JP2014101241A - System and method for feeding purified carbon dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for solving problems of the generation of impurities such as particles and occurrences of wafer damages as a result of the transformation of a high-pressure liquid or supercritical COpumped into a chamber into states of a COgas and dry ice within a pipeline connected to the chamber or within the chamber.SOLUTION: The provided system for feeding purified carbon dioxide comprises: a wafer washing chamber (user point 30); and a carbon dioxide feeder for purifying and feeding carbon dioxide abiding in a liquid or supercritical state into the chamber (circulatory system 10). This feeding system, furthermore, possesses a pipeline 25 for feeding, from the carbon dioxide feeder into the chamber, carbon dioxide abiding in the liquid or supercritical state and additionally possesses gas introduction means (pipeline 26, COgas source 27, and on-off valve 28) for introducing, into at least either of the pipeline 25 and the chamber, a compressed gas such as a carbon dioxide gas, etc. so as to at least partially increase the pressure within the pipeline 25 or within the chamber.

Description

  The present invention relates to a purified carbon dioxide supply system and method for supplying purified carbon dioxide in a liquid or supercritical state into a chamber that can be sealed and opened.

Carbon dioxide (CO ₂ ) is used in various states in a gaseous state, and is used in a liquid state or a supercritical state, for example, in a process such as cleaning or drying. In recent years, the use of liquid CO ₂ or supercritical CO ₂ has also been proposed in a cleaning process in the manufacture of semiconductor devices. When liquid CO ₂ or supercritical CO ₂ is used in the manufacture of semiconductor devices or the like, it is necessary to supply liquid CO ₂ or supercritical CO ₂ purified to a high purity with a very small amount of impurities.

Incidentally, as one of apparatuses for stably supplying high-purity liquid CO ₂ to a use point (for example, a cleaning chamber), there is a circulation purification type carbon dioxide purification supply system as shown in Patent Document 1. Circular purified form carbon dioxide purification supply systems, the liquid CO ₂ is vaporized by a CO ₂ gas using a circulation system for the liquid CO ₂ again by condensing the CO ₂ gas, a CO ₂ in the circulation system The purity of CO ₂ is increased by circulating and repeating vaporization and condensation. FIG. 4 shows a conventional example of the configuration of a circulation purification type carbon dioxide purification supply system based on the technique described in Patent Document 1.

The carbon dioxide purification supply system shown in FIG. 4, a storage tank 11 for storing the liquid CO ₂ of high purity temporarily, a pump 12 for pumping liquid CO ₂ is provided at the outlet of the reservoir 11, provided at the outlet of the pump 12 The filter 13 is provided.

A part of the liquid CO ₂ flowing out from the filter 13 is branched and supplied to a use point 30 (for example, a cleaning chamber in which a semiconductor wafer is cleaned). The pipe from the filter 13 to the use point 30 is provided with an on-off valve 23 for opening and closing the pipe and a pressure gauge 24 for measuring the pressure of the liquid CO ² supplied to the use point 30 through the pipe. Yes.

On the other hand, the remaining liquid CO ₂ flowing out of the filter 13 is sent to the cooler 15 via the pressure regulating valve 14. The pressure regulating valve 14 is provided to make the pressure of the liquid CO ₂ supplied to the use point 30 a prescribed pressure. The liquid CO ₂ supplied and cooled to the cooler 15 is then supplied to the evaporator 16 for gas-liquid separation. A heater is incorporated in the evaporator 16 so that a CO ₂ gas-liquid interface is formed in the evaporator 16.

The liquid CO ₂ supplied to the evaporator 16 is vaporized, and the hardly volatile particles (fine particles) remain on the liquid phase side. Then, the CO ₂ gas purified by being vaporized in the evaporator 16 is sent from the vapor phase side outlet of the evaporator 16 to the condenser 18 through the filter 17 for further removing particles, and the condenser It is liquefied again by being cooled in 18 and returned to the storage tank 11 as liquid CO ₂ . In this configuration, the storage tank 11, the pump 12, the filter 13, the pressure regulating valve 14, the cooler 15, the evaporator 16, the filter 17, and the condenser 18 constitute a CO ₂ circulation system 10 (carbon dioxide supply device). The CO _{2 that} has not been used at the use point 30 is circulated.

