JPH06296897A - Method and device for cleaning closed space - Google Patents

Abstract

PURPOSE:To provide a method and device for cleaning a closed space where a running cost is inexpensive and the closed space is cleaned rapidly and easily. CONSTITUTION:A device for cleaning a closed space is equipped with ultraviolet rays 11 and/or a radiation source, a photoelectric emission material 13 for emitting photoelectrons by the radiation source, an electrode material 14 for forming an electric field, a collection material 14 for collecting fine particles charged by the photoelectrons and a heating part 15-1 for forming the temperature difference in space inside the closed space 10. Circulation of gas is performed by providing the temperature difference in the space by the heating part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for cleaning an enclosed space, and more particularly to a cleaning method and apparatus for collecting and removing fine particles (particles) present in the enclosed space by charging.
The cleaning method and apparatus of the present invention is a clean room in various industries such as home, office, hospital, or semiconductor industry, pharmaceutical industry, food industry, agriculture and forestry industry, pharmaceuticals, precision machinery industry,
A closed space in a sterile room, such as a safety cabinet,
It can be used for cleaning a clean box, a valuables storage, a wafer storage, a sealed transfer space for valuables, and a clean sealed space (in the presence of various gases).

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. 3 by taking gas cleaning in a wafer storage in the semiconductor field as an example. In FIG. 3, the gas 2 in the wafer storage 1 which is a closed space is cleaned by the fan 3 and the high performance filter 4. That is, the gas 2 in the wafer storage 1 is passed through the high-performance filter 4 by suction of the fan 3, the fine particles in the gas 2 are collected and removed, and the gas is purified (a space (place) to be cleaned). 1 and dust collection place 4 for cleaning are separated). With this configuration, it is necessary to compulsorily fluidize the gas with a fan in order to purify the gas.

[0003]

In the above method, the gas cleaning capacity is limited, and the number of circulations of the gas 2 to the high performance filter 4 must be increased for high cleaning. Power costs were high and there was a problem. Further, since the space (place) 1 to be cleaned and the dust collecting place 4 for cleaning are separated, it is necessary to fluidize the gas, and there is a problem such as generation of particles accompanying the fluidization. Further, in a closed space in a vacuum state, since the generated fine particles are in a vacuum state in the system,
There was a problem that it was not possible to collect and remove fine particles quickly.
Therefore, an object of the present invention is to solve the above problems and provide a method and apparatus for cleaning an enclosed space which can be cleaned quickly and easily with low operating cost.

[0004]

In order to achieve the above object, in the present invention, the photoelectron emitting material is exposed to ultraviolet rays and / or
Or, by emitting radiation to emit photoelectrons in the closed space, after charging the fine particles contained in the closed space by the photoelectrons, in removing the charged fine particles in the charged space, A temperature difference is provided in the space to circulate the gas in the space.

Further, in the present invention, an ultraviolet and / or radiation source, a photoelectron emitting material for emitting photoelectrons by the radiation source, an electrode material for forming an electric field, and charged fine particles charged by photoelectrons are provided in a closed space. A charged fine particle collecting material for collecting
A cleaning device for a closed space, comprising: a heating unit for forming a temperature difference in the space.
That is, in removing fine particles in a closed space, a method of charging the fine particles by photoelectrons and collecting and removing the charged fine particles in the same space (place) while circulating a gas in the space by providing a temperature difference in the space And the device.

Next, each structure of the present invention will be described in detail. The photoelectron emitting material may be any material as long as it emits photoelectrons upon irradiation with ultraviolet light, and a material having a smaller photoelectric work function is more preferable.
r, Ca, Y, Gd, La, Ce, Nd, Th, Pr,
Be, Zr, Fe, Ni, Zn, Cu, Ag, Pt, C
d, Pb, Al, C, Mg, Au, In, Bi, Nb,
Any one of Si, Ti, Ta, U, B, Eu, Sn and P or a compound or alloy or mixture thereof is preferable, and these are used alone or in combination of two or more kinds. As the composite material, a physical composite material such as amalgam can also be used.

