WO2020194491A1 - Dispositif d'inspection de défaut - Google Patents

Dispositif d'inspection de défaut Download PDF

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Publication number
WO2020194491A1
WO2020194491A1 PCT/JP2019/012746 JP2019012746W WO2020194491A1 WO 2020194491 A1 WO2020194491 A1 WO 2020194491A1 JP 2019012746 W JP2019012746 W JP 2019012746W WO 2020194491 A1 WO2020194491 A1 WO 2020194491A1
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Prior art keywords
light
optical system
detector
sample
light receiving
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PCT/JP2019/012746
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English (en)
Japanese (ja)
Inventor
誠 保坂
雄太 浦野
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株式会社日立ハイテク
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Priority to PCT/JP2019/012746 priority Critical patent/WO2020194491A1/fr
Publication of WO2020194491A1 publication Critical patent/WO2020194491A1/fr

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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
    • G01N21/956—Inspecting patterns on the surface of objects

Definitions

  • the present invention relates to a defect inspection device that inspects foreign substances and defects on a sample.
  • semiconductor wafers, semiconductor devices, liquid crystal display elements, and printed circuit boards use a defect inspection device that detects the occurrence of abnormalities in order to inspect foreign substances and defects on the substrate and take countermeasures.
  • This type of defect inspection device requires an autofocus system that appropriately controls the focus position of the substrate.
  • the inspection device including the autofocus system include the device described in Patent Document 1.
  • an inspection device for detecting defects existing in a sample placed on a stage a light source device that generates a light beam and an inspection beam used for defect detection from a light beam emitted from the light source device.
  • a beam forming means that is spatially separated from the inspection beam and forms one or more focus detection beams used for focus detection, and an objective lens that projects the inspection beam and the focus detection beam toward the sample.
  • an imaging means that receives the inspection beam emitted from the sample and outputs an image signal
  • a focus detection system that receives the focus detection beam emitted from the sample, and an output signal output from the focus detection system. It has a signal processing device that outputs a focus control signal that controls the relative distance between the sample and the objective lens, and the inspection beam and the focus detection beam illuminate different spatially separated parts on the sample.
  • NA numerical aperture
  • ⁇ wavelength
  • the depth of focus is generally proportional to ⁇ / NA 2
  • the focus tolerance becomes stricter as the sensitivity and resolution of the device increase, and the focus position of the sample to be measured must be controlled with high accuracy. ..
  • the optical characteristics generally change minutely depending on the environment such as temperature and humidity, in various inspection / measurement devices with a shallow depth of focus and high sensitivity or high resolution, the sample may change even if the environment changes minutely. The shift of the focus position may not be tolerated.
  • a focusing error signal is acquired by differential signals between photodetectors whose focus positions are shifted back and forth from each other, and the focus position of a sample is controlled based on this focusing error signal.
  • the device of Patent Document 1 is a device for bright-field observation, that is, a device having an optical system for irradiating illumination light from a direction perpendicular to the surface of the substrate to be inspected, and an inspection to irradiate the substrate to be inspected from a light source.
  • a polarization beam splitter is used to split the beam, the two focus detection beams, and the corresponding three reflected beams from the substrate under inspection toward the detector.
  • the inspection / observation device is a device for dark field observation, that is, a device having an optical system that irradiates the surface of the substrate to be inspected with illumination light from diagonally above, the detected light is scattered light and is polarized. Is not uniquely determined. For this reason, the reflected light cannot be split by the polarizing beam splitter, or the light utilization efficiency is significantly reduced. Further, Patent Document 1 does not describe a solution and a solution for changes in optical characteristics due to environmental changes such as temperature and humidity.
  • the present invention has been made in view of the above problems, and provides a defect inspection apparatus capable of realizing high-precision autofocus required for various inspections / measurements with high sensitivity / high resolution, which is particularly suitable for dark field observation.
  • the purpose is.
  • the defect inspection device is a defect inspection device that inspects the presence or absence of foreign matter or defects on a sample, and is an illumination light emitted from a first light source unit and a first light source unit.
  • An illumination optical system that irradiates the sample with the light, a detection optical system that collects the scattered light generated when the sample is irradiated with the illumination light, and a first detection that detects the scattered light collected by the detection optical system.
  • the autofocus optical system has a device, an autofocus optical system that generates a focusing error signal indicating a displacement of the sample in the focus direction, and a dichromirror, and the autofocus optical system emits servo light having a wavelength different from that of the illumination light.
  • the detection optical system is incident on the first detector, the reflected light is reflected or transmitted through the dichro mirror and is incident on the second detector from the detection optical system, and the focusing error signal is the second detector of the autofocus optical system. It is generated based on the reflected light detected by the detector.
  • the defect inspection device is a defect inspection device that inspects the presence or absence of foreign matter or defects on the sample, and is a stage on which the sample is placed, a light source unit, and a light source unit.
  • the illumination optical system that irradiates the sample with the illumination light emitted from the sample
  • the detection optical system that collects the scattered light from the sample generated when the illumination light is irradiated to the sample, and the scattered light collected by the detection optical system. It has a detector to detect and a signal processing unit to generate a focusing error signal from the detection signal detected by the detector, and the detector has a first light receiving surface and a second direction in which the focus position is shifted in the first direction.
  • the signal processing unit sets the moving speed of the stage to v.
