Twin copper-nickel alloy metal layer and method for manufacturing the same

Abstract

The present application provides a kind of bicrystal copper-nickel alloy metal layer, wherein more than 50% of the volume of the bicrystal copper-nickel alloy metal layer includes a plurality of bicrystal grains, the plurality of bicrystal grains includes a plurality of columnar bicrystal grains, and the nickel content in the bicrystal copper-nickel alloy metal layer is between 0.05at% and 20at%. Furthermore, the present application also provides a preparation method of the aforementioned bicrystal copper-nickel alloy metal layer.

Description

Technical Field

[0001] This invention provides a bicrystalline copper-nickel alloy metal layer and its preparation method, particularly a bicrystalline copper-nickel alloy metal layer with high hardness and its preparation method. Background Technology

[0002] Commonly known techniques often involve rolling or doping with other metals such as titanium (Ti), nickel (Ni), and zinc (Zn) to enhance the mechanical properties of copper. However, these techniques have the following drawbacks.

[0003] Strengthening copper foil containing copper grains through rolling deforms the pure copper grains, improving their mechanical properties but increasing resistance and thermal conductivity. Furthermore, doping other metals into the copper film creates an alloy that increases resistance and decreases conductivity. Moreover, the nanocrystalline copper film itself already possesses high strength; strengthening it through grain refinement may result in poor thermal stability.

[0004] In view of this, there is an urgent need to develop a novel nano-bicrystalline copper metal layer that, in addition to improving strength, retains the characteristics of nano-bicrystalline copper metal layers, so as to be applied to various electronic components. Summary of the Invention

[0005] One object of the present invention is to provide a bicrystalline copper-nickel alloy metal layer that retains the conductive properties of bicrystalline copper (high conductivity and low resistance) while also having excellent hardness.

[0006] In the bicrystalline copper-nickel alloy metal layer of the present invention, more than 50% of the volume of the bicrystalline copper-nickel alloy metal layer comprises a plurality of bicrystalline grains, which include a plurality of columnar bicrystalline grains, and the nickel content in the bicrystalline copper-nickel alloy metal layer is between 0.05 at% and 20 at%. Here, the volume percentage occupied by the aforementioned plurality of bicrystalline grains can be observed or measured from any cross-section of the bicrystalline copper-nickel alloy metal layer. Furthermore, the elemental content can be obtained, for example, by chemical analysis or field emission high-resolution electron microscopy (EPMA) analysis.

[0007] In addition, the present invention also provides a substrate comprising the aforementioned bicrystalline copper-nickel alloy metal layer, comprising: a substrate; and a bicrystalline copper-nickel alloy metal layer as described above, disposed on the substrate or embedded in the substrate.

[0008] Furthermore, the present invention also provides a method for preparing the aforementioned bicrystalline copper-nickel alloy metal layer, comprising the following steps: providing an electroplating apparatus, including an anode, a cathode, an electroplating solution, and a power supply, wherein the power supply is connected to the anode and the cathode respectively, and the anode and the cathode are immersed in the electroplating solution; and using the power supply to provide electricity for electroplating, thereby growing the aforementioned bicrystalline copper-nickel alloy metal layer from a surface of the cathode. The electroplating solution may include a copper salt, an acid, and a nickel salt.

[0009] In the preparation method of this invention, by adding an appropriate amount of nickel salt to the electroplating solution, a bicrystalline copper-nickel alloy metal layer can be formed through a simple co-plating process. Compared with conventional bicrystalline copper metal layers that do not include nickel, the bicrystalline copper-nickel alloy metal layer prepared by this invention, in addition to retaining the bicrystalline structure of bicrystalline copper metal layers that do not include nickel, also has a significantly improved hardness value. Therefore, the bicrystalline copper-nickel alloy metal layer provided by this invention, in addition to retaining the high electrical and thermal conductivity properties of bicrystalline copper metal layers that do not include nickel, also has high strength and can be applied to various electronic components.

[0010] In this invention, more than 50% of the volume of the bicrystalline copper-nickel alloy metal layer may include multiple bicrystalline grains. In one embodiment of the invention, for example, 50% to 99%, 50% to 95%, 50% to 90%, 55% to 90%, 60% to 90%, or 65% to 95% of the volume may include multiple bicrystalline grains; however, the invention is not limited thereto.

[0011] In this invention, the electroplating solution includes a copper salt and a nickel salt, thereby forming a bicrystalline copper-nickel alloy metal layer through co-plating. By adjusting the concentration of the nickel salt in the electroplating solution, a bicrystalline copper-nickel alloy metal layer with a specific nickel content can be formed through co-plating.

[0012] In this invention, the nickel content in the bicrystalline copper-nickel alloy metal layer can be between 0.05 at% and 20 at% with the balance being copper; however, this invention does not exclude the possibility of including other trace impurity metal elements. When the bicrystalline copper-nickel alloy metal layer contains a specific proportion of nickel, the formed bicrystalline copper-nickel alloy metal layer has an improved hardness value. In one embodiment of this invention, the nickel content can be, for example, between 0.1 at% and 20 at%, 0.1 at% and 15 at%, 0.1 at% and 10 at%, 0.1 at% and 5 at%, 0.1 at% and 3 at%, or 0.1 at% and 1 at%; however, this invention is not limited to these.

