JPH1190236A - Photocatalyst and reaction device using photocatalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively treat a harmful substance with the use of a photocatalyst which can simply be manufactured and easily handled and also can be molded to any desired shapes by obtaining the photocatalyst through baking titanium at a specific temperature in an atmosphere containing oxygen and constituting at least, part of the wall face or the space part of a reaction device with the photocatalyst. SOLUTION: This photocatalyst is obtained by baking titanium at a temperature of 650-1200 deg.C in an atmosphere containing oxygen. The titanium material is of the form of at least, one selected from shapes such as plate-like, pleats-like or honeycomb-like, and has a uniform TiO2 thin coat formed on these shapes. In an air cleaning device 4 with a light source for emitting a light to the photocatalyst, the photocatalysts 9-1, 9-2 remove mainly hydrocarbons (non- methane hydrocarbons: H.C) generated in the operation 2 and the H.C introduced into a clean room 1 or generated from a clean room construction material and instruments. The photocatalysts 9-1, 9-2 to be used in this case are those obtained by baking the honeycomb-like titanium at 650-1200 deg.C in the air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photocatalyst, and more particularly to a photocatalyst for decomposing and removing harmful organic substances in air and water, and a reaction apparatus using the photocatalyst.

[0002]

2. Description of the Related Art In recent years, environmental scales (sizes) have varied from a global scale to a living environment for humans and a wafer (substrate) environment for semiconductors, but contaminants (hazardous components) in the environment have attracted attention. The emergence of an effective removal (control) technique for such contaminants is expected. For example, in the semiconductor industry, the quality and precision of products are increasingly increasing in the future, and accordingly, gaseous substances are involved as contaminants. That is, conventionally, only removal of fine particles has been sufficient, but control of gaseous substances will be important in the future. That is, in the conventional filter of the clean room, only the fine particles are removed, and the gaseous contaminants from the outside air are introduced into the clean room without being removed.

[0003] Gaseous pollutants include (1) NOx, SO
x, etc .; (2) basic gases such as NH ₃ and amines; and (3) organic gases (H.C). Of these, in a normal clean room, C is important as a gaseous pollutant. That is, H. C is because it is adsorbed on the substrate and the substrate at the concentration level of a normal clean room, and exerts an adverse effect. H. Causes of C include the introduction of automobile exhaust gas from outside air, degassing from polymer products into clean rooms, and polymer materials (eg, plasticizers of polymer products, mold release materials, antioxidants, etc.) for clean room components. Degassing etc. ("Air Purification", Vol. 33, No. 1, pp. 16-21, 1
995). Further, since part or all of the process device is surrounded by a plastic plate or the like, an organic gas is generated from the plastic. Recently, since the air in the clean room is circulated and used in terms of energy saving, the organic gas in the clean room gradually increases, and contaminates the base material and the substrate. These H. C has an adverse effect even at very low concentrations, such as normal atmospheric concentrations.

[0004] A specific example will be described. Contamination of the wafer substrate (valuables) by C affects the affinity (fit-in) between the substrate and the resist. When the affinity deteriorates, it affects the resist and the film thickness or the adhesion between the substrate and the resist, resulting in a decrease in quality and a decrease in yield. In this way, higher quality products, for which demand will increase in the future, have a higher degree of integration (products become finer and more precise), and gaseous substances such as organic gases, which have not been a problem in the past. Control becomes necessary. ("Air Purification" Vol. 33, No. 1, pp. 16-21, 1995) Next, a method for treating organic matter in water will be described. Conventionally, it is generally well known as a method other than the method using microorganisms. Activated carbon method, ozone method, electrolysis method, chemical oxidation method,
Electrodialysis and the like. Among them, those that are industrialized as actual scales include the activated carbon method, the ozone method,
There are various treatment methods of electrolysis.

[0005] However, these processing methods have the following problems. Activated carbon method: Treatment efficiency is relatively good, but regeneration of activated carbon is troublesome and costly. Ozone method: The efficiency of decolorization, deodorization, and decomposition of organic matter is relatively good, and there is another bactericidal effect. However, ozone is expensive to produce, and unused ozone is released as waste ozone. Therefore, it is necessary to take countermeasures for pollution of leaked ozone. Electrolysis method: Decolorization efficiency as organic matter treatment is relatively good, but sufficient effect is not obtained for organic matter decomposition,
Also, the cost is high.

