CN117907234A - High-precision double-light-path alignment device and method and wafer detection system - Google Patents
High-precision double-light-path alignment device and method and wafer detection system Download PDFInfo
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Abstract
The invention provides a high-precision double-light-path alignment device, a method and a wafer detection system, which are applied to the technical field of automatic optical wafer detection, wherein the high-precision double-light-path alignment device carries out focal plane judgment and light-path alignment through image vision and beat frequency signal amplitude values; the high-precision double-light-path alignment method is that the self-focusing light beam and the detection light beam both pass through an aperture diaphragm and the amplitude of the detector is maximized; the wafer detection system comprises a wafer carrying table, an image acquisition module, a defect judging module and the high-precision double-light-path alignment device, the problem that the light-path alignment precision of the alignment device is reduced under the condition of limited space is solved by introducing beat frequency signals, and meanwhile, the method of the invention does not introduce mechanical disassembly and assembly in the light-path alignment process, and overcomes the defect of light-path alignment error caused by introducing mechanical disassembly and assembly.
Description
Technical Field
The invention relates to the technical field of automatic optical wafer detection, in particular to a high-precision double-light-path alignment device and method and a wafer detection system.
Background
In the automatic optical wafer detection process, whether the wafer can be rapidly and accurately placed on the focal plane of the detection lens directly influences the detection effect and the productivity. The rapid and accurate placement of the wafer at the inspection lens focal plane depends on the accuracy of the self-focusing, i.e., the accuracy of the measurement of the amount of misalignment of the wafer's axial position with the inspection lens focal plane, which depends on the uniformity of the self-focusing beam and the inspection beam spectrum, the wavefront characteristics, and the accuracy of the alignment of the self-focusing beam and the inspection beam.
The traditional method for realizing the consistency of the spectrum and the wavefront characteristics of the self-focusing light beam and the detection light beam is to select light sources with the same or similar wave bands as the self-focusing light source and the detection light source respectively, select a lens with better achromatic effect as the detection lens, and because the two light beams with the same or similar wave bands are consistent in the focal plane of the achromatic lens, the focal plane determined by the self-focusing light path is also the focal plane of the detection light path. The conventional method for achieving alignment of the self-focusing light beam and the detection light beam is based on image vision, that is, two points are determined as references on a common light path of the self-focusing light beam and the detection light beam, and the two light beams are considered to be aligned when the self-focusing light beam and the detection light beam simultaneously pass through the reference points. To achieve high accuracy of the alignment of the optical paths, the distance between the two fiducial points should be large, and a camera is additionally used to record the position of the fiducial point spot.
The existing self-focusing light beam and detection light beam alignment method can obviously reduce alignment accuracy under the condition of limited space. Reasons for the reduced alignment accuracy include: (1) a decrease in reference point pitch results in a decrease in accuracy; (2) The position of the camera recording spot cannot be introduced due to space limitations. In addition, the existing optical path alignment method needs to observe the positions of light spots at two reference points, and the front camera needs to be removed when the positions of the rear light spots are observed, and when the camera is introduced into the optical path again, the installation error of the camera can introduce optical path alignment errors.
Therefore, a method for maintaining high-precision alignment of optical paths under space limitation is needed. Aiming at the defects of the existing light path alignment method, the invention discloses a high-precision double-light path alignment device, a high-precision double-light path alignment method and a wafer detection system. The invention performs light path alignment based on image vision and beat frequency signals, solves the problem of reduced light path alignment precision under the condition of limited space by introducing the beat frequency signals, and meanwhile, the method of the invention can not introduce mechanical disassembly and assembly in the light path alignment process and can not introduce light path alignment errors caused by disassembly and assembly.
