A new approach to dry etching of GaAs, digital etching, has been demonstrated. In digital etching, the etchant and an energetic beam, which induces chemical sputtering at the surface, alternately impinge onto the surface. Electrons and Cl2 gas were used as the energetic beam and the etchant, respectively, in the present experiment. Etching rates of 1/3 monolayer/cycle, independent of Cl2 flux and electron current density, were obtained. The present results show that an inherent self-limiting mechanism is involved and that the etching process is limited by the adsorption of etchant. This digital etching technique is expected to be applied to the fabrication of well-defined quantum wire and quantum box structures.
Characteristics o digital etching using an electron-beam-excited plasma system in GaAs are reported. In digital etching, etchant gas pulses and Ar ions are sequentially impinged onto the substrate surface to be etched. When the energy of Ar ion is -17 eV, etch rates which correspond to the 0.5 monolayer (ML) per cycle of GaAs (0.142 nm) are obtained between 0.3 and 0.5 seconds of Cl2 feed time by using Cl radicals as etchants. With these etching parameters, a rectangular cross-sectional etch profile with smooth surface is obtained. Damages induced in digital etching was characterized by current-voltage measurement of the diode fabricated after the etching.
We have developed a new type of ion source which is excited by a low energy and high current electron beam. The source has an extractable ion current density up to 0.62 A/cm2 and a low acceleration voltage less than 60 V. This ion source will open a new way for low energy ion processing like damageless ion etching, ion beam crystal growth and deposition.
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