Copper surface nanocrystallization interface preparation method based on vacuum sputtering

Abstract

The invention discloses a copper surface nanocrystallization interface preparation method based on vacuum sputtering, and the method comprises the following specific steps: S1, substrate pretreatment: sequentially carrying out acetone and ethanol ultrasonic cleaning and nitrogen blow-drying on an oxygen-free copper substrate, then placing the oxygen-free copper substrate in a vacuum cavity, and carrying out Ar plasma etching to remove surface oxides and form a nanoscale rough surface; s2, magnetron sputtering deposition is conducted, specifically, a direct-current magnetron sputtering system is adopted, metal nanoparticles are deposited on the surface of the substrate, the sputtering power is 50-250 W, and high-purity Ar serves as working gas; s3, electron beam irradiation: carrying out electron beam treatment on the deposited sample under the conditions that the beam density is 1-5 A / cm, the irradiation time is 5-30 minutes and the acceleration voltage is 5-20 kV; and S4, annealing treatment is conducted in the reducing atmosphere. The porosity is reduced, and the density and uniformity of a sintered body are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface engineering, and in particular relates to a method for preparing a nanometer interface on a copper surface based on vacuum sputtering. Background Art

[0002] As third-generation semiconductor devices such as silicon carbide (SiC) and gallium nitride (GaN) evolve toward high frequencies, high voltages, and temperatures exceeding 300°C, traditional Sn-based solders with a melting point below 250°C are no longer sufficient for package interconnects. By combining Cu, Ag, and Au nanoparticle layers on a copper substrate with interface engineering and low-temperature sintering technology, interconnect performance can be significantly improved. The package interconnect materials used in third-generation power semiconductor devices primarily include nanosilver and nanocopper pastes. These nanomaterials, thanks to their size effect, exhibit lower melting points and larger surface areas than traditional bulk materials, making them more active during the interconnection process. This means that nanoscale interconnects can be achieved at lower temperatures. Numerous studies have confirmed that nanocopper and nanosilver particles can be sintered at low temperatures, and the resulting composites have melting points comparable to bulk metals, meeting the application requirements of "low-temperature formation and high-temperature service."

[0003] The application of nanostructured interfaces in the sintering process is currently becoming increasingly important. In chip manufacturing, nanostructured interfaces, due to their unique physical properties, can significantly increase sintering rates. The high surface energy and activity of nanoparticles increase the atomic diffusion rate, thereby accelerating the sintering process. The density and uniformity of the sintered structure directly impact the quality of chip interconnects. Traditional sintering methods often struggle to completely eliminate porosity, resulting in a loose sintered structure that compromises mechanical and electrical properties. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to address the deficiencies in the prior art and provide a method for preparing a nanostructured copper surface interface based on vacuum sputtering.

[0005] A method for preparing a nanostructured copper surface interface based on vacuum sputtering, comprising the following steps: S1. Substrate Pretreatment: The oxygen-free copper substrate was ultrasonically cleaned with acetone and ethanol, dried with nitrogen, and then placed in a vacuum chamber for Ar plasma etching at a power of 30-80 W for 3-10 minutes to remove surface oxides and form a nanoscale roughened surface. S2. Magnetron sputtering deposition: Metal nanoparticles are deposited on the substrate surface using a DC magnetron sputtering system. The sputtering power is 50-250 W, the working gas is high-purity Ar with a flow rate of 10-50 sccm, the sputtering pressure is 0.5-3.0 Pa, the substrate temperature is 25-400°C, and the sputtering time is 1-30 minutes. S3. Electron beam irradiation: The deposited sample is subjected to electron beam treatment with a beam current density of 1 to 5 A / cm², an irradiation time of 5 to 30 minutes, and an accelerating voltage of 5 to 20 kV. S4. Perform annealing in a reducing atmosphere.

[0006] A further improvement of the present invention is that in step S1, the power of the Ar plasma etching is 50 W and the time is 5 minutes.

