A copper-copper connection method and its use

Abstract

The application provides a copper-copper connection method and application thereof, and belongs to the technical field of copper-copper bonding process. The copper-copper connection method comprises the following steps: adopting a convex copper column, depositing a first metal catalyst on the convex end surface of the convex copper column through a salt solution containing the first metal catalyst to prepare a prepared copper column to be connected; keeping the convex end parts of the prepared copper columns to be connected to be oppositely arranged at a spacing of less than 10 microns, making the two convex end parts be connected through chemical plating deposition of a second metal connection structure to realize copper-copper connection; the first metal catalyst comprises at least one of palladium, nickel, silver and platinum; and the second metal comprises at least one of copper, nickel, gold and silver. The copper-copper connection method provided by the application can significantly improve the firmness and reliability of copper-copper connection and reduce process requirements.

Description

Technical Field

[0001] This application relates to the field of copper-copper bonding technology, and in particular to a copper-copper bonding method and its application. Background Technology

[0002] Copper-copper bonding is a core technology used in modern integrated circuit manufacturing and packaging. It is widely used in the stacking of 3D packaged chips and the interlayer bonding of DRAM (Dynamic Random Access Memory) three-dimensional stacking.

[0003] Traditional copper-to-copper bonding processes primarily involve directly connecting two copper conductors through atomic diffusion or bonding them with conductive materials to achieve conductivity. Copper-to-copper diffusion bonding is the main method, but it has several drawbacks: First, copper-to-copper bonding bumps require ultra-flat and smooth cylindrical surfaces, resulting in a long process flow and extremely high requirements for precision chemical mechanical polishing (CMP). Second, the recessed fit between the copper pillars and the truncated pyramid structure demands high alignment accuracy; even slight misalignment can prevent proper bonding, leading to air bubbles and reduced production yield. Third, while using low-melting-point nano-copper particle conductive paste for copper-to-copper bonding is simple, the printing precision is insufficient for high-precision circuit interconnects, and the low conductivity results in significant signal transmission loss.

[0004] Therefore, how to improve the copper-copper connection process to enhance its reliability and reduce process requirements has become an urgent technical problem to be solved. Summary of the Invention

[0005] Therefore, the main objective of this application is to provide a copper-copper connection method and its application to improve the reliability of copper-copper connections and reduce process requirements.

[0006] The first aspect of this application provides a copper-to-copper connection method, comprising the following steps:

[0007] A convex copper pillar is used, and a first metal catalyst is deposited on the surface of the convex end of the convex copper pillar through a salt solution containing a first metal catalyst to prepare a copper pillar to be connected.

[0008] The protruding ends of the copper pillars to be connected are arranged relative to each other with a spacing of less than 10 μm, and a second metal connection structure is deposited between the two protruding ends by chemical plating to achieve copper-copper connection.

[0009] The first metal catalyst includes at least one of palladium, nickel, silver, and platinum;

[0010] The second metal includes at least one of copper, nickel, gold, and silver.

[0011] In some embodiments, the salt solution comprising the first metal catalyst comprises a salt of the first metal catalyst and a pH adjuster; and / or,

[0012] The pH of the salt solution containing the first metal catalyst is 1.5-11.5.

[0013] In some embodiments, the salt of the first metal catalyst includes at least one selected from palladium, nickel, gold, silver and platinum.

[0014] In some embodiments, the palladium salt includes at least one of palladium sulfate, palladium chloride, palladium nitrate, and dichlorotetraminepalladium.

[0015] In some embodiments, the nickel salt includes at least one of nickel sulfate, nickel chloride, nickel carbonate, and nickel aminosulfonate.

[0016] In some embodiments, the gold salt includes at least one of potassium gold cyanide, sodium gold sulfite, and chloroauric acid.

[0017] In some embodiments, the silver salt includes at least one of silver nitrate, silver acetate, and silver methanesulfonate.

[0018] In some embodiments, the platinum salt includes at least one of platinum tetrachloride, sodium hexahydroxyplatinate, potassium hexahydroxyplatinate, and diammonium platinum nitrite.

[0019] In some embodiments, the concentration of the first metal catalyst ion in the salt of the first metal catalyst is 0.01 g / L to 213 g / L.

[0020] In some embodiments, the salt solution comprising the first metal catalyst further includes an auxiliary agent.

[0021] In some embodiments, the adjuvant includes at least one selected from ethylene glycol, ethylenediamine, sodium chloride, ammonium chloride, stannous chloride, and 2,4,6-trimethylpyridine.

[0022] In some embodiments, the concentration of the auxiliary agent in the salt solution comprising the first metal catalyst is 0.01 g / L to 10 g / L.

[0023] In some embodiments, the pH adjuster includes an acidic adjuster and / or an alkaline adjuster.

