Chemical erosion of amorphous hydrogenated boron films

Amorphous-hydrogenated boron (a-B:H) and carbon (a-C:H) thin films were prepared by radio-frequency plasma deposition using (B2H6+H2) or CH4 as a precursor gas. The film composition and density were investigated by ion-beam analysis. The films were eroded by hydrogen electron cyclotron resonance plasmas at floating potential and by atomic hydrogen dissociated by a hot filament. The temperature of the substrates was increased during the erosion process from 330 to 680 K. Erosion rates were measured in situ by ellipsometry. a-B:H films are shown to be much more resistant to erosion by hydrogen ions (H+) and atomic hydrogen (H0) than a-C:H films. In contrast to a-C:H films, no chemical erosion of a-B:H films by H0 was observed at temperatures below 600 K. Ion energies lower than the threshold energy for physical sputtering cause measurable erosion rates for a-B:H films. It is concluded that this is a synergistic effect of simultaneous H0 and H+ bombardment and it is designated as ion-induced chemical erosion.