WO2004010114A2

WO2004010114A2 - Device for wafer inspection

Info

Publication number: WO2004010114A2
Application number: PCT/EP2003/007677
Authority: WO
Inventors: Henning Backhauss
Original assignee: Leica Microsystems Semiconductor Gmbh
Priority date: 2002-07-18
Filing date: 2003-07-16
Publication date: 2004-01-29
Also published as: JP2005533260A; WO2004010114A3; EP1523670A2; AU2003250961A8; AU2003250961A1; DE10232781B4; DE10232781A1

Abstract

The invention relates to a device for wafer inspection. Said device comprises an incident light illumination element having an illumination axis and an imaging element having an imaging axis, both elements being inclined towards each other and oriented towards a region of the surface of the wafer, which is to be inspected. An imaging plane is defined by the illumination axis and the imaging axis by means of the bright field illumination adjustment of the device. The device is characterised in that the illumination axis rotated out of the imaging plane about a dark field angle Ϝ > 0 is arranged in such a way that a dark field illumination is present in the region to be inspected.

Description

Wafer inspection device

The invention relates to a device for wafer inspection with an incident light illuminating device with an illuminating axis and an imaging device with an imaging axis, both of which are directed towards an area of the surface of a wafer to be inspected.

In semiconductor manufacturing, the wafers are coated with photoresist during the manufacturing process. The photoresist first goes through an exposure process and then through a development process. In these processes, it is structured for subsequent process steps. Due to the manufacturing process, a little more photoresist is deposited in the edge area of the wafer than in the middle of the wafer. This creates an edge bead, referred to as "edge bead" in English. Photoresist on the edge of the wafer and the edge bead can lead to contamination of production machines and to the development of defects on the wafer in the subsequent process steps.

To avoid these effects, edge bead removal (EBR) is carried out. Errors in the width of the edge stripping result from inaccurate alignment of the corresponding stripping devices relative to the wafer. Further sources of error are the inaccurate alignment of the illumination devices relative to the wafer when exposing the photoresist. Too much edge stripping leads to a reduction in the usable wafer area and thus to the loss of produced chips. Insufficient edge stripping can lead to contamination of the subsequently applied resist layers or other structures in the edge region of the wafer. Since the productivity of the manufacturing process is reduced in both cases, along with many other defects, the edge coating is removed during the Manufacturing process continuously monitored. The width of the edge stripping is checked and it is checked whether edge stripping has taken place at all.

Devices are known which recognize a wide variety of structures on the surface of a wafer by means of image recognition. The wafer is illuminated in the bright field and scanned with a camera (matrix or line scan camera).

Such an inspection machine from KLA-Tencor Corporation is described in the article "Lithography Defects: Reducing and Managing Yield Killers through Photo Cell Monitoring" by Ingrid Peterson, Gay Thompson, Tony DiBiase and Scott Ashkenaz, Spring 2000, Yield Management Solutions The wafer inspection device described there works with an incident light illumination device which examines microdefects with low contrast with bright field illumination.

In the known devices for wafer inspection, image processing cannot make a simple distinction between edge stripping (EBR) and other edges present in the image. These other edges come from previous process steps. In bright field lighting, all edges are different in color or gray value. Since the different edges partly cross or overlap, the color or the gray value of the edges also change. It is therefore very difficult or impossible with image processing to filter out the edge stripping in this way. A visual inspection by an observer does not lead to better results either, since the human eye is also unable to assign the different edges and the observed color tones or gray values to the different process steps.

It is therefore an object of the present invention to provide a device with which the edge generated by the edge coating is reliably made visible, so that it can be distinguished from other edges visible on the wafer. This object is achieved by a device for wafer inspection with an incident light illuminating device with an illuminating axis and an imaging device with an imaging axis, both of which are inclined towards one another and directed towards an area of the surface of a wafer to be inspected. An imaging plane is defined in that it is spanned by the illumination axis and the imaging axis in the bright field illumination setting of the device. According to the invention, the device is characterized in that the illumination axis is rotated out of the imaging plane by a dark field angle γ> 0 so that there is dark field illumination in the area to be inspected.

