Inspection Equipment

Abstract

To provide an inspection device that can improve the detection accuracy of a characteristic of an MRAM element.SOLUTION: An inspection device 1 includes: a stage 10 that has a magnetoresistive memory element fixed on a stage surface 13; a plurality of electromagnets 20 that generate a first magnetic field in which a direction of a magnetic field component in a vertical direction perpendicular to the stage surface 13 changes from a first direction to a second direction depending on a position on the stage surface 13 and a second magnetic field in which a direction of the magnetic field component in an in-plane direction parallel to the stage surface 13 changes from a third direction to a fourth direction depending on the position on the stage surface 13; an optical system 30 that irradiates the magnetoresistive memory element with illumination light including polarized light and condenses reflection light of the illumination light reflected by the magnetoresistive memory element; and a detector 40 that detects the reflection light in a case where a position of the magnetoresistive memory element in the first magnetic field is changed and the reflection light in a case where the position of the magnetoresistive memory element in the second magnetic field is changed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an inspection device, for example, an inspection device that inspects the magnetic properties of a magnetoresistive memory element. [Background technology]

[0002] Magnetoresistive Random Access Memory (MRAM) devices are nonvolatile memory devices that use magnetic tunnel junctions (MTJs). In semiconductor production lines, early inspection of MRAM devices fabricated on wafers for defects before the devices are completed is crucial for improving MRAM device production yield. Pre-assembly inspection of MRAM devices requires not only nondestructive visual inspection using optical microscopes or electron beams, but also the understanding of their magnetic field characteristics. Optical measurement utilizing the magneto-optical effect known as the magneto-optical Kerr effect (MOKE) is a well-known high-speed magnetic field measurement method. This method applies an external magnetic field to each MRAM device, and by varying the magnetic field strength, the magnetic hysteresis loop at the measurement point can be obtained by measuring the change in polarization of the reflected light.

[0003] Patent document 1 describes an inspection device that uses a gradient magnetic field generated between the yoke of an electromagnet having two coils to scan an MRAM device on a stage and detects defects in the MRAM element using a TDI (TDI Delay Integration) camera. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-072599 Summary of the Invention [Problem to be solved by the invention]

[0005] In the inspection device of Patent Document 1, the horizontal magnetic field is almost constant before and after the magnetic field reversal of the vertical magnetic field (easy axis direction), so it is possible to detect the characteristics of the vertical magnetic field. However, the inspection device of Patent Document 1 has difficulty detecting changes in the characteristics of MRAM elements due to changes in the horizontal magnetic field, and it is not possible to improve the detection accuracy of the magnetic characteristics of MRAM elements.

[0006] The present disclosure has been made to solve such problems, and aims to provide an inspection device that can improve the detection accuracy of the magnetic properties of MRAM elements. [Means for solving the problem]

[0007] An inspection device according to an embodiment includes: a stage having a stage surface on which a magnetoresistive memory element is fixed; a plurality of electromagnets that generate a first magnetic field in which the direction of a magnetic field component in a vertical direction perpendicular to the stage surface changes from a first direction to a second direction opposite to the first direction depending on a position on the stage surface, and a second magnetic field in which the direction of the magnetic field component in an in-plane direction parallel to the stage surface changes from a third direction to a fourth direction opposite to the third direction depending on the position on the stage surface; an optical system that illuminates the magnetoresistive memory element with illumination light including polarized light and collects light reflected from the magnetoresistive memory element; a detector that detects the reflected light when the position of the magnetoresistive memory element is changed in the first magnetic field and the reflected light when the position of the magnetoresistive memory element is changed in the second magnetic field; Equipped with.

[0008] In the above inspection device, When the position of the magnetoresistive memory element is changed so as to change from the first orientation to the second orientation within the first magnetic field, the magnetic field component perpendicular to the first scanning direction and the perpendicular direction may be zero.

[0009] In the above inspection device, When the position of the magnetoresistive memory element is changed so as to change from the third orientation to the fourth orientation within the second magnetic field, the magnetic field component in the second scanning direction and the magnetic field component in the perpendicular direction may be 0.

[0010] In the above inspection device, the plurality of electromagnets includes at least four electromagnets including a first electromagnet, a second electromagnet, a third electromagnet, and a fourth electromagnet; the first electromagnet includes a first coil wound in a predetermined direction around a first vertical portion of an L-shaped first yoke having a first vertical portion extending in the vertical direction and a first in-plane portion extending in the in-plane direction, the second electromagnet includes a second coil wound in the predetermined direction around a second vertical portion of an L-shaped second yoke having a second vertical portion extending in the vertical direction and a second in-plane portion extending in the in-plane direction, the third electromagnet includes a third coil wound in the predetermined direction around a third vertical portion of an L-shaped third yoke having a third vertical portion extending in the vertical direction and a third in-plane portion extending in the in-plane direction, the fourth electromagnet includes a fourth coil wound in the predetermined direction around a fourth vertical portion of an L-shaped fourth yoke having a fourth vertical portion extending in the vertical direction and a fourth in-plane portion extending in the in-plane direction, The first in-plane portion and the second in-plane portion extend in one direction, and an end portion of the first in-plane portion and an end portion of the second in-plane portion face each other in the one direction, The third in-plane portion and the fourth in-plane portion extend in another direction perpendicular to the one direction, and the end portion of the third in-plane portion and the end portion of the fourth in-plane portion face each other in the other direction, the first magnetic field is generated by passing a current in a fifth direction through the first coil, passing a current in a sixth direction opposite to the fifth direction through the second coil, and setting the currents flowing through the third coil and the fourth coil to zero; The second magnetic field may be generated by passing the current in the fifth direction through the first coil and the second coil, and passing the current in the sixth direction through the third coil and the fourth coil.

[0011] In the above inspection device, the detector Detecting the reflected light when the position of the magnetoresistive memory element in the first magnetic field is scanned in the one direction; The reflected light may be detected when the position of the magnetoresistive memory element in the second magnetic field is scanned in the one direction and in a direction at an angle of 45° to the other direction.

[0012] In the above inspection device, an information processing unit that processes an image of the reflected light detected by the detector; The information processing unit The magnetoresistive memory element may be inspected for defects caused by the magnetic field component in the perpendicular direction from a difference image between the image in the magnetic field component in the first direction and the image in the magnetic field component in the second direction.