[0024] In some embodiments, the acidity modifier includes at least one selected from perchloric acid, aminosulfonic acid, sulfuric acid, hydrochloric acid, nitric acid, boric acid, methanesulfonic acid, and citric acid.

[0025] In some embodiments, the alkalinity adjuster includes at least one of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, and ammonia.

[0026] In some embodiments, the concentration of the pH adjuster in the salt solution comprising the first metal catalyst is 0.001 g / L to 75 g / L.

[0027] In some embodiments, the step of depositing a first metal catalyst on the surface of the protruding end of the convex copper pillar specifically includes:

[0028] The surface of the protruding end of the convex copper pillar is immersed in a salt solution containing a first metal catalyst to deposit the first metal catalyst; wherein the immersion conditions include: time of 1 min-6 min; temperature of 20℃-60℃; or,

[0029] A first metal catalyst is electrodeposited on the surface of the protruding end of the convex copper pillar by electroplating; wherein the electroplating conditions include: voltage of 0.2V-6V, or current density of 1ASD-2ASD; temperature of 20℃-70℃; and time of 1min-2min.

[0030] In some embodiments, the convex copper pillar includes a protruding end and a bottom coplanar with the protruding end; the bottom surface of the protruding end is circular, square, or irregular in shape.

[0031] In some embodiments, the maximum outer diameter of the protruding end is 2R, and the height of the protruding end is 0.05R-0.6R.

[0032] In some embodiments, before depositing the first metal catalyst on the surface of the protruding end of the convex copper pillar, a step of resin coating is included.

[0033] In some embodiments, before electroless plating to deposit the second metal connection structure, a step of removing the resin coating on the surface of the copper pillars to be connected is included.

[0034] In some embodiments, the step of achieving a copper-copper connection by chemically depositing a second metal connection structure between the two protruding ends specifically includes:

[0035] Chemical plating is performed by adding a chemical plating solution containing a second metal salt between the two protruding ends, so that a second metal is deposited between the two protruding ends to form a second metal connection structure, thereby realizing a copper-copper connection.

[0036] The electroless plating solution containing the second metal salt includes the second metal salt, a reducing agent, and a complexing agent.

[0037] In some embodiments, the conditions for electroless plating include: a temperature of 36°C to 86°C and a time of 5 min to 120 min.

[0038] The second aspect of this application provides the application of the copper-copper interconnection method described in the first aspect in chip packaging.

[0039] Compared with traditional technologies, this application has at least the following beneficial effects:

[0040] In the copper-copper bonding method described in this application, a first metal catalyst is selectively deposited on the surface of the protruding end of a convex copper pillar to be bonded, thereby making the protruding end of the copper pillar catalytically active for subsequent formation of a second metal bonding structure. Then, the protruding ends of the copper pillars to be bonded are arranged relative to each other with a spacing of less than 10 μm, and a second metal bonding structure is deposited between the two protruding ends using a chemical plating process. During the chemical plating process, the required growth amount of the second metal gradually decreases along the direction extending from the tip of the protruding end to both sides, which facilitates the discharge of hydrogen gas generated during the chemical plating process, reduces the generation of voids in the copper-copper bonding structure, and significantly improves the conductivity and bonding strength of the copper-copper bonding structure. Simultaneously, the process conditions of this application greatly reduce the requirements for solder joint coplanarity and alignment accuracy, allowing for alignment errors within 10 μm, which also significantly improves the production yield and reliability of the process method. Attached Figure Description

[0041] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0042] Figure 1 A schematic diagram of a convex copper column structure;

[0043] Figure 2 A schematic diagram of a method for selectively depositing a first metal catalyst on the surface of the protruding end of a convex copper pillar;

[0044] Figure 3 This is a schematic diagram showing the relative arrangement of the copper pillars to be connected in a copper-to-copper connection.

[0045] Figure 4 This is a schematic diagram of a copper-to-copper connection structure;

[0046] Explanation of reference numerals in the attached drawings: 100-convex copper pillar, 101-first metal catalyst, 102-second metal connecting structure, 200-resin. Detailed Implementation

[0047] The present application will be further described in detail below with reference to the embodiments and examples. These embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to enable a more thorough and comprehensive understanding of the disclosure of the present application. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0049] To address the issues of poor connection reliability and stringent process requirements in traditional copper-copper bonding methods, this application describes a copper-copper bonding method that utilizes convex copper pillars with protruding ends. A first metal catalyst is selectively deposited on the surface of the protruding ends of these pillars to prepare the copper pillars to be bonded, giving the protruding ends catalytic activity for subsequent formation of a second metal bonding structure. Then, the protruding ends of the copper pillars to be bonded are positioned relative to each other with a spacing of less than 10 μm, and a chemical plating process is used to deposit the second metal bonding structure between the two protruding ends. During the chemical plating process, the required growth amount of the second metal gradually decreases along the direction extending from the tip of the protruding ends to both sides, which facilitates the discharge of hydrogen gas generated during the chemical plating process, reduces the formation of voids in the copper-copper bonding structure, and significantly improves the conductivity and bonding strength of the copper-copper bonding structure. Simultaneously, the process conditions of this application greatly reduce the requirements for solder joint coplanarity and alignment accuracy, allowing for alignment errors within 10 μm, which also significantly improves the production yield and reliability of the process method.

