JP6781878B2 - Method of forming a conductive film on a silicon substrate - Google Patents

Description

The present invention provides a method for forming a conductive film on a silicon substrate, which can satisfactorily form a conductive film such as copper, tin, and silver on a silicon substrate on which it is difficult to form a plating film with high adhesion.

Since silicon, which is a semiconductor material, is inherently difficult to conduct electricity, even if an attempt is made to form a conductive film such as copper, silver, or tin on the surface of a silicon substrate, surface treatment by plating or the like is difficult, even if the plating film is formed. Even if it can be formed, it is not easy to secure good adhesion with the substrate.

Therefore, the prior art for forming a conductive film such as copper, tin, and silver after forming a plating film on a semiconductor substrate such as a silicon substrate is as follows.
(1) Patent Document 1
A plating film such as nickel is formed on the lower layer of the conductive track on the front surface of the doped semiconductor such as a photovoltaic cell or a solar cell, and a copper plating film is formed on the lower layer (claims 1 to 3).
Although the trade name is described for the electro-nickel solution forming the nickel film ([0051]), no specific component is mentioned.
Further, the electrolytic copper plating solution for forming the copper film is a monovalent copper ion ([0017]), a reducing agent (sulfate, boranes, hydrazine, etc .; [0018]), and a complexing agent ([0018]). It contains not oxycarboxylic acids, aminocarboxylic acids and the like, but imides, hydantoins and the like; [0019]) and conductive salts (citrate, gluconate and the like; [0021]) and the like.

(2) Patent Document 2
This is a method of forming nickel columns (bumps) on a substrate made of a silicon wafer by using an electrolytic nickel plating solution having a predetermined composition (claims 1 to 9).
The electronickel plating solution contains a nickel salt, a sulfamic acid ion, a buffer (boric acid, citric acid, lactic acid, etc.), a chloride ion, and a predetermined alcan sulfonic acid or alkene sulfonic acid (salt). (Claims 7-9, [0013]-[0016]).
In addition, the nickel plating solution can contain additives such as a wetting agent ([0018]).
As an example of the substrate, a silicon wafer previously coated with a metal such as copper is given ([0021]), while in the embodiment, a silicon wafer not referred to as a metal coating is nickel-plated ([0045]).
Examples 1 to 13 describe an electronickel plating solution containing nickel sulfamate, nickel chloride, boric acid, and propene sulfonate (or naphthalene sulfonate, ethylhexyl sulfate, etc.). ([0046], Table 1).

(3) Patent Document 3
A base metal film is formed on the surface of a substrate (no specific example), immersed in a plating solution containing a predetermined metal complex and electroplated to form a metal film contained in the metal complex on the surface of the base metal film. (Claims 1 and 2). The underlying metal film is titanium, silicon, or the like, and the metal complex contained in the plating solution is copper formate, nickel formate, cobalt formate (claim 2, [0012]).
In the embodiment, the base metal film is titanium, and the metal coated on the titanium is a copper film ([0019] to [0024]), but it is described that titanium can be replaced with silicon and the copper film can be replaced with a nickel film. ([0019]).

Japanese Unexamined Patent Publication No. 2012-237060 JP-A-2016-121377 Japanese Unexamined Patent Publication No. 2011-149097

In general, a transparent conductive film such as an ITO film has a large specific resistance. Therefore, when a conductive film such as copper, silver, or tin is formed on the transparent conductive film, JP-A-3-040452, JP-A-63-255377. As shown in Japanese Patent Application Laid-Open No. 64-076032 and Japanese Patent Application Laid-Open No. 2011-195893, a predetermined plating film is interposed between the transparent conductive film and the conductive film, or copper plating having a predetermined composition is provided. While it is necessary to make full use of specific treatments such as electroplating the conductive film using a bath or the like, the silicon substrate has a large specific resistance like the transparent conductive film described above, so that the conductive film is formed on the silicon substrate. It's not easy to do. For example, as in Patent Document 2, even if electroplating is performed on a silicon substrate using a nickel plating solution containing a predetermined alkene sulfonic acid or a salt thereof and a buffer such as boric acid or citric acid. Since the formed nickel film has a clear poor adhesion to the substrate (see Comparative Example 2 described later), as a practical matter, in the method of Document 2, copper, silver, etc. are formed on the silicon substrate via the nickel film. It is difficult to form the conductive film of the above with good adhesion.

An object of the present invention is to firmly form a conductive film such as copper, tin, or silver on a silicon substrate in close contact with each other.

When forming a conductive film on a silicon substrate, the present inventors basically use a nickel-based base film as an interposition between the substrate and the conductive film, and use the type of the base film and for forming the base film. We have conducted extensive research on the composition of the plating bath.
As a result, a nickel-phosphorus film was selected instead of the nickel film as the nickel-based film, and a predetermined complexing agent, a surface active agent, a brightener, etc. were used in combination in the electronickel-phosphorus plating bath for forming the base film. When added, the undercoat can be firmly formed on the silicon substrate, so that the conductive film can be formed on the silicon substrate with good adhesion, and when the nickel-phosphorus film of the undercoat is heat-treated in a predetermined low temperature range. The present invention has been completed by finding that the adhesion of the base film to the silicon substrate can be further strengthened.

That is, the present invention 1 is a method of forming a conductive film on a silicon substrate.
(S1) A step of forming a base film composed of a nickel-phosphorus film on the silicon substrate using an electric nickel-phosphorus plating bath, and
(S2) A step of forming a conductive film on the base film and
A step (S12) of heat-treating the base film at 30 to 160 ° C. is interposed between the base film forming step (S1) and the conductive film forming step (S2), or
After the above step (S2), a step (S3) of heat-treating the base film and the conductive film at 30 to 160 ° C. is added.
The above nickel-phosphor plating bath is
(a) Soluble nickel salt and
(b) Phosphorus-containing compounds and
(c) A complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, sugars, amino alcohols, polycarboxylic acids, and polyamines.
(d) Nonionic surfactants, surfactants selected from amphoteric surfactants, and
(e) A buffer selected from boric acid, sodium carbonate, sodium hydrogen carbonate, nickel acetate, succinic acid, and ascorbic acid ,
(f) From saccharin and its salt, benzenesulfonic acid and its salt, toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, butinediol, ethylenesianhydrin, coumarin, propagil alcohol It is a method for forming a conductive film on a silicon substrate, which comprises containing a selected brightener.

The present invention 2 is a method for forming a conductive film on a silicon substrate according to the above invention 1, wherein the step (S12) or step (S3) is heat-treated with warm water at 30 to 100 ° C.

In the present invention 3, the complexing agent (c) in the present invention 1 or 2 is citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentacetic acid. A method for forming a conductive film on a silicon substrate, which is at least one of an oxycarboxylic acid, a polycarboxylic acid, an aminocarboxylic acid or a salt thereof selected above.

The present invention 4 is a method for forming a conductive film on a silicon substrate according to any one of the above inventions 1 to 3 , wherein the pH of the nickel-phosphorus plating bath is 3.0 to 8.0. ..

The present invention 5 is a method for forming a conductive film on a silicon substrate according to any one of the above inventions 1 to 4 , wherein the film thickness of the base film is 0.01 to 10.0 μm.

In the sixth aspect of the present invention , in any one of the first to fifth aspects of the present invention , the conductive film is formed by electroplating, electroless plating, sputtering or vapor deposition.
The conductive film is characterized by being a film made of a metal selected from copper, tin, silver, gold, nickel, bismuth, palladium, platinum, aluminum, magnesium, cobalt, zinc and chromium, or an alloy of these metals. This is a method for forming a conductive film on a silicon substrate.

