JP2006124740A - Etching solution and method for controlling concentration of etching solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper etching solution which provides an excellent rate of etching and can ameliorate an odorous environment due to hydrogen chloride while satisfying a low cost characteristic of the copper etching solution. <P>SOLUTION: In an apparatus 5, etching is performed by the etching solution prepared by using cupric chloride of about 2 mol/L in concentration as a principal component and adding ferric chloride to the solution to attain the concentration of ≤1.5 mol/L. The concentration of the cupric chloride and ferric chloride contained in the used etching solution is measured in a sampling apparatus 3, and the concentration control is performed in such a manner that the concentration prior to the etching is attained by regulating the concentration of the cupric chloride and the concentration of the ferric chloride in an apparatus 4 for regulating the replenishing amount of medicaments. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composition of an etching solution for etching a workpiece having a copper film.

  In an electronic component manufacturing process, a work provided with a copper film (hereinafter referred to as a copper work) is infiltrated into an etching solution having an oxidizing power that corrodes a metal, or the etching solution is showered on the copper work. Therefore, a wet etching process for forming a pattern of a printed circuit board, an ITO film, a lead frame, or the like is used. According to this etching process, the copper component undergoes an anodic oxidation reaction and the oxidant component undergoes a cathodic reduction reaction due to the difference in redox potential between the oxidant component in the etching solution and the copper component of the copper workpiece. Formula 1 shows the anodic oxidation reaction formula of the copper film, and Formula 2 shows the cathode reduction reaction formula of the oxidant component Ox.

<Formula 1> Cu → Cu ⁺ + e ⁻
<Formula 2> Ox + ne ⁻ → Red
According to the anodic oxidation reaction formula of Formula 1, copper of the copper workpiece is eluted and etching proceeds. Further, the oxidizing agent component contained in the etching solution generates a product Red having no oxidizing power according to the cathode reduction reaction formula of Formula 2.

  Oxidizing agents used for etching include halogen salts, oxo acids, oxo salts, etc., but generally when copper workpieces are wet etched, copper halides, iron halides, among others, An etchant containing cupric chloride or ferric chloride as a main component of an oxidizing agent is used.

  An etching solution using iron halide as an oxidizing agent (hereinafter referred to as an iron etching solution) has excellent properties such as an excellent etching factor for a copper film and a high etching rate for dissolving copper. However, it also has a negative property that the amount dissolved in copper is relatively small. For this reason, the amount of the etching solution used is large, which is a cost factor, and also costs for the waste liquid treatment, and the unit price of the iron etching solution itself is high, so that the entire etching treatment is expensive.

  On the other hand, an etching solution using copper halide as an oxidizing agent (hereinafter referred to as a copper etching solution) has an etching rate slower than that of an iron etching solution, but when used together with a regeneration aid, copper is twice as much as an iron etching solution. A treatment that has the property of being dissolved as described above and that regenerates cuprous chloride in the waste liquid to make cupric chloride is widely used. In addition, since the unit price of the etching solution itself is low, the etching process can be performed at a lower cost than when an iron etching solution is used.

  Therefore, in recent years, an etching rate is improved by adding an additive to a copper etching solution, and it is often used for an etching process. By improving the etching rate, it has become possible to perform an etching process at a low cost and at a high etching rate. As an additive, there are a case where a surfactant is used (for example, Patent Document 1) and a case where hydrochloric acid is used (for example, Patent Document 2), and the etching rate is often improved by using hydrochloric acid. It is coming.

When a hydrochloric acid of about 3 mol / L is used as an additive in a general copper etching solution having a concentration of 2.0 mol / L, an etching time that takes about 150 to 180 seconds / ounce when no additive is used, Improved to about 70-80 seconds / ounce.
JP-A 63-255531 JP-A-49-000138

  As described above, conventionally, a copper etching solution (hereinafter referred to as a hydrochloric acid-added copper etching solution) using about 3 mol / L hydrochloric acid as an additive has been used. However, since this hydrochloric acid-added copper etchant is corrosive to metals, it requires extra equipment to prevent scattering, and even if such equipment is installed, peripheral equipment deteriorates due to transpiration and scattering. This has a problem that the life of peripheral devices is shortened. For this reason, when considering the overall cost, there is a problem that the low cost, which is an advantage of the copper etching solution, is not always satisfied.

