Copper etchant for removing copper seed layer

Abstract

To provide a copper etchant for copper seed removal that exhibits adequate removal performance for a copper seed layer and suppresses both surface roughness increase of a copper wire or copper electrode and circuit narrowing.SOLUTION: A copper etchant for removing a copper seed layer, which contains an organic acid and hydrogen peroxide and has a pH of 5.0 to 8.0.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper etching solution for removing a copper seed layer. [Background technology]

[0002] In recent years, as electronic devices have become smaller and more sophisticated, there has been a demand for higher density printed wiring boards. In particular, substrates on which semiconductors are mounted require finer wiring patterns, and so the semi-additive process (SAP) shown in Figure 1 is used.

[0003] In the SAP process, a copper seed layer is formed on a substrate using electroless copper or copper sputtering, and then exposed and developed so that resist remains in non-circuit areas. Next, a circuit pattern is formed on the exposed copper seed layer using electrolytic copper plating, the resist is stripped, and the unnecessary copper seed layer between the circuits is removed using a flash etching process.

[0004] In the flash etching process, a copper etchant is used to remove the copper seed layer between the copper wirings, and such a copper etchant is required to have sufficient copper seed layer removal ability.

[0005] As the copper etching solution described above, an etching solution such as a sulfuric acid / hydrogen peroxide system is generally used (for example, Patent Document 1).

[0006] However, when the etching solution of Patent Document 1 is used, the etching solution also has an etching effect on copper wiring or copper electrodes, which causes problems such as an increase in the surface roughness of the copper wiring or copper electrodes and a decrease in circuit width. The increase in surface roughness of the copper wiring or copper electrodes and the decrease in circuit width impair the reliability of the circuit, such as an increase in transmission loss and a decrease in adhesion.

[0007] Therefore, there is a need for the development of a copper etching solution for removing a copper seed layer that has sufficient removability of the copper seed layer and that suppresses an increase in the surface roughness of the copper wiring or copper electrode and circuit thinning. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2012 / 046841 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a copper etching solution for removing copper seeds that has sufficient removability of a copper seed layer and that suppresses an increase in the surface roughness of copper wiring or copper electrodes and circuit thinning. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above object can be achieved by using a copper etching solution for removing a copper seed layer that contains an organic acid and hydrogen peroxide and has a pH of 5.0 to 8.0, and have thus completed the present invention.

[0011] That is, the present invention relates to the following copper etching solution for removing a copper seed layer. 1. A copper etching solution for removing a copper seed layer, which contains an organic acid and hydrogen peroxide and has a pH of 5.0 to 8.0. 2. The copper etching solution for removing a copper seed layer according to Item 1, wherein the organic acid is at least one selected from the group consisting of dicarboxylic acids, tricarboxylic acids, and salts thereof. 3. The copper etching solution for removing a copper seed layer according to Item 1 or 2, further comprising a hydrogen peroxide stabilizer. 4. The copper etching solution for removing a copper seed layer according to Item 3, wherein the hydrogen peroxide stabilizer is at least one selected from the group consisting of lactams, glycols, and phenolsulfonates. 5. The copper etching solution for removing a copper seed layer according to any one of items 1 to 4, further comprising a pH buffer. 6. The copper etching solution for removing a copper seed layer according to Item 5, wherein the pH buffer is at least one selected from the group consisting of inorganic phosphates and citrates. 7. The copper etching solution for removing a copper seed layer according to any one of items 1 to 6, which does not contain sulfuric acid. 8. A method for producing a circuit board, comprising a step of removing a copper seed layer between circuits by using the copper etching solution for removing a copper seed layer according to any one of items 1 to 7. 9. A circuit board obtained by removing a copper seed layer between circuits with the copper etching solution for removing a copper seed layer according to any one of items 1 to 7. [Effects of the Invention]

[0012] The copper etching solution for removing a copper seed layer of the present invention has sufficient removability of a copper seed layer and can suppress an increase in the surface roughness of a copper wiring or copper electrode and a narrowing of the circuit. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating the processing steps of SAP. DETAILED DESCRIPTION OF THE INVENTION

[0014] The copper etching solution for removing a copper seed layer of the present invention will be described in detail below.

