Magnetic property measuring device

Abstract

To provide a magnetic characteristic measuring device capable of measuring the magnetic characteristics of an object to be tested at high speed without causing a decrease in the measurement speed due to responsiveness of an electromagnet, and also to provide a magnetic characteristic measuring device capable of performing the highly sensitive measurement due to integration of magnetization distribution of a memory element as an image using a monitor, and TDI (( Time Delay Integration )) camera, and eliminating the need for long-time imaging which has been conventionally performed.SOLUTION: A magnetic characteristic measuring device 100 includes: magnetic field generating parts 101, 102, each of which generates a magnetic field which is constant in time and depends on locations; a moving part 103 which moves an object to be tested in the magnetic field; and measuring parts 104, 105, each of which measures the magnetic characteristics of the object to be tested moving in the magnetic field.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic characteristic measuring device, and more particularly to a magnetic characteristic measuring device for a magnetic film. [Background technology]

[0002] MRAM, a non-volatile memory element that has recently been put into production, records information using magnetism. Each element that records information is required to have uniform magnetic properties, and the variations in magnetic properties must be measured and managed.

[0003] For example, Patent Document 1 describes an electrical characteristic evaluation device that measures electrical resistance distribution while changing a desired magnetic field.

[0004] Additionally, magnetic properties have been measured using methods such as a magneto-optical Kerr effect (MOKE) microscope, which uses a magneto-optical Kerr effect microscope to change the external magnetic field while monitoring the magnetization of the memory element, in order to determine the magnetic field at which magnetization reversal occurs. The MOKE microscope is a microscope that uses the magneto-optical effect to visualize the magnetization of materials. Among the magneto-optical effects, the polar Kerr effect is a phenomenon in which the polarization of reflected light from light irradiated onto the surface of a magnetic material changes relative to the incident light, and the angle of polarization changes depending on the magnetization component perpendicular to the surface of the magnetic material.

[0005] In other words, the reflected light from an unmagnetized magnetic material has the same polarization angle as the incident light, and if magnetized in the + direction, the polarization angle changes to the + direction, if magnetized in the - direction, the polarization angle changes to the - direction, etc. By inserting an analyzer in the optical path of the reflected light, the amount of light changes according to the polarization angle of the reflected light that passes through the analyzer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-301548 A Summary of the Invention [Problem to be solved by the invention]

[0007] By capturing an image of this change with a camera, a microscope can be made that can image the magnetization. By using this microscope to monitor the magnetization while changing the magnetic field applied to the magnetic material, the magnetic properties of the magnetic material can be imaged.

[0008] In the configuration of Figure 6, laser light that has been linearly polarized by a polarizing element 11 is irradiated onto a wafer 12, and the reflected light is made incident on a camera 14 through an analyzer 13. The amount of light incident on the camera 14 by the analyzer 13 changes according to the polarization angle, so the magnetization distribution is imaged. By sweeping the magnetic field, the magnetic properties of the wafer can be measured from the polarization angle distribution according to the magnetic field.

[0009] As a typical example, consider a case where memory elements 21 are arranged as shown in Fig. 7, and the characteristics of each element are as shown in Fig. 8. Note that the memory elements 21 are illustrated as schematics, and the shape and spacing may differ from this description.

[0010] When the magnetic field is gradually increased from -Hs, the images captured at each point in Figure 9 appear as in Figure 10. From the images obtained, the coercive force of each memory element 21 (in the above example, the magnetic field of image 2 in Figure 10) and its variation can be known. If the size of the memory element 21 is smaller than the camera resolution, the average magnetic characteristics of the observation area are obtained.

[0011] However, when performing the above measurements, it takes time to change the magnetic field according to the magnet's characteristics, and the camera's exposure time needs to be long to detect weak signals, so the measurements take time. In particular, when inspecting the entire surface of a wafer, it is necessary to move the wafer and repeat measurements, which increases the inspection time, which is a problem.

