Foreign object inspection device and foreign object inspection method

Abstract

The present invention provides a foreign object inspection device that can accurately determine whether a foreign object is attached to the front or back surface of a material. [Solution] The device comprises a laser light irradiation unit that irradiates a light-transmitting film by scanning a laser beam linearly from one side of the film; a scattered light detection unit that detects a first scattered light intensity, which is the intensity of scattered light generated from foreign matter adhering to the film due to the P-polarization component of the laser light, and a second scattered light intensity, which is the intensity of scattered light generated from foreign matter adhering to the film due to the S-polarization component of the laser light; and a determination unit that determines whether the foreign matter adhering to the film is attached to one side or the other side, based on the first and second scattered light intensities detected by the scattered light detection unit. The device is configured such that, when the intersection of a scanning plane, which is the same plane as the region through which the scanned laser light passes, and an incident plane, which is a plane perpendicular to the scanning line of the laser light on the film, is taken as a reference line, the scattered light detection unit is positioned on a plane that intersects the incident plane with the reference line at an angle of 40 degrees or more and 50 degrees or less.

Description

Technical Field

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

Background Art

[0002] For example, as a foreign object inspection device for inspecting foreign objects adhering 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, and detects the intensity of the scattered light generated by the irradiation in the incident plane, compares these intensities, and determines whether the foreign object adhering to the object to be inspected adheres to the front surface or the back surface of the object to be inspected.

[0003] Specifically, this foreign object inspection device utilizes the fact that the transmittance of P-polarization and the transmittance of S-polarization with respect to the object to be inspected are different. When the scattered light intensity of P-polarization and the scattered light intensity of S-polarization are about the same, it is determined that the foreign object is on the front surface, and when there is a difference greater than or equal to a reference value, it is determined that the foreign object is on the back surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] <图 However, in the foreign object inspection device described above, the detector arrangement is not equivalent to the polarization of the incident light, making it difficult to determine whether a foreign object is attached to the front or back surface of the object based on the difference in intensity between the scattered light intensity of P-polarized light and the scattered light intensity of S-polarized light. More specifically, the foreign object inspection device described above is susceptible to the difference in scattering characteristics between incident P-polarized light and incident S-polarized light, making it difficult to determine the front or back surface from the difference in scattered light intensity unless the difference in transmittance between P-polarized light and S-polarized light to the object is very large. As a result, the foreign object inspection device described above suffers from an increase in misjudgments, making it difficult to guarantee detection accuracy.

[0006] Therefore, the present invention was made to solve the above-mentioned problems, and its main objective is to accurately determine whether foreign matter is attached to the surface or the back surface of a light-transmitting film. [Means for solving the problem]

[0007] In other words, the foreign matter inspection apparatus according to the present invention detects foreign matter on a light-transmitting film, and comprises: a laser light irradiation unit that scans and irradiates the film with laser light from one side thereof; a scattered light detection unit that detects a first scattered light intensity, which is the intensity of scattered light generated from foreign matter attached to the film due to the P-polarization component of the laser light, and a second scattered light intensity, which is the intensity of scattered light generated from foreign matter attached to the film due to the S-polarization component of the laser light; and a determination unit that determines whether the foreign matter attached to the film is attached to one side or the other side based on the first scattered light intensity and the second scattered light intensity detected by the scattered light detection unit, wherein, with respect to the intersection of a scanning plane that is coplane with the region through which the scanned laser light passes and an incident plane that is perpendicular to the scanning line of the laser light on the film, the scattered light detection unit is arranged on a plane that intersects the incident plane at an angle of 40 degrees or more and 50 degrees or less on the reference line.

[0008] In this invention, the scattered light detection unit is positioned on a plane (referred to as the equivalent plane) that can detect both the P-polarized and S-polarized components of the laser light in a nearly equivalent manner. This allows for the reception of the first scattered light intensity derived from the P-polarized component of the laser light and the second scattered light intensity derived from the S-polarized component of the laser light in a nearly equivalent manner. As a result, the difference between the first and second scattered light intensities when a foreign object is on the surface can be minimized compared to the difference when a foreign object is on the back surface, allowing for more accurate differentiation between these two states. Consequently, even when inspecting a thin film, for example, it is possible to accurately determine whether a foreign object is attached to the surface or the back surface of the film. For example, if the equivalent plane is configured to intersect the incident plane and the reference line at a 45-degree angle, the vibration directions of the P-polarized and S-polarized laser light will be symmetrical with respect to the equivalent plane, and the scattered light detection unit can detect the first scattered light intensity and the second scattered light intensity with approximately equivalent accuracy.

