Bonding head for hybrid bonding and bonding method

Abstract

The invention belongs to the field of hybrid bonding, and particularly discloses a bonding head for hybrid bonding and a bonding method.The bonding head comprises a bonding head body, the lower surface of the bonding head body is of a horizontal structure, and an annular air pressure groove with a downward opening is formed in the lower surface of the bonding head body along the edge; the positive-negative air pressure device is used for adjusting the air pressure in the annular air pressure groove; and the moving rod assembly comprises a main moving rod and a plurality of auxiliary moving rods, the main moving rod and the auxiliary moving rods penetrate through the bonding head body, and the auxiliary moving rods are arranged around the peripheral side of the main moving rod. According to the bonding head, the annular air pressure groove is formed in the bonding head body, the adsorption force on the to-be-bonded chip is increased, in the bonding process, the main moving rod and the auxiliary moving rod can push the to-be-bonded chip to enable the to-be-bonded chip to have enough deformation quantity, the chip cannot be separated from the bonding head body, the bonding effect of hybrid bonding is improved, and the bonding efficiency is improved. And voids on the bonding interface are avoided.

Description

Technical Field

[0001] The present application belongs to the field of hybrid bonding, and more specifically, relates to a bonding head and a bonding method for hybrid bonding. Background Art

[0002] With the continuous development of semiconductor technology, hybrid bonding technology of chips and wafers has broad application prospects. In the hybrid bonding process of chips and wafers, ensuring that the bonding interface is intact and void-free is crucial to improving the quality and reliability of the process.

[0003] In the related art, the bonding head mainly adopts two structures. One is the arc-shaped bonding head, which uses the dense air pressure holes on the bonding head to absorb the chip into a shape that fits the arc-shaped bonding head. After the center of the chip contacts and bonds with the lower wafer, the negative pressure in the air pressure hole is released, and the chip deformation disappears. Due to the effect of gravity, the chip drops around and bonds with the lower wafer. However, for chips with certain pre-deformation and warping, the chip will return to its original shape after release, and the chip does not produce enough deformation, resulting in the bonding wave not being evenly transmitted from the inside to the outside. Part of the chip area contacts and bonds with the lower wafer first, so that a large void area will be generated at the bonding interface, greatly reducing the quality of the bonded chip. Another type of planar bonding head uses negative pressure to absorb the edge of the chip, and then blows positive pressure in the center area of ​​the planar bonding head to deform the chip into a bowl-shaped structure. The center of the chip first contacts the lower wafer, and then the boundary negative pressure is released to make the chip and the wafer completely contact. However, after this structure blows the chip into a bowl shape, the gas area between the chip and the wafer bonding head has a high pressure, which will cause the boundary negative pressure to fail to absorb the chip, causing the chip to detach from the bonding head before the center of the chip contacts the lower wafer. Reducing the positive pressure will not cause enough deformation of the chip. During the hybrid bonding process, the chip does not deform enough, and voids are easily generated at the bonding interface between the chip and the wafer, resulting in low bonding quality. Summary of the invention

[0004] In response to the defects of the prior art, the present application provides a bonding head and a bonding method for hybrid bonding, aiming to solve the problem that during the hybrid bonding process, the existing bonding head is prone to produce voids at the bonding interface between the chip and the wafer due to insufficient deformation of the chip, resulting in low bonding quality.

[0005] The present application provides a bonding head for hybrid bonding, which specifically includes a bonding head body, the lower surface of which is in a horizontal structure and has an annular air pressure groove opening downward along the edge; a positive and negative air pressure device for adjusting the air pressure inside the annular air pressure groove; a moving rod assembly, the moving rod assembly including a main moving rod and a plurality of auxiliary moving rods that are vertically arranged and parallel to each other, the main moving rod and the auxiliary moving rod both pass through the bonding head body and the plurality of auxiliary moving rods are arranged around the main moving rod; and a linear drive member for driving the main moving rod or the auxiliary moving rod to move.

[0006] Through the above technical scheme conceived by the present application, compared with the prior art, since the bonding head body of the present application is provided with an annular air pressure groove, it can increase its adsorption force on the chip to be bonded. During the bonding process, the main moving rod and the auxiliary moving rod can push the chip to be bonded so that it has a sufficient deformation amount, and the chip will not be separated from the bonding head body, so that the chip and the wafer can be better bonded, thereby achieving the beneficial effect of improving the bonding effect of hybrid bonding and avoiding the generation of voids at the bonding interface.

[0007] As a further preference, a plurality of evenly distributed communication holes connected to the annular air pressure groove are formed on the upper surface of the bonding head body, and the positive and negative air pressure devices are connected to the annular air pressure groove through the communication holes.

