JP2863419B2 - Method and apparatus for preventing contamination of substrate or substrate surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for preventing contamination of a substrate or a substrate surface in a space, and particularly to a raw material, a semi-finished product, and a substrate of a product in advanced industries such as semiconductor production and liquid crystal production. And prevention of contamination of the substrate surface. The application fields of the present invention are, for example, (1) prevention of contamination of a wafer in a semiconductor manufacturing process, (2) prevention of contamination of a glass substrate in a liquid crystal manufacturing process, and (3) prevention of contamination of a base material in a precision machine manufacturing process.

Examples of locations to which the method and apparatus for preventing contamination of the present invention are applied include spaces in a clean room such as a semiconductor manufacturing plant, a liquid crystal manufacturing plant, and a precision machine manufacturing plant, for example, all cabinets, clean boxes, and storage of valuables. Includes wafer storage, sealed transfer space for valuables, clean sealed space in the presence of various gases or under reduced pressure or vacuum, transfer space, space containing gas supplied to the cleaning device, air supply for air knife There is space.

[0003]

2. Description of the Related Art The prior art will be described below by taking air purification in a clean room in a semiconductor manufacturing plant as an example.
In a clean room, fine particles (particulate matter)
Gaseous substances such as hydrocarbons (HC) at extremely low concentrations other than methane in the air due to automobile exhaust gas and the like pose a problem as pollutants. In particular, H. C is a gaseous harmful component and must be removed because it has a very low concentration in normal air (indoor air and outside air). Also,
Various solvents (alcohols, ketones, etc.) generated in the operation in the clean room also pose a problem as pollutants.

That is, if the above-mentioned contaminants (fine particles and gaseous contaminants) deposit on the substrate surface of a wafer, semi-finished product, or product, the substrate surface is easily damaged, and the productivity (yield) of semiconductor products is reduced. It is necessary to remove contaminants because they cause this. Both the fine particles and the gaseous substance increase the contact angle on the substrate surface. C has a high tendency to increase the contact angle. Here, the contact angle is a contact angle of wetting by water, and indicates a degree of contamination of the substrate surface. That is, when a hydrophobic (oil-based) substance is attached to the surface of the substrate, the surface repels water and becomes difficult to wet. Then, the contact angle between the substrate surface and the water droplet increases. Therefore, the contamination degree is high when the contact angle is large, and low when the contact angle is small.

[0005] Conventional clean room air purification methods or apparatuses therefor are roughly classified into (1) a mechanical filtration method (such as a HEPA filter), (2) electrostatically collecting fine particles, and using a high voltage. There is a filtration method using a charged or conductive filter (such as a HESA filter). All of these methods are aimed at removing fine particles, such as hydrocarbons other than methane (HC).
It has no effect on the removal of gaseous pollutants which increase the contact angle. On the other hand, gaseous pollutants H. As a method for removing C, a combustion decomposition method, an O ₃ decomposition method, and the like are known. However, these methods use extremely low concentrations of H.V. contained in air introduced into a clean room. There is no effect in removing C.

The present inventors have already proposed a method and an apparatus using an adsorbent or an absorbent to prevent the increase in the contact angle as a method and an apparatus for preventing contamination of the surface of the base material or the substrate. (Japanese Patent Application No. 3-341802, Japanese Patent Application No. 4-180538). In these methods and devices,
H. Since an adsorbent or an absorbent is used for removing C, there is a problem that waste is generated. While these methods and apparatus are effective in some applications, further improvements need to be made to increase their practicality. That is, in order to improve the productivity of semiconductor products, it is necessary to increase the particulate matter and the contact angle. C must be effectively removed.

[0007]

Accordingly, an object of the present invention is to increase the contact angle between the fine particles contained in the air introduced into the clean room, the substrate and the substrate surface. H. which effectively removes C or does not contribute to increasing the contact angle. It is an object of the present invention to provide a method and an apparatus which enable conversion into C.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method for preventing contamination of a substrate or a substrate surface by removing a gas containing at least hydrocarbon which comes into contact with the substrate or the substrate. Means and a means for decomposing hydrocarbons by irradiating light onto the photocatalyst, the concentration of fine particles in the gas is 10 or less, and the concentration of non-methane hydrocarbons is 0.2
After the concentration is reduced to ppm or less, the gas is exposed to the substrate or the substrate surface. Further, according to the present invention, in a device for preventing contamination of the surface of a substrate or a substrate, a dust removing means for passing a gas in contact with the substrate or the substrate, for removing fine particles to class 10 or less, and a non-methane hydrocarbon And a means for decomposing hydrocarbons by irradiating the photocatalyst with light to remove the hydrocarbons to 0.2 ppm or less.

