Yttrium Oxyfluoride Coatings Deposited by Suspension Plasma Spraying Using Coaxial Feeding

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.

Plasma Etching Behavior of YOF Coating Deposited by Suspension Plasma Spraying in Inductively Coupled CHF3/Ar Plasma

“…Then, some of the YOF would be transformed into Y 2 O 3 , while the YOF is mainly volatilized in the form of YF 3 by sufficient heat energy in the plasma jet region [20]. The detailed mechanism is explained in our previous paper [11].…”

“…Then, some of the YOF would be transformed into Y2O3, while the YOF is mainly volatilized in the form of YF3 by sufficient heat energy in the plasma jet region [20]. The detailed mechanism is explained in our previous paper [11]. Figure 5 shows the FE-SEM images of the surface microstructure of the Al2O3 bulk, Y2O3 coating, and YOF coating before and after exposure to the CHF3/Ar plasma for 60 min.…”

“…The SPS coating was carried out under the following conditions; the flow rate of argon as a primary gas was set to 90 standard liters per minute (slm), and the flow rates of nitrogen and hydrogen as secondary gases were set to 54 and 36 slm, respectively, to induce the generation of a plasma arc with an arc current of 230 A. The role of gases is illustrated in our previous paper [11]. The feeding rate of the suspension was 45 standard cubic centimeters per minute (sccm), and the flow rate of nitrogen atomizing gas was 30 sccm.…”

“…The fluorinated layer acts as a protective layer which prevents the coating from reacting with the fluorocarbon plasma [9]. Although Y 2 O 3 is known to be more resistant to plasma than SiO 2 and Al 2 O 3 , it would not be the best plasma-resistant material because fluoride particles whose chemical composition is close to YF 3 are generated as contaminants in the process of the Y 2 O 3 surface being converted to a Y x O y F z layer, due to the reaction with plasma [11,12]. Nowadays, many researchers are paying attention to the Y x O y F z (YOF) layer formed on the surface of the Y 2 O 3 .…”

“…However, there have only been a few reports about dense YOF coating deposited by SPS and its plasma-resistant properties. Recently, a dense YOF coating was successfully deposited by SPS by our group [11]. Our previous paper focused on the optimum process conditions to deposit a dense coating by SPS.…”