Research Progress of High Dielectric Constant Zirconia-Based Materials for Gate Dielectric Application

Round 1

Reviewer 1 Report

In the present manuscript, the authors have reviewed zirconia as a potential high-k gate dielectric covering their synthesis and application in transistors devices.

1. The introduction of the review presented by the authors and subjective references is significantly outdated. Specifically, the CMOS industry has digressed from SiO₂ based dielectrics from over a decade and current status-co in TFT large area electronics is not at all addressed. It is vital to address the significance of the topic relating to the state-of-the-art for the benefit of the readers.
2. Before diving into the details of ZrO₂ deposition techniques, it would be quite useful for the readers if typical properties of dielectric important to the device performance and performance metrics are briefly described, especially EOT, the density of traps, etc. along with possible performance-limiting factors such as various scattering modes, the effect on carrier mobility, Fermi-level pinning
3. The references described under the "thin film deposition" section are also outdated and authors should include more recent reports to describe up-to-date progress.
4. While the performance of the devices using variants of ZrO₂ is only briefly mentioned, they fail to clearly emphasize the role played by the dielectric in the improvement of device performance and at times are misleading.
5. While the ZrO₂ can be used in both CMOS as well as large-area electronics, the performance enhancement due to a certain deposition or additive technique should be clearly acknowledged in relation to its usability in certain applications.
6. Attention to using accurate technical terminology is lacking at many places with the use of terms such as "state density", "ALD process can be deposited", "in the form of crystals"

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The authors have provided a detailed and wide content on the topic. The points to be revised are mentioned below:

1)Providing the definitions of conduction mechanisms related to Schottky emission and trap(defect) assisted tunneling in oxides in the introduction would be contributory for the manuscript. The article in the link below can be helpful:

aip.scitation.org/doi/abs/10.1063/1.3624472?journalCode=apl

2) The subcharacters are in material names are overlooked in some parts of the manuscript and they are written as ZrO2 and SiO2. They should be ZrO₂ and SiO₂.

Author Response

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Reviewer 3 Report

 In this manuscript, the authors provided a comprehensive minireview of researches on “Research Progress of High Dielectric Constant Zirconia-Based Materials for Gate Dielectric Application”, defining synthesis method that improves the properties of ZrO₂ films. The paper reviews the state of art on the development of ZrO2 films as one of the most promising gate dielectric materials for next-generation semiconductor devices. This manuscript could be helpful for the development of extensive studies on ZrO₂ structure and their applications in MOSFET and TFT devices.

I would like to recommend its publication in this journal after address the following recommendations:

• Please, avoid using abbreviations in the abstract;
• The authors should add a section for example after the introduction that reveals the structure and structure-dependent physicochemical properties of ZrO₂ films, their advantages, disadvantages, and methods to improve. In this respect, certain applications can be also underlined.
• A short principle description or the essence of each synthesis method is better to be explained in short. Moreover, the advantages and disadvantages of each method such as low adhesion strength, deposition of amorphous structures that have to be annealed and other limitations in dimensions should be revealed in more detail.
• Low-temperature solution processes (section 3.5) should be included in section 2 (ZrO₂ thin deposition) and each synthesis method such as spin coating, spray pyrolysis, dip coating, and printing should be better revealed.
• In table 1, ref. number should be included at the end of each row. The synthesis method could be also included in the table. More references can be added.
• Overall, more critical view of the reviewed papers is needed;
• Please always highlight the input of your own research groups in the appropriate sections.
• Please, specify the specific dimensions and phase composition of ZrO₂ The results should be scientifically discussed in relation to the comments made in the previous section, for example, “Physicochemical properties of ZrO₂ films”.
• The challenge and trends for ZrO₂ thin film application can be further discussed.
• Since the review means to highlight recent and important developments, some references have to be replaced with recent works. For example, ref. 1, 2, 3, 6, 7, 14, 18, 19, 27, 29, 30, 31, etc.

Author Response

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Reviewer 4 Report

The manuscript constitutes a review of papers dealing with ZrO₂ and ZrO₂-based films, particularly those which report the dielectric constant and related properties like the equivalent oxide thickness. I do not know the policy of Coatings about reviews, so I will assume that the journal is interested in or even invited the review and focus on technical comments.

(1) The notation of dielectric constant is not unified: sometimes small 'k', sometimes capital 'K', sometimes greek 'kappa'.

(2) It is not clear that the theoretical/literature value of ZrO2 dielectric constant is 25 according to line 52, while it is 20-47 according to lines 70-72.

(3) A comment, not a criticism: I remember a prediction that dielectric constant of isostructural HfO2 can be even higher, up to 70 (10.1103/PhysRevB.65.233106).

(4) The refractive index of 2.15-2.18 (line 57) is provided at unknown wavelength. Furthermore, assuming that the wavelength is the frequently considered value of 550 nm, I remember even slightly higher values up to 2.22 (e.g. 10.1016/j.surfcoat.2013.10.052 and Refs. therein).

(5) Some statements are not quantified, e.g. those about the low deposition rate using ALD on line 98 and reasonable deposition rate using CVD on line 123. (Deposition rate using PVD, e.g. 140 nm/min in the aforementioned Ref., is not mentioned at all.)

(6) Line 113: I understand that power per square area is more important (for the reproducibility) than the power in itself.

Author Response

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Reviewer 5 Report

Dear Authors,

The preparation of the review requires considerable effort. Your work is truly admired. However, before starting this work it is advisable to find out who your target audience is and what their interests are. Your manuscript is about the research progress of high dielectric constant zirconia-based materials for gate dielectric application. There is no doubt that zirconium oxide is a very interesting material. Zirconium oxide films offer fascinating aspects related to electronic and optical properties and their applications in photocatalysis and protective coatings. Zirconium oxide has been investigated for a variety of applications related to its distinct chemical, physical, optical, dielectric, and mechanical properties.

All this is true, but you did not indicate the reason why you preferred zirconium oxide as a gate insulator. Why is it more preferable than, for example, HfO2? This, in my opinion, is a significant disadvantage of the work. The issue of replacing SiO2 in CMOS high-k material was discussed at the end of the last century. Many articles have been written about this, in particular, an interesting review [1]. Intel in 2007 made a significant breakthrough in the 45 nm process by using a "high-k" (Hi-k) material (HfO₂) to replace the transistor's silicon dioxide gate dielectric [2].

Possibly, zirconium oxide films applications in solar cells [3] are more interesting and perspective.

1. Wilk, G. D., Wallace, R. M., & Anthony, J. M. (2001). High-κ gate dielectrics: Current status and materials properties considerations. J. Appl. Phys. 89(10), 5243–5275. doi:10.1063/1.1361065.
2. https://www.intel.com/pressroom/kits/advancedtech/doodle/ref_HiK-MG/high-k.htm.
3. Waghmare, M. A., Naushad, M., Alothman, Z. A., Ubale, A. U., Pathan, H. M. (2017). Zirconium oxide films: deposition techniques and their applications in dye-sensitized solar cells. J. Solid State Electrochem. 21(9), 2531–2545. doi:10.1007/s10008-017-3565-8.

Author Response

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Round 2

Reviewer 3 Report

The paper may be accepted in the present form.