Copper-copper bonding structure and bonding method thereof

Abstract

The invention relates to the technical field of copper-copper bonding, in particular to a copper-copper bonding structure and a bonding method thereof.The copper-copper bonding structure comprises a first copper material and a second copper material, a plurality of copper columns are arranged on the bonding face of the first copper material in an array mode, and a plurality of pits used in cooperation with the copper columns are formed in the bonding face of the second copper material in an array mode; the recess is of an inverted quadrangular frustum pyramid structure; according to the invention, the copper column is designed to be matched with the recess of the quadrangular frustum pyramid structure, so that the pressure intensity of a contact area is increased, the copper-copper bonding process is optimized, the bonding process does not need to depend on a method of removing an oxide layer, the chemical risk in a working environment can be effectively reduced, and the health and safety of operators are ensured; the recess is prepared by a wet etching technology, and has a flat inclined surface and excellent high temperature resistance. Not only is the contact surface area increased, but also the pressure intensively applied by the copper column can be effectively guided, so that a high-voltage contact point is formed, and the reliability and stability of connection can be further improved.

Description

Technical Field

[0001] The invention relates to the technical field of copper-copper bonding, in particular to a copper-copper bonding structure. Background Art

[0002] Copper-copper bonding is a technology used for electronic packaging and chip connection, which mainly uses the conductivity and good mechanical properties of copper materials to achieve efficient electrical connection. It generally involves heating and applying pressure to two copper surfaces so that the copper atoms on both sides diffuse into each other at the contact interface, thereby forming a strong metal bond. It is widely used in integrated circuit (IC) packaging, especially in the connection between chips and pins.

[0003] Since the copper surface is easily oxidized, the bonding efficiency will be reduced. The existing technical solution is to carry out the bonding process in a reducing gas environment (such as formic acid) to prevent the copper surface from being oxidized before bonding.

[0004] However, formic acid is highly corrosive and can cause conjunctivitis, eyelid edema, rhinitis, bronchitis, and in severe cases, acute chemical pneumonia. In addition, reducing gases can also react to other substances on the surface of the bonded sample, such as the iron catalyst used to grow carbon nanotubes, which limits the compatibility of copper-copper bonding with carbon nanotube thermal conductive structures. Summary of the invention

[0005] The object of the present invention is to provide a copper-copper bonding structure to solve the problems raised in the above background technology.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A copper-copper bonding structure, comprising a copper material 1 and a copper material 2, wherein a plurality of copper pillars are arranged in an array on the bonding surface of the copper material 1, and a plurality of recesses used in conjunction with the plurality of copper pillars are arranged in an array on the bonding surface of the copper material 2; The depression is an inverted quadrangular pyramid structure.

[0007] Another object of the present invention is to provide a bonding method for a copper-copper bonding structure, comprising the following steps: S1: Making copper pillars on the bonding surface of copper material 1; S2: forming a depression on the bonding surface of copper material 2; S3: Bonding the copper material 1 and the copper material 2 via the copper pillars and the recesses.

[0008] The S1 comprises the following steps: S11: forming an oxide layer on the copper material 1; S12: sputtering a titanium-tungsten isolation layer and a copper seed layer on the bonding surface of the copper material 1; S13: preparing a photoresist on the bonding surface of the copper material 1, and exposing the copper pillar area through exposure and development; S14: forming a plurality of copper pillars distributed in an array by electroplating on the bonding surface of the copper material 1; S15: Dissolve the photoresist on the bonding surface of the copper material 1 with acetone.

[0009] The S2 comprises the following steps: S21: dry-etching the silicon oxide layer by exposing and developing the photoresist to expose the crystal surface of the silicon substrate in the recessed area; S22: wet-etching the silicon substrate using TMAH to form a plurality of depressions by utilizing the different etching rates of different crystal planes; S23: removing the silicon oxide layer using a wet method; S24: re-oxidizing the entire surface of the copper material 2 to form an oxide layer; S25: sputtering a titanium-tungsten isolation layer and a copper seed layer on the bonding surface of the copper material 2;.

[0010] The S3 comprises the following steps: S31: aligning the copper material 1 and the copper material 2 so that the copper pillar is aligned with the recess; S32: Raise the temperature to 250 degrees Celsius; S33: The copper-copper bonding can be completed by hot pressing for five minutes under the condition of 0.2 Newton pressure on each group of copper pillar depressions.

