JP2017096912A - Flaw detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable detection of deep flaws, in other words, flaws of a thick checkup object in its surface, interior and rear face, to be accomplished simultaneously in one round of two-dimensional scanning.SOLUTION: A flaw detecting device comprises: a detecting beam optical system 11 that irradiates a checkup object with a detecting beam; a reflected scattering light detecting head 12 that is arranged on the same side as the detecting beam optical system 11 relative to the checkup object and detects reflected scattering light of the detecting beam reflected by the checkup object; and a transmitted scattering light detecting head 13 that is arranged opposing the reflected scattering light detecting head 12 with the checkup object in-between, and detects transmitted scattering light of the detecting beam transmitted through the checkup object, in which the focal depth of the detecting beam is so adjusted as to contain the thickness of the checkup object within the range of the focal depth.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a defect inspection apparatus suitable for inspecting defects in a glass substrate used for manufacturing a photomask or a liquid crystal display device, particularly for defect inspection such as scratches and adhesion of foreign matter on a plain light-transmitting material. . More specifically, the present invention relates to a defect inspection apparatus suitable for simultaneous inspection of the front surface, the inside and the back surface of an inspection object.

  As an inspection apparatus for detecting a defect in a glass substrate, a laser scattering inspection apparatus is known (for example, see Patent Document 1). In this known inspection apparatus, a laser beam is projected obliquely with respect to a glass substrate to be inspected, scattered light from the glass substrate is received using two photodetectors, and from the two photodetectors. In accordance with the form of the output signal, foreign matter existing on the front side of the glass substrate and foreign matter existing on the back side are discriminated.

  The above-described laser scattering type inspection apparatus is an inspection apparatus effective for detecting foreign matter existing on the surface of a glass substrate. However, if the beam is projected obliquely, a deep inspection cannot be performed. In addition, defects in photomasks and glass substrates need to detect not only foreign matter on the front and back surfaces, but also fine scratches (sleeks) and minute irregularities (pits) formed on the surface of the glass substrate. . Furthermore, if there are bubbles or a local refractive index distribution inside the glass substrate, the exposure light is scattered, which causes a decrease in device manufacturing yield. Therefore, there is a strong demand for the development of an inspection apparatus that can detect voids, which are internal defects of a glass substrate, with high sensitivity.

  Therefore, the differential interference optical system is used to detect defects on the surface of the inspection object based on the phase difference generated in the reflected light from the surface of the inspection object, and at the same time, scattered light on the front surface side and the back surface side of the inspection object. A defect inspection apparatus that can simultaneously detect not only foreign substances existing on the surface of the substrate but also pits and leaks on the surface of the substrate and voids existing inside the substrate in one inspection process has been proposed (for example, patents). Reference 2).

  This defect inspection apparatus generates a scanning beam having a substantially elliptical cross section, and focuses the scanning beam on the surface of the object to be inspected as a scanning beam that is strongly focused and focused on an extremely small area. Two-dimensional scanning is performed, and a defect on the surface of the inspection object is detected by differential interference in a differential interference optical system disposed in the optical path. At the same time, the scattered light is condensed by the scattered light condensing elements arranged on the front surface side and the back surface side of the inspection object. The scattered light condensing element on the surface side of the object to be inspected uses a hemispherical mirror having an elliptical paraboloidal mirror surface on the inner surface. Captures scattered light. Then, the scattered light is reflected by the ring-shaped reflecting mirror that passes through the objective lens at the center toward the other reflecting mirror that forms a pair, and is taken into the first photomultiplier (PMT: photomultiplier tube). The presence or absence of scattered light is detected. On the other hand, the scattered light condensing element on the back side of the object to be inspected is composed of a condensing lens with a glass thickness correction mechanism, a mirror with a hole, and a second photomultiplier that receives reflected light from the mirror. The scattered light caused by the internal defect is detected by receiving the scattered light collected by the condenser lens and reflected by the perforated mirror by the second photomultiplier. By the way, this defect inspection device is intended for inspection of large quartz glass with a width and height exceeding 1 m. The inspection object is placed in the middle of the inspection device and the inspection head is slid sideways. While inspecting from top to bottom.

JP 2003-294653 A JP 2010-112803 A

  However, since the defect inspection apparatus of Patent Document 2 detects a surface defect by capturing an interference phenomenon generated by focusing on the surface of the inspection object, the depth existing on the surface of the inspection object. Although it is possible to detect fine defects of about several nanometers clearly, it is not possible to detect defects inside a thick inspection object. That is, in order to increase the inspection sensitivity, the laser beam is focused on a very small area on the surface of the inspection object, so that a very large energy density is generated at the focal point. The narrowed inspection beam spreads rapidly inside the object to be inspected (diffusibility) and loses light energy, so that the inspection ability is lost. That is, a sufficiently narrowed inspection beam has a detection capability only on the surface of the inspection object, and can maintain detection sensitivity only in the range of several tens of microns to 100 μm from the surface of the inspection object. . For this reason, it is difficult to detect defects inside the inspection object having a thickness on the order of mm without unevenness in inspection sensitivity. Therefore, the defect inspection apparatus of Patent Document 2 cannot detect both flaws at the same time unless two sets of inspection head sets for detecting flaws on the front surface and inspection heads for detecting flaws on the back surface are used at the same time. Can not. Even in that case, it is difficult to simultaneously detect scratches inside the inspection object. That is, it is difficult to inspect deeply, in other words, to inspect defects on the surface, inside, and back surface of a thick inspection object simultaneously by one two-dimensional scanning.

  Further, in order to increase the inspection sensitivity by differential interference, the laser beam is focused on an extremely small area on the surface of the inspection object, thereby generating a very large energy density at the focal point. According to the method, the NA (numerical aperture) is increased to narrow the beam waist so that an elliptical inspection beam is imaged on the surface of the inspection object with a reduced depth of focus. It takes a lot of steps to find the best position, and even if sensitivity is finally reached, the beam expands abruptly when it is slightly out of focus. Becomes worse. That is, it is difficult to make adjustments and it is difficult to find the optimum adjustment point. For this reason, there exists a problem that adjustment of an optical system requires a lot of man-hours and time.

  In addition, defect detection using differential interference is highly sensitive, but on the other hand, it is easily affected by noise, and the minute vibration during feeding of the inspection head causes noise to become sensitive to differential interference. Have. Detection of scratches on the surface of the object to be inspected using differential interference is possible because the phase shift (phase difference) of the light wavelength is affected even by a phase difference of several μm. It is affected by machine vibration. For this reason, the result of adjustment may change immediately. In other words, even if it is slightly deviated, the sensitivity / reproducibility of the device / structure cannot be reproduced. For this reason, high-speed inspection cannot be performed.

