JPH08281233A - Method of washing pipe - Google Patents

Abstract

PURPOSE: To utilize a difference in expansion and shrinkage between an inside wall surface of a pipe and dirt stuck on the wall surface by alternately feeding washing liquids having mutually different temps. in the pipe, to peel and remove the dirt from the wall surface and also to discharge the washing liquid remaining in the inside of the pipe by blowing gas. CONSTITUTION: A first feed unit 14 in a pipe washing device 10 feeds ultrapure water heated to a first setting temp. at a hot ultrapupre water production device 20 into a pipe 12 to be washed, via a feed piping 22. Also, a second feed unit 16 feeds ultrapure water cooled to a second setting temp. at an ultrapure water tank 30 provided with a cooling device 28 into the pipe 12 to be washed, via a feed piping 32. Besides, a gas feed unit 18 feeds gaseous nitrogen ejected from a gaseous nitrogen cylinder 38 into the pipe 12 to be washed, via a feed piping 40. Washing of an electropolished pipe 12 is performed by controlling the operation of each of control valves 27A, 37A, 43A respectively of feed units 14, 16, 18 with a control part. Namely dirt at the wall surface is peeled and removed by alternately feeding the washing liquids having mutually different temps. into the pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe cleaning method, and more particularly to a pipe cleaning method for supplying a gas or liquid used for manufacturing semiconductor integrated circuits and the like.

[0002]

2. Description of the Related Art Generally, in a manufacturing facility for semiconductor integrated circuits and the like, even a small amount of fine dust causes defective products.
For the piping system for supplying gas or liquid used for manufacturing, it is necessary to use a tube from which dirt such as fine dust or oil adhering to the inner wall surface is sufficiently removed in advance. Conventionally, this type of pipe cleaning is performed by immersing the pipe in a cleaning liquid whose temperature has been raised or by flowing a cleaning liquid at a predetermined temperature into the pipe.

[0003]

However, according to the above-mentioned cleaning method, it is not possible to remove even a small amount of dirt attached to fine irregularities on the wall surface in the pipe. On the other hand, semiconductor manufacturing equipment for semiconductor integrated circuits is required to use cleaner piping materials than ever before in order to respond to the ever-increasing high integration, and removes the above-mentioned stains that may remain by conventional cleaning. The need has arisen.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pipe cleaning method capable of effectively removing a small amount of dirt adhering to the inner wall surface of a pipe.

[0005]

In order to achieve the above object, the present invention provides a pipe cleaning method of circulating a cleaning liquid in a pipe to remove dirt adhering to the wall surface of the pipe, and a cleaning liquid having a predetermined temperature. And a second cleaning step of cleaning the inside of the pipe by flowing a cleaning liquid having a temperature different from the cleaning liquid of the predetermined temperature for a predetermined time. A residual cleaning liquid discharge step of blowing a gas into the pipe to remove the cleaning liquid remaining in the pipe from the outside of the pipe after at least one of the first and second cleaning processes. Characterized by repeating.

[0006]

According to the present invention, by alternately flowing the cleaning liquids having different temperatures in the pipe, the wall surface in the pipe and the dirt attached to the wall surface respectively expand or contract. But,
Since the expansion rate or contraction rate of the wall surface in the pipe and the dirt attached to the wall surface and the expansion speed or the contraction speed are different, a gap is generated in the contact surface between the wall surface and the dirt attached to the wall surface.
The cleaning liquid permeates the voids, and the dirt is peeled off from the wall surface. The dirt peeled off from the wall surface is dissolved or suspended in the cleaning liquid, and is removed by being accompanied by the cleaning liquid when the cleaning liquid is discharged from the pipe. Further, by blowing a gas into the pipe to eliminate the cleaning liquid remaining in the pipe, the dirt dissolved or suspended in the residual cleaning liquid can be surely removed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the pipe cleaning method according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a block diagram of a pipe cleaning apparatus based on the pipe cleaning method according to the present invention. As shown in FIG.
Is a first supply unit 14 for supplying ultrapure water kept at the first set temperature to the pipe 12 to be cleaned, and a second set temperature (set temperature different from the first set temperature). It is composed of a second supply unit 16 for supplying the dropped ultrapure water to the pipe to be cleaned 12, and a gas supply unit 18 for supplying nitrogen gas to the pipe to be cleaned 12.

