Light irradiation device, measurement device, observation device, and film thickness measurement device

Abstract

The light irradiation device includes: a light source that emits light; a light pipe into which the light emitted from the light source is input, and which homogenizes the illuminance distribution of the light and outputs the light; a diffusion plate that diffuses the light output from the light pipe; and a light pipe into which the light diffused by the diffusion plate is input, and which homogenizes the illuminance distribution of the light and outputs the light. That is, the light irradiation device includes two light pipes and a diffusion plate provided so as to be sandwiched between the two light pipes.

Description

Technical Field

[0001] One embodiment of the present invention relates to a light irradiation device, a measuring device, an observation device, and a film thickness measurement device. Background Art

[0002] Patent document 1 describes that in an illumination device, by providing diffusers on the input side and output side of a light guide, respectively, the irradiation density is reduced and uniform light is generated. Patent document 2 describes that in a fundus observation device, by providing a diffuser on the output side of a light guide, a pseudo point light source is generated and illumination spots are reduced.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-134992

[0006] Patent Document 2: Re-publication of WO2019 / 240300 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] Here, in a structure where a diffuser is arranged on the output side of a uniformizing optical system such as a light guide, as in the structures of the above-mentioned Patent Documents 1 and 2, light diffused by the diffuser is irradiated onto a subsequent measurement object, and thus the convex and concave portions of the diffuser are sometimes imaged on the optical image of the measurement object. That is, in the above-mentioned structure, the light irradiated onto the measurement object cannot be sufficiently uniformized.

[0009] One aspect of the present invention has been made in view of the above-mentioned actual situation, and an object of the present invention is to provide a light irradiation device, a measuring device, an observation device, and a film thickness measurement device that can appropriately make light irradiated to a measurement object uniform.

[0010] Technical means of solving problems

[0011] [E1]

[0012] A light irradiation device according to one embodiment of the present invention comprises: a light source that emits light; a first homogenizing optical system that receives light emitted from the light source, makes the illuminance distribution of the light uniform, and outputs the light; a diffusion unit that diffuses the light output from the first homogenizing optical system; and a second homogenizing optical system that receives light diffused by the diffusion unit, makes the illuminance distribution of the light uniform, and outputs the light.

[0013] In a light irradiation device in one aspect of the present invention, the illumination distribution of light emitted from a light source is uniformized by a first uniformizing optical system, the light output by the first uniformizing optical system is diffused by a diffusion section, and the illumination distribution of the light diffused by the diffusion section is uniformized by a second uniformizing optical system. By providing the first uniformizing optical system, the uniformized light can be irradiated to the diffusion section. In addition, by providing the diffusion section, the virtual image of the non-uniform light incident on the first uniformizing optical system (i.e., the virtual image on the light source side) is suppressed from being incident on the second uniformizing optical system of the subsequent stage. Furthermore, by providing the second uniformizing optical system, the diffused light from the diffusion section is uniformized, thereby suppressing the convex and concave imaging of the diffusion section on the optical image of the object to be measured that is finally irradiated with the light. Based on the above, according to a light irradiation device in one aspect of the present invention, the light irradiated to the object to be measured can be appropriately uniformized.

[0014] [E2]

[0015] In the light irradiation device described in [E1] above, the first uniformizing optical system may be a first light guide and the second uniformizing optical system may be a second light guide. In this way, since both uniformizing optical systems are composed of light guides, light loss can be suppressed and light can be appropriately uniformized.

[0016] [E3]

[0017] In the light irradiation device described in [E2] above, the diameter of the light input surface of the second light guide may be the same diameter as the diameter of the light output surface of the first light guide. For example, when the diameter of the light output surface of the first light guide is smaller than the diameter of the light input surface of the second light guide, light is input only to a portion of the light input surface of the second light guide, and there is a concern that the light output from the second light guide may not be sufficiently uniformized. By making the diameter of the light input surface of the second light guide the same diameter as the diameter of the light output surface of the first light guide, uniformization of the light output from the second light guide and suppression of a decrease in the amount of light can be achieved.

[0018] [E4]

[0019] In the light irradiation device described in [E2] above, the diameter of the light input surface of the second light guide may be smaller than the diameter of the light output surface of the first light guide. For example, when the diameter of the light output surface of the first light guide is smaller than the diameter of the light input surface of the second light guide, light is input only to a portion of the light input surface of the second light guide, and there is a concern that the light output from the second light guide may not be sufficiently uniformized. By making the diameter of the light input surface of the second light guide smaller than the diameter of the light output surface of the first light guide, uniformization of the light output from the second light guide can be achieved.

[0020] [E5]

[0021] In the light irradiation devices described in [E2] to [E4] above, the diameter of the light output surface of the second light guide may be larger than the diameter of the light input surface of the second light guide. In this way, by forming the second light guide into a tapered shape whose diameter becomes wider toward the light output surface, the irradiation range on the sample can be expanded, and uniform light can be irradiated over a wide range.

[0022] [E6]

[0023] In the light irradiation device described in [E1] above, the first uniformizing optical system may be a first fly-eye lens, and the second uniformizing optical system may be a second fly-eye lens. According to such a structure, light loss can be suppressed and light can be appropriately uniformized, similar to the case where the uniformizing optical system is composed of a light guide.

