Measuring device

Abstract

A measuring device 1 comprises: an integrating sphere 4, in the interior of which a measurement subject S is disposed; an excitation optical system 3 that guides excitation light L1 toward the measurement subject S disposed in the integrating sphere 4; a light detector 6 that detects light to be measured L2 produced by the measurement subject S in the integrating sphere 4 due to irradiation of the excitation light L1; and a first detection optical system 7 that guides the light to be measured L2 from the integrating sphere 4 toward the light detector 6. The optical axis of the excitation light L1 incident on the measurement subject S in the integrating sphere 4 in the excitation optical system 3 and the optical axis of the light to be measured L2 emitted from the integrating sphere 4 in the first detection optical system 7 are oblique. The first detection optical system 7 has an opening section 36 that limits the detection range of the light to be measured L2 in the optical detector 6. An irradiation spot La of the excitation light L1 on the measurement subject S and the opening section 36 are in an optically conjugate relationship.

Description

Technical Field

[0001] The present disclosure relates to a measuring device.

Background Art

[0002] As a measurement method used for inspecting a measurement object such as a semiconductor wafer, for example, photoluminescence measurement (hereinafter referred to as "PL measurement") is known. PL measurement is a method of measuring light emitted by recombination of electrons and holes generated by irradiating a semiconductor material with light having energy higher than the band gap. Conventionally, the quality of a measurement object has been evaluated based on information such as the intensity and wavelength of PL. However, from the viewpoint of quality assurance of semiconductor wafers, improvement in the quantification and reproducibility of defects has been demanded.

[0003] As another measurement method, omnidirectional photoluminescence measurement (hereinafter referred to as "ODPL measurement") is known (see, for example, Non-Patent Document 1). ODPL measurement is a method of measuring the number of photons of excitation light absorbed by a measurement object and the number of emitted photons in all directions using an integrating sphere. In ODPL measurement, since the emission quantum efficiency of band-edge emission affected by non-radiative recombination including impurity density and point defect density can be calculated, quantification of defects is possible.

[0004] In ODPL measurement, as a previous step, measurement of the external quantum efficiency (EQE) of a measurement object using an integrating sphere is performed. Further, as a subsequent step, calculation of the internal quantum efficiency (IQE) of the measurement object using the standard PL spectrum of the measurement object is performed. The external quantum efficiency is the ratio of the number of emitted photons outside the measurement object to the number of photons of excitation light absorbed by the measurement object. The internal quantum efficiency is the ratio of the number of emitted photons generated in the measurement object to the number of photons of excitation light absorbed by the measurement object.

[0005] Since the external quantum efficiency takes into account the influence of the light extraction efficiency from the measurement object on the internal quantum efficiency, if the standard PL spectrum and the external quantum efficiency of the measurement object are obtained, the internal quantum efficiency of the measurement object can be calculated. For example, in the case of GaN crystals, the higher the crystallinity and the fewer the number of defects in the material, the higher the internal quantum efficiency tends to be (see Non-Patent Document 1). That is, the internal quantum efficiency directly reflects the crystal quality of the material. By evaluating the crystal quality of the wafer material during wafer manufacturing, it becomes possible to evaluate factors related to the lifespan and performance of the device.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Measurement using an integrating sphere involves detecting the light incident on the integrating sphere and the omnidirectional light generated from the measurement object. Therefore, generally, when measuring the standard PL spectrum of a measurement object, an integrating sphere is not used (see, for example, Non-Patent Document 2). However, when performing ODPL measurement, from the perspective of measurement convenience, it is preferable that the standard PL spectrum of the measurement object can be measured while the measurement object is placed in the integrating sphere.

[0008] The present disclosure has been made to solve the above problems, and an object thereof is to provide a measuring device capable of measuring the standard PL spectrum of a measurement object while the measurement object is placed in an integrating sphere.

Means for Solving the Problems

[0009] The measuring device according to one aspect of the present disclosure includes an integrating sphere in which a measurement object is placed inside, an excitation optical system that guides excitation light toward the measurement object placed in the integrating sphere, a photodetector that detects the light to be measured generated by the measurement object in the integrating sphere by irradiation with the excitation light, and a first detection optical system that guides the light to be measured from the integrating sphere toward the photodetector. The optical axis of the excitation light incident on the measurement object in the integrating sphere in the excitation optical system and the optical axis of the light to be measured emitted from the integrating sphere in the first detection optical system are skew to each other. The first detection optical system has an aperture that limits the detection range of the light to be measured at the photodetector, and the irradiation spot of the excitation light on the measurement object and the aperture are in an optically conjugate relationship.

