SOLID-STATE REACTION OF PT THIN-FILM WITH SINGLE-CRYSTAL (001) BETA-SIC

Thermally induced solid-state reactions between a 70 nm Pt film and a single-crystal (001) beta-SiC substrate at temperatures from 300-degre es-C to 1000-degrees-C for various time durations are investigated by 2 MeV He backscattering spectrometry, x-ray diffraction, secondary ion mass spectrometry, scanning electron microscopy, and cross-sectional transmission electron microscopy. Backscattering spectrometry shows th at Pt reacts with SiC at 500-degrees-C. The product phase identified b y x-ray diffraction is Pt3Si. At 600-900-degrees-C, the main reaction product is Pt2Si, but the depth distribution of the Pt atoms changes w ith annealing temperature. When the sample is annealed at 1000-degrees -C, the surface morphology deteriorates with the formation of some den drite-like hillocks; both Pt2Si and PtSi are detected by x-ray diffrac tion. Samples annealed at 500-900-degrees-C have a double-layer struct ure with a silicide surface layer and a carbon-silicide mixed layer be low in contact with the substrate. The SiC-Pt interaction is resolved at an atomic scale with high-resolution electron microscopy. It is fou nd that the grains of the sputtered Pt film first align themselves pre ferentially along an orientation of {111}Pt // {001}SiC without reacti on between Pt and SiC. A thin amorphous interlayer then forms at 400-d egrees-C. At 450-degrees-C, a new crystalline phase nucleates discrete ly at the Pt-interlayer interface and projects into or across the amor phous interlayer toward the SiC, while the undisturbed amorphous inter layer between the newly formed crystallites maintains its thickness. T hese nuclei grow extensively down into the substrate region at 500-deg rees-C, and the rest of the Pt film is converted to Pt3Si. Comparison between the thermal reaction of SiC-Pt and that of Si-Pt is discussed.