JP2008505297A - Method and system for supplying carbon dioxide - Google Patents

Abstract

  Novel methods and systems are provided for supplying high pressure carbon dioxide to applications requiring various carbon dioxide flow rates. The method includes supplying a high pressure carbon dioxide feed stream to the buffer volume (80) and determining the amount of carbon dioxide delivered to the application tool (100). The pressure in the buffer volume (80) is maintained at a pressure that exceeds the pressure required by the application tool (100). Further, the temperature in the buffer volume (80) is adjusted to change the density of carbon dioxide, and the size of the buffer volume (80) is corrected based on the change. Carbon dioxide is then pumped out of the buffer volume (80) at various flow rates required by the application tool (100).

Description

  The present invention relates to a method for supplying high pressure carbon dioxide to applications requiring various carbon dioxide flow conditions. Specifically, the present invention relates to supplying carbon dioxide to semiconductor application tools that have instantaneous demands that are significantly higher than average demands.

  The need for instantaneous delivery of fluid has been known for a long time. High pressure gas sources have been utilized in related applications requiring instantaneous demands on the fluid. For example, Knight et al., U.S. Pat. No. 4,977,921, uses a tube trailer modified to store high pressure air or nitrogen to flow gas very instantaneously and clean large lines. Arguing. Beard US Pat. No. 5,417,615 relates to the use of a pressurized gas source for storing high pressure air used to propel amusement park rides.

  Bishop US Pat. No. 6,725,671 discloses the effect of temperature and pressure on the capacity of a natural gas storage system. The temperature and pressure, as well as the wall thickness of the storage container, are selected to minimize the cost of storing natural gas.

  There was a need in the semiconductor industry to provide highly demanded fluids for applications such as cleaning tools. In this regard, Baton US Pat. No. 6,085,762 and Davenhall et al. US Pat. No. 6,403,544 B1 provide a buffer volume for supplying supercritical fluids to semiconductor wafer processing applications. Alternatively, the use of a ballast tank is disclosed. The method includes sending a supercritical fluid pressure pulse to the application.

  Costantini et al., US Pat. No. 6,612,317 B2, discloses the use of a buffer volume or ballast tank to provide supercritical fluid for semiconductor wafer processing applications. Changing the pressure of the fluid in the buffer volume has been disclosed as a means of controlling the fluid sent to the application tool and has been shown to rapidly release the fluid in the buffer volume into the wafer processing chamber. As used throughout this specification and claims, it is understood that the term “buffer volume” refers to a pressurized vessel, such as a ballast tank, that is utilized to deliver fluid to a semiconductor application. Let's go.

  One drawback associated with related art systems is that they are not aware of selecting the temperature of the buffer volume as an important factor in controlling the amount of carbon dioxide that is useful for delivery to semiconductor application tools. Another drawback is that the related art does not provide a means to control the release of pressure in the buffer vessel.

  To overcome these shortcomings, one of the objectives of the present invention is to provide a means of controlling the amount of carbon dioxide that is useful for delivery to an application within the time of a high instantaneous demand.

  Another object of the present invention is to adjust the capacity of the buffer volume without changing the physical dimensions of the buffer volume.

  A further object of the present invention is to size the buffer volume by manipulating the carbon dioxide temperature once the maximum amount of carbon dioxide delivered to the semiconductor application tool has been identified.

  Another object of the present invention is to replace the expensive and excessive pumps required to deliver high flow rates to semiconductor cleaning tools.

  A further object of the present invention is to instantaneously deliver the required carbon dioxide flow rate, thus eliminating the delay required when utilizing a pump to provide the required flow rate.

  Other objects and advantages of the present invention will become apparent to those skilled in the art upon review of the specification, drawings, and appended claims.

  The above objective is accomplished by the method of the present invention.

  According to one aspect of the present invention, a method is provided for supplying high pressure carbon dioxide to an application tool that requires a variety of carbon dioxide flow conditions. The method involves supplying a high pressure carbon dioxide feed stream to the buffer volume, the pressure of the buffer volume to a minimum pressure that exceeds the pressure required by the application tool, and the carbon dioxide stored in the buffer volume at the minimum pressure. Maintaining an average density between the maximum pressure such that the maximum density differs from the average density of carbon dioxide stored in the buffer volume.

  Adjust the average temperature of the buffer volume so that the flow conditions related to the application tool are met, the average density of carbon dioxide stored in the buffer volume at the minimum pressure and carbon dioxide stored in the buffer volume at the maximum pressure Correct the difference between the average density of. The high pressure carbon dioxide feed stream is pumped out of the buffer volume at various flow rates as required by the application tool.

  In accordance with another aspect of the present invention, a system is provided for supplying high pressure carbon dioxide to applications requiring various carbon dioxide flow conditions. The system includes a buffer volume that accepts a high pressure carbon dioxide feed stream, where the pressure in the buffer volume is the minimum pressure above the pressure required by the application tool and the density of carbon dioxide at the minimum pressure. Maintained between a maximum pressure, such as different from the density of carbon dioxide at the maximum pressure, and the temperature in the buffer volume is adjusted.

  A carbon dioxide purification unit is placed upstream of the buffer volume that delivers a high pressure carbon dioxide feed stream, and the application tool receives carbon dioxide from the buffer volume at various flow rates as required by the application tool. It is arranged downstream.

  The invention can be better understood with reference to the following drawings. In the drawings, the same numerals indicate the same functions throughout.

  FIG. 1 represents a schematic diagram of an overall system for delivering carbon dioxide to a semiconductor application tool that requires various flow conditions.

  FIG. 2 illustrates an exemplary 5-minute operating cycle for delivering carbon dioxide in accordance with the present invention.