For example, compounds include oxides, borides, and carbides, and oxides include BaO, SrO, and Ca.
O, Y ₂ O ₅ , Gd ₂ O ₃ , Nd ₂ O ₃ , ThO ₂ , Z
rO ₂ , Fe ₂ O ₃ , ZnO, CuO, Ag ₂ O, La
₂ O ₃ , PtO, PbO, Al ₂ O ₃ , MgO, In ₂
There are O ₃ , BiO, NbO, BeO, etc., and boride includes YB ₆ , GdB ₆ , LaB ₅ , NdB ₆ , CeB.
₆ , EuB ₆ , PrB ₆ , ZrB _{2 and the} like, and as the carbide, UC, ZrC, TaC, TiC, Nb.
C, WC, etc. In addition, as the alloy, brass, bronze,
Phosphor bronze, an alloy of Ag and Mg (Mg is 2 to 20 wt.
%), An alloy of Cu and Be (Be is 1 to 10 wt%) and an alloy of Ba and Al can be used. The alloy of Ag and Mg, the alloy of Cu and Be, and the alloy of Ba and Al can be used. Alloys are preferred. The oxide can also be obtained by heating only the metal surface in air, or by oxidizing with a chemical.

Yet another method is to heat before use,
An oxide layer can be formed on the surface to obtain a stable oxide layer for a long period of time. As an example of this, an alloy of Mg and Ag can form an oxide film on its surface in water vapor at a temperature of 300 to 400 ° C., and this oxide thin film is stable for a long period of time. In addition, the present inventor
As already proposed, a photoelectron emitting material having a multiple structure can also be suitably used (JP-A-1-155857).
Further, a substance capable of emitting photoelectrons in a thin film form may be added to an appropriate base material and used. As an example of this, there is a thin film of Au added as a substance capable of emitting photoelectrons on a quartz glass as a UV transparent substance (base material).

The shape of these materials to be used may be plate-like, pleated, curved, net-like or the like, but a shape having a large irradiation area of ultraviolet rays and a large contact area with the processing space is preferable. The emission of photoelectrons from the photoelectron emitting material can be effectively carried out by appropriately using a reflective surface, a curved reflective surface, or the like, as already proposed by the present inventor (JP-A-63-100955). Gazette). The shapes of the photoelectron emitting material and the reflecting surface differ depending on the shape and structure of the device or the desired efficiency, and can be appropriately determined.

Any type of ultraviolet light may be used as long as the photoelectron emitting material can emit photoelectrons upon irradiation thereof.
Depending on the field of application, those having a sterilizing action are also preferable. The type of UV light depends on the application field, work content,
It can be appropriately determined depending on the use, economy and the like. For example, in the biological field, it is preferable to use deep ultraviolet rays together from the viewpoint of bactericidal action and efficiency. As the ultraviolet ray source, any one can be used as long as it emits ultraviolet rays,
It can be appropriately selected and used depending on the application field, the shape of the device, the structure, the effect, the economical efficiency and the like. For example, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, or the like can be used as appropriate. In the biological field, sterilization wavelength 2
It is preferable to use an ultraviolet ray having a wavelength of 54 nm because the sterilizing effect can be used together.

The fine particles in the closed space are efficiently charged by irradiating the photoelectron emitting material with ultraviolet rays in an electric field. The present inventors have already proposed charging in an electric field (eg, JP-A-61-178050 and JP-A-62-2).
No. 44459, Japanese Patent Application No. 1-120653). In the present invention, since the gas does not flow, the electric field voltage used in the present invention is effective even in a weak electric field, and the electric field voltage is 0.1 V / cm to 2 KV / cm. The suitable strength of the electric field can be determined by carrying out preliminary tests and studies as appropriate depending on the field of use, conditions, device shape, scale, effect, economical efficiency and the like.

