Nano-twinned copper with (110) crystal plane orientation and its preparation method

Abstract

This invention provides a nano-bicrystalline copper with a (110) crystal plane orientation, comprising a plurality of first grains and a plurality of second grains interconnected thereto; wherein each first grain comprises a plurality of first nano-bicrystalline structures stacked together along a preferred direction of the (110) crystal axis, and a plurality of first nano-bicrystalline interfaces are formed between these first nano-bicrystalline structures, the angle between these first nano-bicrystalline interfaces and the thickness direction of the nano-bicrystalline copper with the (110) crystal plane orientation being 30 degrees to 90 degrees; each second grain comprises a plurality of second nano-bicrystalline structures stacked together along a (111) crystal axis. The nano-bicrystalline copper with the (110) crystal plane orientation has a better etching rate, thereby reducing the overall cost of the etching process.

Description

[Technical Field]

[0001] This invention relates to a nano-bicrystalline copper and its preparation method, particularly to a nano-bicrystalline copper with (110) crystal plane orientation and its preparation method. [Previous Technology]

[0002] Due to its high mechanical strength and high conductivity, copper has become the most common interconnect material in the field of microelectronic packaging. In response to the miniaturization of electronic components, copper wire widths have been reduced to tens or even a few micrometers, leading to increased current density and Joule heating. This further makes copper wires prone to forming voids or even open circuits in electronic components, resulting in electromigration and failure.

[0003] In response, existing technology has developed a nano-bicrystalline copper with (111) crystal plane orientation. It utilizes the special structure of coherent twin boundaries in the grains, which makes the nano-bicrystalline copper have better mechanical strength, conductivity, anti-electromigration and thermal stability. Therefore, nano-bicrystalline copper has been widely used in advanced packaging and microelectronics in recent years, such as copper-copper direct bond, copper wire, redistribution line (RDL), through / blind hole filling or lithium battery negative electrode current collector.

[0004] In integrated circuits (ICs), different electronic components are placed in specific locations according to the functions or roles to be achieved by their designers. Therefore, the copper wires used to interconnect electronic components need to have corresponding specific routes or pattern distributions. To achieve this, after a copper layer is formed by electroplating, an etching process (such as wet etching using chemical solutions or reactive-ion etching (RIE) using ion bombardment) is then performed on the copper layer to remove specific areas of the copper layer, so as to present a specific route or pattern distribution. However, the nano-bicrystalline copper with (111) crystal orientation in the prior art is difficult to etch, which results in a longer time required for wet etching or reactive-ion etching and a larger consumption of etching materials, thus increasing the overall cost of the etching process.

[0005] Accordingly, there is still a need to improve the existing structure of nano-twin crystals so that while maintaining the good properties of nano-twin crystals, they also have easy etching properties. This would reduce the time and material costs required for etching processes, and thus help the technological development of subsequent application fields. [Summary of the Invention]

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a nano-bicrystalline copper with (110) crystal plane orientation, which has better surface chemical reaction characteristics than nano-bicrystalline copper with (111) crystal plane orientation, that is, it has a higher etching rate than the prior art nano-bicrystalline copper with (111) crystal plane orientation, thereby reducing the etching process time and material cost when applied in integrated circuit manufacturing process. More specifically, the nano-bicrystalline copper with (110) crystal plane orientation has the advantages of the prior art nano-bicrystalline copper with (111) crystal plane orientation, and further has the characteristic of easy etching.

[0007] In order to achieve the aforementioned objective, the present invention provides a nano-bicrystalline copper with a (110) crystal plane orientation, comprising a plurality of first grains and a plurality of second grains interconnected thereto; wherein each first grain comprises a plurality of first nano-bicrystalline structures stacked together along the (110) crystal axis direction as a preferred orientation, and a plurality of first nano-bicrystalline interfaces are formed between the first nano-bicrystalline structures, the angle between the first nano-bicrystalline interfaces and the thickness direction of the nano-bicrystalline copper with the (110) crystal plane orientation is 30 degrees to 90 degrees; each second grain comprises a plurality of second nano-bicrystalline structures stacked together along the (111) crystal axis direction.

[0008] The first and second grains of the (110) crystal plane orientation nano-bicrystalline copper have a specific nano-bicrystalline structure, that is, the direction of the first nano-bicrystalline interface and the thickness direction of the (110) crystal plane orientation nano-bicrystalline copper have a specific angle, and the (110) crystal axis direction is the preferred direction for stacking the first nano-bicrystalline structure. The nano-bicrystalline copper with (110) crystal plane orientation provided by the present invention has a better etching rate (e.g., greater than 0.1 micrometers / minute), which is higher than that of the prior art nano-bicrystalline copper with (111) crystal plane orientation, thereby reducing the overall cost of etching process.

[0009] According to the present invention, in an image that shows the longitudinal section of the nano-bicrystalline copper with (110) crystal orientation, the "thickness direction of the nano-bicrystalline copper with (110) crystal orientation" is generally perpendicular to the surface on which it is electroplated and deposited.

[0010] According to the present invention, the "nano-bicrystalline interface" refers to the interface between one nano-bicrystalline structure and another adjacent nano-bicrystalline structure in a grain composed of multiple stacked nano-bicrystalline structures.

[0011] According to the present invention, the "angle between the first nano-bicrystalline interface and the thickness direction of the nano-bicrystalline copper with (110) crystal orientation" refers to the angle defined after the direction of each of the first nano-bicrystalline interfaces intersects with the thickness direction of the nano-bicrystalline copper with (110) crystal orientation, and the angle refers to an acute angle or a right angle among the defined angles. For example, after the direction of the first nano-bicrystalline interface intersects with the thickness direction of the nano-bicrystalline copper with (110) crystal orientation, an angle of 60 degrees and 120 degrees (totaling 180 degrees) is defined, then the "angle between the first nano-bicrystalline interface and the thickness direction of the nano-bicrystalline copper with (110) crystal orientation" is an angle of 60 degrees.

