JP6099131B2 - Inspection apparatus and inspection method - Google Patents

Description

  The present invention relates to a technique for inspecting a semiconductor device or a photo device.

  In the semiconductor field, a technique for inspecting a semiconductor device for defects and damage by generating an electromagnetic wave by irradiating a semiconductor device with pulsed light and detecting the electromagnetic wave has been proposed (Patent Document 1).

  Specifically, in the inspection method disclosed in Patent Document 1, pulsed light irradiation is performed on a portion (such as a pn junction) where an internal electric field exists inside a semiconductor device. When pulsed light is irradiated, electron-hole pairs are generated by photoexcitation, and the generated electron-hole pairs are accelerated by an electric field inside the semiconductor device, thereby generating a current. At this time, since the pulsed light is irradiated, a current is generated in a pulse shape, and thus a time change occurs in the current. Then, the electromagnetic wave according to the time change of an electric current is radiated | emitted from a semiconductor device.

  The inspection method of Patent Document 1 diagnoses a failure and a defective portion of a semiconductor device by utilizing the fact that the emitted electromagnetic wave is generated depending on the magnitude and direction of the internal electric field of the semiconductor device. is there.

  In addition, an inspection apparatus that converts so-called photo devices (for example, solar cells and image sensors) that convert light into current has also been proposed (for example, Patent Document 2).

JP 2006-24774 A JP2013-19861A JP 2009-175127 A

  However, in Patent Document 1, it is assumed that an electromagnetic wave is observed without bias in order to inspect a semiconductor device without contact. For this reason, it has been necessary to detect electromagnetic waves radiated depending only on the internal electric field unique to the semiconductor device. In order to avoid damage to the semiconductor device, the intensity of the pulsed light (time average energy) is limited to 0.1 mW to 10 W. For this reason, according to the inspection method of patent document 1, there existed a possibility that the electromagnetic waves radiated | emitted from a semiconductor device might become comparatively weak. In Patent Document 3, the signal strength of the radiated electromagnetic wave is increased by applying a reverse bias voltage.

  Therefore, an object of the present invention is to provide a technique for improving the S / N ratio of electromagnetic wave detection by increasing the electric field intensity of an electromagnetic wave emitted by irradiating a semiconductor device or a photo device with pulsed light.

In order to solve the above problems, a first aspect is an inspection apparatus for inspecting a semiconductor device or a photo device, wherein an irradiation unit that irradiates the semiconductor device or the photo device with a pulsed light, and according to the irradiation of the pulsed light A magnetic field that applies a magnetic field to the semiconductor device or photo device by a detection unit that detects an electromagnetic wave radiated from the semiconductor device or photo device and a pair of magnetic pole portions that are disposed opposite to each other with the semiconductor device or photo device interposed therebetween. and a applying portion, the magnetic field applying unit, apply a magnetic field of a direction to intersect the direction of the electric field existing inside the semiconductor device or a photo device.

In addition, according to a second aspect, in the inspection apparatus according to the first aspect, the magnetic pole that changes the direction of the magnetic field by moving the pair of magnetic pole portions relative to the semiconductor device or the photo device. A part moving mechanism.

According to a third aspect, in the inspection apparatus according to the second aspect, the magnetic pole part moving mechanism is configured to rotate the pair of magnetic pole parts relative to the semiconductor device or the photo device. including.

The fourth aspect further comprises the inspection apparatus according to any one state like aspect of the first to third polarizing element for polarizing the electromagnetic waves generated in response to the irradiation of the pulsed light.

Further, a fifth aspect is an inspection method for inspecting a semiconductor device or a photo device, and (a) the semiconductor device or the photo device is formed by a pair of electrode portions arranged to face each other with the semiconductor device or the photo device interposed therebetween. Applying a magnetic field; (b) irradiating the semiconductor device or photo device to which the magnetic field has been applied in the step (a) with pulsed light; and (c) irradiating in the step (b). saw including a step of detecting electromagnetic waves radiated from the semiconductor device or a photo device in response to said pulsed light, said step (a), intersects the direction of the electric field existing inside the semiconductor device or a photo device This is a step of applying a magnetic field in the direction .

According to the inspection apparatus according to the first aspect, free electrons generated by irradiation with pulsed light are accelerated by receiving Lorentz force by moving in a magnetic field. Thereby, the intensity | strength of the electromagnetic waves radiated | emitted from a semiconductor device or a photo device can be improved.
Further, a Lorentz force can be applied to free electrons by applying a magnetic field in a direction crossing the direction of the electric field.

Moreover, according to the inspection apparatus which concerns on a 2nd aspect, the direction of a magnetic field can be changed so that it may respond | correspond to the direction of an internal electric field. For this reason, Lorentz force can be made to act appropriately on free electrons.

Moreover, according to the inspection apparatus which concerns on a 3rd aspect, it can convert continuously, rotating the direction of a magnetic field.

Moreover, according to the inspection apparatus which concerns on a 4th aspect, the electromagnetic waves polarized in the specific direction are detectable. Thereby, for example, among the generated electromagnetic waves, the electromagnetic waves polarized in the direction in which the Lorentz force acts can be specifically detected. Thereby, the direction-dependent inspection can be performed.