[0013] In this invention, the bicrystalline grains in the bicrystalline copper-nickel alloy metal layer can be formed by stacking multiple nano-bicrystalline grains along a direction within ±15 degrees of the

[111] crystal axis.

[0014] In one embodiment of the present invention, the bicrystalline grain may include a plurality of columnar bicrystalline grains, wherein the columnar bicrystalline grains may be formed by stacking a plurality of nano-bicrystalline grains along a direction within ±15 degrees along the

[111] crystal axis, and the angle between the stacking direction of at least a portion of the nano-bicrystalline grains and the thickness direction of the bicrystalline copper-nickel alloy metal layer is between 0 degrees and 20 degrees. When the columnar bicrystalline grains grow to the surface of the bicrystalline copper-nickel alloy metal layer, more than 50% of the surface area of ​​the bicrystalline copper-nickel alloy metal layer may expose the (111) plane of the nano-bicrystalline grains; at this time, the surface of the bicrystalline copper-nickel alloy metal layer of the present invention may have a preferred (111) orientation. In one embodiment of the present invention, the (111) facets of the nanocrystals exposed on the surface of the bicrystalline copper-nickel alloy metal layer may occupy, for example, 50% to 99%, 55% to 99%, 60% to 99%, 65% to 99%, 70% to 99%, 75% to 99%, 75% to 95%, or 75% to 90% of the total surface area of ​​the bicrystalline copper-nickel alloy metal layer; however, the present invention is not limited thereto. In one embodiment of the present invention, the (111) facets of the nanocrystals exposed on the surface of the bicrystalline copper-nickel alloy metal layer may occupy approximately 95% to 99% of the total surface area of ​​the bicrystalline copper-nickel alloy metal layer; however, the present invention is not limited thereto. Here, the preferred orientation of the surface of the nanocrystalline copper metal layer can be measured using an electron backscattering diffraction (EBSD) spectrometer.

[0015] In one embodiment of the present invention, when the bicrystalline grains of the bicrystalline copper-nickel alloy metal layer have a significant bicrystalline grain thickness and diameter ratio, for example, when the thickness is significantly greater than the diameter, the bicrystalline grains are columnar bicrystalline grains.

[0016] In another embodiment of the present invention, the bicrystalline copper-nickel alloy metal layer may include, in addition to the aforementioned columnar bicrystalline grains stacked within a ±15 degree range along the

[111] crystal axis, a plurality of fine grains whose nanocrystalline stacking direction does not have a preferred orientation, stacked on the columnar bicrystalline grains. The stacking direction (i.e., bicrystalline direction) of the nanocrystalline grains of the fine grains is not particularly limited, and the nanocrystalline grains exposed on the surface of the bicrystalline copper-nickel alloy metal layer may not have a preferred orientation; in other words, the surface of the bicrystalline copper-nickel alloy metal layer does not have a preferred orientation. The fine grains may not have a significant bicrystalline grain thickness and diameter ratio, and the diameter and thickness of the bicrystalline grains are also relatively small, for example, between 100 nm and 500 nm.

[0017] In another embodiment of the present invention, the bicrystalline copper-nickel alloy metal layer may include, in addition to the aforementioned columnar bicrystalline grains stacked along the

[111] crystal axis within a range of ±15 degrees, a plurality of oblique bicrystalline grains stacked on the columnar bicrystalline grains. The oblique bicrystalline grains may be formed by stacking nano-bicrystalline grains along the

[111] crystal axis within a range of ±15 degrees, and the angle between the stacking direction of at least a portion of the nano-bicrystalline grains and the thickness direction of the bicrystalline copper-nickel alloy metal layer may be between 10 degrees and 60 degrees. Since the oblique bicrystalline grains are grains intersecting the thickness direction of the bicrystalline copper-nickel alloy metal layer at the aforementioned angle, the nano-bicrystalline grains exposed on the surface of the bicrystalline copper-nickel alloy metal layer may not have a preferred orientation; in other words, the surface of the bicrystalline copper-nickel alloy metal layer does not have a preferred orientation.

[0018] In this invention, whether it is the aforementioned columnar bicrystalline grain, fine grain or oblique bicrystalline grain, at least a portion of the bicrystalline grains can be interconnected with each other. For example, 50%, 60%, 70%, 80%, 90% or more of the bicrystalline grains can be interconnected with each other.

[0019] In this invention, the thickness of the bicrystalline copper-nickel alloy metal layer can be adjusted as needed. In one embodiment of this invention, the thickness of the bicrystalline copper-nickel alloy metal layer may, for example, be between 0.1 μm and 500 μm, 0.1 μm and 400 μm, 0.1 μm and 300 μm, 0.1 μm and 200 μm, 0.1 μm and 100 μm, 0.1 μm and 80 μm, 0.1 μm and 50 μm, 1 μm and 50 μm, 2 μm and 50 μm, 3 μm and 50 μm, 4 μm and 50 μm, 5 μm and 50 μm, 5 μm and 40 μm, 5 μm and 35 μm, 5 μm and 30 μm, or 5 μm and 25 μm; however, this invention is not limited to these values.