[0009] It is desirable that the incident plane divides the scan lines in a ratio of 1:x (where x is a value between 2 / 3 and 3 / 2). With this configuration, scattered light from foreign objects located at each point on the scan line can be detected with relative equality. For example, it is desirable that the incident plane divides the scan line in a 1:1 ratio, i.e., bisects it.

[0010] The film is attached to a substrate provided on the other side, and it is desirable that the scattered light detection unit is positioned to avoid diffracted light generated from the substrate due to the laser light. With this configuration, the scattered light detection unit is less likely to misdetect diffracted light caused by substrate patterns such as reticles, thereby improving the accuracy of determining the presence of foreign matter.

[0011] The scattered light detection unit preferably has two scattered light detectors arranged opposite each other across the incident plane. In this configuration, the determination unit can determine the surface on which foreign matter is attached by using the detection results of the scattering light detector that can detect the first and second scattered light intensities in a more equivalent manner than the other two scattering light detectors, for the scattered light that may originate from each point on the scan line. For example, by having the two scattering light detectors share the detection of scattered light from each point on the scan line, the detection range of each scattering light detector can be reduced, thereby improving detection accuracy. Alternatively, the determination unit may calculate the scattered light intensity using the detection results of both scattering light detectors.

[0012] As a specific method for determining the adhesion surface, the determination unit may determine whether the foreign matter adhering to the film is adhering to one surface or the other surface, based on the relative magnitudes of the first scattered light intensity and the second scattered light intensity detected by the scattered light detection unit.

[0013] In this invention, since the scattered light detection unit is arranged in an equivalent plane, if there is foreign matter on one side of the film (the laser light irradiation side), the scattered light detection unit should be able to detect it as equivalently as possible regardless of whether S-polarized or P-polarized light is irradiated, and scattered light of equivalent intensity should be obtained. On the other hand, if there is foreign matter on the other side, scattered light of different intensities will be obtained according to the difference in transmittance.

[0014] Therefore, the determination unit may determine that a foreign substance is attached to one side of the film when the relative magnitudes of the first scattered light intensity and the second scattered light intensity satisfy a predetermined condition, and determine that a foreign substance is attached to the other side of the film when the relative magnitudes of the first scattered light intensity and the second scattered light intensity do not satisfy the predetermined condition.

[0015] In addition, the foreign object inspection apparatus according to the present invention further comprises a scattered light intensity group extraction unit that extracts a plurality of first scattered light intensities obtained from a local region containing one foreign object by scanning with laser light as a first scattered light intensity group, and extracts a plurality of second scattered light intensities obtained from the local region by scanning with laser light as a second scattered light intensity group, and it is desirable that the determination unit determines, based on the first scattered light intensity group and the second scattered light intensity group, whether the one foreign object is attached to one surface or the other surface. With this configuration, the scattered light intensity group is compared in a localized region composed of multiple points where foreign matter is attached, thus suppressing the influence of variations in the obtained scattered light intensity and enabling accurate determination of the front and back sides.

[0016] The aforementioned film is preferably a pellicle. Since it is difficult to determine the surface to which foreign matter adheres when the film is thin, such as a pellicle, the foreign matter inspection device of the present invention can be suitably used.

[0017] Furthermore, another foreign matter inspection device according to the present invention detects foreign matter on a light-transmitting film and comprises: a laser light irradiation unit that scans and irradiates the film with circularly polarized or elliptically polarized laser light from one side thereof; a scattered light detection unit that detects the intensity of a first polarization component corresponding to the P polarization component of the laser light and the intensity of a second polarization component corresponding to the S polarization component of the laser light, among the polarization components contained in the scattered light generated from foreign matter adhering to the film due to the laser light; and a determination unit that determines whether the foreign matter adhering to the film is adhering to one side or the other side based on the first and second polarization component intensities detected by the scattered light detection unit, wherein the scattered light detection unit is arranged on a plane that includes the reference line and makes an angle of 40 degrees or more and 50 degrees or less with respect to the incident plane, with respect to the intersection line of the scanning plane which is the same plane as the region through which the scanned laser light passes and the incident plane which is a plane that intersects perpendicularly with the scanning line of the laser light on the film. Even such a foreign object inspection method can achieve the same operational effects as the above-described foreign object inspection apparatus. In addition, since circularly polarized light including P-polarized light and S-polarized light is irradiated, it is not necessary to irradiate the laser light in two separate steps.

