JP6812768B2 - Conductive paste - Google Patents

Description

The present invention relates to a conductive paste used for filling vias or trenches provided in an electronic material such as a multilayer wiring board containing metal nanoparticles having a particle size of 1 to 100 nm as a main component for embedding.

In recent years, the speed of information processing of electronic devices has been increasing, and a high-density multilayer wiring board is required for a substrate mounted on an electronic device. Conventionally, as a high-density multilayer wiring board, a multilayer wiring board in which a build-up layer made of a photosensitive epoxy resin is stacked above and below a glass epoxy substrate has been adopted. Further, with the increase in the number of layers, conductor wiring layers between different layers are also connected by via hole conductors. This via hole conductor is generally used by drilling a via hole at a predetermined position on an insulating substrate of a multilayer wiring board with a drill or the like, and then plating the inner wall of the via hole.

Further, a method of laminating and multi-layering after making a via hole is being studied. In addition, an inner hole connection that connects only the necessary layers is also being considered. In this connection, the via wiring connecting each layer is formed by filling with a conductive paste instead of plating. As the conductive paste, a paste composed of a mixture of a metal powder and a thermosetting resin is filled in a via hole, and laminated and multilayered. However, these methods have a problem that the content of the thermosetting resin is small in order to reduce the via resistance, and the bond between the metal particles is weakened due to the deterioration of the resin by the thermal cycle test, and the resistance changes. It was. Therefore, a method has been proposed in which low melting point solder particles are added to the conductive paste together with the metal powder to connect the metal particles with solder to increase the conductivity of the vias, but the metal particles are dispersed in the solder due to poor wetting. However, the increase in electrical resistance has become a problem in the thermal cycle test. In order to solve the above problems, a conductive paste that can withstand a thermal cycle test by combining a metal finely divided into submicron size and solder has been developed, and the usefulness of inner hole connection is attracting attention. As described above, a method of filling pores and fine grooves of a wiring board with plating or a conductive paste to make them into fine wires is known, but in a high-density wafer-level packaging substrate, wires are formed. With a fine pitch TSV, a method of filling a groove having a width of 6 μm into a minute space of about 1 μm has become necessary.

On the other hand, the diameter of the via hole at present is about 1 to 100 μm, but it is expected that the diameter of the via hole will be 40 to 50 μm or less in the future in applications requiring higher density multi-layering. With this size, a conductive paste made of metal nanoparticles has been studied because it cannot be manufactured with good yield by a plating method that requires many steps. However, since the surface of the metal nanoparticles is covered with an organic material layer, the volume shrinkage after firing is large, and it is considered that high-density filling required for inner via hole connection is difficult. Although viafill materials using silver nanoparticles have been proposed so far (Patent Document 1), since most of the particles are μm silver particles in order to reduce volume shrinkage, via filling of 50 μm or less is possible. Is unsuitable. In addition, a large amount of expensive silver raw material is used, which poses a great economic difficulty. Therefore, a beerfill material using copper nanoparticles having a high cost advantage instead of silver nanoparticles has been proposed (Patent Document 2), but it is necessary to perform filling in a pressurized atmosphere, which causes volume shrinkage. In order to reduce the amount of liquid paraffin, a large amount of liquid paraffin remains, which causes problems such as difficulty in conductivity. In addition to filling via holes, a groove with a line width and depth of about several μm is dug on the semiconductor wafer, and metal nanoparticle paste is poured into the groove to form a wiring pattern, thereby achieving high conductivity and high density. A method for forming a compatible wiring pattern is also being studied.

As described above, in the future mounting technology in which high density is strongly required, the technique of filling metal nanoparticles in holes having a size of 50 μm or less or grooves of 10 μm or less is expected to be useful. However, the fact is that volume shrinkage occurs, which is a major obstacle to practical use.

Japanese Unexamined Patent Publication No. 2011-77177 JP-A-2009-267300

As described above, conductive paste composed of metal nanoparticles is sought after in mounting technology that requires high density, but silver nanoparticles are expensive, voids are generated due to volume shrinkage, and copper nanoparticles. In addition to the generation of voids due to volume shrinkage, there are problems that it is necessary to fill in a pressurized atmosphere and bake in a hydrogen atmosphere. As described above, the conductive paste composed of metal nanoparticles has many problems in practical use, but it can be used as an effective conductive paste for filling a fine space depending on the intended use.

Therefore, the problem to be solved by the present invention is a conductive paste for filling a fine space using metal nanoparticles, which does not require pressurization and a hydrogen atmosphere during firing, and voids due to volume shrinkage after firing. It is an object of the present invention to provide a conductive paste for filling fine vias or trenches using metal nanoparticles that do not generate.

As a result of diligent studies in view of the above circumstances, the present inventors have introduced a polyethylene oxide structure having 8 to 200 carbon atoms instead of an alkyl chain or the like into the dispersion site of the metal nanoparticles in the protective agent to obtain a metal. We have found that the above problems can be solved by using a conductive paste using nanoparticles as a conductive paste (filler) for filling fine vias or trenches, and have completed the present invention.

That is, the present invention
"Item 1. Contains metal nanoparticles (M) in which a polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms is compounded, and an alcohol solvent, an ether solvent, an ester solvent, and a lactam structure having a boiling point of 150 ° C. or higher. A conductive paste used for filling vias or trenches, which comprises at least one solvent (S) selected from the group consisting of solvents.
Item 2. The polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms is
Compounds represented by the following general formula (1),
Compounds represented by the following general formula (2),
The compound represented by the following general formula (3), or having a structure represented by the following general formula (4) at at least one end and having a polyethylene oxide structure having 8 to 200 carbon atoms in the side chain (meth). Acrylic polymer (polymer α) and a phosphoric acid ester having a structure represented by the following general formula (4) at at least one end and represented by -OP (O) (OH) ₂ in the side chain. Item 2. The conductive paste according to Item 1, which is a compound containing a (meth) acrylic polymer (polymer β) having a residue.
W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH _2- SX (1)
[W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH ₂ -S-] _d Y
(2)
[W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH _2- S-R ^a- ] _t Z
(3)
[W in the formulas (1), (2) and (3) is an alkyl group of C _{1 to} C ₈ , n is an integer indicating the number of repetitions of 4 to 100, and X is C _{2 to} C ₁₂ Alkyl group, allyl group, aryl group, arylalkyl group, -R ^1- OH, -R ^1- NHR ² , or -R ^1- (COR ³ ) _m (where R ¹ is saturated with C _{1 to} C ₄ a hydrocarbon group, ^{R 2} is a hydrogen _atom, C 2 -C ₄ acyl _group, C 2 -C ₄ alkoxycarbonyl group _C 1 alkyl group or _C 1 of -C ₄ -C ₈ or on the aromatic ring, the alkoxy group as the substituent is also good benzyloxycarbonyl group, ^{R 3} is a hydroxy _group, an alkoxy group of C 1 -C ₄ alkyl or _C 1 -C _8, m is 1 3 is an integer.), and, Y is a divalent to tetravalent radical which directly bound to a sulfur atom is a carbon _atom, C 1 -C saturated hydrocarbon group or a _C 1 -C ₄ of ₄ Is a group in which 2 to 3 saturated hydrocarbon groups are linked by -O-, -S- or -NHR ^b- (R ^b is a saturated hydrocarbon group of C _{1 to} C ₄ ), and d is 2. an to 4 integer, ^{R a} is an alkyl carbonyloxy group of _C 2 _{~C 5,} Z is a divalent to hexavalent group that binds directly to the sulfur atom is a carbon _{atom, C} 2 ~ C ₆ saturated hydrocarbon groups, C _{2 to} C ₆ saturated hydrocarbon groups are -O-, -S- or -NHR ^c- (R ^c is a saturated hydrocarbon group of C _{1 to} C ₄ ) 2 ~ 3 linked groups or isocyanuric acid-N, N', N "-triethylene group, where t is an integer of 2-6.]
RS- (4)
[In the general formula (4), R is a linear or branched alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a linear alkoxy group having 1 to 18 carbon atoms, and 1 to 18 carbon atoms. Branched alkoxy groups, aralkyloxy groups, substituted phenyloxy groups, linear alkylcarbonyloxy groups with 1 to 18 carbon atoms, branched alkylcarbonyloxy groups with 1 to 18 carbon atoms, carboxy groups, salts of carboxy groups, Linear alkoxycarbonyl group with 1 to 18 carbon atoms, branched alkoxycarbonyl group with 1 to 18 carbon atoms, phosphate group, linear alkyl phosphate group with 1 to 6 carbon atoms, 1 to 6 carbon atoms At least one functional group selected from the group consisting of a branched alkyl phosphate group, a sulfonic acid group, a linear alkyl sulfonic acid group having 1 to 6 carbon atoms, and a branched alkyl sulfonic acid group having 1 to 6 carbon atoms. Represents a linear or branched alkyl group having a group and having 1 to 8 carbon atoms. ]
Item 3. The polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms is
Compounds represented by the following general formula (1),
Item 2. The conductive paste according to Item 1, which is a compound represented by the following general formula (2) or a compound represented by the following general formula (3).
W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH _2- SX (1)
[W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH ₂ -S-] _d Y
(2)
[W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH _2- S-R ^a- ] _t Z
(3)
[W in the formulas (1), (2) and (3) is an alkyl group of C _{1 to} C ₈ , n is an integer indicating the number of repetitions of 4 to 100, and X is C _{2 to} C ₁₂ Alkyl group, allyl group, aryl group, arylalkyl group, -R ^1- OH, -R ^1- NHR ² , or -R ^1- (COR ³ ) _m (where R ¹ is saturated with C _{1 to} C ₄ a hydrocarbon group, ^{R 2} is a hydrogen _atom, C 2 -C ₄ acyl _group, C 2 -C ₄ alkoxycarbonyl group _C 1 alkyl group or _C 1 of -C ₄ -C ₈ or on the aromatic ring, the alkoxy group as the substituent is also good benzyloxycarbonyl group, ^{R 3} is a hydroxy _group, an alkoxy group of C 1 -C ₄ alkyl or _C 1 -C _8, m is 1 3 is an integer.), and, Y is a divalent to tetravalent radical which directly bound to a sulfur atom is a carbon _atom, C 1 -C saturated hydrocarbon group or a _C 1 -C ₄ of ₄ Is a group in which 2 to 3 saturated hydrocarbon groups are linked by -O-, -S- or -NHR ^b- (R ^b is a saturated hydrocarbon group of C _{1 to} C ₄ ), and d is 2. an to 4 integer, ^{R a} is an alkyl carbonyloxy group of _C 2 _{~C 5,} Z is a divalent to hexavalent group that binds directly to the sulfur atom is a carbon _{atom, C} 2 ~ C ₆ saturated hydrocarbon groups, C _{2 to} C ₆ saturated hydrocarbon groups are -O-, -S- or -NHR ^c- (R ^c is a saturated hydrocarbon group of C _{1 to} C ₄ ) 2 ~ 3 linked groups or isocyanuric acid-N, N', N "-triethylene group, where t is an integer of 2-6.]
Item 4. Item 2. The conductive paste according to any one of Items 1 to 3, wherein the solvent (S) is at least one solvent selected from the group consisting of an alcohol solvent having a boiling point of 150 ° C. or higher and an ether solvent.
Item 5. Item 2. The conductivity according to any one of Items 1 to 4, wherein the metal nanoparticles (M) are silver nanoparticles, copper nanoparticles, silver-core copper-shell nanoparticles, or copper-core silver-shell nanoparticles. paste.
Item 6. Item 2. The conductive paste according to any one of Items 1 to 5, wherein the content of the polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms to be composited with the metal nanoparticles is 2 to 15% by mass.
Item 7.
The conductive paste according to any one of claims 1 to 6, wherein the conductive paste is for filling vias, the diameter of the via is 0.5 to 10 μm, and the depth is 0.5 to 10 μm. ..
Item 8.
The conductive paste according to any one of claims 1 to 6, wherein the conductive paste is for filling a trench, and the size of the trench is 0.5 to 10 μm in width and 0.5 to 10 μm in depth.
Item 9. A filling material having vias in which the conductive paste according to any one of Items 1 to 6 is filled with a fired conductor.
Item 10. A filling having a trench formed by filling the conductive paste according to any one of Items 1 to 6 with a fired conductor. About.

