Effect of CaF₂ on fluorocarbon plasma resistance and thermal properties of CaO-Al₂O₃-SiO₂ glasses

The effect of CaF2 addition on plasma resistance and thermal properties of CaO-Al2O3-SiO2 (CAS) glasses was investigated. The amount of SiO2 and Al2O3 was fixed to 42.9 and 9.1 (in mol%), respectively, while total amount of CaO and CaF2 was 48 mol% and the ratios of CaO:CaF2 were changed from 10:0 to 8:2.As the amount of CaF2 of CAS glass increased, CF4/O2/Ar plasma etch rate of glass decreased proportionally. In case of sample with CaO:CaF2 = 8:2, its etch rate had 5.04 ± 0.14 ㎚/min, which was about 20 times lower than that of quartz glass and was improved by more than 25% compared to the glass without CaF2. All glass samples maintained the initial surface and roughness even after plasma etching. In addition, the glass transition (Tg), crystallization (Tc), and the first melting temperature (Tf1) temperatures decreased with the amount of increased CaF2. F− ion in CAS glasses not only enhances the plasma resistance but also facilitates glass melting and forming operations.