Wafer surface activation bonding apparatus and bonding method

Abstract

The application discloses a wafer surface activation bonding device and a bonding method, and relates to the technical field of wafer processing. The device comprises a clamp, a movable support rod and a bombardment particle emission device. The clamp comprises oppositely arranged first and second sample holders, and the first and second sample holders are each provided with a hard nonmetal back plate. Two wafers to be bonded are fixed on the hard nonmetal back plate, and the surface area of the two wafers to be bonded that is in contact with each other is a bonding area, which is surrounded by the surface of the hard nonmetal back plate. The movable support rod is arranged at least on the outer side of any one of the first and second sample holders, so that relative extrusion between the first and second sample holders is realized, and the bonding area of the surfaces of the two wafers to be bonded is fully contacted under the action of pressure. The bombardment particle beam spot emitted by the bombardment particle emission device uniformly covers the bonding area of the two wafers to be bonded. The application can effectively avoid the introduction of metal contamination at the bonding interface, and has the advantages of simple process, good compatibility and the like.

Description

Technical Field

[0001] This invention relates to the field of wafer processing technology, and specifically to a wafer surface activation bonding apparatus and bonding method. Background Technology

[0002] Wafer bonding technology is a technique that tightly binds wafers of different materials and functions at low or room temperature, enabling the fabrication of complex structures and high-performance devices. It is a key process for achieving three-dimensional integration, manufacturing microelectromechanical systems (MEMS), developing advanced packaging, and even realizing heterogeneous integration of various functional materials such as semiconductors, glass, and ceramics.

[0003] Commonly used bonding methods include anodic bonding, eutectic bonding, atomic diffusion bonding, hydrophilic bonding, and surface activated bonding (SAB). Among these, anodic bonding utilizes a high-voltage electric field and high temperature (typically 300°C–400°C) to induce chemical bonds between glass and silicon. While it offers high bond strength and good hermeticity, it is only suitable for bonding specific materials, and the high temperature introduces thermal stress. Eutectic bonding involves heating a metal interlayer (such as gold-tin) to its eutectic point (approximately 280°C) to form a liquid alloy, which then solidifies. It offers high bond strength and good thermal and electrical conductivity, but also faces challenges such as thermal stress, interfacial voids, and complex process control. Atomic diffusion bonding (such as Au-Au bonding) utilizes high temperatures (200°C–400°C) and pressure to induce inter-atomic diffusion in metals, making it a key technology for achieving three-dimensional interconnects. However, due to the presence of the metal interlayer, metal elements (such as Cu, Au, Sn, etc.) may diffuse into the active region during subsequent processes, contaminating semiconductor devices and causing electrical performance degradation, thus limiting its application in some applications (such as radio frequency semiconductor devices). Hydrophilic bonding relies on hydrogen bonds formed by surface hydroxyl groups for pre-bonding, but it requires annealing at temperatures above 800°C to transform into strong covalent bonds. This extremely high temperature generates enormous thermal stress and limits its application on wafers containing pre-fabricated circuits or temperature-sensitive materials, severely restricting its use in heterogeneous material integration. Compared with the methods mentioned above, surface activation bonding based on rapid atomic (or ion) bombardment shows significant advantages. Its basic principle is to use a rapid atomic beam (or ions) to bombard the wafer surface in an ultra-high vacuum environment, and remove contaminants and native oxide layers through physical sputtering, thereby exposing a clean, atomically active surface with high-density dangling bonds. Subsequently, the two activated surfaces are brought into direct contact at room temperature, and high-strength bonding can be formed by short-range van der Waals forces and chemical bonds.

[0004] The advantages of surface-activated bonding are primarily reflected in its room-temperature bonding characteristics. Since it can be performed at room temperature, it successfully avoids the fatal thermal stress caused by the mismatch in thermal expansion coefficients of heterogeneous materials, thus providing a key process solution for heterogeneous integration in fields such as power electronics and optoelectronics. Secondly, surface-activated bonding generally does not require any binders or intermediate metal layers, avoiding the additional thermal resistance, electrical resistance, or long-term reliability risks caused by introducing third-party materials. However, for some heterogeneous materials that are difficult to form sufficiently strong chemical bonds (such as diamond-GaN bonding), it is still necessary to deposit some ultrathin intermediate layer material at the bonding interface to achieve a high bonding strength when the two bonding interfaces come into contact.

[0005] Surface activated bonding has stringent requirements for surface flatness and roughness, typically requiring a surface roughness of less than 1 nm (or even 0.5 nm), thus demanding high precision in polishing processes. Furthermore, in practical applications of surface activated bonding, because bonding occurs in an ultra-high vacuum environment, electrostatic chucks are usually used to hold the wafer to be bonded. Electrostatic chucks offer irreplaceable advantages in terms of no particulate contamination, full-range clamping, and high-precision temperature control, making them a standard feature in modern semiconductor processes. However, their disadvantages include high cost, potential charge-related process risks, complex operation and maintenance, and limitations imposed by material type. Therefore, some surface activated bonding equipment still uses mechanical chucks to hold the bonding samples. Traditional mechanical chuck components (such as the backplate) are usually made of stainless steel. To ensure uniform activation of the bonding surface, the beam spot of the fast argon atom (or ion) beam needs to be larger than the wafer bonding surface. During surface activation, some fast argon atoms (or ions) inevitably bombard the stainless steel backplate holding the wafer, thereby sputtering metal elements such as Fe from the stainless steel backplate and depositing them on the bonding surface, thus introducing the risk of metal contamination to a certain extent. Summary of the Invention

[0006] The purpose of this invention is to address the problems in the prior art by providing a wafer surface activation bonding device and bonding method that can effectively avoid introducing metal contamination at the bonding interface. It can achieve high-strength and high-reliability bonding of wafers made of various materials under relatively mild conditions (especially low temperature or room temperature), while also having the advantages of simple process and good compatibility.

