Method of forming seed pattern for plating and conductive film pattern

【0001】

[Technical field to which the invention belongs]

The present invention relates to a method for forming a seed pattern for plating and a conductive film pattern, and more particularly to a method for forming a fine seed pattern for plating on a substrate by an inkjet method and a method for forming a conductive film pattern on the seed pattern. This method can be used in the fields of electricity and electronics for forming electrodes of PDPs and LCDs, forming conductive circuits on printed circuit boards, forming light-shielding patterns, and the like.

【0002】

[Conventional technology]

In recent years, with the miniaturization of wiring, wiring formation by the inkjet (IJ) method has been attracting attention as a promising technology from the viewpoint of cost reduction and environmental protection measures.

【0003】

In the field where a thick film is required when forming wiring or the like composed of a conductive film pattern by the IJ method, a method of stacking films by repeating the number of IJ drawings is adopted in order to increase the film thickness. Rather than repeating drawing, plating to form a thick wiring film leads to cost reduction. Therefore, a method has been proposed in which a catalyst composed of fine particles of a noble metal such as Pd is precipitated on a substrate as a nucleus, and electroless plating is performed by the action of this catalyst to form a conductive film pattern (see, for example, Patent Document 1). ). In this case, the polysilane solution is discharged into a predetermined pattern using an IJ apparatus, the solvent is burned off to form a polysilane film pattern, and then the redox reaction between a noble metal salt such as Pd salt and polysilane is used to obtain this. A catalyst of noble metal fine particles is precipitated on the polysilane film pattern, and then a conductive film pattern is formed.

【0004】

[Patent Document 1]

Japanese Unexamined Patent Publication No. 2001-230527 (Claims, etc.) [0005]

[Problems to be Solved by the Invention]

However, in the method described in the prior art, polysilane remains between the substrate and the plating film, and even though polysilane has conductivity, the residual polysilane has the desired conductivity of the conductive film. There is a problem of adverse effects. Further, in order to apply the polysilane solution to IJ drawing, it is quite difficult to solve problems such as adjusting the viscosity of the solution and controlling the volatility of the solvent. Further, in this conventional technique, in order to form the catalyst which is the core of plating on the substrate, an extra step of having to perform polysilane which is not originally required by IJ drawing is required, and a part other than the pattern is required. A washing step is also required to remove the catalyst adhering to the plating. As described above, there is a problem that waste liquid treatment is involved because two steps of polysilane film formation and catalyst precipitation are required before forming the conductive film and a cleaning step is also required. Furthermore, in this conventional technique, a Pd salt or the like is used for precipitation of the catalyst, but since this Pd salt is strongly alkaline, there is a risk of damaging the nozzle head of the IJ apparatus.

【0006】

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a method for forming a seed pattern for plating and a method for forming a conductive film pattern, which do not require a polysilane pattern forming step.

【0007】

[Means for solving problems]

The present inventors have a dispersion liquid in which ultrafine metal particles are dispersed independently, that is, a metal in which ultrafine particles do not aggregate, fluidity is maintained, and ink properties for inkjet are excellent. We have found that the above-mentioned problems of the prior art can be solved by an inkjet method using nano-ink, which is an ultrafine particle independent dispersion, and have completed the present invention.

【0008】

The seed pattern forming method for plating of the present invention uses nanoinks (hereinafter, also referred to as metal ultrafine particle independent dispersions) containing ultrafine metal particles selected from Cu, Ag, Au and Pd, a dispersant and an organic solvent. The seed line is drawn directly on the substrate by the inkjet method, and the dispersant and the solvent are evaporated by heating to form a seed pattern for plating. Since polysilane is not used, a high-purity plating seed pattern can be formed by a simple method without requiring a cleaning step and a waste liquid treatment step.

【0009】

The viscosity of the nano ink is preferably 3 to 20 cps. If the viscosity of the nano ink exceeds 20 cps, it is difficult to secure the adhesion to the substrate, and if the viscosity of the nano ink is less than 3 cps, the drawn line width will widen. The pattern cannot be formed. The nano-ink contains 0.1 to 15 wt%, preferably 0.1 to 10 wt% of ultrafine metal particles. If it is out of the range of 0.1 to 15 wt%, it is difficult to secure the adhesion with the substrate. In the case of the present invention, since an organic solvent is used as the solvent for the nanoink, the viscosity and concentration can be freely adjusted. To reduce the ultrafine particle content (concentration) and viscosity of the metal, the solvent itself may be used for diluting, and for thickening, a highly viscous solvent such as α-terpineol may be mixed. The viscosity can be adjusted.

