JP2006105926A - Inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus for accurately detecting defects on the surface of an object to be inspected even if the spectral characteristics of illumination light change. <P>SOLUTION: The inspection apparatus comprises illumination means 12-18 for irradiating the object 10A to be inspected with illumination light from a light source 11; image-forming means 17-19 for forming the image of the object to be inspected irradiated with illumination light; an imaging means 20 for decomposing the image of the object to be inspected into a plurality of color components for imaging for each color component; and detection means 21-24 for decomposing the illumination light into a plurality of color components for detecting for each color component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inspection apparatus used for defect inspection of a surface of an object to be inspected, and more particularly to an inspection apparatus suitable for highly accurate defect inspection using a semiconductor wafer, a liquid crystal glass substrate, or the like as an object to be inspected.

There is known an inspection apparatus that irradiates a test object such as a semiconductor wafer or a liquid crystal glass substrate with illumination light, captures a black and white image of the test object, and detects defects on the surface of the test object by image processing. In addition, an inspection apparatus that captures a color image of an object to be detected in order to increase the amount of information when detecting a defect is also known (see, for example, Patent Documents 1 to 4). In this apparatus, a defect is detected by regarding a change in color information of a color image as a change in spectral characteristics of an object to be detected.
JP 7-159333 A Japanese Patent Laid-Open No. 2002-5846 JP 2002-14052 A JP 2004-170109 A

  However, the color information of the color image of the test object includes not only the spectral characteristics of the test object but also information related to the spectral characteristics of the illumination light. For this reason, in the above method, in which the change in the color information of the color image is regarded as a change in the spectral characteristic of the object to be measured (that is, the spectral characteristic of the illumination light is regarded as unchanged), the color information varies due to the change in the spectral characteristic of the illumination light. As a result, defects may not be detected accurately. Note that the spectral characteristics of the illumination light are likely to change when the intensity of the illumination light is adjusted. In addition, the spectral characteristics of the illumination light may change due to changes in the light source and illumination optical system over time.

  An object of the present invention is to provide an inspection apparatus that can accurately detect defects on the surface of an object to be inspected even if the spectral characteristics of illumination light change.

The inspection apparatus according to claim 1, an illuminating unit that irradiates a test object with illumination light from a light source, an imaging unit that forms an image of the test object irradiated with the illumination light, and the test An image pickup unit that separates an object image into a plurality of color components and picks up the image for each color component, and a detection unit that separates the illumination light into a plurality of color components and detects each color component.
According to a second aspect of the present invention, in the inspection apparatus according to the first aspect, the illumination light from the outside of the optical path is transmitted through the optical path of the imaging means while transmitting the inspection light from the object to be examined. An optical member that reflects a part of the optical member and transmits the other part is disposed, the imaging means forms the image based on the inspection light that has passed through the optical member, and the illuminating means A part of the illumination light reflected by the optical member is irradiated onto the object to be inspected, and the detection means separates another part of the illumination light transmitted through the optical member into a plurality of color components to obtain each color component. Every one is detected.

According to a third aspect of the present invention, in the inspection apparatus according to the first or second aspect, the image pickup signal for each color component output from the image pickup unit and the detection for each color component output from the detection unit. A generating means for generating data for inspection based on the signal is provided.
According to a fourth aspect of the present invention, in the inspection apparatus according to the third aspect, the generation unit generates chromaticity coordinates of an image of the test object as the data.

  According to the inspection apparatus of the present invention, it is possible to accurately detect defects on the surface of an object to be inspected even if the spectral characteristics of illumination light change.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the inspection apparatus 10 according to the first embodiment includes a light source 11, illumination systems (12 to 18), an imaging system (17 to 19), an image sensor 20, and a monitor system (21 to 24). ) And the signal processing unit 25. The test object 10A is a semiconductor wafer, a liquid crystal glass substrate, or the like, and is placed on a stage (not shown). A fine pattern is repeatedly formed on the surface of the test object 10A using, for example, an exposure machine such as a stepper. In order to detect this pattern disturbance (that is, a defect), the inspection apparatus 10 of the first embodiment is used. The inspection apparatus 10 is suitable for high-accuracy defect inspection of the surface of the test object 10A.

