Defect inspecting device, and defect inspecting method

Abstract

The present invention provides a defect inspecting device and defect inspecting method capable of reducing influence due to height variation of a sample surface and achieving high sensitivity.　In order to achieve the above-mentioned purpose, this defect inspecting device includes: an illumination unit that irradiates a sample with light emitted from a light source; a detection unit that detects scattered light generated from the sample; a sample height detection unit that measures a variation amount of the sample in a direction perpendicular to a surface of the sample; a photoelectric conversion unit that converts the scattered light detected by the detection unit into an electric signal; and a signal processing unit that processes the electric signal converted by the photoelectric conversion unit to detect a defect of the sample. The detection unit has a mechanism for adjusting its position after divergence from an opening in accordance with the variation amount of the surface of the sample acquired by the sample height detection unit, and a mechanism for separately detecting scattered light, which has been generated from the sample after divergence from the opening, at a plurality of elevation angles for detection. The signal processing unit has a mechanism for correcting the positions of a plurality of images formed by divergence from the opening in accordance with the variation amount of the surface of the sample acquired by the sample height detection unit.

Description

Defect inspection device and defect inspection method

[0001] The present invention relates to a defect inspection apparatus and a defect inspection method.

[0002] 2. Description of the Related Art In manufacturing lines for semiconductor substrates, thin film substrates, and the like, inspections for defects present on the surfaces of semiconductor substrates, thin film substrates, and the like are carried out in order to maintain and improve product yields.

[0003] For example, Patent Document 1 is known as background technology in this technical field. Patent Document 1 describes a configuration "configured to divide the full collection NA of the collection subsystem into different segments and to direct scattered light collected in the different segments to separate detectors," and as an example, describes an aperture mirror arranged in the Fourier plane of the collection subsystem, saying "the aperture mirror transmits scattered light collected in one segment of the collection NA while reflecting scattered light collected in another segment of the collection NA." Patent Document 1 also discloses a technology for suppressing surface scattering from the wafer surface by "configuring to separate scattered light in one of the different segments based on polarization to form different portions of the scattered light."

[0004] Special table 2014-504370 publication

[0005] Defect inspection used in the manufacturing process of semiconductors and other products requires the following: (1) detecting minute defects; (2) measuring the dimensions of detected defects with high precision; (3) inspecting the sample nondestructively, i.e., without altering the sample; (4) obtaining substantially consistent inspection results, for example, regarding the number, location, dimensions, and type of defects, when inspecting the same sample; and (5) inspecting a large number of samples within a certain period of time.

[0006] In the technology described in Patent Document 1, in order to enable inspection of minute defects of 20 nm or less, the optical path is branched using an "aperture mirror" provided on the Fourier plane of the objective lens to discriminate from background scattered light, and for each branched optical path, the optical path is further branched using polarized light.

[0007] Inspection methods that use branched optical paths are significantly affected by height fluctuations on the sample surface that occur during inspection. During inspection, the sample rotates at high speeds of several thousand rotations per minute (RPM). Height fluctuations in the direction perpendicular to the sample surface occur due to sample warping, the chuck, air currents, and the wobble of the rotation axis. At their highest speeds, these height fluctuations occur at the same frequency as the sample's rotation. These height fluctuations cause the sample surface to shift out of focus with respect to the detection system, reducing the image resolution on the sensor surface. As a result, the image no longer fits within the pixel, resulting in a decrease in the signal output from the pixel. Furthermore, the image is focused at different positions on the sensor for each branched optical path. As a result, scattered light is detected from the same region, and the correspondence between the pixels on the sensor for each branched optical path is lost. This results in the inability to sum the sensor pixels for each branched optical path.

[0008] One example of the present invention is a defect inspection device that includes an illumination unit that irradiates a sample with light emitted from a light source, a detection unit that detects scattered light generated from the sample, a sample height detection unit that measures the amount of sample movement in a direction perpendicular to the sample surface, a photoelectric conversion unit that converts the scattered light detected by the detection unit into an electrical signal, and a signal processing unit that processes the electrical signal converted by the photoelectric conversion unit to detect defects in the sample, wherein the detection unit includes a mechanism that branches an aperture in response to the amount of sample surface movement acquired by the sample height detection unit and then adjusts its position, and a mechanism that branches the aperture to separate and detect scattered light generated from the sample at a plurality of detection elevation angles, and the signal processing unit includes a mechanism that corrects the positions of a plurality of images formed by branching the aperture in response to the amount of sample surface movement acquired by the sample height detection unit.

[0009] According to the present invention, it is possible to provide a defect inspection apparatus and a defect inspection method that can reduce the influence of height variations on the sample surface and achieve high sensitivity.

[0010] 13 is a schematic diagram of the entire configuration of a defect inspection apparatus in Example 1. FIG. 14 is a diagram showing a first example of an illumination intensity distribution shape realized by an illumination unit in Example 1. FIG. 15 is a diagram showing a second example of an illumination intensity distribution shape realized by an illumination unit in Example 1. FIG. 16 is a diagram showing a third example of an illumination intensity distribution shape realized by an illumination unit in Example 1. FIG. 17 is a diagram showing a fourth example of an illumination intensity distribution shape realized by an illumination unit in Example 1. FIG. 18 is a diagram showing a fifth example of an illumination intensity distribution shape realized by an illumination unit in Example 1. FIG. 19 is a diagram showing optical elements provided in an illumination intensity distribution control unit in Example 1. FIG. 19 is a diagram showing an illumination distribution shape and a scanning direction on a sample surface in Example 1. FIG. 20 is a diagram showing a trajectory of an illumination spot by scanning in Example 1. FIG. 21 is a side view of the arrangement and detection direction of a detection unit in Example 1. FIG. 22 is a plan view of the arrangement and detection direction of a detection unit in Example 1. FIG. 23 is a configuration diagram of the detection unit in Example 1. FIG. 24 is a diagram showing the arrangement of an illumination spot and a photoelectric conversion unit in Example 1. FIG. 25 is a diagram seen from above on the paper. FIG. 26 is a schematic diagram of the three-dimensional arrangement of a sample and a detection unit in Example 1. FIG. 27 is a diagram showing a cross section of a photoelectric conversion unit in Example 1. FIG. 1 is a diagram showing the relationship between the absorptance of the anti-reflection film of the photoelectric conversion unit and the angle of incidence in Example 1. FIG. 2 is a schematic configuration diagram of a sample height detection unit in Example 1. FIG. 3 is a configuration diagram of a detection unit in Example 1, and is a diagram explaining height direction displacement of a sample surface, imaging position shift, and imaging blur. FIG. 4 is a diagram explaining imaging position shift and imaging blur at a high-angle detection unit before height displacement in Example 1. FIG. 5 is a diagram explaining imaging position shift and imaging blur at a high-angle detection unit after height displacement in Example 1. FIG. 6 is a diagram explaining imaging position shift and imaging blur at a low-angle detection unit before height displacement in Example 1. FIG. 7 is a diagram explaining imaging position shift and imaging blur at a low-angle detection unit after height displacement in Example 1. FIG. 8 is a functional block diagram explaining details of a signal processing unit in Example 1. FIG. 9 is a configuration diagram of a detection unit in Example 2, and is a diagram explaining details of height direction displacement of a sample surface and an optical element adjustment mechanism. FIG. 10 is a functional block diagram of a signal processing unit in Example 2. FIG. 11 is a functional block diagram of another signal processing unit in Example 2. FIG. 12 is a diagram explaining a cross-correlation filter by a filter processing unit in Example 3.Fig. 10 is a diagram for explaining a cross-correlation filter by a filter processing unit in Example 3. Fig. 11 is a functional block diagram of a signal processing unit in Example 3. Fig. 12 is a configuration diagram of a detection unit in Example 4. Fig. 13 is a functional block diagram of a signal processing unit in Example 5. Fig. 14 is a configuration diagram of a detection unit in Example 6.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the embodiment, a defect inspection apparatus used for defect inspection carried out in the manufacturing process of semiconductors and the like will be described.

