JP2015064271A - Optical axis adjustment method and inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of detecting misalignment of an optical axis position of a laser beam while suppressing degradation in inspection efficiency.SOLUTION: An inspection device 100 adjusts an optical axis position of pump light LP 13 linearly polarized in a second direction orthogonal to a first direction with respect to measurement probe light LP 11 linearly polarized in the first direction and radiated to a solar cell 9. More specifically, a beam splitter BP 1 splits part of the measurement probe light LP 11 and the measurement pump light LP 13, and a polarizer 126 causes either the split measurement probe light LP 11 or the split measurement pump light LP 13 to be incident on an image sensor 127. The inspection device 100 adjusts the optical axis position of the measurement pump light LP 13 on the basis of comparison between an incident position of the measurement probe light LP 11 and that of the measurement pump light LP 13 detected by the image sensor 127.

Description

  The present invention relates to a technique for detecting or adjusting an optical axis position shift of a laser beam.

  A semiconductor inspection apparatus that inspects a semiconductor device in a non-contact manner by detecting an electromagnetic wave radiated from the semiconductor device when irradiated with pulsed laser light is known (Patent Document 1).

  The applicant of the present application has proposed a technique for inspecting a photo device by irradiating the photo device with pulsed light and detecting an electromagnetic wave radiated from the photo device accordingly (Patent Document 2).

  Furthermore, a technique has been proposed in which the pump-probe measurement method is used to scan the irradiation area of the pump light with the probe light to visualize the photoexcited carriers (Non-Patent Document 1). In Non-Patent Document 1, using a photoconductive switch of low-temperature grown gallium arsenide, which is a typical terahertz wave generating element, as a sample, the dynamics of photoexcited carriers can be observed with sub-picosecond time resolution and several micrometer spatial resolution. Have been described.

JP 2010-60317 A JP2013-19861A JP 2009-175127 A

Masagou Fujiwara, et al., Research on carrier dynamics of low-temperature grown gallium arsenide (LT-GaAs) photoconductive switch by pump-probe laser terahertz emission microscope (millimeter wave and terahertz wave device system), IEICE technical report. , Electronic device 110 (342), 87-90, 2010-12-09

  By the way, in order to correctly evaluate physical properties in a measuring apparatus, it is required to maintain a measuring system with high accuracy. Specifically, in the pump / probe measurement method, two laser beams (pump light and probe light) with different spot diameters are irradiated onto the inspection object, but the positional relationship between the optical axes is slightly shifted. Since the relative irradiation position of the laser beam changes, there is a possibility that a large error occurs in the measurement data. For this reason, the optical axis adjustment of these two laser beams may be appropriately performed.

  Conventional optical axis adjustment has been performed by a method of visually confirming a spot position of a laser beam irradiated on an inspection object. In this optical axis adjustment method, in order to accurately specify the position of each optical axis on the inspection object during measurement, it is necessary to shield one of them. For this reason, it may be necessary to temporarily interrupt the inspection by the two laser light irradiations, and there is a possibility that the inspection efficiency is lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique for detecting an optical axis position shift of laser light while suppressing a decrease in inspection efficiency.

  In order to solve the above-mentioned problem, the first mode is linearly polarized in the first direction, and linearly polarized in the second direction orthogonal to the first direction with respect to the first laser light irradiated on the inspection object. An optical axis adjustment method for adjusting the optical axis position of the second laser light irradiated to the inspection object, wherein (a) a part of the first laser light directed to the inspection object is divided and imaged And (b) dividing a part of the second laser beam directed toward the inspection object and causing it to enter the imaging unit, and (c) the step detected in the step (a) Based on the comparison between the incident position of the first laser light and the incident position of the second laser light detected by the imaging unit in the step (b), the light of the second laser light toward the inspection object Adjusting the position of the shaft.

  Further, the second aspect is an optical axis adjustment method according to the first aspect, wherein the step (a) is such that a part of the divided first laser light is adapted to the first direction. The step (b) is performed so that a part of the divided second laser light is adapted to the second direction. In addition, the light is incident on the imaging unit via the polarizer.

  According to a third aspect, in the optical axis adjustment method according to the first or second aspect, the step (b) includes (b-1) incidence of the second laser light acquired by the imaging unit. Displaying an image indicating the position.

  A fourth aspect is an optical axis adjustment method according to any one of the first to third aspects, and (e) the incident position of the first laser light detected in the step (a). And adjusting the optical axis of the first laser beam toward the inspection object.

