New Magnetic Multilayer for a Direct On-chip EMI Shielding Layer on a Mold Substrate in the sub-100 MHz Frequency Range

A new type of metallic/magnetic multilayer system was investigated as a direct on-chip electromagnetic interference (EMI) shielding layer for the sub-100 MHz frequency range. It was found that a multilayer of [Cu (100 nm)/Ni-Fe-Cu-Mo (NFCM) (100 nm)]10/[Ta (5 nm)/NFCM (50 nm)]55/[Ta (5 nm)/NFCM (300 nm)]10 exhibited a high shielding effect at around 50 MHz for both glass and mold substrates. This structure also exhibited a better shielding effect at 170 kHz than the conventional magnetic shielding. These results are due to magneto-static interactions between multilayer units, which was evidenced by a hysteresis loop typical for a single-layer soft magnetic film. It is suggested that the coupling reduces the energy of the domain wall resonance and shifts the resonance peak to lower frequency. It was also found that substitution of CrTi layer for the Ta layer further improved the shielding effect in the lower frequency region. This multilayer system is a promising candidate for the direct-on-chip shielding layer covering the kHz to sub-100 MHz frequency range, which is suitable for application in power modules used for mobile devices and electric vehicles.