Grinding method for mixed bonding metal wiring layer

Abstract

The invention relates to a grinding method for a mixed bonding metal wiring layer. The grinding method comprises the following steps: carrying out a first grinding process on a copper layer by using a first grinding disc and a first grinding pad, and removing the copper layer on one side, back to a wafer, of a dielectric layer until a barrier layer is exposed; performing a second grinding process on the dielectric layer and the barrier layer by using a second grinding disc and a second grinding pad, removing the barrier layer on one side of the dielectric layer back to the wafer, and removing a part of the dielectric layer; performing a third grinding process on the copper layer by using a third grinding disc and a third grinding pad, so that the thickness of the copper layer is lower than that of the dielectric layer; the shore hardness of the first grinding pad and the shore hardness of the third grinding pad are 60-80, and the shore hardness of the second grinding pad is 20-30. According to the grinding method of the metal wiring layer for hybrid bonding, the recess of the copper layer can be controlled and reduced, and the surface roughness of the dielectric layer and the copper layer is reduced, so that the bonding force between the metal wiring layers during hybrid bonding is improved, and the grinding process is simplified.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a grinding method for a metal wiring layer used for hybrid bonding. Background Art

[0002] Hybrid bonding is an advanced integrated circuit packaging technology, mainly used to achieve high-density, high-performance interconnection between different chips. Its main feature is to replace traditional bumps or solder balls with direct Cu-Cu bonding, which can achieve ultra-fine pitch stacking and packaging in a very small space. In order to ensure a good connection effect, special treatment and processing are required on the chip surface to form a metal wiring layer to achieve the final smooth bonding. The copper-copper hybrid bonding technology is to form a metal wiring layer on each of the two wafers to be bonded together, and the metal wiring layer includes copper and dielectric layers.

[0003] At present, the industry uses chemical mechanical polishing (CMP) to form the metal wiring layer of copper-copper hybrid bonding. Generally, a three-disk polishing process is used to achieve Cu removal and control of the concave copper layer (Cu dishing) and surface roughness (Ra) to form the metal wiring layer. The specific process is to first polish the Cu material through two polishing disks P1 and P2, and then polish the polishing disk P3 with a barrier layer polishing liquid by setting a fixed time to control the CMP of the barrier layer and part of the dielectric layer. Such a process requires P1 and P2 to set different Cu grinding rates respectively, and the endpoint control on P1 requires the use of a large number of Cu monitor wafers (monitor wafers) for setting, which increases the process cost; at the same time, the P3 process does not accurately control the thickness of the barrier layer and the dielectric layer, which may increase the concave of the copper layer, resulting in greater roughness of the copper layer and the dielectric layer, thereby reducing the bonding force between the metal wiring layers during hybrid bonding.

[0004] Therefore, a grinding method for a metal wiring layer for hybrid bonding is needed, which can control and reduce the depression of the copper layer, reduce the surface roughness of the dielectric layer and the copper layer, simplify the grinding process, and reduce the process cost. Summary of the invention

[0005] Therefore, the present invention provides a grinding method for a metal wiring layer for hybrid bonding, so as to solve the problem in the prior art that the grinding process of the copper layer is complex, the process cost is high, the thickness control of the barrier layer and the dielectric layer is not precise enough, resulting in large depressions in the copper layer of the metal wiring layer, large roughness of the copper layer and the dielectric layer, and further resulting in low bonding force between the metal wiring layers during hybrid bonding.

[0006] The present invention provides a grinding method for a metal wiring layer for hybrid bonding, comprising:

[0007] Providing a wafer to be ground; one side of the wafer includes a metal wiring layer to be ground, the metal wiring layer includes a copper layer, a barrier layer, and a dielectric layer, the copper layer covers the barrier layer and the dielectric layer, and the barrier layer is located between the copper layer and the dielectric layer;

[0008] Performing a first grinding process on the copper layer using a first grinding disc and a first grinding pad to remove the copper layer on the side of the dielectric layer facing away from the wafer until the barrier layer is exposed; the Shore hardness of the first grinding pad is 60 to 80;

[0009] Performing a second grinding process on the dielectric layer and the barrier layer using a second grinding disc and a second grinding pad to remove the barrier layer on the side of the dielectric layer facing away from the wafer and to remove part of the dielectric layer; the Shore hardness of the second grinding pad is 20 to 30;

[0010] The copper layer is subjected to a third grinding process by using a third grinding disc and a third grinding pad, so that the thickness of the copper layer is lower than the thickness of the dielectric layer; the Shore hardness of the third grinding pad is 60-80.

