JP2012058220A - Magnetic field sensor and method of manufacturing magnetic field sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field sensor capable of measuring the spatial distribution of a magnetic field, a magnetic field gradient or a signal corresponding to the magnetic field gradient with a high resolution, and a method of manufacturing the magnetic field sensor.SOLUTION: A magnetic field sensor includes magnetic fine particles in a sharpened tip of a probe by immersing the tip of the probe or the overall probe in a magnetic fluid.

Description

  The present invention relates to a magnetic field sensor for inspecting magnetic domains of magnetic recording media and wiring of electronic components with high resolution, and a method of manufacturing the magnetic field sensor.

  With the advancement of an advanced information society, the importance of high-density magnetic recording is increasing, and at the same time, there is a demand for higher accuracy in magnetic recording read / write technology and magnetic domain inspection technology. In particular, improvement of spatial resolution and improvement of magnetic field strength resolution are being promoted toward higher accuracy of magnetic domain inspection technology. On the other hand, as the electronic parts are reduced and the wiring density per unit volume is improved, the number of defective portions is increased, and the precision of the non-destructive wiring inspection technique using a magnetic field is being promoted.

  In addition, in order to ensure the reliability of magnetic recording media and electronic parts, the need for inspection of all products is increasing. As a result, the cost reduction of the magnetic domain inspection and the wiring inspection by the magnetic field is demanded. In particular, the cost reduction is being promoted simultaneously with the improvement of the accuracy of the magnetic field sensor.

  In Non-Patent Document 1, it is proposed that a magnetic force microscope (MFM) is effective for inspecting a magnetic recording medium. In MFM, it has been proposed that a needle-shaped portion made of silicon (hereinafter referred to as a probe) is covered with a magnetic thin film and the magnetic thin film is magnetized to be used as a magnetic field sensor. When this magnetic field sensor is brought close to the magnetic domain to be measured, the probe receives a magnetic force due to the magnetic field generated from the magnetic domain, and “distortion of the cantilever that supports the probe (corresponding to the magnetic field gradient)” or “probe” A change in resonance frequency (corresponding to the gradient of the magnetic field gradient) of the needle and the cantilever that supports it is induced. By measuring these quantities electrically or optically, signal measurements corresponding to magnetic field gradients or “magnetic field gradients” are made.

  Using the MFM, it is possible to measure a magnetic field gradient generated by an electric current or a “magnetic field gradient”. By bringing the magnetic field sensor close to the vicinity of the current path, a magnetic force due to the magnetic field generated from the current path is applied to the probe, and the magnitude of the current is estimated from the magnetic force.

  The needle-like magnetic field sensor used in the MFM is hereinafter referred to as a magnetic probe. 2. Description of the Related Art Conventional magnetic probes used in MFM include a probe made of silicon having a quadrangular pyramid shape and a structure in which a magnetic material is coated or a wire made of a magnetic material is sharpened. Examples of magnetic materials used in the magnetic probe include nickel (Ni), iron (Fe), cobalt (Co), rare earth elements, iron oxide, and a mixture of these. Generally, an alloy of cobalt (Co), chromium (Cr), and platinum (Pt) is used. Patent Document 1 discloses a film in which a magnetic metal is formed on the entire surface of a probe made of silicon for an atomic force microscope by a sputtering method or the like.

  The conventional magnetic probe is a magnetic thin film having a thickness of 10 nm to 100 nm and covers a probe made of silicon. When the tip radius of curvature of the probe is about 2 nm to 10 nm, the tip radius of curvature is 22 nm to 210 nm after coating with the magnetic thin film.

  The coating film made of a magnetic material is produced by the RF sputtering method on the entire base material made of silicon having a quadrangular pyramid shape. Therefore, the spatial resolution in the measurement of the intensity distribution of the magnetic field gradient or “magnetic field gradient” by the MFM does not become higher than the curvature radius of the tip.

  Since a conventional magnetic probe is coated with a magnetic material by RF sputtering, the data obtained by MFM measurement searches for the intensity distribution of the magnetic field gradient or “magnetic field gradient gradient” above the object to be measured. The spatial resolution of the magnetic field gradient distribution measurement or “magnetic field gradient gradient” distribution measurement depends on the three-dimensional shape of the probe, and at the same time the spatial resolution in the length direction of the probe is It is lower than the spatial resolution in a plane perpendicular to the length direction of the needle. In order to determine the three-dimensional magnetic field gradient distribution or the three-dimensional “magnetic field gradient gradient” distribution with high spatial resolution, the area of the sensor portion for detecting the magnetic field gradient or “magnetic field gradient gradient” should be as small as possible. . For example, for an area of 1 nm × 1 nm, the “three-dimensional magnetic field gradient or gradient of magnetic field gradient” distribution is determined at about 1 nm.

  In the conventional magnetic probe, since the magnetic material is coated on the entire probe by the RF sputtering method, the signal obtained by the MFM measurement corresponds to the magnetic force received by the entire probe. Therefore, a signal accompanying a change in probe position due to a magnetic field gradient or “magnetic field gradient” in a region on the surface of the probe far from the measurement target, such as a region at the base of the probe (region away from the tip of the probe) The change is longer by a fixed amount than the signal change accompanying the change in the probe position due to the magnetic field gradient in the region of the probe surface close to the measurement object or the “magnetic field gradient”. Further, a magnetic field gradient or “magnetic field gradient” from a region other than the measurement target is included as an offset in the measured signal.

