Wafer bonding method and wafer bonding system

Abstract

The invention provides a wafer bonding method and a wafer bonding system, and belongs to the technical field of semiconductor material processing. The wafer bonding method comprises the following steps: preparing an isolating film layer on a to-be-bonded surface of an original wafer to form a film-forming wafer; a step for performing plasma activation on the surface of the film-forming wafer; a step for laser repairing the film-formed wafer that has been subjected to the plasma activation step; a step for aligning the two film-forming wafers that have been subjected to the laser repair step; and a step for bonding the two film-forming wafers that have been subjected to the alignment step. The wafer bonding system is used for executing the wafer bonding method and can solve the problem that lattice damage defects are formed in the wafer in the process of executing the existing ultrahigh vacuum normal temperature bonding technology.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material processing technology, and in particular to a wafer bonding method and a wafer bonding system. Background Technology

[0002] Ultra-high vacuum room temperature bonding technology is a key technology in the fields of micro-nano manufacturing, semiconductor packaging and precision device integration. By directly bonding two or more materials at room temperature, it can solve many adverse effects caused by the difference in thermal expansion coefficients of heterogeneous materials in traditional bonding technology.

[0003] The key to achieving ultra-high vacuum room temperature bonding technology lies in making the interface to be bonded sufficiently clean and active. The industry generally uses ion activation technology to achieve this effect.

[0004] During the activation process, high-energy ions bombard the bonding surfaces of the wafer, removing oxides and surface contaminants to create high-energy dangling bonds, thereby improving surface activity. However, when particles penetrate the material and collide with atoms in the crystal lattice, the atoms leave their original positions and remain at amorphous lattice sites. At room temperature, these interstitial atom pairs are relatively stable, and their state is not easily changed, forming vacancies, dislocations, or even amorphous defects. When these defect clouds accumulate, they form damage clusters, severely affecting the interfacial electrical and thermal conductivity. Summary of the Invention

[0005] This invention provides a wafer bonding method and a wafer bonding system to solve the problem of lattice damage defects formed in wafers during the execution of existing ultra-high vacuum room temperature bonding technology.

[0006] To achieve this objective, the present invention adopts the following technical solution: A wafer bonding method includes: a step of preparing an isolation film layer on the bonding surface of a raw wafer to form a film-forming wafer; The process of plasma activation of the surface of the film-forming wafer; The process of laser repair of the film-forming wafer after plasma activation; An alignment process is performed on the two film-forming wafers that have undergone laser repair. A bonding process is performed on the two film-forming wafers that have undergone the alignment process.

[0007] Furthermore, the material of the isolation film layer is different from the material of the original wafer.

[0008] Furthermore, the thickness of the isolation film layer is less than 10 nm.

[0009] Furthermore, the laser repair process includes controlling the laser beam to act on the wafer surface along a preset path.

[0010] Furthermore, the processes of preparing the isolation film layer to form a film wafer, the plasma activation process, the laser repair process, the alignment process, and the bonding process are all performed in a vacuum environment.

[0011] Furthermore, the plasma activation process, the laser repair process, the alignment process, and the bonding process are all performed in a vacuum environment, and the transfer of the film-forming wafer between each process is also performed in a vacuum environment.

[0012] A wafer bonding system, comprising: A film-forming chamber for accommodating a raw wafer and forming a film-forming wafer by preparing an isolation film layer on the surface of the raw wafer; A surface activation chamber is used to activate the surface of the film-forming wafer; A laser repair chamber includes a support portion and a laser emitter. The support portion is used to support the film-forming wafer, and the laser emitter is used to emit laser light onto the film-forming wafer supported by the support portion. The bonding chamber includes a first carrier and a second carrier disposed opposite to each other, the first carrier and the second carrier being used to hold the film-forming wafer, respectively; At least one of the first carrier and the second carrier is disposed on an alignment platform, the alignment platform being movable to adjust the first carrier and the second carrier to maintain the relative position between the film-forming wafers; At least one of the first carrier and the second carrier is provided with a force output section, which is used to output a bonding force to press the film-forming wafer held by the first carrier and the second carrier together to form a bonding wafer; The transfer chamber includes a robotic arm for picking up and placing the original wafer, the film-forming wafer, or the bonding wafer in each chamber.

