JP4354855B2 - Copper etching replenisher and copper foil film etching method - Google Patents

Description

  The present invention relates to a copper etching replenisher and a copper foil film etching method, and more particularly to a copper etching replenisher and a copper foil film etching method suitable for etching a highly accurate fine circuit.

  The circuit of the tape carrier package wiring board has been miniaturized year by year, and in order to cope with this, the thickness of the copper thin film used for the wiring board has been reduced. Recently, a copper thin film of 8 μm or less has been used. Also, in a wafer level chip size package or a plasma display, a copper circuit is formed by etching a deposited copper film of several thousand to several μm on a silicon substrate or a glass substrate.

  So far, aqueous solutions of ferric chloride, cupric chloride, etc. have been used as copper etchants, but these are for etching thick copper foils, and at concentrations where these etchants were conventionally used. When the copper thin film is etched, the etching is completed in a very short time, so that it is difficult to manage the circuit width dimension.

  Therefore, as a method of delaying etching, there are methods such as lowering the temperature and lowering the spray pressure, but none of them is sufficient because the circuit cross-sectional shape is deteriorated.

  In addition, there is a method of reducing the concentration of the etchant, but this method reduces the relative speed of etching between circuits, and in several parallel circuits, the outer circuit becomes thin and the side etching width increases. End up.

  In addition, the etching resist is eroded, the copper of the anchor part between the circuits (the part where the copper surface is made uneven to enter the resin layer to increase the adhesion strength) is likely to remain, and the accuracy of concentration management by specific gravity decreases. This causes problems.

  From this background, in Patent Document 1, ferric sulfate having a low copper etching ability is used as an active ingredient in etching liquid, and in Patent Document 2, copper non-corrosive inorganic salt is added to an etching liquid containing ferric chloride as an active ingredient. It was added to slow the etching rate.

  In addition, the control of these etching solutions measures the oxidation-reduction potential, and when the number of treatments per hour is large and the oxidation-reduction potential is lowered, ferric chloride or ferric sulfate is replenished, and the number of treatments is small. When oxidation precedes oxidation-reduction potential, ferrous chloride, ferrous sulfate, etc. are replenished.

JP 11-256368 A JP 2000-248386 A

  However, Patent Document 1 or Patent Document 2 uses a replenisher solution for lowering the oxidation-reduction potential and a replenisher solution for increasing the oxidation-reduction potential, assuming fluctuations in the processing amount. Since the ratio of ferrous chloride, ferrous sulfate, etc. to hydrochloric acid, sulfuric acid, etc. in the replenisher solution to reduce the amount is one-component replenishment, processing with extremely small etching ratios, spray conditions for etching equipment, etc. Excessive replenishment caused a problem that the specific gravity of the etching solution decreased and the metal concentration after replenishment changed, and it was difficult to maintain a stable etching rate.

  Accordingly, an object of the present invention is to provide an etching replenisher that does not cause a problem of change in etching rate in etching a copper thin film, and a copper thin film etching method using the same.

  The present inventors have reached the present invention as a result of intensive studies in view of the above. That is, the present invention is a salt of a metal that can form a compound having a copper etching ability and can take a plurality of oxidation numbers, and the metal having an oxidation number lower than the oxidation number in the metal constituting the compound having a copper etching ability And (I) :( II) = 5: 1 to 45: 1 (weight ratio) It is a copper etching replenisher characterized by being in the range.

  Further, the present invention is a metal salt that can take a plurality of oxidation numbers, and uses an etching solution containing a compound having copper etching ability and an acid having an anion of the anion of the salt as an essential component. When etching a copper thin film, the copper etching replenisher of the present invention and an acid corresponding to the acid (II) are replenished to the etchant (preferably, the oxidation-reduction potential of the etchant is measured and the measurement result is Based on the acid (II), the copper etch replenisher of the present invention is replenished to the etchant so as to keep the oxidation-reduction potential of the etchant constant, and the hydrogen ion concentration of the etchant is kept constant. A copper thin film etching method characterized in that the corresponding acid is supplied to the etching solution).

  An effect of the present invention is to provide an etching replenisher that does not cause a problem of change in etching rate due to air oxidation in etching a copper thin film, and a copper thin film etching method using the same.

