JP4903539B2 - Induced magnetic field detector - Google Patents

Description

The present invention relates to the induced magnetic field detecting equipment.

  FIG. 10 is a block diagram showing an outline of a basic configuration of the conventional most common scanning laser SQUID microscope.

  As shown in the figure, the scanning laser SQUID microscope 200 includes a laser generator 201 that generates laser light 202. The laser beam 202 is intensity-modulated by a laser modulation signal generated in synchronization with a predetermined reference signal 210 determined in advance, and is collected by the optical system 204 and then sampled (inspected object). ) 205 is irradiated. When the sample 205 is irradiated with the focused laser beam 203, a photo-induced current is generated in the sample 205, and the magnetism 206 is induced by the current. The intensity of the magnetism 206 is detected by the SQUID magnetic sensor 207.

  In this case, the position of the irradiation point of the focused laser beam 203 on the sample 205 is configured to be directly below the SQUID magnetic sensor 207 disposed on the opposite side with respect to the position of the sample 205. This is a necessary condition for the SQUID magnetic sensor 207 to accurately detect the magnetic field generated by laser light irradiation.

  The magnetic field intensity detected by the SQUID magnetic sensor 207 is input to the lock-in amplifier 209 as the magnetic field signal 208. The lock-in amplifier 209 combines the phase difference between the magnetic field signal 208 and the reference signal 210, extracts the same component as the frequency of the reference signal 210 from the magnetic field signal 208, and outputs it as the intensity signal 212. By performing this series of signal acquisition by scanning the stage on the XY plane with respect to the sample 205, a magnetic field distribution image in the sample can be acquired. From this magnetic field distribution, a disconnection or the like in the inspection object can be obtained. Defects can be detected.

  As an application of such a scanning laser SQUID microscope, application to inspection and analysis of LSI is being studied. For example, Patent Document 1 discloses a technique for inspecting a scanning laser SQUID microscope in a wafer state and a mounted state of a semiconductor chip. Further, in this document, for example, as shown in FIG. 11, a laser light source 151, an optical system 153 for condensing laser light, a laser beam 162, and a semiconductor chip 170 irradiated with the laser beam 162, A SQUID magnetometer 112, a control device 156 that controls the entire apparatus, a fixing member 160 that fixes the relative positional relationship between the optical system 153 and the SQUID magnetometer 112, a display device 158, and the like are disclosed (Patent Literature). 1 (see, for example, FIG. 14). The optical system 153 and the SQUID magnetometer 112 are different from the case of FIG. 10 in that they are arranged on the same side of the semiconductor chip 170 to be inspected.

  Further, as another conventional technique in which the optical system and the SQUID magnetometer are on the same side, a scanning SQUID microscope shown in FIGS. 12A and 12B has been proposed (see Patent Document 2). For example, see FIG.

  FIG. 12B discloses a case where the laser light irradiation position P and the SQUID 252 are arranged on the same side with respect to the inspection target W on the stage 310, and the heat insulating case 253 is formed in a hollow cylindrical shape. Three sets of pickup coils 251 and SQUIDs 252 are housed in the heat insulating case 253, and the laser light from the laser light source 221 is introduced into the objective lens 227 along the central axis of the heat insulating case 253. ing.

  Note that if the configuration shown in FIG. 10 is applied to an inspection of a semiconductor chip mounted on a substrate, the presence of the substrate may hinder laser irradiation on the semiconductor chip to be inspected. . In this case, the magnetic field itself is not generated from the semiconductor chip and the inspection is impossible. However, as shown in FIG. 11, the optical system 153 and the SQUID magnetometer 112 are on the same side of the semiconductor chip 170 to be inspected. There is no influence of the substrate, and it is considered that the semiconductor chip after mounting as well as the semiconductor chip before mounting can be inspected. The same applies to the configuration of FIG.

  On the other hand, there is proposed a SQUID microscope apparatus that observes the surface of a sample using near-field light (Evanescent Light) instead of condensing laser light on the sample with an objective lens (see Patent Document 3). This SQUID microscope apparatus is configured such that the tip of an optical fiber subjected to a predetermined process is brought close to the wavelength of light (several hundred nm) from the sample, and the sample is excited by near-field light generated from the tip. Near-field light is an evanescent wave (wave that disappears), and can only exist in the range of the wavelength of the light, so it is clearly distinguished from laser light.

Therefore, the SQUID microscope apparatus using such unique properties of near-field light can perform observation from the surface of the sample to a depth of about several nanometers with high accuracy. For example, the thickness mounted on the substrate is several It is impossible to nondestructively inspect the internal circuit of a 100 μm semiconductor chip.
JP 2002-313859 A JP 2001-50934 A JP 2003-287522 A

  However, when a semiconductor chip is inspected, the generated magnetic field is weak (several pT). Therefore, in the conventional configuration shown in FIG. 11, the position where the laser beam 162 is irradiated on the semiconductor chip (inspection target) 170 is next to the SQUID magnetometer 112, so that a high spatial resolution of μm level is realized. In other words, the condition that the inspection object must be sufficiently approached in the order of several μm cannot be satisfied, and a weak magnetic field cannot be detected with high accuracy.

