JPH0957030A - Precision filter for high purity gas and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter capable of removing inevitable foreign matter and giving high purity gas. SOLUTION: Fine metal particles of <=10μm average particle diameter, short metal fibers, metal fibers of <=10μm fiber diameter or a combination of them is sintered to form a sintered porous body 2 and the surface of the porous body 2 including the surfaces of the inner walls of the pores and inevitable foreign matter sticking to the surfaces of the inner walls is coated with a liq.- soluble inorg. thin film material 3 to obtain the objective filter having <=1μm pore diameter and >=40% porosity. The porous body 2 is immersed in an inorg. thin film suspension 3A having <=10cps melt viscosity, the suspension is sucked into the pores in the porous body by evacuation and it is stuck and dried to produce the filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for gas filtration in order to supply a high-purity gas having an extremely high purity, such as a gas filled in a manufacturing apparatus in a semiconductor manufacturing process. Precision filter for high purity gas and its manufacturing method.

[0002]

2. Description of the Related Art It is well known that the development of semiconductors has made great progress in recent years and has contributed to the miniaturization and multi-functionalization of electronic equipment. Came.

For example, most of the manufacturing process is performed in a clean room, and the purity of various gases used in each process is high precision filtration for removing particles of 0.01 μm or more with high accuracy of 99.99999999 level or more. Technology and filter materials are required,
Further, it is required to have heat resistance to withstand baking heat treatment when using this.

Unlike the conventional mechanical filtration mechanism, the filtration mechanism in such high-precision filtration is based on the adsorption phenomenon that most of the impurities in the fluid to be treated are adsorbed on the filter pore wall surface. In order to improve the adsorptivity, the pore surface area has been increased and constituent materials that are easily adsorbed have been improved, and a high-accuracy filter with low pressure loss has been obtained in part.

For example, the applicant of the present application is PCT WO (public)
No. 93/06912 (Japanese Patent Application No. 5-506457) proposes a filter having excellent filtering characteristics. This filter has a laminated structure in which a fine layer made of fine particles of stainless steel is integrated and sintered by laminating and sintering it on a support having relatively large pores. It is intended to provide a filter adapted by combining with a reinforcing action.

This technique involves immersing a support having relatively coarse pores in a suspension of fine powder or fine short fibers selected to have fine predetermined pores without containing a binder. By suctioning and then suctioning, a fine layer is formed on the surface, and since this filter is also an all-metal product, it is easy to combine with other metal members such as pipes, and the pressure strength is increased. Further, it is becoming popular as a material having both heat resistance and corrosion resistance.

[0007]

However, even in such a high-efficiency filter, the problem is not completely solved. For example, the problem of corrosion resistance or the problem of particulate contamination which is inevitably generated during the manufacture of the filter has been a problem in recent years. It is still not sufficient when quality requirements are assumed.

That is, with respect to the problem of corrosion resistance, a metal filter, for example, a stainless filter, can be dealt with to some extent depending on the selection of the material, the delicate adjustment of the component composition, the additive component, etc., but the type of gas used. However, it is difficult to give such characteristics to each of them in terms of current technology and cost.

Therefore, in such a case, the user is forced to make an early update in a relatively short period of time, and the resulting expense and the effect of the suspension of operation during that period are major problems. For example, HCL gas and HF used in semiconductor manufacturing
When gases such as stainless steel are to be filtered by a stainless steel filter, these gases are highly corrosive, so about 1
The current situation is that the information is updated about a year.

In addition, by that time, the corrosion of the filter itself is gradually progressing, and the corrosion phenomenon is not limited to the problem of the deterioration of the filtration function due to the enlargement of the pore diameter, but occurs, for example, with the corrosion. Secondary problems such as changes in gas composition due to corrosive gases and contamination due to corrosion products also occur.

Further, in terms of high purification of the gas to be treated, even if the filter itself is manufactured in a clean room, a filter product that completely eliminates the inevitable foreign substances generated in the manufacturing process and remaining It is difficult to solve at the current level of technology, and of course the technology must be improved when considering high quality semiconductor products in the future.

