JP4412301B2 - Cleaning system - Google Patents

Description

  The present invention relates to a cleaning system for cleaning a material to be cleaned while circulating a heated cleaning liquid, and performing electrolysis while circulating a part of the cleaning liquid to further increase the cleaning effect by the oxidizing power of the electrolytic solution.

  In the VLSI manufacturing process, there is a cleaning process that cleans and removes resist and contaminants adhering to a semiconductor substrate such as a silicon wafer. Conventionally, the cleaning technology has conventionally used resist residues, fine particles, metals, natural oxide films, etc. This is a peeling cleaning process, and a mixed solution (SPM) of concentrated sulfuric acid and hydrogen peroxide or a solution (SOM) in which ozone gas is blown into concentrated sulfuric acid is often used. When hydrogen peroxide or ozone is added to high-concentration sulfuric acid, the sulfuric acid is oxidized to produce persulfuric acid. It is known that persulfuric acid has a high cleaning ability because it generates a strong oxidizing power when self-decomposing, and is useful for cleaning the wafer and the like. As a method for producing persulfuric acid, in addition to the above method, there is also known a method in which an aqueous solution containing sulfate ions is electrolyzed in an electrolytic bath to obtain persulfuric acid-dissolved water and used for washing (Patent Documents 1 and 2) reference).

  By the way, in the SPM described above, it is necessary to replenish the hydrogen peroxide solution in order to recover the oxidizing power due to persulfuric acid when the persulfuric acid generated by the hydrogen peroxide water is self-decomposed and the oxidizing power decreases. When the sulfuric acid concentration falls below a certain concentration, it is exchanged with a new high concentration sulfuric acid. However, in the above method, since the sulfuric acid solution is diluted with water in hydrogen peroxide water, it is difficult to keep the liquid composition constant, and the liquid is discarded and renewed every predetermined time or every processing batch. It is necessary. For this reason, there are problems that the cleaning effect is not constant and a large amount of chemicals must be stored. On the other hand, in the SOM, the liquid is not diluted, and although the liquid renewal cycle can be generally longer than that of the SPM, the cleaning effect is inferior to that of the SPM.

  In addition, in SPM, the amount of persulfuric acid that can be generated by adding high-concentration sulfuric acid that has filled the washing tank once and hydrogen peroxide water several times is small and has a limit. Further, in the SOM method, the generation efficiency of persulfuric acid with respect to the ozone blowing amount is very low. Therefore, in these methods, there is a problem that the concentration of persulfuric acid produced is limited and the cleaning effect is also limited.

In contrast, the inventors of the present application do not simply obtain the production of persulfuric acid by electrolysis, but recycle persulfate ions by repeating washing and electrolytic reaction while circulating this to reduce the amount of sulfuric acid used. We have proposed a greatly reduced cleaning system. The apparatus will be described with reference to FIG. 2. A single wafer cleaning apparatus 10 is provided as a cleaning apparatus for cleaning the semiconductor substrate 100. In this apparatus, a cleaning liquid is sprayed on the semiconductor substrate 100 to be cleaned. The drain side of the single wafer cleaning apparatus 10 is connected to a solution storage tank 20 via a return pipe 15, and a liquid supply pipe 25 is connected to the solution storage tank 20. The liquid feeding pipe 25 is provided with a liquid feeding pump 26 and a cooler 27 for cooling the liquid to be fed, and the front end side of the liquid feeding pipe 25 is connected to the electrolytic reaction device 30. . The electrolytic reaction device 30 is configured such that the cleaning liquid is electrolyzed while being passed, and the electrolytic cleaning liquid is configured to be supplied to the single-wafer type cleaning device 10 through the liquid feeding pipe 35. Immediately before the single wafer cleaning apparatus 10, a heating device 36 for heating the cleaning liquid supplied through the liquid feeding pipe 35 is provided.