  In the conventional configuration shown in FIG. 12, the laser beam irradiation position P on the inspection target W is diagonally beside the SQUID 252 and the pickup coil 251, and the distance is greater than the radius of the objective lens 227. The above-mentioned necessary condition for accurately detecting the magnetic field cannot be satisfied. Therefore, as in the case of FIG. 11, there is a problem that a weak magnetic field cannot be detected with high accuracy.

The present invention, in consideration of such problems of the prior, and an object thereof is to provide an induced magnetic field detecting equipment that can detect more accurately the weak magnetic field.

In order to solve the above problems, the first aspect of the present invention includes a stage for holding an inspection object,
A laser light generating unit for generating laser light;
A laser light irradiation unit for irradiating the inspection object held on the stage with the laser light;
A loop-shaped pickup coil for converting the magnetic field generated from the inspection object by the irradiated laser light into a current signal;
An induced magnetic field detection device comprising: a SQUID magnetic field detection unit that outputs information on the magnetic field based on the current signal;
The laser light irradiation unit and the pickup coil are arranged on the same side as the holding position of the inspection object with respect to the stage, and above the portion of the inspection object irradiated with the laser light The pickup coil is arranged in
The laser light irradiation unit condenses the laser light from the laser light generation unit and passes the inside of the pickup coil, and the laser light from the laser light generation unit to the condensing lens system A laser light guiding unit for guiding to
The pickup coil and the SQID magnetic field detection unit are disposed in a container that stores liquid nitrogen,
The container is provided with a hollow space through which the laser beam passes, and for storing the liquid nitrogen around the hollow space ,
The converging lens system is arranged in front Symbol in empty space,
A induced magnetic field detecting device the hollow space inside the loop you position formed by the which the pick-up coil in contact with the liquid nitrogen in the vessel.

The first to fourth inventions related to the present invention will be described below.
That is, the first invention is a stage for holding an inspection object;
A laser light generating unit for generating laser light;
A laser light irradiation unit for irradiating the inspection object held on the stage with the laser light;
A pickup coil for converting a magnetic field generated from the inspection object by the irradiated laser light into a current signal;
An induced magnetic field detection device comprising: a SQUID magnetic field detection unit that outputs information on the magnetic field based on the current signal;
The laser light irradiation unit and the pickup coil are arranged on the same side as the holding position of the inspection object with respect to the stage, and above the portion of the inspection object irradiated with the laser light The induced magnetic field detection device in which the pickup coil is disposed.
The second shot Ming, the laser light emitted from the laser light irradiation unit is induced magnetic field detecting device of the light the first shot that passes outside of the pickup coil.

The third shots Ming, the laser beam irradiation unit includes a condenser lens system for condensing the laser beam passed through the outside of the pick-up coil, the condenser lens of a laser beam from the laser beam generating unit A laser light guiding unit for guiding to the system,
And the pickup coil, the SQUID and the magnetic field detection unit is an induced magnetic field detecting device of the second shot bright accommodated in the container for storing the liquid nitrogen.

The fourth shot Ming, a holding step of holding the test object on the stage,
An irradiation step of irradiating the inspection object held on the stage with a laser beam by a laser beam irradiation unit;
A conversion step of converting a magnetic field generated from the inspection object by the irradiated laser light into a current signal using a pickup coil;
An induced magnetic field detection method comprising a SQUID magnetic field detection step of outputting information on the magnetic field based on the current signal,
The laser light irradiation unit and the pickup coil are arranged on the same side as the holding position of the inspection object with respect to the stage, and the part above the inspection object irradiated with the laser light is located above This is an induced magnetic field detection method in which a pickup coil is arranged.

  The present invention exhibits an effect that a weak magnetic field can be detected with higher accuracy.

Hereinafter, an embodiment of the induced magnetic field detection apparatus of the present invention and a reference example related to the present invention will be specifically described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a conceptual diagram showing the configuration of a scanning laser SQUID microscope according to Embodiment 1 of the present invention. The configuration of this embodiment will be described with reference to FIG.

  As shown in FIG. 1, this scanning laser SQUID microscope, a laser light generating unit 1 that irradiates laser light 2, a laser light guiding unit 12, a SQUID (Superconducting Quantum Interference Device) 13, The optical apparatus 14 with a condensing lens, the pick-up coil 15, the container 19 which accommodates the liquid nitrogen 18, the XY stage 20, and the laser path control part 102 are provided. Then, an imaging unit 31 for obtaining an output signal from the SQUID 13 and forming an image signal for displaying the measurement result on the display unit 32, and a control unit 101 for controlling the operation of the XY stage control device are attached. ing.

  The concept including the laser light guide member (laser light guide member) 12 and the optical device 14 with a condensing lens according to the present embodiment is an example of the laser light irradiation unit of the present invention.

  The laser light generation unit 1 is a device that temporally modulates and outputs a laser light 2 that is not directly induced to a magnetic field that is an observed physical quantity. This laser beam 2 is configured to be sent to the inspection object 16 via the laser beam guiding member 12 and the optical device 14 with a condensing lens.