  The light source 11 is a halogen lamp, for example. In this case, the illumination light from the light source 11 becomes visible white light. The intensity of the illumination light can be adjusted according to the current value supplied to the light source 11. The intensity of the illumination light is adjusted by adjusting the intensity of the incident light to the image sensor 20 (that is, the inspection light L3 generated from the test object 10A and reaching the image sensor 20), and the light intensity with which the image signal of the image sensor 20 can be obtained. Often done to fit range.

  The illumination system (12 to 18) includes a collector lens 12a, a relay lens 12b, a filter 13, an aperture stop 14, a field stop 15, a condenser lens 16, a half mirror 17, and an objective lens 18. The The half mirror 17 is an episcopic prism, and the half mirror 17 and the objective lens 18 are shared with the imaging system (17 to 19). The imaging system (17 to 19) includes a half mirror 17, an objective lens 18, and an imaging lens 19. That is, it is an epi-illumination type optical system that illuminates the test object 10A via the objective lens 18.

  In the illumination system (12 to 18), the illumination light from the light source 11 is collected by the collector lens 12a, enters the condenser lens 16 through the filter 13, the aperture stop 14, and the field stop 15, and is parallel by the condenser lens 16. It is converted into light and enters the half mirror 17. As indicated by the dotted line, the optical system from the collector lens 12 a to the condenser lens 16 has a so-called Koehler illumination arrangement in which an image of the light source 11 is formed on the pupil plane of the objective lens 18. The filter 13 is a filter for absorbing heat rays (infrared component).

  The half mirror 17 is disposed on the optical path 10B of the imaging system (17 to 19), and is incident from the outside of the optical path 10B (that is, the optical path IL with the illumination optical systems 12 to 16) (that is, the condenser lens 16 side). A part (L1) of the illumination light is reflected and the other part (L2) is transmitted. That is, the amplitude of the illumination light from the light source 11 is divided in two directions. The intensity ratio between the illumination lights L1 and L2 divided by the half mirror 17 is constant.

  In the illumination system (12 to 18), a part of the illumination light L1 reflected by the half mirror 17 is irradiated to the object 10A to be examined through the objective lens 18. Since the illumination light L1 enters the test object 10A from a direction parallel to the optical path 10B of the imaging system (17 to 19), the test object 10A is illuminated from a substantially vertical direction. A part of the illumination light L2 transmitted through the half mirror 17 is guided to the monitor system (21 to 24) without contributing to the illumination of the object 10A.

  Here, the spectral characteristic S (λ) of the illumination light L1 incident on the test object 10A is, for example, as shown in FIG. The horizontal axis of FIG. 2 represents the wavelength λ, and the vertical axis represents the intensity of each wavelength. Further, the area surrounded by the waveform of the spectral characteristic S (λ) and the horizontal axis shown in FIG. 2 represents the intensity of the illumination light L1. The intensity of the illumination light L1 can be adjusted according to the current value supplied to the light source 11 as described above.

However, adjustment of the intensity of the illumination light L1 also changes the spectral characteristics of the illumination light L1. When the light source 11 is a halogen lamp, the blue component (around 450 nm) is relatively increased when the intensity is increased, and the red component (around 650 nm) is relatively increased when the intensity is decreased. Furthermore, the change in the spectral characteristics of the illumination light L1 may be caused by a change with time of the light source 11 or the illumination system (12 to 18).
In the inspection apparatus 10 of the present embodiment, in order to monitor such a change in spectral characteristics of the illumination light L1, a monitor system (21 to 24) is provided on the optical path of a part of the illumination light L2 that has passed through the half mirror 17. Provided. The monitor system (21-24) includes a color separation prism 21 and three light receiving sensors 22-24. The color separation prism 21 is provided with two filter films 2A and 2B having different spectral characteristics. The filter film 2A has spectral characteristics that mainly reflect the blue component and transmit the green and red components. The filter film 2B has spectral characteristics that mainly reflect the green component and transmit the red component.

