Copper complex ink and method for producing copper film

Abstract

Provided are a copper complex ink and a method for producing a copper film, which are capable of producing copper wiring that has excellent storage stability, low volume resistivity, and high smoothness. [Solution] A copper complex ink containing a copper complex represented by the general formula (HCOO)2Cu((CH3)2C(NH2)CH2OH)2, in which the proportion of precipitated particles within 30 days from production is less than 50 area %, and the maximum particle diameter of the precipitated particles is less than 10 μm.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a copper complex ink and a copper film. [Background technology]

[0002] In recent years, printed electronics has been developed as a wiring technology for semiconductor elements, electronic circuits, etc. Printed electronics has attracted attention because it can reduce manufacturing costs compared to existing semiconductor manufacturing technologies such as photolithography.

[0003] Inks using complexes have been developed as inks for such printed electronics (for example, Patent Document 1, etc.). Patent Document 1 discloses that it is possible to provide a conductive ink for copper-nickel alloy electrodes, a substrate with copper-nickel alloy electrodes, which is low-cost, has excellent atmospheric stability, and enables metal wiring with a smooth surface, and a method for manufacturing the same. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2022 / 130892A1 [Patent Document 2] WO2010 / 018771A1 Summary of the Invention [Problem to be solved by the invention]

[0005] Metal wiring can be obtained, for example, by applying a metal complex ink to form a thin film, followed by a heat treatment. However, when metal wiring is produced using conventional metal complex inks, particularly copper complex inks, the volume resistivity of the resulting copper wiring is high to begin with, and the copper complex ink has a problem with storage stability, which causes the volume resistivity of the copper wiring obtained using the copper complex ink to become even higher after storage.

[0006] Furthermore, it is preferable that the surface of metal wiring has high smoothness, but the smoothness of copper wiring obtained using conventional copper complex inks is low, and the smoothness of copper wiring obtained using copper complex inks after storage is even lower.

[0007] Therefore, an object of the present invention is to provide a copper complex ink and a method for producing a copper film that are excellent in storage stability and that can produce copper wiring with low volume resistivity and high smoothness. [Means for solving the problem]

[0008] In order to solve the above problems, the copper complex ink of the present invention contains a copper complex represented by the general formula (HCOO)2Cu((CH3)2C(NH2)CH2OH)2, and the proportion of precipitated particles within 30 days from production is less than 50 area %, and the maximum particle diameter of the precipitated particles is less than 10 μm.

[0009] In the copper complex ink of the present invention, the proportion of the precipitated particles present on the day of production may be 0% by area.

[0010] The copper complex ink of the present invention exhibits a shear rate of 5.34 S -1 In this case, the viscosity may be 1 to 10 Pa·s, and the rate of change in viscosity 30 days after production relative to the viscosity on the day of production may be 20% or less.

[0011] The copper complex ink of the present invention has a shear rate of 0.01 S for 30 days after production. -1 The viscosity when the shear rate is 100S -1 In this case, the value obtained by dividing the value by the viscosity may be less than 10.

[0012] In order to solve the above problems, the method for producing a copper film of the present invention includes a heat treatment step of heat treating the copper complex ink of the present invention to form a copper film. [Effects of the Invention]

[0013] The present invention can provide a copper complex ink and a method for producing a copper film that are excellent in storage stability and can produce copper wiring with low volume resistivity and high smoothness. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view of an example of a stirrer that can be used in a method for producing a copper complex ink. [Figure 2] 1 shows images of the copper complex inks of Examples 1 to 3 observed with a laser microscope. [Figure 3] 1 shows images of the copper complex inks of Examples 4 to 6 observed with a laser microscope. [Figure 4] 1 shows images of the copper complex inks of Comparative Examples 1 to 4 observed with a laser microscope. [Figure 5] 1 is an enlarged SEM image of a cross section of a copper film in Example 1. [Figure 6] 1 is an enlarged SEM image of a cross section of a copper film in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, one embodiment of the method for producing the copper complex ink and copper film of the present invention will be described.

[0016] [Copper complex ink] The copper complex ink contains the following copper complex, and may also contain solvents and additives as appropriate.

[0017] Examples of solvents that can be contained in the copper complex ink include hydrocarbon-based solvents, alcohol-based solvents, ketone-based solvents, ester-based solvents, ether-based solvents, glycol-based solvents, glyme-based solvents, halogen-based solvents, aromatic solvents, and heterocycle-containing solvents. I would like to add.