Moreover, according to the inspection method which concerns on a 5th aspect, the generated free electron is accelerated by receiving Lorentz force by moving in a magnetic field. Thereby, the intensity | strength of the electromagnetic waves radiated | emitted from a semiconductor device or a photo device can be improved.
Further, a Lorentz force can be applied to free electrons by applying a magnetic field in a direction crossing the direction of the electric field.

1 is a schematic configuration diagram of an inspection apparatus according to a first embodiment. It is a schematic block diagram of the irradiation part and detection part which are shown by FIG. It is a schematic sectional drawing which shows the pn junction part of a photo device. It is a figure for demonstrating the movement of a free electron in the state which does not apply a magnetic field. It is a figure for demonstrating the movement of a free electron in the state to which the magnetic field was applied. It is a schematic plan view which shows a part of surface of a photo device. It is a schematic plan view which shows a part of surface of a photo device. It is a flowchart of a test | inspection of a photo device. It is a schematic diagram of the imaging image showing electromagnetic wave intensity distribution. It is a figure which shows the restoration example of the time waveform of an electromagnetic wave pulse. It is a schematic block diagram of the irradiation part and detection part of the inspection apparatus which concern on 2nd Embodiment. It is a schematic block diagram of the irradiation part and detection part of the inspection apparatus which concern on 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, and is not an example which limits the technical scope of this invention. In addition, in FIG. 1 and the subsequent drawings, the size and number of each part may be exaggerated or simplified as necessary for easy understanding.

<1. First Embodiment>
<1.1. Configuration and function of inspection device>
FIG. 1 is a schematic configuration diagram of an inspection apparatus 100 according to the first embodiment. 2 is a schematic configuration diagram of the irradiation unit 12 and the detection unit 13 shown in FIG. The inspection apparatus 100 is an apparatus that inspects the characteristics of the photo device 9.

  Examples of the photo device 9 include photo devices such as solar cells, photodiodes, image sensors such as CMOS sensors and CCD sensors. Further, the surface 9S of the photo device 9 of the present embodiment may be substantially planar or curved.

  However, the inspection object of the inspection apparatus 100 is not limited to the photo device 9, and may be a semiconductor device including, for example, an integrated circuit (IC or LSI), a resistor, a capacitor, or the like.

  As shown in FIG. 1, the inspection apparatus 100 includes a stage 11, an irradiation unit 12, a detection unit 13, a visible camera 14, a motor 15, a control unit 16, a monitor 17, and an operation input unit 18.

  The stage 11 fixes the photo device 9 on the stage 11 by fixing means (not shown). As the fixing means, one using a holding tool for holding the substrate, an adhesive sheet, or an adsorption hole formed on the surface of the stage 11 is assumed. However, other fixing means may be employed as long as the photo device 9 can be fixed. In the present embodiment, the stage 11 holds the photo device 9 so that the irradiation unit 12 and the detection unit 13 are arranged on the surface 9S side of the photo device 9.

  As shown in FIG. 2, the irradiation unit 12 includes a femtosecond laser 121. For example, the femtosecond laser 121 emits pulsed light (pulsed light LP1) having a wavelength including a visible light region of 360 nm (nanometers) or more and 1 μm (micrometers) or less. As a specific example, linearly polarized pulsed light having a center wavelength of around 800 nm, a period of several kHz to several hundred MHz, and a pulse width of about 10 to 150 femtoseconds is emitted from the femtosecond laser. Of course, pulse light in other wavelength regions (for example, visible light wavelengths such as blue wavelength (450 to 495 nm) and green wavelength (495 to 570 nm)) may be emitted.

  The pulsed light LP1 emitted from the femtosecond laser 121 is divided into two by the beam splitter B1. One of the divided pulse lights (pulse light LP11) is applied to the photo device 9. At this time, the irradiation unit 12 performs irradiation with the pulsed light LP11 from the surface 9S side.

  Further, the pulsed light LP11 is applied to the photo device 9 so that the optical axis of the pulsed light LP11 is obliquely incident on the surface 9S of the photo device 9. In the present embodiment, the irradiation angle is set so that the incident angle is 45 degrees. However, the incident angle is not limited to such an angle, and can be appropriately changed within a range of 0 to 90 degrees.

  FIG. 3 is a schematic cross-sectional view showing the pn junction 95 of the photo device 9. In the photo device 9 according to the present embodiment, a pn junction 95 is formed by joining a p-type semiconductor layer 91 and an n-type semiconductor layer 93. In the vicinity of the pn junction 95, a depletion layer 97 in which electrons and holes hardly exist is formed by generating a diffusion current in which electrons and holes are diffused and combined with each other. In this region, a force for pulling electrons and holes back to the n-type and p-type regions is generated, so an electric field (internal electric field E1) is generated inside the photo device. It is known that such an internal electric field E1 unique to the photo device 9 is generated not only at the pn junction 95 but also at the metal / semiconductor interface, for example.