  Therefore, the red component of the illumination light L <b> 2 that has entered the monitor system (21 to 24) passes through the filter films 2 </ b> A and 2 </ b> B of the color separation prism 21 and enters the light receiving sensor 22. Further, the green component passes through the filter film 2A, is reflected by the filter film 2B, and enters the light receiving sensor 23. Further, the blue component is reflected by the filter film 2 </ b> A and enters the light receiving sensor 24. The three light receiving sensors 22 to 24 photoelectrically convert each incident light and detect it. That is, in the monitor system (21 to 24), the illumination light L2 is separated into three color components (red, green and blue) and detected for each color component.

  The spectral sensitivity characteristics of the monitor systems (21 to 24) are the product of the prism branching ratio at which the monitor light L2 reaches the light receiving sensors 22 to 24 by the color separation prism 21 and the light receiving sensitivity characteristics of the light receiving sensors 22 to 24, respectively. It is represented by The magnitudes of the output signals of the light receiving sensors 22 to 24 when the intensity light of one unit at the wavelength λ is incident on the monitor light L2 are the spectral sensitivity characteristics ρr (λ) and ρg (λ) of the monitor systems (21 to 24). , ρb (λ).

  The spectral sensitivity characteristics ρr (λ), ρg (λ), and ρb (λ) of the monitor systems (21 to 24) of the light reaching the light receiving sensors 22 to 24 are as shown in FIG. 3, for example. The horizontal axis in FIG. 3 represents the wavelength λ, and the vertical axis represents the sensitivity of each wavelength. The spectral sensitivity characteristic ρr (λ) of the monitor system (21 to 24) is a sensitivity characteristic of the red component received by the light receiving sensor 22. Similarly, the spectral sensitivity characteristics ρg (λ) and ρb (λ) of the monitor systems (21 to 24) are the sensitivity characteristics of the green and blue components received by the light receiving sensors 23 and 24.

  Therefore, the spectral characteristics of the light incident on the light receiving sensor 22 (red component of the illumination light L2) are the spectral characteristics S (λ) of the illumination light L2 shown in FIG. 2 and the spectral characteristics of the monitor systems (21 to 24) shown in FIG. It is represented by the product of the sensitivity characteristic ρr (λ). Similarly, the light incident on the light receiving sensor 23 (green component of the illumination light L2) and the light incident on the light receiving sensor 24 (blue component of the illumination light L2) are respectively spectral characteristics S (λ) of the illumination light L2. And the spectral sensitivity characteristics ρg (λ) and ρb (λ) of the monitor system (21 to 24) shown in FIG.

  Further, the detection signal intensity Sr of the red component by the light receiving sensor 22 is obtained by setting the spectral characteristic (S (λ) · ρr (λ)) of the incident light to the light receiving sensor 22 at the wavelength λ, as shown in the following equation (1). It corresponds to the integrated value. Similarly, the detection signal intensity Sg of the green component by the light receiving sensor 23 and the detection signal intensity Sb of the blue component by the light receiving sensor 24 are applied to the light receiving sensors 23 and 24 as shown in the following equations (2) and (3). This corresponds to a value obtained by integrating the spectral characteristics (S (λ) · ρg (λ), S (λ) · ρb (λ)) of the incident light with the wavelength λ.

Sr = ∫S (λ) · ρr (λ) dλ (1)
Sg = ∫S (λ) · ρg (λ) dλ (2)
Sb = ∫S (λ) · ρb (λ) dλ (3)
Then, the red component detection signal intensity Sr by the light receiving sensor 22, the green component detection signal intensity Sg by the light receiving sensor 23, and the blue component detection signal intensity Sb by the light receiving sensor 24 are output to the signal processing unit 25, respectively. The

  Therefore, in the signal processing unit 25, based on the sum of the detection signal intensities Sr, Sg, Sb from the three light receiving sensors 22 to 24, the intensity of the illumination light L2 (that is, the intensity of the illumination light L1 incident on the test object 10A). ) Can be monitored. Furthermore, the change in the spectral characteristics of the illumination light L2 (that is, the change in the spectral characteristics of the illumination light L1 incident on the test object 10A) can be monitored based on the relative ratio of the detection signal intensities Sr, Sg, Sb.

