JPH0134090B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a filter device for removing foreign substances such as suspended particles from processing liquids used in manufacturing semiconductor devices, such as etching liquids and cleaning liquids. Recently, due to the demand for higher integration of semiconductor devices, the line width of circuit patterns formed on wafers is becoming less than 1 μm, and the accuracy thereof is becoming less than 0.3 μm. In order to form such a circuit pattern, it is necessary to minimize the adhesion of fine particles or lines of foreign matter onto the wafer. Even the adhesion of minute foreign matter may cause a missing circuit pattern or a defect in the electrical function near the part where the foreign matter is attached. The adhesion of minute foreign matter to the wafer from the air is
This is prevented by forming semiconductor devices in a controlled clean environment such as a clean room or even a clean bench.On the other hand, the adhesion of minute foreign matter to the wafer from processing solutions such as etching or cleaning processing is prevented. This can be prevented by filtering the treated solution in advance using a filter using a polymer membrane. By the way, examples of processing liquids used in the manufacture of semiconductor devices include HCl, H ₂ , SO ₄ ,
_HNO3 , _H2O2 , HF, _{NH4F , H3PO4 , NH4OH}
There are a wide variety of liquid inorganic chemicals, such as liquid organic chemicals such as trichlorethylene, acetone, and alcohols, which are mainly used as cleaning solvents, and pure water. It is difficult to expect that the circuit pattern defects, electrical function defects, etc. described above will be eliminated unless they are sufficiently removed. However, in filters using polymer membranes,
There is a limit to the chemical resistance depending on the membrane material used, so it is necessary to limit the applicable treatment liquid depending on the membrane material used, or to restrict its concentration or PH value from the viewpoint of life. Additionally, filters using polymer membranes have poor heat resistance, and the safe operating temperature is approximately 60℃.
It can be recognized that the temperature is within ~80℃, and therefore, it is difficult to apply it when you want to reduce the viscosity of a processing liquid that is highly viscous at room temperature by heating it to increase the temperature and thereby perform efficient filtration in a short time. In the case of high-temperature filtration, such as when trying to sterilize (ultra)pure water by heating, filters using polymer membranes similarly have problems in terms of heat resistance, and in general, cross-flow filtration type filters In order to increase the filtration area of the filter while maintaining the cross-flow filtration effect without reducing the flow rate, the device requires a long filter, which makes the filter expensive and the shape of the filter device is impractically long. There is a problem in that there are cases where this happens. The present invention has been made in view of the above points,
The objective is to have sufficient corrosion resistance against a wide variety of processing solutions used in the manufacture of semiconductor devices, to be able to perform high-temperature filtration, and to achieve filtration by connecting multiple filters in series. To provide a cross-flow filtration type filter device for a semiconductor device processing liquid, which can increase the filtration area while maintaining the effect of cross-flow filtration without reducing the flow rate of the processing liquid to be processed, and can have a compact shape. It is in. According to the present invention, a cylindrical filtration layer made of porous ceramic, and a cylindrical filtration layer that is superimposed concentrically on the outside of the filtration layer to support the filtration layer and has a larger pore diameter than the pores of the filtration layer. a cylindrical support layer made of porous ceramic, two cylindrical first and second filters arranged substantially parallel to each other, and arranged parallel to the first filter;
a cylindrical sealed container that accommodates the first filter and the second filter; the container is provided at one end of the container, and the liquid from the outside of the container is directed to the container through one end of the first filter; an inlet for introducing the liquid into the internal space of the first filter; and an inlet provided inside the container on the other end side of the container, and the liquid introduced into the first filter is introduced into the first filter. a guiding means for guiding the liquid from the other end to the internal space of the second filter through one end of the second filter; and a guiding means provided on the wall of the container and guided to the second filter. a first outlet for leading out the liquid to the outside of the container through the other end of the second filter; a second outlet for leading out the filtrate filtered into the space inside the container through each of the filtration layers and the support layer to the outside of the container; The above objectives are achieved. The ceramic filtration layer and support layer in the present invention may be formed using ceramic materials such as alumina, mullite, cordierite, etc.
