Low-temperature (≤150 °C) chemical vapor deposition of pure cobalt thin films

Abstract

High purity soft-magnetic cobalt films were grown by cyclic thermal–chemical vapor deposition (CVD) process using dicobalt octacarbonyl as metal organic precursor, at an optimum substrate temperature of 125 °C. Physical, electrical, and magnetic properties of CVD grown Co films were compared with physical vapor deposition (PVD) grown Co films. Films were analyzed by x-ray photoelectron spectroscopy, x-ray diffraction, four-point resistivity probe, scanning electron microscopy, hysteresis loop tracer, vibrating sample magnetometry, and atomic force microscopy. The authors observed in-plane uniaxial magnetic anisotropy in the CVD-grown cobalt film with cyclic pulse-purge technique. Typical film properties obtained were low volume resistivity (<20 μΩ cm), >99.5% purity, 100% growth linearity as a function of number of cycles, good step coverage in a SiO2 trench, low coercivity (<15 Oe), high saturation magnetization (∼1.5 T), and low root-mean-square surface roughness (7 Å). Compared to our PVD films, CVD Co films are magnetically softer, smoother, and less textured.