Inspection device and inspection method

Abstract

To accurately derive color unevenness of a light emitting element.SOLUTION: An inspection device 1 for inspecting a sample S having a plurality of light-emitting elements formed thereon, comprises: an excitation light source 20 which generates excitation light which is applied to the sample S; a dichroic mirror 60 which splits fluorescence from the sample S by transmitting or reflecting the fluorescence depending on wavelength thereof; a camera 81 which captures an image of the fluorescence reflected by the dichroic mirror 60; a camera 82 which captures an image of the fluorescence passed through the dichroic mirror 60; and a control device 100 which, on the basis of a first fluorescence image obtained by the camera 81 and a second fluorescence image obtained by the camera 82, derives color unevenness information of the light-emitting elements. In the dichroic mirror 60, an edge shift width, which is a width of a wavelength band in which transmittance and reflectance vary in accordance with change in wavelength, is wider than a full width at half maximum of a normal fluorescence spectrum of the light-emitting elements.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] One aspect of the present invention relates to an inspection apparatus and an inspection method. [Background technology]

[0002] As a method for determining whether a group of light-emitting elements formed on a wafer is formed to be good or bad, a method is known in which the photoluminescence emitted by the light-emitting elements is observed and the quality of the light-emitting elements is determined based on the brightness of the photoluminescence (see, for example, Patent Document 1).

[0003] In the method described in Patent Document 1, photoluminescence (specifically, fluorescence) emitted by a light-emitting element is separated into a long wavelength side and a short wavelength side by an optical element, and the images of the two are simultaneously measured by two imaging units. With this configuration, it is possible to derive color spot information of the light-emitting element based on the ratio of the luminance values ​​of the long wavelength side and the short wavelength side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-10834 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, an example of an optical element that separates the fluorescence into a long wavelength side and a short wavelength side is a dichroic mirror that reflects light of a specific wavelength and transmits light of other wavelengths. A problem with such an optical element is that it cannot properly separate fluorescence with a narrow wavelength range. If the fluorescence is not properly separated according to wavelength, there is a risk that the color spot of the light-emitting element cannot be derived with high accuracy.

[0006] One aspect of the present invention has been made in view of the above-described circumstances, and has an object to derive color spots of a light-emitting element with high accuracy by appropriately separating fluorescence according to wavelength. [Means for solving the problem]

[0007] An inspection device according to one embodiment of the present invention is an inspection device for inspecting an object on which a plurality of light-emitting elements are formed, and includes an excitation light source that generates excitation light to be irradiated onto the object, an optical element that separates fluorescence from the object by transmitting or reflecting it depending on the wavelength, a first imaging unit that images the fluorescence reflected in the optical element, a second imaging unit that images the fluorescence that has transmitted through the optical element, and a processing unit that derives color spot information of the light-emitting element based on a first fluorescence image acquired by the first imaging unit and a second fluorescence image acquired by the second imaging unit, and an edge transition width, which is the width of the wavelength band in which the transmittance and reflectance change depending on the change in wavelength in the optical element, is wider than the full width at half maximum of the normal fluorescence spectrum of the light-emitting element.

[0008] In the inspection device according to one aspect of the present invention, the edge transition width, which is the width of the wavelength band in which the transmittance and reflectance change according to the change in wavelength in the optical element, is made wider than the full width at half maximum of the normal fluorescence spectrum of the light-emitting element. For example, when an optical element with a narrow edge transition width is used, it is likely to be difficult to appropriately separate fluorescence with a narrow wavelength width. In this regard, as in the inspection device according to one aspect of the present invention, an optical element with an edge transition width wider than the full width at half maximum of the normal fluorescence spectrum, that is, an optical element that is sufficiently wide in consideration of the wavelength width of the fluorescence, is used, so that the fluorescence can be easily separated according to wavelength. This makes it possible to derive color spot information with high accuracy from the first fluorescence image and the second fluorescence image based on each fluorescence separated according to wavelength.

[0009] In the above inspection device, the edge transition width of the optical element may be 150 nm or less. If the edge transition width is made too wide, the resolution of the optical element may decrease, which may affect the original function of the optical element, which is to separate fluorescence into short and long wavelength sides. In this regard, by making the edge transition width wider than the full width at half maximum of the normal fluorescence spectrum and 150 nm or less, it is possible to easily separate the fluorescence into short and long wavelength sides while dealing with fluorescence with a narrow wavelength width.

[0010] In the above inspection device, the optical element may be a dichroic mirror. With this configuration, it is possible to easily separate the fluorescence according to wavelength.

[0011] In the above inspection device, the processing unit may derive color mottle information of the light emitting element by further considering the rate of change in transmittance or reflectance with respect to the change in wavelength in the optical element. The color mottle information is derived by considering, for example, the ratio of brightness of each separated fluorescent image. When an optical element with a wide edge transition width is used, the transmittance and reflectance change according to the change in wavelength, and therefore the ratio of brightness of each fluorescent image is considered to be different from that when a normal optical element (optical element with a narrow edge transition width) is used. In this regard, by deriving color mottle information by considering the rate of change in transmittance or reflectance with respect to the change in wavelength in the optical element, the influence of using an optical element with a wide edge transition width can be removed, and color mottle information can be derived with high accuracy.

[0012] In the above inspection device, the processing unit may derive color spot information between a plurality of light-emitting elements, thereby making it possible to output color spot information for each object and, for example, to perform pass / fail judgment for each light-emitting element.

[0013] In the above inspection device, the processing unit may derive color spot information in each light-emitting element, thereby making it possible to output the color spot information for each light-emitting element, and to identify, for example, abnormal parts in each light-emitting element.

[0014] In the above inspection device, the processing unit may correct the wavelength shift for each pixel of the fluorescent image according to its position within the field of view of the imaging unit. The angle of light incident from the object to the optical element differs depending on the position within the field of view of the imaging unit. The difference in the angle of incidence to the optical element causes a difference in the central wavelength of the fluorescence (wavelength shift). In other words, the position within the field of view causes a difference in the central wavelength of the fluorescence (wavelength shift) for each pixel. In this regard, as described above, by correcting the wavelength shift according to the position within the field of view of the imaging unit, it is possible to suppress the wavelength shift caused by the position within the field of view and properly acquire the original fluorescence for each pixel.

[0015] In the above inspection device, the processing unit may correct the wavelength shift for each pixel based on the incident angle of the fluorescence onto the optical element for each pixel estimated according to the position within the field of view and the optical characteristics of the optical element related to the amount of change in wavelength according to the incident angle of the fluorescence. Since the relationship between the position within the field of view and the incident angle onto the optical element and the amount of change in wavelength according to the incident angle are specified in advance, the amount of change in wavelength for that pixel can be derived from the position within the field of view, so that the wavelength shift can be easily and appropriately corrected for each pixel.

[0016] In the above inspection device, the processing unit may correct the wavelength shift for each pixel so that the wavelength dispersion of each pixel in the field of view is reduced, thereby suppressing the variation in the central wavelength of the fluorescence for each pixel in the field of view, and thus making it possible to appropriately correct the wavelength shift due to the position in the field of view.

[0017] The above inspection device may further include a spectroscope that resolves the fluorescence by wavelength and measures the spectrum, and the processing unit, in a preprocessing performed before deriving the color spot information, may identify a first fluorescence intensity, which is the original fluorescence intensity, and a second fluorescence intensity, which is an abnormal fluorescence intensity smaller than the first fluorescence intensity, based on the spectrum, and may determine the illumination luminance of the excitation light to be irradiated to the object so that the first fluorescence intensity is greater than the second fluorescence intensity by a predetermined value or more, and the excitation light source may generate the excitation light with the illumination luminance determined by the processing unit. The original fluorescence has a higher increase rate when the illumination luminance of the excitation light is increased than the abnormal fluorescence caused by impurities or defects. In other words, when the illumination luminance of the excitation light is low, the difference in intensity between the original fluorescence and the abnormal fluorescence is small, and there is a risk that the original fluorescence will be buried in the abnormal fluorescence, whereas when the illumination luminance of the excitation light is high, the difference in intensity between the original fluorescence and the abnormal fluorescence is large, and the original fluorescence is prevented from being buried in the abnormal fluorescence. As described above, in the preprocessing, the illumination luminance of the excitation light is determined so that the first fluorescence intensity, which is the original fluorescence intensity, is sufficiently greater than the second fluorescence intensity, which is the abnormal fluorescence intensity. This makes it possible to determine the illumination luminance of the excitation light so that the original fluorescence is not buried, and to accurately derive color spot information.