  Therefore, a large offset having no coordinate dependency is added to the signal obtained by the MFM measurement, and as a result, the resolution related to the measurement of the intensity of the magnetic field gradient or “magnetic field gradient gradient” is deteriorated.

  A conventional magnetic probe is produced by an RF sputtering method. In a vacuum container in an RF sputtering apparatus, a lot of magnetic material is deposited in a region other than the probe, such as a sample stage, and the utilization efficiency of the material is not high. In particular, in the case of a magnetic probe, only the vicinity of the probe tip needs to be coated with a magnetic material.

  Since the conventional magnetic probe is manufactured by the RF sputtering method, it is necessary to arrange the base material made of the above-mentioned quadrangular pyramidal silicon in a vacuum apparatus. Since a vacuum apparatus is used, the manufacturing cost is high, and the increase in area is not easy compared to a wet thin film forming process such as a spin coating method.

JP 2003-240700 A   D. Rugar, H .; J. et al. Mamin, P.M. Guetner, S.M. E. Lambert, J .; E. Stem, I.M. McFadyen, and T.M. Yogi, J .; Appl. Phys. 68 (3), 1169-1183 (1990)

  As the advanced information processing society advances and the importance of high-density magnetic recording increases, the improvement of spatial resolution, magnetic field or magnetic field gradient or “magnetic field gradient gradient” in magnetic recording readout, recording technology, and inspection technology There is a need for improved intensity resolution. In order to improve the spatial resolution in magnetic field gradient distribution measurement or “magnetic field gradient gradient” distribution measurement, a magnetic probe having a magnetic material in a region of 1 μm or less from the probe tip is required. In this case, the magnetic field gradient distribution or “magnetic field gradient” distribution of the measurement result has an accuracy of 1 μm or less. In particular, in order to improve the spatial resolution in a two-dimensional plane parallel to the measurement target surface, a magnetic probe capable of achieving a spatial resolution of 22 nm or less is required. By fulfilling these requirements, magnetic recording media can measure magnetic field gradients derived from magnetic domains of 22 nm or less or two-dimensional distribution of “magnetic field gradient gradients”, and electronic components can measure wiring of 22 nm or less. The reliability of magnetic recording media and electronic parts is ensured.

In addition, with the reduction of electronic parts, the wiring density per unit volume has been improved, so that the yield of wiring manufacturing has deteriorated, and the need for inspection of all products has been increasing in order to ensure the reliability of electronic parts. In order to spread the inspection technology, it is required to reduce the cost of the magnetic field sensor used in the inspection technology.

  The present invention responds to the above problems in order to solve the problem of spatial resolution in the measurement technique of magnetic field gradient or “magnetic field gradient”, the problem of intensity resolution of magnetic field gradient or “magnetic field gradient”, and the problem of cost. It is an object of the present invention to provide a magnetic probe as a magnetic field sensor for measuring a magnetic field gradient or “magnetic field gradient” and a method for manufacturing the magnetic probe.

  According to the present invention, there is provided a magnetic field sensor comprising a needle-like portion or a plate-like portion made of a nonmagnetic material, and magnetic fine particles arranged at least at one location of the needle-like portion or the plate-like portion. Provided.

  According to the present invention, there is also provided a magnetic field sensor comprising: a needle-like part or a plate-like part made of a non-magnetic material; and magnetic fine particles arranged at least in one place on the needle-like part or the plate-like part. A manufacturing method is provided.

  According to the magnetic field sensor and the method of manufacturing the magnetic field sensor of the present invention, the “magnetic probe including a magnetic material in an area of 1 μm or less from the probe tip”, “three-dimensional magnetic field gradient distribution or three-dimensional magnetic field gradient gradient”. A magnetic probe capable of achieving a spatial resolution of 22 nm or less in distribution measurement can be provided, or a method of manufacturing a magnetic probe that is “low cost” compared to a magnetic probe that is a conventional magnetic field sensor. can do. As a result, a magnetic recording medium can measure a three-dimensional distribution of a magnetic field gradient or “magnetic field gradient” derived from a magnetic domain of 22 nm or less, and an electronic component can measure a wiring of 22 nm or less. Reliability is ensured.