  When light having energy exceeding the forbidden band width is irradiated to the pn junction portion 95, free electrons and free holes generated in the pn junction portion 95 are transferred to the n-type semiconductor layer 93 side by the internal electric field E1. The remaining free holes move to the p-type semiconductor layer 91 side. In a photo device such as a solar cell, this current is extracted to the outside through electrodes attached to the n-type semiconductor layer 93 and the p-type semiconductor. For example, in the case of a solar cell, the movement of free electrons and free holes generated at the pn junction 95 is used as a direct current.

  When a change occurs in the current, an electromagnetic wave having an intensity proportional to the time derivative of the current is generated according to Maxwell's equation. That is, when the photoexcited carrier generation region such as the depletion layer 97 is irradiated with the pulsed light LP11, the photocurrent is instantaneously generated and extinguished. An electromagnetic wave pulse LT1 is generated in proportion to the temporal differentiation of the instantaneously generated photocurrent.

  In the present embodiment, the electromagnetic wave pulse detected by the detection unit 13 is an electromagnetic wave pulse in the terahertz region mainly having a frequency of 0.01 THz to 10 THz (hereinafter also referred to as an electromagnetic wave pulse LT1).

  When the photo device 9 is a solar cell, the surface 9S is desirably a light receiving surface. This is because the light receiving surface of the solar cell is normally configured so as to easily absorb light, and thus the electromagnetic wave can be generated satisfactorily by irradiating the light receiving surface with the pulsed light LP11.

  Returning to FIG. 2, the other pulse light split by the beam splitter B1 enters the detector 132 as the probe light LP12 via the delay unit 131 and the mirror. Further, the electromagnetic wave pulse LT1 generated in response to the irradiation of the pulsed light LP11 is collected by the parabolic mirrors M1 and M2 and enters the detector 132.

  The detector 132 includes, for example, a photoconductive switch as an electromagnetic wave detection element. The photoconductive switch is classified into a dipole type, a bow tie type, a spiral type, and the like according to the antenna shape of the microstrip line manufactured on the substrate. In particular, the use of a spiral photoconductive switch capable of detecting circularly polarized electromagnetic waves as the detector 132 makes it possible to detect electromagnetic waves satisfactorily.

  When the probe light LP12 is irradiated to the detector 132 in a state where the electromagnetic wave pulse LT1 is incident on the detector 132, a current corresponding to the electric field strength of the electromagnetic wave pulse LT1 is instantaneously generated in the photoconductive switch. The current corresponding to the electric field strength is converted into a digital quantity via an I / V conversion circuit, an A / D conversion circuit, or the like. In this way, the detection unit 13 detects the electric field strength of the electromagnetic wave pulse LT1 that has passed through the photo device 9 in response to the irradiation with the probe light LP12. It is also conceivable to apply other elements such as a nonlinear optical crystal to the detector 132.

  The delay unit 131 is an optical element for continuously changing the arrival time of the probe light LP12 from the beam splitter B1 to the detector 132. The delay unit 131 is fixed to a moving stage (not shown) that moves in the incident direction of the probe light LP12. The delay unit 131 includes a folding mirror 10M that folds the probe light LP12 in the incident direction.

  The delay unit 131 precisely changes the optical path length of the probe light LP12 by driving the moving stage and moving the folding mirror 10M based on the control of the control unit 16. Thereby, the delay unit 131 changes the time difference between the time for the electromagnetic wave pulse LT1 to reach the detection unit 13 and the time for the probe light LP12 to reach the detection unit 13. Therefore, by changing the optical path length of the probe light LP12 by the delay unit 131, the timing (detection timing or sampling timing) at which the detection unit 13 (detector 132) detects the electric field intensity of the electromagnetic wave pulse LT1 can be delayed. it can.

  It is also conceivable to change the arrival time of the probe light LP12 to the detection unit 13 in another manner. Specifically, an electro-optic effect may be used. That is, an electro-optic element whose refractive index changes by changing the applied voltage may be used as the delay element. Specifically, an electro-optical element disclosed in Patent Document 3 (Japanese Patent Laid-Open No. 2009-175127) can be used.

  Further, the optical path length of the pulsed light LP11 (pump light) or the optical path length of the electromagnetic wave pulse LT1 emitted from the photo device 9 may be changed. Also in this case, the time for the electromagnetic wave pulse LT1 to reach the detector 132 can be shifted relative to the time for the probe light LP12 to reach the detector 132. Thereby, the detection timing of the electric field intensity of the electromagnetic wave pulse LT1 in the detector 132 can be delayed.

  Further, a reverse bias voltage application circuit 99 for applying a reverse bias voltage at the time of inspection is connected to the photo device 9. For example, in the case of a photo device 9 solar cell, a reverse bias voltage application circuit 99 is connected to electrodes formed on the light receiving surface and the opposite surface of the solar cell, and a reverse bias voltage is applied. By applying the reverse bias voltage, the depletion layer of the pn junction 95 can be enlarged. Thereby, since the electric field strength of the electromagnetic wave pulse LT1 detected by the detector 132 can be increased, the detection sensitivity of the electromagnetic wave pulse LT1 in the detection unit 13 can be improved. However, the reverse bias voltage application circuit 99 can be omitted.