  The particles transferred to the liquid phase in the evaporator 16 are discharged (blowed) out of the system by opening a valve 19 provided at the liquid phase outlet of the evaporator 16. Since the pump 12 may generate dust, the filter 13 removes particles generated by the pump 12.

In order to supply CO ₂ (liquefied carbon dioxide gas) to such a circulation system 10, a CO ₂ source 20 such as a gas cylinder or a cold evaporator (CE) is provided, and the CO ₂ from the CO ₂ source 20 is supplied. It is designed to be purified by the circulation system 10.

The circulation purification type carbon dioxide purification supply system is effective in removing non-volatile particles such as metal particles from CO ₂ , and has high purity required in the recent ultra-miniaturized semiconductor device manufacturing process. Of CO ₂ can be continuously supplied.

In the system shown in FIG. 4, the liquid CO ₂ purified by the circulation system 10 is pumped toward the use point 30 by the pump 12, and the liquid CO ₂ pressurized by the pump 12 is supercritical by heating of the heater 22. It is made CO ₂ and goes out of the system. However, the heater does not necessarily need to be installed, and a heater that heats the high-pressure liquid CO ₂ to a supercritical state may be installed at a use point 30 outside the system (immediately before supplying CO ₂ to the chamber). Good.

JP 2006-326429 A JP2003-206497 JP 2011-192835 A

As described above, CO ₂ is supplied from the carbon dioxide supply device to the wafer cleaning chamber in a high-pressure liquid or supercritical state.

Here, since the chamber is opened when the wafer is set in the wafer cleaning chamber, the pressure in the chamber drops to atmospheric pressure immediately after the setting. For this reason, at the initial stage of supplying the high-pressure liquid or supercritical CO ₂ into the chamber through the pipe from the carbon dioxide supply device, the high-pressure liquid or supercritical CO ₂ is once depressurized in the pipe connected to the chamber, and CO _2. The gas and dry ice are supplied to the chamber. The dry ice generated at this time may block the piping and the filter. Further, the dry ice may collide with piping, a filter, a chamber, a wafer or the like, thereby generating impurities such as particles or causing damage to the wafer.

Further, when supplying CO ₂ to the chamber, it is desirable to supply at a low flow rate as much as possible from the viewpoint of damage to the wafer. When CO ₂ is supplied in a high-pressure liquid or supercritical state, for the above-described reason, the initial supply stage is that the high-pressure liquid or supercritical CO ₂ is depressurized and a part of the CO ₂ is gasified. Since it is supplied, it is difficult to supply at a low flow rate.

In Patent Documents 2 and 3, CO ₂ gas is pressurized and supplied into a closed chamber, and the temperature in the chamber is raised, whereby the CO ₂ gas supplied into the chamber is converted into supercritical CO _2. Is disclosed. However, in the invention disclosed in these documents, a high-pressure liquid or supercritical CO ₂ is supplied into a chamber under atmospheric pressure or passes through a pipe connected to the chamber under atmospheric pressure as described above. It does not recognize the problem by. On the other hand, according to the present invention, the high-pressure liquid or supercritical CO ₂ pumped into the chamber changes into a state of CO ₂ gas and dry ice in the pipe connected to the chamber or in the chamber. Therefore, an object of the present invention is to provide a method for solving the problems of generation of impurities such as particles and damage to the wafer.

  One embodiment of the present invention is a purified carbon dioxide that includes a use point (for example, in a wafer cleaning / drying chamber) and a carbon dioxide supply device that purifies carbon dioxide and supplies the carbon dioxide to the use point in a liquid or supercritical state. This relates to the supply system. This supply system has, as the carbon dioxide supply means, a supply pipe for supplying the liquid or supercritical carbon dioxide from the carbon dioxide supply device into the wafer cleaning / drying chamber at the use point. Further, the present invention further comprises gas introducing means for introducing a pressurized gas (for example, carbon dioxide gas) into at least a part of the carbon dioxide supply means to increase the pressure of at least a part of the carbon dioxide supply means. This is a feature of the embodiment.