[0050] The first aspect of this application provides a copper-to-copper connection method, comprising the following steps:

[0051] A convex copper pillar is used, and a first metal catalyst is deposited on the surface of the convex end of the convex copper pillar through a salt solution containing a first metal catalyst to prepare a copper pillar to be connected.

[0052] The protruding ends of the copper pillars to be connected are arranged relative to each other with a spacing of less than 10 μm, and a second metal connection structure is deposited between the two protruding ends by chemical plating to achieve copper-copper connection.

[0053] The first metal catalyst includes at least one of palladium, nickel, silver, and platinum;

[0054] The second metal includes at least one of copper, nickel, gold, and silver.

[0055] The copper-copper bonding method described in this application uses convex copper pillars with protruding ends, eliminating the need for flat, smooth surfaces. This significantly reduces the requirements for coplanar consistency and alignment accuracy between the convex copper pillars, allowing for alignment deviations within 10 μm. Specifically, by selectively depositing a first metal catalyst on the surface of the protruding ends of the convex copper pillars, and then using chemical plating to deposit a second metal bonding structure to "bind" the copper-copper connections, the required growth amount of the second metal gradually decreases along the direction extending from the tip of the protruding ends to both sides—that is, "the second metal grows from the inside out." This significantly reduces the bubble inclusion content in the copper-copper bonding structure, decreases void formation, and improves the strength and reliability of the copper-copper bonding.

[0056] In this application, the protruding end of the convex copper pillar refers to the part of the convex copper pillar that needs to be connected during the copper-copper connection process.

[0057] In this application, the convex copper pillar contains at least one protruding end.

[0058] In some embodiments, the second metal comprises an alloy of two or more metallic elements selected from copper, nickel, gold, and silver, and may be a copper-nickel alloy, a copper-gold alloy, or a copper-silver alloy.

[0059] In some embodiments, the salt solution comprising the first metal catalyst comprises a salt of the first metal catalyst and a pH adjuster; and / or,

[0060] The pH of the salt solution including the first metal catalyst is 1.5-11.5, and can be 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11 or 11.5.

[0061] In some embodiments, the salt of the first metal catalyst includes at least one selected from palladium, nickel, gold, silver and platinum.

[0062] In some embodiments, the palladium salt includes at least one of palladium sulfate, palladium chloride, palladium nitrate, and dichlorotetraminepalladium.

[0063] In some embodiments, the nickel salt includes at least one of nickel sulfate, nickel chloride, nickel carbonate, and nickel aminosulfonate.

[0064] In some embodiments, the gold salt includes at least one of potassium gold cyanide, sodium gold sulfite, and chloroauric acid.

[0065] In some embodiments, the silver salt includes at least one of silver nitrate, silver acetate, and silver methanesulfonate.

[0066] In some embodiments, the platinum salt includes at least one of platinum tetrachloride, sodium hexahydroxyplatinate, potassium hexahydroxyplatinate, and diammonium platinum nitrite.

[0067] In some embodiments, the concentration of the first metal catalyst ion in the salt of the first metal catalyst is 0.01 g / L-213 g / L, and can be 0.01 g / L, 0.05 g / L, 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.5 g / L, 1 g / L, 2 g / L, 5 g / L, 8 g / L, 9.11 g / L, 10 g / L, 61 g / L or 213 g / L.

[0068] In some embodiments, the salt solution comprising the first metal catalyst further includes an auxiliary agent.

[0069] In some embodiments, the adjuvant includes at least one selected from ethylene glycol, ethylenediamine, sodium chloride, ammonium chloride, stannous chloride, and 2,4,6-trimethylpyridine.

[0070] In some embodiments, the concentration of the auxiliary agent in the salt solution comprising the first metal catalyst is 0.01 g / L to 10 g / L, and can be 0.01 g / L, 0.05 g / L, 0.1 g / L, 0.2 g / L, 0.25 g / L, 0.5 g / L, 1 g / L, 2 g / L, 5 g / L, 8 g / L, or 10 g / L.

[0071] In some embodiments, in the salt solution comprising the first metal catalyst, the auxiliary is composed of ethylenediamine and 2,4,6-trimethylpyridine in a mass ratio of 0.22:0.43.

[0072] In some embodiments, the auxiliary in the salt solution comprising the first metal catalyst is composed of ammonium chloride, ethylenediamine, and concentrated sulfuric acid.

[0073] In some embodiments, the pH adjuster includes an acidic adjuster and / or an alkaline adjuster.