[0013] Furthermore, it also includes a flipping chamber for performing the flipping of the original wafer or the film-forming wafer.

[0014] Furthermore, the film-forming chamber, the bonding chamber, the surface activation chamber, the flipping chamber, and the laser repair chamber are respectively connected to the transmission chamber and can be selectively connected; Furthermore, each chamber in the bonding system is equipped with an independent vacuum pump, and the entire wafer bonding system can be selectively switched to a vacuum state.

[0015] The beneficial effects of this invention are: On the one hand, a two-step design, which involves first preparing an isolation film layer of a different material from the wafer body on the bonding surface of the original wafer before wafer bonding and then performing plasma activation, can achieve dual protection of the atomic arrangement of the original wafer body: First, the interface formed by the heterogeneous material superposition between the isolation film layer and the wafer body will disrupt the continuity of atomic channels within the wafer body due to the essential difference in the atomic arrangement rules of the two, preventing high-energy ions from entering the body through the channel effect and interfering with the atomic arrangement; Second, the interface between the isolation film layer and the original wafer can act as a physical barrier, confining the atomic arrangement disorder (such as lattice distortion and defects) generated during plasma activation within the film layer. Even if this disorder is transmitted to the deeper layers of the film layer, the difference in the atomic arrangement of the heterogeneous materials will form a damage transmission barrier at the isolation interface, ultimately ensuring that the lattice damage remains only in the isolation film layer and does not spread to the wafer body, thus ensuring the integrity of the atomic arrangement within the wafer body.

[0016] On the other hand, defects within thinner isolation layers (less than 10 nm thick) can be rapidly repaired by laser in a short time. The time required for the thinner isolation layer material to absorb laser light and achieve photon energy conversion is extremely short, as is the time for atomic or molecular rearrangement for lattice repair. This has no impact on the original wafer, especially for wafers that are not resistant to high temperatures. For wafers with specific structures formed through ion implantation, this avoids the diffusion of ion-implanted materials caused by prolonged high-temperature processing.

[0017] The entire process is carried out in a vacuum environment and is not exposed to the atmosphere. The laser repair process does not affect the surface activity of the film-forming wafer after plasma activation, and direct bonding between the two wafers can still be achieved at low temperatures. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a bonding method in one embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of a bonding system in one embodiment of the present invention.

[0021] Figure label: 1: Front-end chamber; 2: Transmission chamber; 3: Film-forming chamber; 4: Laser repair chamber; 5: Bonding chamber; 6: Flipping chamber; 7: Surface activation chamber; 21: Robotic arm. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] This embodiment provides a wafer bonding system for performing ultra-high vacuum room temperature bonding of wafers. For example... Figure 1 and Figure 2 As shown, the wafer bonding system includes a film deposition chamber 3, a surface activation chamber 7, a laser repair chamber 4, a bonding chamber 5, and a flipping chamber 6. Each chamber is connected to the transfer chamber 2 via a valve and can be selectively connected. Each chamber is independently equipped with a vacuum pump to ensure that the process is carried out in a controlled vacuum environment, preventing the wafer from being exposed to the atmosphere. In addition, each chamber independently maintains specific environmental parameters (such as pressure and atmosphere), thereby ensuring the stability and independence of the process conditions at each stage.