  In addition, the condensing element that collects the scattered light scattered on the surface side of the object to be inspected tries to make the scattered light incident from a narrow opening that penetrates a part of the elliptic paraboloid, so only a part of the scattered light is incident. There is a problem that cannot be captured. In other words, scattered light with a shallow incident angle (scattered light scattered along the surface of the object to be inspected) and scattered light with an extremely deep incident angle (scattered light that scatters outside the rotating parabolic mirror even when entering from the opening) ) Cannot be captured, and there is only a small range that can be effectively used as a surface for reflecting scattered light. In addition, the ring-shaped reflecting mirror that receives the scattered light from the hemispherical mirror also penetrates the objective lens at the center, so the body of the objective lens serves as a shield to effectively use part of the collected scattered light. There is a problem that cannot be done. For this reason, there exists a problem that the condensing efficiency of the scattered light reflected on the surface side of a to-be-inspected object is low, and detection sensitivity is bad.

  In addition, the rotating paraboloid mirror is difficult to adjust because the depth of focus of the inspection beam is short. Even a slight shift will desensitize the sensitivity. Since it takes time to find the best position, it is difficult to adjust.

  In addition, the inspection beam, which is focused on a very small area on the surface of the inspection object for defect detection using differential interference, spreads abruptly inside the inspection object. In the case of an object, the light energy of the scattered light itself generated due to internal voids or defects on the back surface becomes extremely small and cannot be detected, or even if it can be detected, the sensitivity is very poor. Therefore, in the case of an inspected object having a thickness, there is a problem that extreme variations in detection sensitivity occur between the front surface and the back surface of the inspected object. In addition, the condensing element that collects scattered light also has a problem that sensitivity varies due to the influence of spherical aberration or the like derived from a condensing lens with a glass thickness correction mechanism, or the sensitivity itself deteriorates. For this reason, it becomes difficult to ensure the detection sensitivity on the back side of the inspection object.

  An object of the present invention is to provide a defect inspection apparatus that enables a deep inspection. In other words, an object of the present invention is to provide a defect inspection apparatus capable of simultaneously inspecting defects on the front surface, inside, and back surface of a thick inspection object by one two-dimensional scanning.

  To achieve this object, the defect inspection apparatus according to claim 1 is arranged on the same side as the inspection beam optical system with respect to the inspection object, and an inspection beam optical system that irradiates the inspection beam toward the inspection object. A reflected scattered light detection head for detecting the reflected scattered light of the inspection beam reflected by the inspection object, and transmission of the inspection beam transmitted through the inspection object disposed opposite to the reflected scattered light detection head and the inspection object And a transmitted scattered light detection head for detecting scattered light, and the depth of focus of the inspection beam is adjusted so that the thickness of the inspection object is within the range of the depth of focus.

  According to a second aspect of the present invention, in the defect inspection apparatus according to the first aspect, the beam waist of the inspection beam is adjusted so as to be formed in the thickness of the inspection object. According to a third aspect of the present invention, in the defect inspection apparatus according to the second aspect, the beam waist of the inspection beam is formed at the center of the thickness of the inspection object.

  According to a fourth aspect of the present invention, in the defect inspection apparatus according to any one of the first to third aspects, the reflected / scattered light detection head includes a reflected / scattered light collector, a first reflected / condensing mirror, The reflection / scattering light collector has a second reflection light mirror and a reflection / scattering light detection sensor, and the reflection / scattering light concentrator has an outer peripheral surface configured as a mirror surface and is capable of irradiating an inspection beam on an inspection object. As a double structure of a reverse truncated conical cylinder that houses the objective lens and a cylinder that is disposed so as to surround the outer side of the reverse truncated cone part and whose inner peripheral surface is a mirror surface, A space for guiding the reflected and scattered light from the inspection object is formed in a space between the conical cylinder and the outer cylinder, and the first reflected light mirror is provided with a slit for passing the inspection beam, and the reflected and scattered light. The imaging lens between the reflected and scattered light collector and the imaging lens on the exit of the collector Characterized in that it is installed in a position that does not intersect.

  According to a fifth aspect of the present invention, in the defect inspection apparatus according to any one of the first to fourth aspects, the transmitted scattered light detection head includes a transmitted scattered light collector and a transmitted scattered light detection sensor. In addition, the transmitted and scattered light concentrator captures and separates the scattered light by capturing a funnel-shaped condensing tube whose inner peripheral surface is a mirror surface and an inspection beam that is disposed at the entrance of the condensing tube and passes straight through the object to be inspected. And an inspection beam capturing element that is configured to allow only scattered light to enter a transmitted scattered light detection sensor connected to the lower end of the light collecting cylinder.

  According to a sixth aspect of the present invention, in the defect inspection apparatus according to any one of the first to fifth aspects, the inspection beam optical system, the reflected scattered light detection head, and the transmitted scattered light detection head are separately provided on the surface plate and the A holder for holding an inspection object is cantilevered by an XY stage provided on the surface plate, and is opposed to one of the columns standing on the surface plate. The inspection beam is scanned while the inspection object moves in two directions orthogonal to each other between the light detection head and the transmitted scattered light detection head.

  Furthermore, in the defect inspection method according to the present invention, an inspection beam whose depth of focus is adjusted so that the thickness of the inspection object is within the depth of focus is irradiated to the inspection object, and the inspection beam is applied to the inspection object. The reflected and scattered light of the inspection beam reflected by the inspection object is detected on the same side as the irradiation side, and transmitted through the inspection object at a position opposite to the inspection beam between the detection position of the reflected and scattered light of the inspection beam. The transmitted scattered light of the inspection beam is detected.

  8. The defect inspection apparatus and method according to claim 1, wherein the inspection beam having a focal depth equal to or greater than the thickness of the inspection object is scanned so that the thickness of the inspection object is within the range of the focal depth of the inspection beam. Therefore, the diameter of the beam spot does not change greatly from the front surface to the back surface of the object to be inspected, and is kept almost constant, so that the inspection sensitivity does not vary greatly. For this reason, if there is foreign object adhesion or scratches on the surface of the object to be inspected, internal voids, or foreign object adhesion or scratches on the back surface, scattered light is generated and scattering is arranged on the front side and back side of the object to be inspected. The light is collected by a light collector and detected by a photomultiplier. Therefore, it is possible to simultaneously inspect defects on the front surface, the inside, and the back surface of the inspection object by one two-dimensional scanning. Moreover, the diameter of the beam spot does not change significantly from the front surface to the back surface of the object to be inspected, and the inspection sensitivity is not greatly varied. , Enabling simultaneous inspection of the inside and back side.

