TWI844761B - Twinned copper layer, substrate having the same and method for preparing the same - Google Patents

Abstract

A twinned copper layer is disclosed, wherein more than 35% in volume of the twinned copper layer comprises plural twinned grains, more than 30% of the twinned grains are flake grains, and a ratio of a length to a thickness of at least a part of the flake grains is greater than or equal to 2. In addition, a substrate having the aforesaid twinned copper layer and a method for preparing the aforesaid twinned copper layer are also disclosed.

Description

Double crystal copper metal layer, substrate having the same and preparation method thereof

The present disclosure relates to a double crystal copper metal layer, a substrate having the same and a preparation method thereof, and in particular to a double crystal copper metal layer with high strength, a substrate having the same and a preparation method thereof.

Conventional technology often uses rolling or doping with other metals such as titanium (Ti), nickel (Ni), and zinc (Zn) to strengthen the mechanical properties of copper. However, this conventional technology has the following shortcomings.

If copper foil containing copper grains is strengthened by rolling, the pure copper grains will be deformed, making its mechanical properties better but increasing the resistance and thermal conductivity. In addition, if other metals are doped into the copper film, the resistance will increase. Furthermore, the copper film with a bicrystalline structure has high strength. If the bicrystalline copper foil is strengthened by grain refinement, the resulting bicrystalline copper foil may have poor thermal stability.

In view of this, there is an urgent need to develop a novel twin-crystal copper metal layer that not only has improved strength but also retains the properties of the twin-crystal copper metal layer for application in various electronic components.

An object of the present disclosure is to provide a bicrystalline copper metal layer having excellent hardness value and/or thermal stability.

In the bicrystalline copper metal layer disclosed herein, more than 35% of the volume of the bicrystalline copper metal layer includes a plurality of bicrystalline grains, more than 30% of the plurality of bicrystalline grains are lamellar bicrystalline grains, and the ratio of the length to the thickness of at least a portion of the lamellar bicrystalline grains is greater than or equal to 2. Here, the percentage of the bicrystalline grains and the percentage of the lamellar bicrystalline grains can be observed or measured from any cross section of the bicrystalline copper metal layer.

In addition, the present disclosure further provides a substrate including the aforementioned dual-crystal copper metal layer, including: a substrate; and a dual-crystal copper metal layer as described above, disposed on the substrate or embedded in the substrate.

Furthermore, the present disclosure further provides a method for preparing the aforementioned twin-crystal copper metal layer, comprising the following steps: providing an electroplating device, comprising an anode, a cathode, an electroplating solution, and an electric power source, wherein the electric power source is connected to the anode and the cathode respectively, and the anode and the cathode are immersed in the electroplating solution; and using the electric power source to provide electricity for electroplating, and growing the aforementioned twin-crystal copper metal layer from a surface of the cathode. Here, the electroplating solution includes a copper salt and an acid, but does not include a chlorine ion.

In the preparation method of the twin-crystal copper metal layer disclosed in the present invention, when the electroplating solution does not include chlorine ions, a twin-crystal copper metal layer with a special structure can be prepared. In particular, in the twin-crystal copper metal layer disclosed in the present invention or a substrate containing the same, the twin-crystal grains are lamellar twin-crystal grains, and the lamellar twin-crystal grains have a significant length-to-thickness ratio. Compared with the nano twin-crystal copper metal layer including columnar twin-crystal grains in the past, the twin-crystal copper metal layer disclosed in the present invention can increase the strength by more than 60%. In addition, even after the twin-crystal copper metal layer disclosed in the present invention is subjected to high-temperature annealing treatment, most of the twin-crystal grains still exist stably. Therefore, the dual-crystal copper metal layer disclosed in the present invention can exhibit excellent thermal stability and can be applied to various electronic components, such as connectors of electronic components.

In the present disclosure, more than 30% of the bicrystalline grains may be tabular bicrystalline grains. In one embodiment of the present disclosure, for example, 30% to 100%, 30% to 99%, 30% to 95%, 35% to 95%, 35% to 90%, 40% to 90%, 40% to 85%, 45% to 85%, 45% to 80%, or 50% to 80% of the bicrystalline grains may be tabular bicrystalline grains; however, the present disclosure is not limited thereto.