[0074] In some embodiments, the acidity modifier includes at least one selected from perchloric acid, aminosulfonic acid, sulfuric acid, hydrochloric acid, nitric acid, boric acid, methanesulfonic acid, and citric acid.

[0075] In some embodiments, the alkalinity adjuster includes at least one of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, and ammonia.

[0076] In some embodiments, the concentration of the pH adjuster in the salt solution comprising the first metal catalyst is 0.001 g / L to 75 g / L, and can be 0.001 g / L, 0.005 g / L, 0.01 g / L, 0.1 g / L, 0.2 g / L, 0.24 g / L, 0.285 g / L, 0.5 g / L, 0.6 g / L, 0.8 g / L, 1 g / L, 1.5 g / L, 2 g / L, 5 g / L, 10 g / L, 30 g / L, or 75 g / L.

[0077] In this application, the solvent in the salt solution containing the first metal catalyst is water.

[0078] In some embodiments, the step of depositing a first metal catalyst on the surface of the protruding end of the convex copper pillar specifically includes:

[0079] The surface of the protruding end of the convex copper pillar is immersed in a salt solution containing a first metal catalyst to deposit the first metal catalyst; wherein the immersion conditions include: a time of 1-6 min, which can be 1 min, 2 min, 3 min, 4 min, 5 min, or 6 min; and a temperature of 20-60℃, which can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, or 60℃; or,

[0080] A first metal catalyst is electrodeposited on the surface of the protruding end of the convex copper pillar using an electroplating method. The electroplating conditions include: a voltage of 0.2-6V (0.2V, 0.3V, 0.4V, 0.5V, or 0.6V) or a current density of 1-2 ASD (1ASD, 1.2ASD, 1.5ASD, 1.8ASD, or 2ASD); a temperature of 20-70℃ (25℃, 30℃, 40℃, 50℃, 60℃, or 70℃); and a time of 1-2 min (1 min, 1.2 min, 1.5 min, 1.8 min, or 2 min).

[0081] In some embodiments, the step of depositing the first metal catalyst on the surface of the protruding end of the convex copper pillar using a salt solution comprising the first metal catalyst specifically includes:

[0082] After being soaked in a salt solution of a first metal catalyst, the protruding end surface of the convex copper pillar is transferred to a dimethylamine borane (DMAB) aqueous solution for reduction, and the first metal catalyst is deposited on the protruding end surface of the convex copper pillar.

[0083] In some embodiments, the mass concentration of the dimethylamine borane (DMAB) aqueous solution is 5%; the reduction conditions include a temperature of 25°C and a time of 1 min.

[0084] In some embodiments, the convex copper pillar includes a protruding end and a bottom coplanar with the protruding end; the bottom surface of the protruding end is circular, square, or irregular in shape.

[0085] In some embodiments, the maximum outer diameter of the protruding end is 2R, and the height of the protruding end is 0.05R-0.6R, which can be 0.05R, 0.075R, 0.08R, 0.1R, 0.15R, 0.16R, 0.2R, 0.3R, 0.4R, 0.5R, 0.52R, 0.53R, or 0.6R.

[0086] In some implementations, see Figure 1 The convex copper pillar consists of a protruding end and a bottom that is coplanar with the protruding end; the maximum outer diameter of the protruding end is 2R, and the height of the protruding end (let's call it h) is 0.05R-0.6R.

[0087] In some embodiments, before depositing the first metal catalyst on the surface of the protruding end of the convex copper pillar, a step of resin coating on the surface of the convex copper pillar other than the protruding end is included. For a method of selectively depositing the first metal catalyst on the surface of the protruding end of the convex copper pillar, see [link to relevant documentation]. Figure 2 Specifically, the surface of the convex copper pillar 100 other than the protruding end is coated with resin so that the surface of the convex copper pillar 100 other than the protruding end is coated with resin 200. Then, a first metal catalyst 101 is selectively deposited on the surface of the protruding end of the convex copper pillar 100 to form a copper pillar to be connected composed of the convex copper pillar 100 and the first metal catalyst 101.

[0088] In some embodiments, before electroless plating to deposit the second metal connection structure, a step of removing the resin coating on the surface of the copper pillars to be connected is included.

[0089] In the copper-copper bonding step, the coating resin is removed before the step of depositing the second metal bonding structure, leaving a gap around the copper pillars to be bonded for microfluidic heat dissipation, thereby improving the overall performance of the system.

[0090] In some embodiments, the step of achieving a copper-copper connection by chemically depositing a second metal connection structure between the two protruding ends specifically includes:

[0091] Chemical plating is performed by adding a chemical plating solution containing a second metal salt between the two protruding ends, so that a second metal is deposited between the two protruding ends to form a second metal connection structure, thereby realizing a copper-copper connection.

[0092] The electroless plating solution containing the second metal salt includes the second metal salt, a reducing agent, and a complexing agent.