[0024] [E7]

[0025] In the light irradiation device described in any one of [E1] to [E6] above, the diffusion unit may be a diffusion plate. According to such a configuration, the light can be easily uniformized by sandwiching the diffusion plate between the two light guides.

[0026] [E8]

[0027] A measuring device according to one aspect of the present invention comprises: a light irradiation device as described in any one of [E1] to [E7] above; and an imaging unit that captures an image of measurement light generated by light irradiated from the light irradiation device to an object to be measured. With such a structure, the object to be measured can be irradiated with uniform light, and the measurement light generated from the object to be measured can be captured with high accuracy.

[0028] [E9]

[0029] An observation device according to one aspect of the present invention comprises: a light irradiation device as described in any one of [E1] to [E7] above; and an imaging unit that captures light irradiated from the light irradiation device to a measurement object, i.e., observation light. With such a configuration, uniformized light can be irradiated to the measurement object, and the observation light can be captured with high accuracy.

[0030] [E10]

[0031] An observation device according to one aspect of the present invention comprises: a light irradiation device as described in any one of [E1] to [E7] above; an imaging unit that captures light irradiated from the light irradiation device to a measurement object, i.e., observation light, and outputs imaging data; and a film thickness deriving unit that derives the film thickness of the measurement object based on the imaging data. With such a configuration, the measurement object can be irradiated with uniformized light, and the film thickness of the measurement object can be derived with high accuracy.

[0032] Effects of the Invention

[0033] According to one aspect of the present invention, it is possible to provide a light irradiation device, a measuring device, an observation device, and a film thickness measurement device that can appropriately make uniform the light irradiated to a measurement object. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural diagram of a measuring device including the light irradiation device of this embodiment.

[0035] Figure 2 yes Figure 1 Detailed structural diagram of the diffuser plate shown.

[0036] Figure 3 It is a structural diagram of a measuring device of the first comparative example.

[0037] Figure 4 It is a structural diagram of a measuring device of the second comparative example.

[0038] Figure 5 (a) is a diagram showing the imaging result of the measuring device of the first comparative example, Figure 5 (b) is a diagram showing the imaging result of the measuring device of the second comparative example, Figure 5 (c) is a diagram showing the imaging result of the measuring device according to this embodiment.

[0039] Figure 6 It is a structural diagram of a light guide according to a modified example.

[0040] Figure 7 It is a structural diagram of a light irradiation device according to a modified example.

[0041] Figure 8 It is a structural diagram of a light irradiation device according to a modified example.

[0042] Fig. 9 It is a structural diagram of an observation device including a light irradiation device of a modified example.

[0043] Fig.10 It is a structural diagram of a film thickness measuring device including a light irradiation device according to a modified example. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In each of the drawings, the same or corresponding parts are given the same reference numerals, and repeated descriptions are omitted.

[0045] Figure 11 is a structural diagram of a measuring device 1 including a light irradiation device 2 of the present embodiment. The measuring device 1 is an inspection device for inspecting a sample S (measurement object). The sample S is, for example, a semiconductor device having a plurality of light-emitting elements formed on a substrate. In addition, the sample S may also be a substrate or an epitaxial layer before various devices are formed. The light-emitting element is, for example, an LED, a small LED, a μLED, an SLD element, a laser element, a vertical laser element (VCSEL), and the like. The measuring device 1 irradiates, for example, a specified range on the sample S with excitation light of uniform intensity, and captures the photoluminescence (specifically, light emission such as fluorescence) generated in the specified range, and inspects the sample S based on the obtained image data.

[0046] The measuring device 1 can also perform a quality judgment of each light-emitting element by observing the photoluminescence (specifically, fluorescence or other light-emitting elements) of a plurality of light-emitting elements formed on the sample S, for example. The quality judgment of the light-emitting element can be performed, for example, by probing (i.e., based on electrical characteristics). However, for a microscopic LED such as a μLED, it is physically difficult to perform probing by contacting a probe to perform measurement. In this regard, the quality judgment method of the light-emitting element based on photoluminescence can perform quality judgment by obtaining a fluorescence image, and thus can effectively perform quality judgment on a large number of light-emitting elements without being restricted by physical properties.

[0047] like Figure 1 As shown, the measuring device 1 includes a light irradiation device 2 and an imaging unit 26. The light irradiation device 2 is a device that irradiates uniform light to the sample S and excites the sample S uniformly. The light irradiation device 2 includes: a light source 11, light guide lenses 12, 13, an optical fiber cable 14, light guides 15, 17 (a first uniformization optical system, a second uniformization optical system), a diffusion plate 16 (diffusion unit), a light guide lens 18, mirrors 19, 20, light guide lenses 21, 22, a half-reflecting half-mirror 23, an objective lens 24, and an imaging lens 25. In addition, the sample S is held by a chuck (not shown) of a substrate that vacuum absorbs the sample S, for example. In this case, the chuck (not shown) can be moved by an XY stage (not shown) that moves the chuck in the XY direction (front and back, left and right directions).

[0048] The light source 11 generates excitation light to be irradiated to the sample S, and emits the excitation light to the sample S. The light source 11 may be, for example, a white light source that can generate light having a wavelength that excites the light emitting element of the sample S. Examples of white light sources include LEDs, lasers, halogen lamps, mercury lamps, D2 lamps, plasma light sources, and the like.

