JP2010138429A - Electrolytic copper plating method using insoluble anode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, in a conventional electrolytic copper plating method using an insoluble anode, it is difficult to suppress an rapid increase of the dissolved oxygen concentration in an electrolytic copper plating solution caused by supplying copper oxide (II) as a copper source. <P>SOLUTION: When electrolytic copper plating using an insoluble anode is applied to an object to be plated immersed in an electrolytic copper plating solution into which copper sulfate is added, copper oxide is replenished as a copper source to the electrolytic copper plating solution, and at that time, iron (II) sulfate is added to the electrolytic copper plating solution in order to suppress the dissolved oxygen concentration in the electrolytic copper plating solution, that increases by the supply of copper oxide (II). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolytic copper plating method using an insoluble anode, and more specifically, an insoluble anode in which electrolytic copper plating is performed using an insoluble anode on a plating object immersed in an electrolytic copper plating solution to which copper sulfate is added. The present invention relates to an electrolytic copper plating method.

Electrolytic copper plating using an electrolytic copper plating solution to which copper sulfate is added has been widely adopted for the formation of wiring patterns on wiring boards.
Conventionally, in such electrolytic copper plating, a soluble anode has been used as the anode, but the use of an insoluble anode that facilitates plating solution management and the like has also increased.
In electrolytic copper plating using such an insoluble anode, there is no replenishment of copper due to dissolution of the soluble anode, so the copper concentration in the electrolytic copper plating solution decreases. Therefore, it is necessary to replenish the electrolytic copper plating solution with a copper component such as copper (II) oxide.

By the way, in electrolytic copper plating using an insoluble anode, dissolved oxygen increases as oxygen generated at the anode by electrode reaction dissolves in the electrolytic copper plating solution. When such dissolved oxygen increases in the electrolytic copper plating solution, there are adverse effects such as oxidation of additives added to the electrolytic copper plating solution.
For this reason, the following Patent Document 1 proposes an electrolytic copper plating method for maintaining the dissolved oxygen concentration in the electrolytic copper plating solution at 30 mg / L or less by stirring the electrolytic copper plating solution with air or stirring with an inert gas. .
JP 2007-169700 A

According to the electrolytic copper plating method proposed in the aforementioned Patent Document 1, it is possible to suppress an increase in dissolved oxygen concentration in the electrolytic copper plating solution due to oxygen generated during electrolytic copper plating.
However, according to the study by the present inventor, it has been found that the dissolved oxygen concentration in the electrolytic copper plating solution also increases when copper (II) oxide is supplied to the electrolytic copper plating solution as a copper source. The increase in dissolved oxygen in the electrolytic copper plating solution due to the replenishment of copper (II) oxide is abrupt, and it cannot be completely suppressed by stirring the ordinary electrolytic copper plating solution, and dissolved oxygen in the electrolytic copper plating solution. High concentration continues. For this reason, the oxidation of additives such as brighteners added in the electrolytic copper plating solution proceeds, the balance of the additives in the electrolytic copper plating solution is lost, and plating failure may occur.
Therefore, the present invention uses a conventional insoluble anode in which it is difficult to suppress the state where the dissolved oxygen concentration in the electrolytic copper plating solution generated by replenishing the electrolytic copper plating solution with copper (II) oxide as a copper source is rapidly increased. An insoluble anode that can suppress the state of rapidly increasing the dissolved oxygen concentration in the electrolytic copper plating solution when the electrolytic copper plating solution is solved and copper (II) oxide as the copper source is replenished to the electrolytic copper plating solution It is in providing the used electrolytic copper plating method.

As a result of repeated investigations to solve the above problems, the present inventor replenished electrolytic copper plating solution using an insoluble anode with copper (II) oxide as a copper source and added iron sulfate. The present inventors have found that a rapid increase in the dissolved oxygen concentration in the copper plating solution can be suppressed, and have reached the present invention.
That is, in the present invention, when subjecting a plating object immersed in an electrolytic copper plating solution added with copper sulfate to electrolytic copper plating using an insoluble anode, copper oxide is used as a copper source for the electrolytic copper plating solution. In order to suppress the dissolved oxygen concentration that increases in the electrolytic copper plating solution due to the replenishment of the copper oxide, a metal element belonging to the group VIII iron group element of the periodic table is added to the electrolytic copper plating solution. Is added to the electrolytic copper plating solution in the electrolytic copper plating method using an insoluble anode.
In the present invention, by adding a metal element added to the electrolytic copper plating solution to the electrolytic copper plating solution as a sulfate or a hydrate thereof, a sulfite or a chloride salt, an iron group element is contained in the electrolytic copper plating solution. Metal element ions belonging to can be present.
As the metal element added to the electrolytic copper plating solution, iron, nickel, or cobalt can be suitably used.

According to the electrolytic copper plating method using the insoluble anode according to the present invention, when copper (II) oxide is replenished as a copper source to the electrolytic copper plating solution to which copper sulfate is added, the dissolved oxygen concentration is rapidly increased. Even if the increase is suppressed or the dissolved oxygen concentration is increased, it can be rapidly decreased and decomposition of the additive can be suppressed.
As a result, the oxidation of additives such as brighteners added in the electrolytic copper plating solution proceeds, and the balance of the additives in the electrolytic copper plating solution may be lost, resulting in poor plating. Can be eliminated.

  As an electrolytic copper plating solution used in the present invention, for example, an electrolytic copper plating solution having a composition shown in Table 1 below can be raised.

