CN101416283A - Method of removing conductive metal oxide thin-film and apparatus thereof - Google Patents

Abstract

The present invention provides a method and an apparatus for removing a conductive metal oxide film up to the end without residue. The positive electrode 13 and the first negative electrode 14 are arranged side by side in a non-contact state opposite to the conductive metal oxide film 12 on the surface of the substrate 11 . Between the positive electrode 13 and the first negative electrode 14 , a plurality of second negative electrodes 17 are provided in a contact state in the width direction of the conductive metal oxide thin film 12 . A voltage is applied to the electrodes 13 , 14 , 17 in a state where an electrolytic solution exists between these electrodes 13 , 14 , 17 and the conductive metal oxide thin film 12 . The substrate 11 is moved relative to the electrodes 13 , 14 , 17 so that the conductive metal oxide thin film 12 passes the positive electrode 13 after passing the negative electrodes 14 , 17 . The conductive metal oxide thin film can be efficiently removed up to the final end without generating flaws or stress deformation, enabling recycling of expensive functional glass substrates and the like.

Description

Method and device for removing conductive metal oxide film

technical field

The present invention relates to a method for removing a conductive metal oxide thin film formed on a base material by, for example, sputtering deposition, so that it can be reused, and an apparatus for implementing the method.

Background technique

For example, a high-function glass substrate formed with ITO (indium and tin oxide, a film having transparent conductivity) has good optical properties (transmittance, etc.) and mechanical properties (flatness, etc.), and is used, for example, in flat panel displays . However, since the high-performance glass substrate is expensive, when the ITO formed on the surface does not meet the quality control standards, the ITO is removed for reuse to reduce costs.

As a method of removing the conductive metal oxide thin film such as ITO, there is a method of removing by mechanical rubbing or a method of removing by chemical etching. Among them, in the former method, as shown in FIG. 11 , the conductive metal oxide thin film 1 a formed on the surface of the workpiece 1 is removed by rubbing with the abrasive brush 2 .

In the latter method, as shown in FIG. 12 , the workpiece 1 is immersed in a chemical reagent 3 that dissolves the conductive metal oxide thin film 1a through a chemical reaction, thereby removing the impurities formed on the surface of the workpiece 1 . Conductive metal oxide thin film 1a (for example, refer to Patent Documents 1 and 2).

Patent Document 1: Japanese Patent Laid-Open No. 6-321581

Patent Document 2: Japanese Patent Application Laid-Open No. 9-86968

disclosure of invention

However, in the method of removing by mechanical rubbing, rubbing with an abrasive brush may leave rubbing marks (flaws) or stress deformation on the surface of the workpiece. Once scratch marks are left, they cannot be reused. In addition, when the object to be processed is a flat panel display, since the glass thickness of the glass substrate is about 0.5 mm, there is a possibility that it will be broken by mechanical rubbing by contact. Therefore, it is necessary to finely adjust the pressure of the grinding brush, and it takes a long time to completely peel off.

On the other hand, the method of removing by chemical etching uses a chemical agent such as a strong acid or a strong base, so chemical stress may be generated on the substrate surface and a degenerated layer may be formed on the substrate surface. In addition, great attention should be paid to the disposal, not only the operability is poor, but also the waste liquid treatment of the used electrolyte must be carried out. In addition, in order to recover rare metals, an extraction operation must be performed separately, which is very uneconomical.

The problem to be solved by the present invention is that in the method of mechanical rubbing, the substrate cannot be reused due to rubbing marks or stress deformation, and it is necessary to carry out fine pressure adjustment of the abrasive brush, and it takes a long time to completely peel off. Time and other issues; in the method of chemical etching, sometimes a deteriorated layer is formed on the surface of the substrate, which not only deteriorates the operability, but also must carry out waste liquid treatment on the used electrolyte, and in order to recover rare metals, additional extraction is required operational rather than economical issues.

