WO2010015695A1 - Inspection device and method for optical investigation of object surfaces, in particular wafer edges - Google Patents

Inspection device and method for optical investigation of object surfaces, in particular wafer edges Download PDF

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Publication number
WO2010015695A1
WO2010015695A1 PCT/EP2009/060254 EP2009060254W WO2010015695A1 WO 2010015695 A1 WO2010015695 A1 WO 2010015695A1 EP 2009060254 W EP2009060254 W EP 2009060254W WO 2010015695 A1 WO2010015695 A1 WO 2010015695A1
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WIPO (PCT)
Prior art keywords
edge
object
characterized
digital camera
image
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PCT/EP2009/060254
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German (de)
French (fr)
Inventor
Dietrich Drews
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Nanophotonics Ag
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Priority to DE102008041134.5 priority Critical
Priority to DE102008041134 priority
Application filed by Nanophotonics Ag filed Critical Nanophotonics Ag
Publication of WO2010015695A1 publication Critical patent/WO2010015695A1/en

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using infra-red, visible or ultra-violet light
    • G01N21/84Systems specially adapted for particular applications
    • G01N21/88Investigating the presence of flaws or contamination
    • G01N21/95Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
    • G01N21/9501Semiconductor wafers
    • G01N21/9503Wafer edge inspection
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using infra-red, visible or ultra-violet light
    • G01N21/84Systems specially adapted for particular applications
    • G01N21/88Investigating the presence of flaws or contamination
    • G01N21/8851Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • G01N2021/8896Circuits specially adapted for system specific signal conditioning

Abstract

The invention relates to an inspection device and an inspection method for optically investigating object surfaces, in particular wafer edges. In the inspection method, a digital image is taken of an object edge (18) using a digital camera (14). During recording of the edge image, a background illumination of the side of the object (10) facing away from the digital camera (14) is turned on, wherein the light of the background illumination radiated in the direction of the digital camera (14) is partially shaded by the object. Also, a flat main surface (22) surrounding the edge of the object and proximate thereto is illuminated using a plane illumination device (30) such that a bright field image of the main surface (22) is generated. An edge of the object (10) is determined from pixel information from the image by way of a contrast between the object edge (18) and the background and a transition line (bevel line) is determined by way of a contrast between the object edge (18) and the main surface (22).

Description

Inspektionsvorrichtung- and methods for optical examination of object surfaces, in particular of wafer edge

description

The invention relates to an inspection apparatus and an inspection method for the optical examination of surfaces of objects in an edge surrounding an otherwise substantially flat object, in particular of edges unstructured wafers by means of at least one of the object surface facing and to the object edge f o kussierbaren digital camera and a plane illumination device, the relatively is arranged for digital camera and to the object surface such that an image of a field illumination will be generated to the object edge subsequent major planar surface of the object surface in the edge environment under HeII-.

The optical inspection process of semiconductor wafers for defects (outbreaks, scratches, marks, particles, etc.) is an important part of the manufacturing process of computer chips. in general, the inspection includes both the planar object or Waferober- and bottom as well as its edge. The present invention particularly relates to the inspection of the edge.

The terms used herein to refer to the inspected object are to be understood as follows:

- "Objektoberfiäche" is understood as a generic term that refers to the entire surface of the object, and in particular includes the defined hereinafter major faces and edges of objects.

With "main surface", the planar, opposite Oberbzw. undersides of the generally disc-shaped object (wafer), respectively. "edge" or "edge of the object" is the one hand adjoining the main surface and on the other hand, the object on the outer circumference surface defining portion, so that connects the major surfaces and usually both an upper and lower inclined portion ( "Bevel") as a stirnsθitigen circumferential portion also ( "Apex") includes.

The "edge environment" describes a surface section, which includes both the edge and a section of the main surface in the transition region to the edge. As an "edge" or "edge of the object" is referred to the recognizable under the respective angle Übergangsiinie between the object edge and the environment.

- When "Bevelline" is referred to the recognizable under the respective viewing angle transition line between the Objektober- or subpage and the bevel of the edge of the object as a "structural feature" is a deviation of the edge profile in the perpendicular projection onto the object plane of the or. major surfaces is defined to understand from a predetermined uniform or steady contour. In a circular wafer, such a structural feature, for example, a radial notch (Notch) or a straight edge portion (chord) is.

Inspection means for wafer edge often use an arrangement consisting of a digital camera that faces the object surface, and in particular be focused on the object edge. Further, in such an inspection apparatus, one or more lighting devices are used.

