JP2007246979A - Electroless plating liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroless plating liquid which can form a cobalt based alloy on wiring of copper or the like as a protective film at high selectivity, can prevent the surface contamination of the exposed wiring and electromigration to an interlayer insulation film, can evade anxieties about the increase of wiring resistance and the deposition of plating metal to the part other than the wiring, further does not include components as environmental hormones, and can suppress adverse influence on the using environment. <P>SOLUTION: The electroless plating liquid is used for selectively forming a protective film on the surface of exposed wiring upon the fabrication of a semiconductor device having a wiring structure, and comprises: cobalt ions; the ions of a second metal different from cobalt; a chelating agent; a reducing agent; a sulfonic acid type anionic surfactant; and tetraalkyl ammonium hydroxide expressed by formula (1); wherein, R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are each a group selected from the group consisting of alkyl groups and hydroxyalkyl groups. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electroless plating solution used for selectively forming a protective film on the exposed surface of a wiring in the manufacture of a semiconductor device having a wiring structure using copper or a copper alloy as a wiring material. is there.

  Conventionally, an aluminum alloy has been mainly used for fine wiring of a high-density integrated circuit formed on a semiconductor substrate. However, in order to further increase the speed of the semiconductor device, it is necessary to use copper or a copper alloy having a specific resistance lower than that of an aluminum alloy as a wiring material. Furthermore, copper is expected as a wiring material for next-generation semiconductor devices because it has an electromigration resistance that is about an order of magnitude higher than that of aluminum-based alloys.

  As a copper wiring forming process of a semiconductor device, a process (damascene process) of embedding metal in wiring trenches and contact holes is employed. In this damascene process, a metal such as copper or a copper alloy is embedded in a wiring groove or contact hole previously formed in an interlayer insulating film, and then the excess metal is removed by chemical mechanical polishing (CMP) and planarized. Is a process.

  In this type of wiring, after planarization, the surface of the wiring is exposed to the outside, and when an embedded wiring is further formed thereon, an interlayer insulating film is further formed on the wiring. Although grooves are formed, there are concerns about surface contamination of the exposed wiring and electromigration to the laminated interlayer insulating film. Therefore, conventionally, a wiring protective film such as silicon nitride is formed on the entire surface of the semiconductor substrate as well as the wiring forming portion whose surface is exposed.

  However, since the electromigration resistance at the interface between the silicon nitride film and copper is weak and the silicon nitride film itself has a high dielectric constant, there is a problem that the wiring delay (RC delay due to the resistor R and the capacitor C) increases. is doing. Therefore, it has been proposed to use cobalt tungsten phosphorus (CoWP) as a material which has improved RC delay and is excellent in electromigration resistance and is effective in preventing copper diffusion (US Pat. No. 5,958,810 (Patent) Literature 1)).

This CoWP has the advantage that it can be selectively deposited only on the copper wiring by electroless plating.
When performing CoWP electroless plating, sodium hypophosphite is generally used as a reducing agent. It is known that sodium hypophosphite is an inactive reducing agent that does not proceed on copper and therefore cannot be plated directly on copper (eg, GOMallory, JB Hajdu, “Electroless Plating-Fundamentals & Applications—” , American Electroplaters And Surface Finishers Society, Florida, page 318, 1990).

Therefore, it is necessary to form the CoWP film by electroless plating after providing a seed layer such as palladium on the copper wiring. However, the palladium that forms the seed layer in this way may react with the copper that forms the wiring layer to increase the resistance of the copper. In addition, palladium may adhere to the surface of the insulator other than the wiring, and the CoWP film may be formed on the surface of the insulator other than the wiring. For this reason, there exists a problem that the insulation between wiring requested | required when forming fine wiring is reduced.

  In order to avoid the influence on the copper wiring due to the reaction of palladium with copper in this way, it is necessary to use palladium as a catalyst or to use the present plan. As such a reducing agent, dimethylamine borane (DMAB) is used. The CoWB electroless plating method used has also been proposed (US Pat. No. 5,169,680 (Patent Document 2), JP-A-2003-49280 (Patent Document 3)). However, since dimethylamine borane (DMAB) has a strong reducing power, the stability of the electroless plating solution is inferior, and there is a problem that cobalt may be deposited in places other than the copper wiring.

