JP2015178656A - Copper etchant and method of producing circuit wiring board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper etchant which can sufficiently inhibit the undercut phenomenon and a method of producing a circuit wiring board using the same.SOLUTION: A copper etchant comprises metal chloride comprising iron chloride and/or copper chloride, and acid, and also comprises metal salt of polyoxyalkylene alkyl ether sulfate.

Description

  The present invention relates to a copper etching solution and a circuit wiring board manufacturing method using the same.

  For electronic devices, circuit wiring boards in which circuit wiring containing copper is formed on the surface of the board are widely used. As one method for forming circuit wiring on the surface of a substrate, wet etching is known in which a metal layer provided on a substrate is etched using an etchant. In such wet etching, after a metal layer containing copper is formed on a substrate, a resist layer having an opening pattern formed so as to expose a part of the metal layer is formed on the metal layer. . Then, the exposed portion of the metal layer is etched by spraying an etching solution in the thickness direction of the metal layer, and a recess is formed in the metal layer as the etching of the exposed portion proceeds. The bottom and side parts appear. At this time, etching is promoted because the etching solution is strongly applied to the bottom. On the other hand, since it is difficult for the etching solution to hit the side portion, etching is suppressed on the surface of the side portion. As a result, it is considered that a phenomenon called undercut in which the line width becomes narrower from the bottom portion toward the top portion in the obtained circuit wiring can be suppressed. This undercut phenomenon leads to a serious problem such that the circuit wiring becomes denser and the wire width becomes narrower, causing disconnection or short circuit.

  Various etching solutions have been proposed so far. For example, Patent Document 1 below includes one or more salts containing metal ions selected from ferric ions and cupric ions, mineral acids and / or organic acids, sulfonium compounds, and surfactants. A copper etchant containing is disclosed.

JP 2008-14428 A

  However, the copper etching solution described in Patent Document 1 has the following problems.

  That is, the copper etchant cannot be said to have a sufficient etching suppression effect on the side portions. That is, the copper etching solution has room for improvement in terms of sufficiently suppressing the undercut phenomenon in the obtained circuit wiring.

  This invention is made | formed in view of the said situation, and it aims at providing the manufacturing method of a circuit wiring board using the copper etching liquid which can fully suppress an undercut phenomenon, and this.

  As a result of intensive studies to solve the above problems, the present inventor effectively solved the above problems by adding a metal salt of polyoxyalkylene alkyl ether sulfate, which is an anionic surfactant, to the etching solution as a surfactant. As a result, the present invention has been completed.

  That is, the present invention is a copper etching solution containing a metal chloride composed of iron chloride and / or copper chloride and an acid, and a copper etching solution containing a metal salt of polyoxyalkylene alkyl ether sulfate.

According to this copper etchant, the following effects are achieved when manufacturing a circuit wiring board.
That is, in manufacturing a circuit wiring board, after a metal layer containing copper is formed on the substrate, a resist layer having an opening pattern formed on the metal layer so as to expose a part of the metal layer is formed. Formed to obtain the structure. And when the copper etching liquid mentioned above is supplied toward the thickness direction of the metal layer in this structure, the exposed part among the metal layers of this structure will be etched. Then, with the progress of the etching of the surface, a concave portion is formed in the metal layer, and the bottom portion and the side portion appear. At this time, in the vicinity of the bottom surface, the convection velocity of the copper etching solution is increased, so that etching of the bottom surface is promoted. On the other hand, in the vicinity of the surface of the side portion, the convection speed of the copper etching solution is low, and thus etching is sufficiently suppressed. When the circuit wiring board is obtained in this way, the reduction in the width of the top portion in the circuit wiring is sufficiently suppressed, and as a result, the undercut phenomenon can be sufficiently suppressed.

The inventor presumes the reason why the above effect is obtained by the copper etching solution of the present invention as follows.
That is, the bottom surface near the recess which appears in the process of etching the metal layer, each other and CuCl ₃ ^2-ions are deposited on the surface of the copper in the etching reaction, and the negative ions constituting the acid rebound, CuCl ₃ ^2- Ions are diffused and etching proceeds faster. On the other hand, in the vicinity of the surface of the side portion, the convection velocity of the copper etching solution is reduced, so that oxygen atoms of the metal salt of polyoxyalkylene alkyl ether sulfate are adsorbed on Cu. As a result, etching is sufficiently suppressed. Thus, according to the copper etching solution of the present invention, the inventor presumes that the undercut phenomenon can be sufficiently suppressed.

