JP2011206637A - Method and apparatus for treatment of waste liquid containing acid or base and hydrogen peroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method for waste liquid which removes hydrogen peroxide contained in waste liquid containing acids or bases and hydrogen peroxide without distillation or neutralization treatment.SOLUTION: The treatment method includes: an irradiation process where ultraviolet rays are irradiated to the waste liquid to decompose the hydrogen peroxide contained therein; a measurement process where the hydrogen peroxide concentration of the waste liquid having been subjected to the irradiation process is measured; and a control process where the hydrogen peroxide concentration measured in the measurement process is compared with a reference value of the hydrogen peroxide concentration and when the measured concentration exceeds the reference value, at least one step selected from the following (a), (b) and (c) is performed: (a) starting to return the waste liquid having been subjected to the irradiation process and mix the returned waste liquid with the waste liquid before the irradiation process, or increasing the returning amount and mixing amount; (b) changing an ultraviolet irradiation condition to the waste liquid in the irradiation process to one where the decomposition of the hydrogen peroxide is accelerated; and (c) starting to add an accelerator for accelerating the decomposition of the hydrogen peroxide by the ultraviolet rays to the waste liquid before the irradiation process, or increasing the amount of added accelerator.

Description

  The present invention relates to a treatment method and a treatment apparatus for waste liquid containing an acid or base and hydrogen peroxide.

  A waste liquid containing an acid or base and hydrogen peroxide is discharged from the manufacturing process of the semiconductor element. Typical examples of the waste liquid include sulfuric acid / hydrochloric acid / hydrofluoric acid / ammonia hydrogen peroxide-added hydrogen peroxide (SPM), hydrochloric acid / hydrogen peroxide (HPM), hydrofluoric acid / hydrogen peroxide (FPM), or ammonia / hydrogen peroxide (APM). It is a waste liquid containing. A waste liquid containing an acid or base and hydrogen peroxide is generally discharged through a decomposition treatment of hydrogen peroxide using a catalyst, an enzyme agent, a reducing agent, etc. after neutralizing the acid or base.

  It is desirable to reuse the acid and base contained in the waste liquid. However, when hydrogen peroxide is contained in the waste liquid, it is necessary to remove it, so that an acid or base neutralization treatment is essential before that. Acid and base cannot be reused from waste liquid that has undergone neutralization. For this reason, realization of the method of removing hydrogen peroxide contained in a waste liquid is desired, without performing neutralization processing.

  SPM containing sulfuric acid is used at a high temperature of about 150 ° C. in the manufacturing process of semiconductor elements, and has been discharged from the manufacturing apparatus in a state diluted with a large amount of water. In recent years, the production apparatus has been improved and discharged from the apparatus without being diluted with a large amount of water, that is, in a state where the effective acid concentration is high. Recycling acid (base) from waste liquid with high effective acid (base) concentration while maintaining high effective acid (base) concentration is very important both from the viewpoint of semiconductor device manufacturing cost and environmental protection. This is a long-awaited technology.

  Patent Document 1 (Japanese Patent Laid-Open No. 6-127908) discloses a sulfuric acid regenerating apparatus that regenerates waste sulfuric acid containing a resist organic material and hydrogen peroxide discharged from a resist stripping apparatus into sulfuric acid. Patent document 1 makes it a subject to remove the organic substance contained in a waste sulfuric acid in order to prevent mixing of the organic substance in the sulfuric acid after reproduction | regeneration, The said apparatus decomposes and removes an organic substance using an oxidizing agent and / or an ultraviolet-ray. An organic matter decomposition device is provided. Patent Document 1 describes that in the regenerator, an organic substance is decomposed by positively adding an oxidizing agent such as hydrogen peroxide to waste sulfuric acid.

  In the regenerator of Patent Document 1, hydrogen peroxide initially contained in the waste sulfuric acid and hydrogen peroxide added in the organic matter decomposing apparatus are distilled below the boiling point of sulfuric acid in order to prevent mixing into the sulfuric acid after regeneration ( The first distillation column). The purity of the sulfuric acid that has passed through the first distillation column is increased by distillation at a higher temperature (second distillation column), and is re-supplied to the resist stripping device through the sulfuric acid supply pipe. That is, the apparatus of Patent Document 1 includes first and second distillation columns, which are based on the premise that hydrogen peroxide is positively added to decompose organic matter, and a resist stripping apparatus. It is considered that the regenerated sulfuric acid is continuously supplied to the resist stripping step by constructing a sulfuric acid recycle circuit including a sulfuric acid regenerator. The apparatus of Patent Document 1 exhibits extremely excellent performance for the purpose of continuously supplying regenerated sulfuric acid to a specific process. However, on the other hand, if the regeneration and reuse of acids and bases in the waste liquid is carried out in batch or in another device or place without building a regeneration circuit, the device comprising at least two distillation columns Since the manufacturing cost and the operating cost are unnecessarily large, the device of Patent Document 1 is not suitable. In the first place, if the boiling point of the acid or base is not sufficiently larger than the boiling point of hydrogen peroxide, after removing the hydrogen peroxide from the waste liquid containing the acid or base and hydrogen peroxide by the apparatus of Patent Document 1, Or the base cannot be reused.

JP-A-6-127908

  In view of such circumstances, the present invention is a method and apparatus for treating a waste liquid containing an acid or base and hydrogen peroxide, and does not depend on the relationship of the boiling point of the acid or base to the boiling point of hydrogen peroxide. Another object is to provide a treatment method and a treatment apparatus for decomposing and removing hydrogen peroxide contained in the waste liquid without performing the neutralization treatment of the acid or base.

