JPH06132272A - Chemical recovering system of wet cleaner - Google Patents

Abstract

PURPOSE:To provide a chemical recovering system which enables used chemicals to be recovered and managed, adjusting them to the designated concentration suitable for being reused in separate process, within the chemical recovery system of a cleaner. CONSTITUTION:This system is equipped with a cooling and diluting vessel 7 with a built-in cooling coil 7a connected to the drainage side of a cleaning vessel 1, a dilute water supply pipe 9 connected to the vessel, and dilute water supply valve 8 interposed in the dilute water supply pipe, and a concentration meter 10 for detecting the concentration of the chemicals in the cooling and diluting vessel, and in the first place, used chemicals at high temperature and in high concentration discharged from a cleaning vessel is cooled, being introduced into a cleaning and diluting vessel. Next, the quantity of supplied dilute water is controlled so that the concentration of the chemicals inside the vessel may be designated concentration while adding dilute water to the cooling and diluting vessel, and after dilution and adjustment into designated concentration, they are recovered to a recovery tank 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for recovering used chemicals generated from a wet cleaning device used in a semiconductor wafer processing step.

[0002]

2. Description of the Related Art As is well known, in the process of processing semiconductor wafers, wafer cleaning is performed for the purpose of removing contaminants. Here, for contamination of organic substances, for example, sulfuric acid or the like is used as a cleaning chemical, and the wafer is cleaned by immersing the wafer in a cleaning tank filled with the chemical. By the way, since impurities are dissolved and the chemical solution gradually deteriorates as the wafer cleaning process is repeated, the chemical solution used for a certain period is discharged from the cleaning tank and recovered, and is replaced with a new chemical solution.

Next, taking a cleaning apparatus using sulfuric acid as a chemical solution as an example, a conventional chemical solution recovery system for a cleaning tank is shown in FIGS. In the figure, 1 is a cleaning tank, 2 is a chemical solution contained in the cleaning tank, 3 is a cooling tank connected to the drain side of the cleaning tank 1, 4 is a chemical solution recovery tank, and in the system of FIG. The cooling tank 3 has a built-in cooling coil 3a. Here, in order to collect a high temperature and high concentration used chemical liquid (for example, sulfuric acid having a concentration of 98% and a temperature of 150 ° C.) from the cleaning tank 1, the drain valve is operated while the cooling water is flowing through the cooling coil 3 a of the cooling tank 3. 5 is opened and the chemical liquid 2 discharged from the cleaning tank 1 is introduced into the cooling tank 3 to cool the high temperature chemical liquid 2 to about 45 ° C. near room temperature, and then the outlet valve 6 of the cooling tank 3 is opened to store the chemical liquid 2 inside the facility. It is transferred to the recovery tank 4 of No. 1 and collected. In addition, in the method of FIG.
The cooling water supply pipe line 3b is connected to the cooling tank 3, the cooling water is supplied to the cooling tank 3 through the valve 3c at the time of collecting the chemical liquid, and the chemical liquid 2 introduced from the cleaning tank 1 is diluted with the cooling water to keep the temperature near room temperature. After cooling to the liquid temperature, the outlet valve 6 is opened to collect in the recovery tank 4.

The chemical solution recovered in the recovery tank 4 is
Usually, the waste liquid is treated by a waste liquid treatment system in the plant, or is handed over to an industrial waste liquid treatment company for treatment.

[0005]

By the way, recently, it has been considered to adjust the used chemical solution recovered from the cleaning device to a predetermined concentration and manage it, and then to recycle it in another process. There is. Then, Fig. 4,
In the conventional chemical solution recovery system shown in FIG. 5, the concentration of the chemical solution recovered in the recovery tank 4 is determined by the concentration of the chemical solution 2 used for the wafer cleaning process in the cleaning tank 1 (method of FIG. 4) or the cooling tank 3 Since it is determined by the amount of cooling water supplied from the outside (system of FIG. 5), the concentration of the chemical solution recovered from the recovery system is not constant, and the recovered chemical solution cannot be immediately reused in another process as it is. Therefore, in order to reuse the chemical solution recovered by the recovery system in a different process, it is necessary to adjust the concentration of the recovered chemical solution again in a processing facility different from that of the chemical solution recovery system. However, with this method, the processing cost including the equipment cost of the processing equipment and the operation management cost is high, and the system for recycling the used chemical liquid is economically unprofitable.

