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

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

 Inspection device and method for the optical examination of object surfaces, in particular of wafer edges

description

The invention relates to an inspection device and an inspection method for the optical examination of object surfaces in an edge environment of an otherwise substantially planar object, in particular of edges of unstructured wafers, by means of at least one of the object surface facing and on the object edge fotkußbaren digital camera and a plane lighting device, the relative to the digital camera and to the object surface is arranged such that an image of a plane adjoining the object edge planar main surface of the object surface is generated in the edge environment under Heidelfeldbeleuchtung.

The optical inspection process of semiconductor wafers for defects (breakouts, scratches, imprints, particles, etc.) is an important part of the manufacturing process of computer chips. The inspection usually includes both the planar object or wafer top and bottom side and its edge. The present invention particularly relates to the inspection of the edge.

The terms used herein to designate 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 following defined major surfaces and edges of the object.

"Main surface" refers to the planar, opposite upper or lower sides of the generally disk-shaped object (wafer). "Edge" or "object edge" is on the one hand adjacent to the main surface and on the other hand, the object outer peripherally delimiting surface portion which thus connects the major surfaces and usually both an upper or lower oblique portion ("bevel") and a vorirnsitigen circumferential portion ("Apex").

The "edge environment" describes a section of the area that includes both the edge and a section of the main surface in the transition area to the edge.The term "edge" or "object edge" refers to the transition line between the edge of the object and the environment that can be seen from the respective angle.

- "Bevelline" is the transition line between the object's top and bottom side and the bevel of the object's edge, which can be seen from the respective perspective.The "structural feature" is a deviation of the edge profile in the vertical projection to the object plane Main surfaces defined by a given uniform or continuous contour. In the case of a circular wafer, such a structural feature is, for example, a radial notch (notch) or a straight edge section (circular chord).

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

From DE 103 13 202 B3 a device of the type mentioned is known in which the object edge of the wafer consisting of the upper Bevei (bevel), the apex and the lower Bevel completely in Range of the darkness of an LED light source lie, while the reflected light from the wafer top or upper main surface directly into the camera, the wafer top is aiso in the bright field area. Using a plane mirror arranged underneath the wafer and oriented parallel thereto, the lower image or lower main surface of the wafer is also recorded in the same image, which, insofar as can be seen, are also in the dark field region. The upper Bevel is thus illuminated under grazing light from the light source and the apex and the lower Bevel are completely in the shadow of the light source. The light that passes through the wafer is reflected by the mirror surface directly into the camera so that it is imaged as a HeNfeld background following the bottom. As a result, the wafer edge is depicted as a narrow strip in the dark field area, on one side of which the direct reflection from the wafer top side and on the other side the direct reflection from the plane mirror join. The lighting conditions on the upper side and the lower side of the wafer edge are very different for the aforementioned reasons.

The disadvantage here is that the edge region of interest is partially imaged directly and partially reflected on the mirror. Since the wafer edge is in the dark field overall, it can not be located exactly in the image. In addition, the subsequent bright field image of the wafer top side on the one hand and the mirror on the other hand outshines the transition region to the edge, so that resolution losses can be expected here.

DE 103 24 474 A1 describes a device comprising a reflected-light illumination device and an imaging device with which the surface of a wafer coated with photoresist is received in the healing field. In contrast to the present invention, this device is used to inspect a patterned wafer. _Λ

- 4 _

By polarization of the light and camera-side analysis of the polarization state of the light reflected at the surface of the Depiackung of the wafer is examined in its edge region in addition to the wafer underside another illumination device is provided, the light rays are partially shaded on the way to the camera from the wafer edge, so that the edge of the wafer rim appears as a light-dark transition.

While the investigation of the edge region in the last-mentioned document does not go beyond the control of the removal and is therefore unsuitable for the investigation of an unstructured wafer for defects of the type mentioned above, no gap-free examination of the wafer can be carried out with the device known from DE 10331 202 B3 be ensured by the main surface over the entire edge area including Bevei and Apex.

