Alignment device for wafer bonding

Abstract

The utility model discloses an alignment device for wafer bonding. The alignment device comprises: an infrared source for providing an infrared beam for aligning a first wafer and a second wafer; the confocal optical system is located on one side of the first wafer and used for transmitting the infrared light beams to the second surface of the first wafer and the first surface, opposite to the first surface, of the second wafer through the first wafer so as to obtain positioning of a first identifier on the second surface and positioning of a second identifier on the first surface respectively; and the movement mechanism is respectively connected with the first wafer and the second wafer, and moves the position of the first wafer and / or the second wafer based on the positioning of the first identifier and the second identifier, so that the first identifier and the second identifier are vertically aligned by means of an infrared light beam. According to the utility model, alignment errors caused by deviation of optical axes of the two sets of optical systems and movement errors caused by avoidance of the movement platform in order to obtain the wafer identifier on the other side can be avoided, so that the alignment precision is improved, and the wafer bonding precision is further improved.

Description

Technical Field

[0001] This utility model relates to the technical field of semiconductor processes, and specifically to an alignment device for wafer bonding. Background Technology

[0002] Wafer bonding technology refers to a technique that combines two clean wafers into a single unit using external force. Wafer alignment accuracy is a key parameter in wafer bonding. Typically, during wafer bonding, two sets of visible light optical systems are used to identify and locate markings on the two wafers, thus achieving wafer alignment.

[0003] In existing technologies, such as Figure 1 As shown, the two wafers used for bonding each correspond to a set of optical systems, namely, an optical system 103 on one side of the lower wafer 101 and an optical system 104 on one side of the upper wafer 102. In step S110, the lower wafer 101 is positioned using the optical system 103. Then, in step S120, the upper wafer 102 is positioned using the optical system 104. Next, in step S130, alignment calibration is performed using the positioning data of the lower wafer 101 and the upper wafer 102 obtained by the two sets of optical systems 103 and 104 respectively. Finally, in step S140, the lower wafer 101 and the upper wafer 102 are bonded.

[0004] However, because currently two optical systems are required to align and bond the upper and lower wafers, there is a misalignment between the optical axes of the two systems, and this misalignment changes with the movement of each system, making complete compensation impossible. Furthermore, in... Figure 1 In traditional alignment methods, visible light cannot penetrate the upper wafer 102 to image the markings on the lower wafer 101. Therefore, if only one optical system is used to acquire images of the markings on both wafers, the motion platform needs to be moved back and forth to avoid these obstacles so that visible light can illuminate the other wafer and image its markings. This back-and-forth movement of the motion platform introduces movement errors. These deviations ultimately affect the wafer alignment accuracy. Whether it's the alignment error caused by the optical axis misalignment of the two optical systems or the movement error caused by the motion platform avoiding these obstacles, both will lead to a decrease in wafer alignment accuracy, thus affecting the wafer bonding accuracy.

[0005] In order to solve the above-mentioned problems in the prior art, there is an urgent need in the field for an alignment technology for wafer bonding that can avoid alignment errors caused by the optical axis deviation of the two optical systems corresponding to the two wafers, as well as movement errors caused by the motion platform avoiding the wafer marking on the other side, thereby improving alignment accuracy and thus improving the accuracy of wafer bonding. Utility Model Content

[0006] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed descriptions that follow.

[0007] In order to overcome the above-mentioned defects in the prior art, the present invention provides an alignment device for wafer bonding, which can avoid alignment errors caused by the optical axis deviation of the two optical systems corresponding to the two wafers, as well as movement errors caused by the moving platform avoiding the wafer marking on the other side, thereby improving the alignment accuracy and thus improving the accuracy of wafer bonding.

[0008] Specifically, according to one aspect of the present invention, an alignment device for wafer bonding includes: an infrared light source providing an infrared beam for aligning a first wafer and a second wafer; a confocal optical system located on one side of the first wafer for transmitting the infrared beam through the first wafer to a second surface of the first wafer and a first surface of the second wafer opposite thereto, to obtain the positioning of a first mark on the second surface and a second mark on the first surface, respectively; and a motion mechanism connected to the first wafer and the second wafer, moving the position of the first wafer and / or the second wafer based on the positioning of the first mark and the second mark, so that the first mark and the second mark are vertically aligned by means of the infrared beam.