[0012] 1 is a schematic diagram of the overall configuration of a defect inspection apparatus according to this embodiment. In Fig. 1, the defect inspection apparatus 10 includes an illumination unit 101, a detection unit 102, photoelectric conversion units 103-1 and 103-2 (hereinafter, sometimes collectively referred to as the photoelectric conversion unit 103), a stage 104 on which a sample 1 can be placed and which can be moved in a direction perpendicular to the surface by an actuator, a signal processing unit 105, a sample height detection unit 106, a control unit 53, a display unit 54, and an input unit 55.

[0013] The illumination unit 101 appropriately includes a laser light source 2, an attenuator 3, an emitted light adjustment unit 4, a beam expander 5, a polarization control unit 6, and an illumination intensity distribution control unit 7. The laser light beam emitted from the laser light source 2 is adjusted to a desired beam intensity by the attenuator 3, adjusted to a desired beam position and beam traveling direction by the emitted light adjustment unit 4, adjusted to a desired beam diameter by the beam expander 5, adjusted to a desired polarization state by the polarization control unit 6, and adjusted to a desired intensity distribution by the illumination intensity distribution control unit 7, and is then illuminated onto an inspection target region of the sample 1.

[0014] The angle of incidence of the illumination light relative to the sample surface is determined by the position and angle of the reflecting mirror of the output light adjusting unit 4, which is disposed in the optical path of the illumination unit 101. The angle of incidence of the illumination light is set to an angle suitable for detecting minute defects. A larger illumination angle of incidence, i.e., a smaller illumination elevation angle (the angle between the sample surface and the illumination optical axis), weakens the scattered light from minute irregularities on the sample surface (called haze), which creates noise in the scattered light from minute foreign particles on the sample surface, making it more suitable for detecting minute defects. Therefore, if scattered light from minute irregularities on the sample surface interferes with the detection of minute defects, the angle of incidence of the illumination light is preferably set to 75 degrees or more (an elevation angle of 15 degrees or less). On the other hand, in oblique incidence illumination, the absolute amount of scattered light from minute foreign particles increases as the illumination angle of incidence decreases. Therefore, if a lack of scattered light from defects interferes with the detection of minute defects, the angle of incidence of the illumination light is preferably set to 60 degrees or more and 75 degrees or less (an elevation angle of 15 degrees or more and 30 degrees or less). Furthermore, when performing oblique incidence illumination, by controlling the polarization of the illumination in the polarization control unit 6 of the illumination unit 101 to be P-polarized, the scattered light from defects on the sample surface increases compared to other polarized light. Furthermore, if scattered light from minute irregularities on the sample surface interferes with the detection of minute defects, by changing the polarized light of the illumination to be S-polarized, the scattered light from minute irregularities on the sample surface decreases compared to other polarized light.

[0015] 1, if necessary, a mirror 21 can be inserted into the optical path of the illumination unit 101, and other mirrors can be placed as needed to change the illumination optical path, so that illumination light is irradiated from a direction substantially perpendicular to the sample surface (perpendicular illumination). At this time, the illumination intensity distribution on the sample surface is controlled by the illumination intensity distribution control unit 7v in the same manner as in oblique incidence illumination. By inserting a beam splitter in the same position as the mirror 21, it is possible to obtain both oblique incidence illumination and scattered light from concave defects on the sample surface (polishing scratches or crystal defects in crystalline materials), making perpendicular illumination, which is incident substantially perpendicularly on the sample surface, suitable.

[0016] As the laser light source 2, in order to detect minute defects near the surface of the sample, a laser light source that emits a short wavelength (355 nm or less) ultraviolet or vacuum ultraviolet laser beam with a wavelength that does not easily penetrate the interior of the sample and has a high output of 2 W or more is used. The diameter of the emitted beam is about 1 mm. In order to detect defects inside the sample, a laser light source that emits a visible or infrared laser beam with a wavelength that easily penetrates the interior of the sample is used.

[0017] The attenuator 3 includes a first polarizing plate, a half-wave plate rotatable around the optical axis of the illumination light, and a second polarizing plate. The light incident on the attenuator 3 is converted into linearly polarized light by the first polarizing plate, and the polarization direction is rotated in a desired direction according to the azimuth angle of the slow axis of the half-wave plate before passing through the second polarizing plate. By controlling the azimuth angle of the half-wave plate, the light intensity can be attenuated at a desired ratio. If the degree of linear polarization of the light incident on the attenuator 3 is sufficiently high, the first polarizing plate is not necessarily required. The attenuator 3 is one in which the relationship between the input signal and the attenuation rate has been calibrated in advance. The attenuator 3 can be an ND filter with a gradation density distribution, or a plurality of ND filters with different densities can be switched between.

[0018] The output light adjustment unit 4 includes multiple reflecting mirrors. While an example using two reflecting mirrors will be described here, this is not limiting and three or more reflecting mirrors may be used as appropriate. A three-dimensional Cartesian coordinate system (XYZ coordinates) is hypothetically defined, and it is assumed that light incident on the reflecting mirrors travels in the +X direction. The first reflecting mirror is positioned to deflect the incident light in the +Y direction (incidence and reflection in the XY plane), and the second reflecting mirror is positioned to deflect the light reflected by the first reflecting mirror in the +Z direction (incidence and reflection in the YZ plane). The position and direction (angle) of the light emitted from the output light adjustment unit 4 are adjusted by translating each reflecting mirror and adjusting its tilt angle. As described above, by arranging the incident / reflecting surface (XY plane) of the first reflecting mirror and the incident / reflecting surface (YZ plane) of the second reflecting mirror so that they are perpendicular to each other, it is possible to independently adjust the position and angle of the light (traveling in the +Z direction) emitted from the output light adjustment unit 4 in the XZ plane and in the YZ plane.

