WO2009091034A1 - Surface inspection apparatus and surface inspection method - Google Patents

Surface inspection apparatus and surface inspection method Download PDF

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Publication number
WO2009091034A1
WO2009091034A1 PCT/JP2009/050556 JP2009050556W WO2009091034A1 WO 2009091034 A1 WO2009091034 A1 WO 2009091034A1 JP 2009050556 W JP2009050556 W JP 2009050556W WO 2009091034 A1 WO2009091034 A1 WO 2009091034A1
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WIPO (PCT)
Prior art keywords
light
linearly polarized
polarized light
inspection
brightness
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PCT/JP2009/050556
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French (fr)
Japanese (ja)
Inventor
Kazuhiko Fukazawa
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Nikon Corporation
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Application filed by Nikon Corporation filed Critical Nikon Corporation
Priority to JP2009550059A priority Critical patent/JP5440782B2/en
Publication of WO2009091034A1 publication Critical patent/WO2009091034A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/9501—Semiconductor wafers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/956—Inspecting patterns on the surface of objects
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10—Measuring as part of the manufacturing process
    • H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

  • the present invention relates to a surface inspection apparatus and method for inspecting the surface of a semiconductor wafer, a liquid crystal substrate or the like.
  • abnormal patterns line and space patterns such as wiring patterns formed on the surface of semiconductor wafers and liquid crystal substrates (hereinafter collectively referred to as “substrates”) Inspection is performed.
  • a substrate is placed on a tiltable stage, illumination light (non-polarized light) for inspection is irradiated on the surface of the substrate, and diffracted light generated from a repetitive pattern on the substrate (for example, The image of the substrate is captured on the basis of the first-order diffracted light), and the abnormal portion of the repetitive pattern is specified based on the contrast (contrast) of the image (see, for example, Patent Document 1).
  • a surface inspection apparatus can perform an abnormal inspection of repetitive patterns with different repetitive pitches on the substrate by adjusting the tilt of the stage.
  • diffraction inspection As a technique for inspecting a repetitive pattern formed on the surface of a substrate, in addition to inspection using diffracted light as described above (hereinafter, such inspection is referred to as diffraction inspection), inspection using specularly reflected light (hereinafter referred to as specular reflection inspection) Such inspection is referred to as specular reflection inspection), and inspection using a change in polarization state due to structural birefringence of a pattern (hereinafter, such inspection is referred to as PER inspection). According to these inspection methods, it is possible to detect a line width defect, a resist coating defect, and the like based on defocus and dose shift of the exposure apparatus at high speed and with high accuracy.
  • specular reflection inspection is sensitive to changes in film thickness and has high detection sensitivity for resist coating defects and dose shifts, but this is due to luminance changes due to thin film interference. Even if defocus or dose shift occurs to such an extent that the pattern is not formed, luminance can be obtained from the influence of thin film interference.
  • the brightness of the diffracted light is the lowest (zero) at a place where the pattern is not formed with respect to the defocus and dose shift, and the brightness is obtained when the pattern is formed. Does not change linearly.
  • the luminance is maximized at the best focus position, and the luminance is reduced due to pattern collapse.
  • the luminance is high when the edge portion of the pattern is sharp, and the luminance is reduced with respect to the collapse of the pattern as in the case of the focus.
  • the present invention has been made in view of such problems, and an object thereof is to provide a surface inspection apparatus and method capable of specifying the cause of an abnormality.
  • the surface inspection apparatus includes an inspection light illumination unit that irradiates inspection light onto a surface of a substrate to be tested having a predetermined repetitive pattern, and the inspection that is irradiated with the inspection light.
  • a diffracted light detector that detects diffracted light from the surface of the substrate, a polarization illumination unit that irradiates the surface of the test substrate with first linearly polarized light, and the test substrate that is irradiated with the first linearly polarized light
  • a polarization converter that converts reflected light from the surface of the light into second linearly polarized light having a vibration direction different from that of the first linearly polarized light, a polarization detector that detects the second linearly polarized light, and the diffracted light detector
  • An inspection unit that inspects the presence or absence of an abnormality in the repetitive pattern based on the diffracted light detected in Step 2 and the second linearly polarized light detected by the polarization detection unit, and the inspection unit includes the abnormality The previously determined difference for each cause of Correlation and the luminance of the source of the size and the diffracted light, based on the correlation between the abnormal cause of the size and the second luminance linearly polarized light, so as to identify the cause
  • the repetitive pattern is formed using an exposure apparatus, the correlation between the focus shift amount and the brightness of the diffracted light in the exposure apparatus, and the focus shift amount and the first And the correlation between the dose deviation in the exposure apparatus and the brightness of the diffracted light, and the correlation between the dose deviation and the brightness of the second linear polarization, respectively.
  • a database unit that creates a database in response, and the inspection unit checks the luminance of the diffracted light detected by the diffracted light detection unit with the luminance of the diffracted light on the database, and the polarization detection unit By comparing the detected luminance of the second linearly polarized light with the luminance of the second linearly polarized light on the database, the amount of focus deviation is obtained. Preferably it is ask the shift amount of the dose.
  • the surface inspection apparatus includes a condition setting unit that sets an apparatus condition so that the diffracted light is generated, and the correlation between the cause of the abnormality and the luminance of the diffracted light is determined by the condition setting unit. It is preferable to be obtained for each diffracted light based on a plurality of the apparatus conditions obtained by changing the setting.
  • the surface inspection method includes a first step of irradiating the surface of the test substrate having a predetermined repetitive pattern with the inspection light, and diffraction from the surface of the test substrate irradiated with the inspection light.
  • the cause of the abnormality is identified based on the correlation between the magnitude of the cause of the abnormality determined in advance and the brightness of the diffracted light and the correlation between the magnitude of the cause of the abnormality and the brightness of the second linearly polarized light. It is supposed to be.
  • the repetitive pattern is formed by using an exposure apparatus, and the correlation between the focus shift amount and the brightness of the diffracted light in the exposure apparatus, and the focus shift amount and the first And the correlation between the dose deviation in the exposure apparatus and the brightness of the diffracted light, and the correlation between the dose deviation and the brightness of the second linear polarization, respectively.
  • a pre-step of creating a database in response, and in the sixth step the brightness of the diffracted light detected in the second step is compared with the brightness of the diffracted light on the database, and The brightness of the second linearly polarized light detected in step 5 is collated with the brightness of the second linearly polarized light on the database. It is preferable to determine the shift amount of the shift amount or the dose of the carcass.
  • the surface inspection method may further include a sub-step for setting an apparatus condition so that the diffracted light is generated, and a correlation between the cause of the abnormality and the brightness of the diffracted light is set in the sub-step. It is preferable that it is calculated
  • the cause of the abnormality can be specified.
  • FIG. 1 shows an example of a surface inspection apparatus according to this embodiment, and this apparatus inspects a surface defect (abnormality) of a semiconductor wafer 10 which is a substrate to be tested.
  • the surface inspection apparatus 1 includes a holder 5 for mounting and holding the wafer 10, and the wafer 10 transported by a transport device (not shown) is placed on the holder 5 and fixed and held by vacuum suction.
  • the holder 5 passes through the center of the wafer 10 fixed and held in this way (the center of the holder 5) and rotates the wafer 10 about the axis AX perpendicular to the surface of the wafer 10 (rotation within the surface of the wafer 10). Hold as possible.
  • the holder 5 can tilt (tilt) the wafer 10 about an axis passing through the surface of the wafer 10, and can adjust the incident angle of inspection illumination light (inspection light or linearly polarized light described later). It is like that.
  • the surface inspection apparatus 1 further includes an illumination optical system 20 that irradiates the surface of the wafer 10 fixedly held by the holder 5 with the illumination light for inspection as parallel light, and the wafer 10 when irradiated with the illumination light for inspection.
  • a condensing optical system 30 that condenses reflected light, diffracted light, and the like, and a CCD camera 40 that receives the light collected by the condensing optical system 30 and detects an image of the surface of the wafer 10 are configured.
  • the illumination optical system 20 includes a light source 21 such as a metal halide lamp or a mercury lamp, a wavelength selection unit 22 that selectively transmits light having a specific wavelength, and an optical fiber 23 that guides light transmitted through the wavelength selection unit 22.
  • the illumination side concave mirror 25 that reflects the illumination light emitted from the optical fiber 23 is mainly configured.
  • the light from the light source 21 passes through the wavelength selector 22, and illumination light having a specific wavelength is emitted from the optical fiber 23 to the illumination-side concave mirror 25, and illumination light emitted from the optical fiber 23 to the illumination-side concave mirror 25. Since the emitting part of the optical fiber 23 is disposed at the focal position of the illumination-side concave mirror 25, the illumination-side concave mirror 25 irradiates the surface of the wafer 10 held by the holder 5 as a parallel light beam. The relationship between the incident angle and the exit angle of the illumination light with respect to the wafer 10 can be adjusted by tilting the holder 5 and changing the mounting angle of the wafer 10.
  • an illumination-side polarizing filter 24 is provided between the optical fiber 23 and the illumination-side concave mirror 25 so that the illumination-side polarizing filter 24 can be inserted into and removed from the optical path.
  • the illumination-side polarizing filter 24 is removed from the optical path.
  • the diffraction inspection is performed.
  • the PER inspection is performed with the illumination side polarizing filter 24 inserted in the optical path (details of the illumination side polarizing filter 24 will be described later). To do).
  • the outgoing light (reflected light or diffracted light) from the surface of the wafer 10 is condensed by the condensing optical system 30.
  • the condensing optical system 30 is mainly configured by a light-receiving side concave mirror 31 disposed to face the holder 5, and emitted light (reflected light or diffracted light) collected by the light-receiving side concave mirror 31 is a CCD camera 40.
  • the image of the wafer 10 is formed on the image sensor 42 through the imaging lens 41. As a result, an image of the surface of the wafer 10 is formed on the image sensor 42 of the CCD camera 40.
  • a light receiving side polarizing filter 32 is provided between the light receiving side concave mirror 31 and the CCD camera 40 so as to be inserted into and removed from the optical path. As shown in FIG. 1, the light receiving side polarizing filter 32 is removed from the optical path. In this state, the diffraction inspection is performed, and as shown in FIG. 2, the PER inspection is performed with the light receiving side polarizing filter 32 inserted in the optical path (details of the light receiving side polarizing filter 32 will be described later). To do).
  • the CCD camera 40 photoelectrically converts the image of the surface of the wafer 10 formed on the image sensor 42 to generate an image signal, and outputs the image signal to the image processing inspection unit 45.
  • a database unit 46 and an image display device 47 are electrically connected to the image processing inspection unit 45.
  • the image processing inspection unit 45 converts the image of the wafer 10 into a digital image of a predetermined bit (for example, 8 bits) based on the image signal of the wafer 10 input from the CCD camera 40.
  • the database unit 46 stores image data of non-defective wafers (shots) and image data of wafers (shots) when defocusing or dose shift occurs, and the image processing inspection unit 45 stores images of the wafers 10.
  • the image data of the wafer 10 and the image data of the database unit 46 are compared to inspect whether there is an abnormality (defect or the like) on the surface of the wafer 10. Then, the inspection result by the image processing inspection unit 45 and the image of the wafer 10 at that time are output and displayed on the image display device 47.
  • the repeated pattern 12 is a resist pattern (for example, a wiring pattern) in which a plurality of line portions 2 ⁇ / b> A are arranged at a constant pitch P along the short direction (X direction). Between adjacent line parts 2A is a space part 2B.
  • the arrangement direction (X direction) of the line portions 2A is referred to as “repeating direction of the repeating pattern 12”.
  • the design value of the line width D A of the line portion 2A in the repetitive pattern 12 is set to 1 ⁇ 2 of the pitch P.
  • a wafer on which a repeated pattern is formed by changing the focus amount and the dose amount of the exposure apparatus is prepared.
  • the exposure and development are performed while changing the focus amount and the dose amount in a matrix for each exposure shot.
  • such a wafer is referred to as an FEM wafer.
  • the recipe creation process will be described. First, as shown in FIG. 10, the FEM wafer is transferred onto the holder 5 (step S101), and alignment is performed (step S102).
  • an image of diffracted light generated on the FEM wafer is taken (step S103).
  • the holder 5 is rotated so that the illumination direction on the surface of the wafer and the repeat direction of the repeat pattern 2 coincide with each other, and the pattern pitch is P, and the inspection light is irradiated onto the wafer surface.
  • the incident angle ⁇ i and the exit angle ⁇ r are set so that the n-th order diffracted light corresponding to the pitch P of the repeated pattern 12 is generated.
  • the illumination light quantity is optimized at the tilt angle at which the diffracted light is generated, and an image of the diffracted light is captured.
  • the best focus and best dose shot is used as the reference shot, and the illumination light quantity is set so that the brightness of the image to be captured becomes the optimum brightness.
  • inspection light is applied to the surface of the FEM wafer (10) in a state where the illumination side polarizing filter 24 and the light receiving side polarizing filter 32 are removed from the optical path (see FIG. 1).
  • diffracted light for example, first-order diffracted light
  • the light from the light source 21 passes through the wavelength selection unit 22 and is emitted from the optical fiber 23 to the illumination side concave mirror 25, and is converted into a parallel light beam by the illumination side concave mirror 25 and held in the holder 5. Irradiate the surface.
  • the diffracted light emitted from the surface of the FEM wafer (10) is collected by the light-receiving side concave mirror 31 and imaged on the image sensor 42 of the CCD camera 40.
  • the CCD camera 40 is formed on the image sensor 42.
  • the diffraction image of the FEM wafer (10) is photoelectrically converted to generate an image signal, and the image signal is output to the image processing inspection unit 45.
  • the image processing inspection unit 45 cuts out the captured images in units of shots for the images captured under the plurality of diffraction conditions, and calculates the average brightness and standard for each shot. A deviation or the like is obtained (step S104). Then, from among images captured under a plurality of diffraction conditions, an image that maximizes the luminance change, that is, the diffraction condition is selected for the luminance change according to the change in the focus amount and the luminance change according to the change in the dose amount (however, Except for diffraction conditions that are judged to be uneven depending on the thickness of the underlying film).
  • FIG. 12 an example of the image of the diffracted light generated on the FEM wafer is shown in FIG. From FIG. 12, it can be seen that the average luminance detected for each shot in the FEM wafer 10f changes according to changes in the focus amount and the dose amount. Note that the thick frame at the center in FIG. 12 is a reference shot, and the magnitude of the average luminance detected for each shot is represented by shades of hatching.
  • the diffracted light may be zero-order diffracted light (that is, regular reflection light).
  • the image processing inspection unit 45 registers the diffraction condition (tilt angle, illumination wavelength ⁇ , etc.) at that time in the database unit 46 as a recipe, and the focus amount under the diffraction condition.
  • the average brightness (and standard deviation and the like) for each shot with respect to the change in dose amount is registered in the database unit 46 (step S105).
  • step S106 an image of the FEM wafer by PER inspection is taken (step S106).
  • the PER inspection performs an abnormality inspection of the repetitive pattern 12 by using a change in the volume ratio between the line portion 2A and the space portion 2B in the repetitive pattern 12 as described above.
  • the ideal volume ratio (design value) is 1: 1.
  • the change in the volume ratio is caused by deviation from the appropriate value of the exposure focus, and appears for each shot area of the wafer 10.
  • the volume ratio can also be referred to as the area ratio of the cross-sectional shape.
  • the illumination-side polarizing filter 24 and the light-receiving-side polarizing filter 32 are inserted on the optical path (see FIG. 2).
  • the configuration of the apparatus when performing the PER inspection will be described hereinafter. A description will be given in order.
  • the holder 5 rotatably holds the wafer 10 about the axis AX as the rotation axis, and the repeat direction of the repeat pattern 12 on the wafer 10 (the X direction in FIGS. 3 and 4) It can be rotated in the surface.