[0011] Optionally, the first grinding process is over-grinding, and the stop layer of the first grinding process is a barrier layer; the polishing liquid in the first grinding process is a Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min to 9000A / min.

[0012] In the first grinding process, after the copper layer is ground until the barrier layer is exposed, the copper layer is further ground so that the plane of the copper layer is lower than the surface of the dielectric layer on the side facing away from the wafer.

[0013] Optionally, in the first grinding process, optical endpoint detection technology is used to monitor the grinding progress;

[0014] After it is monitored that the barrier layer is exposed, the copper layer is continuously ground for a first period of time to form a first recessed copper layer; the thickness of the first recessed copper layer is lower than the thickness of the dielectric layer.

[0015] Optionally, the first time length is 10s to 30s, and the thickness of the first recessed copper layer is 60nm to 80nm lower than the thickness of the dielectric layer.

[0016] Optionally, in the second grinding process, the grinding rate of the barrier layer and the dielectric layer is 800A / min to 1000A / min, and the grinding rate of the copper layer is 200A / min to 400A / min;

[0017] In the second grinding process, after removing the barrier layer on the side of the dielectric layer facing away from the wafer, the dielectric layer is ground until the plane of the dielectric layer is lower than the surface of the first recessed copper layer facing away from the wafer, and the first recessed copper layer forms a raised copper layer.

[0018] Optionally, in the second grinding process, the dielectric layer and the barrier layer are ground for a second time period, and the first recessed copper layer forms a raised copper layer; the thickness of the dielectric layer and the thickness of the barrier layer are both lower than the thickness of the raised copper layer.

[0019] Optionally, the polishing liquid in the third grinding process is a Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min to 9000A / min;

[0020] In the third grinding process, the raised copper layer is ground until the plane where the raised copper layer is located is lower than the surface of the dielectric layer on the side facing away from the wafer, and the raised copper layer forms a second recessed copper layer.

[0021] Optionally, in the third grinding process, the raised copper layer is ground for a third time period, and the raised copper layer forms a second recessed copper layer; the thickness of the second recessed copper layer is lower than the thickness of the dielectric layer.

[0022] Optionally, the second time duration is 50s to 70s, and the thickness of the raised copper layer is 10nm to 20nm higher than the thickness of the dielectric layer;

[0023] The third time length is 5s to 8s, and the thickness of the second recessed copper layer is 1nm to 5nm lower than the thickness of the dielectric layer.

[0024] Optionally, the material of the barrier layer is one or more of Ta, TaN, Ti, and TiN;

[0025] The material of the dielectric layer is silicon oxide;

[0026] The material of the first polishing pad and the material of the third polishing pad are polyurethane;

[0027] The material of the second polishing pad is non-woven fabric.

[0028] The technical solution of the present invention has the following advantages:

[0029] (1) The grinding method of the metal wiring layer for hybrid bonding provided by the present invention, first, using a first grinding pad with higher hardness, through a first grinding process, completely remove the copper layer on the side of the dielectric layer facing away from the wafer, until the barrier layer is exposed, and all the copper layers on the barrier layer can be polished through a one-step process; secondly, using a second grinding pad with lower hardness, through a second grinding process, remove all the barrier layers on the side of the dielectric layer facing away from the wafer, and remove part of the dielectric layer, which can protect the dielectric layer and the barrier layer surface from being scratched, thereby reducing the surface roughness of the dielectric layer; finally, using a third grinding pad with higher hardness, through a third grinding process, polish the copper layer, so that the thickness of the copper layer is lower than the thickness of the dielectric layer, which can control and reduce the depression of the copper layer, and reduce the surface roughness of the copper layer. Therefore, the grinding method of the metal wiring layer for hybrid bonding provided by the present invention can control and reduce the depression of the copper layer, and at the same time can reduce the surface roughness of the dielectric layer and the copper layer, thereby improving the bonding force between the metal wiring layers during hybrid bonding, and can also simplify the grinding process of the metal wiring layer, save the cost and time required for hardware and process preparatory preparation, and ensure stable output of process results.

[0030] (2) In the grinding method for the metal wiring layer for hybrid bonding provided by the present invention, in the first grinding process, after the copper layer is ground with Cu polishing liquid until the barrier layer is exposed, the copper layer is continued to be ground so that the plane where the copper layer is located is lower than the surface of the dielectric layer on the side facing away from the wafer, and the grinding rate of the copper layer is 8000A / min to 9000A / min. This scheme only needs one step to polish all the copper layers on the barrier layer without changing the grinding rate of the copper layer. After the barrier layer is exposed, the copper layer is continued to be ground, which can ensure that the copper layer on the side of the dielectric layer facing away from the wafer is completely removed, thereby simplifying the grinding process of the copper layer and saving the cost and time required for hardware and process pre-preparation.

