JP2015172497A - Magnetic substance permeability-measuring device, and magnetic substance permeability-measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic substance permeability-measuring device and a magnetic substance permeability-measuring method, that can measure a permeability of a magnetic substance of an arbitrary size and shape, and can evaluate a distribution of permeability within a wafer, in the wafer or the like on a production process line.SOLUTION: There is provided a probe including: a microstrip conductor that is configured to sandwich a dielectric body by a microstrip conductor 3 and a ground conductor 4; a magnetic substance that is caused to be tightly adhered to the microstrip conductor via an insulator; a through-hole 6 that is connected to an end part of the microstrip conductor inside the dielectric body; and an electric lead-out line connected to the through-hole 6. There is provided a magnetic substance permeability-measuring device including: the probe; a magnetic field application unit for applying a magnetic field to the magnetic substance; a signal measuring instrument that measures a difference in amplitude information or complex information on a signal depending upon presence or absence of the magnetic field application by the magnetic field application unit; and processing means that obtains, by optimization processing, a permeability of the magnetic substance from the difference in the signal measured by the signal measuring instrument.

Description

  The present invention relates to a magnetic permeability measuring apparatus and a magnetic permeability measuring method.

  Many methods for measuring the high-frequency magnetic permeability (usually several MHz to several GHz) of a magnetic material have been proposed since the 1950s, but all of them use a coil (or antenna) (for example, Non-Patent Documents 1 to 3). Or a transmission line, a waveguide, or the like (for example, see Non-Patent Document 4). On the other hand, the method of measuring the resistivity by contacting the material with a short needle (see, for example, Non-Patent Document 5) is a widely used method, which measures the resistivity of the material and measures the magnetic permeability. It is not a thing.

The inventor has invented that magnetic permeability can be evaluated by placing a meander-shaped probe close to a magnetic thin film (Patent Document 2). However, according to this method, the upper limit frequency of permeability evaluation was limited to about 15 GHz due to the bending angle during the conversion from the probe to the coaxial cable and the impedance mismatch of the through hole (Non-patent Document 7).

Therefore, the inventor intends to suppress the bending of the conductor and the mismatching of the through hole as much as possible under the conditions applicable to the magnetic permeability evaluation of a magnetic material of an arbitrary size, and to minimize the linear microstrip. We have developed a probe with impedance matching within 50Ω ± 1Ω for the through-hole probe and the right angle part. This made it possible for the first time in the world to measure broadband permeability up to 30 GHz without depending on the sample size.

Japanese Patent Application No. 2008-224695 Japanese Patent Application 2010-169349

P.A.Calcagno, D.A.Thompson, “Semiautomatic permeance tester for thick magnetic films”, Rev. Sci. Instrum, 1975, 46, p.904 B.C.Webb, M.E.Re, C.V.Jahnes and M.A.Russak, “High-frequency permeability of laminated and unlaminated, narrow thin-film magnetic stripes”, J. Appl. Phys., 1991, vol 69, p.5611-5615 M. Yamaguchi, S. Yabukami and K.I.Arai, “A New 1MHz-2GHz Permeance Meter For Metallic Thin Films”, IEEE Trans. Magn., 1997, 33, p.3619 H.B.Weir, “Automatic Measurement of Complex Dielectric Constant and Permeability at Microwave Frequencies”, Proc IEEE, 1975, 62, p.33 L.B.Valdes, “Resistivity measurements on germanium for transistors”, Proc. IRE, 1954, p.420-427 S.Yabukami, T.Uo, M.Yamaguchi, KIArai, and M.Takezawa, “High sensitivity permeability measurements of striped films obtained by input impedance”, IEEE Transactions, Magn., 2001, vol.37, p.2774- 2778 Akira Sato, Nobu Sugigami, Tetsuya Ozawa, Yasunori Miyazawa, Kunio Yanagi, Hiroshi Shimada, Makoto Munakata, Takayasu Shiokawa, “Broadband thin film permeability measurement using microstrip probe”, Journal of the Magnetics Society of Japan Vol. 36 , No. 3, pp.235-238 (2012). Y. Shimada, J. Numazawa, Y. Yoneda and A. Hosono: J. Magn. Soc. Jpn., 15, 327 (1991).

Inventor invented measuring the complex permeability of a magnetic thin film by optimizing the magnetic thin film by placing a meander-shaped probe close to the magnetic thin film in Patent Document 2 and considering the skin effect from high-frequency impedance measurement (Patent Document 2). ). However, with this method, the upper limit frequency of the permeability evaluation was limited to about 15 GHz due to the impedance mismatch of the bend, the through hole, and the meander pattern during the conversion from the probe to the coaxial cable.