【0010】

It is preferable to use a substrate whose surface has been roughened in advance in order to achieve close contact between the substrate and the plating film. In this case, if the surface roughness is too large, the fineness of the pattern of the plating film is hindered, and if the surface roughness is insufficient, the adhesion between the plating film and the substrate cannot be ensured. The optimum value of roughness is Rmax = 20 to 500 nm. This roughening treatment method may be a chemical etching method, a liquid honing method, a sandblasting method, or the like.

【0011】

When drawing in the seed pattern forming method for plating of the present invention, it is preferable to maintain the temperature of the substrate at 60 to 100 ° C. In the formation of a fine seed pattern, there is a method of hydrophobizing the substrate surface, but depending on the degree of surface roughness, the drawing line width may not be controlled only by the hydrophobizing treatment. In such a case, it is effective to heat the substrate to a predetermined temperature and perform drawing while maintaining that temperature. Outside this temperature range, the desired drawing line width cannot be achieved. For example, the line width of the pattern obtained by drawing while maintaining the substrate temperature at 100 ° C is 1/5 to 1/14 of the line width obtained by drawing while maintaining the room temperature.

【0012】

The conductive film pattern forming method of the present invention is characterized in that a seed pattern for plating is formed by the above method, and then a conductive film pattern is formed on the seed pattern by electroless plating. Thus, the photolithography step becomes unnecessary, the number of steps can be reduced, and a conductive film pattern having a desired line width and good conductivity can be provided. In addition, high adhesion of this conductive film pattern to the substrate to be processed can be achieved.

【0013】

BEST MODE FOR CARRYING OUT THE INVENTION

In the nano ink, which is an independent dispersion of metal ultrafine particles used in the present invention, ultrafine metal particles selected from Cu, Ag, Au and Pd are individually and uniformly dispersed independently and uniformly, and the fluidity is maintained. It is useful as an inkjet ink for forming a seed pattern.

【0014】

The metal ultrafine particles can be produced, for example, by an evaporation method in a low vacuum gas, and according to this production method, metal ultrafine particles having a particle size of 100 nm or less, preferably 10 nm or less can be produced. .. In order to make such ultrafine metal particles suitable for use as ink for inkjet printers, solvent replacement is performed in the final step (third step) as described below, and this In order to increase the dispersion stability of the ultrafine particles, a dispersant is added in a predetermined step. For this reason, the ultrafine metal particles are individually and uniformly dispersed, and the fluid state is maintained, so that a nanoink suitable for the inkjet method can be obtained.

【0015】

In the case of inkjet ink, in order to realize ink supply stability, ink droplet formation flight stability, high-speed responsiveness of the printer head, etc., at the temperature (0 to 50 ° C) during normal operation, It is required to have a predetermined viscosity and surface tension. The nanoink used in the method of the present invention satisfies this ink characteristic.

【0016】

When the desired metal ultrafine particle independent dispersion is produced using the metal ultrafine particles obtained by the low vacuum gas evaporation method as the nanoink used in the method of the present invention, first, in the first step, in a vacuum chamber. When the metal is evaporated in an atmosphere where the pressure of the inert gas such as He is 10 Torr or less and the vapor of the evaporated metal is cooled and collected, one or more kinds of first solvents are put in the vacuum chamber. When the steam is introduced and the surface of the metal is brought into contact with the first solvent vapor at the stage of grain growth, the obtained primary particles are independently and uniformly dispersed in the first solvent in a colloidal form, and then the dispersion is obtained. The first solvent is removed in the second step of. The reason for removing the first solvent in this way is to remove by-products generated by denaturing the coexisting first solvent when the metal vapor evaporated in the first step condenses. Further, in order to produce such a dispersion liquid when it is necessary to use a metal ultrafine particle independent dispersion liquid dispersed in a low boiling point solvent, water, an alcohol solvent, etc., which is difficult to use in the first step, depending on the application of the ink. But also.