[0012] In some embodiments of the present invention, the angle between the first nano-bicrystalline interface and the thickness direction of the nano-bicrystalline copper with (110) crystal plane orientation is 45 degrees to 90 degrees. In other embodiments of the present invention, the angle between the first nano-bicrystalline interface and the thickness direction of the nano-bicrystalline copper with (110) crystal plane orientation is 60 degrees to 90 degrees.

[0013] In some embodiments of the present invention, a plurality of second nano-bicrystalline interfaces are formed between the second nano-bicrystalline structures, and the angle between the second nano-bicrystalline interfaces and the thickness direction of the nano-bicrystalline copper with (110) crystal plane orientation is 60 degrees to 90 degrees.

[0014] In some embodiments of the present invention, the twin spacing between any two adjacent first nanocrystalline interfaces can be from 20 nm to 170 nm. In other embodiments of the present invention, the twin spacing between any two adjacent first nanocrystalline interfaces can be from 50 nm to 170 nm. In other embodiments of the present invention, the twin spacing between any two adjacent first nanocrystalline interfaces can be from 40 nm to 120 nm. In other embodiments of the present invention, the twin spacing between any two adjacent first nanocrystalline interfaces can be from 20 nm to 70 nm. In other embodiments of the present invention, the twin spacing between any two adjacent first nanocrystalline interfaces can be from 30 nm to 70 nm. In other embodiments of the present invention, the twin spacing between any two adjacent first nanocrystalline interfaces can be from 20 nm to 50 nm.

[0015] In some embodiments of the present invention, the texture coefficient (TC) of stacking along the (110) crystal axis direction is greater than 1.0. In other embodiments of the present invention, the texture coefficient of stacking along the (110) crystal axis direction is greater than 2.0. In other embodiments of the present invention, the texture coefficient of stacking along the (110) crystal axis direction is greater than 2.5. In other embodiments of the present invention, the texture coefficient of stacking along the (110) crystal axis direction is greater than 2.0 and less than 2.99. It should be understood that when the texture coefficient of a particular crystal axis or crystal plane direction is significantly higher than the texture coefficients of other crystal axes or crystal plane directions, the particular crystal axis or crystal plane is generally considered to be a preferred direction; specifically, when the texture coefficient of a particular crystal axis or crystal plane direction is greater than 2.0, the particular crystal axis or crystal plane is generally considered to be a preferred direction.

[0016] In some embodiments of the present invention, the texture factor of stacked materials along the (100) crystal axis direction is less than 1. In other embodiments of the present invention, the texture factor of stacked materials along the (100) crystal axis direction is less than 0.4. In other embodiments of the present invention, the texture factor of stacked materials along the (100) crystal axis direction is less than 0.3. In other embodiments of the present invention, the texture factor of stacked materials along the (100) crystal axis direction is less than 0.1.

[0017] In some embodiments of the present invention, the texture factor of stacked crystals along the (111) crystal axis direction is less than 1. In other embodiments of the present invention, the texture factor of stacked crystals along the (111) crystal axis direction is less than 0.6. In other embodiments of the present invention, the texture factor of stacked crystals along the (111) crystal axis direction is less than 0.5. In other embodiments of the present invention, the texture factor of stacked crystals along the (111) crystal axis direction is less than 0.1.

[0018] In some embodiments of the present invention, in a longitudinal section of the nano-bicrystalline copper with (110) crystal plane orientation, the first grains and the second grains occupy more than 80% of the longitudinal section. In other embodiments of the present invention, in a longitudinal section of the nano-bicrystalline copper with (110) crystal plane orientation, the first grains and the second grains occupy more than 90% of the longitudinal section. In still other embodiments of the present invention, in a longitudinal section of the nano-bicrystalline copper with (110) crystal plane orientation, the first grains and the second grains occupy more than 90% and less than 99% of the longitudinal section.

[0019] In some embodiments of the present invention, the average width of the first grains and the second grains may each be independently from 0.1 micrometers (μm) to 50 μm. In other embodiments of the present invention, the average width of the first grains and the second grains may each be independently from 0.1 μm to 30 μm. In other embodiments of the present invention, the average width of the first grains and the second grains may each be independently from 0.1 μm to 20 μm. In other embodiments of the present invention, the average width of the first grains and the second grains may each be independently from 0.1 μm to 10 μm. The average width of the grains may be determined by the intercept method.

[0020] According to the present invention, the "longitudinal section of nano-bicrystalline copper with (110) crystal plane orientation" can be presented by any image obtained by prior art capable of displaying the microstructure of copper. For example, the "longitudinal section of nano-bicrystalline copper with (110) crystal plane orientation" can be an image obtained by taking pictures of the longitudinal section of the nano-bicrystalline copper with (110) crystal plane orientation through a focused ion beam (FIB) microscope (i.e., a focused ion beam system), but is not limited thereto. In addition, the aforementioned "longitudinal section" refers to a section obtained by taking a section along the thickness direction of the nano-bicrystalline copper with (110) crystal plane orientation.

[0021] In some embodiments of the present invention, the nano-bicrystalline copper with (110) crystal plane orientation further includes a transition layer formed on the surface of the first grains and the second grains, and the transition layer includes a plurality of third grains that do not have a nano-bicrystalline structure.

[0022] In some embodiments of the present invention, the thickness of the transition layer may be from 0.1 micrometers (μm) to 5 μm. In other embodiments of the present invention, the thickness of the transition layer may be from 0.1 μm to 4 μm. In other embodiments of the present invention, the thickness of the transition layer may be from 0.1 μm to 3 μm. In other embodiments of the present invention, the thickness of the transition layer may be from 0.1 μm to 2 μm.