In addition, an anionic, cationic or nonionic surfactant is generally added to the electroless plating solution for the purpose of adjusting the stability of the plating bath and the deposition rate. Polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, and their sulfates and phosphates may be used as an effective component for good plating bath stability and deposition rate optimization. These compound substances are considered to be endocrine disruptors (environmental hormones) or suspected, and there is a concern about the influence on electroless plating workers and the surrounding environment.
US Pat. No. 5,695,810 US Pat. No. 5,169,680 JP 2003-49280 A (GOMallory, JBHajdu, "Electroless Plating-Fundamentals &Applications-", American Electroplaters And Surface Finishers Society, Florida, page 318,1990)

  An object of the present invention is to solve the above-described problems of the prior art, more specifically, to prevent deterioration of the reliability of a semiconductor device due to contamination of copper and copper alloy wiring and copper diffusion, An object of the present invention is to provide an electroless plating solution capable of selectively forming a protective film having a diffusion preventing ability uniformly only on the wiring.

The electroless plating solution of the present invention is an electroless plating solution used for selectively forming a protective film on the surface of the wiring exposed when manufacturing a semiconductor device having a wiring structure,
The electroless plating solution contains cobalt ions, ions of a second metal different from cobalt, a chelating agent, a reducing agent, a sulfonic acid type anionic surfactant, and a tetraalkylammonium hydroxide represented by the following formula (1). It is characterized by containing.

In the above formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent any group selected from the group consisting of an alkyl group and a hydroxyalkyl group.

  In the electroless plating solution, by using a sulfonic acid type anionic surfactant, the stability of the plating solution is good without using palladium, and selectively has a diffusion preventing ability only on the wiring. An electroless plating solution capable of forming a protective film can be obtained.

Further, tetraalkylammonium hydroxide represented by the formula (1) R ¹ R ² R ³ R ⁴ NOH (wherein R ¹ , R ² , R ³ and R ⁴ are as defined above) is converted to an alkali metal. By using it as a pH adjuster that does not contain, it is possible to prevent alkali metal from being contained in the plating solution and the protective film formed by electroless plating.

Hereinafter, the electroless plating solution of the present invention will be specifically described.
The electroless plating solution of the present invention is an electroless plating solution suitably used to form a protective film containing cobalt on the surface of metallic copper or copper alloy and having a uniform diffusion preventing ability.

  As a source of cobalt ions contained in the electroless plating solution of the present invention, a water-soluble cobalt (II) salt is blended. The salt is not particularly limited, and examples thereof include cobalt sulfate, cobalt chloride, cobalt bromide, cobalt acetate, cobalt oxalate, cobalt nitrate, and cobalt hydroxide. These cobalt salts can be used alone or in combination.

In the present invention, among these exemplified cobalt salts, cobalt sulfate, cobalt nitrate, and cobalt hydroxide are preferable. Although the quantity of the cobalt salt mix | blended is suitably determined by the kind of cobalt salt to be used, it is 0.001-1 mol / liter normally as a cobalt ion, Preferably it is 0.01-1 mol / liter.

In the present invention as well, the electroless plating solution contains a second metal ion in addition to the cobalt ion.
In the present invention, the second metal ion different from cobalt is selected from the ions of the fourth periodic metal, the fifth periodic metal and the sixth periodic metal in the periodic table of elements other than cobalt, and the atomic group ion containing the metal. Is done. As specific elements,
4th period chromium, nickel, copper, zinc,
5th period molybdenum, technetium, ruthenium, rhodium, palladium, silver,
Examples of the sixth period include tungsten, rhenium, osmium, iridium, platinum, and gold.
In the present invention, among these second metals, tungsten and / or molybdenum is preferable.

In the present invention, as these second metals, for example,
Metal oxides, such as tungsten dioxide, tungsten trioxide, molybdenum dioxide and molybdenum trioxide etc.
Metal salts such as tungsten pentachloride, tungsten hexachloride,
Tungstic acid, molybdic acid tungstate, molybdate,
Mention may be made of heteropolyacids such as tungstophosphoric acid and their salts.

  In the electroless plating solution of the present invention, the second metal as described above is usually used in an amount of 0.001 to 1 mol / liter, preferably 0.01 to 1 mol / liter in terms of zero-valent metal. Is done.