Against this background, the inventors have made it their task to improve the inspection device or the inspection method in such a way that all types of defects on the object surface can be identified from the recorded image contents as completely as possible and with location accuracy.

The object is achieved 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 the subject of the dependent claims.

According to the invention, the inspection method provides that during the recording of the edge image, a background lighting is switched on on the side of the object facing away from the digital camera whose light radiates in the direction of the digital camera, wherein the light emitted in the direction of the digital camera is partly from the object is shaded to the edge of the site. The edge of the object is determined from pixel information of the image produced by the digital camera based on a contrast between the object edge and the background, and a bevel of pixel information of the digital camera image based on a contrast between the object edge and the main surface.

Accordingly, in the inspection device according to the invention on the side facing away from the digital camera side of the object, a backlight device is arranged in the shape that is emitted from their light towards the digital camera, the light emitted in the direction of the digital camera partially shaded from the object to the object edge when the digital camera is focused on the edge area. The inspection device according to the invention further comprises an image processing device which has an edge detection means which is arranged from pixel information of the image generated 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 based on a contrast between the object edge and the main surface to identify a transition line (Bevelline) on the other.

Thus, unlike in DE 103 13 202 B3, the inspection device or the inspection method according to the invention thus provides a separate background illumination which illuminates directly into the digital camera, provided that it is not shadowed by the object and thus a contrast between the directly recorded object edge and the background creates. This makes it possible for the first time to establish a clear relationship between the population line identified on the basis of the contrast between the object edge and the main surface and the edge identified on the basis of the contrast between the edge of the object and the background light. Apart from the previously mentioned DE 10324474 A1, further prior art is known which describes a background light source on the side of the wafer facing away from an optical sensor. For example, Japanese Laid-Open Patent Application No. 59125627 A discloses a device in which a bundle of parallel light beams is irradiated perpendicularly to the wafer surface in the edge region and the unshaded portion of this light beam is detected by means of a two-dimensional photosensor disposed on the opposite side of the wafer the wafer is turned. The same arrangement is known in principle from US Pat. No. 5,438,209 A, which, instead of the photosensor, uses a camera line. Both devices are devices for determining the position of a score and not the generic inspection device for receiving a dark field image of the wafer surface. The lighting is a pure backlight, so that a dark field recording hereby is not possible. The accuracy of the position determination of Notch is ensured only by the parallelism of the light beams, which ensures a sharp shadow.

Another device for determining the note position in a wafer is known from the publication JP 2000031245 A. This has a camera whose optical axis is aligned perpendicular to the top of the wafer and on its center and which receives a two-dimensional overall image of the wafer surface, without the wafer is rotated thereby. The illumination device is pivoted away from the optical axis of the camera for this purpose, so that no direct reflection of the light from the Waferoberfiäche falls into the camera. The immediate vicinity of the wafer is lightened by the fact that the light of the illumination device is the material of the wafer support (diffused) scattered. This creates a Contrast between the wafer support and the wafer, so that the edge of the printer is depicted as a dark border in front of the lighter overlay. This device allows the identification of the wafer edge and in particular a Notch. However, it is not intended and suitable for identifying and localizing defects on the wafer surface with sufficient accuracy. This is also a device for determining the Notch position. Also, the asymmetrical arrangement of the Beieuchtungseinrichtung relative to the center axis of the wafer for a shadow, which makes it difficult to localize the wafer edge with high accuracy, since not the light emitted in the direction of the digital camera is partially shaded by the object edge, but already the light on the way to the Waferaufiage. Finally, the contrast is dependent on the material and the nature of the wafer surface on the one hand and the overlay on the other hand and can not be influenced.

In contrast, the invention relates to an inspection device for the detection of surface defects, which allows an improved localization of these surface defects and at the same time a detection of the surface defects up to the outermost object edge, ie to the object edge.