The operation of the cleaning system will be described. Sulfuric acid is accommodated in the solution storage tank 20, and this is sequentially sent to the electrolytic reaction apparatus 30 by the liquid feed pump 26. At this time, the cooler 27 cools to a temperature suitable for the electrolytic reaction (for example, 40 ° C.). In the electrolytic reaction apparatus 30, the sulfate ions in the solution undergo an oxidation reaction to generate persulfate ions, thereby obtaining a persulfate solution. This persulfuric acid solution is sent to the single wafer cleaning device 10 through the liquid feeding pipe 35, and at that time, heated to a temperature suitable for cleaning (for example, 130 ° C.) by the heating device 36, and then sprayed onto the semiconductor substrate 100. Then, a cleaning process is performed. The drainage liquid is sequentially sent to the solution storage tank 20 through the return pipe 15, and further sent to the electrolytic reaction apparatus 30 through the liquid feeding pipe 25 as described above, and the electrolysis and cleaning are repeated.
JP 2001-192874 A Special table 2003-511555 gazette

  In the above cleaning system, the semiconductor substrate can be effectively cleaned while recycling sulfuric acid by repeating cleaning with a cleaning liquid and electrolysis as described above. However, in order to perform effective cleaning in the cleaning apparatus, it is necessary to heat the cleaning liquid to a high temperature and use it for cleaning. On the other hand, in the electrolytic reaction apparatus, if the electrolytic solution is at a high temperature, it is difficult to perform an efficient electrolytic reaction, and thus it is necessary to cool the cleaning liquid used in the cleaning apparatus. Since the temperature of the electrolytic solution used for electrolysis has decreased, it is necessary to heat it again to a high temperature during cleaning. That is, when cleaning and electrolysis are alternately repeated by circulating the cleaning liquid, it is necessary to heat and cool the cleaning liquid each time. For this reason, especially the energy for heating to high temperature becomes enormous, and it is one factor which raises the running cost of the whole system.

  The present invention has been made against the background of the above circumstances, and an object thereof is to provide a cleaning system capable of reducing the operating cost by reducing the energy required for heating the cleaning liquid.

Among the cleaning systems of the present invention, the invention according to claim 1 is 100 ° C. or more and less than 200 ° C. with a cleaning unit composed of a single wafer cleaning device that sprays a cleaning liquid on the material to be cleaned to clean the material to be cleaned. A cleaning liquid line for circulating a heated concentrated sulfuric acid cleaning liquid, and an electrolytic solution line for circulating the electrolytic solution through an electrolytic reaction device that performs electrolysis while passing the electrolytic solution. The electrolytic solution line is divided on the downstream side of the cleaning unit, and the upstream side of the cleaning unit , and at least upstream of the upstream and downstream sides of the cleaning unit, the electrolytic reaction between the cleaning solution line and the electrolytic solution line A mixing common line is provided on the downstream side of the apparatus, and a solution storage tank is provided at a diversion end of the mixing common line.

That is, according to the present invention, the heated cleaning liquid circulates in the cleaning liquid line, the electrolytic solution circulates in the electrolytic solution line, and electrolysis is performed at least on the upstream side and the downstream side of the cleaning unit. Since the liquid and the cleaning liquid are temporarily mixed and then separated, the amount of liquid to be heated and cooled is reduced, and thus the amount of energy for heating and cooling is reduced and the operating energy is reduced. From the viewpoint of not reducing the temperature of the cleaning solution, it is desirable to mix with the electrolytic solution on the downstream side of the cleaning unit. Further, the cleaning effect at the cleaning section is improved by the suitable heating temperature of the cleaning liquid. Below this temperature range, the peel cleaning effect is reduced. On the other hand, if the temperature exceeds 200 ° C., the cleaning liquid evaporates and stable cleaning becomes difficult, so the appropriate temperature of the cleaning liquid is set to the above range. Furthermore, the liquid flow rate flowing through the cleaning liquid line and the electrolytic solution line through the mixing common line can be easily adjusted by the solution storage tank, and can be smoothly divided. In addition, ions with strong oxidizing power contained in the electrolyte can act on contaminants in the cleaning solution with higher contact efficiency, and further clean up the cleaning solution by further decomposing the contaminants to maintain a high degree of cleaning. It becomes possible.