  Returning to FIG. 1, the visible camera 14 is constituted by a CCD camera, for example, and includes an LED and a laser as a light source for photographing. The visible camera 14 is used for photographing the entire photo device 9 or photographing a position irradiated with the pulsed light LP11. Image data acquired by the visible camera 14 is transmitted to the control unit 16 and displayed on the monitor 17 or the like.

  The motor 15 drives an XY table (not shown) that moves the stage 11 in a two-dimensional plane. The motor 15 moves the photo device 9 held on the stage 11 relative to the irradiation unit 12 by driving the XY table. The inspection apparatus 100 can move the photo device 9 to an arbitrary position within the two-dimensional plane by the motor 15. The inspection apparatus 100 can inspect a wide range (inspection target region) of the photo device 9 by irradiating the pulsed light LP11 with the motor 15.

  Instead of moving the photo device 9, or while moving the photo device 9, a moving means for moving the irradiation unit 12 and the detection unit 13 in a two-dimensional plane may be provided. Also in these cases, the electromagnetic wave pulse LT1 can be detected for each region of the photo device 9. Further, the motor 15 may be omitted, and the stage 11 may be manually moved by an operator.

  The control unit 16 has a configuration as a general computer including a CPU, a ROM, a RAM, an auxiliary storage unit (for example, a hard disk), etc. (not shown). The control unit 16 is connected to the femtosecond laser 121 of the irradiation unit 12, the delay unit 131 and the detector 132 of the detection unit 13, and the motor 15, and controls the operation of these elements by sending control signals. Receive various data from these elements.

  More specifically, the control unit 16 receives data related to the electric field strength of the electromagnetic wave pulse LT1 from the detector 132. Further, the control unit 16 controls the movement of a moving stage (not shown) that moves the delay unit 131, or the delay unit 131 such as the moving distance of the folding mirror 10M from a linear scale or the like provided on the moving stage. The data related to the position of is received from the delay unit 131.

  In addition, the control unit 16 includes a time waveform restoration unit 21, an electromagnetic wave pulse analysis unit 23, and an image generation unit 25, and causes these processing units to execute various arithmetic processes. These processing units are functions realized by the CPU operating according to the program. Note that some or all of the functions of these processing units may be realized by a CPU included in another computer, or may be realized by hardware using a dedicated arithmetic circuit.

  The time waveform restoration unit 21 constructs a time waveform of the electromagnetic wave pulse LT1 based on the electric field strength detected by the detection unit 13 (detector 132) for the electromagnetic wave pulse LT1 generated in the photo device 9. Specifically, by changing the optical path length of the probe light LP12 (the optical path length of the first optical path) by moving the folding mirror 10M of the delay unit 131, the time for the probe light to reach the detector 132 is changed. To do. Thereby, the timing at which the electric field intensity of the electromagnetic wave pulse LT1 is detected by the detector 132 is changed. As a result, the time waveform restoration unit 21 restores the time waveform of the electromagnetic wave pulse LT1 by detecting the electric field strength of the electromagnetic wave pulse LT1 at different phases and plotting it on the time axis.

  The electromagnetic wave pulse analysis unit 23 analyzes the time waveform restored by the time waveform restoration unit 21. The electromagnetic wave pulse analyzing unit 23 detects the intensity change of the emitted electromagnetic wave pulse LT1 by detecting the peak of the electric field intensity in the time waveform of the electromagnetic wave pulse LT1 restored by the time waveform restoring unit 21, and the photo device 9 characteristics are analyzed. Further, the electromagnetic wave pulse analysis unit 23 may perform frequency analysis of the electromagnetic wave pulse LT1 by performing Fourier transform.

  The image generation unit 25 visualizes an electric field intensity distribution of the electromagnetic wave pulse LT1 emitted when the pulsed light LP11 is irradiated with respect to the inspection target region (a part or the whole of the photo device 9) of the photo device 9. Generate. Specifically, the image generation unit 25 generates an electric field intensity distribution image in which a difference in electric field intensity is expressed by a color or a pattern for each measurement position.

  A monitor 17 and an operation input unit 18 are connected to the control unit 16. The monitor 17 is a display device such as a liquid crystal display, and displays various image information to the operator. The monitor 17 includes an image of the surface 9S of the photo device 9 photographed by the visible camera 14, a time waveform of the electromagnetic wave pulse LT1 restored by the time waveform restoration unit 21, an analysis result by the electromagnetic wave pulse analysis unit 23, or an image generation unit. The electric field intensity distribution image generated by 25 is displayed. The monitor 17 displays a GUI (Graphical User Interface) screen necessary for setting inspection conditions.

  The operation input unit 18 includes various input devices such as a mouse and a keyboard. The operator can perform a predetermined operation input via the operation input unit 18. Note that the monitor 17 may function as the operation input unit 18 by configuring the monitor 17 as a touch panel.