According to the present invention, firing is possible under a non-pressurized atmosphere condition and a nitrogen atmosphere (effect 1), volume shrinkage due to firing is small (effect 2), and voids are not generated due to volume shrinkage (effect 3). The space can be filled.

6 is a scanning electron microscope image of a cross section of a silicon chip filled with a groove having a width of 1.0 μm and a depth of 1.0 μm obtained in Example 1. 6 is a scanning electron microscope image of a cross section of a silicon chip filled with a groove having a width of 2.0 μm and a depth of 1.0 μm obtained in Example 2. 6 is a scanning electron microscope image of a cross section of a silicon chip filled with a groove having a width of 0.5 μm and a depth of 1.0 μm obtained in Example 8. It is a scanning electron microscope image of the cross section of the silicon chip filled with the groove of width 0.5 μm, depth 1.0 μm obtained in Example 8, and is the area range used when determining the volume shrinkage ratio. 6 is a scanning electron microscope image of a cross section of a silicon chip filled with a groove having a width of 0.5 μm and a depth of 1.0 μm obtained in Comparative Example 6. It is a scanning electron microscope image of the cross section of a silicon chip filled with the groove of width 0.5 μm and depth 1.0 μm obtained in Comparative Example 6, and is the area range used when determining the volume shrinkage ratio.

Next, an embodiment of the present invention will be described in detail.

<Metal species in metal nanoparticles>
The metal species of the metal nanoparticles (M) of the present invention is not particularly limited as long as the polyethylene oxide structure-containing organic compound described later can be combined, and is preferably copper (Cu) -based or silver (Ag). The system is preferred. Examples of copper-based and silver-based nanoparticles include copper nanoparticles, silver nanoparticles, silver-core copper-shell nanoparticles, and copper-core silver-shell nanoparticles. Of these, copper nanoparticles are preferable because of their low cost and excellent migration resistance.

<Organic compound containing polyethylene oxide structure>
The polyethylene oxide moiety in the protective agent (organic compound containing a polyethylene oxide structure having 8 to 200 carbon atoms) used in the present invention has excellent affinity with a specific solvent used in the present invention, such as an alcohol solvent having a boiling point of 150 ° C. or higher. Therefore, the aggregation of the metal nanoparticles can be strongly suppressed, and the metal nanoparticles can be highly dispersed. That is, since the metal nanoparticles are packed at high density, voids are not generated due to the decomposition and removal of the protective agent and the solvent by heat treatment, and high density filling is possible in a non-pressurized atmosphere. And. Further, the metal nanoparticles synthesized by using the protective agent of the present invention have a small protective agent abundance of about 2 to 10% and do not interfere with the necking phenomenon between the metal particles during firing.

As examples of metal nanoparticles (composite of organic compound and metal nanoparticles) in which a polyethylene oxide-containing organic compound having 8 to 200 carbon atoms is compounded, which is used in the present invention, Japanese Patent No. 4784847 and Japanese Patent Application Laid-Open No. 2013-60637 are used. Alternatively, Japanese Patent No. 5077728 can be mentioned, and the compound can be synthesized by the method described herein. These are characterized in that the thioether type (RS-R') compound has an appropriate affinity adsorption effect on the surface of metal particles and a rapid desorption property by heating, and has low temperature fusion characteristics. It has been developed as a metal nanoparticle to show.

Further, as another example, among the polymer compounds having a thioether group described in JP-A-2010-209421, metal nanoparticles in which a polymer compound having a polyethylene oxide moiety having 8 to 200 carbon atoms is compounded, and further. Among the polymer compounds having a thioether group and a phosphoric acid ester group described in Japanese Patent No. 4697356, metal nanoparticles in which a polymer compound having a polyethylene oxide moiety having 8 to 200 carbon atoms is compounded can be mentioned. .. The production of these polyethylene oxide structure-containing polymer compounds can be carried out according to the methods described in these publications. Further, in the present invention, these polyethylene oxide structure-containing phosphoric acid ester-type organic compounds have a thioether group and also have a phosphoric acid ester group, and by having these groups, the surface of the metal nanoparticles is subjected to. Therefore, it is possible to impart an appropriate affinity adsorption effect and rapid desorption by heating.

Among these, thioether-type organic compounds represented by the following formulas (1) to (3) are preferable.

<Thioether (RSR') type organic compound>
As an example for explaining the effect of the present invention, copper-based and silver-based nanoparticles in which thioether-type organic compounds represented by the following general formulas (1) to (3) are combined will be described in detail.
W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH _2- SX (1)
[W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH ₂ -S-] _d Y
(2)
[W- (OCH ₂ CH ₂ ) _n- O-CH ₂ -CH (OH) -CH _2- S-R ^a- ] _t Z
(3)
[W in the formulas (1), (2) and (3) is an alkyl group of C _{1 to} C ₈ , n is an integer indicating the number of repetitions of 4 to 100, and X is C _{2 to} C ₁₂ Alkyl group, allyl group, aryl group, arylalkyl group, -R ^1- OH, -R ^1- NHR ² , or -R ^1- (COR ³ ) _m (where R ¹ is saturated with C _{1 to} C ₄ a hydrocarbon group, ^{R 2} is a hydrogen _atom, C 2 -C ₄ acyl _group, C 2 -C ₄ alkoxycarbonyl group _C 1 alkyl group or _C 1 of -C ₄ -C ₈ or on the aromatic ring, the alkoxy group as the substituent is also good benzyloxycarbonyl group, ^{R 3} is a hydroxy _group, an alkoxy group of C 1 -C ₄ alkyl or _C 1 -C _8, m is 1 3 is an integer.), and, Y is a divalent to tetravalent radical which directly bound to a sulfur atom is a carbon _atom, C 1 -C saturated hydrocarbon group or a _C 1 -C ₄ of ₄ Is a group in which 2 to 3 saturated hydrocarbon groups are linked by -O-, -S- or -NHR ^b- (R ^b is a saturated hydrocarbon group of C _{1 to} C ₄ ), and d is 2. an to 4 integer, ^{R a} is an alkyl carbonyloxy group of _C 2 _{~C 5,} Z is a divalent to hexavalent group that binds directly to the sulfur atom is a carbon _{atom, C} 2 ~ C ₆ saturated hydrocarbon groups, C _{2 to} C ₆ saturated hydrocarbon groups are -O-, -S- or -NHR ^c- (R ^c is a saturated hydrocarbon group of C _{1 to} C ₄ ) 2 ~ 3 linked groups or isocyanuric acid-N, N', N "-triethylene group, where t is an integer of 2-6.]