[0013] In the above inspection device, an information processing unit that processes an image of the reflected light detected by the detector; The information processing unit The magnetoresistive memory element may be inspected for defects due to the magnetic field component in the in-plane direction from a difference image between the image in the magnetic field component in the third direction and the image in the magnetic field component in the fourth direction. [Effects of the Invention]

[0014] According to the inspection device of the present disclosure, it is possible to provide an inspection device that can improve the detection accuracy of the magnetic properties of MRAM. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view illustrating an inspection device according to a first embodiment. [Figure 2] FIG. 2 is a perspective view illustrating an electromagnet of the inspection device according to the first embodiment. [Figure 3] 1 is a graph illustrating magnetic properties in the easy axis direction of the MRAM element using the VSM according to the first embodiment, where the horizontal axis indicates the external magnetic field and the vertical axis indicates the magnetization. [Figure 4] 1 is a graph illustrating magnetic characteristics in the hard axis direction of the MRAM element using VSM according to the first embodiment, where the horizontal axis indicates an external magnetic field and the vertical axis indicates magnetization. [Figure 5] 10 is a diagram illustrating the energization of a coil when a magnetic field having a magnetic field component in a direction perpendicular to the stage surface is applied to an MRAM element according to the first embodiment. FIG. [Figure 6] 1 is a graph illustrating magnetic flux density in the α-axis direction along the first scan axis, and the β-axis and γ-axis directions perpendicular to the first scan axis in embodiment 1, where the horizontal axis indicates position along the α-axis and the vertical axis indicates magnetic flux density. [Figure 7] 4 is a diagram illustrating magnetic flux density vectors in an αγ plane according to the first embodiment. FIG. [Figure 8] 10 is a diagram illustrating the energization of a coil when a magnetic field having a magnetic field component in a direction parallel to the stage surface is applied to an MRAM element according to the first embodiment. FIG. [Figure 9] 1 is a graph illustrating magnetic flux density in the α-axis direction along the second scan axis, and the β-axis and γ-axis directions perpendicular to the second scan axis in embodiment 1, where the horizontal axis indicates position along the α-axis and the vertical axis indicates magnetic flux density. [Figure 10] 4 is a diagram illustrating magnetic flux density vectors in an αβ plane according to the first embodiment. FIG. [Figure 11] 1 is a diagram illustrating the magnetic characteristics of an MRAM element, in which the horizontal axis indicates the external magnetic field and the vertical axis indicates the Kerr rotation angle. [Figure 12] 1 is a diagram illustrating the magnetic characteristics of an MRAM element, in which the horizontal axis indicates the external magnetic field and the vertical axis indicates the Kerr rotation angle. [Figure 13] FIG. 1 is a plan view illustrating a wafer according to a first embodiment. [Figure 14] FIG. 2 is a configuration diagram illustrating the details of the inspection device according to the first embodiment. [Figure 15] FIG. 2 is a flowchart illustrating a method for inspecting a wafer including MRAM elements according to the first embodiment. [Figure 16] 4 is a flowchart illustrating a method for inspecting magnetic properties in the perpendicular direction of the MRAM element according to the first embodiment. FIG. [Figure 17] 4 is a flowchart illustrating a method for inspecting the magnetic properties in the in-plane direction of the MRAM element according to the first embodiment. FIG. [Figure 18] FIG. 10 is a flowchart illustrating a method for inspecting magnetic properties in the perpendicular direction of an MRAM element according to the second embodiment. [Figure 19] 10 is a flowchart illustrating a method for inspecting the magnetic properties in the in-plane direction of an MRAM element according to the second embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. In addition, the same elements in each drawing are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0017] (Embodiment 1) An inspection apparatus according to a first embodiment will be described. FIG. 1 is a cross-sectional view illustrating the inspection apparatus according to the first embodiment. FIG. 2 is a perspective view illustrating an electromagnet of the inspection apparatus according to the first embodiment. In FIG. 1, hatching of some components has been omitted, and some reference numerals have been omitted to avoid cluttering the drawing. This also applies to the following figures. As shown in FIGS. 1 and 2, the inspection apparatus 1 includes a stage 10, multiple electromagnets 20, an optical system 30, a detector 40, and an information processing unit 50. Below, <1. Stage>, <2. Multiple electromagnets>, <3. Optical system>, <4. Detector>, and <5. Information processing unit> will be described. After that, <6. Details of the inspection apparatus> and <7. Inspection method> will be described. In addition, in <2. Multiple electromagnets>, <2-1. Magnetic properties of MRAM element>, <2-2. Application of magnetic field perpendicular to the stage surface>, and <2-3. Application of magnetic field parallel to the stage surface> will be described.

[0018] <1. Stage> The stage 10 includes a moving part 11 and a main body part 12. The upper surface of the moving part 11 is called the stage surface 13. Thus, the stage 10 has the stage surface 13. The stage 10 fixes a magnetoresistive memory element (hereinafter referred to as an MRAM element) on the stage surface 13. For example, the stage 10 places a sample such as a wafer WF including an MRAM element on the stage surface 13. In the following description, the sample will be described as a wafer WF. Note that the sample is not limited to a wafer WF, and may be a semiconductor device or the like, as long as it includes an MRAM element.

[0019] The moving part 11 of the stage 10 may have a wafer chuck for fixing the wafer WF. The wafer WF is fixed on the stage surface 13 by the wafer chuck using vacuum or static electricity. The stage 10 may have XYZθ drive axes with actuators such as linear motors, ball screws, VCMs, and piezoelectric elements to move the wafer WF. The moving part 11 moves relative to the main body part 12 based on the XYZθ drive axes. An inspection plane WO is introduced as a plane parallel to the stage surface 13.

[0020] Here, for convenience of explanation of the inspection apparatus 1, an XYZ Cartesian coordinate system is introduced. For example, the direction perpendicular to the inspection surface W0 is the Z-axis direction, and the plane parallel to the inspection surface W0 is the XY plane. For convenience, the Z-axis direction is referred to as the vertical direction or the perpendicular direction, the +Z-axis direction is referred to as the upward direction, and the -Z-axis direction is referred to as the downward direction. The XY plane is referred to as the horizontal plane, and the direction parallel to the XY plane is referred to as the horizontal direction or the in-plane direction. Note that the terms vertical direction, vertical direction, upward, downward, horizontal plane, horizontal direction, and in-plane direction are used for convenience and do not indicate the directions in which the actual inspection apparatus 1 is disposed. The stage 10 inspects the MRAM elements included in the wafer WF by scanning in a predetermined direction in the XY plane.