[0009] Furthermore, in some embodiments of this utility model, the infrared light source is an adjustable light source, used to switch infrared beams of different wavelengths according to the type of thin film prepared on the wafer surface.

[0010] Furthermore, in some embodiments of the present invention, the second surface of the first wafer includes at least two first identifiers, and the first surface of the second wafer includes at least two second identifiers, which are used to determine the movement deflection angle of the first wafer and / or the second wafer.

[0011] Furthermore, in some embodiments of this utility model, the alignment device for wafer bonding includes: at least two sets of the confocal optical systems and their corresponding infrared light sources, wherein the at least two sets of the confocal optical systems and their corresponding infrared light sources are distributed on the same side of the first wafer, for imaging the first mark on the second surface of the first wafer and the second mark on the first surface of the second wafer.

[0012] Furthermore, in some embodiments of this utility model, at least two sets of the confocal optical systems and their corresponding infrared light sources are symmetrical about the center of the first wafer, with the at least two first markings on the first wafer serving as alignment references.

[0013] Furthermore, in some embodiments of this utility model, the confocal optical system includes a first aperture, a second aperture, and an image acquisition device. The first aperture and the second aperture are located on the conjugate planes of the focal planes of the first wafer and the second wafer, respectively. The first aperture is located in front of the image acquisition device, and the second aperture is located in front of the infrared light source. The infrared beam emitted by the infrared light source becomes a point light source after passing through the second aperture and is focused on a first mark on the focal plane of the first wafer and a second mark on the focal plane of the second wafer, respectively. The image acquisition device only receives the images of the first mark and the second mark formed by the light focused by the first aperture.

[0014] Furthermore, in some embodiments of this utility model, the confocal optical system includes a beam splitter located at the intersection of the optical axis of the infrared light source and the optical axis of the image acquisition device, so as to reflect the infrared beam emitted by the infrared light source onto the focal planes of the first wafer and the second wafer respectively, and the reflected light from the focal planes of the first wafer and the second wafer passes through the beam splitter again to reach the image acquisition device for marking and imaging the first mark and the second mark.

[0015] Furthermore, in some embodiments of this utility model, the confocal optical system includes a second aperture stop and a collimating lens, wherein the second aperture stop is located between the infrared light source and the beam splitter, and the first lens is located between the second aperture stop and the beam splitter, for filtering the light source from the non-focusing surface.

[0016] Furthermore, in some embodiments of this utility model, the motion mechanism includes a lateral moving part and a longitudinal moving part. The lateral moving part is used to make the first wafer and / or the second wafer move laterally for identification and searching, and the longitudinal moving part is used to make the first wafer and / or the second wafer move longitudinally for identification and focusing.

[0017] Furthermore, in some embodiments of this utility model, the longitudinal moving part further includes a rotating shaft for rotating the first wafer and / or the second wafer at an angle to perform marking and focusing. Attached Figure Description

[0018] The above-described features and advantages of this invention can be better understood after reading the following detailed description of the embodiments of this disclosure in conjunction with the accompanying drawings. In the drawings, the components are not necessarily drawn to scale, and components having similar related characteristics or features may have the same or similar reference numerals.

[0019] Figure 1 This is a flowchart of the traditional wafer bonding process in the prior art;

[0020] Figure 2 A schematic diagram of an alignment device for wafer bonding according to some embodiments of the present invention is shown.

[0021] Figure 3 This diagram illustrates the structure of the alignment device provided according to some embodiments of the present invention when aligning a wafer;

[0022] Figure 4 The diagram shows a structural schematic representing a first identifier and a second identifier according to some embodiments of the present invention;

[0023] Figure 5 A flowchart of a wafer bonding method according to some embodiments of the present invention is shown; and

[0024] Figure 6 A flowchart of a wafer bonding process provided according to some embodiments of the present invention is shown.

