Wafer ejector pin, wafer bonding device and wafer bonding method

Abstract

The invention relates to a wafer ejector pin, a wafer bonding device and a wafer bonding method. The wafer ejector pin comprises a pin body provided with an air inlet channel and an outlet, the air inlet channel is used for being communicated with an air source, and the outlet is formed in one end, in the axial direction, of the pin body and communicated with the air inlet channel; the elastic piece is connected with the end, provided with the outlet, of the needle body in a sealed mode, a sealed cavity is formed between the elastic piece and the needle body, and the outlet is communicated with the sealed cavity; wherein when the gas source fills gas into the sealing cavity through the gas inlet channel, the elastic piece deforms due to the pressure change of the gas in the sealing cavity, so that the elastic piece forms an arc-shaped surface in contact with a wafer. According to the invention, after the wafer ejector pin is pre-pressed, the stress at the center of the wafer is greatly reduced, and the product yield is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing, specifically to a wafer ejector pin, a wafer bonding apparatus, and a wafer bonding method. Background Technology

[0002] With the continuous shrinking of semiconductor device feature sizes and the development of 3D integration technology, wafer bonding technology has become a key process for achieving heterogeneous integration, wafer-level packaging, and improved device performance. At the most advanced technology nodes, such as high-bandwidth memory and heterogeneous chip integration, the overlay precision requirements between different layers of the bonded wafer are approaching 10 nanometers or even below. This stringent precision requirement means that any minute stress or deformation during the bonding process becomes a significant source of error.

[0003] Existing wafer bonding equipment, especially those employing the "bonding wave" principle to eliminate interface gases, typically includes a critical "pre-compression" step in their standard process flow. This step is usually performed by a pin located at the center of the upper chuck. Its operation is as follows: After the two wafers are initially aligned, a pin integrated at the center of the upper chuck moves slightly downward relative to the upper chuck, applying a localized, vertically downward pre-pressure to the central region of the upper wafer. This action aims to induce a controllable, localized elastic deformation of the upper wafer towards the lower wafer, thereby allowing the center point of the upper wafer to initially contact the lower wafer, forming an initial bonding point. Subsequently, the adsorption vacuum at the center of the upper chuck is released, and the bonding interface spontaneously propagates from the wafer center to the wafer edge through intermolecular forces, thereby orderly expelling the interface gas and preventing the formation of pores.

[0004] However, after the bonding process is completed by the above-mentioned "pre-compression", the pre-compression of the ejector pins acts on the center point of the wafer, forming a high local pressure near the center point. This causes the wafer to undergo plastic deformation that is difficult to recover. After the pre-compression is completed, the plastic deformation is difficult to completely eliminate, resulting in wafer distortion. This leads to the formation of a prominent error hotspot in the center region of the wafer. This error hotspot means that the error value in the center region is much larger than that in other regions, which seriously affects the device yield. Summary of the Invention

[0005] The technical problem to be solved by this application is to provide a wafer ejector pin, a wafer bonding device and a wafer bonding method, which can greatly reduce the stress formed on the central region of the wafer after the ejector pin is pre-pressed, thereby improving the product yield.

[0006] According to a first aspect of the present application, a wafer ejector pin is provided, comprising: a pin body having an air inlet channel and an outlet, the air inlet channel being connected to a gas source, and the outlet being disposed at one end of the pin body along the axial direction and connected to the air inlet channel; an elastic member being sealed to the end of the pin body having the outlet, and forming a sealed cavity between the elastic member and the pin body, the outlet being connected to the sealed cavity; wherein, when the gas source fills the sealed cavity with gas through the air inlet channel, the elastic member deforms due to the change in gas pressure within the sealed cavity, causing the elastic member to form an arc-shaped surface that contacts the wafer.

[0007] In one embodiment, the wafer ejector pin further includes a sealing element; a recessed sealing groove is provided on the end wall of the pin body where the outlet is located, and the sealing element is located in the sealing groove to seal and connect the elastic element to the pin body.

[0008] In one embodiment, the elastic element is a single-layer elastic membrane; or, the elastic element is formed by stacking at least two layers of elastic membranes, wherein the elastic modulus of the elastic membrane disposed near the needle body is greater than the elastic modulus of the elastic membrane disposed away from the needle body.