[0007] To achieve the above objectives, the present invention adopts the following solution: In a first aspect, a wafer surface activation bonding apparatus is provided, comprising: The fixture includes a first sample holder and a second sample holder arranged opposite to each other. Both the first sample holder and the second sample holder are provided with a rigid non-metallic back plate. Two wafers to be bonded are fixed on the rigid non-metallic back plates of the first sample holder and the second sample holder. The area where the surfaces of the two wafers to be bonded are in contact with each other is the bonding area, which is surrounded by the surface of the rigid non-metallic back plate. A movable support rod is provided on the outside of at least one of the first sample holder and the second sample holder. The movable support rod drives the relative compression between the first sample holder and the second sample holder, so that the bonding areas of the two wafer surfaces to be bonded are fully in contact under pressure. The bombardment particle emission device emits a beam of bombardment particles that uniformly covers the bonding regions of the two wafers to be bonded.

[0008] As a preferred embodiment, the first sample holder and the second sample holder further include a stainless steel plate, which is fixed in parallel with the rigid non-metallic back plate, and a flexible pad is filled between the stainless steel plate of the first sample holder and / or the rigid non-metallic back plate. The lower surface of the rigid non-metallic backplate of the first sample holder is provided with a non-metallic clamp, which fixes the edge of the first wafer to be bonded to the lower surface of the rigid non-metallic backplate of the first sample holder. The upper surface of the rigid non-metallic back plate of the second sample holder has a wafer groove. The second wafer to be bonded is placed in the wafer groove, and the depth of the wafer groove is less than the thickness of the second wafer to be bonded. The bonding surface of the second wafer to be bonded faces upward. The size of the second wafer to be bonded is smaller than the size of the first wafer to be bonded that is not obscured by the non-metallic fixture; The upper surface of the rigid non-metallic backplate of the second sample holder also has a clamping groove. The position of the clamping groove corresponds to the position of the non-metallic clamp. The depth of the clamping groove is greater than the protrusion height of the non-metallic clamp and less than the thickness of the rigid non-metallic backplate of the second sample holder, so as to avoid the non-metallic clamp blocking the two wafer surfaces to be bonded when they come into contact.

[0009] As a preferred embodiment, the rigid non-metallic backplate and non-metallic clamp are made of any one of silicon, silicon nitride, aluminum nitride, silicon carbide, silicon oxide, and aluminum oxide.

[0010] As a preferred embodiment, the first sample holder includes a first support and a second support. The first support includes a rigid non-metallic backplate and a lateral support rod for the backplate. A through-hole with a stepped edge is provided in the central area of ​​the rigid non-metallic backplate. The first wafer to be bonded is placed in the through-hole, and its edge is supported by the stepped edge of the through-hole. The bonding surface of the first wafer to be bonded faces downward. The lateral support rod of the backplate can move relative to the second support. The second support includes two layers of stainless steel plates. The size of the lower stainless steel plate is smaller than the size of the through-hole of the rigid non-metallic backplate, and it can extend into the through-hole of the rigid non-metallic backplate and press against the back of the first wafer to be bonded. The two layers of stainless steel plates are flexibly connected and filled with a flexible pad. The second sample holder includes a third support. The first support consists of a support frame and a fourth support frame. The third support frame includes a stainless steel support rod and a second sample holder stainless steel plate fixed on the stainless steel support rod. The second wafer to be bonded is placed on the upper surface of the second sample holder stainless steel plate. The fourth support frame includes a rigid non-metallic backplate and a stainless steel support rod sleeve. The rigid non-metallic backplate has a through hole in its central area. The size of the through hole is larger than the size of the second sample holder stainless steel plate, and the size of the second sample holder stainless steel plate is smaller than the size of the through hole on the rigid non-metallic backplate of the first support frame. The surface of the second sample holder stainless steel plate is lower than the surface of the rigid non-metallic backplate of the fourth support frame. The height difference between the two is less than the thickness of the second wafer to be bonded. The rigid non-metallic backplate of the fourth support frame is fixed on the stainless steel support rod sleeve.

[0011] As a preferred embodiment, the flexible pad is made of any one of polyimide, polyetheretherketone, polytetrafluoroethylene, perfluoroether rubber, and fluororubber.

