Inspection device and inspection method

Abstract

To perform quality determination of a light-emitting element with high accuracy.SOLUTION: An inspection device 1 inspects a sample S including a plurality of light-emitting elements formed on a substrate, and comprises: a light source part 20 generating excitation light for irradiating the light-emitting element; cameras 81, 82 detecting emission of the light-emitting element irradiated with the excitation light; a keyboard 120 receiving inputting of information on luminous color of the light-emitting element; and a control device 100 determining a wavelength of the excitation light on the basis of the information on luminous color by the keyboard 120, and controlling the light source part 20 to generate the excitation light of the wavelength. The control device 100 determines, as the wavelength of the excitation light, a wavelength that is longer than absorption edge wavelength of the substrate of the sample S and shorter than peak wavelength of emission spectrum of the light-emitting element identified from the information on the luminous color.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 substrate is a known method, probing is performed by measuring the light emission (electroluminescence) generated when a needle is placed on the light-emitting elements and electricity is passed through the light-emitting elements. However, for example, for minute light-emitting elements such as μLEDs formed on a wafer, probing by placing a needle on each of the light-emitting elements to perform measurement is physically difficult. As another method, for example, a method is known in which the light-emitting elements are irradiated with excitation light and the photoluminescence emitted by the light-emitting elements is observed to determine whether the light-emitting elements are good or bad (see, for example, Patent Document 1). According to this method, it is possible to efficiently determine whether the minute light-emitting elements such as the above-mentioned μLEDs are good or bad. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-132308 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, in a method for determining pass / fail by observing photoluminescence, it is required to appropriately acquire (observe) the light emission of the light-emitting element to be measured and to determine the pass / fail of the light-emitting element with high accuracy.

[0005] One embodiment of the present invention has been made in view of the above circumstances, and an object of the present invention is to determine the acceptability of a light-emitting element with high accuracy. [Means for solving the problem]

[0006] An inspection device according to one embodiment of the present invention is an inspection device for inspecting an object having a plurality of light-emitting elements formed on a substrate, and includes a light source unit that generates excitation light to be irradiated to the light-emitting elements, a light detection unit that detects the emission of the light-emitting elements irradiated with the excitation light, an input unit that receives information regarding the emission color of the light-emitting elements, and a control unit that determines the wavelength of the excitation light based on the information regarding the emission color received by the input unit and controls the light source unit so that excitation light of said wavelength is generated, and the control unit determines the wavelength of the excitation light to be longer than the absorption edge wavelength of the substrate of the object and shorter than the peak wavelength of the emission spectrum of the light-emitting elements identified from the information regarding the emission color.

[0007] In the inspection device according to one aspect of the present invention, input of information on the emission color of the light-emitting element is accepted, and the wavelength of the excitation light is set to a wavelength shorter than the peak wavelength of the emission spectrum of the light-emitting element. In this way, the wavelength of the excitation light is determined according to the emission color of the light-emitting element, and the wavelength of the excitation light is set to be shorter than the peak wavelength of the emission spectrum of the light-emitting element, so that the emission of the light-emitting element can be appropriately detected. In addition, in the inspection device according to one aspect of the present invention, the wavelength of the excitation light is set to a wavelength longer than the absorption edge wavelength of the substrate of the object. This prevents the substrate from absorbing light and making it difficult for the excitation light to reach the light-emitting element, and also prevents the substrate from being excited by the excitation light, so that light other than the emission of the light-emitting element can be prevented from being detected. As described above, the inspection device according to one aspect of the present invention can appropriately obtain the emission of the light-emitting element to be measured, and can perform a pass / fail judgment of the light-emitting element with high accuracy based on the emission.

[0008] The control unit may determine the wavelength of the excitation light to be shorter than the wavelength obtained by subtracting the full width at half maximum of the emission spectrum from the peak wavelength of the emission spectrum of the light-emitting element. This allows the wavelength of the excitation light to be shorter than most of the wavelength bands included in the emission spectrum, making it possible to appropriately detect the emission of the light-emitting element.

[0009] The light source unit may have a white light source of the excitation light and a plurality of first bandpass filters that transmit excitation light of different wavelength bands, and the control unit may switch the first bandpass filters according to the determined wavelength of the excitation light. In this way, by changing the wavelength of the excitation light by switching the bandpass filters, it is not necessary to provide a plurality of light sources to change the wavelength, and the device can be made smaller.

[0010] The light source unit may have a plurality of light sources generating excitation light of different wavelengths, and the control unit may switch between the plurality of light sources according to the determined wavelength of the excitation light. With this configuration, it is possible to change the wavelength of the excitation light with a simple device configuration without providing a plurality of bandpass filters.

