Effects of Electron Beam Irradiation and Subsequent Cl_2 Exposure on Photo-Oxidized c(4×4) GaAs : Mechanism of In Situ EB Lithographic Patterning

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The effects of electron beam (EB) irradiation and subsequent Cl_2 exposure on GaAs surface photo-oxides were investigated using X-ray photoelectron spectroscopy. Photo-oxides formed by visible-light-enhanced oxidation of c(4×4) GaAs surfaces were irradiated by an electron beam of 1.5 keV energy with doses ranging from 7.1×10^<16> to 2.1×10^<18> electrons/cm^2. Chlorine was subsequently dosed up to 20 langmuirs using a AgCl electrochemical cell. Chlorine was not adsorbed on the photo-oxides, whereas it was readily adsorbed on EB-irradiated photo-oxides. EB irradiation induced the reduction of As^<5+> and As^<3+> oxides to less-oxidized As suboxides and/or elemental As, as well as partial removal of surface oxygen. An increase in the amount of Ga oxides was also observed. Chlorine exposure resulted in preferential removal of the EB-induced As suboxides and/or elemental As, as well as removal of As in the GaAs substrate and formation of Ga-Cl bonds. We attribute this to the desorption of AsCl_3, and conclude that this "etching" of the surface As oxide is the key to patterning a photo-oxide mask.
社団法人応用物理学会の論文
1994-10-01