From this point of view, the present invention is intended for high-precision gases such as those used in semiconductor manufacturing, which are free from the internal generation of impurities such as the above-mentioned unavoidable foreign substances and which are excellent in corrosion resistance and filtration characteristics. It provides a precision filter and its manufacturing method.

[0013]

The precision filter for a high purity gas of the present invention is for a high purity gas for obtaining a high purity gas capable of adsorbing and trapping impurity particles of 0.1 μm or less mixed in the gas. Precision filter with an average particle size of 10 μm
The following metal fine particles, metal short fibers, or fiber diameter 10 μm
While forming a sintered porous body that is sintered using at least one or more of the following metal fibers, the sintered porous body includes pore inner wall surface and unavoidable foreign matter adhered to the inner wall surface, By being coated with a liquid-soluble inorganic thin film material, it has a pore diameter of 1 μm or less and a porosity of 40% or more.

Further, the manufacturing method is a method for manufacturing a precision filter for a high-purity gas, which is capable of adsorbing and capturing impurity particles of 0.1 μm or less mixed in the gas to obtain a high-purity gas. Sintering using at least one kind of fine metal particles having an average particle size of 10 μm or less, metal short fibers, or metal fibers having a fiber diameter of 10 μm or less in a thin film liquid of an inorganic suspension having a viscosity of 10 cps or less While immersing the porous body and reducing the pressure from one surface of the sintered porous body to the other surface at a predetermined pressure, the thin-film liquid is sucked into the pores of the sintered porous body and at least the void is formed. The method is characterized in that the surface of the sintered porous body is coated with a thin film material by applying the thin film solution including the unavoidable foreign substances remaining on the inner wall surface of the pores and the inner wall surface of the pores and then drying. .

The precision filter having the above-mentioned structure is constituted by a sintered porous body composed of fine metal particles having an average particle size of 10 μm or less, metal short fibers, or metal fibers having a fiber diameter of 10 μm or less as a base, and further its surface. Since it is covered with an inorganic thin film material, the size of the obtained pores is sufficient to achieve microfiltration.

Further, the coating with the thin film material can reduce the chance of water adhesion and enhance the gas displacing property by smoothing the surface of each metal particle or fiber itself.

In particular, when the sintered porous body is formed by sintering the metal short fibers having the above-mentioned constitution, the orientation of each short fiber is arranged at random so that three-dimensional voids can be formed and fine pores can be formed. A void and a sintered body having a high porosity can be obtained.

Further, by using an inorganic liquid-soluble material as the thin film material, it is possible to sufficiently penetrate the inside of the pores of the sintered porous body while maintaining sufficient pores by appropriately adjusting the melt viscosity. For example, a uniform coating with a thickness of, for example, 5 μm or less, preferably 1 μm or less can be covered, and the corrosion problem that is a defect of metal can be covered to contribute to the improvement of corrosion resistance as a whole, and a chemical reaction with a non-treatment gas. Also has the advantage that it can be suppressed. Preferably in the thin film material,
For example, if a sol containing SiO ₂ or Al ₂ O ₃ and dispersed in a solution is used, the melt viscosity can be adjusted by the dispersion ratio and a low-viscosity liquid material can be obtained.

As a result, the precision filter according to the above construction can suppress the chemical reaction with the non-treated gas, protect the metallic porous body as the base from corrosion, and enhance the heat resistance and pressure resistance.

Further, the coating of the sintered porous body having the above-mentioned structure with such a thin film material is a thin film material including inevitable foreign substances which are unavoidably left inside in the manufacturing process of the metal filter. Since it is possible to cover, for example, in the conventionally used uncoated filter, the problem that the unavoidable foreign matter often flows out with the filtration process has occurred, but by adopting the manufacturing method of the above configuration The risk of doing is eliminated.

The fine particles such as the metal fine particles and the metal short fibers forming the sintered porous body have a particle size of 10 μm or less, and the metal fiber has a fiber diameter of 10 μm or less. When a large one is used so as to exceed these values, no matter how much the surface is coated with a thin film material, the obtained pores become large and a suitable pore size for high purity gas cannot be obtained. As a result, the number of pores also decreases and the filtration performance decreases.