[0020] In this invention, the diameter of the columnar bicrystalline grains or the oblique bicrystalline grains can be between 0.1 μm and 50 μm, respectively. In one embodiment of this invention, the diameter of the columnar bicrystalline grains or the oblique bicrystalline grains can, for example, be between 0.1 μm and 45 μm, 0.1 μm and 40 μm, 0.1 μm and 35 μm, 0.5 μm and 35 μm, 0.5 μm and 30 μm, 1 μm and 30 μm, 1 μm and 25 μm, 1 μm and 20 μm, 1 μm and 15 μm, or 1 μm and 10 μm; however, this invention is not limited to these. In this invention, the diameter of a columnar bicrystalline grain or an oblique bicrystalline grain can be a length measured in a direction substantially perpendicular to the bicrystalline direction of the bicrystalline grain; more specifically, the diameter of a columnar bicrystalline grain or an oblique bicrystalline grain can be a length (e.g., the maximum length) measured in a direction substantially perpendicular to the stacking direction of the bicrystalline planes of the bicrystalline grain (i.e., the bicrystalline plane extension direction).

[0021] In this invention, the thickness of the columnar bicrystalline grains or the oblique bicrystalline grains can be between 0.1 μm and 500 μm, respectively. In one embodiment of this invention, the thickness of the columnar bicrystalline grains or the oblique bicrystalline grains can, for example, be between 0.1 μm and 500 μm, 0.1 μm and 400 μm, 0.1 μm and 300 μm, 0.1 μm and 200 μm, 0.1 μm and 100 μm, 0.1 μm and 80 μm, 0.1 μm and 50 μm, 1 μm and 50 μm, 2 μm and 50 μm, 3 μm and 50 μm, 4 μm and 50 μm, 5 μm and 50 μm, 5 μm and 40 μm, 5 μm and 35 μm, 5 μm and 30 μm, or 5 μm and 25 μm. In this invention, the thickness of columnar bicrystalline grains or oblique bicrystalline grains can be the thickness measured in the direction of the bicrystalline direction of the bicrystalline grains; more specifically, the thickness of columnar bicrystalline grains or oblique bicrystalline grains can be the thickness measured in the stacking direction of the bicrystalline planes of the bicrystalline grains (e.g., the maximum thickness).

[0022] In this invention, the so-called "bicrystalline direction of a bicrystalline grain" refers to the stacking direction of the bicrystalline planes in a bicrystalline grain. The bicrystalline planes of the bicrystalline grain may be substantially perpendicular to the stacking direction of the bicrystalline planes.

[0023] In this invention, a cross-section of the bicrystalline copper-nickel alloy metal layer can be used to measure the angle between the bicrystalline grain's bicrystalline direction and the thickness direction of the bicrystalline copper-nickel alloy metal layer. Similarly, a cross-section of the bicrystalline copper-nickel alloy metal layer can be used to measure the thickness of the bicrystalline copper-nickel alloy metal layer, the diameter and thickness of the bicrystalline grains, and other characteristics. Alternatively, the surface of the bicrystalline copper-nickel alloy metal layer can be used to measure the diameter and thickness of the bicrystalline grains. In this invention, there are no particular limitations on the measurement method; scanning electron microscopy (SEM), transmission electron microscopy (TEM), focused ion beam (FIB) systems, or other suitable means can be used for measurement.

[0024] In this invention, the bicrystalline copper-nickel alloy metal layer of this invention can be formed by co-plating. The cathode in the electroplating apparatus can serve as a substrate, and the formed bicrystalline copper-nickel alloy metal layer can be disposed on or embedded in the substrate. Here, the cathode can be a substrate with a metal layer on its surface, or a metal substrate. The substrate can be a silicon substrate, a glass substrate, a quartz substrate, a metal substrate, a plastic substrate, a printed circuit board, a III-V group material substrate, or a laminated substrate thereof; and the substrate can have a single-layer or multi-layer structure.

[0025] In this invention, the electroplating solution may include a copper salt, an acid, and a nickel salt. Examples of copper salts in the electroplating solution may include, but are not limited to, copper sulfate, copper methanesulfonate, or combinations thereof; examples of acids in the electroplating solution may include, but are not limited to, hydrochloric acid, sulfuric acid, methanesulfonic acid, or combinations thereof; examples of nickel salts in the electroplating solution may include, but are not limited to, nickel sulfate, nickel methanesulfonate, or combinations thereof. Furthermore, the electroplating solution may also include an additive, such as gelatin, a surfactant, a lattice modifier, or a combination thereof.

[0026] In this invention, DC electroplating, pulse electroplating, or a combination of both can be used to form a bicrystalline copper-nickel alloy metal layer.

