JP2013213708A - High frequency magnetic field detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency magnetic field detecting device having submicron spatial resolution and capable of measurement to the high frequency region.SOLUTION: A high frequency magnetic field detecting device 1 includes: a magnetic force microscope 2; a first high frequency oscillator 3 which applies a first high frequency signal 3A to an object to be measured 4 of the magnetic force microscope 2; a coil for beat generation 5 which is installed close to the object to be measured 4; and a second high frequency oscillator 6 which applies a second high frequency signal 6A whose frequency is different from that of the first high frequency signal 3A to the coil 5. Detection of a high frequency magnetic field by the magnetic force microscope 2 can be carried out with high sensitivity by applying the first high frequency signal 3A, the second high frequency signal 6A and a beat signal which is a difference frequency between the first and the second high frequency signal to the object to be measured 4 and by making the value of the frequency of the beat signal the same as the value of the resonance frequency of a probe 24 of the magnetic force microscope 2.

Description

  The present invention relates to a high-frequency magnetic field detection apparatus having a spatial resolution of submicron or less, and more particularly to a high-frequency magnetic field detection apparatus for a high-frequency magnetic field generated by a measurement object to which a high-frequency signal is applied.

  Large-scale integrated circuits used in computers and information communications are constantly being miniaturized and increased in speed with the development of the information society, and problems such as malfunction due to electromagnetic interference inside the IC become serious. Yes. In addition, in a radio frequency integrated circuit (RFIC) of a cellular phone, a problem of performance deterioration due to electromagnetic interference due to downsizing and high frequency of the chip has become apparent. In order to solve these problems, it is necessary to clarify the generation source, mixing destination, and propagation path of high-frequency electromagnetic noise on the circuit. For this purpose, it is necessary to obtain a two-dimensional distribution of the high-frequency electromagnetic field to be measured with sufficient spatial resolution. However, with further miniaturization of the high-frequency integrated circuit, a spatial resolution of sub-micron or less is now required.

  Existing high-frequency magnetic field noise measurement methods include a coiled magnetic probe (spatial resolution 10 μm, frequency band: 7 GHz) (see Non-Patent Document 1) and a magneto-optical probe (spatial resolution 10 μm, frequency band: 2.5 GHz) (non-patent). However, none of the currently required spatial resolution of integrated circuits is sufficient, and the development of new methods is required.

  In addition, a technique for performing high-resolution two-dimensional magnetic field measurement using a magnetic force microscope has been developed (see Patent Document 1). However, this method focuses on viewing recorded information on a high-density magnetic recording medium, and does not measure an electromagnetic field generated in a high frequency band.

In contrast, the inventors have succeeded in measuring a near electromagnetic field generated from a coplanar waveguide (CPW) to which a high frequency is applied using a magnetic force microscope (MFM), and have made various improvements. (Refer nonpatent literature 3-5.).
However, although these methods can measure the near electromagnetic field generated from the CPW with sufficient spatial resolution, it cannot measure the desired high frequency band, and is still not sufficient as a high frequency electromagnetic field measurement method. .

JP 2009-069133 A

N. Ando et al., J. Magn., Soc. Jpn., 30,429, (2006) N. Adachi et al., IEEE Trans. Mang. 46, 6, 1986 (2010) Jun Endo et al., Magnetics Study Group, MAG-10-207 (2010) Endo, et al., J. Appl., Phy., 109, 07D326 (2011) Yu Endo et al., Proceedings ECC 2011, 203-206 (2011)

  In order to solve the problem of electromagnetic interference inside the IC due to the miniaturization of IC chips and the increase in operating frequency associated with the development of electronic devices, it is desirable to develop a method for non-contact measurement of high-frequency magnetic fields on IC chips. It is. However, as described in the background art, there is no prior art that satisfies both spatial resolution and high-frequency characteristics at the same time. A technique that simultaneously satisfies the requirements for spatial resolution and high-frequency characteristics is desired by adding an appropriate device to the magnetic force microscope.

  In view of the above problems, an object of the present invention is to provide an apparatus for measuring a high frequency magnetic field in the gigahertz band having a submicron spatial resolution.