[0018] The copper complex ink may also contain additives such as adhesion promoters, surface conditioners, antifoaming agents, and rheology control agents.

[0019] <Copper complex> Copper complexes are complexes represented by the general formula (HCOO)2Cu((CH3)2C(NH2)CH2OH)2. In this complex, two molecules of (CH3)2C(NH2)CH2OH (2-aminomethyl-propanol, hereafter sometimes referred to as "AMP") are coordinated to copper formate (Cu(HCOO)2) as a ligand. Hereinafter, the copper complex represented by (HCOO)2Cu((CH3)2C(NH2)CH2OH)2 will be referred to as "Cu-AMP".

[0020] The copper complex ink of the present invention preferably has a 0% by area ratio of precipitated particles on the day of production. Copper complex inks produced by conventional methods (e.g., Patent Document 1) contain a large amount of precipitated particles immediately after production, including large particles with diameters of 10 μm or more. The presence of a large amount of precipitated particles results in copper wiring produced using this copper complex having a high volume resistivity and low smoothness.

[0021] In the present invention, the absence of precipitated particles immediately after production makes it possible to form copper wiring with low volume resistivity and high smoothness. An example of a method for producing the copper complex ink of the present invention will be described later.

[0022] In the copper complex ink of the present invention, the proportion of precipitated particles is less than 50% by area within 30 days after production. As described above, due to the presence of a large amount of precipitated particles, copper wiring produced using this copper complex has high volume resistivity and low smoothness. One characteristic of copper complex ink is that precipitated particles gradually appear and increase over time after production. However, if the proportion of precipitated particles is less than 50% by area, copper wiring with low volume resistivity and high smoothness can be formed.

[0023] The proportion of precipitated particles within 30 days after production is preferably less than 40 area %, more preferably less than 2 area %, and even more preferably less than 0.5 area %. The fewer precipitated particles there are in the copper complex ink, the lower the volume resistivity and the more smooth the copper wiring that can be produced.

[0024] In the copper complex ink of the present invention, even if precipitated particles are present, the maximum particle size of the precipitated particles is less than 10 μm. If the particle size is 10 μm or more, the smoothness of the copper wiring produced using this copper complex will be extremely low.

[0025] The maximum particle size refers to the particle size of the largest particle among the precipitated particles. The smaller the maximum particle size of the precipitated particles, the higher the smoothness of the copper wiring produced using this copper complex. The maximum particle size of the precipitated particles is preferably less than 5 μm, more preferably less than 3 μm, and even more preferably less than 1 μm.

[0026] The copper complex ink of the present invention exhibits a shear rate of 5.34 S -1 In this case, the viscosity may be 1 to 10 Pa·s. A viscosity of 1 to 10 Pa·s allows the copper complex ink to pass through the screen with ease, resulting in excellent screen printing properties. If the viscosity is less than 1 Pa·s, the viscosity may be too low and printing may not be possible in the shape of a wiring or the like. If the viscosity is greater than 10 Pa·s, the viscosity may be too high and the copper complex ink may not pass through the screen, resulting in printing not being possible at all.

[0027] The copper complex ink of the present invention may have a viscosity change rate of 20% or less 30 days after production relative to the viscosity on the day of production. Copper complex inks produced by conventional production methods (e.g., Patent Document 1) have poor storage stability and tend to experience a significant decrease in viscosity over time after production. Therefore, when producing copper wiring, it may be necessary to change the production conditions of the copper wiring depending on the change in viscosity. However, since the copper complex ink of the present invention has a small viscosity change rate due to storage, copper wiring can be produced using copper complex ink 30 days after production under the same conditions as when using copper complex ink immediately after production.

[0028] The copper complex ink of the present invention has a shear rate of 0.01 S for 30 days after production. -1 The viscosity when the shear rate is 100S -1 The value obtained by dividing the viscosity by the viscosity in the case of (1) may be less than 10. This value serves as a guideline for indicating the thixotropy of a copper complex ink intended for screen printing. When a copper complex ink is used for screen printing, i.e., at high shear rates, it exhibits excellent liquid-like fluidity behavior, thereby improving screen elimination. It is important that the copper complex ink, which has a slow shear rate after passing through the screen and being printed, behaves like a solid so that it can retain its printed shape. From this perspective, a value of less than 10 results in excellent printing properties, such as screen printing. Furthermore, while a value of 10 or more does not pose a problem with printing properties, if the presence ratio of precipitated particles, described below, exceeds 50 area %, this value may be greater than 10. This value can serve as a guideline for predicting the presence of precipitated particles.

