JP3659953B2 - Surface defect inspection equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface defect inspection for inspecting defects on the surface of an object having a thin film on the surface or an object having a flat surface, such as the wafer or liquid crystal glass substrate in a manufacturing process line of the wafer or liquid crystal glass substrate. Relates to the device.
[0002]
[Prior art]
In photolithographic process lines such as liquid crystal panels, if the resist applied on the substrate surface has defects such as uneven film thickness or dust adhesion, pattern line width defects after etching, pinholes in the pattern, etc. Appears as bad. Therefore, in general, the entire substrate is inspected for the presence or absence of the defects.
[0003]
Conventionally, for such defect inspection, a method of illuminating a substrate (hereinafter referred to as a subject) with a light projecting device and searching for defects visually has been adopted. As an example of an inspection light projection apparatus suitable for such an application, an outline of the apparatus previously filed by the present applicant (Japanese Patent Application No. 4-31922) is described with reference to FIGS. explain.
[0004]
The light beam from the high-intensity light source 201 passes through the heat ray absorption filter 203 and is converted into uniform illumination light by the diffusion plate 204 and then becomes a light beam whose spectral width is limited by the interference filter 205 (hereinafter referred to as narrow-band light). . Subsequently, the object 211 is illuminated after being reflected by the plane mirror 206 and converted into a convergent light beam by the large-diameter Fresnel lenses 207 and 208. Immediately after the Fresnel lens 208, there is a liquid crystal diffusion plate 209, which normally acts as a diffusion plate, so that the subject 211 is illuminated with diffused light from a large surface light source.
[0005]
On the other hand, as shown in FIG. 27, when a voltage is applied to the liquid crystal diffusion plate 209 by the power supply 210, the liquid crystal becomes colorless and transparent. At this time, the subject 211 is illuminated with convergent light.
[0006]
In the inspection light projecting device having such a configuration, the unevenness of the film thickness of the subject 211 is inspected under the diffused light illumination device shown in FIG. This is because when the resist film thickness changes, the optical path difference between the reflected light from the resist front and back surfaces changes, and when illuminated with quasi-monochromatic light, the change in film thickness becomes light and dark interference fringes. It is possible to recognize the unevenness.
[0007]
The adhesion of the dust 212 to the subject 211 is inspected under convergent light illumination (FIG. 27). That is, since the light beam reflected by the plane of the subject 211 converges at the position S, when the observer's eye 213 is placed at a position avoiding this, only the light scattered by the point 212 other than the plane, that is, the dust 212 is visually observed. Is recognized.
[0008]
In the convergent light illumination, the following defects are also detected. FIG. 13 is a schematic diagram of a cross section of a specimen after resist development, and shows a state in which a film formation layer 61 is provided on a substrate 60 (a glass plate or a wafer) and a patterned resist 62 is left thereon. Show. FIG. 14 is an enlarged view of part 65 of FIG. Thus, the surface of the subject can be roughly divided into three parts. That is, the flat portion A on the resist remaining film and the flat portion B without the resist, and the side surfaces C and D of the step between them. Among these, defects such as uneven film thickness in the flat portion A can be detected by the above-described diffused light illumination device that observes regular reflection light.
[0009]
Now, while the normal side is as shown in FIG. 15C, the side of the defective part is deformed as shown in FIG. 16C, for example. Such different shapes show different light scattering angle distributions, and therefore, when observed with scattered light with convergent light illumination, the defects on the side surfaces C and D are recognized as luminance differences from normal parts. .
[0010]
On the other hand, the film thickness unevenness is inspected under the diffused light illumination device shown in FIG. This is because when the resist film thickness changes, the optical path difference between the reflected light from the resist front and back surfaces changes, and when illuminated with quasi-monochromatic light, the change in film thickness becomes light and dark interference fringes. It is possible to recognize the unevenness.
[0011]
This examination light projecting apparatus is used in combination with a swinging and rotating mechanism of a subject that was previously filed and published by the present applicant (Japanese Patent Laid-Open No. 5-109849). In other words, in the actual examination, the subject 211 is illuminated by the light projecting device, and is rotated and rotated to determine the incident / reflection angle of the light beam to the subject 211 and the direction of the diffracted light by the periodic pattern on the subject. The entire surface of the subject 211 can be inspected while being adjusted by a person so that the observation of scattered light or reflected reflected light is not hindered.
[0012]
[Problems to be solved by the invention]
Since the work described above is a visual inspection by an operator, the degree of freedom of observation is large and an excellent inspection ability can be exhibited. On the other hand, however, variations in detection ability due to individual differences among workers and differences in observation conditions are unavoidable. Especially when inspections are performed frequently and over a long period of time, they cause worker fatigue and provide a certain level of inspection ability. It becomes even more difficult to maintain. Also, dust generation from workers has always been a problem, and automation of the inspection has been desired.
[0013]
As an automated method, an image can be easily obtained by installing an imaging lens and an image sensor such as a CCD instead of the eye 213 shown in FIGS. It is to extract defects. However, this method includes the first to fourth problems described below.
[0014]
<First problem>
The incident angle of the illumination light with respect to the subject 211 is greatly different depending on the place. FIG. 29 is a diagram for explaining this, and FIG. 28 is simplified. In FIG. 29, 209 is a diffusion plate, 211 is a subject, 214 is an imaging lens, and 215 is an image sensor.
[0015]
In such a configuration, the incident angle θ of the light beam that exits the diffusion plate 209 and is reflected by the subject 211 and reaches the image sensor 215 via the imaging lens 214.₀Is the maximum value θ at both ends of the subject 211_0maxAnd the minimum value θ_0minContinuously changing between.
[0016]
Here, taking the observation of film thickness unevenness as an example, the refractive index of the thin film (= resist) is n, the film thickness is h, and the wavelength of illumination light (monochrome) is λ.₀, (Determined by Snell's law) If the refraction angle of the rays inside the thin film is θ ′ and the phase change upon reflection on the lower surface of the thin film is φ (0 ≦ φ <2π), the interference fringes due to the thin film become bright lines condition is
2nhcos θ ′ + (φ / 2π) ・ λ₀= Mλ₀, M = 0, ± 1, ± 2, (1)
(M: interference order). That is, the incident angle θ of the illumination light₀In the arrangement of FIG. 29 in which the angle changes, even if the film thickness of the subject 211 is uniform over the entire surface, the incident angle θ₀According to the distribution, a light and dark distribution is formed on the subject. The film thickness unevenness is observed brightly in one place and dark in another place. Therefore, in the conventional inspection apparatus, as described above, it is necessary to inspect the entire surface of the subject 211 while changing the incident condition of the illumination by swinging and rotating the subject 211.