Disclosure of Invention
In view of this, the embodiments of the present application provide a high-precision dual-optical-path alignment device, a method and a wafer inspection system, so as to maintain high-precision optical-path alignment under space limitation, and facilitate quick and accurate placement of a wafer on an inspection lens focal plane. The embodiment of the application provides the following technical scheme:
in one aspect, an embodiment of the present application provides a high-precision dual optical path alignment device, including:
A lighting module including a light source for generating an initial light beam;
the acousto-optic module is used for splitting the initial beam into a self-focusing beam and a detection beam;
The objective lens module is used for focusing the self-focusing light beam and the detection light beam to a region to be detected;
the imaging module is used for imaging and displaying the reflected light of the to-be-detected area;
The detector is used for receiving beat frequency light generated by the self-focusing light beam and the detection light beam and converting the beat frequency light into an electric signal;
The transmission module is used for transmitting the light paths of the self-focusing light beam and the detection light beam;
the control module is used for controlling the light path adjustment of the self-focusing light beam and the detection light beam;
The self-focusing light beam and the detection light beam are transmitted to the objective lens module through the transmission module respectively, the alignment device enters a rough alignment stage based on image vision judgment, the control module adjusts to enable the self-focusing light beam and the detection light beam to pass through a light path defined by an aperture diaphragm in the objective lens module, then enters a fine alignment stage based on beat frequency signal amplitude judgment, the control module adjusts to enable the beat frequency signal amplitude of the detector to be maximum, and at the moment, the self-focusing light beam and the detection light beam are completely aligned.
Further, the light source in the lighting module comprises monochromatic laser, broad spectrum laser, LED light source and halogen light source.
Further, the acousto-optic module comprises an acousto-optic frequency shifter, an acousto-optic modulator, an acousto-optic filter or an acousto-optic deflector.
Furthermore, both the two light beams generated by the acousto-optic module can be used as the self-focusing light beam or the detecting light beam, and the ratio of the power of the self-focusing light beam split by the acousto-optic module to the power of the detecting light beam depends on the driving power of the acousto-optic frequency shifter.
Further, the imaging module is a two-dimensional camera comprising CMOS, SCMOS, CCD, line-scan or single-pixel detector comprising PD, APD, PMT.
Further, the detector is a photodiode or a photomultiplier, and the detector is arranged at any position behind the objective lens.
Further, an optical fiber incident end in the transmission module is connected with a coupling lens, an emergent end is connected with a collimating lens, and the transmission module further comprises a first beam combining/beam splitter and a second beam combining/beam splitter.
Further, the control module adjusts the included angle and the coincidence degree of the self-focusing light beam and the detection light beam by controlling and adjusting the transmission module.
On the other hand, the embodiment of the application provides a high-precision dual-light-path alignment method, which comprises the following steps:
s1: the lighting module generates an initial light beam;
s2: the acousto-optic module splits the initial beam into a self-focusing beam and a detection beam;
s3: the self-focusing light beam and the detection light beam are respectively transmitted to the front beam combination of the objective lens module through the transmission module;
S4: the control module adjusts the transmission module to enable the self-focusing light beam and the detection light beam to pass through a light path defined by an aperture diaphragm in the objective lens module;
s5: the control module adjusts the transmission module to enable the beat frequency signal amplitude of the detector to be maximum.
Further, the acousto-optic module can adjust the relative power of the self-focusing light beam and the detection light beam in real time, and the control module can adjust the included angle and the contact ratio of the self-focusing light beam and the detection light beam.
In another aspect, an embodiment of the present application provides a wafer inspection system, including:
Wafer carrier: the wafer is used for fixing the wafer to be tested;
an image acquisition module: the method comprises the steps of shooting by a camera array to obtain a detection image corresponding to the whole surface of the wafer;
And a defect judging module: judging whether the surface of the wafer has defects or not according to the detection image;
The high-precision dual-optical-path alignment device further comprises any one of the high-precision dual-optical-path alignment devices, wherein the self-focusing light beam is used for detecting whether the wafer is positioned on the focal plane of the objective lens module, and the detection light beam is used for detecting the wafer defect and measuring the critical dimension of the wafer.
Further, the wafer inspection system may enhance the inspection beam by adjusting the driving power of the acousto-optic module when the wafer inspection system enters the inspection stage.
