Improvement of Soft Magnetic Properties of Si/NiFe/FeCoB Thin Films at Gigahertz Band Frequency Range by Multilayer Configuration

Frequency dependence of relative permeability up to 9 GHz in Si/NiFe/FeCoB thin films was measured. In 200-nm-thick FeCoB thin film, mu´ reached about 70 and remained up to 3 GHz then decreased precipitously. Furthermore, mu´´ indicated its resonance frequency f _r at 6.4 GHz and produced prominent peak around the frequency. It was found that permeability characteristics increased loss term and lost its prompt responsivity when increasing thickness of FeCoB layer. Then a film with multilayer configuration was suggested in order to suppress the loss. The problems in multilayer configuration were solved and a multilayer film with fine soft magnetic properties was developed by insertion of Si/NiFe layers as intermediate layer. The multi-FeCoB-layer film with Si/NiFe intermediate layer indicated loss-suppressed permeability and good performance in permeablity at high frequency range