[0021] For example, the stage 10 can move the wafer WF in a predetermined direction, including the X-axis direction and the Y-axis direction, within a plane parallel to the inspection surface WO. The stage 10 can also rotate the wafer WF on the stage surface 13 around a rotation axis extending in a direction perpendicular to the inspection surface WO. Furthermore, the stage 10 can move the wafer WF on the stage surface 13 in a direction perpendicular to the inspection surface WO.

[0022] <2. Multiple electromagnets> The plurality of electromagnets 20 may include at least four electromagnets 20a to 20d, including electromagnets 20a to 20d. The at least four electromagnets 20a to 20d are collectively referred to as electromagnets 20. Electromagnets 20a and 20b are arranged facing each other in the X-axis direction. Electromagnets 20c and 20d are arranged facing each other in the Y-axis direction. Note that the number of electromagnets 20 may be five or more, as long as it includes at least four electromagnets 20a to 20d. In this case, the electromagnets 20 are not limited to being arranged facing each other in the X-axis and Y-axis directions.

[0023] The electromagnets 20a to 20d may include coils 21a to 21d, respectively. The coils 21a to 21d are collectively referred to as coils 21. By controlling the direction of the current flowing through coils 21, the direction of the magnetic field generated by the electromagnet 20 can be controlled.

[0024] The electromagnets 20a to 20d may be fixed to yokes 22a to 22d, respectively. The yokes 22a to 22d are collectively referred to as yoke 22. The yoke 22 has, for example, an L-shape. The yoke 22 is L-shaped and has a vertical portion 23 extending in a direction perpendicular to the stage surface 13 and an in-plane portion 24 extending in a direction parallel to the stage surface 13. The coil 21 is wound around the vertical portion 23 in a predetermined direction.

[0025] Specifically, electromagnet 20a includes a coil 21a wound in a predetermined direction around vertical portion 23a of L-shaped yoke 22a, which has vertical portion 23a extending in a direction perpendicular to stage surface 13 and in-plane portion 24a extending in a direction parallel to stage surface 13. Electromagnet 20b includes a coil 21b wound in a predetermined direction around vertical portion 23b of L-shaped yoke 22b, which has vertical portion 23b extending in a direction perpendicular to stage surface 13 and in-plane portion 24b extending in a direction parallel to stage surface 13. Electromagnet 20c includes a coil 21c wound in a predetermined direction around vertical portion 23c of L-shaped yoke 22c, which has vertical portion 23c extending in a direction perpendicular to stage surface 13 and in-plane portion 24c extending in a direction parallel to stage surface 13. The electromagnet 20d includes a coil 21d wound in a predetermined direction around a vertical portion 23d of an L-shaped yoke 22d having a vertical portion 23d extending in a direction perpendicular to the stage surface 13 and an in-plane portion 24d extending in a direction parallel to the stage surface 13.

[0026] The vertical portions 23a to 23d are collectively referred to as vertical portion 23, and the in-plane portions 24a to 24d are collectively referred to as in-plane portion 24. Coils 21a to 21d are wound in the same predetermined direction on the vertical portions 23a to 23d, respectively. The vertical portions 23a to 23d extend in the Z-axis direction. The vertical portions 23a to 23d pass through the central axes of the electromagnets 20a to 20d, respectively. The upper ends of each of the yokes 22a to 22d, i.e., the upper ends of the vertical portions 23a to 23d, are connected to a connecting plate 25. The lower ends of the vertical portions 23a to 23d are connected to one end of the in-plane portions 24a to 24d, respectively.

[0027] The in-plane portion 24a of the yoke 22a and the in-plane portion 24b of the yoke 22b extend in the X-axis direction. One end of the in-plane portion 24a is connected to the lower end of the vertical portion 23a, which passes through the center of the electromagnet 20a. Therefore, the in-plane portion 24a extends in the +X-axis direction from the lower end of the vertical portion 23a. One end of the in-plane portion 24b is connected to the lower end of the vertical portion 23b, which passes through the center of the electromagnet 20b. Therefore, the in-plane portion 24b extends in the -X-axis direction from the lower end of the vertical portion 23b. The end of the in-plane portion 24a and the end of the in-plane portion 24b face each other in the X-axis direction.

[0028] The in-plane portion 24c of the yoke 22c and the in-plane portion 24d of the yoke 22d extend in the Y-axis direction. One end of the in-plane portion 24c is connected to the lower end of the vertical portion 23c, which passes through the center of the electromagnet 20c. Therefore, the in-plane portion 24c extends in the +Y-axis direction from the lower end of the vertical portion 23c. One end of the in-plane portion 24d is connected to the lower end of the vertical portion 23d, which passes through the center of the electromagnet 20d. Therefore, the in-plane portion 24d extends in the -Y-axis direction from the lower end of the vertical portion 23d. The end of the in-plane portion 24c and the end of the in-plane portion 24d face each other in the Y-axis direction.

[0029] <2-1. Magnetic properties of MRAM elements> Next, the magnetic characteristics of the MRAM measured by a vibrating sample magnetometer (hereinafter referred to as VSM) will be described. Fig. 3 is a graph illustrating the magnetic characteristics in the easy axis direction of the MRAM element measured by the VSM according to the first embodiment, where the horizontal axis indicates the external magnetic field and the vertical axis indicates the magnetization. Fig. 4 is a graph illustrating the magnetic characteristics in the hard axis direction of the MRAM element measured by the VSM according to the first embodiment, where the horizontal axis indicates the external magnetic field and the vertical axis indicates the magnetization.

[0030] As shown in FIG. 3, the magnetization of an MRAM element perpendicular to the top surface of the wafer WF is easily reversed by changing an external magnetic field. The direction perpendicular to the top surface of the wafer WF, i.e., the direction perpendicular to the stage surface 13, is called the easy axis direction. On the other hand, as shown in FIG. 4, the magnetization of an MRAM element parallel to the top surface of the wafer WF is difficult to reverse by changing an external magnetic field. The direction parallel to the top surface of the wafer WF, i.e., the direction parallel to the stage surface 13, is called the hard axis direction. Thus, the easy axis direction perpendicular to the top surface of the wafer WF and the hard axis direction parallel to the top surface of the wafer WF have different magnetic properties. For this reason, it is necessary to inspect the magnetic properties in two directions, the easy axis direction and the hard axis direction, to inspect defects in MRAM elements.

