A comparison of on-chip inductors with magnetic materials from previous studies is presented and examined. Results from on-chip inductors with magnetic material integrated into a 90 nm CMOS processes are presented. The inductors use copper metallization and amorphous Co-Zr-Ta magnetic material. Inductance densities of up to 1700 nH/mm2 were obtained thanks to inductance increases of up to 31 times, significantly greater than previously published on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. Co-Zr-Ta was chosen for its good combination of high permeability, good stability at high temperature (> 250degC), high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The Co-Zr-Ta alloy can operate at frequencies up to 9.8 GHz, but trade-offs exist between frequency, inductance, and quality factor. Our inductors with thick copper and thicker magnetic films have dc resistances as low as 0.04 Omega, and quality factors of up to 8 at frequencies as low as 40 MHz.

Review of On-Chip Inductor Structures With Magnetic Films

The development of advanced electromagnetic devices has been constrained by a lack of soft magnetic materials with a suitably high saturation magnetization (over 20 kilogauss) and a large permeability roll-off frequency (greater than 1 gigaherz). For example, magnetic hard-disk-drive technology is rapidly approaching the perceived superparamagnetic limit at which the stored bits become thermally unstable1 — disks with higher anisotropy are more stable but are not usable because magnetic write heads become saturated. Here we describe a new soft magnetic material with a saturation magnetization of 24 kilogauss and a large permeability of 1,000–1,400 in a wide frequency range of up to about 1.2 gigaherz. This new material promises to have wide application in devices such as magnetic recording heads and integrated inductors.

Properties of a new soft magnetic material

Nanocomposites combine favorable features of the constituents on the nanoscale to obtain new functionalities. The present paper is concerned with the preparation of polymer-based nanocomposites consisting of metal nanoparticles in a polymer matrix and the resulting functional properties. Emphasis is placed on vapor phase deposition which inter alia allows the incorporation of alloy clusters with well defined composition and tailored filling factor profiles. Examples discussed here include optical composites with tuned particle surface plasmon resonances for plasmonic applications, magnetic high frequency materials with cut-off frequencies well above 1 GHz, sensors that are based on the dramatic change in the electronic properties near the percolation threshold, and antibacterial coatings which benefit from the large effective surface of nanoparticles and the increased chemical potential which both strongly enhance ion release.

Metal-Polymer Nanocomposites for Functional Applications†

Magnetic properties of nanoparticle composites, consisting of aligned ferromagnetic nanoparticles embedded in a nonmagnetic matrix, have been determined using a model based on phenomenological approaches. Input materials parameters for this model include the saturation magnetization (Ms), the crystal anisotropy field (Hk), a damping parameter (α) that describes the magnetic losses in the particles, and the conductivity (σ) of the particles; all particles are assumed to have identical properties. Control of the physical characteristics of the composite system—such as the particle size, shape, volume fraction, and orientation—is necessary in order to achieve optimal magnetic properties (e.g., the magnetic permeability) at GHz frequencies. The degree to which the physical attributes need to be controlled has been determined by analysis of the ferromagnetic resonance (FMR) and eddy current losses at varying particle volume fractions. Composites with approximately spherical particles with radii smaller than 10...

Magnetic properties of metallic ferromagnetic nanoparticle composites

GHz magnetic film inductors

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=1.2 T, ρ=500 μΩ cm, fr=2 GHz were used for the inductors. L=7.6 nH, R=6.5 Ω, 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.

Microfabrication and characteristics of magnetic thin-film inductors in the ultrahigh frequency region

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 core's while its quality factor was lower than the air core's. 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.

K. Ito

Papers

Microfabrication and characteristics of magnetic thin-film inductors in the ultrahigh frequency region

Magnetic RF integrated thin-film inductors