US20250003102A1 - Acidic electrolytic copper plating liquid, method for forming preform layer, method for producing joining sheet, method for producing joining substrate, and method for producing joined body - Google Patents

Acidic electrolytic copper plating liquid, method for forming preform layer, method for producing joining sheet, method for producing joining substrate, and method for producing joined body Download PDF

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US20250003102A1
US20250003102A1 US18/705,691 US202218705691A US2025003102A1 US 20250003102 A1 US20250003102 A1 US 20250003102A1 US 202218705691 A US202218705691 A US 202218705691A US 2025003102 A1 US2025003102 A1 US 2025003102A1
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copper
preform layer
bonding
producing
substrate
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Junta INOUE
Daiki Furuyama
Takuma Katase
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Mitsubishi Materials Corp
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Mitsubishi Materials Corp
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D15/00—Electrolytic or electrophoretic production of coatings containing embedded materials, e.g. particles, whiskers, wires
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/12—Process control or regulation
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/38—Electroplating: Baths therefor from solutions of copper
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/16—Electroplating with layers of varying thickness
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/60—Electroplating characterised by the structure or texture of the layers
    • C25D5/623—Porosity of the layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/12—Semiconductors
    • C25D7/123—Semiconductors first coated with a seed layer or a conductive layer

Definitions

  • the present invention relates to an acidic electrolytic copper plating solution for forming a porous preform layer for bonding two members used in the assembly, implementation, or other processes of electronic components.
  • the present invention relates to a method for forming a preform layer using this acidic electrolytic copper plating solution.
  • the present invention relates to a method for producing a bonding sheet formed of a copper sheet with a preform layer, a method for producing a bonding substrate formed of a substrate with a preform layer, and a method for producing a bonded body using the bonding sheet or the bonding substrate.
  • a technique for producing a film includes causing electrolytic deposition on a film (hereinafter, simply referred to as electrodeposition) by a composite plating method using polymer fine particles as a dispersant to produce a porous film through decomposition and desorption of the polymer fine particles (see Non Patent Document 1).
  • electrodeposition electrolytic deposition on a film
  • a composite plating method using polymer fine particles as a dispersant to produce a porous film through decomposition and desorption of the polymer fine particles
  • Ni Patent Document 1 nickel plating using a Watt bath is employed as a matrix of a composite plating, and highly crosslinked type acrylic polymer fine particles are added to the bath as a dispersant.
  • a soft iron plate of which one surface has been coated is used as a base material, the base material is subjected to a pre-treatment of alkali degreasing, and then nickel plating is performed in a plating bath containing nickel sulfate, nickel chloride, and boric acid.
  • the plated film is subjected to a pore-forming treatment after co-deposition by heat treatment in the atmosphere at 500° C. for 1 hour to obtain a porous material.
  • a first objective of the present invention is to provide an acidic electrolytic copper plating solution capable of forming a porous preform layer with a simple process.
  • a second objective of the present invention is to provide a method for forming a preform layer using this acidic electrolytic copper plating solution.
  • a third objective of the present invention is to provide a method for producing a bonding sheet formed of a copper sheet with a preform layer.
  • a fourth objective of the present invention is to provide a method for producing a bonding substrate formed of a substrate with a preform layer.
  • a fifth objective of the present invention is to provide a method for producing a bonded body using the bonding sheet or the bonding substrate.
  • a method for forming a preform layer including:
  • a method for producing a bonding sheet including: a step of forming a porous preform layer on one surface or both surfaces of a copper sheet by the method for forming a preform layer according to [2].
  • a method for producing a bonded body including:
  • a method for producing a bonding substrate including: a step of forming a porous preform layer on one surface of a substrate by the method for forming a preform layer according to [2].
