Wafer bonding pressure control mechanism and method

Abstract

The present application relates to wafer bonding device technical field, especially in a kind of wafer bonding pressure control mechanism and method.The mechanism includes main drive unit, and the bonding pressure rod that is linked with main drive unit, main drive unit drives bonding pressure rod displacement along bonding pressure direction, and bonding pressure is exerted to wafer by bonding pressure rod, the bonding pressure rod is linked with main drive unit by pressure maintaining cylinder, and the bonding pressure rod is arranged at the end of piston rod of pressure maintaining cylinder;It also includes a displacement sensor, and the displacement sensor detects the displacement change of bonding pressure rod, and the displacement sensor is electrically connected with main drive unit.The present application combines main drive unit with pressure maintaining cylinder, forms a kind of composite operation control system, and the control and adjustment of bonding pressure are realized by controlling the air pressure of pressure maintaining cylinder, to ensure the stability of bonding pressure.

Description

Technical Field

[0001] This invention relates to the field of wafer bonding equipment technology, and specifically to a wafer bonding pressure control mechanism and method. Background Technology

[0002] Direct wafer bonding is one of the most researched bonding methods in recent years. This method places the highest demands on the surface morphology and surface treatment processes of silicon wafers, thus often resulting in bonding failures or performance instability. Direct wafer bonding generally refers to the process of bonding two surface-treated wafers together. When bonding failures or performance instability occur, it usually results in the scrapping of two or more wafers, leading to extremely high cost losses.

[0003] See Figure 1 The diagram shown illustrates the current wafer bonding process. Its workflow is as follows:

[0004] First, two surface-treated wafers 91 and 92 are aligned in parallel, with a gap of several tens of micrometers between them. The edge of wafer 91 is positioned by a vacuum chuck 93.

[0005] Then, a certain bonding pressure is applied to the upper wafer 91 by the bonding pressure bar 90, causing the upper wafer 91 to deform along the center and contact the center area of ​​the lower wafer 92.

[0006] Next, the vacuum chuck 93 at the edge of the deformed wafer 91 is released, so that the upper wafer 91 will automatically recover and be pre-bonded with the lower wafer 92.

[0007] Finally, after the pre-bonding is completed, the bonding lever 90 can be removed to take out the bonded wafer pair.

[0008] As mentioned above, during the wafer bonding process, the bonding pressure applied by the bonding bar 90 has a significant impact on the bonding performance between wafer pairs, and it is extremely important to effectively and accurately control the bonding pressure.

[0009] In existing wafer bonding equipment, the bonding pressure bar 90 is displaced by a single cylinder. This method makes the bonding pressure bar 90 susceptible to friction, gaps, and inertia during displacement, making it difficult to balance high speed and high precision. Furthermore, the bonding pressure is adjusted via a single cylinder, resulting in a limited force control range or low precision, which cannot meet the requirements for micron-level or even higher precision applications. The lack of effective control over bonding pressure in existing bonding equipment leads to wafer pair bonding failures or unstable performance. Therefore, controlling the bonding pressure bar 90 to achieve both high-speed, high-precision stroke positioning, while also finely adjusting the contact pressure during wafer contact, becomes crucial for improving wafer bonding performance. To address this, the inventors propose the following technical solution. Summary of the Invention

[0010] The first technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and propose a wafer bonding pressure control mechanism. This mechanism can effectively control the bonding pressure, improve the bonding power of wafer pairs, and ensure the performance of wafer pairs after bonding.

[0011] To solve the first technical problem mentioned above, the present invention adopts the following technical solution: a wafer bonding pressure control mechanism, which includes a main drive unit and a bonding pressure rod connected to the main drive unit. The main drive unit drives the bonding pressure rod to move along the bonding pressure direction and applies bonding pressure to the wafer through the bonding pressure rod. The bonding pressure rod is connected to the main drive unit through a pressure holding cylinder and is located at the end of the piston rod of the pressure holding cylinder. The mechanism also includes a displacement sensor to detect changes in the displacement of the bonding pressure rod. The displacement sensor is electrically connected to the main drive unit.

[0012] Furthermore, in the above technical solution, the main drive unit adopts a voice coil motor, and the main drive unit cooperates with a grating ruler.

[0013] Furthermore, in the above technical solution, a magnetic spring is provided on the pressure-holding cylinder, and when the gas pressure inside the pressure-holding cylinder is zero, the magnetic force provided by the magnetic spring is opposite to the gravity, balancing the gravity at the bonding rod and making the bonding pressure generated by the bonding rod equal to zero.