[0015] 1. Copper etchant for removing copper seed layer The copper etching solution for removing a copper seed layer of the present invention (hereinafter also simply referred to as "copper etching solution") is characterized by containing an organic acid and hydrogen peroxide and having a pH of 5.0 to 8.0. The copper etching solution for removing a copper seed layer of the present invention is a copper etching solution containing an organic acid and hydrogen peroxide water so as to have a pH within a specific range, thereby reducing damage to electroplated copper portions, suppressing an increase in the surface roughness of the copper wiring or copper electrode and circuit narrowing, and allowing for preferential etching and removal of copper seed layer portions between circuits where copper removal is required. In the copper etching solution for removing a copper seed layer of the present invention, hydrogen peroxide acts as an oxidizing agent, and the organic acid acts as a chelating agent or etching aid. In the copper etching solution for removing a copper seed layer of the present invention, copper is etched by using a combination of an organic acid and hydrogen peroxide, but the copper seed layer is selectively etched over the electroplated copper. Therefore, when removing unnecessary copper seed layer between circuits, damage to the circuit portions formed by electroplating copper is suppressed, and an increase in the surface roughness of the copper wiring or copper electrode and circuit narrowing are suppressed. Furthermore, since the copper etching solution for removing a copper seed layer of the present invention has a pH within a specific range, it can suppress an increase in the surface roughness of copper wiring or copper electrodes and thinning of the circuit.

[0016] The pH of the copper etching solution of the present invention is 5.0 to 8.0. If the pH is less than 5.0, an increase in the surface roughness of the copper wiring or copper electrode and thinning of the circuit cannot be suppressed. If the pH is more than 8.0, the copper seed layer cannot be sufficiently removed. The pH of the copper etching solution is preferably 6.0 to 7.0.

[0017] (organic acid) The organic acid is not particularly limited, and any organic acid used in copper etching solutions can be used, including dicarboxylic acids, tricarboxylic acids, and salts thereof.

[0018] Examples of dicarboxylic acids include oxalic acid, tartaric acid, malic acid, malonic acid, succinic acid, and adipic acid. These dicarboxylic acids may be in the form of a salt. The dicarboxylic acid salt is not particularly limited, and examples thereof include known metal salts, such as sodium salts, potassium salts, and ammonium salts.

[0019] Examples of tricarboxylic acids include citric acid and nitrilotriacetic acid. These tricarboxylic acids may be in the form of salts. The tricarboxylic acid salts are not particularly limited and include known metal salts, such as sodium salts, potassium salts, and ammonium salts.

[0020] The organic acids may be used singly or in combination of two or more. In particular, it is preferable to use a mixture of two or more organic acids. By using a mixture of two or more organic acids, the etching of the copper seed layer between the circuits can be completed in a shorter time.

[0021] The content of the organic acid in the copper etching solution is not particularly limited, but is preferably 10 to 60 g / L, more preferably 20 to 55 g / L, and even more preferably 30 to 40 g / L. When the lower limit of the organic acid content is within the above range, the copper seed layer removability of the copper etching solution is further improved. When the upper limit of the organic acid content is within the above range, an increase in the surface roughness of the copper wiring or copper electrode and circuit thinning are further suppressed.

[0022] (hydrogen peroxide) The hydrogen peroxide is not particularly limited, and may be dissolved in water to be used as hydrogen peroxide water.

[0023] The content of hydrogen peroxide in the copper etching solution is not particularly limited, but is preferably 15 to 100 g / L, more preferably 25 to 70 g / L, and even more preferably 30 to 50 g / L, calculated as hydrogen peroxide. When the lower limit of the hydrogen peroxide content is within the above range, the copper etching solution's ability to remove the copper seed layer is further improved. When the upper limit of the hydrogen peroxide content is within the above range, an increase in the surface roughness of the copper wiring or copper electrode and circuit thinning are further suppressed.

[0024] (Hydrogen peroxide stabilizer) The copper etching solution of the present invention may contain a hydrogen peroxide stabilizer. By containing a hydrogen peroxide stabilizer in the copper etching solution, the stability of hydrogen peroxide in the copper etching solution over time is further improved.