  Another aspect of the present invention relates to a method of supplying purified carbon dioxide that supplies purified carbon dioxide in a liquid or supercritical state to a chamber. In the supply method according to the present invention, when an object for carbon dioxide cleaning is put into the chamber, first, the inside of the chamber and the inside of the supply pipe for supplying the liquid or supercritical carbon dioxide to the chamber And a pressure gas (for example, carbon dioxide gas) is introduced into the space including at least the pressure in the supply pipe and the chamber, and then the introduction of the pressurized gas is stopped and the supply is performed. The liquid or supercritical carbon dioxide is supplied to the chamber through a pipe.

  As described above, according to the present invention, the pressure in the chamber and the supply pipe for supplying high-pressure liquid or supercritical carbon dioxide to the chamber is applied to a predetermined pressure, that is, to the chamber and the supply pipe. After the pressure gas (for example, carbon dioxide gas) is introduced to raise the pressure (0.518 MPa) at which dry ice is not generated (or hardly generated), the liquid or supercritical carbon dioxide is supplied to the chamber via the supply pipe. It is characterized by supplying.

  Therefore, according to the present invention, it is possible to suppress the generation of impurities such as particles during the supply of carbon dioxide and damage to the wafer. Further, since the supply flow rate of carbon dioxide at the initial supply stage can be reduced, damage to the wafer can be minimized.

1 is a block diagram showing a configuration of a circulation purification type carbon dioxide purification supply system according to a first embodiment of the present invention. The enthalpy diagram of CO ₂ gas. The block diagram which shows the structure of the circulation purification type carbon dioxide refinement | purification supply system by the 2nd Embodiment of this invention. The block diagram which shows the prior art example of a structure of the circulation purification type carbon dioxide refinement | purification supply system based on the technique described in patent document 1. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments will be described in comparison with the prior art (system of FIG. 4). FIG. 1 is a block diagram showing the configuration of a circulation purification type carbon dioxide purification supply system according to the first embodiment of the present invention, and FIG. 2 is an enthalpy diagram of CO ₂ gas.

First, the state characteristics of CO ₂ gas will be described.

As shown in FIG. 2, when carbon dioxide is 0.518 MPa or less, it cannot exist as a liquid and is in a gas or solid (dry ice) state. Considering the adiabatic change here, when CO ₂ in the pressurized gas state is depressurized, most of it remains in the gas state and almost no dry ice is generated, whereas the CO ₂ in the liquid state is depressurized to 0.5 MPa or less. Then at least 20% or more changes to dry ice.

  Next, a circulation system for carbon dioxide purification provided in the carbon dioxide purification supply system of this embodiment will be described. The circulation system 10 (carbon dioxide supply device) of this embodiment is common to the conventional system shown in FIG.

In a state (standby state) where CO ₂ is not supplied to the use point 30 (in the wafer cleaning / drying chamber in this example), the liquid CO ₂ in the storage tank 11 is pressurized by the pump 12 and then the pressure is adjusted. The pressure is reduced by the valve 14 and circulates along a path that returns to the storage tank 11 again through the evaporator 16, the filter 17, and the like. The circulation system 10 may use a heat exchanger instead of the cooler 15 and the evaporator 16. The wafer cleaning / drying chamber may be any one that performs cleaning and / or drying of the wafer. Although the heater 22 is shown in FIG. 1, the heater is not necessarily installed, and the heater for heating the high-pressure liquid CO ₂ to a supercritical state is a use point 30 outside the system or its use point 30. It may be installed immediately before.

When CO ₂ is needed at the use point 30, the on-off valve 23 is opened to supply a part of the circulating CO ₂ to the use point 30, but the residual that was not pumped to the use point 30 Since CO ₂ continues to circulate in the circulation system 10, the pressure in the system does not change.

Here, a conventional CO ₂ supply process will be described in detail for comparison with the present invention.

