Citation

McDaniel GY, Fenstermaker ST, Lampert WV, Holloway PH. J. Appl. Physics 2004; 96(9): 5357-5364.

Copyright

(Copyright © 2004, American Institute of Physics)

DOI

10.1063/1.1797550

PMID

unavailable

Abstract

Rhenium (Re) thin-film contacts (100-nm thick) were deposited on carbon-rich, nominally stoichiometric, and silicon-rich 6H-SiC surfaces, which were moderately doped with nitrogen (1.28×10 18 cm -3). Morphology (Dektak), phase formation (x-ray diffraction), chemistry (Auger electron spectroscopy), and electrical properties (I- V) were characterized for the as-deposited and annealed (120 min, 1000°C, vacuum <1 × 10 -6 Torr) contacts. As-deposited films were nonohmic. Films grown on carbon-rich surfaces were nonspecular, granular, and often delaminated during characterization. At room temperature in air, the Re films on stoichiometric SiC remained optically specular reflecting for 3 h, but then became hazy from oxidation. The Re films on silicon-rich surfaces, stored in air at room temperature, resisted ex situ oxidation for approximately 24 h. The annealed samples remained specular without visible signs of oxidation. The annealing resulted in a reduction in surface roughness for all the films regardless of substrate chemistry. The phase separation between carbon and rhenium was observed based on the formation of interfacial Re clusters and a ∼10-nm graphite surface layer after annealing. Auger data showed that Si layers (5-10 nm) deposited to create Si-rich surfaces were partially consumed to form rhenium suicide during annealing, and the sharp Re/Si/SiC interface became more diffused with Re detected ∼50 nm deeper into the structure. The annealing of Re films on moderately doped (1.28×10 18 cm -3) SiC resulted in ohmic contacts with an average specific contact resistance of 7.0×10 -5 ω cm 2 for stoichiometric and 1.6×10 -5 ω cm 2 for silicon-rich samples. The annealed contacts on carbon-rich surfaces remained rectifying. © 2004 American Institute of Physics.

Language: en

Keywords

Silicon carbide; Oxidation; Ohmic contacts; Morphology; X ray diffraction analysis; Crystal structure; Auger electron spectroscopy; Surface roughness; Band-gap; Carbon rich surfaces; Phase formations; Rhenium; Substrate chemistry