In order not to leave rubbing marks and stress deformation on the substrate as much as possible, and without using chemical reagents such as strong acid or alkali, the conductive metal oxide film of the substrate can be effectively removed, even at the end of the substrate. To the extent that there is no residual film, the removal method of the conductive metal oxide thin film of the present invention has the following most important features:

The positive electrode and the first negative electrode are opposite to the conductive metal oxide film formed on the surface of the substrate and arranged side by side in a non-contact state, and at the same time in the front section or the back section or the front section and the back section of the first negative electrode, The second negative electrode is opposite to the conductive metal oxide film formed on the surface of the substrate, and a plurality of them are arranged in the width direction of the conductive metal oxide film in a contact state, and then the positive electrode, the second In a state where an electrolyte solution exists between the 1 negative electrode, the second negative electrode, and the conductive metal oxide thin film, a voltage is applied to the positive electrode, the first negative electrode, and the second negative electrode to make the conductive film formed on the surface of the substrate The conductive metal oxide film moves relative to the positive electrode, the first negative electrode, and the second negative electrode, so that the conductive metal oxide film passes through the positive electrode after passing through the first negative electrode and the second negative electrode, thereby utilizing The reduction reaction removes the conductive metal oxide film on the surface of the substrate.

In the removal method of the conductive metal oxide thin film of the present invention, between the positive electrode and the first negative electrode, a plurality of second negative electrodes are arranged in a contact state in the width direction of the conductive metal oxide thin film. , whereby the conductive metal oxide thin film formed on the surface of the substrate can be removed to such an extent that no film remains even at the ends of the substrate.

In the method for removing the conductive metal oxide thin film of the present invention, as the positive electrode and the first negative electrode, a staggered configuration narrower than the width of the conductive metal oxide thin film may also be used. the electrodes.

In the method for removing the conductive metal oxide thin film of the present invention, the conductive metal oxide formed on the surface of the substrate can be effectively removed by using an electrolytic solution having a resistivity of 10 ² Ω·cm to 10 ⁶ Ω·cm. Thin films.

The method of removing the conductive metal oxide thin film of the present invention can be implemented by using the device of the present invention. The device comprises: a positive electrode and a first negative electrode arranged side by side in a non-contact state opposite to the conductive metal oxide film formed on the surface of the substrate; In the latter stage, facing the conductive metal oxide film and disposing a plurality of second negative electrodes in a contact state in the width direction of the conductive metal oxide film; storing and supplying the positive electrode, the first negative electrode, and the first negative electrode. 2. an electrolytic solution tank for an electrolytic solution between the negative electrode and the conductive metal oxide thin film formed on the surface of the substrate, immersing the positive electrode, the first negative electrode, the second negative electrode and the substrate in the electrolytic solution ; a power supply for applying a voltage to the positive electrode, the first negative electrode, and the second negative electrode; The electrode moves so that the conductive metal oxide film passes through the first negative electrode and the second negative electrode and then passes through the moving mechanism of the positive electrode.

In the removal device of the conductive metal oxide thin film of the present invention, the positive electrode and the first negative electrode may be continuously arranged in a zigzag shape narrower than the width of the conductive metal oxide thin film, or electrodes with a higher conductivity than the conductive metal oxide thin film. The thin metal oxide thin film is continuously arranged in a curved shape with a narrow width.

In the present invention, 1) by arranging a plurality of second negative electrodes in a contact state in the width direction of the conductive metal oxide film in the front section or rear section or the front section and the rear section of the first negative electrode, it is not necessary to place a plurality of second negative electrodes on the substrate. Effectively removes only the conductive metal oxide film leaving scratches or stress deformation.

2) By continuously disposing the positive electrode and the first negative electrode in a zigzag shape narrower than the width of the conductive metal oxide film or wider than the conductive metal oxide film in the width direction of the conductive metal oxide film The narrow curved shape can effectively remove the conductive metal oxide thin film formed on the surface of the substrate to such an extent that no film remains even at the edge of the substrate.

In addition, since no chemical reagents such as strong acids or bases are used, environmental pollution can also be reduced, and resources such as rare metals such as base materials can be recycled, which contributes to cost reduction.

A brief description of the drawings

Fig. 1(a) is a diagram explaining the basic principle of the present invention, and Fig. 1(b) is a diagram explaining a problem.

Fig. 2 is a schematic diagram illustrating Example 1 of the present invention, (a) is a side view, and (b) is a plan view.

Fig. 3 is a graph showing the relationship between the moving speed and the electrolytic reduction current in Example 1 of the present invention.