  In order to achieve the above object, a high-frequency magnetic field detection apparatus of the present invention is installed in the vicinity of a magnetic force microscope, means for applying a first high-frequency signal to the measurement object of the magnetic force microscope, and the measurement object. A coil, and means for applying a second high-frequency signal having a frequency different from that of the first high-frequency signal to the coil. The measurement object includes a first high-frequency signal, a second high-frequency signal, A beat signal that is a difference frequency between the first and second high-frequency signals is applied.

  In the above configuration, the magnetic force microscope preferably includes a stage on which the measurement object is placed, and a probe of the magnetic force microscope whose position is changed by receiving an electric field and / or a magnetic field generated by the measurement object. A detection unit for detecting a change in the position of the probe, a position control unit for scanning the probe over the measurement object at a predetermined interval, a relative position between the probe and the measurement object, and an electric field between the probe and the measurement object. Or a means for obtaining a one-dimensional or two-dimensional scanning information of a positional displacement amount of the probe by associating a displacement amount displaced by receiving a force from a magnetic field or both.

  According to the high frequency magnetic field detection apparatus of the present invention, a high frequency current having a predetermined frequency is applied to an electronic circuit or the like which is a measurement object of a normal magnetic force microscope (MFM), and a high frequency magnetic field having a certain intensity and frequency is applied. Is generated. A coil is installed at a predetermined height on an object to be measured such as an electronic circuit, and a high-frequency current having a frequency slightly different from the carrier frequency is applied to the coil to generate a high-frequency magnetic field having a certain intensity and frequency. Since the frequency of the high-frequency magnetic field generated by the measurement object and the high-frequency magnetic field generated by the coil are slightly different from each other, a beat signal of a magnetic field including two high-frequency magnetic field components appears when both are superimposed. By making the frequency of the beat signal and the resonance frequency of the magnetic force microscope probe with the magnetic coating on the chip surface close to the same value, it is possible to detect a high frequency magnetic field with a magnetic force microscope with higher sensitivity. .

In the above configuration, preferably, a means for applying a DC magnetic field is provided to both the measurement object and the probe.
According to the above configuration, the measured electromagnetic field is calculated by processing the information when the DC magnetic field is applied to the magnetic force microscope probe by the permanent magnet or the electromagnet that flows a DC current and when the DC magnetic field is not applied. From the distribution, the electric field distribution and the magnetic field distribution can be separated.

In the above configuration, the object to be measured is preferably an active element such as a transistor or a diode, a passive element such as a capacitor, an inductor, or a wiring, a power supply circuit, an electronic circuit, an integrated circuit, an LSI chip, a VLSI chip, or a combination thereof. It is a measurement object that induces a high frequency electromagnetic field by applying a high frequency.
The surface of the probe is covered with one of a soft magnetic thin film, a hard magnetic thin film, a soft magnetic thin film, and a hard magnetic thin film. The magnetic thin film coated on the magnetic force microscope probe is preferably one of Fe—Co, Ni—Fe, Ni—Co, Co—Zr—Nb, ferrite, and Co—Cr—Pt.
Further, as a means for applying a magnetic field to both the probe and the measurement object, one that applies an alternating magnetic field with an electromagnet is preferable.
The frequency of the beat signal is preferably the mechanical resonance frequency of the probe.

  According to the high-frequency magnetic field detection device of the present invention, a high-frequency electromagnetic field generated when a high frequency is applied to a microelectronic circuit such as a high-frequency integrated circuit (RFIC) of a cellular phone is obtained with a spatial resolution of submicron level. Measurement can be performed without contacting the measurement object. By adding the apparatus configuration of the present invention to an existing magnetic force microscope, it is possible to easily obtain a two-dimensional map of an electromagnetic field generated on an electronic circuit, and to provide information useful for circuit design. Furthermore, only a magnetic field component can be separated into a two-dimensional map. As a result, in the high-frequency integrated circuit, the generation source, mixing destination, propagation path, and the like of electromagnetic noise can be clarified, and the problem of electromagnetic interference can be solved.

