Wafer bonding alignment method and device

Abstract

The invention provides a wafer bonding alignment method and device, and the method comprises the steps: providing a first carrying platform and a second carrying platform which are vertically arranged, a lens and a light source, enabling the lens and the light source to be located at the two sides, deviating from each other, of the first carrying platform and the second carrying platform, enabling the light source and the lens to be installed on a pedestal, and enabling the first carrying platform and the second carrying platform to be of a structure capable of transmitting light; the first carrying table carries a first wafer, and the second carrying table carries a second wafer; moving the first carrying table to an alignment position and keeping the first carrying table still; the light source emits light, and the base frame is moved until the lens searches the first alignment mark on the first wafer; moving the second carrying table until the lens searches the second alignment mark on the second wafer; fine adjustment is carried out through the second carrying table, so that the second alignment mark and the first alignment mark are completely aligned. Through the configuration, mechanical movement and errors can be reduced, the alignment marks of the upper wafer and the lower wafer can be detected at the same time, the alignment movement process can be observed in real time, the wafer bonding process is simplified, and the alignment efficiency and the alignment precision are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit manufacturing, and in particular to a wafer bonding alignment method and device. Background Art

[0002] Existing wafer bonding alignment usually requires multiple steps of calibration and position error compensation, including: wedge error compensation, lens optical alignment, position error compensation, nano-motion platform calibration, finding alignment marks on the wafer, etc., which basically involve optical alignment, physical alignment and air flotation stability. Among them, lens optical alignment is an important prerequisite that affects the overall alignment accuracy. Specifically, in the traditional wafer bonding alignment method, two groups of upper and lower lenses are used. The left and right groups of upper and lower lenses are first aligned and accurate through the calibration eye. Then, the upper and lower wafers need to be moved to the alignment position by moving the upper and lower platforms, and then fine-tuned and compensated based on the calibration eye position deviation recorded when the platform moves to the alignment position twice, so as to align the alignment marks of the upper and lower wafers. In this way, there are the following problems:

[0003] (1) When the upper and lower lenses are optically aligned, it is usually done automatically by the system. However, if the error is too large, manual adjustment is required, which makes the operation cumbersome. In addition, the calibration of the upper and lower lenses will also produce errors, affecting the alignment accuracy. In addition, the large number of lenses increases the lens material cost.

[0004] (2) The unloading platform needs to move between the alignment position and the loading position, and the error will continue to accumulate, resulting in larger errors. In addition, a larger space is required, and corresponding electrical and mechanical components need to be configured, which increases the complexity of the machine.

[0005] (3) Due to the limitation of the imaging optical path, the alignment marks of the upper and lower wafers cannot be detected simultaneously, the movement process of the upper and lower wafers cannot be observed in real time, the status of the alignment parts cannot be judged in time, and the alignment parts cannot be calibrated or replaced in time, resulting in the inability to discover the problem in time when the error is too large, thereby reducing the handling efficiency.

[0006] It should be noted that the information disclosed in the background technology section of this application is only intended to deepen the understanding of the general background technology of this application, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0007] The object of the present invention is to provide a wafer bonding alignment method and device, which can simplify the wafer alignment process, reduce mechanical movement, reduce errors, and improve alignment accuracy and alignment efficiency.

[0008] To achieve the above object, the present invention provides a wafer bonding alignment method, which comprises:

[0009] A first stage, a second stage, a lens and a light source are provided, which are arranged vertically. The lens and the light source are respectively located on two sides of the first stage and the second stage which are away from each other. The light source and the lens are mounted on the same base frame, and the lens is located on the optical path of the light source to receive transmitted light. The first stage carries a first wafer, and the second stage carries a second wafer. Both the first stage and the second stage are made into structures capable of transmitting light.

[0010] Move the first stage to the alignment position and keep it stationary;

[0011] The light source emits light toward the first stage, and moves the base frame until the lens searches for a first alignment mark on the first wafer;

[0012] Moving the second stage until the lens finds a second alignment mark on the second wafer;

[0013] The second stage is then used for fine adjustment to ensure that the second alignment mark is completely aligned with the first alignment mark.

[0014] Optionally, the wafer bonding alignment method further includes:

[0015] After searching for the first alignment mark, recording the coordinate position of the first alignment mark;

[0016] After searching for the second alignment mark, recording the coordinate position of the second alignment mark;

[0017] Based on the coordinate position of the first alignment mark and the coordinate position of the second alignment mark, the relative position of the first alignment mark and the second alignment mark is obtained, and the second stage is controlled to perform fine adjustment according to the relative position.

