Foreign matter inspection device and foreign matter inspection method

Abstract

In order to accurately determine whether foreign matter has adhered to a front surface or a back surface, this foreign matter inspection device for detecting foreign matter adhered to a light-transmitting film is configured to comprise: an inspection light irradiation unit for irradiating foreign matter at a prescribed inspection position with P-polarized inspection light and S-polarized inspection light from a plurality of directions; a scattered light detection unit for detecting first scattered light generated from the P-polarized inspection light emitted from each of the plurality of directions, and second scattered light generated from the S-polarized inspection light emitted from each of the plurality of directions; and a determination unit that determines whether the foreign matter has adhered to one surface or the other surface of the film on the basis of the intensity of the first scattered light and the intensity of the second scattered light detected by the scattered light detection unit.

Description

Foreign Object Inspection Device and Foreign Object Inspection Method

[0001] The present invention relates to a foreign object inspection device and a foreign object inspection method.

[0002] For example, as a foreign object inspection device for inspecting foreign objects attached to an object to be inspected having light transmissivity, the one shown in Patent Document 1 is considered. This foreign object inspection device irradiates the surface of the object to be inspected with inspection light of P-polarization and S-polarization, respectively, detects the intensity of the scattered light generated thereby, compares these intensities, and determines whether the foreign object attached to the object to be inspected is attached to the front surface or the back surface of the object to be inspected.

[0003] Japanese Patent Publication (Examined) No. 06-005382

[0004] However, the above foreign object inspection device irradiates inspection light from one direction with respect to a foreign object. For example, depending on the shape of the foreign object, different scattered light intensities may be detected when irradiating the same foreign object from the front direction and when irradiating from the lateral direction. Then, there is a possibility that the result of the front / back determination may differ depending on the direction in which the inspection light is irradiated with respect to the foreign object, and there is a problem that the detection accuracy cannot be ensured.

[0005] Therefore, the present invention has been made to solve the above-described problems, and its main object is to accurately determine whether a foreign object is attached to the front surface or the back surface of a film having light transmissivity.

[0006] That is, the foreign object inspection device according to the present invention is configured to detect a foreign object attached to a film having light transmissivity, and includes an inspection light irradiation unit that irradiates inspection light of P-polarization and inspection light of S-polarization from a plurality of directions to the foreign object at a predetermined inspection position, a scattered light detection unit that detects first scattered light generated from the inspection light of P-polarization irradiated from each of the plurality of directions and second scattered light generated from the inspection light of S-polarization irradiated from each of the plurality of directions, and a determination unit that determines whether the foreign object is attached to one surface or the other surface of the film based on the intensity of the first scattered light and the intensity of the second scattered light detected by the scattered light detection unit.

[0007] In this invention, by irradiating a foreign object at a predetermined inspection position with inspection light from multiple directions, it is possible to detect the intensity of multiple scattered lights corresponding to the shape of the foreign object (e.g., silhouette) as viewed from each direction. This reduces the influence of the foreign object's shape compared to irradiating with inspection light from only one direction, and allows for accurate determination of whether the foreign object is attached to one side or the other side of the film. Specifically, accurate determination can be achieved by using the intensity of scattered light suitable for determining the front and back sides from among the intensities of scattered light generated by the inspection light from each direction, or by using all the intensities of scattered light generated by the inspection light from each direction.

[0008] Preferably, the aforementioned multiple directions extend radially from the predetermined inspection position when the film is viewed from one side. With this configuration, foreign objects can be detected by viewing them from the surroundings, and the influence of the shape of foreign objects, which vary in shape, can be more easily reduced.

[0009] More specifically, it is desirable that the multiple directions are arranged at equal intervals along the circumferential direction centered on the predetermined inspection position when the film is viewed from one side. Furthermore, it is desirable that the multiple directions evenly divide the entire circumference surrounding the predetermined inspection position when the film is viewed from one side. For example, when irradiating from three directions, it is preferable to configure the system so that the 360 ​​degrees around the foreign object are divided into 120-degree intervals by each direction.