FIG. 4 is a diagram illustrating a reduction state when the electrolytic reduction current is too large with respect to the moving speed.

Fig. 5 is a schematic plan view illustrating Example 2 of the present invention.

FIG. 6 is a diagram illustrating a case where the final end portion of the conductive metal oxide thin film can be restored in Example 2 of the present invention shown in FIG. 5 .

Fig. 7 is a schematic plan view illustrating Example 3 of the present invention.

FIG. 8 is a diagram illustrating the case where the final terminal portion of the conductive metal oxide thin film can be restored in Example 3 of the present invention shown in FIG. 7 .

Fig. 9 is a schematic side view illustrating Example 4 of the present invention.

Fig. 10 is a diagram showing an example of a recovery device after performing an electrolytic reduction treatment on a conductive metal oxide thin film according to the present invention.

FIG. 11 is a diagram illustrating a method of removing a metal thin film by mechanical rubbing.

FIG. 12 is a diagram illustrating a method of removing a metal thin film by chemical etching.

Reference numerals: 11 substrate, 12 conductive metal oxide film, 12a conductive metal, 13 positive electrode, 14 first negative electrode, 15 electrolyte, 16 power supply, 17 second negative electrode.

The best way to practice the invention

In the present invention, after the adhesive force is weakened by non-contact electrolytic elution, when the conductive metal formed on the substrate is removed, between the positive electrode and the first negative electrode, in the width direction of the conductive metal oxide film By arranging a plurality of second negative electrodes in a contact state, it is possible to effectively remove the conductive metal oxide thin film of the substrate without leaving any film at the end of the substrate.

Example

Hereinafter, after explaining the basic principle of the present invention with reference to FIG. 1 , the best mode and various forms for carrying out the present invention will be described in detail with reference to FIGS. 2 to 10 .

The present invention is a processing method that leaves as few flaws or stress deformation as possible on the substrate, and is a method of removing a conductive metal oxide thin film that does not use strong acid or alkali.

That is, in the present invention, as shown in FIG. 1(a), above the base material 11, such as an insulator or a conductor, on which a conductive metal oxide thin film 12 is formed on the surface, for example, non-contact state is arranged side by side. A wide positive electrode 13 and a negative electrode (hereinafter referred to as the first negative electrode) 14 of the active metal oxide thin film 12 .

Then, for example, the positive electrode 13 and the first negative electrode 14 are immersed in the electrolytic solution 15 disposed in the electrolytic solution tank, and a DC voltage or a pulse voltage is applied from the power supply 16 to move the substrate 11, so that the conductive metal oxide The thin film 12 passes the positive electrode 13 after passing the first negative electrode 14 .

In this way, a closed circuit of power supply 16 (+)-positive electrode 13-electrolyte 15-conductive metal oxide film 12-electrolyte 15-the first negative electrode 14-power supply 16 (-) is formed, from the vicinity of positive electrode 13 The surface of the conductive metal oxide thin film 12 generates fine bubbles of H ₂ .

At this time, H ₂ generated on the surface of the conductive metal oxide thin film 12 near the positive electrode 13 serves as a reducing agent to remove O ₂ in the conductive metal oxide thin film 12 . In addition, since this H ₂ is generated at the interface of the conductive metal oxide thin film 12, this reaction is an effective reduction reaction.

The conductive metal oxide thin film 12 without bonding by O ₂ becomes only a metal element, and exists on the surface of the substrate 11 in a state where bonding force is weakened. The conductive metal 12a weakened in bonding with the base material 11 can be reliably removed from the base material 11 by rubbing with weak stress, for example, using a soft object such as a rotating foam.

However, as shown in FIG. 1(a), if the positive electrode 13 and the first negative electrode 14 are in a non-contact state with the conductive metal oxide film 12, there will be The electrolytic solution 15 between the conductive metal oxide thin films 12 becomes a resistance, and the conductive metal oxide thin films 12 cannot be removed effectively. Conversely, if the positive electrode 13 and the first negative electrode 14 are in contact with the conductive metal oxide film 12, a large number of bubbles (hydrogen and oxygen) will adhere to the two electrodes 13, 14, and the current density of the electrodes 13, 14 will decrease. As a result, the removal effect of the conductive metal oxide thin film 12 is reduced and cannot be completely removed.