The present invention is an invention that makes it possible to measure the upper limit frequency of magnetic permeability up to 30 GHz without depending on the sample size. In the previous example related to magnetic permeability measurement of magnetic materials, there is no structure in which the straight microstrip conductor and the lead wire are bent at right angles as in this patent, and up to 30 GHz without depending on the sample size for the first time by the present invention It is considered possible to evaluate the permeability of.

  In order to achieve the above object, a probe according to the present invention includes a linear microstrip line in which a dielectric is sandwiched between a linear microstrip conductor and a ground conductor, a magnetic body in which an insulator is sandwiched together with the microstrip conductor, and the dielectric It is a probe comprising a through hole connected to an end portion of the straight microstrip conductor and an electrical lead wire connected to the through hole.

A magnetic permeability measurement apparatus according to the present invention includes a magnetic field application unit for applying a magnetic field to the probe and the magnetic body, and amplitude information or complex information of a signal depending on whether a magnetic field is applied by the magnetic field application unit. It has a signal measuring device for measuring the difference, and a processing means for obtaining the magnetic permeability of the magnetic material from the difference between the signals measured by the signal measuring device by an optimization process.

  In the magnetic permeability measuring apparatus according to the present invention, the magnetic body is preferably a magnetic thin film. In the magnetic permeability measuring apparatus according to the present invention, it is preferable that the microstrip conductor has a linear structure and is configured so as not to bend the conductor pattern as much as possible.

The present invention makes it possible to evaluate permeability in a wide band up to 30 GHz without depending on the sample size. It has significant advantages in terms of material development and production line management.

It is a perspective view which shows the probe for magnetic permeability measurement apparatuses of the magnetic body of embodiment of this invention. 1 is a side view of a magnetic permeability probe according to an embodiment of the present invention and a magnetic thin film. It is a top view of the microstrip conductor surface of the probe for magnetic permeability measuring apparatus of the magnetic material according to the embodiment of the present invention. It is a top view of the ground conductor surface of the probe for magnetic permeability measurement apparatus of the magnetic body of the embodiment of the present invention. It is the graph which measured the characteristic impedance inside a probe with the time domain reflection measuring apparatus. It is a structure of the magnetic permeability measuring apparatus of this invention. It is a flowchart of a magnetic permeability measurement. It is a perspective view in which an electromagnetic field is localized by the skin effect in the magnetic permeability measuring apparatus. It is the magnetization curve of the CoFeB thin film and FeCoB / Ru thin film which were used for the measurement. It is a measurement result of the hard axis magnetization of a CoFeB thin film (no bias magnetic field). It is a measurement result of a hard axis magnetization of a CoFeB thin film (bias magnetic field applied to the easy axis direction of 500 Oe). It is a measurement result of the hard axis magnetization of a CoFeB thin film (with a bias magnetic field of 1000 Oe applied in the easy axis direction). It is a measurement result of the hard axis magnetization of a CoFeB thin film (bias magnetic field applied 2500 Oe in the direction of easy axis). It is a measurement result of a hard axis magnetization of a CoFeB thin film (with a bias magnetic field of 3000 Oe applied in the easy axis direction). It is a measurement result of a hard axis magnetization of a CoFeB thin film (a bias magnetic field of 3500 Oe applied in the easy axis direction). It is a measurement result of the hard axis magnetization of a FeCoB / Ru thin film (no bias magnetic field). It is a measurement result of a hard axis magnetization of a FeCoB / Ru thin film (a bias magnetic field of 250 Oe applied in the easy axis direction). It is a measurement result of hard axis magnetization of a FeCoB / Ru thin film (bias magnetic field applied to the easy axis direction of 500 Oe). It is a measurement result of a hard axis magnetization of a FeCoB / Ru thin film (bias magnetic field applied to the easy axis direction is 750 Oe). This is a measurement result of the hard axis permeability of a FeCoB / Ru thin film (applying a bias magnetic field of 1000 Oe in the easy axis direction). Relationship between bias magnetic field applied in the direction of easy axis and static permeability Relationship between bias magnetic field and ferromagnetic resonance frequency Graph in which measurement error occurs due to resonance at the characteristic frequency Equivalent circuit including inductance component and capacitance component due to close proximity of magnetic thin film Graph with improved permeability measurement error in Fig. 23 Arrangement so that the right angle part of the probe and the through hole is not close to the magnetic thin film Probe that suppresses impedance mismatch by making the right-angled part curved.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows the structure of the probe, FIG. 2 shows a side view of the probe for the magnetic permeability measuring device and the magnetic thin film, FIG. 3 shows a top view of the microstrip conductor surface, and FIG. 4 shows a top view of the ground conductor surface. The probe is composed of a linear microstrip that is matched to 49.5 Ω to 51.5 Ω, including a linear microstrip conductor, orthogonal part, and through hole. The probe is a fluororesin substrate (CGN-500NF, manufactured by Nakatsukasei Kogyo Co., Ltd., dielectric constant = 2.3, thickness 0.5 mm, copper thickness = 18 mm) etched into a straight microstrip line (length 12.8 mm, width 1.34 mm) processed. In addition, a phosphor bronze receptacle (SMA) was electrically connected to the end of the microstrip conductor at a right angle. The core diameter of the connector is 1.27 mm, the diameter of the surrounding coaxial conductor is 2.9 mm, and the characteristic impedance is approximately 50Ω. FIG. 5 shows the characteristic impedance of the probe measured by the time domain reflection method (TDR). The termination was matched with a 50Ω resistor. The probe is set to 49.5 Ω to 51.5 Ω including the orthogonal part, and multiple reflections can be suppressed as much as possible. Since the high-frequency current flowing through the microstrip conductor excites a high-frequency magnetic field in the width direction, the high-frequency impedance corresponds to the permeability in the hard axis direction. A high-frequency impedance of the magnetic thin film is measured by sandwiching a polyvinyl film (thickness of about 10 μm) as an insulator between the probe and the magnetic thin film and pressing a meander line against the magnetic thin film. Note that the same measurement can be performed by using a coplanar structure instead of the microstrip structure.