[0010] To effectively reduce the influence of the shape of a foreign object on the determination of its adhesion surface, it is desirable that the shape of the foreign object reflected in the detector by inspection light irradiated from multiple directions differs from one another. For example, if inspection light is irradiated onto a foreign object from two directions facing each other, the shape of the foreign object reflected in the detector by the inspection light from each direction may be the same or symmetrical, which is undesirable. Therefore, it is preferable that the multiple directions extend so that they do not directly face each other. Specifically, if the number of directions is odd, and they are arranged at equal intervals, it is possible to illuminate the foreign object from various directions while preventing the appearance of the foreign object reflected in the detector by the inspection light from each direction from overlapping.

[0011] To improve the accuracy of determining the surface to which foreign matter is attached, it is desirable that the inspection light irradiation unit irradiates the inspection position with inspection light at the Brewster angle or an angle close to it.

[0012] The inspection light irradiation unit preferably irradiates the film with inspection light in a wavelength range where the transmittance of S-polarized light differs most significantly from the transmittance of P-polarized light, taking into account the physical properties of the film, such as its refractive index, thickness, and optical coating. More specifically, it is preferable to irradiate the film with inspection light in a wavelength range where the transmittance of S-polarized light is 0.8 times or less than the transmittance of P-polarized light. More preferably, it is 0.7 times or less. This makes it possible to increase the difference between the intensity of the first scattered light and the intensity of the second scattered light detected when a foreign substance is attached to one side and when it is attached to the other side, thereby improving the accuracy of determining which side the foreign substance is attached to.

[0013] As for specific methods of determining the adhesion surface, the determination unit may determine that a foreign substance is attached to one side of the film if the relative magnitudes of the intensities of the first scattered light and the second scattered light satisfy a predetermined condition, and determine that a foreign substance is attached to the other side of the film if the relative magnitudes of the intensities of the first scattered light and the second scattered light do not satisfy the predetermined condition.

[0014] Furthermore, the foreign matter inspection method according to the present invention is a method for detecting foreign matter attached to a light-transmitting film, characterized in that the foreign matter at a predetermined inspection position is irradiated with P-polarized inspection light from multiple directions, a first scattered light generated from the P-polarized inspection light irradiated from each of the multiple directions is detected, an S-polarized inspection light is irradiated with S-polarized inspection light from the multiple directions, a second scattered light generated from the S-polarized inspection light irradiated from each of the multiple directions is detected, and based on the intensity of the detected first scattered light and the intensity of the second scattered light, it is determined whether the foreign matter is attached to one side or the other side of the film. Even with such a foreign matter inspection method, the same effects and advantages as the foreign matter inspection device described above can be achieved.

[0015] According to the present invention configured in this way, it is possible to accurately determine whether foreign matter is attached to the surface or the back surface of a light-transmitting film.

[0016] This is an overall schematic diagram showing a foreign object inspection device according to one embodiment of the present invention. This is a perspective view illustrating multiple directions of laser light irradiated onto a foreign object in the same embodiment. This is a plan view illustrating multiple directions of laser light irradiated onto a foreign object in the same embodiment. This is a diagram showing experimental results of measuring S / P transmittance in each wavelength range. This is an overall schematic diagram showing a foreign object inspection device of a modified embodiment. This is a plan view illustrating multiple directions of laser light irradiated onto a foreign object in the modified embodiment. This is a plan view illustrating multiple directions of laser light irradiated onto a foreign object in the modified embodiment.

[0017] <An Embodiment of the Present Embodiment> An embodiment of the foreign object inspection apparatus according to the present invention will be described below with reference to the drawings. In addition, all of the following figures are schematic representations that have been appropriately omitted or exaggerated for the sake of clarity. The same components are denoted by the same reference numerals and their descriptions are appropriately omitted.

[0018] The foreign matter inspection device 100 of this embodiment inspects foreign matter K adhering to a light-transmitting film F.