[0031] (3) In the grinding method for the metal wiring layer for hybrid bonding provided by the present invention, in the first grinding process, the optical endpoint detection technology is used to monitor the grinding progress, and the reflection spectrum of light on different layers can accurately determine which layer is polished, and it can be accurately determined whether the copper layer on the barrier layer is completely removed; then continue to grind for a first time to form a first recessed copper layer, which can ensure that the copper layer on the side of the dielectric layer facing away from the wafer is completely removed, thereby simplifying the grinding process of the copper layer, forming the final dielectric layer and saving the cost and time required for hardware and process preparation.

[0032] (4) In the grinding method for the metal wiring layer for hybrid bonding provided by the present invention, in the second grinding process, after removing the barrier layer located on the side of the dielectric layer facing away from the wafer, the dielectric layer is ground until the plane of the dielectric layer is lower than the surface of the first recessed copper layer facing away from the wafer, and the first recessed copper layer forms a raised copper layer. The grinding rate of the barrier layer and the dielectric layer is 800A / min to 1000A / min, and the grinding rate of the copper layer is 200A / min to 400A / min. By controlling the grinding rate of different layers, this scheme can ensure that the barrier layer on the side of the dielectric layer facing away from the wafer is completely removed. By accurately grinding the dielectric layer to the required thickness and forming the raised copper layer from the first recessed copper layer, the final dielectric layer can be ground in a one-step process, thereby simplifying the process flow. In addition, the surface roughness of the dielectric layer can be reduced, thereby improving the bonding force between the metal wiring layers during hybrid bonding.

[0033] (5) In the grinding method of the metal wiring layer for hybrid bonding provided by the present invention, in the third grinding process, the raised copper layer is ground until the plane where the raised copper layer is located is lower than the surface of the dielectric layer on the side facing away from the wafer, and the raised copper layer forms a second recessed copper layer. The polishing liquid is Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min~9000A / min. The third grinding process uses the same polishing liquid and copper layer grinding rate as the first grinding process, which can reduce costs; the third grinding process can increase the contact area between the dielectric layer in the metal wiring layer during hybrid bonding by accurately grinding the raised copper layer to the required thickness and forming the second recessed copper layer from the raised copper layer. The second recessed copper layer will expand and contact the bonding during bonding, ensuring that the metal wiring layer can be completely bonded, thereby improving the bonding force between the metal wiring layers during hybrid bonding.

[0034] (6) In the grinding method of the metal wiring layer for hybrid bonding provided by the present invention, the second time length is 50s to 70s, and the value of the thickness of the raised copper layer being higher than the thickness of the dielectric layer is 10nm to 20nm; the third time length is 5s to 8s, and the value of the thickness of the second recessed copper layer being lower than the thickness of the dielectric layer is 1nm to 5nm. By controlling the second time length and the third time length, the thickness of the dielectric layer and the thickness of the copper layer in the finally formed metal wiring layer can be accurately controlled, which can improve the process efficiency, simplify the process flow, reduce the process cost, and ensure the output of the process result; at the same time, by controlling the third time length, the recess of the copper layer can be controlled and reduced, so that the thickness of the second recessed copper layer is lower than the thickness of the dielectric layer by 1nm to 5nm. This range can not only increase the contact area between the dielectric layers in the metal wiring layer during hybrid bonding, but also ensure that the second recessed copper layer expands and contacts the bonding during bonding, thereby ensuring that the metal wiring layer can be fully bonded and improving the bonding force between the metal wiring layers during hybrid bonding. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 A schematic flow chart of a method for grinding a metal wiring layer for hybrid bonding according to an embodiment of the present invention;

[0037] Figures 2 to 5 A schematic structural diagram of each step of a method for grinding a metal wiring layer for hybrid bonding according to an embodiment of the present invention;

[0038] Figure 6 The present invention is a schematic diagram of a specific process of a method for grinding a metal wiring layer for hybrid bonding according to an embodiment of the present invention.

[0039] 100-wafer; 10-copper layer; 20-barrier layer; 30-dielectric layer; 11-first recessed copper layer; 12-raised copper layer; 13-second recessed copper layer. DETAILED DESCRIPTION

[0040] Copper-copper hybrid bonding technology is to bond two wafers together, each of which completes the metal wiring layer of the last step of the process. There are only two materials on this layer: copper and dielectric layer. The dielectric layer can be silicon oxide or polymer material, both of which have their own advantages and disadvantages. The material to be used is determined according to the process needs. Since wafer bonding involves two material interfaces, copper and dielectric layer, it is called hybrid bonding. Hybrid bonding greatly increases the density of metal wiring, allowing ADC to process pixels in parallel, greatly improving the ability of image processing, such as global shutter, frame per second of the video, etc.