[0008] As a further preference, the plurality of secondary moving rods are arranged in one or more circles around the main moving rod as the center.

[0009] As a further preferred embodiment, a first through hole which is plugged and adapted to the main moving rod is opened in the middle of the bonding head body, and a plurality of second through holes which are plugged and adapted to the secondary moving rods are also opened on the bonding head body.

[0010] As a further preference, the projection plane of the annular air pressure groove along the vertical direction is located within the projection plane of the chip to be bonded along the vertical direction.

[0011] As a further preference, the bottom ends of the main moving rod and the auxiliary moving rod are both arc-shaped.

[0012] The present application discloses a bonding method, which is performed using the above-mentioned bonding head and comprises the following steps: S1: The annular air pressure groove on the bonding head body is used to adsorb the chip to be bonded through the positive and negative air pressure devices; S2: Adjust the position of the bonding head body so that the chip to be bonded is located above the wafer to be bonded; S3: The linear drive member first drives the main moving rod to descend and pushes the chip to be bonded until the lower surface of the chip to be bonded and the corresponding part of the main moving rod contact the upper surface of the wafer to be bonded to complete the bonding; S4: the linear drive member then drives the auxiliary moving rod to descend and push the chip to be bonded until the lower surface of the chip to be bonded and the corresponding portion of the auxiliary moving rod contact the upper surface of the wafer to be bonded to complete the bonding; S5: the annular air pressure groove releases air pressure to separate the chip to be bonded from the bonding head body, and the edge of the lower surface of the chip to be bonded contacts and bonds with the upper surface of the wafer to be bonded, thereby completing the complete bonding of the chip to be bonded and the wafer to be bonded; S6: The bonding head body, the main moving rod and the auxiliary moving rod are reset.

[0013] As a further preferred embodiment, the step S1 further includes activating the lower surface of the chip to be bonded.

[0014] As further preferred embodiment, in step S2, the wafer to be bonded is fixed on the base by negative pressure.

[0015] As a further preferred embodiment, the step S5 further includes annealing the bonded chip and wafer.

[0016] In general, the above technical solutions conceived by this application have the following technical advantages compared with the prior art: 1. In the present application, the bonding head body is provided with an annular air pressure groove. Compared with the traditional hole for adsorbing the chip, the annular air pressure groove can increase the adsorption force on the chip to be bonded, and improve the stability of the bonding head body adsorbing the chip to be bonded. During the bonding process, the main moving rod and the auxiliary moving rod can push the chip to be bonded in turn, so that it has a sufficient deformation amount, and at the same time, the bonding wave is diffused from the middle of the chip to be bonded to the surrounding, and the chip will not be separated from the bonding head body during this process, so that the chip and the wafer can be better bonded, the bonding effect of the hybrid bonding of the chip and the wafer is improved, and the generation of voids at the bonding interface is avoided, thereby improving the bonding quality.

[0017] 2. Compared with the problem of releasing the chip to be bonded after the chip to be bonded and the wafer to be bonded achieve point contact in the traditional bonding method, the present application pushes the chip to be bonded by lowering the main moving rod until the lower surface of the chip to be bonded contacts the upper surface of the wafer to be bonded to complete the bonding, and then the auxiliary moving rod is lowered to push the chip to be bonded so that the surrounding of the chip to be bonded is deformed, and more contact is generated at the bonding interface of the wafer to be bonded, thereby promoting the diffusion of the bonding wave and further improving the bonding effect of the chip and the wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the bonding head provided by the present application; Figure 2 is a schematic diagram of a top view of a bonding head body in an embodiment provided by the present application; Figure 3 It is a schematic diagram of the structure of the bonding head body provided by the present application from a bottom view; Figure 4 is a schematic diagram of a top view of the bonding head body in another embodiment provided by the present application; Figure 5 It is a schematic diagram of the overall structure of the main moving rod provided by the present application; Figure 6 This is a simulation diagram of point contact between the center of the chip and the wafer after bonding using the traditional bonding method; Figure 7 This is the effect diagram of bonding using traditional bonding methods; Figure 8 It is a schematic diagram of the change of the y coordinate of the lower surface of the chip with the position of the chip after bonding by the traditional bonding method; Fig. 9 It is a simulation diagram of a chip and a wafer being bonded using the bonding method provided in the present application; Fig.10 This is a diagram showing the bonding effect using the bonding method provided by the present application; Fig.11 It is a schematic diagram of the change of the y coordinate of the lower surface of the chip with the position of the chip after bonding by the bonding method provided by the present application; Fig.12 It is a schematic diagram of the bonding method provided in this application.

