JP2016102776A - Inspection device and method for inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device with simple configuration that can detect defects of a sample and also can measure positional information of defects of the sample in a thickness direction thereof, and a method for the inspection.SOLUTION: The inspection device according to an embodiment of the present invention, includes: a lighting unit 10 for generating two light beams to light a sample 20 from two different directions; a first detector 16 for detecting scattered light from the sample 20; a second detector 17 for detecting scattered light from the sample 20; a first comparator 51 for detecting a defect by comparing a first detecting signal from the first detector 16 with a threshold level; a second comparator 52 for detecting a defect by comparing a second detecting signal from the second detector 17 with the threshold level; and a positional information acquisition unit 53 for acquiring positional information on a defect of the sample in a thickness direction according to a difference in timings of detecting a defect.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inspection apparatus and an inspection method.

  As an inspection apparatus for inspecting a defect of a sample, there are a bright field inspection apparatus using a bright field illumination optical system and a dark field inspection apparatus using a dark field illumination optical system. In these inspection apparatuses, the entire surface of the sample is scanned to detect the position of the defect. Furthermore, in order to classify the depth of the defect, it is necessary to change the focus position in the optical axis direction at each defect position. Therefore, in order to classify the depth of the defect, the inspection time becomes long.

  Patent Document 1 discloses an inspection apparatus that inspects a transparent body such as a glass substrate. In the inspection apparatus disclosed in Patent Document 1, inspection is performed using two reflective bright field optical systems. That is, the linear light source and the camera (line sensor) are respectively arranged on both surfaces of the glass substrate. Two cameras capture images on both sides of the glass substrate. When a defect candidate is found in both images, it is regarded as a defect, and when a defect candidate is found only in one image, it is regarded as a pseudo defect.

  Further, the distance between two images appearing in the same camera with respect to the same defect candidate is obtained, and whether the defect is on the main surface, the inside or the back surface of the substrate is specified based on this distance. For example, a case where there is a defect near the back surface of the glass substrate will be described. When illuminated from the back surface of the glass substrate, if there is a defect in the optical path of the light that has passed through the back surface of the glass substrate, the light is scattered by the defect and a dark signal is generated. That is, the defect is detected by light traveling from the back surface of the glass substrate toward the main surface.

  Furthermore, when there is no defect in the optical path of light from the back surface of the glass substrate toward the main surface, the light that has passed through the back surface of the glass substrate is reflected by the main surface of the glass substrate. If there is a defect in the optical path of the light reflected by the main surface of the glass substrate, the light is scattered by the defect and a dark signal is generated. That is, a defect is detected by light traveling from the main surface to the back surface of the glass substrate. Therefore, it is possible to distinguish whether the defect is inside or on the back surface of the glass substrate by the distance between the two images. Similarly, by illuminating from the main surface of the glass substrate, it is possible to distinguish whether the defect is inside or on the main surface of the glass substrate.

International Publication No. 2006/057125

  However, in the configuration of Patent Document 1, cameras (line sensors) and linear light sources are disposed on both sides of the substrate. Therefore, the light source and the camera are arranged on the back side. Therefore, in patent document 1, there exists a problem that the structure of an optical system will become complicated. Further, Patent Document 1 is a bright field inspection, and is not a means for obtaining information in the thickness direction at the same time as the inspection in the dark field inspection.

  The present invention has been made in the background of such circumstances, and an object thereof is to provide an inspection apparatus and an inspection method capable of measuring positional information of defects in the thickness direction of a sample with a simple configuration. It is what.

  The inspection apparatus according to the first aspect of the present embodiment generates two light beams as illumination light for illuminating the sample, and the illuminating device that illuminates the sample from different directions, and the scattered light from the sample. A first detector for detecting defects, a second detector for detecting scattered light from the sample, and a first detection signal from the first detector for comparing with a threshold value to detect a defect. A comparison unit, a second comparison unit that detects the defect by comparing a second detection signal from the second detector with a threshold value, a detection timing of the defect by the first comparison unit, A position information acquisition unit that acquires position information of the defect in the thickness direction of the sample in accordance with a time difference from the detection timing of the defect by the second comparison unit. According to this configuration, the position information of the defect in the thickness direction of the sample can be measured simultaneously with the defect detection with a simple configuration.

  In the inspection apparatus, the illumination device generates two light fluxes of a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength, and the first detection. The detector detects scattered light via a first filter that blocks light of the second wavelength, and the second detector detects scattered light via a second filter that blocks light of the first wavelength. You may make it do. Since scattered light having different wavelengths is detected by the first detector and the second detector, the position information of the defect in the thickness direction of the sample can be measured with higher accuracy even when the defect is close.

  The inspection apparatus may further include a lens on which the two light beams are incident, and the lens may illuminate the sample from different directions.

  The inspection apparatus may further include an objective lens that receives scattered light from the sample, and a light branching unit that branches the scattered light from the objective lens, and the one light branched by the light branching unit The second detector may detect the other light detected by the first detector and branched by the light branching unit.

  In the inspection apparatus, the illumination device generates two light beams of a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength, and the light branching unit However, the scattered light of the first wavelength and the scattered light of the second wavelength may be branched according to the wavelength.

  In the inspection apparatus, the sample is illuminated such that the illumination position by the two light beams shifts in accordance with the position of the sample in the thickness direction, and the illumination position by the two light beams is shifted in the direction shifted. A stage for moving the sample is provided. Thereby, the positional information on the defect in the thickness direction can be appropriately measured.