[0049] The light guide lens 12 guides the excitation light emitted from the light source 11 toward the light guide lens 13. The light guide lens 13 guides the excitation light reaching through the light guide lens 12 toward the optical fiber cable 14. The light guide lenses 12 and 13 are, for example, convex lenses.

[0050] The optical fiber cable 14 is an optical fiber cable for guiding light. The optical fiber cable 14 guides the excitation light reaching through the light guide lens 13 toward the light guide 15. As the optical fiber cable 14, for example, a polarization-maintaining optical fiber or a single-mode optical fiber can be used.

[0051] The light guide 15 (first light guide) is an optical system that receives the excitation light emitted from the light source 11 (light that arrives via the optical fiber cable 14), makes the illumination distribution of the excitation light uniform, and outputs it. The light guide 15 is an optical element that makes the incident light uniform by reflecting it multiple times from the side surfaces of a polygonal column or a polygonal pyramid, and then outputs it. By providing the light guide 15, the uniform excitation light is incident on the diffuser 16 of the subsequent stage.

[0052] The diameter and length of the light input surface of the light guide 15 depend on the diffusion angle of light incident on the light input surface of the light guide 15 (for example, the NA of the optical fiber cable 14) or the total reflection angle of the light guide 15 (for example, the NA of the light guide 15). In addition, the diameter of the light output surface of the light guide 15 depends on the size of the light irradiation range on the sample S, etc. In addition, when the diameter of the light guide 15 is set to D and the smaller NA of the optical fiber cable 14 and the NA of the light guide 15 is set to α, the length L of the light guide 15 only needs to be greater than D / α, for example, it can be greater than D / α+1. In addition, it is preferably greater than 3D / α. The longer the length of the light guide 15 is, the higher the degree of light uniformity can be.

[0053] The diffuser plate 16 is a plate-shaped member that diffuses the excitation light emitted from the light guide 15. The diffuser plate 16 is provided at a position sandwiched between the preceding light guide 15 and the succeeding light guide 17, which are provided as separate members. Figure 2 Detailed structural diagram of the diffuser 16. The diffuser 16 is, for example, a structure in which a single surface 16a on the light guide 17 side is set to be frosted glass-like. The single surface 16a can be formed smooth by, for example, etching the surface with hydrogen fluoride. By providing the diffuser 16, the virtual image of the uneven light incident on the light guide 15 (i.e., the virtual image on the light source 11 side) is suppressed from being incident on the subsequent light guide 17. The diffuser 16 may not be a structure in which a single surface 16a is set to be frosted glass-like, and may be, for example, a microlens array. In addition, as long as it can diffuse light in the same manner as the diffuser 16, the diffuser may be a structure other than the diffuser 16, for example, a translucent member (for example, a translucent film) or the like.

[0054] The light guide 17 (second light guide) is an optical system that receives the excitation light diffused by the diffuser 16, makes the illumination distribution of the excitation light uniform, and outputs it. The light guide 17 is an optical element that makes the incident light uniform by reflecting it multiple times from the side surfaces of a polygonal prism or a polygonal pyramid, and then outputs it. By providing the light guide 17, the diffused light from the diffuser 16 can be made uniform, thereby suppressing the convex and concave portions of the diffuser 16 from being imaged on the optical image of the sample S that is finally irradiated with light.

[0055] The diffused light diffused by the diffuser plate 16 is input to the light input surface of the light guide 17, so the diameter and length of the light input surface of the light guide 17 depend on the total reflection angle of the light guide 17 (for example, the NA of the light guide 17), etc. In addition, the diameter of the light output surface of the light guide 17 depends on the size of the light irradiation range on the sample S, etc. Furthermore, when the diameter of the light guide 17 is set to D and the NA of the light guide 17 is set to β, the length L of the light guide 17 only needs to be greater than D / β, for example, it can be greater than D / β+1. Furthermore, it is preferably greater than 3D / β. The longer the length of the light guide 17 is, the higher the degree of light uniformity can be.

[0056] The diameter of the light input surface of the light guide 17 may be the same as the diameter of the light output surface of the light guide 15. In addition, the diameter of the light input surface of the light guide 17 may be smaller than the diameter of the light output surface of the light guide 15. In this case, the diameter of the light input surface of the light guide 17 is allowed to be in the range of 100% to 50% of the diameter of the light output surface of the light guide 15.

[0057] In addition, the diameter of the output surface of the light guide 17 is allowed under the condition that the irradiation range on the sample S projected on the output surface is larger than the effective field size of the camera observing the sample S. For example, if the pattern image of the sample S is taken into consideration, the diameter may be slightly larger than the field size. On the other hand, if the sample S is excited, the irradiation range on the sample S needs to be sufficiently larger than the field size.

[0058] The light-guiding lens 18 guides the excitation light emitted from the light pipe 17 toward the mirror 19. The mirror 19 guides the excitation light arriving via the light-guiding lens 18 toward the mirror 20. The mirror 20 guides the excitation light arriving via the mirror 19 toward the light-guiding lens 21. The light-guiding lens 21 guides the excitation light arriving via the mirror 20 toward the light-guiding lens 22. The light-guiding lens 22 guides the excitation light arriving via the light-guiding lens 21 toward the half-mirror 23. The light-guiding lenses 18, 21, and 22 are, for example, convex lenses.