[0017]
However, when trying to extract film thickness unevenness using an image processing device, if the same film thickness unevenness looks different depending on the location or multiple images with different incident conditions must be processed, the processing It is easily guessed that it will be very complicated and difficult.
[0018]
Similarly, for the defect detection on the side surface of the step, the scattered light to be observed varies depending on the position on the subject.
[0019]
If the subject 211 is about the size of a wafer, the incident angle θ₀Although the change of is small, if you try to inspect the liquid crystal glass substrate at once or in 2 to 4 divisions, θ₀The change in size becomes quite large, and the above problem is unavoidable.
[0020]
<Second problem>
This is a point where normal illumination with respect to the subject 211 is impossible. As can be seen from Equation (1), at normal incidence (θ₀= Θ ′ = 0 °), the detection sensitivity of the film thickness unevenness becomes the largest.
[0021]
However, the diffuser plate 209 and the image sensor 215 are arranged as shown in FIG.₀Is close to 0 °, the shadowed portion of the image sensor 215 is not illuminated and cannot be observed.
[0022]
Further, if a half mirror is provided between the diffuser plate 209 and the subject 211 and the observation optical path is bent, the shadow disappears. However, in this case, a half mirror larger than the subject 211 is required, which corresponds to a wide field of view. Becomes difficult.
[0023]
<Third problem>
This is a point where it is difficult to obtain coordinates on the subject 211. In the arrangement shown in FIG. 29, the subject 211 is tilted with respect to the observation optical axis. Therefore, in order to obtain a sharp image on the entire surface, the imaging surface of the image sensor 215 must also be tilted (Scheinproof condition). At the same time, the closer to the imaging lens 214 of the subject 211, the distorted image has a larger magnification. Therefore, if the position coordinates are to be obtained for the cause analysis of defects, a means for calibrating the coordinates must be taken.
[0024]
<Fourth problem>
When the dust 212 on the subject 211 is detected by the apparatus of FIG. 27, the entire surface shines with the diffracted light by the wiring pattern on the subject 211, so the contrast of the scattering points does not increase so much and is difficult to extract by image processing. It is a point to become.
[0025]
The present invention has been made to solve the above-described problems. The entire configuration can be made compact, the interference light detection sensitivity can be maximized, and automatic defect inspection for defects and / or film thickness unevenness is possible. An object of the present invention is to provide a surface defect inspection apparatus.
[0026]
[Means for Solving the Problems]
     In order to achieve the object, the invention corresponding to claim 1 is:Diffuse light beam irradiation for irradiating diffuse light from above the subjectA light source;A parallel light beam irradiating means for irradiating the subject with a diffused light beam from the diffused light beam irradiation light source as a substantially parallel light beam;Of irradiation meansparallelCondensing means for condensing light from the subject irradiated by a light beam;Through the light collecting meansFrom the subjectLight ofImaging means for imagingAn angle setting unit that sets an angle formed by the optical axis of the parallel beam irradiating unit and the optical axis of the imaging unit with respect to the normal line of the subject, and image processing on the image captured by the imaging unit. Image processing means for extracting defects, and incident direction setting means for adjusting the incident direction of the diffused beam irradiation light source in three dimensions with respect to the subject.It is the surface defect inspection apparatus characterized by comprising.
[0027]
  In order to achieve the object, the invention corresponding to claim 2It is as follows. That is, the imaging unit is arranged at a position for imaging regular reflection light from the surface of the subject irradiated by the parallel light beam irradiation unit.The surface defect inspection apparatus according to claim 1.
[0029]
  To achieve the object, the claims3The invention corresponding to is as follows. That is,The angle setting means optimally observes the angles formed by the optical axis of the parallel light beam irradiation means and the optical axis of the imaging means with respect to the normal line of the subject according to the type and defect of the subject. Adjust the angle to meet the conditionThe surface defect inspection apparatus according to claim 1.
[0030]
  To achieve the object, the claims4The invention corresponding to is as follows. That is,The angle setting means can set the optical axis of the imaging means coaxially with the normal line of the subject and arbitrarily set the angle of the optical axis of the parallel light beam irradiation means.The surface defect inspection apparatus according to claim 1.
[0031]
  To achieve the object, the claims5The invention corresponding to is as follows. That is,The said angle setting means is provided with the moving stage which can move the said diffused beam irradiation light source on a confocal plane.This is a surface defect inspection apparatus.
[0032]
  To achieve the object, the claims6The invention corresponding to is as follows. That is,The parallel light beam irradiating means and the condensing means are shared by the same collimator lens.The surface defect inspection apparatus according to claim 1.
[0036]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0037]
First, an embodiment for detecting the film thickness unevenness, dust, and scratches of the subject will be described.
[0038]
<First embodiment>
FIG. 1 is a side view of an optical system according to a first embodiment of the surface defect inspection apparatus of the present invention. The light beam emitted from the halogen lamp 2 that is a light source for detecting unevenness in film thickness passes through the heat ray absorption filter 3 and is converted into a parallel light beam group by the condenser lens 4. These are integrated with the lamp house 1.
[0039]
A plurality of narrow-band interference filters (not shown) are housed in the rotation holder 5, and a desired interference filter can be inserted into the optical path by rotating them with a motor (not shown).