If the 0 ° setting is exceeded, a transition from bright field lighting to dark field lighting is achieved. The quality of the dark field illumination increases for larger dark field angles γ. The choice of the dark field angle γ depends in particular on the scattering behavior of the surface structure and the surface materials of the wafer or already structured or coated wafers.

With this device, it is possible to inspect particularly well, predominantly small structures on the entire wafer, which are distinguished by small differences in height compared to the background or the environment and which are not or only very poorly detectable with the bright field illumination structure known from the prior art were. For example, edge breakouts and edge irregularities of the wafer edge can be examined. Furthermore, identification codes applied to the wafer can be examined with the device according to the invention.

With the dark field illumination achieved in this way, the edge of the EWC can be reliably made visible in the edge region of the wafer, since it appears in the image as a much brighter line than the edges of previous process steps. When adjusting the device, it proves to be particularly advantageous if the illumination axis and intersect the imaging axis at the point of incidence where the imaging axis meets the wafer. However, an acceptable dark-field illumination is also generated in those cases in which the illumination axis runs somewhat outside the point of impact. It is crucial that light from the illuminated area of the wafer surface still enters the imaging beam path. The respective setting depends on the properties of the surface examined (scattering behavior, material, structures, etc.)

Likewise, the imaging plane can in principle be inclined with respect to the wafer surface. In terms of design, however, it turns out to be easier if the imaging plane is perpendicular to the wafer surface, since this makes the adjustment of the device easier.

There are also various options for aligning the imaging axis relative to the wafer. For example, the imaging axis can coincide with a wafer normal through the point of impact, that is to say that the imaging axis is collinear with the wafer normal. This clearly means that the imaging axis of the imaging device, for example a camera, is directed perpendicularly from above onto the wafer. This can also be achieved by arranging the imaging device itself laterally and the imaging beam path with the

Imaging axis is laterally coupled into the device via an optical coupling element (e.g. mirror, prisms, etc.). The imaging axis is then deflected by the coupling element in such a way that it runs collinearly with the wafer normal.

It is also possible to arrange the imaging axis inclined by an imaging angle β> 0 with respect to the wafer normal through the point of incidence. In this case, the best imaging properties are obtained when the imaging angle β is equal to the illumination angle α, the illumination angle α being defined in this embodiment of the device by the inclination of the illumination axis with respect to the wafer normal through the point of incidence. It has been shown that a good representation of the photoresist (EBR edge) previously removed from the edge in the dark field is achieved if the dark field angle γ, by which the illumination axis is rotated out of the imaging plane, preferably assumes values between 5 ° and 45 °, ie if applies 5 ° <γ <45 °.

The lighting device can be equipped with both a polychromatic and a monochromatic light source. For example, the light source can be a mercury vapor pressure lamp or a cold light source with a coupled fiber bundle for transmitting the light. The use of an LED or a laser with beam expansion is also conceivable. Both a divergent and a convergent illumination beam path can be used. In a preferred embodiment, a telecentric illumination beam path is preferred, slight deviations from the strictly telecentric beam guidance being permissible without loss of the illumination quality.

The imaging device usually consists of a lens and a camera or a camera line arranged after it, onto which the area to be inspected is imaged. Depending on the imaging scale specified by the lens, areas of different sizes can therefore be inspected with the camera image.

For the inspection of wafer defects in the area of the wafer edge, an imaging device is preferably used which comprises an objective lens and a line scan camera. An optimal dark-field representation of the lacquer edge of edge-stripped photoresist layers is achieved if the dark-field illumination is carried out by inclining the incident light illumination device from the central region of the wafer in the direction of the wafer edge.

Alignment marks on the wafer or striking edge structures, such as the so-called Fiat or Notch, can be used as a reference point for localizing observed defects. For simplification, however, the wafer edge itself is preferably used. In order to make this wafer edge more visible, a particularly advantageous embodiment is used the device, a wafer underside illumination device is additionally arranged, which is positioned below the wafer in the region of the wafer edge. This wafer underside illumination device radiates from below beyond the wafer edge and illuminates the imaging device. In this way, a clear light / dark transition emerges in the camera image or in the camera line, which exactly reproduces the wafer edge.