  A fifth aspect is an optical axis adjustment method according to any one of the first to fourth aspects, wherein the first laser light is probe light, and the second laser light is the probe. This is pump light having a spot diameter larger than that of light.

  Moreover, a 6th aspect is linearly polarized in the 2nd direction orthogonal to the 1st laser beam irradiated to a test | inspection object and linearly polarized in a 1st direction, and is in the said test | inspection object. In an inspection apparatus that inspects an inspection object by irradiating the inspection object with the irradiated second laser light, a dividing unit that divides a part of the first laser light and a part of the second laser light; An imaging unit on which the first laser beam divided by the dividing unit and the second laser beam divided by the dividing unit are incident;

  Moreover, a 7th aspect is further provided with the display part which displays the image acquired by the said imaging part in the inspection apparatus which concerns on a 6th aspect.

  According to the optical axis adjustment method according to the first aspect, a part of the laser light extracted from the first laser light and the second laser light is incident on the imaging unit, whereby the position of each optical axis is specified. The For this reason, the shift | offset | difference of an optical axis is detectable during the test | inspection with respect to a test object.

  Further, according to the optical axis adjustment method according to the second aspect, even if the first laser beam and the second laser beam overlap, imaging is performed by switching between the first laser beam and the second laser beam by using a polarizer. Can be incident on the part.

  According to the optical axis adjustment method according to the third aspect, the operator can visually grasp the shift of the incident position of the second laser light with respect to the imaging unit based on the image data.

  In addition, according to the optical axis adjustment method according to the fourth aspect, the optical axis of the first laser beam can be returned to the origin. Thus, the first laser beam and the second laser beam can be accurately irradiated onto the target position of the inspection object.

  Further, according to the optical axis adjusting method according to the fifth aspect, in the pump / probe measurement, the optical axis position of the pump light can be adjusted with respect to the optical axis position of the probe light. For this reason, optical axis adjustment can be performed during pump-probe measurement.

  According to the inspection apparatus according to the sixth aspect, it is possible to detect the shift of the optical axis of the second laser light with respect to the first laser light by the imaging unit. Therefore, the necessity of optical axis position adjustment can be easily determined.

  Moreover, according to the inspection apparatus which concerns on a 7th aspect, the operator can grasp | ascertain visually the shift | offset | difference of the incident position with respect to the imaging part of a 2nd laser beam based on image data.

It is a schematic structure figure of an inspection device concerning an embodiment. It is a block diagram which shows the connection relation of a control part and another element. It is a flowchart figure of an optical axis adjustment. It is a figure which shows an example of the flow of optical axis adjustment in a pump probe measurement. It is a figure which shows the fluctuation | variation of the time waveform of electromagnetic waves when the relative optical axis position of the probe light for measurement and the pump light for measurement shifts.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the size and number of each part may be exaggerated or simplified as needed for easy understanding.

<1. Embodiment>
<1.1 Configuration and function>
FIG. 1 is a schematic configuration diagram of an inspection apparatus 100 according to the embodiment. The inspection apparatus 100 irradiates a test object, which is a semiconductor device or a photo device, with pulsed light, and radiates electromagnetic waves (for example, a frequency of 0.1 THz to 10 THz) emitted from the test object in response to the irradiation of the pulsed light. The terahertz wave is detected to inspect the inspection object.

  In the present application, a semiconductor device refers to an electronic device that includes a semiconductor, a transistor, an integrated circuit (IC or LSI), a resistor, a capacitor, or the like. A photo device refers to an electronic device that uses the photoelectric effect of a semiconductor, such as a photodiode, an image sensor such as a CMOS sensor or a CCD sensor, a solar cell, or an LED. Hereinafter, the case where the inspection object is a flat solar cell 9 which is a kind of photo device will be described in detail. The surface 9S of the solar cell 9 has a planar shape, but may have another shape (for example, a curved shape).

  As shown in FIG. 1, the inspection apparatus 100 includes a stage 11, an irradiation unit 12, a detection unit 13, a measurement delay unit 14 </ b> A, a detection delay unit 14 </ b> B, a stage moving mechanism 15, and a control unit 16.

  The stage 11 holds the solar cell 9 fixed on the stage 11 by fixing means (not shown). Examples of the fixing means include those using a sandwiching tool for sandwiching the solar cell 9, an adhesive sheet, or an adsorption hole formed on the surface of the stage 11. However, other fixing means may be employed as long as the solar cell 9 can be held.