[0027] In one embodiment of the present invention, a bicrystalline copper-nickel alloy metal layer is prepared by direct current electroplating. The current density of the direct current electroplating can be, for example, between 0.5 ASD and 30 ASD, 1 ASD and 30 ASD, 2 ASD and 30 ASD, 2 ASD and 25 ASD, 2 ASD and 20 ASD, 2 ASD and 15 ASD, or 2 ASD and 10 ASD; however, the present invention is not limited thereto.

[0028] In another embodiment of the present invention, a bicrystalline copper-nickel alloy metal layer is prepared by pulse electroplating. The positive current density of the pulse electroplating can be, for example, between 0.5 ASD and 30 ASD, 1 ASD and 30 ASD, 2 ASD and 30 ASD, 2 ASD and 25 ASD, 2 ASD and 20 ASD, 2 ASD and 15 ASD, or 2 ASD and 10 ASD; while the negative current density can be, for example, between 0.1 ASD and 10 ASD, 0.1 ASD and 8 ASD, 0.1 ASD and 5 ASD, 0.1 ASD and 3 ASD, 0.3 ASD and 3 ASD, or 0.3 ASD and 1 ASD; however, the present invention is not limited thereto. When pulse electroplating is used to prepare a bicrystalline copper-nickel alloy metal layer, in one embodiment of the present invention, the bicrystalline grains in the prepared bicrystalline copper-nickel alloy metal layer may include columnar bicrystalline grains; in another embodiment of the present invention, when the thickness of the electroplated bicrystalline copper-nickel alloy metal layer is increased, the bicrystalline grains in the prepared bicrystalline copper-nickel alloy metal layer may, in addition to including columnar bicrystalline grains, selectively include fine grains, oblique bicrystalline grains or combinations thereof, stacked on columnar bicrystalline grains.

[0029] In one embodiment of the present invention, after a bicrystalline copper-nickel alloy metal layer is grown on the surface of the cathode, the bicrystalline copper-nickel alloy metal layer can be selectively annealed. This can further improve the hardness of the bicrystalline copper-nickel alloy metal layer. Here, the annealing temperature can be between 50°C and 250°C. When the annealing temperature exceeds this range, the bicrystalline structure in the bicrystalline copper-nickel alloy metal layer may decrease or disappear. In one embodiment of the present invention, the annealing temperature can be between 50°C and 250°C, 75°C and 250°C, 75°C and 200°C, 100°C and 200°C, 100°C and 175°C, or 100°C and 150°C; however, the present invention is not limited to these. Furthermore, in the present invention, the annealing time is not particularly limited, for example, it can be between 30 minutes and 10 hours, 30 minutes and 8 hours, 30 minutes and 5 hours, or 1 hour and 5 hours; however, the present invention is not limited to these.

[0030] The shape of the bicrystalline copper-nickel alloy metal layer provided by this invention is not particularly limited, and it can be a foil, film, wire, or bulk material; however, this invention is not limited to these. Furthermore, the bicrystalline copper-nickel alloy metal layer provided by this invention can have a single-layer or multi-layer structure. Moreover, the bicrystalline copper-nickel alloy metal layer provided by this invention can be combined with other materials to form a multi-layer composite structure.

[0031] The bicrystalline copper-nickel alloy metal layer provided by this invention can be applied to various electronic products, such as through-silicon vias in three-dimensional integrated circuits (3D-IC), pin vias in packaging substrates, various metal wires, substrate circuits, or connectors; however, this invention is not limited to these. Attached Figure Description

[0032] The features of the present invention will be made more apparent below with reference to the accompanying drawings and detailed description.

[0033] Figure 1 This is a backscattering electron diffraction pattern of the bicrystalline copper metal specimen of Comparative Example 1 of the present invention.

[0034] Figure 2 This is a backscattering electron diffraction pattern of the bicrystalline copper-nickel alloy metal specimen of Embodiment 1 of the present invention.

[0035] Figure 3 This is a focused ion beam image of the bicrystalline copper-nickel alloy metal specimen of Example 1 of the present invention.

[0036] Figure 4 This is a comparison chart of the hardness of the test pieces of Example 1 and Comparative Example 1 before annealing and after annealing at different temperatures for one hour.

[0037] Figure 5This is a comparison chart of the hardness of the test pieces of Example 1 and Comparative Example 1 of the present invention after annealing at 100°C for one hour and five hours.

[0038] Figure 6 This is a comparison chart of the hardness of the test pieces of Example 1 and Comparative Example 1 of the present invention after annealing at 200°C for one hour and five hours.

[0039] Figure 7 This is a backscattering electron diffraction pattern of the bicrystalline copper metal specimen of Comparative Example 2 of the present invention.

[0040] Figure 8 This is a backscattering electron diffraction pattern of the bicrystalline copper-nickel alloy metal specimen of Embodiment 2 of the present invention.

[0041] Figure 9 This is a focused ion beam image of the bicrystalline copper-nickel alloy metal specimen of Embodiment 2 of the present invention.

[0042] Figure 10 This is a comparison chart of the hardness of the test pieces of Example 2 and Comparative Example 2 of the present invention before annealing and after annealing at different temperatures for one hour.