Compared with the prior art, the beneficial effects achieved by the at least one technical scheme adopted by the embodiment of the application at least comprise:
1. According to the invention, the step of judging the amplitude value of the beat frequency signal is added in the traditional automatic optical path alignment method based on image vision, so that the optical path alignment precision in an automatic optical wafer detection system is improved, and the requirement of wafer detection is better met.
2. The invention overcomes the defect that the camera needs to be detached and reinstalled when the two datum points observe the position of the rear light spot in the existing light path alignment method, does not introduce mechanical disassembly and assembly of the camera in the light path alignment process, and avoids the light path alignment error caused by the installation error of the camera.
3. The invention can not reduce the precision caused by the reduced distance between the datum points when the space is limited.
4. The light source in the lighting module can be selected from monochromatic laser, broad-spectrum laser, LED light source and halogen light source, and the light beam quality meets the focusing and detecting requirements.
5. The frequency shift of the initial light beam in the acousto-optic module is equal to the driving frequency of the initial light beam, the generated self-focusing light beam and the generated detection light beam meet the requirements of frequency spectrum and wavefront consistency, meanwhile, the complexity of a light path detection system is reduced, and the efficiency and reliability of the light path detection system are improved.
6. According to the invention, two light beams generated by the acousto-optic module can be used as self-focusing light beams and detection light beams, and when a wafer detection system enters a detection stage, the detection light beams can be enhanced by adjusting the driving power of the acousto-optic module, so that the detection requirement is better met.
7. The imaging module can select a two-dimensional camera or a single-pixel detector according to specific application requirements and budget, wherein the two-dimensional camera can capture a large amount of detailed information of an image and provide rich visual data; the image can be captured in a wide visual field range, and the shooting range is large; the real-time video stream can be provided, and the method is suitable for monitoring and recording dynamic conditions; compared with a two-dimensional camera, the single-pixel detector is low in manufacturing cost, simple in structure and easy to maintain and replace; for computing and reconstructing an image, a single-pixel camera may perform better than a multi-pixel camera in environments where light is very dark.
8. The detector can select a photoelectric signal device such as a photodiode or a photomultiplier, is easy to integrate, and meets the requirements of miniaturization and integration of a wafer detection system.
9. The coupling lens and the collimating lens are selected before and after the optical fiber in the transmission module, and the coupling lens concentrates the self-focusing light beam and the detection light beam to be transmitted into the optical fiber, so that the optical energy efficiency can be improved and the loss can be reduced; the collimating lens changes the propagation direction of light rays, and changes scattered light rays into parallel light rays at the position of the optical fiber outlet, so that the light rays can propagate for a long distance without being diverged, and the whole system achieves ideal effects in various aspects of transmission quality, distance, installation cost and the like.
10. The control module of the invention not only can manually control and adjust the angle of the transmission module, but also can mechanically control and adjust the angle more finely based on algorithm analysis, thereby meeting the requirement of the stability of the wafer detection system.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic illustration of an environment in which a high-precision dual-optical-path alignment apparatus of the present invention is implemented;
FIG. 2 is a schematic diagram of an initial light source beam splitting process in a high-precision dual-optical-path alignment device according to the present invention;
FIG. 3 is a schematic illustration of an alignment process in a high precision dual optical path alignment device of the present invention;
FIG. 4 is a step diagram of a high precision dual optical path alignment method of the present invention;
FIG. 5 is a schematic diagram of beat signals when the optical paths are completely aligned in the high-precision dual-optical-path alignment device according to the present invention;
FIG. 6a is a schematic diagram of a beat signal with an optical path angle of 5 ° in a high-precision dual-optical-path alignment device according to the present invention;
FIG. 6b is a schematic diagram of a beat signal with an optical path angle of 10 ° in a high-precision dual-optical-path alignment device according to the present invention;