[0029] [Method of manufacturing copper complex ink] The method for producing the copper complex ink is not particularly limited, but the copper complex ink can be produced, for example, by the method described below.

[0030] (Raw material for copper complex ink) The raw materials for copper complex ink can be Cu(HCOO)2·4H2O powder and (CH3)2C(NH2)CH2OH solid. Because two molecules of (CH3)2C(NH2)CH2OH coordinate to Cu(HCOO)2, the molar ratio when mixing these is preferably Cu(HCOO)2·4H2O:(CH3)2C(NH2)CH2OH = 1:2, with an allowable range of 1:1.8 to 2.2. The mixture of Cu(HCOO)2·4H2O powder and (CH3)2C(NH2)CH2OH solid can be mixed using the following mixing process.

[0031] (CH3)2C(NH2)CH2OH is in a solid state at room temperature (5°C to 35°C), and considering that it will be coordinated to Cu(HCOO)2, it is considered preferable to heat (CH3)2C(NH2)CH2OH to make it liquid. However, in the manufacturing method of this embodiment, copper complex ink can be manufactured without any problems even if it is used in a solid state.

[0032] <Crushing process> Cu(HCOO)2·4H2O may increase in weight by absorbing moisture from the air and may also aggregate to form lumps. Therefore, to crush these lumps and facilitate mixing of the raw materials, a crushing step of crushing Cu(HCOO)2·4H2O powder may be included before the stirring step described below.

[0033] <Mixing process> The raw materials for copper complex ink can be prepared by mixing powdered Cu(HCOO)2·4H2O and solid (CH3)2C(NH2)CH2OH to form a mixture, then adding the mixture to the container of the mixer described below and carrying out the stirring process. Alternatively, these raw materials can be separately placed in their own containers and then stirred without mixing them.

[0034] <Stirring process> This process involves stirring a mixture of Cu(HCOO)2·4H2O powder and (CH3)2C(NH2)CH2OH solid using a stirrer.

[0035] (mixer) The agitator may be a container having an inner wall surface and a rotating member that rotates slightly inside the inner wall surface, and agitates the mixture that exists in a film-like form between the rotating member and the inner wall surface by centrifugal force generated by the rotation of the rotating member. The rotating member is cylindrical and positioned with a small gap between it and the inner wall surface, and has multiple holes that penetrate inward and outward.

[0036] An example of an agitator that can be used in the agitation step is the high-speed agitator 300 disclosed in Patent Document 2. More specifically, a thin film swirling high-speed mixer (Filmix (registered trademark), manufactured by Primix Corporation) can be used.

[0037] As shown in FIG. 1, the high-speed mixer 300 disclosed in Patent Document 2 has a container 310 and a rotating member 330 that rotates at high speed around a rotation axis 350 that extends vertically through the center of the container 310.

[0038] The container 310 has a substantially cylindrical inner wall surface 311 and defines a cylindrical space 312 having a predetermined length in the vertical direction. The rotating shaft 350 can be rotated at high speed by a high-torque motor (not shown) mounted on the top of the container 310. The cylindrical space 312 is separated into an upper space 312a and a lower space 312b by an inward flange 313. A material supply port 314 connected to the lower space 312b is provided at the bottom of the container 310, and the mixture may be supplied to the container 310 through this material supply port 314. Alternatively, the mixture may be supplied into the container 310 from above. An outlet 315 connected to the upper space 312a is provided at the top of the container 310, and the produced copper complex ink may be discharged to the outside of the container 310 through this outlet 315. Alternatively, the material supply port 314 and the outlet 315 may be closed, and the mixture may be stirred in a batchwise manner to produce the copper complex ink.

[0039] In addition, the high-speed mixer 300 is provided with a jacket 320 through which cooling water circulates, surrounding the lower space 312b of the container 310, and a cooling water circulation path 321 is also formed in the upper space 312a, surrounding it.

[0040] Rotating member 330 is in the form of a cylindrical member 332 having an outer circumferential surface 331 that faces inner wall surface 311 via a small gap S of about 1 to 3 mm in lower space 312b, and is supported by rotating shaft 350 via support member 352. This cylindrical member 332 also has a plurality of holes 333 formed therethrough that penetrate inward and outward.

[0041] It is desirable that at least cylindrical member 332 of rotating member 330 is formed of a material having excellent abrasion resistance, such as fine ceramics, or that outer peripheral surface 331 of cylindrical member 332 is coated with a material having excellent abrasion resistance, such as fine ceramics. Similarly, at least the region of inner wall surface 311 of container 310 that faces rotating member 330 across gap S may be coated with a material having excellent abrasion resistance, such as fine ceramics. An example of such fine ceramics is alumina ceramics.

