阅读说明：本技术 层叠膜结构及层叠膜结构的制造方法 (Laminated film structure and method for manufacturing laminated film structure ) 是由 岛田和哉 速水雅仁 坂田俊彦 着能真 于 2020-12-24 设计创作，主要内容包括：对于像以往那样进行的在被处理物上形成氧化物层、并通过镀覆在其上形成金属膜的方法而言,金属膜的密合性低,且可以得到平坦的被处理面,但不易于在通孔的内壁面形成金属膜。用金属膜的形成方法制作的金属膜的密合性高,且也能形成于通孔的内壁上,所述金属膜的形成方法的特征在于,具有如下工序：第一成膜工序,使被处理物的被处理面与包含氟和氧化物前体的反应溶液接触,从而在前述被处理面上形成氧化物层；氟去除工序,将前述氧化物层的氟去除；催化剂负载工序,使催化剂溶液与前述氧化物层接触,从而使前述氧化物层负载催化剂；及,第二成膜工序,使化学镀液与前述氧化物层接触,从而在前述氧化物层上使金属膜析出。(In the conventional method of forming an oxide layer on a workpiece and forming a metal film thereon by plating, the metal film has low adhesion and a flat surface to be processed can be obtained, but it is not easy to form a metal film on the inner wall surface of a through hole. A method for forming a metal film, which is capable of forming a metal film having high adhesion even on the inner wall of a through-hole, comprising the steps of: a first film formation step of bringing a surface to be treated of a treatment object into contact with a reaction solution containing fluorine and an oxide precursor to form an oxide layer on the surface to be treated; a fluorine removal step of removing fluorine in the oxide layer; a catalyst supporting step of bringing a catalyst solution into contact with the oxide layer to support a catalyst on the oxide layer; and a second film forming step of bringing an electroless plating solution into contact with the oxide layer to deposit a metal film on the oxide layer.)

1. A laminated film structure, comprising:

an object to be treated comprising an insulator or an insulator having a conductive layer formed on the surface thereof in advance, and

an oxide layer formed on the surface of the object to be processed,

the oxide layer has a fluorine content of 0.01 mass% or more and 1.0 mass% or less.

2. The laminated film structure according to claim 1, wherein the oxide layer contains at least one element species selected from the group consisting of titanium, silicon, tin, zirconium, zinc, nickel, indium, vanadium, chromium, manganese, iron, cobalt, and copper.

3. The laminated film structure of claim 1 or 2, having:

a catalyst layer disposed on the oxide layer, and

a metal layer disposed on the catalyst layer.

4. The laminated membrane structure according to claim 3, wherein the catalyst layer comprises at least one element selected from the group consisting of gold, palladium, and silver.

5. The laminated film structure of claim 4, wherein the metal layer has a 2 nd metal layer formed thereon.

6. The laminated film structure of any one of claims 3 to 5, wherein the metal layer comprises at least one of nickel or copper.

7. A method for manufacturing a laminated film structure, comprising the steps of:

a first film forming step of bringing a surface to be processed of an object to be processed, which includes an insulator or an insulator having a conductive layer formed on a surface thereof in advance, into contact with a reaction solution containing fluorine and an oxide precursor to form an oxide layer on the surface to be processed; and

and a fluorine removal step of removing fluorine in the oxide layer.

8. The method of manufacturing a laminated film structure according to claim 7, wherein the oxide precursor contains at least one or more elements selected from the group consisting of titanium, silicon, tin, zirconium, zinc, nickel, indium, vanadium, chromium, manganese, iron, cobalt, and copper.

9. The method of manufacturing a laminated film structure according to claim 7 or 8, wherein the reaction liquid contains at least one of a borate, an aluminum salt, and hydrogen peroxide.

10. The method of manufacturing a laminated film structure according to claim 7 or 8, comprising the steps of:

a catalyst supporting step of forming a catalyst layer by bringing a catalyst solution into contact with the oxide layer; and

and a second film forming step of forming a metal layer on the catalyst layer by electroless plating.

11. The method of manufacturing a laminated film structure according to claim 10, wherein the catalyst liquid contains at least one element selected from the group consisting of gold, palladium, and silver.

12. The method of manufacturing a laminated film structure according to claim 10 or 11, comprising an electrolytic plating step of forming a 2 nd metal layer on the metal layer by electrolytic plating.

13. The method of manufacturing a laminated film structure according to any one of claims 10 to 12, wherein the metal layer formed by the electroless plating method contains at least one element selected from the group consisting of nickel and copper.

14. The method of manufacturing a laminated film structure according to claim 7,

the thickness of the oxide layer is 200nm or more,

the fluorine removal step is a step of:

an annealing step of annealing the oxide layer at 100 ℃ to 150 ℃, and

and a step of bringing the oxide layer into contact with an alkali solution having a pH of 10.5 or more after the annealing step.

15. The method of manufacturing a laminated film structure according to claim 7,

the thickness of the oxide layer is less than 200nm,

the oxide layer is formed of an amphoteric oxide,

the fluorine removal step is any of the following steps:

annealing the oxide layer at 150 ℃ or higher; or

An annealing step of annealing the oxide layer at 100 ℃ or higher and 150 ℃ or lower, and

and a step of bringing the oxide layer into contact with an alkali solution having a pH of 10.5 or more after the annealing step.

16. The method of manufacturing a laminated film structure according to claim 7,

the thickness of the oxide layer is less than 200nm,

the oxide layer is formed of a substance other than an amphoteric oxide,

the fluorine removal step is any of the following steps:

annealing the oxide layer at 150 ℃ or higher; or

And a step of bringing the oxide layer into contact with an alkaline solution having a pH of 10.5 or more.

Technical Field

The present invention relates to a laminated film structure in which a metal film is formed on an insulating substrate such as a resin substrate, a ceramic substrate, a glass substrate, a quartz substrate, or a silicon substrate, or on a metal such as copper, aluminum, or silver, a method for manufacturing the laminated film structure, an apparatus for forming the laminated film structure, and an electronic product using the laminated film structure.

Background

Conventionally, a plating method has been used to form a metal film on an object to be processed. In this method, a metal film is first formed on the surface of an object to be treated by electroless plating, and then the metal film is increased in thickness by electrolytic plating.