Hereinafter, the present invention will be described in detail by taking, as an example, the case where the gas contacting the surface of the substrate or the substrate is air. As the dust removing means in the present invention, any means can be used as long as it can remove fine particles in the air to a low concentration, and a known means can be appropriately used. Generally, a well-known dust filter that efficiently collects fine particles to a low concentration,
Alternatively, charging and collection of fine particles using photoelectrons already proposed by the present inventors (eg, Japanese Patent Publication No. 3-5859,
262954, JP-A-4-171610).

In a system using a filter, generally, HE
PA filters, ULPA filters, and electrostatic filters are preferred because they are simple and effective. Usually, one or more of these filters are used in appropriate combination. Next, a method using photoelectrons will be described. In this method, a photoelectron emitting material is irradiated with ultraviolet rays to generate photoelectrons,
The fine particles are removed by charging the fine particles with the photoelectrons and collecting the charged fine particles using a collector.

The configuration of this system will be described below. The photoelectron emitting material may be any material that emits photoelectrons by irradiating ultraviolet rays. The smaller the photoelectric work function is, the better. Ba, Sr, C
a, Y, Gd, La, Ce, Nd, Th, Pr, Be,
Zr, Fe, Ni, Zn, Cu, Ag, Pt, Cd, P
b, Al, C, Mg, Au, In, Bi, Nb, Si,
One of Ti, Ta, U, B, Bu, Sn, P, and W, or a compound or alloy or a mixture thereof is preferable, and these can be used alone or in combination of two or more. As the composite material, a physical composite material such as amalgam can 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
O ₃ , BiO, NbO, BeO, etc., and borides include YB ₆ , GdB ₆ , LaB ₅ , NdB ₆ , Ce
_{B 6, BuB 6, PrB 6} , ZrB 2 include, as a further carbide UC, ZrC, TaC, TiC, Nb
C and WC.

The alloys include brass, bronze, phosphor bronze, an alloy of Ag and Mg (Mg is 2 to 20 wt%), Cu
Of Be and Al (Be is 1 to 10 wt%) and Ba and Al
An alloy of Ag and Mg, an alloy of Cu and Be, and an alloy of Ba and Al are preferable. The oxide can also be obtained by heating only the metal surface in air or oxidizing it with a chemical.
As still another method, it is possible to form an oxide layer on the surface by heating before use to obtain a stable oxide layer for a long time. As an example, an oxide film can be formed on the surface of an alloy of Mg and Ag in water vapor at a temperature of 300 to 400 ° C., and this oxide thin film is stable for a long period of time.

Further, a photoelectron emitting material having a multi-layered structure as already proposed by the present inventor can also be suitably used (Japanese Patent Application No. 1-155857). Further, a substance capable of emitting photoelectrons can be added to a suitable base material in the form of a thin film and used (Japanese Patent Application No. 2-278123). As an example of this, there is a substance in which Au is added in the form of a thin film as a substance capable of emitting photoelectrons on quartz glass as an ultraviolet transmitting substance (base material) (Japanese Patent Application No. 2-295423). When a photoelectron emitting material is used by being added to a base material, as has been already proposed by the present inventors, a conductive substance can be added and used. (Japanese Patent Application No. 3-258718)
issue).

The shapes of these materials used are rod-like, linear,
Lattice shape, plate shape, pleated shape, curved surface shape, cylindrical shape, wire mesh shape, etc. can be used, and a shape with a large UV irradiation area is good. Depending on the device, fine particles existing in the cleaning space (described later) may be used. What can move quickly to a fine particle collection device (later mentioned) is preferred. Depending on the type of particle collection device,
An ultraviolet light source, for example, an ultraviolet lamp, and a photoelectron emitting material may be disposed (coated) in a thin film on the surface and / or in the vicinity thereof and integrated. (Japanese Patent Application No. 3-22685
issue). The shape to be used can be appropriately determined depending on the scale of the stocker and the type of the particle collecting device as described later.

