JP4884128B2 - Method and apparatus for removing conductive metal oxide thin film - Google Patents

Description

  The present invention relates to a method for removing a conductive metal oxide thin film formed on a substrate by, for example, sputter deposition so that it can be reused, and an apparatus for carrying out the method.

  For example, a high-performance glass substrate on which ITO (a film having transparent conductivity with an oxide of indium and tin) is excellent in optical performance (such as transmittance) and mechanical performance (such as flatness). Used for flat panel displays. However, since this high-performance glass substrate is expensive, when the ITO formed on the surface does not satisfy the quality control standard, the ITO is removed and reused to reduce the cost.

  As a method of removing the conductive metal oxide thin film such as ITO, there are a method of removing by mechanical abrasion and a method of removing by chemical etching. Of these methods, the former method is to remove the conductive metal oxide thin film 1 a formed on the surface of the workpiece 1 by rubbing with a polishing brush 2 as shown in FIG. 10.

In the latter method, as shown in FIG. 11, the conductive metal formed on the surface of the workpiece 1 is immersed in a chemical solution 3 that chemically dissolves the conductive metal oxide thin film 1a. The oxide thin film 1a is removed (for example, Patent Documents 1 and 2).
JP-A-6-321581 JP-A-9-86968

  However, since the method of removing by mechanical rubbing rubs the polishing brush, there are cases where rubbing marks (wrinkles) and stress deformation occur on the surface of the workpiece. When scratch marks are generated, it becomes impossible to reuse the glass substrate as it is. Moreover, when the object to be processed is a flat panel display, the glass thickness of the glass substrate is about 0.5 mm. Therefore, delicate pressure adjustment of the brush is necessary, and it takes a long time to completely peel off.

  On the other hand, the method of removing by chemical etching uses a strong acid or strong alkali chemical solution, so that chemical stress is generated on the substrate surface, and an altered layer may be formed on the substrate surface. In addition, it is necessary to pay sufficient attention to handling, not only the workability is deteriorated, but also the electrolytic solution after use needs to be treated as a waste solution. Also, the collection of rare metals is very uneconomical because it requires a separate extraction operation.

  The problems to be solved by the present invention are that mechanical scratching causes scratch marks and stress deformation, making it impossible to reuse the substrate, and delicate pressure adjustment of the brush is necessary, and complete peeling takes a long time. In the method using chemical etching, a deteriorated layer may be formed on the surface of the substrate, and workability is deteriorated. In addition, it is necessary to dispose the used electrolytic solution as a waste liquid. This requires that a separate extraction operation is required for collection, which is uneconomical.

The method for removing the conductive metal oxide thin film of the present invention comprises:
In order to efficiently remove the conductive metal oxide thin film over almost the entire area without requiring precise position control,
In order to face the conductive metal oxide thin film formed on the surface of the base material in the direction of relative movement with the base material, a positive electrode, an insulator, and a negative electrode are arranged in order,
The negative electrode is positioned so as to be in contact with the conductive metal oxide thin film on the surface of the base material, and the electrolyte solution is placed between the positive electrode and the negative electrode and the conductive metal oxide thin film on the base material surface. In the interposed state, apply a voltage to the positive electrode and the negative electrode,
In the method for removing the conductive metal oxide thin film, by removing the conductive metal oxide thin film on the surface of the base material by a reduction reaction by relatively moving the positive electrode and the negative electrode and the base material,
The main feature is to remove bubbles on the surface of the base material generated by the reduction reaction by supplying an electrolytic solution from the positive electrode in a direction opposite to the negative electrode.

In the method for removing a conductive metal oxide thin film of the present invention, a negative electrode is brought into contact with the conductive metal oxide on the surface of the base material, thereby converting the surface of the conductive metal oxide immediately below the positive electrode into a negative electrode. Electrolysis of the electrolyte solution between the positive electrode and the positive electrode generates OH ^{− on} the surface of the positive electrode and H ⁺ on the surface of the conductive metal oxide, and the conductive oxide surface is reduced by the generated H ⁺ .

At that time, the generated H ⁺ is flowed on the raw substrate by the electrolytic solution, and the conductive metal oxide thin film to be reduced is partially reduced, thereby inhibiting the conductivity and the conductivity. Metal oxide may not be reduced cleanly.

However, in the present invention, by supplying the electrolyte from the positive electrode in the direction opposite to the negative electrode, the generated H ^{+ and the} like bubbles are positively excluded to the substrate side where the reduction has been completed. Such a problem does not occur.

