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 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 long-wavelength and short-wavelength sides by an optical element, and the respective images are simultaneously measured by two imaging units. With this configuration, it is possible to derive color mottling information of the light-emitting element based on the ratio of the luminance values ​​on the long-wavelength and short-wavelength sides. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-10834 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, an example of an optical element that separates fluorescence into long-wavelength and short-wavelength components is a dichroic mirror, which reflects light of a specific wavelength and transmits light of other wavelengths. A problem with such optical elements is that they cannot properly separate fluorescence with a narrow wavelength range. If the fluorescence is not properly separated according to wavelength, it may be difficult to accurately derive the color mottling of the light-emitting element.

[0006] One aspect of the present invention has been made in view of the above circumstances, and an object of the present invention is 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 according to its wavelength; a first imaging unit that images the fluorescence reflected by the optical element; a second imaging unit that images the fluorescence that has passed through the optical element; and a processing unit that derives color spot information of the light-emitting element based on the first fluorescence image acquired by the first imaging unit and the second fluorescence image acquired by the second imaging unit, wherein the edge transition width, which is the width of the wavelength band in which the transmittance and reflectance change according to a 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 an 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 with wavelength, of the optical element is 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 transition width is used, it may be difficult to appropriately separate fluorescence with a narrow wavelength range. In this regard, by using an optical element with an edge transition width wider than the full width at half maximum of the normal fluorescence spectrum, i.e., one that is sufficiently wide in consideration of the wavelength range of the fluorescence, as in the inspection device according to one aspect of the present invention, the fluorescence can be easily separated according to wavelength. This makes it possible to derive color mottling information with high accuracy from the first fluorescence image and the second fluorescence image based on the fluorescence separated according to wavelength.

[0009] In the above-described 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 be reduced, potentially affecting the optical element's inherent function of separating fluorescence into short and long wavelength components. 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 fluorescence into short and long wavelength components while accommodating fluorescence with a narrow wavelength range.

[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-described inspection device, the processing unit may derive color mottle information for the light-emitting element by further considering the rate of change in transmittance or reflectance with respect to a change in wavelength in the optical element. The color mottle information is derived, for example, by considering the ratio of the luminance of each separated fluorescent image. When an optical element with a wide edge transition width is used, the transmittance and reflectance change with a change in wavelength, and therefore the ratio of the luminance of each fluorescent image may differ from that when a normal optical element (an 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 a change in wavelength in the optical element, the influence of using an optical element with a wide edge transition width can be eliminated, and color mottle information can be derived with high accuracy.

[0012] In the inspection device, the processing unit may derive color mottle information between a plurality of light-emitting elements, thereby making it possible to output the color mottle information for each object and, for example, determine whether each light-emitting element is good or bad.

[0013] In the above-described inspection device, the processing unit may derive color mottle information within each light-emitting element, thereby making it possible to output the color mottle information for each light-emitting element, and to identify, for example, abnormalities within each light-emitting element.

[0014] In the above-described inspection device, the processing unit may correct the wavelength shift for each pixel of the fluorescence image according to its position within the field of view of the imaging unit. The angle of light incident on the optical element from the object varies depending on its position within the field of view of the imaging unit. Differences in the angle of incidence on the optical element result in differences in the center wavelength of the fluorescence (wavelength shift). In other words, differences in the center wavelength (wavelength shift) of the fluorescence for each pixel occur depending on its position within the field of view. In this regard, as described above, by correcting the wavelength shift according to its position within the field of view of the imaging unit, it is possible to suppress the wavelength shift due to its position within the field of view and appropriately 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 angle of incidence of the fluorescence onto the optical element for each pixel estimated according to its position within the field of view, and the optical characteristics of the optical element related to the amount of change in wavelength depending on the angle of incidence of the fluorescence. Because the relationship between the position within the field of view and the angle of incidence onto the optical element, and the amount of change in wavelength depending on the angle of incidence, are specified in advance, the amount of change in wavelength for that pixel can be derived from the position within the field of view, making it possible to easily and appropriately correct the wavelength shift for each pixel.

[0016] In the above-described inspection device, the processing unit may correct the wavelength shift for each pixel so as to reduce the dispersion of the wavelength of each pixel within the field of view, thereby suppressing the variation in the central wavelength of the fluorescence for each pixel within the field of view, thereby enabling appropriate correction of the wavelength shift due to the position within the field of view.

[0017] The inspection device may further include a spectrometer that resolves the fluorescence by wavelength and measures the spectrum. In a preprocessing step performed before deriving the color mottling information, the processing unit identifies, based on the spectrum, 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. The processing unit determines the illumination luminance of the excitation light to be irradiated onto the object so that the first fluorescence intensity is greater than the second fluorescence intensity by a predetermined value or more. The excitation light source may generate the excitation light with the illumination luminance determined by the processing unit. The original fluorescence increases at a higher 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, which may result in the original fluorescence being overwhelmed by the abnormal fluorescence. However, when the illumination luminance of the excitation light is high, the difference in intensity between the original fluorescence and the abnormal fluorescence is large, which may result in the original fluorescence being overwhelmed by 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-described inspection device, when the excitation light having the determined illumination brightness is generated by the excitation light source and the fluorescence is captured by the first and second image capturing units, and the amount of light incident on at least one of the first and second image capturing units becomes saturated, the processing unit may insert a filter that limits the amount of light upstream of the saturated image capturing unit, thereby making it possible to appropriately prevent the image capturing units from becoming saturated even when the illumination brightness of the excitation light is increased.