  The treatment method of the present invention is a treatment method of a waste liquid containing an acid or base and hydrogen peroxide, wherein the waste liquid containing an acid or base and hydrogen peroxide is irradiated with ultraviolet rays, and the peroxidation contained in the waste liquid. An irradiation step for decomposing hydrogen, a measurement step for measuring the concentration of hydrogen peroxide in the waste liquid that has undergone the irradiation step, a concentration of the hydrogen peroxide measured in the measurement step, and a reference value for the concentration In contrast, when the measured concentration exceeds the reference value, a control step is performed in which at least one selected from the following (a), (b) and (c) is performed. (A) Start at least part of the reflux of the waste liquid that has undergone the irradiation step and mixing of the waste liquid that has been refluxed with respect to the waste liquid before the irradiation step is performed, or the reflux and mixing are already When being performed, the amount of the reflux and mixing of the waste liquid that has undergone the irradiation step is increased. (B) The irradiation condition of the ultraviolet light to the waste liquid in the irradiation step is changed in a direction in which the decomposition of hydrogen peroxide contained in the waste liquid is promoted. (C) To start the addition of an accelerator that promotes the decomposition of hydrogen peroxide by ultraviolet irradiation with respect to the waste liquid before the irradiation step is performed, or when the addition has already been performed, The amount of the accelerator added to the waste liquid before the irradiation step is performed is increased.

  The treatment apparatus of the present invention is a waste liquid treatment apparatus containing an acid or base and hydrogen peroxide, and an ultraviolet irradiation mechanism for irradiating the waste liquid containing an acid or base and hydrogen peroxide with ultraviolet light, and the ultraviolet light irradiation. And a measurement mechanism for measuring the concentration of hydrogen peroxide in the waste liquid after the operation, and at least one selected from the following (A), (B), and (C). (A) A reflux mechanism for circulating at least a part of the waste liquid after irradiation with the ultraviolet light and mixing with the waste liquid before the ultraviolet light irradiation, and the hydrogen peroxide measured in the measurement mechanism. When the measured concentration exceeds the reference value by comparing the concentration with the reference value of the concentration, the recirculation and mixing by the recirculation mechanism is started or the recirculation and mixing has already been performed. A recirculation control mechanism for increasing the amount of the recirculation and the waste liquid to be mixed. (B) When the concentration of the hydrogen peroxide measured in the measurement mechanism is compared with a reference value of the concentration and the measured concentration exceeds the reference value, the waste liquid by the ultraviolet irradiation mechanism An ultraviolet ray control mechanism that changes the irradiation condition of ultraviolet rays to the direction in which the decomposition of hydrogen peroxide contained in the waste liquid is accelerated. (C) an accelerator addition mechanism for adding an accelerator that promotes decomposition of hydrogen peroxide by irradiation of ultraviolet rays to the waste liquid before being irradiated with the ultraviolet rays, and the peroxidation measured in the measurement mechanism When the concentration of hydrogen is compared with the reference value of the concentration and the measured concentration exceeds the reference value, the addition of the accelerator by the accelerator addition mechanism is started, or the accelerator A promoter control mechanism that increases the amount of the promoter added when the addition of is already done.

  The treatment method and treatment apparatus of the present invention provide a peroxidation contained in a waste liquid containing an acid or base and hydrogen peroxide without a distillation column, that is, without depending on the relationship of the boiling point of the acid or base to the boiling point of hydrogen peroxide. Hydrogen can be decomposed and removed. As a result, the treatment method and treatment apparatus of the present invention are not limited to sulfuric acid having a very high boiling point compared to hydrogen peroxide, but also waste liquid containing hydrochloric acid, hydrofluoric acid or ammonia having a boiling point equal to or less than that of hydrogen peroxide. It can also be applied to.

  The treatment method and treatment apparatus of the present invention, unlike a treatment method that decomposes hydrogen peroxide using a catalyst, an enzyme agent, a reducing agent, or the like and a treatment device that employs the method, carry out neutralization treatment of acid or base. Without decomposing, hydrogen peroxide contained in the waste liquid containing acid or base and hydrogen peroxide can be decomposed and removed.

  According to the treatment method and the treatment apparatus of the present invention, it is possible to remove hydrogen peroxide contained in the waste liquid at low cost, and reuse of the acid or base contained in the waste liquid is realized at low cost. Furthermore, according to the treatment method of the present invention, hydrogen peroxide contained in the waste liquid can be removed while maintaining the effective acid (base) concentration. That is, the treatment method of the present invention is particularly advantageous when the acid or base is reused from a waste liquid having a high effective acid (base) concentration while the concentration is high.

  The treatment method and treatment apparatus of the present invention are also suitably applied to the case where the acid or base contained in the waste liquid is not reused, for example, when the waste liquid after treatment is discharged, and also at this time, the treatment of the waste liquid Is low cost.

It is a schematic diagram which shows an example of the processing apparatus of this invention. In the processing apparatus of this invention, it is a schematic diagram which shows an example of the processing tank which irradiates a waste liquid with an ultraviolet-ray. In the processing apparatus of this invention, it is a schematic diagram which shows another example of the processing tank which irradiates a waste liquid with an ultraviolet-ray. It is a schematic diagram which shows another example of the processing apparatus of this invention. It is a schematic diagram which shows another example of the processing apparatus of this invention. It is a schematic diagram which shows another example of the processing apparatus of this invention. It is a schematic diagram which shows an example different from the above of the processing apparatus of this invention. It is a schematic diagram which shows an example different from the above of the processing apparatus of this invention.