[0009] In one embodiment, the air intake channel is connected to the air source via an air path, and a control valve is provided on the air path. The control valve is used to control the opening and closing of the air path and to control the gas flow rate in the air path; and / or, the control valve has a communication unit that is connected to a host computer for communication.

[0010] According to a second aspect of the embodiments of this application, a wafer bonding apparatus is provided, suitable for vertically bonding two wafers, comprising: a chuck including an upper chuck and a lower chuck, the upper chuck having a through-hole central hole, the upper chuck being used to adsorb one of the two wafers, and the lower chuck being used to adsorb the other of the two wafers; a wafer ejector pin as described in any of the preceding claims, the wafer ejector pin being disposed in the central hole of the upper chuck, and the elastic element facing the lower chuck; and a driving mechanism for driving the upper chuck and the wafer ejector pin to move toward the lower chuck respectively.

[0011] In one embodiment, the centerline of the wafer ejector pin is collinear with the centerline of the upper and lower chucks. According to a third aspect of the embodiments of this application, a wafer bonding method is provided, implemented using a wafer bonding apparatus as described in any of the preceding claims, wherein the two wafers to be bonded are a first wafer and a second wafer, and the wafer bonding method includes: Control the gas source to input gas into the sealed cavity until the gas pressure in the sealed cavity of the wafer ejector pin reaches the target gas pressure; Control the first wafer to move towards the second wafer until the first wafer and the second wafer are in a pre-contact state, wherein there is an air gap between the first wafer and the second wafer; The wafer ejector pin is controlled to move toward the first wafer, so that the elastic element applies pressure to the first wafer, causing the central region of the first wafer to contact the second wafer; The bonding between the first wafer and the second wafer is completed.

[0012] In one embodiment, the wafer bonding method further includes: The target gas pressure is determined based on the parameters of the first wafer and the second wafer; under the target gas pressure, the elastic element deforms and the contact surface with the first wafer is an arc-shaped surface.

[0013] In one embodiment, controlling the movement of the first wafer toward the second wafer until the first wafer and the second wafer are in a pre-contact state includes: The first wafer is adsorbed and fixed on the upper chuck, and the second wafer is adsorbed and fixed on the lower chuck, wherein the upper chuck is adsorbed and connected to the center and edge of the first wafer respectively; The upper chuck is controlled to move the first wafer downwards to the chuck until an air gap is formed between the first wafer and the second wafer; The bonding of the first wafer and the second wafer includes: The upper chuck is controlled to gradually release the vacuum adsorption on the center and edge of the first wafer, thereby eliminating the air gap from the center of the first wafer to the edge of the first wafer in sequence, and completing the bonding of the first wafer and the second wafer.

[0014] In one embodiment, controlling the wafer ejector pin to move toward the first wafer includes: The wafer ejector pin is controlled to move downwards a preset distance, the preset distance being determined based on the distance the first wafer moves to the second wafer; The air pressure in the sealed cavity is controlled to be adjusted from the target air pressure to the pre-bonding air pressure, wherein the pre-bonding air pressure is greater than or equal to the target air pressure, so that the elastic element applies pressure to the first wafer.

[0015] Compared with the prior art, the beneficial effects of this application are as follows: by setting an elastic element at the end of the needle body and forming a sealed cavity between the elastic element and the needle body, and by introducing gas into the sealed cavity through the air inlet channel, the elastic element undergoes controllable deformation, thereby forming an arc-shaped contact surface adapted to the wafer surface on the side of the elastic element away from the needle body. In this way, in the wafer bonding process, the wafer ejector pin of this application can achieve surface contact with the central region of the wafer, rather than point contact, avoiding the generation of extremely high local pressure at the center point of the wafer and reducing stress generation. In addition, it makes the wafer only undergo elastic deformation, avoiding plastic deformation, preventing the formation of error hot spots during the bonding process, and improving bonding uniformity. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the mating of a wafer ejector pin with a wafer according to an exemplary embodiment; Figure 2 This is a schematic axial cross-sectional view of a wafer ejector pin according to an exemplary embodiment; Figure 3 yes Figure 2 A schematic diagram of the deformation of the elastic element in the wafer ejector pin shown; Figure 4 yes Figure 2 A schematic diagram of one end face of the wafer ejector pin where the ejector pin body is connected to the elastic element. Figure 5 This is a schematic diagram of a wafer ejector pin according to another exemplary embodiment.