[0014] Furthermore, in the above technical solution, the displacement sensor is an eddy current sensor, which includes: a sensor body and a sensing metal plate.

[0015] Furthermore, in the above technical solution, the pressure-holding cylinder is connected to the main drive unit through a connecting seat, and the pressure-holding cylinder is fixed on the connecting seat; the piston rod cooperates with a positioning guide sleeve.

[0016] Furthermore, in the above technical solution, the mechanism also includes a controller, and the main drive unit, the control unit of the pressure-holding cylinder, the displacement sensor and the controller are electrically connected.

[0017] The second technical problem to be solved by this invention is to provide a wafer bonding pressure control method. This method controls the bonding pressure applied to the wafer through a wafer bonding pressure control mechanism. The method includes the following steps: First, the main drive unit drives the connector to move to the starting position. In this position, the bonding pressure rod for applying bonding pressure to the wafer is located above the wafer. The bonding pressure rod is mounted on the connector via a pressure-holding cylinder. The pressure output by the pressure-holding cylinder is F1. Simultaneously, a magnetic spring is installed on the pressure-holding cylinder. The magnetic force F2 generated by this magnetic spring is opposite in direction to F1, and the magnetic force F2 is used to counteract the gravity of the pressure-holding cylinder piston rod and the bonding pressure rod, ultimately causing the bonding pressure rod to experience a downward force equal to the bonding pressure. First, the bonding force F0 is applied. Second, the main drive unit drives the connector to move downward from the starting position. When the bonding rod contacts the wafer, the bonding rod is subjected to the elastic force F generated by the wafer. When the elastic force F is greater than the bonding pressure F0, the bonding rod will overcome the bonding pressure F0 and retract upward, ensuring that the pressure on the wafer is equal to the bonding pressure F0. Then, as the bonding rod retracts upward, the displacement sensor detects the displacement change of the bonding rod relative to the connector. After detecting the displacement sensor signal, the controller will control the main drive unit to stop working or reverse, so that the connector no longer moves downward or rises in the opposite direction. Finally, the wafer completes bonding under the action of the bonding pressure F, and the wafer bonding pressure control mechanism resets and waits for another operation.

[0018] Furthermore, in the above technical solution, the main drive unit adopts a voice coil motor, and the drive unit cooperates with a grating ruler to form a closed-loop control for movement along the bonding direction, providing positioning accuracy for the operation of the connector via the grating ruler.

[0019] Furthermore, in the above technical solution, the displacement sensor is an eddy current sensor, which includes: a sensor body and a sensing metal plate. The displacement sensor, the main drive unit and the controller are electrically connected to form a closed-loop control for movement along the bonding direction.

[0020] Furthermore, in the above technical solution, the displacement sensor, the pressure-holding cylinder control unit, and the controller are electrically connected. When the displacement sensor detects a change in the displacement of the bonding rod relative to the connecting seat, the controller receives the signal and, through the control unit, causes the pressure-holding cylinder to release air, thereby reducing the pressure of the pressure-holding cylinder.

[0021] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0022] First, this invention combines the main drive unit with the pressure holding cylinder to form a composite operation control system. When the bonding rod contacts the wafer, it generates bonding pressure on the wafer. At the same time, the main drive unit stops running or rises in the reverse direction when the bonding rod contacts the wafer, so that the bonding pressure acting on the wafer is provided solely by the pressure holding cylinder. By controlling the air pressure of the pressure holding cylinder, the bonding pressure can be controlled and adjusted to ensure the stability of the bonding pressure.

[0023] Secondly, the main drive unit of the present invention, together with the grating ruler and displacement sensor, forms a closed-loop control to precisely control the displacement of the bonding pressure bar, and ensures that when the bonding pressure bar contacts the wafer and retracts, the main drive unit stops running or rises in the opposite direction, so as to avoid the bonding pressure acting on the wafer from exceeding the set value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the existing wafer bonding process;

[0025] Figure 2 This is a schematic diagram of a first embodiment of the control mechanism of the present invention;

[0026] Figure 3 This is a schematic diagram of Embodiment 2 of the control mechanism of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0028] This invention relates to a technical solution for controlling wafer bonding pressure in a wafer bonding machine, specifically a mechanism and method for controlling the bonding pressure provided by the bonding pressure bar.

[0029] Combination Figure 2 As shown, the wafer bonding pressure control mechanism of the present invention includes: a main drive unit 1, a connecting seat 2, a bonding pressure rod 3, a pressure holding cylinder 4, and a displacement sensor 5.

