Ion energy distributions in low pressure inductively coupled plasmas in E mode with varying noble gas content*

In this study, we investigate ion energy control in hydrogen plasmas, which are important for plasma etching due to their lightweight nature. This results in ions with smaller momentum impacting the plasma substrate. The ions transfer less kinetic energy compared to heavier ions, thereby reducing substrate damage. We used a retarding field energy analyzer to measure ion energy and ion flux in both pure hydrogen plasmas and hydrogen-noble gas plasmas, with concentrations of hydrogen ranging from 50% to 100%. The plasma was maintained at 100 W power (E-mode) in an inductively coupled Gaseous Electronics Conference reference cell, at pressures between 15 Pa and 30 Pa. The flow rates of the noble gas and hydrogen are adjusted and the total pressure is changed so that the partial pressure of hydrogen remains at 15 Pa, whilst the partial pressure of noble gas is varied. The results show that the ion flux changes by 2% when helium is added, in contrast to increasing the total pressure in pure hydrogen plasma and when argon is added which changes the ion flux by 20-23%. This indicates that noble gases can optimize plasma processing techniques, especially in applications requiring precise

control over ion flux.