JPH04330910A - Ceramic gas filter for manufacturing semiconductor - Google Patents

Abstract

PURPOSE:To prevent contamination on the secondary side caused by the inflow of gas to be filtered and the evaporation of a sealant when using a ceramic gas filter in the semiconductor manufacture-related fields. CONSTITUTION:In a tubular ceramic gas filter formed by laminating a filter layer 2 and a support layer 3, ceramic powder particles of high purity are attached to fine pores in both the ends to make the diameter of the fine pores equal to or smaller than that in the filter layer 2 to form a seal layer 4 in the ends. Therefore, the ceramic powder particles of high purity makes the flow through the seal layer 4 equal to or smaller than that through the filter layer, causing the gas to be filtered not to flow directly from support layer 3 to the secondary side, and the evaporation of the sealant during baking or in use is prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubular ceramic gas filter used in the field of semiconductor manufacturing to remove fine dust contained in gas.

0002

2. Description of the Related Art A tubular ceramic gas filter is formed into a tubular shape in which either a filtration layer 11 made of fine particles and a support layer 12 made of coarse particles are stacked on the inside, as shown in FIG. , both layers are exposed on the end face.

When this ceramic gas filter is made into a module and the gas to be filtered is filtered by flowing from the support layer 12 side to the filtration layer 11 side, the gas to be filtered passes through the filtration layer 11 as shown by the arrow in FIG. There is a possibility that the gas flows from the end face to the secondary side (filtered side) through the support layer 12 and contaminates the filtered gas on the secondary side. This is because the amount of ventilation increases in proportion to the square of the pore diameter.

[0004] Conventionally, in order to cope with this problem, a tubular ceramic gas filter is known which has sealing portions impregnated with glass at both ends. This ceramic gas filter is manufactured by applying glass powder to the end and impregnating it by heating.

[0005]

[Problems to be Solved by the Invention] However, when the above-mentioned conventional tubular ceramic gas filter is used for filtering gas for semiconductor manufacturing, alkali metals, which are components of the glass, are removed during baking (degassing) or during use. Substances with high vapor pressure, such as alkaline earth metals, evaporate and flow to the secondary side, contaminating the filtered gas, which may become a source of contamination for semiconductor products.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a ceramic gas filter for semiconductor manufacturing that can prevent contamination of the secondary side due to the inflow of gas to be filtered and the evaporation of the sealant.

[0007]

[Means for Solving the Problems] In order to solve the above problems, a moramic gas filter for semiconductor manufacturing of the present invention has the following features:
In a tubular ceramic gas filter for semiconductor manufacturing in which a filtration layer and a support layer are laminated, high-purity ceramic powder particles are attached to the pores at both ends, and the pore diameter of that part is equal to or smaller than the pore diameter of the filtration layer. It is equipped with a smaller sealing layer.

[0008]

[Function] In the above means, the amount of ventilation in the sealing layer is equal to or smaller than the amount of ventilation in the filtration layer due to the high purity ceramic powder particles.

Examples of ceramic powder particles include oxide ceramics such as alumina, mullite, zirconia, and titania, and non-oxide ceramics such as silicon carbide and silicon nitride. It is preferable to use an alkali metal, an alkaline earth metal,
Preferably, it does not contain heavy metals or the like.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a half-sectional side view showing an embodiment of a ceramic gas filter for semiconductor manufacturing according to the present invention.

This ceramic gas filter 1 has a filtration layer 2 made of fine particles of high purity (99.99%) alumina ceramics, and a support layer 3 made of coarse particles of the same ceramic, with the filtration layer 2 on the inside. Powder particles of alumina ceramics similar to those of both layers are attached to the pores of the support layer 3 at both ends thereof, and the pore diameter is adjusted to the pore diameter of the filtration layer 2. A sealing layer 4 having an equivalent thickness of 0.13 μm is provided.