[0017] Explanation of reference numerals in the attached figures 1. Needle body; 11. Air inlet channel; 12. Sealing groove; 13. Outlet; 2. Elastic element; 3. Lower chuck; 4. Wafer; 5. Sealing cavity. Detailed Implementation

[0018] Unless otherwise defined, the technical or scientific terms used in this specification and claims shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. Specific embodiments of this application will be described below in conjunction with the accompanying drawings. It should be noted that, in order to provide a concise description, this specification cannot exhaustively describe all features of the actual embodiments. Without departing from the spirit and scope of this application, those skilled in the art can modify and substitute the embodiments of this application, and the resulting embodiments are also within the protection scope of this application.

[0019] In related technologies, devices employing the "bonding wave" principle to eliminate interfacial gases experience pre-compression via ejector pins. Because the pre-compression force acts on the wafer's center point, high local pressure easily forms near this point, causing not only local elastic deformation but also irreversible plastic deformation and even lattice distortion. This deformation does not completely disappear after the pre-compression process ends but is "frozen" in the bonding interface as residual stress. Consequently, the stress concentration area introduced by ejector pin pre-compression forms a fixed, reproducible error hotspot on the wafer. This error hotspot typically manifests as a specific overlay error pattern between different wafer layers, originating from the wafer center, severely impacting the performance and yield of devices in this region.

[0020] To address the aforementioned technical problems, this application provides a wafer ejector pin that can significantly reduce stress at the wafer center point during ejector pin pre-pressing, thereby improving product yield.

[0021] refer to Figures 1 to 5 In one specific embodiment, the wafer ejector pin includes: a pin body 1, with an air inlet channel 11 for communicating with an air source (not shown); and an outlet 13 disposed at a first end of the pin body 1 along the axial direction and communicating with the air inlet channel 11. Specifically, the outlet 13 may be disposed on the peripheral sidewall of the first end of the pin body, or the outlet 13 may be disposed on the end face of the first end of the pin body, so that the air inlet channel 11 communicates with the outside through the outlet 13. The needle body has an inlet at its second axial end that communicates with the air inlet channel 11. The inlet is connected to the air source via an air passage (not shown). The elastic element 2 is sealed to the first end of the needle body 1 and forms a sealed cavity 5 between the elastic element 2 and the needle body 1. The sealed connection can be that the elastic element 2 is sealed to the peripheral sidewall or the end face of the first end of the needle body 1. The outlet 13 is connected to the sealed cavity 5. When the air source fills the sealed cavity 5 with gas through the air inlet channel 11, the elastic element 2 deforms due to the change in gas pressure in the sealed cavity 5, so that the elastic element 2 forms an arc-shaped surface that contacts the wafer.

[0022] In this embodiment, an elastic element 2 is provided at the end of the needle body 1, and a sealed cavity 5 is formed between the elastic element 2 and the needle body 1. Gas can be introduced into the sealed cavity 5 through the air inlet channel 11, thereby applying pressure to the elastic element 2 and causing the elastic element 2 to undergo controllable deformation. As a result, an arc-shaped contact surface adapted to the surface of the wafer 4 is formed on the side of the elastic element 2 away from the needle body 1. In this way, in the wafer bonding process, the wafer ejector pin of this application can achieve surface contact with the central area of ​​the wafer, rather than point contact, avoiding the generation of extremely high local pressure at the center point of the wafer and reducing stress generation. In addition, the wafer only undergoes elastic deformation, avoiding plastic deformation, preventing the formation of error hot spots during the bonding process, and improving bonding uniformity.