The chain-like functional group having an ethylene oxide structure as a repeating unit in the general formulas (1) to (3) functions as a solvent-affinitive portion. It is preferable to use a polyethylene oxide structure having 8 to 200 carbon atoms, and it is more preferable to use one having 8 to 100 carbon atoms.

Further, since the chain-like functional group having an ethylene oxide structure as a repeating unit in the general formulas (1) to (3) has a smaller number of carbon atoms, it is less likely to inhibit the phenomenon (necking) of fusion of metal particles. A filler having about 8 to 12 carbon atoms is more preferable as a filler having high reliability.

On the other hand, the chain-like functional group having an ethylene oxide structure as a repeating unit in the general formulas (1) to (3) has excellent dispersion stability with about 50 to 100 carbon atoms, and highly disperses metal nanoparticles. , It is more preferable in that it improves the high-density filling performance in a non-pressurized atmosphere.

Therefore, the number of carbon atoms is in the range of 8 to 200 (corresponding to the case where n in the general formula is 4 to 100) or more preferably 8 to 100 carbon atoms (n in the general formula is 4 to 50) depending on the usage situation. It can be adjusted as appropriate within the range of).

W in the general formulas (1) to (3) has 1 to 8 carbon atoms in a linear or branched form from the viewpoint of industrial availability and dispersion stability when used as a protective agent. It is preferably an alkyl group having 1 to 4 carbon atoms from the viewpoint of stability in an aqueous medium.

A structure in which X in the general formula (1) contains a carboxyl group, an alkoxycarbonyl group, a carbonyl group, an amino group, and an amide group as a partial structure can form a thioether group and a polydentate ligand. Therefore, it is preferable because the coordinating force on the surface of the metal nanoparticles becomes strong.

Y is an ether of the general formula (2) (C-O-C), thioether (C-S-C) having a structure including as a partial structure a, ^{R a} is methylene carboxy group in the general formula (3) (-CH ₂ COO-) or ethylene carboxy group (-CH ₂ CH ₂ COO-), where Z is an ethylene group, 2-ethyl-2-methylenepropane-1,3-diyl group, 2,2-bis The one having a methylenepropane-1,3-diyl group is most preferable.

<Manufacturing method of thioether type organic compound>
As described above, in the present invention, the thioether type organic compound is preferably a compound represented by the general formulas (1) to (3). The method for producing these thioether-type organic compounds will be described in detail below.

As a method for easily producing a thioether type organic compound, for example, a method of reacting a polyether compound (a1) having a glycidyl group at the end with a thiol compound (a2) can be mentioned.

The polyether compound (a1) having a glycidyl group at the terminal can be represented by the following general formula (5).

(In the formula, W, R ¹ , and n are the same as described above.)

As a method for synthesizing the polyether compound (a1) having a glycidyl group at the end, for example, a chlorohydrin compound produced after addition-opening of a polyethylene glycol monoalkyl ether to the oxylan ring of epichlorohydrin in the presence of Lewis acid. Can be heated and reclosed in a concentrated alkali, or reacted in one step using a strong base such as excess alkoxide or concentrated alkali. As a method for obtaining a higher purity polyether compound (a1). Is a method of Gandour et al. (Gandour, et al) in which polyethylene glycol monomethyl ether is used as an alkoxide using potassium t-butoxide, this is condensed with epichlorohydrin, and then heating is continued to reshape the epoxy ring. , J. Org. Chem., 1983, 48, 1116.) Is preferably applied mutatis mutandis.

The terminal oxylan ring of the polyether compound (a1) having a glycidyl group at the terminal can be opened with a thiol compound (a2) to obtain a desired thioether type organic compound. This reaction utilizes a thiol group nucleophilic reaction, and various activation methods can be mentioned for this reaction.

For example, synthesis by activating an epoxide with a Lewis acid is widely performed, and specifically, it is known to use zinc tartrate or a lanthanide-based Lewis acid. In addition, a method using a Lewis base is often performed.

Furthermore, a method of utilizing fluorine ions as a base catalyst is described in James H. et al. It is detailed in Clark's review. Penso et al. Have applied this as a ring-opening method for epoxides with excellent regioselectivity, and the addition ring-opening reaction of thiols to epoxides proceeds under mild conditions by using quaternary ammonium fluoride as a catalyst. I am reporting that.

In particular, from the viewpoint that the thioether-type organic compound used in the present invention can be obtained with high efficiency, a method using fluorine ions as a base catalyst is preferable. By applying this method, after the reaction between the polyether compound (a1) having a glycidyl group at the end and the thiol compound (a2), a thioether type organic compound can be obtained without any special purification.

Various thiol compounds (a2) can be reacted with the polyether compound (a1). Examples include alkanethiols and benzenethiols, as well as thioglycol, thioglycolic acid and its esters, mercaptopropionic acid and its esters, which are widely used as radical polymerization chain transfer agents and are easily available. Mercaptopolycarboxylic acids such as thiomalic acid, thiocitonic acid and their esters may be reacted. In addition, compounds having a plurality of thiol groups in the molecule, that is, alkylenedithiols such as ethanedithiol, trimethylolpropane = tris (3-mercaptopropionate), pentaerythritol = tetrakis (3-mercaptopropionate), Dipentaerythritol-hexakis (3-mercaptopropionate) and the like can also be reacted and introduced in the same manner. Since the resulting compound has a plurality of thioether structures in the molecule, it is possible to express affinity for copper-based nanoparticles by a plurality of regions.

<Phosphate ester type organic compound containing polyethylene oxide structure>
As an example for explaining the effect of the present invention, copper-based and silver-based nanoparticles in which a phosphate ester-type organic compound containing a polyethylene oxide structure is compounded will be described in detail.

The compound used in the present invention is a (meth) acrylic polymer having a structure represented by the following general formula (4) at at least one terminal and having a polyethylene oxide chain having 8 to 200 carbon atoms in a side chain (meth). The polymer α) has a structure represented by the following general formula (4) at at least one end, and has a phosphate ester residue represented by −OP (O) (OH) ₂ in the side chain ( A compound containing a meta) acrylic polymer (polymer β),
RS- (4)
[In the general formula (4), R is a linear or branched alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a linear alkoxy group having 1 to 18 carbon atoms, and 1 to 18 carbon atoms. Branched alkoxy groups, aralkyloxy groups, substituted phenyloxy groups, linear alkylcarbonyloxy groups with 1 to 18 carbon atoms, branched alkylcarbonyloxy groups with 1 to 18 carbon atoms, carboxy groups, salts of carboxy groups, Linear alkoxycarbonyl group with 1 to 18 carbon atoms, branched alkoxycarbonyl group with 1 to 18 carbon atoms, phosphate group, linear alkyl phosphate group with 1 to 6 carbon atoms, 1 to 6 carbon atoms At least one functional group selected from the group consisting of a branched alkyl phosphate group, a sulfonic acid group, a linear alkyl sulfonic acid group having 1 to 6 carbon atoms, and a branched alkyl sulfonic acid group having 1 to 6 carbon atoms. Represents a linear or branched alkyl group having a group and having 1 to 8 carbon atoms. ]

Here, the suitable carbon number of the polyethylene oxide structure is the same as that of the above-mentioned thioether type organic compound.

