KR20060002636A - A method of recycling used etchant containing phosphoric acid - Google Patents

Abstract

The present invention relates to a method for regenerating a phosphoric acid-containing waste etching solution generated in a process such as semiconductor and TFT-LCD by precipitation separation method, wherein distilled filtrate (high concentration phosphoric acid) obtained by distilling the phosphoric acid-containing waste etching solution under reduced pressure is diluted with distilled water. And adding a precipitant to the dilute solution (phosphate aqueous solution) to separate and remove metal impurities in the dilute solution (phosphate aqueous solution) in the form of a precipitate.

The present invention can recover high purity phosphoric acid by removing more than 99.9% of the metal ions dissolved in the phosphoric acid-containing waste etching solution, and continuously regenerate the phosphoric acid-containing waste etching solution by reconstituting the phosphoric acid-containing etching solution using the recovered high purity phosphoric acid. Can be.

Precipitant, Metal Impurities, Sediment, Separation, Filtering, Waste Etch, High Purity Phosphoric Acid, Regeneration, Ion Exchange Resin, Electrochemical Activation.

Description

{A method of recycling used etchant containing phosphoric acid}             

1-4 are process schematic diagrams of the present invention.

The present invention relates to a method for regenerating waste acid-containing waste etchant generated in a manufacturing process such as semiconductor and TFT-LCD (Thin Film Transistor-Liquid Crystal Display) by precipitation separation method.

Phosphoric Acid (H ₃ PO ₄ ) and other mixed acids containing nitric acid and acetic acid (hereinafter referred to as "phosphoric acid-containing mixed acids") as main components for etching aluminum and molybdenum in the manufacture of TFT-LCD, etc. In the phosphoric acid-containing mixed acid used in the etching process, a trace amount of a metal component including aluminum and molybdenum is dissolved.

Hereinafter, in the present invention, the above-mentioned phosphoric acid-containing mixed acid used for etching aluminum, etc., during TFT-LCD manufacturing is abbreviated as "phosphate-containing etching liquid", and aluminum, molybdenum, etc. during manufacturing of TFT-LCD, etc. The phosphoric acid-containing mixed solution, which is used to etch a metal film of the metal and in which a small amount of a metal component including aluminum, molybdenum and the like is dissolved, is abbreviated as "phosphate-containing waste etching liquid".

More specifically, the present invention relates to a method for regenerating a phosphoric acid-containing waste etching solution by removing 99.9% or more of metal ions dissolved in the phosphoric acid-containing waste etching solution to recover high-purity phosphoric acid, and reconstituting the phosphoric acid-containing etching solution. .

In more detail, processes in which phosphoric acid-containing etching liquids are used in manufacturing processes such as semiconductors and TFT-LCDs may be described. The phosphoric acid-containing etching liquid may be a process for removing mechanical defects generated during the cutting and polishing process during the silicon single crystal wafer manufacturing process. (Ii) a process of selectively depositing a silicon nitride film as an insulating film in the manufacture of semiconductor devices, and (i) selectively etching an electrode made of aluminum / molybdenum during TFT-LCD manufacturing.

A method of recovering high-purity phosphoric acid from the phosphoric acid-containing waste liquor used in the above processes and using the same for reconstituting the phosphoric acid-containing etchant, that is, a method of regenerating the phosphoric acid-containing etchant, has not been developed until now.

Therefore, until now, the phosphoric acid-containing waste etching solution has been simply processed by a conventional neutralization precipitation method and then used in the fertilizer manufacturing process. However, since the high purity phosphoric acid is expensive, the high purity phosphoric acid is recovered from the phosphoric acid-containing waste etching solution and reused. It is economically undesirable compared with.

As a conventional technique for purifying phosphoric acid, a distillation method is widely used, but in this case, fluorides such as silicon tetrafluoride are removed, but metals such as aluminum, molybdenum, and magnesium are not removed, and thus the limit cannot be used for regeneration of the waste etching solution containing phosphoric acid. There was.

