JPH10296198A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive, easy and harmless method for cleaning a substrate by which an object to be cleaned is hardly damaged. SOLUTION: An aq. electrolytic soln. 3 filled in an electrolytic cell 1 is separated into a cathode cell 1A and an anode cell 1B by an ion separation membrane 2 consisting of a porous neutral membrane through which water an flow freely. Then in batch operation, the interval between the ion separation membrane and the electrodes is set to a cathode 6A especially between the electrodes in use so as to be widened as it goes to the upper part and in continuous operation, an appropriate through-hole is provided especially in the cathode 6A. Consequently, the electrolytic soln. between the electrode plate and the separation membrane is not saturated, hydrogen gas and ion are efficiently generated in the cathode water and are brought into contact with an object surface to be cleaned and thereby, the contaminant depositing on the object surface to be cleaned is removed without damaging the object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method with less damage to an object to be cleaned, and more particularly to a semiconductor substrate itself such as a silicon wafer or a non-alkali glass alone, or a metal substrate or a metal oxide on the substrate. The present invention relates to a cleaning method suitable for cleaning a substrate on which a wiring structure is formed.

[0002]

2. Description of the Related Art For cleaning a substrate having a single-layer or multi-layer wiring structure using a metal, a metal oxide or the like formed on the surface,
A chemical that does not corrode the exposed material is used. However, since the substrate on which the line structure is formed requires extremely high precision as a product, it strongly acts on the substrate surface material to completely remove the contaminants adhering thereto. It is common to use a powerful chemical as a substrate cleaning liquid.

Typical examples of such a substrate cleaning liquid include a mixture of ammonia, hydrochloric acid, sulfuric acid and hydrogen peroxide, or a solution such as hydrofluoric acid. When the material which is easily corroded is exposed, it is difficult to selectively remove only the contaminants on the surface without corroding aluminum or the like, and often damages the material on the substrate surface. . Also, when forming a multilayer wiring layer on a substrate, it is necessary to use a different chemical for each process according to the difference in the material exposed on the surface in each process so that each material is not corroded. Therefore, the cleaning efficiency and the yield are deteriorated.

On the other hand, when a substrate made of a material having relatively high chemical resistance, such as glass, is washed using a mixed solution of sulfuric acid and an aqueous solution of hydrogen peroxide, corrosion problems do not occur. , B, Mg, Al, Ca, Zn, Ba, etc., a phenomenon (leaching phenomenon) may occur, and the characteristics of the substrate may be impaired.

[0005] In any case, however, in the case of a cleaning solution using a deleterious agent which has been conventionally used, a great deal of cost and labor are required for post-processing of the used cleaning solution. In addition, when cleaning is performed using these cleaning liquids, a protruding substance called a peak is generated on the substrate,
There is a need for a method for reducing this.

[0006]

As described above,
When cleaning is performed using a conventional substrate cleaning liquid, it is difficult to perform sufficient cleaning without causing a problem of corrosion of the substrate or the wiring structure. Therefore, if a cleaning method that does not damage the substrate and its wiring structure can be provided while securing the original action of the cleaning liquid for completely removing contaminants from the substrate, its significance is extremely significant.

That is, if a useful cleaning method that does not cause a problem of corrosion on the substrate and its wiring structure can be provided, it is possible to provide a single-layer or multi-layer cleaning method without disadvantage such as breakage of the substrate or the wiring structure. Be able to wash. In particular, for a substrate with a multilayer wiring structure on which a thin film made of a material susceptible to chemicals such as metals and metal oxides is formed, there is no need to worry about damage to the substrate, and the cleaning solution used must be applied to each layer. Since it is not necessary to change to another, the yield can be significantly increased.

[0008] The present invention has been made in view of the above problems, and an object of the present invention is to provide a cleaning method that causes less damage to a cleaning object, particularly a material that is easily corroded by a chemical such as a metal or a metal oxide. It is an object of the present invention to provide a cleaning method suitable for cleaning a substrate having a thin film formed thereon. More specifically, a cleaning method suitable for cleaning at least a semiconductor substrate itself such as a silicon wafer alone or an alkali-free glass alone, or a substrate on which a wiring structure made of a metal or a metal oxide or the like is formed. Is to do.

