition of the layers in stacks is commented scarcely based on EDX results without showing any figures. It would be more informative to show these results. Was XPS study performed to clarify the chemical composition of layers and possible contamination from process residuals (e.g. Ti and Cl).
3. All stacks show buckling after staying in open air for a certain time. What is the reason for this and what could be the strategy to prevent it?
4. The last sentence in the Abstract is not correct – the stacks do not show lower leakage current than AlF3.
5. On line 204 the authors stated: “AlF3 appears to have grainier structure than PI.” What are the results, which support this statement.
6. Please give the capacitors' area.
7. Fig.11 is commented but not cited in the text.

Author Response

Dear reviewer,

Thank you for taking the time to review the manuscript. I'm going to answer some questions.

 

1. In lithium-ion batteries, aluminum fluoride (AlF₃) can be used as a solid electrolyte interface layer. Polyimide (PI) has good insulating properties and is used in the field of microelectronics. So we used a combination of AlF₃ and PI to try to get low-k materials.
2. EDX is just used to determine the presence of these components （Al, F, C, O...）in the film. Unfortunately, XPS has not been used to analyze film compositions.
3. Pure AlF₃ or PI (approximately 100 nm or even thicker) doesn't show this phenomenon. The monolayer (approximately 10 nm) is too thin and shrinks under atmospheric pressure due to pressure. This problem can be solved if AlF₃ and PI are thickened during deposition. But at the same time, the overall film thickness will increase a lot.
4. In reference 12, with the increase of deposition temperature (160 ℃ to 280 ℃), AlF₃ tends to crystallize. Compared with PI, ALF₃ appears rougher than PI at 170 ℃.

 

Yours sincerely,

Author

Reviewer 2 Report

The paper has merits being topical and useful for advanced materials and technology,  In the same time the manuscript has demerits need to be solved  before  publication . The revision has to take into account the following : a)The novel character of proposed ALD coating is not sustained with references chosen properly. The references are pretty old , the majority being older than 10 years.Also the references are cited only in the introduction and in my opinion the results and discussion need to be 
 As an example it is a need to present in detail the difference betewen the present deposition with the one existing in reference 20 where one of the authors here is the first author. 

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thank you for taking the time to review the manuscript. I'm going to answer some questions.

 

Some literatures which more than 10 years are used to describe the development of low dielectric constant materials in the last few decades. The first author of  reference 20 gives me an idea for polyimide deposition by ALD.

 

Yours sincerely,

Author 

Reviewer 3 Report

Dear Authors, 
I have carefully read your draft paper and concluded that your study is useful and interesting and may be acceptable for publication after some minor revisions. Also, I have a few questions and concerns with your work as presented, which I invite you to address or explain, and which are attached below. 
Sincerely, 
Reviewer. 

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thank you for taking the time to review the manuscript. About your questions:

 

1. Totally 9 samples.
2. The standard of AlF₃ and PI depositions are as same as references 12 and 20. 
3. We measured leakage current density.
4. For nanolaminate films, each sample has been measured four times, as shown in Fig11. The tolerance is basically stable and can be ignored.
5. When the deposition process is over, the whole silicon wafer was cut for SEM measurement. In the SEM measurement, one side of the cross-section is fixed on the specimen substrate.
6. SEM-EDS equipment has dedicated personnel to maintain and inspect every day. Therefore, the problem of contamination should not exist.

Yours sincerely,

Author

Round 2

Reviewer 3 Report

Dear authors,
Your manuscript is of great interest to readers and I have therefore recommended it for publication in this journal.
Best regards,
The reviewer