Abstract
The recently discovered yttrium oxyfluoride (YOF) coating has been found to be a highly promising plasma-resistant material which can be coated onto the inner wall of the dry etching chambers used in the manufacturing of the three-dimensional stacking circuits of semiconductors, such as vertical NAND flash memory. Here, the coating behavior of the YOF coating which was deposited by suspension plasma spraying was investigated using a high-output coaxial feeding method. Both the deposition rate and density of YOF coatings increased with the plasma power, which was determined by the gas ratio of Ar/H2/N2 and the arc current. The coating thicknesses were 58 ± 3.4, 25.8 ± 2.1, 5.6 ± 0.6, and 0.93 ± 0.4 µm at plasma powers of 112, 83, 67, and 59 kW, respectively, for 20 scans with a feeding rate of the suspension at 0.045 standard liters per minute (slm). The porosities were 0.15% ± 0.01%, 0.25% ± 0.01%, and 5.50% ± 0.40% at corresponding plasma powers of 112, 83, and 67 kW. High-resolution X-ray diffraction (HRXRD) shows that the major and minor peaks of the coatings which were deposited at 112 kW stem from trigonal YOF and cubic Y2O3, respectively. Increasing the flow rate of the atomizing gas from 15 slm to 30 slm decreased the porosity of the YOF coating from 0.22% ± 0.03% to 0.07% ± 0.03%. The Vickers hardness of the YOF coating containing some Y2O3 deposited at 112 kW was 550 ± 70 HV.
Highlights
In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated
With axial feeding, the axially supplied suspension can penetrate the core zone of the plasma jet, which makes the coating efficiency higher than that of radial feeding. This equipment has three cathodes and anodes which are operated by three independent power supplies, which makes it possible to generate a high power without the cathodes being eroded by the plasma
Regarding the choice of the gas mixture and the current, we were guided by the work of Kitamura et al [6] and by our preliminary experiments
Summary
In order to manufacture a semiconductor circuit, etching, cleaning, and deposition processes are repeated. The coating of the inner wall of the semiconductor equipment with a plasma-resistant material has been attempted to minimize the etching of the coating and particle contaminant generation. When the Y2 O3 coating layer is exposed to fluorine plasma, fluorine-containing particles are generated in the gas phase and land on the surface, contaminating the wafer surface [14]. For this reason, YF3 was suggested as a new material to replace Al2 O3 and Y2 O3 because it is more resistant to plasma and has higher dielectric strength than Y2 O3 [14,15]. The high plasma power of the Axial III multi-electrodes has beneficial effects on particle melting and coating behavior
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