  Accordingly, the present invention provides a copper etching solution that solves the above-mentioned problems, adds an excellent etching rate, and improves the odor environment due to hydrogen chloride while satisfying the low cost of the copper etching solution. With the goal.

  The present invention is characterized in that iron halide is added to an etching solution mainly composed of divalent copper halide so as to have a concentration of 1.5 mol / L or less.

  As an additive, iron halide is used to improve the etching rate. Some iron halides dissolve into trivalent iron ions and some become divalent iron ions. The trivalent iron ions act as oxidizing agents, and the divalent iron ions are oxidized once. If it is not trivalent iron ion, it will not act as an oxidizing agent. Therefore, in the case of an iron halide that becomes a divalent iron ion, it is oxidized once and used. By doing in this way, an etching liquid comes to contain a trivalent iron ion, and the ion which has an oxidizing power increases in an etching liquid. As a result, an etching solution having a good reaction performance can be obtained without adding hydrochloric acid as in the prior art, and the etching time is not deteriorated even when used in place of an etching solution containing hydrochloric acid as an additive. In addition, by adjusting the amount of iron halide added, it is possible to substitute a device that uses a conventional hydrochloric acid-added etching solution with almost no change in the device. Further, since no hydrochloric acid is used, the odor environment is not deteriorated and the life of peripheral machines can be extended.

  The invention according to claim 2 is an invention in which the halogen is chlorine, and the invention according to claim 3 is an invention specifically showing that the preferred value of the concentration of copper halide is about 2 mol / L. It is. The concentration range of about 2 mol / L means a range of about 1.5 to 2.5 mol / L.

  Thereby, the copper etching liquid of this invention can be comprised using the general purpose copper chloride etching agent and iron chloride etching agent which can be generally obtained now cheaply.

  The invention according to claim 4 is an invention related to maintaining a deteriorated etching solution in the composition of the present invention, and is characterized by regenerating copper halide or iron halide and adjusting the concentration.

  Thereby, the density | concentration of the said iron halide and copper halide can be adjusted with respect to a used etching liquid, and the composition of an etching liquid can be made the same with the composition of the copper etching liquid of this invention. In addition, the etching solution to which the divalent iron halide is added can be oxidized to a trivalent iron halide by this process, and the composition of the etching solution can be the same as the composition of the copper etching solution of the present invention.

  As described above, according to the present invention, the trivalent halogen-valent iron (iron etchant) is added to the etchant (copper etchant) mainly composed of divalent copper halide at a low cost. A high-performance etching solution can be realized. That is, by adding an iron etchant that is inexpensive and easily regenerated to a high-speed and low-degradation iron etchant, the etch factor can be improved and a fine etch pattern can be finely finished. Further, since the main component is copper halide, the amount of waste liquid when regenerated is small and the processing cost can be reduced.

  Further, since vaporized hydrogen chloride is not generated, peripheral machines are not deteriorated, life can be extended, and the etching rate can be improved while satisfying the low cost that is an advantage of the copper etching solution. . Moreover, since there is no transpiration of hydrogen chloride, the odor environment can be improved. Moreover, it can substitute for the peripheral machine of a chlorine addition copper etching liquid, requiring almost no change of a machine. In addition, general-purpose copper chloride etchants and iron chloride etchants that are generally available at low cost can be used. Furthermore, the composition of the etching solution can be made the same as the composition of the present invention by adjusting the concentration by applying a regeneration process to the used etching solution.

  An example of the composition of the etching solution of the present invention is shown below. Here, the copper halide is cupric chloride and the iron halide is ferric chloride.

  In the following, this composition example, a copper etching solution without using an additive, a hydrochloric acid-added copper etching solution, and an etching solution with hydrochloric acid and sodium chloride as additives are etched when the same copper workpiece is etched. Table 1 shows a comparison of the time required for the above (hereinafter referred to as etching time). The work is a piece cut out of a printed wiring board plated with a copper film, and shows the time required to dissolve 1 ounce of the 35 μm copper film by an etching process in which an etching solution is sprayed (shown) from above. . In the following example, the concentration of cupric chloride in the copper etching solution is about 2 mol, but similar results can be obtained even if the concentration is different within the range of about 1.5 to 2.5 mol.