  The laser light guiding member 12 is for suppressing the attenuation of the laser light inside the liquid nitrogen and for efficiently supplying the laser light from the laser light generating unit 1 to a target place. For example, an optical fiber is preferably used. can do.

  In the present embodiment, a laser path control unit 102 is provided in the passage path of the laser light 2. The laser path control unit 102 is for finely adjusting the relative positions of the laser light guiding member 12, the optical device 14 with a condensing lens, and the pickup coil 15.

  The initial position of the optical axis of the laser beam 2 coincides with the central axis of the pickup coil 15, but in order to optimize the measurement sensitivity of the magnetic field, the optical axis of the laser beam 2 is quickly translated from the central axis. It is configured to be possible.

  In general, a magnetic field is not always generated from the same location as the portion irradiated with laser light. Therefore, in consideration of the case where the magnetic field is generated from a place slightly deviated from the irradiation position and the magnetic field cannot be sufficiently detected by the pickup coil 15, the sensitivity is always maintained in the best state as the XY stage 20 is scanned. In addition, the position of the optical axis of the laser beam 2 is finely adjusted in real time. The fine adjustment range is limited to a predetermined range in the vicinity of the scanning sample point, and does not extend to adjacent sample points.

  In order to perform the fine adjustment, the laser path control unit 102, the laser light guiding member 12, and the optical device 14 with a condensing lens are integrated, and the laser path control unit 102 is driven by a motor (not shown). What is necessary is just to set it as the structure moved slightly in -Y direction. As a result, the optical axis position of the laser beam guiding member 12 can be finely adjusted.

  The laser beam 2 travels through the laser beam guiding member 12 disposed along the central axis of the container 19 containing the liquid nitrogen 18 via the laser path control unit 102. The laser light 2 is guided by the laser light guiding member 12 to the inside of the optical device 14 with a condensing lens provided in the container 19. The laser light emitted from the laser light guiding member 12 inside the optical device 14 with the condensing lens is condensed by the condensing lens 23 (see FIG. 3), and then passes through the center of the loop-shaped pickup coil 15. Then, the object 16 is irradiated on the inspection object 16.

  The pickup coil 15 is for detecting the generated magnetic field 3, and a weak current signal generated in the pickup coil 15 by the magnetic field is input to the SQUID 13 body.

  The liquid nitrogen 18 is for improving the electrical conductivity by cooling the pickup coil 15, the SQUID 13, and the like. The container 19 is made of stainless steel, for example, and as shown in FIG. 1, is supported by a support device 103 that also serves as a Z-axis control device so that the vertical position can be adjusted. For example, when the manufacturing lot of the mounted semiconductor chip that is the inspection object 16 changes, and the height of the semiconductor chip changes, the support device 103 moves in the Z-axis direction, and the container 19 The distance between the bottom surface and the inspection object 16 is adjusted. Alternatively, as will be described in detail later, the support device 103 moves the container 19 in the Z-axis direction even when the resolution needs to be changed according to the inspection content of the inspection object 16. Note that the Z-axis control device operates according to a control signal from the control unit 101.

  As shown in FIG. 2, the shape of the container 19 is a shape in which a cylindrical bottom portion is narrowed in a funnel shape, and a glass window 19 a that transmits laser light is provided in the center portion of the bottom surface. . The outer diameter and height of the container 19 is about 10 cm or less, and the glass window 19a has a diameter of several tens to several hundreds of micrometers and is substantially the same as the diameter of the pickup coil 15.

  Further, as shown in FIG. 3, the outer shape of the optical device 14 with a condensing lens is a hollow cylindrical shape having a diameter of, for example, about 5 cm, has a watertight structure, and a condensing lens 23 is provided therein. ing. The condensing lens 23 is for focusing on the inspection object 16, and an optical fiber as the laser light guiding member 12 is inserted up to the upper part of the condensing lens 23, and the laser light is collected from the end thereof. The light lens is irradiated. A glass window 14a for laser light output is provided in the center of the bottom of the optical device 14 with a condensing lens, and the inspection target 16 is irradiated with the laser light condensed through the glass window 14a. The diameter of the glass window 14a is, for example, several tens to several hundreds μm.

  The XY stage 20 on which the inspection object 16 is placed is moved in the XY direction by the XY stage control device 21. The moving direction and moving amount are controlled by the control unit 101. On the other hand, as described above, the detection signal from the SQUID 13 provided in the container 19 is input to the control unit 101. This signal is converted into an image signal by the imaging unit 31 and displayed as an image on the display unit 32.

  Next, the principle and operation of the scanning laser SQUID microscope of the present embodiment will be described, and an embodiment of the induced magnetic field detection method of the present invention will be described at the same time.

