Semi-insulating GaAs (100) was exposed to hydrogen atoms that were produced in a remote microwave plasma. The flux of hydrogen atoms was determined by isothermal calorimetry. Hydrogen atom partial pressures between 3 and 51 mTorr were found to etch GaAs continuously at rates that ranged from 3 to 40 nm/min at tern B eratures above 200 "C. The rate coefficients could be fitted to the Arrhenius equation, k= 105.2'o. nm min-* Torr-' e-".a5'o.05 eVfltT, between 200 and 360 "C. The surfaces etched crystallographically and were found to become arsenic deficient. The possible intluence of hydrogen atom absorption by GaAs is considered. 0 1995 American Institute of Physics.

No abstract

To simulate the low energy ion bombardment that occurs in reactive ion etching (RIE) using alkanes, GaAs and InP were exposed to 20, 100, and 500 eV carbon ions, using a mass-separated carbon ion beam in an ultrahigh vacuum chamber. The InP sample structure consisted of a 40 Å ultrathin, epitaxial InP layer on InGaAs. The changes induced by ion bombardment and the effects of subsequent damage-removal treatments were determined by in situ polar-angle dependent x-ray photoelectron spectroscopy. Initially, carbon ion irradiation caused minor sputtering of the semiconductors and preferential removal of the group V constituents, with concurrent formation of carbon-semiconductor phases. The depth of these phases and the extent of the damage increased with increasing bombardment energy. An amorphous carbon residue formed after further bombardment. Several damage removal techniques were applied to the carbon bombarded surfaces. It was found that heating was ineffective in annealing the damage, although surface Fermi level movements were observed. Ozone oxidation did not remove the residual carbon efficiently, yet the underlying semiconductor components were readily oxidized. Hydrogen ion bombardment was effective in removing the carbon bombardment induced damage. The implications of these results for alkane based RIE processes are discussed.

GaAs (100) wafers were etched in mixtures of hydrogen atoms and methyl radicals. The atoms were formed in a remote hydrogen plasma, and a fraction of these were converted into methyl radicals by introducing methane into the flow system upstream from the semiconductor surface. The flux of hydrogen atoms into the reaction chamber was determined by isothermal calorimetry. The methyl radical flux passing over the substrate was then calculated using previously determined rate parameters for the reaction between atomic hydrogen and methane, and a simple modeling program. The GaAs etch rates were about an order of magnitude faster when methyl radicals were present in the hydrogen atom stream, and were found to follow a first-order dependence on the partial pressure of methyl radicals. Absolute rate constants were determined and an Arrhenius activation energy of 1.2 kcal mol-l was calculated. The values of K and E, are consistent with a diffusion-controlled process. SEM photographs of the surface revealed small crystallographic features that made the surface appear very rough. XPS analysis indicated that these surfaces were arsenic deficient. A mechanism is proposed for the etching of GaAs by a combination of methyl radicals and hydrogen atoms.

No abstract