JP7457537B2 - Composition for electroless gold plating - Google Patents

Description

The present invention relates to a composition for electroless gold plating on the surface of a silicon semiconductor.

Gold, being a material with high electrical conductivity, chemical stability and ductility, is used in a variety of applications such as printed circuit boards, wire bonding materials, ornaments, etc. Gold plating methods are commonly used for such applications.
Known gold plating methods include electrolytic gold plating and electroless gold plating. Known electroless gold plating methods include autocatalytic electroless gold plating, base catalytic gold plating, and displacement gold plating. In particular, displacement gold plating is a gold plating method in which gold is deposited by an electrical displacement reaction between the base metal of the plated surface and gold ions and/or gold ion complexes.

In recent years, a method of electrolessly plating the surface of silicon with gold using a displacement gold plating method has been reported (Patent Document 1). Such methods use a gold plating composition that includes a source of gold ions and hydrofluoric acid. Hydrofluoric acid dissolves the oxide film on the surface of silicon, and a substitution reaction between silicon and gold ionizes silicon and deposits gold, thereby forming gold plating on the surface of silicon. Furthermore, a method of electroless gold plating on the surface of silicon carbide instead of silicon has also been reported (Patent Document 2).
The above composition for gold plating is also used in methods for producing polycrystalline silicon substrates for solar cells and various composite materials (Patent Documents 3 to 7). On the other hand, as an alternative, gold plating compositions containing a gold ion source and an alkali metal hydroxide may be used (Patent Documents 8 and 9).

Furthermore, in recent years, a method has been reported in which gold plating formed by displacement gold plating is applied to silicon etching (Patent Document 10). Specifically, by depositing gold on the surface of silicon, the gold deposit exhibits a catalytic action, making it possible to vertically etch the silicon under the gold deposit.

Patent No. 5945429 Patent No. 6603491 Patent No. 4049329 Patent No. 5261475 Patent No. 5281847 Japanese Patent No. 5306670 Japanese Patent No. 5663625 Patent No. 6553596 Patent No. 6573603 Patent No. 6121959

An object of the present invention is to provide a composition for electroless gold plating on the surface of a silicon semiconductor, which can reduce the rate at which gold is deposited on the surface of the silicon semiconductor.

The present inventors found that when a gold plating composition containing a gold ion source and hydrofluoric acid was used in the process of electroless gold plating on the surface of a silicon semiconductor, an oxide film formed on the surface of the silicon semiconductor extremely quickly. As the gold melts and gold precipitates extremely quickly, we have confirmed that excessive gold precipitates on the surface of the silicon semiconductor, making it difficult to control the structure of the gold plating. As a result of intensive research to facilitate such structural control, we found that acetonitrile was added to the gold plating composition, or hexafluorosilicic acid and/or tetrafluoroboric acid was used instead of hydrofluoric acid. The present invention has been completed based on the discovery that the rate at which gold is deposited on the surface of a silicon semiconductor can be reduced by adding gold.

That is, the present invention relates to the following.
[1] A composition for electroless gold plating on the surface of a silicon semiconductor, containing a gold ion source, a fluorine compound, and acetonitrile.
[2] In [1], the fluorine compound is one or more fluorine compounds selected from the group consisting of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, hexafluorosilicic acid, and tetrafluoroboric acid. Compositions as described.
[3] A composition for electroless gold plating on the surface of a silicon semiconductor, comprising a gold ion source and hexafluorosilicic acid and/or tetrafluoroboric acid.
[4] The composition according to [3], further comprising acetonitrile.
[5] The composition according to any one of [1] to [4], wherein the silicon semiconductor is silicon, silicon oxide, and/or silicon carbide.
[6] The composition according to any one of [1] to [5], which has a pH of 7 or less.
[7] A method for depositing gold, comprising the step of applying the composition according to any one of [1] to [6] to the surface of a silicon semiconductor.