  • a method for producing a bonded body including:
  • the acidic electrolytic copper plating solution according to the aspect of [1] contains a soluble copper salt, a specific azole compound which serves as a copper ion electrodeposition inhibitor including two or more nitrogen atoms, an acid, and water. Therefore, in a case where electrolytic plating is carried out, the azole compound, which serves as a copper ion electrodeposition inhibitor, also adsorbs to a cathode surface together with copper ions. Accordingly, the electrodeposition of copper ions is strongly suppressed, the nucleation of copper is given priority, and a porous preform layer including copper particles is formed as a copper plating film on the cathode surface.
  • the copper sheet or substrate is disposed on the cathode side in the acidic electrolytic copper plating solution according to the aspect of [1], and electrolytic copper plating is carried out. Therefore, unlike the conventional method for producing a porous film, as a copper plating film, the porous preform layer including copper particles of which the surfaces are coated with copper nanoparticles and having an average porosity of 11% to 78% can be formed on one surface or both surfaces of the copper sheet or the substrate with a simple process.
  • the bonding sheet which includes the porous preform layer on one surface or both surfaces of the copper sheet with a high strength of the sheet itself, can be produced with a simple process.
  • the base material, the electronic component, and the bonding sheet produced by the method according to the aspect of [3] are laminated so that the bonding sheet is disposed between the base material and the electronic component, and the base material and the electronic component are heated under pressure in the laminating direction; and thereby, the bonded body is produced. Therefore, since the preform layer serves as a bonding layer, the bonded body with a high bonding strength can be produced.
  • the porous preform layer is formed on one surface of the substrate by the method according to the aspect of [2]. Therefore, the bonding substrate having a high strength when bonded can be produced.
  • the bonding substrate produced by the method according to the aspect of [5] and the electronic component are laminated, and the bonding substrate and the electronic component are heated under pressure in the laminating direction; and thereby, the bonded body is produced. Therefore, since the preform layer serves as a bonding layer, the bonded body including the bonding substrate and the electronic component, which are firmly bonded, can be obtained.
  • FIG. 1 is a diagram showing a situation in which porous preform layers are formed on both surfaces of a copper sheet by an electrolytic copper plating method of the present embodiment.
  • FIG. 2 is a diagram schematically showing a bonding sheet including the copper sheet with the porous preform layers formed on both surfaces of the copper sheet of the present embodiment.
  • FIG. 3 A is a diagram showing a situation in which porous preform layers are formed on one surface of a substrate whose surface is made of copper or nickel by an electrolytic copper plating method of the present embodiment.
  • FIG. 3 B is a diagram schematically showing a bonding substrate with the porous preform layers formed on one surface of the substrate.
  • FIG. 4 is a diagram showing a first method for producing a bonded body by using the bonding sheet of the present embodiment
  • FIG. 4 ( a ) is a diagram showing a state in which the bonding sheet is placed on a base material
  • FIG. 4 ( b ) is a diagram showing a step of placing an electronic component on the bonding sheet and then carrying out heating under pressure
  • FIG. 4 ( c ) is a diagram showing a bonded body produced by the heating under pressure.
  • FIG. 5 is a diagram showing a second method for producing a bonded body by using the bonding substrate of the present embodiment
  • FIGS. 5 ( a ) to ( d ) are diagrams showing a step of forming preform layers on a part of the substrate by electrolytic copper plating to produce the bonding substrate
  • FIGS. 5 ( e ) to ( h ) are diagrams showing a step of placing an electronic component on the preform layers of the bonding substrate and then carrying out heating under pressure to produce the bonded body.
  • FIG. 6 A is an electron scanning microscope image obtained by imaging a preform layer of Example 1 of the present invention at a magnification of 50000 times.
  • FIG. 6 B is an electron scanning microscope image obtained by imaging a preform layer of Example 1 of the present invention at a magnification of 100000 times.
  • An acidic electrolytic copper plating solution of the present embodiment contains a soluble copper salt, an azole compound which has 2 or more and 3 or less nitrogen atoms in a five-membered ring represented by Formulae (1) to (4) and serves as a copper ion electrodeposition inhibitor, an acid, and water. Any solution can be used as long as these components are contained. As necessary, a brightening agent, a surfactant, an antioxidant, and other agents can be added.
