JP2010095761A - Copper electroplating method using insoluble anode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper electroplating method using an insoluble anode which suppresses the increase in the concentration of dissolved oxygen so as to suppress the decomposition of an additive. <P>SOLUTION: The copper electroplating method using an insoluble anode is characterized in that, when a copper sulfate plating liquid is replenished with copper oxide as a copper source, a carbonate compound is added to the plating liquid, so as to generate carbon dioxide, and dissolved oxygen is exhausted from the plating liquid by the carbon dioxide. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolytic copper plating method using an insoluble anode capable of suppressing an increase in dissolved oxygen in a plating solution.

Electrolytic copper plating is widely used when copper wiring of a wiring board is formed by plating. In the case of electrolytic copper plating, the case where a soluble anode is used as the anode has been the mainstream, but since the liquid management is easy, the case where an insoluble anode is used is also increasing.
When an insoluble anode is used, the copper concentration in the liquid decreases because there is no copper dissolution from the anode. Therefore, it is necessary to replenish copper components such as copper oxide (2).

By the way, in the case of electrolytic copper plating, oxygen is generated at the anode by the electrode reaction, and dissolved oxygen increases as this dissolves in the plating solution. When the dissolved oxygen in the copper plating solution increases, there are various adverse effects (Japanese Patent Laid-Open No. 2007-169700).
As dissolved oxygen increases in the copper plating solution as described above, there are various adverse effects. Therefore, in Patent Document 1, the amount of dissolved oxygen in the electrolytic copper plating solution is obtained by stirring the plating solution with air or stirring with an inert gas. Is maintained at 30 mg / L or less.
JP 2007-169700 A

By the way, in the case of copper sulfate plating using an insoluble anode, when copper oxide is replenished as a copper component, copper oxide and sulfuric acid in the plating solution react to produce copper sulfate and water. In some cases, the dissolved oxygen in the plating solution increases. When copper oxide is added to the copper plating solution, additives such as brighteners added to the plating solution are decomposed. An increase in dissolved oxygen accelerates the decomposition of these additives. As a result, the balance of the additives is lost, and there is a problem that defective plating occurs.
Therefore, the present invention has been made to solve the above-mentioned problems, and the object of the present invention is to perform an electrolysis using an insoluble anode capable of suppressing an increase in dissolved oxygen concentration and suppressing decomposition of an additive in copper sulfate plating. To provide a copper plating method.

In the electrolytic copper plating method using the insoluble anode according to the present invention, when copper oxide is replenished as a copper source to the copper sulfate plating solution, a carbonic acid compound is added to the plating solution to generate carbon dioxide gas. Dissolved oxygen is discharged from the plating solution by a gas.
Moreover, it is good to add a copper oxide and a carbonic acid compound to a plating solution, to make it circulate, and to supply in an electrolytic vessel in the adjustment tank connected with the electrolytic vessel in which the copper sulfate plating solution is accommodated.
As the carbonic acid compound, one that generates carbon dioxide gas when added to an electrolytic copper plating solution, such as copper carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, or the like is used. Among these carbonate compounds, copper carbonate capable of replenishing copper at the same time was suitable.
Note that copper carbonate alone as a copper supply source is not preferable because copper carbonate has many impurities, and is added in combination with copper oxide having high purity.
The addition amount of the carbonic acid compound is preferably at least 1 mol% with respect to the copper oxide.

  According to the electrolytic copper plating method using the insoluble anode according to the present invention, when copper oxide is replenished as a copper source in copper sulfate plating, an increase in dissolved oxygen concentration can be suppressed and decomposition of the additive can be suppressed. There is an effect.

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
As described above, when only copper oxide (2) is added to the copper sulfate plating solution as a copper source supplement, CuO reacts with free sulfuric acid in the plating solution to become copper sulfate and water.
CuO + H ₂ SO ₄ → CuSO ₄ + H ₂ O
During this dissolution reaction, dissolved oxygen rises. The additive component in the plating solution reacts with this oxygen and is oxidized, losing its original function. As a result, the balance of the additives is lost and a defect occurs in the plating process.

  In this embodiment, when copper oxide (2) is replenished, a small amount of a compound that generates carbon dioxide in the plating solution is added together. The generated carbon dioxide gas discharges oxygen generated by dissolution of copper oxide (2) from the plating solution and suppresses decomposition of the additive.

A composition example of the copper sulfate plating solution is shown below.
Copper sulfate 50 ~ 300g / L
Sulfuric acid 10 ~ 200g / L
Chloride ion 5-60ppm
Other Additives As other additives, there are brighteners that promote the electrodeposition effect, levelers that suppress the electrodeposition effect of the convex portions, and polymers composed of nonionic surfactants. When the dissolved oxygen in the copper plating solution increases, these additives are decomposed and the original function is lowered.

