EP1532479A1

EP1532479A1 - Device and method for inspecting an object

Info

Publication number: EP1532479A1
Application number: EP03792406A
Authority: EP
Inventors: Franz Cemic; Lambert Danner; Uwe Graf; Robert Mainberger; Dirk SÖNKSEN; Volker Knorz
Original assignee: Leica Microsystems CMS GmbH; Vistec Semiconductor Systems GmbH
Current assignee: Leica Microsystems CMS GmbH
Priority date: 2002-08-23
Filing date: 2003-08-21
Publication date: 2005-05-25
Also published as: US20050259245A1; AU2003253422A1; WO2004019108A1; US7271889B2; DE10239548A1; JP2005536732A

Abstract

The invention relates to a device and method for inspecting an object (2) involving the use of a bright field illumination beam path (4) of a bright field light source (5), said beam path being formed so that it passes through the projection optics (3), and involving the use of a dark field illumination beam path (6) of a dark field light source (7), this beam path being formed so that it also passes through the projection optics (3). The object (2) can be projected by the projection optics (3) onto the least one detector (8), and the object (2) is simultaneously illuminated by both light sources (5, 7). In order to simultaneously detect bright field images and dark field images without involving complicated filtering operations, the inventive device or method for inspecting an object (2) is characterized in that the light used for the dark field illumination is pulsed and in that the pulse intensity of the light used for the dark field illumination is greater by at least one order of magnitude than the intensity of the continuous light, which is used for the bright field illumination, during a pulsed interval.

Description

Device and method for inspecting an object

The present invention relates to a device and a method for inspecting an object, with a bright-field illumination beam path of a bright-field light source designed with respect to imaging optics, with a dark-field illumination beam path of a dark-field light source designed with respect to the imaging optics, the object with the imaging optics being at least a detector is imaged and the object is simultaneously illuminated by the two light sources.

Devices of the generic type have been known for some time. In optical inspection technology in particular, complex structures on flat substrates are inspected frame by frame. This is particularly the case in the semiconductor industry for the optical examination of structured surfaces of masks and wafers. Here, for example, existing defects are to be detected or classified. Defects can include, for example, dust grains, bubbles in the resist, resist residues on wafers, breakouts from edges or scratches.

A microscope with a Koehler bright field illumination can serve as the device, for example. Thus, with regard to the microscope objective - that is to say the imaging optics and possibly the effective detector area - bright field illumination is formed by the Köhler illumination. Dark field illumination can be implemented in a known manner in a microscope, for example by using a dark field microscope objective. In such a lens, the light serving for dark field illumination is guided between the imaging optics for the bright field imaging and a mirrored lens housing in such a way that it is directed onto the lens in an angular range or aperture range Object strikes that lies outside the numerical aperture of the imaging optics for the bright field imaging. To determine the brightfield or darkfield illumination beam path, the effective detection area of the detector or the entire detection beam path running between the object and the detector may need to be taken into account, in particular if the aperture areas of the brightfield and darkfield illumination beam paths are almost adjacent to one another.

Experience has shown that detection of raised and lowered structures with bright field lighting alone is not possible or only to a limited extent. For this reason, an additional inspection has been carried out, which is carried out with the aid of dark field lighting provided in the device. This type of illumination is particularly suitable for the detection of the raised and lowered structures, and these structures can be defective structures. With dark field illumination, planar structures remain invisible. Elevated structures, on the other hand, appear rich in contrast as bright lines on a dark background. Irregularities in these lines indicate possible defects.

From DE 199 03 486 A1 a method for simultaneous brightfield and darkfield illumination is known, in which at least one of the two bundles of rays uses the color - i.e. the wavelength of light -, polarization or modulation, i.e. Amplitude or frequency modulation is encoded. The bright field image is separated from the dark field image by means of appropriate filters or detector devices.

Furthermore, from DT 2 021 784, DE 23 31 750 C3 and DE 37 14 830 A1 illumination devices for microscopes are known, in which it is possible to switch between bright field and dark field illumination. No simultaneous brightfield-darkfield illumination is provided here.

A combined brightfield and darkfield illumination with two light sources is known from EP 0 183 946 B1, in which one

Switching from bright field to dark field lighting via mechanical Shutters are made, which are each assigned to a light source. It is also provided here that both types of lighting are used simultaneously, that is to say both shutters are open. In this mode, however, the dark field image is outshone by the bright field image, so that a simultaneous detection of an object with both lighting modes is not possible.