The sintered porous body has a pore diameter of 1 μm or less and a porosity of 40% or more. The reason for restricting in this way is that it is used as a gas filter used in the production of ultra-precision products such as semiconductors, and in order to perform efficient filtration, the pore diameter and porosity are It is preferable to increase and.

The lower limit of the particle diameter or the fiber diameter is not particularly specified, but a more preferable range from the feasible range is 0.1 to 0.1 in the particle diameter of fine powder.
The thickness is 10 μm, more preferably 0.1 to 3 μm, and in the case of metal fibers, the fiber diameter is about 0.3 to 5 μm.

On the other hand, in the method of manufacturing such a filter, an inorganic suspended liquid having a melt viscosity of the thin film liquid of 10 cps or less is used, and the thickness of the thin film material formed by this is used. The thin and uniform coating is made possible by dipping the sintered porous body in a thin film solution and sucking the thin film solution into the sintered porous body while suctioning under reduced pressure from one surface of the sintered porous body. However, the method of pulling up from the liquid and drying is adopted.

By using such a method, the thin film material sufficiently penetrates into the inside of each pore, and the sintered porous body has a thickness that does not close the pores even though they are fine pores. Coating the surface of.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described below with reference to the drawings. A precision filter 1 for high-purity gas (hereinafter referred to as a precision filter) has a sintered porous body 2 coated with a thin film material 3 to the inside of pores. The sintered porous body 2 is formed by sintering fine metal particles, metal short fibers or metal fibers whose size is regulated in advance.

In this example, the sintered porous body 2 has a structure as shown in FIGS.
As shown in FIG. 5, a holding filter 4 having a relatively large thickness is stacked to form a laminated filter 5.

The holding member 4 has, for example, a particle size of 20 to 60 μm.
On the other hand, the sintered porous body 2 is made of short metal fibers having a diameter of about 0.3 to 1 μm and a pore diameter of about 0.05 to 0.1 μm. ing.

The sintered porous body 2 is, in this example, the holding member 4 described above.
In addition, as shown in FIG. 1, a cup type having an outer diameter of 20 mm and a length of 60 mm is formed, and the sintered porous body 2 is disposed on the outer surface thereof.
Moreover, the thickness is formed to about 0.5 mm.

By using such a laminated structure, it is formed so that a greater filtration efficiency can be obtained within a predetermined filtration surface, and in the case where the filter has a disk shape, for example, these fine powders are used. Besides, the metal fibers may be used. The fiber diameter and distribution density used can be changed layer by layer, or the short fibers can be laminated and used.

In particular, when short fibers having a fiber diameter of 0.1 to 8 μm and an aspect ratio (L / D) of 2 to 30 are used, the distribution of each short fiber is in a random direction and has a straight needle shape. While being sintered, it is possible to form minute and three-dimensional pores, and it is a low pressure loss, which is very preferable.

With such a laminated structure, the sintered porous body 2 is, for example, about 1 mm or less (usually 0.5 mm or less).
Since it is relatively thin and fine, there is also an advantage that the pressure loss can be reduced.

In this example, the sintered porous body 2 using such short metal fibers has been described as having a porosity of 40% or more, but the specific constitution, form and application are variously modified. It does not matter, for example, the whole is composed only of the above-mentioned short fibers, or in place thereof, only fine metal particles are used, or those obtained by appropriately mixing and adjusting the both are used, or the shape thereof is not limited to the above, such as a cylinder or a cone. Alternatively, the shape may be a cylinder, a cone or any other shape without departing from the object of the present invention. In particular, the disk type is easy to manufacture, while the cup type and the cylindrical type are advantageous in that the filtration area is increased.

The material of the holding member 4 is not limited, and various metals can be adopted. For example, if Cu, Al or the like is used, it can contribute to cost reduction, while titanium, nickel steel, chrome steel, etc. If high alloy steel such as stainless steel is used, it has excellent pressure resistance and heat resistance.
It is preferable to use a material such as 304L material.

As the thin film material 3, for example, colorless and transparent "grass modoki" (trade name of TSB Co., Ltd.), which is SiO ₂ , can be suitably adopted. "Glass modki"
Can be melted with a solvent such as methanol, and its viscosity can be adjusted to 3.5 cps or less. Such a low viscosity makes it easy to reduce the coating thickness to 5 μm or less, preferably 0.01 to 1 μm. You can do it.

