Alignment device and alignment method

Abstract

The application provides an alignment device and a method thereof, and belongs to the technical field of wafer packaging. The device specifically comprises a first collimation unit, a first refraction unit, a second collimation unit, a second refraction unit, a beam combining and light splitting prism and an imaging collection unit. The optical paths of two reflected lights reaching the imaging collection unit are consistent. Through the processing scheme, the clarity of mark imaging is improved, the response speed of the imaging collection unit is improved, the response error is reduced, and high-precision alignment between two reference plates is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wafer packaging, in particular to an alignment device and an alignment method. BACKGROUND

[0002] With the development of electronic industry, the function of chip is more and more complex, and the size is smaller and smaller, and new semiconductor technologies are emerging to meet the demand, such as wafer level packaging, 3D chip stacking, 3D device, silicon-on-insulator wafer, etc., the development of these technologies drives the development of wafer bonding technology.

[0003] Wafer bonding is a technology that makes wafers into one through van der Waals force, molecular force or even atomic force between atoms at the wafer interface under the action of external energy. There are many existing wafer bonding processes, among which direct wafer bonding is widely used because it does not need adhesive, is carried out at normal pressure, is resistant to high temperature and has high yield. In wafer bonding, the upper and lower wafers usually need to establish a connection between the wires to realize a complete device on two or more wafers.

[0004] The degree of alignment between the upper and lower wafers is a very important parameter for wafer bonding.

[0005] In the prior art, there are problems of large error and insufficient absolute accuracy in wafer alignment, and the alignment operation is affected by the transmittance of the reference version. SUMMARY

[0006] Therefore, in order to overcome the shortcomings of the prior art, the present application provides an alignment device and an alignment method, which realizes high-precision alignment of the first reference version and the second reference version.

[0007] In order to achieve the above purpose, the present application provides the following technical solutions:

[0008] An alignment device for directly positioning a first reference version and a second reference version relative to each other, comprising: a first collimating unit, a first refractive unit, a second collimating unit, a second refractive unit, a beam combining and splitting prism, and an imaging and collecting unit; the first collimating unit collimates a first light beam and refracts it to the first reference version through the first refractive unit, the first reflected light from the first reference version passes through the beam combining and splitting prism and irradiates the imaging and collecting unit to form a first light path; the second collimating unit collimates a second light beam and refracts it to the second reference version through the second refractive unit, the second reflected light from the second reference version passes through the beam combining and splitting prism and irradiates the imaging and collecting unit to form a second light path; the optical path of the first reflected light to the imaging system is consistent with the optical path of the second reflected light to the imaging system.

[0009] Specifically, the light path compensation structure is further included, the first reflected light is first reflected by 90 degrees when passing through the inclined surface of the beam splitting prism, is reflected by 180 degrees after reaching the surface of the beam splitting prism, and then is transmitted to the imaging collection unit through the inclined surface of the beam splitting prism; the second reflected light first enters the light path compensation structure, and then is directly reflected to the imaging collection unit through the inclined surface of the beam splitting prism.

[0010] Specifically, the light path compensation structure is a compensation prism arranged between the second refractive unit and the beam splitting prism, and is used for compensating for the light path difference that the second reflected light is reflected one time less than the first reflected light in the beam splitting prism, so that the light path of the first reflected light to the imaging system is consistent with the light path of the second reflected light to the imaging system.

[0011] Specifically, the light path compensation structure and the second refractive unit form a first prism group, and are used for compensating for the light path difference that the second reflected light is reflected one time less than the first reflected light in the beam splitting prism, so that the light path of the first reflected light to the imaging system is consistent with the light path of the second reflected light to the imaging system.

[0012] Specifically, the light path compensation structure and the beam splitting prism form a second prism group, and are used for compensating for the light path difference that the second reflected light is reflected one time less than the first reflected light in the beam splitting prism, so that the light path of the first reflected light to the imaging system is consistent with the light path of the second reflected light to the imaging system.

[0013] Specifically, the image formed by the first light path or the second light path is a Kohler illumination image or a critical illumination image.