  The irradiation unit 12 includes a femtosecond laser 121 as a light source that emits pulsed light. For example, the femtosecond laser 121 emits pulsed light (pulsed light LP1) having a wavelength including a visible light region of 300 nm (nanometers) or more and 1.5 μm (micrometers) or less. As a preferred 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 of 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 half mirror HM1. One of the divided pulse lights (measurement pulse light LP10) is guided to the solar cell 9. The light intensity of the measurement pulse light LP10 is, for example, about several hundred mW. The other pulse light (detection pulse light LP21) is guided to the detector 131 of the detection unit 13 that detects electromagnetic waves. The light intensity of the detection pulse light LP21 is, for example, about 5 mW.

  The measurement pulse light LP10 is divided into measurement probe light LP11 and measurement pump light LP13 by a half mirror HM2 disposed on the optical path. In the following description, the measurement probe light LP11 and the measurement pump light LP13 may be collectively referred to as “measurement laser light”.

  The measurement probe light LP11 is modulated by several kHz (for example, 2 kHz or 4 kHz) by the optical chopper 123. An AOM (Acousto-Optic Modulator) or the like may be used as the modulation element. The measurement probe light LP11 reflects the mirror group M10 and reaches the half-wave plate 124. Then, the light is linearly polarized in the first direction by passing through the half-wave plate 124.

  A measurement delay unit 14A is provided on the optical path of the measurement pump light LP13 from the half mirror HM2 to the solar cell 9. The measurement delay unit 14A continuously changes the time for the measurement pump light LP13 to reach the solar cell 9. The measurement delay unit 14A includes a measurement delay stage 141A and a measurement delay stage moving mechanism 143A.

  The measurement delay stage 141A is configured by a retro reflector including a folding mirror M8 that folds the measurement pump light LP13 in the incident direction. The measurement delay stage moving mechanism 143A translates the measurement delay stage 141A along the incident direction of the measurement pump light LP13 based on the control of the control unit 16. As the measurement delay stage 141A moves in parallel, the optical path length of the measurement pump light LP13 is continuously changed.

  When the portion of the solar cell 9 where the internal electric field exists is irradiated with the measurement probe light LP11 having energy exceeding the forbidden band width, photoexcited carriers (free electrons and free holes) are generated and accelerated by the internal electric field. The As a result, a pulsed current is generated, and the electromagnetic wave LT1 is generated accordingly. It is known that the internal electric field is generated at, for example, a pn junction or a Schottky junction.

  The electromagnetic wave LT1 is generated depending on the state (strength, direction, etc.) of the internal electric field. That is, the electromagnetic wave LT1 is generated depending on the pn junction or the wiring state connected to the pn junction. For this reason, by detecting the electromagnetic wave LT1, it is possible to examine the characteristics of the solar cell 9 and to perform inspections such as defect determination.

  The measurement delay stage 141A is a device that changes the time difference between the time when the measurement probe light LP11 reaches the solar cell 9 and the time when the measurement pump light LP13 reaches the solar cell 9. A signal (electromagnetic wave LT1) obtained by the measurement probe light LP11 with the difference in time from when the measurement pump light LP13 excites the solar cell 9 to when the measurement probe light LP11 excites the solar cell 9 as a delay time. Are measured as a function of delay time. Thereby, the ultrafast response of the solar cell 9 with respect to optical excitation is measured with high time resolution in the femtosecond region (pump / probe measurement method).

  Note that the arrival time of the measurement pump light LP13 to the solar cell 9 can be changed by a configuration different from that of the measurement delay stage 141A. Specifically, it can be considered to use the electro-optic effect. That is, an electro-optic element whose refractive index changes by changing the applied voltage may be used as the delay element. For example, an electro-optical element disclosed in Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2009-175127) can be used.

  It is also conceivable to change the optical path length of the measurement probe light LP11 instead of changing the optical path length of the measurement pump light LP13. Also in this case, the time for the measurement probe light LP11 to reach the detector 131 can be relatively delayed with respect to the measurement pump light LP13.

  The measurement pump light LP13 reflected from the folding mirror M8 passes through the half-wave plate 125 and is linearly polarized in the second direction. The second direction is a direction orthogonal to the polarization direction (first direction) of the measurement probe light LP11 linearly polarized by the half-wave plate 124. Thus, in this embodiment, the measurement probe light LP11 and the measurement pump light LP13 are linearly polarized in directions orthogonal to each other. For this reason, even if the measurement probe light LP11 and the measurement pump light LP13 are overlapped, interference with each other can be suppressed. Therefore, the electromagnetic wave response in the pump / probe measurement can be accurately measured.