[0025] The hydrogen peroxide stabilizer is not particularly limited, and any stabilizer that is used as a hydrogen peroxide stabilizer in an aqueous solution can be used. Examples of such hydrogen peroxide stabilizers include lactams, glycols, and phenolsulfonates. The lactams are not particularly limited, and examples include 4-pentane lactam and ε-caprolactam. The glycols are not particularly limited, and examples include ethylene glycol, propylene glycol, and diethylene glycol. The phenolsulfonates are not particularly limited, and examples include sodium p-phenolsulfonate and p-toluenesulfonic acid. Among these, ε-caprolactam is preferred.

[0026] The hydrogen peroxide stabilizers may be used alone or in combination of two or more.

[0027] The content of the hydrogen peroxide stabilizer in the copper etching solution is not particularly limited, but is preferably 1 to 30 g / L, more preferably 3 to 25 g / L, and even more preferably 5 to 20 g / L. When the lower limit of the hydrogen peroxide stabilizer content is within the above range, the hydrogen peroxide in the copper etching solution becomes more stable. Even if the upper limit of the hydrogen peroxide stabilizer content is above the above range, stability is achieved, but a dramatic improvement in effectiveness is unlikely to be observed. Therefore, by setting the upper limit within the above range, economic efficiency is improved.

[0028] (pH buffer) The copper etching solution of the present invention may contain a pH buffering agent, which makes the pH of the copper etching solution more stable.

[0029] The pH buffering agent is not particularly limited, and any agent that is used as a pH buffering agent for copper etching solutions can be used. Examples of such pH buffering agents include inorganic phosphates and carboxylates.

[0030] The inorganic phosphate is not particularly limited, and examples thereof include sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium hypophosphite, sodium phosphate, and sodium hydrogen phosphate.

[0031] The carboxylate salt is not particularly limited, and examples thereof include sodium carboxylate salts such as sodium citrate, disodium citrate, trisodium citrate, sodium acetate, and sodium tartrate; potassium carboxylate salts such as potassium citrate, dipotassium citrate, tripotassium citrate, potassium acetate, potassium tartrate, and sodium potassium tartrate; and ammonium carboxylate salts such as diammonium hydrogen citrate, triammonium citrate, ammonium acetate, and ammonium tartrate.

[0032] The pH buffering agents may be used alone or in combination of two or more.

[0033] The content of the pH buffer in the copper etching solution is not particularly limited, but is preferably 5 to 160 g / L, more preferably 7 to 100 g / L, even more preferably 8 to 50 g / L, and particularly preferably 10 to 30 g / L. When the lower limit of the pH buffer content is within the above range, the pH of the copper etching solution becomes more stable. Even if the upper limit of the pH buffer content is above the above range, it can still be used as a buffer, but a dramatic improvement in effect is unlikely to be observed, so having the upper limit within the above range improves economic efficiency.

[0034] [Other ingredients] The copper etching solution of the present invention may further contain other components, such as a pH adjuster and a fungicide.

[0035] (pH adjuster) The pH adjuster is not particularly limited, and various pH adjusters used in copper etching solutions can be used.

[0036] Specific examples of pH adjusters that can be used include acids such as hydrochloric acid and phosphoric acid; and alkalis such as sodium hydroxide, potassium hydroxide, and aqueous ammonia.

[0037] These pH adjusters can be used alone or in combination of two or more.

[0038] The content of the pH adjuster in the copper etching solution is not particularly limited, as long as it is an amount that can adjust the pH of the copper etching solution of the present invention to 5.0 to 8.0. For example, when sodium hydroxide is used as the pH adjuster, the content of the pH adjuster in the copper etching solution is preferably about 15 to 35 g / L, more preferably about 20 to 30 g / L.

[0039] (Anti-mold agent) The antifungal agent is not particularly limited, and various antifungal agents used in copper etching solutions can be used.

[0040] As the antifungal agent, it is preferable to use a copper compound, and specifically, copper acetate, copper chloride, copper nitrate, copper carbonate, copper oxide, etc. can be used.

[0041] These antifungal agents can be used alone or in combination of two or more.

[0042] The content of the antifungal agent in the copper etching solution is not particularly limited, and is preferably about 0.01 to 0.2 g / L, more preferably about 0.05 to 0.15 g / L, in terms of copper concentration.