By using the composition for electroless gold plating of the surface of a silicon semiconductor of the present invention, it is possible to reduce the rate at which gold is deposited on the surface of a silicon semiconductor. Thereby, the structure of the gold plating on the surface of the silicon semiconductor can be easily controlled, and desired physical properties of the precipitate can be obtained. Furthermore, since an appropriate amount of gold can be deposited on the surface of the silicon semiconductor, the amount of gold consumed can be suppressed, which is economical. By forming gold plating accurately and densely on the surface of a silicon semiconductor, the application to etching described in the background art can also be facilitated. Furthermore, since it is not necessary to use a gold plating composition containing an alkali metal hydroxide as described in the background art, it is also possible to avoid adverse effects on semiconductor properties due to residual alkali metal.

Figure 1 shows a process for depositing gold on the surface of a patterned silicon semiconductor, with Figure 1A showing a cross-sectional view of the silicon semiconductor and Figure 1B showing a plan view of the horizontal silicon semiconductor as seen from above.

Unless otherwise defined herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. All patents, applications, and other publications and information referred to herein are incorporated by reference in their entirety.

[Composition (1) for electroless gold plating on the surface of silicon semiconductor]
One aspect of the present invention is a composition for electroless gold plating on the surface of a silicon semiconductor (hereinafter sometimes referred to as "composition (1) of the present invention"), which contains a gold ion source, a fluorine compound, and acetonitrile. ) regarding.
The composition (1) of the present invention can also be applied to the surface of a silicon semiconductor on which a pattern has been formed. The present inventors discovered that when a gold plating composition containing hydrofluoric acid was used in the process of electroless gold plating on the surface of a silicon semiconductor, gold was deposited excessively on the surface of the silicon semiconductor and the pattern was A phenomenon in which gold was deposited outside the pattern (hereinafter sometimes referred to as "outside pattern deposition") was confirmed (Figure 1). By using the composition (1) of the present invention to reduce the rate at which gold is deposited on the surface of a silicon semiconductor, it is possible to suppress out-of-pattern deposition.

In the present invention, the "gold ion source" can specifically be a water-soluble gold salt such as chloroauric acid salt. From the viewpoint of safety and waste disposal issues, it is preferred to use a cyanide-free gold ion source. The gold ion source preferably has a concentration of 0.5 to 25mM, particularly preferably 1 to 10mM, and particularly preferably 1.5 to 10mM, from the viewpoint of the physical properties of the precipitate, especially precipitation properties and economical efficiency. More preferably, the concentration is 5mM.

In the present invention, the "fluorine compound" is one or more fluorine compounds selected from the group consisting of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, hexafluorosilicic acid, and tetrafluoroboric acid. The fluorine compound may be hexafluorosilicic acid and/or tetrafluoroboric acid from the viewpoint of reducing the rate at which the oxide film on the surface of the silicon semiconductor dissolves and the rate at which gold is deposited on the surface of the silicon semiconductor. preferable. The concentration of the fluorine compound is preferably from 0.1 to 2.7 M, particularly preferably from 0.5 to 2.0 M, from the viewpoint of physical properties of the precipitate, particularly reactivity and controllability. , more preferably a concentration of 0.7 to 1.2M.

In the present invention, "acetonitrile" preferably has a concentration of 0.02 to 2M, particularly preferably 0.2 to 1.5M, from the viewpoint of suppressing the gold precipitation rate and economical efficiency. More preferably, the concentration is between 0.5 and 1M.
In the present invention, "silicon semiconductor" refers to a semiconductor containing an inorganic silicon compound having a siloxane bond and/or an organosilicon compound having a carbon-silicon bond. The silicon semiconductor is preferably silicon, silicon oxide, and/or silicon carbide from the viewpoint of physical properties of precipitates.