[0011] Beneficial effects of the present invention: 1. The present invention increases the pressure of the contact area by designing the concave cooperation between the copper column and the tetrahedral structure, thereby optimizing the copper-copper bonding process, so that there is no need to rely on the method of removing the oxide layer during the bonding process. Since there is no need to use toxic reducing gas, the chemical risks in the working environment can be effectively reduced to ensure the health and safety of operators.

[0012] 2. The depression of the present invention is prepared by wet etching technology, and has a smooth slope and excellent high temperature resistance. It not only provides an increased contact surface area, but also effectively guides the concentrated pressure applied by the copper column to form a high-pressure contact point, further improving the reliability and stability of the connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work. Figure 1 It is a three-dimensional schematic diagram of the overall structure of the present invention; Figure 2 is a three-dimensional schematic diagram of the copper material 2 in the present invention; Figure 3 is a three-dimensional schematic diagram of copper material 1 in the present invention; Figure 4 This is a flow chart of the copper material-copper column manufacturing process in the present invention; Figure 5 It is a flow chart of the copper material two upper depressions in the present invention; Figure 6 It is a schematic diagram of the bonding structure of copper material 1 and copper material 2 in the present invention; Figure 7 It is a statistical graph of the shear strength of the bonded structure under different conditions; The reference numerals are as follows: 1-copper material 1, 2-copper material 2, 3-copper pillar, 4-recess, 5-oxide layer, 6-titanium tungsten isolation layer, 7-photoresist. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Embodiment 1: See also Figure 1 to Figure 3 In an embodiment of the present invention, a copper-copper bonding structure includes a copper material 1 and a copper material 2, wherein a plurality of copper pillars 3 are arranged in an array on the bonding surface of the copper material 1, and a plurality of recesses 4 used in conjunction with the plurality of copper pillars 3 are arranged in an array on the bonding surface of the copper material 2; It is a concave 4 inverted tetrahedral structure.

[0016] The contact area pressure during bonding is effectively increased by the coordinated arrangement of the copper pillar 3 and the recess 4 .

[0017] Embodiment 2: See also Figures 1 to 6 Based on Example 1, this embodiment provides a bonding method for a copper-copper bonding structure, comprising the following steps: S1: Making a copper pillar 3 on the bonding surface of the copper material 1; S2: forming a depression 4 on the bonding surface of the copper material 2; S3: Bonding the copper material 1 and the copper material 2 through the copper pillar 3 and the recess 4.

[0018] S1 includes the following steps: S11: forming an oxide layer 5 on the copper material 1; S12: sputtering a titanium-tungsten isolation layer 6 and a copper seed layer on the bonding surface of the copper material 1; S13: forming a photoresist 7 on the bonding surface of the copper material 1, and exposing the area of ​​the copper pillar 3 by exposure and development; S14: forming a plurality of copper pillars 3 distributed in an array by electroplating on the bonding surface of the copper material 1; S15: dissolving the photoresist 7 on the bonding surface of the copper material 1 with acetone.

[0019] S2 includes the following steps: S21: dry-etching the silicon oxide layer by exposing and developing the photoresist to expose the crystal surface of the silicon substrate in the recessed area; S22: wet-etching the silicon substrate using TMAH, and utilizing the different etching rates of different crystal planes to form a plurality of recesses 4; S23: removing the silicon oxide layer using a wet method; S24: re-oxidizing the entire surface of the copper material 2 to form an oxide layer 5; S25: sputtering a titanium-tungsten isolation layer 6 and a copper seed layer on the bonding surface of the copper material 2;.

[0020] S3 includes the following steps: S31: aligning the copper material 1 and the copper material 2 so that the copper pillar 3 is aligned with the recess 4; S32: Raise the temperature to 250 degrees Celsius; S33: The copper-copper bonding can be completed by hot pressing for five minutes under the condition of 0.2 Newton pressure on each group of copper pillar depressions.

[0021] The present invention proposes an innovative copper-copper bonding technology, which increases the pressure in the contact area by designing the copper column 3 to cooperate with the depression 4 of the quadrangular pyramid structure, thereby optimizing the copper-copper bonding process.

