The present application generally relates to integrated magnetic inductors.
Fully integrated radio frequency (RF) devices, including voltage controlled oscillators, low-noise amplifiers, and frequency filters, are used in mobile electronic devices. Typically, integrated RF devices have a large number of inductors that are incorporated into RF integrated circuits (RFICs). The inductors can consume a large area of the RFIC, and the inductors' quality (Q) factors can be important for power management and RF signal processing in the RFIC. Thus, the inductors can have an effect on the performance of the integrated RF device, which can affect the performance of the mobile electronic device incorporating the integrated RF device.
Previously, air core inductors (see e.g.,
Instead of an air core inductor, a magnetic inductor can be used with RF devices. The magnetic inductor can use a film of a high permeability material located above the inductor coil (see e.g.,
The present application generally pertains to an integrated magnetic inductor. The inductor can include inductor coil(s), magnetic film(s), and a substrate. The magnetic film(s) can be placed between the neighboring segments of the inductor coil(s), and the thickness of the magnetic film(s) can be greater than the coil thickness. A gap may be present between the magnetic film(s) and the coil(s). In addition, the magnetic film(s) of the inductor includes exchange-coupled magnetic material(s) that have magnetically soft and hard phases. The soft magnetic phase has a higher saturation magnetization (Ms) and smaller magnetic anisotropy field (Hk) than the Ms and Hk of the hard magnetic phase. By controlling a volume fraction of the hard (or soft) magnetic phase in the exchange-coupled magnetic material, high Ms and large Hk can be achieved.
One advantage of the present application is that high permeability and high ferromagnetic resonance frequency (fFMR) can be realized.
Another advantage of the present application is that the structure of the inductor minimizes the effect of magnetic loss of the magnetic materials on the inductor electrical characteristics.
Still another advantage of the present application is that the technology can be applicable to any type of planar integrated inductor regardless of size, coil geometries, and operating frequency.
A further advantage of the present application is an inductor with a small form-factor, low power consumption, and good RF signal processing for the RFICs within electronic devices.
Other features and advantages of the present application will be apparent from the following more detailed description of the identified embodiments, taken in conjunction with the accompanying drawings which show, by way of example, the principles of the application.
Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts.
In one embodiment, the magnetic film 104 can be made from an exchange-coupled magnetic material(s). The exchange-coupled magnetic material can include magnetically soft and hard phases. The soft magnetic phase has higher saturation magnetization (Ms) and smaller magnetic anisotropy field (Hk) than the Ms and Hk of the hard magnetic phase. The exchange-coupled magnetic material used in the magnetic film 104 can be in the form of a composite or a film. The soft magnetic phase can include spinel Ni—Zn—Co, Ni—Co, Ni—Zn, Mn—Zn, Ni—Zn—Cu ferrites, BaZnFe10O27, Ba3ME2Fe24O41 (ME=Co, Ni, Zn, Cu), Ni—Fe, Fe—Al—O, Fe—Hf—O, Fe—Sm—O, Co—Fe—Hf—O, Fe—Si—Al, Co—Zr—Ta, Fe—Al—N, Fe—Zr—N, Fe—Co—B, Fe—Co—B—Si, Fe—Co—N, Fe—Si, Ni—Fe—Co, or Fe—Al. The hard magnetic phase includes CoFe2O4, BaFe12O19, SrFe12O19, Mn—Bi, Mn—Al, Nd—Fe—B, Sm—Co, Fe—Pt, Sm—Fe—N, Fe—Cr—Co—Mo, Mn—Al—C, Al—Ni—Co, Pt—Co, Sm—Co—Fe—Cu or Fe—Cr—Co.
An example of an exchange-coupled magnetic material that can be used with the present application is described in commonly-assigned U.S. patent application Ser. No. 14/941,201, entitled “Methods for Manufacturing Core-Shell Exchange Coupled Magnetic Particles” and filed on Nov. 13, 2015, which is incorporated herein by reference. In another embodiment, the exchange-coupled magnetic material can include single-phase ferromagnetic materials, single-phase ferrimagnetic materials and combinations thereof. However, in still other embodiments, other types of exchange-coupled magnetic materials can be used.
As shown in
In one embodiment of the inductor 100, the coil 102 can have 2.5 spiral turns, a coil area of 1×1 mm2, a coil width of 50 μm, a space of 50 μm between the coil segments, and a thickness of 7 μm; the substrate 106 can be glass having a εr=5.5, a tan δε=0 and a σ=0 S/m; and the magnetic film 104 can have a thickness of 50 μm, a μ′ at 1 GHz of 11.8, a μ′ at 2 GHz of 13.3, a loss (tan δμ) at 1 GHz of 0.03 and a loss (tan δμ) at 2 GHz of 0.07.
In one embodiment, to characterize the magnetic properties of the exchange-coupled magnetic material used in the magnetic film 104, the calculated Ms and Hk of the exchange-coupled magnetic material are shown in
Ms=Mhardfhard+Msoftfsoft (1)
Ms and Hk: Saturation magnetization and anisotropy field of the exchange-coupled magnetic material, respectively
Msoft/hard and Ksoft/hard: Saturation magnetization and anisotropy constant of soft/hard magnetic phases, respectively
Hsoft/hard and fsoft/hard: Anisotropy field and volume fraction of soft/hard magnetic phases, respectively
For example, CoFe2O4 ferrite and Fe40Co60 were used as the magnetic hard and soft phases, respectively, of the exchange-coupled magnetic material. For the single-phase CoFe2O4, i.e., an fhard of 1, the Ms and Hk are 5,300 Gauss and 9,400 Oe. For the single-phase Fe40Co60, i.e., an fhard of 0, the Ms and Hk are 23,000 Gauss and 20 Oe. The calculated results show that both Ms and Hk are controllable with different volume fractions of fhard of the CoFe2O4, the hard magnetic phase material. The calculated results of Ms and Hk for different fhard are summarized in Table 2.
The calculated Ms and Hk of the exchange-coupled magnetic material in
where μ′ is the real part and μ″ is the imaginary part of permeability, ω is the angular driving frequency, γ is the gyromagnetic constant (1.76×107 rad/Oe·s), and α is the damping constant
It is noted that the μ′ of the exchange-coupled magnetic materials, e.g., fhard of 0.09 or 0.12, is higher than that of the single phase CoFe2O4, i.e., an fhard of 1, and the fFMR is larger than that of the single phase Fe40Co60, i.e., an fhard of 0. Accordingly, the exchange-coupled magnetic material improves the μ′ and fFMR over single phase magnetic materials.
It should be understood that the identified embodiments are offered by way of example only. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the embodiments without departing from the scope of the present application. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the application. It should also be understood that the phraseology and terminology employed herein is for the purpose of description only and should not be regarded as limiting.
This application claims the benefit of U.S. Provisional Application No. 62/316,757, entitled “Integrated Magnetic Inductors” and filed on Apr. 1, 2016, which application is hereby incorporated by reference in its entirety.
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