  • the soluble copper salt include copper sulfate, copper oxide, and copper carbonate; copper alkane sulfonates such as copper methane sulfonate and copper propanoate; copper alkanol sulfonates such as copper isethionate and copper propanol sulfonate; organic acid coppers such as copper acetate, copper citrate, and copper tartrate, and the like.
  • copper alkane sulfonates such as copper methane sulfonate and copper propanoate
  • copper alkanol sulfonates such as copper isethionate and copper propanol sulfonate
  • organic acid coppers such as copper acetate, copper citrate, and copper tartrate, and the like.
  • examples of the acid include an organic acid and an inorganic acid.
  • specific examples of the acids include sulfuric acid; alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid; alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid; organic acids such as citric acid, tartaric acid, and formic acid, and the like.
  • alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid
  • alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid
  • organic acids such as citric acid, tartaric acid, and formic acid, and the like.
  • water include pure water such as ion exchange water and distilled water.
  • the azole compound which has two or more and three or less nitrogen atoms in a five-membered ring and serves as a copper ion electrodeposition inhibitor, will be described.
  • Specific examples of the azole compound represented by Formulae (1) to (4) 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, and the like.
  • the imidazole is a kind of the azole compound represented by Formula (1), and is represented by Formula (5).
  • 2-Aminoimidazole is a kind of the azole compound represented by Formula (1), and is represented by Formula (6).
  • Pyrazole is a kind of the azole compound represented by Formula (2), and is represented by Formula (7).
  • 3-Aminoimidazole is a kind of the azole compound represented by Formula (2), and is represented by Formula (8).
  • 1,2,3-Triazole is a kind of the azole compound represented by Formula (3), and is represented by Formula (9).
  • 1,2,4-Triazole is a kind of the azole compound represented by Formula (4), and is represented by Formula (10).
  • 3-Amino-1,2,4-triazole is a kind of the azole compound represented by Formula (4), and is represented by Formula (11).
  • 3,5-Diamino-1,2,4-triazole is a kind of the azole compound represented by Formula (4), and is represented by Formula (12).
  • 3-Amino-5-methylthio-1H-1,2,4-triazole is a kind of the azole compound represented by Formula (4), and is represented by Formula (13).
  • the acidic electrolytic copper plating solution of the present embodiment can be prepared by mixing the above-described soluble copper salt, the azole compound which has 2 or more and 3 or less nitrogen atoms in a five-membered ring and serves as the copper ion electrodeposition inhibitor described above, an acid, and water.
  • the prepared acidic electrolytic copper plating solution has a soluble copper salt concentration of 0.1 mol/L or more, and preferably 0.1 mol/L or more and 1.0 mol/L or less. In a case where the soluble copper salt concentration is less than 0.1 mol/L, the preform layer as the copper plating film cannot be formed.
  • a concentration of the azole compound, serving as the copper ion electrodeposition inhibitor is 10 mmol/L or more and 50 mmol/L or less and preferably 10 mmol/L or more and 30 mmol/L or less.
  • an acid concentration is not particularly limited, but is preferably pH 0 to 5, and more preferably pH 1 to 3.
  • a chloride ion concentration is 10 ppm or less and preferably 5 ppm or less. In a case where the chloride ion concentration is more than 10 ppm, the chloride ions adsorb to the copper surface, and the formation of the preform layer as the copper plating film is impaired.
  • a method for producing a bonding sheet including a copper sheet with a preform layer will be described, and the method includes forming the preform layers on one surface or both surfaces of the copper sheet by using the acidic electrolytic copper plating solution described above.
  • an acidic electrolytic copper plating solution 3 which is as described above, is put into a plating tank 2 of an electrolytic copper plating apparatus 1 , and in this acidic electrolytic copper plating solution 3 , a copper sheet 4 to be plated and two copper materials 5 and 5 , which are respectively made of electrolytic copper and oxygen-free copper, are disposed so that one of the copper materials 5 and 5 faces one surface of the copper sheet 4 and the other of the copper materials 5 and 5 faces the other surface of the copper sheet 4 .