<Method for producing phosphoric acid ester-type organic compound containing polyethylene oxide>
As the thiol compound (Q) used to obtain a polymer compound having a structure represented by the general formula (4) in the molecule, a thiol compound generally used as a chain transfer agent can be used. Specifically, thioglycol, 2-mercaptopropanol, 3-mercaptopropanol, 8-mercaptooctanol, 2,3-dihydroxypropanethiol, 2-methoxyethanethiol, 2-ethoxyethanethiol, 2-hexyloxyethanethiol, 2- (2-Ethylhexyloxy) ethanethiol, 2-benzyloxyethanethiol, 2- (4-methoxybenzyloxy) ethanethiol, 2-phenyloxyethanethiol, 2- (4-methoxyphenyloxy) ethanethiol, 2 -(2,4-Dimethoxyphenyloxy) ethanethiol, 6- (4-hydroxymethylphenyloxy) hexanethiol, 2-acetoxyethanethiol, 2-heptanoyleoxyethanethiol, 2-octanoyloxyethanethiol, 2- Octadecanoyloxyethanethiol, 2-isobutyryloxyethanethiol, 2-pivaloyloxyethanethiol, thioglycolic acid, β-mercaptopropionic acid, 7-mercaptooctanoic acid, 2-mercaptopropionic acid, 2-mercapto Succinic acid and inorganic salts of these carboxylic acids, ammonium salts and organic amine salts, methyl thioglycolate, ethyl thioglycolate, octyl thioglycolate, ethyl β-mercaptopropionate, octyl β-mercaptopropionate, β- Dodecyl mercaptopropionate, β-mercaptopropionic acid-2- (methoxyethyl), β-mercaptopropionic acid-2- (methoxyethoxyethoxy), β-mercaptopropionic acid-2- (4-methoxybutoxy), thioglycolic acid -2-Ethylhexyl, β-mercaptopropionic acid -2-ethylhexyl, β-mercaptopropionic acid-3-methoxybutoxy, 2-mercaptoethyl phosphate, 2-mercaptoethylphosphinic acid, 2-mercaptopropyl phosphate, 2-mercapto Propylphosphinic acid, ω-mercaptoethoxyethyl phosphate, ω-mercaptopropyloxypropyl phosphate, 2-mercaptoethyl dimethyl phosphate, 2-mercaptoethyl phosphinate dimethyl, 2-mercaptoethyl diethyl phosphate, 2-mercaptopropyl diethyl Phosphate, 2-mercaptoethyl diisopropyl phosphate, 2-mercaptoethyldiisobutyl phosphate, 2-mercaptoethyl sulfer , 2-mercaptoethyl sulfonic acid, 2-mercaptopropyl sulfonic acid, 2-mercaptoethyl methyl sulphonate, methyl 2-mercaptoethyl sulphonate, 2-mercaptoethyl ethyl sulphonate, ethyl 2-mercaptoethyl sulphonate, methyl 2 -Mercaptopropyl sulfonate, ethyl 2-mercaptopropyl sulfonate, etc. can be mentioned. Among them, when thioglycol, 2,3-dihydroxypropanethiol, thioglycolic acid, β-mercaptopropionic acid, ethyl β-mercaptopropionate, and 2-ethylhexyl β-mercaptopropionate are reactive, easily available, and thinned. From the viewpoint of surface smoothness, methyl β-mercaptopropionate is most preferable.

The polymerizable compound to be reacted with the thiol compound (Q) is not particularly limited, and a known polymerizable compound can be used. Specifically, it is (meth) acrylic acid, (meth) acrylic acid ester compound, vinyl alcohol ester compound, styrene compound, allyl alcohol compound, allylamine compound and the like.

In the protective agent for metal nanoparticles of the present invention, a protective agent can be designed according to the metal species to be used and desired physical properties by appropriately selecting a polymerizable compound having a functional group having an affinity for metal. It is possible and characteristic. Specifically, a carboxy group, a phosphoric acid group, a sulfonic acid group, or a heteroaromatic group (for example, an imidazole group) having a slightly strong adsorptive capacity to a metal, showing a moderate interaction and depending on the liquidity of the dispersion medium. Amino groups whose adsorptivity changes (eg, dimethylaminoethyl group, dimethylaminopropyl group), hydroxy groups (hydroxyethyl group, hydroxypropyl group), which have less interaction with the metal surface than the former, and aromatic groups (eg, hydroxyethyl group, hydroxypropyl group). By using a polymerizable compound having a benzyl group), it is possible to freely impart the functional group to the protective agent for metal nanoparticles, and the ratio thereof can be freely changed. The adsorptivity can also be changed freely.

For example, by using a polymerizable compound having a polyethylene oxide chain such as polyalkylene glycol methacrylate as the polymerizable compound, the polyethylene oxide chain can be added to the polymer compound having the structure represented by the general formula (4) in the molecule. Can be incorporated.

Similarly, as the polymerizable compound, a carboxy group is used by using (meth) acrylic acid or the like, an amino group is used by using dimethylaminoethyl methacrylate or the like, and phosphorus is used by using methacryloyloxyethyl phosphate or the like. The acid group is a hydroxy group by using hydroxyethyl methacrylate or the like, the sulfonic acid group using a modified (meth) acrylic acid ester having a sulfonic acid group as a polymerizable compound, and the hetero by using a heteroaromatic vinyl compound. Aromatic groups can be introduced. In this way, an amino group, a carboxy group, an imidazole group, a phosphoric acid group, a sulfonic acid group and the like can be incorporated into the polymer compound having the structure represented by the general formula (4) in the molecule.

Specific examples of these polymerizable compounds include 2-dimethylaminoethyl methacrylate, vinyl imidazole, 2-methacryloyloxyethyl phosphate, and 2-acrylamide-2-methylpropanesulfonic acid.

The polymerization method of the protective agent for metal nanoparticles of the present invention may be an ordinary radical polymerization method, in which a thiol compound and a polymerizable compound are dissolved in an appropriate solvent, a percarboxylic acid ester or the like is added as a polymerization initiator, and the mixture is heated. ..

<Synthesis of metal nanoparticles in which an organic compound containing a polyethylene oxide structure having 8 to 200 carbon atoms is compounded>
As an example for explaining the effect of the present invention, the method for producing metal nanoparticles in which a polyethylene oxide structure-containing organic compound having 8 to 200 carbon atoms is used in the present invention is a divalent method in the presence of a thioether type organic compound. It is characterized by having a step of mixing a copper ion compound or a monovalent silver ion compound with a solvent, and a step of reducing copper ions or silver ions.

As the divalent copper ion compound, generally available copper compounds can be used, and sulfates, nitrates, carboxylates, carbonates, chlorides, acetylacetonate complexes and the like can be used. When a complex with zero-valent copper nanoparticles is obtained, it may start from a divalent compound or be produced from a monovalent compound, and may have water or water of crystallization. Specifically, when expressed excluding water of crystallization, CuSO ₄ , Cu (NO ₃ ) ₂ , Cu (OAc) ₂ , Cu (CH ₃ CH ₂ COO) ₂ , Cu (HCOO) ₂ , CuCO ₃ , CuCl ₂ , Cu ₂ O, C ₅ H ₇ CuO _{2 and the} like. Additionally, or heating the salts, basic salts obtained by or exposed to a basic atmosphere, for example _{Cu (OAc) 2 · CuO,} Cu (OAc) 2 · 2CuO, Cu 2 Cl (OH) 3 , etc. It can be used most preferably. These basic salts may be prepared in the reaction system, or may be prepared separately outside the reaction system. Further, a general method of adding ammonia or an amine compound to form a complex to secure solubility and then using it for reduction is also applicable.

As the monovalent silver ion compound, generally available silver compounds can be used, such as silver nitrate, silver oxide, silver acetate, silver fluoride, silver acetylacetonate, silver benzoate, silver carbonate, and silver citrate. , Silver hexafluorophosphate, silver lactate, silver nitrite, silver pentafluoropropionate and the like, and silver nitrate or silver oxide is preferably used from the viewpoint of ease of handling and industrial availability.

These copper or silver ion compounds are dissolved or mixed in a medium in which a thioether type organic compound is previously dissolved or dispersed. As the medium that can be used at this time, water, ethanol, acetone, ethylene glycol, diethylene glycol, glycerin and a mixture thereof are preferably used, although it depends on the structure of the organic compound used, and the water-ethylene glycol mixture is particularly suitable. preferable.

The concentration of the thioether-type organic compound in various media is preferably adjusted to the range of 0.3 to 10% by mass from the viewpoint of facilitating the control of the subsequent reduction reaction.

In the medium prepared above, the copper or silver ion compound is added in a lump or divided manner and mixed. When a medium that is difficult to dissolve is used, a method may be used in which the medium is previously dissolved in a small amount of a good solvent and then added to the medium.

The ratio of the thioether-type organic compound to be mixed with the copper or silver ion compound is preferably selected as appropriate according to the protective ability of the thioether-type organic compound in the reaction medium, but usually 1 mol of the copper or silver ion compound is used. The thioether-type organic compound is preferably prepared in the range of 1 mmol to 30 mmol (about 2 to 60 g when a polymer having a molecular weight of 2000 is used), and particularly preferably used in the range of 15 to 30 mmol. Here, the same can be performed by using a phosphoric acid ester type organic compound containing a polyethylene oxide structure, and the amount of the organic compound used per 1 mol of the copper or silver ion compound is also the same as in the previous period.

Subsequently, the reduction of copper or silver ions is carried out using various reducing agents. Examples of the reducing agent include hydrazine compounds, hydroxylamines and derivatives thereof, metal hydrides, phosphinates, aldehydes, enols, hydroxyketones, etc., which undergo a reduction reaction of copper or silver at a temperature of 80 ° C. or lower from ice-cold temperature. A compound that can be advanced is preferable because it gives a complex with less precipitate formation.

In the reduction of copper ions, specifically, a strong reducing agent such as hydrazine hydrate, unsymmetrical dimethylhydrazine, aqueous hydroxylamine solution, and sodium borohydride is suitable. Since these have the ability to reduce copper compounds to zero valence, they are suitable for producing a composite of an organic compound and nano-copper particles by using divalent and monovalent copper compounds as reduced copper.