  In the inspection apparatus, a scanner that scans the illumination light may be provided in a direction orthogonal to a direction in which the illumination position of the two light beams is shifted. By doing so, a wide area can be illuminated, so that throughput can be improved.

  The inspection method according to the second aspect of the present embodiment includes a step of generating two light beams as illumination light for illuminating the sample, a step of illuminating the sample from different directions of the two light beams, a first detector, Detecting a scattered light from the sample by a second detector, detecting a defect by comparing a first detection signal from the first detector with a threshold value, and the second detection A step of detecting the defect by comparing a second detection signal from the detector with a threshold, a detection timing of the defect in the first detection signal, and a detection timing of the defect in the second detection signal And obtaining the position information of the defect in the thickness direction of the sample in accordance with the time difference between. According to this method, the position information of the defect in the thickness direction of the sample can be measured simultaneously with the defect detection with a simple configuration.

  In the inspection method, the two light beams include a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength, and the first detector Scattered light is detected via a first filter that blocks light of the second wavelength, and the second detector detects scattered light via a second filter that blocks light of the first wavelength. It may be. Since scattered light having different wavelengths is detected by the first detector and the second detector, the position information of the defect in the thickness direction of the sample can be measured with higher accuracy even when the defect is close.

  In the inspection method, the sample may be illuminated from different directions by the lens on which the two light beams are incident.

  In the inspection method, the objective lens receives scattered light from the sample, the scattered light from the objective lens is branched by a light branching unit, and one of the lights branched by the light branching unit is detected by the first detection unit. The second detector may detect the other light that is detected by the detector and branched by the light branching means.

  In the inspection method, the two light fluxes include a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength, and the light branching unit has a wavelength. In response to this, the scattered light of the first wavelength and the scattered light of the second wavelength may be branched.

  In the inspection method described above, the sample is illuminated such that the illumination position of the two light beams shifts in accordance with the position of the sample in the thickness direction, and the illumination sample is shifted in a direction in which the illumination position of the two light beams is shifted. The first detector and the second detector may detect the scattered light while moving. Thereby, the positional information on the defect in the thickness direction can be appropriately measured.

  In the inspection method described above, the first detector and the second detector may detect the scattered light while scanning the illumination light in a direction orthogonal to a direction in which the illumination position of the two light beams deviates. . By doing so, a wide area can be illuminated, so that throughput can be improved.

  According to the present invention, it is possible to provide an inspection apparatus and an inspection method capable of measuring position information of defects in the thickness direction of a sample with a simple configuration.

It is a figure which shows the structure of the test | inspection apparatus concerning this embodiment. In the inspection apparatus which concerns on Embodiment 1, it is a figure which shows the mode of the illumination light which injects into a defect. It is a figure which shows the 1st and 2nd detection signal in case the surface of a sample has a defect, It is a figure which shows the 1st and 2nd detection signal when there is a defect inside a sample. It is a figure which shows the 1st and 2nd detection signal when a back surface of a sample has a defect, It is a figure which shows typically the Z direction position and defect detection timing of a defect. It is a block diagram which shows the structure of a processing apparatus. In the inspection apparatus which concerns on Embodiment 2, it is a figure which shows the mode of the illumination light which injects into a defect. It is a figure which shows the structure of the inspection apparatus which concerns on Embodiment 3. FIG.

  Hereinafter, a specific configuration of the present embodiment will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same contents.

Embodiment 1 FIG.
The inspection apparatus according to the present embodiment is an inspection apparatus that detects a defect in a transparent sample. Specifically, the inspection apparatus detects a defect by illuminating a sample using a dark field illumination optical system and detecting light scattered by the defect. The transparent sample is, for example, a transparent substrate such as a glass wafer used for manufacturing a semiconductor or a display. For example, the material of the sample is sapphire glass or quartz glass. In the present embodiment, description will be made assuming that the sample is a glass wafer blank. Further, the inspection apparatus acquires the position information of the defect in the thickness direction of the sample using the two-beam illumination. That is, the inspection apparatus can specify the position of the defect in the thickness direction.

  The configuration of the inspection apparatus will be described with reference to FIG. FIG. 1 is a diagram schematically showing the configuration of the inspection apparatus 100. The inspection apparatus 100 includes an illumination device 10, a scanner 13, a lens 14, an XY stage 15, a first detector 16, a second detector 17, a first filter 18, and a second filter 19. The sample 20 to be inspected is placed on the XY stage 15. In the following description, description will be made using an XYZ orthogonal coordinate system in which the optical axis direction in the illumination optical system is the Z direction and the in-plane direction of the sample 20 is the X direction and the Y direction. The inspection apparatus 100 illuminates the sample 20 using the dark field illumination optical system 101.

  First, the configuration of the dark field illumination optical system 101 will be described. In the present embodiment, the illumination device 10 generates two light beams that illuminate the sample 20. Therefore, the lighting device 10 includes a first light source 11 and a second light source 12. The first light source 11 emits the first illumination light L1. The second light source 12 emits the second illumination light L2. The first illumination light L1 and the second illumination light L2 illuminate the sample 20 as different light beams.

