JPH11217591A - Cleaning water for electronic materials - Google Patents

Abstract

(57) Abstract: In wet cleaning of an electronic material, metal contamination and fine particle contamination attached to the surface of the electronic material can be simultaneously removed without using a surfactant, thereby shortening the cleaning process. Provide cleaning water for electronic materials. A cleaning water for electronic materials, comprising an aqueous solution in which hydrogen fluoride, hydrogen peroxide and oxygen gas are dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to cleaning water for electronic materials. More specifically, the present invention can reduce the cleaning process by simultaneously removing metal contamination and fine particle contamination attached to the surface of the electronic material without using a surfactant in wet cleaning of the electronic material. It relates to cleaning water for materials.

[0002]

2. Description of the Related Art Conventionally, cleaning of silicon substrates for semiconductors, glass substrates for liquid crystals, quartz substrates for photomasks, etc.
Mainly use concentrated chemicals based on hydrogen peroxide, such as a mixture of hydrogen peroxide and sulfuric acid, a mixture of hydrogen peroxide, hydrochloric acid and water, and a mixture of hydrogen peroxide, ammonia and water. Rinse with ultrapure water after washing at high temperature
This has been done by CA cleaning. RCA cleaning is an effective method for removing metal components on a semiconductor surface, but also removes fine particles attached to the semiconductor surface. However, in such a method, aqueous hydrogen peroxide, high concentration of acid,
The chemical solution cost is high due to the use of a large amount of alkali, etc., and the cost is extremely high, such as the cost of ultrapure water for rinsing, the cost of waste liquid treatment, and the cost of air conditioning for exhausting chemical vapor and preparing fresh clean air. . In recent years, the wet cleaning process has been reviewed in order to reduce these costs and to reduce the burden on the environment such as the use of a large amount of water, the large amount of disposal of drugs, and the emission of exhaust gas. Conventional RCA
As an alternative to cleaning, a cleaning process comprising the following five steps has been developed. Step 1: Organic substance contamination and metal contamination are removed from the electronic material surface using ozone-containing ultrapure water. Step 2: Using ultrapure water containing hydrogen fluoride, hydrogen peroxide and a surfactant, transmitting ultrasonic waves to remove fine particle contamination and metal contamination remaining in Step 1. Step 3: Using ultrapure water containing ozone, transmitting the ultrasonic wave as necessary, and removing the surfactant adhered in Step 2. Step 4: The chemical oxide film generated in step 3 is removed using dilute hydrofluoric acid. Step 5: A final rinse is performed while transmitting ultrasonic waves using ultrapure water. According to this cleaning process, a dilute aqueous chemical solution is used as cleaning water, and all cleaning can be performed at room temperature, so that the amount of chemicals and energy used can be significantly reduced. However, since cleaning requires five steps, it has been required to further shorten the cleaning process.

[0003]

SUMMARY OF THE INVENTION According to the present invention, in wet cleaning of an electronic material, metal contamination and fine particle contamination attached to the surface of the electronic material are simultaneously removed without using a surfactant, thereby shortening the cleaning process. The purpose of the present invention is to provide a cleaning water for electronic materials that can be used.

[0004]