On the other hand, the present inventors have already proposed a photocatalyst in which an active substance is supported on the surface of a light-transmitting linear article, and a gas treatment and a water treatment using the same (Japanese Patent Application Laid-Open No. HEI 9-260572). 7-256089, JP-A-8-10576
No., JP-A-8-71573). Further, as a photocatalyst, on an appropriate base material, the TiO ₂ sol - those to be carried by the gel method is known. However, in the case of supporting by the sol-gel method, depending on the type and surface state of the base material, Ti
There was a problem that O ₂ was not sufficiently supported, and peeled and flowed out over time. These photocatalysts are effective depending on the application destination, but further improvement is necessary in practical use.
In particular, in practical use, it is required to be easy to manufacture, easy to handle, and capable of being formed into an arbitrary shape (a shape that matches the application and the shape of the device).

[0007]

DISCLOSURE OF THE INVENTION In view of the above prior art, the present invention provides a photocatalyst which can be easily manufactured, is easy to handle, and can be formed into an arbitrary shape, and a harmful substance using the photocatalyst can be effectively removed. An object of the present invention is to provide a reactor capable of performing the treatment.

[0008]

In order to solve the above-mentioned problems, according to the present invention, Ti is heated to 650 ° C. in an oxygen-containing atmosphere.
A photocatalyst characterized by being fired at a temperature of 1200 ° C. In the photocatalyst, Ti is in a form of at least one of plate, pleated, honeycomb, filter, fibrous, net, linear, granular, and spherical, and a uniform TiO ₂ thin film is formed on the surface thereof. Has formed. Further, in the present invention, in a reactor for removing harmful components having a photocatalyst and a light source for irradiating the photocatalyst, at least a part of a wall or a space of the reactor is made of Ti in an oxygen atmosphere.
The photocatalyst calcined at a temperature of 50 ° C to 1200 ° C is used.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made based on the following two findings. 1) A photocatalyst, for example, one in which TiO ₂ as an active ingredient is supported on a suitable base material (eg, glass) by a sol-gel method,
Decompose and remove harmful organic substances (15th Air Purification and Contamination Control Research Conference, p30
9, 1997). However, the photocatalyst contains the active component (TiO 2).
₂ ) In the case of supporting on the base material by the sol-gel method, the vapor deposition method, or the coating method, since the adhered force of the supported active component is weak depending on the type of the base material and its surface shape, the active component is separated. This causes problems such as outflow to the rear, causing problems in practical use. 2) On the other hand, 650 ° C. in an oxygen-containing atmosphere
When fired at a temperature of ~ 1200 ° C, the surface of Ti becomes TiO
_It becomes ₂ and exerts a photocatalytic action by ultraviolet irradiation. Usually, TiO ₂ is effective when the film thickness is 3 μm or more, preferably 5 μm or more. By using a sintering temperature and a sintering time to achieve the film thickness, it can be produced on the Ti surface.

Next, the present invention will be described in detail for each configuration. The Ti material used in the present invention has a temperature of 650 ° C. to 1200 ° C.
° C., preferably oxygen atmosphere at 700 ° C. to 1000 ° C. (eg, air, O ₂ gas) by firing in, as long as the surface to form a rutile crystal structure or an anatase type, either can be used . The above-mentioned temperature range is a characteristic of the present invention, and is an appropriate range for easily forming a uniform thin film of TiO ₂ on Ti in a short time. That is, if the temperature is low, the efficiency of TiO ₂ generation is low, and if it is too high, a uniform thin film is not obtained. Also, 120
At a high temperature of 0 ° C. or higher, problems occur in the structure, material, and handling of the electric furnace. According to the results of these studies, it has been found from the results of these studies that the calcination at the above-mentioned temperature results in a dense and uniform TiO ₂ thin film, which is a practically effective photocatalyst.