  • the distance between the first light receiving surface and the second light receiving surface in the moving direction of the stage is ⁇ X and the magnification of the detection optical system is M
  • the detection signal and time (t + ⁇ X /) on the second light receiving surface at time t. (Mv)) the focusing error signal is calculated based on the detection signal on the first light receiving surface.
  • FIG. 1 shows a configuration example of the defect inspection device 1000 according to the first embodiment.
  • the defect inspection device 1000 includes a light source unit 101, a TTL illumination optical system 111, an oblique illumination optical system 112, an objective lens 102, an objective pupil optical unit 103, a splitter 104, an imaging lens 105, a detector 106, and a light source for focus adjustment.
  • Unit 121 polarization beam splitter 122, 1/4 wavelength plate 123, dichro mirror 124, focusing error signal acquisition optical component 125, focus adjustment detector 126, signal processing unit 200, overall control unit 301, display unit 302, calculation It has a unit 303, a storage unit 304, a stage drive unit 151, an XYZ- ⁇ stage 152 (hereinafter referred to as “stage 152”), and a pattern chip 191.
  • the illumination light emitted from the light source unit 101 is reflected by the mirror 110, and the optical path is bent in the direction of the mirror 113.
  • the illumination light incident on the mirror 113 is further reflected and incident on the oblique illumination optical system 112.
  • the orthorhombic illumination optical system 112 linearly collects the incident illumination light.
  • the linearly focused illumination light irradiates the inspection target substrate 2 from diagonally above.
  • the mirror 110 can be taken in and out of the optical path of the illumination light emitted from the light source unit 101.
  • the illumination light is incident on the TTL illumination optical system 111.
  • the illumination light incident on the TTL illumination optical system 111 is linearly condensed and incident on the objective pupil optical unit 103, and the optical path is bent in the direction of the objective lens 102.
  • the illumination light that has passed through the objective lens 102 irradiates the inspection target substrate 2 placed on the stage 152 from the normal direction thereof.
  • the polarizer 104 may be arranged between the imaging lens 105 and the detector 106 or immediately before the detector 106.
  • the polarizer 104 has a rotation mechanism and a mechanism for retracting off the optical axis.
  • the rotation mechanism allows the polarizer 104 to be set to an arbitrary detection angle. Further, the retracting mechanism can switch between the use and non-use of the polarizer 104.
  • the electric signal output from the detector 106 is input to the signal processing unit 200.
  • the signal processing unit 200 has a computer as a basic configuration. That is, the signal processing unit 200 is composed of an input / output device, a storage device, a control device, an arithmetic device, and the like.
  • the signal processing unit 200 determines the presence or absence of a defect or the like by comparing the electric signal corresponding to the inspection area on the inspection target substrate 2 with the electric signal obtained from another area, and outputs the information of the detected defect. ..
  • the defect feature amount and position information including the signal strength of the defect detected by the signal processing unit 200 are stored in the storage unit 304 via the overall control unit 301 and displayed on the display unit 302.
  • the inspection target substrate 2 is scanned by the stage 152 driven by the stage drive unit 151, and the entire surface is inspected.
  • thermometer 2002 and a barometer 2003 for monitoring temperature and atmospheric pressure are installed in the device internal space 2001 in which the illumination optical system and the detection optical system are installed, and the measured value of the environmental state of the device internal space 2001 is measured by the overall control unit 301. Is always output to.
  • the autofocus system for controlling the inspection target substrate 2 or the detector 106 at a desired position will be described.
  • the S-polarized light emitted from the focus adjustment light source unit 121 is reflected by the polarization beam splitter 122, adjusted to circular polarization by the 1/4 wave plate 123, and reflected by the dichro mirror 124.
  • the dichroic mirror 124 is a special optical material that transmits the wavelength band of light emitted from the light source unit 101 used for inspection and reflects the wavelength band of light emitted from the light source unit 121 for focus adjustment used for focus adjustment. It is a mirror using, and is also called a dichroic mirror.
  • the examination target substrate 2 is irradiated substantially vertically through the imaging lens 105, the polarizer 104, the objective pupil optical unit 103, and the objective lens 102, which are a part of the detection optical system, and the inspection target substrate 2 is reflected.
  • the reflected light from the substrate 2 to be inspected passes through the objective lens 102, the objective pupil optical unit 103, the polarizing element 104, and the imaging lens 105, which are part of the detection optical system, in the opposite direction, and is reflected by the dichroic mirror 124. ..
  • the stage drive unit 151 is controlled through the overall control unit 301, and the Z position of the stage 152 is adjusted in particular to control the inspection target substrate 2 to a desired position.
  • the concavo-convex pattern in the illumination area R I is absent, it is impossible to detect the signal with illumination light in the detection optical system , The illumination optical system and the detection optical system cannot be adjusted based on the signal. Therefore, by measuring a detection signal installed at substantially the same position and the inspection target board 2 samples with a concavo-convex pattern, can be detected by the detection optics diffracted light and scattered light generated from the illumination area R I The illumination optical system and the detection optical system can be adjusted.
  • the structure having this uneven pattern is the pattern chip 191 described later.
  • FIG. 2 shows a more detailed configuration of the illumination optical system and the detection optical system.
  • the light source unit 101 includes a laser light source 1011, an attenuator 1012, an ND filter 1013, a wave plate 1014, and a beam expander 1015.
