JPH11186207A - Cleaning water for electronic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide cleaning water for electronic materials, which has an enhanced cleaning effect, does not require deionization of the cleaning water when utilizing a surplus of the cleaning water as the source material for ultrapure deionized water, enabling recovery and reuse easy, by containing an oxidizing or reducing agent and carbonic acid and controlling pH of the cleaning water for electronic materials without using any chemical. SOLUTION: The cleaning water for electronic materials contains an oxidizing or reducing agent and carbonic acid, and enables to yield cleaning water having a desirable value of oxidation-reduction potential and of pH by adjusting the contained amount of the oxidizing or reducing agent and the carbonic acid depending on the object to be cleaned. For example, in using ozone as the oxidizing agent, ozone sent from an ozone generator 4 is solved into the ultrapure deionized water sent from a subsystem 2 of an ultrapure deionized water preparation system, in a gas permeable membrane module 3. Then, carbon dioxide gas sent from a carbon dioxide gas supplier 6 is solved in a gas permeable membrane module 5, to produce the cleaning water for electronic materials containing ozone and carbonic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to cleaning water for electronic materials. More specifically, the present invention relates to cleaning water for electronic materials used in wet cleaning performed in industries dealing with electronic materials such as silicon substrates for semiconductors and glass substrates for liquid crystals.

[0002]

2. Description of the Related Art Conventionally, a silicon substrate for a semiconductor, a glass substrate for a liquid crystal, and the like have been used for cleaning a mixture of sulfuric acid and hydrogen peroxide, a mixture of hydrochloric acid, hydrogen peroxide and water, and ammonia water, which is called RCA cleaning. It has been cleaned by high-temperature cleaning using a concentrated chemical based on hydrogen peroxide, such as a mixture of aqueous hydrogen peroxide and water. If this cleaning method is adopted, the cost of chemicals, the cost of ultrapure water for rinsing, the cost of waste liquid treatment, and the cost of air conditioning that exhausts chemical vapors and creates clean air will be reduced. In order to reduce the burden on the environment such as mass disposal and emission of exhaust gas, the wet cleaning process has recently been reviewed. The present inventors have previously disclosed in Japanese Patent Application Laid-Open No. 8-316187 that efficient removal of metal contaminants and organic contaminants on a semiconductor substrate without using chemicals such as high-concentration hydrochloric acid and hydrogen peroxide. A cleaning method using washing water prepared by blowing ozone into an acidic aqueous solution containing a chlorine compound has been proposed as a cleaning method that enables the treatment of waste liquid after cleaning.
The present inventors have further researched after that, and have developed various types of electronic material cleaning water in which the oxidation-reduction potential and pH have been appropriately adjusted according to the object to be cleaned and the purpose of cleaning. Adjustment of the oxidation-reduction potential of the cleaning water for electronic materials is performed by adding an oxidizing agent such as hydrogen peroxide, ozone, oxygen gas, oxidizing chlorine, hydrogen gas,
This is performed by dissolving a reducing agent such as sodium hyposulfite (Na ₂ S ₂ O ₄ ). The pH is adjusted by dissolving an acid such as hydrochloric acid, sulfuric acid, nitric acid or hydrofluoric acid, or an alkali such as ammonia or potassium hydroxide. The present inventors also provide a cleaning water supply apparatus that can stably supply even when the usage amount of electronic material cleaning water at a point of use fluctuates and that does not wastefully discard ultrapure water. The company has developed an electronic material cleaning water supply device that sends electronic material cleaning water to the point of use through the main pipe and returns the electronic material cleaning water that has not been used at the point of use to return to reuse. The washing water not used at the point of use is circulated and reused as it is, or returned to the first-stage primary pure water production section and used as raw water of ultrapure water. In order to simplify the quality control of the cleaning water for electronic materials, it is desirable that the cleaning water not used at the point of use be returned to the primary pure water production department to be used as raw water. Cleaning water for electronic materials
If the concentration of the oxidizing agent contained is the same,
The lower the pH, the higher the oxidation-reduction potential and the higher the cleaning effect. For this purpose, hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or the like is often added as an acid to adjust the pH. As these acids, the use of high-purity reagents of the electronic industrial grade has the problem of increasing the cost of chemicals. Furthermore, when such electronic material washing water is returned to the primary pure water production section and used as raw water of ultrapure water, it is necessary to remove these acids in advance, and the primary pure water production section There is a problem that the ion load increases.