[0012] As a preferred embodiment, a sputtering target is disposed between the first sample holder and the second sample holder. The sputtering target is fixed to one end of a target transverse support rod that can rotate around an axis. The target transverse support rod is fixed to a vertical rod that can move up and down and rotate around an axis. The surface area of ​​the sputtering target is larger than the area of ​​the bombardment particle beam emitted by the bombardment particle emission device. By rotating the horizontal and vertical support rods of the target material, the surface of the sputtering target material is made to face the first or second wafer to be bonded. After particle bombardment, a film containing the target material component is deposited on the surface of the two wafers to be bonded. The film containing the target material component serves as a nano-intermediate layer of the bonding interface.

[0013] As a preferred embodiment, two sputtering targets are disposed between the first sample holder and the second sample holder. The two sputtering targets are respectively fixed to one end of two target lateral support rods that can rotate around an axis. The two target lateral support rods are respectively fixed to two vertical rods that can move up and down and rotate around an axis. The surface area of ​​the two sputtering targets is larger than the area of ​​the bombardment particle beam emitted by the bombardment particle emission device, and they are respectively oriented towards the first wafer to be bonded and the second wafer to be bonded. After the two sputtering targets are bombarded by the two bombardment particle emission devices, a film layer containing the target material components is deposited on the surface of the two wafers to be bonded, serving as a nano-intermediate layer of the bonding interface.

[0014] As a preferred embodiment, the sputtering target is made of any one of silicon, silicon nitride, aluminum nitride, silicon carbide, silicon oxide, and aluminum oxide.

[0015] Secondly, a bonding method using the aforementioned wafer surface activation bonding apparatus is provided, comprising the following steps: The two wafers to be bonded are placed on the first sample holder and the second sample holder, respectively. Set the wafer surface activation parameters, including the energy, beam intensity and activation time of the bombardment particle emission device, and use the bombardment particle beam to bombard the surfaces of two wafers to be bonded for activation. By driving the movable support rod, the first sample holder and the second sample holder are moved relative to each other, so that the bonding surfaces of the two wafers to be bonded come into contact with each other under pressure and are held for a set time. The first and second sample holders are separated by driving the movable support rod, the bonding is completed, and the bonded composite wafer is taken out.

[0016] As a preferred embodiment, the setting of wafer surface activation parameters, including the energy, beam intensity, and activation time of the bombardment particle emission device, and prior to the step of activating the two wafer surfaces to be bonded by bombarding them with the bombardment particle beam, further includes: By setting unique sputtering parameters, a sputtering target is moved to face the first wafer to be bonded or the second wafer to be bonded. After particle bombardment, a film containing the target material is deposited on the surface of the two wafers to be bonded, serving as a nano-intermediate layer for the bonding interface. Alternatively, sputtering parameters for two sputtering targets are set, and the two sputtering targets are moved to face the first and second wafers to be bonded, respectively. After bombarding the two sputtering targets with particles by two bombardment particle emission devices, a film containing the target material components is deposited on the surface of the two wafers to be bonded, serving as a nano-intermediate layer for the bonding interface.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: Due to their low cost and ease of maintenance, mechanical chucks are still widely used in surface activated bonding (SAB) equipment for securing bonded wafers. Traditional mechanical chuck components (such as the backplate) are typically made of metal (e.g., stainless steel). To ensure uniform activation of the bonding surface, the beam size of the bombarding particles (fast argon atoms or ions) needs to be larger than the bonding area on the wafer surface. During surface activation, some fast argon atoms or ions inevitably bombard the metal backplate, sputtering metal elements (such as Fe) from the backplate and depositing them into the bonding area. This introduces metal contamination at the bonding interface, which can adversely affect the performance of high-frequency devices based on the bonding material. This invention fixes two wafers to be bonded onto rigid non-metallic backing plates of a first and second sample holder. The bonding area is surrounded by the surface of the rigid non-metallic backing plates, which not only avoids the introduction of metal contamination but also allows the deposition of a nanofilm containing the backing plate material on the wafer surface bonding area during surface activation. For wafers that are difficult to bond directly, chemical bonds can be formed between these materials to achieve wafer bonding. The invention also includes movable support rods on the outside of the first and / or second sample holders. Driving these movable support rods causes relative compression between the first and second sample holders, ensuring full contact between the bonding areas of the two wafers under pressure. A bombardment particle beam is emitted through a bombardment particle emission device, uniformly covering the bonding areas of the two wafers, achieving surface activation bonding. This invention enables high-strength, high-reliability bonding of wafers made of various materials under relatively mild conditions (especially low temperature or room temperature), while also possessing advantages such as simple process and good compatibility. This invention can drive the development of 3D integration technology towards higher density, better performance, and lower cost.

[0018] Furthermore, the wafer surface activation bonding apparatus of this invention is equipped with a sputtering target, which allows for in-situ deposition of thin films (of the same or different materials) on the surfaces of two wafers to be bonded, thus promoting bonding, followed by surface activation. This facilitates better control of the chemical composition of the bonding interface and avoids surface contamination caused by exposure to the atmosphere during the process from film deposition in other coating equipment to placement in the SAB apparatus. The bonding apparatus and method proposed in this invention enhance the formation of chemical bonds on the bonding surface and reduce interfacial voids, thereby achieving higher wafer bonding quality. In addition, for two wafers prone to chemical bonding, a nano-intermediate layer is deposited on the surface before surface activation. During the subsequent surface activation process, the nano-intermediate layer is subjected to rapid argon atom or ion bombardment. Ideally, the bombardment stops immediately when the nano-intermediate layer is sputtered away, significantly reducing the surface amorphization caused by bombardment. This results in lower interfacial thermal resistance between the two bonded wafers, which aids in heat dissipation for the power devices fabricated later.