[0043] Figure 11 This is a comparison chart of the hardness of the test pieces of Example 2 and Comparative Example 2 of the present invention after annealing at 100°C for one hour and five hours.

[0044] Figure 12 This is a comparison chart of the hardness of the test pieces of Example 2 and Comparative Example 2 of the present invention after annealing at 200°C for one hour and five hours.

[0045] Figure 13 This is the phase diagram for a copper-nickel alloy. Detailed Implementation

[0046] The following provides different embodiments of the present invention. These embodiments are used to illustrate the technical content of the present invention and are not intended to limit the scope of the invention. A feature of one embodiment can be applied to other embodiments through suitable modifications, substitutions, combinations, or separations.

[0047] It should be noted that, unless otherwise specified, having “one” component is not limited to having a single component, but may include one or more of the component.

[0048] In this document, unless otherwise specified, the term "characteristic A" or "and / or" and "characteristic B" means that A exists alone, B exists alone, or A and B exist simultaneously; the term "characteristic A" and "and" or "and" and "and" and "characteristic B" means that A and B exist simultaneously; the terms "including", "containing", "having", and "containing" refer to, but are not limited to, these.

[0049] Furthermore, unless otherwise specified, in this document, “one component on another component” or similar statements do not necessarily imply that the component is in contact with the other component.

[0050] Furthermore, unless otherwise specified herein, a numerical value may encompass a range of ±10%, and more particularly, a range of ±5%. Unless otherwise specified, a numerical range comprises multiple subranges defined by the smaller endpoint, the smaller quartile, the median, the larger quartile, and the larger endpoint.

[0051] Example 1 - Bicrystalline copper-nickel alloy metal specimen

[0052] In this embodiment, a 12-inch silicon wafer plated with 100nm titanium / 200nm copper is cleaved into 2cm x 3cm test pieces (as cathodes). The surface of the test pieces is cleaned with citric acid to remove oxides, and then the area to be electroplated is defined using acid and alkali resistant tape. The total electroplating area is 2cm x 2cm.

[0053] The electroplating solution used in this embodiment was prepared from copper sulfate pentahydrate crystals. A total of 196.54 g of copper sulfate pentahydrate (containing 50 g / L copper ions) was used, along with 4.5 ml of additives, 100 g of 96% sulfuric acid, and 0.1 ml of 12N hydrochloric acid. The solution was stirred with a magnet until the copper sulfate pentahydrate was uniformly mixed in 1 liter of solution. The electroplating solution was then divided into two containers. One container contained 10 ml of 0.1M NiSO4, serving as the electroplating solution for this embodiment; the other container, without NiSO4, served as the electroplating solution for the comparative example. The magnet at the bottom of the electroplating tank rotated at 1200 revolutions per minute to maintain the uniformity of ion concentration, and electroplating was carried out at room temperature under one atmosphere of pressure. The hydrochloric acid added to the electroplating solution allowed the copper target (serving as the anode) in the electroplating tank to dissolve normally, thus balancing the copper ion concentration in the electroplating solution. Here, a computer-controlled power supply (Keithley 2400) is used, and DC current electroplating is employed, with the forward current density set to 6 (A / dm²). 2 After electroplating for approximately 20 minutes (using ASD), a bicrystalline copper-nickel alloy metal sample with a thickness of approximately 20 μm can be obtained. In other embodiments of the present invention, a bicrystalline copper-nickel alloy metal sample with the desired thickness can be plated by controlling the electroplating current.

[0054] After the test piece is prepared, it undergoes electropolishing. The electropolishing solution consists of 100 ml of phosphoric acid, 1 ml of acetic acid, and 1 ml of glycerol. The test piece to be electropolished is then clamped to the anode and a voltage of 1.75V is applied for 10 minutes to achieve the desired electropolishing effect. The thickness of the electropolished test piece is approximately 19 μm. Electropolishing not only smooths the surface of the bicrystalline copper-nickel alloy test piece but also makes subsequent hardness testing results more accurate.

[0055] Comparative Example 1 - Bicrystalline Copper Metal Specimen

[0056] The preparation method of the bicrystalline copper metal specimen in this comparative example is similar to that of the preparation method of the bicrystalline copper-nickel alloy metal specimen in Example 1, except that this comparative example uses the electroplating solution without NiSO4 as described in Example 1 for electroplating.

[0057] The electropolished specimens of Example 1 and Comparative Example 1 were subjected to backscattered electron diffraction (EBSD) and focused ion beam (FIB) to analyze the preferred surface orientation and specimen microstructure, respectively.

[0058] Figure 1 and Figure 2 The images are backscattered electron diffraction patterns of the bicrystalline copper metal specimen of Comparative Example 1 and the bicrystalline copper-nickel alloy metal specimen of Example 1, respectively. Figure 3 This is a focused ion beam image of the bicrystalline copper-nickel alloy metal specimen of Example 1 of the present invention.