[0018] Further, the foreign object inspection method according to the present invention scans and irradiates a laser beam on one surface of a film having light transmissivity, and the intensity of scattered light generated from foreign objects adhering to the film due to the P-polarized light component of the laser beam, which is the first scattered light intensity, and the intensity of scattered light generated from foreign objects adhering to the film due to the S-polarized light component of the laser beam, which is the second scattered light intensity, are detected. Based on the detected first scattered light intensity and second scattered light intensity, it is determined whether the foreign objects adhering to the film are adhering to the one surface or the other surface. The foreign object inspection method is characterized in that the scattered light is detected on a plane that intersects the reference line at an angle of 40 degrees or more and 50 degrees or less with respect to the incident plane, where the reference line is the intersection line of the scanning plane that forms the same plane as the region through which the scanned laser beam passes and the incident plane that is perpendicular to the scanning line of the laser beam on the film. Even such a foreign object inspection method can achieve the same operational effects as the above-described foreign object inspection apparatus.

Effects of the Invention

[0019] According to the present invention configured as described above, it is possible to accurately determine whether foreign objects are adhering to the front surface or the back surface of the film having light transmissivity.

Brief Description of the Drawings

[0020] [Figure 1] It is an overall schematic diagram showing a foreign object inspection apparatus according to an embodiment of the present invention. [Figure 2] It is a perspective view schematically showing a scanning mode and the like for the film of the same embodiment. [Figure 3] It is a perspective view for explaining the scanning plane and the incident plane of the same embodiment. [Figure 4] It is a schematic diagram for explaining the equivalent plane of the same embodiment. [Figure 5]It is an overall schematic diagram showing the foreign object inspection device of the second embodiment. [Figure 6] It is an overall schematic diagram showing the foreign object inspection device of the third embodiment. [Figure 7] It is an explanatory diagram for explaining the function of the extraction unit of the third embodiment.

Embodiments for Carrying Out the Invention

[0021] <One Embodiment of the Present Invention> Hereinafter, an embodiment of a foreign object inspection device according to the present invention will be described with reference to the drawings. Note that, for the sake of clarity, all the figures shown below are schematically drawn with appropriate omissions or exaggerations. The same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0022] The foreign object inspection device 100 of the present embodiment inspects foreign objects attached to a film F having light transmissivity.

[0023] As shown in FIG. 1, the film F is a protective film (pellicle) that prevents foreign objects from adhering to a reticle R, which is a type of photomask. The film F of the present embodiment is fixed to a holding frame W and attached to the reticle R, covering the surface of the reticle R on which a pattern (not shown) is formed. Hereinafter, the back surface of the film F is the surface (lower surface) on the reticle side, which faces the pattern of the reticle R. On the other hand, the front surface of the film F is the surface (upper surface) facing the side opposite to the photomask, which faces the outside.

[0024] More specifically, the film F is a protective film (EUV pellicle) that prevents foreign objects from adhering to the reticle R in an exposure process using an extreme ultraviolet (EUV) light source. Note that the protective film is not limited to the EUV pellicle and may be other pellicles.

[0025] <Device Configuration> As shown in Figure 1, the foreign object inspection apparatus 100 of this embodiment includes a laser light irradiation unit 2 that irradiates the surface of a film F placed on a measuring stage S with laser light L1, a scattered light detection unit 3 that detects scattered light L2 generated by the irradiation of laser light L1, and an information processing device 4 that determines the surface on which foreign objects are attached to the film F based on the intensity of the scattered light L2 detected by the scattered light detection unit 3.

[0026] The following describes the structure of each section, from parts 2 to 4.

[0027] As shown in Figures 1 and 2, the laser beam irradiation unit 2 is positioned on the surface side of the film F and irradiates the surface of the film F with laser light L1 by scanning in a straight line. The scanning line SL, represented by a bidirectional arrow in Figure 2, is the trajectory of the inspection point on the film where the laser light is irradiated, and is a line segment with a length corresponding to one linear scan.