  In the scanning laser SQUID microscope configured as described above, an inspection object (mounting semiconductor chip or the like) 16 is placed and fixed on the XY stage 20, and the laser light 2 is condensed and irradiated on the inspection object 16. To do. When the inspection target 16 is irradiated with the laser beam 2, energy conversion occurs while the laser beam 2 enters. In many inspection objects, the laser beam 2 is converted into thermal energy, and the temperature of the focal point rises. When the inspection object is a semiconductor such as an IC, electric charges are generated by photoelectric conversion, and a diffusion current is generated by a concentration gradient. In a depletion layer having an internal electric field, a drift current is generated and may be directly converted into a current.

  In this way, when light is converted into heat and current, magnetic spin changes and currents are generated due to this, and magnetic flux generated from the inspection object and magnetic flux passing through the inspection object. Bring subtle changes to This change is picked up by the pickup coil 15 and measured by the SQUID 13 to obtain a magnetic signal reflecting the physical characteristics of the surface of the inspection object 16 and the internal electrical characteristics. Then, by sequentially scanning the laser irradiation position, the entire inspection object 16 can be inspected, and the obtained magnetic signal can be imaged.

  As described above, the scanning laser SQUID microscope according to the present embodiment irradiates the surface of the inspection object with the focused laser beam and measures the change in the magnetic field induced thereby by the SQUID. It is an example of an induced magnetic field detection apparatus that measures an induced magnetic field distribution reflecting physical characteristics and the like in a non-contact manner and performs processing such as imaging.

  Next, the operation of the apparatus according to the present embodiment will be described more specifically.

  When actually inspecting, the semiconductor device as the inspection object 16 is fixed on the XY stage 20 and the laser light 2 is output from the laser light generating unit 1. The laser light generation unit 1 is provided with a wavelength switching function so that the wavelength of the output laser light 2 can be switched. The wavelength used depends on the light absorption band of the irradiation object, and the measurement result may vary depending on the wavelength even for the same object, so by adding a wavelength switching function to the laser light generation unit 1, A wider range of samples can be measured, and various observation results can be obtained.

  The wavelength range of the laser beam 2 is generally in the range of about 300 nm to 1200 nm.

  First, the laser beam 2 output from the laser beam generation unit 1 travels through the laser beam guiding member 12, but is optimally routed through the laser path control unit 102 and the optical device 14 with a condenser lens. Irradiated in a focused state. Excitation energy is supplied to the inspection object 16 by this irradiation, and a weak magnetic field (several pT) is generated by energy conversion. The generated weak magnetic field is reliably detected by the pickup coil 15 provided close to a distance of several μm just above the laser irradiation position of the inspection object 16 and measured by the SQUID 13.

  A measurement signal from the SQUID 13 is supplied to the control unit 101, converted into an image signal by a known imaging unit 31, and then supplied to a display unit 32 such as a liquid crystal display. The display unit 32 can inspect electrical characteristics such as disconnection with higher accuracy in addition to inspection of physical characteristics such as peeling of the inspection object by a method such as comparing the measured image with a reference image. It can be done.

  In the scanning laser SQUID microscope shown in FIG. 1, the laser light 2 passes through the inside of the pickup coil 15. Therefore, the laser beam 2 for generating the magnetic field and the pickup coil 15 for detecting the magnetic field are both disposed on the same side (upper side in FIG. 1) with respect to the inspection object 16. For this reason, induction of the magnetic field by the laser light and detection of the generated magnetic field can be performed on the same side with respect to the inspection object.

  As described above, according to the present embodiment, even when the semiconductor chip that is the inspection object 16 is mounted on the substrate and it is difficult to transmit the laser beam or the generated magnetic field from one side, the magnetic field can be efficiently generated. Generation and detection are possible. Furthermore, since the generated weak magnetic field is reliably detected by the pickup coil 15 brought close to a distance of several μm immediately above the laser irradiation position of the inspection object 16, highly accurate detection can be performed.

  That is, since the laser beam 2 and the pickup coil 15 are substantially coaxial, the generated magnetic field can be detected with high sensitivity. The instantaneous current generated in the inspection object 16 generates a magnetic field according to Ampere's law, but this magnetic field becomes weaker as the distance from the magnetic field generation point increases. That is, since the magnetic field can be detected with higher sensitivity as the magnetic field generation point and the detection point are closer, it is preferable that the laser beam irradiation point on the inspection object 16 and the pickup coil 15 be as close as possible. In the present invention, this can be achieved by arranging the optical axis of the laser beam 2 and the pickup coil 15 substantially coaxially.

  In addition, the optical device 14 with a condensing lens shown in FIG. 3 is good also as a replaceable structure. This makes it possible to replace the optical device 14 with a condensing lens having a different focal length. For example, even when the height of the internal circuit of the semiconductor IC as the inspection target 16 from the XY stage 20 is different, Non-destructive inspection becomes possible.

Next, another embodiment of the present invention, which is a modification of the container 19 shown in FIG. 1, will be described with reference to FIGS. 4 (A) and 4 (B).

  FIG. 4B is a schematic diagram for explaining a container 401 which is a modified example of the container 19. FIG. 4A is a schematic view showing a P-P ′ cross section of FIG.

