Acidic electrolytic copper plating solution

Abstract

To provide an acidic electrolytic copper plating solution capable of stably forming a porous copper layer of high porosity and a small crystal grain size by a plating method.SOLUTION: The acidic electrolytic copper plating solution including a soluble copper salt, an azole-based compound, a carboxylic acid and water, is characterized in that the content of the azole-based compound is in the range of 5 mmol / L or higher and 100 mmol / L or lower, and the content of the carboxylic acid is in the range of 5 mg / L or higher and 500 mg / L or lower. The azole-based compound preferably comprises 2 to 3 nitrogen atoms in a five membered ring.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an acidic electrolytic copper plating solution used to form a porous copper layer on the surface of a member. [Background technology]

[0002] In recent years, the performance of semiconductor devices has been improving, and micro-bonding technology has become increasingly important. Flip-chip mounting is a widely used mounting technique for IC chips, and as shown in Patent Document 1, for example, a method is provided in which a solder layer is formed on a protruding electrode and the electrode is joined by soldering. Furthermore, as shown in Patent Documents 1 and 2, for example, bonding techniques such as the TLP method (Transient Liquid Phase Diffusion Bonding) and the SLID method (Solid-Liquid Interdiffusion) have been proposed, which bond solid and liquid phases by diffusing them into each other.

[0003] A technology for solid-phase diffusion bonding of copper components has been proposed as a next-generation packaging technology for even finer pitches. However, when joining substrates with multiple Cu pillars, the distance between the Cu pillars to be joined must be precisely adjusted, which necessitates processing using methods such as CMP. Furthermore, a technique has been proposed in which a porous copper layer (preform layer) is formed on the joining surface of a Cu pillar and the Cu pillars are bonded together using solid-phase diffusion bonding, as shown in Patent Document 3. When pressure is applied during bonding, the porous copper layer (preform layer) acts as a cushion, making it possible to bring the Cu pillars into contact with each other and bond them together even if there is variation in the height of the Cu pillars. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6061276 [Patent Document 2] Patent No. 6369620 [Patent Document 3] Japanese Patent Application Publication No. 2018-046148 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when joining Cu pillars together, in order to ensure that the Cu pillars contact each other even when there is a large variation in the Cu pillar heights, it is necessary to further increase the porosity of the porous copper layer. Furthermore, in order to ensure sufficient bonding strength after bonding, the porous copper layer is required to have a fine crystal grain size.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an acidic electrolytic copper plating solution that can stably form a porous copper layer having a high porosity and a small crystal grain size by a plating method. [Means for solving the problem]

[0007] In order to solve the above problems, an acidic electrolytic copper plating solution according to a first aspect of the present invention comprises a soluble copper salt, an azole compound, a carboxylic acid, water, and an acid, wherein the content of the azole compound is in the range of 5 mmol / L to 100 mmol / L, and the content of the carboxylic acid is in the range of 5 mg / L to 500 mg / L.

[0008] The acidic electrolytic copper plating solution of Aspect 1 of the present invention contains an azole compound in a range of 5 mmol / L to 100 mmol / L, and therefore, during electroplating, the azole compound is adsorbed onto the cathode surface together with copper ions, thereby strongly suppressing copper electrodeposition and prioritizing copper nucleation, resulting in the formation of a porous copper layer composed of copper particles on the cathode surface. The acidic electrolytic copper plating solution of the first aspect of the present invention contains carboxylic acid in a range of 5 mg / L to 500 mg / L, so that Cu ions and carboxylic acid form a complex, which further suppresses copper electrodeposition and increases the porosity of the porous copper layer. Furthermore, the growth of deposited copper particles is suppressed, making it possible to form a porous copper layer with a small crystal grain size. Therefore, even if there is variation in the height of the Cu pillars, the Cu pillars to be joined can be brought into contact with each other and firmly joined.

[0009] The acidic electrolytic copper plating solution of Aspect 2 of the present invention is characterized in that, in the acidic electrolytic copper plating solution of Aspect 1, the azole compound is one represented by the following formulas (1) to (4) having 2 to 3 nitrogen atoms in a five-membered ring: [ka] In the above formulas (1) to (4), R1 to R4 may be the same or different from one another and are any of an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, and an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atom of any of these groups is substituted with a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in the alkyl chain, or a mercapto group, or any of an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in the alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, and a hydrogen atom.

[0010] The acidic copper electroplating solution of the second aspect of the present invention contains an azole compound having the structure shown in the above formulas (1) to (4), which reliably inhibits copper electrodeposition and allows the formation of a porous copper layer composed of copper particles on the cathode surface. Furthermore, the acidic copper electroplating solution contains a carboxylic acid in a range of 5 mg / L to 500 mg / L, which reliably allows the formation of a porous copper layer with high porosity and small average particle size. Therefore, even if there is variation in the height of the Cu pillars, the Cu pillars to be joined can be brought into contact with each other and joined more firmly. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an acidic electrolytic copper plating solution that can stably form a porous copper layer having high porosity and small crystal grain size by a plating method. [Brief explanation of the drawings]

[0012] [Figure 1] 1A and 1B are explanatory diagrams showing a method for forming a porous copper layer using an acidic electrolytic copper plating solution according to one embodiment of the present invention, in which (a) is a schematic diagram of an electrolytic copper plating apparatus, and (b) is an explanatory diagram of a substrate on which a porous copper layer has been formed in a pattern. [Figure 2] FIG. 1 is an explanatory diagram of a porous copper layer formed using an acidic electrolytic copper plating solution according to one embodiment of the present invention. [Figure 3] FIG. 4 is an explanatory view showing a method for producing a bonded body using the porous copper layer shown in FIG. [Figure 4] FIG. 1 is an explanatory diagram showing a method for producing a bonded body for measuring Char strength in an example. [Figure 5] 1 shows SEM photographs of the cross sections of porous copper layers observed in Examples: (a) Inventive Example 1, (b) Comparative Example 1, and (c) Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0013] An acidic copper electrolytic plating solution according to an embodiment of the present invention will be described below with reference to the drawings.

[0014] The acidic electrolytic copper plating solution according to this embodiment forms a porous copper layer that is used, for example, in semiconductor devices, when joining multiple protruding electrodes (Cu pillars) provided on a semiconductor chip or substrate.

[0015] The acidic electrolytic copper plating solution of this embodiment contains a soluble copper salt, an azole compound, a carboxylic acid, water, and an acid, and the content of the azole compound is in the range of 5 mmol / L to 100 mmol / L, and the content of the carboxylic acid is in the range of 5 mg / L to 500 mg / L. The acidic copper electrolytic plating solution of this embodiment may contain other components, such as a brightener, a surfactant, an antioxidant, etc., as needed.

[0016] Specific examples of soluble copper salts include copper sulfate, copper oxide, copper carbonate, copper alkanesulfonates such as copper methanesulfonate and copper propanoate, copper alkanolsulfonates such as copper isethionate and copper propanolsulfonate, and copper organic acids such as copper acetate, copper citrate, and copper tartrate. These can be used alone or in combination of two or more.

[0017] The acid may be an organic acid or an inorganic acid. Examples of such acids include sulfuric acid; alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid; and alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid. These may be used alone or in combination. Examples of water include pure water such as ion-exchanged water and distilled water.

[0018] Examples of the azole compounds include imidazole, 2-aminoimidazole, pyrazole, 3-aminoimidazole, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 3-amino-5-methylthio-1H-1,2,4-triazole, etc. These azole compounds are those represented by the above formulas (1) to (4) having two to three nitrogen atoms in a five-membered ring.

[0019] The imidazole is a type of azole compound represented by the above formula (1), and is represented by the following formula (5). 2-Aminoimidazole is a type of azole compound represented by the above formula (1), and is represented by the following formula (6). Pyrazole is a type of azole compound represented by the above formula (2), and is represented by the following formula (7). 3-Aminoimidazole is a type of azole compound represented by the above formula (2), and is represented by the following formula (8). 1,2,3-triazole is a type of azole compound represented by the above formula (3), and is represented by the following formula (9).

[0020] [ka]

[0021] 1,2,4-triazole is a type of azole compound represented by the above formula (4), and is represented by the following formula (10). 3-Amino-1,2,4-triazole is a type of azole compound represented by the above formula (4), and is represented by the following formula (11). 3,5-Diamino-1,2,4-triazole is a type of azole compound represented by the above formula (4), and is represented by the following formula (12). 3-Amino-5-methylthio-1H-1,2,4-triazole is a type of azole compound represented by the above formula (4), and is represented by the following formula (13).

[0022] [ka]

[0023] The azole compound adsorbs onto the cathode surface together with copper ions during electroplating, suppressing copper electrodeposition and functioning as a copper ion electrodeposition inhibitor. By suppressing copper electrodeposition in this way, copper nucleation is prioritized on the cathode surface, resulting in the formation of a porous copper layer composed of copper particles.

[0024] Examples of the carboxylic acid include acetic acid, propionic acid, oxalic acid, citric acid, gluconic acid, and glycinic acid. Carboxylic acid forms a complex with Cu ions, further inhibiting copper electrodeposition and increasing the porosity of the porous copper layer.Furthermore, the growth of deposited copper particles is inhibited, resulting in the formation of a porous copper layer with small crystal grain size.

[0025] The acidic copper electroplating solution of the present embodiment can be prepared by mixing the soluble copper salt, the azole compound having 2 to 3 nitrogen atoms in a five-membered ring as the copper ion electrodeposition inhibitor, an acid, and water.

[0026] Here, the content of soluble copper salts in the prepared acidic copper electroplating solution is preferably 0.01 mol / L or more. If the content of the soluble copper salt is 0.01 mol / L or more, a porous copper layer can be stably formed as a copper plating film. In the acidic copper electroplating solution, the lower limit of the azole compound content is preferably 5 mmol / L or more, more preferably 10 mmol / L or more, and the upper limit of the azole compound content is preferably 100 mmol / L or less, more preferably 30 mmol / L or less.

[0027] In the prepared acidic copper electroplating solution, the content of the azole compound that functions as a copper ion electrodeposition inhibitor is set to be within the range of 5 mmol / L or more and 100 mmol / L or less. If the content of the azole compound is less than 5 mmol / L, the effect of suppressing the electrodeposition of copper ions is poor, and a porous copper layer as a copper plating film cannot be stably formed. On the other hand, if the content of the azole compound exceeds 100 mmol / L, the electrodeposition of copper ions is suppressed too much, resulting in a brittle copper plating film with significantly reduced strength. Alternatively, the azole compound cannot dissolve in the solution and precipitates. In the acidic copper electrolytic plating solution, the lower limit of the carboxylic acid content is preferably 10 mg / L or more, more preferably 50 mg / L or more, and the upper limit of the carboxylic acid content is preferably 300 mg / L or less, more preferably 150 mg / L or less.

[0028] In the prepared acidic electrolytic copper plating solution, the carboxylic acid content is set to be within the range of 5 mg / L or more and 500 mg / L or less. If the content of the carboxylic acid is less than 5 mg / L or exceeds 500 mg / L, the porosity of the porous copper layer will not be improved, and the crystal grain size may not be refined. In the acidic copper electrolytic plating solution, the lower limit of the carboxylic acid content is preferably 10 mg / L or more, more preferably 50 mg / L or more, and the upper limit of the carboxylic acid content is preferably 300 mg / L or less, more preferably 150 mg / L or less.

[0029] In the prepared acidic electrolytic copper plating solution, there are no particular restrictions on the concentrations of the above-mentioned soluble copper salt, azole compound, and components other than carboxylic acid, such as water and acid, but it is preferable to adjust the pH of the acidic electrolytic copper plating solution to be within the range of 0 to 5, and more preferably within the range of 1 to 3.

[0030] Next, a method for forming a patterned porous copper layer on the surface of a substrate using the acidic copper electrolytic plating solution of this embodiment will be described with reference to FIGS. 1 and 2. FIG.

[0031] 1, an acidic electrolytic copper plating solution 3 according to the present embodiment is placed in a plating tank 2 of an electrolytic copper plating apparatus 1, a substrate 4a having a copper or nickel surface and a patterned resist film 4b is placed in the acidic electrolytic copper plating solution 3, and a copper material 5 is placed opposite one side of the substrate 4a. The substrate 4a is then connected as a cathode to a cathode 6, and the copper material 5 is connected as a soluble anode to an anode 7, to perform electrolytic copper plating. A resist film 4b is formed on the surface of the substrate 4a in advance so as to have openings at predetermined intervals, and as a result, a porous copper layer 8 made of copper particles 12 is formed as a copper plating film in the openings of the resist film 4b formed on one side of the substrate 4a.

[0032] Here, the conditions for electrolytic copper plating in the acidic electrolytic copper plating solution 3 are, for example, to apply a current density of 0.1 A / dm2 to the substrate 4a to be plated using a DC power source. 2 ~5A / dm 2 Approximately, preferably 0.4A / dm 2 ~1.0A / dm 2 The liquid temperature is maintained at about 30 to 150 minutes, preferably about 60 to 120 minutes, and air and jet stirring or rocking stirring is performed. When electrolytic copper plating is performed under the above conditions, the azole-based compound, which acts as a copper ion electrodeposition inhibitor, is adsorbed onto the cathode surface of the substrate 4a along with the copper ions. The presence of the azole-based compound strongly inhibits the electrodeposition of copper ions, favoring copper nucleation, and a porous copper layer 8 composed of copper particles 12 is formed on the cathode surface as a copper plating film. Furthermore, the carboxylic acid forms a complex with the copper ions, increasing the porosity of the porous copper layer 8 and reducing the crystal grain size.

[0033] After the electrolytic copper plating is performed, the substrate 4a on which the porous copper layer 8 is formed is taken out of the acidic electrolytic copper plating solution 3, and the resist film 4b is removed. The substrate 4a is then washed with a cleaning solvent such as ethanol, water, or acetone, and dried in the atmosphere using dry air. As a result, a porous copper layer 8 is formed in a pattern on one side of the substrate 4a, as shown in Figure 1(b). Cu pillars are bonded to each of the porous copper layers 8 formed in a pattern. In order to prevent surface oxidation, the substrate 4a on which the porous copper layer 8 is formed is preferably immersed for a predetermined period of time in a rust inhibitor containing benzotriazole and a surfactant as its main components.

[0034] Here, the thickness of the porous copper layer 8 formed on the surface of the substrate 4a is preferably within the range of 15 μm to 50 μm. If the thickness of the porous copper layer 8 is 15 μm or more, the strength of the porous copper layer 8 itself is ensured and handling is easy. On the other hand, if the thickness of the porous copper layer 8 is 50 μm or less, the porous copper layer 8 conforms to the irregularities on the surfaces of the substrate or electronic component described below during bonding, improving the bonding strength of the bonded body.

[0035] 2, the porous copper layer 8 is formed in the form of an aggregate of copper particles, in which copper particles 12 are piled up on the surface of the substrate 4a. The porous copper layer 8 made of these copper particles 12 preferably has an average porosity in the range of 10% to 80%. If the average porosity is 10% or more, copper particles that contribute to the sintering of the porous copper layer 8 are secured, improving the sinterability of the copper particles. If the average porosity is 80% or less, the porosity in the porous copper layer 8 does not become higher than necessary, ensuring the strength of the porous copper layer 8 and the sinterability of the copper particles. The average porosity is more preferably 15% or more, and more preferably 70% or less.

[0036] The average porosity of the porous copper layer 8 described above is calculated by image analysis of a cross section of the porous copper layer 8 using a scanning electron microscope. The arithmetic mean of the porosities (P) calculated by the following formula (A) is defined as the average porosity. Specifically, the measurement is performed by taking photographs three times in different fields of view, and the average value of the calculated porosities is defined as the average porosity. P(%) = (S2 / S1) × 100 (A) In the formula (A), P is the porosity of the porous copper layer 8, S1 is the total area of ​​the porous copper layer 8, and S2 is the area of ​​the pores in the porous copper layer 8.

[0037] As shown in the enlarged view of FIG. 2, the surface of each copper particle 12 is covered with copper nanoparticles 12 a having an average particle size smaller than that of the copper particles 12 . Copper plating is performed using the acidic electrolytic copper plating solution 3 of this embodiment, whereby the azole compound is adsorbed onto the copper surface and a complex with copper ions is formed by the carboxylic acid, suppressing copper electrodeposition and prioritizing nucleation, resulting in the formation of copper nanoparticles 12a on the surfaces of the copper particles 12. Due to this characteristic structure, when the porous copper layer 8 is pressurized, the copper particles are easily sintered together, facilitating the formation of a robust bonding layer.

[0038] Here, the average particle size of the copper nanoparticles is difficult to calculate from a microscope image because the copper particles are composed of fine copper particles and nanoparticles that are even finer than the copper particles, and the average particle size is calculated from BET measurement. Thus, the average particle size of the copper nanoparticles calculated from BET measurement is preferably 50 nm or more and 300 nm or less. If the average particle size of the copper nanoparticles is within this range, the copper particles will be easily sintered. The average particle size of the copper nanoparticles is more preferably within the range of 50 nm to 200 nm.

