Michael Christopher Kautzky

Atomic Layer Deposition Al

Al2O3 films made with atomic layer deposition (ALD) have been developed for use as isolation layers in CPP tunneling magnetoresistive readers. A low-temperature deposition process was developed to permit integration with a self-aligned patterning scheme. The resulting films show excellent thickness uniformity (<2% within-wafer), leakage current density (Jleak<1times10-18 A/cm2) and breakdown properties (Fbd>9 MV/cm). TEMs of sub-100 nm TMR readers fabricated using these processes show>95% conformality on junction sidewalls, indicating nonselective growth of ALD Al2O3 on the various stack and bottom shield surfaces. Permanent magnets with well-controlled junction grain structure and coercivities in excess of 2500 Oe have been deposited with existing processes. FEM modeling shows the effective stabilizing field from the magnets at the junction edge scales inversely with ALD layer thickness, in agreement with device-level free layer stability metrics showing improvements at lower ALD thicknesses. As the conformal ALD layer thickness is easily tuned, this technology provides flexibility in trading off reader amplitude and stability that should support scaling of the abutted TMR design out to 1 Tb/in2 and beyond.

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Dense, smooth, and high-purity FexCo(1−x) thin films have been grown by chemical vapor deposition using a coflow of Fe(CO)5 and Co2(CO)8 precursors. High precursor fluxes and precise control over both the substrate temperature and relative precursor pressures are keys to reproducibly obtaining high quality films with the desired stoichiometry. Films with the composition Fe0.55Co0.45 show excellent soft magnetic properties: the saturation magnetization of 2.45 ± 0.05 T approaches the theoretical maximum, and the coercivity is less than 20 Oe. Conformal films have also been grown successfully in a trench structure with an aspect ratio of 4:1.