[0018] Optionally, the wafer bonding alignment method further satisfies at least one of the following:

[0019] When moving the first stage to the alignment position, it includes: driving the first stage to move from the loading position to the alignment position along the Y-axis direction;

[0020] When the base frame is moved, it includes: driving the base frame to move along the X-axis direction and the Y-axis direction;

[0021] When the second stage is moved to the alignment position and kept moving, it includes: driving the second stage to move along the X-axis direction and the Y-axis direction, and rotating around the Z-axis direction.

[0022] Optionally, the first carrier absorbs the first wafer through a first suction cup, and the second carrier absorbs the second wafer through a second suction cup, the first suction cup is provided with a hollow structure to transmit light, and the second suction cup is provided with an observation eye, and the position of the observation eye matches the position of the second alignment mark.

[0023] Optionally, the lens, the second stage, the first stage and the light source are arranged in sequence from top to bottom.

[0024] Optionally, after the first alignment mark and the second alignment mark are completely aligned, the method further includes: controlling the first wafer and the second wafer to perform wafer bonding.

[0025] To achieve the above-mentioned purpose, the present invention further provides a wafer bonding alignment device, which comprises a base frame; a control device; and a first carrier, a second carrier, a lens and a light source arranged vertically; the lens and the light source are respectively located on two sides of the first carrier and the second carrier that are away from each other; the light source and the lens are both mounted on the base frame, and the lens is located on the optical path of the light source to receive transmitted light, and the first carrier and the second carrier are both configured to have a structure capable of transmitting light; the first carrier carries a first wafer, and the second carrier carries a second wafer;

[0026] The control device is configured to perform the following processing:

[0027] Controlling the first stage to move to the alignment position and keep it stationary;

[0028] Controlling the light source to emit light toward the first stage, and controlling the base frame to move until the lens finds a first alignment mark on the first wafer;

[0029] Controlling the second stage to move until the lens finds a second alignment mark on the second wafer;

[0030] The second stage is controlled to perform fine adjustment so that the second alignment mark and the first alignment mark are completely aligned.

[0031] Optionally, the first carrier absorbs the first wafer through a first suction cup, and the second carrier absorbs the second wafer through a second suction cup, the first suction cup is provided with a hollow structure to transmit light, and the second suction cup is provided with an observation eye, and the position of the observation eye matches the position of the second alignment mark.

[0032] Optionally, the lens, the second stage, the first stage and the light source are arranged in sequence from top to bottom.

[0033] Optionally, the control device is also configured to: obtain the relative position of the first alignment mark and the second alignment mark based on the coordinate position of the first alignment mark and the coordinate position of the second alignment mark, and control the nano-motion platform on the second carrier to perform fine-tuning according to the relative position.

[0034] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects:

[0035] The present invention only needs to provide one lens, which greatly reduces the number of lenses, reduces the material cost of the lenses, and also eliminates the step of aligning and calibrating the upper and lower lenses of the left and right groups, thereby avoiding the error caused by the alignment calibration of the lenses. In addition, the present invention overcomes the limitation of the imaging optical path through the light-transmitting design of the first carrier, that is, under the same lens, the alignment marks of the upper and lower wafers can be detected at the same time, and there is no need to move the two carriers to the alignment position for detection by moving the first carrier, thereby reducing the mechanical movement of the first carrier, and then reducing the error caused by the movement of the first carrier, improving the alignment accuracy, and the reduction of mechanical movement also helps to reduce the probability of bubbles appearing in the middle of the bonding layer of the two wafers, reduce wafer losses, and ensure bonding quality. In addition, the present invention also reduces the alignment calibration steps, simplifies the entire wafer bonding alignment process, and effectively improves the alignment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0037] Figure 1 A schematic structural diagram of a wafer bonding alignment device provided in an embodiment of the present invention.

[0038] Figure 2 A flow chart of a wafer bonding alignment method provided in an embodiment of the present invention.