  In the present invention, the supply of the electrolyte solution from the positive electrode in the direction opposite to the negative electrode can be performed between the positive electrode and the negative electrode even by a method in which the electrolyte solution passes through the comb-like portion or the plurality of holes formed in the negative electrode. The method of doing may be used.

In the present invention described above, the electrolytic solution having a resistivity of 10 ² Ω · cm to 10 ⁶ Ω · cm can be used to efficiently remove the conductive metal formed on the substrate. It becomes possible.

The method for removing the conductive metal oxide thin film of the present invention comprises:
A positive electrode, an insulator, and a negative electrode arranged in order so as to face the conductive metal oxide thin film formed on the surface of the base material in the direction of relative movement with the base material and only the negative electrode is in contact with the substrate. Electrodes,
An electrolyte supply means for supplying an electrolyte solution from the positive electrode in a direction opposite to the negative electrode so as to interpose the electrolyte solution between the positive electrode and the negative electrode and the conductive metal oxide thin film on the surface of the substrate; ,
A power source for applying a voltage to the positive electrode and the negative electrode;
Comprising a relative movement means between the positive electrode and the negative electrode and the substrate;
This can be done by using the apparatus for removing a conductive metal oxide thin film of the present invention in which bubbles on the surface of the substrate generated by the reduction reaction are removed by the supplied electrolytic solution.

  The electrolytic solution supply means in the conductive metal oxide thin film removing apparatus of the present invention is provided with an electrolytic solution supply nozzle for supplying an electrolytic solution toward the positive electrode at a position opposite to the positive electrode of the negative electrode, and a negative electrode. The part of the electrode immersed in the electrolytic solution may be provided with a comb-like portion or a plurality of holes, or may be provided with an electrolytic solution supply nozzle between the positive electrode and the negative electrode.

  In the apparatus for removing a conductive metal oxide thin film of the present invention, when the positive electrode, the insulator, and the negative electrode arranged in this order are arranged to be inclined with respect to the relative movement direction with respect to the base material, a wider range is obtained. The conductive metal oxide thin film can be removed.

  In the present invention, since the electrolyte solution is supplied from the positive electrode in the direction opposite to the negative electrode to remove the bubbles on the surface of the substrate generated by the reduction reaction, the installation interval between the positive electrode and the negative electrode can be shortened, The conductive metal oxide thin film remaining unreduced at the rear end of the substrate can be reduced. In addition, the processing speed can be increased.

  Further, since no strong acid or strong alkali chemical solution is used, the environmental load can be reduced, and resource cycles such as rare metals such as base materials can be realized, which is economically advantageous.

Hereinafter, the basic principle of the present invention will be described with reference to FIG. 1, and various embodiments will be described in detail with reference to FIGS. 2 to 9 together with the best mode for carrying out the present invention.
The present invention is a processing method that leaves as little wrinkles and stress deformation on a substrate as possible, and a method for removing a conductive metal oxide thin film that does not use strong acid or strong alkali.

  In FIG. 1, 14 is a metal positive electrode having a thickness of about several millimeters, 15 is a metal negative electrode having a thickness of 0.1 to several millimeters, and these electrodes 14 and 15 are insulators or conductors. The conductive metal oxide thin film (for example, ITO) 12 formed on the surface of the base material (for example, glass) 11 is disposed so as to face the substrate, and is applied by the DC voltage power supply 16. Reference numeral 17 denotes an insulator (for example, rubber having a thickness of about 2 mm) disposed between the positive electrode 14 and the negative electrode 15.

A part of the positive electrode 14 and the negative electrode 15 is immersed in the electrolytic solution 13, and the negative electrode 15 is in contact with the conductive metal oxide thin film 12 on the surface of the substrate 11. In this way, the surface of the conductive metal oxide thin film 12 immediately below the positive electrode 14 is converted into a negative electrode, and the electrolytic solution 13 between the negative electrode and the positive electrode 14 is electrolyzed. OH ⁻ is generated on the surface, H ⁺ is generated on the surface of the conductive metal oxide thin film 12, and the surface of the conductive metal oxide thin film 12 is reduced and removed by the generated H ⁺ .

However, in such a removal method, the electrolytic metal 13 accompanying the movement of the base material 11 causes the generated H ⁺ to flow on the raw base material 11, and the conductive metal oxide thin film 12 to be reduced is partially removed. Therefore, the conductivity is hindered, and the conductive metal oxide thin film 12 may not be reduced cleanly.