  Further, since the defect inspection is based on the detection of scattered light, unlike the inspection using the differential interference optical system, accuracy is not required for the adjustment for focusing, so that the adjustment of the optical system does not require much man-hours and time. In addition, the structure / device is less susceptible to noise such as minute vibrations during feeding of the inspection head and has good reproducibility of adjustment, so that high-speed inspection is possible.

  According to the invention described in claim 2, if the position of the beam waist is in the inspection object W (in the thickness t direction), it is shifted to some extent from the center and close to the front surface side or back surface side of the inspection object. Even when set to, the detection sensitivity does not vary greatly between the front side and the back side of the inspection object. According to the invention of claim 3, since the beam waist is formed at the center of the thickness of the inspection object, the depth of focus is symmetric with respect to the inspection object, and the inspection object is evenly within the range of the depth of focus. Therefore, the inspection sensitivity is substantially equal between the front surface side and the back surface side of the object to be inspected, and no variation occurs.

  In addition, according to the inventions of claims 4 and 5, since scattered light scattered along the object to be inspected can be taken at 360 ° around the scattered light generation location, scattered light scattered in various directions can be captured. Light can be collected efficiently and detection sensitivity can be increased. Moreover, the light can be collected efficiently without being affected by the depth of focus.

  In addition, according to the invention described in claim 6, it is possible to realize a desktop type defect inspection apparatus for a small inspected object.

It is a perspective view which shows one Embodiment of the desktop defect inspection apparatus to which the defect inspection apparatus by this invention is applied. It is a right view of the same desktop defect inspection apparatus. It is a left view of the desktop defect inspection apparatus. It is a front view of the desktop defect inspection apparatus. It is a perspective view showing one embodiment of an inspection optical system. It is a perspective view which shows the same inspection optical system from a different angle. It is a perspective view showing one embodiment of a reflected scattered light detection head and a transmitted scattered light detection head. It is the figure which looked at the reflected scattered light detection head and transmitted scattered light detection head from the left side view. It is the perspective view which showed one Embodiment of the reflected scattered light collector from the bottom face side. It is a perspective view which shows the center half cut longitudinal cross-section of the said reflective scattering light collector. It is explanatory drawing which shows an example of the relationship between an inspection beam and a to-be-inspected object.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  1 to 4 show an example of a desktop defect inspection apparatus as an embodiment of the defect inspection apparatus of the present invention. This desktop defect inspection apparatus is suitable as an apparatus for inspecting, for example, quartz glass for semiconductors, blanks, resists, and the like.

  This tabletop defect inspection apparatus is mounted on a surface plate 1, a column 2 that is erected vertically thereon, an optical base 3 that can be moved up and down on the column 2, and a surface plate 1. An XY stage that is slid by motor drive in two axial directions orthogonal to each other in the X direction and the Y direction, and a small inspection object, for example, an inspection object W for a photomask, which is mounted on the XY stage, is fixedly supported. The inspection beam optical system 11, the reflected scattered light detection head 12, and the surface plate 1, which are arranged so as to sandwich the inspection object holder 6 in the vertical direction and are mounted on the optical base 3 on the column 2. And a transmitted scattered light detection head 13 supported by the head. The desktop defect inspection apparatus according to the present embodiment moves the inspection object in two axial directions perpendicular to each other in a horizontal plane with respect to the substantially fixed inspection optical system except for the autofocus control in the Z-axis direction. However, relatively two-dimensional scanning is performed. In addition, as the surface plate 1 and the column 2, the stone surface plate and stone pillar with few influences of thermal expansion are generally used.

  In this embodiment, the XY stage is mounted on the surface plate 1 and moves in the left-right direction of the surface plate 1 (reciprocating motion in a plane parallel to the optical base 3). A Y-axis direction feed mechanism 5 mounted on the X-axis direction feed mechanism 4 and moving in the front-rear direction of the surface plate 1 (reciprocating motion in a plane orthogonal to the optical base 3); An inspection object holder 6 is placed on the mechanism 5 and places and holds the inspection object W. The X-axis direction feeding mechanism 4 and the Y-axis direction feeding mechanism 5 hold the inspection object W in the XY direction. It is provided to be movable in the direction. The X-axis direction feed mechanism 4 and the Y-axis direction feed mechanism 5 are driven by, for example, a linear motor or an AC servomotor, although not shown.

  Further, as shown in FIG. 2, the inspection object holder 6 mounted on the Y-axis direction feeding mechanism 5 protrudes toward the column 2 side from the end of the Y-axis direction feeding mechanism 5. The cantilever is supported by a mover (a member fed by a screw) 5a. A space set between the transmitted scattered light detection head 13 supported by the surface plate 1 and the inspection beam optical system 11 and the reflected scattered light detection head 12 mounted on the optical base 3 on the column 2. It arrange | positions so that the to-be-inspected object holder 6 may be moved to XY direction. As shown in FIG. 7, the inspection object holder 6 suppresses the receiving seat 6 a formed of a recess that supports the edge of the inspection object W by dropping and the edge of the inspection object W fitted in the receiving seat 6 a. Locking means 60 is provided around it. Although it is not particularly necessary to fix the inspection object W during the low-speed inspection, it is desirable that the inspection object W is pressed and fixed by the locking means 60 during the high-speed inspection. The locking means 60 may be, for example, a pressing plate spring, but in this embodiment, a locking claw that is slidable forward and backward (in the depth direction) of the surface plate 1 is employed, and is not shown. It is provided so as to be always energized with the force of. Accordingly, after the locking claw 60 is pulled down, the inspection object W is set, and then the inspection claw W is automatically fixed by releasing the locking claw 60.

  As shown in FIG. 2, the optical base 3 includes a lower base 8 fixed to the column 2, an upper base 9 slidably connected to the lower base 8, and the upper base 9 as Z It is attached to the column 2 so as to be able to move up and down via a lifting mechanism 7 composed of a feed mechanism (not shown) for feeding in the axial direction (vertical direction) and a DC motor 10 with an encoder. The DC motor 10 is driven by a control signal from the autofocus mechanism and includes an inspection optical system (inspection beam optical system 11, reflected scattered light detection head 12, and auto force optical system 45 mounted on the optical base 3. The focus position (waist beam position) is preferably roughly determined at the center position of the thickness t of the inspection object W so that the inspection object W always falls within the range of the focal depth of the inspection beam. So that autofocus is controlled. A limit switch 7a is disposed between the lower base 8 and the upper base 9, and stroke ends at both upper and lower ends are determined.