[0019] Furthermore, complete and sufficient contact between the bonding regions of the two wafer surfaces is a prerequisite for achieving high-quality wafer bonding. In traditional SAB devices, the backplates holding the two wafers to be bonded are usually rigidly fixed to support rods. When it is difficult to ensure absolute parallelism between the two wafer bonding surfaces, the bonding regions cannot make complete and sufficient contact, resulting in numerous interface voids and failing to meet application requirements. In the wafer surface activation bonding device of this invention, the first sample holder consists of a rigid non-metallic backplate, a stainless steel plate, a flexible padding material with low outgassing rate, and a stainless steel support rod. The rigid non-metallic backplate is connected to the stainless steel plate by an elastic or extensible connector, maintaining a near-parallel relationship. Flexible padding material is uniformly filled between them, and the stainless steel plate is fixed to the stainless steel support rod. Due to the buffering effect of the flexible padding material, even if the upper and lower rigid non-metallic backplates deviate from parallelism, the two wafer bonding regions can still make complete and sufficient contact, thereby improving bonding quality.

[0020] Furthermore, the method for fixing the first wafer to be bonded on the sample holder in this invention is simple. It only requires using a non-metallic clamp to hold the edge of the first wafer to be bonded and fix it to the lower surface of the non-metallic back plate of the first sample holder. Alternatively, an even simpler method is to place the first wafer to be bonded in a stepped through hole in the rigid non-metallic back plate of the first sample holder, and use the stepped edge to support the wafer. Therefore, the bonding process is relatively simple. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the structure of the wafer surface activation bonding device according to Embodiment 1 of the present invention; Figure 2 Flowchart of a bonding method using a wafer surface activation bonding device in Embodiment 1 of the present invention; Figure 3 A schematic diagram of the structure of the wafer surface activation bonding device in Embodiment 2 of the present invention; Figure 4 Flowchart of the bonding method using a wafer surface activation bonding device in Embodiment 2 of the present invention; Figure 5 A schematic diagram of the structure of the wafer surface activation bonding device in Embodiment 3 of the present invention; Figure 6 Flowchart of the bonding method using a wafer surface activation bonding device in Embodiment 3 of the present invention; Figure 7A schematic diagram of the structure of the wafer surface activation bonding device in Embodiment 4 of the present invention; Figure 8 Flowchart of the bonding method using a wafer surface activation bonding device in Embodiment 4 of the present invention; Figure 9 Physical image of a Si / SiC wafer bonded according to Embodiment 1 of the present invention; Figure 10 Transmission electron microscope image of a wafer bonded according to Embodiment 1 of the present invention; Figure 11 A scanned image of the elemental distribution of a wafer bonded according to an embodiment of the present invention; In the attached figures: 10. First sample holder; 10-1. First support; 10-2. Second support; 101. Rigid non-metallic back plate of the first sample holder; 102. Stainless steel plate of the first sample holder; 102-1. First stainless steel plate of the second support; 102-2. Second stainless steel plate of the second support; 103. Flexible pad; 104. Stainless steel support rod of the first sample holder; 105. Lateral support rod of the back plate; 106. Lateral support rod of the first sputtering target for the wafer to be bonded; 107. Vertical rod of the first sputtering target for the wafer to be bonded; 108. Second sputtering target for the wafer to be bonded. 109. Horizontal support rod for the second wafer sputtering target; 110. Vertical rod for the second wafer sputtering target; 20. Non-metallic fixture; 20. Second sample holder; 20-1. Third support; 20-2. Fourth support; 201. Rigid non-metallic back plate for the second sample holder; 202. Stainless steel plate for the second sample holder; 204. Stainless steel support rod for the second sample holder; 204-1. Stainless steel support rod for the third support; 204-2. Stainless steel support rod sleeve for the fourth support; 30. First wafer sputtering target; 40. Second wafer sputtering target. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0024] It should be noted that, in the description of the embodiments of the present invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0025] Example 1: Please see Figure 1In this embodiment of the invention, the wafer surface activation bonding device is provided with a clamp for holding two wafers to be bonded, including a first sample holder 10 and a second sample holder 20. The first sample holder 10 is located directly above the second sample holder 20. The first sample holder 10 is composed of a silicon backplate, a silicon clamp, a stainless steel plate, a polytetrafluoroethylene (PTFE) material pad, and a stainless steel support rod. The silicon backplate is connected to the stainless steel plate by a telescopic connector. The silicon backplate and the stainless steel plate are kept parallel and the PTFE material pad is uniformly filled between them. The stainless steel plate is fixed on the stainless steel support rod. The edge of the first wafer to be bonded is clamped by the silicon clamp and fixed at the center of the lower surface of the non-metallic backplate. The bonding surface of the first wafer to be bonded faces downward. The second sample holder 20 consists of a silicon backplate, a stainless steel plate, and a stainless steel support rod. The silicon backplate is fixed on the stainless steel plate, and the stainless steel plate is fixed on the stainless steel support rod. A groove is opened in the center area of ​​the upper surface of the silicon backplate. The second wafer to be bonded is placed in the groove. The depth of the groove is less than the thickness of the second wafer to be bonded. The bonding surface of the second wafer to be bonded faces upward. In this embodiment, the dimensions of the two silicon backplates are larger than the dimensions of the upper and lower wafers to be bonded, which are fixed in their respective central regions. The two wafers are of different sizes, with the first wafer to be bonded, fixed on the silicon backplate, being larger. The bonding surfaces of the upper and lower wafers are positioned opposite each other. The area where the two wafer surfaces contact each other during bonding is the bonding area. The bonding area of ​​each wafer surface is surrounded by the surface of the silicon backplate. The beam spot areas of the two fast argon atom (or ion) beams used for wafer surface activation are projected onto the two silicon backplates, respectively. These beam spots are larger than the bonding area of ​​the wafer surfaces they bombard, but smaller than the area enclosed by the outer perimeter of the silicon backplate surface. The beam spots of the fast argon atom (or ion) beams uniformly cover the bonding area of ​​the wafers. The stainless steel support rod of the second sample holder 20 can move up and down, enabling the bonding areas of the two wafer surfaces to fully contact under pressure.