It is a block diagram which shows the high frequency magnetic field detection apparatus of this invention. It is a figure which shows the Z-axis component of the magnetic field which the magnetic field which the measuring object in the high frequency magnetic field detection apparatus of this invention emits, the magnetic field which the coil for beat generation emits, and synthesize | combined them. It is the figure which shows the calculation example 1 of the time change of the magnetic field which assumed the intensity | strength of the magnetic field which a measurement object generate | occur | produces, and the magnetic field which a coil for beat generation generate | occur | produces each, and synthesize | combined both, (A) is a beat generation | occurrence | production. When the coil for use is directly above the probe of the magnetic force microscope (180 °), (B) shows the case where the positions of both are shifted (135 °). It is the figure which shows the calculation example 2 of the time change of the magnetic field which assumed the intensity | strength of the magnetic field which a measurement object generate | occur | produces, and the magnetic field which a coil for beat generation generate | occur | produces each, and synthesize | combined both, (A) is a beat generation | occurrence | production. When the coil for use is directly above the probe (180 °), (B) shows the case where the positions of both are shifted (135 °). It is a figure which shows the calculation example 3 of the time change of the magnetic field which assumed the intensity | strength of the magnetic field which a measurement target object and the magnetic field which a coil for beat generation generate | occur | produce respectively numerically, and synthesize | combined both, (A) is a beat generation | occurrence | production. When the coil for use is directly above the probe (180 °), (B) shows the case where the positions of both are shifted (135 °). It is a figure which shows the calculation example 4 of the time change of the magnetic field which assumed the intensity | strength of the magnetic field which a measurement object generate | occur | produces, and the magnetic field which a coil for beat generation generate | occur | produces each, and synthesize | combined both, (A) is a beat generation | occurrence | production. When the coil for use is directly above the probe (180 °), (B) shows the case where the positions of both are shifted (135 °). In the high-frequency magnetic field detection apparatus of the present invention, a magnetic field generated by a beat generating coil by generating a high-frequency magnetic field by applying a high-frequency signal to a dummy coil instead of a magnetic field generated when a high-frequency signal is applied to an object to be measured. It is a block diagram of the modification of the high frequency magnetic field detection apparatus for producing | generating a beat signal and confirming the operation | movement confirmation of this invention together. It is a figure which shows the displacement amount of the probe for magnetic force microscopes of Example 1. FIG. It is the frequency dependence of the vibration intensity by the magnetic field of the beat signal of the probe for the magnetic force microscope of Example 2. It is a figure which shows the displacement amount of the probe for magnetic force microscopes of a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a high-frequency magnetic field detection apparatus 1 according to the present invention. As shown in FIG. 1, the high-frequency magnetic field detection device 1 of the present invention includes a magnetic force microscope 2, a first high-frequency oscillator 3 that applies a first high-frequency signal 3 </ b> A to a measurement object 4 of the magnetic force microscope 2, The coil 5 is disposed in the vicinity of the measurement object 4, and the second high-frequency oscillator 6 that applies a second high-frequency signal 6 A having a frequency different from that of the first high-frequency signal 3 A to the coil 5. Has been. An electric field or a magnetic field or both an electric field and a magnetic field based on a beat signal of the first high-frequency signal 3A and the second high-frequency signal 6A are applied to the measurement object 4. The coil 5 is also called a beat generating coil.

  The magnetic force microscope 2 includes a stage 22 on which the measurement object 4 is mounted, a probe 24 for the magnetic force microscope 2 that changes its position under the force of an electric field and / or a magnetic field generated by the measurement object 4, A cantilever 25 that holds the probe 24, a detection unit 30 that detects a change in the position of the probe 24, and a position control unit 26 that scans the probe 24 on the surface of the measurement object 4 at a predetermined interval. The relationship between the relative position of the probe 24 and the measurement object 4 and the amount of displacement by which the probe 24 is displaced by receiving the force of the electric field and / or magnetic field, And means 35 for obtaining two-dimensional scanning information. The detection unit 30 includes an optical position detector 29, a detection circuit 31, and a lock-in amplifier 33. Means for obtaining one-dimensional or two-dimensional scanning information is constituted by a control computer 35 described later.