The first supply unit 14 has a warm ultrapure water producing device 20 for heating ultrapure water to a desired temperature, and the ultrapure water heated to the first set temperature by the hot ultrapure water producing device 20. Water is supplied to the pipe to be cleaned 12 via the supply pipe 22. The water supply of the ultrapure water from the hot ultrapure water producing device 20 to the pipe to be cleaned 12 is performed by driving a pump 24 installed in the middle of the supply pipe 22, and the pipe to be cleaned 1
The ultrapure water supplied to No. 2 is returned to the warm ultrapure water producing apparatus 20 through the circulation pipe 25 connected to the pipe to be cleaned 12. Further, a filter 26 for capturing and removing fine particles contained in the ultrapure water sent by the pump 24 is installed downstream of the pump 24 to prevent the fine particles from flowing into the pipe 12 to be cleaned. . Further, the supply pipe 22 and the circulation pipe 25 are provided with control valves 27A and 27B, respectively. When connecting the second supply unit 16 or the gas supply unit 18 to the pipe to be cleaned 12, this control is performed. The valves 27A and 27B are controlled to shut off the supply of ultrapure water from the warm ultrapure water producing apparatus 20 to the pipe 12 to be cleaned. At this time, the control valve 27A switches the direction in which the ultrapure water is sent, and returns the ultrapure water sent by the pump 24 to the hot ultrapure water producing apparatus 20 through the circulation pipe 25.
The control valve 27B shuts off the circulation pipe 25. still,
The operation of the control valves 27A and 27B is controlled by a control unit (not shown).

The second supply unit 16 has an ultrapure water tank 30 equipped with a cooling device 28 for cooling the ultrapure water to a desired temperature. The ultrapure water tank 30 cools the ultrapure water to a second set temperature. The ultrapure water thus prepared is supplied to the pipe to be cleaned 12 via the supply pipe 32. The water supply of the ultrapure water from the ultrapure water tank 30 to the pipe 12 to be cleaned is performed by driving a pump 34 installed in the supply pipe 32.
The ultrapure water supplied to the above is returned to the ultrapure water tank 30 through a circulation pipe 35 connected to the pipe to be cleaned 12. Also,
A filter 36 for capturing and removing fine particles contained in the ultrapure water sent by the pump 34 is provided downstream of the pump 34.
Is installed to prevent fine particles from flowing into the pipe 12 to be cleaned. Further, the supply pipe 32 and the circulation pipe 35 are provided with control valves 37A and 37B, respectively. When connecting the first supply unit 14 or the gas supply unit 18 to the pipe to be cleaned 12, this control is performed. Valve 3
7A and 37B are controlled to cut off the supply of ultrapure water from the ultrapure water tank 30 to the pipe 12 to be cleaned. At this time, the control valve 37A switches the direction in which the ultrapure water is sent, returns the ultrapure water sent by the pump 34 to the ultrapure water tank 20 through the circulation pipe 35, and the control valve 37B sets the circulation pipe 3
Cut off 5. The operation of the control valves 37A and 37B is controlled by the control unit.

The gas supply unit 18 has a nitrogen gas cylinder 38 filled with nitrogen gas, and supplies the nitrogen gas injected from the nitrogen gas cylinder 38 into the pipe 12 to be cleaned through a supply pipe 40. The nitrogen gas supplied to the pipe to be cleaned 12 removes the ultrapure water remaining in the pipe, and the removed ultrapure water is discharged together with the nitrogen gas to the outside of the pipe through the discharge pipe 41 connected to the pipe to be cleaned 12. Is discharged. Also,
A filter 42 for supplementarily removing fine particles contained in the supplied nitrogen gas is installed in the middle of the supply pipe 40 to prevent fine particles in the gas from flowing into the pipe 12 to be cleaned. Further, the supply pipe 40 and the discharge pipe 41 are provided with control valves 43A and 43B, respectively, and when connecting the first supply unit 14 or the second supply unit 16 to the pipe to be cleaned 12, The control valves 43A and 43B are controlled to cut off the supply of nitrogen gas from the nitrogen gas cylinder 38 to the pipe 12 to be cleaned. The operation of the control valves 43A and 43B is controlled by the control unit.