  Hereinafter, while showing the treatment apparatus of the present invention (treatment apparatus for waste liquid containing acid or base and hydrogen peroxide) in the drawings, the apparatus and the treatment method of the present invention (for waste liquid containing acid or base and hydrogen peroxide) Processing method) will be described.

  An apparatus 51 shown in FIG. 1 includes a storage tank 12 that temporarily stores waste liquid 1 containing an acid or base and hydrogen peroxide, an introduction pipe 11 that introduces the waste liquid 1 into the storage tank 12, and a waste liquid. 1, a treatment tank 14 for irradiating ultraviolet rays, a pipe 13 and a pump P for sending the waste liquid 1 from the storage tank 12 to the treatment tank 14, a discharge pipe 15 for discharging the waste liquid 1 from the treatment tank 14 to the outside of the apparatus 51, and a discharge pipe 15, a measuring device 18 that measures the concentration of hydrogen peroxide in the waste liquid 1 that has passed through the treatment tank 14, and a control device 31 are provided. The control device 31 compares the concentration measured by the measurement device 18 with the reference value of the concentration, and when the measured concentration exceeds the reference value, the irradiation condition of the ultraviolet light to the waste liquid 1 in the treatment tank 14 is determined. Then, the hydrogen peroxide contained in the waste liquid 1 is changed in a direction that promotes decomposition. The apparatus 51 includes a processing tank 14 as an ultraviolet irradiation mechanism, a measuring apparatus 18 as a measurement mechanism, and a control device 31 as the ultraviolet control mechanism (B).

  The waste liquid 1 is sent to the storage tank 12 through the introduction pipe 11 and then sent to the treatment tank 14 through the pipe 13 by the pump P. In the treatment tank 14, a step (irradiation step) of irradiating the waste liquid 1 with ultraviolet rays to decompose hydrogen peroxide contained in the waste liquid is performed. The waste liquid 1 that has undergone the irradiation process is sent out of the apparatus 51 through the discharge pipe 15. At that time, the concentration of hydrogen peroxide in the waste liquid 1 that has undergone the irradiation process is measured by a measuring device 18 provided in the middle of the discharge pipe 15 (measuring process). The control device 31 compares the concentration of hydrogen peroxide measured by the measuring device 18 with the reference value of the concentration, and when the measured concentration exceeds the reference value, the ultraviolet light to the waste liquid 1 in the treatment tank 14 is The irradiation conditions are changed in a direction in which the decomposition of hydrogen peroxide contained in the waste liquid 1 is promoted (control process).

  In the apparatus 51 and the processing method implemented in the apparatus 51, the decomposition / removal efficiency of hydrogen peroxide contained in the waste liquid 1 is improved. Furthermore, in this apparatus and method, hydrogen peroxide can be stably decomposed and removed even when the concentration of hydrogen peroxide contained in the waste liquid 1 to be treated changes with time. In addition, the waste liquid 1 sent out from the apparatus 51 through the discharge pipe 15 can be freely handled by those skilled in the art. For example, the waste liquid 1 is stored, reused or discharged after further processing is performed as necessary. The same applies to the devices 52 to 56 shown in the following figures.

  The “reference value” to be compared in the control device 31 (control process) can be arbitrarily set by the user of the device 51. The reference value is, for example, the upper limit concentration of hydrogen peroxide required when the acid or base from the waste liquid 1 is reused or when the waste liquid 1 is discharged. The upper limit concentration is, for example, 100 ppm when reused, and, for example, 20 ppm when discharged.

  In the apparatus 51 and the processing method implemented in the apparatus 51, when the concentration of hydrogen peroxide in the waste liquid 1 that has been subjected to the irradiation process measured by the measuring apparatus 18 exceeds a reference value, the control apparatus 31 performs hydrogen peroxide. The irradiation condition of ultraviolet rays is changed in the direction in which the decomposition of is promoted. Here, depending on the specific configuration of the device 51, more specifically, the concentration of hydrogen peroxide measured by the measuring device 18 is changed until the effect is actually obtained after the irradiation condition of the ultraviolet rays changes. There may be a time lag when it starts to fall and falls below the reference value. In such a case, if the reference value is set to the upper limit concentration, waste liquid having a hydrogen peroxide concentration that temporarily exceeds the upper limit concentration may be discharged from the apparatus 51. When such discharge becomes a problem, a concentration obtained by subtracting a certain value from the upper limit concentration may be used as a reference value.

  When the concentration of hydrogen peroxide in the waste liquid 1 measured by the measuring device 18 is equal to or lower than the reference value of the concentration, the control device 31 includes the waste liquid 1 in the waste liquid 1 under the irradiation condition of the ultraviolet light to the waste liquid 1 in the treatment tank 14. It may be changed in a direction in which decomposition of hydrogen peroxide generated becomes gentle.

  The ultraviolet irradiation condition to be controlled is, for example, the ultraviolet irradiation amount with respect to the unit amount of the waste liquid 1. The amount of irradiation is adjusted by, for example, changing the time for which the waste liquid 1 passes through the treatment tank 14 or changing the intensity of the ultraviolet rays applied to the waste liquid 1 in the treatment tank 14.

  Specifically, in the above control step, the concentration of hydrogen peroxide measured in the measurement step is compared with the reference value of the concentration, and when the measured concentration exceeds the reference value, the unit amount of the irradiation step Increasing the amount of ultraviolet irradiation to the waste liquid 1. The control device 31 compares the concentration of hydrogen peroxide measured by the measuring device 18 with the reference value of the concentration, and when the measured concentration exceeds the reference value, the unit amount of the waste liquid 1 by the treatment tank 14. Increase the amount of UV irradiation to the.