  The first light source 11 and the second light source 12 are laser light sources, and generate laser beams having different wavelengths. The wavelength of the first illumination light L1 is the wavelength λ1, and the wavelength of the second illumination light L2 is the wavelength λ2. The wavelengths λ1 and λ2 are different wavelengths. It is preferable that the wavelength λ1 and the wavelength λ2 are as close as possible. That is, it is preferable to use two wavelengths λ1 and λ2 that are close to the extent that they can be separated by the first and second filters described later. By doing in this way, the difference in the detection sensitivity of the defect in the 1st detector 16 and the 2nd detector 17 can be reduced.

  In addition, the light source used for the illuminating device 10 is not limited to the laser light source, but may be a lamp light source or an LED light source. In the present embodiment, two light sources are used as the illumination device 10 that generates two light beams. However, a configuration in which one light source is branched may be used. That is, one of the two branched by a beam splitter or a dichroic mirror may be the first illumination light L1, and the other may be the second illumination light L2. When only one light source is used, a non-monochromatic light source such as a lamp light source is used.

  The 1st illumination light L1 and the 2nd illumination light L2 each propagate as a parallel light beam. The first illumination light L1 and the second illumination light L2 become separate parallel light fluxes and enter the scanner 13. That is, the first illumination light L1 and the second illumination light L2 are incident on different positions of the scanner 13.

  The scanner 13 deflects the first illumination light L1 and the second illumination light L2 in order to scan the illumination position on the sample 20. For example, a galvanometer mirror or a polygon mirror can be used as the scanner 13. The scanner 13 scans two light beams in a direction perpendicular to the paper surface. Here, the scanning direction of the illumination light by the scanner 13 is defined as the Y direction. The first illumination light L 1 and the second illumination light L 2 reflected by the scanner 13 enter the lens 14. In the present embodiment, illumination light is scanned using a polygon mirror as the scanner 13 so as to move in the Y direction at 12 mm / 51 μsec on the surface of the sample 20. The time interval between each scan is 250 μsec.

  The lens 14 is an objective lens and is disposed immediately above the sample 20. The sample 20 is a transparent substrate as described above, and is, for example, a glass wafer having a thickness of 0.5 mm. The lens 14 condenses the first illumination light L1 and the second illumination light L2 on the sample 20. More specifically, the lens 14 condenses the first illumination light L1 and the second illumination light L2 on the surface of the sample 20. The first illumination light L1 and the second illumination light L2 collected by the lens 14 illuminate the same position on the surface of the sample 20. For example, the first illumination light L1 incident on a partial region of the lens 14 is collected at a position where the optical axis of the lens 14 and the surface of the sample 20 intersect. Similarly, the second illumination light L2 incident on a partial region of the lens 14 is condensed at a position where the optical axis of the lens 14 and the surface of the sample 20 intersect. Therefore, the first illumination light L1 and the second illumination light L2 propagating in different directions intersect at the surface of the sample 20. At the focal position, the beam diameters of the first illumination light L1 and the second illumination light L2 are about 70 μm. That is, on the surface of the sample 20, the first illumination light L1 and the second illumination light L2 form a circular spot having a diameter of 70 μm.

  The first illumination light L1 and the second illumination light L2 are incident on the lens 14 at a position shifted from the optical axis of the lens 14. Further, the first illumination light L1 and the second illumination light L2 are incident on different positions of the lens 14. For example, in FIG. 1, the first illumination light L <b> 1 enters a partial region in the left half of the lens 14, and the second illumination light L <b> 2 enters a partial region in the right half of the lens 14. Furthermore, on the XY plane at the lens 14, the incident position of the first illumination light L1 is symmetrical with the incident position of the second illumination light.

  For example, the incident angle of the first illumination light L1 and the second illumination light L2 with respect to the sample 20 is 45 °. That is, the first illumination light L1 refracted by the lens 14 is incident on the sample 20 at an incident angle of 45 °, and the second illumination light L2 refracted by the lens 14 is incident on the sample at an incident angle of −45 °. 20 is incident. As described above, the first illumination light L1 and the second illumination light L2 are incident on the sample 20 obliquely. That is, the optical axes of the first illumination light L1 and the second illumination light L2 are inclined from the optical axis of the lens 14. In the present embodiment, since the two light fluxes of the first illumination light L1 and the second illumination light L2 are used, the depth of focus of the entire two light fluxes becomes shallower than in the case of one light flux. Therefore, defect depth classification is possible.

  Furthermore, a first detector 16 and a second detector 17 are arranged on the sample 20. The first detector 16 and the second detector 17 are photodetectors such as a photomultiplier and a photodiode. In the present embodiment, the inspection apparatus 100 includes a dark field illumination optical system 101. Therefore, the first detector 16 and the second detector 17 detect the scattered light from the sample 20 without passing through the lens 14. When there is a defect at a location illuminated by the first illumination light L1 and the second illumination light L2, light is scattered by the defect. A part of the scattered light scattered by the defect does not enter the lens 14 but enters the first detector 16 or the second detector 17. That is, the first detector 16 and the second detector 17 detect scattered light that has passed outside the lens 14. In the XY plane, the first detector 16 and the second detector 17 are arranged at symmetrical positions with respect to the optical axis.

  A first filter 18 is disposed in front of the first detector 16. The first filter 18 is, for example, a bandpass filter, which transmits light having a wavelength λ1 and shields light having a wavelength λ2. Accordingly, the first detector 16 detects the scattered light of the first illumination light L1 that has entered the defect. That is, the first detector 16 detects the scattered light having the wavelength λ1 scattered by the defect. Thus, the 1st detector 16 detects only the scattered light of wavelength (lambda) 1 among the scattered light scattered in the direction of the 1st detector 16 by the defect.