In the cleaning liquid line, the upstream side and the downstream side are expressed based on the flow of the cleaning liquid with reference to the cleaning part. For convenience, the cleaning liquid line extends from the cleaning part to the end of the mixing common line. The portion from the separation end to the cleaning portion is the upstream side of the cleaning portion.
Also, in the electrolyte line, the upstream side and downstream side are expressed based on the flow of the cleaning liquid with reference to the electrolytic reaction apparatus, and for the sake of convenience, the electrolytic reaction is performed from the electrolytic reaction apparatus to the diversion end of the mixing common line. The downstream side of the apparatus is the upstream side of the electrolytic reaction apparatus from the separation end to the electrolytic reaction apparatus.

The invention of the cleaning system according to claim 2 is the invention according to claim 1, wherein the electrolyte line is branched from the downstream side of the electrolytic reactor , and is upstream of the cleaning unit and downstream of the cleaning unit. And the upstream side of the solution storage tank joins the cleaning liquid line.

  According to the second aspect of the present invention, the electrolytic solution and the cleaning liquid are mixed upstream and downstream of the cleaning unit. By adjusting the flow rate ratio, it is possible to adjust the degree of influence of the cleaning liquid temperature and the degree of influence on the operating energy in the cleaning unit. In addition, by mixing the electrolytic solution upstream of the cleaning unit, it is possible to obtain the oxidizability of the electrolytic solution and enhance the cleaning effect in the cleaning unit. At this time, the electrolytic solution may be heated and supplied to the cleaning unit. Also in this case, since heating may be performed for a part of the electrolytic solution, the energy required for heating is relatively small. Moreover, you may make it mix electrolyte solution in the upstream of the heating apparatus which heats cleaning liquid. In view of the adverse effect on the cleaning liquid temperature, it is desirable to mix many flow rates downstream of the cleaning section. Further, the mixing of the electrolytic solution may not be performed constantly but intermittently.

  The invention of the cleaning system according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the cleaning liquid is concentrated sulfuric acid having a sulfuric acid concentration of 8M or more and less than 18M.

  When sulfuric acid is used as the cleaning liquid, the sulfuric acid concentration greatly affects the production efficiency of persulfate ions in the electrolytic reaction apparatus when it is sent to the electrolytic reaction apparatus as the electrolytic solution. Specifically, the persulfuric acid generation efficiency increases as the sulfuric acid concentration decreases. On the other hand, when the sulfuric acid concentration is lowered, the solubility of an organic compound such as a resist in the cleaning portion is lowered when the solution is sent to the cleaning portion, and it is difficult to peel off the material to be cleaned. From these viewpoints, the sulfuric acid concentration of the solution used in the system is desirably in the range of, for example, 9M to less than 18M. For the same reason, it is more desirable that the lower limit is 12M and the upper limit is 17M.

  The invention of the cleaning system according to claim 4 is the invention according to any one of claims 1 to 3, wherein a flow rate ratio between the cleaning liquid line and the electrolytic solution line is 2: 1 to 1: 1. Features.

  According to the fourth aspect of the invention, by adjusting the flow rate of the cleaning liquid flowing through the cleaning liquid line and the electrolytic solution line, it is possible to adjust the cleaning effect, the adjustment effect of the electrolytic solution generation, and the energy efficiency reduction effect. When the flow rate ratio of the cleaning liquid exceeds 2, the effect of reducing energy required for heating is reduced. On the other hand, when the flow rate ratio of the cleaning liquid is less than 1, a sufficient cleaning action cannot be obtained. Therefore, the above flow rate ratio is desirable.

  According to a fifth aspect of the present invention, there is provided a cleaning system according to any one of the first to fourth aspects, further comprising heating means for heating the cleaning liquid upstream of the cleaning section.

According to the invention described in claim 5, the cleaning effect can be enhanced by heating the cleaning liquid by the heating means on the upstream side of the cleaning section. Therefore, it is desirable that the heating means be as close as possible to the cleaning section.
Examples of the heating means include a heater, a heater using heat exchange with hot water, steam, and the like, but the present invention is not limited to a specific one.