Thus, the lighting systems known from the prior art are either not suitable for simultaneous brightfield and darkfield illumination or simultaneous illumination in both modes is possible, but the images obtained in this way cannot be used or can only be separated from one another with increased effort.

The present invention is therefore based on the object of specifying and developing a device and a method for inspecting an object in such a way that simultaneous detection of brightfield and darkfield images is possible, without the need for complex filtering operations.

The device according to the invention for inspecting an object achieves the above object by the features of patent claim 1. According to this, such a device is characterized in that the light used for dark field illumination is pulsed and that the pulse intensity of the light used for dark field illumination is greater than at least one order of magnitude the intensity of the continuous light used for bright field illumination related to a pulse interval.

According to the invention, it was first recognized that the luminous efficacy is very different in brightfield illumination and darkfield illumination. With bright field illumination, the light reflected on the object is almost exclusively detected, whereas with dark field illumination, almost exclusively the light scattered on the object is detected. The intensity ratios in a simultaneous detection are therefore very different, for example 100: 1 or 1000: 1. In a manner according to the invention, the pulse intensity of the light used for dark field illumination is therefore chosen to be at least one order of magnitude greater than that on one Pulse interval-related intensity of the continuous light used for bright-field illumination, specifically based on the intensity ratios of the light of the two light sources on the object or in the object plane of the imaging system. As a result, the intensity of the light scattered by the dark field illumination on the object can be compared in a particularly advantageous manner or at least in the same order of magnitude as the intensity of the light reflected by the bright field illumination on the object, so that the properties, for example the dynamic range, of one or more detectors are not increased Requirements must be made.

In a further manner according to the invention, the light serving for dark field illumination is pulsed. Strictly speaking, simultaneous illumination by the two light sources is therefore only given when the pulsed light from the dark field light source illuminates the object. As a result, however, the provision of shutters in the illumination beam paths is not necessary in a very particularly advantageous manner, since either only bright field illumination or simultaneous bright field and dark field illumination is present quasi-continuously. To this extent, object image data can be continuously detected with the detector or with a detector system having a detector, wherein only bright field images of the object and bright field images together with dark field images of the object can be detected or evaluated in accordance with the chronological sequence of the lighting conditions. In principle, the pulse repetition frequency of the dark field light source can be adapted to the readout characteristic of the detector.

A light source can be used as the dark field light source, the light output of which, in relation to continuous operation, does not have to be 10 or 1000 times as high as that of the continuously operated light source for bright field illumination. The light output to be provided by the dark field light source relates to the output of the individual pulses. According to the invention, this light output is to be selected at least one order of magnitude larger than the intensity of the continuous light serving for bright field illumination, based on a pulse interval. The dark field image of the object is only due to this high intensity of the dark field light pulses Simultaneous bright field illumination without additional filters or similarly separating detection devices, but can be detected directly from the captured image. In contrast, in the previously known devices, additional filters, demodulation means, etc. were always required in order to separate the dark field image from the bright field image. Suitable light sources, which can be used as dark field light sources, are advantageously available on the market in a large selection and in some cases inexpensively. For example, a xenon flash lamp, a laser or an LED can be used as dark field light sources.

Specifically, the pulse intensity of the light used for dark field illumination is 10 to 10,000 times greater than the intensity of the continuous light used for bright field illumination related to a pulse interval. Since in particular the intensity of the light scattered on the object depends on the object property or on the property of the object surface, the intensity ratio of the two light sources can be selected depending on the object to be inspected, in particular the type of objects to be inspected, e.g. for masks for the semiconductor industry. Ultimately, the intensity of the continuously operating bright-field light source for bright-field illumination will be selected such that an optimal contrast can be achieved with the detector or with the detector system. The intensity of the pulsed dark field light source is then selected such that an optimal contrast can also be achieved in dark field illumination and that the two image data detected in the different illumination modes have an optimal intensity ratio relative to one another.

