The characterization of a magnetron-sputter-type negative-ion source

Abstract

Characteristics of an 8-in.-diam magnetron-sputter-type negative-ion source (MSNIS) were investigated. A negative sputtered ion beam is generated by a cesium-induced sputter type secondary negative-ion beam emission process. The plasma properties were obtained using a cylindrical Langmuir probe method. The measured electron temperature was approximately 2–5 eV, while the plasma density and plasma potential were of the order of 1011–1012 cm−3 and 5–20 V, respectively, depending on the pressure and power. A retarding field analyzer with four biasable grids measured the energy distributions of sputtered Mo− beams. The transparency of the analyzer was 22.4%. The negative-ion energy is defined by the potential of sputter cathode. The process pressure was found to have a negligible effect on ion-beam energy, but did affect the ion-beam energy spread. At low pressures (approximately 4×10−4 Torr), the energy spread was 2% of the beam energy, while an average energy spread of less than 5% of beam energy was measured at 10−3 Torr. The result shows that a well-defined negative metal ion beam can be effectively produced on a large scale.