Effect of rapid thermal annealing on the structure and magnetic properties of chemical vapor deposition cobalt layers

This paper presents the results obtained on cobalt layers after rapid thermal annealing in N-2 ambient at temperatures between 525 and 800 degrees C. The cobalt layers were deposited by chemical vapor deposition from Co(CO)(3)NO on to oxidized-Si substrates at 450 degrees C. As the anneal temperature increases from 525 to 800 degrees C the percentage layer resistivity decrease goes from 35% to 55%. The lowest resistivity achieved was similar to 11 mu Omega cm for 300-nm-thick layers and similar to 14 mu Omega cm for 180 -nm layer annealed in the range of 650-800 degrees C. XRD analysis shows that a mixture of fcc and hep cobalt grains is present in the as-deposited material. As the annealing temperature increases the fcc Co peaks increase due to crystallization of the material. This was confirmed by surface and microstructure analysis using SEM and AFM. The grain, size had significantly increased to 200-300 nm ranges for (b)oth 180- and 300-nm layers. From the hysteresis loops it was found that the coercivity values are significantly reduced to 25 Oe from 350 and 140 Oe due to high-temperature annealing to give soft magnetic property. (c) 2005 American Institute of Physics.