[0019] As shown in Figure 1, film F is a protective film (pellicle) that prevents foreign matter K from adhering to the reticle R, which is a type of photomask. In this embodiment, film F is fixed to a retaining frame W and attached to the reticle R, covering the surface of the reticle R on which a pattern (not shown) is formed. In the following, the back surface of film F is the surface facing the reticle (bottom surface), which is the surface facing the pattern of the reticle. On the other hand, the front surface of film F is the surface facing away from the photomask (top surface), which is the surface facing outwards.

[0020] More specifically, film F is a protective film (pellicle) that prevents foreign matter K from adhering to the reticle R during the exposure process. The protective film is, for example, an EUV pellicle, a DUV pellicle, or other pellicle used in semiconductor manufacturing exposure processes.

[0021] <Device Configuration> As shown in Figure 1, the foreign object inspection device 100 of this embodiment detects foreign objects K attached to a film F placed on a measuring stage S, and comprises an inspection light irradiation unit 2 that irradiates a laser beam LB as inspection light from an oblique angle to a predetermined inspection position SP, a scattered light detection unit 3 that detects scattered light generated by the laser beam LB, and an information processing device 4 that determines the attachment surface of the foreign object K attached to the film F based on the intensity of the scattered light detected by the scattered light detection unit 3.

[0022] The measurement stage S moves the foreign object K together with the film F to align the foreign object K to a predetermined inspection position SP where the laser beam LB is irradiated.

[0023] The following describes the structure of each section, from section 2 to section 4.

[0024] As shown in Figures 1 and 2, the inspection light irradiation unit 2 is positioned on the surface side of the film F and irradiates foreign matter K on the film at a predetermined inspection position SP with P-polarized laser light LB and S-polarized laser light LB, respectively. P-polarized light is polarized light that vibrates parallel to the plane of incidence on the film F, and S-polarized light is polarized light that vibrates perpendicular to the plane of incidence on the film F.

[0025] As shown in Figures 1 to 3, the inspection light irradiation unit 2 of this embodiment has three laser light irradiators 21a to 21c. Each laser light irradiator 21a to 21c includes a laser light source 22a to 22c that emits laser light LB, for example, a semiconductor laser, a polarization switcher 23a to 23c that switches the laser light LB to P-polarized or S-polarized, and an irradiation optical system 24a to 24c which is composed of optical elements such as a focusing lens, mirror or slit and emits the laser light LB toward the foreign object K.

[0026] Polarization switches 23a to 23c selectively switch the polarization of the laser beam LB using, for example, a λ / 2 plate, a polarizing beam splitter, a polarizer, or other optical crystal. In this embodiment, the polarization switches 23a to 23c are provided between the laser light sources 22a to 22c and the irradiation optical systems 24a to 24c, but they may be provided at other positions before the laser beam LB is irradiated onto the foreign object K. Polarization switches 23a to 23c may selectively guide P-polarized laser beam LB and S-polarized laser beam LB emitted from different light sources to the irradiation optical systems 24a to 24c (for example, by switching each light source on or off).

[0027] Furthermore, since the inspection light irradiation unit 2 irradiates the foreign matter K (inspection position SP) attached to the film F with P-polarized laser light LB and S-polarized laser light LB, it is desirable that the incident angle on the film be an angle where the difference between the transmittance of P-polarized light and S-polarized light on the film F is large. Specifically, it is desirable that the incident angle of the laser light LB be set to, for example, the Brewster angle at which the reflectance of P-polarized light on the surface of the film F becomes 0, or an angle near that angle. Here, an angle near the Brewster angle refers to, for example, an angle within a range of ±5° of the Brewster angle. Note that the laser light irradiators 21a to 21c may irradiate the foreign matter K with laser light LB at different incident angles, or they may irradiate with laser light LB at the same incident angle.

[0028] Furthermore, it is desirable that the inspection light irradiation unit 2 of this embodiment emits laser light LB in a wavelength range where the difference between the transmittance of P-polarized light and the transmittance of S-polarized light to the film F is large. Specifically, it is preferable to irradiate with laser light in a wavelength range where "transmittance of S-polarized light / transmittance of P-polarized light" is 0.8 or less. More preferably, it is 0.7 or less.