[0010] In this measuring device, the optical axis of the excitation light incident on the measurement object in the integrating sphere in the excitation optical system is skew to the optical axis of the light to be measured emitted from the integrating sphere in the first detection optical system. Thereby, it is possible to prevent the excitation light reflected by the measurement object in the integrating sphere from being directly detected by the photodetector. Further, in this measuring device, the irradiation spot of the excitation light on the measurement object arranged in the integrating sphere and the aperture arranged in the first detection optical system are in an optically conjugate relationship. Thereby, the influence of multiple scattering in the integrating sphere can be suppressed, and only the light to be measured generated on the surface of the measurement object by the incidence of the excitation light can be taken out from the integrating sphere and detected. Therefore, in this measuring device, the standard PL spectrum of the measurement object can be measured while the measurement object is arranged in the integrating sphere.

[0011] The excitation light directed toward the measurement object by the excitation optical system and the light to be measured generated by the measurement object in the integrating sphere may pass through the same port of the integrating sphere. In this case, it becomes easier to share the optical components constituting the excitation optical system and the first detection optical system, and the device can be simplified and miniaturized.

[0012] The excitation light directed toward the measurement object by the excitation optical system may pass through one port of the integrating sphere, and the light to be measured generated by the measurement object in the integrating sphere may pass through another port different from the one port of the integrating sphere. In this case, it becomes easy to ensure the skew angle between the optical axis of the excitation light incident on the measurement object in the integrating sphere in the excitation optical system and the optical axis of the light to be measured emitted from the integrating sphere in the first detection optical system. Therefore, it is possible to more reliably prevent the excitation light reflected by the measurement object in the integrating sphere from being directly detected by the photodetector.

[0013] The first detection optical system may have a shielding member that shields stray light of the light to be measured. In this case, it is possible to prevent the stray light of the light to be measured from affecting the optical components constituting the excitation optical system and the first detection optical system.

[0014] The shielding member may be constituted by a cylindrical member. In this case, the stray light of the light to be measured can be shielded with a simple configuration.

[0015] The measuring device may further include a second detection optical system that guides the measurement light diffusely reflected inside the integrating sphere from the integrating sphere toward the photodetector, and a switching unit that optically connects one of the first detection optical system and the second detection optical system to the photodetector. In this case, by guiding the measurement light diffusely reflected inside the integrating sphere from the integrating sphere toward the photodetector using the second detection optical system, it is possible to measure the external quantum efficiency of the measurement object using the integrating sphere. By switching the optical system connected to the photodetector by the switching unit, it is possible to perform the measurement of the standard PL spectrum and the measurement of the external quantum efficiency in the same apparatus while maintaining the state in which the measurement object is placed in the integrating sphere.

[0016] The switching unit may be configured to include an attenuation element that is disposed so as to be movable forward and backward on the optical axis of the measurement light. In this case, saturation of the measurement light at the photodetector can be preferably prevented.

Advantages of the Invention

[0017] According to the present disclosure, it is possible to measure the standard PL spectrum of the measurement object while the measurement object is placed in the integrating sphere.

Brief Description of the Drawings

[0018]

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Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, a preferred embodiment of a measuring device according to one aspect of the present disclosure will be described in detail. [Outline of the Measuring Device]

[0020] FIG. 1 is a schematic diagram showing the configuration of a measuring device according to an embodiment of the present disclosure. The measuring device 1 shown in the figure is configured as a device for performing a non-destructive inspection of a measurement object S, for example. In the present embodiment, a compound semiconductor crystal is exemplified as the measurement object S. More specifically, the measurement object S is a gallium nitride (GaN) semiconductor crystal. The GaN semiconductor is a material expected to be applied to high-frequency devices and power devices in addition to visible / ultraviolet light-emitting devices. It is known that the characteristics of devices using GaN semiconductors are greatly affected by structural defects such as threading dislocations, point defects, and the incorporation of trace impurities. The measuring device 1 is configured as a device for inspecting both the distribution of structural defects and the quantitativeness of defects in a GaN semiconductor crystal in order to improve the device yield and promote mass production.

[0021] In the measuring device 1, in order to inspect the distribution of structural defects and the quantitativeness of defects in the GaN semiconductor crystal, an omnidirectional photoluminescence measurement (hereinafter referred to as "ODPL measurement") is performed on the measurement object S. In the ODPL measurement, as a previous step, the external quantum efficiency (EQE) of the measurement object S using an integrating sphere is measured. Further, as a subsequent step, the calculation of the internal quantum efficiency (IQE) of the measurement object S using the standard photoluminescence spectrum (hereinafter referred to as "standard PL spectrum") of the measurement object S is performed.