[0028] In this embodiment, the laser beam irradiation unit 2 scans the film F linearly along the Y direction with the laser beam L1, and the measurement stage S moves in the X direction, so that the laser beam L1 is irradiated over the entire predetermined inspection area on the surface of the film F.

[0029] Specifically, as shown in Figure 1, the laser beam irradiation unit 2 includes a laser light source 21 using a laser tube such as a HeNe laser that emits laser beam L1, a scanning mirror 22 such as a galvanometer mirror that linearly scans the laser beam L1 back and forth in the Y direction, and a scanning lens 23 such as an fθ lens that focuses the laser beam L1 onto the surface of the film F.

[0030] Furthermore, the laser beam irradiation unit 2 is configured to irradiate with P-polarized laser beam L1 and S-polarized laser beam L1, switching between them. Specifically, a polarization switching unit 24 is provided between the laser light source 21 and the scanning mirror 22 to switch the laser beam L1 emitted from the laser light source 21 between P-polarized and S-polarized.

[0031] The polarization switching unit 24 selectively switches the polarization of the laser light L1 using, for example, a λ / 2 plate, a polarizing beam splitter, a polarizer, or other optical crystal. The polarization switching unit 24 may be located at a position different from the laser light source 21 and the scanning mirror 22 before the laser light L1 is irradiated onto the film F.

[0032] Here, P-polarization is the polarization that vibrates parallel to the incident plane of the laser light L1 irradiated onto the surface of the film F, as shown in Figure 2. S-polarization is the polarization that vibrates perpendicular to the incident plane.

[0033] Furthermore, since the laser beam irradiation unit 2 irradiates the film F with P-polarized laser beam L1 and S-polarized laser beam L1, it is desirable that the incident angle 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 beam L1 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 range of ±5° of the Brewster angle.

[0034] As shown in Figures 1 and 2, the scattered light detection unit 3 detects scattered light L2 generated from foreign matter adhering to the film F when irradiated with laser light L1. This scattered light detection unit 3 is located on the surface side of the film F.

[0035] Specifically, the scattered light detection unit 3 has two scattered light detectors (a first scattered light detector 31 and a second scattered light detector 32), each configured to detect scattered light L2 generated on the scan line SL.

[0036] In this embodiment, the laser light irradiation unit 2 is configured to switch between P-polarized laser light L1 and S-polarized laser light L1 and irradiate the film F. Accordingly, each scattered light detector 31, 32 detects the intensity of the first scattered light generated when the P-polarized laser light L1 is irradiated onto the film F as the first scattered light intensity, and detects the intensity of the second scattered light generated when the S-polarized laser light L1 from the laser light irradiation unit 2 is irradiated onto the film F as the second scattered light intensity.

[0037] Specifically, each scattered light detector 31, 32 converts the intensity of the scattered light L2 into an electrical signal and outputs it to the information processing device 4. Each scattered light detector 31, 32 is, for example, a PMT (photomultiplier tube) or a line sensor. The scattered light detection unit 3 may further include optical elements such as lenses and / or slits interposed between the surface of the film F and each scattered light detector 31, 32 to focus the scattered light L2 from the film F.

[0038] <Specific arrangement of the scattered light detection unit 3> Next, we will describe the specific arrangement of the scattered light detection unit 3.

[0039] Here, as shown in Figures 2 and 3, the plane that is coplanar with the region through which the laser beam L1, scanned on the surface of the film F, passes is called the scanning plane SP. This scanning plane SP intersects the surface of the film F (XY plane) on the scanning line SL (Y axis). Also, the plane that intersects the scanning line SL of the laser beam L1 perpendicularly on the surface of the film F is called the incident plane IP. In this embodiment, the incident plane IP can be represented by the XZ plane, which bisects the scanning line SL.

[0040] As shown in Figures 2 to 4, the scattered light detection unit 3 is positioned to receive scattered light L2 from P-polarized laser light L1 and scattered light L2 from S-polarized laser light L1 as equally as possible.

[0041] Specifically, if the intersection line of the scanning plane SP and the incident plane IP of the laser beam L1 is defined as the reference line BL, the scattered light detection unit 3 is positioned on the equivalent plane EP, which is a plane that intersects the incident plane IP at a 45-degree angle with the reference line BL. In other words, the equivalent plane EP is a plane that intersects both the scanning plane SP and the incident plane IP at a 45-degree angle. Note that the angle between the incident plane IP and the equivalent plane EP is not limited to 45 degrees, but can be in the range of 40 to 50 degrees.