  The measurement probe light LP11 that has passed through the half-wave plate 124 and the measurement pump light LP13 that has passed through the half-wave plate 125 are guided to the half mirror HM3. Further, the measurement probe light LP11 and the measurement pump light LP13 that have passed through the half mirror HM3 are partly divided by the beam splitter BS1. The divided laser light is guided to the image sensor 127 through the polarizer 126. The beam splitter BS1 is constituted by, for example, a half mirror. Further, the remaining laser light that has passed through the beam splitter BS1 as it is, the measurement probe light LP11 and the measurement pump light LP13 are guided to the solar cell 9.

  The polarizer 126 includes a polarizing plate that transmits only light linearly polarized in a specific direction. Although detailed illustration is omitted, the polarizer 126 is configured such that the polarization direction of light to be transmitted can be arbitrarily changed by rotating the polarizing plate. By operating the polarizer 126, the polarization direction transmitted by the polarizing plate is adjusted to either the polarization direction (first direction or second direction) of the measurement probe light LP11 or the measurement pump light LP13. As a result, the measurement laser light that reaches the image sensor 127 can be switched to one of the measurement probe light LP11 and the measurement pump light LP13.

  The image sensor 127 includes a plurality of light receiving elements (CCD or CMOS) arranged in a two-dimensional plane. When the measurement probe light LP11 or the measurement pump light LP13 is incident on the image sensor 127, image data indicating the incident position is acquired. The acquired image data is transmitted to the control unit 16 described later and displayed on the monitor 17 (display unit).

  Since the laser light reaching the image sensor 127 can be made into either the measurement probe light LP11 or the measurement pump light LP13 by the polarizer 126, each incident position can be specified individually. Therefore, each optical axis position can be specified accurately.

  If the polarizer 126 is not used, one of the two laser beams for measurement may be blocked by a shutter or the like. In this case, the shutter may be arranged at a position before the measurement probe light LP11 and the measurement pump light LP13 are coaxially combined. In addition, when a shutter is used, it becomes impossible to irradiate the solar cell 9 which is an inspection object. That is, in order to confirm the deviation of the optical axis position, it is necessary to interrupt the pump / probe measurement.

  However, in the case where an image sensor 127 that individually detects each of the two laser beams for measurement is provided, the shutter position is arranged on the optical path of the laser beam after being divided, so that the pump / probe measurement is performed. Even without interrupting, it is possible to confirm the deviation of the optical axis position.

<Electromagnetic wave detection mechanism>
The electromagnetic wave LT1 radiated from the solar cell 9 is collected by the parabolic mirrors M1 and M2. More specifically, the parabolic mirrors M1 and M2 collect the electromagnetic wave LT1 radiated to the same side as the surface 9S irradiated with the measurement probe light LP11. The condensed electromagnetic wave LT1 is incident on the detector 131 of the detection unit 13.

  The detector 131 includes a photoconductive switch on which the detection pulsed light LP21 is incident. The detection pulse light LP 21 is modulated by several kHz by the optical chopper 145. When the detection pulsed light LP21 is applied to the detector 131 in a state where the electromagnetic wave LT1 is incident on the detector 131, a current corresponding to the electric field strength of the electromagnetic wave LT1 is instantaneously generated in the photoconductive switch. The current corresponding to the electric field strength is appropriately converted into a digital quantity via a lock-in amplifier, an A / D conversion circuit, etc. (not shown). Thus, the detection unit 13 detects the electric field strength of the electromagnetic wave LT1 radiated from the solar cell 9 in response to the irradiation with the detection pulsed light LP21. It is also conceivable to apply other elements such as a nonlinear optical crystal to the detector 131.

  On the optical path of the detection pulsed light LP21 from the half mirror HM1 to the detector 131, a detection delay unit 14B is provided. The detection delay unit 14B changes the time for the detection pulsed light LP21 to reach the detector 131. The detection delay unit 14B includes a detection delay stage 141B and a detection delay stage moving mechanism 143B.

  The detection delay stage 141B is configured by a retroreflector including a return mirror M8 that returns the detection pulse light LP21 in the incident direction. The detection delay stage moving mechanism 143B translates the detection delay stage 141B along the incident direction of the detection pulse light LP21 based on the control of the control unit 16. As the detection delay stage moving mechanism 143B moves in parallel, the optical path length of the detection pulse light LP21 is continuously changed.

  The detection delay stage 141B changes the time difference between the time for the electromagnetic wave LT1 to reach the detector 131 and the time for the detection pulsed light LP21 to reach the detector 131. That is, the timing (detection timing or sampling timing) at which the detector 131 detects the electric field intensity of the electromagnetic wave LT1 is delayed by changing the optical path length of the detection pulse light LP21 by the detection delay stage 141B.