FIG. 6c is a schematic diagram of a beat signal with an included angle of 20 ° in a high-precision dual-optical-path alignment device according to the present invention;
FIG. 7a is a schematic diagram of a beat signal with a light path overlap ratio of 95% in a high-precision dual-light-path alignment device according to the present invention;
FIG. 7b is a schematic diagram of a beat signal with a light path overlap ratio of 90% in a high-precision dual-light-path alignment device according to the present invention;
FIG. 7c is a schematic diagram of a beat signal with an optical path overlap ratio of 80% in a high-precision dual-optical-path alignment device according to the present invention;
The figure shows: 1. the device comprises an illumination module, 2, an acousto-optic module, 3, an objective lens module, 31, an aperture diaphragm, 4, an imaging module, 5, a detector, 6, a transmission module, 60, an optical fiber, 601, a coupling lens, 602, a collimating lens, 61, a self-focusing light beam input end, 62, a detection light beam input end, 63, a first beam splitter/combiner, 64, a second beam splitter/combiner, 7, a sample to be tested, 8 and a wafer carrier.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
By adopting the high-precision double-light-path alignment device provided by the embodiment of the application, the high-precision alignment of the light paths can be kept under the limitation of space, and the wafer can be conveniently and rapidly placed on the focal plane of the detection lens. Fig. 1 is a schematic diagram of an application scenario of the high-precision dual-optical-path alignment device. The implementation environment comprises a high-precision double-light-path alignment device, a sample 7 to be tested in a region to be tested and a wafer carrier 8. With reference to fig. 2 and 3, the high-precision dual optical path alignment apparatus includes:
A lighting module 1 comprising a light source for generating an initial light beam;
an acousto-optic module 2 for splitting the initial beam into a self-focusing beam and a detection beam;
An objective lens module 3 for focusing the self-focusing light beam and the detection light beam to a region to be measured;
The imaging module 4 is used for imaging and displaying the reflected light of the to-be-detected area;
A detector 5 for receiving beat light generated from the self-focusing light beam and the detection light beam and converting it into an electric signal;
a transmission module 6 for transmitting the optical paths of the self-focusing light beam and the detection light beam;
The control module is used for controlling the light path adjustment of the self-focusing light beam and the detection light beam;
The self-focusing light beam is transmitted to the self-focusing light beam input end 61 by the transmission module 6, the detection light beam is transmitted to the detection light beam input end 62 by the transmission module 6 and then is combined before the objective lens module 3, the device enters a rough alignment stage based on image vision judgment, the control module adjusts to enable the self-focusing light beam and the detection light beam to pass through a light path defined by the aperture diaphragm 31 in the objective lens module 3, then enters a fine alignment stage based on beat frequency signal amplitude judgment, and the control module adjusts to enable the beat frequency signal amplitude of the detector 5 to be maximum, and at the moment, the self-focusing light beam and the detection light beam are completely aligned. The invention performs high-precision alignment of the self-focusing light beam and the detection light beam based on image vision and beat frequency signals, adds the step of judging the amplitude of the beat frequency signals in the traditional automatic light path alignment method based on image vision, improves the light path alignment precision in an automatic optical wafer detection system, and better meets the requirement of wafer detection.
FIG. 2 is a schematic diagram illustrating an initial light source beam splitting process according to an embodiment of the present invention, where the self-focusing light beam and the detection light beam are obtained by splitting the same light source, so as to reduce complexity of the light path detection system and improve efficiency and reliability thereof. In some embodiments, the light sources in the lighting module 1 comprise monochromatic lasers, broad spectrum lasers, LED light sources, halogen light sources, the beam quality meeting the focusing and detection requirements. The acousto-optic module 2 comprises an acousto-optic frequency shifter, an acousto-optic modulator, an acousto-optic filter or an acousto-optic deflector to realize acousto-optic offset, two beams of light generated by the acousto-optic module 2 can be used as self-focusing beams or detection beams, and the ratio of the power of the self-focusing beams and the power of the detection beams split by the acousto-optic module 2 depends on the driving power of the acousto-optic frequency shifter.
