Characteristics of TiN Thin Films Deposited by Substrate Temperature Variables Using Scanning Acoustic Microscopy

Round 1

Reviewer 1 Report

Comments to the authors

The manuscript entitled "Characteristics of TiN Thin Films Deposited by Substrate Temperature Variables Using Scanning Acoustic Microscopy", investigates the DC sputtered TiN thin films properties including residual lattice stress, grain size evolution and adhesion strength as a function of substrate temperature.

 

The results show that the residual stress and adhesion strength are significantly improved as the substrate temperature increases. However, these findings aren't novel since there are many works in the literature found almost the same results with different or similar techniques.

 

In my opinion, the main strength of this work is the introduction of Leaky Surface Acoustic Wave (LSAW) velocity technique to evaluate the residual stress and adhesion properties of TiN films, since this velocity is proportional to the adhesion strength and inversely proportional to the residual stress, as the substrate temperature increases. The decrease of film’s grain boundaries results in reducing the acoustic wave barriers and increasing the acoustic wave velocity, certifying the successful application of this technique in TiN thin film system.

 

There are only a few points needed to be reconsidered by the authors:

 

1. According to the authors' findings, the residual stress decreases as the substrate temperature increases. This stress relieve can be attributed to the deformation of the lattice or the defects creation during deposition. By using the Bragg's law for the (111) XRD peak positions, the authors can measure the d(111) interplanar spacing which will normally be decreased as the deposition temperature increases. This will shed light on the lattice structure deformation and stress relieve.

 

2. A summarized table must be inserted with the following results: residual stress, grain size, roughness, acoustic wave velocity and interplanar spacing, for the different substrate temperatures.

 

After the above minor revisions, the manuscript can be published in the Applied Science Journal.               

Comments for author File: Comments.docx

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The article is devoted to the study of the problem of low-temperature production of tin films with the necessary adhesive and mechanical characteristics. The highlight of this work is the use of an ultrasonic microscope to measure the surface acoustic leakage wave (LSAW). The results obtained in this work are interesting and can be applied to evaluate the residual stresses and adhesive properties of thin films by the V(z) method. The results of the study are generally well presented, but there are several points that need clarification.

1. The structure of films is not discussed in the article. In my opinion, this aspect is also important, especially when discussing the mechanical and adhesive properties of films.
2. Figure 2a does not show an X-ray of the original Si substrate. Please provide information about the calibration and accuracy of determining the position of 111 and 222 reflexes, as well as FWHM.
3. It can be seen from Fig. 1 that the deposited TiN films have a columnar structure. AFM images also indicated the presence of heights and pits on the films’ surface. Despite this, the roughness values of the film are no more than 1.24 nm. Please justify it.
4. There is no comparative analysis of residual stresses, adhesion, speed characteristics of TiN films with literature data. If this is difficult, then we would like to know the authors' opinion about the prospects for the use of TiN films studied in this work.

Author Response

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Author Response File: Author Response.docx