[0031] <2-2. Application of a magnetic field perpendicular to the stage surface> 5 is a diagram illustrating the energization of coil 21 when a magnetic field having a magnetic field component perpendicular to stage surface 13 according to embodiment 1 is applied to the MRAM element. As shown in FIG. 5, when a magnetic field having a magnetic field component perpendicular to stage surface 13 is applied to the MRAM element, currents in opposite directions are applied to coils 21a and 21b of electromagnets 20a and 20b that face each other in the X-axis direction. On the other hand, no current is applied to coils 21c and 21d of electromagnets 20c and 20d that face each other in the Y-axis direction.

[0032] In other words, a magnetic field having a magnetic field component perpendicular to the stage surface 13 is generated by passing a current in a predetermined direction through coil 21a, passing a current in the opposite direction to the predetermined direction through coil 21b, and setting the current flowing through coils 21c and 21d to zero. A magnetic field having a magnetic field component perpendicular to the stage surface 13 is called the first magnetic field. Also, the direction perpendicular to the stage surface 13 is called the vertical direction. In the case of the first magnetic field, the α-axis direction parallel to the X-axis direction is the scan axis. The scan axis in the case of the first magnetic field is called the first scan axis. The direction perpendicular to the α-axis direction in the XY plane is the β-axis direction. The β-axis is in the same direction as the Y-axis. The direction perpendicular to the α-axis and β-axis directions is the γ-axis. The γ-axis is in the same direction as the Z-axis. The β-axis and γ-axis are perpendicular to the first scan axis.

[0033] 6 is a graph illustrating magnetic flux density in the α-axis direction along the first scan axis, and in the β-axis and γ-axis directions perpendicular to the first scan axis according to embodiment 1, where the horizontal axis represents position along the α-axis and the vertical axis represents magnetic flux density. FIG. 7 is a diagram illustrating magnetic flux density vectors in the αγ plane according to embodiment 1.

[0034] As shown in Figures 6 and 7, the direction of the vertical magnetic field component of the first magnetic field changes from one direction to the other depending on the position on the stage surface 13. The magnetic field component parallel to the stage surface 13 is constant. That is, between the end of the in-plane portion 24a of the yoke 22a and the end of the in-plane portion 24b of the yoke 22b, the magnetic field component in the γ-axis direction reverses, the magnetic field component in the α-axis direction is constant at a predetermined value, and the magnetic field component in the β-axis direction is zero. Thus, when the position of the MRAM element is changed so that the direction of the magnetic field component in the γ-axis direction changes from one direction to the other in the first magnetic field, the magnetic field components perpendicular to the α-axis and γ-axis directions are zero. Here, a magnetic field component of zero does not mean strictly zero, but also means zero within a range that includes unavoidable measurement errors.

[0035] By moving the wafer WF along the first scan axis, the sign of the vertical magnetic field component applied to the MRAM elements contained in the wafer WF can be changed while the magnetic field component in the β-axis direction can be kept at zero.

[0036] In this way, the multiple electromagnets 20 generate a magnetic field including a magnetic field component in the easy axis direction. The easy axis direction is, for example, the Z-axis direction perpendicular to the stage surface 13. The multiple electromagnets 20 generate a first magnetic field in which the direction of the magnetic field component in the perpendicular direction changes from a first direction to a second direction opposite to the first direction depending on the position on the stage surface 13.

[0037] <2-3. Application of a magnetic field in a direction parallel to the stage surface> 8 is a diagram illustrating the energization of coil 21 when a magnetic field having a magnetic field component parallel to stage surface 13 according to embodiment 1 is applied to the MRAM element. As shown in FIG. 8, when a magnetic field having a magnetic field component parallel to stage surface 13 is applied to the MRAM element, currents of the same predetermined direction are applied to coils 21a and 21b of electromagnets 20a and 20b that face each other in the X-axis direction. On the other hand, currents of the opposite direction to that of coils 21a and 21b are applied to coils 21c and 21d of electromagnets 20c and 20d that face each other in the Y-axis direction.

[0038] In other words, a magnetic field having a magnetic field component parallel to the stage surface 13 is generated by passing a current in a predetermined direction through coils 21a and 21b and a current in the opposite direction to the predetermined direction through coils 21c and 21d. A magnetic field having a magnetic field component parallel to the stage surface 13 is called the second magnetic field. The direction parallel to the stage surface 13 is called the in-plane direction. When an XYZ Cartesian coordinate system is fixed to multiple electromagnets 20, in the case of the second magnetic field, the α-axis direction, which is at a 45° angle with the X-axis and Y-axis, is the scan axis. The scan axis in the case of the second magnetic field is called the second scan axis. The direction perpendicular to the α-axis direction in the XY plane is called the β-axis direction. The direction perpendicular to the α-axis direction and the β-axis direction is called the γ-axis. The γ-axis is in the same direction as the Z-axis.

[0039] 9 is a graph illustrating magnetic flux density in the α-axis direction along the second scan axis, and in the β-axis and γ-axis directions perpendicular to the second scan axis according to embodiment 1, where the horizontal axis represents position along the α-axis and the vertical axis represents magnetic flux density. FIG. 10 is a diagram illustrating magnetic flux density vectors in the αβ plane according to embodiment 1.

[0040] As shown in Figures 9 and 10, the direction of the in-plane magnetic field component of the second magnetic field changes from one direction to the other depending on the position on the stage surface 13. The magnetic field component in the vertical direction perpendicular to the stage surface 13 is zero. That is, in the space surrounded by the end of the in-plane portion 24a of the yoke 22a, the end of the in-plane portion 24b of the yoke 22b, the end of the in-plane portion 24c of the yoke 22c, and the end of the in-plane portion 24d of the yoke 22d, the magnetic field component in the β-axis direction is reversed, and the magnetic field components in the α-axis direction and the γ-axis direction are zero. Thus, when the position of the MRAM element is changed so that the direction of the magnetic field component in the β-axis direction changes from one direction to the other in the second magnetic field, the magnetic field components in the α-axis direction and the γ-axis direction are zero. Here, a magnetic field component of zero means not only strictly zero but also zero within a range that includes unavoidable measurement errors.

[0041] By moving the wafer WF along the second scan axis, the sign of the magnetic field component in the β-axis direction applied to the MRAM element contained in the wafer WF can be changed, while the magnetic field component in the α-axis direction and the magnetic field component in the γ-axis direction can be kept at zero.