  On the optical base 3, an inspection beam optical system 11 that irradiates an inspection beam 61 toward the inspection object W, a reflected scattered light detection system 12 that receives reflected and scattered light from the inspection object W, and an inspection An autofocus mechanism 45 for keeping the beam at the target focal position is mounted. In the defect detection apparatus of the present embodiment, the optical system is fixed, and scanning is performed by moving the inspection object W. Therefore, the transmission scattered light detection system 13 that receives the transmission scattered light that has passed through the inspection object W is fixed. It is mounted on the board 1. The transmitted scattered light detection head 13 is disposed on the opposite side of the reflected scattered light detection head 12 with the inspection object W interposed therebetween, and is fixed to the stone surface plate 1. In the inspection beam optical system 11 of the present embodiment, since the inspection beam 61 is perpendicularly incident on the inspection object W, the optical base 3 is driven by the autofocus mechanism 45, and the autofocus mechanism 45 is moved. The positional relationship between the included inspection beam optical system 11 and the reflected / scattered light detection system 12 is fixed and movable in the Z-axis direction.

  Therefore, the entire surface of the inspection object W is scanned two-dimensionally by the relative movement of the inspection beam optical system 11, the reflected scattered light detection head 12 and the transmitted scattered light detection head 13. Note that the XY stage in this embodiment is continuously fed in the X direction during scanning, and sent in the Y direction during switching between forward movement and backward movement in the X direction.

  Next, FIG. 5 and FIG. 6 show an example of the inspection optical system. The inspection optical system includes an inspection beam optical system 11 that scans the inspection beam 61 on the inspection object W, and a first scattered light detection optical system (reflection scattering) that detects the reflected and scattered light of the inspection beam 61 from the inspection object W. (Referred to as a light detection head) 12 and a second scattered light detection optical system (referred to as a transmitted scattered light detection head) 13 for detecting scattered light that has passed through the inspection object W. It arrange | positions so that it may oppose. In the case of the present embodiment, the inspection object optical system 11 and the reflected scattered light detection head 12 are provided in front of the column 2 because the inspection object W is horizontally arranged by the inspection object holder 6 and moves in the XY direction on the horizontal plane. The transmission scattered light detection head 13 mounted on the optical base 3 is provided on the surface plate 1.

  The inspection beam optical system 11 that irradiates the inspection object 61 with the inspection beam 61 includes, for example, a semiconductor laser 14 serving as a light source, a collimator lens 15, an expander plano-concave lens 16, an expander plano-convex lens 17, a relay lens 18, and a first lens. A mirror (total reflection mirror) 19, a second mirror 20, an fθ lens 21, a polygon mirror 22, an imaging lens 23, and an objective lens 24 are included. The spot shape (cross-sectional shape) of the inspection beam 61 may be any beam width that is necessary and sufficient to cover the size of a foreign object, scratch, or defect to be detected, and may be a perfect circle, an ellipse, or a non-circular (polygon). Or an irregular contour shape with a jagged contour shape).

  The polygon mirror 22 has an arbitrary number of reflecting surfaces, for example, 14 reflecting surfaces, and its rotation axis is set to scan the incident scanning beam in the Y-axis direction. A driving circuit (not shown) is connected to the polygon mirror, and rotates at a predetermined rotational speed by a driving signal from the driving circuit. Accordingly, the scanning beam is periodically emitted from the polygon mirror 22 while being periodically deflected. An optical sensor 63 for detecting the start of scanning is disposed in front of the polygon mirror 22, and a signal output from the optical sensor 63 is used as a scan timing information signal for the polygon mirror 22. Therefore, the beam can be counted. The number of spots constituting the scan line is determined in advance, and the order of the spots represents the position itself, so that it is possible to grasp where the spot is. Note that the stage position (which is known from the encoder signal output) is also input to the signal processing circuit, so that all synchronization can be achieved.

  The laser beam / inspection beam 61 generated by the semiconductor laser 14 is converted into an expanded parallel light beam through the collimator lens 15, the expander composed of the expander plano-concave lens 16 and the expander plano-convex lens 17, and the relay lens 18. Then, the direction is changed by the first mirror 19 and the second mirror 20 and is incident on the fθ lens 21. The inspection beam 61 is incident on the polygon mirror 22. The inspection beam 61 scanned by the polygon mirror 22 is incident on the f-θ lens 21, the imaging lens 23 and the objective lens 24.

  Here, the inspection beam 61 irradiated onto the inspection object W through the objective lens 24 preferably has a thickness t of the inspection object W so that the inspection object W is within the range of the focal depth b of the inspection beam 61. It is adjusted to focus at the approximate center position. For example, as shown in FIG. 11, a beam waist 61w is formed at the approximate center position of the thickness t of the inspection object W by adjusting the optical system, and the depth of focus when passing through the back surface of the inspection object W ( The range of Rayleigh length b) is set. Here, if the beam waist 61w is not set in the inspection object W and approximately in the center in the thickness t direction, sensitivity variation occurs between the front surface side and the back surface side of the inspection object. In an inspection that does not pose a problem even if an imbalance in detection sensitivity occurs between the back surface and the back surface side, there is no problem even if it is off to some extent from the center position. That is, if the position of the beam waist 61w is in the inspection object W (in the thickness t direction), the inspection object is inspected even if the position is set to be close to the front surface side or the back surface side of the inspection object to some extent from the center. There is no great variation in detection sensitivity between the front side and the back side of the object. In some cases, the thickness t of the object to be inspected may be merely within the range of the focal depth, and the beam waist 61w does not necessarily exist in the object W to be inspected. Even if the beam waist 61w is set outside the inspection object W, if the inspection object W is within the focal depth range, the detection sensitivity is reduced to some extent. It can be implemented sufficiently.

  Increasing the depth of focus b means that the NA (numerical aperture) is reduced so that the beam waist 61w is not restricted to a very small area, that is, the density of light energy is lowered and the inspection sensitivity is lowered. Therefore, it is naturally not selected that the depth of focus b is set deeper than necessary (the Rayleigh length is increased). Therefore, setting the focal depth b of the inspection beam 61 to be equal to or greater than the thickness t of the inspection object W means that the focal depth b is not infinitely deeper than the thickness of the inspection object W. It is obvious to those skilled in the art that even if the depth of focus b is made deeper than the thickness, it should not be made deeper than necessary. For example, in the case of defect inspection of quartz glass having a thickness of 17 mm, it is necessary and sufficient to set the focal depth to at least 17 mm, preferably about 18 to 22 mm, more preferably about 20 mm. Incidentally, the diameter of the beam waist in the inspection beam 61 having a focal depth of 20 mm is, for example, about 30 μm. Here, the adjustment of the optical system for setting the beam waist 61w at the center of the thickness t of the inspection object W is not limited to a specific method. For example, a simple method such as preparing a sample having a defect in the center and adjusting the optical system using the sample can be performed. Further, the beam waist diameter can be adjusted, for example, by adjusting a relay lens.