[0009]

In order to achieve the above object, in the present invention, a first tank and a second tank separated from each other by an ion separation membrane composed of a porous neutral membrane are provided.
An electrolysis step of performing electrolysis by using the electrolyte solution contained in the first tank as the cathode side with the electrolyte solution in the first tank and the electrolyte solution in the second tank as the anode side; A cleaning step of removing contaminants present on the surface of the object to be cleaned by bringing the electrolyte solution in the first tank subjected to electrolysis in the decomposition step into contact with the surface of the object to be cleaned. Is provided.

More specifically, the cleaning method according to the present invention comprises, in a batch method, an electrolytic cell containing an electrolyte solution, and a porous liquid separating the electrolytic cell into a first tank and a second tank. An ion separation membrane with a neutral membrane, a cathode inserted into the electrolyte solution in the first tank, and an anode inserted into the electrolyte solution in the second tank, wherein the cathode and / or The interval between the anode and the ion separation membrane is set so as to increase as going upward, while the electrolytic device is being subjected to electrolysis or immediately after being subjected to electrolysis. The method is characterized by including a washing step of removing contaminants present on the surface of the object to be washed with the electrolyte solution in the tank.

The distance from the ion separation membrane is set wider as going upward. Not only the cathode and the anode, but either the cathode or the anode may be set, but at least the cathode is set as such. Is preferred. That is, the present inventors have confirmed that the effect of cleaning the substrate is improved when the cathode is used instead of the anode. Although no firm theory has been established for this phenomenon, in addition to the effect of preventing bubbles from intervening between the electrode and the ion separation membrane to saturate the reaction, hydrogen generated on the cathode is It is considered that the dissolution into the solution may lead to an effect of improving the characteristics of the electrolyte solution as a substrate cleaning solution.

In the continuous type, an electrolytic cell containing an electrolyte solution, a porous neutral membrane ion separation membrane for separating the electrolytic cell into a first tank and a second tank, and the first tank And a cathode inserted into the electrolyte solution in the second tank, wherein the cathode and / or
Alternatively, the electrolyte solution in the first tank is applied to the surface of the object to be cleaned while being subjected to electrolysis or immediately after being subjected to electrolysis in the electrolytic device characterized by having a through hole in the anode. It is characterized by including a cleaning step for removing existing contaminants.

[0013] The cathode and / or the anode may have a through-hole not only for the cathode and the anode but also for either the cathode or the anode.
At least the cathode is preferably set as such. That is, the present inventors have confirmed that the effect of cleaning the substrate is improved when the cathode is used instead of the anode. Although no firm theory has been established for this phenomenon, in addition to the effect of preventing bubbles from intervening between the electrode and the ion separation membrane to saturate the reaction, hydrogen generated on the cathode is It is considered that the dissolution into the solution may lead to an effect of improving the characteristics of the electrolyte solution as a substrate cleaning solution.

In fact, while being subjected to electrolysis in the electrolytic apparatus, hydrogen generated on the cathode dissolves in the electrolytic solution to form an active complex, which increases the cleaning effect of the substrate. It is something that can be fully conceived. Actually, since the cleaning ability of the cathodic electrolyzed water left for a while after being subjected to the electrolysis is reduced, it is considered that an active component having a short life is generated or fine bubbles of hydrogen. By the electrolysis, the electrolyte solution in the first tank becomes alkaline. By bringing the surface of the object to be cleaned into contact with the alkaline electrolytic ionic liquid, the surface can be effectively cleaned.

In addition to such a phenomenon, which has not been known at all, a conventional method not using electrolysis (ie, a method in which hydrogen is dissolved into weak alkaline water by bubbling or pressurizing hydrogen gas, etc.) In (2), water having the same action as the electrolytic ion water according to the present invention cannot be obtained.

