JP2004139998A - Electricity removal method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electricity removal method for removing static electricity by a normal temperature dry method using activated air. <P>SOLUTION: An activated air generator 1 is connected to a cleaning chamber 8. The activated air generator 1 comprises a centrifugal movement / coriolis force generator 2 and a gas liquid separator 4. 1 and dissociates water to generates ions, which generates water droplets in a gas swirl, activates the water droplets, ionize gaseous molecules, and generates ionized air in the gas swirl. The gas liquid separator 4 supplies to the cleaning chamber 8 the activated air taken out by separating the water droplets from the gas swirl. The activated air including ionized air and water cluster forms a high humidity atmosphere. The activated air flows and contacts to materials to be cleaned in the cleaning chamber 8 and carries out cleaning thereof. The ionized air neutralizes the charge of the materials to be cleaned. The water cluster separates deposits from the surface of the materials to be cleaned. The flowing activated air strips and removes deposits from materials to be cleaned. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a static elimination method for removing static electricity.

Products such as semiconductor (IC, LSI, etc.) devices, magnetic disks (CDs), and color liquid crystals are manufactured in an ultra-clean and clean atmosphere under strict conditions that do not allow the entry of extremely fine dust. Parts such as a wafer as a material of the above, an aluminum plate as a material of a CD, and a glass plate as a color liquid crystal material are highly cleaned prior to introduction into a production line. In the manufacturing process of precision machines and equipment, cleaning processing of parts is one of extremely important processes.

There are three types of cleaning of the Si wafer in the LSI manufacturing process: finishing cleaning during the manufacturing of the Si wafer itself, purchasing a Si wafer from a wafer maker, pre-processing cleaning during the LSI manufacturing, and cleaning in each process during the LSI manufacturing. There is.

Washing is, of course, washing and cleaning to remove adhered substances to the object to be cleaned or to remove dirt generated on the surface, thereby bringing the object to be cleaned to the original clean surface state.

Generally, it is considered that the contaminant is attached to an object to be cleaned such as a Si wafer by one of the following mechanisms or a combined force of the following mechanisms. That is, (1) physical adsorption by van der Waals force, (2) electric force such as clonal force, (3) chemisorption by chemical reaction, (4) mechanical hooking. As for the contamination due to chemical adsorption, it is difficult to remove contaminants only by mechanical cleaning, and chemical cleaning becomes indispensable. Contamination due to other mechanisms can be more easily removed by mechanical cleaning or physical cleaning combined with chemical cleaning.

Conventionally, chlorofluorocarbon (R-113) has been used exclusively for the cleaning of these parts. However, the use of chlorofluorocarbon has been banned, and its replacement is currently in progress. The CFC substitute cleaning agents are classified into three types: aqueous, semi-aqueous, and solvent. Although each system has its own advantages and disadvantages, cleaning solutions containing chemical components are not desirable anyway. In this regard, water, especially pure water and ultrapure water, can be said to be safe.

The following are described as references.
JP-A-06-251892 JP-A-02-203976

洗浄 Thus, cleaning is roughly divided into two types: physical cleaning, which mechanically removes adhering contaminants, and chemical cleaning, which dissolves and removes it. Water, especially ultrapure water, has a very good cleaning ability by itself, and mechanical cleaning using ultrapure water is an important cleaning method in a semiconductor manufacturing process.

The major issues in ultrapure water cleaning are (1) how to produce ultrapure water of high purity close to theoretical pure water economically, (2) how to efficiently clean and dry, (3) It is said to be how to increase the cleaning ability of ultrapure water. In particular, regarding (2) and (3), attention has been paid to high-temperature pure water. If the temperature of the ultrapure water is raised, the surface tension is reduced, and the cleaning ability can be increased by activating the molecular motion of water molecules and attached matter. However, this method cannot be applied to those having no heat resistance (interesting in interesting water, Shoji Kubota, Nikkan Kogyo Shimbun, pp. 115-132, 1994). Moreover, as long as cleaning water is used, a drying step is required for post-processing of cleaning.

の An object of the present invention is to provide a static elimination method for eliminating static electricity at room temperature and dry using activated air.

In order to achieve the above object, the static elimination method according to the present invention removes static electricity by air containing air ions and water clusters.