In order to ensure the adhesion of the metal film, in the electroless plating, after roughening treatment for imparting fine irregularities to the surface of the object to be treated by means of wet etching or the like in advance, it is necessary to support a catalytic metal such as palladium on the surface of the object to be treated. Then, by electroless plating, the catalyst metal supported on the surface of the object to be treated serves as a nucleus, and a metal film is formed thereon.

On the other hand, as a technique for forming a metal film without roughening a treatment object, a method is known in which an oxide layer is formed on a surface of a treatment object, and a metal film is formed thereon by plating or the like.

The following methods are known for producing an oxide layer: a method of modifying the surface of a treated object with a silane coupling agent and then coating or impregnating an oxide colloidal solution (patent document 1); a method using a sputtering method (non-patent document 1); and a method of depositing an oxide layer on a surface to be treated by contacting the surface with an aqueous solution containing metal ions (patent document 2).

Among methods for depositing an oxide on a surface to be treated, a method for forming a metal film on a surface of glass, resin, ceramic, quartz, silicon, or the like has been attracting attention. Further, the surface to be treated does not need to be roughened for adhesion.

However, as in patent document 1 and non-patent document 1, the formation of an oxide layer on a surface to be processed by a method such as a colloidal solution or sputtering is possible on a flat surface to be processed, but the formation on the inner wall surface of a through hole is not easy, and as a result, there is a problem that the formation of a metal film is not uniform. Further, as in patent document 2, the method of depositing an oxide layer on a surface to be treated by contacting with an aqueous solution containing metal ions has problems that the aqueous solution contains an organic solvent, the deposition operation is complicated, and uniform deposition is difficult.

It is known that a Liquid Phase Deposition method (hereinafter also referred to as "LPD method") containing fluorine can form a stable oxide layer. The above-mentioned problems of the methods of patent documents 1 and 2 and non-patent document 1 can be solved by supporting a catalyst on an oxide layer formed by the LPD method and then forming a metal film by an electroless plating method.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4508680

Patent document 2: japanese patent laid-open publication No. 2016-533429

Non-patent document

Non-patent document 1: fushan county industrial technology center research report N0.25(2011)

Disclosure of Invention

Problems to be solved by the invention

However, it was found that: when an oxide layer is formed on a surface to be treated by the LPD method and then a metal film is formed by the plating method, unevenness, a minute swelling portion, and the like are generated in the final metal film under certain conditions.

Means for solving the problems

The present inventors have conducted intensive studies and, as a result, have found that: the reason why the unevenness, the micro-expansion, the crack or the peeling occurs when the metal film is formed by the electroless plating method after the oxide layer is formed by the LPD method and the catalyst is supported on the oxide layer is fluorine remaining on the surface to be treated, and the present invention has been conceived. That is, the present invention provides a laminated film structure and a method for manufacturing the laminated film structure, which solve such problems.

Specifically, the laminated film structure of the present invention is characterized by comprising:

an object to be treated comprising an insulator or an insulator having a conductive layer formed on the surface thereof in advance,

An oxide layer formed on the surface of the object,

A catalyst layer formed on the oxide layer, and

a metal film layer formed on the catalyst layer,

the oxide layer has a fluorine content of 0.01 mass% or more and 0.1 mass% or less.

The method for manufacturing a laminated film structure of the present invention includes the steps of:

a first film forming step of bringing a surface to be treated of an object to be treated, which includes an insulator or an insulator having a conductive layer formed on the surface thereof in advance, into contact with a reaction solution containing fluorine and an oxide precursor to form an oxide layer on the surface to be treated;

a fluorine removal step of removing fluorine in the oxide layer;

a catalyst supporting step of bringing a catalyst solution into contact with the oxide layer to support a catalyst on the oxide layer; and

and a second film forming step of bringing an electroless plating solution into contact with the oxide layer to deposit a metal film on the oxide layer.

The laminated film structure of the present invention further includes an oxide layer in which fluorine is removed before the metal film is formed. Specifically, the laminated film structure of the present invention is characterized by comprising:

an object to be treated comprising an insulator or an insulator having a conductive layer formed on a surface thereof in advance; and

an oxide layer formed on the surface of the insulator,

the oxide layer has a fluorine content of 0.01 mass% or more and 0.1 mass% or less.

In addition, the same manufacturing method further includes an oxide layer formed by removing fluorine. Specifically, the method for manufacturing a laminated film structure according to the present invention includes the steps of:

a first film forming step of bringing a surface to be processed of an object to be processed, which includes an insulator or an insulator having a conductive layer formed on a surface thereof in advance, into contact with a reaction solution containing fluorine and an oxide precursor to form an oxide layer on the surface to be processed; and

and a fluorine removal step of removing fluorine in the oxide layer.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, since the oxide layer is formed on the surface to be treated by bringing the reaction solution containing fluorine and the oxide precursor into contact with the object to be treated, the obtained oxide layer is formed on the surface to be treated of the object to be treated by chemical bonding and is less likely to be peeled off without a sintering step.

In addition, in the present invention, since the step of removing fluorine remaining in the oxide layer is added after the oxide layer is formed, defects due to the detachment of fluorine remaining in the oxide layer can be avoided for a metal film or the like deposited in a subsequent step, and the metal film can be stably formed.

Further, the oxide layer has a higher catalyst supporting property than the surface to be treated itself, and as a result, the metal film obtained by electroless plating is also similarly less likely to peel off from the surface to be treated.

Further, since the oxide precursor is in contact with the surface to be treated in a completely ionized state by containing fluorine in the reaction solution, these ions can be diffused even in a narrow portion such as a through hole. As a result, the oxide layer can be uniformly formed on the surface to be processed of the object to be processed including the through hole, and therefore, the metal film can be more uniformly formed than in the electroless plating.

Further, since the oxide layer formed in the present invention has higher adsorption and diffusion properties of the catalyst than the surface to be treated itself, the catalyst can be supported at a higher density, and as a result, the adhesion between the metal film and the oxide layer is also high.

The oxide layer formed in the present invention is formed directly on the surface of the object to be treated without using a coupling agent or the like. Therefore, the annealing step for removing stress and improving adhesion of the metal film can be performed without considering the decomposition of the coupling agent.

The metal film formed in the present invention adheres to the object to be treated via the oxide layer, and does not peel off even if the surface of the object to be treated is not roughened. Therefore, a metal film having high smoothness can be obtained, which has low loss due to the skin effect and does not affect transmission loss even when used in a high frequency band used in 5 th generation mobile communication system (5G), in-vehicle millimeter wave radar antenna, MHL3.0 used for high-speed transmission, Thunderbolt interface, or the like.

