Hollow oval magnetron for large-area low-energy ions

A novel device, the ‘‘hollow oval magnetron,’’ was designed and characterized. The device has a hollow electrode with an oval cross section. It sustains a large-area uniform plasma with low-energy ions under low pressure and moderate rf power (Ni ∼1011 cm−3, Γi ∼0.5 mA/cm2, Ei ∼30 eV, and P∼5 mTorr). The energy distribution of ion current onto the hollow electrode has a broad spread ΔEi /Ēi ∼1 in the rf mode, and a narrow peak ΔEi/ Ēi ∼0.1 with a low-energy tail in the dc mode. The device is a good candidate for low-energy high-rate plasma-material processing.