Magnetic detection system

Abstract

To prevent a decrease in detection sensitivity due to static electricity in a magnetic detection system that can be used as a foreign object detection system.SOLUTION: A magnetic detection system 100 includes a shield box 200 having magnetic shields S1 to S3 surrounding a measurement space 230, a magnetic sensor 40 fixed to the shield box 200 within the measurement space 230, a sample stage 300 at least a portion of which is inserted into the measurement space 230, a table 310 fixed to the sample stage 300 and on which a sample 320 is placed, and drive mechanisms 141 and 142 that change the position of the sample stage 300. The table 310 has a protruding portion 311 that protrudes from the sample stage 300 without overlapping the sample stage 300, and at least the protruding portion 311 of the table 310 is made of a material that is positioned on a more positive side in the triboelectric series than the material constituting the sample stage 300.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a magnetic detection system, and more particularly to a magnetic detection system that can be used as a foreign object detection system.

Background Art

[0002] Patent Document 1 discloses a magnetic detection system including a drive mechanism that changes the relative positional relationship between a shield box to which a magnetic sensor is fixed and a sample stage. Further, Patent Document 2 discloses a device that removes static electricity with which an object to be inspected is charged using an electrostatic eliminator before the object to be inspected is carried into a magnetic shield box in which a magnetic sensor is disposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the device described in Patent Document 1, due to the friction with air generated by the movement of the sample stage, the sample stage itself may be charged with static electricity. When the sample stage is charged with static electricity, the magnetic field generated by the static electricity becomes noise, resulting in a problem of reduced detection sensitivity. Although such static electricity can be removed using the electrostatic eliminator described in Patent Document 2, since the friction between the sample stage and air always occurs during measurement, simply removing the static electricity before carrying the sample stage into the shield box may result in insufficient removal of the static electricity.

[0005] In the present disclosure, a technique for preventing a decrease in detection sensitivity due to static electricity is described in a magnetic detection system that can be used as a foreign object detection system.

Means for Solving the Problems

[0006] A magnetic detection system according to an embodiment of the present disclosure includes a shield box having a magnetic shield surrounding a measurement space, a magnetic sensor fixed to the shield box within the measurement space, a sample stage at least partially inserted into the measurement space, a table fixed to the sample stage on which a sample is placed, and a drive mechanism for changing the position of the sample stage. The table has a protruding portion that protrudes from the sample stage without overlapping the sample stage, and at least the protruding portion of the table is made of a material that is located on the positive side in the triboelectric series compared to the material constituting the sample stage.

[0007] A magnetic detection system according to another embodiment of the present disclosure includes a shield box having a magnetic shield surrounding a measurement space, a magnetic sensor fixed to the shield box within the measurement space, a sample stage at least partially inserted into the measurement space, a table fixed to the sample stage on which a sample is placed, and a drive mechanism for changing the position of the sample stage. Both the sample stage and the table are made of a material having a work function of 4 eV or less.

Advantages of the Invention

[0008] According to the present disclosure, a technique for preventing a decrease in detection sensitivity due to static electricity is provided in a magnetic detection system that can be used as a foreign object detection system.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the technology according to the present disclosure will be described in detail with reference to the accompanying drawings.

[0011] FIG. 1 is a schematic perspective view showing the appearance of a magnetic detection system 100 according to an embodiment of the present disclosure.

[0012] As shown in FIG. 1, the magnetic detection system 100 according to this embodiment includes a frame 110, a shield box 200 supported by the frame 110, and a sample stage 300. The frame 110 includes a guide 111 extending in the X direction, a guide 113 extending in the Z direction, and a movable beam 120 configured to be movable in the X direction along the guide 111. The shield box 200 is connected to the guide 113, and the sample stage 300 is connected to the movable beam 120.

[0013] The movable beam 120 is configured to be movable in the X direction by a drive mechanism 141 including a motor or the like. A guide 112 extending in the Y direction is provided on the movable beam 120, and the sample stage 300 is configured to be movable in the Y direction along the guide 112. The movement of the sample stage 300 in the Y direction along the guide 112 is performed by a drive mechanism 142 including a motor or the like. On the other hand, the shield box 200 is configured to be movable in the Z direction along the guide 113. The movement of the shield box 200 in the Z direction along the guide 113 is performed by a drive mechanism 143 including a motor or the like. Thereby, the relative positional relationship between the shield box 200 and the sample stage 300 in the X, Y, and Z directions can be changed by the drive mechanisms 141 to 143.

