Preparation method of hybrid bonding structure and hybrid bonding structure

Abstract

The invention relates to the technical field of semiconductor structures, and discloses a preparation method of a hybrid bonding structure and the hybrid bonding structure, and the preparation method comprises the steps: forming first metal layers which are arranged at intervals on the surface of one side of a first wafer; forming a first passivation layer on the surface of the first metal layer; forming second metal layers arranged at intervals on the surface of one side of the second wafer; forming a second passivation layer on the surface of the second metal layer; forming a polymer layer on the surface of the second wafer at the side part of the second metal layer; the thickness of the polymer layer is greater than or equal to the total thickness of the first metal layer and the second metal layer; carrying out thermocompression bonding on the first wafer and the second wafer; the first metal layer and the second metal layer are bonded and connected into an integrated structure through the first passivation layer and the second passivation layer; and the surface of the first wafer at the side part of the first metal layer is correspondingly contacted with the polymer layer and is bonded and connected with the polymer layer. Compared with the prior art, the hybrid bonding interface strength and the reliability and stability of the hybrid bonding structure can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor structures, and in particular to a preparation method of a hybrid bonding structure and the hybrid bonding structure. Background Art

[0002] 3D interconnect technology is used to electrically interconnect two or more chips to achieve high-bandwidth and high-density signal transmission. As the interconnect pitch and gap become smaller, hybrid bonding technology has attracted attention due to its advantage of high interconnect density. The hybrid bonding structure of Cu and rigid dielectrics (SiO2, SiN, SiCN) has extremely high requirements for surface flatness, cleanliness, and roughness, and is prone to poor interface bonding. Using polymers instead of rigid dielectrics in the Cu / polymer hybrid bonding method can reduce the extremely high cleanliness standards for the bonding surface. The deformation of the polymer interface during the bonding process is conducive to increasing the effective bonding area, and the polymer has a higher tolerance for particles.

[0003] At present, there are two technical routes for Cu / polymer hybrid bonding: ① Cu interface bonding first and then polymer interface bonding. This scheme usually performs plasma activation on the copper interface to remove the oxide layer before bonding, but there is a risk of introducing particles, increasing the roughness of the metal bonding interface and changing the properties of the polymer; ② Polymer interface bonding first and then Cu interface bonding, but slip may occur during polymer bonding, affecting the alignment accuracy of Cu interface bonding. In addition, the existing Cu / polymer hybrid bonding method requires that Cu and polymer have the same height, and must undergo flattening processes such as CMP or fly cutting before bonding. CMP and fly cutting have the risk of scratching the polymer surface and easily produce bonding voids. And because the polymer is only partially solidified before bonding, it has limited support for the metal layer, and the flattening process may cause the bottom metal layer to break. Since the polymer and Cu layers are at the same height, there is a risk of polymer entering the metal bonding interface and causing interconnection failure when the two wafers are aligned and bonded.

[0004] Therefore, a solution is needed to improve the bonding alignment accuracy of the metal layer and eliminate the treatment of the polymer interface before bonding to avoid the generation of bonding voids in the hybrid bonding structure, thereby improving the hybrid bonding interface strength and hybrid bonding yield, and improving the reliability and stability of the hybrid bonding structure. Summary of the invention

[0005] In view of this, the present invention provides a preparation method of a hybrid bonding structure and a hybrid bonding structure to solve the problem in the related art that the metal bonding interface of the hybrid bonding structure will slip during bonding, the polymer flattening process will scratch the polymer surface to produce bonding voids, the polymer support will be reduced, and the bottom metal layer will be broken.

[0006] In a first aspect, the present invention provides a method for preparing a hybrid bonding structure, the preparation method comprising:

[0007] providing a first wafer;

[0008] Forming a plurality of first metal layers arranged at intervals on a surface of one side of the first wafer;

[0009] forming a first passivation layer on a surface of the first metal layer facing away from the first wafer; the material of the first passivation layer is a polycrystalline structure;

[0010] providing a second wafer;

[0011] Forming a plurality of second metal layers arranged at intervals on a surface of one side of the second wafer;

[0012] forming a second passivation layer on a surface of the second metal layer facing away from the second wafer; the material of the second passivation layer is a polycrystalline structure;

[0013] forming a polymer layer on the surface of the second wafer at the side of the second metal layer; the thickness of the polymer layer is greater than or equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer;

[0014] The first wafer and the second wafer are hot-pressed and bonded together to form a hybrid bonding structure; the first metal layer and the second metal layer are bonded to form an integrated structure through the first passivation layer and the second passivation layer; the first passivation layer and the second passivation layer are correspondingly contacted and bonded together; the first wafer surface on the side of the first metal layer is correspondingly contacted and bonded together with the polymer layer.

[0015] The preparation method of the hybrid bonding structure provided by the present invention, on the one hand, only needs to form a polymer layer on the surface of the second wafer on the side of the second metal layer, and the thickness of the polymer layer is greater than or equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer, so that when the first wafer and the second wafer are hot-pressed bonded, the surface of the first wafer on the side of the first metal layer contacts and is bonded together with the polymer layer, so there is no need to perform a flattening process on the polymer layer, which can effectively prevent the generation of bonding voids in the hybrid bonding structure, reduce the risk of introducing particles in the flattening process, and make the polymer layer scratch-free. It can also increase the effective bonding area and reduce the risk of slippage in the bonding process, thereby improving the hybrid bonding interface strength and hybrid bonding yield; on the other hand, by forming the first passivation layer and the second passivation layer of the polycrystalline structure, the surface oxidation of the first metal layer and the second metal layer can be suppressed, the bonding temperature of the metal bonding interface can be reduced, and the first metal layer and the second metal layer can be preferentially bonded at low temperature, thereby improving the bonding alignment accuracy of the metal layer interface, improving the hybrid bonding interface strength and hybrid bonding yield, and improving the reliability and stability of the hybrid bonding structure.