Referring to FIG. 4, first, the on-off valve 23 is opened, and the high-pressure liquid or supercritical CO ₂ purified by the circulation system 10 is supplied to the use point 30 (inside the wafer cleaning / drying chamber). (Step 1). This liquid or supercritical CO ₂ is used for cleaning and drying the wafer in the chamber. When the supply of CO ₂ is completed, the on-off valve 23 is closed (step 2). Then, the inside of the chamber and the piping from the chamber to the on-off valve 23 are opened to the atmosphere by the blow valve of the chamber (step 3). As a result, the pressure in the chamber returns to normal pressure. Next, the chamber is opened and the wafer is taken out from the chamber (step 4). Then, a new wafer is put into the chamber, and the chamber is closed (step 5). After step 5, the process returns to step 1.

  There are concerns about the following problems 1 and 2 in such a conventional method.

Problem 1: In steps 1 to 5 before step 1 is performed, the pressure inside the chamber and the piping from the chamber to the on-off valve 23 is atmospheric pressure. By opening the on-off valve 23 in step 1 from this state, purified high-pressure liquid or supercritical CO ₂ is supplied to the chamber, but the moment the on-off valve 23 is opened is supplied to the chamber. The liquid or supercritical CO ₂ is reduced to near atmospheric pressure due to pressure loss due to the on-off valve 23 and piping from the on-off valve to the chamber. Thereafter, as the CO ₂ is supplied, the pressure in the chamber increases, so the pressure reduction width of the CO ₂ decreases, and the on-off valve 23 is closed when the pressure in the chamber increases to a predetermined pressure. (Step 2).

The CO ₂ circulates in a liquid state and is supplied to the chamber in a liquid state. As described above, immediately after the opening / closing valve 23 is opened, the liquid CO ₂ is depressurized to near atmospheric pressure. In this case, the characteristics of the CO ₂ as described above (see FIG. 2) CO ₂ changes into a gas and a more than 20% of the dry ice. The dry ice generated at this time may clog the pipe, and if the filter is installed in the pipe, it may also clog the pipe, the filter, the inner wall of the chamber, a wafer, etc. This may cause the generation of impurities and damage to the wafer.

Problem 2: As described in Problem 1, at the moment when the on-off valve 23 is opened, the liquid or supercritical CO ₂ supplied to the chamber causes a pressure loss due to the on-off valve 23 and piping from the on-off valve to the chamber. The pressure is reduced to near atmospheric pressure. At this time, the flow rate of CO ₂ supplied to the chamber becomes faster as the pressure reduction width of the CO ₂ is larger, or as the pressure loss due to the on-off valve and the piping is smaller.

On the other hand, when the influence on the wafer in the chamber is considered, if the CO ₂ supply flow rate is increased, damage due to physical impact on the wafer is considered. Therefore, in terms of damage to the wafer, the CO ₂ supply rate Slower is preferable. In order to slow down the supply flow rate of CO ₂ , there is a method of reducing the pressure reduction width or increasing the pressure loss. Since the pressure reduction width is determined when the on-off valve 23 is open, the supply flow rate of CO ₂ is adjusted by adjusting the opening of the on-off valve 23 or adjusting the opening by newly providing another valve in the pipe. It is common to do.

Here, the liquid CO ₂ supplied in the initial stage is depressurized at the opening / closing valve 23 or the outlet of the other valve to become CO ₂ gas, so that the flow rate rapidly increases. Since the flow rate of the liquid CO ₂ is adjusted by adjusting the opening of the on-off valve 23 or the other valve, the gas flow rate is controlled by adjusting the liquid flow rate, and severe adjustment is difficult.

  An embodiment of the present invention that addresses such problems will be exemplified below.

(Embodiment 1)
As shown in FIG. 1, in this embodiment, a gas introduction means for introducing CO ₂ gas into a pipe 25 from the on-off valve 23 to the use point 30 (in the wafer cleaning chamber in this example) is provided. This gas introduction means is installed in another pipe 26 connected to the pipe 25, a CO ₂ gas source 27 connected to the upstream end of the pipe 26, and a pipe 26 connecting the CO ₂ gas source 27 to the pipe 25. And an open / close valve 28.