  In the inspection apparatus 10 of the present embodiment, the monitor system (21 to 24) is configured by the color separation prism 21 and the three light receiving sensors 22 to 24. Therefore, the detection signal intensities Sr, Sg, and Sb for each color component are simultaneously provided. It is possible to capture, and it is possible to accurately monitor changes in the intensity and spectral characteristics of the illumination light L2 (that is, changes in the intensity and spectral characteristics of the illumination light L1 incident on the test object 10A). Furthermore, since the monitor system (21 to 24) is provided on the transmission optical path of the half mirror 17 and takes in unnecessary light (L2) that does not contribute to illumination of the test object 10A, without losing the intensity of the illumination light L1, That monitoring can be done.

  On the other hand, in the test object 10A irradiated with the illumination light L1, inspection light is generated based on light reflected or diffracted by a fine pattern (uneven structure) formed on the surface thereof. Inspection light from the test object 10A is collected by the objective lens 18, passes through the half mirror 17 (inspection light L3), and enters the imaging lens 19. The objective lens 18 is an infinite system, and the inspection light L3 is incident on the image sensor 20 via the imaging lens 19, and the object 10A to be examined is applied to the imaging surface of the image sensor 20 by the action of the objective lens 18 and the imaging lens 19. Form an image of Similarly to the monitor system, the imaging system is branched to the imaging elements 20R, 20G, and 20B at the respective spectral branching ratios determined by the color separation prism 26, and images are formed on the respective imaging surfaces.

  The spectral characteristic of the image at the point (X, Y) on the imaging surface of the imaging element 20, that is, the spectral characteristic of the inspection light L3 incident on the point (X, Y) on the imaging surface is the point (X, Y) on the imaging surface. Is represented by the product of the spectral reflection characteristic Γuv (λ) (for example, FIG. 4) of the point (u, v) on the test object 10A conjugated with the spectral characteristic S (λ) (FIG. 2) of the illumination light L1. (For example, FIG. 5). The vertical axis in FIG. 4 represents reflectance, and the vertical axis in FIG. 5 represents intensity. The spectral sensitivity characteristic of each imaging optical system with respect to the inspection light L3 is represented by the product of the branching ratio of the color separation prism 26 and the sensitivity of the imaging devices 20R, 20G, and 20B. Sensitivity characteristics Rr (λ), Rg (λ), and Rb (λ) are assumed.

Then, mainly the red component of the inspection light L3 enters the imaging element 20R through the color separation filter. The spectral characteristics of the red component are, for example, the spectral characteristics Γuv (λ) · S (λ) of the inspection light L3 shown in FIG. 5 and the spectral sensitivity characteristics Rr (λ) at the point (X, Y) on the imaging surface of the imaging device 20R. ) And the product (for example, FIG. 6). The vertical axis in FIG. 6 represents intensity.
Similarly, mainly the green component and the blue component of the inspection light L3 are incident on the image sensor 20G and the image sensor 20B through the color separation filter, respectively. The spectral characteristics of the green component and blue component are, for example, the spectral characteristics Γuv (λ) · S (λ) and spectral sensitivity characteristics Rg (λ) of the inspection light L3 at the point (X, Y) on the imaging surface, for example. , Rb (λ), for example (FIG. 6).

  Further, an imaging signal Tr (X, Y) at a point (X, Y) on the imaging device 20R corresponding to the point (u, v) on the object 10A to be examined is represented by the following equation (4): This corresponds to a value obtained by integrating the spectral characteristics (S (λ) · Γuv (λ) · Rr (λ)) of the point (X, Y) on the image sensor 20R with the wavelength λ. Similarly, the image signals Tg (X, Y) and Tb (X, Y) of the green and blue components at the point (X, Y) on the image sensors 20G and 20B are expressed by the following equations (5) and (6). As shown in FIG. 4, the spectral characteristics (S (λ) · Γuv (λ) · Rg (λ), S (λ) · Γuv (λ) · Rb of the received light at the point (X, Y) on the image sensors 20G and 20B (λ)) corresponds to a value obtained by integrating each with the wavelength λ.