In the present disclosure, the ratio of the length and thickness of at least some of the lamellar bicrystalline grains may be greater than or equal to 2. In an embodiment of the present disclosure, the ratio of the length (L) and thickness (T) of at least some of the lamellar bicrystalline grains may be: 2≦L/T≦10, 2≦L/T≦9, 2≦L/T≦8, 2≦L/T≦7, 2≦L/T≦6 or 2≦L/T≦5; but the present disclosure is not limited thereto. In the present disclosure, the thickness direction of the lamellar bicrystalline grains may be the twinning direction of the lamellar bicrystalline grains; more specifically, the thickness direction of the lamellar bicrystalline grains is the stacking direction of the twinning planes of the lamellar bicrystalline grains.

In the present disclosure, more than 35% of the volume of the dual-crystal copper metal layer may include a plurality of dual-crystal grains. In one embodiment of the present disclosure, for example, 35% to 99%, 35% to 95%, 35% to 90%, 40% to 90%, 40% to 85%, 45% to 85%, 45% to 80%, or 50% to 80% of the volume may include a plurality of dual-crystal grains; however, the present disclosure is not limited thereto.

In the present disclosure, the angle between the twin planes of at least some of the twin crystal grains and the thickness direction of the twin crystal copper metal layer may be between 0 degrees and 30 degrees. In addition, in the present disclosure, the angle between the twin planes of at least some of the plurality of twin crystal grains and the surface of the substrate is between 60 degrees and 90 degrees. Here, the twin planes of the twin crystal grains and the thickness direction of the twin crystal copper metal layer and/or the twin planes of the twin crystal grains and the surface of the substrate present a special angle range, so the twin crystal grains are relatively scattered and irregularly stacked. Compared to conventional nano twinned copper metal layers in which the twinned planes of twinned grains and the thickness direction of the twinned copper metal layer have an angle of nearly 90 degrees, or twinned copper metal layers in which the twinned planes of twinned grains are parallel to the surface of the substrate, the twinned copper metal layer disclosed herein can increase strength by more than 60%.

In the present disclosure, the twin-crystal copper metal layer may include: 0.05 at% to 20 at% of at least one element selected from the group consisting of silver, nickel, zinc, lead, aluminum, gold, platinum, magnesium and cadmium; and the balance of copper. In the present disclosure, by adding a specific proportion of metal elements other than copper, a twin-crystal copper alloy metal layer may be formed, and the twin-crystal copper alloy metal layer also has an improved hardness value or excellent thermal stability. When a twin-crystal copper metal layer containing a metal element other than copper is to be formed, the electroplating solution used in the preparation method disclosed herein may further include a salt of at least one of the aforementioned elements; and the amount of the salt of at least one element added may be added according to the proportion of the element in the twin-crystal copper metal layer to be formed.

In one embodiment of the present disclosure, the electroplating solution may further include a silver salt, such as silver nitrate. When silver is added to the electroplating solution, the formed twin-crystal copper metal layer may further include silver. Since the electrical conductivity and thermal conductivity of silver itself are better than those of copper, and it will not form a compound with copper; therefore, a small amount of added silver can significantly increase the hardness value of the twin-crystal copper metal layer without losing electrical conductivity and thermal conductivity.

In the present disclosure, the proportion of the metal elements other than copper added may account for 0.05 at% to 20 at% of the total elements of the twin-crystal copper metal layer. In an embodiment of the present disclosure, the proportion of the metal elements other than copper added may be, for example, 0.1 at% to 20 at%, 0.1 at% to 15 at%, 0.1 at% to 10 at%, 0.1 at% to 5 at%, 0.1 at% to 3 at% or 0.1 at% to 1 at%; but the present disclosure is not limited thereto.