In the present invention, "electroless gold plating" refers to gold plating by, for example, an autocatalytic electroless gold plating method, a base catalytic gold plating method, and a displacement gold plating method. The autocatalytic electrolytic gold plating method is a method in which gold is deposited using a reducing agent using gold as a catalyst. Base catalytic gold plating is a method of depositing gold using a reducing agent using a base metal as a catalyst. Displacement gold plating is a method of depositing gold by an electrical displacement reaction between the base metal of the surface to be plated and gold ions and/or gold ion complexes. Two or more of these plating methods can be used in combination. The electroless gold plating is preferably a displacement gold plating method from the viewpoint of the physical properties of the precipitate.

In the present invention, a "pattern" refers to a fine structure having a portion where a mask is present and a portion where a mask is not present. The width of the gap between the masks is preferably 0.5 to 20 μm, particularly preferably 1 to 10 μm, from the viewpoint of the physical properties of the precipitate. For example, the pattern is a resist pattern.
In the present invention, "mask" refers to a protective film against gold plating. Where the mask exists, the gold plating process does not proceed, and the surface of the silicon semiconductor under the mask does not change before and after the gold plating process. The components constituting the mask are not particularly limited as long as they are selected depending on the processing chemicals used during the gold plating process. For example, a mask is a resist.
The composition (1) of the present invention preferably has a pH of 7 or less, particularly preferably 4 or less, and more preferably less than 3 from the viewpoint of stability and precipitation rate of the composition. preferable.

[Composition (2) for electroless gold plating of silicon semiconductor surfaces]
Another aspect of the present invention relates to a composition for electroless gold plating of a silicon semiconductor surface, comprising a gold ion source and hexafluorosilicic acid and/or tetrafluoroboric acid (hereinafter, sometimes referred to as "composition (2) of the present invention"). From the viewpoint of reducing the rate at which gold is deposited on the silicon semiconductor surface, composition (2) of the present invention preferably further comprises acetonitrile.
The composition (2) of the present invention can also be applied to the surface of a silicon semiconductor on which a pattern is formed. By using the composition (2) of the present invention, the rate at which the oxide film on the surface of the silicon semiconductor dissolves can be reduced, and the rate at which gold deposits on the surface of the silicon semiconductor can be reduced, thereby suppressing deposition outside the pattern.

In the present invention, the "gold ion source" can specifically be a water-soluble gold salt such as chloroauric acid salt. From the viewpoint of safety and waste disposal issues, it is preferred to use a cyanide-free gold ion source. The gold ion source preferably has a concentration of 0.5 to 25mM, particularly preferably 1 to 10mM, and particularly preferably 1.5 to 10mM, from the viewpoint of the physical properties of the precipitate, especially precipitation properties and economical efficiency. More preferably, the concentration is 5mM.

In the present invention, "hexafluorosilicic acid" and/or "tetrafluoroboric acid" are used to reduce the rate at which an oxide film on the surface of a silicon semiconductor dissolves and to reduce the rate at which gold is deposited on the surface of a silicon semiconductor. Therefore, the concentration is preferably 0.1 to 2.7M, particularly preferably 0.5 to 2.0M, and even more preferably 0.7 to 1.2M.
In the present invention, "silicon semiconductor" refers to a semiconductor containing an inorganic silicon compound having a siloxane bond and/or an organosilicon compound having a carbon-silicon bond. The silicon semiconductor is preferably silicon, silicon oxide, and/or silicon carbide from the viewpoint of physical properties of precipitates.

In the present invention, "electroless gold plating" refers to gold plating by, for example, an autocatalytic electroless gold plating method, a base catalytic gold plating method, and a displacement gold plating method. The autocatalytic electrolytic gold plating method is a method in which gold is deposited using a reducing agent using gold as a catalyst. Base catalytic gold plating is a method of depositing gold using a reducing agent using a base metal as a catalyst. Displacement gold plating is a method of depositing gold by an electrical displacement reaction between the base metal of the surface to be plated and gold ions and/or gold ion complexes. Two or more of these plating methods can be used in combination. The electroless gold plating is preferably a displacement gold plating method from the viewpoint of the physical properties of the precipitate.
In the present invention, "acetonitrile" preferably has a concentration of 0.02 to 2M, particularly preferably 0.2 to 1.5M, from the viewpoint of suppressing the gold precipitation rate and economical efficiency. More preferably, the concentration is between 0.5 and 1M.