[0039] The average particle size of the above-mentioned copper nanoparticles is measured by the BET method using the porous copper layer 8. In the BET method, the substrate 4a on which the porous copper layer 8 is formed is cut to a predetermined size, filled into a measurement cell, and measured using the BET single-point method. The mass of the substrate 4a is subtracted from the measured value, and the result is converted to the mass of the porous copper layer 8 itself. The particle size of the copper nanoparticles is calculated from the calculated BET measurement value using the following formula (B). Note that the coefficient 335.95 in the following formula (B) is a value calculated from the theoretical values ​​of the copper density, the surface area of ​​the copper nanoparticles, and the volume of the copper nanoparticles. The average particle size (d) of the copper nanoparticles is the average value of three measurements made using the BET method. d(nm)=335.95 / (BET measurement value (m 2 / g)) (B)

[0040] Next, a method for producing a bonded body using the substrate 4a on which the porous copper layer 8 is formed will be described. First, a substrate 4a having a porous copper layer 8 formed on its surface is prepared as shown in Fig. 3. An electronic component 17 (such as a silicon chip element or an LED chip element) is prepared as a member to be joined. Next, electronic components 17 are placed on the porous copper layer 8 formed on the surface of substrate 4a. In this state, the laminated electronic components 17 and substrate 4a are heated in a nitrogen atmosphere at a temperature of 250°C to 350°C for 1 to 30 minutes, with porous copper layer 8 interposed between them. In some cases, substrate 4a and electronic components 17 may be bonded together while applying a pressure of 1 MPa to 20 MPa in the lamination direction. As a result, as shown in FIG. 3(c), the porous copper layer 8 becomes a bonding layer 15, and the substrate 4a and the electronic component 17 are bonded together by this bonding layer 15, thereby producing a bonded body 18.

[0041] The acidic electrolytic copper plating solution of this embodiment configured as described above contains an azole compound in a range of 5 mmol / L to 100 mmol / L, so that during electroplating, the azole compound is adsorbed onto the cathode surface together with copper ions, thereby strongly suppressing copper electrodeposition and prioritizing copper nucleation, resulting in the formation of a porous copper layer composed of copper particles on the cathode surface. The acidic electrolytic copper plating solution of this embodiment contains carboxylic acid in the range of 5 mg / L to 500 mg / L, so that Cu ions and carboxylic acid form complexes, which further suppresses copper electrodeposition and increases the porosity of the porous copper layer. Furthermore, the growth of deposited copper particles is suppressed, making it possible to form a porous copper layer with a small crystal grain size. Therefore, even if there is variation in the height of the Cu pillars, the Cu pillars to be joined can be brought into contact with each other and firmly joined.

[0042] In the acidic copper electroplating solution of this embodiment, when the azole compound is one of the above formulas (1) to (4) having two to three nitrogen atoms in a five-membered ring, copper electrodeposition can be reliably suppressed and a porous copper layer composed of copper particles can be formed on the cathode surface. Furthermore, since the carboxylic acid is contained in the range of 5 mg / L to 500 mg / L, a porous copper layer with high porosity and small average particle size can be reliably formed. Therefore, even if there is variation in the height of the Cu pillars, the Cu pillars to be joined can be brought into contact with each other and joined more firmly.

[0043] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. For example, in the present embodiment, a porous copper layer 8 is formed in a pattern on the surface of the substrate 4a, and the electronic component 17 is bonded via this porous copper layer 8. However, this is not limited to this, and it is sufficient that the bonded members are bonded via the porous copper layer. [Example]

[0044] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below.

[0045] First, an acidic copper electroplating solution containing copper sulfate pentahydrate as a soluble copper salt, an azole compound, and a carboxylic acid was prepared as shown in Tables 1 and 2. In addition to the copper sulfate pentahydrate, the azole compound, and the carboxylic acid, water and sulfuric acid were added to adjust the pH to 2.5.

[0046] A Si substrate was prepared, and a Ti layer (100 nm thick) and a Cu layer (500 nm thick) were sputter-deposited on the surface of the Si substrate. A porous copper layer was formed on the surface of the Si substrate and copper chip using the acidic electrolytic copper plating solution described above. The plating conditions were a bath temperature of 30°C, pH of 2.5, and a current density as shown in Tables 3 and 4. The plating time was adjusted so that the porous copper layer would be 2 μm thick.

[0047] To measure the bonding strength of the bonded structure, an oxygen-free copper substrate (5 mm × 5 mm, 3 mm thick) and a copper chip (1 mm × 1 mm, 2 mm thick) were prepared, and a porous copper layer was formed on the surface of the substrate and the copper chip using the acidic copper electroplating solution described above. The plating conditions were a bath temperature of 30°C, pH of 2.5, and a current density as shown in Tables 3 and 4. The plating time was adjusted so that the porous copper layer would be 2 μm thick.