Therefore, in the present invention, by supplying the electrolytic solution 13 from the positive electrode 14 in the direction opposite to the negative electrode 15, the H ⁺ generated on the surface of the conductive metal oxide thin film 12 generated by the reduction reaction is reduced. The air bubbles are pushed out to the side where the reduction is completed and actively removed.

As means for supplying the electrolytic solution 13 from the positive electrode 14 in the direction opposite to the negative electrode 15, for example, as shown in FIG. 2, the positive electrode 14 is positioned at a position opposite to the positive electrode 14 of the negative electrode 15. An electrolytic solution supply nozzle 18 for supplying the electrolytic solution 13 is installed. And the comb-tooth shaped part 15a is provided in the part immersed in the electrolyte solution 13 of the negative electrode 15 as shown in FIG. 3, or the several hole 15b as shown in FIG. 4 is provided. The comb-like portion 15 a or the plurality of holes 15 b are arranged so that the electrolyte solution 13 flows uniformly toward the positive electrode 14. Further, if necessary, the arrangement and size of the comb-like portion 15a or the plurality of hole portions 15b are appropriately adjusted so that the electrolytic solution 13 is supplied mainly to a place where H ⁺ bubbles are likely to be generated.

By adopting such a configuration, the electrolytic solution 13 supplied from the electrolytic solution supply nozzle 18 passes through the comb-like portion 15a or the plurality of holes 15b, and is in the direction opposite to the negative electrode 15 from the positive electrode 14. H ⁺ bubbles generated on the surface of the conductive metal oxide thin film 12 by the reduction reaction are pushed to the side where the reduction is completed, and the positive electrode 14 and the negative electrode 14 are negative. The conductive metal oxide thin film 12 positioned between the electrodes 15 is not partially reduced.

  Therefore, the positive electrode 14 and the negative electrode 15 can be placed close to each other, and the width in the moving direction of the conductive metal oxide thin film 12 remaining unreduced at the rear end portion in the moving direction of the substrate 11 is reduced. The conductive metal oxide thin film 12 can be removed over almost the entire area. At that time, precise position control is not required.

In addition, since the electrolyte 13 flows in the same direction as the movement direction of the base material 11, the H ⁺ bubbles generated on the surface of the conductive metal oxide thin film 12 by the reduction reaction are pushed to the side where the reduction is completed. Even if the moving speed of the base material 11 is increased, the H ⁺ is not flowed onto the unreduced base material 11.

  5 to 7 show a gap between a metal positive electrode 14 having a thickness of 1 mm to several tens of mm and a metal negative electrode 15 having a thickness of 0.1 mm to several mm (several mm to several tens mm). Thus, means for supplying the electrolytic solution 13 from the positive electrode 14 in the direction opposite to the negative electrode 15 is shown.

  In FIG. 5, the flow rate is uniform over the entire width of the substrate 11 between the positive electrode 14 and the resin or rubber insulator 17 having a thickness of 0.2 mm to several mm by the electrolyte supply nozzle 18. Then, the electrolyte solution 13 is supplied so that the electrolyte solution 13 flows between the positive electrode 14 and the conductive metal oxide thin film 12 (1 to 3 mm).

  According to the example shown in FIG. 5, the electrolyte solution 13 does not pass under the negative electrode 15 as in the example shown in FIG. 2, so that the comb-like portion 15 a for passing the electrolyte solution 13 passes through the negative electrode 15. There is no need to provide a plurality of holes 15b.

  6 replaces the electrolyte supply nozzle 18 shown in FIG. 5 with a box-shaped electrolyte supply nozzle 19 in order to make the flow rate of the electrolyte 13 more uniform over the entire width of the substrate 11. 13 is supplied.

  The box-shaped electrolyte supply nozzle 19 is a box having a length of about 1 mm to several mm in the left-right direction on the paper surface. The box-shaped electrolyte supply nozzle 19 is provided inside the box as necessary so that the flow of the electrolyte 13 is uniform in the width direction. A baffle or the like is installed.

  However, since the distance between the positive electrode 14 and the negative electrode 15 is increased by the thickness of the box-shaped electrolyte supply nozzle 19, the lower end of the box-shaped electrolyte supply nozzle 19 is several mm smaller than the lower end of the positive electrode 14. It is desirable to install ~ tens of mm above. By doing so, the movable range of the negative electrode 15 and the insulator 17 is increased, and the negative electrode 15 is actively deformed as shown in FIG. 6, thereby narrowing the interval between the positive electrode 14 and the negative electrode 15. be able to.