The conditions suitable for the reduction reaction vary depending on the copper compound used as a raw material, the type of reducing agent, the presence or absence of complexation, the medium, and the type of the thioether type organic compound. For example, when copper (II) acetate is reduced with sodium borohydride in an aqueous system, zero-valent nanocopper particles can be prepared even at an ice-cooled temperature. On the other hand, when hydrazine is used, the reaction is slow at room temperature, and a smooth reduction reaction occurs only after heating to about 60 ° C. When reducing copper acetate with ethylene glycol / aqueous system, the reaction is carried out at 60 ° C. for about 2 hours. It takes a reaction time. When the reduction reaction is completed in this way, a reaction mixture containing a complex of the organic compound and the copper-based nanoparticles is obtained.

Due to the effect of the protective agent, the copper nanoparticles prepared in this way can be highly dispersed as in the state before drying even if the solvent is added again after the moisture is completely removed to form a dry body powder. Is.

Further, when a mixed solution in which nanosilver is added to a mixed solution of the thioether type organic compound, the medium, and the copper ion compound is prepared in advance, and then a reducing agent is added to reduce the copper ions by the above method, nanosilver is obtained. Silver core copper shell nanoparticles having a surface coated with copper can be obtained.

On the contrary, when the mixed solution in which nanocopper is added to the mixed solution of the thioether type organic compound, the medium, and the silver ion compound is prepared in advance, and then a reducing agent is added to reduce the silver ions by the above method, Copper core silver shell nanoparticles having a nanocopper surface coated with silver can be obtained.

<Manufacturing method of dispersion>
After the reduction reaction, a step of removing the metal compound residue, the reducing reagent residue, the excess polyethylene oxide structure-containing organic compound, and the like is provided as necessary. Reprecipitation, centrifugation or ultrafiltration can be applied to the purification of the complex, by washing the reaction mixture containing the resulting complex with a washing solvent such as water, ethanol, acetone and a mixture thereof. , The above-mentioned impurities can be washed away.

<Conductive paste for filling vias or trenches>
The conductive paste for filling vias or trenches of the present invention (hereinafter, may be referred to as the conductive paste of the present invention) is a metal nanoparticle (A) in which a polyethylene oxide-containing organic compound (A) having 8 to 200 carbon atoms is compounded. A conductive paste containing M) and a solvent. As described above, the metal nanoparticles-organic compound complex (metal nanoparticles composited with an organic compound, which corresponds to the notation (M) in the present specification) can be obtained as an aqueous dispersion, but can be purified. In the final step, instead of adding a cleaning solvent to the composite, a solvent that is easy to use as a filling paste is added, or the medium is exchanged, so that the suitability of the conductive paste of the present invention can be imparted.

The higher the concentration of metal contained in the conductive paste of the present invention, the higher the density of filling, but on the other hand, it is necessary to supply the paste to the filling space by coating, dispenser, mask printing, screen printing or the like. Therefore, a solvent (S), which will be described later, is required so that the characteristics as a filling paste are suitable. Further, it is necessary to adjust the concentration of the metal contained in the material by further adding an additive. Therefore, the metal concentration of the paste is adjusted so as to have the maximum metal concentration in the viscosity range suitable for the printing method. Generally, about 50 to 95% is preferable because it is easy to supply to the filling space.

The conductive paste of the present invention can also be used by further adding metal nanoparticles having a particle diameter of about 200 to 1000 nm.

The conductive paste of the present invention can also be used with further reducing power by adding a flux component.

The conductive paste prepared in this way is stable for about 1 to 3 months regardless of the prepared concentration when stored in a closed container.

The level that is said to be practically sufficient in the technical field of the present invention is that the filling of 80% or more can be confirmed from the image in the silicon mold filling test described later. The conductive paste of the present invention achieves a filling of 80% or more, preferably 90% or more. Further, the volume shrinkage after firing of the conductive paste film in a dry state by the thin film observation device described later is practically required to be 10% or less, and preferably 5% or less.

<Solvent (S)>
Examples of the solvent (S) that can be used in the present invention include an alcohol solvent having a boiling point of 150 ° C. or higher, an ether solvent having a boiling point of 150 ° C. or higher, an ester solvent having a boiling point of 150 ° C. or higher, and a lactam structure-containing solvent having a boiling point of 150 ° C. or higher. Etc. can be preferably used.

Here, the alcohol-based solvent having a boiling point of 150 ° C. or higher is specifically a monohydric alcohol type such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, terpineol, ethylene glycol, propylene glycol, diethylene glycol, etc. Dihydric alcohol types such as triethylene glycol, propanediol, butanediol, pentanediol, hexanediol and heptanediol, trihydric alcohol types such as propanetriol, butanetriol, pentantriol, hexanetriol and heptanetriol, and propanetetraol. , Butane tetraol, pentan tetraol, hexane tetraol, heptane tetraol, pentan pentaol, hexane pentaol and other polyhydric alcohol types. It is also possible to use alcohol compounds having a cyclic structure such as benzenetriol, biphenylpentaol, benzenepentaol and cyclohexanehexaol. In addition, compounds having an alcohol group such as citric acid and ascorbic acid may be used. In addition, propylene glycol monomethyl ether, 3-methoxybutanol, propylene glycol-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol methyl ether, diethylene glycol monoethyl ether, and dipropylene glycol, which are alcohol derivatives containing an ether structure. -N-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol-n-butyl ether, ethylene glycol monobutyl ether acetate and the like may be used.

Here, specific examples of the ether solvent having a boiling point of 150 ° C. or higher include polyethylene glycol and polypropylene glycol having a molecular weight of 200 to 400.

Here, the ester solvent having a boiling point of 150 ° C. or higher is specifically cyclohexanol acetate, dipropylene glycol dimethyl ether, propylene glycol diacetate, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, 1 , 4-Butanediol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, crown ethers having a cyclic structure, and the like.

Here, the lactam structure-containing solvent having a boiling point of 150 ° C. or higher is specifically β-lactam such as β-lactam, ε-caprolactam, σ-lactam, N-methyl-2-pyrrolidone, pyroglutamic acid, piracetam, and penicillin. Examples include system compounds.

Among them, from the viewpoint of heat reduction action during decomposition and volatilization, it is preferable to use an alcohol solvent having a boiling point of 150 ° C. or higher and an ether solvent having a boiling point of 150 ° C. or higher.

Among them, more preferably, an alcohol solvent having a boiling point of 150 ° C. or higher, such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and heptanediol. An ether solvent of 150 ° C. or higher is preferable.

Of these, ethylene glycol, diethylene glycol, and polyethylene glycol having a molecular weight of 200 to 400 are more preferable.

The amount used can be in the range of 5 to 50% with respect to the metal, and more preferably in the range of 5 to 15%.

<Filling>
In the present invention, examples of the member (filled material) to be filled with the conductive paste of the present invention include metals (including alloys and intermetallic compounds), ceramics, plastics, and composite materials thereof. In the present invention, ceramics (including silicon chips) or plastics are particularly preferable. The material to be filled here has a fine space such as a via or a trench, and the conductive paste of the present invention can be used to fill the space. In the present invention, since the nanoparticles as described above are used, it can be adopted in the case of filling a via hole (through substrate via: TSV) penetrating a semiconductor.
In the present invention, the via has a diameter of 0.5 to 2.0 μm and a depth of 0.5 to 2.0 μm, and the trench has a width of 0.5 to 2.0 μm and a depth of 0.5 to 2.0 μm, particularly from the viewpoint of using metal nanoparticles. Those having a thickness of 0.5 to 2.0 μm are preferable. Here, "via" refers to a through or non-penetrating hole provided in the substrate.

The temperature at which the conductive paste of the present invention is applied to the via or trench of the material to be filled and the copper nanoparticles or silver nanoparticles are fused as it is (without pressurization) or in a slightly pressurized atmosphere. It can be heated to to produce a filler (sometimes referred to as a filler). At this time, it can be carried out under any of a forming gas containing hydrogen, a nitrogen atmosphere, or an atmosphere of formic acid-containing nitrogen contained by passing formic acid, but it is preferably carried out in a nitrogen atmosphere from the viewpoint of handleability. .. As described above, the effect of the present invention is that sufficient performance can be exhibited even in firing in a nitrogen atmosphere, which has been desired but difficult in the past.

The slight pressurization referred to here refers to a range of 1.1 atm to 5 atm (1100 hPa to 5000 hPa).

Further, the paste can be pushed into the via and the trench portion by the gas by applying the paste under a reduced pressure atmosphere of 0.9 to 0.01 atm (900 hPa to 1 hPa) and returning the paste to normal pressure with an inert gas or the like.

