Optical microscope images of copper/polyimide based inductors fabricated in a CMOS process. Top: stripe with magnetic material. Middle: stripe with slotted magnetic material. Bottom: four-turn elongated spiral inductor with magnetic material.
Cross-sectional SEM images of thick copper wires surrounded by CoZrTa magnetic material forming an inductor that is integrated on top of a seven-metal level CMOS process. Two levels of CoZrTa magnetic material were deposited around the thick inductor wires using magnetic vias to complete the magnetic circuit.
magnetic hysteresis loops of the hard and easy axes of magnetization for Co–4.5%Ta–4.0%Zr (at. %). The slope corresponds to the permeability. The Inset shows that the coercivity is only resulting in minimal hysteretic losses when used to build inductors. The magnetostriction coefficient of the CoZrTa alloy was 0.2 ppm strain.
Permeability vs applied magnetic field of amorphous CoZrTa as a function of film thickness. A drop in permeability with increasing film thickness occurs because of the growing demagnetization field caused by the increasing film thickness.
Real and imaginary components of the complex permeability spectra vs film thickness. The imaginary component becomes large with increasing thickness. Dashed lines correspond to modeled spectra.
The complex permeability spectra of laminated vs unlaminated thick CoZrTa. Eight laminations that were thick each were formed and eliminated the multiple resonant modes.
Measurements of long transmission lines with different linewidths. The arrow show the comparison between transmission lines with two levels of CoZrTa vs without magnetic material. The magnetic alloy consists of four laminations that are thick.
Measurements of inductors surrounded with magnetic material using different magnetic via widths.
Measurements and simulations of the (a) sheet inductance and (b) shunt inductance for inductors with different via widths. Measurements show a decreasing shunt inductance with decreasing via width whereas the sheet inductance does not change.
time constant (inductance vs ac resistance) of a family of different inductors using thick copper or thick aluminum metallization with two layers of CoZrTa except as indicated. The diagonal lines indicate the corresponding factors. Simulations of the copper inductors are shown as dashed lines.
Inductance vs frequency of spiral inductors. The inductance is well over causing a roll-off from the resonant frequency of the inductor. The copper wires are wide. The sizes of the two-turn and six-turn spiral are and , respectively and the dc resistances are 0.86 and , respectively.
Plots calculated using an analytical model of the quality factor. (a) factor vs film thickness. (b) factor vs the number of laminations for a magnetic film.
Quality factor of long lines with two levels of thick CoZrTa using four laminations vs eight laminations. Increasing the laminations not only reduces the eddy current losses but also reduces the inductance causing a net shift in the peak quality factor.
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