In order to be able to carry out an inspection of the entire wafer edge, the wafer is placed on a holding device which can be rotated about its center. For automated inspection of the wafer edge, this pick-up device is coupled to a motor drive, which performs an exact rotation of the pick-up device. For automatic inspection of the edge area of the wafer, the device is assigned a data readout device which sequentially reads the image data of the line scan camera during the rotational movement of the wafer on the recording device. A computer, which is connected to the device, controls the motor drive and the data reading device. Alternatively, an encoder is provided that triggers the camera and / or the data readout device (e.g. frame grabber)

Various parameters or defects can then be determined with the computer from the image data recorded sequentially during the rotation of the wafer. For example, the position of the so-called wafer flat or the position of the so-called wafer notch on the wafer edge can be determined.

To determine the position and quality of the edge stripping (EBR) of the wafer, the wafer is rotated at least once by 360 °. The image data recorded sequentially during this rotation are evaluated, the brightest line in the image (or the brightest pixel in the image with a line camera) characterizing the position of the EBR edge. In contrast, the edges of previous process steps appear only as low-intensity lines or pixels of the line scan camera. From the position of the EBR edge relative to the wafer edge, which is If the lighting device is made visible, the extent of the edge stripping or its deviations from the target values relative to the wafer edge can be determined.

The device according to the invention is explained in more detail below with reference to the schematic drawings. The figures show in detail:

1: A plan view of a device for wafer inspection in the entire wafer area;

2 shows a side view of a device for wafer inspection over the entire wafer area;

3: A top view of a device for wafer inspection of the wafer edge or the edge stripping;

4: A side view of a device for wafer inspection of the wafer edge or the edge stripping;

5: A side view, rotated by 90 ° with respect to FIG. 4, of a device for wafer inspection of the wafer edge or the edge stripping;

6: A spatial arrangement of a device for wafer inspection in the area of the wafer edge or for inspection of the edge stripping.

In order to simplify the illustration, an imaging axis was selected in the examples shown below that is perpendicular to the wafer surface. This proves to be not only simpler in the drawing, but also constructive, since the device is easier to adjust.

1 shows a device 1 for wafer inspection with a wafer 2 to be inspected. The wafer 2 is placed on a receiving device 3 (covered in this illustration) which holds the wafer 2 in place by means of vacuum suction. The required vacuum is taken up by the Device 3 supplied by means of a vacuum line 4, which is connected to a vacuum system, not shown, for generating the vacuum.

An incident light illuminating device 5 is directed onto an area of the wafer 2 to be inspected and receives its light from a light source 7 via an optical fiber bundle 6. The incident light illuminating device 5 is arranged inclined with respect to the surface of the wafer 2. An imaging device 9 is arranged on a displaceable support element 8. The imaging device 9 has an imaging axis 10. At the point of impact 11 of this imaging axis 10 on the wafer 2, a wafer normal 12 is defined, that is, a construction line that is perpendicular to the wafer 2 at the point of impact 11. In the illustration, the wafer normal 12 and the point of impact 11 coincide.

In the embodiment of the device for wafer inspection shown, the imaging axis 10 is inclined with respect to the wafer normal 12, i.e. the imaging device 9 is arranged inclined to the surface of the wafer 2. As a result, the imaging axis 10 and the wafer normal 12 span a plane 13, which is represented by a broken line in the top view. This plane 13 corresponds to the imaging plane that is spanned by the imaging axis 10 and the illumination axis 14 in the bright field setting of the device.

The incident light illuminating device 5 has an illuminating axis 14, which according to the invention is inclined relative to the plane 13 by the illuminating angle α. In the illustrated embodiment of the device for wafer inspection, the illumination axis 14 strikes the wafer 2 at the point of impact 11, that is to say at the same point at which the imaging axis 10 also strikes the wafer 2. Therefore, in the present case the illumination angle α is defined as the inclination of the illumination axis 14 with respect to the wafer normal 12. The adjustment of the illumination angle α is carried out by means of the α adjustment device 24 to which the incident light illumination device is attached. The α adjustment device 24 is attached to a γ adjustment device 24, which in turn is attached to the Support rail 15 is arranged. It proves to be advantageous if the imaging angle β is equal to the illumination angle α. However, somewhat different illumination angles α and imaging angles β are still achieved in a good image.