As the collecting material (dust collecting material) for the charged fine particles, any material can be used as long as it can collect the charged fine particles. Dust collecting plate, dust collecting electrode in an ordinary charging device, various electrode materials, and electrostatic filter method are generally used, but the collecting part itself such as steel wool electrode or tungsten wool electrode constitutes a wool-like structure. Things are also valid. Electret materials can also be preferably used. Further, the method of collecting using an ion exchange filter (or fiber), which has been already proposed by the present inventor, is also effective (JP-A-63-63)
54959, 63-77557, 63-846.
No. 56).

The ion exchange filter is practically preferable because it can simultaneously collect the coexisting acidic gas, alkaline gas, odorous gas, etc. in addition to collecting the charged fine particles. The type, amount and ratio of the anion exchange filter and cation exchange filter used depend on the charge state and concentration of the charged fine particles in the gas, or the type and concentration of the accompanying acidic gas, alkaline gas, odorous gas, etc. Can be appropriately determined. For example, an anion exchange filter is effective in collecting negatively charged fine particles and acidic gas, and a cation exchange filter is effective in collecting positively charged fine particles and alkaline gas. The amount and ratio of the filter used correspond to the concentration and concentration ratio of the substances to be collected, and the amount corresponding to these should be taken into consideration in consideration of the application field, shape, structure, effect, economical efficiency of the device, etc. It may be decided as appropriate.

For collection, these collection methods may be used alone, or two or more of these methods may be used in combination as appropriate. As the electrode material for the electric field, those used in ordinary charging devices can be preferably used. That is, a known one can be used. The electrode material for an electric field can be used also as or integrated with the charged particle collecting material (dust collecting material).
For example, among the above-mentioned charged particulate matter collecting materials, various electrode materials such as a dust collecting plate, a dust collecting electrode, or a wool-like electrode material such as a steel wool electrode and a tungsten wool electrode are used as an electric field electrode and a collection of charged particulate matter. It is preferable because it can be combined with the above.

Further, a material other than the electrode material such as an electret material or an ion exchange filter (a material characterized by collecting fine particles) can be integrally used with the above-mentioned appropriate electric field electrode material. The irradiation source for emitting photoelectrons from the photoelectron emitting material may be any one as long as it emits photoelectrons upon irradiation. In addition to the ultraviolet rays described in this example, electromagnetic waves, lasers, and radiations can be appropriately selected and used according to application fields, device scales, shapes, effects, and the like. Among these, ultraviolet rays and / or radiation are usually preferable in terms of effects and operability.

By irradiating with radiation instead of irradiating with ultraviolet rays, the fine particles are similarly charged and the same effect can be obtained. The present inventor has already proposed irradiation of radiation (Japanese Patent Application Laid-Open No. 62-24459).
Each component, instrument, etc. for collecting charged and charged fine particles (irradiation source, photoelectron emission material, electrode, charged fine particle collection material)
Can be installed at an appropriate position depending on the application field, device scale, and the like. In addition, a heating unit (use of convection due to temperature difference) is installed in a part of the closed space to circulate gas in the space.

Next, the heating unit for providing the temperature difference will be described. The heating unit is provided by installing a heating source at an appropriate position below the closed space. It is preferable that the heating source is usually installed in the charge collecting portion of the fine particles because the circulation of the gas in the space becomes effective. Well-known means can be used as the heating source, and examples thereof include a heater (heat transfer coil, hot water) and an infrared lamp. Of course, in the present invention, it suffices that heat convection is generated, and therefore it does not prevent cooling of an appropriate position above the sealed space.