  (A) A magnetic field sensor provided with magnetic fine particles at the tip of a probe. (B) It is an expansion schematic diagram of the probe tip part of a magnetic field sensor provided with magnetic fine particles at the probe tip.   This is a magnetic field sensor provided with magnetic fine particles at a location other than the tip of the probe.   The magnetic field sensor includes a magnetic film provided at the tip of the probe and a protective film for preventing separation of the magnetic particles.   This is a magnetic field sensor provided with a magnetic fine particle at a place other than the tip of the probe and a protective film for preventing the separation of the magnetic fine particle.   A magnetic field sensor provided with magnetic fine particles on the surface of a cantilever.   This magnetic field sensor has magnetic particles provided on the surface of the cantilever and a protective film for preventing the separation of magnetic particles.   This is a magnetic field sensor in which a wire-like material is sharpened and magnetic fine particles are provided at the tip.   (A) It is a perspective view of the magnetic field sensor provided with the some magnetic fine particle in the fixed area | region of the cantilever surface. (B) It is a side view of the magnetic field sensor provided with several magnetic fine particles in the fixed area | region of the cantilever surface. (C) It is a front view of the magnetic field sensor provided with several magnetic fine particles in the fixed area | region of the cantilever surface.   It is a magnetic field sensor of the type which supports the cantilever part of FIG. 8 with two leaf springs.   This is a magnetic field sensor in which two cantilevers are arranged in parallel and magnetic fine particles are arranged on one cantilever.   This is a magnetic field sensor in which a plurality of magnetic fine particles are arranged on the entire probe.   (A) It is the schematic diagram which showed the state in which a probe approaches a magnetic fluid. (B) It is the schematic diagram which showed the state which the probe tip contacted the magnetic fluid. (C) It is the schematic diagram which showed the state which the magnetic fine particle adhered to the probe tip.   It is the structure of the atomic force microscope for producing the magnetic field sensor which concerns on this invention.   (A) It is the schematic diagram which showed the state in which a cantilever approaches a magnetic fluid. (B) It is the schematic diagram which showed the state which the cantilever contacted the magnetic fluid. (C) A schematic view showing a state where magnetic fine particles are attached to the cantilever surface.   (A) It is a schematic diagram of the state by which the resist was apply | coated to the cantilever surface. (B) It is the schematic diagram which showed a mode that a part of resist surface of (a) was irradiated with light through a mask and a resist was exposed. (C) shows the structure after removal of the exposed areas. (D) It is a schematic diagram which shows a mode that the magnetic fine particle was made to adhere to the groove | channel produced by (c). (E) It is the figure which removed the resist.   (A) It is the schematic diagram which showed the state in which the cantilever provided with the probe approached magnetic fluid. (B) It is the schematic diagram which showed the state where the cantilever provided with the probe was buried in the magnetic fluid. (C) It is the schematic diagram which showed the state which the magnetic fine particle adhered to the whole cantilever provided with the probe.   (A) It is the schematic diagram which showed the state in which a probe approaches the magnetic fluid which the liquid level raised by the magnetic field. (B) It is the schematic diagram which showed the state which a probe contacts the magnetic fluid which the liquid level raised by the magnetic field. (C) It is the schematic diagram which showed the state in which the magnetic fine particle adhered to the probe.   It is the apparatus structure of the magnetic force microscope using the magnetic field sensor of this invention.   It is explanatory drawing of the magnetic force microscope using the magnetic field sensor of this invention, and a three-dimensional magnetic field gradient distribution reconstruction method.   (A) It is an electron microscope image of the probe before attaching magnetic fine particles. (B) An electron microscope image of the probe after the magnetic fine particles are attached by the method of FIG. (C) It is the electron microscope image which expanded the probe tip part in (b).   FIG. 25 is a “gradient of magnetic field gradient” distribution image over the floppy disk obtained by using the magnetic field sensor according to the embodiment of the present invention in FIG. 24.   FIG. 25 is a “magnetic field gradient gradient” distribution image over a horizontal magnetic recording type hard disk obtained by using the magnetic field sensor of the embodiment of the present invention in FIG. 24.   25 is a “magnetic field gradient gradient” distribution image over a perpendicular magnetic recording type hard disk obtained by using the magnetic field sensor of the embodiment of the present invention in FIG. 24.   (A) It is an electron microscope image of the probe after magnetic fine particles were made to adhere by the method of FIG. (B) It is the electron microscope image which expanded the probe tip part in (a).

FIG. 1A shows the structure of the magnetic field sensor. FIG. 1B shows an enlarged schematic diagram of the magnetic field sensor unit. The tip of the cantilever is provided with a probe 1 made of silicon having a triangular pyramid shape, and magnetic tips 2 are further provided at the tip thereof. As shown in FIG. 2, the magnetic fine particles 2 do not necessarily have to be at the tip of the probe 1. Further, as shown in FIGS. 3 and 4, in order to prevent the magnetic fine particles 2 from being peeled off, the structure may be covered with a thin film 3 made of a nonmagnetic material such as silicon nitride.

  The structure shown in FIGS. 1, 2, 3, and 4 according to the present invention improves the spatial resolution of magnetic field gradient distribution measurement or “magnetic field gradient gradient” distribution measurement. In the case of the conventional magnetic probe, since the magnetic material is coated on the entire surface of the probe, the entire surface of the probe is included in the measurement signal of the magnetic field gradient or “magnetic field gradient”. In the case of FIG. 1, FIG. 2, FIG. 3, FIG. 4, the signal to be measured is a magnetic field gradient or “magnetic field gradient” at the coordinates where the magnetic fine particle 2 is located. The spatial resolution of distribution measurement is improved. For example, when 10 nm magnetic fine particles 2 are attached, a three-dimensional magnetic field gradient distribution or a three-dimensional “magnetic field gradient gradient” distribution can be determined with a spatial resolution of 10 nm.

