Measuring device

Abstract

A measurement device 1 comprises an excitation optical system 3 for guiding excitation light L1 toward an object S under measurement, an illumination optical system 10 for forming an illumination spot Lb on the object S under measurement from illumination light L3, and an imaging unit 11 for imaging the illumination spot Lb on the object S under measurement. The illumination optical system 10 comprises a light-transmitting member comprising a central region 51 having a first color and a peripheral region 52 that surrounds the central region 51 and has a second color different from the first color. The excitation optical system 3 and illumination optical system 10 are optically connected such that, in the field of view of the imaging unit 11, the emission spot La of the excitation light L1 on the object S under measurement is included in a central spot region Lc illuminated by the illumination light L3 that has passed through the central region 51 and is surrounded by a peripheral spot region Ld illuminated by the illumination light L3 that has passed through the peripheral region 52.

Description

Technical Field

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

Background Art

[0002] As a measuring 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, for example, a semiconductor material with light having energy higher than the bandgap. In PL measurement, while the distribution of crystal structure defects can be detected, from the viewpoint of quality assurance of semiconductor wafers, improvement in the quantitativeness and reproducibility of defects is required.

[0003] As another measuring 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.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When irradiating a measurement object with excitation light as in the above-described PL measurement or ODPL measurement, it is preferable to be able to observe the irradiation spot of the excitation light on the measurement object within the field of view from the viewpoint of ensuring the ease of adjusting the irradiation spot of the excitation light. For observing the irradiation spot of the excitation light, for example, an imaging unit composed of a camera or the like can be used. However, when the optical axis of the excitation light directed toward the measurement object is inclined with respect to the imaging axis, it becomes difficult to directly observe the irradiation spot of the excitation light with the imaging unit. Also, when the sensor of the imaging unit does not have sufficient sensitivity with respect to the wavelength of the excitation light or the wavelength of the light generated by the measurement object due to the irradiation of the excitation light, it becomes difficult to directly observe the irradiation spot of the excitation light with the imaging unit.

[0006] Further, when the excitation light is light having relatively high energy such as ultraviolet light, it is conceivable that the measurement object deteriorates due to the irradiation of the excitation light. In this case, it is preferable to reduce the opportunity of irradiating the measurement object with the excitation light as much as possible, and there is also a situation where it is desired to avoid irradiating the measurement object with the excitation light separately from the measurement for observing the irradiation spot of the excitation light.

[0007] The present disclosure has been made to solve the above problems, and an object thereof is to provide a measuring apparatus capable of observing the irradiation spot of the excitation light on the measurement object within the field of view without irradiating the measurement object with the excitation light.

Means for Solving the Problems

[0008] A measuring device according to one aspect of the present disclosure includes an excitation optical system that guides excitation light toward a measurement object, an illumination optical system that forms an illumination spot by illumination light on the measurement object, and an imaging unit that images the illumination spot on the measurement object. The illumination optical system includes a light transmission member having a central region having a first color and a peripheral region having a second color different from the first color and surrounding the central region. The excitation optical system and the illumination optical system are optically connected such that, within the field of view of the imaging unit, the irradiation spot of the excitation light on the measurement object is included in the central spot region by the illumination light passing through the central region and surrounded by the peripheral spot region by the illumination light passing through the peripheral region.

[0009] In this measuring device, due to the light transmission member included in the illumination optical system, in the measurement object irradiated with the illumination light, a peripheral spot region is formed in a second color different from the first color around the central spot region. Therefore, by preliminarily aligning the irradiation spot of the excitation light with the central spot region of the illumination light, the irradiation spot of the excitation light on the measurement object within the field of view can be observed without irradiating the measurement object with the excitation light. In this configuration, since the opportunity of irradiating the measurement object with the excitation light other than during measurement can be reduced, even when the excitation light is light having relatively high energy such as ultraviolet light, it is possible to suppress deterioration of the measurement object due to the irradiation of the excitation light. Further, since the peripheral spot region surrounding the central spot region is formed in a second color different from the first color, it becomes easy to observe the entire image of the measurement object.