[0019] The beam expander 5 has two or more lens groups and functions to expand the diameter of the incident parallel beam. For example, a Galilean beam expander equipped with a combination of concave and convex lenses is used. The beam expander 5 is mounted on a translation stage with two or more axes, allowing its position to be adjusted so that its center coincides with a predetermined beam position. The beam expander 5 also has a function for adjusting the tilt angle of the entire beam expander 5 so that the optical axis of the beam expander 5 coincides with the optical axis of a predetermined beam. The expansion rate of the beam diameter can be controlled by adjusting the spacing between the lenses (zoom mechanism). When the light incident on the beam expander 5 is not parallel, adjusting the spacing between the lenses simultaneously expands the beam diameter and collimates it (makes the beam quasi-parallel). The beam can also be collimated by installing a collimating lens upstream of the beam expander 5, independent of the beam expander 5. The beam diameter is expanded by about 5 to 10 times by the beam expander 5, and the beam emitted from the light source with a diameter of 1 mm is expanded to about 5 to 10 mm.

[0020] The polarization control unit 6 is composed of a half-wave plate and a quarter-wave plate, and controls the polarization state of the illumination light to an arbitrary polarization state. In the optical path of the illumination unit 101, a beam monitor 22 measures the state of the light incident on the beam expander 5 and the state of the light incident on the illumination intensity distribution control unit 7.

[0021] 2 to 6 are schematic diagrams showing the positional relationship between the illumination light axis 120 guided to the sample surface from the illumination unit 101 and the illumination intensity distribution shape. Note that the configuration of the illumination unit 101 in Figures 2 to 6 shows only a part of the configuration of the illumination unit 101, and the emitted light adjustment unit 4, mirror 21, beam monitor 22, etc. are omitted.

[0022] FIG. 2 is a schematic diagram of a cross section of the incident plane (plane including the illumination optical axis and the normal to the sample surface) of oblique incidence illumination in this embodiment. Oblique incidence illumination is inclined with respect to the sample surface within the incident plane. A substantially uniform illumination intensity distribution is created within the incident plane by the illumination unit 101. The length of the portion with uniform illumination intensity is approximately 100 μm to 4 mm, in order to inspect a wide area per unit time.

[0023] FIG. 3 is a schematic diagram of a cross section of a plane that includes the sample surface normal and is perpendicular to the plane of incidence for oblique incidence illumination in this embodiment. Within this plane, the illumination intensity distribution on the sample surface exhibits an illumination intensity distribution in which the intensity is weaker at the periphery than at the center. More specifically, the intensity distribution resembles a Gaussian distribution that reflects the intensity distribution of light incident on the illumination intensity distribution control unit 7, or a first-order Bessel function or sinc function that reflects the aperture shape of the illumination intensity distribution control unit 7. The length of the illumination intensity distribution within this plane (the length of the region with an illumination intensity of 13.5% or more of the maximum illumination intensity) is shorter than the length of the portion of the incident plane where the illumination intensity is uniform, approximately 2.5 μm to 20 μm, in order to reduce haze generated from the sample surface.

[0024] The illumination intensity distribution control unit 7 includes optical elements such as an aspherical lens, a diffractive optical element, a cylindrical lens array, a light pipe, etc. The optical elements constituting the illumination intensity distribution control unit 7 are installed perpendicular to the illumination optical axis, as shown in Figures 2 and 3.

[0025] As shown in Fig. 4, the optical elements constituting the illumination intensity distribution control unit 7 can be installed at an angle to the optical axis. Furthermore, as shown in Figs. 5 and 6, the intensity distribution at the incident plane of the oblique incidence illumination shown in Figs. 2 and 3 can be swapped with the intensity distribution at the plane perpendicular to the incident plane. In other words, a configuration is possible in which the portion of the incident plane where the illumination intensity is uniform is shorter than the portion of the incident plane where the illumination intensity is uniform.

[0026] The illumination intensity distribution control unit 7 includes optical elements that affect the phase distribution and intensity distribution of the incident light. FIG. 7 is a diagram showing the optical elements included in the illumination intensity distribution control unit 7 in this embodiment. As shown in FIG. 7 , a diffractive optical element 71 (DOE) is used as the optical element constituting the illumination intensity distribution control unit 7. The diffractive optical element 71 is formed by forming a fine undulation pattern with dimensions equal to or smaller than the wavelength of the light on the surface of a substrate made of a material that transmits the incident light. For ultraviolet light, fused silica is used as the material that transmits the incident light. To suppress light attenuation due to passage through the diffractive optical element 71, it is preferable to use a material that is coated with an anti-reflection film. The fine undulation pattern is formed by lithography. By passing the light that has become quasi-parallel after passing through the beam expander 5 through the diffractive optical element 71, an illumination intensity distribution on the sample surface corresponding to the undulation pattern of the diffractive optical element 71 is formed. The undulating shape of the diffractive optical element 71 is designed and manufactured to a shape calculated based on Fourier optics theory so that the illumination intensity distribution formed on the sample surface becomes a long, uniform distribution within the incident plane. The optical element provided in the illumination intensity distribution control unit 7 is equipped with a translation adjustment mechanism on two or more axes and a rotation adjustment mechanism on two or more axes so that the relative position and angle with respect to the optical axis of the incident light can be adjusted. In addition, a focus adjustment mechanism for movement in the optical axis direction is provided. Note that alternative optical elements having the same function as the diffractive optical element 71 may also be used, such as an aspherical lens, a combination of a cylindrical lens array and a cylindrical lens, or a combination of a light pipe and an imaging lens.

[0027] Next, we will explain modified illumination intensity distributions formed on the sample surface by the illumination unit 101. Instead of the illumination intensity distribution described above that is elongated (linear) in one direction and has substantially uniform intensity in the longitudinal direction, an illumination intensity distribution with a Gaussian distribution in the longitudinal direction can also be used. A Gaussian distribution illumination that is elongated in one direction can be formed by configuring the illumination intensity distribution control unit 7 to include a spherical lens and forming an elliptical beam elongated in one direction using the beam expander 5, or by configuring the illumination intensity distribution control unit 7 with multiple lenses including a cylindrical lens. By placing some or all of the spherical or cylindrical lenses in the illumination intensity distribution control unit 7 parallel to the sample surface, an illumination intensity distribution that is elongated in one direction on the sample surface and narrow in the perpendicular direction is formed. Compared to creating a uniform illumination intensity distribution, this method has the advantages of less fluctuation in the illumination intensity distribution on the sample surface due to fluctuations in the state of light incident on the illumination intensity distribution control unit 7, resulting in a more stable illumination intensity distribution. It also has the advantage of higher light transmittance and greater efficiency compared to using a diffractive optical element or microlens array for the illumination intensity distribution control unit 7.

[0028] The state of the illumination light in the illumination unit 101 is measured by the beam monitor 22. The beam monitor 22 measures and outputs the position and angle (traveling direction) of the illumination light that has passed through the exit light adjustment unit 4, or the position and wavefront of the illumination light that is incident on the illumination intensity distribution control unit 7. The position of the illumination light is measured by measuring the center of gravity of the light intensity of the illumination light. Specific position measurement means include an optical position sensor (PSD: Position Sensitive Detector) or an image sensor such as a CCD sensor or CMOS sensor. The angle of the illumination light is measured by an optical position sensor or image sensor installed at a position farther away from the light source than the position measurement means, or at the position where the light is focused by a collimating lens. The illumination light position and illumination light angle detected by the sensor are input to the control unit 53 and displayed on the display unit 54. If the illumination light position or angle deviates from the predetermined position or angle, the exit light adjustment unit 4 adjusts it so that it returns to the predetermined position.