  • the output of the laser oscillated from the laser light source 1011 is adjusted by the attenuator 1012, the amount of light is adjusted by the ND filter 1013, the polarization state is adjusted by the wave plate 1014, and the beam diameter and shape are adjusted by the beam expander 1015. It is controlled and emitted as illumination light.
  • the optical path of the illumination light emitted from the light source unit 101 is guided to the TTL illumination optical system 111 or the oblique illumination optical system 112 depending on the presence or absence of the mirror 110. That is, when the mirror 110 moved by the drive device (not shown) is installed at a position outside the optical path of the illumination light, the illumination light emitted from the light source unit 101 is the TTL illumination optical system 111 through the mirror unit 1102. Incident in. On the other hand, when the mirror 110 moved by the drive device (not shown) is installed on the optical path of the illumination light, the illumination light emitted from the light source unit 101 is reflected by the mirror 110 and incident on the mirror unit 1101. Further, it is reflected by the mirror unit 1101 and incident on the oblique illumination optical system 112. The illumination light incident on the TTL illumination optical system 111 or the oblique illumination optical system 112 is formed into a long light beam in one direction, and then emitted from the TTL illumination optical system 111 or the oblique illumination optical system 112.
  • the laser light source 1011 is suitable for a short wavelength, high output, high brightness, and high stability, and the third, fourth, or fifth harmonic of the YAG laser (wavelengths are 355, 266, 213, 193, and 183 nm, respectively). ) Is used.
  • the angle and position of the illumination light incident on the oblique illumination optical system 112 or the TTL illumination optical system 111 are controlled by the mirror unit 1101 or 1102, respectively, so that the illumination light is irradiated to a desired position on the inspection target substrate 2. Is adjusted to.
  • the mirror units 1101 and 1102 are each composed of a plurality of planar mirrors, and the angle and position of the illumination light are adjusted by adjusting the angle and position of the planar mirrors.
  • FIG. 3 shows the detection optical system.
  • the detection optical system 170 includes an objective lens 102, a polarizer 104, and an imaging lens 105. After being generated from the substrate 2 to be inspected by the detection optical system 170, the reflected light is detected by forming an image of the reflected light collected by the objective lens 102 on the detector 106. Further, it has an objective pupil optical unit 103 and guides vertical illumination light to the inspection target substrate 2.
  • the reflected light from the detection optical system 170 is incident on the dichroic mirror 124.
  • the dichroic mirror 124 transmits light in the same wavelength band as the light emitted from the light source unit 101, and reflects light in the same wavelength band as the light emitted from the focus adjustment light source unit 121, which will be described later. If the positional relationship between the detector 106 and the focus adjustment light source unit 121 is opposite to the positional relationship in FIG. 1, light in the same wavelength band as the light emitted from the light source unit 101 is reflected for focus adjustment. It is configured to transmit light in the same wavelength band as the light emitted from the light source unit 121.
  • the reflected light transmitted through the dichroic mirror 124 is incident on the mirror 108 which can be inserted and removed from the optical path.
  • the reflected light reflected by the mirror 108 is incident on the two-dimensional detector 109.
  • the two-dimensional detector 109 is provided at a conjugate position with the detector 106, and can detect a two-dimensional image having substantially the same image plane as the detector 106.
  • the mirror 108 is a half mirror or a total reflection mirror, and when the half mirror is used, the signals of the detector 106 and the two-dimensional detector 109 can be simultaneously detected.
  • the detector 106 is held by the stage 107.
  • the detector 106 is a one-dimensional detector such as a CCD linear image sensor or a CMOS linear image sensor.
  • the stage 107 has an X, Y, Z translation mechanism and a two-axis rotation mechanism, whereby the position and orientation (azimuth angle, tilt angle) of the detector are adjusted.
  • This adjustment is that the longitudinal direction of the orientation and the image plane of the image formed by imaging each optical imaging system an illumination area R I described below, the longitudinal direction and the light-receiving surface of the detector 106 matches It is done in.
  • the azimuth is the rotation angle in the plane perpendicular to the optical axis of each detection optical system
  • the tilt angle is the inclination angle with respect to the plane perpendicular to the optical axis.
  • the detection resolution of the detection optical system depends on the numerical aperture NA of the detection optical system and the detection wavelength ⁇ .
  • the detection resolution is 1.22 ⁇ / NA based on the diameter of the Airy disk, and a point having no spatial spread on an object is detected as a point image having a spread of about the detection resolution.
  • High resolution can be achieved with a short wavelength and a high numerical aperture.
  • an objective lens with a deep ultraviolet wavelength and a numerical aperture of about 0.4 is used, a resolution of about 0.8 ⁇ m can be obtained.
  • FIG. 4 shows a side view showing the configurations of the autofocus optical system and the detection optical system.
  • the autofocus optical system will be described in detail.
  • This optical system has an advantage that the optical system is simply configured with a small number of optical components, and the curved surface of the cylindrical lens makes it easy to design characteristics such as the inclination of the focusing error signal described later.
  • the light emitted from the focus adjustment light source unit 121 (hereinafter referred to as "servo light") is focused by the lens 127, and the luminous flux diameter is reduced to the smallest on the beam waist surface in the drawing. After that, it reflects the polarization beam splitter 122, passes through the 1/4 wave plate 123, and reflects the dichroic mirror 124. After that, the substrate 2 to be inspected is irradiated through the imaging lens 105, the polarizer 104, the objective pupil optical unit 103, and the objective lens 102.