The measuring object 4 is composed of an electronic circuit used in a high frequency band, for example. The probe 24 provided with a magnetic coat is placed close to the surface of the measurement object 4 and is scanned two-dimensionally over the surface of the measurement object 4 at a predetermined interval by an operation control unit (not shown) of the cantilever 25. To do. In the magnetic force microscope 2, the cantilever 25 supporting the probe 24 is irradiated with laser light 27A emitted from the laser device 27, and the laser reflected light 28 from the cantilever 25 is read by the optical position detector 29 and detected as an optical lever signal 29A. The signal is processed by the circuit 31 and sent to the lock-in amplifier 33 as a signal 32. This method is known as an optical lever method in the magnetic force microscope 2 and can read the vibration of the cantilever 25 with high sensitivity.
Here, the “optical lever method” is a method generally used as a method for detecting the movement of the probe 24 for a magnetic force microscope. In the “optical lever method”, the displacement by which the probe 24 is moved by a magnetic force is measured as a change in the beam position of reflected light by the probe 24 of the laser beam 27 irradiated to the probe 24 for a magnetic force microscope.

The method for detecting the vibration of the cantilever 25 is not limited to the optical lever method. Another method for detecting the vibration of the cantilever 25 will be described below.
(1) A method in which a piezoresistive element is connected in parallel to the cantilever 25 and detection is performed by a change in the resistance value of the piezo element accompanying the vibration of the cantilever 25.
(2) A method in which an electrode is provided in the vicinity of the cantilever 25 and electrostatic capacity generated between the electrode and the cantilever 25 is used. This can measure the vibration of the cantilever 25 by a change in capacitance.
(3) A method using a Fabry-Perot interferometer.

  The measurement object 4 is placed on the piezo element driving stage 22 and is precisely controlled by a stage controller as the position controller 26. The positional relationship between the magnetic force microscope probe 24 and the measurement object 4 is correlated as position information 26A by the control computer 35, and a two-dimensional map of the vibration change of the magnetic force microscope probe 24 due to the electromagnetic field. Is obtained.

(Beat signal detection)
Next, detection of the beat signal will be described.
A high frequency signal 3A output from the first high frequency oscillator 3 is applied to the measurement object 4, and a high frequency signal 6A output from the second high frequency oscillator 6 is applied to the beat generating coil 5. Here, by slightly shifting the frequency of the first high-frequency signal 3A output from the first high-frequency oscillator 3 and the frequency of the second high-frequency signal 6A output from the second high-frequency oscillator 6, Selection is made so as to generate a beat signal by superimposing the two high-frequency signals 3A and 6A.

  The high frequency signal 3A of the first high frequency oscillator 3 and the high frequency signal 6A of the second high frequency oscillator 6 are mixed by a frequency mixer 41, thereby generating a beat signal, that is, a reference signal 23 of a difference frequency. This can be guided to the lock-in amplifier 33 and synchronized with the optical lever signal 29A for highly sensitive detection.

  The measurement object 4 is operated at a high frequency such as an electric element such as a transistor or a diode that operates at a high frequency, an active element such as a semiconductor laser, a passive element such as a capacitor, an inductor, or a wiring, a power supply circuit, an integrated circuit, or a combination thereof. In some cases, all of those that generate a high-frequency electromagnetic field are targeted, but here, as an example, a coplanar waveguide (hereinafter referred to as CPW) was used. Needless to say, the circuit is not limited to CPW as long as it is operated by a microwave, such as a strip circuit or a microstrip circuit.

The magnetizing coil 46 is supplied with a direct current from a direct-current magnetic field generating power supply 47, generates a direct-current magnetic field, and is used to magnetize a magnetic material coated on the surface of the probe 24 of the magnetic force microscope. . The magnetizing coil 46 emits a high-frequency electromagnetic field generated by a high-frequency input by the measurement object 4 in a state where a DC magnetic field is applied from a DC magnetic field generating power supply 47 or a DC magnetic field is not generated. The high frequency electric field and the high frequency magnetic field can be separated by detecting with a lever method or the like. When the measurement is performed without a DC magnetic field, the probe 24 of the magnetic force microscope receives both the high-frequency electric field and the high-frequency magnetic field, but when a DC magnetic field is applied, the contribution of only the high-frequency electric field can be measured.
Therefore, the contribution of only the high-frequency magnetic field can be measured by subtracting the signal with the latter DC magnetic field applied from the former signal without the DC magnetic field.