The irradiation source for emitting photoelectrons from the photoelectron emitting material may be any source that 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 depending on the application field, the scale of the device, the shape, the effect, and the like. Of these, in terms of effects and operability,
Ultraviolet light is usually preferred. The type of the ultraviolet light may be any as long as the photoelectron emitting material can emit photoelectrons by irradiation, and depending on the application field, a material having a sterilizing (sterilizing) action is also preferable. The type of UV light depends on the field of application,
It can be appropriately determined according to the work content, application, economy, and the like. For example, in the biological field, it is preferable to use far ultraviolet rays in combination from the viewpoints of sterilization and efficiency.

As the ultraviolet light source, any one that emits ultraviolet light can be used, and it can be appropriately selected and used depending on the field of application, the shape, structure, effect, economy, etc. of the device. For example, a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube and the like can be used as appropriate. In the biological field, it is preferable to use an ultraviolet ray having a sterilization (sterilization) wavelength of 254 nm because the sterilization (sterilization) effect can be used in combination. next,
The position and shape of the photoelectron emitting material and the electric field electrode will be described. The photoelectron emitting material and / or the electrode are installed in a part of a space at an appropriate position in the space where the fine particles are present so that an electric field can be formed between the electrode and the photoelectron emitting material. An electric field (electric field) is formed between (+). Photoelectrons are efficiently emitted from the photoelectron emitting material by the electric field.

The positions and shapes of the photo-emissive material and the electrodes can be appropriately selected depending on the scale of the apparatus and the type of the particle trapping device. Any method can be used as long as it can effectively charge the fine particles and effectively collect the charged fine particles. Depending on the type of the particle collecting device, an ultraviolet light source, for example, an ultraviolet lamp having a shape surrounded by a photoelectron emitting material and an electrode can be appropriately used. (Japanese Patent Application 3-261289
issue). These shapes can be appropriately determined by a preliminary test or the like in consideration of the application field, the scale of the device, the shape, the effect, the economy, and the like.

Further, a collecting material (dust collecting material) for charged fine particles.
Can be used as long as it can collect charged fine particles. Various electrode materials such as dust collecting plates and dust collecting electrodes in ordinary charging devices and electrostatic filter systems are generally used, but a wool-like structure in which the collector itself forms an electrode such as a steel wool electrode or a tungsten wool electrode Are also valid. Electrec materials can also be suitably used. Among the above-mentioned charged particle collecting materials, various electrode materials such as a wool-shaped electrode material such as a dust collecting plate or a dust collecting electrode or a steel wool electrode or a tungsten wool electrode serve as an electric field electrode and also collect charged particles. It is preferable because it can be done.

The electric field voltage used in the present invention is 0.1 V / cm
２2 kV / cm. A suitable electric field strength can be determined by appropriate preliminary tests and studies depending on the application field, conditions, apparatus shape, scale, effect, economy, and the like. By removing fine particles, the concentration of fine particles can be reduced to class 1000 (1000 particles / ft ³ )
Or less, preferably class 10 or less. Here, the class is a unit of particle concentration and represents the number of particles in 1 ft ³ .

Next, the means for decomposing hydrocarbons by light irradiation on the photocatalyst used in the present invention will be described. In order to remove non-methane hydrocarbons (gaseous harmful components), it is necessary to increase the contact angle. A photocatalyst that decomposes the C component is used. Non-methane hydrocarbons cause pollution at concentrations in normal air (room air and outside air). Further, among various non-methane hydrocarbons, the component that increases the contact angle is considered to differ depending on the type of substrate (wafer, glass material, etc.) and the type and properties of the thin film on the substrate. As a result of the inventor's intensive study, the non-methane hydrocarbon was used as an index,
The present inventors have found that it is effective to remove them to m or less, preferably to 0.1 ppm or less, and arrived at the present invention.