Conventionally, even if an attempt is made to plate a conductive film such as copper or tin on a silicon substrate, it is not easy to form the conductive film smoothly by plating, as in the case of forming a conductive film on a transparent electrode film. Even if a film could be formed, there was a problem that sufficient adhesion could not be secured and adhesion was poor.
In the present invention, a nickel-based base film is interposed between the silicon substrate and the conductive film, a nickel-phosphorus film is selected for the nickel-based film, and an electronickel-phosphorus plating bath is used as a predetermined complexing agent. A base film is formed by specializing in a composition in which a surfactant and a brightener coexist, and is predetermined at an intermediate stage between the base film forming step and the conductive film forming step, or at a later stage of the conductive film forming step. By performing the heat treatment in the low temperature range (30 to 160 ° C.), the undercoat can be firmly adhered to the silicon substrate, and the conductive film can be formed on the silicon substrate through the undercoat with good adhesion.

Incidentally, in Examples 1 to 4 of Patent Document 2 described above, nickel chloride, nickel sulfamate, a buffer (boric acid), and an additive (propensulfonate) are provided on a substrate made of a silicon wafer. It is described that a nickel film is formed by using an electro-nickel-plated sulfamic acid bath containing the above (claims 1 to 5, [0045] to [0048] and Table 1), and further, the nickel-plated bath. It is described that in addition to boric acid, citrate, lactic acid and the like can be used as the buffer, and that a wetting agent and the like can be added ([0016], [0018]). The propene sulfonate is synonymous with allyl sulfonate.
Therefore, in accordance with Patent Document 2, based on each of the plating baths (Table 1) of Examples 1 to 5 of Document 2, an electronickel plating bath further added with citric acid is used on the silicon substrate. It is possible to form a nickel film, but even if electroplating is actually performed using this nickel sulfamic acid bath, the nickel film formed on the silicon substrate will peel off and the adhesion will be insufficient. It was not possible to realize the strong adhesion as in the invention (see Comparative Example 2 described later).

In the method of the present invention, only a step of underlaying a nickel-phosphorus film on a silicon substrate (S1) and a step of forming a conductive film on the base film (S2) are performed, and practically, the silicon substrate is covered. Although the conductive coating can be satisfactorily formed, between these steps and (S1) (S2), or, after the step (S2), the addition of heat-treating undercoat or more conductive coating in, it can strengthen the adhesion of the primer coating to the silicon substrate.

The present invention is a method of forming a conductive film of copper, tin, silver, etc. on a silicon substrate via a base film made of a nickel-phosphorus film, wherein the base film is a predetermined complexing agent and a surfactant. In the middle of the process of forming an electrodeposition film using an electronickel-phosphorus bath having a specific composition containing a brightener, etc., and forming this base film, and the step of forming a conductive film on the base film , or Is a method for strengthening the adhesion of the nickel-phosphorus base film to a silicon substrate by heat-treating the base film or the conductive film in a predetermined low temperature range (30 to 160 ° C.) after the step of forming the conductive film. Is.
The silicon substrate is a concept that includes a single crystal silicon semiconductor or a polycrystalline silicon semiconductor in which an impurity is doped in a silicon wafer or the like, or a silicon semiconductor in which an amorphous silicon layer is formed.

The present invention 1 comprises the following base forming step (S1), conductive film forming step (S2) , and heat treatment step (S12) or (S3) .
The heat treatment step (S12) or (S3) will be described later.
(S1) Step of forming a base film composed of a nickel-phosphorus film on a silicon substrate using an electric nickel-phosphorus plating bath (S2) Step of forming a conductive film on the base film Then, in the above step (S1) The electronickel-phosphorus plating bath used is
(a) Soluble nickel salt and
(b) Phosphorus-containing compounds and
(c) A complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, sugars, amino alcohols, polycarboxylic acids, and polyamines.
(d) Nonionic surfactants, surfactants selected from amphoteric surfactants, and
(e) With a predetermined buffer
(f) A predetermined brightener is an essential ingredient.

The soluble nickel salt (a) may supply nickel ions in the plating bath, and may be nickel sulfate, nickel chloride, nickel ammonium sulfate, nickel oxide, nickel acetate, nickel carbonate, nickel oxalate, nickel sulfamate, or organic. Examples thereof include nickel salts of sulfonic acid, and nickel sulfate, nickel oxide and the like are preferable.
Examples of the phosphorus-containing compound (b) include phosphorous acid, hypophosphorous acid, pyrophosphoric acid, orthophosphoric acid, hydroxyethylenediaminediphosphonic acid, nitrilotris (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid) and These salts are mentioned.
The soluble nickel salt (a) can be used alone or in combination, and its content in the plating bath is 0.001 to 3.0 mol / L, preferably 0.05 to 2.0 mol / L, more preferably 0.0. It is 1 to 1.5 mol / L.
The phosphorus-containing compound (b) can be used alone or in combination, and its content in the plating bath is 0.05 to 2.0 mol / L, preferably 0.1 to 1.0 mol / L, more preferably 0. It is .1 to 0.8 mol / L.

The complexing agent (c) contained in the electronickel-phosphorus plating bath is a compound that mainly forms a nickel complex in the plating bath, and slows down the change in the cathode current density with respect to the change in the electrode potential to form a nickel-based film. It has a function of facilitating precipitation, and is selected from the group consisting of aminocarboxylic acids, oxycarboxylic acids, sugars, aminoalcohols, polycarboxylic acids, and polyamines.
Examples of the aminocarboxylic acids include ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), diethylenetriaminetetraacetic acid (DTPA), triethylenetetraminehexacetic acid (TTHA), ethylenediaminetetrapropionic acid, and nitrilotriacetic acid (NTA). , Iminodiacetic acid (IDA), iminodipropionic acid (IDP), metaphenylenediamine tetraacetic acid, 1,2-diaminocyclohexane-N, N, N', N'-tetraacetic acid, diaminopropionic acid and salts thereof. NTA and EDTA are preferable.
Examples of the oxycarboxylic acids include tartaric acid, citric acid, malic acid, gluconic acid, glycolic acid, lactic acid, glucoheptonic acid and salts thereof, and citric acid, tartaric acid, gluconic acid and salts thereof are preferable.
The above sugars include glucose (dextrose), fructose (fructose), lactose (lactose), maltulose (maltulose), isomaltulose (palatinose), xylose, sorbitol, xylitol, mannitol, martitol, erythritol, reduced water candy, and lactitol. , Reduced isomaltulose, gluconolactone and the like, and sugar alcohols such as sorbitol, xylitol, mannitol and martitol are preferable.
Examples of the amino alcohols include monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, and tripropanolamine, and triethanolamine and tripropanolamine are preferable.
Examples of the polycarboxylic acids include succinic acid, oxalic acid, glutaric acid, adipic acid, malonic acid and salts thereof, and succinic acid is preferable.
Examples of the polyamines include methylenediamine, ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine and the like, and ethylenediamine is preferable.
As the complexing agent (c), oxycarboxylic acids, aminocarboxylic acids and sugars are preferable, and citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid and diethylenetriamine-5 Acetic acid and salts thereof, sorbitol, mannitol, martitol and the like are suitable.
The complexing agent (c) can be used alone or in combination, and its content in the plating bath is 0.001 to 2 mol / L, preferably 0.05 to 0.8 mol / L, and more preferably 0. It is 1 to 0.5 mol / L.