その他添加剤としては、電析作用を促進するブライトナー、凸部の電析作用を抑制するレベラー、非イオン界面活性剤からなるポリマー等を上げることができる。
かかる電解銅めっき液に、銅源の補給として酸化銅(II)のみを添加すると、下記化１に示す様に、CuOは電解銅めっき液中の遊離硫酸と反応し、硫酸銅と水になる。

Examples of other additives include a brightener that promotes the electrodeposition effect, a leveler that suppresses the electrodeposition effect of the convex portion, and a polymer composed of a nonionic surfactant.
When only copper (II) oxide is added to the electrolytic copper plating solution as a copper source, CuO reacts with free sulfuric acid in the electrolytic copper plating solution to form copper sulfate and water, as shown in the following chemical formula 1. .

  During the dissolution reaction of copper (II) oxide, the concentration of dissolved oxygen in the electrolytic copper plating solution increases rapidly, and additive components such as brighteners in the electrolytic copper plating solution are oxidized and lose their original function. For this reason, the balance of the additive in the electrolytic copper plating solution may be lost, and there may be a problem in the plating process.

In this regard, in the present invention, before and after adding copper (II) oxide as a copper source supplement to the electrolytic copper plating solution, by adding a metal element belonging to the Group VIII iron group element of the periodic table, During the dissolution reaction of copper (II) oxide, a rapid increase in the dissolved oxygen concentration in the electrolytic copper plating solution can be suppressed, or even if the dissolved oxygen concentration is increased, it can be rapidly lowered. For this reason, the oxidative decomposition of the additive in the electrolytic copper plating solution can be suppressed, and the balance of the additive in the electrolytic copper plating solution can be maintained.
Thus, before and after adding copper oxide (II), by adding a metal element belonging to the group VIII iron group element of the periodic table, the concentration of dissolved oxygen in the electrolytic copper plating solution is rapidly increased. The suppression can be attributed to the fact that ions of metal elements belonging to Group VIII iron group elements of the periodic table in the electrolytic copper plating solution react with dissolved oxygen in the electrolytic copper plating solution.

As the metal element belonging to the Group VIII iron group element of the periodic table, iron, nickel or cobalt can be preferably used. In particular, iron can be preferably used.
Moreover, it is preferable to add as a metal element added to an electrolytic copper plating solution in the form which ionizes easily in an electrolytic copper plating solution. As such a form, sulfate or its hydrate, sulfite, or chloride salt can be raised.
The metal element belonging to the Group VIII iron group element of the periodic table is preferably added simultaneously with the addition of copper (II) oxide, but from 5 minutes before the addition of copper (II) oxide to copper (II) oxide. It can be added within a period of up to 5 minutes after addition.
The amount of the metal element added is 0.05 mol% or more, preferably about 0.01 to 10.0 mol%.
Even if a metal element belonging to the Group VIII iron group element of the periodic table is added to the electrolytic copper plating solution, there is an adverse effect such that the added metal element is deposited on the plating object or deposited on the anode. I can't.

Instead of the electrolytic copper plating solution to which copper sulfate was added, a 1.2 mol / L sulfuric acid aqueous solution was prepared. When dissolved oxygen in this sulfuric acid aqueous solution was measured, about 7.5 mg / L of dissolved oxygen was detected.
Next, 0.006 mol of iron (II) sulfate heptahydrate was added to the sulfuric acid aqueous solution, and then 0.1 mol of copper (II) oxide was added, and the change over time in the dissolved oxygen concentration was measured. The result is shown in FIG.
As is apparent from FIG. 1, it is possible to suppress an increase in dissolved oxygen concentration that occurs when copper (II) oxide is dissolved.

In Example 1, in place of iron (II) sulfate heptahydrate, cobalt mol (II) sulfate heptahydrate was used in the same manner as in Example 1, except that 0.1 mol of copper oxide ( II) was added and the time course of dissolved oxygen concentration was measured. The result is shown in FIG.
As is apparent from FIG. 2, the dissolved oxygen concentration increases rapidly when copper (II) oxide is dissolved, but the dissolved oxygen concentration rapidly decreases.

Comparative example

In Example 1, 0.1 mol of copper (II) oxide was added without adding iron (II) sulfate heptahydrate, and the change with time in the dissolved oxygen concentration was measured. The result is shown in FIG.
As is apparent from FIG. 3, the dissolved oxygen concentration rapidly increases when the copper (II) oxide is dissolved, and the state where the dissolved oxygen concentration is increased is maintained for a while.

2 is a graph showing the change with time of the dissolved oxygen concentration in Example 1. FIG. 6 is a graph showing the change with time of the dissolved oxygen concentration in Example 2. It is a graph which shows a time-dependent change of the dissolved oxygen concentration of a comparative example.

Claims (3)

When applying electrolytic copper plating to an object to be plated immersed in an electrolytic copper plating solution to which copper sulfate has been added using an insoluble anode,
Copper oxide is replenished as a copper source to the electrolytic copper plating solution, and at that time, in order to suppress the dissolved oxygen concentration that increases in the electrolytic copper plating solution by replenishing the copper oxide, the electrolytic copper plating solution is cycled. An electrolytic copper plating method using an insoluble anode, characterized in that a metal element belonging to the group VIII iron group element of the table is added to the electrolytic copper plating solution.   The electrolytic copper plating method using the insoluble anode according to claim 1, wherein the metal element added to the electrolytic copper plating solution is added to the electrolytic copper plating solution as a sulfate or a hydrate thereof, a sulfite or a chloride salt.   The electrolytic copper plating method using the insoluble anode according to claim 1 or 2, wherein iron, nickel, or cobalt is used as a metal element added to the electrolytic copper plating solution.

Images