[0041] Hybrid bonding technology has many application areas. For example, HBM (High Bandwidth Memory) uses 2.5D packaging technology to stack the CPU and more than 8 DRAM chips. The connection between the processor and the memory is through the chip's micro bond to connect the metal wires of the underlying interposer to another chip. In this way, the density of I / O and wiring can be greatly increased. Among the new applications of hybrid bonding technology, the most eye-catching one is High Performance Computing (HPC). HPC occupies the most significant share in the production capacity of wafer foundry.

[0042] At present, the industry uses chemical mechanical polishing (CMP) to form the metal wiring layer of copper-copper hybrid bonding. Generally, a three-disk polishing process is used to achieve Cu removal and control of the concave copper layer (Cu dishing) and surface roughness (Ra) to form the metal wiring layer. The specific process is to first polish the Cu material through two polishing disks P1 and P2, and then polish the polishing disk P3 with a barrier layer polishing liquid by setting a fixed time to control the CMP of the barrier layer and part of the dielectric layer. Such a process requires P1 and P2 to set different Cu grinding rates respectively, and the endpoint control on P1 requires the use of a large number of Cu monitor wafers (monitor wafers) for setting, which increases the process cost; at the same time, the P3 process does not accurately control the thickness of the barrier layer and the dielectric layer, which may increase the concave of the copper layer, resulting in greater roughness of the copper layer and the dielectric layer, thereby reducing the bonding force between the metal wiring layers during hybrid bonding.

[0043] In order to solve the problems in the prior art of the complicated grinding process of the copper layer, high process cost, inaccurate control of the thickness of the barrier layer and the dielectric layer, resulting in large depression of the copper layer of the metal wiring layer, large roughness of the copper layer and the dielectric layer, and thus low bonding force between the metal wiring layers during hybrid bonding, the present invention provides a grinding method for the metal wiring layer for hybrid bonding, comprising: providing a wafer to be ground; one side of the wafer comprises a metal wiring layer to be ground, the metal wiring layer comprises a copper layer, a barrier layer, and a dielectric layer, the copper layer covers the barrier layer and the dielectric layer, and the barrier layer is located between the copper layer and the dielectric layer; using The first grinding disc and the first grinding pad perform a first grinding process on the copper layer to remove the copper layer on the side of the dielectric layer facing away from the wafer until the barrier layer is exposed; the Shore hardness of the first grinding pad is 60-80; the second grinding disc and the second grinding pad perform a second grinding process on the dielectric layer and the barrier layer to remove the barrier layer on the side of the dielectric layer facing away from the wafer and remove part of the dielectric layer; the Shore hardness of the second grinding pad is 20-30; the third grinding disc and the third grinding pad perform a third grinding process on the copper layer to make the thickness of the copper layer lower than the thickness of the dielectric layer; the Shore hardness of the third grinding pad is 60-80.

[0044] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In the description of the present invention, it should be noted that the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a grinding method for a metal wiring layer for hybrid bonding, comprising:

[0047] S101, providing a wafer to be ground; Figure 2 As shown, one side of the wafer 100 includes a metal wiring layer to be polished, and the metal wiring layer includes a copper layer 10, a barrier layer 20, and a dielectric layer 30. The copper layer 10 covers the barrier layer 20 and the dielectric layer 30, and the barrier layer 20 is located between the copper layer 10 and the dielectric layer 30.

[0048] In specific implementation, the wafer may be a bare wafer or a chip with various functional layers formed on the bare wafer, etc. The dielectric layer may be silicon oxide or other non-conductive materials, and the barrier layer between the copper layer and the dielectric layer is relatively thin, generally 100nm to 200nm.

[0049] S102, performing a first grinding process on the copper layer using a first grinding disk and a first grinding pad to remove the copper layer on the side of the dielectric layer facing away from the wafer until the barrier layer is exposed; the Shore hardness of the first grinding pad is 60-80.

[0050] In specific implementation, since the copper layer is relatively hard, a first polishing pad with a Shore hardness of 60 to 80 is selected to polish the copper layer. This can speed up the polishing rate of the copper layer, thereby completely removing the copper layer on the side of the dielectric layer facing away from the wafer, and is beneficial to reducing the surface roughness of the copper layer.