[0025] Figure label:

[0026] Steps S110 to S140;

[0027] 101 Lower wafer;

[0028] 102 Wafer;

[0029] 103, 104 Optical systems;

[0030] 200 Alignment device;

[0031] 210 Infrared light source;

[0032] 220 Confocal Optical System;

[0033] 221 Beam Spectroscope;

[0034] 222 First aperture;

[0035] 223 Image acquisition device;

[0036] 224 Second aperture;

[0037] 225 collimating lens;

[0038] 226 First lens;

[0039] 227 Second lens;

[0040] 310 First wafer;

[0041] 311, 321 First surface;

[0042] 312 Second surface;

[0043] 320 Second Wafer;

[0044] 330 First Identifier;

[0045] 340 Second identifier; and

[0046] Steps S410 to S460. Detailed Implementation

[0047] The following specific embodiments illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. Although the description of this utility model will be presented in conjunction with preferred embodiments, this does not mean that the features of this utility model are limited to this embodiment. On the contrary, the purpose of describing the utility model in conjunction with the embodiments is to cover other options or modifications that may be derived based on the claims of this utility model. To provide a deep understanding of this utility model, many specific details will be included in the following description. This utility model may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this utility model, some specific details will be omitted in the description.

[0048] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0049] Furthermore, the terms "upper," "lower," "left," "right," "top," "bottom," "horizontal," and "vertical" used in the following description should be understood as the orientations shown in the relevant paragraphs and accompanying drawings. These relative terms are for illustrative purposes only and do not imply that the described device must be manufactured or operated in a specific orientation; therefore, they should not be construed as limiting the scope of this invention.

[0050] It is understood that although terms such as "first," "second," and "third" may be used herein to describe various components, regions, layers, and / or parts, these components, regions, layers, and / or parts should not be limited by these terms, and these terms are only used to distinguish different components, regions, layers, and / or parts. Therefore, the first component, region, layer, and / or part discussed below may be referred to as the second component, region, layer, and / or part without departing from some embodiments of this utility model.

[0051] As mentioned above, in the prior art, such as Figure 1 As shown, the two wafers used for bonding each correspond to a set of optical systems, namely, an optical system 103 on one side of the lower wafer 101 and an optical system 104 on one side of the upper wafer 102. In step S110, the lower wafer 101 is positioned using the optical system 103. Then, in step S120, the upper wafer 102 is positioned using the optical system 104. Next, in step S130, alignment calibration is performed using the positioning data of the lower wafer 101 and the upper wafer 102 obtained by the two sets of optical systems 103 and 104 respectively. Finally, in step S140, the lower wafer 101 and the upper wafer 102 are bonded.

[0052] However, because currently two optical systems are required to align and bond the upper and lower wafers, there is a misalignment between the optical axes of the two systems, and this misalignment changes with the movement of each system, making complete compensation impossible. Furthermore, in... Figure 1 In traditional alignment methods, visible light cannot penetrate the upper wafer 102 to image the markings on the lower wafer 101. Therefore, if only one optical system is used to acquire images of the markings on both wafers, the motion platform needs to be moved back and forth to avoid these obstacles so that visible light can illuminate the other wafer and image its markings. This back-and-forth movement of the motion platform introduces movement errors. These deviations ultimately affect the wafer alignment accuracy. Whether it's the alignment error caused by the optical axis misalignment of the two optical systems or the movement error caused by the motion platform avoiding these obstacles, both will lead to a decrease in wafer alignment accuracy, thus affecting the wafer bonding accuracy.

[0053] To address the aforementioned problems in the prior art, this invention provides an alignment device for wafer bonding that can avoid alignment errors caused by the optical axis deviation of the two optical systems corresponding to the two wafers, as well as movement errors caused by the motion platform avoiding the wafer marking on the other side, thereby improving alignment accuracy and thus enhancing the precision of wafer bonding.

[0054] The working principle of the alignment device for wafer bonding described above will be described below with reference to some embodiments of wafer bonding methods. Those skilled in the art will understand that these embodiments of wafer bonding methods are merely non-limiting implementations provided by this invention, intended to clearly demonstrate the main concept of this invention and provide specific solutions convenient for public implementation, rather than limiting all operating methods or functions of the alignment device for wafer bonding. Similarly, the alignment device for wafer bonding is also only a non-limiting implementation provided by this invention and does not limit the entities implementing the steps in these wafer bonding methods.

[0055] Please refer to Figure 2 , Figure 2 A schematic diagram of an alignment device for wafer bonding provided according to some embodiments of the present invention is shown.