[0011] The inspection device may further include a plurality of second bandpass filters that transmit light of different wavelength bands, and the control unit may switch the second bandpass filters installed in the optical path from the light-emitting element to the light detection unit according to the determined wavelength of the excitation light. This allows an appropriate second bandpass filter to be set in conjunction with the determination of the wavelength of the excitation light according to the color of the light emitted by the light-emitting element. This allows an appropriate bandpass filter for detecting the light emission to be smoothly set.

[0012] The inspection device may further include a plurality of first wavelength separation elements that separate the excitation light and the emission light by using first separation wavelengths having wavelengths different from each other, and the control unit may switch the first wavelength separation elements installed on the optical path from the light source unit to the light emitting element and on the optical path from the light emitting element to the light detection unit according to the determined wavelength of the excitation light. This makes it possible to set an appropriate first wavelength separation element in conjunction with the determination of the wavelength of the excitation light according to the emission color of the light emitting element. This makes it possible to smoothly set an appropriate wavelength separation element for detecting the emission light.

[0013] The inspection device further includes a plurality of second wavelength separation elements that separate an emission light having a wavelength longer than the second separation wavelength and an emission light having a wavelength shorter than the second separation wavelength by using a second separation wavelength that is different from each other, and the light detection unit has a first photodetector that detects an emission light having a wavelength longer than the second separation wavelength among the emission lights, and a second photodetector that detects an emission light having a wavelength shorter than the second separation wavelength among the emission lights, and the control unit may switch the second wavelength separation element installed on the optical path from the light emitting element to the first photodetector and the second photodetector according to the determined wavelength of the excitation light. This makes it possible to set an appropriate second wavelength separation element in conjunction with the determination of the wavelength of the excitation light according to the emission color of the light emitting element. This makes it possible to smoothly set an appropriate wavelength separation element for detecting the emission light in a configuration in which the emission light on the long wavelength side and the emission light on the short wavelength side are detected by two photodetectors.

[0014] The inspection device further includes a plurality of second bandpass filters that transmit emission light in different wavelength bands, a plurality of first wavelength separation elements that use a mutually different wavelength as a first separation wavelength to separate the excitation light and the emission light using the first separation wavelength, and a plurality of second wavelength separation elements that use a mutually different wavelength as a second separation wavelength to separate emission light having a wavelength longer than the second separation wavelength and emission having a wavelength shorter than the second separation wavelength, wherein the light source unit has a white light source of excitation light and a plurality of first bandpass filters that transmit excitation light in different wavelength bands, the light detection unit has a first photodetector that detects emission light having a wavelength longer than the second separation wavelength among the emission light, and a second photodetector that detects emission light having a wavelength shorter than the second separation wavelength among the emission light, and the control unit may be configured to switch the first bandpass filter, the second bandpass filter, the first wavelength separation elements, and the second wavelength separation elements together in accordance with the determined wavelength of the excitation light. This makes it possible to set each configuration suitable for detecting emitted light more smoothly in conjunction with the determination of the wavelength of the excitation light according to the emitted color of the light emitting element.

[0015] An inspection method according to one aspect of the present invention is a method for inspecting an object having a plurality of light-emitting elements formed on a substrate, and includes the steps of inputting information related to the emission color of the light-emitting elements, deriving the absorption edge wavelength of the substrate of the object and the peak wavelength of the emission spectrum of the light-emitting elements based on the information about the emission color, and controlling the light source unit so that the wavelength of excitation light irradiated from the light source unit to the light-emitting elements is longer than the absorption edge wavelength and shorter than the peak wavelength. Effect of the Invention

[0016] According to one aspect of the present invention, it is possible to determine the quality of a light-emitting element with high accuracy. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a calibration diagram of an inspection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an emission spectrum. [Diagram 3] 1 is a flowchart of an inspection method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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.

[0019] 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 substrate. The light-emitting elements are, for example, LEDs, mini-LEDs, μLEDs, SLD elements, laser elements, vertical cavity laser elements (VCSELs), and the like. In this embodiment, the substrate of the sample S includes not only a layer of silicon or sapphire, but also a layer of GaN or the like formed on the layer by epitaxial growth. The inspection device 1 judges the quality of each light-emitting element by observing photoluminescence (specifically, light emission such as fluorescence) for a plurality of light-emitting elements formed in the sample S. It is considered that the quality of the light-emitting element is judged, for example, by probing (i.e., based on electrical characteristics). However, for example, for a fine LED such as μLED, probing by placing a needle to perform measurement is physically difficult. In this regard, the method for determining whether a light-emitting element is good or bad based on photoluminescence according to this embodiment can determine whether the element is good or bad by acquiring a fluorescent image, and therefore can efficiently determine whether a large number of light-emitting elements are good or bad without being bound by physical constraints.