[0059] The half-reflecting mirror 23 is a dielectric half-reflecting mirror that separates the excitation light from the luminescence by reflecting light of a certain wavelength and transmitting light of other wavelengths. The half-reflecting mirror 23 can be a dichroic mirror made of optical materials such as dielectric multilayer films. Specifically, the half-reflecting mirror 23 is configured to reflect the excitation light toward the objective lens 24 and transmit light of a wavelength range different from the excitation light, that is, photoluminescence (specifically, fluorescence, etc.) from the light-emitting element of the sample S toward the imaging lens 25.

[0060] The objective lens 24 is a structure for observing the sample S, and focuses the excitation light guided by the half-mirror mirror 23 onto the sample S.

[0061] The imaging lens 25 is a lens that forms an image of the light emitted from the sample S that has passed through the half mirror 23 and reaches the sample S, and guides the light to the imaging unit 26 .

[0062] The imaging unit 26 is a camera that captures the luminescence from the sample S formed by the imaging lens 25. That is, the imaging unit 26 is a camera that captures the luminescence (measurement light) generated by the light irradiated from the light irradiation device 2 to the sample S. The imaging unit 26 is, for example, an area image sensor such as a CCD or MOS. In addition, the imaging unit 26 may also be composed of a line sensor or a TDI (Time Delay Integration) sensor.

[0063] In the measuring device 1, the analyzing unit (not shown) can determine the quality of each light emitting element of the sample S based on the light emitted from the sample S captured by the imaging unit 26. In addition, in the measuring device 1, other inspections can be performed based on the light emitted from the sample S captured by the imaging unit 26.

[0064] Next, the effects of the light irradiation device 2 of the present embodiment and the measurement device 1 including the light irradiation device 2 will be described with reference to comparative examples.

[0065] Figure 3 1 is a diagram showing a structure of a measuring device 100 according to a first comparative example. The measuring device 100 has the same structure as the measuring device 1 except that it includes a single light guide 150 instead of the structure of the measuring device 1 including two light guides 15 and 17 and the diffuser 16 .

[0066] In such a measuring device 100, when the light input surface side is viewed from the light output surface side of the light guide 150, it appears that there are a plurality of light sources on the light input surface side due to total reflection at the side surface of the light guide 150. By virtually illuminating from various directions using these plurality of light sources, the light output surface of the light guide 150 is uniformly illuminated without depending on the anisotropy of the light quantity of the light source. By optically relaying this, the sample S is uniformly illuminated. Here, if there is no reflective surface in the relay optical system and the sample S is a single surface, there is no problem in uniformly illuminating the sample S.

[0067] However, in actual observation of the sample S, there is a case where the sample S is located on a single surface (surface) of the transparent substrate, and a reflective surface is generated at a position away from the single surface (for example, the back of the sample S). In addition, it is considered that there are multiple lenses inside the objective lens 24, and the reflectivity of the surface of the lens is not 0. In this case, although the reflection image from the surface of the sample S reflects the light output surface of the light guide 150, the reflection image from the other surface (the back of the sample S or the surface of the lens of the objective lens 24) reflects the position offset from the light output surface of the light guide 150. Therefore, if the reflected position is close to the light input surface of the light guide 150, the unevenness of the light incident on the light input surface will appear as a virtual image in the camera image. The appearance of such a virtual image is more significant when the illumination itself is sufficiently uniform.

[0068] Figure 5 (a) is a diagram showing the imaging result of the measuring device 100 of the first comparative example. Figure 5 As shown in (a), a virtual image VI appears in the image captured by the imaging unit 26 due to reflection from an unexpected reflection surface other than the surface of the sample S. Such a virtual image VI cannot be avoided by using only the light guide 150 as long as there is a reflection surface other than the surface of the sample S.

[0069] Figure 4 2 is a diagram showing the structure of a measuring device 200 of a second comparative example. The measuring device 200 has the same structure as the measuring device 1 except that the measuring device 1 includes a light guide 270 and a diffuser 260 provided on the light input surface side of the light guide 270 instead of the structure consisting of the two light guides 15 and 17 and the diffuser 16. Figure 3 In addition to the structure of the measurement device 100 shown, a diffuser plate 260 is provided on the light input surface side of the light guide 270. Although the appearance of the above-mentioned virtual image is suppressed by providing the diffuser plate 260 on the light input surface side, if the incident light to the diffuser plate 260 is non-uniform due to the optical fiber light source or the like, the non-uniformity remains and the excitation light cannot be fully uniformized.

[0070] Figure 5(b) is a diagram showing the imaging result of the measuring device 200 of the second comparative example. Figure 5 As shown in (b), the image captured by the camera unit 26 is Figure 5 When compared with the image captured by the measuring device 100 shown in (a), the appearance of the virtual image VI is suppressed. Figure 5 In the captured image shown in (b), the appearance of the virtual image VI is not completely suppressed, and light unevenness remains.

[0071] In addition, as another structure, for example, a diffuser is provided on the light output surface side of a light guide. However, in such a structure, although the incident light to the diffuser is uniformized, a problem is that the rough surface pattern (convexoconcavity) of the diffuser is imaged on the sample S.

[0072] In contrast, the light irradiation device 2 of the measurement device 1 of the present embodiment includes: a light source 11 that emits light; a light guide 15 that receives light emitted from the light source 11, makes the illuminance distribution of the light uniform, and outputs the light; a diffuser 16 that diffuses the light output from the light guide 15; and a light guide 17 that receives light diffused by the diffuser 16, makes the illuminance distribution of the light uniform, and outputs the light. That is, the light irradiation device 2 includes two light guides 15 and 17, and the diffuser 16 that is provided so as to be sandwiched by the two light guides 15 and 17.