  • the light reflected from the substrate 2 to be inspected propagates in the opposite direction, passes through the objective lens 102, the objective pupil optical unit 103, the polarizer 104, and the imaging lens 105, and is reflected again by the dichroic mirror 124. After that, by passing through the 1/4 wave plate 123 again, the polarized light is converted into P-polarized light, transmitted through the polarizing beam splitter 122, and transmitted through the focusing error signal acquisition optical component 125 composed of the cylindrical lens 128 to focus. The light is received by the adjusting detector 126. The focus adjustment detector 126 is placed on the stage 129, and its position is adjusted as necessary.
  • the light receiving surface and the beam waist surface of the detector 106 are in an imaging relationship with the surface of the substrate 2 to be inspected, that is, the light receiving surface and the beam waist surface of the detector 106 are each optically optical. It is regarded as an equivalent conjugate surface.
  • the light receiving surface of the detector 106 and the surface of the inspection target substrate 2 are in an imaging relationship with the light having the wavelength of the emitted light of the light source unit 101, and the beam waist surface and the surface of the inspection target substrate 2 are for focus adjustment.
  • the light having the wavelength of the emitted light (servo light) of the light source unit 121 is in an imaging relationship.
  • the light receiving surface of the focus adjustment detector 126 is positioned on the stage 129 so as to have a perfect circular distribution when the beam waist surface and the inspection target substrate 2 are in an imaging relationship. From now on, the state in which the beam waist surface and the substrate 2 to be inspected are in an imaging relationship will be referred to as focusing.
  • FIG. 5 shows a schematic diagram showing a configuration example of the focus adjustment detector 126. Due to the effect of the cylindrical lens 128, the focus adjustment detector 126 has a profile such as a circle or an ellipse depending on the Z position of the substrate to be inspected and the focus position (Y direction position in FIG. 4) of the focus adjustment detector 126. Light is incident. As described above, it is desirable that the position of the focus adjustment detector 126 is adjusted by the stage 129 to a position having a circular profile on the light receiving surface of the focus adjustment detector 126 in the focused state.
  • the focus adjustment detector 126 has, for example, four light receiving surfaces A, B, C, and D, and the light receiving surfaces A, B, C, and D have substantially the same light receiving amounts at the time of focusing.
  • the long axis or the short axis of the elliptical profile substantially coincides with each other in the ⁇ 45 degree direction in the figure.
  • the stage 129 is adjusted so that the arrangement is in the plane. In FIG.
  • FIG. 6 shows a diagram showing an example of a focusing error signal.
  • the focusing error signal becomes 0 because the light receiving amounts of the light receiving surfaces A, B, C, and D are substantially the same, and when the inspection target substrate 2 is + ⁇ Z defocused, the focusing error signal becomes 0. Since a large amount of light is incident on the light receiving surfaces A and C, the focusing error signal increases according to + ⁇ Z to a positive (+) value, and when the inspection target substrate 2 is defocused by ⁇ Z, the light receiving surface Since a large amount of light is incident on B and D, the focusing error signal becomes a negative (-) value according to - ⁇ Z. Therefore, it is possible to obtain an S-shaped signal as shown in the figure.
  • the direction and magnitude of the shift of the focus (Z azimuth) of the inspection target substrate 2 can be known from the sign of the focusing error signal, so that the overall control unit 301 controls the inspection target substrate so that the focusing error signal becomes 0.
  • Feedback control of the focus position of 2 becomes possible.
  • the focusing characteristics may differ between the detection optical system and the autofocus optical system due to environmental factors such as pressure and temperature, and the focusing characteristics may differ between the detection optical system and the autofocus optical system depending on the wavelength band.
  • the target value (control target in the figure) of the focusing error signal may be offset from 0.
  • the focus position of the substrate 2 to be inspected is controlled by controlling the height Z (position in the focus direction) of the stage 152 based on the value of the focusing error signal, but the imaging lens 105 and the objective It is also possible by controlling the distance to and from the lens 102. Further, it is also possible to adjust the focus position of the detector 106 based on the value of the focusing error signal, but in this case, the focusing error signal does not change even if the focus position of the detector 106 is controlled. It will be controlled by feed forward.
  • FIG. 7 shows a configuration example (plan view) of the pattern chip 191.
  • the pattern chip 191 is installed in the vicinity of the inspection target substrate 2, and the height of the surface thereof becomes substantially equal to the inspection target substrate 2. It is desirable to be installed in such a way.
  • the height Z of the stage 152 is corrected by using the difference in surface height between the two, so that the adjustment using the pattern chip 191 and the inspection target substrate are performed.
  • the height of the detection target pattern can be made substantially the same as that at the time of the inspection of 2.
  • the pattern chip 191 has an uneven pattern that generates diffracted light or scattered light in the pattern region 601 on the surface.
  • the longitudinal direction of the illumination area R I formed into linear and Y-direction, a width direction of the illumination area R I (the direction perpendicular to the longitudinal direction) and the X direction.
  • the pattern region 601 has a plurality of small pattern regions 602a, 602b, 602c, ... Arranged in the Y direction.
  • pattern small region 602 The area sizes of the pattern small areas 602a, 602b, 602c, ... And the patterns formed therein are common to each other.