[0043] (solvent) In the copper etching solution of the present invention, the above components are preferably contained in a solvent.

[0044] As the solvent, known solvents constituting copper etching solutions can be used, such as water, alcohols, etc. Water is preferred from the viewpoint of ease of handling and safety.

[0045] The content of the solvent is not particularly limited, and may be the remainder after adding the above-mentioned components.

[0046] The copper etching solution of the present invention preferably does not contain sulfuric acid. When the copper etching solution of the present invention does not contain sulfuric acid, an increase in the surface roughness of the copper wiring or copper electrode and thinning of the circuit can be further suppressed.

[0047] 2. Copper etching solution manufacturing method The copper etching solution of the present invention can be produced by any known method without any particular limitation, for example, by adding the organic acid and hydrogen peroxide to a solvent such as water, and optionally adding other components such as the hydrogen peroxide stabilizer, pH buffer, pH adjuster, and antifungal agent, followed by stirring.

[0048] The stirring time is not particularly limited as long as the copper etching solution can be made uniform, and may be about 5 to 10 minutes. The temperature of the copper etching solution during stirring is not particularly limited, and may be preferably 15 to 40°C, and more preferably 20 to 35°C.

[0049] 3. Copper seed layer removal method The method for removing a copper seed layer using the copper etching solution of the present invention is not particularly limited, and the copper seed layer can be removed by a conventionally known method, such as a method of immersing a substrate from which the copper seed layer is to be removed in the copper etching solution and stirring it, or a method of spraying the copper etching solution onto the substrate from which the copper seed layer is to be removed.

[0050] The temperature of the copper etching solution when removing the copper seed layer is not particularly limited, but is preferably 20 to 40°C, more preferably 25 to 35°C.

[0051] The treatment time for removing the copper seed layer is not particularly limited as long as the copper seed layer on the substrate can be sufficiently removed. For example, when the method involves immersing the substrate from which the copper seed layer is to be removed in a copper etching solution, the immersion time can be approximately 3 to 5 minutes. When the method involves spraying the copper etching solution onto the substrate from which the copper seed layer is to be removed, the spraying time can be approximately 10 seconds to 3 minutes.

[0052] In the method of spraying the copper etching solution onto the substrate from which the copper seed layer is to be removed, the pressure during the spraying is preferably 0.05 to 0.3 MPa, more preferably 0.07 to 0.2 MPa.

[0053] 4. Circuit board manufacturing method The method for producing a circuit board of the present invention includes a step of removing the copper seed layer between circuits with the copper etching solution for removing a copper seed layer of the present invention. In the production method of the present invention, the copper seed layer is sufficiently removably formed, and an increase in the surface roughness of the copper wiring or copper electrode and thinning of the circuit are suppressed because the copper etching solution for removing a copper seed layer of the present invention described above is used.

[0054] In the above process, examples of the method for removing the copper seed layer from the circuit board using the copper etching solution for removing the copper seed layer include a method of immersing the circuit board with the exposed copper seed layer between circuits in the etching solution for removing the copper seed layer and removing it by flash etching, and a method of spraying the etching solution for removing the copper seed layer onto the circuit board with the exposed copper seed layer between circuits.

[0055] The liquid temperature (treatment temperature) of the copper etching solution for removing the copper seed layer in the above step may be adjusted as appropriate, and is preferably 20 to 40°C, more preferably 25 to 35°C, for example.

[0056] The treatment time in the above step may be appropriately set depending on the thickness of the copper seed layer, and for example, when the circuit board is immersed in the etching solution for removing the copper seed layer, the immersion time may be about 3 to 5 minutes. When the etching solution for removing the copper seed layer is sprayed onto the circuit board, the spraying time may be about 10 seconds to 3 minutes.

[0057] By the above process, the copper seed layer between the circuits is removed by the copper etching solution for removing the copper seed layer, thereby producing a circuit board. Thus, the circuit board obtained by removing the copper seed layer between the circuits by the copper etching solution for removing the copper seed layer also constitutes one aspect of the present invention. [Example]

[0058] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0059] Examples and Comparative Examples A copper etching solution of Comparative Example 1 was prepared according to the formulation shown in Table 1. Copper etching solutions of Examples 1 to 8 were prepared according to the formulation shown in Table 2. The copper etching solutions were prepared by sequentially adding the components shown in Tables 1 and 2 to water.