[0007] A further improvement of the present invention is that in step S2, the metal nanoparticles are Ag nanoparticles, the sputtering power is 50-200 W, and the substrate temperature is 25-300°C.

[0008] A further improvement of the present invention is that in step S2, the metal nanoparticles are Au nanoparticles, the sputtering power is 50-200 W, and the substrate temperature is 25-300°C.

[0009] A further improvement of the present invention is that in step S2, the metal nanoparticles are Cu nanoparticles, the sputtering power is 80-250 W, and the substrate temperature is 200-400°C.

[0010] A further improvement of the present invention is that in step S3, the scanning speed of the electron beam irradiation is 1 to 10 mm / s, the beam spot diameter is 0.1 to 2 mm, and the gap ratio of the nanoparticles after irradiation is ≤5%.

[0011] A further improvement of the present invention is that in step S4, the annealing temperature is 200-500°C.

[0012] A further improvement of the present invention is that, in step S4, the annealing treatment time is 30 to 120 minutes.

[0013] A further improvement of the present invention is that in step S4, the heating rate during the annealing treatment is 3-10°C / min.

[0014] Compared with the prior art, the method for preparing a nanostructured copper surface interface based on vacuum sputtering provided by the present invention achieves at least the following beneficial effects: The nanostructured interface formed by the present invention, through its tiny particle filling effect, can form a denser and more uniform sintered structure. Nanoparticles can fill smaller gaps, reducing porosity, thereby improving the density and uniformity of the sintered body. Combined with dynamic target material control, substrate crystal plane orientation optimization, and interface electronic engineering strategies, this method achieves high-density, uniform distribution of multiple metal nanoparticles and functional control. This method is feasible for industrial production and has the advantages of wide applicability, high bonding strength, and strong oxidation resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1Flowchart of the present invention. DETAILED DESCRIPTION

[0016] Various exemplary embodiments of the present invention will now be described in detail. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions, and values set forth in these embodiments do not limit the scope of the present invention. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0017] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0018] See Figure 1 , a method for preparing a nanostructured copper surface interface based on vacuum sputtering, the specific steps comprising: S1. Substrate Pretreatment: The oxygen-free copper substrate was ultrasonically cleaned with acetone and ethanol, dried with nitrogen, and then placed in a vacuum chamber for Ar plasma etching at a power of 30-80 W for 3-10 minutes to remove surface oxides and form a nanoscale roughened surface. S2. Magnetron sputtering deposition: Metal nanoparticles are deposited on the substrate surface using a DC magnetron sputtering system. The sputtering power is 50-250 W, the working gas is high-purity Ar with a flow rate of 10-50 sccm, the sputtering pressure is 0.5-3.0 Pa, the substrate temperature is 25-400°C, and the sputtering time is 1-30 minutes. S3. Electron beam irradiation: The deposited sample is subjected to electron beam treatment with a beam current density of 1 to 5 A / cm², an irradiation time of 5 to 30 minutes, and an accelerating voltage of 5 to 20 kV. S4. Perform annealing in a reducing atmosphere.

[0019] A further improvement of the present invention is that in step S1, the power of the Ar plasma etching is 50 W and the time is 5 minutes.

[0020] A further improvement of the present invention is that in step S2, the metal nanoparticles are Ag nanoparticles, the sputtering power is 50-200 W, and the substrate temperature is 25-300°C.

[0021] A further improvement of the present invention is that in step S2, the metal nanoparticles are Au nanoparticles, the sputtering power is 50-200 W, and the substrate temperature is 25-300°C.

[0022] A further improvement of the present invention is that in step S2, the metal nanoparticles are Cu nanoparticles, the sputtering power is 80-250 W, and the substrate temperature is 200-400°C.

[0023] A further improvement of the present invention is that in step S3, the scanning speed of the electron beam irradiation is 1 to 10 mm / s, the beam spot diameter is 0.1 to 2 mm, and the gap ratio of the nanoparticles after irradiation is ≤5%.

[0024] A further improvement of the present invention is that in step S4, the annealing temperature is 200-500°C.