[0039] In the figure: 1-lens, 2-light source, 3-first stage, 4-second stage, 31-first suction cup, 5-base, 6-air floating, 7-optical path, 101-first wafer, 102-second wafer, 103-first alignment mark, 104-second alignment mark. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention are described below in conjunction with the drawings in the embodiments of the present invention. Among them, in the description of the embodiments of the present invention, the terms used in the following embodiments are only for the purpose of describing specific embodiments, and are not intended to be used as limitations on the present invention. As used in the specification of the present invention and the appended claims, the singular expressions "a", "said", "above", "the" and "this" are intended to also include expressions such as "one or more", unless there is a clear contrary indication in the context. It should also be understood that in the following embodiments of the present invention, "at least one", "one or more" refer to one or more than two (including two). The term "and / or" is used to describe the association relationship of associated objects, indicating that three relationships can exist; for example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship.

[0041] References to "one embodiment" or "some embodiments" etc. described in this specification mean that one or more embodiments of the present invention include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways. The term "connection" includes direct connection and indirect connection, unless otherwise specified. "First" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0042] In the embodiments of the present invention, words such as "exemplarily" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplarily" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplarily" or "for example" is intended to present related concepts in a specific way.

[0043] The embodiments of the present invention provide a wafer bonding alignment method and device, which are intended to simplify the wafer bonding alignment process, improve the alignment efficiency, solve the problem of cumulative error of mechanical movement, and improve the alignment accuracy.

[0044] Figure 1 The structure diagram of the wafer bonding alignment device according to some embodiments disclosed in the present invention is shown. Figure 1 As shown, an embodiment of the present invention provides a wafer bonding alignment device, which includes: a base frame 5; and a lens 1, a second stage 4, a first stage 3 and a light source 2 arranged in sequence from top to bottom; in other embodiments, the lens 1, the second stage 4, the first stage 3 and the light source 2 can also be arranged in sequence from bottom to top, so that the light source 2 is at the top position of the base frame 5, and the lens 1 is at the bottom position of the base frame 5, which is different from Figure 1 The light source 2 shown in the figure is at the bottom of the base frame 5, and the lens 1 is at the top of the base frame 5. Alternatively, the light source 2 is arranged on the side of the second stage 4 away from the first stage 3, and the lens 1 is arranged on the side of the first stage 3 away from the second stage 4. Therefore, the lens 1 and the light source 2 can be respectively located on the two sides of the first stage 3 and the second stage 4 away from each other.

[0045] Wherein: the light source 2 and the lens 1 are both mounted on the base frame 5, so that the light source 2 and the lens 1 remain relatively fixed, and the light source 2 and the lens 1 are adjusted synchronously, so that the light source 2 and the lens 1 can remain relatively stable, and the dynamic stability of the entire device is improved. It should be noted that after the light source 2 and the lens 1 are mounted on the base frame 5, the relative positions of the two have been fixed, the lens 1 is always located on the optical path 7 of the light source 2 to receive the transmitted light, and the upper and lower spacing between the lens 1 and the light source 2 is appropriate, ensuring that the lens 1 can clearly display the image.

[0046] The lens 1 of the present invention can adopt a high-precision microscope to ensure the image quality. The light source 2 of the present invention can adopt an ordinary light source or an infrared light source or other suitable light sources, which is not limited by the present invention.

[0047] In addition, the first stage 3 carries the first wafer 101, and the second stage 4 carries the second wafer 102, and the first wafer 101 and the second wafer 102 are arranged parallel to each other. Figure 1 As can be seen, the light source 2 is disposed on the back side of the first wafer 101 away from the second wafer 102 , and the lens 1 is disposed at a relative position of the back side of the second wafer 102 away from the first wafer 101 .

[0048] Further research has found that in the existing related technologies, due to the limitation of the imaging optical path, it is impossible to detect the alignment marks of the upper and lower wafers at the same time, so it is necessary to move the upper and lower wafers to the alignment position (i.e., the detection position) by moving the upper and lower platforms, resulting in the wafer alignment accuracy being affected by the return error of the mechanical moving parts, and it is impossible to observe the alignment movement process of the upper and lower wafers in real time. Therefore, it is difficult to achieve high-precision alignment in the traditional wafer bonding alignment method, and as described in the background technology, the entire alignment process is complicated and requires multiple steps of alignment calibration, which reduces the alignment efficiency.

[0049] To this end, the first stage 3 and the second stage 4 of the present invention are both made to have a structure capable of transmitting light. Figure 1 Taking the installation orientation shown as an example, when the first stage 3 and the second stage 4 are both in the alignment position, when the light source 2 emits light toward the first stage 3, the light can be transmitted upward through the first stage 3 and the first wafer 101, and then fall on the second wafer 102, and finally the lens 1 can simultaneously detect the alignment mark on the first wafer 101 and the alignment mark on the second wafer 102. As can be understood by those skilled in the art, the first stage 3 and the second stage 4 usually absorb the wafer through a chuck, specifically, the first stage 3 absorbs the first wafer 101 through the first chuck 31, and the second stage 4 absorbs the second wafer 102 through the second chuck (not marked).