[0042] In this way, the multiple electromagnets 20 generate a magnetic field including a magnetic field component in the hard axis direction. The hard axis direction is, for example, a direction perpendicular to the easy axis direction. The multiple electromagnets 20 generate a second magnetic field in which the direction of the magnetic field component in the in-plane direction parallel to the stage surface 13 changes from a third direction to a fourth direction opposite to the third direction depending on the position on the stage surface 13.

[0043] <3.Optical system> The optical system 30 may include an optical microscope. The optical microscope forms an image of the surface of the wafer WF. The optical system 30 illuminates the MRAM elements with illumination light including polarized light, and collects light reflected from the MRAM elements by the illumination light. The optical system 30 includes a light source 31, lenses L1 to L3, a polarizer 32, a mirror M1, an objective lens 33, and an analyzer 34. The optical system 30 may include other optical elements.

[0044] A light source 31 emits illumination light. The illumination light is, for example, laser light. The illumination light emitted from the light source 31 is converted by a polarizer 32 to include linearly polarized light. The illumination light including linearly polarized light is reflected by a mirror M1 and focused on a wafer WF by an objective lens 33. The mirror M1 is, for example, a non-polarizing beam splitter.

[0045] The objective lens 33 is used to form an image of a pattern on the wafer WF, and is generally made of a non-magnetic material. If the wafer WF includes an MRAM element, the polarization angle of the linearly polarized light changes due to the magneto-optical Kerr effect.

[0046] Figure 11 illustrates the magnetic characteristics of an MRAM device, with the horizontal axis representing the external magnetic field and the vertical axis representing the Kerr rotation angle. As shown in Figure 11, when the external magnetic field is increased from zero, the Kerr rotation angle increases. However, the Kerr rotation angle saturates once it reaches a certain value and no longer changes even when the external magnetic field is increased. Next, when the external magnetic field is decreased from the saturated state, the Kerr rotation angle decreases. Even when the external magnetic field is reduced to zero, the Kerr rotation angle remains. When the external magnetic field is further decreased, the Kerr rotation angle reaches a certain value and saturates. Therefore, it no longer changes even when the external magnetic field is reduced. When the external magnetic field is increased from the saturated state, the Kerr rotation angle increases. The path of the Kerr rotation angle value differs between when the external magnetic field is increased and when it is reduced. Thus, the Kerr rotation angle forms a hysteresis curve that follows different routes when the external magnetic field is increased and when it is reduced.

[0047] FIG. 12 is a diagram illustrating the magnetic characteristics of an MRAM element, with the horizontal axis representing the external magnetic field and the vertical axis representing the Kerr rotation angle. FIG. 12 also shows a schematic representation of an image including the polarization state of the MRAM element when the external magnetic field H is H1, H2, and H3. As shown in FIG. 12, images captured while gradually increasing the external magnetic field show brightness corresponding to different Kerr rotation angles for the external magnetic fields H=H1, H2, and H3. There is a correlation between the Kerr rotation angle and the brightness detected by the detector 40. Therefore, the coercive force of each MRAM element (the magnetic field of the H2 image in the above example) and its variation can be obtained from the image obtained by the detector 40. If the size of the MRAM element is smaller than the camera resolution or optical resolution, the average magnetic characteristics of the observation area are obtained.

[0048] The light reflected by the wafer WF passes through the objective lens 33 and the mirror M1 and enters the analyzer 34. The analyzer 34 detects the change in the polarization angle of the linearly polarized light contained in the reflected light. The reflected light that passes through the analyzer 34 enters the detector 40.

[0049] 4. Detector The detector 40 detects the reflected light to acquire the pattern of the wafer WF. The detector 40 may include a line sensor 41. The line sensor 41 may include, for example, a TDI (Time Delay Integration) sensor. The detector 40 detects the reflected light when the position of the MRAM element is changed in the first magnetic field and when the position of the MRAM element is changed in the second magnetic field. For example, the detector 40 detects the reflected light when the position of the MRAM element in the first magnetic field is scanned in the first scan axis direction. The detector 40 also detects the reflected light when the position of the MRAM element in the second magnetic field is scanned in the second scan axis direction.

[0050] The inspection device 1 irradiates the wafer WF with illumination light that has been linearly polarized by the polarizer 32, and causes the reflected light to enter the detector 40 through the analyzer 34. The amount of light that enters the detector 40 through the analyzer 34 changes according to the polarization angle, so the magnetization distribution is imaged. By changing the magnetic field applied to the MRAM elements, the magnetic characteristics of the MRAM elements in the wafer WF can be measured from the distribution of polarization angles according to the magnetic field.

[0051] FIG. 13 is a plan view illustrating a wafer WF according to the first embodiment. As shown in FIG. 13, the wafer WF includes multiple die DIEs. Only the solid film of the perpendicularly magnetized film before the die DIEs are formed may be inspected. The die DIEs are, for example, rectangular with short and long sides in the X-axis and Y-axis directions. The multiple die DIEs are arranged on the wafer WF with spatial periodicity in the X-axis and Y-axis directions. The die DIEs include multiple MRAM elements. The MRAM elements have memory areas arranged in an array with periodicity. The line sensor 41 acquires images in the forward direction while moving, for example, in the X-axis direction, across the multiple die DIEs. After acquiring a row of images along the X-axis, the line sensor 41 moves in the Y-axis direction and acquires another row of images along the X-axis from the reverse direction. To inspect all of the die DIEs on the wafer WF, images may be acquired in both the forward and reverse directions without gaps, including a few pixels for filtering and scan correction.

[0052] <5. Information Processing Unit> The information processing unit 50 processes the image of the reflected light detected by the detector 40. For example, the information processing unit 50 may be an information processing device such as a server device or a personal computer. The information processing unit 50 inspects the MRAM element for defects due to the vertical magnetic field component from a differential image between an image of a magnetic field component in one direction in the vertical direction in the first magnetic field and an image of a magnetic field component in the opposite direction. The information processing unit 50 also inspects the MRAM element for defects due to the in-plane magnetic field component from a differential image between an image of a magnetic field component in one direction in the in-plane direction in the second magnetic field and an image of a magnetic field component in the opposite direction.

[0053] <6. Details of the inspection equipment> Next, details of the inspection apparatus of embodiment 1 will be described. Fig. 14 is a configuration diagram illustrating details of the inspection apparatus according to embodiment 1. As shown in Fig. 14, the inspection apparatus 1 may further include devices W1 to W3 related to the transport of the wafer WF, members B1 to B4 related to the base of the inspection apparatus 1, and a power supply and control unit 60.