[0022] The external quantum efficiency is the ratio of the number of emitted light photons emitted outside the measurement object to the number of excitation light photons absorbed by the measurement object. The graph shown in FIG. 2 shows, as an example, the spectrum of the light to be measured output from the integrating sphere when the excitation light is input to the integrating sphere without placing a sample in the integrating sphere (graph A in FIG. 2) and the spectrum of the light to be measured output from the integrating sphere when the excitation light is input to the integrating sphere with a sample placed in the integrating sphere (graph B in FIG. 2). The number of excitation light photons absorbed by the measurement object corresponds to the difference between the spectrum of graph A and the spectrum of graph B in the wavelength region of the excitation light (region D1 in FIG. 2). The number of emitted light photons emitted outside the measurement object corresponds to the difference between the spectrum of graph A and the spectrum of graph B in the emission wavelength region of the light to be measured (region D2 in FIG. 2).

[0023] The internal quantum efficiency is the ratio of the number of luminescent photons generated in the measurement object to the number of excitation photons absorbed by the measurement object. The external quantum efficiency takes into account the influence of the light extraction efficiency from the measurement object on the internal quantum efficiency. The light extraction efficiency from the measurement object is a known value determined by the material of the measurement object. For example, the light extraction efficiency of a GaN crystal is estimated to be 2.55% (see Non-Patent Document 2 above).

[0024] Therefore, if the standard PL spectrum and the external quantum efficiency of the measurement object S are obtained, the internal quantum efficiency of the measurement object S can be derived. For example, in the case of a GaN crystal, the higher the crystallinity and the fewer the number of defects in the material, the higher the internal quantum efficiency tends to be (see, for example, Non-Patent Document 1 mentioned above). That is, the internal quantum efficiency directly reflects the crystal quality of the material, and by evaluating the crystal quality of the wafer material during wafer manufacturing, it becomes possible to evaluate factors related to the lifetime and performance of the device.

[0025] To calculate the internal quantum efficiency, it is necessary to measure the standard PL spectrum of the measurement object. Measuring using an integrating sphere means detecting the light incident on the integrating sphere and the omnidirectional light generated from the measurement object. When attempting to measure the standard PL spectrum using an integrating sphere, for example, as shown in Figure 3, in order to detect omnidirectional light emission, in addition to the peak (peak A in Figure 3) that the standard PL spectrum originally has, a peak of the spectrum (peak B in Figure 3) will occur. For this reason, generally, an integrating sphere is not used when measuring the standard PL spectrum of the measurement object. In contrast, in the measuring device 1, from the perspective of measurement convenience, the configuration is devised so that the standard PL spectrum of the measurement object S can be measured while the measurement object S is placed in the integrating sphere. Hereinafter, the configuration of this measuring device 1 will be described in detail. [Configuration of Measuring Device]

[0026] As shown in Fig. 1, the measuring device 1 includes an excitation light source 2, an excitation optical system 3, an integrating sphere 4, an XY stage 5, a photodetector 6, a first detection optical system 7, a second detection optical system 8, and a calculation unit 12. In this embodiment, the excitation optical system 3, the integrating sphere 4, the photodetector 6, the first detection optical system 7, and the second detection optical system 8 are accommodated in a housing 13 made of a member such as metal. The excitation light source 2, the XY stage 5, and the calculation unit 12 are externally attached to the housing 13.

[0027] The excitation light source 2 is a device that outputs excitation light L1 to the measurement object S. The excitation light source 2 may be either a coherent light source or an incoherent light source. As the coherent light source, for example, an excimer laser (wavelength 193 nm), the second harmonic of a YAG laser (wavelength 532 nm), the fourth harmonic of a YAG laser (wavelength 266 nm), a semiconductor laser (e.g., an InGaN semiconductor laser (wavelength 375 nm to 530 nm), a red semiconductor laser, an infrared semiconductor laser), a semiconductor-excited all-solid-state UV laser (wavelength 320 nm), a HeCd laser (wavelength 325 nm), etc. can be used. As the incoherent light source, for example, a mercury lamp (wavelength 365 nm), an LED light source, etc. can be used. The excitation light L1 output from the excitation light source 2 may be either pulsed light or CW light. When the measurement object S is a GaN semiconductor crystal, as the excitation light source 2, among the above light sources, for example, the fourth harmonic of a YAG laser (wavelength 266 nm), a semiconductor-excited all-solid-state UV laser (wavelength 320 nm), a HeCd laser (wavelength 325 nm) is used.

[0028] The excitation optical system 3 is an optical system that guides the excitation light L1 toward the measurement object S. The excitation optical system 3 includes, for example, a variable attenuation filter 16, a mirror 17, a separation optical element 18, and a lens 19. The variable attenuation filter 16 is an element for changing the intensity of the excitation light L1 irradiated on the measurement object S, and adjusts the intensity of the excitation light L1 heading toward the measurement object S.