[0023] On the one hand, the elastic element 2 has a certain degree of flexibility. At the moment of contact between the elastic element 2 and the wafer 4, it can effectively buffer the impact brought by the contact moment, avoid damage to the surface of the wafer 4 due to rigid contact, reduce stress generation, and improve the yield of the wafer 4. On the other hand, under the control of the pressure in the sealed cavity 5, the elastic element 2 can bulge to form an arc-shaped surface, achieve flexible ground contact with the wafer 4, effectively expand the contact area, thereby dispersing the pre-pressure. Moreover, when the wafer 4 is arched by the pre-pressure, it can effectively adapt to the curvature change of the wafer 4. During the arching deformation of the wafer 4, the pressure of the wafer ejector pin is always smoothly transmitted to the wafer 4 through the contact surface, so that the wafer only forms elastic deformation, avoids plastic deformation, and thus suppresses the generation of residual stress and prevents the formation of error hot spots during the bonding process. On the other hand, during the arching deformation of wafer 4, the deformation of elastic element 2 can be adjusted in real time by utilizing the variable air pressure in sealed cavity 5, thereby adjusting the curvature of the arc surface in real time. This ensures that the curvature of the arc surface is the same as the curvature of the arching of wafer 4, thus maintaining 100% contact between the arc surface and wafer 4 (i.e., the contact area between the elastic element and the wafer is almost the same as the area of ​​the arc surface). This maximizes the area of ​​force application, reduces pressure, reduces the generation of plastic deformation of wafer 4, reduces residual stress, and improves bonding uniformity.

[0024] Specifically, before pre-pressing, the relative positions of the wafer pin and the wafer 4 are as follows: the two wafers 4 to be bonded (divided into the first wafer and the second wafer) are close but not in contact, the elastic element 2 on the wafer pin faces the first wafer and can move towards the second wafer; the function of the wafer pin is to pre-press the two wafers 4 so that they contact each other at the pre-pressing part to obtain the initial bonding point.

[0025] See Figure 1 , Figure 2 As shown, before pre-pressurization, the gas source is activated and gas is injected into the sealed cavity 5, causing the elastic element 2 to bulge outwards from the needle body 1, thus forming an arc-shaped surface for contact with the wafer in advance. During pre-pressurization, the wafer ejector moves towards the first wafer until the arc-shaped surface of the elastic element 2 abuts against the first wafer. The wafer ejector applies pressure towards the second wafer to the first wafer, causing the first wafer to elastically arch towards the second wafer. The arched portion of the first wafer contacts the second wafer, and the edge of the first wafer curls up. The contact position forms an initial bonding point, completing the pre-pressurization process. Preferably, the pre-pressurization portion of the wafer ejector on the first wafer is the central region of the first wafer.

[0026] It should be noted that the elastic element 2 and the needle body 1 can be fixed by adhesive bonding or by snap-fitting, etc., and there is no limitation here.

[0027] In one specific implementation, see Figure 2 , Figure 4As shown, the wafer ejector pin also includes a sealing element (not shown); a recessed sealing groove 12 is provided on the end face of the pin body 1; the sealing element is located in the sealing groove 12, sealingly connecting the elastic element 2 to the end wall of the pin body 1. In this embodiment, the sealing groove 12 is an annular groove, and the elastic element 2 is sealedly connected to the sealing groove 12 by means of the sealing element, thereby obtaining a sealed edge of the sealing cavity 5, which can effectively prevent gas leakage and ensure the airtightness of the sealing cavity 5.

[0028] The location of the aforementioned sealing groove 12 is not limited to the end face of the needle body 1; it can also be located on the outer circumferential surface of the needle body 1. It is only necessary to achieve a seal between the elastic element 2 and the needle body 1 to ensure the airtightness of the sealing cavity 5.

[0029] In one specific embodiment, the sealing element is any one of the following components: a sealing ring, a sealing adhesive, or a sealing gasket.

[0030] Specifically, the sealing element is a sealing ring, which can be made of fluororubber or nitrile rubber. The sealing ring is embedded in the sealing groove 12, and the diameter of the sealing ring can be greater than the groove depth, so that while the elastic element 2 is fixed to the end of the needle body, the sealing ring is pressed tightly onto the needle body 1, thereby achieving a seal.

[0031] The sealing element is a sealant, which can be made of high-temperature resistant epoxy or silicone sealant. The sealant is filled in the sealing groove 12. When the elastic element 2 is fixed to the end of the needle body 1, the sealant is bonded to the elastic element 2 and cured, thereby achieving a seal.

[0032] The sealing ring is a sealing gasket. The material of the sealing gasket can be metal or polytetrafluoroethylene. The sealing gasket is installed in the sealing groove 12. The elastic element 2 can be provided with a protrusion corresponding to the sealing groove 12. When the elastic element 2 is fixed to the end of the needle body 1, the protrusion is inserted into the sealing groove 12 and abuts against the sealing gasket to achieve a seal.