[0019] In the above-described 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-described inspection device, when the excitation light source generates excitation light with the determined illumination brightness and the first and second image capturing units capture fluorescence, the processing unit may suppress the amount of incident light by adjusting the duty ratio of the pulsed light. The image capturing units can be saturated by the amount of incident light, i.e., the fluorescence intensity x time, but by changing the duty ratio of the pulsed light to adjust the fluorescence incidence time, saturation of the image capturing units can be appropriately suppressed without changing the fluorescence intensity (the ratio between normal fluorescence and abnormal fluorescence).

[0021] In the above-described 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 image capturing unit and the second image capturing unit, thereby making it possible to make the number of pulsed light included in each exposure time the same and preventing the amount of incident fluorescent light from differing between the exposure times.

[0022] In the above-described 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 as defective light-emitting elements having a luminance in which the variation in the center of gravity of the fluorescent wavelength is greater than a predetermined value, and determine as non-defective light-emitting elements having a luminance in which the variation in the center of gravity of the fluorescent wavelength is equal to or less than the predetermined value. The center of gravity (central wavelength) of the fluorescent wavelength is more likely to fluctuate (vary) in a luminance band that is deemed defective. Therefore, by determining as defective light-emitting elements having a luminance (luminance band) in which the variation in the center of gravity of the fluorescent wavelength is greater than a predetermined value, it is possible to easily determine whether a 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 due to illumination and consequent drift in the fluorescence wavelength.

[0024] The inspection device may further include a holding member for holding the object, and the holding member may suction only the peripheral portion of the object. By suctioning only the peripheral portion of the object with the holding member, the object is held in a state where the central portion of the object is floating (not in contact with the holding member), and wavelength shifts due to temperature changes of the object can be more appropriately suppressed.

[0025] In the above-described inspection device, the processing unit may change the shading of the fluorescence image each time the object and the illumination luminance of the excitation light are changed, thereby enabling appropriate shading to be applied depending on the object and the illumination luminance.

[0026] In the inspection apparatus, the excitation light source may switch the illumination intensity of the excitation light multiple times, so that data can be acquired at different illumination intensities, thereby enabling more accurate pass / fail judgment.

[0027] An inspection method according to one aspect of the present invention derives color mottling information of a light-emitting element based on a first fluorescence image obtained by irradiating an object having a plurality of light-emitting elements formed thereon with excitation light, and capturing an image of 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 capturing an image of the fluorescence that has passed through the optical element. The inspection method includes the steps of: resolving the fluorescence by wavelength and measuring its spectrum; identifying, based on the spectrum, a first fluorescence intensity that is the original fluorescence intensity and a second fluorescence intensity that is an abnormal fluorescence intensity that is smaller than the first fluorescence intensity; determining the illumination luminance of the excitation light to be irradiated onto the object so that the first fluorescence intensity is greater than the second fluorescence intensity by a predetermined value or more; and generating the excitation light of the determined illumination luminance.

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

[0030] According to an inspection device and an inspection method according to an aspect of the present invention, the color spots of the light-emitting element can be derived with high accuracy by appropriately separating the fluorescence according to wavelength. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a configuration diagram of an inspection device according to an embodiment of the present invention. [Figure 2] 1A and 1B are diagrams illustrating an emission spectrum and characteristics of a dichroic mirror. [Figure 3] FIG. 10 is a diagram showing the results of sorting each light-emitting element according to the evaluation index. [Figure 4] FIG. 10 is a diagram illustrating correction of a deviation of the center wavelength. [Figure 5] 10 is a flowchart of an inspection method executed by the inspection device. [Figure 6] FIG. 10 is a diagram illustrating a difference in the angle of incidence depending on the position in the field of view. [Figure 7] FIG. 10 is a diagram illustrating spectral intensity according to illumination luminance. [Figure 8] FIG. 1 is a diagram illustrating the configuration of an optical system that uses a spectroscope. [Figure 9] 10 is a flowchart showing a process for adjusting illumination brightness. [Figure 10] FIG. 10 is a diagram illustrating adjustment of the duty ratio. [Figure 11] 10A and 10B are diagrams illustrating a quality determination of a light emitting element according to variations in the center of gravity of the fluorescent wavelength. DETAILED DESCRIPTION OF THE INVENTION

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

[0033] FIG. 1 is a configuration diagram of an inspection apparatus 1 according to the present embodiment. The inspection apparatus 1 is an apparatus for inspecting a sample S (object). The sample S is, for example, a semiconductor device in which multiple 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 surface lasers (VCSELs), etc. The inspection apparatus 1 observes the photoluminescence (specifically, fluorescence) of the multiple light-emitting elements formed on the sample S to derive color mottling information among the multiple light-emitting elements (details will be described later) and determine the pass / fail status of each light-emitting element. It should be noted that such light-emitting elements can also be inspected by, for example, probing (i.e., based on electrical characteristics). However, for minute LEDs such as μLEDs, probing, which involves placing a needle on the LED to perform measurements, is physically difficult. In this regard, the photoluminescence-based light-emitting element inspection method according to the present embodiment enables inspection by acquiring fluorescent images, thereby enabling efficient inspection of a large number of light-emitting elements without being bound by physical constraints.