  In the apparatus 51 and the above method implemented in the apparatus 51, in the measurement process (in the measurement apparatus 18), the concentration of hydrogen peroxide in the waste liquid 1 that has undergone the irradiation process (through the treatment tank 14) is continuously measured and controlled. In the process (in the control device 31), the measured concentration and the reference value may be continuously compared, and the above-described change in the ultraviolet irradiation condition may be continuously performed. In this case, the decomposition and removal efficiency of hydrogen peroxide contained in the waste liquid 1 is further improved. Further, even when the concentration of hydrogen peroxide contained in the waste liquid 1 to be treated changes with time, the followability of the treatment with respect to the change is improved, and hydrogen peroxide can be more stably decomposed and removed. .

  The waste liquid 1 which is the target of the treatment method and treatment apparatus of the present invention contains an acid or base and hydrogen peroxide. The waste liquid 1 is, for example, a waste liquid discharged from a semiconductor element manufacturing process, more specifically, a substrate cleaning process or a resist stripping process. The waste liquid 1 is discharged from the semiconductor device manufacturing apparatus, directly or once stored, and then sent to the storage tank 12 through the introduction pipe 11.

  The acid contained in the waste liquid 1 is, for example, sulfuric acid, hydrochloric acid, or hydrofluoric acid. The base contained in the waste liquid 1 is, for example, ammonia. The waste liquid 1 is a waste liquid containing, for example, sulfuric acid / hydrogen peroxide (SPM), hydrochloric acid / hydrogen peroxide (HPM), hydrofluoric acid / hydrogen peroxide (FPM), or ammonia / hydrogen peroxide (APM).

  In the treatment tank 14 and the irradiation step, the waste liquid 1 is irradiated with ultraviolet rays (UV), and the decomposition reaction of hydrogen peroxide represented by the following formula (1) proceeds. “.OH” in the formula (1) is a hydroxy radical.

H ₂ O ₂ + (UV irradiation) → 2 (.OH) → OH + 1/2 (H ₂ O ₂ ) (1)

  As shown in Formula (1), when the waste liquid 1 is irradiated with ultraviolet rays, the hydrogen peroxide contained in the waste liquid 1 is decomposed to generate hydroxy radicals. Approximately half of the generated hydroxy radicals return to hydrogen peroxide, but the remaining hydroxy radicals react with each other or with substances contained in the waste liquid and disappear. The hydrogen peroxide is finally decomposed into water and oxygen by repeating the reaction and the decomposition reaction represented by the formula (1) by irradiation with ultraviolet rays. When the waste liquid contains an organic substance, for example, a resist material discharged from the resist stripping process, the hydroxy radical may decompose the organic substance to further generate carbon dioxide gas.

  As for the wavelength of the ultraviolet-ray irradiated to the waste liquid 1, 100-280 nm is preferable. For example, a mercury lamp, excimer laser, or light emitting diode (LED) can be used as the ultraviolet light source in this wavelength range.

  The temperature of the waste liquid 1 in the irradiation process is not limited. For example, when the acid is sulfuric acid, the temperature is preferably about 10 to 50 ° C.

  The structure of the treatment tank 14 is not limited as long as the waste liquid 1 in the tank 14 can be irradiated with ultraviolet rays. An example of the treatment tank 14 is shown in FIGS.

  The processing tank 14A shown in FIG. 2 is a kind of processing tank having the simplest structure. The interior of the treatment tank 14A is a space in which the waste liquid 1 sent to the treatment tank 14A through the pipe 13 is retained. The waste liquid 1 maintains a liquid level with a set height inside the treatment tank 14A. An ultraviolet light source 41 is disposed in the upper part of the treatment tank 14 </ b> A, at a position exposed from the liquid level of the waste liquid 1. A partition wall 43 is arranged inside the treatment tank 14A. By arranging the partition wall 43, the residence time of the waste liquid 1 in the treatment tank 14A is lengthened, and the waste liquid 1 is irradiated with ultraviolet rays as uniformly as possible. Has been. The waste liquid 1 sent to the treatment tank 14A through the pipe 13 is irradiated with ultraviolet rays from the light source 41 while it stays in the treatment tank 14A, and then passes through the discharge pipe 15 connected to the treatment tank 14A. Sent out. The apparatus 51 provided with such a processing tank 14A can be constructed at low cost. Note that the inner wall surface of the treatment tank 14A is preferably subjected to a treatment that efficiently reflects ultraviolet rays, for example, a mirror treatment.

  In the treatment tank 14A, the irradiation condition of the ultraviolet light to the waste liquid 1 can be controlled, for example, as follows: The time for the waste liquid 1 to pass through the treatment tank 14A is adjusted. This adjustment can be performed by changing the output of the pump P; it changes the intensity of the ultraviolet rays irradiated to the waste liquid 1. For example, the processing tank 14A having two or more light sources 41 is used, and the number of light sources 41 to be turned on is changed; the height of the liquid level of the waste liquid 1 in the processing tank 14A is adjusted. This adjustment can be performed by changing the balance between the amount of the waste liquid 1 sent to the treatment tank 14A and the amount of the waste liquid 1 sent from the treatment tank 14A.

  The processing tank 14B shown in FIG. 3 includes a pipe 42 through which the waste liquid 1 flows. One end of the pipe 42 is connected to the pipe 13 that sends the waste liquid 1 to the treatment tank 14B. The other end of the pipe 42 is connected to a discharge pipe 15 that sends out the waste liquid 1 after ultraviolet irradiation from the treatment tank 14B. Furthermore, the processing tank 14 </ b> B includes a plurality of ultraviolet light sources 41 arranged along the outer wall surface of the pipe 42. The pipe 42 is made of a material that transmits ultraviolet rays, for example, polytetrafluoroethylene.