Specifically, the lighting module 1 generates an initial light beam, which is divided into zero-order transmitted light and first-order diffracted light after passing through the acousto-optic module 2, the zero-order light and the first-order light enter the optical fiber 60 through the coupling lens 61, respectively, the first-order light has a certain frequency shift relative to the zero-order light, the frequency shift is equal to the driving frequency of the acousto-optic module 2, the sum of the power of the first-order light and the power of the zero-order light is equal to the power of the light source, the ratio of the power depends on the driving power of the acousto-optic module 2, and when the driving power makes the diffraction efficiency of the acousto-optic module 2 be 50%, the power of the first-order light and the power of the zero-order light are equal. The self-focusing light beam and the detection light beam adopted by the invention completely meet the requirements of frequency spectrum and wavefront consistency.
Fig. 3 is a schematic diagram of an alignment process in the high-precision dual-optical-path alignment device of the present invention, in fig. 2, the first-order light is used as a self-focusing light beam, the zero-order light is used as a detection light beam, the detection light beam is inputted from an optical fiber 60 and then collimated by a collimating lens 62, the self-focusing light beam is transmitted to a self-focusing light beam input end 61 by a transmission module 6, the detection light beam is transmitted to the detection light beam input end 62 by the transmission module 6, the detection light beam is reflected by a second beam splitter/combiner 64 and then combined with the self-focusing light beam by a first beam splitter/combiner 63, and the combined light beam is focused to a sample 7 to be tested by an objective lens module 3. The reference point determined by the aperture stop 31 is used to coarsely align the self-focusing light beam, the detection light beam based on the image vision. The imaging module 4 is used for wafer inspection. The detector 5 is used to fine-align the self-focusing light beam and the detection light beam based on the beat signal. It should be understood that the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
In some embodiments, the imaging module 4 is a two-dimensional camera, comprising CMOS, SCMOS, CCD, line-scan or single-pixel detector, comprising PD, APD, PMT, which can be selected according to specific application needs and budget, wherein the two-dimensional camera can capture a large amount of detailed information of an image, providing rich visual data; the image can be captured in a wide visual field range, and the shooting range is large; the real-time video stream can be provided, and the method is suitable for monitoring and recording dynamic conditions; compared with a two-dimensional camera, the single-pixel detector is low in manufacturing cost, simple in structure and easy to maintain and replace; for computing and reconstructing an image, a single-pixel camera may perform better than a multi-pixel camera in environments where light is very dark.
In some embodiments, the detector 5 is a photodiode or a photomultiplier, and the detector 5 is mounted at any position after the objective lens module 3, so that the integration is easy, and the requirements of miniaturization and integration of the wafer detection system are met. The optical fiber 60 in the transmission module 6 is connected with a coupling lens 61 at the incident end and a collimating lens 62 at the exit end, and the coupling lens 61 concentrates the self-focusing light beam and the detection light beam to be transmitted into the optical fiber 60, so that the light energy efficiency can be improved and the loss can be reduced; the collimating lens 62 changes the propagation direction of the light rays, which changes the scattered light rays into parallel light rays at the exit of the optical fiber 60, so that the light rays can propagate over a long distance without diverging. It should be understood that the high-precision dual-optical-path alignment device of the present invention is not limited to the use of a set of coupling lenses 61 and collimating lenses 62, both of which are typically used in the front-to-back stage of the overall optical fiber communication system, and the selection and application needs to be based on actual design requirements to achieve the desired effect of the overall system in terms of transmission quality, distance, installation cost, etc.
In some embodiments, the transmission module 6 further includes a first beam splitter/combiner 63 and a second beam splitter/combiner 64, which effectively manage and control the transmission of light beams, where the beam splitter is used to transmit information from one single light source to the optical path positions of multiple targets, and where the beam combiner is used to process the optical path positions of information received from multiple sources simultaneously, so as to reduce the beam loss as far as possible. The control module adjusts the included angle and the coincidence ratio of the self-focusing light beam and the detection light beam through controlling the adjusting transmission module 6, so that the angle of the transmission module 6 can be manually controlled and adjusted, and the wafer detection system can be mechanically controlled and adjusted more finely based on algorithm analysis, thereby meeting the requirement of the stability of the wafer detection system.