Further, the oxide layer can be formed more easily without requiring a process of modifying the surface of the object to be treated with the silane coupling agent in advance.

Drawings

Fig. 1 is a diagram illustrating the principle of the method for forming a metal film of the present invention.

Fig. 2 is a diagram illustrating a metal film forming process according to the present invention. The object to be processed is only an insulating substrate.

Fig. 3 is a diagram illustrating a metal film forming process according to the present invention. In the case where the object to be processed has a metal layer formed in advance on an insulating substrate.

Fig. 4 is a diagram illustrating the structure of the metal film forming apparatus of the present invention.

Fig. 5 is a photograph showing the position where the fluorine content in the oxide layer is measured.

Detailed Description

The following describes a method for forming a laminated film structure according to the present invention with reference to examples. In the following description, an embodiment of the present invention is illustrated, but the present invention is not limited to the following description. The following description may be modified within the scope not departing from the gist of the present invention. In the following description, "up" refers to a direction away from a reference surface to be processed, and "down" refers to a direction toward the surface to be processed. The terms "directly above" and "directly below" mean a structure in which no other layer is interposed. The laminated film structure of the present invention also includes a structure in which only 1 oxide layer is formed on a target object having a target surface. That is, the layer laminated on the surface to be treated may be 1 layer.

The method for forming a laminated film structure of the present invention is characterized by comprising the steps of:

a first film forming step of bringing a surface to be treated of a treatment object into contact with a reaction solution containing fluorine and an oxide precursor to form an oxide layer on the surface to be treated,

A fluorine removal step of removing fluorine in the oxide layer;

a catalyst supporting step of bringing a catalyst solution into contact with the oxide layer to support a catalyst on the oxide layer; and

and a second film forming step of bringing an electroless plating solution into contact with the oxide layer to deposit a metal film on the oxide layer. The principle of the method for forming a metal film of the present invention is summarized below.

Fig. 1 illustrates a method of forming a laminated film structure of the present invention. Referring to fig. 1(a), in the first film formation step, the surface 12 to be treated of the object 10 is brought into contact with a reaction solution containing fluorine and oxide precursor ions. The surface to be treated 12 is cleaned by a chemical solution cleaning, UV, plasma irradiation, or the like before treatment.

As a result, an oxide of the oxide precursor ions is deposited by a reaction described later, and an oxide layer 114 is formed on the surface to be processed 12 (fig. 1 (a)). Thereafter, the contact with the reaction solution was stopped, and washing with water was performed, thereby removing the reaction solution. Even if the cleaning is performed with water, the oxide layer 114 is not damaged.

Next, a fluorine removal step of removing fluorine remaining in the oxide layer 114 is performed (fig. 1 b). As described above, in the present invention, the oxide layer 114 is formed in a liquid phase using a reaction solution containing fluorine. Therefore, the oxide layer 114 is formed to contain fluorine. By removing this fluorine, damage to the metal film 20 to be laminated later can be avoided. As a method of removing fluorine, annealing treatment and chemical treatment by an alkali solution can be used. These can be used as appropriate depending on the film type and film thickness of the oxide layer 114.

Next, the catalyst supporting step will be explained. The object 10 to be treated, in which the oxide layer 114 from which fluorine is removed is formed on the surface 12 to be treated, is brought into contact with the catalyst solution 30 (fig. 1 c). The catalyst 30a in the catalyst solution 30 is supported on the oxide layer 114, or is diffused inside the oxide layer 114, and is thereby supported on the oxide layer 114. Thereafter, the contact with the catalyst solution 30 is stopped, and washing with water is performed, thereby removing the catalyst solution 30. Even if the cleaning is performed with water, the catalyst 30a on the oxide layer 114 is not damaged (fig. 1 (d)).

Next, the second film forming step will be described. The metal film 20 is formed on the oxide layer 114 by bringing the oxide layer 114 supporting the catalyst 30a into contact with the electroless plating solution 118 (fig. 1 (e)).

In this manner, by using a reaction solution containing fluorine and oxide precursor ions for forming the oxide layer 114, the oxide layer 114 on the surface 12 to be treated of the object 10 is bonded in a state accompanied by chemical bonding. Therefore, even when sintering is not performed, a very strong layer can be formed, and the adhesion between the metal film 20 formed thereon and the object 10 to be processed is very high.

After the metal film 20 is formed, film formation by electrolytic plating may be performed. At this time, since the metal film 20 is already formed, the surface of the object 10 is made conductive, and electrolytic plating can be easily performed.

Here, there is no problem even if the first film forming step, the fluorine removal step, the catalyst supporting step, the second film forming step, and the electrolytic plating are performed before and after the heat treatment. In the present invention, since the content of fluorine remaining in the oxide layer 114 is reduced to a certain amount or less, even if the heat treatment is performed, the remaining fluorine does not push up the uppermost metal film 20 or the like, and damage such as unevenness, slight expansion, peeling, and cracks does not occur on the metal film 20.

A product manufactured by the method for forming a laminated film structure of the present invention is referred to as an electronic product 1. The electronic product 1 includes not only electronic-related products such as circuit boards, semiconductor circuits, and electronic components, but also products using the metal film 20 of the present invention as a protective film or a finishing film for decoration. The present invention will be described in detail below.

< object to be treated >

Examples of the object 10 to be treated include an insulating substrate and an insulating substrate having a conductive layer formed in advance on the surface thereof. The insulating substrate includes a resin substrate, a ceramic substrate, a glass substrate, a silicon substrate, and the like, and these can be used as a circuit substrate of various electronic devices.

As the resin substrate, a resin substrate made of a fluorine-based resin such as polyimide resin, methacrylic resin, epoxy resin, liquid crystal polymer, polycarbonate resin, PFA, PTFE, ETFE, or the like can be suitably used. In addition, the resin substrate may contain glass fibers in order to improve mechanical strength.

As the ceramic substrate, a ceramic substrate made of alumina such as alumite or sapphire, aluminum nitride, silicon carbide, zirconia, yttria, titanium nitride, barium titanate, or the like can be suitably used.

