JP2018135544A - Method of producing metal film - Google Patents

Abstract

Provided is a metal film deposition method capable of uniformly depositing the entire film thickness even when the area of the solid electrolyte membrane is large or when the ratio of the deposition area to the substrate area (coverage) is large. To do.
A solid electrolyte membrane is disposed between an anode and a cathode, an aqueous solution containing metal ions is disposed between the anode and the solid electrolyte membrane, and a voltage is applied between the anode and the cathode. In the film-forming method of applying and pressurizing the aqueous solution L to apply a pressure P due to the liquid pressure of the aqueous solution L to the solid electrolyte membrane 5 and forming a metal coating C made of a metal ion metal on the surface of the substrate 6, The upper limit value and lower limit value of the average pressure Y of the applied pressure P are set between the upper limit value and the lower limit value defined by the following formula using the coverage X, and the upper limit value: Yup = 2.5 or less. lower limit: If coverage X is less than 67% greater than ^{0%, Yud = (2.5 × 10 -8} ) X 5 - (4 × 10 -6) X 4 + 0.0002X 3 -0.0065X 2 + 0.079X + 1 .8, Yud = 0.5 when the coverage ratio X is greater than 67% and less than 100%.
[Selection] Figure 2

Description

  The present invention relates to a method for forming a metal film, in which a metal film is formed on the surface of a substrate.

  Patent Document 1 discloses a method for forming a metal film that can stably coat a metal film with a uniform film quality on a substrate.

  Specifically, a solid electrolyte membrane is disposed between the anode and the cathode, the cathode is connected to the substrate while the solid electrolyte membrane is in contact with the substrate, a voltage is applied between the anode and the cathode, and the solid electrolyte membrane is In this method, a metal film made of metal ions is deposited on the surface of a substrate by precipitating metal ions contained in the metal on the cathode side.

  In this film forming method, a solution containing metal ions is disposed between the anode and the solid electrolyte membrane, and the solution is pressurized when the solid electrolyte membrane is brought into contact with the substrate, so that the solution is pressurized by the liquid pressure. A pressure is applied to the solid electrolyte membrane, and a metal coating is formed while pressurizing the substrate through the solid electrolyte membrane.

  By the way, when the area of the solid electrolyte membrane is increased or the ratio of the film formation area to the substrate area (coverage) is increased, air is likely to be entrained when the solid electrolyte membrane is brought into contact with the substrate. Even if the applied pressure is increased, the entrained air cannot be released to the outside, and a region where the substrate and the solid electrolyte membrane cannot be adhered to each other is formed. It becomes difficult.

JP 2014-51701 A

  The present invention has been made in view of the above problems, and even when the area of the solid electrolyte membrane is large, or even when the ratio of the film formation area to the substrate area (coverage) is large, the entire film thickness is uniformly formed into a metal. It is an object of the present invention to provide a method for forming a metal film that can be formed into a film.

In order to achieve the above object, a metal film forming method according to the present invention includes a solid electrolyte membrane disposed between an anode and a cathode, and an aqueous solution containing metal ions disposed between the anode and the solid electrolyte membrane, The solid electrolyte membrane is brought into contact with a substrate, a voltage is applied between the anode and the cathode, the aqueous solution is pressurized, and a pressure applied by the hydraulic pressure of the aqueous solution is applied to the solid electrolyte membrane, and the solid electrolyte membrane In the metal film forming method, the metal ions are deposited from the inside of the substrate on the cathode side, and a metal film made of metal of the metal ions is formed on the surface of the substrate. This is a metal film forming method in which the value and the lower limit value are set between the upper limit value and the lower limit value defined by the following formula using the coverage X.
Upper limit value: Yup = 2.5 or less Lower limit value: When coverage X is greater than 0% and less than 67%,
Yud = (2.5 × 10 ⁻⁸ ) X ⁵ − (4 × 10 ⁻⁶ ) X ⁴ + 0.0002X ³ −0.0065X ² + 0.079X + 1.8
If coverage X is greater than 67% and less than 100%,
Yud = 0.5
Where, average pressure Y (MPa) = applied load / contact area of solid electrolyte membrane,
Coverage ratio X (%) = film formation area / substrate area.

  The method for forming a metal coating of the present invention sets the average pressure Y of the applied pressure applied to the solid electrolyte membrane from an aqueous solution containing metal ions disposed between the anode and the solid electrolyte membrane in an optimum pressure range, The upper limit value and the lower limit value are defined using mathematical formulas with the coverage ratio X consisting of the film formation area / substrate area as a variable.

  By forming the film while setting the pressure applied to the solid electrolyte film from the aqueous solution within the above-mentioned optimum range, the entire solid electrolyte film can be brought into contact with the substrate as uniformly as possible. It is also possible to prevent the solid electrolyte membrane from being damaged.

