Leveling device and method of wafer chuck and bonding equipment

Abstract

The invention provides a leveling device of a wafer chuck, a leveling method of the wafer chuck and bonding equipment. The leveling device of the wafer chuck comprises an adapter which comprises a bonding head adapter port, an air cavity and a flexible port, the bonding head adapter port is detachably and fixedly connected with a bonding head of a bonding device, one end of the air cavity is provided with an air inlet for introducing constant-flow air, and the other end of the air cavity is provided with an air outlet for introducing constant-flow air; the other end of the flexible interface is in contact with a wafer chuck of the bonding equipment through the flexible interface; the sensor is used for detecting the air pressure in the air cavity; and the controller is used for controlling the leveling device to level the wafer chuck.

Description

Technical Field

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

[0002] In the field of semiconductor manufacturing technology, semiconductor devices need to be stacked vertically to continuously improve device density and performance. In the process of vertically stacking devices, the flip-chip bonding method is used to prevent dust and other particles from being deposited on the wafer and contaminating the bonded wafer. Here, the parallelism between the flip-chip chuck and the chip bonding head will directly affect the bonding effect of the flip-chip bonding.

[0003] The chuck leveling measurement method in the prior art usually adopts the method of measuring the contact surface of the micrometer or optically detecting the horizontality of the chuck and the bonding head. The contact surface measurement method of the micrometer will inevitably damage the surface of the chuck and the bonding head, and it cannot be reused, thereby increasing the leveling cost. Traditional optical detection wafer defect detection methods, such as microscopic detection, Raman scattering, photoluminescence or X-ray diffraction topography (XRT), can only provide information on local areas on the wafer, and there is a high degree of integration of multiple disciplines, so it is difficult to accurately operate and maintain in practical applications, which affects the efficiency and accuracy of detection.

[0004] In order to overcome the above-mentioned defects of the prior art, the art is in urgent need of a wafer chuck leveling technology for adjusting the parallelism of the chuck and the bonding head, which not only avoids damaging the device surface and reduces the leveling cost, but also effectively reduces the maintenance difficulty and improves the efficiency and accuracy of detection. Summary of the invention

[0005] A brief summary of one or more aspects is given below to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all conceived aspects, and is neither intended to identify the key or decisive elements of all aspects nor to define the scope of any or all aspects. Its only purpose is to give some concepts of one or more aspects in a simplified form as a prelude to a more detailed description that will be given later.

[0006] In order to overcome the above-mentioned defects in the prior art, the present invention provides a wafer chuck leveling device, a wafer chuck leveling method, and a bonding device, which are used to adjust the parallelism of the chuck and the bonding head, which not only avoids damaging the device surface and reduces the leveling cost, but also effectively reduces the maintenance difficulty and improves the efficiency and accuracy of detection.

[0007] Specifically, a wafer chuck leveling device provided according to the first aspect of the present invention includes: an adapter, including a bonding head adapter, an air cavity and a flexible interface, wherein the bonding head adapter is detachably fixedly connected to a bonding head of a bonding device, one end of the air cavity is provided with an air inlet for introducing a constant flow of gas, and the other end thereof contacts the wafer chuck of the bonding device via the flexible interface; a sensor for detecting the air pressure inside the air cavity; and a controller, which is configured to: in response to the flexible interface of the adapter contacting a first position on the wafer chuck, obtain a first air pressure collected by the sensor via the sensor; in response to the flexible interface contacting a second position on the wafer chuck, obtain a second air pressure collected by the sensor via the sensor; determine a leveling control instruction for compensating for the height difference between the first position and the second position according to the difference between the second air pressure and the first air pressure; and transmit the leveling control instruction to the lifting mechanism of the wafer chuck to control it to level the wafer chuck.

[0008] Furthermore, in some embodiments of the present invention, the leveling device also includes: a constant flow gas source, which injects a constant flow gas into the air cavity through the air inlet, so that the air pressure inside the air cavity decreases as the volume of the air cavity increases, and increases as the volume of the air cavity decreases.