  In FIG. 1, the beat generating coil 5 is configured to be switched between a case where it is electrically connected to the second high frequency oscillator 6 and a means for applying an alternating magnetic field. For example, the means for applying the alternating magnetic field is the AC magnetic field generating power supply 48. When the beat generating coil 5 is connected to the AC magnetic field generating power supply 48, the magnetization of the magnetic material coated on the surface of the probe 24 of the magnetic force microscope can be AC demagnetized.

  Further, if a DC current can be supplied to the beat generating coil 5 by a switching method, a magnetic material coated on the surface of the probe 24 of the magnetic force microscope with a DC magnetic field even when the magnetizing coil 46 is not provided. Can be re-magnetized.

Here, the principle by which the high-frequency magnetic field of the measuring object 4 can be measured with high sensitivity by the high-frequency magnetic field detection apparatus 1 of the present invention will be described.
FIG. 2 is a diagram showing the magnetic field generated by the measurement object 4 and the magnetic field generated by the beat signal generating coil 5 and the Z-axis component of the combined magnetic field in the high-frequency magnetic field detection apparatus 1 of the present invention. The measurement object 4 is, for example, a microelectronic circuit.
First, the main symbols are defined.
S ₁ : High-frequency magnetic field signal generated from the beat generating coil 5 mounted immediately above the cantilever 25 S ₂ : High-frequency magnetic field signal generated from the measurement object 4 H ₁ : Generated from the beat generating coil 5 mounted immediately above the cantilever 25 Magnetic field vector H ₂ : z-axis component of the magnetic field generated from the measuring object 4 f ₁ : frequency of the magnetic field signal generated from the beat generating coil 5 mounted immediately above the cantilever 25 f ₂ : magnetic field generated from the measuring object 4 Signal frequency δ: Phase difference between magnetic field signal of beat generating coil 55 and magnetic field signal generated from measurement object 4 θ ₁ : angle formed by S ₁ with z axis θ ₂ : angle formed by S ₂ with z axis

A beat signal generated when two high-frequency signals 3A and 6A having frequencies close to each other are superimposed on the measurement object 4 will be described using the following formula.
The beat generating coil 5 a high-frequency magnetic field generated from the measured object 4 as S ₁ and S _2, respectively, defined by the following equation (1).

Formula 1

Considering each z-axis component, S _1z is given by (2) below.

Formula 2

The composite magnetic field H _{z in the} z-axis direction is given by the following equation (3).

Formula 3

Substituting into equation (3), the following equation (4) is obtained. Here, f ₁ −f ₂ , which expresses Δω, which is the difference between the angular frequency ω ₁ and the angular frequency ω ₂ , is the frequency of the beat signal.

Formula 4

Formula 5

In the following, numerical calculation is performed for various combinations of H ₁ and H ₂ using Equation (5) to examine how the beat signal appears. As a condition, the direction of the magnetic field on the measurement object 4 side is parallel to the z axis. This corresponds to the case where θ ₂ = 0 °, and corresponds to the degree of freedom that the probe 24 for the magnetic force microscope has in the z-axis direction. Regarding the angle θ ₁ formed by S _{1 and the} z axis, the cases of θ ₁ = 180 ° and 135 ° were examined. This is a value determined by the positional relationship between the beat generating coil 5 and the probe 24 of the magnetic force microscope. 180 ° is when the coil 5 is directly above the probe 24 of the magnetic force microscope, and 135 ° is both of them. It is an example when the position has shifted | deviated.

FIG. 3 is a diagram showing a calculation example 1 of the time change of the magnetic field obtained by numerically assuming the intensity of the magnetic field generated by the measurement object 4 and the intensity of the magnetic field generated by the beat generating coil 5, (A) shows the case where the beat generating coil 5 is directly above the probe 24 of the magnetic force microscope (180 °), and (B) shows the case where the positions of both are shifted (135 °).
In FIG. 3A, the magnetic field vector H ₁ = 0.10 Oe (Oersted) generated from the beat generating coil 5 mounted immediately above the cantilever 25, and the frequency component (z component) H _{2 of} the magnetic field generated from the measurement object 4. = Time change of high-frequency waveform is calculated as 0.0037 Oe. The beat signal is not so prominent in both cases of θ ₁ = 180 ° and 135 ° (FIG. 3B).