Since the focus of the digital camera in the inspection device according to the invention lies on the object edge, in particular the edge of the object is sharply imaged, which enables a precise localization of the object. Furthermore, this has the advantage that the background lighting device, which is located farther away, is blurred and therefore no artifacts of the background disturb the image impression, in particular can serve as a backlight a simple lamp, which due to the fuzzy as an extended light spot on the sensor of the digital camera is shown. Of course, as a backlighting device, too a direct or indirect and / or diffuse emitting surface light source can be selected.

According to the invention, the inspection of the object edge also includes that of the transition to the main surface of the object. Here, the Bevelline is of particular interest. The Bevel may, in addition to the mentioned defects in the form of scratches, eruptions, dust grains, imprints or the like also defects in the form of Bearbeitungsuπgsfehlern, nem- Nch polishing defects have. The wafer edge usually gets a polished surface. If the polishing process of the edge is done properly, the Bevelline and the wafer edge must always be parallel, deviations from this are polishing defects. Such polishing defects do not lead to high-contrast scattered light reflections or dark spots, as the aforementioned defects do under bright or dark field illumination. Polishing errors thus lead to more or less pronounced deviations of the bevel from their soil position on the wafer. Fluctuations in Beveliine due to buffing are, however, overlaid with artefacts of the measurements, such as vibrations or eccentricity of the wafer during the measurements, so that a statement about their actual position can not be easily made. Therefore, it is provided according to the invention to unambiguously identify the object edge as well as the bevel at the same time.

The image processing device preferably has an edge analyzer which is set up to monitor the relative position of the bees to the edge.

The edge detection means detects, by means of a simple algorithm, non-circular motion of the wafer (horizontal vibration in the wafer plane) due to centering inaccuracy or wafer flutter (vertical vibration perpendicular to the wafer plane) due to unevenness or resonant excitation. So far one tried to minimize the mentioned sources of error by active and sometimes mechanically very complex centering and damping measures. In contrast to any defects, however, horizontal or vertical vibrations provide a periodic, low-frequency course of the wafer edge in the image and can therefore be easily identified. The exact edge detection of the device according to the invention therefore allows to dispense with complex active centering and damping measures and to correct any errors in the context of image processing by means of suitable correction means or routines.

Monitoring the relative position of the bevelline to the edge is done by identifying the population and boundary line from the contrast differences in the image, then determining the distance of both lines in the image along an approximately perpendicular line to the edge. If the wafer is not well centered, so the distance wafer edge - camera changes, can be closed taking into account the imaging geometry on the real distance bevel line - wafer edge. This distance must always be constant within certain tolerances on the normal wafer edge.

In a preferred embodiment, the edge detection means comprises a structure recognition means which is set up to identify a structural feature of the object edge from pixel information of the dark field image on the basis of the contrast difference between the object edge and the background illumination.

Such a structural feature is, for example, the contour of a notch in the wafer edge. This has a known shape and can therefore be easily identified by an algorithm or a comparison of the recorded edge image with stored in a memory forms. However, in this way not only a notch but also any other structural features, while For example, in the form of a straight edge portion (on an otherwise circular wafer) can be detected. All regular structural features can thus be easily identified and, in particular, distinguished from an irregular outbreak. As a result, a simple inspection of the structural feature itself is made possible. In particular, defects in the structural feature, the complete absence of the structural feature, a shape deviation of the structural feature from a desired geometry 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 line and the edge along such a feature. This also applies if no constant distance is expected here but another profile of the bevelline following the outline of the structural merameter (nominal geometry).

Preferably, the image processing device is also set up to determine a coordinate system on the basis of the identified edge and / or the identified structural feature.

By way of example, a reference point for the azimuthal angle (ie the angle of rotation of the wafer) can be determined unambiguously on the basis of the identified structural feature. For example, the center of a notch may be taken as the coordinate zero point of the azimuthal angle, allowing accurate angular position indication of each identified surface defect (or defect fragment).