[0093] In this application, the solvent in the chemical plating solution containing the second metal salt is water.

[0094] In some embodiments, the conditions for electroless plating include: a temperature of 36-86°C, which can be 36°C, 40°C, 50°C, 60°C, 70°C, 80°C or 86°C; and a time of 5 min-120 min, which can be 5 min, 7 min, 10 min, 20 min, 25 min, 30 min, 50 min, 80 min, 100 min or 120 min.

[0095] Figure 3 This is a schematic diagram showing the relative arrangement of the copper pillars to be connected in a copper-to-copper connection. Figure 4 This is a schematic diagram of a copper-to-copper connection structure. (See also...) Figures 3-4 This application achieves copper-copper connection by setting the protruding ends of the copper pillars to be connected opposite each other, setting the first metal catalysts 101 of the copper pillars to be connected opposite each other in pairs, and then using a chemical plating solution to deposit a second metal connection structure 102 between the copper pillars to be connected.

[0096] In some embodiments, the electroless plating solution includes: a thick copper plating solution, model EC-2, purchased from Guangdong Dongshuo Technology Co., Ltd.; a gold plating solution, model SRG, purchased from MK in South Korea; and a nickel plating solution, model 5183, purchased from Guangdong Dongshuo Technology Co., Ltd.

[0097] The second aspect of this application provides the application of the copper-copper interconnection method described in the first aspect in chip packaging.

[0098] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0099] In this application, the sources of the raw materials in the embodiments are as follows:

[0100] Resin adhesive: purchased from DuPont, model SAF2120;

[0101] Thick copper: purchased from Guangdong Dongshuo Technology, model EC-2;

[0102] Gold-dissolving solution: purchased from MK in South Korea, model SRG;

[0103] Nickel melting solution: purchased from Guangdong Dongshuo Technology, model number 5183.

[0104] Example 1

[0105] The specific steps for copper-to-copper connection are as follows:

[0106] Select two convex copper pillars with protruding ends, and the convex copper pillars are chiral and symmetrical. Each convex copper pillar (composed of copper) consists of a cylindrical base and protruding ends located on and coplanar with the cylindrical base (see [reference]). Figure 1 The diameter of the bottom surface (circular bottom surface) of the protruding end is 400µm (set as 2R), and the height of the protruding end is 30µm (set as h, h=0.15R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0107] Resin adhesive is used to cover the perimeter of the convex copper post, excluding the protruding end, as well as other conductor surfaces, leaving only the protruding end of the convex copper post exposed, in order to enable subsequent copper-copper connections. A convex copper pillar covered with resin adhesive is immersed in a salt solution containing a first metal catalyst (composed of 0.2 g / L PdSO4, 0.24 g / L concentrated hydrochloric acid, 0.22 g / L ethylene glycol, 0.43 g / L 2,4,6-trimethylpyridine, and the balance water) at 55°C for 1 min. Then, it is immersed in a 5% (w / w) aqueous solution of dimethylamine borane (DMAB) at room temperature (25°C) for 1 min to reduce the convex end surface, depositing the first metal catalyst palladium on the surface of the convex end. The covering resin adhesive is then removed. The convex ends of the convex copper pillars of the two circuit boards after the first metal catalyst deposition are arranged opposite each other, ensuring that the tops of the opposite convex ends of the two circuit boards are 5-8 μm apart. A thickened copper solution is injected between the two boards for chemical plating at 36°C for 50 min, depositing a second metal (copper) between the two convex ends to form a second metal connection structure, thus achieving a copper-copper connection. After the connection is completed, rinse the residual liquid with deionized water and dry it with nitrogen to obtain a copper-copper connected circuit board.

[0108] Example 2

[0109] The specific steps for copper-to-copper connection are as follows:

[0110] Two convex copper pillars with protruding ends are selected as encapsulation substrates, and the convex copper pillars are chiral and symmetrical. The convex copper pillars (composed of copper) of the two encapsulation substrates are composed of a cylindrical base and a protruding end located on the cylindrical base and coplanar with it. The diameter of the bottom surface (circular bottom surface) of the protruding end is 25µm (set as 2R), and the height of the protruding end is 5µm (set as h, h=0.4R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0111] Resin adhesive is used to cover the circumference and other conductive surfaces of the convex copper pillars, leaving only the convex ends exposed, to facilitate subsequent copper-copper bonding. The resin-coated convex copper pillars are then immersed in a salt solution containing a first metal catalyst (composed of 0.15 g / L palladium sulfate, 0.4 g / L ammonium chloride, 0.02 g / L ethylenediamine, 1.84 g / L concentrated sulfuric acid, and the remainder water) at 45°C for 1 minute, depositing the first metal catalyst palladium on the surface of the convex ends. The resin adhesive is then removed. The convex ends of the two circuit boards with the first metal catalyst deposited are positioned opposite each other, ensuring a 0-0.2 μm distance between the tips of the opposing convex ends. A chemical plating solution is injected between the two boards at 86°C for 30 minutes, depositing the second metal (gold) to achieve copper-copper bonding. After bonding, the residual liquid is rinsed with deionized water and dried with nitrogen gas to obtain the copper-copper bonded circuit board.