In the present invention, the term "pattern" refers to a fine structure having a portion where a mask is present and a portion where a mask is not present. From the viewpoint of the physical properties of the precipitate, the width of the gap between the masks is preferably 0.5 to 20 μm, and particularly preferably 1 to 10 μm. For example, the pattern is a resist pattern.
In the present invention, the "mask" refers to a protective film against gold plating. In the area where the mask is present, the gold plating does not proceed, and the surface of the silicon semiconductor under the mask does not change before and after the gold plating. The components constituting the mask are not particularly limited as long as they are selected according to the processing chemicals used during the gold plating. For example, the mask is a resist.
The composition (2) of the present invention preferably has a pH of 7 or less, particularly preferably 4 or less, and further preferably less than 3, from the viewpoints of the stability and deposition rate of the composition.

[Composition (3) for electroless gold plating on the surface of silicon semiconductor]
Another aspect of the present invention is a composition for electroless gold plating on a patterned silicon semiconductor surface (hereinafter referred to as "composition (3) of the present invention"), which includes a gold ion source and a fluorine compound. ). The fluorine compound may be hexafluorosilicic acid and/or tetrafluoroboric acid from the viewpoint of reducing the rate at which the oxide film on the surface of the silicon semiconductor dissolves and the rate at which gold is deposited on the surface of the silicon semiconductor. preferable. The composition (3) of the present invention preferably further contains acetonitrile from the viewpoint of reducing the rate of gold precipitation on the surface of the silicon semiconductor.

In the present invention, the "gold ion source" can specifically be a water-soluble gold salt such as chloroauric acid salt. From the viewpoint of safety and waste disposal issues, it is preferred to use a cyanide-free gold ion source. The gold ion source preferably has a concentration of 0.5 to 25mM, particularly preferably 1 to 10mM, and particularly preferably 1.5 to 10mM, from the viewpoint of the physical properties of the precipitate, especially precipitation properties and economical efficiency. More preferably, the concentration is 5mM.

In the present invention, the "fluorine compound" is one or more fluorine compounds selected from the group consisting of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, hexafluorosilicic acid, and tetrafluoroboric acid. From the viewpoint of reducing the rate at which the oxide film on the surface of the silicon semiconductor dissolves and reducing the rate at which gold precipitates on the surface of the silicon semiconductor, the fluorine compound is preferably hexafluorosilicic acid and/or tetrafluoroboric acid. From the viewpoint of the physical properties of the precipitate, particularly reactivity and controllability, the fluorine compound is preferably at a concentration of 0.1 to 2.7 M, more preferably at a concentration of 0.5 to 2.0 M, and even more preferably at a concentration of 0.7 to 1.2 M.

In the present invention, a "pattern" refers to a fine structure having a portion where a mask is present and a portion where a mask is not present. The width of the gap between the masks is preferably 0.5 to 20 μm, particularly preferably 1 to 10 μm, from the viewpoint of the physical properties of the precipitate. For example, the pattern is a resist pattern.
In the present invention, "mask" refers to a protective film against gold plating. Where the mask exists, the gold plating process does not proceed, and the surface of the silicon semiconductor under the mask does not change before and after the gold plating process. The components constituting the mask are not particularly limited as long as they are selected depending on the processing chemicals used during the gold plating process. For example, a mask is a resist.