[0020] 1, the inspection device 1 includes a chuck 11, an XY stage 12, a light source unit 20, a plurality of wavelength separation elements 40 (first wavelength separation elements), an objective lens 51, a Z stage 52, a plurality of wavelength separation elements 60 (second wavelength separation elements), imaging lenses 71 and 72, cameras 81 (light detection unit, first light detector), 82 (light detection unit, second light detector), a dark box 90, a control device 100 (control unit), a monitor 110, a keyboard 120 (input unit), and a plurality of bandpass filters 202 and 203 (second bandpass filters). The dark box 90 contains the components other than the control device 100, the monitor 110, and the keyboard 120 among the above-mentioned components, and is provided to prevent the components contained therein from being affected by external light. Each component housed in the dark box 90 may be mounted on a vibration isolation table in order to improve the quality of images captured by the cameras 81 and 82 (improving image quality and preventing image positional deviation).

[0021] 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 substrate 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.

[0022] The light source unit 20 generates excitation light to be irradiated to the light-emitting element. The light source unit 20 has one excitation light source 21 and an optical system 22. The excitation light source 21 is a light source that generates excitation light to be irradiated to the sample S and irradiates the excitation light to the sample S. The excitation light source 21 may be, for example, a white light source that can generate light including a wavelength that excites the light-emitting element of the sample S. The white light source is, for example, an LED, a laser, a halogen lamp, a mercury lamp, a D2 lamp, a plasma light source, or the like. Note that 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 21 constant.

[0023] The optical system 22 includes an optical fiber cable 22a, a light guide lens 22b, and a plurality of bandpass filters 22c (first bandpass filters). The optical fiber cable 22a is an optical fiber cable for guiding light connected to the excitation light source 21. For example, a polarization-maintaining fiber or a single-mode fiber can be used as the optical fiber cable 22a. The light guide lens 22b is, for example, a single or compound convex lens, and guides the excitation light that arrives via the optical fiber cable 22a toward the wavelength separation element 40.

[0024] The bandpass filters 22c are filters that transmit excitation light of different wavelength bands. That is, the bandpass filters 22c filter different wavelength band regions. Only one of the bandpass filters 22c is selected by a control device 100, which will be described later, and is set by switching. The bandpass filter 22c is provided between the light guide lens 22b and the wavelength separation element 40 for the purpose of preventing the wavelength of the excitation light emitted from the excitation light source 21 from changing over time.

[0025] The wavelength separation elements 40 separate the excitation light and the emission light by using a first separation wavelength, which is different from each other. That is, the wavelength separation elements 40 have different separation wavelengths that are the reference for separating the excitation light and the emission light. Only one of the wavelength separation elements 40 is selected by a control device 100 described later and is set by switching. The wavelength separation element 40 is a dichroic mirror made of an optical material such as a dielectric multilayer film, and reflects light of a specific wavelength and transmits light of other wavelengths. Specifically, the wavelength separation element 40 is configured to reflect the excitation light toward the objective lens 51 and transmit photoluminescence (specifically, emission of fluorescence, etc.), which is light of a wavelength band different from the excitation light, from the light emitting element toward the wavelength separation element 60.

[0026] The objective lens 51 is a component for observing the sample S, and focuses the excitation light guided by the wavelength separation element 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.

[0027] The wavelength separation elements 60 use different wavelengths as second separation wavelengths to separate emitted light having a wavelength longer than the second separation wavelength from emitted light having a wavelength shorter than the second separation wavelength. That is, the wavelength separation elements 60 have different separation wavelengths that are the basis for separating emitted light on the long wavelength side from emitted light on the short wavelength side. Only one of the wavelength separation elements 60 is selected by the control device 100 described later and is set by switching. The wavelength separation element 60 is a dichroic mirror made of an optical material such as a dielectric multilayer film, and reflects light of a specific wavelength and transmits light of other wavelengths. This dichroic mirror may not only have a characteristic in which the transmittance (reflectance) changes sharply with respect to the wavelength, but also have a characteristic in which the transmittance (reflectance) changes gradually with respect to the wavelength with a width of about 100 nm. The dichroic mirror may have a characteristic that the transmittance (reflectance) changes between wavelengths of 400 nm and 900 nm, or between wavelengths of 400 nm and 700 nm. The wavelength separation element 60 is configured not to transmit (reflect) emitted light having a wavelength shorter than the second separation wavelength, and to transmit fluorescent light having a wavelength longer than the second separation wavelength. The short-wavelength emitted light reflected by the wavelength separation element 60 is, for example, emitted light having a wavelength included in the normal emission spectrum (emission of the original emission wavelength), and the long-wavelength fluorescent light transmitted by the wavelength separation element 60 is emitted light having a wavelength not included in the normal emission spectrum (emission of the long-wavelength side). The 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 that is a peak in the intensity of the fluorescence from the light-emitting element measured by a spectroscope. In more detail, the wavelength separation element 60 is considered to transmit a part of the emission light having a wavelength shorter than the second separation wavelength and to reflect a part of the emission light having a wavelength longer than the second separation wavelength, but since it generally reflects the emission light having a wavelength shorter than the second separation wavelength and transmits the emission light having a wavelength longer than the second separation wavelength, hereinafter, it will be simply described as "the wavelength separation element 60 reflects the emission light having a wavelength shorter than the second separation wavelength and transmits the emission light having a wavelength longer than the second separation wavelength." The emission light having a wavelength longer than the second separation wavelength (emission light on the long wavelength side) reaches the imaging lens 71 through the wavelength separation element 60.Emission light having a wavelength shorter than the second separation wavelength (emission light having an original emission wavelength) reaches the imaging lens 72 via the wavelength separation element 60. Note that the wavelength separation element 60 does not necessarily have to be a dichroic mirror, and may be realized by, for example, a combination of a half mirror and bandpass filters 202 and 203.