The surfactant (d) contained in the electronickel-phosphorus plating bath is selected from nonionic surfactants and amphoteric surfactants, and enhances the adhesion between the silicon substrate and the base film.
The nonionic surfactants generally include C1 to C20 alkanols, phenols, naphthols, bisphenols, (poly) C1 to C25 alkylphenols, (poly) arylalkylphenols, C1 to C25 alkylnaphthols, and C1 to C25 alkoxylations. Condensation of 2 to 300 mol of ethylene oxide (EO) and / or propylene oxide (PO) with phosphoric acid (salt), sorbitan ester, polyalkylene glycol, C1-C22 aliphatic amine, C1-C22 aliphatic amide, etc. , C1 to C25 alkoxylated phosphate (salt) and the like. For example, polyoxyethylene cumin phenol ether, polyoxyethylene dodecylphenyl ether, dibutyl-β-naphthol polyethoxylate, polyoxyethylene styrene phenyl ether, ethylenediylene / tetrapolyoxyethylene / polyoxypropylene, polyethylene glycol, lauryl alcohol poly. Phenol and the like are suitable.
Examples of the amphoteric surfactant include carboxybetaine, imidazoline betaine, sulfobetaine, and aminocarboxylic acid. For example, betaine lauryldimethylaminoacetate, amidopropylbetaine stearate, amidopropyldimethylamine laurate oxide and the like are suitable. Sulfation of ethylene oxide and / or the condensation product of propylene oxide with alkylamines or diamines, or sulfonated adducts can also be used.
The surfactant (d) can be used alone or in combination, and its content in the plating bath is 0.1 to 50 g / L, preferably 1 to 40 g / L, and more preferably 5 to 35 g / L.
As described above, the nickel-phosphorus plating bath of the present invention requires the addition of nonionic and amphoteric surfactants from the viewpoint of increasing adhesion. In addition to these surfactants, cationic and anionic surfactants are required. It does not preclude the combined addition of surfactants.
However, even if a cationic or anionic surfactant is added alone without adding the predetermined surfactant of the present invention to the plating bath, it does not contribute to the stability of the plating bath and the adhesion of the base film. It is as shown in the test example (see Comparative Example 7) described later.

The predetermined buffer (e) contained in the nickel-phosphorus plating bath improves the adhesion of the base film to the silicon substrate and also acts as a stabilizer for the plating bath.
Examples of the predetermined buffer (e) include boric acid, sodium carbonate, sodium hydrogencarbonate, nickel acetate, succinic acid, ascorbic acid and the like, and boric acid and sodium carbonate are preferable.
The buffering agent (e) can be used alone or in combination, and its content in a plating bath is 0.05 to 1.5 mol / L, preferably 0.05 to 1.0 mol / L, and more preferably 0. It is .1 to 0.6 mol / L.

The predetermined brightener (f) contained in the nickel-phosphorus plating bath acts to improve the adhesion of the nickel-phosphorus film to the silicon substrate.
Examples of the predetermined brightener (f) include saccharin and its salt, benzenesulfonic acid and its salt, p-toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, and butinediol (specifically. Examples thereof include 2-butin-1,4-diol, etc.), ethylene cyanhydrin, coumarin, propagyl alcohol, etc., and in particular, benzenesulfonic acid or a salt thereof and saccharin, naphthalenesulfonic acid or a salt thereof and saccharin, etc. , Butindiol and benzenesulfonic acid or its salt, Butindiol and naphthalenesulfonic acid or its salt, allylsulfonic acid or its salt and saccharin, allylsulfonic acid or its salt and propagyl alcohol, benzenesulfonic acid or its salt and propagil It is preferable to use two or more kinds such as alcohol, naphthalene sulfonic acid or a salt thereof and propagyl alcohol in combination.
The brightener (f) can be used alone or in combination, and its content in the plating bath is 0.001 to 0.15 mol / L, preferably 0.005 to 0.07 mol / L, and more preferably 0. It is 0.01 to 0.05 mol / L.

The purpose of the electronickel-phosphorus plating bath of the present invention is to form a nickel-phosphorus film on a silicon substrate as a base, and the pH of the plating bath is preferably 3.0 to 8.0, preferably 4.0. It is ~ 6.0.
Further, in the base forming step (S1), the cathode current density at the time of electroplating is 0.01 to 5.0 A / dm2, and the preferable range is 0.05 to 2.0 A / dm2.
In the process of forming the base film (S1), the nickel-phosphorus film to be the base film need not be formed thick as long as it can impart sufficient conductivity and adhesive force to form the conductive film on the upper layer. Therefore, the film thickness is 0.01 to 10.0 μm, preferably 0.01 to 8.0 μm, and more preferably 0.01 to 5.0 μm.

Next, a step (S2) of forming a conductive film as an upper layer film on the nickel-phosphorus film coated in the base film forming step (S1) will be described.
The above conductive film is not particularly limited as long as it is a known film having conductivity, but from, for example, copper, tin, silver, gold, nickel, bismuth, palladium, platinum, aluminum, magnesium, cobalt, zinc, and chromium. Examples include selected metals or alloys of these metals.
As the metal constituting the conductive metal, silver, copper, nickel, tin, palladium, gold and bismuth are preferable. Examples of the metal alloys include nickel-tungsten alloys, nickel-molybdenum alloys, nickel-tin alloys, tin-silver alloys, tin-bismus alloys, tin-copper alloys, tin-zinc alloys, and gold-tin alloys. Suitable.
The conductive film can be formed by electroplating, electroless plating, sputtering, vapor deposition, or the like. Among them, the plating method is preferable from the viewpoint of productivity, but sputtering or vapor deposition is not excluded.

The present invention is characterized in that a conductive film is formed on a silicon substrate via a base film. The conductive film may be formed in a single layer, but is formed in a plurality of layers such as two layers and three layers. You can also do it.
To give an example of a multi-layer conductive film, a metal selected from nickel, copper, cobalt, bismuth, zinc, chromium, iron, etc., or an alloy of these metals is used as the lower layer (that is, the side facing the base film). Examples thereof include a two-layer conductive film having tin, copper, gold, silver and the like as upper layers.
Further, when the uppermost layer of the conductive film of the plurality of layers is formed of tin, nickel, cobalt, chromium, silver, palladium, alloys thereof and the like, the surface of the uppermost layer can be given a beautiful silver appearance.

On the other hand, the present invention 1 is a conductive film forming method in which a heat treatment step is further added to the undercoat film forming step (S1) and the conductive film forming step (S2) as described above .
The first method of heat treatment involves interposing a heat treatment step (S12) between the base film forming step (S1) and the conductive film forming step (S2), and this intermediate heat treatment method comprises the following steps.
(S1) Step of forming a base film composed of a nickel-phosphorus film on a silicon substrate using an electric nickel-phosphorus plating bath (S12) Step of heat-treating the base film at 30 ° C. or higher (S2) Conductivity on the base film Step of forming a film By heat-treating the undercoat at 30 ° C or higher after forming the undercoat, the adhesion of the undercoat to the silicon substrate can be further improved, and the conductive film can be further strengthened on the silicon substrate. Can form close contact.
The heat treatment temperature is preferably 30 to 160 ° C., particularly preferably 30 to 100 ° C.
Even if the heat treatment temperature is raised , the effect of improving the adhesion is not so different, and on the contrary, thermal strain is generated in the base film, which adversely affects the adhesion, or there is a risk of oxidizing the base film and wasted energy. Productivity is also reduced by the input of. In view of this point, the upper limit of the heat treatment temperature is preferably about 160 ° C. Further, in the present invention, the adhesion of the base film to the silicon substrate is similar to that of the heat treatment even if the heat treatment is not performed after the base film forming step (S1) ( see Reference Examples 1 to 3 described later ). The lower limit of the heat treatment was about 30 ° C.
On the other hand, the second method of heat treatment is a method in which a heat treatment step (S3) is added after the conductive film forming step (S2), and the post-stage heat treatment method comprises the following steps.
(S1) Step of forming a base film composed of a nickel-phosphorus film on a silicon substrate using an electric nickel-phosphorus plating bath (S2) Step of forming a conductive film on the base film (S3) The base film and conductivity Step of heat-treating the film at 30 ° C. or higher The temperature conditions of the heat treatment in the second method may be the same as those in the first method.
The above heat treatment (common to both the intermediate and post-stage heat treatment methods) can be selected from various modes such as oven heating, hot air heating with a dryer, and immersion in hot water or an oil bath. For example, hot water treatment at 30 to 100 ° C. When (boiled in hot water) is selected, the heat treatment is performed in a low temperature range by boiling, so that the heat energy can be reduced and the treatment can be simplified, and the productivity can be improved.