[0009] Furthermore, in some embodiments of the present invention, the bonding head is integrated with a first air channel for vacuum adsorption of the parts to be bonded, and the constant flow gas source is connected to the air inlet of the air cavity via the first air channel, or the constant flow gas source is connected to the air inlet of the air cavity via an external second air channel.

[0010] Furthermore, in some embodiments of the present invention, the flexible interface includes an accordion-type suction nozzle, which is shortened to a corresponding first length as the wafer chuck is squeezed at a first position, shortened to a corresponding second length as the wafer chuck is squeezed at a second position, and stretched to its original third length as the squeezing is eliminated, so as to adjust the volume of the air cavity.

[0011] Furthermore, in some embodiments of the present invention, a plurality of negative pressure holes are provided on the bond head adapter for providing negative pressure to the edge of the bond head so that the adapter can be detachably fixedly connected to the bond head.

[0012] Further, in some embodiments of the present invention, the controller is connected to the position adjustment mechanism of the bonding head, and is also configured to: translate the adapter via the position adjustment mechanism to align with the first position on the wafer chuck, and lift the adapter to a preset height so that its flexible interface contacts the first position; and in response to completing the collection of the first air pressure, translate the adapter via the position adjustment mechanism to align with the second position on the wafer chuck, and lift the adapter to the preset height so that its flexible interface contacts each second position.

[0013] Furthermore, in some embodiments of the present invention, the first position is located at the center of the wafer chuck, and a plurality of the second positions are distributed in a plurality of radial directions of the wafer chuck.

[0014] Further, in some embodiments of the present invention, the plurality of radial directions are distributed at intervals of 90° or 180°, wherein each of the radial directions has at least one second position.

[0015] Further, in some embodiments of the present invention, the lifting mechanism of the wafer chuck includes a plurality of adjusting arms, wherein each of the adjusting arms is connected to a leveling point on the back of the wafer chuck, and each of the radial directions passes through the longitudinal projection position of at least one corresponding leveling point, and the step of transmitting the leveling control instruction to the lifting mechanism of the wafer chuck to control it to level the wafer chuck includes: transmitting the leveling control instruction for compensating for the height difference between the first position and each of the second positions to the corresponding adjusting arms of the lifting mechanism to control it to lift and lower the height of the corresponding leveling point of the wafer chuck.

[0016] In addition, the bonding equipment provided according to the second aspect of the present invention includes: a wafer chuck, used to adsorb the wafer to be bonded; a chuck lifting mechanism, connected to multiple leveling points on the back of the wafer chuck via multiple adjustment arms; a bonding head, used to adsorb circuit elements to be bonded; a position adjustment mechanism, used to drive the bonding head to perform translation and lifting movements; and a leveling device for the wafer chuck as described in any one of the first aspects of the present invention, whose adapter is fixedly connected to the bonding head during the leveling process and is removed during the bonding process.

[0017] In addition, the wafer chuck leveling method provided according to the third aspect of the present invention includes the following steps: fixing the adapter of the wafer chuck leveling device as described in any one of the first aspect of the present invention to the bonding head of a bonding device, and introducing a constant flow of gas into the air cavity of the adapter; translating the adapter to align it with a first position on the wafer chuck to be leveled of the bonding device; lifting and lowering the adapter so that its flexible interface contacts the first position, and collecting the first air pressure inside the air cavity; translating the adapter to align it with a second position on the wafer chuck; lifting and lowering the adapter so that its flexible interface contacts the second position, and collecting the second air pressure inside the air cavity; determining a leveling control instruction to compensate for the height difference between the first position and the second position based on the difference between the second air pressure and the first air pressure; and transmitting the leveling control instruction to the chuck lifting mechanism of the bonding device to control it to level the wafer chuck. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 1 A schematic structural diagram of a bonding device provided according to some embodiments of the present invention is shown.

[0020] Figure 2 A schematic structural diagram of a position adjustment mechanism provided according to some embodiments of the present invention is shown.

