Research Progress of Target Preparation by Plasma Spraying

The sputtering target is the raw material of magnetron sputtering to prepare the thin film. The target has several development directions in industrial production, including large size, high purity, and high utilization. Due to the circular magnetic field generated by the circular permanent magnet on the surface of the target, the target will produce uneven erosion. The actual utilization rate of the tabular target is only 20%-35%, but the real utilization rate of the circular target is 80%. The size of the target also determines the efficiency of production. Although the main preparation methods of the target have been developed for several years, they are challenging to manufacture the large size and rotary target in terms of technology and economic benefits. In this work, the basic technical requirements of target preparation were summarized duo to the performance of targets as an essential role in preparing the thin film, such as purity, density, texture, grain size, and uniformity of grain distribution. The characteristics of melt casting, powder metallurgy, and plasma spraying were introduced. The target with ultra-purity can be prepared by melt casting, but production is of the characteristics of the complex process, high energy consumption, and target with coarse grain. Powder metallurgy can produce alloy and oxide targets at a relatively low cost, but the target has high porosity and low purity. Plasma spraying has been developed into technology for preparing the target from a well-established coating technology, which can easily make large size targets and tubular targets with various kinds of raw materials required. In addition, plasma spraying also has the characteristics of simple production, low cost, waste target repair and reuse in preparing targets. The research progress on preparing the target of metal, ceramic, and alloy and repairing residual targets by plasma spraying is reviewed. However, the target prepared by plasma spraying has some problems, such as high porosity, low density, and discontinuous microstructure. The pores in the target can be divided into three types: lamellar pores with incomplete interparticle bonding, high-temperature droplets that absorb gas during flight and form spherical holes after cooling, and microcracks in the vertical direction are caused by stress during cooling. The porosity of the tissue dramatically limits the development of plasma spraying preparation of sputtering targets. The target can only be used when the target density requirements are not very strict, such as mobile phones, hardware, architecture, energy-saving glass, etc. All the factors, including spraying parameters, spraying environment, raw material state, doping elements, and coating post-treatment, are the primary factors that affect the target performance. Moreover, it analyzes how these factors act and how to avoid or utilize them. Through the reasonable selection of spraying process parameters, the powder keeps melting state and sufficient momentum, coating stress release, and good formation of internal microstructure. Furthermore, the purity and density of the spraying target can be further improved. It aims at the features of preparing the target by plasma spraying and the future research direction is prospected. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.