If the firing temperature is in the range of 150 to 350 ° C, fusion is possible, and if the firing time is in the range of 1 to 60 minutes, sufficient performance is exhibited, but from the viewpoint of shortening the work, it is 5 to 15 minutes. Baking is preferred. If the conductive paste of the present invention is used, sufficient performance can be exhibited even in such a short-time firing.
Further, if necessary, it is also possible to perform firing using a temperature profile, such as performing temporary firing in which the solvent is volatilized at a low temperature and then performing main firing in the range of 150 to 350 ° C.

Filling the vias with the conductor paste can be performed by any method, for example, screen printing, dispenser filling, press injection, or the like.

By filling the via with a conductor paste, drying the via, and then firing the via, a conductor-filled substrate in which the conductor formed by the firing is filled in the hole can be manufactured.

Hereinafter, the present invention will be described with reference to Examples. Unless otherwise specified, "%" is based on mass.
(Synthesis Example 1)
<Synthesis of copper nanoparticles in which a polyethylene oxide structure-containing organic compound (A) (thioether type organic compound) having 8 to 200 carbon atoms is compounded>
Copper (II) acetate monohydrate (3.00 g, 15.0 mmol), ethyl 3- (3- (methoxy (polyethoxy) ethoxy) -2-hydroxypropylsulfanyl) propionate [polyethylene glycol methylglycidyl ether (polyethylene glycol chain) Addition compound of ethyl 3-mercaptopropionate to molecular weight 2000 (91 carbon atoms), the following formula] (0.451 g)

, And ethylene glycol (10 mL) were heated while blowing nitrogen at a flow rate of 50 mL / min, and degassed by aeration and stirring at 125 ° C. for 2 hours. The mixture was returned to room temperature and a solution of hydrazine hydrate (1.50 g, 30.0 mmol) diluted with 7 mL of water was slowly added dropwise using a syringe pump. About 1/4 of the amount was slowly added dropwise over 2 hours, the addition was stopped once, and the mixture was stirred for 2 hours to confirm that the foaming had subsided, and then the remaining amount was further added down over 1 hour. The temperature of the obtained brown solution was raised to 60 ° C., and the mixture was further stirred for 2 hours to terminate the reduction reaction.
<Preparation of aqueous dispersion>
Subsequently, this reaction mixture is circulated in a hollow fiber type ultrafiltration membrane module (HIT-1-FUS1582, 145 cm ² , fractional molecular weight 150,000) manufactured by Daisen Membrane Systems, Inc., and the same amount as the exuding filtrate. While adding a 0.1% aqueous solution of hydrazine hydrate, the mixture was circulated and purified until the filtrate from the ultrafiltration module became about 500 mL. When the supply of the 0.1% hydrazine hydrate aqueous solution was stopped and concentrated by the ultrafiltration method as it was, 2.85 g of the aqueous dispersion (a) of the complex of the thioether-containing organic compound (A) and the copper nanoparticles was obtained. Obtained. The non-volatile content in the aqueous dispersion (a) is 16%, and the weight loss by TG-DTA measurement (TG / DTA 6200 manufactured by SII Nanotechnology) shows that the obtained copper nanoparticles contain 3% polyethylene oxide structure. It was confirmed that organic matter was present.
<Preparation of conductive paste>
Each of the above 5 mL of the aqueous dispersion (a) is sealed in a 50 mL three-necked flask, and while heating to 40 ° C. using a water bath, nitrogen is flowed at a flow rate of 5 ml / min under reduced pressure to completely drain the water. To obtain 1.0 g of dry powder of copper nanoparticle composite. Next, 0.11 g of ethylene glycol nitrogen bubbling for 30 minutes was added to the obtained dry powder in a glove bag replaced with argon gas, and then mixed in a mortar for 10 minutes to obtain a copper nanoparticle paste having a non-volatile content of 90% ( a-1) was obtained.

(Test Example 1)
<Evaluation of volume shrinkage in filling copper nanoparticle paste (a-1) into a silicon mold having a width of 1.0 μm and 2.0 μm and a depth of 1.0 μm>
The copper nanoparticle paste (a-1) obtained in Synthesis Example 1 has a width of 1.0 μm and a depth of 1.0 μm (Example 1) and a width of 2.0 μm and a depth of 1.0 μm (Example 2). It was applied using a metal spatula on a silicon chip in which two types of grooves of L / S (line / space) = 1/1) were dug. Then, firing was carried out in a nitrogen atmosphere at 250 ° C. in a non-pressurized atmosphere. The firing was carried out at 43 ° C./min, the temperature was maintained at each temperature for 10 minutes, and then natural cooling was performed to obtain a silicon chip filler (filling test piece).

The filling test pieces of Examples 1 and 2 are cut and exposed by polishing the cut surface with a cross section polisher (SM-09020CP manufactured by JEOL Ltd.), and exposed by scanning electron microscope (JEOL Ltd.). The filling performance was evaluated by observing with FE-SEM (field emission scanning electron microscope) JSM-7100F).

As a result of the above filling performance evaluation, large voids were formed in the grooves on both the silicon chips of Example 1 (width 1.0 μm, depth 1.0 μm) and Example 2 (width 2.0 μm, depth 1.0 μm). It was confirmed that copper nanoparticles were packed at a high density. In the scanning electron microscope images shown in FIGS. 1 and 2, no cracks due to volume shrinkage or peeling from the wall surface of the concave structure of the chip were observed.

(Test Example 2)
<Volume shrinkage test of copper nanoparticle paste (a-1) by thin film observation device>
The volume shrinkage of the copper nanoparticle paste (a-1) before and after firing was 120 by preparing a coating film of the copper nanoparticle paste (a-1) on a glass slide having a width of 5 × 5 mm and a thickness of 10 μm using a squeegee. After heating at ° C. for 10 minutes to remove the organic solvent in the copper nanoparticle paste, the thickness of the dried film before firing and the film thickness at 150 ° C. (Example 3) and 200 ° C. (Example 3), respectively. The film thickness after firing at Example 4), 250 ° C. (Example 5), 300 ° C. (Example 6), and 350 ° C. (Example 7) was measured by a thin film observation device (laser microscope: VK-8700 (Co., Ltd.)). It was measured using (Keence)) and calculated from the following formula.

Volume shrinkage (%) = [(dry film thickness after firing-film thickness before firing) / film thickness before firing] x 100
From the above evaluation, the volume shrinkage rate in the state where the solvent is removed can be evaluated. The firing was carried out at 43 ° C./min, held for 10 minutes, and then naturally cooled.

The evaluation results of Examples 3 to 7 are shown below.

The dry film thickness before firing at a firing temperature of 150 ° C. (Example 3) was 8.96 μm, the film thickness after firing was 8.78 μm, and the volume shrinkage was 2.1%. The dry film thickness before firing at a firing temperature of 200 ° C. (Example 4) was 8.88 μm, the film thickness after firing was 8.60 μm, and the volume shrinkage was 3.2%. The dry film thickness before firing at a firing temperature of 250 ° C. (Example 5) was 9.12 μm, the film thickness after firing was 8.80 μm, and the volume shrinkage was 3.5%. The dry film thickness before firing at a firing temperature of 300 ° C. (Example 6) was 9.02 μm, the film thickness after firing was 8.67 μm, and the volume shrinkage was 3.9%. The pre-firing dry film thickness at a firing temperature of 350 ° C. (Example 7) was 8.91 μm, the post-firing film thickness was 8.50 μm, and the volume shrinkage was 4.6%. As a result of the evaluation, the volume shrinkage of the dried film of the copper nanoparticle paste (a-1) synthesized by using the polyethylene oxide structure-containing organic compound (A) as a dispersant was 5% or less even in the 350 ° C. firing. This indicates that the copper nanoparticle paste (a-1) is suitable as a filler for a fine space provided on a substrate such as a via or a trench that does not cause volume shrinkage.

(Test Example 3)
<Evaluation of volume shrinkage when copper nanoparticle paste (a-1) is filled in a silicon mold with a depth of 1 μm and a line width of 0.5 μm without excess>
The copper nanoparticle paste (a-1) obtained in Synthesis Example 1 was placed in a metal mold (L / S (line width / line spacing) = 1: 1) having a depth of 1 μm and a line width of 0.5 μm. The squeegee was filled with a spatula. Then, in order to remove the excess copper nanoparticle paste, a Kimwipe (Nippon Paper Crecia wiper S200) was used to wipe the silicon mold filled with the copper nanoparticle paste (a-1) several times. I paid. Then, it was calcined under a nitrogen atmosphere at 250 ° C. under no pressure. The firing was carried out at 43 ° C./min, held for 10 minutes, and then naturally cooled to obtain a copper nanoparticle-filled silicon mold (Example 8).

FIG. 3 shows the SEM observation result of the cross section obtained by cutting the obtained copper nanoparticle-filled silicon mold, polishing it with a cross section polisher, and then performing platinum sputtering treatment. As a result of the experiment, it was confirmed that no excess copper nanoparticles were found in the line portion of the silicon mold and all of them could be wiped off. In addition, no cracks were observed in the sintered body due to volume shrinkage, and no peeling from the concave wall surface of the mold was observed.