  • the holder 5 keeps the wafer 10 in a horizontal state, stops at a predetermined rotational position, and changes the repetitive direction of the repetitive pattern 12 on the wafer 10 with the illumination light incident surface (illumination light described later) (Direction of travel) is held at an angle of 45 degrees.
  • the illumination-side polarization filter 24 is disposed between the optical fiber 23 and the illumination-side concave mirror 25, and its transmission axis is set to a predetermined direction, and light from the illumination unit 21 is linearly polarized according to the transmission axis. Convert to At this time, since the exit portion of the optical fiber 23 is disposed at the focal position of the illumination-side concave mirror 25, the illumination-side concave mirror 25 is a test substrate by converting the light transmitted through the illumination-side polarization filter 24 into a parallel beam. The wafer 10 is illuminated. Thus, the light emitted from the optical fiber 23 becomes the first linearly polarized light L1 (see FIG. 6A) via the illumination side polarizing filter 24 and the illumination side concave mirror 25, and the entire surface of the wafer 10 is obtained. Is irradiated.
  • the traveling direction of the first linearly polarized light L1 (the direction of the principal ray of the linearly polarized light L1 reaching an arbitrary point on the surface of the wafer 10) is substantially parallel to the optical axis O1 from the optical fiber 23.
  • the optical axis O1 is inclined by a predetermined angle with respect to a normal line (axis AX) passing through the center of the holder 5.
  • the first linearly polarized light L1 is incident on the wafer 10 as p-polarized light. That is, as shown in FIG. 6A, a plane including the traveling direction of the linearly polarized light L1 and the vibration direction of the electric vector (vibrating surface of the linearly polarized light L1) is included in the incident surface A2 of the linearly polarized light L1.
  • the vibration plane of the linearly polarized light L ⁇ b> 1 is defined by the transmission axis of the illumination side polarizing filter 24.
  • the incident angles of the linearly polarized light L1 at each point of the wafer 10 are the same because of the parallel light, and correspond to the angle formed by the optical axis O1 and the normal line (axis AX).
  • the repeating direction (X direction) of the repetitive pattern 12 is the incident surface A2 of the linearly polarized light L1 (linearly polarized light on the surface of the wafer 10).
  • the angle formed by the vibration plane direction of the linearly polarized light L1 on the surface of the wafer 10 and the repeating direction (X direction) of the repeating pattern 12 is also 45 degrees.
  • the direction of the vibrating surface of the linearly polarized light L1 on the surface of the wafer 10 (direction V in FIG. 7) is inclined 45 degrees with respect to the repeating direction (X direction) of the repeating pattern 12.
  • the light enters the repetitive pattern 12 so as to cross the repetitive pattern 12 at an angle.
  • the angle state between the first linearly polarized light L1 and the repeated pattern 12 is uniform over the entire surface of the wafer 10. Note that the angle state between the first linearly polarized light L1 and the repetitive pattern 12 is the same even if 45 degrees is replaced with any of 135 degrees, 225 degrees, and 315 degrees. The reason why the angle formed by the direction of the vibration surface (V direction) and the repeat direction (X direction) in FIG. 7 is set to 45 degrees is to maximize the sensitivity of the abnormality inspection of the repeat pattern 12.
  • the regular reflection direction is a direction that is included in the incident surface A2 of the linearly polarized light L1 and is inclined by an angle equal to the incident angle of the linearly polarized light L1.
  • the reason why the first linearly polarized light L1 is ovalized by reflection at the repeated pattern 12 and the elliptically polarized light L2 is generated from the repeated pattern 12 will be briefly described.
  • the direction of the vibration surface (the V direction in FIG. 7) is divided into two polarization components V X and V Y shown in FIG.
  • One polarization component V X is a component parallel to the repetition direction (X direction).
  • the other polarization component V Y is a component perpendicular to the repetition direction (X direction).
  • the two polarization components V X and V Y are independently subjected to different amplitude changes and phase changes.
  • the amplitude change and the phase change are different due to the anisotropy of the repetitive pattern 12, and is called structural birefringence.
  • the reflected lights of the two polarization components V X and V Y have different amplitudes and phases, and the reflected light obtained by combining these becomes elliptically polarized light L2 (see FIG. 6B).
  • the wavelength of light to be irradiated needs to be sufficiently long with respect to the pattern.
  • the light used for the PER inspection uses light having a long wavelength unlike the light used for the diffraction inspection.
  • the degree of ovalization caused by the anisotropy of the repetitive pattern 12 is the polarization component L3 perpendicular to the vibration plane of the linearly polarized light L1 shown in FIG. 6A among the elliptically polarized light L2 shown in FIG. (See FIG. 6C).
  • the magnitude of the polarization component L3 depends on the material and shape of the repetitive pattern 12 and the angle formed by the vibration plane direction (V direction) and the repetitive direction (X direction) in FIG. For this reason, when the angle formed between the V direction and the X direction is kept at a constant value (45 degrees in the present embodiment), even if the material of the repeating pattern 12 is constant, the shape of the repeating pattern 12 changes to an elliptical shape.
  • the degree of conversion (the magnitude of the polarization component L3) changes.
  • the repetitive pattern 12 has a concavo-convex shape in which the line portions 2A and the space portions 2B are alternately arranged along the X direction, and is formed as designed with an appropriate exposure focus.
  • line width D B is equal to the line width D a and the space portion 2B of the line portion 2A, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: 1.
  • the size of the polarization component L3 is the largest.
  • the volume ratio between the line portion 2A and the space portion 2B deviates from about 1: 1.
  • the size of the polarization component L3 is smaller than the ideal case.
  • a change in the magnitude of the polarization component L3 is illustrated in FIG.
  • the horizontal axis in FIG. 9 is the line width D A of the line portion 2A.
  • the repetitive pattern 12 with the vibration plane direction (V direction) in FIG. 7 inclined by 45 degrees with respect to the repetitive direction (X direction) of the repetitive pattern 12 is used.
  • the elliptically polarized light L2 generated by reflection in the regular reflection direction has a degree of ovalization (the magnitude of the polarization component L3 in FIG. 6C) having the shape of the repeated pattern 12 (line portion 2A and space). The volume ratio with respect to the part 2B).
  • the traveling direction of the elliptically polarized light L2 is included in the incident surface A2 of the linearly polarized light L1, and is inclined symmetrically with respect to the traveling direction of the linearly polarized light L1 with respect to the normal line (axis AX) passing through the center of the holder 5.
  • the optical axis O2 of the condensing optical system 30 is set so as to be inclined in the regular reflection direction with respect to the normal (axis AX) passing through the center of the holder 5. Therefore, the elliptically polarized light L2 that is the reflected light from the repetitive pattern 12 travels along the optical axis O2.
  • the light-receiving side polarizing filter 32 is disposed between the light-receiving side concave mirror 31 of the condensing optical system 30 and the CCD camera 40, and transmits the specularly reflected light from the surface of the wafer 10 to transmit the second linearly polarized light L4 (FIG. 6). (See (c)).
  • the direction of the transmission axis of the light receiving side polarizing filter 32 is set to be perpendicular to the transmission axis of the illumination side polarizing filter 32 described above.
  • the vibration direction of the second linearly polarized light L4 in the plane perpendicular to the traveling direction of the second linearly polarized light L4 is the same as that of the first linearly polarized light L1 in the plane perpendicular to the traveling direction of the first linearly polarized light L1. It is set to be substantially perpendicular to the vibration direction.
  • the elliptically polarized light L2 passes through the light receiving side polarizing filter 32, only the linearly polarized light L4 corresponding to the polarized component L3 in FIG. 6C of the elliptically polarized light L2 is extracted and guided to the CCD camera 40.
  • a reflected image of the wafer 10 by the second linearly polarized light L4 is formed on the image sensor 42 of the CCD camera 40, respectively.
  • the brightness of the reflected image of the wafer 10 is substantially proportional to the light intensity of the linearly polarized light L4 and changes according to the shape of the repeated pattern 12.
  • the reflected image of the wafer 10 is brightest when the repeated pattern 12 has an ideal shape.
  • the illumination side polarizing filter 24 and the light receiving side polarizing filter 32 are inserted on the optical path (see FIG. 2), and the FEM wafer is placed on the surface of the FEM wafer (10).
  • the regular reflected light (elliptical polarized light L2) reflected by the surface of the FEM wafer (10) is detected by the CCD camera 40 via the light receiving side polarizing filter 32.
  • the light from the light source 21 passes through the wavelength selection unit 22 and is emitted from the optical fiber 23, converted into the first linearly polarized light L 1 by the illumination side polarization filter 24, and converted into a parallel light flux by the illumination side concave mirror 25.
  • the surface of the FEM wafer (10) held by the holder 5 is irradiated. Then, the specularly reflected light (elliptical polarized light L2) reflected by the surface of the FEM wafer (10) is condensed by the light receiving side concave mirror 31 and converted into the second linearly polarized light L4 by the light receiving side polarizing filter 32, and the CCD camera 40 The image is formed on the image sensor 42, and the CCD camera 40 photoelectrically converts the reflected image of the FEM wafer (10) by the second linearly polarized light L 4 formed on the image sensor 42 to generate an image signal. Is output to the image processing inspection unit 45.
  • the holder When taking an image of the FEM wafer by PER inspection, the holder is set so that the angle formed by the illumination direction (the direction of the vibrating surface of the linearly polarized light L1) on the surface of the wafer and the repeating direction of the repeating pattern 12 is 45 degrees. 5 is rotated and the holder 5 is tilted so that the incident angle of the linearly polarized light L1 and the outgoing angle of the elliptically polarized light L2 are equal (in the regular reflection direction). Then, imaging is performed under a plurality of PER conditions in which the illumination wavelength is changed by the wavelength selection unit 22.
  • the best focus and best dose shot is set as the reference shot, and the illumination light quantity is set so that the brightness of the image to be captured becomes the optimum brightness.
  • the exposure time of the CCD camera 40 may be changed and set without changing the amount of illumination light.
  • the image processing inspection unit 45 cuts out the captured images in units of shots for images captured under the plurality of PER conditions, and obtains average brightness, standard deviation, and the like in each shot (Ste S107). Then, an image that maximizes the luminance change, that is, the PER condition is selected from the images captured under a plurality of PER conditions, with respect to the luminance change according to the change in the focus amount and the luminance change according to the change in the dose amount (however, The PER condition that is determined to be uneven depending on the film thickness of the base film is excluded).
  • FIG. 13 shows that the average luminance detected for each shot in the FEM wafer 10f changes according to changes in the focus amount and the dose amount. Note that the thick frame at the center in FIG. 13 is a reference shot, and the magnitude of the average luminance detected for each shot is represented by shades of hatching.
  • the angle formed between the illumination direction on the wafer surface (the direction of the vibrating surface of the linearly polarized light L1) and the repeating direction of the repeating pattern 12 is 67.5 degrees or 22.5 degrees, in addition to 45 degrees, In the case of 135 degrees, 112.5 degrees, or 157.5 degrees, an image is picked up in the same manner, and an image (that is, PER condition) that maximizes the luminance change is selected together with the case of 45 degrees. Good.
  • the image processing inspection unit 45 registers the PER condition (illumination wavelength, tilt angle, etc.) at that time in the database unit 46 as a recipe, The average brightness (and standard deviation, etc.) for each shot with respect to the change in dose is registered in the database unit 46 (step S108).
  • the recipe creation process is performed as described above, there are two types of average luminance for each shot with respect to changes in the focus amount and the dose amount, respectively for the diffraction inspection and the PER inspection, and the amount of change in focus and dose in the diffraction inspection. And the average luminance, and the correlation between the focus and dose variation in the PER inspection and the average luminance are obtained, and these databases are created in the database unit 46. For example, as shown in FIG.
  • the average luminance c0 at the time of the reference shot having the best focus and the best dose is obtained in the diffraction inspection, and further, the amount of focus shift with respect to the best focus ( Change amount) is ⁇ a1, ⁇ a2, ⁇ a3, and the deviation amount (change amount) of the dose with respect to the best dose is ⁇ b1, ⁇ b2, ⁇ b3, from the luminance distribution shown in FIG. Average luminances c1 to c11 are obtained. Further, in the PER inspection, the average luminance d0 at the time of the reference shot having the best focus and the best dose is obtained.
  • the deviation amount of the focus is ⁇ a1, ⁇ a2, ⁇ a3, dose from the luminance distribution shown in FIG.
  • Average luminances d1 to d5 are obtained when the amount of deviation is ⁇ b1, ⁇ b2, ⁇ b3.
  • the luminance distribution for each shot is shown with coarse accuracy in FIGS. 12 to 14, but actually, the luminance distribution is more diverse.
  • FIG. 15 shows an example of the correlation between the focus shift amount in the diffraction inspection and the PER inspection and the shot average lowering luminance based on the best focus shot when the focus shift amount is constant.
  • the correlation between the focus and dose shift amount (change amount) in the diffraction inspection and the average luminance, and the focus and dose shift amount in the PER inspection Since the amount of focus and dose deviation is specified by combining the correlation with the average luminance, the amount of focus and dose deviation including polarity can be specified with high accuracy. In addition, this makes it possible to quickly identify a defective part at the time of exposure, so that it is possible to adjust the exposure apparatus and the like in a short time, and it can be expected to improve the yield of the wafer, and also to improve the throughput. . Further, by knowing the amount of deviation between focus and dose, it becomes possible to manage the state of the exposure apparatus and the state of the coater.
  • the inspection process is performed based on the created recipe.
  • the wafer 10 which is a substrate to be tested is transferred onto the holder 5 (step S201), and alignment is performed (step S202).
  • an image of the wafer 10 is taken with the recipe (diffraction condition) registered in the previous step S105 (step S203).
  • the illumination side polarization filter 24 and the light reception side polarization filter 32 are removed from the optical path (see FIG. 1), light from the light source 21 passes through the wavelength selection unit 22 and is transmitted from the optical fiber 23 to the illumination side. The light is emitted to the concave mirror 25 and is irradiated onto the surface of the wafer 10 held by the holder 5 as a parallel light beam by the illumination-side concave mirror 25.
  • the diffracted light emitted from the surface of the wafer 10 is collected by the light-receiving-side concave mirror 31 and imaged on the image sensor 42 of the CCD camera 40, and the CCD camera 40 is formed on the image sensor 42.
  • the diffraction image is photoelectrically converted to generate an image signal, and the image signal is output to the image processing inspection unit 45.
  • an image of the wafer 10 is taken with the recipe (PER condition) registered in the previous step S108 (step S204).
  • the light from the light source 21 passes through the wavelength selection unit 22 and is emitted from the optical fiber 23 with the illumination side polarizing filter 24 and the light receiving side polarizing filter 32 inserted in the optical path (see FIG. 2).
  • the illumination-side polarizing filter 24 converts the light into the first linearly polarized light L1, and the illumination-side concave mirror 25 irradiates the surface of the wafer 10 held by the holder 5 with a parallel light beam.
  • the specularly reflected light (elliptical polarized light L2) reflected by the surface of the wafer 10 is collected by the light receiving side concave mirror 31 and converted into the second linearly polarized light L4 by the light receiving side polarizing filter 32, and the image sensor 42 of the CCD camera 40 is used.
  • the CCD camera 40 forms an image signal by photoelectrically converting the reflected image of the wafer 10 by the second linearly polarized light L4 formed on the image sensor 42, and the image signal is converted into an image processing inspection unit 45. Output to.
  • the image processing inspection unit 45 cuts out the captured images for each of the images captured in steps S203 and S204, and obtains the average brightness, standard deviation, etc. in each shot (step S205). Thereby, the average luminance for each shot in the diffraction inspection and the average luminance for each shot in the PER inspection are obtained.
  • the average luminance in the diffraction inspection is collated with the average luminance (in the diffraction inspection) on the database (registered in the database unit 46), and the average luminance in the PER inspection on the database (in the PER inspection).