[0040]
Since the refractive index n of the thin film to be observed is 1.62 (positive resist) and the thickness h is about 1.5 μm, the optical path difference of interference is about 2 nh to 5 μm. Therefore, the coherent length of illumination light λ₀ ²/ Δλ (λ₀.About.0.6 .mu.m; center wavelength, .DELTA..lambda .; half-width of spectrum) is used so that an interference filter of .DELTA..lamda. = 10 nm is used. Center wavelength λ₀If the variable range is a range in which the interference order of the uniform film thickness portion changes by 1, the region with uniform film thickness for the arbitrary φ in equation (1) is a bright line and dark line of interference fringes. Can be set freely. That is, the variable range is λ₀₁To λ₀₂(Λ₀₁<Λ₀₂) From equation (1)
2nhcos θ ′ + (φ / 2π) ・ λ₀₁= (M + 1) λ₀₁
2nhcos θ ′ + (φ / 2π) ・ λ₀₂= Mλ₀₂                      (2)
If the wavelength dependence of n and φ is ignored and m is eliminated from both equations with θ ′ = 0,
1 / 2nh = 1 / λ₀₁-1 / λ₀₂                                (3)
Get.
[0041]
That is, as the optical thickness nh of the thin film to be inspected is smaller, a wider variable range is required. Therefore, all the thin films to be inspected are matched with the one having the minimum optical thickness nh.₀If the variable range is set, an area having a uniform film thickness can be set to an arbitrary interference fringe (for example, a dark line) for any thin film regardless of the structure below the thin film (that is, even if φ changes). Center wavelength λ₀Can be selected.
[0042]
In the present embodiment, λ is set so that n = 1.62, h = 1.1 μm.₀The range of 550 nm to 650 nm is such that the center wavelength can be selected at intervals of 10 nm. Therefore, the rotary holder 5 includes eleven interference filters and one hole for white light illumination. The light beam narrowed by the interference filter is condensed on the end face of the fiber bundle 7 by the condenser lens 6.
[0043]
The illumination light is guided by the fiber bundle 7 in order to facilitate adjustment and maintenance by installing a light source unit from the lamp house 1 to the condenser lens 6 at the lower part of the entire apparatus. The light beam emitted from the fiber bundle 7 becomes a secondary light source whose intensity distribution is averaged by the diffusion plate 9. The diaphragm 10 blocks an unnecessary light beam, and these are integrated as a secondary light source unit 8. The diffusion plate 9 is installed on the focal plane of the collimator lens 12, and the light beam reflected by the half mirror 11 becomes a parallel light beam by the collimator lens 12 and enters the subject 21 perpendicularly.
[0044]
The collimator lens 12 has a diameter that covers one field of view (the entire surface of the liquid crystal glass substrate or one of several divided surfaces), and is installed at a certain distance from the subject 21. As for the imaging performance of the observation system (described later), the smaller the interval, the more advantageous. However, in order not to detect dust on the surface of the collimator lens 12 and to pass illumination light for detecting a scattering point described later, from several cm. An interval of a few tens of centimeters is taken. The light beam reflected by the subject 21 passes through the collimator lens 12 again to become convergent light, and the component that has passed through the half mirror 11 enters the imaging lens 13. The imaging lens 13 forms an image of the surface of the subject 21 on the imaging surface of the monochrome CCD 14. At this time, if the imaging lens 13 is installed so that its entrance pupil is located in the vicinity of the focal plane of the collimator lens 12 (that is, a position substantially conjugate with the diffusion plate 9), the light beam reflected by the subject 21 is efficiently obtained. Collected and an observation field of uniform illumination can be obtained.
[0045]
When a periodic wiring pattern is imaged by the CCD 14, if the pixel period of the CCD 14 and the period of the wiring pattern image substantially coincide with each other, moire occurs in the captured image. Therefore, the focal length of the imaging lens 13 is appropriately selected. Therefore, it is necessary to set the observation magnification so that moire does not occur.
[0046]
In this embodiment, therefore, a zoom lens is employed as the imaging lens 13 so that various wiring pattern cycles can be accommodated. However, since the entrance pupil position of the imaging lens 13 changes when zooming, the translation pupil stage (not shown) moves the imaging lens 13 and the CCD 14 in the direction of the optical axis in order to cancel this and return the entrance pupil to the position described above. ). In addition, since the pixel period of the CCD 14 is generally different between the horizontal direction and the vertical direction, the moire may disappear by rotating the CCD 14 around the optical axis. Therefore, a rotation stage for this purpose may be provided. The plates 15 and 16 are for preventing unnecessary objects from being illuminated by the illumination light transmitted through the half mirror 11 and forming an image superimposed on the image of the subject 21 on the imaging surface of the CCD 14. It is a flat plate with antireflection treatment such as black paint.
[0047]
On the other hand, the dust detection light source unit 17 includes a halogen lamp (not shown), a heat ray absorption filter, and a condensing lens 6 inside, and a white light beam is incident on the end face of the fiber bundle of the line illumination 18. The line illumination 18 is formed by arranging each fiber in the fiber bundle in a straight line with a length of 30 cm on the emission side, and produces a thin sheet-like illumination light together with a semi-cylindrical condensing lens 19. A cross section of the condenser lens 19 is shown in FIG. The condensing lens 19 is a half-cut acrylic cylinder, and aluminum is deposited on the cut surface to form an anti-slope B. The light beam emitted from the fiber end A of the line illumination 18 is emitted as a nearly parallel light beam C. . The condensing lens 19 has such a shape because the line illumination 18 and the condensing lens 19 transport the subject 21 and the stage (when the incident angle to the subject 21 is close to 90 °). This is to prevent interference with (not shown).
[0048]
Further, the arrangement of line illumination will be described with reference to FIGS. FIG. 2 shows the positional relationship between the line illumination 18, the subject 21, and the collimator lens 12, and is an example in which one subject 21 is inspected in four divisions. A broken line 23 is a movement range of the subject 21. The four line illuminations 18 are moved to a moving stage (not shown) that changes the incident direction φ with respect to the subject 21 within a range of Δφ around O as a rotation axis while maintaining a constant distance L to the center O of the observation visual field 22. Each is placed, and is set to an appropriate incident direction φ where the diffracted light from the wiring pattern is least incident on the observation system for each type of subject 21.
[0049]
The reason why the four line illuminations 18 are installed at symmetrical positions so as to have the same incident direction φ with respect to the subject 21 is to illuminate the inside of the observation visual field 22 almost uniformly and complement the subject 21. This is to compensate for the detection sensitivity anisotropy of a defect having directionality such as a scratch on the surface.
