JP2002239568A - Treating method of waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treating method of waste liquid which can efficiently treat waste liquid discharged from in a chemical mechanical polish process (CMP waste liquid), containing colloidal silica, copper compounds, hydrogen peroxide, and COD components, and stably obtain high-quality treated water at a low cost. SOLUTION: The CMP waste liquid, which contains colloidal silica, copper compounds, hydrogen peroxide, and COD components, and the like are treated with primary pH adjustment, membrane separation, and secondary pH adjustment in sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a waste liquid containing colloidal silica as a main component and containing a copper compound, and more particularly to a method for treating a waste liquid suitable for a chemical mechanical polishing waste liquid. .

[0002]

2. Description of the Related Art Chemical mechanical polishing (Chemical Me)
chemical Polish, hereinafter abbreviated as CMP)
Indicates that the surface of the silicon wafer base material is L
It is introduced in the middle of a semiconductor manufacturing process for processing SI, and is employed for flattening the surface of an unprocessed bare silicon wafer. This CMP is frequently used as the degree of integration of the semiconductor is improved, that is, as the multilayer structure of the LSI is advanced, and the CMP waste liquid discharged from the semiconductor factory tends to increase year by year.

[0003]

By the way, in CMP, abrasive particles containing colloidal silica as a main component are dissolved in an electrolyte solution such as an ammonium salt, an oxidizing agent such as hydrogen peroxide, an acid such as nitric acid, potassium hydroxide or the like. A polishing slurry that is dispersed in water containing an inorganic alkali agent, an organic dispersant such as an organic alkali, or the like is used, but the following problems occur when the CMP waste liquid is treated.

[0004] CMP slurries are mainly composed of colloidal silica, and have a solid concentration of several thousand to several tens of thousands mg / L.
In addition, among the CMP processes, CMP for polishing copper wiring contains a high concentration of a copper compound, hydrogen peroxide, and a COD component. The coagulant needs to be increased significantly. That is, it is necessary to improve the chemical injection equipment in the coagulation and sedimentation, and the running cost increases with an increase in the chemical injection amount.

Since the amount of sludge after sedimentation and separation is greatly increased due to the mixing of the polishing slurry with a high solid matter concentration and the accompanying increase in the amount of chemical injection, not only an increase in sludge concentration equipment and dehydration equipment is required, but also When mixed with fluorinated waste liquid,
The sludge sedimentation performance during coagulation and sedimentation and the fluorine removal performance in fluorine-based waste liquid are slightly affected, and suddenly the fluorine-based waste liquid treatment equipment cannot obtain water quality below the originally targeted discharge standard value.

[0006] Since the CMP waste liquid contains a high concentration of a copper compound, hydrogen peroxide and a COD component, it is difficult to recover water and reuse the slurry only by a conventional treatment method.

The present invention has been made in view of such circumstances, and can efficiently treat a CMP waste liquid containing colloidal silica, a copper compound, hydrogen peroxide, and a COD component, and is stable, inexpensive and highly efficient. It is an object of the present invention to provide a wastewater treatment method capable of obtaining quality treated water.

[0008]

In order to achieve the above object, the present invention provides a method for treating a waste liquid according to claim 1, wherein a CMP waste liquid containing colloidal silica, a copper compound and hydrogen peroxide is subjected to ozone treatment, It is characterized in that processing is performed in the order of pH adjustment, membrane separation, and secondary pH adjustment.

Further, a waste liquid treatment method according to claim 2 of the present invention is characterized in that, in the invention described in claim 1, the primary pH adjustment is pH 5 or less.

[0010] A waste liquid treatment method according to a third aspect of the present invention is characterized in that, in the second aspect, the secondary pH adjustment is pH 5.5 or more.

According to the present invention, a C agent such as a complexing agent or a rust inhibitor is used.
The OD component utilizes hydrogen peroxide contained in the waste liquid, and supplies ozone gas thereto to decompose and remove the OD component. In this case, by using hydrogen peroxide, the oxidation-reduction potential is 2.07.
The ozone / hydrogen peroxide combined oxidation effect, which has a stronger oxidizing power of 2.85 V than the ozone treatment of V alone, can be obtained.
The copper complex is decomposed by decomposing and removing the COD component.

Next, by adjusting the primary pH to pH 5 or less, copper is ionized.

Next, the waste liquid is subjected to membrane separation after ionizing the copper, whereby the waste liquid is separated into a concentrated colloidal silica concentrate concentrated at a high concentration and a permeated water containing the ionized copper. In this case, since the COD component is removed before the membrane separation, fouling of the membrane due to the COD component hardly occurs, and the frequency of cleaning the separation membrane can be reduced. As the separation membrane, an organic polymer membrane such as polysulfone or polyacrylonitrile or an inorganic fired membrane such as silica, that is, a ceramic membrane can be used.

[0014] Next, the permeated water containing copper ions is converted into a hydroxide and precipitated and separated. Copper produces hydroxide at pH 5 or higher, so that the pH is 5.5 or higher, preferably pH 7 or higher.
To rise. Thereby, clear treated water can be obtained.

