JP2007255949A - Flaw inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flaw inspection device capable of detecting the flaw on a measuring surface with high accuracy at a high speed, while having a simple and inexpensive constitution. <P>SOLUTION: The flaw inspection device is equipped with a light source 21 for irradiating a measuring target S, which has a pattern surface Sc parallel to measuring surfaces Sa and Sb, with a measuring light L1, an optical scanning part 23 for scanning the measuring light L1 with respect to the measuring target S, a photodetector 32, arranged at a position that avoids the detection lights L2 reflected from the measuring surfaces Sa and Sb and the diffracted light M1 and/or the scattered light M2 from the pattern surface Sc, when the measuring target S is irradiated with the measuring light L1 and a shading cylinder 4 for at least preventing the stray light M that has been diffracted and/or scattered by the pattern surface Sc and arrives at the photodetector 32 to be detected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defect inspection apparatus such as a reticle / mask using light scattering.

  2. Description of the Related Art Conventionally, there is known a foreign substance inspection apparatus that can perform a foreign substance inspection with a simple structure and without increasing the size of a light receiving optical system.

  Specifically, this kind of foreign matter inspection apparatus includes, for example, a laser light source that emits a light beam, a galvano scanner mirror that scans and polarizes the light beam, a scanning lens, and a stage on which a measurement target (for example, a reticle) is placed. And a driving device for moving the stage in the X and Y directions. The light beam emitted from the laser light source is scanned and deflected by the galvano scanner mirror and then directed to the scanning lens. The light beam emitted from the scanning lens scans the surface of the reticle to be measured in the X direction on the scanning line. On the other hand, by moving the stage in the Y direction at a certain speed in synchronization with the scanning of the light beam in the X direction on the scanning line by the galvano scanner mirror, it is possible to inspect the entire surface of the measurement target surface. (For example, refer to Patent Document 1).

In addition, in order to prevent the influence of stray light and accurately inspect foreign matter, at least one slit is provided between the light receiving lens and the inspection surface or between the light receiving lens and the light detector and the optical axis of the light receiving lens. There is known a foreign substance inspection apparatus arranged in a plane perpendicular to the plane (for example, see Patent Document 2).
JP-A-7-229844 JP-A-8-15168

  However, in the conventional configuration, particularly in the configuration of Patent Document 1, the intensity of diffracted light from the pattern is very strong. For example, if the light reflected or scattered in the light receiving optical system enters the photodetector, it is erroneously detected. This causes a problem that foreign matter on the measurement surface cannot be detected (discriminated) with high accuracy by the photodetector.

  On the other hand, in the configuration of Patent Document 2, there is a problem in the arrangement of the slits such as how to fix the slits between the light receiving lens and the inspection surface or between the light receiving lens and the photodetector. If it cannot be arranged, the effect of stray light remains. Even if the slit can be arranged at an appropriate position, no countermeasure is taken against the light entering from the outside, and the foreign matter cannot be detected with high accuracy due to the influence of the external entering light.

  The present invention has been made paying attention to such problems, and its main purpose is to provide an excellent defect capable of detecting a defect on a measurement surface with high accuracy and high speed while having a simple and inexpensive configuration. It is to provide an inspection device.

  That is, the defect inspection apparatus according to the present invention includes a light source for irradiating a measurement surface having a measurement surface and a pattern surface parallel to the measurement surface, and a light scanning for scanning the measurement light with respect to the measurement target. And light that is diffracted and / or scattered from the measurement surface is detected as detection light when the measurement light scanned by the optical scanning unit is irradiated onto the measurement object, and diffracted light from the pattern surface and / or Alternatively, a photodetector formed by dispersing the scattered light at a position where it is not in focus, and a stray light diffracted and / or scattered on the pattern surface, which is disposed between the measurement object and the photodetector. It is characterized by comprising a light-shielding cylinder that at least prevents the light from reaching the photodetector.

  Here, the “detection light” is a concept including light reflected, diffracted, or scattered by a defect when the measurement surface has a defect when the measurement object is irradiated with the measurement light. In addition, “defect” means, for example, “separate object from the measurement object” such as dust attached to the measurement object, and “defect” is in the measurement object itself such as a scratch on the surface of the measurement object. It is a concept that includes “things”.