Next, the photocatalyst will be described. The photocatalyst material may be any as long as it is excited by light irradiation and decomposes non-methane hydrocarbons involved in increasing the contact angle.
Generally, semiconductor materials are preferable because they are effective, easily available, and have good workability. In terms of effectiveness and economy, S
e, Ge, Si, Ti, Zn, Cu, Al, Sn, G
a, In, P, As, Sb, C, Cd, S, Te, N
i, Fe, Co, Ag, Mo, Sr, W, Cr, Ba,
Any of Pb, their compounds, alloys, or oxides is preferable, and these are used alone or in combination of two or more.

For example, as elements, Si, Ge, Se,
Compounds include AlP, AlAs, GaP, AlSb,
GaAs, InP, GaSb, InAs, InSb, C
dS, CdSe, ZnS, MoS ₂ , WTe ₂ , Cr ₂
Te ₃ , MoTe, Cu ₂ S, WS ₂ , and oxides such as TiO ₂ , Bi ₂ O ₃ , CuO, Cu ₂ O, ZnO, M
oO ₃ , InO ₃ , Ag ₂ O, PbO, SrTiO ₃ ,
BaTiO ₃ , Co ₃ O ₄ , Fe ₂ O ₃ , NiO and the like are available.

The installation shape and position of the photocatalyst material are fixed in an airflow and fixed to a wall surface, and the photocatalyst material can be used by being suspended in the airflow. Immobilization of the photocatalyst material, coating the photocatalyst material on the surface of glass or gaseous substance or coating the photocatalyst material on a suitable material such as plate, cotton, net, film or fiber, or wrapping, or You may pinch and fix and use. An example is the coating of titanium dioxide on glass fiber cloth by the sol-gel method. The photocatalyst can be used in powder form,
An appropriate shape can be used by a known method such as sintering, vapor deposition, or sputtering.

These can be appropriately selected according to the scale and shape and type of the apparatus, the type and shape of the light source, the type of photocatalyst, the desired effect, the economic efficiency, and the like. Further, in order to improve the photocatalytic action, Pt, Ag, Pd, KO is added to the photocatalytic material.
Substances such as H, RuO ₂ , and Co ₃ O ₄ can be added and used. As a light source for light irradiation, any light source that emits a wavelength that the photocatalyst material absorbs may be used. Light in the visible and / or ultraviolet region is effective, and an ultraviolet lamp or sunlight can be used as appropriate. . Usually, an ultraviolet lamp is preferable because of its high processing speed.

When photoelectrons are used as the dust removing means, it is preferable that the type of ultraviolet light has a wavelength that is absorbed by the photocatalyst material and a wavelength that has an energy equal to or higher than the photoelectric threshold of the photoelectron emission material used. What is necessary is just to select a lamp that emits a wavelength in the light absorption region determined by the type of the material.
For example, when TiO ₂ is used as a photocatalyst material, a lamp that emits light having a wavelength in the near ultraviolet region is used because light absorption is in the near ultraviolet region. As a light source, one or more of a mercury lamp, a hydrogen discharge tube, a xenon discharge tube, a Lyman discharge tube, and the like are appropriately used.

[0027]

The substances which contaminate the substrate or the substrate surface and increase the contact angle include (1) SOx, NOx, HCl,
Hazardous gases such as NH ₃ , (2) fine particles, (3) H.
C, and as a result of the study by the present inventor, it has been found that in normal air (in the ambient air in a normal clean room) or in N ₂ used in a clean room such as a semiconductor manufacturing plant or a liquid crystal manufacturing plant, the contact is made. For the corner, the fine particles and H. C
The effect is large. That is, SOx, NOx, H
Cl and NH ₃ have little effect on the increase of the contact angle at ordinary concentration levels in air. Therefore, dust removal and H. The effect is obtained by removing C. In particular, H. C is a non-methane hydrocarbon as an index, and it is effective to remove this to 0.2 ppm or less, preferably 0.1 ppm or less.

H. in air The C component is said to be a mixture of hundreds or thousands or more of components. It is unknown which component of the C component is involved in increasing the contact angle and to what extent. For this reason, the details of the mechanism for preventing the contact angle from increasing due to the photocatalyst are largely unknown, but are considered as follows. The increase in contact angle is described in
It is presumed that a substance having a particularly high molecular weight or a substance having a high activity among the C components has a great influence, and it is considered that these are effectively decomposed by the action of a photocatalyst.