  FIG. 7 shows the positive electrode 14, the negative electrode 15, the insulator 17, and the box-shaped electrolyte supply nozzle 19 shown in FIG. 6 that are inclined several degrees to several tens of degrees when viewed from the side. When arranged so as to be inclined, the flow of the electrolyte solution 13 is made more uniform.

  In FIG. 8, the positive electrode 14, the negative electrode 15, the insulator 17, and the like described above are arranged with an inclination of several degrees to several tens of degrees when viewed from the plane with respect to the moving direction of the base material 11. In this case, for example, in the case of the base material 11 on which the conductive metal oxide thin film 12 is formed on the entire surface, a slightly unreduced conductive metal oxide thin film 12 remains at one corner of the base material 11. The conductive metal oxide thin film 12 can be removed over a wider range.

  In the present invention described above, since the conductive metal oxide thin film 12 is finely divided (0.1 μm or less) as a metal solid after electrolytic reduction treatment, for example, as shown in FIG. What is necessary is just to peel a metal. In addition, in FIG. 9, what uses together mechanical peeling by the flexible material 21 as assistance is shown.

  After that, the reduced metal removed together with the electrolytic solution 13 is accumulated in the recovery tank 23 through the electrolytic solution collecting pan 22, and microbubbles are mixed by the microbubble generator 24. As a result, the metal bubbles are clustered using the microbubbles as a nucleus and can be collected by the filter. In addition, 26 in FIG. 9 shows a pump.

As described above, the present invention is a characteristic processing method for applying a negative voltage to a workpiece, not a general electrolytic elution removal reaction for applying a positive voltage to the workpiece, as described above. .
Note that since the electrolytic reaction here may generate H _{2 in} a very small region at the interface of the conductive metal oxide thin film, little current is required.

Accordingly, as the electrolytic solution 13 to be used, a generally used neutral salt solution or a mixture of a neutral salt solution in tap water, river water, or the like can be used. Preferably, the resistivity is 10 ² Ω · Those adjusted from cm to 10 ⁶ Ω · cm, more preferably from 10 ³ Ω · cm to 10 ⁴ Ω · cm are preferable.

That is, the resistivity of the electrolytic solution 13 in the present invention is equal to the resistance value of the electrolytic solution 13 between the positive electrode 14 and the negative electrode 15 and the resistance value between the negative electrode 15 to the conductive metal oxide thin film 12 to the positive electrode 14. The range is from 10 ² Ω · cm in consideration of the type of the conductive metal oxide thin film 12, the height of the positive electrode 14, and the distance between the positive electrode 14 and the negative electrode 15. 10 ⁶ Ω · cm. When the resistivity of the electrolytic solution 13 is smaller than 10 ² Ω · cm, the conductive metal oxide thin film 12 is not passed through, and the positive electrode 14 and the negative electrode 15 are brought into conduction through the electrolytic solution 13. The reduction of the oxide in the physical thin film 12 hardly occurs. On the other hand, if it is larger than 10 ⁶ Ω · cm, the conductivity is lowered, and unless a high voltage is applied, the oxide cannot be completely reduced, which is economically undesirable.

  Thus, in the present invention, since the electrolytic solution 13 having a relatively high resistivity is suitable, it is possible to use tap water, river water, etc., which is not preferable as the electrolytic solution 13 conventionally, and is economical and safe. Also excellent in terms of sex.

ITO having a thickness of 1500 × 10 ⁻¹⁰ m formed on a glass substrate having a thickness of 0.7 mm and a size of 370 mm × 470 mm is used for the apparatus of the present invention shown in FIGS. It was removed by the inventive method.

When removing ITO, tap water is used as the electrolyte, a 60 V DC voltage is applied between the positive electrode and the negative electrode (both electrode widths are 600 mm) (current: 1.5 A), and the workpiece is 2 m / When moved in minutes, the width in the feeding direction of ITO remaining unreduced at the rear end of the glass substrate decreased to 1 mm or less (area: 1 mm × 370 mm = 370 mm ² ).

In Example 1, when the positive electrode, the negative electrode, and the like are arranged with an inclination of 30 degrees when viewed from the plane with respect to the moving direction of the glass substrate, the ITO remaining unreduced at the rear end of the glass substrate is Example 1. It was reduced from 370mm ² to 1.73mm ^2.

  The present invention is not limited to the above-described example, such as the shape of the hole 15b provided in the negative electrode 15 is not limited to a circle, and the embodiment is appropriately changed within the scope of the technical idea described in each claim. Needless to say, you can.