The illumination angle α is not directly visible in FIG. 1, but is only indicated by the fact that part of the inclined housing can be seen by the incident light illumination device 5. However, it is clearly visible that the illumination axis 14 is rotated out of the plane 13 by a dark field angle γ by rotation about the wafer normal 12.

By suitable choice of the dark field angle γ> 0, dark field illumination is generated in the area to be inspected on the surface of the wafer 2. The dark field angle γ is adjusted by means of the γ adjusting device 24, which allows the incident light illumination device 5 to be pivoted about the wafer normal 12. Tests have shown that basically setting the dark field angle γ in the range 0 ° <γ <50 ° achieves dark field illumination. Particularly good dark field settings can be obtained by choosing the dark field angle γ with angular positions in the range 10 ° <γ <25 °. In the present exemplary embodiment, a dark field angle γ = 20 ° was selected.

In order to be able to inspect different areas of the wafer 2, the

Imaging device 9 can be moved over the wafer surface by moving the support element 8. Since the imaging device 9 and the illumination device 5 are rigidly connected to one another via a common, adjustable mounting rail 15, the entire device 1 is moved over the surface of the wafer 2 to the desired area to be inspected by moving the mounting element 8. In order to make it easier to locate any areas of the wafer surface of the wafer 2 that are to be inspected, the wafer 2 is additionally rotatably mounted on the holding device 3 (not shown). The rotary movement is symbolically indicated by a curved double arrow. Usually lies the Wafer 2 firmly on the receiving device 3 by vacuum suction, and the receiving device 3 itself is rotatable.

By suitable displacement of the support element 8, the incident light illuminating device 5 and the imaging device 9 can thus be displaced together and any areas on the wafer 2 to be inspected can therefore be examined. The respectively recorded image data of the imaging device 9, which consists, for example, of a lens and a camera, are transmitted to a data readout device 17 via a data line 16.

2 shows a side view of a device 1 for wafer inspection. On the lower part of a stand 20 there is a holding device 3 on which a wafer 2 is placed. The receiving device 3 is supplied with vacuum by means of a vacuum line 4, so that the wafer 2 can be sucked in. The receiving device 3 is rotatable about its vertical axis, which is indicated by a double arrow. In this way, the wafer 2 can also be rotated.

An imaging device 9 consisting of an objective 18 and a camera 19 is directed onto an area of the surface of the wafer 2 to be inspected. The imaging device 9 has an imaging axis 10 which is inclined with respect to the surface of the wafer 2 and which

Wafer surface hits point 11. A construction line that is perpendicular to the surface of the wafer 2 at this point of impact 11 is defined as the wafer normal 12. The inclination of the imaging axis 10 with respect to this wafer normal 12 defines the imaging angle β.

An incident light illuminating device 5 is also directed onto the area of the wafer surface to be inspected. The incident light illuminating device 5 has an illuminating axis 14 which is inclined by an illuminating angle α with respect to the wafer normal 12. It should be noted that the imaging axis 10 and the wafer normal 12 span a plane 13 which corresponds in the illustration to the plane of the drawing. This level 13 corresponds to the mapping level that in Bright field setting of the device can be spanned by the imaging axis 10 and the illumination axis 14.

Since the illumination axis 14 of the incident-light illumination device 5 is rotated out of this plane 13 by the dark field angle γ, as shown in FIG. 1, the illumination angle α drawn in FIG. 2 does not correspond to the actual illumination angle to scale. Rather, the illumination angle α shown in the plane of the drawing is shortened by projecting the actual spatial position of the illumination axis 14.

The incident light illuminating device 5 is attached to the device by means of the γ adjusting device 25 and the imaging device 9 is attached to it by means of an adjusting rail 21

Support rail 15 is arranged, which is rigidly connected to the support member 8. In the advantageous embodiment of the device shown here, the spatial position of the imaging device 9 can be varied and determined by means of the adjusting rail 21, so that different imaging angles β can be set.