[0034] 1, the inspection apparatus 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 houses all of the above-mentioned components except the control device 100 and the monitor 110, and is provided to prevent the components housed therein from being affected by external light. Note that the components housed 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 misalignment).

[0035] The chuck 11 is a holding member that holds the sample S. The chuck 11 holds the sample S, for example, by vacuum-suctioning a wafer of the sample S. The XY stage 12 is a stage that moves the chuck 11, which holds the sample S, in the X and Y directions (front-back and left-right directions), i.e., in the direction along the surface of the chuck 11 on which the sample S is placed. The XY stage 12 moves the chuck 11 in the X and Y directions under the control of the control device 100 so that each of the multiple light-emitting elements is sequentially illuminated by 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 used to accurately align the vertical and horizontal positions of the sample S. The provision of the rotation stage reduces the time required for alignment and the total time required for data processing.

[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 that can generate light including a wavelength that excites the light-emitting element of the sample S, and may be, for example, an LED, laser, halogen lamp, mercury lamp, D2 lamp, plasma light source, or the like. The inspection device 1 may further include a sensor that monitors the illumination brightness in order to keep the brightness of the excitation light emitted from the excitation light source 20 constant. Furthermore, in order to minimize shading, a diffuser plate or a fly's eye lens may be used at the position where the excitation light is emitted from the excitation light source 20 to uniformize the brightness distribution.

[0037] The optical system 30 includes an optical fiber cable 31 and a light-guiding lens 32. The optical fiber cable 31 is a light-guiding optical fiber cable 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-guiding lens 32 is, for example, a single or compound convex lens, and guides the excitation light that has arrived via the optical fiber cable 31 toward the dichroic mirror 40. Note that 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 that 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 (more specifically, fluorescence) from the light-emitting element, which is light in a wavelength band different from the excitation light, toward the dichroic mirror 60. As shown in FIG. 2, the normal emission spectrum FS of the excitation light is lower in wavelength than the normal emission spectrum (normal fluorescence spectrum) ES of the fluorescence. In other words, the dichroic mirror 40 reflects the excitation light, which is light in a low wavelength band, toward the objective lens 51 and transmits the fluorescence, which is light in a higher wavelength band than the excitation light, toward the dichroic mirror 60. This is also evident 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 adjusts the focus by moving the objective lens 51 in the Z direction (up and down), i.e., in a direction intersecting the surface of the chuck 11 on which the sample S is placed.

[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 illustrating the emission spectrum and the characteristics of the dichroic mirrors 60 and 40. In FIG. 2, the horizontal axis represents wavelength, the left vertical axis represents emission luminance, and the right vertical axis represents transmittance. As shown by characteristic D2 of the dichroic mirror 60 in FIG. 2, in the dichroic mirror 60, the transmittance (and reflectance) of fluorescence changes with wavelength in a specific wavelength band SW, but the transmittance (and reflectance) of fluorescence is constant regardless of wavelength in wavelength bands other than the specific wavelength band SW (i.e., wavelengths lower than the wavelength band SW and wavelengths higher than the wavelength band SW). Since transmittance and reflectance have a negative correlation such that an increase in one causes a decrease in the other, the term "transmittance (and reflectance)" may be used hereinafter to refer to the fluorescence transmittance alone. Note that "constant transmittance of fluorescence regardless of wavelength" refers not only to a completely constant case but also to a case where, for example, the change in transmittance for a 1-nm change in wavelength is 0.1% or less. 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 "fluorescence transmittance is approximately 0%" includes a transmittance of approximately 0% + 10%, and "fluorescence transmittance is approximately 100%" includes a transmittance of approximately 100% - 10%. In the following, the width of the wavelength band SW over which the transmittance of fluorescence changes with changes in wavelength may be referred to 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 range SW is approximately 425 mm to 525 mm, and the edge transition width WE is approximately 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 range SW generally includes the wavelength range of the normal fluorescence spectrum ES. This allows the fluorescence from the sample S to be appropriately separated by the dichroic mirror 60. Note that the wavelength range of the normal fluorescence spectrum ES (original emission wavelength) may be, for example, a wavelength 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 peaked when actually measured using a spectrometer.

[0043] 2, the dichroic mirror 60 reflects almost all of the fluorescence on the wavelength side shorter than the wavelength band SW, transmits almost all of the fluorescence on the wavelength side higher 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 short 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 long wavelength side) reaches an imaging lens 72.

[0044] The imaging lens 71 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 from the fluorescence emitted by the light-emitting element. The camera 81 captures the shorter wavelength fluorescence by detecting the image formed by the imaging lens 71. The camera 81 outputs the captured short wavelength fluorescence image (first fluorescence image) to the control device 100. The camera 81 is, for example, an area image sensor such as a CCD or 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 between the dichroic mirror 60 and the imaging lens 71 to prevent the intrusion of excitation light. The inspection device 1 may further include a bandpass filter between the dichroic mirror 60 and the camera 81 to prevent the mixing of long-wavelength fluorescence due to surface reflection of the dichroic mirror 60 when measuring short-wavelength fluorescence.