[0025] A further improvement of the present invention is that, in step S4, the annealing treatment time is 30 to 120 minutes.

[0026] A further improvement of the present invention is that in step S4, the heating rate during the annealing treatment is 3-10°C / min.

[0027] Example 1: Preparation of Ag nanostructures on oxygen-free copper surface.

[0028] (1) Substrate pretreatment: Ultrasonic cleaning: To prevent impurities from interfering with film formation during sputtering, copper needs to be cleaned. Oxygen-free copper (OFC, purity ≥99.99%) samples are ultrasonically cleaned in acetone and ethanol for 10 minutes each. Plasma etching: The samples are placed in a vacuum chamber (background vacuum ≤5×10⁻ 4 Pa, Ar gas (flow rate 20 sccm), and an RF plasma source (power 50W, frequency 13.56 MHz) were turned on for 5 minutes of etching. During this process, Ar⁺ bombards the surface, removing the oxide layer (Cu₂O / CuO) and adsorbed gases, while also forming nanoscale pits, increasing surface activity and strengthening the sputtered layer's bonding strength.

[0029] (2) Ag nanoparticle sputtering deposition: An Ag target (99.999% purity, 60 mm diameter, 3 mm thickness) was used, with a sputtering power of 120 W (corresponding to a target current density of 0.8 A / cm²). The substrate temperature was set to 80°C, and sputtering was performed at a pressure of 1.5 Pa for 10 minutes.

[0030] (3) Post-processing optimization: Electron beam irradiation: High-energy electrons (10 keV) bombard the Ag nanoparticles, inducing surface atomic rearrangement and localized melting, filling the interparticle gaps. Electron beam evaporation parameters were set at a beam current density of 2 A / cm², an accelerating voltage of 10 kV, and a scanning speed of 5 mm / s for 10 minutes.

[0031] Annealing: Use a H2 / N2 (1:9) mixed atmosphere at 300°C for 60 minutes at a heating rate of 5°C / min. This can reduce residual oxides and inhibit oxidation of the Cu substrate.

[0032] Example 2: Preparation of Au nanostructures on oxygen-free copper surface.

[0033] (1) Substrate pretreatment: Ultrasonic cleaning: To prevent impurities from interfering with film formation during sputtering, copper needs to be cleaned. Oxygen-free copper (OFC, purity ≥99.99%) samples are ultrasonically cleaned in acetone and ethanol for 10 minutes each. Plasma etching: The samples are placed in a vacuum chamber (background vacuum ≤5×10⁻ 4 Pa, Ar gas (flow rate 20 sccm), and an RF plasma source (power 50W, frequency 13.56 MHz) were turned on for 5 minutes of etching. During this process, Ar⁺ bombards the surface, removing the oxide layer (Cu₂O / CuO) and adsorbed gases, while also forming nanoscale pits, increasing surface activity and strengthening the sputtered layer's bonding strength.

[0034] (2) Au nanoparticle sputtering deposition: An Au target (99.999% purity, 60 mm diameter, 3 mm thickness) was used, the sputtering power was 100 W, the substrate temperature was set to 200 °C, and the sputtering was carried out at a pressure of 1.0 Pa for 8 minutes.

[0035] (3) Post-processing optimization: Electron beam irradiation: The electron beam evaporator parameters were set to a beam current density of 3 A / cm², an accelerating voltage of 10 kV, and a scanning speed of 5 mm / s for 10 min.

[0036] Annealing treatment: using a H2 / N2 (1:9) mixed atmosphere, keeping the temperature at 250°C for 90 minutes, and heating rate of 5°C / min, to obtain uniform Au nanoparticles (particle size 30 nm).

[0037] Example 3: Preparation of Cu nanostructure on oxygen-free copper surface.