From DE 103 13 202 B3 a device of the initially mentioned type is known in which consisting the object edge of the wafer from the upper Bevei (bevel), the apex and the lower Bevel lie entirely in the region of Dunkelfeides an LED light source, while the of the wafer top side or upper major surface reflected light einfäilt directly into the camera, the wafer top aiso in the bright field range. Using arranged one below the wafer and parallel to this aligned plane mirror and the bottom or lower major surface of the wafer is recorded in the same image, which as far as visible also lie, in the dark field area. The upper bevel is thus illuminated under grazing incidence of light from the light source and the apex as well as the lower Bevel lie entirely in the shadow of the light source. The light which passes through the wafer, so that it is mapped as HeNfeld background subsequent to the underside reflected from the mirror surface directly into the camera. As a result, the wafer edge is imaged as a narrow strip in the dark field area on one side of the direct reflection from the wafer top side and on the other side to join the direct reflection of the plane mirror. The lighting conditions at the top and bottom of the wafer edge for the aforementioned reasons are very different.

The disadvantage here is that the edge region of interest is imaged partially directly and partially reflected on the mirror. However, since the wafer edge as a whole is in the dark field, it can not be accurately located in the figure. In addition, over which radiates thereto followed by bright field image of the wafer top side on the one hand and the mirror on the other hand the transition region to the edge, so that we can expect with this loss in resolution.

DE 103 24 474 A1 describes a device comprising an incident illumination device and with which the surface of a photoresist-coated wafer is accommodated in the medicinal field imaging means. Unlike the present invention, this device is used for inspection of a patterned wafer.Λ

- 4 _

the Entiackung of the wafer in the edge region is examined by polarization of the light and camera-side analysis of the polarization state of the light reflected at the surface of light In addition, a further illumination device is provided on the wafer underside, whose light beams are partially shaded towards the camera from the wafer edge, so that the edge of the Waferran- of the light-dark transition appears.

During the investigation of the edge region in the latter document does not go beyond the deal of control of Entiackung and therefore is not suitable for the investigation of an unstructured wafer for defects of the type mentioned, can with the known from DE 10331 202 B3 device no complete investigation of the wafer be ensured from the main surface over the entire edge region including Bevei and Apex.

The inventors have made it in this context to the task of improving the inspection device and the inspection method to the effect that from the recorded image content all kinds of defects on the object surface can be as completely as possible and locally precisely identified.

The object is solved by an inspection device having the features of claim 1 and an inspection method having the features of claim 17. Advantageous developments of the invention are subject of the subclaims.

The inspection method provides according to the invention provides that during recording of the edge image, a background lighting is switched on the side remote from the digital camera side of the object, which radiates light in the direction of the digital camera, wherein the light emitted in the direction of the digital camera light partially shaded by the object to the edge of the object becomes. The edge of the object is determined from pixel information of the generated image with the digital camera based on a contrast between the edge of the object and the background as well as a Übergangsiinie (Bevelline) from pixel information of the generated image with the digital camera based on a contrast between the object edge and the main surface.

Accordingly, on the side remote from the digital camera side of the object disposed a backlight device in the inventive inspection apparatus and indeed in the form that is emitted by its light in the direction of the digital camera, wherein the light emitted in the direction of the digital camera light partially shaded by the object to the edge of the object is, when the digital camera is focused on the edge region. The inspection device according to the invention further comprises an image processing means comprising an edge detection means, which is adapted from pixel information of the generated image with the digital camera based on a contrast between the object edge and the backlight an edge of the object on the one hand and on the basis of a contrast between the object edge and the main surface to identify a transition line (Bevelline) on the other.

Unlike in DE 103 13 202 B3, the inspection device according to the invention or the inspection method provides therefore a separate backlight before, the lights directly in the digital camera, so far as it is not shaded by the object, and thus a contrast between the directly recorded object edge and the background creates. Thus it is now possible to clearly link between the identified based on the contrast between the object edge and the main surface Bevellinie and identified based on the contrast between the object edge and the backlight edge. It is known in addition to the already mentioned DE 10324474 A1 further prior art that describes a backlight source on the opposite side of the wafer of an optical sensor. Such a device is, for example, from Japanese Unexamined Patent Publication JP 59125627 A is known in which a bundle of parallel light rays is irradiated perpendicular to the wafer surface in the edge region and the non-shaded portion of this light beam is detected by a disposed on the opposite side of the wafer-scale photo sensor while the wafer is rotated. In principle, the same arrangement 5,438,209 A is known from publication US, but which instead of the photosensor a Kamerazeiie. In both devices there are devices for determining the position of marks and not the generic inspection apparatus for receiving a dark field image of the wafer surface. The lighting is purely a backlight, so that a dark field image is not possible with this. The accuracy of the position determination of the Notch is ensured in each case solely by the parallelism of light beams, which ensures a sharp shadows.

