Defect inspection device and optical system

Abstract

This defect inspection device includes: an illumination unit that irradiates a sample with illumination light emitted from a light source; a detection unit that is disposed in an oblique direction with respect to the sample and detects scattered light generated from the sample; a pupil division mechanism that divides the pupil of the detection unit into a first detection angle and a second detection angle; a first photoelectric conversion unit that converts scattered light at the first detection angle detected by the detection unit into an electric signal; a second photoelectric conversion unit that converts scattered light at the second detection angle detected by the detection unit into an electric signal; and a signal processing unit that processes the electric signals converted by the first photoelectric conversion unit and the second photoelectric conversion unit to detect a defect in the sample. The pupil division mechanism divides the pupil such that the pupil allocation corresponds to the object being inspected or the inspection conditions.

Description

Defect inspection device and optical system

[0001] The present invention relates to a defect inspection device and an optical system of a detection unit thereof, for example, a defect inspection device that inspects minute defects present on a sample surface and determines and outputs the position, type, and size of the defects, and the optical system of the detection unit thereof.

[0002] In manufacturing lines for semiconductor substrates, thin film substrates, etc., inspections are carried out for defects present on the surfaces of semiconductor substrates, thin film substrates, etc., in order to maintain and improve product yields. Known examples of conventional defect inspection techniques include those disclosed in Japanese Patent Application Publication No. 2014-504370 (Patent Document 1).

[0003] Patent Document 1 describes a configuration "configured to divide the collection numerical aperture (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." The document 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 scattered light."

[0004] In Patent Document 2, in order to detect scattered light generated from minute defects, multiple detection systems are arranged in a direction tilted relative to the sample surface, and each detection system forms an image of the linear illumination irradiated onto the sample surface at a sensor position to determine defects. When the optical system is arranged so that the linear illumination image can be detected obliquely, the working distance between the detection unit and the linear illumination unit on the sample surface changes within the field of view. This causes focus shift, resulting in a decrease in the resolution of the image formed on the sensor surface. To prevent this, Patent Document 1 describes tilting the sensor so that it is conjugate with the inspected substrate W, depending on the inclination of the detection direction relative to the inspected substrate W, thereby enabling an image of the inspected substrate W to be formed obliquely on the detector.

[0005] JP-T-2014-504370A JP-A-2007-033433A

[0006] Defect inspection used in the manufacturing process of semiconductors and the like requires the detection of minute defects, the measurement of the dimensions of detected defects with high precision, the inspection of samples non-destructively (i.e., without altering the sample), the obtaining of substantially consistent inspection results in terms of, for example, the number, position, dimensions, and type of detected defects when inspecting the same sample, and the inspection of a large number of samples within a certain period of time.

[0007] In the technology described in Patent Document 1, in order to enable inspection of minute defects of 20 nm or less, an optical path is branched using an "aperture mirror" provided on the Fourier plane of the objective lens to discriminate from background scattered light, and each branched optical path is further branched according to polarization.

[0008] In inspection methods that branch the optical path, the propagation directions of scattered light from defects and background scattered light differ depending on the condition of the sample surface to be inspected, so the optical path branching conditions that give the highest sensitivity also differ.The optical path branching conditions that give the highest sensitivity also differ depending on inspection conditions such as the incident direction of the illumination.

[0009] An object of the present invention is to provide a defect inspection apparatus that can achieve optimum optical path branching conditions depending on the inspection object or inspection conditions.

[0010] In order to solve the above problems, for example, the configuration described in the claims is adopted. One example of such a defect inspection device includes an illumination unit that irradiates a sample with illumination light emitted from a light source, a detection unit that is disposed obliquely with respect to the sample and detects scattered light generated from the sample, a pupil splitting mechanism that divides a pupil of the detection unit into a first detection angle and a second detection angle, a first photoelectric conversion unit that converts the scattered light at the first detection angle detected by the detection unit into an electrical signal, a second photoelectric conversion unit that converts the scattered light at the second detection angle detected by the detection unit into an electrical signal, and a signal processing unit that processes the electrical signals converted by the first photoelectric conversion unit and the second photoelectric conversion unit to detect defects in the sample, wherein the pupil splitting mechanism divides the pupil so as to achieve a pupil distribution according to an inspection target or inspection conditions.

[0011] According to the present invention, the pupil of the detection unit is divided into portions according to the inspection object or inspection conditions, thereby discriminating background scattered light and detecting light scattered from minute defects with high sensitivity. Problems, configurations, and effects other than those described above will become clear from the following description of the embodiments.