Hereinafter, an electric nickel-phosphorus plating bath for forming a base film (nickel-phosphorus film) on a silicon substrate, a plating bath for forming a conductive film, and a conductive film on the silicon substrate via the base film. Examples of the method for forming the film will be described, and examples of the evaluation test of the adhesion of the nickel-phosphorus film to the silicon substrate will be described in sequence.
It should be noted that the present invention is not limited to the following examples and test examples, and it goes without saying that any modification can be made within the scope of the technical idea of the present invention.

<< Example of a method for forming a conductive film on a silicon substrate >>
Of the following Examples 1 to 30 , Example 1 is an example of a nickel-phosphorus film (base film) / copper film (conductive film), and the phosphorus-containing compound (b) is a hydrogen phosphite, which is complexed. The agent (c) is citric acid, the surfactant (d) is a nonionic surfactant, the buffer (e) is boric acid, and the brightener (f) is nickel-phosphorus, which is a combined component of saccharin and allylsulfonic acid. This is an example in which a base film is formed using a sulfamic acid bath, heat treatment is performed, and then a conductive film of copper is formed by electroplating (example of the above intermediate heat treatment method).
Example 2 is an example in which the water-soluble nickel salt is changed based on the above-mentioned Example 1. Examples 3 to 4 are examples in which the phosphorus-containing compound (b) is modified based on Example 1. Example 5 is an example in which the phosphorus-containing compound (b) is modified based on Example 2. Examples 6 to 7 are examples in which the complexing agent (c) is changed based on Example 1, Example 6 is based on nitrilotriacetic acid, Example 7 is based on gluconate, and Example 8 is based on Example 5. This is an example in which the complexing agent (c) is changed to sorbitol. Example 9 is an example in which the buffer (e) is changed to sodium carbonate based on Example 1. Examples 10 to 13 are examples in which the brightener (f) is changed based on Example 1, Example 10 is a combination of saccharin and benzenesulfonic acid, and Example 11 is a combination of allylsulfonic acid and propagyl alcohol. Example 12 is a combination example of benzenesulfonic acid and butinediol, and Example 13 is a combination example of naphthalenesulfonate and butinediol. Examples 14 to 15 are examples in which the type of the nonionic surfactant (d) is changed based on Example 1, and Example 16 uses the surfactant (d) as an amphoteric surfactant based on Example 1. This is an example of changing to. Example 17 is an example in which the composition of the electrolytic copper plating bath for forming the conductive film is changed based on Example 1.
Example 18 is an example in which the conductive film is changed to a nickel film based on Example 1. Example 19 is an example in which the conductive film is changed to a tin film based on Example 1. Example 20 is an example in which the conductive film is changed to a tin-bismuth alloy film based on Example 1. Example 21 is an example in which the conductive film is changed to a silver film formed by electroless plating based on Example 1. Example 22 is an example in which the conductive film is changed to a palladium film based on Example 1. Examples 23 to 27 are examples in which the heat treatment conditions are changed based on Example 1.
Examples 28 to 30 are examples in which the above intermediate heat treatment method is changed to a method of heat treatment after the conductive film forming step (S2) (post-stage heat treatment method), and Example 28 is based on Example 1. (The conductive film is copper), Example 29 is based on Example 19 (the conductive film is tin), and Example 30 is an example based on Example 21 (the conductive film is silver).
Reference Example 1 is an example based on Example 1 in which the heat treatment between the formation of the base film and the conductive film is eliminated. Reference Example 2 is also an example in which the heat treatment is eliminated based on Example 2, and Reference Example 3 is an example in which the heat treatment is eliminated based on Example 3.

On the other hand, among the following Comparative Examples 1 to 8, Comparative Example 1 is a blank example in which the base film is not formed on the silicon substrate and is directly electroplated using a plating bath for forming a conductive film.
Comparative Example 2 is an example in which the compound (b) containing phosphorus is lacking in the plating bath based on Example 1, and is conducted by electroplating on an aluminum alloy through a nickel base film instead of a nickel-phosphorus film. This is an example of forming a sex film. That is, in view of the fact that the above-mentioned Patent Document 2 describes that buffering agents and wetting agents such as boric acid, citric acid, and lactic acid can be used ([0016], [0018]), the above-mentioned Patent Document 2 A nickel film was formed using an electro-nickel plating bath containing citric acid and a buffering agent specifically disclosed in Examples 1 to 5 ([0046], Table 1), so to speak, nickel of Patent Document 2. This is an example based on the bath.
Comparative Example 3 is an example in which the electroplating bath for forming an undercoat film lacks the complexing agent (c) of the present invention based on Example 1, and Comparative Example 4 is also an example in which the plating bath contains the surfactant (d) of the present invention. Comparative Example 5 is an example in which the buffer (e) of the present invention is lacking in the plating bath, and Comparative Example 6 is an example in which the brightener (f) of the present invention is lacking in the plating bath.
Comparative Example 7 is an example in which a cationic surfactant is used in place of the surfactant of the present invention in the electroplating bath for forming the base film.
Comparative Example 8 is an example in which a nickel base film is formed on a silicon substrate instead of a nickel-phosphorus film by using a known watt bath, and a conductive film is formed on the nickel base film by electroplating.

(1) Example 1
First, a 5 cm × 5 cm square silicon substrate was used as a sample and sequentially processed based on the following steps (S1), (S12), and (S2) (Examples 2 to 30 and Comparative Examples 1 to 8 below). Is the same).
(S1) Substrate formation step The above sample (silicon substrate) is alkaline degreased with sodium hydroxide (3% by weight) at 25 ° C. for 3 minutes, and the nickel-phosphorus plating bath and electroplating conditions of (A) below are used. An undercoat was formed on the sample and washed with water at 25 ° C. for about 30 seconds.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
The sodium hydrogen phosphite hydrate is a phosphorus-containing compound (b), citric acid is a complexing agent (c), ethylene oxide adduct of cuminphenol is a nonionic surfactant (d), and boric acid is a buffer. e), saccharin and allylsulfonic acid are composite brighteners (f).
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%
(S12) Heat Treatment Step The silicon substrate on which the nickel-phosphorus film was formed was boiled in hot water under the following conditions.
[Heat treatment conditions]
Water bath temperature: 70 ° C
Water bath time: 3 minutes (S2) Step of forming a conductive film A conductive film was formed on a heat-treated silicon substrate by the copper plating bath of (B) below and electroplating conditions, washed with water, and then dried.
(B) Conductive film: Copper An electrolytic copper-plated bath was constructed with the following composition.
Copper sulfate pentahydrate (as Cu2 +) 0.8 mol / L
Sulfuric acid 1.0 mol / L
Hydrochloric acid 1.8 mol / L
Bis (3-sulfopropyl) disulfide 1.0 mg / L
Polyethylene glycol (molecular weight 4000) 1.0 g / L
Polyethyleneimine 3.0 mg / L
[Electroplating conditions]
Bath temperature: 25 ° C
Current density: 5A / dm2
Plating time: 15 minutes [Plating film thickness]
Film thickness: 17 μm

(2) Example 2
Based on the above-mentioned Example 1, the nickel-phosphor plating bath and the electroplating conditions of the step (S1) were changed as follows (the water-soluble nickel salt was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel Sulfate Hexahydrate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.3 μm
Phosphorus content: 6.0%