  In the method for forming a metal coating according to the present invention, the solid electrolyte membrane is brought into contact with the substrate and the cathode is brought into contact with the substrate in the state in which an aqueous solution containing metal ions is arranged between the anode and the solid electrolyte membrane. Electrically conducting. In this state, by applying a voltage between the anode and the cathode, the metal ions contained in the aqueous solution move from the anode side toward the cathode side, pass through the inside of the solid electrolyte membrane, and pass through the cathode of the solid electrolyte membrane. Can be deposited on the side. As a result, a metal film made of a metal ion metal in an aqueous solution can be formed on the surface of the substrate without consuming the anode.

  Furthermore, the metal ions in the solid electrolyte membrane are deposited at the time of film formation, and metal ions are supplied to the solid electrolyte membrane from the aqueous solution on the anode side. Therefore, by supplying an aqueous solution as needed, it becomes possible to continuously form a metal film having a desired film thickness on the surfaces of a plurality of substrates without exchanging the anode.

  In addition, the method for forming a metal coating according to the present invention applies pressure to the solid electrolyte membrane by pressurizing an aqueous solution containing metal ions when the solid electrolyte membrane is brought into contact with the substrate. Since the metal coating is formed while pressing the substrate through the solid electrolyte membrane, the solid electrolyte membrane can uniformly press the substrate surface by the hydraulic pressure of the pressurized aqueous solution based on the Pascal principle. . By applying a voltage between the anode and the cathode in such a pressurized state, a metal film having a uniform thickness can be formed on the surface of the substrate.

  As can be understood from the above description, according to the metal film deposition method of the present invention, the average applied pressure applied to the solid electrolyte membrane from the aqueous solution containing metal ions disposed between the anode and the solid electrolyte membrane. Even when the area of the solid electrolyte membrane is large or the ratio of the film formation area to the substrate area (coverage) is large, by forming the film while setting the pressure Y within the optimum pressure range, the entire film thickness can be made uniform. Metal film can be formed.

It is the flowchart explaining the film-forming method of the metal film of this invention. FIG. 2 is a flowchart for explaining a metal film forming method following FIG. 1. It is the figure which showed the optimal range of the average pressure of the applied pressure given to the solid electrolyte membrane from the aqueous solution containing a metal ion.

Embodiments of a metal film forming method of the present invention will be described below with reference to the drawings.
(Embodiment of metal film deposition method)
1 and 2 are flow charts illustrating the metal film forming method of the present invention in order. In the illustrated method for forming a metal coating, a solid electrolyte membrane 5 is disposed between an anode 1 and a cathode 2, and a hydraulic chamber 4 containing an aqueous solution L containing metal ions between the anode 1 and the solid electrolyte membrane 5. The solid electrolyte membrane 5 is brought into contact with the substrate 6, a voltage is applied from the power source 3 to the circuit connecting the anode 1 and the cathode 2, and simultaneously the aqueous solution L is pressurized (in the X direction). Is applied to the solid electrolyte membrane 5.

  Here, the anode 1 has only to have corrosion resistance to the aqueous solution L containing metal ions and has a predetermined conductivity. For example, the anode 1 has a lower ionization tendency than the metal ions contained in the aqueous solution L, and It is composed of gold or the like, which is a noble metal rather than a metal ion metal.

  On the other hand, the cathode 2 only needs to have corrosion resistance with respect to the aqueous solution L containing metal ions and have a predetermined conductivity, and further has a shape and dimensions on which the substrate 6 can be placed. .

  Here, the substrate 6 is made of nickel, for example, and the metal ions contained in the aqueous solution L are, for example, tin ions.

  The solid electrolyte membrane 5 is formed from a membrane or film made of a solid electrolyte. This solid electrolyte membrane 5 is particularly limited as long as metal ions can be impregnated inside by contacting with the aqueous solution L containing metal ions, and metal derived from metal ions can be deposited on the cathode 2 side when a voltage is applied. Is not to be done. Examples of the material of the solid electrolyte membrane 5 include a membrane having an ion exchange function such as a fluorine resin such as Nafion (registered trademark) manufactured by DuPont, a hydrocarbon resin, a polyamic acid film, and a selemion manufactured by Asahi Glass. be able to.

  The aqueous solution L is in contact with the solid electrolyte membrane 5 through the lower opening of the hydraulic chamber 4, a pressure plate 7 is disposed above the hydraulic chamber 4, and the anode 1 is attached to the lower surface of the pressure plate 7. Yes.

  Here, in this film forming method, the upper limit value and the lower limit value of the average pressure Y of the applied pressure P are set between the upper limit value and the lower limit value defined by the following formula using the coverage X. In addition, the optimal range of the average pressure of the applied pressure based on the following formula is shown in FIG.