[0045] The imaging lens 72 is a lens that forms an image of the fluorescence (fluorescence on the long wavelength side) that has passed 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) that has passed through the dichroic mirror 60 out of 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 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 controls the XY stage 12 to adjust the irradiation area of ​​the excitation light (the irradiation area on the sample S). The control device 100 controls the Z stage 52 to adjust the focus of the excitation light. The control device 100 controls the excitation light source 20 to adjust the emission of the excitation light and the wavelength, amplitude, and other characteristics of the excitation light. The control device 100 controls the cameras 81 and 82 to make adjustments related to the acquisition of fluorescence images. The control device 100 also derives color spot information of the light-emitting elements of the sample S based on the fluorescence images 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 the 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 the computer system. The monitor 110 is a display device that displays a fluorescent image that is the 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 (fluorescent image on the short wavelength side) acquired by the camera 81 and the fluorescent image (fluorescent image on the long wavelength side) acquired by the camera .

[0049] The control device 100 first identifies the position of the light-emitting element based on the fluorescence 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 fluorescence image to the position of the XY stage 12. Alternatively, 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 fluorescence image. The control device 100 then derives the average luminance within the light-emitting area of ​​each light-emitting element based on the short-wavelength fluorescence image and the average luminance within the light-emitting area of ​​each light-emitting element based on the long-wavelength fluorescence image, and associates the address position and luminance (average luminance on the short-wavelength side and 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 relative to the average luminance of a group of light-emitting elements including the light-emitting element to be derived and its surrounding light-emitting elements. The control device 100 derives the evaluation index, for example, from 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 fluorescence image. Furthermore, the control device 100 acquires new fluorescence images (a fluorescence image on the short wavelength side and a fluorescence image on the long wavelength side) by changing the irradiation area, and derives an evaluation index for each light-emitting element included in the fluorescence image. After deriving the evaluation indexes for all the light-emitting elements, the control device 100 sorts (rearranges) the light-emitting elements in descending order of the evaluation index. Figure 3 shows the results of sorting the light-emitting elements by evaluation index. In Figure 3, the vertical axis represents the evaluation index according to the magnitude of luminance, and the horizontal axis represents the ranking of each light-emitting element. As shown in Figure 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, 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 central wavelength, and derives color variations among 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 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 derived center wavelength based on the luminance on the short wavelength side and the luminance on the long wavelength side is shifted from its original value depending on the rate of change in transmittance (or reflectance) with respect to wavelength change in the dichroic mirror 60. The process of correcting such a shift in the center wavelength will be described with reference to FIG. 4.

[0052] FIG. 4 is a diagram illustrating the correction of a shift in the central wavelength. In FIGS. 4(a) and 4(b), the horizontal axis represents wavelength, and the vertical axis represents transmittance (and reflectance). Also, FIGS. 4(a) and 4(b) show the characteristic D22 of a dichroic mirror whose transmittance (amount of transmitted light) changes at a rate of a% / nm. If the wavelength at which the reflectance of the dichroic mirror is 50% is λ(50%)nm, and the center of the rectangular emission wavelength 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 are equal. As shown in FIG. 4(a), if 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, then the following equations (1) to (4) hold. The wavelength shift parameter can be rephrased as "the difference between the amount of transmitted light and the amount of reflected light divided by the total amount of light." Light output 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 center 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 true. 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 equations (1) to (3), the following equation (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', and then dividing this value by twice the amount of change in transmittance (amount of transmitted light). Therefore, the control device 100 may derive the shift amount of the central wavelength, Δλ, by using the above formula (14), further taking into consideration the rate of change in transmittance or reflectance with respect to a change in wavelength in the dichroic mirror 60, and may derive the accurate central wavelength for each light-emitting element by correcting (subtracting) the shift amount Δλ from the previously derived center wavelength.

[0056] Next, the processing 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, under the control of the control device 100, the excitation light source 20 irradiates the irradiation area of ​​the sample S with excitation light (step S2). The excitation light source 20 generates and emits light containing 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-guiding lens 32 of the optical system 30 to reach 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), and 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 also 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 the average luminance on the long-wavelength side) for each light-emitting element (step S6).

[0061] Next, the control device 100 calculates the sum of the luminance on the short wavelength side and the luminance on the long wavelength side for each light-emitting element, and calculates an evaluation index from the absolute luminance and relative luminance of the sum (step S7). The control device 100 calculates the evaluation index, for example, from the product of the absolute luminance and the relative luminance. Alternatively, the control device 100 calculates 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 determines whether the above-mentioned evaluation indexes have been derived for all light-emitting elements (light-emitting elements to be evaluated) of the sample S (step S8). If it is determined in step S8 that the evaluation indexes have not been derived, the control device 100 determines a new irradiation area so as to include the light-emitting elements before the evaluation index was derived (step S9). Thereafter, the processing from step S2 onwards is performed again.

[0063] If it is determined in step S8 that evaluation indices 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 and identifies defective elements (defective pixels) (step S10). Specifically, the control device 100 sorts the light-emitting elements in descending order of evaluation index, and determines that light-emitting elements with evaluation indices equal to or greater than the threshold are non-defective elements (good pixels), and that light-emitting elements with evaluation indices smaller than the threshold are defective elements (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 between the luminance on the short wavelength side and 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 with respect to a 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 previously derived central wavelength.