[0050]
FIG. 3 shows another example in which the incident direction φ is set with the center O ′ of the line illumination 18 as the rotation axis. The method of FIG. 3 has an advantage that the variable range Δφ can be increased, and the method of FIG. 2 is advantageous in terms of illumination efficiency because the center line of the illumination field by the line illumination 18 always passes through the center of the observation field 22. For the setting of the line illumination 18, FIG. 2 or FIG. 3 or a compromise of both may be adopted according to the type and size of the subject.
[0051]
Here, it returns to FIG. 1 again and continues description. The subject 21 illuminated by the line illumination 18 is imaged by the imaging lens 13 and the CCD 14 which are the same as those for detecting the film thickness unevenness. At this time, in order to prevent attenuation of weak scattered light, the half mirror 11 is moved in a direction perpendicular to the paper surface by a parallel movement stage (not shown) and removed from the observation optical path. When the half mirror 11 is thick and the change in the optical path length cannot be ignored, a compensation plate having the same material and thickness and having an antireflection coating on the surface may be inserted into the optical path instead of the half mirror 11.
[0052]
The collimator lens 12 has a function of collecting scattered light having an equal scattering angle from the entire surface of the subject 21, that is, in a direction perpendicular to the subject 21, and guiding it to the entrance pupil of the imaging lens 13. However, since the scattering point can be observed without the collimator lens 12, it may be removed from the optical path if necessary. The background plate 20 placed under the subject 21 at a constant interval substantially parallel to the subject 21 is a flat plate having a surface subjected to antireflection treatment in the same manner as the plates 15 and 16 described above. When a partially transparent subject 21 such as a liquid crystal glass substrate is inspected, it is inevitable that a part of the illumination light passes through the subject 21 and illuminates the background. The background plate 20 acts to create a simple background that does not interfere. Further, the distance from the subject 21 is set to a distance of several centimeters so that the illumination light of the line illumination 18 that has passed through the subject 21 does not hit the background plate 20.
[0053]
Next, the configuration of the control unit and the image processing unit will be described with reference to FIG. The image processing device 35 takes an inspection image from the CCD 14 under the control of the host computer 31, performs image processing to extract defects such as film thickness unevenness and dust, and stores data such as type, number, position, and area of the host computer 31. Send to. The monitor TV 34 displays the inspection image and the processed image. The image storage device 36 stores inspection images and processed images as necessary. Each control unit is controlled by the sequencer 37 in accordance with an instruction from the host computer 31. The optical system control unit 38 controls the optical system movable mechanism such as the rotary holder 5 of the interference filter 5 and the moving stage of the half mirror 11 and the light amounts of the light sources 2 and 17. The stage control unit 39 controls the suction stage that moves the subject 21 within the observation field by vacuum suction and support of the subject 21 and the positioning mechanism thereof. The substrate transfer control unit 40 controls the transfer unit that takes out the specimens one by one from the stocker and places them on the adsorption stage, and returns the specimen 21 after the inspection from the stage to the stocker. Note that the stage and the transport unit are not shown. The operator gives necessary instructions to the inspection apparatus by operating the keyboard 32 in accordance with the menu screen displayed on the monitor TV 30. The memory 33 stores inspection conditions (optical system settings and image processing conditions) for each type of subject, inspection data, and the like.
[0054]
Subsequently, the operation of the inspection apparatus of the present embodiment will be described mainly with reference to FIGS. When the operator instructs to start the examination together with the type of the subject 21 using the keyboard 32, the conditions corresponding to the subject 21 are read into the host computer 31 from the examination conditions stored in the memory 33 in advance, and the sequencer 37. The optical system control unit 38 sets the optical system via.
[0055]
The optical system controller 38 sets the selection of the interference filter, the incident direction of the line illumination 18, the zooming of the imaging lens 13, and the accompanying movement / positioning in the optical axis direction. Next, the first subject 21 is taken out of the stocker by the transport unit and placed on the adsorption stage. When inspecting the subject 21 in four divisions, the adsorption stage moves and positions the subject 21 so that a quarter of the subject 21 comes to the center of the observation field as shown in FIG. In the inspection, the halogen lamp 2 is first turned on, and the amount of light is adjusted according to the inspection conditions.
[0056]
When the amount of light reaches a predetermined value, the inspection image is taken into the image processing device 35 from the CCD 14. At this time, as shown in FIG. 6, the inspection image 101 includes an edge 102 of the subject 21, and an image in which only the uneven thickness portion 104 is brightened in a dark region having a uniform thickness in the subject 21. It has become. The image processing device 35 extracts only the inspection region 103 from this image by masking, extracts only the portion 104 having uneven thickness through shade correction, binarization processing, and the like, and sends data such as position and area to the host computer 31. send. Next, the halogen lamp 2 is turned off, the light source unit 17 is turned on, and the half mirror 11 is removed from the optical path. At this time, the inspection image 105 is as shown in FIG. 7, and only the scattering point 108 due to dust appears bright in a dark region. From this, only the scattering point 108 is extracted by the same image processing, and data such as the position is sent to the host computer 31. The process of image processing is defined by the inspection conditions.
[0057]
It is also possible to obtain the film thickness unevenness and dust scattering points on the same inspection screen by appropriately adjusting the light quantities of the halogen lamp 2 and the light source unit 17 and simultaneously lighting them. The remaining three quarters of the subject 21 are similarly examined.
[0058]
When the inspection of one subject 21 is completed, the host computer 31 integrates the defect data of the subject 21 inspected in four divisions, and the inspection criteria including the type, number, etc. of the defects in the inspection conditions. The quality of the subject 21 is determined in light of the comparison. The inspected subject 21 is sent from the adsorption stage to the inspected stocker by the transport unit, and one inspection is completed. In the above operation, the halogen lamp 2 and the light source unit 17 may be turned on and off by opening and closing a shutter provided in the optical path.
[0059]
In the above embodiment, a combination of the halogen lamp 2 and the interference filter inserted and supported in the rotary holder 5 is used in order to make the center wavelength of the quasi-monochromatic light for inspecting the thickness unevenness variable. Instead, a monochromator or the like may be used, or a light source such as a laser that is originally quasi-monochromatic light may be used. The interference filter may be placed on the front surface of the imaging lens 13 instead of the light source side.