(1) Upper limit value: Yup = 2.5 or less (a line in FIG. 3).
(2) Lower limit: When coverage X is greater than 0% and less than 67%,
Yud = (2.5 × 10 ⁻⁸ ) X ⁵ − (4 × 10 ⁻⁶ ) X ⁴ + 0.0002X ³ −0.0065X ² + 0.079X + 1.8 (b curve in FIG. 3).
If coverage X is greater than 67% and less than 100%,
Yud = 0.5 (c line in FIG. 3).
Where, average pressure Y (MPa) = applied load / contact area of solid electrolyte membrane,
Coverage ratio X (%) = film formation area / substrate area.

  If the area of the solid electrolyte membrane 5 is large, or the ratio of the area of the film formation to the area of the substrate 6 (coverage) by forming the film at a pressure set within the average pressure range shown in the above equation and FIG. Even if this is large, it becomes possible to form a metal film uniformly over the entire film thickness.

  Note that when the coverage is extremely large, for example, more than 67%, the frequency of entraining the gas when the solid electrolyte membrane 5 is brought into contact with the substrate 6 is increased. By forcibly discharging the gas using a vacuum pump or the like while defining the numerical formula range, the solid electrolyte membrane 5 and the substrate 6 can be brought into more uniform contact, and a more uniform film thickness can be achieved. It becomes possible to form a film.

  The aqueous solution L in the hydraulic chamber 4 can be pressurized with the applied pressure P by sliding the pressure plate 7 toward the lower solid electrolyte membrane 5 side in the hydraulic chamber 4 (X direction).

  By pressurizing the aqueous solution L, the solid electrolyte membrane 5 is impregnated with the aqueous solution L (metal ions therein), and metal ions are deposited on the cathode 2 side from the inside of the solid electrolyte membrane 5.

  Although not shown, a supply tank that supplies the aqueous solution L containing metal ions to the hydraulic chamber 4 is in fluid communication with the hydraulic chamber 4, and the aqueous solution is reduced as the aqueous solution L in the hydraulic chamber 4 decreases. L can be supplied at any time.

  As shown in FIG. 2, metal ions C are deposited on the surface of the substrate 6 by depositing metal ions from the inside of the solid electrolyte membrane 5 on the cathode 2 side.

(Experiment and results of verifying the film formation mode by applying pressure and film thickness from aqueous solution)
The present inventors conducted an experiment to compare and verify the form of film formation generated under each condition while changing the applied pressure and film thickness from an aqueous solution.

<Sample>
Copper was used as the metal component for film formation, and a copper / titanium / glass substrate (thickness 50 nm / 300 nm / 1 mm, size 1 × 30 × 30 mm, manufactured by Kyodo International Co., Ltd.) was used as the substrate. The deposition conditions for the copper film were 1M copper sulfate aqueous solution as the electrolyte, ion exchange membrane Nafion117 (DuPont) as the electrolyte membrane, and foamed copper (# 3835, Goodfellow) as the anode. Then, the distance between electrodes was 1 cm, the amount of electrolyte was 54 cm ³ , the substrate temperature was 60 ° C., the pressure was 1 MPa, the pulse was 8 mA × 8 seconds × 60 ° C., and the deposited film thickness was 500 μm. For heating the electrolyte, a ribbon heater (TFHU, manufactured by Tokyo Glass Instruments Co., Ltd.) was attached to the actual machine head. Further, in the pretreatment (removal of raw material polymer and metal impurities) of the electrolyte membrane, the electrolyte membrane was boiled in 3% hydrogen peroxide water for 1 hour and then boiled in 1M sulfuric acid solution for 1 hour.

<Outline of experiment>
In-plane pressure distribution measurement was performed with a conductive ink type (I-SCAN, manufactured by Nitta Corporation). In the conductive ink type, row and column silver electrodes are wired on two films (PET), respectively, and pressure sensitive conductive ink is coated on the silver electrodes. The intersection of the row and column electrodes becomes a sensing point. When pressure is applied, the electrical resistance value changes, the electrical resistance value is converted to an 8-bit digital value, and the electrical resistance value taken into the personal computer is converted to pressure. . Therefore, the measurement range can be set by changing the composition of the piezoelectric conductive ink.
Here, probes for low pressure measurement (maximum measurement pressure 0.7 MPa) and high pressure measurement (maximum measurement pressure 3.5 MPa) were used.

<Experiment result 1>
In the hydraulic method, when the solid electrolyte membrane is brought into contact with the substrate, a solution containing metal ions is pressurized, so that the metal coating is formed while the substrate is pressurized through the solid electrolyte membrane with the liquid pressure of this solution. Do the film. As a result, according to Pascal's principle, the solid electrolyte membrane can uniformly pressurize the substrate surface by the liquid pressure of the pressurized solution. A metal film having a uniform thickness can be formed on the surface of the substrate by applying a voltage between the anode and the cathode in such a pressurized state. However, when the liquid pressure is low and not uniform, it is not clear at present how the form of the metal coating changes when the film is formed with a long deposition time.