The shape of the Ti material may be plate, pleated, honeycomb, filter, fibrous, net, linear, granular or spherical, depending on the application, the shape, scale, required performance, and economy of the reactor. Depending on, for example, one kind or a combination of two or more kinds can be used. Further, by using Ti as the material of the reactor itself (or a part thereof), a reactor with a photocatalyst can be easily manufactured, which is one of the features of the present invention. That is, by using a Ti material for a part of the material of the reaction device, the reaction device with a photocatalyst can be obtained immediately after firing.

Next, a light source for irradiating light will be described. The light source may be any one having a wavelength that excites the photocatalyst, and a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a xenon lamp, or the like can be used.
Sunlight is available as appropriate. The position of the light source can be appropriately selected depending on the application field, the type of the light source, and the shape of the device. Usually, it is preferable to install a light source at the center of the reactor because all the light emitted radially from the light source is effectively used. Further, depending on the place of use, the well-known harmful gas removing means can be used in combination with the removal of organic substances by the photocatalyst of the present invention. Well-known harmful gas removing means include activated carbon, activated carbon fiber, zeolite, ion exchange filters (fibers), and organic polymer polymers (organic polymer beads).

[0013]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Embodiment 1 FIG. 1 shows a schematic configuration diagram of air cleaning using a removal apparatus of the present invention for removing a trace amount of harmful gas in a clean room in a semiconductor factory. In FIG. 1, class 1,000
In the clean room 1 (number of particles of 0.1 μm or more),
In operation 2, NOx, NH ₃ , H.O. C and fine particles 3 are generated, and hydrocarbons (non-methane hydrocarbons, HC) are contained in clean room air at 1.2 to 1.2%.
1.5 ppm is present. Since these contaminants (the gaseous pollutants and fine particles) contaminate the raw materials, products and semi-finished products of the semiconductor factory, an air purifier 4 is installed to collect and remove the harmful gases and fine particles. Have been done.

The apparatus 4 mainly includes a pretreatment filter 5, a fan 6, an ion exchange filter (cation type and anion type).
7. ULPA filters 8 _-1 and 8 _-2 , photocatalysts 9 _-1 and 9 _{-2 of} the present invention, and an ultraviolet lamp 10. The air to be treated 11 containing gas is sucked by the fan 6, the treated clean air is discharged in the direction of arrow 12, and the clean air 12 is supplied to the semiconductor manufacturing apparatus 13. Each configuration will be described. The pretreatment filter 5 is a filter mainly composed of glass fiber with low air resistance. Here, coarse particles (particles having a relatively large particle diameter) in the suction air 11 are first removed. The ion exchange filter 7 is a filter for removing ionic gas such as NH ₃ and NOx generated in the operation 2 in a clean room, and has been proposed by the present inventors (eg, Japanese Patent Publication No.
67325, Japanese Patent Publication No. Hei 6-24626) can be used as appropriate, so that NH ₃ and NOx are 5 ppb.
Removed to:

The ULPA filter _28-1 is a particulate filter for removing particulate such as a clean room generated by the work 2. Thereby, the fine particles in the clean room of class 1,000, the fine particles generated by the operation 2 and the fine particles generated by the operation of the fan 6 are removed to class 10 or less. The photocatalysts 9 _-1 and 9 _-2 are mainly composed of hydrocarbons (non-methane hydrocarbons: HC) generated in operation 2 and H.C. introduced into the clean room 1 or generated from clean room components and equipment. C is decomposed and removed, and the air cleaning device 4 prevents an increase in the contact angle of the wafer in the semiconductor manufacturing device 13. The photocatalysts 9 _-1 and 9 here
_{No. -2} is obtained by firing honeycomb-shaped Ti in air at 900 ° C. for 10 minutes. The ultraviolet lamp 10 is provided with the honeycomb-shaped T
The thin film TiO ₂ formed on the i surface is irradiated to act as a photocatalyst. Thereby, H. C is converted to a safe (harmless) form that does not affect the increase in the contact angle of the wafer.