[0054] The devices W1 to W3 for transporting the wafer WF include a wafer transport robot W1, a wafer pre-alignment device W2, and a wafer supply cassette W3. The wafer transport robot W1 transports the wafer WF to be inspected from the wafer supply cassette W3 into the inspection device 1. The wafer pre-alignment device W2 corrects the rotation angle and shift of the wafer WF. After being adjusted by the wafer pre-alignment device PWA, the wafer WF is transported to the stage 10 of the inspection device 1.

[0055] Components B1 to B4 related to the base of the inspection device 1 include a stone surface plate (Base) B1, an active vibration isolation table (Isolator) B2, a wedge B3, and a dispersion plate B4. The stone surface plate B1 serves as a base on which components such as the stage 10 and optical system 30 are placed. The active vibration isolation table B2 suppresses vibrations of components on the stone surface plate B1. The wedge B3 adjusts the level of the stone surface plate B1 and the active vibration isolation table B2. The dispersion plate B4 distributes the load of the device relative to the floor. The power supply and control unit 60 supplies power to the inspection device 1 and controls each component of the inspection device 1.

[0056] The optical system 30 may further include lenses L4 to L9, mirrors M2 to M4, and filters 35 to 36. Illumination light emitted from the light source 31 passes through the filter 35 via the lens L4, thereby containing a predetermined wavelength band. The illumination light that passes through the filter 35 is reflected by the mirror M2 via the lens L5. The illumination light reflected by the mirror M2 passes through the lenses L1 and L2 and is then transmitted through the polarizer 32. The polarizer 32 converts the illumination light to contain linearly polarized light. The illumination light containing linearly polarized light is reflected by the mirror M1 and focused on the wafer WF by the objective lens 33 via the lens L6. The mirror M2 is, for example, a non-polarizing beam splitter.

[0057] The light reflected by the wafer WF passes through the objective lens 33, lens L6, and mirror M1 and enters the analyzer 34. The analyzer 34 functions as an analyzer that detects changes in the polarization angle of the linearly polarized light contained in the reflected light. The reflected light that passes through the analyzer 34 and lens L7 is filtered by a filter 36 to include a predetermined wavelength band. The reflected light that passes through the filter 36 is reflected by mirror M3 via lens L8. The reflected light that is reflected by mirror M3 enters the line sensor 41 via lens L3. The AF sensor 37 is a component for focusing the light on the wafer WF surface. The AF sensor 37 irradiates light onto the wafer WF using mirror M4 and captures the reflected light to perform focus adjustment. The AF sensor 37 uses laser light with wavelengths longer or shorter than those of the illumination light and reflected light used in the optical system 30.

[0058] The detector 40 acquires the pattern of the wafer WF. The detector 40 may have multiple line sensors A1 and A2 and a review monitor 42. The number of line sensors A1 and A2 is not limited to two, but may be three or more. The detector 40 may include, for example, a TDI (Time Delay Integration) sensor. The review monitor 42 detects reflected light that has passed through a mirror M3 via a lens L9. The review monitor 42 may include a CCD (Charge-Coupled Device) sensor. The CCD sensor may be used for review. The optical path between the line sensors L1 and L2 and the review monitor 42 is switched by inserting the mirror M3.

[0059] <7. Testing Method> Next, an inspection method will be described. Fig. 15 is a flow chart illustrating an inspection method for a wafer WF including an MRAM element according to embodiment 1. As shown in step S11 of Fig. 15, first, the wafer WF is placed on the inspection apparatus 1. Specifically, the wafer transport robot W1 transports the wafer WF to be inspected from the wafer supply cassette W3 into the inspection apparatus 1.

[0060] Next, as shown in step S12, the wafer pre-alignment device W2 corrects the rotation angle and shift of the wafer WF. After the wafer WF is adjusted by the wafer pre-alignment device W2, it is transferred to the stage 10 of the inspection device 1. Next, as shown in step S13, the wafer WF is aligned on the stage 10. For example, the wafer WF is aligned using a laser interferometer 14.

[0061] Next, as shown in step S14, the magnetic properties of the MRAM elements are inspected in the perpendicular direction. Also, as shown in step S15, the magnetic properties of the MRAM elements are inspected in the in-plane direction. The order of steps S14 and S15 is not limited to this. After inspecting the magnetic properties of the MRAM elements in the in-plane direction in step S14, the magnetic properties of the MRAM elements in the perpendicular direction may be inspected in step S15. Next, as shown in step S16, after the inspection, the wafer WF is removed from the stage 10.

[0062] 16 is a flowchart illustrating a method for inspecting the magnetic properties of the MRAM element in the vertical direction according to the first embodiment. As shown in step S21 of FIG. 16, a first magnetic field having a magnetic field component in the vertical direction is generated. For example, currents in opposite directions are applied to the coils 21a and 21b of the electromagnets 20a and 20b facing each other in the X-axis direction. On the other hand, no current is applied to the two coils 21c and 21d of the electromagnets 20c and 20d facing each other in the Y-axis direction. In this way, a first magnetic field having a magnetic field component in the direction perpendicular to the stage surface 13 is generated using the multiple electromagnets 20.

[0063] Next, as shown in step S22, the wafer WF on the stage 10 is moved. Specifically, the wafer WF is scanned along the α-axis, which is the first scan axis. When moving within the first magnetic field, the α-axis direction, which is the first scan axis, is the X-axis direction. In this way, the MRAM element is scanned within the first magnetic field.

[0064] Next, as shown in step S23, the detector 40 acquires an image of the magneto-optical effect in the MRAM elements of the wafer WF. Specifically, the polarization angle due to the magneto-optical effect of the MRAM elements is measured. Then, from the differential images before and after the magnetic polarity change during the scan, defect inspection is performed using a first magnetic field having a vertical magnetic field component. In this manner, the MRAM elements are inspected.

[0065] Next, as shown in step S24, it is determined whether to end the process. If the answer is No, meaning that there are still MRAM elements to be tested, the process returns to step S21 and steps S21 to S24 are repeated. On the other hand, if the answer is Yes, meaning that there are no MRAM elements to be tested, the process ends.