Furthermore, with the aid of such an image processing device, it is possible to deduce the course of the true physical object edge from the identified edge in the case of a known shaping of the edge profile. The center of the apex, which forms the radially outermost edge of the object, is determined in the simplest case by using a known shape of the edge profile and the viewing angle at which the camera is placed on the Object edge looks, a constant distance of the Apexmitte is assumed to the identified edge. This distance can be stored as a system- and / or profile-specific setting in a memory of the image processing device and subtracted when calculating the position of the true edge of the object from the position of the identified edge. As the coordinate reference point of the radial component of the coordinate system, the true object edge, ie, the center of the apex, is then preferably selected. This and the coordinate zero point of the azimuthal angle preferably form the origin of a two-dimensional coordinate system.

If the coordinate system is defined in two dimensions, the position of the bevelline with respect to the coordinate system can preferably be determined by means of the image processing device.

This allows polishing errors also with respect to their angular position relative to the structural feature, the Wavemotch, to be determined.

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 preferably swiveled out of the object plane by a viewing angle> 0 °.

If, at the same time, the viewing direction of the digital camera is swiveled out of the object plane by a viewing angle <90 °, this allows the acquisition of the entire edge environment including the apex, bevel and an edge-near part of the main surface. The above applies analogously when the beam path is deflected on the way to the camera. Will the object from this perspective of his Top and inspected from its bottom, one gets a complete picture of the edge environment. The two halves of the image can thus be joined together in the center of the apex in the coordinate zero point of the radial component, wherein the zero coordinates of the azimuthal angle determined in both partial images are superimposed. Thus, all defects can be represented in a common coordinate system.

The viewing direction from which the image is taken from the edge of the object by means of a digital camera can, when viewed on the object plane, be perpendicular to the object edge or a tangent to the object edge. That is, the optical axis of the camera is oriented (possibly after deflection) according to this embodiment so as to define together with the guide an optical plane coincident with a radial plane of the wafer. The advantage of this embodiment is that fewer image distortions occur.

Preferably, a first edge illumination device is provided, which is arranged so as to be real to the digital camera and to the object edge so that an image of the object edge can be generated under dark field illumination.

In dark field illumination, the light emitted by the illumination device is reflected by the intact object surface so that it does not enter the optics of the digital camera, so that the image of the object surface remains predominantly dark. If a defect in the surface area is in the form of a depression (scratch, eruption) or in the form of an increase (dust grain, impurity), then usually one or the other reflex of the defect will be reflected in the optics of the digital camera. This creates a bright image of defect fragments. The inventors have also recognized that different sections of the defects are illuminated depending on the illumination situation, ie that different fragments are displayed under different light incidence directions. In order to obtain a more complete picture of the entire defect, a second or alternative is therefore advantageous Edge lighting device provided which is arranged relative to the digital camera and the object edge so that an image of the object edge can be generated under bright field illumination.

In bright field illumination, the light emitted by the illumination device is reflected by the intact object surface directly into the optics of the digital camera, so that the image of the object surface appears predominantly bright. If a defect in the surface area is in the form of a depression (scratch, eruption) or in the form of an increase (dust grain, impurity), the light is scattered in other directions and does not fall into the optics of the majority of the defects the digital camera. This creates a dark image of defect fragments.

Especially in the case of bright field illumination, the optical axis of the camera is preferably oriented so that the defined together with the image line optical plane of the line scan camera is pivoted out of the radial plane. Admittedly, this will lead to more image distortions. However, this arrangement allows the bright field image of the wafer edge to be realized in a simple manner by inserting the bright field illumination device in a mirror-image arrangement relative to the camera arrangement relative to the radial plane through the focal point on the wafer surface. In this embodiment, the background lighting device is preferably swung out by the same amount and in the same direction from the radial plane, so that it lies on the optical axis of the camera. The image processing device is furthermore preferably set up to identify surface defects in the edge region from the image point information of the dark field image and / or the light field of the object edge on the basis of the contrasts generated as described above.

The detected defect fragments are first identified by the image processing device separately in the sub-images of the dark field recording and the bright field recording. This is preferably done by first assigning contiguous pixels whose contents (intensity, gray or color values) lie within a predetermined value range (intensity, gray or color value intervalls) to the same defect fragment. The defect fragments determined in this way are then combined by means of an algorithm for belonging to the same defect. From two (or more) partial images of the object surface, a virtual surface image is thus generated, so that the sum of the information from the bright field image and the dark field image allows a more comprehensive image of the entire defect to be produced.