Another device for determining the position in a wafer-marks is known from the published patent application JP 2000031245 A. This includes a camera, whose optical axis is aligned perpendicular to the top surface of the wafer and at the center thereof and which receives a two-dimensional picture of the wafer surface without the wafer is rotated thereby. The illumination device is pivoted away for this purpose from the optical axis represents camera, such that no direct reflection of light from the wafer surface falls within the camera. The immediate area of ​​the wafer is lightened by the fact that the light of the lighting device the material of the wafer support (diffuse) is scattered. In this way, a contrast between the Waferaufiage and the wafer, so that the diodes run Wa is as a dark edge in front of the lighter ready edition. This device allows the identification of the wafer edge, and in particular a Notch. It is, however, not intended and suitable to identify defects on the wafer surface with sufficient accuracy and localize. It is also here solely a device for determining the notch position. Also, the asymmetric arrangement of the Beieuchtungseinrichtung makes relative to the central axis of the wafer for a shadow, which makes it difficult to locate the wafer edge with high accuracy, since not emitted in the direction of the digital camera light is partially shaded by the object edge, but already the light on the way to Waferaufiage. Finally, the contrast is dependent on the material and the nature of the wafer surface on the one hand and the support on the other hand and can not be influenced.

On the contrary, the invention relates to an inspection apparatus for detection of surface defects, which thus allows improved localization of these surface defects and at the same time detection of surface defects up to the outermost edge of the object to the edge of the object.

Since the focus of the digital camera is in the inventive inspection device on the object edge, the edge of the object is particularly in focus, allowing accurate location of the object. Furthermore, this has the advantage that the background beieuchtungseinrichtung soft, is farther, blurs and therefore no artifacts of the background to disturb the picture, in particular can serve as a backlight device a simple lamp that due to the uncertainty as extended light spot on the sensor of the digital camera is mapped. Of course, a directly or indirectly and / or diffusely radiating surface light source may be selected as Hintergrundbeleuchtungseiπrichtung.

To the inspection of the object edge in the present invention also includes the transition to the main surface of the object. Here, the Bevelline of particular interest. The bevel may in addition to the aforementioned defects in the form of scratches, chips, dust, grains, marks or the like also defects in the form of Bearbeituπgsfehlern, namely Nch Polierfehlem having. The wafer edge typically receives a polished surface. If the polishing process of the edge is carried out properly, the Bevelline and derWaferrand must always run parallel, Deviations represent polishing errors. Such polishing errors do not lead to high contrast stray light reflections or dark spots, as do the aforementioned defects under light or dark field illumination. Polishing errors therefore lead to more or less strong deviations of Bevelline of their Soilposition on the wafer. Fluctuations in Beveliine due to polishing errors, however, are overlaid with artifacts of the measurements such as vibration or eccentricity of the wafer during the measurements, so it was a statement about their actual position can not meet easily. Therefore, it is inventively provided simultaneously to identify the object edge clearly beside the Bevelline.

Preferably, the image processing means to a Kantenanaiysemit- tel, soft is adapted to monitor the relative position of the Bevelline to the edge.

The edge detection means detects by means of a simple algorithm a non-circular drive of the wafer (horizontal vibration in the wafer plane) as a result of Zentrierungenauigkeit or fluttering of the wafer (the vertical oscillation perpendicular to the wafer plane) due to an unevenness or a resonant excitation. So far, efforts were made, the sources of error mentioned by active and partly mechanically very costly centering and containment measures to minimize. Compared to any defects horizontal or vertical vibrations provide but a periodic, low-frequency profile of the wafer edge in the image and therefore can be identified easily. Therefore the exact edge detection of the device according to the invention allows to elaborate active centering and containment measures to renounce and to correct any error in the context of image processing using appropriate correction means or routines.

Monitoring the relative position of the Bevelline to the edge happens this basis by the Bevelline and edge line to be identified from the differences in contrast in the image, the distance between the two lines in the image along an approximately vertical line is determined to the edge. If the wafer centered not good, so the distance wafer edge changes - camera can not be the real distance Bevel-line considering the imaging geometry - are closed wafer edge. This distance must be within certain tolerances on normal wafer edge always be constant.

In a preferred embodiment, the edge detection means comprises a pattern recognition means that is configured to identify a structural feature of the object edge of pixel information of the dark field image based on the contrast difference between the object edge and the backlight.