According to another aspect of the present invention, there is provided a cleaning method, wherein the electrolyte solution is an aqueous ammonium halide solution. The aqueous ammonium halide solution does not include ions that adversely affect the semiconductor element, such as Na ⁺ ions. Therefore, even when a semiconductor element is formed on the surface of the object to be cleaned, there is an advantage that cleaning can be performed without deteriorating the characteristics of the semiconductor element. In addition,
From the same viewpoint, ammonia water may be adopted as the electrolyte solution. The aqueous ammonium halide solution is preferably an aqueous ammonium chloride solution.

According to another aspect of the present invention, the pH of the electrolyte solution in the first tank is detected, and the pH is adjusted from 8.0 to 1
The electrolyte solution in the first tank, which is in the range of 0.5,
There is provided a cleaning method for performing cleaning by contacting the surface of the object to be cleaned in the cleaning step. When the electrolysis is continued, the pH in the first tank rises to about 10.5. Therefore, for example, washing may be performed with an electrolyte solution having a pH of about 8.0 to 10.5. That is, if an amphoteric metal such as aluminum is used for the wiring structure on the substrate surface, it may be dissolved in a highly alkaline solution,
The pH in the first tank is preferably about 8.0 to 10.5.

According to another aspect of the present invention, there is provided a cleaning method in which a metal or metal oxide thin film is formed on a surface of the alkali-free glass or silicon wafer. Since the alkaline electrolytic ionic liquid is unlikely to corrode metals and metal oxides, it is suitable for cleaning an object to be cleaned having a wiring structure formed of a metal or metal oxide thin film on the surface.

Here, if the above-mentioned electrolysis step is performed by an electrolysis apparatus which is set so that the distance between the electrode and the ion separation membrane is increased as it goes upward, the washing can be performed more effectively. That is, by setting the distance between the electrode and the ion separation membrane to be wider as going upward, bubbles generated on the electrode due to electrolysis are easily separated from the electrode, and the bubbles are separated between the electrode and the ion separation membrane. To prevent the reaction from becoming saturated. In other words, with such a simple configuration, it is possible to prevent bubbles generated on the electrode from being excessively interposed between the electrode and the ion separation membrane, and to smoothly move ions. At the same time, the reaction on the electrode can proceed smoothly.

In particular, as one aspect of the present invention, in the case where washing is performed while electrolysis proceeds, it is important that the movement of ions in the electrolytic solution and the reaction on the electrode proceed without interruption. (Otherwise, it is no different from the case where washing is performed in a state where electrolysis is stopped), but with a simple configuration in which the distance between the electrode and the ion separation membrane is set to be wider as going upward. The intrinsic significance of the aspect in which the washing is performed while the decomposition proceeds can be revealed.

The electrolytic apparatus according to the present invention comprises an electrolytic cell, an electrolytic aqueous solution stored in the electrolytic cell, an electrode inserted in the electrolytic aqueous solution, and a porous material for separating the electrolytic aqueous solution so that the anode side and the cathode are separated from each other. A device for producing electrolytic ionic water by passing a current through the electrode, wherein at least a cathode of the electrode has a through hole.

The electrolytic apparatus according to the present invention comprises an electrolytic cell, an electrolytic aqueous solution stored in the electrolytic cell, an electrode inserted in the electrolytic aqueous solution, and a porous material for separating the electrolytic aqueous solution so that an anode side and a cathode separate the electrolytic solution. A device for producing electrolytic ionic water by passing a current through the electrode, wherein the porous ion separation membrane has a pore size of 0.0
It is a neutral film of 4 μm to 20.0 μm.

Here, when the cathode electrode has no through hole, the generation of gas is small, and the dissolution of hydrogen and the formation of fine bubbles in the electrolytic ion water on the cathode side, which is the center of the present invention, become insufficient. Such electrolytic ionized water cannot be obtained.
On the other hand, if the cathode electrode is formed into a mesh (that is, a state similar to the case where the number of through holes is extremely increased), hydrogen gas bubbles grow too quickly, and the generated hydrogen gas immediately becomes a huge bubble. As a result, the electrolyte ion water escapes from the cathode side electrolytic ion water, so that the electrolytic ion water according to the present invention cannot be obtained. Therefore, the total opening area of all the through holes of the electrode is preferably 15% to 55% of one side area of the electrode plate (FIG. 5). The inner diameter of the through hole is 0.
Preferably it is 1 to 10 mm.