ADVANTAGE OF THE INVENTION According to the present invention, air ions contained in active air and water clusters act on each other to effectively remove various kinds of deposits such as contaminants and other contaminants adhering to an object to be washed, such as contaminants. No dust or the like re-adheres to the surface of the object to be cleaned treated by the method of the present invention for a certain period of time, so that a clean state can be maintained.

Furthermore, the treatment of the present invention is different from washing with a washing liquid, in that the active air is humid air, but the object to be washed does not get wet even when it touches the object to be washed, so that the drying treatment after washing is not necessary, and immediately after washing. It can be carried into the next process to reduce the operating time of the line.

Therefore, excellent effects can be obtained by applying the present invention to cleaning of various precision parts, including cleaning of a Si wafer in an LSI manufacturing process.

The present invention is a static elimination method for removing static electricity by air containing air ions and water clusters. It is said that air ions remove static electricity and the bonding strength of the attached matter to the object to be cleaned is weakened by the water cluster. Has an action.

The phenomenon in which nearby air is ionized when water droplets split in connection with rain or other precipitation has long been known as the Lennard effect. Leonard discovered that when a water droplet hits a metal plate and breaks, ions are generated in the nearby air. Simpson then repeated the Leonard experiment and measured it with a more precise instrument, and found that water droplets could split in air and produce similar results to the Leonard effect. The authors report that they are negative ions irrespective of the charge of the water droplet and that the water droplet obtains the same amount of positive charge as the ion generated during fission (Meteorological Electrochemistry Hisao Nao Hatakeyama, Minoru Kawano) Iwanami Shoten 1965, pp. 26-27).

負 Negative ions generated by the Leonard effect and the Simpson effect can be extracted to the outside by separating them from water droplets. A negative ion generator utilizing the Leonard effect is described in JP-A-4-141179, and a negative ion generator utilizing the Simpson effect is introduced in Japanese Patent Application No. 5-261396. This device injects a liquid into a swirling flow of an air flow to break it into fine water droplets, then performs gas-liquid separation, and extracts air containing negative ions as supply air. Is basically humid.

It has been found that humid air containing fine water droplets that squirt a liquid into the swirling flow of airflow and split it has dust-removal, bacteria-removal, deodorization and gas component removal effects, humidity control effects, and antistatic effects. I have. Initially, these effects were all thought to be due to the effect of generating fine water droplets, and then to the effect of negative ions in the air.

(4) The components generated by the activation treatment were thought to be two kinds, air ions and fine water droplets, but also contained water clusters. According to the classification of FIG. 1, a cluster indicates a structure of a substance composed of two to 1,000 atoms or molecules (Koji Kajimoto, “Chemistry of Clusters”, 1992, p3, ( See) Baifukan Co., Ltd.).

(4) Most of the components contained in the active air are water vapor and the amount of negative ions and fine water droplets is negligible compared to the water vapor content. It is presumed that most of the water vapor contained in the active air is probably water clusters.

{Liquid water forms an aggregate-cluster such as (H2O) n (n = 1, 2,...) By hydrogen bonding, ice has n = ∝, and water vapor has the smallest n. Water in which n is small has high activity. According to the cluster model, the smaller clusters have a smaller number of interacting water molecules than the larger clusters, so the surface area can be increased with less energy. That is, small water clusters have low surface tension and low viscosity.

Therefore, the water cluster in the active air obtained by the activation treatment plays an important role in penetrating under the attached matter and releasing it on the article to be washed when the article to be washed is washed.

The humid active air obtained by the water activation treatment contains air ions and water clusters, and the air ions remove bacteria and static electricity adhering to the surface of the object to be cleaned, and remove the adhering substances to the object to be cleaned. The bonding strength is weakened by the water cluster, and the deposits are removed from the surface of the object to be cleaned by the flow of the active air. In the installation space of the object to be cleaned, it is necessary to blow active air onto the surface of the object to be cleaned. The wind speed of the active air required for removing the deposit is 2 m / sec or more, preferably 5 m / sec or more.