  • these pattern small regions 602a, 602b, 602c, ... are collectively referred to as "pattern small region 602".
  • the length of the pattern small area 602 in the Y direction is shorter than the length of the illumination area RI in the Y direction (for example, 1/4 or less). Therefore, a plurality of pattern small regions 602 are included in the range of the illumination region RI in the Y direction. For example, four or more pattern small regions 602 are included within the illumination area R I.
  • the pattern small area 602 has a dot single row pattern area 611, a line and space (hereinafter, referred to as “L & S”) pattern area 612, and a dot L & S pattern area 613.
  • the illumination region RI is represented by an ellipse for convenience, but in reality, the intensity distribution of the illumination light is an elliptical Gaussian distribution long in the Y direction, and the intensity relative to the distribution center is 1 / e 2. regions to be more than equivalent to the illumination area R I.
  • the width of the illumination area R I is a condensing width of the Gaussian distribution that is focused in the X direction, a high detection resolution and illumination power densities in the X direction by the illumination area R I is used narrow thin linear illumination light It is possible to realize highly sensitive defect inspection.
  • the width of the illumination region RI in the X direction is 0.5 ⁇ m to 1.5 ⁇ m.
  • the narrower the width the more advantageous it is for increasing the sensitivity, but it is necessary to increase the aperture angle for condensing the illumination, and the depth of focus is narrowed, which makes it difficult to maintain the stability of the inspection. Practically, about 0.8 ⁇ m is suitable.
  • FIG. 8 shows an inspection procedure executed by the defect inspection device 1000. This process is executed by the signal processing unit 200 and the overall control unit 301.
  • the inspection target object (inspection target substrate 2) is put into the apparatus and installed on the stage 152 (step S702).
  • the inspection conditions are set (step S703).
  • the inspection conditions include illumination conditions (eg, illumination angle: oblique / vertical / both oblique and vertical) and detection conditions.
  • the illumination optical system and the detection optical system are adjusted and set (steps S704 to S707, S710).
  • the focal position of the illumination light is positioned on the surface of the inspection target substrate 2 for adjusting the illumination optical system, and the light receiving surface of the detector 106 and the inspection target substrate 2 are used for adjusting the detection optical system. It includes forming an imaging relationship with the surface and aligning the one-dimensional detector constituting the detector 106 with the linear reflected light.
  • the objects of adjustment and setting are the illumination optical system and the detection optical system selected to be used in step S703.
  • the time elapsed since the last adjustment of the target optical system is obtained, and it is determined whether or not the predetermined time in which the state can be maintained after the adjustment is completed has been exceeded (step S704). If the predetermined time has elapsed, the process proceeds to step S710. When the predetermined time has not elapsed, it is determined whether or not the change in the environmental conditions (temperature change, atmospheric pressure change, etc. in the device internal space 2001) since the previous adjustment exceeds the predetermined threshold value (step S705). If the change exceeds the threshold value, the process proceeds to step S710. If it does not exceed, partial adjustment using the pattern chip (step S706) is executed.
  • the position adjustment and the magnification adjustment of the detection optical system and the height adjustment of the stage on which the inspection target substrate 2 is placed are performed.
  • the illumination optical system and the detection optical system are set based on the adjustment parameters saved at the time of the previous adjustment (step S707).
  • the inspection is executed (step S708), the inspection result is saved and displayed (step S709), and the inspection is completed (step S720).
  • step S704 and step S705 if either of them is Yes, the entire optical system using the pattern chip is adjusted and the adjustment parameters are updated.
  • the overall adjustment of the optical system using the pattern chip for example, the position adjustment of the illumination optical system, the focus adjustment, the position adjustment of the power adjustment and the detection optical system, the focus adjustment, the magnification adjustment, and the stage on which the inspection target substrate 2 is placed. Adjust the height.
  • step S704 and step S705 are No, the optical system is set using the adjustment parameters obtained by the adjustment using the pattern chip 191 in the inspection before the previous time.
  • the height of the stage on which the inspection target substrate 2 is placed is constantly controlled so that the focusing error signal becomes the target value by the above-mentioned autofocus adjustment method.
  • the target value of the focusing error signal is the amount of reflected light from the pattern chip received by, for example, the detector 106 in the partial adjustment using the pattern chip shown in step S706 or the total adjustment using the pattern chip shown in S710. It is considered that the focusing error signal when the value reaches a substantially maximum value is a value to be controlled, and the focusing error signal value at this time is updated as the target value of the focusing error signal.
  • the adjustment using the pattern chip 191 is performed and the state is sufficiently adjusted. You can inspect at.
  • the overall adjustment using the pattern chip 191 is omitted, so that it is possible to avoid taking time for adjustment more than necessary.
  • the inspection throughput can be increased.
  • FIG. 9 shows a side view showing different configurations of the autofocus optical system and the detection optical system.
  • the servo light emitted from the focus adjustment light source unit 121 is converted into substantially parallel light by the collimated lens 130, and is focused only on one side by the cylindrical lens 131, so that the luminous flux diameter on the one side is minimized on the beam waist surface in the drawing. It is squeezed. Therefore, the beam waist surface shows a linear profile, and it is possible to have substantially the same shape as the linear illumination often used in inspection.
  • the optical path passes through the same optical path as the optical path described with reference to FIG. 4, and passes through the polarizing beam splitter 122.