  The spatial resolution of three-dimensional magnetic field gradient distribution measurement or three-dimensional “magnetic field gradient gradient” distribution measurement is improved by the structure shown in FIGS. 1, 2, 3, and 4. In the case of a conventional magnetic probe, since the magnetic material is coated on the entire probe surface, the spatial resolution greatly depends on the probe shape. In the case of the magnetic field sensor shown in FIGS. 1, 2, 3, and 4, the spatial resolution is determined by the diameter of the magnetic fine particle 2. Furthermore, when the magnetic fine particles 2 are spherically symmetric, it is possible to perform measurement with the same spatial resolution in all three dimensions. For example, when the diameter of the magnetic fine particle 2 is 10 nm, a three-dimensional magnetic field gradient distribution or a three-dimensional “magnetic field gradient gradient” distribution can be measured with a spatial resolution of 10 nm.

  The structure shown in FIGS. 1, 2, 3, and 4 improves the intensity resolution of the magnetic field gradient or “magnetic field gradient”. In the case of a conventional magnetic probe, since a magnetic material is coated on the entire surface of the probe, an offset signal having no probe position dependency is added to the measured signal. Therefore, a signal component that changes due to a change in the probe position such as scanning corresponds to the “radius of curvature of the tip of the probe 1” corresponding to “the size of the entire surface area of the probe 1” compared to the overall signal level. It becomes smaller in the order corresponding to the “surface area of the sphere”. Therefore, an analog-digital converter with a high voltage resolution is required, and at the same time, the intensity resolution of the magnetic field gradient or “magnetic field gradient” is reduced. In the present invention, the signals corresponding to the intensity of the magnetic field gradient or “magnetic field gradient gradient” obtained from the measurement are all derived from the magnetic fine particles 2, so that the magnetic field gradient or “magnetic field gradient gradient” intensity is Measurement resolution is improved.

  In the production of the structure shown in FIGS. 1, 2, 3, and 4, the material cost can be reduced as compared with the conventional magnetic probe. The magnetic material to be used corresponds to the volume of the magnetic fine particles 2 and has a lower material cost than the conventional magnetic probe covering the entire surface. Conventional magnetic probes are usually coated with a magnetic material by an RF sputtering method. However, since the magnetic material is deposited in a region other than the object to be coated in the vacuum apparatus, the material is wasted.

  The structure shown in FIG. 2 has an additional advantage over FIG. In the case of FIG. 1, since the magnetic fine particles 2 are located at the tip of the triangular pyramid-shaped probe 1, the magnetic fine particles are used when measuring the surface irregularities by bringing the probe tip close to the sample as an atomic force microscope. 2 may be damaged or detached from the probe 1. In the case of FIG. 2, since the magnetic fine particles 2 are arranged in one specific region excluding the tip of the probe 1, it is expected that the influence of the separation or damage of the magnetic fine particles 2 due to the proximity interaction is reduced. As shown in FIG. 3, this problem is alleviated when the magnetic fine particles 2 are covered and protected by the protective film 3 made of a nonmagnetic material in order to prevent peeling and damage. In the conventional magnetic probe, a reduction in resolution due to peeling of the magnetic material by acquiring a surface shape image has been an important issue. In the case of FIG. 2 of the present invention, the problem is solved. In FIG. 2, the resolution of the apparent two-dimensional magnetic field gradient distribution or the two-dimensional “magnetic field gradient gradient” distribution due to the separation of the magnetic field gradient or the “magnetic field gradient gradient” detection unit from the tip by a certain distance Can be solved by obtaining Dirichlet and Neumann boundary conditions, solving basic equations of static magnetic field, and analyzing three-dimensional magnetic field gradient distribution or “gradient of magnetic field gradient” distribution

  FIG. 5 shows an example of the structure of the magnetic field sensor according to the present invention. When not used as a probe for an atomic force microscope, it is not always necessary to provide the sharp probe 1. As shown in FIG. 5, at least one magnetic fine particle 2 is provided on the surface or inside of the cantilever 4. In order to prevent the magnetic fine particles 2 from peeling off and preventing damage, they may be covered and protected by a protective film 3 made of a nonmagnetic material as shown in FIG.

  The magnetic field sensor according to the present invention in FIG. 5 is similar to FIGS. 1 and 2 which are examples of the present invention, “spatial resolution of magnetic field gradient distribution measurement or“ magnetic field gradient gradient ”distribution measurement”, “magnetic field gradient or“ magnetic field gradient ”. There is an advantage over the conventional magnetic probe in terms of “intensity resolution” and “low material cost”. Since the sharp probe 1 is not provided as compared with FIGS. 1 and 2, the surface irregularities cannot be measured with high accuracy.

  FIG. 7 shows an example of the structure of the magnetic field sensor according to the present invention. It is a magnetic field sensor provided with at least one magnetic fine particle 2 at the tip of a base material 5 with one end of a curved metal wire sharpened. As shown in FIG. 2, it is not always necessary to provide the magnetic fine particles 2 at the tip. Since the entire sensor exhibits conductivity, it can also be used as a probe for a scanning tunneling microscope. Compared with the conventional magnetic probe, there are advantages regarding “magnetic field gradient distribution measurement or“ magnetic field gradient gradient ”distribution measurement spatial resolution” “magnetic field gradient or“ magnetic field gradient gradient ”intensity resolution” and “low material cost”.