  A second filter 19 is disposed in front of the second detector 17. The second filter 19 is, for example, a bandpass filter, which transmits light having a wavelength λ2 and shields light having a wavelength λ1. Therefore, the second detector 17 detects the scattered light of the second illumination light L2 incident on the defect. That is, the second detector 17 detects the scattered light having the wavelength λ2 scattered by the defect. Thus, the second detector 17 detects only the scattered light having the wavelength λ2 among the scattered light scattered in the direction of the second detector 17 due to the defect.

  By arranging the first filter 18 and the second filter 19 on the incident side of the first detector 16 and the second detector 17, respectively, the scattered light having the wavelength λ1 and the scattered light having the wavelength λ2 are detected independently. be able to. The sample 20 is placed on the XY stage 15. The XY stage 15 holds the edge portion of the sample 20. That is, the XY stage 15 is in contact with only the edge portion of the sample 20, and the lower side of the center of the sample 20 is a space. While the XY stage 15 moves the sample 20 in the X direction, the first detector 16 and the second detector 17 detect scattered light. For example, the XY stage 15 moves in the X direction at a speed of 100 mm / sec. The first detector 16 outputs a first detection signal corresponding to the detected scattered light intensity to a processing device (not shown in FIG. 1). The second detector 17 outputs a second detection signal corresponding to the detected scattered light intensity to the processing device.

  The processing device includes an information processing device such as a personal computer and an electronic circuit such as an A / D converter. The inspection method according to the present embodiment can be realized when the processing device performs predetermined processing on the first and second detection signals. The processing device detects a defect according to a comparison result between the detection signal and the threshold value. Since the dark field illumination optical system 101 is used, the detection signal increases at the timing when the illumination light enters the defect. Therefore, when the detection signal exceeds a preset threshold value, the processing apparatus determines that a defect exists. On the other hand, if the detection signal does not exceed the threshold value, the processing apparatus determines that there is no defect. Since the coordinates of the XY stage 15 and the angle of the scanner 13 are input to the processing apparatus, the processing apparatus can specify the illumination position on the XY plane. That is, the timing when the detection signal exceeds the threshold value is set as the defect detection timing, and the processing device specifies the defect coordinates from the illumination position at the defect detection timing. Furthermore, the processing apparatus can identify the position of the defect in the thickness direction by performing predetermined processing on the first and second detection signals. Processing in the processing device will be described later.

  FIG. 2 is a diagram illustrating a state of illumination light incident on the defect. In FIG. 2, defects existing on the surface of the sample 20 are shown as defects 21, and defects existing on the back surface of the sample 20 are shown as defects 23. Further, a defect existing inside the sample 20 is shown as a defect 22. Hereinafter, the case where the defect 21, the defect 22, or the defect 23 exists is demonstrated, respectively. In FIG. 2, the sample 20 is moved in the arrow direction (+ X direction) by the XY stage 15. The size of the defect is sufficiently smaller than the beam diameter, for example, about 1 μm to 10 μm.

  The sample 20 is made of a transparent material such as glass. For this reason, the 1st illumination light L1 and the 2nd illumination light L2 permeate | transmit the inside of the sample 20. FIG. Further, the first illumination light L1 and the second illumination light L2 are refracted at the interface between the sample 20 and air. As described above, the first illumination light L1 and the second illumination light L2 are different light fluxes and pass through different positions of the lens 14. Then, the lens 14 collects the first illumination light L1 and the second illumination light L2 on the surface of the sample 20. The first illumination light L1 and the second illumination light L2 intersect at the surface of the sample 20 and propagate through the sample 20. In FIG. 2, the first illumination light L1 is incident on the sample 20 obliquely from the upper left side (−X side), and the second illumination light L2 is incident on the sample 20 obliquely from the upper right side (+ X side). doing.

  Therefore, the position through which the first illumination light L1 and the second illumination light L2 pass changes according to the thickness direction (Z direction) of the sample 20. For example, in FIG. 2, the first illumination light L <b> 1 and the second illumination light L <b> 2 pass through the same position of the sample 20 on the surface of the sample 20. On the other hand, on the back side of the sample 20, the first illumination light L1 passes through the right side of the second illumination light. Thus, the illumination positions of the first illumination light L1 and the second illumination light L2 in the X direction are shifted according to the position in the Z direction. The closer to the back side of the sample 20, the greater the amount of deviation of the illumination positions of the first illumination light L1 and the second illumination light L2. On the inside and back surface of the sample 20, the illumination position by the first illumination light L1 and the illumination position by the second illumination light L2 are shifted in the X direction. That is, the second illumination light L2 illuminates a position different from the illumination position of the first illumination light L1. Since the XY stage 15 is moved in the X direction, the timing at which the first illumination light L1 and the second illumination light L2 enter the defect differs depending on the depth of the defect. As described above, the XY stage 15 moves the sample 20 in the direction in which the illumination position is shifted (X direction).

  First, the case where the defect 21 exists on the surface of the sample 20 will be described. When there is a defect 21 on the surface of the sample 20, the first illumination light L1 and the second illumination light L2 enter the defect 21 at the same time. When the illumination light enters the defect 21, the scattered light intensity increases and the detection signal exceeds the threshold value. Therefore, as shown in FIG. 3, the defect is detected at the same timing in the first detection signal of the first detector 16 and the second detection signal of the second detector 17. That is, the defect detection timing based on the first detection signal and the defect detection timing based on the second detection signal are substantially the same timing.