  According to the inspection beam optical system 11, the inspection beam 61 scanned by the polygon mirror 22 moves the inspection object W two-dimensionally in the X direction (width direction) and the Y direction (depth direction) perpendicular thereto. Therefore, the entire surface of the inspection object W is scanned. However, the reflected beam that is reflected straight from the front surface, inside, and back surface of the inspection object W and returns to the incident direction is not used for detection of defects, but only scattered light is used for detection of defects and the like. The optical system is adjusted so that the reflected beam does not return to the semiconductor laser 14 side.

  Therefore, a reflected / scattered light detection head 12 is mounted on the optical base 3. The reflected / scattered light detection head 12 converts the scattered light into an electrical signal, the reflected / scattered light collector 25, the first reflection / condensing mirror 26, the condenser lens 27, the second reflected light mirror 28, and the like. It is composed of a reflected scattered light PMT (photomultiplier: photomultiplier tube) 29 as a reflected scattered light detection sensor.

  For example, as shown in FIGS. 9 and 10, the reflected scattered light collector 25 has a double structure of an outer cylinder 30 and an inner inverted truncated cone 31, and an inner inverted truncated cone 31. The objective lens 24 is housed in a compact structure. Here, the outer cylinder 30 and the inner inverted truncated cone 31 are connected and integrated at equal intervals by, for example, a plurality of thin stays 34 that do not become shields against scattered light at both ends. The inner inverted truncated cone 31 is arranged so that the diameter decreases downward (inverse cone), and a circular space 32 in which the objective lens 24 is accommodated is formed on the upper side having a large diameter. . An elliptical slit 33 communicating with the space 32 in which the objective lens 24 is accommodated is formed in the lower part of the inverted truncated cone 31, and the inspection beam 61 emitted from the objective lens 24 passes through the slit 33 and is inspected. It is provided to go to the object W. The outer peripheral surface 36 of the inverted truncated cone 31 constitutes a mirror surface, and the inner peripheral surface 35 of the outer cylinder 30 also constitutes a mirror surface. Moreover, at the entrance 37 facing the object to be inspected W, the diameter of the inverted truncated cone 31 constituting the inner mirror surface can be set to a necessary and sufficient minimum diameter or close to it, so that the opening area can be widened. Therefore, the reflected scattered light entering between the opposed outer cylinder 30 and inner cylinder 31 is taken into the inverted mortar-shaped mirror surface including the scattered light reflected substantially in the horizontal direction, and the incident scattered light is always emitted. The light is collected at the mouth 38 and collected at the first reflecting / condensing mirror 26 disposed on the exit port 38. For this reason, there is no blind spot in the collection of the reflected scattered light, it is possible to collect 360 °, and it is easy to manufacture with a large aperture. The condensing lens 27 is sandwiched between the two reflecting mirrors of the first reflecting / condensing mirror 26 and the second reflecting / lighting mirror 28, and the light is condensed on the reflected scattered light PMT 29. Since there is no blind spot, the light collection efficiency is good.

  As shown in FIG. 8, the first reflecting / condensing mirror 26 and the second reflecting / lighting mirror 28 are connected to the reflecting / scattering light collector 25 on the exit port 38 of the reflected / scattering light collector 25. It is installed at a position that does not intersect the objective lens 24 between the image lens 23. The first reflecting / condensing mirror 26 and the second reflecting / lighting mirror 28 are arranged in parallel with an inclination of 45 ° with the condensing lens 27 interposed therebetween. In addition, since the first reflecting / condensing mirror 26 intersects the optical axis of the inspection beam 61, an elongated slit 39 through which the inspection beam 61 passes is provided in the center portion. The slit 39 is a long hole corresponding to the width of the spot trajectory of the inspection beam 61 to be scanned, that is, the scanning width (a long hole slightly longer than the scanning width), and irradiates the inspection object W. Only the inspection beam 61 and the reflected light of the inspection beam 61 that is regularly reflected from the surface of the inspection object W are allowed to pass, and the width and length are not allowed to pass the scattered light that is reflected from the surface of the inspection object W. . The first reflecting / condensing mirror 26 has a size necessary to reflect the reflected / scattered light emitted from the exit port 38 of the reflected / scattered light collector 25 without omission, and collects the reflected / scattered light. The total reflection mirror has a width and length that covers the exit port 38 of the vessel 25. The second reflection / condensing mirror 28 is also a total reflection mirror having the same size as that of the first reflection / condensing mirror 26, but the slit 39 is not provided at the center. Therefore, all of the reflected scattered light from the object W captured by the reflected scattered light collector 25 is not leaked, and the first reflected condenser mirror 26, the condenser lens 27, and the second reflective condenser mirror 28 are not leaked. Is incident on the PMT 29 for reflected and scattered light. Then, it is converted into an electrical signal by the PMT 29 for reflected / scattered light, amplified by an amplifier as necessary, and supplied to the signal processing circuit. For this reason, there is no obstruction in the optical path, and there is no blind spot, so 360 ° light can be collected and the light collection efficiency is good. That is, the detection sensitivity is improved.

  On the other hand, the transmitted turbulent light detection head 13 provided on the surface plate 1 includes a transmitted scattered light collector 40 and a transmitted scattered light PMT 41 as a reflected scattered light detection sensor that converts the scattered light into an electric signal. Has been. Here, the transmitted scattered light concentrator 40 is, for example, a hollow funnel-shaped collecting tube 42 made of aluminum that has a mirror-finished inner peripheral surface, and has an opening at the upper end where the transmitted scattered light is incident. The center of the unit is provided with an inspection beam capturing element 43 that captures an inspection beam 61 that passes straight through the inspection object W and separates it from the scattered light, and transmits the scattered light only connected to the lower end of the light collecting tube 42. It is set as the structure which injects into PMT41 for use. Although not shown, the funnel-shaped condensing tube 42 and the inspection beam capturing element 43 inside the funnel are connected at equal intervals by, for example, a plurality of thin stays that are not shielded against scattered light. It has become.

  In the case of this embodiment, the inspection beam capturing element 43 is formed, for example, in the center of a cylindrical block having an elliptical concave portion (having a bottom and not penetrating) having a length corresponding to the scan width. It is like a so-called black hole in which at least the recess is partitioned with a material having a low reflectance, or the inner surface of the recess is covered with a material with a low reflectance to confine the inspection beam incident on the recess. The outer surface of the block constituting the inspection beam capturing element 43 is preferably a mirror surface. The transmitted scattered light is guided to the exit side while passing or reflecting around the inspection beam capturing element 43 and detected by the transmitted scattered light PMT disposed at the exit. In place of the black hole element, a bundle of optical fibers may be arranged in the center, and the inspection beam that is transmitted straight may be led out of the transmission condensing mirror so that it cannot be detected by the transmission PMT. Scattered light incident on the PMTs 29 and 41 of the reflected scattered light detection head 12 and the transmitted scattered light detection head 13 is photoelectrically converted and supplied as a detection signal to the signal processing device. The signal processing circuit is mounted on the optical base 3 although not shown.