[0019] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 10. Main moving rod; 20. Auxiliary moving rod; 30. Bonding head body; 301. Second through hole; 302. First through hole; 303. Annular air pressure groove; 304. Connecting hole; 305. Third through hole; 40. Wafer to be bonded; 50. Chip to be bonded; 110. Base. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0021] Reference Figure 1-5The present application discloses a bonding head for hybrid bonding, which includes a bonding head body 30, a positive and negative air pressure device, a moving rod assembly and a linear drive member; the bonding head body 30 is a rectangular parallelepiped structure, and is made of rigid materials, including but not limited to structural steel materials. The size of the bonding head body 30 can be selected according to the size of the chip to match the chip size, so as to avoid chip offset during the bonding process between the chip and the wafer; the lower surface of the bonding head body 30 (the contact surface with the chip to be bonded 50) is horizontally structured and an annular air pressure groove 303 with an opening downward is opened along the edge, that is, the lower surface of the bonding head body 30 is provided with air pressure grooves all around, and the air pressure grooves all around are formed. The pressure grooves are interconnected, and the annular air pressure groove 303 can generate negative pressure to adsorb the chip 50 to be bonded before chip bonding, so that the edge of the chip 50 to be bonded is in contact with the lower surface of the bonding head body 30. When the chip 50 to be bonded contacts the wafer 40 to be bonded, the air pressure is released, the chip 50 to be bonded descends, and a bonding wave is generated between the chip and the wafer to perform bonding. The annular air pressure groove 303 is used to adsorb the chip in this application because under the same pressure, the contact area between the annular air pressure groove 303 and the chip is greater than the contact area between the hole and the chip. According to the relationship between pressure and force F=P*S, it can be seen that the former can more firmly adsorb the chip 50 to be bonded.

[0022] Among them, the key to the spontaneous diffusion of bonding waves lies in whether the chip surface adsorption force can overcome the chip elastic deformation stress, the air resistance of the bonding gap, and the internal stress caused by chip warping. The hybrid bonding of the chip and the wafer is adhered together through the water molecules or the bridge between the silicon dioxide between the chip and the wafer interface. Therefore, in order for the chip and the wafer to be spontaneously bonded, the chip surface adsorption force when the distance between the chip and the wafer is beyond the above-mentioned molecular action distance must be greater than the chip elastic deformation stress, the air resistance of the bonding gap, and the internal stress caused by warping. For example, the chip and the wafer are attached by water molecules, and the distance that the hydrogen bond water molecule chain can link generally cannot exceed 0.828nm. Therefore, when the chip and the wafer are bonded at a distance greater than or equal to 0.828nm, the chip surface adsorption force must be greater than the chip elastic deformation stress, the air resistance of the bonding gap, and the internal stress caused by chip warping. The DMT contact model is suitable for high-hardness solids with a small radius of curvature. The DMT model assumes that the adsorption force only occurs in the non-contact part, and the adsorption force of the contact part is balanced with the compression of the contact area. The adsorption force of the non-contact area proposed by Muller based on the Lennard-Jones interaction potential is expressed as follows:

[0023] in, p represents the adsorption force in the non-contact area, W It represents the gap between the chip and the wafer in the non-contact area. According to Muller's conclusion, its value is related to the chip bonding position. Its determination method is a conventional technical means, which will not be described here. represents the work done by the adsorption force, i.e., the surface energy, Represents the distance between molecules, usually 0.3nm~0.5nm. The adsorption force of the chip is proportional to the surface energy of the chip surface. The surface energy of the chip or wafer surface can be significantly increased by surface activation process (plasma activation process, etc.). Since the surface energy of the chip will be dissipated to a certain extent during the bonding process, and the elastic deformation stress and air resistance of the chip will change, if the surface energy increased by the surface activation process is not enough or there are unactivated areas on the chip surface, the diffusion of the bonding wave during the bonding process between the chip and the wafer cannot be completely spontaneous. The diffusion speed of the bonding wave will decrease when it diffuses to a certain position, so additional force is needed to assist the diffusion of the bonding wave. In addition, if the total time for the bonding wave to diffuse from the center to the edge position is greater than the time from the release of the chip edge to the contact bonding with the wafer, the edge position of the chip will be bonded earlier than the middle position, and the bonding wave cannot continue to diffuse. A large air void will be generated at the bonding interface. Therefore, it is necessary to apply additional force to assist the diffusion of the bonding wave at the position where the diffusion speed of the bonding wave decreases before the chip edge contacts and bonds with the wafer to increase the diffusion speed of the bonding wave.