The surface of the electrode is preferably covered with an inert metal such as platinum.

The pore size of the porous ion separation membrane is 0.04
It is preferably in the range from μm to 20.0 μm. The pore size of the porous ion separation membrane is 0.03 μm to 10.0 μm.
More preferably, it is 0.04 μm to 3.0 μm.
It is even more preferable if it is μm. The porous ion separation membrane according to the present invention is a porous neutral membrane, and as its material,
For example, polyvinyl halide or polyvinylidene halide (both are not limited in the number of halogen substitutions, and include not only straight-chain but also branched-chain ones). More specifically, those made of polyvinyl chloride or polyvinylidene chloride using polyester nonwoven fabric or polyethylene screen as aggregate,
Alternatively, a product made of polyvinyl fluoride or a product made of polyvinylidene fluoride can be used. These may be added with titanium oxide or the like.

[0026]

FIG. 1 is a sectional view schematically showing a cleaning apparatus used in a batch type embodiment of the present invention. The interior of the electrolytic cell 1 is separated by an ion separation membrane 2 into a cathode cell 1A and an anode cell 1B. The ion separation membrane 2 is generally formed of a polyester nonwoven fabric. A negative electrode 6A and a positive electrode 6B are inserted into the cathode cell 1A and the anode cell 1B, respectively. The negative electrode 6A is connected to the cathode of the DC power supply 4, and the positive electrode 6B is connected to the anode of the DC power supply 4 via the switch 5.

A solution circulation path 7A having a suction port and a discharge port is provided on the upper and lower sides of the side surface of the cathode vessel 1A, respectively. A pump 9A is attached to the solution circulation path 7A. When the pump 9A is operated, the solution in the cathode chamber 1A is sucked into the solution circulation path 7A from the suction port, and the filter 8A
To remove the particles, and return the particles from the outlet to the inside of the cathode tank 1A. Further, the temperature distribution in the tank can be reduced by sucking the solution from near the liquid surface and returning the solution from the bottom surface. Similarly, the anode tank 1B is also provided with a solution circulation path 7B, a filter 8B, and a pump 9B. The temperature of the liquid in the tank is monitored by the controller 12 via the temperature sensors 11A and 11B, and the temperature controllers 13A and 13B are used as necessary to adjust the cleaning temperature according to the cleaning target.
Thereby, the liquid temperature in the tank is adjusted. The temperature sensor 11A attached to the inner wall surface of the cathode chamber 1A has a pH value of
It is integrated with a sensor, and monitors the pH of the cathode chamber 1A as described later. The cleaning apparatus of FIG. 1 is provided with a pure water supply tank 14, an electrolyte supply tank 15, a mixer 16, and a distributor 17. The pure water supplied from the pure water supply tank 14 is supplied to the electrolyte supply tank. The electrolyte supplied from the mixer 15 is mixed with the electrolyte by the mixer 16 and the distributor 1
7 and, if necessary, an electrolyte solution.
A and the anode tank 1B.

FIG. 2 is a sectional view schematically showing a cleaning apparatus used in the continuous embodiment of the present invention. Electrolyte supply tank 1
5 is supplied with electrolyte by a pump 9C, and simultaneously pure water is supplied from a pure water supply tank 14 by a pump 9D.
The electrolyte solution and pure water are mixed by the mixer 16 and sent to the electrolytic cell 1 via the cathode buffer tank 18A and the anode buffer tank 18B. The electrolytic cell 1 is separated into a cathode cell 1A and an anode cell 1B by an ion separation membrane 2. The ion separation membrane 2 is generally formed of a polyester nonwoven fabric. A negative electrode 6A and a positive electrode 6B are inserted into the cathode cell 1A and the anode cell 1B, respectively. Cathode electrode 6
A is connected to the cathode of the DC power supply, and the positive electrode 6B is connected to the anode of the DC power supply via a switch.

