Role of GaAs surface cleaning in plasma deposition of silicon nitride films for encapsulated annealing

Abstract

The role of GaAs surface cleaning and plasma reactor cleaning prior to deposition of silicon nitride films for encapsulated annealing has been investigated. X-ray photoelectron spectroscopy was employed to determine the surface characteristics of GaAs treated with HCl, HF, and NH4OH solutions preceded by a degreasing procedure. The HCl clean left the least amount of oxygen on the surface. Fluorine contamination resulting from the CF4 plasma used to clean the reactor was found to be located at the film-substrate interface by Auger electron spectroscopy with argon-ion sputtering. A modified deposition procedure was developed to eliminate the flourine contamination. Plasma deposition of silicon nitride encapsulating films was found to modify the I-V characteristics of Schottky diodes subsequently formed on the GaAs surface. The reverse current of the diodes was slightly reduced. Substrates implanted with Si at 100 keV and a dose of 5×1012/cm2 showed a peak electron concentration of 1.7×1017/cm3 at a depth of 0.1 μm with 60% activation after encapsulation and annealing at 800 °C for 7 min.