  The waste liquid 1 sent to the processing tank 14B through the pipe 13 flows in the pipe 42 of the processing tank 14B as it is. At that time, the ultraviolet light from the light source 41 passes through the pipe 42 and is irradiated to the waste liquid 1, and the hydrogen peroxide contained in the waste liquid 1 is decomposed. Thereafter, the waste liquid 1 is sent out from the treatment tank 14 </ b> B through the discharge pipe 15 connected to the pipe 42. In the treatment tank 14B, since the distance between the ultraviolet light source 41 and the waste liquid 1 can be kept small, the efficiency of decomposing hydrogen peroxide contained in the waste liquid 1 is increased. In addition to this, hydrogen peroxide contained in the waste liquid 1 is decomposed by appropriately selecting and designing the diameter and shape of the pipe 42, the type and arrangement of the light source 41, and the path of the pipe 42 in the treatment tank 14B. Efficiency is further improved.

  In the treatment tank 14B, the irradiation condition of the ultraviolet light to the waste liquid 1 can be controlled, for example, as follows: The time for the waste liquid 1 to pass through the treatment tank 14B is adjusted. This adjustment can be performed by changing the output of the pump P or changing the length of the pipe 42 through which the waste liquid 1 passes using a valve or the like; the intensity of the ultraviolet rays irradiated to the waste liquid 1 is changed. For example, the processing tank 14B has two or more light sources 41, and the number of light sources 41 to be turned on is changed.

  As shown in FIG. 3, the pipe 42 is usually arranged in the treatment tank 14 </ b> B in a bent state. Thereby, the processing tank 14B can be made compact. Furthermore, depending on the arrangement of the light sources 41, the single liquid source 41 can simultaneously irradiate the waste liquid 1 flowing through the plurality of pipes 42 with ultraviolet rays.

  In the treatment tank 14B, by appropriately selecting the type of material constituting the pipe 42, corrosion of the treatment tank 14B due to the acid or base contained in the waste liquid 1 is suppressed, and the treatment cost of the waste liquid 1 and the maintenance cost of the apparatus 51 are reduced. Becomes lower. In addition, the contamination of the waste liquid 1 due to the corrosion of the treatment tank 14B is reduced, and the reuse of the acid or base having a high purity is facilitated. Among acids and bases, the corrosiveness of sulfuric acid is particularly strong, so that the treatment tank 14B is suitable when the waste liquid 1 contains sulfuric acid. When processing the waste liquid 1 containing sulfuric acid, it is preferable that the piping 42 is comprised with resin which permeate | transmits an ultraviolet-ray, for example, polytetrafluoroethylene.

  It is preferable that the inner wall surface of the treatment tank 14B is subjected to a treatment that efficiently reflects ultraviolet rays, for example, a mirror treatment.

  As long as the hydrogen peroxide contained in the waste liquid 1 can be decomposed by irradiation of the waste liquid 1 with ultraviolet rays, the irradiation step in the treatment method of the present invention can be carried out using any apparatus and combining the apparatuses as necessary. The said apparatus is not limited to processing tank 14A, 14B shown to FIG.

  The measuring device 18 is, for example, a hydrogen peroxide sensor.

  The measurement step in the treatment method of the present invention can be carried out by applying a known method for measuring the concentration of hydrogen peroxide in the solution, for example, a titration method, a UV absorption method, or a near infrared absorption method. In the case of a waste liquid containing sulfuric acid or a waste liquid containing ammonia, not only the concentration of hydrogen peroxide is directly measured, but also the chemical oxygen demand (COD) of waste liquid 1 is measured, and the measured COD value is converted into peroxidation. The concentration of hydrogen may be used.

  A person skilled in the art can appropriately control the control of the ultraviolet irradiation conditions using the measuring device 18 and the control device 31.

  FIG. 4 shows another example of the processing apparatus of the present invention. An apparatus 52 shown in FIG. 4 includes a storage tank 12 that temporarily stores waste liquid 1 containing an acid or base and hydrogen peroxide, an introduction pipe 11 that introduces the waste liquid 1 into the storage tank 12, and a waste liquid. 1, a treatment tank 14 for irradiating ultraviolet rays, a pipe 13 and a pump P for sending the waste liquid 1 from the storage tank 12 to the treatment tank 14, a discharge pipe 15 for discharging the waste liquid 1 from the treatment tank 14 to the outside of the apparatus 51, and a discharge pipe 15, a measuring device 18 for measuring the concentration of hydrogen peroxide in the waste liquid 1 that has passed through the treatment tank 14, and at least a part of the waste liquid 1 that has been provided in the middle of the discharge pipe 15 and has passed through the treatment tank 14. A valve 16 that branches off from the pipe 15, a reflux pipe 17 that circulates the waste liquid 1 branched off in the valve 16 to the storage tank 12 and mixes it with the waste liquid 1 before being irradiated with ultraviolet rays, and a control device 32 are provided. The control device 32 compares the concentration measured by the measuring device 18 with the reference value of the concentration, and controls the operation of the valve 16 when the measured concentration exceeds the reference value, and passes through the treatment tank 14. The waste liquid 1 is circulated to the storage tank 12 through the reflux pipe 17, and the amount mixed with the waste liquid 1 in the storage tank 12 is controlled. More specifically, in this case, the recirculation and mixing by the valve 16 and the recirculation pipe 17 are started, or the amount of the waste liquid 1 to be recirculated and mixed when the recirculation and mixing are already performed. increase. The apparatus 52 includes a treatment tank 14 as an ultraviolet irradiation mechanism, a measurement apparatus 18 as a measurement mechanism, a valve 16 and a circulation pipe 17 as the circulation mechanism (A), and a control device 32 as the circulation control mechanism (A). .