A chelating agent is blended in the electroless plating solution of the present invention in order to stabilize metal ions such as cobalt.
As examples of chelating agents that can be used in the present invention, general chelating agents such as carboxylic acids and salts thereof, aminocarboxylic acids and salts thereof, oxycarboxylic acids and salts thereof, and the like can be used. Preferable examples of the chelating agent that can be used in the present invention include acetic acid, glycine, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and salts thereof, pyrophosphoric acid and salts thereof, and the like. These chelating agents can be used alone or in combination. Especially in this invention, a citric acid is especially preferable among these. The mixing amount of the chelating agent in the electroless plating solution of the present invention is usually 0.001 mol / liter to 2 mol / liter, preferably 0.01 mol / liter to 1.5 mol / liter.

A reduction reaction is used to deposit metal ions such as cobalt ions and second metal ions contained in the electroless plating solution of the present invention on the exposed wiring surface (surface to be plated) as metal. The reducing agent for advancing the reduction reaction in the electroless plating solution of the present invention preferably does not contain an alkali metal such as sodium.

  By using a reducing agent that does not contain an alkali metal as described above, the coating film formed from the electroless plating solution of the present invention contains no alkali metal and forms a coating film having good film characteristics. can do.

Examples of such a reducing agent include monoalkylamine boranes, dialkylamine boranes, and trialkylamine boranes that do not contain an alkali metal such as sodium. Specific examples of these reducing agents include dimethylamine borane (hereinafter referred to as DMAB).

A reducing agent such as dimethylalkylborane blended in the electroless plating solution of the present invention not only serves as a reducing agent for precipitating cobalt ions and second metal ions, but also deposits and forms an electroless plating layer. It also acts as a source of boron (B) in the cobalt-based alloy (for example, CoWB).

Moreover, hypophosphorous acid and hypophosphite can be mentioned as a suitable reducing agent in this invention. In this case as well, hypophosphorous acid and hypophosphite, which are reducing agents, also act as a source of phosphorus (P) in a cobalt-based alloy (for example, CoWP) constituting the electroless plating layer to be deposited. To do.

The reducing agent as described above is usually blended in the electroless plating solution of the present invention in an amount of 0.001 mol / liter to 1 mol / liter, preferably 0.01 mol / liter to 1 mol / liter.
In general, an electroless plating solution is blended with a surfactant in order to ensure the stability of the plating bath and further to adjust the deposition rate of the metal.

  Examples of the surfactant blended in the electroless plating solution for such a purpose include an anionic surfactant, a cationic surfactant, and a nonionic surfactant. In particular, as an effective surfactant for ensuring the stability of the electroless plating solution and optimizing the deposition rate of metal, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, and their sulfate esters or Phosphate esters are used. Such a surfactant is necessary for smooth electroless plating. On the other hand, the above-mentioned compound used for electroless plating solution is an endocrine disrupting substance (environmental hormone). Considering the effects on electroless plating workers and the surrounding environment, it is desirable to use surfactants that do not have endocrine disrupting effects.

In the present invention, in consideration of such effects on workers and the surrounding environment, a sulfonic acid type anionic surfactant having no endocrine disrupting action is used as the surfactant. Specific examples of such surfactants include alkylbenzene sulfonic acid, alkyl diphenyl ether sulfonic acid, naphthalene sulfonic acid formalin condensate, and ammonium salts thereof. These can be used alone or in combination. Furthermore, you may use together with another nonionic surfactant. The amount of the sulfonic acid type anionic surfactant to be blended is usually 0.0001% by mass to 1% by mass, preferably 0.001% by mass to 0.5% by mass. In the present invention, the surfactants can be used alone or in combination.

In the electroless plating solution of the present invention, tetraalkylammonium hydroxide is blended in order to adjust the pH value. This tetraalkylammonium hydroxide can be represented by the following formula (1).

In the above formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent any group selected from the group consisting of an alkyl group and a hydroxyalkyl group.
This compound is a pH adjuster that does not contain an alkali metal.

In the present invention, examples of the compound represented by the formula (1) used as a pH regulator include tetramethylammonium hydroxide (hereinafter referred to as “TMAH”), tetraethylammonium hydroxide, tetrabutyl hydroxide. Examples include ammonium, methyltriethylammonium hydroxide, ethyltrimethylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide, and 2-hydroxyethyltriethylammonium hydroxide.

The compound represented by the formula (1) as described above is used in an amount capable of adjusting the pH value of the electroless plating solution of the present invention to a range of usually 5 to 14, preferably 7 to 11.
In the electroless plating solution of the present invention, known additives such as a buffer, a corrosion inhibitor, and an accelerator can be blended as necessary in addition to the above components. For example, boric acid is mentioned as an additive that acts as a buffer / accelerator.