  The copper etching solution is 0.1 to 50% by mass of the metal chloride, 0.1 to 50% by mass of the acid, and 0.03 to 4.5% by mass of the metal salt of the polyoxyalkylene alkyl ether sulfate. It is preferable to contain.

  In this case, the undercut phenomenon can be more effectively suppressed as compared with the case where any of the metal chloride content, acid content, and polyoxyalkylene alkyl ether sulfate metal salt content is outside the above range. .

  In the copper etching solution, the metal salt of the polyoxyalkylene alkyl ether sulfate is preferably polyoxyethylene lauryl ether sulfate Na (hereinafter referred to as “laureth sulfate Na”).

  In this case, the undercut phenomenon can be particularly effectively suppressed.

  In the said copper etching liquid, it is preferable that the said acid contains hydrochloric acid.

In this case, the ratio of chloride ions that react with copper deposited on the surface by the etching reaction to form CuCl ₃ ²⁻ ions in the copper etching solution in the vicinity of the bottom surface of the recess that appears in the process of etching the metal layer. The amount of CuCl ₃ ²⁻ ions to be diffused can be increased. For this reason, the etching with respect to the bottom part surface of a recessed part can advance faster.

  According to another aspect of the present invention, there is provided a circuit wiring board manufacturing method for manufacturing a circuit wiring board by forming circuit wiring on the board, wherein the metal layer containing copper and the metal layer are exposed on the board. A structure preparation step for preparing a structure obtained by sequentially forming a resist layer having an opening pattern formed thereon, and an exposed portion of the metal layer of the structure prepared in the structure preparation step. An etching step of forming the circuit wiring on the substrate by forming a recess in the metal layer by etching using the above-described copper etching solution, and in the etching step, the copper etching solution is the metal It is a manufacturing method of a circuit wiring board supplied toward the thickness direction of a layer.

  According to this manufacturing method, after a metal layer containing copper is formed on a substrate, a resist layer having an opening pattern formed so as to expose a part of the metal layer is formed on the metal layer. A structure is obtained. And when the copper etching liquid mentioned above is supplied toward the thickness direction of a metal layer, the part exposed among the metal layers of this structure will be etched. Then, with the progress of the etching of the surface, a concave portion is formed in the metal layer, and the bottom portion and the side portion appear. At this time, in the vicinity of the bottom surface, the convection velocity of the copper etching solution is increased, so that etching of the bottom surface is promoted. On the other hand, in the vicinity of the surface of the side portion, the convection speed of the copper etching solution is low, and thus etching is sufficiently suppressed. When the circuit wiring board is obtained in this way, the reduction in the width of the top portion in the circuit wiring is sufficiently suppressed, and as a result, the undercut phenomenon can be sufficiently suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the copper etching liquid which can fully suppress an undercut phenomenon, and the manufacturing method of a circuit wiring board using the same are provided.

It is a partial cut surface end view which shows an example of the circuit board obtained by the manufacturing method of the circuit wiring board of this invention. It is a partial cut surface end view which shows the structure used with the manufacturing method of the circuit wiring board of this invention. FIG. 3 is a partial cross-sectional end view showing a state where the structure of FIG. 2 is etched using a copper etchant.

  Hereinafter, the manufacturing method of the circuit wiring board of this invention is demonstrated.

  First, a circuit wiring board obtained by the method for manufacturing a circuit wiring board of the present invention will be described with reference to FIG. FIG. 1 is a partially cut end view showing an example of a circuit board obtained by the method for manufacturing a circuit wiring board of the present invention.

  As shown in FIG. 1, the circuit wiring board 100 includes a substrate 1 and circuit wiring 2 provided on the surface of the substrate 1.

  Next, a method for manufacturing the circuit wiring board 100 described above will be described with reference to FIGS. 2 is an end view of a partially cut surface showing a structure used in a method for manufacturing a circuit wiring board, and FIG. 3 is a partially cut surface showing a state where the structure of FIG. 2 is etched using a copper etching solution. It is an end view.

  First, as shown in FIG. 2, the structure 10 is prepared (structure preparation process). The structure 10 includes a resist layer 3 in which an opening pattern 3a is formed on a substrate 1 so as to expose a metal layer 2 containing copper and a part of the metal layer 2 (hereinafter, “exposed portion”) 2a. It is obtained by forming sequentially. The opening pattern 3a can be obtained by exposing the resist layer before the opening pattern 3a is formed with a predetermined pattern and then removing the exposed part or the unexposed part.