[0023] In some embodiments of the present invention, the first grains may each be independently columnar crystals, and the second grains may each be independently columnar crystals. Each columnar crystal independently has a long axis direction, and the plurality of first nano-bicrystalline structures in the first grains are stacked together along the long axis direction of the first grains, and the plurality of second nano-bicrystalline structures in the second grains are stacked together along the long axis direction of the second grains.

[0024] According to the present invention, the thickness of the nano-bicrystalline copper with (110) crystal plane orientation can be adjusted according to actual needs. For example, the thickness of the nano-bicrystalline copper with (110) crystal plane orientation can be 1 μm to 500 μm, 1 μm to 350 μm, 1 μm to 200 μm, 1 μm to 100 μm, 1 μm to 80 μm, 5 μm to 80 μm, 10 μm to 80 μm, or 20 μm to 80 μm, but is not limited thereto. In some embodiments of the present invention, the thickness of the nano-bicrystalline copper with (110) crystal plane orientation can be 40 μm to 80 μm.

[0025] In some embodiments of the present invention, the etching rate of the (110) oriented nano-bicrystalline copper with sodium persulfate (Na₂S₂O₈) is greater than 0.1 μm / min. In other embodiments of the present invention, the etching rate of the (110) oriented nano-bicrystalline copper with sodium persulfate is greater than 0.13 μm / min. In other embodiments of the present invention, the etching rate of the (110) oriented nano-bicrystalline copper with sodium persulfate is greater than 0.135 μm / min. In other embodiments of the present invention, the etching rate of the (110) oriented nano-bicrystalline copper with sodium persulfate is greater than 0.14 μm / min.

[0026] Furthermore, the present invention provides a method for preparing the aforementioned nano-twinned copper with (110) crystal plane orientation, comprising the following steps: Step (a): providing an electroplating apparatus, the electroplating apparatus comprising an anode, a cathode and an electroplating solution, wherein the anode and cathode are immersed in the electroplating solution; wherein the electroplating solution comprises a copper salt, an acid, a twinning growth additive and an electroplating accelerator, the twinning growth additive comprising an animal glue and an additive, the additive comprising carrageenan, gum arabic, pectin, agar, xanthan gum, chitin, cellulose, collagen, fibrin, keratin, casein, lignin or a combination thereof; based on the total volume of the electroplating solution, the content of the twinning growth additive is 75 parts per million (i.e., 75 parts per million). The current density during the electroplating process is greater than or equal to 1 ampere per square inch (A / dm², ASD) and less than or equal to 20 ASD.

[0027] By adding a specific type and concentration of twin crystal growth additive to the electroplating solution and performing the electroplating process using a specific current density range, the nano-twin copper with (110) crystal orientation formed by electroplating can have the specific nano-twin grain microstructure as described above, thus having a better etching rate (e.g., greater than 0.1 micrometers / minute), thereby reducing the overall cost of the etching process.

[0028] According to the present invention, the animal glue refers to an extract made from connective tissues such as animal skin, bones or tendons. For example, the animal glue may be gelatin and its source may be pig skin, but it is not limited thereto.

[0029] In some embodiments of the present invention, the added ingredient may be collagen, fibroin, keratin, casein, or a combination thereof. In other embodiments of the present invention, the collagen is derived from fish scales.

[0030] In some embodiments of the present invention, the weight ratio of the animal glue to the added ingredient may be 1:5 to 1:15.

[0031] In some embodiments of the present invention, the electroplating accelerator may be sodium 3-mercapto-1-propanesulfonate (MPS), sodium bis 3-sulfopropyl disulfide (SPS), sodium 3-(benzothiazol-2-ylthio)-1-propanesulfonate (ZPS), sodium N,N-dimethyl-dithiocarbamyl propyl sulfonic acid sodium salt (DPS), 3-(carbamimidoylthio)-1-propanesulfonic acid (UPS), or a combination thereof.

[0032] In some embodiments of the present invention, the content of the copper salt is from 180 g / L to 250 g / L, and the content of the acid is from 20 ml / L to 75 ml / L, based on the total volume of the electroplating solution.

[0033] In some embodiments of the present invention, the content of the electroplating accelerator may be from 1 ppm to 10 ppm, based on the total volume of the electroplating solution.

[0034] In some embodiments of the present invention, the copper salt may be copper sulfate (CuSO4), copper methanesulfonate (Cu(CH3SO3)2), or a combination thereof. In other embodiments of the present invention, in step (a), the copper salt may be copper sulfate.

[0035] In some embodiments of the present invention, the acid may be sulfuric acid, hydrochloric acid, methanesulfonic acid or a combination thereof.

[0036] In some embodiments of the present invention, the acid may be a combination of sulfuric acid and hydrochloric acid, and the content of sulfuric acid is 20 ml / L to 70 ml / L and the content of hydrochloric acid is 0.1 ml / L to 1 ml / L, based on the total volume of the electroplating solution. In other embodiments of the present invention, the content of sulfuric acid is 40 ml / L to 70 ml / L, based on the total volume of the electroplating solution.

[0037] In some embodiments of the present invention, in step (a), the electroplating apparatus further includes a power supply source, which is connected to the anode and the cathode respectively, and is used to provide power for performing the electroplating process in step (b). In some embodiments of the present invention, the power supply source may be a direct current power supply source.

[0038] In some embodiments of the present invention, the anode may be iridium oxide (IrO2) coated with titanium metal, platinum (Pt), copper (Cu), or phosphor bronze coated with titanium metal, but is not limited thereto; the cathode may be titanium (Ti), aluminum (Al), 304 stainless steel, copper, or a printed circuit board (PCB), but is not limited thereto. The printed circuit board may be a structure in which a dielectric layer and a surface copper layer are sequentially formed on a base copper layer, and the dielectric layer in the printed circuit board has a plurality of blind vias.

