Ken-Ichi Arai

Sandwich-type ferromagnetic RF integrated inductor

The first microfabrication of a sandwich type ferromagnetic RF integrated spiral inductor for the 2 GHz range is demonstrated. The two ferromagnetic CoNbZr films sandwich the spiral to enhance the magnetic flux linkage across the coil current. The inductance, L, of 7.9 nH and the qualify factor, Q, of 12.7 were obtained for a 200 /spl mu/m/spl times/400 /spl mu/m size 4-turn rectangular spiral at f=2 GHz. The inductance was better than that of an air core of the same coil size by 19%, and the Q was better by 23%.

Sandwich type ferromagnetic RF integrated inductor

The first microfabrication of a sandwich type ferromagnetic RF integrated spiral inductor for the 2 GHz range is demonstrated. The two ferromagnetic CoNbZr films sandwich the spiral to enhance the magnetic flux linkage across the coil current. The inductance, L, of 7.9 nH and the qualify factor, Q, of 12.7 were obtained for a 200 /spl mu/m/spl times/400 /spl mu/m size 4-turn rectangular spiral at f=2 GHz. The inductance was better than that of an air core of the same coil size by 19%, and the Q was better by 23%.

Application of bi-directional thin-film micro wire array to RF integrated spiral inductors

Vertically and horizontally aligned micro wire arrays with the magnetic hard axis perpendicular to the length of the wire are micro-fabricated from zero-magnetostrictive CoNbZr film. Annealing produced a 180-degree domain pattern, small coercive force and good permeability. Using the micro wire array with line/space=9 /spl mu/m/2 /spl mu/m, an RF integrated inductor exhibited L=7.5 nH(+11% of air cores), R=7.6 /spl Omega/ and Q=6.3 (almost same as the air cores).

Equivalent circuit analysis of an RF integrated ferromagnetic inductor

An RF integrated air-core inductor and a ferromagnetic thin-film inductor having a ferromagnetic film on top of the spiral have been microfabricated. An equivalent circuit of the RF integrated spiral inductor with ferromagnetic film has been derived to analyze the contribution of the permeability of the magnetic film to the inductance of the inductor. The scattering parameters (S-parameters) have been measured to derive the equivalent circuit parameters of the inductors. Using the amorphous Co/sub 85/Nb/sub 12/Zr/sub 3/ film with slots, the inductance increased and the capacitance between the magnetic film and the coil and between the magnetic film and the ground could be neglected up to 5 GHz.

Magnetic RF integrated thin-film inductors

The magnetic thin film inductor with a 4-turn, 337/spl times/337 /spl mu/m/sup 2/ size spiral coil showed inductance 21% larger than the air cores while its quality factor was lower than the air cores. Keeping the similar quality factor as the air core, the micro patterned magnetic film inductor showed 11% inductance enhancement. The proposed inductor can be made on the passivation of integrated semiconductor devices.

Equivalent Circuit Analysis of RF-Integrated Inductors with/without Ferromagnetic Material

In this paper, the detailed procedure to extract π-type equivalent circuit parameters of RF-integrated spiral inductors with/without ferromagnetic material is presented. RF-integrated spiral inductors have been fabricated and the Tohoku University group (TU) and The Tokyo Institute of Technology group (TIT) separately acquired equivalent circuit parameters of an air-core spiral. The S-parameters were measured to extract the equivalent circuit parameters. The extracted parameters were perfectly identical. Extended 3D EM simulation clarified the effectiveness of ferromagnetic materials up to 5 GHz as well as the wave shortening effect by the permittivity of Si beyond the 10 GHz range. The 3D-EM-simulated parameters conformed to the extracted parameters in the low frequency range.

Two-port type ferromagnetic RF integrated inductor

Two-port type rf integrated inductor with on-top magnetic layer was fabricated. Equivalent circuit analysis of the ferromagnetic RF integrated inductor was performed for the first time. Structure of the possible equivalent circuit is proposed. Parasitic capacitance of the ferromagnetic film is negligibly small if the film is applied slits. Ferromagnetic Co/sub 85/Nb/sub 12/Zr/sub 3/ film with slits effectively enhanced the inductance up to 5 GHz.

High sensitivity permeability measurements of striped films obtained by input impedance

We propose a new method to measure the permeability of striped films. The permeability can be obtained by the change in the input impedance of the film. The sensitivity of these measurements are compared with the figure-eight coil method. The sensitivity of the method is estimated over 100 times greater than a conventional figure-eight coil method. The permeability of striped CoNbZr films (100 /spl mu/m wide) can be measured accurately using this permeameter.

Highly sensitive permeability measurements obtained by electrical impedance

Abstract We propose a highly sensitive method of obtaining permeability. Permeability was obtained from electrical impedance of strips by using wafer probe. The permeability of a CoNbZr strip was evaluated as a function of magnetic field intensity. Measured values approached those of the Landai–Lifshitz–Gilbert (LLG) theory with decreasing field intensity. The proposed method is better than the conventional shielded loop coil method when measuring permeability in a small area.