[0010] The light transmission member may be a colored pinhole with an opening in the central region. In this case, even when the size of the central region is reduced, the manufacture of the light transmission member becomes easy.

[0011] In the light transmission member, the peripheral region may be provided annularly around the central region. In this case, the visibility of the irradiation spot of the excitation light on the measurement object is enhanced.

[0012] The shapes of the central region and the peripheral region may coincide with the shape of the imaging region in the imaging unit. In this case, since the shape of the central region is the same as the shape of the captured image in the imaging unit, it becomes easy to observe the entire imaging region.

[0013] The light-transmitting member may further have a peripheral region that has a third color different from the second color and surrounds the peripheral region. In this case, it becomes even easier to observe the overall image of the measurement object.

Advantages of the Invention

[0014] According to the present disclosure, it is possible to observe the excitation light irradiation spot on the measurement object in the visual field without irradiating the measurement object with excitation light.

Brief Description of the Drawings

[0015]

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Embodiments for Carrying out the Invention

[0016] 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]

[0017] 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 the GaN semiconductor 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 yield of the device and promote mass production.

[0018] 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") of the measurement object is performed. 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 is performed.

[0019] 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 the 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 the 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).

[0020] The internal quantum efficiency is the ratio of the number of emitted 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 "Determination of absolute value of quantum efficiency of radiation in high quality GaN single crystals using an integrating sphere" Kazunobu Kojima et al., Journal of Applied Physics 120, 015704 (2016)).

[0021] Therefore, 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 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.

[0022] To calculate the internal quantum efficiency, it is necessary to measure the standard PL spectrum of the measurement object. Measurement using an integrating sphere is to detect 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 FIG. 3, in order to detect omnidirectional light emission, in addition to the peak (peak A in FIG. 3) originally possessed by the standard PL spectrum, a peak of the spectrum (peak B in FIG. 3) will occur. Therefore, 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 such that the standard PL spectrum of the measurement object can be measured while the measurement object is placed in the integrating sphere. Hereinafter, the configuration of this measuring device 1 will be described in detail. [Configuration of Measuring Device]

[0023] 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, an illumination light source 9, an illumination optical system 10, an imaging unit 11, and an arithmetic unit 12. In this embodiment, the excitation optical system 3, the integrating sphere 4, the photodetector 6, the first detection optical system 7, the second detection optical system 8, the illumination light source 9, the illumination optical system 10, and the imaging unit 11 are accommodated 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.

[0024] 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 HeCd laser (wavelength 325 nm), a semiconductor-excited all-solid-state UV laser (wavelength 320 nm), a semiconductor laser (e.g., an InGaN semiconductor laser (wavelength 375 nm to 530 nm), a red semiconductor laser, an infrared semiconductor laser), etc. can be used. As the incoherent light source, for example, a mercury lamp (wavelength 365 nm), an LED light source, an SLD 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, a HeCd laser, or a semiconductor-excited all-solid-state UV laser is used.

[0025] 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.

[0026] The separation optical element 18 is an element that separates the optical axis of the excitation light L1 heading toward the measurement object S in the integrating sphere 4 from 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 reflection surface 22 that reflects the measured light L2 and the illumination light L3 described later. At the reflection 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 in the integrating sphere 4 and the optical axis of the measured light L2 output from the integrating sphere 4 and heading toward the photodetector 6 are separated.

[0027] The lens 19 is constituted by, for example, a convex lens. The lens 19 condenses the excitation light L1 and the illumination light L3 directed toward the integrating sphere 4 onto the surface of the measurement object S. That is, the lens 19 forms an irradiation spot La of the excitation light L1 and an illumination spot Lb of the illumination light L3 on the measurement object S in the integrating sphere 4 (see Fig. 8(a)). Further, the lens 19 collimates the light to be measured L2 and the illumination light L3 from the integrating sphere 4.

[0028] The integrating sphere 4 is a device that diffusely reflects light on the inner wall of the spherical body 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.

[0029] 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 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 light to be measured L2 diffusely reflected in the integrating sphere 4 passes through the second port 25.