[0026] Please see Figure 2 ,based on Figure 1 The wafer bonding method of the bonding device shown is as follows: 1) Place the two wafers to be bonded on the silicon backplanes of the first sample holder 10 and the second sample holder 20, respectively; 2) Set the wafer surface activation parameters, including the energy, beam intensity and activation time of the argon atom (or ion) beam, and bombard the bonding surfaces of the two wafers to be bonded with two fast argon atom (or ion) beams for 120 seconds each. 3) Drive the support rod upward to make the bonding surfaces of the two wafers contact each other under pressure and hold for 600 seconds; 4) Separate the upper and lower sample holders, the bonding is complete, and take out the bonded composite wafer.

[0027] Example 2: Please see Figure 3 In this embodiment of the invention, the wafer surface activation bonding apparatus includes a first sample holder 10 and a second sample holder 20. The first sample holder 10 consists of a first support 10-1 and a second support 10-2. The first support 10-1 is located directly below the second support 10-2. The first support 10-1 consists of an aluminum nitride backplate and a transverse support rod 105. The aluminum nitride backplate has a through hole with a stepped edge in its central region. The width of the stepped edge of the through hole is 0.5 mm. The first wafer to be bonded is placed in the through hole and supported by the stepped edge. The bonding surface of the first wafer to be bonded faces... Below, the aluminum nitride backplate is fixed on the horizontal support rod 105 of the backplate, which can move up and down; the second bracket 10-2 is composed of a first stainless steel plate, a fluororubber material gasket, a second stainless steel plate and a stainless steel support rod. The first stainless steel plate is connected to the second stainless steel plate by an elastic connector, and the two are kept parallel. The fluororubber material gasket is evenly filled between the two stainless steel plates. The size of the first stainless steel plate is slightly smaller than the size of the through hole on the aluminum nitride backplate, so that it can penetrate into the through hole and press against the back of the first wafer to be bonded. The second stainless steel plate is mounted on the fixed stainless steel support rod. The second sample holder 20 consists of a third support 20-1 and a fourth support 20-2. The third support 20-1 is composed of a stainless steel plate and a stainless steel support rod. The stainless steel plate is fixed on the stainless steel support rod, which can move up and down. The second wafer to be bonded is placed on the upper surface of the stainless steel plate, and the two surfaces have the same shape and size. The fourth support 20-2 consists of an aluminum nitride backplate and a stainless steel support rod. The aluminum nitride backplate has a through hole in its central area. The size of the through hole is slightly larger than the size of the stainless steel plate of the third support 20-1, and the size of the stainless steel plate of the third support 20-1 is slightly smaller than the size of the through hole on the aluminum nitride backplate of the first support 10-1. The stainless steel plate of the third support 20-1 is nested in the through hole of the aluminum nitride backplate of the fourth support 20-2. The surface of the stainless steel plate of the third support 20-1 is slightly lower than the surface of the aluminum nitride backplate of the fourth support 20-2. The height difference between the two surfaces is less than the thickness of the second wafer to be bonded. The aluminum nitride backplate of the fourth support 20-2 is fixed on the sleeve 204-2 of the stainless steel support rod of the fourth support.