[0012] Furthermore, conventionally, coercivity was measured using a magnetic hysteresis loop. In other words, an external magnetic field was applied to the test specimen, and the magnetization of the test specimen was measured while sweeping the magnetic field strength. For example, as shown in Figure 11, this resulted in a cycle of measuring the + side coercivity and the - side coercivity. Therefore, as shown in Figure 12, both time was required to measure the + side coercivity and time was required to measure the - side coercivity, which caused a problem of increased inspection time.

[0013] An object of the present invention is to provide a means for performing high-speed measurement that shortens the measurement time. [Means for solving the problem]

[0014] One embodiment of a magnetic property measuring device comprises a magnetic field generating unit that generates a magnetic field that is constant over time but varies depending on the location, a moving unit that moves a test subject through the magnetic field, and a measuring unit that measures the magnetic properties of the test subject moving through the magnetic field.

[0015] According to the magnetic characteristic measuring device of one embodiment, there is no decrease in measurement speed due to the responsiveness of the electromagnet, and the magnetic characteristics of the test object can be measured at high speed.

[0016] The magnetic characteristic measuring device of one embodiment includes a laser unit that irradiates a laser beam onto a test object,

[0017] An imaging unit may be provided that captures the polarized light of the reflected light from the test object in synchronization with the movement, and detects the magnetic characteristics as an image.

[0018] According to the magnetic characteristic measuring device of one embodiment, multiple locations can be measured simultaneously.

[0019] The magnetic characteristic measuring device of one embodiment may include a heating laser unit that irradiates the test piece with laser light to raise the temperature of the test piece.

[0020] According to the magnetic characteristic measuring device of one embodiment, it is possible to measure magnetic characteristics accompanying temperature changes.

[0021] In one embodiment of the magnetic characteristic measuring device, the heating laser unit may irradiate a part of the test object.

[0022] According to the magnetic characteristic measuring device of one embodiment, it is possible to raise the temperature only in the places required for the magnetic characteristics.

[0023] The magnetic characteristic measuring device of one embodiment may include a swing mirror that deflects the beam of the laser light, and the swing mirror may be configured to synchronize its deflection direction with the movement of the stage.

[0024] According to one embodiment of the magnetic property measuring device, even if the stage moves, the heating laser can continue to heat the same point on the wafer at all times.

[0025] In one embodiment of the magnetic characteristic measuring device, the heating laser unit may be configured to calibrate the amount of laser light with respect to temperature in advance, so as to keep the temperature of the test object substantially constant.

[0026] According to one embodiment of the magnetic characteristic measuring device, the magnetic characteristics of a test object at a predetermined temperature can be measured.

[0027] In one embodiment of the magnetic characteristic measuring device, the calibration value of the laser light may be calibrated in advance for a plurality of temperatures, and the temperature may be raised to any desired temperature.

[0028] According to the magnetic characteristic measuring device of one embodiment, the magnetic characteristics of a test object can be measured at any temperature.

[0029] In one embodiment of the magnetic characteristic measuring device, the test object may be a semiconductor.

[0030] According to the magnetic characteristic measuring device of one embodiment, the magnetic characteristics of a semiconductor can be measured, and the quality of the semiconductor can be inspected. Effect of the Invention

[0031] According to the magnetic property measuring device of the present invention, the measurement speed does not decrease due to the response of the electromagnet, and the magnetic properties of the test object can be measured at high speed. In addition, according to the magnetic property measuring device of the present invention, the magnetization distribution of the memory element is monitored as an image and integrated using a TDI (Time Delay Integration) camera, so that highly sensitive measurement is possible and the long imaging time required in the past is not necessary. [Brief description of the drawings]

