As transistor size in semiconductor has scaled down to 10 nm, particulate contamination has become of a critical issue. In the fluorine plasma environment, the etching occurs simultaneously with the physical etching and the generation of contaminant particles due to the chemical reaction. In the fluorine-based plasma environment, a material having excellent corrosion resistance such as Y2O3 is used as a coating layer, but there is a problem that contaminant particles are generated. YOF ceramics are expected to be a plasma resistant material producing less contamination particles in the semiconductor equipment industry. In this study, YOF powders were synthesized by solid-state reaction and YOF coatings were fabricated using suspension plasma spray. The synthesis of YOF powders was carried out by mixing Y2O3 and YF3 at different molar ratios and solid phase reaction was induced during their heat treatment in argon or air atmosphere. It was confirmed that the shape and particle size of the synthesized YOF powder can be controlled by carefully adjusting Y2O3 and YF3 as raw materials. In the case of suspension plasma spray coating with synthesized YOF powder. it was shown that the desired composition and crystal phase would be obtained if the molar ratio of the mixed raw materials was controlled by considering the evaporation and oxidation of YOF
In the single rapid scan experiment, it was confirmed that Y2O3 and YF3 powders were severly fragmented into individual particles inside plasma jet rather than being synthesized as YOF particles during the flight of each suspension droplet. In that process, the melting point of YF3 was low such that evaporation or oxidation occurred partially due to high enthalpy of the plasma jet. As the higher enthalpy of plasma, each Y2O3 and YF3 splats deposited on the substrate were in-situ synthesized into YOF coating layer, because the solidification of splats becomes slower due to high plasma enthalpy. However, it has been observed that a high plasma enthalpy produced vertical cracks in the in-situ synthesized coating layer. In order to avoid this problem, 2-step process was introduced to obtain YOF coating layer without cracks : a post-heat treatment after spray coating. At plasma condition with low enthalpy, the coating layer which contained unheated Y2O3 and YF3 particles was formed on the substrate without cracks. Then, additional heat treatment at 400 ~ 500 ℃ was shown to accelerate the solid phase reaction between the splats and produce a dense YOF coating without cracks.