[0014] FIGS. 2 and 3 are schematic perspective views for explaining the structure of the shield box 200, and show states viewed from different directions.

[0015] As shown in FIGS. 2 and 3, the shield box 200 has a main body portion 210 made of resin or the like, and a connecting portion 220 that connects the main body portion 210 to the guide 113. The main body portion 210 is provided with magnetic shields S1 to S3 made of a high magnetic permeability material such as permalloy. The magnetic shields S1 to S3 are arranged so as to surround the measurement space 230, with the magnetic shield S1 being located on the innermost side and the magnetic shield S3 being located on the outermost side. The main body portion 210 includes a plurality of parts. Among them, the part 211 is located on the inner wall side of the magnetic shield S1, the part 212 is located between the magnetic shields S1 and S2, the part 213 is located between the magnetic shields S2 and S3, and the part 214 is located on the outer wall side of the magnetic shield S3. A sensor holder 400 that holds the sensor main body portion 10 is fixed to the part 211, whereby the sensor main body portion 10 is fixed to the shield box 200 within the measurement space 230.

[0016] The magnetic shield S1 is a cylindrical body that covers both sides in the Y direction and both sides in the Z direction of the measurement space 230, and has a pair of flat portions that constitute the XY plane and a curved portion that connects the pair of flat portions in an arc shape. The part 211 of the main body portion 210 covers the inner wall of one of the flat portions of the magnetic shield S1 from the Z direction. The magnetic shield S2 is located outside the magnetic shield S1 and is a plate-like body that is curved in a C shape so as to cover one side in the X direction and both sides in the Z direction of the measurement space 230. The magnetic shield S3 is located further outside the magnetic shield S2 and is a plate-like body that is curved in a C shape so as to cover both sides in the Y direction and one side in the Z direction of the measurement space 230. The magnetic shield S3 may be a cylindrical body that covers both sides in the Y direction and both sides in the Z direction, similar to the magnetic shield S1.

[0017] Thereby, the measurement space 230 is shielded doubly or triply from the Y direction and the Z direction by the magnetic shields S1 to S3, and is shielded from the X direction by the magnetic shield S2. The other side in the X direction of the measurement space 230 is open, and a part of the sample stage 300 is inserted into the measurement space 230 from this portion.

[0018] FIG. 4 is a schematic perspective view for explaining the structure of the sample stage 300.

[0019] As shown in FIG. 4, the sample stage 300 has a mounting portion 301 and a connecting portion 302 that connects the mounting portion 301 and the drive mechanism 142. A table 310 is placed on the mounting portion 301. A sample 320 to be inspected is placed on the table 310. The table 310 has a protruding portion 311 that protrudes from the mounting portion 301 of the sample stage 300 without overlapping the mounting portion 301 of the sample stage 300, and the sample 320 is placed on this protruding portion 311. In the example shown in FIG. 4, the table 310 is flat, and its surface constitutes the XY plane. During measurement, as shown in FIG. 5, the mounting portion 301 and the table 310 are inserted into the measurement space 230.

[0020] The table 310 is made of a material that is located on the positive side in the triboelectric series compared to the material constituting the sample stage 300. The triboelectric series is a list that arranges substances that are easily charged positively to substances that are easily charged negatively in order, and a part of it is shown in FIG. 6. As an example, for the material of the sample stage 300, a resin material such as polyvinyl chloride that is easy to mold can be used, and for the material of the table 310, glass that is located on the positive side of polyvinyl chloride in the triboelectric series can be used.

[0021] When a material that is positioned on the positive side in the triboelectric series rather than the material constituting the sample stage 300 is used as the material of the table 310, even when static electricity is generated due to friction with air caused by the movement of the sample stage 300 and the table 310 within the measurement space 230, the table 310 itself is less likely to be charged with static electricity. This is because a material positioned on the positive side in the triboelectric series, such as glass, is located close to air in the triboelectric series, so it is less likely to generate static electricity due to friction with air. In particular, since glass is located very close to air in the triboelectric series, almost no static electricity is generated due to friction with air. Therefore, if the sample 320 is placed on the protruding portion 311 of the table 310, even if the sample stage 300 itself is charged with static electricity, it is possible to prevent a decrease in detection sensitivity due to this.