  FIG. 8 shows an example of the structure of the magnetic field sensor of the present invention. One or more magnetic fine particles 2 are arranged in a stripe-shaped region on the surface or inside of the cantilever 4 fixed at one end. Hereinafter, this region in which one or more magnetic fine particles 2 are arranged is referred to as a stripe magnetic field detection region. The thickness T of the stripe magnetic field detection region shown in FIG. 8B is preferably several times the diameter of the magnetic fine particle 2 or less.

  The magnetic field sensor of the present invention in FIG. 8 has an advantage with respect to “spatial resolution of magnetic field gradient distribution measurement or“ magnetic field gradient gradient ”distribution measurement”. When the magnetic field sensor of FIG. 8 is scanned in the thickness direction T, it is possible to measure a two-dimensional magnetic field gradient distribution or a two-dimensional “magnetic field gradient gradient” distribution with a spatial resolution T. In this case, since the obtained signal is a signal integrated in the W direction, the resolution in the W direction of the measured magnetic field gradient or “gradient of the magnetic field gradient” does not become W or less.

  FIG. 9 shows an example of the magnetic field sensor of the present invention in which the cantilever 4 in FIG. 8 has a different shape. Compared to the cantilever 4, the spring constant can be easily adjusted, and the sensitivity can be improved.

  FIG. 10 shows an example of the structure of the magnetic field sensor of the present invention. As shown in FIG. 10, two cantilevers 4 made of the same structure and material are arranged in parallel via a gap. In the case of this magnetic field sensor, the difference between the signals of the two cantilevers is measured as a magnetic field gradient or “magnetic field gradient gradient” signal. As a result, the influence of the electrostatic force that the cantilever 4 receives from the sample is offset, and an accurate magnetic field gradient or “magnetic field gradient gradient” can be measured. The magnetic field sensor of the present invention shown in FIG. 10 is conventional in terms of “magnetic field gradient distribution measurement or“ magnetic field gradient gradient ”distribution measurement spatial resolution”, “magnetic field gradient or“ magnetic field gradient gradient ”intensity resolution”, and “low material cost”. There are advantages compared to magnetic probes.

  FIG. 11 shows an example of the structure of the magnetic field sensor of the present invention. Magnetic fine particles 2 are disposed on the entire probe 1 and cantilever 4. Regarding this arrangement, it is desirable that the magnetic fine particles 2 are arranged uniformly. Further, in order to prevent the magnetic fine particles 2 from peeling off, the whole may be covered with a nonmagnetic material.

  In the production of the structure shown in FIG. 11, the material cost and manufacturing cost can be reduced and the area can be easily increased as compared with the conventional magnetic probe. Conventional magnetic probes are usually coated with a magnetic material by an RF sputtering method. However, since the magnetic material is also deposited in a region other than the object to be coated in the vacuum apparatus, the material is wasted.

  One example of the manufacturing method of FIGS. 1 and 2 which is an example of the present invention is shown in FIG. As shown in FIG. 12 (a), the probe 1 is brought close to the magnetic fluid droplet 6. After the tip of the probe 1 is contacted or immersed in the magnetic fluid droplet 6 as shown in FIG. 12B, the probe is moved away from the substrate as shown in FIG. The magnetic fine particles 2 contained in the attached droplets are used for magnetic field gradient or “magnetic field gradient gradient” detection. The magnetic sensor of FIG. 7 is manufactured by the same method.

  A method for controlling the number of magnetic fine particles 2 attached to the tip of the probe 1 will be described below. As shown in FIG. 1A, the probe 1 is normally disposed at the end of the cantilever 4. The entire structure is self-oscillated. In this state, when the tip of the probe is brought close to the magnetic fluid droplet 6 shown in FIG. 12 and the magnetic fine particles 2 are adhered, the mechanical resonance frequency determined by the structure and material of the probe 1 and the cantilever 4 is adhered. It changes by an amount corresponding to the mass of the magnetic fine particles. The relationship between the mass adhering to the tip of the probe 1 and the mechanical resonance frequency is expressed by the following equation (1).