[0030] The photodetector 6 is a device that detects the light to be measured L2 generated by the measurement object 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 the array type) and the like 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 light to be measured L2.

[0031] The first detection optical system 7 is an optical system that guides the light to be measured L2 from the integrating sphere 4 toward the photodetector 6 in the 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 light to be measured 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.

[0032] 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 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 in a state of being obliquely intersecting at a certain angle.

[0033] In the example of Fig. 5, the optical axis of the excitation light L1 incident on the integrating sphere 4 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 emitted from the integrating sphere 4 is perpendicular to the surface (XY plane) of the measurement object S. In this way, by making the optical axes of the excitation light L1 and the light to be measured L2 skew to each other, 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.

[0034] The first detection optical system 7 is provided with an aperture 36 that restricts 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. Further, the photodetector input end 35 is constituted by a bundle fiber 37 in which the strands of the optical fiber are bundled. 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 light to be measured L2 in the photodetector 6.

[0035] 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 light to be measured 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. By having the irradiation spot La and the aperture 36 in an optically conjugate relationship, 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 the measuring apparatus 1, the standard PL spectrum of the measurement object S can be measured while the measurement object S is arranged in the integrating sphere 4.

[0036] The second detection optical system 8 is an optical system that guides the measurement light L2 diffusely reflected within 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 via 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) formed by bundling optical fiber strands, similar to the photodetector input end 35 of the first detection optical system 7.

[0037] 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. The switching unit 31 includes, for example, as shown in FIG. 6, a pair of light guides 41A and 41B and an off-axis paraboloidal 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 paraboloidal mirror 42 has a variable reflection surface orientation by driving means such as a stepping motor. By optically coupling the off-axis paraboloidal 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.

[0038] As a configuration for observing the irradiation spot of the excitation light L1 on the measurement object S, the measuring device 1 includes, as shown in FIG. 1, an illumination light source 9, an imaging unit 11, and an illumination optical system 10. The illumination light source 9 is a device that outputs illumination light L3 for the measurement object S. As the illumination light source 9, for example, an LED capable of outputting white light can be used. The imaging unit 11 is a part that images the illumination spot Lb (see FIGS. 8(a) and (b)) on the measurement object S by the illumination light L3. As the imaging unit 11, for example, a device having sensitivity in the visible range can be used. Examples of such a device include a color CMOS and a color CCD camera.

[0039] The illumination optical system 10 includes, in addition to the common lens 19, the separation optical element 18, and the dichroic mirror 32 with the first detection optical system 7, a light transmission member 45, a dichroic mirror 46, and lenses 47 and 48. The light transmission member 45 is a member for imparting a color for identifying the irradiation spot of the excitation light L1 to the illumination light L3. The light transmission member 45 is formed in a disk shape by a light-transmissive member such as acrylic or glass.

[0040] As shown in FIG. 7, the light transmission member 45 has a circular central region 51 having a first color and an annular peripheral region 52 having a second color different from the first color and surrounding the central region 51. Here, the light transmission member 45 is constituted by a colored pinhole 53 in which the central region 51 opens, and the first color is colorless. Any color can be used for the second color of the peripheral region 52, for example, green. In the illumination light L3 that has passed through the light transmission member 45, the color of the portion that has passed through the central region 51 remains white, and the color of the portion that has passed through the peripheral region 52 changes from white to green.

[0041] FIG. 8(a) is a schematic diagram showing the optical connection state between the excitation optical system and the illumination optical system. As shown in the figure, the illumination light L3 that has passed through the light transmission member 45 is guided by the dichroic mirror 32 or the like to the measurement object S in the integrating sphere 4. The illumination light L3 is collimated by the lens 47 and then focused by the lens 19 to form an image on the surface of the measurement object S. Thereby, an illumination spot Lb by the illumination light L3 is formed on the surface of the measurement object S.