  The inspection apparatus 100 includes a magnetic field application unit 3. The magnetic field application unit 3 includes a pair of magnetic pole portions 31 disposed to face each other with the photo device 9 interposed therebetween. The pair of magnetic pole portions 31 is composed of an electromagnet or a permanent magnet (neodymium magnet or the like), and forms a magnetic field between the opposing magnetic pole portions 31. In the present embodiment, the pair of magnetic pole portions 31 face each other in the direction parallel to the surface 9S, and the direction of the generated magnetic field is parallel to the surface 9S of the photo device 9. However, the direction of the magnetic field is not limited to the direction parallel to the surface 9S, and may be arbitrarily changed according to the purpose.

  The magnetic field application unit 3 includes a magnetic pole part rotation mechanism 33 that rotates the pair of magnetic pole parts 31. The magnetic pole part rotation mechanism 33 rotates the pair of magnetic pole parts 31 by 360 degrees along the outer periphery of the photo device 9 in an opposed state while sandwiching the photo device 9 by a rotational driving force such as a motor (not shown). Thereby, the direction of the magnetic field formed between the pair of magnetic pole portions 31 can be rotated. Therefore, the magnetic field application unit 3 can generate an electric field in an arbitrary direction parallel to the surface 9S of the photo device 9.

  When the photo device 9 is installed in the magnetic field generated by the magnetic field applying unit 3, Lorentz force acts on free electrons generated in response to the irradiation of the pulsed light LP11. By the Lorentz force acting, electrons can be accelerated in the acting direction. This point will be described with reference to FIGS. 4 and 5. FIG.

  FIG. 4 is a diagram for explaining a trend of free electrons 41 in a state where no magnetic field is applied. FIG. 5 is a diagram for explaining a trend of the free electrons 41 in a state where a magnetic field is applied.

  First, as shown in FIG. 4, when there is no magnetic field by the magnetic field application unit 3, the free electron 41 is subjected to a force F <b> 11 toward the n-type semiconductor layer 93 side by the internal electric field E <b> 1 of the depletion layer 97. In the example shown in FIG. 4, since the direction of the internal electric field E1 is the −Z direction, the direction of the force F11 is the + Z direction and is accelerated toward the + Z side.

  On the other hand, as shown in FIG. 5, when the magnetic field H <b> 1 is applied by the magnetic field application unit 3, the Lorentz force F <b> 13 acts on the free electrons 41. In the example shown in FIG. 5, the direction of the magnetic field H1 is the + X direction. Since the free electrons 41 move in the + Z direction by the internal electric field E1, the Lorentz force F13 in the -Y direction acts on the free electrons 41. Then, a combined force F15 obtained by combining the force F11 in the + Z direction and the Lorentz force F13 in the -Y direction acts on the free electrons 41.

  Since the resultant force F15 is greater than the force F11, the free electrons 41 can be accelerated more greatly. For this reason, the electric field strength (amplitude) of the emitted electromagnetic wave can be increased by applying the magnetic field H1. Thereby, S / N of the electromagnetic wave detection in the detector 132 can be improved.

  The magnitude of the Lorentz force F13 acting on the free electrons 41 is determined depending on the component in the direction orthogonal to the internal electric field E1 among the components in each direction of the magnetic field H1. Therefore, the largest Lorentz force F13 can be applied by setting the direction of the magnetic field H1 to a direction orthogonal to the direction of the internal electric field E1. Therefore, it is conceivable that the direction of the internal electric field existing at each position of the photo device 9 is specified from the structure of the photo device 9 and a magnetic field is applied so as to be orthogonal to the direction of the internal electric field. The direction of the internal electric field can be specified, for example, from the junction direction of the p-type semiconductor and the n-type semiconductor at the pn junction, the contact direction of the metal and the semiconductor in the Schottky barrier diode, and the like.

  Returning to FIG. 1, the inspection apparatus 100 includes a polarizing element 20 that polarizes the electromagnetic wave pulse LT1 generated from the photo device 9 in response to the irradiation of the pulsed light LP11. The polarizing element 20 is disposed on the optical path between the photo device 9 and the detector 132. That is, the detector 132 detects the electromagnetic wave pulse LT1 changed by the polarizing element 20.

  As described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-24774), the direction of the electric field vector (polarization direction) of the electromagnetic wave radiated from the semiconductor device is parallel to the direction of the current. Therefore, for example, it is possible to narrow down to the electromagnetic wave pulse LT1 that is changed to the direction (−Y direction) of the Lorentz force F13 shown in FIG. This merit will be described with reference to FIGS.

  6 and 7 are schematic plan views showing a part of the surface 9S of the photo device 9. FIG. In FIG. 6, the direction of the magnetic field H1 is the -X direction, whereas in FIG. 7, the magnetic field H1 is the + X direction. 6 and 7 show two crystal grains 51. FIG. As shown in FIGS. 6 and 7, it is assumed that the points A to D where the pulsed light LP11 is irradiated are set. The points A and D are outside the crystal grain 51, and the points B and C are inside the crystal grain 51. The point D is on the + Y side of the point C, and a defect 53 that prevents the movement of the free electrons 41 exists between the point C and the point D.