  The waste liquid 1 is sent to the storage tank 12 through the introduction pipe 11 and then sent to the treatment tank 14 through the pipe 13 by the pump P. In the treatment tank 14, a step (irradiation step) of irradiating the waste liquid 1 with ultraviolet rays to decompose hydrogen peroxide contained in the waste liquid is performed. The waste liquid 1 that has undergone the irradiation process is sent out of the apparatus 51 through the discharge pipe 15. At that time, the concentration of hydrogen peroxide in the waste liquid 1 that has undergone the irradiation process is measured by a measuring device 18 provided in the middle of the discharge pipe 15 (measuring process). The control device 32 performs the above-described control (control process).

  When the apparatus 52 is started up or when the concentration of hydrogen peroxide contained in the waste liquid 1 in the storage tank 12 becomes high, decomposition / removal of hydrogen peroxide in the treatment tank 14 may not reach a desired level. is there. At this time, in the processing method implemented in the device 52 and the device 52, the valve 16 is operated to circulate at least a part of the waste liquid sent out from the processing tank 14 to the storage tank 12, and the waste liquid in the storage tank 12 is returned. The concentration of hydrogen peroxide in 1 can be reduced, and the irradiation process can be performed again on the circulated waste liquid 1. That is, the decomposition of hydrogen peroxide contained in the waste liquid 1 becomes more reliable.

  The “reference value” to be compared in the control device 32 (control process) can be arbitrarily set by the user of the device 52. The reference value is, for example, the upper limit concentration of hydrogen peroxide required when the acid or base from the waste liquid 1 is reused or when the waste liquid 1 is discharged.

  In the apparatus 52 and the processing method implemented in the apparatus 52, when the concentration of hydrogen peroxide in the waste liquid 1 after the irradiation process measured by the measuring apparatus 18 exceeds the reference value, the controller 32 causes the circulation mechanism to The recirculation / mixing of the waste liquid 1 starts or the recirculation / mixing amount of the waste liquid 1 is increased. Here, depending on the specific configuration of the device 52, more specifically, from the start of the recirculation / mixing of the waste liquid 1 or from the increase of the recirculation / mixing amount of the waste liquid 1 until the effect is actually obtained. In this case, a time lag may occur until the concentration of hydrogen peroxide measured by the measuring device 18 starts to decrease and falls below the reference value. In such a case, if the reference value is set to the upper limit concentration, waste liquid having a hydrogen peroxide concentration that temporarily exceeds the upper limit concentration may be discharged from the device 52. When such discharge becomes a problem, a concentration obtained by subtracting a certain value from the upper limit concentration may be used as a reference value.

  When the concentration of hydrogen peroxide in the waste liquid 1 measured by the measuring device 18 is equal to or less than the reference value of the concentration, the control device 32 may reduce the amount of reflux / mixing of the waste liquid 1 by the reflux mechanism. -Mixing may be stopped.

  In the apparatus 52 and the above-described method implemented in the apparatus 52, the reflux / mixing amount of the waste liquid 1 by the reflux mechanism may be zero, or the reflux / mixing may always be performed.

  In the apparatus 52 and the above method implemented in the apparatus 52, in the measurement process (in the measurement apparatus 18), the concentration of hydrogen peroxide in the waste liquid 1 that has undergone the irradiation process (through the treatment tank 14) is continuously measured and controlled. In the process (in the control device 32), the reflux and mixing of the waste liquid 1 described above may be continuously controlled by continuously comparing the measured concentration and the reference value. In this case, even when the concentration of hydrogen peroxide contained in the waste liquid 1 to be treated changes with time, the followability of the treatment to the change is improved, and hydrogen peroxide can be more stably decomposed and removed. Become.

  The reflux mechanism is not limited to the valve 16 and the reflux pipe 17 shown in FIG. The return destination of the waste liquid 1 is not limited to the storage tank 12. The recycled waste liquid 1 may be mixed with the waste liquid 1 before the irradiation process is performed.

  A person skilled in the art can appropriately construct control of the ring flow rate of the waste liquid 1 using the measuring device 18 and the control device 32.

  FIG. 5 shows another example of the processing apparatus of the present invention. An apparatus 53 shown in FIG. 5 includes a storage tank 12 that temporarily stores waste liquid 1 containing acid or base and hydrogen peroxide, an introduction pipe 11 that introduces the waste liquid 1 into the storage tank 12, and a waste liquid. 1, a treatment tank 14 for irradiating ultraviolet rays, a pipe 13 and a pump P for sending the waste liquid 1 from the storage tank 12 to the treatment tank 14, a discharge pipe 15 for discharging the waste liquid 1 from the treatment tank 14 to the outside of the apparatus 51, and a discharge pipe 15, ultraviolet light is irradiated to a measuring device 18 that measures the concentration of hydrogen peroxide in the waste liquid 1 that has passed through the treatment tank 14 and an accelerator 2 that promotes the decomposition of hydrogen peroxide by ultraviolet irradiation. The accelerator tank 21 to be added to the previous waste liquid 1, the valve 19 for adjusting the addition amount of the accelerator 2, and the controller 33 are provided. The control device 33 compares the concentration measured by the measuring device 18 with the reference value of the concentration, and controls the operation of the valve 19 when the measured concentration exceeds the reference value, and promotes to the waste liquid 1. The amount of agent 2 added is controlled. More specifically, in this case, the addition of the accelerator 2 by the valve 19 and the accelerator tank 21 is started, or the addition amount of the accelerator 2 to the waste liquid 1 when the addition has already been performed. Increase. The accelerator tank 21 is connected to the storage tank 12, and the accelerator 2 is added to the waste liquid 1 in the storage tank 12. The apparatus 53 includes a treatment tank 14 as an ultraviolet irradiation mechanism, a measurement apparatus 18 as a measurement mechanism, a valve 19 and a promoter tank 21 as the accelerator addition mechanism (C), and a promoter control mechanism (C). And a control device 33.