The present inventors have noticed that if the use of the surfactant in the above step 2 can be omitted, steps 3 and 4 become unnecessary.
As a result of intensive research, they found that an aqueous solution in which hydrogen fluoride, hydrogen peroxide, and oxygen gas were dissolved can simultaneously remove particulate contamination and metal contamination on the surface of electronic materials.
Based on this finding, the present invention has been completed. That is, the present invention provides (1) a washing water for electronic materials, which comprises an aqueous solution in which hydrogen fluoride, hydrogen peroxide and oxygen gas are dissolved. Furthermore, in a preferred embodiment of the present invention, (2) the concentration of hydrogen fluoride is 0.1.
The washing water for electronic materials according to item (1), wherein
(3) The hydrogen peroxide having a concentration of 0.1 to 10% by weight.
(1) The washing water for electronic materials according to (1), (4) the washing water for electronic materials according to (1), wherein the dissolved oxygen gas concentration is 20 mg / liter or more, and (4) the electronic material to be cleaned. Is a silicon substrate for semiconductor, a glass substrate for liquid crystal or a quartz substrate for photomask, the washing water for electronic materials according to (1),
(5) A method for cleaning electronic materials, wherein the cleaning is performed while transmitting ultrasonic waves to the cleaning water for electronic materials according to (1), and (6) the frequency of the ultrasonic waves is 400 KHz or more. A method for cleaning an electronic material according to a certain paragraph (5) can be mentioned.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The cleaning water for electronic materials of the present invention comprises an aqueous solution in which hydrogen fluoride, hydrogen peroxide and oxygen gas are dissolved. In the cleaning water of the present invention, the concentration of hydrogen fluoride is not particularly limited, but is preferably 0.1 to 1% by weight. If the concentration of hydrogen fluoride is less than 0.1% by weight, there is a possibility that the removal of metal contamination and organic substance contamination attached to the surface of the electronic material becomes insufficient. When the concentration of hydrogen fluoride exceeds 1% by weight, the cleaning effect is not improved in accordance with the increase in the concentration, and the required amount of rinsing water may be excessive. In the washing water of the present invention, the concentration of hydrogen peroxide is not particularly limited, but is preferably 0.1 to 10% by weight. If the concentration of hydrogen peroxide is less than 0.1% by weight, there is a possibility that the removal of metal contamination or organic substance contamination attached to the surface of the electronic material becomes insufficient. If the concentration of hydrogen peroxide exceeds 10% by weight, the cleaning effect is not improved in accordance with the increase in the concentration, and the required amount of rinsing water may be excessive. In the cleaning water of the present invention, hydrogen peroxide removes metal contamination, organic contamination, and the like attached to the surface of the electronic material by oxidative decomposition, and forms an oxide film on the surface of the electronic material to be cleaned, thereby contaminating the surface. Capture a part of an object.
Hydrogen fluoride is considered to remove an oxide film that has taken in metal contamination and organic contamination by an etching action.
Therefore, it is preferable that the concentrations of hydrogen fluoride and hydrogen peroxide are well-balanced, and it is preferable that the concentration of hydrogen fluoride be appropriately increased or decreased according to the concentration of hydrogen peroxide. In the cleaning water of the present invention, the concentration of oxygen gas is:
It is preferably at least 20 mg / liter,
More preferably, it is liter or more. If the concentration of oxygen gas is less than 20 mg / liter, there is a possibility that the removal of fine particles and the like adhering to the surface of the electronic material may be insufficient.

The purity of the water used for producing the electronic material cleaning water of the present invention is not particularly limited, and can be selected according to the required surface cleanliness of the object to be cleaned. When using electronic materials such as silicon substrates for liquid crystal, glass substrates for liquid crystal, quartz substrates for photomasks, and other precision electronic components, ultrapure water with sufficiently high purity, high-purity hydrofluoric acid, high-purity It is preferable to dissolve hydrogen peroxide solution and high-purity oxygen gas. Ultrapure water has an electrical resistivity at 25 ° C. of 18 MΩ · cm or more, organic carbon of 10 μg / liter or less, and fine particles of 10,000 or less.
It is preferably 0 / liter or less. Further, if necessary, ultrafine foreign substances in the electronic material cleaning water can be removed using a filter. The method for producing the electronic material cleaning water of the present invention is not particularly limited. For example, it can be produced by bubbling oxygen gas into water in which a predetermined concentration of hydrogen fluoride and hydrogen peroxide are dissolved. But,
In order to prevent volatilization of hydrogen fluoride, it is preferable to add hydrofluoric acid and aqueous hydrogen peroxide to water in which oxygen gas of a predetermined concentration is dissolved in advance. Compared to the amount of water in which oxygen gas is dissolved, the amounts of hydrofluoric acid and hydrogen peroxide added are overwhelmingly small, so the concentration of oxygen gas before adding hydrofluoric acid and hydrogen peroxide is added. However, the dissolved oxygen gas concentration of the electronic material cleaning water obtained almost as it is is obtained.