[0016] In an optional embodiment, the step of thermocompression bonding the first wafer and the second wafer together to form a hybrid bonding structure includes:

[0017] The first wafer is thermally pressed and bonded to the second wafer at a first temperature and a first pressure, so that the first passivation layer and the second passivation layer are in contact with each other and bonded together;

[0018] At a second temperature and a second pressure, the first wafer surface at the side of the first metal layer contacts and is bonded to the polymer layer;

[0019] The second temperature is greater than the first temperature.

[0020] The preparation method of the hybrid bonding structure provided by the present invention hot-presses and bonds the first wafer and the second wafer together. First, the wafer is kept warm and pressurized at a first temperature and a first pressure. Due to the presence of the passivation layer, the metal layers can be melt-bonded and combined into one at a lower first temperature. Bonding the first metal layer and the second metal layer first can improve the alignment accuracy of the metal layers, thereby improving the strength and stability of the metal bonding interface. Secondly, at a second temperature and a second pressure, the surface of the first wafer on the side of the first metal layer contacts and is bonded to the polymer layer accordingly. The second temperature is greater than the first temperature. The bonding and curing of the polymer layer are achieved at the higher second temperature, thereby further improving the stability and reliability of the hybrid bonding structure.

[0021] In an optional embodiment, at the first temperature and the first pressure, the step of contacting and bonding the first passivation layer and the second passivation layer together correspondingly further includes:

[0022] At the first temperature and the first pressure, the first metal layer and the second metal layer are bonded and connected to form an integrated structure through the first passivation layer and the second passivation layer.

[0023] In an optional embodiment, there is a gap between the polymer layer and the first metal layer, and between the polymer layer and the second metal layer; the thickness of the polymer layer is greater than the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer;

[0024] The step of contacting and bonding the first wafer surface on the side of the first metal layer with the polymer layer at the second temperature and the second pressure also includes:

[0025] At the second temperature and the second pressure, the first metal layer and the second metal layer expand to fill the gap; the polymer layer deforms to completely fill the gap and solidifies.

[0026] The preparation method of the hybrid bonding structure provided in the present embodiment has gaps between the polymer layer and the first metal layer, and between the polymer layer and the second metal layer. At a second temperature with a higher temperature, the first metal layer and the second metal layer release stress in the horizontal direction and expand slightly to fill the gap. At the same time, the polymer is deformed under pressure to completely fill the gap and solidify during the heating process. The present method can form a gap to leave space for the expansion of the first metal layer and the second metal layer in the horizontal direction, avoid the situation where the first metal layer and the second metal layer are broken due to excessive stress in the vertical direction, improve the strength and stability of the metal bonding interface, and thus improve the electrical interconnection reliability and mechanical reliability of the hybrid bonding structure; by setting the thickness of the polymer layer to be greater than the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer, the excess polymer layer can be used to completely fill the gap, prevent the generation of bonding voids in the hybrid bonding structure, improve the hybrid bonding interface strength and hybrid bonding yield, and improve the reliability and stability of the hybrid bonding structure.

[0027] In an optional embodiment, the width of the gap is 500 nm to 1000 nm.

[0028] In an optional embodiment, the first temperature is 150°C-180°C;

[0029] The second temperature is 250°C-300°C.

[0030] In an optional embodiment, the material of the polymer layer is a photosensitive polymer;

[0031] The materials of the first metal layer and the second metal layer are copper;

[0032] The materials of the first passivation layer and the second passivation layer are Pd or Au with a polycrystalline structure;

[0033] The thickness of the first passivation layer and the thickness of the second passivation layer are less than or equal to 10 nm.

[0034] In an optional embodiment, the step of forming a plurality of first metal layers arranged at intervals on a surface of one side of the first wafer includes:

[0035] Forming a first seed layer on a surface of one side of the first wafer; the first seed layer includes a stacked titanium layer and a copper layer;

[0036] Forming a plurality of first metal layers arranged at intervals on a surface of the first seed layer facing away from the first wafer;

[0037] After the step of forming a first passivation layer on a surface of the first metal layer facing away from the first wafer, the step further includes:

[0038] removing the first seed layer at a side portion of the first metal layer;

[0039] and / or:

[0040] The step of forming a plurality of second metal layers arranged at intervals on a surface of one side of the second wafer includes:

[0041] forming a second seed layer on a surface of one side of the second wafer; the second seed layer comprises a stacked titanium layer and a copper layer;

[0042] forming a plurality of second metal layers arranged at intervals on a surface of the second seed layer facing away from the second wafer;

[0043] After the step of forming a second passivation layer on a surface of the second metal layer facing away from the second wafer, the step further includes:

[0044] The second seed layer at a side portion of the second metal layer is removed.

[0045] The preparation method of the hybrid bonding structure provided by the present invention can improve the bonding strength between the first metal layer and the first wafer by forming a first seed layer, and the bonding strength between the first titanium layer in the first seed layer and the first wafer is strong, and the bonding strength between the copper layer and the metal layer is strong, while the copper layer in the first seed layer also becomes a part of the first metal layer, further improving the bonding strength between the first metal layer and the first wafer; and / or can improve the bonding strength between the second metal layer and the second wafer by forming a second seed layer, and the bonding strength between the second titanium layer in the second seed layer and the second wafer is strong, and the bonding strength between the copper layer and the metal layer is strong, while the bonding strength between the second metal layer and the second wafer is improved, while the copper layer in the second seed layer also becomes a part of the second metal layer, further improving the bonding strength between the second metal layer and the second wafer.