[0014] Specifically, the control unit and the micro-motion platform are further included, the control unit is connected to the imaging collection unit, the micro-motion platform is connected to the first reference plate and the second reference plate respectively, information collected by the imaging collection unit is transmitted to the control unit, when it is judged that the image is not aligned, the control unit drives the micro-motion platform to move at least one of the first reference plate and the second reference plate, so that the first reference plate and the second reference plate are aligned.

[0015] Specifically, the two half-glasses are further included, the half-glasses are respectively arranged between the first refractive unit and the beam splitting prism and between the second refractive unit and the beam splitting prism; the half-glasses convert P light into S light; the beam splitting prism is a PBS beam splitting prism, and is used for absorbing P light and reflecting S light; the half-glasses and the PBS beam splitting prism provide single light for the imaging collection unit.

[0016] Specifically, the first collimation unit comprises a first light source and a first collimation lens; the first refraction unit comprises a first light splitting prism and a first imaging lens; the second collimation unit comprises a second light source and a first collimation lens; the second refraction unit comprises a second light splitting prism and a second imaging lens; and the imaging collection unit comprises a third imaging lens and a camera; the first imaging lens and the second imaging lens respectively comprise a magnification compensation element and an image quality compensation element for compensating for performance differences between the two optical paths.

[0017] Specifically, the third imaging lens comprises a magnification compensation element and an image quality compensation element for compensating for magnification and aberration of the entire optical system.

[0018] Compared with the prior art, the present application has the advantages that: by arranging the collimation unit and the refraction unit, the light beams illuminate two reference plates, and the optical path of the first reflected light to the imaging system and the optical path of the second reflected light to the imaging system are consistent, and by image comparison, it can be determined whether the two reference plates are aligned; the imaging collection unit simultaneously collects two patterns, and there is no response error between the two pattern collections. Moreover, the device is not limited by the marking material, and the clarity and accuracy of the marking are not affected, and high-precision measurement can be achieved. The alignment device can achieve high-precision alignment between wafers and wafers, and between chips and chips. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 is a structural schematic diagram of an alignment device in an embodiment of the present application;

[0021] Figure 2 is a schematic diagram of the upper optical path of the alignment device in an embodiment of the present application;

[0022] Figure 3 is a schematic diagram of the lower optical path of the alignment device in an embodiment of the present application;

[0023] Figure 4 is a structural schematic diagram of an alignment device in an embodiment of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application will be described in detail below with reference to the drawings.

[0025] Following, the embodiments of the present application are described through specific examples, and other advantages and effects of the present application can be easily understood by those skilled in the art from the disclosure. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. The present application can also be implemented or applied through other different specific embodiments, and various modifications or changes can be made to the details in the specification based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0026] It should be noted that the various aspects of the embodiments described below are within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms and that any specific structure and / or function described herein is merely illustrative. Based on the teachings herein one skilled in the art should appreciate that an aspect described herein can be implemented independently of any other aspects and that an aspect can be implemented both as any number of software and / or hardware structures and as any number of combinations of software and / or hardware structures. For example, an apparatus can be implemented as any number and combination of the aspects described herein. Additionally, the features described herein can be implemented as part of one or more separate devices or components, or as part of an integrated device or component. Further, the aspects described herein can be implemented as part of a cloud-based service.

[0027] It should also be noted that the drawings included in the following description are included for illustrative purposes only and are not intended to limit the scope of the present application. The drawings are included to illustrate various aspects of the present application and to explain the principles and operations of the present application. The drawings are not intended to be limiting in any way.

[0028] In addition, in the following description, specific details are provided to thoroughly understand examples. However, one of ordinary skill in the art will understand that the described aspects can be practiced without these specific details.

[0029] As shown in Figure 1 The embodiments of the present application provide an alignment device 100 for directly positioning a first reference plate 101 and a second reference plate 103 relative to each other. The alignment device 100 includes a first collimating unit 10, a second collimating unit 20, a first refractive unit 30, a second refractive unit 40, a beam combining and splitting prism 131, and an imaging and collecting unit 60.

[0030] The first collimating unit 10 is used for collimating the first light beam. In some embodiments, the first collimating unit 10 can only include the first collimating lens 112, or can include the first light source 111 and the first collimating lens 112, or can include other optical elements for filtering the first light beam and the first collimating lens 112.

