JP6330703B2 - Terahertz microscope and focus control method - Google Patents

Description

  The present technology relates to a terahertz wave microscope using terahertz electromagnetic waves and an optical system focus control method used therefor.

  In the semiconductor device manufacturing system described in Patent Document 1, a method of inspecting a semiconductor device in a non-contact manner using a terahertz electromagnetic wave (hereinafter simply referred to as a terahertz wave) is used. In this inspection method, terahertz waves generated by irradiating a semiconductor device to be inspected with an excitation pulse laser, such as an ultrashort pulse laser, are affected by electric field distribution and wiring defects inside the semiconductor device. Using this, the defect of the semiconductor device is inspected (for example, see Patent Document 1).

  In such an inspection method using a terahertz wave, it is required to detect the terahertz wave generated from the inspection object with high efficiency. When the terahertz wave generated from the inspection target is weak or when the convergence efficiency to the detection element is low, the detection efficiency of the terahertz wave is lowered.

  Therefore, in the terahertz wave microscope described in Patent Document 2, detection is performed by placing a terahertz source (observation target) and a terahertz detector at two focal positions of a low-loss terahertz condensing optical system (elliptical reflection surface). It is possible to improve the convergence efficiency to the element.

JP 2006-156978 A JP 2014-219306 JP

  In such a terahertz wave microscope, if the position of the observation object changes and deviates from the focus of the optical system, the intensity of the terahertz wave in the detector is reduced, and the conversion efficiency from electromagnetic waves to current is reduced. Then, since the intensity of the detection signal is lowered, the detection accuracy, that is, the observation accuracy is lowered.

  An object of the present technology is to provide a terahertz wave microscope and a focus control method that can increase observation accuracy.

In order to achieve the above object, a terahertz wave microscope according to the present technology includes a support portion, a light source, an optical mechanism, and a control mechanism.
The support part supports an observation target.
The light source generates excitation light.
The optical mechanism is configured to detect a terahertz wave generated from the observation target by irradiating the observation target with the excitation light.
The control mechanism is configured to measure a focus error of the observation object supported by the support unit, and based on the measurement information, the support mechanism is configured to focus the optical mechanism on the position of the observation object. And a relative movement of the optical mechanism.
In the present technology, the control mechanism is configured to focus the optical mechanism on the observation target supported by the support unit. Therefore, since the intensity reduction of the terahertz wave acquired by the optical mechanism can be prevented, the optical mechanism can obtain an appropriate detection signal. Thereby, observation accuracy can be raised.

The optical mechanism may include an excitation light irradiation unit, an extraction unit, and a detection unit.
The excitation light irradiation unit has a first focal point and irradiates the observation target with the excitation light.
The extraction unit has a second focal point and a third focal point, and extracts a terahertz wave generated from the observation target.
The detection unit detects the terahertz wave extracted by the extraction unit.
The control mechanism controls the relative movement so that the first focus and the second focus are aligned with the position of the observation target, and the third focus is aligned with the position of the detection unit. It may be configured as follows.

The terahertz wave microscope may further include a generation unit that generates probe light from the excitation light from the light source.
The optical mechanism may include a probe light irradiation unit and an optical delay unit.
The probe light irradiation unit has a fourth focal point, and irradiates the detection unit with the probe light generated by the generation unit.
The optical delay unit adjusts an optical path length of the probe light.
The control mechanism may be configured to execute the control of the relative movement so that the third focus and the fourth focus are aligned with the position of the detection unit.
Thereby, even in an optical mechanism that detects terahertz waves by synchronous detection using probe light, it is possible to prevent a decrease in the intensity of the terahertz waves acquired by the detector. As a result, the observation accuracy is improved.

The control mechanism may include an imaging unit and a processing unit configured to obtain the measurement information based on the image data of the observation target captured by the imaging unit.
Thereby, the control mechanism can measure the measurement information, that is, the focus error by image processing.

The control mechanism may include an acquisition unit that acquires an offset value of a focal length of the optical mechanism according to the observation target. In this case, the control mechanism is configured to control the relative movement so that the focus of the optical mechanism is adjusted to the position of the observation target based on the measurement information and the acquired offset value. Also good.
By using an offset value in consideration of the thickness of the observation target in the focus control, the observation accuracy can be improved.