[0021] Figure 3 A schematic structural diagram of a wafer chuck leveling device provided according to some embodiments of the present invention is shown.

[0022] Figure 4 A schematic structural diagram of a negative pressure hole provided according to some embodiments of the present invention is shown.

[0023] Reference numerals:

[0024] 10 Wafer chuck

[0025] 20 Chuck lifting mechanism

[0026] 30 Bonding head

[0027] 301 Negative pressure hole

[0028] 40 Position adjustment mechanism

[0029] 50 Leveling device

[0030] 512 Air cavity

[0031] 513 Flexible Interface

[0032] 52 Sensors

[0033] 53 Constant flow air source DETAILED DESCRIPTION

[0034] The following specific embodiments illustrate the implementation of the present invention, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Although the description of the present invention will be introduced in conjunction with the preferred embodiment, this does not mean that the features of this invention are limited to this implementation. On the contrary, the purpose of introducing the invention in conjunction with the implementation is to cover other options or modifications that may be extended based on the claims of the present invention. In order to provide a deep understanding of the present invention, the following description will include many specific details. The present invention can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present invention, some specific details will be omitted in the description.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In addition, the terms "upper", "lower", "left", "right", "top", "bottom", "horizontal" and "vertical" used in the following description should be understood as the directions shown in the paragraph and the related drawings. Such relative terms are only used for the convenience of description and do not mean that the device described therein must be manufactured or operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0037] It is understood that although the terms "first", "second", "third", etc. 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 a second component, region, layer and / or part without departing from some embodiments of the present invention.

[0038] As mentioned above, in the field of semiconductor manufacturing technology, semiconductor devices need to be stacked vertically to continuously improve device density and performance. In the process of vertically stacking devices, the flip-chip bonding method can be used to prevent dust and other particles from being deposited on the wafer and contaminating the bonded wafer. Here, the parallelism between the flip-chip chuck and the chip bonding head will directly affect the bonding effect of the flip-chip bonding.

[0039] The chuck leveling measurement method in the prior art usually adopts the method of measuring the contact surface of the micrometer or optically detecting the horizontality of the chuck and the bonding head. The contact surface measurement method of the micrometer will inevitably damage the surface of the chuck and the bonding head, and it cannot be reused, thereby increasing the leveling cost. Traditional optical detection wafer defect detection methods, such as microscopic detection, Raman scattering, photoluminescence or X-ray diffraction topography (XRT), can only provide information on local areas on the wafer, and there is a high degree of integration of multiple disciplines, so it is difficult to accurately operate and maintain in practical applications, which affects the efficiency and accuracy of detection.

[0040] In order to overcome the above-mentioned defects in the prior art, the present invention provides a wafer chuck leveling device, a wafer chuck leveling method, and a bonding device, which are used to adjust the parallelism of the chuck and the bonding head, which not only avoids damaging the device surface and reduces the leveling cost, but also effectively reduces the maintenance difficulty and improves the efficiency and accuracy of detection.

[0041] In some non-limiting embodiments, the wafer chuck leveling device provided in the first aspect of the present invention can be configured in the bonding device provided in the second aspect of the present invention. The wafer chuck leveling method provided in the third aspect of the present invention can be implemented via the wafer chuck leveling device.

[0042] Please refer to Figure 1-2 , Figure 1 A schematic structural diagram of a bonding device provided according to some embodiments of the present invention is shown. Figure 2 A schematic structural diagram of a position adjustment mechanism provided according to some embodiments of the present invention is shown.

[0043] like Figure 1-2 As shown, the bonding device includes a wafer chuck 10, a chuck lifting mechanism 20, a bonding head 30, a position adjustment mechanism 40 and a leveling device 50 of the wafer chuck 10. The wafer chuck 10 is used to absorb the wafer to be bonded. The chuck lifting mechanism 20 is connected to multiple leveling points on the back of the wafer chuck 10 via multiple adjustment arms. The bonding head 30 is used to absorb the circuit elements to be bonded (for example, grains with circuit elements such as chips).

