Magnetron sputtering of permalloy for thin-film heads

Thick permalloy films, as needed für magnetic recording heads, lend themselves to sputtering with the high-rate magnetron method. Special magnetron cathodes, with a field strength about three times higher than usual, have been used. With a 6 mm thick target, more than 900 substrates (diameter 7.62 cm) can be deposited with one micron of permalloy. The sputtering rates were about 100 to 150 nm/min. DC bias of about 100 V and a magnetic field of ≥35 A/cm were needed for anisotropy and soft magnetic film properies. Argon-nitrogen mixtures were used as the sputtering gas, the nitrogen content being 0 to 2.8 %. Electrical resistivity and coercivity values are given for film thicknesses between 0.13 and 2 microns. Film composition was measured by X-ray fluorescence and AES methods. Though the nitrogen content in the film is smaller than 0.5 % (mole fraction), the coercivity shows a rapid decrease from 0.4 to 0.2 A/cm with increasing nitrogen in the sputtering gas. The same results have been found also for NiFe films, sputtered in a conventional RF-diode sputtering machine.