A focus control method using a terahertz wave microscope comprising: a support unit that supports an observation target; and an optical mechanism configured to detect a terahertz wave generated from the observation target by irradiating the observation target with excitation light. .
The focus control method includes measuring a focus error of the observation target supported by the support unit.
Based on the measurement information of the focus error, the relative movement of the support portion and the optical mechanism is controlled so that the focus of the optical mechanism is adjusted to the position of the observation target.

As described above, according to the present technology, it is possible to improve the observation accuracy with the terahertz wave microscope.
Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

FIG. 1A is a diagram illustrating a basic optical system of a terahertz wave microscope according to the present technology. FIG. 1B shows a state where defocus has occurred in the optical system shown in FIG. 1A. FIG. 2 shows the overall configuration of the terahertz wave microscope according to the first embodiment of the present technology. FIG. 3 is a flowchart showing the operation of the terahertz wave microscope. 4A and 4B are diagrams showing the operation of the optical mechanism in steps 105 and 106 in FIG. FIG. 5A shows the optical path length of the combined excitation light and terahertz and the optical path length of the probe light. FIG. 5B shows a state in which an optical path difference between these optical path lengths is generated in FIG. 5A. FIG. 6 shows a detection signal obtained by the detection unit. FIG. 7 shows a focused state of an optical system including an excitation light irradiation unit, an extraction unit, a detection unit, and a probe light irradiation unit. FIG. 8 is a flowchart showing processing according to the second embodiment of the terahertz wave microscope.

  1. Principle of terahertz microscope

  FIG. 1A is a diagram illustrating a basic optical system of a terahertz wave microscope according to the present technology. The terahertz wave microscope is an apparatus that observes an observation target T with a terahertz wave W. The terahertz wave microscope includes an excitation light source 11 that generates excitation light L0, and an optical mechanism 120 configured to detect the terahertz wave W generated from the observation target T by irradiating the observation target T with the excitation light L0. With.

  The excitation light source 11 is a light source that generates a pulse laser for excitation that excites the observation target T. For the excitation light source 11, for example, an ultrashort pulse laser having a wavelength of 2 μm or less and a pulse width of 100 ps or less is used as a pulse laser.

  The observation target T is typically a semiconductor device mainly using a semiconductor material, for example, a light emitting device such as a semiconductor laser or a light emitting diode. Alternatively, the observation target T may be an IC (Integrated Circuit) or other device using a semiconductor material. When the observation target T is an electronic component, these electronic components are often electronic components mounted on a mounting board. In FIGS. 1A and 1B, the mounting substrate is not shown. The observation target T is supported by a support unit (not shown).

  The optical mechanism 120 includes an excitation light irradiation unit 22, an extraction unit 24, and a detection unit 26. The excitation light irradiation unit 22 has a function of condensing the excitation light L0 on the observation target T.

The extraction unit 24 is arranged so as to sandwich the observation target T between the extraction light irradiation unit 22 and the extraction unit 24. When the observation target T mainly including a semiconductor material is irradiated with a pulse laser, a terahertz wave W having a frequency of 10 ¹⁰ (Hz) to 10 ¹⁴ (Hz), for example, is generated from the observation target T. The extraction unit 24 has a function of extracting the terahertz wave W generated from the observation target T and focusing it on the detection unit 26 at the subsequent stage.

  The excitation light irradiation unit 22 and the extraction unit 24 are each configured by a condensing optical system mainly including one or a plurality of lenses. For example, a dielectric lens is used as the extraction unit 24.

  The detection unit 26 has a function of receiving the terahertz wave extracted by the extraction unit 24 and converting it into an electrical signal. The detection unit 26 typically includes a photoconductive element. The photoconductive element is also called a photoconductive antenna (PCA) and has a structure capable of detecting terahertz waves. The structure thereof may be a known one, and for example, the photoconductive element disclosed in Japanese Patent Application Laid-Open No. 2014-219306 is suitable.