[0073] In the light irradiation device 2, the illuminance distribution of the light emitted from the light source 11 is made uniform by the light guide 15, the light outputted from the light guide 15 is diffused by the diffuser 16, and the illuminance distribution of the light diffused by the diffuser 16 is made uniform by the light guide 17. By providing the light guide 15, the uniformized light is irradiated to the diffuser 16. In addition, by providing the diffuser 16, the virtual image of the non-uniform light incident on the light guide 15 is suppressed from being incident on the subsequent light guide 17. Furthermore, by providing the light guide 17, the diffused light from the diffuser 16 is made uniform, so that the convex and concave of the diffuser 16 are suppressed from being formed on the optical image of the sample S finally irradiated with the light. Based on the above, according to the light irradiation device 2 of the measurement device 1 of this embodiment, the light irradiated to the sample S can be appropriately uniformized.

[0074] Figure 5 (c) is a diagram showing the imaging result of the measuring device 1 of this embodiment. Figure 5 As shown in (c), the image captured by the imaging unit 26 of the measuring device 1 and Figure 5 (a) and Figure 5Compared with the image of the comparative example shown in (b), the appearance of virtual images is fully suppressed. This is because the virtual images caused by reflections from unexpected reflection surfaces are also uniformized by using the diffusion surface of the diffusion plate 16 to separate the multiple light sources that appear to be on the light input surface side, and the virtual images are not visually recognized to be overlapped. In this way, it can be confirmed from the imaging results that the light can be uniformized in the measurement device 1.

[0075] In the light irradiation device 2 of this embodiment, the first uniformizing optical system may be the light guide 15, and the second uniformizing optical system may be the light guide 17. Thus, by configuring both of the two uniformizing optical systems as light guides, light loss can be suppressed and light can be uniformized appropriately.

[0076] In the light irradiation device 2 of the present embodiment, the diameter of the light input surface of the light guide 17 may be the same diameter as the diameter of the light output surface of the light guide 15. In addition, in the light irradiation device 2 of the present embodiment, the diameter of the light input surface of the light guide 17 may be smaller than the diameter of the light output surface of the light guide 15. For example, in a case where the diameter of the light output surface of the light guide 15 is smaller than the diameter of the light input surface of the light guide 17, light is input only to a part of the light input surface of the light guide 17, and there is a concern that the light output from the light guide 17 may not be sufficiently uniformized. In particular, in a case where the diameter of the light input surface of the light guide 17 is the same diameter as the diameter of the light output surface of the light guide 15, uniformization of the light output from the light guide 17 and suppression of a decrease in the light quantity can be achieved, and a reduction in the irradiation area on the sample S can be prevented.

[0077] In the light irradiation device 2 of the present embodiment, the diffusion portion may be the diffusion plate 16. According to such a configuration, the diffusion plate 16 is sandwiched between the two light guides 15 and 17, so that light can be easily uniformized.

[0078] The measuring device 1 of this embodiment includes: the above-mentioned light irradiation device 2; and an imaging unit 26 that captures the luminescence (measurement light) generated by the light irradiated from the light irradiation device 2 to the sample S. According to such a structure, the sample S can be irradiated with uniform light, and the luminescence (measurement light) generated from the sample S can be captured with high accuracy.

[0079] As mentioned above, although the light irradiation device 2 of this embodiment and the measurement device 1 including the light irradiation device 2 are demonstrated, this invention is not limited to the said embodiment.

[0080] Figure 61 is a structural diagram of a light guide 17A of a modified example. The light guide 17A is a structure equivalent to the second light guide (second uniformizing optical system). The diameter of the light output surface of the light guide 17A is formed to be larger than the diameter of the light input surface of the light guide 17A. More specifically, the light guide 17A is formed into a tapered shape whose diameter increases from the light input surface side to the light output surface side. According to such a structure, the irradiation range on the sample S can be expanded, and uniform light can be irradiated over a wide range.

[0081] Figure 7 2A is a diagram showing a structure of a light irradiation device 2A according to another modified example. The light irradiation device 2A includes a lens unit 350 at a front stage and a lens unit 370 at a rear stage so as to sandwich the diffusion plate 16 .

[0082] The lens unit 350 has fly-eye lenses 352 and 353 (first fly-eye lenses) as the first uniformizing optical system, and has field lenses 351 and 354 in a manner of sandwiching the fly-eye lenses 352 and 353. That is, in the front-stage lens unit 350, the field lens 351, the fly-eye lens 352, the fly-eye lens 353, and the field lens 354 are arranged in order from the light source 11 side toward the diffuser 16 direction.

[0083] The field lens 351 sets the light from the light source 11 as parallel light. The fly-eye lens 352 focuses the excitation light set as parallel light by the field lens 351 to each relative fly-eye lens 353. In this way, the excitation light can be effectively used without waste. The fly-eye lens 353 projects the distribution of the incident light to infinity. The light distribution is overlapped by the single lens in the fly-eye lens, and the light is uniformized. Then, the subsequent field lens 354 changes the distribution of light from the fly-eye lens 353 from infinity to close-range irradiation. The light from the field lens 354 is guided to the diffuser 16.