[0032] [Figure 1] 1 is a diagram showing an outline of a magnetic characteristic measuring device according to a first embodiment. [Diagram 2] 1 is a diagram showing the relationship between the moving direction of the test object and the scanning direction of the TDI camera 105. FIG. [Diagram 3] FIG. 2 is a diagram showing an example of a scan by the TDI camera 105. [Figure 4] FIG. 13 is a diagram showing an outline of a magnetic characteristic measuring device according to a second embodiment. [Diagram 5] FIG. 13 is a diagram showing an outline of a magnetic characteristic measuring device according to a third embodiment. [Figure 6] FIG. 1 is a diagram illustrating an example of a magnetic characteristic measuring device. [Figure 7] FIG. 1 is a diagram showing an example of an image captured when measuring characteristics of a memory element. [Figure 8] 1 is a graph showing the relationship between an external magnetic field and a Kerr rotation angle. [Figure 9] 1 is a graph showing the relationship between an external magnetic field and a Kerr rotation angle. [Figure 10] FIG. 1 is a diagram showing an example of an image captured when measuring characteristics of a memory element. [Figure 11] 1 is a graph showing the relationship between an external magnetic field and a Kerr rotation angle. [Figure 12] 1 is a graph showing the relationship between time and magnetic field change in magnetic property measurement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] (Embodiment 1) Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram of a magnetic property measuring device according to embodiment 1. In Fig. 1, the magnetic property measuring device 100 includes an electromagnet 101, an electromagnet 102, a stage 103, a Kerr rotation angle detection optical system 104, a TDI camera 105, and a base 106.

[0034] Electromagnets 101 and 102 are magnetic field generating units that generate a magnetic field that is constant over time and varies depending on the location. For example, electromagnets 101 and 102 are composed of coils, and generate a magnetic field that is constant over time by applying a constant voltage and current to the coils.

[0035] Furthermore, the positions of the electromagnets 101 and 102 are fixed. For example, the electromagnets 101 and 102 are fixed at positions at a predetermined distance from the space in which the stage 103 moves. The electromagnets 101 and 102 are spaced apart from each other, and there is a space between the electromagnets 101 and 102 in which the Kerr rotation angle detection optical system 104 can observe the test object.

[0036] 1, electromagnet 101 generates a magnetic field in an upward direction (positive direction of the Z axis) relative to the drawing. Electromagnet 102 generates a magnetic field in a downward direction (negative direction of the Z axis) relative to the drawing. By combining electromagnets 101 and 102 in this way, electromagnets 101 and 102 can generate a magnetic field that is constant over time and varies depending on the location.

[0037] The stage 103 is a moving part that moves the test object in the magnetic field. For example, the stage 103 is a stage on which the test object is placed and moved. The stage 103 moves from the electromagnet 102 side to the electromagnet 101 side via the observation position of the Kerr rotation angle detection optical system 104.

[0038] The Kerr rotation angle detection optical system 104 is a part of a measurement unit that measures the magnetic properties of a test object moving in a magnetic field. Specifically, the Kerr rotation angle detection optical system 104 measures the magnetic properties of the test object by measuring the polarized light when light is irradiated onto the test object.

[0039] The TDI camera 105 is part of a measurement unit that measures the magnetic properties of a test object moving in a magnetic field. Specifically, the TDI camera 105 performs integral exposure of the moving object.

[0040] The surface plate 106 is a surface plate on which the stage 103 moves.

[0041] With the above configuration, the magnetic property measuring device measures the magnetic properties of the test object. Next, the operation of imaging the moving test object with the TDI camera 105 will be explained. Figure 2 is a diagram showing the relationship between the movement direction of the test object and the scanning direction of the TDI camera 105. As shown in Figure 2, the test object moves in the positive direction of the X-axis. In contrast, since the TDI camera 105 is fixed, the scanning direction of the image is the negative direction of the X-axis.

[0042] Fig. 3 is a diagram showing an example of scanning by the TDI camera 105. As shown in Fig. 3, the TDI camera 105 captures an image for each TDI clock.

[0043] The captured images are superimposed by shifting them in the X direction by the distance the test object moves during the time until the next capture timing. By repeating this superimposition, images captured at the same position on the test object can be superimposed. As a result, the results of multiple captures of the test object can be accumulated.