[0042] Rotating member 330 can be rotated at high speeds, for example, so that the peripheral speed of rotating member 330 (relative speed with respect to inner wall surface 311) is 0.1 m / s to 50 m / s. To rotate rotating member 330 at such a peripheral speed while still providing a stirring effect, a high-torque, high-output motor is required, and the dimensions of container 310 and rotating member 330 are selected in accordance with the available motor. When the peripheral speed of rotating member 330 is constant, the processing capacity of this high-speed mixer 300 is approximately proportional to the area of ​​outer peripheral surface 331 of rotating member 330. Therefore, increasing the radial dimensions of container 310 and rotating member 330 is sufficient to increase processing capacity.

[0043] When a mixture is supplied to the high-speed mixer 300, the mixture is pressed against the inner wall surface 311 of the container 310 by the centrifugal force of the rotating member 330 rotating at high speed, and is introduced so as to spread throughout the gap S between the outer circumferential surface 331 of the cylindrical member 332 of the rotating member 330 and the inner wall surface 311 of the container 310. In this embodiment, since a plurality of holes 333 are formed in the cylindrical member 332, the mixture adhering to the inner surface of the cylindrical member 332 is also smoothly introduced into the gap S.

[0044] During stirring by the high-speed mixer 300, the mixture is subjected to a stirring action due to the powerful shear energy between the rotating member 330 and the inner wall surface 311, and may become heated due to heat caused by friction. However, the mixture is cooled appropriately by the cooling water flowing through the cooling water circulation jacket 320 and the cooling water circulation path 321, thereby preventing the mixture from becoming excessively hot.

[0045] Furthermore, if the outer surface 331 of the rotating member 330 and the inner wall surface 311 of the container 310 are coated with a material with excellent abrasion resistance such as fine ceramics, it is possible to effectively prevent the mixture from being contaminated with minute foreign matter such as metal wear powder due to the mixture being subjected to a strong shear force while present in the gap S between them.

[0046] (Mixing conditions) The stirring process using a stirrer allows the centrifugal force generated by the rotation of the rotating element to stir the mixture that exists in the form of a film between the rotating element and the inner wall surface, and in the stirring process, (CH3)2C(NH2)CH2OH is coordinated as a ligand to Cu in Cu(HCOO)2·4H2O to form a copper complex ((HCOO)2Cu((CH3)2C(NH2)CH2OH)2).

[0047] The specific conditions for forming a copper complex by coordinating (CH3)2C(NH2)CH2OH as a ligand to Cu in Cu(HCOO)2·4H2O are as follows: the peripheral speed of the rotating member is 0.5 m / s to 21.0 m / s, the temperature of the mixture is 10°C to 30°C, and the stirring time of the mixture is 5 to 500 minutes.

[0048] <Circumferential speed of rotating member> When the peripheral speed of the rotating element is set to 0.5 m / s to 21.0 m / s, the mixture, which exists in a film-like form between the outer surface of the cylindrical element and the inner wall of the container, can have a steep velocity gradient with a thickness of just 1 to 3 mm. For example, when the peripheral speed is 21.0 m / s, the velocity gradient is 0 to 20 m / s. This velocity gradient causes the mixture to be continuously subjected to powerful shear forces, and this powerful energy achieves a remarkably high level of dispersion. This is thought to be because such powerful shear energy acts on the mixture that a phenomenon similar to a sudden turbulent transition continuously occurs in the mixture.

[0049] <Mixture temperature> The mixture generates heat during stirring due to the constant application of strong shear forces. A sudden rise in the mixture temperature can make it difficult to control the coordination bond formation. Therefore, by controlling the temperature of the mixture during stirring to between 10°C and 30°C, the progress of the coordination bond can be controlled while preventing the mixture from becoming excessively hot. It is more preferable to control the temperature of the mixture within the range of 15°C to 25°C. Furthermore, if the temperature of the mixture rises rapidly to around 50°C, the coordination bond will also progress rapidly, so it is important to keep a close eye on the mixture while stirring.

[0050] <Mixture stirring time> Although it depends on the temperature conditions of the mixture and the peripheral speed conditions of the rotating member, by stirring the mixture for 5 to 500 minutes, (CH3)2C(NH2)CH2OH can be sufficiently coordinated to Cu(HCOO)2.

