Low-resistance spin-dependent tunnel junctions with HfAlOx barriers for high-density recording-head application

Abstract

Spin-dependent tunnel junctions with the structure (Ta 70 /spl Aring//NiFe 70 /spl Aring//MnIr 80 /spl Aring//CoFe 35 /spl Aring//HfAlO/sub x//CoFe 35 /spl Aring//NiFe 40 /spl Aring//TiW(N) 150 /spl Aring/) were fabricated on top of 600-/spl Aring/-thick ion-beam-smoothed low-resistance Al electrodes. HfAlO/sub x/ barriers were formed by natural oxidation (5 min at 1 torr in pure O/sub 2/) of 5-/spl Aring/-thick (2-/spl Aring/ Hf+3-/spl Aring/ Al) films or 6-/spl Aring/-thick (2-/spl Aring/ Hf+4-/spl Aring/ Al) films. Resistance/spl times/area (R/spl times/A) products of 0.65 /spl Omega//spl times//spl mu//sup 2/ and 2.1 /spl Omega//spl times//spl mu/m/sup 2/ were achieved with 9.5% and 13.5% tunnel magnetoresistance signal (TMR), respectively. Current inhomogeneity effects on the measured (R/spl times/A) products and TMR values were calculated in particular for junctions with resistance below 1 /spl Omega//spl times//spl mu/m/sup 2/. Transmission electron microscopy indicates that HfAlO/sub x/ forms a continuous amorphous barrier that follows conformally the topography of the bottom electrode. X-ray photoelectron spectroscopy analysis indicates that 2.5% metallic Hf is left inside the barrier closer to the bottom electrode. These low-resistance tunnel junctions are attractive for read-head applications at recording densities above 100 Gbit/in/sup 2/.