Ion beam diagnostic studies of high current RF ion source

A compact high current RF ion source has been designed and developed for production of low energy high current density microbeam for high speed fabrication of micropatterns on substrates of various materials. In order to obtain micron size high current beams, it is essential that ion beam should have very low emittance, high angular current density and low energy spread. Systematic studies have been carried out to investigate these properties and measurements of ion beams of various gaseous elements shows the energy spread of < 4eV and the normalized emittance of about < 0.01 mm-mrad-eV for the range currents between 0.5 - 1.5 mA. Angular current density > 30 mA/Sr for heavy ion such as Xe and 45 mA/Sr for light ions such as protons have been obtained. These angular current densities are three orders larger than that obtained in the conventional ion sources used in production of micro/nano sized ion beams. Various methods have been adapted to improve emittance, energy spread and angular current density. The extraction characteristics of the ion source show the extracted current densities through 2 mm aperture are in the range of 50-80 mA/cm2 at RF power of < 200 W for ions of almost all gaseous elements. This ion source has been found to produce highly stable ion beam over 10's of hours of continuous operation. In this article the methods employed in improving the basic characteristics of the ion beam, measurements and the experimental results will be presented. (author)