JP3255769B2 - How to plate on insulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to glass, plastic,
The present invention relates to a method for forming a highly conductive plating layer on an insulating substrate having no conductivity such as porcelain.

[0002]

2. Description of the Related Art As a method of forming a conductive thin film on an insulator (substrate) such as glass, plastic, and porcelain, a physical vapor deposition method, a chemical vapor deposition method, and the like are generally used. Among these, methods such as vacuum deposition and sputtering are generally used as physical vapor deposition. Materials used for the conductive thin film include metals such as Cu, Au, Pd, Cr, and Al. Currently, Cr and Al are often used. Also,
The sputtering method is used when, for example, ITO (an oxide of In and Sn), which is widely used as a transparent conductive film of a display element, is formed.

The chemical vapor method is a method of forming a film on a substrate by reacting a gas at a high temperature. This method has been used to produce Nesa films.

Another method of forming a conductive thin film is to deposit a metal on an insulator by electroless plating. In this case, the substrate surface is first treated with a Pt or Pd catalyst, and then metal plating is performed. It is common to roughen the surface in advance to improve the adhesion to the substrate.

[0005]

The method of depositing a metal by physical vapor deposition requires a high processing temperature and takes a long time to form a film depending on the type of the metal. Is limited and versatile. At present, even when the present invention is applied to the formation of Cr, which is often used as a conductive thin film, there is a problem in terms of manufacturing cost because the formation of the film takes time.

The method of manufacturing an ITO film, which is widely used as a transparent conductive film by sputtering, has a high deposition speed, is relatively easy to deposit a uniform film, and is advantageous in terms of production cost. The film has lower conductivity than metal, and is insufficient for the purpose of requiring high conductivity as high as metal. Materials that can be used for chemical vapor deposition are limited to Nesa films and the like, and cannot be used for the purpose of requiring high conductivity comparable to that of metals for the same reason as in the case of ITO films.

In the method of forming a film by electroless plating, Cu is used.
This is effective for the purpose of requiring high conductivity because a thin film of can be attached. However, in this case, there is a disadvantage that the adhesion between the thin film and the substrate is weak, and in order to solve this, the surface of the substrate is usually roughened. This pretreatment for surface roughening is not suitable for the purpose of requiring transparency or the problem of surface smoothness, such as glass.
Further, for the purpose of forming a fine conductive pattern on the substrate surface as in recent years, surface roughening is not appropriate with precision.

The present invention provides a method capable of mass-producing a low-cost thin film having a high conductivity equivalent to that of a metal on an insulating substrate having a smooth surface with good adhesion to the substrate.

[0009]

According to the present invention, there is provided a method for plating on an insulator comprising a composition containing an oxide, for example,
Step 1 of forming a conductive film such as an O film (In / Sn oxide) on an insulator, Step 2 of subjecting this to an electrolytic treatment in an electrolytic solution, and then using an acid, a chelating agent or a combination thereof. There is a step 3 for performing a surface treatment and a step 4 for plating a metal thereon.

The main feature of the present invention is that unique processes 2 and 3 are performed before plating is performed.

[0011]

According to step 1, the conductive film adheres strongly to the insulator surface.

In step 2, from inside the conductive film to on the conductive film surface,
Elements precipitate. For example, when the conductive film is ITO,
Sn, which is more easily reduced than In, is selectively deposited. The oxidation number of the precipitated Sn is unknown, but is from 0 valence to 4
It is considered a mixture of values. This deposition is considered to have progressed by the ionization reaction by electrolysis, and is considered to be deposited on the surface as metal Sn, hydroxide Sn, and oxide Sn according to the oxidation number.

In step 2, depending on the conductivity of the bath, etc., S
The elution amount of elements such as n can be controlled, and surface modification (which leads to strong adhesion of the plating film) can be easily performed. Without performing step 2, borofluoric acid, hydrochloric acid,
It dissolves the conductive film, such as a ferric chloride-hydrochloric acid solution. Even if it is directly treated, finally, the strength and adhesion of the plating film cannot be obtained.

In step 3, the elements deposited on the surface of the conductive film are removed, and the surface is further modified. A clear change that can be observed is that after step 3, the wettability of the conductive film surface with water is improved. The reason for this improvement is not clear, but is considered as follows.

I) An active and clean surface is obtained by peeling off the surface layer of the conductive film. Ii) An element (Sn or the like) is formed on the crystal surface of the conductive film (In / Sn oxide film or the like) by electrolytic reduction. ) Is generated, which makes it very chemically and physically active. Iii) Since the conductive film surface is transformed from an oxide to a hydroxide by electrolysis, the wettability to water is improved. And the like.

On the surface having undergone steps 2 and 3, a step 4
When the plating film adheres to the plating film, the plating film adheres strongly. The reason for this is not clear, but is considered as follows.