[0024] The positive and negative air pressure devices can adjust the air pressure inside the annular air pressure groove 303, so as to achieve adsorption and release of the chip to be bonded 50. After the bonding head body 30 adsorbs the chip to be bonded 50, it is convenient to bond with the wafer to be bonded 40. The positive and negative air pressure devices are commonly used air pressure devices in the art and are not described in detail here. The moving rod assembly includes a main moving rod 10 and a plurality of auxiliary moving rods 20 that are vertically arranged and parallel to each other. The main moving rod 10 and the auxiliary moving rod 20 are also made of rigid materials. The main moving rod 10 passes through the middle part of the bonding head body 30 (i.e., the main moving rod 1 0 coincides with the center position of the bonding head body 30), multiple secondary moving rods 20 all penetrate the bonding head body 30 and are arranged around the circumference of the main moving rod 10, and the main moving rod 10 or the secondary moving rod 20 is driven to move in the vertical direction (z-axis direction) by a linear driving member. In actual use, the linear driving member can adopt multiple groups of linear cylinders or linear motors or electromagnetic driving devices and other power equipment, which can be adopted according to actual needs. The movement speed and final movement displacement distance of the main moving rod 10 and the secondary moving rod 20 can be adjusted according to needs.

[0025] In this embodiment, when the main moving rod 10 and the auxiliary moving rod 20 move downward and contact the chip to be bonded 50, the chip to be bonded 50 is deformed, and the lower surface (bonding interface) of the chip to be bonded 50 contacts and bonds with the surface to be bonded of the wafer to be bonded 40, and the bonding wave spreads. The main moving rod 10 descends to push the middle part of the chip to be bonded 50 to contact and bond with the wafer to be bonded 40, and then the auxiliary moving rod 20 descends to deform the chip to be bonded 50 and contact and bond with the wafer to be bonded 40, so that the chip to be bonded 50 has sufficient deformation. Finally, the air pressure in the annular air pressure groove 303 is released to completely bond the chip to be bonded 50 and the wafer to be bonded 40, thereby improving the bonding quality between the chip to be bonded 50 and the wafer to be bonded 40. After the main moving rod 10 moves downward and contacts the chip 50 to be bonded, the chip 50 to be bonded is deformed into a bowl shape. When the lower surface of the chip 50 to be bonded contacts and bonds with the corresponding position of the wafer 40 to be bonded, the main moving rod 10 stops moving. Since the air layer between the chip and the wafer has a certain hindering effect on the bonding, the secondary moving rod 20 then moves downward to push the lower surface of the chip 50 to be bonded to contact and bond with the corresponding position of the wafer 40 to be bonded, thereby promoting the diffusion of the bonding wave. The bonding head of the present application reduces the risk of the chip 50 to be bonded being separated from the bonding head body 30 during the bonding process, causing the chip 50 to be bonded to be misaligned, can promote the transmission of the bonding wave, and helps to reduce the generation of holes in the bonding between the chip and the wafer.

[0026] Specifically, the upper surface of the bonding head body 30 is provided with a plurality of connecting holes 304 which are evenly arranged to form a rectangular edge array and are connected to the annular air pressure groove 303. The positive and negative air pressure devices are connected to the annular air pressure groove 303 through the connecting holes 304, so that when the annular air pressure groove 303 adsorbs the chip 50 to be bonded, the chip 50 to be bonded is subjected to uniform force and adsorption is stable; the projection surface of the annular air pressure groove 303 along the vertical direction is located within the projection surface of the chip 50 to be bonded along the vertical direction, so that the annular air pressure groove 303 can stably adsorb the chip 50 to be bonded, and at the same time, the length of each side of the lower surface of the bonding head body 30 is greater than the corresponding length of each side of the chip 50 to be bonded, so that the lower surface of the bonding head body 30 can adsorb the edge of the chip.

[0027] More specifically, the depth of the annular air pressure groove 303 is half the height of the bonding head body 30, and the thickness of the connecting hole 304 is also half the height of the bonding head body 30. The positive and negative air pressure devices adsorb the chip 50 to be bonded through the connecting hole 304 and the annular air pressure groove 303, so that the four sides of the chip 50 to be bonded fit with the lower surface of the bonding head body 30. In the process of the annular air pressure groove 303 adsorbing the chip 50 to be bonded, the chip surface does not need to be an ideal plane. Since the chip will produce certain strain and warping after processing, and the chip has its own weight, it is only necessary to ensure that the four sides of the pressure-bearing parts of the chip 50 to be bonded fit with the lower surface of the bonding head body 30. The present application uses the annular air pressure groove 303 instead of the traditional hole to adsorb the chip, which increases the adsorption pressure, so that the chip 50 to be bonded can be more firmly adsorbed on the lower surface of the bonding head body 30.