The gas introducing means may be connected directly to the wafer cleaning / drying chamber or to a pipe connected to the chamber. As the CO ₂ gas source 27, a gas cylinder, a cold evaporator (CE), or the like can be used. However, the present invention is not limited to this, and any suitable CO ₂ gas supply source may be used. Considering the contamination of the chamber, CO ₂ gas to be introduced may have who are purified, preferably equal or better cleanliness and CO ₂ in the CO ₂ source 20, CO more preferably storage tank 11 A cleanliness level equal to or higher than ₂ is sufficient. On the other hand, a method of providing a filter in the pipe 26 is also preferable.

In this example, CO ₂ gas is used, but the same effect can be expected even if an inert gas is supplied under pressure. Even in such a case, the cleanliness level is preferably equal to or higher than that of CO ₂ in the CO ₂ source 20, and more preferably equal to or higher than that of CO ₂ in the storage tank 11.

The CO ₂ supply process of this embodiment will be described with reference to FIG. 1. When CO ₂ is required at the use point 30, first, the open / close valve 28 is opened while the open / close valve 23 is closed, and the purified CO 2 is opened. ₂ Purified CO ₂ gas from the gas source 27 is supplied to the use point 30 (in the wafer cleaning / drying chamber) (step 21). As the CO ₂ gas is supplied, the pressure in the chamber rises from the atmospheric pressure, and the on-off valve 28 is closed when the pressure in the chamber rises to a predetermined pressure (step 22). Whether or not the pressure in the chamber has become equal to or higher than a predetermined pressure is determined by the pressure gauge 24 of the pipe 25.

Thereafter, the on-off valve 23 is opened, and the high-pressure liquid or supercritical CO ₂ purified by the circulation system 10 is supplied to the use point 30 (in the wafer cleaning / drying chamber) (step 1 of the prior art described above). . Thereafter, the above-described steps 2 to 4 of the prior art are performed to clean and dry the wafer and take out the wafer from the chamber. In order to perform the CO ₂ supply step, the present embodiment includes a control device that controls the on-off valves 23 and 28.

In step 22, it is desirable to increase the pressure in the chamber to a pressure of 0.518 MPa for suppressing dry ice, and then supply liquid or supercritical CO ₂ to the chamber. Furthermore, in order to suppress a physical impact on the wafer, it is more desirable if the pressure is higher than the pressure in the storage tank 11. The same applies when an inert gas is used.

  In this example, the pressure in both the chamber and the pipe 25 is increased by the step 22 described above, but either one or only a part of them may be increased. Alternatively, the pressure may be increased stepwise, such as first increasing the pressure of a part of the chamber and the pipe 25 and then increasing another part of the pressure.

  According to the method described above, the following effects 1 and 2 can be obtained.

Effect 1: In the stage before performing the above-described step 21, the pressure in the chamber in which a new wafer is set and in the pipe connected to the chamber is atmospheric pressure. However, since the CO ₂ supplied in the step 21 is not a liquid but a gas, almost no dry ice is generated. Thereafter, in step 22, it is confirmed that the pressure gauge of the pipe 25 connected to the chamber has reached 0.5 MPa, and a high-pressure liquid or supercritical CO ₂ is supplied into the chamber through the pipe 25. At this time, the pressure in the pipe 25 and in the chamber connected to the pipe 25 is 0.5 MPa or more, and the generation of dry ice due to the reduced pressure does not occur. Therefore, the problem 1 caused by it can be suppressed.

Effect 2: As described above, in the stage before the step 21 is performed, the pressure in the chamber and the pipe connected to the chamber is atmospheric pressure. At this stage, the CO ₂ pressure reduction range is the largest, so that it is difficult to adjust the flow rate. However, since CO ₂ gas is introduced into the pipe 25 and the chamber under atmospheric pressure at this stage, the flow rate can be adjusted more severely than in the case of introducing liquid CO ₂ . Then, the introduction of CO ₂ gas after increasing the pressure in the chamber above 0.5 MPa, since supplying the high-pressure liquid or supercritical CO ₂ to said chamber through the pipe 25, CO ₂ pressure decrease at this time Is not so difficult to adjust the flow rate. Therefore, since the CO ₂ supply flow rate to the wafer can be adjusted slowly, damage to the wafer can be minimized.

