Low Temperature Cleaning of Ge and GaAs Surfaces Using Hydrogen Dissociated with a Remote Noble-Gas Discharge

The native oxides of Ge and GaAs have long been known to preclude the formation of suitable MIS structures. In situ cleaning of Ge and GaAs surfaces has been achieved at 300–375 °C using a novel technique employing hydrogen that is dissociated using a remote Ar discharge. Such a technique circumvents the problems of cross contamination introduced from a directly excited hydrogen discharge due to erosion of the quartz tube walls by the active hydrogen. Reconstructed surfaces characteristic of clean Ge and GaAs surfaces have been observed with Reflection High Energy Electron Diffraction (RHEED) following such a treatment. Auger and X-ray Photoelectron Spectroscopy (XPS) analyses show that such a treatment removes both oxygen and carbon contamination from the surface. XPS window scans on the Ga-3d and the As-3d peaks show that the treatment is successful in removing oxygen bonded to both Ga and As on the GaAs surface.Following the in situ cleaning, excellent MIS structures on Ge and GaAs have been realized with a novel structure that utilizes an ultra-thin Si interlayer (1.5 nm) between the insulator-oxide and the clean semicondutor surface. The Si interlayer prevents any sub-cutaneous oxidation of the underlying semiconductor while exploiting the advantages of the excellent Si-SiO2 interface. The entire structure is fabricated in a single-chamber remote plasma CVD unit.