By a suitable choice of the illumination angle α and the dark field angle γ, the user of the device can therefore adapt the dark field illumination to his particular problem, e.g. B. adapt to the size, height or optical properties (such as contrast, reflectivity, etc.) of the structures to be investigated. This makes it particularly easier to examine low-contrast structures than with previously known bright-field lighting devices.

The mounting rail 15 with the imaging device 9 attached to it is rigidly connected to a displaceable mounting element 8 which is attached to the vertical part of the stand 20. The incident light illumination device 5 is arranged on a γ adjustment device (not shown here), which is also rigidly connected to the support element 8. The support element 8 is horizontally displaceable, so that the unit consisting of incident light illuminating device 5 and imaging device 9 can be displaced together. In this way, the impact point 11 and thus the dark field area can be positioned on any areas of the surface of the wafer 2 to be inspected by moving the support element 8. In order to make it easier to find desired areas to be inspected, the wafer 2 can be rotated about a vertical axis by means of the rotatable receiving device 3. The image data generated by the camera during the inspection are transmitted to a data readout device 17 via a data line 16. There they stand for further processing and evaluation, e.g. B. using a computer.

FIG. 3 shows a top view of a device 1 for wafer inspection, in which the area to be inspected lies in the area of the wafer edge.

The wafer 2 is placed on a receiving device 3 (hidden in this illustration), which holds the wafer 2 in place by means of vacuum suction. The required vacuum is fed to the receiving device 3 by means of a vacuum line 4.

An incident light illuminating device 5 is directed onto the area of the wafer edge 23 of the wafer 2 to be inspected, which device receives its light via a light guide bundle 6 from a light source 7. The incident light illuminating device 5 is arranged inclined with respect to the surface of the wafer 2. An imaging device 9 is arranged on a displaceable support element 8 by means of a support rail 15. The imaging device 9 has an imaging axis 10. At the point of impact

11 of this imaging axis 10 on the wafer 2, the wafer normal 12 is defined, that is, a construction line that is perpendicular to the wafer 2 at the point of impact 11. The wafer standards fall in the illustration shown here

12 and the point of impact 11 on each other. An optimal dark field representation of the lacquer edge of edge-stripped photoresist layers is achieved in that the incident light illuminating device 5 is directed from the central region of the wafer 2 in the direction of the wafer edge 23.

In the embodiment of the device for wafer inspection shown, the imaging axis 10 is around the normal to the wafer 12 Imaging angle β inclined, ie the imaging device 9 is arranged inclined with respect to the surface of the wafer 2. As a result, the imaging axis 10 and the wafer normal 12 span a plane 13, which is represented by a broken line in the top view. This plane 13 corresponds to the imaging plane that is spanned by the imaging axis 10 and the illumination axis 14 in the bright field setting of the device.

The incident light illuminating device 5 has an illuminating axis 14 which, according to the invention, is inclined by the illuminating angle α relative to the wafer normal 12 and rotated out of the plane 13 by the dark field angle γ. In the illustrated embodiment of the device for wafer inspection, the illumination axis 14 strikes the wafer 2 at the point of impact 11, that is to say at the same point at which the imaging axis 10 also strikes the wafer 2. Therefore, in the present case the illumination angle α is defined as the inclination of the illumination axis 14 with respect to the wafer normal 12. In the example shown, the illumination angle α is equal to the imaging angle β. The illumination angle α is not directly visible in FIG. 3, but is only indicated by the fact that a part of the inclined housing can be seen by the incident light illumination device 5. However, it is clearly visible that the illumination axis 14 is rotated out of the plane 13 by a dark field angle γ.

By suitable choice of the dark field angle γ> 0, dark field illumination is generated in the area to be inspected on the surface of the wafer 2. The dark field angle γ is set by means of the γ adjusting device 25, which allows the incident light illuminating device 5 to be pivoted about the wafer normal 12.

Experiments have shown that basically setting the dark field angle γ in the range γ> 0 ° achieves dark field illumination. If the 0 ° setting is exceeded, a transition from bright field lighting to dark field lighting is achieved. The quality of the dark field illumination increases for larger dark field angles γ. A good Structures in the dark field are obtained by selecting the dark field angle γ with angular positions in the range 5 ° <γ <40 °. In the present exemplary embodiment, a dark field angle γ = 20 ° was selected.