A filter consisting of these filtration layers and support layers can be manufactured in the form of a flat plate having a filtration layer on one side, a tubular body having a filtration layer on its inner or outer surface, or the like. The filter manufactured as described above is applied to the cross-flow filtration type filter device of the present invention. Next, one preferred embodiment of the filter device according to the present invention will be explained with reference to the drawings. The tubular filter 1 shown in FIGS. 1 and 2 has a support layer 4 made of porous ceramic having a large number of pores of 15 μm to 20 μm, formed using alumina (Al ₂ O ₃ ) with a purity of 99.9%. An alumina strip (alumina slurry) was applied twice to the inner surface of the filter, which was then fired to form a filter layer 5 made of porous ceramic (alumina with a purity of 99.9%) that is substantially integrated with the support layer 4. It is something. Here, in order for a large number of pores in the filtration layer 5 to have a pore size smaller than that of the pores in the support layer 4, the alumina strip is applied to the inner surface of the support layer 4 so that the alumina powder particle size gradually becomes smaller. This was done by controlling the particle size range of the alumina powder. The thickness d of the filtration layer 5 is approximately 10 μm after firing, and the thickness d of the filtration layer 5 determines the size of filterable foreign matter.
The average pore diameter of the pores was 0.2 μm, and the maximum pore diameter was 1.0 μm to 1.5 μm according to the bubble point measurement method.
As mentioned above, this filter 1 is not made up of one type of pore size as a whole, but is an asymmetric filter in which a filtration layer 5 with a small pore size is formed on the inner surface of a support layer 4 with a large pore size. , it is possible to reduce the filtration pressure loss compared to conventional filters, and increase the filtration amount per unit area, unit time, and unit filtration pressure, and in addition, it has a sufficient mechanical property compared to filters made of organic polymer membranes. In addition to having mechanical strength, it also has excellent heat resistance and corrosion resistance. Therefore, it is possible to filter contaminant fine particles in chemicals used in etching solutions used in semiconductor device manufacturing, such as concentrated oxidizing acids, and also to filter high-temperature filtration (100°C to several 100°C) of pure water for semiconductor cleaning, primarily for the purpose of sterilization.
It is possible. For example, outer diameter D ₁ 19mm, inner diameter D ₂ 15mm, length
A ring-shaped filter piece carefully cut to a length of 15 mm from a 760 mm filter 1 has a radial crushing strength of 740 kg/
cm ² (average), and even when a water pressure difference of 20 atm or more was applied between the inside and outside of the filter 1, it did not break down, and a normal pressure difference of 30 atm was guaranteed. Next, a filter device according to the present invention using two filters manufactured in the same manner as the filter 1 in addition to the filter 1 will be described with reference to FIGS. 3 and 4. Filters 2 and 3 were manufactured in the same manner as filter 1, and polypropylene resin disks 6 and 7 were directly heat-fused and bonded to both ends of filters 1, 2, and 3 without using a connecting agent. It is fixed. The disks 6 and 7 can be fixed to the filters 1, 2 and 3 by the method described in Japanese Patent Application No. 57-206485, for example. The disk 6 is formed with through holes 8, 9, and 10 that communicate with the insides of the filters 1, 2, and 3, respectively, and the other disk 7 also has a similar through hole (not shown).
is formed. Flow path guide disks 13 and 14 made of, for example, polypropylene resin are arranged so that gaskets 11 and 12 made of, for example, chemical-resistant fluororesin rubber are brought into close contact with one surface of each of the disks 6 and 7. There is. The pin 15 is used for mutual positioning of the disc 6, packing 11, and disc 13, and for positioning the disc 7.
and are used for mutual positioning of the gasket 12 and disc 14, respectively. Circular through holes 16 and 17 and oval through holes 18 and 19 for shorting are formed in the gaskets 11 and 12, respectively.
The through hole 16 is arranged in a circular center with the through hole 8, and the through hole 18 is arranged across the through holes 9 and 10. The through hole 17 of the packing 12 is a through hole (not shown) formed in the disc 7 corresponding to the filter 3.
The through hole 19 is arranged at the center of the circle and extends over two through holes (not shown) formed in the disk 7 corresponding to the filters 2 and 2. Disk 1
3 and 14, through holes 20 and 21 are arranged at the center of the through holes 16 and 17, respectively, and a through hole 18
and recesses 22 and 23 arranged opposite to 19.
is formed. The through hole 20 defines an inlet for the processing liquid to be filtered.
1 is a first outlet for the processing liquid to be filtered through the recess 22, the filter 3, and the through holes 9, 10, 17.
and 18, the recess 22 defines a communication path that communicates the interiors of one end of each of the filters 2 and 3 with each other, and the recess 23 defines a communication path between the filters 1 and 2.