[0044] The position adjustment mechanism 40 is used to drive the bonding head 30 to translate and lift the leveling device 50 of the wafer chuck 10, and its adapter is fixedly connected to the bonding head 30 during the leveling process and is removed during the bonding process. Specifically, in some embodiments of the bonding process, the position adjustment mechanism 40 can first drive the bonding head 30 to translate to the pick-up position to obtain the circuit elements to be bonded. Afterwards, the bonding head 30 and the circuit elements to be bonded are driven to translate to the preset bonding position below the wafer chuck 10. Thereafter, the bonding head 30 is lifted upward to bond the circuit elements to the front of the wafer chuck 10 lowered by the chuck lifting mechanism 20.

[0045] Please refer to Figure 3 , Figure 3 A schematic structural diagram of a leveling device for a wafer chuck 10 provided according to some embodiments of the present invention is shown.

[0046] like Figure 3 As shown, the leveling device 50 of the wafer chuck 10 includes an adapter, a sensor 52 and a controller. The adapter includes a bonding head adapter, an air cavity 512 and a flexible interface 513. The bonding head adapter is detachably fixedly connected to a bonding head 30 of a bonding device, one end of the air cavity 512 is provided with an air inlet for introducing a constant flow of gas, and the other end thereof contacts the wafer chuck 10 of the bonding device via the flexible interface 513. The sensor 52 is used to detect the air pressure inside the air cavity 512. The controller is configured to: in response to the flexible interface 513 of the adapter contacting a first position on the wafer chuck 10, obtain a first air pressure collected by the sensor 52; in response to the flexible interface 513 contacting a second position on the wafer chuck 10, obtain a second air pressure collected by the sensor 52; determine a leveling control instruction to compensate for the height difference between the first position and the second position based on the difference between the second air pressure and the first air pressure; and transmit the leveling control instruction to the lifting mechanism of the wafer chuck 10 to control it to level the wafer chuck 10.

[0047] The leveling device 50 of the wafer chuck 10 also includes a constant flow gas source 53. The constant flow gas source 53 injects a constant flow of gas into the air cavity 512 via an air inlet, so that the air pressure inside the air cavity 512 decreases as the volume of the air cavity 512 increases, and increases as the volume of the air cavity 512 decreases. Specifically, the bonding head 30 is integrated with a first air channel for vacuum adsorption of the bonded parts, and the constant flow gas source 53 is connected to the air inlet of the air cavity 512 via the first air channel, or the constant flow gas source 53 is connected to the air inlet of the air cavity 512 via an external second air channel.

[0048] The flexible interface 513 includes an accordion-type suction nozzle, which is shortened to a corresponding first length when the wafer chuck 10 is squeezed at a first position, shortened to a corresponding second length when the wafer chuck 10 is squeezed at a second position, and extended to an original third length when the squeezing is eliminated, so as to adjust the volume of the air cavity 512. The volume of the air cavity 512 can be set to the total volume of the fixed part and the telescopic part of the suction nozzle.

[0049] Please refer to Figure 4 , Figure 4 A schematic structural diagram of a negative pressure hole provided according to some embodiments of the present invention is shown.

[0050] like Figure 4 As shown, a plurality of negative pressure holes 301 are provided on the bonding head adapter, which are used to provide negative pressure to the edge of the bonding head 30 so that the adapter can be detachably fixedly connected to the bonding head 30 .

[0051] Please continue to refer to Figure 1 , the leveling device 50 translates the adapter via the position adjustment mechanism 40 to align with the first position on the wafer chuck 10, and lifts the adapter to a preset height so that its flexible interface 513 contacts the first position. In response to completing the collection of the first air pressure, the adapter is translated via the position adjustment mechanism 40 to align with the second position on the wafer chuck 10, and the adapter is lifted to a preset height so that its flexible interface 513 contacts each second position. Here, the first position is located at the center of the wafer chuck 10. Multiple second positions are distributed in multiple radial directions of the wafer chuck 10. Multiple radial directions are distributed at intervals of 90° or 180°, wherein each radial direction has at least one second position.