[0024] As a feasible implementation, the film-forming chamber 3 is used to accommodate the original wafer and prepare an isolation film layer on the surface of the original wafer to form a film-forming wafer. The material of the isolation film layer is not specifically limited; materials such as Si, SiO2, AlN, SiC, SiCN, W, Mo, Nb, Si3N4, TiN, TaN, Ta2O5, Pt, Pd, and diamond can all be used as the isolation film layer. The film-forming apparatus in the film-forming chamber 3 can be configured as an atomic layer deposition apparatus, a physical vapor deposition apparatus, or a chemical vapor deposition apparatus. These are mature technologies, and a suitable film-forming apparatus can be configured in the film-forming chamber 3 according to process requirements without specific limitations. By depositing an ultrathin isolation film layer in a vacuum environment, the composition of the film layer can be effectively controlled to avoid the introduction of impurities and to improve the uniformity of film thickness.

[0025] As a feasible implementation, the surface activation chamber 7 is used to activate the surface of the film-forming wafer. The surface activation chamber 7, the film-forming chamber 3 and the transfer chamber 2 are connected and can be selectively connected. The film-forming wafer is transferred into the surface activation chamber 7 by the robot arm 21 in the transfer chamber 2. The surface activation chamber 7 is equipped with a plasma excitation device, which can break the chemical bonds on the surface of the film-forming wafer by plasma to increase the number of dangling bonds, thereby improving the surface activity.

[0026] As a feasible implementation, the laser repair chamber 4 is equipped with a support unit and a laser emitter. The support unit is used to support the film-forming wafer, and the laser emitter is used to emit laser light onto the film-forming wafer supported by the support unit, which can perform laser annealing on the supported film-forming wafer. During the laser annealing process, the laser energy density and scanning speed can be controlled according to the material of different isolation layers to achieve localized and rapid processing of the wafer surface. Laser annealing can promote atomic rearrangement in the isolation layer and repair lattice damage.

[0027] It should be noted that the laser emitter used in this embodiment is a fiber optic laser emitter. The laser energy density and scanning speed are set according to the isolation film material and the isolation film thickness. The energy density for different isolation film materials and thicknesses can be obtained experimentally. By pre-adjusting the laser irradiation of the isolation film material surface with different energy densities, the microstructure image (the image of the microstructure obtained after observing the sample with a transmission electron microscope) is observed. When the thickness of the amorphous damage layer in the image is <1nm, the requirements for laser energy density and scanning speed are met. The test method and device are existing technologies, and will not be described in detail in this embodiment.

[0028] As a feasible implementation method, the support unit can utilize various mature solutions, including but not limited to: electrostatic chucks, which achieve stable fixation and precise temperature control of the wafer through electrostatic adsorption; and mechanical clamping support stages, which use high-temperature resistant clamps to uniformly hold the wafer from the edge. All of the above methods can serve as the support unit for the wafers used in laser annealing.

[0029] As one feasible implementation, the wafer bonding system further includes a flip chamber 6, which is used to flip the original wafer or the film-deposited wafer, realizing the conversion of the wafer's front and back orientation. The flip chamber 6 includes a drive unit and a clamp connected to the drive unit; the clamp is used to clamp or release the original wafer or the film-deposited wafer with the sidewall of the original wafer or the film-deposited wafer as a reference. The drive unit is driven by a servo motor, the clamp is connected to the drive unit, and the drive unit controls the opening and closing of the clamp. The clamp performs the clamping or releasing action by opening and closing contacting the non-functional area of ​​the wafer sidewall.

[0030] During the bonding process, the bonding surfaces of the two film-forming wafers must face each other. After the first film-forming wafer is loaded into the bonding chamber 5 with its front side facing up, the second film-forming wafer first enters the flipping chamber 6, where it is safely held by a jig. Then, a rotating shaft drives it to complete a precise 180-degree flip, changing its bonding surface from facing up to facing down. Afterward, this flipped film-forming wafer is transferred back to the bonding chamber 5 and placed vertically opposite the first film-forming wafer, thus achieving the relative positioning of the two bonding surfaces, facilitating the subsequent pressure bonding process.