[0018] In the above inspection device, when the excitation light having the determined illumination luminance is generated by the excitation light source and the fluorescence is captured by the first and second imaging units, and the amount of light incident on at least one of the first and second imaging units becomes saturated, a filter for limiting the amount of light may be inserted in front of the imaging unit that becomes saturated. This makes it possible to appropriately prevent the imaging units from becoming saturated even when the illumination luminance of the excitation light is increased.

[0019] In the above inspection device, the excitation light source may generate pulsed excitation light. By irradiating the pulsed light, the normal fluorescence and the abnormal fluorescence are always compared at their peak intensities, making it possible to easily and reliably determine whether the first fluorescence intensity is sufficiently greater than the second fluorescence intensity.

[0020] In the above inspection device, when the excitation light having the determined illumination luminance is generated by the excitation light source and the fluorescence is captured by the first and second imaging units, and the amount of incident light to at least one of the first and second imaging units becomes saturated, the processing unit may suppress the amount of incident light by adjusting the duty ratio of the pulsed light. The imaging unit may be saturated by the amount of incident light, i.e., the intensity of the fluorescence x time, but by changing the duty ratio of the pulsed light to adjust the incidence time of the fluorescence, it is possible to appropriately suppress saturation of the imaging unit without changing the intensity of the fluorescence (the ratio between normal fluorescence and abnormal fluorescence).

[0021] In the above inspection device, the excitation light source may synchronize the frequency of the pulsed light to an integer multiple of the reciprocal of the exposure time of the first imaging unit and the second imaging unit, thereby making it possible to make the number of pulsed lights included in each exposure time the same, and to prevent the amount of incident fluorescent light from differing between each exposure time.

[0022] In the above inspection device, the processing unit may derive the luminance and the center of gravity of the fluorescent wavelength of each light-emitting element based on the first and second fluorescent images, and determine a light-emitting element with a luminance in which the variation in the center of gravity of the fluorescent wavelength is greater than a predetermined value as a defective product, and determine a light-emitting element with a luminance in which the variation in the center of gravity of the fluorescent wavelength is equal to or less than the predetermined value as a good product. The center of gravity (central wavelength) of the fluorescent wavelength is more likely to fluctuate (vary) in a luminance band that is defective. Therefore, by determining a light-emitting element with a luminance (luminance band) in which the variation in the center of gravity of the fluorescent wavelength is greater than a predetermined value as a defective product, it is possible to easily determine whether the product is good or bad with high accuracy.

[0023] The inspection device may further include a holding member for holding the object, and the holding member may have a temperature control function. By providing the holding member for holding the object with a temperature control function, it is possible to suppress drift in the temperature of the object caused by illumination and the associated drift in the fluorescence wavelength.

[0024] The inspection device may further include a holding member for holding the object, and the holding member may adsorb only the peripheral portion of the object. By the holding member adsorbing only the peripheral portion of the object, the object is held in a state in which the center portion of the object is floating (not in contact with the holding member), and the wavelength shift caused by the temperature change of the object can be more appropriately suppressed.

[0025] In the above inspection device, the processing unit may change the shading of the fluorescent image every time the object and the illumination luminance of the excitation light are changed, thereby making it possible to apply appropriate shading according to the object and the illumination luminance.

[0026] In the above inspection apparatus, the excitation light source may switch the illumination luminance of the excitation light multiple times, so that data is acquired at different illumination luminances, allowing a more accurate pass / fail determination to be made.

[0027] An inspection method according to one aspect of the present invention derives color spot information of the light-emitting elements based on a first fluorescence image obtained by irradiating an object having a plurality of light-emitting elements formed thereon with excitation light, and imaging the fluorescence reflected by an optical element that separates the fluorescence from the object by transmitting or reflecting it according to its wavelength, and a second fluorescence image obtained by imaging the fluorescence that has transmitted through the optical element, the inspection method including the steps of: resolving the fluorescence by wavelength and measuring a spectrum; identifying a first fluorescence intensity, which is the original fluorescence intensity, and a second fluorescence intensity, which is an abnormal fluorescence intensity smaller than the first fluorescence intensity, based on the spectrum; determining an illumination luminance of the excitation light to be irradiated to the object such that the first fluorescence intensity is greater than the second fluorescence intensity by a predetermined value or more; and generating excitation light of the determined illumination luminance.

[0028] The above inspection method may further include a step of inserting a filter to limit the amount of light before the imaging unit when the amount of incident light of the imaging unit that acquires the fluorescence image becomes saturated due to the excitation light having the determined illumination brightness being irradiated onto the object.

[0029] The above inspection method may further include a step of suppressing the amount of incident light by adjusting the duty ratio of the excitation light, which is pulsed light, when the amount of incident light in the imaging unit that acquires the fluorescent image becomes saturated due to the excitation light having the determined illumination brightness being irradiated onto the object. Effect of the Invention

[0030] According to an aspect of the present invention, the inspection device and inspection method can accurately derive color spots of the light-emitting element by appropriately separating the fluorescent light according to wavelength. [Brief description of the drawings]

[0031] [Figure 1] 1 is a configuration diagram of an inspection device according to an embodiment of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating an emission spectrum and characteristics of a dichroic mirror. [Diagram 3] FIG. 13 is a diagram showing the sorting results of each light-emitting element according to the evaluation index. [Figure 4] 11A and 11B are diagrams illustrating correction of a deviation of a central wavelength. [Diagram 5] 11 is a flowchart of an inspection method executed by the inspection device. [Figure 6] 11A and 11B are diagrams illustrating differences in the angle of incidence depending on the position within the field of view. [Figure 7] FIG. 13 is a diagram showing the spectral intensity according to the illumination luminance. [Figure 8] FIG. 1 is a configuration diagram of an optical system using a spectroscope. [Figure 9] 13 is a flowchart showing a process of adjusting illumination luminance. [Figure 10] FIG. 11 is a diagram illustrating adjustment of a duty ratio. [Figure 11] 11A and 11B are diagrams for explaining pass / fail judgment of a light emitting element according to the variation in the center of gravity of the fluorescent wavelength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0033] FIG. 1 is a configuration diagram of an inspection device 1 according to the present embodiment. The inspection device 1 is a device for inspecting a sample S (object). The sample S is, for example, a semiconductor device in which a plurality of light-emitting elements are formed on a wafer. The light-emitting elements are, for example, LEDs, mini LEDs, μLEDs, SLD elements, laser elements, vertical cavity laser elements (VCSELs), and the like. The inspection device 1 derives color spot information between the plurality of light-emitting elements by observing photoluminescence (specifically, fluorescence) of the plurality of light-emitting elements formed in the sample S (details will be described later), and judges the pass / fail of each light-emitting element. It is also conceivable that such an inspection of the light-emitting elements may be performed, for example, by probing (i.e., based on electrical characteristics). However, for example, for fine LEDs such as μLEDs, probing for measuring by placing a needle is physically difficult. In this regard, the inspection method of light-emitting elements based on photoluminescence according to the present embodiment can perform inspection by acquiring a fluorescent image, so that a large number of light-emitting elements can be efficiently inspected without being bound by physical constraints.

[0034] As shown in Fig. 1, the inspection device 1 includes a chuck 11, an XY stage 12, an excitation light source 20, an optical system 30, a dichroic mirror 40, an objective lens 51, a Z stage 52, a dichroic mirror 60 (optical element), imaging lenses 71 and 72, a bandpass filter 75, cameras 81 (first imaging unit) and 82 (second imaging unit), a dark box 90, a control device 100 (processing unit), and a monitor 110. The dark box 90 contains the above-mentioned components other than the control device 100 and the monitor 110, and is provided to prevent the components contained therein from being affected by external light. Each component contained in the dark box 90 may be mounted on a vibration isolation table to improve the quality of images captured by the cameras 81 and 82 (improving image quality and preventing image positional deviation).