The glass substrate is an amorphous substrate composed of a silica network, and may contain a network forming agent (network forming oxide) such as aluminum, boron, phosphorus, etc., and a network modifying agent (network modifying oxide) such as alkali metal, alkaline earth metal, magnesium, etc.

The quartz substrate is a wafer made of synthetic quartz. The silicon substrate is a wafer made of single crystal silicon or polycrystalline silicon.

The conductive layer formed in advance on the insulating substrate is mainly used as a circuit pattern, and the conductive layer may be not only a highly conductive metal such as aluminum, copper, or silver formed by wet etching, dry etching, or the like on the insulating substrate, but also a conductive transparent material such as ITO (indium titanium oxide), FTO (fluorine-containing tin oxide), ATO (antimony-containing oxide), or the like. The shape of the object to be processed may be a wafer, a panel, a film, or the like, and may be a surface having a different shape such as a through hole (through hole), a blind through hole (non-through hole), or a groove (groove).

Fig. 2 and 3 schematically show a process of forming a metal film according to the present invention in a form in which a target object 10 is an insulating substrate. Fig. 2 shows a case where the object 10 to be processed is only an insulating substrate 10a, and fig. 3 shows a case where the object 10 to be processed has a conductive layer 10b formed in advance on the insulating substrate 10 a. Respectively, a cross section including the through hole 10h is shown.

Refer to fig. 2(a) and 3 (a). In the object 10, it is preferable to perform a cleaning operation on the surface 12 to be treated as a pretreatment in the first film forming step for forming the oxide layer 114. For example, acid treatment, alkali treatment, ultraviolet irradiation treatment, electron beam (ion beam) irradiation treatment, plasma treatment, and the like are preferably performed.

The surface 12 of the object 10 to be processed is the surface on which the metal film 20 is finally formed. The surface to be processed 12 is not only the surface of the object to be processed 10, but also includes an inner wall 10hi of the through hole 10h when the object to be processed 10 has the through hole 10 h. In the present invention, since the oxide layer 114 is formed of a liquid phase, the oxide layer 114 can be formed also on the inner wall 10hi of the through hole 10 h.

Even if the portion where the metal film 20 is not formed is the surface of the object 10, it is not the surface 12 to be processed. In fig. 1, the rear surface (lower side in the drawing) of the object 10 is not the object surface 12. By masking such a surface in advance, the oxide layer 114 can be prevented from being formed.

When the conductive layer 10b is formed on the surface of the insulating substrate 10a of the object to be processed 10 (fig. 3 a), the surface to be processed 12 is the surface of the conductive layer 10 b. When a through hole 10h is formed in the insulating substrate 10a having the conductive layer 10 formed on the surface thereof, the inner wall 10hi of the through hole 10h also serves as the surface to be processed 12. At this time, the inner wall 10hi of the through hole 10h includes a cross-sectional portion 12b of the conductive layer 10b on the surface and a cross-sectional portion 12a of the insulating substrate 10a connected thereto. Therefore, the surface to be processed 12 may be an insulating surface or a conductive surface.

< first film Forming step >

The first film formation step of forming the oxide layer 114 is a step of bringing a reaction solution containing fluorine and oxide precursor ions into contact with the surface 12 to be treated of the object 10. More specifically, the object 10 to be treated is immersed in a water tank filled with a reaction solution containing fluorine and at least one ion selected from the group consisting of titanium, silicon, tin, zirconium, zinc, nickel, indium, vanadium, chromium, manganese, iron, cobalt, and copper, or may be sprayed or coated as appropriate.

The oxide layer 114 is formed directly above the surface to be processed, and may be formed on the surface of an insulator. That is, the conductive layer 10b may be included between the surface of the insulator and the oxide layer 114. In other words, the surface to be treated may be an insulator or a conductive layer.

Fig. 2(b) and 3(b) show a state where the oxide layer 114 is formed. The oxide layer 114 is formed of a liquid phase, and thus the oxide layer 114 is also formed on the inner wall 10hi of the via hole 10 h. In fig. 2(b) and 3(b), the oxide layer 114 formed on the inner wall 10hi of the through hole 10h is denoted by a symbol "14 i". The oxide layer 114 is formed from a liquid phase and thus forms a dense continuous film. Here, the continuous film means: no gap is formed between the surfaces to be processed 12, and no portion is formed on the entire surface to be processed 12 (so-called "film loss").

Since the oxide layer 114 is formed of a liquid phase, the oxide layer 114 is uniformly formed on the inner wall of the via hole or the blind via hole.

The reaction solution may be composed of an aqueous solution containing fluorine and oxide precursor ions of titanium, silicon, tin, zirconium, zinc, nickel, indium, vanadium, chromium, manganese, iron, cobalt, copper, and the like.

The oxide precursor ion may be represented by Mⁿ⁺(M: precursor element, n: valence number of ion) and can be obtained by dissolving a fluoride or an oxide of the precursor element in hydrofluoric acid. In addition, fluoride may be added separately. Examples of the fluoride include sodium salt, potassium salt, magnesium salt, calcium salt, and ammonium salt.

In addition, the oxide precursor ion may be in the form of a fluorine complex (e.g., MF)₆ ^2-In addition, M: precursor element) may be present, and may be H₂MF₆Or sodium salt, potassium salt, magnesium salt, calcium salt, and ammonium salt. Since the reaction solution contains fluorine, there is a possibility that the surface to be treated of the object to be treated such as a ceramic substrate or a glass substrate is dissolved (etched), and thus the pH can be controlled to prevent etching.

The contact temperature between the object to be treated 10 and the reaction solution is preferably high, more preferably 20 to 80 ℃, and still more preferably 30 to 70 ℃. The reaction time is determined according to the desired film thickness of the oxide layer 114. The reaction time and the film thickness have a substantially linear relationship, and the film thickness of several nm to several tens μm can be obtained by adjusting the reaction time.

The composition of the reaction solution may be such that the precursor element is 1mmol/L or more and fluorine is contained to dissolve the precursor element completely.

The reaction solution contains an additive such as a borate, an aluminum salt, or hydrogen peroxide, thereby increasing the film formation rate of the oxide layer 114. Therefore, an element of boron or aluminum may also be included in the oxide layer 114. To remove hexafluorotitanic acid ion (TiF)₆ ^2-) This mechanism will be explained by taking as an example the case where the oxide precursor is used.