  A metal salt that can form a compound having a copper etching ability and that can form a compound having a plurality of oxidation numbers, which is used in the copper etching replenisher of the present invention, and the oxidation number of the metal that forms the compound having a copper etching ability The metal salt (I) having a lower oxidation number corresponds to a metal salt having a lower oxidation number because the etching active component in the copper etchant is consumed and reduced by the copper etching. Copper can be exemplified, and examples of the anion constituting the salt include chloride ion, sulfate group, phosphate group and the like.

  Preferred compounds as such salt (I) are ferrous chloride, cuprous chloride, ferrous sulfate and the like.

  The acid (II) used in the copper etching replenisher of the present invention may be any acid having an acid group as the anion of the salt (I), and examples thereof include hydrochloric acid, sulfuric acid, and phosphoric acid.

  The salt (I) and acid (II) in the copper etching replenisher of the present invention should be 5: 1 to 45: 1 (weight ratio), preferably 20: 1 to 30: 1.

  If the ratio of the salt (I) is too small (the ratio of the acid (II) is too large), the hydrogen ion concentration increases, the specific gravity decreases due to excessive supply of the acid (II) when replenishing the etching solution, The etching speed is reduced. That is, the etching replenisher according to the present invention is used together with an acid corresponding to acid (II) supplied separately from the replenisher as described later, so that the ratio of the acid (II) in the replenisher is too large. This is because the hydrogen ion concentration cannot be controlled by separately supplying an acid corresponding to the acid (II) to the etching solution.

  On the other hand, if the amount of salt (I) is too large, the etching rate is reduced due to crystal precipitation. Further, when the acid (II) is extremely small, the salt (I) cannot be stably dissolved in the aqueous solution.

  The copper etching replenisher of the present invention is an aqueous solution containing these, and other additives can be added as desired within a range that does not impair the effects of the present invention. For example, a chloride ion releasing salt that improves the dissolution rate of copper (when using metal chloride as the salt (I)), and a sulfate ion releasing salt (using metal sulfate as the salt (I)) And the like, and amines for improving etching performance, surfactants for improving wettability, and detergents for metal surfaces.

  Next, the copper thin film etching method of the present invention will be described.

  The etching solution used in the present invention is a metal salt that can take a plurality of oxidation numbers and is an aqueous solution containing a compound having copper etching ability as an active ingredient. Examples of the metal constituting the salt which is an active ingredient include iron and copper, and examples of the anion constituting the salt include chloride ion, sulfate radical, phosphate radical and the like.

  Preferred compounds as an active ingredient of such an etching solution are ferric chloride, cupric chloride, ferric sulfate and the like.

  The concentration of the active ingredient in these etching solutions is not particularly limited and may be in the same range as that of conventional etching solutions. For example, the concentration is 1 to 25% by mass, preferably about 2 to 15% by mass with respect to the entire etching solution. It is good to do.

  In addition, a small amount of acid corresponding to the acid (II) may be added to the etching solution used in the present invention in order to prevent the formation of hydroxide, and is generally 0.05 to 5% by mass, preferably What is necessary is just about 0.1-3 mass%.

  In the etching solution used in the present invention, a chloride ion-releasing salt (a metal chloride is used as the salt (I), which improves the dissolution rate of copper, as desired, as long as the effect of the present invention is not adversely affected. Case), sulfate radical ion releasing salt (when using metal sulfate as salt (I)), etc., amines for improving etching performance, surfactant for improving wettability And metal surface cleaners.

  The copper thin film etching method of the present invention etches a copper thin film using the etching solution as described above, but the etching may be performed by either an immersion method or a spray method, and the temperature of the etching solution is not particularly limited and is desired. However, the temperature is generally 10 to 70 ° C., and is practically 20 to 50 ° C. in view of the material of the apparatus, the etching rate, the difficulty of control, and the like. For example, when etching is performed using a spray method, the pressure is preferably about 0.02 to 0.4 PMa, for example, but preferably 0.05 to 0.2 MPa in terms of maintenance of the apparatus. .

  The thickness of the copper thin film etched according to the present invention is preferably 0.1 to 8 μm, for example.