Next, the volume shrinkage of the copper nanoparticle paste in the silicon mold groove obtained in Example 8 was evaluated from the SEM image (FIG. 4). The volume shrinkage was calculated by the following formula from the ratio of the area (Ya) filled with copper nanoparticles in the total area (Xa) of the silicon mold groove.

Volume shrinkage rate (%) = (1-copper nanoparticle filling area (Ya) / total area (Xa)) × 100

As a result of the evaluation, (Ya) was 0.388 μm ² , (Xa) was 0.424 μm ² , and the volume shrinkage was as small as 8.5%. This indicates that the copper nanoparticle paste (a-1) synthesized by using the polyethylene oxide structure-containing organic compound (A) as a dispersant is suitable for filling a minute space of about 1 μm in practical use. ing.

(Comparative Synthesis Example 1)
<Synthesis of the complex of the octylamine low molecular weight dispersant _{(C 8 H 19 N) (} B) and copper nanoparticles>
5.6 g of copper nitrate, 9.2 g of octylamine as a protective agent, and 2.1 g of linoleic acid were added to 1 liter of trimethylpentane, and the mixture was stirred and mixed to dissolve. To this mixed solution, 1 liter of a propanol solution containing 0.01 mol / liter sodium borohydride was added dropwise over 1 hour to reduce copper. Further, the mixture was stirred for 3 hours to obtain a black liquid. The obtained black liquid was concentrated by an evaporator, and then 2 liters of methanol was added thereto to form a brown precipitate, and then the precipitate was collected by suction filtration. The resulting precipitate was redistributed in trimethylpentane, filtered and dried to give copper nanoparticles (b) as a black solid. When the obtained copper nanoparticles were observed with a transmission electron microscope (TEM), the primary particle size of the obtained copper nanoparticles was 6 nm. Next, by weight reduction by TG-DTA measurement, it was confirmed that 15% octylamine was present in the obtained copper nanoparticles.

Next, in a glove bag in which 1.0 g of the obtained dry powder of copper nanoparticles was replaced with argon gas, 0.11 g of terpineol (manufactured by Wako Pure Chemical Industries, Ltd.) bubbled with nitrogen for 30 minutes was added, and then mixed in a dairy pot for 10 minutes. A copper nanoparticle paste (b-1) having a non-volatile content of 90% was obtained.

(Comparative Test Example 1)
<Volume shrinkage test of copper nanoparticle paste (b-1) by thin film observation device>
A coating film was prepared on a glass slide in the same manner as in Test Example 1 except that the copper nanoparticle paste (b-1) obtained in Comparative Synthesis Example 1 was used, and heated at 120 ° C. for 10 minutes to obtain copper nanoparticles. After drying to remove the organic solvent in the particle paste (b-1), the thickness of the dried film before firing was measured at 150 ° C. (Comparative Example 1) and 200 ° C. (Comparative Example 2) for 10 minutes, respectively. The volume shrinkage after firing at 250 ° C. (Comparative Example 3), 300 ° C. (Comparative Example 4), and 350 ° C. (Comparative Example 5) was evaluated. The firing was carried out at 43 ° C./min, held for 10 minutes, and then naturally cooled.

The evaluation results of Comparative Examples 1 to 5 are shown below.

The dry film thickness before firing at a firing temperature of 150 ° C. (Comparative Example 1) was 8.12 μm, the film thickness after firing was 4.43 μm, and the volume shrinkage was 45.4%. The dry film thickness before firing at a firing temperature of 200 ° C. (Comparative Example 2) was 8.23 μm, the film thickness after firing was 3.87 μm, and the volume shrinkage was 53.0%. The dry film thickness before firing at a firing temperature of 250 ° C. (Comparative Example 3) was 8.01 μm, the film thickness after firing was 3.67 μm, and the volume shrinkage was 54.2%. The dry film thickness before firing at a firing temperature of 300 ° C. (Comparative Example 4) was 8.11 μm, the film thickness after firing was 3.54 μm, and the volume shrinkage was 56.4%. The dry film thickness before firing at a firing temperature of 350 ° C. (Comparative Example 5) was 8.19 μm, the film thickness after firing was 3.53 μm, and the volume shrinkage was 56.9%. As a result of the evaluation, the dried film of the copper nanoparticle paste (b-1) synthesized by using octylamine (B) as a dispersant showed a large volume shrinkage of 45% or more even when fired at 150 ° C. This indicates that since the boiling point of octylamine is as low as 176 ° C., octylamine is volatilized by firing and the dried film undergoes volume shrinkage.

(Comparative Test Example 2)
<Evaluation of volume shrinkage when copper nanoparticle paste (b-1) is filled in a silicon mold with a depth of 1 μm and a line width of 0.5 μm without excess>
A copper nanoparticle-filled silicon mold (Comparative Example 6) was obtained by the same method as in Test Example 3 except that the copper nanoparticle paste (b-1) obtained in Synthesis Example 2 was used. The calcination was carried out in a nitrogen atmosphere at 250 ° C. under no pressure. The firing was carried out at 43 ° C./min, held for 10 minutes, and then naturally cooled.

The SEM observation results are shown in FIG. Unlike Example 6 using the copper nanoparticle paste (a-1), a large volume shrinkage occurs. This is because the dispersant octylamine volatilized by firing.

Next, the volume shrinkage of the copper nanoparticle paste (b-1) in the silicon mold groove obtained in Comparative Example 6 was adjusted to the copper in the total area (Xb) of the silicon mold groove as in Test Example 3. It was determined from the ratio of the area (Yb) filled with nanoparticles (Fig. 6).

Volume shrinkage rate (%) = (1-copper nanoparticle filling area (Yb) / total area (Xb)) × 100

As a result of the evaluation, (Yb) was 0.127 μm ² , (Xb) was 0.503 μm ² , and the volume shrinkage was as large as 74.8%. This indicates that, in practical use, the copper nanoparticle paste (b-1) using a low molecular weight protective agent is not suitable for filling a microspace.

(Comparative Synthesis Example 2)
<Synthesis of a complex of polyvinylpyrrolidone (C), which is a polymer dispersant, and copper nanoparticles>
A 3000 mL glass four-necked flask was placed in the oil bath. While blowing nitrogen into it at a flow rate of 50 mL / min, 2500 mL of ammonia water with a concentration of 0.5 mol / L of copper hydroxide (Cu (OH) ₂ ) (manufactured by Wako Pure Chemical Industries, Ltd.) (10 g, 0.1 mol) was added. The pH was adjusted to 10 by further adding 0.5 mol / L ammonia acetate to prepare a solution containing a copper ammine complex. Next, 25 g of polyvinylpyrrolidone (molecular weight 10,000, manufactured by Wako Pure Chemical Industries, Ltd.) was added to this solution and dissolved by stirring, and then 5 g of hydrazine monohydrate (Wako Pure Chemical Industries, Ltd.) was added to reach 60 ° C. By heating and carrying out a reduction reaction for 2 hours, an aqueous dispersion of copper nanoparticles having a primary molecular weight of 69 nm was obtained.

Subsequently, this aqueous dispersion of copper nanoparticles is circulated in a hollow fiber type ultrafiltration membrane module (HIT-1-FUS1582, 145 cm ² , fractional molecular weight 150,000) manufactured by Daisen Membrane Systems Co., Ltd. and exuded. While adding the same amount of 0.1% hydrazine hydrate aqueous solution as the filtrate, the filtrate from the ultrafiltration module was circulated to about 6000 mL for purification. The supply of the 0.1% hydrazine hydrate aqueous solution was stopped and concentrated by the ultrafiltration method as it was to obtain 30 g of an aqueous dispersion of copper nanoparticles having a non-volatile content of 32.1%.

Subsequently, 30 g of the obtained aqueous dispersion of copper nanoparticles was sealed in a 100 mL three-mouthed flask, and while heating to 40 ° C. using a water bath, nitrogen was flowed at a flow rate of 5 ml / min under reduced pressure. By completely removing water, 9.2 g of a dry powder (c) of polyvinylpyrrolidone-coated copper nanoparticles was obtained. From the weight reduction by TG-DTA measurement, it was confirmed that 4.2% polyvinylpyrrolidone was present in the obtained copper nanoparticles.

Next, 1.0 g of ethylene glycol nitrogen-bubbled for 30 minutes was added to the obtained dry powder in a glove bag replaced with argon gas, and then mixed in a mortar for 10 minutes to obtain a copper nanoparticle paste having a non-volatile content of 90%. (C-1) was obtained.

(Comparative Test Example 3)
<Volume shrinkage test of copper nanoparticle paste (c-1) by thin film observation device>
A coating film was prepared on a glass slide in the same manner as in Test Example 1 except that the copper nanoparticle paste (c-1) obtained in Comparative Synthesis Example 2 was used, and heated at 120 ° C. for 10 minutes to obtain copper nanoparticles. After drying to remove the organic solvent in the particle paste (c-1), the thickness of the dried film before firing was measured at 150 ° C. (Comparative Example 7) and 200 ° C. (Comparative Example 8) for 10 minutes, respectively. The volume shrinkage after firing at 250 ° C. (Comparative Example 9), 300 ° C. (Comparative Example 10), and 350 ° C. (Comparative Example 11) was evaluated. The firing was carried out at 43 ° C./min, held for 10 minutes, and then naturally cooled.