The ULPA filter _8-2 is a filter for removing generated particles from the photocatalyst and its vicinity, is usually unnecessary, and is placed on the assumption emergency. These, NH ₃ concentration, NOx concentration levels 80~250ppb in the clean room, any 5ppb or less, non-methane hydrocarbons 0.1ppm or less, particle concentration Class 1
The clean air 12 does not increase the contact angle of 0 or less,
The wafer in the semiconductor manufacturing apparatus 13 is prevented from being contaminated.
When harmful gas is generated in the clean room, it adheres to products and semi-finished products, increases the contact angle, and lowers the yield (decreases productivity). Therefore, reducing the concentration of the harmful gas to a certain concentration or less is important for clean room management. The order of combination of the photocatalyst and the known harmful gas removing means in the embodiment is not limited at all, and can be determined as appropriate by conducting a preliminary test. Note that the contact angle is an index indicating the degree of contamination of the solid surface.If the solid surface is contaminated, the contact angle of water well reflects the state of contamination, and if the degree of contamination is large, the contact angle increases. Conversely, if the degree of contamination is small, the contact angle is small.

Embodiment 2 FIG. 2 shows a schematic configuration diagram of a stocker (storage) 14 for preventing an increase in the contact angle of a wafer installed in a clean room 1 of a class 1,000 semiconductor factory in Embodiment 1. In clean room air, hydrocarbons (HC) are present at 1.4 to 1.6 ppm. The origin of the hydrocarbon is that introduced from outside air and degassing from clean room components. Incidentally, the hydrocarbon concentration outside the clean room (outside air) is 0.8 to 1.2 ppm, which is lower than that in the clean room. This is due to the generation of hydrocarbons from clean room components in the clean room (Ultra Clean Technology,
Vol. 7, No. 4, p. 15-20, 1995). These hydrocarbons adhere to the wafer substrate surface, resulting in a decrease in yield. The extent of this hydrocarbon contamination can be represented by the contact angle (Air Purification, Vol. 33, No. 1,
p. 16-21, 1995).

The stocker 14 is a device for preventing contamination of the wafer 17 (preventing an increase in the contact angle). The stocker 14 is a plate-like device having a thin-film TiO ₂ formed by firing plate-like Ti in air at 800 ° C. for 10 minutes. It is composed of a photocatalyst 9, an ultraviolet lamp 10, and a shielding material 15 for avoiding direct ultraviolet irradiation on a product or a semi-finished product such as a wafer. Arrows 11 and 12 indicate the direction of air flow in the stocker, and are caused by a slight temperature difference between the upper and lower portions of the photocatalyst 9 caused by irradiation of the ultraviolet lamp 10. Due to the air flow, the H.O. Air containing a harmful gas such as C and NH ₃ is supplied to a reaction section A having a photocatalyst 9.
And are effectively processed. As a result, the NH ₃ concentration in the stocker 1 changes from the initial concentration of 250 ppb to 1
ppb or less; The C concentration becomes 0.1 ppm or less, and the air in the stocker 14 becomes ultra-clean air that does not increase the contact angle of the wafer 17. B is a wafer storage part of the stocker 14, and 16 is a wafer storage case.

Embodiment 3 FIG. 3 shows a schematic configuration diagram of a water treatment apparatus 20 using the photocatalyst of the present invention. In FIG. 3, biochemically treated raw water for drinking water is introduced into a reaction part A from a raw water inlet 21. In the reaction part A, trace organic substances, particularly organic chlorine compounds, in the raw water are oxidatively decomposed and treated. Water is discharged from outlet 12. The water treatment apparatus 20 mainly includes a reaction section A including a photocatalyst 9 and an ultraviolet lamp 10, an air supply section including a fan 18 for sending bubbles 17 to promote a reaction in the reaction section, and an air diffuser 19. C. The photocatalyst 9 is obtained by sintering granular Ti at 800 ° C. for 10 minutes in the air to form a thin film TiO ₂ on the surface.