[0046] In a second aspect, the present invention provides a hybrid bonding structure, the hybrid bonding structure comprising:

[0047] First Wafer;

[0048] A plurality of first metal layers arranged at intervals are located on a surface of one side of the first wafer;

[0049] A first passivation layer is located on a surface of the first metal layer facing away from the first wafer; the material of the first passivation layer is a polycrystalline structure;

[0050] The second passivation layer is located on a surface of the first passivation layer facing away from the first metal layer; the first passivation layer and the second passivation layer are in contact with each other and bonded together; the material of the second passivation layer is a polycrystalline structure;

[0051] A plurality of second metal layers arranged at intervals are located on a surface of the second passivation layer facing away from the first passivation layer; the first metal layer and the second metal layer are bonded and connected to form an integral structure through the first passivation layer and the second passivation layer;

[0052] A second wafer; located on a surface of the second metal layer facing away from the first metal layer;

[0053] The polymer layer is located on the second wafer surface on the side of the second metal layer; the thickness of the polymer layer is equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer; the first wafer surface on the side of the first metal layer is in contact with the polymer layer and bonded together.

[0054] The hybrid bonding structure provided by the present invention, on the one hand, by setting a polymer layer on the surface of the second wafer on the side of the second metal layer, the thickness of the polymer layer is equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer, which can effectively prevent the generation of bonding voids in the hybrid bonding structure, reduce the risk of particles and scratches on the polymer layer, and increase the effective bonding area, thereby improving the hybrid bonding interface strength and the hybrid bonding yield; on the other hand, by setting the first passivation layer and the second passivation layer, the surface oxidation of the first metal layer and the second metal layer can be suppressed, the bonding temperature of the metal bonding interface can be reduced, and low-temperature bonding of the first metal layer and the second metal layer can be achieved, thereby improving the hybrid bonding interface strength and the hybrid bonding yield, and improving the reliability and stability of the hybrid bonding structure.

[0055] In an optional embodiment, the hybrid bonding structure further includes:

[0056] A first titanium layer is located on a surface of the first metal layer facing the first wafer;

[0057] The second titanium layer is located on a surface of the second metal layer facing the second wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related technologies, the drawings required for use in the specific embodiments or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0059] Figure 1A , Figure 1B and Figure 1C It is a structural schematic diagram of a method for preparing a bonding structure in the related art.

[0060] Figure 2 It is a schematic flow chart of a method for preparing a hybrid bonding structure according to an embodiment of the present invention.

[0061] Figure 3 It is a structural schematic diagram of forming a first seed layer on one side surface of a first wafer in a method for preparing a hybrid bonding structure according to an embodiment of the present invention.

[0062] Figure 4 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Figure 3 Schematic diagram of the structure of a patterned photoresist layer formed on the basis.

[0063] Figure 5 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Figure 4 A schematic diagram of a structure in which a first metal layer and a first passivation layer are formed on the basis.

[0064] Figure 6 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Figure 5 A schematic structural diagram of removing the photoresist layer and the first passivation layer on the side of the first metal layer.

[0065] Figure 7 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Figure 6 Schematic diagram of the structure of the first seed layer on the side of the first metal layer removed.

[0066] Figure 8 It is a structural schematic diagram of forming a second seed layer, a second metal layer, and a second passivation layer on a first wafer surface in a method for preparing a hybrid bonding structure according to an embodiment of the present invention.

[0067] Fig. 9 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Figure 8 Schematic diagram of the structure of the second seed layer on the side of the second metal layer removed.

[0068] Fig.10 and Fig.11 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Fig. 9 Schematic diagram of the structure of the polymer layer formed on the basis.

[0069] Fig.12 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Figure 7 and Fig.11 A schematic diagram of a structure in which a first wafer and a second wafer are thermally pressed and bonded together.

[0070] Fig.13 In a method for preparing a hybrid bonding structure according to an embodiment of the present invention, Fig.12 A schematic diagram of a structure in which a first wafer and a second wafer are thermally pressed and bonded together.

[0071] Fig.14 It is a specific schematic diagram of a method for preparing a hybrid bonding structure according to an embodiment of the present invention.

[0072] Fig.15 is a structural schematic diagram of a hybrid bonding structure according to an embodiment of the present invention.

[0073] Reference numerals:

[0074] 1. Wafer; 2. Metal layer; 3. Polymer; 11. First wafer; 12. First metal layer; 13. First passivation layer; 14. First seed layer; 141. First titanium layer; 142. Copper layer; 15. Photoresist layer; 21. Second wafer; 22. Second metal layer; 23. Second passivation layer; 24. Second seed layer; 241. Second titanium layer; 242. Copper layer; 30. Polymer layer. DETAILED DESCRIPTION

[0075] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0076] In the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. Various structural schematic diagrams according to embodiments of the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified for the purpose of clear expression, and some details may be omitted. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships between them are only exemplary, and may be deviated due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs. In the context of the present invention, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be a middle layer / element between them. In addition, if a layer / element is "on" another layer / element in one orientation, then when the orientation is reversed, the layer / element may be "under" the other layer / element.

[0077] 3D interconnect technology is used to electrically interconnect two or more chips to achieve high-bandwidth and high-density signal transmission. As the interconnect pitch and gap become smaller, hybrid bonding technology has attracted attention due to its advantages of high interconnect density, and has relevant applications in CMOS (complementary metal oxide semiconductor) image sensors and 3D NAND (3D flash memory) products. Hybrid bonding mainly includes metal / SiO2, metal / SiN, metal / SiCN, metal / polymer and other structures, and Cu is often used as the interconnect metal. However, the hybrid bonding structure of Cu and rigid medium (SiO2, SiN, SiCN) has extremely high requirements for surface flatness, cleanliness, and roughness, and poor interface bonding is prone to occur. In the Cu / polymer hybrid bonding method, the use of polymers instead of rigid media can reduce the extremely high standards for the bonding surface. The deformation of the polymer interface during the bonding process is conducive to increasing the effective bonding area, and the polymer has a higher tolerance for particles.