  The present invention is preferably a circulation purification type like the carbon dioxide purification supply system, but is not limited thereto.

(Embodiment 2)
FIG. 3 is a block diagram showing a configuration of a circulation purification type carbon dioxide purification supply system according to the second embodiment of the present invention. In this figure, the same components as those of the first embodiment shown in FIG. This embodiment is different from the first embodiment, the purified CO ₂ gas introducing means for introducing CO ₂ gas which has been purified to the pipe 25 only are different, and other configurations are the same. Although the heater 22 is shown in FIG. 3, the heater is not necessarily installed, and the heater for heating the high-pressure liquid CO2 to the supercritical state is the use point 30 outside the system or immediately before it. It may be installed in.

  Regarding the configuration of the gas introducing means of this embodiment, as shown in FIG. 3, one end (downstream end) of another pipe 26 is connected to the pipe 25, and the other end (upstream end) of the pipe 26 is connected to the storage tank 11. An on-off valve 28 is installed in a portion of the pipe 26 that is connected to the upper space in the storage tank and is in the vicinity of the pipe 25. The gas introducing means may be connected directly to the wafer cleaning / drying chamber or to a pipe connected to the chamber. On the other hand, a method of providing a filter in the pipe 26 is also preferable.

The CO ₂ supply process of the present embodiment will be described based on FIG. 3. When CO ₂ is required at the use point 30, first, the open / close valve 28 is opened while the open / close valve 23 is closed, and the storage tank 11 is opened. The purified CO ₂ gas staying in the upper space is supplied to the use point 30 (in the wafer cleaning / drying chamber) (step 31). As the CO ₂ gas is supplied, the pressure in the chamber rises from the atmospheric pressure, and the on-off valve 28 is closed when the pressure in the chamber rises to a predetermined pressure (step 32). Whether or not the pressure in the chamber has become equal to or higher than a predetermined pressure is determined by the pressure gauge 24 of the pipe 25.

Thereafter, the on-off valve 23 is opened, and the high-pressure liquid or supercritical CO ₂ purified by the circulation system 10 is supplied to the use point 30 (in the wafer cleaning / drying chamber) (step 1 of the prior art described above). . Thereafter, the above-described steps 2 to 4 of the prior art are performed to clean and dry the wafer and take out the wafer from the chamber. In order to perform the CO ₂ supply step, the present embodiment includes a control device that controls the on-off valves 23 and 28.

In step 32, it is desirable to increase the pressure in the chamber to a pressure of 0.518 MPa for suppressing dry ice, and then supply liquid or supercritical CO ₂ to the chamber. Furthermore, in order to suppress a physical impact on the wafer, it is more desirable if the pressure is higher than the pressure in the storage tank 11.

  In this example, the pressure in both the chamber and the pipe 25 is increased by the step 32 described above, but only one or a part of them may be increased. Alternatively, the pressure may be increased stepwise, such as first increasing the pressure of a part of the chamber and the pipe 25 and then increasing another part of the pressure.

The same effects 1 and 2 as in the first embodiment described above can also be obtained by the method of this embodiment. In the present embodiment, on the CO ₂ gas source such as a gas cylinder or a cold evaporator (CE) is not required, to supply the CO ₂ equivalent purity CO ₂ finally the reservoir 11 to be supplied Can do.

  As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and the present invention is implemented by changing the shape, material, and the like without departing from the technical idea thereof. It goes without saying that it is possible.