[0065] Finally, the control device 100 determines whether the central wavelength is within a specified wavelength range and classifies light-emitting elements that are not within the specified wavelength range as defective (defective pixels), and grades each light-emitting element that is within the specified wavelength range for each predetermined wavelength range, and derives color mottling information among the plurality of light-emitting elements based on the grade (step S12).The control device 100 may determine the quality of each light-emitting element and sample S based on the color mottling 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 on which a plurality of light-emitting elements are formed, and is equipped with an excitation light source 20 that generates excitation light to be irradiated onto the sample S, an optical element (dichroic mirror 60) that separates the fluorescence from the sample S by transmitting or reflecting it according to its wavelength, a camera 81 that images the fluorescence reflected by the dichroic mirror 60, a camera 82 that images the fluorescence that has passed 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. The edge transition width WE, which is the width of the wavelength band in which the transmittance and reflectance change according to changes 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 Figure 2).

[0069] In the inspection device 1, the dichroic mirror 60 has an edge shift width, which is the width of the wavelength band over which the transmittance and reflectance change with wavelength, that is 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 may be impossible to properly separate fluorescence with a narrow wavelength range. Suppose 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 and reflected wavelengths change within a range of only 15 nm. Even if the wavelength of the normal fluorescence spectrum shifts beyond this range, the transmittance or reflectance will simply be 100%, and no information on the wavelength change can be obtained. Furthermore, the change in the ratio of reflected light to transmitted light increases the closer the high-intensity peak of the normal fluorescence spectrum is to the center wavelength of the edge shift width, and decreases the further it is from the center wavelength. In other words, this change largely depends on the spectral shape of the emitted wavelength. Actual light-emitting elements may not emit simple light (e.g., a Gaussian-distributed spectrum) but may have multiple peaks. Thus, when an optical element with a narrow edge transition width is used, it is nearly impossible to accurately estimate the amount of wavelength change. In contrast, the inspection device 1 according to this embodiment uses a dichroic mirror 60 whose edge transition width is wider than the full width at half maximum of the normal fluorescence spectrum, i.e., a width sufficiently wide relative to the wavelength width of the fluorescence, making it possible to easily separate the fluorescence according to wavelength. This allows color mottling information to be derived with high accuracy from the first fluorescence image and the second fluorescence image based on the 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 were too wide, the resolution of the dichroic mirror would decrease, potentially affecting the dichroic mirror's primary function of separating fluorescence into short and long wavelength components. 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 components while still accommodating fluorescence with a narrow wavelength range.

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

[0072] The control device 100 may derive color mottle information of the light-emitting element by further considering the rate of change in transmittance or reflectance with respect to a 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 fluorescence image. When a dichroic mirror 60 with a wide edge transition width is used, the transmittance and reflectance change with a change in wavelength, and therefore the ratio of the luminance of each fluorescence image may differ from that when a normal dichroic mirror (an 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 a change in wavelength in the dichroic mirror 60, the influence of using a dichroic mirror 60 with a wide edge transition width can be eliminated, and color mottle information can be derived with high accuracy.

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

[0074] Although the present embodiment has been described above, the present invention is not limited to the above embodiment. For example, although the dichroic mirrors 40 and 60 are described as being used as optical elements, the present invention is not limited to this. For example, a configuration combining a half mirror, a short-pass filter, and a long-pass filter may be used as the optical element. Furthermore, for example, a configuration combining a half mirror and a dichroic filter with a wide edge transition width may be used as the optical element. In this case, for example, the dichroic mirror 60 with a wide edge transition width may 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] Furthermore, although the control device 100 has been described as deriving color mottle information between a plurality of light-emitting elements, this is not limiting, and the control device 100 may derive color mottle information within each light-emitting element. In this case, the control device 100 can output color mottle information for each light-emitting element, and can identify abnormalities, etc. within each light-emitting element based on the color mottle information.

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

[0077] (wavelength shift correction according to position within the field of view) FIG. 6 illustrates the difference in the angle of incidence depending on the position within the field of view of the cameras 81 and 82. FIG. 6 shows the objective lens 51, which guides fluorescence from the sample S toward the dichroic mirror 60, and the dichroic mirror 60. The objective lens 51 and dichroic mirror 60 shown here have the same configuration and are positioned in the same manner as the objective lens 51 and dichroic mirror 60 shown in FIG. 1. Generally, when an infinity-corrected objective lens 51 is used, light (fluorescence) emitted from a single point on the sample S becomes parallel after passing through the objective lens 51. This holds true for each point (each pixel) within the field of view of the cameras 81 and 82. However, while the light beams at each point are parallel, the light beams at different points are not parallel. Therefore, the angle of light incident on the dichroic mirror 60 varies depending on the point (pixel) within the field of view of the cameras 81 and 82 from which the light originates. 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 of view size of cameras 81 and 82 is ±0.47 mm (0.94 mm square) and objective lens 51 is a 10x lens, the angular difference between light beam L1 on one end side and light beam L2 on the other end side within the field of view shown in Fig. 6 is assumed to be ±1.31 degrees. With such an angular difference, for example, when the central wavelength is about 460 nm, the wavelength difference between light beams L1 and L2 is about ±1.8 nm, when the central wavelength is about 520 nm, the wavelength difference between light beams L1 and L2 is about ±2.6 nm, and when the central wavelength is about 600 nm, the wavelength difference between light beams L1 and L2 is about ±3.0 nm.