(4) When the temperature of the object to be cleaned is lower than the ambient temperature in the cleaning chamber, a dew condensation phenomenon occurs on the object to be cleaned. When dew condensation occurs, water droplets are generated. When the water droplets are dried, they may be formed as stains on the surface of the object to be cleaned. In order to prevent this, it is necessary to maintain the temperature of the object to be cleaned at a temperature higher than the ambient temperature of the cleaning space. However, it is sufficient to maintain the temperature of the cleaning object at a temperature 1 ° C. higher than the ambient temperature of the cleaning space. ADVANTAGE OF THE INVENTION According to this invention, high-level washing | cleaning is possible in dry atmosphere using active air of a range of a normal temperature.

(Embodiment)
FIG. 2 shows a basic system of the present invention. In FIG. 2, the present invention is one in which an active air generator 1 is provided in a cleaning room 8. The active air generator 1 is roughly composed of a combination of a centrifugal force / Coriolis force generator 2 and a gas-liquid separator 4. The centrifugal force / Coriolis force generator 2 is functionally an ion dissociation mechanism, a water droplet activation mechanism, and a gas molecule ionization mechanism.

水 To the centrifugal force / Coriolis force generator 2, the water in the tank 9 is pumped up by the pump 10 and supplied, and the air in the cleaning chamber 8 is sucked and supplied by the high-speed airflow generator 3. The gas-liquid separation device 4 separates air output from the centrifugal force / Coriolis force generation device 2 from water droplets, and sends the air droplets into the cleaning chamber 8 under pressure. The washing room 8 is provided with a temperature controller 19 in the tank 9 to heat the circulating water.

FIG. 2 shows a situation in which the cleaning chamber 8 and the input side of the high-speed airflow generator 3 and the output side of the gas-liquid separator 4 are connected by pipes. It does not mean that it is installed outside the room. The active air generator may be installed in the cleaning room 8 and the air inlet of the high-speed air flow generator 3 and the air inlet of the gas-liquid separator 4 may be opened indoors.

The mechanism of active air generation is functionally ion dissociation processing performed by an ion dissociation mechanism, droplet activation processing and gas molecule ionization processing performed by water droplet activation and gas molecule ionization mechanisms, and gas-liquid separation mechanism And the gas-liquid separation process performed in this order, but each process is not always clearly distinguishable.

Fig. 3 shows an example of a specific device. The embodiment shows an example in which a device for generating negative ions using the Simpson effect is used for an active air generator.

In FIG. 3, a centrifugal force / Coriolis force generator 2 is a mechanism for performing ion dissociation processing of a liquid, activation processing of water droplets, and ionization processing of gas molecules. A spiral screw guide 14 shown in FIG. 4 is disposed along the axis, a nozzle pipe 15 is provided on the axis, and a water tank 16 is provided on the lower peripheral surface.

水 The water in the tank 9 is pumped into the water tank 16 by the pump 10, and the water in the water tank 16 is pumped by the pump 17 and sent to the nozzle pipe 15. The tank 9 is equipped with a temperature controller 19 and adjusts the supply water to a required temperature.

The screw guide 14 guides the air flow in the pneumatic transport tube 13 and turns the tube axis in a spiral shape. Since the nozzle pipe 15 is located at the axis of the pneumatic transport pipe 13 and the gas makes a swirling motion around the nozzle pipe 15, the screw guide 14 is not always necessary. Is used to define the direction of the turning direction of the airflow so that the Coriolis force points in the direction of the angular velocity vector of the earth rotation. However, if the direction of gas supply from the high-speed airflow generator 3 is set to be tangential to the inner circumference of the pneumatic transport tube 13, the direction of airflow rotation is naturally set to clockwise or counterclockwise swirl. Is done.

ノ ズ ル A nozzle 18 is opened at a key point on the peripheral surface along the axis of the nozzle pipe 15, and the nozzle 18 jets the water supplied from the water tank 16 into the swirling airflow in the pneumatic transport pipe 13. The water is ejected from the nozzle 18 at high pressure, and gains energy to split into fine water droplets.

(4) The high-speed airflow generator 3 is a fan for blowing air. In the embodiment, the air in the cleaning chamber 8 is sucked, and is blown into the pneumatic transport pipe 13 through the air inlet 5.