[0078] Currently, there are two technical routes for Cu / polymer hybrid bonding: ① Cu interface bonding is performed first and then polymer interface bonding. This scheme usually performs plasma activation on the copper interface to remove the oxide layer before bonding, but there is a risk of introducing particles, increasing the roughness of the metal bonding interface and changing the properties of the polymer; ② Polymer interface bonding is performed first and then Cu interface bonding, but slip may occur during polymer bonding, affecting the alignment accuracy of the Cu interface bonding.

[0079] In addition, existing Cu / polymer hybrid bonding methods such as Figure 1A to Figure 1C As shown in FIG. 1 , the hybrid bonding structure is formed by bonding two identical parts, and after forming metal layers 2 and polymer 3 of the same height on the surfaces of the upper and lower wafers 1, the two wafers 1 are bonded together. Since this method requires the metal layer 2 (Cu layer) on the surface of the wafer 1 to be at the same height as the polymer 3, the polymer 3 must be planarized by CMP or fly cutting before bonding. Figure 1A and Figure 1B , while CMP and fly cutting will produce scratches on the polymer surface4, which can easily cause bonding voids5 in the subsequent hybrid bonding process, such as Figure 1C As shown. And because the polymer is only partially solidified before bonding, it has limited support for the metal layer, and the planarization process may cause the bottom metal layer to break. Because the polymer and the Cu layer are at the same height, there is a risk of polymer entering the metal bonding interface and causing interconnect failure when the two wafers are aligned and bonded.

[0080] like Figure 2 As shown, this embodiment provides a method for preparing a hybrid bonding structure, which includes but is not limited to steps S101 to S108.

[0081] Step S101, providing a first wafer 11;

[0082] Step S102, forming a plurality of first metal layers 12 arranged at intervals on a surface of one side of the first wafer 11, such as Figure 7 As shown;

[0083] Step S103, forming a first passivation layer 13 on a surface of the first metal layer 12 facing away from the first wafer 11, such as Figure 7 As shown; the material of the first passivation layer 13 is a polycrystalline structure;

[0084] Step S104, providing a second wafer 21;

[0085] Step S105, forming a plurality of second metal layers 22 arranged at intervals on one side surface of the second wafer 21;

[0086] Step S106, forming a second passivation layer 23 on a surface of the second metal layer 22 facing away from the second wafer 21, such as Fig. 9 As shown; the material of the second passivation layer 23 is a polycrystalline structure;

[0087] Step S107, forming a polymer layer 30 on the surface of the second wafer 21 at the side of the second metal layer 22; the thickness of the polymer layer 30 is greater than or equal to the total thickness of the first metal layer 12, the first passivation layer 13, the second passivation layer 23 and the second metal layer 22, such as Fig.11 As shown;

[0088] In a specific implementation, the thickness of the first passivation layer 13 and the second passivation layer 23 is very small, and the influence on the total thickness is small.

[0089] Step S108, hot-press bonding the first wafer 11 and the second wafer 21 together to form a hybrid bonding structure; the first metal layer 12 and the second metal layer 22 are bonded to form an integral structure through the first passivation layer 13 and the second passivation layer 23; the first passivation layer 13 and the second passivation layer 23 are in corresponding contact and bonded together; the surface of the first wafer 11 on the side of the first metal layer 12 is in corresponding contact and bonded together with the polymer layer 30.

[0090] In specific implementation, the first passivation layer / second passivation layer can inhibit the oxidation of the first metal layer / second metal layer and help reduce the bonding temperature. Since the materials of the first passivation layer and the second passivation layer are polycrystalline structures, the atoms in the first metal layer / second metal layer can quickly diffuse to the bonding surface through the grain boundary of the first passivation layer / second passivation layer during bonding, so a very high temperature is not required to achieve the bonding of the first metal layer and the second metal layer. In the absence of a passivation layer, the atoms in the first metal layer / second metal layer can only diffuse through the lattice, and the diffusion speed is slow, requiring a higher temperature to complete the bonding of the first metal layer and the second metal layer.

[0091] The preparation method of the hybrid bonding structure provided in this embodiment, on the one hand, forms a polymer layer on the surface of the second wafer on the side of the second metal layer, and the thickness of the polymer layer is greater than or equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer, so that when the first wafer and the second wafer are hot-pressed bonded, the surface of the first wafer on the side of the first metal layer and the polymer layer are in corresponding contact and bonded together, and there is no need to perform a flattening process on the polymer layer, which can effectively prevent the generation of bonding voids in the hybrid bonding structure, reduce the risk of introducing particles in the flattening process, and make the polymer layer scratch-free. It can also increase the effective bonding area and reduce the risk of slippage in the bonding process, thereby improving the hybrid bonding interface strength and hybrid bonding yield; on the other hand, by forming the first passivation layer and the second passivation layer of the polycrystalline structure, the surface oxidation of the first metal layer and the second metal layer can be suppressed, the bonding temperature of the metal bonding interface can be reduced, and the first metal layer and the second metal layer can be preferentially bonded at low temperature, thereby improving the bonding alignment accuracy of the metal layer interface, improving the hybrid bonding interface strength and hybrid bonding yield, and improving the reliability and stability of the hybrid bonding structure. Therefore, the preparation method of the hybrid bonding structure provided in this embodiment can prevent the generation of bonding voids in the hybrid bonding structure, realize low-temperature bonding of the first metal layer and the second metal layer, improve the hybrid bonding interface strength and hybrid bonding yield, and improve the reliability and stability of the hybrid bonding structure.

[0092] In some optional embodiments, the step of thermocompression bonding the first wafer 11 and the second wafer 21 together to form a hybrid bonding structure includes:

[0093] At a first temperature and a first pressure, the first wafer 11 and the second wafer 21 are thermally pressed and bonded together, and the first passivation layer 13 and the second passivation layer 23 are contacted and bonded together accordingly. Fig.12 As shown;

[0094] At the second temperature and the second pressure, the first wafer surface at the side of the first metal layer 12 is in contact with the polymer layer and bonded together. Fig.13 As shown; the second temperature is greater than the first temperature.