As a method of forming a cobalt alloy plating film using the electroless plating solution of the present invention, a liquid temperature of 20 to 1 is applied to a semiconductor substrate that has been subjected to necessary pretreatments such as cleaning of the surface to be plated according to a conventional method.
A method of dipping until a plating film having a film thickness necessary for an electroless plating solution at 00 ° C., preferably 35 to 90 ° C., can be employed.

  As a wiring material constituting the wiring structure formed on the semiconductor substrate, copper is generally used. This copper film is not limited to pure copper, and the content ratio of copper such as copper-silicon and copper-aluminum is 95, for example. You may consist of a copper alloy which is the mass% or more. In this wiring, the interlayer insulating film in which the wiring groove is formed is covered with a hard metal such as tantalum or titanium and / or a barrier metal such as a nitride or oxide thereof, and the wiring metal is electroplated. The semiconductor substrate is deposited by a damascene method of chemical mechanical polishing (CMP).

  Here, the metal forming the barrier metal film is not limited to a pure product, and may be an alloy such as tantalum-niobium. In addition, when the barrier metal film is formed of nitride, tantalum nitride, titanium nitride, or the like is not necessarily pure. The material of the barrier metal film is particularly preferably tantalum and / or tantalum nitride. The barrier metal film is often formed of one of tantalum, titanium, and the like, but different materials such as a tantalum film and a tantalum nitride film may be formed on the same substrate as the barrier metal film. Good.

In addition, as the interlayer insulating film, a silicon oxide film (PETEOS film (Plasma Enhanced-TEOS film), HDP film (High Density Plasma Enhanced-TEOS film)) formed by a vacuum process such as chemical vapor deposition, or thermal CVD is used. etc. resulting silicon oxide film), a small amount of boron and boron phosphorus silicate film added with phosphorus (BPSG film SiO _2), FSG fluorine-doped _{SiO 2 (fluorine-doped silicate glass} ) and an insulating film called, SiON ( An insulating film called silicon oxynitride), silicon nitride, or the like can be given.

Furthermore, as a low dielectric constant interlayer insulating film, alkoxysilane, silane, alkylsilane, arylsilane, siloxane in the presence of oxygen, carbon monoxide, carbon dioxide, nitrogen, argon, H ₂ O, ozone, ammonia, etc. An interlayer insulating film made of a polymer obtained by plasma polymerization of a silicon-containing compound such as alkylsiloxane, and further an interlayer insulating film made of polysiloxane, polysilazane, polyarylene ether, polybenzoxazole, polyimide, silsesquioxane, etc. Can also be used. Further, the low dielectric constant silicon oxide insulating film can be obtained by applying a raw material on a substrate by, for example, a spin coating method and then heating in an oxidizing atmosphere.

Examples of the low dielectric constant silicon oxide insulating film thus obtained include an HSQ film (Hydrogen Silsesquioxane film) using triethoxysilane as a raw material, and an MSQ film using tetraethoxysilane and a small amount of methyltrimethoxysilane as a raw material ( Methyl Silsesquioxane film) and other low dielectric constant insulating films made from silane compounds. By mixing suitable organic polymer particles, etc. with a low dielectric constant insulating film made of such a material, the organic polymer particles are burned out in the heating process to form vacancies. As a result, the dielectric constant of the insulating film is further reduced.

  The insulating film having a low dielectric constant can also be formed using an organic polymer such as a polyarylene polymer, a polyarylene ether polymer, a polyimide polymer, or a benzocyclobutene polymer as a raw material.

  The electroless plating solution of the present invention forms a seed layer made of a cobalt-based alloy, which is a diffusion prevention film material, on the copper wiring with a very high selectivity with respect to the semiconductor substrate on which such copper wiring is exposed. Suitable for

Next, the electroless plating solution of the present invention will be described with reference to examples, but the present invention is not limited thereto.
[Example 1]
(1) Preparation of Electroless Plating Solution A glass beaker having a capacity of 5000 ml was charged with 2000 ml of 25% by mass TMAH aqueous solution heated to 80 ° C., and 150 g of tungsten trioxide was dissolved in this TMAH aqueous solution.

  Next, in another glass beaker with a capacity of 5000 ml, 2500 ml of 25% by mass of a TMAH hydroxide aqueous solution, 850 g of citric acid, 150 g of boric acid, and 180 g of cobalt sulfate heptahydrate were mixed and dissolved. .