[0050] Therefore, in this embodiment, the first suction cup 31 on the first stage 3 and the second suction cup on the second stage 4 are both made to have a structure capable of transmitting light. The position of the light source 2 should satisfy that the light emitted by it falls on the light-transmitting structure of the first suction cup 31 or the light-transmitting structure of the second suction cup. When the two wafer alignment marks are detected at the same time, the upper and lower alignment marks can appear in the lens of the lens 1 at the same time. Figure 1 It can be seen that the lens 1, the second carrier 4, the first carrier 3 and the light source 2 are arranged in sequence from top to bottom, and finally the lens 1 observes the alignment accuracy of the upper and lower alignment marks through the observation eye (the observation eye is a light-transmitting structure) on the second suction cup.

[0051] With such an arrangement, the present invention overcomes the limitation of the imaging optical path, and can detect the alignment marks of the upper and lower wafers at the same time under a single lens 1, without having to detect the alignment marks of the upper and lower wafers separately by moving the first carrier 3 multiple times. Specifically, since the first carrier 3 itself is provided with a structure for transmitting light, when detecting the alignment mark on the second wafer 102, the first carrier 3 can continue to stay in its alignment position, so that with the first carrier 3 as a reference, the light source 2 continues to illuminate the upper and lower wafers in the direction of the first carrier 3, and the alignment marks of the upper and lower wafers are simultaneously displayed in the field of view of the lens 1, which can reduce the mechanical movement of the first carrier 3, reduce the error caused by mechanical movement, and improve the alignment accuracy. Because of this, the present invention can also observe the alignment movement process of the upper and lower wafers in real time, and judge the status of the alignment parts in time to determine whether calibration or replacement of the alignment parts is required.

[0052] In more detail, Figure 1As shown, alignment marks are formed in specific areas on the substrates of the first wafer 101 and the second wafer 102. Specifically, a first alignment mark 103 is formed in a specific area on the substrate of the first wafer 101, and a second alignment mark 104 is formed in a specific area on the substrate of the second wafer 102. These marks can be made by photolithography on the dielectric layer or metal layer on the wafer, and then dry or wet etching. The first alignment mark 103 and the second alignment mark 104 are both light-transmitting areas that allow light to pass through the first wafer 101 and the second wafer 102 to reach the lens 1. The first alignment mark 103 and the second alignment mark 104 can be made into various graphics, which is not limited by the present invention. Optionally, any one of the first alignment mark 103 and the second alignment mark 104 can adopt a cross shape, a swastika shape, concentric circles, an octagon or other various graphics. In one embodiment, the first alignment mark 103 and the second alignment mark 104 can be a set of mutually nested graphics. In some other embodiments, the first alignment mark 103 and the second alignment mark 104 may also be grating patterns, and their grating constants satisfy the near-infrared light diffraction conditions. In short, the first alignment mark 103 and the second alignment mark 104 may be any suitable visible pattern in the art, as long as the image positioning accuracy can be ensured and the alignment accuracy is not affected.

[0053] Based on the above wafer bonding alignment device, Figure 2 A wafer bonding alignment method is shown, the method comprising:

[0054] S01: Move the first stage 3 to the alignment position and keep it stationary;

[0055] S02: The light source 2 emits light toward the first stage 3, and moves the base frame 5 until the lens 1 searches for the first alignment mark 103 on the first wafer 101; in this embodiment, the first alignment mark 103 is located within the field of view of the lens 1, is captured by the lens 1, and the coordinate position of the first alignment mark 103 is recorded;

[0056] S03: Move the second stage 4 until the lens 1 searches for the second alignment mark 104 on the second wafer 102; it should be noted that in this step, the first stage 3 continues to remain in the alignment position and does not move, and the base frame 5 also remains stationary; and in this embodiment, the second alignment mark 104 is located within the field of view of the lens 1, is captured by the lens 1, and the coordinate position of the second alignment mark 104 is recorded;

[0057] S04: Fine-tune the second stage 4 to fully align the first alignment mark 103 and the second alignment mark 104; when the first alignment mark 103 and the second alignment mark 104 are fully aligned, the central axis of the first alignment mark 103 coincides with the central axis of the second alignment mark 104.