[0112] Example 3

[0113] The specific steps for copper-to-copper connection are as follows:

[0114] Two convex copper pillars with protruding ends are selected, and the convex copper pillars are chiral symmetrical. The convex bumps (composed of copper) of the two circuit boards are composed of a square base and a protruding end located on the square base and coplanar with it. The side length of the bottom surface (square bottom surface) of the protruding end is 100µm (set as 2R), and the height of the protruding end is 30µm (set as h, h=0.6R). The square base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0115] Resin adhesive is used to cover the circumference and other conductive surfaces of the convex copper pillars, leaving only the convex ends exposed, to facilitate subsequent copper-copper bonding. The resin-coated copper pillar bumps are then immersed in a salt solution containing a first metal catalyst (composed of 0.15 g / L palladium sulfate, 0.4 g / L ammonium chloride, 0.02 g / L ethylenediamine, 1.84 g / L concentrated sulfuric acid, and the remainder water) at 50°C for 1 minute, depositing the first metal catalyst palladium on the surface of the convex ends. The resin adhesive is then removed. The convex ends of the two circuit boards with the first metal catalyst deposited are positioned opposite each other, ensuring a 2-5 μm distance between the tips of the opposing convex ends. Nickel plating solution is injected between the two boards for chemical plating at 83°C for 25 minutes, depositing the second metal (nickel), thus achieving copper-copper bonding. After bonding, the remaining liquid is rinsed with deionized water and dried with nitrogen gas to obtain the copper-copper bonded circuit board.

[0116] Example 4

[0117] The specific steps for copper-to-copper connection are as follows:

[0118] Two high-bandwidth memory chips with convex copper pillars having protruding ends are selected. The convex copper pillars (composed of copper) of the two high-bandwidth memory chips are composed of a cylindrical base and a protruding end located on the cylindrical base and coplanar with it. The diameter of the bottom surface (circular bottom surface) of the protruding end is 25µm (set as 2R), and the height of the protruding end is 5µm (set as h, h=0.4R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0119] Resin adhesive is used to cover the perimeter and other conductive surfaces of the convex copper pillars, leaving only the convex ends exposed, to facilitate subsequent copper-copper bonding. The resin-coated convex copper pillars are then immersed in a salt solution containing a first metal catalyst (composed of 213 g / L palladium nitrate, 10 g / L perchloric acid, and the remainder water) and electroplated at 0.3V and 50°C for 1 minute, depositing the first metal catalyst palladium on the surface of the convex ends. The resin adhesive is then removed. The convex ends of the two circuit boards with the first metal catalyst deposited are positioned opposite each other, ensuring a 0-1 μm distance between the tips of the opposing convex ends of the two first high-bandwidth memory chips. Thickened copper is injected between the two boards for chemical plating at 36°C for 5 minutes, depositing the second metal (copper) to achieve copper-copper bonding. After bonding, the residual liquid is rinsed with deionized water and dried with nitrogen to obtain the copper-copper bonded high-bandwidth memory chip.

[0120] Example 5

[0121] The specific steps for copper-to-copper connection are as follows:

[0122] Two glass substrates with convex copper pillars at protruding ends are selected, and the convex copper pillars are chirally symmetrical. One glass substrate has a convex copper pillar (composed of copper) consisting of a cylindrical base and a protruding end located on and coplanar with the cylindrical base. The diameter of the bottom surface (circular bottom surface) of the protruding end is 50µm (set as 2R), and the height of the protruding end is 13µm (set as h, h=0.52R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry... The first central axis of symmetry coincides with the second central axis of symmetry; the convex copper pillar (composed of copper) of the other glass substrate consists of a square base and a protruding end located on the square base and coplanar with it. The diagonal length of the bottom surface of the protruding end (square bottom surface, side length of 40µm) is 56.57µm (set as 2R), and the height of the protruding end is 15µm (set as h, h=0.53R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0123] Resin adhesive is used to cover the perimeter and other conductive surfaces of the convex copper pillars, leaving only the convex ends exposed, to facilitate subsequent copper-copper bonding. The resin-coated convex copper pillars are then immersed in a salt solution containing a first metal catalyst (composed of 240 g / L nickel sulfate hexahydrate, 30 g / L nickel chloride hexahydrate, 30 g / L boric acid, and the remainder water). Electroplating is performed at a current density of 2 ASD and a temperature of 50°C for 1 minute to deposit the first metal catalyst nickel on the surface of the convex ends. The resin adhesive is then removed. The convex ends of the two glass substrates with deposited first metal catalyst are positioned opposite each other, ensuring a distance of 0-2 μm between the tips of the opposing convex ends. Thickened copper is injected between the two substrates for chemical plating at a temperature of 36°C for 7 minutes. After deposition of the second metal (copper), copper-copper bonding is achieved. After bonding, the residual liquid is cleaned with deionized water and dried with nitrogen to obtain the copper-copper bonded glass substrates.