[0079] In this embodiment, the control device 100 corrects such wavelength shift. That is, the control device 100 corrects the wavelength shift for each pixel of the fluorescence image according to its position within 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 angle of incidence of the fluorescence onto the dichroic mirror 60 for each pixel estimated according to its position within the field of view and the optical characteristics of the dichroic mirror 60 related to the amount of wavelength change according to the angle of incidence of the fluorescence. The control device 100 previously acquires the relationship between the position within the field of view and the angle of incidence onto the optical element, as well as the amount of wavelength change according to the angle of incidence (optical characteristics of the dichroic mirror 60). Therefore, by inputting the position of each pixel of the fluorescence image, the control device 100 can derive the amount of wavelength change (shift amount) through calculation (simulation). Then, the control device 100 determines the amount of wavelength correction (offset) so as to reduce the amount of wavelength change (wavelength shift) for each pixel.

[0080] In addition to the above-described correction, the control device 100 may also correct the wavelength shift for each pixel so as to reduce the wavelength dispersion of each pixel within the field of view. The results of the above-described simulation are merely corrections based on design values. Therefore, for example, if the installation angle of the dichroic mirror 60 deviates from the design value, it may be impossible to perform highly accurate wavelength shift correction. Even in such cases, by performing wavelength shift correction for each pixel so as to reduce the wavelength dispersion of each pixel within the field of view, it is possible to make the wavelengths within the field of view approximately the same regardless of the design value, and to appropriately correct wavelength shifts due to position within the field of view. Note that the control device 100 may perform only this correction without performing the above-described simulation-based correction.

[0081] (Adjusting the illumination brightness of the excitation light) Next, adjustment of the illumination luminance of the excitation light will be described. When irradiating a sample S, which is a semiconductor device, with excitation light and performing fluorescence observation, a broad fluorescence spectrum is obtained that includes wavelengths of fluorescence (abnormal fluorescence) emitted from impurities or defects in the sample S. That is, in fluorescence observation, a broad fluorescence spectrum is obtained that includes both the wavelengths of the original fluorescence and the wavelengths of the abnormal fluorescence. Here, the abnormal fluorescence becomes stronger approximately in proportion to the illumination luminance of the excitation light, while the original fluorescence becomes stronger approximately squared relative to 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 depending on the illumination luminance of excitation light. As shown in FIG. 7, when the illumination luminance is relatively low (see the graphs with illumination luminances of 0 or 5 in FIG. 7), it is difficult to distinguish the difference between the first and second fluorescence intensities from the spectral intensity. That is, under conditions where the excitation light is weak, the original fluorescence to be observed is obscured by 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 with illumination luminance of 128 in FIG. 7), the first fluorescence intensity is sufficiently large, making it possible to distinguish the original fluorescence luminance (first fluorescence intensity) from the abnormal fluorescence luminance (second fluorescence intensity) due to 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 preprocessing step performed before deriving color mottle information, the illumination luminance of the excitation light is adjusted so that the illumination luminance of the excitation light is strong enough to enable differentiation between the first and second fluorescent intensities. Specifically, the illumination luminance of the excitation light is adjusted by an inspection device 500 shown in FIG. 8. Note that while FIG. 8 shows only the configuration for adjusting the illumination luminance of the excitation light, in reality, the inspection device 500 also includes the configuration for deriving color mottle information, such as the imaging unit shown in FIG. 1, and the corresponding configuration can be switched between the process for adjusting the illumination luminance of the excitation light (preprocessing) and the process for deriving color mottle 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 toward 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 (preprocessing) related to adjusting the illumination luminance of the excitation light, the control device 100 identifies a first fluorescent intensity, which is the original fluorescent intensity, and a second fluorescent intensity, which is an abnormal fluorescent intensity smaller than the first fluorescent intensity, based on the fluorescence spectrum measured by the spectroscope 520, and determines the illumination luminance of the excitation light to be irradiated onto the sample S so that the first fluorescent intensity is greater than the second fluorescent 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 fluorescent intensity is greater than the second fluorescent intensity by 10 times or more. Then, in a process of deriving color mottling information after preprocessing, the excitation light source 20 generates excitation light with the illumination luminance determined by the control device 100.

[0086] 9 is a flowchart showing the illumination brightness adjustment process performed by the control device 100. Note that part of the process described below as being performed by the control device 100 may also be performed by the person performing the inspection. As shown in FIG. 9, the control device 100 switches the configuration of the inspection device 500 to a configuration using the spectroscope 520 (a configuration for performing preprocessing) 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 fluorescence spectrum 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 light intensity is not equal to or less than 1 / 10 of the first fluorescent light intensity, the control device 100 increases the illumination luminance of the excitation light emitted from the excitation light source 20 by a predetermined value (step S6), and the processing from step S4 onwards is performed again. In this way, the processing of changing (increasing) the illumination luminance is repeatedly performed until it is determined in step S5 that the second fluorescent light intensity is equal to or less than 1 / 10 of the first fluorescent light 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 as the illumination luminance in the observation system (processing for deriving color mottling 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 mottling information) and starts the process of deriving color mottling 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.