[0058] It is also worth mentioning that when searching for the first alignment mark 103, the second stage 4 has not entered its alignment position, which does not affect the search for the first alignment mark 103; in addition, after searching for the first alignment mark 103, the position of the base frame 5 is fixed and no longer changes. When searching for the second alignment mark 104, the second stage 4 enters its alignment position. However, due to the existence of errors, it is necessary to further move the second stage 4 to adjust the position to ensure that the first alignment mark 103 and the second alignment mark 10 can be fully aligned.

[0059] For ease of description, an XYZ rectangular coordinate system is defined below, wherein the Z axis corresponds to the vertical direction (ie, vertical direction), and the X axis and the Y axis correspond to two mutually perpendicular directions in the horizontal direction.

[0060] Preferably, step S04 further includes: based on the coordinate position of the second alignment mark 104 and the coordinate position of the first alignment mark 103, the relative position of the second alignment mark 104 and the first alignment mark 103 is obtained, and the second stage 4 is controlled to move slightly according to the relative position. In this way, the position of the second stage 4 can be accurately adjusted to ensure the alignment accuracy. When the second stage 4 is fine-tuned, the second stage 3 is generally driven to move along the X-axis direction and along the Y-axis direction, and to rotate around the Z-axis direction. It can be understood that a motor is set in the X-axis direction, and a motor is set on each side of the Y-axis direction. The rotation around the Z-axis can be achieved by rotating the two motors on the left and right sides of the Y-axis in opposite directions.

[0061] As can be understood by those skilled in the art, normally, all tables (including the first table 3 and the second table 4) are respectively mounted on corresponding stages, which are in turn mounted on a marble platform, and a nano-motion platform (nanostage) and a chuck are embedded in any one of the tables, wherein the nano-motion platform is used for fine-tuning, the table only moves in the Z-axis direction, and the table needs to be suspended on the table when it moves.

[0062] In addition, to ensure the accuracy of movement, all movements are usually carried out in an air-floating state, including the base frame 5 being suspended on the marble platform when moving, the first carrier 3 and the second carrier 4 being suspended on their respective loading platforms when moving, and the loading platforms being suspended on the marble platform when moving. Taking the base frame 5 as an example, when the base frame 5 is not moving, the base frame 5 falls directly on the marble platform. When it needs to move, the base frame 5 is suspended on the marble platform through air flotation 6. It is understandable that during movement, a layer of air film is formed between the base frame 5 and the marble platform. This layer of air film can realize the contactless support of the marble platform to the base frame 5, reduce mechanical friction and wear during movement, and can also use the pressure distribution of the gas to realize the horizontal adjustment of the base frame 5. Alternatively, during movement, the base frame 5 can also be suspended on the marble platform through magnetic levitation.

[0063] Preferably, in step S01, when moving the first stage 3 to the alignment position, the process includes: driving the first stage 3 to move from the loading position to the alignment position along the Y-axis direction. At this time, the first stage 3 only needs to move in a single direction, which saves space, saves corresponding electrical and mechanical component configurations, and simplifies the machine structure.

[0064] Preferably, in step S02, when the base frame 5 is moved, the method includes: driving the base frame 5 to move along the X-axis direction and the Y-axis direction, so that the base frame 6 can drive the lens 1 to search for the alignment mark in time. It should also be noted that, generally, there is no need to adjust the position in the Z-axis direction. Only when the zoom of the lens cannot clearly display the alignment mark, the Z-axis position of the stage or the Z-axis position of the lens needs to be adjusted.

[0065] Preferably, in step S03, when the second stage 4 is moved to the alignment position and kept moving, it includes: driving the second stage 4 to move along the X-axis direction and the Y-axis direction, and to rotate around the Z-axis direction. At this time, the movement of the second stage 4 is actually a coarse adjustment.

[0066] Continue to refer to Figure 2 After the alignment is completed, bonding begins, including: controlling the first wafer 101 and the second wafer 102 to perform wafer bonding. During wafer bonding, the surface to be bonded of the first wafer 101 and the surface to be bonded of the second wafer 102 are parallel and perpendicular to the Z axis. Generally, the second stage 4 is controlled to descend to reduce the distance between the first wafer 101 and the second wafer 102, and then the first wafer 101 and the second wafer 102 are controlled to perform wafer bonding according to a conventional bonding operation mode.