[0022] The arrangement in the triboelectric series is generally determined by the work function, excluding some exceptions such as lead. That is, a substance with a smaller work function is arranged on the positive side in the triboelectric series, and a substance with a larger work function is arranged on the negative side in the triboelectric series. Focusing on this point, as the material of the table 310, it is preferable to use a material with a work function of 4 eV or less. As the material of the table 310, it is preferable to use a material that is located closer to air in the triboelectric series. However, if it is a material with a work function of 4 eV or less, since the difference from air in the triboelectric series is small, the generation of static electricity due to friction with air can be suppressed. Specifically, by configuring the table 310 with a material that is positioned on the positive side of aluminum in the triboelectric series, it is possible to suppress the generation of static electricity due to friction with air.

[0023] The entire table 310 does not necessarily have to be constituted by a material that is positioned on the positive side in the triboelectric series rather than the material constituting the sample stage 300. It may be sufficient that only the portion where the sample 320 is placed, that is, the protruding portion 311, is constituted by the above material.

[0024] FIG. 7 is a schematic perspective view for explaining the structure of the sensor holder 400.

[0025] The sensor holder 400 is a molded product made of resin or the like. As shown in FIG. 7, it has a plate-like portion 401 constituting the XY plane and a sensor housing portion 402 protruding in the Z direction from the plate-like portion 401. The XY plane of the plate-like portion 401 is fixed to the XY plane of the part 211 of the shield box 200. A sensor main body portion 10 including a magnetic sensor is held in the sensor housing portion 402.

[0026] FIGS. 8 and 9 are diagrams for explaining the structure of the sensor main body portion 10. FIG. 8 is a schematic perspective view, and FIG. 9 is a schematic exploded perspective view.

[0027] As shown in FIGS. 8 and 9, the sensor main body portion 10 includes a chip-shaped magnetic sensor 40 mounted on the surface of the sensor substrate 30 and magnetic flux concentrators 51 to 53. The magnetic sensor 40 has a substantially rectangular parallelepiped shape and has an element formation surface 41 and a back surface 42 constituting the YZ plane, an upper surface 43 and a lower surface 44 constituting the XY plane, and side surfaces 45 and 46 constituting the XZ plane. The element formation surface 41 is a surface on which a magnetosensitive element is formed. The magnetic sensor 40 is mounted on the sensor substrate 30 such that the lower surface 44 faces the sensor substrate 30 and the element formation surface 41 is orthogonal to the surface of the sensor substrate 30. Magnetic yokes M1 to M3 made of permalloy or the like are formed on the element formation surface 41 of the magnetic sensor 40, and a magnetosensitive element is arranged in the vicinity of the magnetic gap formed by the magnetic yoke M1 and the magnetic yokes M2 and M3. Thereby, the magnetic flux passing through the magnetic gap is applied to the magnetosensitive element.

[0028] FIG. 10 is a schematic perspective view showing a state in which the magnetic yokes M1 to M3 are removed from the magnetic sensor 40.

[0029] As shown in FIG. 10, magnetosensitive elements R1 to R4 are formed on the element formation surface 41 of the magnetic sensor 40. The magnetosensitive elements R1 to R4 all have the Y direction as the magnetosensitive direction. The magnetosensitive elements R1 and R2 are arranged near the magnetic gap formed by the magnetic yokes M1 and M2, and the magnetosensitive elements R1 and R2 are arranged near the magnetic gap formed by the magnetic yokes M1 and M3. The magnetosensitive elements R1 to R4 are bridge-connected between the terminal electrodes 61 and 62, and a differential signal corresponding to the magnetic field appears at the terminal electrodes 63 and 64.