[0028] Furthermore, multiple auxiliary moving rods 20 are arranged in one or more circles around the main moving rod 10. In this embodiment, the auxiliary moving rods 20 are arranged as six rods with the same diameter and equal length. The six auxiliary moving rods 20 surround the main moving rod 10 to form a layer and are in a circular array. The diameter of the circular array formed by the auxiliary moving rod 20 group (the radius position is based on the axial position of the 6 auxiliary moving rods 20) is 0.46 times the length of the chip 50 to be bonded. When the auxiliary moving rods 20 are arranged in multiple layers, the deformation of the chip 50 to be bonded can be further increased, thereby improving the bonding quality. After the main moving rod 10 moves downward to cause the chip 50 to be bonded to produce a bowl-shaped deformation and come into contact with the surface to be bonded of the wafer 40 to be bonded, a bonding wave is generated at the bonding interface. Since the chip has internal stress or the van der Waals force on the bonding surface is not large enough, the bonding wave stops at a certain position. The auxiliary moving rod 20 group moves downward to come into contact with the corresponding position of the chip 50 to be bonded, and continues to move downward to allow the chip 50 to be bonded to be deformed and come into contact with the surface to be bonded of the lower wafer, thereby increasing the contact area and promoting the transmission of the bonding wave.

[0029] like Figure 2 As shown, in this embodiment, the main moving rod 10 and the secondary moving rod 20 are both clearance-matched with the bonding head body 30, and a first through-hole 302 which is plugged and matched with the main moving rod 10 is provided in the middle of the bonding head body 30. A plurality of second through-holes 301 which surround the first through-hole 302 and are plugged and matched with the secondary moving rod 20 are also provided on the bonding head body 30. The number of the second through-holes 301 is six, and the six second through-holes 301 are arranged in a circular array. The main moving rod 10 and the secondary moving rod 20 can only be moved in the vertical direction, and the other directions are constrained, thereby improving the movement stability of the main moving rod 10 and the secondary moving rod 20; the bottom ends of the main moving rod 10 and the secondary moving rod 20 are both arc-shaped, so as to avoid the generation of large concentrated stress after contacting the chip 50 to be bonded, thereby causing damage to the chip 50 to be bonded.

[0030] The diameter of the main moving rod 10 is selected according to the size of the chip 50 to be bonded. Usually, the center point of the chip to be bonded first contacts and bonds with the surface to be bonded of the wafer 40 to be bonded. In order to increase the initial contact area, the diameter of the first through hole 302 and the diameter of the main moving rod 10 can be appropriately increased. The specific size can be selected according to the needs. In this embodiment, the main moving rod 10 is a cylindrical structure, such as Figure 5 In (a), the first through hole 302 is a circular through hole. Figure 4 As shown, in another feasible embodiment, the main moving rod 10 is a rounded rectangular structure, such as Figure 5 In (b), a third through hole 305 of a rounded rectangular structure is opened in the middle of the bonding head body 30 in this embodiment, and the rounded rectangular hole corresponds to the main moving rod 10 of the rounded rectangular structure. Compared with the first embodiment, this example increases the contact area between the center of the chip 50 to be bonded and the surface to be bonded of the wafer 40 to be bonded. In the first embodiment, the contact mode between the center of the chip 50 to be bonded and the surface to be bonded of the wafer 40 to be bonded is point contact, and in this embodiment, the contact mode between the center of the chip 50 to be bonded and the surface to be bonded of the wafer 40 to be bonded is surface contact. The rounded rectangular main moving rod 10 helps the propagation of the bonding wave and reduces the generation of voids.

[0031] The bonding head in the present application has lower requirements on the shape of the chip 50 to be bonded, and there is no need to make the chip 50 to be bonded completely fit with the lower surface of the bonding head body 30, so it is more convenient and quick to use.