  • a cylindrical lens 128 is arranged at a position separated by a focal length from the image plane of the surface of the substrate 2 to be inspected in the focused state, and is converted into an electric signal by the focus adjustment detector 126.
  • the light incident on the focus adjustment detector 126 can have a circular shape on the light receiving surface in the focused state and an elliptical shape in the defocused state. Since the collimating lens 130 adjusts the luminous flux diameter on the focus adjusting detector 126, the position of the collimating lens 130 may be adjusted so as to be in a substantially divergent or substantially converged state after transmission.
  • the linear illumination is performed by adjusting the focus with light in substantially the same region as the linear illumination used for the inspection.
  • FIG. 10 shows a side view showing still another configuration of the autofocus optical system and the detection optical system.
  • the focus adjusting light source unit 121 has a plurality of emission units 121a, 121b, and 121c. It passes through the lens array 135 corresponding to each emitted light (servo light), and becomes three narrowed points on the beam waist surface. Subsequent optical paths pass through the same optical paths as those described in FIG. 4, pass through the polarizing beam splitter 122, pass through the cylindrical lens array 132 corresponding to each emitted light, and are converted into an electric signal by the focus adjustment detector 126. Be done.
  • the focus adjustment detector 126 also has light receiving units 126a, 126b, and 126c corresponding to the emitted light, and has three sets of four detection surfaces (see FIG. 5).
  • This optical configuration is a multi-point illumination of the configuration shown in FIG.
  • Focusing error signals are generated for the number of multiple points.
  • a synthesized focusing error signal is generated by simply averaging or weighting and adding them, and is used for control.
  • the inspection target is on average a good focus position for each area of the linear illumination.
  • the focus of the board can be adjusted.
  • by weighting and synthesizing the focusing error signals of each of the multiple points for example, focus adjustment that emphasizes the vicinity of the center of linear illumination, focus adjustment that emphasizes inspection of the upper or lower portion, and the like can be realized.
  • the optical system can be miniaturized by using a small optical component such as a microlens.
  • FIG. 11 shows a side view showing still another configuration of the autofocus optical system and the detection optical system.
  • the focusing error signal acquisition optical component 125 is composed of the knife edge 133.
  • the side surface of the knife edge 133 is arranged on the image forming surface of the surface of the substrate 2 to be inspected in the focused state, the tip of the knife edge 133 does not block the luminous flux in the focused state, and the knife edge 133 is in the defocused state. Arrange so that the tip blocks a part of the luminous flux.
  • the light after passing through the focusing error signal acquisition optical component 125 is converted into an electric signal by the focus adjustment detector 126.
  • the focus adjustment detector 126 has, for example, two light receiving surfaces.
  • FIG. 12A shows an example (schematic diagram) of the luminous flux on the focus adjustment detector 126 during focusing and defocusing.
  • the same amount of light is incident on the two light receiving surfaces A and B of the focus adjustment detector 126 without the tip of the knife edge 133 blocking the luminous flux.
  • the light beam portion that is shielded from light changes depending on the direction of deviation of the focus position.
  • a relatively large amount of light is incident on the surface B.
  • FIG. 12B shows a configuration example of the focus adjustment detector 126 in this modified example.
  • the focus adjustment detector 126 has, for example, two light receiving surfaces A and B, and is arranged so that substantially the same amount of light is incident on the light receiving surfaces A and B during focusing, and the light receiving surfaces during defocusing. Arrange so that a large amount of light is incident only on A or the light receiving surface B.
  • the focusing error signal can be generated by, for example, AB, and an S-shaped signal as shown in FIG. 6 can be obtained.
  • FIG. 13 shows a schematic view showing an embodiment of the defect inspection apparatus according to the second embodiment.
  • the optical system for autofocus is almost completely shared with the detection optical system. Since the light source for autofocus is not separately provided, autofocus is applied using the reflected light including scattering from the inspection target substrate 2 as in the inspection.
  • the configuration of the detector 106 is different from that of the first embodiment, and the signal processing unit 200 generates a focusing error signal based on the signal from the detector 106.
  • FIG. 14 shows a schematic diagram showing an example of a focusing error signal acquisition method by differentiating the detection signal.
  • the above figure is a schematic diagram showing the relationship between the output of the detector (for example, the sum of the light amounts of the one-dimensional detector) and the defocus amount of the inspection target substrate 2.
  • the output of the detector for example, the sum of the light amounts of the one-dimensional detector
  • the defocus amount of the inspection target substrate 2 is generally assumed.
  • the goal is to control the substrate 2 to be inspected to the in-focus position where the output is maximized.
  • a signal obtained by differentiating the upper figure as shown in the lower figure is obtained, the value becomes zero at the time of focusing, and an S-shaped signal whose value changes to ⁇ according to the defocus amount can be obtained. It can be used as a focusing error signal. That is, when the output of a normal detector is I ( ⁇ Z), if a signal I ( ⁇ Z + d) defocused in the + direction and a signal I ( ⁇ Z ⁇ d) defocused in the-direction are obtained, a focusing error is obtained.
  • the signal can be generated from ⁇ I ( ⁇ Z + d) ⁇ I ( ⁇ Z ⁇ d) ⁇ / (2d).
  • a method of acquiring the signal I ( ⁇ Z + d) defocused in the + direction and the signal I ( ⁇ Z ⁇ d) defocused in the ⁇ direction will be described.