  4A and 4B, the container 401 and the laser light guide member 412 are different from the configuration shown in FIG. This laser beam guiding member 412 is attached to the front of the opening of the hollow space 403 of the container 401 containing the liquid nitrogen 18. The container 401 is provided with a cylindrical hollow space 403 having different diameters at an upper part 403a and a lower part 403b. The laser beam 2 that has exited the laser beam guiding member 412 passes through the central axis of the hollow space 403 and passes through a condenser lens 23 provided at a large diameter portion of the hollow space 403.

  In the hollow space 403, the upper portion 403a has a large inner diameter and the lower portion 403b has a small inner diameter, and the lower portion 403b passes through the inside of the loop-shaped pickup coil 15.

  The pickup coil 15 is disposed in the container 401, and the laser beam 2 passes through the central portion thereof. If comprised in this way, the pick-up coil 15 can contact the liquid nitrogen 18, and since the laser beam 2 passes through the hollow space 403, it is not influenced by the liquid nitrogen 18. In addition, since the container 401 has the hollow space 403, the glass window 19a as shown in FIG. 1 is unnecessary.

Next, another embodiment of the present invention which is a further modification of the container 401 shown in FIGS. 4A and 4B will be described with reference to FIG.

  FIG. 5 is a schematic diagram for explaining a modified example of the container 401.

  That is, the optical device 140 with a condensing lens shown in FIG. 5 is a replaceable cylindrical case in which the condensing lens 23 is housed. An opening window through which laser light can pass is provided at the center of each of the upper surface and the lower surface of the optical device 140 with a condensing lens. Further, the lower surface and the outer peripheral surface of the optical device with a condensing lens 140 are processed with high accuracy together with the surface of the upper portion 403a, and can be fitted with an accuracy of about several μm. In addition, about the component similar to FIG. 4, the same code | symbol was attached | subjected and description was abbreviate | omitted.

  A modification of the SQUID magnetic field detection unit 100 shown in FIG. 1 will be described.

  FIG. 6 is a conceptual diagram for explaining the configuration and operation of a modified example of the scanning laser SQUID microscope shown in FIG. FIG. 7 is a conceptual diagram showing a Q-Q ′ cross section of FIG. 6.

  That is, the SQUID magnetic field detection unit 1100 shown in FIG. 6 is different from the SQUID magnetic field detection unit 100 shown in FIG. 1 in that the optical device with a condensing lens 14 can move in the Z direction.

  First, the reason why the optical device 14 with a condensing lens is movable in the Z direction will be described.

  In other words, the necessary resolution varies depending on the inspection content of the inspection object 16. Therefore, the support device 103 changes the distance between the pickup coil 15 and the inspection object 16 in order to achieve a predetermined resolution.

  On the other hand, since the focal length of the condensing lens 23 incorporated in the optical device 14 with a condensing lens does not change, the optical device 14 with a condensing lens is moved relative to the container 19 according to the amount of movement of the container 19 by the support device 103. Need to be moved relatively.

  Here, the differences will be mainly described, and the same components are denoted by the same reference numerals, and description thereof will be omitted.

  As shown in FIGS. 6 and 7, the SQUID magnetic field detection unit 1100 includes a motor 51 and a ball screw 52 provided as a rotation shaft of the motor 51 on the upper portion of the side wall. The substantially L-shaped drive unit 53a that can move in the vertical direction by the rotation of the ball screw 52 is configured such that the screw hole provided on the short side thereof engages with the ball screw 52. In addition, a drive part 53 b having the same shape as the substantially L-shaped drive part 53 a is disposed opposite to the container 19. The pair of drive parts 53a and 53b hold the optical device 14 with a condensing lens at a predetermined position at the long end part. The short side of the drive unit 53b is provided with a hole, which is fitted with the pin 57 with high accuracy and can be smoothly moved up and down. The drive parts 53a and 53b are fixed so as to be integrated with each other by semicircular fixing members 53c and 53d on the short side. A linear scale 55 is provided at the center of the inner wall of the container 19, and a sensing unit 56 is provided on the long side of the drive unit 53 a correspondingly. The sensing unit 56 outputs the position detection result to the control unit 101. The motor 51 is rotated by a control signal from the control unit 101.

  In the present embodiment, as an example, the distance of one turn of the ball screw 52 is 10 mm, and one rotation of the motor is controlled by 10,000 pulses. Note that since the required resolution in the Z direction varies depending on the inspection object, these values may also vary. Therefore, the positioning accuracy by the motor 51 is also different.

In this case, the drive units 53a and 53b can be moved with a resolution of 10 × 10 ⁻³ / 10 ⁴ = 1 μm.

  Under the above configuration, the motor 51, the optical device with a condensing lens 14, and the like perform the following operations.