[0033] In one specific embodiment, the elastic element 2 is a single-layer elastic membrane; or, the elastic element 2 is formed by stacking at least two layers of elastic membrane.

[0034] Specifically, the elastic element 2 is a single-layer elastic film, which can be made of polyurethane, silicone, or epoxy resin. The single-layer elastic film has a simple structure, is easy to install, and can deform uniformly under pressure, ensuring consistent stress on the wafer surface and effectively avoiding plastic deformation caused by localized stress concentration. Preferably, in actual production, the thickness of the elastic film can be adjusted according to the parameters of the wafer 4 to be bonded (such as wafer size, thickness, and bonding pressure) to ensure that the elastic film has the required elastic deformation under pressure.

[0035] The elastic element 2 can be formed by stacking at least two layers of elastic membranes. The multiple layers of elastic membranes can be fixed by bonding or hot pressing. The multi-layer structure can improve the overall strength and durability of the elastic element 2. At the same time, the elastic properties of the elastic element 2 can be adjusted by adjusting the material, thickness and stacking order of each layer of elastic membranes. In one specific embodiment, in the elastic element 2 formed by stacking at least two layers of elastic membranes, the elastic modulus of the elastic membrane located closer to the needle body 1 is greater than the elastic modulus of the elastic membrane located farther away from the needle body 1.

[0036] It should be noted that, in this embodiment, the elastic modulus refers to the material's ability to resist elastic deformation under stress. The larger the elastic modulus, the less likely the material is to deform; the smaller the elastic modulus, the more easily the material deforms. The elastic membrane located away from the needle body 1 is in direct contact with the wafer surface. In this embodiment, the elastic membrane closer to the needle body 1 uses a high elastic modulus, which can effectively support the overall structure when the elastic element 2 contacts the wafer; the elastic membrane farther from the needle body 1 uses a low elastic modulus, which can better conform to the wafer surface when the elastic element 2 contacts the wafer, thereby achieving a uniform distribution of pre-pressure.

[0037] In one specific embodiment, the surface of the elastic element 2 that contacts the wafer is a smooth surface. In this embodiment, by setting the surface of the elastic element 2 that contacts the wafer to a smooth surface, the pre-pressure is applied evenly to the wafer surface, thus avoiding stress concentration. Specifically, if the contact surface is rough and has tiny protrusions, when the wafer ejector pin applies pre-pressure, the pre-pressure will concentrate at the protrusions, generating a large local pressure, which will cause stress concentration on the wafer and affect the bonding quality.

[0038] In one specific embodiment, the air intake channel 11 is connected to an air source via an air path, and a control valve is provided on the air path. The control valve is used to control the opening and closing of the air path and to control the gas flow rate in the air path; and / or, the control valve has a communication unit that is connected to a host computer. In this embodiment, the control valve can be a solenoid valve, used to control the gas on / off and flow rate, thereby adjusting the degree of deformation of the elastic element 2; the control valve is electrically connected to the host computer, which is used to open and close the control valve according to the production process, and to adjust the opening degree of the control valve according to actual production needs (thickness of the wafer 4 to be bonded, bonding pressure, etc.).

[0039] In a second aspect, this application provides a wafer bonding apparatus suitable for vertically bonding two wafers 4, see [link to application details]. Figure 1As shown, it includes: a chuck, comprising an upper chuck (not shown) and a lower chuck 3, the upper chuck having a through-hole in the center, the upper chuck being used to hold one of the two wafers 4 (i.e., the first wafer), and the lower chuck 3 being used to hold the other of the two wafers 4 (i.e., the second wafer); a wafer ejector pin as described in any of the above embodiments, the wafer ejector pin being inserted into the center hole of the upper chuck, with the elastic element 2 facing the lower chuck 3; and a driving mechanism (not shown), which may include multiple driving sources, the platform on which the upper chuck is located and the wafer ejector pin being connected to different driving sources respectively, for driving the upper chuck and the wafer ejector pin to move toward the lower chuck 3 respectively.