The present invention has been made in view of the above points, and an object thereof is to solve the above-mentioned problems and to reuse a used chemical in another process in a chemical recovery system of a cleaning apparatus. It is to provide a chemical solution recovery system that can be collected and managed by adjusting it to a specified concentration.

[0007]

The above object can be achieved by the present invention by constructing a chemical liquid recovery system as follows. (1) A cooling / diluting tank with a built-in cooling coil connected to the drain side of the cleaning tank, a dilution water supply pipe connected to the tank, a dilution water supply valve inserted in the dilution water supply pipe, and cooling・ It is equipped with a concentration meter that detects the concentration of the chemical liquid in the diluting tank, and first introduces the chemical liquid discharged from the washing tank into the cooling / diluting tank to cool it, and then while adding dilution water to the cooling / diluting tank, The supply amount of the diluting water is controlled so that the concentration of the chemical liquid in the tank becomes the designated concentration to obtain the recovered chemical liquid controlled to the designated concentration.

(2) A cooling / dilution tank with a built-in cooling coil connected to the drain side of the cleaning tank, a dilution water supply pipe connected to the tank, and a dilution water supply valve inserted in the dilution water supply pipe. And a liquid level meter that detects the liquid level in the cooling / diluting tank. First, supply the dilution water to the cooling / diluting tank to a predetermined liquid level, and then from the cleaning tank. While the discharged chemical liquid was introduced into the cooling / diluting tank, the specified amount was controlled by controlling the supply amount of the chemical liquid so that the combined liquid surface level of the dilution water and the chemical liquid would be the liquid surface level corresponding to the specified concentration. Obtain the recovered drug solution.

(3) In the preceding paragraph (2), a pre-cooling tank with a built-in cooling coil is provided in the preceding stage of the cooling / diluting tank, and the chemical liquid discharged from the washing tank is temporarily stored in the pre-cooling tank and cooled to room temperature, and then the latter stage. Add to the cooling / diluting tank.

[0010]

In the configuration of the above (1), the high temperature and high concentration chemical solution discharged from the cleaning tank is introduced into the cooling / diluting tank, and the chemical solution is cooled by heat exchange with the cooling coil, while the concentration meter is used. The dilution water (pure water) is added while measuring the concentration of the chemical liquid in the cooling / dilution tank, and when the concentration of the chemical liquid in the tank reaches the specified concentration, the supply of the dilution water is stopped. As a result, the chemical solution recovered in the chemical solution recovery system is adjusted and managed to a specified concentration, and the recovered chemical solution obtained here can be directly transferred to another process for reuse.

On the other hand, in the constitution of the above item (2), the chemical concentration on the cleaning tank side and the volume of the cooling / diluting tank are known,
At the time of collecting the chemical solution, a certain level of dilution water was first supplied and stored in the cooling / diluting tank, and the chemical solution discharged from the cleaning tank was put into the cooling / dilution tank while the dilution water and the chemical solution were combined. If the supply amount of the chemical liquid is controlled so that the liquid surface level corresponds to the designated concentration, the recovered chemical liquid adjusted to the designated concentration in the cooling / diluting tank can be obtained.

Further, in this case, if a high temperature chemical solution (for example, sulfuric acid) is directly added to the diluting water, a violent exothermic reaction may occur and the temperature may rise above the heat resistant temperature of the cooling / diluting tank. Therefore, in this case, a pre-cooling tank with a built-in cooling coil is provided in the preceding stage of the cooling / diluting tank as described in (3) above, and the high-temperature chemical liquid discharged from the cleaning tank is temporarily stored in this pre-cooling tank and then cooled. If it is introduced into the cooling / diluting tank, the reaction heat is small and the chemical solution can be safely diluted to the specified concentration.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In each embodiment, the same members corresponding to FIGS. 4 and 5 are designated by the same reference numerals. Embodiment 1 FIG. 1 shows an embodiment corresponding to claim 1 of the present invention. In this embodiment, a cooling coil 7a is provided on the drain side of the cleaning tank 1 as in the cooling tank of FIG. A built-in cooling / diluting tank 7 is installed, and a dilution water supply pipe 9 is externally connected to the tank 7 via a dilution water supply valve 8. Further, a concentration meter for measuring the concentration of a chemical solution in the tank. Equipped with 10. Further, 11 is a liquid stirrer. The used chemical liquid 2 in the cleaning tank 1 is, for example, sulfuric acid (liquid temperature 150 ° C., concentration 98%).