[0028] The plurality of bandpass filters 202 are filters that transmit light of different wavelength bands. That is, the plurality of bandpass filters 202 have different wavelength band regions to be filtered. Only one of the plurality of bandpass filters 202 is selected by the control device 100 described later and set by switching. The bandpass filter 202 is provided between the wavelength separation element 60 and the camera 81 to prevent unnecessary light emission on the long wavelength side. The bandpass filter 202 may be configured by a shortpass filter. The plurality of bandpass filters 203 are filters that transmit light emission of different wavelength bands. That is, the plurality of bandpass filters 203 have different wavelength band regions to be filtered. Only one of the plurality of bandpass filters 203 is selected by the control device 100 described later and set by switching. The bandpass filter 203 is provided between the wavelength separation element 60 and the camera 82 to prevent the mixing of light emission on the long wavelength side due to surface reflection of the wavelength separation element 60 in the measurement of light emission on the short wavelength side. The bandpass filter 203 may be configured by a longpass filter.

[0029] The imaging lens 71 is a lens that forms an image of the emission light on the long wavelength side and guides the emission light to the camera 81. The camera 81 is an imaging unit that images the emission light from the sample S. More specifically, the camera 81 images and detects the emission light (emission light on the long wavelength side) having a wavelength longer than the above-mentioned second separation wavelength among the emissions from the light-emitting element. The camera 81 outputs the image of the emission light on the long wavelength side, which is the imaging result, 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.

[0030] The imaging lens 72 is a lens that forms an image of the emission of the original emission wavelength and guides the emission to the camera 82. The camera 82 is an imaging unit that images the emission from the sample S. More specifically, the camera 82 images and detects the emission of the wavelength shorter than the above-mentioned second separation wavelength among the emission from the light-emitting element and included in the normal emission spectrum ES of the light-emitting element (emission of the original emission wavelength). The camera 82 outputs the emission image of the original emission wavelength, which is the imaging result, 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 by a line sensor or a TDI sensor.

[0031] The control device 100 is a computer, and is physically configured to include a memory such as a RAM or a 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 (a smartphone, a tablet terminal, etc.). The control device 100 functions by executing a program stored in the memory on the CPU of a computer system. The control device 100 controls the XY stage 12, the excitation light source 21, 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 performs focus adjustment related to the excitation light by controlling the Z stage 52. The control device 100 controls the excitation light source 21 to adjust the emission of the excitation light and the wavelength, amplitude, etc. of the excitation light. The control device 100 controls the cameras 81 and 82 to perform adjustment related to the acquisition of a luminescence image.

[0032] Furthermore, the control device 100 judges the pass / fail of the light-emitting elements of the sample S based on the emission images captured by the cameras 81 and 82. The control device 100 judges the pass / fail of the light-emitting elements based on the long wavelength emission image captured by the camera 81 and the emission image of the original emission wavelength captured by the camera 82. For example, the control device 100 judges the pass / fail of the light-emitting elements based on the emission image of the original emission wavelength captured by the camera 82, and after the judgment, judges the pass / fail of the light-emitting elements judged to be pass / fail in the judgment based on the long wavelength emission image captured by the camera 81.

[0033] The control device 100 first identifies the position of the light-emitting element based on the light emission 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 light emission 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 light emission image. Then, the control device 100 derives the average luminance in the light-emitting area of ​​each light-emitting element based on the light emission image of the original light emission wavelength, and links the address position and the luminance (average luminance in the light-emitting area) for each light-emitting element. The control device 100 derives an evaluation index from the absolute luminance and the relative luminance for each address (each light-emitting element). The relative luminance is the luminance ratio of the light-emitting element to be derived to the average luminance of a light-emitting element group 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, for example, from the product of the absolute luminance and the 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 light-emitting image. In addition, the control device 100 obtains a new light-emitting image (light-emitting image of the original light-emitting wavelength) by changing the irradiation area, and derives an evaluation index for each light-emitting element included in the light-emitting image. After deriving the evaluation index for all light-emitting elements, the control device 100 sorts (rearranges) the light-emitting elements in descending order of the evaluation index. When sorting is performed, it is found that the evaluation index becomes suddenly smaller at a certain point (change point). For example, the control device 100 may use such a change point as a threshold and determine that a light-emitting element having an evaluation index equal to or greater than the threshold is a good product (good pixel), and a light-emitting element having an evaluation index smaller than the threshold 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).