  Next, a case where the defect 22 exists inside the sample 20 will be described. When the defect 22 exists inside the sample 20, the timing at which the first illumination light L <b> 1 enters the defect 22 is shifted from the timing at which the second illumination light L <b> 2 enters the defect 22. That is, since the XY stage 15 moves in the + X direction, the first illumination light L1 enters the defect 22 after the second illumination light L2 enters the defect 22. Therefore, as shown in FIG. 4, the defect detection timing by the first illumination light L1 is delayed from the defect detection timing by the second illumination light L2.

  Next, the case where the defect 23 exists in the back surface of the sample 20 is demonstrated. When the defect 23 exists on the back surface of the sample 20, the timing at which the first illumination light L1 enters the defect 22 and the timing at which the second illumination light L2 enters the defect 22 are further shifted. That is, since the XY stage 15 moves in the + X direction, the first illumination light L1 enters the defect 22 after the second illumination light L2 enters the defect 22. Therefore, as shown in FIG. 5, the defect detection timing by the first illumination light L1 is further delayed from the defect detection timing by the second illumination light L2.

  The moving speed of the XY stage 15 in the X direction is known. The incident angle, the spread angle, and the spot diameter of the first illumination light L1 and the second illumination light L2 are also known. Furthermore, the thickness of the sample 20 and the refractive index of the sample 20 at wavelengths λ1 and λ2 are also known. Therefore, the position information acquisition unit 53 can specify the position of the defect in the Z direction from the time difference in the defect detection timing. That is, from the above known information, the time difference in defect detection timing can be converted into the position of the defect in the Z direction.

  FIG. 6 shows the relationship between the defect detection timing and the position in the Z direction. As described above, the deviation of the defect detection timing becomes larger toward the −Z side. For example, when the thickness of the glass wafer is 0.5 mm, the stage speed is 100 mm / sec, and the incident angle of illumination light is 45 °, the detection timing of the defect 22 inside the sample 20 is shifted by about 2.7 msec. When the beam diameter is 70 μm and the defect size is 10 μm, the width of the defect indicated by the detection signal shown in FIGS. 3 to 5 corresponds to about 0.4 μsec.

  Thus, the time interval between the defect detection timing based on the first detection signal and the defect detection timing based on the second detection signal changes according to the depth of the defect. The processing device detects the position of the defect in the Z direction according to this time interval. That is, the processing apparatus obtains defect position information in the Z direction (thickness direction) according to the interval of the defect detection timing.

  A configuration of a processing apparatus for performing the above processing will be described with reference to FIG. FIG. 7 is a block diagram illustrating a configuration of the processing device 50. The processing device 50 includes a first comparison unit 51, a second comparison unit 52, and a position information acquisition unit 53. The processing device 50 receives the first detection signal from the first detector 16 and the second detection signal from the second detector 17.

  The first comparison unit 51 detects a defect by comparing the first detection signal with a threshold value. That is, when the first detection signal exceeds the threshold value, the first comparison unit 51 determines that a defect exists. The second comparison unit 52 detects the defect by comparing the second detection signal with a threshold value. That is, when the second detection signal exceeds the threshold value, the second comparison unit 52 determines that there is a defect. The threshold value in the first comparison unit 51 and the threshold value in the second comparison unit 52 may be the same value or different values. For example, the threshold value may be adjusted according to the difference in sensitivity depending on the illumination wavelength. Since the position of the XY stage 15 and the deflection angle of the scanner 13 are input to the processing device 50, the defect position can be detected based on the detection results of the first comparison unit 51 and the second comparison unit 52.

  The position information acquisition unit 53 obtains defect position information in the Z direction according to the time difference between the defect detection timing by the first comparison unit 51 and the defect detection timing by the second comparison unit 52. Thereby, the depth classification of a defect can be performed. The position information acquisition unit 53 obtains a time difference between the defect detection timing by the first comparison unit 51 and the defect detection timing by the second comparison unit. And the position information acquisition part 53 detects the Z direction position of a defect according to a time difference. As described above, the time difference increases as the back surface side of the sample 20 moves. Therefore, it is possible to detect the position information of the defect in the Z direction according to the time difference.

  In the present embodiment, the dark field illumination optical system 101 is arranged on one surface side of the sample 20. By doing so, it is not necessary to arrange an optical component on the back surface side of the sample 20, so that the optical system can be simplified as compared with Patent Document 1. In particular, since the optical components such as the scanner 13 and the lens 14 can be shared with the first illumination light L1 and the second illumination light L2, the number of components can be reduced.

  In the present embodiment, defect detection and acquisition of position information in the Z direction can be performed simultaneously. That is, a defect can be detected based on the comparison results of the first comparison unit 51 and the second comparison unit 52, and the Z position of the defect can be detected according to the timing difference of defect detection. Accordingly, the inspection apparatus 100 according to the present embodiment can detect a defect and specify a position in the thickness direction by one scan. Thus, throughput can be improved. On the other hand, in the inspection by the normal optical system, after detecting the defect, it is necessary to change the focal position in the Z direction at the defect position. Therefore, the inspection can be performed with a higher throughput than the inspection by the normal optical system.