【0017】

In the second step, a second solvent, which is a low molecular weight polar solvent, is added to the dispersion obtained in the first step to precipitate the ultrafine metal particles contained in the dispersion, and the supernatant is allowed to stand. The first solvent used in the first step is removed by removing it by decantation or the like. This second step is repeated a plurality of times to substantially remove the first solvent. Then, in the third step, a new third solvent is added to the sediment obtained in the second step to perform solvent substitution to obtain the desired metal ultrafine particle independent dispersion. As a result, a metal ultrafine particle independent dispersion liquid in which metal ultrafine particles having a particle size of 100 nm or less are dispersed in an independent state can be obtained. In the above case, the dispersant can be added in the first step and / or the third step, if necessary. When added in the third step, a dispersant that does not dissolve in the solvent used in the first step can also be used.

【0018】

The dispersant that can be used in the above production method is not particularly limited, and one or more selected from alkylamines, carboxylic acid amides, and aminocarboxylic acid salts are used. In particular, the alkylamine may be a primary to tertiary amine, a monoamine, a diamine, or a triamine. An alkylamine having 4 to 20 carbon atoms in the main chain is preferable, and an alkylamine having 8 to 18 carbon atoms in the main chain is more preferable from the viewpoint of stability and handleability. If the carbon number of the main chain of the alkylamine is shorter than 4, the basicity of the amine is too strong and there is a tendency to corrode the metal ultrafine particles, and there is a problem that the metal ultrafine particles are finally dissolved. Further, when the carbon number of the main chain of the alkylamine is longer than 20, when the concentration of the metal ultrafine particle independent dispersion is increased, the viscosity of the dispersion increases and the handleability becomes slightly inferior. There is a problem that carbon tends to remain in the metal film after firing and the specific resistance value increases. Further, all series of alkylamines work effectively as dispersants, but primary alkylamines are preferably used from the viewpoint of stability and handleability.

【0019】

Specific examples of the above alkylamines include primary amines such as butylamine, octylamine, dodecylamine, hexadodecylamine, octadecylamine, cocoamine, tallowamine, hydride tallowamine, oleylamine, laurylamine, and stearylamine. , Secondary amines such as dicocoamine, dihydrogenated taroamine, and distearylamine, as well as dodecyldimethylamine, didodecylmonomethylamine, tetradecyldimethylamine, octadecyldimethylamine, cocodimethylamine, dodecyltetradecyldimethylamine, And tertiary amines such as trioctylamine and others, and other diamines such as naphthalenediamine, stearylpropylenediamine, octamethylenediamine, and nonanediamine.

【0020】

Specific examples of the carboxylic acid amide and aminocarboxylic acid salt include stearic acid amide, palmitate amide, lauric acid lauryl amide, oleic acid amide, oleic acid diethanolamide, oleic acid lauryl amide, stearanilide, and oleylaminoethylglycine. And so on. One or more of these alkylamines, carboxylic acid amides, and aminocarboxylic acid salts can be used, thereby acting as a stable dispersant. The content of the alkylamine is usually in the range of about 0.1 to 10% by weight, preferably 0.2 to 7% by weight, based on the weight of the ultrafine metal particles. If the content is less than 0.1% by weight, the metal ultrafine particles do not disperse independently, and agglomerates thereof are generated, resulting in poor dispersion stability. If the content exceeds 10% by weight, there is a problem. There is a problem that the viscosity of the obtained dispersion becomes high and a gel-like substance is finally formed.

【0021】

Regarding the above solvent, it is necessary to select a polar solvent such as water or alcohol or a non-polar hydrocarbon solvent according to the properties of the substrate to be treated such as a glass substrate, a plastic substrate, or a ceramic substrate. In addition, the solvent selection conditions may be determined depending on the use of the obtained film. For example, the first solvent is a solvent for producing metal ultrafine particles used in the vaporization method in gas, and is a solvent having a relatively high boiling point so that the metal ultrafine particles can be easily liquefied when they are cooled and collected. is there. The first solvent includes alcohols having 5 or more carbon atoms, for example, a solvent containing at least one selected from terpineol, citroneol, geraniol, phenethyl alcohol and the like, or organic esters such as benzyl acetate and stearer. Any solvent containing at least one selected from ethyl acid, methyl oleate, ethyl phenylacetate, glyceride and the like may be used, and it can be appropriately selected depending on the constituent elements of the metal ultrafine particles to be used or the use of the dispersion.

