Kinetics of Si(100) nitridation first stages by ammonia: Electron- beam-induced thin film growth at room temperature

Abstract

Kinetics of the first stages of Si(100) nitridation by pure ammonia have been investigated for the first time by Auger electron spectroscopy, low energy electron diffraction, and thermal desorption mass spectrometry. Thin nitride film growth is quite slow within the pressure and temperature ranges investigated (10−7–10−5 Torr and room temperature—1030 °C, respectively). At high temperatures (T>800 °C), our results confirm previous studies for Si(100) nitridation by atomic nitrogen; in particular, the kinetics obey a layer-by- layer mode of growth. Moreover, the first reacted layer formation rate is proportional to the ammonia pressure and limited by the dissociation rate of ammonia on the surface. Further growth upon nitridation is limited by diffusion of the reacting species through the reacted layer. The nitride film–silicon interface is quite abrupt. At low temperatures (T≲600 °C), the growth rate is negligible due to a small thermal dissociation rate of ammonia and a lower mobility of the reacting species. Room temperature reaction is enhanced by the electron bombardment giving rise to thin films and growth rates comparable to those obtained at the highest temperatures. This electron-beam-induced nitridation at room temperature is attributed to ammonia dissociation and nitrogen K-shell ionization under electron bombardment.