In a possible embodiment of the device, the dark field light source emits pulsed light. In this case, it is a light source that only works in the pulsed mode. Alternatively, it can also be provided that the dark field light source emits continuous light or that a partial beam of the bright field light source for the bright field illumination is coupled out for the dark field illumination beam path. The continuous light is then divided into individual pulses by means of at least one optical component. This optical component can be a shutter rotating shutter wheel, an electro-optical or an acousto-optical modulator act, the optical component being arranged in the dark field illumination beam path.

In a very particularly preferred embodiment, the readiness and / or evaluation readiness of the detector and / or the detection system is synchronized with the pulse sequence of the light serving for dark field illumination. With this measure, on the one hand, the properties of the detector and / or the detection system can be adapted to the currently prevailing lighting conditions, so that, for example, overdriving of the detector can be prevented in an advantageous manner. On the other hand, this measure allows the image data of the respective lighting mode to be assigned to the individual lighting modes with the aid of the detection system and / or an evaluation system connected downstream of the detection system, so that a targeted image data evaluation can take place which takes into account the respective characteristics of the detected images.

Specifically, the synchronization can take place on the basis of a pulse sequence signal from the dark field light source or on the basis of a control signal from the optical component. If the pulsed dark field light source has a trigger output that outputs a corresponding trigger signal when a light pulse is emitted, this signal can be used to synchronize the detector or the detection system. As an alternative to this, synchronization would be possible, for example, by detection of the pulse sequence of the dark field light source on the basis of a partial beam which is blocked out by the dark field light source and is directed onto a photodiode. The output signal of this photodiode can then be used for synchronization. If a continuously operating light source is used as the dark field light source and this light is divided into individual pulses by means of an optical component, the control signal of the optical component can serve as a synchronization signal for the detector and / or for the detection system. Furthermore, a delay circuit can be provided for synchronization with which For example, electronic time differences or temporal offsets can be compensated.

In a preferred embodiment, the optical axis of the bright field illumination beam path is essentially perpendicular to the surface of the object to be inspected or is essentially perpendicular to the object plane of the imaging optics. This condition is met, for example, in the case of an inspection system in the form of a microscope in that the microscope has a Köhler illumination system, since the optical axis of the bright-field illumination beam path is essentially perpendicular to the object plane of the imaging optics. If objects with essentially planar surface structures are to be inspected with the inspection system - for example wafers or masks for the semiconductor industry - the object to be inspected is expediently aligned and / or positioned such that its surface is arranged perpendicular to the optical axis of the bright field illumination beam path is. When inspecting at least partially transparent masks for the semiconductor industry, bright field illumination in transmitted light mode is also conceivable, the optical axis of the bright field illumination beam path then also being essentially perpendicular to the surface of the object to be inspected.

In another embodiment, the optical axis of a detection beam path running between the object and the detector is essentially perpendicular to the surface of the object to be inspected. To this extent, this can be an arrangement of the detection beam path, such as is present in a conventional microscope. The bright field illumination beam path can thus overlap in regions with the detection beam path or can run coaxially.

The optical axis of the dark field illumination beam path can be arranged at least in regions coaxially to the optical axis of the bright field illumination beam path and / or coaxially to the optical axis of the detection beam path. This is particularly the case when an inspection device designed as a microscope is used Dark field objective is used, wherein the illumination beam paths of the two light sources can be arranged in a similar manner, as is known for example from EP 0 183 946 B1.

In a preferred embodiment, the optical axis of the dark field illumination beam path has an angle between 5 and 90 degrees to the optical axis of the bright field illumination beam path and / or to the optical axis of the detection beam path. This is, for example, an arrangement of the kind known from FIG. 5 from DE 199 03 486 A1, the dark field illumination beam path thus being guided past the microscope objective on the object side, so to speak. The angle between the optical axis of the dark-field illumination beam path and the optical axis of the bright-field illumination beam path can be set in a particularly advantageous manner in such a way that optimal results are achieved in the detection of the images that are recorded with the dark field illumination. Thus, the angle setting can be changed depending on the object structures to be detected. This can be achieved, for example, by the optical components of the dark field illumination beam path; if necessary, the illumination aperture of the dark field illumination can also be varied and a further adaptation to the object structures to be detected can thus be carried out.