  The copper thin film etching method of the present invention replenishes the etching solution with the copper etching replenisher of the present invention and the acid corresponding to the acid (II) when the copper thin film is etched using the above etching solution. Preferably, the oxidation-reduction potential of the etching solution is measured, and based on the measurement result, the copper etching replenisher of the present invention is replenished to the etching solution so as to keep the oxidation-reduction potential of the etching solution constant, and An acid corresponding to the acid (II) is supplied to the etching solution so as to keep the hydrogen ion concentration of the etching solution constant.

  That is, there are two factors that change the oxidation-reduction potential in the etching solution. One is that an active etching component, for example, ferric chloride (which will be described as an example of ferric chloride hereinafter) reacts with copper and is consumed as ferric ions change into ferrous ions as etching progresses. This is a reduction in the redox potential.

  Another factor is an increase in oxidation-reduction potential due to the etching solution being subjected to air oxidation. When etching is performed by a spray method, etc., for example, when ferrous ions are oxidized by oxygen in the air and changed to ferric ions due to spraying of the spray, the ratio of ferric ions becomes too large and redox The potential increases.

Further, such air oxidation proceeds by the reaction of the following formula.
4FeCl ₂ + O ₂ + 4HCl → 4FeCl ₃ + 2H ₂ O
(Here, the hydrochloric acid on the left side is the hydrochloric acid when a small amount of hydrochloric acid is added to the etching solution to prevent the formation of the hydroxide and improve the etching rate immediately after the start of etching, otherwise ferric chloride is decomposed. (Hydrochloric acid produced or supplied hydrochloric acid)
Since the copper thin film to be etched of the present invention has an extremely small amount of copper to be etched, the above-described factors that lower the oxidation-reduction potential are offset by the factors that increase the oxidation-reduction potential of the etching solution. Rise.

  In response to this increase in the oxidation-reduction potential, the oxidation-reduction potential of the etching solution can be controlled by supplying an aqueous ferrous chloride solution to the etching solution. That is, when the oxidation-reduction potential exceeds the set value, the copper etching replenisher of the present invention is supplied to the etching solution to lower the oxidation-reduction potential, and the supply may be stopped when the oxidation-reduction potential reaches the set value.

  Here, in order to know the change of the redox potential, the redox potential may be measured by a known method, and a commercially available redox electrode can be used.

  In the etching method of the present invention, the specific value of the oxidation-reduction potential that is set to be kept constant varies depending on the material to be etched, the desired etching rate, and the etching environment. The potential may be obtained and set in advance.

  Further, one of the factors that change the hydrogen ion concentration in the etching solution is that hydrochloric acid is consumed during air oxidation as described above, and the other factor is evaporation. The same applies to hydrochloric acid, which is a volatile acid, as well as to sulfuric acid or phosphoric acid, although to a different extent.

  Therefore, in the present invention, an acid corresponding to the acid (II) is also replenished so as to keep the hydrogen ion concentration of the etching solution constant.

  Here, since the copper etching replenisher of the present invention contains the acid (II) as described above, the acid corresponding to the acid (II) supplied so as to keep the hydrogen ion concentration of the etching liquid constant. Some of these are already replenished by the copper etching replenisher of the present invention, but as described above, the factors that change the hydrogen ion concentration in the etchant are independent of that of the oxidation-reduction potential. Therefore, in order to finally control the total amount of acid supplied to the etching solution, the acid (II) is used to keep the hydrogen ion concentration of the etching solution constant, in addition to the copper etching replenisher of the present invention. It is necessary to supply an acid corresponding to.

  In order to keep the hydrogen ion concentration constant, for example, the pH may be measured by a pH meter using a pH electrode. Preferably, the potential (electromotive force or potential difference) at the pH electrode is measured, and the etching solution When the potential falls below the set value, the acid corresponding to the acid (II) is supplied to increase the potential, and when the pH electrode potential reaches the set value, the supply may be stopped.

  In the etching method of the present invention, the specific value of the potential at the pH electrode that is set to be constant varies depending on the material to be etched, the desired etching rate, and the etching environment. The potential at the electrode may be obtained in advance and set.

  In addition, in the etching method of the present invention, when supplying an acid corresponding to the acid (II), other additives can be added as desired within a range that does not impair the effects of the present invention as in the case of the replenishing solution. A small amount of the salt corresponding to the salt (I) can be blended, but in this case, since it affects the redox potential, it does not affect the control of the redox potential by supplying the copper etchant replenisher. It needs to be about.

  In the copper thin film etching method of the present invention, moisture may be lost due to evaporation depending on the etching conditions. In that case, if desired, water may be supplied to the etching solution based on the measurement result of the specific gravity of the etching solution to remove the etching solution. A means for controlling the specific gravity may be provided.

  EXAMPLES Examples of the present invention will be described below to further explain the present invention, but the present invention is not limited to these.

(Example 1)
A specific gravity measuring means and means for supplying water based on the result to an etcher having an effective etching length of 900 mm and a liquid holding amount of 800 liters, a means for measuring the oxidation-reduction potential and supplying the replenisher according to the result, and The pH electrode potential was measured, and a means for supplying hydrochloric acid based on the result was connected.

  The substrate to be etched is COF 160 mm × 100 m, the copper thin film thickness is 5 μm, and the etching ratio is 30%. As the etching resist, a dry film having a thickness of 8 μm was used. The line width / line spacing is 13 μm / 7 μm. The replenisher for keeping the oxidation-reduction potential of the etching solution constant was an aqueous solution having a ferrous chloride concentration of 25 mass%, a sodium chloride concentration of 1.0 mass%, and a hydrochloric acid concentration of 1.0 mass%. The hydrochloric acid was a hydrochloric acid aqueous solution having a concentration of 15% by mass.

An etching solution in which 25 g / liter of copper was dissolved in an aqueous solution having a ferric chloride concentration of 12 mass%, a sodium chloride concentration of 1.0 mass%, and a hydrochloric acid concentration of 1.3 mass% was charged into an etcher tank. The etching solution was heated to 35 ° C., the spray pressure was 0.5 kg / cm ² , and the conveyor speed was 2.1 m / min.

  The specific gravity control set value was 1.135, water was automatically supplied when the specific gravity exceeded the set value, and the water supply was stopped when the specific gravity was below the set value.

  The control setting value of the oxidation-reduction potential was set to 420 mV, and the replenisher was automatically supplied when the oxidation-reduction potential exceeded the control setting value, and the supply was stopped when it became equal to or lower than the control setting value.

  The set value of the pH electrode potential was set to 460 mV, hydrochloric acid was automatically supplied when the pH electrode potential fell below the control set value, and the supply was stopped when the set value exceeded the control set value.

  When the substrate 3000 m was processed, the analysis and measurement results of the etching solution were as shown in Table 1 below. It turns out that it is controlled with high precision. Resist erosion and deformation were not observed, the cross-sectional shape was normal, there was no copper residue between circuits, and no defective products related to etching were generated. The finished line width was 10-12 μm. There were 125 liters of replenisher and 5 liters of hydrochloric acid supplied during this period.

(Example 2)
The same apparatus and etching target as in Example 1 were used, except that an aqueous solution having a ferrous sulfate concentration of 25% by mass and a sulfuric acid concentration of 1.0% by mass was used as a replenishing solution, and 15% by mass in place of hydrochloric acid. Using an sulfuric acid, an etchant prepared by dissolving 15 g / l of copper in an aqueous solution having a ferric sulfate concentration of 14% by mass and a sulfuric acid concentration of 1.0% by mass is charged into an etcher tank, and the specific gravity control setting value is 1.200. The control set value for the oxidation-reduction potential was 450 mV, and the set value for the pH electrode potential was 420 mV.

  The measurement results are as shown in Table 2 below, and it can be seen that the measurement is accurately controlled. Resist erosion and deformation were not observed, the cross-sectional shape was normal, there was no copper residue between circuits, and no defective products related to etching were generated. The finished line width was 10-12 μm. During this time, the replenisher supplied was 220 liters and sulfuric acid aqueous solution 5 liters.

(Example 3)
The same apparatus and etching target as in Example 1 were used, except that an aqueous solution having a cuprous chloride concentration of 25% by mass and a hydrochloric acid concentration of 1.0% by mass was used as the replenisher, and the hydrochloric acid was the same as in Example 1. An aqueous hydrochloric acid solution having a concentration of 15% by mass was used, and an etchant prepared by dissolving 20 g / l of copper in an aqueous solution having a cupric chloride concentration of 20% by mass and a hydrochloric acid concentration of 9.0% by mass was charged into an etcher tank. The control setting value of 1.21 was set to 1.121, and the control setting value of the oxidation-reduction potential was set to 400 mV.