[0034] The control device 100 also detects bright points (light emission spots) in the light emission area of ​​each light emitting element based on the light emission image on the long wavelength side, and associates the address position with the number of bright points for each light emitting element. Such bright points (light emission spots) on the long wavelength side of the normal emission spectrum are abnormal light emission points. The control device 100 then determines whether or not a certain number of bright points are included in the light emission image on the long wavelength side for light emitting elements determined to be good in the quality determination based on the light emission image of the original light emission wavelength described above, and determines light emitting elements that do not include the certain number of bright points as good products (good pixels), and light emitting elements that include the certain number of bright points as defective products (defective pixels). In such an example, even if a light emitting element is determined to be good based on the light emission image of the original light emission wavelength, it may be determined to be defective based on the fluorescent image on the long wavelength side.

[0035] The control device 100 may perform a pass / fail judgment of the light-emitting elements based on the emission image of the original emission wavelength acquired by the camera 82, and then may perform a pass / fail judgment of the light-emitting elements determined to be defective in the judgment based on the emission image of the long wavelength side acquired by the camera 81. The control device 100 may also perform a pass / fail judgment of all the light-emitting elements based on the emission image of the long wavelength side. In this way, the control device 100 may perform a pass / fail judgment based on the emission image of the long wavelength side only for the light-emitting elements determined to be good based on the emission image of the original emission wavelength, may perform a pass / fail judgment based on the emission image of the long wavelength side only for the light-emitting elements determined to be defective based on the emission image of the original emission wavelength, or may perform a pass / fail judgment based on the emission image of the long wavelength side for all the light-emitting elements regardless of the pass / fail judgment result based on the emission image of the original emission wavelength.

[0036] The control device 100 outputs a pass / fail judgment result for each light-emitting element. The pass / fail judgment result is displayed, for example, on the monitor 110. The control device 100 may also identify a defective portion (for example, a bright spot on the long wavelength side) in the light-emitting element and output the position of the defective portion (output so as to be displayed on the monitor 110).

[0037] In order to perform the above-mentioned pass / fail judgment with higher accuracy, the control device 100 performs a predetermined control according to information on the emission color of the light-emitting element. The information on the emission color of the light-emitting element is received, for example, by a user through the keyboard 120 and input to the control device 100.

[0038] The control device 100 determines the wavelength of the excitation light based on the information on the emission color received by the keyboard 120. Specifically, the control device 100 determines the wavelength of the excitation light to be longer than the absorption edge wavelength of the substrate of the sample S and shorter than the peak wavelength of the emission spectrum of the light-emitting element identified from the information on the emission color. The absorption edge wavelength of the substrate is the longest wavelength at which light absorption occurs in the substrate. The absorption edge wavelength of the substrate is determined by the band gap of the base material. Light with a wavelength longer than the absorption edge wavelength of the substrate passes through the substrate. As described above, the substrate of the sample S includes not only a layer of silicon or sapphire, but also a layer of GaN or the like formed by epitaxial growth on the layer. By making the wavelength of the excitation light longer than the absorption edge wavelength of the substrate, the substrate is prevented from being excited by the excitation light (the emission from the substrate). In addition, by making the wavelength of the excitation light shorter than the peak wavelength of the emission spectrum, the light-emitting element can be appropriately excited and the light emission from the light-emitting element can be appropriately obtained. More specifically, the control device 100 determines the wavelength of the excitation light to be a wavelength shorter than the wavelength obtained by subtracting the full width at half maximum of the emission spectrum of the light emitting element from the peak wavelength of the emission spectrum of the light emitting element (taking the difference between the full width at half maximum).

[0039] FIG. 2 is a diagram for explaining the emission spectrum under each condition. In FIG. 2, the horizontal axis indicates wavelength, and the vertical axis indicates brightness (AU). In FIG. 2, the thin dashed line indicates the emission spectrum of sample S when the wavelength of excitation light is 370 nm, the thick dashed line indicates the emission spectrum of sample S when the wavelength of excitation light is 355 nm, and the solid line indicates the emission spectrum of sample S when electricity is applied. In a scene where sample S is commercialized and used, electricity is applied to the light-emitting element. Therefore, even when the quality of the light-emitting element is judged by irradiation with excitation light, the emission spectrum may be close to the emission spectrum when electricity is applied to the light-emitting element. Note that the level of the brightness of the light emitted is actually different when the light-emitting element is excited by excitation light and when electricity is applied, but since the shape of the emission spectrum is important here, the difference in the level of brightness is appropriately adjusted and illustrated.