[0031] The second collimating unit 20 is used for collimating the second light beam. In some embodiments, the second collimating unit 20 can only include the second collimating lens 122, or can include the second light source 121 and the second collimating lens 122, or can include other optical elements for filtering the second light beam and the second collimating lens 122.

[0032] The first refracting unit 30 is used for irradiating the collimated first light beam to the first reference plate 101. In some embodiments, the first refracting unit 30 includes the first light splitting prism 113 and the first imaging lens 114.

[0033] The second refracting unit 40 is used for irradiating the collimated second light beam to the second reference plate 103. In some embodiments, the second refracting unit 40 includes the second light splitting prism 123 and the second imaging lens 124.

[0034] The imaging collection unit 60 is used for collecting reflected light and acquiring information therein. In some embodiments, the imaging collection unit 60 includes the third imaging lens 132 and the camera 133.

[0035] The first collimating unit 10 collimates the first light beam, and the collimated light beam is refracted to the first reference plate 101 through the first refracting unit 30. The first reflected light from the first reference plate 101 passes through the first refracting unit 30, then passes through the beam combining light splitting prism 131, and is irradiated to the imaging collection unit 60 to form a first light path. The second collimating unit 20 collimates the second light beam, and the collimated light beam is refracted to the second reference plate 103 through the second refracting unit 40. The second reflected light from the second reference plate 103 passes through the second refracting unit 40, then passes through the beam combining light splitting prism 131, and is irradiated to the imaging collection unit 60 to form a second light path.

[0036] The optical path of the first reflected light to the imaging collection unit 60 is consistent with the optical path of the second reflected light to the imaging collection unit 60. In some embodiments, the optical path of the first light path and the optical path of the second light path can also be consistent.

[0037] The use method of the above device is as follows:

[0038] (1) The first light beam and the second light beam are respectively irradiated to the first reference plate 101 and the second reference plate 103.

[0039] (2) The first reflected light from the first reference plate 101 passes through the beam splitting prism 131 and is irradiated to the imaging collection unit 60; the first reflected light carries the mark information on the first reference plate 101; the second reflected light from the second reference plate 103 passes through the beam splitting prism 131 and is irradiated to the imaging collection unit 60; the second reflected light carries the mark information on the second reference plate 103; the optical path of the first reflected light to the imaging collection unit 60 is consistent with the optical path of the second reflected light to the imaging collection unit 60;

[0040] (3) The imaging collection unit 60 generates corresponding images according to the two light beams respectively;

[0041] (4) When the two images overlap, it is determined that the first reference plate 101 and the second reference plate 103 are aligned.

[0042] The above device, by setting the collimating unit and the refracting unit, makes the light beam illuminate two reference plates, and the optical path of the first reflected light to the imaging system is consistent with the optical path of the second reflected light to the imaging system, and through image comparison, whether the two reference plates are aligned can be determined; the imaging collection unit collects two patterns at the same time, and there is no response error between the collection of the two patterns. Moreover, the device is not limited by the mark material, and the clarity and accuracy of the mark are not affected, and high-precision measurement can be realized. The alignment device can realize high-precision alignment between wafers and wafers, and chips and chips.

[0043] In an embodiment, the alignment device further comprises an optical path compensation structure. The optical path compensation structure is used to make the first reflected light first reflect 90 degrees when passing through the inclined surface of the beam splitting prism 131, and then reflect 180 degrees after reaching the surface of the beam splitting prism 131, and then enter the imaging collection unit 60 through the inclined surface of the beam splitting prism 131; the second reflected light first enters the optical path compensation structure, and then directly reflects into the imaging collection unit 60 through the inclined surface of the beam splitting prism 131.

[0044] In an embodiment, as shown in Figure 1 the optical path compensation structure is a compensation prism 125, which is arranged between the second refracting unit 40 and the beam splitting prism 131, and is used to compensate for the optical path difference that the second reflected light is reflected one time less than the first reflected light in the beam splitting prism 131, so that the optical path of the first reflected light to the imaging collection unit 60 is consistent with the optical path of the second reflected light to the imaging collection unit 60.