The gas-liquid separator 4 uses a cyclone separator in the embodiment. The cyclone separator is effective for centrifugal separation of gas and liquid as long as an air flow including fine water droplets discharged from the exhaust port 7 of the pneumatic transport pipe 13 can achieve a certain level of wind speed and wind pressure. The air separated into gas and liquid passes through the supply pipe 11 and is introduced into the cleaning chamber 8 from the outlet 11a.

In the embodiment, the high-speed airflow generator 3 is started, water in the water tank 16 is pumped up by the pump 17, and the strong airflow generated in the air-powered transport pipe 13 from each nozzle 18 of the nozzle pipe 15 is swirled. Spout against the direction of flow.

The water jetted into the pneumatic transport pipe 13 receives gas pressure, splits in a swirling air stream and is dissociated into ions, splits into fine water droplets, and pneumatically transports inside the pipe while turning along the screw guide 14. Is done. During this time, the water droplets flow in the axial direction while moving toward the tube wall under the action of the centrifugal force generated by the swirling flow of the air flow and the Coriolis force, and the water droplet interface that contacts the gas is activated while splitting into smaller water droplets When the dipole is oriented on the surface of the water droplet, oxygen molecules existing at the gas-side interface are ionized, and the air is activated.

The air containing water droplets flows into the gas-liquid separation device 4 from the exhaust port 7 of the pneumatic transportation pipe 13 to remove water droplets remaining in the air, and then is subjected to laminarization treatment, and is supplied as active air to the supply pipe 11. And is introduced into the cleaning chamber 8 from the blowing hole 11a. Thus, an atmosphere of humid active air is formed in the cleaning chamber 8. On the other hand, the air in the cleaning chamber 8 receives the suction force of the high-speed airflow generator 3 and is sucked into the return pipe 12 from the suction hole 12a, and if necessary, supplies newly introduced outside air to re-centrifugal force / Coriolis. The pressure is sent to the force generator 2.

水 Water droplets adhered to the tube wall of the pneumatic transport tube 13 and water droplets separated by the gas-liquid separator are collected in the water tank 16. Since a large amount of positive ions are contained in the water droplet, the tube wall is grounded and neutralized.

In the above, the embodiment shows the horizontal centrifugal force / Coriolis force generator, but the arrangement direction is not limited at all. The specification of the active air generator is, for example, as follows.

◎ Centrifugal / Coriolis force generator Dimensions: 450mm diameter x 900mm length
Inlet empty tower speed: 12m / sec
Exit superficial velocity: 10m / sec
◎ Gas-liquid separation device Dimensions: 410φ in diameter x 620mm in height
Inlet empty tower speed: 10m / sec
Exit superficial velocity: 8m / sec
◎ Fan Air volume: Max 13m ³ / min
The temperature controller 6.5 KW heater The active air generator shown in FIG. 3 is operated, and the temperature and humidity in the cleaning chamber, the particle size distribution of fine water droplets, and the ions are measured immediately near the active air outlet 11 a opening into the cleaning chamber 8. The amount was measured.

The particle size distribution number data of the fine water droplets was obtained from data measured in a single mode using a particle counter KC-18 and KC-01A of RION (Rion), a wind speed of 4 m / sec, a water pressure of 0.5 kg / cm ² , and city water. Used at the time of use. The ion concentration was measured under the same conditions using an ion counter (83-1001A) manufactured by RION.

The measurement results are as follows.

◎ Temperature and humidity of washing room Indoor temperature about 22 ℃
Indoor humidity about 95%
◎ Number of particle size distribution of fine water droplets (single mode)
It is as shown in Table 1.

Note) Calculated as 0.01 CF = 2.8 × 10 −4 m ³ .

◎ Ion concentration Table 2

From the results in Tables 1 and 2, when the abundances of fine water droplets and air ions (particularly negative ions) are determined by weight ratio, the results are as follows. The negative ion molecules were assumed to be O _2- (H ₂ O) n, where n = 10.

Total amount of fine water droplets (from 0.1 μm to 2 μm) 2-3 × 10 −6 g / m ³
Negative ion amount 6 × 10-11 g / m ³
On the other hand, the weight of water vapor contained in the air in the cleaning room at a room temperature of 22 ° C. and a room humidity of 95% is about 18 g / m ³ when calculated from a psychrometric chart. A water content of about 18 g / m ³ contained in the obtained active air is considered to be a water cluster.