【0022】

The second solvent may be any solvent as long as it can precipitate the metal ultrafine particles contained in the dispersion obtained in the first step and extract / separate and remove the first solvent. For example, a low molecular weight polar solvent. There is acetone and the like. As the third solvent, a non-polar hydrocarbon having 6 to 20 carbon atoms in the main chain, water, alcohol having 15 or less carbon atoms, or the like, which is liquid at room temperature, can be appropriately selected and used. In the case of non-polar hydrocarbons, if the number of carbon atoms is less than 6, it dries too quickly and there is a problem in handling the dispersion liquid, and if the number of carbon atoms exceeds 20, the viscosity of the dispersion liquid tends to increase. Further, there is a problem that carbon tends to remain in the case of firing. In the case of alcohol as well, there is a problem that the viscosity of the dispersion tends to increase when the number of carbon atoms exceeds 15, and carbon tends to remain when firing.

【0023】

Examples of the third solvent include long-chain alkanes such as hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, nonadecan, eikosan, and trimethylpentane, and cyclohexane and cycloheptane. Cyclic alkanes such as cyclooctane, aromatic hydrocarbons such as benzene, toluene, xylene, trimethylbenzene and dodecylbenzene, and alcohols such as hexanol, heptanol, octanol, decanol, cyclohexanol and terpineol can be used. These solvents may be used alone or in the form of mixed solvents. For example, it may be a mineral spirit that is a mixture of long-chain alkanes.

【0024】

In the case of the third solvent, it may be necessary to use a solvent different from that used in the first step (solvents having different purity even if they are the same), and the present invention is suitable for such cases. is there. The amount of the solvent used may be appropriately set according to the use of the metal ultrafine particle independent dispersion liquid. The concentration of ultrafine metal particles can be adjusted at any time by heating in vacuum after the dispersion liquid is produced. Further, in the present invention, when a dispersion is produced using metal ultrafine particles obtained by a chemical reduction method such as a liquid phase reduction method, for example, bishexafluoroacetyl is used as a raw material for producing the metal ultrafine particles. It is also possible to use a reducing raw material which is a metal-containing organic compound such as acetonate copper, bisacetylacetonate nickel, and bisacetylacetonate cobalt.

【0025】

The reduction method is performed, for example, as follows. With the dispersant added to the raw material, the raw material is thermally decomposed at a predetermined temperature to generate ultrafine metal particles. Almost all of the generated metal ultrafine particles are recovered in an independently dispersed state. The particle size of these ultrafine metal particles is about 100 nm or less. By substituting the metal ultrafine particles with a third solvent which is a solvent for producing dispersed metal ultrafine particles as described above, the desired metal ultrafine particle independent dispersion can be obtained. The obtained dispersion liquid maintains a stable dispersion state even when concentrated by heating in vacuum.

【0026】

In order to improve the adhesion of the metal film, which is the seed pattern for plating, a metal-containing organic compound (metal-containing organic compound) such as an organic silicon compound or an organic manganese compound is added to the above metal ultrafine particle independent dispersion liquid. You may. As the organosilicon compound, if it is soluble in a non-polar hydrocarbon or the like which is a liquid main solvent (third solvent) at room temperature and has a decomposition temperature of about 150 to 250 ° C, it can be appropriately used. For example, diphenylsilane, tetraallylsilane, decamethyltetrasiloxane and the like can be used. The amount of silicon added may be about 0.5 wt% to 10 wt% with respect to the weight of ultrafine particles of metal (for example, copper). If it is less than 0.5 wt%, the adhesiveness will not be improved, and if the amount added is larger, the adhesiveness will be improved. However, if it exceeds about 10 wt%, the resistance value of the film will increase and plating will occur. become worse. Further, as the organic manganese compound, for example, manganese octanate, manganese naphthenate, manganese linoleate and the like can be used. As the addition amount, 0.5 to 10 wt% can be used as the weight of manganese with respect to the weight of the metal (copper) ultrafine particles. If it is less than 0.5 wt%, the adhesion will not be improved, and if it exceeds 10 wt%, the resistance value of the film will increase and the plating will worsen.

【0027】

In addition to the above organic silicon compounds and organic manganese compounds, metal-containing organic compounds effective for ensuring adhesion include, for example, silicon, manganese, chromium, nickel, titanium, magnesium, aluminum, germanium, tantalum, niobium and vanadium. There is a fatty acid salt which is an organic compound containing at least one metal selected from the above. Among the fatty acid salts of these metals, those having a low decomposition temperature (about 300 ° C or less) are effective. For example, as a compound containing magnesium and aluminum, (C₁₇H₃₅COO)₂Mg, (C₁₇H₃₅COO)₃You can give Al.