That is, a substance having a large molecular weight or a substance having a high activity can be effectively converted into H.O. H. small in molecular weight depending on C type. Decomposed into C, carbon dioxide and water.
H. small in molecular weight. Since C, carbon dioxide, and water do not contribute to the increase in the contact angle, exposing such air to the surface of the substrate or the substrate has the effect of preventing the surface of the substrate or the substrate from increasing the contact angle.

On the other hand, when harmful gases such as SOx are generated in or around the clean room and their concentrations are high, they are affected by these gas components, and these concentrations are low to such an extent that they are not normally affected. This may also be affected when the substrate or substrate is sensitive or when the surface is in a special state (for example, when the substrate surface is coated with a special thin film). In such a case, a method (apparatus) for collecting fine particles by irradiating harmful gas with ultraviolet rays and / or radiation (Japanese Patent Application No. 3-22686) has already been proposed by the present inventors. It is preferable to use them in an appropriate combination. In such a case, another well-known harmful gas removing material, for example, activated carbon, ion exchange resin or the like may be used in appropriate combination. As the activated carbon, an activated carbon to which an acid, an alkali, or the like is impregnated, or which is appropriately modified by a known method can be used.

Further, H. Also for the purpose of removing C.C., irradiation of ultraviolet and / or radiation, which has already been proposed by the present inventor, results in H.C. A method of trapping fine particles of C (Japanese Patent Application No. 3-105092), a method of collecting using an adsorbent or an absorbent (Japanese Patent Application Nos. 3-341802 and 4-18).
0538, PCT / JP92 / 01579) in the field of application, device type, scale, H.O. It can be used in an appropriate combination depending on the concentration of C, coexisting components, required performance and the like.

[0032]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Embodiment 1 FIG. 1 shows an example in which the method of the present invention is applied to purification of supply air for an air knife in a semiconductor manufacturing plant. In FIG. 1, reference numeral 1 denotes a clean room of class 10000, in which air 2 contains coarse filter 3, H.264 which increases the contact angle.
A pollution control device 7 comprising a photocatalyst 4 for decomposing C, an ultraviolet lamp 5 for irradiating the photocatalyst with ultraviolet light, and a dust filter 6.
Is processed in the clean room 1. After passing through the device 7, the air 2 is dedusted and It is clean air 8 in which C component is decomposed, and the wafer (substrate)
Is supplied to an air knife device 9 for cleaning the water.

Hereinafter, this example will be described in detail. The outside air 10 before entering the clean room 1 is first processed by the coarse filter 11 and the air conditioner 12. Next, when the air enters the clean room 1, the dust is removed by the HEPA filter 13, and the H.P. Air 14 having a concentration of class 10000 in which C coexists. That is, the extremely low concentration of H. mainly generated from automobiles. C is the coarse filter 11, the air conditioner 1
2 and the HEPA filter 13 are not removed,
It is introduced into the clean room 1. H. in air 14 and 2 The concentration of C is non-methane. 0.5 to 0.8 at C
ppm.

The air 2 is firstly removed by the coarse filter 3. This filter is installed in order to prevent the photocatalyst from being physically contaminated by the dust (particulate matter) and deteriorating the performance when dust is generated in the clean room 1. Then, the H. The air containing C is composed of a photocatalyst (titanium dioxide coated on glass fiber) 4 and an ultraviolet lamp (high pressure lamp) 5. C is introduced into the C. C is non-methane H. It is decomposed to 0.2 ppm or less, preferably 0.1 ppm or less, using C as an index.

Accordingly, H.V. having a large molecular weight involved in increasing the contact angle is used. C and active H. C is H. C. The molecular weight of H.I. Decomposed into C or carbon dioxide or water. The dust filter 6 is provided with fine particles having a concentration of class 10000 in the clean room and H.E. It efficiently collects fine particles flowing out from the C decomposition section or its surroundings (dust removing section), and uses an ULPA filter. The ULPA filter removes particulates to class 10 or less. H. photocatalysis. In this example, the position of the dust removal unit by the C disassembly unit and the filter is H.264. C
The decomposition part is the front, and the dust removal part is the back, but there is no particular limitation. The concentration of fine particles in the gas exposed to the substrate or substrate surface is class 10 or less, and the concentration of non-methane hydrocarbon is 0.2 ppm.
Any position or configuration may be used as long as the following is achieved.