  Further, “disposing the photodetector at a position where the diffracted light and / or scattered light from the pattern surface does not focus” includes disposing the photodetector so as to weaken the amount of incident light.

  “Stray light” is not only light that is diffracted on the pattern surface and emitted directly to the photodetector, but also generated by diffraction on the pattern surface, and multiple diffraction between the pattern surface and the surface to be measured. And the like and the like emitted toward the photodetector.

  In such a case, since the photodetector is arranged at a position where the diffracted light and / or scattered light from the pattern surface does not focus, the influence of the diffracted light and / or scattered light from the pattern is reduced. By avoiding this, it becomes possible to detect defects on the measurement surface with high accuracy by the photodetector. In addition, a light-shielding tube disposed between the measurement object and the light detector suitably eliminates the influence of stray light diffracted and / or scattered on the pattern surface and light entering from the outside, thereby improving accuracy. Defects can be detected well.

  As described above, the light detector is arranged at a position where the diffracted light and / or scattered light from the pattern surface is not focused, and a light shielding cylinder is disposed between the measurement target and the light detector. Although it is configured, it is preferable to prevent stray light and external incoming light from reaching the photodetector, including those due to multiple diffraction / scattering that are difficult to predict where they will come from. Can be suitably detected. Therefore, erroneous detection due to diffracted light and / or scattered light from the pattern surface, stray light, or external incident light is prevented as much as possible, and defects on the measurement surface can be detected with high accuracy and at high speed.

  That is, it is possible to provide an excellent defect inspection apparatus capable of detecting defects on the measurement surface with high accuracy and high speed while having a simple and inexpensive configuration.

  In order to effectively prevent stray light from reaching the photodetector while having a simple configuration, it is preferable that at least a part of the light shielding tube is positioned in the vicinity of the measurement target.

  In order to effectively shield light entering between the measurement object and the photodetector, it is desirable that the light shielding cylinder extends continuously from the vicinity of the measurement object to the photodetector. .

  If the light shielding cylinder has a tapered shape on the measurement object side, the light shielding cylinder can be easily disposed close to the measurement object, and enters from between the measurement object and the light shielding cylinder. Unnecessary light can be suitably shielded.

  As a desirable mode of the light shielding cylinder of the present invention, the light shielding cylinder includes a hollow light shielding cylinder body having an internal space surrounded by a light shielding side wall, and the detection light from the light shielding side wall toward the center of the light shielding cylinder body. One having a light shielding plate or a plurality of light shielding plates protruding to a position where the progress is not blocked is mentioned.

  As described above, according to the defect inspection apparatus of the present invention, the photodetector is arranged at a position where the diffracted light and / or scattered light from the pattern surface does not focus, so that the diffracted light from the pattern and It is possible to avoid the influence of scattered light and detect defects on the measurement surface with high accuracy by the photodetector. In addition, a light-shielding tube disposed between the measurement object and the light detector suitably eliminates the influence of stray light diffracted and / or scattered on the pattern surface and light entering from the outside, thereby improving accuracy. Defects can be detected well.

  As described above, the light detector is arranged at a position where the diffracted light and / or scattered light from the pattern surface is not focused, and a light shielding cylinder is disposed between the measurement target and the light detector. Although it is configured, it is preferable to prevent stray light and external incoming light from reaching the photodetector, including those due to multiple diffraction / scattering that are difficult to predict where they will come from. Can be suitably detected. Therefore, erroneous detection due to diffracted light and / or scattered light from the pattern surface, stray light, or external incident light is prevented as much as possible, and defects on the measurement surface can be detected with high accuracy and at high speed.

  That is, it is possible to provide an excellent defect inspection apparatus capable of detecting defects on the measurement surface with high accuracy and high speed while having a simple and inexpensive configuration.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1, 2, and 3, the defect inspection apparatus A according to the present embodiment has a glass surface Sa and a pellicle surface Sb (the glass surface Sa and / or the pellicle surface Sb are the “measurement surface” of the present invention. And a stage 1 on which a sample S (corresponding to “measuring object” of the present invention) having a parallel pattern surface Sc sandwiched between the surfaces Sa and Sb is placed. The light irradiation system 2 that irradiates the sample S while scanning the measurement light L1, and when the measurement light L1 scanned by the light irradiation system 2 is irradiated to the sample S, diffraction and / or Alternatively, a light detection system 3 configured to detect scattered light as detection light L2 and to be disposed at a position (a position where the focal point is not focused) that avoids diffracted light M1 and / or scattered light M2 from the pattern surface Sc, and light irradiation System 2 and At least preventing stray light M, which is provided between the detection system 3 and diffracted and / or scattered on the pattern surface Sc, and external approach light N entering from the outside, from reaching the light detection system 3 and being detected. And a light-shielding cylinder 4. Hereinafter, although each part is demonstrated concretely, in this embodiment, description is advanced by making glass surface Sa into a test surface among glass surface Sa and pellicle surface Sb.