FIG. 4 shows a calculation example 2 of the time change of the magnetic field obtained by numerically assuming the intensity of the magnetic field generated by the measurement object 4 and the intensity of the magnetic field generated by the beat generating coil 5 and combining them. In FIG. 4A, the magnetic field vector H ₁ = 0.10 Oe generated from the beat generating coil 5 mounted immediately above the cantilever 25, and the frequency component (z component) H ₂ = 0. The time change of the high-frequency waveform is calculated as 037 Oe. In both cases of θ ₁ = 180 ° (FIG. 4A) and 135 ° (FIG. 4B), the beat signal appears prominently.

FIG. 5 is a diagram showing a calculation example 3 of the time change of the magnetic field obtained by numerically assuming the intensity of the magnetic field generated by the measurement object 4 and the intensity of the magnetic field generated by the beat generating coil 5 and combining them. In FIG. 5A, the magnetic field vector H ₁ = 0.10 Oe generated from the beat generating coil 5 mounted immediately above the cantilever 25, and the frequency component (z component) H ₂ = 0 of the magnetic field generated from the measurement object 4. The time change of the high frequency waveform is calculated as .37Oe. Even under this condition, a beat signal appears remarkably in both cases of θ ₁ = 180 ° (FIG. 5A) and 135 ° (FIG. 5B).

FIG. 6 is a diagram illustrating a calculation example 4 of temporal change of the magnetic field obtained by numerically assuming the magnetic field generated by the measurement target 4 and the strength of the magnetic field generated by the beat generating coil 5 and combining them. In FIG. 6A, the magnetic field vector H ₁ = 0.10 Oe generated from the beat generating coil 5 mounted immediately above the cantilever 25, and the frequency component (z component) H ₂ = 3 of the magnetic field generated from the measurement object 4. The time change of the high-frequency waveform is calculated as 71 Oe. The beat signal is not so noticeable in both cases of θ ₁ = 180 ° (FIG. 6A) and 135 ° (FIG. 6B).

  As is clear from these calculation examples, when the high-frequency magnetic field generated from the measurement object 4 and the high-frequency magnetic field generated from the beat generating coil 5 mounted immediately above the cantilever 25 are mixed at an intensity ratio that satisfies a certain condition, It became clear that a beat signal corresponding to the frequency difference between two high frequencies was generated. By selecting a value close to the mechanical resonance frequency of the magnetic force microscope probe 24 as the frequency of the beat signal, a high-frequency magnetic field that cannot be followed by the probe 24 can be measured with high accuracy.

The above-described features of the high-frequency magnetic field detection device 1 of the present invention can be achieved by adding the configuration of the present invention to a magnetic force microscope device that has been established and is commercially available, and thus cannot be achieved by a conventional magnetic force microscope device. It is possible to detect a high-frequency magnetic field that has not been present, and in a high-frequency integrated circuit, it is possible to clarify the generation source, mixing destination, propagation path, and the like of electromagnetic noise, and to solve the electromagnetic interference problem.
Hereinafter, the present invention will be described in more detail with reference to examples.

(Probe)
The probe 24 used in the example is a Co-Pt-Cr magnetic film having a thickness of about 25 nm or a Si probe 24 having a Ni-Fe magnetic film having a thickness of 50 nm coated on the surface (the tip radius of the probe 24). R: 50-60 nm).
The resonance frequency f _Res of the obtained magnetic force microscope probe 24 is 20.0 to 30.0 kHz, the spring constant k is 1.3 N / m, and the resonance sharpness Q value measured at atmospheric pressure is 80.8. The direction of magnetization is perpendicular to the probe 24.