[0022] In the traditional copper-copper bonding process, removing the oxide layer on the copper surface is usually an important step to ensure good electrical connection and mechanical bonding. However, the commonly used deoxidation method may involve toxic reducing gases, which poses a potential risk to the health and safety of operators. To this end, the present invention designs a new connection structure, which utilizes the cooperation between the copper column 3 and the recess 4 of the tetrahedral structure, so that there is no need to rely on the method of removing the oxide layer during the bonding process. Since there is no need to use toxic reducing gases, the present invention can effectively reduce the chemical risks in the working environment and ensure the health and safety of operators.

[0023] The depression 4 is made by wet etching technology, and has a flat bevel and excellent high temperature resistance. Its design not only provides an increased contact surface area, but also effectively guides the concentrated pressure applied by the copper pillar to form a high-voltage contact point; the wet etching process ensures the flatness of the depression surface and the precise consistency of the geometric shape, which is crucial in the copper-copper bonding process and can further improve the reliability and stability of the connection.

[0024] The increased contact area pressure brought about by design optimization enables close contact between copper atoms, thereby improving the bonding firmness and electrical performance. The structural design of the present invention has a certain adaptability and can be applied to the connection of various electronic packaging and microelectronic devices to meet higher technical requirements in the future.

[0025] Embodiment 3: See also Figure 7 On the basis of Example 2, in order to verify the high temperature resistance of the copper-copper bonding structure of the present invention, annealing was carried out at 700 degrees Celsius after bonding. The experiment found that the shear strength of the samples hot pressed at 250 degrees Celsius or above was further improved after annealing, which fully proved the high temperature resistance of the new structure.

[0026] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A copper-copper bonding structure, characterized in that: It comprises a copper material 1 (1) and a copper material 2 (2), wherein a plurality of copper pillars (3) are arranged in an array on the bonding surface of the copper material 1 (1), and a plurality of recesses (4) for use with the plurality of copper pillars (3) are arranged in an array on the bonding surface of the copper material 2 (2); The depression (4) is an inverted quadrangular pyramid structure.

2. The bonding method of a copper-copper bonding structure according to claim 1, characterized in that: The following steps are involved: S1: Making a copper pillar (3) on the bonding surface of the copper material 1 (1); S2: forming a depression (4) on the bonding surface of the copper material 2 (2); S3: Bonding the copper material 1 (1) and the copper material 2 (2) via the copper pillar (3) and the recess (4).

3. The bonding method of a copper-copper bonding structure according to claim 2, characterized in that: The S1 comprises the following steps: S11: forming an oxide layer (5) on the copper material (1); S12: sputtering a titanium-tungsten isolation layer (6) and a copper seed layer on the bonding surface of the copper material 1 (1); S13: forming a photoresist (7) on the bonding surface of the copper material 1 (1), and exposing the area of ​​the copper pillar (3) by exposure and development; S14: forming a plurality of copper pillars (3) distributed in an array by electroplating on the bonding surface of the copper material 1 (1); S15: Dissolve the photoresist (7) on the bonding surface of the copper material 1 (1) with acetone.

4. The bonding method of a copper-copper bonding structure according to claim 2, characterized in that: The S2 comprises the following steps: S21: dry-etching the silicon oxide layer by exposing and developing the photoresist to expose the crystal surface of the silicon substrate in the recessed area; S22: using TMAH wet etching to etch the silicon substrate, taking advantage of the different etching rates of different crystal planes, to form a plurality of depressions (4); S23: removing the silicon oxide layer using a wet method; S24: re-oxidizing the entire surface of the copper material 2 (2) to form an oxide layer (5); S25: sputtering a titanium-tungsten isolation layer (6) and a copper seed layer on the bonding surface of the copper material 2 (2); 5. The bonding method of a copper-copper bonding structure according to claim 2, characterized in that: The S3 comprises the following steps: S31: aligning the copper material 1 (1) and the copper material 2 (2) so that the copper pillar (3) is aligned with the recess (4); S32: Raise the temperature to 250 degrees Celsius; S33: The copper-copper bonding can be completed by hot pressing for five minutes under the condition that each group of copper pillar depressions is subjected to a pressure of 0.2 Newton.

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