[0029] The wavefront measurement of the illumination light is performed to measure the parallelism of the light incident on the illumination intensity distribution control unit 7. If the wavefront measurement reveals that the light incident on the illumination intensity distribution control unit 7 is not quasi-parallel but is diverging or converging, the light can be made closer to quasi-parallel by displacing the lens group of the upstream beam expander 5 in the optical axis direction. Furthermore, if the wavefront measurement reveals that the wavefront of the light incident on the illumination intensity distribution control unit 7 is partially tilted, a spatial light phase modulator, which is a type of spatial light modulator (SLM), can be inserted upstream of the illumination intensity distribution control unit 7 to provide an appropriate phase difference at each position on the light beam cross section so as to flatten the wavefront, thereby making the illumination light closer to quasi-parallel. The wavefront accuracy measurement and adjustment means described above suppresses the wavefront accuracy (deviation from a predetermined wavefront (design value or initial state)) of the light incident on the illumination intensity distribution control unit 7 to λ / 10 rms or less.

[0030] The illumination intensity distribution on the sample surface adjusted by the illumination intensity distribution control unit 7 is measured by the illumination intensity distribution monitor 24. As shown in FIG. 1 , even when vertical illumination is used, the illumination intensity distribution on the sample surface adjusted by the illumination intensity distribution control unit 7v is also measured by the illumination intensity distribution monitor 24. The illumination intensity distribution monitor 24 focuses an image of the sample surface on an image sensor such as a CCD sensor or a CMOS sensor via a lens, and detects it as an image. The image of the illumination intensity distribution detected by the illumination intensity distribution monitor 24 is processed by the control unit 53, and the position of the center of gravity of the intensity, the maximum intensity, the position of the maximum intensity, the width and length of the illumination intensity distribution (the width and length of the illumination intensity distribution region where the intensity is equal to or greater than a predetermined intensity or a predetermined ratio of the maximum intensity value), etc. are calculated and displayed on the display unit 54 together with the contour shape and cross-sectional waveform of the illumination intensity distribution.

[0031] When performing oblique incidence illumination, variations in the height of the sample surface cause variations in the position of the illumination intensity distribution and disturbances in the illumination intensity distribution due to defocusing. To prevent this, the height of the sample surface is measured, and if the height is shifted, the deviation is corrected by adjusting the height using the illumination intensity distribution control unit 7 or the Z axis of the stage 104.

[0032] The illuminance distribution shape (illumination spot 20) formed on the sample surface by the illumination unit 101 and the sample scanning method will be described with reference to FIGS. 8 and 9. FIG.

[0033] As shown in Figure 8, the sample 1 is assumed to be a circular semiconductor silicon wafer. The stage 104 includes a translation stage, a rotation stage, and a Z-stage for adjusting the height of the sample surface (none of which are shown). As mentioned above, the illumination spot 20 has an illumination intensity distribution that is long in one direction, which direction is designated S2, and a direction substantially perpendicular to S2 is designated S1. The rotational motion of the rotation stage scans in the circumferential direction S1 of a circle centered on the rotation axis of the rotation stage, and the translational motion of the translation stage scans in the translation direction S2 of the translation stage.

[0034] As shown in FIG. 9, while the sample is rotated once by scanning in the scanning direction S1, the illumination spot 20 is scanned in the scanning direction S2 by a distance equal to or less than the longitudinal length of the illumination spot 20, so that the illumination spot traces a spiral trajectory T on the sample 1, and the entire surface of the sample 1 is scanned.

[0035] Next, a description will be given of pupil branching of the detection unit 102. A plurality of detection units 102 are arranged so as to detect scattered light in a plurality of directions emanating from the illumination spot 20. Examples of the arrangement of the detection units 102 relative to the sample 1 and illumination spot 20 will be described with reference to FIGS.

[0036] FIG. 10 shows a side view of the arrangement of the detection unit 102. The angle between the normal to the sample 1 and the detection direction (the direction toward the center of the detection aperture) of the detection unit 102 is defined as the detection zenith angle. The detection unit 102 is configured using a high-angle detection unit 102h with a detection zenith angle of 45 degrees or less, a low-angle detection unit 102l with a detection zenith angle of 45 degrees or more, and a high-angle detection unit 102h' and a low-angle detection unit 102l' that are positioned symmetrically with respect to the normal to the sample 1. The high-angle detection unit 102h and the low-angle detection unit 102l each detect scattered light using a common objective lens, which splits the scattered light at the Fourier plane of the objective lens. The detection unit 102 also consists of multiple detection units to cover scattered light in multiple directions.

[0037] FIG. 11 shows a plan view of the arrangement of the detection unit 102. The angle between the direction of travel of the oblique incident illumination and the detection direction in a plane parallel to the surface of the sample 1 is defined as the detection azimuth angle. The detection unit 102 suitably comprises a front detection unit 102f, a rear detection unit 102b, and a front detection unit 102f' and a rear detection unit 102b' that are positioned symmetrically relative to the front detection unit 102f and rear detection unit 102b' with respect to the illumination incident plane. For example, the front detection unit 102f is installed with a detection azimuth angle of 0 degrees or more and 90 degrees or less, and the rear detection unit 102b is installed with a detection azimuth angle of 90 degrees or more and 180 degrees or less. A low-angle detection unit and a high-angle detection unit are provided for each detection azimuth. This is not a limitation, and the number and positions of the detection units may be changed as appropriate.

[0038] FIG. 12 is a diagram illustrating the configuration of the detection unit in this embodiment. In FIG. 12, scattered light generated from the illumination spot 20 is collected by an objective lens 1021. To efficiently detect scattered light, the detection NA of the objective lens 1021 is preferably set to 0.3 or greater. The lower end of the objective lens 1021 is cut out as necessary to prevent interference with the sample 1. An imaging lens 1023 forms an image of the illumination spot 20 at the position of an aperture 1024. The aperture 1024 is set to pass only light from the region of the image of the illumination spot 20 that is to be detected by the photoelectric conversion unit 103. When the illumination spot 20 has a Gaussian distribution profile in the S2 direction, the aperture 1024 passes only the central portion of the Gaussian distribution where the light intensity is strong in the S2 direction, and blocks the regions at the beam edges where the light intensity is weak. Furthermore, the size of the image formed in the S1 direction is set to be approximately the same as that of the illumination spot 20, thereby suppressing disturbances such as air scattering that occur when illumination passes through air. 1025 is a condenser lens that re-condenses the image of the aperture 1024 that has been formed. The Fourier plane of the objective lens 1021 is relayed by the condenser lens 1025, and a polarization control filter 1022 is disposed on the Fourier plane. As the polarization control filter 1022, for example, a half-wave plate whose rotation angle can be controlled by a drive mechanism such as a motor is used.