In addition, in the electrode configuration of Fig. 1 (a), if the first negative electrode passes through the terminal end of the conductive metal oxide film 12, the interval between the conductive metal oxide film 12 and the first negative electrode 14 will expand, so the flow The amount of current passing through the conductive metal oxide thin film 12 drops sharply, and the current necessary for reduction cannot flow.

That is, in the electrode configuration of FIG. 1( a), the rear end portion of the conductive metal oxide thin film 12 is shown in FIG. 1( b), and only the space X between the positive electrode 13 and the first negative electrode 14 is not reduced. . In addition, in the electrode arrangement of FIG. 1( a ), due to the resistance of the electrolytic solution 15 between the first negative electrode 14 and the conductive metal oxide thin film 12 , the voltage at which the current necessary for reduction flows increases.

Therefore, in the present invention, for example, between the positive electrode 13 and the first negative electrode 14 immersed in the electrolytic solution 15 in the electrolytic solution tank, as shown in FIG. In this state, a plurality of second negative electrodes 17 are arranged. 18 in FIG. 2 is a pressing mechanism such as a spring that presses the second negative electrode 17 and the conductive metal oxide film 12 .

In the present invention, the interval L between the second negative electrodes 17 is greater than or equal to the interval X (mm) between the positive electrode 13 and the first negative electrode 14, preferably the interval between the positive electrode 13 and the first negative electrode 14 10 times or less of X (mm) (see Fig. 2(b)).

If the interval L between the second negative electrodes 17 is smaller than the interval X (mm) between the positive electrode 13 and the first negative electrode 14, the current density of the electrode will be reduced due to a large amount of bubbles (hydrogen) attached to the second negative electrode 14. decrease (incomplete (non-uniform) removal of the conductive metal oxide thin film 12 occurs). Conversely, if it exceeds 10 times the distance X (mm) between the positive electrode 13 and the first negative electrode 14, both the efficiency of reducing current and the effect of the additional contact electrode will decrease.

In the present invention, the current value I (A) necessary for reduction is preferably the relative movement speed (cm/min) of the positive electrode 13, the first negative electrode 14, the second negative electrode 17 and the substrate 11 and the electrode of the positive electrode 13. The multiplied value of the width Y (cm) is not less than 0.003 times and not more than 0.01 times (see FIG. 3 ).

This is because, if it is less than 0.003 times, the reduction will be insufficient, and only the surface portion of the conductive metal oxide thin film 12 can be reduced and removed.

If it exceeds 0.01 times, the conductive metal oxide thin film 12 is excessively reduced, and the conductive metal oxide thin film 12 is peeled off from the substrate 11 while reducing, and the interval between the positive electrode 13 and the conductive metal oxide thin film 12 expands. The current flowing through the conductive metal oxide thin film 12 drops sharply, making it difficult to flow the current required for reduction.

If the positive electrode 13 passes through the peeled part, it can be reduced again, and after this happens repeatedly, as shown in FIG. 4 , a narrow unreduced part remains.

According to the present invention having such a structure, by using the second negative electrode 17 provided in the front stage or the rear stage or the front stage and the rear stage of the first negative electrode 14, the first negative electrode 14 and the conductive metal oxide thin film 12 are present. The resistance of the electrolyte solution 15 disappears, the removal efficiency of the conductive metal oxide film 12 can be improved, and the current required for reduction can be reduced at the same time. In addition, by arranging a plurality of second negative electrodes 17 at intervals L, it is possible to reduce a drop in current density of the electrodes due to a large number of air bubbles adhering to the electrodes 13 , 14 , and 17 .

Instead of the present invention shown in FIG. 2, the configuration shown in FIG. 5 may also be used.

In the example shown in FIG. 5, the positive electrode 13 and the first negative electrode 14 shown in FIG. jagged.

By arranging the positive electrode 13 and the first negative electrode 14 in a zigzag shape, as shown in FIG. , can be reduced to the final end of the conductive metal oxide thin film 12 .

In addition, instead of the example shown in FIG. 5, the example shown in FIG. 7 is used. As shown in FIG. The wide and narrow curved shape of the metal oxide thin film 12 can undergo electrolytic reduction at the hatched portion in FIG. 8 to obtain the same effect.

