Plasma Properties of a Negative Ion Plasma Reactive Ion Etching System

Abstract

In high density reactive ion etching (RIE) systems it has been found that there is an aspect ratio charging effect which causes damage, RIE lag and loss of ion current to the bottom of high aspect structures. It has been shown by a number of authors, that one way of reducing these effects is to reduce the electron temperature of the plasma which is above the wafer. We have characterized the plasma properties of a medium to high density plasma system which uses a magnetic filter in an inductively coupled plasma (ICP) to produce a low temperature negative ion plasma above the wafer. At 4 mTorr, the electron temperature of this negative ion plasma is 1/3 of that for the same system without the filter. We present uniformity data and electron temperature data versus pressure and magnetic potential.