Masahiro Yamaguchi

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. Fe61Al13O26 with Ms=1.2u200aT, ρ=500 μΩu200acm, fr=2u200aGHz were used for the inductors. L=7.6u200anH, R=6.5u200aΩ, and 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 Fe61Al13O26 film with Cr underlayer. The L was increased over the flux saturated inductor by 8.6% without any degrade of quality factor.

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%.

High-frequency noise suppression in downsized circuits using magnetic granular films

Noise suppression in downsized circuits utilizing magnetic granular films is demonstrated. Films of Fe-Al-O with thickness of 2 /spl mu/m which exhibit very high /spl mu/ dispersion in the quasimicrowave band were found to work as noise suppressors. The films were attached onto a micro-strip line and the transmission characteristics were compared. This work is the first to verify that films with only 2 /spl mu/m thickness can play a role in suppression of high frequency conduction noise in the quasimicrowave band. The results suggest a possibility of thin film noise suppressors which can be integrated into micron scale semiconductor circuits.

Effect of radio-frequency noise suppression on the coplanar transmission line using soft magnetic thin films

We demonstrated the radio-frequency (rf) noise suppressor using soft magnetic films on a coplanar transmission line from 0.1 to 20 GHz. The coplanar transmission line is composed of magnetic film/polyimide/Cu transmission line/seed layer (Cu/Ti)/glass substrate with the dimension of 50 μm width of the signal line and 3 μm thickness (characteristic impedance: 50 Ω). The magnetic films (CoPdAlO, CoZrO, and CoNbZr) as a noise suppressor are prepared by rf sputtering. The saturation magnetization of each magnetic film is about 10 kG. The magnetic anisotropy field and the ferromagnetic resonance frequency are 230, 89, and 6 Oe and 4.2, 2.5, and 0.7 GHz, respectively. The power loss of the coplanar line with magnetic films is significantly larger than without magnetic and nonmagnetic films due to ferromagnetic resonance losses.

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%.

Magnetic thin-film inductors for RF-integrated circuits

Abstract Thin-film spiral inductors with micropatterned Fe–Al–O and CoNbZr films for the impedance matching elements in 1xa0GHz-drive mobile communication handset application have been demonstrated. Narrow slit trains along the easy axis direction control the ferromagnetic resonance frequency through the change of shape anisotropy energy and magnetostatic energy. The inductance was advantageous over the air-core spiral while Q was almost the same.

Granular thin films with high RF permeability

In this article, we have studied high permeability films with the granular structure for use in the magnetic recording technologies. Also we discuss the advantages, drawbacks and some new development of the granular films.

Soft magnetic applications in the RF range

Abstract Soft magnetic thin-film applications in the RF range are systematically described based on the complex permeability profile of the films. This work demonstrates the metallic thin-film permeability measurements up to 6xa0GHz under the existence of traveling electric field, two types of ferromagnetic RF integrated inductor with the best properties of L=7.9xa0nH and Q=12.7 at 2xa0GHz for a 200×400xa0μm size four-turn rectangular spiral, and a high frequency carrier type thin-film magnetic field sensor (or so-called GMI sensor) with the AC field sensitivity of 4.8 × 10 − 6 A m − 1 / Hz (6 × 10 − 12 T/ Hz ) .

RF integrated noise suppressor using soft magnetic films

RF integrated noise suppressors were fabricated by integration of soft magnetic films on coplanar transmission lines. The vertical structure of suppressor was composed of the magnetic film (2 mm/spl times/15 mm/spl times/1, 2 /spl mu/m)/2-/spl mu/m-thick polyimide/15.2-mm-long and 3-/spl mu/m-thick Cu transmission line/seed layer (Ti/Cu)/1 mm-thick glass substrate. The coplanar transmission lines were prepared by electroplated Cu with 50 /spl Omega/-characteristic impedance. The width of the signal line was 50 /spl mu/m. The magnetic films, e.g., CoPdAlO and CoNbZr films were deposited by rf magnetron sputtering. Compared with those of the nonintegrated noise suppressor, the magnitude of signal attenuation at resonance point of integrated noise suppressor greatly increased from - 4 to - 30 dB for the 1-/spl mu/m-thick CoNbZr film, and from -15 to - 57 dB for the 2-/spl mu/m-thick CoPdAlO film, respectively.

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).