For dissolving oxygen gas in water, it is preferable to deaerate water to reduce the degree of saturation of dissolved gas, and then supply oxygen gas to dissolve oxygen gas in water. Here, the gas saturation is a value obtained by dividing the amount of gas dissolved in water by the gas solubility at a pressure of 10 ⁵ Pa and a temperature of 20 ° C. For example, a pressure 10 ⁵ Pa, since the solubility of oxygen gas in water at a temperature of 20 ° C. is a 44.0 mg / l, pressure 10 ⁵ Pa, at a temperature 20 ° C., the gas dissolved in water only oxygen gas And the amount of dissolution is 4
The saturation of water, which is 4.0 mg / liter, is 1.0 times,
The only gas dissolved in water is oxygen gas, and the dissolved amount of water is 22.0 mg / liter. The saturation of water is 0.5.
It is twice. Water in equilibrium with air at a pressure of 10 ⁵ Pa and a temperature of 20 ° C. dissolves 14.9 mg / l of nitrogen gas and 9.1 mg / l of oxygen gas and has a saturation degree of 1.
Since it is in a state of 0 times, the saturation of water is 0.1 times by degassing so that the dissolved amount of the gas is 1.5 mg / liter of nitrogen gas and 0.9 mg / liter of oxygen gas. In the present invention, when dissolving oxygen gas in water, it is preferable to deaerate the water in advance to lower the degree of saturation, make a space in the gas dissolution capacity in water, and then dissolve the oxygen gas. In the present invention, the removal of the dissolved gas and the dissolution of the oxygen gas can be performed using the gas permeable membrane module in multiple stages. For example, providing a gas permeable membrane module in two stages, performing decompression membrane degassing for all dissolved gases using the gas permeable membrane module in the preceding stage, and dissolving oxygen gas using the gas permeable membrane module in the subsequent stage Can be. By providing a gas permeable membrane module in two stages and performing decompression membrane degassing for all dissolved gases and dissolving oxygen gas, oxygen gas is dissolved in water almost quantitatively without wasteful release. be able to.

The method of contacting the electronic material cleaning water of the present invention with an electronic material contaminated with organic substances, metals, fine particles and the like is not particularly limited, and may be appropriately selected according to the type of contamination, the amount of adhesion, and the like. Can be. For example, a contaminated electronic material can be immersed in electronic-material cleaning water to perform batch cleaning, or can perform single-wafer cleaning in which one by one is processed. Examples of the single-wafer cleaning method include spin cleaning in which cleaning water for electronic materials is flowed while rotating contaminated electronic materials. When cleaning the electronic material contaminated with fine particles or the like using the electronic material cleaning water of the present invention, it is preferable to transmit ultrasonic waves to the electronic material cleaning water. By transmitting ultrasonic waves to the electronic material cleaning water, fine particles and the like can be effectively removed. There is no particular limitation on the method of transmitting ultrasonic waves to the electronic material cleaning water.For example, in batch cleaning, ultrasonic waves can be transmitted to a tank storing electronic material cleaning water, and in spin cleaning, Ultrasonic waves can be transmitted to the nozzle portion of the washing water for electronic material to be poured. The frequency of the transmitted ultrasonic wave is preferably 400 kHz or more, and more preferably about 1 MHz or more. The frequency of the ultrasonic wave is several tens of kHz conventionally used
When the degree is particularly small, not only may the removal of the fine particles from the electronic material contaminated with the fine particles be insufficient, but also due to the cavitation effect brought by the ultrasonic waves,
There is a risk of damaging the object to be cleaned. The cleaning water for electronic materials of the present invention has an excellent effect not only at the removal of metal contamination and organic contamination but also at the removal of fine particle contamination at room temperature, and a conventionally used surfactant is added. Exhibits the effect of removing particulate contamination comparable to washing water. For this reason, by cleaning a silicon substrate or the like using the cleaning water of the present invention, it is not necessary to add a surfactant to the cleaning water. As a result, cleaning with ozone-containing ultrapure water, which was conventionally necessary for removing attached surfactant,
Further, two steps of cleaning for removing a chemical oxide film generated due to ozone can be omitted, and the cleaning process of an electronic material such as a silicon substrate can be significantly streamlined.