Thin film material 3 composed of such a solution inorganic substance
As shown in FIG. 3, it is possible to cover the inner surface of the pores with the unavoidable foreign matter 7 such as dust adhering to the inner wall surface of the pores, and the unavoidable foreign matter 7 adhering to the voids flows out during the filtration process. Can be prevented.

By adopting the above-mentioned "grass modoki", for example, when the film thickness is 1.8 μm,
The hardness after standing for 1 hour at room temperature becomes a hard coat with a pencil hardness of about 3H, and becomes harder as time passes and the temperature of the standing environment rises, and becomes 9H when left at 100 ° C for 2 hours.

Further, regarding its heat resistance, there is no problem at a temperature of about 500 ° C., and the sintered porous body 2 which is the base material.
Is also effective for blocking voids due to abrasion of the sintered porous body 2 because of its high hardness.

As another embodiment of the present invention, in order to secure the adhesion between the thin film material 3 and the sintered porous body 2, for example, a base treatment different from that of the thin film material 3 is provided between them. By preliminarily treating the surface of the sintered porous body 2 with a material, it is possible to increase the adhesion of the thin film material 3 and make it stronger. As the base treatment material, various kinds of preliminary film materials called normal primers having a strong affinity for both the sintered porous body 2 and the thin film material 3 are used.

Further, as shown in FIG. 3, inevitable foreign matter 7
The minute projections 9 are thereby formed in the portion including and including, which can contribute to the improvement of the characteristics by increasing the surface area and making the pores smaller. The precision filter 1 thus formed has a filtration accuracy of 0.01 μm or less and a porosity of 42.
Was 50%.

FIG. 4 shows still another embodiment of the present invention. Usually, the filter 1 is attached or extended with a holding member 4A such as a metal tube for holding the filter by connecting the filter 1 to the filter, for the sake of handling. In such a case, a deep groove 10 is formed in the boundary portion 6 where the sintered porous body 2 and the holding member 4A are joined, and the gas is retained in the groove 10. Such gas retention is a serious problem in applications requiring high purity such as semiconductor manufacturing gas.

However, if the boundary portion 6 between the two is covered with the thin film material 3 as in the present example, the groove existing in the joint boundary portion 6 is repaired and the residual gas remains. It can be prevented.

As described above, the precision filter 1 improves the corrosion resistance, which is its drawback, while suppressing the outflow of the residual impurities 7 while maintaining the convenience as a filter medium made of metal, thereby reducing the maintenance of the apparatus. For longer life.

Next, referring to FIG. 1, the manufacturing method of the present invention will be described. The precision filter 1 of the present invention is, in this example,
It has a cup shape, and its opening is closed by a holding member 4A made of a metal plate material. Therefore, a void O is formed inside the cup-shaped body. The sintered porous body 2 is immersed in a thin film liquid 3A of an inorganic suspension having a melt viscosity of 10 cps or less by dissolving the thin film material having the above-described structure, and an intake pipe 11 communicating with the space O and having a pump P interposed therebetween. By sucking, the thin film liquid 3A is sucked from one surface A formed by the outer peripheral surface of the sintered porous body 2 toward the other surface B facing the space O.

By this suction, the thin film liquid 3A contains the pores of the sintered porous body 2 and the unavoidable foreign substances 7 remaining on the inner wall surface of the sintered porous body 2, and covers the thin film liquid 3A while covering the sintered porous body 2 with the thin film liquid. Pull out from 3A and dry. As a result, the fine filter 1 in which the whole is covered with the thin film material 3 is formed while forming the microscopic pores in the sintered porous body 2.

The processing conditions at this time are, for example, 4c for the thin film material.
In the case of the above-mentioned "glass fluffy" of a low-viscosity solution of ps or less, it is about 1 at a reduced pressure of about 0.2 to 0.7 kg / cm ^2.
It will be possible if it is processed in about 5 minutes. Further, the depressurization pressure affects the coating thickness of the obtained product. For example, if the treatment is carried out at a high pressure, the obtained thin film material 3 becomes thin and voids,
The unavoidable foreign matter 7 adhering to the wall surface or the like can be caused to flow out by the flow of the thin film liquid 3A, but conversely, when the pressure is low, the thin film material 3 on which the coating layer is formed becomes slightly thicker,
Further, the unavoidable foreign matter 7 can be left in the pores by being covered with the thin film layer 3. The adjustment is arbitrarily selected as needed.