[0051] S103, performing a second grinding process on the dielectric layer and the barrier layer using a second grinding disk and a second grinding pad to remove the barrier layer on the side of the dielectric layer facing away from the wafer and to remove part of the dielectric layer; the Shore hardness of the second grinding pad is 20-30.

[0052] During specific implementation, a second polishing pad with a Shore hardness of 20 to 30 is selected to polish the dielectric layer and the barrier layer. This can protect the surfaces of the dielectric layer and the barrier layer from being scratched during the polishing process, thereby completely removing the barrier layer on the side of the dielectric layer facing away from the wafer, and removing part of the dielectric layer, which is beneficial to reducing the surface roughness of the dielectric layer in the metal wiring layer.

[0053] S104, performing a third grinding process on the copper layer using a third grinding disk and a third grinding pad, so that the thickness of the copper layer is lower than the thickness of the dielectric layer; the Shore hardness of the third grinding pad is 60-80.

[0054] In specific implementation, a third grinding pad with a Shore hardness of 60 to 80 is selected to grind the copper layer, so that the thickness of the copper layer can be accurately controlled so that the thickness of the copper layer is lower than that of the dielectric layer, and it is beneficial to reduce the surface roughness of the copper layer.

[0055] The grinding method of the metal wiring layer for hybrid bonding provided in this embodiment, firstly, using a first grinding pad with higher hardness, completely removes the copper layer on the side of the dielectric layer facing away from the wafer through a first grinding process, until the barrier layer is exposed, and all the copper layers on the barrier layer can be polished through a one-step process; secondly, using a second grinding pad with lower hardness, removing all the barrier layers on the side of the dielectric layer facing away from the wafer through a second grinding process, and removing part of the dielectric layer, can protect the dielectric layer and the barrier layer surface from being scratched, thereby reducing the surface roughness of the dielectric layer; finally, using a third grinding pad with higher hardness, polishing the copper layer through a third grinding process, so that the thickness of the copper layer is lower than the thickness of the dielectric layer, can control and reduce the depression of the copper layer, and reduce the surface roughness of the copper layer. Therefore, the grinding method of the metal wiring layer for hybrid bonding provided by the present invention can control and reduce the depression of the copper layer, and at the same time can reduce the surface roughness of the dielectric layer and the copper layer, thereby improving the bonding force between the metal wiring layers during hybrid bonding, and can also simplify the grinding process of the metal wiring layer, save the cost and time required for hardware and process preparation in advance, and ensure stable output of process results.

[0056] Further, in some embodiments, the first grinding process is over-grinding, and the stop layer of the first grinding process is a barrier layer; the polishing liquid in the first grinding process is a Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min to 9000A / min, for example, 8000A / min, 8300A / min, 8500A / min, 8700A / min or 9000A / min.

[0057] In the first grinding process, after the copper layer is ground until the barrier layer is exposed, the copper layer is further ground so that the plane of the copper layer is lower than the surface of the dielectric layer on the side facing away from the wafer.

[0058] In the grinding method for the metal wiring layer for hybrid bonding provided in the present embodiment, in the first grinding process, after the copper layer is ground with Cu polishing liquid until the barrier layer is exposed, the copper layer is continued to be ground so that the plane where the copper layer is located is lower than the surface of the dielectric layer on the side facing away from the wafer, and the grinding rate of the copper layer is 8000A / min to 9000A / min. This scheme only needs one step to polish all the copper layers on the barrier layer without changing the grinding rate of the copper layer, and after the barrier layer is exposed, the copper layer is continued to be ground, which can ensure that the copper layer on the side of the dielectric layer facing away from the wafer is completely removed, thereby simplifying the grinding process of the copper layer and saving the cost and time required for hardware and process pre-preparation.

[0059] Furthermore, in some embodiments, Figure 3 As shown, in the first grinding process, the grinding progress is monitored using optical endpoint detection technology;

[0060] After it is detected that the barrier layer 20 is exposed, the copper layer 10 is continuously ground for a first time period to form a first recessed copper layer 11 ; the thickness of the first recessed copper layer 11 is less than the thickness of the dielectric layer 30 .

[0061] In the grinding method for the metal connection layer for hybrid bonding provided by the present invention, in the first grinding process, the optical endpoint detection technology is used to monitor the grinding progress, and the reflection spectrum of light on different layers can accurately determine which layer is polished, and it can be accurately determined that the copper layer on the barrier layer is completely removed; then continue to grind for a first time to form a first recessed copper layer, which can ensure that the copper layer on the side of the dielectric layer facing away from the wafer is completely removed, thereby simplifying the grinding process of the copper layer, forming a final dielectric layer and saving the cost and time required for hardware and process pre-preparation.