Examples of the carbonic acid compound that is added together with copper oxide to generate carbon dioxide include copper carbonate, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like.
Of these, copper carbonate can be supplied, so copper carbonate supply is more desirable.
The carbonic acid compound may be added simultaneously with the addition of copper oxide or before and after the addition of copper oxide.

Copper carbonate (CuCO ₃ ) reacts with sulfuric acid to generate carbon dioxide gas.
CuCO ₃ + H ₂ SO ₄ → CuSO ₄ + CO ₂ + H ₂ O
When copper carbonate is added together (at the same time or before and after addition of copper oxide) when copper oxide (2) is replenished, oxygen generated from the copper oxide is discharged from the plating solution by the generation of carbon dioxide gas.
Thereby, consumption of the additive can be suppressed.
The amount of copper carbonate added is preferably 1 mol% or more of the added copper oxide (2).

Sodium carbonate (Na ₂ CO ₃ ) reacts with sulfuric acid to generate carbon dioxide gas.
Na ₂ CO ₃ + H ₂ SO ₄ → Na ₂ SO ₄ + CO ₂ + H ₂ O
When sodium carbonate is added together with copper oxide (2) at the same time (at the same time or before and after addition of copper oxide), oxygen generated from the copper oxide is discharged from the plating solution by the generation of carbon dioxide gas.
Thereby, consumption of the additive can be suppressed.
The amount of sodium carbonate added is preferably 1 mol% or more of the added copper oxide.

Potassium bicarbonate (KHCO ₃ ) reacts with sulfuric acid to generate carbon dioxide (so is sodium bicarbonate).
KHCO ₃ + H ₂ SO ₄ → K ₂ SO ₄ + H ₂ O + CO ₂ (gas)
When potassium hydrogen carbonate is added together (at the same time or before and after addition of copper oxide) at the time of copper oxide (2) replenishment, oxygen generated from the copper oxide is discharged from the plating solution by the generation of carbon dioxide gas.
Thereby, consumption of the additive can be suppressed.
The amount of potassium bicarbonate added is preferably 1 mol% or more of the added copper oxide.

<Comparative example>
1) A 1.2 mol / L sulfuric acid aqueous solution was prepared instead of the copper sulfate plating solution. When dissolved oxygen in this sulfuric acid aqueous solution was measured, 8 mg / L of dissolved oxygen was detected.
2) After about 5 minutes, 0.6 mol copper oxide (2) was added. As a result, dissolved oxygen increased with the dissolution of copper oxide (2) (FIG. 1).
Consumption of the additive component was confirmed.

<Example 1>
1) A 1.2 mol / L sulfuric acid aqueous solution was prepared instead of the copper sulfate plating solution. When dissolved oxygen in this sulfuric acid aqueous solution was measured, 8 mg / L of dissolved oxygen was detected.
2) After about 5 minutes, 0.6 mol copper oxide (2) and 0.03 mol copper carbonate were added.
As a result, an increase in dissolved oxygen during dissolution of copper oxide (2) could be suppressed (FIG. 2).

<Example 2>
1) A 1.2 mol / L sulfuric acid aqueous solution was prepared instead of the copper sulfate plating solution. When dissolved oxygen in this sulfuric acid aqueous solution was measured, 8 mg / L of dissolved oxygen was detected.
2) After about 5 minutes, 0.6 mol copper oxide (2) and 0.03 mol sodium carbonate were added. As a result, when copper oxide (2) was dissolved, an increase in dissolved oxygen could be suppressed (FIG. 3).

<Example 3>
1) A 1.2 mol / L sulfuric acid aqueous solution was prepared instead of the copper sulfate plating solution. When dissolved oxygen in this sulfuric acid aqueous solution was measured, 8 mg / L of dissolved oxygen was detected.
2) After about 5 minutes, 0.6 mol copper oxide (2) and 0.03 mol potassium hydrogen carbonate were added. As a result, when copper oxide (2) was dissolved, an increase in dissolved oxygen could be suppressed (FIG. 4).

It is a graph which shows the dissolved oxygen concentration change in a comparative example. 2 is a graph showing changes in dissolved oxygen concentration in Example 1. 6 is a graph showing changes in dissolved oxygen concentration in Example 2. 6 is a graph showing changes in dissolved oxygen concentration in Example 3.

Claims (2)

In the electrolytic copper plating method using an insoluble anode,
When copper oxide is replenished as a copper source to a copper sulfate plating solution, a carbonic acid compound is added to the plating solution to generate carbon dioxide, and dissolved oxygen is discharged from the plating solution by the carbon dioxide gas. Electrolytic copper plating method using a soluble anode.   2. The electrolytic copper plating method using an insoluble anode according to claim 1, wherein copper carbonate is added as a carbonate compound.

Images