[0035] The chuck 11 is a holding member for holding the sample S. The chuck 11 holds the sample S, for example, by vacuum-adsorbing the wafer of the sample S. The XY stage 12 is a stage for moving the chuck 11 holding the sample S in the XY directions (front-back and left-right directions), that is, in the direction along the mounting surface of the chuck 11 on which the sample S is placed. The XY stage 12 moves the chuck 11 in the XY directions under the control of the control device 100 so that each of the multiple light-emitting elements is sequentially irradiated with the excitation light. The inspection device 1 may further include a rotation stage (Θ stage, not shown). Such a rotation stage may be provided, for example, above the XY stage 12 and below the chuck 11, or may be provided integrally with the XY stage 12. The rotation stage is for precisely aligning the vertical and horizontal positions of the sample S. By providing the rotation stage, the time required for alignment and the like can be shortened, and the total time required for data processing can be shortened.

[0036] The excitation light source 20 is a light source that generates excitation light to be irradiated onto the sample S and irradiates the sample S with the excitation light. The excitation light source 20 may be any light source capable of generating light including a wavelength that excites the light emitting element of the sample S, and may be, for example, an LED, a laser, a halogen lamp, a mercury lamp, a D2 lamp, a plasma light source, or the like. The inspection device 1 may further include a sensor that monitors the illumination luminance in order to keep the luminance of the excitation light emitted from the excitation light source 20 constant. In order to minimize shading, a diffusion plate or a fly-eye lens may be used at the position where the excitation light is emitted from the excitation light source 20 to uniformize the luminance distribution.

[0037] The optical system 30 includes an optical fiber cable 31 and a light guide lens 32. The optical fiber cable 31 is an optical fiber cable for guiding light connected to the excitation light source 20. For example, a polarization-maintaining fiber or a single-mode fiber can be used as the optical fiber cable 31. The light guide lens 32 is, for example, a single or composite convex lens, and guides the excitation light that has arrived via the optical fiber cable 31 toward the dichroic mirror 40. In order to prevent the wavelength of the excitation light emitted from the excitation light source 20 from changing over time, the inspection device 1 may include a bandpass filter (not shown) between the excitation light source 20 and the dichroic mirror 40.

[0038] The dichroic mirror 40 is a mirror made of a special optical material, and reflects light of a specific wavelength and transmits light of other wavelengths. Specifically, the dichroic mirror 40 is configured to reflect the excitation light toward the objective lens 51 and transmit photoluminescence (specifically, fluorescence) from the light-emitting element, which is light of a wavelength band different from that of the excitation light, toward the dichroic mirror 60. As shown in FIG. 2, the region of the normal emission spectrum FS of the excitation light is on the lower wavelength side than the region of the normal emission spectrum (normal fluorescence spectrum) ES of the fluorescence. That is, the dichroic mirror 40 reflects the excitation light, which is light of a low wavelength band, toward the objective lens 51 and transmits the fluorescence, which is light of a higher wavelength band than the excitation light, toward the dichroic mirror 60. This is also clear from the characteristic D1 of the dichroic mirror 40 shown in FIG. 2.

[0039] The objective lens 51 is a component for observing the sample S, and focuses the excitation light guided by the dichroic mirror 40 onto the sample S. The Z stage 52 moves the objective lens 51 in the Z direction (up and down direction), i.e., in a direction intersecting with the mounting surface of the chuck 11 on which the sample S is placed, to perform focus adjustment.

[0040] The dichroic mirror 60 is a mirror made of a special optical material that reflects light of a specific wavelength and transmits light of other wavelengths. In other words, the dichroic mirror 60 is an optical element that separates the fluorescence from the sample S by transmitting or reflecting it according to its wavelength.

[0041] FIG. 2 is a diagram for explaining the characteristics of the emission spectrum and the dichroic mirrors 60 and 40. In FIG. 2, the horizontal axis indicates the wavelength, the left vertical axis indicates the emission luminance, and the right vertical axis indicates the transmittance. As shown in the characteristic D2 of the dichroic mirror 60 in FIG. 2, in the dichroic mirror 60, the transmittance (and reflectance) of the fluorescence changes according to the change in the wavelength in a specific wavelength band SW, and the transmittance (and reflectance) of the fluorescence is constant regardless of the change in the wavelength in wavelength bands other than the specific wavelength band SW (i.e., on the lower wavelength side than the wavelength band SW and on the higher wavelength side than the wavelength band SW). Since the transmittance and the reflectance have a negative correlation in which one changes in the direction in which it increases, the other changes in the direction in which it decreases, hereinafter, the terms "transmittance (and reflectance)" may not be used, but may simply be used as "transmittance". Note that "the transmittance of the fluorescence is constant regardless of the change in the wavelength" includes not only the case where it is completely constant, but also the case where the change in the transmittance for a change in wavelength of 1 nm is 0.1% or less, for example. On the lower wavelength side of the wavelength band SW, the transmittance of fluorescence is approximately 0% regardless of changes in wavelength, and on the higher wavelength side of the wavelength band SW, the transmittance of fluorescence is approximately 100% regardless of changes in wavelength. Note that "the transmittance of fluorescence is approximately 0%" includes a transmittance of approximately 0%+10%, and "the transmittance of fluorescence is approximately 100%" includes a transmittance of approximately 100%-10%. In the following, the width of the wavelength band SW where the transmittance of fluorescence changes depending on changes in wavelength may be described as the "edge transition width WE."

[0042] As shown in FIG. 2, the edge transition width WE of the dichroic mirror 60 is at least wider than the full width at half maximum WH of the normal fluorescence spectrum ES of the light-emitting element. The full width at half maximum WH is, for example, about 10 nm. That is, the edge transition width WE is, for example, wider than 10 nm. In the example shown in FIG. 2, the wavelength band SW is about 425 mm to 525 mm, and the edge transition width WE is about 100 nm, which is sufficiently wider than the full width at half maximum WH of the normal fluorescence spectrum ES. The edge transition width WE is, for example, 150 nm or less. The wavelength band SW generally includes the wavelength band of the normal fluorescence spectrum ES. Thereby, the fluorescence from the sample S is appropriately separated by the dichroic mirror 60. Note that the wavelength band of the normal fluorescence spectrum ES (original emission wavelength) may be, for example, a wavelength that is known in advance from the specifications of the light-emitting element, or may be a wavelength at which the intensity of the fluorescence from the light-emitting element is actually measured by a spectroscope.

[0043] 2, the dichroic mirror 60 reflects almost all of the fluorescence on the lower wavelength side than the wavelength band SW, transmits almost all of the fluorescence on the higher wavelength side than the wavelength band SW, and transmits the fluorescence in the wavelength band SW at a transmittance according to the wavelength (reflects it at a reflectance according to the wavelength). The fluorescence reflected by the dichroic mirror 60 (fluorescence on the shorter wavelength side) passes through a bandpass filter 75 and reaches an imaging lens 71. The fluorescence transmitted through the dichroic mirror 60 (fluorescence on the longer wavelength side) reaches an imaging lens 72.

[0044] The imaging lens 71 is a lens that forms an image of the fluorescence (shorter wavelength fluorescence) reflected by the dichroic mirror 60 and guides the fluorescence to the camera 81. The camera 81 captures the fluorescence (shorter wavelength fluorescence) reflected by the dichroic mirror 60 among the fluorescence from the light emitting element. The camera 81 captures the fluorescence on the shorter wavelength side by detecting the image formed by the imaging lens 71. The camera 81 outputs the captured fluorescence image (first fluorescence image) on the shorter wavelength side to the control device 100. The camera 81 is, for example, an area image sensor such as a CCD or a MOS. The camera 81 may also be configured with a line sensor or a TDI (Time Delay Integration) sensor. The bandpass filter 75 is a filter provided to prevent the intrusion of excitation light, and is provided between the dichroic mirror 60 and the imaging lens 71. In addition, the inspection device 1 may further include a bandpass filter between the dichroic mirror 60 and the camera 81 to prevent contamination of longer wavelength fluorescence due to surface reflection of the dichroic mirror 60 when measuring shorter wavelength fluorescence.

[0045] The imaging lens 72 is a lens that forms an image of the fluorescence (fluorescence on the long wavelength side) transmitted through the dichroic mirror 60 and guides the fluorescence to the camera 82. The camera 82 captures the fluorescence (fluorescence on the long wavelength side) transmitted through the dichroic mirror 60 among the fluorescence from the light emitting element. The camera 82 captures the fluorescence on the long wavelength side by detecting the image formed by the imaging lens 72. The camera 82 outputs the captured fluorescence image (second fluorescence image) on the long wavelength side to the control device 100. The camera 82 is, for example, an area image sensor such as a CCD or a MOS. The camera 82 may also be configured with a line sensor or a TDI sensor. The inspection device 1 may further include a bandpass filter between the dichroic mirror 60 and the camera 82 to prevent unnecessary emission of light on the long wavelength side.