  • the copper sheet 4 is connected to a negative electrode 6 as a cathode, and the two copper materials 5 and 5 are connected to a positive electrode 7 as soluble anodes.
  • a voltage is applied to the copper sheet 4 and the copper materials 5 and 5 to form preform layers 8 as copper plating films on both surfaces of the copper sheet 4 .
  • this copper sheet 4 is a copper foil, and the thickness of the copper sheet 4 is exaggerated in FIG. 1 .
  • the copper foil constituting the copper sheet 4 pure copper or a copper alloy can be used.
  • oxygen-free copper, tough pitch copper, phosphorous deoxidized copper, or other coppers can be used.
  • As the copper foil a rolled copper foil obtained by rolling such a copper material, or an electrolytic copper foil produced by an electrolytic copper plating method, or other ways can be used.
  • the copper materials 5 are used as the soluble anodes herein, an insoluble anode such as Pt/Ti can be used instead of the copper materials 5 .
  • an insoluble anode such as Pt/Ti
  • FIG. 3 A Another electrolytic copper plating method is shown in FIG. 3 A .
  • the same elements as those shown in FIG. 1 are designated by the same reference numerals.
  • a substrate 4 a whose surface is made of copper or nickel is disposed in the acidic electrolytic copper plating solution 3 of the electrolytic copper plating apparatus 1 , and the copper material 5 is disposed to face one surface of this substrate 4 a to perform electrolytic copper plating in the same manner as the electrolytic copper plating shown in FIG. 1 .
  • a resist film 4 b is formed on the surface of the substrate 4 a in advance to have openings at predetermined intervals.
  • the porous preform layers 8 containing copper particles 12 are formed as copper plating films in the openings of the resist film 4 b formed on one surface of the substrate 4 a.
  • a current density in the copper sheet 4 or substrate 4 a to be plated is set to about 0.1 A/dm 2 to 5 A/dm 2 , preferably 0.4 A/dm 2 to 1.0 A/dm 2 by using a direct current supply, and air and jet stirring or rocking stirring is then performed for about 30 minutes to 150 minutes and preferably about 60 minutes to 120 minutes, for example.
  • the azole compound which serves as a copper ion electrodeposition inhibitor, also adsorbs to the cathode surface, which is the surface of the copper sheet 4 or substrate 4 a , together with copper ions.
  • the electrodeposition of copper ions is strongly suppressed due to the presence of the azole compound, the nucleation of copper is given priority, and the porous preform layers 8 containing the copper particles 12 are formed as copper plating films on the cathode surface.
  • the copper sheet 4 on which the preform layers 8 shown in FIG. 1 have been formed is taken out from the acidic electrolytic copper plating solution 3 .
  • the substrate 4 a on which the preform layers shown in FIG. 3 A have been formed is taken out from the acidic electrolytic copper plating solution 3 , and the resist film 4 b is removed.
  • the copper sheet 4 or the substrate 4 a is cleaned with a cleaning solvent such as ethanol, water, or acetone, and dried in the atmosphere with a dry air.
  • a bonding sheet 10 including the porous preform layers 8 on both surfaces of the copper sheet 4 is thus obtained.
  • a bonding substrate 20 including the porous preform layers 8 on one surface of the substrate 4 a is obtained.
  • the obtained bonding sheet 10 or bonding substrate 20 is preferably immersed in a rust preventive agent containing benzotriazole and a surfactant as main components for a predetermined time in order to prevent surface oxidation.
  • each porous preform layer 8 on the copper sheet 4 or substrate 4 a is preferably 15 ⁇ m to 50 ⁇ m. In a case where the thickness of each preform layer is less than 15 ⁇ m, the strength of each preform layer itself is decreased, and the preform layer is difficult to handle. In a case where the thickness of the preform layer is more than 50 ⁇ m, the preform layer is difficult to follow irregularities of each surface of the base material or electronic component described later during the bonding, and the bonding strength of the bonded body may decrease.