[0052] In some embodiments, the lifting mechanism of the wafer chuck 10 may include a plurality of adjustment arms. Each adjustment arm is connected to a leveling point on the back of the wafer chuck 10, and each radial direction passes through the longitudinal projection position of at least one corresponding leveling point.

[0053] In some embodiments, the step of transmitting the leveling control instruction to the lifting mechanism of the wafer chuck 10 to control it to level the wafer chuck 10 includes: transmitting the leveling control instruction for compensating the height difference between the first position and each second position to the corresponding adjustment arm of the lifting mechanism, so as to control the height of the corresponding leveling point of the lifting wafer chuck 10.

[0054] The following will describe the working principle of the wafer chuck leveling device in conjunction with some embodiments of the wafer chuck leveling method. Those skilled in the art will understand that these embodiments of the wafer chuck leveling method are only some non-limiting implementation methods provided by the present invention, which are intended to clearly demonstrate the main concept of the present invention and provide some specific solutions that are convenient for the public to implement, rather than to limit all functions or all working modes of the wafer chuck leveling device. Similarly, the wafer chuck leveling device is also only some non-limiting implementation methods provided by the present invention, and does not constitute a limitation on the execution subject or execution order of each step in these wafer chuck leveling methods.

[0055] Specifically, the device of the wafer chuck 10 can firstly fix the adapter of the leveling device 50 of the wafer chuck 10 to the bonding head 30 of a bonding device, and introduce a constant flow of gas into the air cavity 512 of the adapter.

[0056] Afterwards, the adapter is translated to align with the first position on the wafer chuck 10 to be leveled of the bonding device. Afterwards, the adapter is lifted and lowered to make its flexible interface 513 contact the first position, and the first air pressure inside the air cavity 512 is collected. Afterwards, the adapter is translated to align with the second position on the wafer chuck 10. Afterwards, the adapter is lifted and lowered to make its flexible interface 513 contact the second position, and the second air pressure inside the air cavity 512 is collected, and then the leveling control instruction for compensating the height difference between the first position and the second position is determined according to the difference between the second air pressure and the first air pressure.

[0057] Finally, the leveling control command is transmitted to the chuck lifting mechanism 20 of the bonding device to control it to level the wafer chuck 10. Specifically, the leveling control command for compensating the height difference between the first position and each second position is transmitted to the corresponding adjustment arm of the lifting mechanism to control it to lift the height of the corresponding leveling point of the wafer chuck 10.

[0058] In summary, the wafer chuck leveling device, wafer chuck leveling method, and bonding equipment provided by the present invention are used to adjust the parallelism of the chuck and the bonding head, thereby avoiding damage to the device surface and reducing the leveling cost.

[0059] Although the above methods are illustrated and described as a series of actions for simplicity of explanation, it should be understood and appreciated that these methods are not limited by the order of the actions, because according to one or more embodiments, some actions may occur in a different order and / or concurrently with other actions from those illustrated and described herein or not illustrated and described herein but understandable to those skilled in the art.

[0060] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the 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 the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein, but should be granted the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wafer chuck leveling device, characterized in that: include: An adapter, comprising a bonding head adapter, an air cavity and a flexible interface, wherein the bonding head adapter is detachably fixedly connected to a bonding head of a bonding device, one end of the air cavity is provided with an air inlet for introducing a constant flow of gas, and the other end thereof contacts a wafer chuck of the bonding device via the flexible interface; a sensor for detecting the air pressure inside the air cavity; and The controller is configured to: in response to the flexible interface of the adapter contacting a first position on the wafer chuck, obtain a first air pressure collected by the sensor; in response to the flexible interface contacting a second position on the wafer chuck, obtain a second air pressure collected by the sensor; determine a leveling control instruction to compensate for the height difference between the first position and the second position based on the difference between the second air pressure and the first air pressure; and transmit the leveling control instruction to the lifting mechanism of the wafer chuck to control it to level the wafer chuck.