  The optical mechanism 120 has a first focus F1, a second focus F2, and a third focus F3. Specifically, the excitation light irradiation unit 22 has a first focus F1 disposed on the observation target T side. The extraction unit 24 has a second focal point F2 arranged on the observation target T side and a third focal point F3 arranged on the detection unit 26 side. When the first focus F1 and the second focus F2 are at the position of the observation target T and the third focus F3 is at the position of the detection unit 26, the intensity of the detection signal detected by the detection unit 26 is the highest, That is, since a signal with a high signal-to-noise ratio is obtained, highly accurate observation can be performed.

  In the terahertz wave microscope configured as described above, when the focal point (first focal point F1) is deviated from the position of the observation target T as shown by the white arrow (displacement amount D) in FIG. Occur. That is, when the first focus F1 deviates from the position of the observation target T, the amount of light irradiated to the observation target becomes insufficient, the energy density of the excitation light L0 at the position of the observation target T decreases, and the light from the observation target T decreases. The amount of radiation of the terahertz wave W is reduced.

  For example, the position of the observation target T may fluctuate and be out of focus due to deformation of the mounting substrate due to a change in ambient temperature over time. Alternatively, when the substrate is a flexible substrate or a substrate having a three-dimensional mounting surface, such as a curved surface or a non-planar mounting surface, defocusing is likely to occur. Alternatively, when a plurality of observation targets T are provided on one mounting substrate, the focus may change for each observation target T.

  The change in position of the observation target T (that is, defocus) means a change in the generation position of the terahertz wave from the observation target T. Accordingly, the amount of radiation of the terahertz wave to the detection unit 26 by the extraction unit 24 becomes insufficient, and the intensity of the terahertz wave in the detection unit 26 decreases, so that the conversion efficiency from the terahertz wave to the current decreases.

  The reduction in the radiation amount of the terahertz wave described above and the reduction in the conversion efficiency from the terahertz wave to the current have a synergistic effect and cause a reduction in the intensity of the detection signal by the detection unit 26.

  2. First embodiment

  1) Configuration of terahertz wave microscope

  FIG. 2 shows the overall configuration of the terahertz wave microscope according to the first embodiment of the present technology. In the following description, the same elements as those shown in FIG. 1A are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  The optical system of the terahertz wave microscope 100 includes an excitation light source 11, a modulator 13, half mirrors 12 and 14, an optical mechanism 20, and reflection mirrors 16, 17, 18, and 19. The optical mechanism 20 mainly includes an excitation light irradiation unit 22, an extraction unit 24, a detection unit 26, a probe light irradiation unit 28, and an optical delay unit 23.

  The half mirror 12 has a function of reflecting a part of the pulse laser emitted from the excitation light source 11 and guiding the reflected light to the modulator 13. The modulator 13 has a function of modulating the intensity of the reflected light from the half mirror 12. For example, an optical chopper is used as the modulator 13. The half mirror 14 has a function of reflecting the modulated pulse laser output from the modulator 13 and guiding the reflected light to the excitation light irradiation unit 22.

  The excitation light irradiation unit 22, the extraction unit 24, and the detection unit 26 have the same configuration as that shown in FIG. 1A. The probe light irradiation unit 28 has a function of irradiating the observation target T with the probe light L1. The probe light L1 is a part of the pulse laser that passes through the half mirror 12. In this case, the half mirror 12 functions as a “generating unit” that generates the probe light L1. The pulse laser transmitted through the half mirror 12 is guided to the probe light irradiation unit 28 via the reflection mirrors 16 to 19 disposed at appropriate positions and the optical delay unit 23.

  The probe light irradiation unit 28 has a fourth focal point F4 disposed on the detection unit 26 side. During observation of the observation target T, the probe light irradiation unit 28 is maintained in a state where the fourth focal point F4 is disposed at the position of the detection unit 26.

  The optical delay unit 23 includes, for example, two reflection mirrors 231 and 232, and a delay stage 23A that supports these movably. The reflection mirrors 231 and 232 constitute, for example, a retro reflector.

  The optical delay unit 23 configured in this manner changes the optical path length of the probe light L1 incident on the probe light irradiation unit 28 when the delay stage 23A moves in the light traveling direction (z direction in FIG. 2). Can be made. Since the arrival time of the pulse laser at the detection unit 26 also changes according to the optical path length, the optical delay unit 23 can output the probe light L1 (sampling pulse laser) at a predetermined timing. . By controlling the output timing of the probe light L1 by the optical delay unit 23, the detection timing of the terahertz wave by the detection unit 26 is controlled. As a result, the detection unit 26 can acquire a time waveform of the electric field intensity of the terahertz wave (see FIG. 6).