[0091] Furthermore, when the excitation light source 20 generates and irradiates pulsed excitation light, the control device 100 may adjust the duty ratio of the pulsed light to reduce the amount of light incident on the cameras 81, 82 and avoid the saturation of the cameras 81, 82 described above. 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 to when the illumination luminance of the excitation light is low enough to prevent saturation of the cameras 81, 82 (when the sample S is dark). This shortens the time the fluorescence is incident on the cameras 81, 82 and reduces the amount of incident light without changing the intensity of the fluorescence. Note that, based on the control of the control device 100, the excitation light source 20 preferably synchronizes the frequency of the pulsed light to an integer multiple of the reciprocal of the exposure time of the cameras 81, 82, thereby making the number of pulsed light included in each exposure time the same and unifying the amount of incident fluorescence light for each exposure time.

[0092] Furthermore, in the pre-processing described above, 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, we will explain the method for determining the quality of light-emitting elements according to wavelength variations. In this method, the inventors focused 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 (varies more) 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. Such variation is thought to occur because in defective products, impurities and leakage currents cause a decrease in voltage and a decrease in energy, making the fluorescence more likely to shift toward longer wavelengths.

[0094] FIG. 11 is a diagram illustrating the pass / fail determination of light-emitting elements according to the variation in the center of gravity of the fluorescent wavelength. FIG. 11 shows an example of the results when all the light-emitting elements of sample S are sorted in order of PL luminance (fluorescence luminance). The horizontal axis of FIG. 11(a) represents the fluorescent luminance, and the vertical axis represents the center of gravity of the emission (fluorescence) wavelength. The circles in FIG. 11(a) represent the results for each light-emitting element. The horizontal axis of FIG. 11(b) represents the fluorescent luminance, and the vertical axis represents the number (frequency) of light-emitting elements. As shown in FIG. 11(b), the number (frequency) of light-emitting elements in a certain luminance band peaks, and gradually decreases in both the direction of increasing luminance and the direction of decreasing luminance. Furthermore, as shown in FIG. 11(a), the variation in the fluorescent wavelength of the light-emitting elements is small in a luminance band with relatively high luminance (a good product), whereas the variation in the fluorescent wavelength of the light-emitting elements is large in a luminance band with relatively low luminance (a defective product). The control device 100 determines light-emitting elements in a luminance band with 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 a short-wavelength fluorescence image (first fluorescence image) and a long-wavelength fluorescence image (second fluorescence image). The control device 100 then sorts the light-emitting elements in order of luminance, determining that light-emitting elements in a luminance band in which the variation in fluorescence wavelength is greater than a predetermined value are defective, and determining that light-emitting elements in a luminance band in which the variation in fluorescence wavelength is equal to or less than the predetermined value are non-defective. For example, after sorting, the control device 100 derives the fluctuation (standard deviation) of the fluorescence wavelength for every certain number (e.g., every 10) starting from the defective side (low luminance side), and determines the luminance at which the fluctuation converges to a predetermined value or less as the threshold for determining whether the element is non-defective 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 preprocessing) by the above-mentioned spectrometer 520. This allows the center of gravity of the fluorescence wavelengths to be derived with higher accuracy.

[0097] Finally, the effects of the aspects 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 its position within 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 depending on its position within 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. In other words, the position within the field of view causes a difference (wavelength shift) in the central wavelength of the fluorescence 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 cameras 81 and 82, it is possible to suppress the wavelength shift due to the position within the field of view and appropriately acquire the original fluorescence for each pixel.

[0099] The control device 100 may correct the wavelength shift for each pixel based on the angle of incidence of the fluorescence onto the dichroic mirror 60 for each pixel estimated according to its position within the field of view, and the optical characteristics of the dichroic mirror 60 related to the amount of change in wavelength depending on the angle of incidence of the fluorescence. Because the relationship between the position within the field of view and the angle of incidence onto the dichroic mirror 60 and the amount of change in wavelength depending on the angle of incidence are specified in advance, the amount of change in wavelength for that pixel can be derived from its position within the field of view, making it possible to easily and appropriately correct the wavelength shift for each pixel.

[0100] The control device 100 may correct the wavelength shift for each pixel so as to reduce the dispersion of the wavelengths of each pixel within the field of view, thereby suppressing the variation in the central wavelength of the fluorescence for each pixel within the field of view, thereby making it possible to appropriately correct the wavelength shift due to the position within the field of view.

[0101] The inspection device 500 may further include a spectrometer 520 that resolves the fluorescence by wavelength and measures the spectrum. In a preprocessing step performed before deriving the color mottling information, the control device 100 identifies, based on the spectrum, 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. The control device 100 may determine 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 the excitation light with the illumination luminance determined by the control device 100. The original fluorescence increases at a higher 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 the original fluorescence may be overwhelmed by the abnormal fluorescence. However, 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 overwhelmed by 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 brightness 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 that limits the amount of light upstream of the saturated cameras 81, 82. This makes it possible to appropriately prevent saturation of the cameras 81, 82 even when the illumination brightness of the excitation light is increased.

[0103] The excitation light source 20 may generate pulsed excitation light. By irradiating 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.