[0029] The separation optical element 18 is an element that separates the optical axis of the excitation light L1 directed toward the measurement object S and the optical axis of the measurement light L2 generated by the measurement object S due to the irradiation of the excitation light L1. In the present embodiment, as shown in FIG. 4, the separation optical element 18 is constituted by a so-called aperture mirror and has an opening 21 that allows the excitation light L1 to pass through and a reflecting surface 22 that reflects the measurement light L2 to be described later. On the reflecting surface 22, the measurement light L2 is reflected at a position shifted from the opening 21. Thereby, the optical axis of the excitation light L1 directed toward the measurement object S and the optical axis of the measurement light L2 output from the integrating sphere 4 and directed toward the photodetector 6 are separated.

[0030] The lens 19 is constituted by, for example, a convex lens. The lens 19 condenses the excitation light L1 directed toward the integrating sphere 4 onto the surface of the measurement object S. That is, the lens 19 forms an irradiation spot La (see FIG. 5) of the excitation light L1 on the measurement object S in the integrating sphere 4. Further, the lens 19 collimates the measurement light L2 from the integrating sphere 4.

[0031] The integrating sphere 4 is a device that diffusely reflects light on the inner wall of a spherical body provided with a reflective coating and spatially integrates it. The shape of the integrating sphere 4 is not limited to a spherical shape and may be a hemispherical shape. The measurement object S is disposed inside the integrating sphere 4. In the present embodiment, the tip portion of the arm 23 connected to the XY stage 5 extends inside the integrating sphere 4, and the measurement object S is held at the tip portion of the arm 23. Thereby, the measurement object S can be scanned in the XY plane direction inside the integrating sphere 4.

[0032] The integrating sphere 4 has a first port 24 and a second port 25. The first port 24 opens in a direction orthogonal to the scanning plane (XY plane) of the measurement object S by the XY stage 5. The second port 25 opens in a direction (X direction or Y direction) orthogonal to the opening direction of the first port 24. In the present embodiment, the first port 24 serves as a port for standard PL spectrum measurement, and the second port 25 serves as a port for external quantum efficiency measurement. In the standard PL spectrum measurement, both the excitation light L1 directed toward the measurement object S by the excitation optical system 3 and the measurement light L2 generated by the measurement object S in the integrating sphere 4 pass through the first port 24 of the integrating sphere 4. In the external quantum efficiency measurement, the excitation light L1 directed toward the measurement object S by the excitation optical system 3 passes through the first port 24, and the measurement light L2 diffusely reflected in the integrating sphere 4 passes through the second port 25.

[0033] The photodetector 6 is a device that detects the measurement light L2 generated by the measurement object S in the integrating sphere 4 by the irradiation of the excitation light L1. The photodetector 6 is optically connected to one of the first detection optical system 7 and the second detection optical system 8 via the switching unit 31. As the photodetector 6, for example, CMOS, CCD, EM-CCD, photomultiplier tube, SiPM (MPPC), APD (SPAD), photodiode (including array-shaped ones), etc. can be used. In the present embodiment, the photodetector 6 is constituted by a BT-CCD (a multi-channel photodetector incorporating a back-illuminated type CCD). The photodetector 6 outputs a signal based on the detection result to the arithmetic unit 12. The photodetector 6 may incorporate an element (for example, a variable attenuation filter) for suppressing the saturation of the measurement light L2.

[0034] The first detection optical system 7 is an optical system that guides the measurement light L2 from the integrating sphere 4 toward the photodetector 6 in the standard PL spectrum measurement. The first detection optical system 7 includes a dichroic mirror 32, a mirror 33, and a lens 34 in addition to the common lens 19 and the separation optical element 18 of the excitation optical system 3. The measurement light L2 output from the first port 24 of the integrating sphere 4 is guided by the first detection optical system 7 and input to the photodetector 6 via the photodetector input end 35.

[0035] FIG. 5 is a schematic diagram showing the optical connection state between the excitation optical system and the first detection optical system in the standard PL spectrum measurement. As shown in the figure, in the standard PL spectrum measurement, when performing the measurement of the standard PL spectrum with the measurement object S placed in the integrating sphere 4, the optical axis of the excitation light L1 directed toward the measurement object S and the optical axis of the light to be measured L2 generated by the measurement object S due to the irradiation of the excitation light L1 are separated by the above-described separation optical element 18. For this reason, the optical axis of the excitation light L1 incident on the measurement object S in the integrating sphere 4 via the lens 19 in the excitation optical system 3 and the optical axis of the light to be measured L2 emitted from the integrating sphere 4 in the first detection optical system 7 are obliquely intersecting at a certain angle.