In the present disclosure, at least part of the flaky grains may have a length between 0.5 μm and 20 μm. In one embodiment of the present disclosure, the length of the flaky grains may be, for example, between 0.5 μm and 15 μm, 0.5 μm and 10 μm, 1 μm and 10 μm, 1 μm and 5 μm, or 2 μm and 5 μm; but the present disclosure is not limited thereto. In one embodiment of the present disclosure, more than 30% of the flaky grains may have a length within the above range, for example, 30% to 99%, 30% to 95%, 30% to 90%, 35% to 90%, 40% to 90%, 40% to 85%, 40% to 80%, 45% to 80%, or 50% to 80% of the flaky grains may have a length within the above range; but the present disclosure is not limited thereto. In the present disclosure, the length of a lamellar bi-crystalline grain may be a length measured in a direction substantially perpendicular to the bi-crystalline direction of the lamellar bi-crystalline grain; more specifically, the length of a lamellar bi-crystalline grain may be a length (e.g., a maximum length) measured in a direction substantially perpendicular to the stacking direction of the bi-crystalline planes of the lamellar bi-crystalline grain (i.e., the direction in which the bi-crystalline planes extend).

In the present disclosure, the thickness of at least part of the plate-like grains may be between 0.01 μm and 10 μm, 0.01 μm and 9 μm, 0.05 μm and 9 μm, 0.05 μm and 8 μm, 0.1 μm and 8 μm, 0.1 μm and 7 μm, 0.15 μm and 7 μm, 0.15 μm and 6 μm, 0.2 μm and 6 μm, or 0.2 μm and 5 μm; but the present disclosure is not limited thereto. In an embodiment of the present disclosure, more than 30% of the bi-crystalline grains may have a thickness within the above range, for example, 30% to 99%, 30% to 95%, 30% to 90%, 35% to 90%, 40% to 90%, 40% to 85%, 40% to 80%, 45% to % or 50% to 80% of the flaky grains may have a thickness within the above range; but the present disclosure is not limited thereto. In the present disclosure, the thickness of the flaky bi-crystalline grains may be the thickness measured in the direction of the bi-crystalline direction of the flaky bi-crystalline grains; more specifically, the thickness of the flaky bi-crystalline grains may be the thickness measured in the stacking direction of the bi-crystalline planes of the flaky bi-crystalline grains (e.g., the maximum thickness).

In the twin-crystal copper metal layer disclosed herein, the twin-crystal directions of two adjacent grains in a plurality of twin-crystal grains may intersect. Here, the angle between the twin-crystal directions of the two adjacent grains may be between 5 degrees and 60 degrees. The mechanical strength of the twin-crystal copper metal layer may be enhanced through the structure of the two adjacent grains intersecting.

In the twin-crystal copper metal layer of the present disclosure, more than 30% of the area of a surface of the twin-crystal copper metal layer may expose at least a portion of the twin grain boundaries of the twin crystal grains. In an embodiment of the present disclosure, the twin grain boundaries of the twin crystal grains exposed on the surface of the twin-crystal copper metal layer may account for, for example, 30% to 99%, 35% to 99%, 35% to 95%, 35% to 90%, 35% to 85%, 35% to 80%, 35% to 75%, 35% to 70%, 35% to 65%, 35% to 60%, 35% to 55%, 40% to 55% or 40% to 50% of the total area of the surface of the twin-crystal copper metal layer; however, the present disclosure is not limited thereto.

In the twin-crystal copper metal layer of the present disclosure, more than 20% of the area of a surface of the twin-crystal copper metal layer may expose at least a portion of the (111) plane of the twin-crystal grains. In an embodiment of the present disclosure, the (111) plane of the twin-crystal grains exposed on the surface of the twin-crystal copper metal layer may account for, for example, 20% to 50%, 20% to 45%, 25% to 45%, 25% to 40%, 30% to 40%, or 30% to 35% of the total area of the surface of the twin-crystal copper metal layer; however, the present disclosure is not limited thereto. In addition, in the twin-crystal copper metal layer disclosed herein, more than 10% of the area of a surface of the twin-crystal copper metal layer may expose at least a portion of the (211) plane of the twin-crystal grains. In an embodiment of the present disclosure, the (211) plane of the twin-crystal grains exposed on the surface of the twin-crystal copper metal layer may account for, for example, 10% to 40%, 10% to 35%, 10% to 30%, 15% to 30%, 15% to 25% or 15% to 20% of the total area of the surface of the twin-crystal copper metal layer; but the present disclosure is not limited thereto. Here, the preferred direction of the twin-crystal grains on the surface of the twin-crystal copper metal layer may be measured by an electron backscatter diffraction (EBSD).