In each of the above-described embodiments, the pipe 25 is supplied with a high-pressure liquid or supercritical CO ₂ from the circulation system 10 (carbon dioxide supply device) to the use point 30 (within the wafer cleaning / drying chamber). A configuration for introducing CO ₂ gas was shown. However, the present invention is not limited to this configuration, and may be a configuration in which CO ₂ gas is introduced into the wafer cleaning / drying chamber itself or a pipe directly communicating with the inside of the wafer cleaning / drying chamber. That is, in a stage before high-pressure liquid or supercritical CO ₂ is supplied to the wafer cleaning / drying chamber, CO ₂ is introduced into the space including the inside of the chamber and the inside of the pipe directly communicating with the chamber. ₂ Any gas can be used as long as the pressure in the chamber and the pipe directly communicating with the chamber can be set to a pressure at which the liquid CO ₂ does not become gas or dry ice or is difficult to become. It may be a configuration.

10 circulation system 11 the storage tank 12 pump 13, 17 filter 14 pressure regulating valve 15 condenser 16 evaporator 18 condenser 19 blow valve 20 CO ₂ source (for example liquefied carbon dioxide cylinder)
22 Heater 23, 28 On-off valve 24 Pressure gauge 25, 26 Pipe 27 CO ₂ gas source 30 Use point (for example, in wafer cleaning chamber)

Claims (8)

A purified carbon dioxide supply system comprising carbon dioxide purification means for purifying carbon dioxide into a liquid or supercritical state, and carbon dioxide supply means for supplying the liquid or supercritical carbon dioxide to a use point. ,
A purified carbon dioxide supply system, further comprising gas introduction means for introducing a pressurized gas into at least a part of the carbon dioxide supply means.   The purified carbon dioxide supply system according to claim 1, wherein the pressurized gas is carbon dioxide gas.   The purified carbon dioxide supply system according to claim 2, wherein the gas introduction means introduces the carbon dioxide gas so that an internal pressure of at least a part of the carbon dioxide supply means is 0.5 MPa or more. . The carbon dioxide supply means has a purified carbon dioxide supply pipe for connecting the inside of the use point wafer cleaning / drying chamber and the carbon dioxide purification means,
4. The purified carbon dioxide supply system according to claim 1, wherein the gas introduction unit introduces a pressurized gas into at least one of the chamber and the supply pipe. 5. A first on-off valve installed in the supply pipe;
The gas introduction means including a carbon dioxide gas introduction pipe connected to the supply pipe on the downstream side of the first on-off valve and a second on-off valve installed in the carbon dioxide gas introduction pipe;
A control device for controlling the first and second on-off valves,
When the wafer to be cleaned or dried is put into the chamber, the control device first opens the second on-off valve with the first on-off valve closed, and pressurizes the supply pipe. When carbon dioxide gas is introduced as a gas, and the pressure in the supply pipe reaches 0.5 MPa or more, the second on-off valve is closed, the first on-off valve is opened, and the carbon dioxide 5. The purified carbon dioxide supply system according to claim 4, wherein the liquid or supercritical carbon dioxide is supplied from a purification means to the chamber through the supply pipe. The carbon dioxide purification means includes an evaporator that vaporizes liquid carbon dioxide, a condenser that is provided downstream of the evaporator and that liquefies carbon dioxide in a gaseous state, and is provided downstream of the condenser. And a storage tank for storing the liquefied carbon dioxide,
6. The purified carbon dioxide supply system according to claim 1, wherein the gas introduction means introduces carbon dioxide gas existing in a gas phase in the storage tank. In a method for supplying purified carbon dioxide, which supplies purified carbon dioxide in a liquid or supercritical state to a chamber,
When an object for carbon dioxide cleaning or drying is put into the chamber, first, a space including at least the inside of the chamber and the inside of a supply pipe for supplying the liquid or supercritical carbon dioxide to the chamber The pressurized gas is introduced to increase the pressure in the supply pipe and the chamber, and then the introduction of the pressurized gas is stopped, and the liquid or supercritical state is introduced into the chamber via the supply pipe. A method for supplying purified carbon dioxide, comprising supplying carbon dioxide.   When the pressure in the supply pipe and the chamber reaches 0.5 MPa or more due to the introduction of carbon dioxide gas as the introduction of the pressurized gas, the introduction of the carbon dioxide gas is stopped, and the pressure is reduced via the supply pipe. The method for supplying purified carbon dioxide according to claim 7, wherein the liquid or supercritical carbon dioxide is supplied to a chamber.

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