[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. In Examples and Comparative Examples, the cleaning effect was evaluated by the following method. (1) Object to be cleaned A silicon substrate having a diameter of 6 inches is immersed in a copper chloride aqueous solution in which alumina fine particles having a diameter of 1 μm or less are dispersed for 3 minutes, and then rinsed with ultrapure water to prepare a contaminated silicon substrate to be cleaned. did. This contaminated silicon substrate contains fine particles 22,
000 / substrate and 1.0 × 10 ¹⁴ atoms / cm ² of copper. (2) Cleaning operation Single-wafer spin cleaning in which cleaning water that receives ultrasonic waves from an ultrasonic irradiation nozzle [Pretec, Fine Jet] incorporating a 1.6 MHz ultrasonic oscillator is jetted onto a contaminated silicon substrate. The device was used. The flow rate of washing water is 800ml /
The rotation speed of the substrate was 500 rpm, and the cleaning time was 1 minute. After the washing, the substrate was rinsed with ultrapure water for 30 seconds, the rotation speed was increased to 1,500 rpm, the temperature was held for 20 seconds, and drying was performed. (3) Evaluation (3-1) Particles Using an apparatus for inspecting foreign matter on a substrate using a laser scattering method,
The fine particles on the silicon substrate were measured. (3-2) Copper concentration The copper concentration on the silicon substrate surface was measured by total reflection X-ray fluorescence analysis. The lower limit of detection by this method is 2.0 × 10 ⁹
Atoms / cm ² . (3-3) Carbon The amount of carbon on the silicon substrate surface was measured by FT-IR analysis. The lower limit of detection by this method is 1.0 × 10 ¹² atoms / cm ² . Example 1 Hydrofluoric acid and hydrogen peroxide were added to ultrapure water in which oxygen gas was dissolved, and the concentrations of hydrogen fluoride and hydrogen peroxide were both 0.5% by weight. The concentration is 30mg /
One liter of washing water for electronic materials was prepared. When the contaminated silicon substrate was cleaned using this cleaning water, the number of adhered fine particles on the cleaned substrate was 100 particles / substrate or less, and both copper and carbon were below the detection limit. Comparative Example 1 Hydrofluoric acid and hydrogen peroxide were added to ultrapure water in equilibrium with the atmosphere, and the concentrations of hydrogen fluoride and hydrogen peroxide were both 0.5% by weight. Gas concentration is about 8mg
/ Liter of electronic material washing water was prepared. When the contaminated silicon substrate was cleaned using the cleaning water, the number of fine particles adhered to the cleaned substrate was 7,000 / substrate.
Both copper and carbon were below the detection limit. Comparative Example 2 Hydrofluoric acid, hydrogen peroxide and a surfactant [Wako Pure Chemical Industries, Ltd., NCW-60] were added to ultrapure water in equilibrium with the atmosphere.
1A], the concentrations of hydrogen fluoride and hydrogen peroxide are both 0.5% by weight, and the concentration of surfactant is 50 mg.
/ Liter, and a washing water for electronic materials having a dissolved oxygen gas concentration of about 8 mg / liter was prepared. When the contaminated silicon substrate was cleaned using the cleaning water, the number of adhered fine particles on the cleaned substrate was 100 particles / substrate or less, copper was below the detection limit, and carbon was 5.0 × 10 ¹² atoms / cm 2. ^{Was 2} . Table 1 shows the results of Example 1 and Comparative Examples 1 and 2.

[0010]

[Table 1]

As shown in Table 1, in Example 1 in which cleaning was performed using the cleaning water for electronic materials of the present invention comprising ultrapure water in which hydrogen fluoride, hydrogen peroxide and oxygen gas were dissolved. In this method, both the fine particles and copper of the contaminated silicon substrate are removed, and no organic matter adheres to the silicon substrate.
On the other hand, in Comparative Example 1 using cleaning water in which only hydrogen fluoride and hydrogen peroxide were dissolved, copper on the contaminated silicon substrate was removed, and no organic matter was attached. One part remains without being removed, and it is necessary to remove fine particles by another process. In Comparative Example 2 using cleaning water in which hydrogen fluoride, hydrogen peroxide, and a surfactant were dissolved, both fine particles and copper of the contaminated silicon substrate were removed. Since organic substances are attached, cleaning using ozone-containing water for removing organic substances and cleaning for removing a chemical oxide film generated due to ozone-containing water are required.

[0012]

The use of the cleaning water for electronic materials of the present invention makes it unnecessary to add a surfactant to the cleaning water for cleaning electronic materials such as silicon substrates. It is possible to omit two steps of cleaning with ozone-containing ultrapure water necessary for removal and cleaning with dilute hydrofluoric acid for removing a chemical oxide film generated due to ozone. The step of cleaning an electronic material such as a substrate can be greatly simplified.

Claims (1)

[Claims] 1. A cleaning water for electronic materials, comprising an aqueous solution in which hydrogen fluoride, hydrogen peroxide and oxygen gas are dissolved.