Remarkably enhanced plasma resistance of Y2O3-and Y-rich thin films through controllable reactive sputtering

Reactive sputtering was employed to fabricate yttrium-based oxide and metal-rich thin films by reacting oxygen with sputtered yttrium atoms, utilizing a metal target. The discharge voltages exhibited an abrupt change beyond a critical current at a specific combination of oxygen flow rate and pumping speed, suggesting a transition in the target state from a poisoned mode to a metallic mode. The deposition rates of oxide thin films in the metallic mode were more than eight times higher than those in the poisoned mode. The oxide films exhibited a cubic crystalline structure with a minor monoclinic phase and demonstrated exceptionally high etch resistance against fluorine-based plasma, with hardness and elastic modulus approaching those of sintered Y2O3. Additionally, higher current conditions promoted the formation of metal-rich films with both high electrical conductivity and etch resistance comparable to that of oxide films, yielding a nearly YF3-like surface post-etching. XPS and TEM analyses revealed surface modifications after plasma etching, characterized by the formation of a highly fluorinated layer with varying thickness and chemical composition, depending on the thin film nature. These results underscore the practical viability of reactive sputtering for the fabrication of micrometer-thick, high-quality plasma-resistant films suitable for application in plasma etching equipment.