In addition, as shown in FIG. 9, the second negative electrode 17 may be arranged in a state of being in contact with the terminal end of the conductive metal oxide film 12, for example, on the substrate 11 (conductive metal oxide film 12). When moving, the second negative electrode 17 can be moved synchronously with the substrate 11 to maintain the relative positional relationship with the final end of the conductive metal oxide thin film 12 .

In the present invention described above, since the electroconductive metal oxide thin film 12 is micronized (0.1 μm or less) as a metal solid after the electrolytic reduction treatment, the reduced metal can be peeled off by the water jet 20 as shown in FIG. 10 . FIG. 10 shows an example in which mechanical peeling of the flexible material 21 is used in combination as an auxiliary means.

Then, the electrolytic solution is stored together with the removed reduced metal in the recovery tank 23 by the electrolytic solution collecting pan 22 , and the micro air bubbles are mixed by the micro air bubble generator 24 . Thereby, since fine air bubbles are formed as nuclei, metal fine particles are formed into agglomerates, which can be collected by the filter, and thus the reduced metal is recovered by the filter 25 . 26 in Fig. 10 denotes a pump.

As described above, the present invention is not a commonly practiced electrolytic elution removal reaction in which a positive voltage is applied to a workpiece, but a processing method characterized by applying a negative voltage to the workpiece.

The electrolysis reaction here requires little current since it generates _H2 in an extremely small area at the interface of the conductive metal oxide film.

Thereby, used electrolytic solution 15 can be commonly used neutral saline solution, tap water, river course water or the electrolytic solution mixed with neutral saline solution in tap water or river course water etc., between base material 11 and positive electrode 13, negative electrode 14 When they are not in contact, as described above, the resistivity is preferably adjusted to 10 ² Ω·cm to 10 ⁶ Ω·cm, more preferably 10 ³ Ω·cm to 10 ⁴ Ω·cm.

This is because, in the present invention, when the positive electrode 13 and the first negative electrode 14 are not in contact with the base material 11, the electrolytic solution 15 with high conductivity having a resistivity of less than 10 ² Ω·cm is applied to both electrodes 13, The voltage between 14 does not pass through the conductive metal oxide thin film 12, but is in a conductive state through the electrolyte solution 15 between the two electrodes 13, 14, so the removal efficiency of the conductive metal oxide thin film 12 decreases. In addition, if the resistivity exceeds 10 ⁶ Ω·cm, a high voltage must be applied, which is not conducive to cost control.

In this way, since the present invention is applicable to the electrolytic solution 15 with relatively high resistivity, tap water or river water, etc., which were previously unsuitable as the electrolytic solution 15 can be used, which is ideal in terms of cost and safety.

Incidentally, tap water was used as the electrolytic solution, and a 100 mm×100 mm workpiece having ITO having a film thickness of 1500×10 ⁻¹⁰ m formed on a glass substrate was immersed in the aforementioned electrolytic solution as shown in FIG. 2 .

In the same electrolytic solution, the positive electrode made of Cu, the first negative electrode, and the second negative electrode (both the width of the positive electrode and the first negative electrode are 120 mm, and the distance X between the two electrodes are 10 mm. In addition, the second negative electrode Extremely 2).

A DC voltage (current: 6 A) of 150 V was applied between the positive electrode, the first negative electrode, and the second negative electrode, and the material to be processed was moved at 1 m/min. After the first negative electrode passed the conductive metal oxide thin film, the movement was stopped for 60 seconds to reduce the final end of the conductive metal oxide thin film.

After implementing the above-mentioned present invention, ITO is removed up to the final end of the conductive metal oxide thin film, and recycling of the glass substrate can be realized.

In addition, the positive electrode and the first negative electrode of the above-mentioned experimental example were divided into 12 parts in the width direction of the workpiece and arranged in a zigzag shape, and one second negative electrode was provided for each first negative electrode obtained by dividing. Except for all the conditions, the experiment was carried out in the same manner as in the above-mentioned experimental example. As a result, ITO is removed up to the final end of the conductive metal oxide thin film, and the glass substrate can be recycled.