[0039] The pupil plane is relayed by a relay lens composed of an imaging lens 1023, a condenser lens 1025, an imaging lens 10213, and a condenser lens 10214, and a knife edge 1026 (a branching optical element) is installed on the pupil plane. The knife edge 1026 branches the scattered light condensed into a high-angle detection unit 102h having a detection zenith angle of 45 degrees or less and a low-angle detection unit 102l having a detection zenith angle of 45 degrees or more. The angles between the chief ray of the branched scattered light and the normal to the sample surface are different. In FIG. 12 , the angle between the chief ray 10218 of the scattered light detected by the low-angle detection unit 102l and the normal 10217 to the sample surface is larger than the angle between the chief ray 10219 of the scattered light detected by the high-angle detection unit 102h and the normal 10217 to the sample surface. The branching angle of the detection zenith angle is not necessarily 45 degrees and can be changed as appropriate. Furthermore, a polarizing beam splitter 1027 is installed on each pupil plane of the light that has been relayed and branched by the imaging lens 10215 and the condenser lens 10216. This allows the light whose polarization direction has been converted by the polarization control filter 1022 to be separated according to the polarization direction. In this case, the low-angle detection unit 102l performs detection using the photoelectric conversion units 103-1 and 103-3. Furthermore, the high-angle detection unit 102h performs detection using the photoelectric conversion units 103-2 and 103-4. Reference numeral 1028 denotes an imaging lens that forms an image of the illumination spot 20 on the photoelectric conversion unit 103. A cylindrical lens can also be used as the imaging lens 1028 to form an image in only one direction.

[0040] In this embodiment, the combination of the polarization control filter 1022 and the polarizing beam splitter 1027 allows the photoelectric conversion unit 103 to detect only light of a specific polarization direction from the light collected by the polarization control filter 1021. However, as an alternative, for example, the polarization control filter 1022 can be a wire grid polarizer with a transmittance of 80% or more, and only light of a desired polarization direction can be extracted without using the polarization beam splitter 1027. Alternatively, a wave plate that attenuates only the background scattered light by utilizing the difference in polarization between the background scattered light and the scattered light generated by defects can be used as the polarization control filter 1022. In this case, a segmented wave plate must be used because the polarized components attenuated in the Fourier plane are different. When blocking polarized components that do not need to be detected, a beam diffuser can be used instead of the imaging lens 1028 to prevent unnecessary light from becoming stray light.

[0041] Next, a configuration in which the photoelectric conversion unit 103 is tilted with respect to the optical axis will be described. FIG. 13 is a diagram showing the arrangement of the illumination spot and the photoelectric conversion unit in this embodiment. FIG. 14 is a view of FIG. 13 as viewed from above. As shown in FIGS. 13 and 14 , the optical axis 121 is tilted with respect to the normal direction of the light-receiving unit 1031. The light-receiving unit 1031 of the photoelectric conversion unit 103 is arranged parallel to the longitudinal direction δ of the optical image 25 formed on the light-receiving unit 1031 by the detection unit 102, based on the linear illumination spot 20 irradiated on the surface of the sample 1. The pair of cylindrical lenses 10210 and 10211 form a cylindrical beam expander, which makes the spread of the optical image 25 formed by the illumination spot 20 in the short-side direction γ smaller than the spread of this optical image 25 in the longitudinal direction.

[0042] The photoelectric conversion unit 103 captures the optical image 25 and outputs it as an electrical signal. The photoelectric conversion unit 103 includes an array of light receiving units and an anti-reflection film at a position conjugate with the illumination spot irradiated on the surface of the sample 1. The light receiving surface of the photoelectric conversion unit 103 is not conjugate with the sample surface in the short-side direction γ. However, because the short-side direction γ is also the short-side direction of the illumination spot 20, the image height of the optical image 25 is low and almost no defocusing occurs. Therefore, by increasing the imaging magnification of the optical image 25 in the short-side direction γ, it is possible to reduce the variation in the angle of incidence on the light receiving unit 1031.

[0043] 15 is a schematic diagram of the three-dimensional arrangement of the sample 1 and the detection unit 102 in this embodiment. As shown in FIG. 15, the optical axis 121 of the detection unit 102, shown with reference to the objective lens 1021, is inclined at an angle θ with respect to the normal direction Z of the sample 1. The projection of the optical axis 121 onto the sample surface is inclined at an angle φ with respect to the longitudinal direction S2 of the illumination spot 20.

[0044] If an optical axis 121 that detects light from the detection unit 102 is shifted by an angle θ with respect to the normal direction of the sample 1 and by an angle φ with respect to the longitudinal direction of the illumination spot 20, then in three-dimensional space, this optical axis 121 is represented by a vector v0 of the following equation (1):

[0045]

[0046] The angle α formed by this vector v0 and the longitudinal direction of the illumination spot 20 is calculated by the following equation (2).

[0047]

[0048] At this time, the defect inspection device 100 detects a section of 2L in the longitudinal direction of the illumination spot 20 using the photoelectric conversion unit 103. Depending on the position x from the center of the field of view, the working distance (the distance between the sample 1 and the detection unit 102) changes as ΔZ shown in the following equation (3).

[0049]

[0050] The imaging magnification M is determined by the objective lens 1021 and the imaging lens 1028. The position of the image formed here is expressed by the following equation (4).

[0051]

[0052] Generally, a line sensor is positioned so as to be perpendicular to the optical axis, which is the center of the light beam emitted by the imaging lens. However, in this embodiment, by tilting the photoelectric conversion unit 103, image detection without defocusing is achieved regardless of changes in the field of view at the working distance. In this case, the optical axis 121 incident on the photoelectric conversion unit 103 and the pixel array vector v1 on the light receiving surface are set so as to be within the plane spanned by the longitudinal direction of the illumination spot 20 and the vector v0, and the angle β between the vector v1 and the vector v0 satisfies the following equation (5).

[0053]

[0054] Here, the angle α is the angle between the vector v2 and the vector v0, and satisfies the formula (6).

[0055]

[0056] According to equation (5), as the imaging magnification M increases, the angle β between vector v0 and vector v1 decreases, and the angle of incidence increases. When M = 2, the light ray with the largest angle of incidence enters the photoelectric conversion unit 103 at an angle close to 90 degrees. The absorptance of the anti-reflection film 1033 of the photoelectric conversion unit 103 depends on the angle of incidence, and the absorptance becomes very small at angles of incidence close to 90 degrees. To prevent this, the imaging magnification M is set to 2x or less.

[0057] Under these conditions, it is possible to maximize the angle between the vector v1 and the optical axis 121 incident on the photoelectric conversion unit 103 from the imaging lens 1028. When the numerical aperture of the incident light beam on the objective lens 1021 is N, the spread of the light beam emitted to the photoelectric conversion unit 103 is calculated by multiplying the spread of the light beam emitted to the imaging lens 1028 by the reciprocal of the imaging magnification M.

[0058] As described above, when a lens with a large numerical aperture is used as the objective lens 1021 to set the imaging magnification M to 2x or less, light is incident on the photoelectric conversion unit 103 from a wide range of directions. If the range of angles of incidence of light on the photoelectric conversion unit 103 is wide due to the characteristics of the anti-reflection film 1033, the light absorption rate of the photoelectric conversion unit 103 decreases, making it difficult to achieve high sensitivity. For this reason, the imaging magnification M is set to 1x or more. As a result, the angle β becomes smaller than the angle α, and typically becomes smaller by 5 degrees or more when a magnification of about 1.3x is applied.