The invention of the cleaning system according to claim 6 is characterized in that, in the invention according to any one of claims 1 to 5 , at least an anode of the electrodes used in the electrolytic reaction device is a diamond electrode.

According to the sixth aspect of the present invention, high durability is exhibited even in the production of highly oxidizable persulfate ions and the like, and the electrolytic reaction can be effectively performed. The diamond electrode is preferably used for at least the anode, but can also be used for the cathode and the bipolar electrode.

A diamond electrode is made of a semiconductor material such as a silicon wafer or a metal material as a substrate, and after synthesizing a conductive diamond thin film on the surface of the substrate, the substrate is removed by melting or the like, or in a plate shape under the condition that the substrate is not used. A self-standing type conductive polycrystalline diamond that has been deposited and synthesized can be mentioned. In addition, a laminate on a metal substrate such as Nb, W, or Ti can also be used. However, when the current density is increased, there is a problem that the diamond film may be peeled off from the substrate. preferable.
The conductive diamond thin film is a conductive thin film that is doped with a predetermined amount of boron, nitrogen, or the like during synthesis of the diamond thin film, and is generally boron-doped. If the doping amount is too small, the technical significance does not occur. If the doping amount is too large, the doping effect is saturated. Therefore, a doping amount in the range of 50 to 20,000 ppm with respect to the carbon amount of the diamond thin film is suitable. . In the present invention, the conductive diamond electrode is usually a plate-like one, but a network structure having a plate-like shape can also be used. That is, in the present invention, the shape and number of electrodes are not particularly limited. In the electrolytic treatment performed using the conductive diamond electrode, the current density on the surface of the conductive diamond electrode is set to 10 to 100,000 A / m ^2, and a solution containing sulfate ions is parallel to the diamond electrode surface and the liquid passage speed is set. It is desirable to perform contact treatment at 1 to 10,000 m / hr.

A seventh aspect of the present invention is the cleaning system according to any one of the first to sixth aspects, further comprising temperature adjusting means for maintaining the liquid in the mixed common line at 80 to 130 ° C.

  When the electrolytic solution is a persulfuric acid solution, it is particularly desirable to maintain the solution storage tank at 80 to 130 ° C. When the temperature exceeds 130 ° C, the self-decomposition of persulfate ions proceeds early and the oxidizing power cannot be obtained over a long period of time. Absent.

The invention of the cleaning system according to claim 8 is characterized in that, in the invention according to any one of claims 1 to 7 , a cooling means for cooling the electrolyte solution is provided upstream of the electrolytic reaction apparatus.

According to the eighth aspect of the invention, the cleaning liquid can be cooled to an appropriate temperature and supplied to the electrolytic reaction apparatus as an electrolytic solution suitable for the electrolytic reaction. As this suitable temperature, 10-90 degreeC can be shown, for example. Examples of the cooling means include air coolers and water coolers, but the present invention is not limited to specific ones. When the temperature range is exceeded, the electrolysis efficiency decreases and the wear of the electrode also increases. On the other hand, if the temperature is lower than the above temperature, the temperature of the entire cleaning liquid is lowered when mixed with the cleaning liquid, and the heat energy for heating it becomes enormous. For the same reason, it is more desirable to set the lower limit to 40 ° C. and the upper limit to 80 ° C.

The invention of the cleaning system according to claim 9 is the invention according to any one of claims 1 to 8 , wherein the material to be cleaned is a semiconductor substrate.

According to invention of Claim 9 , contaminants, such as a resist on a semiconductor substrate, can be peeled and removed effectively. In particular, by using sulfuric acid as the cleaning liquid and electrolyzing it, the oxidizing power of persulfate ions can be used to effectively clean and remove the contaminants. 2. Description of the Related Art Conventionally, in a semiconductor substrate processing process or the like, prior to a cleaning process, a step of oxidizing and ashing a resist, which is an organic substance, using a dry etching or ashing process is usually incorporated as a pretreatment process. This process has a problem of increasing the apparatus cost and the processing cost. In the system of the present invention, an excellent cleaning effect can be obtained as described above. Therefore, even when a cleaning process is performed without incorporating a pretreatment process such as the above-described dry etching or ashing process, a resist or the like can be sufficiently obtained. A removal effect is obtained. That is, the present invention makes it possible to establish a process in which these pretreatment steps are omitted.

