| Summary: | 博士 === 國立中興大學 === 材料科學與工程學系所 === 106 === This study prepared yttrium oxide (Y2O3), Yttrium fluoride (YF3) and yttrium oxyfluoride (YOF)-based anti-plasma etching coatings using the atmospheric plasma spraying method, and investigated the mechanical properties of various coatings and their chemical reaction mechanisms under carbon tetrafluoride-based oxygen plasma etching, and observed their etching behaviors on the layer of quartz chamber and the pollution conditions of wafer particles. At plasma spraying power of 15 kW, the said three kinds of coatings had better mechanical properties and membrane structure characteristics. Among the three coatings, the porosity of both YOF and YF3 coatings were smaller than 3%, and that of Y2O3 was 6%, which is due to the fact that the melting points of YOF and YF3, standing at 1,150C and 1,378C, respectively, were lower than that of Y2O3 (2,425C). Particles with a lower melting point can completely melt during meltallizing and form dense coatings. Vickers hardness tests indicated that the Y2O3 coating had the highest hardness because the bond energy (685 KJ/mol) of Y-O was higher than that (605 KJ/mol) of Y-F. The dielectric voltage withstand tests suggested that the breakdown electric field (5.5 kV) of the YOF coating was higher than that (4.9 kV) of the YF3 coating and that (3.2 kV) of the Y2O3 coating, which was ascribed to the fact that the YOF coating had the lowest porosity.
After the Y2O3, YF3 and YOF coatings were plasma etching through Carbon tetrafluoride-based oxygen, the Y2O3 and YF3 coatings would form the altered layers of YOF and on recoated surface, with the thicknesses being 5.2 nm and 6.8 nm, respectively. Due to the fact of Y2O3 was less vulnerable to the attack of fluoride ions, the thickness of the altered layer of YOF was less than that of YF3. And no altered layer of YOF was observed. Although the YOF altered layer was formed from Y2O3 coating, the particles were further polluted because of the volume expansion of the YOF altered layer and the coating surface cracks and friction. Originally, the YF3 was fluorinated, and a stable altered layer was formed free of particle pollution. However, during the etching process, the YF3 coating was likely to be bonded with oxygen atoms, causing a smaller line width in etching the quartz layer. The above shortcomings were not observed on the YOF coating. The etch rate test found that the YF3 etch rate of 147 nm/min greater than Y2O3 (126 nm/min) and YOF (96 nm/min) and YOF coatings were more anti-plasma erosion. The above experiments and analysis results fully demonstrated that YOF can be used to form a new anti-plasma etching coating.
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