Tr (X, Y) = ∫S (λ) · Γuv (λ) · Rr (λ) dλ (4)
Tg (X, Y) = ∫S (λ) · Γuv (λ) · Rg (λ) dλ (5)
Tb (X, Y) = ∫S (λ) · Γuv (λ) · Rb (λ) dλ (6)
The imaging signal Tr (X, Y) at the point (X, Y) of the imaging device 20R, the imaging signal Tg (X, Y) at the point (X, Y) of the imaging device 20G, and the point ( The imaging signals Tb (X, Y) of X, Y) are output to the signal processing unit 25, respectively. That is, the image pickup devices 20R, 20G, and 20B separate the image of the test object 10A into three color components (red, green, and blue) and pick up images for each color component, and the result (image signals Tr (X, Y), Tg). (X, Y), Tb (X, Y)) is output to the signal processing unit 25 in the subsequent stage.

  In the inspection apparatus 10 of the present embodiment, the imaging signals Tr (X, Y), Tg (X, Y), and Tb (X, Y) for each color component can be taken into the signal processing unit 25 at the same time. Incidentally, as can be seen from the above formulas (4) to (6), the color information of the color image of the test object 10A includes not only the spectral characteristic (Γuv (λ)) of the test object 10A but also the illumination light. Information on the spectral characteristic (S (λ)) of L1 is also included.

Next, signal processing in the signal processing unit 25 will be described.
In the signal processing unit 25, the imaging signals Tr (X, Y), Tg (X, Y), Tb (X, Y) for each color component output from the imaging elements 20R, 20G, and 20B and the monitor system (21 to 21) are displayed. 24) based on the detection signal intensities Sr, Sg, and Sb for each color component output from (24), data for inspection with respect to the object to be inspected 10A (image intensities represented by equations (7) to (9) described later) Γ (X, Y) and chromaticity coordinates cx (X, Y), cy (X, Y)) are generated.

  In addition, when generating data for inspection, in addition, spectral sensitivity characteristics Rr (λ), Rg (λ), Rb (λ) of the imaging system and spectral sensitivity characteristics ρr (λ) of the monitor systems (21 to 24) are used. , ρg (λ), ρb (λ), the correction value Hr (X, X) taking into account the spectral reflection characteristics of the half mirror 17, the spectral transmission characteristics of the objective lens 18 and the imaging lens 19, illumination unevenness, and the like. Y), Hg (X, Y), Hb (X, Y) are used. The correction values Hr (X, Y), Hg (X, Y), Hb (X, Y) are values at the point (X, Y) on the imaging surface of the imaging elements 20R, 20G, 20B. It is obtained in advance for each point (for each pixel) and stored in the memory of the signal processing unit 25.

  The correction values Hr (X, Y), Hg (X, Y), Hb (X, Y) can be obtained by using the spectral sensitivity characteristics Rr (λ), Rg (λ), Rb ( (λ) and a spectral sensitivity characteristic ρr (λ), ρg (λ), ρb (λ) of the monitor system and a method of executing a calculation process using known data such as the spectral characteristics of each optical element (17 to 19). Conceivable. In addition, an optical element (for example, an aluminum mirror) having a uniform reflectance in a predetermined wavelength range required for inspection is placed on the stage instead of the object to be inspected 10A, and image signals from the image sensors 20R, 20G, and 20B. By calculating the ratio of Tr (X, Y), Tg (X, Y), Tb (X, Y) and the detection signal intensity Sr, Sg, Sb of the monitor system (21-24), the correction value Hr (X , Y), Hg (X, Y), Hb (X, Y) may be measured.

  In the signal processing unit 25, correction values Hr (X, Y), Hg (X, Y), Hb (X, Y) stored in the memory in advance, and imaging signals output from the imaging elements 20R, 20G, and 20B. Tr (X, Y), Tg (X, Y), Tb (X, Y) and detection signal strengths Sr, Sg, Sb output from the monitor system (21-24) are expressed by the following equation (7). By substituting into, the image intensity Γ (X, Y) at the point (X, Y) on the imaging surface of the imaging elements 20R, 20G, 20B is generated as inspection data.