In the step 4, the deposition of the plating on the electrolytic surface does not proceed in a plane and uniformly spread manner, but becomes a granular precipitation in which the deposition proceeds in the form of islands. It is considered that there is a gap and no internal stress is generated in the plating film. The reason why the plating is deposited in the form of islands is that elements such as Sn are partially desorbed from the surface of the conductive film such as ITO by electrolysis, and therefore, the surface conductivity becomes a discontinuous island shape. It is thought to be.

In the present invention, the insulator and the conductive film, and the conductive film and the plating film are strongly adhered together, so that a strong conductive thin film can be formed as a whole.

[0019]

DETAILED DESCRIPTION According to the method of the present invention, before plating an insulator, a conductive film is formed on the insulator in step 1. The adhesion between the conductive film and the insulator is strong. For this purpose, a film forming method other than the plating method, sputtering, a vapor deposition method, or the like can be used.

In this step 1, it is not necessary to roughen the surface of the insulator as in the conventional plating method. Therefore, a film can be formed with good adhesion even on a smooth insulator surface. This means that the present invention can sufficiently cope with patterning with a fine line width of 30 μm or less. Note that any insulator such as glass, plastic, and porcelain can be used as the insulator.

The conductive film underlying the plating is later plated thereon to secure the final conductivity. Therefore, unlike the conventional conductive film formation by the metal sputtering method, the conductive film having a high conductivity is provided. There is no need to choose from materials. It is sufficient to have a certain degree of conductivity (that is, a size that enables the electrolytic treatment in step 2). Therefore, in selecting this material, a low-cost material having good productivity and workability may be selected. Instead of a metal, one having a composition containing an oxide such as an ITO or Nesa film is selected. For example, ITO can be used to form a very thin conductive film, the film formation cost is very low compared to metal sputter film formation, the adhesion is high even on a smooth substrate, and the fine processing can be performed by photolithography. , Etc. have the advantage.

The oxide does not necessarily have to be an oxide of a plurality of elements (for example, ITO).

In step 2, before plating (step 4), the above-described elements are deposited from the inside of the conductive film on the conductive film surface.

The degree of the deposition varies depending on the conditions of the electrolysis, but at least the surface condition of the conductive film is greatly changed by the electrolysis treatment as compared with that before the electrolysis treatment.

The electrolytic solution that can be used in the present invention contains at least an arbitrary electrolyte for adjusting the electric conductivity (lactic acid in the case of the examples described later). And, practically preferably,
An inhibitor for making the electrolysis on the surface uniform is mixed with the electrolytic solution. Note that, in some cases, a layer based on the electrolytic solution (mainly an inhibitor) is formed on the conductive film surface by the process 2.

As the inhibitor, those used in ordinary electrodeposition coating, for example, a polymer colloid having a polar group can be used. As a result, the polymer colloid is deposited on the surface by electrolysis, and the polymer film ( A representative example of the layer based on the electrolyte solution is formed. Also, in this case,
If a photopolymerization initiator is added to the polymer colloid, the formed film has a function as a resist that can be exposed and developed by a photographic method.

Examples of the inhibitor include those containing an acrylic resin having a cationic group, epoxy resins having a cationic group, urethane resins, polybutadiene resins, and polyamide resins.

Electrolysis conditions (conductivity, inhibitor concentration,
General-purpose conditions can be used for the current, time, and the like.

In step 3, (if a layer based on the components contained in the electrolytic solution [eg, the above polymer film] exists,
After the portion of the layer to be plated is removed by a process such as photosensitization and development), the substance deposited therefrom in step 2 is removed from the conductive film surface with an acid, a chelating agent or a combination thereof. Which of these is used may be determined in consideration of the properties of the base material and the like.

As the acid or chelating agent, any one can be used as long as it can perform the above-mentioned action.
As the acid, not only inorganic acids such as borofluoric acid, hydrochloric acid, sulfuric acid and nitric acid but also organic acids such as methanesulfonic acid, ethanesulfonic acid, acetic acid and lactic acid can be used. Its concentration is
Although it may be appropriately selected, in the case of borofluoric acid, it is usually 0.1 to 42% by weight.

As the chelating agent, ethylenediaminetetraacetylic acid, N, N, N ', N'-tetrakis (2-hydroxypropyl) ethylenediamine (usually available concentration: 0.1 to 0.5 mol) is used. it can.

The time required for the operation is generally about 10 seconds to 5 minutes regardless of the size.

According to the step 3, the wettability of the surface of the conductive film is remarkably improved. The adhesion between this conductive film and the plating film deposited thereon in step 4 is extremely high as described above. This method can also eliminate the disadvantage that the adhesion of the conventional electroless plating in film adhesion is weak.

