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Etching waste water processing method of silicon wafer and processing device

A technology for etching wastewater and treatment method, which is applied in the fields of energy wastewater treatment, water/sewage treatment, water/sewage multi-stage treatment, etc. It can reduce the water content of sludge, improve dehydration, and reduce the necessary amount of addition.

Active Publication Date: 2014-01-29
KURITA WATER INDUSTRIES LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] Add acid such as sulfuric acid to the etching wastewater of silicon wafers to neutralize the sodium hydroxide in the wastewater, and at the same time make silicon dioxide (SiO 2 ) precipitation and coagulation separation of the precipitated silica, since the separated sludge is often in the form of a gel, the water content of the separated sludge is high, and sludge with excellent dehydration properties cannot be obtained.
In order to solve the above problems, the necessary addition amount of coagulant is increased, and as a result, there are problems that the amount of sludge generation increases and the quality of treated water is unstable.

Method used

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  • Etching waste water processing method of silicon wafer and processing device
  • Etching waste water processing method of silicon wafer and processing device
  • Etching waste water processing method of silicon wafer and processing device

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Experimental program
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preparation example Construction

[0066] [Preparation of Modified Sludge]

[0067] In the present invention, the mixing part separates sludge and acid and adds it to raw water as modified sludge. The acid mixing amount at this time is set to an amount that can sufficiently progress both the neutralization of excess sodium hydroxide and the precipitation of silica from sodium silicate according to the water quality of the raw water as described above. Usually, such as figure 1 As shown, when the modified sludge is prepared by mixing return sludge and acid in the mixing tank 4 and then added to raw water, the added acid can make the pH of the modified sludge about 4 to 6.

[0068] In addition, in the present invention, it is important to mix sludge and acid so that the surface of the sludge is sufficiently modified by the acid and then added to the raw water. Therefore, as figure 1 As shown, it is preferable to install a mixing tank 4 to mix the acid and sludge, and the mixing time, that is, the sludge resid...

Embodiment 1

[0076] The silicon wafer etching wastewater with a pH value of 13.0 and a Si concentration of 2000mg / L was used as raw water, and passed figure 1 The device shown is processed. The amount of SS produced from this wastewater was 4 g / L. Sulfuric acid was used as the acid, and Crefloc (registered trademark) PA823 (acrylamide-based anionic polymer coagulant manufactured by Kurita Kogyo Co., Ltd.) was used as the polymer coagulant, and the amount of the polymer coagulant added to the wastewater was 5 mg / L. .

[0077] The capacity (size) and pH conditions of each tank are as follows.

[0078]

[0079] Capacity: 1.0L

[0080] pH: 7~8

[0081]

[0082] Capacity: 1.0L

[0083] pH: 7~8

[0084]

[0085] Size: diameter 250mm, height of straight barrel 300mm

[0086] pH: 7~8

[0087]

[0088] Capacity: 0.3L

[0089] pH: 4~6

[0090] The raw water is treated according to the flow rate of 3.0L / hr.

[0091] Part of the solid-liquid separation sludge in the sedimentation t...

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Abstract

A task of the invention is realize the following functions in a method of adding acid in etching waste water of silicon wafer for precipitating silicon dioxide and performing solid liquid separation for the precipitated silicon dioxide: reducing a necessary adding amount of flocculant, reducing the volume of the generated sludge, reducing water content of the sludge, improving dehydration property and realizing water quality stability of the processed water. For settling the task, after the acid is combined with partial solid liquid separation sludge, the mixture is added into the etching waste water of the silicon wafer. Through adding acid into the sludge and mixing, the surface of the sludge is modified by the acid therefore the silicon dioxide is precipitated from the surface of the sludge. As a result, the amount of the water absorbed by the sludge can be maximumly restrained. Therefore, the sludge with low water content and excellent dehydration property can be obtained. Furthermore the necessary adding amount of the flocculant is little, and therefore the amount of the generated sludge is reduced. Furthermore solid-liquid separation performance of the sludge is improved, and therefore the quality of the processed water is stable.

Description

technical field [0001] The present invention relates to a kind of treatment method and treatment device of the waste water discharged when etching a silicon wafer with aqueous sodium hydroxide solution, particularly relate to adding acid to the etching waste water of this silicon wafer to precipitate silicon dioxide (SiO 2 ) and the silicon dioxide (SiO 2 ) In the method of solid-liquid separation, it is possible to reduce the necessary addition of coagulant, reduce the volume of generated sludge (reduction in the amount of sludge generated), reduce the moisture content of sludge and improve dehydration, and achieve stable water quality. Treatment methods and treatment devices. Background technique [0002] Used in the silicon wafer manufacturing process of integrated circuits such as ICs and LSIs, monolithic semiconductor elements such as transistors or diodes, using inner peripheral cutting machines or wire saws to cut through the Czochralski method (CZ method) or float a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C02F1/00C02F9/04
CPCY02W10/37
Inventor 林一树一柳直人长井悟
Owner KURITA WATER INDUSTRIES LTD