In the present invention, "silicon semiconductor" refers to a semiconductor containing an inorganic silicon compound having a siloxane bond and/or an organosilicon compound having a carbon-silicon bond. The silicon semiconductor is preferably silicon, silicon oxide, and/or silicon carbide from the viewpoint of physical properties of precipitates.
In the present invention, "electroless gold plating" refers to gold plating by, for example, an autocatalytic electroless gold plating method, a base catalytic gold plating method, and a displacement gold plating method. The autocatalytic electrolytic gold plating method is a method in which gold is deposited using a reducing agent using gold as a catalyst. Base catalytic gold plating is a method of depositing gold using a reducing agent using a base metal as a catalyst. Displacement gold plating is a method of depositing gold by an electrical displacement reaction between the base metal of the surface to be plated and gold ions and/or gold ion complexes. Two or more of these plating methods can be used in combination. The electroless gold plating is preferably a displacement gold plating method from the viewpoint of the physical properties of the precipitate.

In the present invention, "acetonitrile" preferably has a concentration of 0.02 to 2M, particularly preferably 0.2 to 1.5M, from the viewpoint of suppressing the gold precipitation rate and economical efficiency. More preferably, the concentration is between 0.5 and 1M.
The composition (3) of the present invention preferably has a pH of 7 or less, particularly preferably 4 or less, and more preferably less than 3 from the viewpoint of stability and precipitation rate of the composition. preferable.

[Method of depositing gold]
Another aspect of the present invention is a method for depositing gold (hereinafter referred to as "the method of the present invention"), which includes the step of applying any of the compositions (1) to (3) of the present invention to the surface of a silicon semiconductor. ).
The temperature at which any of the compositions (1) to (3) of the present invention is used in the above step is preferably 10 to 50°C, more preferably 15 to 30°C, from the viewpoint of precipitation rate.
The amount of any of the compositions (1) to (3) of the present invention used in the above step is not particularly limited as long as it is an amount sufficient to be applied to the surface of a silicon semiconductor. For example, the amount used is sufficient to immerse the surface of a silicon semiconductor.
The step may be performed under static conditions or under stirring conditions. Stirring conditions are not particularly limited, but from the viewpoint of precipitation rate, 50 to 1500 rpm is preferable, and 100 to 1000 rpm is more preferable.
The time for the step is not particularly limited, but from the viewpoint of precipitation rate, it is preferably 15 seconds to 10 minutes, more preferably 30 seconds to 5 minutes.

Example 1 Effect of Reducing the Rate of Gold Deposition on the Surface of a Silicon Semiconductor A silicon substrate (n-Si (100) Low <0.02 Ωcm, Nilaco Corporation) on which no pattern was formed was cut to a size of 0.5 cm x 1 cm. The silicon substrate was immersed in each composition (0.1 L) of Example 1 (3 mM tetrachloroauric (III) acid, 1 M hydrofluoric acid, 1 M acetonitrile, pH 2-3), Example 2 (3 mM tetrachloroauric (III) acid, 1 M hexafluorosilicic acid, pH <1), Example 3 (3 mM tetrachloroauric (III) acid, 1 M hexafluorosilicic acid, 1 M acetonitrile, pH <1), and Comparative Example (3 mM tetrachloroauric (III) acid, 1 M hydrofluoric acid, pH 2-3) at room temperature (25°C) for 1 minute under stationary conditions, and gold was deposited. Thereafter, the silicon substrate was rinsed for 10 seconds (overflowing with pure water) and dried by nitrogen blowing. The amount of gold deposited on the silicon substrate was evaluated by measuring the fluorescent X-ray intensity of the gold deposited on the silicon substrate using a fluorescent X-ray thickness meter (FT9500X, Hitachi High-Tech Science) (measurement time: 30 seconds, excitation voltage: 45 kV, tube current: 1000 μA, measured element: gold, analysis line: Lα, ROI (energy range for determining fluorescent X-ray intensity): 9.52 to 9.89 keV).