[0059] 16 is a cross-sectional view of the image sensor 1036 that constitutes the photoelectric conversion unit 103 in this embodiment. In FIG. 16, the image sensor 1036 is configured by laminating, in order from the surface, an anti-reflection film 1033, a light receiving unit 1031, and a wiring unit 1032. Incident light beams 122A to 122C are light beams that enter the image sensor 1036.

[0060] Incident light 122A is light on the optical axis 121 shown in FIGS. 13 and 14. Incident light 122B and 122C are light incident at angles different from the optical axis 121. The anti-reflection film 1033 is a film for preventing surface reflection of each of the incident light 122A to 122C. The light receiving unit 1031 is in an array shape, and performs photoelectric conversion for each partitioned region, i.e., each pixel. The wiring unit 1032 independently extracts the electricity output by the light receiving unit 1031 to the outside. A sensor with such a structure in which the light receiving unit 1031 is located closer to the light incident side than the wiring unit 1032 is known as a backside illumination sensor. In this embodiment, the incident light is incident at a predetermined angle from the normal direction of the light receiving unit. Therefore, in CMOS image sensors with a structure known as FSI (Front Side Illumination), in which the wiring is on the light incident side, light is absorbed by the wiring, and not enough light can be incident on the light receiving section.

[0061] As shown by incident light beams 122A to 122C, light beams are incident from various directions on the light receiving section 1031. Therefore, the anti-reflection film 1033 must have a high absorptance for these incident light beams 122A to 122C in order to obtain good sensitivity.

[0062] 17 is a graph showing the characteristics of an anti-reflection coating 1033 formed from a single layer of hafnium oxide (HfO2) with a thickness of 25 nm. The horizontal axis of the graph represents the angle of incidence, and the vertical axis of the graph represents the absorptance. Curve 10333 represents the absorptance characteristics for S-polarized light. Curve 10334 represents the absorptance characteristics for P-polarized light. The absorptance of P-polarized light decreases as the angle of incidence increases, but the absorptance drops to 0.5 when the angle of incidence is around 60 degrees.

[0063] Furthermore, the absorption rate for S-polarized light increases up to an incident angle of approximately 70 degrees, and is 70% or higher in the incident angle range of 0 to 80 degrees. However, the photoelectric conversion units 103-1 and 103-2 must be tilted by a predetermined angle to achieve image detection without defocusing, regardless of changes in the working distance within the field of view. In other words, it is desirable to tilt the normal to the light-receiving surface of the photoelectric conversion unit 103-1 by, for example, 10 to 80 degrees from the optical axis 121-1 of the detection unit 102-1.

[0064] Fig. 18 is a schematic diagram of the sample height detection unit in this embodiment. In Fig. 18, the sample height detection unit 106 uses height sensors 1061-1, 1061-2, and 1061-3, such as laser interferometers, to measure the height of the sample at multiple points in real time during inspection. By measuring the height displacement of the inspection area in advance before detecting scattered light in the inspection area, delays during inspection can be prevented.

[0065] When performing oblique incidence illumination, the height displacement of the sample surface causes a displacement of the illumination intensity distribution position and disturbance of the illumination intensity distribution due to defocusing. In this embodiment, to suppress this, the height of the sample surface is measured, and if the height is shifted, the illumination intensity distribution control unit 7 or the height adjustment on the Z axis of the stage 104 is used to correct the image shift caused by the displacement of the sample surface.

[0066] During measurement, the height of the sample surface in the Z-axis direction displaces by several tens to several hundreds of μm at a frequency of several tens to several hundreds of Hz. Causes of this displacement include misalignment of the rotation axis and vibration of the stage. This Z-axis displacement of the sample surface displaces the position of the image formed on the sensor surface. The displacement amount of each divided image due to the Z-axis displacement Δw is given by equation (7):

[0067]

[0068] It is proportional to Δu and differs for each detection elevation angle.

[0069] 19 to 23 are diagrams illustrating the relationship between height-direction displacement of the sample surface and image position shift. As shown in FIG. 19, when the height of the sample surface changes and the observed foreign particle 1041d changes to 1041e, the image of foreign particle 1041d is imaged as shown in FIG. 20 in photoelectric conversion unit 103-2, where scattered light with a large detection point apex angle is imaged. However, when the sample height changes, the image of foreign particle 1041e is imaged as shown in FIG. 21. The horizontal axis of each graph represents the distance in the δ direction on the light-receiving surface of photoelectric conversion unit 103. The image positions of 10421d and 10421e on the respective light-receiving surfaces are significantly different. In contrast, in the photoelectric conversion unit 103-1 where scattered light with a small detection point apex angle is imaged, the image of foreign particle 1041d becomes image 10422d in Figure 22, whereas the image of foreign particle 1041e when the sample height is displaced becomes image 10422e in Figure 23. In this case, the positional deviation is smaller compared to the divided images with a small detection elevation angle, depending on the direction of the chief ray. As a result, when all the divided images are integrated, the image becomes blurred, resulting in a decrease in sensitivity.

[0070] 24 is a functional block diagram of the signal processing unit 105 in this embodiment. The sample height detection unit 106 (for example, an optical sensor) detects the Z-axis displacement of the detection area on the sample surface in real time and stores it in memory 241.

[0071] The imaging position calculation unit 242 calculates the deviation of the imaging position from the Z-axis displacement of the detection area. For one or more of the detection point apex angles 102l with large detection point apex angles and the detection point apex angles 102h with small detection point apex angles that respectively constitute the detection units 102f, 102b, 102f', and 102b' shown in Figure 11, the imaging signals in the direction of the large detection point apex angle and the direction of the small detection point apex angle are divided into two or more groups and integrated by the photoelectric conversion unit 103.

[0072] The imaging position correction unit 243 corrects the imaging position shift of signals with large imaging position shifts (i.e., groups containing many signals of scattered light with large detection point apex angles), and the signal integration unit 244 integrates the images of all groups. This prevents a decrease in sensitivity due to imaging position shifts. The mechanism in Figure 24 can operate in real time during inspection at a frequency of several tens to several hundreds of Hz, preventing a decrease in sensitivity to Z-axis displacement due to inspection.

[0073] The signal combining unit 244 can also operate as follows. The signal combining unit 244 groups scattered light whose detected elevation angles are similar (the difference between the detected elevation angles is within a predetermined range) to form one or more scattered light groups. The signal combining unit 244 first combines the images of the members of each group to generate the same number of temporary combined images as the number of groups. The imaging position correcting unit 243 corrects the imaging position for each temporary integrated image (i.e., group). The signal combining unit 244 generates a final integrated image by re-integrating each temporary integrated image after the imaging position has been corrected.

[0074] To summarize the above, the defect inspection device 10 is configured to detect and integrate foreign particles at the same position on the sample 1 on the same coordinates on the light-receiving surface of the photoelectric conversion units 103-1 and 103-2 after branching at the knife edge 1026, for scattered light having similar angles of incidence with respect to the condenser lens 1025, and to correct image position shift to a greater extent for scattered light with a larger apex angle of the detection point. This makes it possible to accurately detect even minute defects and accurately correct image shift caused by displacement of the sample surface in the Z direction.

