JP2007180172A - Manufacturing method of board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a board capable of restraining any undercut and of preventing any unetched portion from remaining. <P>SOLUTION: The manufacturing method of a board is one to manufacture a board having wiring consisting of copper or copper alloy. The wiring is formed by etching copper or copper alloy with a first etching solution not substantially containing a compound that forms coordinate bond with copper ion, and then by etching the copper or copper alloy with a second etching solution containing a compound that forms coordinate bond with copper ion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a substrate having a wiring made of copper or a copper alloy.

  In the production of a printed wiring board, when a copper wiring is formed by a photoetching method, an iron chloride etching solution, a copper chloride etching solution, an alkaline etching solution or the like is used as an etching solution. However, these etching solutions have a problem that copper under an etching resist called undercut dissolves. In particular, when the wiring pattern is fine, the undercut must be minimized.

Conventionally, an etching method capable of suppressing undercut has been studied. For example, Patent Document 1 below discloses an etching method using an etching solution containing cupric chloride, hydrochloric acid, a 2-aminobenzothiazol compound, polyethylene glycol, and a polyamine compound.
JP-A-6-57453

  However, in the etching method described in Patent Document 1, there is a possibility that suppression of undercut may be insufficient, and a portion where copper remains (hereinafter referred to as “unetched portion”) remains in a portion that is originally etched. there is a possibility. If an unetched portion remains, a short circuit may occur between the wirings.

  In order to solve the above-described conventional problems, the present invention provides a method for manufacturing a substrate that can suppress undercutting and prevent remaining unetched portions.

The method for producing a substrate of the present invention is a method for producing a substrate having a wiring made of copper or a copper alloy,
After etching copper or a copper alloy with a first etchant substantially free of a compound that forms a coordinate bond with copper ions, copper or copper with a second etchant containing a compound that forms a coordinate bond with copper ions The wiring is formed by etching an alloy.

  When the wiring pattern is formed using the substrate manufacturing method of the present invention, the undercut is few and the remaining of the unetched portion can be prevented, so that a fine and dense wiring pattern can be formed. Therefore, for example, when applied to the manufacture of a printed wiring board, it can be manufactured with a high yield.

  In the method for producing a substrate of the present invention, first, copper or a copper alloy is used in a first etching solution that does not substantially contain a compound that forms a coordinate bond with copper ions (hereinafter also referred to as “coordination bond-forming compound”). (Hereinafter, also simply referred to as “copper”) is etched. Next, copper is etched with a second etching solution containing a coordination bond forming compound to form a wiring. Since the coordination bond-forming compound forms a coordination bond with copper ions, it forms a hardly soluble film on the copper surface when copper is etched. Therefore, when the second etching solution is used, undercut can be suppressed. However, with only the second etching solution, there is a possibility that an unetched portion remains due to the film. Therefore, as described above, when copper is etched with the first etching solution that does not contain the coordination bond forming compound and then the copper is etched with the second etching solution that contains the coordination bond forming compound, the undercut is formed. In addition, the remaining of unetched portions can be prevented. Thereby, a fine and dense wiring pattern can be formed. The first etching solution may be an etching solution that does not substantially contain a coordination bond forming compound. If the film is not formed, a small amount (for example, 0.01 g / liter or less) of the coordinate bond is formed. Forming compounds may be included.

  As the first etching solution, for example, a solution containing an oxidizing metal ion source and at least one acid selected from inorganic acids and organic acids can be used. Examples of the oxidizing metal ion source include a cupric ion source such as a cupric salt and a ferric ion source such as a ferric salt. Specific examples of the cupric ion source include copper chloride, copper sulfate, copper bromide, organic acid copper salts, copper hydroxide, and the like. Specific examples of the ferric ion source include iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, and iron salts of organic acids. Among the oxidizing metal ion sources, it is preferable to use a cupric ion source from the viewpoint of etching rate stability. In particular, the use of copper chloride (cupric chloride) is preferable because the etching rate is increased.

