Interfacial reaction and adhesion between SiC and thin sputtered cobalt films

Thin sputtered cobalt films on SiC were annealed in an Ar/4 vol% H₂ atmosphere at temperatures between 500 and 1450 °C for various times. The reaction process and the reaction-product morphology were characterized using optical microscopy, surface profilometry, X-ray diffraction, scanning electron microscopy and electron probe microanalysis. The relative adhesive strength between the film and substrate was determined by the scratch test method. Below 850 °C sputtered cobalt with a thickness of 2 m on SiC showed no detectable reaction products. Cobalt initially reacted with SiC at 850 °C producing Co₂Si and unreacted cobalt in the reaction zone. At 1050 °C the first-formed Co₂Si layer reacted to CoSi, and carbon precipitates were formed in the reaction zones. Sputtered thin cobalt layers reacted completely with SiC after annealing at 1050 °C for 2 h. Above 1250°C only CoSi was observed with carbon precipitates having an oriented structure in the reaction zone. Above 1450°C, a significant amount of graphitic carbon in the reaction zone was detected.