  In the cleaning system of the present invention, cleaning treatment can be performed on various materials to be cleaned. However, as described above, electronic material substrates such as silicon wafers, liquid crystal glass substrates, and photomask substrates are targeted. Therefore, it is suitable for a cleaning process. More specifically, it can be used for a peeling process of an organic compound such as a resist residue attached on a semiconductor substrate. Further, it can be used for a foreign matter removing process such as fine particles and metal adhering to the semiconductor substrate.

As described above, according to the cleaning system of the present invention, the cleaning unit is composed of a single wafer cleaning apparatus that sprays the cleaning liquid onto the material to be cleaned and cleans the material to be cleaned. A cleaning liquid line for circulating a heated concentrated sulfuric acid cleaning liquid, and an electrolytic solution line for circulating the electrolytic solution through an electrolytic reaction device that performs electrolysis while passing the electrolytic solution. The electrolytic solution line is divided on the downstream side of the cleaning unit, and the upstream side of the cleaning unit , and at least upstream of the upstream and downstream sides of the cleaning unit, the electrolytic reaction between the cleaning solution line and the electrolytic solution line Since a mixing common line is provided on the downstream side of the apparatus, and a solution storage tank is provided at a diversion end of the mixing common line, the amount of cleaning liquid that requires heating and the amount of cleaning liquid that requires electrolysis are reduced without impairing the cleaning effect. Each with less there is an effect of reducing the running cost.

Below, one Embodiment of this invention is described based on FIG. In addition, the same code | symbol is attached | subjected about the structure similar to a conventional apparatus.
In this embodiment, a single wafer cleaning device 10 as a cleaning unit, a solution storage tank 20 for storing a cleaning liquid and decomposing a dissolved material, and an electrolytic reaction device 30 are provided.
The downstream side of the single wafer cleaning apparatus 10 and the solution storage tank 20 are connected by a cleaning liquid return pipe 1, and the solution storage tank 20 and the upstream side of the cleaning apparatus 10 are connected by a cleaning liquid feed pipe 2. Yes. A liquid feed pump 3 and a heating device 4 are interposed in the cleaning liquid feed pipe 2.

On the other hand, the solution storage tank 20 and the upstream side of the electrolytic reaction apparatus 30 are connected by an electrolyte solution feeding pipe 6, and the electrolyte solution feeding pipe 6 is provided with a feeding pump 8 and a cooler 9. It is installed. The electrolytic solution feeding pipe 7 is connected to the downstream side of the electrolytic reaction device 30. The electrolytic solution feeding pipe 7 branches into a feeding branch pipe 7a and a feeding branch pipe 7b. Connected to the cleaning liquid return pipe 1, the liquid feeding branch pipe 7 b joins the cleaning liquid feeding pipe 2.
The cleaning liquid return pipe 1 and the cleaning liquid feeding pipe 2 constitute a cleaning liquid line, and the electrolytic solution feeding pipe 6, the electrolytic solution feeding pipes 7, 7 a and 7 b, and the cleaning liquid return pipe 1 constitute the electrolytic solution. A line is configured, and a path (a part of the cleaning liquid feeding pipe 2 and the cleaning liquid return pipe 1) from the joining point of the electrolytic solution feeding pipe 7b and the cleaning liquid feeding pipe 2 to the solution storage tank 20 is the present invention. It functions as a mixed common line.