[0036] In the example of FIG. 5, the optical axis of the excitation light L1 incident on the measurement object S is inclined with respect to the surface (XY plane) of the measurement object S, and the optical axis of the light to be measured L2 is perpendicular to the surface (XY plane) of the measurement object S. Considering the light distribution characteristics of the light to be measured L2 generated from the measurement object S, the mode of being able to measure the PL component on the normal line as shown in FIG. 5 is the optimal arrangement in performing the standard PL measurement. When the optical axis of the light to be measured L2 is perpendicular to the surface of the measurement object S, it becomes possible to include the entire measurement object S within the range of the depth of field (to be in focus), and it becomes most difficult to be affected by aberrations of lenses and the like. On the other hand, the optical axis of the excitation light L1 may be perpendicular to the surface of the measurement object S. In this case, although the optical axis of the light to be measured L2 is inclined with respect to the surface of the measurement object S, by using a shift lens or a tilt lens in the excitation optical system 3, it becomes possible to include the entire measurement object S within the range of the depth of field, and it becomes possible to measure the PL component. In this way, by the optical axes of the excitation light L1 and the light to be measured L2 being obliquely intersecting, it is possible to prevent the excitation light L1 reflected by the measurement object S in the integrating sphere 4 from being directly detected by the photodetector 6.

[0037] The first detection optical system 7 is provided with an aperture 36 that restricts the detection range of the measurement light L2 in the photodetector 6. In the present embodiment, the photodetector 6 is a fiber input type detector. Further, the photodetector input end 35 is constituted by a bundle fiber 37 formed by bundling the strands of an optical fiber. Therefore, in the present embodiment, the end face 37a of the bundle fiber 37 corresponds to the aperture 36 that restricts the detection range of the measurement light L2 in the photodetector 6.

[0038] As shown in FIG. 5, the excitation light L1 directed toward the measurement object S is condensed by the lens 19 and forms an image on the surface of the measurement object S. The measurement light L2 generated in the measurement object S by the irradiation of the excitation light L1 is collimated by the lens 19 and then condensed by the lens 34, and forms an image on the end face 37a (aperture 36) of the bundle fiber 37. That is, the irradiation spot La of the excitation light L1 on the measurement object S and the aperture 36 are in an optically conjugate relationship. Since the irradiation spot La and the aperture 36 are in an optically conjugate relationship, the influence of multiple scattering in the integrating sphere 4 can be suppressed, and only the measurement light L2 generated on the surface of the measurement object S by the incidence of the excitation light L1 can be taken out from the integrating sphere 4 and detected. Therefore, in the measuring device 1, the standard PL spectrum of the measurement object S can be measured with the measurement object S placed in the integrating sphere 4.

[0039] The second detection optical system 8 is an optical system that guides the measurement light L2 diffusely reflected in the integrating sphere 4 from the integrating sphere 4 toward the photodetector 6 in the external quantum efficiency measurement. In the second detection optical system 8, the measurement light L2 output from the second port 25 of the integrating sphere 4 is input to the photodetector 6 through a photodetector input end 38 different from that of the first detection optical system 7. The photodetector input end 38 is constituted by a bundle fiber 39 (see FIG. 6) formed by bundling the strands of an optical fiber, for example, in the same manner as the photodetector input end 35 of the first detection optical system 7.

[0040] The switching unit 31 is a part that optically connects one of the first detection optical system 7 and the second detection optical system 8 to the photodetector 6. As shown in FIG. 6, for example, the switching unit 31 includes a pair of light guides 41A and 41B and an off-axis parabolic mirror 42. The light guide 41A is optically connected to the photodetector input end 35 (bundle fiber 37) on the first detection optical system 7 side. The light guide 41B is optically connected to the photodetector input end 38 (bundle fiber 39) on the second detection optical system 8 side. The direction of the reflecting surface of the off-axis parabolic mirror 42 is variable by driving means such as a stepping motor, for example. By optically coupling the off-axis parabolic mirror 42 with one of the light guides 41A and 41B, only one of the excitation light L1 from the light guide 41A and the excitation light L1 from the light guide 41B is guided toward the photodetector 6.

[0041] The calculation unit 12 is a part that calculates the external quantum efficiency and the internal quantum efficiency of the measurement object S based on the signal output from the photodetector 6. Physically, it is a computer system configured with a memory such as a RAM and a ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, a storage unit such as a hard disk, and a display unit such as a display. Examples of the computer system include a personal computer, a cloud server, and a smart device (such as a smartphone and a tablet terminal). The calculation unit 12 may be configured by a PLC (programmable logic controller) or may be configured by an integrated circuit such as an FPGA (Field-programmable gate array).