[0028] Please see Figure 4 ,based on Figure 3 The wafer bonding method of the bonding device shown is as follows: 1) Place the two wafers to be bonded on the first support 10-1 of the first sample holder 10 and the third support 20-1 of the second sample holder 20, respectively; 2) Set the wafer surface activation parameters, including the energy, beam intensity and activation time of the argon atom (or ion) beam. First, use a fast argon atom (or ion) beam to bombard the bonding surface of the second wafer to be bonded for 100 seconds to activate it. After the activation of the second wafer surface is completed, use another fast argon atom (or ion) beam to bombard the bonding surface of the first wafer to be bonded for 300 seconds to activate it. 3) Drive the stainless steel support rod of the second sample holder 20 to move upward, so that the two wafer surfaces come into contact with each other. Then continue to push the first support 10-1 to move upward, so that the upper surface of the first wafer to be bonded comes into contact with the lower surface of the first stainless steel plate of the second support 10-2, and the bonding surfaces of the two wafers come into contact with each other under pressure and remain in contact for 360 seconds. 4) Separate the upper and lower sample holders, the bonding is complete, and take out the bonded composite wafer.

[0029] Example 3: Please see Figure 5 In this embodiment, the wafer surface activation bonding apparatus, based on the apparatus of Embodiment 2, further includes a sputtering target made of silicon, which is fixed to one end of a horizontal support rod that can rotate around an axis. The horizontal support rod is fixed to a vertical rod that can move up and down and rotate around an axis. The surface area of ​​the sputtering target is larger than the beam spot area when a fast argon atom (or ion) beam is projected onto its surface. The sputtering target can be moved to a position directly below the first wafer to be bonded or directly above the second wafer to be bonded at a certain distance. By rotating the horizontal support rod and the vertical rod, the surface of the sputtering target is made to face the first or second wafer to be bonded. The surface of the target is bombarded by a fast argon atom (or ion) beam, thereby depositing a silicon thin film on the surface of the first and second wafers to be bonded. This film can serve as a nano-intermediate layer for the bonding interface.

[0030] Please see Figure 6 ,based on Figure 5 The wafer bonding steps of the bonding apparatus shown are as follows: 1) Place the two wafers to be bonded on the first sample holder 10 and the second sample holder 20; 2) Set the sputtering parameters of the sputtering target, including the energy, beam intensity and sputtering time of the argon atom (or ion) beam. Move the sputtering target to a position a certain distance directly below the first wafer to be bonded, and make the surface of the target face the bonding surface of the first wafer to be bonded. Use a fast argon atom (or ion) beam to bombard the surface of the target, thereby depositing a silicon thin film with a thickness of 3 nanometers on the surface of the first wafer to be bonded. 3) Move the sputtering target to a position a certain distance directly above the second wafer to be bonded, and make the surface of the target face the bonding surface of the second wafer to be bonded. Then bombard the surface of the target again with a fast argon atom (or ion) beam, thereby depositing a silicon thin film with a thickness of 3 nanometers on the surface of the second wafer to be bonded. 4) Rotate the vertical rod to remove the sputtering target from the area between the two wafers to be bonded; 5) Set the surface activation parameters, including the energy, beam intensity and sputtering time of the argon atom (or ion) beam, and bombard the bonding surfaces of the two wafers to be bonded with two fast argon atom (or ion) beams for 350 seconds to activate them. 6) Drive the stainless steel support rod of the second sample holder 20 to move upward, so that the bonding surfaces of the two wafers come into contact with each other under pressure and remain in contact for a certain period of time; 7) Separate the first sample holder 10 and the second sample holder 20 from top to bottom. After bonding is completed, take out the bonded composite wafer.

[0031] Example 4: Please see Figure 7 In this embodiment, the wafer surface activation bonding apparatus is based on the apparatus of embodiment two, and is further provided with two sputtering targets, which are respectively fixed to one end of two horizontal support rods. The two horizontal support rods are respectively fixed to two vertical rods that can rotate around an axis. The surface area of ​​the two sputtering targets is larger than the beam spot area of ​​the fast argon atom (or ion) beam projected onto their surfaces. The first wafer to be bonded sputtering target 30 is located below the second wafer to be bonded sputtering target 40. The surfaces of the first wafer to be bonded sputtering target 30 and the second wafer to be bonded sputtering target 40 face the first wafer to be bonded and the second wafer to be bonded, respectively. The surface of the target is bombarded by the fast argon atom (or ion) beam, thereby depositing a film containing the target material components on the surface of the first wafer to be bonded and the second wafer to be bonded. This film can serve as a nano-intermediate layer of the bonding interface.

[0032] Please see Figure 8 ,based on Figure 7 The wafer bonding method of the bonding device shown is as follows: 1) Place the two wafers to be bonded on the first sample holder 10 and the second sample holder 20, respectively; 2) Set the sputtering parameters of the two sputtering targets, including the energy, beam intensity and sputtering time of the argon atom (or ion) beam. Move the first wafer sputtering target 30 and the second wafer sputtering target 40 to a position at a certain distance directly below the first wafer and directly above the second wafer, respectively. Use a fast argon atom (or ion) beam to bombard the surface of the target, thereby depositing a film containing the target components on the surface of the first wafer and the second wafer. 3) Rotate the two vertical rods to move the two sputtering targets out of the area between the two wafers to be bonded; 4) Set the surface activation parameters, including the energy, beam intensity and sputtering time of the argon atom (or ion) beam, and activate the bonding surfaces of the two wafers to be bonded by bombarding them with a fast argon atom (or ion) beam; 5) Drive the stainless steel support rod of the second sample holder 20 to move upward, so that the bonding surfaces of the two wafers come into contact with each other under pressure and remain in contact for a certain period of time. 6) Separate the upper and lower sample holders to complete the bonding and remove the bonded composite wafer.