On the other hand, referring to fig. 4, an embodiment of the present application provides a high-precision dual optical path alignment method, including the following steps:
s1: the lighting module generates an initial light beam;
s2: the acousto-optic module divides the initial beam into a self-focusing beam and a detection beam;
S3: the self-focusing light beam and the detection light beam are respectively transmitted to the front beam combination of the objective lens module through the transmission module;
S4: the control module adjusts the transmission module to enable the self-focusing light beam and the detection light beam to pass through the light path defined by the aperture diaphragm in the objective lens module;
s5: the control module adjusts the transmission module to maximize the beat signal amplitude of the detector.
In particular, the implementation of the present invention is divided into two steps. The first step is to roughly align the self-focusing beam and the detection beam based on the image vision, specifically, roughly adjusting the optical fiber 60, the collimating lens 62, and the first beam splitter/combiner 63 so that the self-focusing beam passes through the aperture stop 31, and roughly adjusting the optical fiber 60, the collimating lens 62, and the second beam splitter/combiner 64 so that the detection beam also passes through the aperture stop 31. The second step is to precisely align the self-focusing beam and the detection beam based on the beat signal, specifically, precisely adjust the optical fiber 60, the collimator lens 62, the first beam splitter/combiner 63, and the second beam splitter/combiner 64 so as to maximize the beat signal output by the detector 5. When the self-focusing light beam and the detection light beam are completely aligned, the beat signal output by the detector 5 is normalized to 1 in amplitude as shown in fig. 5.
FIG. 6a shows the amplitude of the beat signal decreasing to 0.98 when the self-focusing and detection beams reach the detector 5 at an angle of 5 °; FIG. 6b shows the amplitude of the beat signal decreasing to 0.94 when the self-focusing and detection beams reach the detector 5 at an angle of 10; fig. 6c shows that when the self-focusing beam and the detecting beam reach the detector 5 at an included angle of 20 °, the amplitude of the beat signal decreases to 0.76, and it can be found that the amplitude of the beat signal continuously decreases with increasing included angle.
Fig. 7a shows the amplitude of the beat signal falling to 0.95 when the overlap ratio of the self-focusing beam and the detection beam is 95%, fig. 7b shows the amplitude of the beat signal falling to 0.90 when the overlap ratio of the self-focusing beam and the detection beam is 90%, and fig. 7c shows the amplitude of the beat signal falling to 0.80 when the overlap ratio of the self-focusing beam and the detection beam is 80%, and it can be found that the amplitude of the beat signal continuously falls as the overlap ratio decreases. The beat signal drops more significantly when the self-focusing and detection beams are not fully overlapped at the detector 5 with an included angle, so that the amplitude of the beat signal is a criterion for accurate optical path alignment.
In another aspect, an embodiment of the present application provides a wafer inspection system, including:
wafer stage 8: for fixing the sample 7 to be measured;
an image acquisition module: the method comprises the steps of shooting by a camera array to obtain a detection image corresponding to the whole surface of a wafer;
And a defect judging module: judging whether the surface of the wafer has defects or not according to the detection image;
The device also comprises any high-precision dual-optical-path alignment device, wherein the self-focusing light beam is used for detecting whether the wafer is positioned on the focal plane of the objective lens module 3, and the detection light beam is used for detecting the wafer defect and measuring the critical dimension of the wafer. Based on the present disclosure, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways.
In some embodiments, when the inspection stage is entered, the wafer inspection system may enhance the inspection beam by adjusting the driving power of the acousto-optic module 2, better meeting the inspection requirements.