Air is supplied from the fan 18 to the raw water through the air diffuser 19, and the air rises as bubbles in the reaction section A, and the action in the reaction section A is promoted by the stirring action or the like. In the reaction section A, the organic matter in the raw water, especially the organic chlorine compounds (eg, trichloroethylene, tetrachloroethylene) is effectively decomposed by the photocatalysis by the photocatalyst 9 of the present invention irradiated with the ultraviolet lamp 10, and the safe water supply is performed. Becomes That is, all the organic chlorine compounds were decomposed and removed to an inlet concentration of 310 ppm to 1 ppm or less. Depending on the field of application, the type of light source, the scale, type, and shape of the device, the light source 10 may be installed outside the water treatment apparatus 1 and the ultraviolet light from the light source may be applied to the internal photocatalyst 9. The processing amount of this apparatus is 5 m ³ / h, and the usage amount of the photocatalyst is 10% with respect to the volume of the raw water to be treated.

Example 4 The following sample air from a semiconductor factory was put into a stocker having the structure shown in FIG. 2, and the photocatalyst of the present invention was irradiated with ultraviolet rays to form a contact angle on a wafer stored in the stocker and a Cr film on the wafer. The film was formed, and the conformity (adhesion) of the film with the wafer was measured. In addition, the identification of hydrocarbons adsorbed on wafers in the stocker and the concentration of non-methane hydrocarbons in the stocker were examined. Further, as a comparison, the same examination was performed without the photocatalyst material. Size of stocker; 100 liters Light source; germicidal lamp (main wavelength: 254 nm), photocatalyst; plate Ti in air, 200, 300, 40
0, 500, 600, 650, 700, 800, 90
It was fired at 0, 1000, 1200 ° C. Production method of photocatalyst; Plate-like Ti was placed in a heating furnace and heated at the above temperature for 10 minutes.

Measurement of contact angle; water drop contact angle method [Co., Ltd.]
CA-DT type, manufactured by Kyowa Interface Science] Film formation on wafer; Cr 300 nm thick, sputtering method Adhesion of formed Cr; Scratch test (RHES
Measurement of non-methane hydrocarbons in stockers; Gas chromatograph (GC) Identification of hydrocarbons adsorbed on wafers; GC / MS method C concentration: 1.2 to 1.5 ppm (non-methane hydrocarbon) Wafer in stocker: 5 cm wafer, 1 cm × 8
cm, and placed in the storage after the following pre-treatments Pre-treatment of wafers; O ₃ after cleaning with detergent and alcohol
UV irradiation during generation (UV / O ₃ cleaning)

Results (1) Ti material fired at 900 ° C. (TiO ₂ / Ti) FIG. 4 shows the change in contact angle (angle) and adhesive force (mN) of Ti material fired at 900 ° C. with time. It is a graph. In FIG. 4, the contact angle is-は-when there is a photocatalyst,
When there is no photocatalyst, it is indicated by-●-, and the adhesive force is shown by-△-when there is a photocatalyst, and by-▲-when it does not. Thus, when the photocatalyst was added, there was no change even with the passage of time. In addition, when there was no photocatalyst, the wafer was taken out after 40 hours and 140 hours, and the hydrocarbon attached to the wafer was desorbed by heating, and the measurement was performed by the GC / MS method.
Phthalates were detected respectively. It was not detected when a photocatalyst was installed.

The concentration of non-methane hydrocarbons in the stocker was 2 hours, 35 hours, 10 hours when photocatalyst was added.
After 0 hour and 200 hours, both were 0.1 ppm or less. 2 hours, 35 hours, 1 without photocatalyst
After the lapse of 00 hours and 200 hours, both 1.2 to 1.
It was 4 ppm. FIG. 5 shows the result of X-ray diffraction analysis of the present TiO ₂ . From FIG. 5, it was found that it was rutile-type TiO ₂ . (2) Influence of sintering temperature In order to examine the influence of the sintering temperature of the Ti material, the Ti materials at the respective sintering temperatures are similarly set in a stocker, and the wafer storage 14
The contact angle after 0 hour was measured. FIG. 6 shows the result.