  Next, as shown in FIG. 3, the exposed portion 2a of the metal layer 2 of the structure 10 is etched using a copper etchant to form a recess 4 in the metal layer 2 (etching step). At this time, the copper etching solution is supplied in the thickness direction of the metal layer 2. Here, the copper etching solution contains a metal chloride composed of iron chloride and / or copper chloride, an acid, and a metal salt of polyoxyalkylene alkyl ether sulfate. The supply of the copper etching solution can be performed, for example, by spraying the copper etching solution toward the exposed portion 2 a of the metal layer 2.

  In this way, circuit wiring 7 is formed on the substrate 1.

  Finally, the circuit wiring board 100 is obtained by removing the resist layer 3.

  According to the above manufacturing method, when the above-described copper etching solution is supplied in the thickness direction of the metal layer 2 of the structure 10, the exposed portion 2a of the metal layer 2 of the structure 10 is etched. Then, with the progress of the etching of the surface, the concave portion 4 is formed in the metal layer 2 and the bottom portion 6 and the side portion 5 appear. At this time, in the vicinity of the surface of the bottom portion 6, the convection speed of the copper etching solution is increased, so that etching of the surface of the bottom portion 6 is promoted. On the other hand, in the vicinity of the surface of the side portion 5, the convection speed of the copper etching solution is low, so that etching is sufficiently suppressed. For this reason, in the circuit wiring 7 of the circuit wiring board 100 obtained, the fall of the width | variety a of the top part 7a is fully suppressed. As a result, since the difference between the width b of the bottom portion 7b and the width a of the top portion 7a can be reduced, the undercut phenomenon of the circuit wiring 7 can be sufficiently suppressed.

<Structure>
Next, the structure 10 described above will be described in detail.

(substrate)
The substrate 1 is not particularly limited, and any substrate known as a circuit wiring substrate can be used. Specifically, examples of the substrate 1 include polyimide and polyethylene terephthalate.

(Metal layer)
The metal layer 2 is made of a metal containing copper. Therefore, even if this metal is a metal comprised only with copper, the metal comprised with the alloy of copper and another metal may be sufficient.

(Resist layer)
The resist layer should just be comprised with the layer which is not melt | dissolved in copper etching liquid. As such a resist layer, for example, a dry film resist or a liquid solder resist can be used.

<Copper etchant>
Next, the copper etching solution will be described in detail.

  The copper etching solution contains a metal chloride, an acid, and a metal salt of polyoxyalkylene alkyl ether sulfate.

(Metal chloride)
The metal chloride consists of iron chloride and / or copper chloride. Here, the iron ions constituting the iron chloride may be ferrous ions or ferric ions. The copper ions constituting the copper chloride may be cuprous ions or cupric ions.

(acid)
Examples of the acid include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, propionic acid, and butyric acid. You may use these individually by 1 type or in combination of 2 or more types. The acid preferably includes hydrochloric acid. In this case, in the vicinity of the surface of the bottom 6 of the recess 4 formed when the exposed portion 2a of the metal layer 2 is etched, the chloride reacts with copper deposited on the surface by the etching reaction to form CuCl ₃ ^2- ions. The ratio of physical ions will increase in the copper etching solution, and the diffused CuCl ₃ ^2- ions can be increased. For this reason, the etching with respect to the surface of the bottom part 6 of the recessed part 4 can advance faster.

(Metal salt of polyoxyalkylene alkyl ether sulfate)
The metal salt of polyoxyalkylene alkyl ether sulfate has an oxyalkylene group and an alkyl group. Examples of the oxyalkylene group include an oxymethylene group, an oxyethylene group, and an oxypropylene group. As the alkyl group, an alkyl group having 1 to 40 carbon atoms is usually used, and an alkyl group having 6 to 18 carbon atoms is preferably used. In particular, the oxyalkylene group is preferably an oxyethylene group and the alkyl group is a lauryl group, that is, the metal salt of polyoxyalkylene alkyl ether sulfate is preferably laureth sulfate. In this case, the undercut phenomenon of the circuit wiring 7 can be suppressed particularly effectively.

  Here, the number of repeating units of the oxyethylene group in the laureth sulfate Na is preferably 1 to 40, and more preferably 1 to 10.