  • a focus shift amount or a dose shift amount is obtained, and the presence or absence of abnormality in the repeated pattern 12 is inspected.
  • the average luminance in the diffraction inspection is c6 and the average luminance in the PER inspection is d5
  • the focus shift amount is -a2
  • the dose shift amount is -b3.
  • a standard deviation or the like may be collated. In this way, it is possible to perform inspection in a short time because it is compared with the luminance data on the database.
  • the information is registered in the database unit 46 (that is, The number of diffraction conditions (for diffraction inspection) may be increased to a plurality.
  • the number of diffraction conditions for diffraction inspection
  • the average brightness when the focus shift amount is ⁇ a1, ⁇ a2, ⁇ a3 and the dose shift amount is ⁇ b1, ⁇ b2, ⁇ b3, for a plurality of diffraction conditions (c0 to In addition to the condition of c11, another condition) is registered.
  • the number of conditions of average brightness to be collated on the database increases, so that the amount of focus and dose deviation can be specified more accurately.
  • the number of PER conditions registered in the database unit 46 may be increased to a plurality, and the same effect as in the case of increasing the number of diffraction conditions can be obtained.
  • the linearly polarized light L1 is p-polarized light
  • the present invention is not limited to this.
  • s-polarized light instead of p-polarized light may be used.
  • the s-polarized light is linearly polarized light whose vibration surface is perpendicular to the incident surface. Therefore, as shown in FIG.
  • the wafer 10 when the repeating direction (X direction) of the repeating pattern 12 on the wafer 10 is set to an angle of 45 degrees with respect to the incident surface A2 of the linearly polarized light L1 that is s-polarized light, the wafer The angle formed by the direction of the vibrating surface of the s-polarized light on the surface 10 and the repeating direction (X direction) of the repeating pattern 12 is also set to 45 degrees.
  • the p-polarized light is advantageous for acquiring abnormal information related to the edge shape of the line portion 2A of the repetitive pattern 12.
  • the s-polarized light is advantageous for efficiently capturing abnormal information on the surface of the wafer 10 and improving the SN ratio.
  • the repetitive direction (X direction) of the repetitive pattern 12 is set to an angle other than 45 degrees with respect to the incident surface of the linearly polarized light L1, and the direction of the vibration surface of the linearly polarized light L1 on the surface of the wafer 10 and the repetitive pattern 12 It is preferable to set the angle formed by the repeat direction (X direction) to 45 degrees.
  • the linearly polarized light L1 is generated using the illumination light from the light source 21 and the illumination-side polarization filter 24.
  • the present invention is not limited to this, and a laser is used as the light source. If used, the illumination side polarizing filter 24 is not necessary.
  • an amplification type solid-state imaging device such as a CMOS can be used.
  • the average luminance for each shot is obtained for the image captured by the CCD camera 40. This is effective when a uniform repetitive pattern exists in each shot as in a memory circuit. For example, when there is an area where no repeated pattern exists in each shot, such as a logic circuit, the area where the pattern exists in each shot may be partially cut out to obtain the average luminance.

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Abstract

A surface inspection apparatus (1) comprises an image processing inspection part (45) which inspects presence/absence of abnormality in repeated patterns on the surface of a wafer (10) based on diffracted light and second linearly-polarized light detected by a CCD camera (40). Based on the correlation between the shift amounts of a focus and dose previously registered in a data base part (46) and the luminance of the diffracted light and the correlation between the shift amounts of the focus and dose and the luminance of the second linearly-polarized light, the image processing inspection part (45) obtains the shift amount of the focus or that of the dose.

Description

表面検査装置および表面検査方法Surface inspection apparatus and surface inspection method
　本発明は、半導体ウェハや液晶基板等の表面を検査する表面検査装置および方法に関する。 The present invention relates to a surface inspection apparatus and method for inspecting the surface of a semiconductor wafer, a liquid crystal substrate or the like.
　半導体回路素子や液晶表示素子の製造工程では、半導体ウェハや液晶基板（以降、総じて「基板」と称する）の表面に形成された繰り返しパターン（配線パターン等のライン・アンド・スペースのパターン）の異常検査が行われる。自動化された表面検査装置では、チルト可能なステージの上に基板を載置し、基板の表面に検査用の照明光（非偏光）を照射し、基板上の繰り返しパターンから発生する回折光（例えば、１次回折光）に基づいて基板の画像を取り込み、この画像の明暗差（コントラスト）に基づいて繰り返しパターンの異常箇所を特定する（例えば、特許文献１を参照）。さらに、このような表面検査装置は、ステージをチルト調整することにより、基板上の繰り返しピッチが異なる繰り返しパターンの異常検査を行うことができる。 In the manufacturing process of semiconductor circuit elements and liquid crystal display elements, abnormal patterns (line and space patterns such as wiring patterns) formed on the surface of semiconductor wafers and liquid crystal substrates (hereinafter collectively referred to as “substrates”) Inspection is performed. In an automated surface inspection apparatus, a substrate is placed on a tiltable stage, illumination light (non-polarized light) for inspection is irradiated on the surface of the substrate, and diffracted light generated from a repetitive pattern on the substrate (for example, The image of the substrate is captured on the basis of the first-order diffracted light), and the abnormal portion of the repetitive pattern is specified based on the contrast (contrast) of the image (see, for example, Patent Document 1). Furthermore, such a surface inspection apparatus can perform an abnormal inspection of repetitive patterns with different repetitive pitches on the substrate by adjusting the tilt of the stage.
　基板の表面に形成された繰り返しパターンを検査する技術として、上述のような回折光を用いた検査（以降、このような検査を回折検査と称する）の他、正反射光を用いた検査（以降、このような検査を正反射検査と称する）や、パターンの構造性複屈折による偏光状態の変化を利用した検査（以降、このような検査をＰＥＲ検査と称する）等がある。これらの検査方法によれは、露光装置のデフォーカスやドーズシフトに基づく線幅不良、レジスト塗布不良等を、高速かつ高精度で検出することができる。 As a technique for inspecting a repetitive pattern formed on the surface of a substrate, in addition to inspection using diffracted light as described above (hereinafter, such inspection is referred to as diffraction inspection), inspection using specularly reflected light (hereinafter referred to as diffraction inspection) Such inspection is referred to as specular reflection inspection), and inspection using a change in polarization state due to structural birefringence of a pattern (hereinafter, such inspection is referred to as PER inspection). According to these inspection methods, it is possible to detect a line width defect, a resist coating defect, and the like based on defocus and dose shift of the exposure apparatus at high speed and with high accuracy.
　なお、正反射検査は膜厚の変化に敏感で、レジスト塗布不良やドーズシフトについて検出感度は高いが、これは薄膜の干渉による輝度変化によるものである。この変化はパターンが形成されない程度までデフォーカスやドーズシフトが発生しても、薄膜の干渉の影響から輝度を得ることができる。また、回折検査では、デフォーカスおよびドーズシフトに対しパターンが形成されない箇所で回折光の輝度が最低（零）となり、パターンが形成されると輝度が得られるが、回折光の輝度はデフォーカスおよびドーズシフトに対してリニアに変化しない。また、ＰＥＲ検査では、フォーカスのベスト位置において輝度が最大となり、パターン崩れに対して輝度が低下する。また、ドーズに関しても、パターンのエッジ部分がシャープである場合は輝度が高く、フォーカスの場合と同様にパターン崩れに対して輝度が低下する。
特開平１０－２３２１２２号公報 Note that specular reflection inspection is sensitive to changes in film thickness and has high detection sensitivity for resist coating defects and dose shifts, but this is due to luminance changes due to thin film interference. Even if defocus or dose shift occurs to such an extent that the pattern is not formed, luminance can be obtained from the influence of thin film interference. In the diffraction inspection, the brightness of the diffracted light is the lowest (zero) at a place where the pattern is not formed with respect to the defocus and dose shift, and the brightness is obtained when the pattern is formed. Does not change linearly. In the PER inspection, the luminance is maximized at the best focus position, and the luminance is reduced due to pattern collapse. As for the dose, the luminance is high when the edge portion of the pattern is sharp, and the luminance is reduced with respect to the collapse of the pattern as in the case of the focus.
Japanese Patent Laid-Open No. 10-232122
　しかしながら、上述のような正反射検査、回折検査、およびＰＥＲ検査においては、基板上の何らかの異常を検出することは可能であるが、異常の原因を特定することができなかった。 However, in the specular reflection inspection, diffraction inspection, and PER inspection as described above, some abnormality on the substrate can be detected, but the cause of the abnormality cannot be specified.
　本発明は、このような問題に鑑みてなされたものであり、異常の原因を特定することが可能な表面検査装置および方法を提供することを目的とする。 The present invention has been made in view of such problems, and an object thereof is to provide a surface inspection apparatus and method capable of specifying the cause of an abnormality.
　このような目的達成のため、本発明に係る表面検査装置は、所定の繰り返しパターンを有する被検基板の表面に検査光を照射する検査光照明部と、前記検査光が照射された前記被検基板の表面からの回折光を検出する回折光検出部と、前記被検基板の表面に第１の直線偏光を照射する偏光照明部と、前記第１の直線偏光が照射された前記被検基板の表面からの反射光を前記第１の直線偏光と振動方向が異なる第２の直線偏光に変換する偏光変換部と、前記第２の直線偏光を検出する偏光検出部と、前記回折光検出部で検出された前記回折光および、前記偏光検出部で検出された前記第２の直線偏光に基づいて、前記繰り返しパターンにおける異常の有無を検査する検査部とを備え、前記検査部は、前記異常の原因毎に予め求められた前記異常の原因の大きさと前記回折光の輝度との相関および、前記異常の原因の大きさと前記第２の直線偏光の輝度との相関に基づいて、前記異常の原因を特定するようになっている。 In order to achieve such an object, the surface inspection apparatus according to the present invention includes an inspection light illumination unit that irradiates inspection light onto a surface of a substrate to be tested having a predetermined repetitive pattern, and the inspection that is irradiated with the inspection light. A diffracted light detector that detects diffracted light from the surface of the substrate, a polarization illumination unit that irradiates the surface of the test substrate with first linearly polarized light, and the test substrate that is irradiated with the first linearly polarized light A polarization converter that converts reflected light from the surface of the light into second linearly polarized light having a vibration direction different from that of the first linearly polarized light, a polarization detector that detects the second linearly polarized light, and the diffracted light detector An inspection unit that inspects the presence or absence of an abnormality in the repetitive pattern based on the diffracted light detected in Step 2 and the second linearly polarized light detected by the polarization detection unit, and the inspection unit includes the abnormality The previously determined difference for each cause of Correlation and the luminance of the source of the size and the diffracted light, based on the correlation between the abnormal cause of the size and the second luminance linearly polarized light, so as to identify the cause of the abnormality.
　なお、上述の表面検査装置において、前記繰り返しパターンは露光装置を用いて形成されており、前記露光装置におけるフォーカスのズレ量と前記回折光の輝度との相関および、前記フォーカスのズレ量と前記第２の直線偏光の輝度との相関、並びに、前記露光装置におけるドーズのズレ量と前記回折光の輝度との相関および、前記ドーズのズレ量と前記第２の直線偏光の輝度との相関をそれぞれ求めてデータベースを作成するデータベース部を備え、前記検査部は、前記回折光検出部で検出された前記回折光の輝度を前記データベース上の前記回折光の輝度と照合するとともに、前記偏光検出部で検出された前記第２の直線偏光の輝度を前記データベース上の前記第２の直線偏光の輝度と照合することにより、前記フォーカスのズレ量または前記ドーズのズレ量を求めることが好ましい。 In the surface inspection apparatus described above, the repetitive pattern is formed using an exposure apparatus, the correlation between the focus shift amount and the brightness of the diffracted light in the exposure apparatus, and the focus shift amount and the first And the correlation between the dose deviation in the exposure apparatus and the brightness of the diffracted light, and the correlation between the dose deviation and the brightness of the second linear polarization, respectively. A database unit that creates a database in response, and the inspection unit checks the luminance of the diffracted light detected by the diffracted light detection unit with the luminance of the diffracted light on the database, and the polarization detection unit By comparing the detected luminance of the second linearly polarized light with the luminance of the second linearly polarized light on the database, the amount of focus deviation is obtained. Preferably it is ask the shift amount of the dose.
　また、上述の表面検査装置において、前記回折光が発生するように装置条件を設定する条件設定部を備え、前記異常の原因の大きさと前記回折光の輝度との相関は、前記条件設定部により設定変更されて得られた複数の前記装置条件に基づく前記回折光毎に求められることが好ましい。 The surface inspection apparatus includes a condition setting unit that sets an apparatus condition so that the diffracted light is generated, and the correlation between the cause of the abnormality and the luminance of the diffracted light is determined by the condition setting unit. It is preferable to be obtained for each diffracted light based on a plurality of the apparatus conditions obtained by changing the setting.
　また、本発明に係る表面検査方法は、所定の繰り返しパターンを有する被検基板の表面に検査光を照射する第１のステップと、前記検査光が照射された前記被検基板の表面からの回折光を検出する第２のステップと、前記被検基板の表面に第１の直線偏光を照射する第３のステップと、前記第１の直線偏光が照射された前記被検基板の表面からの反射光を前記第１の直線偏光と振動方向が異なる第２の直線偏光に変換する第４のステップと、前記第２の直線偏光を検出する第５のステップと、前記第２のステップで検出された前記回折光および、前記第５のステップで検出された前記第２の直線偏光に基づいて、前記繰り返しパターンにおける異常の有無を検査する第６のステップとを有し、前記第６のステップにおいて、前記異常の原因毎に予め求められた前記異常の原因の大きさと前記回折光の輝度との相関および、前記異常の原因の大きさと前記第２の直線偏光の輝度との相関に基づいて、前記異常の原因を特定するようになっている。 The surface inspection method according to the present invention includes a first step of irradiating the surface of the test substrate having a predetermined repetitive pattern with the inspection light, and diffraction from the surface of the test substrate irradiated with the inspection light. A second step of detecting light; a third step of irradiating the surface of the test substrate with a first linearly polarized light; and a reflection from the surface of the test substrate irradiated with the first linearly polarized light. A fourth step of converting light into a second linearly polarized light having a vibration direction different from that of the first linearly polarized light, a fifth step of detecting the second linearly polarized light, and a second step detected by the second step. A sixth step of inspecting whether there is an abnormality in the repetitive pattern based on the diffracted light and the second linearly polarized light detected in the fifth step, and in the sixth step, The cause of the abnormality The cause of the abnormality is identified based on the correlation between the magnitude of the cause of the abnormality determined in advance and the brightness of the diffracted light and the correlation between the magnitude of the cause of the abnormality and the brightness of the second linearly polarized light. It is supposed to be.
　なお、上述の表面検査方法において、前記繰り返しパターンは露光装置を用いて形成されており、前記露光装置におけるフォーカスのズレ量と前記回折光の輝度との相関および、前記フォーカスのズレ量と前記第２の直線偏光の輝度との相関、並びに、前記露光装置におけるドーズのズレ量と前記回折光の輝度との相関および、前記ドーズのズレ量と前記第２の直線偏光の輝度との相関をそれぞれ求めてデータベースを作成するプレステップを有し、前記第６のステップにおいて、前記第２のステップで検出された前記回折光の輝度を前記データベース上の前記回折光の輝度と照合するとともに、前記第５のステップで検出された前記第２の直線偏光の輝度を前記データベース上の前記第２の直線偏光の輝度と照合することにより、前記フォーカスのズレ量または前記ドーズのズレ量を求めることが好ましい。 In the above surface inspection method, the repetitive pattern is formed by using an exposure apparatus, and the correlation between the focus shift amount and the brightness of the diffracted light in the exposure apparatus, and the focus shift amount and the first And the correlation between the dose deviation in the exposure apparatus and the brightness of the diffracted light, and the correlation between the dose deviation and the brightness of the second linear polarization, respectively. And a pre-step of creating a database in response, and in the sixth step, the brightness of the diffracted light detected in the second step is compared with the brightness of the diffracted light on the database, and The brightness of the second linearly polarized light detected in step 5 is collated with the brightness of the second linearly polarized light on the database. It is preferable to determine the shift amount of the shift amount or the dose of the carcass.