[0031] As one feasible implementation, the bonding chamber 5 includes a first carrier and a second carrier disposed opposite to each other, the first carrier and the second carrier being used to hold the film-forming wafer respectively; at least one of the first carrier and the second carrier is disposed on an alignment platform, the alignment platform being movable to adjust the first carrier and the second carrier to maintain the relative position between the film-forming wafer; at least one of the first carrier and the second carrier is provided with a force output part, the force output part being used to output bonding force to press the film-forming wafer held by the first carrier and the second carrier together to form a bonded wafer.

[0032] As a feasible implementation, the first and second carriers include electrostatic chucks, whose surfaces are typically made of materials with excellent thermal conductivity and insulation, such as alumina ceramic or anodic aluminum oxide. They are internally embedded with heating elements and cooling channels, enabling precise temperature control of the adsorbed wafers and ensuring the bonding process takes place under optimal thermal conditions. The alignment platform can specifically employ a precision motion system with multi-degree-of-freedom (X, Y, Z, θx, θy, θz) nanometer-precision adjustment capabilities. This system typically uses a combination of piezoelectric ceramic actuators and linear motor systems to provide precise driving force, and integrates a high-resolution laser interferometer or vision alignment system as a position feedback sensor. This system can detect and correct the positional deviations of the two wafers in the horizontal and vertical directions in real time, achieving sub-micron level alignment accuracy. The force output unit can specifically be a high-precision ball screw mechanism driven by a servo motor. The force output unit monitors and provides feedback on the positive pressure applied to the wafer in real time through a force sensor, and can precisely output bonding forces from a few Newtons to several thousand Newtons according to the process formulation, performing wafer bonding by setting a preset pressure value.

[0033] As a feasible implementation method, the laser repair chamber 4 and the bonding chamber 5 are connected to the transmission chamber 2 through gate valves and can achieve selective communication through the gate valves. The whole process is carried out in a vacuum environment and will not be exposed to the atmospheric environment. The surface of the film-forming wafer repaired by laser will not be exposed to the atmosphere, will not come into contact with pollutants or be oxidized, and its surface activity will not be affected. At the same time, the laser repair process will not affect the surface activity of the film-forming wafer after plasma activation, and direct bonding between the two wafers at low temperature can still be achieved.

[0034] As a feasible implementation, a front-end chamber 1 is also included. The front-end chamber 1 is connected to and selectively communicates with the transfer chamber 2. The front-end chamber 1 serves as a buffer between the raw wafer and / or the bonded wafer and the external environment, and is used to contain the raw wafer and / or the bonded wafer. The front-end chamber 1 ensures that the surface condition of the wafer to be bonded is not contaminated or interfered with by the external environment (such as particles, temperature and humidity fluctuations) before entering core processes such as film deposition and bonding. Secondly, for the completed bonded wafer, the front-end chamber 1 provides a stable temporary storage environment, ensuring the stability of the vacuum environment in the process chamber and enabling batch loading and unloading of wafers, thus improving overall production efficiency.

[0035] In this embodiment, the raw wafer refers to a semiconductor wafer substrate that is to be processed and has not been treated by the wafer bonding system of this application. It can be a single wafer made of materials such as silicon, silicon carbide, gallium arsenide, gallium nitride, and diamond. The film-deposited wafer refers to a wafer on the surface of the raw wafer after an isolation film layer has been prepared by the film-depositing chamber 3 of the bonding system. After subsequent surface activation and surface repair treatment, when two such film-deposited wafers are aligned and pressed together in the bonding chamber 5, they can be directly bonded to form a stable connection at low temperature through intermolecular forces, thus forming a bonded wafer.