[0046] The control device 100 controls the XY stage 12, the excitation light source 20, the Z stage 52, and the cameras 81 and 82. Specifically, the control device 100 adjusts the irradiation area of ​​the excitation light (the irradiation area of ​​the sample S) by controlling the XY stage 12. The control device 100 controls the Z stage 52 to perform focus adjustment related to the excitation light. The control device 100 controls the excitation light source 20 to perform emission adjustment of the excitation light and adjustment of the wavelength and amplitude of the excitation light. The control device 100 controls the cameras 81 and 82 to perform adjustment related to acquisition of the fluorescence image. In addition, the control device 100 derives color spot information of the light-emitting element of the sample S based on the fluorescence image captured by the cameras 81 and 82 (details will be described later). The control device 100 is a computer, and is physically configured to include memories such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a hard disk. Examples of such a control device 100 include a personal computer, a cloud server, and a smart device (smartphone, tablet terminal, etc.). The control device 100 functions by executing a program stored in memory on the CPU of a computer system. The monitor 110 is a display device that displays a fluorescent image that is a measurement result.

[0047] Next, the function of the control device 100 related to deriving color spot information of the light-emitting element will be described in detail.

[0048] The control device 100 derives color spot information of the light-emitting element based on the fluorescent image (shorter wavelength fluorescent image) acquired by the camera 81 and the fluorescent image (longer wavelength fluorescent image) acquired by the camera .

[0049] The control device 100 first identifies the position of the light-emitting element based on the fluorescent image and identifies the light-emitting area of ​​each light-emitting element. The position of the light-emitting element is identified, for example, by converting the position in the fluorescent image and the position of the XY stage 12. The control device 100 may acquire a pattern image of the entire sample S in advance and recognize (identify) the position of the light-emitting element from the pattern image or the fluorescent image. The control device 100 then derives the average luminance in the light-emitting area of ​​each light-emitting element based on the fluorescent image on the short wavelength side, and derives the average luminance in the light-emitting area of ​​each light-emitting element based on the fluorescent image on the long wavelength side, and links the address position and the luminance (the average luminance on the short wavelength side and the average luminance on the long wavelength side) for each light-emitting element. The control device 100 derives the sum of the luminance on the short wavelength side and the luminance on the long wavelength side for each address (each light-emitting element), and derives an evaluation index from the absolute luminance and relative luminance of the sum. The relative luminance is the luminance ratio of the light-emitting element to be derived to the average luminance of a group of light-emitting elements including the light-emitting element to be derived and the light-emitting elements around the light-emitting element. The control device 100 derives the evaluation index from, for example, the product of absolute luminance and relative luminance. Alternatively, the control device 100 derives the evaluation index from the product of absolute luminance and the nth power of relative luminance (n is a natural number, for example, 2). The control device 100 derives the above-mentioned evaluation index for each light-emitting element included in the same fluorescent image. In addition, the control device 100 obtains a new fluorescent image (a fluorescent image on the short wavelength side and a fluorescent image on the long wavelength side) by changing the irradiation area, and derives the evaluation index for each light-emitting element included in the fluorescent image. After deriving the evaluation index for all the light-emitting elements, the control device 100 sorts (rearranges) the light-emitting elements in descending order of the evaluation index. FIG. 3 is a diagram showing the sorting result of the light-emitting elements according to the evaluation index. In FIG. 3, the vertical axis indicates the evaluation index according to the magnitude of the luminance, and the horizontal axis indicates the ranking of each light-emitting element. As shown in FIG. 3, the evaluation index suddenly decreases at a certain point (a change point). The control device 100 may use such a change point as a threshold value, for example, and determine that a light-emitting element having an evaluation index smaller than the threshold value is a defective product (defective pixel).The threshold value may be determined in advance, for example, by using a reference semiconductor device for threshold determination and comparing the pass / fail judgment result of the light-emitting element based on fluorescence (photoluminescence) with the pass / fail judgment result based on probing (the pass / fail judgment result based on electrical characteristics).

[0050] Furthermore, the control device 100 derives the center of gravity (central wavelength) of the fluorescent wavelength for each light-emitting element from the ratio between the luminance on the short wavelength side and the luminance on the long wavelength side. The control device 100 may determine whether the central wavelength is within a specified wavelength range (for example, within a range of 440 nm to 460 nm), and determine that a light-emitting element that is not within the specified wavelength range is a defective product (defective pixel). The control device 100 grades each light-emitting element for each specified range of the central wavelength, and derives color spots between multiple light-emitting elements based on the grade.

[0051] As described above, in the dichroic mirror 60 according to this embodiment, the edge transition width WE of the wavelength band SW in which the transmittance and reflectance of fluorescence change with the change in wavelength is sufficiently wide (specifically, wider than the full width at half maximum WH of the normal fluorescence spectrum ES) as shown in FIG. 2. When such a dichroic mirror 60 is used, the central wavelength based on the luminance on the short wavelength side and the luminance on the long wavelength side is derived with a deviation from the original value according to the rate of change in the transmittance (or reflectance) relative to the change in wavelength in the dichroic mirror 60. The process of correcting such a deviation in the central wavelength will be described with reference to FIG. 4.

[0052] FIG. 4 is a diagram for explaining the correction of the deviation of the central wavelength. In FIG. 4(a) and FIG. 4(b), the horizontal axis indicates the wavelength, and the vertical axis indicates the transmittance (and reflectance). Also, FIG. 4(a) and FIG. 4(b) show the characteristic D22 of a dichroic mirror whose transmittance (amount of transmitted light) changes at a rate of a% / nm. Now, if the wavelength at which the reflectance of the dichroic mirror is 50% is λ(50%)nm, and the center of the emission wavelength having a rectangular distribution is λ(50%) as shown in FIG. 4(a), the amount of reflected light (amount of reflected light) R and the amount of transmitted light (amount of transmitted light) T become equal. Then, as shown in FIG. 4(a), the amount of transmitted light at the minimum wavelength of the rectangular emission wavelength is T1, the amount of reflected light is R1, the amount of transmitted light at the maximum wavelength is T2, the amount of reflected light is R2, the emission wavelength width is W, and the wavelength shift parameter is S, the following formulas (1) to (4) are established. The wavelength shift parameter can be expressed as "the difference between the amount of transmitted light and the amount of reflected light divided by the total amount of light." Light emission amount L = R + T…(1) Reflected light amount R=(R1+R2)*W / 2…(2) Transmitted light amount T=(T1+T2)*W / 2…(3) Wavelength shift parameter S = (TR) / (T+R) = 0…(4)

[0053] Figure 4(b) shows a state in which the central wavelength derived under the conditions of Figure 4(a) is shifted by Δλ. As shown in Figure 4(b), when the emission wavelength shifts by Δλ, the amount of transmitted light increases by aΔλ over the entire range of emission wavelengths. In this case, if the amount of transmitted light at the minimum emission wavelength is T1', the amount of reflected light is R1', the amount of transmitted light at the maximum wavelength is T2', the amount of reflected light is R2', and the wavelength shift parameter is S', then the following equations (5) to (12) hold. R1' = R1 - aΔλ ... (5) R2´=R2-aΔλ…(6) T1´=T1+aΔλ…(7) T2´=T2+aΔλ…(8) Reflected light amount R´=(R1´+R2´)*W / 2=R-aWΔλ…(9) Transmitted light amount T´=(T1´+T2´)*W / 2=T+aWΔλ…(10) Wavelength shift parameter S´=(T´-R´) / (T´+R´)=2aWΔλ / L…(11)

[0054] Here, from the above-mentioned formulas (1) to (3), the following formula (12) is established. L / W=R1+T1=100%=1…(12) From equations (11) and (12), S´=2aΔλ / (100%)=2aΔλ…(13) From equation (13), Δλ=S´ / 2a…(14)

[0055] As shown in the above formula (14), the shift amount of the central wavelength, Δλ, is equal to the value obtained by dividing the difference between the amount of transmitted light and the amount of reflected light by the total amount of light, S', by twice the change amount a of the transmittance (amount of transmitted light). Therefore, the control device 100 may derive the shift amount of the central wavelength, Δλ, by further considering the rate of change in the transmittance or reflectance with respect to the change in wavelength in the dichroic mirror 60, specifically by using the above formula (14), and may derive the accurate central wavelength for each light-emitting element by correcting (subtracting) the shift amount Δλ from the previously derived central wavelength.