【0028】

According to the present invention, apart from the method using the metal ultrafine particle independent dispersion liquid to which the metal-containing organic compound is added, the dispersion liquid containing only the metal-containing organic compound is used directly on the insulating substrate by the inkjet method. After forming a base conductive film pattern on the surface and firing it, a nanoink composed of the above-mentioned metal ultrafine particle independent dispersion liquid to which a metal-containing organic compound may be added may be used, and this base electroless conductive pattern is directly applied by an inkjet method. A method of forming a seed line on the seed line and then heating to evaporate the dispersant and the solvent in the ink to form a seed pattern, and then forming a conductive film pattern by electroless plating on the seed pattern is also a treatment. It is useful for ensuring the adhesion between the substrate and the conductive film pattern. For example, a manganate octanate solution (solvent: tetradecane) is first inkjet-coated on a substrate to be treated, and the solution is calcined in the air under the conditions of, for example, 230 ° C. Get a film. On this film, an independent dispersion of metal ultrafine particles is inkjet-coated under the same conditions as above, and this is heated to evaporate the dispersant and solvent, and then electroless plating is performed. The specific resistance value of the obtained conductive film pattern is about 2 μmΩ · cm, and the adhesion and film quality are good.

【0029】

[Example]

Hereinafter, examples and comparative examples of the present invention will be described. (Example 1) Using a glass substrate, a Cu seed pattern was formed as follows. Α-Terpineol was mixed with Cu nano ink dispersed in a tetradecane solvent to adjust the viscosity to 5 cps and the concentration to 5 wt%. Using an inkjet device, this nanoink is ejected onto a glass substrate heated to 100 ° C to form a seed line, the solvent and dispersant are removed at 250 ° C, and a linear Cu seed pattern with a width of 50 μm is formed. Formed. Then, the glass substrate on which the seed pattern was formed was immersed in a Cu electroless plating bath (composition: a known plating bath containing copper sulfate as a main component) for 30 minutes. As a result, a Cu thin film having a film thickness of about 5 μm was formed on the Cu seed pattern, and a conductive film pattern could be obtained. The resistivity of the film was 2.7 μmΩ · cm, and when a tape test was performed on the adhesion, no peeling of the Cu film was observed from the substrate.

【0030】

When the substrate heating temperature was set to 60 ° C, the concentration of Cu fine particles was set to 10 wt%, the viscosity was set to 20 cps, and the surface roughened state of the substrate was set to Rmax = 70 nm, the above operation was repeated. Similar results were obtained.

【0031】

(Comparative Example 1) The method described in Example 1 was repeated. However, without heating the substrate, Cu nanoink was ejected onto the substrate at room temperature to form a seed line, and the solvent and dispersant were removed at 250 ° C. The line width of the formed linear Cu seed pattern was 700 μm, and the seed pattern could not be refined.

【0032】

(Comparative Example 2) The method described in Example 1 was repeated. However, a seed pattern was formed using 20 wt% Cu nanoink instead of 5 wt% Cu nanoink, and electroless plating was performed in the same manner as in Example 1. In this case, the precipitation speed of Cu at the initial stage of plating was increased, but as a result of a tape test performed on the obtained conductive film pattern, peeling occurred between the substrate and the Cu film. Further, when the roughened state of the substrate surface was set to Rmax = 5 nm and the operation of Example 1 was repeated, peeling occurred between the substrate and the Cu film.

【0033】

[Effect of the invention]

According to the seed pattern forming method of the present invention, a high-purity plating seed pattern can be formed by a simple method without using polysilane and thus not requiring a washing / waste liquid treatment step. By using nanoinks in a specific viscosity / concentration range, it is possible to secure conductivity and excellent adhesion to the substrate. If the surface of the substrate to be processed is roughened in advance to a predetermined degree, the substrate and the plating film can be effectively adhered to each other and the pattern can be refined. Further, since the drawing is performed while maintaining the temperature of the substrate at 60 to 100 ° C during drawing, a satisfactory line width can be achieved even when the drawing line width cannot be controlled by the degree of surface roughness. Further, according to the conductive film pattern forming method of the present invention, since the conductive film pattern is formed on the above-mentioned seed pattern for plating by electroless plating treatment, the photolithography step becomes unnecessary, the steps can be reduced, and the steps can be reduced. A conductive film pattern having a desired line width and good conductivity can be provided, and high adhesion of the conductive film pattern to the substrate to be processed can be achieved.