  In addition, the desktop defect inspection apparatus according to the present embodiment performs autofocus control to eliminate the influence of stage vibration caused by cantilever support of the inspection object W, and the focal position of the objective lens 24 is constant. Thus, the inspection optical system is moved in the Z-axis direction together with the optical base 3.

  Here, the autofocus (AF) control mechanism according to the present embodiment generates a focus error signal by, for example, an optical lever method. Specifically, for example, by using the imaging lens 23 and the objective lens 24 of the inspection beam optical system 11, an AF laser diode 46, an AFLD collimator 47, a first AF mirror (total reflection mirror) 48, and an AF relay lens 49 are used. The AF control mechanism is configured by the second AF mirror 50 and the AF control sensor 51, and is mounted on the optical base 3. In the present embodiment, for example, an AF control sensor 51 that constitutes a bridge circuit with elements divided into four is adopted, but the present invention is not limited to this, and a general two-divided sensor may be used. The focus detection beam 62 emitted from the AF laser diode 46 is incident on the optical path of the inspection beam 61 through the AFLD collimator 47, the first AF mirror 48, the AF relay lens 49, and the second AF mirror 50 in this order. Then, the light enters the polygon mirror 22 through the fθ lens 21. The focus detection beam 62 reflected by the polygon mirror 22 passes through the fθ lens 21 again, passes through the imaging lens 23 and the objective lens 24, and is focused on the surface of the inspection object W. Unlike the inspection beam 61 passing through the optical axis, the focus detection beam 62 emitted from the objective lens is incident on the surface of the inspection object W at an oblique angle. Since the AF beam uses the trigonometric principle, it is better to make the incident angle as large as possible. The focus detection beam 62 reflected from the surface of the inspection object W passes through the objective lens 24 again, and proceeds as a return light while shifting the position of the reverse optical path. Then, the light enters the polygon mirror 22 through the imaging lens 23 and the fθ lens 21 and is descanned. Further, the light is reflected by the polygon mirror 22, passes through the fθ lens 21, the second AF mirror 50, and the AF relay lens 49, and is reflected by the first AF mirror 48. Then, the light enters the AF control sensor (beam displacement element) 51.

  When the focus detection beam 62 is focused on the surface of the inspection object W at the set focus position, the focus detection spots formed on the AF substrate 51 are evenly positioned on the dividing line, and two sets of light receiving regions The same amount of light is incident on. When the inspection object W is displaced in the optical axis direction (Z-axis direction) of the objective lens, the amount of light incident on the four light receiving areas of the AF substrate 51 changes, and therefore, based on output signals from the four light receiving areas. Thus, a focus control signal for driving the inspection head in the optical axis direction can be formed.

  Output signals from the four light receiving regions are supplied to a driving device that displaces the optical base 3 in the optical axis direction. In the present embodiment, the optical base 3 is driven in the optical axis direction according to the detected focus error, and is controlled so that the object W is always within the range of the focal depth of the inspection beam. In the case of the present embodiment, the position of the beam waist 61w is controlled so as to fall within the approximate center of the thickness t of the inspection object W.

  In the above-described autofocus control mechanism, the beam waist 61w is approximately the center of the thickness t of the inspection object W using, for example, a sample having a defect in the center while displacing the inspection head in the optical axis direction prior to the inspection. The optical system is adjusted so that it is formed at the position. The diameter of the beam waist 61w is adjusted by adjusting an optical system such as a relay lens or an expander. Then, the outputs of the AF substrate 51 of the autofocus mechanism are adjusted so that the focal position or the distance between the surface of the object to be inspected at that time and the objective lens 24 is kept constant. Are set so that the output intensities of the bridge circuits in the light receiving area are equal to each other. In the state set in this way, the autofocus mechanism is operated to output a focus control signal. Then, a drive signal is supplied to the motor, and autofocus control is performed so that the thickness of the inspection object W is within the depth of focus of the inspection beam during inspection.

  The optical system base 3 is equipped with a review optical system 52. The review optical system 52 includes, for example, a microscope 53, a microscope CCD camera 54, and a microscope objective lens 55, and is arranged in parallel with the inspection beam optical system 11. Further, an LED spot illumination 56 for illumination and a reflection mirror 57 for guiding illumination light from the illumination light source 56 to the observation position are mounted around the microscope objective lens 55. Since the offset value between the optical axis position of the review camera 54 and the optical axis position of the inspection beam 61 is known and stored in a memory or software, the surface of the actually inspected position is a microscope CCD camera. When switching to observation by 54, the surface is moved in the X-axis direction based on the offset value, and the surface of the actually inspected part (position where a defect such as a foreign object or a flaw is considered to be present) is actually observed.

  The detection principle of a foreign object or a flaw by detecting scattered light by the desktop defect inspection apparatus configured as described above will be described below.

  First, origin search is performed, and coordinate system information is acquired. Next, various conditions according to the type of the inspection object W, the inspection type, and the inspection level are read. Thereafter, the polygon mirror 22 and the laser 14 are driven. Then, the autofocus mechanism 45 is activated, and the optical base 3 is lowered in the Z-axis direction toward the inspection object W to a predetermined position. After the inspection is started, the stage / inspection object holder 6 is continuously fed at a predetermined speed in the X-axis direction while scanning to a predetermined width, for example, 5 mm width (depth direction / Y direction), and after crossing the inspection object W. The feed is given in the depth direction / Y direction by a predetermined pitch. The inspection beam is moved (X-axis direction) so that the spot is not removed while being repeated with a constant scan width (Y-axis direction). Return while scanning again. The scans are set so that they overlap partially on the way back and forth. By repeating this, the entire surface of the inspection object W is scanned.

  When the inspection beam 61 of the inspection beam optical system 11 is irradiated perpendicularly to the surface of the inspection object W, if there is a foreign object on the surface of the inspection object W, scattered light is generated by the foreign object. This scattered light mainly travels in the direction opposite to the traveling direction of the inspection beam 61 (referred to as reflected scattered light), but part of the scattered light also travels in the traveling direction of the inspection beam 61 and passes through the inspection object W. Transmitted light (transmitted scattered light). Further, when bubbles (voids) or local refractive index distributions exist inside the inspection object W, scattered light is also generated from these voids. In the case of the scattered light generated inside the inspection object W, the scattered light is mainly transmitted, but a part of the scattered light travels toward the surface side of the inspection object W as reflected scattering light. Further, the scattered light generated when foreign matter or scratches are present on the back surface of the inspection object W is mainly transmitted scattered light, similar to the scattered light generated inside the inspection object W, but partly Becomes reflected and scattered light and travels to the surface side of the inspection object W.