[0062] Further, in some embodiments, the first time length is 10s to 30s, for example, 10s, 25s, 20s, 25s or 30s, and the thickness of the first recessed copper layer is 60nm to 80nm lower than the thickness of the dielectric layer, for example, 60nm, 65nm, 70nm, 75nm or 80nm.

[0063] In specific implementation, the optical endpoint detection technology is used to monitor the grinding progress and the first time length is set to 10s to 30s. After the barrier layer is exposed, the copper layer is continued to be ground for 10s to 30s to ensure that the thickness of the first recessed copper layer is 60nm to 80nm lower than the thickness of the dielectric layer.

[0064] Furthermore, in some embodiments, Figure 4 As shown, in the second grinding process, the grinding rate of the barrier layer 20 and the dielectric layer 30 is 800A / min to 1000A / min, such as 800A / min, 850A / min, 900A / min, 950A / min or 1000A / min, and the grinding rate of the copper layer is 200A / min to 400A / min, such as 200A / min, 250A / min, 300A / min, 350A / min or 400A / min;

[0065] In the second grinding process, after removing the barrier layer 20 located on the side of the dielectric layer 30 facing away from the wafer 100, the dielectric layer 30 is ground until the plane of the dielectric layer 30 is lower than the surface of the first recessed copper layer 11 facing away from the wafer 100, and the first recessed copper layer 11 forms a raised copper layer 12.

[0066] In the grinding method for the metal wiring layer for hybrid bonding provided in the present embodiment, in the second grinding process, after removing the barrier layer located on the side of the dielectric layer facing away from the wafer, the dielectric layer is ground until the plane of the dielectric layer is lower than the surface of the first recessed copper layer facing away from the wafer, and the first recessed copper layer forms a raised copper layer. The grinding rates of the barrier layer and the dielectric layer are 800A / min to 1000A / min, and the grinding rate of the copper layer is 200A / min to 400A / min. By controlling the grinding rates of different layers, the present scheme can ensure the complete removal of the barrier layer on the side of the dielectric layer facing away from the wafer. By accurately grinding the dielectric layer to the required thickness and forming the raised copper layer from the first recessed copper layer, the final dielectric layer can be ground in a one-step process, thereby simplifying the process flow. In addition, the surface roughness of the dielectric layer can be reduced, and the bonding force between the metal wiring layers during hybrid bonding can be improved.

[0067] Furthermore, in some embodiments, in the second grinding process, the dielectric layer and the barrier layer are ground for a second time period, and the first recessed copper layer forms a raised copper layer; the thickness of the dielectric layer is lower than the thickness of the raised copper layer.

[0068] Furthermore, in some embodiments, Figure 5 As shown, the polishing liquid in the third grinding process is a Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min to 9000A / min, for example, 8000A / min, 8300A / min, 8500A / min, 8700A / min or 9000A / min;

[0069] In the third grinding process, the raised copper layer 12 is ground until the plane of the raised copper layer 12 is lower than the surface of the dielectric layer 30 facing away from the wafer, and the raised copper layer 12 forms a second recessed copper layer 13 .

[0070] In the grinding method for the metal wiring layer for hybrid bonding provided in this embodiment, in the third grinding process, the raised copper layer is ground until the plane where the raised copper layer is located is lower than the surface of the dielectric layer on the side facing away from the wafer, and the raised copper layer forms a second recessed copper layer. The polishing liquid is Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min~9000A / min. The third grinding process uses the same polishing liquid and copper layer grinding rate as the first grinding process, which can reduce costs; the third grinding process can increase the contact area between the dielectric layer in the metal wiring layer during hybrid bonding by accurately grinding the raised copper layer to the required thickness and forming the second recessed copper layer from the raised copper layer. The second recessed copper layer will expand and contact the bonding during bonding, ensuring that the metal wiring layer can be completely bonded, thereby improving the bonding force between the metal wiring layers during hybrid bonding.

[0071] Furthermore, in some embodiments, in the third grinding process, the raised copper layer 12 is ground for a third time period to form a second recessed copper layer 13 ; the thickness of the second recessed copper layer 13 is less than the thickness of the dielectric layer 30 .