  The optical mechanism 20 includes a stage 22A that moves the excitation light irradiation unit 22 in the optical axis direction (that is, the z direction). Similarly, the optical mechanism 20 includes stages 24A, 26A, and 28A that move the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28 in the optical axis direction, respectively.

  The terahertz wave microscope 100 includes a support unit 40 that supports the observation target T, a control unit 10, a camera 15 (imaging unit), stage controllers 32, 34, 36, and 38, a support unit controller 35, a delay stage controller 33, A preamplifier 37 and a lock-in amplifier 39 are provided.

  The support unit 40 is configured to support the mounting substrate S or the like on which the observation target T is mounted, and is configured to move the mounting substrate S in two dimensions. The two dimensions are the xy plane that is the plane of the mounting substrate S. The support unit controller 35 has a function of controlling the movement of the support unit 40.

  The control unit 10 includes a computer having hardware such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The control unit 10 has a function of comprehensively controlling the camera 15, the stage controllers 32, 34, 36, 38, the support unit controller 35, the delay stage controller 33, the preamplifier 37, and the lock-in amplifier 39. The control unit 10 has a function of acquiring the signal obtained by the detection unit 26 and outputting the observation result of the observation target T based on the signal.

  The camera 15 is configured to acquire image light of the observation target T and send the image data to the control unit 10. An illumination optical system (not shown) separate from the excitation light source 11 is provided, and the camera 15 acquires reflected light from the observation target T of the illumination light as image light. A light source of an illumination optical system (not shown) is configured to have, for example, a ring shape provided in the vicinity of the observation target T or in the vicinity of the excitation light irradiation unit 22, but of course from a position different from them. The structure which generate | occur | produces illumination light may be sufficient. The reflected light from the observation target T enters the camera 15 via the excitation light irradiation unit 22 and the half mirror 14. That is, the camera 15 can observe the irradiation state of the excitation light on the observation target T.

  Or it is not restricted to the form where a separate illumination optical system is used, The excitation light source 11 may be used as a light source of an illumination optical system. In this case, the image light acquired by the camera 15 is light that is reflected and scattered by the observation target T by the excitation light L0.

  Each stage controller 32, 34, 36, 38 has a function of controlling movement of each stage 22 </ b> A, 24 </ b> A, 26 </ b> A, 28 </ b> A in the z direction according to control by the control unit 10. The support unit controller 35 has a function of controlling movement of the support unit 40 in the xy plane in accordance with control by the control unit 10. The delay stage controller 33 has a function of controlling the movement of the delay stage 23 </ b> A of the optical delay unit 23 in the z direction according to control by the control unit 10.

  The preamplifier 37 has a function of amplifying the detection signal output from the detection unit 26. The lock-in amplifier 39 has a function of acquiring a signal proportional to the intensity of the terahertz wave at a desired timing by synchronous detection based on the amplified signal. The signal obtained by the lock-in amplifier 39 is sent to the control unit 10.

  2) Operation of terahertz wave microscope

  FIG. 3 is a flowchart showing the operation of the terahertz wave microscope 100. For convenience of explanation, the subject of this operation will be described as the control unit 10.

  As an initial setting of the terahertz wave microscope 100, the control unit 10 acquires data related to the mounting substrate S on which the observation target T to be processed is mounted. Specifically, the control unit 10 acquires at least coordinate data of the observation target T in the xy plane on the mounting substrate S (step 101). When a plurality of observation targets T are mounted on the mounting substrate S, the control unit 10 acquires coordinate data for each observation target T.

  The mounting substrate S is supported by the support unit 40. The support unit controller 35 moves the support unit 40 according to control based on the coordinate data of the observation target T by the control unit 10 (step 102). Specifically, the support controller 35 has the optical axis of the optical mechanism 20 (here, the optical axis in the z direction common to the excitation light irradiation unit 22, the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28). The support unit 40 is moved in the xy plane so as to pass through the observation target T.