  Moreover, as a metal of the metal salt of polyoxyalkylene alkyl ether sulfate, a monovalent metal is usually used. Examples of the monovalent metal include Na and K.

  In the copper etching solution of the present invention, the metal chloride is 0.1 to 50% by mass, the acid is 0.1 to 50% by mass, and the polyoxyalkylene alkyl ether sulfate metal salt is 0.03 to 4.5% by mass. It is preferable that

  In this case, the undercut phenomenon in the circuit wiring 7 obtained is less than when the metal chloride content, acid content, or polyoxyalkylene alkyl ether sulfate metal salt content is outside the above range. It can suppress more effectively.

  Here, it is preferable that the content rate of a metal chloride is 15-40 mass%. In this case, compared with the case where the content rate of a metal salt compound exceeds 40 mass%, a metal salt compound becomes difficult to precipitate. In addition, when the metal chloride content is 15 to 40% by mass, the etching rate is less likely to be unstable as compared with the case where the metal salt compound content is less than 15% by mass.

  Moreover, it is preferable that the content rate of an acid is 15-35 mass%. In this case, compared to the case where the acid content exceeds 35% by mass, the resist layer 3 is less likely to be damaged and the loss due to acid scattering is less likely to occur. Here, the damage of the resist layer 3 means that the resist layer 3 is deformed (or partially dissolved) by the acid and the shape of the resist layer 3 is not maintained, and the loss due to the scattering of the acid is copper etching. It means that the volatilization of the acid contained in the liquid occurs more than necessary, and the etching efficiency deteriorates. Moreover, an etching rate becomes larger compared with the case where the acid content rate is 15-35 mass% compared with the case where the acid content rate is less than 15 mass%.

(Other ingredients)
The copper etching solution may further contain water, alcohol and the like.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the copper etchant is used to etch the exposed portion 2a of the metal layer 2 of the structure 10 in the method of manufacturing the circuit wiring board 100. It can be applied not only to the manufacture of the above, but also to the case where the seed layer is etched by the semi-additive method.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

(Examples 1-3 and Comparative Examples 1-3)
Copper chloride, hydrochloric acid, water, and the surfactant shown in Table 1 were mixed to obtain a copper etching solution. At this time, the concentrations of copper chloride and hydrochloric acid in the copper etching solution were 30% by mass and 25% by mass, respectively, and the surfactant concentration (unit: mass%) in the copper etching solution was as shown in Table 1. . Here, the following were specifically used as the copper chloride and the surfactant.
(1) Copper chloride trade name “copper chloride dihydrate”, manufactured by Pure Chemical Co., Ltd. (2) Surfactant (2-1) Laureth sulfate Na
Product name “Sinoline SPE-1350”, manufactured by Kao Corporation, molecular weight 434
(2-2) Na dodecylbenzenesulfonate
Product name "Na dodecylbenzenesulfonate", manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 349
(2-3) Polyoxyethylene lauryl ether trade name “Polyoxyethylene lauryl ether”, manufactured by Junsei Chemical Co., Ltd., molecular weight 1112
(2-4) Dodecyltrimethylammonium chloride trade name “Dodecyltrimethylammonium chloride”, manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 264

  On the other hand, CCL (trade name “MC18-25-00CEM”, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) was prepared. Next, a resist material (trade name “Dry Film 202J30”, manufactured by Nichigo Morton Co., Ltd.) was adsorbed by heat on the copper foil to form a resist layer. Subsequently, the resist layer is exposed using an exposure apparatus (product name “EXM-120”, manufactured by Oak Co.), and a linear opening pattern having a width of 30 μm is formed so as to expose a part of the copper foil. The book was formed. Thus, a structure was obtained.

  Next, the copper etching solution obtained as described above was sprayed on the structure from the resist layer side to form a recess in the exposed portion of the metal layer, and circuit wiring was formed on the substrate. At this time, the pressure of the copper etching solution was 0.25 MPa, the flow rate was 25 L / min, and the spraying time of the copper etching solution was 85 seconds.

  Finally, the resist layer was removed with a 3% by mass aqueous sodium hydroxide solution (manufactured by Junsei Kagaku). Thus, a circuit wiring board was obtained. In the obtained circuit wiring board, 101 circuit wirings were formed on the board.

