Microstructural control of Y2O3 coating on quartz glass for the reduced thermal mismatch stress

Y2O3 can be applied as a plasma resistant coating for quartz glass used in the plasma etching apparatus. For such an application, a thick coating layer is required. However, when the thickness of the coating reaches to a critical thickness, a cracking in the coated layer occurs due to the residual tensile stress developed as a result of thermal expansion mismatch between the coating layer and the Substrate. The critical thickness was calculated as similar to70 nm when the heat treatment temperature was 1000degreesC. To increase the critical thickness of the coating layer, a porous intermediate layer was introduced. Sol-gel spin coating method was used to deposit the multi-layered Y2O3 films. Three layered (dense/porous/dense)-Y2O3 coating with a thickness more than 200 nm was fabricated without crack generation. The porous self-buffer layer was effective in relieving the residual stress.