The resulting digital image of the object surface is then usually fed to a manual or automatic evaluation, the results of the evaluation are used to decide according to the specifications of the chip manufacturer on the usability of the wafer and to perform a sorting according to quality criteria.

The second edge illumination device, the background illumination device and the plane illumination device can be controlled separately from one another by means of a suitable control unit. In this way, it is possible to ensure that in each recording mode there is sufficient or optimum contrast between the main area in the bright field, the wafer edge in the bright or dark field and the background illumination, the simultaneous detection of the population, the wafer edge and defects in the bright field dark field allowed If, for example, there are defects in the form of eruptions directly at the edge of the wafer, then these too can easily be identified as a deviation from the continuous edge curve. The information about the shape of the contour of the wafer thus offers (in addition to the one described above) an additional possibility for the detection of defects. In this case, the separate backlighting enables a contrast adjustment that deviates from the contrast center of gravity or from the center of intensity, gray or color value of a defect lying in the dark field or bright field. Outbreaks are thus easily distinguishable from a surface defect of another type. Due to the separate illumination control, the method according to the invention is furthermore independent of the reflectivity of the wafer surface, for example due to different coatings and / or structures.

If the coordinate system is set in two dimensions, the position of the surface defect (s) found in relation to this coordinate system can be determined in the inventive inspection method. The position determination can include, for example, both the extent of the defect or defect fragment, including its center of gravity and orientation. Overall, the accuracy and reproducibility of the information about each defect are increased by the inventive identification of the object edge and the structural feature.

Deviations from this can easily be detected with the method according to the invention and the device according to the invention, if the image processing device is set up to determine the position of the bevelline with respect to the coordinate system and / or the identified wafer edge.

In a further preferred embodiment, the edge analysis means is set up to determine the diameter of the object edge and / or the bevelling on the basis of the identified edge.

If, according to a preferred embodiment, the inspection device has a motor-driven turntable for rotatably supporting the object, the digital camera being set up to record a digital image of the object in synchronism with the rotation of the turntable, a plurality of image lines of the object edge can be taken sequentially with such a line camera while the object is rotating together with the turntable. For this purpose, the triggering of the camera can follow, for example, by means of a synchronization pulse by the drive motor (eg stepping motor). The sequentially recorded image lines of the object edge in different angular position of the object are then combined to form a (panoramic) image of the object edge.

The method steps of the image processing, in particular the identification of the edge, the Bevelline or the structural features, the determination of a coordinate or reference system and the determination of the position of defects and Bevelline in the reference system, individually or collectively both as software and as Hardware or in combination of software and hardware.

Other objects, features and advantages of the invention will be explained in more detail using an exemplary embodiment with the aid of the drawings. Show it: 1 is a plan view of an embodiment of the inventive 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

4 shows a histogram of the brightness curve of a picture line.

Figures 1 and 2 show in simplified form an embodiment of the inspection device according to the invention for inspecting an upper edge environment of a semiconductor wafer 10. The wafer 10 rests on a turntable 12, which is driven by a motor, preferably by means of a stepping motor, and the wafer 10 during the measurement in rotation added. A motor control and / or an absolute or relatively positional sensor system (not shown) 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 device further has a digital camera 14, which is aligned and focused by means of an optical system 16 on the edge 18 of the wafer 10. The digital camera 14 is specially designed for edge inspection of the wafer 10 by tilting at an oblique angle, ie> 0 ° and <90 °, preferably between 30 ° and 60 ° and more preferably below about 45 ° to the object plane or top 22 of the Wafer 10 is aligned with the edge 18. The digital camera 14 thereby detects an edge environment that forms part of the top - -

or main surface 22 of the wafer 10, whose upper, slightly oblique edge region or Bevel 24, and at least part of the stirπseiti- gen edge region or apex 26 includes.