[0044] According to the magnetic property measuring device of the first embodiment, the magnetic field applied to the memory element changes depending on the stage position, so the magnetic field generated by the electromagnet can be constant and there is no need to change the current flowing through the coil. Therefore, the magnetic property measuring device of the first embodiment can perform high-speed measurements without a decrease in measurement speed due to the responsiveness of the electromagnet. Furthermore, in the magnetic property measuring device of the first embodiment, the magnetization distribution of the memory element is monitored as an image and accumulated using a TDI camera, making it possible to perform highly sensitive measurements and eliminating the need for long-term imaging as was previously required. Specifically, since the test object moves through a magnetic field that is positionally constant, the magnetic properties can be measured simply by measuring -Hs from the magnetic field +Hs through the magnetic field 0.

[0045] Moreover, according to the magnetic property measuring device of the first embodiment, the change in polarization caused by the reflected light from the test object is captured as an image, so that the magnetic properties can be measured as an image of the test object, and the magnetic properties of multiple locations can be measured simultaneously. That is, according to the magnetic property measuring device of the first embodiment, the magnetic properties can be measured by irradiating the test object while it is moving, continuously measuring the polarization angle of the reflected light, and monitoring the polarization angle with respect to the position. A TDI (Time Delay Integration) camera can be used for this continuous measurement while it is moving. This camera captures images synchronized with the movement, and by accumulating the images, it is possible to capture images of a moving object at high speed and with high sensitivity, and is widely used in semiconductor inspection devices. By using this camera, it is possible to capture images of a moving object continuously, and it is possible to detect minute polarization angles with high sensitivity.

[0046] (Embodiment 2) In the second embodiment, an example in which a permanent magnet is used instead of an electromagnet will be described. Fig. 4 is a diagram showing an outline of a magnetic property measuring device according to the second embodiment. In Fig. 4, a magnetic property measuring device 200 includes a permanent magnet 201, a permanent magnet 202, a stage 103, a Kerr rotation angle detection optical system 104, a TDI camera 105, and a base 106. In Fig. 4, the same components as those in Fig. 1 are given the same numbers, and descriptions thereof will be omitted.

[0047] The permanent magnets 201 and 202 are magnetic field generating units that generate a magnetic field that is constant over time and varies depending on the location. The permanent magnets 201 and 202 generate a magnetic field that is constant over time. Furthermore, the positions of the permanent magnets 201 and 202 are fixed. For example, the permanent magnets 201 and 202 are fixed at a position a predetermined distance from the space in which the stage 103 moves. The permanent magnets 201 and 202 are spaced apart from each other, and there is a space between the permanent magnets 201 and 202 where the Kerr rotation angle detection optical system 104 can observe the test object.

[0048] 4, permanent magnet 201 generates a magnetic field in an upward direction (positive direction of the Z axis) with respect to the drawing. Also, permanent magnet 202 generates a magnetic field in a downward direction (negative direction of the Z axis) with respect to the drawing. By combining permanent magnet 201 and permanent magnet 202 in this way, permanent magnet 201 and permanent magnet 202 can generate a magnetic field that is constant over time and varies depending on the location.

[0049] Thus, with the magnetic property measuring device of the second embodiment, the magnetic field generated by the magnet is constant and does not vary over time, so a permanent magnet can be used without an electromagnet. As a result, with the magnetic property measuring device of the second embodiment, power to drive an electromagnet is not required, and not only is it faster, but it is also more energy-efficient and less expensive.

[0050] (Embodiment 3) In the third embodiment, an example having a configuration for heating a test object will be described. Fig. 5 is a diagram showing an outline of a magnetic property measuring device according to the third embodiment. In Fig. 5, the magnetic property measuring device includes an electromagnet 101, an electromagnet 102, a stage 103, a Kerr rotation angle detection optical system 104, a TDI camera 105, a base 106 (not shown), a heating laser unit 301, an oscillating mirror 302, a beam splitter 303, and a lens 304.