(4) The centrifugal force / Coriolis force generating device is characterized by using a rotating coordinate system in addition to an inertial system to generate centrifugal force and Coriolis force in order to give high energy to water. At this time, as the superficial velocity (m / sec) of the high-speed airflow increases, the energy increases and a large amount of water clusters are generated. When the superficial velocity was set at 1.8 m / sec, 50 particles of 5 μm / 0.01 CF were detected by the particle counter.

In the embodiment, the outlet 11a of the supply pipe 11 is opened at the ceiling of the cleaning chamber 8, the suction hole 12a of the return pipe 12 is opened at the bottom, and the flow path of the active air is provided between the outlet 11a and the suction hole 12a. Is formed. The transporting machine 20 for transporting the object to be cleaned M is provided with a heater 21 and is installed in the flow path of the active air. The cleaning is performed by blowing active air onto the cleaning object M. Examples will be described below.

(Example 1)
Static neutralization experiments various materials and pulverized and classified to -325 mesh or less powder, BET specific surface area of ^(m 2 / gr) and weighed to measure, so that the total surface area is in the range of 800～1,000M ² A sample was prepared.

Various powder materials are evenly spread on a 25 × 25 cm square, 2 mm thick copper plate, placed in a washing room of 35 W × 35 L × 5 Hcm, sealed, and then supplied with the supplied air by a breeze (0.1 m / sec). After the sample was set, the amount of positive ions and the amount of negative ions were measured after 2 minutes and 5 minutes in the outlet. Table 3 shows the results.

(1) The experimental conditions are as follows.

(A) Cleaning room temperature: 23 ± 1 ° C
Humidity: 85 ± 2% RH
(B) Active air generator Model: 200Z
Air volume: 1m ³ / min

(2) Discussion The following is considered from the above measurement results.

(A) Metal powder (copper powder, stainless steel powder, aluminum powder, etc.) is in a state of being neutralized electrostatically.

(B) The resin powder (acrylic powder, PVC powder, etc.) has a large amount of both negative and positive ions consumed. From this, it is easily predicted that the resin powder is electrostatically charged and has a large electrostatic adhesion. Therefore, it can be said that the charge removal effect by the negative ions and the positive ions is large.

(C) Dust such as cotton (cotton), silk, dandruff (head scaling) and the like are consumed by a large amount of negative ions and a small amount of positive ions. Also, paper dust is consumed in large quantities only by negative ions. Therefore, it can be said that the charge removal effect by the negative ions is large.

(D) A large amount of negative ions are consumed in glass and silica powder. Therefore, it can be said that the charge removal effect by the negative ions is large.

(Example 2)
Experiment of cleaning process in various manufacturing processes (1) Sample Sample 1: 6-inch silicon wafer for semiconductor sliced, wrapped and polished from single crystal silicon Sample 2: 14-inch aluminum plate for hard disk chamfered, wrapped and polished ,
(2) The samples 1 and 2 were washed under the following conditions.

(A) Cleaning room ◎ Dimension: 40W × 40L × 10Hcm
◎ Room temperature: 21 ± 1 ℃
Indoor humidity: 90 ± 2% RH
◎ Object to be cleaned Temperature: 24 ± 1 ° C (Heating from below the object to be cleaned)
◎ Supply air Wind speed: 5m / sec
Negative ion amount: 220,000 to 230,000 / cc
Positive ion amount: 1,000 to 1.300 / cc
(B) Active air generator Model: 500Z
Water used: distilled water Water temperature: 24 ± 1 ° C
(C) Observation method Particles (particle system: 1 μm or more) adhered to the surface (measurement area: 9 cm ² ) of the objects to be cleaned (samples 1 and 2) were observed using an optical microscope (magnification: 1,000). The number (number) was observed and measured in a clean chamber.

(3) Results The results are shown in Table 4.

(4) Discussion The above results are performed in three stages, for example, a cleaning (ultrasonic wave + oscillation) process using a Freon solvent, a cleaning (ultrasound + oscillation) process using pure water, and a pre-drying process using IPA. The cleaning effect is almost the same as that of the conventional wet cleaning method.