[0029] For example, if film F is a pellicle for DUV exposure, it is preferable to use a wavelength range around 500 nm. Figure 4 shows the experimental results of measuring the "transmittance of S-polarized light / transmittance of P-polarized light" in each wavelength range for four types of pellicles for DUV exposure.

[0030] As shown in Figures 1 and 2, the scattered light detection unit 3 is positioned on the surface side of the film F and detects scattered light generated from the foreign object K at the inspection position SP by irradiation with laser light LB.

[0031] The scattered light detection unit 3 of this embodiment detects the first scattered light SL1 generated from the P-polarized laser light LB irradiated from each of the laser light irradiators 21a to 21c, and the second scattered light SL2 generated from the S-polarized laser light LB irradiated from each of the laser light irradiators 21a to 21c.Hereafter, when the first scattered light SL1 and the second scattered light SL2 are not distinguished, they will simply be referred to as scattered light.

[0032] The scattered light detection unit 3 includes a detection optical system 31 composed of optical elements such as lenses and / or mirrors that collect scattered light from a foreign object K, and a scattered light detector 32 that detects the scattered light collected by the detection optical system 31, converts the intensity of the detected scattered light into an electrical signal, and outputs it to the information processing device 4.

[0033] The scattered light detection unit 3 of this embodiment is configured by combining an optical microscope and a camera. Specifically, the detection optical system 31 is a lens etc. incorporated into the optical microscope and camera, and the detector 32 is an image sensor such as a CCD mounted on the camera. Image data captured by this image sensor is output from the camera to the information processing device 4 as data indicating the intensity of the detected scattered light. More specifically, for example, the grayscale (pixel value) of the pixel corresponding to the inspection position SP in the image data is treated as data indicating the intensity of the scattered light. The sum or average of the pixel values ​​of the pixels corresponding to the inspection position SP may be used as the intensity of the scattered light, or the number or proportion of pixels among the pixels corresponding to the inspection position SP that have a pixel value of or greater than a predetermined threshold may be used as the intensity of the scattered light.

[0034] The information processing device 4 is a computer having a CPU, memory, input / output interface, AD converter, etc., and based on the foreign object K inspection program stored in memory, the CPU and peripheral devices cooperate to perform at least the function of a determination unit 41.

[0035] The determination unit 41 determines whether the foreign object K is attached to the front or back surface of the film F based on the intensity of the first scattered light SL1 and the second scattered light SL2 indicated by the signal received from the scattered light detection unit 3. In this embodiment, the determination unit 41 determines the front and back surfaces using the image captured by the aforementioned camera while the P-polarized laser light LB is irradiated and the image captured while the S-polarized laser light LB is irradiated.

[0036] The determination result from this determination unit 41 can be displayed on a display unit 42 such as a display screen.

[0037] The determination unit 41 determines the surface on which the foreign substance K is attached by utilizing the difference in transmittance of P-polarized light and S-polarized light to the film F. Specifically, the determination unit 41 determines that the foreign substance K is attached to the surface of the film F if the relative magnitudes of the intensity of the first scattered light SL1 and the intensity of the second scattered light SL2 satisfy predetermined conditions, and determines that the foreign substance K is attached to the back surface of the film F if the relative magnitudes of the intensity of the first scattered light SL1 and the second scattered light SL2 do not satisfy predetermined conditions.

[0038] For example, the determination unit 41 determines that the foreign matter K is attached to the surface of the film F when the second scattered light SL2 is greater than 0.8 times the first scattered light SL1, and determines that the foreign matter K is attached to the back surface of the film F when the second scattered light SL2 is 0.8 times or less the first scattered light SL1. Note that these determination conditions change depending on the wavelength of the laser light and the size of the foreign matter, and are not limited to the above.