  The copper etching solution using ferric chloride as an additive in this composition example contains about 2 mol of cupric chloride and about 1 mol of ferric chloride per liter. When this etching solution was sprayed onto the copper workpiece, it took about 70 seconds to dissolve the 1 ounce copper film. Similar results can be obtained even if the concentration of ferric chloride is changed within a range of about 0.5 to 1.5 mol.

  The copper etching solution not using the additive of Comparative Example 1 contains about 2 mol of cupric chloride per liter. When this etchant was sprayed onto the copper workpiece, it took about 140 s to dissolve the 1 ounce copper film.

  The hydrochloric acid-added copper etching solution of Comparative Example 2 contains about 2 mol of cupric chloride and about 3 mol of hydrochloric acid per liter. Although this etching solution has high etching performance, it has a problem that the odor environment is deteriorated by hydrochloric acid, and peripheral devices are deteriorated. When this etching solution was sprayed onto the workpiece, it took about 70 seconds to dissolve the 1 ounce copper film.

  The etching solution of Comparative Example 3 containing hydrochloric acid and sodium chloride as additives contains about 2 mol of cupric chloride, about 0.2 mol of hydrogen chloride, and about 1.0 mol of sodium chloride per liter. This etching solution uses sodium chloride in order to reduce the amount of hydrochloric acid used in the conventional hydrochloric acid-added copper etching solution. When this etching solution was sprayed onto the workpiece, it took about 110 s to dissolve the 1 ounce copper film.

  As described above, the etching time for the copper etching solution without using the additive of Comparative Example 1 and the etching solution with the hydrochloric acid and sodium chloride of Comparative Example 3 as additives were compared with the copper etching solution of the present composition example. This is necessary for a longer time than the first embodiment, and the etching efficiency is poor. Further, the etching solution doped only with hydrochloric acid of Comparative Example 2 can be etched in the same etching time as the composition example of the present invention, but the problem of deteriorating peripheral machines and the problem of deteriorating odor environment as described above. Therefore, it can be said that the composition has the subject of the present application.

  Therefore, the etching solution of the composition example of the present invention can improve the etching rate with a composition that satisfies the low cost and improves the odor environment and the life of the apparatus.

An adjustment example of the concentration adjustment method of the present invention will be described based on the example of the etching apparatus of FIG.
In the etching apparatus 5, the copper film of the copper workpiece is etched. By etching, the copper component undergoes an anodic oxidation reaction (Formula 3). At the same time, trivalent iron ions and divalent copper ions, which are oxidant components in the etching solution, undergo a cathodic reduction reaction (formulas 4 and 5) to generate reactants having no oxidizing power (formulas 6 and 7). ).
<Formula 3> Cu → Cu ⁺ + e ⁻
<Formula 4> Fe ³⁺ + e ⁻ → Fe ²⁺
<Formula 5> Cu ²⁺ + e ⁻ → Cu ⁺
<Formula 6> Fe ²⁺ + 2Cl ⁻ → FeCl ₂
<Formula 7> Cu ⁺ + Cl ⁻ → CuCl ↓
By such a reaction, trivalent iron ions and divalent copper ions in the etching solution are reduced.

  Since the etching solution is circulated and used, the content of trivalent iron ions and divalent copper ions in the etching solution is gradually lowered by the above-described action, and the etching performance is also lowered. Therefore, in order to recover the content of trivalent iron ions and divalent copper ions, the sampling solution 3 is used to regenerate the etching solution.

  The sampling device 3 periodically samples the etching solution from the etching device 5 during the etching process. The content ratio of trivalent iron ions and divalent copper ions in the extracted sample is measured using the specific gravity, conductivity, method using a reagent, and the like of the sample.