Γ (X, Y) = Tr (X, Y) · Hr (X, Y) / Sr + Tg (X, Y) · Hg (X, Y) / Sg
+ Tb (X, Y) .Hb (X, Y) / Sb (7)
Further, the signal processing unit 25 uses the following formulas (8) and (9), and the chromaticity coordinates cx (X, Y), cy of the image of the test object 10A at the point (X, Y) on the imaging surface. (X, Y) is generated as inspection data. The chromaticity coordinates cx (X, Y) and cy (X, Y) are coordinate components of the xy chromaticity diagram in the CIE color system.

cx (X, Y) = {Tr (X, Y) · Hr (X, Y) / Sr} / Γ (X, Y) (8)
cy (X, Y) = {Tg (X, Y) .Hg (X, Y) / Sg} / Γ (X, Y) (9)
Then, using the generated image intensity Γ (X, Y) and chromaticity coordinates cx (X, Y), cy (X, Y), a defect inspection of the surface of the test object 10A is performed. Since a fine pattern is repeatedly formed on the surface of the test object 10A, if there is no defect, the generated image intensity Γ (X, Y) and chromaticity coordinates cx (X, Y), cy (X, Y) varies at a spatially constant period. However, if there is a defect, the periodicity of the image intensity Γ (X, Y) and the chromaticity coordinates cx (X, Y), cy (X, Y) will be disturbed. Therefore, for example, if periodic disturbance appears in any one of the three test data (Γ (X, Y), cx (X, Y), cy (X, Y)), The position can be detected as pattern disturbance (that is, a defect).

At this time, in the inspection apparatus 10 of the present embodiment, illumination light incident on the object 10A is detected based on the detection signal intensities Sr, Sg, Sb from the three light receiving sensors 22-24 of the monitor system (21-24). Since changes in the intensity and spectral characteristics of L1 are monitored, even if the spectral characteristics (S (λ)) of the illumination light L1 change, it is possible to accurately detect defects on the surface of the test object 10A.
Further, in the signal processing unit 25 of the inspection apparatus 10 according to the present embodiment, calculation formulas (formulas (7) to (9)) in consideration of the detection signal intensities Sr, Sg, and Sb output from the monitor systems (21 to 24). ) To obtain the intensity Γ (X, Y) and chromaticity coordinates cx (X, Y), cy (X, Y) of the image of the object 10A to be examined on the imaging surface of the imaging device 20. Even if the spectral characteristics (S (λ)) change, it is possible to accurately detect defects on the surface of the object 10A.

  Further, in the signal processing unit 25 of the inspection apparatus 10 according to the present embodiment, calculation formulas (expressions (7) to (7)) including correction values Hr (X, Y), Hg (X, Y), and Hb (X, Y). 9)) to obtain the inspection data (Γ (X, Y), cx (X, Y), cy (X, Y)), the spectral sensitivity characteristics Rr (λ) of the image sensors 20R, 20G, and 20B. , Rg (λ), Rb (λ) and the spectral sensitivity characteristics ρr (λ), ρg (λ), ρb (λ) of the monitor system (21 to 24) are corrected for accurate inspection. Data (Γ (X, Y), cx (X, Y), cy (X, Y)) can be obtained. Therefore, a more accurate defect inspection can be performed.

Further, in the inspection apparatus 10 of the present embodiment, in order to obtain the chromaticity coordinates cx (X, Y), cy (X, Y) as inspection data, not only the presence / absence of a defect, but also the kind of analogy is performed. You can also.
When changing the magnification of the image of the test object 10A by switching the objective lens 18 and the imaging lens 19 of the inspection apparatus 10, different correction values Hr (X, Y), Hg (X , Y), Hb (X, Y) are set to generate inspection data (Γ (X, Y), cx (X, Y), cy (X, Y)).
(Second Embodiment)
As shown in FIG. 7, the inspection device 30 of the second embodiment is provided with a perforated mirror 31 and an objective lens 32 instead of the half mirror 17 and the objective lens 18 of FIG. 1. The objective lens 32 has a dark field illumination unit 3A on the outside thereof. The perforated mirror 31 totally reflects a part (L4) of the annular illumination light incident from outside the optical path 10B (that is, the optical path IL) (that is, the condenser lens 16 side) of the imaging system (31, 32, 19). The other part (L5) is transmitted from the opening 3B to the monitor system (21 to 24).