[0036] Example 1 Two raw wafers, a GaN wafer and a diamond wafer, are prepared. The two raw wafers are introduced into the wafer bonding system through front-end chamber 1, and then transferred to film deposition chamber 3 through transfer chamber 2. A 5nm thick Al2O3 isolation film is then formed on the bonding surfaces of each raw wafer. After film deposition, the two wafers are sequentially transferred to surface activation chamber 7 through transfer chamber 2 for plasma activation (300W plasma activation power, Ar gas). The plasma-activated wafers are then transferred back to transfer chamber 2. After activation, the two film-forming wafers are respectively transferred to laser repair chamber 4 for repair (laser repair energy density 0.6 J / cm2). One of the film-forming wafers is transferred to the first carrier in bonding chamber 5 via transfer chamber 2, and the other film-forming wafer is transferred to the flipping chamber 6 via transfer chamber 2 for flipping before being transferred to the second carrier in bonding chamber 5 for bonding (bonding conditions: room temperature, pressure 50 kN, vacuum degree 5E-6 Pa). The bonded wafers formed by this method have a bonding strength greater than 1.5 J / m2. The thickness of the amorphous damage layer in the material observed in the TEM image is <1 nm.

[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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wafer bonding method, characterized in that, include: The process of preparing an isolation film layer on the bonding surface of the original wafer to form a film-forming wafer; The process of plasma activation of the surface of the film-forming wafer; The process of laser repair of the film-forming wafer after plasma activation; An alignment process is performed on the two film-forming wafers that have undergone laser repair. A bonding process is performed on the two film-forming wafers that have undergone the alignment process.

2. The wafer bonding method according to claim 1, characterized in that, The material of the isolation film layer is different from the material of the original wafer.

3. The wafer bonding method according to claim 1, characterized in that, The thickness of the isolation film is less than 10 nm.

4. The wafer bonding method according to claim 1, characterized in that, The laser repair process includes controlling the laser beam to act on the surface of the film-forming wafer along a preset path.

5. The wafer bonding method according to claim 1, characterized in that, The processes of preparing the isolation film layer to form a film wafer, the plasma activation process, the laser repair process, the alignment process, and the bonding process are all performed in a vacuum environment.

6. The wafer bonding method according to claim 1, characterized in that, The plasma activation process, the laser repair process, the alignment process, and the bonding process are all performed in a vacuum environment, and the transfer of the film-forming wafer between each process is also performed in a vacuum environment.

7. A wafer bonding system, characterized in that, include: A film-forming chamber (3) is used to contain the original wafer and to form a film-forming wafer by preparing an isolation film layer on the surface of the original wafer. Surface activation chamber (7) is used to activate the surface of the film-forming wafer; The laser repair chamber (4) includes a support portion and a laser emitter. The support portion is used to support the film-forming wafer, and the laser emitter is used to emit laser light onto the film-forming wafer supported by the support portion. The bonding chamber (5) includes a first carrier and a second carrier disposed opposite to each other, the first carrier and the second carrier being used to hold the film-forming wafer respectively; At least one of the first carrier and the second carrier is disposed on an alignment platform, the alignment platform being movable to adjust the first carrier and the second carrier to maintain the relative position between the film-forming wafers; At least one of the first carrier and the second carrier is provided with a force output section, which is used to output a bonding force to press the film-forming wafer held by the first carrier and the second carrier together to form a bonding wafer; The transfer chamber (2) includes a robotic arm (21) for picking up and placing the original wafer, the film-forming wafer or the bonding wafer in each chamber.

8. The wafer bonding system according to claim 7, characterized in that, It also includes a flip chamber (6) for performing the flipping of the original wafer or the film-forming wafer.

9. The wafer bonding system according to claim 8, characterized in that, The film-forming chamber (3), the bonding chamber (5), the surface activation chamber (7), the flipping chamber (6), and the laser repair chamber (4) are respectively connected to the transmission chamber (2) and can be selectively connected.

10. The wafer bonding system according to claim 9, characterized in that, Each chamber in the bonding system is equipped with an independent vacuum pump, and the entire wafer bonding system can be selectively switched to a vacuum state.

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