[0072] Further, in some embodiments, the second duration is 50s to 70s, such as 50s, 55s, 60s, 65s or 70s, and the thickness of the raised copper layer is 10nm to 20nm higher than the thickness of the dielectric layer, such as 10nm, 13nm, 15nm, 17nm or 20nm;

[0073] The third time duration is 5s to 8s, such as 5s, 6s, 7s or 8s, and the thickness of the second recessed copper layer is 1nm to 5nm lower than the thickness of the dielectric layer, such as 1nm, 2nm, 3nm, 4nm or 5nm.

[0074] In the grinding method for the metal wiring layer for hybrid bonding provided in this embodiment, the second time length is 50s to 70s, and the value by which the thickness of the raised copper layer is higher than the thickness of the dielectric layer is 10nm to 20nm; the third time length is 5s to 8s, and the value by which the thickness of the second recessed copper layer is lower than the thickness of the dielectric layer is 1nm to 5nm. By controlling the second time length and the third time length, the thickness of the dielectric layer and the thickness of the copper layer in the finally formed metal wiring layer can be accurately controlled, which can improve process efficiency, simplify the process flow, reduce process costs, and ensure the output of process results; at the same time, by controlling the third time length, the recess of the copper layer can also be controlled and reduced, so that the thickness of the second recessed copper layer is lower than the thickness of the dielectric layer by 1nm to 5nm. This range can not only increase the contact area between the dielectric layers in the metal wiring layer during hybrid bonding, but also ensure that the second recessed copper layer expands and contacts during bonding, thereby ensuring that the metal wiring layer can be fully bonded and improving the bonding force between the metal wiring layers during hybrid bonding.

[0075] Further, in some embodiments, the material of the barrier layer is one or more of Ta, TaN, Ti, and TiN;

[0076] The material of the dielectric layer is silicon oxide;

[0077] The material of the first polishing pad and the material of the third polishing pad are polyurethane;

[0078] The material of the second polishing pad is non-woven fabric.

[0079] refer to Figure 6 This embodiment also provides a specific process of a grinding method for a mixed bonding metal wiring layer, including steps S201-S205:

[0080] S201, providing a wafer 100 to be ground; one side of the wafer 100 includes a metal wiring layer to be ground, the metal wiring layer includes a copper layer 10, a barrier layer 20, and a dielectric layer 30, the copper layer 10 covers the barrier layer 20 and the dielectric layer 30, the barrier layer 20 is located between the copper layer 10 and the dielectric layer 30, wherein the material of the dielectric layer 30 is silicon oxide, and the material of the barrier layer 20 is Ta / TaN, such as Figure 2 shown.

[0081] S202, grinding the copper layer 10 using Cu polishing liquid, a first grinding disk and a polyurethane grinding pad with a Shore hardness of 60 to 80, and monitoring the grinding progress using optical endpoint detection technology, removing the copper layer 10 located on the side of the dielectric layer 30 facing away from the wafer 100 until the barrier layer 20 is exposed; the grinding rate of the copper layer is 8000A / min to 9000A / min.

[0082] S203, after the optical endpoint detection technology monitors that the barrier layer 20 is exposed, the copper layer 10 is continuously ground for 10s to 30s using the Cu polishing liquid, the first grinding disk, and the polyurethane grinding pad with a Shore hardness of 60 to 80 to form a first recessed copper layer 11; the thickness of the first recessed copper layer 11 is 60nm to 80nm lower than the thickness of the dielectric layer 30; the grinding rate of the copper layer is 8000A / min to 9000A / min, such as Figure 3 shown.

[0083] S204, grinding the dielectric layer 30 and the barrier layer 20 for 50s to 70s using a second grinding disk and a non-woven fabric grinding pad with a Shore hardness of 20 to 30, removing the barrier layer 20 located on the side of the dielectric layer 30 facing away from the wafer 100, and removing part of the dielectric layer 30, so that the first recessed copper layer 11 forms a raised copper layer 12; the thickness of the dielectric layer 30 is 10nm to 20nm lower than the thickness of the raised copper layer 12; the grinding rate of the barrier layer and the dielectric layer is 800A / min to 1000A / min, and the grinding rate of the copper layer is 200A / min to 400A / min, such as Figure 4 shown.

[0084] S205, grinding the raised copper layer 12 for 5s to 8s using a third grinding disk and a polyurethane grinding pad with a Shore hardness of 60 to 80, so that the raised copper layer 12 forms a second recessed copper layer 13; the thickness of the second recessed copper layer 13 is 1nm to 5nm lower than the thickness of the dielectric layer 30; the grinding rate of the raised copper layer is 8000A / min to 9000A / min, such as Figure 5 shown.