[0030] The main drive unit 1 is used to drive the connector 2 to achieve bonding in the bonding direction ( Figure 2 The main drive unit 1 in this invention employs a voice coil motor. Since the voice coil motor is a linear motor based on the Lorentz force principle, it features high frequency response, high precision, direct drive, and precise operation, ensuring accurate displacement of the connector 2 in this invention. Alternatively, the voice coil motor can be combined with a linear encoder to form a closed-loop control system operating along the bonding direction, providing positioning accuracy of 7µm @ 3σ (or higher).

[0031] The bonding pressure bar 3 is used to apply bonding pressure to the wafer. A pressure holding cylinder 4 is mounted on the connecting seat 2, and the bonding pressure bar 3 is located at the end of the piston rod 41 of the pressure holding cylinder 4. The main drive unit 1 drives the connecting seat 2 to move along the bonding pressure direction, causing the pressure holding cylinder 4 and the bonding pressure bar 3 to move synchronously, thus applying bonding pressure to the wafer through the bonding pressure bar 3.

[0032] The connecting seat 2 is for convenient mechanical installation of the entire mechanism. Alternatively, the connecting seat 2 can be omitted, and the pressure-holding cylinder 4 can be directly connected to the output end of the main drive unit 1, as shown below. Figure 3 As shown.

[0033] The internal air pressure and air source of the pressure-holding cylinder 4 are controlled by the control unit 40, which in turn controls the pressure regulating valve to control the air pressure of the pressure-holding cylinder 4. In this invention, the bonding pressure of the wafer is provided by the air pressure of the pressure-holding cylinder. For example, if the pressure applied by the pressure-holding cylinder 4 to the bonding rod 3 is zero, then, without considering other external forces, the pressure of the bonding rod 3 on the wafer is zero the instant it contacts the wafer 9 downwards. If the pressure applied by the pressure-holding cylinder 4 to the bonding rod 3 is F1, then, without considering other external forces, the pressure of the bonding rod 3 on the wafer is F1 the instant it contacts the wafer 9 downwards. Therefore, F1 can be adjusted by gradually adjusting the internal air pressure of the pressure-holding cylinder 4 until the optimal value is reached. This adjustment method is simple and convenient, and allows for a wide range of force control adjustment.

[0034] The displacement sensor 5 is used to detect the displacement change of the bonding rod 3 relative to the connecting seat 2. The displacement sensor 5 is electrically connected to the main drive unit 1. The displacement sensor 5 employs eddy current sensing. The eddy current sensor 5 is a non-contact displacement measurement sensor based on the principle of electromagnetic induction, and it typically includes: a sensor body 51 and a sensing metal plate 52. When the distance between the sensor body 51 and the sensing metal plate 52 changes, the eddy current induced on the sensing metal plate will change, and the displacement change is measured by detecting the change in eddy current.

[0035] The displacement sensor 5 in this invention is used to detect the displacement change of the bonding rod 3 relative to the connecting seat 2. During installation, the sensor body 51 can be fixed relative to the pressure-holding cylinder 4, and the sensing metal plate 52 can be fixed relative to the piston rod 41 or the bonding rod 3. Figure 2As shown, in this embodiment, the sensor body 51 is directly fixedly connected to the cylinder body of the pressure-holding cylinder 4. The sensing metal plate 52 is fixed to the piston rod 41 via a carrier plate 53. When the main drive unit 1 drives the connecting seat 2 to move along the bonding pressure direction, the pressure-holding cylinder 4, the bonding pressure rod 3, and the displacement sensor 5 move synchronously, and the eddy current generated by the sensing metal plate 52 in the displacement sensor 5 does not change. When the bonding pressure rod 3 contacts the wafer 9 and retracts, the distance between the sensing metal plate 52 and the sensor body 51 changes, and the change in distance is detected by the change in eddy current.

[0036] This invention employs a displacement sensor 5 with eddy current sensing, enabling micro-distance displacement detection with a measurement accuracy of 1 micrometer (or higher). This allows for precise height control of the contact process between the bonding rod 3 and the wafer 9.

