Exchange-coupled IrMn/CoFe multilayers for RF-integrated inductors

The high-frequency characteristics of the RF integrated inductors with antiferromagnetic/ferromagnetic (AF/F) multilayers (MLs) are studied. Each AF layer is 8-nm IrMn and F is Co50Fe50 with a 200-nm splitting into N = 1 to 5 repeats of MLs. This exchange coupled {IrMn/CoFe(d nm)}(N) MLs are deposited on top of the two-port inductors with five-turn square spiral coils, a dimension of 100 mu m x 100 mu m and line/space of 5 mu m/2 mu m. The inductor surface and magnetic layer is separated by 1-mu m-thick SiO2. The enhancement of inductance (Delta L) is 20% compared to an air-core of the same coil size. The resonance peak gradually shifted to a higher frequency with increasing N, and reached at a maximum of 4.3 GHz when N = 5. This is in good agreement with our magnetic data which revealed that the anisotropy field (H-k) and ferromagnetic resonance frequency (f(FMR)) of {IrMn/CoFe(d nm)}(N) MLs are increased with increasing N. The quality factor, Q is improved by 6.8% at 1.5 GHz for the {IrMn/CoFe(40 nm)}(N=5) integrated inductors compared to air-core inductors.