[0060]
<Second embodiment>
The optical system in FIG. 1 can be modified as follows.
[0061]
FIG. 8 shows a second embodiment of the present invention. The irradiating means and the condensing means are composed of one collimator lens 12 and are arranged immediately in front of the subject 21, and are almost the same as the observation visual field of the subject 21. The subject 21 is irradiated with light from the light source, that is, the fiber bundle 7, having the same size as a substantially parallel light beam, and reflected light from the surface of the subject 21 is allowed to pass therethrough.
[0062]
The fiber bundle 7 is disposed in the vicinity of the focal plane of the collimator lens 12, and narrow band light is incident on the collimator lens 12.
[0063]
The observation means comprises an imaging lens 13 and a CCD camera 14, has an entrance pupil at an axially symmetric position with the fiber bundle 7 around the optical axis of the collimator lens 12, and observes the surface of the subject 21.
[0064]
Also in the second embodiment configured as described above, the collimator lens 12 having a size substantially equal to the observation visual field is provided in the vicinity of the subject 21, thereby illuminating the entire visual field at the same incident angle, and the film thickness. Unevenness can be observed as equal thickness interference fringes. Further, there is an advantage that the half mirror 11 of the embodiment of FIG.
[0065]
<Third embodiment>
FIG. 9 shows an optical system according to a third embodiment of the present invention, which has the structure described below. A diffused beam irradiation light source, for example, a light source comprising a halogen lamp 2 shown in FIG. 1 and a fiber bundle 7 for illuminating a subject 21 for guiding a narrow-band light beam emitted from the light source to a first collimator lens 12 described later. Yes. As described above, the imaging means is composed of a CCD camera 14 that regularly arranges pixels and images light from the subject. The optical path dividing element, for example, the half mirror 11 has a common optical path substantially perpendicular to the subject surface 21 side, and divides the common optical path into a reflected optical path and a transmitted optical path. The first collimator lens 12 is disposed in the reflected light path of the half mirror 11 and converts the diffused light beam from the diffused light beam irradiation light source into a substantially parallel light beam. The second collimator lens 12 ′ is disposed in the transmission optical path of the half mirror 11 and condenses the light from the subject 21 on the CCD camera 14. Image processing means, for example, an image processing apparatus 35 shown in FIG. 4 performs image processing on an image captured by the CCD camera 14 and extracts defects. The CCD camera 14 is disposed in the vicinity of the focal point of the collimator lens 12 ′ and observes the surface of the subject 21.
[0066]
In this case, the exit end face of the fiber bundle 7 that guides the narrow-band light beam is disposed in the vicinity of the focal point of the collimator lens 12. The half mirror 11 is arranged in a state inclined at approximately 45 degrees with respect to the surface of the subject 21 and reflects or transmits light. The collimator lens 12 irradiates the subject 21 through the half mirror 11 with the light from the fiber bundle 7 substantially parallel. The collimator lens 12 ′ is arranged so that the optical axis of the reflected light from the surface of the subject 21 coincides with the optical axis thereof, and collects the reflected light from the surface of the subject 21.
[0067]
The third embodiment described above includes the following configuration as in the first embodiment. That is, the above-mentioned diffused light beam irradiation means is provided with a plurality of narrowband interference filters or monochromators so that the interference wavelength can be set for the center wavelength of the light beam emitted from the halogen lamp 2 with respect to the film thickness of the subject 21. Including those.
[0068]
Further, the light source described above also includes wavelength selection means for selecting the center wavelength according to the film thickness of the subject 21 or the refractive index of the film thickness. Further, the imaging means described above is composed of a CCD camera in which pixels are regularly arranged, and includes a scaling means for changing the magnification so that the period of the pixels does not coincide with the period of the pattern formed on the substrate. Including things. Further, the imaging means described above includes an imaging lens arranged so that the entrance pupil is located in the vicinity of the focal plane of the focusing means, and the magnification of the imaging lens can be changed to a magnification that does not cause moire. . In addition, the imaging lens described above uses a zoom lens, and returns the changed entrance pupil position to the vicinity of the focal plane of the condensing means so as to cancel the change in the entrance pupil position due to the zooming operation of the zoom lens. Also included are those having pupil position adjusting means. Further, the above-described image processing means takes in an inspection image from the imaging means under the control of the host computer 31 shown in FIG. 4, and binarizes the image taken out by masking the inspection area from this inspection image. In addition, the data having the function of transferring data obtained by extracting defects on the surface of the subject 21 to the host computer 31 described above is also included. Further, the host computer 31 described above includes a computer having a function of determining the quality of the subject 21 by comparing the defect information data transferred from the image processing means with the inspection standard.
[0069]
Thus, according to the third embodiment, not only the same effects as in the first embodiment can be obtained, but also one of the common optical path reflected light path or the transmitted light path substantially perpendicular to the subject 21 side of the half mirror 11 and Since the first and second collimator lenses 12 and 12 'are arranged on the other side, it is needless to say that the same effect as that of the first embodiment described above can be obtained. By irradiating light vertically, the detection sensitivity of interference light is maximized, the half mirror 11 is brought closer to the subject 21, and the first and second collimator lenses 12 and 12 'are brought closer to the half mirror 11. The whole can be made compact.
[0070]
The third embodiment described above is not limited to the above-described example. For example, the arrangement positions of the fiber bundle 7, the CCD camera 14, and the imaging lens 13 may be reversed.
[0071]
<Fourth embodiment>
FIG. 10 shows an optical system according to a fourth embodiment of the present invention, in which a first collimator lens 12 is arranged with its optical axis inclined with respect to the surface of the subject 21, and a fiber bundle 7 as a narrow band light source. Is irradiated onto the subject 21 as a substantially parallel light beam. The second collimator lens 12 ′ is arranged so that the optical axis of the reflected light from the surface of the subject 21 coincides with the optical axis.
[0072]
An imaging lens 13 and a CCD 14 are arranged in the vicinity of the focal point of the collimator lens 12 ', so that the surface of the subject 21 can be observed.