[0075] As described above, according to this embodiment, by splitting the optical path using an optical splitting means placed at or near the pupil position of the focusing means, it is possible to discriminate between scattered light and background scattered light. Furthermore, the photoelectric conversion unit is placed conjugate to the sample and tilted with respect to the optical axis, enabling blur-free imaging and detection in the longitudinal direction of the illumination and imaging and detection from a direction not perpendicular to the longitudinal direction of the illumination. This makes it possible to position the imaging and detection system without being restricted by the azimuth angle, making it possible to image almost the entire light scattered from minute defects present on the sample surface, thereby achieving high-speed and high-sensitivity detection.

[0076] In the first embodiment, the signal processing unit 105 corrects the image position shift. In the present embodiment, however, the position of the optical elements of the detection optical system is adjusted to correct a change in the PSF (Point Spread Function) of the image, which is an image blur.

[0077] 25 is a diagram showing the configuration of the detection unit 102 in this embodiment, and is a diagram for explaining the details of the height direction displacement of the sample surface and the optical element adjustment mechanism. In FIG. 25, the same components as those in FIG. 19 are assigned the same reference numerals, and their explanation will be omitted.

[0078] Due to differences in the chief ray, even if the displacement amount of the sample height is the same, the PSFs are significantly different, as can be seen by comparing the image 10421e in Figure 21 with the image 10422e in Figure 23. This difference in PSF causes a decrease in sensitivity during integration.

[0079] 25, a mechanism 10212 for adjusting the position along the optical axis is attached to one or more of the imaging lens 1028 and the photoelectric conversion units 103-1 and 103-2. For example, a micrometer with a piezoelectric motor can be used as the mechanism 10212 for adjusting the position.

[0080] 26 is a functional block diagram of the signal processing unit 105 in this embodiment. The adjustment amount calculation unit 261 calculates the adjustment distance in the optical axis direction from the Z-axis displacement of the sample surface stored in the memory 241, and the detection system adjustment control unit 262 adjusts a part of the detection unit 102 (one or more optical elements) in the optical axis direction. This reduces the difference in the changes in PSF due to the Z-axis displacement of the sample surface, reduces blurring of the integrated image, and prevents a decrease in sensitivity.

[0081] In FIG. 25 , the position of which optical element is to be adjusted can be determined as follows. When the optical system from the objective lens 1021 to the imaging lens 1028 is considered to be a composite lens, the behavior of the composite lens can be calculated. Therefore, when the position of any optical element is moved, the behavior of the composite lens resulting from that movement can also be calculated. The adjustment amount calculation unit 261 can calculate each PSF change by, for example, randomly selecting one or more optical elements from the objective lens 1021 to the photoelectric conversion unit 103 and calculating the behavior of the composite lens when that element is moved. The adjustment amount calculation unit 261 can determine the optical element whose position should be adjusted and the amount of positional movement by searching for a combination of optical elements and position adjustment amounts that minimizes each PSF change. The search may be performed randomly, or a search algorithm based on an appropriate evaluation function may be used. Alternatively, if the optical elements whose PSFs should be preferentially corrected are predetermined (for example, by prioritizing optical elements with smaller sizes), the positions of those optical elements may be adjusted in order.

[0082] The signal processing unit 105 may simultaneously adjust the position of the optical elements and perform the signal processing described in Example 1 to prevent a decrease in sensitivity. A functional block diagram of the signal processing unit in this case is shown in FIG. 27. The imaging position correction unit 243 and the adjustment amount calculation unit 261 determine the correction amount and adjustment amount for each sample height in advance. The correction amount and adjustment amount are set so that the imaging position shift and PSF change caused by changes in sample height are minimized, thereby preventing a decrease in sensitivity.

[0083] In this embodiment, the mitigation of sensitivity changes caused by sample height displacement using a cross-correlation filter will be described.

[0084] Figures 28 and 29 show the characteristics of the cross-correlation filter in this embodiment. Figure 28 shows a cross-correlation filter corresponding to the image 10421e of scattered light with a large detection point apex angle and a large PSF change, while Figure 29 shows a cross-correlation filter corresponding to the image 10422e of scattered light with a small detection point apex angle. These are 4σ Gaussian fitting curves for each image, and are convolved with the signal after the imaging position has been corrected by the imaging position correction unit 243. This convolution is performed similarly before and after the sample height displacement. This blurs the signal intensities of the images 10421d and 10422d before the sample height displacement, but reduces the difference in signal intensity before and after the sample height displacement. In other words, the signal processing unit has a cross-correlation filter, which is a mechanism for reducing the difference in signal intensity between when the image is defocused and when it is in focus.

[0085] The shape of this cross-correlation filter can be arbitrarily determined by checking in advance the change in the image due to the height displacement of the sample for each detection point apex angle and detection azimuth angle. In addition, by arbitrarily determining the shape of the cross-correlation filter for the amount of height displacement of the sample detected by the sample height detection unit 106 and multiplying it by the signal of each image, it is possible to reduce the difference in signal intensity due to the height displacement of the sample.

[0086] FIG. 30 is a functional block diagram of the signal processing unit in this embodiment. In FIG. 30, the specimen height detection unit 106 (e.g., an optical sensor) detects Z-axis displacement of the detection area on the specimen surface in real time and stores the detected displacement in memory 241. The signals, for which the imaging positions have been corrected by the imaging position correction unit 243, are convolved with a cross-correlation filter by the filter processing unit 245. The convolved signals are integrated by the signal integration unit 244. It is also possible to select a cross-correlation filter according to the amount of specimen height displacement by the filter selection unit 246, and perform processing in the filter processing unit 245 using the selected filter. The mechanism in FIG. 30 can operate in real time at a frequency of several tens to several hundreds of Hz during inspection, preventing sensitivity changes before and after Z-axis displacement due to inspection.

[0087] In Examples 1 to 3, the detection system is disposed obliquely relative to the sample, but the detection system can also be disposed perpendicular to the sample. In this case, the photoelectric conversion unit does not need to be oblique to the optical axis, and is disposed on a plane conjugate with the sample.

[0088] Fig. 31 is a diagram showing the configuration of the detection unit in this embodiment. In Fig. 31, the same components as in Fig. 12 are given the same reference numerals, and their description will be omitted. Note that 1029 is a beam diffuser that prevents unnecessary light from becoming stray light.

[0089] In Figure 31, as in Figure 12, the scattered light is split into three regions for each detection point apex angle and detected by each. In the example shown in Figure 31, the detected scattered light is split into three regions for each detection point apex angle and detected by photoelectric conversion units 103-1, 103-2, and 103-3, respectively; however, the number of branches can be determined arbitrarily, and the scattered light can be split into two or more regions. In this configuration, as in Examples 1 to 3, image shift and PSF changes occur due to displacement of the sample surface, and these image shift and PSF changes differ for each detection point apex angle. To prevent a decrease in sensitivity due to these factors, correction is performed using the configurations shown in Examples 1 to 3.

[0090] According to this embodiment, the photoelectric conversion unit 103 does not need to be disposed at an angle to the optical axis, so that a CCD or TDI can be used in addition to a CMOS sensor.