[0067] It is worth noting that the above wafer bonding alignment device may also include a control device, which is configured to execute the wafer bonding alignment method described in any embodiment of this document.

[0068] An embodiment of the present invention further provides a readable medium having a program stored thereon, and when the program is executed by a processor, the wafer bonding alignment method described in any embodiment of the present invention is executed.

[0069] The control device may further include a controller, a processor and a memory. The memory is used to store a program so that the program can be executed by the processor. The controller may output a drive signal to control the movement of the corresponding drive module. In practice, the control device may be implemented using a control console provided on the wafer bonding machine.

[0070] The movements of the first carrier 3, the second carrier 4 and the base frame 5 are usually driven and controlled by the corresponding driving modules. Specifically, the wafer bonding alignment device also includes a driving module that is communicatively connected to the control device. Since the driving module is a technical content that is easily understood by those skilled in the art, the driving module will not be described in detail. The following is only an exemplary description.

[0071] In some possible implementations, the driving module includes a first driving module, a second driving module and a third driving module, and these driving modules are independent of each other.

[0072] The first driving module is connected to the base frame 5 to drive the base frame 5 to move along the X-axis direction or along the Y-axis direction relative to the first stage 3. Therefore, the base frame 5 can move along the X-axis direction and the Y-axis direction to adjust the position. The second driving module is connected to the first stage 3 to drive the first stage 3 to move in the horizontal direction. Preferably, the first stage 3 only needs to move along the Y-axis direction, and the Y-axis direction corresponds to the conveying direction of the manipulator. The manipulator is used to convey the wafer to be bonded to any stage. The third driving module is connected to the second stage 4 to drive the second stage 4 to move in the horizontal direction. In practice, the second stage 4 includes coarse movement and fine movement, and both coarse movement and fine movement include movement in the X-axis direction and the Y-axis direction, and rotation around the Z-axis direction. Among them, the fine movement of the second stage 4 is mainly realized by a nano-motion platform. Most of the existing nano-motion platforms can use piezoelectric drive modules to control the piezoelectric drive modules to drive the second stage 4 to produce small displacements in the Y-axis direction and the X-axis direction.

[0073] Usually, the corresponding positioning module is also used to measure the positions of the base frame 5, the first stage 3 and the second stage 4, so that the positions of the base frame 5, the first stage 3 and the second stage 4 can be driven and controlled by the corresponding positioning module. Generally, the positioning module uses a grating ruler to detect the positions of the first stage 3 and the second stage 4. In addition, the limit sensor can also be used to ensure that the stage moves within a safe range without interference.

[0074] The above first to third driving modules and the positioning module are technical contents that are easily understood by those skilled in the art, and thus will not be described in detail.

[0075] Further, in the present embodiment, a transparent structure or a hollow structure is provided on the first suction cup 31 on the first carrier 3 to transmit light. More preferably, a hollow structure is provided on the first suction cup 31. Compared with a transparent structure, a hollow structure is simpler to manufacture, more convenient to process, and has a better light transmission effect. Neither the transparent structure nor the hollow structure affects the adsorption function of the suction cup. In particular, when the first carrier 3 is located below the second carrier 4 and used as a downloading platform, since the air path involved in the downloading platform is usually simpler than that of the upper platform, the downloading platform has a certain space to be made into a larger area of ​​hollowing. At this time, there is no special restriction on the position of the first alignment mark 103 on the first wafer 101. Therefore, the hollowing on the first suction cup 31 and the position of the first alignment mark 103 can match or not match, as long as the light can pass through the hollowing to irradiate the first wafer 101 and observe the first alignment mark 103.

[0076] In addition, even if the existing loading platform has its own observation eye, the existing observation eye is mostly used to observe the edge position of the wafer, rather than to observe the alignment mark of the wafer. Therefore, when the second loading platform 4 of the present invention is used as a loading platform, the position of the observation eye on the second suction cup is adjusted so that the observation eye on the second suction cup matches the position of the second alignment mark 104 on the second wafer 102, and then the second alignment mark 104 within the range of the observation eye can be directly observed through the lens 1. It can be understood that because the air paths involved in the loading platform are numerous and complex, and when two wafers are bonded at the same time, the loading platform is generally pressed down and the vacuum is released in different areas. Therefore, the second suction cup is limited and cannot be hollowed out in a large area, and only a small observation eye can be designed. Therefore, the position of the observation eye on the second suction cup should match the position of the second alignment mark 104.