Next, the pipe cleaning apparatus 1 constructed as described above.
0 is used to explain the tube cleaning method of the present invention. In this embodiment, as the pipe 12 to be cleaned, an electrolytic polishing pipe made of stainless steel and having a length of 4 m, which is often used in piping equipment requiring a high degree of cleaning, will be described. In advance, the hot ultrapure water producing device 20 of the first supply unit 14 and the cooling device 28 of the second supply unit 16 are activated to heat the ultrapure water to 80 ° C. in the first supply unit 14, In the supply unit 16, ultrapure water is cooled to 25 ° C. Along with this, the pumps 24 and 34 of both supply units 14 and 16 are driven to filter the ultrapure water in both supply units to the filters 26 and 3, respectively.
Circulate and filter at step 6. At this time, the control valves 27A, 3
7A is switched to the circulation pipes 25 and 35 side, and both control valves 27B and 37B are closed. On the other hand, in the gas supply unit 18, the nitrogen gas cylinder 38 is connected with the control valves 43A and 43B both closed, and the nitrogen gas is ejected when the control valves 43A and 43B are opened. Further, the electrolytic polishing tube 12 to be cleaned is connected to a predetermined position.

The cleaning of the electrolytic polishing tube 12 is performed according to the supply schedule shown in FIG. That is, the control unit (not shown) controls the operation of the control valve of each supply unit as follows. First, the control valve 27A is connected to the electrolytic polishing tube 12.
Switch to the side and open the control valve 27B,
Warm ultrapure water heated to 0 ° C. is passed through the electrolytic polishing tube 12 for 3 minutes to clean the inside of the tube. Warm ultrapure water to electrolytic polishing tube 12
After circulating for a minute, the control valve 27A is switched to the circulation pipe 25 side and the control valve 27B is closed to shut off the supply of hot ultrapure water.

Next, open the control valves 43A and 43B,
Nitrogen gas is injected into the electropolishing tube 12 for 10 seconds, and the hot ultrapure water remaining in the tube is discharged to the outside of the tube. After injecting nitrogen gas for 10 seconds, the control valves 43A and 43B are closed to interrupt the injection of nitrogen gas. Next, the control valve 37A is switched to the electropolishing tube 12 side, the control valve 37B is opened, and cold ultrapure water cooled to 25 ° C. is supplied to the electropolishing tube 12.
The inside of the tube is washed by circulating it for a minute. After the cold ultrapure water is passed through the electrolytic polishing tube 12 for 2 minutes, the control valve 37A is switched to the circulation pipe 35 side and the control valve 37B is closed to cut off the supply of the cold ultrapure water.

Open the control valves 43A and 43B again,
Nitrogen gas is injected into the electropolishing tube 12 for 10 seconds, and cold ultrapure water remaining in the tube is discharged to the outside of the tube. After injecting nitrogen gas for 10 seconds, the control valves 43A and 43B are closed to interrupt the injection of nitrogen gas. The above steps are repeated 3 times to complete the washing. According to this method, the ultrapure water having different temperatures is alternately passed through the electrolytic polishing tube 12, whereby the wall surface inside the tube and the dirt attached to the wall surface expand or contract. However, the wall surface inside the pipe and the dirt attached to the wall surface are
Since the expansion rate or contraction rate and the expansion rate or the contraction rate are different, a gap is created on the contact surface between the wall surface and the dirt adhering to the wall surface, and the cleaning liquid permeates into the space to remove the dirt from the wall surface. To be removed. Further, after cleaning, nitrogen gas is blown into the pipe to remove the cleaning liquid remaining in the pipe, so that the dirt dissolved or suspended in the residual cleaning liquid can be surely removed.