[0042] More specifically, as shown in Figure 4, the first scattered light detector 31 and the second scattered light detector 32 are provided on two equivalent planes EP1 and EP2, respectively, which intersect the incident plane IP at a 45-degree angle along the reference line BL. Here, the first scattered light detector 31 and the second scattered light detector 32 are provided symmetrically across the incident plane IP, but these detectors 31 and 32 may also be positioned offset from each other.

[0043] Each scattered light detector 31, 32 is provided so as to be able to detect scattered light L2 on each equivalent plane EP1, EP2. For example, the light-receiving surface or light-receiving element of each scattered light detector 31, 32 may be arranged on each equivalent plane EP1, EP2 to detect scattered light L2 that has traveled along each equivalent plane EP1, EP2. Alternatively, if there are optical elements such as lenses and / or slits, the optical elements may be arranged on each equivalent plane EP1, EP2 to guide the scattered light L2 that has traveled along each equivalent plane EP1, EP2 to the light-receiving surface or light-receiving element of each scattered light detector 31, 32.

[0044] In addition, the scattered light detection unit 3 is positioned to avoid diffracted light generated from the pattern of the reticle R due to irradiation by the laser light L1. This position is set taking into consideration the incident angle of the laser light L1, the thickness of the reticle R, the shape of the pattern, and the receiving elevation and receiving horizontal angles of the scattered light detection unit 3. The "position to avoid diffracted light" referred to here is a position where diffracted light is not received, or a position where, even if diffracted light is received, the intensity of the detected diffracted light is below a predetermined threshold for foreign object detection.

[0045] The information processing device 4 is a computer having a CPU, memory, input / output interface, AD converter, etc. Based on a foreign object inspection program stored in memory, the CPU and peripheral devices cooperate to perform at least the functions of a scanning control unit 41 and a determination unit 42.

[0046] The scanning control unit 41 controls the scanning mode of the laser beam L1 by the laser beam irradiation unit 2. Specifically, the scanning control unit 41 controls the operation of the scanning mirror 22 described above to control the scanning range and incident angle of the laser beam L1. The scanning control unit 41 also controls the operation of the polarization switching unit 24 to irradiate each point in the inspection area on the surface of the film F with P-polarized laser beam L1 and S-polarized laser beam L1, respectively.

[0047] The determination unit 42 determines whether the foreign object is attached to the surface or back surface of the film F based on the first scattered light intensity and the second scattered light intensity indicated by the signals received from the first scattered light detector 31 and / or the second scattered light detector 32. The determination result from this determination unit 42 can be displayed on a display unit 43 such as a display.

[0048] <Specific method for determining the surface to which foreign matter is attached> The determination unit 42 determines the surface on which foreign matter is attached by utilizing the difference in transmittance of P-polarized light and S-polarized light to the film F. Specifically, the determination unit 42 first adjusts the intensity of the laser light L1 so that the first scattered light intensity and the second scattered light intensity, which are detected when foreign matter is present on the surface of the film F, are approximately the same, before the foreign matter inspection begins. The determination unit 42 then determines, after the inspection has started, that if the relative magnitudes of the first scattered light intensity and the second scattered light intensity satisfy a predetermined condition, the foreign matter is attached to one side of the film F, and if the relative magnitudes of the first scattered light intensity and the second scattered light intensity do not satisfy a predetermined condition, the determination unit 42 determines that the foreign matter is attached to the other side of the film F.

[0049] More specifically, the determination unit 42 determines that the foreign matter is attached to one side if the ratio of the detected first scattered light intensity and the second scattered light intensity is within a first range (for example, 0.9 to 1.1), and that the intensities are approximately the same. On the other hand, the determination unit 42 determines that the foreign matter is attached to the back side if the ratio of the detected first scattered light intensity and the second scattered light intensity is within a second range (for example, greater than 1.2), and that the intensities are different.

[0050] In addition to such surface and back surface determination, the determination unit 42 may also determine that it is unclear whether the foreign matter is attached to the surface or back surface of the film F if the ratio of the first scattered light intensity to the second scattered light intensity is within a third range (for example, 1.1 to 1.2).