[0040] In this embodiment, the upper chuck vacuum-adsorbs the first wafer, and the lower chuck 3 fixes the second wafer. The upper and lower chucks 3 are centered and aligned, and the centers of the first and second wafers are aligned. The upper chuck moves the first wafer, and the wafer ejector pins can move independently relative to the upper chuck. Furthermore, the wafer ejector pins can move independently relative to the upper chuck to apply pre-pressure to the first wafer. The drive source that drives the independent movement of the wafer ejector pins can communicate with a host computer (i.e., the control system that implements the bonding process). The host computer can then control the displacement of the wafer ejector pins to control the magnitude of the pre-pressure applied to the wafer. The pre-pressure is adjusted according to the thickness of the wafer 4 to ensure that the pre-pressure matches the pressure required for bonding, thereby improving the bonding yield.

[0041] In one specific embodiment, the centerline of the wafer ejector pin is collinear with the line connecting the centers of the upper and lower chucks 3, so as to facilitate contact with the center of the wafer 4. In this embodiment, the collinearity of the centerline of the wafer ejector pin with the centerline of the upper and lower chucks 3 ensures that the pre-pressure is precisely applied to the center of the wafer 4, achieving uniform transmission of the bonding wave from the center to the edge. The bonding wave refers to the contact leading edge that diffuses outward from the center during the bonding process, ensuring effective gas removal between wafers and reducing void defects.

[0042] Preferably, for the arc-shaped surface formed by the elastic deformation of the elastic element 2, the center line of the wafer pin can also be set through the vertex of the arc-shaped surface to ensure that the vertex of the arc-shaped surface first contacts the center of the wafer 4.

[0043] In a third aspect, this application provides a wafer bonding method, implemented using the wafer bonding apparatus described in the above embodiments, the wafer bonding method comprising: Control the gas source to input gas into the sealed cavity 5 in the wafer ejector pin until the gas pressure in the sealed cavity 5 reaches the target gas pressure; Control the first wafer to move towards the second wafer until the first wafer and the second wafer are in a pre-contact state, wherein there is an air gap between the first wafer and the second wafer; The wafer ejector pin is controlled to move toward the first wafer, so that the elastic element applies pressure to the first wafer, so that the central region of the first wafer comes into contact with the second wafer; The bonding between the first wafer and the second wafer is completed.

[0044] In this embodiment, gas is first filled into the sealed cavity 5 of the wafer ejector pin. When the first wafer and the second wafer are in a pre-contact state, the wafer ejector pin is controlled to move downward so that the elastic element contacts the first wafer and applies pressure. Because there is positive pressure in the sealed cavity, the elastic element bulges outward, which can achieve surface contact with the central area of ​​the first wafer, rather than point contact, thus avoiding the generation of extremely high local pressure at the center point of the wafer and reducing stress generation.

[0045] In one embodiment, the target gas pressure within the sealed cavity 5 of the wafer ejector pin is determined based on the parameters of the two wafers to be bonded (such as wafer size, thickness, and bonding pressure). When the gas pressure within the sealed cavity 5 reaches the target pressure, the elastic element 2 deforms, causing the contact surface between the elastic element 2 and the wafer 4 to be bonded to be an arc-shaped surface. Gas is supplied into the sealed cavity 5 by controlling the gas source until the gas pressure within the sealed cavity 5 reaches the target pressure. This embodiment coordinates the target gas pressure with the parameters of the wafers to be bonded, thereby better controlling the pressure applied by the elastic element to the first wafer, avoiding excessive pressure that could cause extremely high pressure at the center of the wafer, or insufficient attraction that would prevent the center of the first wafer from contacting the center of the second wafer.

[0046] In one embodiment, controlling the wafer ejector pin to move towards the first wafer causes the elastic element to apply pressure to the first wafer, causing the central region of the first wafer to contact the second wafer, specifically including: Control the wafer ejector pin to move downwards by a preset distance, the preset distance being determined based on the distance the first wafer moves to the second wafer; The air pressure in the sealed cavity is adjusted from the target air pressure to the pre-bonding air pressure. The pre-bonding air pressure is greater than or equal to the target air pressure, so that the elastic element applies pressure to the first wafer.