[0051] Conventional copper complex inks tend to have precipitated particles immediately after production, or precipitated particles that occur over time after production, with the number of particles increasing. Copper wiring produced using copper complex ink with a large amount of precipitated particles has a high volume resistivity and poor smoothness. However, according to the production method of the present embodiment, there are no precipitated particles at the beginning of production, and the generation of precipitated particles over time can be suppressed. Therefore, by using the produced copper complex ink, it is possible to form copper wiring with a low volume resistivity and high smoothness.

[0052] The stirring conditions may be such that the peripheral speed of the rotating member is 5.0 m / s to 21.0 m / s and the stirring time of the mixture is 5 minutes to 40 minutes. By adopting such stirring conditions, the generation of precipitated particles due to storage of the produced copper complex ink can be further suppressed.

[0053] [Method of manufacturing copper film] Next, one embodiment of the copper film manufacturing method of the present invention will be described. The copper film obtained can be used in applications where conductivity is required for heat-treated films, such as copper wiring, conductive adhesives, and die attach materials, and the shape, thickness, etc. can be set as desired.

[0054] <Heat Treatment Process> The method for producing a copper film includes a heat treatment step in which the copper complex ink of the present invention is heat treated to form a copper film.

[0055] The heat treatment conditions may be any conditions that volatilize the ligands, such as formic acid or AMP, from the copper complex ink, and the water, if unavoidably contained in the ink, and precipitate copper particles. For example, the treatment conditions include raising the temperature from room temperature to 250°C at a rate of 20°C / min in an inert atmosphere, such as nitrogen gas or argon gas, so as not to be in air, and then heating at 250°C for 10 minutes.

[0056] (Other processes) The method for producing a copper film of the present invention may include other steps in addition to the heat treatment step. For example, before the heat treatment, a film formation step may be performed in which a copper complex ink is applied to an object to be coated, such as an alumina substrate, a polyimide film, a PET film, or an electronic substrate including glass, by screen printing, inkjet printing, gravure printing, gravure offset printing, dispenser, or the like to form a copper complex film. Furthermore, an anti-oxidation treatment may be performed to prevent oxidation of the surface of the copper film after the heat treatment.

[0057] [Copper film] Copper films obtained by heating copper complex ink produced by conventional manufacturing methods have many fine pores, which act as electrical resistance, resulting in high volume resistivity. Furthermore, if the copper film does not have high smoothness, it cannot be used for high-frequency applications. On the other hand, copper films obtained by the copper complex ink produced by the manufacturing method of the present invention and the copper film manufacturing method of the present invention can have the properties of low volume resistivity and high smoothness. High smoothness leads to excellent conductivity and durability. For example, copper films with volume resistivity of less than 100 μΩ·cm and average film roughness Sa of less than 6 μm can be obtained. [Example]

[0058] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In these examples and comparative examples, a copper complex ink was first prepared, and the storage stability of the prepared copper complex ink and the physical properties of a copper film formed using the copper complex ink were evaluated.

[0059] [Manufacturing copper complex ink] Example 1 (Mixing process) A 10 g mixture was prepared by mixing powdered Cu(HCOO)2·4H2O (copper formate tetrahydrate) and solid (CH3)2C(NH2)CH2OH (2-aminomethylpropanol) in a molar ratio of 1:2. No grinding step was performed to crush the Cu(HCOO)2·4H2O powder, and no pre-heating step was performed to liquidify the (CH3)2C(NH2)CH2OH.

[0060] (Mixing process) The stirring process employed the thin film swirling method, using a thin film swirling high-speed mixer (Filmix (registered trademark) FM-30-L, manufactured by Primix Corporation) as the stirrer. 10 g of the mixture was placed in the stirrer's container and stirred, and (CH3)2C(NH2)CH2OH was coordinated as a ligand to Cu in Cu(HCOO)2·4H2O to produce a copper complex ink.

[0061] The conditions for the stirring step were a rotation speed of the rotating member of 15,000 rpm, a peripheral speed of 20.42 m / s, and stirring for 15 minutes while maintaining the temperature of the mixture below 25°C.

[0062] Table 1 shows the molar ratio of Cu(HCOO)2·4H2O (copper formate tetrahydrate) and (CH3)2C(NH2)CH2OH (2-aminomethylpropanol), the amount of the mixture charged, the presence or absence of a grinding step and a liquefaction treatment of (CH3)2C(NH2)CH2OH, and the stirring speed, peripheral speed, temperature of the mixture, and treatment time in the stirring step. Similarly, the conditions for Examples 2 to 6 and Comparative Examples 1 to 5 are also shown in Table 1.