[0042] In the calculation unit 12, in the standard PL spectrum measurement, measurement data of the standard PL spectrum is generated based on the signal output from the photodetector 6, and the measurement data is stored in the storage unit. In the external quantum efficiency measurement, the calculation unit 12 calculates the external quantum efficiency of the measurement object S based on the signals (measurement signal and reference signal) output from the photodetector 6, and stores the calculated data in the storage unit. Further, the calculation unit 12 calculates the internal quantum efficiency of the measurement object S based on the measurement data of the standard PL spectrum and the calculated data of the external quantum efficiency, and stores the calculated data in the storage unit. The calculation unit 12 may output the obtained measurement data of the standard PL spectrum, the calculated data of the external quantum efficiency, and the calculated data of the internal quantum efficiency to a monitor or the like. [Procedure for ODPL Measurement Using a Measuring Device]

[0043] FIG. 7 is a flowchart of ODPL measurement using a measuring device. As shown in the figure, in the ODPL measurement using the measuring device 1, a preparation step (step S01), a standard PL spectrum measurement step (step S02), an external quantum efficiency measurement step (step S03), and an internal quantum efficiency calculation step (step S04) are performed in order.

[0044] In the preparation step S01, as shown in FIG. 8, first, the switching unit 31 is set (step S11). Here, the off-axis parabolic mirror 42 of the switching unit 31 is driven to optically connect the second detection optical system 8 to the photodetector 6. Next, the excitation light source 2 outputs the excitation light L1 (step S12), and the intensity of the excitation light L1 is adjusted (step S13). The adjustment of the intensity of the excitation light L1 is performed by adjusting a variable attenuation filter 16 or a variable attenuation filter built in the photodetector 6 so that the light output from the integrating sphere 4 due to the incidence of the excitation light L1 does not saturate the photodetector 6. After adjusting the intensity of the excitation light L1, the output of the excitation light L1 is stopped (step S14). Then, the arm 23 of the XY stage 5 is removed from the integrating sphere 4, the measurement object S is held, and the measurement object S is placed in the integrating sphere 4 while being held by the arm 23 (step S15).

[0045] In the standard PL spectrum measurement step S02, as shown in FIG. 9, first, the switching unit 31 is set (step S21). Here, the off-axis parabolic mirror 42 of the switching unit 31 is driven to optically connect the first detection optical system 7 to the photodetector 6. Next, the excitation light source 2 outputs the excitation light L1, and the excitation light L1 is incident on the measurement object S in the integrating sphere 4 (step S22), and the exposure time of the photodetector 6 is set (step S23). After setting the exposure time of the photodetector 6, the measured light L2 output from the first port 24 of the integrating sphere 4 by the irradiation of the excitation light L1 is guided to the photodetector 6 by the first detection optical system 7, and the standard PL spectrum of the measurement object S is measured (step S24). After the measurement is completed, the output of the excitation light is stopped (step S25), and the measurement data is saved (step S26).

[0046] In the external quantum efficiency measurement step S03, as shown in FIG. 10, first, the switching unit 31 is set (step S31). Here, the off-axis parabolic mirror 42 of the switching unit 31 is driven to optically connect the second detection optical system 8 to the photodetector 6. Next, the excitation light source 2 outputs the excitation light L1, and the excitation light L1 is incident on the measurement object S in the integrating sphere 4 (step S32), and the exposure time of the photodetector 6 is set (step S33). After setting the exposure time of the photodetector 6, the measured light L2 output from the second port 25 of the integrating sphere 4 by the irradiation of the excitation light L1 is guided to the photodetector 6 by the second detection optical system 8, and the measurement of the diffuse reflected light is carried out (step S34). After the measurement is completed, the output of the excitation light L1 is stopped (step S35), and the measurement object S is taken out of the integrating sphere 4 (step S36).

[0047] After taking out the measurement object S, the output of the excitation light L1 is started again (step S37), and a reference measurement is performed (step S38). In the reference measurement, with the measurement object S not placed in the integrating sphere 4, the measurement light L2 output from the second port 25 of the integrating sphere 4 is guided to the photodetector 6 by the second detection optical system 8, and the measurement of the diffuse reflected light is performed (step S38). After the measurement is completed, the output of the excitation light L1 is stopped (step S39). Then, based on the measurement result of step S34 and the measurement result of step S38, the ratio of the number of emitted light photons emitted outside the measurement object S to the number of photons of the excitation light L1 absorbed by the measurement object S is calculated. Thereby, the external quantum efficiency of the measurement object S is calculated (step S40), and the calculated data is saved (step S41).

[0048] In the internal quantum efficiency calculation step S04, as shown in FIG. 11, the measurement data of the standard PL spectrum measurement saved in step S26 and the calculation data of the external quantum efficiency saved in step S41 are read respectively (step S51). Next, based on the measurement data of the standard PL spectrum measurement that has been read, the calculation data of the external quantum efficiency, and the light extraction efficiency of the measurement object S known for the material, the internal quantum efficiency of the measurement object S is calculated (step S52). The calculated data is saved, and the process is completed (step S53).