  In the present embodiment, the sample 20 is illuminated with the first illumination light L1 and the second illumination light L2 having different wavelengths, and the first detector 16 and the second detector 17 detect scattered light having different wavelengths. Yes. In other words, the first filter 18 and the second filter 19 are arranged in front of the first detector 16 and the second detector 17, respectively, so that the light of the other wavelength is not detected. In this way, even when two defects are close to each other, it is possible to detect them separately. Further, the position of the defect in the thickness direction is measured according to the time difference between the timings when the defect is detected by the first and second detectors. Therefore, the position of the defect can be measured with high resolution.

  In addition, it is preferable to reduce the beam diameter of the first illumination light L1 incident on the lens 14 and increase the depth of focus of the light flux of the first illumination light L1. Similarly, it is preferable to reduce the beam diameter of the second illumination light L2 incident on the lens 14 and increase the focal depth of the light flux of the second illumination light L2. By doing so, the spread of each beam diameter on the back surface can be reduced, so that defects can be detected with high resolution. In addition, the resolution in the thickness direction near the surface of the sample 20 is improved by reducing the beam diameter.

  In the above description, the first illumination light L1 and the second illumination light L2 intersect on the surface of the sample 20, but the depth at which the first illumination light L1 and the second illumination light L2 intersect is limited to the surface of the sample 20. It's good if you can. For example, the first illumination light L <b> 1 and the second illumination light L <b> 2 may intersect at the back surface of the sample 20 or may intersect within the sample 20. The lens 14 may refract the first illumination light L1 and the second illumination light L2 so that the illumination position of the first illumination light L1 and the illumination position of the second illumination light are shifted according to the position in the Z direction.

  By changing the distance between the lens 14 and the sample 20, it is possible to make the depth with good defect detection sensitivity. For example, when the sensitivity inside the sample 20 is increased, the first illumination light L1 and the second illumination light L2 intersect within the sample 20. Furthermore, the beam diameter on the surface of the sample 20 can be changed by changing the distance between the lens 14 and the sample 20. As a result, the throughput can be changed without changing the NA of the lens 14.

  In the above description, the XY stage 15 holds the edge portion of the sample 20. However, if the XY stage 15 may contact the back surface of the sample 20, the stage holding the entire sample 20 may be a transparent stage. Is possible. By doing so, it is possible to prevent the sample 20 from being bent. Alternatively, the stage that holds the entire sample 20 can be made of a non-transparent material. For example, if the back surface of the sample 20 may be contacted and the back surface of the sample 20 is not inspected, the entire sample 20 can be held on a non-transparent stage. In this case, since the signal from the back surface is detected with a fixed timing difference, the signal due to the scattered light from the back surface can be separated.

  Note that defects having a large size are detected at the same timing. For example, in the case of a defect of about 300 μm larger than the separation interval of the illumination light inside the sample 20, the defect detection timing by the first comparison unit 51 and the defect detection timing by the second comparison unit 52 overlap. In addition, if the size is large, the sensitivity of the illumination light L1 and the illumination light L2 changes with respect to the left and right edges of the defect 21. For example, the sensitivity varies depending on the incident direction of the illumination light and the direction of the edge. For this reason, a defect having a large size may be classified by a bright field review after inspection.

  Note that the XY stage 15 moves the sample 20 in the direction in which the movement position of the XY stage 15 deviates from the illumination position. By doing so, the XY stage 15 can move the illumination position in the X direction at an appropriate speed. Position information of defects in the Z direction can be accurately measured. The scanner 13 scans the first and second illumination lights in the Y direction. The scanning speed by the scanner 13 is sufficiently fast with respect to the amount of deviation of the illumination position. Therefore, when the scanner 13 scans the first illumination light L1 and the second illumination light L2 in the Y direction, a wide area in the Y direction can be illuminated in a short time. Thus, throughput can be improved.

  In the above description, the illumination position is changed using the XY stage 15, but the illumination position may be changed by moving the entire optical system. For example, the illumination position may be changed by moving the scanner 13, the lens 14, the first detector 16, and the second detector 17. As described above, the means for changing the illumination position in the sample 20 is not limited to the XY stage 15, and it is sufficient that the incident position of the illumination light with respect to the sample 20 can be changed relatively.

  The position information acquired by the position information acquisition unit 53 is not limited to the defect coordinates in the Z direction. For example, when the resolution in the Z direction is low, it may only be determined whether the defect is on the front surface, inside, or back surface of the sample 20. Further, two detectors may be provided on the back side of the sample 20 and the same processing may be performed. By doing so, the position of the defect in the Z direction can be measured with higher accuracy.

Embodiment 2. FIG.
The inspection apparatus according to this embodiment will be described with reference to FIG. FIG. 8 is a diagram illustrating a state of the first illumination light L1 and the second illumination light L2 that illuminate the sample 20 in the inspection apparatus 100. FIG. Note that the configuration and processing of the inspection apparatus 100 are the same as the configuration and processing shown in the first embodiment, and thus description of the overlapping contents is omitted. In the present embodiment, the first illumination light L1 and the second illumination light L2 have the same wavelength. The first filter 18 and the second filter 19 shown in FIG. 1 are removed. Therefore, the first detector 16 and the second detector 17 detect scattered light having the same wavelength.

  As in the first embodiment, the first detection signal from the first detector 16 is compared with a threshold value to detect a defect. The second detection signal from the second detector 17 is compared with a threshold value to detect a defect. As in the first embodiment, it is possible to acquire defect position information in the thickness direction based on a time difference in defect detection timing. When there is a defect in the inside or the back surface of the sample 20, one defect is illuminated twice at different timings. That is, the timing at which the first illumination light L1 and the second illumination light L2 enter the defect is shifted. Thus, for example, for one defect, the first detection signal exceeds the threshold value twice. Similarly, the second detection signal exceeds the threshold value twice for one defect. The processing device 50 acquires defect position information in the thickness direction based on the time difference between the two defect detection timings. By doing so, the position information of the defect in the Z direction can be acquired as in the first embodiment.