[0003]

SUMMARY OF THE INVENTION The present invention adjusts the pH of the electronic material cleaning water without using a chemical to enhance the cleaning effect, and removes excess electronic material cleaning water not used at the point of use. When used as raw water of ultrapure water, it is an object of the present invention to provide washing water for electronic materials that does not require deionization of excess washing water and is easy to collect and reuse.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have dissolved carbon dioxide gas in ultrapure water, so that ultrapure water can be used without using a chemical. It has been found that the pH can be adjusted and surplus electronic material washing water not used at the point of use can easily remove CO ₂ by decarboxylation treatment. It was completed. That is,
The present invention provides (1) washing water for electronic materials, which comprises an oxidizing or reducing agent and carbonic acid. Further, as a preferred embodiment of the present invention, (2) the washing water for electronic materials according to (1), wherein carbonic acid is contained by dissolving carbon dioxide gas; The washing water for electronic materials according to item (2), wherein the washing is performed using a permeable membrane module, and (4) carbonic acid is contained by adding a high-concentration carbonated water prepared in advance. Cleaning water for electronic materials according to item (1),
(5) The electronic material cleaning water according to (1), wherein the oxidizing agent is a gas component; (6) the electronic material cleaning water according to (5), wherein the gas component is ozone or oxygen gas; (7) The electronic material washing water not used at the point of use or used at the point of use is returned to the upstream side of the decarbonation unit of the primary pure water production section. The method for collecting and reusing the washing water for electronic materials described in (8) The washing water for electronic materials that was not used at the point of use or used at the point of use was decarbonated with a dedicated decarbonating device. Thereafter, the method for collecting and reusing the washing water for electronic materials according to item (1), wherein the method is returned to the primary pure water producing unit or the subsystem, can be mentioned.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The cleaning water for electronic materials of the present invention contains an oxidizing agent or a reducing agent and carbonic acid. The oxidizing agent to be contained is not particularly limited, and examples thereof include hydrogen peroxide, ozone, oxygen gas, and oxidizing chlorine. The reducing agent to be contained is not particularly limited, and examples thereof include hydrogen gas and sodium hyposulfite (Na ₂ S ₂ O ₄ ). Washing water for electronic materials of the present invention containing an oxidizing agent,
The present invention can be suitably used for cleaning metal contamination and organic contamination on the surface of an electronic material. The cleaning water for electronic materials of the present invention containing a reducing agent can be suitably used for removing fine particles and the like on the surface of electronic materials. In the present invention, there is no particular limitation on the method of including carbonic acid in the cleaning water for electronic materials.For example, carbon dioxide gas can be directly bubbled and dissolved in ultrapure water, and carbonic acid can be dissolved using a gas permeable membrane module. It is also possible to dissolve the gas, or prepare a carbonated water in which carbon dioxide is dissolved in high concentration in advance,
This can be added to ultrapure water. In the preparation of the washing water for electronic materials of the present invention, the order in which the oxidizing agent or the reducing agent and the carbonic acid are contained is not particularly limited, and the oxidizing agent or the reducing agent can be added and then the carbonic acid can be contained. In addition, after containing carbonic acid, an oxidizing agent or a reducing agent may be contained. Examples of the electronic material cleaning water of the present invention include cleaning water containing hydrogen peroxide and carbonic acid, cleaning water containing ozone and carbonic acid, cleaning water containing oxygen gas and carbonic acid, containing oxidizing chlorine and carbonic acid. Washing water, washing water containing hydrogen gas and carbon dioxide, and the like.