[0047] In this embodiment, the preset distance can be pre-set in the control system of the wafer bonding device. The drive mechanism drives the upper chuck to move the first wafer downward by a certain displacement s, so that the first wafer and the second wafer are in a pre-contact state. Then, the wafer ejector pin is driven to move downward by the same displacement s, so that the end of the wafer ejector pin is exposed, that is, the elastic element protrudes from the surface of the upper chuck and the first wafer in contact. That is, the preset distance is the displacement s, or the preset distance is slightly greater than the displacement s. It is determined according to the initial state of the upper chuck and the wafer ejector pin. The initial state is the relative position state of the upper chuck and the wafer ejector pin when the upper chuck has not moved downward. If the end of the wafer ejector pin is not exposed, the preset distance is greater than the displacement s. If the end of the wafer ejector pin is exposed, the preset distance is equal to the displacement s. Furthermore, in this embodiment, the gas pressure within the sealed cavity is adjusted at least twice to provide the pre-pressure required for the process of the first wafer. Specifically, before the wafer ejector pin moves, the gas pressure within the sealed cavity is first adjusted to an initial gas pressure, which can be the target gas pressure. The specific gas pressure value is determined so as not to affect the movement of the wafer ejector pin in the upper chuck. When the wafer ejector pin moves downward and its elastic element protrudes from the surface of the upper chuck that contacts the first wafer, the gas pressure within the sealed cavity is then adjusted to the pre-bonding gas pressure, causing the elastic element to apply pressure to the first wafer, resulting in contact between the first wafer and the second wafer. In this embodiment, the displacement of the wafer ejector pin can be controlled by a host computer, i.e., the size of the preset distance, and the size of the gas pressure within the sealed cavity can be adjusted according to the thickness of the wafer, i.e., the size of the pre-pressure is adjusted accordingly, ensuring that the pre-pressure matches the pressure required for bonding, thereby improving the bonding yield.

[0048] In one embodiment, controlling the movement of the first wafer towards the second wafer until the first and second wafers are in a pre-contact state specifically includes: adsorbing and fixing the first wafer onto the upper chuck, and adsorbing and fixing the second wafer onto the lower chuck 3, wherein the upper chuck is adsorbed and connected to the center and edge of the first wafer respectively; controlling the upper chuck to drive the first wafer to move towards the lower chuck 3 until an air gap is formed between the first and second wafers, thus achieving the pre-contact state between the first and second wafers. This embodiment uses regional vacuum adsorption between the upper chuck and the first wafer, facilitating subsequent bonding.

[0049] In one embodiment, the bonding of the first wafer and the second wafer is specifically achieved by: controlling the wafer ejector pin to move relative to the upper chuck and then to the lower chuck 3, so that the elastic element 2 applies pressure to the first wafer, causing the central region of the first wafer to contact the second wafer, and completing the initial bonding of the first wafer and the second wafer; and controlling the upper chuck to gradually release the vacuum adsorption on the center and edge of the first wafer, so that the air gap is eliminated sequentially from the center of the first wafer to the edge of the first wafer, and completing the bonding of the first wafer and the second wafer.

[0050] Specifically, before pre-pressing, the center and edges of the first wafer are vacuum-adsorbed by the upper chuck, keeping the first wafer flat; the second wafer is vacuum-adsorbed by the lower chuck 3, keeping the second wafer flat; the gas source is activated, supplying gas into the sealing cavity 5 until the gas pressure in the sealing cavity 5 reaches the target gas pressure, and the elastic element 2 bulges out to form an arc-shaped surface under the control of the pressure in the sealing cavity 5; during pre-pressing before bonding, the upper chuck moves the first wafer to the lower chuck 3, and the first wafer and the second wafer are in a pre-contact state. The pre-contact state means that there is an air gap between the first wafer and the second wafer. The air gap refers to the tiny gap between the first wafer and the second wafer where air can exist; after that, the wafer ejector pin can perform pre-pressing.

[0051] During pre-pressing, the drive mechanism drives the wafer ejector pin to move downward relative to the upper chuck, so that the arc-shaped surface of the elastic element 2 contacts the first wafer, and the wafer ejector pin applies pressure to the first wafer through the elastic element 2. Under the action of pressure, the central region of the first wafer elastically arches out towards the second wafer and contacts the second wafer, thereby completing the initial bonding between the first wafer and the second wafer. Afterward, the upper chuck gradually releases the vacuum adsorption on the center and edge of the first wafer, that is, it releases the wafer center region first and then the wafer edge. The bonding wave spreads from the wafer center region to the wafer edge to eliminate the air gap and complete the bonding between the first wafer and the second wafer.

