JP3397117B2 - Cleaning water and cleaning method for electronic materials - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to cleaning water for electronic materials. More specifically, according to the present invention, in wet cleaning of electronic materials, it is possible to shorten the cleaning process by simultaneously removing metal contamination and fine particle contamination attached to the surface of the electronic material without using a surfactant. It relates to washing 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.
Uses concentrated hydrogen peroxide-based chemicals such as a mixture of hydrogen peroxide and sulfuric acid, a mixture of hydrogen peroxide and hydrochloric acid, and a mixture of hydrogen peroxide, ammonia and water. After washing at high temperature, rinse with ultrapure water, so-called R
It has been done by CA cleaning. RCA cleaning is an effective method for removing the metal components on the semiconductor surface, but at the same time, the fine particles attached to the semiconductor surface are also removed. However, in such a method, hydrogen peroxide solution, high concentration of acid,
The cost of chemicals is high because a large amount of alkali is used, and the cost of rinsing ultrapure water, the cost of waste liquid treatment, the cost of air conditioning for exhausting chemical vapors to newly prepare clean air, and other costs are high. . In order to reduce these costs and further reduce the environmental load such as large amount of water use, large amount of drug disposal, and emission of exhaust gas, the wet cleaning process has been recently reviewed. Conventional RCA
As an alternative to cleaning, a cleaning process consisting of the following five steps has been developed. Step 1: Using ozone-containing ultrapure water, remove organic contaminants and metallic contaminants from the surface of the electronic material. Step 2: Using ultrapure water containing hydrogen fluoride, hydrogen peroxide, and a surfactant, while transmitting ultrasonic waves, fine particle contamination and metal contamination remaining in step 1 are removed. Step 3: Using ozone-containing ultrapure water, the surfactant attached in step 2 is removed while transmitting ultrasonic waves as needed. Step 4: The diluted hydrofluoric acid is used to remove the chemical oxide film generated in step 3. Step 5: Perform final rinsing using ultrasonic waves while transmitting ultrasonic waves. According to this cleaning process, since the diluted chemical solution is used as cleaning water and all cleaning can be performed at room temperature, the chemicals and energy used can be greatly reduced. However, since washing requires 5 steps, it has become necessary to further shorten the washing process.

[0003]

SUMMARY OF THE INVENTION According to the present invention, in wet cleaning of electronic materials, without using a surfactant, metal contamination and fine particle contamination adhering to the surface of the electronic material can be simultaneously removed to shorten the cleaning process. The purpose of the present invention is to provide 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, step 3 and step 4 will be unnecessary,
As a result of intensive research, they have found that an aqueous solution of hydrogen fluoride, hydrogen peroxide and oxygen gas can simultaneously remove fine particle contamination and metal contamination on the surface of an electronic material.
The present invention has been completed based on this finding. That is, the present invention comprises (1) an aqueous solution in which 0.1 to 1% by weight of hydrogen fluoride, 0.1 to 10% by weight of hydrogen peroxide and 20 mg / liter or more of oxygen gas are dissolved. (2) Electronic water cleaning water, wherein (2) hydrogen fluoride, hydrogen peroxide and oxygen gas are dissolved in ultrapure water, (3) electronic water cleaning water in advance Cleaning water for electronic materials according to any one of the items 1 and 2, wherein hydrofluoric acid and hydrogen peroxide water are added to water in which oxygen gas is dissolved, (4) Degassing water And reducing the saturation of the dissolved gas, and then supplying the oxygen gas to dissolve the oxygen gas in the water, the cleaning water for electronic materials according to any one of the first and third aspects, and (5) An electric power, characterized in that cleaning is performed while transmitting ultrasonic waves to the cleaning water for electronic materials according to item 1. The method of cleaning material, there is provided a.

[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 washing water of the present invention, the concentration of hydrogen fluoride is not particularly limited, but it is preferably 0.1 to 1% by weight. If the concentration of hydrogen fluoride is less than 0.1% by weight, there is a risk that the removal of metal contamination, organic contamination, etc. adhering to the surface of the electronic material will be insufficient. When the concentration of hydrogen fluoride exceeds 1% by weight, the cleaning effect is not improved according to the increase in concentration, and the required amount of rinse water may be excessive. In the washing water of the present invention, the concentration of hydrogen peroxide is not particularly limited, but it 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 metal contamination or organic contamination attached to the surface of the electronic material may be insufficiently removed. When the concentration of hydrogen peroxide exceeds 10% by weight, the cleaning effect is not improved according to the increase of the concentration, and the required amount of rinse water may be excessive. In the cleaning water of the present invention, the hydrogen peroxide removes metal contamination, organic contamination, etc. adhering 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 to contaminate it. Take in a part of the thing.
It is considered that hydrogen fluoride removes an oxide film incorporating 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 to appropriately increase or decrease the concentration of hydrogen fluoride according to the concentration of hydrogen peroxide. In the cleaning water of the present invention, the concentration of oxygen gas is
20 mg / liter or more is preferable, and 30 mg / liter
More preferably, it is liter or more. When the concentration of oxygen gas is less than 20 mg / liter, the removal of fine particles and the like adhering to the surface of the electronic material may be insufficient.