[0095] The preparation method of the hybrid bonding structure provided in the present embodiment is to hot-press bond the first wafer and the second wafer together. First, the heat and pressure are maintained at a first temperature and a first pressure. Due to the presence of the passivation layer, the metal layers can be melt-bonded into one at a lower first temperature. Bonding the first metal layer to the second metal layer first can improve the alignment accuracy of the metal layers, thereby improving the strength and stability of the metal bonding interface. Secondly, at the second temperature and the second pressure, the surface of the first wafer on the side of the first metal layer is in contact with the polymer layer and bonded together. The second temperature is greater than the first temperature. The bonding and curing of the polymer layer are achieved at the higher second temperature, thereby further improving the stability and reliability of the hybrid bonding structure.

[0096] In some optional embodiments, at the first temperature and the first pressure, the step of contacting and bonding the first passivation layer and the second passivation layer together correspondingly further includes:

[0097] At the first temperature and the first pressure, the first metal layer and the second metal layer are bonded and connected to form an integrated structure through the first passivation layer and the second passivation layer.

[0098] In some optional embodiments, such as Figure 11 to Figure 13 As shown, there is a gap between the polymer layer 30 and the first metal layer 12, and between the polymer layer 30 and the second metal layer 22; the thickness of the polymer layer 30 is greater than the total thickness of the first metal layer 12, the first passivation layer 13, the second passivation layer 23 and the second metal layer 22;

[0099] The step of contacting and bonding the surface of the first wafer 11 on the side of the first metal layer 12 with the polymer layer 30 at the second temperature and the second pressure, further includes:

[0100] At the second temperature and the second pressure, the first metal layer 12 and the second metal layer 22 expand to fill the gap; the polymer layer 30 deforms to completely fill the gap and solidifies. Fig.13 shown.

[0101] The preparation method of the hybrid bonding structure provided in the present embodiment has gaps between the polymer layer and the first metal layer, and between the polymer layer and the second metal layer. At a second temperature with a higher temperature, the first metal layer and the second metal layer release stress in the horizontal direction and expand slightly to fill the gap. At the same time, the polymer is deformed under pressure to completely fill the gap and solidify during the heating process. The present method can form a gap to leave space for the expansion of the first metal layer and the second metal layer in the horizontal direction, avoid the situation where the first metal layer and the second metal layer are broken due to excessive stress in the vertical direction, improve the strength and stability of the metal bonding interface, and thus improve the electrical interconnection reliability and mechanical reliability of the hybrid bonding structure; by setting the thickness of the polymer layer to be greater than the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer, the excess polymer layer can be used to completely fill the gap, prevent the generation of bonding voids in the hybrid bonding structure, improve the hybrid bonding interface strength and hybrid bonding yield, and improve the reliability and stability of the hybrid bonding structure.

[0102] In some optional embodiments, the width of the gap is 500 nm to 1000 nm.

[0103] In some optional embodiments, the first temperature is 150°C to 180°C;

[0104] The second temperature is 250°C to 300°C.

[0105] In some optional embodiments, the material of the polymer layer 30 is a photosensitive polymer;

[0106] The materials of the first metal layer 12 and the second metal layer 22 are copper;

[0107] The materials of the first passivation layer 13 and the second passivation layer 23 are polycrystalline Pd or Au;

[0108] The thickness of the first passivation layer 13 and the thickness of the second passivation layer 23 are less than or equal to 10 nm.

[0109] In a specific implementation, the material of the first metal layer 12 and the second metal layer 22 is copper. In one example, the first metal layer 12 and the second metal layer 22 are copper pillars.

[0110] The photosensitive polymer is a thermosetting photoresist polymer, such as a polyimide material. The function of the photosensitive polymer is to provide mechanical support for the copper pillars and to electrically insulate adjacent copper pillars. The photoresist polymer is cured by heat, and for example, a benzocyclobutene resin (BCB) material, a photosensitive polyimide material, or a photosensitive dry film material can be selected.

[0111] In some optional embodiments, the material of the first wafer and the second wafer is silicon or silicon carbide.

[0112] In some optional embodiments, the step of forming a plurality of first metal layers 12 arranged at intervals on a surface of one side of the first wafer 11 includes:

[0113] A first seed layer 14 is formed on one side of the first wafer 11; the first seed layer includes a stacked first titanium layer 141 and a copper layer 142, such as Figure 3 As shown;

[0114] A plurality of first metal layers 12 are formed on a surface of the first seed layer 14 facing away from the first wafer 11. Figure 6 As shown;

[0115] After the step of forming the first passivation layer 13 on the surface of the first metal layer 12 facing away from the first wafer 11, the following step is further included:

[0116] The first seed layer 14 on the side of the first metal layer 12 is removed. Figure 7 As shown;

[0117] and / or:

[0118] The step of forming a plurality of second metal layers arranged at intervals on one side surface of the second wafer 21 includes:

[0119] A second seed layer 24 is formed on one side surface of the second wafer 21; the second seed layer 24 includes a stacked second titanium layer 241 and a copper layer 242;

[0120] A plurality of second metal layers 22 arranged at intervals are formed on a surface of the second seed layer 24 facing away from the second wafer 21;

[0121] After the step of forming the second passivation layer 23 on the surface of the second metal layer 22 facing away from the second wafer 21, the following step is further included:

[0122] The second seed layer 24 at the side of the second metal layer 22 is removed.

