JP2007113092A - Plating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method whose process is facilitated, and capable of forming a thick film at a high speed, and also, capable of selectively forming a plated layer on a desired region without irregularity. <P>SOLUTION: In the plating method, at least a part of a base material is provided with the layer to be plated in which activated sulfur is present on the surface, and the base material is subjected to electroless plating treatment, so as to selectively form a plated layer on the layer to be plated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plating method for forming a plating layer on a portion to be plated.

  An electroless plating method is known as a plating method for fine portions of a substrate, such as providing wiring on the surface of a semiconductor wafer. For example, when a gold plating layer is formed on a silicon substrate or the like by electroless plating, first, a copper foil is provided on the substrate, the surface of the copper foil is activated by palladium, and a nickel plating layer is provided thereon. Next, a thick gold plating layer is formed by forming a thin gold plating layer by substitutional electroless gold plating and finally performing autocatalytic electroless plating (see, for example, Patent Document 1).

  As described above, in the conventional method, in order to form the plating layer on the substrate, it is necessary to form many layers. Further, such a conventional method has a problem that the deposition rate of electroless plating is very slow. For example, even if a substrate to be plated is immersed in a plating bath for 3 to 4 hours in a high-temperature bath of 80 ° C. or higher, and a highly accurate temperature control is performed, the plating layer can be formed to a thickness of about 1 μm. could not. Further, in the above-described method, it is very difficult to manage the temperature in the plating tank and the ion concentration on the surface of the substrate for a long time, which is a major factor in plating unevenness.

  For this reason, such an electroless plating method has not been put into practical use for devices that require electrical accuracy, such as electronic device components.

  On the other hand, in addition to the method described above, an electroless plating solution (see Patent Document 2) for preventing abnormal precipitation or undepositing by adjusting the concentrations of copper ions, reducing agents, pH adjusting agents, etc. A plating method (see Patent Document 3) that improves the uniformity of the plating film thickness by preparing a flow of the plating solution has been proposed.

  However, it has been difficult to uniformly form a plating layer on a substrate having an unevenness or a substrate having holes, and to selectively form a plating layer in a predetermined region.

  For this reason, there has been a demand for a plating method that can easily form a thick film at a high speed and can form a plating layer selectively in a desired region without unevenness.

JP 2003-129252 A JP-A-9-111464 JP 2004-162129 A

  In view of such circumstances, the present invention provides a plating method that can be easily formed, can form a thick film at high speed, and can selectively form a plating layer in a desired region without unevenness. .

According to a first aspect of the present invention for solving the above-mentioned problems, a plating layer having activated sulfur on the surface is provided on at least a part of the substrate, and the substrate is subjected to electroless plating treatment. The plating method is characterized in that a plating layer is selectively formed on the layer to be plated.
In the first aspect, the activated sulfur is present in the layer to be plated, so that in the electroless plating process, the metal that is a constituent component of the plating precipitates with sulfur as a nucleus and is selectively deposited on the layer to be plated. A plating layer can be formed on the substrate.

According to a second aspect of the present invention, in the plating method according to the first aspect, the layer to be plated is formed by sulfurating a layer not containing sulfur and having activated sulfur on the surface. There exists in the plating method characterized by existing.
In the second aspect, a layer to be plated can be formed by applying sulfuration treatment to a layer not containing sulfur to make sulfur activated.

According to a third aspect of the present invention, in the plating method according to the second aspect, the sulfur-free layer is formed of a resin layer, and the sulfuration treatment is at least one selected from the group consisting of sulfurous acid and sulfuric acid. The plating method is characterized in that it is a treatment with a treatment solution containing selenium.
In the third aspect, by treating the resin layer not containing sulfur with a treatment liquid containing at least sulfurous acid or sulfuric acid, a layer to be plated having sulfur on the surface is obtained. In the electroless plating treatment, the metal contains sulfur. A plating layer can be selectively formed on the layer to be plated as a nucleus.

According to a fourth aspect of the present invention, in the plating method according to the second aspect, the layer not containing sulfur is made of a metal layer, and the plated layer is made of the metal and sulfur of the metal layer by the sulfuration treatment. In the plating method, wherein the layer to be plated is formed.
In the fourth aspect, a state in which metal and sulfur are bonded to the surface of the layer to be plated can be formed by subjecting the metal layer not containing sulfur to sulfuration treatment.