A solution circulation path 7A having a suction port and a discharge port is provided on a side surface of the cathode buffer tank 18A. A pump 9E is attached to the solution circulation path 7A. When the pump 9E is operated, the solution in the cathode buffer tank 18A is sucked from the outlet into the solution circulation path 7A, and the cathode tank 1A is discharged.
After performing electrolysis in A, it comes into contact with the object 21 to be cleaned, and then returns to the cathode buffer tank 18A through the filter 8A. A temperature sensor and a temperature control device may be provided in the inside 18A of the cathode buffer tank. Further, in the cathode buffer tank 18A, the temperature distribution in the tank can be reduced by sucking the solution from near the liquid surface and returning the solution from the bottom surface. At the same time, an overflow drain pipe 19 is provided near the liquid surface in the cathode buffer tank 18A, and is constantly discharged depending on the amount of the electrolyte solution supplied from the electrolyte supply tank 15 and the pure water supply tank 14. Similarly, the anode tank 1B is also provided with a solution circulation path 7B, a filter 8B, and a pump 9F.

A liquid quality sensor 20 is mounted near the cathode-side outlet of the electrolytic cell 1 so as to measure pH, oxidation-reduction potential, etc., and to monitor the liquid quality of the cathode cell 1A as described later. ing.

Next, a method of cleaning an object to be cleaned using the cleaning apparatus shown in FIG. 1 will be described. Cathode cell 1A and anode cell 1
B, an aqueous solution of ammonium chloride (NH ₄ Cl) 3 having a concentration of 200 to 500 ppm is placed in the solution circulation path 7A.
And 7B above the inlet. The pumps 9A and 9B are operated to circulate the NH ₄ Cl aqueous solution 3.

The switch 5 is closed, and the negative electrode 6A and the positive electrode 6 are closed.
A DC voltage is applied between B and a constant current flows between the electrodes to perform electrolysis. The concentration of ammonium chloride is about 500ppm
In the case of the above, an appropriate current value for generating water effective for cleaning is 0.7 to 11.0 A / dm ² (0.007 to 0.11).
0 A / cm ² ).

At this time, the NH 4 ⁺ ions in the anode tank 1B move to the cathode tank 1A through the ion separation membrane 2, and the Cl ⁻ ions in the cathode tank 1A pass through the ion separation membrane 2 to the anode tank 1B. Move to. Also, on the surface of the negative electrode 6A,

[0034]

## STR1 ## Since a reaction represented by 2H ⁺ + 2e ⁻ → H ₂ occurs, the H ⁺ ion concentration decreases. On the surface of the positive electrode 6B,

[0035]

## STR2 ## Since the reaction represented by 4OH ⁻ → O ₂ + 2H ₂ O + 4e ⁻ occurs, the OH ⁻ ion concentration decreases, and accordingly, the H ⁺ ion concentration increases.

Therefore, by electrolyzing the NH ₄ Cl aqueous solution, the solution in the cathode tank 1A becomes alkaline electrolytic ionized water containing NH ₄ ⁺ ions, and the solution in the anode tank 1B becomes acidic electrolytic water containing Cl ⁻ ions. It becomes electrolytic ion water.

As described above, in the case of the batch type, the electrolysis is performed by an electrolytic apparatus in which the distance between the electrodes 6A and 6B and the ion separation membrane 2 is set to be wider as going upward. It can be done effectively. As shown in FIG. 3, the wider the distance from the ion separation membrane 2 as going upward, as shown in FIG. 3, the case of only the cathode 6A (FIG. 2 (A)) and the case of only the anode 6B (FIG. 2 (B)) ,
Alternatively, in the case of both the cathode 6A and the anode 6B (FIG.
Any of (C)) can be adopted. When the electrolysis is performed, bubbles (mainly, hydrogen on the cathode and oxygen on the anode) are generated on the electrodes, which are generated by the electrodes 6A and 6B.
If it is excessively interposed between and the ion separation membrane 2, the reaction will be saturated. The saturation of the reaction appears as an increase in the voltage applied to the electrode. In addition, as a practical problem, bubbles may be clogged in the holes of the ion separation membrane 2 to hinder the movement of ions and stop the reaction. However, by setting the distance between the electrode and the ion separation membrane to be wider as going upward, bubbles generated on the electrode by electrolysis (mainly, hydrogen on the cathode and oxygen on the anode) are separated from the electrode. This makes it possible to prevent the bubble from intervening between the electrode and the ion separation membrane to saturate the reaction. Then, the ions can be smoothly moved, and the reaction on the electrode can proceed smoothly.