Such structural feature, for example, the contour of a notch (notch) in the wafer edge. This has a known shape and can therefore be easily identified by an algorithm or a comparison of the acquired edge image with stored in a memory forms. However, in this way not only a notch, but also any other structural features, examples of play, are recognized (on an otherwise circular wafer) in the form of a straight edge portion. All regular structural features can be identified and, in particular different from an irregular outbreak so easily. In this way, a simple inspection of the feature itself is possible. In particular, defects in the structural feature, the complete absence of structural feature which a deviation in shape of the feature of a desired geometry up to the presence of several structural features along the wafer edge can be automatically detected and displayed. it is also possible to monitor the relative position between the bevel and the edge line along such a structural feature. This applies even if here is no constant distance but another, following the outline of the structure Wish corn course of Bevelline is expected (target geometry).

Preferably, the image processing means is further arranged to define a coordinate system on the basis of the identified edge and / or the identified structural feature.

Based on the identified structural feature, a reference point for the azimuthal angle (the rotation angle of the wafer so) for example, can clearly be determined. So the center of a notch can be taken as the coordinate origin of the azimuthal angle, for example, allowing a precise angular position data of each identified surface defect (or defect fragment).

Furthermore, it can be concluded with such an image processing device from the identified edge with a known shape of the edge profile on the course of true physical object edge. The center of the apex soft, forming the radially outermost edge of the object is determined in the simplest case by assuming at a known shape of the edge profile and the observation angle at which the camera looks at the object edge, a constant distance between the Apexmitte to the identified edge , This distance can be stored as a system and / or profile-specific settings in a memory of the image processing device and subtracted when calculating the location of the true edge of the object from the position of the identified edge. the true edge of the object that is the center of the apex is then preferably chosen as Koordinatennuilpunkt the radial component of the coordinate system. This and the coordinate origin of the azimuthal angle preferably form the origin of a two-dimensional coordinate system.

Is the coordinate system defined in two dimensions, the location of the bevel- may preferably be by means of the image processing device line are determined in relation to the coordinate system.

This allows polishing error also regarding your angular position relative to Sturkturmerkmal to determine the Wavemotch.

The digital camera is preferably a Zeiienkamera which is arranged so that the recorded with the line camera single image line is located in a plane which is perpendicular to the plane of the object or object edge.

The viewing direction of the digital camera is preferred swung to a viewing angle of> 0 ° from the object plane.

at the same time when the viewing direction of the digital camera is swung out to a viewing angle <90 ° from the object plane, this allows the inclusion of the entire edge area including apex, Bevel and a near-edge portion of the major surface. The above applies analogously when the beam path is deflected towards the camera. If the object is inspected from this perspective, from its top side and its underside, to obtain a complete image of the edge area. The two halves of the picture can be joined together in the coordinate zero point of the radial component in the center of the apex So, the detected in two fields coordinate zero points of the azimuth angle are superimposed. Thus, any defects in a common coordinate system can be displayed.

The viewing direction from which the image of the object edge is taken up by a digital camera can be viewed in the projection onto the object plane, perpendicular to the object edge or a Tangete are object edge. That is, the optical axis of the camera (possibly after deflection) according to this embodiment is oriented such that it defines a plane along with the optical Biidzeiie coinciding with a radial plane of the wafer. The advantage of this embodiment is that less image distortion.

Preferably, a first edge lighting device is provided, which is arranged realiv the digital camera and the object edge so that an image of the object edge may be generated under dark field illumination.

In the dark field illumination emitted from the illumination device of the intact object surface is reflected so that it is not incident on the optics of the digital camera, so that the image of the object surface remains predominantly dark. Is located in the surface region of a defect in the form of a depression (scratches, outbreak) or in the form of an increase (of dust, pollution), then added from Teiiflächen the defect of one or another reflex will occur in the appearance of the digital camera. The result is thus a bright image of defect fragments. The inventors have recognized beyond that tung situation different sections of the defects are illuminated depending Beieuch-, so the possibilities fragments show under different light incidence directions To get a more complete picture of the entire defect, therefore advantageously alternatively or additionally, a second edge-lighting device is provided which is arranged relative to the digital camera and the object edge so that an image of the object edge may be generated under bright field illumination.

In the bright field illumination emitted from the illumination device of the intact surface of the object is directly reflected in the appearance of the digital camera, so that the image of the object surface appears predominantly bright. Is located in the surface region of a defect in the form of a recess (scratches, outbreak) or in the form of an increase (of dust, contamination), then a rule of the majority of areas of the defect, the light is scattered in other directions and does not fall into the optical the digital camera. The result is thus a dark image of defect fragments.