With this configuration, when the high temperature and high concentration chemical solution 2 is collected from the cleaning tank 1, the drain valve 5 is opened and the chemical solution 2 discharged from the cleaning tank 1 is stored in the cooling / diluting tank 7 and cooled. After the chemical solution 2 is cooled to a temperature close to room temperature (for example, about 45 ° C.) by heat exchange with the cooling water flowing in the coil 7a, the dilution water supply valve 8 is opened and the dilution water (pure water is supplied to the cooling / dilution tank 7). Supply). Then, while stirring the chemical liquid and the diluting water with the liquid stirrer 11, the concentration meter 10 measures and monitors the chemical liquid concentration in the tank, and when the chemical liquid concentration is diluted to a predetermined concentration (for example, 70%), The dilution water supply valve 8 is closed by the signal from the densitometer 10 to stop the supply of the dilution water, and then the valve 6 is opened to transfer the chemical liquid diluted in the cooling / diluting tank 7 to the recovery tank 4 for storage. As a result, the used chemical liquid 2 collected from the cleaning tank 1 can be collected in the collection tank 4 as the collected chemical liquid 13 adjusted to a designated concentration and managed. It should be noted that the recovery chemicals are collected in the recovery tank 4
If a filter 12 is provided in the pipe when transferring to a filter, solid impurities such as dust mixed in the chemical solution can be removed from the filter 1.
The collected chemical liquid 13 can be cleaned by collecting and removing it in 2. In addition, the series of operations for collecting the chemical solution described above can be fully automated by using a programmable controller, a sequencer, or the like.

Then, the recovered chemical liquid 13 stored in the recovery tank 4 is brought into another process and reused when necessary. Example 2 FIG. 2 shows an example corresponding to claim 2 of the present invention. In this example, a liquid level meter 1 is provided in a cooling / diluting tank 7 instead of the concentration meter in Example 1.
It is equipped with 4. The concentration of the chemical liquid 2 used in the cleaning tank 1 and the volume of the cooling / diluting tank 7 are known in advance.

With such a structure, when the chemical solution 2 in the cleaning tank 1 is collected, the dilution water supply valve 8 is first opened and the cooling / dilution tank 7 is opened.
While the liquid level height in the tank is measured by the level meter 14, the dilution water is introduced until it reaches a predetermined level, and then the valve 8 is closed. Next, the drain valve 5 of the cleaning tank 1 is opened to cool and dilute the chemical solution 2
When the liquid level of the tank 7 reaches a level corresponding to the specified chemical concentration, the drain valve 5 is added based on the signal of the level meter 14
Close. As a result, the dilution is adjusted to a previously designated concentration based on the ratio between the amount of dilution water stored in the tank in advance and the chemical solution discharged from the cleaning tank side. The high temperature chemical liquid 2 introduced from the cleaning tank 1 into the cooling / diluting tank 7 is cooled by the cooling coil 7a. Thereafter, as in the first embodiment, the recovered chemical liquid is cooled and diluted from the recovery tank 7 to the recovery tank 4
Move to and store.

Embodiment 3 FIG. 3 shows an embodiment in which the precooling tank according to claim 3 of the present invention is combined with the embodiment 2, and a cooling coil 15a is provided in the preceding stage of the cooling / diluting tank 7. A pre-cooling tank 15 having a built-in is provided. In addition, 16 is an outlet valve of the precooling tank 15, and 17 and 18 are thermometers for measuring the liquid temperature in the tank.