[0012] 1 is an overall schematic configuration diagram showing an embodiment of a defect inspection apparatus; FIG. 1 is a diagram showing a first example of an illumination intensity distribution shape realized by an illumination unit; FIG. 2 is a diagram showing a first example of an illumination intensity distribution shape realized by an illumination unit; FIG. 3 is a diagram showing a second example of an illumination intensity distribution shape realized by an illumination unit; FIG. 4 is a diagram showing a third example of an illumination intensity distribution shape realized by an illumination unit; FIG. 5 is a diagram showing an example of an optical element provided in an illumination intensity distribution control unit; FIG. 6 is a diagram showing an illumination distribution shape and a scanning direction on a sample surface; FIG. 7 is a diagram showing a trajectory of an illumination spot by scanning; FIG. 8 is a diagram showing the arrangement of a detection unit and a detection direction as viewed from the side; FIG. 9 is a diagram showing the arrangement of a detection unit and a detection direction as viewed from the top; FIG. 10 is a diagram showing a first example of the configuration of the detection unit; FIG. 11 is a diagram showing the arrangement of an illumination spot and a photoelectric conversion unit; FIG. 12 is a diagram showing the arrangement of an illumination spot and a photoelectric conversion unit; FIG. 13 is a diagram showing the arrangement of a sample and a detection unit; FIG. 14 is a cross-sectional configuration diagram of an image sensor; FIG. 15 is a diagram showing the incidence angle dependence of the absorptance of an anti-reflection coating; FIG. 16 is a diagram showing a first example of the pupil division angle dependence of the SN ratio of scattered light from a defect; FIG. 17 is a diagram showing a second example of the pupil division angle dependence of the SN ratio of scattered light from a defect. FIG. 1 is a diagram showing a first example of a knife edge that divides a pupil. FIG. 2 is a diagram showing the configuration of a detection unit in the case of oblique incidence illumination. FIG. 3 is a diagram showing the configuration of a detection unit in the case of perpendicular illumination. FIG. 4 is a diagram showing a second example of a knife edge that divides a pupil. FIG. 5 is a diagram showing the second example of the detection unit configuration as viewed from above. FIG. 6 is a diagram showing the second example of the detection unit configuration as viewed from a side. FIG. 7 is a diagram showing a third example of the detection unit configuration as viewed from above. FIG. 8 is a diagram showing the configuration of a detection unit when the polarization to be detected is changed. FIG. 9 is a diagram showing the configuration of a detection unit when the polarization of illumination is changed. FIG. 10 is a diagram showing a third example of a knife edge that divides a pupil. FIG. 11 is a diagram showing a drive mechanism for the knife edge. FIG. 12 is a diagram showing a fourth example of the detection unit configuration as viewed from a side.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the examples described below, and various modifications are included. The examples described below are described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the configurations described. Furthermore, it is possible to replace part of the configuration of one example with another example, and it is also possible to add another example to the configuration of one example. It is also possible to add, delete, or replace part of the configuration of each example with other configurations.

[0014] In the following embodiment, a case will be described in which the present invention is applied to a defect inspection apparatus used for defect inspection carried out in the manufacturing process of semiconductors and the like.

[0015] 1 is a schematic diagram of the present embodiment. The defect inspection device 10 includes, as its main components, an illumination unit 101, a detection unit 102, photoelectric conversion units 103-1 and 103-2, a stage 104 on which a sample W can be placed and which can be moved in a direction perpendicular to the surface by an actuator, a signal processing unit 105, a control unit 53, a display unit 54, and an input unit 55.

[0016] 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, adjusted to a desired intensity distribution by the illumination intensity distribution control unit 7, and illuminates an inspection target region of the sample W.

[0017] 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.

[0018] As shown in Figure 1, if necessary, by inserting a mirror 21 into the optical path of the illumination unit 101 and appropriately arranging other mirrors, the illumination optical path can be changed 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, oblique incidence illumination and perpendicular illumination can be performed simultaneously. To obtain scattered light from concave defects on the sample surface (polishing scratches or crystal defects in crystalline materials), perpendicular illumination, which is incident substantially perpendicularly on the sample surface, is suitable.

[0019] To detect minute defects near the surface of a sample, the laser light source 2 must emit a short-wavelength (355 nm or less) ultraviolet or vacuum ultraviolet laser beam that does not easily penetrate the interior of the sample, and must have a high output of 2 W or more. The diameter of the emitted beam is approximately 1 mm. To detect defects inside the sample, a laser light source emitting a visible or infrared laser beam with a wavelength that easily penetrates the interior of the sample is used.

[0020] 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 slow axis azimuth angle 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.

[0021] 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. Here, 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 installed to deflect the incident light in the +Y direction (incidence and reflection in the XY plane), and the second reflecting mirror is installed to deflect the light reflected by the first reflecting mirror in the +Z direction (incidence and reflection in the YZ plane). The position and propagation direction (angle) of the light emitted from the output light adjustment unit 4 are adjusted by translating each reflecting mirror and adjusting the 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 emitted light adjustment unit 4 in the XZ plane and in the YZ plane.

