Citation: Tien, C.-L.; Chiang, C.-Y.; Lin, S.-C. Optimization of Electron-Beam Evaporation Process Parameters for ZrN Thin Films by Plasma Treatment and Taguchi Method. Plasma 2023, 6, 478–491. https://doi.org/10.3390/ plasma6030033 Academic Editor: Andrey Starikovskiy Received: 21 June 2023 Revised: 29 July 2023 Accepted: 1 August 2023 Published: 4 August 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plasma Article Optimization of Electron-Beam Evaporation Process Parameters for ZrN Thin Films by Plasma Treatment and Taguchi Method Chuen-Lin Tien 1,2, * , Chun-Yu Chiang 2 and Shih-Chin Lin 3 1 Department of Electrical Engineering, Feng Chia University, Taichung 40724, Taiwan 2 Ph.D. Program of Electrical and Communications Engineering, Feng Chia University, Taichung 40724, Taiwan 3 Mechanical and Systems Research Laboratory, Industrial Technology Research Institute, Hsinchu 310401, Taiwan * Correspondence: cltien@fcu.edu.tw; Tel.: +886-4-24517250 (ext. 3809) Abstract: This study presents the optimal process parameters of zirconium nitride (ZrN) thin films prepared by ion-assisted deposition (IAD) technology combined with electron-beam evaporation based on plasma surface treatment and the Taguchi method. We use Minitab statistical software (Version 20.2.0) and L9 orthogonal array parameter design combined with the response surface method (RSM). The quadratic polynomial regression equation was optimized by the RSM. Based on the control factor screening test of the Taguchi method, we determined the most critical factor combination for the process and derived the optimized process parameters of the ZrN thin films. In the coating experiments, we successfully achieved the optimal combination of good refractive index, adequate residual stress, and lower surface roughness on B270 glass substrates. These results indicate that the optimized preparation process can simultaneously achieve several desirable properties, improving the performance and application of ZrN thin films. Furthermore, our research method not only reduces the number of experiments and costs but also improves the efficiency of research and development. By screening key factors and optimizing process parameters, we can find the best process parameter more rapidly, reduce the demand for expenses given materials and equipment costs, and contribute to improving the electron-beam evaporation process. According to the experimental results, it can be observed that under certain conditions, the properties of ZrN thin films reached optimal values. These results are highly useful for optimizing the process parameters of ZrN thin films and provide a basis for further improvement of the thin film properties. Keywords: zirconium nitride; electron-beam evaporation; ion-assisted deposition; optimization parameters 1. Introduction Thin film devices play an important role in engineering and modern industry. Due to different coating materials, different manufacturing methods, and different deposition parameters, thin films have different optical and mechanical characteristics. The optical transmittance, surface roughness, refractive index, and residual stress are important in- dicators for evaluating the performance of thin films. Zirconium nitride (ZrN) films find extensive applications in the fields of decorative coatings and hard coatings to exhibit the effect of golden yellow appearance. In addition, ZrN thin film also has excellent properties such as high hardness, corrosion resistance, thermal stability, and electrical resistance, which gives it a wide range of application potential in various fields [1]. Zirconium nitride is widely used in decoration, lamps, metal furniture, hardware products, architectural hardware, sports equipment, ceramics and glass products, etc. Among physical vapor deposition processes, evaporation, and sputtering are com- monly used thin film coating methods. For the preparation of ZrN thin films, electron-beam evaporation is a widely used technique. However, in addition to electron-beam evapo- ration, other methods can also deposit ZrN thin films, including pulsed laser deposition, Plasma 2023, 6, 478–491. https://doi.org/10.3390/plasma6030033 https://www.mdpi.com/journal/plasma