| Electron stimulated oxidation (ESO) and rhenium (Re) metallizations on α-silicon carbide (6H-SiC) were studied. ESO was quantified versus electron beam exposure, total vacuum pressure, beam energy Ep (3 to 6 keV), and current Ip (25 to 500 nA), while monitoring chemical change using Auger electron spectroscopy (AES). Vacuum chamber pressures below 2.6 × 10 −8 Torr required beam irradiation to induce oxidation. A positive linear correlation between oxidation rate and total chamber pressure was observed. Rate did not correlate with concentration of a particular ambient species (H2O, CO, or CO2). Oxidation rate decreased with increased Ep suggesting surface secondary electrons stimulate oxidation. Dependence of oxidation rate on Ip indicated current limited dissociation below 200 nA.; Rhenium contacts (1000 angstroms thick) were deposited on carbon-rich, stoichiometric, and silicon-rich 6H-SiC surfaces. Morphology (Dektak), texture (X-ray diffraction (XRD)), chemistry (AES), and electrical properties (current/voltage (I–V)) were characterized for as-deposited and annealed (120 minute, 1000°C, <1 × 10−6 Torr) contacts.; As-deposited films were non-ohmic with total contact resistances of 59, 1620 and 110 ohms for carbon-rich, stoichiometric, and silicon-rich surfaces, respectively. Films grown on carbon-rich surfaces were non-specular, granular, and often delaminated during characterization. Island-growth was observed on stoichiometric surfaces with thickness variations of ∼800 angstroms. Films remained specular for 3 hours, but then became hazy from oxidation. Textured (101) growth was observed on silicon-rich surfaces. Thickness varied by ∼250 angstroms and films resisted ex-situ oxidation for more than 24 hours.; Annealed samples remained specular without visual signs of oxidation. Films were smoothed with thickness variance less than 100 angstroms. Phase separation was observed based on formation of interfacial Re clusters and ∼100 angstrom graphite surface layers. Auger confirmed as-deposited Si layers (50 to 100 angstroms) were consumed by reaction during annealing and Re/Si and Si/SiC interfaces were diffused ∼500 angstroms more compared to as-deposited interfaces. Annealed contacts were largely ohmic with averaged total contact resistances reduced to 11,3.2, and 1.4Ω for carbon-rich, stoichiometric, and silicon-rich samples, respectively. Average specific contact resistances of 7.0 × 10−5 Ωcm2 for stoichiometric and 1.6 × 10−5 Ωcm2 for silicon-rich samples were observed. |