The ITO removed by the above experimental example was collected by the recovery device described in Fig. 10 (the mesh of the filter: 1 μm, the capacity of the recovery tank: 50 liters, the amount of fine air bubbles generated: 2 liters/minute, the discharge amount to the filter: 10 liters /min) after recovery, In and Sn can be recovered as metal solids. In addition, 1 minute after the mixing of fine air bubbles, discharge to the filter was started.

Component analysis of the recovered metals with an X-ray microanalyzer confirmed that In and Sn, which are components of ITO, were detected at a ratio of In:Sn=9:1, and ITO could be recovered at this component ratio.

The present invention is not limited to the examples described above. For example, an example in which an electrolyte solution is supplied to a necessary part of a base material or an electrode can be used instead of an example in which the base material or an electrode is immersed in an electrolyte solution. The technical idea described in each claim Of course, the embodiment can be appropriately changed within the scope of the invention. In addition, the recovery of the reduced metal mixed in the electrolytic solution is not limited to the method shown in FIG. 10 .

Claims (7)

1. The removal method of conductive metal oxide thin film, it is characterized in that positive electrode and the first negative electrode are opposite to the conductive metal oxide thin film formed on the substrate surface and arranged side by side in a non-contact state, and at the same time The front section or the back section or the front section and the back section of the first negative electrode, a plurality of second negative electrodes are arranged in a contact state in the width direction of the conductive metal oxide film, and then, on these positive electrodes, the first Negative electrode, the 2nd negative electrode and the state that electrolytic solution exists between described electroconductive metal oxide thin film, apply voltage to described positive electrode, 1st negative electrode, 2nd negative electrode, make the electroconductivity formed on the base material surface The metal oxide film moves relative to the positive electrode, the first negative electrode, and the second negative electrode, so that the conductive metal oxide film passes through the positive electrode after passing through the first negative electrode and the second negative electrode, thereby utilizing reduction The reaction removes the conductive metal oxide film on the surface of the substrate. 2. The method for removing a conductive metal oxide film according to claim 1, wherein the interval between the plurality of disposed second negative electrodes is greater than the interval between the positive electrode and the first negative electrode. , and less than or equal to 10 times the distance between the positive electrode and the first negative electrode. 3. The removal method of the conductive metal oxide surface as claimed in claim 1 or 2, wherein the positive electrode and the first negative electrode are positive electrodes narrower than the width of the conductive metal oxide film. and the first negative electrode are arranged as zigzag electrodes. 4. The method for removing the surface of a conductive metal oxide according to claim 1 or 2, wherein the electrolytic solution is an electrolytic solution having a resistivity of 10 ² Ω·cm to 10 ⁶ Ω·cm. 5 . The method for removing the surface of a conductive metal oxide according to claim 3 , wherein the electrolytic solution is an electrolytic solution having a resistivity of 10 ² Ω·cm to 10 ⁶ Ω·cm. 6. The removal device of conductive metal oxide thin film, it is the device that implements the removal method of conductive metal oxide thin film described in claim 1, it is characterized in that, possesses: The positive electrode and the first negative electrode that are arranged side by side in a non-contact state opposite to the object film; in the front section or back section or front section and back section of the first negative electrode, the conductive metal oxide film is opposite and A plurality of second negative electrodes are arranged in a contact state in the width direction of the conductive metal oxide film; an electrolyte solution is supplied to the positive electrode, the first negative electrode, the second negative electrode and the conductive electrode formed on the surface of the substrate. The mechanism between the active metal oxide films, or the electrolyte tank that stores the electrolyte solution in which the positive electrode, the first negative electrode, the second negative electrode and the substrate are immersed in the electrolyte solution; for the positive electrode and the A power source for applying a voltage to the first negative electrode and the second negative electrode; The metal oxide thin film passes through the movement mechanism of the positive electrode after passing through the first negative electrode and the second negative electrode. 7. The removing device of conductive metal oxide thin film as claimed in claim 6, is characterized in that, described positive electrode and the first negative electrode are the positive electrode and the first negative electrode that will be narrower than the width of conductive metal oxide thin film. One negative electrode is continuously arranged in a zigzag shape, or a positive electrode narrower than the width of the conductive metal oxide film and a first negative electrode are continuously arranged in a meander shape.

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