　また、上述の表面検査方法において、前記回折光が発生するように装置条件を設定するサブステップを有し、前記異常の原因の大きさと前記回折光の輝度との相関は、前記サブステップで設定変更されて得られた複数の前記装置条件に基づく前記回折光毎に求められることが好ましい。 The surface inspection method may further include a sub-step for setting an apparatus condition so that the diffracted light is generated, and a correlation between the cause of the abnormality and the brightness of the diffracted light is set in the sub-step. It is preferable that it is calculated | required for every said diffracted light based on the said several apparatus conditions obtained by changing.
　本発明によれば、異常の原因を特定することができる。 According to the present invention, the cause of the abnormality can be specified.
本発明に係る表面検査装置の全体構成を示す図である。It is a figure showing the whole surface inspection device composition concerning the present invention. 表面検査装置の光路上に偏光フィルタが挿入された状態を示す図である。It is a figure which shows the state by which the polarizing filter was inserted on the optical path of a surface inspection apparatus. 半導体ウェハの表面の外観図である。It is an external view of the surface of a semiconductor wafer. 繰り返しパターンの凹凸構造を説明する斜視図である。It is a perspective view explaining the uneven structure of a repeating pattern. 直線偏光の入射面と繰り返しパターンの繰り返し方向との傾き状態を説明する図である。It is a figure explaining the inclination state of the entrance plane of a linearly polarized light and the repeating direction of a repeating pattern. 直線偏光と楕円偏光の振動方向を説明する図である。It is a figure explaining the vibration direction of linearly polarized light and elliptically polarized light. 直線偏光の振動面の方向と繰り返しパターンの繰り返し方向との傾き状態を説明する図である。It is a figure explaining the inclination state of the direction of the vibration surface of linearly polarized light, and the repeating direction of a repeating pattern. 直線偏光の振動面の方向が繰り返し方向に平行な偏光成分と垂直な偏光成分とに分かれる様子を説明する図である。It is a figure explaining a mode that the direction of the vibration surface of a linearly polarized light is divided | segmented into the polarization component parallel to a repetition direction, and a perpendicular | vertical polarization component. 偏光成分の大きさと繰り返しパターンのライン部の線幅との関係を説明する図である。It is a figure explaining the relationship between the magnitude | size of a polarization component, and the line | wire width of the line part of a repeating pattern. 本発明に係る表面検査方法を示す第１のフローチャートである。It is a 1st flowchart which shows the surface inspection method which concerns on this invention. 本発明に係る表面検査方法を示す第２のフローチャートである。It is a 2nd flowchart which shows the surface inspection method which concerns on this invention. 回折検査によるＦＥＭウェハの画像を示す模式図である。It is a schematic diagram which shows the image of the FEM wafer by a diffraction test | inspection. ＰＥＲ検査によるＦＥＭウェハの画像を示す模式図である。It is a schematic diagram which shows the image of the FEM wafer by PER inspection. フォーカスおよびドーズのズレ量に対する平均輝度を示す模式図である。It is a schematic diagram which shows the average brightness | luminance with respect to the deviation | shift amount of a focus and a dose. 回折検査およびＰＥＲ検査におけるフォーカスのズレ量と平均輝度との相関の一例を示すグラフである。It is a graph which shows an example of the correlation with the deviation | shift amount of focus and average brightness | luminance in a diffraction test and PER test | inspection.
符号の説明Explanation of symbols
　　１　表面検査装置
　１０　ウェハ（被検基板）
　１２　繰り返しパターン
　２０　照明光学系（各照明部）
　３０　集光光学系
　３２　受光側偏光フィルタ（偏光変換部）
　４０　ＣＣＤカメラ（各検出部）
　４５　画像処理検査部（検査部および条件設定部）
　４６　データベース部
　Ｌ１　直線偏光（第１の直線偏光）
　Ｌ２　楕円偏光
　Ｌ３　偏光成分
　Ｌ４　直線偏光（第２の直線偏光） 1 Surface inspection device 10 Wafer (Subject to be tested)
12 Repeat pattern 20 Illumination optical system (each illumination unit)
30 Condensing optical system 32 Light receiving side polarizing filter (polarization converter)
40 CCD camera (each detector)
45 Image processing inspection unit (inspection unit and condition setting unit)
46 Database section L1 Linearly polarized light (first linearly polarized light)
L2 Elliptical polarization L3 Polarization component L4 Linear polarization (second linear polarization)
　以下、図面を参照して本発明の好ましい実施形態について説明する。図１に本実施形態に係る表面検査装置の一例を示しており、この装置により被検基板である半導体ウェハ１０の表面欠陥（異常）を検査する。この表面検査装置１は、ウェハ１０を載置保持するホルダ５を備え、不図示の搬送装置によって搬送されてくるウェハ１０を、ホルダ５の上に載置させるとともに真空吸着によって固定保持する。ホルダ５は、このように固定保持したウェハ１０の中心（ホルダ５の中心）を通りウェハ１０の表面に垂直な軸ＡＸを回転軸として、ウェハ１０を回転（ウェハ１０の表面内での回転）可能に保持する。また、ホルダ５は、ウェハ１０の表面を通る軸を中心に、ウェハ１０をチルト（傾動）させることが可能であり、検査用照明光（後述する検査光もしくは直線偏光）の入射角を調整できるようになっている。 Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a surface inspection apparatus according to this embodiment, and this apparatus inspects a surface defect (abnormality) of a semiconductor wafer 10 which is a substrate to be tested. The surface inspection apparatus 1 includes a holder 5 for mounting and holding the wafer 10, and the wafer 10 transported by a transport device (not shown) is placed on the holder 5 and fixed and held by vacuum suction. The holder 5 passes through the center of the wafer 10 fixed and held in this way (the center of the holder 5) and rotates the wafer 10 about the axis AX perpendicular to the surface of the wafer 10 (rotation within the surface of the wafer 10). Hold as possible. The holder 5 can tilt (tilt) the wafer 10 about an axis passing through the surface of the wafer 10, and can adjust the incident angle of inspection illumination light (inspection light or linearly polarized light described later). It is like that.
　表面検査装置１はさらに、ホルダ５に固定保持されたウェハ１０の表面に検査用照明光を平行光として照射する照明光学系２０と、検査用照明光の照射を受けたときのウェハ１０からの反射光や回折光等を集光する集光光学系３０と、集光光学系３０により集光された光を受けてウェハ１０の表面の像を検出するＣＣＤカメラ４０とを備えて構成される。照明光学系２０は、メタルハライドランプや水銀ランプ等の光源２１と、特定の波長を有する光を選択的に透過させる波長選択部２２と、波長選択部２２を透過した光を案内する光ファイバ２３と、光ファイバ２３から射出された照明光を反射させる照明側凹面鏡２５とを主体に構成される。 The surface inspection apparatus 1 further includes an illumination optical system 20 that irradiates the surface of the wafer 10 fixedly held by the holder 5 with the illumination light for inspection as parallel light, and the wafer 10 when irradiated with the illumination light for inspection. A condensing optical system 30 that condenses reflected light, diffracted light, and the like, and a CCD camera 40 that receives the light collected by the condensing optical system 30 and detects an image of the surface of the wafer 10 are configured. . The illumination optical system 20 includes a light source 21 such as a metal halide lamp or a mercury lamp, a wavelength selection unit 22 that selectively transmits light having a specific wavelength, and an optical fiber 23 that guides light transmitted through the wavelength selection unit 22. The illumination side concave mirror 25 that reflects the illumination light emitted from the optical fiber 23 is mainly configured.
　そして、光源２１からの光は波長選択部２２を透過し、特定の波長を有する照明光が光ファイバ２３から照明側凹面鏡２５へ射出され、光ファイバ２３から照明側凹面鏡２５へ射出された照明光は、光ファイバ２３の射出部が照明側凹面鏡２５の焦点位置に配置されているため、照明側凹面鏡２５により平行光束となってホルダ５に保持されたウェハ１０の表面に照射される。なお、ウェハ１０に対する照明光の入射角と出射角との関係は、ホルダ５をチルト（傾動）させてウェハ１０の載置角度を変化させることにより調整可能である。 The light from the light source 21 passes through the wavelength selector 22, and illumination light having a specific wavelength is emitted from the optical fiber 23 to the illumination-side concave mirror 25, and illumination light emitted from the optical fiber 23 to the illumination-side concave mirror 25. Since the emitting part of the optical fiber 23 is disposed at the focal position of the illumination-side concave mirror 25, the illumination-side concave mirror 25 irradiates the surface of the wafer 10 held by the holder 5 as a parallel light beam. The relationship between the incident angle and the exit angle of the illumination light with respect to the wafer 10 can be adjusted by tilting the holder 5 and changing the mounting angle of the wafer 10.
　また、光ファイバ２３と照明側凹面鏡２５との間には、照明側偏光フィルタ２４が光路上へ挿抜可能に設けられており、図１に示すように、照明側偏光フィルタ２４を光路上から抜去した状態で回折検査が行われ、図２に示すように、照明側偏光フィルタ２４を光路上に挿入した状態でＰＥＲ検査が行われるようになっている（照明側偏光フィルタ２４の詳細については後述する）。 In addition, an illumination-side polarizing filter 24 is provided between the optical fiber 23 and the illumination-side concave mirror 25 so that the illumination-side polarizing filter 24 can be inserted into and removed from the optical path. As shown in FIG. 1, the illumination-side polarizing filter 24 is removed from the optical path. In this state, the diffraction inspection is performed. As shown in FIG. 2, the PER inspection is performed with the illumination side polarizing filter 24 inserted in the optical path (details of the illumination side polarizing filter 24 will be described later). To do).
　ウェハ１０の表面からの出射光（反射光もしくは回折光）は集光光学系３０により集光される。集光光学系３０は、ホルダ５に対向して配設された受光側凹面鏡３１を主体に構成され、受光側凹面鏡３１により集光された出射光（反射光もしくは回折光）は、ＣＣＤカメラ４０の撮像レンズ４１を経て撮像素子４２上に達し、ウェハ１０の像が結像される。この結果、ウェハ１０の表面の像がＣＣＤカメラ４０の撮像素子４２上に形成される。 The outgoing light (reflected light or diffracted light) from the surface of the wafer 10 is condensed by the condensing optical system 30. The condensing optical system 30 is mainly configured by a light-receiving side concave mirror 31 disposed to face the holder 5, and emitted light (reflected light or diffracted light) collected by the light-receiving side concave mirror 31 is a CCD camera 40. The image of the wafer 10 is formed on the image sensor 42 through the imaging lens 41. As a result, an image of the surface of the wafer 10 is formed on the image sensor 42 of the CCD camera 40.
　また、受光側凹面鏡３１とＣＣＤカメラ４０との間には、受光側偏光フィルタ３２が光路上へ挿抜可能に設けられており、図１に示すように、受光側偏光フィルタ３２を光路上から抜去した状態で回折検査が行われ、図２に示すように、受光側偏光フィルタ３２を光路上に挿入した状態でＰＥＲ検査が行われるようになっている（受光側偏光フィルタ３２の詳細については後述する）。 In addition, a light receiving side polarizing filter 32 is provided between the light receiving side concave mirror 31 and the CCD camera 40 so as to be inserted into and removed from the optical path. As shown in FIG. 1, the light receiving side polarizing filter 32 is removed from the optical path. In this state, the diffraction inspection is performed, and as shown in FIG. 2, the PER inspection is performed with the light receiving side polarizing filter 32 inserted in the optical path (details of the light receiving side polarizing filter 32 will be described later). To do).
　ＣＣＤカメラ４０は、撮像素子４２上に形成されたウェハ１０の表面の像を光電変換して画像信号を生成し、画像信号を画像処理検査部４５に出力する。画像処理検査部４５には、データベース部４６と、画像表示装置４７とが電気的に接続されている。画像処理検査部４５は、ＣＣＤカメラ４０から入力されたウェハ１０の画像信号に基づいて、ウェハ１０の画像を所定のビット（例えば８ビット）のデジタル画像に変換する。データベース部４６には、良品ウェハ（ショット）の画像データや、デフォーカスやドーズシフトが生じたときのウェハ（ショット）の画像データが予め記憶されており、画像処理検査部４５は、ウェハ１０の画像（デジタル画像）を生成すると、ウェハ１０の画像データとデータベース部４６の画像データとを比較して、ウェハ１０表面における異常（欠陥等）の有無を検査する。そして、画像処理検査部４５による検査結果およびそのときのウェハ１０の画像が画像表示装置４７で出力表示される。 The CCD camera 40 photoelectrically converts the image of the surface of the wafer 10 formed on the image sensor 42 to generate an image signal, and outputs the image signal to the image processing inspection unit 45. A database unit 46 and an image display device 47 are electrically connected to the image processing inspection unit 45. The image processing inspection unit 45 converts the image of the wafer 10 into a digital image of a predetermined bit (for example, 8 bits) based on the image signal of the wafer 10 input from the CCD camera 40. The database unit 46 stores image data of non-defective wafers (shots) and image data of wafers (shots) when defocusing or dose shift occurs, and the image processing inspection unit 45 stores images of the wafers 10. When the (digital image) is generated, the image data of the wafer 10 and the image data of the database unit 46 are compared to inspect whether there is an abnormality (defect or the like) on the surface of the wafer 10. Then, the inspection result by the image processing inspection unit 45 and the image of the wafer 10 at that time are output and displayed on the image display device 47.
　ところで、ウェハ１０の表面には、図３に示すように、複数のチップ領域１１がＸＹ方向に配列され、各チップ領域の中に所定の繰り返しパターン１２が形成されている。繰り返しパターン１２は、図４に示すように、複数のライン部２Ａがその短手方向（Ｘ方向）に沿って一定のピッチＰで配列されたレジストパターン（例えば、配線パターン）である。隣り合うライン部２Ａ同士の間は、スペース部２Ｂである。なお、ライン部２Ａの配列方向（Ｘ方向）を「繰り返しパターン１２の繰り返し方向」と称する。なお、繰り返しパターン１２におけるライン部２Ａの線幅ＤAの設計値をピッチＰの１／２とする。 On the surface of the wafer 10, as shown in FIG. 3, a plurality of chip regions 11 are arranged in the XY direction, and a predetermined repetitive pattern 12 is formed in each chip region. As shown in FIG. 4, the repeated pattern 12 is a resist pattern (for example, a wiring pattern) in which a plurality of line portions 2 </ b> A are arranged at a constant pitch P along the short direction (X direction). Between adjacent line parts 2A is a space part 2B. The arrangement direction (X direction) of the line portions 2A is referred to as “repeating direction of the repeating pattern 12”. The design value of the line width D A of the line portion 2A in the repetitive pattern 12 is set to ½ of the pitch P.
　本実施形態の表面検査装置１を用いた表面検査方法について、図１０および図１１に示すフローチャートを参照しながら以下に説明する。なお予め、ウェハ１０の表面検査に先立って、露光装置のフォーカス量とドーズ量を変化させて繰り返しパターンを形成したウェハを作成する。このとき、露光ショット毎にフォーカス量とドーズ量をマトリックス状に変化させて露光し現像する。以下、このようなウェハをＦＥＭウェハと称することにする。 The surface inspection method using the surface inspection apparatus 1 of the present embodiment will be described below with reference to the flowcharts shown in FIGS. Prior to the surface inspection of the wafer 10, a wafer on which a repeated pattern is formed by changing the focus amount and the dose amount of the exposure apparatus is prepared. At this time, the exposure and development are performed while changing the focus amount and the dose amount in a matrix for each exposure shot. Hereinafter, such a wafer is referred to as an FEM wafer.