[0040] Now, assume that the light-emitting element of the sample S to be observed is a blue LED (the emitted light color is blue). In this case, the emission wavelength width of the light-emitting element is, for example, 420 nm to 480 nm. Also assume that the absorption edge wavelength of the GaN substrate of the sample S is 365 nm. Under such conditions, as shown in FIG. 2, when the wavelength of the excitation light is set to 355 nm, that is, when the wavelength of the excitation light is made shorter than the absorption edge wavelength of the substrate, the emission spectrum ("PL(355)" in FIG. 2) is significantly different from the emission spectrum ("EL" in FIG. 2) when electricity is applied to the light-emitting element. This is considered to be due to the influence of the emission from the substrate by making the wavelength of the excitation light shorter than the absorption edge wavelength of the substrate. On the other hand, as shown in FIG. 2, when the wavelength of the excitation light is set to 370 nm, that is, when the wavelength of the excitation light is made longer than the absorption edge wavelength of the substrate, the emission spectrum ("PL(370)" in FIG. 2) is close to the emission spectrum ("EL" in FIG. 2) when electricity is applied to the light-emitting element. In this way, by making the wavelength of the excitation light longer than the absorption edge wavelength of the substrate of the sample S, it is possible to obtain an appropriate emission spectrum without being affected by the emission from the substrate. In the above example, the wavelength of the excitation light may be in the range of 365 nm to 420 nm, which is between the short wavelength edge of the emission spectrum and the absorption edge wavelength of the substrate. Note that, if the wavelength of the excitation light is made as long as possible within the above range, the contrast of the emission intensity is increased without exciting the intermediate region of the quantum well. Note that, for example, when the light emitting element is a green LED (emitting green light), the emission wavelength width of the light emitting element is, for example, 490 nm to 550 nm. In this case, the wavelength of the excitation light may be in the range of 365 nm to 490 nm, which is the absorption edge wavelength of the substrate.

[0041] The control device 100 controls the light source unit 20 so that excitation light of the determined wavelength is generated. Specifically, the control device 100 selects a bandpass filter 22c that transmits the excitation light of the determined wavelength so that the excitation light of the determined wavelength is emitted from the light source unit 20 and irradiated to the light emitting element, and installs the bandpass filter 22c on the optical path from the light source unit 20 to the wavelength separation element 40. In this way, the control device 100 switches the bandpass filter 22c according to the wavelength of the determined excitation light. Note that the inspection device 1 may have a plurality of excitation light sources 21 that generate excitation light of different wavelengths. In this case, the excitation light source 21 may be composed of a plurality of light sources capable of generating monochromatic light different from each other, and the plurality of light sources are, for example, LEDs, SLDs, lasers, etc. In this case, the control device 100 selects an excitation light source 21 capable of generating excitation light of the determined wavelength and generates the excitation light, thereby generating excitation light of a desired wavelength in the same manner as in the above-mentioned aspect of switching and setting the bandpass filter 22c. That is, the control device 100 may switch between the multiple excitation light sources 21 depending on the determined wavelength of the excitation light.

[0042] The control device 100 may switch the bandpass filter 202 installed on the optical path from the light-emitting element to the camera 81 according to the determined wavelength of the excitation light. In this case, the control device 100 selects the bandpass filter 202 capable of preventing leakage light of the excitation light from the wavelength separation element 60 and unnecessary emission on the long wavelength side, for example, taking into consideration the emission color of the light-emitting element related to the determination of the wavelength of the excitation light. The control device 100 may also switch the bandpass filter 203 installed on the optical path from the light-emitting element to the camera 82 according to the determined wavelength of the excitation light. In this case, the control device 100 selects the bandpass filter 203 capable of preventing leakage light of the excitation light from the wavelength separation element 60 and emission on the long wavelength side from being mixed into the measurement of emission on the short wavelength side, for example, taking into consideration the emission color of the light-emitting element related to the determination of the wavelength of the excitation light.

[0043] The control device 100 may switch the wavelength separation element 40 installed on the optical path from the light source unit 20 to the light emitting element and on the optical path from the light emitting element to the cameras 81, 82 according to the determined wavelength of the excitation light. In this case, the control device 100 selects the wavelength separation element 40 that can reflect the excitation light toward the objective lens 51 and transmit the emitted light toward the wavelength separation element 60, taking into consideration, for example, the emission color of the light emitting element and the wavelength of the excitation light.

[0044] The control device 100 may switch the wavelength separation element 60 installed in the optical path from the light emitting element to the camera 81 and the camera 82 according to the determined wavelength of the excitation light. In this case, the control device 100 selects a wavelength separation element 60 that can appropriately separate the emission of the original emission wavelength from the emission of the longer wavelength side (the second separation wavelength is appropriate), taking into consideration, for example, the emission color of the light emitting element.

[0045] The control device 100 may integrally switch the bandpass filter 22c, the bandpass filters 202 and 203, the wavelength separation element 40, and the wavelength separation element 60 in accordance with the determined wavelength of the excitation light. That is, the control device 100 may simultaneously switch the bandpass filter 22c, the bandpass filters 202 and 203, the wavelength separation element 40, and the wavelength separation element 60 in conjunction with the determination of the wavelength of the excitation light.