2. The leveling device according to claim 1, characterized in that: Also includes: A constant flow gas source is used to inject a constant flow gas into the air cavity through the air inlet, so that the air pressure inside the air cavity decreases as the volume of the air cavity increases, and increases as the volume of the air cavity decreases.

3. The leveling device according to claim 2, characterized in that: The bonding head is integrated with a first air channel for vacuum adsorbing the bonded parts, and the constant flow air source is connected to the air inlet of the air cavity via the first air channel, or The constant flow gas source is connected to the air inlet of the air cavity via an external second air channel.

4. The leveling device according to claim 1, characterized in that: The flexible interface includes an accordion-type suction nozzle, which is shortened to a corresponding first length as the wafer chuck is squeezed at a first position, shortened to a corresponding second length as the wafer chuck is squeezed at a second position, and stretched to its original third length as the squeezing is eliminated, so as to adjust the volume of the air cavity.

5. The leveling device according to claim 1, characterized in that: The bonding head adapter is provided with a plurality of negative pressure holes for providing negative pressure to the edge of the bonding head so that the adapter can be detachably fixedly connected to the bonding head.

6. The leveling device according to claim 1, characterized in that: The controller is connected to the position adjustment mechanism of the bonding head and is further configured to: The adapter is translated by the position adjustment mechanism to align with a first position on the wafer chuck, and the adapter is raised and lowered to a preset height so that its flexible interface contacts the first position; as well as In response to completing the collection of the first gas pressure, the adapter is translated via the position adjustment mechanism to align with the second position on the wafer chuck, and the adapter is raised and lowered to the preset height so that its flexible interface contacts each of the second positions.

7. The leveling device according to claim 6, characterized in that: The first position is located at the center of the wafer chuck, and a plurality of the second positions are distributed in a plurality of radial directions of the wafer chuck.

8. The leveling device according to claim 7, characterized in that: The plurality of radial directions are distributed at intervals of 90° or 180°, wherein each of the radial directions has at least one second position.

9. The leveling device according to claim 8, characterized in that: The lifting mechanism of the wafer chuck includes a plurality of adjustment arms, wherein each of the adjustment arms is connected to a leveling point on the back of the wafer chuck, and each of the radial directions passes through the longitudinal projection position of at least one corresponding leveling point. The step of transmitting the leveling control instruction to the lifting mechanism of the wafer chuck to control it to level the wafer chuck includes: transmitting the leveling control instruction that compensates for the height difference between the first position and each of the second positions to the corresponding adjusting arms of the lifting mechanism, respectively, to control it to lift and lower the height of the corresponding leveling point of the wafer chuck.

10. A bonding device, characterized in that: include: Wafer chuck, used to absorb the wafer to be bonded; A chuck lifting mechanism connected to a plurality of leveling points on the back of the wafer chuck via a plurality of adjustment arms; A bonding head, used to absorb the circuit components to be bonded; A position adjustment mechanism, used for driving the bonding head to perform translation and lifting movements; as well as The wafer chuck leveling device according to any one of claims 1 to 9, wherein the adapter is fixedly connected to the bonding head during the leveling process and is removed during the bonding process.

11. A method for leveling a wafer chuck, characterized in that: The following steps are involved: The adapter of the wafer chuck leveling device according to any one of claims 1 to 9 is fixedly connected to a bonding head of a bonding device, and a constant flow of gas is introduced into the air cavity of the adapter; Translating the adapter so as to align it with a first position on a wafer chuck to be leveled of the bonding device; Lifting and lowering the adapter so that its flexible interface contacts the first position, and collecting a first air pressure inside the air cavity; translating the adapter to align it with a second position on the wafer chuck; Lifting and lowering the adapter so that its flexible interface contacts the second position, and collecting the second air pressure inside the air cavity; determining, according to a difference between the second air pressure and the first air pressure, a leveling control instruction for compensating for a height difference between the first position and the second position; as well as The leveling control instruction is transmitted to the chuck lifting mechanism of the bonding device to control it to level the wafer chuck.

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