With the configuration of the device for wafer inspection described here, in particular the edge region of the wafer 2 and thus also the

Edge stripping of photoresist layers can be checked. The position of the outer edge of the photoresist layer remaining after the edge removal has been determined. The position of the edge of this lacquer layer is given relative to a reference point. For example, the position of this edge in the camera image can be specified in relation to the first pixel of the image or to the first pixel of the respective image line. Alternatively, it is conceivable to choose a mechanical stop for the wafer support or possibly an additional alignment mark on the wafer 2 as a reference point.

However, it has proven to be particularly advantageous to specify the position of the photoresist edge relative to the wafer edge 23. This requires an exact determination of the wafer edge 23 of the wafer 2 in the image of the imaging device 9. This can be difficult with low-contrast images.

For this purpose, the embodiment shown in FIG. 3 has an additional underside illumination device 22, which is arranged below the wafer 2 in its edge region. The background illumination of the underside of the wafer 2 generated in this way produces a striking light / dark transition in the camera image along the wafer edge 23 shown. The wafer underside illumination device 22 thus provides an exact representation of the wafer edge 23 in the image. The edge of the edge-stripped photoresist is then determined by determining the brightest line in the image, in each case based on the image of the wafer edge 23. The distance from the edge of the lacquer to the wafer edge 23 is then a measure of the edge stripping. In addition, it can be checked whether the edge stripping has taken place or whether it has been completed. The measured values of the edge stripping can then be made using the semiconductor manufacturers' target production specifications be compared. In the event of deviations, the manufacturing processes can be adapted accordingly to ensure an optimal yield in the manufacturing process.

FIG. 4 shows a side view of a device for wafer inspection, as has already been shown in FIG. 3.

On the lower part of a stand 20 there is a holding device 3 on which a wafer 2 is placed. The receiving device 3 is supplied with vacuum by means of a vacuum line 4, so that the wafer 2 can be sucked in. The receiving device 3 is rotatable about its vertical axis, which is indicated by a double arrow. In this way, the wafer 2 is also rotated.

An imaging device 9 consisting of an objective 18 and a camera 19 is directed onto an edge region of the surface of the wafer 2 to be inspected. The imaging device 9 has an imaging axis 10 which is inclined with respect to the surface of the wafer 2 and which

A reflected light illuminating device 5 is also directed onto the edge region of the wafer surface to be inspected. The incident light illuminating device 5 has an illuminating axis 14 which is inclined by an illuminating angle α with respect to the wafer normal 12. In the present embodiment of the device, the illumination angle α is equal to the imaging angle β.

It should be noted that the imaging axis 10 and the wafer normal 12 span a plane 13 which corresponds in the illustration to the plane of the drawing. This plane 13 corresponds to the imaging plane that is spanned by the imaging axis 10 and the illumination axis 14 in the bright field setting of the device. Since the lighting axis 14 of the incident light illuminating device 5 is rotated out of this plane 13 by a dark field angle γ, as shown in FIG. 1, the illuminating angle α drawn in FIG. 4 does not correspond to the actual illuminating angle α to scale. Rather, the illumination angle α shown in the plane of the drawing is shortened by projecting the actual spatial position of the illumination axis 14.

As already described for FIG. 3, dark field illumination is generated on the surface of the wafer 2 by a suitable choice of the dark field angle γ> 0 in the edge region to be inspected. This allows the user of the device to adjust the dark field lighting to his particular problem, e.g. B. adapt to the size, height or optical properties (such as contrast, reflectivity, etc.) of the structures to be examined. This makes it particularly easier to examine low-contrast structures than with previously known bright-field lighting devices.

The incident light illuminating device 5 is arranged by means of a γ adjusting device (not shown here) and the imaging device 9 is arranged on the mounting rail 15 by means of an adjusting rail 21, which is rigidly connected to the mounting element 8. In the advantageous embodiment of the device shown here, the spatial position of the

Imaging device 9 can be varied and determined by means of the adjusting rail 21, so that different imaging angles β can be set.