  In the manufacturing method of FIG. 12, when controlling the number of magnetic fine particles 2 to be attached, a device configuration for bringing the probe 1 and the cantilever 4 close to the magnetic fluid droplet 6 in a state where the probe 1 and the cantilever 4 are self-excited is shown in FIG. Shown in In FIG. 13, the displacement of the cantilever 4 that supports the probe 1 is detected by measuring the position of the reflected light of the laser 8 emitted from the laser diode 7. The position of the reflected light on the back surface of the cantilever 4 of the laser 8 is measured by a split photodiode 9. The output of the photodiode 9 is converted into a voltage signal by the preamplifier 10, amplified, and sent to the automatic gain control circuit 11 and the frequency detection circuit 12. The signal sent to the automatic gain control circuit 11 is sent to the phase shifter 13, and its output is applied to the piezoelectric element 14 to become a signal for vibrating the cantilever 4 including the probe 1. By adjusting the phase of the signal applied to the piezoelectric element in the phase shifter 13, the cantilever 4 including the probe 1 can be self-excited and the resonance frequency of the cantilever 4 in the self-excited oscillation state is sent to the frequency detection circuit 12. To measure. The output corresponding to the resonance frequency of the cantilever 4 measured by the frequency detection circuit 12 is sent to the feedback control circuit 15 and applied to the scanner 16 as a signal for controlling between the probe 1 and the sample. The scanner 16 performs high-precision distance control between the probe 1 and the sample after rough adjustment between the probe 1 and the sample by a stepping motor. As shown in FIG. 12, the above-described “self-oscillation system”, “mechanism for detecting the resonance frequency of the cantilever 4 including the probe 1”, and “high-precision position control of the probe 1 and the sample” The distance between the surface of the droplet 6 and the probe 1 can be controlled with high accuracy, and the number of magnetic fine particles 2 attached to the tip of the probe 1 can be controlled.

  The manufacturing method of FIG. 5 is shown in FIG. As shown in FIG. 12, as shown in FIG. 14, one end of the surface of the cantilever 4 is brought close to the surface of the magnetic fluid droplet 6 as shown in FIG. 14 (a), and as shown in FIG. 14 (b). The magnetic fine particles 2 are attached to the surface of the cantilever 4 as shown in FIG. In order to precisely control the number of magnetic fine particles 2 to be attached, the apparatus configuration of FIG. 13 is used.

  The manufacturing method of FIGS. 8 and 9 is shown in FIG. A resist 17 is applied to the surface of the cantilever 4. Thereafter, a photomask 18 is placed on the top of the cantilever 4 provided with the resist 17, and an ultraviolet ray 19 is irradiated to partially expose the photomask 18. Thereafter, the photosensitive portion 20 is developed and removed, and the surface of the cantilever 4 on the resist 17 application side is immersed in the magnetic fluid droplet 6. After adhering the magnetic fine particles 2, the resist 17 is removed, leaving the magnetic fine particles 2 only on the photosensitive portion 20. If part of the magnetic fine particles 2 is also removed when the resist 17 is removed, the resist 17 is subjected to hydrophobic treatment, and a magnetic fluid droplet 6 using water as a solvent is used. 2 is used as a magnetic field sensor while the resist 17 is not removed. In order to protect the magnetic fine particles 2 from thinness, the protective film 3 may be made of a nonmagnetic material after the magnetic fine particles 2 are attached.

  The manufacturing method of FIG. 11 is shown in FIG. After the entire cantilever 4 including the probe 1 is immersed in the magnetic fluid droplet 6 as shown in FIG. 16B, the cantilever 4 is taken out from the magnetic fluid droplet 6. After removing the cantilever 4 from the magnetic fluid droplet 6 in order to remove the solvent contained in the magnetic fluid droplet 6, the entire cantilever 4 may be heated to remove the solvent after FIG. 16C. . Further, in order to improve the adhesion of the magnetic fluid droplet 6 to the probe 1, the magnetic fluid droplet 6 including the magnetic fine particles 2 having a functional group is used, and at the same time, the functional fluid is applied to the surface of the probe 1. The probe 1 having a functional group chemically bonded to the group may be used.

  FIG. 17 shows a method for improving the manufacturing efficiency of the magnetic field sensor of FIGS. 1, 2, and 7 of the present invention. When impurities of nonmagnetic material other than the magnetic fine particles 2 are mixed in the magnetic fluid droplet 6, the impurities may adhere to the probe 1 or the cantilever 4 to which the magnetic fine particles 2 are attached. Therefore, as shown in FIG. 17A, for example, a static magnetic field generation source 21 such as a coil is disposed on the top of the cantilever 4 provided with the probe 1, and the probe 1 and the cantilever 4 and the magnetic fluid droplet 6 are entirely disposed. Apply a static magnetic field. In this case, a high-purity magnetic fluid region is formed on the surface of the magnetic fluid droplet 6, and the probe 1 is brought into contact with or immersed in the region, so that the manufacturing efficiency of the magnetic field sensor can be improved.