[0046] Next, an inspection method will be described with reference to Fig. 3. Fig. 3 is a flowchart of an inspection method performed using the inspection device 1. The inspection method is a method for inspecting a sample S in which a plurality of light emitting elements are formed on a substrate.

[0047] 3, first, information regarding the emission color of the light emitting element is inputted from the keyboard 120 (step S1, inputting step). The inspection device 1 accepts the input of the information regarding the emission color.

[0048] Next, the inspection device 1 determines the wavelength of the excitation light based on the information on the emission color (step S2). Specifically, the inspection device 1 derives the absorption edge wavelength of the substrate of the sample S and the peak wavelength of the emission spectrum of the light-emitting element based on the information on the emission color (deriving step).

[0049] Next, the inspection device 1 sets the bandpass filter 22c of the light source unit 20 so that the wavelength of the excitation light is the determined wavelength (step S3). That is, the inspection device 1 controls the light source unit 20 so that the wavelength of the excitation light is longer than the absorption edge wavelength of the substrate and shorter than the peak wavelength of the emission spectrum (controlling step).

[0050] Next, the inspection device 1 integrally sets the bandpass filter 22c, the bandpass filters 202 and 203, the wavelength separation element 40, and the wavelength separation element 60 in accordance with the determined wavelength of the excitation light (step S4).

[0051] Next, the inspection device 1 irradiates the light emitting element with excitation light and detects light emitted (fluorescence) from the light emitting element (step S5).Then, the inspection device 1 judges the quality of the light emitting element based on the light emitted from the light emitting element (step S6).

[0052] Next, the effects of the inspection device 1 according to this embodiment will be described.

[0053] The inspection device 1 is an inspection device for inspecting a sample S having a plurality of light-emitting elements formed on a substrate, and includes a light source unit 20 that generates excitation light to be irradiated to the light-emitting elements, cameras 81, 82 that detect the emission of the light-emitting elements irradiated with the excitation light, a keyboard 120 that accepts input of information related to the emission color of the light-emitting elements, and a control device 100 that determines the wavelength of the excitation light based on the information related to the emission color received by the keyboard 120 and controls the light source unit 20 so that excitation light of that wavelength is generated, and the control device 100 determines the wavelength of the excitation light to be longer than the absorption edge wavelength of the substrate of the sample S and shorter than the peak wavelength of the emission spectrum of the light-emitting elements identified from the information related to the emission color.

[0054] In such an inspection device 1, input of information on the emission color of the light-emitting element is accepted, and the wavelength of the excitation light is set to a wavelength shorter than the peak wavelength of the emission spectrum of the light-emitting element. In this way, the wavelength of the excitation light is determined according to the emission color of the light-emitting element, and the wavelength of the excitation light is set to be shorter than the peak wavelength of the emission spectrum of the light-emitting element, so that the emission of the light-emitting element can be appropriately detected. In addition, in an inspection device according to one aspect of the present invention, the wavelength of the excitation light is set to a wavelength longer than the absorption edge wavelength of the substrate of the sample S. This prevents light from being absorbed by the substrate, making it difficult for the excitation light to reach the light-emitting element. In addition, excitation of the substrate by the excitation light is prevented, and light other than the emission of the light-emitting element can be prevented from being detected. As described above, according to the inspection device 1, the emission of the light-emitting element to be measured can be appropriately acquired, and the pass / fail judgment of the light-emitting element can be performed with high accuracy based on the emission.

[0055] The control device 100 may determine the wavelength of the excitation light to be shorter than the wavelength obtained by subtracting the full width at half maximum of the emission spectrum from the peak wavelength of the emission spectrum of the light-emitting element. This allows the wavelength of the excitation light to be shorter than most of the wavelength bands included in the emission spectrum, making it possible to appropriately detect the emission of the light-emitting element.

[0056] The light source unit 20 has a white light source of excitation light and a plurality of bandpass filters 22c that transmit excitation light of different wavelength bands, and the control device 100 may switch the bandpass filters 22c according to the determined wavelength of the excitation light. In this way, by changing the wavelength of the excitation light by switching the bandpass filters 22c, it is not necessary to provide a plurality of excitation light sources 21 to change the wavelength, and the inspection device 1 can be made smaller.

[0057] The light source unit 20 may have a plurality of excitation light sources 21 that generate excitation light of different wavelengths, and the control device 100 may switch between the plurality of excitation light sources 21 according to the determined wavelength of the excitation light. With this configuration, it is possible to change the wavelength of the excitation light with a simple device configuration without providing a plurality of bandpass filters 22c.