Similarly, in the case of the continuous type, as described above, the cleaning can be more effectively performed by using an electrolytic apparatus using electrodes in which the electrodes 6A and 6B are provided with through holes. When the electrolysis is performed, bubbles (mainly, hydrogen on the cathode and oxygen on the anode) are generated on the electrodes, which are excessively interposed between the electrodes 6A and 6B and the ion separation membrane 2. Then, the reaction is saturated. The saturation of the reaction appears as an increase in the voltage applied to the electrode. In addition, as a practical problem, bubbles may be clogged in the holes of the ion separation membrane 2 to hinder the movement of ions and stop the reaction. However, by forming a through hole in the electrode, bubbles generated on the electrode by electrolysis (mainly, hydrogen on the cathode and oxygen on the anode) are generated between the ion separation membrane and the electrode 6A, and between the ion separation membrane and the electrode 6B. It is possible to prevent the reaction from saturating out of the space through the through hole to the back side of the electrode. Then, the ions can be smoothly moved, and the reaction on the electrode can proceed smoothly.

After the pH of the electrolytic ionic water in the cathode chamber 1A becomes 8 or more, the substrate to be cleaned is immersed in the electrolytic ionic water in the cathode chamber 1A for about 3 minutes. The pH of the cathode chamber 1A is monitored by a PH sensor integrated with the temperature sensor 11A. After immersion, the substrate to be cleaned is taken out of the cathode tank 1A, rinsed with pure water and dried. Rinsing with pure water is performed by immersing the substrate to be cleaned in an overflow bath to overflow the pure water, and then opening the bottom surface of the overflow bath to rapidly discharge the pure water. Note that spin cleaning, spray cleaning, or the like may be used.

[0040]

EXAMPLES The ability of the alkali-free glass to remove particles was evaluated by the above method. As the particle counter, an apparatus using laser scattered light was used. Using a continuous single-wafer type washing machine, the total number of particles adhering to a 390 × 490 mm square glass substrate was counted. When the cleaning was performed using electrolytic ionic water, the removal rate was 7%.
It was 3.5%. As a result of washing with an aqueous solution of ammonium chloride, the removal rate was 55.7%, and when further washing was performed with pure water, the removal rate was reduced to 32.0%.
It has been clarified that the cleaning method according to the above-described embodiment can provide a cleaning ability that has not been obtained until now.

FIG. 6 shows the result of observing the surface of the alkali-free glass substrate with an atomic force microscope (AFM). A large number of protrusions are seen on the untreated substrate (FIG. 6-a). The substrate washed with pure water (FIG. 6-b) and the substrate washed with ammonium chloride (FIG. 6-c) show no reduction in protrusions, but the substrate washed with electrolytic ionized water (FIG. 6-d) It was found that the protrusions were clearly reduced, and the result showed that the washing ability of the electrolytic ionized water was high.

FIG. 7 shows the result of observing the surface of a silicon wafer substrate with a scanning electron microscope (SEM) to show the effect of the present invention.
It can be seen that before the cleaning (FIG. 7-A) and after the cleaning (FIG. 7-B), the deposits on the substrate surface (the ones that appear white in FIG. 7-A) can be effectively removed.

The alkaline electrolytic ionized water after electrolysis did not substantially corrode metals, metal oxides and the like. For example, a thickness 54.78 formed on a glass substrate
nm Al film in alkaline electrolytic ion water at 40 ° C.
The film thickness after immersion for 0 minutes was 53 to 84 nm. For this reason, even when various materials are exposed on the substrate surface, the materials can be efficiently cleaned without corroding these materials.