Using hexafluorotitanic acid ion (TiF)₆ ^2-) In this case, TiO as the oxide layer 114 can be formed by the reaction described below₂Forming a film on the surface to be processed.

TiF₆ ^2-+2H₂O＝TiO₂+6F^-+4H⁺… (1) the reaction is TiF₆ ^2-By adding additives such as borate, aluminum salt, hydrogen peroxide, etcAnd (4) speed.

For example, when boric acid is added, F on the right side of the formula (1)^-By the reaction of formula (2) to BF₄ ^-. As a result, the reaction of the formula (1) proceeds rightward, and the formation of titanium oxide on the surface to be treated of the object to be treated can be accelerated. The reaction initiator is not limited to boric acid, and may be a salt such as sodium borate, ammonium borate, or potassium borate.

H₃BO₃+4H⁺+4F^-＝H⁺BF₄ ^-+3H₂O…(2)

Similarly, when an aluminum ion source is added as a reaction initiator, AlF is produced by the reaction of the formula (3)₆ ^3-Whereby the reaction of formula (1) proceeds to the right. As a result, the formation of titanium oxide on the surface to be treated of the object to be treated can be accelerated. The aluminum ion source may suitably use, in addition to metallic aluminum, inorganic acid salts such as aluminum chloride, aluminum nitrate, and aluminum sulfate, and organic acid salts such as aluminum citrate, aluminum lactate, and aluminum acetate.

Al³⁺+6F^-＝AlF₆ ^3- …(3)

Although not having the ability to complex with fluoride ions, hydrogen peroxide can be suitably used as a reaction initiator. Hydrogen peroxide has the property of hydrolyzing fluorotitanic acid ions. As a result, a titanium peroxide complex is produced. This is a precursor of titanium oxide, and by bringing this state into contact with the surface to be treated of the object to be treated, titanium oxide can be precipitated on the surface to be treated of the object to be treated, and the formation of an oxide layer can be promoted.

In the reaction, the oxide layer 114 is formed on the surface 12 of the object 10 to be treated, and may be generated as particles in the reaction solution. In this case, in order to remove particles in the reaction solution, a step of collecting a part of the reaction solution, filtering the part with a filter, and returning the part may be performed. This is referred to as a filtration step.

< fluorine removal step >

Fluorine remains in the oxide layer 114 formed in fig. 2(c) and 3 (c). The residual fluorine does not disappear or volatilize by washing with water or leaving. On the other hand, when the metal film 20 is laminated on the oxide layer 114 in the subsequent step, residual fluorine is released from the oxide layer 114 by chemical treatment at the time of lamination, heat treatment after lamination, or the like, and hinders the metal film 20. Therefore, after the oxide layer 114 is formed, a fluorine removal step is performed.

In the laminated film structure obtained by the method for forming a laminated film structure of the present invention, the fluorine content in the oxide layer 114 is 0.01 mass% or more and 1.0 mass% or less. The residual fluorine content in the oxide layer 114 is preferably as small as possible, and may be 0 mass%. However, it is difficult to set the residual fluorine in the oxide layer 114 formed by the treatment in the liquid to 0 by using the reaction liquid containing fluorine. Therefore, the fluorine content may be equal to or less than the detection limit of the detection device. For example, 0.01 mass%.

On the other hand, if the fluorine content in the oxide layer 114 is more than 1.0 mass%, defects such as unevenness, micro-expansion, cracks, and peeling may occur when the metal film 20 is laminated or when fluorine is released from the oxide layer 114 by a change with time after lamination, and the metal film 20 is pushed upward. In addition, the supported amount of the catalyst for electroless plating is reduced, and the metal film in electroless plating becomes difficult to grow.

In the specific fluorine removal step, as will be understood from the examples described later, the preferable fluorine removal step differs depending on the film thickness of the oxide layer 114 and the metal species used in the oxide layer. When the film thickness of the oxide layer 114 is 200nm or more, fluorine in the oxide layer 114 can be removed by using an annealing treatment at 100 to 150 ℃ and an alkali solution treatment based on a solution having a ph of 10.5 or more in combination regardless of the metal species.

In addition, when the metal species of the oxide layer 114 is an amphoteric oxide such as Sn (tin), Al (aluminum), Zn (zinc), Be (beryllium), Ga (gallium), Ge (germanium), Pb (lead), Sb (antimony), Bi (bismuth), Cd (cadmium) and the like, the oxide layer 114 can Be subjected to fluorine removal by a combination of an annealing treatment at 100 to 150 ℃ and an alkali solution treatment using a solution having a ph of 10.5 or higher, or an annealing treatment at 150 ℃ or higher.

When the film thickness is less than 200nm, if the metal species of the oxide layer 114 is not an amphoteric oxide, fluorine in the oxide layer 114 can be removed by annealing at 150 ℃ or higher or alkali treatment at ph10.5 or higher.

< catalyst supporting step >

In the catalyst supporting step, it is preferable to support the activated catalyst 30a by applying electroless plating in the subsequent stage. That is, the catalyst solution 30 is a solution containing ions of gold, palladium, silver, or the like, and is brought into contact with the object 10 to be treated on which the oxide layer 114 is formed. The object 10 to be treated having the oxide layer 114 can be immersed in a water tank filled with the catalyst solution 30, sprayed, coated, or the like. Fig. 2(d) and 3(d) show a state in which the catalyst 30a is supported on the oxide layer 114. The supported catalyst 30a is also referred to as a catalyst layer. That is, a catalyst layer is formed directly above the oxide layer 114.

The catalyst 30a is supported on the oxide layer 114, and is generally supported in an ionic state by surface adsorption and diffusion in the oxide layer 114. In the subsequent electroless plating step, the reducing agent contained in the plating solution is reduced to a metal and acts as a catalytic nucleus, thereby activating plating.

When the catalyst 30a needs to be metallized in advance before the electroless plating step, it is exposed to the metal containing divalent tin ions (Sn) before the catalyst supporting step²⁺) In the solution of (3), Sn is supported²⁺And thus sensitized, by exposure to the catalyst solution 30. Alternatively, it may be accomplished by exposure to a reducing agent after exposure to the catalyst solution 30 and prior to electroless plating.

Here, when SnO is formed as the oxide layer 114, a large amount of Sn is contained therein²⁺Since it functions as a reducing agent, the catalyst 30a can be supported in a metallic state in the catalyst supporting step.