[0060] [Table 1]

[0061] [Table 2]

[0062] (characteristic evaluation) The following microcircuit board was prepared as a test piece for evaluating characteristics. Microcircuit Board Substrate: 8-inch Si wafer, ABF laminated product Ra=29nm Sputtering: Titanium sputtering film 25nm, copper sputtering film 100nm Resist: 4~5μm Copper sulfate plating: 3 μm film thickness L / S (μm): Circuits are formed by arranging L / S in the following order: 10 / 10, 7 / 7, 5 / 5, 3 / 3, 2.5 / 2.5, 2 / 2, 2.1 / 1.8, 2.3 / 1.7, 1.8 / 2.2

[0063] The above-mentioned microcircuit board was etched by the following etching method using the copper etching solutions of the Examples and Comparative Examples.

[0064] Etching Method (1) Using a single-sided spray device, the microcircuit board is treated under the condition of a spray pressure of 0.1 MPa. (2) The time when the copper seed layer in the solid area disappears visually is defined as the reference (just etching), and the time when the processing time is doubled is defined as 100% over-etching. (3) When the processing time has tripled, the over-etching is considered to be 200%.

[0065] The microcircuit boards etched by the above etching method were evaluated by the following evaluation methods.

[0066] (Removability of sputtered film) The sputtered copper residues in the solid area and the L / S=10 / 10 area after spray etching at the time of just etching were confirmed using an FE-SEM (10,000x magnification) and evaluated according to the following evaluation criteria. ○: The copper seed layer between the circuits has been removed ×: The copper seed layer remains between the circuits.

[0067] (Surface roughness of copper wiring) The surface roughness (Ra) before and after etching (overetching 200%) was measured using a shape analysis laser microscope at a magnification of 1500 times.

[0068] (Amount of copper wiring reduced) The amount of copper wiring film loss before and after etching (overetching 100%) was measured using FE-SEM.

[0069] The results are shown in Table 3.

[0070] [Table 3]

[0071] Examples 9 and 10 Copper etching solutions of Examples 9 and 10 were prepared by the same preparation method as in Example 1, except for the formulation shown in Table 4. In Examples 9 and 10, a copper compound was added so that the copper concentration was 5 g / L in terms of copper, assuming a situation in which copper accumulates due to continuous use of the copper etching solution.

[0072] [Table 4]

[0073] The copper etching solutions of Examples 9 and 10 were used to evaluate bath stability by the following method.

[0074] (bath stability) The hydrogen peroxide concentration in the copper etching solution was measured by redox titration, measuring the initial concentration, and the concentration after 3 and 24 hours.

[0075] The results are shown in Table 5.

[0076] [Table 5]

Claims

1. A copper etching solution for removing a copper seed layer, comprising an organic acid and hydrogen peroxide, and having a pH of 5.0 to 8.

0.

2. 2. The copper etching solution for removing a copper seed layer according to claim 1, wherein the organic acid is at least one selected from the group consisting of dicarboxylic acids, tricarboxylic acids, and salts thereof.

3. The copper etching solution for removing a copper seed layer according to claim 1 or 2, further comprising a hydrogen peroxide stabilizer.

4. 4. The copper etching solution for removing a copper seed layer according to claim 3, wherein the hydrogen peroxide stabilizer is at least one selected from the group consisting of lactams, glycols, and phenolsulfonates.

5. The copper etching solution for removing a copper seed layer according to claim 1 or 2, further comprising a pH buffer.

6. 6. The copper etching solution for removing a copper seed layer according to claim 5, wherein the pH buffer is at least one selected from the group consisting of inorganic phosphates and citrates.

7. 3. The copper etching solution for removing a copper seed layer according to claim 1, which does not contain sulfuric acid.

8. A method for manufacturing a circuit board, comprising a step of removing the copper seed layer between circuits with the copper etching solution for removing the copper seed layer according to claim 1.

9. A circuit board obtained by removing the copper seed layer between circuits with the copper etching solution for removing a copper seed layer according to claim 1.

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