Study of electron behavior in a pulsed ion sheath

Abstract

In many plasma processing applications, like plasma immersion ion implantation (PIII), the substrate is immersed in low pressure plasma and is biased with negative voltage pulses. In typical PIII, the pulse duration is much larger than the ion response time, and hence the ion matrix sheath expands and ion implantation happens on the biased substrate. It is assumed that for pulse duration shorter than ion response times, the ions remain stationary and electrons are repelled by the negative bias. In the present investigation, the negative pulse duration is varied between ion and electron plasma response times; so as to study the electron behavior assuming ions are stationary. The results indicate that the electrons that are lost to the walls come from the ion matrix sheath and probably from the bulk plasma as well. The pulse duration, when it is less than the ion response time, plays a crucial role in determining the number of electrons lost to the walls.