FIG. 6 is a diagram showing the configuration of this measurement system. It consists of a personal computer, network analyzer (Agilent Technologies 8722ES), probe, Helmholtz coil, and DC power supply. The probe is connected to the network analyzer via a nonmagnetic coaxial cable. The permeability coefficient (S ₂₁ ) of the magnetic thin film is measured from these devices, the data is taken into a personal computer by GP-IB, and the complex permeability is obtained by the optimization process.

FIG. 7 shows a flowchart of the measurement method. The measurement procedure of this system is connected as shown in Fig. 6, and a polyvinyl film (thickness of about 10 μm) is sandwiched between the lobe and the magnetic thin film. Then, the magnetic thin film is saturated by applying a DC magnetic field of about 5000 Oe in a Helmholtz coil and calibrated with a network analyzer. By doing so, the electrical length of the probe and cable, the DC impedance of the magnetic thin film, the nonmagnetic signal, etc. are removed. Thereafter, the DC magnetic field is released, the transmission coefficient (S ₂₁ ) of the contribution of the magnetic thin film is measured, and the impedance of the magnetic thin film is obtained by the equation (1). FIG. 8 shows the shape of the evaluation sample. As the frequency increases, the current flows only on the surface of the thin film due to the skin effect. As shown in Fig. 8, assuming that the impedance Z is determined by biasing the current in the film thickness direction due to the skin effect, the complex permeability is optimized by the Newton-Raphson method using equations (2) to (4). To do.

Figure 9 shows the measurement results of the MH loops of the evaluated CoFeB thin film (45 mm × 25 mm, 0.5 mm thickness) and FeCoB / Ru thin film ((50 mm × 40 mm, thickness 0.2 mm)). Each has strong uniaxial anisotropy of about 300 Oe, and the ferromagnetic resonance frequency is higher than 6 GHz.

10 to 15 show the evaluation results of the complex permeability of the CoFeB thin film (45 mm × 25 mm, 0.5 mm thickness) in the hard axis direction. FIG. 10 shows no bias, and FIGS. 11 to 15 show hard axis permeability when a DC magnetic field of 500 Oe, 1000 Oe, 2500 Oe, 3000 Oe, and 3500 Oe is applied to the easy axis. ● □ are measured values, and solid and broken lines are calculated values in consideration of ferromagnetic resonance and eddy current based on Non-Patent Document 8. The evaluation results roughly correspond to the theoretical values, indicating that the permeability can be measured over a wide band up to 30 GHz. This indicates that the characteristic impedance matching inside the probe in the present invention is effective. Since the upper limit frequency of 30 GHz is determined by the ferromagnetic resonance frequency when a DC magnetic field of about 5000 Oe is applied and the background measurement is performed, the measurement band is increased by increasing the magnetic field strength during background measurement. Further, the frequency can be increased.

16 to 20 show the evaluation results of the complex permeability in the hard axis direction of the FeCoB / Ru thin film (50 mm x 40 mm, 0.2 mm thickness). FIG. 16 shows no bias, and FIGS. 17 to 20 show hard axis permeability when a DC magnetic field of 250 Oe, 500 Oe, 750 Oe, and 1000 Oe is applied to the easy axis. ● □ are measured values, and solid and broken lines are calculated values in consideration of ferromagnetic resonance and eddy current based on Non-Patent Document 8. The evaluation results roughly correspond to the theoretical values. The reason why the SN ratio is worse than the measurement result of the CoFeB thin film is that the film thickness is 0.2 mm, which is about 40% thinner. The reason why the measurement band is lower than the measurement result of CoFeB thin film is that the sample is large, so it is necessary to set the gap of the iron yoke combined with the Helmholtz coil so that the background magnetic field is 5000 Oe. This is because it has become smaller.