  Here, it is assumed that the inside of the crystal grain 51 is a region where the movement of the free electrons 41 generated by the irradiation of the pulsed light LP11 is slow or hindered due to, for example, recombination easily occurring. However, depending on the type of the crystal grain 51 and the like, the movement of the free electrons 41 may be faster in the inside than in the outside of the crystal grain 51.

  As shown in FIG. 6, when the magnetic field H <b> 1 in the −X direction is applied, the direction of the internal electric field E <b> 1 is the −Z direction, so that the free electrons 41 generated at the points A to D are in the + Y direction. Lorentz force F13 (FIG. 5) acts. For this reason, the electromagnetic wave pulse LT1 polarized in the + Y direction is generated. By using the polarizing element 20, it is possible to detect only the electromagnetic wave pulse LT1 polarized in the + Y direction.

  As shown in FIG. 6, the points A and D are regions where the free electrons 41 move relatively quickly. For this reason, radiated electromagnetic wave intensity EA1, ED1 becomes comparatively large. On the other hand, since the point B is inside the crystal grain 51 having relatively poor quality, the movement of the free electrons 41 is relatively slow. For this reason, compared with the points A and D, the electromagnetic wave intensity EB1 is relatively small. Further, at the point C, the defect 53 exists in the direction (+ Y direction) in which the Lorentz force F13 acts. For this reason, the electromagnetic wave intensity EC1 at the point C is lower than the electromagnetic wave intensity EB1.

  On the other hand, as shown in FIG. 7, when the magnetic field H <b> 1 in the + X direction is applied, the direction of the internal electric field E <b> 1 is the −Z direction, and thus the free electrons 41 generated at the points A to D include −Y A directional Lorentz force F13 (FIG. 5) acts. For this reason, the electromagnetic wave pulse LT1 to be changed in the -Y direction is generated. By using the polarizing element 20, it is possible to detect only the electromagnetic wave pulse LT1 polarized in the −Y direction.

  As shown in FIG. 7, the point A is an area outside the crystal grains 51 having relatively poor quality, and is a region where the free electrons 41 move relatively quickly. For this reason, the electromagnetic wave intensity EA2 at the point A is relatively high. On the other hand, since the free electrons 41 generated at the points B and C move inside the crystal grains 51, the electromagnetic wave strengths EB2 and EC2 are low. Further, at the point D, since the defect 53 exists on the −Y side, the electromagnetic wave intensity ED2 is lower than the electromagnetic wave intensity EB2 and EC2.

  In the conventional inspection, only an electromagnetic wave that changes in the direction of the internal electric field E1 can be inspected. However, in the inspection apparatus 100, electrons can be moved in a direction different from the internal electric field E1 by applying the magnetic field H1. For this reason, according to the inspection apparatus 100, the photo device 9 can be inspected in a direction different from the internal electric field E1.

  Further, for example, by changing the direction of the magnetic field H1 as in the point D, the influence of the defect 53 causes the intensity of the electromagnetic wave intensity to be extremely reduced (or increased). Thereby, it becomes easy to specify the location of the defect 53, and inspection accuracy can be improved.

  The above is the description of the configuration of the inspection apparatus 100. Next, an inspection flow of the photo device 9 performed using the inspection apparatus 100 will be described.

<1.2. Operation>
FIG. 8 is a flowchart of inspection of the photo device 9. In the following description, each operation of the inspection apparatus 100 is executed under the control of the control unit 16 unless otherwise specified. Moreover, the flowchart shown in FIG. 8 is an example, and the order of operations may be changed as appropriate.

  When the inspection of the photo device 9 is started, the photo device 9 to be inspected is fixed to the stage 11 (FIG. 8: Step S11). In step S11, the photo device 9 may be carried into the stage 11 by an operator, or the photo device 9 may be carried into the stage 11 by a transport device (not shown). At this time, as described above, the photo device 9 is installed so that the pulsed light LP11 is irradiated toward the surface 9S of the photo device 9.

  When the photo device 9 is fixed, the control unit 16 drives the motor 15 to move the photo device 9 to a predetermined inspection position (FIG. 8: Step S12). This inspection position is a position set in advance via the operation input unit 18 or the like.

  It is determined whether the direction of the magnetic field applied by the magnetic field application unit 3 needs to be adjusted (FIG. 8: Step S13). The direction of the magnetic field is adjusted (FIG. 8: Step S14). Specifically, the pair of magnetic pole portions 31 is rotated by driving the magnetic pole portion rotating mechanism 33. Then, the direction of the magnetic field formed by the pair of magnetic pole portions 31 is continuously converted. Thereby, the direction of the magnetic field applied to the photo device 9 is adjusted.

  The magnetic field application unit 3 applies a magnetic field to the photo device 9 (FIG. 8: Step S15). Then, the irradiation unit 12 irradiates the photo device 9 to which the magnetic field H1 is applied with the pulsed light LP11 (FIG. 8: Step S16). Then, the electromagnetic wave pulse LT1 is detected by the detector 132 (FIG. 8: Step S17).