  As with the measurement delay stage 141A, it can be considered that the detection delay stage 141B uses the electro-optic effect. Further, instead of changing the optical path length of the detection pulse light LP21, the optical path length of the measurement probe light LP11 or the optical path length of the electromagnetic wave LT1 emitted from the solar cell 9 may be changed. In any case, the time for the electromagnetic wave LT1 to reach the detector 131 can be relatively delayed with respect to the time for the detection pulsed light LP21 to reach the detector 131. That is, the detection timing of the electric field intensity of the electromagnetic wave LT1 in the detector 131 can be delayed.

  In addition, the inspection apparatus 100 includes a reverse bias voltage application circuit 99 that applies a reverse bias voltage to the solar cell 9 at the time of inspection. A reverse bias voltage application circuit 99 is connected to electrodes (front electrode and back electrode) formed on the light receiving surface and the opposite surface of the solar cell 9, respectively, and a reverse bias voltage is applied. The magnitude of the voltage applied to the solar cell 9 by the reverse bias voltage application circuit 99 may be changeable based on control from the control unit 16.

  By applying the reverse bias voltage, the depletion layer of the pn junction can be enlarged. Thereby, since the electric field strength of the electromagnetic wave LT1 detected by the detector 131 can be increased, the detection sensitivity of the electromagnetic wave LT1 in the detection unit 13 can be improved. However, the reverse bias voltage application circuit 99 can be omitted.

  The stage moving mechanism 15 is a device that moves the stage 11 in a two-dimensional plane, and is configured by, for example, an XY table. The stage moving mechanism 15 moves the solar cell 9 held on the stage 11 relative to the irradiation unit 12. The inspection apparatus 100 can move the solar cell 9 to an arbitrary position within the two-dimensional plane by the stage moving mechanism 15. By moving the solar cell 9 horizontally by the stage moving mechanism 15, it is possible to scan the range (measurement range) to be measured by the pump / probe measurement method with the laser beam for measurement.

  It is also conceivable to configure the inspection apparatus 100 so that the measurement range can be scanned by changing the optical path of the laser beam for measurement with a galvanometer mirror, a polygon mirror or the like while the position of the solar cell 9 is fixed. . Moreover, you may enable it to scan a measurement range combining the change of the optical path of the laser beam for a measurement, and the movement of the solar cell 9. FIG.

  FIG. 2 is a block diagram illustrating a connection relationship between the control unit 16 and other elements. The control unit 16 is configured as a general computer including a CPU, a ROM, a RAM, and the like (not shown). As shown in FIG. 2, the control unit 16 includes a femtosecond laser 121, a detector 131, a measurement delay stage moving mechanism 143A, a detection delay stage moving mechanism 143B, a stage moving mechanism 15, a polarizer 126, and an image sensor 127. And a reverse bias voltage application circuit 99 for controlling the operation of each of these elements or receiving data from each of these elements.

  A monitor 17, an operation input unit 18, and a camera 19 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. On the monitor 17, an image (see FIG. 4 described later) obtained from the detection signal of the measurement probe light LP11 or the measurement pump light LP13 output from the image sensor 127, an image of the surface 9S of the solar cell 9 taken by the camera 19 is displayed. Etc. are displayed.

  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.

  In addition, an image generation unit 21 and a time waveform restoration unit 23 are connected to the control unit 16.

  The image generation unit 21 visualizes the electric field intensity distribution image of the electromagnetic wave LT1 radiated by the measurement laser light irradiation in the inspection range of the solar cell 9 (part or all of the solar cell 9). Is generated. In the electric field intensity distribution image, the difference in the electric field intensity is visually expressed by, for example, different colors or different patterns.

  The time waveform restoration unit 23 restores the time waveform of the electromagnetic wave LT1 radiated from the solar cell 9 based on the electric field strength detected by the detector 131. Specifically, by moving the detection delay stage 141B, the time for the detection pulsed light LP21 to reach the detector 131 is changed, and the electric field intensity of the electromagnetic wave LT1 detected at each phase is acquired. And the time waveform of electromagnetic wave LT1 is decompress | restored by plotting this acquired electric field strength on a time-axis.

  A storage unit 31 that stores various data is connected to the control unit 16. The storage unit 31 may include a portable medium (for example, a magnetic medium, an optical disk medium, a semiconductor memory, or the like), a main storage memory, or the like in addition to a fixed disk such as a hard disk. The control unit 16 and the storage unit 31 may be connected via a network line.