  When detecting scattered light having the same wavelength, separation is difficult if a defect is close to the sample 20. That is, when the two defects are not isolated, it is difficult for the processing device 50 to determine whether the light is scattered light due to the same defect or whether the light is scattered light due to the two defects. If the defect is isolated about the separation interval of the illumination light on the back surface of the sample 20, the depth of the defect can be detected.

Embodiment 3 FIG.
The inspection apparatus according to the present embodiment will be described with reference to FIG. FIG. 9 is a diagram illustrating a configuration of the inspection apparatus 100. In the present embodiment, the positions of the first illumination light source 11 and the second illumination light source 12 and the positions of the first detector 16 and the second detector 17 are interchanged with respect to the first embodiment. Specifically, the first illumination light L 1 from the first illumination light source 11 and the second illumination light L 2 from the second illumination light source 12 illuminate the sample 20 from the outside of the lens 14. Then, the first detector 16 and the second detector 17 detect the scattered light that has passed through the lens 14.

  The first illumination light L <b> 1 from the first illumination light source 11 is condensed on the sample 20 by the lens 31. The second illumination light L <b> 2 from the second illumination light source 12 is condensed on the sample 20 by the lens 32. Thus, the first illumination light L1 and the second illumination light L2 pass through the outside of the lens 14 and illuminate the sample 20. The first illumination light L1 and the second illumination light L2 become two light beams that illuminate the same portion of the sample 20 from different directions. The first illumination light L1 and the second illumination light L2 have different wavelengths λ1 and λ2 as in the first embodiment.

  And the lens 14 is arrange | positioned just above the illumination location of the sample 20. FIG. Therefore, the lens 14 which is an objective lens receives scattered light from the illumination location of the sample 20. The scattered light refracted by the lens 14 enters the dichroic mirror 33. The dichroic mirror 33 is a light branching unit that branches light according to the wavelength. That is, the scattered light having the wavelength λ 1 is transmitted through the dichroic mirror 33, and the scattered light having the wavelength λ 2 is reflected by the dichroic mirror 33.

  The scattered light having the wavelength λ 1 that has passed through the dichroic mirror 33 is condensed on the first detector 16 by the lens 34. The scattered light having the wavelength λ <b> 2 reflected by the dichroic mirror 33 is condensed on the second detector 17 by the lens 35. Thereby, as in the first embodiment, the first detector 16 detects the scattered light having the wavelength λ1 scattered by the defect, and the second detector 17 detects the scattered light having the wavelength λ2 scattered by the defect. . Therefore, by performing the processing of the first embodiment, it is possible to acquire defect position information in the Z direction from the difference in defect detection timing.

  In the configuration shown in FIG. 9 as well, the sample 20 can be illuminated in the dark field as in the first and second embodiments. In the configuration of the present embodiment, it is not necessary to arrange the first filter 18 and the second filter 19 before the first detector 16 and the second detector 17. Further, as the first detector 16 and the second detector 17, it is possible to use a line sensor in which pixels are arranged in one column. For example, a one-dimensional line sensor in which pixels are arranged along a direction perpendicular to the paper surface of FIG. 9 can be used as the first detector 16 and the second detector 17. As the first detector 16 and the second detector 17, a CCD or a photomultiplier can be used.

  When a line sensor is used, the lenses 31 and 32 may be cylindrical lenses, and the illumination light may be elliptical. In this way, a wide area can be illuminated at a time. That is, the pixels are arranged along the longitudinal direction of the spot shape of the illumination light. And it scans in the direction orthogonal to the longitudinal direction of the spot shape of illumination light. By carrying out like this, it can test | inspect in a short time.

  Further, the configuration of the present embodiment can be used in combination with the second embodiment. In this case, the light can be branched using a light branching means other than the dichroic mirror 33. For example, the light toward the first detector 16 and the light toward the second detector 17 can be branched using a half mirror. On the other hand, for example, only the first detector 16 may be used in a state where the light is not branched and the dichroic mirror 33 is not provided.

Other embodiments.
Pulse light can also be used as the first illumination light L1 and the second illumination light L2. Then, the irradiation timing of the two pulse lights is shifted and the sample 20 is irradiated. A trigger is applied at the timing of oscillation to detect scattered light. By doing in this way, even if the light of the same wavelength is used, the scattered light by the 1st illumination light L1 and the 2nd illumination light L2 can be isolate | separated and detected with two detectors.

  For example, a pulsed laser light source is used as the illumination device 10, or the first illumination light L1 and the second illumination light L2 are modulated to obtain pulsed light. Two pulsed laser light sources may be mounted on the illumination device 10. Then, the oscillation of the illumination light L1 and the light reception of the first detector 16 are synchronized, and the oscillation of the second illumination light L2 and the light reception of the second detector 17 are synchronized. Alternatively, pulse laser light from one pulse laser light source may be branched and one pulse laser light may be delayed. When it is desired to delay the two pulse laser beams by 0.1 μsec, it is necessary to pass one of the beams by an extra 30 m in the atmosphere. Therefore, by using a pulse delay element or the like, one pulse can be delayed by a desired time. As the pulse delay element, a pair of high-reflectivity mirrors, an optical element made of glass, or an optical fiber can be used. In the case of branching, a light receiving unit for synchronous monitoring composed of a half mirror or the like is provided in the branched optical path.