Just in case the bright field illumination, the optical axis of the camera is preferably oriented such that the defined together with the image plane of the optical line scan camera is swiveled out of the radial plane. While the stronger image distortions will have to be accepted. However, this arrangement can realize the bright field image derWaferkante in a simple manner by the bright field illumination device is used based in a mirror-image arrangement for the camera assembly to the radial plane passing through the focus point on the wafer surface. In this embodiment, the background illumination device is preferably by the same amount and in the same direction from the radial plane pivoted so that it lies on the optical axis of the camera. The Büdverarbeitungseinrichtung is further preferably configured from the pixel information of the dark field image and / or the Hellfel- image of the object based on the edge as described above contrasts generated surface defects in the edge region to be identified.

The defect identified fragments are first identified by means of the image processing device in the partial images of the dark field image and bright field image separately. This is preferably done by first contiguous pixels whose contents are (intensity, gray or color values) within a predetermined range of values ​​(intensity, gray or Farbwertintervails) are associated with the same defect fragment. The defect fragments thus obtained are then combined using an algorithm to belong to the same defect. Of two (or more) sub-images of the object surface, a virtual surface image is thus generated, so that can be produced by the sum of the information from the bright-field image and the dark-field image a more complete picture of the entire defect.

The thus generated digital image of the object surface is then supplied to typically a manual or automatic evaluation, the results of the evaluation are used to decide according to the requirements of the chip manufacturer on the usability of the wafer and to perform a sorting according to quality criteria.

The second edge lighting device, the backlight device and the plane illumination device can be controlled by a suitable control unit particularly preferably separated from each other. This can ensure that, in any recording mode, a sufficient or optimal contrast between the main surface in the bright field, the wafer edge in the light or dark field and the backlight is given, the ne simultaneous detection of Bevelli-, the wafer edge and defects in the bright field or dark field allows being, for example, directly at the wafer edge defects in the form of outbreaks, these can also be easily identified as a departure from the continuous boundary curve. Thus, the information on the course of the contour of the wafer has (in addition to that described above), an additional possibility for detection of defects. The separate backlight enables a contrast adjustment, the contrast sitäts- from the center of gravity and from the inten- deviates gray or color values ​​of a center of gravity located in a dark field or Helldfeld defect. Outbreaks are easily distinguished in this way from a Oberflächeπdefekt different kind. Due to the separate illumination control method of the invention is also independent of the reflectivity of the Wafero- berfläche for example due to different Beschichtun- gene and / or structures.

Is the coordinate system defined in two dimensions, in the inventive Iπspektionsverfahren the position of the found or surface defects or defect fragments with respect to this coordinate system can be determined. The location determination may include, for example, both the extent of the defect or defect fragment including its center of gravity and orientation. Overall, be increased by the inventive identification of the object edge and of the feature, the accuracy and reproducibility of the data relating to any defect.

Deviations from this can be readily detected with the inventive method and the inventive device, when the image processing means is arranged to determine the position of the Bevelline in relation to the coordinate system and / or the identified Wa Ferrand.

In a further preferred embodiment of the Kantenanalyse- medium is arranged to determine the diameter of the object edge and / or the Bevelline basis of the identified edge.

, The inspection device according to a preferred embodiment of a motor-driven turntable for rotatably Hal- esterification of the object, wherein the digital camera is adapted to receive synchronously with the rotation of the turntable a digital image of Objektkaπte sequentially a plurality of image lines of the object edge may be included with such a line scan camera while the object rotates together with the rotary table. For this purpose, the triggering of the camera can follow, for example by means of a synchronization pulse by the drive motor (z. B. stepper motor). The sequentially captured image lines of the object edge in a different angular position of the object are then joined to form a (panoramic) image of the object edge.

The process steps of the image processing, in particular the identifi- zierens of the rim Bevelline or the structural features of determining a coordinate or reference system and determining the location of defects and the Bevelline in the reference system, can be used individually or together, both as a software as well as be implemented in hardware or combination of software and hardware.

Other objects, features and advantages of the invention will be explained in more detail below using an exemplary embodiment with reference to the drawings. In the drawings: Figure 1 is a plan view of an embodiment of the inventions dungsgemäßeπ inspection device with dark field illumination;.

Fig. 2 is a side view of the embodiment of FIG. 1;

Fig. 3 is a plan view of an embodiment of the inspection device according to the invention with bright-field illumination, and

Fig. 4 shows a histogram of the brightness curve of an image line.

Figures 1 and 2 show a simplified representation of an embodiment of the inspection apparatus of the invention for inspecting an upper edge vicinity of a semiconductor wafer 10. The wafer 10 is located on a rotary table 12 on which a motor, preferably by means of stepper motor driven, and the wafer 10 during the measurement in rotation added. A motor controller and / or an absolute or relative position imaging sensor system (not shown respectively) may be provided to output a control pulse, which is used on the one hand to control the rotational movement and on the other hand, to synchronize the recording of the object edge with the rotational movement.