[0045] As shown in Figure 2As shown, the first light source 111 emits light of a certain value, the first collimating lens 112 converges and collimates the light emitted by the first light source 111, and the collimated light is incident on the first beam splitter 113. The first beam splitter 113 divides the light from the first light source 111 into two equal parts. One part passes through the 45-degree reflecting surface and is incident on the light trap surface and disappears directly. The other part is reflected by the 45-degree reflecting surface and enters the third imaging lens 132 to uniformly illuminate the mark in area 102.

[0046] In some embodiments, the first collimating lens 112, the first beam splitter 113, and the first imaging lens 114 constitute a Kohler illumination system or critical illumination system for providing illumination to region 102.

[0047] The first reflected light passes through the optical path of the imaging system, which consists of the first imaging lens 114, the first beam splitter 113, the beam combiner 131, and the third imaging lens 132. The beam is first reflected 90 degrees by the 45-degree reflecting surface of the beam combiner 131, and then reflected 180 degrees after reaching the surface of the beam combiner 131. The reflected light passes through the 45-degree reflecting surface of the beam combiner 131 again and enters the third imaging lens 132, until it reaches the camera 133 of the imaging system. At this point, the mark on the first reference plate 101 is imaged onto the camera 133.

[0048] like Figure 3 As shown, the second light source 121 emits light of a certain value. The second collimating lens 122 converges and collimates the light emitted by the second light source 121. The collimated light is incident on the second beam splitter 123. The second beam splitter 123 divides the light from the second light source 121 into two equal parts. One part passes through the 45-degree reflecting surface and is incident on the light trap surface and disappears directly. The other part is reflected by the 45-degree reflecting surface and enters the third imaging lens 132 to uniformly illuminate the mark in area 104.

[0049] In one embodiment, the second collimating lens 122, the second beam splitter 123, and the second imaging lens 124 constitute a Kohler illumination system or critical illumination system for providing illumination to region 104.

[0050] The second reflected light passes through the optical path of the imaging system, which consists of the second imaging lens 124, the second beam splitter 123, the compensation prism 125, the beam combiner 131, and the third imaging lens 132. After being reflected by the 45-degree reflecting surface of the beam combiner 131, the light beam is incident on the third imaging lens 132 and then on the imaging system camera 133; at this point, the mark on the second reference plate 103 is imaged onto the camera 133.

[0051] In one embodiment, the optical path compensation structure and the second refractive unit 41 form a first prism group for compensating the optical path difference that the second reflected light is reflected one time less than the first reflected light in the beam combining prism 131, so that the optical path of the first reflected light to the imaging system and the optical path of the second reflected light to the imaging system are consistent.

[0052] In one embodiment, the optical path compensation structure and the beam combining prism 131 form a second prism group for compensating the optical path difference that the second reflected light is reflected one time less than the first reflected light in the beam combining prism, so that the optical path of the first reflected light to the imaging system and the optical path of the second reflected light to the imaging system are consistent.

[0053] In one embodiment, the first imaging lens 114 and the second imaging lens 124 respectively contain magnification compensation elements and image quality compensation elements for compensating the performance difference between the two optical paths.

[0054] In one embodiment, the third imaging lens 132 contains magnification compensation elements and image quality compensation elements for compensating the magnification and aberration of the entire optical system.

