Effects of Electric Bias on Different Sc-Doped AlN-Based Film Bulk Acoustic Resonators

Round 1

Reviewer 1 Report

The experimental procedure should be better detailed. For example, what was the distance target-substrate? What was the deposition time? What are the characteristics of the used target? What are the characteristics (size, doping type, resistivity...) of the used Si substrate? How the doping process was performed? How many samples of each film were produced?

The quality and resolution of the Figure 5 should be improved.

In discussion of results, it would be important to compare the obtained results with those reported in literature.

 

Author Response

Response letter

 

We really appreciate for your carefully reading the manuscript and the constructive comment. In the following pages, we address the reviewer’s comments point by point.

 

 

 

1. The experimental procedure should be better detailed. For example, what was the distance target-substrate? What was the deposition time? What are the characteristics of the used target? What are the characteristics (size, doping type, resistivity...) of the used Si substrate? How the doping process was performed? How many samples of each film were produced?

Author reply: The silicon substrate we adopted in this work is high resistivity silicon whose crystallographic orientation is <111>. The silicon substrate is not a doped silicon. The size of the Si substrate wafer is 8 inches. The AlN and AlScN films are sputter deposited by Sigma fxP PVD system, with physical vapor deposition (PVD) technology. The target material for depositing AlScN film is Al-Sc alloy (the mass ratio of Al and Sc is 20%). The distance between the metal target and silicon substrate is ~6 cm.

The samples for XRD are made of cutting the 8-inch wafer into 1*1 cm² small pieces by diamond pen on our own. The measurement is completed by the Core Facility of Wuhan University; thus, we do not know the exact detail of measurement of piezoelectric material by XRD.

 

The corresponding revised text in the manuscript:

Page 2, Line 82: “The piezoelectric films were deposited under 200℃ by a magnet sputter (Sigma fxP system) using physical vapor deposition (PVD) technology with sputter power of 6 kW and biased power of 161 W. The targets for AlN and AlScN are Al metal and Al-Sc alloy (the mass ratio of Sc and Al is 20%) and was ~6 cm from the 8 inches high resistivity Si substrate, which is in the orientation of <111>”

Page 2, Line 95: “After slicing the 8 inches device wafer into 1 cm² piece by a diamond pen, the structures of piezoelectric films were characterized by X-ray diffraction (XRD) measurement”

 

2. The quality and resolution of the Figure 5 should be improved.

Author reply: We have revised Figure 5 in the newly revised manuscript.

 

The corresponding revised Figure:

Page 4, Line 114, Figure 3:

 

Figure 3. Resonant characteristics of FBAR under different E_DC. (a) Measured admittance curve versus frequency at various E_DC of AlN based FBAR. (b) f_s and f_p as a function of E_DC of AlN, Al_0.8Sc_0.2N and Al_0.7Sc_0.3N-based FBARs.

 

Page 5, Line 159, Figure 4:

 

Figure 4. Electromechanical equivalent Mason model of FBARs.

 

Page 6, Line 191, Figure 4:

 

Figure 5. The extracted values of equivalent piezoelectric parameters with different E_DC. (a) Stiffness coefficient c₃₃; (b) Piezoelectric coefficient e₃₃; (c) Relative dielectric constant ε_r.

 

3. In discussion of results, it would be important to compare the obtained results with those reported in literature.

Author reply: The differences of this work compared with reported work are as follows: 1. Reported work only present single piezoelectric material, for example, AlN or Al_0.7Sc_0.3N. In this work, we present the effect of direct current field on three different Sc doped concentration of AlN slab; 2. We also give the theory basis of the effect of electric bias on these three materials, which is a step forward than reported works.

 

The corresponding revised text in the manuscript:

Page 7, Line 210: “In this work, compared with the research on effect of E_DC on single one material, for example AlN [19] or Al_0.7Sc_0.3N [10], we adopted three different Sc doped concentration of AlN piezoelectric material and give the comparison of experimental results of effects of E_DC these three materials. Besides, by providing the theory basis of the change of resonant parameters under E_DC, we step forward on studying of electric bias modulated resonators”

 

Author Response File: Author Response.pdf

Reviewer 2 Report

In this work, the authors applied an external direct current biased field method to study the practical feasibility in adjusting fs of AlN and AlScN FBAR. The results indicated that the equivalent values of c33 increases with the change of EDC values, and the electric filed influenced stiffening effect of the pie-zoelectric films. This article needs a minor revision before it can be published.

1.       First I don’t see why it’s feasible to apply the electromechanical equivalent Mason model to extract the equivalent values of stiffness coefficient, piezoelectric coefficient and dielectric constant of the piezoelectric materials?

2.       The SEM images are confusing: what does the scale bar refer to in each image?

3.       Some important experimental details are unclear. For instance, how are the samples prepared for and characterized by XRD?

4.       This article has various grammar mistakes and shall be proof read by a native speaker. For example, “values of c33 increases” should be “values of c33 increase”, and “for negative to positive” should be “from negative to positive”.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf