Copper complex ink and copper film production method

Abstract

Provided are a copper complex ink and a copper film production method, with which it is possible to produce a copper wire that has excellent storage stability, has a low volume resistivity, and is highly smooth.　This copper complex ink contains a copper complex represented by general formula (HCOO)2Cu((CH3)2C(NH2)CH2OH)2. In the ink, the proportion of precipitate particles that exist 30 days after being produced is less than 50 area%, and the maximum particle size of the precipitate particles is less than 10 µm.

Description

Copper complex ink and method for producing copper film

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

[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.

[0004] WO2022 / 130892A1 WO2010 / 018771A1

[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.

[0008] In order to solve the above problems, the copper complex ink of the present invention is a copper complex having a general formula (HCOO) ２ Cu((CH ３ ) ２ C(NH ２) CH ２ OH) ２ The copper complex contains a copper complex represented by the formula: wherein the proportion of precipitated particles present within 30 days after production is less than 50 area %, and the precipitated particles have a maximum particle size of less than 10 μm.

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

[0010] The copper complex ink of the present invention has 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 viscosity 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.

[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.

[0014] Fig. 1 is a cross-sectional view of an example of a stirrer that can be used in the method for producing a copper complex ink. Fig. 2 is an observation image of the copper complex inks of Examples 1 to 3 observed by a laser microscope. Fig. 3 is an observation image of the copper complex inks of Examples 4 to 6 observed by a laser microscope. Fig. 4 is an observation image of the copper complex inks of Comparative Examples 1 to 4 observed by a laser microscope. Fig. 5 is an enlarged SEM image of the cross section of the copper film in Example 1. Fig. 6 is an enlarged SEM image of the cross section of the copper film in Comparative Example 1.

[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: It may also contain a solvent or additive 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.

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

[0019] <Copper complex> The copper complex has the general formula (HCOO) ２ Cu((CH ３ ) ２ C(NH ２ ) CH ２ OH) ２ This complex is represented by (CH ３ ) ２ C(NH ２ ) CH ２ OH (2-amino-methyl-propanol, hereinafter sometimes referred to as "AMP") is used as a ligand, copper formate (Cu(HCOO) ２ ) is in a state where two molecules are coordinated to (HCOO). ２ Cu((CH ３ ) ２ C(NH ２ ) CH ２ OH) ２ The copper complex represented by the formula (I) is sometimes 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 based on conventional production 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 ink having 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] The copper complex ink of the present invention has a proportion of precipitated particles of less than 50 area % within 30 days after production. As described above, the presence of a large amount of precipitated particles resulted in copper wiring produced using this copper complex ink having 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 area %, copper wiring with low volume resistivity and high smoothness can be formed.

[0023] The proportion of precipitated particles present 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 ink will be extremely reduced.

[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 ink. 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 has a shear rate of 5.34 S －１ In this case, the viscosity may be 1 to 10 Pa·s. When the viscosity is 1 to 10 Pa·s, the copper complex ink has good removability when passing through the screen, resulting in excellent screen printability. If the viscosity is less than 1 Pa·s, the viscosity is too low and there is a risk that the ink will not be able to be printed in a shape such as a wiring. If the viscosity is greater than 10 Pa·s, the viscosity is too high and the copper complex ink will not pass through the screen, which may result in printing being impossible.

[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 according to conventional production methods (e.g., Patent Document 1) have poor storage stability and tend to have 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, with the copper complex ink of the present invention, the rate of change in viscosity due to storage is small, so that even if the copper complex ink is produced 30 days after production, copper wiring can be produced under the same conditions as when using the 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 the copper complex ink is screen printed, i.e., at high shear rates, it exhibits excellent liquid-like fluidity behavior, thereby improving screen removability. 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 maintain the printed shape. From this perspective, when this value is less than 10, excellent printing properties, such as screen printing, are achieved. Furthermore, if this value is 10 or more, there is no problem with printing properties, but if the presence ratio of precipitated particles, described below, exceeds 50 area %, this value may be 10 or more, and this value can serve as a guideline for predicting the presence of precipitated particles.

[0029] [Method for Producing 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 materials for copper complex ink) The raw materials for copper complex ink include Cu(HCOO) ２ ・4H ２ O powder and (CH ３ ) ２C(NH ２ ) CH ２ A solid of (CH OH) can be used. ３ ) ２ C(NH ２ ) CH ２ OH is Cu (HCOO) ２ Since two molecules are coordinated to Cu(HCOO), the molar ratio when mixing these is Cu(HCOO) ２ ・4H ２ O: (CH ３ ) ２ C(NH ２ ) CH ２ It is preferable that the molar ratio of Cu(HCOO) is 1:2, and the allowable range is 1:1.8 to 2.2. ２ ・4H ２ O powder and (CH ３ ) ２ C(NH ２ ) CH ２ The OH solid mixture can be stirred in the following stirring step.

[0031] In addition, (CH ３ ) ２ C(NH ２ ) CH ２ OH is in a solid state at room temperature (5°C to 35°C), and Cu(HCOO) ２ Considering the coordination to (CH ３ ) ２ C(NH ２ ) CH ２ It is considered preferable to heat OH to make it liquid, but 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 ・4H ２ O absorbs moisture from the atmosphere, increases in weight, and may aggregate to form lumps. Therefore, in order to pulverize these lumps and facilitate the mixing of the raw materials, Cu(HCOO) ２ ・4H ２ The method may include a pulverization step of pulverizing the O powder.

[0033] <Mixing process> The raw material for copper complex ink is Cu(HCOO) ２ ・4H ２ O powder and (CH ３ ) ２ C(NH ２ ) CH ２ After mixing the raw materials with the solid OH to form a mixture, the mixture may be placed in a container of a stirrer described below and then the stirring step may be performed. Alternatively, these raw materials may be placed in their own containers without being mixed, and then the stirring step may be performed.

[0034] <Stirring process> In this process, Cu(HCOO) ２ ・4H ２ O powder and (CH ３ ) ２ C(NH ２ ) CH ２ This is a step of stirring the mixture of OH and solids using a stirrer.

[0035] (Agitator) The agitator may be a device that includes a container having an inner wall surface and a rotating member that rotates slightly inside the inner wall surface, and that uses centrifugal force generated by the rotation of the rotating member to agitate a mixture that exists in a film-like form between the rotating member and the inner wall surface. 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] The rotating member 330 is in the form of a cylindrical member 332 having an outer circumferential surface 331 that faces the inner wall surface 311 in the lower space 312b with a small gap S of about 1 to 3 mm between it and the inner wall surface 311, and is supported by a rotating shaft 350 via a support member 352. The cylindrical member 332 is also formed with a plurality of holes 333 that penetrate inward and outward.

[0041] It is desirable that at least the cylindrical member 332 of the rotating member 330 is formed of a material having excellent abrasion resistance, such as fine ceramics, or that the outer peripheral surface 331 of the cylindrical member 332 is coated with a material having excellent abrasion resistance, such as fine ceramics. Similarly, at least the region of the inner wall surface 311 of the container 310 that faces the rotating member 330 across the 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] The rotating member 330 can be rotated at high speeds, for example, so that the peripheral speed of the rotating member 330 (relative speed with respect to the inner wall surface 311) is 0.1 m / s to 50 m / s. A high-torque, high-output motor is required to rotate the rotating member 330 at such a peripheral speed while still providing a stirring effect. The dimensions of the container 310 and the rotating member 330 are selected to accommodate the available motor. The processing capacity of this high-speed mixer 300 is approximately proportional to the area of ​​the outer peripheral surface 331 of the rotating member 330, assuming that the peripheral speed of the rotating member 330 is constant. Therefore, increasing the radial dimensions of the container 310 and the rotating member 330 is sufficient to increase the processing capacity.

[0043] When a mixture is supplied to the high-speed agitator 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 agitator 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 tiny foreign matter such as metal wear powder due to the mixture being subjected to a strong shear force when present in the gap S between them.

[0046] (Stirring Conditions) In the stirring step using a stirrer, the mixture present in a film form between the rotating member and the inner wall surface can be stirred by the centrifugal force generated by the rotation of the rotating member, and in the stirring step, Cu(HCOO) ２ ・4H ２ O to Cu (CH ３ ) ２ C(NH ２ ) CH ２ Copper complex ((HCOO) ２ Cu((CH ３ ) ２ C(NH ２ ) CH ２ OH) ２ ) can be formed.

[0047] Cu(HCOO) ２ ・4H ２ O to Cu (CH ３ ) ２ C(NH ２ ) CH ２ An example of specific conditions for forming a copper complex by coordinating OH as a ligand is a peripheral speed of the rotating member of 0.5 m / s to 21.0 m / s, a temperature of the mixture of 10°C to 30°C, and a stirring time of the mixture of 5 minutes to 500 minutes.

[0048] <Peripheral speed of rotating element> When the peripheral speed of the rotating element is set to 0.5 m / s to 21.0 m / s, the mixture that exists in the form of a film between the outer surface of the cylindrical element and the inner wall surface 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. Due to this velocity gradient, the mixture is continuously subjected to a powerful shear force, and this powerful energy achieves a significantly 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] <Temperature of the mixture> The mixture generates heat during stirring due to the continuous application of a strong shear force. A sudden rise in the temperature of the mixture can make it difficult to control the coordination bond. Therefore, by controlling the temperature of the mixture during stirring to 10°C to 30°C, it is possible to prevent the mixture from becoming excessively hot and control the progress of the coordination bond. It is more preferable to control the temperature of the mixture within the range of 15°C to 25°C. Note that if the temperature of the mixture rises suddenly to around 50°C, the coordination bond will also progress rapidly, so it is important to stir while closely monitoring the mixture.