[0051] The determination unit 42 may also determine whether the surface to which foreign matter is attached is based on whether the magnitude of the difference between the first scattered light intensity and the second scattered light intensity is greater than or less than a predetermined value.

[0052] <Effects of this embodiment> In the foreign object inspection device 100 of this embodiment, configured in this way, the scattered light detection unit 3 is positioned on an equivalent plane EP that can detect both the P-polarized and S-polarized laser light L1 in a nearly equivalent manner, and can receive the first scattered light intensity and the second scattered light intensity of the scattered light from the foreign object in a nearly equivalent manner. As a result, the difference in intensity between the first scattered light intensity and the second scattered light intensity when the foreign object is on the surface can be made as small as possible compared to the difference in intensity between the first scattered light intensity and the second scattered light intensity when the foreign object is on the back surface, so that these two states can be distinguished more accurately. With this, for example, even when inspecting a thin film, the surface on which foreign objects are attached to the film can be accurately determined.

[0053] In this embodiment, the laser 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 the reticle R.

[0054] In this embodiment, by having two scattered light detectors 31 and 32 share the detection of scattered light L2 from each point on the scan line, the detection range per scattered light detector can be reduced, thereby improving detection accuracy. Furthermore, the influence of diffracted light from the pattern can be reduced.

[0055] <Second Embodiment> In the above embodiment, the device was configured to switch between irradiating with P-polarized laser light L1 and S-polarized laser light L1. However, in the second embodiment, as shown in Figure 5, the foreign object inspection device 100 irradiates the film F with circularly polarized laser light L1 from the laser light irradiation unit 2. The circularly polarized laser light L1 only needs to contain P-polarized and S-polarized components, and may be elliptically polarized light in which the intensities of each component are different.

[0056] The scattered light detection unit 3 of the second embodiment detects the intensity of the first polarization component corresponding to the P polarization component of the laser light L1, and the intensity of the second polarization component corresponding to the S polarization component of the laser light L1, among the polarization components contained in the scattered light L2 generated from foreign matter adhering to the film F due to the circularly polarized laser light L1.

[0057] Specifically, the scattered light detection unit 3 includes a first polarization component detector 33 for detecting the intensity of the first polarization component, a second polarization component detector 34 for detecting the intensity of the second polarization component, and a splitting optical system 35 that splits the scattered light L2 generated from foreign matter adhering to the film F into two and guides them to the two polarization component detectors 33 and 34, respectively.

[0058] The first polarization component detector 33 has an analyzer 331 that selectively transmits the first polarization component contained in the scattered light L2, and the second polarization component detector 34 has an analyzer 331 that selectively transmits the second polarization component contained in the scattered light L2. The splitting optical system 35 can be configured, for example, with a beam splitter.

[0059] The first polarization component is, for example, the polarization component with particularly high intensity among the polarization components contained in the scattered light generated when P-polarized laser light is irradiated onto a foreign object. Specifically, the first polarization component corresponding to the P-polarized component is detected using an analyzer with an angle corresponding to the angle of the high-intensity polarization component (the direction in the plane perpendicular to the direction of propagation). The same applies to the second polarization component corresponding to the S-polarized component. The first polarization component may be any polarization component with low intensity among the polarization components contained in the scattered light caused by P-polarized laser light, and it is acceptable as long as it is a polarization component that has a characteristic intensity corresponding to the P-polarized component. The same applies to the second polarization component.

[0060] With the foreign object inspection device 100 of the second embodiment configured in this way, it is not necessary to scan with P-polarized laser light L1 and S-polarized laser light L1 in two separate steps.

[0061] <Third Embodiment> As shown in Figure 6, the information processing device 4 of the third embodiment also functions as an extraction unit 44. The functions of the extraction unit 44 will be described below with reference to Figure 7.

[0062] Figure 7 is a magnified view of film F with foreign matter attached, seen from the surface side. The grid-like region IA is a hypothetical representation of the inspection region IA, which is the area on the surface of film F where the laser beam L1 is scanned. Each square represents a point on the inspection region IA where scattered light is obtained by scanning the laser beam L1. The dotted line region LA is a hypothetical representation of the local region LA, which is the area within the inspection region IA that contains one piece of foreign matter.