[0030] The magnetic flux concentrators 51 to 53 are blocks made of a magnetic material such as ferrite, and all serve to collect the magnetic field emitted from the sample 320 to the magnetic sensor 40. The magnetic flux concentrators 51 to 53 overlap with the magnetic yokes M1 to M3 when viewed from the X direction. That is, the magnetic flux concentrators 51 to 53 are arranged in the Y direction on the element formation surface 41, and the magnetosensitive elements R3 and R4 are arranged between the magnetic flux concentrators 51 and 52 when viewed from the X direction, and the magnetosensitive elements R1 and R2 are arranged between the magnetic flux concentrators 51 and 53 when viewed from the X direction.

[0031] The magnetic flux concentrator 51 has the X direction as the longitudinal direction and mainly serves to collect the magnetic field in the X direction to the magnetic yoke M1. The magnetic flux concentrator 52 has a portion that covers the side surface 45 and the back surface 42 of the magnetic sensor 40, and the magnetic flux concentrator 53 has a portion that covers the side surface 46 and the back surface 42 of the magnetic sensor 40. Thereby, the magnetic field in the X direction collected by the magnetic flux concentrator 51 is bent in the Y direction by the magnetic yoke M1 and flows to the magnetic flux concentrators 52 and 53 through the magnetic yokes M2 and M3. Then, the magnetic field passing through the magnetic gap between the magnetic yoke M1 and the magnetic yokes M2 and M3 is detected by the magnetosensitive elements R1 to R4. In the examples shown in FIGS. 8 and 9, a compensation coil C is wound around the magnetic flux concentrator 51. A canceling current flows through the compensation coil C so that the magnetic field applied to the magnetosensitive elements R1 to R4 is canceled.

[0032] The sensor main body 10 having such a configuration is brought closer to the sample 320 placed on the surface of the table 310 by moving the shield box 200 in the Z direction using the drive mechanism 143. The distance between the sample 320 and the sensor main body 10 in the Z direction is preferably as close as possible within a range where the two do not interfere. After adjusting the position of the sensor main body 10 in the Z direction using the drive mechanism 143, as shown in FIG. 11, the sample stage 300 is displaced in the XY directions using the drive mechanisms 141 and 142, whereby the sample 320 is scanned by the sensor main body 10. A magnetic field is applied to the sample 320 in advance. Thus, when a metal foreign object 321 such as iron (Fe) is mixed in the sample 320, the magnetic field generated by the magnetized metal foreign object 321 can be detected.

[0033] Here, although the positional relationship between the metal foreign object 321 and the sensor main body 10 is in the Z direction, by sufficiently reducing the distance between the sample 320 and the sensor main body 10 in the Z direction, as shown in FIG. 12 which is a schematic diagram, the X-direction component of the magnetic field generated by the metal foreign object 321 can be collected by the magnetic flux concentrators 51 to 53 and applied to the magnetosensitive elements R1 to R4. In FIG. 12, reference numeral 322 represents the direction and intensity of the magnetic field generated by the metal foreign object 321. Thus, by setting the longitudinal direction (X direction) of the magnetic flux concentrator 51 perpendicular to the separation direction (Z direction) between the sample 320 and the sensor main body 10, the distance between the sample 320 and the magnetosensitive elements R1 to R4 can be made closer, and thereby it becomes possible to obtain high detection sensitivity.

[0034] As described above, in the magnetic detection system 100 according to the present embodiment, since the table 310 is made of a material that is located on the plus side in the triboelectric series compared to the material constituting the sample stage 300, static electricity is less likely to be generated due to the friction between the table 310 and the air when the magnetic sensor 40 scans on the surface of the sample 320 in the XY plane direction. Thereby, it becomes possible to suppress a decrease in detection sensitivity due to static electricity.

[0035] FIG. 13 is a graph showing the relationship between the length of the protruding portion 311 of the table 310 and the sensor output when the sample 320 is not present. The horizontal axis indicates the length of the protruding portion 311 in the X direction with respect to the element formation surface 41 of the magnetic sensor 40. The sensor output indicated by the symbol N represents the output level obtained when measuring without inserting the sample stage 300 into the measurement space 230, that is, the level of background noise.