In this specification, identical and similar parts of the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, the description is relatively simple for the embodiments described later, and reference is made to the description of the foregoing embodiments for relevant points.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (12)
1. A high precision dual optical path alignment device, comprising:
A lighting module including a light source for generating an initial light beam;
the acousto-optic module is used for splitting the initial beam into a self-focusing beam and a detection beam;
The objective lens module is used for focusing the self-focusing light beam and the detection light beam to a region to be detected;
the imaging module is used for imaging and displaying the reflected light of the to-be-detected area;
The detector is used for receiving beat frequency light generated by the self-focusing light beam and the detection light beam and converting the beat frequency light into an electric signal;
The transmission module is used for transmitting the light paths of the self-focusing light beam and the detection light beam;
the control module is used for controlling the light path adjustment of the self-focusing light beam and the detection light beam;
The self-focusing light beam and the detection light beam are transmitted to the objective lens module through the transmission module respectively, the alignment device enters a rough alignment stage based on image vision judgment, the control module adjusts to enable the self-focusing light beam and the detection light beam to pass through a light path defined by an aperture diaphragm in the objective lens module, then enters a fine alignment stage based on beat frequency signal amplitude judgment, the control module adjusts to enable the beat frequency signal amplitude of the detector to be maximum, and at the moment, the self-focusing light beam and the detection light beam are completely aligned.
2. The high precision dual optical path alignment device of claim 1, wherein the light source in the illumination module comprises a monochromatic laser, a broad spectrum laser, an LED light source, a halogen light source.
3. The high precision dual optical path alignment device of claim 1, wherein the acousto-optic module comprises an acousto-optic frequency shifter, an acousto-optic modulator, an acousto-optic filter, or an acousto-optic deflector.
4. A high precision dual optical path alignment device as claimed in claim 3 wherein both beams of light generated by the acousto-optic module can be used as the self-focusing beam or the detection beam, and the ratio of the power of the self-focusing beam and the detection beam split by the acousto-optic module depends on the driving power of the acousto-optic frequency shifter.
5. The high precision dual optical path alignment device of claim 1, wherein the imaging module is a two-dimensional camera comprising CMOS, SCMOS, CCD, line-scan or single-pixel detector comprising PD, APD, PMT.
6. The high-precision dual optical path alignment apparatus of claim 1, wherein the detector is a photodiode or a photomultiplier, and the detector is mounted at any position behind the objective lens.
7. The high-precision dual-optical-path alignment device according to claim 1, wherein the optical fiber in the transmission module is connected with a coupling lens at an incident end and a collimating lens at an emergent end, and the transmission module further comprises a first beam-combining/beam-splitting device and a second beam-combining/beam-splitting device.
8. The high precision dual optical path alignment device of claim 1, wherein the control module adjusts the angle and the overlap ratio of the self-focusing light beam and the detection light beam by controlling and adjusting the transmission module.
9. The high-precision double-light-path alignment method is characterized by comprising the following steps of:
s1: the lighting module generates an initial light beam;
s2: the acousto-optic module splits the initial beam into a self-focusing beam and a detection beam;
s3: the self-focusing light beam and the detection light beam are respectively transmitted to the front beam combination of the objective lens module through the transmission module;
S4: the control module adjusts the transmission module to enable the self-focusing light beam and the detection light beam to pass through a light path defined by an aperture diaphragm in the objective lens module;
s5: the control module adjusts the transmission module to enable the beat frequency signal amplitude of the detector to be maximum.
10. The method of claim 9, wherein the acousto-optic module is capable of adjusting the relative powers of the self-focusing beam and the detecting beam in real time, and the control module is capable of adjusting the included angle and the overlap ratio of the self-focusing beam and the detecting beam.
11. A wafer inspection system, comprising:
Wafer carrier: the wafer is used for fixing the wafer to be tested;
an image acquisition module: the method comprises the steps of shooting by a camera array to obtain a detection image corresponding to the whole surface of the wafer;
And a defect judging module: judging whether the surface of the wafer has defects or not according to the detection image;
The high precision dual optical path alignment device of any of claims 1-8, wherein a self-focusing beam is used to detect whether the wafer is at an objective lens module focal plane, the detection beam is used to detect the wafer defect and measure a critical dimension of the wafer.
12. The wafer inspection system of claim 11, wherein the wafer inspection system can enhance the inspection beam by adjusting the driving power of the acousto-optic module when the inspection phase is entered.
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