FIG. 21 shows the relationship between the bias magnetic field applied in the direction of the easy axis and the static permeability. ● □ is extracted from FIGS. 10 to 20, and the solid line and the broken line are calculated values in consideration of ferromagnetic resonance and eddy current based on Non-Patent Document 8. It is understood that the measured values and the theoretical values of the CoFeB thin film and the FeCoB / Ru thin film almost correspond to each other, and the magnetic permeability is accurately measured. FIG. 22 shows the relationship between the bias magnetic field and the ferromagnetic resonance frequency. ● □ is extracted from FIGS. 10 to 20, and the solid line and the broken line are calculated values in consideration of ferromagnetic resonance and eddy current based on Non-Patent Document 8. It is understood that the measured values and the theoretical values of the CoFeB thin film and the FeCoB / Ru thin film almost correspond to each other, and the magnetic permeability is accurately measured.

Since the method of the present invention can also be applied to a large-diameter wafer, when the sample is brought close to the probe, resonance occurs at a specific frequency due to capacitive coupling between the probe inductance, the probe conductor, and the sample, and the measurement band. May narrow. FIG. 23 shows such a typical example. There is an error when measuring permeability around 5 GHz. This is thought to be due to resonance at about 5 GHz due to the inductance between the magnetic film and the capacitance between the probe and the sample, including the contribution of the magnetic film. In this case, the inductance and capacitance are estimated in advance, and the LC resonance effect is corrected by correcting the effect of the LC resonance when calculating the impedance using Equation (5) based on the equivalent circuit shown in FIG. And the permeability can be measured over a wide band. In FIG. 24, R is the resistance of the magnetic thin film contribution, L is the inductance of the magnetic thin film contribution, C is the capacitance of the magnetic thin film and the microstrip conductor, Z is the reactance of the magnetic thin film contribution, and Y is C Admittance. FIG. 25 shows the permeability evaluation result optimized by removing the LC resonance contribution using FIG. 24 and equation (5). Both the real part and the imaginary part of the relative permeability can reduce the error around 5 GHz, and a value close to the theoretical value is obtained.

(１)

(２)

(３)

(４)

ただし、ρは抵抗率、lは試料長さ、wは試料幅、tは膜厚、fは周波数、μ_rは複素比透磁率である。

（５）


As another solution, as shown in FIG. 26, it is possible to reduce the error of impedance mismatch by arranging the orthogonal portion of the probe and the through hole so as not to be close to the magnetic thin film. This is also effective in suppressing resonance by not allowing only one of the two orthogonal portions to be close to the magnetic thin film. As shown in FIG. 27, for example, the probe is formed of a flexible substrate, the probe conductor is curved downward, and the two orthogonal portions are slightly separated from the magnetic thin film while the probe conductor is close to the magnetic thin film. By suppressing the impedance mismatch, there is an effect of widening the band.

(1)

(2)

(3)

(4)

However, [rho is resistivity, l is the sample length, w is sample width, t is the film thickness, f is the frequency, mu _r is the complex relative permeability.

(5)

1 Magnetic thin film 2 Dielectric (Fluororesin substrate)
3 Microstrip conductor 4 Ground conductor (ground conductor surface)
5 Insulator 6 Through Hole 7 Right Angle 8 Connector 9 Probe 10 Coaxial Cable 11 Network Analyzer 12 Control PC 13 Core Wire 14 Magnetic Field 15 Current 16 Board
17 Power supply 18 Helmholtz coil 19 Eddy current 20 Curve

Claims (3)

A linear microstrip line with a dielectric sandwiched between a linear microstrip conductor and a ground conductor;
A magnetic body sandwiching an insulator together with the microstrip conductor;
A through hole connected to the end of the straight microstrip conductor within the dielectric;
Probe comprising an electrical lead wire connected to the through hole A magnetic field application unit for applying a magnetic field to the probe according to claim 1 and the magnetic body according to claim 1;
A signal measuring instrument for measuring a difference in amplitude information or complex information of a signal depending on presence / absence of magnetic field application by the magnetic field application unit;
The processing means for obtaining the magnetic permeability of the magnetic body according to claim 1 by an optimization process from a difference between signals measured by the signal measuring instrument,
A magnetic permeability measuring apparatus comprising a magnetic material. 2. The magnetic permeability measuring apparatus according to claim 1, wherein the magnetic body is a magnetic thin film.

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