[0039] In some other embodiments of the present invention, the current density during the electroplating process is greater than or equal to 1 ASD and less than or equal to 10 ASD.

[0040] In some embodiments of the present invention, the temperature during the electroplating process can be from -5°C to 60°C. In other embodiments of the present invention, the temperature during the electroplating process can be from 20°C to 60°C. In still other embodiments of the present invention, the temperature during the electroplating process can be from 20°C to 40°C.

[0041] In some embodiments of the present invention, the flow rate of the electroplating solution during the electroplating process can be from 1 liter / minute (L / min) to 3 L / min.

[0042] In this specification, the range represented by "small value to large value" means, unless otherwise specified, that the range is greater than or equal to the small value and less than or equal to the large value. For example, an angle of 30 degrees to 90 degrees means that the range of the difference can be "greater than or equal to 30 degrees and less than or equal to 90 degrees".

Implementation Method

[0043] Hereinafter, several embodiments and comparative examples are listed to illustrate the implementation of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content of the following embodiments. It should be understood that the embodiments listed in this specification are only for illustrative purposes and are not intended to limit the scope of the present invention. Those skilled in the art can make various modifications and changes based on their ordinary knowledge without departing from the spirit of the present invention to implement or apply the content of the present invention.

[0044] Example 1: Preparation of nano-bicrystalline copper with (110) crystal plane orientation

[0045] An electroplating apparatus is provided, comprising an electroplating tank (a 1.5 L modified Hastelloy tank), a water pump, a jet pipe, a cathode, an anode, an electroplating solution, and a power supply. The electroplating solution is placed in the electroplating tank, and the jet pipe, cathode, and anode are all immersed in the electroplating solution. The power supply is connected to the cathode and anode respectively, and the water pump is connected to the jet pipe. The distance between the anode and the cathode is 10 cm. The cathode is a titanium plate, and the anode is a titanium mesh coated with iridium oxide. The electroplating solution comprises copper sulfate, sulfuric acid, hydrochloric acid, a twinning growth additive, and an electroplating accelerator. Based on the total volume of the electroplating solution, the content of copper sulfate is 240 g / L, the content of sulfuric acid is 60 ml / L, the content of hydrochloric acid is 0.2 ml / L, the content of the twinning growth additive is 80 ppm, and the content of the electroplating accelerator is 1 ppm to 10 ppm. The twin crystal growth additive uses animal glue and collagen, fibroin, keratin, casein or a combination thereof as additives, and the weight ratio between animal glue and additives is 1:8; the electroplating accelerator uses sodium polydisulfide dipropane sulfonate.

[0046] Subsequently, the components in the electroplating solution were uniformly mixed using a magnet at a stirring speed of approximately 800 rpm. Then, an electroplating process was performed using the electroplating apparatus to form the nano-bicrystalline copper with a (110) crystal plane orientation as described in Example 1 on the cathode surface. The electroplating process used a DC power supply (manufacturer: GITEK, model: GR-3030H) with a current density of 5 ASD as the power source. The temperature during the electroplating process was approximately 30°C, and the electroplating area was approximately 30 square centimeters (approximately 3 centimeters wide and 10 centimeters long). Simultaneously, the flow rate of the electroplating solution was maintained at 2 L / min during the electroplating process using a water pump and a jet pipe. The average thickness of the nano-bicrystalline copper with a (110) crystal plane orientation in Example 1 was 60 μm.

[0047] Example 2: Preparation of nano-bicrystalline copper with (110) crystal plane orientation

[0048] The preparation process of Example 2 is similar to that of Example 1, except that the content of the bicrystalline growth additive in the electroplating solution used in Example 2 is 120 ppm. Apart from the aforementioned differences, Example 2 was prepared using the same preparation process as Example 1 to obtain the nano-bicrystalline copper with (110) crystal plane orientation. The average thickness of the nano-bicrystalline copper with (110) crystal plane orientation in Example 2 is 60 μm.

[0049] Example 3: Preparation of nano-bicrystalline copper with (110) crystal plane orientation

[0050] The preparation process of Example 3 is similar to that of Example 1, the main difference being that the content of the bicrystalline growth additive in the electroplating solution used in Example 3 is 160 ppm. Apart from the aforementioned differences, Example 3 was prepared using the same preparation process as Example 1 to obtain the nano-bicrystalline copper with (110) crystal plane orientation of Example 3. The average thickness of the nano-bicrystalline copper with (110) crystal plane orientation in Example 3 is 60 μm.

[0051] Example 4: Preparation of nano-bicrystalline copper with (110) crystal plane orientation

[0052] An electroplating apparatus is provided, comprising an electroplating tank (a 1.5 L modified Hastelloy tank), a water pump, a jet pipe, a cathode, an anode, an electroplating solution, and a power supply. The electroplating solution is placed in the electroplating tank, and the jet pipe, cathode, and anode are all immersed in the electroplating solution. The power supply is connected to the cathode and anode respectively, and the water pump is connected to the jet pipe. The distance between the anode and the cathode is 10 cm. The cathode is a printed circuit board, which has a structure in which a dielectric layer (made of glass fiber) and a surface copper layer are sequentially formed on the surface of a base copper layer. The dielectric layer in the printed circuit board has blind vias (approximately 80 μm in diameter and approximately 35 μm in depth; and the sidewalls of the blind vias have a copper layer with a thickness of approximately 0.5 μm) arranged in an array. The anode is a titanium mesh coated with iridium oxide. The electroplating solution comprises copper sulfate, sulfuric acid, hydrochloric acid, a twinning growth additive, and an electroplating accelerator. Based on the total volume of the electroplating solution, the content of copper sulfate is 240 g / L, the content of sulfuric acid is 60 ml / L, the content of hydrochloric acid is 0.2 ml / L, the content of the twinning growth additive is 120 ppm, and the content of the electroplating accelerator is 1 ppm to 10 ppm. The twinning growth additive is selected from animal glue and collagen, fibroin, keratin, casein, or combinations thereof as additives, with a weight ratio of animal glue to additives of 1:8; the electroplating accelerator is selected from sodium polydithiopropane sulfonate.