With such a structure, when collecting the used chemical solution 2 from the cleaning tank 1, first, the drain valve 5 is opened to transfer the chemical solution 2 from the cleaning tank 1 to the pre-cooling tank 15, where it is connected to the cooling coil. The chemical solution 2 is cooled to near room temperature by heat exchange.
On the other hand, in parallel with this, in the cooling / diluting tank 7, a predetermined amount of dilution water is supplied and stored in the same manner as described in the second embodiment. When the liquid temperature of the pre-cooling tank 15 decreases, the outlet valve 16 of the pre-cooling tank 15 is opened based on the signal from the thermometer 17, and the low temperature chemical liquid is stored in the cooling / diluting tank 7 in advance. When the liquid level in the tank 7 reaches the level corresponding to the specified concentration after pouring it into the diluting water, the outlet valve 16 is closed based on the signal from the level meter 14 to stop the chemical liquid injection from the precooling tank 15. To do. As a result, the chemical solution can be diluted to the specified concentration without the generation of intense reaction heat in the cooling / diluting tank 7. Furthermore, after measuring the liquid temperature in the cooling / diluting tank 7 with a thermometer 18 and confirming that the liquid temperature is sufficiently cooled to room temperature, the outlet valve 6 of the cooling / diluting tank 7 is opened to collect. The chemical solution is transferred to the recovery tank 4.

[0019]

As described above, according to the chemical liquid recovery system of the present invention, the used chemical liquid generated from the cleaning tank is
It is possible to collect and manage the chemical solution by adjusting it to the specified concentration in the recovery system. As a result, the used chemical solution in the cleaning tank, which has been discarded until now, can be directly recycled from the chemical solution recovery system to another process.

Moreover, since the structure of the existing chemical liquid recovery system can be used as it is, and only a few devices can be additionally provided, it is possible to establish a sufficiently profitable system for recycling the used chemical liquid.

[Brief description of drawings]

FIG. 1 is a system flow diagram of a chemical liquid recovery system corresponding to Example 1 of the present invention.

FIG. 2 is a system flow diagram of a chemical liquid recovery system corresponding to Example 2 of the present invention.

FIG. 3 is a system flow diagram of a chemical liquid recovery system corresponding to Example 3 of the present invention.

FIG. 4 is a system flow diagram of a conventional chemical recovery system.

5 is a system flow diagram of a conventional chemical liquid recovery system different from that in FIG.

[Explanation of symbols]

 1 Cleaning Tank 2 Used Chemical Solution 4 Recovery Tank 7 Cooling / Diluting Tank 7a Cooling Coil 8 Diluting Water Supply Valve 9 Diluting Water Supply Pipeline 10 Concentration Meter 13 Collecting Chemical Solution 14 Liquid Level Meter 15 Precooling Tank 15a Cooling Coil

Claims (3)

[Claims] 1. A system for recovering used chemicals used in a wet cleaning apparatus, which cools a high-temperature, high-concentration chemical discharged from a cleaning tank, dilutes it to a specified concentration, and then recovers it. A cooling / dilution tank with a built-in cooling coil connected to the drain side of the cleaning tank, a dilution water supply pipe connected to the tank, and a dilution water supply valve inserted in the dilution water supply pipe,
The cooling / diluting tank is equipped with a concentration meter that detects the concentration of the chemical liquid, and the chemical liquid discharged from the cleaning tank is first introduced into the cooling / diluting tank for cooling, and then while adding the dilution water to the cooling / diluting tank. A chemical solution recovery system for a wet cleaning device, characterized in that the chemical solution recovery amount is controlled so that the chemical solution concentration in the tank becomes a specified concentration to obtain a recovered chemical solution controlled to a specified concentration. 2. A system for recovering used chemicals used in a wet cleaning apparatus, which cools high-temperature, high-concentration chemicals discharged from a cleaning tank, dilutes it to a specified concentration, and then recovers it. A cooling / dilution tank with a built-in cooling coil connected to the drain side of the cleaning tank, a dilution water supply pipe connected to the tank, and a dilution water supply valve inserted in the dilution water supply pipe,
It is equipped with a liquid level meter that detects the liquid level in the cooling / diluting tank. First, diluting water is supplied to the cooling / diluting tank up to a predetermined liquid level and then discharged from the cleaning tank. While introducing the chemical solution into the cooling / diluting tank, the supply amount of the chemical solution is controlled so that the combined liquid level of the diluting water and the chemical solution corresponds to the specified concentration. A chemical solution recovery system for a wet cleaning device, which is characterized in that 3. The chemical liquid recovery system according to claim 2, wherein a precooling tank having a built-in cooling coil is provided in front of the cooling / diluting tank, and the chemical liquid discharged from the cleaning tank is temporarily stored in the precooling tank and cooled to room temperature. A chemical solution recovery system for a wet cleaning device, which is later put into a cooling / diluting tank in the latter stage.