<1.2. Optical axis adjustment>
Next, the flow of optical axis adjustment will be described with reference to FIG. FIG. 3 is a diagram showing an example of the flow of optical axis adjustment in pump / probe measurement. In the following description, the operation of each element of the inspection apparatus 100 is performed under the control of the control unit 16 unless otherwise specified.

  First, a sample (here, solar cell 9) is placed on the stage 11 (step S1). Then, the measurement system is adjusted (step S2). In this step S2, for example, an appropriate position of the solar cell 9 is irradiated with the measurement probe light LP11, and the electromagnetic wave LT1 radiated from the solar cell 9 according to the irradiation can be appropriately detected by the detector 131. The posture and position of each element such as the optical system are adjusted.

  When step S2 is completed, information on the optical axis position of the measurement probe light LP11 is acquired (step S3). Specifically, the polarizer 126 is operated so as to transmit the measurement probe light LP11 linearly polarized in the first direction. As a result, the measurement pump light LP13 is blocked, and only the measurement probe light LP11 reaches the image sensor 127. The detection signal of the measurement probe light LP11 acquired by the image sensor 127 is transmitted to the control unit 16. The control unit 16 generates an image based on the received detection signal and displays the image on the monitor 17 (step S4).

  FIG. 4 is a diagram illustrating an example of an image I1 displayed on the monitor 17. As shown in FIG. 4, the measurement probe light LP11 is detected as a spot SP1. In the present embodiment, the center position of the spot SP1 of the measurement probe light LP11 is stored in the storage unit 31 as the origin position.

  Returning to FIG. 3, when the position information of the measurement probe light LP11 is stored, the polarizer 126 is operated to rotate the polarizing plate by 90 degrees (step S5). As a result, the laser light that passes through the polarizer 126 and reaches the image sensor 127 is switched from the measurement probe light LP11 to the measurement pump light LP13. In this state, the optical axis of the measurement pump light LP13 is adjusted (step S6).

  In step S 6, as described in step S 4, the control unit 16 generates an image based on the detection signal sent from the image sensor 127 and displays the image on the monitor 17. Accordingly, for example, as indicated by a broken line in FIG. 4, the operator can confirm the optical axis position of the measurement pump light LP13 with respect to the measurement probe light LP11 based on the incident position of the measurement pump light LP13. it can.

  The deviation of the incident position of the measurement pump light LP13 means the deviation of the optical axis position of the measurement pump light LP13. For this reason, the optical axis position is adjusted so that the optical axis of the measurement pump light LP13 becomes a required position. Specifically, the measurement pump so that the center position of the spot SP2 of the measurement pump light LP13 shown on the monitor 17 matches, for example, the center position (origin position) of the spot SP1 of the measurement probe light LP11. Adjustment of the optical system on the optical path of the light LP13 (for example, position adjustment of the measurement delay stage 141A) is executed. The adjustment of the optical axis position may be performed manually. Of course, the optical axis position may be automatically adjusted by controlling the drive mechanism (motor) that drives each element of the optical system by the control unit 16.

  When the adjustment of the optical axis position of the measurement pump light LP13 is completed, pump-probe measurement is started (step S7). In the pump / probe measurement, the measurement delay stage 141A is driven, whereby the measurement probe light LP11 is delayed with respect to the measurement pump light LP13, and the fluctuation of the electromagnetic wave response of the solar cell 9 due to this is measured. . Moreover, the electromagnetic wave LT1 radiated | emitted from each site | part may be measured by scanning the solar cell 9 with the laser beam for a measurement.

  During the pump / probe measurement, the displacement of the optical axis position of the measurement pump light LP13 is monitored as needed by the image sensor 127 and adjusted as necessary (steps S8 and S9). Specifically, the measurement sensor pump light LP13 is detected by the image sensor 127 by operating the polarizer 126 during the pump-probe measurement. Then, an image similar to the image I1 (see FIG. 4) showing the spot SP2 is displayed on the monitor 17. Based on this image, it is determined whether or not the adjustment of the optical axis position of the measurement pump light LP13 is necessary (step S8).

  Whether or not the optical axis adjustment is necessary may be determined based on other information, not based on the image of the spot SP2 such as the image I1 (see FIG. 4). As an example, the coordinates (for example, center coordinates) of the spot SP2 may be automatically acquired, and the coordinate information may be presented to the operator via the monitor 17 or the like.