[0022] 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 overall tilt angle so that the optical axis of the beam expander 5 coincides with the optical axis of a predetermined beam. The expansion ratio of the beam diameter can be controlled by adjusting the lens spacing (zoom mechanism). When the light incident on the beam expander 5 is not parallel, adjusting the lens spacing simultaneously expands the beam diameter and collimates it (makes the beam quasi-parallel). The beam collimation can also be achieved by installing a collimating lens upstream of the beam expander 5, independent of the beam expander 5. The beam diameter expansion ratio achieved by the beam expander 5 is approximately 5 to 10 times, expanding a beam with a diameter of 1 mm emitted from the light source to approximately 5 to 10 mm.

[0023] 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.

[0024] 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.

[0025] FIG. 2 shows a schematic cross-section of the incident plane (plane including the illumination optical axis and the sample surface normal) of oblique incidence illumination. Oblique incidence illumination is inclined relative to the sample surface within the incident plane. The illumination unit 101 creates a substantially uniform illumination intensity distribution within the incident plane. The length of the uniform illumination intensity portion is approximately 100 μm to 4 mm, in order to inspect a wide area per unit time. FIG. 3 shows a schematic cross-section of a plane including the sample surface normal and perpendicular to the incident plane of oblique incidence illumination. Within this plane, the illumination intensity distribution on the sample surface exhibits a weaker intensity at the periphery than at the center. More specifically, the intensity distribution resembles a Gaussian distribution reflecting the intensity distribution of light incident on the illumination intensity distribution control unit 7, or a first-order Bessel function or sinc function of the first kind reflecting 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 having 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, and is approximately 2.5 μm to 20 μm, in order to reduce haze generated from the sample surface. The illumination intensity distribution control unit 7 includes optical elements such as an aspherical lens, a diffractive optical element, a cylindrical lens array, and a light pipe, which will be described later. The optical elements that make up the illumination intensity distribution control unit 7 are installed perpendicular to the illumination optical axis, as shown in Figures 2 and 3.

[0026] Furthermore, 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 Fig. 5 and Fig. 6, it is also possible to interchange the intensity distribution on the incident surface of the oblique incidence illumination shown in Fig. 2 and Fig. 3 with the intensity distribution on a surface perpendicular to the incident surface. In other words, it is also possible to configure the portion of the incident surface where the illumination intensity is uniform to be shorter than the portion of the incident surface where the illumination intensity is uniform.

[0027] The illumination intensity distribution control unit 7 includes optical elements that affect the phase and intensity distribution of the incident light. The optical element constituting the illumination intensity distribution control unit 7 is a diffractive optical element 71 (DOE) (Figure 7). The diffractive optical element 71 is a substrate made of a material that transmits incident light, with fine undulations formed on the surface with dimensions equal to or smaller than the wavelength of the light. For ultraviolet light, fused silica is used as the material that transmits incident light. To reduce light attenuation due to passage through the diffractive optical element 71, an anti-reflection coating is preferably used. The fine undulations of the diffractive optical element are formed using lithography. By passing the quasi-parallel light after passing through the beam expander 5 through the diffractive optical element 71, an illumination intensity distribution on the sample surface corresponding to the undulations of the diffractive optical element 71 is formed. The undulations of the diffractive optical element 71 are designed and manufactured to a shape calculated based on Fourier optics theory so that the illumination intensity distribution formed on the sample surface is a long and uniform distribution within the incident plane. The optical element provided in the illumination intensity distribution control unit 7 is provided 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. Furthermore, a focus adjustment mechanism that adjusts by movement in the optical axis direction is also provided. Alternative optical elements that have the same function as the diffractive optical element 71 may include 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.

[0028] Modifications of the illumination intensity distribution formed on the sample surface by the illumination unit 101 are described below. Instead of an illumination intensity distribution 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 with 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 a microlens array for the illumination intensity distribution control unit 7.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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 . Assume that the sample W is 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 described above, the illumination spot 20 has an illumination intensity distribution that is elongated in one direction, designated S2, and a direction substantially perpendicular to S2, designated S1. The rotational motion of the rotational stage scans in the circumferential direction S1 of a circle centered on the rotation axis of the rotational stage, and the translational motion of the translational stage scans in the translational direction S2 of the translational stage. During one rotation of the sample 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, causing the illumination spot to trace a spiral trajectory T on the sample W, thereby scanning the entire surface of the sample W.

[0034] The pupil-divided detection unit will be described below.

[0035] An example of the arrangement of the detection unit 102 relative to the sample W and the illumination spot 20 will be described with reference to FIGS. 10 to 12 . FIG. 10 shows a side view of the arrangement of the detection unit 102. The angle between the normal to the sample W and the detection direction of the detection unit is defined as the detection zenith angle. The detection unit 102 includes a high-angle detection unit 102h, whose detection zenith angle is equal to or less than a predetermined angle, and a low-angle detection unit 102l, whose detection zenith angle is equal to or greater than a predetermined angle. The optical system configuration of the detection unit 102 will be described later with reference to FIG. 12 . Each of the high-angle detection unit 102h and the low-angle detection unit 102l detects scattered light using a common objective lens, which splits the scattered light at the Fourier plane of the objective lens. In this embodiment, the boundary between the detection zenith angle of the high-angle detection unit 102h and the detection zenith angle of the low-angle detection unit 102l can be easily changed.