[0037] This invention includes a magnetic spring 6 on the pressure-holding cylinder 4. As mentioned earlier, when the pressure applied by the pressure-holding cylinder 4 to the bonding rod 3 is zero, at the instant the bonding rod 3 contacts the wafer 9 downwards, the pressure exerted by the bonding rod 3 on the wafer is not zero due to its own gravity. The magnetic spring 6 is provided to balance this gravity. Figure 2 For example, the magnetic spring 6 can be installed inside the pressure-holding cylinder 4 (or in other locations). The magnetic spring 6 provides an upward balancing force to the piston rod 41 to counteract the weight of the piston rod 41 and the bonding pressure rod 3 and carrier plate 53 mounted on the piston rod 41. Ultimately, when the internal air pressure of the pressure-holding cylinder 4 is zero, the balancing force provided by the magnetic spring 6 makes the bonding pressure generated by the bonding pressure rod 3 equal to zero.

[0038] The present invention also includes a controller 8, which can be a PLC, an industrial computer, or a dedicated motion control card. The controller 8 is electrically connected to the main drive unit 1, the grating ruler, and the displacement sensor 5.

[0039] The following is combined Figure 2 The bonding pressure control method of the present invention will be described in detail.

[0040] First, the main drive unit 1 drives the connector 2 to move to the starting position. In this position, the bonding pressure rod 3, which applies bonding pressure to the wafer 9, is located above the wafer 9. If the pressure output of the pressure holding cylinder 4 is set to F1, the magnetic force F2 generated by the magnetic spring is opposite to F1, and the magnetic force F2 is used to counteract the gravity of the piston rod 41 of the pressure holding cylinder 4 and the bonding pressure rod 3. The bonding pressure rod 3 is subjected to a downward force F0 = F1, and this force F0 is used as the bonding pressure.

[0041] Secondly, the main drive unit 1 drives the connector 2 to move downward from the starting position. When the bonding pressure bar 3 contacts the wafer 9, the bonding pressure bar 3 is subjected to the elastic force F generated by the wafer 9. When the elastic force F is greater than the bonding pressure F0, the bonding pressure bar 3 will overcome the bonding pressure F0 and retract upward, thus ensuring that the pressure on the wafer 9 at the moment of contact with the bonding pressure bar 3 is exactly equal to the bonding pressure F0.

[0042] Then, since the main drive unit 1 is still working, to prevent it from continuing to drive the connector 2 downwards, the displacement sensor 5 is used to stop or reverse the main drive unit 1. Specifically, as the bonding rod 3 retracts upwards, the sensing metal plate 52 in the displacement sensor 5 also moves upwards with the piston rod 41. The distance between the sensing metal plate 52 and the sensor body 51 changes, and this change is detected by the alteration of eddy currents. After detecting the signal from the displacement sensor 5, the controller 8 will control the main drive unit 1 to stop working or reverse, preventing the connector 2 from moving downwards or rising in the opposite direction.

[0043] Finally, wafer 9 completes bonding under bonding pressure F0, and the wafer bonding pressure control mechanism resets to await the next operation.

[0044] In this invention, the control unit 40 of the pressure-holding cylinder 4 can also be connected to the controller 8. When the displacement sensor 5 detects the displacement change of the bonding rod 3 relative to the connector 2, the controller 8, after detecting the signal from the displacement sensor 5, commands the pressure-holding cylinder 4 to release air through the control unit 40, thereby reducing the pressure of the pressure-holding cylinder 4 to avoid excessive pressure that may be generated on the wafer 9.

[0045] Additionally, to ensure the precise operation of the piston rod 41, a positioning guide sleeve 7 can be installed at the piston rod 41. To prevent damage to the wafer 9 caused by the bonding rod 3 failing to retract upon accidental contact with it, a limiting mechanism can be installed to limit the downward movement of the bonding rod 3. For example, see... Figure 3 As shown, the limiting member 71 interferes with the carrier plate 53, limiting the downward movement limit of the bonding pressure bar 3.

[0046] This invention combines a main drive unit with a pressure-holding cylinder to form a composite operation control system. By controlling the air pressure in the pressure-holding cylinder, the bonding pressure can be controlled and adjusted, ensuring its stability. Furthermore, during operation, bonding pressure is generated by the bonding rod contacting the wafer. Simultaneously, the bonding rod retracts, and at the same time, the main drive unit stops operating or reverses its direction, preventing the bonding pressure acting on the wafer from exceeding the set value.