(Equipment used for measurement)
High-frequency oscillator 3: (Agilent 33250A)
High-frequency oscillator 6: (Agilent E-8267D)
Lock-in amplifier 33: (NF-circuit design block company make, LI-575)
Laser device 27: (ALT red laser diode, ALT-9A90, wavelength = 632 nm)
Optical position detection device 29: (manufactured by Hamamatsu Photonics, s3932)

FIG. 7 shows a high-frequency magnetic field detection apparatus 1 according to the present invention, in which a high-frequency magnetic field is generated by applying a high-frequency signal to the dummy coil 52 instead of a magnetic field generated when a high-frequency signal is applied to the measurement object 4. It is a block diagram of the modification of the high frequency magnetic field detection apparatus 1 for producing | generating a beat signal with the magnetic field which the coil 5 for generation | occurrence | production generates, and confirming the operation | movement of this invention.
Instead of the CPW that is the measurement object 4, the dummy coil 52 is installed at the position of the measurement object 4, and the high-frequency signal 3 </ b> A is applied from the first high-frequency oscillator 3 to the dummy coil 52. It will be shown below that the high-frequency magnetic field generated from the dummy coil 52 can be measured with high sensitivity using the probe 24 for a magnetic force microscope. Since the high-frequency magnetic field detection apparatus 1A of FIG. 7 does not have the CPW 4, the stage 22 and the position control unit 26 on which the CPW 4 is placed are not shown.

  A signal having a signal intensity of 18 dBm is input to the beat generating coil 5 at a frequency of 10 MHz, and a signal having a signal intensity of 20.9 dBm is input to the dummy coil 52 instead of the measurement object 4 in a frequency range of 10 MHz + 20 to 25 kHz. Was entered.

  FIG. 8 is a diagram illustrating the amount of displacement of the probe 24 for the magnetic force microscope according to the first embodiment. This figure shows data measured by replacing the beat signal of the high-frequency magnetic field generated by the beat generating coil and the dummy coil 52 with the optical lever signal 29A as the movement of the probe 24 of the magnetic force microscope manufactured in this embodiment by the magnetic field. It is. The vertical axis is the signal intensity obtained by the optical lever method as the movement of the magnetic force microscope probe 24 by the magnetic field, and the horizontal axis is the frequency change of the beat signal when the dummy coil 52 is scanned in the frequency range of 10 MHz + 20 to 28 kHz. is there. A high output voltage is obtained at a position corresponding to the resonance frequency of the probe 24.

Next, instead of generating a high frequency magnetic field by the dummy coil 52, a high frequency was applied to the CPW 4, and the generated high frequency magnetic field was measured.
First, CPW4 was produced by the following method. An electron beam resist is applied to a glass substrate 4C having a relative dielectric constant of 7.0, a pattern is formed by electron beam drawing, and then a direct current magnetron sputtering method is used to deposit chromium, copper, and chromium at a thickness of 5 nm, 300 nm, and 5 nm, respectively. Then, a CPW4 pattern was formed by a lift-off method.

  The distance (lift height) between the probe 24 and the CPW 4 that is the measurement object 4 was 500 nm. A 100 MHz signal was output from the first high-frequency transmitter 3 and applied to the CPW 4. The beat generating coil 5 was swept in the vicinity of 99.975 MHz to generate a magnetic field beat signal on the CPW 4.

Next, in the configuration of FIG. 1, when a high-frequency magnetic field is generated by applying two high-frequency signals shifted in frequency so as to generate beat signals to both the beat generating coil and the measurement object 4. The amount of displacement by the probe 24 was examined.
FIG. 9 shows the frequency dependence of the vibration intensity due to the magnetic field of the beat signal of the probe 24 for the magnetic force microscope of the second embodiment. As is apparent from FIG. 9, it is clear that the vibration intensity signal of the probe 24 is increased by changing the frequency of the beat signal to match the resonance frequency of the probe 24, and a high-frequency magnetic field can be detected with high sensitivity. It is. By selecting the frequency of the beat signal as the resonance frequency of the probe 24 and scanning the circuit on which the high-frequency magnetic field is to be measured, a two-dimensional map of the high-frequency magnetic field can be obtained.