  It is also conceivable to provide a determination means for automatically determining whether or not the optical axis adjustment is necessary. For example, whether or not it is necessary to adjust the optical axis position is automatically determined based on a predetermined threshold based on a distance or direction in which the acquired coordinates are separated from ideal coordinates (here, the coordinates of the origin position). You may be made to do.

  If adjustment of the optical axis position of the measurement pump light LP13 is necessary, it is adjusted as appropriate (step S9). The adjustment of the optical axis position of the measurement pump light LP13 in step S9 can be performed in the same manner as in step S6.

  When it is determined that the optical axis adjustment of the measurement pump light LP13 is unnecessary (No in step S8), or when the optical axis adjustment of the measurement pump light LP13 is completed, the optical axis position of the measurement probe light LP11 is adjusted. It is determined whether it is necessary (step S10). Since the optical axis of the measurement probe light LP11 may deviate from the initial position (origin position) specified in step S3 with the passage of time, the optical axis position is monitored.

  Specifically, the polarizer 126 is operated so that the measurement pump light LP13 is blocked and only the measurement probe light LP11 is transmitted, and the measurement probe light LP11 reaches the image sensor 127. Then, an image showing the spot SP1 is displayed on the monitor 17 like an image I1 shown in FIG. Based on this image, the deviation of the measurement probe light LP11 from the origin position is confirmed.

  Whether or not the optical axis position needs to be adjusted with respect to the measurement probe light LP11 is the same as the image I1 (see FIG. 4), or the incident position on the image sensor 127 (the center coordinates of the spot SP1, etc.) as in step S8. Based on the determination.

  If adjustment of the optical axis position is necessary, adjustment is performed as appropriate (step S11). The optical axis position of the measurement probe light LP11 is adjusted by, for example, polarizing the posture and position of the mirror group M10. The adjustment of the optical axis position may be performed manually. Of course, the optical axis position of the measurement probe light LP11 may be automatically adjusted by the control unit 16 controlling a drive mechanism (motor) that changes the posture and position of each element of the mirror group M10. .

  Until it is determined in step S12 that the pump / probe measurement is completed, steps S8 to S11 are executed as appropriate, thereby monitoring and adjusting the optical axis position of the laser beam for measurement.

  As described above, in the present embodiment, the relative optical axis position of the measurement pump light LP13 with respect to the optical axis position of the measurement probe light LP11 specified in step S3 is adjusted during pump / probe measurement. . Further, even if the optical axis position of the measurement probe light LP11 is deviated from the initial position specified in step S3, the measurement probe light LP11 is adjusted during the measurement by monitoring the incident position of the measurement probe light LP11. Can do.

  FIG. 5 is a diagram showing the fluctuation of the time waveform of the electromagnetic wave LT1 when the relative optical axis positions of the measurement probe light LP11 and the measurement pump light LP13 are shifted. In FIG. 5, a part of the solar cell 9 irradiated with the measurement probe light LP11 and the measurement pump light LP13 in a spot shape is schematically illustrated. The spot SP5 indicates the position where the measurement pump light LP13 is irradiated, and the spots SP61, SP62 and SP63 shown in the spot SP5 indicate the positions where the measurement probe light LP11 is irradiated. ing. The time waveforms 81 to 83 shown in FIG. 5 are restored from the electromagnetic waves detected when the measurement probe light LP11 is irradiated to the spots SP61 to SP63, respectively. The horizontal axis of the time waveforms 81 to 83 indicates time, and the vertical axis indicates electromagnetic wave intensity.

  As shown in FIG. 5, when the optical axis position of the measurement probe light LP11 is deviated from the measurement pump light LP13, the irradiation position of the measurement probe light LP11 changes. Specifically, when the spot 61 in the spot SP5 is to be irradiated with the measurement probe light LP11, the spot 61 is shifted to the spot 62 or 63. Then, as shown in FIG. 5, not the time waveform 81 but the time waveform 82 or 83 is acquired as the measurement result of the time waveform.

  On the other hand, in this embodiment, the incident position of the laser beam for measurement in the image sensor 127 can be detected, and based on this, the deviation of the optical axis of each laser beam can be detected. As a result, the optical axis position of each laser beam can be adjusted appropriately, so that electromagnetic wave data can be collected with good reproducibility.

  In the present embodiment, the measurement laser beam is divided by the beam splitter BS1, and the deviation of the optical axis is detected from a part of the measurement laser beam. For this reason, even during the measurement of electromagnetic waves, it is possible to detect the deviation of the optical axis without affecting the measurement environment. That is, since the optical axis deviation can be detected and the deviation can be appropriately corrected even during the measurement of the pump and the probe, the electromagnetic wave data can be collected with high reproducibility.

