Measuring device

Abstract

A measuring device 1 comprises an exciting light source 2, an integrating sphere 4 inside which an object S to be measured is placed, an excitation optical system 3, a light detector 6 for detecting light L2 to be detected, and a first detection optical system 7, wherein: the first detection optical system 7 has an opening portion 36 for restricting a detection zone of the light L2 to be detected; the excitation optical system 3 and the first detection optical system 7 include a separating optical element 18 for separating an optical axis of exciting light L1 and an optical axis of the light L2 to be detected, a lens 19 (first condensing element), and a lens 34 (second condensing element); the optical axis of the exciting light L1 incident on the object S being measured, and the optical axis of the light L2 to be detected, emitted from the integrating sphere 4, are caused to intersect obliquely by means of the separating optical element 18 and the lens 19; and an irradiation spot La and the opening portion 36 are caused to have an optically conjugate relationship by means of the lens 19 and the lens 34.

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 bandgap. 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 ensuring the quality of semiconductor wafers, improvement in the quantitativeness 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 lifetime 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 light incident on the integrating sphere and 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 excitation light source that outputs excitation light, an integrating sphere in which a measurement object is disposed inside, an excitation optical system that guides the excitation light toward the measurement object disposed 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 measurement light from the integrating sphere toward the photodetector. The first detection optical system has an aperture that limits the detection range of the light to be measured in the photodetector. The excitation optical system and the first detection optical system include a separation optical element that separates the optical axis of the excitation light directed toward the measurement object in the integrating sphere and the optical axis of the light to be measured output from the integrating sphere and directed toward the photodetector, a first condensing element that forms an irradiation spot of the excitation light on the measurement object, and a second condensing element that condenses the light to be measured on the aperture. 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 obliquely crossed by the separation optical element and the first condensing element, and the irradiation spot of the excitation light on the measurement object and the aperture are in an optically conjugate relationship by the first condensing element and the second condensing element.

[0010] In this measuring device, in the excitation optical system, the optical axis of the excitation light incident on the measurement object in the integrating sphere and the optical axis of the light to be measured emitted from the integrating sphere in the first detection optical system are obliquely intersected by a separating optical element and a first condensing element. 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 by the first condensing element and the second condensing element. 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 separating optical element may be constituted by a perforated mirror having an aperture for passing the excitation light and a reflecting surface for reflecting the light to be measured. In this case, the separating optical element can be simply configured. Further, compared with the case where the optical axis of the excitation light and the optical axis of the light to be measured are separated using a filter or the like, unnecessary attenuation of the intensity of the excitation light and the intensity of the light to be measured can be avoided.

[0012] The optical axis of the excitation light incident on the integrating sphere may be inclined with respect to the surface of the measurement object, and the optical axis of the light to be measured emitted from the integrating sphere may be perpendicular to the surface of the measurement object. In this case, it becomes easy to construct the first detection optical system for guiding the light to be measured to the photodetector.

[0013] The optical axis of the excitation light incident on the integrating sphere may be perpendicular to the surface of the measurement object, and the optical axis of the light to be measured emitted from the integrating sphere may be inclined with respect to the surface of the measurement object. In this case, it becomes easy to construct the excitation optical system for guiding the excitation light to the measurement object in the integrating sphere.

[0014] The first condensing element may be arranged such that the surface of the measurement object is positioned within the depth of focus of the first condensing element. Thereby, even when the optical axis of the light to be measured is inclined with respect to the surface of the measurement object, it becomes easy to focus on the measurement object.

[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 suitably 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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[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. [Schematic of 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, when inspecting both the distribution of structural defects and the quantitativeness of defects in a 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 internal quantum efficiency (IQE) of the measurement object S is calculated using the standard photoluminescence spectrum (hereinafter referred to as "standard PL spectrum") of the measurement object S.

[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 emitted light photons generated in the measurement object to the number of excitation light 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 described above). 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.

[0025] To calculate the internal quantum efficiency, it is necessary to measure the standard PL spectrum of the measurement object. Measurement using an integrating sphere involves detecting the light incident on the integrating sphere and the omnidirectional light generated from the measurement object S. When attempting to measure the standard PL spectrum using an integrating sphere, for example, as shown in FIG. 3, in order to detect omnidirectional light emission, in addition to the peak (peak A in FIG. 3) that the standard PL spectrum originally has, a peak of the spectrum (peak B in FIG. 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 an arithmetic unit 12. In the present 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 housed in a housing 13 made of a member such as metal. The excitation light source 2, the XY stage 5, and the arithmetic 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), a second harmonic of a YAG laser (wavelength 532 nm), a fourth harmonic of a YAG laser (wavelength 266 nm), a semiconductor laser (e.g., InGaN semiconductor laser (wavelength 375 nm - 530 nm), red semiconductor laser, 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, a 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), etc. are 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 (first condensing element). 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 heading toward the measurement object S and the optical axis of the measured light L2 generated in the measurement object S by 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 measured light L2 described later. At the reflecting surface 22, the measured light L2 is reflected at a position shifted from the opening 21. Thereby, the optical axis of the excitation light L1 heading toward the measurement object S and the optical axis of the measured light L2 output from the integrating sphere 4 and heading 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 within the integrating sphere 4. Further, the lens 19 collimates the light to be measured L2 from the integrating sphere 4.