In addition, the single wafer cleaning apparatus 10 includes a liquid spray nozzle 11, and a tip side ejection portion of the liquid spray nozzle 11 is located in the single wafer cleaning apparatus 10. The cleaning liquid feeding pipe 2 is connected to the liquid spray nozzle 11.
In the single wafer cleaning apparatus 10, a substrate mounting table 12 is disposed in the ejection direction of the liquid spray nozzle 11. A semiconductor substrate 100 is placed on the substrate platform 12. It is desirable that the substrate mounting table 12 or the liquid spray nozzle 11 be relatively movable so that droplets uniformly strike the surface of the semiconductor substrate 100.

  The solution storage tank 20 includes a temperature regulator 21 for adjusting (heating or cooling) the temperature of the stored solution. The structure of the temperature regulator 21 is not specifically limited as this invention, For example, it can comprise by combining a heater, a cooler, etc.

  In the electrolytic reaction apparatus 30, electrolytic reaction tanks 31 and 32 are connected in parallel. In the electrolytic reaction tank 31, an anode 31a and a cathode 31b are arranged, and further, bipolar electrodes 31c... 31c are arranged at a predetermined interval between the anode 31a and the cathode 31b. In the electrolytic reaction tank 31, the solution is configured to pass between the electrodes, and the outlet thereof is connected to the electrolyte solution feeding pipe 7.

  On the other hand, the electrolytic reaction tank 32 has the same configuration as that of the electrolytic reaction tank 31, and an anode 32a and a cathode 32b are arranged. Further, a bipolar electrode is provided with a predetermined interval between the anode 32a and the cathode 32b. 32c... 32c are arranged. The DC power source 33 is connected to the anode 32a and the cathode 32b. Similarly, liquid can be passed between the electrodes, and an electrolyte solution feeding pipe 7 is connected to the outlet side thereof.

A DC power source 33 is connected in series to the anode 31a, the cathode 31b, the anode 32a, and the cathode 32b, thereby enabling DC electrolysis in the electrolytic reaction tanks 31, 32. By connecting the electrolytic reaction tanks 31 and 32 in series to the DC power supply 33, the energization amount in the electrolytic reaction tanks 31 and 32 can be made the same.
In addition, the electrolytic reaction tanks 31 and 32 are connected in parallel to the electrolyte solution feeding pipe 6 and the electrolyte solution feeding pipe 7 so that the electrolytic gas generated on one side flows into the other electrolytic gas. Can be avoided.

  In this embodiment, the electrodes 31a, 31b, 31c, 32a, 32b, 32c are constituted by diamond electrodes. The diamond electrode is manufactured by forming a diamond thin film on a substrate and doping boron in a range of preferably 50 to 20,000 ppm with respect to the carbon content of the diamond thin film. The electrolytic reaction tanks 31 and 32 and the DC power source 33 constitute an electrolytic reaction apparatus.

Next, the operation of the sulfuric acid recycling type single wafer cleaning system configured as described above will be described.
The solution storage tank 20 contains sulfuric acid, which is mixed with ultrapure water to obtain a sulfuric acid solution having a sulfuric acid concentration of less than 8 to 18M. This is fed to the single wafer cleaning device 10 and the electrolytic reaction device 30 through the cleaning liquid feeding pipe 2 and the electrolytic solution feeding pipe 6 by the liquid feeding pumps 3 and 8, respectively. At this time, the sulfuric acid solution is heated to less than 130 to 200 ° C. by the heating device 4 and supplied to the single wafer cleaning device 10. For example, the liquid is supplied to the cleaning device 10 at a flow rate of 8 L / min, and the liquid is supplied to the electrolytic reaction device 30 at a flow rate of 6 L / min.

  In the single wafer cleaning apparatus 10, high-temperature sulfuric acid droplets are ejected from the liquid spray nozzle 11 for a certain period of time. The semiconductor substrate 100 is mounted on the substrate mounting table 12, and the substrate 100 is rotated by the substrate mounting table 12, and the liquid spray nozzle 11 is relatively positioned so that the liquid droplets uniformly hit the surface of the semiconductor substrate 100. The surface of the substrate 100 is cleaned by the sulfuric acid droplets, and the resist and the like are peeled off and removed. The ejected sulfuric acid solution scatters and drops after the substrate 100 is cleaned, and is discharged into the cleaning liquid return pipe 1 together with the dissolved resist. In the cleaning liquid return pipe 1, the sulfuric acid solution moves to the solution storage tank 20. In the solution storage tank 20, the cleaning liquid is maintained at 100 to 130 ° C. by the temperature regulator 21.