[0051] Moreover, the Kerr rotation angle detection optical system 104 includes a laser unit 141, a lens 142, a polarizing element 143, a beam splitter 144, a lens 145, and a polarizing beam splitter 146. In Fig. 5, the same components as those in Fig. 1 are given the same numbers, and the description thereof will be omitted.

[0052] The heating laser unit 301 emits a laser to be irradiated onto the test object. Any wavelength and light source that can heat up the test object can be applied to the heating laser unit 301.

[0053] Oscillating mirror 302 is a mirror device that reflects the light from heating laser unit 301 in any direction. Oscillating mirror 302 deflects the heating laser beam so that it can follow the moving stage 103. Specifically, the reflecting direction of oscillating mirror 302 is controlled by a controller (not shown). This controller changes the direction in which heating laser unit 301 reflects the laser light along with the movement of the test object on stage 103, so that the part of the test object that is irradiated with the laser light does not change even when the test object is moving.

[0054] The beam splitter 303 reflects the laser light from the heating laser unit 301 toward the test object. The beam splitter 303 also transmits the laser light from the laser unit 141 toward the test object. The beam splitter 303 then transmits the light whose polarization has been changed in the test object due to the Kerr effect toward the TDI camera 105 (via the beam splitter 144).

[0055] The lens 304 is a lens that collects the laser light from the temperature increasing laser unit 301 and the laser light from the laser unit 141 .

[0056] The laser unit 141 emits laser light for measuring the Kerr effect. The lens 142 is a collimator lens that refracts the laser light from the laser unit 141 into parallel light.

[0057] The polarizing element 143 is an element that transmits only a predetermined polarized light of the laser light from the laser unit 141 .

[0058] The beam splitter 144 transmits the laser light from the laser unit 141 toward the beam splitter 303. The beam splitter 144 also reflects the light from the beam splitter 303 (i.e., the light whose polarization has been changed in the test object due to the Kerr effect) toward the TDI camera 105.

[0059] The lens 145 is a lens that focuses the image pickup surface of the TDI camera 105 . The polarizing beam splitter 146 is an optical element that separates the incident light into S-polarized light and P-polarized light.

[0060] In this way, according to the magnetic characteristic measuring apparatus of the third embodiment, even if the stage moves, the heating laser can continue to heat the same point on the wafer at all times.

[0061] Furthermore, the magnetic property measuring device of the third embodiment is provided with a heating laser unit that irradiates the test piece with laser light to raise the temperature of the test piece, thereby making it possible to measure magnetic properties that vary with temperature.

[0062] Moreover, the magnetic characteristic measuring device of the third embodiment can heat only the portion required for magnetic characteristic measurement by irradiating the heating laser unit on a portion of the test piece.

[0063] In addition, the magnetic property measuring device of embodiment 3 is equipped with an oscillating mirror that deflects the beam of laser light, and the oscillating mirror synchronizes its deflection direction with the stage movement, so that the heating laser can continue to heat the same point on the wafer at all times even if the stage moves.

[0064] In addition, in the magnetic property measuring device of embodiment 3, the heating laser unit calibrates the amount of laser light in advance with respect to temperature, and keeps the temperature of the test piece approximately constant, thereby enabling the magnetic properties of the test piece at a specified temperature to be measured.

[0065] Furthermore, in the magnetic property measuring device of embodiment 3, the calibration value of the laser light is calibrated in advance for a plurality of temperatures, and by making it possible to raise the temperature to any desired temperature, it is possible to measure the magnetic properties of the test object at any desired temperature.