[0073]
According to the fourth embodiment, not only the same effect as the third embodiment can be obtained, but also the half mirror 11 of the embodiment of FIG. 9 is not required.
[0074]
<Fifth embodiment>
Next, an embodiment for detecting a defect related to the step side surface of the patterned layer on the surface of the subject will be described.
[0075]
FIG. 11 is a diagram showing an optical system according to a fifth embodiment of the present invention. A light beam emitted from a halogen lamp, which is a light source (not shown), is converted into a narrow band light through an interference filter and then diffused light beam irradiation means such as a fiber bundle. 7 is incident.
[0076]
The exit end face of the fiber bundle 7 is installed at a position not on the optical axis of the collimator lens 12 on the rear focal plane of the parallel light beam irradiation means, for example, the collimator lens 12. The exit end face can be moved on the same focal plane by an angle setting means such as a moving stage (not shown), and the incident angle θ of the illumination center ray with respect to the optical axis of the collimator lens 12._oCan be set to any value. The collimator lens 12 is installed such that its optical axis is perpendicular to the subject 21 and at an appropriate distance from the subject. The collimator lens 12 is sized to cover the examination region of the subject 21.
[0077]
With the configuration as shown in FIG. 11, the light beam emitted from the fiber bundle 7 becomes a parallel light beam by the collimator lens 12, and the incident angle θ_oIlluminate the subject 21 with. The specularly reflected light beam that has been specularly reflected by the subject 21 passes through the collimator lens 12 and converges to the converging point 29 again.
[0078]
On the other hand, the scattered light (broken line in FIG. 11) emitted from the subject 21 in the vertical direction is collected by the collimator lens 12 and focused on the rear focal point. The imaging lens 13 is installed so that the entrance pupil is positioned in the vicinity thereof, and the image of the subject 21 is formed on the imaging surface of the imaging means, for example, the CCD 14. For the above-described reason, a zoom lens is employed as the imaging lens 13.
[0079]
Next, the configuration of the control unit and the image processing unit in FIG. 11 will be described. Since the configuration is almost the same as that in FIG. Image processing means, for example, an image processing device 35 takes an inspection image from the CCD 14 under the control of the host computer 31, performs image processing to extract defects, and sends data such as the type, number, position, and area to the host computer 31. The monitor TV 34 displays the inspection image and the processed image.
[0080]
The image storage device 36 stores inspection images and processed images as necessary. Each control unit is controlled by the sequencer 37 in accordance with an instruction from the host computer 31. The optical system control unit 38 controls the light amount of the light source, the position of the emission end face of the fiber bundle 7 and the like. The stage control unit 39 controls the suction stage that moves the subject 21 within the observation field by vacuum suction and support of the subject 21 and the positioning mechanism thereof. The substrate transfer control unit 40 controls the transfer unit that takes out the specimens one by one from the stocker and places them on the adsorption stage, and returns the specimen 21 after the inspection from the stage to the stocker.
[0081]
Note that the stage and the transport unit are not shown. The operator gives necessary instructions to the inspection apparatus by operating the keyboard 32 in accordance with the menu screen displayed on the monitor TV 30. The memory 33 stores inspection conditions (optical system settings and image processing conditions) for each type of subject, inspection data, and the like.
[0082]
Subsequently, the operation of the inspection apparatus of the fifth embodiment will be described. When the operator instructs to start the examination together with the type of the subject 21 using the keyboard 32, the conditions corresponding to the subject 21 are read into the host computer 31 from the examination conditions stored in the memory 33 in advance, and the sequencer 37. The optical system control unit 38 sets the optical system via.
[0083]
What is set by the optical system control unit 38 is the light amount of the light source, the exit end face position of the fiber bundle 1, the zooming of the imaging lens 13, and the accompanying movement / positioning in the optical axis direction. Next, the first subject 21 is taken out of the stocker by the transport unit and placed on the adsorption stage. After the subject 21 is sucked and fixed, the suction stage is moved and positioned so as to be in the center of the observation field.
[0084]
Subsequently, the inspection image is taken into the image processing device 35 from the CCD 14. At this time, the inspection image 50 includes, for example, an edge 51 of the subject as shown in FIG. 12, and an image in which only the side defect portion 53 has a different brightness in a uniform luminance region without defects in the subject 21. It has become. The image processing device 35 takes out only the inspection area 52 from this image by masking, extracts only the defective portion 53 through shade correction, binarization processing, etc., and sends the data such as the position and area to the host computer 31.
[0085]
When the inspection of one subject 21 is completed in this way, the host computer 31 determines the quality of the subject 21 by comparing the type and number of defects with the inspection criteria included in the inspection conditions. . Then, the inspected subject 21 is sent from the adsorption stage to the inspected stocker by the transport unit.
[0086]
In the fifth embodiment described above, the angle of the optical axis of the parallel beam irradiation means such as the collimator lens 12 with respect to the optical axis of the focusing means such as the focusing point 29 can be arbitrarily set, so that any film thickness unevenness can be easily extracted. it can.
[0087]
Although the halogen lamp is used as the light source in the fifth embodiment, a high-luminance light source such as a laser or a metal halide lamp may be used instead. Further, the light source may be installed directly on the rear focal plane of the collimator lens 12 without guiding the illumination light by the fiber bundle 7. Further, the interference filter may be placed not on the light source side but on the front surface of the imaging lens 13.
[0088]
<Sixth embodiment>
The optical system of FIG. 11 can be modified as follows. FIG. 17 is a diagram showing the optical system of the sixth embodiment, in which the imaging lens 13 and the CCD 14 are installed at positions removed from the optical axis of the collimator lens 12, and the observation angle θ is the regular reflection of the subject 21. Off from the direction. At this time, the fact that the entrance pupil of the imaging lens 13 is located in the vicinity of the rear focal plane of the collimator lens 12 is the same as in FIG. 11 of the fifth embodiment.
[0089]
In this embodiment, the imaging lens 13 and the CCD 14 are installed at a position removed from the optical axis of the collimator lens 12, so that the degree of freedom of observation can be increased as compared with the embodiment of FIG.