　初めに、レシピ作成工程について説明すると、図１０に示すように、まず、ＦＥＭウェハをホルダ５上に搬送し（ステップＳ１０１）、アライメントを実施する（ステップＳ１０２）。 First, the recipe creation process will be described. First, as shown in FIG. 10, the FEM wafer is transferred onto the holder 5 (step S101), and alignment is performed (step S102).
　アライメントを行った後、ＦＥＭウェハで生じる回折光の画像を撮像する（ステップＳ１０３）。回折光の画像を撮像する際、ウェハの表面上における照明方向と繰り返しパターン２の繰り返し方向とが一致ようにホルダ５を回転させるともに、パターンのピッチをＰとし、ウェハの表面に照射する検査光の波長をλとし、検査光の入射角をθiとし、ｎ次回折光の出射角をθrとしたとき、次の（１）式を満足するように設定を行う。 After alignment, an image of diffracted light generated on the FEM wafer is taken (step S103). When taking an image of the diffracted light, the holder 5 is rotated so that the illumination direction on the surface of the wafer and the repeat direction of the repeat pattern 2 coincide with each other, and the pattern pitch is P, and the inspection light is irradiated onto the wafer surface. Is set so as to satisfy the following equation (1), where λ is the incident angle of the inspection light, θi is the incident angle of the inspection light, and θr is the emission angle of the nth-order diffracted light.
　Ｐ×｛ｓｉｎ（θr）－ｓｉｎ（θi）｝＝±ｎ×λ　…（１） P × {sin (θr) −sin (θi)} = ± n × λ (1)
　すなわち、繰り返しパターン１２のピッチＰに対応したｎ次回折光が発生するように、入射角θiおよび出射角θr（すなわち、ホルダ５のチルト角）を設定する。このように、回折光が発生するチルト角において、照明光量を最適化し、回折光の画像を撮像する。なおこのとき、ベストフォーカスかつベストドーズのショットを基準ショットとし、撮像する画像の輝度が最適な輝度になるように照明光量を設定する。またこのとき、他のチルト角においても回折光が発生しないか確認し、回折光が発生する他の条件がある場合は同様に設定を行う。さらに、照明波長λも変化させながら同様に回折光が発生する条件を求め、撮像を行う。 That is, the incident angle θi and the exit angle θr (that is, the tilt angle of the holder 5) are set so that the n-th order diffracted light corresponding to the pitch P of the repeated pattern 12 is generated. In this way, the illumination light quantity is optimized at the tilt angle at which the diffracted light is generated, and an image of the diffracted light is captured. At this time, the best focus and best dose shot is used as the reference shot, and the illumination light quantity is set so that the brightness of the image to be captured becomes the optimum brightness. At this time, it is confirmed whether or not diffracted light is generated at other tilt angles. If there are other conditions for generating diffracted light, the same setting is performed. Further, the conditions for generating diffracted light are similarly obtained while changing the illumination wavelength λ, and imaging is performed.
　なお、回折光の画像を撮像するには、まず、照明側偏光フィルタ２４および受光側偏光フィルタ３２を光路上から抜去した状態（図１を参照）で、ＦＥＭウェハ（１０）の表面に検査光を照射し、ＦＥＭウェハ（１０）の表面から出射される回折光（例えば１次回折光）をＣＣＤカメラ４０で検出する。このとき、光源２１からの光が波長選択部２２を透過して光ファイバ２３から照明側凹面鏡２５へ射出され、照明側凹面鏡２５により平行光束となってホルダ５に保持されたＦＥＭウェハ（１０）の表面に照射される。そして、ＦＥＭウェハ（１０）の表面から出射された回折光が受光側凹面鏡３１により集光されてＣＣＤカメラ４０の撮像素子４２上に結像され、ＣＣＤカメラ４０は、撮像素子４２上に形成されたＦＥＭウェハ（１０）の回折像を光電変換して画像信号を生成し、画像信号を画像処理検査部４５に出力する。 In order to capture an image of diffracted light, first, inspection light is applied to the surface of the FEM wafer (10) in a state where the illumination side polarizing filter 24 and the light receiving side polarizing filter 32 are removed from the optical path (see FIG. 1). And diffracted light (for example, first-order diffracted light) emitted from the surface of the FEM wafer (10) is detected by the CCD camera 40. At this time, the light from the light source 21 passes through the wavelength selection unit 22 and is emitted from the optical fiber 23 to the illumination side concave mirror 25, and is converted into a parallel light beam by the illumination side concave mirror 25 and held in the holder 5. Irradiate the surface. The diffracted light emitted from the surface of the FEM wafer (10) is collected by the light-receiving side concave mirror 31 and imaged on the image sensor 42 of the CCD camera 40. The CCD camera 40 is formed on the image sensor 42. The diffraction image of the FEM wafer (10) is photoelectrically converted to generate an image signal, and the image signal is output to the image processing inspection unit 45.
　このように複数の回折条件で回折光の画像を撮像すると、画像処理検査部４５は、複数の回折条件で撮像した画像についてそれぞれ、撮像した画像をショット単位で切り出し、各ショットにおける平均輝度、標準偏差等を求める（ステップＳ１０４）。そして、複数の回折条件で撮像した画像の中から、フォーカス量の変化に応じた輝度変化およびドーズ量の変化に応じた輝度変化について、輝度変化が最大となる画像すなわち回折条件を選択する（ただし、下地の膜厚の状態によりムラと判断した回折条件は除く）。ここで、ＦＥＭウェハで生じる回折光の画像の一例を図１２に示す。図１２から、フォーカス量およびドーズ量の変化に応じて、ＦＥＭウェハ１０ｆにおいてショット毎に検出される平均輝度が変化することがわかる。なお、図１２における中央の太枠が基準ショットであり、ショット毎に検出される平均輝度の大小をハッチングの濃淡で表わしている。 When images of diffracted light are captured under a plurality of diffraction conditions in this way, the image processing inspection unit 45 cuts out the captured images in units of shots for the images captured under the plurality of diffraction conditions, and calculates the average brightness and standard for each shot. A deviation or the like is obtained (step S104). Then, from among images captured under a plurality of diffraction conditions, an image that maximizes the luminance change, that is, the diffraction condition is selected for the luminance change according to the change in the focus amount and the luminance change according to the change in the dose amount (however, Except for diffraction conditions that are judged to be uneven depending on the thickness of the underlying film). Here, an example of the image of the diffracted light generated on the FEM wafer is shown in FIG. From FIG. 12, it can be seen that the average luminance detected for each shot in the FEM wafer 10f changes according to changes in the focus amount and the dose amount. Note that the thick frame at the center in FIG. 12 is a reference shot, and the magnitude of the average luminance detected for each shot is represented by shades of hatching.
　なお、繰り返しパターン１２の繰り返し方向が他と異なる部分がある場合には、できる限り方向を変えて同様に撮像し、このような条件を加えた全ての画像から、輝度変化が最大となる画像を選択する。また、回折光は０次の回折光（すなわち、正反射光）であっても構わない。 If there is a part where the repeat direction of the repeat pattern 12 is different from the others, the image is taken in the same manner while changing the direction as much as possible, and an image with the maximum luminance change is obtained from all the images to which such conditions are added. select. The diffracted light may be zero-order diffracted light (that is, regular reflection light).
　輝度変化が最大となる回折条件を選択すると、画像処理検査部４５は、そのときの回折条件（チルト角や照明波長λ等）をレシピとしてデータベース部４６に登録するとともに、当該回折条件におけるフォーカス量およびドーズ量の変化に対するショット毎の平均輝度（および標準偏差等）をデータベース部４６に登録する（ステップＳ１０５）。 When the diffraction condition that maximizes the change in luminance is selected, the image processing inspection unit 45 registers the diffraction condition (tilt angle, illumination wavelength λ, etc.) at that time in the database unit 46 as a recipe, and the focus amount under the diffraction condition. The average brightness (and standard deviation and the like) for each shot with respect to the change in dose amount is registered in the database unit 46 (step S105).
　次に、ＰＥＲ検査によるＦＥＭウェハの画像を撮像する（ステップＳ１０６）。 Next, an image of the FEM wafer by PER inspection is taken (step S106).
　ところで、前述したように、繰り返しパターン１２におけるライン部２Ａの線幅ＤAの設計値をピッチＰの１／２としている。設計値の通りに繰り返しパターン１２が形成された場合、ライン部２Ａの線幅ＤAとスペース部２Ｂの線幅ＤBは等しくなり、ライン部２Ａとスペース部２Ｂとの体積比は略１：１になる。これに対して、繰り返しパターン１２を形成する際の露光フォーカスが適正値から外れると、ピッチＰは変わらないが、ライン部２Ａの線幅ＤAが設計値と異なってしまうとともに、スペース部２Ｂの線幅ＤBとも異なってしまい、ライン部２Ａとスペース部２Ｂとの体積比が略１：１から外れる。 Incidentally, as described above, it is set to 1/2 of the pitch P of the design value of the line width D A of the line portion 2A in the repetitive pattern 12. If repeated pattern 12 is formed as the design value, the line width D B of the line width D A and the space portion 2B of the line portion 2A are equal, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: 1 In contrast, when the exposure focus at the time of forming the repeating pattern 12 deviates from a proper value, the pitch P does not change, with the line width D A of the line portion 2A becomes different from a design value, of the space portion 2B It becomes different even with the line width D B, the volume ratio of the line portion 2A and the space portion 2B is approximately 1: deviates from 1.
　ＰＥＲ検査は、上記のような繰り返しパターン１２におけるライン部２Ａとスペース部２Ｂとの体積比の変化を利用して、繰り返しパターン１２の異常検査を行うものである。なお、説明を簡単にするため、理想的な体積比（設計値）を１：１とする。体積比の変化は、露光フォーカスの適正値からの外れに起因し、ウェハ１０のショット領域ごとに現れる。なお、体積比を断面形状の面積比と言い換えることもできる。 The PER inspection performs an abnormality inspection of the repetitive pattern 12 by using a change in the volume ratio between the line portion 2A and the space portion 2B in the repetitive pattern 12 as described above. In order to simplify the description, the ideal volume ratio (design value) is 1: 1. The change in the volume ratio is caused by deviation from the appropriate value of the exposure focus, and appears for each shot area of the wafer 10. The volume ratio can also be referred to as the area ratio of the cross-sectional shape.
　ＰＥＲ検査では、照明側偏光フィルタ２４および受光側偏光フィルタ３２が光路上に挿入されるが（図２を参照）、このようなＰＥＲ検査の原理について、以降、ＰＥＲ検査を行う際の装置の構成とともに順に説明する。 In the PER inspection, the illumination-side polarizing filter 24 and the light-receiving-side polarizing filter 32 are inserted on the optical path (see FIG. 2). With regard to the principle of such PER inspection, the configuration of the apparatus when performing the PER inspection will be described hereinafter. A description will be given in order.
　前述したように、ホルダ５は、軸ＡＸを回転軸としてウェハ１０を回転可能に保持しており、ウェハ１０における繰り返しパターン１２の繰り返し方向（図３および図４におけるＸ方向）を、ウェハ１０の表面内で回転させることが可能である。ＰＥＲ検査を行うとき、ホルダ５は、ウェハ１０を水平な状態に保つとともに、所定の回転位置で停止し、ウェハ１０における繰り返しパターン１２の繰り返し方向を、後述の照明光の入射面（照明光の進行方向）に対して、４５度だけ斜めになるように保持する。 As described above, the holder 5 rotatably holds the wafer 10 about the axis AX as the rotation axis, and the repeat direction of the repeat pattern 12 on the wafer 10 (the X direction in FIGS. 3 and 4) It can be rotated in the surface. When performing the PER inspection, the holder 5 keeps the wafer 10 in a horizontal state, stops at a predetermined rotational position, and changes the repetitive direction of the repetitive pattern 12 on the wafer 10 with the illumination light incident surface (illumination light described later) (Direction of travel) is held at an angle of 45 degrees.
　照明側偏光フィルタ２４は、光ファイバ２３と照明側凹面鏡２５との間に配設されるとともに、その透過軸が所定の方位に設定され、透過軸に応じて照明部２１からの光を直線偏光に変換する。このとき、光ファイバ２３の射出部が照明側凹面鏡２５の焦点位置に配置されているため、照明側凹面鏡２５は、照明側偏光フィルタ２４を透過した光を平行光束にして、被検基板であるウェハ１０を照明する。このように、光ファイバ２３から射出された光は、照明側偏光フィルタ２４および照明側凹面鏡２５を介し第１の直線偏光Ｌ１（図６（ａ）を参照）となって、ウェハ１０の表面全体に照射される。 The illumination-side polarization filter 24 is disposed between the optical fiber 23 and the illumination-side concave mirror 25, and its transmission axis is set to a predetermined direction, and light from the illumination unit 21 is linearly polarized according to the transmission axis. Convert to At this time, since the exit portion of the optical fiber 23 is disposed at the focal position of the illumination-side concave mirror 25, the illumination-side concave mirror 25 is a test substrate by converting the light transmitted through the illumination-side polarization filter 24 into a parallel beam. The wafer 10 is illuminated. Thus, the light emitted from the optical fiber 23 becomes the first linearly polarized light L1 (see FIG. 6A) via the illumination side polarizing filter 24 and the illumination side concave mirror 25, and the entire surface of the wafer 10 is obtained. Is irradiated.
　第１の直線偏光Ｌ１の進行方向（ウェハ１０表面上の任意の点に到達する直線偏光Ｌ１の主光線の方向）は、光ファイバ２３からの光軸Ｏ１に略平行である。光軸Ｏ１は、ホルダ５の中心を通る法線（軸ＡＸ）に対して所定の角度だけ傾けられている。 The traveling direction of the first linearly polarized light L1 (the direction of the principal ray of the linearly polarized light L1 reaching an arbitrary point on the surface of the wafer 10) is substantially parallel to the optical axis O1 from the optical fiber 23. The optical axis O1 is inclined by a predetermined angle with respect to a normal line (axis AX) passing through the center of the holder 5.
　また、第１の直線偏光Ｌ１はウェハ１０に対してｐ偏光で入射する。つまり、図６（ａ）に示すように、直線偏光Ｌ１の進行方向と電気ベクトルの振動方向とを含む平面（直線偏光Ｌ１の振動面）が、直線偏光Ｌ１の入射面Ａ２内に含まれる。直線偏光Ｌ１の振動面は、照明側偏光フィルタ２４の透過軸により規定される。なお、ウェハ１０の各点における直線偏光Ｌ１の入射角は、平行光のため互いに同じであり、光軸Ｏ１と法線（軸ＡＸ）とのなす角度に相当する。 The first linearly polarized light L1 is incident on the wafer 10 as p-polarized light. That is, as shown in FIG. 6A, a plane including the traveling direction of the linearly polarized light L1 and the vibration direction of the electric vector (vibrating surface of the linearly polarized light L1) is included in the incident surface A2 of the linearly polarized light L1. The vibration plane of the linearly polarized light L <b> 1 is defined by the transmission axis of the illumination side polarizing filter 24. The incident angles of the linearly polarized light L1 at each point of the wafer 10 are the same because of the parallel light, and correspond to the angle formed by the optical axis O1 and the normal line (axis AX).