<2. Modification>
Although the embodiment has been described above, the present invention is not limited to the above, and various modifications are possible.

  For example, in the above embodiment, the optical axis position of the measurement probe light LP11 is first specified, and the optical axis position of the measurement pump light LP13 is adjusted with respect to this optical axis position (FIG. 4, step S3). , S6). However, the optical axis position of the measurement pump light LP13 may be specified and the optical axis position of the measurement probe light LP11 may be adjusted with respect to this optical axis position.

  Further, the inspection apparatus to which the present invention is applied has a configuration of the inspection apparatus 100 shown in FIG. 1, that is, a measurement laser beam is incident obliquely on the surface 9S of the solar cell 9 (specifically, , Incident angle = 45 °), and is not limited to detecting the electromagnetic wave LT1 radiated to the incident surface side. For example, the present invention is also applied to an inspection apparatus configured to make a measurement laser beam incident perpendicularly to the surface 9S of the solar cell 9 and detect the electromagnetic wave LT1 radiated to the opposite side of the incident surface. Is possible.

  In the above embodiment, the optical axis adjustment (steps S8 to S11) of the measurement probe light LP11 and the measurement pump light LP13 is performed during the pump / probe measurement. However, the optical axis adjustment may be performed when the pump / probe measurement is not being performed, such as when the pump / probe measurement is interrupted or after the pump / probe measurement is completed.

  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. In addition, the configurations described in the above embodiments and modifications can be appropriately combined as long as they do not contradict each other.

DESCRIPTION OF SYMBOLS 100 Inspection apparatus 11 Stage 12 Irradiation part 121 Femtosecond laser 124,125 Wavelength plate 126 Polarizer 127 Image sensor (imaging part)
DESCRIPTION OF SYMBOLS 13 Detection part 131 Detector 14A Measurement delay part 14B Detection delay part 15 Stage moving mechanism 16 Control part 17 Monitor (display part)
31 storage unit 9 solar cell (inspection object)
9S surface 99 reverse bias voltage application circuit I1 image LP1 pulse light LP10 measurement pulse light LP11 measurement probe light LP13 measurement pump light LP21 detection pulse light LT1 electromagnetic wave M8 folding mirror M10 mirror group SP1, SP2, SP5, SP61 to SP63 spot

Claims (7)

Second laser light that is linearly polarized in the first direction and linearly polarized in the second direction orthogonal to the first direction with respect to the first laser light that is irradiated on the inspection object and irradiated on the inspection object An optical axis adjustment method for adjusting the optical axis position of
(a) dividing a part of the first laser beam directed toward the inspection object and making it incident on an imaging unit;
(b) dividing a part of the second laser beam directed toward the inspection object and causing it to enter the imaging unit;
(c) Based on a comparison between the incident position of the first laser beam detected in the step (a) and the incident position of the second laser beam detected in the imaging unit in the step (b). Adjusting the position of the optical axis of the second laser beam toward the inspection object;
An optical axis adjusting method. The optical axis adjustment method according to claim 1,
The step (a) is a step of causing a part of the divided first laser light to be incident on the imaging unit via a polarizer that is operated so as to be adapted to the first direction,
The step (b) is a step of causing a part of the divided second laser light to be incident on the imaging unit via the polarizer operated to fit in the second direction. Adjustment method. In the optical axis adjustment method according to claim 1 or 2,
The step (b)
(b-1) displaying image data indicating the incident position of the second laser beam acquired by the imaging unit;
An optical axis adjusting method. The optical axis adjustment method according to any one of claims 1 to 3,
(e) adjusting the optical axis of the first laser beam toward the inspection object based on the incident position of the first laser beam detected in the step (a);
An optical axis adjustment method further comprising: The optical axis adjustment method according to any one of claims 1 to 4, wherein:
The optical axis adjustment method, wherein the first laser light is probe light, and the second laser light is pump light having a spot diameter larger than that of the probe light. First laser light that is linearly polarized in the first direction and applied to the inspection object, and second laser light that is linearly polarized in the second direction orthogonal to the first direction and applied to the inspection object In an inspection device that inspects an inspection object by irradiating the inspection object,
A dividing unit for dividing a part of the first laser beam and a part of the second laser beam;
An imaging unit on which the first laser beam divided by the dividing unit and the second laser beam divided by the dividing unit are incident;
An inspection device. The inspection apparatus according to claim 6, wherein
A display unit for displaying an image acquired by the imaging unit;
An inspection apparatus further comprising:

Images