[0036] Although FIG. 1 shows one detection unit 102, multiple detection units 102 are arranged to detect scattered light emanating from the illumination spot 20 in multiple azimuths. FIG. 11 shows a plan view of the arrangement of the detection units 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 W is defined as the detection azimuth angle. The detection unit 102 suitably includes 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. The number and positions of the detection units may be changed as appropriate.

[0037] FIG. 12 shows an example of a specific configuration diagram of the detection unit 102. Scattered light generated from the illumination spot 20 is collected by an objective lens 1021, and the polarization direction is controlled by a polarization control filter 1022. The polarization control filter 1022 may be, for example, a half-wave plate whose rotation angle can be controlled by a drive mechanism such as a motor. 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 surface W. The imaging lens 1023 forms an image of the illumination spot 20 at the position of an aperture 1024. The aperture 1024 is set to transmit only light from the image of the illumination spot 20 in the region to be detected by the photoelectric conversion unit 103. When the illumination spot 20 has a Gaussian profile in the S2 direction, the aperture 1024 passes only the central portion of the Gaussian profile where the amount of light is strong in the S2 direction, and blocks the areas at the beam edges where the amount of light is weak. Furthermore, the size of the illumination spot 20 in the S1 direction is approximately the same as the image formed by the illumination spot 20, suppressing disturbances such as air scattering that occur when the illumination passes through air. The condenser lens 1025 re-condenses the image formed by the aperture 1024.

[0038] The knife edge (branching optical element) 1026 is arranged so that its tip is located on the Fourier plane (pupil plane) P of the objective lens 1021. The knife edge 1026 branches, for example, into a high-angle detection section 102h having a detection zenith angle of 45 degrees or less and a low-angle detection section 102l having a detection zenith angle of 45 degrees or more. The knife edge 1026 is equipped with a linear motion mechanism 10213, which can move the boundary of the divided area with respect to the pupil plane P. An example of a linear motion mechanism is a linear stage. This allows the division angle of the zenith angle to be changed as appropriate, rather than necessarily being 45 degrees.

[0039] The polarizing beam splitter 1027 separates the light whose polarization direction has been converted by the polarization control filter 1022 according to its polarization direction. The diffuser 1029 absorbs light of a polarization direction not used for detection by the photoelectric conversion unit 103, thereby preventing unnecessary light from becoming stray light. The imaging lens 1028 forms an image of the illumination spot 20 on the photoelectric conversion unit 103. A cylindrical lens may also be used as the imaging lens 1028 to form an image in only one direction. Note that in this embodiment, the polarization control filter 1022 is a half-wave plate, and in combination with the polarizing beam splitter 1027, only light of a specific polarization direction from the light collected by the objective lens 1021 is detected by the photoelectric conversion unit 103. However, it is also possible to use a wire grid polarizer with a transmittance of 80% or more as the polarization control filter 1022 and extract only light of a desired polarization direction without using the polarizing beam splitter 1027.

[0040] In the optical system of the detection unit shown in Figure 12, the optical system from the objective lens 1021 to the condenser lens 1025 is sometimes called the condenser optical system, and the optical system from the condenser lens 1025 to the photoelectric conversion unit 103 is sometimes called the imaging optical system.

[0041] 13 and 14 show examples of the arrangement of the photoelectric conversion unit 103. The optical axis 121 is inclined 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 of an optical image 25 formed on the light receiving unit 1031 by the detection unit 102 from a linear illumination spot 20 irradiated onto the surface of the sample W. The pair of cylindrical lenses 10210 and 10211 constitute 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 1031 and an anti-reflection film (not shown) at a position conjugate with the illumination spot 20 irradiated onto the surface of the sample W. 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 units 1031.

[0043] 15 shows a schematic diagram of the three-dimensional arrangement of the sample W and the detection unit 102. The optical axis 121 of the detection unit 102 is inclined by an angle θ (zenith angle) with respect to the normal direction Z of the sample W. The projection of the optical axis 121 onto the sample surface is inclined by an angle φ (azimuth angle) with respect to the longitudinal direction S2 of the illumination spot 20.

