Wide band direct on-chip EMI shielding layer with metallic/magnetic multilayer

Abstract A new type of direct on-chip electromagnetic interference (EMI) shielding layer for the 10 MHz to 1 GHz frequency range is investigated. A multilayer system consisting of non-magnetic metal layers and magnetic layers is found to exhibit a larger shielding effect than a conventional Cu layer owing to multiple reflections of electromagnetic waves. A multilayer stack of Cu (400 nm)/[Ta (5 nm)/Ni-Fe-Cu-Mo (50 nm)]4/Cu (400 nm) is found to exhibit a larger shielding effect than Cu (3 µm) in the frequency range of 200–400 MHz. A Ta break layer is found to reduce the coercivity of Ni-Fe-Cu-Mo layer and contribute to enhancing the peak in this frequency range. Another type of multilayer stack of [Cu (100 nm)/Ni-Fe-Cu-Mo (100 nm)]10 is found to exhibit a larger shielding effect than Cu (3 μm) over the wide frequency range of 20 MHz to 1 GHz. One remarkable feature of this sample was a peak in the shielding effect at around 60 MHz. The combination of this peak with the ferromagnetic resonance peak creates a wide-band shielding effect. Weak magneto-static coupling between magnetic layers may contribute to the peak at 60 MHz via domain wall resonance. By using these multilayer structures, a thin direct-on-chip shielding layer that covers a wide frequency range can be obtained. This technology is suitable for application in mobile devices and electric vehicles, where EMI in the MHz range, which is due to switching power modules is an issue.