(3) Example 3
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the compound containing phosphorus was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium hypophosphite 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 5.0
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.1A / dm2
Plating time: 2 minutes [Plating film]
Film thickness: 0.01 μm
Phosphorus content: 4.5%

(4) Example 4
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the compound containing phosphorus was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Nitrilotris (methylenephosphonic acid) 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.5%

(5) Example 5
Based on the above Example 2, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the compound containing phosphorus was changed).
The processing conditions of the steps (S12) to (S2) are the same as those of the second embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel Sulfate Hexahydrate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium hypophosphate 0.5 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.3 μm
Phosphorus content: 5.5%

(6) Example 6
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the complexing agent was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Nitrilotriacetic acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.0
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.1 μm
Phosphorus content: 7.0%

(7) Example 7
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the complexing agent was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Sodium gluconate 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 5.0
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%

(8) Example 8
Based on the above Example 5, the nickel-phosphorus plating bath and the electroplating conditions in the step (S1) were changed as follows (the complexing agent was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the fifth embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel Sulfate Hexahydrate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Hypophosphorous acid 0.5 mol / L
Sorbitol 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.3 μm
Phosphorus content: 5.5%

(9) Example 9
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (buffering agent was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Sodium carbonate 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 3.0%

(10) Example 10
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the brightener was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Benzenesulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 3.0%

(11) Example 11
Based on the above-mentioned Example 2, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the brightener was changed).
The processing conditions of the steps (S12) to (S2) are the same as those of the second embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel Sulfate Hexahydrate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Phosphorous acid 0.4 mol / L
Citric acid 0.3 mol / L
Allyl sulfonic acid 0.02 mol / L
Propargyl alcohol 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.3 μm
Phosphorus content: 6.0%

(12) Example 12
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the brightener was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Butindiol 0.02 mol / L
Benzenesulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%

(13) Example 13
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the brightener was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Butindiol 0.02 mol / L
Sodium naphthalene sulfonate 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.0%

(14) Example 14
Based on the above-mentioned Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the surfactant was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Ethylenediamine tetrapolyoxyethylene (EO 2 mol)
-Polyoxypropylene (PO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 3.0%

(15) Example 15
Based on Example 5 above, the nickel-phosphorus plating bath and electroplating conditions in step (S1) were changed as follows (surfactant was changed).
The processing conditions of the steps (S12) to (S2) are the same as those in the fifth embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel Sulfate Hexahydrate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Hypophosphorous acid 0.5 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Ethylenediamine tetrapolyoxyethylene (EO 2 mol)
-Polyoxypropylene (PO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.0
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 5.5%

(16) Example 16
Based on the above Example 1, the nickel-phosphorus plating bath and the electroplating conditions of the step (S1) were changed as follows (the surfactant was changed to an amphoteric surfactant).
The processing conditions of the steps (S12) to (S2) are the same as those in the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Amidopropyl lauryl dimethylamine oxide 20 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 3.0%

(17) Example 17
Based on the above-mentioned Example 1, the electrocopper plating bath and the electroplating conditions used in the conductive film forming step (S2) were changed as follows.
The processing conditions of the steps (S1) to (S12) are the same as those of the first embodiment.
(B) Conductive film: Copper An electrolytic copper-plated bath was constructed with the following composition.
Copper sulfate pentahydrate (as Cu2 +) 0.1 mol / L
Ethylenediamine 0.3 mol / L
Ammonium sulphate 1.5 mol / L
Glycine 0.3 mol / L
α, α'-bipyridyl 30 mg / L
pH (adjusted with 28% ammonia) 7.0
[Electroplating conditions]
Bath temperature: 50 ° C
Current density: 1A / dm2
Plating time: 13 minutes [Plating film thickness]
Film thickness: 3 μm

(18) Example 18
Based on the above-mentioned Example 1, in the step of forming the conductive film (S2), the conductive film was changed to a nickel film.
The processing conditions of the steps (S1) to (S12) are the same as those of the first embodiment.
(B) Conductive film: Nickel An electro-nickel plating bath was constructed with the following composition.
Nickel sulphate hexahydrate (as Ni2 +) 0.15 mol / L
Nickel chloride (as Ni2 +) 0.5 mol / L
Boric acid 0.7 mol / L
pH (adjusted with 28% ammonia) 4.0
[Electroplating conditions]
Bath temperature: 60 ° C
Current density: 1A / dm2
Plating time: 5 minutes [Plating film thickness]
Film thickness: 1.0 μm

(19) Example 19
Based on the above-mentioned Example 2, the conductive film was changed to a tin film in the conductive film forming step (S2).
The processing conditions of the steps (S1) to (S12) are the same as those of the second embodiment.
(B) Conductive film: tin An electric tin-plated bath was constructed with the following composition.
Stannous Methanesulfonic Acid (as Sn2 +) 0.5 mol / L
Methanesulfonic acid 1.0 mol / L
Polyoxyethylene cumylphenyl ether (EO 10 mol) 10 g / L
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 2A / dm2
Plating time: 10 minutes [Plating film thickness]
Film thickness: 10 μm

(20) Example 20
Based on the above Example 5, the conductive film was changed to a tin-bismuth alloy film in the conductive film forming step (S2).
The processing conditions of the steps (S1) to (S12) are the same as those of the fifth embodiment.
(B) Conductive film: tin-bismuth alloy An electric tin-bismuth alloy plating bath was constructed with the following composition.
Stannous Methanesulfonic Acid (as Sn2 +) 0.6 mol / L
Bismuth methanesulfonate (as Bi3 +) 0.02 mol / L
Methanesulfonic acid 1.0 mol / L
Polyoxyethylene cumylphenyl ether (EO 10 mol) 10 g / L
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 2A / dm2
Plating time: 5 minutes [Plating film thickness]
Film thickness: 5.0 μm
Bismuth precipitation rate: 2%

(21) Example 21
Based on the above-mentioned Example 1, the conductive film was changed to a silver film in the step of forming the conductive film (S2), and this silver film was formed by electroless plating.
The processing conditions of the steps (S1) to (S12) are the same as those of the first embodiment.
(B) Conductive film: Silver An electroless silver-plated bath was constructed with the following composition.
Silver nitrate (as Ag +) 0.01 mol / L
Imide succinate 0.05 mol / L
Imidazole 0.05 mol / L
[Electroplating conditions]
Bath temperature: 50 ° C
Plating time: 60 minutes [Plating film thickness]
Film thickness: 1 μm

(22) Example 22
Based on the above Example 5, the conductive film was changed to a palladium film in the conductive film forming step (S2).
The processing conditions of the steps (S1) to (S12) are the same as those of the fifth embodiment.
(B) Conductive film: Palladium An electric palladium-plated bath was constructed with the following composition.
Palladium sulfate (as Pd2 +) 0.02 mol / L
Sulfuric acid 0.4 mol / L
Phosphoric acid 0.6 mol / L
Sulfurous acid 0.006 mol / L
[Electroplating conditions]
Bath temperature: 25 ° C
Current density: 0.6A / dm2
Plating time: 20 minutes [Plating film thickness]
Film thickness: 1.5 μm

(23) Example 23
Based on the above Example 1, the water bath conditions in the heat treatment step (S12) were changed.
The processing conditions of the step (S1) and the step (S2) are the same as those of the first embodiment.
(S12) Heat Treatment Step A silicon substrate formed with a nickel-phosphorus film as a base film was boiled in hot water under the following conditions.
[Heat treatment conditions]
Water bath temperature: 50 ° C
Water bath time: 10 minutes