[0123] In a specific implementation, the materials of the first metal layer 12 and the second metal layer 22 are both copper; the copper layer 142 corresponding to the position of the first metal layer 12 becomes a part of the first metal layer 12, that is, the first metal layer 12 and the copper layer 142 in contact with it are bonded to form an integral copper layer; the copper layer 242 corresponding to the position of the second metal layer 22 becomes a part of the second metal layer 22, that is, the second metal layer 22 and the copper layer 242 in contact with it are bonded to form an integral copper layer. The thickness of the copper layer 142 and the copper layer 242 is less than 500nm.

[0124] The preparation method of the hybrid bonding structure provided in the present embodiment forms a first seed layer, and the bonding force between the first titanium layer in the first seed layer and the first wafer is strong, and the bonding force between the copper layer and the metal layer is strong, so the bonding strength between the first metal layer and the first wafer can be improved, and at the same time, the copper layer in the first seed layer also becomes a part of the first metal layer, further improving the bonding strength between the first metal layer and the first wafer; and / or forms a second seed layer, and the bonding force between the second titanium layer in the second seed layer and the second wafer is strong, and the bonding force between the copper layer and the metal layer is strong, so the bonding strength between the second metal layer and the second wafer can be improved, and at the same time, the copper layer in the second seed layer also becomes a part of the second metal layer, further improving the bonding strength between the second metal layer and the second wafer.

[0125] In some optional embodiments, a specific method for forming a plurality of first metal layers 12 and first passivation layers 13 arranged at intervals on a surface of the first seed layer 14 facing away from the first wafer 11 is as follows:

[0126] A patterned photoresist layer 15 is formed on a surface of the first seed layer 14 facing away from the first wafer 11; the side of the photoresist layer 15 exposes the surface of the first seed layer 14, such as Figure 4 As shown;

[0127] Forming a plurality of first metal layers 12 arranged at intervals on the exposed surface of the first seed layer 14;

[0128] A first passivation layer 13 is formed on a surface of the photoresist layer 15 facing away from the first wafer 11 and a surface of the first metal layer 12 facing away from the first wafer 11. Figure 5 As shown;

[0129] The first passivation layer 13 and the photoresist layer 15 on the side of the first metal layer 12 are removed, and the first passivation layer 13 on the surface of the first metal layer 12 is retained. Figure 6 As shown;

[0130] The first seed layer 14 on the side of the first metal layer 12 is removed. Figure 7 shown.

[0131] During specific implementation, the specific formation method of the second metal layer 22 and the second passivation layer 23 is the same as the steps of forming the first metal layer 12 and the first passivation layer 13 .

[0132] like Fig.14 The present invention also provides a specific flow chart of a method for preparing a hybrid bonding structure, comprising the following steps:

[0133] Step S201 , providing a first wafer 11 .

[0134] Step S202, forming a first seed layer 14 on one side of the first wafer 11; the first seed layer includes a stacked first titanium layer 141 and a copper layer 142, such as Figure 3 shown.

[0135] Step S203, forming a patterned photoresist layer 15 on a surface of the first seed layer 14 facing away from the first wafer 11; the side of the photoresist layer 15 exposes the surface of the first seed layer 14, such as Figure 4 shown.

[0136] Step S204 , forming a plurality of first metal layers 12 arranged at intervals on the exposed surface of the first seed layer 14 .

[0137] Step S205, forming a first passivation layer 13 on a surface of the photoresist layer 15 facing away from the first wafer 11 and a surface of the first metal layer 12 facing away from the first wafer 11, such as Figure 5 shown.

[0138] Step S206, removing the first passivation layer 13 and the photoresist layer 15 on the side of the first metal layer 12, and retaining the first passivation layer 13 on the surface of the first metal layer 12, such as Figure 6 shown.

[0139] Step S207, removing the first seed layer 14 on the side of the first metal layer 12, such as Figure 7 shown.

[0140] In specific implementation, the specific process of preparing the first wafer in steps S202 to S207 is as follows: first, sputter the first titanium layer and the copper layer on the surface of the first wafer in sequence; second, apply photoresist on the copper layer, and expose and develop to form a patterned photoresist layer; third, electroplate the exposed copper layer surface to obtain the first metal layer, and treat the first metal layer with dilute sulfuric acid after electroplating; then, sputter the first passivation layer with a thickness not exceeding 10nm on the surface of the photoresist layer and the surface of the first metal layer; finally, remove the first passivation layer and the photoresist layer on the side of the first metal layer by lift-off process, ashing treatment, and wet etching to remove the first titanium layer and the copper layer on the side of the first metal layer. Among them, the material of the first metal layer is copper, the material of the first passivation layer is Pd or Au of polycrystalline structure, the material of the first wafer is silicon, and the thickness of the first passivation layer is less than 10nm.

[0141] Step S208 , providing a second wafer 21 .

[0142] Step S209, forming a second seed layer 24, a plurality of second metal layers 22 arranged at intervals, and a second passivation layer 23 on a surface of one side of the second wafer 21 in sequence according to the same steps as steps S102 to S207. Figure 8 and Fig. 9 shown.

[0143] In specific implementation, the specific process of preparing the second wafer in step S209 is as follows: first, sputter the second titanium layer and the copper layer on the surface of the second wafer in sequence; second, apply photoresist on the copper layer, and expose and develop to form a patterned photoresist layer; third, electroplate the exposed copper layer surface to obtain the second metal layer, and treat the second metal layer with dilute sulfuric acid after electroplating; then, sputter the second passivation layer with a thickness not exceeding 10nm on the surface of the photoresist layer and the surface of the second metal layer; finally, remove the second passivation layer and the photoresist layer on the side of the second metal layer by lift-off process, ashing treatment, and wet etching to remove the second titanium layer and the copper layer on the side of the second metal layer. Among them, the material of the second metal layer is copper, the material of the second passivation layer is polycrystalline Pd or Au, the material of the second wafer is silicon, and the thickness of the second passivation layer is less than 10nm.