  The measurement results are as shown in Table 3 below, and it can be seen that the measurement is accurately controlled. Resist erosion and deformation were not observed, the cross-sectional shape was normal, and some copper was observed between the circuits, but no defective product related to etching was generated. The finished line width was 7-8 μm. During this time, the replenisher supplied was 180 liters and hydrochloric acid 42 liters.

(Example 4)
The same apparatus and etching target as in Example 1 were used, except that the same ferrous chloride concentration as in Example 1 was 25% by mass, sodium chloride concentration was 1.0% by mass, and hydrochloric acid concentration was 1.0% by mass. An aqueous solution having a hydrochloric acid concentration of 15% by mass containing 1.5% by mass of ferrous chloride was used instead of 15% by mass of hydrochloric acid, a ferric chloride concentration of 12% by mass, and a sodium chloride concentration of 1 An etching solution prepared by dissolving 25 g / l of copper in an aqueous solution having a mass concentration of 0.0 mass% and a hydrochloric acid concentration of 1.3 mass% is charged into an etcher tank, the control setting value of specific gravity is set to 1.135, and the control setting value of oxidation-reduction potential is set to It implemented similarly to Example 1 by setting 420 mV and the set value of pH electrode potential to 460 mV.

  The measurement results are as shown in Table 4 below, and it can be seen that the measurement is accurately controlled. Resist erosion and deformation were not observed, the cross-sectional shape was normal, there was no copper residue between circuits, and no defective products related to etching were generated. The finished line width was 10-12 μm. The replenisher supplied during this period was 124 liters, and hydrochloric acid containing a small amount of ferrous chloride was 5 liters.

(Comparative Example 1)
The same apparatus and etching target as in Example 1 were used except that an aqueous solution having a ferrous chloride concentration of 25.0% by mass, a sodium chloride concentration of 1.0% by mass and a hydrochloric acid concentration of 10.0% by mass was used as the replenisher. Otherwise, the same procedure as in Example 1 was performed. That is, hydrochloric acid is an aqueous hydrochloric acid solution having a concentration of 15% by mass, and 25 g / liter of copper is added to the aqueous solution having a ferric chloride concentration of 12% by mass, a sodium chloride concentration of 1.0% by mass and a hydrochloric acid concentration of 1.3% by mass. The dissolved etching solution was charged into an etcher tank, the etching solution was heated to 35 ° C., the spray pressure was 0.5 kg / cm ² , and the conveyor speed was 2.1 m / min.

  The specific gravity control set value was 1.135, the redox potential control set value was 420 mV, and the pH electrode potential set value was 460 mV.

  The measurement results are shown in Table 5 below. The ratio of hydrochloric acid in the replenisher was large, the pH electrode potential increased uniformly, and the specific gravity decreased accordingly. For this reason, circuit narrowing due to etching rate change (decrease) occurred. The finished line width was 6-12 μm. The replenisher supplied during this period was 820 liters. Since the pH electrode potential increased uniformly, hydrochloric acid was not supplied to the etching solution.

Claims (3)

A salt of a metal that can form a compound having a copper etching ability and that can take a plurality of oxidation numbers, and has a lower oxidation number than that of the metal that constitutes the compound having a copper etching ability (I) And an acid (II) whose anion is an anion of the salt thereof as an essential component, and (I) :( II) = 5: 1 to 45: 1 (weight ratio) Characteristic copper replenisher. Etching a copper thin film using an etching solution containing a metal salt capable of taking a plurality of oxidation numbers and having copper etching ability and an acid having an anion of the anion of the salt as an essential component At this time, a copper etching replenisher according to claim 1 and an acid corresponding to the acid (II) are replenished to the etchant. The copper oxide replenisher according to claim 1 is replenished to the etchant so as to keep the redox potential of the etchant constant based on the measurement result of the redox potential of the etchant. The copper thin film etching method according to claim 2, wherein an acid corresponding to the acid (II) is replenished to the etching solution so as to keep the hydrogen ion concentration constant.