Effect of reactive-ion bombardment on the properties of silicon nitride and oxynitride films deposited by ion-beam sputtering

Silicon nitride and oxynitride films of very low hydrogen content have been deposited on silicon at low temperatures (150–200 °C) using ion-beam sputtering. A dual-ion-beam sputtering technique, making simultaneous use of an energetic argon-ion beam to sputter silicon nitride from a target and a low-energy oxygen or nitrogen ion beam to react with the sputtered films on the substrate, has been employed to control the composition of the films. A precise control of film composition independent of deposition rate has been achieved through the control of oxygen/nitrogen ion-beam parameters and gas flow ratios. The films have been characterized by the measurement and study of refractive index, chemical etch rate, infrared absorption, and x-ray photoelectron spectra. A direct correlation between film properties with oxygen content has been obtained for silicon oxynitride films. The electrical properties have been studied by the measurement of the characteristics of metal-insulator-semiconductor capacitors fabricated using the deposited films. In situ ion-beam oxidation of silicon prior to the oxynitride deposition has resulted in a film with a low insulator charge number density (3.5×1011 cm−2) and interface trap density (4×1011 cm−2 eV−1), which is suitable for device applications.