In the present disclosure, the thickness of the bicrystalline copper metal layer can be adjusted as required. In one embodiment of the present disclosure, the thickness of the bicrystalline copper metal layer can be, for example, 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; but the present disclosure is not limited thereto.

In the present disclosure, the substrate used for electroplating can be a substrate with a metal layer on the 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 material substrate or a laminated substrate thereof; and the substrate can have a single-layer or multi-layer structure.

In the present disclosure, the so-called "binning direction of twinned grains" or "binning direction of lamellar grains" refers to the stacking direction of twinning planes in twinned grains or lamellar twinned grains, that is, the thickness direction of twinned grains or lamellar twinned grains. Among them, the twinning planes in twinned grains or lamellar twinned grains can be substantially perpendicular to the stacking direction of twinning planes. In the present disclosure, twinned grains are formed by stacking multiple twins along the [111] crystal axis direction. In the present disclosure, two elements are "substantially perpendicular" means that the angle between the two elements can be between 80 degrees and 100 degrees, 85 degrees and 95 degrees, or 88 degrees and 92 degrees.

In the present disclosure, a cross section of a twin-crystal copper metal layer can be used to measure the angle between the twin-crystal direction of the twin-crystal grains and the thickness direction of the twin-crystal copper metal layer, or the angle between the twin-crystal direction of the twin-crystal grains and the substrate. Similarly, a cross section of a twin-crystal copper metal layer can be used to measure the thickness of the twin-crystal copper metal layer, the length and thickness of the twin-crystal grains/lamellar grains, and other characteristics. Alternatively, the length and thickness of the twin-crystal grains/lamellar grains can also be measured on the surface of the twin-crystal copper metal layer. In the present disclosure, there is no particular limitation on the measurement method, and the measurement may be performed using a scanning electron microscope (SEM), a transmission electron microscope (TEM), a focused ion beam (FIB), or other suitable means.

In the preparation method disclosed herein, examples of copper salts in the electroplating solution may include, but are not limited to, copper sulfate, copper methanesulfonate, or a combination thereof; and examples of acids in the electroplating solution may include, but are not limited to, sulfuric acid, methanesulfonic acid, or a combination thereof. In addition, the electroplating solution may further include an additive, such as gelatin, a surfactant, a lattice modifier, or a combination thereof.

In the preparation method disclosed herein, direct current plating, high-speed pulse plating, or a combination of direct current plating and high-speed pulse plating may be used. In one embodiment of the present disclosure, direct current plating is used to prepare a bicrystalline copper metal layer. The current density of the direct current plating may be, for example, 0.5 ASD to 20 ASD, 0.5 ASD to 15 ASD, 0.5 ASD to 10 ASD, 0.5 ASD to 5 ASD, 1 ASD to 5 ASD, 1 ASD to 3 ASD, or 1 ASD to 2 ASD; however, the present disclosure is not limited thereto.

The appearance of the twin-crystal copper metal layer provided by the present disclosure is not particularly limited, and can be copper foil, film, wire or block; but the present disclosure is not limited thereto. In addition, the twin-crystal copper metal layer provided by the present disclosure can have a single-layer or multi-layer structure. Furthermore, the twin-crystal copper metal layer provided by the present disclosure can be combined with other materials to form a multi-layer composite structure.

The dual-crystal copper metal layer provided in the present disclosure can be applied to various electronic products, such as through-silicon vias of three-dimensional integrated circuits (3D-IC), pin through holes of package substrates, various metal wires, substrate wiring, or connectors, etc.; but the present disclosure is not limited thereto.

The following will be accompanied by drawings and detailed descriptions to make the features of the present disclosure more obvious.

The following provides different embodiments of the present disclosure. These embodiments are used to illustrate the technical content of the present disclosure, but are not used to limit the scope of the present disclosure. A feature of an embodiment can be applied to other embodiments through appropriate modification, replacement, combination, and separation.