[0056] Next, a process procedure of the inspection method (deriving color spot information of light-emitting elements) executed by the inspection device 1 will be described with reference to Fig. 5. Fig. 5 is a flowchart of the inspection method executed by the inspection device 1.

[0057] 5, in the inspection device 1, first, an irradiation area on the sample S is determined (step S1). Specifically, the control device 100 controls the XY stage 12 to determine the irradiation area of ​​the excitation light.

[0058] Next, the excitation light source 20 irradiates the irradiation area of ​​the sample S with excitation light in response to the control of the control device 100 (step S2). The excitation light source 20 generates and emits light including a wavelength that excites the light-emitting element of the sample S. The excitation light passes through the optical fiber cable 31 and the light guide lens 32 of the optical system 30, reaches the dichroic mirror 40, is reflected by the dichroic mirror 40, and is collected on the irradiation area of ​​the sample S via the objective lens 51. The light-emitting element of the sample S emits fluorescence in response to the excitation light. The fluorescence passes through the dichroic mirror 40 and is separated into fluorescence on the short wavelength side and fluorescence on the long wavelength side by the dichroic mirror 60. The fluorescence on the short wavelength side is imaged by the imaging lens 71 and guided to the camera 81. The fluorescence on the long wavelength side is imaged by the imaging lens 72 and guided to the camera 82.

[0059] The camera 81 captures an image of the fluorescence on the short wavelength side (step S3). The camera 82 captures an image of the fluorescence on the long wavelength side (step S3). The cameras 81 and 82 output the captured fluorescence images to the control device 100.

[0060] Next, the control device 100 identifies the position of the light-emitting element based on the fluorescence image (step S4), and identifies the light-emitting area of ​​each light-emitting element. The control device 100 then derives the luminance (average luminance) within the light-emitting area of ​​each light-emitting element based on the short-wavelength fluorescence image, and derives the luminance (average luminance) within the light-emitting area of ​​each light-emitting element based on the long-wavelength fluorescence image (step S5). The control device 100 then associates the address position with the luminance (average luminance on the short-wavelength side and average luminance on the long-wavelength side) for each light-emitting element (step S6).

[0061] Next, the control device 100 derives a total value of the luminance on the short wavelength side and the luminance on the long wavelength side for each light-emitting element, and derives an evaluation index from the absolute luminance and relative luminance of the total value (step S7). For example, the control device 100 derives the evaluation index from the product of the absolute luminance and the relative luminance. Alternatively, the control device 100 derives the evaluation index from the product of the absolute luminance and the nth power of the relative luminance (n is a natural number, for example, 2).

[0062] Next, the control device 100 judges whether the above-mentioned evaluation indexes have been derived for all the light-emitting elements (light-emitting elements to be judged) of the sample S (step S8). If it is judged in step S8 that the evaluation indexes have not been derived, the control device 100 determines a new irradiation region so as to include the light-emitting elements before the evaluation index was derived (step S9). Then, the process from step S2 onwards is performed again.

[0063] If it is determined in step S8 that the evaluation indexes have been derived for all light-emitting elements, the control device 100 compares the evaluation index of each light-emitting element with a predetermined threshold value and identifies defective products (defective pixels) (step S10). Specifically, the control device 100 sorts (rearranges) the light-emitting elements in descending order of evaluation index, and determines that light-emitting elements with evaluation indexes equal to or greater than the threshold value are good products (good pixels), and that light-emitting elements with evaluation indexes smaller than the threshold value are defective products (defective pixels).

[0064] Next, for each light-emitting element determined to be a non-defective in step S10, the control device 100 derives the center of gravity (central wavelength) of the fluorescence wavelength from the ratio of the luminance on the short wavelength side to the luminance on the long wavelength side (step S11). In deriving the central wavelength, the control device 100 may further take into consideration the rate of change in transmittance or reflectance relative to the change in wavelength in the dichroic mirror 60, specifically derive Δλ, which is the shift amount of the central wavelength, using the above formula (14), and may derive an accurate central wavelength for each light-emitting element by correcting (subtracting) the shift amount Δλ from the central wavelength derived in advance.

[0065] Finally, the control device 100 judges whether the central wavelength is within a specified wavelength range, and classifies the light-emitting elements that are not within the specified wavelength range as defective products (defective pixels), and grades each light-emitting element that is within the specified wavelength range for each predetermined wavelength range, and derives color spot information between the multiple light-emitting elements based on the grade (step S12). The control device 100 may judge the quality of each light-emitting element and the sample S based on the color spot information.

[0066] Next, the effects of this embodiment will be described.

[0067] The effects of the inspection device 1 according to this embodiment will be described.

[0068] The inspection device 1 of this embodiment is an inspection device for inspecting a sample S in which a plurality of light-emitting elements are formed, and includes an excitation light source 20 that generates excitation light to be irradiated onto the sample S, an optical element (dichroic mirror 60) that separates fluorescence from the sample S by transmitting or reflecting it according to the wavelength, a camera 81 that images the fluorescence reflected at the dichroic mirror 60, a camera 82 that images the fluorescence that has transmitted through the dichroic mirror 60, and a control device 100 that derives color spot information of the light-emitting element based on a first fluorescence image acquired by the camera 81 and a second fluorescence image acquired by the camera 82, and the edge transition width WE, which is the width of the wavelength band in which the transmittance and reflectance change according to the change in wavelength in the dichroic mirror 60, is wider than the full width at half maximum WH of the normal fluorescence spectrum ES of the light-emitting element (see FIG. 2).

[0069] In the inspection device 1, the edge shift width, which is the width of the wavelength band in which the transmittance and reflectance change according to the change in wavelength in the dichroic mirror 60, is set wider than the full width at half maximum of the normal fluorescence spectrum of the light-emitting element. For example, if an optical element with a narrow edge shift width is used, it is considered that it is not possible to properly separate fluorescence with a narrow wavelength width. Suppose that the wavelength width of the normal fluorescence spectrum of the light-emitting element is 5 nm, and the edge shift width of the optical element is 5 nm. In this case, the transmitted wavelength and the reflected wavelength change within a range of only 15 nm, and even if the wavelength of the normal fluorescence spectrum shifts beyond this range, the transmittance or reflectance will only become 100%, and no information on how much the wavelength has changed can be obtained. In addition, the amount of change in the ratio of reflected light to transmitted light is larger the closer the high-luminance peak of the normal fluorescence spectrum is to the center wavelength of the edge shift width, and smaller the further it is from the center wavelength. In other words, the amount of change is largely dependent on the spectral shape of the emission wavelength. An actual light-emitting element may not emit light simply (for example, a spectrum with a Gaussian distribution) but may have multiple peaks. In this way, when an optical element with a narrow edge transition width is used, it is nearly impossible to accurately estimate the amount of change in wavelength. In this regard, as in the inspection device 1 according to this embodiment, by using a dichroic mirror 60 whose edge transition width is wider than the full width at half maximum of the normal fluorescence spectrum, that is, which is sufficiently wide in consideration of the wavelength width of the fluorescence, the fluorescence can be easily separated according to wavelength. This makes it possible to derive color spot information with high accuracy from the first fluorescence image and the second fluorescence image based on each fluorescence separated according to wavelength.

[0070] In this embodiment, the edge transition width of the dichroic mirror 60 is set to 150 nm or less. If the edge transition width is made too wide, the resolution of the dichroic mirror will decrease, and this may affect the dichroic mirror's original function of separating fluorescence into short and long wavelength sides. In this regard, by setting the edge transition width to be wider than the full width at half maximum of the normal fluorescence spectrum and 150 nm or less, it is possible to easily separate fluorescence into short and long wavelength sides while accommodating fluorescence with a narrow wavelength width.

[0071] As described above, in this embodiment, the use of the dichroic mirror 60 as the optical element makes it possible to easily separate the fluorescence according to wavelength.

[0072] The control device 100 may derive the color mottle information of the light emitting element by further considering the rate of change in the transmittance or reflectance with respect to the change in wavelength in the dichroic mirror 60. The color mottle information is derived by considering, for example, the ratio of the luminance of each separated fluorescent image. When a dichroic mirror 60 with a wide edge transition width is used, the transmittance and reflectance change according to the change in wavelength, so that the ratio of the luminance of each fluorescent image is considered to be different from that when a normal dichroic mirror (an optical element with a narrow edge transition width) is used. In this regard, by deriving the color mottle information by considering the rate of change in the transmittance or reflectance with respect to the change in wavelength in the dichroic mirror 60, the influence of using a dichroic mirror 60 with a wide edge transition width can be removed, and the color mottle information can be derived with high accuracy.