  The control unit 10 generates a pulse laser from the excitation light source 11 and irradiates the observation target T with the pulse laser (step 103). On the other hand, the camera 15 acquires image light reflected from the observation target T via the excitation light irradiation unit 22, and the control unit 10 acquires the image data (step 104).

  Based on the image data, the control unit 10 measures the focus error of the position of the observation target T by the optical mechanism 20 and obtains measurement information (step 105). Based on the measurement information (focus error), the control unit 10 controls the movement of the optical mechanism 20 relative to the support unit 40 (step 106). Instead of the focus error being measured by the control unit, a calculation unit built in the camera may measure the focus error. In this case, the control unit and the calculation unit function as a “processing unit”.

  In such processing of Steps 105 and 106, the control unit 10, the stage controllers 32, 34, 36, and 38, the support unit controller 35, and the delay stage controller 33 function as a “control mechanism”.

  4A and 4B are diagrams illustrating the operation of the optical mechanism 20 in steps 105 and 106. FIG.

  In step 105, the control unit 10 specifically executes the following process. The control unit 10 measures a focus error, which is a displacement amount D (see FIG. 1B) of the first focus F1 of the excitation light irradiation unit 22 from the position of the observation target T, and obtains measurement information thereof. The focus error is obtained by a known method such as a phase difference method or a contrast method.

  In step 106, the control unit 10 controls the movement of the stage controller 32 in the optical axis direction (z direction) so that the first focus F1 is aligned with the position of the observation target T based on the measurement information. Specifically, the control unit 10 outputs movement amount information such that the focus error is substantially zero to the stage controller 32, and the stage controller 32 sets the excitation light irradiation unit 22 according to the movement amount information. To drive.

  In step 106, the control unit 10 controls the movements of the stage controllers 34, 36, and 38 based on the focus error measurement information (displacement amount D) as described above. Specifically, the control unit 10 outputs movement amount information such that the focus error is substantially zero to the stage controllers 34, 36, and 38. The stage controllers 34, 36, and 38 drive the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28, respectively, according to the movement amount information.

  Referring to FIG. 4A, as described above, each of the stage controllers 32, 34, 36, and 38 corresponds to the displacement amount D, the excitation light irradiation unit 22, the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28. Move. Accordingly, the first focus F1 and the second focus F2 are adjusted to the position of the observation target T, and the third focus F3 and the fourth focus F4 are adjusted to the position of the detection unit 26. That is, the excitation light irradiation unit 22, the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28 are integrally moved by the displacement amount D.

  Here, in the state shown in FIG. 4A, the observation phase shift occurs, so that it cannot be said that the state is optimal as it is. FIG. 6 shows a detection signal obtained by the detection unit 26. The horizontal axis represents time, and the vertical axis represents the electric field strength. At the optimum sampling timing Tp, the maximum electric field strength can be obtained. However, when the observation phase is shifted, that is, the sampling timing is shifted from Tp to Tp ′, the detection signal, which is the electric field strength, decreases accordingly.

  Specifically, as shown in FIG. 5A, the observation phase includes the optical path length of the optical path OP1 that combines the excitation light L0 (see FIG. 2) and the terahertz wave W, and the optical path OP2 of the probe light L1 (see FIG. 2). It is determined by the optical path difference of the optical path length. The respective optical path lengths are compared before and after the integral movement of each stage 22A, 24A, 26A, 28A in FIG. 4A. Then, as shown in FIG. 5B, the optical path length of the optical path OP1 becomes longer by the displacement amount D, while the optical path length of the optical path OP2 becomes shorter by D, so that the optical path difference is newly generated by 2D and shifted to the observation phase. Will occur.

  To eliminate this observation phase shift, the optical path OP2 may be lengthened by 2D. Therefore, as shown in FIG. 4B, the control unit 10 outputs to the delay stage controller 33 movement amount information such that the observation phase shift, that is, the optical path difference 2D becomes substantially zero. The delay stage controller 33 drives the delay stage 23A according to the movement amount information. Since the optical delay unit 23 according to the present embodiment has a folded optical path such as a retroreflector, the delay stage controller 33 moves the delay stage 23A by the displacement amount D.

  As described above, the terahertz wave microscope 100 according to the present embodiment performs feedback control for focusing on the image light of the observation target T obtained by the camera 15 and the excitation light irradiation unit 22.

