Solid-state reaction of Pt thin film with single-crystal (001) β–SiC

Abstract

Thermally induced solid-state reactions between a 70 nm Pt film and a single-crystal (001) β-SiC substrate at temperatures from 300 °C to 1000 °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 that Pt reacts with SiC at 500 °C. The product phase identified by x-ray diffraction is Pt₃Si. At 600–900 °C, the main reaction product is Pt₂Si, but the depth distribution of the Pt atoms changes with annealing temperature. When the sample is annealed at 1000 °C, the surface morphology deteriorates with the formation of some dendrite-like hillocks; both Pt₂Si and PtSi are detected by x-ray diffraction. Samples annealed at 500–900 °C have a double-layer structure with a silicide surface layer and a carbon-silicide mixed layer below in contact with the substrate. The SiC—Pt interaction is resolved at an atomic scale with high-resolution electron microscopy. It is found that the grains of the sputtered Pt film first align themselves preferentially along an orientation of (111)_Pt//(001)_SiC without reaction between Pt and SiC. A thin amorphous interlayer then forms at 400 °C. At 450 °C, a new crystalline phase nucleates discretely at the Pt-interlayer interface and projects into or across the amorphous interlayer toward the SiC, while the undisturbed amorphous interlayer between the newly formed crystallites maintains its thickness. These nuclei grow extensively down into the substrate region at 500 °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.