　また、ウェハ１０に入射する直線偏光Ｌ１がｐ偏光であるため、図５に示すように、繰り返しパターン１２の繰り返し方向（Ｘ方向）が直線偏光Ｌ１の入射面Ａ２（ウェハ１０の表面における直線偏光Ｌ１の進行方向）に対して４５度の角度に設定された場合、ウェハ１０の表面における直線偏光Ｌ１の振動面の方向と繰り返しパターン１２の繰り返し方向（Ｘ方向）とのなす角度も、４５度に設定される。 Further, since the linearly polarized light L1 incident on the wafer 10 is p-polarized light, as shown in FIG. 5, the repeating direction (X direction) of the repetitive pattern 12 is the incident surface A2 of the linearly polarized light L1 (linearly polarized light on the surface of the wafer 10). When the angle is set to 45 degrees with respect to the traveling direction of L1, the angle formed by the vibration plane direction of the linearly polarized light L1 on the surface of the wafer 10 and the repeating direction (X direction) of the repeating pattern 12 is also 45 degrees. Set to
　言い換えると、第１の直線偏光Ｌ１は、ウェハ１０の表面における直線偏光Ｌ１の振動面の方向（図７におけるＶの方向）が繰り返しパターン１２の繰り返し方向（Ｘ方向）に対して４５度傾いた状態で、繰り返しパターン１２を斜めに横切るようにして繰り返しパターン１２に入射する。 In other words, in the first linearly polarized light L1, the direction of the vibrating surface of the linearly polarized light L1 on the surface of the wafer 10 (direction V in FIG. 7) is inclined 45 degrees with respect to the repeating direction (X direction) of the repeating pattern 12. In this state, the light enters the repetitive pattern 12 so as to cross the repetitive pattern 12 at an angle.
　このような第１の直線偏光Ｌ１と繰り返しパターン１２との角度状態は、ウェハ１０の表面全体において均一である。なお、４５度を１３５度，２２５度，３１５度のいずれかに言い換えても、第１の直線偏光Ｌ１と繰り返しパターン１２との角度状態は同じである。また、図７の振動面の方向（Ｖ方向）と繰り返し方向（Ｘ方向）とのなす角度を４５度に設定するのは、繰り返しパターン１２の異常検査の感度を最も高くするためである。 The angle state between the first linearly polarized light L1 and the repeated pattern 12 is uniform over the entire surface of the wafer 10. Note that the angle state between the first linearly polarized light L1 and the repetitive pattern 12 is the same even if 45 degrees is replaced with any of 135 degrees, 225 degrees, and 315 degrees. The reason why the angle formed by the direction of the vibration surface (V direction) and the repeat direction (X direction) in FIG. 7 is set to 45 degrees is to maximize the sensitivity of the abnormality inspection of the repeat pattern 12.
　そして、第１の直線偏光Ｌ１を用いて繰り返しパターン１２を照明すると、繰り返しパターン１２から正反射方向に楕円偏光Ｌ２が発生する（図６（ｂ）を参照）。この場合、楕円偏光Ｌ２の進行方向が正反射方向に一致する。正反射方向とは、直線偏光Ｌ１の入射面Ａ２内に含まれ、直線偏光Ｌ１の入射角に等しい角度だけ傾いた方向である。 Then, when the repeated pattern 12 is illuminated using the first linearly polarized light L1, elliptically polarized light L2 is generated from the repeated pattern 12 in the regular reflection direction (see FIG. 6B). In this case, the traveling direction of the elliptically polarized light L2 coincides with the regular reflection direction. The regular reflection direction is a direction that is included in the incident surface A2 of the linearly polarized light L1 and is inclined by an angle equal to the incident angle of the linearly polarized light L1.
　ここで、第１の直線偏光Ｌ１が繰り返しパターン１２での反射により楕円化し、繰り返しパターン１２から楕円偏光Ｌ２が発生する理由について簡単に説明する。第１の直線偏光Ｌ１は、繰り返しパターン１２に入射すると、振動面の方向（図７のＶ方向）が、図８に示す２つの偏光成分ＶX，ＶYに分かれる。一方の偏光成分ＶXは、繰り返し方向（Ｘ方向）に平行な成分である。他方の偏光成分ＶYは、繰り返し方向（Ｘ方向）に垂直な成分である。そして、２つの偏光成分ＶX，ＶYは、それぞれ独立に、異なる振幅変化と位相変化とを受ける。振幅変化と位相変化が異なるのは、繰り返しパターン１２の異方性に起因して複素反射率（すなわち複素数の振幅反射率）が異なるからであり、構造性複屈折（form birefringence）と呼ばれる。その結果、２つの偏光成分ＶX，ＶYの反射光は互いに振幅と位相が異なり、これらの合成による反射光は楕円偏光Ｌ２となる（図６（ｂ）を参照）。ここで、構造性複屈折を発生させるためには、照射する光の波長がパターンに対して十分に長い必要がある。また、照射する光の波長がパターンに対して長くなると回折光は観察しにくくなるため、ＰＥＲ検査をする際に用いる光は回折検査をする際に用いる光とは異なり長い波長の光を用いる。 Here, the reason why the first linearly polarized light L1 is ovalized by reflection at the repeated pattern 12 and the elliptically polarized light L2 is generated from the repeated pattern 12 will be briefly described. When the first linearly polarized light L1 is incident on the repetitive pattern 12, the direction of the vibration surface (the V direction in FIG. 7) is divided into two polarization components V X and V Y shown in FIG. One polarization component V X is a component parallel to the repetition direction (X direction). The other polarization component V Y is a component perpendicular to the repetition direction (X direction). The two polarization components V X and V Y are independently subjected to different amplitude changes and phase changes. The reason why the amplitude change and the phase change are different is that the complex reflectivity (that is, the complex amplitude reflectivity) is different due to the anisotropy of the repetitive pattern 12, and is called structural birefringence. As a result, the reflected lights of the two polarization components V X and V Y have different amplitudes and phases, and the reflected light obtained by combining these becomes elliptically polarized light L2 (see FIG. 6B). Here, in order to generate structural birefringence, the wavelength of light to be irradiated needs to be sufficiently long with respect to the pattern. In addition, since the diffracted light becomes difficult to observe when the wavelength of the irradiated light is longer than the pattern, the light used for the PER inspection uses light having a long wavelength unlike the light used for the diffraction inspection.
　また、繰り返しパターン１２の異方性に起因する楕円化の程度は、図６（ｂ）で示す楕円偏光Ｌ２のうち、図６（ａ）で示す直線偏光Ｌ１の振動面に垂直な偏光成分Ｌ３（図６（ｃ）を参照）と考えることができる。そして、この偏光成分Ｌ３の大きさは、繰り返しパターン１２の材質および形状と、図７の振動面の方向（Ｖ方向）と繰り返し方向（Ｘ方向）とのなす角度に依存する。このため、Ｖ方向とＸ方向とのなす角度を一定の値（本実施形態では４５度）に保つ場合、繰り返しパターン１２の材質が一定であっても、繰り返しパターン１２の形状が変化すると、楕円化の程度（偏光成分Ｌ３の大きさ）が変化することになる。 The degree of ovalization caused by the anisotropy of the repetitive pattern 12 is the polarization component L3 perpendicular to the vibration plane of the linearly polarized light L1 shown in FIG. 6A among the elliptically polarized light L2 shown in FIG. (See FIG. 6C). The magnitude of the polarization component L3 depends on the material and shape of the repetitive pattern 12 and the angle formed by the vibration plane direction (V direction) and the repetitive direction (X direction) in FIG. For this reason, when the angle formed between the V direction and the X direction is kept at a constant value (45 degrees in the present embodiment), even if the material of the repeating pattern 12 is constant, the shape of the repeating pattern 12 changes to an elliptical shape. The degree of conversion (the magnitude of the polarization component L3) changes.
　繰り返しパターン１２の形状と偏光成分Ｌ３の大きさとの関係について説明する。図４に示すように、繰り返しパターン１２は、ライン部２Ａとスペース部２ＢとをＸ方向に沿って交互に配列した凹凸形状を有し、適正な露光フォーカスで設計値通りに形成されると、ライン部２Ａの線幅ＤAとスペース部２Ｂの線幅ＤBが等しく、ライン部２Ａとスペース部２Ｂとの体積比が略１：１となる。このような理想的な形状の場合、偏光成分Ｌ３の大きさは最も大きくなる。これに対し、露光フォーカスが適正値から外れると、ライン部２Ａとスペース部２Ｂとの体積比が略１：１から外れる。このとき、偏光成分Ｌ３の大きさは理想的な場合と比較して小さくなる。偏光成分Ｌ３の大きさの変化を図示すると、図９のようになる。図９の横軸は、ライン部２Ａの線幅ＤAである。 A relationship between the shape of the repeated pattern 12 and the size of the polarization component L3 will be described. As shown in FIG. 4, the repetitive pattern 12 has a concavo-convex shape in which the line portions 2A and the space portions 2B are alternately arranged along the X direction, and is formed as designed with an appropriate exposure focus. line width D B is equal to the line width D a and the space portion 2B of the line portion 2A, the volume ratio of the line portion 2A and the space portion 2B is substantially 1: 1. In the case of such an ideal shape, the size of the polarization component L3 is the largest. On the other hand, when the exposure focus deviates from an appropriate value, the volume ratio between the line portion 2A and the space portion 2B deviates from about 1: 1. At this time, the size of the polarization component L3 is smaller than the ideal case. A change in the magnitude of the polarization component L3 is illustrated in FIG. The horizontal axis in FIG. 9 is the line width D A of the line portion 2A.
　このように、第１の直線偏光Ｌ１を用いて、図７の振動面の方向（Ｖ方向）が繰り返しパターン１２の繰り返し方向（Ｘ方向）に対して４５度だけ傾いた状態で、繰り返しパターン１２を照明すると、正反射方向に反射して生じた楕円偏光Ｌ２は、その楕円化の程度（図６（ｃ）における偏光成分Ｌ３の大きさ）が、繰り返しパターン１２の形状（ライン部２Ａとスペース部２Ｂとの体積比）に応じたものとなる。楕円偏光Ｌ２の進行方向は、直線偏光Ｌ１の入射面Ａ２内に含まれ、ホルダ５の中心を通る法線（軸ＡＸ）に対して直線偏光Ｌ１の進行方向と対称に傾いている。 In this way, using the first linearly polarized light L1, the repetitive pattern 12 with the vibration plane direction (V direction) in FIG. 7 inclined by 45 degrees with respect to the repetitive direction (X direction) of the repetitive pattern 12 is used. , The elliptically polarized light L2 generated by reflection in the regular reflection direction has a degree of ovalization (the magnitude of the polarization component L3 in FIG. 6C) having the shape of the repeated pattern 12 (line portion 2A and space). The volume ratio with respect to the part 2B). The traveling direction of the elliptically polarized light L2 is included in the incident surface A2 of the linearly polarized light L1, and is inclined symmetrically with respect to the traveling direction of the linearly polarized light L1 with respect to the normal line (axis AX) passing through the center of the holder 5.
　なお、集光光学系３０の光軸Ｏ２は、ホルダ５の中心を通る法線（軸ＡＸ）に対して正反射方向に傾くように設定される。したがって、繰り返しパターン１２からの反射光である楕円偏光Ｌ２は、この光軸Ｏ２に沿って進むことになる。 The optical axis O2 of the condensing optical system 30 is set so as to be inclined in the regular reflection direction with respect to the normal (axis AX) passing through the center of the holder 5. Therefore, the elliptically polarized light L2 that is the reflected light from the repetitive pattern 12 travels along the optical axis O2.
　受光側偏光フィルタ３２は、集光光学系３０の受光側凹面鏡３１とＣＣＤカメラ４０との間に配設され、ウェハ１０表面からの正反射光を透過させて第２の直線偏光Ｌ４（図６（ｃ）を参照）に変換する。受光側偏光フィルタ３２の透過軸の方位は、上述した照明側偏光フィルタ３２の透過軸に対して垂直になるように設定される。すなわち、第２の直線偏光Ｌ４の進行方向と垂直な面内における第２の直線偏光Ｌ４の振動方向が、第１の直線偏光Ｌ１の進行方向と垂直な面内における第１の直線偏光Ｌ１の振動方向に対して略垂直になるように設定される。 The light-receiving side polarizing filter 32 is disposed between the light-receiving side concave mirror 31 of the condensing optical system 30 and the CCD camera 40, and transmits the specularly reflected light from the surface of the wafer 10 to transmit the second linearly polarized light L4 (FIG. 6). (See (c)). The direction of the transmission axis of the light receiving side polarizing filter 32 is set to be perpendicular to the transmission axis of the illumination side polarizing filter 32 described above. That is, the vibration direction of the second linearly polarized light L4 in the plane perpendicular to the traveling direction of the second linearly polarized light L4 is the same as that of the first linearly polarized light L1 in the plane perpendicular to the traveling direction of the first linearly polarized light L1. It is set to be substantially perpendicular to the vibration direction.
　したがって、楕円偏光Ｌ２が受光側偏光フィルタ３２を透過すると、楕円偏光Ｌ２の図６（ｃ）における偏光成分Ｌ３に相当する直線偏光Ｌ４のみが抽出されて、ＣＣＤカメラ４０に導かれる。その結果、ＣＣＤカメラ４０の撮像素子４２上には、第２の直線偏光Ｌ４によるウェハ１０の反射像がそれぞれ形成される。なお、ウェハ１０の反射像の明暗は、直線偏光Ｌ４の光強度に略比例し、繰り返しパターン１２の形状に応じて変化する。また、ウェハ１０の反射像が最も明るくなるのは、繰り返しパターン１２が理想的な形状の場合である。 Therefore, when the elliptically polarized light L2 passes through the light receiving side polarizing filter 32, only the linearly polarized light L4 corresponding to the polarized component L3 in FIG. 6C of the elliptically polarized light L2 is extracted and guided to the CCD camera 40. As a result, a reflected image of the wafer 10 by the second linearly polarized light L4 is formed on the image sensor 42 of the CCD camera 40, respectively. The brightness of the reflected image of the wafer 10 is substantially proportional to the light intensity of the linearly polarized light L4 and changes according to the shape of the repeated pattern 12. The reflected image of the wafer 10 is brightest when the repeated pattern 12 has an ideal shape.
　ＰＥＲ検査によるＦＥＭウェハの画像を撮像するには、まず、照明側偏光フィルタ２４および受光側偏光フィルタ３２を光路上に挿入した状態（図２を参照）で、ＦＥＭウェハ（１０）の表面に第１の直線偏光Ｌ１を照射し、ＦＥＭウェハ（１０）の表面で反射した正反射光（楕円偏光Ｌ２）を受光側偏光フィルタ３２を介してＣＣＤカメラ４０で検出する。このとき、光源２１からの光が波長選択部２２を透過して光ファイバ２３から射出され、照明側偏光フィルタ２４で第１の直線偏光Ｌ１に変換されるとともに、照明側凹面鏡２５により平行光束となってホルダ５に保持されたＦＥＭウェハ（１０）の表面に照射される。そして、ＦＥＭウェハ（１０）の表面で反射した正反射光（楕円偏光Ｌ２）が受光側凹面鏡３１により集光され、受光側偏光フィルタ３２で第２の直線偏光Ｌ４に変換されてＣＣＤカメラ４０の撮像素子４２上に結像され、ＣＣＤカメラ４０は、撮像素子４２上に形成された第２の直線偏光Ｌ４によるＦＥＭウェハ（１０）の反射像を光電変換して画像信号を生成し、画像信号を画像処理検査部４５に出力する。 In order to capture an image of the FEM wafer by the PER inspection, first, the illumination side polarizing filter 24 and the light receiving side polarizing filter 32 are inserted on the optical path (see FIG. 2), and the FEM wafer is placed on the surface of the FEM wafer (10). The regular reflected light (elliptical polarized light L2) reflected by the surface of the FEM wafer (10) is detected by the CCD camera 40 via the light receiving side polarizing filter 32. At this time, the light from the light source 21 passes through the wavelength selection unit 22 and is emitted from the optical fiber 23, converted into the first linearly polarized light L 1 by the illumination side polarization filter 24, and converted into a parallel light flux by the illumination side concave mirror 25. The surface of the FEM wafer (10) held by the holder 5 is irradiated. Then, the specularly reflected light (elliptical polarized light L2) reflected by the surface of the FEM wafer (10) is condensed by the light receiving side concave mirror 31 and converted into the second linearly polarized light L4 by the light receiving side polarizing filter 32, and the CCD camera 40 The image is formed on the image sensor 42, and the CCD camera 40 photoelectrically converts the reflected image of the FEM wafer (10) by the second linearly polarized light L 4 formed on the image sensor 42 to generate an image signal. Is output to the image processing inspection unit 45.