[0039] Figure 5 shows the results of irradiating particles 1 and 2, which are foreign matter attached to the pellicle, with P-polarized laser light and S-polarized laser light, respectively, and detecting the intensity of scattered light, both when they are attached to the surface and when they are attached to the back surface. A 488 nm laser beam was used for irradiation. From these results, the "S-polarized scattered light intensity / P-polarized scattered light intensity (S / P scattered light intensity ratio)" was 1.6 to 1.8 when particles 1 and 2 were attached to the surface, and 0.7 to 1.0 when they were attached to the back surface.

[0040] Note that the determination unit 41 may determine the adhesion surface of the foreign object K based on whether the magnitude of the difference between the intensity of the first scattered light SL1 and the intensity of the second scattered light SL2 is within a predetermined range or outside the predetermined range.

[0041] <Direction of the laser beam LB irradiated onto the foreign object K> As shown in FIGS. 2 and 3, the inspection light irradiation unit 2 of the present embodiment is configured to irradiate the foreign object K at a predetermined inspection position SP from three directions using three laser beam irradiators 21a to 21c. The three laser beam irradiators 21a to 21c are arranged on a concentric circle centered on a predetermined inspection position SP (foreign object K) when viewed from above the film F (from the surface side).

[0042] Also, when the directions of the laser beams projected from the respective laser beam irradiators 21a to 21c toward the predetermined inspection position SP (foreign object K) are defined as direction A to direction C, these three directions extend radially centered on the predetermined inspection position SP (foreign object K) when viewed from above the film F. Each of the directions A to C is arranged adjacent to each other at intervals of 120 degrees in the circumferential direction centered on the predetermined inspection position SP (foreign object K), dividing the periphery of the predetermined inspection position SP (foreign object K) into three equal parts.

[0043] Here, direction A to direction C are the directions in which the laser beams travel straight from the respective laser beam irradiators 21a to 21c toward the (foreign object K) at the predetermined inspection position SP, and are the optical paths of the laser beams irradiated toward the predetermined inspection position SP (foreign object K) via the irradiation optical system 24.

[0044] <Foreign object inspection method> Hereinafter, a foreign object inspection method using the foreign object inspection apparatus 100 according to the present invention will be described. First, the foreign object K attached to the film F is moved to a predetermined inspection position SP. Then, the foreign object K at the predetermined inspection position SP is irradiated with the P-polarized laser beam LB in order from directions A to C, and the first scattered light SL1 generated from the P-polarized laser beam LB irradiated from each of directions A to C is detected.

[0045] Next, the foreign object K is irradiated with the S-polarized laser beam LB in order from directions A to C, and the second scattered light SL2 generated from the S-polarized laser beam LB irradiated from each of directions A to C is detected.

[0046] Based on the intensities pa to pc of the detected first scattered light and the intensities sa to sc of the second scattered light, it is characterized in that it is determined whether the foreign matter K adheres to one surface or the other surface of the film F.

[0047] As a specific determination mode, the intensity pa and the intensity sa, the intensity pb and the intensity sc, and the intensity pc and the intensity sc may be compared respectively, and the front-back determination may be performed using the set with the largest intensity difference, or the average of the intensities pa to pc and the average of the intensities sa to sc may be compared, etc.

[0048] The order of irradiating the P-polarized laser light LB and the S-polarized laser light LB may be reversed. Also, the laser light may be irradiated collectively from each of the directions A to C.

[0049] Also, first, the wavelength range used for the inspection may be calculated and determined. Specifically, the P-polarized laser light LB and the S-polarized laser light LB are irradiated to the film F in a wide wavelength range, and the "transmittance of S-polarized light / transmittance of P-polarized light" in each wavelength range is measured. Then, for the measured "transmittance of S-polarized light / transmittance of P-polarized light", the wavelength range where it becomes 0.8 or less is selected. To realize a wide wavelength range, a plurality of lasers with different wavelengths may be used, or incoherent light such as a white light source may be used. Also, instead of the transmittance, the transmittance may be estimated from the reflectance.