[0144] After this step, the width / diameter of the second metal layer on the second wafer is the same as the width / diameter of the first metal layer on the first wafer; the width / diameter of the second passivation layer is the same as the width / diameter of the first passivation layer.

[0145] Step S210, forming a polymer layer 30 on the surface of the second wafer 21 at the side of the second metal layer 22; the thickness of the polymer layer 30 is greater than the total thickness of the first metal layer 12, the first passivation layer 13, the second passivation layer 23 and the second metal layer 22; there is a gap between the polymer layer 30 and the first metal layer 12, such as Fig.10 and Fig.11 shown.

[0146] In specific implementation, a layer of thermosetting photosensitive polymer (preferably a polymer with low curing temperature and short curing time) is obtained by spin coating or lamination on the surface of the second wafer 21 on the side of the second metal layer 22, and the thickness of the polymer layer 30 is greater than the total thickness of the first metal layer 12, the first passivation layer 13, the second passivation layer 23 and the second metal layer 22. 4) A window is opened at the corresponding position of the second metal layer, the opening width is greater than the width / diameter of the second metal layer, and the exposure, development and pre-curing are performed so that there is a gap between the polymer layer 30 and the first metal layer 12. The specific thickness ratio of the polymer layer and the second metal layer and the opening size are optimized according to the process parameters.

[0147] Step S211, at a first temperature and a first pressure, the first passivation layer 13 and the second passivation layer 23 are in contact with each other and bonded together; the first metal layer 12 and the second metal layer 22 are bonded to form an integral structure through the first passivation layer 13 and the second passivation layer 23; there is a gap between the polymer layer 30 and the first metal layer 12, and between the polymer layer 30 and the second metal layer 22, such as Fig.12 shown.

[0148] In specific implementation, the first wafer and the second wafer are aligned up and down and then hot-pressed and bonded together. In the initial stage of bonding, the first temperature and the first pressure are kept warm and pressed for a short time at a low temperature. Due to the presence of the first passivation layer and the second passivation layer, the first metal layer and the second metal layer can be melt-bonded and combined into one at a low temperature, and the polymer layer initially fills a part of the gap. In order to avoid the risk of electrical interconnection failure caused by the polymer layer squeezing into the metal bonding surface due to deformation, the pre-curing parameters before bonding are appropriately adjusted to change the plasticity of the polymer, and the optimized bonding parameters are used to achieve no polymer squeezing into the metal bonding layer when the metal layer contacts.

[0149] Step S212, at a second temperature and a second pressure, the surface of the first wafer 11 on the side of the first metal layer 12 is in contact with the polymer layer 30 and bonded together; the second temperature is greater than the first temperature; the first metal layer 12 and the second metal layer 22 expand to fill the gap; the polymer layer 30 deforms to completely fill the gap and solidifies, such as Fig.13 shown.

[0150] In specific implementation, the temperature is raised to the polymer curing temperature. At the second temperature and the second pressure, due to the high temperature and vertical force, the first metal layer / the second metal layer releases stress in the horizontal direction and expands slightly. The polymer layer is deformed under pressure to completely fill the gap and solidifies during the heating process. Finally, the polymer layer tightly wraps the metal layer, and the polymer layer and the silicon interface on the surface of the first wafer are bonded.

[0151] like Fig.15 As shown, this embodiment provides a hybrid bonding structure, and the hybrid bonding structure includes:

[0152] A first wafer 11;

[0153] A plurality of first metal layers 12 arranged at intervals are located on one side surface of the first wafer 11;

[0154] The first passivation layer 13 is located on a surface of the first metal layer 12 facing away from the first wafer 11; the material of the first passivation layer 13 is a polycrystalline structure;

[0155] The second passivation layer 23 is located on a surface of the first passivation layer 13 facing away from the first metal layer 12; the first passivation layer 13 and the second passivation layer 23 are in contact with each other and bonded together; the material of the second passivation layer 23 is a polycrystalline structure;

[0156] A plurality of second metal layers 22 arranged at intervals are located on a surface of the second passivation layer 23 facing away from the first passivation layer 13; the first metal layer 12 and the second metal layer 22 are bonded and connected to form an integral structure through the first passivation layer 13 and the second passivation layer 23;

[0157] The second wafer 21 is located on a surface of the second metal layer 22 facing away from the first metal layer 12;

[0158] The polymer layer 30 is located on the surface of the second wafer 21 on the side of the second metal layer 22; the thickness of the polymer layer 30 is equal to the total thickness of the first metal layer 12, the first passivation layer 13, the second passivation layer 23 and the second metal layer 22; the surface of the first wafer 11 on the side of the first metal layer 12 is in contact with the polymer layer 30 and bonded together.

[0159] The hybrid bonding structure provided in this embodiment, on the one hand, by setting a polymer layer on the surface of the second wafer on the side of the second metal layer, the thickness of the polymer layer is equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer, which can effectively prevent the generation of bonding voids in the hybrid bonding structure, reduce the risk of particles and scratches on the polymer layer, and increase the effective bonding area, thereby improving the hybrid bonding interface strength and hybrid bonding yield; on the other hand, by setting the first passivation layer and the second passivation layer, the surface oxidation of the first metal layer and the second metal layer can be suppressed, the bonding temperature of the metal bonding interface can be reduced, and low-temperature bonding of the first metal layer and the second metal layer can be achieved, thereby improving the hybrid bonding interface strength and hybrid bonding yield, and improving the reliability and stability of the hybrid bonding structure.

[0160] In some optional embodiments, the hybrid bonding structure further comprises:

[0161] The first titanium layer 141 is located on a surface of the first metal layer 12 facing the first wafer 11;

[0162] The second titanium layer 241 is located on a surface of the second metal layer 22 facing the second wafer 21 .

