Y₂O₃ thin film as an inorganic plating compliant with RoHS regulations of chromium-containing materials is deposited by a two-step process, magnetron sputtering deposition of an yttrium metal and following oxidization. We discussed crystalline property and resistance to harsh environments of the films deposited by this method.

In the first magnetron sputtering deposition process, the Y metal was deposited with RF (Radio frequency) power of 30 W. The Ar process gas was used at the flow rate of 10 sccm (standard cubic centimeter per minute) and pressure in the process chamber during the deposition was fixed at 3 Pa. The substrate was (100)-oriented Si wafer. Immediately after the sputtering deposition for 30 min, the Y film was installed into a furnace and heated in the atmosphere for 30 min as the second oxidization process. From in-plane X-ray diffraction (XRD), we found that in-plane oriented Y₂O₃ was grown on the Si substrate and the (440) diffraction peak was intensified with increasing oxidization temperature up to 675°C. Above this temperature, the Y₂O₃ was translated to randomly orientated polycrystalline film. On the other hand, the deposited film using a single-step process with an Y₂O₃ target was amorphous in our experimental conditions.

We investigated resistance of the in-plane oriented Y₂O₃ film to halogen plasma. The plasma gas was CF₄ or SF₆. We compared the etching rate between the Si wafer and the Y₂O₃ film. The etching rate of Y₂O₃ and ratio to that of Si were 2 nm/min and 0.05 for CF₄, and < 4 nm/min and < 0.0056 for SF₆. The result indicates high resistance of the Y₂O₃ film to the halogen plasma, especially for SF₆; the Y₂O₃ film has a potential ability as a plating material to avoid erosion of an inside wall of semiconductor process chambers using halogen plasma.

This work is partly supported by Grant-in-Aid for Scientific Research (C) (19560029) from The Ministry of Education, Culture, Sports, Science and Technology, Japan.

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