[0053] Subsequently, the components in the electroplating solution were uniformly mixed using a magnet at a stirring speed of approximately 800 rpm. Then, an electroplating process was performed using the electroplating apparatus to form nano-bicrystalline copper with a (110) crystal plane orientation, as described in Example 4, on the surface of the printed circuit board and in the blind holes. The electroplating process used a DC power supply (manufacturer: GITEK, model: GR-3030H) with a current density of 1 ASD as the power source. The temperature during the electroplating process was approximately 25°C, and the electroplating time was approximately 180 minutes. Simultaneously, the electroplating solution was maintained at a flow rate of 2 L / min during the electroplating process using a water pump and jet pipe. The average thickness of the nano-bicrystalline copper with a (110) crystal plane orientation in Example 4 was 40 μm.

[0054] Comparative Example 1: Nano-twinned copper with (111) crystal plane orientation

[0055] An electroplating apparatus is provided, comprising an electroplating tank (a 1.5 L modified Hastelloy tank), a water pump, a jet pipe, a cathode, an anode, an electroplating solution, and a power supply. The electroplating solution is placed in the electroplating tank, and the jet pipe, cathode, and anode are all immersed in the electroplating solution. The power supply is connected to the cathode and anode respectively, and the water pump is connected to the jet pipe. The distance between the anode and the cathode is 10 cm. The cathode is a titanium plate, and the anode is a titanium mesh coated with iridium oxide. The electroplating solution comprises copper sulfate, sulfuric acid, hydrochloric acid, a twinning growth additive, and an electroplating accelerator. Based on the total volume of the electroplating solution, the content of copper sulfate is 240 g / L, the content of sulfuric acid is 30 ml / L, the content of hydrochloric acid is 0.1 ml / L, the content of the twinning growth additive is 40 ppm, and the content of the electroplating accelerator is 1 ppm to 10 ppm. The twin crystal growth additive is made from animal glue and collagen, fibroin, keratin, casein or a combination thereof as additives; the electroplating accelerator is sodium polydithiopropane sulfonate.

[0056] Subsequently, the components in the electroplating solution were uniformly mixed using a magnet at a stirring speed of approximately 800 rpm, and then an electroplating process was performed using the electroplating apparatus to form nano-bicrystalline copper with a (111) crystal plane orientation, as in Comparative Example 1, on the cathode surface. The electroplating process used a DC power supply (manufacturer: GITEK, model: GR-3030H) with a current density of 8 ASD as the power source. The temperature during the electroplating process was approximately 30°C, and the electroplating area was approximately 4 square centimeters (approximately 2 cm wide and 2 cm long). The electroplating solution was maintained at a flow rate of 2 L / min during the electroplating process using a water pump and a jet pipe. The average thickness of the nano-bicrystalline copper with a (111) crystal plane orientation in Comparative Example 1 was 60 μm.

[0057] Comparative Example 2: Electroplated Copper

[0058] The preparation process of Comparative Example 2 is similar to that of Example 1, with the main differences being: (1) the electroplating solution used in Comparative Example 2 consists only of copper sulfate at a concentration of 240 g / L, sulfuric acid at a concentration of 60 ml / L, and hydrochloric acid at a concentration of 0.2 ml / L, meaning that the electroplating solution does not contain twinning growth additives or electroplating accelerators; and (2) the current density of the electroplating process is 8 ASD, and the electroplating area is approximately 4 square centimeters (approximately 2 cm wide and 2 cm long). Apart from the aforementioned differences, Comparative Example 2 was prepared using the same preparation process as Example 1 to obtain the electroplated copper of Comparative Example 2. The average thickness of the electroplated copper of Comparative Example 2 is 60 μm.

[0059] Analysis 1: Copper Microstructure Analysis

[0060] Analysis 1-1: Observation of grains and nano-bicrystalline interfaces

[0061] Analysis 1-1 uses nano-bicrystalline copper with (110) crystal plane orientation from Examples 1 to 4 and nano-bicrystalline copper with (111) crystal plane orientation from Comparative Example 1. The longitudinal sections of these copper groups were obtained by cold embedding in resin and polishing. Subsequently, the longitudinal sections of these copper groups were photographed at magnifications of 1000x to 2000x using a FIB microscope (Focused Ion Beam Microsystems) (manufacturer: FEI, model: Versa 3D) to observe the microstructure of the nano-bicrystalline grains in each group. The FIB images of Examples 1 to 4 and Comparative Example 1 are shown in Figures 1 to 5, respectively.

[0062] Please refer to Figure 1 first. In this figure, the nano-bicrystalline copper 1 with (110) crystal orientation of Example 1 is formed on the surface of the substrate S (i.e., the cathode). Multiple columnar grains can be clearly observed in the nano-bicrystalline copper 1 with (110) crystal orientation of Example 1. These grains are formed by stacking nano-bicrystalline crystals, so that the grains show alternating light and dark and parallel nano-bicrystalline interfaces. At the same time, the direction of each nano-bicrystalline interface is approximately perpendicular to the thickness direction of the nano-bicrystalline copper with (110) crystal orientation. That is, the angle between the direction of the nano-bicrystalline interface and the thickness direction of the nano-bicrystalline copper with (110) crystal orientation is approximately 60 to 90 degrees. It should be understood that the nano-bicrystalline copper 1 with (110) crystal orientation in Example 1 is grown from the surface of the substrate S in the opposite direction (i.e., from the top in the image of FIG1). Therefore, the growth direction of the grain is generally perpendicular to the surface of the substrate S, and the growth direction of the grain is also the thickness direction of the copper.