On the other hand, the solution fed to the electrolyte feed pipe 6 is cooled to a temperature of 10 to 90 ° C. suitable for the electrolytic reaction by the cooler 9 and supplied to the electrolytic reaction device 30.
In the electrolytic reaction tank 31, when the anode 31a and the cathode 31b are energized by the DC power source 33, the bipolar electrodes 31c ... 31c and the bipolar electrodes 32c ... 32c are polarized, and the anode and cathode appear at predetermined intervals. The solution sent to the electrolytic reaction tanks 31 and 32 is passed between these electrodes. At this time, it is desirable to set the output of the liquid feed pump 8 so that the liquid flow rate is 1 to 10,000 m / hr. In the above energization, it is desirable to energization control such that the current density at the diamond electrode surface is 10~100,000A / ^{m 2.}

  When the solution is energized in the electrolytic reaction tanks 31 and 32, the sulfate ions in the solution undergo an oxidation reaction to generate persulfate ions, thereby obtaining a high concentration persulfate ion-containing solution. The persulfate ion-containing solution having a high concentration in this way is fed through the electrolyte solution feeding pipe 7 and branched to the solution feeding branch pipes 7a and 7b, and the main electrolyte solution has a flow rate of, for example, 4 L / min. Is sent to the cleaning liquid return pipe 1 through the liquid supply branch pipe 7a and mixed with the cleaning liquid after the cleaning. A part of the electrolytic solution is sent from the electrolytic solution feeding pipe 7 to the feeding branch pipe 7b at a flow rate of 2 L / min, for example, and joined to the washing liquid feeding pipe 2 immediately before the cleaning device 10 for cleaning. Provided. Since this electrolytic solution is a part of the electrolytic solution, the temperature of the cleaning solution that has already been heated is lowered. However, if this portion is heated excessively, adverse effects on the degree of cleaning can be eliminated. On the other hand, since it contains persulfate ions having strong oxidizing power, it contributes to stripping cleaning of resist and the like and further decomposition of the resist during cleaning in the single wafer cleaning apparatus 10.

In the solution storage tank 20, the contaminants that have migrated into the solution are oxidatively decomposed and cleaned by mixing the electrolyte solution by the oxidizing power by the self-decomposition of persulfate ions. At this time, the temperature of the solution is maintained at 80 to 130 ° C., and the decomposition of persulfate ions proceeds moderately so that the decomposition is effectively performed. If this temperature is higher than 130 ° C., the self-decomposition of persulfate ions proceeds at an early stage, making it difficult to effectively decompose the contaminants. Moreover, if it is less than 80 degreeC, the self-decomposition | disassembly of a persulfate ion does not fully advance and a decomposition | disassembly of a contaminant is not made | formed effectively similarly.
The solution in which the persulfate ion concentration is reduced by self-decomposition in the solution storage tank 20 is sent again to the electrolytic reaction device 30 through the electrolyte solution feeding pipe 6, and an electrolytic reaction is performed in the same manner as described above, so that persulfate ions are converted. It is regenerated and returned to the solution storage tank 20 through the electrolyte solution feeding pipe 7. In this manner, the persulfate ion-containing solution can be repeatedly used while regenerating the persulfate ions, so that the dissolved matter can be effectively decomposed.

  Moreover, since the solution sent from the solution storage tank 20 to the single wafer cleaning device 10 and used for cleaning is a part of the entire solution, the heating energy when heating the solution with the heating device 4 is also the entire solution. Compared with the case of heating, it can be greatly reduced. For example, if the flow rate of the cleaning liquid flowing through the cleaning liquid line is 2: 1 with respect to the flow rate flowing through the electrolytic solution line, the heating energy can be reduced to approximately 1/3 compared to the case where the entire amount is heated. If the flow rate ratio is 1: 1, it can be reduced to about 1/4.

