Substrate heating effects on composition, structure and ferromagnetic resonance properties of CoFeB thin films

We investigate the ferromagnetic resonance and crystallinity properties of CoFeB thin films grown on Si (100), at substrate temperatures from 20 degrees C to 800 degrees C. The X-ray diffraction data show that the CoFeB films are amorphous when deposited at a substrate deposition temperature of less than 500 degrees C. X-ray diffraction peak analysis matched the crystalline peaks of films grown at 500 degrees C to a face-centered cubic (110) Co7Fe3 phase. Increasing the substrate deposition temperatures increased above 600 degrees C leads to the formation of a face-centered cubic silicide FeCo2Si (220) and oxide Fe2CoO4 (400). Upon crystallization into different phases at a substrate deposition temperature above 500 degrees C, the soft ferromagnetic properties of CoFeB are lost. The coercivity of the deposited thin films increases from 20 Oe at room temperature to a maximum of 275 Oe at 700 degrees C. The peak-to-peak ferromagnetic resonance linewidth at 15 GHz, increases from 80 Oe at room temperature to 790 Oe at 500 degrees C. The grain size of the as-deposited samples increases with substrate temperature from 20-nm at room temperature to 241-nm at 800 degrees C as determined by atomic force microscopy.