The digital camera is preferably a line scan camera whose image line lies in the radial plane shown as dashed line 20. This case is shown in FIG. However, the line scan camera can also be swiveled out of the radial plane 20 by an angle, which, in conjunction with a bright field illumination device (FIG. 3) pivoted out of the radial plane by the same angle in the other direction, is used to generate a bright field image of the wafer edge can be, as already described above.

Furthermore, a first edge illumination device 28 is provided which, in this example, is designed in the form of a focused light gun of high intensity on both sides of the digital camera. The number of light sources and their arrangement are not relevant to the invention as long as no direct reflections of the light source at the wafer edge into the camera optics 16 occur. Therefore, a single light source may suffice or several may be provided, up to a quasi-flat, arcuate light source, in the center or focus of which the object edge lies. While such a planar light source illuminates the edge region uniformly irrespective of its geometry due to its large angle spectrum, the individual light source has the advantage of being easy to focus and thus of generating a light spot of high intensity on the object surface.

With the shown arrangement of the digital camera 14 and the illumination device 28, a dark field image of the wafer edge 18 can be generated, since the optical axis of the camera 14 is perpendicular to the wafer. ferkante stands and the lighting device 28 are pivoted out of the radial plane 20. Therefore, the light rays reflected at an intact object edge 18 at the angle of reflection α with respect to the radial plane 20 do not fall into the lens of the camera. Due to the symmetrical arrangement of both light sources, the incidence and angle of departure of the optical axes of both light sources coincide mutually. The object edge 18 is thus in the normal case in the dark field.

On the side facing away from the digital camera 14 of the wafer 10 is a backlight 32, here as a nearly point-like, non-collimated emitting light source. This is arranged with respect to the edge of the wafer 10 and the digital camera 14 so that the light emanating from it is emitted at least in part in the direction of the digital camera. At the same time, however, the light emitted in the direction of the digital camera is shadowed by the wafer 10 approximately halfway through the image window (the wafer edge does not have to run centrally in the image, as in this case). Since the digital camera is focused on the object edge 18, the more distant background illumination device 32 is imaged as a blurred area light spot on the sensor of the camera. In contrast to such a bright background, the object surface and in particular the wafer edge lying in the dark field are imaged as a dark surface with a sharp edge.

In addition, a possible arrangement of a planar illumination device 30 is shown in FIG. 2. The planar illumination device 30 is arranged such that its light is reflected directly from the upper main surface 22 of the wafer 10 into the camera optical system 16. As a result, a bright field image of the main surface 22 is generated, as far as the angle of view of the camera detects it. As a result, 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 illumination devices 28, 30, particularly large, so that the Bevelline, so the linear transition from Bevel 24 to the main surface 22, can be particularly easily detected. In connection with the precise edge detection according to the invention, the width of the Bevel and thus the polishing accuracy of the object edge over the entire circumference of the wafer can be detected with particularly high precision.

The invention can also be combined with a bright field image of the entire edge region, in which case a further extended second edge illumination device is required, which flatly illuminates the entire profile of the imaged wafer edge. The different lighting devices then have to be operated alternately and / or in combination for the different lighting purposes in order to enable the most efficient and high-contrast image acquisition.

FIG. 3 likewise shows in a simplified representation such an embodiment of the inspection device according to the invention for inspecting an upper edge environment of a semiconductor wafer 10 only in plan view. This is distinguished by a changed position of the camera 14 ', which is swung out of the radial plane 20, and a second edge illumination device 29, which is swung out by the same angle in the opposite direction from the radial plane and, unlike the first edge illumination device 28, the object edge 18th appears in the bright field.

In the side view, not shown, a viewing direction of the digital camera is also preferred in this embodiment, which by a viewing angle> 0 ° and <90 °, particularly preferred is pivoted out of the object plane between 30 ° and 60 ° and most preferably by 45 °.

The planar illumination device and the background illumination device also differ only with respect to their arrangement in that their light is likewise pivoted out of the latter at the same angle at which the camera is swung out of the radial plane 20.