[0056] like Figure 2 As shown, in some embodiments of this invention, the alignment device 200 for wafer bonding mainly includes an infrared light source 210, a confocal optical system 220, and a motion mechanism (not shown in the figures). The infrared light source 210 can provide an infrared beam capable of penetrating the first wafer 310 for aligning the first wafer 310 and the second wafer 320. The confocal optical system 220 can be located on the first wafer 310 (e.g., Figure 2 On one side of the upper wafer (of the first wafer 310), an infrared beam is transmitted through the first wafer 310 to the second surface of the first wafer 310 and the first surface of the opposite second wafer 320, so as to obtain the positioning of the first mark on the second surface and the second mark on the first surface, respectively. A motion mechanism can be connected to the first wafer 310 and the second wafer 320 respectively, and based on the positioning of the first mark and the second mark, moves the position of the first wafer 310 and / or the second wafer 320 to vertically align the first mark and the second mark using the infrared beam.

[0057] Specifically, optionally, the infrared light source 210, as the illumination source, can be an adjustable light source. This allows for switching between different wavelengths of infrared beams based on the type of thin film prepared on the surface of different product wafers, achieving the optimal illumination environment, thereby improving image quality and further enhancing alignment accuracy. In actual semiconductor processes, the thin films prepared on the surface of different product wafers vary, resulting in different effects on the reflection of the infrared beam. Therefore, using the same fixed light source will not provide the optimal illumination environment, affecting the alignment accuracy of different product wafers.

[0058] Furthermore, since high-purity silicon allows for precise control over the amount of doping elements, it reduces the impact of impurities in raw materials, thereby improving the performance and reliability of the final product. Existing semiconductor equipment is primarily designed around silicon devices. In this embodiment, the first wafer 310 and / or the second wafer 320 can be made of high-purity silicon wafers, which facilitates subsequent processing and fabrication. However, conventional visible light cannot penetrate silicon wafers, and even ultraviolet light cannot penetrate them. Therefore, in this embodiment, the infrared light source 210 can be an infrared beam capable of penetrating high-purity silicon wafers for marking and aligning the upper and lower wafers.

[0059] Please combine further Figure 3 Common understanding Figure 3 This diagram illustrates a structural schematic of an alignment device according to some embodiments of the present invention during wafer alignment. Figure 3 As shown, when the infrared light source 210 is a near-infrared light source, this wavelength can be imaged through the silicon wafer. The infrared beam emitted by the infrared light source 210 can pass through the first surface 311 of the first wafer 310 and be transmitted to the second surface 312 of the first wafer 310 and the first surface 321 of the opposite second wafer 320, so that the first mark 330 on the second surface 312 of the first wafer 310 and the second mark 340 on the first surface 321 of the second wafer 320 can be imaged by the confocal optical system 220, thereby avoiding Figure 1 The prior art shown requires a moving platform to avoid mechanical errors caused by the alignment beam. At the same time, the upper and lower wafers can be identified and aligned in real time before wafer bonding.

[0060] Continue as Figure 3 As shown, in some embodiments of this utility model, the second surface 312 of the first wafer 310 may include a first mark 330, and the first surface 321 of the second wafer 320 may include a second mark 340. For example, the first mark 330 may be located at the center of the second surface 312 of the first wafer 310, and the second mark 340 may be located at the center of the first surface 321 of the second wafer 320. By adjusting the positions of the first wafer 310 and the second wafer 320 through a motion mechanism, the first mark 330 at the center of the first wafer 310 and the second mark 340 at the center of the second wafer 320 are aligned vertically, thereby achieving alignment of the first wafer 310 and the second wafer 320.

[0061] Furthermore, in some preferred embodiments, the second surface 312 of the first wafer 310 may include at least two first identifiers 330, and the first surface 321 of the second wafer 320 may also include at least two corresponding second identifiers 340. Through the at least two first identifiers 330 on the first wafer 310 and the at least two second identifiers 340 on the second wafer 320, the required movement deflection angle for adjusting the first wafer 310 and / or the second wafer 320 can be calculated during wafer position adjustment. For ease of calculation, preferably, the at least two first identifiers 330 in this embodiment can be symmetrical about the center of the first wafer 310; similarly, the at least two second identifiers 340 can also be symmetrical about the center of the second wafer 320.

