Fluorination of Al2O3 and Y2O3 surfaces was investigated by irradiating high-density, helicon-wave CF4O2 and SF6O2 plasmas. The Al2O3 surface bombarded by high-flux positive ions of the CF4O2 plasma was fluorinated significantly. On contrast, Y2O3 was less fluorinated than Al2O3 when they were irradiated by the same CF4O2 plasma. The analysis of the Al2O3 surface irradiated by the CF4O2 plasma suggests that the fluorination is triggered by reactions between fluorocarbon deposit and Al–O bonding with the assistance of ion bombardment. On the other hand, irradiation of the SF6O2 plasma induced less significant fluorination on the Al2O3 surface. This suggests a lower reaction probability between sulfur fluoride deposit and Al–O bonding. The difference in the fluorination of the Al2O3 and Y2O3 surfaces induced by the irradiations of the CF4O2 and SF6O2 plasmas is understood by comparing the bonding energies of C–O, S–O, Al–O, and Y–O.

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