When the electrolysis was continued, the pH of the electrolytic ionized water in the cathode cell rose to about 9.3 to 9.5. Therefore, for example, you may wash with electrolytic ion water whose pH is about 8.0-9.5. Although the case where ammonium chloride is used as the electrolyte has been described, other electrolytes may be used. For example, an ammonium halide such as ammonium fluoride may be used. However, when a semiconductor element such as a transistor is formed on a substrate to be cleaned, N
It is preferable to use an electrolyte that does not contain ions that adversely affect the electrical characteristics of the semiconductor element, such as a ⁺ and K ⁺ ions.

In the above embodiment, the case where the substrate to be cleaned is immersed in the electrolytic ionic water in the cathode layer in a state where the electric current is passed through the electrolyte solution has been described. May be immersed. However, from various experimental results, it is considered that a slightly higher cleaning effect can be obtained by flowing a current even during immersion of the substrate to be cleaned.

In the above embodiment, the case where the substrate to be cleaned was immersed in the alkaline electrolytic ionized water after the electrolysis was described. However, the surface of the substrate to be cleaned may be contacted with the electrolytic ionized water by another method. For example, the electrolytic ion water in the cathode layer may be sprayed on the substrate surface, or the electrolytic ion water may be dropped on the substrate surface rotating at high speed. Also,
Although the cleaning of the alkali-free glass alone has been specifically described in the above-described embodiment, the cleaning method according to the present invention is not limited to the semiconductor substrate itself such as a silicon wafer alone or an alkali-free glass alone, but also includes a metal Alternatively, not only a substrate having a wiring structure formed of a metal oxide or the like but also other components can be washed under mild conditions.

Next, examples of the concentration of hydroxy ion (OH ⁻ ) in the cathode reduced water according to the present invention will be described.

A 500 ppm aqueous solution of ammonium chloride was electrolyzed for 15 minutes at a constant current of 3 amps using the apparatus shown in FIG.
5. Cathode-reduced water having an oxidation-reduction potential of -700 mV or less was obtained. Then, the hydroxy ion (OH
^- ) The concentration was determined by the weak base titration method. The results are shown below.

[0049]

[Table 1] OH in negative electrode water of electrolytically treated ammonium chloride solution
^- Concentration

Before the titration, the pH of the cathodic reduced water was 9.5, and its hydroxy ion concentration [OH ⁻ ] (mol
/ L) is the ionic product of water shown below (Kw = 1)
0 ^-14 , 22 ° C).

[0051]

(Equation 1) Here, under the conditions of this experiment, since the activity count f can be set to 1, the hydroxy ion concentration [OH ⁻ ] (mol / l)
Is calculated as follows.

[0052]

(Equation 2) The hydroxy ion concentration calculated in this way differs from that obtained by the weak base titration method on the order of about 100 times.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0054]

As described above, according to the present invention,
The following effects can be obtained.

In the structure of the conventional electrolytic cell, most of the hydrogen ions that have moved to the cathode side have been released into the atmosphere as hydrogen gas. It has become possible to efficiently obtain electrolytic ionized water in which hydrogen gas is dissolved.

The water containing a large amount of hydrogen obtained by the method according to the present invention has a washing effect that cannot be obtained by other methods, for example, hydrogen-containing water obtained by bubbling or the like. It has become possible to obtain special electrolytic ionic water which is considered to be in an active state of hydrogen.

Thus, the object to be cleaned can be effectively cleaned without corroding metals, metal oxides and the like. In addition, since most cleaning objects can be cleaned under mild conditions without corroding them, the cleaning efficiency of a substrate having a multilayer wiring structure can be improved. Unlike a conventional cleaning solution for a substrate for a powerful drug such as a mixed solution obtained by adding a hydrogen peroxide solution to sulfuric acid or hydrofluoric acid, post-processing of a used cleaning solution is easy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a batch type cleaning apparatus according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a continuous cleaning apparatus according to the present invention.

FIG. 3 is a sectional view schematically showing a cleaning apparatus according to the present invention.

FIG. 4 is a conceptual diagram schematically showing an electrode according to the present invention.

FIG. 5 is a diagram showing an example of a batch-type electrolytic cell for producing cathode-reduced water according to the present invention.

