Gas Mixing Effect on Ion Current Spectrum and Its Application to Optimize Implantation Source Gas-Composition

In a Penning discharge ion source, He (small atomic number) and Ar (large atomic number) gases are shown to play the roles of diluent and excimer, respectively, when mixed with O2. The gas composition is optimized at Ar(0.1%)–He(90%)–O2(10%), producing a high O+ ion current as well as good operation and maintenance of the implanter. In both N2–O2 gas mixture and N x O y compound gas, the O+ ion current is almost proportional to the oxygen content. A high NO+ molecular current is obtained with NO compound gas, rather than with N2(50%)–O2(50%) gas mixture. The present results are a valuable guide to the selection of other gas mixtures for implantation.