[0066] Furthermore, by using a semiconductor as the test object, the magnetic property measuring device of the third embodiment can measure the magnetic properties of the semiconductor and inspect the quality of the semiconductor. For example, to use it as a practical MRAM device, it is necessary that the properties do not deteriorate in a high-temperature environment. The production of MRAM includes processes that are subject to high temperatures, and when the device is mounted, it is necessary to withstand the soldering temperature. Therefore, when measuring the magnetic properties of MRAM, it is also important to measure in a high-temperature environment. By irradiating the entire or part of the observation area with laser light, the temperature is raised, making it possible to measure the magnetic properties in a high-temperature environment. By heating only a part of the observation area, the fluctuation in magnetic properties due to temperature can be seen with a single image.

[0067] The present invention is not limited to the above-mentioned embodiment, and can be appropriately modified within the scope of the present invention. For example, the electromagnets 101 and 102 may be disposed at any position as viewed from the XY plane in FIG. 1, provided that the position is for moving the test object into the magnetic field. Similarly, the permanent magnets 201 and 202 may be disposed at any position as viewed from the XY plane in FIG. 4, provided that the position is for moving the test object into the magnetic field. The laser unit 141 is a light source for measuring the Kerr effect, and may be a light-emitting element other than a laser, such as a light-emitting diode. In the third embodiment, the permanent magnets 201 and 202 may be used instead of the electromagnets 101 and 102, as in the second embodiment. [Explanation of symbols]

[0068] 100 Magnetic property measuring device 101,102 Electromagnet 103 Stage 104 Rotation angle detection optical system 105 Camera 106 Fixed Plate 141 Laser section 142 Lens 143 Polarizing element 144,303 Beam splitter 145,304 Lenses 146 Polarizing Beam Splitter 200 Magnetic property measuring device 201,202 Permanent magnets 301 Laser for heating 302 Swinging Mirror

Claims

1. A magnetic field generating unit that generates a magnetic field that is constant over time and varies depending on the location; A moving unit that moves the test object in the magnetic field; a measurement unit for measuring the magnetic properties of the test object moving in the magnetic field; A laser unit that irradiates a laser beam onto a test object; An image unit that captures the polarized light of the reflected light from the test object in synchronization with the movement and detects the magnetic characteristics as an image, The magnetic field generating unit has a first magnet and a second magnet, The positions of the first magnet and the second magnet are fixed, the first magnet and the second magnet are both electromagnets, or the first magnet and the second magnet are both permanent magnets; A magnetic characteristic measuring device, wherein the direction of the magnetic field generated by the first magnet and the second magnet is parallel to the direction in which the laser light of the laser unit irradiates the test object.

2. 2. The magnetic characteristic measuring device according to claim 1, further comprising a heating laser unit for irradiating the test piece with a laser beam to raise the temperature of the test piece.

3. The magnetic characteristic measuring device according to claim 2 , wherein the heating laser unit irradiates a part of the test object.

4. A swing mirror is provided to deflect the light beam of the laser light of the heating laser unit, 4. The magnetic characteristic measuring apparatus according to claim 2, wherein the deflection direction of said oscillating mirror is synchronized with the movement of the stage.

5. 5. The magnetic characteristic measuring device according to claim 2, wherein the temperature increasing laser unit pre-calibrates the amount of laser light relative to temperature to keep the temperature of the test object substantially constant.

6. 6. The magnetic characteristic measuring device according to claim 5, wherein the calibration value of said laser light is calibrated in advance for a plurality of temperatures, and said laser light can be heated to any desired temperature.

7. 7. The magnetic characteristic measuring apparatus according to claim 1, wherein the test object is a semiconductor.

8. The direction of the magnetic field generated by the first magnet and the direction of the magnetic field generated by the second magnet are opposite to each other, 8. The magnetic characteristic measuring device according to claim 1, wherein the measuring section measures polarized light when the test object moving in the magnetic field is irradiated with light.

9. 9. The magnetic characteristic measuring device according to claim 8, wherein the direction in which the moving section moves the test object in the magnetic field is perpendicular to the direction of the magnetic field generated by the first magnet and the direction of the magnetic field generated by the second magnet.

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