In addition, as a conventional technique for purifying phosphoric acid, a solvent extraction method and a method of filtering using a porous filter having an average particle diameter of pores of nano or micro level are known from the paper and US Patent No. 4,277,448. Metal ions such as aluminum and molybdenum contained in the etchant could not be effectively removed, and thus, they could not be used for regeneration of the phosphate-containing waste etchant.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of efficiently regenerating a phosphoric acid-containing waste etchant by recovering and reusing high purity phosphoric acid from a phosphoric acid-containing waste etchant by solving the problems of the prior art as described above.

The present invention is to provide a method for regenerating the phosphoric acid-containing waste etching solution by recovering the high-purity phosphoric acid from the phosphoric acid-containing waste etching solution generated in the manufacturing process, such as semiconductor and TFT-LCD, and then reconstituting the phosphoric acid-containing etching solution.

To this end, the present invention is to provide a method for separating and removing the co-precipitation by forming molybdenum as a central element in the metal impurity in the phosphoric acid-containing waste etching solution.

More specifically, in the present invention, a precipitant is added to a diluent (aqueous phosphate solution) obtained by distilling the distilled filtrate (high concentration phosphoric acid) obtained by distillation under reduced pressure of a phosphoric acid-containing waste etching solution to form a precipitate containing molybdenum as a central element. It is intended to provide a method of causing co-precipitation of a complex compound in which other metal impurities are a central element, and removing the generated precipitate by a method such as centrifugation.

Regeneration method of the phosphoric acid-containing waste etching solution of the present invention to achieve such a problem, a diluent by adding a precipitant to the dilution (aqueous phosphoric acid solution) diluted distilled water distilled filtrate (high concentration phosphoric acid) obtained by distilling the phosphoric acid-containing waste etching solution under reduced pressure (Aqueous phosphate solution) is characterized in that it comprises a step of separating, removing the metal impurities in the form of precipitate.

In addition, the present invention is characterized by including the following steps.

  -Below-

(Iii) distilling under reduced pressure the phosphoric acid-containing waste etchant;

(Ii) diluting the distillation filtrate (high concentration phosphoric acid) obtained by the distillation under reduced pressure with distilled water;

(Iii) adding a precipitant to the diluent (aqueous phosphoric acid solution) obtained in the dilution step to convert metal impurities in the dilution into a precipitate;

(Iii) separating and removing precipitates of metal impurities in a dilute solution (phosphate aqueous solution);

(Iii) treating and / or filtering activated diluent (aqueous phosphate solution) from which precipitates of metal impurities are separated and removed;

(Iii) recovering high purity phosphoric acid by subjecting activated carbon treatment and / or filtered dilution (aqueous phosphoric acid solution) to sublimation;

(Iii) A process for reconstituting an etching solution containing phosphoric acid using the recovered high purity phosphoric acid.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 to 4 are process schematic diagrams of the present invention.

First, the present invention is distilled under reduced pressure to phosphate-containing waste etching solution in order to remove a compound having strong oxidizing properties, such as nitric acid contained in the phosphoric acid-containing waste etching solution as shown in FIGS.

The vacuum distillation may be adopted as a vacuum distillation method and a thin film vacuum distillation method using a thin film evaporator.

 Since high-viscosity phosphoric acid easily polymerizes when heated, it is more preferable to adopt a thin film vacuum distillation method at a relatively low temperature range from room temperature to 150 ° C.

Through the vacuum distillation process to increase the phosphoric acid content in the phosphoric acid-containing waste etching solution to more than 90% by weight.

The distillate separated in the distillation under reduced pressure is more preferably supplied and reused in the process of reconstituting the phosphate-containing etching solution with high-purity phosphoric acid recovered from the phosphate-containing waste etching solution as shown in FIGS.