[0032] In this embodiment, the thickness of the chip 50 to be bonded should not be too thick, and its thickness can be selected according to actual needs. When the thickness of the chip 50 to be bonded is too thick, it is difficult to achieve a sufficient deformation amount. Insufficient deformation amount will lead to two results. First, when the main moving rod 10 moves downward to deform the chip 50 to be bonded, when the center position of the chip 50 to be bonded has not yet contacted the surface to be bonded of the wafer 40 to be bonded, the surrounding of the chip 50 to be bonded may be separated from the bonding head body 30 in advance, resulting in uneven diffusion of the final bonding wave and more voids at the bonding interface; second, when the main moving rod 10 contacts the chip 50 to be bonded when moving downward, the large reaction force of the chip 50 to be bonded on the main moving rod 10 during the process of the main moving rod 10 continuing to move downward will cause the end of the main moving rod 10 to be bent or damaged. The lower surface of the chip 50 to be bonded does not need to be an ideal plane under the condition that the functional requirements are met. During the process of the bonding head body 30 adsorbing the chip 50 to be bonded, the four sides of the chip 50 to be bonded are in contact with the lower surface of the bonding head body 30. The chip 50 to be bonded does not need to be completely and tightly fitted with the lower surface of the bonding head body 30. Due to the warping and gravity caused by the pre-processing and pre-treatment steps, the center position of the chip 50 to be bonded and the contact positions with the annular air pressure grooves 303 of the bonding head body 30 do not need to be tightly fitted with the bonding head.

[0033] Figure 6-11 A simulation comparison of the bonding effect of the bonding head of the present application and the traditional bonding method is provided. The chip 50 to be bonded and the wafer 40 to be bonded are both made of silicon material. The thickness of the chip 50 to be bonded is set to 400um, and the length and width are both 13mm. The thickness of the wafer 40 to be bonded is set to 700um, and the gap between the wafer 40 to be bonded and the chip 50 to be bonded is set to 100um. Considering that the chip 50 to be bonded will have certain internal stress and warpage in the pre-treatment process, the chip 50 to be bonded is set to a curved shape with a central warpage of 70um.

[0034] Figure 6 In order to apply a downward load to the center of the chip to be bonded 50, the center of the chip to be bonded 50 and the wafer to be bonded 40 are in point contact. In the conventional bonding method, the chip to be bonded 50 is usually released after the chip to be bonded 50 and the wafer to be bonded 40 are in point contact. At this time, since the chip to be bonded 50 has a tendency to recover the initial deformation, before the bonding wave reaches the edge area, the edge area of ​​the chip to be bonded 50 will contact and adhere to the wafer to be bonded 40 earlier than the middle area, resulting in the middle area of ​​the chip to be bonded 50 not being able to contact the wafer to be bonded 40, and finally forming a large cavity at the bonding interface. Figure 7 This is the effect diagram after bonding using the traditional bonding method. From the corresponding two local enlarged images, it can be seen that there is a large gap in the middle of the chip 50 to be bonded, and the gap in the middle is significantly larger than the edge gap. The gap corresponds to the height of the cavity, and the maximum cavity height is 5.316um. Figure 8 This is a one-dimensional graph showing the change in the y coordinate of the lower surface of the chip to be bonded 50 as the position of the chip to be bonded 50 changes after bonding using a conventional bonding method. It can be seen that the edge position of the chip to be bonded 50 drops significantly earlier than the middle position. Fig. 9 This is a bonding diagram after the secondary rigid moving rod 20 contacts the chip 50 to be bonded in this embodiment, causing the chip 50 to be bonded to be deformed and to contact and adhere to the wafer 40 to be bonded. Fig.10 The effect diagram of the bonding method of this embodiment is shown in the two corresponding partial enlarged diagrams. It can be seen that the middle and edge positions of the chip 50 to be bonded have good contact with the wafer 40 to be bonded, and there is no obvious gap. Figure 7 The magnification ratios of the two local enlarged images are the same. For this embodiment, different simulation analyses were performed on the position where the secondary rigid moving rod 20 applies a load to the upper surface of the chip 40, and it was found that when the position where the secondary rigid moving rod 20 applies a load is between 0.3d and 0.46d (d is half the length of the chip), the coordinate position of the lower surface of the chip 50 to be bonded is the flattest, and the bonding effect is the best. Fig.11The one-dimensional graph of the y coordinate of the lower surface of the chip 50 to be bonded changes with the position of the chip 50 to be bonded when the load position applied by the secondary rigid moving rod 20 is 0.46d (d is half the length of the chip), in which the maximum void height is 1.377um, which is significantly smaller than the traditional bonding method. Fig.11 It can be seen that the coordinate position of the lower surface of the chip 50 to be bonded is relatively flat, indicating that no obvious voids are generated during the bonding process.