[0058] The inspection device 1 further includes a plurality of bandpass filters 202, 203 that transmit light of different wavelength bands, and the control device 100 may switch between the bandpass filter 202 installed on the optical path from the light-emitting element to the camera 81 and the bandpass filter 203 installed on the optical path from the light-emitting element to the camera 82 according to the determined wavelength of the excitation light. This makes it possible to set appropriate bandpass filters 202, 203 in conjunction with the determination of the wavelength of the excitation light according to the emission color of the light-emitting element. This makes it possible to smoothly set appropriate bandpass filters 202, 203 for detecting the emission light.

[0059] The inspection device 1 further includes a plurality of wavelength separation elements 40 that separate the excitation light and the emission light by using a first separation wavelength having a different wavelength from each other, and the control device 100 may switch the wavelength separation elements 40 installed on the optical path from the light source unit 20 to the light emitting element and on the optical path from the light emitting element to the cameras 81, 82 according to the determined wavelength of the excitation light. This makes it possible to set an appropriate wavelength separation element 40 in conjunction with the determination of the wavelength of the excitation light according to the emission color of the light emitting element. This makes it possible to smoothly set an appropriate wavelength separation element 40 for detecting the emission light.

[0060] The inspection device 1 further includes a plurality of wavelength separation elements 60 that separates an emission light having a wavelength longer than the second separation wavelength and an emission light having a wavelength shorter than the second separation wavelength by using a second separation wavelength having a different wavelength from each other, a camera 81 that detects an emission light having a wavelength longer than the second separation wavelength among the emission lights, and a camera 82 that detects an emission light having a wavelength shorter than the second separation wavelength among the emission lights, and the control device 100 may switch the wavelength separation element 60 installed on the optical path from the light emitting element to the camera 81 and the camera 82 according to the determined wavelength of the excitation light. This allows the wavelength separation element 60 to be set appropriately in conjunction with the determination of the wavelength of the excitation light according to the emission color of the light emitting element. This allows the wavelength separation element 60 to be set appropriately for detecting the emission light in a configuration in which the emission light on the long wavelength side and the emission light on the short wavelength side are detected by two photodetectors.

[0061] The control device 100 may integrally switch the bandpass filter 22c, the bandpass filters 202 and 203, the wavelength separation element 40, and the wavelength separation element 60 in accordance with the determined wavelength of the excitation light. This makes it possible to set each configuration suitable for detecting the emitted light more smoothly in conjunction with the determination of the wavelength of the excitation light in accordance with the emission color of the light-emitting element.

[0062] In the inspection device 1, the light detection unit is configured using area sensors such as the camera 81 as the first light detector and the camera 82 as the second light detector, but the light detection unit may be configured using a single point sensor as each light detector. The single point sensor is, for example, a photodiode, a PIN-photodiode, an avalanche photodiode, a photomultiplier tube, a photoresistor, etc. Also, the single point sensor has a light receiving unit configured of a material such as Si, GaAs, InP, GaP, InGaAs, InSb, etc. When the light detection unit is configured as described above, for example, the sample S may be moved by the XY stage 12 to detect light emission from a specific point, or the light emission may be scanned and detected while the sample S is moved by the XY stage 12. Also, by further providing an optical scanning unit having a galvanometer mirror or the like in the optical system, light emission from a specific point on the sample S may be detected, or light emission from the sample S may be scanned and detected. When performing the above-mentioned scanning detection, for example, it is possible to observe the unevenness of the surface of the sample S from the shift in wavelength, or dynamically observe the Raman shift of the sample S. [Explanation of symbols]

[0063] 1...inspection device, 20...light source section, 21...excitation light source, 22c...bandpass filter, 40...wavelength separation element, 60...wavelength separation element, 81, 82...camera, 100...control device, 120...keyboard, 202, 203...bandpass filter.

Claims

1. An inspection device for inspecting an object, comprising: A light source unit that generates excitation light to be irradiated onto the object; a wavelength separation element that separates light emitted at a wavelength longer than a separation wavelength from light emitted at a wavelength shorter than the separation wavelength, and whose transmittance (reflectance) for the wavelength changes gradually within a predetermined range; a light detection unit including a first single point sensor that detects the emission of light from the object irradiated with the excitation light, and detects the emission of light having a wavelength longer than the separation wavelength among the emission, and a second single point sensor that detects the emission of light having a wavelength shorter than the separation wavelength among the emission; and a control unit that controls a stage that moves the object or a scanning unit provided within an optical system.

2. The inspection device according to claim 1 , wherein the control unit observes unevenness or Raman shift on the surface of the object by scanning and detecting light emitted from the object.

3. 3. The inspection device according to claim 1, wherein the first single-point sensor and the second single-point sensor are a photodiode, a PIN photodiode, an avalanche photodiode, a photomultiplier tube, or a photoresistor.

4. 3. The inspection device according to claim 1, wherein the first single point sensor and the second single point sensor have a light receiving portion including at least one of Si, GaAs, InP, GaP, InGaAs, and InSb.

Images