[0055] The first collimating lens 112 and the second collimating lens 122 respectively converge and collimate the light emitted by the first light source 111 and the second light source 121, and the collimated light respectively enters the first light splitting prism 113 and the second light splitting prism 123, and the first light splitting prism 113 and the second light splitting prism 123 respectively reflect different lights to the first reference plate 101 and the second reference plate 103; the first imaging lens 114 and the second imaging lens 124 detect the reference points on the first reference plate 101 and the second reference plate 103, the first reflected light is first reflected by 90 degrees through the 45-degree reflecting surface of the beam combining light splitting prism 131, and then reflected by 180 degrees after reaching the surface of the beam combining light splitting prism 131, and the reflected light again enters the third imaging lens 132 through the 45-degree reflecting surface of the beam combining light splitting prism 131, and then reaches the imaging system camera 133. The second reflected light passes through the imaging system light path composed of the second imaging lens 124, the second light splitting prism 123, the compensation prism 125, the beam combining light splitting prism 131, and the third imaging lens 132. After the light beam is reflected by the 45-degree reflecting surface of the beam combining light splitting prism 131, it enters the third imaging lens 132, and then reaches the imaging system camera 133, and the camera 133 compares the image information. When it is judged that the two reference plates are aligned, the bonding operation is performed; when it is judged that the two reference plates are not aligned, the control unit 150 calculates the positional deviation amount of the first reference plate 101 and the second reference plate 103 through a specific algorithm, and feeds back to the micro-motion platform. The micro-motion platform includes a precision motion stage 105 and a precision motion stage 106 with five degrees of freedom motion capability, and the control unit 150 controls the precision motion stage 105 and the precision motion stage 106 to move to realize high-precision compensation of the horizontal deviation and the rotation angle, eliminate the horizontal error caused by the vertical motion, and eliminate the horizontal position system deviation during measurement caused by the non-perpendicularity of the alignment system optical axis and the substrate surface. The precision motion stage 105 is connected to the first reference plate 101, the precision motion stage 106 is connected to the second reference plate 103, and the control unit 150 drives the micro-motion platform to move at least one of the first reference plate 101 and the second reference plate 103, so that the first reference plate 101 and the second reference plate 103 are aligned. After the movement is finished, the alignment is performed again, and when it is judged that the two reference plates are aligned, the bonding operation is performed.

[0056] As shown in Figure 4 An embodiment provides an alignment device 600, which includes a first collimating unit 11, a second collimating unit 21, a first refracting unit 31, a second refracting unit 41, a beam combining light splitting prism 131, and an imaging collecting unit 61.

[0057] The first collimating unit 11 is used for collimating the first light beam. In some embodiments, the first collimating unit 11 can only include the first collimating lens 112, can include the first light source 111 and the first collimating lens 112, and can also include other optical elements for filtering the first light beam and the first collimating lens 112.

[0058] The second collimating unit 21 is used for collimating the second light beam. In some embodiments, the second collimating unit 21 can only include the second collimating lens 122, or can include the second light source 121 and the second collimating lens 122, or can include other optical elements for filtering the second light beam and the second collimating lens 122.

[0059] The first refracting unit 31 is used for irradiating the collimated first light beam to the first reference plate. In some embodiments, the first refracting unit 31 includes the first light splitting prism 113, the first imaging lens 114, and the first half-wave plate 115.

[0060] The second refracting unit 41 is used for irradiating the collimated second light beam to the second reference plate. In some embodiments, the second refracting unit 40 includes the second light splitting prism 123, the second imaging lens 124, and the second half-wave plate 125.

[0061] The imaging collecting unit 61 is used for collecting the reflected light and obtaining information therein. In some embodiments, the imaging collecting unit 60 includes the third imaging lens 132 and the camera 133.

[0062] The beam combining light splitting prism 131 is a PBS beam combining light splitting prism.

[0063] The first light source 111 emits a certain amount of light, the first collimating lens 112 converges and collimates the light emitted by the first light source 111, the collimated light is incident to the first PBS light splitting prism 113, the first PBS light splitting prism 113 splits the light from the first light source 111 into P light and S light, the P light transmits through the PBS splitting surface and is incident to the light trap surface to disappear directly, and the S light is reflected by the first PBS splitting surface and then enters the first imaging lens 114 to uniformly irradiate the marks on the 102 area.

[0064] The first reflected light passes through the imaging system light path composed of the first imaging lens 114, the first PBS light splitting prism 113, the first half-wave plate 115, the PBS beam combining light splitting prism 131, and the third imaging lens 132. The P light becomes S light after passing through the half-wave plate 115, the S light is first reflected by 90 degrees after passing through the splitting surface of the PBS beam combining light splitting prism 131, and then reflected by 180 degrees after reaching the prism surface, at this time the polarization state is P light, the P light again transmits through the splitting surface of the PBS beam combining light splitting prism 131 and is incident to the third imaging lens 132, and then to the camera 133; at this time, the marks on the first reference plate 101 are imaged to the camera 133.