By installing sand filtration and activated carbon equipment at a later stage, the treated water can be further stabilized.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a waste liquid treatment method according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a flowchart of a waste liquid treatment system according to the present invention.

In the present invention, the waste liquid to be treated is
Colloidal silica, copper compounds, hydrogen peroxide and COD
It is a CMP waste liquid containing components.

This waste liquid treatment equipment comprises an ozone treatment tower 1 for mainly removing COD components, a primary pH adjusting tank 3, a membrane separation device 5, and a secondary pH adjusting tank 6.

The CMP waste liquid is introduced into the ozone treatment tower 1. Ozone gas generated by the ozone generator 2 is supplied to the ozone treatment tower 1, and the ozone gas is applied to the CM by the ozone.
COD components in the P waste liquid are decomposed and removed. At this time, by utilizing the hydrogen peroxide contained in the waste liquid, the effect of the combined oxidation can be obtained, and the hydrogen peroxide can be decomposed.

The treated water treated in the ozone treatment tower 1 is 1
Next, it is introduced into the pH adjustment tank 3. This primary pH adjustment tank 3
Is adjusted to pH 5 or less by an acid injected from the primary pH adjusting chemical storage tank 4. And this primary p
In the treated water introduced into the H adjusting tank 3, copper in the treated water is ionized.

Then, the treatment liquid treated in the primary pH adjusting tank 3 is passed through a membrane separation device 5. Here, the colloidal silica, which is the main component of the CMP slurry, is discharged out of the system as concentrated water. On the other hand, the ionized copper passes through the separation membrane and enters the permeated water.

The permeated water is introduced into a secondary pH adjusting tank 6. An alkaline solution is injected into the secondary pH adjustment tank 6 from a chemical storage tank 7 for secondary pH adjustment, and the pH of the secondary pH adjustment tank 6 is adjusted to 5.5 or more by the alkaline solution. Then, the copper in the permeated water introduced into the secondary pH adjusting tank 6 is converted into hydroxide.

The treatment solution treated in the secondary pH adjusting tank 6 is introduced into the sedimentation tank 8, where it is separated by precipitation and copper is discharged out of the system as sludge.

Thereafter, the treated water treated in the sedimentation tank 8 is introduced into the activated carbon tower 10 through the sand filtration tower 9, whereby COD components and solids remaining in the treated water are removed.

[0026]

EXAMPLE The CMP waste liquid used in this example was 1,200 mg / L of colloidal silica, 0.1 g of copper per solid-Cu / g-TS, 215 mg of COD by a complexing agent, a rust inhibitor and the like. / L and a weakly acidic waste liquid with a pH of 6.2.

After the waste liquid is treated with ozone, the pH of the waste liquid is adjusted to pH 4,5.
And water was passed through a ceramic membrane separator. Further, the permeated water was adjusted to pH 7 to obtain treated water. Table 1 shows a comparison between the treated water and the raw water.

[0028]

[Table 1]

Table 1 shows each water quality according to the present embodiment. The COD component contained in the raw water is decomposed and removed, and copper is reduced to 1/20 the content per solid with respect to the raw water.
Has been reduced to Further, the colloidal silica is contained in the concentrated water and is not contained in the permeated water.

[0030]

As described above, by employing the method for treating a CMP waste liquid according to the present invention, a CMP containing colloidal silica, a copper compound, hydrogen peroxide and a COD component is performed.
Waste liquid can be efficiently treated, clear treated water can be obtained, and CMP slurry, which is very expensive and accounts for about 60% of the CMP process, can be recovered.
MP slurry can be reused and waste can be reduced. Further, since the COD component is removed before the membrane separation, fouling of the membrane due to the COD component hardly occurs, and the frequency of cleaning the separation membrane can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a waste liquid treatment system for implementing a waste liquid treatment method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ozone treatment tower, 2 ... Ozone generator, 3 ... Primary pH adjustment tank, 4 ... Chemical storage tank for primary pH adjustment, 5 ... Membrane separation device, 6 ... Secondary pH adjustment tank, 7 ... Secondary pH Adjustment chemical storage tank, 8: sedimentation tank, 9: sand filtration tower, 10: activated carbon tower

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA07 KA01 KA71 KB13 KB30 MC01 MC03 MC39 MC62 PB08 PB23 PC01 4D038 AA08 AB68 AB79 BA04 BB16 BB20 4D050 AA13 AB31 AB33 AB57 BB02 BB09 CA09 CA16

Claims (3)

[Claims] 1. A waste liquid containing colloidal silica, a copper compound and hydrogen peroxide is treated with ozone, primary pH adjustment, membrane separation,
A method for treating a waste liquid, wherein the treatment is performed in the order of secondary pH adjustment. 2. The method for treating waste liquid according to claim 1, wherein the primary pH adjustment is pH 5 or less. 3. The method for treating waste liquid according to claim 2, wherein the secondary pH adjustment is pH 5.5 or more.