[0062] In this regard, the alignment device 200 for wafer bonding may include at least two sets of confocal optical systems 220 and their corresponding infrared light sources 210. Figure 3 (Not shown in the diagram) These confocal optical systems 220 are used to identify and locate at least two first identifiers 330 and at least two second identifiers 340 on the first wafer 310 and the second wafer 320, respectively. These at least two sets of confocal optical systems 220 and their corresponding infrared light sources 210 can be evenly distributed on the same side of the first wafer 310 (or the second wafer 320). In this embodiment, using multiple confocal optical systems 220 on one side to image the upper and lower wafers can reduce... Figure 1 The prior art shown in the diagram suffers from alignment errors due to the optical axis misalignment between the upper and lower optical systems.

[0063] Optionally, corresponding to the positions of at least two first identifiers 330 and at least two second identifiers 340 on their respective wafers in the preferred embodiments described above, at least two sets of confocal optical systems 220 and their corresponding infrared light sources 210 can be further symmetrical about the center of the first wafer 310, using at least two first identifiers 330 on the first wafer 310 as alignment references, thereby adjusting the position of the second wafer 320 so that at least two second identifiers 340 on the second wafer 320 are aligned with the first identifiers 330. In some other embodiments, the position of the first wafer 310 can also be adjusted using at least two second identifiers 340 on the second wafer 320 as alignment references, or the positions of the first wafer 310 and the second wafer 320 can be adjusted together, as long as each first identifier 330 on the first wafer 310 is perpendicularly aligned with each second identifier 340 on the second wafer 320.

[0064] Please refer to Figure 4 , Figure 4 A schematic diagram of the structure representing the first and second identifiers according to some embodiments of the present invention is shown.

[0065] The identifier can include various different types of shapes. Optionally, such as Figure 4 As shown, the first identifier 330 and the second identifier 340 can be nested topographic patterns, which are easily acquired by the confocal optical system 220 and can also improve the alignment accuracy of the upper and lower wafers. For example, the distance between each edge of the second identifier 340 and the corresponding edge of the first identifier 330 can be used to determine whether the first identifier 330 and the second identifier 340 are aligned. Furthermore, the nested topographic patterns can also include bar graphics, ring graphics, etc.

[0066] Please continue to return Figure 2 In traditional optical microscopes, reflected light from off-focus areas interferes with the image, overlapping with the focused image and thus reducing image contrast. However, in this utility model... Figure 2 The confocal optical system 220 shown can effectively solve this problem. In the preferred embodiment of this invention, for the infrared light source 210, the confocal optical system 220 can specifically be an infrared confocal microscope.

[0067] Specifically, combined Figure 2 and Figure 3 It is generally understood that the confocal optical system 220 mainly includes a first aperture 222, a second aperture 224, and an image acquisition unit 223. The first aperture 222 and the second aperture 24 can be located on the conjugate planes of the focal planes of the first wafer 310 and the second wafer 320 (the object under test). The first aperture 222 can be located in front of the image acquisition unit 223, and the second aperture 224 can be located in front of the infrared light source 210. Furthermore, a collimating lens 225 can be disposed in front of the second aperture 224 to filter out light sources that are not in focus. The infrared light source 210, the second aperture 224, and the collimating lens 225 can be connected and fixed by a mechanical structure.

[0068] The working principle of the confocal optical system 220 is as follows: the infrared beam emitted by the infrared light source 210 can become a point light source through the second aperture 224 and be focused on the first mark 330 on the focal plane of the first wafer 310 and the second mark 340 on the focal plane of the second wafer 320, respectively. The image acquisition unit 223 can only receive the images of the first mark 330 and the second mark 340 formed by the light focused by the first aperture 222.