[0073] The control device 100 derives color spot information between a plurality of light-emitting elements. This makes it possible to output color spot information in units of samples S, and to perform, for example, a pass / fail judgment of each light-emitting element based on the color spot information.

[0074] Although the present embodiment has been described above, the present invention is not limited to the above embodiment. For example, the dichroic mirrors 40 and 60 are described as being used as optical elements, but the present invention is not limited to this, and for example, a configuration in which a half mirror, a short-pass filter, and a long-pass filter are combined may be used as an optical element. Also, for example, a configuration in which a half mirror and a dichroic filter with a wide edge transition width are combined may be used as an optical element. In this case, for example, the dichroic mirror 60 with a wide edge transition width can be composed of a half mirror and a dichroic filter with a wide edge transition width arranged on the side of the cameras 81 and 82.

[0075] In addition, although the control device 100 has been described as deriving color spot information between a plurality of light-emitting elements, this is not limiting, and the control device 100 may derive color spot information within each light-emitting element. In this case, the control device 100 can output color spot information for each light-emitting element, and can identify abnormalities and the like within each light-emitting element based on the color spot information.

[0076] Next, as further embodiments of the present invention, wavelength shift correction according to the position within the field of view (see FIG. 6), adjustment of the illumination luminance of the excitation light (see FIG. 7 to FIG. 10), and pass / fail judgment of the light-emitting element according to the wavelength variation (fluctuation) (see FIG. 11) will be described.

[0077] (wavelength shift correction according to position within the field of view) FIG. 6 is a diagram for explaining the difference in the angle of incidence according to the position in the field of view of the cameras 81 and 82. FIG. 6 shows the objective lens 51 that guides the fluorescence from the sample S toward the dichroic mirror 60, and the dichroic mirror 60. The objective lens 51 and the dichroic mirror 60 here have the same configuration as the objective lens 51 and the dichroic mirror 60 shown in FIG. 1, and are in the same positional relationship. Here, when the objective lens 51 that is generally infinity corrected is used, the light (fluorescence) emitted from one point on the sample S becomes parallel light after passing through the objective lens 51. This is true for each point (each pixel) in the field of view of the cameras 81 and 82. However, although the light beams are parallel at each point, the light beams at different points are not parallel to each other. For this reason, the angle of light incident on the dichroic mirror 60 differs depending on which point (pixel) in the field of view of the cameras 81 and 82 the light comes from. The optical characteristics of the dichroic mirror 60 change depending on the angle of incidence of the fluorescence. That is, in the dichroic mirror 60, the wavelength (center wavelength) at which the transmittance becomes 50% changes depending on the angle of incidence of the fluorescent light (that is, the position of the pixel within the field of view).

[0078] As an example, when the field size of the cameras 81 and 82 is ±0.47 mm (0.94 mm square) and the objective lens 51 is a 10x lens, the angle difference between the light beam L1 on one end side and the light beam L2 on the other end side in the field of view shown in Fig. 6 is ±1.31 degrees. With such an angle difference, for example, when the central wavelength is about 460 nm, the wavelength difference between the light beams L1 and L2 is about ±1.8 nm, when the central wavelength is about 520 nm, the wavelength difference between the light beams L1 and L2 is about ±2.6 nm, and when the central wavelength is about 600 nm, the wavelength difference between the light beams L1 and L2 is about ±3.0 nm.

[0079] In this embodiment, the control device 100 corrects such a wavelength shift. That is, the control device 100 corrects the wavelength shift for each pixel of the fluorescence image according to the position in the field of view of the cameras 81 and 82. Specifically, the control device 100 corrects the wavelength shift for each pixel based on the incidence angle of the fluorescence to the dichroic mirror 60 for each pixel estimated according to the position in the field of view and the optical characteristics of the dichroic mirror 60 related to the amount of change in wavelength according to the incidence angle of the fluorescence. Since the control device 100 has previously acquired the relationship between the position in the field of view and the incidence angle to the optical element, and the amount of change in wavelength according to the incidence angle (optical characteristics of the dichroic mirror 60), the control device 100 can derive the amount of change in wavelength (amount of shift) by calculation (simulation) by inputting the position of each pixel of the fluorescence image. Then, the control device 100 determines the amount of correction (offset) of the wavelength so as to reduce the amount of change in wavelength (wavelength shift) of each pixel.

[0080] In addition to the above-mentioned correction, the control device 100 may correct the wavelength shift for each pixel so that the dispersion of the wavelength of each pixel in the field of view is small. The above-mentioned simulation result is a correction based on the design value. Therefore, for example, when the installation angle of the dichroic mirror 60 deviates from the design value, it may not be possible to perform wavelength shift correction with high accuracy. Even in such a case, by performing wavelength shift correction for each pixel so that the dispersion of the wavelength of each pixel in the field of view is small, the wavelengths in the field of view can be made approximately the same regardless of the design value, and the wavelength shift caused by the position in the field of view can be appropriately corrected. Note that the control device 100 may perform only this correction without performing the above-mentioned correction based on the simulation.

[0081] (Excitation light illumination brightness adjustment) Next, the adjustment of the illumination luminance of the excitation light will be described. When the sample S, which is a semiconductor device, is irradiated with the excitation light and fluorescence observation is performed, a broad fluorescence including the wavelength of the fluorescence (abnormal fluorescence) emitted from impurities or defective parts in the sample S is obtained. That is, in the fluorescence observation, a broad fluorescence including both the wavelength of the original fluorescence and the wavelength of the abnormal fluorescence is obtained. Here, the abnormal fluorescence becomes stronger almost in proportion to the illumination luminance of the excitation light, whereas the original fluorescence becomes stronger approximately in the square of the illumination luminance of the excitation light. Therefore, when the illumination luminance of the excitation light is relatively low, the difference between the luminance of the original fluorescence (original fluorescence intensity: first fluorescence intensity) and the luminance of the abnormal fluorescence (abnormal fluorescence intensity: second fluorescence intensity) is small, whereas when the illumination luminance of the excitation light is relatively high, the difference between the first fluorescence intensity and the second fluorescence intensity is large.

[0082] FIG. 7 is a diagram showing the spectral intensity of fluorescence according to the illumination luminance of excitation light. As shown in FIG. 7, when the illumination luminance is relatively low (see the graph of illumination luminance: 0 or 5 in FIG. 7), it is difficult to distinguish the difference between the first fluorescence intensity and the second fluorescence intensity from the spectral intensity. That is, under conditions of weak excitation light, the original fluorescence to be observed is buried in the abnormal fluorescence and is difficult to observe. On the other hand, as shown in FIG. 7, when the illumination luminance is relatively high (see the graph of illumination luminance: 128 in FIG. 7), the first fluorescence intensity is sufficiently large, so that it is possible to distinguish the original fluorescence luminance (first fluorescence intensity) from the abnormal fluorescence luminance (second fluorescence intensity) caused by defects or the like from the spectral intensity. In this case, the emission luminance and wavelength of the light-emitting element can be accurately observed.

[0083] In this embodiment, in a pre-processing performed before deriving color spot information, the illumination luminance of the excitation light is adjusted so that the illumination luminance of the excitation light is strong enough to distinguish between the first fluorescent intensity and the second fluorescent intensity. Specifically, the illumination luminance of the excitation light is adjusted by an inspection device 500 shown in Fig. 8. Note that Fig. 8 shows only a configuration for adjusting the illumination luminance of the excitation light, but in reality, the inspection device 500 also includes a configuration related to the derivation of color spot information, such as the imaging unit shown in Fig. 1, and the corresponding configuration can be switched between the process related to the adjustment of the illumination luminance of the excitation light (pre-processing) and the process related to the derivation of color spot information.

[0084] 8, the inspection device 500 includes a half mirror 510 and a spectroscope 520 after the dichroic mirror 40. The half mirror 510 is configured to be able to reflect at least a portion of the fluorescence from the sample S in the direction of the spectroscope 520. The spectroscope 520 resolves the fluorescence input via the half mirror 510 into wavelengths and measures the spectrum of the fluorescence (see FIG. 7).