[Example 1]
A cleaning process was performed under the following conditions using the cleaning system shown in FIG.
a) Cleaning liquid temperature to the single wafer cleaning device: 170 ° C
b) Cleaning solution temperature in the solution storage tank: 100 ° C
c) Cleaning fluid line flow rate: 8 L / min
d) Electrolyte line injection flow rate: 2 L / min
e) Electrolyte line storage tank flow rate: 4 L / min

[Comparative Example 1]
The same apparatus was used for cleaning under the following conditions. However, since the cleaning liquid circulates in one line, the conventional operating conditions are reproduced.
a) Cleaning liquid temperature to the single wafer cleaning machine: 170 ° C
b) Cleaning solution temperature in the solution storage tank: 100 ° C
c) Cleaning fluid line flow rate: 0 L / min
d) Electrolyte line injection flow rate: 10 L / min
e) Electrolyte line storage tank flow rate: 0 L / min

  Table 1 shows the data in the two examples. In all examples, the degree of wafer cleaning after cleaning has reached a level at which it can proceed to the next process. However, the system of Comparative Example 1 requires a lot of energy for heating and is inferior in running cost.

1 is an overall view showing a cleaning system in an embodiment of the present invention. 1 is an overall view showing a cleaning system before the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cleaning liquid return pipe 2 Cleaning liquid feeding pipe 3 Liquid feeding pump 4 Heating device 6 Electrolyte liquid feeding pipe 7 Electrolyte liquid feeding pipe 7a Liquid feeding branch pipe 7b Liquid feeding branch pipe 8 Liquid feeding pump 9 Cooler 10 Cleaning apparatus 20 Solution storage tank 21 Temperature controller 22 Temperature controller 30 Electrolytic reactor 31 Electrolytic reactor 32 Electrolytic tank 33 DC power supply
100 Semiconductor substrate

Claims (9)

A cleaning liquid line for circulating a cleaning solution of concentrated sulfuric acid heated to 100 ° C. or more and less than 200 ° C. via a cleaning unit consisting of a single wafer cleaning device that sprays the cleaning liquid on the material to be cleaned to clean the material to be cleaned;
An electrolytic solution line for circulating the electrolytic solution through an electrolytic reaction device that performs electrolysis while passing the electrolytic solution,
The cleaning liquid line and the electrolytic solution line are diverted downstream of the cleaning unit,
And an upstream side of the cleaning section A upstream, at least the upstream side of the downstream side, comprises a mixture common line electrolytic reactor downstream of the electrolyte line with the cleaning fluid line are joined,
A cleaning system comprising a solution storage tank at a diversion end of the mixing common line. The electrolytic solution line branches on the downstream side of the electrolytic reaction apparatus , and merges with the cleaning liquid line at the upstream side of the cleaning unit and the downstream side of the cleaning unit and the upstream side of the solution storage tank. The cleaning system according to claim 1.   The cleaning system according to claim 1 or 2, wherein the cleaning liquid is concentrated sulfuric acid having a sulfuric acid concentration of 8M or more and less than 18M.   The cleaning system according to claim 1, wherein a flow rate ratio between the cleaning liquid line and the electrolytic solution line is 2: 1 to 1: 1.   The cleaning system according to claim 1, further comprising a heating unit that heats the cleaning liquid upstream of the cleaning unit. Wherein of the electrodes used in the electrolytic reaction apparatus, cleaning system according to any one of claims 1 to 5, characterized in that at least an anode is a diamond electrode. The cleaning system according to any one of claims 1 to 6 , further comprising temperature adjusting means for maintaining the liquid in the mixing common line at 80 to 130 ° C. The cleaning system according to any one of claims 1 to 7 , further comprising a cooling unit that cools the electrolyte solution upstream of the electrolytic reaction apparatus. Cleaning system according to any one of claims 1 to 8, wherein the cleaning material is a semiconductor substrate.

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