According to a fifth aspect of the present invention, in the plating method according to the fourth aspect, the sulfuration treatment is a treatment with a treatment liquid containing at least one selected from the group consisting of sulfurous acid and sulfuric acid. There is a plating method to do.
In the fifth aspect, the portion to be plated is treated with a treatment liquid containing at least sulfurous acid or sulfuric acid, whereby the plated layer having sulfur on the surface is obtained.

According to a sixth aspect of the present invention, in the plating method according to the fourth aspect, the sulfuration treatment removes the alloy by etching after forming an alloy containing sulfur. Is in the way.
In the sixth aspect, an alloy containing sulfur is formed on the portion to be the plated layer, and then the alloy is removed by etching, whereby the plated layer having sulfur on the surface is obtained.

According to a seventh aspect of the present invention, in the plating method according to any one of the fourth to sixth aspects, the metal layer is made of Ni or NiCr.
In the seventh aspect, by making the metal layer Ni or NiCr, adhesion with a plating layer such as gold can be improved.

According to an eighth aspect of the present invention, there is provided the plating method according to the first aspect, wherein the plated layer is obtained by activating the surface of a sulfur-containing resin.
In the eighth aspect, by activating the sulfur-containing resin at the site to be the plated layer, a plated layer having sulfur on the surface is formed, and in the electroless plating process, the metal that is a constituent component of the plated layer is A plating layer can be selectively formed on the layer to be plated using sulfur existing on the surface as a nucleus.

According to a ninth aspect of the present invention, in the plating method according to any one of the first to eighth aspects, the plating layer is made of copper or a metal having a smaller ionization tendency than copper. .
In the ninth aspect, the metal forming the plating layer is copper or a metal having a smaller ionization tendency than copper, so that the metal is effectively deposited with sulfur as a nucleus in the electroless plating treatment, and plating without unevenness is achieved. Become a layer.

According to a tenth aspect of the present invention, in the plating method according to the ninth aspect, the plating layer is made of gold, and the palladium replacement treatment is not performed before the electroless plating treatment. It is in.
In the tenth aspect, a plating layer made of gold can be formed without performing a palladium replacement process.

Hereinafter, details of the present invention will be described based on embodiments.
(Embodiment 1)
FIG. 1 is a view showing wiring formed on a silicon substrate using the plating method of the present invention. In the plating method of the present invention, a plating layer having activated sulfur is provided on the substrate surface, and a plating layer is selectively formed on the plating layer by electroless plating treatment. By such a method, for example, as shown in FIG. 1, a wiring 42 composed of a base layer 16 that is a layer to be plated and a plating layer 32 is formed on the silicon substrate 10 via the silicon dioxide film 11. In the present embodiment, the base layer 16 is a layer made of NiCr, and the plating layer 32 is a layer made of gold.

  2 and 3 are diagrams showing the wiring formation process. The plating method according to the present embodiment will be described with reference to FIGS.

  First, as shown in FIG. 2A, the silicon substrate 10 is thermally oxidized in a diffusion furnace at about 1100 ° C. to form a silicon dioxide film 11.

  Next, as shown in FIG. 2B, a metal layer 15 made of NiCr and having a thickness of about 20 nm is formed on the silicon dioxide film 11 by sputtering, for example. Next, as shown in FIG. 2C, the base layer 16 is formed by patterning the formed metal layer 15 into a predetermined shape by photolithography.

  Next, as shown in FIG. 2D, a resist film 50 having a predetermined shape is formed in a region other than the base layer 16 by applying and patterning a resist on the silicon dioxide film 11.

  Next, as shown in FIG. 2 (e), at least the underlayer 16 is placed in a sulfur treatment tank 1000 filled with a treatment liquid 100 made of high-concentration sulfuric acid and hydrogen peroxide of 80% or more and maintained at 80 ° C. By immersing for a minute, the surface of the base layer 16 that is a portion to be plated is sulfurated. At this time, it is only necessary that the base layer 16 is immersed in the processing liquid 100, and of course, the entire silicon substrate 10 may be immersed in the processing liquid 100.

  The term “sulfurization treatment” used herein refers to the presence of sulfur on the surface of the underlayer 16, and preferably a treatment for chemically bonding metal ions of the underlayer 16 and sulfur ions in the treatment liquid. That means.