[0090]
<Seventh embodiment>
FIGS. 18A and 18B show the optical system of the seventh embodiment in trigonometry, where FIG. 18A is a front view thereof, FIG. 18B is a side view thereof, and FIG. 18C is a plan view thereof. In this example, a plurality of (two in FIG. 18) fiber bundles 7 and 7 'for guiding illumination light are provided, and the incident angle θ of the fiber bundles 7 and 7'.₁, Θ₂And incident direction φ₁, Φ₂Is provided with an incident direction setting means (not shown).
[0091]
Since the resist pattern on the object 21 spreads two-dimensionally, the sensitivity of defect detection can be improved by illuminating the side surfaces of the steps in different directions simultaneously with a plurality of illuminations, and is sharp for the entire field of view. An image can be obtained.
[0092]
<Eighth embodiment>
FIG. 19 shows an optical system of the eighth embodiment. A half mirror 11 is provided between the collimator lens 12 and the imaging lens 13, and the illumination light from the fiber bundle 7 is reflected by the half mirror 11 to be examined. 21 is illuminated. In this example, the imaging lens 13 is positioned on the optical axis of the collimator lens 12, whereas the exit end face of the fiber bundle 7 has an angle θ._oOnly off the optical axis.
[0093]
In the fifth embodiment of FIG. 11 described above, the angle θ_oIs decreased, the fiber bundle 7 and the imaging lens 13 come into contact with each other._oHowever, in this example, there is no such limitation, and scattered light in the very vicinity of specularly reflected light can be observed.
[0094]
<Ninth embodiment>
FIG. 20 is a diagram showing an optical system of the ninth embodiment, in which an independent collimator lens 12 'is provided for illumination light, and the exit end face of the fiber bundle 7 is installed at the front focal point thereof. The collimator lens 12 ′ is rotationally symmetric with respect to its optical axis, so that the subject 21 is incident on the incident angle θ._oIlluminate with the parallel light flux. This example is advantageous for observing scattered light at a large angle with respect to specular reflection.
[0095]
<Tenth embodiment>
FIG. 21 is a side view showing an optical system according to the tenth embodiment of the present invention. A light beam emitted from a halogen lamp, which is a light source (not shown), enters the fiber bundle 7. The light beam emitted from the exit end face of the fiber bundle 7 enters the diffuser plate 42 located near the rear focal point of the collimator lens 12 via the half mirror 11.
[0096]
As shown in FIG. 22, the central portion of the diffusing plate 42 is shielded by a shielding plate 43 that does not transmit light having a diameter slightly larger than an entrance pupil of an imaging lens 45 described later, and forms an annular light source unit. doing.
[0097]
The light beam emitted from the light source unit is reflected by the half mirror 11 installed at an angle of 45 degrees with respect to the optical axis of the collimator lens 12 and illuminates the subject 21 as a parallel light beam group by the collimator lens 12. The collimator lens 12 has a size that covers the examination region of the subject 21, and is installed so that its optical axis is perpendicular to the subject 21 and at an appropriate distance from the subject 21. . The light regularly reflected by the subject 21 passes through the collimator lens 12 again and becomes convergent light.
[0098]
Among these, the light beam transmitted through the half mirror 11 forms an annular image of the light source on the shielding plate 44 shown in FIG. The shielding plate 44 is around the imaging lens 45 and serves to block light reaching the imaging surface of the CCD 14 without passing through the imaging lens 45. Therefore, if the imaging lens 45 is a type that is screwed into the CCD 14 like a normal TV photographing lens, this shielding plate is unnecessary. Now, since there is a shielding plate 43 at the center of the light source unit, the specularly reflected light from the subject 21 does not enter the imaging lens 45, and only scattered light near the specularly reflected light enters the imaging lens 45, An image of the subject 21 is created on the CCD 14 imaging surface.
[0099]
As described above, in the tenth embodiment, a single illumination unit can illuminate the subject 21 by creating a parallel light flux group rotationally symmetric with respect to the optical axis of the observation unit. Therefore, the subject 21 can be observed simultaneously by scattered light in all directions near the regular reflection.
[0100]
Note that this embodiment is advantageous in terms of the brightness of the inspection image because the entrance pupil of the imaging lens can be used widely compared to a configuration that shields the central portion of the imaging lens, which will be described later.
[0101]
When the light source is changed from a halogen lamp to a high-intensity light source such as a metal halide lamp in the tenth embodiment described above, higher detection capability can be obtained. Further, the light source unit may directly place a ring-shaped light source instead of the diffusion plate 42. Further, if there is a margin in the amount of light, if an interference filter is inserted in the light source unit, shielding by the shielding plate 43 can be performed well even when the collimator lens 12 has chromatic aberration.
[0102]
<Eleventh embodiment>
FIG. 24 shows an optical system according to the eleventh embodiment. The optical system is configured in substantially the same way as in FIG. 21. The fiber bundle 7, the diffusion plate 42, the shielding plate 43, the imaging lens 45 and the CCD 14 constituting the light source unit are collimated. The lens 12 is installed at a position off the optical axis. Here, the diffusion plate 42 and the shielding plate 43, the imaging lens 45 and the shielding plate 44 are in the vicinity of the rear focal plane of the collimator lens 12 and are in a conjugate positional relationship as in the tenth embodiment. is there. Since this embodiment does not require a half mirror, it is advantageous in terms of the amount of light, and provides some flexibility in illumination and observation angles.
[0103]
<Twelfth embodiment>
FIG. 25 shows an optical system of the twelfth embodiment, in which an independent collimator lens 12 'is provided for illumination light, and a diffusion plate 42 and a shielding plate 43 are installed in the vicinity of the front focal point thereof. The imaging lens 45 and the shielding plate 44 are in the vicinity of the rear focal point of the second collimator lens 12, and the diffusion plate 42 and the shielding plate 43 are interposed via the first and second collimator lenses 12 ′ and 12 and the subject 21. Are in a conjugate relationship with each other.
[0104]
In this embodiment, scattered light near the specular reflection from the subject 21 can be observed under illumination light having a larger incident angle than in the eleventh embodiment. Such an incident angle of illumination light varies depending on the type of the subject 21 to be inspected (for example, the inclination angle of the side surface of the pattern step). Therefore, it is necessary to select an appropriate optical system.