Next, a method for manufacturing the ceramic gas filter 1 will be explained. First, 40 parts by weight of alumina powder with a particle size of 0.2 μm and a purity of 99.99% and 60 parts by weight of water were crushed and mixed in a ball mill for 24 hours to obtain a highly concentrated slurry, and 25 parts by weight of this highly concentrated slurry was mixed with water. 75 parts by weight and stirred with a magnetic stirrer to obtain a 10% by weight slurry.

Next, the end of a tubular filter body made of alumina ceramics, in which a support layer with a pore diameter of 2 to 3 μm is formed on a filtration layer with a pore diameter of 0.13 μm, is immersed in the slurry, and the end pores are removed. When the slurry seeped into the part by capillary action, it was pulled up and dried, and then fired at a temperature of 1200°C to obtain a tubular ceramic gas filter with sealing layers at both ends.

The pore diameter of the sealing layer of the obtained ceramic gas filter was measured using a mercury intrusion porosimeter, and the results were as shown in FIG. This measurement result shows that the pore diameter of the sealing layer is 0.13 μm, which is the same as the pore diameter of the filtration layer.

[0015] The preparation of the slurry is not limited to the case where water is used as a solvent, but a Metrose solution or a PVA solution may also be used as a solvent, and by adjusting its viscosity, the length of penetration into the filter body can be controlled.

[0016] The slurry concentration is preferably 1 to 35% by weight; if it is less than 1% by weight, the filling rate into the pores will be low and the efficiency will be poor, while if it exceeds 35% by weight, it will be difficult to see the surface of the filter body. It becomes clogged and cannot enter the pores. Formation of the sealing layer can be controlled by the length of immersion in the slurry.

[0017] The firing process after drying varies depending on the material.
It is preferable to carry out the firing at a firing temperature equal to or lower than that used for forming the filter layer.

Furthermore, the sealing layer is not limited to the case where the pore diameter at the end of the support layer is the same as that of the filtration layer; It may be formed smaller.

The above-mentioned ceramic gas filter 1 has the following features:
As shown in FIG. 3, it is modularized into size units. This size unit is a cylindrical housing made of stainless steel or the like, and has a gas inlet 5 at one end (the right end in FIG. 3) and a gas outlet 6 at the other end (the left end in FIG. 3). A ceramic gas filter 1 whose one end is hermetically sealed by a footed disc 8 made of fluororesin is housed in the chamber 7 with a circular plate 9 made of stainless steel in contact with the other end. It is configured.

[0020] In the above-mentioned size unit, the inlet 5
The gas to be filtered flows from the support layer 3 of the ceramic gas filter 1 through the filtration layer 2 and the dust is separated from the support layer 3 of the ceramic gas filter 1, as shown by the arrow in the figure, and the filtered gas flows to the secondary side and is discharged from the outlet 6.

[0021]

[Effects of the Invention] As explained above, according to the present invention, the air flow rate of the sealing layer is equal to or lower than the air flow rate of the filtration layer due to the high purity ceramic powder particles.
The gas to be filtered does not flow directly from the support layer to the secondary side, and the sealant does not evaporate during baking or during use, unlike conventional methods, and the gas to be filtered and the sealant do not evaporate. Contamination on the secondary side can be prevented, and contamination of semiconductor products from the ceramic gas filter can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a side view of a half cross section showing an embodiment of a ceramic gas filter for semiconductor manufacturing according to the present invention.

FIG. 2 is an explanatory diagram showing the measurement results of the pore diameter of the sealing layer of the ceramic gas filter.

FIG. 3 is a side sectional view of a size unit using the ceramic gas filter.

FIG. 4 is a side sectional view of a conventional ceramic gas filter.

[Explanation of symbols]

1 Ceramic gas filter 2 Filtration layer 3 Support layer 4 Sealing layer

Claims (1)

[Claims] Claim 1: In a tubular ceramic gas filter for semiconductor manufacturing in which a filtration layer and a support layer are laminated, high-purity ceramic powder particles are attached to the pores at both ends, and the pore diameter of the part is adjusted to the pore size of the filtration layer. A ceramic gas filter for semiconductor manufacturing, characterized by comprising a sealing layer with a pore size equal to or smaller than the pore diameter.