[0050] <Mixing time of the mixture> Although it depends on the temperature conditions of the mixture and the peripheral speed conditions of the rotating member, by setting the mixing time of the mixture to 5 to 500 minutes, (CH ３ ) ２ C(NH ２ ) CH ２ Cu OH (HCOO) ２ can be sufficiently coordinated to

[0051] Conventional copper complex inks may have precipitated particles immediately after production, or may have precipitated particles that increase in number over time after production. Copper wiring manufactured using copper complex ink with a large amount of precipitated particles has a high volume resistivity and poor smoothness. However, according to the manufacturing 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 manufactured copper complex ink, it is possible to form copper wiring with a low volume resistivity and high smoothness.

[0052] The stirring conditions may include a peripheral speed of the rotating member of 5.0 m / s to 21.0 m / s and a stirring time of the mixture of 5 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 for Producing Copper Film] Next, one embodiment of the method for producing a copper film 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 Step> 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 and AMP, from the copper complex ink, and, if water is unavoidably contained in the ink, also volatilize the water, thereby precipitating copper particles. For example, the heat 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 an air atmosphere, and then heating at 250°C for 10 minutes.

[0056] (Other Steps) The method for producing a copper film of the present invention may include other steps in addition to the heat treatment step described above. 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 electronic substrate including an alumina substrate, a polyimide film, a PET film, or glass, by screen printing, inkjet printing, gravure printing, gravure offset printing, a 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 inks produced by conventional manufacturing methods have many fine holes, 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 film manufacturing method of the present invention using the copper complex ink produced by the manufacturing method of the present invention can have the properties of low volume resistivity and high smoothness. High smoothness results in excellent conductivity and durability. For example, copper films having a volume resistivity of less than 100 μΩ cm and an average film roughness Sa of less than 6 μm can be obtained.

[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] [Production of copper complex ink] Example 1 (Mixing step) Cu(HCOO) ２ ・4H ２ Powder of copper formate tetrahydrate (CH ３ ) ２ C(NH ２ ) CH ２ 10 g of a mixture was prepared by mixing solids of Cu(HCOO) and Cu(HCOO). ２ ・4H ２ No grinding step for grinding the powder of O was carried out, and ３ ) ２ C(NH ２ ) CH ２ The OH was not preliminarily heated to a liquid state.

[0060] (Stirring step) In the stirring step, a thin film swirling method was adopted, and a thin film swirling high-speed mixer (Filmix (registered trademark) FM-30-L manufactured by Primix Corporation) was used as the stirrer. 10 g of the mixture was placed in the container of the stirrer and stirred to obtain Cu(HCOO). ２ ・4H ２ O to Cu (CH ３ ) ２ C(NH ２ ) CH ２ Copper complex ink was prepared by coordinating OH as a ligand.

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

[0062] Table 1 shows Cu(HCOO) ２ ・4H ２ O (copper formate tetrahydrate) and (CH ３ ) ２ C(NH ２ ) CH ２ The molar ratio of the mixture with OH (2-amino-methyl-propanol), the amount of the mixture charged, the grinding process and (CH ３ ) ２ C(NH ２ ) CH ２The conditions for Examples 2 to 6 and Comparative Examples 1 to 5 below are shown in Table 1, including whether or not OH liquefaction treatment was performed, and the stirring speed, peripheral speed, temperature of the mixture, and treatment time in the stirring step.

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

[0064] Example 3 A copper complex ink was produced under the same conditions as in Example 1, except that 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 time was changed from 15 minutes to 20 minutes.

[0065] Example 4 A copper complex ink was produced under the same conditions as in Example 1, except that 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 time was changed from 15 minutes to 30 minutes.

[0066] Example 5 A copper complex ink was produced under the same conditions as in Example 1, except that 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 time was changed from 15 minutes to 240 minutes.

[0067] Example 6 A copper complex ink was produced under the same conditions as in Example 1, except that 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 time was changed from 15 minutes to 480 minutes.

[0068] Comparative Example 1 (Crushing Step) Before the mixing step, Cu(HCOO) ２ ・4H ２ A grinding step was carried out to grind the Cu(HCOO) powder. Specifically, the Cu(HCOO) powder was ground using a mortar until it was completely powdered and free of lumps. ２ ・4H ２ The O chunks were crushed.