[0059] like Figure 1 and Figure 2 As shown, the measurement results of the backscattered electron diffractometer show that almost all the volume (more than 95% of the volume) of the bicrystalline copper metal sample of Comparative Example 1 and the bicrystalline copper-nickel alloy metal sample of Example 1 consists of columnar bicrystalline grains that are interconnected, and the diameter of the columnar bicrystalline grains is in the range of about 0.5 μm to 3 μm. In addition, the bicrystalline grains are formed by stacking nano-bicrystalline crystals along the

[111] crystal axis, and the bicrystalline planes of the nano-bicrystalline crystals are substantially parallel to the cathode surface (i.e., the stacking direction of the nano-bicrystalline crystals is substantially parallel to the thickness direction of the sample). Therefore, almost all the surfaces of the samples (more than 95% of the area) expose the (111) planes of the nano-bicrystalline crystals, indicating that the bicrystalline copper metal sample of Comparative Example 1 and the bicrystalline copper-nickel alloy metal sample of Example 1 have the preferred orientation of (111).

[0060] like Figure 3As shown, the focused ion beam measurement results indicate that most of the grains in the bicrystalline copper-nickel alloy metal sample of Example 1 exhibit dense bicrystals. More than 95% of the volume of the bicrystalline copper-nickel alloy metal sample comprises bicrystalline grains. The bicrystal orientation of more than 95% of the bicrystalline grains forms an angle of approximately 0 degrees with the thickness direction of the bicrystalline copper-nickel alloy metal sample, and the bicrystal orientation of more than 95% of the bicrystalline grains forms an angle of approximately 90 degrees with the surface of the substrate, indicating that the bicrystal planes of the bicrystalline grains are substantially parallel to the surface of the substrate. Furthermore, the thickness of more than 95% of the bicrystalline grains in the bicrystalline copper-nickel alloy metal sample is approximately between 1 μm and 20 μm.

[0061] Hardness test

[0062] The electropolished specimens obtained in Example 1 and Comparative Example 1 were cleaned with citric acid solution, and then water droplets on the surface of the specimens were removed with a nitrogen spray gun. Subsequently, the bicrystalline copper metal specimen of Comparative Example 1 and the bicrystalline copper-nickel alloy metal specimen of Example 1 were annealed separately in a furnace tube under a vacuum pressure of 10... -3 The annealing temperatures were 100°C, 150°C, and 200°C, and the annealing times were one hour and five hours, respectively. The specimens of Example 1 and Comparative Example 1 before and after annealing were tested using a Vickers hardness tester. The machine punched a diamond-shaped hole in the specimen, and the computer calculated the hardness of the specimens before and after annealing.

[0063] Figure 4 This is a comparison of the hardness of the specimens from Example 1 and Comparative Example 1 before annealing and one hour after annealing at different temperatures. Table 1 below shows the comparison results of the total strengthening degree of the specimens from Example 1 and Comparative Example 1. The comparison of the total strengthening degree is based on the hardness value of the specimen from Comparative Example 1 before annealing. Figure 4 The area marked by the rectangle.

[0064] Table 1

[0065] Annealing temperature / time Total reinforcement level (%) Room temperature (before annealing) 29.74 100℃ / hour 30.28 150℃ / hour 11.45 200℃ / hour 14.46

[0066] Depend on Figure 4 The results in Table 1 show that, before annealing, the hardness of the bicrystalline copper-nickel alloy metal specimen of Example 1 was higher than that of the bicrystalline copper metal specimen of Comparative Example 1; this indicates that adding an appropriate amount of nickel can effectively improve the hardness of the bicrystalline copper metal specimen. Furthermore, the bicrystalline copper-nickel alloy metal specimen of Example 1, after annealing at 100°C for 1 hour, achieved a hardness of 191 HV; compared to the bicrystalline copper metal specimen of Comparative Example 1 without annealing, the hardness of the bicrystalline copper-nickel alloy metal specimen of Example 1 was increased by 30.28%. This result shows that annealing at a low temperature can further improve the hardness of the bicrystalline copper-nickel alloy metal specimen of Example 1.

[0067] Figure 5 and Figure 6 The figures show a hardness comparison of the test pieces from Example 1 and Comparative Example 1 after annealing at 100°C and 200°C for one hour and five hours, respectively. The results show that even after prolonged annealing, the hardness value of the bicrystalline copper-nickel alloy metal test piece from Example 1 did not decrease significantly, indicating its excellent thermal stability.

[0068] Example 2 - Bicrystalline copper-nickel alloy metal specimen

[0069] The preparation method of the bicrystalline copper-nickel alloy metal specimen in this embodiment is similar to that in Example 1, except that pulse electroplating is used in this embodiment, with a positive current of 8 ASD, a negative current of 0.7 ASD, and an electroplating time of approximately 24 minutes, resulting in a specimen thickness of approximately 23 μm. After the specimen is completed, electropolishing is performed in a manner similar to that in Example 1, resulting in a specimen thickness of approximately 22 μm after electropolishing.

[0070] Comparative Example 2 - Bicrystalline Copper Metal Specimen

[0071] The preparation method of the bicrystalline copper metal specimen in this comparative example is similar to that of the bicrystalline copper-nickel alloy metal specimen in Example 2, except that this comparative example uses an electroplating solution without NiSO4 for electroplating.