A communication path is defined as a guiding means that communicates the inside of each of the ends with each other. Filter 1,
A cylindrical container 24 made of polypropylene resin that accommodates 2 and 3 is fitted at both ends with disks 6 and 7, respectively, and is melt-welded to each other along the circumferential direction using polypropylene resin material. A space 25 is formed between the filters 1, 2, and 3 and the container 24 to collect the filtered processing liquid. A lid 2 made of, for example, polypropylene resin is screwed onto threaded portions 26 and 27 formed at both ends of the container 24, respectively.
8 and 29 tightly press the gaskets 11 and 12 to the disks 6 and 7, respectively, and the disks 13 and 14 to the gaskets 11 and 12, respectively, by tightening the screws. Container 24 as a closed container, lid 28, 2
Cylindrical connecting pipes 30, 31, 32 respectively planted in 9
and 33, the connecting pipes 30 and 31 are connected to the space 2
5, and the connecting pipe 32 is connected to the through hole 20,
The connecting pipes 33 communicate with the through holes 21, respectively. The connecting pipes 30, 31, 32, and 33 are each made of, for example, polypropylene resin, and can be implanted in the container 24 and the lids 28, 29, respectively, by melt overlay welding of the same resin material. In the filter device 40 of the cross-flow filtration type formed in this way, when the processing liquid to be filtered is supplied to the connecting pipe 32, this processing liquid is first introduced into the filter 1, and then passes through the recess 23. After being supplied to the filter 2 and further introduced into the filter 3 via the recess 22, it is led out to the outside from the connecting pipe 33, and is again supplied to the connecting pipe 32 via a liquid pressure feeding means such as a pump, where it is circulated. . While passing through filters 1, 2, and 3 in order, filters 1, 2,
Fine foreign matter is removed from the processing liquid passing through the passage consisting of pores 3, and the filtered processing liquid is taken out into the space 25, and this processing liquid is passed through, for example, a connecting pipe 31 as a second outlet. is led out to the outside,
It is used as a processing solution for manufacturing semiconductor devices. When the concentration of fine foreign matter (contaminants) in the process liquid to be filtered that is being circulated reaches a certain level, it is generally discarded. In addition, the connecting pipe 30 is
It is provided to balance the pressure between the space 25 and the outside, but if necessary or at regular intervals,
Filtered processing liquid or other liquid may be pumped from the connecting tube 30 into the space 25 to unclog the pores of the filters 1, 2 and 3 and to wash the filters 1, 2 and 3. By the way, in the specific example, an assembly 41 (referred to as a cartridge) consisting of filters 1, 2 and 3 and discs 6 and 7 shown in FIG. 3 is welded to the container 24 at the discs 6 and 7. However, instead of this, the space between the disks 6 and 7 and the container 24 is sealed using a Teflon (registered trademark) rubber or silicone rubber packing or seal ring, and the cartridge 41 is It may be configured to be replaceable. Further, as a reference example, a vertical filtration type filter device may be formed using an asymmetric flat filter made of high purity alumina, and a vertical filtration type filter device may be formed using the cylindrical filter of the above specific example. A device may also be formed. The filters 1, 2, 3 and the packings 11, 12 are made of polypropylene resin in the above specific example, but depending on the processing liquid to be filtered or its concentration, they may be made of vinyl chloride, vinyl acetate, polystyrene, polysulfone, polyamide, acetal, etc. It may be formed using one selected from thermoplastic resins such as polycarbonate, or a combination of two or more types. In addition, these may be made of a ceramic material such as alumina, mullite, or cordierite, and in this case, other materials such as adhesion between the filters 1, 2, and 3 and the discs 6 and 7 may be formed. Mutual adhesion can be achieved using various glass solders selected in relation to the processing liquid.
Epoxy resins or silicone resins may optionally be applied as adhesives. If the filter device 40 is made entirely of ceramic material without using the packings 11 and 12, after applying a glaze of glass solder powder to each joint, place this integral assembly in a heating furnace to stabilize it. The glass solder powder may be held at a temperature to melt and solidify the glass solder powder, thereby fixing each joint.In this case, glass solder having the same melting temperature may be used to fix the glass solder powder in one step. Or using two or more types of glass solders with different melting temperatures,
The fixing may be performed in two or more steps so that inspection can be performed during the process. Examples of the present invention will be shown below. Example High purity alumina porous asymmetric filter 1,
2, 3 (outer diameter D ₁ 19mm, inner diameter D ₂ 15mm, length l370
mm, average filtration layer pore diameter 0.2 μm, maximum pore diameter 1.5 μm by bubble point measurement) were prepared, and these were connected in series as shown in Figure 3, and other parts were made of polypropylene resin. A cross-flow filtration type filter device 40 was manufactured.