(Example 3)
Purification experiment of atmospheric air transported from the active air generator (1) To investigate the performance of removing contaminants contained in the active air sent into the cleaning room, activate the atmosphere considered to be the most extreme polluting atmosphere. A processing experiment was conducted by incorporating it into an air generator.

A centrifugal force / Coriolis force generator having the above specifications was used, and a gas-liquid separator was a particle separator described in Japanese Patent Application No. 6-5870. This device has been developed for the purpose of strongly removing particles contained in a gas including ultrafine particles, and generally has a structure shown in FIG. That is, in FIG. 5, a conical cylinder 25 is installed in two stages in a cylindrical body 24 having a gas inlet 22 and a gas outlet 23. The blowing port 22 is an opening for introducing gas containing particles from the lower peripheral surface of the body of the cylindrical body 24 into the cylindrical body, and the blowing port 23 is provided at the top of the cylindrical body 24 to remove the particles. This is an opening for exhausting air. The conical cylinder 25 is a conical hollow cylinder having openings of large and small diameters at the top and bottom, and is disposed immediately below the outlet 23 with the large-diameter opening facing upward. The gas containing the particles forms an upward swirling flow A and rises on the inner wall of the cylindrical body 24, and a part of the gas is exhausted as an exhaust flow C from the outlet 23. The particles are inverted at the upper part of the body 24 to form a downward swirling flow B and descend the conical cylinder 25 to form a negative pressure region in a space above the conical cylinder 25, and particles remaining in the exhaust flow C are sucked.

In this embodiment, instead of the gas-liquid separator of FIG. 2, the particle separator of FIG. 7 is used, the inlet 22 is connected to the outlet of the centrifugal force / Coriolis force generator, and the active air is supplied to the outlet 23. Press out more and send to the cleaning room.

(2) Experimental conditions Air volume: 2.5 m ³ / min
Water used: Distilled water ◎ Intake air condition Temperature: 23 ° C
Humidity: 55% RH
Negative ion amount: 90 / cc
Positive ion amount: 100 / cc
◎ Activated air condition Temperature: 21 ℃
Humidity: 91% RH
Negative ion amount: 220,000 to 230,000 / cc
Positive ion amount: 1,000 to 1.300 / cc
(3) Measuring instrument Number of particles: Particle counter manufactured by Rion Co., Ltd. Model: KC-01A
Measurement: Single Mode
(4) Measurement results Table 5 shows the measurement results.

(Note 1) Supply air was passed through an atmosphere cooled to −150 ° C. to collect condensed water, and the following items were measured.

(1) Evaporation residue: Gravimetric method (2) Cation (Na, K, Ca, Mg, etc.): Atomic absorption spectrophotometry (3) Anion ( _C1- , _NO3- , _SO4-3, etc.): Ion chromatography Graphic method (4) Silicon (Si): Spectrophotometric method No result was obtained for any of the above items.

(5) Consideration From the measurement results, it is considered that the active air is a clean atmosphere, and the particles detected by the particles and the counter are not solid particles but water clusters due to water molecules are measured. Therefore, it was found that the air contaminated in the cleaning room was cleaned by the active air generator.

電 The static elimination method according to the present invention is applicable and useful for static elimination.

Diagram showing differences in names according to the number of constituent molecules Diagram showing the basic system of the present invention FIG. 1 shows an embodiment of the present invention. The figure which shows the example of arrangement of a screw guide The figure which shows an example of the gas-liquid separation apparatus used for the Example of this invention.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 active air generator 2 centrifugal force / Coriolis force generator 3 high-speed airflow generator 4 gas-liquid separator 5 suction port 6 liquid suction port 7 exhaust port 8 washing room 9 tank 10 pump 11 supply pipe line 11a outlet hole 12 return pipe Road 12a Suction hole 13 Pneumatic transport pipe 14 Screw guide 15 Nozzle pipe 16 Water tank 17 Pump 18 Nozzle 19 Temperature controller 20 Transporter 21 Heater M Object to be cleaned

Claims (1)

A static elimination method for removing static electricity by air containing air ions and water clusters.

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