Efficient production of negative hydrogen ions in RF plasma by using a self-biased grid electrode

Abstract

ABSTRACT:Volume production of negative hydrogen ions is established efficiently in a pure hydrogen RF discharge plasma by using a self-biased grid electrode for production of low electron-temperature and high density plasma. Using this electrode both high and low electron temperature plasmas are produced in the regions separated by the grid electrode in the chamber, in which the electron temperature in the downstream region is controlled by the mesh size and plasma production parameters. The production rate of negative ions depends strongly on the electron temperature varied by the RF input power and hydrogen pressure. In the case of the grid electrode with the 5 mesh/in., the negative hydrogen ions are produced effectively in the downstream region in the hydrogen pressure range of 0.9 − 2.7 Pa. In addition, the production rate of the negative ion H − raises from 62 % to 87 % at 0.9 Pa by changing the RF power from 20 W to 80 W.