[0085] In a process (pre-processing) relating to adjustment of the illumination luminance of the excitation light, the control device 100 identifies a first fluorescence intensity, which is the original fluorescence intensity, and a second fluorescence intensity, which is an abnormal fluorescence intensity smaller than the first fluorescence intensity, based on the fluorescence spectrum measured by the spectroscope 520, and determines the illumination luminance of the excitation light to be irradiated to the sample S such that the first fluorescence intensity is greater than the second fluorescence intensity by a predetermined value or more. The control device 100 adjusts the illumination luminance so that the illumination luminance of the excitation light irradiated from the excitation light source 20 is increased, for example, until the first fluorescence intensity is greater than 10 times the second fluorescence intensity. Then, in a process of deriving color spot information after pre-processing, the excitation light source 20 generates excitation light with the illumination luminance determined by the control device 100.

[0086] Fig. 9 is a flowchart showing the adjustment process of illumination luminance by the control device 100. Note that part of the process described below as being performed by the control device 100 may be performed by the inspection implementer. As shown in Fig. 9, the control device 100 switches the configuration of the inspection device 500 to a configuration using the spectroscope 520 (configuration for performing pre-processing) shown in Fig. 8 (step S1), and switches the wavelength of the excitation light to a wavelength for excitation (step S2). Note that the control device 100 may insert a bandpass filter instead of switching the wavelength of the excitation light.

[0087] Next, the control device 100 inserts a filter that excludes the excitation wavelength before the spectrometer 520 (step S3). Then, the control device 100 identifies the first fluorescence intensity and the second fluorescence intensity based on the spectrum of the fluorescence measured by the spectrometer 520 (step S4). The control device 100 determines whether the second fluorescence intensity is 1 / 10 or less of the first fluorescence intensity (whether the first fluorescence intensity is 10 times or more of the second fluorescence intensity) (step S5).

[0088] If it is determined in step S5 that the second fluorescent intensity is not 1 / 10 or less of the first fluorescent intensity, the control device 100 increases the illumination luminance of the excitation light irradiated from the excitation light source 20 by a predetermined value (step S6), and the processing from step S4 onwards is performed again. In this manner, the processing of changing (increasing) the illumination luminance is repeatedly performed until it is determined in step S5 that the second fluorescent intensity is 1 / 10 or less of the first fluorescent intensity.

[0089] If it is determined in step S5 that the second fluorescent intensity is 1 / 10 or less of the first fluorescent intensity, the control device 100 determines the illumination luminance at that time to be the illumination luminance in the observation system (processing for deriving color spot information) (step S7).Then, the control device 100 switches the configuration of the inspection device 500 to the configuration of the observation system (processing for deriving color spot information) and starts the process of deriving color spot information (step S8).

[0090] In addition, when the excitation light of the determined illumination brightness is generated by the excitation light source 20 and the fluorescence is captured by the cameras 81, 82 (see Figure 1), the control device 100 may insert a filter to limit the amount of light incident on at least one of the cameras 81, 82, which becomes saturated, in front of the cameras 81, 82 that become saturated.

[0091] Furthermore, when the excitation light source 20 generates and irradiates excitation light that is pulsed light, the control device 100 may adjust the duty ratio of the pulsed light to suppress the amount of light incident on the cameras 81, 82 and avoid the above-mentioned saturation of the cameras 81, 82. That is, as shown in FIG. 10, the control device 100 may reduce the duty ratio of the pulsed light when the illumination luminance of the excitation light is high enough to saturate the cameras 81, 82 (when the sample S is bright) compared with when the illumination luminance of the excitation light is low enough that saturation of the cameras 81, 82 is not a problem (when the sample S is dark), thereby shortening the incidence time of the fluorescence on the cameras 81, 82 and suppressing the amount of incident light without changing the intensity of the fluorescence. Note that it is preferable that the excitation light source 20 synchronizes the frequency of the pulsed light with an integer multiple of the reciprocal of the exposure time of the cameras 81, 82 based on the control of the control device 100, thereby making the number of pulsed lights included in each exposure time the same, thereby unifying the amount of incident light of the fluorescence in each exposure time.

[0092] Furthermore, in the above-mentioned pre-processing, the control device 100 may perform processing to integrally multiply the signal of only the abnormal fluorescence when the illumination luminance is low, and remove only the spectrum of the abnormal fluorescence from the signal spectrum when the illumination luminance is high.

[0093] (Determining the quality of light-emitting elements according to wavelength variations) Next, a method for determining the quality of light-emitting elements according to the variation in wavelength will be described. In this method, the inventors focus on the fact that "the center of gravity (central wavelength) of the fluorescent wavelength of each light-emitting element in sample S is more likely to fluctuate (vary) in the luminance band of a defective product," and perform quality determination according to the variation in the center of gravity of the fluorescent wavelength. It is believed that such variation occurs because in defective products, impurities and leakage currents reduce the voltage and energy amount, making the fluorescence more likely to shift toward longer wavelengths.

[0094] FIG. 11 is a diagram for explaining the pass / fail judgment of the light-emitting element according to the variation in the center of gravity of the fluorescence wavelength. FIG. 11 shows an example of the result when all the light-emitting elements of the sample S are sorted (rearranged) in the order of PL luminance (fluorescence luminance). The horizontal axis of FIG. 11(a) shows the fluorescence luminance, the vertical axis shows the center of gravity of the emission (fluorescence) wavelength, and the circles in FIG. 11(a) show the results of each light-emitting element. The horizontal axis of FIG. 11(b) shows the fluorescence luminance, and the vertical axis shows the number (frequency) of the light-emitting elements. As shown in FIG. 11(b), the number (frequency) of the light-emitting elements in a certain luminance band is at the peak, and the number (frequency) of the light-emitting elements gradually decreases in each direction of the direction of increasing luminance and the direction of decreasing luminance. Also, as shown in FIG. 11(a), the variation in the fluorescence wavelength of the light-emitting element is small in a luminance band with a relatively high luminance (good product), while the variation in the fluorescence wavelength of the light-emitting element is large in a luminance band with a relatively low luminance (defective product). The control device 100 judges the light-emitting element in the luminance band with a large variation as defective.

[0095] That is, the control device 100 derives the center of gravity of the luminance and fluorescence wavelength of each light-emitting element based on the short-wavelength fluorescence image (first fluorescence image) and the long-wavelength fluorescence image (second fluorescence image). The control device 100 then sorts the light-emitting elements in order of luminance, and judges light-emitting elements in a luminance band in which the variation in the fluorescence wavelength is greater than a predetermined value as defective, and judges light-emitting elements in a luminance band in which the variation in the fluorescence wavelength is equal to or less than the predetermined value as non-defective. For example, after sorting, the control device 100 derives the fluctuation (standard deviation) of the fluorescence wavelength for a certain number (for example, 10) starting from the defective side (low luminance side), and judges the luminance at which the fluctuation converges to a predetermined value or less as the threshold value for determining whether the element is good or defective.

[0096] Note that when deriving the center of gravity of the fluorescence wavelengths from the measurement results (fluorescence images) by the two cameras 81 and 82, the control device 100 may perform correction taking into consideration the measurement results (results acquired in pre-processing) by the above-mentioned spectrometer 520. This makes it possible to derive the center of gravity of the fluorescence wavelengths with higher accuracy.

[0097] Finally, the effects of each aspect described as further embodiments will be described.

[0098] The control device 100 may correct the wavelength shift for each pixel of the fluorescence image according to the position in the field of view of the cameras 81 and 82. The angle of light incident on the dichroic mirror 60 from the sample S differs according to the position in the field of view of the cameras 81 and 82. The difference in the angle of incidence on the dichroic mirror 60 causes a difference (wavelength shift) in the center of gravity (central wavelength) of the fluorescence wavelength. That is, the position in the field of view causes a difference (wavelength shift) in the central wavelength of the fluorescence related to each pixel. In this regard, as described above, by correcting the wavelength shift according to the position in the field of view of the cameras 81 and 82, the wavelength shift caused by the position in the field of view can be suppressed, and the original fluorescence related to each pixel can be appropriately acquired.

[0099] The control device 100 may correct the wavelength shift for each pixel based on the incident angle of the fluorescence on the dichroic mirror 60 for each pixel estimated according to the position in the field of view, and the optical characteristics of the dichroic mirror 60 related to the amount of change in wavelength according to the incident angle of the fluorescence. Since the relationship between the position in the field of view and the incident angle on the dichroic mirror 60, and the amount of change in wavelength according to the incident angle are specified in advance, the amount of change in wavelength for that pixel can be derived from the position in the field of view, and therefore the wavelength shift can be easily and appropriately corrected for each pixel.