  FIG. 18 shows an apparatus configuration of a magnetic force microscope which is an example of use of the magnetic field sensor of the present invention. In FIG. 18, the displacement of the cantilever 4 that supports the probe 1 is detected by measuring the position of the reflected light of the laser 8 emitted from the laser diode 7. The position of the reflected light on the back surface of the cantilever 4 of the laser 8 is measured by a split photodiode 9. The output of the photodiode 9 is converted into a voltage signal by the preamplifier 10, amplified, and sent to the automatic gain control circuit 11 and the frequency detection circuit 12. The signal sent to the automatic gain control circuit 11 is sent to the phase shifter 13, and its output is applied to the piezoelectric element 14 to become a signal for vibrating the cantilever 4 including the probe 1. By adjusting the phase of the output in the phase shifter 13, the cantilever 4 provided with the probe 1 can be self-excited and the resonance frequency of the cantilever 4 in the self-excited oscillation state is measured by the frequency detection circuit 12. The output corresponding to the resonance frequency of the cantilever 4 measured by the frequency detection circuit 12 is sent to the feedback control circuit 15 and applied to the scanner 16 as a signal for controlling between the probe 1 and the sample. The scanner 16 performs high-precision distance control between the probe 1 and the sample after adjustment between the rough probe 1 and the sample by the stepping motor. With the above-described “self-excited oscillation system”, “mechanism for detecting the resonance frequency of the cantilever 4 including the probe 1”, and “high-precision position control of the probe 1 and the sample”, the magnetic field sensor provided by the present invention is used. The probe 1 having a certain magnetic fine particle 2 is two-dimensionally scanned over the measurement object 22 such as a magnetic recording medium, and the two-dimensional distribution of the “magnetic field gradient” can be measured. Furthermore, when measuring a three-dimensional “gradient of magnetic field gradient” distribution, the magnetic field sensor is scanned three-dimensionally. In addition, when the measurement object is covered with a nonmagnetic material, the two-dimensional “magnetic field gradient” distribution derived from the leakage magnetic field above the nonmagnetic material is measured twice by changing the distance between the magnetic field sensor and the sample. To obtain two two-dimensional “magnetic field gradient” distributions. From these two results, the two-dimensional “magnetic gradient gradient” distribution and the two-dimensional “magnetic gradient gradient” distribution are calculated by image calculation and used as Dirichlet boundary conditions and Neumann boundary conditions in the fundamental equations of the electromagnetic field. Thus, a three-dimensional “gradient of magnetic field gradient” distribution can be calculated even inside the non-magnetic material.

ｚ１−ｚ２）で割る操作３０を経ることによって、静磁場の基礎方程式におけるノイマン境界条件３１を得る。また、１枚の画像データ２９をディリクレ境界条件３２として用いることによって、３次元の磁場勾配分布像３３を得ることができ、非磁性材料内部の磁場勾配の分布を断層的に可視化したデータ３４を得ることが実現される。An example of the usage method of FIGS. 8 and 9 according to the present invention will be described below. The magnetic field sensors of FIGS. 8 and 9 have a high spatial resolution only in the direction T shown in FIG. For example, when the 10 nm magnetic fine particles 2 are attached in a thin film, a spatial resolution of 10 nm can be achieved in the T direction. On the other hand, the spatial resolution in the W and L directions depends on the sizes of W and L, and the resolution is determined by the resolution of the mask in the magnetic field sensor manufacturing process of FIGS. 8 and 9 shown in FIG. When the magnetic field sensor of FIGS. 8 and 9 is used as a magnetic force microscope, the direction of the film thickness T composed of the magnetic fine particles 2 of the magnetic force detection unit of the magnetic field sensor is parallel to the measurement object as shown in FIG. Scan the magnetic field sensor to keep. Hereinafter, an image acquisition method when the magnetic field sensor of FIGS. 8 and 9 is used will be described. In FIG. 19, laser 8 is irradiated from a laser diode 7 to a part of the magnetic field sensor, and the displacement of the entire sensor due to the magnetic field sensor receiving a magnetic force is measured based on the position of the reflected light. The position of the reflected light of the laser 8 is detected by the divided photodiode 9, and the output signal is converted into a voltage by the preamplifier 10, amplified, and sent to the phase detector 23. FIG. 19 shows an example of inspection of an electronic component. An AC voltage is applied to the electronic component by an oscillator 24, the intensity and phase of the magnetic field generated in synchronization with the frequency of the signal is detected by the phase detector 23, and the output is stored in the control unit 25. The control unit sends a scanning signal to the XYZ-θ drive stage 27 via the high-voltage amplifier 26, and stores the output of the phase detector 23 synchronized with the scanning signal as image data. 8 and 9, in order to achieve T in FIG. 8B with respect to spatial resolution in all directions, the XYZ-θ drive stage 27 has a mechanism for rotating the sample 28 with respect to the magnetic field sensor. Prepare. Thereby, the spatial resolution of T in FIG. 8B can be achieved in all directions within the two-dimensional plane by performing Radon transformation on the obtained image data for each data angle. The above radon conversion operation is performed with two coordinates (z = z1 and z = z2) in which the distance z between the magnetic field sensor and the sample is changed.

The Neumann boundary condition 31 in the basic equation of the static magnetic field is obtained through the operation 30 divided by z1-z2). Further, by using one piece of image data 29 as the Dirichlet boundary condition 32, a three-dimensional magnetic field gradient distribution image 33 can be obtained, and data 34 in which the magnetic field gradient distribution inside the nonmagnetic material is visualized in a tomographic manner. Obtaining is realized.

  The result of manufacturing the magnetic field sensor of the present invention shown in FIG. 1 by the method of FIG. 12 is shown below. FIG. 20A shows a scanning electron microscope (SEM) image of the probe 1 before the magnetic fine particles 2 are attached, and FIG. 20B shows the probe 1 after the magnetic fine particles 2 are attached. An SEM image of the magnetic fine particle 2, FIG. 20C is an enlarged image of the tip of the probe 1. It can be seen that the magnetic fine particles 2 are attached to the tip of the probe.