[0063] Example 2 The stirring time in the stirring step was changed to 10 minutes from 15 minutes in Example 1. The other conditions were the same as in Example 1, and a copper complex ink was produced.

[0064] Example 3 The rotation speed of the rotating member in the stirring step was changed from 15,000 rpm to 10,000 rpm (circumferential speed 13.62 m / s), and the stirring treatment time was changed from 15 minutes to 20 minutes. The other conditions were the same as in Example 1, and a copper complex ink was produced.

[0065] Example 4 The rotation speed of the rotating member in the stirring step was changed from 15,000 rpm to 5,000 rpm (circumferential speed 6.81 m / s), and the stirring treatment time was changed from 15 minutes to 30 minutes. The other conditions were the same as in Example 1, and a copper complex ink was produced.

[0066] Example 5 The rotation speed of the rotating member in the stirring step was changed from 15,000 rpm to 1,000 rpm (circumferential speed 1.36 m / s), and the stirring treatment time was changed from 15 minutes to 240 minutes. The other conditions were the same as in Example 1, and a copper complex ink was produced.

[0067] Example 6 The rotation speed of the rotating member in the stirring step was changed from 15,000 rpm to 500 rpm (circumferential speed 0.68 m / s), and the stirring treatment time was changed from 15 minutes to 480 minutes. The other conditions were the same as in Example 1, and a copper complex ink was produced.

[0068] Comparative Example 1 (Crushing process) Before the mixing process, a grinding process was carried out to grind the Cu(HCOO)2·4H2O powder. Specifically, the Cu(HCOO)2·4H2O lumps were ground using a mortar until they were completely powdered and free of lumps.

[0069] (Mixing process) A 30 ml screw cap tube containing a stirrer was charged with solid (CH3)2C(NH2)CH2OH, which was then heated to 45 °C to liquefy the solid. Then, while stirring, Cu(HCOO)2·4H2O (copper formate tetrahydrate) powder was added to the screw cap tube and mixed to prepare a 10 g mixture of Cu(HCOO)2·4H2O (copper formate tetrahydrate) and (CH3)2C(NH2)CH2OH (2-aminomethylpropanol) in a molar ratio of 1:2.

[0070] (Mixing process) For the stirring process, a magnetic stirrer was used instead of the thin film rotation method, and a hot stirrer REXIM RSH-4DN (manufactured by AS ONE Corporation) was used as the stirrer. The screw tube containing the mixture was placed in the hot stirrer and the mixture was stirred, and (CH3)2C(NH2)CH2OH was coordinated as a ligand to Cu in Cu(HCOO)2·4H2O to produce a copper complex ink.

[0071] The stirring conditions were a stirrer rotation speed of 100 rpm and stirring for 4320 minutes. The temperature of the mixture was initially 45°C, but since stirring with the hot stirrer was performed at a temperature of 25°C without heating the mixture, the temperature gradually decreased from 45°C to 25°C.

[0072] Comparative Example 2 The rotation speed of the stirrer in the stirring step was changed from 100 rpm to 500 rpm, and the stirring time was changed from 4320 minutes to 1440 minutes. The other conditions were the same as in Comparative Example 1, and a copper complex ink was produced.

[0073] Comparative Example 3 The temperature of (CH3)2C(NH2)CH2OH was increased to 60°C, and the stirring time was changed from 4320 minutes to 1440 minutes. The other conditions were the same as in Comparative Example 1, and a copper complex ink was produced.

[0074] Comparative Example 4 The temperature of (CH3)2C(NH2)CH2OH was increased to 75°C, and the stirring time was changed from 4320 minutes to 1440 minutes. The other conditions were the same as in Comparative Example 1, and a copper complex ink was produced.

[0075] Comparative Example 5 The stirring process was carried out without heating (CH3)2C(NH2)CH2OH in its solid state. The mixture was kept at 25°C without heating, and the stirrer rotation speed during the stirring process was changed from 100 rpm to 500 rpm, but a copper complex ink could not be produced.

[0076] [Table 1]

[0077] [Evaluation of physical properties using copper complex ink] The produced copper complex ink was used to evaluate the following physical properties.

[0078] Observation of precipitated particles The copper complex inks of Examples 1 to 6 and Comparative Examples 1 to 4 were left to stand and stored for 30 days at room temperature (5°C to 35°C). A drop of each of the copper complex inks immediately after production and after 30 days of storage was placed on a glass slide, and the specimens were sandwiched between cover glasses to ensure a uniform field of view. The presence or absence of precipitated particles was observed using a laser microscope.