FIG. 4 shows an idealized histogram of the brightness distribution of an image line from the edge environment of a wafer without defect. The histogram shows the brightness progression from left to right along the radial image coordinate outward from the planar major surface to beyond the wafer edge. H1 designates the brightness value of the direct reflection from the main plane lying in the heli-field of the plane illumination device, H2 the brightness value of the edge lying in the bright field of the second edge illumination device and H3 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 relationships are possible as long as a sufficient contrast remains, which makes the transitions of the areas of main surface, edge and background distinguishable.

The edge in this illustration includes the upper bevel, the apex, and a portion of the bottom bevel. This is due to the previously described oblique camera position, which is also outside the projection of the wafer on the main plane. The lower Bevel runs out of the bright field of the second Kantenbeieuchtungseinrichtung, which is why the brightness of the edge drops to the value 0 before the wafer edge. This is followed (radially outward) by 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 also from another angle from which the entire imaged edge lies in the healing field sufficient contrast to identify the wafer edge.

ßezugszeichenliste

10 wafers

12 turntable

14, 14 'digital camera

16 optics

18 wafer edge

20 radial plane

22 main surface, upper side of the wafer 4 upper edge region, Bevel 6 front edge region, Apex 8 first edge illumination device 9 second edge illumination device 0 level illumination device 2 background lighting device

