Collimated deposition of hard bias magnetic films via long-throw techniques

Abstract

We present an optimization of long-throw sputter-deposited Cr/CoCrPt films, specifically for (lifted-off) hard bias applications in an AMR/GMR head. Deposition was carried out in the target-to-substrate (T/S) range of 7–9 in., with pressure down to 0.25 mTorr. On increasing the T/S by 1 in., a 5% reduction in coercivity was observed, and shown to be only partially explained by the deposition rate reduction. On the other hand, lower gas pressure during the CoCrPt deposition significantly increased the coercivity. Higher target power and higher substrate bias also increased the coercivity. All the observed T/S, pressure, target power, and bias dependencies suggest enhanced coercivity is associated with higher CoCrPt adatom mobility. X-ray diffraction data showed the relative intensity of the (0002) to the (1010) peak to be decreased both with higher CoCrPt deposition power or substrate bias; more in-plane c-axis texture could explain the increased coercivity. A sputter etch of the wafer before Cr deposition increased the coercivity by about 300 Oe. A combination of these techniques may be used to compensate for the deterioration in magnetic properties due to the long-throw. Optimal properties of 1790 Oe coercivity and 3.5 memu/cm2 Mrt were achieved.