[0072] The electropolished specimens of Example 2 and Comparative Example 2 were subjected to backscattered electron diffraction and focused ion beam analysis to determine the preferred surface orientation and specimen microstructure, respectively.

[0073] Figure 7 and Figure 8 The images are backscattered electron diffraction patterns of the bicrystalline copper metal specimen of Comparative Example 2 and the bicrystalline copper-nickel alloy metal specimen of Example 2, respectively. Figure 9 This is a focused ion beam image of the bicrystalline copper-nickel alloy metal specimen of Embodiment 2 of the present invention.

[0074] like Figure 9 As shown, within a range of approximately 5 μm from the substrate surface, the bicrystalline grains in the bicrystalline copper-nickel alloy metal specimen of Example 2 are columnar bicrystalline grains. Outside this range, the bicrystalline grains in the bicrystalline copper-nickel alloy metal specimen of Example 2 also include oblique bicrystalline grains and fine grains, stacked on top of the columnar bicrystalline grains. The angle between the stacking direction of the oblique bicrystalline grains and the thickness direction of the specimen is between 10 and 60 degrees, while the stacking direction of the fine grains is not preferred. This result verifies... Figure 7 and Figure 8 The reason why the sample does not have a preferred orientation is indicated by the diffraction pattern of the backscattering electron diffractometer.

[0075] The electropolished specimens obtained in Example 2 and Comparative Example 2 were subjected to hardness testing using the same method described above. Figure 10 This is a comparison chart of the hardness of the specimens from Example 2 and Comparative Example 2 before annealing and one hour after annealing at different temperatures. Table 2 below shows the comparison results of the total strengthening degree of the specimens from Example 2 and Comparative Example 2. The comparison of the total strengthening degree is based on the hardness value of the specimen from Comparative Example 2 before annealing. Figure 10 The area marked by the rectangle.

[0076] Table 2

[0077] Annealing temperature / time Total reinforcement level (%) Room temperature (before annealing) 37.90 100℃ / hour 39.57 150℃ / hour 35.04 200℃ / hour 35.16

[0078] Depend on Figure 10 The results in Table 2 show that, before annealing, the hardness of the bicrystalline copper-nickel alloy metal specimen of Example 2 was higher than that of the bicrystalline copper metal specimen of Comparative Example 2; this indicates that adding an appropriate amount of nickel can effectively improve the hardness of the bicrystalline copper metal specimen. Furthermore, the bicrystalline copper-nickel alloy metal specimen of Example 2, after annealing at 100°C for 1 hour, achieved a hardness of 234.2 HV; compared to the bicrystalline copper metal specimen of Comparative Example 2 without annealing, the hardness of the bicrystalline copper-nickel alloy metal specimen of Example 2 was increased by 39.57%. This result shows that annealing at a low temperature can further improve the hardness of the bicrystalline copper-nickel alloy metal specimen of Example 2.

[0079] Figure 11 and Figure 12 The figures show a comparison of the hardness of the specimens from Example 2 and Comparative Example 2 after annealing at 100°C and 200°C for one hour and five hours, respectively. The results show that even after prolonged annealing, the hardness value of the bicrystalline copper-nickel alloy metal specimen from Example 2 did not decrease significantly, indicating its excellent thermal stability.

[0080] resistivity test

[0081] The resistivity of the electropolished specimens obtained in Example 2 and Comparative Example 2 was tested. The resistivity of the specimens was calculated by the following formula (I) after four-point measurement.

[0082] ρ=Rs×T=[CF×(V / I)]×T (I)

[0083] Where ρ is the resistivity of the test piece (μΩ-cm); Rs is the resistance of the piece (Ω); T is the thickness of the test piece (cm); CF is the correction factor; V is the DC voltage passing through the voltage probe; and I is the fixed DC current passing through the current probe.

[0084] The measurement results show that the resistivity of the nickel-free bicrystalline copper metal sample of Comparative Example 2 is about 2.18 μΩ-cm; the resistivity of the bicrystalline copper-nickel alloy metal sample of Example 2 is about 2.07-3.44 μΩ-cm. This shows that adding an appropriate amount of nickel can not only enhance the hardness of nano-bicrystalline copper, but also maintain the characteristics of high conductivity and low resistance of nano-bicrystalline copper.

[0085] In summary, this invention, through co-plating, can easily deposit bicrystalline copper-nickel alloys with preferred orientations (as in Example 1) and random orientations (as in Example 2), followed by selective annealing. The resulting alloy exhibits high... <111> The hardness of the bicrystalline copper-nickel alloy metal specimen (as in Example 1) is significantly better than that of the specimen excluding nickel. <111> The hardness of the bicrystalline copper metal specimen (as in Comparative Example 1). In this embodiment, a bicrystalline copper-nickel alloy metal specimen with extremely high hardness (as in Example 2) can also be deposited by pulse electroplating, and the hardness of the specimen can be directly enhanced without additional work hardening.