The evaluation results of Comparative Examples 7 to 11 are shown below.

The dry film thickness before firing at a firing temperature of 150 ° C. (Comparative Example 7) was 8.67 μm, the film thickness after firing was 7.73 μm, and the volume shrinkage was 10.8%. The dry film thickness before firing at a firing temperature of 200 ° C. (Comparative Example 8) was 8.71 μm, the film thickness after firing was 7.65 μm, and the volume shrinkage was 12.2%. The dry film thickness before firing at a firing temperature of 250 ° C. (Comparative Example 9) was 8.60 μm, the film thickness after firing was 7.41 μm, and the volume shrinkage was 13.8%. The dry film thickness before firing at a firing temperature of 300 ° C. (Comparative Example 10) was 8.69 μm, the film thickness after firing was 7.4 μm, and the volume shrinkage was 14.9%. The pre-firing dry film thickness at a firing temperature of 350 ° C. (Comparative Example 11) was 8.66 μm, the post-firing film thickness was 7.21 μm, and the volume shrinkage was 16.7%. As a result of the evaluation, the dry film of the copper nanoparticle paste (c-1) synthesized by using polyvinylpyrrolidone (C) as a dispersant showed a volume shrinkage of 10% or more even at 150 ° C. firing, which is insufficient in practical use. It was a good performance.

After filling, the filling paste of the present invention utilizes the fact that the filling portion has a melting point close to that of bulk copper, heat dissipation, and electrical conductivity, and is particularly fine for pattern production on a semiconductor chip, electrode molding by paste press fitting, and the like. It can be suitably used for filling grooves or holes that have been subjected to various patterns. In addition, since the filling portion does not remelt even after repeated heating, secondary and tertiary mounting can be performed without restrictions on the reflow temperature, which can contribute to the expansion of the mounting procedure.

Claims (7)

A group consisting of metal nanoparticles (M) in which a polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms is compounded, an alcohol solvent having a boiling point of 150 ° C. or higher, an ether solvent, an ester solvent, and a lactam structure-containing solvent. A conductive paste containing at least one solvent (S) selected from the above.
The content of the polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms is 2 to 10% by mass.
The concentration of metal nanoparticles (M) is 50 to 95% by mass,
The particle size of the metal nanoparticles (M) is 1 to 100 nm, and
The volume shrinkage when the dry coating film of the conductive paste is fired at 350 ° C. is 5% or less.
A conductive paste used for filling vias or trenches, characterized in that. The polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms is
Compounds represented by the following general formula (1),
Compounds represented by the following general formula (2),
The compound represented by the following general formula (3), or having a structure represented by the following general formula (4) at at least one end and having a polyethylene oxide structure having 8 to 200 carbon atoms in the side chain (meth). Acrylic polymer (polymer α) and a phosphoric acid ester having a structure represented by the following general formula (4) at at least one end and represented by -OP (O) (OH) 2 in the side chain. The conductive paste according to claim 1, which is a compound containing a (meth) acrylic polymer (polymer β) having a residue.
W- (OCH2CH2) n-O-CH2-CH (OH) -CH2-SX (1)
[W- (OCH2CH2) n-O-CH2-CH (OH) -CH2-S-] dY (2)
[W- (OCH2CH2) n-O-CH2-CH (OH) -CH2-S-Ra-] tZ (3)
[W in the general formulas (1), (2) and (3) is an alkyl group of C1 to C8, n is an integer indicating the number of repetitions of 4 to 100, and X is an alkyl group of C2 to C12. , Allyl group, aryl group, arylalkyl group, -R1-OH, -R1-NHR2, or -R1- (COR3) m (where R1 is a saturated hydrocarbon group of C1-C4 and R2 is a hydrogen atom. An acyl group of C2 to C4, an alkoxycarbonyl group of C2 to C4, or a benzyloxycarbonyl group which may have an alkyl group of C1 to C4 or an alkoxy group of C1 to C8 as a substituent on the aromatic ring. R3 is a hydroxy group, an alkyl group of C1 to C4 or an alkoxy group of C1 to C8, and m is an integer of 1 to 3), and Y is a carbon atom that is directly bonded to a sulfur atom. ~ 4 valent groups, the saturated hydrocarbon group of C1 to C4 or the saturated hydrocarbon group of C1 to C4 is -O-, -S- or -NHRb- (Rb is a saturated hydrocarbon group of C1 to C4. There are 2 to 3 linked groups, d is an integer of 2 to 4, Ra is an alkylcarbonyloxy group of C2 to C5, and Z is a carbon atom that is directly bonded to the sulfur atom. A 2- to 6-valent group in which a C2-C6 saturated hydrocarbon group and a C2-C6 saturated hydrocarbon group are -O-, -S- or -NHRc- (Rc is a C1-C4 saturated hydrocarbon group). It is a group in which 2 to 3 are linked with (), or an isocyanuric acid-N, N', N "-triethylene group, and t is an integer of 2 to 6.]
RS- (4)
[In the general formula (4), R is a linear or branched alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a linear alkoxy group having 1 to 18 carbon atoms, and 1 to 18 carbon atoms. Branched alkoxy groups, aralkyloxy groups, substituted phenyloxy groups, linear alkylcarbonyloxy groups with 1 to 18 carbon atoms, branched alkylcarbonyloxy groups with 1 to 18 carbon atoms, carboxy groups, salts of carboxy groups, Linear alkoxycarbonyl group with 1 to 18 carbon atoms, branched alkoxycarbonyl group with 1 to 18 carbon atoms, phosphate group, linear alkyl phosphate group with 1 to 6 carbon atoms, 1 to 6 carbon atoms At least one functional group selected from the group consisting of a branched alkyl phosphate group, a sulfonic acid group, a linear alkyl sulfonic acid group having 1 to 6 carbon atoms, and a branched alkyl sulfonic acid group having 1 to 6 carbon atoms. Represents a linear or branched alkyl group having a group and having 1 to 8 carbon atoms. ] The polyethylene oxide structure-containing organic compound (A) having 8 to 200 carbon atoms according to claim 1 is
Compounds represented by the following general formula (1),
The conductive paste according to claim 1, which is a compound represented by the following general formula (2) or a compound represented by the following general formula (3).
W- (OCH2CH2) n-O-CH2-CH (OH) -CH2-SX (1)
[W- (OCH2CH2) n-O-CH2-CH (OH) -CH2-S-] dY (2)
[W- (OCH2CH2) n-O-CH2-CH (OH) -CH2-S-Ra-] tZ (3)
[W in the formulas (1), (2) and (3) is an alkyl group of C1 to C8, n is an integer indicating the number of repetitions of 4 to 100, and X is an alkyl group of C2 to C12. Allyl group, aryl group, arylalkyl group, -R1-OH, -R1-NHR2, or -R1- (COR3) m (where R1 is a saturated hydrocarbon group of C1-C4 and R2 is a hydrogen atom, C2. ~ C4 acyl group, C2 to C4 alkoxycarbonyl group, or benzyloxycarbonyl group which may have an alkyl group of C1 to C4 or an alkoxy group of C1 to C8 as a substituent on the aromatic ring, and is R3. Is a hydroxy group, an alkyl group of C1 to C4 or an alkoxy group of C1 to C8, and m is an integer of 1 to 3), and Y is a carbon atom that directly bonds to a sulfur atom. It is a tetravalent group, and the saturated hydrocarbon group of C1 to C4 or the saturated hydrocarbon group of C1 to C4 is -O-, -S- or -NHRb- (Rb is a saturated hydrocarbon group of C1 to C4. ) Is a group in which 2 to 3 are linked, d is an integer of 2 to 4, Ra is an alkylcarbonyloxy group of C2 to C5, and Z is a carbon atom that is directly bonded to a sulfur atom. It is a 2 to 6 valent group, and the saturated hydrocarbon group of C2 to C6 and the saturated hydrocarbon group of C2 to C6 are -O-, -S- or -NHRc- (Rc is a saturated hydrocarbon group of C1 to C4. There are 2 to 3 linked groups, or isocyanuric acid-N, N', N "-triethylene group, and t is an integer of 2 to 6.] The conductive paste according to claim 1, wherein the solvent (S) is at least one solvent selected from the group consisting of an alcohol solvent having a boiling point of 150 ° C. or higher and 350 ° C. or lower and an ether solvent. The conductive paste according to claim 1, wherein the metal nanoparticles (M) are silver nanoparticles, copper nanoparticles, silver-core copper-shell nanoparticles, or copper-core silver-shell nanoparticles. The conductive paste according to any one of claims 1 to 5 , wherein the conductive paste is for filling vias, the diameter of the via is 0.5 to 10 μm, and the depth is 0.5 to 10 μm. .. The conductive paste according to any one of claims 1 to 5 , wherein the conductive paste is for filling a trench, and the size of the trench is 0.5 to 10 μm in width and 0.5 to 10 μm in depth.

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