The inspection apparatus further comprises a digital camera 14, which is aligned by means of an optical system 16 to the edge 18 of the wafer 10 and focused. The digital camera 14 is set up specifically to edge inspection of the wafer 10 by at an oblique angle, that is> 0 ° and <90 °, preferably between 30 ° and 60 ° and particularly preferably at about 45 ° to the object plane or upper side 22 of the wafer 10 is aligned with the edge of the eighteenth The digital camera 14 ER thus holds an edge around which a part of the top - -

or main surface 22 of the wafer 10, which includes upper, slightly inclined edge portion or bevel 24, and at least a portion of the gene stirπseiti- edge portion or apex 26th

The digital camera is preferably a line camera, whose Bildzeiie is located in the illustrated as a dashed line 20 radial plane. This case is shown in FIG. 1 However, the line camera can be swung out also at an angle from the radial plane 20, which used in conjunction with the same angular amount pivoted in the other direction from the radial plane bright field illumination device (vgi. Fig. 3) for the generation of a bright-field image of the wafer edge can be as described above.

It is also a first edge illumination device 28 is provided, which in each case a focused light gun high intensity is embodied in this example in the form of both sides of the digital camera. The number of light sources and the arrangement thereof are not substantially present, as long as no direct reflections from the light source at the wafer edge in the camera optical system 16 are incident. Therefore, a single light source may be sufficient or a plurality may be provided to a quasi-two-dimensional, arc-shaped light source, the object edge is located in the center or focus. While such a surface light source due to its large angular spectrum of the edge portion uniformly illuminated virtually independent of its geometry, the single light source has the advantage of being easily focus sierbar and thus to produce a light spot of high intensity on the object surface.

With the arrangement shown, the Digitaikamera 14 and the illuminating device 28, a dark-field image of the wafer edge can be generated 18, since the optical axis of the camera 14 is perpendicular to the wafer edge and the illuminating means are swung out 28 from the radial plane twentieth Therefore, the object of an intact edge 18 under the angle of α relative to the radial plane 20 of the reflected light beams do not fall into the lens of the camera. Due to the symmetrical arrangement of the two light sources, the incident and exit angles of the optical axes fall together both light sources alternately. The object edge 18 is thus in Normaifall in the dark field.

On the side facing away from the digital camera 14 of the wafer 10 is a backlight device 32, here as an almost point-like, non-collimated light source radiating. This is with respect to the edge of the wafer 10 and the digital camera 14 arranged so that the light emitted by its light is radiated at least in parts in the direction of the digital camera. At the same time the light irradiated toward the digital camera, light is shaded by the wafer 10 at about the half of the picture window (the wafer edge does not need to in this case centrally in the image run). Since the digital camera is focused on the edge of the object 18, the more distant backlight device 32 is represented as a fuzzy area light spot on the sensor of the camera. Compared to such a surface light background the object surface, and in particular lying in the dark field wafer edge are mapped as dunkie surface with a sharp edge.

2 shows a possible arrangement of a plane illumination device 30 is additionally shown the Ebenenbeleuchtung- seinrichtung30 is arranged so that its light is reflected from the upper major surface 22 of the wafer 10 directly into the camera lens sixteenth There is thereby produced a Hellfeldbiid the main surface 22, as far as the angle of view of the camera captures them. In this way, the contrast difference between the main surface 22 in the bright-field image and the oblique edge 24 which is already in the dark field of both lighting devices 28, 30, particularly large, so that the Bevelline, that the linear transition from the bevel 24 to the major surface 22, more easily recognized can be. In connection with the invention, accurate edge detection, the width of the bevel, and thus the polishing accuracy of the edge of the object over the entire circumference of the wafer but can be detected with particularly high precision.

Also, the invention with a bright field image of the entire edge portion is combined, in this case, a further expanded second edge lighting device is needed, which surface illuminates the entire profile of the wafer edge shown. The different lighting devices are then used for different lighting purposes mutually and / or operate combined to provide the most efficient, high-contrast imaging.

Figure 3 also shows a simplified representation of such an embodiment of the inspection apparatus of the invention for inspecting an upper edge vicinity of a semiconductor wafer 10 only in the top view. This differs by a change in position of the camera 14 'which is pivoted out of the radial plane 20 and a second edge lighting device 29 which is swung by the same angle in the opposite direction from the radial plane and, unlike the first edge lighting device 28, the object edge 18 can appear in the bright field.