[0066] FIG. 17 is a flowchart illustrating a method for inspecting the in-plane magnetic characteristics of an MRAM device according to the first embodiment. As shown in step S31 of FIG. 17, a second magnetic field having an in-plane magnetic field component is generated. For example, when an XYZ Cartesian coordinate system is fixed to the multiple electromagnets 20, currents of the same predetermined direction are applied to the coils 21a and 21b of the electromagnets 20a and 20b facing each other in the X-axis direction. Meanwhile, currents of the opposite direction to the coils 21a and 21b are applied to the coils 21c and 21d of the electromagnets 20c and 20d facing each other in the Y-axis direction. In this manner, a second magnetic field having an in-plane magnetic field component parallel to the stage surface 13 is generated. In this embodiment, the multiple electromagnets 20 are rotated 45° in a horizontal plane to align the second scan axis with the X-axis of the XYZ Cartesian coordinate system fixed to the stage 10.

[0067] Next, as shown in step S32, the wafer WF on the stage 10 is moved. Specifically, the wafer WF is moved along the α-axis, which serves as the second scan axis. In this way, the MRAM element is moved within the second magnetic field.

[0068] Next, as shown in step S33, the detector 40 acquires an image of the magneto-optical effect in the MRAM element of the wafer WF. Specifically, the polarization angle due to the magneto-optical effect of the MRAM element is measured. In this manner, the MRAM element is inspected.

[0069] Next, as shown in step S34, it is determined whether to end the process. If the answer is No, meaning that there are still MRAM elements to be tested, the process returns to step S31 and steps S31 to S34 are repeated. On the other hand, if the answer is Yes, meaning that there are no MRAM elements to be tested, the process ends.

[0070] Next, the effects of this embodiment will be described. The inspection device 1 of this embodiment can generate a first magnetic field in which the orientation of the perpendicular magnetic field component changes from a first orientation to a second orientation depending on the position on the stage surface 13, and a second magnetic field in which the orientation of the in-plane magnetic field component changes from a third orientation to a fourth orientation depending on the position on the stage surface 13, in order to inspect defects in MRAM elements. Therefore, it is possible to detect magnetic properties not only in the easy axis direction but also in the hard axis direction, and the detection accuracy of MRAM properties can be improved.

[0071] The inspection device of Patent Document 1 detects defects in MRAM elements by scanning the MRAM elements in a gradient magnetic field formed by an electromagnet including two coils. The inspection device of Patent Document 1 measures saturation magnetization characteristics by applying a magnetic field in the easy axis direction, which is a magnetic field component perpendicular to the gradient magnetic field. This allows the inspection device of Patent Document 1 to inspect wafer defects. However, to understand the characteristics of MRAM elements, it is necessary to inspect not only the characteristics in the easy axis direction, which is the direction in which magnetization is easiest, but also the magnetization characteristics in the hard axis direction. In particular, the anisotropic magnetic field in the hard axis direction must be inspected without changing the magnetic characteristics in the easy axis direction, which change with a small magnetic field. Because the inspection device of Patent Document 1 cannot detect magnetic characteristics in the hard axis direction, it is unable to improve the detection accuracy of MRAM characteristics.

[0072] In contrast, the inspection device 1 of this embodiment can detect the magnetization characteristics in the easy axis direction without changing the magnetization characteristics in the hard axis direction, and can also detect the magnetization characteristics in the hard axis direction without changing the magnetization characteristics in the easy axis direction, thereby improving the detection accuracy of the MRAM characteristics.

[0073] Furthermore, the inspection device 1 of this embodiment performs inspection by moving the MRAM element within the first magnetic field and the second magnetic field. In contrast, a method of changing the magnetic field by fixing the stage 10 and changing the current flowing through the electromagnet requires time to change the current. Furthermore, for highly sensitive detection, the exposure time of the camera must be extended. In particular, when inspecting the entire surface of the wafer WF, it is necessary to repeatedly perform measurements by moving each MRAM element on the wafer WF to the inspection position and then changing the current flowing through the electromagnet. Therefore, the increase in inspection time becomes a problem.

[0074] In this embodiment, there is no need to change the current flowing through the coil 21 of the electromagnet 20 during testing, so the time required to change the current can be reduced. Also, the magnetic properties can be detected by moving the MRAM element, which reduces the exposure time of the detector 40.

[0075] (Embodiment 2) Next, an inspection device according to embodiment 2 will be described. The inspection device 1 of embodiment 1 described above rotates the multiple electromagnets 20 by 45° after inspecting the magnetic properties in the vertical direction, and scans the MRAM elements. On the other hand, the inspection device of this embodiment rotates the stage 10 by 45° after inspecting the magnetic properties in the vertical direction, and scans the MRAM elements.

[0076] 18 is a flowchart illustrating a method for inspecting magnetic properties in the vertical direction of an MRAM device according to the second embodiment. As shown in step S41 of FIG. 18, a first magnetic field having a magnetic field component in the vertical direction is generated. For example, currents in opposite directions are applied to the coils 21a and 21b of the electromagnets 20a and 20b facing each other in the X-axis direction. On the other hand, no current is applied to the two coils 21c and 21d of the electromagnets 20c and 20d facing each other in the Y-axis direction. In this way, a first magnetic field having a magnetic field component in the direction perpendicular to the stage surface 13 is generated using multiple electromagnets 20.

[0077] Next, as shown in step S42, the wafer WF on the stage 10 is moved. Specifically, the wafer WF is scanned along the α-axis, which is the first scan axis. When moving within the first magnetic field, the α-axis direction, which is the first scan axis, is the X-axis direction. In this way, the MRAM element is scanned within the first magnetic field.

[0078] Next, as shown in step S43, the detector 40 acquires an image of the magneto-optical effect in the MRAM elements of the wafer WF. Specifically, the polarization angle due to the magneto-optical effect of the MRAM elements is measured. Then, from the differential images before and after the change in magnetic field polarity during the scan, defect inspection is performed using a first magnetic field having a vertical magnetic field component. In this manner, the MRAM elements are inspected.

[0079] Next, as shown in step S44, it is determined whether to end the process. If the answer is No, meaning that there are still MRAM elements to be tested, the process returns to step S41 and steps S41 to S44 are repeated. On the other hand, if the answer is Yes, meaning that there are no MRAM elements to be tested, the process ends.

[0080] FIG. 19 is a flowchart illustrating a method for inspecting the in-plane magnetic characteristics of an MRAM device according to the second embodiment. As shown in step S51 of FIG. 19, a second magnetic field having an in-plane magnetic field component is generated. For example, an XYZ Cartesian coordinate system is fixed to multiple electromagnets 20. Currents of the same predetermined direction are applied to the coils 21a and 21b of electromagnets 20a and 20b, which face each other in the X-axis direction. Meanwhile, currents of the opposite direction to the coils 21a and 21b are applied to the coils 21c and 21d of electromagnets 20c and 20d, which face each other in the Y-axis direction. In this manner, a second magnetic field having an in-plane magnetic field component parallel to the stage surface 13 is generated. In this embodiment, the stage 10 is rotated 45° in the horizontal plane, and the second scan axis is aligned with the X-axis of the XYZ Cartesian coordinate system fixed to the stage 10.