As a result, it was confirmed that the fluorescent X-ray intensity values of Examples 1 to 3 (232, 222, 227 cps) were lower than the fluorescent X-ray intensity value of the Comparative Example (246 cps). The above results are summarized in Table 1. The fluorescent X-ray intensity value is the average value of five measurements.

Therefore, it has been found that adding acetonitrile to a gold plating composition containing hydrofluoric acid reduces the rate at which gold is deposited on a silicon substrate. It has also been found that using hexafluorosilicic acid instead of hydrofluoric acid as the fluorine compound also reduces the rate of gold precipitation on the silicon substrate. Additionally, the combination of hexafluorosilicic acid and acetonitrile was also found to reduce the rate of gold deposition on silicon substrates.
In addition, in each composition of Examples 1 and 3, apart from the above consideration, acetonitrile was mixed with other organic solvents (polar solvents: isopropanol, diethylene glycol, methanol, ethylene glycol, glycerin, water, N-methyl-2-pyrrolidinone). , 1,3-dimethyl-2-imidazolidinone, and dimethyl sulfoxide), but these organic solvents were not practical because they lowered the stability of the gold plating composition. In addition, nonpolar solvents have low solubility in water and do not mix with gold plating compositions, making them impractical.
From the above results, by using acetonitrile and/or hexafluorosilicic acid as a fluorine compound, it is possible to easily control the structure of gold plating on the surface of silicon semiconductors by reducing the rate of gold precipitation on the surface of silicon semiconductors. It is thought that it is possible to do so.

Example 2: Inhibition effect of deposition outside the pattern by acetonitrile A silicon substrate (n-Si (100) Low <0.02 Ωcm, Nilaco Corporation) on which a resist pattern (OFPR-800LB, film thickness about 1.8 μm, Tokyo Ohka Kogyo Co., Ltd.) with L/S=1 μm/1 μm was formed was cut to a size of 0.5 cm x 1 cm. The silicon substrate was immersed in each composition (0.1 L) of Example 4 (tetrachloroauric (III) acid 3 mM, hydrofluoric acid 1 M, acetonitrile 1 M, pH 2-3), Example 5 (tetrachloroauric (III) acid 3 mM, hexafluorosilicic acid 1 M, acetonitrile 1 M, pH <1), and Comparative Example (tetrachloroauric (III) acid 3 mM, hydrofluoric acid 1 M, pH 2-3) at room temperature (25° C.) while stirring (100 rpm) for 2 minutes to precipitate gold. The silicon substrate was then rinsed for 10 seconds (overflowing with pure water) and dried by nitrogen blowing. The surface of the silicon substrate was observed with a field emission scanning electron microscope (Regulus8230, Hitachi High-Technologies) to confirm the presence or absence of deposition outside the pattern.

As a result, a large amount of extra-pattern precipitation was observed in the comparative example, but only a small amount was observed in Example 4, and only a very small amount was observed in Example 5. Further, in both Examples 4 and 5 and Comparative Example, it was confirmed that a large amount of gold was deposited on the silicon substrate and the gold deposition was not inhibited. The above results are summarized in Table 2.

Therefore, it has been found that by adding acetonitrile to a gold plating composition containing hydrofluoric acid, it is possible to suppress precipitation outside the pattern. It was also found that by using hexafluorosilicic acid instead of hydrofluoric acid as the fluorine compound in the composition, it was possible to further suppress precipitation outside the pattern.
In addition, apart from the above consideration, acetonitrile can be used with other organic solvents (polar solvents: isopropanol, diethylene glycol, methanol, ethylene glycol, glycerin, water, N-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone). A study was also conducted to replace the organic solvents with organic solvents (Non, dimethyl sulfoxide), but these were not practical as they lowered the stability of the gold plating composition. In addition, nonpolar solvents have low solubility in water and do not mix with gold plating compositions, making them impractical.
From the above results, it is considered that by using acetonitrile, the rate at which gold is deposited on the surface of the silicon semiconductor can be reduced, thereby making it easier to control the structure of gold plating on the surface of the silicon semiconductor.