The temperature difference is effective at 3 ° C. or higher. The higher the temperature difference is, the more effective it is. You can Usually the temperature difference is 3 to 30 ° C. The type of heating source to be used and the position of installation of the heating source can be appropriately determined by conducting a preliminary test depending on the field of use, apparatus shape, structure, material, required performance, type of medium gas and the like. In the present invention, the gas existing in the closed space can be similarly carried out in other gas such as nitrogen or argon other than air. The present invention relates to the cleaning of a closed space (still space), but it goes without saying that it can be similarly implemented even when there is a slight flow of gas.

[0019]

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto. Example 1 Air cleaning in a wafer storage of a semiconductor factory will be described with reference to the basic configuration diagram of the present invention shown in FIG.

The air cleaning of the wafer storage 10, which is a closed space, is performed by an ultraviolet lamp 11, an ultraviolet reflecting surface 12, a photoelectron emitting material 13, an electrode 14 for setting an electric field, and charging, which are installed outside the wafer storage 10. Fine particle collector 14 (in this configuration, the electrode also serves as the collector), heater 15-1
Will be implemented in. That is, the fine particles (particles) 16 in the wafer storage 10 are charged by the photoelectrons 17 emitted from the photoelectron emitting material 13 irradiated by the ultraviolet lamp 11 to become charged fine particles 18 (charge part), and the charged fine particles 1
8 is collected (collecting section) by the collecting material 14 for charged fine particles.
That is, the charged fine particles are simultaneously collected and removed in the space where the fine particles are charged.

Here, the processing air 19 containing the fine particles 16
Is a heater 15- in the charging / collecting section A for fine particles.
Due to the temperature difference between the upper and lower sides caused by the heating by 1, the fine particles are efficiently circulated in the charging / collecting section. 20
Is the air after treatment. In the case of the stocker, it is practically important how quickly ultra-cleaning can be performed (for example, class 1000 air can be cleaned below class 1). Since the particulate removal efficiency in the circulation is usually 75 to 95% (determined by the shape of the apparatus and the operating conditions), it is possible to achieve ultra-cleaning in a short time by effectively performing the circulation.

In this way, the fine particles (particulate matter) in the wafer storage 10 are collected and removed, and the space B to be cleaned is cleaned.
Are cleaned, and the wafer storage is cleaned with clean air. In the above, for the irradiation of the photoelectron emitting material with ultraviolet rays, the curved reflecting surface 12 is used, and the ultraviolet rays are efficiently emitted from the ultraviolet lamp 11 to the plate-like photoelectron emitting material. The electrode 14 is installed to charge the particles 16 in an electric field. That is, an electric field is formed between the photoelectron emitting material 13 and the electrode 14.

The particles are charged efficiently by irradiating the photoelectron emitting material 13 with ultraviolet rays in an electric field. The voltage of the electric field here is 20 V / cm. The collection of charged particles is performed using the dust collecting plate 14. The ultraviolet lamp 11 in this example is a germicidal lamp (main wavelength: 254 nm), and the photoelectron emitting material 13 is a quartz glass for ultraviolet irradiation coated with Au50Å. 21
Is a wafer and 22 is a wafer case.

Example 2 In Example 1, the case where the heating source is an infrared lamp is shown in FIG.
Shown in. An infrared lamp 15-2 is used as a heating source,
Infrared rays from the infrared lamp 15-2 are charged by the quartz window and charged.
By irradiating the air in the collection part A to heat it, a temperature difference is generated to effectively circulate the processing gas 19 containing the fine particles 16. As a result, the space B to be cleaned can be made extremely clean in a short time. The symbols in FIG. 2 are the same as those in FIG.
Has the same meaning as.