  The concentration of the oxidizing metal ion source is, for example, 14 to 190 g / liter, preferably 33 to 140 g / liter in terms of metal ion concentration. If the concentration is too low, the etching rate decreases. On the other hand, when too high, it will become difficult to melt | dissolve and an etching rate will become unstable. When cupric chloride is used as the oxidizing metal ion source, the concentration of cupric chloride is, for example, 30 to 402 g / liter, preferably 70 to 296 g / liter.

  The concentration of at least one acid selected from the inorganic acids and organic acids is, for example, 7 to 180 g / liter, and preferably 18 to 110 g / liter. If the acid concentration is too low, a stable etching rate cannot be obtained. If the acid concentration is too high, the copper dissolution stability is lowered, or reoxidation occurs on the copper surface. Examples of the inorganic acid include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and the like. Examples of the organic acid include formic acid, acetic acid, oxalic acid, maleic acid, benzoic acid, glycolic acid and the like. Among the acids, hydrochloric acid is preferable from the viewpoints of etching rate stability and copper dissolution stability.

  As the second etching solution, for example, a solution containing an oxidizing metal ion source, at least one acid selected from inorganic acids and organic acids, and a coordination bond forming compound can be used. About the said oxidizing metal ion source and at least 1 acid chosen from the said inorganic acid and organic acid, the thing similar to a 1st etching liquid can be used.

  The coordination bond forming compound may be any compound that can form a hardly soluble film on the copper surface by forming a coordination bond with copper ions. For example, an azole compound, a nitrogen-containing polymer, or a compound having at least one group selected from an amino group, an imino group, a carboxyl group, a carbonyl group, and a hydroxyl group, and a sulfur atom, and having 7 or less carbon atoms (Hereinafter simply referred to as “sulfur-containing compound”).

  The azole compound is selected from the group consisting of diazole compounds, oxazole compounds, thiazole compounds, triazole compounds, oxadiazole compounds, thiadiazole compounds, tetrazole compounds, oxatriazole compounds, and thiatriazole compounds. However, it is not limited to these.

  Specific examples of the azole compound include oxazole, isoxazole, 5-t-butylisoxazole-3-carboxylic acid, thiazole, isothiazole, 2-amino-4-methyl-thiazole, 2-mercapto-2-thiazoline. , Imidazole, pyrazole, 1-methyl-2-mercaptoimidazole, 1- (β-hydroxyethyl) -2-methylimidazole, 2-aminobenzimidazole, 3-β-aminoethylpyrazole, triazole, 3-amino-1, 2,4-triazole, 4-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 3-amino-1,2,4-triazole-5-carboxylic acid, 1 , 2,3-benzotriazole, oxadiazole, 2,5-bis (4-aminopheny L) -1,3,4-oxadiazole, thiadiazole, 2- (N-nitro-N-methylamino) -1,3,4-thiadiazole, tetrazole, 5-aminotetrazole, 1- (β-aminoethyl) ) Tetrazole, 5-mercapto-1-phenyltetrazole, oxatriazole, thiatriazole, 5-amino-1,2,3,4-thiatriazole and the like.