[0044] In this way, if the optical axis 121 that detects light from the detection unit 102 is offset by an angle θ with respect to the normal direction Z of the sample W and an angle φ with respect to the longitudinal direction S2 of the illumination spot 20, then in three-dimensional space, this optical axis 121 is represented by a vector v0 shown in (Equation 1): v0 = (sin θ sin φ, sin θ cos φ cos θ) ... (Equation 1) The angle α between the vector v0 and the longitudinal direction S2 of the illumination spot 20 is calculated by (Equation 2): α = arccos (sin θ cos φ) ... (Equation 2) In this case, the defect inspection device 10 detects a section of 2L in the longitudinal direction S2 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 W and the detection unit 102) Δz is expressed as (Equation 3). Δz=x(sin θ·cos φ), |x|<L (Equation 3) In (Equation 3), |x|<L indicates that the distance from the center of the field of view is equal to or less than L, that is, the position is within the illumination spot 20. The same applies to (Equation 4).

[0045] The imaging magnification M is determined by the condenser lens 1025 and the imaging lens 1028. The position ΔZ of the image formed here is expressed as in (Equation 4). ΔZ=M ２x(sinθ·cosφ), |x|<L ... (Equation 4) Generally, a line sensor is positioned perpendicular to the optical axis 121, which is the center of the light beam emitted by the imaging lens 1028. However, in this embodiment, by tilting the photoelectric conversion unit 103, image detection without defocusing is achieved regardless of changes in the working distance Δz within the field of view. 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 to lie within a plane spanned by the longitudinal direction S2 of the illumination spot 20 and the vector v0, and the angle β between the vector v1 and the vector v0 is set to satisfy (Equation 5): tan α=M·tan β ... (Equation 5) Here, the angle α is the angle between the longitudinal vector v2 of the illumination spot 20 and the vector v0, and satisfies (Equation 6). cosα=sinθ·cosφ (Equation 6) From (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 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, it is desirable to set the imaging magnification M to 2x or less.

[0046] Under these conditions, it is possible to maximize the angle β 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 condenser lens 1025 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.

[0047] As described above, in order to set the imaging magnification M to 2x or less, particularly when a lens with a large numerical aperture is used as the objective lens 1021, light will be 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 coating, the light absorption rate of the photoelectric conversion unit 103 will be low, 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.

[0048] 16 shows a cross-sectional view of the image sensor 1036 that constitutes the photoelectric conversion unit 103. The image sensor 1036 is configured by laminating, in this 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.

[0049] 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 the incident light 122A to 122C. The light receiving unit 1031 is in an array shape and performs photoelectric conversion for each divided 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 122 is incident at a predetermined angle from the normal direction of the light receiving unit 1031. 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, preventing sufficient light from reaching the light receiving section.

[0050] 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.

[0051] FIG. 17 shows HfO ２1 is a graph showing the characteristics of an anti-reflection coating 1033 formed in a single layer of 25 nm. The horizontal axis of the graph represents the angle of incidence, and the vertical axis represents the absorptance. Curve 10333 represents the absorptance characteristics for S-polarized light, and curve 10334 represents the absorptance characteristics for P-polarized light. The absorptance of P-polarized light decreases as the angle of incidence increases, but it drops to 0.5 at an angle of incidence of approximately 60 degrees. Furthermore, the absorptance of S-polarized light increases up to an angle of incidence of approximately 70 degrees, and exhibits an absorptance of 70% or more in the range of angles of incidence from 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 of the detection unit 102.

[0052] <Pupil Division Adjustment Using a Knife Edge with a Linear Motion Mechanism> This section describes a method for adjusting the pupil division of the detector depending on the inspection target or inspection conditions. The intensity distribution of scattered light from defects and background scattered light varies depending on the surface condition of the sample being inspected. For example, in the case of a film-coated wafer that has undergone an oxidation process to form a protective film covering the semiconductor wafer surface during semiconductor manufacturing, the signal-to-noise ratio (SNR) (ratio of defect-scattered light to background scattered light) on the low-angle detector side, which has a larger detection zenith angle, is higher than that of a bare wafer without a film. Therefore, for film-coated wafers, sensitivity can be improved by widening the aperture of the low-angle detector. Therefore, depending on the inspection target, the knife edge 1026 is moved by the linear motion mechanism 10213 (see Figure 12) to adjust the division angle and change the aperture distribution. The linear motion mechanism 10213 and knife edge 1026 are sometimes collectively referred to as the pupil division mechanism.

[0053] 18 and 19 are graphs showing the characteristics of defect measurement sensitivity versus the division angle of the zenith angle by knife edge 1026. Fig. 18 is a graph for a bare wafer, and Fig. 19 is a graph for a film-coated wafer. The highest sensitivity can be obtained by setting the division angle to 40 degrees (see Fig. 18) when the inspection object is a bare wafer, and by setting the division angle to 60 degrees (see Fig. 19) when the inspection object is a wafer with an oxide film.

[0054] Here, the pupil division angle is set for each of the multiple detection units. Depending on the intensity distribution of scattered light, sensitivity can be improved by setting different division angles for the front detection unit 102f and the rear detection unit 102b.