The support rail 15 is arranged on a displaceable support element 8 which is fastened to the vertical part of the stand 20. The support element 8 is horizontally displaceable, so that the unit consisting of incident light illuminating device 5 and imaging device 9 can be displaced together.

By horizontal displacement of the support element 8, the point of impact 11 and at the same time the illumination area can be positioned on any edge areas of wafer 2 to be inspected or on differently sized areas Wafer diameter can be adjusted. In order to make it easier to find desired edge regions to be inspected, the wafer 2 can additionally be rotated about a vertical axis by means of the rotatable receiving device 3. The image data generated by the camera during the inspection are transmitted to a data readout device 17 via a data line 16. There they are available for further processing and evaluation, for example by means of a computer (not shown).

In the illustration chosen here, it is clearly visible that the underside illumination device 22 is arranged below the wafer 2 and at the same time on the imaging axis 10. The wafer underside illumination device 22 is thus positioned under the wafer 2 in such a way that it is imaged directly on the camera 19. For the inspection of the wafer edge, it proves to be advantageous if a line camera is used as the camera 19 and an LED line with a Fresnel lens in front is used as the wafer underside illumination device 22. By exact adjustment of the LED line under the wafer 2, it is possible that it is imaged directly and in exact alignment on the line of the line camera 19.

A wide variety of lenses 18 can be used in combination with the camera 19, both telecentric and non-telecentric lenses. An example of a non-telecentric lens is the Rodagon® 1: 4/60 mm lens from Rodenstock, Germany, with a focal length F = 60 mm, an object field of approx. 0.028 mm x 57 mm, magnification M = 1: 2 , An example of a telecentric lens is the Sill S5LPJ2005 lens, from Sill Optics, Wendelstein, Germany.

By choosing the lens and the magnification, various parameters can be optimized for the application. If necessary, filters and diaphragms (not shown) have to be inserted into the beam path to optimize dark field lighting.

The example of a device for wafer inspection described here has a polychromatic cold light source with fiber optics and a telecentric beam path as incident light illumination device 5. An easy to Adjusting structure results from the fact that the illumination angle α is chosen equal to the imaging angle β. In principle, however, this is not necessary for the design of good dark field illumination of the area to be inspected on the wafer 2, since good dark field illumination is also achieved for other angular relationships.

A complete inspection of the entire wafer edge 23 or of the paint edge located in its vicinity (after edge removal) is carried out by positioning the line camera 19 in relation to the surface of the wafer 2 in such a way that an edge region which runs radially on the wafer 2 is imaged on the camera line becomes. In this arrangement, the imaging particle is preferably β> 0 °, as shown in the illustration.

To inspect the entire wafer edge 23, the wafer 2 is rotated about its vertical axis of rotation by rotating the receiving device 3. During a 360 ° rotation, the data readout device 17, for example a computer with a frame grabber, reads the line camera of the wafer 2 several times, e.g. at equal intervals. The image data are then evaluated using special software and the position of the photoresist edge in relation to the wafer edge 23 is determined from each. The position of the wafer flat or wafer notch can also be determined using the same method.

FIG. 5 shows the device for wafer inspection shown in FIG. 4 in a side view, which is rotated through 90 °. The same device elements are designated by the same reference numerals.

An imaging device 9 and a lighting device 5 arranged inclined according to the invention are on an area to be inspected

Wafers 2 directed in the region of its wafer edge 23. The positioning of the underside illumination device 22 below the wafer edge 23 is clearly visible. The underside illumination device 22 is oriented such that it illuminates the wafer 2 from below and radiates beyond its wafer edge 23. The light radiating beyond the wafer edge 23 is detected by the imaging device 9, so that the edge of the wafer edge 23 appears in the generated image as a striking light / dark transition. The evaluation then takes place as already described in FIG. 4.

FIG. 6 shows a spatial arrangement of a device for wafer inspection, as has already been described in FIGS. 3, 4 and 5. Same

Device elements are designated with the same reference numbers. Here, too, the imaging device 9 and the incident light illuminating device 5 inclined according to the invention are directed at an area of the wafer 2 to be inspected in the area of its wafer edge 23. A wafer underside illumination device 22 illuminates the wafer 2 from below. The image data recorded by the imaging device 9 are transmitted to a data readout device 17 via a data line 16. In the present example, this is designed as a computer.