[0163] In the description of this specification, the description with reference to the terms "this embodiment", "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless otherwise clearly and specifically defined. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0164] In the above description, the technical details of the patterning and etching of each layer are not described in detail. However, those skilled in the art should understand that various technical means can be used to form layers, regions, etc. of desired shapes. In addition, in order to form the same structure, those skilled in the art can also design methods that are not completely the same as the methods described above. In addition, although the various embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage.

[0165] The above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described above, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the concept of the present invention. The scope of protection of the present invention is determined by the scope of the attached claims.

Claims

1. A method for preparing a hybrid bonding structure, characterized in that: include: providing a first wafer; Forming a plurality of first metal layers arranged at intervals on a surface of one side of the first wafer; forming a first passivation layer on a surface of the first metal layer facing away from the first wafer; The material of the first passivation layer is a polycrystalline structure; providing a second wafer; Forming a plurality of second metal layers arranged at intervals on a surface of one side of the second wafer; forming a second passivation layer on a surface of the second metal layer facing away from the second wafer; the material of the second passivation layer is a polycrystalline structure; forming a polymer layer on the surface of the second wafer at a side of the second metal layer; The thickness of the polymer layer is greater than or equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer; The first wafer and the second wafer are hot-pressed and bonded together to form a hybrid bonding structure; the first metal layer and the second metal layer are bonded into an integrated structure through the first passivation layer and the second passivation layer; the first passivation layer and the second passivation layer are in corresponding contact and bonded together; the surface of the first wafer on the side of the first metal layer is in corresponding contact and bonded together with the polymer layer.

2. The method for preparing a hybrid bonding structure according to claim 1, characterized in that: The step of thermocompression bonding the first wafer and the second wafer together to form a hybrid bonding structure includes: Thermally pressing and bonding the first wafer and the second wafer at a first temperature and a first pressure, so that the first passivation layer and the second passivation layer are in contact with each other and bonded together; At a second temperature and a second pressure, the first wafer surface at a side of the first metal layer is in corresponding contact with the polymer layer and bonded together; The second temperature is greater than the first temperature.

3. The method for preparing a hybrid bonding structure according to claim 2, characterized in that: The step of contacting and bonding the first passivation layer and the second passivation layer together at the first temperature and the first pressure also includes: At the first temperature and the first pressure, the first metal layer and the second metal layer are bonded and connected to form an integral structure through the first passivation layer and the second passivation layer.

4. The method for preparing a hybrid bonding structure according to claim 2, characterized in that: There is a gap between the polymer layer and the first metal layer, and between the polymer layer and the second metal layer; the thickness of the polymer layer is greater than the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer; The step of contacting and bonding the first wafer surface on the side of the first metal layer with the polymer layer at the second temperature and the second pressure, further includes: At the second temperature and the second pressure, the first metal layer and the second metal layer expand to fill the gap; The polymer layer deforms to completely fill the gap and solidifies.

5. The method for preparing a hybrid bonding structure according to claim 4, characterized in that: The width of the gap is 500nm-1000nm.

6. The method for preparing a hybrid bonding structure according to claim 2, characterized in that: The first temperature is 150°C to 180°C; The second temperature is 250°C to 300°C.

7. The method for preparing a hybrid bonding structure according to claim 1, characterized in that: The material of the polymer layer is a photosensitive polymer; The materials of the first metal layer and the second metal layer are copper; The material of the first passivation layer and the second passivation layer is Pd or Au with a polycrystalline structure; The thickness of the first passivation layer and the thickness of the second passivation layer are less than or equal to 10 nm.

8. The method for preparing a hybrid bonding structure according to claim 1, characterized in that: The step of forming a plurality of first metal layers arranged at intervals on a surface of one side of the first wafer includes: Forming a first seed layer on a surface of one side of the first wafer; the first seed layer comprises a stacked titanium layer and a copper layer; Forming a plurality of first metal layers arranged at intervals on a surface of the first seed layer facing away from the first wafer; After the step of forming a first passivation layer on a surface of the first metal layer facing away from the first wafer, the method further includes: removing the first seed layer at a side of the first metal layer; and / or: The step of forming a plurality of second metal layers arranged at intervals on a surface of one side of the second wafer comprises: forming a second seed layer on a surface of one side of the second wafer; the second seed layer comprises a stacked titanium layer and a copper layer; forming a plurality of second metal layers arranged at intervals on a surface of the second seed layer facing away from the second wafer; After the step of forming a second passivation layer on a surface of the second metal layer facing away from the second wafer, the method further includes: The second seed layer at a side portion of the second metal layer is removed.

9. A hybrid bonding structure, characterized in that: include: First Wafer; A plurality of first metal layers arranged at intervals and located on a surface of one side of the first wafer; A first passivation layer is located on a surface of the first metal layer facing away from the first wafer; The material of the first passivation layer is a polycrystalline structure; A second passivation layer is located on a surface of the first passivation layer facing away from the first metal layer; The first passivation layer and the second passivation layer are in contact with each other and bonded together; The material of the second passivation layer is a polycrystalline structure; A plurality of second metal layers arranged at intervals and located on a surface of the second passivation layer facing away from the first passivation layer; The first metal layer and the second metal layer are bonded and connected into an integral structure through the first passivation layer and the second passivation layer; The second wafer; Located on a surface of the second metal layer facing away from the first metal layer; a polymer layer located on the second wafer surface at a side of the second metal layer; The thickness of the polymer layer is equal to the total thickness of the first metal layer, the first passivation layer, the second passivation layer and the second metal layer; the first wafer surface on the side of the first metal layer is in corresponding contact with the polymer layer and bonded together.

10. The hybrid bonding structure according to claim 9, characterized in that: The hybrid bonding structure further comprises: A first titanium layer is located on a surface of the first metal layer facing the first wafer; The second titanium layer is located on a surface of the second metal layer facing the second wafer.

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