Mechanism of germanium plasma nitridation

Abstract

The mechanisms of plasma nitridation of germanium (Ge) and silicon (Si) substrates are discussed based on plasma characteristics and oxynitride film properties. Optical emission spectroscopy (OES) study and x-ray photoelectron spectroscopy were utilized to characterize the plasma and film properties, respectively. In this study, high pressure (1.8Torr) remote inductive coupled plasma and low pressure (<50mTorr) radial line slot antenna (RLSA) plasma nitridation processes are utilized to form germanium oxynitride (GeON) and silicon oxynitride (SiON) film. OES results show that high pressure remote plasma nitridation is a radical dominant process. In this process, hydrogen containing neutral radicals (NH* and H*) were important to nitride Ge and Si substrates. This process required high substrate temperature to nitride Ge substrate, whereas Si substrates could be nitrided at low substrate temperature. Low pressure RLSA plasma nitridation is an ion dominant process. In this, N2+ ion species acted as dominant reactive species. Using this process, germanium could be nitrided at low substrate temperature without hydrogen and high nitrogen concentration (∼22at.%) GeON was obtained.