[0042] In the examples of FIGS. 8(a) and 8(b), the optical axis of the illumination light L3 directed toward the measurement object S in the integrating sphere 4 coincides with the optical axis of the light to be measured L2 output from the integrating sphere 4. Therefore, the optical axis of the excitation light L1 directed toward the measurement object S is skew to the optical axis of the illumination light L3 directed toward the measurement object S. Here, 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 as described above, and the optical axis of the illumination light L3 is perpendicular to the surface (XY plane) of the measurement object S. The illumination light L3 reflected by the surface of the measurement object S is guided to the imaging unit 11 by a dichroic mirror 32 or the like. The illumination light L3 is collimated by the lens 19 and then focused by the lens 48 to form an image on the imaging surface of the imaging unit 11.

[0043] As shown in FIG. 8(b), the excitation optical system 3 and the illumination optical system 10 are optically connected such that, within the field of view of the imaging unit 11, the irradiation spot La of the excitation light L1 on the measurement object S is included in the central spot region Lc formed by the illumination light L3 passing through the central region 51 and surrounded by the peripheral spot region Ld formed by the illumination light L3 passing through the peripheral region 52. In the example of FIG. 8(b), the irradiation spot La of the excitation light L1 is located substantially at the center of the white circular central spot region Lc, and the green annular peripheral spot region Ld is located around it.

[0044] By arranging a target equivalent to the measurement object S in the integrating sphere 4 and pre-aligning the irradiation spot La of the excitation light L1 with the central spot region Lc of the illumination light L3, when performing actual standard PL spectrum measurement and external quantum efficiency measurement, the irradiation spot La of the excitation light L1 on the measurement object S within the field of view can be observed without irradiating the measurement object S with the excitation light L1. Further, since the peripheral spot region Ld surrounding the central spot region Lc has a second color, it is also possible to observe the structure of the measurement object S around the irradiation spot La of the excitation light L1 with the imaging unit 11.

[0045] When aligning the irradiation spot La of the excitation light L1 and the central spot region Lc of the illumination light L3, for example, a target jig equivalent to the measurement object S is arranged in the integrating sphere 4. For example, a mark such as a round shape is attached to the center of the target jig. In this state, the angles of the separation optical element 18 and the dichroic mirror 46 are adjusted, and the positions of the irradiation spot La of the excitation light L1 and the central spot region Lc of the illumination light L3 are respectively aligned with the mark of the target jig, thereby enabling the alignment of the irradiation spot La of the excitation light L1 and the central spot region Lc of the illumination light L3.

[0046] 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).

[0047] In the standard PL spectrum measurement, the calculation unit 12 generates measurement data of the standard PL spectrum based on the signal output from the photodetector 6 and stores the measurement data 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]

[0048] Figure 9 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), an excitation light irradiation spot confirmation step (step S02), a standard PL spectrum measurement step (step S03), an external quantum efficiency measurement step (step S04), and an internal quantum efficiency calculation step (step S05) are carried out in order.

[0049] In the preparation step S01, as shown in Figure 10, first, the setting of the switching unit 31 is performed (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 carried out by adjusting the variable attenuation filter 16 or the 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).

[0050] In the excitation light irradiation spot confirmation step S02, as shown in Figure 11, first, the illumination light source 9 outputs the illumination light L3 (step S21). Next, the illumination spot Lb of the illumination light L3 formed on the measurement object S in the integrating sphere 4 due to the irradiation of the illumination light L3 is imaged by the imaging unit 11 (step S22). By observing the central region 51 and the peripheral region 52 at the irradiation spot La on the measurement object S in the field of view, the irradiation spot La of the excitation light L1 on the measurement object S can be confirmed. After confirming the irradiation spot La of the excitation light L1, if necessary, the position adjustment of the measurement object S by the XY stage 5 is performed (step S23), and the output of the irradiation light is stopped (step S24).

[0051] In the standard PL spectrum measurement step S03, as shown in FIG. 12, 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 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 S32), and the exposure time of the photodetector 6 is set (step S33). After setting the exposure time of the photodetector 6, the measurement 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 S34). After the measurement is completed, the output of the excitation light is stopped (step S35), and the measurement data is saved (step S36).

