Effects of lmpurities on Dielectric Properties and Plasma Resistance of Al2O3 Ceramics for Application of Microwave Window

摘要

The effects of impurities on dielectric properties at loGHz and fluorine plasma resistance of Al2O3 ceramics have been investigated. Both the dielectric constant and the Q factor decrease with decreasing Al2O3 content. Especially the Q factor is largely affected by impurities, e.g., it is changed from 30000 of the 4N-Al2O3 to 1000 of the 92-Al2O3. Among impurities, alkaline metals such as Na and K significantly deteriorate the Q factor, even when the contents are considerably small of ~ 100ppm. By decreasing impurities, etching rate is decreased, when exposed to fluorine plasma in the reaction ion etching equipment. From the microstructure observation of exposed surfaces, it is revealed that the SiOz rich phases are preferentially attacked by the plasma. By the impurity control, the high performance Al2O2 microwave window with high Q factor and good plasma resistance has been fabricated.