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

Dissolving oxygen gas in water is preferably performed by degassing the water to reduce the saturation of the dissolved gas and then supplying oxygen gas to dissolve the 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, since the solubility of oxygen gas in water at a pressure of 10 ⁵ Pa and a temperature of 20 ° C is 44.0 mg / liter, the only gas dissolved in water at a pressure of 10 ⁵ Pa and a temperature of 20 ° C is oxygen gas. And the amount of dissolution is 4
The degree of 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 is 22.0 mg / liter. The saturation degree of water is 0.5.
Double. Further, water in equilibrium in contact with air at a pressure of 10 ⁵ Pa and a temperature of 20 ° C. dissolves 14.9 mg / liter of nitrogen gas and 9.1 mg / liter of oxygen gas and has a saturation degree of 1.
Since the state is 0 times, the degree of saturation of water when the amount of dissolved gas is 1.5 mg / liter of nitrogen gas and 0.9 mg / liter of oxygen gas by degassing is 0.1 times. In the present invention, when the oxygen gas is dissolved in water, it is preferable that the water is degassed in advance to reduce the degree of saturation to make room for the gas dissolution capacity in water, and then the oxygen gas is dissolved. In the present invention, the gas permeable membrane module can be used in multiple stages to remove dissolved gas and dissolve oxygen gas. For example, a gas permeable membrane module is provided in two stages, decompression membrane deaeration for all dissolved gases is performed using the gas permeable membrane module in the previous stage, and oxygen gas is dissolved using the gas permeable membrane module in the subsequent stage. You can By installing the gas permeable membrane module in two stages and degassing the reduced pressure membrane for all dissolved gases and dissolving oxygen gas, oxygen gas is dissolved in water almost quantitatively without wasting it. be able to.

There is no particular limitation on the method of bringing the cleaning water for electronic materials of the present invention into contact with electronic materials contaminated with organic substances, metals, fine particles, etc., and may be appropriately selected according to the type of contamination, the amount of adhesion, etc. You can For example, the contaminated electronic material may be immersed in cleaning water for electronic materials to perform batch cleaning, or single-wafer cleaning in which one by one is processed. Examples of the single-wafer cleaning method include spin cleaning in which contaminated electronic material is rotated and washing water for electronic material is poured. When the electronic material cleaning water of the present invention is used to clean an electronic material contaminated with fine particles, it is preferable to transmit ultrasonic waves to the electronic material cleaning water. By transmitting ultrasonic waves to the cleaning water for electronic materials, it is possible to effectively remove fine particles and the like. There is no particular limitation on the method of transmitting ultrasonic waves to the electronic material cleaning water, for example, in batch cleaning, it is possible to transmit ultrasonic waves to a tank storing the electronic material cleaning water, in spin cleaning, Ultrasonic waves can be transmitted in the nozzle portion of the washing water for electronic materials to be poured. The frequency of the transmitted ultrasonic waves is preferably 400 kHz or higher, more preferably about 1 MHz or higher. The frequency of ultrasonic waves is tens of kHz, which is conventionally used
If the degree is small, not only the removal of fine particles from the electronic material contaminated with fine particles may be insufficient, but also due to the cavitation effect caused by 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 on the removal of metal contamination and organic contamination at room temperature but also on the removal of particulate contamination at room temperature. Exhibits the effect of removing fine particle contamination that is comparable to cleaning water. Therefore, by washing the silicon substrate or the like with the washing water of the present invention, it becomes unnecessary to add a surfactant to the washing water. As a result, cleaning with ozone-containing ultrapure water, which was conventionally required to remove the adhered surfactant,
Furthermore, it becomes possible to omit the two steps of cleaning for removing the chemical oxide film generated due to ozone, and the cleaning process of electronic materials such as a silicon substrate can be greatly streamlined.