Example 2 Air cleaning of a wafer storage (wafer storage stocker) in a semiconductor factory of a class 10000 clean room was performed.
This will be described with reference to the basic configuration diagram of the present invention shown in FIG. As the air cleaning of the wafer storage 21, the removal of fine particles will be described first. Particle removal is performed by an ultraviolet lamp 22, an ultraviolet reflection surface 23, a photoelectron emission material 24, an electrode 25 for setting an electric field, and a charged particle collection material 25 (particle collection device) installed on one side of the wafer storage 21. It is implemented in. In addition, in this structure, an electrode is implemented also as a collector.

That is, the fine particles (particulate matter) 26 in the wafer storage 21 are supplied from an ultraviolet lamp (sterilizing lamp).
Is charged by the photoelectrons 27 emitted from the photoelectron emitting material 24 irradiated with the ultraviolet rays, and becomes charged fine particles 28. The charged fine particles 28 are collected by the charged fine particle collecting material 25 (fine particle collecting device B). The processing target space portion (cleaning space portion, A) where the wafer exists is highly purified. 32a,
32b and 32c show the flow of air in the storage. That is, since the air that has moved to the charging / collecting section (B) of the fine particles is heated by irradiation of the ultraviolet lamp, an ascending air current is generated and moves in the storage 21 as indicated by arrows 32a, 32b, and 32c. Due to the movement of the air, the fine particles 26 in the storage are
Is effectively moved to the device B for charging and collecting fine particles, so that the inside of the storage 21 is quickly cleaned.

Here, the light shielding material 29 is provided between the space A to be processed and the particle collecting part B,
UV light from the wafer carrier 30 in the wafer carrier 30 is prevented from being directly irradiated. Photoemission material 2 here
Reference numeral 4 denotes a glass material surface in which Au is added in the form of a thin film. A photoelectron emitting material having such a structure is disclosed by another inventor of the present invention (Japanese Patent Application No. 2-295423). In this way, the fine particles (particulate matter) 26 in the wafer storage 21 are collected and removed.

In the above description, the irradiation of the photoelectron emitting material with ultraviolet rays uses the curved reflecting surface 23 and the ultraviolet lamp 22.
UV light is efficiently radiated to the plate-shaped photoelectron emitting material 24. The electrode 25 is provided to emit photoelectrons from the photoelectron emitting material 24 in an electric field. That is, an electric field is formed between the photoelectron emission material 24 and the electrode 25 (photoelectron emission portion). The fine particles are charged by photoelectrons 27 generated by irradiating the photoelectron emission material 24 with ultraviolet light in an electric field.
Is implemented more efficiently. The electric field voltage here is 5
0 V / cm. The collection of charged particles is performed using the electrode 25. The electrode material is a metal mesh Cu—Zn material plated with gold, and is used at a position 1 cm away from the photoelectron emission material (total length A).
(Position of 0.03 with respect to distance 1 of + B).

Next, H. The C removal will be described. H.
The C removal is performed by a photocatalyst (a coating of titanium dioxide on glass fibers) 33 irradiated with an ultraviolet lamp (germicidal lamp) 22. The air in the class 10000 clean room where the storage 21 is installed enters the wafer storage 21 by opening and closing the storage 21. This air contains H.I. C is 0.8 to 1. as a non-methane hydrocarbon.
Contains 5ppm. The H. The air containing C is the air flow 3
3a, 33b, and 33c, which come into contact with the photocatalyst 33 and have a large molecular weight. C and active H. C is effectively H. Depending on the type of C, H.V. Decomposed into C or carbon dioxide or water. H. C is decomposed by using non-methane hydrocarbons as an index until it becomes 0.1 ppm or less.