[0049] [Operation and effect of the measuring device] As described above, in this measuring device 1, the optical axis of the excitation light L1 incident on the measurement object S in the integrating sphere 4 in the excitation optical system 3 and the optical axis of the light to be measured L2 emitted from the integrating sphere 4 in the first detection optical system 7 are skew to each other. Thereby, it is possible to prevent the excitation light L1 reflected by the measurement object S in the integrating sphere 4 from being directly detected by the photodetector 6. Further, in this measuring device 1, the irradiation spot La of the excitation light L1 on the measurement object S disposed in the integrating sphere 4 and the aperture 36 disposed in the first detection optical system 7 are in an optically conjugate relationship. Thereby, the influence of multiple scattering in the integrating sphere 4 can be suppressed, and only the light to be measured L2 generated on the surface of the measurement object S by the incidence of the excitation light L1 can be taken out from the integrating sphere 4 and detected. Therefore, in this measuring device 1, the standard PL spectrum of the measurement object S can be measured while the measurement object S is disposed in the integrating sphere 4.

[0050] In the present embodiment, the excitation light L1 directed to the measurement object S by the excitation optical system 3 and the light to be measured L2 generated by the measurement object S in the integrating sphere 4 pass through the same first port 24 of the integrating sphere 4. In this case, it becomes easier to share the optical components constituting the excitation optical system 3 and the first detection optical system 7, and the apparatus can be simplified and miniaturized.

[0051] In the present embodiment, the measuring device 1 further includes a second detection optical system 8 that guides the light to be measured L2 diffusely reflected in the integrating sphere 4 from the integrating sphere 4 toward the photodetector 6, and a switching unit 31 that optically connects the photodetector 6 to one of the first detection optical system 7 and the second detection optical system 8. In this case, by guiding the light to be measured L2 diffusely reflected in the integrating sphere 4 from the integrating sphere 4 toward the photodetector 6 using the second detection optical system 8, the external quantum efficiency of the measurement object S using the integrating sphere 4 can be measured. By switching the optical system connected to the photodetector 6 by the switching unit 31, the measurement of the standard PL spectrum and the measurement of the external quantum efficiency can be performed in the same apparatus while maintaining the state where the measurement object S is disposed in the integrating sphere 4.

[0052] [Modification Example] The present disclosure is not limited to the above-described embodiments. For example, as shown in FIG. 12, the excitation light L1 and the light to be measured L2 may pass through different ports. In the example of FIG. 12, the integrating sphere 4 has a third port 26 (one port) in addition to the first port 24 and the second port 25. The third port 26 is provided on the opposite side of the second port 25. The third port 26 is orthogonal to the opening direction of the first port 24 and opens in a direction opposite to the opening direction of the second port 25.

[0053] In this modification, the excitation light L1 directed from the excitation optical system 3 toward the measurement object S passes through the third port 26 of the integrating sphere 4. The third port 26 may also serve as a port for introducing the arm 23 of the XY stage 5 (see FIG. 1) into the integrating sphere 4. Further, the light to be measured L2 generated by the measurement object S in the integrating sphere 4 passes through the first port 24 (another port) of the integrating sphere 4. According to such a configuration, it becomes easy to ensure the skew angle between the optical axis of the excitation light L1 incident on the measurement object S in the integrating sphere 4 in the excitation optical system 3 and the optical axis of the light to be measured L2 emitted from the integrating sphere 4 in the first detection optical system 7. Therefore, it is possible to more surely prevent the excitation light L1 reflected by the measurement object S in the integrating sphere 4 from being directly detected by the photodetector 6.

[0054] Further, the aperture 36 that limits the detection range of the light to be measured L2 in the photodetector 6 does not necessarily have to be constituted by the end face 37a of the bundle fiber 37. In the example of FIG. 13, the photodetector input end 35 is directly provided in the photodetector 6 without passing through the bundle fiber 37, and the aperture 36 that limits the detection range of the light to be measured L2 is constituted by a pinhole 51 arranged to be in contact with the photodetector input end 35 of the photodetector 6. Even with such a configuration, the irradiation spot La of the excitation light L1 on the measurement object S and the aperture 36 can be made in an optically conjugate relationship.

[0055] As shown in FIG. 14, the first detection optical system 7 may have a shielding member 55 that shields stray light of the light to be measured L2. In the example of FIG. 14, the shielding member 55 is constituted by a pinhole 56 disposed between the integrating sphere 4 and the lens 19 on the optical path of the light to be measured L2. With such a configuration, it is possible to prevent the stray light of the light to be measured L2 from affecting the optical components constituting the excitation optical system 3 and the first detection optical system 7.