In the non-illustrated side view of a viewing direction of the digital camera as preferred, which is a viewing angle> 0 ° and <90 °, particularly preferably between 30 ° and 60 ° and most preferably swung out by 45 ° from the object plane is also in this embodiment.

Also, the level background illumination device and the illumination device differ only in arrangement in that their light respectively to the equal and opposite angle by which the camera from the Radialebeπe 20 is pivoted, is also pivoted out of this.

4 shows a histogram of the idealized Helligkeitsveriaufes a picture line from the edge vicinity of a wafer is shown without defect. The histogram shows the brightness curve from left to right along the radial image coordinate away from the planar major surface to above the wafer edge. H1 denotes the brightness value of the direct reflection of the in-Helifeld the planar illumination device main plane, H2 according to the invention which independently adjustable brightness value lying in the bright field of the second edge lighting device edge and H3 to also independently adjustable brightness value of the incident directly into the camera light from the backlight device. In addition to the illustrated case H1 <H2 <H3 other relations are possible as long as sufficient contrast is that makes the transitions of the areas main face, edge and background distinguishable.

The edge includes the top bevel, the apex and a part of the lower Bevel in this figure. This is due to the previously described oblique camera position, which is also located outside the projection of the wafer on the main level. The lower bevel runs out from the bright field of the second Kantenbeieuchtungseinrichtung, and therefore the brightness of the edge before the wafer edge falls to 0. This is followed by (radially outward) includes the image of the background illumination, whose intensity value is set even lower than that of the edge lying in the bright field, so that even under a different angle from which the entire edge shown in the medicinal field would be a sufficient contrast for identifying the Waferran- of vorläge.

ßezugszeichenliste

10 wafer

12 turntable

14, 14 'digital camera

16 optics

18 wafer edge

20 radial plane

22 main surface, top surface of the wafer 4 upper edge portion 6 Bevel end-side edge portion, Apex 8 first edge lighting device 9 second edge illumination device illuminating device 2 0 level background illumination device

