Fabrication of Low-Resistance Ferromagnetic Tunnel Junctions Using Plasma Oxidation

Abstract

Ferromagnetic tunnel junctions , Ta/Ni₈₀Fe₂₀/Cu/Ni₈₀Fe₂₀/IrMn/Co₇₅Fe₂₅/Al-oxide/Co₇₅Fe₂₅/Ni₈₀Fe₂₀/Ta, were fabricated using ICP oxidation, and the detailed annealing temperature dependence of the TMR effect was investigated. Thickness of the Al layer was varied from 6.6 to 7.7 Å before oxidation, and the oxidation time was optimized for each thickness. The 1-μm² junctions were micro fabricated usinge-beam lithography. When the Al thickness was 6.6 Å, the RA decreased to 60-100 Ω·μm² and the TMR ratio became 30%. The lower the RA was, the lower the TMR ratio became.