Claims

^ claims 1. Inspection device for the optical examination of object surfaces in an edge environment of an otherwise substantially planar object (10), in particular wafer edges, with at least one of the object surface facing and on the object edge (18) focusable digital camera (14) and a plane lighting device (30) which is arranged relative to the digital camera (14) and to the object surface such that an image of a planar major surface (22) of the object surface adjoining the object edge can be generated in the edge environment under bright field illumination, characterized by backlighting means (32) the side of the object (10) facing away from the digital camera (14) is arranged so that it emits light in the direction of the digital camera (14), wherein the light emitted in the direction of the digital camera (14) is partially shaded by the object (10) is, and an image processing device, the edge Having detected, which is arranged, from pixel information of the digital camera (14) generated image based on a contrast between the object edge (18) and the backlight an edge of the object (10) on the one hand and based on a contrast between the object edge (18) and the Main surface (22) to identify a transition line (Beveiüne) on the other hand. 2. Inspection device according to claim 1, characterized in that the image processing device has a Kantenanalysemittei, which is adapted to monitor the relative position of the Bevelline to the edge. 3. The spectroscopic device according to claim 1, wherein the image processing device has a structure recognition means configured to display a structural feature of the object edge from pixel information of the image generated by the digital camera on the basis of the contrast between the object edge ) and the backlighting. 4. Inspection device according to claim 3, characterized in that the Biidverarbeitungseinrichtung is arranged to determine a coordinate system based on the identified edge and the identified Strukturmerkmais. 5. inspection device according to claim 4, characterized in that the image processing means is adapted to determine the position of the Bevelline with respect to the coordinate system. 6. Inspection device one of the preceding claims, characterized in that the viewing direction of the digital camera (14) is pivoted out by a viewing angle> 0 ° from the object plane. 7. Inspection device one of the preceding claims, characterized in that the viewing direction of the digital camera (14) by a viewing angle <90 ° is pivoted out of the object plane. 8. Inspection device according to one of the preceding claims, characterized by a first edge illumination device (28) which is real to the digital camera (14) and the object edge (18) arranged so that an image of the object edge (18) can be generated under dark field illumination. 9. Inspection device according to one of the preceding claims, characterized by a second edge illumination device (29) which is arranged relative to the digital camera (14) and the object edge (18) so that an image of the object edge (18) can be generated under bright field illumination. 10. Inspection device according to claim 8 or 9, characterized in that the image processing device is set up to identify surface defects in the edge region from the pixel information of the dark field image and / or the highlight image of the object edge (18) on the basis of contrasts. Inspection apparatus according to claim 10 in conjunction with claim 4, characterized in that the image processing means is arranged to determine the position of the surface defects with respect to the coordinate system. 12. Inspection device according to claim 9, characterized in that the second edge illumination device (29), the backlight device (32) and the plane lighting device (30) are controlled separately from each other. 13. Inspection device according to claim 2, characterized in that the edge analysis means is adapted to determine the basis of the identified edge of the diameter of the object edge. 14. Inspection device according to claim 2, characterized in that the edge analysis means is adapted to determine the diameter of Bevelliπe. 15. Inspection device according to one of the preceding claims, characterized by a motor-driven turntable (12) for rotatable Hai- sion of the object (10), wherein the digital camera (14) is arranged, in synchronism with the rotation of the turntable (12) a digital image of the Object edge (18) record. 16. An inspection method for the optical examination of object surfaces in an edge environment of an otherwise substantially planar object (10), in particular wafer edges (18), with the steps Taking a digital image from an object edge (18) of the object surface by means of a digital camera (14) and Illuminating a plane main surface (22) of the object surface adjoining the object edge in the edge environment by means of a planar illumination device (30), so that the light emanating from the plane illumination device (30) and reflected at the main surface (22) enters the digital camera (14). and a bright field image of the main surface (22) is generated, - - characterized by the steps Illuminating the background while taking the edge image by means of a on the digital camera (14) facing away from the object (10) arranged backlight (32) whose light emits in the direction of the digital camera (14), wherein in the direction of the digital camera (14 ) emitted light is partially shaded by the object (10), - Detecting an edge of the object (10) from pixel information of the image generated with the digital camera (14) based on a contrast between the object edge (18) and the background and - Determining a transition line (Bevelline) of pixel information of the image generated with the digital camera (14) based on a contrast between the object edge (18) and the main surface (22). 17. Inspection method according to claim 16, characterized in that the relative position of the Bevelline is monitored to the edge. 18. Inspection method according to claim 16 or 17, characterized in that a structural feature of the object edge (18) from pixel information of the digital camera (14) generated image on the basis of the contrast between the object edge (18) and the backlight is identified. 19. Inspection method according to claim 18, characterized in that a coordinate system is determined on the basis of the determined edge and the identified structural feature. 20. An inspection method according to claim 19, characterized in that the position of the Beveiline is determined with respect to the coordinate system. 21. Inspection method according to claim 16, characterized in that the image of the object edge (18) is recorded from a viewing direction which is swiveled out of the object plane by a viewing angle> 0 °. 22. Inspection method according to 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 by a viewing angle <90 ° from the object plane. 23. Inspection method according to one of claims 16 to 22, characterized by Illuminating the object edge (18) by means of a first edge illumination device (28) so that the light emitted by the edge illumination device (28) and reflected at the object edge (18) does not enter the digital camera (14) and produces a dark field image of the object edge (18) becomes. 24. Inspection method according to one of claims 16 to 22, characterized by Illuminating the object edge (18) by means of a second edge illumination device (28), so that the light emerging from the edge illumination device (28) and at the object edge (18) reflected light into the digital camera (14) and a bright field image of the object edge (18) is generated. 25. Inspection method according to claim 23 or 24, characterized in that surface defects in the edge region from the pixel information of the dark field image and / or the bright field of the object edge (18) are identified by means of contrasts. 26. Inspection method according to claim 25 in conjunction with claim 20, characterized in that the position of the surface defects with respect to the coordinate system is determined. 27. An inspection method according to claim 24, characterized in that the second edge illumination device, the backlight device (32) and the Ebenebeleuchtungseiπ- direction (30) are controlled separately from each other so that at the same time a bright field image of the object edge (18) and a Heilfeldbild the main surface (22 ) and sufficient contrast exists between the object edge (18) and the background and between the object edge (18) and the major surface (22). 28. Inspection method according to one of claims 16 to 27, characterized in that based on the identified edge of the diameter of the object is determined. 29. Inspection method according to one of claims 16 to 28, characterized that the diameter of the beveiline is determined.