It should be noted that, in this document, unless otherwise specified, “a” element is not limited to a single element but may include one or more elements.

In this document, unless otherwise specified, the so-called feature A "or" or "and/or" feature B means that A exists alone, B exists alone, or A and B exist at the same time; the so-called feature A "and" or "and" or "and" feature B means that A and B exist at the same time; the so-called "include", "comprise", "have" and "contain" mean including but not limited to these.

Furthermore, herein, unless specifically stated otherwise, “an element is on another element” or similar descriptions do not necessarily mean that the element contacts the other element.

In addition, in this document, unless otherwise specified, a numerical value may include a range of ±10% of the numerical value, in particular, a range of ±5% of the numerical value. Unless otherwise specified, a numerical range is composed of multiple sub-ranges defined by a lower endpoint, a lower quartile, a median, an upper quartile, and a higher endpoint.

Example 1 - Twin-crystal copper metal layer with 0.1 at% silver content

In this embodiment, a 12-inch silicon wafer plated with 100 nm titanium/200 nm copper was split into 2 cm x 3 cm test pieces, and the surface of the test piece was cleaned with citric acid to remove the oxide, and then the area to be plated was defined with acid-resistant and alkali-resistant tape. The total plated area was 2 cm x 2 cm.

The electroplating solution used in this embodiment is composed of copper sulfate pentahydrate powder, sulfuric acid, silver nitrate aqueous solution and DP-101L additive provided by Tim Hung Company. Among them, the addition amount of copper sulfate pentahydrate powder is 196.61 g, the addition amount of sulfuric acid (96%) is 100 g, and the silver nitrate aqueous solution is prepared to 0.1 M and then 10 ml can be added. The additive can be added from 10 ml to 20 ml. Finally, deionized water is added to the total solution to 1 L and a magnet is used to stir until the solution is evenly mixed. After mixing, the electroplating solution is poured into the electroplating tank, and the magnet is set to 1200 revolutions per minute to maintain the flow of the electroplating solution. Electroplating is performed at room temperature and atmospheric pressure. The power supply (Keithley 2400) is controlled by a computer, and direct current electroplating is used. The current density is 1.5 ASD (A/dm ² ) and electroplating is performed for one hour to obtain a 20 µm thick sheet-shaped bi-crystalline copper. When the specimen is completed, the specimen is electropolished. The composition of the electropolishing solution is 100 ml of phosphoric acid plus 1 ml of acetic acid and 1 ml of glycerol. At this time, the specimen to be electropolished is clamped to the anode and a voltage of 1.75 V is applied for 10 minutes to achieve the effect of electropolishing. The thickness of the specimen after electropolishing is about 19 µm. The electrolytically polished specimens were subjected to EBSD and FIB analysis to analyze the surface preferred orientation and specimen microstructure, respectively, and the hardness was measured using a Vickers hardness tester.

Figure 1 is a backscattered electron diffraction diagram of the double crystal copper metal layer of the present embodiment. Figure 2 is a focused ion beam image diagram of the double crystal copper metal layer of the present embodiment.

As shown in Figure 1, the backscattered electron diffraction measurement results show that about 32.7% of the surface of the twin copper metal layer is (111) and 19.3% is (211).

As shown in FIG2 , the measurement results of the focused ion beam show that most of the grains in the twinned copper metal layer 12 have very dense twins. More than 50% of the volume of the twinned copper metal layer 12 includes twinned grains. The twinned planes of more than 50% of the twinned grains (as shown by the arrows) have an angle between 0 and 30 degrees with the thickness direction of the twinned copper metal layer 12; and the twinned planes of more than 50% of the twinned grains (as shown by the arrows) have an angle between 60 and 90 degrees with the surface of the substrate 11. More than 50% of the twin grains in the twin copper metal layer 12 have a thickness between about 1 μm and 10 μm, and more than 50% of the twin grains have a thickness between about 0.2 μm and 5 μm. The angle between the twin directions of two adjacent grains may be between 5 degrees and 60 degrees.