[0063] The extraction unit 44 extracts a plurality of first scattered light intensities obtained from a local region LA by scanning the laser light L1 as a first scattered light intensity group, and extracts a plurality of the second scattered light intensities obtained from a local region LA by scanning the laser light L1 as a second scattered light intensity group.

[0064] More specifically, the extraction unit 44 extracts a group of first scattered light intensities obtained from multiple points located within a certain distance of each other on the coordinate system of the inspection area IA, when first scattered light intensities exceeding a predetermined threshold are obtained from these points, as a first scattered light intensity group. The certain distance is, for example, a distance corresponding to the size of the assumed foreign object. The extraction unit 44 then extracts the second scattered light intensities obtained from the same multiple points as a second scattered light intensity group. The region formed by the collection of these multiple points corresponds to the local region LA containing the aforementioned foreign substance.

[0065] Furthermore, if the extraction unit 44 obtains scattered light intensities above a predetermined threshold from multiple adjacent points, it may extract a group of first scattered light intensities obtained from those points as a first scattered light intensity group. Alternatively, the extraction unit 44 may extract a second scattered light intensity group first, or it may extract the first scattered light intensity and the second scattered light intensity separately.

[0066] The determination unit 42 of the third embodiment determines, based on the first scattered light intensity group and the second scattered light intensity group, whether the one foreign object is attached to one surface or the other surface.

[0067] For example, the determination unit 42 performs a front / back determination by comparing the maximum scattered light intensities included in each scattered light intensity group, comparing the number of scattered light intensities in each scattered light intensity group that exceed a preset threshold, or comparing the sum of the scattered light intensities included in each scattered light intensity group. Alternatively, the determination may be performed after smoothing calculations, such as taking the average of the scattered light intensities included in each scattered light intensity group.

[0068] In addition, the determination unit 42 may decide which of the above-mentioned front / back determination methods to use based on the proportion and number of saturated scattered light intensities included in each scattered light intensity group.

[0069] With the foreign object inspection device 100 of the third embodiment configured in this way, the scattered light intensity group in the local region LA, which is composed of multiple points on which the foreign object is attached, is compared. Therefore, the influence of variations in the obtained scattered light intensity is suppressed, and the front / back determination can be made more effectively than when comparing the scattered light intensity at each point on the inspection region IA. For example, with this configuration, even if the first and second scattered light intensities obtained from a certain point are both saturated and cannot be compared in intensity, it is still possible to determine the front and back of a foreign object at that point by combining it with other points.

[0070] <Other Embodiments> However, the present invention is not limited to the embodiments described above.

[0071] The scattered light detection unit 3 may consist of one or more scattered light detectors. When multiple scattered light detectors are used, the position of the incident plane that determines the placement of each scattered light detector may be set for each scattered light detector. For example, if there are scattered light detectors a to n, the incident plane IPa may be set to intersect the scan line perpendicularly within the detection range of scattered light detector a, the incident plane IPb may be set to intersect the scan line perpendicularly within the detection range of scattered light detector b, and so on. The intersection line between each of these incident planes IPn and the scan plane may be set as the reference line BLn, and scattered light detector n may be positioned on the equivalent plane EPn which intersects the incident plane IPn at an angle of 40 to 50 degrees with this reference line BLn. In this case as well, within the detection range of each scattered light detector, the first scattered light intensity and the second scattered light intensity generated from each point on the scan line can be detected in a nearly equivalent manner.

[0072] The film 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.

[0073] The foreign object inspection device may detect, in addition to or instead of foreign objects, scratches on the surface or back surface of the film F, or through holes formed in the film F.

[0074] Furthermore, various modifications and combinations of the embodiments are permitted, as long as they do not contradict the spirit of the present invention. [Explanation of Symbols]

[0075] 100... Foreign object inspection device F... Film 2. Laser beam irradiation area 21 ···Laser beam irradiation section 22 ··· Scanning Optical Systems 3. Scattered light detection unit 31 ···First scattered light detector 32 ···Second scattered light detector 4. Information Processing Device 41 ···Scanning Control Unit 42 ...judgment section 43...Display section 44...Extraction part L1 ···Laser light L2...Scattered light SL ··· scan lines IP...Incidence plane SP ··· Scanning plane EP...equivalent plane