  The waste liquid 1 is sent to the storage tank 12 through the introduction pipe 11 and then sent to the treatment tank 14 through the pipe 13 by the pump P. In the treatment tank 14, a step (irradiation step) of irradiating the waste liquid 1 with ultraviolet rays to decompose hydrogen peroxide contained in the waste liquid is performed. If the accelerator 2 is added to the waste liquid 1 in the storage tank 12, an irradiation process is implemented with respect to the waste liquid 1 which the accelerator 2 mixed. The waste liquid 1 that has undergone the irradiation process is sent out of the apparatus 51 through the discharge pipe 15. At that time, the concentration of hydrogen peroxide in the waste liquid 1 that has undergone the irradiation process is measured by a measuring device 18 provided in the middle of the discharge pipe 15 (measuring process). The control device 33 performs the above-described control (control process).

  When the apparatus 53 is started up or when the concentration of hydrogen peroxide contained in the waste liquid 1 in the storage tank 12 becomes high, decomposition / removal of hydrogen peroxide in the treatment tank 14 may not reach a desired level. is there. At this time, in the apparatus 53 and the processing method implemented in the apparatus 53, the valve 19 is operated, the accelerator 2 is added from the accelerator tank 21 to the waste liquid 1, and the waste liquid 1 mixed with the accelerator 2 is irradiated with ultraviolet rays. Irradiation can be performed. That is, the decomposition of hydrogen peroxide contained in the waste liquid 1 becomes more reliable.

  The “reference value” to be compared in the control device 33 (control process) can be arbitrarily set by the user of the device 53. The reference value is, for example, the upper limit concentration of hydrogen peroxide required when the acid or base from the waste liquid 1 is reused or when the waste liquid 1 is discharged.

  In the apparatus 53 and the processing method implemented in the apparatus 53, when the concentration of hydrogen peroxide in the waste liquid 1 after the irradiation process measured by the measuring apparatus 18 exceeds the reference value, the controller 33 adds the accelerator. Addition of accelerator 2 by the mechanism begins or the amount of accelerator 2 added is increased. Here, depending on the specific configuration of the device 53, more specifically, until the effect is actually obtained after the addition of the accelerator 2 is started or the amount of the accelerator 2 is increased. There may be a time lag until the concentration of hydrogen peroxide measured by the measuring device 18 starts to decrease and falls below the reference value. In such a case, if the reference value is set to the upper limit concentration, waste liquid having a hydrogen peroxide concentration that temporarily exceeds the upper limit concentration may be discharged from the apparatus 53. When such discharge becomes a problem, a concentration obtained by subtracting a certain value from the upper limit concentration may be used as a reference value.

  In the apparatus 53 and the above-described method performed in the apparatus 53, the amount of the accelerator 2 added may be zero, and the accelerator 2 may always be added.

  In the apparatus 53 and the method implemented in the apparatus 53, in the measurement process (in the measurement apparatus 18), the concentration of hydrogen peroxide in the waste liquid 1 that has undergone the irradiation process (through the treatment tank 14) is continuously measured and controlled. In the process (in the control device 33), the addition of the accelerator 2 described above may be continuously controlled by continuously comparing the measured concentration with a reference value. In this case, even when the concentration of hydrogen peroxide contained in the waste liquid 1 to be treated changes with time, the followability of the treatment to the change is improved, and hydrogen peroxide can be more stably decomposed and removed. Become.

  The accelerator 2 is not particularly limited. The accelerator 2 includes a substance that consumes hydrogen peroxide, or a substance that consumes hydroxy radicals (.OH) generated by the decomposition of hydrogen peroxide by irradiation with ultraviolet rays. The accelerator 2 is, for example, ozone. Ozone consumes hydroxy radicals.

  Hydroxy radicals (.OH) generated by decomposition of hydrogen peroxide by ultraviolet irradiation decompose organic substances. That is, hydroxy radicals (.OH) are consumed also by organic substances. For this reason, the accelerator 2 may contain an organic substance, specifically, a solution containing an organic substance. The organic substance is, for example, an organic solvent or a resin, and the resin includes a resist material discharged from the semiconductor element manufacturing process.

  When the accelerator 2 contains an organic substance, considering the reuse of the acid or base contained in the waste liquid 1, the amount of the organic substance is preferably such that it is almost consumed by the reaction with the hydroxy radical in the irradiation step. The amount is about several ppm in terms of concentration. When the waste liquid 1 to be treated contains an organic substance from the beginning such as a waste liquid discharged from the resist stripping process, it is preferable to pay attention to the concentration of the organic substance in the waste liquid 1 after the addition of the accelerator 2 containing the organic substance. Of course, when it does not matter that organic matter is contained in the waste liquid that has passed through the treatment method or treatment apparatus of the present invention, paying attention to simply accelerating the decomposition of hydrogen peroxide by consuming hydroxy radicals, Including accelerator 2 may be used.

  The accelerator 2 can be added to the waste liquid 1 to be treated at any point before the irradiation of the waste liquid 1 with ultraviolet rays is completed. For example, in the apparatus 54 shown in FIG. 6, the accelerator 2 is added to the waste liquid 1 between the storage tank 12 and the processing tank 14. In the apparatus 55 shown in FIG. 7, the accelerator 2 is added to the waste liquid 1 in the treatment tank 14.

