RF-compensated Langmuir Probe Diagnostics of Pulsed Plasma Ion Implantation System

Abstract

The core of this project focuses on the development of a method for prediction of ion implantation dose in processing plasmas. The vital variable is fluence, i.e. ion implantation dose, which is currently predicted by Lieberman model during high-voltage Plasma Ion Implantation (PII). Chapter \ref{chap:intro} starts with an introduction of plasma ion implantation. In chapter \ref{chap:model}, a review of Lieberman model's assumptions as well as a discussion on the limitations of model and the observed discrepancies with measurements are provided.

Having a better, more accurate model to get the fluence, is necessary for improving the implantation procedure. Inductively Coupled Plasma (ICP) chambers are used widely for plasma ion implantation. One of the ICP chambers in University of Saskatchewan, ICP-600, is provided with a radio-frequency antenna to provide the power to heat the electrons and therefore ionise the gas. The apparatus is discussed in detail in chapter \ref{chap:apparatus}.

To have an understanding of the evolution of the plasma during plasma ion implantation (PII), a full characterisation of plasma is required before and during PII. Acquiring plasma parameters accurately has the utmost importance while characterising plasma with a Langmuir probe. Eliminating radio-frequency waves from the acquired current-voltage curves in a RF-driven plasma has the most effect toward improving electron temperature measurements in such plasmas. In chapter \ref{chap:Langmuir}, the importance of RF-compensation in design and implementation of Langmuir probes is discussed in detail. Also, a discussion on different current-voltage analysis theories is provided.

The results of this work is presented in chapter \ref{chap:results}. Demonstrating the importance, RF-compensated results in the steady state argon plasma will be presented in the first part of the chapter. Finally, the time-resolved characterisation of plasma during PII for a metal target, namely stainless steel and a semiconductor target, i.e. silicon, will be presented and discussed in the later part of the same chapter. These experimental data are an important step in order to develop a more accurate model for plasma ion implantation through detecting and taking into account the effective instabilities during the process.