Example 3 Effect of suppressing extra-pattern precipitation by hexafluorosilicic acid and/or tetrafluoroboric acid A resist pattern (OFPR-800LB, film thickness approximately 1.8 μm, Tokyo Ohka Kogyo Co., Ltd.) with L/S = 1 μm/1 μm is formed. The prepared silicon substrate (n-Si (100) Low <0.02 Ωcm, Nilaco Co., Ltd.) was cut into a size of 0.5 cm×1 cm. Example 6 (Tetrachloroauric acid (III) acid 3mM, hexafluorosilicic acid 1M, pH < 1), Example 7 (Tetrachloroauric acid (III) acid 3mM, Tetrafluoroboric acid 1M, pH < 1), Example 8 (tetrachloroauric(III) acid 3mM, hexafluorosilicic acid 1M, tetrafluoroboric acid 1M, pH < 1), and comparative example (tetrachloroauric(III) acid 3mM, hydrofluoric acid 1M, pH 2-3). ) The silicon substrate was immersed in each composition (0.1 L) for 2 minutes at room temperature (25° C.) with stirring (100 rpm) to deposit gold. Thereafter, the silicon substrate was rinsed for 10 seconds (overflow with pure water) and dried with nitrogen blow. The surface of the silicon substrate was observed using a field emission scanning electron microscope (Regulus 8230, Hitachi High Technologies) to confirm the presence or absence of precipitation outside the pattern.

As a result, a large amount of deposition outside the pattern was confirmed in the comparative example, but only a small amount was confirmed in example 6, none was confirmed in example 7, and only a small amount was confirmed in example 8. Furthermore, in all of examples 6 and 7 and the comparative example, it was confirmed that a large amount of gold was deposited on the silicon substrate and that the gold deposition was not inhibited, but in example 7, only a small amount of gold was deposited on the silicon substrate. The above results are summarized in Table 3.

Therefore, it has been found that by using hexafluorosilicic acid or tetrafluoroboric acid instead of hydrofluoric acid as the fluorine compound, it is possible to suppress precipitation outside the pattern caused by the gold plating composition. It was also found that by using a combination of hexafluorosilicic acid and tetrafluoroboric acid instead of hydrofluoric acid as the fluorine compound, it was possible to suppress precipitation outside the pattern caused by the gold plating composition.
From the above results, by using hexafluorosilicic acid and/or tetrafluoroboric acid as a fluorine compound, the rate at which the oxide film on the surface of the silicon semiconductor dissolves is reduced, and the rate at which gold is deposited on the surface of the silicon semiconductor is reduced. It is thought that by doing so, it is possible to easily control the structure of gold plating on the surface of a silicon semiconductor.

The various features of the present invention described in this specification can be combined in various ways, and all aspects obtained by such combinations, including combinations not specifically described in this specification, are all aspects of the present invention. Within range. Those skilled in the art will also appreciate that many different modifications can be made without departing from the spirit of the invention, and equivalents containing such modifications are also included within the scope of the invention. Accordingly, it should be understood that the embodiments described herein are illustrative only and are not intended to limit the scope of the invention.

Claims (6)

A composition for electroless gold plating of a silicon semiconductor surface, comprising a gold ion source, a fluorine compound, and acetonitrile. The composition according to claim 1, wherein the fluorine compound is one or more fluorine compounds selected from the group consisting of hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, hexafluorosilicic acid, and tetrafluoroboric acid. The composition according to claim 1 or 2, wherein the fluorine compound is hexafluorosilicic acid and/or tetrafluoroboric acid . The composition according to any one of claims 1 to 3 , wherein the silicon semiconductor is silicon, silicon oxide, and/or silicon carbide. The composition according to any one of claims 1 to 4 , having a pH of 7 or less. A method for depositing gold comprising the step of applying a composition according to any one of claims 1 to 5 to a surface of a silicon semiconductor.