As described above, removal of fine particles (dust removal) and H. By the decomposition of C, the cleaning space A is cleaned and the inside of the storage becomes ultra-clean air. Thus, contamination of the wafer surface is prevented by exposing the ultra-clean air to the wafer surface. As a result, an increase in the contact angle on the wafer is prevented. The combination of the method (apparatus) already proposed by the inventor described above with the method of the present invention, and The use and combination of materials for removing harmful gases other than C can be appropriately selected and used. The conditions for using the dust filter and the photocatalyst can be appropriately determined. That is,
Preliminary tests are conducted as appropriate depending on the concentration and type of contaminants (fine particles, HC, and other harmful gases) in the clean room used, the type of application equipment, structure, scale, required performance, efficiency, economy, etc. Can be decided.

In the present embodiment, the case where the medium is air has been described. However, it is needless to say that the present invention can be similarly carried out when fine particles or gaseous harmful substances are contained as impurities in another gas such as nitrogen or argon. . The space to which the present invention can be applied refers to, besides the above-mentioned atmospheric pressure, a pressurized state, a depressurized state, and a vacuum state, and can be similarly implemented.

Example 3 The apparatus shown in FIG. C was decomposed. The glass substrate was exposed to the clean air thus obtained, and the contact angle was measured. At the outlet of the pollution control device, the concentration of fine particles and non-methane H. The concentration of C was measured. The same measurement was performed on the apparatus shown in FIG. 1 from which the ultraviolet lamp and the photocatalyst were removed (that is, only the dust filter was used) and the apparatus from which the dust filter was removed (that is, only the photocatalyst was used). The same measurement was performed when the glass substrate was exposed to the air.

Fine particle concentration in clean room before test condition treatment: Class 1
000 in a clean room before treatment Concentration of C:
0.8 to 1.0 ppm Dust removal filter: ULPA (Nippon Pall Co., Ltd., Gas Clean Filter SGLF6101) Photocatalyst: Titanium dioxide coated on glass fiber, manufactured by sol-gel method. Light source: High pressure lamp Contact angle measuring instrument: CA-D type contact angle meter manufactured by Kyowa Interface Science Co., Ltd. Pretreatment of glass substrate: After cleaning with detergent and alcohol, O
₃ UV irradiation when generated

[0045] The relationship between the contact angle exposure is time and the measurement of the glass substrate θ to result air is shown in FIG. In FIG. 3, the present invention A
(Use coarse filter, photocatalyst, dust filter)
Indicated by As a comparison, the sample (A) of the present invention from which the ultraviolet lamp and the photocatalyst were removed (B) was-□-, the sample from which only the dust filter was removed (C) was-△-, and the sample before treatment in a clean room was obtained. Exposure to air (D)
Indicated by The frequency at which the contact angle of the used contact angle meter can be detected (detection lower limit of the contact angle) is 3 to 4 degrees. In the case of the present invention using the coarse filter, the photocatalyst, and the dust filter at the same time, the detection limit is initially (↓ )showed that. The concentration of fine particles at the outlet of the device is class 10 or less (measuring device: light scattering type particle counter). The concentration of C was 0.1 ppm or less (measuring device: gas chromatograph).

Example 4 The following sample gas was put into a storage having the structure shown in FIG. 2, and an electric field voltage was applied and ultraviolet irradiation was performed. The particle concentration and particle concentration in the storage were measured using a particle counter (particle counter). The contact angle on the wafer stored in the storage was examined using a contact angle measuring device. In addition, the concentration of non-methane hydrocarbons in the storage was measured. As a comparison, the same operation was performed when the ultraviolet lamp was not turned on and the electric field voltage was not applied.

Test conditions Storage size: 30 liters Photoelectron emission material; Quartz glass with thin film Au added Electrode material: Wire mesh Cu-Zn 1 cm from photoelectron emission material (opposed to photoelectron emission material) Installed at a position of 0.03 with respect to the total distance to the wall surface 1) Charged particulate collection material; Also used as electrode material Ultraviolet lamp; Sterilization lamp Electric field voltage; 50V / cm Sample gas (inlet gas); Medium gas ... Air concentration (class) ... 10,000 (class: the number of 0.1μm or more particles of 1ft ³⁾