In principle, it is conceivable that the light from the bright field light source and / or the dark field light source has a coding. The technology known from DE 199 03 486 A1 is combined with the device according to the invention. Under certain circumstances, this can result in advantages in the image data evaluation if, for example, the pulsed light of the dark field light source has a wavelength of 488 nm, the light of the bright field light source has a wavelength of 365 nm and the detector comprises a color CCD camera. Then the detected image data can be assigned to the respective lighting mode solely in terms of color information during data evaluation. In general, the coding can be done by polarization, amplitude, frequency, pulse frequency modulation and / or be formed by the selection of a wavelength or a wavelength range.

A white light source, preferably a direct current lamp, can serve as the bright field light source. Usually, xenon, high-pressure mercury lamps or other arc lamps in direct current operation are used for inspection devices for the inspection of wafers and masks for the semiconductor industry, corresponding color filters or reflection filters being able to filter out all but one wavelength of the emission spectrum of the light source, which is then used for object illumination. Lasers or LEDs (light-emitting diodes) that emit continuous light are also conceivable.

The dark field light source can be configured as a xenon flash lamp, a laser or an LED or LED arrangement, the dark field light source emitting pulsed light. The pulse durations of the pulses of the dark field light source to be used are usually in a range from 1 ms to 0.01 ms, but preferably 0.1 ms. The pulse power of the individual pulses is typically of the order of 1 watt.

In a preferred embodiment, the detector comprises a CCD camera, wherein a monochrome and / or a color CCD camera can be used. With a monochrome CCD camera, the spatial resolution is generally higher than with a color CCD camera. A monochrome CCD camera is preferably used in particular for inspection devices and for coordinate measuring devices for inspecting or measuring coordinates of wafers and masks in the semiconductor industry, where high spatial resolution is required. In particular, the CCD camera control can be synchronized with the pulse sequence signal of the dark field light source with regard to the detection or readout behavior of the CCD camera.

Basically, the device according to the invention is coupled to a control computer. This control computer usually not only controls an automatic image data acquisition of several automatically inspected ones Objects, but also has a storage unit on which the detected object data or extracted measurement results are stored and / or evaluated.

In procedural terms, the above-mentioned object is achieved by the features of the independent claim 17. Accordingly, in the method for inspecting an object, the object is simultaneously illuminated on the one hand with a bright field light source for bright field illumination and on the other hand with a dark field light source for dark field illumination, and the object is imaged on at least one detector using imaging optics. The method according to the invention for inspecting an object is characterized in that the light used for dark field illumination is pulsed, the pulse intensity of the light used for dark field illumination being at least one order of magnitude greater than the intensity of the non-pulsed light used for bright field illumination related to a pulse interval.

The method according to the invention is preferably used to operate a device according to one of the claims 1 to 16. To avoid repetition, reference is made to the previous part of the description.

In a particularly preferred manner, the object inspection is carried out automatically. Thus, a program can run on a control computer assigned to the device, after which different predetermined areas of the object are detected. For this purpose, the device can be coupled to a positioning system which positions the object relative to the imaging optics and is preferably also controlled by the control computer. Furthermore, it is conceivable to automatically feed several objects to the device - for example via a loading robot - and to detect object by object fully automatically in each case. The control computer can further comprise a program module with which the detected image data can be evaluated with regard to possible defects of the respective object. In general, methods of digital image processing can be used, with a comparison of the detected object areas can be provided with a known calibration object. For documentation or logging of the detected defects, the corresponding image areas of the respective object or only their coordinates can be stored on the storage unit of the control computer.

There are now various possibilities for advantageously designing and developing the teaching of the present invention. For this purpose, on the one hand, reference should be made to the claims subordinate to claims 1 and 17 and, on the other hand, to the following explanation of the preferred exemplary embodiments of the invention with reference to the drawing. In connection with the explanation of the preferred exemplary embodiments of the invention with reference to the drawing, generally preferred refinements and developments of the teaching are also explained. The drawing shows:

1 shows a schematic illustration of a first exemplary embodiment of a device according to the invention,

2 shows a schematic illustration of a second exemplary embodiment of a device according to the invention,

3a shows a schematic representation of a diagram of the temporal

The course of the light intensities of the illuminating light of the bright-field light source and the dark-field light source at the location of the object in the exemplary embodiment from FIG. 2,

Fig. 3b is a schematic representation of a diagram of the temporal

The course of the light intensities of the light of the bright-field light source and the dark-field light source reflected and scattered at the object at the location of the detector in the exemplary embodiment from FIG. 2, Fig. 3c is a schematic representation of a diagram of the temporal

The course of the light intensities of the light from the bright field light source and the dark field light source reflected and scattered at the object at the location of the detector in the exemplary embodiment from FIG. 2, wherein another object was detected and

Fig. 4 is a schematic representation of a diagram of a time course of a light pulse of the dark field light source and a detection interval of the detector.