As shown in Figures 1 and 2, more than 50% of the twin crystal grains are lamellar grains. In addition, as shown in Figure 1, the maximum length (L) of the lamellar grains measured in the extension direction of the twin crystal plane is about 10 μm, and the maximum thickness (T) measured in the stacking direction of the twin crystal plane is about 3.5 μm, so the ratio of length to thickness (L/T) exceeds 2. As shown in Figure 2, the maximum length (L) of the lamellar grains measured in the extension direction of the twin crystal plane is about 10 μm, and the maximum thickness (T) measured in the stacking direction of the twin crystal plane is about 2 μm, so the ratio of length to thickness (L/T) exceeds 2.

In addition, after being measured by a Vickers hardness tester, the hardness value of the twin-crystal copper metal layer containing 0.1 at% silver content of this embodiment is about 262.8±17.9 Hv (n=5). The results of this embodiment show that the twin-crystal copper metal layer containing 0.1 at% silver content has an excellent hardness value.

Example 2 - Twin-crystal copper metal layer with 0.1 at% silver content

The twin-crystal copper metal layer of this embodiment is prepared in the same manner as in Example 1. Then, the obtained specimen is placed in a furnace for annealing, the vacuum pressure is 10 ^-3 torr, the annealing temperature is 200°C, and the annealing time is one hour. The annealed specimen is subjected to backscattered electron diffraction and focused ion beam analysis to analyze the surface preferred direction and the specimen microstructure, respectively, and the hardness is measured using a Vickers hardness tester.

Figure 3 is a backscattered electron diffraction diagram of the double crystal copper metal layer after annealing of the present embodiment. Figure 4 is a focused ion beam image diagram of the double crystal copper metal layer after annealing of the present embodiment.

As shown in FIG. 3 and FIG. 4 , even after the twin-crystal copper metal layer is annealed, it still maintains a twin-crystal grain structure similar to that of Example 1. In addition, after being measured by a Vickers hardness tester, the hardness of the twin-crystal copper metal layer after annealing in this example is about 237.2±14 Hv (n=5). This result shows that the twin-crystal copper metal layer containing 0.1 at% silver content has not only an excellent hardness value, but also good thermal stability.

Example 3 - Twin-crystal copper metal layer with silver content of 0.3 at% and 0.6 at%

The twin-crystal copper metal layer of this embodiment is prepared in the same manner as in Example 1, except that the concentration of silver nitrate in the electroplating solution is adjusted to 20 ml and 30 ml.

After analyzing the surface preferred direction and the microstructure of the specimen by backscattered electron diffraction and focused ion beam, the twin-crystal copper metal layer containing 0.3 at% or 0.6 at% silver content of this embodiment has a twin-crystal grain structure similar to that of Example 1. In addition, after being measured by a Vickers hardness tester, the hardness of the twin-crystal copper metal layer containing 0.3 at% or 0.6 at% silver content is approximately 305.6±32.9 Hv (n=5) and 266.4±23.9 Hv (n=5), respectively.

Example 4 - Silver-free bicrystalline copper metal layer

The bicrystalline copper metal layer of this embodiment is prepared in the same manner as in Example 1, except that the silver nitrate in the electroplating solution is removed and the film thickness is controlled to 5 μm. In addition, the test piece is annealed in a furnace with a vacuum pressure of 10 ^-3 torr, annealing temperatures of 250°C and 300°C, and annealing time of one hour.

Figure 5 is a backscattered electron diffraction diagram of the double crystal copper metal layer before annealing of the present embodiment. Figure 6 is a focused ion beam image diagram of the double crystal copper metal layer before annealing of the present embodiment.

After analyzing the surface preferred direction and the microstructure of the specimen by backscattered electron diffraction and focused ion beam, the silver-free twin-crystal copper metal layer of this embodiment has a twin-crystal grain structure similar to that of Example 1 before annealing, after annealing at 250°C, and after annealing at 300°C.

Example 5 - Silver-free twin-crystal copper metal

The twin-crystal copper metal layer of this embodiment is prepared in the same manner as in Example 1, except that the silver nitrate in the electroplating solution is removed. After being measured by a Vickers hardness tester, the hardness of the twin-crystal copper metal layer of this embodiment without silver is approximately 255.8±10.55 Hv (n=5).