Next, as shown in FIGS. 1 to 4, the distillation filtrate (high concentration phosphoric acid) obtained in the vacuum distillation process is diluted with distilled water, followed by a dilution process for preparing a dilution liquid (aqueous phosphoric acid solution).

The dilution process is then carried out at an appropriate concentration to increase the efficiency of the treatment process.

In the dilution process, it is preferable to adjust the concentration of phosphoric acid in the diluent to be 50% or less, and in the dilution process, it is preferable to use distilled water whose content of metal impurities is deionized water of 10 ppt (part per trilion) or less for each element. desirable.

Next, a precipitant is added to the dilution liquid (phosphate aqueous solution) obtained in the dilution process as shown in FIGS. 1 to 4 to change the metal impurities in the dilution liquid into a precipitate form.

In the process, molybdenum present in various chemical species forms in diluent solution (phosphate aqueous solution) becomes a central element to form a complex compound with a precipitant, and the complex compound polymerizes to form a precipitate to separate the diluent and metal impurities. Is carried out. More specifically, molybdenum among the metal components in the dilute phosphoric acid-containing etch solution forms a precipitate, and other metal impurities that may form complexes with the added precipitant are precipitated together in the form of precipitation and are easily separated and removed. It is for conversion.

The precipitant is Di-thio-Carbamate, Ammonium-Pyrolydine-di-thio-Carbamate, Sodium-diethyl-di- Thio-carbamate and the like.

Next, the process of separating and removing the metal impurities transformed by precipitation as shown in Figures 1 to 4. Metal impurities transformed by sedimentation can be separated and removed by centrifugal separation or pressure filtering. Specifically, when the precipitate and the dilution filtrate is rotated at a high speed in the centrifuge, the precipitate and the filtrate can be separated. In this process, pressurized filtration can be applied according to conditions such as treatment capacity.

Next, as shown in FIGS. 1 to 4, the process of filtering and / or filtering activated diluent (filtrate) from which precipitates of metal impurities are separated and removed.

The diluent (filtrate) may be treated only with activated carbon, may be filtered only, or may be activated carbon and then filtered.

The activated carbon treatment may be carried out by passing the diluted filtrate into a separation tube filled with activated carbon.

In this method, the unreacted precipitant and the metal complex including the organic component in the dilute filtrate are adsorbed and removed on the surface of the porous activated carbon fine particles.

The filtering treatment is performed by a reverse osmosis membrane filtering method or a nano filtering method.

The filtering process is a process to remove the residual precipitant and other impurities present in the trace amount in the diluent to obtain a high purity dilution filtrate.

Nano-filtering is carried out using a porous polymer membrane having a pore size of 0.0001 ~ 0.001㎛.

As the material of the polymer porous membrane, various polymers such as polyimide, polyamide, Teflon, and the like may be used.

Next, the distillate (phosphate aqueous solution) treated with activated carbon and / or filtered as described above is subjected to a reduced pressure distillation process to recover high purity phosphoric acid by separating and removing distilled water by distillation under reduced pressure as shown in FIG. 1. The distillation under reduced pressure is a process of concentrating the purified diluent (aqueous phosphate solution) into a high-purity phosphate solution having a phosphoric acid concentration of 90% or more, so that the highly viscous phosphoric acid is polymerized by heating in a low temperature range of room temperature to 150 ° C. It is more preferable to employ a thin film vacuum distillation method.

Distilled water from the distillation under reduced pressure distillation is supplied to the dilution process of the distillation filtrate (high concentration phosphoric acid) described above is preferable for waste reduction and sequencing of the process.

Next, the present invention is completed through a process of reconstituting a phosphoric acid-containing etching solution using high purity phosphoric acid recovered in the vacuum distillation process as shown in FIG. 1.