(24) Example 24
Based on the above Example 1, the water bath conditions in the heat treatment step (S12) were changed.
The processing conditions of the step (S1) and the step (S2) are the same as those of the first embodiment.
(S12) Heat Treatment Step A silicon substrate formed with a nickel-phosphorus film as a base film was boiled in hot water under the following conditions.
[Heat treatment conditions]
Water bath temperature: 100 ° C
Water bath time: 1 minute

(25) Example 25
Based on the above-mentioned Example 1, the heating conditions in the heat treatment step (S12) were changed.
The processing conditions of the step (S1) and the step (S2) are the same as those of the first embodiment.
(S12) Heat Treatment Step A silicon substrate having a nickel-phosphorus film as a base film was heated with hot air by a dryer under the following conditions.
[Heat treatment conditions]
Hot air heating temperature: 100 ° C
Heating time: 20 minutes

(26) Example 26
Based on the above-mentioned Example 1, the heating conditions in the heat treatment step (S12) were changed.
The processing conditions of the step (S1) and the step (S2) are the same as those of the first embodiment.
(S12) Heat Treatment Step A silicon substrate formed with a nickel-phosphorus film as a base film was oven-heated under the following conditions.
[Heat treatment conditions]
Oven heating temperature: 100 ° C
Heating time: 15 minutes

(27) Example 27
Based on the above-mentioned Example 1, the heating conditions in the heat treatment step (S12) were changed.
The processing conditions of the step (S1) and the step (S2) are the same as those of the first embodiment.
(S12) Heat Treatment Step A silicon substrate formed with a nickel-phosphorus film as a base film was oven-heated under the following conditions.
[Heat treatment conditions]
Oven heating temperature: 150 ° C
Heating time: 10 minutes

(28) Example 28
The 28th embodiment is based on the 1st embodiment.
In the first embodiment, the treatment was sequentially performed in the order of the base film forming step (S1) → heat treatment step (S12) → conductive film forming step (S2), but in the present Example 28, the undercoat forming step (S1) → This is an example of a so-called post-stage heat treatment method in which a copper film is used as a conductive film and is sequentially processed by a step of forming a conductive film (S2) → a heat treatment step (S3).
That is, based on Example 1, the heat treatment (S3) was performed after the conductive film forming step (S2) without performing the intermediate stage heat treatment (S12) after the base film forming step (S1). Yes, the heat treatment conditions (boiled temperature: 70 ° C., hot water boiling time: 3 minutes) are the same as in Example 1.

(29) Example 29
The 29th embodiment is based on the 19th embodiment.
In the present Example 29, similarly to the above-mentioned Example 28, the tin film is sequentially treated by the base film forming step (S1) → the conductive film forming step (S2) → the heat treatment step (S3), and the tin film is conductive. This is an example of a so-called post-stage heat treatment method as a film.
That is, based on Example 19, the heat treatment (S3) was performed after the conductive film forming step (S2) without performing the intermediate stage heat treatment (S12) after the base film forming step (S1). Yes, the heat treatment conditions (water bath temperature: 70 ° C., water bath time: 3 minutes) are the same as in Example 1 which is the basis of Example 19.

(30) Example 30
This Example 30 is based on the above-mentioned Example 21.
In the 30th embodiment, similarly to the 28th embodiment, the silver film is sequentially treated by the base film forming step (S1) → the conductive film forming step (S2) → the heat treatment step (S3), and the silver film is conductive. This is an example of a so-called post-stage heat treatment method as a film.
That is, based on Example 21, the heat treatment (S3) was carried out after the conductive film forming step (S2) without performing the heat treatment (S12) in the intermediate stage after the base film forming step (S1). Yes, the heat treatment conditions (water bath temperature: 70 ° C., water bath time: 3 minutes) are the same as in Example 1 which is the basis of Example 21.

(31) Reference example 1
This Reference Example 1 is based on the above-mentioned Example 1.
In Example 1, the treatment was sequentially performed in the order of the base film forming step (S1) → the heat treatment step (S12) → the conductive film forming step (S2), but in this Reference Example 1 , the heat treatment in the intermediate step was not performed.
That is, without going through the heat treatment step (S12), after the base film forming step (S1), the process directly shifted to the conductive film forming step (S2).

(32) Reference example 2
This Reference Example 2 was based on the above-mentioned Example 2, and was not heat-treated like the above-mentioned Reference Example 1 .
That is, in this Reference Example 2 , the process directly shifts to the conductive film forming step (S2) after the undercoat forming step (S1) without going through the heat treatment step (S12).

(33) Reference example 3
This Reference Example 3 was based on the above-mentioned Example 3, and was not heat-treated like the above-mentioned Reference Example 1 .
That is, in this Reference Example 3 , the heat treatment step (S12) was omitted, and after the base film forming step (S1), the process directly shifted to the conductive film forming step (S2).

(34) Comparative Example 1
Based on the first embodiment, the steps (S1) to (S12) are not performed, and the copper plating bath according to (B) is immediately used on the silicon substrate based on the step (S2) (the same (B)). Electroplating was performed (under the plating conditions of).
However, although an attempt was made to form a conductive film (copper film) on the silicon substrate, only powdery precipitates were formed, and a copper plating film was not formed.

(35) Comparative Example 2
The step (S1) was performed using the plating bath in which the phosphorus compound (b) was removed from the plating bath for forming the base of Example 1, and this is a compliant example of Patent Document 2 described above.
That is, the steps (S1), (S12), and (S2) were sequentially performed based on the first embodiment, but the step (S1) does not contain a phosphorus compound as shown in the following (A). A nickel undercoat was formed under the plating bath and plating conditions.
The processing conditions of the step (S12) and the step (S2) are the same as those of the first embodiment.
(A) Composition of nickel-plated bath and electroplating conditions An electro-nickel-plated bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.1 μm

(36) Comparative Example 3
Based on the above-mentioned Example 1, the step (S1) was carried out using the plating bath in which the complexing agent (c) of the present invention was removed from the plating bath for forming the base film of Example 1.
As a result, precipitation occurred in the plating bath, and an undercoat was not formed on the silicon substrate.
Therefore, the subsequent steps (S12) and (S2) could not be processed.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes

(37) Comparative Example 4
Based on the above-mentioned Example 1, the step (S1) was carried out using the plating bath in which the surfactant (d) of the present invention was removed from the plating bath for forming the base film of Example 1.
The processing conditions of the step (S12) and the step (S2) are the same as those of the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 1.0%

(38) Comparative Example 5
Based on the above-mentioned Example 1, the step (S1) was carried out using the plating bath in which the buffer (e) of the present invention was removed from the plating bath for forming the base film of Example 1.
The processing conditions of the step (S12) and the step (S2) are the same as those of the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 1.0%

(39) Comparative Example 6
Based on the above-mentioned Example 1, the step (S1) was carried out using the plating bath in which the brightener (f) of the present invention was removed from the plating bath for forming the base film of Example 1.
The processing conditions of the step (S12) and the step (S2) are the same as those of the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Polyoxyethylene cumin phenol ether (EO 10 mol) 10 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 1.0%

(40) Comparative Example 7
Based on the above-mentioned Example 1, the step (S1) was carried out using a plating bath in which the surfactant of the plating bath for forming the base film of Example 1 was changed from the nonionic surfactant of the present invention to the cationic surfactant. went.
The processing conditions of the step (S12) and the step (S2) are the same as those of the first embodiment.
(A) Composition of nickel-phosphor plating bath and electroplating conditions An electronickel-phosphorus plating bath was constructed with the following composition.
Nickel sulfamate (as Ni2 +) 0.45 mol / L
Nickel chloride (as Ni2 +) 0.03 mol / L
Boric acid 0.2 mol / L
Sodium Hydrogen Phosphate 2.5 Hydrate 0.4 mol / L
Citric acid 0.3 mol / L
Saccharin 0.02 mol / L
Allyl sulfonic acid 0.01 mol / L
Lauryl trimethyl ammonium chloride 20 g / L
pH (adjusted with 24% sodium hydroxide) 4.5
[Electroplating conditions]
Bath temperature: 40 ° C
Current density: 0.5A / dm2
Plating time: 10 minutes [Plating film]
Film thickness: 0.2 μm
Phosphorus content: 1.0%