Since such conditions vary variously depending on the pore characteristics of the sintered porous body used and the characteristics of the thin film material 3, an appropriate range should be determined in advance, and the wettability of both should be determined. For the purpose of improvement, it is preferable that the surface of the sintered porous body 2 is preliminarily subjected to a surface treatment in the same manner as described above before use.

As the base treatment, for example, a plurality of layers of coating treatment may be performed with a solution of the same composition having different viscosities divided into several times, or a composite structure may be formed using different types of solutions.

[0049]

As described above, the precision filter of the present invention is characterized in that the surface of particles or fibers having a regulated size is coated with a thin film material, so that the filtration characteristics and corrosion resistance can be improved. It is possible to increase the purity of various gases used in semiconductor manufacturing.

Further, by adopting the manufacturing method, it is possible to efficiently manufacture from a small amount and to stabilize the quality without the need for large-scale equipment and complicated steps.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a method for producing a precision filter of the present invention.

FIG. 2 is a cross-sectional view showing an enlarged cross section in the thickness direction of the precision filter.

FIG. 3 is an enlarged perspective view showing a short metal fiber forming a sintered porous body together with a coating material.

FIG. 4 is a cross-sectional view showing another embodiment of the precision filter.

[Explanation of symbols]

 2 Sintered porous body 3 Thin film material 3A Thin film liquid 4 Holding member 6 Bonding boundary 7 Inevitable foreign matter

Claims (7)

[Claims] 1. A precision filter for a high-purity gas, which obtains a high-purity gas capable of adsorbing and trapping impurity particles of 0.1 μm or less mixed in the gas, the metal fine particles having an average particle diameter of 10 μm or less, A sintered porous body is formed by sintering using at least one kind of metal short fibers or metal fibers having a fiber diameter of 10 μm or less, and the sintered porous body is formed on the inner wall surface of pores and the inner wall surface. A precision filter for a high-purity gas having a pore diameter of 1 μm or less and a porosity of 40% or more by being covered with a liquid-soluble inorganic thin film material including inevitable foreign substances that adhere. 2. The high purity gas for a high purity gas according to claim 1, wherein the thin film material is a liquid-soluble inorganic coating material containing SiO ₂ or Al ₂ O ₃ and has a coating thickness of 5 μm or less. Precision filter. 3. The precision filter for high purity gas according to claim 1, wherein the thin film material is formed of two or more kinds of laminated coating layers having different compositions. 4. The sintered porous body is integrally bonded to a holding member for holding the sintered porous body via a bonding boundary portion, and the thin film material covers the bonding boundary portion toward the holding member side. The precision filter for high purity gas according to any one of claims 1 to 3, wherein 5. The precision filter for high-purity gas according to claim 1, wherein the high-purity gas is a gas filled in a manufacturing apparatus for manufacturing the semiconductor. 6. A method for producing a precision filter for a high-purity gas, which obtains a high-purity gas by adsorbing and capturing impurity particles of 0.1 μm or less mixed in the gas, which has a melt viscosity of 10 cps or less. In a thin film liquid of inorganic suspension,
While immersing the sintered porous body that has been sintered using at least one kind of fine metal particles having an average particle size of 10 μm or less, metal short fibers, or metal fibers having a fiber diameter of 10 μm or less, one of the sintered porous bodies From the surface to the other surface at a predetermined pressure to suck the thin film solution into the pores of the sintered porous body and at least the pore inner wall surface and the unavoidable foreign matter remaining on the pore inner wall surface. A method for producing a precision filter for high-purity gas, which comprises coating the surface of a sintered porous body with a thin film material by applying the thin film solution including the above and then drying. 7. The high-purity porous sintered body according to claim 6, wherein the surface of the sintered porous body is preliminarily coated with an undercoating material in order to enhance the adhesion of the thin film liquid. Method for manufacturing precision filter for gas.