[0047] Of course, the above description is only a specific embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A wafer bonding pressure control mechanism, comprising: The main driving unit (1) and the bonding pressure bar (3) connected to the main driving unit (1) are characterized in that the main driving unit (1) drives the bonding pressure bar (3) to move along the bonding pressure direction, and applies bonding pressure to the wafer (9) through the bonding pressure bar (3). The bonding rod (3) is connected to the main drive unit (1) through the pressure holding cylinder (4), and the bonding rod (3) is located at the end of the piston rod (41) of the pressure holding cylinder (4); The mechanism also includes a displacement sensor (5) to detect the displacement change of the bonding rod (3), and the displacement sensor (5) is electrically connected to the main drive unit (1); The pressure-holding cylinder (4) is equipped with a magnetic spring (6), and when the gas pressure inside the pressure-holding cylinder (4) is equal to zero, the magnetic force provided by the magnetic spring (6) is opposite to the gravity, balancing the gravity at the bonding rod (3) and making the bonding pressure generated by the bonding rod (3) equal to zero. The pressure-holding cylinder (4) is connected to the main drive unit (1) through the connecting seat (2), and the pressure-holding cylinder (4) is fixed on the connecting seat (2).

2. The wafer bonding pressure control mechanism according to claim 1, characterized in that: The main drive unit (1) is a voice coil motor and is coupled with a grating ruler.

3. The wafer bonding pressure control mechanism according to claim 1, characterized in that: The displacement sensor (5) is an eddy current sensor, which includes: a sensor body (51) and a sensing metal plate (52).

4. The wafer bonding pressure control mechanism according to any one of claims 1-3, characterized in that: The piston rod (41) is engaged with a positioning guide sleeve (7).

5. The wafer bonding pressure control mechanism according to any one of claims 1-3, characterized in that: The mechanism also includes a controller (8), to which the main drive unit (1), the control unit (40) of the pressure-holding cylinder (4) and the displacement sensor (5) are electrically connected.

6. A wafer bonding pressure control method, wherein the method controls the bonding pressure applied to the wafer through a wafer bonding pressure control mechanism, characterized in that, The method includes the following steps: First, the main drive unit (1) drives the connector (2) to move to the starting position. In this position, the bonding pressure bar (3) used to apply bonding pressure to the wafer is located above the wafer (9). The bonding pressure bar (3) is installed on the connector (2) through the pressure holding cylinder (4). The pressure output by the pressure holding cylinder (4) is F1. At the same time, a magnetic spring (6) is set on the pressure holding cylinder (4). The magnetic force F2 generated by the magnetic spring (6) is opposite to F1. The magnetic force F2 is used to counteract the gravity of the piston rod (41) of the pressure holding cylinder (4) and the bonding pressure bar (3). Finally, the downward force on the bonding pressure bar (3) is equal to the bonding pressure F0. Secondly, the main drive unit (1) drives the connector (2) to move downward from the starting position. When the bonding rod (3) contacts the wafer (9), the bonding rod (3) is subjected to the elastic force F generated by the wafer (9). When the elastic force F is greater than the bonding pressure F0, the bonding rod (3) will overcome the bonding pressure F0 and retract upward, ensuring that the pressure on the wafer (9) is equal to the bonding pressure F0. Then, as the bonding rod (3) retracts upward, the displacement sensor (5) detects the displacement change of the bonding rod (3) relative to the connecting seat (2). After the controller (8) detects the signal from the displacement sensor (5), it will control the main drive unit (1) to stop working or reverse, so that the connecting seat (2) no longer moves downward or rises in the opposite direction. Finally, the wafer (9) completes bonding under the action of bonding pressure F0, and the wafer bonding pressure control mechanism resets to wait for the next operation.

7. The wafer bonding pressure control method according to claim 6, characterized in that: The main drive unit (1) adopts a voice coil motor, and the main drive unit (1) cooperates with a grating ruler to form a closed-loop control for movement along the bonding direction, providing positioning accuracy for the operation of the connector (2) through the grating ruler.

8. The wafer bonding pressure control method according to claim 6, characterized in that: The displacement sensor (5) is an eddy current sensor, which includes a sensor body (51) and a sensing metal plate (52). The displacement sensor (5), the main drive unit (1) and the controller (8) are electrically connected to form a closed-loop control for movement along the bonding direction.

9. The wafer bonding pressure control method according to claim 8, characterized in that: The control unit (40) of the displacement sensor (5) and the pressure holding cylinder (4) is electrically connected to the controller (8). When the displacement sensor (5) detects the displacement change of the bonding rod (3) relative to the connecting seat (2), the controller (8) receives the signal and, through the control unit (40), causes the pressure holding cylinder (4) to exhaust gas, thereby reducing the pressure of the pressure holding cylinder (4).

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