[0100] The control device 100 may correct the wavelength shift for each pixel so that the dispersion of the wavelength of each pixel in the field of view is reduced. This suppresses the variation in the central wavelength of the fluorescence for each pixel in the field of view, making it possible to appropriately correct the wavelength shift due to the position in the field of view.

[0101] The inspection device 500 further includes a spectrometer 520 that resolves the fluorescence into wavelengths and measures a spectrum. In a preprocessing performed before deriving the color spot information, the control device 100 identifies a first fluorescence intensity, which is an original fluorescence intensity, and a second fluorescence intensity, which is an abnormal fluorescence intensity smaller than the first fluorescence intensity, based on the spectrum, and determines the illumination luminance of the excitation light to be irradiated onto the sample S so that the first fluorescence intensity is greater than the second fluorescence intensity by a predetermined value or more. The excitation light source 20 may generate excitation light with the illumination luminance determined by the control device 100. The original fluorescence has a higher increase rate when the illumination luminance of the excitation light is increased than the abnormal fluorescence caused by impurities or defects. In other words, when the illumination luminance of the excitation light is low, the difference in intensity between the original fluorescence and the abnormal fluorescence is small, and there is a risk that the original fluorescence will be buried in the abnormal fluorescence, whereas when the illumination luminance of the excitation light is high, the difference in intensity between the original fluorescence and the abnormal fluorescence is large, and the original fluorescence is prevented from being buried in the abnormal fluorescence. As described above, in the preprocessing, the illumination luminance of the excitation light is determined so that the first fluorescence intensity, which is the original fluorescence intensity, is sufficiently greater than the second fluorescence intensity, which is the abnormal fluorescence intensity. This makes it possible to determine the illumination luminance of the excitation light so that the original fluorescence is not buried, and to accurately derive color spot information.

[0102] When the amount of light incident on at least one of the cameras 81, 82 becomes saturated as a result of excitation light having the determined illumination luminance being generated by the excitation light source 20 and fluorescence being captured by the cameras 81, 82, the control device 100 may insert a filter for limiting the amount of light upstream of the saturated cameras 81, 82. This makes it possible to appropriately prevent the cameras 81, 82 from becoming saturated even when the illumination luminance of the excitation light is increased.

[0103] The excitation light source 20 may generate the excitation light that is a pulsed light. By irradiating the pulsed light, the normal fluorescence and the abnormal fluorescence are always compared at their peak luminance, so that it is possible to easily and reliably determine whether the first fluorescence intensity is sufficiently greater than the second fluorescence intensity.

[0104] When the amount of light incident on at least one of the cameras 81, 82 becomes saturated as a result of excitation light having the determined illumination luminance being generated by the excitation light source 20 and fluorescence being captured by the cameras 81, 82, the control device 100 may suppress the amount of incident light by adjusting the duty ratio of the pulsed light. The cameras 81, 82 may become saturated depending on the amount of incident light, i.e., the intensity of the fluorescence x time, but by changing the duty ratio of the pulsed light to adjust the incident time of the fluorescence, it is possible to appropriately suppress saturation of the cameras 81, 82 without changing the intensity of the fluorescence (the ratio between normal fluorescence and abnormal fluorescence).

[0105] The excitation light source 20 may synchronize the frequency of the pulsed light with an integer multiple of the reciprocal of the exposure time of the cameras 81 and 82. This allows the number of pulsed lights included in each exposure time to be the same, and prevents the amount of incident fluorescent light from differing between the exposure times.

[0106] The control device 100 may derive the luminance and the center of gravity of the fluorescence wavelength of each light-emitting element based on the short-wavelength fluorescence image (first fluorescence image) and the long-wavelength fluorescence image (second fluorescence image), and may determine that a light-emitting element with a luminance in which the variation in the center of gravity of the fluorescence wavelength is greater than a predetermined value is defective, and determine that a light-emitting element with a luminance in which the variation in the center of gravity of the fluorescence wavelength is equal to or less than the predetermined value is good. The center of gravity (central wavelength) of the fluorescence wavelength is more likely to fluctuate (vary) in a luminance band that is defective. For this reason, by determining that a light-emitting element with a luminance (luminance band) in which the variation in the center of gravity of the fluorescence wavelength is greater than a predetermined value is defective, it is possible to easily determine whether the product is good or bad with high accuracy.

[0107] It is known that the emission wavelength of an LED depends on the temperature of the device. Therefore, it is desirable that the chuck 11 is black to eliminate the influence of changes in illumination intensity due to reflection of illumination light. However, if the chuck 11 is black, there is a risk that the illumination will cause the sample temperature to drift, and the emission wavelength will also drift. To prevent this, it is preferable that the chuck 11, which is the part that adsorbs the sample S, is equipped with a mechanism for controlling the temperature (temperature control function). Alternatively, it is preferable that the chuck 11 adsorbs only the peripheral part of the sample S and holds the sample S in a state where the bottom of the sample S is floating. This makes it possible to prevent a shift in the measurement wavelength due to temperature changes. In addition, the above-mentioned temperature control function may be used to perform measurement with the sample S intentionally heated. It is known that the amount of leakage current in the crystal defects of the sample S is strongly affected by temperature. Therefore, by heating the sample S, the influence of the decrease in brightness and the shift in wavelength due to leakage from the defects can be increased.

[0108] It is known that the emission intensity of an LED is not the first order of the illumination intensity, but increases in proportion to the higher orders. This is highly likely to differ for each process of the sample S. In addition, the luminance of the illumination may need to be changed accordingly. In addition, the luminance distribution of the illumination irradiated to the sample S cannot be completely flat. In other words, the PL luminance may have different shading for each sample S within the screen. To prevent this, it is preferable to change the shading of the fluorescence image at least every time a device of a different process is measured. In addition, it is more preferable to obtain the shading of the fluorescence image from the actual sample for each sample S and each time the intensity of the illumination light is changed. In other words, the control device 100 (processing unit) may change the shading of the fluorescence image every time the illumination luminance of the sample S and the excitation light is changed.

[0109] A defective LED may have a leak current, and if the illumination luminance of the excitation light for such an LED is comparable to the leak current, the fluorescence luminance may be significantly affected by this leak current. It has been found that when a fluorescence image is acquired at an illumination luminance at which a photocurrent flows near the leak current that is the criterion for judging a defect, and at an illumination luminance stronger than that, the amount of change in the fluorescence luminance increases. Therefore, it is preferable to acquire fluorescence data while switching the illumination luminance of the excitation light source for obtaining fluorescence multiple times. For example, when the increase in the fluorescence luminance is evaluated between the result of exposure at luminance 1 for 10 ms and the result of exposure at luminance 10 for 1 ms, it is possible to judge that the increase is abnormally large or that there is no increase at all as defective. In this way, the excitation light source 20 may switch the illumination luminance of the excitation light multiple times.

[0110] The inspection device 1 may have a function of observing the shape of each light-emitting element formed in the sample S in addition to the function of inspecting the light emission from the sample S. When measuring the shape (pattern) of each light-emitting element, illumination with a longer wavelength than the emission wavelength of each light-emitting element observed by light emission may be used. This allows the shape of the electrodes and the like located deep inside the light-emitting layer of each light-emitting element to be observed well. [Explanation of symbols]

[0111] 1... inspection device, 11... chuck (holding member), 20... excitation light source, 81... camera (first imaging section), 82... camera (second imaging section), 100... control device (processing section), S... sample (object).

Claims

[Claim 1] An inspection apparatus for inspecting a plurality of light-emitting elements, comprising: An excitation light source that generates excitation light to be irradiated onto an object; an optical element that separates the fluorescence from the object by transmitting or reflecting it according to the wavelength, and in which the ratio of the transmittance and the reflectance to the wavelength changes monotonically in a predetermined wavelength range; a first image capturing unit configured to capture an image of the fluorescence reflected by the optical element; a second imaging unit that images the fluorescent light transmitted through the optical element; a spectroscope that resolves the fluorescence from the object into wavelengths and measures a spectrum; a processing unit that derives a central wavelength of fluorescence from the object based on a first fluorescent image acquired by the first imaging unit and a second fluorescent image acquired by the second imaging unit, The processing unit corrects the central wavelength based on a measurement result of the spectrometer.

Images