[0091] In this embodiment, a configuration in which the second and third embodiments are performed simultaneously will be described.

[0092] 32 is a functional block diagram of the signal processing unit in this embodiment. The reduction in the difference in signal intensity due to the displacement of the sample height by the cross-correlation filter according to Embodiment 3 and the reduction in the difference in signal intensity due to the displacement of the sample height by adjusting the optical element according to Embodiment 2 are combined to suppress the reduction in detection sensitivity. This allows the amount of adjustment of the optical element required to prevent the desired reduction in sensitivity to be smaller than when only Embodiment 2 is used.

[0093] In the first embodiment, a configuration as shown in Fig. 33 can also be considered for the example of the detection unit shown in Fig. 12. That is, as shown in Fig. 33, one relay on the Fourier plane consisting of the imaging lens 10213 and the condenser lens 10214 in Fig. 12 is omitted, and the polarization control filter 1022 and the knife edge 1026 are arranged close to each other. This makes it possible to shorten the length of the entire optical system.

[0094] Although the embodiments have been described above, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0095] 2: laser light source, 5: beam expander, 6: polarization control unit, 7: illumination intensity distribution control unit, 24: illumination intensity distribution monitor, 10: defect inspection device, 53: control unit, 54: display unit, 55: input unit, 101: illumination unit, 102: detection unit, 103: photoelectric conversion unit, 104: stage, 105: signal processing unit, 106: specimen height detection unit, 1021: objective lens, 1022: polarization control filter, 102 3: imaging lens, 1024: aperture, 1025: condensing lens, 1026: knife edge, 1027: polarizing beam splitter, 1028: imaging lens, 1029: beam diffuser, 10210, 10211: cylindrical lens, 10212: position adjusting mechanism, 10213: imaging lens, 10214: condensing lens, 10215: imaging lens, 10216: condensing lens

Claims

1. A defect inspection device comprising: an illumination unit which irradiates a sample with light emitted from a light source; a detection unit which detects scattered light generated from the sample; a sample height detection unit which measures the amount of sample movement in a direction perpendicular to the surface of the sample; a photoelectric conversion unit which converts the scattered light detected by the detection unit into an electrical signal; and a signal processing unit which processes the electrical signal converted by the photoelectric conversion unit to detect defects in the sample, wherein the detection unit has a mechanism which adjusts its position after branching an aperture in response to the amount of movement of the sample surface obtained by the sample height detection unit, and a mechanism which branches an aperture to separate and detect the scattered light generated from the sample at a plurality of detection elevation angles, and wherein the signal processing unit has a mechanism which corrects the positions of a plurality of images formed by branching an aperture in response to the amount of movement of the sample surface obtained by the sample height detection unit.

2. A defect inspection device as described in claim 1, wherein the detection unit is arranged in an oblique direction relative to the sample, and the photoelectric conversion unit has a mechanism in which the light receiving surface is arranged conjugate to the sample and inclined relative to the optical axis.

3. A defect inspection device according to claim 1, wherein the signal processing section has a different filter processing mechanism for each aperture and a mechanism for suppressing a decrease in sensitivity due to wafer surface vibration.

4. A defect inspection device as described in claim 3, characterized in that the filter processing mechanism has a mechanism for correcting the residual error of the detection unit correction corresponding to the amount of variation in the surface of the sample acquired by the sample height detection unit.

5. A defect inspection device according to claim 1, wherein the signal processing section has a mechanism for reducing the difference between signals when defocused and when focused.

6. A defect inspection device according to claim 2, further comprising a mechanism for measuring the deviation of the sample surface in the vertical direction.

7. A defect inspection device comprising: an illumination unit which irradiates a sample with light emitted from a light source; a detection unit which detects scattered light generated from the sample; a sample height detection unit which measures the amount of movement of the sample in a direction perpendicular to the surface of the sample; a photoelectric conversion unit which converts the scattered light detected by the detection unit into an electrical signal; and a signal processing unit which processes the electrical signal converted by the photoelectric conversion unit to detect defects in the sample, wherein the detection unit is arranged in an oblique direction with respect to the sample and has a mechanism which branches an aperture to separate and detect the scattered light generated from the sample at a plurality of detection elevation angles, and the photoelectric conversion unit has a light receiving surface which is arranged conjugate to the sample and inclined with respect to the optical axis.

8. A defect inspection device as described in claim 7, wherein the detection unit has a mechanism for adjusting the position after dividing an opening in response to the amount of variation in the sample surface acquired by the sample height detection unit, and the signal processing unit has a mechanism for correcting the positions of multiple images formed by dividing the opening in response to the amount of variation in the sample surface acquired by the sample height detection unit.

9. A defect inspection device according to claim 8, wherein the signal processing section has a different filter processing mechanism for each aperture and a mechanism for suppressing a decrease in sensitivity due to wafer surface vibration.

10. A defect inspection device as described in claim 9, characterized in that the filter processing mechanism has a mechanism for correcting the residual error of the detection unit correction corresponding to the amount of variation in the surface of the sample acquired by the sample height detection unit.

11. A defect inspection device according to claim 8, wherein the signal processing section has a mechanism for reducing the difference between signals when defocused and when focused.

12. A defect inspection device according to claim 7, further comprising a mechanism for measuring deviation of the sample surface in the vertical direction.

13. An optical system used in the detection section of the defect inspection device described in claim 7, comprising: an objective lens that collects the scattered light from the sample arranged on a first surface; a branching optical element that is arranged on a second surface that forms a pupil with respect to the first surface by the objective lens and a relay lens, and that branches the scattered light collected by the objective lens into first scattered light and second scattered light; a first imaging optical system that collects the first scattered light branched by the branching optical element and guides it to a first photoelectric conversion section; and a second imaging optical system that collects the second scattered light and guides it to a second photoelectric conversion section, wherein the optical path of the first scattered light on the first surface side is inclined at a first angle with respect to the normal to the first surface, and the optical path of the second scattered light on the first surface side is inclined at a second angle larger than the first angle with respect to the normal to the first surface.

14. A defect inspection method comprising the steps of: irradiating a sample with light emitted from a light source; measuring the amount of variation of the sample in a direction perpendicular to the surface of the sample; dividing an aperture corresponding to the measured amount of variation of the sample surface and then adjusting its position; separating and detecting scattered light generated from the sample at a plurality of detection elevation angles; converting the detected scattered light into an electrical signal; correcting the positions of multiple images of the detected scattered light in relation to the converted electrical signal in accordance with the measured amount of variation of the sample surface; and detecting defects in the sample.

15. A defect inspection method comprising the steps of: irradiating a sample with light emitted from a light source; detecting scattered light generated from the sample by dividing an aperture in a detection unit arranged in an oblique direction with respect to the sample, separating and detecting the scattered light generated from the sample at a plurality of detection elevation angles; measuring the amount of movement of the sample in a direction perpendicular to the surface of the sample; converting the detected scattered light into an electrical signal by a photoelectric conversion unit whose light-receiving surface is arranged conjugate to the sample and inclined with respect to the optical axis; and processing the converted electrical signal to detect defects in the sample.

Images