1 and 2 show a schematic representation of a device 1 for inspecting an object 2. This device 1 is an optical inspection device with which masks and wafers for the semiconductor industry can be examined in particular for defects. The device 1 has a bright-field illumination beam path 4 of a bright-field light source 5 that is designed with respect to imaging optics 3. With regard to the imaging optics 3, a dark field illumination beam path 6 of a dark field light source 7 is also provided. The object 2 is imaged on the detector 8 with the imaging optics 3, the detection beam path 9 running from the object 2 to the detector 8. Object 2 is illuminated simultaneously by the two light sources 5 and 7.

According to the invention, the light from the dark field light source 7 serving for dark field illumination is pulsed. FIG. 3a shows a schematic diagram of the logarithm of the light intensities of the two light sources 5 and 7 (Ig I) in arbitrary units as a function of the time t. Here, the temporal intensity curve relates to the illumination intensity curve of the light of the two light sources 5 and 7 present on the object 2. For the sake of simplicity, the temporal intensity curve 10 of only one light pulse of the dark field light source 7 is shown. The temporal intensity profile of the bright field light source 5 is shown with reference number 11. The bright field light source 5 emits continuous light of a constant intensity. The diagram from FIG. 3a shows that the pulse intensity 11 of the light used for dark field illumination is approximately two orders of magnitude greater than that related to the pulse interval Intensity 12 of the continuous light used for bright field lighting. Thus, the pulse intensity 11 of the light used for dark field illumination in this exemplary embodiment is approximately 100 times greater than the intensity 12 of the continuous light used for bright field illumination related to a pulse interval. This has the advantage that the dark field image can be separated from the bright field image without additional aids, such as filters, because it appears brighter directly on the detector 8 than the bright field image itself.

3b and 3c correspond to the light intensity present at the detector 8 on the one hand of the light from the bright field light source 5 reflected on the object 2 and on the other hand of the light of the dark field light source 7 scattered at the object 2. In the diagrams of FIG. 3b and 3c show the light intensities of the light of the two light sources 5 and 7 reflected or scattered on the object in arbitrary units as a function of time t. In the time intensity curve shown in FIG. 3c, the detection is based on a different object than was the case in the detected time intensity curve from FIG. 3b. 3b and 3c that the two objects differ with regard to the intensity of the scattered light component on the object surfaces.

The dark field light source 7 shown in FIG. 2 is an arc lamp that emits pulsed light. The dark field light source 7 shown in FIG. 1 is also an arc lamp, which, however, emits continuous light of a constant intensity. The light from the dark field light source 7 from FIG. 1 is divided into individual pulses after collimation by means of a lens 12 with the aid of an optical component 13 in the form of a rotating shutter wheel. The shutter wheel rotates about the axis of rotation 14 and has circumferentially arranged, translucent areas through which the light of the dark field light source 7 can pass. A, for example, circular area is masked out by the aperture 15, so that in the further course of the dark field illumination beam path 6 there is only an annular illumination cross section. The readiness for readout and evaluation of the detector 8 and of the detection system 16 arranged downstream of the detector 8 is synchronized with the pulse sequence of the light from the dark field light source 7 serving for dark field illumination. In FIG. 1, the synchronization line 17 connects the optical component 13 to the detection system 16. In FIG. 2, the synchronization line 17 connects the dark field light source 7 from FIG. 2 to the detection system 16. The optical component 13 from FIG 1 and the dark field light source 7 from FIG. 2 are provided with a trigger signal. The trigger signal of the optical component 13 can be generated, for example, by means of a light barrier (not shown). The dark field light source 7 from FIG. 2 generates a trigger signal due to its internal control. The detector 8 is connected to the downstream detection system 16 by means of the control and readout line 32. A delay circuit 18 is also provided for synchronization, the offset or delay value of which can be changed in an adjustable manner.