[0031] The integrating sphere 4 is a device that diffusely reflects light on the inner wall of the spherical body coated 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 light to be measured L2 generated by the measurement object S inside 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 light to be measured L2 diffusely reflected inside 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 upon irradiation with 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 this 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 (e.g., 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 standard PL spectrum measurement. The first detection optical system 7 includes, in addition to the common lens 19 and the separation optical element 18 with the excitation optical system 3, a dichroic mirror 32, a mirror 33, and a lens 34 (the second condensing element). 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 standard PL spectrum measurement. As shown in the figure, in 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 measurement light L2 generated by the measurement object S upon irradiation with 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 measurement light L2 emitted from the integrating sphere 4 in the first detection optical system 7 are in a state of being 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. When considering the light distribution characteristics of the light to be measured L2 generated from the measurement object S, making it possible to measure the PL component on the normal line as shown in Fig. 5 is the optimal arrangement for performing 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 depth of field range (bring it into focus), and it becomes least susceptible to the influence of aberrations such as those of a lens. On the other hand, the optical axis of the excitation light L1 may also 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 depth of field range, and it becomes possible to measure the PL component. In this way, by having the optical axes of the excitation light L1 and the light to be measured L2 intersect obliquely, 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 limits the detection range of the light to be measured L2 in the photodetector 6. In the present embodiment, the photodetector 6 is a fiber input type detector. Also, 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 limits the detection range of the light to be measured 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 (opening 36) of the bundle fiber 37. That is, the irradiation spot La of the excitation light L1 on the measurement object S and the opening 36 are in an optically conjugate relationship. Since the irradiation spot La and the opening 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 toward the photodetector 6 from the integrating sphere 4 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, for example, a bundle fiber 39 (see Fig. 6) in which the strands of the optical fiber are bundled, similar to 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 side of the first detection optical system 7. The light guide 41B is optically connected to the photodetector input end 38 (bundle fiber 39) on the side of the second detection optical system 8. The off-axis parabolic mirror 42 has a variable reflection surface orientation by driving means such as a stepping motor. When the off-axis parabolic mirror 42 is optically coupled to 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 arithmetic 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 arithmetic 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 arithmetic 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 arithmetic 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 Performing 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 this 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 into 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 inside 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 from 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 light to be measured 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 respectively read (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 apparatus 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 L2 to be measured emitted from the integrating sphere 4 in the first detection optical system 7 are skew to each other by the separating optical element 18 and the lens 19. 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 apparatus 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 by the lens 19 and the lens 34. Thereby, the influence of multiple scattering in the integrating sphere 4 can be suppressed, and only the light L2 to be measured 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 apparatus 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 separating optical element 18 is constituted by a perforated mirror having an aperture 21 that allows the excitation light L1 to pass through and a reflecting surface 22 that reflects the light L2 to be measured. In this case, the separating optical element 18 can be simply configured. Further, unnecessary attenuation of the intensity of the excitation light L1 and the intensity of the light L2 to be measured can be avoided as compared with the case where the optical axes of the excitation light L1 and the light L2 to be measured are separated using a filter or the like.

[0051] In the present embodiment, the optical axis of the excitation light L1 incident on the integrating sphere 4 is inclined with respect to the surface of the measurement object S, and the optical axis of the light L2 to be measured emitted from the integrating sphere 4 is perpendicular to the surface of the measurement object S. In this case, it becomes easy to construct the first detection optical system 7 that guides the light L2 to be measured to the photodetector 6.

[0052] In this embodiment, the measuring device 1 further includes a second detection optical system 8 that guides the measurement light L2 diffusely reflected inside the integrating sphere 4 from the integrating sphere 4 toward the photodetector 6, and a switching unit 31 that optically connects one of the first detection optical system 7 and the second detection optical system 8 to the photodetector 6. In this case, by guiding the measurement light L2 diffusely reflected inside the integrating sphere 4 from the integrating sphere 4 toward the photodetector 6 using the second detection optical system 8, it is possible to measure the external quantum efficiency of the measurement object S using the integrating sphere 4. 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 arranged in the integrating sphere 4.

[0053] [Modification Example] The present disclosure is not limited to the above-described embodiment. In the above-described embodiment, the optical axis of the excitation light L1 incident on the integrating sphere 4 is inclined with respect to the surface of the measurement object S, and the optical axis of the measurement light L2 emitted from the integrating sphere 4 is perpendicular to the surface of the measurement object S. However, the relationship between the inclination of the optical axis of the excitation light L1 and the optical axis of the measurement light L2 may be reversed. That is, as shown in FIG. 12, the optical axis of the excitation light L1 incident on the integrating sphere 4 may be perpendicular to the surface of the measurement object S, and the optical axis of the measurement light L2 emitted from the integrating sphere 4 may be inclined with respect to the surface of the measurement object S. In this case, it becomes easy to construct the excitation optical system 3 that guides the excitation light L1 to the measurement object S inside the integrating sphere 4.