  The signal (see FIG. 6) obtained by the detection unit 26 differs depending on whether or not a defect or the like occurs in the observation target T. Therefore, the control unit 10 can detect the presence or absence of a defect by, for example, threshold determination or signal pattern matching determination.

  FIG. 7 shows an actual in-focus state of the optical system including the excitation light irradiation unit 22, the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28. Thus, the first focal point F1 of the excitation light irradiation unit 22 and the second focal point F2 of the extraction unit 24 coincide at the position of the observation target T. Further, the third focus F3 of the extraction unit 24 and the fourth focus F4 of the probe light irradiation unit 28 coincide with each other at the position of the detection unit 26.

  As described above, in the present embodiment, even when the position of the observation target T varies from the intended position, the focus of the optical mechanism 20 is adjusted to the observation target T supported by the support unit 40. Therefore, the terahertz wave microscope 100 can prevent a decrease in the intensity of the terahertz wave acquired by the detection unit 26, and the detection unit 26 can obtain an appropriate detection signal. Thereby, observation accuracy can be raised.

  That is, since the focusing of the terahertz wave detection unit 26 by the extraction unit 24 is optimal and the intensity of the terahertz wave in the detection unit 26 is optimal, the conversion efficiency from the terahertz wave to the current is optimal. Thereby, the detection part 26 can obtain a signal with a high SN ratio, and can improve observation accuracy.

  In particular, in this embodiment, since the optical delay unit 23 is driven so as to eliminate the optical path difference corresponding to the observation phase shift, a detection signal with higher accuracy can be obtained.

  When there are a plurality of observation targets T on the mounting substrate S, the control unit 10 executes the flow shown in FIG. For example, when observing a plurality of observation targets mounted on a mounting board having a non-planar mounting surface, the focus position differs for each observation target even if it is the same type of observation target. It is an advantageous technique that can be dealt with.

  2. Second embodiment

  In the first embodiment, the camera 15 acquires light reflected by the surface of the observation target T as image light. As shown in FIG. 7, in the in-focus state, the first focus F1 of the excitation light irradiation unit 22 often coincides with the second focus F2 inside the observation target T instead of the surface thereof. Therefore, the focal point of the optical system including the camera 15 and the excitation light irradiation unit 22 may not coincide with the focal points of the optical system including the excitation light irradiation unit 22 and the extraction unit 24 (the first focal point F1 and the second focal point F2). .

  In order to avoid such a situation, the control unit 10 of the terahertz wave microscope 100 according to the second embodiment of the present technology acquires, for example, an offset value of the focal length of the optical mechanism 20. In this case, the control unit 10 functions as an “acquisition unit”. The control unit 10 is configured to perform focus control based on a calculated value obtained by adding the offset value to the focus error.

  FIG. 8 is a flowchart showing the processing. In FIG. 8, processes different from those in FIG. 3 are steps 201 and 206.

  In step 201, the control unit 10 acquires thickness data (“E1” shown in FIG. 7) of the observation target T. In Step 206, the control unit 10 controls the movement of the optical mechanism 20 based on the measurement information that is the measured focus error and the thickness data. For example, when the state in which the first focus F1 and the second focus F2 are substantially at the center in the optical axis direction of the observation target T is set as the in-focus state, the offset value is 1 of the thickness E1 of the observation target T. Calculated as / 2. That is, a value obtained by adding (or subtracting) the offset value E1 / 2 to the focus error is an actual focus error.

  As described above, in the present embodiment, by using the offset value in consideration of the thickness of the observation target T, an appropriate in-focus state can be obtained according to the observation target T, and the observation accuracy is improved. be able to.

  When a plurality of observation targets T are provided on the mounting substrate S, the control unit 10 may acquire thickness data for each observation target T or each type of the observation target T.

The offset value is not limited to a form that is 1/2 of the thickness E1 of the observation target T. For example, the offset value may be different depending on the type of the observation target T (here, material, structure, and / or shape, etc.).
[Other various embodiments]

  The present technology is not limited to the embodiments described above, and other various embodiments can be realized.