4 shows a schematic diagram of the temporal intensity profile 10 of a light pulse which has a half-value width of less than 0.1 ms indicated by the two arrows. The time interval 19 running from t1 to t3 characterizes the duration in which the detector 8 is in readiness for reading out for the light of the dark field light source 7 scattered on the object. In this case, the time t2 ideally lies in the middle between the start and end values t1 and t3 of the time window 19, the time t2 characterizing the center of the light pulse.

The geometric arrangement of the optical beam paths is discussed below. The bright-field illumination beam path 4 in FIGS. 1 and 2 runs from the bright-field light source 5 via the beam splitter 20 to the object 2. The light from the bright-field light source 5 is largely reflected on the beam splitter 20 in the direction of imaging optics 3.

The dark field illumination beam path 6 in FIG. 1 initially runs from the dark field light source 7 to the beam splitter 21, on which the light from the dark field light source 7 is shown in a mirrored area solid lines - is reflected in the direction of the imaging optics 3. It is shown only schematically how the light from the dark field light source 7 reflected at the beam splitter 21 is guided coaxially outside the bright field illumination beam path 4 in the direction of the object 2, with the drawing of a focusing optics required for this purpose being dispensed with. The central region of the beam splitter 21 is transparent - shown in dash-dot lines - so that the light from the bright-field light source 5 and the light scattered or reflected on the object 2 in the bright-field illumination beam path 4 or in the detection beam path 9 can pass the beam splitter 21 in this region.

The dark field illumination beam path 6 in FIG. 1 runs from the dark field light source 7 to the object 2, first via the coupling optics 22, which couple the light from the dark field light source 7 into the light guide 23. The light emerging from the light guide 23 is focused with the focusing optics 24 into the focus area of the imaging optics 3 onto the object 2.

1 and 2 that the optical axis 25 of the bright field illumination beam path 4 between the beam splitter 20 and the object 2 is perpendicular to the surface 26 of the object 2 to be inspected. At the same time, the optical axis 25 of the bright-field illumination beam path 4 is arranged perpendicular to the object plane of the imaging optics 3, which coincides with the surface 26 of the object 2 facing the imaging optics 3 and is therefore not shown separately. The optical axis 27 of the detection beam path 9 running between the object 2 and the detector 8 is likewise perpendicular to the surface 26 of the object 2 to be inspected and perpendicular to the object plane of the imaging optics 3.

The optical axis 28 of the dark field illumination beam path 6 in FIG. 1 is between the beam splitter 21 and the object 2 coaxial to the optical axis 25 of the bright field illumination beam path 4 and coaxial to the optical axis 27 of the detection beam path 9. 2 shows that the optical axis 28 of the dark field illumination beam path 6 has an angle 29 - indicated by the curved double arrow - to the optical axis 25 of the bright field illumination beam path 4 and to the optical axis 27 of the detection beam path 9.

The bright field light source 5 is a direct current lamp. The detector 8 is a CCD camera.

The detection system 16 also includes a control computer (not shown separately) with which the individual components of the device 1 are controlled. In particular, the object inspection is carried out automatically by means of a program running on the control computer. For this purpose, the detection system 16 of the device 1 is coupled via a line 31 to a positioning system 30, which is also controlled by the control computer and positions the object 1. The positioning system 30 positions the object 2 along the direction shown by the double arrow in FIGS. 1 and 2 in the positioning system 30. Furthermore, object positioning in the two opposite directions is provided perpendicular to it, that is, out of the plane of the drawing in FIGS. 1 and 2.

In conclusion, it should be pointed out that the exemplary embodiments discussed above serve only to describe the claimed teaching, but do not restrict it to the exemplary embodiments.

LIST OF REFERENCE NUMBERS

Device Object Imaging Optics Brightfield Illuminated Beam Path Brightfield Light Source Darkfield Illuminated Beam Path Darkfield Light Source Detector Detection Beam Path Time Intensity Course of a Light Pulse of (7) Time Intensity Course of Light from (5) Lens Optical Component, Rotating Shutter Wheel Rotation Axis of (13) Iris Detection System Synchronization Line Delay Switching Time Interval Beam Interval 1 beam splitter 2 coupling optics 3 optical fibers 4 focusing optics 5 optical axis from (4) 6 surface to be inspected from (2) 7 optical axis from (9) 8 optical axis from (6) 9 angles between (27) and (28) 0 positioning system 1 Line between (16) and (30) 2 control and readout line