[0084] The lens unit 370 has fly-eye lenses 372 and 373 (second fly-eye lenses) as the first uniformizing optical system, and field lenses 371 and 374 in a manner of sandwiching the fly-eye lenses 372 and 373. That is, in the rear-stage lens unit 370, the field lens 371, the fly-eye lens 372, the fly-eye lens 373, and the field lens 374 are arranged in order from the diffuser plate 16 side toward the sample S direction.

[0085] The field lens 371 sets the light diffused by the diffuser plate 16 as parallel light. The fly-eye lens 372 focuses the excitation light set as parallel light by the field lens 371 to each relative fly-eye lens 373. In this way, the excitation light can be effectively used without waste. The fly-eye lens 373 projects the distribution of the incident light to infinity. The light distribution is overlapped by the single lens in the fly-eye lens, and the light is homogenized. Then, the subsequent field lens 374 changes the distribution of light from the fly-eye lens 373 from infinity to close-range irradiation. The light from the field lens 374 is guided to the sample S via each optical system.

[0086] In this way, by providing the diffusion plate 16 on the irradiation surface between the fly-eye lenses 352, 353 of the front-stage lens unit 350 and the fly-eye lenses 372, 373 of the rear-stage lens unit 370, the information of the light source shape is temporarily divided, and the above-mentioned virtual image can be effectively removed. That is, by using the fly-eye lens as the structure of the uniformizing optical system, the loss of light quantity can be suppressed and the light can be appropriately uniformized, similarly to the case where the uniformizing optical system is composed of a light guide.

[0087] Figure 8 2B is a structural diagram of a light irradiation device 2B of another modified example. The light irradiation device 2B is a structure that uses a fly-eye lens as a uniformization optical system in the same manner as the light irradiation device 2A. Here, in the structure using the fly-eye lens, scattering occurs at the connecting surface (boundary) of the smaller lens, so there is a limit in removing the virtual image. The light irradiation device 2B is a structure that uses a fly-eye lens and improves the problems in the case of using the above-mentioned fly-eye lens.

[0088] The light irradiation device 2B includes the lens unit 350 similarly to the light irradiation device 2A, and has a light guide 460 instead of the diffuser 16 and the lens unit 370 of the light irradiation device 2A. That is, the light irradiation device 2B includes the light guide 460 as a structure corresponding to the diffuser and the second uniformizing optical system.

[0089] The light guide 460 is a light guide whose light input surface is a diffusion surface 460a. In this way, the diffusion part is not necessarily limited to the diffusion plate, and can be a diffusion surface provided on one side of the light guide as in this modified example. The diffusion surface 460a is formed in a frosted glass shape, for example. According to such a structure, even if scattering occurs in the fly-eye lens, the light is uniformized in the subsequent light guide 460, and the virtual image can be effectively removed.

[0090] Furthermore, the light irradiation device according to one aspect of the present invention can realize uniform light irradiation on a region, and thus can be used in devices other than the above-described measurement device 1 . Fig. 9 2 is a diagram showing the configuration of an observation device 500 including a light irradiation device 2C according to a modified example. Fig.10 2 is a diagram showing a configuration of a film thickness measurement device 600 including a light irradiation device 2D according to a modified example.

[0091] Fig. 9The observation device 500 shown irradiates a prescribed range on the sample S with light of uniform intensity, photographs the light reflected within the prescribed range, and observes the surface of the sample S based on the obtained image data. In this way, compared with photographing the light emission such as fluorescence in the above-mentioned measuring device 1, the reflected light of the sample S is photographed in the observation device 500. The sample S here can be, for example, the surface coating of a car or the like or a portion to which a surface coating is applied. In this case, the observation device 500 can observe the surface coating portion by photographing the light reflected from the surface coating portion. Such observation results are used, for example, as illumination for evaluating a mirror surface (especially a surface with a multilayer structure). In addition, the observation device 500 can also be used for surface defect inspection.

[0092] like Fig. 9 As shown, the observation device 500 includes a light irradiation device 2C and an imaging unit 26. The light irradiation device 2C includes a plurality of light sources 11, light guide lenses 12, 13, and an optical fiber cable 14. Each light source 11 can output light of different wavelengths. In the light irradiation device 2C, while changing the light source 11 of the emitted light, light of various wavelengths is irradiated to the sample S. The observation device 500 has the same basic structure as the measurement device 1 except that a plurality of light sources 11 are provided and the reflected light from the sample S is imaged.

[0093] In the light irradiation device 2C, the light uniformized by the light guide 15, the diffuser plate 16, and the light guide 17 is irradiated to the sample S via the optical systems, and the reflected light from the sample S is imaged by the imaging lens 25 on the imaging unit 26. According to such an observation device 500, the uniformized light is irradiated to the sample S, so that the reflected light (observation light) can be imaged with high precision, and the above-mentioned surface defect inspection and the like can be performed with high precision.

[0094] Fig.10 The film thickness measuring device 600 shown in the figure irradiates a prescribed range on a sample S with light of uniform intensity, captures the light reflected multiple times within the prescribed range, and obtains the film thickness distribution within the range based on the obtained image data. The sample S in this case may be, for example, a light-emitting element such as an LED, a small LED, a μLED, an SLD element, a laser element, a vertical laser element (VCSEL), an OLED, or a light-emitting element whose emission wavelength is adjusted by including a fluorescent substance such as nanodots.