[0052] The above description of the embodiments is intended to enable those skilled in the art to understand and apply this application. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, this application is not limited to the embodiments described herein, and any improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A wafer top pin, comprising: The wafer needle comprises: a needle body provided with an air inlet channel and an outlet, the air inlet channel being used for communication with an air source, and the outlet being arranged at one end of the needle body in the axial direction and being in communication with the air inlet channel; an elastic member being sealingly connected with the end of the needle body provided with the outlet and forming a sealed cavity with the needle body, the outlet being in communication with the sealed cavity; wherein when the air source fills the sealed cavity with air through the air inlet channel, the elastic member deforms under the change of air pressure in the sealed cavity, so that the elastic member forms an arc-shaped surface in contact with the wafer.

2. The wafer needle of claim 1, wherein, The wafer needle further comprises a sealing member; the end wall of the needle body provided with the outlet is provided with a recessed sealing groove, and the sealing member is located in the sealing groove to sealingly connect the elastic member with the needle body.

3. The wafer needle of claim 1, wherein the needle body is formed of a material that is transparent to electromagnetic radiation. The elastic member is a single-layer elastic film; or the elastic member is formed by at least two layers of elastic films stacked together, and the elastic modulus of the elastic film close to the needle body is greater than that of the elastic film away from the needle body.

4. The wafer needle of claim 1, wherein, The air inlet channel is connected with the air source through an air path, and a control valve is arranged on the air path, the control valve being used for controlling the opening and closing of the air path and the air flow in the air path; and / or the control valve is provided with a communication unit in communication with an upper computer.

5. A wafer bonding apparatus adapted for vertical bonding of two wafers, characterized by, The wafer needle comprises: a chuck comprising an upper chuck and a lower chuck, the upper chuck being provided with a central hole, the upper chuck being used for adsorbing one of the two wafers, and the lower chuck being used for adsorbing the other of the two wafers; the wafer needle is arranged in the central hole of the upper chuck, and the elastic member of the wafer needle faces the lower chuck; a driving mechanism is used for driving the upper chuck and the wafer needle to move towards the lower chuck respectively.

6. The wafer bonding apparatus of claim 5, wherein, The center line of the wafer needle is collinear with the center line of the upper chuck and the lower chuck.

7. A wafer bonding method characterized by, The wafer bonding method comprises: controlling the air source to input air into the sealed cavity in the wafer needle until the air pressure in the sealed cavity reaches a target air pressure; controlling the first wafer to move towards the second wafer until the first wafer and the second wafer are in a pre-contact state, the pre-contact state being that there is an air gap between the first wafer and the second wafer; controlling the wafer needle to move towards the first wafer, so that the elastic member applies pressure to the first wafer, and the central region of the first wafer is in contact with the second wafer; completing the bonding of the first wafer and the second wafer.

8. The wafer bonding method of claim 7, wherein, The wafer bonding method further comprises: determining the target air pressure according to the parameters of the first wafer and the second wafer; and 9. The wafer bonding method of claim 7, wherein, controlling the first wafer to move towards the second wafer until the first wafer and the second wafer are in a pre-contact state, the pre-contact state being that there is an air gap between the first wafer and the second wafer. The wafer bonding method further comprises: controlling the first wafer to move towards the second wafer until the first wafer and the second wafer are in a pre-contact state, the pre-contact state being that there is an air gap between the first wafer and the second wafer. The upper chuck drives the first wafer to move downwards to the lower chuck until the air gap between the first wafer and the second wafer is formed; The bonding of the first wafer and the second wafer includes: The upper chuck gradually releases the vacuum adsorption on the center and the edge of the first wafer, so that the air gap is eliminated from the center of the first wafer to the edge of the first wafer in sequence, and the bonding of the first wafer and the second wafer is completed.

10. The wafer bonding method of claim 7, wherein, The control of the wafer top needle moving to the first wafer includes: The wafer top needle is controlled to move downwards by a preset distance, and the preset distance is determined according to the distance of the first wafer moving to the second wafer; The air pressure in the sealed cavity is adjusted from the target air pressure to the pre-bonding air pressure, and the pre-bonding air pressure is greater than or equal to the target air pressure, so that the elastic member applies pressure to the first wafer.

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