  As a result, a part of the illumination light L4 totally reflected by the perforated mirror 31 is guided to the dark field illumination unit 3A of the objective lens 32. In the illumination system (12 to 16, 31, 32), the object to be examined 10A is illuminated in the dark field via the dark field illumination unit 3A of the objective lens 32. Changes in the intensity and spectral characteristics of the illumination light L4 incident on the test object 10A are monitored by the illumination light L5 transmitted through the opening 3B of the perforated mirror 31 and incident on the monitor system (21-24).

  In the inspection apparatus 30 of the second embodiment, the object to be examined 10A is illuminated in the dark field, so the specularly reflected light from the object to be examined 10A does not enter the imaging system (31, 32, 19), and the object to be examined 10A. Only the inspection light from can be guided to the image sensor 20 through the opening 3B of the hollow mirror 31 of the imaging system (31, 32, 19). Therefore, it is possible to obtain an image in which the edge portion of the fine pattern of the test object 10A is emphasized.

  Also in the inspection apparatus 30 of the second embodiment, the detection signal intensities Sr, Sg, Sb from the three light receiving sensors 22-24 of the monitor system (21-24) are the same as the inspection apparatus 10 of the first embodiment described above. Therefore, even if the spectral characteristic (S (λ)) of the illumination light L4 changes, the surface of the test object 10A is monitored. It is possible to accurately detect defects.

  Furthermore, by using the above calculation formulas (formulas (7) to (9)), the intensity Γ (X, Y) of the image of the test object 10A on the imaging surface of the image sensor 20 and the chromaticity coordinates cx (X , Y), cy (X, Y). At this time, it is preferable to use correction values Hr (X, Y), Hg (X, Y), Hb (X, Y) different from those in the above-described inspection under bright field illumination. The difference between the correction values is due to the use of the hollow mirror 31 and the objective lens 32 instead of the half mirror 17 and the objective lens 18 of FIG.

In addition, when the objective lens 32 with the dark field illumination unit 3A is used as in the second embodiment, the mirror unit (epi-illumination prism) of the illumination system is switched between the half mirror 17 and the perforated mirror 31 so that It is possible to inspect the defect of the object 10A while switching between bright field illumination and dark field illumination.
(Modification)
In the above-described embodiment, the monitor system (21 to 24) includes the color separation prism 21 and the light receiving sensors 22 to 24, and the imaging system (20R, 20G, 20B, 26) includes the color separation prism 26 and the image sensor. Although comprised with 20R, 20G, and 20B, this invention is not limited to this. For example, a single-plate image sensor in which a color separation filter is incorporated in each pixel on the imaging surface may be used. At this time, the spectral sensitivity characteristic of the monitor system is the spectral sensitivity of the image sensor. Further, instead of the monitor system (21 to 24), a color image pickup device (having the same configuration as the above-described single-plate image pickup device) is used, and the sum of the image pickup signals of all R pixels is set as a detection signal intensity Sr, , The total of the imaging signals of all B pixels may be used as the detection signal strengths Sg and Sb. In this case, the detection signal intensities Sr, Sg, Sb for each color component can be taken in simultaneously. However, the light receiving sensor is preferable because it is less expensive than the image sensor.

Further, instead of using the color separation prisms 21 and 26, a filter having a predetermined spectral transmission characteristic is disposed on the front surface of each of the three light receiving sensors (RGB), and the three light receiving sensors are sequentially disposed on the optical path. The detection signal intensities Sr, Sg, and Sb for each color component may be taken in the order of time series.
Further, instead of the monitor system (21 to 24), one light receiving sensor is provided, and an RGB filter (each having a predetermined filter spectral transmittance and a spectral sensitivity characteristic of the light receiving sensor) is provided in front of the light receiving sensor. In addition, the detection signal intensities Sr, Sg, and Sb for each color component may be taken in the order of time series by sequentially arranging the spectral sensitivity characteristics of the monitor system on the optical path.

  Further, in the middle of the illumination optical path from the light source 11 to the half mirror 17 (or the hollow mirror 31) (for example, in the vicinity of the filter 13), RGB filters provided in the turret similar to the above are sequentially arranged on the optical path. Based on the detection signal intensity from the light receiving sensor, the detection signal intensity Sr, Sg, Sb for each color component may be taken in the order of time series. In this case, the image pickup signals Tr (X, Y), Tg (X, Y), and Tb (X, Y) for each color component are taken in from the image pickup device 20 of the imaging system in the order of time series.