[0038] (1) Substrate pretreatment: Ultrasonic cleaning: To prevent impurities from interfering with film formation during sputtering, copper needs to be cleaned. Oxygen-free copper (OFC, purity ≥99.99%) samples are ultrasonically cleaned in acetone and ethanol for 10 minutes each. Plasma etching: The samples are placed in a vacuum chamber (background vacuum ≤5×10⁻ 4Pa, Ar gas (flow rate 20 sccm), and an RF plasma source (power 50W, frequency 13.56 MHz) were turned on for 5 minutes of etching. During this process, Ar⁺ bombards the surface, removing the oxide layer (Cu₂O / CuO) and adsorbed gases, while also forming nanoscale pits, increasing surface activity and strengthening the sputtered layer's bonding strength.

[0039] (2) Cu nanoparticle sputtering deposition: A Cu target (purity 99.999%, diameter 60 mm, thickness 3 mm) was used, the sputtering power was 180 W, the substrate temperature was set to 300 °C, and the sputtering was carried out at a pressure of 2.0 Pa for 20 minutes.

[0040] (3) Post-processing optimization: Direct annealing treatment: use H2 / N2 (1:9) mixed atmosphere, keep at 400℃ for 120 minutes, and heat up at a rate of 5℃ / min.

[0041] In summary, the present invention forms a nano-interface, and through its tiny particle filling effect, it can form a denser and more uniform sintered structure, which is suitable for fields such as electronic packaging, catalytic electrodes and flexible sensors, ensuring product quality.

[0042] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A method for preparing a nanostructured copper surface interface based on vacuum sputtering, characterized in that: The specific steps include: S1. Substrate Pretreatment: The oxygen-free copper substrate was ultrasonically cleaned with acetone and ethanol, dried with nitrogen, and then placed in a vacuum chamber for Ar plasma etching at a power of 30-80 W for 3-10 minutes to remove surface oxides and form a nanoscale roughened surface. S2. Magnetron sputtering deposition: Metal nanoparticles are deposited on the substrate surface using a DC magnetron sputtering system. The sputtering power is 50-250 W, the working gas is high-purity Ar with a flow rate of 10-50 sccm, the sputtering pressure is 0.5-3.0 Pa, the substrate temperature is 25-400°C, and the sputtering time is 1-30 minutes. S3. Electron beam irradiation: The deposited sample is subjected to electron beam treatment with a beam current density of 1 to 5 A / cm², an irradiation time of 5 to 30 minutes, and an accelerating voltage of 5 to 20 kV. S4. Perform annealing in a reducing atmosphere.

2. The method for preparing a copper surface nanostructured interface based on vacuum sputtering according to claim 1, characterized in that: In step S1, the power of Ar plasma etching is 50 W and the etching time is 5 minutes.

3. The method for preparing a copper surface nanostructured interface based on vacuum sputtering according to claim 1, characterized in that: In the step S2, the metal nanoparticles are Ag nanoparticles, the sputtering power is 50-200W, and the substrate temperature is 25-300°C.

4. The method for preparing a nanostructured copper surface interface based on vacuum sputtering according to claim 1, characterized in that: In the step S2, the metal nanoparticles are Au nanoparticles, the sputtering power is 50-200W, and the substrate temperature is 25-300°C.

5. The method for preparing a nanostructured copper surface interface based on vacuum sputtering according to claim 1, wherein: In step S2, the metal nanoparticles are Cu nanoparticles, the sputtering power is 80-250 W, and the substrate temperature is 200-400°C.

6. The method for preparing a nanostructured copper surface interface based on vacuum sputtering according to claim 1, characterized in that: In step S3, the scanning speed of the electron beam irradiation is 1-10 mm / s, the beam spot diameter is 0.1-2 mm, and the gap ratio of the nanoparticles after irradiation is ≤5%.

7. The method for preparing a nanostructured copper surface interface based on vacuum sputtering according to claim 1, characterized in that: In step S4, the annealing temperature is 200-500°C.

8. The method for preparing a copper surface nanostructured interface based on vacuum sputtering according to claim 1, characterized in that: In the step S4, the annealing treatment time is 30 to 120 minutes.

9. The method for preparing a nanostructured copper surface interface based on vacuum sputtering according to claim 1, characterized in that: In the step S4, the heating rate during the annealing treatment is 3-10°C / min.

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