[0033] Please see Figure 9 The Si / SiC wafer bonded using the embodiment of the present invention shows that, except for some wafer edges with voids caused by contaminants, most areas are well bonded, indicating that the wafer surface activation bonding device and bonding method proposed in the embodiment of the present invention can achieve high-quality wafer bonding.

[0034] Please see Figure 10 The interface quality was further verified at the microscale using transmission electron microscopy images of the wafer bonded according to Embodiment 1 of the present invention. It can be seen that after introducing a silicon backplane to assist bonding, the atomic-level interface between Si and SiC is tightly connected, and no microcracks or delamination due to uneven thermal / mechanical stress were observed.

[0035] Please see Figure 11 Using the elemental distribution scanning results of the wafer bonded in Embodiment 1 of this invention, the composition of the interface transition region was clearly defined through annular dark-field images and precise distribution analysis of C and Si elements. Experimental results show that a continuous and uniform amorphous silicon layer was successfully induced at the Si / SiC contact interface. The presence of this amorphous layer is a key indicator of the successful implementation of silicon backplane-assisted bonding.

[0036] In summary, the wafer surface activation bonding apparatus and bonding method proposed in this invention not only avoids introducing metal contamination at the wafer bonding interface, but also, for wafers that are difficult to bond directly, deposits a film layer containing easily bondable materials on the wafer surface during surface activation. These materials can then form chemical bonds, achieving wafer bonding. For wafers that easily form chemical bonds, a nanofilm is deposited on the surface before surface activation. During the subsequent surface activation process, this film is subjected to rapid argon atom (or ion) bombardment. Ideally, the bombardment stops when the nanofilm is sputtered away, thus significantly reducing the surface amorphization caused by bombardment. This results in lower interfacial thermal resistance between the two bonded wafers, aiding in heat dissipation of power devices fabricated based on the bonded wafers. Furthermore, the method for fixing the first wafer to be bonded on the sample holder of the apparatus is simple, and a flexible pad with a low outgassing rate is uniformly filled between the non-metallic backplate and the stainless steel plate of the first sample holder. Due to the buffering effect of the flexible pad, the bonding areas of the two wafers can be fully contacted, thereby improving the bonding quality.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A wafer surface activation bonding apparatus, characterized in that, include: The fixture includes a first sample holder (10) and a second sample holder (20) arranged opposite to each other. Both the first sample holder (10) and the second sample holder (20) are provided with a rigid non-metallic back plate. Two wafers to be bonded are fixed on the rigid non-metallic back plates of the first sample holder (10) and the second sample holder (20). The area where the surfaces of the two wafers to be bonded contact each other is the bonding area. The bonding area is surrounded by the surface of the rigid non-metallic back plate. A movable support rod is provided on the outside of at least one of the first sample holder (10) and the second sample holder (20). The movable support rod drives the relative compression between the first sample holder (10) and the second sample holder (20), so that the bonding areas of the two wafer surfaces to be bonded are fully in contact under pressure. The bombardment particle emission device emits a beam of bombardment particles that uniformly covers the bonding regions of the two wafers to be bonded.

2. The wafer surface activation bonding apparatus according to claim 1, characterized in that, The first sample holder (10) and the second sample holder (20) also include stainless steel plates, which are fixed in parallel with the rigid non-metallic back plate, and flexible pads (103) are filled between the stainless steel plates of the first sample holder (10) and / or the rigid non-metallic back plate of the second sample holder (20). The lower surface of the first sample holder rigid non-metallic back plate (101) is provided with a non-metallic clamp (110), and the edge of the first wafer to be bonded is fixed on the lower surface of the first sample holder rigid non-metallic back plate (101) by the non-metallic clamp (110). The upper surface of the rigid non-metallic back plate (201) of the second sample holder has a wafer groove. The second wafer to be bonded is placed in the wafer groove, and the depth of the wafer groove is less than the thickness of the second wafer to be bonded. The bonding surface of the second wafer to be bonded faces upward. The size of the second wafer to be bonded is smaller than the size of the first wafer to be bonded that is not obscured by the non-metallic fixture (110); The upper surface of the rigid non-metallic backplate (201) of the second sample holder is also provided with a clamping groove. The position of the clamping groove corresponds to the position of the non-metallic clamp (110). The depth of the clamping groove is greater than the protrusion height of the non-metallic clamp (110) and less than the thickness of the rigid non-metallic backplate (201) of the second sample holder, so as to avoid the non-metallic clamp (110) blocking the two wafer surfaces to be bonded when they come into contact.

3. The wafer surface activation bonding apparatus according to claim 2, characterized in that, The rigid non-metallic backplate and non-metallic clamp (110) are made of any one of silicon, silicon nitride, aluminum nitride, silicon carbide, silicon oxide and aluminum oxide.