Furthermore, in the above-described embodiment, the present invention can also be applied to a case where two dichroic mirrors and three monochrome imaging elements having different spectral characteristics are provided (three-plate type). One spectral characteristic of the two dichroic mirrors mainly reflects the blue component and transmits the green and red components. The other spectral characteristic mainly reflects the green component and transmits the red component.
Further, in the above-described embodiment, an example in which the light receiving unit of the monitor system is provided at the rear stage of the half mirror 17 (or the hollow mirror 31) and unnecessary light that does not contribute to the illumination of the test object 10A is taken in for monitoring. However, the present invention is not limited to this. A part of the illumination light may be branched in the middle of the illumination optical path from the light source 11 to the half mirror 17 (or the hollow mirror 31), and a monitor light receiving unit may be arranged on the optical path.

  Furthermore, in the above-described embodiment, the inspection data (image intensity Γ (X, Y) and chromaticity coordinates cx (X) are obtained by signal processing that takes into account the monitoring results (detection signal intensity Sr, Sg, Sb for each color component). , Y), cy (X, Y)) has been described as an example, but the present invention is not limited to this. The current value supplied to the light source 11 may be feedback controlled based on the monitor result (detection signal intensity Sr, Sg, Sb for each color component) to keep the spectral characteristics of the illumination lights L1, L4 constant. In this case, it is preferable to adjust the intensity of the illumination lights L1 and L4 using an ND filter.

  In the above-described embodiment, the light source 11 (such as a halogen lamp) that emits white light in the visible range as illumination light has been described as an example, but the present invention is not limited thereto. The present invention can also be applied to the case of using a light source that emits illumination light other than the visible range (for example, a mercury lamp in the ultraviolet range).

It is a figure which shows the structure of the test | inspection apparatus 10 of 1st Embodiment. It is a figure which shows the spectral characteristic S ((lambda)) of the illumination light L1. FIG. 6 is a diagram showing spectral sensitivity characteristics ρr (λ), ρg (λ), and ρb (λ) of the color separation prism 21. It is a figure which shows the spectral reflection characteristic (GAMMA) uv ((lambda)) of the point (u, v) on to-be-tested object 10A. 3 is a diagram illustrating spectral characteristics at a point (X, Y) on the imaging surface of the imaging element 20. FIG. 3 is a diagram illustrating spectral characteristics of incident light (red, green, and blue) on each pixel of the image sensor 20. FIG. It is a figure which shows the structure of the test | inspection apparatus 30 of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,30 Inspection apparatus 11 Light source 12a Collector lens 12b Relay lens 13 Filter 14 Aperture stop 15 Field stop 16 Condenser lens 17 Half mirror 18, 32 Objective lens 19 Imaging lens 20 Imaging element 21 Color separation filter 22-24 Light receiving sensor 25 Signal Processing unit 31 Hollow mirror 3A Dark field illumination unit 3B Opening

Claims (4)

Illuminating means for illuminating the object to be examined with illumination light from a light source;
An image forming means for forming an image of the object to be examined irradiated with the illumination light;
Imaging means for decomposing the image of the test object into a plurality of color components and imaging each color component;
An inspection apparatus comprising: a detection unit that decomposes the illumination light into a plurality of color components and detects each of the color components. The inspection apparatus according to claim 1,
An optical member that transmits the inspection light from the object to be inspected and reflects a part of the illumination light from the outside of the optical path and transmits the other part is disposed on the optical path of the imaging means. ,
The imaging means forms the image based on the inspection light transmitted through the optical member,
The illumination means irradiates a part of the illumination light reflected by the optical member onto the object to be examined.
The detection device is configured to detect another color component by separating another part of the illumination light transmitted through the optical member into a plurality of color components. The inspection apparatus according to claim 1 or 2,
The image processing apparatus includes a generation unit that generates inspection data based on an imaging signal for each color component output from the imaging unit and a detection signal for each color component output from the detection unit. Inspection device. The inspection apparatus according to claim 3,
The generating device generates chromaticity coordinates of the image of the test object as the data.

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