  In step S17, for example, an inspection method for measuring the electromagnetic wave intensity at each measurement point by fixing the detection timing, and an inspection method for restoring the electromagnetic wave pulse by changing the detection timing by driving the delay unit 131. And is feasible.

  Further, in step S17, only the electric field intensity of the electromagnetic wave pulse LT1 polarized in a specific direction may be detected by the detector 132 using the polarizing element 20. For example, as described with reference to FIG. 6 or FIG. 7, it is possible to detect only the electric field strength of the electromagnetic wave pulse LT1 polarized in the direction in which the Lorentz force F13 acts by using the polarizing element 20.

  Next, it is determined whether or not all measurements have been completed (FIG. 8: Step S18). For example, when there is an unmeasured place or when measurement is required by changing the direction of the magnetic field H1, “NO” is determined in the step S18, and the process returns to the step S12. For example, when the measurement location needs to be changed, the photo device 9 is moved in step S12. In addition, when it is necessary to change the direction of the magnetic field H1, the direction of the magnetic field H1 to be applied is appropriately changed in step S13 and step S14. On the other hand, if all measurements are completed, “YES” is determined in step S18, and the inspection apparatus 100 ends the inspection process of the photo device 9.

  FIG. 9 is a schematic diagram of an imaging image i11 representing the electromagnetic wave intensity distribution. The imaging image i11 is an image expressing the electromagnetic wave intensity measured with the detection timing fixed at each measurement point in step S17 so as to be identifiable according to the intensity. The example shown in FIG. 9 shows the result of inspecting the solar cell that is the photo device 9. As an image representing the solar cell, an image taken by the visible camera 14 may be employed, or an illustration image imitating the solar cell may be used. In the schematic diagram shown in FIG. 9, for convenience of explanation, the electric field strength is colored in three stages, but may be distinguished in more stages.

  As shown in FIG. 9, in the case of a solar cell, generally, the closer the measurement position is to the electrode (light receiving surface electrode 96), the higher the degree of absorption of photoexcited carriers. For this reason, also in the imaging image i11, the electric field strength is increased near the electrodes.

  By generating such an imaging image i11, the magnitude of the electromagnetic wave intensity can be grasped at once over a wide range of the photo device 9. For example, by measuring the magnitude (amplitude) of electromagnetic wave intensity at a specific position, various defects such as a depletion layer defect and an electrode contact defect can be detected.

  FIG. 10 is a diagram illustrating a restoration example of the time waveform of the electromagnetic wave pulse LT1. In FIG. 10, the horizontal axis indicates time, and the vertical axis indicates electric field strength. A plurality of probe lights LP12 having different timings (t1 to t8) reaching the detector 132 are conceptually shown below the graph.

  The time waveform 40 shown in FIG. 10 is acquired by driving the delay unit 131 in step S17 shown in FIG. More specifically, the electric field intensity of the electromagnetic wave pulse LT1 is measured at a plurality of timings (t1 to t8) by driving the delay unit 131 to delay and change the timing of the electromagnetic wave pulse LT1.

  For example, when the delay unit 131 is driven so that the probe light LP12 reaches the detector 132 at the detection timing t1, the detector 132 detects the electromagnetic wave intensity ET1. In addition, when the detection timing is delayed by t2 to t8 by adjusting the delay unit 131, the electromagnetic wave intensities ET2 to ET8 are detected by the detector 132, respectively.

  Thus, when restoring the time waveform of the electromagnetic wave pulse LT1 radiated from the photo device 9, the detection timing is changed by controlling the delay unit 131, and the electric field intensity of the electromagnetic wave pulse LT1 at each detection timing is changed. Measured. Then, the time waveform restoration unit 21 plots the acquired electromagnetic wave intensity on the graph along the time axis, whereby the time waveform 40 of the electromagnetic wave pulse LT1 is restored.

  By analyzing the time waveform 40, for example, the amplitude of the electromagnetic wave pulse LT1 can be acquired. The electromagnetic wave pulse analysis unit 23 can perform frequency analysis by executing Fourier transform on the time waveform 40. By performing the frequency analysis, the characteristics of the photo device 9 can be analyzed more finely.

  Note that a reverse bias voltage application circuit 99 may be connected to the electrode formed in the photo device 9 to apply a reverse bias voltage. When the photo device 9 is a solar cell, it is connected to the front surface electrode (light receiving surface electrode 96) and the back surface electrode. By applying the reverse bias voltage, the internal electric field E1 can be increased, so that the intensity of the electromagnetic wave pulse LT1 can be increased.

<2. Second Embodiment>
In the inspection apparatus 100 shown in FIG. 1, the optical axis of the pulsed light LP11 is set to enter obliquely (incident angle 45 degrees) with respect to the surface 9S of the planar photo device 9. However, the incident angle of the pulsed light LP11 is not limited to this.