[0006] The oxidation-reduction potential of the cleaning water for electronic materials varies depending on the pH of the cleaning water as well as the concentration of the oxidizing or reducing agent contained. FIG. 1 shows that the oxidizing agent has a high concentration, a medium concentration,
FIG. 4 is a schematic explanatory view showing the relationship between pH and oxidation-reduction potential of electronic material cleaning water contained at a low concentration. When compared at the same pH, the higher the concentration of the oxidizing agent, the higher the oxidation-reduction concentration of the washing water.
The lower the value, the higher the redox potential. When removing metal contamination and organic matter contamination attached to the electronic material surface, generally, the higher the oxidation-reduction potential of the cleaning water, the higher the cleaning effect, so the acid is added to the cleaning water containing the oxidizing agent to lower the pH. Is done. Mineral acid such as hydrochloric acid is added to lower the pH of the washing water for electronic materials and raise the oxidation-reduction potential to enhance the effect of removing organic matter contamination and metal contamination. Then, when reprocessing in the primary pure water production department, the load of ions to be removed increases, but by adjusting the pH using carbon dioxide or carbon dioxide gas instead of mineral acids such as hydrochloric acid, the primary pure water is removed. In the production section, carbon dioxide can be easily removed by the decarbonation device, and the load on the ion exchange device installed downstream of the decarbonation device can be reduced. Carbon dioxide is very soluble in water, and its concentration is correctly reflected in the drop in pH. For example, carbon dioxide gas 100
Dissolving mg / l lowers the pH to about 4.5. The washing water for electronic materials of the present invention can be used as the washing water having desired oxidation-reduction potential and pH by adjusting the amounts of the oxidizing agent or reducing agent and the carbonic acid to be contained in accordance with the object to be washed.

The cleaning water for electronic materials of the present invention adjusts the pH of the cleaning water using carbonic acid. The cleaning water whose pH has been adjusted using carbonic acid is adjusted to pH using a conventional mineral acid such as hydrochloric acid. If the pH is the same as that of the adjusted washing water, an equivalent washing effect is obtained. It has been conventional to dissolve carbonic acid in ultrapure water to lower the specific resistance of ultrapure water and suppress the generation of static electricity on the wafer when cleaning the ultrapure water itself by spraying the wafer with high pressure. However, dissolving carbonic acid in washing water containing an oxidizing agent or a reducing agent has not been performed. The washing water for electronic materials of the present invention, which has not been used at the point of use, can be returned to the primary pure water producing unit or the ultrapure water producing device after the decarbonation treatment and reused. Since the carbonic acid in the washing water can be easily removed by decarbonation, the amount of salts does not increase, and the load on the desalination device of the ultrapure water production device does not increase. The point of returning the surplus of the washing water for electronic material containing carbonic acid is not particularly limited as long as it is upstream of the decarbonation apparatus, but a water tank located in the middle between the pretreatment step and the primary pure water production unit is particularly suitable. It is. When recovering the electronic material washing water of the present invention in which the oxidizing agent is ozone, the ozone is decomposed into oxygen by ultraviolet irradiation, contact with a catalyst or activated carbon, and the like. It is preferable to return. The method for decarboxylation of the electronic material cleaning water of the present invention is not particularly limited, and can be performed, for example, by passing carbonic acid-containing cleaning water through a normal gas-liquid contact device. Washing water containing carbonic acid is usually pH
It is 5 or less. Carbonic acid is not ionized like carbonate ion and bicarbonate ion, but is dissolved as carbon dioxide (CO ₂ ). Is released to the gas phase. The gas-liquid contact can be performed, for example, by spraying washing water from above and supplying gas such as air from below in a gas-liquid contact tower filled with a filler. Alternatively, a method may be employed in which gas is diffused in a tank for storing the electronic material cleaning water, and carbon dioxide is stripped. Alternatively, decarboxylation can be performed using a degassing membrane device.