  The processing method of the present invention may include control steps for performing each of the above (a) to (c) in any combination. The treatment method of the present invention may include a control step for performing all of the above (a) to (c). An example of the processing apparatus of the present invention for carrying out such a processing method is shown in FIG. The apparatus 56 of FIG. 8 includes an ultraviolet irradiation mechanism, a measurement mechanism, and all the mechanisms (A) to (C). Reference numeral 34 in FIG. 8 is a control device that also serves as a reflux control mechanism, an ultraviolet light control mechanism, and an accelerator control mechanism.

  The processing apparatus of this invention may be equipped with the mechanism of said (A)-(C) in arbitrary combinations.

  The treatment method and the treatment apparatus of the present invention make it possible to decompose and remove hydrogen peroxide in a waste liquid containing an acid or base and hydrogen peroxide and to reuse the acid or base. With the processing method and processing apparatus of the present invention, for example, the manufacturing cost of semiconductor elements can be reduced and the environment can be protected.

DESCRIPTION OF SYMBOLS 1 Waste liquid 2 Promoter 11 Introducing pipe 12 Storage tank 13 Piping 14, 14A, 14B Treatment tank 15 Discharge pipe 16 Valve 17 Recirculation pipe 18 Measuring device 19 Valve 21 Promoter tank 31, 32, 33, 34 Control device 41 (ultraviolet light ) Light source 42 Piping 51, 52, 53, 54, 55, 56 (Waste liquid treatment) device

Claims (10)

An irradiation step of irradiating a waste liquid containing an acid or base and hydrogen peroxide with ultraviolet rays to decompose hydrogen peroxide contained in the waste liquid;
A measuring step of measuring the concentration of hydrogen peroxide in the waste liquid that has undergone the irradiation step;
When the concentration of hydrogen peroxide measured in the measurement step is compared with the reference value of the concentration, and the measured concentration exceeds the reference value, the following (a), (b) and A control step of performing at least one selected from (c);
A method for treating a waste liquid containing acid or base and hydrogen peroxide.
(A) starting at least a part of the reflux of the waste liquid that has undergone the irradiation step and mixing of the waste liquid that has been refluxed with respect to the waste liquid before the irradiation step is performed, or Increasing the amount of the reflux and mixing of the waste liquid that has undergone the irradiation step when already done,
(B) changing the irradiation condition of the ultraviolet light to the waste liquid in the irradiation step in a direction in which the decomposition of hydrogen peroxide contained in the waste liquid is promoted;
(C) To start the addition of an accelerator that promotes the decomposition of hydrogen peroxide by ultraviolet irradiation with respect to the waste liquid before the irradiation step, or when the addition has already been performed, The amount of the accelerator added to the waste liquid before the irradiation step is performed is increased. (B)
The processing method according to claim 1, wherein, in the irradiation step, the irradiation amount of ultraviolet light with respect to the waste liquid of unit amount is increased.   The processing method according to claim 1, wherein the accelerator is a solution containing organic matter or ozone.   The treatment method according to claim 1, wherein the acid is sulfuric acid, hydrochloric acid, or hydrofluoric acid.   The processing method according to claim 1, wherein the base is ammonia. An ultraviolet irradiation mechanism for irradiating the waste liquid containing acid or base and hydrogen peroxide with ultraviolet rays;
A measurement mechanism for measuring the concentration of hydrogen peroxide in the waste liquid after irradiation with the ultraviolet light;
A waste liquid treatment apparatus comprising an acid or a base and hydrogen peroxide, comprising at least one selected from the following (A), (B), and (C).
(A) A reflux mechanism that circulates at least a part of the waste liquid after irradiation with the ultraviolet rays and mixes with the waste liquid before the ultraviolet irradiation, and the hydrogen peroxide measured in the measurement mechanism When the measured concentration exceeds the reference value by comparing the concentration with the reference value of the concentration,
A recirculation control mechanism that initiates the recirculation and mixing by the recirculation mechanism or increases the amount of the waste liquid to be recirculated and mixed when the recirculation and mixing are already performed;
(B) When the concentration of the hydrogen peroxide measured by the measurement mechanism is compared with a reference value of the concentration, and the measured concentration exceeds the reference value,
An ultraviolet ray control mechanism for changing the irradiation condition of the ultraviolet ray to the waste liquid by the ultraviolet ray irradiation mechanism in a direction in which decomposition of hydrogen peroxide contained in the waste liquid is promoted;
(C) an accelerator addition mechanism for adding an accelerator that promotes decomposition of hydrogen peroxide by irradiation of ultraviolet rays to the waste liquid before being irradiated with the ultraviolet rays, and the peroxidation measured in the measurement mechanism When the measured concentration exceeds the reference value by comparing the concentration of hydrogen with the reference value of the concentration,
An accelerator control mechanism that starts the addition of the accelerator by the accelerator addition mechanism or increases the amount of the accelerator added when the accelerator is already added. The irradiation condition of the ultraviolet ray is an irradiation amount of the ultraviolet ray for the unit amount of the waste liquid,
The processing apparatus according to claim 6, wherein the ultraviolet ray control mechanism increases an amount of irradiation of the ultraviolet ray by the ultraviolet ray irradiation mechanism when the measured concentration exceeds the reference value.   The processing apparatus according to claim 6, wherein the accelerator is a solution containing organic matter or ozone.   The processing apparatus according to claim 6, wherein the acid is sulfuric acid, hydrochloric acid, or hydrofluoric acid. The processing apparatus according to claim 6, wherein the base is ammonia.

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