Prior to fabrication, filters 1, 2, and 3 were all cleaned by ultrasonic cleaning in a pure water bath for about 30 minutes, mainly to remove foreign substances that had penetrated into the pores. On the other hand, other parts made of polypropylene resin were subjected to ultrasonic cleaning for 1 time in a tricloethylene bath for semiconductors.
The sample was then washed with methanol, rinsed with pure water, and dried in a dust-proof indoor dryer at 40°C. After the previous ultrasonic cleaning, filters 1, 2, and 3 were housed in an electric furnace lined with nickel plates and heated to 500°C.
The surface was degreased by heating. Assembly into the filter device 40 shown in FIG. 4 was carried out generally by the means described above, but was carried out in a dust-proof room using gloves to avoid contamination. After assembly, the filter device 40 was subjected to cross-flow filtration for approximately 30 minutes with ultrapure water that had been subjected to ultrafiltration and reverse filtration for the purpose of cleaning before use.
In this case, it took 32 seconds to obtain a filtration amount of 1 at a filtration pressure of 0.9 kg. This corresponds to a filtration efficiency of 2.2 m ³ /Hr.m ² calculated from the surface area of the filter used, which is almost the same as that of a hollow polymer membrane filter having a similar volume. After pre-cleaning with ultrapure water, tap water was assumed to be the processing liquid for semiconductor devices, and the tap water was applied to the filter device 40 to quantify the number of foreign particles before and after filtration. As a result, the following values were obtained. was gotten.

[Table] Based on these results, filters 1 and 2 with an average pore diameter of 0.2 μm
It can be seen that 96.5% of the particulate foreign matter in the tap water with a size of 0.2 to 1.0 μm was removed by 3 and 3. 1.0μm, which exists in a very small amount in the pore size distribution in the filter
Approximately 0.1% of particles of 5 to 10 μm are present in the filtered water without being removed by the passages larger than the pore size, but it is thought that this can be removed by means such as refiltration. As described above, the filter according to the filter device of the present invention is not affected by oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid.
Moreover, it has been found that it can be preferably applied to the filtration of processing liquids in semiconductor device manufacturing because it can have sufficient filtration characteristics.According to the apparatus of the present invention, a plurality of filters can be connected in series by a guiding means Because of the connection, the filtration area can be increased without reducing the flow rate of the processing liquid to be filtered, and therefore, the effect of cross-flow filtration can be sufficiently maintained.
In addition, since the shape is compact and a plurality of filters of the same type can be used, it is economically advantageous in terms of manufacturing, and the filtration area can be easily adjusted.

[Brief explanation of drawings]

1 is a perspective view of a preferred specific example of the filter according to the device of the present invention, FIG. 2 is an explanatory cross-sectional view taken along the line -2 of the filter shown in FIG. 1, and FIG. 3 is a perspective view of the filter according to the present invention shown in FIG. Exploded diagram of the device, No. 4
1 is a perspective view of one preferred embodiment of a filter device according to the invention using the filter shown in FIG. 1; FIG. 1, 2, 3...filter, 4...support layer, 5...
...filtration layer.

Claims (1)

[Scope of Claims] 1. A cylindrical filtration layer made of porous ceramic, and a cylindrical filtration layer that is superimposed concentrically on the outside of the filtration layer to support the filtration layer and has a pore diameter larger than that of the pores of the filtration layer. two cylindrical first and second filters arranged substantially parallel to each other, and arranged parallel to the first filter;
a cylindrical sealed container that accommodates the first filter and the second filter; the container is provided at one end of the container, and the liquid from the outside of the container is directed to the container through one end of the first filter; an inlet for introducing the liquid into the internal space of the first filter; and an inlet provided inside the container on the other end side of the container, and the liquid introduced into the first filter is introduced into the first filter. a guiding means for guiding the liquid from the other end to the internal space of the second filter through one end of the second filter; and a guiding means provided on the wall of the container and guided to the second filter. a first outlet for leading out the liquid to the outside of the container through the other end of the second filter; a second outlet for leading out the filtrate filtered into the space inside the container through each of the filtration layers and the support layer to the outside of the container; .