[0035] like Fig.12 As shown, the present application also discloses a bonding method, which is performed using the above-mentioned bonding head and includes the following steps: S1: Reference Fig.12 In (a), the annular air pressure groove 303 on the bonding head body 30 is used to adsorb the chip 50 to be bonded by the positive and negative air pressure devices, so that the chip 50 to be bonded is bonded to the lower surface of the bonding head body 30. Specifically, the edge of the chip 50 to be bonded can be bonded to the bonding head body 30, and the middle of the chip may not be completely bonded to the lower surface of the bonding head body 30 due to gravity or the initial warping center position; before bonding, the lower surface (bonding interface) of the chip 50 to be bonded is activated, including acid-base pretreatment, nitrogen or oxygen plasma etching, etc. Due to different activation methods, the size of the van der Waals force of the bonding interface is different, and the diffusion rate of the bonding wave is also different. In actual operation, different activation methods are used according to the situation to meet the bonding requirements between the chip 50 to be bonded and the wafer 40 to be bonded.

[0036] S2: The position of the bonding head body 30 is adjusted by a mechanical arm or a precision mechanical hand device so that the chip 50 to be bonded is located above the wafer 40 to be bonded; the wafer 40 to be bonded is fixedly mounted on the base 110 by negative pressure, and a plurality of vacuum holes are evenly opened on the upper surface of the base. The wafer 40 to be bonded is placed on the base for fixed installation; after the bonding head body 30 absorbs the chip 50 to be bonded and stabilizes it, its position is adjusted so that the middle of the chip 50 to be bonded is located directly above the wafer 40 to facilitate bonding. The bonding between the chip to be bonded 50 and the wafer to be bonded 40, and there is a certain height difference between the bonding interface between the chip to be bonded 50 and the wafer to be bonded 40, and the height difference matches the moving distance of the main moving rod 10 and the deformation degree of the chip to be bonded 50. Therefore, the height difference between the chip to be bonded 50 and the wafer to be bonded 40 before bonding is within the maximum deformation degree range that the chip to be bonded 50 can reach. In actual operation, the height difference can be artificially adjusted to adapt to the bonding needs of the chip to be bonded 50 and the wafer to be bonded 40.

[0037] S3: Reference Fig.12In (b), the linear drive member first drives the main moving rod 10 to descend and pushes the chip to be bonded 50 until the lower surface of the chip to be bonded 50 and the corresponding portion of the main moving rod 10 are in contact with the upper surface of the wafer to be bonded 40 to complete the bonding, that is, the main moving rod 10 pushes the chip to be bonded 50 so that the lower surface of the chip to be bonded 50 and the corresponding portion of the main moving rod 10 are in contact with the upper surface of the wafer to be bonded 40 to complete the bonding. Generally speaking, this step is used to achieve contact between the center portion of the lower surface of the chip to be bonded 50 and the center portion of the upper surface of the wafer to be bonded 40. Specifically, the main moving rod 10 slowly pushes the middle position of the chip to be bonded 50 downward to produce a bowl-shaped deformation. The middle position of the chip to be bonded 50 is deformed until point contact is made with the bonding interface of the wafer to be bonded 40. Due to the van der Waals force, the two are bonded. The displacement of the main moving rod 10 can be adjusted according to the deformability of the chip to be bonded 50 and the initial bonding gap height between the chip and the wafer to avoid chip breakage due to excessive deformation during the bonding process and local damage to the chip.

[0038] S4: Reference Fig.12 In (c), the linear drive member drives the secondary moving rod 20 to descend and push the chip 50 to be bonded, until the lower surface of the chip 50 to be bonded and the corresponding part of the secondary moving rod 20 are in contact with the upper surface of the wafer 40 to be bonded to complete the bonding, and when the chip 50 to be bonded contacts the surface of the wafer 40 to be bonded, the secondary moving rod 20 stops moving, that is, the secondary moving rod 20 pushes the chip 50 to be bonded, so that the lower surface of the chip 50 to be bonded and the corresponding part of the secondary moving rod 20 are in contact with the upper surface of the wafer 40 to be bonded to complete the bonding. Generally speaking, this step is used to achieve the contact of the surrounding of the central part of the lower surface of the chip 50 to be bonded with the surrounding of the central part of the upper surface of the wafer 40 to be bonded. In view of the fact that the chip surface activation effect is not obvious and the van der Waals force of the bonding interface is not strong enough, the surrounding of the chip 50 to be bonded is deformed by the secondary moving rod 20, and more contact is generated with the bonding interface of the wafer 40 to be bonded, thereby promoting the diffusion of the bonding wave.