  • the total thickness of the bonding sheet 10 obtained as described above is at least 25 ⁇ m. In other words, the thickness of the bonding sheet 10 is 25 ⁇ m or more.
  • the total thickness is preferably 25 ⁇ m to 140 ⁇ m. In a case where the total thickness is less than the lower limit of 25 ⁇ m, the strength of the bonding sheet itself may decrease. In a case where the total thickness is more than 140 ⁇ m, provided that the base material is a substrate, and the substrate to which the electronic component is bonded has warpage, the warpage may not be mitigated.
  • the total thickness of the bonding sheet is measured as follows.
  • the bonding sheet is completely coated with an epoxy resin, and then cut in a direction perpendicular to a surface direction of the bonding sheet, and the cut surface is polished with an argon ion beam.
  • the processed surface subjected to polishing is observed with an electron scanning microscope (SEM), the thicknesses of the bonding sheet are randomly measured at 100 or more points, and an average value thereof is defined as the thickness of the bonding sheet.
  • the bonding sheet 10 including the copper sheet 4 with the porous preform layers 8 formed on both surfaces of the copper sheet 4 shown in FIG. 2 will be described in detail.
  • the porous preform layers 8 are formed in the form of an aggregate of the copper particles 12 , which are accumulated on both surfaces of the copper sheet 4 .
  • the preform layers 8 containing the copper particles 12 each have an average porosity of 11% or more and 78% or less. In a case where the average porosity is less than 11%, the amount of the copper particles 12 that contribute to the sintering of the porous preform layers 8 is small, and the sinterability of the copper particles 12 decreases.
  • the average porosity of the preform layers 8 is preferably 11% or more and 17% or less.
  • each of the surfaces of the copper particles 12 is coated with copper nanoparticles 12 a having an average grain size smaller than the average grain size of the copper particles 12 . Therefore, each of the porous preform layers 8 is composed of the copper particles 12 and the copper nanoparticles 12 a with which each of the surface of the copper particles 12 is coated. Copper plating is carried out with the acidic electrolytic copper plating solution that is characteristic of the present embodiment to cause the azole compound to adsorb to a copper surface. Accordingly, the electrodeposition of copper is suppressed, and nucleation is given priority; and as a result, the copper nanoparticles 12 a are formed on a surface of each copper particle 12 .
  • the copper particles 12 are easily sintered together when the porous preform layer 8 is pressurized to facilitate the formation of the robust bonding layer. It is difficult to calculate the average grain size of the copper nanoparticles 12 a by the microscopic image because the fine copper particles 12 and the copper nanoparticles 12 a , which are finer than the copper particles 12 are composited. Thus, the average grain size is calculated from a BET measurement value. As described above, the average grain size of the copper nanoparticles 12 a calculated from the BET measurement value is 9.59 nm or more and 850 nm or less.
  • the average grain size of the copper nanoparticles 12 a is preferably within a range of 50 nm or more and 300 nm or less.
  • the above-described average porosity of the preform layer 8 is calculated by image analysis of a cross-section of the preform layer 8 using an electron scanning microscope.
  • the arithmetic average of the porosity (P) determined by Equation (A) is defined as an average porosity. Specifically, imaging is performed three times in different visual fields, and an average value of the calculated porosity is defined as an average porosity.
  • Equation (A) P is a porosity of the preform layer 8 , S 1 is the total area of the preform layer 8 , and S 2 is an area of void portions in the preform layer 8 .
  • the above-described average grain size of the copper nanoparticles 12 a is calculated from the specific surface area of the porous preform layer 8 measured by the BET method.
  • the measurement by the BET method is performed using Macsorb HM-model-1201 manufactured by MOUNTECH.