4. The wafer surface activation bonding apparatus according to claim 1, characterized in that, The first sample holder (10) includes a first support (10-1) and a second support (10-2). The first support (10-1) includes a rigid non-metallic backplate and a backplate transverse support rod (105). A through hole with a stepped edge is provided in the central area of ​​the rigid non-metallic backplate. The first wafer to be bonded is placed in the through hole, and its edge is supported by the step of the through hole. The bonding surface of the first wafer to be bonded faces downward. The backplate transverse support rod (105) can move relative to the second support (10-2). The second support (10-2) includes two stainless steel plates. The size of the lower stainless steel plate is smaller than the through hole size of the rigid non-metallic backplate. It can extend into the through hole of the rigid non-metallic backplate and press against the back of the first wafer to be bonded. The two stainless steel plates are flexibly connected and filled with a flexible pad (103). The second sample holder (20) includes a third support (20-1) and a fourth support. The first support (10-1) includes a stainless steel support rod and a second sample holder stainless steel plate (202) fixed on the stainless steel support rod. The second wafer to be bonded is placed on the upper surface of the second sample holder stainless steel plate (202). The fourth support (20-2) includes a rigid non-metallic back plate and a stainless steel support rod sleeve. The rigid non-metallic back plate has a through hole in its central area. The size of the through hole is larger than the size of the second sample holder stainless steel plate (202). The size of the second sample holder stainless steel plate (202) is smaller than the size of the through hole on the rigid non-metallic back plate of the first support (10-1). The surface of the second sample holder stainless steel plate (202) is lower than the surface of the rigid non-metallic back plate of the fourth support (20-2). The height difference between the two is less than the thickness of the second wafer to be bonded. The rigid non-metallic back plate of the fourth support (20-2) is fixed on the stainless steel support rod sleeve.

5. The wafer surface activation bonding apparatus according to claim 2 or 4, characterized in that, The flexible pad (103) is made of any one of polyimide, polyetheretherketone, polytetrafluoroethylene, perfluoroether rubber and fluororubber.

6. The wafer surface activation bonding apparatus according to claim 1, characterized in that, A sputtering target is provided between the first sample holder (10) and the second sample holder (20). The sputtering target is fixed at one end of a target horizontal support rod that can rotate around an axis. The target horizontal support rod is fixed on a vertical rod that can move up and down and rotate around an axis. The surface area of ​​the sputtering target is larger than the area of ​​the bombardment particle beam emitted by the bombardment particle emission device. By rotating the horizontal and vertical support rods of the target material, the surface of the sputtering target material is made to face the first or second wafer to be bonded. After particle bombardment, a film containing the target material component is deposited on the surface of the two wafers to be bonded. The film containing the target material component serves as a nano-intermediate layer of the bonding interface.

7. The wafer surface activation bonding apparatus according to claim 1, characterized in that, Two sputtering targets are arranged between the first sample holder (10) and the second sample holder (20). The two sputtering targets are respectively fixed to one end of two target horizontal support rods that can rotate around an axis. The two target horizontal support rods are respectively fixed to two vertical rods that can move up and down and rotate around an axis. The surface area of ​​the two sputtering targets is larger than the area of ​​the bombardment particle beam emitted by the bombardment particle emission device, and they are respectively facing the first wafer to be bonded and the second wafer to be bonded. After the two sputtering targets are bombarded by the two bombardment particle emission devices, a film containing the target material is deposited on the surface of the two wafers to be bonded as a nano intermediate layer of the bonding interface.

8. The wafer surface activation bonding apparatus according to claim 6 or 7, characterized in that, The sputtering target is made of any one of silicon, silicon nitride, aluminum nitride, silicon carbide, silicon oxide, and aluminum oxide.

9. A bonding method using the wafer surface activation bonding apparatus according to any one of claims 1 to 8, characterized in that, Includes the following steps: The two wafers to be bonded are placed on the first sample holder (10) and the second sample holder (20), respectively; Set the wafer surface activation parameters, including the energy, beam intensity and activation time of the bombardment particle emission device, and use the bombardment particle beam to bombard the surfaces of two wafers to be bonded for activation. By driving the movable support rod, the first sample holder (10) and the second sample holder (20) move relative to each other, so that the bonding surfaces of the two wafers to be bonded come into contact with each other under pressure and remain in contact for a set time. The first sample holder (10) and the second sample holder (20) are separated by driving the movable support rod, the bonding is completed, and the bonded composite wafer is taken out.

10. The bonding method according to claim 9, characterized in that, The setting of wafer surface activation parameters, including the energy, beam intensity, and activation time of the bombardment particle emission device, and prior to the step of activating the two wafer surfaces to be bonded by bombarding them with the particle beam, also includes: By setting unique sputtering parameters, a sputtering target is moved to face the first wafer to be bonded or the second wafer to be bonded. After particle bombardment, a film containing the target material is deposited on the surface of the two wafers to be bonded, serving as a nano-intermediate layer for the bonding interface. Alternatively, sputtering parameters for two sputtering targets are set, and the two sputtering targets are moved to face the first and second wafers to be bonded, respectively. After bombarding the two sputtering targets with particles by two bombardment particle emission devices, a film containing the target material components is deposited on the surface of the two wafers to be bonded, serving as a nano-intermediate layer for the bonding interface.

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