In order to investigate the cleaning effect of the electrolytic polishing tube 12 in this method, the number of particles remaining in the tube was measured as follows. A nitrogen gas cylinder 44 is connected to one end of the electropolishing tube 12 that has been cleaned, and nitrogen gas is injected into the electropolishing tube 12 through the filter 46 at 8 m / s. The particle concentration in the exhaust gas flowing out from the other end is measured by the air particle counter 48 for 10 minutes.

In order to compare the cleaning effects, the electrolytically polished tubes 12 and 2 which were cleaned by continuously circulating ultrapure water heated to 80 ° C. for 20 minutes (the same time as the total water-flowing time in the above method) were cleaned.
The number of particles remaining in the electropolished tube 12 washed with continuous flow of ultrapure water cooled to 5 ° C. for 20 minutes was also measured by the same method. Table 1 shows the particle removal rate by each cleaning method from each measurement result.

[0017] As can be seen from Table 1, the tube cleaning method of this example is more effective in removing particles than the conventional cleaning method using ultrapure water at a constant temperature.

As described above, according to the pipe cleaning method of the present embodiment, particles which could not be removed by the conventional method can be removed, and the number of particles remaining in the pipe after cleaning can be reduced.
In the present embodiment, the temperature of the ultrapure water flowing through the electropolishing tube 12 was 80 ° C. and 25 ° C. However, the combination of the temperatures of the ultrapure water flowing is not limited to this, and the temperature Should be different. At this time, the larger the temperature difference, the better.

Further, in this embodiment, one step of washing was repeated four times, but the number of times of repeating is not limited to this, and may be five times, for example. Further, in this embodiment,
Nitrogen gas was injected and removed to remove ultrapure water from the electrolytic polishing tube 12, but the gas for removing ultrapure water is not limited to this, and any gas with a low risk may be used. It may be air, for example.

[0020]

As described above, according to the pipe cleaning method of the present invention, the expansion rate or contraction rate of the wall surface in the tube and the dirt adhering to the wall surface of the tube is caused by alternately flowing the cleaning liquids having different temperatures. Since the stain on the wall surface is peeled off and removed by utilizing the difference of the above, it is possible to surely and easily remove the stain.

As a result, it becomes possible to remove stains that could not be removed by the conventional pipe cleaning method, so that the pipe cleaning effect can be improved. Therefore, the pipe cleaning method of the present invention is extremely effective, for example, for cleaning pipes of liquids and gases used in semiconductor manufacturing, where a small amount of dust is disliked.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a pipe cleaning apparatus to which a pipe cleaning method according to the present invention is applied.

[Fig. 2] Operation schedule of pipe cleaning device

FIG. 3 is a schematic diagram of an apparatus used to measure the number of particles remaining on the inner surface of the pipe after cleaning.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Pipe cleaning device 12 ... Pipe to be cleaned (electrolytic polishing pipe) 14 ... First supply unit 16 ... Second supply unit 18 ... Gas supply unit 20 ... Warm ultrapure water production device 30 ... Ultrapure water tank 38 ... Nitrogen gas cylinder

Claims (1)

[Claims] 1. A pipe cleaning method for flowing a cleaning liquid into a pipe to remove dirt adhering to a wall surface of the pipe, wherein a cleaning liquid having a predetermined temperature is flowed into the pipe for a predetermined time to clean the inside of the pipe. A cleaning step, a second cleaning step of cleaning the inside of the tube by flowing a cleaning solution having a temperature different from that of the predetermined temperature into the tube for a predetermined time, and after at least one of the first and second cleaning steps A pipe cleaning method comprising repeating a cleaning operation at least once, which comprises a step of blowing a gas into the pipe and discharging a cleaning liquid remaining in the pipe to the outside of the pipe.