  • the copper sheet 4 with the preform layers 8 is cut into a size of 2 mm square, and a measurement cell is filled with the cut sheets to measure the specific surface area by a single-point BET method.
  • the mass of the copper sheet 4 is subtracted from a measurement value, and the value is converted into the mass of the preform layer 8 itself.
  • the grain size of the copper nanoparticles 12 a is calculated from the calculated BET measurement value from Equation (B).
  • a coefficient of 335.95 in Equation (B) is a value calculated from theoretical values of the density of copper, the surface area of the copper nanoparticles 12 a , and the volume of the copper nanoparticles 12 a .
  • the average grain size (d) of the copper nanoparticles 12 a is an average value of the values obtained by performing measurement three times by the BET method.
  • a substrate such as an oxygen-free copper plate, various heat dissipation boards, a flame retardant type 4 (FR4) board, or a substrate such as kovar
  • a substrate such as an oxygen-free copper plate, various heat dissipation boards, a flame retardant type 4 (FR4) board, or a substrate such as kovar
  • an electronic component such as a silicon chip device or an LED chip device
  • the bonding sheet 10 is disposed at a predetermined position on the base material 16
  • the electronic component 17 is disposed on the bonding sheet 10 .
  • the base material 16 and the electronic component 17 are held at a nitrogen atmosphere in a heating furnace at a temperature of 250° C. to 350° C.
  • the bonding sheet 10 becomes a bonding layer 15 , and the electronic component 17 is bonded to the base material 16 via this bonding layer 15 to obtain a bonded body 18 .
  • a bonding substrate 40 including a substrate 46 with porous preform layers 8 formed on a surface of the substrate 46 is used to form a bonded body 44 .
  • the porous preform layers 8 shown in FIG. 5 are the same as the porous preform layers 8 shown in FIG. 2 .
  • the substrate surface of the substrate 46 is made of copper or nickel.
  • this substrate 46 is an oxygen-free copper plate, or a Si substrate whose surface is metallized with copper, or an oxygen-free copper plate provided with a Ni plating layer on a substrate surface.
  • the electronic component 47 shown in FIG. 5 is the same as the electronic component 17 shown in FIG. 4 .
  • the substrate 46 of which a substrate surface is made of copper or nickel is prepared.
  • the surface of the substrate 46 is masked and patterned with a resist film 41 to have openings 46 a at predetermined intervals.
  • electrolytic copper plating is carried out in the acidic electrolytic copper plating solution 3 described above to form the porous preform layers 8 in the openings 46 a as shown in FIG. 5 ( c ) .
  • the resist film 41 is removed to produce the bonding substrate 40 with the porous preform layers 8 formed on the substrate 46 .
  • This electrolytic copper plating can be performed by the method described above.
  • the preform layers 8 are formed only on the openings 46 a , the preform layers 8 may be formed on the entire surface of the substrate 46 without providing the resist film 41 .
  • the electronic component 47 is bonded onto the porous preform layers 8 of the bonding substrate 40 .
  • the bonding substrate 40 on which the porous preform layers 8 are formed is placed on a pressurizing plate 42 .
  • the electronic component 47 is placed on the preform layers 8 to obtain a laminate.
  • the laminate including the bonding substrate 40 and the electronic component 47 is heated while being pressurized by the pressurizing plate 42 and a pressurizing plate 43 in the laminating direction.
  • the pressurizing and heating conditions are the same as the pressurizing and heating conditions for the base material 16 and electronic component 17 shown in FIG. 4 ( a ). Accordingly, as shown in FIG. 5 ( h ) , the preform layers 8 become bonding layers 45 , and the bonding substrate 40 and the electronic component 47 are bonded to obtain the bonded body 44 .
  • an oxygen-free copper plate with no preform layer on a surface thereof or a substrate whose bonding surface is metallized with copper may be prepared as the substrate, and a preform layer may be formed on a bonding surface of the electronic component.
  • a preform layer may be formed on the substrate, and a preform layer may be further formed on the bonding surface of the electronic component. Since the preform layers are formed on both the substrate and the electronic component, the bonding strength between the substrate and the electronic component can be further increased, which is preferred.
  • Examples of the present invention will be described in detail together with Comparative Examples.
  • electrolytic copper plating was carried out on a Si wafer patterned by the method shown in FIG. 5 .
  • a copper ion electrodeposition inhibitor which is tetrazole with a type No. 10
  • a copper ion electrodeposition inhibitor which is 5-amino-1H-tetrazole with a type No. 11
  • These azole compounds do not belong to Formulae (1) to (4) described above.
  • a copper layer having a thickness of about 500 nm was formed on an Si wafer (thickness: 1.2 mm) by a sputtering method and the Si wafer was used.
  • the surface of the Si wafer that included this copper layer (hereinafter, also simply referred to as the Si wafer) was patterned with a photoresist to provide 6002 perfectly circular openings with a diameter of 75 ⁇ m per die (15 mm square).
  • a hydrophilization treatment with a plasma cleaner was performed.
  • the Si wafer was pre-wet with pure water, then immersed in a sulfuric acid aqueous solution having a concentration of 10% by mass to conduct acid cleaning. The acid-cleaned Si wafer was washed with water. Electrolytic copper plating was carried out on one surface (patterned surface) of the Si wafer by using the plating apparatus 1 shown in FIG. 3 A containing the following copper plating solution.
  • a copper plating bath was prepared with the following solution composition. The plating conditions are also shown together. Characteristic items out of the compositions of the plating bath and the plating conditions of Example 1 are shown in Table 2.
  • Example 1 as the copper ion electrodeposition inhibitor, 3,5-diamino-1,2,4-triazole (No. 8 shown in Table 1) represented by Formula (12) described above was used.
  • FIGS. 6 A and 6 B show electron scanning microscope images of the surface of the preform layer of Example 1.
  • any of the concentration of the copper sulfate pentahydrate, the type of the copper ion electrodeposition inhibitor, the concentration of the copper ion electrodeposition inhibitor, or the chloride ion concentration was set to the same as or changed from those in Example 1.
  • the current density of cathode during the plating was also the same as or changed from that in Example 1.
  • Electrolytic copper plating was carried out in the same manner as in Example 1 except the above-described matters. Characteristic items out of the compositions of the plating baths and the plating conditions in Examples 2 to 20 and Comparative Examples 4 to 10 are shown in each of Table 2 described above and Table 3 described below.
  • Electrolytic copper plating was carried out in the same manner as in Example 1 to form porous preform layers containing copper particles as copper plating films on the Si wafers in Examples 2 to 20 and Comparative Examples 4 and 5.
  • Comparative Examples 6 to 10 since the electrodeposition of copper ions was defective, copper plating films were not uniformly formed on the Si wafers.
  • Comparative Example 1 the concentration of the copper sulfate pentahydrate was set to 1.0 mol/L, the cathode current density during the plating was set to 3.0 A/dm 2 , and copper plating was carried out on the Si wafer in the same manner as in Example 1.
  • the copper ion electrodeposition inhibitor was not used.
  • the chloride ion concentration was 80 ppm in the copper plating solution.
  • Comparative Example 2 the concentration of the copper sulfate pentahydrate was set to 1.0 mol/L, the cathode current density during the plating was set to 3.0 A/dm 2 , and copper plating was carried out on the Si wafer in the same manner as in Example 1.
  • the copper ion electrodeposition inhibitor was not used.
  • the chloride ion concentration was 5 ppm in the copper plating solution.
  • Comparative Example 3 the concentration of the copper sulfate pentahydrate was set to 1.0 mol/L, the cathode current density during the plating was set to 3.0 A/dm 2 , and copper plating was carried out on the Si wafer in the same manner as in Example 1.
  • Comparative Example 3 in order to compare the azole compounds with organic compounds other than the azole compounds, as the copper ion electrodeposition inhibitor, a common additive containing 50 ppm of disodium 3,3-dithiobis(1-propanesulfonate) and 300 ppm of polyethylene glycol (Mw: 3400) was used. The chloride ion concentration was 80 ppm in the copper plating solution.
  • the chloride ion concentration in the copper plating solution after bath preparation was measured by an ion chromatography method (manufactured by Thermo SCIENTIFIC, apparatus name: Dionex ICS-2100, separation column: Dionex IonPacTM AS12A (4 ⁇ 200 mm)).
  • the average porosity of the porous preform layers of 25 types of the bonding substrates obtained in Examples 1 to 20 and Comparative Examples 1 to 5, and the average grain size of the copper nanoparticles with which each of the copper particles constituting the preform layer was coated were determined by the methods described above. The results are shown in Table 2 and Table 3 described above.
  • the chip 47 was disposed on the preform layers 8 of 25 types of the bonding substrates 40 obtained in Examples 1 to 20 and Comparative Examples 1 to 5, and as shown in FIG. 5 ( g ) , heating was carried out under pressure to obtain each bonded body 44 .
  • the chip 47 was formed of a 2.5 mm square Si wafer (thickness: 1.2 mm) in which an uppermost surface was subjected to copper metallization.
  • This bonding was carried out by holding the bonded body 44 at a temperature of 300° C. under a pressure of 30 MPa for 30 minutes in a nitrogen atmosphere by using a pressurizing and heating bonding apparatus (manufactured by ALPHA-DESIGN Co., Ltd.; HTB-MM).
  • the shear strengths of 25 types of the bonded bodies were measured as follows.
  • the shear strength of the bonded body was measured by using a shear strength evaluation tester (bond tester manufactured by Nordson Corporation; Dage series 4000). Specifically, the measurement of the shear strength was carried out by fixing the Si wafer serving as a substrate of the bonded body horizontally, pressing the chip from the side in a horizontal direction by a shear tool at a position 50 ⁇ m above the surface (upper surface) of the bonding layer to measure the strength when the chip was broken. The moving speed of the share tool was set to 0.1 mm/sec. The strength test was performed three times per condition, and the arithmetic average value of the obtained values was used as the measurement value of the bonding strength.
  • the shear strengths of 25 types of the bonded bodies are shown in Tables 2 and 3 described above.
  • the bonding strength was 15 MPa or more, the bonding strength was evaluated as “good”, in a case where the bonding strength was 1.7 MPa or more and less than 15 MPa, the bonding strength was evaluated as “slightly defective”, and in a case where the bonding strength was less than 1.7 MPa, the bonding strength was evaluated as “defective”.
  • “-” indicates a case where the chip 47 and the bonding substrate 40 were not bonded even though an attempt was made to bond the chip 47 and the bonding substrate 40 , or a case where the chip 47 was peeled off before the bonding strength was measured. The results are shown in Tables 2 and 3.
  • the chloride ion concentration was too high as “50 ppm”. Therefore, the chloride ions adsorbed to the copper surface to inhibit the formation of the preform layer as the copper plating film.
  • the concentration of 3,5-diamino-1,2,4-triazole serving as the copper ion electrodeposition inhibitor was too low as “0.15 mmol/L”. As a result, sufficient surface adsorption to form the porous copper plating film was not obtained; and thereby, the porous copper plating film was not formed. Therefore, the bonding strength was not measured. The bonding strength was determined as “defective”.
  • the average porosity of the preform layer and the average grain size calculated from the BET value were appropriately controlled.
  • the average porosity of the preform layer formed on the Si wafer was within a range of 11% or more and 78% or less as described above.
  • the bonding substrate in each of Examples 1 to 20 and the chip were bonded, the bonding substrate and the chip were firmly bonded, and all bonding evaluations were “good.”
  • the acidic electrolytic copper plating solution of the present embodiment can be used in the step of forming the porous preform layer for bonding two members to each other.

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