Study of Reactive Ion Etching of the Si3N4/GaAs Interface in CF4 Plasmas by X-Ray Photoelectron Spectroscopy and X-Ray

The etching mechanism of the Si3N4-GaAs(0Ol) interface in CF 4 plasmas is studied by two complementary spectrosco-pies, x-ray photoelectron spectroscopy (XPS) and x-ray photoelectron diffraction (XPD). Following the removal of the Si3N4 layer, the etching reaction is shown to be rate-limited by the formation of a highly fluorinated gallium layer. The total fluoride thickness grows very slowly with increased plasma exposure. Elemental arsenic located between the gallium fluoride layer and the GaAs (001) substrate is also observed in the XPS spectra. The plasma etching_reaction produces some structural damage within the GaAs lattice. The thickness of the damaged layer is estimated using a homogeneous multilayer model and the XPD patterns. After annealing at 400 ~ elemental As is removed and the structural damage is reduced. Dry etching technology for GaAs devices has been widely developed, for example in plasma etching of Si3N4 films on GaAs substrates or in ion beam etching for gate formation in GaAs MESFETs (1, 2). These techniques are very useful for fine patterning as they allow control of the etching process (etch rate and anisotropy), which is not th