The apparatus configuration in the measurement was the same as in FIG. 1, and the CPW 4 similar to that in Example 2 was used as the measurement object 4. The difference from the second embodiment is that measurement is performed when a current is passed through the DC magnetic field generating coil 46 using the DC magnetic field generating power supply 47 and a DC magnetic field is applied to the measurement object 4 and the probe 24 for the magnetic force microscope ( 1) and the measurement of the two vibration intensity signals in the measurement (2) when no DC current is applied without passing an electric current.
When a high frequency signal is applied to the CPW 4, a high frequency electromagnetic field is generated, and the signal strength of the measurement (1) is subtracted from the signal strength of the measurement (2) in order to separate the high frequency electric field and the high frequency magnetic field. Only a high frequency magnetic field generated by CPW4 could be detected on the order of μm.

(Comparative example)
Next, a comparative example for the embodiment will be described.
The comparative example is the same as the previous example 1 except that the second high frequency signal 6A is not input to the beat generating coil as compared with the example 1. That is, since the second high-frequency oscillator 6 is not used, the condition is set so that no beat signal is generated. In this comparative example, the sensitivity of the measurement apparatus when no beat signal is generated under the same measurement conditions is evaluated.
FIG. 10 is a diagram showing the amount of displacement of the magnetic force microscope probe 24 of the comparative example. As is apparent from FIG. 10, no peak is observed in the frequency corresponding to the resonance frequency of the probe 24 for the magnetic force microscope, and it is clear that high-sensitivity high-frequency magnetic field measurement cannot be performed.

  The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Nor.

1: High-frequency magnetic field detection device 2: Magnetic force microscope 3: First high-frequency oscillator 3A: First high-frequency signal 4: Measurement object 5: Coil 6: Second high-frequency oscillator 6A: Second high-frequency signal 22: Stage 23: Reference signal 24: Probe 25: Cantilever 26: Position controller 26A: Position information 27: Laser device 27A: Laser light 28: Laser reflected light 29: Optical position detector 29A: Optical lever signal 30: Detector 31: Detection circuit 32: signal 33: lock-in amplifier 35: computer 41: frequency mixer 46: magnetizing coil 47: DC magnetic field generating power supply 48: AC magnetic field generating power supply 52: dummy coil

Claims (8)

A magnetic force microscope,
Means for applying a first high-frequency signal to the measurement object of the magnetic force microscope;
A coil installed close to the measurement object;
Means for applying a second high frequency signal having a frequency different from that of the first high frequency signal to the coil;
Have
The first high frequency signal, the second high frequency signal, and a beat signal that is a difference frequency between the first and second high frequency signals are applied to the measurement object. Magnetic field detection device.   The magnetic force microscope includes a stage on which the measurement object is placed, a magnetic force microscope probe that changes its position under the force of the electric field and / or magnetic field generated by the measurement object, and the position of the probe A detection unit for detecting a change, a position control unit for scanning the measurement object at a predetermined interval, a relative position between the probe and the measurement object, and an electric field or magnetic field. Or a means for obtaining a one-dimensional or two-dimensional scanning information of a positional displacement amount of the probe by relating displacement amounts that are displaced by receiving a force from both of them. High frequency magnetic field detection device.   The high-frequency magnetic field detection device according to claim 1, further comprising means for applying a DC magnetic field to both the measurement object and the probe.   The measurement object is an active element such as a transistor or a diode, a passive element such as a capacitor, an inductor, or a wiring, a power supply circuit, an electronic circuit, an integrated circuit, an LSI chip, a VLSI chip, or a combination thereof, and applies a high frequency. The high-frequency magnetic field detection device according to claim 1, wherein the high-frequency magnetic field detection device is a measurement object that induces a high-frequency electromagnetic field.   The surface of the probe is coated with any one of a soft magnetic thin film, a hard magnetic thin film, a soft magnetic thin film, and a hard magnetic thin film. High frequency magnetic field detection device.   6. The high-frequency magnetic field detection apparatus according to claim 1, further comprising means for applying an alternating magnetic field to both the probe and the object to be measured in the previous period.   The high-frequency magnetic field detection apparatus according to claim 1, wherein the frequency of the beat signal is a mechanical resonance frequency of the probe.   6. The magnetic thin film coated on the probe is any one of Fe—Co, Ni—Fe, Ni—Co, Co—Zr—Nb, ferrite, and Co—Cr—Pt. The high frequency magnetic field detection apparatus according to 1.