  Among the azole compounds, an azole having only a nitrogen atom as a hetero atom in the ring is preferable. This is because the effect of suppressing undercut is improved, and the azole may be a monocyclic compound or a compound in which a ring is condensed. In particular, imidazole compounds, triazole compounds, and tetrazole compounds are preferable, and two or more of these azoles may be used in combination. Examples of the imidazole compound include alkyl imidazoles such as imidazole, 2-methylimidazole, 2-undecyl-4-methylimidazole, 2-phenylimidazole, benzimidazole, 2-methylbenzimidazole, 2-undecylbenzimidazole, Examples thereof include benzimidazoles such as 2-phenylbenzimidazole and 2-mercaptobenzimidazole. Of these, benzimidazole is preferred. Examples of the triazole compound include 1,2,3-triazole, 1,2,4-triazole, 5-phenyl-1,2,4-triazole, 5-amino1,2,4-triazole, benzotriazole, 1-methyl-benzotriazole, tolyltriazole and the like can be mentioned. Of these, benzotriazole is preferred. Examples of the tetrazole compounds include 1H-tetrazole, 5-amino-1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, 5-mercapto-1H-tetrazole, 1-phenyl-5 Examples include mercapto-1H-tetrazole, 1-cyclohexyl-5-mercapto-1H-tetrazole, and 5,5′-bis-1H-tetrazole. Among these, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole and 5-amino-1H-tetrazole are preferable, and 5-phenyl-1H-tetrazole and 5-amino-1H-tetrazole are particularly preferable.

  Specific examples of the sulfur-containing compound having an amino group include thiourea, thiourea dioxide, N-methylthiourea, 1,3-dimethylthiourea, and 1,3-diethylthiourea. Specific examples of the sulfur-containing compound having an imino group include ethylenethiourea. Specific examples of the sulfur-containing compound having a carboxyl group include thioglycolic acid, α-mercaptopropionic acid, 3-mercaptopropionic acid, 2,2′-thiodiglycolic acid, thiomalic acid, mercaptosuccinic acid, L- Examples include cysteine and L (-)-cystine. Specific examples of the sulfur-containing compound having a carbonyl group include 2-thiobarbituric acid. Specific examples of the sulfur-containing compound having a hydroxyl group include thioglycol.

  Examples of the nitrogen-containing polymer include polyethyleneimine, polyallylamine, polydiallylamine, polyamine sulfone, and polyacrylamide. Nitrogen-containing copolymers may also be used. Examples of the nitrogen-containing copolymer include a copolymer containing at least two selected from primary to tertiary amine, primary to tertiary amine salt, quaternary ammonium salt, acrylamide and sulfur dioxide in the monomer.

  The concentration of the coordination bond forming compound in the second etching solution is preferably 0.1 to 50 g / liter, more preferably 0.1 to 15 g / liter, and most preferably 0.2 to 10 g / liter. It is. If the concentration is too low, the undercut is not sufficiently suppressed, and if it is too high, the etching rate decreases.

  The first and second etching solutions include at least one selected from a cationic surfactant, glycol, and glycol ether in order to improve the stability of the solution, perform uniform etching, and make the surface shape after etching uniform. One may be included. Examples of the cationic surfactant include alkyl-type quaternary ammonium salts such as benzalkonium chloride and alkyltrimethylammonium chloride. Examples of the glycol include ethylene glycol, diethylene glycol, propylene glycol, and polyalkylene glycol. Examples of the glycol ether include propylene glycol monoethyl ether, ethylene glycol monobutyl ether, 3-methyl-3-methoxybutanol, dipropylene glycol methyl ether, diethylene glycol butyl ether and the like.

  For the first and second etching solutions, in order to improve the stability of the solution, perform etching without unevenness, and make the surface shape after etching uniform, methanol, ethanol, 1-propanol, 2-propanol, Alcohols such as butanol and benzyl alcohol, amides such as N, N-dimethylformamide, dimethylimidazolidinone and N-methylpyrrolidone, solvents such as sulfoxides such as dimethyl sulfoxide, fatty acid salts, alkyl sulfate esters, alkyl phosphorus Anionic surfactants such as acids, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, block polymers of polyoxyethylene and polyoxypropylene, lauryl dimethylamino acetate betaine, stearyl dimethylamino Acid betaine, lauryl dimethylamine oxide, betaine and lauryl hydroxy sulfobetaine, amphoteric surfactants such as amino acids, may be added various additives as necessary.

  The first and second etching solutions can be easily prepared by dissolving the above-described components in water. The water is preferably water from which ionic substances and impurities such as ion-exchanged water, pure water, and ultrapure water have been removed.