[0036] In the example shown in FIG. 13, when the length of the protruding portion 311 in the X direction is 3 cm, the sensor output is 64 mV, which is almost the same level as the background noise. This means that the protruding portion 311 of the table 310 is not charged with static electricity. On the other hand, when the length of the protruding portion 311 in the X direction is 1 cm, the sensor output is 104 mV, which is slightly higher than the background noise. This is presumably because although the table 310 itself is not charged with static electricity, the magnetic sensor 40 picks up the noise caused by the static electricity carried by the sample stage 300 due to the proximity of the distance between the magnetic sensor 40 and the sample stage 300.

[0037] Furthermore, when the table 310 is not protruded from the placement portion 301 of the sample stage 300 and is arranged so that the entire table 310 overlaps with the placement portion 301 of the sample stage 300, the sensor output at a position 1 cm from the end in the X direction of the placement portion 301 (denoted as -1 cm in FIG. 13) is 421 mV, indicating that it is strongly affected by the noise caused by the static electricity carried by the sample stage 300. By approximating these plotted points with a curve, it can be seen that if the length of the protruding portion 311 in the X direction is 2.7 cm or more, the influence of static electricity is almost eliminated.

[0038] However, when the length of the protruding portion 311 in the X direction increases, it becomes difficult to stably place the table 310 on the placement portion 301 of the sample stage 300. Therefore, when the length of the protruding portion 311 in the X direction is large, as shown in FIG. 14, a movable holding portion 303 is provided on the sample stage 300, and the table 310 is sandwiched between the placement portion 301 and the holding portion 303, so that the table 310 can be stably placed on the placement portion 301.

[0039] FIG. 15 is a schematic perspective view for explaining the first modification.

[0040] In the first modification shown in FIG. 15, it is different from the above-described embodiment in that the table 310 is composed of two transparent glass plates G1 and G2. The sample 320 is sandwiched between the glass plates G1 and G2 at a protruding portion that does not overlap with the placement portion 301 of the sample stage 300. In this way, if the sample 320 is sandwiched between two transparent glass plates G1 and G2, the sample 320 is more stably supported and the sample 320 can be visually recognized.

[0041] FIG. 16 is a schematic perspective view for explaining the second modification.

[0042] In the second modification shown in FIG. 16, it is different from the above-described embodiment in that the table 310 does not protrude from the placement portion 301 of the sample stage 300. In this way, when the table 310 is not protruded from the placement portion 301 of the sample stage 300, by using materials with a work function of 4 eV or less for both the sample stage 300 and the table 310, it is possible to suppress a decrease in detection sensitivity due to static electricity. As an example, glass may be used for both the sample stage 300 and the table 310. Alternatively, wood may be used for the material of the sample stage 300 and glass may be used for the material of the table 310.

[0043] Even in this case, as the materials of the sample stage 300 and the table 310, it is preferable to use materials that are located on the positive side of the triboelectric series rather than aluminum in both cases. As the material of the table 310, it is preferable to use a material that is located on the positive side of the triboelectric series rather than the material constituting the sample stage 300. Also, in this example, as shown in FIG. 15, the sample 320 may be sandwiched between two transparent glass plates G1 and G2.

[0044] As described above, the embodiments of the technology according to the present disclosure have been described. However, the technology according to the present disclosure is not limited to the above embodiments, and various modifications can be made without departing from the gist thereof, and it goes without saying that those are also included in the scope of the technology according to the present disclosure.

[0045] The technology according to the present disclosure includes, but is not limited to, the following configuration examples.

[0046] A magnetic detection system according to an embodiment of the present disclosure includes a shield box having a magnetic shield surrounding a measurement space, a magnetic sensor fixed to the shield box within the measurement space, a sample stage at least partially inserted into the measurement space, a table fixed to the sample stage on which a sample is placed, and a drive mechanism for changing the position of the sample stage. The table has a protruding portion that protrudes from the sample stage without overlapping the sample stage, and at least the protruding portion of the table is made of a material that is located on the positive side of the triboelectric series rather than the material constituting the sample stage. According to this, even when the sample stage is charged with static electricity due to the movement of the sample stage, since at least the protruding portion of the table is made of a material that is less likely to be charged, it is possible to reduce noise due to static electricity.