Claims

^ claims
facing the first inspection device for the optical examination of surfaces of objects in an edge surrounding an otherwise substantially flat object (10), in particular of wafer edges, with at least one of the object surface and the object edge (18) of focusable digital camera (14) and a plane illumination device (30) which relative to the digital camera (14) and is arranged to Objektoberfiäche so that a picture of a to the object edge subsequent major planar surface (22) of the object surface in the edge environment can be created under bright-field illumination, characterized by a backlight means (32) responsive to äst arranged to the side of the object (10) facing away from the digital camera (14) that the light emitted in the direction of the digital camera (14) light partially from the object (10) is emitted by its light in the direction of the digital camera (14), shaded is, and an image processing device, which an edge erkennungsmättel has, which is arranged einserseits image generated from pixel information of the digital camera (14) based on a contrast between the object edge (18) and the backlight an edge of the object (10) and by way of contrast between the object edge (18) and the fiäche main (22) to identify a transition line (Beveiüne) on the other.
2. An inspection apparatus according to claim 1, characterized in that the image processing means comprises a Kantenanalysemittei, which is arranged to monitor the relative position of Bevelline to the edge.
3. [nspektioπsvorrichtung according to any one of the preceding claims, characterized in that the image processing means comprises a pattern recognition means, soft is adapted to a structural feature of the object edge (18) of pixel information of the digital camera (14) the image formed using the contrast between the object edge (18 ) and the backlight to identify.
4. Inspection device according to claim 3, characterized in that the Biidverarbeitungseinrichtung is arranged to define a coordinate system on the basis of the identified edge and the identified structure shopping corn.
5. An inspection apparatus according to claim 4, characterized in that the image processing means is arranged to determine the position of the Bevelline with respect to the coordinate system.
6. An inspection apparatus of any preceding claim, characterized in that the viewing direction of the digital camera (14) is pivoted to a viewing angle> 0 ° from the object plane.
7. An inspection apparatus of any preceding claim, characterized in that the viewing direction of the digital camera (14) is pivoted to a viewing angle <90 ° from the object plane.
8. Inspection apparatus according to any one of the preceding claims, characterized by a first edge lighting means (28) which is realiv the digital camera (14) and the object edge (18) arranged so that an image of the object edge (18) can be produced under dark field illumination.
9. An inspection apparatus according to any one of the preceding claims, characterized by a second edge lighting means (29) which is relative to the digital camera (14) and the object edge (18) arranged so that an image of the object edge (18) can be produced under bright field illumination.
10. Inspection device according to claim 8 or 9, characterized in that the image processing means is arranged, from the pixel information of the dark field image and / or the HeII- the object edge (18) felbildes based on contrasts surface defects in the edge region to be identified.
11. An inspection apparatus according to claim 10 in conjunction with claim 4, characterized in that the image processing means is arranged to determine the location of surface defects with respect to the coordinate system.
12. An inspection apparatus according to claim 9, characterized in that the second edge lighting means (29), the background illumination device (32) and the plane illumination device (30) are controllable separately.
13. An inspection apparatus according to claim 2, characterized in that the edge analyzing means is adapted to determine the diameter of the object edge based on the identified edge.
14. An inspection apparatus according to claim 2, characterized in that the edge analyzing means is adapted to determine the diameter of the Bevelliπe.
15. An inspection apparatus according to any one of the preceding claims, characterized by a motor-driven rotary table (12) for rotatably Hal- esterification of the object (10), wherein the digital camera (14) is adapted in synchronism with the rotation of the turntable (12) a digital image of receiving object edge (18).
16. The inspection method for the optical examination of surfaces of objects in an edge surrounding an otherwise substantially flat object (10), in particular of wafer edges (18), comprising the steps of
~ Acquiring a digital image of an object edge (18) of the object surface by means of a digital camera (14) and
- illuminating a at the object edge subsequent major planar surface (22) of the object surface in the edge vicinity Mitteis a plane illumination device (30), so that from the plane illumination device (30) outgoing and on the main area (22) reflected light in the digital camera (14) is incident, and a bright field image of the main surface (22) is generated, - -
characterized by the steps
- illuminating the background during recording of the edge image arranged by means of a on which the digital camera (14) side facing away from the object (10) backlight device (32) emits the light toward the digital camera (14), wherein the (in the direction of the digital camera 14 ) emitted light in part from the object (10) is shaded,
- determining an edge of the object (10) from pixel information of the digital camera (14) the image formed based on a contrast between the object edge (18) and the background and
- determining a transition line (Bevelline) from Bildpunktinfor- mation of the digital camera (14) the image formed based on a contrast between the object edge (18) and the main surface (22).
17. The inspection method according to claim 16, characterized in that the relative position of Bevelline is monitored to the edge.
18. The inspection method according to claim 16 or 17, characterized in that a structural feature of the object edge (18) of pixel information of the digital camera (14) the generated image is identified based on the contrast between the object edge (18) and the backlight.
19. The inspection method according to claim 18, characterized in that a coordinate system is determined on the basis of the detected edge and the identified structural feature.
20. The inspection method according to claim 19, characterized in that the position of Beveiline is determined with respect to the coordinate system.
21. The inspection method any one of claims 16 to 20, characterized in that the image of the object edge (18) is taken from a viewing direction which is pivoted to a viewing angle> 0 ° from the object plane.
22. The inspection method any one of claims 16 to 21, characterized in that the image of the object edge (18) is taken from a viewing direction which is pivoted to a viewing angle <90 ° from the object plane.
23. The inspection method according to any one of claims 16 to 22, characterized by
Illuminating the object edge (18) by means of a first edge lighting means (28) so that the from the edge illuminating means (28) outgoing and at the edge of the object (18), reflected light not incident into the digital camera (14) and a dark field image of the object edge (18) generates becomes.
24. The inspection method according to any one of claims 16 to 22, characterized by
is illuminating the object edge (18) by means of a second edge lighting means (28) so that the from the edge illuminating means (28) outgoing and at the edge of the object (18) is incident reflected light in the digital camera (14) and generates a bright field image of the object edge (18) ,
25. The inspection method according to claim 23 or 24, characterized in that surface defects in the edge region of the formations Bildpunktin- of the dark field image and / or the Hellfelbildes the object edge (18) are identified based on contrasts.
26. The inspection method according to claim 25 in conjunction with claim 20, characterized in that the position of the surface defects is determined with respect to the coordinate system.
27. The inspection method according to claim 24, characterized in that the second edge the illumination device, the backlight device (32) and the Ebenenbeleuchtungseiπ- direction (30) are driven separately from one another so that at the same time a bright-field image of the object edge (18) and a cure-field image of the main surface (22 ) is generated and a sufficient contrast between the object edge (18) and the background and between the object edge (18) and the main surface (22).
28. The inspection method according to any one of claims 16 to 27, characterized in that it is determined on the basis of the identified edge of the diameter of the object.
29. The inspection method according to any one of claims 16 to 28, characterized in that the diameter of Beveiline is determined.
PCT/EP2009/060254 2008-08-08 2009-08-06 Inspection device and method for optical investigation of object surfaces, in particular wafer edges WO2010015695A1 (en)

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DE102008041134 2008-08-08

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DE112009001936B4 (en) 2014-03-13

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