　なお、ＰＥＲ検査によるＦＥＭウェハの画像を撮像する際、ウェハの表面上における照明方向（直線偏光Ｌ１の振動面の方向）と繰り返しパターン１２の繰り返し方向とのなす角度が４５度になるようにホルダ５を回転させるともに、直線偏光Ｌ１の入射角と楕円偏光Ｌ２の出射角とが等しく（正反射方向に）なるようにホルダ５をチルトさせる。そして、波長選択部２２により照明波長を変化させた複数のＰＥＲ条件で撮像を行う。またこのとき、ベストフォーカスかつベストドーズのショットを基準ショットとし、撮像する画像の輝度が最適な輝度になるように照明光量を設定する。なお、照明光量を変えずに、ＣＣＤカメラ４０の露光時間を変えて設定するようにしてもよい。 When taking an image of the FEM wafer by PER inspection, the holder is set so that the angle formed by the illumination direction (the direction of the vibrating surface of the linearly polarized light L1) on the surface of the wafer and the repeating direction of the repeating pattern 12 is 45 degrees. 5 is rotated and the holder 5 is tilted so that the incident angle of the linearly polarized light L1 and the outgoing angle of the elliptically polarized light L2 are equal (in the regular reflection direction). Then, imaging is performed under a plurality of PER conditions in which the illumination wavelength is changed by the wavelength selection unit 22. At this time, the best focus and best dose shot is set as the reference shot, and the illumination light quantity is set so that the brightness of the image to be captured becomes the optimum brightness. Note that the exposure time of the CCD camera 40 may be changed and set without changing the amount of illumination light.
　このように複数のＰＥＲ条件で撮像すると、画像処理検査部４５は、複数のＰＥＲ条件で撮像した画像についてそれぞれ、撮像した画像をショット単位で切り出し、各ショットにおける平均輝度、標準偏差等を求める（ステップＳ１０７）。そして、複数のＰＥＲ条件で撮像した画像の中から、フォーカス量の変化に応じた輝度変化およびドーズ量の変化に応じた輝度変化について、輝度変化が最大となる画像すなわちＰＥＲ条件を選択する（ただし、下地の膜厚の状態によりムラと判断したＰＥＲ条件は除く）。ここで、ＰＥＲ検査によるＦＥＭウェハの画像の一例を図１３に示す。図１３から、フォーカス量およびドーズ量の変化に応じて、ＦＥＭウェハ１０ｆにおいてショット毎に検出される平均輝度が変化することがわかる。なお、図１３における中央の太枠が基準ショットであり、ショット毎に検出される平均輝度の大小をハッチングの濃淡で表わしている。 When imaging is performed under a plurality of PER conditions as described above, the image processing inspection unit 45 cuts out the captured images in units of shots for images captured under the plurality of PER conditions, and obtains average brightness, standard deviation, and the like in each shot ( Step S107). Then, an image that maximizes the luminance change, that is, the PER condition is selected from the images captured under a plurality of PER conditions, with respect to the luminance change according to the change in the focus amount and the luminance change according to the change in the dose amount (however, The PER condition that is determined to be uneven depending on the film thickness of the base film is excluded). Here, an example of the image of the FEM wafer by the PER inspection is shown in FIG. FIG. 13 shows that the average luminance detected for each shot in the FEM wafer 10f changes according to changes in the focus amount and the dose amount. Note that the thick frame at the center in FIG. 13 is a reference shot, and the magnitude of the average luminance detected for each shot is represented by shades of hatching.
　なお、ウェハの表面上における照明方向（直線偏光Ｌ１の振動面の方向）と繰り返しパターン１２の繰り返し方向とのなす角度については、４５度以外に、６７．５度または２２.５度、さらには、１３５度、１１２．５度または１５７．５度の場合についても同様に画像を撮像し、４５度の場合と合わせて輝度変化が最大となる画像（すなわちＰＥＲ条件）を選択するようにしてもよい。 The angle formed between the illumination direction on the wafer surface (the direction of the vibrating surface of the linearly polarized light L1) and the repeating direction of the repeating pattern 12 is 67.5 degrees or 22.5 degrees, in addition to 45 degrees, In the case of 135 degrees, 112.5 degrees, or 157.5 degrees, an image is picked up in the same manner, and an image (that is, PER condition) that maximizes the luminance change is selected together with the case of 45 degrees. Good.
　輝度変化が最大となるＰＥＲ条件を選択すると、画像処理検査部４５は、そのときのＰＥＲ条件（照明波長やチルト角等）をレシピとしてデータベース部４６に登録するとともに、当該ＰＥＲ条件におけるフォーカス量およびドーズ量の変化に対するショット毎の平均輝度（および標準偏差等）をデータベース部４６に登録する（ステップＳ１０８）。 When the PER condition that maximizes the luminance change is selected, the image processing inspection unit 45 registers the PER condition (illumination wavelength, tilt angle, etc.) at that time in the database unit 46 as a recipe, The average brightness (and standard deviation, etc.) for each shot with respect to the change in dose is registered in the database unit 46 (step S108).
　以上のようにしてレシピ作成工程が行われるが、フォーカス量およびドーズ量の変化に対するショット毎の平均輝度は、回折検査およびＰＥＲ検査についてそれぞれ２種類ずつ存在し、回折検査におけるフォーカスおよびドーズの変化量と平均輝度との相関、並びに、ＰＥＲ検査におけるフォーカスおよびドーズの変化量と平均輝度との相関がそれぞれ求められ、これらのデータベースがデータベース部４６で作成されることになる。例えば、図１４に示すように、ＦＥＭウェハ１０ｆを用いることにより、回折検査において、ベストフォーカスかつベストドーズである基準ショットのときの平均輝度ｃ０が求められ、さらに、ベストフォーカスに対するフォーカスのズレ量（変化量）を±ａ１，±ａ２，±ａ３とし、ベストドーズに対するドーズのズレ量（変化量）を±ｂ１，±ｂ２，±ｂ３としたときに、図１２に示す輝度分布からそれぞれの場合の平均輝度ｃ１～ｃ１１が求められる。また、ＰＥＲ検査において、ベストフォーカスかつベストドーズである基準ショットのときの平均輝度ｄ０が求められ、さらに、図１３に示す輝度分布から、フォーカスのズレ量が±ａ１，±ａ２，±ａ３、ドーズのズレ量が±ｂ１，±ｂ２，±ｂ３である場合の平均輝度ｄ１～ｄ５が求められる。なお、説明容易化のため、図１２～図１４においてショット毎の輝度分布を粗い精度で示しているが、実際はもっと多様な輝度分布となる。 Although the recipe creation process is performed as described above, there are two types of average luminance for each shot with respect to changes in the focus amount and the dose amount, respectively for the diffraction inspection and the PER inspection, and the amount of change in focus and dose in the diffraction inspection. And the average luminance, and the correlation between the focus and dose variation in the PER inspection and the average luminance are obtained, and these databases are created in the database unit 46. For example, as shown in FIG. 14, by using the FEM wafer 10f, the average luminance c0 at the time of the reference shot having the best focus and the best dose is obtained in the diffraction inspection, and further, the amount of focus shift with respect to the best focus ( Change amount) is ± a1, ± a2, ± a3, and the deviation amount (change amount) of the dose with respect to the best dose is ± b1, ± b2, ± b3, from the luminance distribution shown in FIG. Average luminances c1 to c11 are obtained. Further, in the PER inspection, the average luminance d0 at the time of the reference shot having the best focus and the best dose is obtained. Further, the deviation amount of the focus is ± a1, ± a2, ± a3, dose from the luminance distribution shown in FIG. Average luminances d1 to d5 are obtained when the amount of deviation is ± b1, ± b2, ± b3. For ease of explanation, the luminance distribution for each shot is shown with coarse accuracy in FIGS. 12 to 14, but actually, the luminance distribution is more diverse.
　図１５に、フォーカスのズレ量を一定とした場合の、回折検査およびＰＥＲ検査におけるフォーカスのズレ量とベストフォーカスショットを基準とするショット平均低下輝度との相関の一例を示す。図１５からわかるように、回折検査だけ、もしくはＰＥＲ検査だけの相関を用いても、平均輝度からフォーカスのズレ量をある程度予想することは可能であるが、図１５における丸印で示すように、ショット平均低下輝度が同じでもズレの極性が異なる場合があり、ＰＥＲ検査（もしくは回折検査）だけではズレの極性が判らず、極性を含めたフォーカスのズレ量を特定することができない。 FIG. 15 shows an example of the correlation between the focus shift amount in the diffraction inspection and the PER inspection and the shot average lowering luminance based on the best focus shot when the focus shift amount is constant. As can be seen from FIG. 15, it is possible to predict the amount of focus deviation from the average luminance to some extent even using only the diffraction inspection or the correlation of the PER inspection, but as shown by the circles in FIG. Even if the shot average reduced luminance is the same, the polarity of the deviation may be different, and the polarity of the deviation cannot be determined only by the PER inspection (or diffraction inspection), and the amount of focus deviation including the polarity cannot be specified.
　これに対し、本実施形態の表面検査装置１および方法によれば、回折検査におけるフォーカスおよびドーズのズレ量（変化量）と平均輝度との相関、並びに、ＰＥＲ検査におけるフォーカスおよびドーズのズレ量と平均輝度との相関を組み合わせて、フォーカスおよびドーズのズレ量を特定するため、極性を含めたフォーカスおよびドーズのズレ量をそれぞれ精度よく特定することができる。またこれにより、露光時の不具合箇所を早く特定することができるため、露光装置等を短時間で調整することが可能になり、ウェハの歩留まりを改善することが期待でき、スループットの向上も期待できる。さらに、フォーカスおよびドーズのズレ量を把握することで、露光装置の状態管理やコータの状態管理が可能になる。 On the other hand, according to the surface inspection apparatus 1 and method of the present embodiment, the correlation between the focus and dose shift amount (change amount) in the diffraction inspection and the average luminance, and the focus and dose shift amount in the PER inspection Since the amount of focus and dose deviation is specified by combining the correlation with the average luminance, the amount of focus and dose deviation including polarity can be specified with high accuracy. In addition, this makes it possible to quickly identify a defective part at the time of exposure, so that it is possible to adjust the exposure apparatus and the like in a short time, and it can be expected to improve the yield of the wafer, and also to improve the throughput. . Further, by knowing the amount of deviation between focus and dose, it becomes possible to manage the state of the exposure apparatus and the state of the coater.
　このようにレシピを作成した後、作成したレシピに基づいて検査工程を行う。この検査工程においては、図１１に示すように、まず、被検基板であるウェハ１０をホルダ５上に搬送し（ステップＳ２０１）、アライメントを実施する（ステップＳ２０２）。 After creating the recipe in this way, the inspection process is performed based on the created recipe. In this inspection process, as shown in FIG. 11, first, the wafer 10 which is a substrate to be tested is transferred onto the holder 5 (step S201), and alignment is performed (step S202).
　アライメントを行った後、先のステップＳ１０５で登録したレシピ（回折条件）にてウェハ１０の画像を撮像する（ステップＳ２０３）。このとき、照明側偏光フィルタ２４および受光側偏光フィルタ３２が光路上から抜去された状態（図１を参照）で、光源２１からの光が波長選択部２２を透過して光ファイバ２３から照明側凹面鏡２５へ射出され、照明側凹面鏡２５により平行光束となってホルダ５に保持されたウェハ１０の表面に照射される。そして、ウェハ１０の表面から出射された回折光が受光側凹面鏡３１により集光されてＣＣＤカメラ４０の撮像素子４２上に結像され、ＣＣＤカメラ４０は、撮像素子４２上に形成されたウェハ１０の回折像を光電変換して画像信号を生成し、画像信号を画像処理検査部４５に出力する。 After performing the alignment, an image of the wafer 10 is taken with the recipe (diffraction condition) registered in the previous step S105 (step S203). At this time, in a state where the illumination side polarization filter 24 and the light reception side polarization filter 32 are removed from the optical path (see FIG. 1), light from the light source 21 passes through the wavelength selection unit 22 and is transmitted from the optical fiber 23 to the illumination side. The light is emitted to the concave mirror 25 and is irradiated onto the surface of the wafer 10 held by the holder 5 as a parallel light beam by the illumination-side concave mirror 25. Then, the diffracted light emitted from the surface of the wafer 10 is collected by the light-receiving-side concave mirror 31 and imaged on the image sensor 42 of the CCD camera 40, and the CCD camera 40 is formed on the image sensor 42. The diffraction image is photoelectrically converted to generate an image signal, and the image signal is output to the image processing inspection unit 45.
　次に、先のステップＳ１０８で登録したレシピ（ＰＥＲ条件）にてウェハ１０の画像を撮像する（ステップＳ２０４）。このとき、照明側偏光フィルタ２４および受光側偏光フィルタ３２が光路上に挿入された状態（図２を参照）で、光源２１からの光が波長選択部２２を透過して光ファイバ２３から射出され、照明側偏光フィルタ２４で第１の直線偏光Ｌ１に変換されるとともに、照明側凹面鏡２５により平行光束となってホルダ５に保持されたウェハ１０の表面に照射される。そして、ウェハ１０の表面で反射した正反射光（楕円偏光Ｌ２）が受光側凹面鏡３１により集光され、受光側偏光フィルタ３２で第２の直線偏光Ｌ４に変換されてＣＣＤカメラ４０の撮像素子４２上に結像され、ＣＣＤカメラ４０は、撮像素子４２上に形成された第２の直線偏光Ｌ４によるウェハ１０の反射像を光電変換して画像信号を生成し、画像信号を画像処理検査部４５に出力する。 Next, an image of the wafer 10 is taken with the recipe (PER condition) registered in the previous step S108 (step S204). At this time, the light from the light source 21 passes through the wavelength selection unit 22 and is emitted from the optical fiber 23 with the illumination side polarizing filter 24 and the light receiving side polarizing filter 32 inserted in the optical path (see FIG. 2). The illumination-side polarizing filter 24 converts the light into the first linearly polarized light L1, and the illumination-side concave mirror 25 irradiates the surface of the wafer 10 held by the holder 5 with a parallel light beam. Then, the specularly reflected light (elliptical polarized light L2) reflected by the surface of the wafer 10 is collected by the light receiving side concave mirror 31 and converted into the second linearly polarized light L4 by the light receiving side polarizing filter 32, and the image sensor 42 of the CCD camera 40 is used. The CCD camera 40 forms an image signal by photoelectrically converting the reflected image of the wafer 10 by the second linearly polarized light L4 formed on the image sensor 42, and the image signal is converted into an image processing inspection unit 45. Output to.
　次に、画像処理検査部４５は、ステップＳ２０３およびＳ２０４で撮像した画像についてそれぞれ、撮像した画像をショット単位で切り出し、各ショットにおける平均輝度、標準偏差等を求める（ステップＳ２０５）。これにより、回折検査におけるショット毎の平均輝度およびＰＥＲ検査におけるショット毎の平均輝度が求められる。 Next, the image processing inspection unit 45 cuts out the captured images for each of the images captured in steps S203 and S204, and obtains the average brightness, standard deviation, etc. in each shot (step S205). Thereby, the average luminance for each shot in the diffraction inspection and the average luminance for each shot in the PER inspection are obtained.