[0063] Figures 2 and 3 show that the microstructure of the nano-bicrystalline copper with (110) crystal plane orientation in Examples 2 and 3 is similar to that in Example 1. That is, multiple grains can also be clearly observed in the nano-bicrystalline copper with (110) crystal plane orientation in Examples 2 and 3. These grains are formed by the stacking of nano-bicrystalline crystals, thus presenting alternating light and dark and parallel nano-bicrystalline interfaces in the grains. At the same time, the angle between the direction of the nano-bicrystalline interface and the thickness direction (i.e., the electroplating deposition direction) of the nano-bicrystalline copper with (110) crystal plane orientation is about 60 to 90 degrees. In addition, Figure 3 also shows that the angle between the direction of some nano-bicrystalline interfaces and the thickness direction of the nano-bicrystalline copper with (110) crystal plane orientation in Example 3 is about 45 degrees (which can also be seen from Figure 7C).

[0064] Please refer to Figure 4 again. Since the substrate S (i.e., the cathode) used to prepare the nano-bicrystalline copper 1 with (110) crystal orientation in Example 4 is a printed circuit board, which is composed of a bottom copper layer B and a dielectric layer D formed on the surface of the bottom copper layer B, and the dielectric layer D has an opening H (a blind hole), the nano-bicrystalline copper 1 with (110) crystal orientation in Example 4 is formed not only on the surface of the dielectric layer D, but also in the opening H (i.e., formed on the bottom surface and sidewall surface of the opening H). In the nano-bicrystalline copper 1 with (110) crystal orientation in Example 4, multiple grains can be clearly observed. These grains are formed by stacking nano-bicrystalline crystals, thus presenting alternating light and dark nano-bicrystalline interfaces that are parallel to each other. At the same time, the orientation of the nano-bicrystalline interfaces is generally perpendicular to the thickness direction of the nano-bicrystalline copper with (110) crystal orientation. That is, the angle between the orientation of the nano-bicrystalline interfaces and the thickness direction of the nano-bicrystalline copper with (110) crystal orientation is about 60 degrees to 90 degrees.

[0065] Refer to Figure 5 again. The nano-bicrystalline copper with (111) crystal orientation in Comparative Example 1 exhibits a structure similar to that in Examples 1 to 3. That is, multiple grains can also be clearly observed in the nano-bicrystalline copper with (111) crystal orientation in Comparative Example 1. These grains are formed by stacking nano-bicrystalline crystals, thus presenting alternating light and dark and parallel nano-bicrystalline interfaces in the grains. At the same time, the angle between the direction of the nano-bicrystalline interface and the thickness direction (i.e., the electroplating deposition direction) of the nano-bicrystalline copper with (111) crystal orientation is about 60 degrees to 90 degrees.

[0066] Analysis 1-2: Determination of the proportion of nano-bicrystalline grains

[0067] Analysis 1-2 further selected Figures 1 to 3, and used ImageJ software to select and calculate the area of ​​the grains with nano-bicrystalline interfaces, and then divided by the area of ​​the copper longitudinal section in Figures 1 to 3, thereby obtaining the cross-sectional area ratio of nano-bicrystalline grains in nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 3. The results are listed in Table 1 below. Table 1: Cross-sectional area ratio of nano-bicrystalline grains in nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 3 Group The percentage of cross-sectional area of ​​nano-bicrystalline grains (%) Example 1 93 Example 2 93 Example 3 94

[0068] Analysis 1-3: Determining the preferred orientation

[0069] (1) Texture coefficient

[0070] This analysis uses nano-bicrystalline copper with (110) crystal plane orientation from Examples 1 to 4, nano-bicrystalline copper with (111) crystal plane orientation from Comparative Example 1, and electroplated copper from Comparative Example 2 as test samples. The microstructure characteristics of the nano-bicrystalline grains in each group were analyzed using an X-ray diffractometer (XRD; manufacturer: Bruker, model: D8 Advance). Furthermore, the texture coefficient of stacking in different crystal axis directions (or crystal plane directions) was obtained to determine the preferred orientation of the grains. Specifically, the samples of each group were placed in an XRD and measured in a scanning range of 40° to 80° with 2θ. The results are shown in Figures 6A to 6F in sequence. Subsequently, the texture coefficients of the grains in the (111), (100), and (110) crystal axis directions were calculated using the Harris method for the characteristic peak intensities of the (111), (100), and (110) crystal axes, and are listed in Table 2 below. The texture coefficients were calculated using the following formula: Texture coefficient (TC) (hkl) = [I (hkl) / I0(hkl)] / {Σ[I (hkl) / I0(hkl)] / n}; I represents the characteristic peak intensity measured in a certain crystal plane direction; I0 represents the standard peak intensity in a certain crystal plane direction; hkl represents the crystal plane index; n represents the total number of measured crystal plane directions; Taking the XRD measurement results of Example 1 as an example, the standard peak intensities of the three crystal planes (111), (100), and (110) are 9990, 4280, and 1710, respectively, while the characteristic peak intensities of the three crystal planes (111), (100), and (110) are 1127, 312, and 705, respectively. Substituting the aforementioned measurement results into the above formula, the texture coefficients of the three crystal planes (111), (100), and (110) (or crystal axis directions) are calculated as follows: TC(111) = [(1127 / 9990)] / {[(1127 / 9990)+(312 / 4280)+(705 / 1710)] / 3}=0.57; TC(111) = [(312 / 4280)] / {[(1127 / 9990)+(312 / 4280)+(705 / 1710)] / 3}=0.37; and TC(111) = [(705 / 1710)] / {[(1127 / 9990)+(312 / 4280)+(705 / 1710)] / 3}=2.07. Table 2: Texture coefficient results for the crystal axis directions of (111), (100) and (110) in nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 4, nano-bicrystalline copper with (111) crystal plane orientation in Comparative Example 1 and electroplated copper in Comparative Example 2. Group Texture coefficient (111) Crystal axis direction (100) Crystal axis direction (110) Crystal axis direction Example 1 0.57 0.37 2.07 Example 2 0.12 0.10 2.78 Example 3 0.09 0.06 2.86 Example 4 0.34 0.19 2.46 Comparative Example 1 2.82 0.08 0.10 Comparative Example 2 1.21 0.50 1.29