  In the above embodiment, the optical mechanism 20 moves in the z direction and the focus control is performed on the observation target T that is fixed in the z direction. However, the optical mechanism 20 (here, a mechanism including the excitation light irradiation unit 22, the extraction unit 24, the detection unit 26, the probe light irradiation unit 28, and the optical delay unit 23) is fixed in the z direction and supports the observation target T. The support part 40 to be moved may be configured to move in the z direction under the control of the control part 10.

  In the above embodiment, the excitation light irradiation unit 22, the extraction unit 24, the detection unit 26, the probe light irradiation unit 28, and the optical delay unit 23 are individually provided with stages 22A, 24A, 26A, and 28A, respectively. It was configured to move individually (the movement amount (displacement amount D) is the same). However, at least two of these five elements may be configured to move by one common stage. For example, the extraction unit 24, the detection unit 26, and the probe light irradiation unit 28 may be integrally attached to one common stage. In this case, these elements are attached to the common stage so that the third focal point F3 and the fourth focal point F4 coincide with the position of the detection unit 26. Or the extraction part 24, the detection part 26, the probe light irradiation part 28, and the optical delay part 23 may be integrally attached to one common stage.

  In the said embodiment, the excitation light irradiation part 22, the extraction part 24, the detection part 26, and the probe light irradiation part 28 were arrange | positioned on the straight line in the z direction. However, a mirror or the like may be arranged between the excitation light irradiation unit 22 and the probe light irradiation unit 28, and the optical path may be folded one or more times.

  In the above embodiment, the camera 15 is used as means for obtaining focus error measurement information. However, a distance meter may be used. As the distance meter, for example, a laser distance meter is used. For example, the reference position of the observation target T with respect to the optical mechanism 20 is determined in advance, and the distance meter is configured to measure the positional deviation of the observation target T from the reference position (the deviation in the z direction in FIG. 2). The control unit 10 uses the measurement information as a focus error.

  As shown in FIG. 1, the present technology can also be applied to a terahertz wave microscope that does not include the optical delay unit 23 shown in FIG. In this case, a device that generates a gate signal instead of the sampling pulse laser is provided in place of the optical delay unit 23 in order to obtain a detection signal by the detection unit 26.

  In the above embodiment, a part including a semiconductor material is taken as an example of the observation target T, but a living body (for example, a living tissue or a cell) may be the observation target. In this case, the irradiation optical system from the light source includes the excitation light source 11 and a device including a semiconductor material. And the detection part 26 detects the terahertz wave which the terahertz wave which generate | occur | produces from a semiconductor material is irradiated to a biological body, and was reflected or permeate | transmitted from the biological body.

  It is also possible to combine at least two feature portions among the feature portions of each embodiment described above.

In addition, this technique can also take the following structures.
(1)
A support part for supporting the observation object;
A light source that generates excitation light;
An optical mechanism configured to detect terahertz waves generated from the observation object by irradiating the observation object with the excitation light;
The support unit and the optical mechanism are configured to measure a focus error of the observation target supported by the support unit, and based on the measurement information, focus the optical mechanism on the position of the observation target. And a control mechanism configured to control relative movement of the terahertz wave microscope.
(2)
The terahertz wave microscope according to (1),
The optical mechanism is
An excitation light irradiation unit having a first focal point and irradiating the observation object with the excitation light;
An extraction unit that has a second focal point and a third focal point, and extracts a terahertz wave generated from the observation target;
A detection unit for detecting the terahertz wave extracted by the extraction unit,
The control mechanism controls the relative movement so that the first focus and the second focus are aligned with the position of the observation target, and the third focus is aligned with the position of the detection unit. Configured as a terahertz wave microscope.
(3)
The terahertz wave microscope according to (2),
A generator that generates probe light from the excitation light from the light source;
The optical mechanism is
A probe light irradiating unit that has a fourth focal point and irradiates the probe with the probe light generated by the generating unit;
An optical delay unit for adjusting the optical path length of the probe light, and
The control mechanism is further configured to execute control of the relative movement so that the third focus and the fourth focus are aligned with the position of the detection unit.
(4)
The terahertz wave microscope according to any one of (1) to (3),
The control mechanism is
An imaging unit;
A terahertz wave microscope comprising: a processing unit configured to obtain the measurement information based on the image data of the observation target imaged by the imaging unit.
(5)
The terahertz wave microscope according to any one of (1) to (4),
The control mechanism has an acquisition unit that acquires an offset value of a focal length of the optical mechanism according to the observation target, and focuses the optical mechanism based on the measurement information and the acquired offset value. A terahertz wave microscope configured to execute control of the relative movement so as to be matched with a position of an observation target.
(6)
A focus control method using a terahertz wave microscope comprising: a support unit that supports an observation object; and an optical mechanism configured to detect terahertz waves generated from the observation object by irradiating the observation object with excitation light. And
Measure the focus error of the observation object supported by the support part,
A focus control method that controls relative movement of the support unit and the optical mechanism so that the focus of the optical mechanism is adjusted to the position of the observation target based on measurement information of the focus error.