  • FIG. 15 shows a configuration example (schematic diagram) of a detector corresponding to the acquisition of a focusing error signal.
  • the detector 106 has a light receiving surface 106a for detecting reflected light and light receiving surfaces 106b, 106c, 106d, 106e for using autofocus.
  • the light receiving surfaces 106b and 106d are displaced in the ⁇ direction
  • the light receiving surfaces 106c and 106e are displaced in the + direction.
  • the focus position of the light receiving surface 106a is on the paper surface
  • the focus position of the light receiving surface 106b (106d) and the focus position of the light receiving surface 106c (106e) are located above and below the paper surface, respectively.
  • the acquisition signals at the time t of the light receiving surfaces 106b, 106c, 106d, and 106e are set to S1 (t), S2 (t), S3 (t), and S4 (t), respectively, and between the light receiving surface 106b and the light receiving surface 106c and Let ⁇ X be the distance between the light receiving surface 106e and the light receiving surface 106d, and v be the moving speed of the substrate 2 to be inspected in the X direction.
  • the focusing error signal at the upper part of the detector 106 is generated at S2 (t) -S1 (t + ⁇ X / v), and the focusing error signal at the lower part of the detector 106 is generated at S4 (t + ⁇ X / v) -S3 (t).
  • the difference between S2 and S1 and the difference between S3 and S4 are not considered between signals at the same time, but the time difference is taken into consideration by calculating the difference using the reflected light from the same pattern (defect). This is to reduce the error due to the difference in the amount of light depending on the pattern (defect).
  • the reflected light from the inspection target substrate 2 depends on the moving direction of the inspection target substrate 2. In this example, it is assumed that the light reflected from the inspection target substrate 2 reaches the sensor on the left side in order from the sensor on the right side in the figure, and the magnification of the detection optical system is 1. Discussed as double.
  • the focusing error signal at the upper part of the detector 106 is generated by S2 (t) -S1 (t + ⁇ X / (Mv)), and the focusing error signal at the lower part of the detector 106 is S4 (t + ⁇ X). / (Mv))-S3 (t) will be generated.
  • ⁇ defocus occurs between the sensors in the vertical direction, that is, between S1 (light receiving surface 106b) and S4 (light receiving surface 106e) or between S2 (light receiving surface 106c) and S3 (light receiving surface 106d). Since it is attached, it is possible to obtain a focusing error signal by taking the difference. However, when the moving direction of the substrate 2 to be inspected is only in the left-right direction, it is not possible to obtain a difference by using the reflected light from the same pattern (defect).
  • the focusing error signal may be generated from the difference between the upper and lower sensor outputs at the same time, and the time average of the focusing error signal may be taken. ..
  • the air conversion distance can be changed by changing the thickness of the cover layer such as the cover glass arranged in front of each light receiving surface. It is possible to realize the defocus of. That is, with respect to the thickness of the cover glass arranged in front of the light receiving surface 106a, a thin cover glass is arranged in front of the light receiving surface 106b and the light receiving surface 106d, and a thick cover glass is arranged in front of the light receiving surface 106c and the light receiving surface 106e, or a wedge shape. It is possible to realize the same effect by arranging the cover glass 1500 of the above in front of the light receiving surface 106b and the light receiving surface 106c and the light receiving surface 106e and the light receiving surface 106d.
  • the optical system required for normal inspection can be realized only by arranging the light receiving surface in the detector 106 and defocusing, so that there is an advantage that the optical system can be simplified.
  • FIG. 16 shows a side view showing different configurations of the autofocus optical system and the detection optical system.
  • the detector 106-1 is arranged to defocus + d with respect to the focal plane
  • the detector 106-2 is arranged to defocus ⁇ d with respect to the focal surface
  • the reflected light transmitted through the half mirror 134 is a detector.
  • the light reflected from the half mirror 134 is incident on the detector 106-2 at 106-1.
  • a ⁇ defocus signal can be obtained.
  • the focusing error signal can be generated from the difference between the outputs of the detector 106-1 and the detector 106-2 at the same time.
  • the signal for defect inspection is calculated by the sum of the detector 106-1 and the detector 106-2.
  • the obtained signal is always a defocused signal, it is necessary to design the value of d within the allowable defocus amount range.
  • FIG. 17A shows a side view showing still another configuration of the autofocus optical system and the detection optical system.
  • the detector 106 is tilted with respect to the focal plane. At this time, since the focus is defocused on the left and right light receiving surfaces on the drawing in opposite directions, it is possible to generate a focusing error signal by taking the difference between the signals on the left and right light receiving surfaces.
  • FIG. 17B shows a configuration example (schematic diagram) of a detector corresponding to the acquisition of a focusing error signal.
  • the detector 106 has, for example, the light receiving surfaces of S1, S2, and S3.
  • S1 is defocused in the minus direction
  • S2 is in focus
  • S3 is defocused in the + direction. Focusing error when the acquisition signals at time t are S1 (t), S2 (t), and S3 (t), the distance between S1 and S3 is ⁇ X, and the moving speed of the inspection target substrate 2 in the left-right direction is v.
  • the signal is generated in S3 (t) -S1 (t + ⁇ X / v).
  • the reflected light from the inspection target substrate 2 depends on the moving direction of the inspection target substrate 2.
  • the magnification of the detection optical system is 1. Discussed as double.