　そして、ショット毎に、回折検査における平均輝度を（データベース部４６に登録された）データベース上の（回折検査における）平均輝度と照合するとともに、ＰＥＲ検査における平均輝度をデータベース上の（ＰＥＲ検査における）平均輝度と照合することにより、フォーカスのズレ量またはドーズのズレ量を求め、繰り返しパターン１２における異常の有無を検査する。例えば、図１４に示す場合、回折検査における平均輝度がｃ６であり、ＰＥＲ検査における平均輝度がｄ５であるとき、フォーカスのズレ量が－ａ２となり、ドーズのズレ量が－ｂ３となる。なお、平均輝度に加え、標準偏差等を照合するようにしてもよい。このようにすれば、データベース上の輝度データと照合するため短時間で検査を行うことが可能になる。 Then, for each shot, the average luminance in the diffraction inspection is collated with the average luminance (in the diffraction inspection) on the database (registered in the database unit 46), and the average luminance in the PER inspection on the database (in the PER inspection). By comparing with the average luminance, a focus shift amount or a dose shift amount is obtained, and the presence or absence of abnormality in the repeated pattern 12 is inspected. For example, in the case shown in FIG. 14, when the average luminance in the diffraction inspection is c6 and the average luminance in the PER inspection is d5, the focus shift amount is -a2, and the dose shift amount is -b3. In addition to the average luminance, a standard deviation or the like may be collated. In this way, it is possible to perform inspection in a short time because it is compared with the luminance data on the database.
　なお、上述の実施形態において、回折検査における平均輝度とＰＥＲ検査における平均輝度だけで、フォーカスのズレ量またはドーズのズレ量を完全に判別することができない場合、データベース部４６に登録する（すなわち、回折検査を行う）回折条件の数を複数に増やしても構わない。例えば図１４に示す場合、フォーカスのズレ量が±ａ１，±ａ２，±ａ３、ドーズのズレ量が±ｂ１，±ｂ２，±ｂ３である場合の平均輝度を、複数の回折条件について（ｃ０～ｃ１１となる条件に加えて別条件のものを）それぞれ登録する。このようにすれば、データベース上で照合する平均輝度の条件数が増えるため、フォーカスおよびドーズのズレ量をより精度よく特定することができる。一方、データベース部４６に登録する（すなわち、ＰＥＲ検査を行う）ＰＥＲ条件の数を複数に増やすようにしてもよく、回折条件の数を増やす場合と同様の効果を得ることができる。 In the above-described embodiment, when it is not possible to completely determine the focus shift amount or the dose shift amount only by the average brightness in the diffraction inspection and the average brightness in the PER inspection, the information is registered in the database unit 46 (that is, The number of diffraction conditions (for diffraction inspection) may be increased to a plurality. For example, in the case shown in FIG. 14, the average brightness when the focus shift amount is ± a1, ± a2, ± a3 and the dose shift amount is ± b1, ± b2, ± b3, for a plurality of diffraction conditions (c0 to In addition to the condition of c11, another condition) is registered. In this way, the number of conditions of average brightness to be collated on the database increases, so that the amount of focus and dose deviation can be specified more accurately. On the other hand, the number of PER conditions registered in the database unit 46 (that is, performing PER inspection) may be increased to a plurality, and the same effect as in the case of increasing the number of diffraction conditions can be obtained.
　また、上述の実施形態において、直線偏光Ｌ１がｐ偏光である例を説明したが、これに限定されるものではない。例えば、ｐ偏光ではなくｓ偏光にしてもよい。ｓ偏光とは、振動面が入射面に垂直な直線偏光である。このため、図５に示すように、ウェハ１０における繰り返しパターン１２の繰り返し方向（Ｘ方向）が、ｓ偏光である直線偏光Ｌ１の入射面Ａ２に対して４５度の角度に設定された場合、ウェハ１０の表面におけるｓ偏光の振動面の方向と繰り返しパターン１２の繰り返し方向（Ｘ方向）とのなす角度も、４５度に設定される。なお、ｐ偏光は、繰り返しパターン１２のライン部２Ａのエッジ形状に拘わる異常情報を取得するのに有利である。また、ｓ偏光は、ウェハ１０の表面の異常情報を効率よく捉えて、ＳＮ比を向上させるのに有利である。 In the above-described embodiment, the example in which the linearly polarized light L1 is p-polarized light has been described, but the present invention is not limited to this. For example, s-polarized light instead of p-polarized light may be used. The s-polarized light is linearly polarized light whose vibration surface is perpendicular to the incident surface. Therefore, as shown in FIG. 5, when the repeating direction (X direction) of the repeating pattern 12 on the wafer 10 is set to an angle of 45 degrees with respect to the incident surface A2 of the linearly polarized light L1 that is s-polarized light, the wafer The angle formed by the direction of the vibrating surface of the s-polarized light on the surface 10 and the repeating direction (X direction) of the repeating pattern 12 is also set to 45 degrees. Note that the p-polarized light is advantageous for acquiring abnormal information related to the edge shape of the line portion 2A of the repetitive pattern 12. Further, the s-polarized light is advantageous for efficiently capturing abnormal information on the surface of the wafer 10 and improving the SN ratio.
　さらに、ｐ偏光やｓ偏光に限らず、振動面が入射面に対して任意の傾きを持つような直線偏光でも構わない。この場合、繰り返しパターン１２の繰り返し方向（Ｘ方向）を直線偏光Ｌ１の入射面に対して４５度以外の角度に設定し、ウェハ１０の表面における直線偏光Ｌ１の振動面の方向と繰り返しパターン１２の繰り返し方向（Ｘ方向）とのなす角度を、４５度に設定することが好ましい。 Furthermore, not only p-polarized light and s-polarized light, but also linearly polarized light whose vibration surface has an arbitrary inclination with respect to the incident surface may be used. In this case, the repetitive direction (X direction) of the repetitive pattern 12 is set to an angle other than 45 degrees with respect to the incident surface of the linearly polarized light L1, and the direction of the vibration surface of the linearly polarized light L1 on the surface of the wafer 10 and the repetitive pattern 12 It is preferable to set the angle formed by the repeat direction (X direction) to 45 degrees.
　また、上述の実施形態では、光源２１からの照明光と照明側偏光フィルタ２４を利用して、直線偏光Ｌ１を作り出すように構成されているが、これに限られるものではなく、レーザを光源として使用すれば照明側偏光フィルタ２４は必要ない。また、ＣＣＤカメラ４０に替えて、ＣＭＯＳ等の増幅型固体撮像素子を用いることも可能である。 In the above-described embodiment, the linearly polarized light L1 is generated using the illumination light from the light source 21 and the illumination-side polarization filter 24. However, the present invention is not limited to this, and a laser is used as the light source. If used, the illumination side polarizing filter 24 is not necessary. Further, instead of the CCD camera 40, an amplification type solid-state imaging device such as a CMOS can be used.
　また、上述の実施形態において、ＣＣＤカメラ４０で撮像した画像について、ショット毎の平均輝度を求めているが、これはメモリ回路のように各ショットにおいて均一な繰り返しパターンが存在する場合に有効であり、例えばロジック回路等のように、各ショットにおいて繰り返しパターンの存在しない領域が存在する場合には、各ショットにおけるパターンの存在する領域を部分的に切り出して平均輝度を求めるようにしてもよい。 In the above-described embodiment, the average luminance for each shot is obtained for the image captured by the CCD camera 40. This is effective when a uniform repetitive pattern exists in each shot as in a memory circuit. For example, when there is an area where no repeated pattern exists in each shot, such as a logic circuit, the area where the pattern exists in each shot may be partially cut out to obtain the average luminance.

Claims (6)

  1. 　所定の繰り返しパターンを有する被検基板の表面に検査光を照射する検査光照明部と、
    　前記検査光が照射された前記被検基板の表面からの回折光を検出する回折光検出部と、
    　前記被検基板の表面に第１の直線偏光を照射する偏光照明部と、
    　前記第１の直線偏光が照射された前記被検基板の表面からの反射光を前記第１の直線偏光と振動方向が異なる第２の直線偏光に変換する偏光変換部と、
    　前記第２の直線偏光を検出する偏光検出部と、
    　前記回折光検出部で検出された前記回折光および、前記偏光検出部で検出された前記第２の直線偏光に基づいて、前記繰り返しパターンにおける異常の有無を検査する検査部とを備え、
    　前記検査部は、前記異常の原因毎に予め求められた前記異常の原因の大きさと前記回折光の輝度との相関および、前記異常の原因の大きさと前記第２の直線偏光の輝度との相関に基づいて、前記異常の原因を特定することを特徴とする表面検査装置。     An inspection light illumination unit that irradiates the surface of the test substrate having a predetermined repeating pattern with inspection light; and
    A diffracted light detector for detecting diffracted light from the surface of the substrate to be inspected irradiated with the inspection light;
    A polarized illumination unit that irradiates the surface of the test substrate with first linearly polarized light;
    A polarization converter that converts reflected light from the surface of the test substrate irradiated with the first linearly polarized light into second linearly polarized light having a vibration direction different from that of the first linearly polarized light;
    A polarization detector for detecting the second linearly polarized light;
    An inspection unit that inspects whether there is an abnormality in the repetitive pattern based on the diffracted light detected by the diffracted light detection unit and the second linearly polarized light detected by the polarization detection unit;
    The inspection unit correlates the magnitude of the cause of the abnormality determined in advance for each cause of the abnormality and the brightness of the diffracted light, and the correlation between the magnitude of the cause of the abnormality and the brightness of the second linearly polarized light. The surface inspection apparatus is characterized by identifying the cause of the abnormality based on the above.
  2. 　前記繰り返しパターンは露光装置を用いて形成されており、
    　前記露光装置におけるフォーカスのズレ量と前記回折光の輝度との相関および、前記フォーカスのズレ量と前記第２の直線偏光の輝度との相関、並びに、前記露光装置におけるドーズのズレ量と前記回折光の輝度との相関および、前記ドーズのズレ量と前記第２の直線偏光の輝度との相関をそれぞれ求めてデータベースを作成するデータベース部を備え、
    　前記検査部は、前記回折光検出部で検出された前記回折光の輝度を前記データベース上の前記回折光の輝度と照合するとともに、前記偏光検出部で検出された前記第２の直線偏光の輝度を前記データベース上の前記第２の直線偏光の輝度と照合することにより、前記フォーカスのズレ量または前記ドーズのズレ量を求めることを特徴とする請求項１に記載の表面検査装置。     The repeating pattern is formed using an exposure apparatus,
    The correlation between the amount of focus shift in the exposure apparatus and the brightness of the diffracted light, the correlation between the amount of focus shift and the brightness of the second linearly polarized light, and the amount of shift in dose and the diffraction in the exposure apparatus A database unit for creating a database by obtaining a correlation with the luminance of light and a correlation between the amount of deviation of the dose and the luminance of the second linearly polarized light,
    The inspection unit checks the luminance of the diffracted light detected by the diffracted light detection unit with the luminance of the diffracted light on the database, and the luminance of the second linearly polarized light detected by the polarization detection unit. 2. The surface inspection apparatus according to claim 1, wherein the shift amount of the focus or the shift amount of the dose is obtained by comparing the brightness with the brightness of the second linearly polarized light on the database.
  3. 　前記回折光が発生するように装置条件を設定する条件設定部を備え、
    　前記異常の原因の大きさと前記回折光の輝度との相関は、前記条件設定部により設定変更されて得られた複数の前記装置条件に基づく前記回折光毎に求められることを特徴とする請求項１もしくは請求項２に記載の表面検査装置。     A condition setting unit for setting an apparatus condition so that the diffracted light is generated;
    The correlation between the magnitude of the cause of the abnormality and the brightness of the diffracted light is obtained for each of the diffracted lights based on a plurality of the apparatus conditions obtained by changing the setting by the condition setting unit. The surface inspection apparatus according to claim 1 or 2.
  4. 　所定の繰り返しパターンを有する被検基板の表面に検査光を照射する第１のステップと、
    　前記検査光が照射された前記被検基板の表面からの回折光を検出する第２のステップと、
    　前記被検基板の表面に第１の直線偏光を照射する第３のステップと、
    　前記第１の直線偏光が照射された前記被検基板の表面からの反射光を前記第１の直線偏光と振動方向が異なる第２の直線偏光に変換する第４のステップと、
    　前記第２の直線偏光を検出する第５のステップと、
    　前記第２のステップで検出された前記回折光および、前記第５のステップで検出された前記第２の直線偏光に基づいて、前記繰り返しパターンにおける異常の有無を検査する第６のステップとを有し、
    　前記第６のステップにおいて、前記異常の原因毎に予め求められた前記異常の原因の大きさと前記回折光の輝度との相関および、前記異常の原因の大きさと前記第２の直線偏光の輝度との相関に基づいて、前記異常の原因を特定することを特徴とする表面検査方法。     A first step of irradiating the surface of the test substrate having a predetermined repeating pattern with inspection light;
    A second step of detecting diffracted light from the surface of the test substrate irradiated with the inspection light;
    A third step of irradiating the surface of the test substrate with a first linearly polarized light;
    A fourth step of converting reflected light from the surface of the test substrate irradiated with the first linearly polarized light into second linearly polarized light having a vibration direction different from that of the first linearly polarized light;
    A fifth step of detecting the second linearly polarized light;
    And a sixth step of inspecting whether there is an abnormality in the repetitive pattern based on the diffracted light detected in the second step and the second linearly polarized light detected in the fifth step. And
    In the sixth step, the correlation between the magnitude of the cause of the abnormality determined in advance for each cause of the abnormality and the brightness of the diffracted light, and the magnitude of the cause of the abnormality and the brightness of the second linearly polarized light A surface inspection method characterized by identifying the cause of the abnormality based on the correlation of
  5. 　前記繰り返しパターンは露光装置を用いて形成されており、
    　前記露光装置におけるフォーカスのズレ量と前記回折光の輝度との相関および、前記フォーカスのズレ量と前記第２の直線偏光の輝度との相関、並びに、前記露光装置におけるドーズのズレ量と前記回折光の輝度との相関および、前記ドーズのズレ量と前記第２の直線偏光の輝度との相関をそれぞれ求めてデータベースを作成するプレステップを有し、
    　前記第６のステップにおいて、前記第２のステップで検出された前記回折光の輝度を前記データベース上の前記回折光の輝度と照合するとともに、前記第５のステップで検出された前記第２の直線偏光の輝度を前記データベース上の前記第２の直線偏光の輝度と照合することにより、前記フォーカスのズレ量または前記ドーズのズレ量を求めることを特徴とする請求項４に記載の表面検査方法。     The repeating pattern is formed using an exposure apparatus,
    The correlation between the amount of focus shift in the exposure apparatus and the brightness of the diffracted light, the correlation between the amount of focus shift and the brightness of the second linearly polarized light, and the amount of shift in dose and the diffraction in the exposure apparatus A pre-step of creating a database by obtaining a correlation with the luminance of light and a correlation between the amount of deviation of the dose and the luminance of the second linearly polarized light,
    In the sixth step, the brightness of the diffracted light detected in the second step is checked against the brightness of the diffracted light on the database, and the second straight line detected in the fifth step 5. The surface inspection method according to claim 4, wherein the shift amount of the focus or the shift amount of the dose is obtained by comparing the luminance of polarized light with the luminance of the second linearly polarized light on the database.
  6. 　前記回折光が発生するように装置条件を設定するサブステップを有し、
    　前記異常の原因の大きさと前記回折光の輝度との相関は、前記サブステップで設定変更されて得られた複数の前記装置条件に基づく前記回折光毎に求められることを特徴とする請求項４もしくは請求項５に記載の表面検査方法。     A sub-step for setting apparatus conditions so that the diffracted light is generated;
    5. The correlation between the magnitude of the cause of the abnormality and the brightness of the diffracted light is obtained for each of the diffracted lights based on the plurality of apparatus conditions obtained by changing the setting in the sub-step. Alternatively, the surface inspection method according to claim 5.
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