Comparison Example

The plating solution used in this comparative example is composed of copper sulfate pentahydrate powder, sulfuric acid, hydrochloric acid and DP-101L additive provided by Timhung Company. Among them, the addition amount of copper sulfate pentahydrate powder is 196.61 g, the addition amount of sulfuric acid (96%) is 100 g, hydrochloric acid (38.5%) is added 0.1 ml, the additive is added 4.5 ml, and finally deionized water is added to the total solution to 1 L and a magnet is used to stir until the solution is evenly mixed. After mixing, the plating solution is poured into the plating tank, and the magnet is set to 1200 revolutions per minute to maintain the flow of the plating solution. The plating is carried out at room temperature and atmospheric pressure. The power supply (Keithley 2400) was controlled by a computer, and direct current electroplating was used. The current density was 6 ASD (A/dm ² ) and electroplating was carried out for 20 minutes to obtain a columnar nano-twin copper with a height of ＜111＞ and a preferred direction of 20 µm. When the specimen was completed, the specimen was electropolished. The composition of the electropolishing solution was 100 ml of phosphoric acid plus 1 ml of acetic acid and 1 ml of glycerol. At this time, the specimen to be electropolished was clamped to the anode and a voltage of 1.75 V was applied for 10 minutes to achieve the effect of electropolishing. The thickness of the specimen after electropolishing was about 19 µm. The electrolytically polished specimens were subjected to backscattered electron diffraction (EBSD) and focused ion beam (FIB) analysis to analyze the surface preferred orientation and specimen microstructure, respectively, and the hardness was measured using a Vickers hardness tester. After the Vickers hardness test, the hardness of the silver-free twin-crystal copper metal layer of this comparative example was approximately 195 Hv.

As shown in the above experimental results, the twin-crystal copper metal layer with silver added in Examples 1 to 3 can have a hardness of up to 305 Hv, which is significantly increased by more than 60% compared to the twin-crystal copper metal layer with a hardness of 195 Hv in the comparative example. In addition, the twin-crystal copper metal layer in Examples 4 and 5, although not including silver, still has a higher hardness than the twin-crystal copper metal layer in the comparative example. The above experimental results show that the twin-crystal copper metal layer with a special structure in Examples 1 to 5 has a higher strength.

In summary, the present disclosure provides a twin-crystal copper metal layer with a special structure, which includes lamellar grains with a significant length and thickness ratio, and the twin crystal directions of the lamellar grains intersect with each other, thereby improving the hardness of the twin-crystal copper metal layer. In addition, the present disclosure uses a common electroplating method to electroplate different types of metals into the twin-crystal copper metal layer, so that the copper metal layer has the effects of twin crystal strengthening and precipitation hardening or solid solution strengthening at the same time, which can further improve the strength of the copper metal layer. At the same time, the electrical conductivity and thermal conductivity of silver itself are better than those of copper, and it will not form compounds with copper, so the twin-crystal copper-silver alloy can greatly increase the strength by more than 60% without losing too much electrical conductivity and thermal conductivity. In addition, the twin-crystal copper metal layer including silver and excluding silver disclosed in the present invention has high thermal stability. After annealing at 300°C for one hour, most of the twin crystals still exist stably and the strength does not decrease significantly. Therefore, the twin-crystal copper metal layer with high strength, high electrical conductivity, high thermal conductivity and high thermal stability provided by the present invention has great potential for application in various electronic components.

Although the present disclosure has been described through a number of embodiments, it should be understood that many other possible modifications and variations may be made without departing from the spirit of the present disclosure and the scope of the claimed patent application.

11: Substrate 12: Double gold-copper metal layer L: Length T: Thickness

FIG. 1 is a diffraction pattern of a backscattered electron diffraction instrument of a double crystal copper metal layer of Example 1.

FIG. 2 is a focused ion beam image of the twin-crystal copper metal layer of Example 1.

FIG. 3 is a diffraction diagram of a backscattered electron diffraction instrument after annealing of the double crystal copper metal layer of Example 2.

FIG. 4 is a focused ion beam image of the twin-crystal copper metal layer after annealing in Example 2.