In step 4, electroless plating of Cu, Ni, or the like, or electrolytic plating of Cu, Ni, Au, or the like can be used. Depending on the purpose, it can be finished by further plating Ni or gold on Cu or the like.

As described above, by performing mask exposure and development patterning between Step 3 and Step 4, a layer based on the specific electrolyte can be patterned. As a result, the plating film can be attached only to the predetermined portion.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a glass substrate (1
5 cm x 15 cm). IT containing SnO ₂ : 10wt%
An O conductive film was formed over a glass substrate by a sputtering method. The specific resistance was 2 × 10 ⁻⁴ Ω / cm. Next, ITO
The substrate on which the conductive film is formed is used as a cathode to perform an electrolytic treatment in an electrolytic solution. The electrolyte used was a dispersion in which lactic acid and an acrylic resin having an amino group neutralized with lactic acid were colloidally dispersed. The acrylic resin had photosensitivity for the purpose of producing conductor plating of a fine pattern. That is,
Composition containing a copolymer of methyl methacrylate, ethyl acrylate and dimethylaminoethyl methacrylate as an acrylic resin having an amino group, and dipentaerythritol pentaacrylate (weight ratio: methyl methacrylate: ethyl acrylate: dimethylaminoethyl methacrylate) Acrylate = 75: 17: 8, Polymer: dipentaerythritol pentaacrylate = 2:
1) was used.

By performing the electrolytic treatment, the ITO conductive film was covered with the conductive film of the photosensitive resin. Mask exposure and development patterning are performed by a conventional method to pattern into a predetermined shape. The exposed surface of the ITO conductive film was colored by the electrolytic treatment, and it was recognized that a part of the ITO component was deposited on the surface. This is converted to an acid, namely HBF ₄ .
Treated with a 6 wt% solution. This significantly improved the wettability of the surface. Next, it is introduced into a Cu electroless plating solution to perform electroless plating. The plating was first performed while applying a weak current (0.05 A / dm ² ). When the deposition reaction started, the current was stopped and the electroless plating was continued for 3 minutes. By doing so, the initial deposition reaction of the electroless copper plating is reduced to Pd.
It can be started directly on the ITO surface without using a / Sn colloid catalyst or the like, and by switching to an electroless deposition reaction at the time when the precipitation nuclei are formed, a uniform and thick deposited film can be formed. In addition, by not using a Pd / Sn colloid catalyst or the like, copper can be deposited without foreign substances intervening on the ITO surface, and the adhesion is improved.

After the copper plating, the substrate was washed with water, immersed in an electroless nickel plating solution, and plated at 40 ° C. for 5 minutes to obtain a plating thickness of 1500 angstroms.

The conductive film mainly composed of the plating film obtained as described above had high conductivity and excellent adhesion to the substrate. Cross-cut peel test of this conductive film (JIS
K5400), no peeling was observed, and it was confirmed that the film had high peel strength. That is, 10 points were obtained.

Those without the electrolytic treatment (other conditions are the same as above) and those without the acid treatment even before the electrolytic treatment (before the same) are peeled off at the interface between the plating film and the ITO film.
The peel strength was not very high. That is, it was point 0.

Since a step of surface roughening is not required before forming a plating film as in the prior art, even if a fine pattern is formed by photolithography as in the present embodiment, a fine pattern with high precision is possible. Was.

Since the sputtering conditions of ITO vary depending on the material of the substrate, the specific resistance may be larger than that of the present embodiment. SnO ₂ containing Sb as an impurity
In this case, the same result as in the above example was obtained.

[0043]

As described above, according to the present invention, plating with high adhesive strength and high conductivity can be performed on a smooth insulating substrate without roughening the surface of the substrate. Moreover, it is low in cost and suitable for mass production of products.

────────────────────────────────────────────────── ─── Continuing the front page (72) Inventor Isamu Masuyama 3-3 Hiyoshidai, Takatsuki-shi, Osaka 3-3, Masuyama New Technology Research Laboratories (58) Field surveyed (Int.Cl. ⁷ , DB name) ) C23C 28/00 C23C 14/08 C23C 14/20 C23C 18/18

Claims (4)

(57) [Claims] And 1. A process 1 for forming a conductive film made of a composition comprising an oxide on the insulator, and the process 2 to be processed electrolytic in the electrolyte solution which, then acid, a chelating agent or a combination thereof A method of plating on an insulator, comprising a step 3 of performing a surface treatment and a step 4 of plating a metal thereon. 2. The method according to claim 1, wherein the conductive film formed on the substrate has a composition including an oxide of In and Sn. 3. The method according to claim 1, wherein an electroless plating solution is used for plating the metal, and a weak current is applied at the beginning of the plating. 4. The method according to claim 1, wherein an electrolytic plating solution is used for metal plating.