  The case where the support device 103 moves the container 19 by the movement amount A in the plus direction of the Z axis according to a command from the control unit 101 will be described. In this case, the control unit 101 issues a rotation amount command for moving the motor 51 by the movement amount A in the negative direction of the Z axis. As the motor 51 rotates based on this command, the drive units 53a and 53b move downward and the sensing unit 56 also moves. The sensing unit 56 reads the scale information attached to the linear scale 55 and outputs it to the control unit 101. The control unit 101 obtains the actual movement amount B of the optical device 14 with a condensing lens from the sent scale information. The control unit 101 rotates the motor 51 so that the difference between the actual movement amount B and the movement amount A is zero or falls within a predetermined range. Thereby, the focal length of the condensing lens 23 is adjusted with high accuracy.

  As another method of focusing the condenser lens 23, the following operation may be performed in a configuration that does not include the linear scale 55 and the sensing 56.

  That is, the control unit 101 issues a rotation amount command for moving the motor 51 by the movement amount A in the negative direction of the Z axis. As the motor 51 rotates based on this command, the drive units 53a and 53b move downward. At the same time, the test object 16 is irradiated with the laser beam 2 according to a command from the control unit 101, and the magnetic field strength is measured by the SQUID 13. As a result, the rotation of the motor 51 is controlled so that the magnetic field strength becomes maximum, and the position of the optical device 14 with a condensing lens is finely adjusted. Thereby, the focal length of the condensing lens 23 is adjusted with high accuracy.

  Moreover, you may combine suitably the adjustment using the sensing part 56, and the measurement of a magnetic field intensity suitably. Thereby, the accuracy of the adjustment of the focal length of the condenser lens 23 is further improved.

  Thereby, even if the position of the container 19 in the Z-axis direction is changed, the distance between the condenser lens 23 and the object to be inspected exhibits an effect that the in-focus relationship can always be maintained.

In the following, reference example according to the induced magnetic field detecting device of the present invention relating to the present invention will be described with reference to FIG.

As shown in FIG. 8, in the present reference example , unlike the first embodiment shown in FIG. 1, the laser light 2 does not pass through the inside of the container 19 but irradiates the inspection object 16 through the outside thereof. It is like that. Since the other points are the same as those of the first embodiment, the same symbols are added to the same portions.

In the configuration of the laser SQUID microscope shown in this reference example , the path of the laser light emitted from the laser light generation unit 1 is bent downward by the laser path control unit 102 as shown in FIG. Then, the laser light travels around along the outer peripheral surface of the container 19, and then the path is changed obliquely downward by the laser light path adjusting mirror 22, and is condensed by the condenser lens 23 and is focused on the inspection object 16. Irradiated. The laser SQUID microscope shown in this reference example is different from the case of FIG. Such a configuration is also effective when the distance between the object to be inspected and the bottom surface of the container 19 is relatively large (several hundred μm or more).

  Since the laser beam 2 does not pass through the container 19, it is not necessary to provide the container 19 with the glass window 19 a as in the first embodiment.

The laser SQUID microscope of this reference example is configured to perform irradiation of the laser beam 2 for generating a magnetic field and detection of the magnetic field by the pickup coil 15 on the same side as the inspection object 16 as in the first embodiment. It is.

Next, while describing the operation of the scanning laser SQUID microscope of the present embodiment , a reference example of the induced magnetic field detection method of the invention related to the present invention will be described at the same time.

  That is, with the above-described configuration, the laser beam 2 emitted from the laser beam generation unit 1 is routed downward by the laser path controller 102. Then, the laser beam is further changed in the diagonally downward direction by the laser optical path adjusting mirror 22, then condensed by the condenser lens 23, and irradiated on the inspection object 16 from the diagonally upper side. The weak magnetic field generated by this irradiation is detected by the pickup coil 15 in the container 19 disposed substantially directly above the laser irradiation site of the inspection object 16 and measured by the SQUID 13. Then, the measurement result is converted into an image signal by the imaging unit 31 and displayed on the display unit 32.

For this reason, the apparatus of this reference example shown in FIG. 8 can also inspect the semiconductor chip mounted on the substrate with high accuracy, like the apparatus of the first embodiment shown in FIG.

  In the embodiment described above, the imaging unit 31 is provided, and the result measured by the SQUID 13 is displayed as an image. Instead of using an apparatus including the imaging unit 31, a separate data storage unit may be provided, and the measurement result by the SQUID 13 may be temporarily stored in the data storage unit and then processed by an appropriate data processing unit.

  Further, when the measurement result is displayed as an image, it is easy to determine the inspection result. However, it is not always necessary to form an image. In some cases, it may be displayed directly as a numerical value.

  In the first embodiment, the case where the condensing lens 23 is disposed above the pickup coil 15 and the laser light guiding member 12 is provided up to just before the condensing lens 23 has been described. For example, when the fiber diameter is a small diameter that does not cause a problem with respect to the pickup coil 15 and the pickup coil 15 can sufficiently detect the generated magnetic field 3, the fiber itself may be passed through the inside of the pickup coil 15. . In this case, the condensing lens is not arranged or is arranged below the pickup coil 15 if arranged.

  In the above embodiment, the case where a semiconductor IC before or after mounting is used as an inspection object has been described. However, the present invention is not limited thereto, and examples of other objects include solar cells, thin film TFTs for displays, and the like. Is mentioned.