[0069] like Figure 2As shown, in this embodiment, when the first wafer 310 and the second wafer 320 (the object under test) are at the focal plane, the light intensity collected by the image acquisition unit 223 is at its maximum. However, when the first wafer 310 and the second wafer 320 (the object under test) are at the defocus plane, the light spot of the image acquisition unit 223 becomes diffuse, and the light intensity decreases rapidly. Therefore, only the light emitted from points located on the focal planes of the first wafer 310 and the second wafer 320—namely, the first marker 330 on the focal plane of the first wafer 310 and the second marker 340 on the focal plane of the second wafer 320—can pass through the second aperture 224. Light emitted from points outside the focal planes of the first wafer 310 and the second wafer 320 is defocused on the plane of the second aperture 224 and cannot pass through the first aperture 222. Therefore, the first marker 330 and the second marker 340 on the focal plane are the target observation points and appear bright, while other non-target observation points appear dark as the background. This increases the contrast and makes the resulting pattern clearer.

[0070] Combination Figure 3 It is understood that, compared to the prior art, where reflected light from other surfaces of the first wafer 310 (e.g., the first surface 311) interferes with the contrast of the final image captured by the image acquisition unit 223, the confocal optical system 220 used in this invention almost completely removes scattered light other than the focal points of the first wafer 310 and the second wafer 320, i.e., the first mark 330 and the second mark 340. Therefore, a very high contrast image can be obtained, which can greatly reduce the reflected light from other surfaces of the first wafer 310 (e.g., the first surface 311) entering the image acquisition unit 223, improve the clarity of the mark image, and thus improve the alignment accuracy of wafer bonding.

[0071] Furthermore, the confocal optical system 220 may also include a beam splitter 221. The beam splitter 221 may be located at the intersection of the optical axis of the infrared light source 210 and the optical axis of the image acquisition unit 223. It is used to reflect the horizontal infrared beam emitted by the infrared light source 210 after passing through the second aperture 224 and the collimating lens 225 to the focal planes of the first wafer 310 and the second wafer 320, respectively. The reflected light from the focal planes of the first wafer 310 and the second wafer 320 can also pass through the beam splitter 221 again and finally reach the image acquisition unit 223 to perform image imaging of the first mark 330 and the second mark 340.

[0072] Preferably, the confocal optical system 220 may further include other lens components, including a first lens 226 and a second lens 227 that converge the light beam to improve the clarity of the marker imaging. Specifically, the second lens 227 is disposed between the beam splitter 221 and the first wafer 310 and the second wafer 320 (the object under test), while the first lens 226 is disposed between the beam splitter 221 and the image acquisition unit 223. Light reflected by the beam splitter 221 is focused onto the first wafer 310 and the second wafer 320 respectively by the second lens 227, while light passing through the beam splitter 221 can be focused onto the image acquisition unit 223 by the first lens 226. In this embodiment, since the light passes through the second lens 227 twice during the marker acquisition process by the image acquisition unit 223, the point image acquired by the image acquisition unit 223 is sharper, further improving the resolution of the confocal optical system 220.

[0073] Since the light source in some embodiments of this utility model is an infrared light source 210, correspondingly, each component in the above-mentioned confocal optical system 220 can also be selected as a component that works with infrared light. For example, the image acquisition unit 223 can be an infrared camera, and the second lens 227 can be an infrared objective lens, etc.

[0074] In some embodiments of the utility model, the motion mechanism (not shown in the drawings) in the alignment device 200 for wafer bonding may include a lateral moving part and a longitudinal moving part. The lateral moving part allows the first wafer 310 and / or the second wafer 320 to be laterally displaced, i.e., moved in the XY axis direction, which can be used for marker finding. The longitudinal moving part allows the first wafer 310 and / or the second wafer 320 to be longitudinally displaced, i.e., moved in the Z axis direction, which can be used for marker focusing. Optionally, the lateral moving part and the longitudinal moving part may also be integrated together.

[0075] Optionally, the longitudinal moving part may further include a rotating shaft, which may be connected to an angle adjustment motor to further achieve marking focus by rotating the first wafer 310 and / or the second wafer 320 by angle. In this embodiment, the relative position between the first wafer 310 and the second wafer 320 can be adjusted by controlling the motion mechanism to move along the X, Y, and Z axes and rotate by angle.

[0076] Next, please refer to the following: Figure 5 and Figure 6 , Figure 5 A flowchart of a wafer bonding method according to some embodiments of the present invention is shown. Figure 6 A flowchart of a wafer bonding process provided according to some embodiments of the present invention is shown.