[0055] The cutting edge of the knife edge 1026 is placed on the pupil plane P of the condenser lens 1025. Depending on the configuration of the optical system, the pupil plane P may be a relay position. Here, it is referred to as the pupil plane P without distinction. The division method can be easily adjusted by moving the knife edge 1026 using a linear motion mechanism such as a linear stage. Furthermore, the direction in which the knife edge 1026 is moved by the linear motion mechanism 10213 is parallel to the pupil plane P. This allows the cutting edge of the knife edge 1026 to always be located within the pupil plane regardless of the position of the knife edge 1026. If the cutting edge of the knife edge 1026 is defocused with respect to the pupil plane P, the pupil division boundary changes depending on the angle at which the light rays enter the pupil, i.e., the position within the field of view. In contrast, by placing the cutting edge of the knife edge 1026 on the pupil plane P, the effect of keeping the pupil division boundary constant regardless of the position within the field of view is achieved.

[0056] 20 shows an example of the shape of the knife edge 1026. If the cutting edge of the knife edge 1026 is straight, the branching zenith angle θ will not be constant with respect to the azimuth angle φ. In order to divide the pupil at a constant zenith angle θ regardless of the azimuth angle φ, the shape of the cutting edge is curved to suppress changes in the pupil distribution in the zenith angle direction due to the azimuth angle. The curvature of the shape of the cutting edge of the knife edge 1026 is determined by the focal length of the condenser lens 1025 and the angle of the knife edge 1026 with respect to the optical axis 121.

[0057] Furthermore, sensitivity can be improved by adjusting the pupil division of the detection unit, taking into account not only the object being inspected but also the inspection conditions. For example, adjusting the pupil division is effective because the intensity distribution of scattered light changes depending on the angle of incidence of the illumination. Figure 21 shows the case of oblique incidence illumination, in which the illumination optical axis 120 is inclined relative to the sample surface. With oblique incidence illumination, sensitivity can be increased by moving the knife edge 1026 to widen the aperture of the low-angle detector. On the other hand, with perpendicular illumination as shown in Figure 22, higher sensitivity can be achieved by moving the knife edge 1026 to widen the aperture of the high-angle detector.

[0058] Furthermore, the pupil division can be changed depending on the defect type to be detected. The knife edge 1026 is moved to change the division angle in the apex angle direction depending on the angular distribution of scattered light of the defect type. Depending on the shape of the defect type, it may be effective to divide the pupil in the azimuth angle direction rather than the zenith angle direction. The optimum pupil division for a given defect type can be determined by simulation. Therefore, an optical simulation is performed in advance for the defect type to be detected to determine the preferred pupil division direction and division position. The pupil division information shown in the simulation is stored in the control unit 53, and the pupil division information that provides the optimum pupil division according to the inspection content is called up and the pupil division mechanism is controlled. When dividing the pupil in the azimuth angle direction, the pupil can also be divided in the azimuth angle direction by using a knife edge 1026b with a different width in the azimuth angle direction as shown in FIG. 23 and arranging it as shown in FIGS. 24 and 25.

[0059] When dividing in the azimuth angle direction, in the arrangements shown in Figures 24 and 25, the cutting edge of the knife edge 1026b is inclined with respect to the pupil plane, so the edge of the cutting edge is defocused with respect to the pupil plane, making it impossible to divide the pupil accurately. To divide the pupil accurately, it is effective to make the optical axis 121-2 of the detection unit after branching perpendicular to the Z axis (parallel to the sample surface) as shown in Figure 26. However, if it is made completely perpendicular to the Z axis, accurate pupil division will not be possible when dividing in the zenith angle direction. When selectively using division in the zenith angle direction and division in the azimuth angle direction, it is best to determine the direction of the optical axis 121-2 after branching so that the errors in both pupil divisions fall within the tolerance range.

[0060] Because background scattered light and light scattered from defects have different polarization characteristics, sensitivity can be improved by inserting an analyzer into the detection unit to reduce the amount of background scattered light received. Changing the pupil division also changes the polarization information of the background scattered light detected by each detection unit, so sensitivity can be further improved by optimizing the polarization to be detected. For example, one method is to use a half-wave plate as the polarization control filter 1022 and adjust the angle of the half-wave plate appropriately to adjust the polarization transmitted through the polarizing beam splitter 1027. Alternatively, as shown in FIG. 27 , after the optical path is split by the knife edge 1026, half-wave plates 10221 may be placed before the polarizing beam splitter 1027, and the angle of the half-wave plate may be optimized for each detection unit. The knife edge 1026 can be driven by a linear motion mechanism 10213, and the polarization control filter 1022 and half-wave plate 10221 can be rotated around the optical axis by a driving mechanism such as a motor, all of which are controlled by the control unit 53. The control amount may be adjusted by the user, or a table specifying the control amount may be stored in advance.