[0039] S5: Reference Fig.12 In (d), the annular air pressure groove 303 releases air pressure to separate the chip 50 to be bonded from the bonding head body 30, and the edge of the lower surface of the chip 50 to be bonded contacts and bonds with the upper surface of the wafer 40 to be bonded, thereby completing the complete bonding of the chip 50 to be bonded and the wafer 40 to be bonded. The chip 50 to be bonded moves downward under the action of van der Waals force and gravity, and the bonding wave continues to diffuse outward. The chip 50 to be bonded and the surface to be bonded of the wafer 40 to be bonded complete the complete bonding. After the bonding process is completed, the bonded chip and wafer are annealed. Specifically, the existing annealing device can be used for processing, and the electrical and material properties of the semiconductor material can be improved by heating and cooling. In this embodiment, a rapid annealing process (RTP) can be used to eliminate the stress between the chip and the wafer and enhance the bonding force of the bonding interface.

[0040] S6: Reference Fig.12 In (e), the bonding head body 30, the main moving rod 10 and the auxiliary moving rod 20 are driven to reset.

[0041] It should be understood that expressions such as "include" and "may include" used in this application indicate the existence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In this application, terms such as "include" and / or "have" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components or combinations thereof.

[0042] It should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0044] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0045] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A bonding head for hybrid bonding, characterized in that: include: A bonding head body (30), wherein the lower surface of the bonding head body (30) is in a horizontal structure and an annular air pressure groove (303) opening downward is provided along the edge; A positive and negative air pressure device for adjusting the air pressure inside the annular air pressure groove (303); A moving rod assembly, the moving rod assembly comprising a main moving rod (10) and a plurality of auxiliary moving rods (20) which are vertically arranged and parallel to each other, the main moving rod (10) and the auxiliary moving rod (20) both pass through the bonding head body (30), and the plurality of auxiliary moving rods (20) are arranged around the circumference of the main moving rod (10); A linear drive member used for driving the main moving rod (10) or the auxiliary moving rod (20) to move.

2. A bonding head for hybrid bonding according to claim 1, characterized in that: The upper surface of the bonding head body (30) is provided with a plurality of evenly distributed communication holes (304) connected to the annular air pressure groove (303); the positive and negative air pressure devices are connected to the annular air pressure groove (303) through the communication holes (304).

3. A bonding head for hybrid bonding according to claim 1, characterized in that: The plurality of auxiliary moving rods (20) are arranged in one or more circles around the main moving rod (10) as the center.

4. A bonding head for hybrid bonding according to claim 1, characterized in that: A first through hole (302) is provided in the middle of the bonding head body (30) for plugging and matching with the main moving rod (10), and a plurality of second through holes (301) are also provided on the bonding head body (30) for plugging and matching with the auxiliary moving rod (20).

5. A bonding head for hybrid bonding according to claim 1, characterized in that: The projection plane of the annular air pressure groove (303) along the vertical direction is located within the projection plane of the chip (50) to be bonded along the vertical direction.

6. A bonding head for hybrid bonding according to any one of claims 1 to 5, characterized in that: The bottom ends of the main moving rod (10) and the auxiliary moving rod (20) are both arc-shaped.

7. A bonding method, using the bonding head according to any one of claims 1 to 6, characterized in that: The steps include: S1: Using a positive and negative air pressure device, the annular air pressure groove (303) on the bonding head body (30) adsorbs the chip (50) to be bonded; S2: adjusting the position of the bonding head body (30) so that the chip to be bonded (50) is located above the wafer to be bonded (40); S3: the linear drive member first drives the main moving rod (10) to descend and push the chip to be bonded (50) until the lower surface of the chip to be bonded (50) and the corresponding portion of the main moving rod (10) are in contact with the upper surface of the wafer to be bonded (40) for bonding; S4: the linear drive member then drives the auxiliary moving rod (20) to descend and push the chip to be bonded (50) until the lower surface of the chip to be bonded (50) and the corresponding portion of the auxiliary moving rod (20) are in contact with the upper surface of the wafer to be bonded (40) for bonding; S5: the annular air pressure groove (303) releases air pressure to separate the chip to be bonded (50) from the bonding head body (30), and the edge of the lower surface of the chip to be bonded (50) contacts and bonds with the upper surface of the wafer to be bonded (40), thereby completing the complete bonding of the chip to be bonded (50) and the wafer to be bonded (40); S6: The bonding head body (30), the main moving rod (10) and the auxiliary moving rod (20) are reset.

8. A bonding method according to claim 7, characterized in that: The step S1 also includes activating the lower surface of the chip (50) to be bonded.

9. A bonding method according to claim 7, characterized in that: In the step S2, the wafer (40) to be bonded is fixedly mounted on the base (110) by negative pressure.

10. A bonding method according to claim 7, characterized in that: The step S5 also includes annealing the bonded chips and wafers.

Images