< second film Forming step >

In the second film formation step, the metal film 20 is formed using a commercially available electroless plating solution 118. Fig. 2(e) and 3(e) show a state in which the metal film 20 is formed directly above the catalyst 30 a. At this time, the electroless plating method is activated with the catalyst 30a supported in the catalyst supporting step as a nucleus. For example, when copper is selected as the metal film 20, a plating solution using formaldehyde as a reducing agent is used in addition to copper sulfate. When nickel containing phosphorus is selected as the metal film 20, a plating solution containing phosphinic acid as a reducing agent is used in addition to nickel sulfate. The electroless plating solution 118 is selected according to a desired metal species, internal stress, and film formation rate, and is prepared in consideration of the pH of the plating solution and the solubility of the oxide layer 114.

< film formation step by electrolytic plating >

The metal film 20 obtained in the second film formation step may be increased in thickness by electrolytic plating. In this case, the same kind of metal as the metal film 20 obtained in the second film formation step may be subjected to film formation, or a different kind of metal may be used. The electrolytic plating solution may be a commercially available chemical solution, and is selected in consideration of a desired metal species, internal stress, and further film formation rate, and an appropriate current density (ASD value) is set.

< manufacturing apparatus >

Next, a device 70 for forming a laminated film structure according to the present embodiment will be described with reference to fig. 4. The apparatus 70 for forming a laminated film structure is composed of a first film forming section 72, a fluorine removing section 78, a catalyst supporting section 74, and a second film forming section 76. Further, although not shown, a plating apparatus for further plating the finished electronic product 1 may be attached.

The first film formation portion 72 is a portion where the oxide layer 114 is formed in a liquid phase on the surface 12 to be treated of the object to be treated 10. Here, a type in which the object to be treated 10 is immersed in the reaction solution 80 containing fluorine and oxide precursor ions will be described.

The first film formation portion 72 has a first bath 72a for storing a reaction solution 80 containing fluorine and oxide precursor ions. The first bath 72a may be provided with a circulation pipe 72d passing through the filter 72b and a pump 72c disposed in the circulation pipe 72 d. Further, a heater 72j may be provided in the first bath 72 a.

Further, a reaction initiator tank 72e in which a reaction initiator is stored, a pipe 72f for introducing the reaction initiator to the first bath 72a, and a valve 72g for controlling the charging of the reaction initiator into the first bath 72a may be provided.

As described above, the annealing furnace, the alkali solution treatment bath, and the like are appropriately selected for the fluorine removal portion 78 according to the thickness of the oxide layer 114 and the metal species.

The catalyst supporting section 74 immerses the object 10 to be treated provided with the oxide layer 114 in the catalyst solution 30 containing ions of palladium, silver, or the like that can be used as a catalyst for electroless plating. The catalyst solution 30 is stored in the catalyst solution tank 74 a. Further, the plating bath 118 is stored in the plating tank 76a of the electroless plating section 76.

Next, the operation of the metal film forming apparatus 70 will be described along the flow of processing the object 10. The object 10 is formed into an insulating substrate having a through hole 10 h. Here, 2 through holes 10h are made. To which a mask 64 is mounted. The mask 64 is a mask for exposing only the surface 12 of the object 10 to be processed. Here, the inner wall and the periphery of the through hole 10h and a connecting line connecting the through holes 10h are referred to as the surface to be processed 12. In fig. 7, only the mask on the front surface side of the object 10 is shown, but the back surface may be masked.

The object 10 to be treated having the mask 64 applied thereto is immersed in a first bath 72a in which a reaction solution 80 containing fluorine and oxide precursor ions is stored. Thereafter, the reaction initiator is introduced from the reaction initiator tank 72e into the first bath 72a through the pipe 72 f. Thereby, the oxide layer 114 is formed on the surface to be processed 12. The first bath 72a is heated by the heater 72j to raise the temperature of the reaction solution 80 containing fluorine and oxide precursor ions, whereby the oxide layer 114 can be formed without using a reaction initiator.

When the fine particles of the oxide are precipitated and suspended in the reaction solution 80 containing fluorine and oxide precursor ions in the first bath 72a, the pump 72c is operated to circulate the reaction solution 80 containing fluorine and oxide precursor ions while filtering the reaction solution with the circulation pipe 72d passing through the filter 72 b. The particles of the oxide are removed by this circulation.

The object 10 on which the oxide layer 114 is formed is pulled up from the first bath 72a, the mask 64 is removed, and the fluorine removal process is performed in the fluorine removal portion 78. For example, heat treatment at 100 ℃ to 150 ℃. Thereby, fluorine in the oxide layer 114 is removed to 1.0 mass% or less. After that, the object 10 is put into the catalyst supporting portion 74, and the catalyst 30a adheres to the surface of the oxide 114.

The object 10 to be treated having the catalyst 30a supported on the oxide layer 114 is put into the plating tank 76a of the second film forming portion 76. The plating bath 76a stores an electroless plating solution 118 therein. In the electroless plating, the oxidizing agent in the electroless plating solution forms the metal film 20 from the catalyst 30a, and the metal film 20 itself serves as a catalyst, thereby forming the metal film 20. As described above, the electronic product 1 in which the metal film 20 is formed on the surface 12 of the object 10 to be processed is obtained.

Examples

< coating film on untreated LPD film >

When the fluorine removal step was not performed, plating was performed on the oxide layer formed by the LPD method, and the state of the metal film was confirmed. The substrate is made of alkali-free glass, alkali glass, synthetic quartz, or alumina. As the pre-cleaning, the substrate was immersed in 1M sodium hydroxide under ultrasonic irradiation for 10 minutes, further immersed in 0.1M hydrofluoric acid (HF) under ultrasonic irradiation for 10 minutes, and then cleaned with pure water. Tin oxide (SnO) is used as a film seed of the oxide layer₂) And titanium oxide (TiO)₂)。

The oxide layer is prepared from tin oxide (SnO)₂) In the case of using 0.01M stannous fluoride (SnF) as a reaction solution containing fluorine and oxide precursor ions₂: CAS number 7783-47-3), 0.1M boric acid (H) was used as an additive₃BO₃: CAS number 10043-35-3) and 0.3M Hydrogen peroxide (H)₂O₂)。

The oxide layer is composed of titanium oxide (TiO)₂) In the case, 0.3M ammonium hexafluorotitanate ((NH) was used as a reaction solution containing fluorine and oxide precursor ions₄)₂TiF₆: CAS number 16962-40-2), 0.1M boric acid (H) was used as an additive₃BO₃). In both cases the film thickness was adjusted by varying the reaction time.