  When using pulsed light, it is preferable to increase the repetition frequency. By increasing the repetition frequency, the surface of the sample 20 is illuminated so that the spots of continuous pulsed light overlap. Therefore, the entire sample 20 can be inspected. For example, in the case of the configuration shown in Embodiment 1, the repetition frequency is 3 MHz or more.

  Further, when there is a ground pattern or an adhesive layer on the back surface of the sample 20, signals from the back surface can be separated according to the time difference. When a base pattern or an adhesive layer inspects a sample on the back surface, the intensity of scattered light from the back surface increases, resulting in noise. However, since scattered light from the back surface difference is always detected with the same timing difference, noise can be separated.

  Furthermore, according to the time difference, the height of a large pattern or foreign matter on the surface of the sample 20 can be measured. In other words, since the detection timing differs depending on the height of the foreign matter or the like, it is possible to measure the height of the foreign matter defect as well as the defect depth. In the above embodiment, an area sensor in which pixels are arranged in a two-dimensional array may be used for the first detector 16 and the second detector 17.

  As mentioned above, although embodiment of this invention was described, this invention contains the appropriate deformation | transformation which does not impair the objective and advantage, Furthermore, it does not receive the restriction | limiting by said embodiment.

DESCRIPTION OF SYMBOLS 100 Inspection apparatus 10 Illumination apparatus 11 1st illumination light source 12 2nd illumination light source 13 Scanner 14 Lens 15 XY stage 16 1st detector 17 2nd detector 18 1st filter 19 2nd filter 20 Sample 21 Defect 50 Processing apparatus 51 First Comparison Unit 52 Second Comparison Unit 53 Position Information Acquisition Unit

Claims (14)

An illuminating device that generates two light beams as illumination light for illuminating the sample, and illuminates the sample from different directions;
A first detector for detecting scattered light from the sample;
A second detector for detecting scattered light from the sample;
A first comparator for detecting a defect by comparing a first detection signal from the first detector with a threshold;
A second comparison unit for detecting the defect by comparing a second detection signal from the second detector with a threshold;
A position information acquisition unit that acquires position information of the defect in the thickness direction of the sample according to a time difference between the detection timing of the defect by the first comparison unit and the detection timing of the defect by the second comparison unit; , Equipped with an inspection device. The illumination device generates two light fluxes of a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength,
The first detector detects scattered light through a first filter that blocks light of a second wavelength,
The inspection apparatus according to claim 1, wherein the second detector detects scattered light through a second filter that blocks light having a first wavelength. A lens on which the two light beams are incident;
The inspection apparatus according to claim 1, wherein the sample illuminates the sample from different directions by the lens. An objective lens for receiving scattered light from the sample;
A light branching means for branching scattered light from the objective lens, and
The first detector detects one light branched by the light branching means,
The inspection apparatus according to claim 1, wherein the second detector detects the other light branched by the light branching unit. The illumination device generates two light fluxes of a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength,
The inspection apparatus according to claim 4, wherein the light branching unit branches the scattered light having the first wavelength and the scattered light having the second wavelength according to a wavelength. Depending on the position of the sample in the thickness direction, the sample is illuminated such that the illumination position by the two light beams is shifted,
The inspection apparatus according to claim 1, wherein a stage for moving the sample is provided in a direction in which an illumination position by the two light beams is shifted.   The inspection apparatus according to claim 6, wherein a scanner that scans the illumination light is provided in a direction orthogonal to a direction in which an illumination position by the two light beams is shifted. Generating two light fluxes as illumination light for illuminating the sample;
Illuminating the sample from different directions of the two light fluxes;
Detecting scattered light from the sample by the first detector and the second detector, respectively.
Detecting a defect by comparing a first detection signal from the first detector with a threshold;
Detecting the defect by comparing a second detection signal from the second detector with a threshold;
Obtaining position information of the defect in the thickness direction of the sample according to a time difference between the detection timing of the defect in the first detection signal and the detection timing of the defect in the second detection signal; Inspection method with The two luminous fluxes include a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength,
The first detector detects scattered light through a first filter that blocks light of a second wavelength,
The inspection method according to claim 8, wherein the second detector detects scattered light through a second filter that blocks light having a first wavelength.   10. The inspection method according to claim 8, wherein the sample is illuminated from different directions by the lens on which the two light beams are incident. The objective lens receives the scattered light from the sample,
The scattered light from the objective lens is branched by a light branching means,
The first detector detects one light branched by the light branching means,
The inspection method according to claim 8, wherein the second detector detects the other light branched by the light branching unit. The two luminous fluxes include a first illumination light having a first wavelength and a second illumination light having a second wavelength different from the first wavelength,
The inspection method according to claim 11, wherein the light branching unit branches the scattered light having the first wavelength and the scattered light having the second wavelength according to a wavelength. In accordance with the position of the sample in the thickness direction, the sample is illuminated such that the illumination position of the two light beams is shifted,
The inspection method according to any one of claims 8 to 12, wherein the first detector and the second detector detect the scattered light while moving the sample in a direction in which the illumination positions of the two light beams are shifted.   The inspection method according to claim 13, wherein the first detector and the second detector detect the scattered light while scanning the illumination light in a direction orthogonal to a direction in which an illumination position due to the two light beams deviates.

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