[0065] The second light source 121 emits light of a certain value, the second collimating lens 122 converges and collimates the light emitted by the second light source 121, the collimated light is incident to the second PBS beam-splitter prism 123, the second PBS beam-splitter prism 123 divides the light from the second light source 121 into P light and S light, the P light transmits through the PBS beam-splitting surface and is incident to the light trap surface to disappear directly, and the S light is reflected by the second PBS beam-splitting surface and then enters the second imaging lens 124 to be uniformly irradiated on the mark of the 104 area.

[0066] The second reflected light passes through the imaging system light path composed of the second imaging lens 124, the second PBS beam-splitter prism 123, the second half glass 125, the compensating prism 126, the PBS beam-combining prism 131 and the third imaging lens 132. The P light becomes S light by passing through the half glass 125, the S light is first reflected by 90 degrees by the beam-splitting surface of the PBS beam-combining prism 131, at this time the polarization state is S light, the S light is incident to the third imaging lens 132 again and then to the camera 133; thus, the mark on the second reference plate 103 is imaged on the camera 133.

[0067] The first light source 111 and the second light source 121 emit a certain amount of light, the first collimating lens 112 and the second collimating lens 122 converge and collimate the light emitted by the first light source 111 and the second light source 121 respectively, the collimated light is incident to the first PBS light splitting prism 113 and the second PBS light splitting prism 123 respectively, the first PBS light splitting prism 113 and the second PBS light splitting prism 123 respectively split the light from the first light source 111 and the second light source 121 into P light and S light two parts, the P light transmits through the PBS light splitting surface and is incident to the light trap surface to disappear directly, the S light is reflected after passing through the first PBS light splitting surface and enters the first imaging lens 114 and the second imaging lens 124 respectively and is uniformly irradiated on the first reference plate 101 and the second reference plate 103. The first reflected light passes through the first imaging lens 114, then is reflected by the first PBS light splitting prism 113, the P light becomes S light after passing through the first half glass 115, the S light is first reflected by 90 degrees after passing through the light splitting surface of the PBS beam combining light splitting prism 131, then is reflected by 180 degrees after reaching the prism surface, at this time the polarization state is P light, the P light transmits through the light splitting surface of the PBS beam combining light splitting prism 131 again and is incident to the third imaging lens 132, and then reaches the camera 133. The second reflected light passes through an additional compensation prism 126 compared with the first reflected light. The camera 133 compares the image information. When it is judged that the two reference plates are aligned, the bonding operation is performed; when it is judged that the two reference plates are not aligned, the control unit 150 calculates the position deviation amount of the first reference plate 101 and the second reference plate 103 through a specific algorithm, the precision motion stage 105 is connected to the first reference plate 101, the precision motion stage 106 is connected to the second reference plate 103, and the control unit 150 drives the micro-motion platform to move at least one of the first reference plate 101 and the second reference plate 103, so that the first reference plate 101 and the second reference plate 103 are aligned. After the movement is finished, the alignment is performed again, and when it is judged that the two reference plates are aligned, the bonding operation is performed.

[0068] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed in the present application should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An alignment device for directly positioning a first reference plate and a second reference plate relative to each other, characterized in that, include: The system comprises a first collimating unit, a first refractive unit, a second collimating unit, a second refractive unit, a beam combining and splitting prism, an imaging and collecting unit, and an optical path compensation structure. The first refraction unit includes: a first beam splitter and a first imaging lens; the second refraction unit includes: a second beam splitter and a second imaging lens; the imaging collection unit includes: a third imaging lens and a camera; The first collimating unit collimates the first beam and refracts it to the first reference plate after passing through the first refraction unit. The first reflected light from the first reference plate passes through the beam combining and splitting prism and illuminates the imaging collection unit to form a first optical path, causing the mark on the first reference plate to be imaged onto the camera. The second collimating unit collimates the second beam and refracts it to the second reference plate after passing through the second refraction unit. The second reflected light from the second reference plate passes through the beam combining and splitting prism and illuminates the imaging collection unit to form a second optical path, causing the mark on the second reference plate to be imaged onto the camera. The first reflected light is reflected at a 90-degree angle when it passes through the inclined surface of the beam combining and splitting prism, and then reflected at a 180-degree angle after reaching the surface of the beam splitting prism. It then passes through the inclined surface of the beam combining and splitting prism and enters the imaging collection unit. The second reflected light first enters the optical path compensation structure, and then is directly reflected by the inclined surface of the beam combining and splitting prism into the imaging collection unit. The optical path length from the first reflected light to the imaging collection unit and the optical path length from the second reflected light to the imaging collection unit are the same. The camera is configured to generate corresponding images based on two beams respectively, and when the two images overlap, it is determined that the first reference plate and the second reference plate are aligned.