[0095] The film thickness measurement device 600 includes a light irradiation device 2D, imaging units 26 and 29, and an analysis unit 60 (film thickness derivation unit). The light irradiation device 2D includes a dichroic mirror 27 and an imaging lens 28 in addition to the configuration of the light irradiation device 2C described above.

[0096] In the film thickness measurement device 600 , light uniformized by the light guide 15 , the diffuser 16 , and the light guide 17 is irradiated to the sample S via the optical systems, and reflected light from the sample S reaches the dichroic mirror 27 via the half mirror 23 .

[0097] The dichroic mirror 27 is a mirror made of special optical materials, and is an optical element that separates the light reflected multiple times in the sample S by transmitting and reflecting according to the wavelength. The dichroic mirror 27 can also be configured so that the transmittance and reflectance of the light in a specified wavelength band change according to the wavelength. For example, in the dichroic mirror 27, the transmittance (and reflectance) of the light in the specified wavelength band can be slowly changed according to the change of the wavelength, and the transmittance (and reflectance) of the light in the wavelength band other than the specified wavelength band is constant regardless of how the wavelength changes. The light output from the light source 11 contains light of a wavelength included in the specified wavelength band of the dichroic mirror 27.

[0098] The imaging lens 25 forms an image of the reflected light from the sample S that has passed through the dichroic mirror 27, and guides the reflected light to the imaging unit 26. The imaging lens 28 forms an image of the reflected light from the sample S that has been reflected by the dichroic mirror 27, and guides the reflected light to the imaging unit 29. The imaging unit 26 is a camera that photographs the reflected light from the sample S that has been formed by the imaging lens 25. The imaging unit 29 is a camera that photographs the reflected light from the sample S that has been formed by the imaging lens 28. The imaging data of the imaging units 26 and 29 are output to the analysis unit 60. In this way, the imaging units 26 and 29 photograph the light irradiated from the light irradiation device 2D to the sample S, that is, the observation light, and output the imaging data.

[0099] The analysis unit 60 is a computer, and is physically configured to include a memory such as RAM, ROM, a processor such as a CPU (calculation circuit), a communication interface, a storage unit such as a hard disk, etc. The analysis unit 60 functions by executing a program stored in the memory using the CPU of the computer system. The analysis unit 60 can be configured by a microcomputer or an FPGA.

[0100] The analysis unit 60 derives the film thickness of the sample S based on the signal (image data) from the imaging units 26 and 29 that capture light. The analysis unit 60 estimates the film thickness corresponding to each pixel based on the wavelength information of each pixel in the imaging units 26 and 29. More specifically, the analysis unit 60 can derive the wavelength centroid of the light of each pixel based on, for example, the amount of transmitted light specified based on the image data of the imaging unit 26, the amount of reflected light specified based on the image data of the imaging unit 29, the center wavelength of the dichroic mirror 27 (the center wavelength of a predetermined wavelength band), and the width of the dichroic mirror 27, and estimate the film thickness corresponding to each pixel based on the wavelength centroid. The width of the dichroic mirror 27 refers to, for example, the wavelength width from the wavelength at which the transmittance is 0% to the wavelength at which the transmittance is 100% in the dichroic mirror 27.

[0101] Specifically, the analysis unit 60 derives the wavelength centroid of each pixel based on the following formula (1). In the following formula (1), λ represents the wavelength centroid, λ0 represents the central wavelength of the dichroic mirror 27, A represents the width of the dichroic mirror 27, R represents the amount of reflected light, and T represents the amount of transmitted light.

[0102] λ = λ0 + A(T - R) / 2(T + R) (1)

[0103] When λ (wavelength centroid) is derived by the above formula (1), for a pixel where T (amount of transmitted light) = R (amount of reflected light), λ is set to λ0 (the central wavelength of the dichroic mirror 27). In addition, for a pixel where T < R, that is, a pixel where the amount of reflected light is more than the amount of transmitted light, λ is set to λ1 (a wavelength shorter than λ0). In addition, for a pixel where T > R, that is, a pixel where the amount of transmitted light is more than the amount of reflected light, λ is set to λ2 (a wavelength longer than λ0). Thus, the value of λ (wavelength centroid) is shifted (wavelength shift) based on the amount of transmitted light and the amount of reflected light.

[0104] Furthermore, the method for deriving the wavelength centroid is not limited to the above. For example, since λ (wavelength centroid) has a proportional relationship with the following x, the wavelength centroid can be derived according to the following formulas (2) and (3). In the following formula (3), IT represents the amount of transmitted light, and IR represents the amount of reflected light. In addition, when the spectral shape of the measurement object or the line shape of the dichroic mirror 27 is an ideal shape, the parameters a and b in formula (2) can be determined according to the optical characteristics of the dichroic mirror 27.

[0105] λ = ax + b (2)

[0106] x = (IT - IR) / 2(IT + IR) (3)

[0107] Furthermore, since there are actually differences (individual differences) in the spectral characteristics between optical systems or cameras, for the purpose of correcting them, for example, the signal intensity of a substrate with known reflection characteristics can be used as a reference, and x can be derived by the following formula (4). In the following formula (4), ITr represents the amount of transmitted light in the reference, and IRr represents the amount of reflected light in the reference.