  FIG. 11 is a schematic configuration diagram of the irradiation unit 12A and the detection unit 13A of the inspection apparatus 100A according to the second embodiment. In the following description, elements having the same functions as those of the constituent elements of the inspection apparatus 100 according to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  Also in the inspection apparatus 100A, the pulsed light LP1 emitted from the femtosecond laser 121 is split into the pulsed light LP11 and the probe light LP12 by the beam splitter B1. However, in the inspection apparatus 100A, the divided pulsed light LP11 passes through the transparent conductive film substrate (ITO) 19 and enters the pulsed light LP11 perpendicular to the surface 9S of the photo device 9. Then, of the electromagnetic wave pulse LT1 emitted from the photo device 9 in response to the irradiation with the pulsed light LP11, the electromagnetic wave pulse LT1 emitted to the surface 9S side reflects the transparent conductive substrate 19 and is condensed by the lens. And enters the detector 132.

  Also in the inspection apparatus 100A including the irradiation unit 12A and the detection unit 13A, it is possible to detect the electromagnetic wave pulse LT1 emitted from the photo device 9 in accordance with the irradiation of the pulsed light LP11.

<3. Third Embodiment>
100 A of inspection apparatuses which concern on 2nd Embodiment are comprised so that the electromagnetic wave pulse LT1 radiated | emitted to the surface 9S side may be detected with the detector 132. FIG. However, the electromagnetic wave pulse LT1 may be detected from the back side of the photo device 9.

  FIG. 12 is a schematic configuration diagram of the irradiation unit 12B and the detection unit 13B of the inspection apparatus 100B according to the third embodiment. Also in the inspection apparatus 100B, the pulsed light LP1 emitted from the femtosecond laser 121 is split into the pulsed light LP11 and the probe light LP12 by the beam splitter B1. Then, the pulsed light LP11 is incident on the surface 9S of the photo device 9 perpendicularly. Of the electromagnetic wave pulse LT1 emitted from the photo device 9 in response to the irradiation of the pulsed light LP11, the electromagnetic wave pulse LT1 emitted (transmitted) to the back side of the photo device 9 is a parabolic mirror M1, M2, etc. Then, the light enters the detector 132.

  In the inspection apparatus 100B including such an irradiation unit 12B and the detection unit 13B, similarly to the inspection apparatus 100, the electromagnetic wave pulse LT1 radiated from the photo device 9 in response to the irradiation with the pulsed light LP11 can be detected.

  Although the present invention has been described in detail, the above description is illustrative in all aspects, and the present invention is not limited thereto. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

100, 100A, 100B Inspection device 11 Stage 12, 12A, 12B Irradiation unit 121 Femtosecond laser 13, 13A, 13B Detection unit 131 Delay unit 132 Detector 14 Visible camera 15 Motor 16 Control unit 17 Monitor 18 Operation input unit 19 Transparent conductive Substrate 20 polarizing element 21 time waveform restoration unit 23 electromagnetic wave pulse analysis unit 25 image generation unit 3 magnetic field application unit 31 magnetic pole unit 33 magnetic pole unit rotation mechanism 40 time waveform 41 free electron 51 crystal grain 53 defect 9 photo device 91 p-type semiconductor layer 93 n-type semiconductor layer 95 pn junction 97 depletion layer E1 internal electric field F13 Lorentz force F15 synthetic force H1 magnetic field LP11 pulsed light LP12 probe light LT1 electromagnetic wave pulse

Claims (5)

An inspection apparatus for inspecting a semiconductor device or a photo device,
An irradiation unit for irradiating a semiconductor device or a photo device with pulsed light; and
A detector for detecting electromagnetic waves radiated from the semiconductor device or photo device in response to the irradiation of the pulsed light;
A magnetic field applying unit configured to apply a magnetic field to the semiconductor device or the photo device by a pair of magnetic pole portions disposed opposite to each other with the semiconductor device or the photo device interposed therebetween;
Equipped with a,
The magnetic field applying unit, apply a magnetic field of a direction to intersect the direction of the electric field existing inside the semiconductor device or a photo device, testing device. The inspection apparatus according to claim 1 ,
A magnetic pole part moving mechanism that changes the direction of the magnetic field by moving the pair of magnetic pole parts relative to the semiconductor device or the photo device;
An inspection apparatus further comprising: The inspection apparatus according to claim 2 ,
The magnetic pole part moving mechanism includes a magnetic pole part rotation mechanism that rotates the pair of magnetic pole parts relative to the semiconductor device or the photo device. In the inspection device according to any one of claims 1 to 3 ,
A polarizing element that polarizes electromagnetic waves generated in response to the irradiation of the pulsed light,
An inspection apparatus further comprising: An inspection method for inspecting a semiconductor device or a photo device,
(a) applying a magnetic field to the semiconductor device or photo device by a pair of electrode portions disposed opposite to each other with the semiconductor device or photo device interposed therebetween;
(b) irradiating the semiconductor device or photodevice to which the magnetic field is applied in the step (a) with pulsed light;
(c) detecting an electromagnetic wave radiated from the semiconductor device or photo device according to the pulsed light irradiated in the step (b);
Only contains
The step (a) is an inspection method, which is a step of applying a magnetic field in a direction crossing a direction of an electric field existing inside the semiconductor device or photo device .

Images