  In the present embodiment, the treatment liquid 100 composed of 80% or more high-concentration sulfuric acid and hydrogen peroxide is used for the sulfuration treatment, but a treatment liquid containing a strongly acidic liquid containing sulfur element such as sulfurous acid may be used. Good.

  Such a treatment liquid 100 can be reused. In the present embodiment, the treatment time of the surface of the underlayer 16 with the treatment liquid 100 is 80 ° C. and the treatment time is 10 minutes. However, the treatment temperature and treatment time vary depending on the metal constituting the metal layer. It is not limited.

  By performing the above-described sulfuration treatment, the base layer 16 becomes a plated layer 22 having sulfur ions 19 attached to the surface, as shown in FIG. At this time, the chromium ions, which are the metal of the underlayer 16, and the sulfur ions are chemically bonded.

  In the present embodiment, the resist film 50 is formed. However, in this sulfuration treatment, there is no possibility that portions other than the layer 22 to be plated are sulfurated or eroded by the treatment liquid, so that the resist film 50 is covered. It does not have to be.

  Next, as shown in FIG. 3B, at least the layer to be plated 22 is immersed in an electroless plating bath 2000 filled with the electroless plating solution 200. At this time, it is only necessary that the layer 22 to be plated is immersed. Of course, the entire silicon substrate 10 may be immersed in the electroless plating solution 200. In this embodiment, it was immersed at 80 ° C. or more for 1-2 hours. In addition, in the to-be-plated layer 22, when the bond strength of the metal ion and the sulfur ion 19 is strong, since the deposition rate of the metal which comprises the plating layer 32 becomes slow, ashing is performed and the to-be-plated layer 22 is activated. After that, it is preferably immersed in the electroless plating solution 200.

  Here, the electroless plating solution 200 is a plating solution that is generally used in gold electroless plating, and includes a basic compound, a reducing agent, a complexing agent, and gold ions that are deposited metals. . In the plating method of the present invention, metal ions and sulfur ions 19 are bonded to each other, and the substitution reaction is easily performed.

  And, because the entire silicon substrate 10 is immersed in such an electroless plating solution 200, the sulfur ions 19 on the surface of the layer to be plated 22 undergo a substitution reaction with gold ions in the electroless plating solution 200. Gold is deposited with the ions 19 as nuclei, and gold is selectively deposited on the layer 22 to be plated. The gold deposition reaction in the portion where the sulfur ions 19 are attached proceeds very quickly, and the gold deposition rate is slow in the portion where the gold is already deposited. For this reason, the plating layer 32 made of gold having a uniform thickness is formed over the layer to be plated 22 over time.

  Here, in the plating method of the present invention, since the surface of the base layer 16 to be electrolessly plated is subjected to sulfuration treatment, it is not necessary to perform palladium substitution treatment as in the prior art. In this embodiment, the electroless plating is performed while the region other than the base layer 16 is protected by the resist film 50. However, the resist film 50 may be peeled off. This is because gold is selectively deposited on the underlayer 16 because the sulfuration treatment is performed only on the upper surface of the underlayer 16 that needs to be plated.

  Finally, when the silicon substrate 10 is taken out from the electroless plating solution 200, a plating layer 32 of about 2 μm thickness made of gold with a uniform thickness is formed on the underlayer 16 as shown in FIG. A wiring 42 composed of the ground layer 16 and the plating layer 32 is formed.

  As described above, in the plating method of the present invention, the sulfuration treatment is performed to form the plated layer 22 on the base layer 16, and the plated layer 22 is subjected to the electroless plating treatment. The plating layer 32 is selectively formed only on the layer to be plated 22 because the substitution reaction with gold ions occurs easily. At this time, the deposition of gold occurs at a high speed, so that a thick plating layer can be formed in a relatively short time. Furthermore, it is not necessary to perform Pd substitution or the like that has been conventionally used, and it is not necessary to form many layers.

(Embodiment 2)
In this embodiment, for example, a base layer and a plating layer are formed on a part of a conductive layer made of copper (Cu) or the like, and a wiring having a terminal portion to which, for example, a bonding wire is connected is formed. It is an example.

  4 to 6 are diagrams showing a process of forming a wiring having such a terminal portion, and the plating method according to the second embodiment will be described with reference to FIGS. 4 to 6.

  First, as shown in FIG. 4A, the silicon substrate 10 is thermally oxidized in a diffusion furnace at about 1100 ° C. to form a silicon dioxide film 11.