[0008] The cleaning water for electronic materials of the present invention, which has not been used at the point of use, is returned to the primary pure water producing section of the ultrapure water producing device by the component contained in the cleaning water, if it is treated by a dedicated decarbonation device. Alternatively, it can be returned to the secondary pure water production section (subsystem). In the case of returning without decarbonation, it is preferable to return to the primary pure water production section. Since the primary deionized water production section is usually provided with a deaerator, the carbon dioxide in the surplus washing water not used is
It is removed while passing through the primary pure water production section. When the pH of the surplus washing water that has not been used is higher than 5, it can be returned to the primary pure water producing section without decarbonation, and the carbon dioxide can be removed in the primary pure water producing section. FIG. 2 is a system diagram of an embodiment of the electronic material cleaning water utilization system of the present invention in which the oxidizing agent is ozone. The ultrapure water sent from the subsystem 2 (secondary pure water production unit) of the ultrapure water production apparatus dissolves ozone sent from the ozone generator 4 in the gas permeable membrane module 3, and then dissolves the gas permeable membrane module 5. Then, the carbon dioxide gas sent from the carbon dioxide gas supply device 6 is dissolved, and becomes the electronic material cleaning water containing ozone and carbon dioxide.
The electronic material cleaning water is supplied to the use point 7, but the electronic material cleaning water not used at the use point is decomposed and removed by the ozone decomposer 8 and then returned to the return pipe 9 to produce primary pure water. Returned to unit 1. Even for the electronic material cleaning water used at the use point 7, the cleaning water containing few impurities can be returned and reused together with the unused cleaning water. The illustrated primary pure water production section 1 includes a decation tower 1
1, a decarbonation tower 12, a deanionization tower 13, and a reverse osmosis membrane device 14. The surplus washing water returned is
Once the water tank 1 together with the raw water supplied to the primary pure water production unit 1
After being stored at 0, it is sent to the decarbonation tower 12 via the decation tower 11. In the decarbonation tower 12, the air source 1
The air flow from 5 removes carbonic acid in the wash water.
The washing water from which carbon dioxide has been removed in the decarbonation tower 12 is sent to the deanionization tower 13. Since the carbonic acid in the washing water has already been removed in the decarbonation tower 12, the load on the anion exchange resin of the deanionization tower 13 does not occur, and the deanionization tower 1
No. 3 has a low regeneration frequency and can be used for a long time. The primary purified water flowing out of the deanionization tower 13 via the reverse osmosis membrane device is then further purified in the subsystem 2 and used again as ultrapure water.