[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 brightness 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 multiplied by time. However, 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 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 to an integer multiple of the reciprocal of the exposure time of the cameras 81 and 82. This allows the number of pulsed light included in each exposure time to be the same, preventing 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 determine as defective light-emitting elements having a luminance in which the variation in the center of gravity of the fluorescence wavelength is greater than a predetermined value, and determine as non-defective light-emitting elements having a luminance in which the variation in the center of gravity of the fluorescence wavelength is equal to or less than the predetermined value. The center of gravity (central wavelength) of the fluorescence wavelength is more likely to fluctuate (vary) in a luminance band that is considered to be defective. Therefore, determining as defective light-emitting elements having a luminance (luminance band) in which the variation in the center of gravity of the fluorescence wavelength is greater than a predetermined value allows for highly accurate and easy determination of whether a product is good or bad.

[0107] It is known that the emission wavelength of an LED depends on the device temperature. Therefore, it is desirable that the chuck 11 be black to eliminate the effects of changes in illumination intensity due to reflection of the illumination light. However, if the chuck 11 is black, illumination may cause sample temperature drift, which may lead to drift in the emission wavelength. To prevent this, it is preferable that the chuck 11, which adsorbs the sample S, be equipped with a temperature control mechanism (temperature control function). Alternatively, it is preferable that the chuck 11 adsorbs only the peripheral portion of the sample S, holding the sample S with the bottom floating. This prevents deviations in the measurement wavelength due to temperature changes. Furthermore, the above-mentioned temperature control function may be used to deliberately raise the temperature of the sample S before measurement. It is known that the amount of leakage current from crystal defects in the sample S is strongly affected by temperature. Therefore, heating the sample S can increase the effects of brightness reduction and wavelength shift due to leakage from defects.

[0108] It is known that the emission intensity of an LED increases not only linearly with the illumination intensity but also in proportion to higher orders. This is likely to differ for each process of the sample S. It may also be necessary to change the illumination intensity accordingly. Furthermore, the luminance distribution of the illumination irradiating the sample S is never completely flat. In other words, the PL luminance may have different shading within the screen for each sample S. To prevent this, it is preferable to change the shading of the fluorescence image at least each time a device of a different process is measured. It is also more preferable to acquire the shading of the fluorescence image from the actual sample for each sample S and each time the illumination light intensity is changed. That is, the control device 100 (processing unit) may change the shading of the fluorescence image each time the illumination intensity of the sample S and the excitation light is changed.

[0109] Defective LEDs may generate leakage current. If the illumination intensity of the excitation light for such an LED is comparable to the leakage current, the fluorescence intensity can be significantly affected by this leakage current. It has been shown that the amount of change in fluorescence intensity increases when fluorescence images are acquired at an illumination intensity that generates a photocurrent close to the leakage current (the standard for determining a defect) and at an illumination intensity that is even stronger. Therefore, it is preferable to acquire fluorescence data while switching the illumination intensity of the excitation light source used to obtain fluorescence multiple times. For example, by evaluating the increase in fluorescence intensity between a 10-ms exposure at intensity 1 and a 1-ms exposure at intensity 10, an abnormally large increase or no increase at all can be determined to be defective. In this way, the excitation light source 20 may switch the illumination intensity of the excitation light multiple times.

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

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

Claims

1. An optical element having optical characteristics in which transmittance with respect to wavelength changes monotonically in the range of wavelength λ 1 and wavelength λ 2, and separating light from an object by transmitting or reflecting light according to said optical characteristics; a first imaging unit that captures an image of light reflected by the optical element; a second imaging unit that captures an image of light that has passed through the optical element; a processing unit that calculates an amount of transmitted light T based on a first image acquired by the first imaging unit, calculates an amount of reflected light R based on a second image acquired by the second imaging unit, and derives a center of gravity of the wavelengths of light from the object based on the wavelengths λ 1 and λ 2 of the optical element, the amount of transmitted light T, and the amount of reflected light R.

2. The inspection device described in claim 1, wherein the processing unit calculates the amount of deviation from the wavelength of the optical characteristic at which the transmittance or reflectance in the optical characteristic is 50% based on the amount of reflected light R and the amount of transmitted light T, and derives the center of gravity of the wavelength of light from the object.

3. An inspection device as described in claim 2, wherein the processing unit calculates the amount of deviation based on (amount of transmitted light T - amount of reflected light R) / (amount of transmitted light T + amount of reflected light R).

4. The inspection device according to claim 1, wherein the range between the wavelength λ 1 and the wavelength λ 2 of the optical characteristics is 150 nm or less.

5. An inspection device described in any one of claims 1 to 4, wherein the optical element is a dichroic mirror or a dichroic filter.

6. An inspection device described in any one of claims 1 to 5, further comprising a bandpass filter between the optical element and the first imaging unit, and between the optical element and the second imaging unit.

7. An inspection device described in any one of claims 1 to 6, wherein the first imaging unit and the second imaging unit include area image sensors.

8. A method of separating light from an object by transmitting or reflecting it in accordance with an optical characteristic of an optical element having a monotonically changing transmittance with respect to wavelength in a range between wavelengths λ 1 and λ 2; a first imaging step of imaging light reflected by the optical element; a second imaging step of imaging the light transmitted through the optical element; an amount of transmitted light T is calculated based on a first image acquired in the first imaging step, an amount of reflected light R is calculated based on a second image acquired in the second imaging step, and a processing step of deriving the center of gravity of the wavelengths of light from the object based on the wavelengths λ1 and λ2 of the optical element, the amount of transmitted light T, and the amount of reflected light R.

Images