Irradiation time: 30 minutes, 1 hour, 16 hours Particle concentration in clean room before treatment: Class 1
000 in a clean room before treatment Concentration of C:
0.8 to 1.0 ppm Dust removal filter: ULPA (Nippon Pall Co., Ltd., Gas Clean Filter SGLF6101) Photocatalyst: Titanium dioxide coated on glass fiber, manufactured by sol-gel method. Light source: High pressure lamp Contact angle measuring device: CA-D type contact angle meter manufactured by Kyowa Interface Science Co., Ltd. Wafer: A 5-inch wafer is cut into 1 cm x 8 cm and placed in a storage. Pretreatment of wafer; after cleaning with detergent and alcohol, UV irradiation under O ₃ generation

[0049] it was measured particle concentrations above results 0.1μm in the instrument. The results are shown in Table 1 by the number of fine particles in ft ³ (class).

[Table 1]

Table 2 shows the contact angles on the wafer.

[Table 2]

For comparison, Table 3 shows the concentration of fine particles in the storage and the contact angle on the wafer when the lighting of the photocatalyst and the application of the voltage were not performed.

[Table 3] The frequency at which the contact angle of the used contact angle meter can be detected (the lower limit of detection of the contact angle) is 3 to 4 degrees. In addition, non-methane H. in the storage room. The concentration of C was 0.1 ppm or less (measuring device: gas chromatograph).

[0052]

According to the present invention, the following effects can be obtained. (1) H. by dust removing means and photocatalyst With the provision of the C decomposition means, the extremely low concentration of H.O. C is H.H. C and / or carbon dioxide, converted to water. By adding dust to (1) above, a gas or atmosphere (environment) in which an increase in the contact angle was prevented was obtained. If the gas (or atmosphere) obtained in the above (2) is exposed to a substrate or substrate (raw material, semi-finished product, product) such as a semiconductor wafer or liquid crystal glass, contamination of the substrate or substrate surface is prevented. Is done. The photocatalyst material is H.I. Since the performance is stable for a long time as compared with the adsorbent and the absorbent of C, the practicability is improved.

(2) In the case of using photoelectrons already proposed by the present inventor as the dust removing means, the field of application is expanded because the light source can be used in common and the dust removing device using photoelectrons can be easily integrated. Practicality improved. (3) NOx and SOx other than hydrocarbons in the gas to be treated
When the concentration of gaseous harmful components such as is high, the removal method of these harmful components (for example, the method already proposed by the present inventors)
Is appropriately selected and combined with the method for removing hydrocarbons according to the present invention, so that the field of use of the present invention is broadened and pollution is more effectively prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a clean room in which a pollution control device of the present invention is installed.

FIG. 2 is a schematic configuration diagram of a wafer storage provided with the contamination prevention device of the present invention.

FIG. 3 is a graph showing a relationship between an exposure time and a contact angle.

[Explanation of symbols]

1: clean room, 2, 14: air, 3: coarse filter, 4, 33: photocatalyst, 5, 22: ultraviolet lamp, 6:
Dust filter, 7: pollution control device, 8: clean air, 9:
Air knife device, 10: outside air, 11: coarse filter, 1
2: air conditioner, 13: HEPA filter, 21: wafer storage, 23: reflection surface, 24: photoelectron emission material, 25:
Electrodes, 26: fine particles, 27: photoelectrons, 28: charged fine particles, 29: light shielding plate, 30: wafer carrier, 31: wafer, 32: air flow

Claims (2)

(57) [Claims] In a method for preventing contamination of the surface of a substrate or a substrate, a gas containing at least hydrocarbon, which comes into contact with the substrate or the substrate, is removed by dust removing means and means for decomposing hydrocarbons by irradiating light onto a photocatalyst. Purify, the concentration of fine particles in the gas is less than class 10 and the concentration of non-methane hydrocarbon is 0.2
A method for preventing contamination of the surface of a substrate or a substrate, which comprises exposing the gas to the surface of the substrate or the substrate after reducing the concentration to less than ppm. 2. An apparatus for preventing contamination of the surface of a substrate or a substrate, wherein a dust removing means for passing gas in contact with the substrate or the substrate to remove fine particles to a class 10 or less, and a non-methane hydrocarbon concentration. And a means for decomposing hydrocarbons by irradiating light onto a photocatalyst to remove methane to 0.2 ppm or less.