  FIG. 24 shows an SEM image of the magnetic field sensor after the magnetic field sensor of the present invention shown in FIG. 11 is manufactured by the method of FIG. Iron oxide using water as a solvent and a particle size of 10 nm were used as the magnetic fluid. In FIG. 24, it can be seen that the magnetic fine particles 2 are partially attached to the probe 1. The results of measuring the “gradient of the magnetic field gradient” over the magnetic recording medium using this magnetic field sensor are shown in FIGS. FIG. 21 shows a floppy disk, which was measured in a 30 μm × 30 μm region, a scanning time of 1 minute / sheet, and a magnetic field sensor sample distance of 600 nm. FIG. 22 shows a horizontal magnetic recording hard disk, which was measured in an area of 15 μm × 15 μm, a scanning time of 1 minute / sheet, and a distance between magnetic field sensor samples of 220 nm. FIG. 23 shows a perpendicular magnetic recording hard disk, which was measured in an area of 5 μm × 5 μm, a scanning time of 5 minutes / sheet, and a distance between magnetic field sensor samples of 200 nm. All of the above measurements were performed using the magnetic field sensor of FIG. It is shown that a single magnetic field sensor can be used for multiple measurements by changing the sample, and it can be seen that the magnetic field sensor also has durability. Further, it has been confirmed that measurement is possible even after 20 or more probe-sample contact and withdrawal durability tests.

DESCRIPTION OF SYMBOLS 1 Probe 2 Magnetic particle 3 Protective film 4 made of nonmagnetic material Cantilever 5 Wire 6 Magnetic fluid droplet 7 Laser diode 8 Laser 9 Photodiode 10 Preamplifier 11 Automatic gain control circuit 12 Frequency detector 13 Phase shifter 14 Piezoelectric element 15 Feedback control unit 16 Scanner 17 Resist 18 Mask 19 Light for resist exposure 20 Resist photosensitive unit 21 Magnetic field generation source 22 Measurement sample 23 Phase detector 24 Oscillator 25 Control unit 26 High voltage amplifier 27 XYZ-θ stage 28 Electronic component 29 Magnetic field gradient distribution Image 30 Division processing unit 31 Neumann boundary condition 32 Dirichlet boundary condition 33 Three-dimensional magnetic field gradient distribution image 34 Tomographic display in three-dimensional magnetic field gradient distribution

Claims (12)

  A magnetic field sensor comprising: a needle-like part or a plate-like part made of a non-magnetic material; and magnetic fine particles arranged at at least one location of the needle-like part or the plate-like part.   2. The magnetic field sensor according to claim 1, wherein the needle-like portion or the plate-like portion is mainly composed of silicon, tungsten, carbon, silicon oxide, or gallium arsenide. The magnetic field sensor according to claim 1, wherein the needle-like portion or plate-like portion and the magnetic fine particles attached to the needle-like portion or plate-like portion are covered with a thin film made of at least one layer of nonmagnetic material. Magnetic field sensor characterized by having a structure. 2. The magnetic field sensor according to claim 1, wherein the magnetic fine particles contain iron oxide as a main component. 2. The magnetic field sensor according to claim 1, wherein the magnetic fine particles have a functional group on a surface, and the magnetic fine particles and the needle-like portion or the plate-like portion are chemically bonded. 2. The magnetic field sensor according to claim 1, wherein at least one of the magnetic fine particles is arranged within 20 [mu] m from the tip of the probe. A magnetic field sensor characterized by adhering magnetic fine particles to at least one portion of a needle-like part or a plate-like part by immersing or contacting a needle-like part or a plate-like part made of a non-magnetic material with a magnetic fluid. Manufacturing method. 8. The method of manufacturing a magnetic field sensor according to claim 7, comprising at least one layer of non-magnetic material on the needle-like portion or plate-like portion and the magnetic fine particles attached to the needle-like portion or plate-like portion. A method of manufacturing a magnetic field sensor, comprising depositing a coating thin film. 8. The method of manufacturing a magnetic field sensor according to claim 7, wherein at least one magnetic fine particle having a functional group on the surface is attached to at least one portion of the needle-like portion or the plate-like portion. Method 9. The method of manufacturing a magnetic field sensor according to claim 7, wherein the needle-like portion or plate-like portion made of the non-magnetic material is brought into contact with a magnetic fluid droplet in a vibrating state. A magnetic field sensor manufacturing method comprising: adhering while controlling the number or mass of adhering magnetic fine particles and the adhering location based on a change in a vibration state of a part or a plate-like part. 9. The method of manufacturing a magnetic field sensor according to claim 7, wherein magnetic fine particles in the magnetic fluid are unevenly distributed in a part of the liquid droplet in a state where a magnetic field is applied, and the nonmagnetic material is provided at the uneven distribution point. A method for producing a magnetic field sensor, comprising: attaching a magnetic fine particle by contacting or dipping a needle-like part or a plate-like part constituted by: 8. The method of manufacturing a magnetic field sensor according to claim 7, wherein after the magnetic fine particles are attached to the needle-like part or plate-like part made of the nonmagnetic material, the needle-like part or plate-like part is subjected to heat treatment. A method for producing a magnetic field sensor, comprising: removing a solvent contained in a magnetic fluid adhering to a magnetic fluid.

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