Microfabrication and characteristics of magnetic thin-film inductors in the ultrahigh frequency region

Thin-film inductors for 1 GHz-drive mobile communication handset application has been demonstrated. This is the possible practical application of soft magnetic films in 1 GHz range. ${\mathrm{Fe}}_{\mathrm{61}}{\mathrm{Al}}_{\mathrm{13}}{\mathrm{O}}_{26}$ with $M_s\text{=1.2\hspace{0.05em}}\mathrm{T},$ ρ=500 μΩ cm, $f_r\text{=2\hspace{0.05em}}\mathrm{GHz}$ were used for the inductors. $\text{L=7.6\hspace{0.05em}}\mathrm{nH},$ $\text{R=6.5\hspace{0.05em}Ω,}$ and $\text{Q=7.4}$ were obtained at 1 GHz in a 370 μm×370 μm square four turn spiral of line/space=11 μm/11 μm covered with 0.1-μm-thick slitted ${\mathrm{Fe}}_{\mathrm{61}}{\mathrm{Al}}_{\mathrm{13}}{\mathrm{O}}_{26}$ film with Cr underlayer. The L was increased over the flux saturated inductor by 8.6% without any degrade of quality factor.