It is a figure explaining the basic principle of this invention. It is the figure seen from the side in the schematic diagram explaining the 1st example of this invention. It is the figure which showed the 1st example of the shape of the negative electrode used for the 1st example of this invention. It is the figure which showed the 2nd example of the shape of the negative electrode used for the 1st example of this invention. It is the figure seen from the side in the schematic diagram explaining the 2nd example of this invention. It is the figure seen from the side in the schematic diagram explaining the 3rd example of this invention. It is the figure seen from the side in the schematic diagram explaining the 4th example of the present invention. It is the figure seen from the top in the schematic diagram explaining the 5th example of the present invention. It is the figure which showed an example of the collection | recovery apparatus after carrying out the electrolytic reduction process of the electroconductive metal oxide thin film by this invention. It is a figure explaining the method of removing a metal thin film by mechanical abrasion. It is a figure explaining the method of removing a metal thin film by chemical etching.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Base material 12 Conductive metal oxide thin film 13 Electrolytic solution 14 Positive electrode 15 Negative electrode 15a Comb-like part 15b Hole part 16 DC voltage power supply 17 Insulator 18 Electrolyte supply nozzle 19 Box-shaped electrolyte supply nozzle

Claims (8)

In order to face the conductive metal oxide thin film formed on the surface of the base material in the direction of relative movement with the base material, a positive electrode, an insulator, and a negative electrode are arranged in order,
The negative electrode is positioned so as to be in contact with the conductive metal oxide thin film on the surface of the base material, and the electrolyte solution is placed between the positive electrode and the negative electrode and the conductive metal oxide thin film on the base material surface. In the interposed state, apply a voltage to the positive electrode and the negative electrode,
In the method for removing the conductive metal oxide thin film, by removing the conductive metal oxide thin film on the surface of the base material by a reduction reaction by relatively moving the positive electrode and the negative electrode and the base material,
A method for removing a conductive metal oxide thin film, comprising removing an air bubble generated on the surface of the base material by the reduction reaction by supplying an electrolytic solution from the positive electrode in a direction opposite to the negative electrode.   2. The conductive material according to claim 1, wherein the electrolyte solution is supplied from the positive electrode in a direction opposite to the negative electrode through a comb-like portion or a plurality of holes formed in the negative electrode. Method for removing metal oxide thin film.   2. The method for removing a conductive metal oxide thin film according to claim 1, wherein the electrolyte solution is supplied from the positive electrode in a direction opposite to the negative electrode from between the positive electrode and the negative electrode. The method for removing a conductive oxide thin film according to any one of claims 1 to 3, wherein the resistivity of the electrolytic solution is 10 ² Ω · cm to 10 ⁶ Ω · cm. An apparatus for performing the method for removing a conductive metal oxide thin film according to claim 1,
A positive electrode, an insulator, and a negative electrode arranged in order so as to face the conductive metal oxide thin film formed on the surface of the base material in the direction of relative movement with the base material and only the negative electrode is in contact with the substrate. Electrodes,
An electrolyte supply means for supplying an electrolyte solution from the positive electrode in a direction opposite to the negative electrode so as to interpose the electrolyte solution between the positive electrode and the negative electrode and the conductive metal oxide thin film on the surface of the substrate; ,
A power source for applying a voltage to the positive electrode and the negative electrode;
Comprising a relative movement means between the positive electrode and the negative electrode and the substrate;
An apparatus for removing a conductive metal oxide thin film, wherein the supplied electrolyte solution removes bubbles on the surface of the base material generated by the reduction reaction. An electrolytic solution supply nozzle that supplies an electrolytic solution toward the positive electrode is installed at a position opposite to the positive electrode of the negative electrode, and a comb-like portion or a plurality of portions are immersed in the portion of the negative electrode immersed in the electrolytic solution Provide a hole,
The conductive metal oxide thin film according to claim 5, wherein the electrolyte solution is supplied from the positive electrode in a direction opposite to the negative electrode through the plurality of holes. Removal device. An electrolyte supply nozzle is provided between the positive electrode and the negative electrode,
6. The apparatus for removing a conductive metal oxide thin film according to claim 5, wherein the electrolytic solution is supplied from the positive electrode in a direction opposite to the negative electrode by the electrolytic solution supply nozzle. . The conductive metal oxide according to claim 5, wherein the positive electrode, the insulator, and the negative electrode arranged in this order are arranged to be inclined with respect to the relative movement direction with respect to the base material. Thin film removal device.

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