2. The alignment device according to claim 1, characterized in that, The optical path compensation structure is a compensation prism, which is disposed between the second refractive unit and the beam combining and splitting prism. It is used to compensate for the optical path difference that the second reflected light reflects one less time than the first reflected light in the beam combining and splitting prism, so that the optical path of the first reflected light to the imaging system and the optical path of the second reflected light to the imaging system are the same.

3. The alignment device according to claim 1, characterized in that, The optical path compensation structure and the second refractive unit form a first prism group, which is used to compensate for the optical path difference that the second reflected light reflects one less time than the first reflected light in the beam combining and splitting prism, so that the optical path of the first reflected light to the imaging system and the optical path of the second reflected light to the imaging system are the same.

4. The alignment device according to claim 1, characterized in that, The optical path compensation structure and the beam combining and splitting prism form a second prism group, which is used to compensate for the optical path difference that the second reflected light reflects one less time than the first reflected light in the beam combining and splitting prism, so that the optical path of the first reflected light to the imaging system and the optical path of the second reflected light to the imaging system are the same.

5. The alignment device according to claim 1, characterized in that, The image formed by the first or second optical path is a Kohler illumination image or a critical illumination image.

6. The alignment device according to claim 1, characterized in that, It also includes a control unit and a micro-motion platform. The control unit is connected to the imaging collection unit, and the micro-motion platform is connected to the two reference plates on both sides respectively. The information collected by the imaging collection unit is transmitted to the control unit. When it is determined that the image is not aligned, the control unit drives the micro-motion platform to move at least one of the first reference plate and the second reference plate to align the first reference plate and the second reference plate.

7. The alignment device according to claim 1, characterized in that, It also includes two half-glass slides, which are respectively located between the first refractive unit and the beam combining and splitting prism, and between the second refractive unit and the beam combining and splitting prism; the half-glass slides convert P-light into S-light; the beam combining and splitting prism is a PBS beam combining and splitting prism, which is used to absorb P-light and reflect S-light; the half-glass slides and the PBS beam combining and splitting prism provide a single light source for the imaging collection unit.

8. The alignment device according to claim 1, characterized in that, The first collimation unit includes a first light source and a first collimating lens; the second collimation unit includes a second light source and a first collimating lens; the first imaging lens and the second imaging lens respectively include a magnification compensation element and an image quality compensation element, used to compensate for the performance difference between the two optical paths.

9. The alignment device according to claim 8, characterized in that, The third imaging lens includes a magnification compensation element and an image quality compensation element, which are used to compensate for the magnification and aberrations of the entire optical system.

10. The alignment method of the alignment device according to any one of claims 1 to 9, characterized in that, Includes the following steps: (1) The first beam and the second beam illuminate the first reference plate and the second reference plate, respectively; (2) The first reflected light fed back from the first reference plate passes through the beam combining and splitting prism and illuminates the imaging collection unit, so that the mark of the first reference plate is imaged onto the camera; The second reflected light from the second reference plate passes through a beam-splitting prism and illuminates the imaging collection unit, causing the mark on the second reference plate to be imaged onto the camera; the optical path of the first reflected light to the imaging collection unit and the optical path of the second reflected light to the imaging collection unit are the same; (3) The imaging collection unit generates corresponding images based on the two beams respectively; (4) When two images overlap, determine that the first reference plate and the second reference plate are aligned.

Images