[0009]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, the cleaning effect was evaluated by the following method. (1) An object to be cleaned A silicon substrate having a diameter of 6 inches is immersed in an aqueous copper chloride 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 which is an object to be cleaned. did. This contaminated silicon substrate has fine particles 22,
It was contaminated with 000 pieces / substrate and 1.0 × 10 ¹⁴ atoms / cm ² of copper. (2) Cleaning operation Single-wafer spin cleaning in which cleaning water that has received ultrasonic waves from an ultrasonic irradiation nozzle [Pretec, Fine Jet] with a built-in 1.6 MHz ultrasonic oscillator is jetted onto a contaminated silicon substrate. The device was used. Flow rate of wash water is 800 ml /
Minutes, the rotation speed of the substrate was 500 rpm, and the cleaning time was 1 minute. After washing, the plate was rinsed with ultrapure water for 30 seconds, the rotation speed was increased to 1,500 rpm, and held for 20 seconds to dry. (3) Evaluation (3-1) Using a particle foreign substance inspection device on the substrate by the fine particle laser scattering method,
The fine particles on the silicon substrate were measured. (3-2) Copper Concentration The copper concentration on the surface of the silicon substrate was measured by the total reflection fluorescent X-ray analysis method. 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 surface of the silicon substrate was measured by the FT-IR analysis method. The lower limit of detection by this method is 1.0 × 10 ¹² atoms / cm ² . Example 1 Hydrofluoric acid and hydrogen peroxide solution 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. Concentration is 30 mg /
A liter of cleaning water for electronic materials was prepared. When the contaminated silicon substrate was washed with this washing water, the number of adhered fine particles on the substrate after washing was 100 particles / substrate or less, and both copper and carbon were below the detection limit. Comparative Example 1 Hydrofluoric acid and hydrogen peroxide solution 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 8 mg
/ L of cleaning water for electronic materials was prepared. When the contaminated silicon substrate was washed with this washing water, the number of adhered fine particles on the substrate after washing was 7,000 / substrate,
Both copper and carbon were below the detection limit. Comparative Example 2 Hydrofluoric acid, hydrogen peroxide solution, 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 the surfactant is 50 mg.
/ L and the concentration of dissolved oxygen gas was about 8 mg / L, and the cleaning water for electronic materials was prepared. When the contaminated silicon substrate was washed with this washing water, the number of adhered fine particles on the substrate after washing was 100 particles / substrate or less, copper was below the detection limit, and carbon was 5.0 × 10 ¹² atoms / cm 3. ^{Was 2} . The results of Example 1 and Comparative Examples 1 and 2 are shown in Table 1.

[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, which consisted of ultrapure water in which hydrogen fluoride, hydrogen peroxide and oxygen gas were dissolved. In, the fine particles and copper of the contaminated silicon substrate were both removed, and the adhesion of organic substances on the silicon substrate did not occur.
On the other hand, in Comparative Example 1 in which the cleaning water in which only hydrogen fluoride and hydrogen peroxide were dissolved was used, copper on the contaminated silicon substrate was removed and no organic matter adhered, but the contamination of the fine particles was about 3. One part remains without being removed, and it is necessary to remove fine particles by another step. Further, in Comparative Example 2 using cleaning water in which hydrogen fluoride, hydrogen peroxide, and a surfactant were dissolved, both the fine particles and copper on the contaminated silicon substrate were removed. Since the adhesion of the organic matter has occurred, cleaning using ozone-containing water for removing the organic matter and cleaning for removing the chemical oxide film generated due to the ozone-containing water are necessary.

[0012]

EFFECTS OF THE INVENTION By using the cleaning water for electronic materials of the present invention, it becomes unnecessary to add a surfactant to the cleaning water for cleaning electronic materials such as silicon substrates. It is possible to omit the two steps of cleaning with ozone-containing ultrapure water, which was necessary for removal, and cleaning with diluted hydrofluoric acid to remove the chemical oxide film generated due to ozone. The cleaning process for electronic materials such as substrates can be greatly streamlined.

Continuation of the front page (56) Reference JP-A-8-264499 (JP, A) JP-A-7-115077 (JP, A) JP-A-9-92636 (JP, A) JP-A-8-48996 (JP , A) JP 4-114428 (JP, A) JP 7-155709 (JP, A) Special Table 8-502148 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) H01L 21/304 647 C11D 7/00-7/60

Claims (5)

(57) [Claims] 1. 0.1 to 1% by weight hydrogen fluoride and 0.1 to 1
A cleaning water for electronic materials, comprising an aqueous solution in which 0% by weight of hydrogen peroxide and 20 mg / liter or more of oxygen gas are dissolved. 2. Hydrogen fluoride, hydrogen peroxide and oxygen gas
The electronic material according to claim 1, wherein the electronic material is dissolved in pure water.
Wash water. 3. Hydrogen fluoride is added to water in which oxygen gas is previously dissolved.
Claim characterized by adding acid and hydrogen peroxide solution
Cleaning water for electronic materials according to item 1 or 2. 4. Degassing water to reduce saturation of dissolved gas
After that, supply oxygen gas and dissolve oxygen gas in water
The electron according to claim 1 or 3, characterized in that
Wash water for materials. 5. The washing water for electronic materials according to claim 1, wherein the ultrasonic
Of electronic materials characterized by cleaning while transmitting waves
Cleaning method.