11 Pulse intensity of a light pulse from (7) at the location of the object

12 intensity of the light from (5) at the location of the object t1 start of the time interval (19) t2 middle of the light pulse t3 end of the time interval (19)

Claims

claims

1. Device for inspecting an object (2), with a bright field illumination beam path (4) designed with respect to imaging optics (3) of a bright field light source (5), with a dark field illumination beam path (6) designed with respect to the imaging optics (3) darkfield

Light source (7), the object (2) being imaged on at least one detector (8) with the imaging optics (3) and the object (2) being simultaneously illuminated by the two light sources (5, 7), characterized in that light used for dark field lighting is pulsed and that the pulse intensity of the

Dark field illumination light is at least one order of magnitude greater than the intensity of the continuous light used for bright field illumination related to a pulse interval.

2. Device according to claim 1, characterized in that the pulse intensity of the light serving for dark field illumination 10 to

Is 10,000 times greater than the intensity of the continuous light used for bright field illumination, based on a pulse interval.

3. Device according to claim 1 or 2, characterized in that the dark field light source (7) emits pulsed light.

4. Device according to one of claims 1 to 3, characterized in that the dark field light source (7) emits continuous light which can be divided into individual pulses by means of at least one optical component (13).

5. Device according to one of claims 1 to 4, characterized in that the optical component (13) has a shutter, a rotating shutter wheel, an electro-optical or an acousto-optical modulator.

6. Device according to one of claims 1 to 5, characterized in that the readout and / or evaluation readiness of the detector (8) and / or the detection system (16) is synchronized with the pulse sequence of the light serving for dark field illumination, preferably on the basis of a pulse sequence signal the dark field light source (7) or a control signal of the optical component (13).

7. The device according to claim 6, characterized in that a delay circuit (18) is provided for synchronization.

8. Device according to one of claims 1 to 7, characterized in that the optical axis (25) of the bright field illumination beam path (4) is substantially perpendicular to the surface (26) of the object to be inspected (2) or substantially perpendicular to the object plane the

Imaging optics (3) stands.

9. Device according to one of claims 1 to 8, characterized in that the optical axis (27) of a detection beam path (9) extending between the object (2) and the detector (8) substantially perpendicular to the surface (26) of the object to be inspected ( 2) stands or is substantially perpendicular to the object plane of the imaging optics (3).

10. Device according to one of claims 1 to 9, characterized in that the optical axis (28) of the dark field illumination beam path (6) at least in regions coaxially to the optical axis (25) of the bright field illumination beam path (4) and / or coaxial to the optical

Axis (27) of the detection beam path (9).

11. The device according to one of claims 1 to 9, characterized in that the optical axis (28) of the dark field illumination beam path (6) an angle (29) between 5 and 90 degrees to the optical axis (25) of the bright field illumination beam path (4th ) and / or to the optical axis (27) of the detection beam path (9).

12. Device according to one of claims 1 to 11, characterized in that the bright field light source (5) is designed as a white light source, preferably a DC lamp.

13. The device according to one of claims 1 to 12, characterized in that the dark field light source (7) as a xenon flash lamp, a laser or an LED (light-emitting diode) or an LED arrangement. is trained.

14. Device according to one of claims 1 to 13, characterized in that the detector (8) is designed as a CCD camera.

15. Device according to one of claims 1 to 14, characterized by a coupling to a control computer, which preferably has a memory unit on which the detected object data can be stored.

16. A method for inspecting an object (2), the object (2) being simultaneously illuminated on the one hand with a bright field light source (5) for bright field illumination and on the other hand with a dark field light source (7) for dark field illumination, and wherein the object (2) with imaging optics (3) is imaged on at least one detector (8), preferably for operating a device according to one of claims 1 to 16, characterized in that the light serving for dark field illumination is pulsed, the pulse intensity of the light serving for dark field illumination being increased by at least is an order of magnitude greater than the intensity of the non-pulsed light used for bright field illumination, based on a pulse interval.

17. The method according to claim 16, characterized in that the object inspection is carried out automatically.

18. The method according to claim 16 or 17, characterized in that the device (1) is coupled to a positioning system (30) positioning the object (2) and that with the

Positioning system (30) selected object areas are automatically positioned in the inspection position.