Adjustment Method of MEMS Dual-Cantilever Deflection Using Plastic Deformation of Al and Ni Thin Film by Thermal Annealing

Round 1

Reviewer 1 Report

Cantilevers are one kind of key units in MEMS. For the high performance MEMS, one key issues is their deflection mismatch in MEMSs. In this article, the authors developed a simple but new method to regulate the composite thin film stress by step-annealing the constructed Al and Ni dual layered thin films at different temperature, according to the theoretical consideration: Al layer can be used to adjust the film stress by repeating plastic deformation and Ni layer can be used to change the film stress upon heat treatment at approximately 400 °C. The fundamental is correct and the experimental results are good. The article is generally written well. There are some questions for the authors to consider to improve this article.

1.        Can the AlNi alloying interface be formed during the annealing process since Al and Ni can form many kinds of eutectic alloys or normal alloys? Since these alloys are very important to their stiffness and inner stress regulation, it is suggested to characterize the interface carefully. XRD may not be useful for the interface structure characterization.

2.        Please provide the surface SEM images of the key Al-Ni dual-layered thin film after annealing at different process.

Author Response

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Reviewer 2 Report

In this work, the authors reported a defection adjustment method for MEMS cantilevers using a low temperature thermal annealing treatment to alter the stress of the deposited films/coatings. Al and Ni were used as examples in this study and their stress change and the mechanisms during the annealing process were investigated. The structural information is well-characterized with results in support of the analysis. The reviewer would like to recommend the publication of this manuscript in Micromachines after the following questions could be answered. 

 

1. In the study, the annealing temperature was set from 250 ^oC to 400 ^oC for the Al film while 200 ^oC to 400 ^oC for the Ni. Please explain why the annealing temperature is different for the two films, and how do you determine which temperature to use for Al/Ni annealing.  

 

2. In the results section, the authors provided the SEM image of the annealed Al/Ni films to show the morphology after annealing. However, the SEM images before annealing were not presented. Please provide the SEM images for the Al/Ni before annealing as a comparison. 

 

3. In the results section, full width at half maximum (FWHM) was used as part of the structural analysis for the Al/Ni films. Please add the FWHM calculation/illustration into the manuscript 

Author Response

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Reviewer 3 Report

In this manuscript, the authors presented a method to adjust deflection mismatch in microelectromechanical systems (MEMS) dual-cantilevers by using thermal annealing to cause plastic deformation in Aluminum (Al) and Nickel (Ni) thin films. The topic of the paper is unique and significant. Deflection mismatch in MEMS dual-cantilevers can be a serious issue affecting the performance of these systems. The proposed method of using thermal annealing to adjust for this mismatch might present a novel approach to overcome this problem. I am favorable to the publication of this manuscript. Although the font in figures can be improved.

Author Response

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Author Response File: Author Response.pdf