  Therefore, in this experiment, the pressure and deposition time (film thickness) were changed, a tin film was formed on the nickel substrate, and the form change of the tin film was verified. As a result of verification, it was found that when the pressure was increased, the area of the tin coating was increased and the number of undeposited portions was reduced regardless of the difference in the thickness of the tin coating.

  It was also found that when the pressure was 0.5 MPa and the deposition time was increased to increase the thickness of the tin coating from 0.1 μm to 0.4 μm or more, the tin deposition area (tin coating area) increased.

  On the other hand, when the pressure is 0.1 MPa, there are many undeposited parts even if the thickness of the tin coating is changed, the area of the tin coating remains small, and when the pressure is 1.0 MPa, the tin coating does not change. It was also found that even when the film thickness was changed, there were few undeposited parts, and the area of the tin coating remained large and did not change.

<Experiment result 2>
In the hydraulic solid-phase electrodeposition method, if the average pressure applied to the electrolyte is increased, the film deposition coverage approaches the target value regardless of the difference in film thickness. Based on the fact that there is a threshold value for the pressure to be applied in order for the coating coverage to approach the target value, the optimum pressure range by in-plane pressure distribution measurement can be determined using a conductive ink probe (I-SCAN). Verified.

  A 500 μm thick copper film is formed on a 3 x 3 cm substrate with varying dimensions, and a conductive ink probe (I-SCAN) is inserted between the electrolyte film attached to the anode head and the copper film. As a result of measuring the in-plane pressure distribution of the copper coating and verifying the optimum pressure range, the optimum range shown in FIG. 3 was identified.

  FIG. 3 shows the relationship between the coverage ratio (area of copper film formation / substrate area) and the average pressure (load applied to load cell / contact area of electrolyte membrane). Here, the lower limit value of the optimum pressure range was an average pressure value at which the shape of the copper coating could be confirmed by an image and the in-plane pressure distribution in the copper coating was uniform. The upper limit value of the optimum pressure range was 2.5 MPa because the electrolyte membrane was damaged when the average pressure was higher than 2.5 MPa.

  From Fig. 3, the lower limit value of the optimum pressure range is high when the coverage is small, but the lower limit value of the optimum pressure range decreases as the coverage increases, and when the coverage exceeds 67%, the lower limit value of the optimum pressure range is It turned out to be close to constant.

  Here, if the coverage ratio exceeds 67%, gas is entrained when the electrolyte membrane is brought into contact (approach) with the substrate, and even if the pressure is increased, air cannot be vented from the packing, and the substrate and Since the phenomenon that the electrolyte membrane cannot be adhered occurs and it was found that a metal film with a uniform film thickness cannot be formed, by providing a vacuum pump on the substrate mounting side in the apparatus, the gas is forcibly discharged, and the electrolyte membrane is the substrate Thus, it was possible to form a metal film having a uniform film thickness.

  Instead of using a vacuum pump, a shield plate is inserted between the electrolyte membrane and the substrate to form a groove for venting air on the surface of the coating, or a groove (anode head side) into which the electrolyte leakage prevention packing is fitted. A method of forming a vent hole in advance may be used.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Anode, 2 ... Cathode, 3 ... Power supply, 4 ... Fluid pressure chamber, 5 ... Solid electrolyte membrane, 6 ... Substrate, 7 ... Pressure plate, L ... Aqueous solution, C ... Metal coating

Claims (1)

A solid electrolyte membrane is disposed between the anode and the cathode, an aqueous solution containing metal ions is disposed between the anode and the solid electrolyte membrane, the solid electrolyte membrane is brought into contact with the substrate, and the anode and the cathode are disposed between the anode and the cathode. A voltage is applied, the aqueous solution is pressurized to apply a pressure due to the hydraulic pressure of the aqueous solution to the solid electrolyte membrane, the metal ions are precipitated from the inside of the solid electrolyte membrane to the cathode side, and the metal ions In the method of forming a metal film, a metal film made of metal is formed on the surface of the substrate.
A metal film forming method, wherein an upper limit value and a lower limit value of the average pressure Y of the pressurizing force are set between an upper limit value and a lower limit value defined by the following formula using the coverage X.
Upper limit value: Yup = 2.5 or less Lower limit value: When coverage X is greater than 0% and less than 67%,
Yud = (2.5 × 10 ⁻⁸ ) X ⁵ − (4 × 10 ⁻⁶ ) X ⁴ + 0.0002X ³ −0.0065X ² + 0.079X + 1.8
If coverage X is greater than 67% and less than 100%,
Yud = 0.5
Where, average pressure Y (MPa) = applied load / contact area of solid electrolyte membrane,
Coverage ratio X (%) = film formation area / substrate area.

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