Example 3 In the case where the following sample gas was put into the purifier having the configuration shown in FIG. The change with time of the fine particle concentration in the purifier was examined using a particle measuring instrument (particle counter). Purifier size: 70 liters, photoelectron emission material: Quartz glass with Au added in thin film form Electrode material: Cu-Zn plate Charged particulate collection material: Also used as electrode material

Ultraviolet lamp: Sterilization lamp Electric field voltage: 50 V / cm Sample gas (inlet gas): Air (concentration (class): 1
Heating source: A tape heater with a built-in nichrome wire heater is installed at the entrance of the charging / collecting section A. Temperature difference in charging / collecting part A (temperature difference between inlet and outlet of part A): 3 ° C., 5 ° C., 10 ° C., 20 ° C. Required to obtain ultimate cleanliness of class 1 in each temperature difference experiment I checked the proper driving time. As a comparison, the same investigation was carried out also when a heating source was not used. (The above class is the total number of fine particles having a particle size of 0.1 μm or more present in 1 ft ^3. )

The results are shown in FIG. When the heating source was not used, the temperature difference between the upper part and the lower part of the charging / collecting section A was about 2 ° C.
In addition, when the circulating amount of the charging / collecting section A and the space to be cleaned B was measured, it was 8 liters / m when a heating source was not used.
In the case of a temperature difference of 5 ° C. in, it was 15 liter / min. In the embodiments, the case where the medium gas is air has been described, but it is needless to say that the present invention is not limited to the medium gas, and other medium gases such as N ₂ and Ar can be similarly used.

[0028]

EFFECTS OF THE INVENTION With respect to cleaning of a closed space (still space), a temperature difference is provided between charging by irradiation of ultraviolet rays and / or radiation and collection and removal of the charged fine particles from the space to circulate gas in the space. By doing so, the gas to be treated is effectively circulated to the charging / collecting part of the fine particles by photoelectrons, so that the fine particles in the closed space are quickly
It could be removed easily. In other words, the ultra-clean space was created quickly and effectively. Since the sealed space can be handled (processed) as it is, the handling (operation) is easy, and the cleaning method and device are compact and inexpensive.

Since the fine particles generated in the closed space can be collected quickly and effectively, the practicality is further improved. It can be carried out similarly in various gases such as nitrogen and argon, so that it is practically effective. With, it could be widely applied to clean closed spaces in various fields. Since the charged particles can simultaneously collect the charged fine particles (the charged spaces can simultaneously collect the charged fine particles), the apparatus is a compact and inexpensive cleaning method and apparatus. Since the electrode material for the electric field can also serve as the charged particle collecting material or can be integrated, the device can be made compact. From the above, the practical application of cleaning the enclosed space using photoelectrons was further improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a closed space cleaning device of the present invention.

FIG. 2 is a cross-sectional configuration diagram showing another device for cleaning an enclosed space according to the present invention.

FIG. 3 is a schematic configuration diagram showing a conventional cleaning device.

FIG. 4 is a graph showing the relationship between the operating time until reaching class 1 and the temperature difference.

[Explanation of symbols]

10: Wafer storage, 11: UV lamp, 12: Reflecting surface, 13: Photoelectron emitting material, 14: Collection material (also used as an electrode)
15-1: heater, 15-2: infrared lamp, 1
6: fine particles, 17: photoelectrons, 18: charged fine particles, 19,
20: Air flow, 21: Wafer, 22: Wafer case

Front page continuation (72) Inventor Kazuhiko Sakamoto 2-4-1 Minamimotojuku, Urawa City, Saitama Prefecture

Claims (2)

[Claims] 1. A photoelectron emitting material is irradiated with ultraviolet rays and / or radiation under an electric field to emit photoelectrons into a closed space, and the photoelectrons are charged with fine particles contained in the closed space, and then charged. A method for cleaning an enclosed space, characterized in that a temperature difference is provided in the space to circulate a gas in the space when the charged fine particles are removed in the space being charged. 2. An ultraviolet and / or radiation source and a photoelectron emitting material which emits photoelectrons by the radiation source in a closed space.
An enclosed space characterized by having an electrode material for forming an electric field, a charged fine particle collector for collecting charged fine particles charged by photoelectrons, and a heating unit for forming a temperature difference in the space. Cleaning equipment.