A New High-Performance Ion Source Based on Magnetically Neutral Loop Discharge

Abstract

We have developed a new high-performance ion source on the basis of the high-density plasma formation method known as magnetically neutral loop discharge (NLD). The ion source consists of three separate electromagnetic coils, an ion extraction electrode, and a quartz vessel plasma chamber with a one-turn RF antenna coil, which is the main component of conventional RF ion sources. The three electromagnetic coils are located around the periphery of the plasma chamber. The current in the middle coil flows opposite to the currents in the top and bottom coils. With this configuration, our source produces a high plasma density of 1011 cm-3, which is about ten times higher than that of a conventional source under a low gas pressure of 0.1 Pa. In addition, it is possible to control both the ring like plasma diameter and the high-density plasma generation position in the plasma chamber. As a result, we achieved a high ion current density of up to 1 mA/cm2 at 50 V of ion extraction voltage, which is almost five times higher than the conventional source. Furthermore, we also obtained a high ion current uniformity of ±5% over a 6-in.-diameter wafer using the source's plasma space controllability. A processing system that uses this ion source will contribute to faster processing, high-quality processing, and excellent-uniformity processing for ion beam etching, ion beam deposition, and ion beam sputter deposition. Many other applications are also expected.