[0071] As can be seen from the results in Table 2 above, among the three crystal axis directions of (111), (100) and (110), the nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 4 has the highest texture coefficient in the (110) crystal axis direction, which is 2.07, 2.78, 2.86 and 2.46 respectively. It can be seen that the nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 4 has grains formed with the (110) crystal axis as the main stacking direction of the nano-bicrystalline. At the same time, it is generally recognized in the art that when the texture coefficient of a specific crystal axis or crystal plane direction is significantly higher than that of other directions (especially when the texture coefficient is higher than 2.0), it is considered as a preferred orientation. Therefore, the nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 4 does indeed have grains formed with the (110) crystal axis as the preferred orientation for stacking.

[0072] In contrast, the nano-bicrystalline copper with (111) crystal plane orientation in Comparative Example 1 has the highest texture factor (2.82) among the three crystal axis directions (111), (100) and (110), while the texture factors of the (100) crystal axis direction and the (110) crystal axis direction are only 0.08 and 0.10, respectively. This shows that the nano-bicrystalline copper with (111) crystal plane orientation in Comparative Example 1 is stacked with the (111) crystal axis as the preferred orientation. Looking at the electroplated copper of Comparative Example 2, among the three crystal axis directions (111), (100) and (110), the texture coefficients of the (111) crystal axis direction and the (110) crystal axis direction are similar, at 1.21 and 1.29 respectively, while the texture coefficient of the (100) crystal axis direction is 0.50. It can be seen that the electroplated copper of Comparative Example 2 does not have a clear and single stacking direction, nor does it have a preferred orientation.

[0073] (2) Electron backscattering diffraction (EBSD) analysis

[0074] This analysis uses nano-bicrystalline copper with (110) crystal plane orientation from Examples 1 to 3 as test samples. Electron backscattering diffraction technology combined with scanning electron microscope (SEM) is used to obtain the microstructure characteristics of nano-bicrystalline grains of each group at a magnification of 1000x to 2000x. The analysis software is then used to obtain the results indicating the preferred orientation of the grains, which is the OIM (orientation imaging microscopy) image. The results are shown in Figures 7A to 7C in sequence. Among them, the grain area marked in green represents the grains stacked with (110) crystal axis as the preferred orientation, and the grain area marked in blue represents the grains stacked with (111) crystal axis as the preferred orientation.

[0075] As can be seen from the results in Figures 7A to 7C, the green-marked grains occupy most of the area, indicating that the nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 3 does indeed contain grains stacked with the (110) crystal axis as the preferred orientation. At the same time, the blue-marked grain areas can also be observed in Figures 7A to 7C, indicating that the nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 3 also contains grains stacked with the (111) crystal axis.

[0076] Analysis 2: Determination of Etching Rate

[0077] Analysis 2 used nano-twin copper with (110) crystal plane orientation from Examples 1 to 4, nano-twin copper with (111) crystal plane orientation from Comparative Example 1, and electroplated copper from Comparative Example 2 as samples for testing. Specifically, the samples of each group were placed in a 90°C oven for 30 minutes, and then removed and the weight of each group was measured, which is the weight before etching, denoted as Wa, in grams (g). Next, the samples of each group were immersed in a sodium persulfate solution with a concentration of 50 g / L (as etching solution) for 2 minutes, and then removed and placed in a 90°C oven for 30 minutes, and then the weight of each group was measured, which is the weight after etching, denoted as Wb, in grams. The resistance of a sample to etching solution can be represented by its etching rate. A higher etching rate indicates that the sample is easier to etch. The etching rate is calculated by dividing the thickness change of the sample before and after immersion in the etching solution by the immersion time. The thickness change of the sample is calculated by the following formula: {(WaWb) / [2×sample area (cm2)×8.92]}×10000, with units of μm. The results of Wa, Wb, thickness change, and etching rate are listed in Table 3 below. Table 3: Results of etching rate determination for nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 4, nano-bicrystalline copper with (111) crystal plane orientation in Comparative Example 1, and electroplated copper in Comparative Example 2. Group W a (g) W b (g) Sample area (cm 2 ) Thickness variation (μm) Etching rate (μm / minute) Example 1 0.0562 0.0514 1 0.269 0.134 Example 2 0.0582 0.0532 1 0.280 0.139 Example 3 0.0591 0.0540 1 0.286 0.141 Example 4 0.1602 0.1558 0.9 0.274 0.137 Comparative Example 1 0.0675 0.0646 1 0.163 0.081 Comparative Example 2 0.0457 0.0424 1 0.185 0.094

[0078] As can be seen from the results in Table 3 above, the etching rates of the nano-bicrystalline copper with (110) crystal orientation in Examples 1 to 4 are 0.134 μm, 0.139 μm, 0.141 μm and 0.137 μm per minute, respectively. These are all significantly higher than the etching rate of the nano-bicrystalline copper with (111) crystal orientation in Comparative Example 1 (0.081 μm / min) and the etching rate of the electroplated copper in Comparative Example 2 (0.094 μm / min). Therefore, it can be seen that the nano-bicrystalline copper with (110) crystal orientation in Examples 1 to 4 does have the characteristic of easy etching, and the etching rate is greater than 0.1 μm / min.

