An improved form of the oscillating electron electrostatic ion source for ion etching

The performance of the oscillating electron electrostatic ion source has been improved by incorporating a small chimney into the ion exit aperture to reduce the field distortion at the aperture. A focussing electrode placed near the aperture, and at a negative potential with respect to the cathode, has also been added. This increases the ion beam intensity and also increases the total ion beam current by extracting more low energy ions from the source. When the source is used for ion etching, the specimen can be placed at some distance from the source to reduce the heating of the specimen by radiation from the source. Using argon ions, etching rates of copper film of more than 10 μm^?1 h have been observed with this improved source. It has also been found that the ion beam contains electrons which are suppressed with the focusing electrode at more than 100 V. Thus it was found that to satisfactorily etch a glass specimen it was necessary to operate with the focussing electrode at cathode potential to avoid the build up of charges on the glass.