  The etching method at the time of etching using the 1st or 2nd etching liquid is not specifically limited. For example, a method of spraying the etching solution on a portion of the copper layer on the insulating material that is not covered with the etching resist, a method of applying the etching solution to the etching target in a liquid film, and an etching target in the etching solution And the like. Further, before the treatment with the etching solution, in order to improve the wettability of the etching solution, the copper surface may be previously wetted with water, low concentration hydrochloric acid or the like. Also, when using a cupric ion source as the oxidizing metal ion source, the cuprous ions generated in the treatment agent by copper etching are oxidized back to cupric ions to restore the etching ability. A gas such as air containing at least one of oxygen and ozone may be blown into the etching solution by bubbling or an oxidizing agent such as hydrogen peroxide may be added. Further, for example, the produced cuprous ions may be oxidized by means disclosed in Japanese Patent Application Laid-Open No. 7-243062, Japanese Patent No. 2684492, Japanese Patent No. 3220564, and the like. In addition, as for the temperature of the 1st and 2nd etching liquid when etching copper, both 20-50 degreeC is preferable. If the temperature is less than 20 ° C., the etching rate becomes too slow, and the undercut prevention effect may be reduced. On the other hand, when the temperature exceeds 50 ° C., the etching solution is concentrated, so that it may be difficult to maintain the etching performance.

  When etching copper by spraying using the 1st or 2nd etching liquid, it is preferable to carry out by the spray pressure of 0.05-0.3 MPa. If the spray pressure is less than 0.05 MPa, the etching rate becomes too slow, and the undercut prevention effect may be reduced. On the other hand, when the spray pressure exceeds 0.3 MPa, damage to the etching target becomes too large, and uniform etching may be difficult. For example, in order to improve the uniformity of etching, an air discharge nozzle or an air knife may be installed in the spray etching apparatus (see, for example, JP 2000-328267 A).

  In the case where copper is etched by immersing an object to be etched in the first or second etching solution, for example, the etching solution is jetted into a dipping tank for storing the etching solution in order to improve etching uniformity. A nozzle may be installed (for example, refer to Japanese Utility Model Laid-Open No. 2-136359).

  When the first and second etching solutions are repeatedly used, acid or water may be appropriately replenished so that the acid concentration and the copper ion concentration are constant. Further, in order to adjust the concentration of each component in the second etching solution, a replenishing solution may be appropriately added to the second etching solution. As a replenisher of the second etching solution, for example, at least one acid selected from inorganic acids and organic acids is 7 to 360 g / liter (preferably 30 to 360 g / liter), and a coordination bond forming compound is 0.1 to 0.1 g. A replenisher solution containing 50 g / liter (preferably 0.2 to 30 g / liter) can be exemplified.

  The substrate manufacturing method of the present invention is particularly useful for manufacturing a printed wiring board in which a copper wiring pattern is formed by etching. For example, an etching resist is formed on a copper foil, an electroless copper plating film, an electrolytic copper plating film, a copper sputtering film, a multilayer film thereof, etc. on an insulating substrate, and the copper not covered with the etching resist is etched. This is useful when forming a wiring pattern. At this time, the thickness of the copper layer is appropriately set according to the use of the printed wiring board, but when forming a fine wiring, the thickness of the copper layer is preferably 12 μm or less. Further, the thickness of the etching resist is preferably 40 μm or less, and more preferably 10 μm or less. If the thickness of the etching resist is too thick, the etching rate decreases. Examples of the printed wiring board include a rigid substrate, a flexible substrate, a metal core substrate, and a ceramic substrate. Examples of the etching resist include those made of a resin such as a dry film resist and a liquid resist, and those made of one or more layers of metals such as nickel and nickel / gold.