[0124] Example 6

[0125] The specific steps for copper-to-copper connection are as follows:

[0126] Two convex copper pillars with protruding ends are selected, and the convex copper pillars are chiral symmetrical. The convex copper pillars (composed of copper) of the two circuit boards are composed of a square base and a protruding end located on the square base and coplanar with it. The side length of the bottom surface (square bottom surface) of the protruding end is 100µm (set as 2R), and the height of the protruding end is 30µm (set as h, h=0.6R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0127] Resin adhesive is used to cover the perimeter and other conductive surfaces of the convex copper pillars, leaving only the convex ends exposed, to facilitate subsequent copper-copper bonding. The resin-coated convex copper pillars are then immersed in a salt solution containing a first metal catalyst (composed of 1 g / L silver methanesulfonate, 0.285 g / L methanesulfonic acid, and the remainder water) and electroplated at 4V and 25°C for 2 minutes to deposit a first metal catalyst silver layer on the surface of the convex ends. The resin adhesive is then removed. The convex ends of the two circuit boards with the first metal catalyst deposited are positioned opposite each other, ensuring a 0-2 μm distance between the tips of the opposing convex ends. Thickened copper is injected between the two boards for chemical plating at 36°C for 10 minutes, depositing a second metal (copper) to achieve copper-copper bonding. After bonding, the residual liquid is rinsed with deionized water and dried with nitrogen to obtain a high-bandwidth memory chip with copper-copper bonding.

[0128] Example 7

[0129] The specific steps for copper-to-copper connection are as follows:

[0130] Two high-bandwidth memory chips with protruding copper pillars and chiral symmetry are selected. The protruding copper pillars (composed of copper) of the two high-bandwidth memory chips are composed of a cylindrical base and a protruding end located on the cylindrical base and coplanar with it. The diameter of the bottom surface (circular bottom surface) of the protruding end is 50µm (set as 2R), and the height of the protruding end is 10µm (set as h, h=0.4R). The cylindrical base has a first central axis of symmetry perpendicular to the bottom surface of the protruding end, and the protruding end has a second central axis of symmetry perpendicular to the bottom surface of the protruding end. The first central axis of symmetry and the second central axis of symmetry coincide.

[0131] Resin adhesive is used to cover the perimeter and other conductive surfaces of the convex copper pillars, leaving only the convex ends exposed, to facilitate subsequent copper-copper bonding. The resin-coated convex copper pillars are then immersed in a salt solution containing a first metal catalyst (composed of 15 g / L diammonium nitrite platinum, 75 g / L sulfamic acid, and the remainder water) and electroplated at 2 ASD current density and 70°C for 2 minutes to deposit the first metal catalyst platinum on the surface of the convex ends. The resin adhesive is then removed. The convex ends of the two convex copper pillars on the two circuit boards with the first metal catalyst deposited are positioned opposite each other, ensuring a distance of 0-2 μm between the tips of the opposing convex ends. Thickened copper is injected between the two boards for chemical plating at 36°C for 10 minutes, depositing the second metal (copper) to achieve copper-copper bonding. After bonding, the residual liquid is rinsed with deionized water and dried with nitrogen to obtain a high-bandwidth memory chip with copper-copper bonding.

[0132] Experimental Example 1

[0133] Simulated tests were performed on the copper-copper connection strength of the circuit boards / packaging substrates / high-bandwidth memory chips obtained in Examples 1-7, respectively. The test methods were as follows:

[0134] Select a single copper-copper connection structure from a circuit board / packaging substrate / high-bandwidth memory chip, connect one end of the structure to a copper wire, and perform a tensile test. Test ten copper-copper connection structures in each group, and take the average value as the test result.

[0135] Test equipment: Microcomputer-controlled electronic universal testing machine, model CMT6502, from METS Industrial Systems (China) Co., Ltd.

[0136] Implementation standard: GB / T 228-2002;

[0137] Test conditions: Displacement control, speed 50.0 mm / min.

[0138] Record the maximum separation force, i.e., peak force, of the copper-copper joint; and observe the fracture mode of the copper-copper joint structure. The results are shown in Table 1.

[0139] Table 1. Copper-copper joint strength results

[0140]

[0141] As can be seen from the data in Table 1:

[0142] The peak force of the copper-copper connection in Examples 1-7 of this application is in the range of 6.942N-116.305N. Both fracture modes occur on the original structure of the copper pillar bump, and no fracture occurs at the copper-copper connection. This shows that the copper-copper connection in Examples 1-7 is very reliable and there is no failure of the copper-copper connection.