[0077] like Figure 5 As shown, in some embodiments of this utility model, the wafer bonding method may include the following steps. First, step S510 may be performed: obtaining a first wafer.

[0078] Combination Figure 2 and Figure 6 It is understood that in some optional embodiments, the first wafer 310 is mounted using a carrier mechanism, for example, a suction cup structure can be used to fix and adsorb the first wafer 310. The first wafer 310 can be located above as the upper wafer or below as the lower wafer. When the first wafer 310 is used as the upper wafer, since the infrared light source 210 and the confocal optical system 220 in the alignment device 200 for wafer bonding are both located above, optionally, the carrier mechanism for fixing the upper wafer can be a perforated structure or a carrier mechanism made of a near-infrared transparent material, that is, the structure of the carrier mechanism can allow the infrared light emitted by the infrared light source 210 located above to pass through, and there is no limitation here.

[0079] Then, step S520 can be performed: positioning the first mark on the second surface of the first wafer using the alignment device.

[0080] Specifically, combined Figure 2 , Figure 3 and Figure 6 As shown, the infrared laser beam emitted by the infrared light source 210 passes through the second aperture 224 and collimating lens 225, and is then reflected by the beam splitter 221 to the second lens 227, and focused onto the first mark 330 on the second surface 312 of the first wafer 310. The reflected light from the first mark 330 on the second surface 312 of the first wafer 310 can then pass through the beam splitter 221 again, finally reaching the image acquisition unit 223 for displaying the first mark 330. Scattered light outside the first mark 330 and scattered light from the second lens 227 will not reach the image acquisition unit 223, thus obtaining an image of the first mark 330 with very high contrast. Then, in conjunction with the processor, the first mark 330 on the first wafer 310 can be positioned.

[0081] Then, step S530 can be performed: obtain the second wafer.

[0082] Can be combined Figure 2 and Figure 6 It is understood that, optionally, the second wafer 320 can be mounted using a carrier mechanism, for example, a suction cup structure can be used to fix and adsorb the first wafer 310. When the second wafer 320 is used as the lower wafer, since the infrared light source 210 and the confocal optical system 220 in the alignment device 200 are both located above, the structure of the carrier mechanism for fixing the lower wafer does not need to be constrained.

[0083] Then, step S540 can be performed: using the alignment device, a second mark is obtained on the first surface of the second wafer for positioning.

[0084] Specifically, it can be combined with Figure 2 , Figure 3 and Figure 6 As shown, the infrared laser beam emitted by the infrared light source 210 passes through the second aperture 224 and collimating lens 225, and is then reflected by the beam splitter 221 to the second lens 227, where it is focused onto the second mark 340 on the first surface 321 of the second wafer 320. The reflected light from the second mark 340 on the first surface 321 of the second wafer 320 then passes through the beam splitter 221 again, finally reaching the image acquisition unit 223 for displaying the second mark 340. Scattered light from outside the second mark 340 and from the second lens 227 does not reach the image acquisition unit 223, thus obtaining an image of the second mark 340 with very high contrast. Then, in conjunction with the processor, the second mark 340 on the second wafer 320 can be positioned.

[0085] Then, step S550 can be performed: adjust the relative positions of the first wafer and the second wafer based on the position difference between the first identifier and the second identifier.

[0086] Specifically, it can be combined with Figure 3 and Figure 6 As shown, based on the positional difference between the first identifier 330 and the second identifier 340 calculated by the processor, the lateral movement part in the motion mechanism can be controlled to cause the first wafer 310 and / or the second wafer 320 to move laterally, i.e., move in the XY axis direction, for identifier retrieval. Furthermore, the longitudinal movement part in the motion mechanism can also be controlled to cause the first wafer 310 and / or the second wafer 320 to move longitudinally, i.e., move in the Z axis direction, for identifier focusing. Further, the first wafer 310 and / or the second wafer 320 can be rotated angularly via a rotation axis to further achieve identifier focusing.

[0087] Finally, step S560 can be performed: in response to the vertical alignment of the first and second identifiers, the first and second wafers are pressed together to complete wafer bonding.

[0088] like Figure 6 As shown, before wafer bonding, the first wafer 310 and the second wafer 320 can be identified and aligned in real time. After the first mark 330 and the second mark 340 are vertically aligned, the first wafer 310 can be pressed down to perform bonding of the two wafers.