On the other hand, in the present invention, before distillation under reduced pressure of the activated carbon treated and / or filtered treatment dilution (phosphate aqueous solution) as described above (iii) the activated carbon treated and / or filtered treated diluent (aqueous phosphoric acid solution) as shown in Figure 2 Activated and treated with cation exchange resin or (ii) activated carbon treated and / or filtered dilution (aqueous phosphate solution) as shown in FIG. 3, cation exchange resin, anion exchange resin, mixture of cation exchange resin and anion exchange resin or chelate Treatment with resin first, followed by electroactivation and treatment with cation exchange resin, or (iii) activated carbon treatment and / or filtered dilution (aqueous phosphate solution) as shown in FIG. 4, followed by treatment with cation exchange resin and cation again. It may be treated with exchange resin, anion exchange resin, mixture of cation exchange resin and anion exchange resin or chelate resin. The.

In order to electrochemically activate the activated carbon and / or filtered dilution (aqueous phosphate solution), a special electrode is used to apply an alternating current having a voltage of 0.1 to 10 V and a frequency of 50 to 1,000,000 Hz. The method of giving is preferable.

When a direct current is applied to the diluent instead of an alternating current, metal ions may be deposited on the electrode surface, thereby reducing the efficiency of the electrode.

The various ion exchange resins used at this time preferably have a functional group suitable for removing trace ions of the metal compound at a suitable surface density.

The flow rate of the diluent (phosphate aqueous solution) passing through the ion exchange resin is 1.0 to 5.0 sV, more preferably 1.5 to 2.5 sV.

As described above, according to the present invention, a distillation filtrate (high concentration phosphoric acid) obtained by distilling the phosphoric acid-containing waste etching solution under reduced pressure is diluted with distilled water to prepare a dilution solution (aqueous phosphoric acid solution), and then a precipitant is added to the dilution solution to contain the metal contained in the dilution solution. Since the precipitated compounds are separated and removed, the metal impurities can be effectively separated and removed.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

However, the present invention is not limited only to the following examples.

Example 1

Phosphoric acid-containing waste etchant (metal impurity content such as aluminum and molybdenum: 200ppm) discharged from TFT-LCD manufacturing process was put into a vacuum distillation and distilled under reduced pressure at 120 ℃ to separate and remove distillate such as nitric acid. Distillation filtrate (high concentration phosphoric acid) was obtained. At this time, the separated distillate was used by feeding to the re-formation process of the phosphoric acid-containing etching solution.

Subsequently, the distillation filtrate (high concentration phosphoric acid) obtained by the distillation under reduced pressure was diluted with distilled water, and diluted to obtain a concentration of phosphoric acid in the dilution solution to 20% to obtain a dilution solution (phosphate aqueous solution).

Subsequently, di-thio-carbamate as a precipitant was added to the dilute solution (phosphate aqueous solution) to precipitate metal impurities in the dilute solution (high concentration phosphoric acid). At this time, the input amount of the precipitant was 1.5 times the amount of metal ions in the molar ratio, and the input method was a mixing and stirring method.

Subsequently, the precipitate of the metallic impurity in a dilute solution (phosphate aqueous solution) was isolate | separated and removed by centrifugation.

Subsequently, a diluent (aqueous phosphoric acid solution) in which the precipitate was separated and removed as described above was passed through the activated carbon column to remove the micrometal complex and the residual precipitant present in the diluent.

Subsequently, the dilution (phosphate aqueous solution) treated as described above was put in a vacuum distillation and distilled under reduced pressure at 100 ° C to separate high-purity phosphoric acid and distillate (distilled water), and distillate (distilled water) was supplied to the dilution process. It was reused and the high purity phosphoric acid was transferred to the reconstitution process of the phosphoric acid-containing etching solution.

Subsequently, a small amount of the distillate (oxidizing agent such as nitric acid) obtained in the vacuum distillation step of the phosphoric acid-containing waste etching solution and other necessary compounds were mixed with the high-purity phosphoric acid recovered as described above to reconstitute the phosphoric acid-containing etching solution.