L0 ... excitation light L1 ... probe light F1 ... first focus F2 ... second focus F3 ... third focus F4 ... fourth focus 10 ... control unit 11 ... excitation light source 15 ... camera 20, 120 ... optical mechanism 22 ... excitation light irradiation Units 22A, 24A, 26A, 28A ... Stage 23 ... Optical delay unit 23A ... Delay stage 24 ... Extraction unit 26 ... Detection unit 28 ... Probe light irradiation unit 32, 34, 36, 38 ... Stage controller 33 ... Delay stage controller 35 ... Support unit controller 40 ... support unit 100 ... terahertz wave microscope

Claims (5)

A support part for supporting the observation object;
A light source that generates excitation light;
An optical mechanism configured to detect terahertz waves generated from the observation object by irradiating the observation object with the excitation light;
A generator for generating probe light from the excitation light from the light source;
It is configured to measure a focus error of the observation object supported by the support part, and based on the measurement information, the optical mechanism is focused on the position of the observation object so that the focus is on the support part . ; and a configured control mechanism to control the moving of the optical mechanism,
The optical mechanism is
An excitation light irradiation unit having a first focal point and irradiating the observation object with the excitation light;
An extraction unit that has a second focal point and a third focal point, and extracts a terahertz wave generated from the observation target;
A detection unit for detecting the terahertz wave extracted by the extraction unit;
A probe light irradiating unit that has a fourth focal point and irradiates the probe with the probe light generated by the generating unit;
An optical delay unit for adjusting the optical path length of the probe light,
The control mechanism includes the excitation light so that the first focus and the second focus are aligned with the position of the observation target, and the third focus and the fourth focus are aligned with the position of the detection unit. A terahertz wave microscope configured to execute control of individual movements of the irradiation unit, the extraction unit, the detection unit, and the probe light irradiation unit .   The terahertz wave microscope according to claim 1,
  A delay stage controller for controlling movement of the optical delay unit in the optical axis direction;
  Terahertz microscope. The terahertz wave microscope according to claim 1 or 2 ,
The control mechanism is
An imaging unit;
A terahertz wave microscope comprising: a processing unit configured to obtain the measurement information based on the image data of the observation target imaged by the imaging unit. The terahertz wave microscope according to any one of claims 1 to 3 ,
The control mechanism has an acquisition unit that acquires an offset value of a focal length of the optical mechanism according to the observation target, and focuses the optical mechanism based on the measurement information and the acquired offset value. so as to match the position of the observation object, the terahertz wave microscope configured to perform control of moving. A support for supporting an observation target, a light source for generating excitation light, a generating unit that generates a probe light from the excitation light from the light source, by irradiating the excitation light to the observation target, from the observation target A focus control method by a terahertz wave microscope comprising an optical mechanism configured to detect a generated terahertz wave,
The optical mechanism is
An excitation light irradiation unit having a first focal point and irradiating the observation object with the excitation light;
An extraction unit that has a second focal point and a third focal point, and extracts a terahertz wave generated from the observation target;
A detection unit for detecting the terahertz wave extracted by the extraction unit;
A probe light irradiating unit that has a fourth focal point and irradiates the probe with the probe light generated by the generating unit;
An optical delay unit for adjusting the optical path length of the probe light,
Measure the focus error of the observation object supported by the support part,
Based on the measurement information of the focus error, the first focus and the second focus are adjusted to the position of the observation target, and the third focus and the fourth focus are adjusted to the position of the detection unit. A focus control method for controlling individual movements of the excitation light irradiation unit, the extraction unit, the detection unit, and the probe light irradiation unit .

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