(41) Comparative Example 8
Based on the above-mentioned Example 1, the step (S1) was performed by substituting the plating bath for forming the base film (nickel-phosphorus plating bath) of Example 1 with a known watt bath.
The processing conditions of the step (S12) and the step (S2) are the same as those of the first embodiment.
(A) Composition of Watt Bath and Electroplating Conditions A Watt bath was constructed with the following composition.
Nickel sulphate hexahydrate (as Ni2 +) 0.15 mol / L
Nickel chloride (as Ni2 +) 0.5 mol / L
Boric acid 0.7 mol / L
pH (adjusted with 28% ammonia) 4.0
[Electroplating conditions]
Bath temperature: 60 ° C
Current density: 1A / dm2
Plating time: 5 minutes [Plating film]
Film thickness: 1.0 μm

<< Example of evaluation test of adhesion of base film to silicon substrate >>
Therefore, the methods for forming the conductive films of Examples 1 to 30, Reference Examples 1 to 3 and Comparative Examples 1 to 8 are applied to the sample made of the silicon substrate, and an adhesive tape is applied to the obtained conductive film. When the adhesive tape is affixed and peeled off, paying attention to the boundary between the base film and the silicon substrate that are integrally formed with the conductive film, does the base film peel off from the silicon substrate starting from the boundary? Whether or not it was observed was observed, and the superiority or inferiority of the adhesion to the silicon substrate was evaluated based on the following criteria.
⊚: The base film did not peel off from the silicon substrate.
◯: The base film was partially peeled off from the silicon substrate.
X: The base film was completely peeled off from the silicon substrate.

The table below shows the test results.
However, as described above, in Comparative Examples 1 and 3, a conductive film or a base film was not formed on the silicon substrate. Therefore, “−−” in the table below indicates that the peeling test itself was not performed. Shown.
Adhesion Adhesion Adhesion Example 1 ◎ Example 16 ◎ Reference Example 1 ○
Example 2 ◎ Example 17 ◎ Reference Example 2 ○
Example 3 ◎ Example 18 ◎ Reference Example 3 ○
Example 4 ◎ Example 19 ◎
Example 5 ◎ Example 20 ◎ Comparative Example 1 −−
Example 6 ◎ Example 21 ◎ Comparative Example 2 ×
Example 7 ◎ Example 22 ◎ Comparative Example 3 −−
Example 8 ◎ Example 23 ◎ Comparative Example 4 ×
Example 9 ◎ Example 24 ◎ Comparative Example 5 ×
Example 10 ◎ Example 25 ◎ Comparative Example 6 ×
Example 11 ◎ Example 26 ◎ Comparative Example 7 ×
Example 12 ◎ Example 27 ◎ Comparative Example 8 ×
Example 13 ◎ Example 28 ◎
Example 14 ◎ Example 29 ◎
Example 15 ◎ Example 30 ◎

<< Evaluation of test results >>
According to the above table, in Comparative Example 1, an attempt was made to form a conductive film (copper film) directly on the silicon substrate without forming a base film, but a copper film was not obtained and a powdery precipitate was obtained. It was only done.
On the other hand, in Examples 1 to 30 in which a conductive film was formed on the silicon substrate via the nickel-phosphorus base film and the base film was heat-treated , copper, tin, silver, nickel, palladium, etc. were used. Regardless of the type of the conductive film, the undercoat film adhered well to the silicon substrate, and therefore, it was confirmed that the conductive film could be formed on the silicon substrate via the undercoat film with good adhesion.

Next, in Comparative Example 2 or Comparative Example 8, a nickel film was selected instead of a nickel-phosphorus film as the base film formed by electroplating on the silicon substrate. Specifically, Comparative Example 2 is described above. The example based on Patent Document 2 and Comparative Example 8 are examples using a known watt bath, but in any case, the adhesion of the nickel film to the silicon substrate is significantly inferior to that of the nickel-phosphorus film. Therefore, a conductive film (copper film) could not be formed on the silicon substrate with good adhesion.
Comparing Examples 1 to 30 with Comparative Example 2 or Comparative Example 8, when a nickel-based base film is formed on a silicon substrate that is difficult to conduct electricity, the nickel film is inferior in adhesion, so that strong adhesion is obtained. To achieve this, it can be judged that it is important to select a nickel-phosphorus electrodeposition film instead of nickel.
In particular, paying attention to the above-mentioned Patent Document 2 to which Comparative Example 2 is based, the nickel sulfonic acid bath described in the same document 2 uses a substrate made of a silicon wafer as an object to be plated (as in claim 1). 5), boric acid and propene sulfonate (= synonymous with allyl sulfonate), citric acid and lactic acid can be used as a buffer (claims 1 to 2, [0016], [0046]), and wet. It is common with the electro-nickel-phosphorus plating bath of the present invention in that an agent (however, not specifically mentioned) can be used ([0018]), but it is the same as the plating bath of the present invention in that the bath type is a nickel bath. to differ greatly.
In Comparative Example 2, a nonionic surfactant not specifically mentioned in Patent Document 2 was added as a wetting agent (in this respect, Comparative Example 2 is a phosphorus compound (b) from the plating bath for forming a base of the present invention. Despite this, the nickel-phosphorus plating bath of the present invention and the nickel bath of Comparative Example 2 differ greatly in the adhesion of the base film to the silicon substrate. It is presumed that this difference in bath type, that is, the presence or absence of the phosphorus compound added to the plating bath, greatly affected the adhesion to the silicon substrate.

Comparative Example 3 is a plating bath in which the nickel-phosphorus plating bath of the present invention does not contain the complexing agent (c), but the stability of the plating bath is poor due to the lack of the complexing agent, and precipitation occurs in the bath. Since the function was lost, the undercoat film forming step (S1) itself could not be performed.
Therefore, comparing Examples 1 to 30 with Comparative Example 3, in order to smoothly form the base film on the silicon substrate, the addition of a complexing agent having a function of stabilizing the bath to the nickel-phosphorus plating bath is added. It turns out that it is essential.
Further, in Comparative Example 5 in which the nickel-phosphorus plating bath does not contain the buffer (e), the adhesion of the nickel-phosphorus film to the silicon substrate is inferior, and therefore, the conductive film (copper film) has good adhesion on the silicon substrate. Since it cannot be formed, when Examples 1 to 30 are compared with Comparative Example 5, it can be seen that it is necessary to add a buffer to the nickel-phosphorus plating bath in order to firmly adhere the base film on the silicon substrate. ..

Comparative Example 4 is an example in which the nickel-phosphorus plating bath does not contain the specific surfactant (d) of the present invention, and Comparative Example 7 contains a surfactant (cationic surfactant) other than that specified by the present invention. As an example, in any case, the adhesion of the nickel-phosphorus film to the silicon substrate is inferior, and therefore the conductive film (copper film) cannot be formed on the silicon substrate with good adhesion . Comparing 30 with those of Comparative Example 4 or Comparative Example 7, it is necessary to specialize the surfactant added to the nickel-phosphorus plating bath to be nonionic or amphoteric in order to firmly adhere the base film on the silicon substrate. It turns out that there is.
Comparative Example 6 is an example in which the nickel-phosphorus plating bath does not contain the specific brightener (f) of the present invention, but the adhesion of the nickel-phosphorus film to the silicon substrate is inferior, and therefore, the conductive film ( Since the copper film) cannot be formed with good adhesion, when Examples 1 to 30 are compared with Comparative Example 6, in order to firmly adhere the base film on the silicon substrate, the present invention is applied to a nickel-phosphorus plating bath. It can be seen that the addition of the brightener (f) is indispensable, and a composite of a predetermined brightener (f) is particularly preferable.