  The stage 1 is movable in the X axis, the Y axis, and the Z axis, and moves at a constant speed in a direction perpendicular to the scanning direction of the measurement light L1, so that it is combined with the laser beam scanning described later, The entire test surface Sa of the sample S placed on the stage 1 can be measured.

  As shown in FIG. 1, the light irradiation system 2 appropriately expands a laser light source 21 (for example, a HeNe laser light source) that emits a laser beam that is the measurement light L1 and the measurement light L1 emitted from the laser light source 21. A beam expander 22, a scanning mirror 23a (for example, a galvano mirror) that scans the measurement light L1 magnified by the beam expander 22 and focuses it on the surface Sa, and a scanning lens 23b (for example, an fθ lens) And an optical scanning unit 23 composed of

  In this embodiment, the measurement light L1 is incident on the surface Sa to be measured at an angle of 10 to 40 degrees (incidence angle is 50 to 80 degrees), and the entire surface of the surface Sa to be measured using the optical scanning unit 23. Are configured to scan.

  Here, the measurement light L1 is incident at an angle of 10 to 40 degrees from the test surface Sa for the following reason.

  The measurement light L1 enters the test surface Sa as incident light, passes through the test surface Sa, and then reaches the pattern surface Sc (since glass is transparent, the pellicle is also transparent). Therefore, in order to avoid erroneous detection of the diffracted light M1 / scattered light M2 from the pattern surface Sc, the distance between the position where the measurement light L1 reaches the test surface Sa and the position where the measurement light L1 reaches the pattern surface Sc is made as long as possible. There is a need to. For this reason, it is desirable that the measurement light L1 is incident at a low angle with respect to the test surface Sa. However, if it is too low, the position of the test surface Sa (Z-direction position) changes, so that the focus position of the measurement light L1 / photodetection system 3 may deviate, and the actual measurement position is also shifted. Therefore, it is desirable that the measurement light L1 is incident at an angle of 10 to 40 degrees with respect to the test surface Sa.

  The light detection system 3 has an optical axis in the YZ plane of FIG. 3 and is located at a position that is less than the angle of reflection equal to the incident angle from a position that is substantially perpendicular to the surface Sa to be measured, preferably the measurement light L1. On the other hand, it is arranged up to a position where the scattering angle is 90 degrees, and is between the condensing lens system 31, the photodetector 32, and the condensing lens system 31 and the photodetector 32. The slit 33 is provided. Here, the “scattering angle” refers to an angle from the traveling direction of the probe light (measurement light L1) to the optical axis of the photodetector 32 with the scatterer as the center. “˜90 degrees” in FIG. 3 is the complementary angle.

  The condensing lens system 31 is configured by combining one or a plurality of lenses, and is configured such that the detection light is focused on the photodetector 32. The type and combination of lenses may be appropriate depending on the embodiment.

  As the photodetector 32, a PMT (Photo Multiplier Tube) or a line sensor can be used. When the photodetector 32 is a PMT, as shown in FIG. 3, the slit 33 and the scanning line on the test surface Sa are arranged so as to be optically conjugate to form a line sensor. Are arranged so that the line sensor and the scanning line on the surface Sa to be tested are in an optically conjugate position.

  In the present embodiment, the photodetector 32 is arranged in the direction perpendicular to the scanning line of the measuring light L1 and in the vicinity of the center of the scanning line (near the center of the surface Sa), and the photodetector 32. Are arranged between a position where the optical axis is substantially in the direction of the scattering angle of 90 degrees and a position perpendicular to the test surface Sa, and an optical arrangement in which the entire scanning line is viewed by one photodetector 32 is employed.