[0086] Nanocrystalline copper with a preferred orientation exhibits good lattice orientation and is inherently stronger than bulk copper. Since nanocrystalline copper already possesses high strength, further increases in strength are difficult. Therefore, in this invention, a short-duration, rapid, low-temperature annealing process can further enhance the hardness of the nanocrystalline copper-nickel alloy metal specimen. Furthermore, nickel is a high-strength metal, and according to phase diagrams (… Figure 13 As can be seen from the diagram, the nickel-copper alloy of the present invention is interfacial and does not produce eutectoids. Furthermore, the amount of nickel doped in the bicrystalline copper-nickel alloy metal sample is small, thus reducing the probability of electromigration effects without affecting the electrical properties of the component, effectively improving component reliability. In particular, the resistivity of the bicrystalline copper-nickel alloy metal sample of the present invention does not significantly increase after the addition of nickel, maintaining good high conductivity; therefore, the bicrystalline copper-nickel alloy metal layer provided by the present invention is a high-strength, high-conductivity, and high-thermal-conductivity conductor, and can be applied to various electronic components.

Claims

1. A bicrystalline copper-nickel alloy metal layer, characterized in that, The bicrystalline copper-nickel alloy metal layer comprises more than 50% of its volume with multiple bicrystalline grains, including multiple columnar bicrystalline grains, multiple fine grains with non-preferred orientation of nano-bicrystalline stacking, and multiple oblique bicrystalline grains. The multiple fine grains and the multiple oblique bicrystalline grains are stacked on the multiple columnar bicrystalline grains, and the nickel content in the bicrystalline copper-nickel alloy metal layer is between 0.05 at% and 20 at%; The bicrystalline copper-nickel alloy metal layer is formed by co-plating using an electroplating solution comprising a copper salt, an acid, and a nickel salt.

2. The bicrystalline copper-nickel alloy metal layer according to claim 1, characterized in that, The plurality of columnar bicrystalline grains are formed by stacking a plurality of nano-bicrystalline grains in a direction within ±15 degrees along the [111] crystal axis, and the angle between the stacking direction of at least a portion of the plurality of nano-bicrystalline grains and the thickness direction of the bicrystalline copper-nickel alloy metal layer is between 0 degrees and 20 degrees.

3. The bicrystalline copper-nickel alloy metal layer according to claim 1, characterized in that, The surface of this bicrystalline copper-nickel alloy metal layer does not have a preferred surface.

4. The bicrystalline copper-nickel alloy metal layer according to claim 1, characterized in that, The plurality of oblique bicrystalline grains are formed by stacking a plurality of nano-bicrystalline grains in a direction within ±15 degrees along the [111] crystal axis, and the angle between the stacking direction of at least a portion of the plurality of nano-bicrystalline grains and the thickness direction of the bicrystalline copper-nickel alloy metal layer is between 10 degrees and 60 degrees.

5. The bicrystalline copper-nickel alloy metal layer according to claim 1, characterized in that, The diameters of these multiple columnar bicrystalline grains range from 0.1 μm to 50 μm.

6. The bicrystalline copper-nickel alloy metal layer according to claim 1, characterized in that, The thicknesses of these multiple columnar bicrystalline grains range from 0.1 μm to 500 μm.

7. The bicrystalline copper-nickel alloy metal layer according to claim 1, characterized in that, At least some of the multiple columnar bicrystalline grains are interconnected with each other.

8. A method for preparing a bicrystalline copper-nickel alloy metal layer, characterized in that, Includes the following steps: An electroplating apparatus is provided, including an anode, a cathode, an electroplating solution, and a power supply, wherein the power supply is connected to the anode and the cathode respectively, and the anode and the cathode are immersed in the electroplating solution; as well as Using this power supply source to provide electricity for electroplating, a bicrystalline copper-nickel alloy metal layer is grown on one surface of the cathode; The bicrystalline copper-nickel alloy metal layer comprises more than 50% of its volume with multiple bicrystalline grains, including multiple columnar bicrystalline grains, multiple fine grains with non-preferred orientations in the nano-bicrystalline stacking direction, and multiple oblique bicrystalline grains. These fine grains and oblique bicrystalline grains are stacked on top of the columnar bicrystalline grains, and the nickel content in the bicrystalline copper-nickel alloy metal layer is between 0.05 at% and 20 at%. The electroplating solution includes a copper salt, an acid, and a nickel salt.

9. The method according to claim 8, characterized in that, It also includes a step of annealing the bicrystalline copper-nickel alloy metal layer after growing the bicrystalline copper-nickel alloy metal layer on the surface of the cathode.

10. The method according to claim 9, characterized in that, The annealing temperature is between 50°C and 250°C.

11. The method according to claim 8, characterized in that, The electroplating is direct current electroplating.

12. The method according to claim 8, characterized in that, The electroplating is pulse electroplating.

13. The method according to claim 8, characterized in that, The plurality of oblique bicrystalline grains are formed by stacking a plurality of nano-bicrystalline grains in a direction within ±15 degrees along the [111] crystal axis, and the angle between the stacking direction of at least a portion of the plurality of nano-bicrystalline grains and the thickness direction of the bicrystalline copper-nickel alloy metal layer is between 10 degrees and 60 degrees.

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