[0009]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 A silicon wafer having a diameter of 6 inches having a base metal film formed thereon was immersed in water containing 5 μg / liter of copper for 3 minutes, and then dried to prepare 12 contaminated wafers having copper adhered to the surface. In order to determine the copper concentration before the cleaning treatment, three of them were extracted and the surface copper concentration was measured by total reflection X-ray fluorescence analysis. As a result, the average value of the copper concentration of the three contaminated wafers was 1.05 × 10 ¹² atoms / cm ² . After dissolving ozone in ultrapure water using a gas permeable membrane module to bring the dissolved ozone concentration to 1.0 mg / l, further using a gas permeable membrane module to adjust the concentration of carbon dioxide to 100 mg / l. Dissolve and adjust pH to 4.5
To obtain washing water for electronic materials. The three contaminated wafers were washed by immersing them in the electronic material cleaning water for 5 minutes, then rinsed with ultrapure water, and then dried. The concentration of copper on the wafer surface after drying was measured by total reflection X-ray fluorescence analysis. The average of the three images is 0.97 × 10 ¹⁰ atoms / cm ²
Met. When the washing water for electronic materials was passed through a gas-liquid contact tower filled with a plastic filler, the dissolved carbon dioxide gas concentration was reduced to 1 mg / liter, and the ion load was not substantially reduced. . Comparative Example 1 As a washing water for electronic materials, ozone was dissolved using a gas permeable membrane module to adjust the dissolved ozone concentration to 1.0 mg / liter, and then hydrochloric acid was added to adjust the pH to 4.5. The same operation as in Example 1 was repeated except that the electronic material cleaning water was used. The average value of the copper concentration on the surfaces of the three wafers after washing and drying was 0.98 × 10 ¹⁰ atoms / cm ² . Example 2 As a washing water for electronic materials, ozone was dissolved using a gas permeable membrane module to make the dissolved ozone concentration 1.0 mg / liter, and then a saturated carbonated water prepared in advance was added to adjust the pH to 4. The same operation as in Example 1 was repeated, except that the electronic material cleaning water adjusted to 0.5 was used. Washing,
The average value of the copper concentration on the surfaces of the three wafers after drying was 0.3.
It was 95 × 10 ¹⁰ atoms / cm ² . Comparative Example 2 Washing water for electronic materials having a pH of 6.5 without dissolving ozone using a gas permeable membrane module to adjust the concentration of dissolved ozone to 1.0 mg / liter and then adjusting pH as a washing water for electronic materials. The same operation as in Example 1 was repeated, except that was used. The average value of the copper concentration on the surfaces of the three wafers after washing and drying was 3.12 × 10 ¹⁰ atoms / cm ² . Example 1
Table 1 shows the results of Comparative Examples 1 and 2 and Comparative Examples 1 and 2.

[0010]

[Table 1]

From the results shown in Table 1, it is found that 1.0 m of ozone
g / liter and further dissolved in carbon dioxide gas to adjust the pH to 4.5 Example 1 using washing water for electronic materials
In comparison with Comparative Example 1, in which 1.0 mg / L of ozone was dissolved in ultrapure water and the pH was adjusted to 4.5 by adding hydrochloric acid, copper contamination on the wafer surface was reduced. It has been removed to the same extent. That is, the washing effect for electronic materials of the present invention, the pH of which has been adjusted by dissolving carbonic acid, can provide the same cleaning effect as the conventional washing water for electronic materials, of which pH has been adjusted by adding hydrochloric acid. I understand. In addition, even if the washing water for electronic materials of Example 2 containing carbonic acid was used by adding saturated carbonated water prepared in advance, the carbonic acid gas of Example 1 was dissolved using the gas permeable membrane module. The same cleaning effect as the cleaning water for electronic materials is obtained. In contrast, ultrapure water contains ozone 1.
When the washing water for electronic material of Comparative Example 1 in which 0 mg / liter was dissolved and the pH was not adjusted was used, the removal of copper contamination was insufficient.

[0012]

The cleaning water for electronic materials of the present invention is the cleaning water.
Since carbon dioxide is used for pH adjustment, there is no need to add a mineral acid such as hydrochloric acid, and excess washing water not used at the point of use can be returned to the upstream of the decarbonation unit in the primary pure water production department or dedicated The carbonic acid is easily removed by treating with the decarbonation apparatus of the above, and can be reused without applying a load to the deionization apparatus.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the relationship between the pH of the washing water for electronic materials and the oxidation-reduction potential.

FIG. 2 is a system diagram of one embodiment of a system for using the cleaning water for electronic materials of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary pure water production part 2 Subsystem 3 Gas permeable membrane module 4 Ozone generator 5 Gas permeable membrane module 6 Carbon dioxide gas supply 7 Use point 8 Ozone decomposer 9 Return piping 10 Water tank 11 Decationization tower 12 Decarbonation tower 13 Desorption Anion tower 14 Reverse osmosis membrane device 15 Air source

Claims (1)

[Claims] 1. A washing water for electronic materials, comprising an oxidizing or reducing agent and carbonic acid.