[0079] In summary, the nano-bicrystalline copper with (110) crystal orientation of the present invention has a specific nano-bicrystalline grain microstructure that is different from that of the nano-bicrystalline copper with (111) crystal orientation in the prior art. Therefore, the nano-bicrystalline copper with (110) crystal orientation of the present invention can have a higher etching rate, that is, it has the characteristic of easy etching, which can reduce the time and material cost required for etching process, thereby contributing to the development of related technical fields and enhancing its commercial value. [Simplified Explanation of the Diagram]

[0080] Figure 1 is an image of a longitudinal section of the nano-twin copper with (110) crystal plane orientation of Example 1 observed under a FIB microscope at 2000x magnification; Figure 2 is an image of a longitudinal section of the nano-twin copper with (110) crystal plane orientation of Example 2 observed under a FIB microscope at 2000x magnification; Figure 3 is an image of a longitudinal section of the nano-twin copper with (110) crystal plane orientation of Example 3 observed under a FIB microscope at 2000x magnification; Figure 4 is an image of a longitudinal section of the nano-twin copper with (110) crystal plane orientation of Example 4 observed under a FIB microscope at 1000x magnification; Figure 5 is an image of a longitudinal section of the nano-twin copper with (111) crystal plane orientation of Comparative Example 1 observed under a FIB microscope at 2000x magnification; Figures 6A to 6F show the results of X-ray diffraction analysis of nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 4, nano-bicrystalline copper with (111) crystal plane orientation in Comparative Example 1, and electroplated copper in Comparative Example 2, respectively; Figures 7A to 7C show the results of electron backscattering diffraction analysis of nano-bicrystalline copper with (110) crystal plane orientation in Examples 1 to 3, respectively. [Biomaterial Storage]

[0082] None.

Claims

1. A nano-twinned copper with a (110) crystal plane orientation, comprising a plurality of interconnected first grains and a plurality of interconnected second grains; wherein, Each first grain comprises a plurality of first nano-bicrystalline structures stacked together along the (110) crystal axis direction, which is a preferred orientation, and a plurality of first nano-bicrystalline interfaces are formed between the first nano-bicrystalline structures. The angle between the first nano-bicrystalline interfaces and the thickness direction of the nano-bicrystalline copper with the (110) crystal plane orientation is 30 degrees to 90 degrees. Each second grain comprises a plurality of second nano-bicrystalline structures stacked together along the (111) crystal axis direction.

2. The nano-bicrystalline copper with (110) crystal plane orientation as described in claim 1, wherein, The texture coefficient of stacked crystals along the (110) crystal axis is greater than 2.

0.

3. The nano-bicrystalline copper with (110) crystal plane orientation as described in claim 1, wherein, In one longitudinal section of the nano-twin copper with (110) crystal orientation, the first grains and the second grains account for more than 80% of the longitudinal section.

4. The nano-bicrystalline copper with (110) crystal plane orientation as described in claim 1, wherein, The average width of each of the first grains and the second grains is independently between 0.1 micrometers and 50 micrometers.

5. Nanocrystalline copper with (110) crystal plane orientation as described in claim 1, wherein, The nano-bicrystalline copper with (110) crystal plane orientation also includes a transition layer formed on the surface of the first grains and the second grains, and the transition layer includes a plurality of third grains that do not have a nano-bicrystalline structure.

6. The nano-bicrystalline copper with (110) crystal plane orientation as described in claim 1, wherein, The thickness of the nano-bicrystalline copper with (110) crystal plane orientation ranges from 1 micrometer to 500 micrometers.

7. The nano-twinned copper with (110) crystal plane orientation as described in any one of claims 1 to 6, wherein, The etching rate of the nano-bicrystalline copper with (110) crystal plane orientation by sodium persulfate is greater than 0.1 micrometers / minute.

8. A method for preparing nano-bicrystalline copper with (110) crystal plane orientation as described in any one of claims 1 to 7, comprising the following steps: Step (a): providing an electroplating apparatus comprising an anode, a cathode, and an electroplating solution, wherein the anode and cathode are immersed in the electroplating solution; wherein, The electroplating solution contains a copper salt, an acid, a twinning growth additive, and an electroplating accelerator. The twinning growth additive contains an animal glue and an additive, which includes carrageenan, gum arabic, pectin, agar, xanthan gum, chitin, cellulose, collagen, fibroin, keratin, casein, lignin, or a combination thereof. Based on the total volume of the electroplating solution, the content of the twin crystal growth additive is 75 to 180 parts per million; and step (b): performing an electroplating process through the electroplating apparatus and forming the nano-twin copper with (110) crystal orientation on the cathode surface, wherein the current density during the electroplating process is greater than or equal to 1 ampere per square inch and less than or equal to 20 amperes per square inch.

9. A method for preparing nano-bicrystalline copper with (110) crystal plane orientation as described in claim 8, wherein, The cathode may contain titanium, aluminum, 304 stainless steel, copper, or a printed circuit board.

10. A method for preparing nano-bicrystalline copper with (110) crystal plane orientation as described in claim 8, wherein, The electroplating accelerator contains sodium 3-mercapto-1-propanesulfonate, sodium polydithiodipropanesulfonate, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate, sodium N,N-dimethyldithiomethamide propanesulfonate, 3-thio-isothiourea propanesulfonic acid, or combinations thereof.

11. A method for preparing nano-bicrystalline copper with (110) crystal plane orientation as described in claim 8, wherein, Based on the total volume of the electroplating solution, the content of the copper salt is from 180 g / L to 250 g / L, and the content of the acid is from 20 ml / L to 75 ml / L.

Images