  Therefore, the reflected scattered light collector 25 is collected on the reflected scattered light collector 25 arranged on the surface side of the inspection object W, and the transmitted scattered light collector 40 arranged on the back surface side of the inspection object W is collected. Transmitted scattered light is collected. Therefore, when the reflected / scattered light is detected by the reflected / scattered light detection head 12, foreign matter or a defect mainly present on the surface of the inspection object W is detected, and the transmitted / scattered light is detected by the transmitted / scattered light detection head 13. If detected, it may be mainly detected internal defects such as voids inside the inspected object W, foreign matter or scratches attached to the back surface, but these are specified in a strict sense. It is not possible.

  That is, the detection signal from the reflected / scattered light detection head 12 is merely a detection of the reflected / scattered light, and the detection signal from the transmitted / scattered light detection head 13 is only detected from the transmitted / scattered light. Therefore, it can be detected that there is a defect such as adhesion of a foreign substance or a flaw on the front surface, back surface, or inside of the inspection object W at a certain position. In addition, whether the object is detected by the reflected / scattered light detection head 12 or the transmitted / scattered light detection head 13 and the foreign matter or defect exists mainly on the surface of the inspection object W, or It can be roughly judged whether it exists outside (inside or back side).

  However, it cannot be strictly specified whether the foreign matter or defect exists on the surface of the inspection object W or on the other side (inside or on the back surface). When it is necessary to discriminate this more strictly, it is possible to further specify the position of a foreign substance or a flaw by using the review optical system 52 in combination. That is, since the offset value between the optical axis position of the review optical system 52 and the optical axis position of the inspection beam optical system 11 is known and stored in a memory or software, the review optical system is based on the offset value. The surface of the position actually inspected can be actually observed by moving 52 to a place where the inspection is actually performed (a position where a defect such as a foreign object or a flaw is considered to be present). If no defect such as a foreign matter or a flaw on the surface of the inspection object W can be confirmed by the review based on the actual observation, the flaw or the like is a part other than the surface of the inspection object W, that is, a flaw on the inside or the back surface of the inspection object W It can be judged.

  Incidentally, according to the desktop defect inspection apparatus according to the present embodiment, the review by the inspection beam optical system 11 returns to a position (coordinates) that is considered to have a defect such as a foreign object or a flaw after performing the defect inspection once. , By scanning back and forth around the coordinates. Then, the result of the review by the inspection beam optical system 11 is displayed on the display device as a scanned image. And the bright spot of scattered light can be confirmed. Thereafter, when a defect such as a foreign substance or a flaw on the surface cannot be confirmed by a review based on the actual observation at the predetermined position, it can be determined that a defect inside the inspection object W, for example, a void, a flaw on the back surface, or a foreign substance is attached. Incidentally, since the position information / coordinate information of the stage and the defect signal are input to and associated with the signal processing circuit, a map indicating the position of the defect can be formed. Thus, for example, the inspection of quartz glass for semiconductor 6025 was completed in about several minutes / sheet. At present, the inspection of quartz glass for semiconductor 6025 takes about 1 hour / sheet, so that it is not possible to inspect the entire quantity, and the sampling inspection for each lot is currently performed. However, according to the inspection apparatus according to the present embodiment, it is possible to inspect the entire quantity (all goods inspection).

  As described above, since the detection of the scattered light is grasped as a simple luminescent spot, whether it is a foreign matter adhering to the surface of the inspection object W or a defect such as a scratch, or a void generated inside the inspection object W. It cannot be distinguished whether it is caused by a defect such as a foreign matter attached to the back surface or a defect such as a scratch. However, it is possible to distinguish between a review by an inspection laser and a review by a CCD microscope camera.

  In addition, in the above inspection, the scattered light generated in the range of the depth of focus does not cause a difference in the density of large light energy, so that the sensitivity hardly varies between the front surface side and the back surface side of the inspection object W. It can be detected as almost the same luminance. Here, even if the beam waist is not squeezed strongly, even if light energy is dispersed, the thickness direction of the inspection object W is within the focal depth b, and the beam waist 61w is in the region passing through the inspection object W. If the spot diameter does not change greatly, there is a method to compensate for the lack of sensitivity as a whole. For example, this can be achieved by increasing the power of the semiconductor laser or increasing the light collection efficiency. In particular, as the scattered light collector, a reflected scattered light collector 25 and / or a transmitted scattered light collector 40 composed of a double cylindrical mirror having an opening of 360 ° as shown in FIG. 8 is used. In this case, scattered light generated from any part of the inspection beam 61 can be efficiently collected. Accordingly, the combined use of the reflected / scattered light inspection head 11 using the reflected / scattered light collector 25 of the embodiment and the transmitted / scattered light detection head 13 using the transmitted / scattered light collector 40 together makes it possible to collect scattered light. As a result, the sufficient detection sensitivity can be secured without increasing the power of the semiconductor laser.

  When detecting the scattered light and determining the defect, the amplitude of the detection signal from each of the PMTs 29 and 41 of the reflected scattered light detection head 12 and the transmitted scattered light detection head 13 is compared with a predetermined threshold value, and the threshold value is exceeded. It can also be determined that a defect exists.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made. For example, in the above-described embodiment, the defect inspection of the inspection object W has been described. However, in addition to the inspection object W, it can be applied to defect inspection of a pellicle used for protecting a photomask. Since the pellicle is a thin transparent film and not a rigid body, it has a characteristic of being easily deformed during inspection. On the other hand, the inspection optical system of the present invention can perform an accurate defect inspection because the reflected light from the pellicle is incident on the light detection means even if the pellicle surface is displaced or deformed during the inspection.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, an example in which the present invention is applied to a desktop type defect inspection apparatus that mainly targets a small inspection object W has been described. However, the present invention is not particularly limited to this, and a large size is necessary as necessary. It is good also as a structure applied to this to-be-inspected object. Although not shown, it is possible to apply to a relatively large inspection object by fixing the inspection object and driving the inspection head side. In this case, for example, the object to be inspected is fixedly arranged on the base. A first optical base on which the inspection beam optical system 11, the reflected scattered light detection head 12, the autofocus optical system 45, and the review optical system 52 are mounted, and a second optical on which the transmitted scattered light detection head 13 is mounted. The base is disposed horizontally opposite to the inspection object W, and is moved in two axial directions perpendicular to the inspection object W in the vertical plane so that relatively two-dimensional scanning is performed. May be. In this case, since the first optical base and the second optical base are driven in the same direction and moved two-dimensionally in synchronization, the entire surface of the inspection object W can be scanned with the inspection beam.