The results of measuring the contents of metal impurities such as aluminum and molybdenum dissolved in the regenerated phosphoric acid-containing etchant are shown in Table 1.

Example 2

Phosphoric acid-containing waste etchant (metal impurity content such as aluminum and molybdenum: 200ppm) discharged from the TFT-LCD manufacturing process was put into a vacuum distillation and distilled under reduced pressure at 120 ℃ to separate and remove distillate such as nitric acid. Distillation filtrate (high concentration phosphoric acid) was obtained. At this time, the separated distillate was used by feeding to the re-formation process of the phosphoric acid-containing etching solution.

Subsequently, the distillation filtrate (high concentration phosphoric acid) obtained by the distillation under reduced pressure was diluted with distilled water, and diluted to obtain a concentration of phosphoric acid in the dilution solution to 20% to obtain a dilution solution (phosphate aqueous solution).

Subsequently, di-thio-carbamate as a precipitant was added to the dilute solution (phosphate aqueous solution) to precipitate metal impurities in the dilute solution (high concentration phosphoric acid). At this time, the input amount of the precipitant was 1.5 times the amount of metal ions in the molar ratio, and the input method was a mixing and stirring method.

Subsequently, the precipitate of the metallic impurity in a dilute solution (phosphate aqueous solution) was isolate | separated and removed by the pressure filtering method.

Subsequently, the dilution (phosphate aqueous solution) in which the precipitate is separated and removed as described above is passed through the activated carbon column to remove the micro metal complex and residual precipitant present in the diluent, followed by using a polyamide porous membrane having a pore size of 0.001 μm. Nano filtered at room temperature.

Subsequently, an alternating current of 1 V and a frequency of 1,000 kHz was applied to the nano-filtered diluent (aqueous phosphate solution) to electrochemically activate the diluent (aqueous phosphate solution), and then passed through a tower containing a cation exchange resin. .

At this time, the flow rate of the diluted solution (phosphate aqueous solution) was 2.0 sV.

Subsequently, the dilution (phosphate aqueous solution) treated as described above was put in a vacuum distillation and distilled under reduced pressure at 100 ° C to separate high-purity phosphoric acid and distillate (distilled water), and the distillate (distilled water) was supplied to the dilution process and reused. Then, the high purity phosphoric acid was transferred to the recomposition process of the phosphoric acid-containing etching solution.

Subsequently, a small amount of the distillate (oxidizing agent such as nitric acid) obtained in the vacuum distillation step of the phosphoric acid-containing waste etching solution and other necessary compounds were mixed with the high-purity phosphoric acid recovered as described above to reconstitute the phosphoric acid-containing etching solution.

The results of measuring the contents of metal impurities such as aluminum and molybdenum dissolved in the regenerated phosphoric acid-containing etchant are shown in Table 1.

Comparative Example 1

Except that no precipitant was added to the dilute solution (phosphate aqueous solution), the phosphoric acid-containing waste etching solution was purified in the same process and conditions as in Example 1 to recover high purity phosphoric acid, and then the phosphoric acid-containing etching solution was reconstituted.

The results of measuring the contents of metal impurities such as aluminum and molybdenum dissolved in the regenerated phosphoric acid-containing etchant are shown in Table 1.

Metal impurities content measurement result division Waste etching solution before regeneration Etch solution after regeneration Aluminum content (ppm) Molybdenum content (ppm) Aluminum content (ppm) Molybdenum content (ppm) Example 1 100 100 0.01 0.02 Example 2 100 100 0.01 0.01 Comparative Example 1 100 100 0.20 0.15

The present invention can efficiently recycle and use the phosphoric acid-containing waste etchant generated in manufacturing processes such as semiconductors and TFT-LCDs, which is economically advantageous and also advantageous in preventing environmental pollution.

In particular, the present invention has the effect of efficiently recovering high-purity phosphoric acid from the phosphoric acid-containing waste etching solution, which is useful for silicon single crystal wafer manufacturing process, semiconductor device manufacturing process, TFT-LCD manufacturing process and plating process such as anodizing. Can be applied.