[0069] (Mixing step) Put the contents of the mixture into a 30 ml screw tube equipped with a stirrer (CH ３ ) ２ C(NH２ ) CH ２ After adding the OH solid, (CH ３ ) ２ C(NH ２ ) CH ２ The temperature of OH was raised to 45°C, and the solid was liquefied. Then, Cu(HCOO) ２ ・4H ２ Powder of copper formate tetrahydrate was added to the screw tube and mixed to obtain Cu(HCOO). ２ ・4H ２ O (copper formate tetrahydrate) and (CH ３ ) ２ C(NH ２ ) CH ２ 10 g of a mixture of 1:2 molar ratio of OH (2-amino-methyl-propanol) was prepared.

[0070] (Stirring step) In the stirring step, 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 Cu(HCOO) ２ ・4H ２ O to Cu (CH ３ ) ２ C(NH ２ ) CH ２ Copper complex ink was prepared by coordinating OH as a ligand.

[0071] The stirring conditions were a stirrer rotation speed of 100 rpm, and stirring was continued 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 A copper complex ink was produced under the same conditions as in Comparative Example 1, except that 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 4,320 minutes to 1,440 minutes.

[0073] <Comparative Example 3> (CH ３ ) ２ C(NH ２ ) CH２ The temperature of the OH was increased to 60° C., and the stirring time was changed from 4,320 minutes to 1,440 minutes. The other conditions were the same as in Comparative Example 1, and a copper complex ink was produced.

[0074] <Comparative Example 4> (CH ３ ) ２ C(NH ２ ) CH ２ The temperature of the OH was increased to 75° C., and the stirring time was changed from 4,320 minutes to 1,440 minutes. The other conditions were the same as in Comparative Example 1, and a copper complex ink was produced.

[0075] <Comparative Example 5> (CH ３ ) ２ C(NH ２ ) CH ２ The stirring step was carried out in a solid state without heating the OH. The mixture was kept at 25°C without heating, and the stirrer rotation speed during the stirring step was changed from 100 rpm to 500 rpm, but a copper complex ink could not be produced.

[0076]

[0077] [Evaluation of Physical Properties Using Copper Complex Ink] The following physical properties were evaluated using the produced copper complex ink.

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

[0079] The results of observing 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, 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 the images of Examples 1 to 3, Figure 3 shows the images of Examples 4 to 6, and Figure 4 shows the images of Comparative Examples 1 to 4. The scale bars shown in Figures 2 to 4 are 100 μm.

[0080]

[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 area % within the area 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 were 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, a large amount of precipitated particles was generated from the day of production, and the number gradually increased during storage, resulting in precipitated particles accounting for more than 90 area% after 30 days of storage. Also, 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 precipitated particles accounting for more than 80 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 viscosity change and thixotropy.

[0085] The viscosity was measured using a rheometer MCR302e manufactured by Anton Paar, with a disposable parallel plate of φ25 mm. 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 100 sec －１The viscosity was read when the shear rate was 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]

[0088]

[0089] (Results) 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] <Production of Copper Film> Two pieces of masking tape (Clear Line Tape 536, manufactured by Nichiban) with a thickness of approximately 100 μm were attached to an alumina substrate (A476, manufactured by Kyocera) with a 5 mm gap between them. An appropriate amount of ink was applied to the side of the alumina substrate where the masking tape was not attached, and the ink was smoothed with a squeegee. The masking tape was then peeled off, and a coating film with a thickness of approximately 100 μm, a width of approximately 5 mm, and a length of 1.52 mm was produced 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, and 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] <Measurement of Volume Resistivity> Measurement was performed by the four-terminal method using a Hioki EE RM3548 resistance meter and pin-type leads as electrode terminals. The resistance value 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 using the obtained resistance value and calculating "resistance value × width of copper film × thickness of copper film ÷ length of copper film."

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

[0094]

[0095] (Results) 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 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]

[0099] (Results) 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 about half the value of the average film roughness Sa of Comparative Example 1 immediately after production.

[0100] <SEM Observation of Cross Section of Copper Film> Of the copper films produced, the cross section of a copper film produced using a 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. Furthermore, 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 ×. The scale shown in FIGS. 5 and 6 is 1.00 μm.

[0101]

[0102] (Results) As shown in Figures 5 and 6, the copper film in Example 1 was in a state in which the copper particles were more densely packed than the copper film in Comparative Example 1. It is believed that this difference in state caused changes in the volume resistivity and average film roughness Sa of the copper film. Furthermore, as shown in Table 7, the cross section of the copper film in Example 1 had a low porosity even after 30 days of storage (Figure 5), whereas the cross section of the copper film in Comparative Example 1 had a high porosity from the beginning (Figure 6). Because precipitated particles exhibit foaming behavior during the heat treatment process for forming the copper film, a copper film with a large number of precipitated particles tended to have more voids, while a copper film with a small number of precipitated particles tended to be dense.

[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.

[0104] 300 High-speed agitator, 310 Container, 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 circulating 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 wherein the proportion of precipitated particles present within 30 days from production is less than 50 area %, and 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 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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