[Characteristic evaluation]
(1) Etching rate ratio The copper etching liquid obtained by Examples 1-3 and Comparative Examples 1-3 was put into the cylindrical beaker. Then, a stirrer was placed in the copper etching solution, and the copper etching solution was convected along the inner wall surface of the beaker. A copper plate having a thickness of 1 mm × 10 mm × 100 mm was immersed in this convective copper etching solution so that the surface thereof was orthogonal to the radial direction of the beaker and the bottom surface of the beaker. At this time, the copper plate was first immersed in a position where the flow rate of the copper etching solution was 0.1 m / s.

  At this time, the position where the flow velocity was 0.1 m / s was obtained as follows. First, the movement of bubbles in the copper etching solution was photographed as a moving image, and the angular frequency ω (radian / s) was calculated from the movement of the bubbles. Next, the distance r (m) from the center of rotation of the copper etching solution to the copper plate was calculated from the angular frequency ω and the flow velocity value (0.1 m / s) based on the equation r = v / ω. Thus, the position where the flow velocity was 0.1 m / s was obtained.

  Then, the etching rate of the copper plate was calculated 5 minutes, 10 minutes, and 20 minutes after the copper plate was immersed in the copper etching solution. The etching rate of the copper plate was calculated from the difference in thickness of the copper plate before and after the immersion after 5 minutes, 10 minutes and 20 minutes and the immersion time, respectively. Then, the etching rate 1 was calculated by arithmetically averaging the calculated etching rates.

  Next, the copper plate obtained as described above was immersed in a position where the flow rate of the copper etching solution was 0.5 m / s. At this time, the position where the flow velocity was 0.5 m / s was determined in the same manner as described above.

  Then, in the same manner as described above, the copper plate was immersed in a copper etching solution, and the etching rate 2 was calculated.

Then, based on the etching rates 1 and 2 obtained as described above, the following formula:
Etching rate ratio = Etching rate 2 / Etching rate 1
Based on the above, the etching rate ratio was calculated. The results are shown in Table 1.

(2) Etching factor (EF)
Next, the circuit wiring boards obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were embedded in an epoxy resin to produce a circuit wiring board with an epoxy resin. Then, by polishing the circuit wiring board with the epoxy resin, a cross section perpendicular to the longitudinal direction of the circuit wiring was exposed, and the shape of the cross section was observed. Then, from the width b (μm) of the bottom part of the circuit wiring, the width a of the top part of the circuit wiring, and the thickness t (μm) of the circuit wiring, the following formula:
E. F. = 0.5t / (ba)
Based on E. F. Was calculated. The results are shown in Table 1.

  From the results shown in Table 1, the etching rate ratio when the copper etching solutions of Examples 1 to 3 are used is sufficiently larger than the etching rate ratio when the copper etching solutions of Comparative Examples 1 to 3 are used. showed that. In addition, E.E. in the circuit wiring of the circuit wiring board obtained in Examples 1-3. F. Is E. in circuit wiring of the circuit wiring board obtained in Comparative Examples 1-3. F. It turned out to be bigger.

  From the above, it was confirmed that the undercut phenomenon in the circuit wiring can be sufficiently suppressed according to the copper etching solution of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Metal layer 3 ... Resist layer 4 ... Recessed part 7 ... Circuit wiring 10 ... Structure 100 ... Circuit wiring board

Claims (5)

A metal chloride consisting of iron chloride and / or copper chloride;
A copper etchant containing an acid,
A copper etching solution containing a metal salt of polyoxyalkylene alkyl ether sulfate. 0.1 to 50% by mass of the metal chloride,
0.1 to 50% by mass of the acid,
The copper etching liquid of Claim 1 containing 0.03-4.5 mass% of metal salts of the said polyoxyalkylene alkyl ether sulfuric acid.   The copper etching solution according to claim 1 or 2, wherein the metal salt of the polyoxyalkylene alkyl ether sulfate is a metal salt of polyoxyethylene lauryl ether sulfate.   The copper etching liquid as described in any one of Claims 1-3 in which the said acid contains hydrochloric acid. A circuit wiring board manufacturing method for manufacturing a circuit wiring board by forming circuit wiring on a substrate,
A structure preparation step for preparing a structure obtained by sequentially forming a metal layer containing copper and a resist layer having an opening pattern so as to expose a part of the metal layer on the substrate; ,
The exposed portion of the metal layer of the structure prepared in the structure preparation step is etched using the copper etching solution according to any one of claims 1 to 4 to form a recess in the metal layer. An etching step of forming the circuit wiring on the substrate by forming
In the etching process, the copper etching solution is supplied in the thickness direction of the metal layer.

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