The device for wafer inspection according to the invention can be installed as a separate inspection unit in the manufacturing process. However, it is also conceivable to integrate the device according to the invention into an already existing wafer inspection system. For this purpose, for example, an automated handling device for the semi-automatic or fully automatic placement and removal of wafers 2 to be examined is provided in the device.

LIST OF REFERENCES

1) Device for wafer inspection 23)

24) -α adjustment device

2) wafer

25) -γ adjustment device

3) Recording facility

4) Vacuum line

5) incident light .alpha. = Illuminating angle illuminating device .beta. = Imaging angle

6) Optical fiber bundle γ = dark field angle

7) light source

8) sliding support element

9) Imaging facility

10) mapping axis

11) Impact point

12) Wafer standards

13) Mapping level

14) Illumination axis

15) mounting rail

16) Data line

17) Data readout device

18) lens

19) camera

20) tripod

21) Adjustment rail

22) -Wafer underside lighting device

Claims

claims

) Device for wafer inspection with an incident light illumination device with an illumination axis and an imaging device with an imaging axis, both of which are inclined towards one another and onto an area to be inspected

Surface of a wafer are directed, wherein an imaging plane is defined in that it is spanned by the illumination axis and the imaging axis in the bright field illumination setting of the device, characterized in that the illumination axis is rotated out of the imaging plane by a dark field angle γ> 0 so that there is dark field illumination in the area to be inspected.

2) Device according to claim 1, 'characterized in that the illumination axis and the imaging axis intersect at the point of incidence of the imaging axis on the wafer.

3) Device according to claim 1, characterized in that the imaging plane is orthogonal to the wafer surface.

4) Device according to claim 2, characterized in that the imaging plane is orthogonal to the wafer surface and the illumination axis and the imaging axis intersect at the point of incidence of the imaging axis on the wafer. 5) Device according to claim 4, characterized in that a wafer normal is defined by the point of incidence with which the imaging axis is collinear.

6) Device according to claim 4, characterized in that the imaging axis is inclined by an imaging angle β> 0 with respect to the wafer normal through the point of incidence.

7) Device according to claim 6, characterized in that the inclination of the illumination axis with respect to the wafer normal defines an illumination angle α by the point of impact and that the imaging angle β is equal to the illumination angle α.

8) Device according to one of claims 1 to 7, characterized in that the dark field angle γ assumes values in the range 0 ° <γ <50 °.

9) Device according to one of claims 1 to 8, characterized in that the dark field lighting by tilting the

Incident light illumination device from the central area of the wafer in the direction of the wafer edge

10) Device according to one of claims 1 to 9, characterized in that the lighting device comprises a polychromatic light source.

11) Device according to one of claims 1 to 9, characterized in that the lighting device comprises a monochromatic light source. 12) Device according to one of claims 1 to 9, characterized in that the imaging device comprises a lens and a camera.

13) Device according to one of claims 1 to 9, characterized in that the imaging device a lens and a

Line scan includes.

14) Device according to claim 12, characterized in that the area to be inspected is located on the wafer edge and that below the wafer edge an additional wafer underside illumination device is arranged, which extends from below to the wafer edge

Imaging device illuminated.

15) Device according to claim 13, characterized in that a receiving device is provided for placing the wafer, which is rotatable about its vertical axis.

16) Device according to claim 14, characterized in that the receiving device is associated with a motor drive for rotating the receiving device.

17) Device according to one of claims 14 or 15, characterized in that it is assigned a data readout device which the image data of the line camera during the rotary movement of the

Reads wafers sequentially, and that a computer is connected to the device that controls the data readout device.

18) Device according to claim 16, characterized in that the computer after a rotation of the wafer by at least 360 ° from the sequentially recorded image data, the quality and / or the size or position of the edge of edge-stripped photoresist layers, the so-called EBR, relative to Wafer edge determined. 19) Device according to claim 16, characterized in that the computer determines the position of the so-called Fiats on the wafer edge from the sequentially recorded image data.

20) Device according to claim 16, characterized in that the computer determines the position of the so-called notch on the wafer edge from the sequentially recorded image data.