[0054] Also, in this modification example, the lens 19 is arranged such that the surface of the measurement object S is positioned within the depth of focus of the lens 19. As the lens 19, a lens with a deep depth of field, a tilt lens, or a shift lens may be used. In this case, it becomes possible to focus on the entire detection range by the photodetector 6 on the surface of the measurement object S. Thereby, even when the optical axis of the measurement light L2 is inclined with respect to the surface of the measurement object S, it becomes easy to focus on the measurement object S.

[0055] Alternatively, an integrating hemisphere 4A may be used instead of the integrating sphere 4. In the example of FIG. 13, the integrating hemisphere 4A has a first port 24A and a second port 25A. The first port 24A is open in a direction inclined with respect to the scanning plane (XY plane) of the measurement object S by the XY stage 5. The second port 25A is open in a direction perpendicular to the scanning plane (XY plane) of the measurement object S by the XY stage 5.

[0056] In the example of FIG. 13, the excitation light L1 directed toward the measurement object S by the excitation optical system 3 is condensed by the lens 51 and enters the integrating hemisphere 4A through the first port 24A of the integrating hemisphere 4A. Further, the light to be measured L2 generated by the measurement object S in the integrating hemisphere 4A exits the integrating hemisphere 4A through the second port 25A of the integrating hemisphere 4A and is collimated by the lens 52. Even with such a configuration, the optical axis of the excitation light L1 incident on the measurement object S in the integrating hemisphere 4A in the excitation optical system 3 and the optical axis of the light to be measured L2 exiting the integrating hemisphere 4A in the first detection optical system 7 can be made to intersect obliquely by the separation optical element 18 and the lens 51.

[0057] Also, regarding the configuration of the switching unit 31, other embodiments can be adopted. FIG. 14 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 unit 71, an input unit 72, a filter unit 73 (attenuation element), and an output unit 74. The base unit 71 is, for example, in the shape of a rectangular plate and extends in one direction from the input unit 72A, 72B side toward the output unit 74 side.

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

[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 light attenuation filter unit 81 and a low-pass filter unit 82. The light attenuation filter unit 81 has, for example, three light attenuation filters 81A to 81C with different light attenuation 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 light attenuation 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 light attenuation filter unit 81 and the low-pass filter unit 82, the light attenuation 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, 2... excitation light source, 3... excitation optical system, 4... integrating sphere, 6... photodetector, 7... first detection optical system, 8... second detection optical system, 18... separation optical element, 19, 51... lens (first condensing element), 21... aperture, 22... reflecting surface, 31, 61... switching unit, 34... lens (second condensing element), 36... aperture, 73... filter unit (attenuation element), L1... excitation light, L2... measurement light, La... irradiation spot, S... measurement object.

Claims

1. An excitation light source that outputs excitation light, An integrating sphere in which a measurement object is disposed inside, An excitation optical system that guides the excitation light toward the measurement object disposed 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, A first detection optical system for measuring a standard PL spectrum that guides the light to be measured from the integrating sphere toward the photodetector, and includes: The first detection optical system has an aperture that limits a detection range of the light to be measured in the photodetector, The excitation optical system and the first detection optical system, A separation optical element that separates an optical axis of the excitation light toward the measurement object in the integrating sphere and an optical axis of the light to be measured output from the integrating sphere and directed toward the photodetector, A first condensing element that forms an irradiation spot of the excitation light on the measurement object, A second condensing element that condenses the light to be measured on the aperture, and has: An optical axis of the excitation light incident on the measurement object in the integrating sphere in the excitation optical system and an optical axis of the light to be measured exiting from the integrating sphere in the first detection optical system are obliquely crossed by the separation optical element and the first condensing element, A measurement device in which the irradiation spot of the excitation light on the measurement object and the aperture are in an optically conjugate relationship by the first condensing element and the second condensing element.

2. The measurement device according to claim 1, wherein the separation optical element is constituted by a perforated mirror having an aperture that allows the excitation light to pass therethrough and a reflecting surface that reflects the light to be measured.

3. The measurement device according to claim 1 or 2, wherein an optical axis of the excitation light incident on the integrating sphere is inclined with respect to a surface of the measurement object, and an optical axis of the light to be measured exiting from the integrating sphere is perpendicular to the surface of the measurement object.

4. The measurement device according to claim 1 or 2, wherein an optical axis of the excitation light incident on the integrating sphere is perpendicular to a surface of the measurement object, and an optical axis of the light to be measured exiting from the integrating sphere is inclined with respect to the surface of the measurement object.

5. The measurement device according to claim 4, wherein the first condensing element is disposed such that a surface of the measurement object is positioned within a depth of focus of the first condensing element.

6. A second detection optical system for measuring an external quantum efficiency that guides the light to be measured diffusely reflected in the integrating sphere from the integrating sphere toward the photodetector, The measuring device according to any one of claims 1 to 5, further comprising a switching unit that optically connects one of the first detection optical system and the second detection optical system to the photodetector.

7. The measuring 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 light to be measured.

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