If the measured content of trivalent iron ions and divalent copper ions is not within the specified range, cuprous chloride (formula 7) produced by the etching process is regenerated into cupric chloride. Regenerate ferrous chloride to ferric chloride. First, the amount of cuprous chloride and the amount of ferrous chloride generated in the etching process are estimated from the concentration measured by the chemical replenishment amount adjusting device 4. Further, the replenishment amount of hydrochloric acid and hydrogen peroxide water necessary to regenerate the estimated cuprous chloride amount and ferrous chloride amount is determined. The etching solution is replenished with hydrochloric acid and hydrogen peroxide solution from the hydrochloric acid tank 7 and the hydrogen peroxide solution tank 8 by the determined replenishment amount. By this operation, cuprous chloride in the etching solution is oxidized to cupric chloride, and divalent copper ions are increased. It also oxidizes ferrous chloride to ferric chloride, increasing trivalent iron ions. The reaction formulas (Formulas 8 and 9) are shown below.
<Formula 8> CuCl + 0.5H ₂ O ₂ + HCl → CuCl ₂ + H ₂ O
<Formula 9> FeCl ₂ + 0.5H ₂ O ₂ + HCl → FeCl ₃ + H ₂ O
However, the amount of hydrochloric acid added here is slightly larger than the amount necessary for the above reaction. This is because not all of the added hydrochloric acid contributes to the reaction, so it is necessary to add a little excessively, and when the etching solution is acidified, for example, generation of iron hydroxide or calcium hydroxide is prevented, It is because generation | occurrence | production of the sludge resulting from them can also be prevented. The amount of hydrochloric acid added is such that the etching solution contains a dilute concentration of hydrochloric acid, for example, an amount that results in a concentration of 0.1 to 0.3 mol / L. Even if this amount of hydrochloric acid is added, the hydrochloric acid hardly contributes to the etching rate, and on the other hand, hydrogen chloride is hardly scattered or evaporated in the atmosphere. Note that the etching solution to which hydrochloric acid of this level is added also belongs to the technical scope of the present invention.

  Furthermore, in order to adjust the concentration of the etching solution, the replenishment amount of pure water is determined by the chemical replenishment amount adjusting device 4 and pure water is replenished from the pure water tank 2 to the etching solution. As a result, the amount of liquid inside the etching apparatus 5 increases, but the increased liquid overflows and is collected in the drain tank 6. Collect the copper and iron components as much as possible from the wastewater in the drainage tank, and finally discard it.

  Since the amount of iron ions decreases due to overflow (copper ions are replenished by dissolution), the ferric chloride component is replenished to the ratio before deterioration of the ratio of copper ions and iron ions in the deteriorated etchant. return. This process is performed by determining the replenishment amount of ferric chloride by the chemical replenishment amount adjusting device 4 and replenishing the etching solution with a high concentration ferric chloride solution from the iron chloride tank 1. Thereby, the ratio of ferric chloride and cupric chloride returns to the ratio before deterioration.

  By the above operation, the contents of trivalent iron ions and divalent copper ions in the etching solution are recovered until the etching solution of the present invention is obtained.

  By adjusting the composition in this way, a composition suitable for the etching of the present invention is regenerated. By circulating and reusing the regenerated etching solution, the adjusting step of the concentration adjusting method using the etching solution of the present invention can be realized.

  In the above embodiment, the process of spraying the etching solution onto the copper workpiece has been described as an example. However, the etching solution and the etching apparatus of the present invention and the embodiment are an etching method in which the copper workpiece is immersed in an etching bath. It can also be applied to.

A concentration control apparatus for realizing the embodiment of the invention according to claim 4

Explanation of symbols

1-iron chloride tank 2-pure water tank 3-sampling device 4-drug replenishment amount adjusting device 5-etching device 6-drainage tank 7-hydrochloric acid tank 8-hydrogen peroxide water tank

Claims (4)

  An etching solution comprising a divalent copper halide as a main component, wherein an iron halide is added so as to have a concentration of 1.5 mol / L or less.   The etching solution according to claim 1, wherein the divalent copper halide is cupric chloride, and the iron halide is ferric chloride.   The etching solution according to claim 1 or 2, wherein the concentration of the divalent copper halide is about 2 mol / L.   By measuring the concentration of trivalent iron halide and divalent copper halide contained in the used etching solution of the etching tank where the etching was performed, and adding the oxidizing agent based on the measurement result, trivalent An etching solution according to any one of claims 1 to 3, wherein an iron halide and a divalent copper halide are produced, and the concentrations of the iron halide and the divalent copper halide are adjusted. Concentration control method.

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