[0050] In the front-back determination, in addition to the intensity of the scattered light SL, the size of the foreign matter (particle diameter, area on the image, etc.) may also be used as a parameter. In this embodiment, based on the foreign matter image captured by the camera, the particle diameter of the foreign matter is calculated, and the front-back determination may be performed in combination with the intensities pa to pc of the first scattered light and the intensities sa to sc of the second scattered light. For example, the conditions for the front-back determination may be changed according to the calculated particle diameter of the foreign matter.

[0051] <Effects of this embodiment> With the foreign object inspection device 100 of this embodiment configured as described above, by irradiating a predetermined inspection position SP (foreign object K) with laser light from three directions, it is possible to detect the intensity of scattered light according to the shape (e.g., silhouette) of the foreign object K as viewed from three directions. This reduces the influence of the shape of the foreign object K compared to irradiating with laser light from only one direction, and allows for accurate determination of whether the foreign object K is attached to one side or the other side of the film.

[0052] The laser beam LB is irradiated from directions A to C to the designated inspection position SP (foreign object) radially surrounding the entire circumference of the foreign object. This allows for balanced irradiation of the foreign object, reducing the influence of the foreign object's shape and enabling front-to-back determination.

[0053] In this embodiment, the inspection light irradiation unit 2 and the scattered light detection unit 3 are arranged on one side (surface) of the film F, making it suitable for cases where foreign matter inspection of the film F can only be performed from one side. It is particularly advantageous for inspecting pellicles already attached to reticles.

[0054] <Other Embodiments> The present invention is not limited to the embodiments described above.

[0055] In the above embodiment, laser light was irradiated from three directions onto a predetermined inspection location (foreign object), but it may be two directions or four or more directions. Preferably, each direction extends so that it does not directly face the other directions.

[0056] It is preferable that the multiple directions are balanced and arranged in a way that surrounds the predetermined inspection location (foreign object) when viewed from above. Here, "well-balanced" means, for example, as shown in Figure 6, that when the circle representing the entire circumference surrounding the predetermined inspection location (foreign object) is equally divided by the number of directions (in this case, three directions A' to C'), one direction is positioned in each of the resulting regions.

[0057] Each direction may be arranged unevenly as shown in Figure 7. Each direction A'' to C'' is arranged within a predetermined angular range (120 degrees in this case) when viewed from above and from the perspective of the foreign object. Here, they are arranged at equal intervals (60 degrees) along the circumferential direction.

[0058] Furthermore, the inspection light irradiation unit 2 may irradiate the foreign object K with laser light from the entire circumferential direction surrounding it. In this case, a ring lighter or the like may be used as the light irradiator. Alternatively, a white light source that emits non-coherent light may be used as the light source, and the inspection light is not limited to laser light. The inspection light irradiation unit only needs to be able to switch between irradiating P-polarized and S-polarized inspection light. When using a white light source or the like, it is preferable to use filters that selectively transmit light of wavelengths that cause a large difference between the intensity of the first scattered light and the intensity of the second scattered light from the foreign object.

[0059] Film F may be the pellicle before it is attached to the reticle. Alternatively, it may be the reticle or other transparent substrate, or any film that is light-transmitting.

[0060] Instead of foreign matter K, the front / back determination may be performed by checking scratches or other marks formed on the film surface. Alternatively, the front / back determination may be performed for particles other than foreign matter attached to the film.

[0061] For example, in the above embodiment, the configuration involved switching between irradiating with P-polarized laser light and S-polarized laser light, but it is also possible to irradiate the film with circularly polarized laser light from the inspection light irradiation unit.

[0062] In this case, the scattered light detection unit preferably includes a first scattered light detector that detects the first scattered light generated due to the P-polarization component of circularly polarized laser light, a second scattered light detector that detects the second scattered light generated due to the S-polarization component, and a splitting optical system that splits the scattered light generated from foreign matter adhering to the film into two and guides them to the first scattered light detector and the second scattered light detector, respectively.