  Next, as shown in FIG. 4B, a metal layer 13 made of Cu and having a thickness of about 20 nm is formed on the silicon dioxide film 11 by sputtering, for example.

  Next, as shown in FIG. 4C, the conductive layer 14 is formed by patterning the metal layer 13 into a predetermined shape by photolithography.

  Next, as shown in FIG. 4D, a metal layer 15 made of NiCr is formed by, for example, a sputtering method, and is patterned into a predetermined shape by a photolithography method to form an underlayer 16. At this time, the base layer 16 is formed on a part of the conductive layer 14, specifically, in a region to be a terminal portion to which a bonding wire or the like is connected.

  Then, as shown in FIG. 5A, a resist film 55 having a predetermined shape is formed by applying and patterning a resist on the entire surface other than the base layer 16 so as not to contact the base layer 16. That is, although not shown, the resist film 55 is also formed on the conductive layer 14 where the underlayer 16 is not formed.

  Next, as shown in FIG. 5 (b), as in FIG. 2 (e) described above, sulfur filled with the treatment liquid 100 made of high-concentration sulfuric acid and hydrogen peroxide of 80% or more and kept at 80 ° C. By immersing the underlayer 16 formed on one surface of the silicon substrate 10 in the treatment tank 1000 for 10 minutes, the surface of the underlayer 16 that is a portion to be plated is subjected to sulfuration treatment. At this time, it is only necessary that the base layer 16 is immersed in the processing liquid 100, and of course, the entire silicon substrate 10 may be immersed in the processing liquid 100.

  By performing the sulfuration treatment, as shown in FIG. 5C, the plated layer 24 in which the sulfur ions 19 adhere to the surface of the underlayer 16 is obtained.

  Next, as shown in FIG. 6A, at least the plated layer 24 is immersed in the electroless plating bath 2000 filled with the electroless plating solution 200 in the same manner as in FIG. At this time, the plated layer 24 may be immersed, and of course, the entire silicon substrate 10 may be immersed in the electroless plating solution 200. In this embodiment, it was immersed at 80 ° C. or more for 1-2 hours.

  Finally, when the silicon substrate 10 is taken out from the electroless plating solution 200, as shown in FIG. 6B, a plating layer 34 having a thickness of about 2 μm made of gold having a uniform thickness is formed on a part of the surface of the base layer 16. A wiring 44 having a terminal portion formed of the base layer 16 and the plating layer 34 is formed.

  In the plating method of the present embodiment, only the surface of the base layer 16 provided on a part of the conductive layer 14 is subjected to sulfuration treatment to form a layer 24 to be plated, and then electroless plating treatment is performed. The plating layer 34 is selectively formed only on a part on the surface 14. Thus, since the plating method of the present invention can selectively form a plating layer, it is possible to form the plating layer 34 on a part of the conductive layer 14 with high accuracy as in this embodiment. is there.

  In addition, since the plating method of the present invention enables partial plating as described above, it is possible to form a plating with much fewer raw materials than in the past in the manufacturing process of products that require plating. Further, it can be used for manufacturing a high-density integrated circuit used for, for example, a liquid jet head, and the entire product can be mounted at a high density.

  Further, as in the first embodiment, since gold is deposited at a high speed, a thick plating layer can be formed in a relatively short time. Furthermore, it is not necessary to perform Pd substitution or the like that has been conventionally used, and it is not necessary to form many layers. Further, for example, even if a small hole is formed in the conductive layer 14, the hole is closed as the plating grows, and the uniform plating layer 34 is formed as a whole, so that the corrosion resistance and electrical characteristics are not impaired.

  In this embodiment, the resist film 55 is provided and the sulfuration treatment is performed. However, since the silicon substrate 10 is not suspected of being subjected to the sulfurization treatment, the base layer can be provided without providing the resist film 55 during the sulfurization treatment. Sulfur ions 19 can be deposited only on 16. In this embodiment, the electroless plating is performed with the resist film 55 provided. However, since the sulfur ions 19 are attached only on the base layer 16, the resist film 55 is provided during the electroless plating. Even if not, the plating layer 34 can be selectively formed only on the layer 24 to be plated.

  When the resist is formed so as not to come into contact with the base layer 16 as in the present embodiment, the plating layer 34 is formed on the entire surface of the layer 24 to be plated. Of course, when the resist is formed so as to be in contact with the base layer 16, the plating layer 34 is formed only on the plated layer 24 as in the first embodiment.