The substrate on which the oxide layer having a predetermined thickness was formed was cleaned with pure water and then immersed in 0.1M stannous chloride (SnCl)₂) After 2 minutes, use pureWater washing and drying under nitrogen purge. Then, the resultant was immersed in 100ppm of palladium chloride (PdCl)₂: CAS number 7647-10-1) for 1 minute, the catalyst was loaded. Thereafter, the substrate was cleaned with pure water and dried under nitrogen purge.

After the catalyst was supported, electroless plating of NiP or electroless plating of Cu was performed. The film thickness of the metal film is set to 0.8 to 1.0 μm in both cases. After the metal film was formed, the film was washed again with pure water, dried under nitrogen purge, and, if necessary, annealed at 200 ℃ for 1 hour.

After the metal film was formed or after the annealing treatment, the metal film surface was visually observed, and the film thickness was measured by SEM and the fluorine content was measured by a fluorescent X-ray device. The results are shown in Table 1.

In the visual inspection, the presence or absence of "swelling" and "unevenness" was confirmed. The "unevenness" is caused by unevenness of the metal film due to variation in thickness of the metal film, and thus appears as variation in gloss of the metal film. More specifically, the reflectance of light changes and the light becomes matte. The reason for this is the unevenness in the thickness of the catalyst layer. When fluorine remains on the surface to be treated 12, the density of the catalyst decreases, and the thickness of the catalyst layer in this portion becomes thin. It is therefore considered that thickness unevenness may be formed in the catalyst layer.

In the examination, it is determined that "unevenness is not present" if the entire surface of the laminated metal surface has uniform gloss under a fluorescent lamp, and that "unevenness is present" if some of the metal surface has no gloss.

"swelling" occurs because there is a portion where the bonding of the metal film to the substrate surface is insufficient, and the metal film partially floats, resulting in hemispherical protrusions. The reason is as follows: when fluorine remains on the oxide layer and the catalyst is completely repelled, the catalyst is not present in this portion, and the underlying oxide layer and the metal film are not in close contact with each other and float. Further, when heat treatment is applied, residual fluorine is volatilized, and therefore expansion becomes more remarkable.

In the inspection, it was determined that "swelling was present" when 1 hemispherical protrusion was visually observed under a fluorescent lamp on the entire surface of the metal surface to be laminated, and that "swelling was absent" when no protrusion was observed.

[ Table 1]

Referring to table 1, the preliminary samples 1 to 3 were the case where the film species of the oxide layer was Ti, and the preliminary samples 4 to 11 were the case where the film species of the oxide layer was Sn. The preliminary samples 8 to 10 are cases where materials other than alkali-free glass were used for the substrates, and the preliminary sample 11 was a case where electroless Cu plating was performed.

All the surfaces of the metal films had a defect that could be judged to be uneven. In addition, the preliminary samples 1 to 8 and 11 swelled immediately after plating. These samples were not annealed.

Only when the substrate was synthetic quartz or alumina (preliminary samples 9 and 10), the substrate did not swell immediately after plating. However, expansion occurs after the annealing treatment. The fluorine content is not proportional to the film thickness of the oxide layer. However, the fluorine content of all the preliminary samples was more than 1 mass%. It is thus possible to predict that the cause of the expansion and the unevenness generated in the metal film after plating is fluorine in the oxide layer.

< position of fluorine Presence >

Next, the oxide layer of the cross section of the preliminary sample 5 was observed by using TEM-EDX (Transmission Electron Microscope-Energy Dispersive X-ray Spectroscopy), and the amount of fluorine at a point in the film thickness direction was measured. Fig. 5 shows a cross-sectional photograph.

Refer to fig. 5. The white band portion was an oxide layer (thickness 33 nm). The upper and lower parts of the metal film are provided with a substrate. Asperities are observed between the oxide layer and the metal film. This part is considered to be the cause of the unevenness. 4 points almost equidistant from the surface of the oxide layer in the depth direction were determined, and fluorine at the points was measured. The measurement results are shown in table 2.

[ Table 2]

Analysis point	Content of F
		[-]	[atom％]
1	1.42
		2	0.62
3	0.44
		4	0.45

Referring to table 2, it is seen that the surface of the oxide layer is almost locally occupied by fluorine, 1.42 atom% at the point 1 close to the surface, 0.62 atom% at the point 2 deeper in the film thickness direction, and 0.44 atom% and 0.45 atom% at the further deep points 3 and 4.

< removal of fluorine upon standing >

The preliminary sample 5 was placed in the air to investigate how the fluorine content would change, and the results are shown in table 3.

[ Table 3]

Although the number of days of leaving the substrate was changed to 0, 2, 6, 9, and 15, the fluorine content in the oxide layer was about 2.5 mass%, and the change was almost not observed.

< Effect of fluorine removal treatment >

From the above, it is presumed that when a metal film is formed on an oxide film by the LPD method, fluorine remains on the film surface and in the film, and damages such as unevenness and swelling are caused on the metal film. Therefore, a treatment of removing fluorine from the oxide layer is added before forming the metal film by plating. In the sample, after an oxide layer was formed on a substrate, fluorine removal treatment was performed, a catalyst was supported, and electroless plating and electrolytic plating were performed to form a metal film.

The fluorine content of the oxide layer-formed sample after the removal of fluorine was quantitatively measured by fluorescent X-ray, and further, the film damage caused by the removal of fluorine was observed by an optical microscope. Here, regarding the damage, the case where cracks occur in the oxide layer and the case where dissolution disappears are defined as "damaged". In addition, the amount of the supported catalyst was quantified with respect to the sample after the catalyst was supported by using a fluorescent X-ray analyzer. The film thickness of the sample on which the metal film was formed was observed by an electron microscope, and the presence or absence of the unevenness and the swelling was visually judged. The oxide layer and the catalyst layer were formed by the same method as in the case of the preliminary sample.

< annealing-based fluorine removal treatment >

The results of annealing as the fluorine removal treatment are shown in table 4.