Claims

1. A foreign object inspection device for detecting foreign objects on a light-transmitting film, A laser beam irradiation unit that irradiates the aforementioned film with laser light by scanning it from one side thereof, A scattered light detection unit detects a first scattered light intensity, which is the intensity of scattered light generated from foreign matter adhering to the film due to the P-polarization component of the laser light, and a second scattered light intensity, which is the intensity of scattered light generated from foreign matter adhering to the film due to the S-polarization component of the laser light. The system includes a determination unit that determines, based on the first and second scattered light intensities detected by the scattered light detection unit, whether the foreign matter adhering to the film is adhering to one surface or the other surface. If the intersection of the scanning plane, which is the same plane as the region through which the scanned laser light passes, and the incident plane, which is the plane perpendicular to the scanning line of the laser light on the film, is taken as the reference line, A foreign object inspection device in which the scattered light detection unit is positioned on a plane that includes the reference line and makes an angle of 40 degrees or more and 50 degrees or less with the incident plane.

2. The incident plane divides the scan lines in a ratio of 1:x. The foreign object inspection apparatus according to claim 1, wherein x is a value between 2 / 3 and 3 / 2.

3. The aforementioned film is attached to a substrate provided on the other side, The foreign object inspection apparatus according to claim 1 or 2, wherein the scattered light detection unit is positioned to avoid diffracted light generated from the substrate due to the laser light.

4. The foreign object inspection apparatus according to any one of claims 1 to 3, wherein the scattered light detection unit has two scattered light detectors arranged opposite each other across the incident plane.

5. The determination unit, When the relative magnitudes of the first scattered light intensity and the second scattered light intensity satisfy a predetermined condition, it is determined that a foreign substance is adhering to one side of the film. A foreign matter inspection apparatus according to any one of claims 1 to 4, wherein it is determined that a foreign matter is adhering to the other surface of the film when the relative magnitudes of the first scattered light intensity and the second scattered light intensity do not satisfy the predetermined conditions.

6. The system further includes an extraction unit that extracts a plurality of first scattered light intensities obtained from a local region containing one of the foreign matter by scanning the laser light as a first scattered light intensity group, and extracts a plurality of second scattered light intensities obtained from the local region by scanning the laser light as a second scattered light intensity group, The foreign object inspection apparatus according to any one of claims 1 to 5, wherein the determination unit determines, based on the first scattered light intensity group and the second scattered light intensity group, whether the one foreign object is attached to one surface or to the other surface.

7. The foreign object inspection apparatus according to any one of claims 1 to 6, wherein the membrane is a pellicle.

8. A foreign object inspection device for detecting foreign objects on a light-transmitting film, A laser light irradiation unit that irradiates the aforementioned film with circularly polarized or elliptically polarized laser light by scanning from one side thereof, A scattered light detection unit detects the intensity of a first polarization component corresponding to the P polarization component of the laser light and the intensity of a second polarization component corresponding to the S polarization component of the laser light, among the polarization components contained in the scattered light generated from foreign matter adhering to the film due to the laser light. The system includes a determination unit that determines whether the foreign matter adhering to the film is adhering to one surface or the other surface, based on the first and second polarization component intensities detected by the scattered light detection unit. If the intersection of the scanning plane, which is the same plane as the region through which the scanned laser light passes, and the incident plane, which is the plane perpendicular to the scanning line of the laser light on the film, is taken as the reference line, A foreign object inspection device in which the scattered light detection unit is positioned on a plane that includes the reference line and makes an angle of 40 degrees or more and 50 degrees or less with the incident plane.

9. A method for detecting foreign matter on a light-transmitting film, A laser beam is irradiated onto one side of the aforementioned film in a linear scanning manner. The first scattered light intensity, which is the intensity of scattered light generated from foreign matter adhering to the film due to the P-polarization component of the laser light, and the second scattered light intensity, which is the intensity of scattered light generated from foreign matter adhering to the film due to the S-polarization component of the laser light, are detected. A method for inspecting foreign matter, which determines whether a foreign matter adhering to the film is adhering to one surface or the other surface, based on the detected first and second scattered light intensities, If the intersection of the scanning plane, which is the same plane as the region through which the scanned laser light passes, and the incident plane, which is the plane perpendicular to the scanning line of the laser light on the film, is taken as the reference line, A method for inspecting foreign objects, comprising detecting the scattered light on a plane that intersects the incident plane with the reference line at an angle of 40 degrees or more and 50 degrees or less.

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