Claims (11)

In the regeneration treatment of the phosphoric acid-containing waste etching solution by the distillation under reduced pressure distillation and sedimentation, a precipitant is added to the diluent (aqueous phosphoric acid solution) obtained by distilling the distillation filtrate (high concentration phosphoric acid) obtained by distillation under reduced pressure with distilled water. A method for regenerating a phosphate-containing waste etching solution comprising the step of separating and removing the metal impurities in the aqueous solution of phosphoric acid into a precipitate form. A method for regenerating a phosphoric acid-containing waste etchant comprising the following steps.  -Below- (Iii) distilling under reduced pressure the phosphoric acid-containing waste etchant; (Ii) diluting the distillation filtrate (high concentration phosphoric acid) obtained by the distillation under reduced pressure with distilled water; (Iii) adding a precipitant to the diluent (aqueous phosphoric acid solution) obtained in the dilution step to convert metal impurities in the dilution into a precipitate; (Iii) separating and removing precipitates of metal impurities in a dilute solution (phosphate aqueous solution); (Iii) treating and / or filtering activated diluent (aqueous phosphate solution) from which precipitates of metal impurities are separated and removed; (Iii) recovering high purity phosphoric acid by subjecting activated carbon treatment and / or filtered dilution (aqueous phosphoric acid solution) to sublimation; (Iii) A process for reconstituting an etching solution containing phosphoric acid using the recovered high purity phosphoric acid. The method of regenerating a phosphoric acid-containing waste etchant according to claim 2, wherein the precipitate of the metallic impurities in the dilute solution (phosphate aqueous solution) is separated and removed by centrifugal separation or pressure filtering. The method of regenerating phosphate-containing waste etchant according to claim 2, wherein the diluent (phosphate aqueous solution) from which the precipitate of the metal impurity is separated and removed is filtered by a nano filtering method or a reverse osmosis membrane filtering method. The method of claim 2, wherein the activated carbon treatment and / or filtered diluent (aqueous phosphate solution) is electrochemically activated and then treated with a cation exchange resin. The process according to claim 5, wherein the electrochemically activated diluent (aqueous phosphoric acid solution) is treated with a cation exchange resin, and then treated with a cation exchange resin, an anion exchange resin, a mixture of a cation exchange resin and an anion exchange resin or a chelate resin. A method for regenerating a phosphate-containing waste etching solution, characterized in that. The method according to claim 5, wherein the activated carbon treatment and / or filtered dilution (aqueous phosphate solution) is treated with a cation exchange resin, an anion exchange resin, a mixture of a cation exchange resin and an anion exchange resin, or a chelate resin before electrochemically activating. A method of regenerating phosphate-containing waste etching solution.  The method of regenerating a phosphoric acid-containing waste etchant according to claim 5, wherein an alternating current having a voltage of 0.1 to 10 V and a frequency of 50 to 1,000,000 Hz is applied to the nano-filtered diluent (aqueous phosphate solution) to electrochemically activate the diluent. The method of regenerating a phosphoric acid-containing waste etching solution according to claim 2, wherein the distillation filtrate (high concentration phosphoric acid) is diluted with distilled water so that the concentration of phosphoric acid in the dilution liquid (phosphate aqueous solution) is 50% or less. The method of regenerating a phosphoric acid-containing waste etchant according to claim 2, wherein the recovered high-purity phosphoric acid and the distillate obtained by distillation under reduced pressure of the phosphoric acid-containing waste etchant are mixed. The method according to claim 1 or 2, wherein the precipitant is di-thio-carbamate, ammonium-pyrolydine-di-thio-carbamate, Sodium-dimethyl-di-thio-carbamate (Sodium-diethyl-di-thio-Carbamate), characterized in that the regeneration of the phosphate-containing waste etching solution.

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