[0063] For example, the first scattered light detector has an analyzer that selectively transmits the first scattered light caused by the P-polarization component contained in the circularly polarized laser light, and the second scattered light detector has an analyzer that selectively transmits the second scattered light caused by the S-polarization component contained in the circularly polarized laser light. The splitting optical system can be configured, for example, with a beam splitter.

[0064] The information processing device 4 may, in addition to (or instead of) the pixel corresponding to the inspection position in the image data captured by the detector's image sensor, treat pixels corresponding to the surrounding positions of the inspection position as data indicating the intensity of scattered light. With such a configuration, even if the pixel value detected from the pixel corresponding to the inspection position becomes saturated and cannot be compared, the front-to-back determination of the foreign object can be performed by using, for example, the pixel value of the pixel corresponding to the peripheral position surrounding the inspection position as data indicating the intensity of scattered light.

[0065] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention.

[0066] According to the present invention, it is possible to accurately determine whether foreign matter is attached to the surface or the back surface of a light-transmitting film.

[0067] 100... Foreign object inspection device F... Film 2... Inspection light irradiation unit 21a-21c... Laser light irradiator 22... Laser light source 23... Polarization switch 24... Irradiation optical system 3... Scattered light detection unit 31... Detection optical system 32... Scattered light detector 4... Information processing unit 41... Judgment unit LB... Laser light SL1... First scattered light SL2... Second scattered light

Claims

1. A foreign matter inspection device for detecting foreign matter attached to a light-transmitting film, comprising: an inspection light irradiation unit that irradiates the foreign matter at a predetermined inspection position with P-polarized inspection light and S-polarized inspection light from a plurality of directions; a scattered light detection unit that detects first scattered light generated from the P-polarized inspection light irradiated from each of the plurality of directions and second scattered light generated from the S-polarized inspection light irradiated from each of the plurality of directions; and a determination unit that determines whether the foreign matter is attached to one side or the other side of the film based on the intensity of the first scattered light and the intensity of the second scattered light detected by the scattered light detection unit.

2. The foreign object inspection apparatus according to claim 1, wherein the plurality of directions extend radially from the predetermined inspection position when the film is viewed from one side.

3. The foreign object inspection apparatus according to claim 1 or 2, wherein the plurality of directions are arranged at equal intervals along the circumferential direction centered on the predetermined inspection position when the film is viewed from one side.

4. The foreign object inspection apparatus according to any one of claims 1 to 3, wherein the plurality of directions equally divide the entire circumference surrounding the predetermined inspection position when the film is viewed from one side.

5. The foreign object inspection apparatus according to any one of claims 1 to 4, wherein the number of directions is odd.

6. The foreign object inspection apparatus according to any one of claims 1 to 5, wherein the inspection light irradiation unit irradiates inspection light at the Brewster angle or an angle near thereto with respect to the inspection position.

7. The foreign object inspection apparatus according to any one of claims 1 to 6, wherein the inspection light irradiation unit irradiates the film with inspection light in a wavelength range such that the transmittance of S-polarized light to the film is 0.8 times or less than the transmittance of P-polarized light.

8. The foreign matter inspection apparatus according to any one of claims 1 to 7, wherein the determination unit determines that the foreign matter is attached to one surface of the film when the relative magnitudes of the intensity of the first scattered light and the intensity of the second scattered light satisfy a predetermined condition, and determines that the foreign matter is attached to the other surface of the film when the relative magnitudes of the intensity of the first scattered light and the intensity of the second scattered light do not satisfy the predetermined condition.

9. A method for inspecting foreign matter attached to a light-transmitting film, comprising: irradiating the foreign matter at a predetermined inspection position with P-polarized inspection light from multiple directions; detecting first scattered light generated from the P-polarized inspection light irradiated from each of the multiple directions; irradiating the foreign matter at the predetermined inspection position with S-polarized inspection light from the multiple directions; detecting second scattered light generated from the S-polarized inspection light irradiated from each of the multiple directions; and determining whether the foreign matter is attached to one side or the other side of the film based on the intensity of the detected first scattered light and the intensity of the second scattered light.

Images