FIG. 6 shows an atomic force microscope (A) for showing the effect of the present invention.
FM) is a photograph.

FIG. 7 is a scanning electron microscope (SEM) photograph showing the effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolysis tank 1A Cathode tank 1B Anode tank 2 Ion separation membrane 3 Electrolyte aqueous solution 4 DC power supply 5 Switch 6A Negative electrode 6B Positive electrode 7A, 7B Solution circulation path 8A, 8B Filter 9A, 9B, 9C, 9D, 9E, 9F Pump 11A , 11B Temperature sensor 12 Controller 13A, 13B Temperature controller 14 Pure water supply tank 15 Electrolyte supply tank 16 Mixer 17 Distributor 18A Cathode water buffer tank 18B Anode water buffer tank 19 Overflow drain pipe 20 Liquid quality sensor 21 Cleaning object 22 Electrode Plate 23 Through hole

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C25F 7/00 C25F 7/00 K H01L 21/304 341 H01L 21/304 341T

Claims (18)

[Claims] 1. An electrolyte solution contained in a first tank and a second tank separated from each other by a porous ion separation membrane, and the electrolyte solution in the first tank is placed on the cathode side. An electrolysis step of performing electrolysis using the electrolyte solution in the second tank as the anode side, and washing the electrolyte solution in the first tank subjected to electrolysis in the electrolysis step during or immediately after electrolysis. A cleaning step of removing contaminants present on the surface of the object to be cleaned by bringing the surface into contact with the surface of the object. 2. A substrate characterized in that the substrate is cleaned by fine bubbles of OH-ions and secondary ions of active ions or hydrogen contained in electrolytic ionic water generated in the electrolysis step. Cleaning method. 3. An electrolytic apparatus, wherein a distance between the cathode and / or the anode and the ion separation membrane is set to increase as going upward. 4. The electrolytic apparatus according to claim 2, wherein an interval between the cathode and the ion separation membrane is set to increase as going upward. 5. An electrolytic apparatus, wherein a through hole is formed in the electrode plate of the cathode and / or the anode. 6. An electrolytic apparatus, wherein a through hole is formed in the electrode plate of the cathode. 7. The electrolytic apparatus according to claim 4, wherein the inner diameter of the through hole of the electrode is 0.1 mm to 10 mm. 8. The porous ion separation membrane may be made of polyvinyl halide or polyvinylidene halide (in any case, the number of halogen substitution does not matter. In addition, not only linear but also branched ones are included). The electrolytic device according to any one of claims 1 to 7, comprising: 9. The method according to claim 1, wherein the porous ion separation membrane is made of any one of polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, and polyvinylidene fluoride. Electrolysis equipment. 10. The electrolytic apparatus according to claim 1, wherein the porous ion separation membrane is a neutral membrane having a pore size of 0.04 μm to 20.0 μm. 11. The electrolytic apparatus according to claim 1, wherein the cathode and the anode are attached while being separated from a bottom surface of the electrolytic cell. 12. The cleaning method according to claim 1, wherein the electrolyte solution is an aqueous solution of ammonium halide. 13. The cleaning method according to claim 1, wherein the electrolyte solution is an ammonium chloride aqueous solution. 14. The cleaning method according to claim 1, wherein the electrolyte solution is aqueous ammonia. 15. The cleaning is performed by contacting the electrolyte solution in the first tank with the surface of the object to be cleaned in the cleaning step while detecting the pH of the electrolyte solution in the first tank. The cleaning method according to any one of 1 to 10. 16. The electrolyte solution in the first tank is detected while detecting the oxidation-reduction potential of the electrolyte solution in the first tank.
The cleaning method according to claim 1, wherein in the cleaning step, cleaning is performed by bringing the cleaning object into contact with the surface of the object to be cleaned. 17. The cleaning method according to claim 1, wherein the object to be cleaned is non-alkali glass or a silicon wafer. 18. The cleaning method according to claim 10, wherein a thin film of a metal or a metal oxide is formed on a surface of the alkali-free glass or the silicon wafer.