[0085] Further, in some embodiments, the grinding method for the metal wiring layer for hybrid bonding provided by the present invention can be applied to HBM or HPC packaging. After the surfaces of the first chip and the second chip to be interconnected are respectively formed with the grinding method provided by this embodiment, the two metal wiring layers are bonded together using a hybrid bonding technology.

[0086] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for grinding a metal wiring layer for hybrid bonding, characterized in that: include: Providing a wafer to be ground; one side of the wafer includes a metal wiring layer to be ground, the metal wiring layer includes a copper layer, a barrier layer, and a dielectric layer, the copper layer covers the barrier layer and the dielectric layer, and the barrier layer is located between the copper layer and the dielectric layer; Performing a first grinding process on the copper layer using a first grinding disc and a first grinding pad to remove the copper layer located on a side of the dielectric layer facing away from the wafer until the barrier layer is exposed; The Shore hardness of the first polishing pad is 60-80; Performing a second grinding process on the dielectric layer and the barrier layer using a second grinding disk and a second grinding pad to remove the barrier layer located on a side of the dielectric layer facing away from the wafer and to remove a portion of the dielectric layer; The Shore hardness of the second polishing pad is 20 to 30; Performing a third grinding process on the copper layer using a third grinding disk and a third grinding pad, so that the thickness of the copper layer is lower than the thickness of the dielectric layer; The third polishing pad has a Shore hardness of 60-80.

2. The method for polishing a metal wiring layer for hybrid bonding according to claim 1, characterized in that: The first grinding process is over-grinding, and the stop layer of the first grinding process is the barrier layer; the polishing liquid in the first grinding process is Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min to 9000A / min; In the first grinding process, after the copper layer is ground until the barrier layer is exposed, the copper layer is further ground so that the plane where the copper layer is located is lower than the surface of the dielectric layer facing away from the wafer.

3. The method for polishing a metal wiring layer for hybrid bonding according to claim 2, characterized in that: In the first grinding process, the grinding progress is monitored using optical endpoint detection technology; After the barrier layer is detected to be exposed, the copper layer is continuously ground for a first period of time to form a first recessed copper layer; the thickness of the first recessed copper layer is lower than the thickness of the dielectric layer.

4. The method for polishing a metal wiring layer for hybrid bonding according to claim 3, characterized in that: The first time length is 10s to 30s, and the thickness of the first recessed copper layer is 60nm to 80nm lower than the thickness of the dielectric layer.

5. The method for polishing a metal wiring layer for hybrid bonding according to claim 3, characterized in that: In the second grinding process, the grinding rate of the barrier layer and the dielectric layer is 800A / min to 1000A / min, and the grinding rate of the copper layer is 200A / min to 400A / min; In the second grinding process, after removing the barrier layer located on the side of the dielectric layer facing away from the wafer, the dielectric layer is ground until the plane of the dielectric layer is lower than the surface of the first recessed copper layer facing away from the wafer, and the first recessed copper layer forms a raised copper layer.

6. The method for polishing a metal wiring layer for hybrid bonding according to claim 5, characterized in that: In the second grinding process, the dielectric layer and the barrier layer are ground for a second time period, and the first recessed copper layer is formed into the raised copper layer; The thickness of the dielectric layer and the thickness of the barrier layer are both lower than the thickness of the raised copper layer.

7. The method for polishing a metal wiring layer for hybrid bonding according to claim 6, characterized in that: The polishing liquid in the third grinding process is a Cu polishing liquid, and the grinding rate of the copper layer is 8000A / min to 9000A / min; In the third grinding process, the raised copper layer is ground until the plane where the raised copper layer is located is lower than the surface of the dielectric layer facing away from the wafer, and the raised copper layer forms a second recessed copper layer.

8. The method for polishing a metal wiring layer for hybrid bonding according to claim 7, characterized in that: In the third grinding process, the raised copper layer is ground for a third time period, and the raised copper layer forms the second recessed copper layer; the thickness of the second recessed copper layer is less than the thickness of the dielectric layer.

9. The method for polishing a metal wiring layer for hybrid bonding according to claim 8, characterized in that: The second time duration is 50s to 70s, and the thickness of the raised copper layer is 10nm to 20nm higher than the thickness of the dielectric layer; The third time duration is 5s to 8s, and the thickness of the second recessed copper layer is 1nm to 5nm lower than the thickness of the dielectric layer.

10. The method for polishing a metal wiring layer for hybrid bonding according to claim 1, characterized in that: The material of the barrier layer is one or more of Ta, TaN, Ti, and TiN; The material of the dielectric layer is silicon oxide; The material of the first polishing pad and the material of the third polishing pad are polyurethane; The second polishing pad is made of non-woven fabric.

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