New-type focused fast atom beam (F-FAB) source and evaluation of emitted beam density distribution

We have developed a new type of focused fast atom beam (F-FAB) source, which we call radial-surface electrode F-FAB source (RSEFF source), and evaluated its emitted beam density distribution. The F-FAB source consists of two electrodes whose shapes and downstream cathode holes are designed to focus the beam on a point. The neutralization ratio of the beam emitted was 2–10 times higher than that of beams emitted by conventional F-FAB sources. To evaluate the emitted F-FAB density distribution, we used the RSEFF with chlorine gas to etch GaAs workpieces. The etched depth distributions were measured for three different distances between the focus point and the workpiece surface (at the focus point, and at 20 mm above and below the focus point). The results confirmed that the RSEFF source is stable and emits a focused neutral chlorine beam that has the narrowest and highest HMFW (half-maximum, full-width) of the beam density distribution when the workpiece is at the focus point. Moreover, the results showed that the etched depth distribution is effective for evaluating the beam density distribution. We then successfully used the RSEFF to produce contracted pattern etching, demonstrating the applicability of the RSEFF to contracted projection processing.