  When the thickness of the etching resist is thin, it is preferable to use an etching resist having high mechanical strength so that the etching resist is not damaged by a spray hitting force or the like when spraying the etching solution. Further, as the etching resist, it is preferable to use a resist having high adhesiveness with the copper to be etched. Moreover, in order to improve the adhesiveness with the etching resist, the copper coated with the etching resist is, for example, mechanical polishing by buff polishing, scrub polishing, or the like, an organic acid etching solution (for example, CZ-8100 manufactured by MEC Co., Ltd.). ) Or a persulfate-based etching solution or the like, and surface treatment is preferably performed by blackening treatment or the like. Thereby, peeling of the etching resist during the etching process can be prevented, and the shape of the formed wiring can be adjusted.

  When etching an object to be etched in which an etching resist is patterned on a copper layer using the substrate manufacturing method of the present invention, the ratio between the thickness (T) of the copper layer and the space (S) of the etching resist. (T / S) is preferably 0.5 to 1.6. It is because an undercut can be suppressed more easily. For example, when the thickness of the copper layer is 8 μm, the etching resist space is preferably 5 to 16 μm. The space of the etching resist refers to the interval between the lines in the pattern formed by the etching resist.

  The substrate manufacturing method of the present invention is particularly useful for manufacturing a substrate on which a semiconductor chip such as a CSP substrate, a TAB substrate, or a build-up substrate is directly mounted.

When the method for manufacturing a substrate of the present invention is used, undercutting is small and the remaining of an unetched portion can be prevented. For example, a copper wiring having an etching factor exceeding 3.4 can be formed with a high yield. Further, even when the copper layer is thick (for example, 18 μm or more), a copper wiring having a line pitch of 60 μm or less can be formed with a high yield. As a result, a printed wiring board having a fine and high-density wiring pattern can be manufactured with high yield. The etching factor is 2T / (W ₂ −W ₁ ) where the thickness (height) of the copper wiring is T, the width of the top of the copper wiring is W ₁ , and the width of the base of the copper wiring is W _2. The value calculated by.

  Next, an embodiment of a substrate manufacturing method of the present invention will be described with reference to the drawings. 1A to 1D to be referred to are cross-sectional views by process for explaining an embodiment of a method for producing a substrate of the present invention.

  First, as shown to FIG. 1A, the etching target object in which the copper layer 11 was formed on the electrically insulating base material 10 which consists of a polyimide film is prepared. Then, as shown in FIG. 1B, a portion constituting the wiring pattern on the copper layer 11 is covered with an etching resist 12. Examples of the method for forming the etching resist 12 include a method of bonding a dry film resist on the copper layer 11 and then patterning the dry film resist using a known photolithography method.

  Next, the copper layer 11a (see FIG. 1B) not covered with the etching resist 12 is etched with the first etching solution described above. In the etching with the first etching solution, for example, 20 to 85% by mass, preferably 35 to 53% by mass, of copper that must be finally removed by etching may be etched. Next, the remaining copper layer 11a is etched with the second etching solution described above, and the copper layer 11 is patterned as shown in FIG. 1C.

Subsequently, the etching resist 12 is stripped using, for example, a stripping solution such as an aqueous sodium hydroxide solution to obtain the wiring pattern 1 shown in FIG. 1D. According to this method, on which it can prevent remaining unetched portion, the difference in width of the base of the wire (W ₂₎ and the wiring of the top of the width (W ₁₎ and (W ₂ -W ₁₎ can be reduced.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, this invention is limited to a following example and is not interpreted.

  First, ferric chloride and hydrochloric acid are added to ion-exchanged water so that the respective concentrations are 400 g / liter and 30 g / liter (as hydrogen chloride), and the first etching solution used in Examples 1 to 9 is used. Prepared. Furthermore, the component shown in Table 1 was mixed and the 2nd etching liquid used for Examples 1-9 was prepared. On the other hand, a copper-clad laminate (substrate for printed wiring board) in which a copper foil with a thickness of 18 μm is pasted on a glass epoxy substrate (GEA-67N manufactured by Hitachi Chemical Co., Ltd.) is prepared, and the thickness is 25 μm on this copper foil. An electrolytic copper plating film was formed. Then, a 25 μm thick dry film resist (SUNFORT AQ-2536 made by Asahi Kasei) is pasted on this electrolytic copper plating film, and line and space = 50 μm / 50 μm (the line width is 50 μm, the gap between the lines) A line pattern of 50 μm) was formed.