[0105]
<Thirteenth embodiment>
FIG. 26 is a side view showing the optical system of the thirteenth embodiment of the present invention. This embodiment is different from the optical system of FIG. 21 in that the exit end face of the fiber bundle 7 as a light source part is in the vicinity of the rear focal point of the collimator lens 12 and is in a position conjugate with that immediately before the imaging lens 45. It is a point that is installed. The shielding plate 43 has a diameter slightly larger than the exit end face of the fiber bundle 7. Accordingly, the specularly reflected light from the subject 21 is blocked by the shielding plate 43, and only the scattered light near the specularly reflected light is incident on the imaging lens 45, and an image of the subject 21 is formed on the imaging surface of the CCD 14. The point that the subject 21 can be observed simultaneously by scattered light in all directions in the vicinity of regular reflection is the same as in the embodiment of FIG. And the point which can be deform | transformed like FIG. 24 thru | or FIG. 25 is also the same.
[0106]
The optical systems of the fifth to thirteenth embodiments described above may be combined with the optical systems of the first to fourth embodiments, the collimator lens, the imaging lens, and the CCD. . In that case, it is possible to detect all of the film thickness unevenness, dust, scratches and defects on the side surfaces of the pattern step by switching the illumination with one defect inspection apparatus.
[0107]
【The invention's effect】
    According to the present invention,A defect on the entire surface of the object can be observed, and the inspection accuracy can be improved by automatically determining whether or not the defect of the object is good by providing the determination means.
[Brief description of the drawings]
FIG. 1 is a side view showing an optical system of a first embodiment of a surface defect inspection apparatus of the present invention.
2 is a plan view for explaining the arrangement of line illumination in the embodiment of FIG. 1; FIG.
3 is a plan view for explaining the arrangement of line illumination in the embodiment of FIG. 1; FIG.
4 is a block diagram illustrating configurations of a control unit and an image processing unit in FIG. 1. FIG.
5 is an explanatory diagram of the line illumination condenser lens of FIG. 1; FIG.
6 is a view for explaining the inspection image of FIG. 1; FIG.
7 is an explanatory diagram of the inspection image in FIG. 1. FIG.
FIG. 8 is a side view showing an optical system of a second embodiment of the surface defect inspection apparatus of the present invention.
FIG. 9 is a side view showing an optical system of a third embodiment of the surface defect inspection apparatus of the present invention.
FIG. 10 is a side view showing an optical system of a fourth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 11 is a side view showing an optical system of a fifth embodiment of the surface defect inspection apparatus of the present invention.
12 is a diagram for explaining the operation of FIG. 11; FIG.
FIG. 13 is a diagram for explaining a subject of the present invention.
FIG. 14 is a diagram for explaining a subject of the present invention.
FIG. 15 is a diagram for explaining a subject of the present invention.
FIG. 16 is a diagram for explaining a subject of the present invention.
FIG. 17 is a side view showing an optical system of a sixth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 18 is a side view showing an optical system of a seventh embodiment of the surface defect inspection apparatus of the present invention.
FIG. 19 is a side view showing an optical system of an eighth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 20 is a side view showing an optical system of a ninth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 21 is a side view showing an optical system of a tenth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 22 is a diagram for explaining the function and effect of FIG. 21;
FIG. 23 is a diagram for explaining the function and effect of FIG. 21;
FIG. 24 is a side view showing an optical system of an eleventh embodiment of the surface defect inspection apparatus of the present invention.
FIG. 25 is a side view showing an optical system of a twelfth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 26 is a side view showing an optical system of a thirteenth embodiment of the surface defect inspection apparatus of the present invention.
FIG. 27 is a diagram for explaining a conventional technique.
FIG. 28 is a diagram for explaining a conventional technique.
FIG. 29 is a diagram for explaining a conventional technique.
FIG. 30 is a diagram for explaining a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lamp house, 2 ... Halogen lamp, 3 ... Heat ray absorption filter, 4 ... Condenser lens, 5 ... Rotating holder, 6 ... Condensing lens, 7 ... Fiber bundle, 8 ... Secondary light source part, 9 ... Diffusing plate, 10 ... Aperture, 11 ... half mirror, 12, 12 '... collimator lens, 13 ... imaging lens, 14 ... CCD, 15, 16 ... plate, 17 ... light source, 18 ... line illumination, 19 ... condensing lens, 20 ... Background plate, 21 ... subject.

Claims (6)

A diffused beam irradiation light source for irradiating a diffused beam from above the subject ;
A parallel light beam irradiation means for irradiating the subject with a diffused light beam from the diffused light beam irradiation light source as a substantially parallel light beam;
Condensing means for condensing light from the subject irradiated by the parallel light flux of the parallel light flux irradiating means;
Imaging means for imaging light from the subject via the light collecting means;
An angle setting means for setting an angle formed by the optical axis of the parallel light beam irradiation means and the optical axis of the imaging means with respect to the normal line of the subject;
Image processing means for extracting defects by performing image processing on an image captured by the imaging means;
An apparatus for inspecting a surface defect, comprising: an incident direction setting unit that adjusts an incident direction of the diffused light beam irradiation light source in three dimensions with respect to the subject. The surface defect inspection apparatus according to claim 1 , wherein the imaging unit is disposed at a position for imaging regular reflection light from the surface of the subject irradiated by the parallel light beam irradiation unit . The angle setting means optimally observes the angles formed by the optical axis of the parallel light beam irradiation means and the optical axis of the imaging means with respect to the normal line of the subject according to the type and defect of the subject. 2. The surface defect inspection apparatus according to claim 1 , wherein the angle is adjusted so as to satisfy the conditions . 2. The surface defect according to claim 1 , wherein the angle setting means sets an optical axis of the imaging means to be coaxial with a normal line of the subject, and can arbitrarily set an angle of the optical axis of the parallel light beam irradiation means. Inspection device. 2. The surface defect inspection apparatus according to claim 1, wherein the angle setting means includes a moving stage capable of moving the diffused light beam irradiation light source on a confocal plane . 2. The surface defect inspection apparatus according to claim 1, wherein the parallel light beam irradiating means and the condensing means are shared by the same collimator lens .

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