  The transmitted scattered light collector 40 for detecting transmitted scattered light can also be constituted by a bundle of a number of optical fibers arranged along the periphery of the inspection beam capturing element (black hole) 43, for example. In this case, the transmitted scattered light can be detected by arranging the transmitted scattered light PMT 41 at the output end of the optical fiber. Further, a light receiving surface is constituted only by an optical fiber without using the inspection beam capturing element (black hole) 43, and an inspection beam that passes straight through a part of the optical fiber in the center of the optical fiber bundle, that is, the inspection object W. It is also possible to prevent the transmission scattered light PMT 41 from being detected as an open end without connecting the outgoing end of the optical fiber in the region receiving only the light to the transmitted scattered light PMT 41. Of course, in these cases as well, the depth of focus of the inspection beam on the inspection object W is increased so that the thickness of the inspection object W falls within the range of the focal depth, so that not only the surface of the inspection object W but also the inside and the back surface. It does not lose the peculiar effect of being able to detect the presence of defects and attached foreign matter in one inspection.

  It is also possible to detect by continuously irradiating a beam to the inspection object W (not scanning) and sending it to the stage side. Further, in the above-described embodiment, the case where the inspection beam is applied vertically is taken as an example as being applicable to a deep inspection of the inspection object W such as quartz glass having a thickness of 17 mm. However, the present invention is not limited to this, and an inspection beam may be applied obliquely if it is thin such as a silicon wafer. In this case, when there is a defect, it is easier to scatter, and since the scattering directivity becomes stronger, it becomes easier to detect.

  In the above-described embodiment, the example using the double-cylinder structure mirror as the reflected scattered light collector 25 has been mainly described, but the present invention is not particularly limited to this, An elliptic paraboloid mirror (a condensing element described in Japanese Patent Application Laid-Open No. 2010-112803) in which a part of a rotating paraboloid is cut out by two surfaces orthogonal to the optical axis (center axis) may be used. . Even in this case, the depth of focus of the inspection beam on the inspection object W is increased so that the thickness of the inspection object W falls within the range of the focal depth, so that not only the surface of the inspection object W but also the inside and back surfaces are defective. In addition, it does not lose the unique effect that the presence of adhering foreign matter can be detected by a single inspection.

DESCRIPTION OF SYMBOLS 1 Surface plate 2 Column 3 Optical base 4 X-axis direction feed mechanism 5 Y-axis direction feed mechanism 6 Inspection object holder (glass holder)
11 Inspection beam optical system 12 Reflected scattered light detection head 13 Transmitted scattered light detection head 25 Reflected scattered light collector
26 1st reflection condensing mirror
27 Condensing lens
28 Second reflection light mirror 29 PMT for reflected scattered light
30 Outer cylinder 31 Inner inverted truncated cone 32 Objective lens receiving space 33 Slit 34 Outer cylinder inner peripheral surface 35 Inner inverted truncated cone outer peripheral surface 37 Entrance port 38 Exit port 39 Slit 40 Transmitted scattered light Concentrator 41 PMT for transmitted scattered light
42 Condensing tube 43 Inspection beam capturing element 45 Autofocus optical system 52 Optical system for review 61 Inspection beam 61w Beam waist 62 Focus detection beam W Inspection object b Depth of focus (Rayleigh length)
t Thickness of inspection object

Claims (7)

  An inspection beam optical system that irradiates an inspection beam toward the inspection object, and a reflected scattered light of the inspection beam that is disposed on the same side as the inspection beam optical system with respect to the inspection object and is reflected by the inspection object A reflected scattered light detecting head for detecting the transmitted scattered light, and a transmitted scattered light detecting head for detecting the transmitted scattered light of the inspection beam transmitted through the object to be inspected with the reflected scattered light detecting head interposed therebetween. And the depth of focus of the inspection beam is adjusted so that the thickness of the inspection object is within the range of the depth of focus.   The defect inspection apparatus according to claim 1, wherein a beam waist of the inspection beam is adjusted so as to be formed in a thickness of the inspection object.   The defect inspection apparatus according to claim 2, wherein a beam waist of the inspection beam is formed at a center of a thickness of the inspection object. The reflection / scattering light detection head includes a reflection / scattering light collector, a first reflection / condensing mirror, a second reflection light mirror, and a reflection / scattering light detection sensor;
The reflected and scattered light collector has an outer peripheral surface configured as a mirror surface and a reverse truncated conical cylinder that houses the objective lens of the inspection beam optical system so that the inspection beam can be irradiated onto the inspection object; As a double structure with a cylinder which is arranged so as to surround the outer side of the inverted truncated cone part and whose inner peripheral surface is a mirror surface, between the inverted truncated cone cylinder and the outer cylinder Forming a space for guiding reflected and scattered light from the object under test in the space;
The first reflected light mirror is provided with a slit that allows the inspection beam to pass therethrough, and the connection between the reflected scattered light collector and the imaging lens on the exit of the reflected scattered light collector. The defect inspection apparatus according to claim 1, wherein the defect inspection apparatus is installed at a position not intersecting with the image lens.   The transmitted scattered light detection head includes a transmitted scattered light collector and a transmitted scattered light detection sensor, and the transmitted scattered light collector has a funnel-shaped condensing tube having an inner peripheral surface as a mirror surface, and the collector. An inspection beam capturing element that is disposed at the entrance of the light tube and that captures the inspection beam that passes straight through the object to be inspected and separates it from the scattered light; and only scattered light is connected to the lower end of the light collection tube. The defect inspection apparatus according to claim 1, wherein the defect inspection apparatus is configured to be incident on the transmitted scattered light detection sensor.   The inspection beam optical system, the reflected scattered light detection head, and the transmitted scattered light detection head are separately provided facing either a surface plate or a column standing on the surface plate, and the inspection target A holder for holding an object is cantilevered by an XY stage provided on the surface plate, and the inspection object is placed between the inspection beam optical system, the reflected scattered light detection head, and the transmitted scattered light detection head. 6. The defect inspection apparatus according to claim 1, wherein the inspection beam is scanned while moving in two directions orthogonal to each other.   The inspection beam whose depth of focus is adjusted so that the thickness of the inspection object is within the depth of focus is irradiated onto the inspection object, and the same side as the side on which the inspection beam is irradiated to the inspection object And the reflected and scattered light of the inspection beam reflected by the inspection object is detected and transmitted through the inspection object at a position facing the inspection object and the detection position of the reflected and scattered light of the inspection beam. A defect inspection method, wherein transmitted scattered light of the inspection beam is detected.