  The slit 33 has a horizontally long substantially rectangular shape penetrating in the thickness direction of the plate-like member. In the present embodiment, the condenser lens is provided immediately before the light incident side of the light detector 32 so that the longitudinal direction thereof substantially coincides with the longitudinal direction of the distal end opening 411 of the light shielding cylinder 4 described later. A part of the light collected by the system 31 is guided to the photodetector 32.

  The light shielding cylinder 4 has a role of shielding the diffracted light M1 from the pattern surface Sc as shown by a broken line in FIG. 5 so as not to enter the condenser lens of the light detection system 3. A hollow light shielding cylinder body 41 having an enclosed internal space with a substantially rectangular cross-section and a position where the detection light L2 is not obstructed from the inner wall surface of the light shielding side wall 410 toward the center of the light shielding cylinder body 41. One or a plurality of light-shielding plates 42 are provided.

  In this embodiment, the light-shielding cylinder 4 has a tapered shape on the sample S side and has a tip opening 411 that faces the vicinity of the sample S, and is continuous from the vicinity of the sample S to the light detection system 3. It has a shape that stretches. The light shielding cylinder 4 is integrally supported on the light incident side of the photodetector system 3.

  The location of the light shielding plate 42 will be specifically described.

  First, since the pattern surface Sc of the sample S is not in a conjugate position with the slit 33 or the like, these lights do not directly pass through the slit 33 and enter the photodetector 32. However, the diffracted light M1 is much stronger than the scattered light M2 of the defect to be detected, and the light reflected and scattered in the condensing lens system 31 only passes through the slit 33, and is erroneously detected. Cause.

  In order to prevent this, on the light shielding side wall 410 of the light shielding cylinder 4, as shown in FIGS. 3, 4, and 5, a light shielding plate 42a is disposed at the tip portion avoiding the region expected by the light detection system 3. It has become. In the present embodiment, a plurality of light shielding plates 42 are arranged inside the light shielding cylinder 4 in order to further increase the effectiveness. Specifically, as shown in FIG. 5, the light shielding plate 42a that shields the stray light M from the pattern surface Sc and provides a gap through which the detection light L2 passes, and the stray light that passes through the gap above the light shielding plate 42a. In addition to arranging the light shielding plate 42b that shields M, the light shielding plates 42c to 42e are arranged at appropriate intervals.

  Among these, the light shielding plate 42a is configured so that, when the stray light M from the pattern surface Sc is further reflected / scattered by the light shielding plate 42a, it is reflected from the surface Sa to be examined and does not enter the photodetector 32. It has a certain inclination. This inclination α is set to be smaller than the angle at which the diffracted light M1 from the pattern surface Sc just hits the end of the light shielding plate 42a on the sample S side (for example, the light is shielded at an angle of 60 degrees from the test surface Sa). When the light can pass through the gap between the plates 42a, the light shielding plate 42a is set to 55 degrees from the test surface Sa). This is because when light passing through the light shielding plate 42a reaches the inner side (upper side in the drawing) of the light shielding plate 42a, scattering occurs near the range expected by the light detection system 3, which may cause erroneous detection. is there.

  Next, the operation of the defect inspection apparatus A configured as described above will be described with reference to the drawings.

  First, the laser beam emitted from the laser light source 21 is appropriately expanded by the beam expander 22 and focused on the surface Sa to be measured via the scanning mirror 23a and the scanning lens 23b of the optical scanning unit 23 (FIG. 4).

  The measurement light L1 is not detected as the detection light L2 by the photodetector 32 in a place where there is no defect on the test surface Sa.

  On the other hand, in the place where the defect of the test surface Sa exists, the measurement light L1 is reflected, diffracted or scattered by the defect, and is detected as the detection light L2 by the photodetector 32 through the condenser lens system 31 and the slit 33. Detected. However, depending on the degree of reflection / diffraction / scattering, etc., there are some which are blocked by the light blocking plate 42 of the light blocking cylinder 4 and are not detected by the light detector 32 (L3 in FIG. 4).

  Of the measurement light L1, light that has passed through the test surface Sa and reached the pattern surface Sc is diffracted or scattered by the pattern surface Sc, and multiple diffraction is performed between the pattern surface Sc and the glass surface Sa. Or it is multiply scattered and becomes stray light M (see FIG. 5).