[0048] Then, as shown in Figure 4, the substrate and the copper chip were stacked so that the porous copper layer formed on the substrate and the porous copper layer formed on the copper chip were in contact with each other, and they were bonded using a pressure and heat bonding device (HTB-MM manufactured by Alpha Design) under the following conditions: heating temperature: 300°C, heating time: 1 minute, pressure load: 10 MPa, and atmosphere: nitrogen, to obtain a bonded body.

[0049] The porosity and average particle size of the resulting porous copper layer and the shear strength of the bonded body were evaluated as follows.

[0050] (Porosity) A measurement sample was taken from a Si substrate on which a porous copper layer had been formed by electroplating, and a cross section along the thickness direction of the porous copper layer was subjected to CP processing and cross-sectional SEM observation. The cross-sectional SEM image at 10,000x magnification was binarized to calculate the porosity. Figure 5 shows cross-sectional SEM images of Inventive Example 1 and Comparative Examples 1 and 2. It can be seen that a porous copper layer was formed in Inventive Example 1. On the other hand, it can be seen that no porous copper layer was formed in Comparative Examples 1 and 2.

[0051] (Average particle size) BET measurements were performed using a Macsorb HM-model-1201. The Si substrate with the porous copper layer formed on it was cut into 2 mm squares, loaded into a measurement cell, and measured using the BET single-point method. The mass of the copper sheet was subtracted from the measured value, and the result was converted to the mass of the porous copper layer itself. The particle size of the copper nanoparticles was calculated from the calculated BET measurement value using the following formula (B). The coefficient 335.95 in the following formula (B) is a value calculated from the theoretical values ​​of the copper density, the surface area of ​​the copper nanoparticles, and the volume of the copper nanoparticles. The average particle size (d) of the copper nanoparticles was measured three times using the BET method and is the average value. d(nm)=335.95 / (BET measurement value (m 2 / g))

[0052] (Share strength) The shear strength of the bonded body was measured using a shear strength evaluation tester (Bond Tester; Dage Series 4000, manufactured by Nordson Advanced Technology Co., Ltd.). The shear strength was measured by fixing the substrate of the bonded body horizontally and pushing the copper chip horizontally from the side at a position 50 μm above the surface (top surface) of the bonding layer with a shear tool. The shear tool was moved at a speed of 0.1 mm / s, and the strength at which the copper chip broke was measured.

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] [Table 4]

[0057] In Comparative Example 1, the azole compound and the carboxylic acid were not contained, and a porous copper layer could not be formed. In Comparative Examples 2 to 4, no azole compound was contained, and a porous copper layer could not be formed. In Comparative Examples 5 to 7 and 9 to 11, which did not contain carboxylic acid, the porosity was smaller, the average particle size was larger, and the shear strength was lower than in the invention examples with the same current density.

[0058] In Comparative Example 8, the carboxylic acid content was as high as 600 mg / L, and compared with the invention examples with the same current density, the porosity was smaller, the average particle size was larger, and the shear strength was lower. In Comparative Example 12, the carboxylic acid content was as low as 1 mg / L, and compared with the invention examples with the same current density, the porosity was smaller, the average particle size was larger, and the shear strength was lower.

[0059] In contrast, in Examples 1 to 15 of the present invention, the porosity was higher, the average particle size was smaller, the shear strength was higher, and the bondability was excellent compared to the comparative examples with the same current density.

[0060] From the results of the above confirmatory experiments, it was confirmed that the present invention can provide an acidic electrolytic copper plating solution that can stably form a porous copper layer having a high porosity and a small crystal grain size by a plating method. [Explanation of symbols]

[0061] 4a Substrate 8 Porous copper layer

Claims

1. a soluble copper salt, an azole compound, a carboxylic acid, water, and an acid; The acidic electrolytic copper plating solution is characterized in that the content of the azole compound is in the range of 5 mmol / L or more and 100 mmol / L or less, and the content of the carboxylic acid is in the range of 5 mg / L or more and 500 mg / L or less.

2. The acidic electrolytic copper plating solution according to claim 1, wherein the azole compound is represented by the following formulas (1) to (4) having two or more and three or less nitrogen atoms in a five-membered ring: 【Chemical 1】 In the above formulas (1) to (4), R1 to R4 may be the same or different from one another and are any of an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, and an alkoxy group having 10 or less carbon atoms; or a group in which the hydrogen atom of any of these groups is substituted with a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in the alkyl chain, or a mercapto group; or any of an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in the alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, and a hydrogen atom.

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