[0061] It is also effective to consider the polarization of the illumination when adjusting the pupil division. Changing the polarization of the illumination also changes the intensity distribution of the scattered light. Therefore, sensitivity can be improved by searching for illumination polarization conditions and pupil division conditions that make it easier to detect scattered light from defects. For example, as shown in FIG. 28 , if the polarization of the illumination is set to S-polarized by the polarization control unit 6 and oblique incidence illumination is used, high sensitivity can be achieved by widening the aperture of the high-angle detector. Furthermore, changing the polarization of the illumination also changes the polarization characteristics of the scattered light. Therefore, sensitivity can be further improved by adjusting the pupil division conditions according to the polarization of the illumination and optimizing the polarization of the scattered light to be detected according to the change in illumination and the adjusted pupil division conditions.

[0062] The signal processing unit 105 extracts defects by processing the multiple signals output from the photoelectric conversion units 103 of each detector. At this time, the signals are weighted and added together so that the proportion of signals from detectors with low noise is relatively large, thereby improving sensitivity. This weighting coefficient is calculated by comparing the intensities of background scattered light detected by each detector. For example, since background scattered light generated from the sample surface has a strong distribution toward the rear with respect to the irradiation direction of oblique incidence illumination, the weighting coefficient can be determined so that the proportion of signals detected by the front detection unit 102f is larger than that of the rear detection unit 102b.

[0063] Changing the pupil division also changes the intensity ratio of background scattered light between the branched detection units. By optimizing the weighting coefficients between signals according to the pupil division, the proportion of signals from detection units with low noise increases, further improving sensitivity.

[0064] When a knife edge is used to divide a pupil, ringing artifacts occur due to diffraction occurring at the blade edge, resulting in poor imaging performance. Ringing artifacts occur when high-frequency components are abruptly cut off at the pupil plane, which is the Fourier transform plane. To suppress this, it is effective to change the shape of the blade edge of the knife edge 1026 and reduce the steepness of the frequency characteristics. For example, ringing artifacts can be reduced by forming a wavy pattern on the blade edge as shown in FIG. 29. The amplitude and frequency of the wavy pattern are determined by wave optics calculations that take into account the effect of diffraction.

[0065] <Pupil division adjustment using a knife edge equipped with a rotation mechanism> As shown in Fig. 30 , in addition to the linear motion mechanism 10213, a rotation mechanism 10214 may be added to the knife edge 1026. The rotation axis of the rotation mechanism 10214 is perpendicular to the surface of the knife edge 1026. The direction in which the linear motion mechanism 10213 drives the knife edge 1026 is a direction that is not orthogonal to either the zenith angle direction or the azimuth angle direction, and is parallel to the pupil plane. By combining this rotation mechanism and linear motion mechanism, it is possible to divide the pupil at any zenith angle and azimuth angle without having to replace the knife edge.

[0066] <Pupil Division Adjustment Using a Digital Mirror Device> Figure 31 shows an example of an optical system that uses a digital mirror device (DMD) as the pupil division mechanism, dividing the pupil using a DMD 1026c. The DMD has micrometer-sized mirror pixels, and can divide the pupil by switching the light reflection angle for each pixel. In Figure 31, the DMD is placed at the pupil plane of the condenser lens 1025 of the detection unit, perpendicular to the optical axis 121. In this case, because the dividing boundary is located at the pupil plane, the pupil can be divided accurately regardless of its position within the field of view.

[0067] 31, the wavefront (equiphase surface) is tilted with respect to the optical axis 121-2 in the branched high-angle detection unit 102h. This changes the way the image plane is tilted after passing through the imaging lens 1028. By adjusting the direction of the optical axis 121-2 and the focal length of the imaging lens, it is possible to reduce the angle between the optical axis of the photoelectric conversion unit 103-2 and the image plane, thereby reducing the angle of incidence on the sensor.

[0068] 2...laser light source, 3...attenuator, 4...emission light adjustment unit, 5...beam expander, 6...polarization control unit, 7...illumination intensity distribution control unit, 10...defect inspection device, 20...illumination spot, 21...mirror, 22...beam monitor, 24...illumination intensity distribution monitor, 25...optical image, 53...control unit, 54...display unit, 55...input unit, 71...diffractive optical element, 101...illumination unit, 102...detection unit, 103...photoelectric conversion unit, 104...stage, 105...signal processing unit, 120...illumination optical axis, 121...optical axis, 122...incident light, 1021...objective lens, 1 022...Polarization control filter, 1023...Imaging lens, 1024...Aperture, 1025...Condenser lens, 1026...Knife edge, 1026c...Digital mirror device, 1027...Polarizing beam splitter, 1028...Imaging lens, 1029...Diffuser, 1031...Light receiving unit, 1032...Wiring unit, 1033...Anti-reflection film, 1036...Image sensor, 10210, 10211...Cylindrical lens, 10221...Half-wave plate, 10213...Linear motion mechanism, 10214...Rotation mechanism, 10333, 10334...Curve.