  Even if the stray light M generated in this way (stray light Mb due to multiple diffraction or the like) is going to travel toward the light detection system 3, the light-shielding tube 4 has a tapered shape on the sample S side as shown in FIG. In addition, since the tip opening 411 facing the vicinity of the sample S is provided, it is possible to prevent the progress of this portion first. Further, even if there is stray light M (direct stray light Ma) that can enter from the front end opening 411, the light shielding plate 42 disposed inside the light shielding cylinder main body 41 can prevent the progression thereof. In this way, the stray light M can be prevented from progressing to the light detection system 3 in a plurality of stages.

  Furthermore, since it has a shape that continuously extends from the vicinity of the sample S to the light detection system 3, unnecessary light (external incoming light N) does not enter from the outside.

  Therefore, according to the defect inspection apparatus A according to the present embodiment configured as described above, the photodetector 32 is arranged at a position where the diffracted light M1 and / or scattered light M2 from the pattern surface Sc does not focus. Therefore, the amount of incident light of these lights M1 and M2 is reduced, the influence of the diffracted light M1 and / or scattered light M2 from the pattern surface Sc is avoided, and the light detector 32 is a measurement surface with high accuracy. It becomes possible to detect a defect on the test surface Sa. In addition, the light shielding cylinder 4 disposed between the sample S and the photodetector 32 preferably eliminates the influence of stray light M and external incident light N diffracted and / or scattered on the pattern surface Sc. , Defects can be detected with high accuracy.

  In this way, the photodetector 32 is arranged at a position where the diffracted light M1 and / or scattered light M2 from the pattern surface Sc is not focused, and the light shielding cylinder 4 is arranged between the sample S and the light detection system 3. The stray light M and the external incoming light N reach the light detector 32 of the light detection system 3, including those caused by multiple diffraction / scattering, which are difficult to predict where they come from, especially with a simple and inexpensive configuration. The light detector 32 can preferably detect only the detection light L2. Therefore, erroneous detection by the diffracted light M1 and / or scattered light M2, stray light M, and external approach light N from the pattern surface Sc is prevented as much as possible, and foreign matter on the surface Sa to be detected is detected with high accuracy and high speed. It becomes possible to do.

  Further, since the entire scanning line from the optical scanning system can be covered by one detection optical system, the distance from the optical detector at the both ends of the scanning line is greatly different from that when two or more optical detectors are used. Solves problems such as large differences in sensitivity and other effects of stray light due to differences in magnification and solid angle to be expected, and it takes time to adjust the photodetector and requires many parts. Cost problems such as these can be effectively resolved.

  That is, it is possible to provide an excellent defect inspection apparatus A that can detect a defect on the surface Sa to be detected with high accuracy and high speed while having a simple and inexpensive configuration.

  Since the tip opening 411 of the light shielding tube 4 is positioned in the vicinity of the sample S, it is possible to effectively prevent the stray light M from reaching the photodetector 32 with a simple configuration.

  Since the light-shielding cylinder 4 is configured to continuously extend from the vicinity of the sample S to the light detection system 3, the external approach light N entering between the sample S and the light detection system 3 is effectively prevented. Can be shielded from light.

  Since the light-shielding cylinder 4 has a tapered shape on the sample S side, the light-shielding cylinder 4 can be easily placed close to the sample S, and the light entering from between the sample S and the light-shielding cylinder 4 is unnecessary. Light can be suitably shielded.

  In addition, since the plurality of light shielding plates 42 are respectively provided inside the light shielding cylinder main body 41, it is possible to prevent a problem that the mounting position of the light shielding plate 42 is unintentionally shifted due to, for example, an external force. Contributes to exhibiting stable defect detection performance.

  The present invention is not limited to the above embodiment.

  For example, the stage 1 may be an X and Y stage, and the light detection system 3 and the like may be mounted on the Z stage.

  Alternatively, the stage 1 may be fixed and the light detection system 3 and the like may be mounted on the X, Y, and Z stages.

  In the above-described embodiment, the glass surface Sa is the test surface. However, as shown in FIG. 6, the pellicle surface Sb can be the test surface. In this case, the position reaching the pattern surface Sc is farther from the position expected by the light detection system 3, and the arrival point of each light has the relationship shown in FIG.