[0079] The proportion of precipitated particles in the copper complex ink within the observation area using a laser microscope, and the maximum diameter of precipitated particles when precipitated particles were present, were observed, and the results are shown in Table 2. Also, Figures 2 to 4 show images of the copper complex inks observed using a laser microscope after 30 days of storage. Figure 2 shows images of Examples 1 to 3, Figure 3 shows images of Examples 4 to 6, and Figure 4 shows images of Comparative Examples 1 to 4.

[0080] [Table 2]

[0081] (Observation results of precipitated particles) In Examples 1 to 4, copper complex inks with the best storage stability were produced, with almost no precipitated particles observed after 30 days of storage, and even if they did occur, they were extremely small (Table 2, Figures 2 and 3). Furthermore, under the conditions of Examples 5 and 6, although the generation of precipitated particles was observed after 30 days of storage, the proportion of precipitated particles was less than 50% by area within the range observed with a laser microscope, which was within the acceptable range for determining that the copper complex inks could be used without affecting the physical properties of the copper wiring (Table 2, Figure 3).

[0082] In the results of Comparative Examples 1 to 5, although there were cases in which no precipitated particles were observed in the copper complex ink immediately after production, after 7 days of storage, a large amount of precipitated particles was generated, making the ink unusable as a material for copper wiring.

[0083] On the other hand, in the case of the copper complex inks of Comparative Examples 1 and 2, large amounts of precipitated particles were generated from the day of production, and the number gradually increased during storage, resulting in precipitated particles accounting for more than 90% of the area after 30 days of storage.In the case of the copper complex inks of Comparative Examples 3 and 4, no precipitated particles were observed on the day of production, but the number gradually increased during storage, resulting in large precipitated particles accounting for more than 80% of the area after 30 days of storage.

[0084] Viscosity measurement of copper complex ink The copper complex inks of Example 1 and Comparative Example 1 were stored at room temperature (5°C to 35°C), and the viscosity was measured over time to evaluate the change in viscosity and thixotropy.

[0085] Viscosity measurements were performed using an Anton Paar rheometer MCR302e with a φ25 mm disposable parallel plate. The gap between the upper and lower plates was fixed at 0.2 mm, and the shear rate was 0.01 sec -1 from 100 seconds -1 The viscosity was measured while increasing the shear rate to 0.01 sec. -1 Viscosity and shear rate at 100sec -1 The viscosity was measured at a shear rate of 0.01 sec. -1 The viscosity when the shear rate is 100 sec -1 The thixotropy index was calculated by dividing the viscosity by the viscosity at the time of measurement.

[0086] The results of the viscosity change are shown in Table 3, and the evaluation results of the thixotropy are shown in Table 4.

[0087] [Table 3]

[0088] [Table 4]

[0089] (result) The copper complex ink of Example 1 maintained a stable viscosity from production until 180 days after storage, but the copper complex ink of Comparative Example 1 tended to gradually decrease in viscosity. Furthermore, with regard to thixotropy, the copper complex ink of Example 1 remained stable from production until 30 days after storage, but the copper complex ink of Comparative Example 1 tended to gradually decrease in value.

[0090] [Physical properties of copper film] The copper complex inks of Example 1 and Comparative Example 1 were left to stand and stored at room temperature (5°C to 35°C), and a copper film was formed using the stored copper complex ink, and its physical properties were evaluated.

[0091] <Manufacturing of copper film> Two pieces of masking tape (Nichiban Clear Line Tape 536) approximately 100 μm thick were attached to an alumina substrate (Kyocera A476) with a 5 mm gap between them. An appropriate amount of ink was applied to the side of the alumina substrate not covered by the masking tape and smoothed with a squeegee. The masking tape was then removed, leaving a coating film approximately 100 μm thick, 5 mm wide, and 1.52 mm long on the alumina substrate. This coating film was placed in a reflow furnace and heated from room temperature to 250 °C at a rate of 20 °C / min under a nitrogen atmosphere, then held at 250 °C for 10 minutes to obtain a heat-treated copper film. The width and length of the resulting copper film were measured with vernier calipers, and the thickness was measured with a laser microscope.

[0092] <Volume Resistivity Measurement> Measurements were performed using a four-terminal method using a Hioki RM3548 resistance meter and pin-type leads as electrode terminals. The resistance of the copper film was measured by contacting the electrode terminals with both ends of the obtained copper film. The volume resistivity was calculated by multiplying the obtained resistance value by width by thickness and dividing the length.