[0052] In the external quantum efficiency measurement step S04, as shown in FIG. 13, first, the switching unit 31 is set (step S41). 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 S42), and the exposure time of the photodetector 6 is set (step S43). After setting the exposure time of the photodetector 6, the measurement 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 performed (step S44). After the measurement is completed, the output of the excitation light L1 is stopped (step S45), and the measurement object S is taken out of the integrating sphere 4 (step S46).

[0053] After taking out the measurement object S, the output of the excitation light L1 is started again (step S46), and reference measurement is performed (step S47). 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 measurement of the diffuse reflection light is performed (step S48). After the measurement is completed, the output of the excitation light L1 is stopped (step S49). Then, based on the measurement result of step S44 and the measurement result of step S48, 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 S50), and the calculated data is saved (step S51).

[0054] In the internal quantum efficiency calculation step S05, as shown in FIG. 14, the measurement data of the standard PL spectrum measurement saved in step S36 and the calculated data of the external quantum efficiency saved in step S51 are read respectively (step S61). Next, based on the measurement data of the standard PL spectrum measurement that has been read, the calculated data of the external quantum efficiency, and the light extraction efficiency of the measurement object S known according to the material, the internal quantum efficiency of the measurement object S is calculated (step S62). The calculated data is saved, and the process is completed (step S63). [Function and effect of the measuring device]

[0055] As described above, in the measuring device 1, in the measurement object S irradiated with the illumination light L3 by the light transmission member 45 included in the illumination optical system 10, a peripheral spot region Ld is formed in a second color different from the first color around the central spot region Lc. Therefore, by preliminarily aligning the irradiation spot La of the excitation light L1 with the central spot region Lc of the illumination light L3, the irradiation spot La of the excitation light L1 on the measurement object S within the field of view can be observed without irradiating the measurement object S with the excitation light L1. In this configuration, since the opportunity to irradiate the measurement object S with the excitation light L1 other than during measurement can be reduced, even when the excitation light L1 is light having relatively high energy such as ultraviolet light, it is possible to suppress deterioration of the measurement object S due to the irradiation of the excitation light L1. Further, since the peripheral spot region Ld surrounding the central spot region Lc is formed in a second color different from the first color, it is also easy to observe the entire image of the measurement object S.

[0056] In the present embodiment, the light transmission member 45 is constituted by a colored pinhole having an opening in the central region 51. In this case, even when the size of the central spot region Lc is reduced, it becomes easy to manufacture the light transmission member. Further, in the light transmission member 45, since the peripheral region 52 is provided annularly around the central region 51, the visibility of the irradiation spot La of the excitation light L1 on the measurement object S is enhanced. [Modification Example]

[0057] The present disclosure is not limited to the above-described embodiments. For example, in the above-described embodiments, the measuring device 1 for inspecting the distribution of structural defects and the quantitativeness of defects in a semiconductor wafer by ODPL measurement is exemplified. However, the present disclosure can be applied to other measuring devices provided with an excitation optical system for guiding excitation light toward a measurement object. The other measuring devices are not necessarily limited to devices provided with an integrating sphere. Examples of such other measuring devices include a fluorescence microscope, a photoluminescence measuring device, and the like. In the above-described embodiment, as shown in FIG. 8(a), the optical axis of the excitation light L1 directed toward the integrating sphere 4 is obliquely intersecting with the optical axis of the illumination light L3 directed toward the integrating sphere 4. However, in other measuring devices, for example, as shown in FIG. 15, by using a dichroic mirror 55, the optical axis of the excitation light L1 directed toward the measurement object S and the optical axis of the illumination light L3 directed toward the measurement object S may coincide with each other.

[0058] Regarding the light transmission member 45 that forms the central spot region Lc and the peripheral spot region Ld on the measurement object S, various modifications can also be adopted. For example, in the example of FIG. 7, the light transmission member 45 is constituted by a colored pinhole 53 in which the central region 51 is open. However, the central region 51 may be formed of, for example, colorless acrylic instead of a space formed by a pinhole. Even in such a configuration, the irradiation spot La of the excitation light L1 on the measurement object S within the visual field can be observed without irradiating the measurement object S with the excitation light L1.