  Further, the shape and configuration of the light shielding cylinder 4 are not limited to those of the present embodiment, and can be appropriately changed according to the embodiment.

  Further, it does not prevent the defect inspection apparatus from being configured using two or more photodetectors.

  For example, as shown in FIG. 7, the photodetectors K1 and K2 (hereinafter collectively referred to as “photodetector K”) are positioned to avoid the diffracted light M1 and / or scattered light M2 from the pattern surface Sc (for example, The following specific positions can be arranged at the above-mentioned positions where the focal point is not formed, for example, 0, 45, when the direction parallel to the X axis is 0 degree in the XY plane of FIG. Diffracted light / scattered light from the respective patterns having directions of 90 and 135 degrees generally appears in the diffracted light / scattered light region Rx other than the hatched portion shown in FIG.

  In addition, such patterns of 0, 45, 90, and 135 degrees exist on the measurement target S ′.

  Therefore, for example, as in the light detection system shown in FIG. 7, the scanning lines JJ and the optical axis of the light detection system are not orthogonal to the hatched areas Ra, Rb, Rc avoiding the diffracted light / scattered light area Rx. Further, by arranging the photodetector K, it is possible to avoid the influence of diffracted light from the pattern and to detect defects on the measurement surface with high accuracy by the photodetector K.

  In addition, when there is an exceptional pattern other than 0, 45, 90, and 135 degrees (for example, 30 degrees), or for stray light due to multiple diffraction and / or multiple scattering that cannot be predicted, the light shielding cylinder 4 is exceptional. Since diffracted light or the like from the pattern or stray light is prevented from reaching the photodetector K, erroneous detection due to diffracted light or the like from the exceptional pattern or stray light can be suitably prevented.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 is an overall schematic view schematically showing a configuration of a defect inspection apparatus according to an embodiment of the present invention. The side view of the sample which concerns on the same embodiment (when a glass surface is turned up). The figure which shows the arrangement | positioning relationship of the sample which concerns on the same embodiment, a light shielding cylinder, and a photon detection system. The figure which shows an example of the measurement light based on the embodiment, detection light, and stray light. The figure for demonstrating the effect | action of the light shielding cylinder which concerns on the same embodiment. The side view of a sample in another embodiment of the present invention (when the pellicle surface is up). The whole schematic diagram which shows schematically the structure of the foreign material inspection apparatus in other embodiment of this invention. The figure for demonstrating the area | region which can arrange | position a photodetector.

Explanation of symbols

A ... Defect inspection device L1 ... Measurement light L2 ... Detection light M ... Stray light M1 ... Diffracted light M2 ... Scattered light S ... Measurement target (sample)
Sa ... Measurement surface (glass surface)
Sb ... Measurement surface (pellicle surface)
Sc ··· Pattern surface 4 ··· Shading cylinder 21 ··· Light source (laser light source)
23... Optical scanning section 32... Photodetector 41...

Claims (5)

A light source for irradiating measurement light to a measurement surface and a measurement object having a pattern surface parallel to the measurement surface;
An optical scanning unit that scans the measurement light with respect to the measurement object;
When the measurement light scanned by the light scanning unit is irradiated onto the measurement object, light diffracted and / or scattered from the measurement surface is detected as detection light, and diffracted light and / or scattered light from the pattern surface A photodetector that is placed at a position where is not in focus,
A light shielding tube that is arranged between the measurement object and the photodetector and at least prevents stray light diffracted and / or scattered on the pattern surface from reaching the photodetector and being detected. A defect inspection apparatus comprising the defect inspection apparatus.   The defect inspection apparatus according to claim 1, wherein at least a part of the light shielding cylinder is positioned in the vicinity of the measurement target.   The defect inspection apparatus according to claim 2, wherein the light shielding cylinder extends continuously from the vicinity of the measurement object to the photodetector.   The defect inspection apparatus according to claim 1, wherein the light shielding cylinder has a tapered shape on the measurement target side. The light shielding tube has a hollow light shielding tube main body having an internal space surrounded by a light shielding side wall, and is protruded from the light shielding side wall toward the center of the light shielding tube main body to a position where the progress of the detection light is not blocked. The defect inspection apparatus according to claim 1, further comprising a plurality of light shielding plates.