Claims

1. A defect inspection device comprising: an illumination unit which irradiates a sample with illumination light emitted from a light source; a detection unit which is arranged in an oblique direction with respect to the sample and detects scattered light generated from the sample; a pupil splitting mechanism which divides the pupil of the detection unit into a first detection angle and a second detection angle; a first photoelectric conversion unit which converts the scattered light at the first detection angle detected by the detection unit into an electrical signal; a second photoelectric conversion unit which converts the scattered light at the second detection angle detected by the detection unit into an electrical signal; and a signal processing unit which processes the electrical signals converted by the first photoelectric conversion unit and the second photoelectric conversion unit to detect defects in the sample, wherein the pupil splitting mechanism divides the pupil so as to achieve a pupil distribution according to the inspection target or inspection conditions.

2. A defect inspection device according to claim 1, characterized in that the pupil splitting mechanism splits the pupil in the zenith angle direction or the azimuth angle direction.

3. A defect inspection device according to claim 1, characterized in that the pupil division mechanism switches between division in the zenith angle direction and division in the azimuth angle direction depending on the inspection object or inspection conditions.

4. A defect inspection device as claimed in claim 1, characterized in that the pupil dividing mechanism comprises a linear motion mechanism and a knife edge driven by the linear motion mechanism, the cutting edge of the knife edge is positioned so as to be located on the pupil plane of the focusing lens of the detection unit, and the linear motion mechanism moves the cutting edge of the knife edge parallel to the pupil plane.

5. A defect inspection device according to claim 4, characterized in that the pupil splitting mechanism splits the pupil in the zenith angle direction, and the knife edge has a curved cutting edge shape so as to suppress changes in the pupil distribution in the zenith angle direction due to azimuth angle.

6. A defect inspection device according to claim 1, characterized in that the pupil dividing mechanism is provided with a knife edge whose cutting edge is shaped in a wavy pattern, and the cutting edge of the knife edge is positioned so as to be located on the pupil plane of the focusing lens of the detection unit.

7. A defect inspection device as described in claim 1, characterized in that the pupil splitting mechanism comprises a linear motion mechanism, a rotation mechanism, and a knife edge driven by the linear motion mechanism or the rotation mechanism, the rotation axis of the rotation mechanism is perpendicular to the surface of the knife edge, and the direction in which the linear motion mechanism drives the knife edge is a direction that is not perpendicular to either the zenith angle direction or the azimuth angle direction, and is parallel to the pupil plane of the focusing lens of the detection unit.

8. A defect inspection device according to claim 1, characterized in that the pupil splitting mechanism is a digital mirror device arranged at the position of the pupil plane of the focusing lens of the detection unit, perpendicular to the optical axis of the detection unit.

9. A defect inspection device according to claim 1, characterized in that the polarization of the scattered light detected by the detection unit is optimized according to the pupil allocation by the pupil division mechanism.

10. A defect inspection device as claimed in claim 1, characterized in that the pupil splitting mechanism adjusts the pupil distribution in accordance with the polarization of the illumination light irradiated by the illumination unit onto the sample, and the polarization of the scattered light detected by the detection unit is optimized in accordance with the polarization of the illumination light and the pupil distribution adjusted by the pupil splitting mechanism.

11. A defect inspection device as claimed in claim 1, characterized in that the weighting coefficient used when weighting and adding the signal from the first photoelectric conversion unit and the signal from the second photoelectric conversion unit in the signal processing unit is optimized according to the pupil allocation by the pupil division mechanism.

12. A defect inspection device as claimed in claim 1, characterized in that the sample is a semiconductor wafer, and the pupil is divided so as to have a different pupil distribution depending on whether the sample is a semiconductor wafer having a protective film covering the surface of the semiconductor wafer, or a semiconductor wafer not having the protective film.

13. A defect inspection device according to claim 1, wherein the pupil splitting mechanism splits the pupil so that the pupil distribution corresponds to the type of defect to be detected from the sample.

14. A defect inspection device according to claim 1, characterized in that the pupil splitting mechanism splits the pupil so that the pupil distribution corresponds to the angle of incidence of the illumination light on the sample.

15. An optical system of the detection unit in the defect inspection device described in claim 1, comprising: a focusing optical system including an objective lens that focuses scattered light from the sample; a branching optical element arranged on the pupil plane of the objective lens that branches the scattered light from the focusing optical system into first and second scattered light; a first imaging optical system that images the first scattered light on the first photoelectric conversion unit; and a second imaging optical system that images the second scattered light on the second photoelectric conversion unit, wherein the first scattered light is scattered light from the sample whose scattering direction is at a predetermined angle or less with respect to the normal direction of the sample, and the second scattered light is scattered light from the sample whose scattering direction is at the predetermined angle or more with respect to the normal direction of the sample, and the predetermined angle is determined by the position of the branching optical element driven by the pupil division mechanism.

Images