  Next, copper was etched using the first etching solution under the conditions of a liquid temperature of 45 ° C. and a spray pressure of 0.25 MPa. Next, using the second etching solutions of Examples 1 to 9 shown in Table 1, copper was etched under the conditions of a liquid temperature of 50 ° C. and a spray pressure of 0.175 MPa, respectively, to form a copper wiring pattern. The etching time when using the first etching solution was 20 seconds. The etching time when using the second etching solution was set to the time shown in Table 1. Next, the dry film resist was peeled off by spraying a 3% by mass aqueous sodium hydroxide solution.

The obtained laminate is cut, the cross-sectional shape shown in FIG. 1D of the formed wiring pattern is observed, and the difference (W ₂ −W) between the base width (W ₂ ) and the top width (W ₁ ) of the copper wiring. ₁ ) measured. Further, as Comparative Example 1, copper was etched using the first etching solution under the conditions of a liquid temperature of 45 ° C., a spray pressure of 0.25 MPa, and an etching time of 50 seconds, and (W ₂ −W ₁ ) was measured in the same manner. did. The results are shown in Table 2.

As is clear from Table 2, the difference (W ₂ −W ₁ ) between the width (W ₂ ) and the width (W ₁ ) of the top portion of the copper wiring in Examples 1 to 9 is smaller than that of Comparative Example 1. It was confirmed that there was little undercut. Moreover, when the space between wiring in Examples 1-9 was observed with the optical microscope, the unetched location did not remain | survive. From the above results, according to the substrate manufacturing method of the present invention, a printed wiring board having a fine and dense wiring pattern can be manufactured with a high yield.

  The present invention can be applied to the manufacture of various substrates such as a glass substrate, a plastic substrate, and a semiconductor substrate in addition to the manufacture of a printed wiring board.

AD is sectional drawing according to process for demonstrating one Embodiment of the manufacturing method of the board | substrate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wiring pattern 10 Electrical insulating base material 11 Copper layer 12 Etching resist W ₁ Top width of copper wiring W ₂ Base width of copper wiring

Claims (7)

A method for manufacturing a substrate having a wiring made of copper or a copper alloy,
After etching copper or a copper alloy with a first etchant substantially free of a compound that forms a coordinate bond with copper ions, copper or copper with a second etchant containing a compound that forms a coordinate bond with copper ions A method of manufacturing a substrate, comprising etching the alloy to form the wiring.   The method for manufacturing a substrate according to claim 1, wherein the temperatures of the first and second etching solutions when etching copper or a copper alloy are both 20 to 50 ° C. 5.   3. The method of manufacturing a substrate according to claim 1, wherein when etching copper or a copper alloy, the first and second etching solutions are both sprayed at a spray pressure of 0.05 to 0.3 MPa.   The substrate manufacturing method according to claim 1, wherein the first etching solution is a solution containing cupric chloride or ferric chloride and at least one acid selected from an inorganic acid and an organic acid.   The second etching solution is a solution containing cupric chloride or ferric chloride, at least one acid selected from inorganic acids and organic acids, and a compound that forms a coordinate bond with the copper ions. Item 2. A method for manufacturing a substrate according to Item 1.   The substrate manufacturing method according to claim 1, wherein the second etching solution contains a compound that forms a coordination bond with the copper ions in a range of 0.1 to 50 g / liter.   The method for producing a substrate according to claim 1, wherein the compound that forms a coordinate bond with the copper ion is an azole having only a nitrogen atom as a hetero atom in the ring.

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