[0056] As shown in FIG. 15, the shielding member 55 may be constituted by a cylindrical member 57. In the example of FIG. 15, the cylindrical member 57 is, for example, a black frustum-shaped member, and is disposed between the lens 19 and the integrating sphere 4 on the optical path of the light to be measured L2 so as to increase in diameter from the integrating sphere 4 side toward the lens 19 side. The cylindrical member 57 may be in contact with or separated from the first port 24 of the integrating sphere 4. An antireflection coating for suppressing reflection of the light to be measured L2 may be provided inside the cylindrical member 57.

[0057] Also, the configuration of the switching unit 31 can take other aspects. FIG. 16 is a schematic diagram showing another example of the configuration of the switching unit. The switching unit 61 according to this modification has a base portion 71, an input portion 72, a filter unit 73 (attenuation element), and an output portion 74. The base portion 71 has, for example, a rectangular plate shape and extends in one direction from the input portion 72A, 72B side toward the output portion 74 side.

[0058] The input portion 72 is provided with a pair of input terminals 75A, 75B and a pair of mirrors 76, 77. The input terminal 75A is optically connected to the photodetector input end 35 (bundle fiber 37) on the first detection optical system 7 side, and the input terminal 75B is optically connected to the photodetector input end 38 (bundle fiber 39) on the second detection optical system 8 side.

[0059] The filter unit 73 is disposed between the input unit 72 and the output unit 74. The filter unit 73 is composed of a dimming filter unit 81 and a low-pass filter unit 82. The dimming filter unit 81 has, for example, three dimming filters 81A to 81C with different dimming degrees. The low-pass filter unit 82 has, for example, three low-pass filters 82A to 82C with different cut-off wavelengths. The output unit 74 is provided with an output terminal 83 and a mirror 84. The output terminal 83 is optically connected to the photodetector 6.

[0060] The input unit 72, the dimming filter unit 81, and the low-pass filter unit 82 are slidable, for example, in a direction orthogonal to the extending direction of the base unit 71. By sliding the input unit 72, one of the mirrors 76 and 77 is optically connected to the mirror 84 of the output unit 74. Thereby, only one of the measurement light L2 from the input terminal 75A and the measurement light L2 from the input terminal 75B is guided toward the photodetector 6.

[0061] Further, by sliding the dimming filter unit 81 and the low-pass filter unit 82, the dimming filters 81A to 81C and the low-pass filters 82A to 82C can move forward and backward on the optical axis of the measurement light L2 between the input unit 72 and the output unit 74. Thereby, it is possible to adjust the intensity of the measurement light L2 output from the output terminal 83 in multiple steps, and saturation of the measurement light L2 at the photodetector 6 can be preferably prevented.

Explanation of Reference Numerals

[0062] 1... measuring device, 3... excitation optical system, 4... integrating sphere, 6... photodetector, 7... first detection optical system, 8... second detection optical system, 24... first port (another port), 26... third port (one port), 31, 61... switching unit, 36... opening, 55... shielding member, 57... cylindrical member, 73... filter unit (attenuation element), L1... excitation light, L2... measurement light, La... irradiation spot, S... measurement object.

Claims

1. An integrating sphere in which a measurement object is disposed therein; An excitation optical system that guides excitation light toward the measurement object disposed in the integrating sphere; A photodetector that detects measurement light generated by the measurement object in the integrating sphere due to irradiation with the excitation light; A first detection optical system for standard PL spectrum measurement that guides the measurement light from the integrating sphere toward the photodetector, and in the excitation optical system, an optical axis of the excitation light incident on the measurement object in the integrating sphere and an optical axis of the measurement light emitted from the integrating sphere in the first detection optical system are skew to each other, the first detection optical system has an aperture that limits a detection range of the measurement light in the photodetector, and a measurement device in which an irradiation spot of the excitation light on the measurement object and the aperture are in an optically conjugate relationship.

2. The measurement device according to claim 1, wherein the excitation light directed toward the measurement object by the excitation optical system and the measurement light generated by the measurement object in the integrating sphere pass through the same port of the integrating sphere.

3. The measurement device according to claim 1, wherein the excitation light directed toward the measurement object by the excitation optical system passes through one port of the integrating sphere, and the measurement light generated by the measurement object in the integrating sphere passes through another port different from the one port of the integrating sphere.

4. The measurement device according to any one of claims 1 to 3, wherein the first detection optical system has a shielding member that shields stray light of the measurement light.

5. The measurement device according to claim 4, wherein the shielding member is constituted by a cylindrical member.

6. A second detection optical system for external quantum efficiency measurement that guides the measurement light diffusely reflected in the integrating sphere from the integrating sphere toward the photodetector, and a switching unit that optically connects one of the first detection optical system and the second detection optical system to the photodetector, and

7. The measurement device according to claim 6, wherein the switching unit includes an attenuation element disposed so as to be movable forward and backward on the optical axis of the measurement light.

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