  • the magnification of the detection optical system is M times, the focusing error signal is generated in S3 (t) ⁇ S1 (t + ⁇ X / (Mv)).
  • the defect inspection signal is generated from S2.
  • the embodiment of the present invention has been described above.
  • the present invention is not limited to the above-described examples and modifications, and includes various modifications.
  • the above-described embodiment describes the present invention in an easy-to-understand manner, and is not necessarily limited to the one having all the configurations described. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.
  • control lines and information lines indicate what is considered necessary for explanation, and not all control lines and information lines are necessarily shown on the product. In practice, it can be considered that almost all configurations are interconnected.
  • the illustrated defect inspection device is a defect inspection device having two illumination optical systems, a TTL illumination optical system and an oblique illumination optical system, but for a defect inspection apparatus having only one of the illumination optical systems. Is also applicable, and is particularly effective for defect inspection devices having an oblique illumination optical system.
  • the autofocus technique in the present invention is not limited to the defect inspection apparatus, and the presence or absence of a sample pattern and the stage operation direction such as the XY stage or the rotation stage. Regardless of this, it can be applied to various inspection devices, measuring devices, measuring devices, and the like.

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Abstract

L'invention concerne un dispositif d'inspection de défaut ayant un système optique de mise au point automatique approprié pour une observation en champ sombre. Ce dispositif d'inspection de défaut comprend un système optique de détection 170 pour faire converger une lumière diffusée à partir d'un échantillon, un premier détecteur 106 pour détecter la lumière diffusée amenée à converger par le système optique de détection, un système optique de mise au point automatique pour générer un signal d'erreur de focalisation indiquant un écart de position de direction de focalisation de l'échantillon, et un miroir dichroïque 124. Le système optique de mise au point automatique comprend une seconde unité de source de lumière configurée pour émettre une lumière d'asservissement ayant une longueur d'onde différente de la lumière d'éclairage et un second détecteur configuré pour diriger la lumière d'asservissement sur l'échantillon et détecter la lumière réfléchie amenée à converger par le système optique de détection. La lumière diffusée est transmise ou réfléchie par un miroir dichroïque et frappe le premier détecteur. La lumière réfléchie est réfléchie ou transmise par le miroir dichroïque et frappe le second détecteur. Le signal d'erreur de focalisation est généré sur la base de la lumière réfléchie détectée par le second détecteur du système optique de mise au point automatique.
PCT/JP2019/012746 2019-03-26 2019-03-26 Dispositif d'inspection de défaut WO2020194491A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04113305A (ja) * 1990-09-03 1992-04-14 Brother Ind Ltd 焦点合わせ装置
JPH08178623A (ja) * 1994-12-22 1996-07-12 Olympus Optical Co Ltd 光学測定装置
JPH10142489A (ja) * 1996-11-15 1998-05-29 Toray Ind Inc 焦点検出方法およびその装置
JPH11237344A (ja) * 1998-02-19 1999-08-31 Hitachi Ltd 欠陥検査方法およびその装置
US20050089208A1 (en) * 2003-07-22 2005-04-28 Rui-Tao Dong System and method for generating digital images of a microscope slide
JP2007051902A (ja) * 2005-08-17 2007-03-01 Hitachi High-Technologies Corp 写像投影型電子線式検査装置及びその方法
JP2014174052A (ja) * 2013-03-11 2014-09-22 Hitachi High-Technologies Corp 欠陥検査方法及びこれを用いた装置
JP2015523587A (ja) * 2012-05-02 2015-08-13 ライカ バイオシステムズ イメージング インコーポレイテッド ライン走査イメージングにおけるリアルタイムフォーカシング
JP2018503244A (ja) * 2014-12-02 2018-02-01 ケーエルエー−テンカー コーポレイション 検出増強型検査システム及び技術
JP2018519524A (ja) * 2015-06-29 2018-07-19 ケーエルエー−テンカー コーポレイション 半導体ウェハ上の高さを測定するための方法および装置

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04113305A (ja) * 1990-09-03 1992-04-14 Brother Ind Ltd 焦点合わせ装置
JPH08178623A (ja) * 1994-12-22 1996-07-12 Olympus Optical Co Ltd 光学測定装置
JPH10142489A (ja) * 1996-11-15 1998-05-29 Toray Ind Inc 焦点検出方法およびその装置
JPH11237344A (ja) * 1998-02-19 1999-08-31 Hitachi Ltd 欠陥検査方法およびその装置
US20050089208A1 (en) * 2003-07-22 2005-04-28 Rui-Tao Dong System and method for generating digital images of a microscope slide
JP2007051902A (ja) * 2005-08-17 2007-03-01 Hitachi High-Technologies Corp 写像投影型電子線式検査装置及びその方法
JP2015523587A (ja) * 2012-05-02 2015-08-13 ライカ バイオシステムズ イメージング インコーポレイテッド ライン走査イメージングにおけるリアルタイムフォーカシング
JP2014174052A (ja) * 2013-03-11 2014-09-22 Hitachi High-Technologies Corp 欠陥検査方法及びこれを用いた装置
JP2018503244A (ja) * 2014-12-02 2018-02-01 ケーエルエー−テンカー コーポレイション 検出増強型検査システム及び技術
JP2018519524A (ja) * 2015-06-29 2018-07-19 ケーエルエー−テンカー コーポレイション 半導体ウェハ上の高さを測定するための方法および装置

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