[0093] The volume resistivity was measured, and the changes in the value due to storage of the copper complex ink are shown in Table 5.

[0094] [Table 5]

[0095] (result) The results of Example 1 and Comparative Example 1 both show that the volume resistivity tends to increase depending on the storage period of the copper complex ink, but the original value was lower in Example 1. Specifically, the volume resistivity of Example 1 after 180 days of storage was lower than the volume resistivity of Comparative Example 1 immediately after production.

[0096] <Measurement of average film roughness Sa> The average film roughness Sa of the copper film thus formed was measured using a laser microscope VK-X3000 manufactured by Keyence Corporation.

[0097] The average film roughness Sa was measured, and the changes in the value due to storage of the copper complex ink are shown in Table 6.

[0098] [Table 6]

[0099] (result) The results of Example 1 and Comparative Example 1 both show that the average film roughness Sa tends to increase depending on the storage period of the copper complex ink, but the original numerical value was lower in Example 1. Specifically, in the case of Example 1, the value of the average film roughness Sa remained stable up to 120 days after storage, and the average film roughness Sa of Example 1 after 120 days of storage was approximately half the value of the average film roughness Sa of Comparative Example 1 immediately after production.

[0100] <Cross-section observation of copper film using SEM> Among the copper films produced, the cross section of a copper film produced using the copper complex ink after 30 days of storage was observed using a scanning electron microscope (SEM). Fig. 5 shows an SEM image of the cross section of the copper film in Example 1 enlarged 30,000 times, and Fig. 6 shows an SEM image of the cross section of the copper film in Comparative Example 1 enlarged 30,000 times. In addition, SEM images of the cross sections of the copper films after 0 to 180 days of storage were observed at 30,000 times, and the results of evaluating the porosity of the copper films are shown in Table 7. In Table 7, a porosity of less than 50% was evaluated as ○, a porosity of 50% or more but less than 70% was evaluated as △, and a porosity of 70% or more was evaluated as ×.

[0101] [Table 7]

[0102] (result) 5 and 6, the copper particles in the copper film of Example 1 were more densely packed than those in the copper film of Comparative Example 1. This difference in state is thought to be the cause of the changes in the volume resistivity and average film roughness Sa of the copper film. Furthermore, the results in Table 7 show that the cross section of the copper film in Example 1 had a low porosity even after 30 days of storage (FIG. 5), whereas the cross section of the copper film in Comparative Example 1 had a high porosity from the beginning (FIG. 6). Since precipitated particles exhibit foaming behavior during the heat treatment process for forming the copper film, a tendency was observed that a copper film with a large number of precipitated particles would have many voids, and a copper film with a small number of precipitated particles would tend to be dense. [Industrial Applicability]

[0103] The present invention can provide a copper complex ink and a method for producing a copper film that are excellent in storage stability and capable of producing copper wiring with low volume resistivity and high smoothness, and is therefore industrially useful. [Explanation of symbols]

[0104] 300 high-speed agitator, 310 vessel, 311 inner wall surface, 312 cylindrical space, 312a upper space, 312b lower space, 313 inward flange, 314 material supply port, 315 discharge port, 320 jacket, 321 cooling water circulation path, 330 rotating member, 331 outer peripheral surface, 332 cylindrical member, 333 hole, 350 rotating shaft, 352 support member, S gap

Claims

1. General formula (HCOO) ２ Cu((CH ３ ) ２ C(NH ２ ) CH ２ OH) ２ The copper complex includes a copper complex represented by the proportion of precipitated particles within 30 days from production is less than 50% by area, The copper complex ink, wherein the precipitated particles have a maximum particle size of less than 10 μm.

2. The copper complex ink according to claim 1 , wherein the proportion of the precipitated particles present on the day of production is 0 area %.

3. Shear rate is 5.34S －１ 2. The copper complex ink according to claim 1, wherein the viscosity is 1 to 10 Pa·s, and the rate of change in viscosity 30 days after production relative to the viscosity on the day of production is 20% or less.

4. Shear rate of 0.01S within 30 days of manufacture －１ The viscosity when the shear rate is 100S －１ 2. The copper complex ink according to claim 1, wherein the value obtained by dividing by the viscosity in the above formula (1) is less than 10.

5. A method for producing a copper film, comprising a heat treatment step of heat treating the copper complex ink according to claim 1 to form a copper film.

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