[0143] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0144] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A copper-to-copper connection method, characterized in that, Includes the following steps: A convex copper pillar is used, and a first metal catalyst is deposited on the surface of the convex end of the convex copper pillar through a salt solution containing a first metal catalyst to prepare a copper pillar to be connected. The protruding ends of the copper pillars to be connected are arranged relative to each other with a spacing of less than 10 μm, and a second metal connection structure is deposited between the two protruding ends by chemical plating to achieve copper-copper connection. The first metal catalyst includes at least one of palladium, nickel, silver, and platinum; The second metal includes at least one of copper, nickel, gold, and silver.

2. The copper-copper connection method according to claim 1, characterized in that, The salt solution comprising the first metal catalyst comprises a salt of the first metal catalyst and a pH adjuster; and / or, The pH of the salt solution containing the first metal catalyst is 1.5-11.

5.

3. The copper-copper connection method according to claim 2, characterized in that, It meets at least one of the following characteristics: (1) The salt of the first metal catalyst includes at least one of palladium salt, nickel salt, gold salt, silver salt and platinum salt; Optionally, the palladium salt includes at least one of palladium sulfate, palladium chloride, palladium nitrate, and dichlorotetraminepalladium; Optionally, the nickel salt includes at least one of nickel sulfate, nickel chloride, nickel carbonate, and nickel aminosulfonate; Optionally, the gold salt includes at least one of potassium gold cyanide, sodium gold sulfite, and chloroauric acid; Optionally, the silver salt includes at least one of silver nitrate, silver acetate, and silver methanesulfonate; Optionally, the platinum salt includes at least one of platinum tetrachloride, sodium hexahydroxyplatinate, potassium hexahydroxyplatinate, and diammonium platinum nitrite; (2) In the salt of the first metal catalyst, the concentration of the first metal catalyst ion is 0.01 g / L-213 g / L; (3) The salt solution comprising the first metal catalyst further comprises an auxiliary agent; Optionally, the auxiliary agent includes at least one selected from ethylene glycol, ethylenediamine, sodium chloride, ammonium chloride, stannous chloride, and 2,4,6-trimethylpyridine; Optionally, in the salt solution comprising the first metal catalyst, the concentration of the auxiliary agent is 0.01 g / L to 10 g / L; (4) The pH adjuster includes acidic adjusters and / or alkaline adjusters; Optionally, the acidity modifier includes at least one of perchloric acid, aminosulfonic acid, sulfuric acid, hydrochloric acid, nitric acid, boric acid, methanesulfonic acid, and citric acid; Optionally, the alkalinity adjuster includes at least one of sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, and ammonia water; (5) In the salt solution containing the first metal catalyst, the concentration of the pH adjuster is 0.001 g / L to 75 g / L.

4. The copper-to-copper connection method according to claim 1, characterized in that, The step of depositing a first metal catalyst on the surface of the protruding end of the convex copper pillar specifically includes: The surface of the protruding end of the convex copper pillar is immersed in a salt solution containing a first metal catalyst to deposit the first metal catalyst; wherein the immersion conditions include: time of 1 min-6 min; temperature of 20℃-60℃; or, A first metal catalyst is electrodeposited on the surface of the protruding end of the convex copper pillar by electroplating; wherein the electroplating conditions include: voltage of 0.2V-6V, or current density of 1ASD-2ASD; temperature of 20℃-70℃; and time of 1min-2min.

5. The copper-copper connection method according to claim 1, characterized in that, The convex copper pillar includes a protruding end and a bottom that is coplanar with the protruding end; The bottom surface of the protruding end is circular, square, or irregular in shape; Optionally, the maximum outer diameter of the protruding end is 2R, and the height of the protruding end is 0.05R-0.6R.

6. The copper-copper connection method according to claim 1, characterized in that, Before depositing the first metal catalyst on the surface of the protruding end of the convex copper pillar, the method further includes a step of coating the surface of the convex copper pillar other than the protruding end with resin.

7. The copper-copper connection method according to claim 6, characterized in that, Before electroless plating to deposit the second metal connection structure, the process also includes a step of removing the resin coating on the surface of the copper pillars to be connected.

8. The copper-copper connection method according to claim 1, characterized in that, The specific steps for achieving a copper-copper connection by chemically depositing a second metal connection structure between the two protruding ends include: Chemical plating is performed by adding a chemical plating solution containing a second metal salt between the two protruding ends, so that a second metal is deposited between the two protruding ends to form a second metal connection structure, thereby realizing a copper-copper connection. The electroless plating solution containing the second metal salt includes the second metal salt, a reducing agent, and a complexing agent.

9. The copper-copper connection method according to claim 1 or 8, characterized in that, The conditions for electroless plating include: temperature of 30℃-90℃ and time of 5min-120min.

10. The application of the copper-copper interconnection method as described in any one of claims 1-9 in chip packaging.

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