Uniaxial anisotropy and high-frequency permeability of novel soft magnetic FeCoTaN and FeCoAlN films field-annealed at CMOS temperatures

In order to investigate the anisotropy and high-frequency behaviour, soft magnetic FeCoTaN and FeCoAIN films were fabricated by reactive RF-magnetron sputtering. Six-inch targets consisting of Fe47Co36Ta17 and Fe49Co36Al15 Were used to grow the films on oxidized (100)-silicon substrates with a TiN seed layer for better film adhesion. The concentration of nitrogen was adjusted by a flow control system. For applications in, e.g., aluminium CMOS processed components the films were annealed at temperatures of about 400degreesC in a static magnetic field of 50 mT to induce a uniaxial anisotropy in the film plane by activating an atomic ordering process. Controlling the anisotropy by annealing demands a specified elaboration and results in an in-plane uniaxial anisotropy between 3 and 4 mT. Nitrogen in both materials caused the formation of TaN or AlN which mainly supported the suppression of polycrystalline film growth. After deposition the films showed an amorphous structure and turned to be nanocrystalline after the annealing procedure. A saturation polarization in both materials amounted to between 1.1 and 1.2 T. Ferromagnetic resonance frequencies of about 1.9 GHz for FeCoTaN and 1.8 GHz for FeCoAlN, determined by measuring the frequency-dependent permeability by means of a strip line permeameter up to 5 GHz, were observed. The experimental results where compared with a spin dynamic model based on the Landau-Lifschitz and Maxwell's eddy current equation in the total frequency range. (C)0 2004 Published by Elsevier B.V.