[0047] In the above magnetic detection system, at least the protruding portion of the table may be made of a material having a work function of 4 eV or less, may be made of a material located on the positive side of the charging list compared to aluminum, or may be made of glass. According to this, at least the protruding portion of the table becomes less likely to be charged. In this case, at least the protruding portion of the table may be composed of two transparent glass plates, and a sample may be sandwiched between the two glass plates. According to this, the sample is more stably supported and the sample can also be visually recognized.

[0048] A magnetic detection system according to another embodiment of the present disclosure includes a shield box having a magnetic shield surrounding a measurement space, a magnetic sensor fixed to the shield box within the measurement space, a sample stage at least partially inserted into the measurement space, a table fixed to the sample stage on which a sample is placed, and a drive mechanism for changing the position of the sample stage. The sample stage and the table are both made of a material having a work function of 4 eV or less. According to this, since it is difficult for static electricity to be charged on the sample stage and the table due to the movement of the sample stage, it is possible to reduce noise due to static electricity.

[0049] In the above magnetic detection system, the sample stage and the table may both be made of a material located on the positive side of the charging list compared to aluminum. According to this, the sample stage and the table become less likely to be charged. Further, the table may be made of a material located on the positive side of the charging list compared to the material constituting the sample stage, or may be made of glass. According to this, the table becomes less likely to be charged. In this case, at least the protruding portion of the table may be composed of two transparent glass plates, and a sample may be sandwiched between the two glass plates. According to this, the sample is more stably supported and the sample can also be visually recognized.

Description of reference numerals

[0050] 10 Sensor main body 30 Sensor substrate 40 Magnetic sensor 41 Element formation surface 42 Back surface 43 Top surface 44 Bottom surface 45, 46 Side surfaces 51 - 53 Magnetic concentrators 61 - 64 Terminal electrodes 100 Magnetic detection system 110 Frame 111 - 113 Guides 120 Movable beam 141 - 143 Driving mechanism 200 Shield box 210 Main body part 211 - 214 Parts 220 Connecting part 230 Measurement space 300 Sample stage 301 Mounting part 302 Connecting part 303 Holding part 310 Table 311 Protrusion 320 Sample 321 Metallic foreign matter 322 Magnetic field 400 Sensor holder 401 Plate - shaped part 402 Sensor housing part C Compensation coil G1, G2 Glass plates M1 - M3 Magnetic yokes R1 - R4 Magnetosensitive elements S1 - S3 Magnetic shields

Claims

1. A shield box having a magnetic shield surrounding a measurement space, a magnetic sensor fixed to the shield box within the measurement space, a sample stage at least partially inserted into the measurement space, a table fixed to the sample stage on which a sample is placed, a drive mechanism for changing the position of the sample stage, comprising: the table has a protruding portion that protrudes from the sample stage without overlapping the sample stage, at least the protruding portion of the table is made of a material located on the positive side in the triboelectric series compared to the material constituting the sample stage, a magnetic detection system.

2. at least the protruding portion of the table is made of a material having a work function of 4 eV or less, the magnetic detection system according to Claim 1.

3. at least the protruding portion of the table is made of a material located on the positive side in the triboelectric series compared to aluminum, the magnetic detection system according to Claim 1.

4. at least the protruding portion of the table is made of glass, the magnetic detection system according to any one of Claims 1 to 3.

5. at least the protruding portion of the table is composed of two transparent glass plates, and the sample is sandwiched between the two glass plates, the magnetic detection system according to Claim 4.

6. A shield box having a magnetic shield surrounding a measurement space, a magnetic sensor fixed to the shield box within the measurement space, a sample stage at least partially inserted into the measurement space, a table fixed to the sample stage on which a sample is placed, a drive mechanism for changing the position of the sample stage, comprising: both the sample stage and the table are made of materials having a work function of 4 eV or less, a magnetic detection system.

7. both the sample stage and the table are made of materials located on the positive side in the triboelectric series compared to aluminum, the magnetic detection system according to Claim 6.

8. the table is made of a material located on the positive side in the triboelectric series compared to the material constituting the sample stage, the magnetic detection system according to Claim 6.

9. the table is made of glass, the magnetic detection system according to any one of Claims 6 to 8.

10. the table is composed of two transparent glass plates, and the sample is sandwiched between the two glass plates, The magnetic detection system according to claim 9.

Images