Next, after mixing the two solutions prepared as described above, 2 g of dodecylbenzenesulfonic acid was dissolved in this mixed solution.
Furthermore, deionized water and 25% by mass TMAH aqueous solution were used for the obtained mixed solution, and the pH value of the mixing solution was adjusted to 9.0 and the total volume was adjusted to 10 liters.

20 g of DMAB was dissolved in the plating solution thus prepared to prepare a plating solution-1.
(2) Stability evaluation of electroless plating solution 25 ml of the plating solution-1 prepared in a clean glass test tube is weighed, and this is palladium chloride having a concentration of 0.02 g / liter which serves as an initiation catalyst for the electroless plating reaction. After adding 0.2 ml of an aqueous solution to obtain a uniform solution, it was heated to 80 ° C., and the change in the state of the plating solution was observed. When the stability of the prepared plating solution is insufficient, the reduction reaction is started by heating in the presence of palladium chloride, and the metal is deposited.

However, it was found that the plating solution-1 prepared as described above has sufficient stability with no turbidity due to metal deposition for 20 minutes or more even when heated to 80 ° C.
(3) Plating performance evaluation A commercially available silicon substrate on which a copper foil layer is formed by plating is cut into a 5 cm square test piece, washed with deionized water, and its mass (W1) is measured with a precision balance. It was measured.

Subsequently, this test piece was immersed in 100 ml of plating solution-1 heated to 80 ° C. for 20 minutes.
When the test piece was taken out after 20 minutes and washed with deionized water, the surface of the test piece was changed to a silver mirror surface, and it was found that the cobalt-based alloy was plated on the copper surface. Measure the mass (W2) of the test piece after cleaning with a precision balance, calculate the amount of metal plated from the mass change (W2-W1) before and after plating, and calculate the plating rate from the plating time and the area of the test piece did.

The plating rate of the plating solution-1 was 0.6 nm / sec.
Next, it is polished with CSR slurry for copper (product name: CMS7401 and CMS7452) and barrier metal CMP slurry (product name: CMS8401 and CMS8452) manufactured by JSR Corporation, and patterned silicon with exposed copper wiring on the insulating film. A substrate (a substrate with copper damascene wiring made from ATDF, 854 CMP001) was prepared and cut into 3 cm square test pieces. This test piece was washed with deionized water and then immersed in 100 ml of plating solution-1 heated to 80 ° C. for 1 minute. After washing again with deionized water, the plated specimen was observed with a scanning electron microscope, and it was confirmed that no metal was deposited on the insulating film that should not be plated.
[Example 2]
(1) Preparation of electroless plating solution A glass beaker having a capacity of 5000 ml was charged with 150 g of tungsten trioxide and 2000 ml of a 25% by mass TMAH aqueous solution, and heated to 80 ° C. for dissolution.

Next, another 5000 ml glass beaker was charged with 800 g of citric acid and 60 g of cobalt hydroxide, and further 2000 ml of deionized water was added and dissolved.
Then, after mixing the two solutions prepared as described above, 3000 ml of 25 wt% TMAH aqueous solution, 300 ml of 50 wt% hypophosphorous acid aqueous solution and 150 g
Of boric acid was added and dissolved.

  Further, 30 g DMAB and 1 g ammonium alkyldiphenyl ether disulfonate (manufactured by Nippon Emulsifier Co., Ltd., product name: New Coal 271-NH) were added to this solution and dissolved.

Thereafter, using a deionized water and a 25 mass% TMAH aqueous solution, the pH value of the mixing solution was adjusted to 9.0 and the total volume was 10 liters to prepare a plating solution-2.
Then, the stability and plating performance of the electroless plating solution were evaluated in the same manner as in Example 1, and the results shown in Table 1 were obtained.
Example 3
(1) Preparation of electroless plating solution In a glass beaker having a capacity of 5000 ml, 2000 ml of 25% by mass of TMAH aqueous solution heated to 80 ° C. was added, and 150 g of tungsten trioxide was added thereto and dissolved.

  Next, in another glass beaker with a capacity of 5000 ml, 3500 ml of 25% by mass of a hydroxylated TMAH aqueous solution was added, and 850 g of citric acid, 150 g of boric acid, and 180 g of cobalt sulfate heptahydrate were mixed and dissolved. I let you.