[0077] For ease of understanding, the wafer bonding alignment method proposed by the present invention is further described below in conjunction with some preferred embodiments disclosed in the present invention, which includes the following steps:

[0078] (1) The first stage 3 moves to the alignment position. After reaching the alignment position, the first stage 3 remains stationary;

[0079] (2) Start the air float 6 to suspend the base 5 on the marble platform, turn on the light source 2, and move the base 5 to search for the first alignment mark 103. After the lens 1 finds the first alignment mark 103, turn off the air float 6 to control the base 5 to remain stationary;

[0080] (3) Afterwards, the first stage 3 continues to remain stationary at the alignment position, and the second stage 4 is moved to the alignment position, and then the second stage 4 is moved to search for the second alignment mark 104;

[0081] (4) After the lens 1 searches for the second alignment mark 104, since the first alignment mark 103 and the second alignment mark 104 may not be aligned, it is necessary to perform fine adjustments through the nano-motion platform on the second stage 4 to align the first alignment mark 103 and the second alignment mark 104. The alignment of the first stage 3 and the second stage 4 is thus completed.

[0082] Preferably, the control device is configured to calculate the relative position of the first alignment mark 103 and the second alignment mark 104 according to the coordinate position of the first alignment mark 103 and the coordinate position of the second alignment mark 104, and control the nano-motion platform to fine-tune according to the relative position to align the first alignment mark 103 with the second alignment mark 10. Thus, the control device positions and aligns the entire wafer by identifying and reading the coordinate position of the image center of the alignment mark to ensure the wafer bonding accuracy. Thereafter, the pressure head is driven to press the first wafer 101 and the second wafer 102. Before pressing, the first wafer 101 and the second wafer 102 after alignment can also be pressed by a clamping mechanism.

[0083] In summary, according to the technical solution provided by the embodiment of the present invention, during the wafer bonding process, only one lens 1 is needed throughout the whole process, which not only reduces the number of lenses, but also saves the steps of calibrating the upper and lower lenses of the left and right groups, thereby avoiding the error caused by the lens alignment calibration. The same lens can also detect the alignment marks of the upper and lower wafers at the same time, and observe the movement position and alignment of the upper and lower wafers in real time, which is helpful to judge the state of the alignment parts, so as to replace or calibrate the alignment parts in time and improve the alignment efficiency. At the same time, based on the light-transmitting design of the first carrier 34, the calibration eye can be further saved, that is, there is no need to install a calibration eye on the first carrier 3 and the second carrier 4, which further reduces the number of lenses and reduces the lens material cost.

[0084] Here, those skilled in the art should easily understand the technical content of the calibration eye, that is, the calibration eye is actually a lens installed on the stage, and there is a very small pattern in the lens of the calibration eye, which can be observed by a microscope. In the existing related technology, a set of calibration eyes is first installed on the upper stage, and the upper and lower lenses are aligned and calibrated based on the calibration eyes on the upper stage. At the same time, a set of calibration eyes will also be installed on the download stage to perform position compensation calibration when the download stage moves between the alignment position and the loading position. In the traditional method, the download stage needs to move back and forth between the alignment position and the loading position. When the download stage moves to the alignment position for the second time, it will deviate from the alignment position of the first movement. Therefore, it is necessary to calculate the position deviation generated during the reciprocating movement of the download stage by searching for the pattern in the calibration eye on the download stage twice. The present invention omits the calibration eyes on the upload stage and the download stage based on the light-transmitting characteristics of the download stage itself and the design of a single lens.

[0085] The present invention also uses the light-transmitting design of the first carrier 3 so that the imaging optical path is no longer restricted, so that under the same lens, the alignment marks of the two wafers can be detected at the same time, and there is no need to move the first carrier 3 back and forth. In this way, mechanical movement can be reduced, the error caused by mechanical movement can be reduced, and the alignment accuracy can be improved. Moreover, the reduction of mechanical movement also helps to reduce the probability of bubbles appearing between the bonding layers of the two wafers, reduce wafer losses, and ensure bonding quality. Furthermore, the present invention integrates the loading position and alignment position of the first carrier 3 originally designed into one, saving space, and at the same time, the corresponding electrical control, electric, sensing, air flotation, drive, etc. of the pipeline can be omitted, greatly reducing the equipment cost, simplifying the equipment structure, and also simplifying the operation.