  In the present embodiment, in order to improve the adhesion between the conductive layer 14 and the plating layer 34, the base layer 16 made of NiCr is provided on the conductive layer 14 made of copper, but directly on the conductive layer 14 made of copper. It is also possible to provide a plating layer 34. The conventional plating method required a layer to be an adhesion layer, but the plating method of the present invention provides a plating layer directly on the metal layer without providing an adhesion layer or the like on the metal layer. Can do.

(Other embodiments)
In addition, this invention is not limited to embodiment mentioned above.
For example, in the first embodiment, NiCr is used as the material of the metal layer 15 constituting the foundation layer 16 in order to increase the adhesion between the foundation layer 16 and the plating layer 32. However, the metal layer 15 is bonded to sulfur ions. In addition to nickel chromium (NiCr), base metal materials such as nickel (Ni), chromium (Cr), titanium (Ti), tungsten (W), and alloys thereof may be used.

  Further, in Embodiments 1 and 2, the plating layer in which sulfur ions are attached to the surface is formed by sulfuration treatment in which a metal layer not containing sulfur is immersed in a treatment liquid composed of sulfuric acid and hydrogen peroxide. The treatment liquid only needs to be in contact with the portion to be plated for a certain period of time, and may be treated by spraying, for example. The sulfuration treatment method is not limited to the method using the treatment liquid, and for example, a method using a gas containing sulfur element may be used. In addition, a method of forming an alloy containing sulfur on the base layer and removing the alloy by etching may be used. In this method, since sulfur contained in the alloy adheres to the underlayer, the same effect as the method using the treatment liquid can be obtained.

  On the other hand, the metal constituting the plating layer may be a metal having a lower ionization tendency than sulfur, that is, a metal having a large standard monopolar potential, but is preferably a noble metal having a large difference in ionization tendency from sulfur. In this embodiment, gold (Au) is used, but other examples include copper (Cu) and tin (Sn).

  In Embodiments 1 and 2, the example in which the wiring is formed on the substrate using the plating method of the present invention has been described, but it is needless to say that a plating layer may be provided on the entire surface of the substrate.

  In the method of the present invention, for example, when a substrate made of a resin material is used, a plating layer can be provided on the surface of the substrate. Specifically, the part where the plating layer is to be provided is subjected to sulfuration treatment using the above-described treatment liquid, and a part where activated sulfur is present on the substrate surface, that is, a layer to be plated with sulfur ions attached to the surface is formed. Then, the plating layer is formed on the layer to be plated by subjecting the base material to electroless plating in the same manner as in the first or second embodiment.

  In addition, when the substrate on which the plating layer is provided is made of a sulfur-containing resin, the surface is activated by first activating the surface of the sulfur-containing resin by performing UV irradiation, ashing, or the like on the portion where the plating layer is to be provided. A plated layer made of a resin in which sulfur is present is formed. That is, in this case, only the activated sulfur portion of the sulfur-containing resin becomes the layer to be plated. However, when UV irradiation, ashing, or the like is performed, the irradiation time varies depending on conditions, but may be about 30 seconds. And a plating layer can be formed in a to-be-plated site | part by immersing the base material which has the to-be-plated layer in the electroless-plating liquid as mentioned above.

  Thus, when the plating method of the present invention is used, it is possible to selectively form a plating layer not only on the silicon substrate surface or the metal surface but also on the resin surface.

  Furthermore, since the plating layer can be selectively formed only on the plating layer in which sulfur exists, the plating in which sulfur exists only in a desired region even on a substrate with irregularities or a substrate with holes. By providing the layer, a plating layer can be selectively formed. For this reason, the plating method of the present invention can be used for partial plating of a small area such as formation of wiring. In addition, plating can be formed on the plated layer by an environmentally friendly and easy process without using special substances, dangerous substances, environmental pollutants and the like.

