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

Abstract

This paper presents the results obtained on cobalt layers after rapid thermal annealing in N2 ambient at temperatures between 525 and 800°C. The cobalt layers were deposited by chemical vapor deposition from Co(CO)3NO on to oxidized-Si substrates at 450°C. As the anneal temperature increases from 525to800°C the percentage layer resistivity decrease goes from 35% to 55%. The lowest resistivity achieved was ∼11μΩcm for 300-nm-thick layers and ∼14μΩcm for 180-nm layer annealed in the range of 650–800°C. XRD analysis shows that a mixture of fcc and hcp 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 200–300nm ranges for both 180- and 300-nm layers. From the hysteresis loops it was found that the coercivity values are significantly reduced to 25Oe from 350 and 140Oe due to high-temperature annealing to give soft magnetic property.