[0025] (3) the firing time, firing time in the production of temperature and TiO ₂ film thickness relationship TiO ₂ film was investigated the relationship between the temperature and the TiO ₂ film thickness. FIG. 7 shows the relationship between the firing time at each firing temperature and the TiO ₂ film thickness. In FIG. 7, the firing temperature is (a) 1000 ° C.), (b) 900 ° C., (c) 80
0 ° C, (d) 700 ° C, (e) 600 ° C, (f) 500
° C. Below 600 ° C., the thickness of TiO ₂ is small (the performance is low when the film thickness is small). That is, effective Ti
It can be seen that no O ₂ film is formed. Measurement of film thickness: Ellipsometer

(4) Adhesive force of TiO ₂ film (peeling strength) The adhesive force of the TiO ₂ film produced by this method was examined. The firing temperature is 700, 800, 900, 1000 ° C., and the firing time is 10 minutes. For comparison, a TiO ₂ film (100 μm) was added on a Ti material and a glass material by a sol-gel method.
m) was similarly examined. Measurement of adhesion: Scratch tester Results The results are shown in Table 1.

[Table 1]

[0027]

According to the present invention, the following effects can be obtained. 1) Ti in an oxygen-containing atmosphere at 650 ° C to 1200 ° C
By baking at the temperature of (a), (a) a thin-film TiO ₂ was formed on the surface of the Ti material, and a photocatalyst (which exerts a photocatalytic action when irradiated with light). (B) Since TiO ₂ is formed on Ti of the base material, T
iO ₂ is so tightly bound and the base material, separation of the TiO ₂ is unlikely to occur. (C) Since the firing of the Ti material is sufficient, a photocatalyst having an arbitrary shape, for example, a linear shape, a fibrous shape, a filter shape, a honeycomb shape, a spherical shape, and a granular shape was obtained. 2) The above-mentioned photocatalyst can be installed on the wall surface of the reactor or in the space (or used by floating in the space). 3) By using Ti as the material for the reactor or a part thereof, a reactor with a photocatalyst can be easily manufactured by firing. That is, the reaction apparatus can be easily obtained. 4) From the above, application fields and apparatuses for performing treatment using a photocatalyst have been expanded, and practicability has been improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of air purification in a clean room using a reaction apparatus of the present invention.

FIG. 2 is a schematic configuration diagram in which the reaction apparatus of the present invention is provided in a wafer stocker.

FIG. 3 is a schematic configuration diagram in which a reaction apparatus of the present invention is provided in a water treatment apparatus.

FIG. 4 is a graph showing changes in contact angle (degree) and adhesive force (mN) with elapsed time (h).

FIG. 5 is an X-ray diffraction diagram showing the result of X-ray diffraction analysis of TiO ₂ prepared in the present invention.

FIG. 6 is a graph showing a change in a contact angle (degree) according to a firing temperature (° C.) of a Ti plate.

FIG. 7 is a graph showing the relationship between the firing time for each firing temperature and the thickness (μm) of the TiO ₂ film.

[Explanation of symbols]

1: clean room, 2: work, 3: harmful substance, 4: air purifier, 5: pretreatment filter, 6: fan, 7: ion exchange filter, 8: ULPA filter, 9: photocatalyst of the present invention, 10: ultraviolet light Lamp, 11: air to be treated, 1
2: air flow, 13: semiconductor manufacturing equipment, 14: stocker, 15: shading material, 16: wafer storage case, 17:
Wafer, 18: fan, 19: diffuser, 20: water treatment, 21: raw water inlet, 22: treated water outlet, A: reaction section, B: storage section, C: air supply section

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B01D 53/86 B01D 53/36 J

Claims (3)

[Claims] 2. A method according to claim 1, wherein Ti is heated at 650 ° C. to 1 in an oxygen-containing atmosphere.
A photocatalyst characterized by being calcined at a temperature of 200 ° C. 2. The Ti has a plate shape, a pleated shape,
_{2. A} uniform TiO2 thin film formed on at least one of a honeycomb, a filter, a fiber, a net, a line, a grain, and a sphere, and having a uniform TiO2 thin film on the surface thereof. photocatalyst. 3. A reactor for removing harmful components comprising a photocatalyst and a light source for irradiating the photocatalyst with light, wherein at least a part of the wall or space of the reactor is 650-1200 ° C. in an oxygen atmosphere. A reactor for removing harmful components, comprising a photocatalyst calcined at a temperature of