FIG. 5 is a diffraction diagram of a backscattered electron diffraction instrument of the twin-crystal copper metal layer of Example 4 before annealing.

FIG. 6 is a focused ion beam image of the twin-crystal copper metal layer of Example 4 before annealing.

without.

11: Substrate

12: Double gold-copper metal layer

Claims (19)

A twin-crystal copper metal layer, comprising: 0.05at% to 20at% of at least one element selected from the group consisting of silver, nickel, zinc, lead, aluminum, gold, platinum, magnesium and cadmium; and the remainder of copper; wherein more than 35% of the volume of the twin-crystal copper metal layer comprises a plurality of twin-crystal grains, more than 30% of the plurality of twin-crystal grains are lamellar twin-crystal grains, and the ratio of the length to the thickness of at least part of the lamellar twin-crystal grains is greater than or equal to 2. The bicrystalline copper metal layer as described in claim 1, wherein the thickness direction of the bicrystalline lamellar grains is the bicrystalline direction of the bicrystalline lamellar grains. The bicrystalline copper metal layer as described in claim 1, wherein the angle between the bicrystalline planes of at least part of the plurality of bicrystalline grains and the thickness direction of the bicrystalline copper metal layer is between 0 degrees and 30 degrees. The twin-crystal copper metal layer as described in claim 1, wherein the at least one element is silver. The bicrystalline copper metal layer as described in claim 1, wherein the length of at least part of the bicrystalline lamellar grains is between 0.5 μm and 20 μm. A bicrystalline copper metal layer as described in claim 1, wherein the bicrystalline directions of two adjacent grains in the plurality of bicrystalline grains intersect. The twin-crystal copper metal layer as described in claim 1, wherein the plurality of twin-crystal grains are formed by stacking a plurality of twin crystals along the [111] crystal axis direction. A substrate with a dual-crystal copper metal layer, comprising: a substrate; and a dual-crystal copper metal layer as described in any one of claims 1 to 7, disposed on the substrate or embedded in the substrate. A substrate as described in claim 8, wherein the angle between the twin planes of at least a portion of the plurality of twin crystal grains and the surface of the substrate is between 60 degrees and 90 degrees. A method for preparing a bicrystalline copper metal layer comprises the following steps: providing an electroplating device, comprising an anode, a cathode, an electroplating solution, and a power supply source, wherein the power supply source 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 source to provide power for electroplating to grow a bicrystalline copper metal layer from a surface of the cathode. The current density is between 0.5ASD and 20ASD; more than 35% of the volume of the twin-crystal copper metal layer includes a plurality of twin-crystal grains, more than 30% of the plurality of twin-crystal grains are lamellar twin-crystal grains, and the ratio of the length to the thickness of the lamellar twin-crystal grains is greater than or equal to 2; and the electroplating solution includes a copper salt and an acid, and the electroplating solution does not include a chlorine ion. The preparation method as described in claim 10, wherein the thickness direction of the lamellar twin crystal grain is the twin crystal direction of the lamellar twin crystal grain. The preparation method as described in claim 10, wherein the angle between the twin planes of at least part of the plurality of twin crystal grains and the thickness direction of the twin crystal copper metal layer is between 0 degrees and 30 degrees. The preparation method as described in claim 10, wherein the dual-crystal copper metal layer comprises: 0.05at% to 20at% of at least one element selected from the group consisting of silver, nickel, zinc, lead, aluminum, gold, platinum, magnesium and cadmium; and the balance copper. The preparation method as described in claim 13, wherein the plating solution further includes a salt of the at least one element. The preparation method as described in claim 13, wherein the at least one element is silver. The preparation method as described in claim 15, wherein the electroplating solution further includes a silver salt. The preparation method as described in claim 10, wherein the length of at least part of the lamellar twin crystal grains is between 0.5 μm and 20 μm. The preparation method as described in claim 10, wherein the twinning directions of two adjacent grains in the plurality of twinned grains intersect. The preparation method as described in claim 10, wherein the plurality of twin crystal grains are formed by stacking a plurality of twin crystals along the [111] crystal axis direction.