[0089] Although the methods described above are illustrated and depicted as a series of actions for the sake of simplicity, it should be understood and appreciated that these methods are not limited by the order of the actions, as some actions may occur in a different order and / or concurrently with other actions from the illustrations and descriptions herein or not illustrated and described herein but which may be understood by those skilled in the art, according to one or more embodiments.

[0090] In summary, this utility model provides an alignment device for wafer bonding that can avoid alignment errors caused by the optical axis deviation of the two optical systems corresponding to the two wafers, as well as movement errors caused by the moving platform avoiding the wafer marking on the other side, thereby improving alignment accuracy and thus enhancing the precision of wafer bonding.

[0091] The prior description of this disclosure is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not intended to be limited to the examples and designs described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An alignment device for wafer bonding, characterized in that, include: An infrared light source provides an infrared beam for aligning the first and second wafers; A confocal optical system, located on one side of the first wafer, is used to transmit the infrared beam through the first wafer to the second surface of the first wafer and the first surface of the second wafer opposite thereto, so as to obtain the positioning of the first mark on the second surface and the second mark on the first surface, respectively. as well as A motion mechanism, connected to the first wafer and the second wafer respectively, moves the position of the first wafer and / or the second wafer based on the positioning of the first mark and the second mark, so as to make the first mark and the second mark vertically aligned by means of the infrared beam.

2. The alignment device as claimed in claim 1, characterized in that, The infrared light source is an adjustable light source, used to switch infrared beams of different wavelengths according to the type of thin film prepared on the wafer surface.

3. The alignment device as claimed in claim 1, characterized in that, The second surface of the first wafer includes at least two of the first identifiers, and the first surface of the second wafer includes at least two of the second identifiers, which are used to determine the movement deflection angle of the first wafer and / or the second wafer.

4. The alignment device as claimed in claim 3, characterized in that, include: At least two sets of the confocal optical systems and their corresponding infrared light sources are distributed on the same side of the first wafer to image the first mark on the second surface of the first wafer and the second mark on the first surface of the second wafer.

5. The alignment device as claimed in claim 4, characterized in that, At least two sets of the confocal optical systems and their corresponding infrared light sources are symmetrical about the center of the first wafer, with the at least two first markings on the first wafer serving as alignment references.

6. The alignment device as claimed in claim 1, characterized in that, The confocal optical system includes a first aperture, a second aperture, and an image acquisition unit. The first aperture and the second aperture are located on the conjugate planes of the focal planes of the first wafer and the second wafer, respectively. The first aperture is located in front of the image acquisition unit, and the second aperture is located in front of the infrared light source. The infrared light emitted by the infrared light source becomes a point light source after passing through the second aperture, and is focused on the first mark on the focal plane of the first wafer and the second mark on the focal plane of the second wafer, respectively. The image acquisition device only receives the images of the first mark and the second mark formed by the light focused by the first aperture.

7. The alignment device as claimed in claim 6, characterized in that, The confocal optical system includes a beam splitter located at the intersection of the optical axis of the infrared light source and the optical axis of the image acquisition device, so as to reflect the infrared beam emitted by the infrared light source onto the focal planes of the first wafer and the second wafer respectively. The reflected light from the focal planes of the first wafer and the second wafer then passes through the beam splitter and reaches the image acquisition device to perform identification imaging of the first mark and the second mark.

8. The alignment device as claimed in claim 7, characterized in that, The confocal optical system includes a second aperture and a collimating lens, wherein the second aperture is located between the infrared light source and the beam splitter, and the collimating lens is located between the second aperture and the beam splitter, for filtering the light source from the non-focusing surface.

9. The alignment device as claimed in claim 1, characterized in that, The motion mechanism includes a lateral movement section and a longitudinal movement section. The lateral movement section is used to locate and identify the first wafer and / or the second wafer by lateral displacement, and the longitudinal movement section is used to locate and focus the first wafer and / or the second wafer by longitudinal displacement.

10. The alignment device as claimed in claim 9, characterized in that, The longitudinal moving part further includes a rotating shaft for rotating the first wafer and / or the second wafer at an angle to perform identification focusing.

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