  In the above-described embodiment, the case where the central axis of the pickup coil 15 and the optical axis of the laser beam 2 are substantially the same or parallel has been described. However, the present invention is not limited to this. Even if the optical axis of the member 12 or the optical device 14 with the condensing lens is disposed obliquely with respect to the central axis of the pickup coil 15, the irradiated laser light 2 travels obliquely in the container 19. Good. In short, as long as the laser beam passes through the inside of the pickup coil 15 and the pickup coil 15 is disposed above the irradiation position on the inspection object, the path of the laser beam is configured in any way. May be.

  In the above-described embodiment, the configuration in which the XY stage is provided and the inspection object can be automatically scanned in the XY direction is described. However, the present invention is not limited to this. Alternatively, it may be configured such that neither can be scanned.

  In the above-described embodiment, the case where the container 19, the laser light guide member 12, the laser path control unit 102, or the condenser lens 23 can be moved also in the Z direction has been described. A configuration in which the container cannot move in the Z direction may be used.

  The scanning laser SQUID microscope described in the above embodiment irradiates the inspection object from the same side as the pickup coil that detects the magnetic field with the laser beam irradiated from the laser beam irradiation unit and guided by the laser beam guiding member. Because laser light irradiation and magnetic field detection are performed on the same side of the object to be inspected, even semiconductor devices mounted on substrates that are difficult to transmit laser light or generated magnetic fields are irrelevant to the presence of the substrate. It is possible to efficiently generate and detect a magnetic field. Further, since the pickup coil is disposed above the portion of the inspection object to be irradiated with the laser beam, the weak magnetic field can be detected with higher accuracy even in the inspection of the mounted semiconductor chip.

  Further, since the scanning laser SQUID microscope irradiates the inspection object through the inside of the annular pickup coil, the scanning laser SQUID microscope has a compact structure and can detect the magnetic field with high accuracy.

  In the above-described embodiment, a laser path control device that controls the path of the laser light is installed coaxially with the central axis of the pickup coil, and the inspection target is irradiated with the laser light via the laser path control device. Thus, the relative position between the pickup coil and the laser beam can be adjusted, the inspection can be performed in the most suitable magnetic field generation state, and the inspection object has a fine structure and the magnetic field can be adjusted. Even if the generation point is a fine interval, it can be detected with high sensitivity.

  Further, when an optical fiber is used as the laser light guide member 12 as described above (see FIG. 1), the structure can be simplified. Further, when a hollow space is also used as a part of the laser light guiding member as in the modification shown in FIG. 4B, it is not affected by liquid nitrogen or the like.

  Further, in the above-described scanning laser SQUID microscope, when the pickup coil is installed inside the liquid nitrogen container and the laser light is configured to irradiate the inspection object through the outside of the liquid nitrogen container, the laser light is in liquid nitrogen. It is possible to omit the optical fiber or the like, and the route can be directly controlled.

  In the above embodiment, the optical device 14 with the condensing lens has been described on the assumption that the optical axis of the laser light 2 emitted from the laser path control unit 102 is adjusted in the vertical direction. However, since the emission direction of the laser light 2 emitted from the laser path control unit 102 may be inclined from the vertical direction, a configuration example that can cope with such a case will be described below with reference to FIG. Shown in

  FIG. 9A is a conceptual diagram for explaining an optical device 141 with a condensing lens capable of adjusting the optical axis of laser light.

  As shown in the figure, in the optical device 141 with a condensing lens, a rotatable first mirror 41 for reflecting the laser light 2 emitted from the laser path control unit 102, a second mirror 42, and Is provided. Further, in the optical device 141 with a condensing lens, a splitter 44 that separates the laser light 2 into a path to the position detection sensor (PSD) 43 and a path to the condensing lens 23, a position detection sensor 43, and And a condensing lens 23. The position detection sensor 43 is a means for detecting the degree of inclination (amount of positional deviation) of the laser beam 2 emitted from the laser path control unit 102 and outputting the detection result to the control unit 101 (see FIG. 1). is there. The control unit 101 obtains an output from the position detection sensor 43 and controls the rotation angles of the first mirror 41 and the second mirror 42.

  Next, the operation of each unit will be described with reference to FIGS. 9 (A) and 9 (B). Here, in order to facilitate understanding of the description, the case where the inclination of the laser beam 2 occurs in the YZ plane will be described. Even when it occurs in the -Z space, the basic operation is the same as described below.

  First, the path of the laser beam 2a emitted vertically from the laser path controller 102 will be described. In FIG. 9A, the route in this case is indicated by a solid line.

  In the figure, the laser beam 2a is reflected by the first mirror 41, reflected by the position 42a at the center of the rotation axis of the second mirror 42, and proceeds in the downward direction in the figure. Further, the laser light 2a1 (shown by a dotted line in the figure) traveling in the right direction in the figure by the splitter 44 is incident on the center position 43a of the position detection sensor 43, and the laser light straightly traveling in the downward direction in the figure by the splitter 44. Is incident on the center of the condenser lens 23.