(Test Example 1)
In this test example, as shown in FIG. 7, a base layer made of NiCr was formed on the surface of a silicon substrate having a plurality of grooves, and plating was performed on the base layer. First, the entire silicon substrate was immersed in a treatment liquid made of high-concentration sulfuric acid and hydrogen peroxide of 80% or more and maintained at 80 ° C., and the surface of the underlying layer was subjected to sulfuration treatment to form a layer to be plated. Next, the entire silicon substrate was immersed in an electroless plating solution containing a basic compound, a reducing agent, a complexing agent, and gold ions as deposited metals. After a predetermined time, the silicon substrate was taken out from the electroless plating solution, and the surface of the substrate was observed. FIG. 7 is a photograph showing the surface state of the silicon substrate after the plating layer is formed. In addition, the discolored part on the right side in FIG. 7 is a part where the plating layer is formed, and the part that looks like a spot in the central part is not formed completely, but gold is deposited. It is the part that has started and is dotted with gold grains.

  Here, FIGS. 8 to 10 show enlarged photographs of the silicon substrate surface. 8 is an enlarged photograph of the surface of the silicon substrate on which the plating layer on the right side of FIG. 7 is formed, and FIG. 9 is an enlarged photograph of the region in which the groove of FIG. 7 is formed. FIG. 10 is an enlarged photograph of the peripheral edge of the groove, where the upper side corresponds to the inside of the groove and the lower side corresponds to the substrate surface.

  As shown in FIG. 8, a gold plating layer was formed on the surface of the silicon substrate. As is apparent from this, a gold plating layer can be formed on the silicon substrate by using the plating method of the present invention. Further, as shown in FIG. 9, gold was also deposited in the groove of the substrate. That is, according to the plating method of the present invention, a plating layer can be formed also in the groove. Further, it can be seen that the gold grains precipitated in the grooves in this way are larger and more numerous than the gold grains deposited on the silicon substrate surface, as shown in FIG. That is, it can be seen that gold deposition in the groove portion is faster than the substrate surface. And since the plating rate (deposition rate) of the part in which the groove is formed in this way is high, even if a small hole is formed, for example, when forming a wiring or the like, the speed at which the hole is blocked is fast, so the whole is uniform. A plating layer is formed.

It is a figure which shows the wiring provided on the silicon substrate using the plating method of this invention. 6 is a diagram illustrating a wiring formation process according to Embodiment 1. FIG. 6 is a diagram illustrating a wiring formation process according to Embodiment 1. FIG. 6 is a diagram illustrating a wiring formation process according to Embodiment 2. FIG. 6 is a diagram illustrating a wiring formation process according to Embodiment 2. FIG. 6 is a diagram illustrating a wiring formation process according to Embodiment 2. FIG. It is a photograph which shows the surface state of a silicon substrate. It is an enlarged photograph which shows a part of silicon substrate surface. It is an enlarged photograph which shows a part of silicon substrate surface. It is an enlarged photograph which shows a part of silicon substrate surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Silicon substrate 11 Silicon dioxide film, 16 Underlayer, 19 Sulfur ion, 22, 24 Plated layer, 32, 34 Plating layer, 42, 44 Wiring, 50, 55 Resist film, 100 Treatment liquid, 200 Electroless plating liquid, 1000 treatment tank, 2000 electroless plating bath

Claims (10)

A plating layer having activated sulfur on the surface is provided on at least a part of the substrate, and an electroless plating process is performed on the substrate to selectively form a plating layer on the plating layer. The plating method characterized by the above-mentioned. The plating method according to claim 1, wherein the layer to be plated is a layer in which sulfur is not contained and sulfur activated on the surface is present. 3. The plating method according to claim 2, wherein the sulfur-free layer is a resin layer, and the sulfuration treatment is a treatment with a treatment solution containing at least one selected from the group consisting of sulfurous acid and sulfuric acid. A plating method characterized by the above. 3. The plating method according to claim 2, wherein the sulfur-free layer is made of a metal layer, and the plated layer is bonded to the metal of the metal layer and sulfur by the sulfuration treatment to form the plated layer. A plating method characterized by being formed. 5. The plating method according to claim 4, wherein the sulfuration treatment is a treatment with a treatment solution containing at least one selected from the group consisting of sulfurous acid and sulfuric acid. 5. The plating method according to claim 4, wherein the sulfuration treatment removes the alloy by etching after forming an alloy containing sulfur. The plating method according to claim 4, wherein the metal layer is made of Ni or NiCr. The plating method according to claim 2, wherein the layer to be plated is obtained by activating the surface of a sulfur-containing resin. The plating method according to claim 1, wherein the plating layer is made of copper or a metal having a smaller ionization tendency than copper. 10. The plating method according to claim 9, wherein the plating layer is made of gold, and a palladium substitution process is not performed before the electroless plating process.

Images