[ Table 4]

Refer to table 4. In terms of the fluorine content of the LPD film after annealing at the prescribed temperature for 120 minutes, the fluorine content was reduced to less than 1 mass% at a temperature of more than 150 ℃ (samples 3-6 and 9-20). The samples (1, 2, 7, 8) having a fluorine content of more than 1 mass% also had a low catalyst loading compared with the other samples. When these samples were subjected to electroless plating, the film was not subjected to electrolytic plating because swelling and unevenness were observed.

When the fluorine content is less than 1 mass%, the final metal film is not expanded or uneven. In addition, even if the metal film is annealed, no expansion occurs.

As described above, it is understood that when the fluorine content of the oxide layer is 1 mass% or less, the metal film formed on the oxide layer is not damaged, and a uniform metal film can be formed. And will not be influenced by the film species of the oxide layer and the film species of the electroless plating.

< fluorine removal treatment by chemical treatment >

As the fluorine removal treatment, a chemical treatment is performed. The results are shown in Table 5.

[ Table 5]

Refer to table 5. Samples 21 to 29 are the case where the film species of the oxide layer is Ti oxide, samples 30 to 36 are the case where the film species is Sn oxide, and sample 37 is the case where the film species is Si oxide. As the chemical treatment, treatment of immersing in each solution of sulfuric acid, hydrochloric acid, ultrapure water, sodium hydroxide, potassium hydroxide, or the like for 30 minutes was performed. The pH of each solution is shown in Table 5. The fluorine content of the oxide layer after the treatment was measured, and as a result, fluorine was reduced by the treatment under the alkali solution. However, when the film seed of the oxide layer is Sn oxide, the oxide layer itself dissolves and disappears in the alkaline solution. This is considered to be because Sn is an amphoteric oxide.

The samples (24-29, 36, 37) having a fluorine content of 1 mass% or less smoothly passed through the subsequent plating step, and neither swelled nor unevenly distributed when only electroless plating was performed nor when electrolytic plating was performed thereafter. In addition, even if the film is annealed, no swelling occurs.

On the other hand, in the samples (21-23, 30-35) having an oxide layer fluorine content of 1 mass% or more, swelling was observed in the state of the metal film by electroless plating.

As described above, the chemical treatment is preferably an alkali treatment at a pH of 10.5 or more. However, it was found that when the oxide layer is an amphoteric oxide, the film itself is dissolved. Therefore, when the oxide layer is an amphoteric oxide, a fluorine removal treatment by an annealing treatment is preferable.

< fluorine removal treatment when the film thickness is large >

The above samples are thin oxide layers of 200nm or less. However, the oxide layer may require various film thicknesses for various reasons. Therefore, the effect of the fluorine removal treatment of the oxide layer having a thickness of 200nm or more was confirmed. The results are shown in Table 6.

[ Table 6]

Referring to Table 6, the samples (38, 39) in which the oxide layer was formed of Sn oxide and the film thickness was 200nm or more were cracked by annealing at 200 ℃ and 150 ℃ (120 minutes). If the annealing temperature is 100 ℃ or 50 ℃, no cracks are generated (samples 40 to 43). However, as shown in the samples (7, 8) of table 4, fluorine was not removed at an annealing temperature of 100 ℃.

Therefore, chemical treatment based on a base of ph10.5 was further performed. As shown in sample 33 of Table 5, when the film thickness is small, the film is dissolved and disappears. However, the films of the samples (40 to 43) subjected to the annealing treatment at 100 ℃ for 120 minutes were not dissolved, and fluorine removal was performed. However, the sample 44 with an annealing temperature of 50 ℃ dissolves and disappears. It is considered that the appropriate annealing treatment can burn off the oxide layer and impart resistance to the alkali treatment. In this case, the oxide film was not damaged even at pH12 in the alkali treatment. In addition, when samples 38 and 39 in which cracks occurred were subjected to alkali treatment in the same manner, the film peeled from the substrate.

By the annealing treatment at 100 ℃ and the chemical treatment at pH10.5, a uniform metal film was formed on the oxide layer from which fluorine was removed to 1 mass% or less, and no film damage such as swelling or unevenness was caused in the case of only the electroless plating and the case of the electrolytic plating thereafter. Further, even if the film is subjected to annealing treatment, no expansion of the film occurs. It was confirmed that samples 38 to 44 were carried out using Sn, which is an amphoteric oxide of the type of oxide layer, and that fluorine can be removed by the same treatment in the case of Ti, which is an acidic oxide.

From the above, it is understood that, in the case of a film thickness of 200nm or more, fluorine in the oxide layer 114 can be removed by using an annealing treatment at 100 to 150 ℃ and an alkali solution treatment based on a solution having a ph of 10.5 or more in combination regardless of the metal species.

When the film thickness is less than 200nm, the oxide layer 114 is made of amphoteric oxide such as Sn (tin), Al (aluminum), Zn (zinc), Be (beryllium), Ga (gallium), Ge (germanium), Pb (lead), Sb (antimony), Bi (bismuth), Cd (cadmium), and the like, and fluorine in the oxide layer 114 can Be removed by annealing at 100 to 150 ℃ in combination with alkali solution treatment using a solution having a ph of 10.5 or higher, or by annealing at 150 ℃ or higher.

When the film thickness is less than 200nm and the metal species of the oxide layer 114 is not an amphoteric oxide, fluorine in the oxide layer 114 can be removed by annealing at 150 ℃ or higher or alkali treatment at ph10.5 or higher.

Industrial applicability

The laminated film structure and the method for manufacturing the laminated film structure of the present invention can be used not only for electronic-related products such as circuit boards, semiconductor circuits, and electronic components, but also for protective films and finishing films for decoration.

Description of the reference numerals

1 electronic product

10 object to be treated

10a insulating substrate

10b conductive layer

10h through hole

10hi inner wall

12 surface to be treated

12a cross-sectional portion

12b cross-sectional portion

16 ultraviolet ray

118 chemical plating solution

20 metal film

Metal film in 20i vias

30 catalyst solution

30a catalyst

64 mask

70 metal film forming device

72 first film forming part

72a first bath

72b Filter

72d circulation piping

72c pump

72e reaction initiator tank

72f piping

72j heater

72g valve

74 catalyst supporting part

74a catalyst solution tank

76 second film forming part

76a second bath

78 fluorine removal part

80 reaction solution containing fluorine and oxide precursor ions

114 oxide layer

A titanium oxide-containing layer formed on the inner wall of the 114i via hole

118 chemical plating solution