  Next, the path of the laser light 2b emitted from the laser path control unit 102 with a certain angle of inclination will be described with reference to FIGS. 9A and 9B. In FIG. 9A, the path of the laser beam 2b is indicated by a one-dot chain line.

  In FIG. 9A, the laser beam 2b is reflected by the first mirror 41, reflected at a position 42b shifted from the position 42a at the center of the rotation axis of the second mirror 42, and proceeds downward. The laser beam 2b1 traveling in the right direction in the drawing by the splitter 44 is incident on a position 43b shifted downward from the center position 43a of the position detection sensor 43.

  On the other hand, the laser beam that has traveled straight downward is incident on a position shifted from the lens center of the condenser lens 23. The position detection sensor 43 that has detected the positional deviation of the incident light outputs a signal corresponding to the positional deviation amount to the control unit 101. The control unit 101 rotates the first and second mirrors 41 and 42 by α degrees and β degrees, respectively, in order to set the positional deviation amount to zero. The reflected light of the laser beam 2b after the first mirror 41 has rotated α degrees is indicated by a dotted line. Here, the rotation angle (α degree) of the first mirror 41 is controlled so that the reflected light 2 b shown by the dotted line always proceeds to the position 42 a at the center of the rotation axis of the second mirror 42.

  In FIG. 9B, the path of the laser beam 2b after the first and second mirrors 41 and 42 are rotated by α degrees and β degrees, respectively, is indicated by a solid line and a dotted line.

  Thereby, even if the laser beam 2 incident on the optical device 141 with a condensing lens is inclined, the laser beam 2 can be incident on the lens center position of the condensing lens 23.

  The induced magnetic field detection apparatus according to the present invention has an effect of detecting a weak magnetic field with higher accuracy, and is useful as an induced magnetic field detection apparatus.

Conceptual diagram for explaining a scanning laser SQUID microscope according to the first embodiment of the present invention. (A) Partial longitudinal sectional view of the liquid nitrogen container according to Embodiment 1 of the present invention, (B) Bottom view of the liquid nitrogen container according to Embodiment 1 of the present invention. (A) Longitudinal sectional view of optical device with condensing lens of Embodiment 1 of the present invention, (B) Bottom view of optical device with condensing lens of Embodiment 1 of the present invention (A) Schematic sectional view showing a liquid nitrogen container or the like of another embodiment of the present invention , (B) Schematic longitudinal sectional view of a liquid nitrogen container or the like of another embodiment of the present invention FIG. 4 (A), the schematic view of a longitudinal section of another implementation mode of the present invention which is a modification of the liquid nitrogen container shown in FIG. 4 (B) Conceptual diagram for explaining a modification of the scanning laser SQUID microscope according to the first embodiment of the present invention. FIG. 3 is a conceptual diagram showing a Q-Q ′ section of a modification of the scanning laser SQUID microscope according to the first embodiment of the present invention. Schematic diagram for explaining a scanning laser SQUID microscope of a reference example of the present invention (A) Conceptual diagram for explaining an optical device with a condensing lens capable of adjusting the optical axis of the laser beam, (B) A diagram showing a path of the laser beam after the first and second mirrors have moved. Block diagram showing the configuration of a conventional laser SQUID microscope Conceptual diagram showing the configuration of another conventional laser SQUID microscope (A) Conceptual diagram of another conventional laser SQUID microscope viewed from the top, (B) Conceptual diagram of the laser SQUID microscope of FIG.

Explanation of symbols

1 Laser Light Generation Unit 2 Laser Light 3 Generated Magnetic Field 13 SQUID
DESCRIPTION OF SYMBOLS 14 Optical apparatus with a condensing lens 15 Pickup coil 16 Inspection object 17 Mounting board 18 Liquid nitrogen 19 Container 20 XY stage 21 XY stage control apparatus 23 Condensing lens 31 Imaging unit 32 Display part 101 Control part 102 Laser path control part 103 Supporting device

Claims (1)

A stage for holding the inspection object;
A laser light generating unit for generating laser light;
A laser light irradiation unit for irradiating the inspection object held on the stage with the laser light;
A loop-shaped pickup coil for converting the magnetic field generated from the inspection object by the irradiated laser light into a current signal;
An induced magnetic field detection device comprising: a SQUID magnetic field detection unit that outputs information on the magnetic field based on the current signal;
The laser light irradiation unit and the pickup coil are arranged on the same side as the holding position of the inspection object with respect to the stage, and above the portion of the inspection object irradiated with the laser light The pickup coil is arranged in
The laser light irradiation unit condenses the laser light from the laser light generation unit and passes the inside of the pickup coil, and the laser light from the laser light generation unit to the condensing lens system A laser light guiding unit for guiding to
The pickup coil and the SQID magnetic field detection unit are disposed in a container that stores liquid nitrogen,
The container is provided with a hollow space through which the laser beam passes, and for storing the liquid nitrogen around the hollow space,
The condenser lens system is disposed in the hollow space;
An induced magnetic field detection device in which the hollow space is located inside a loop formed by the pickup coil in contact with the liquid nitrogen in the container.