[0086] In general, the technical solution provided by the present invention reduces the alignment calibration steps, greatly simplifies the alignment process of wafer bonding, reduces mechanical movement, effectively solves the accuracy problem caused by errors generated by mechanical movement in the original machine, and can also use the transmission effect of the light source to produce real-time observable images, solving the problem of needing to store alignment marks in advance before the existing alignment process.

[0087] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the present invention, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other at will.

Claims

1. A wafer bonding alignment method, characterized in that: include: A first stage, a second stage, a lens and a light source are provided, which are arranged vertically. The lens and the light source are respectively located on two sides of the first stage and the second stage which are away from each other. The light source and the lens are mounted on the same base frame, and the lens is located on the optical path of the light source to receive transmitted light. The first stage carries a first wafer, and the second stage carries a second wafer. Both the first stage and the second stage are made into structures capable of transmitting light. Move the first stage to the alignment position and keep it stationary; The light source emits light toward the first stage, and moves the base frame until the lens searches for a first alignment mark on the first wafer; Moving the second stage until the lens finds a second alignment mark on the second wafer; The second stage is then used for fine adjustment to ensure that the second alignment mark is completely aligned with the first alignment mark.

2. The wafer bonding alignment method according to claim 1, characterized in that: Also includes: After searching for the first alignment mark, recording the coordinate position of the first alignment mark; After searching for the second alignment mark, recording the coordinate position of the second alignment mark; Based on the coordinate position of the first alignment mark and the coordinate position of the second alignment mark, the relative position of the first alignment mark and the second alignment mark is obtained, and the second stage is controlled to perform fine adjustment according to the relative position.

3. The wafer bonding alignment method according to claim 1 or 2, characterized in that: Also meets at least one of the following: When moving the first stage to the alignment position, it includes: driving the first stage to move from the loading position to the alignment position along the Y-axis direction; When the base frame is moved, it includes: driving the base frame to move along the X-axis direction and the Y-axis direction; When the second stage is moved to the alignment position and kept moving, it includes: driving the second stage to move along the X-axis direction and the Y-axis direction, and rotating around the Z-axis direction.

4. The wafer bonding alignment method according to claim 1 or 2, characterized in that: The first carrier absorbs the first wafer through a first suction cup, and the second carrier absorbs the second wafer through a second suction cup. The first suction cup is provided with a hollow structure to transmit light, and the second suction cup is provided with an observation eye, and the position of the observation eye matches the position of the second alignment mark.

5. The wafer bonding alignment method according to claim 1 or 2, characterized in that: The lens, the second stage, the first stage and the light source are arranged in sequence from top to bottom.

6. The wafer bonding alignment method according to claim 1 or 2, characterized in that: After the first alignment mark and the second alignment mark are completely aligned, the method further includes: controlling the first wafer and the second wafer to perform wafer bonding.

7. A wafer bonding alignment device, characterized in that: Including base frame; control device; and a first stage, a second stage, a lens and a light source arranged vertically; the lens and the light source are respectively located on two sides of the first stage and the second stage away from each other; the light source and the lens are both mounted on the base frame, and the lens is located on the optical path of the light source to receive transmitted light, and the first stage and the second stage are both configured to have a structure capable of transmitting light; the first stage carries a first wafer, and the second stage carries a second wafer; The control device is configured to perform the following processing: Controlling the first stage to move to the alignment position and keep it stationary; Controlling the light source to emit light toward the first stage, and controlling the base frame to move until the lens finds a first alignment mark on the first wafer; Controlling the second stage to move until the lens finds a second alignment mark on the second wafer; The second stage is controlled to perform fine adjustment so that the second alignment mark and the first alignment mark are completely aligned.

8. The wafer bonding alignment device according to claim 7, characterized in that: The first carrier absorbs the first wafer through a first suction cup, and the second carrier absorbs the second wafer through a second suction cup. The first suction cup is provided with a hollow structure to transmit light, and the second suction cup is provided with a hollow observation eye, and the position of the observation eye matches the position of the second alignment mark.

9. The wafer bonding alignment device according to claim 7, characterized in that: The lens, the second stage, the first stage and the light source are arranged in sequence from top to bottom.

10. The wafer bonding alignment device according to claim 7, characterized in that: The control device is also configured to obtain the relative position of the first alignment mark and the second alignment mark based on the coordinate position of the first alignment mark and the coordinate position of the second alignment mark, and control the nano-motion platform on the second stage to perform fine adjustment according to the relative position.

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