[0059] The arrangement pattern of the central region 51 and the peripheral region 52 of the light transmission member 45 can also adopt various modifications. For example, like the light transmission member 45A shown in FIG. 16(a), an annular peripheral region 52 of a second color may be arranged around a circular central region 51 of a first color. For example, like the light transmission member 45B shown in FIG. 16(b), a peripheral region 52 of a second color extending radially from the central region 51 may be arranged around a circular central region 51 of a first color. In the example of FIG. 16(b), four strip-shaped peripheral regions 52 are arranged around the central region 51 with a phase angle of 90°. According to these configurations, when observing the irradiation spot La of the excitation light L1 on the measurement object S within the visual field, the visibility of the illumination spot Lb of the illumination light L3 can be sufficiently ensured.

[0060] Further, for example, like the light transmission member 45C shown in FIG. 16(c), it may further have a peripheral region 54 that has a third color different from the second color and surrounds the peripheral region 52. In this case, since the peripheral region 54 is further extended outside the peripheral region 52, it becomes even easier to observe the entire image of the measurement object S. The third color applied to the peripheral region 52 may be the same as the first color or different from the first color.

[0061] For example, like the light transmission member 45D shown in FIG. 17(a), the shapes of the central region 51 and the peripheral region 52 may match the shape of the imaging region of the imaging unit 11. In the example of FIG. 17(a), the imaging region of the imaging unit 11 (the pixel region of the imaging element constituting the imaging unit 11) is rectangular. Correspondingly, the shapes of both the central region 51 and the peripheral region 52 are rectangular. According to such a configuration, since the shape of the central region 51 is the same as the shape of the captured image by the imaging unit 11, it becomes easy to observe the entire imaging region.

[0062] For example, like the light transmission member 45E shown in FIG. 17(b), the peripheral region 52 may be arranged only at the boundary portion with the central region 51. Further, for example, like the light transmission member 45F shown in FIG. 17(c), the peripheral region 52 arranged at the boundary portion with the central region 51 may be discontinuous in the circumferential direction. In the example of FIG. 17(c), the peripheral region 52 is divided into four in the circumferential direction of the light transmission member 45F. Also in these configurations, when observing the irradiation spot La of the excitation light L1 on the measurement object S within the visual field, sufficient visibility of the illumination spot Lb of the illumination light L3 can be ensured.

Explanation of Reference Numerals

[0063] 1... Measurement device, 3... Excitation optical system, 10... Illumination optical system, 11... Imaging unit, 45, 45A to 45F... Light transmission members, 51... Central region, 53... Colored pinhole, 52, 54... Peripheral regions, L1... Excitation light, La... Irradiation spot, Lb... Illumination spot, Lc... Central spot region, Ld... Peripheral spot region, S... Measurement object.

Claims

1. An excitation optical system that guides excitation light toward a measurement object, An illumination optical system that forms an illumination spot on the measurement object with illumination light, An imaging unit that images the illumination spot on the measurement object, and comprising: The illumination optical system includes a light transmission member having a central region having a first color and a peripheral region having a second color different from the first color and surrounding the central region. The excitation optical system and the illumination optical system are optically connected such that, within the field of view of the imaging unit, the irradiation spot of the excitation light on the measurement object is included in a central spot region by the illumination light passing through the central region and is surrounded by a peripheral spot region by the illumination light passing through the peripheral region. A measuring device.

2. The measuring device according to claim 1, wherein the light transmission member is a colored pinhole with the central region being an opening.

3. The measuring device according to claim 1 or 2, wherein the peripheral region is provided annularly around the central region.

4. The measuring device according to any one of claims 1 to 3, wherein the shapes of the central region and the peripheral region coincide with the shape of the imaging region in the imaging unit.

5. The measuring device according to any one of claims 1 to 4, wherein the light transmission member further has a peripheral region surrounding the peripheral region and having a third color different from the second color.

Images