[0081] Next, as shown in step S52, the wafer WF on the stage 10 is moved. Specifically, the wafer WF is moved along the α-axis, which serves as the second scan axis. In this way, the MRAM element is moved within the magnetic field.

[0082] Next, as shown in step S53, the detector 40 acquires an image of the magneto-optical effect in the MRAM element of the wafer WF. Specifically, the polarization angle due to the magneto-optical effect of the MRAM element is measured. In this manner, the MRAM element is inspected.

[0083] Next, as shown in step S54, it is determined whether to end the process. If the answer is No, meaning that there are still MRAM elements to be tested, the process returns to step S51 and steps S51 to S54 are repeated. On the other hand, if the answer is Yes, meaning that there are no MRAM elements to be tested, the process ends.

[0084] According to this embodiment, the moving part 11 of the stage 10 is rotated instead of the multiple electromagnets 20. This makes it possible to detect the magnetization characteristics of the MRAM element when a magnetic field is applied in the in-plane direction. Therefore, it is possible to suppress positional deviation due to the movement of the multiple electromagnets 20 and the optical system 30.

[0085] The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, combinations of the configurations of embodiments 1 to 4 are also within the scope of the technical concept of the present invention. [Explanation of symbols]

[0086] 1. Inspection equipment 10 stages 11 Moving section 12 Main body 13 Stage surface 14 Laser interferometer 20, 20a, 20b, 20c, 20d electromagnet 21, 21a, 21b, 21c, 21d coils 22, 22a, 22b, 22c, 22d York 23, 23a, 23b, 23c, 23d Vertical section 24, 24a, 24b, 24c, 24d In-plane part 25 Connection plate 30 Optical system 31 Light source 32 Polarizer 33 Objective Lens 34 Analyzer 35, 36 Filter 37 AF sensor 40 detectors 41 Line sensor 42 Review Monitor 50 Information Processing Department 60 Power supply and control unit A1, A2 line sensors B1 stone surface plate B2 Active vibration isolation table B3 Wedge B4 Dispersion plate L1, L2, L3, L4, L5, L6, L7, L8, L9 lenses M1, M2, M3, M4 mirrors W0 inspection surface W1 wafer transport robot W2 Pre-wafer Alignment Equipment W3 Wafer supply cassette WF wafer

Claims

1. a stage having a stage surface on which a magnetoresistive memory element is fixed; a plurality of electromagnets that generate a first magnetic field in which the orientation of a magnetic field component in a vertical direction perpendicular to the stage surface changes from a first orientation to a second orientation opposite to the first orientation depending on a position on the stage surface, and a second magnetic field in which the orientation of the magnetic field component in an in-plane direction parallel to the stage surface changes from a third orientation to a fourth orientation opposite to the third orientation depending on the position on the stage surface; an optical system that illuminates the magnetoresistive memory element with illumination light including polarized light and collects light reflected from the magnetoresistive memory element; a detector that detects the reflected light when the position of the magnetoresistive memory element is changed in the first magnetic field and the reflected light when the position of the magnetoresistive memory element is changed in the second magnetic field; An inspection device equipped with:

2. When the position of the magnetoresistive memory element is changed so as to change from the first orientation to the second orientation within the first magnetic field, the magnetic field component perpendicular to the first scanning direction and the perpendicular direction is 0. The inspection device according to claim 1 .

3. When the position of the magnetoresistive memory element is changed so as to change from the third orientation to the fourth orientation within the second magnetic field, the magnetic field component in the second scanning direction and the magnetic field component in the perpendicular direction are 0. The inspection device according to claim 1 .

4. the plurality of electromagnets includes at least four electromagnets including a first electromagnet, a second electromagnet, a third electromagnet, and a fourth electromagnet; the first electromagnet includes a first coil wound in a predetermined direction around a first vertical portion of an L-shaped first yoke having a first vertical portion extending in the vertical direction and a first in-plane portion extending in the in-plane direction, the second electromagnet includes a second coil wound in the predetermined direction around a second vertical portion of an L-shaped second yoke having a second vertical portion extending in the vertical direction and a second in-plane portion extending in the in-plane direction, the third electromagnet includes a third coil wound in the predetermined direction around a third vertical portion of an L-shaped third yoke having a third vertical portion extending in the vertical direction and a third in-plane portion extending in the in-plane direction, the fourth electromagnet includes a fourth coil wound in the predetermined direction around a fourth vertical portion of an L-shaped fourth yoke having a fourth vertical portion extending in the vertical direction and a fourth in-plane portion extending in the in-plane direction, the first in-plane portion and the second in-plane portion extend in one direction, and an end portion of the first in-plane portion and an end portion of the second in-plane portion face each other in the one direction; the third in-plane portion and the fourth in-plane portion extend in another direction perpendicular to the one direction, and the end portion of the third in-plane portion and the end portion of the fourth in-plane portion face each other in the other direction; the first magnetic field is generated by passing a current in a fifth direction through the first coil, passing a current in a sixth direction opposite to the fifth direction through the second coil, and setting the current flowing through the third coil and the fourth coil to zero; the second magnetic field is generated by passing the current in the fifth direction through the first coil and the second coil and passing the current in the sixth direction through the third coil and the fourth coil. The inspection device according to claim 1 .

5. The detector comprises: Detecting the reflected light when the position of the magnetoresistive memory element in the first magnetic field is scanned in the one direction; detecting the reflected light when the position of the magnetoresistive memory element in the second magnetic field is scanned in the one direction and in a direction at an angle of 45° to the other direction; The inspection device according to claim 4.

6. an information processing unit that processes an image of the reflected light detected by the detector; The information processing unit inspecting the magnetoresistive memory element for defects caused by the magnetic field component in the perpendicular direction from a difference image between the image in the magnetic field component in the first direction and the image in the magnetic field component in the second direction; The inspection device according to claim 1 .

7. an information processing unit that processes an image of the reflected light detected by the detector; The information processing unit inspecting the magnetoresistive memory element for defects caused by the magnetic field component in the in-plane direction from a difference image between the image in the magnetic field component in the third direction and the image in the magnetic field component in the fourth direction; The inspection device according to claim 1 .

Images