Then, after mixing the two solutions prepared as described above, 150 ml of 50% by mass hypophosphorous acid aqueous solution, 10 g of N- (2-hydroxyethyl) ethylenediamine-N, N ′ N'-triacetic acid and 1 g of naphthalenesulfonic acid formalin condensate ammonium salt were added and dissolved.

Furthermore, 10 g of DMAB was added, and then the pH value of the mixing solution was adjusted to 9.0 and the total volume was 10 liters using deionized water and 25% by mass TMAH aqueous solution. Was prepared.

For this plating solution, the stability and plating performance of the electroless plating solution were evaluated in the same manner as in Example 1, and the results shown in Table 1 were obtained.
[Comparative Example 1]
In the procedure for preparing the plating solution described in Example 2, except that dodecylbenzenesulfonic acid was not used, plating solution-4 was prepared with the same composition.
[Comparative Example 2]
Of the preparation procedures of the plating solution described in Example 2, polyoxyethylene tridecyl ether phosphate ester (product name: Phosphanol RS-610, manufactured by Toho Chemical Industry Co., Ltd.) having an HLB value of 10.5 was used. Plating solution-5 was prepared with the same composition except that oxyethylene nonylphenyl ether phosphate ester (product of Toho Chemical Industry Co., Ltd., product name: Phosphanol RE-610) was used.

  Table 1 shows the evaluation results for Comparative Examples 1 and 2 as well.

From the above results, Examples 1 to 3 have sufficient stability to stabilize the plating process while having a sufficient plating rate as compared with Comparative Example 1, and further, the original purpose. It has an ability to selectively form a protective film having a copper diffusion preventing ability only on the exposed wiring surface on the semiconductor substrate having a wiring structure using copper or a copper alloy as a wiring material. I understand.

  In contrast to Comparative Example 2, it can be seen that the plating solution has a stability equal to or higher than that of a conventional plating solution using a surfactant, and further, plating is performed only on the exposed copper wiring. It can be seen that the selectivity is improved.

Protective film formation by electroless plating to selectively form a protective film having copper diffusion prevention capability on the surface of the wiring exposed when manufacturing a semiconductor device having a wiring structure using copper or copper alloy as a wiring material Is proposed as an effective means, but as an electroless plating solution, cobalt ions, ions of a second metal different from cobalt, a chelating agent, a reducing agent, a sulfonic acid type anionic surfactant, and the following formula R ¹ R By using the electroless plating solution of the present invention containing tetraalkylammonium hydroxide represented by ² R ³ R ⁴ NOH (wherein R ¹ , R ² , R ³ , R ⁴ are as defined above) Cobalt alloy can be formed as a protective film only on wiring such as copper with excellent selectivity, surface contamination of the exposed wiring, and electromigration on the laminated interlayer insulation film. It is possible to prevent the emissions. Further, since a seed layer of palladium or the like is not required, it is possible to avoid the possibility that the wiring resistance may increase or the plating metal may be deposited on the wires other than the wires due to the adhesion of palladium on an insulator other than the wires. Furthermore, since these performances can be achieved without using endocrine disrupting substances (environmental hormones) such as conventional polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether, electroless plating workers and The influence on the surrounding environment can be suppressed.

Claims (4)

An electroless plating solution used to selectively form a protective film on the surface of the wiring exposed when manufacturing a semiconductor device having a wiring structure,
The electroless plating solution contains cobalt ions, ions of a second metal different from cobalt, a chelating agent, a reducing agent, a sulfonic acid type anionic surfactant, and a tetraalkylammonium hydroxide represented by the following formula (1). An electroless plating solution characterized by containing;

(In the above formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represents any group selected from the group consisting of an alkyl group and a hydroxyalkyl group).   2. The electroless plating solution according to claim 1, wherein the second metal different from cobalt is a fourth periodic metal, a fifth periodic metal, or a sixth periodic metal in the periodic table of elements other than cobalt. The second metal different from cobalt is tungsten and / or molybdenum, and the source of ions of these second metals is
Metal oxides consisting of tungsten dioxide, tungsten trioxide, molybdenum dioxide and molybdenum trioxide,
A metal salt comprising tungsten pentachloride and tungsten hexachloride,
3. A compound comprising at least one compound selected from the group consisting of tungstic acid, molybdic acid, tungstate, molybdate, tungstophosphoric acid heteropolyacid and tungstophosphoric acid heteropolyacid salt. The electroless plating solution described.   2. The electroless plating solution according to claim 1, wherein the reducing agent is an alkylamine borane.