[0108] x = (IT / ITr - IR / IRr) / 2(IT / ITr + IR / IRr) (4)

[0109] In addition, for the purpose of removing the influence of direct light from the light source, the signal amount in a non-reflective state can be used to derive x by the following formula (5). In the following formula (5), ITb represents the amount of transmitted light in the non-reflective state, and IRb represents the amount of reflected light in the non-reflective state.

[0110] x={(IT-ITb) / (ITr-ITb)-(IR-IRb) / (IRr-IRb)} / 2{(IT-ITb) / (ITr-ITb)+(IR-IRb) / (IRr-IRb)}(5)

[0111] In order to comprehensively implement various corrections for film characteristics, irradiation spectrum, nonlinearity of the dichroic mirror 27, etc., the wavelength centroid (λ) can be approximated by the polynomial of the following formula (6). In addition, each parameter (a, b, c, d, e) in the following formula (6) is determined by measuring a plurality of samples having different wavelength centroids (film thicknesses), for example.

[0112] λ=ax4+bx3+cx2+dx+e (6)

[0113] The relationship between wavelength and film thickness can be explained by the following formula (7). In the following formula (7), n represents the refractive index of the film, d represents the film thickness, m represents a positive integer (1, 2, 3, ...), and λ represents the wavelength centroid. 2nd represents the optical path difference (the optical path difference generated by configuring the film). The analysis unit 60 estimates the film thickness corresponding to each pixel based on the wavelength centroid of each pixel based on the following formula (7).

[0114] 2nd=mλ(m=1,2,3,……)(enhancement condition)

[0115] 2nd=(m-1 / 2)λ(m=1,2,3,……)(weakening condition)…(7)

[0116] Here, the above-mentioned formula (7) representing the relationship between wavelength and film thickness is established when light is incident perpendicularly to the sample S. On the other hand, when light is not incident perpendicularly to the sample S, the above-mentioned formula (7) is not established. Therefore, in order to estimate the film thickness with high accuracy at any measurement point (incident angle), it is necessary to perform calculation (correction processing) corresponding to the measurement point (incident angle).

[0117] When the incident angle of light is θ, the optical path difference is expressed as 2ndcosθ. Therefore, the relationship between the wavelength and the film thickness considering the incident angle θ can be explained by the following formula (8). The analysis unit 60 estimates the film thickness corresponding to the measurement point (incident angle) based on the following formula (8). In this way, the analysis unit 60 can further consider the angle of the light irradiated to the sample S and estimate the film thickness based on the wavelength center of gravity.

[0118] 2ndcosθ=mλ(enhancement condition)

[0119] 2ndcosθ=(m-1 / 2)λ(weakening condition)…(8)

[0120] According to the film thickness measurement apparatus 600 , the sample S can be irradiated with uniform light, and the film thickness of the sample S can be derived with high accuracy.

[0121] Explanation of symbols

[0122] 1…measuring device, 2, 2A, 2B, 2C, 2D…light irradiation device, 11…light source, 15…light guide (first uniformizing optical system, first light guide), 16…diffuser (diffuser), 17, 17A…light guide (second uniformizing optical system, second light guide), 26, 29…imaging unit, 60…analyzer (film thickness deriving unit), 352, 353…fly-eye lens (first uniformizing optical system, first fly-eye lens), 372, 373…fly-eye lens (second uniformizing optical system, second fly-eye lens), 460…light guide (second uniformizing optical system, second light guide), 460a…diffuser surface (diffuser), 500…observation device, 600…film thickness measuring device, S…sample (measurement object).

Claims

1. A light irradiation device, wherein: Include: a light source, which emits light; a first homogenizing optical system which receives the light emitted from the light source, homogenizes the illumination distribution of the light, and outputs the light; a diffusion unit that diffuses the light output from the first uniformizing optical system; and The second uniformizing optical system receives the light diffused by the diffusion unit, makes the illumination distribution of the light uniform, and outputs the light.

2. The light irradiation device according to claim 1, wherein The first homogenizing optical system is a first light guide. The second uniformizing optical system is a second light guide.

3. The light irradiation device according to claim 2, wherein: The diameter of the light input surface of the second light guide is the same as the diameter of the light output surface of the first light guide.

4. The light irradiation device according to claim 2, wherein: The diameter of the light input surface of the second light guide is smaller than the diameter of the light output surface of the first light guide.

5. The light irradiation device according to claim 2, wherein: A diameter of a light output surface of the second light guide tube is larger than a diameter of a light input surface of the second light guide tube.

6. The light irradiation device according to claim 1, wherein The first homogenizing optical system is a first fly-eye lens. The second uniformizing optical system is a second fly-eye lens.

7. The light irradiation device according to claim 1, wherein The diffusion part is a diffusion plate.

8. A measuring device, wherein: Include: The light irradiation device according to any one of claims 1 to 7; and An imaging unit captures an image of measurement light generated by the light irradiated from the light irradiation device to the measurement object.

9. An observation device, wherein: Include: The light irradiation device according to any one of claims 1 to 7; and The imaging unit captures an image of the observation light which is the light irradiated from the light irradiation device to the measurement object.

10. A film thickness measuring device, wherein: Include: The light irradiation device according to any one of claims 1 to 7; an imaging unit that captures an image of observation light, which is light irradiated from the light irradiation device to the measurement object, and outputs imaging data; and A film thickness deriving unit derives a film thickness of the measurement object based on the imaging data.

Images