Therefore, Examples 1 to 30 will be examined in detail.
In Examples 1 to 17 and 23 to 28, the conductive film is a copper film, Example 18 is a nickel film, Examples 19 and 29 are also tin films, and Example 20 is a tin-bismuth alloy film, Examples 21 and 21. Reference numeral 30 is also a silver film, and Example 22 is also a palladium film.
When these examples are put together, copper and tin are put on a silicon substrate via a nickel-phosphorus undercoat formed in the electroplating bath of the present invention containing a predetermined complexing agent, surfactant, brightener and the like. It can be seen that a conductive film made of various single metals such as nickel, silver and palladium, or a tin-bismuth alloy can be formed with good adhesion.

In Examples 1 to 17 in which the conductive film is both a copper film, the types of the complexing agent, the surfactant, the brightener, the nickel salt, the phosphorus compound, etc. of the electroplating bath for forming the base film are changed. However, as long as the condition that the plating bath contains a predetermined component is satisfied, it is judged that the strong adhesion of the base film to the silicon substrate can be maintained even if the composition of the nickel-phosphorus plating bath for forming the base is freely selected. ..
For example, Examples 1 to 5 and 9 to 17 are examples in which citric acid is used as a complexing agent contained in an electroplating bath for forming a base, Example 6 is also nitrilotriacetic acid, and Example 7 is also gluconate. Example 8 is also an example in which a sugar is used, but regardless of which of the specific complexing agents was selected, good adhesion of the base film could be ensured.
In addition, Example 16 is an example in which an amphoteric surfactant is used as the surfactant contained in the electroplating bath for forming a base, and other examples are examples in which a nonionic surfactant is also used, but the nonionic property. Regardless of which of the two sex surfactants was selected, good adhesion of the base film could be ensured as well.
Examples 1 to 9 are a composite of allyl sulfonic acid and saccharin in a brightener contained in an electroplating bath for forming a base, Example 10 is a composite of benzene sulfonic acid and saccharin, and Example 11 is a composite of allyl sulfonic acid and propagyl alcohol. Composite, Example 12 is a composite example of benzenesulfonic acid and butinediol, and Example 11 is a composite example of naphthalenesulfonic acid and butinediol, but any of the specific brighteners may be selected, or any of them. Even if these were combined, good adhesion of the base film could be secured.
Examples 1 and 2 are examples in which the nickel salt is changed, and Examples 1 and 2 and 8 are examples in which the phosphorus compound is changed, but the good adhesion of the base film changes with respect to these free choices. There wasn't.

On the other hand, focusing on the heat treatment of the base film, Examples 23 to 27 are examples in which the heating conditions in the heat treatment step (S12) are changed from Example 1, but in Example 1 (70 ° C., 3 minutes of water bath). On the other hand, even if the heating conditions (heating time, temperature) were changed or the type of heat treatment (water bath, hot air treatment, oven heating, etc.) was changed, the strong adhesion of the base film did not change.
Further, while Examples 1 to 27 are intermediate heat treatment methods in which heat treatment is performed between the base film forming step (S1) and the conductive film forming step (S2), Examples 28 to 30 are conductive film. Although it is a post-stage heat treatment method in which heat treatment is performed after the forming step (S2) of the above, the strong adhesion of the base film to the silicon substrate does not change regardless of which of the intermediate and post-stage heat treatment methods is used. Various conductive films could be formed on the substrate with good adhesion. In Examples 28 to 30, the conductive film is changed to various metals such as copper, tin, and silver, but the various conductive films are formed on the silicon substrate regardless of the heat treatment method in the middle or the latter stage. It can be judged that it can be formed with good adhesion.
In Examples 1 to 30, a heat treatment step (step (S12) or step (S3)) is added to the undercoat film forming step (S1) and the conductive film forming step (S2), whereas this is a reference. Examples 1 to 3 are examples in which this heat treatment step is omitted, but even when the heat treatment is not performed, the base film can be partially peeled off from the silicon substrate, but practical adhesion can be ensured.
Therefore, it does not matter whether or not heat treatment is performed to ensure the adhesion, but by adding the heat treatment step, the adhesion of the base film to the silicon substrate can be further strengthened, and when the conductive film is formed on the silicon substrate. Reliability can be improved. Moreover, the productivity is high because the heat treatment in a predetermined low temperature range may be performed.

According to Examples 1 to 30 , in order to firmly form a base film on a silicon substrate, it is sufficient to form a very thin base film of 0.3 μm or less, and in particular, as seen in Example 3, 0. It can be seen that an extremely thin film such as 01 μm is sufficient.
Therefore, when forming a conductive film such as copper, tin, or silver on a silicon substrate, the conductive film can be firmly adhered to the silicon substrate simply by thinly underlaying the nickel-phosphorus film with electroplating, which is a complicated operation. Can be improved in productivity without the need for.

Claims (6)

In the method of forming a conductive film on a silicon substrate,
(S1) A step of forming a base film composed of a nickel-phosphorus film on the silicon substrate using an electric nickel-phosphorus plating bath, and
(S2) A step of forming a conductive film on the base film and
A step (S12) of heat-treating the base film at 30 to 160 ° C. is interposed between the base film forming step (S1) and the conductive film forming step (S2), or
After the above step (S2), a step (S3) of heat-treating the base film and the conductive film at 30 to 160 ° C. is added.
The above nickel-phosphor plating bath is
(a) Soluble nickel salt and
(b) Phosphorus-containing compounds and
(c) A complexing agent selected from aminocarboxylic acids, oxycarboxylic acids, sugars, amino alcohols, polycarboxylic acids, and polyamines.
(d) Nonionic surfactants, surfactants selected from amphoteric surfactants, and
(e) A buffer selected from boric acid, sodium carbonate, sodium hydrogen carbonate, nickel acetate, succinic acid, and ascorbic acid ,
(f) From saccharin and its salt, benzenesulfonic acid and its salt, toluenesulfonic acid and its salt, naphthalenesulfonic acid and its salt, allylsulfonic acid and its salt, butinediol, ethylenesianhydrin, coumarin, propagil alcohol A method for forming a conductive film on a silicon substrate, which comprises containing a selected brightener. The method for forming a conductive film on a silicon substrate according to claim 1, wherein the step (S12) or step (S3) is heat-treated with warm water at 30 to 100 ° C. The complexing agent (c) is an oxycarboxylic acid, a polycarboxylic acid, or an amino selected from citric acid, tartaric acid, malic acid, glycolic acid, gluconic acid, succinic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, and diethylenetriaminetetraacetic acid. The method for forming a conductive film on a silicon substrate according to claim 1 or 2, wherein the method is at least one of a carboxylic acid or a salt thereof. The method for forming a conductive film on a silicon substrate according to any one of claims 1 to 3 , wherein the pH of the electronickel-phosphorus plating bath is 3.0 to 8.0. The method for forming a conductive film on a silicon substrate according to any one of claims 1 to 4 , wherein the film thickness of the base film is 0.01 to 10.0 μm. The above conductive film is formed by electroplating, electroless plating, sputtering or vapor deposition.
The conductive film is characterized by being a film made of a metal selected from copper, tin, silver, gold, nickel, bismuth, palladium, platinum, aluminum, magnesium, cobalt, zinc, chromium, or an alloy of these metals. The method for forming a conductive film on a silicon substrate according to any one of claims 1 to 5 .