  FIG. 3 illustrates a schematic diagram of the overall system with a single core heat exchanger.

  FIG. 4 illustrates a schematic diagram of the overall system according to another embodiment in which the apparatus upstream of the pressurizing means is modified.

  FIG. 5 illustrates a schematic diagram of the overall system according to another embodiment with a single core heat exchanger located upstream of the pressurizing means.

  FIG. 6 illustrates a schematic diagram of the overall system according to another embodiment in which recirculation is redesigned.

  The manufacture of integrated circuit devices requires many complex steps that are necessary to form various functions on a wafer substrate. Some of the steps include cleaning the substrate with high pressure carbon dioxide. As used herein, the term “high pressure carbon dioxide” refers to carbon dioxide at a pressure above 1,060 psig, which is the critical pressure of carbon dioxide. If the temperature associated with carbon dioxide is below its critical temperature of 88 ° F. and high pressure, it will be seen that the fluid is in the liquid phase. On the other hand, if the temperature associated with carbon dioxide exceeds 88 ° F., the fluid will be in a supercritical phase. Therefore, at pressures above 1,060 psig, carbon dioxide is only one phase, and carbon dioxide is liquid or supercritical (ie, non-discontinuous phase transition).

  The semiconductor cleaning method of the present invention exhibits very high instantaneous demands on high pressure carbon dioxide, but for semiconductor cleaning applications that exhibit a fairly low average demand for high pressure carbon dioxide in a given operating cycle. Provides an effective means of supplying Typically, wafer cleaning applications process one wafer per cycle, where the carbon dioxide requirement varies from a very high amount to substantially zero.

  As illustrated in FIG. 1, the delivery system includes a carbon dioxide bulk tank 10 for holding carbon dioxide delivered to the semiconductor application tool 100. Carbon dioxide from the bulk tank 10 passes through the heat exchangers 29 and 30 and moves to the carbon dioxide purification apparatus 40. This will be described in detail below with reference to special embodiments. A high pressure carbon dioxide stream 75 is generated and delivered to the buffer volume tank / vessel 80. This is used to meet the tool's instantaneous demand for high pressure carbon dioxide.

To illustrate, the application tool 100 requires a maximum instantaneous flow rate of carbon dioxide (S _max ) at some set pressure level (P). The pressure in the buffer volume 80 (P _bv ) must always be at least equal to the set pressure (ie P _bv ≧ P). However, in order to compensate for the slight pressure drop that occurs in the line leading from the buffer volume 80 to the application tool 100, the pressure (P _bv ) in the buffer volume 80 is the minimum required pressure that exceeds the pressure required by the application tool 100 ( P _min ) cannot fall below (ie P _bv ≧ P _min ≧ P).

The average flow rate (F _avg ) of the high pressure carbon dioxide feed stream 75 (F _i ) delivered to the buffer volume 80 is greater than or equal to the average flow rate (S _avg ) of the high pressure carbon dioxide feed stream 85 (S _i ) delivered to the application tool 100. There must be. Therefore, when F _i is greater than S _i , the pressure in the buffer volume 80 increases. On the other hand, when S _i is greater than F _i , the pressure in the buffer volume 80 decreases. Thus, when the flow rate to the application tool 100 exceeds the flow rate of the high pressure carbon dioxide feed stream 75 throughout the course of the processing cycle, the additional carbon dioxide required by the application tool 100 is the carbon dioxide stored in the buffer volume 80. Must be sent from.

  In accordance with the present invention, Applicants have reduced the required amount of carbon dioxide throughout the operating cycle by appropriately adjusting the size of the buffer volume 80 without replacing it or improving its physical properties. I found that I could send it to the application tool. In order to properly adjust the size of the buffer volume 80, the flow rate of carbon dioxide to the buffer volume and application tool 100 can be integrated over time to measure the net change in carbon dioxide in the buffer volume. When the application requires carbon dioxide, the buffer volume provides a net change in carbon dioxide by undergoing a pressure change from maximum pressure to minimum pressure. The temperature in the buffer volume under the maximum and minimum pressure will determine the density of carbon dioxide in the buffer volume. In this way, the size of the buffer volume necessary to replenish the net change in carbon dioxide is determined. Once the buffer volume is controlled, changing the temperature of the volume can change the amount of carbon dioxide delivered from the buffer volume to the application tool without changing its physical properties.

Referring to FIG. 2, the application tool 100 is shown as having a 5 minute cycle. This tool requires 14 pounds / minute high pressure carbon dioxide for the first minute of the cycle, 11 pounds / minute high pressure carbon dioxide for the third minute of the cycle, and at other times of the 5 minute cycle. Does not require carbon dioxide. The average carbon dioxide requirement, S _avg , of the application tool 100 is 5 pounds / minute. Flow rate 75, F _i of high-pressure carbon dioxide feed stream is constant at 5 lbs / min through cycles. The maximum carbon dioxide deficit that the buffer volume 80 must make up is at the end of the third minute of the cycle. The deficit can be calculated for the entire cycle by integrating the difference between F _i and S _i , or alternatively, recording a visual representation on the graph.

  As shown in FIG. 2, in the third minute, an extra 10 pounds of carbon dioxide was sent to the application in high pressure carbon dioxide feed stream 85 rather than entering the buffer volume through high pressure carbon dioxide feed stream 75. Thus, the buffer volume 80 must have 10 pounds of carbon dioxide buffer capacity.

The buffer capacity required by any application tool 100 can be calculated in a similar manner as shown in FIG. Once the required buffer capacity for the buffer volume 80 is known, the buffer volume 80 can be made to match the size. In addition to the required buffer capacity, it is necessary to examine the density of carbon dioxide at the maximum and minimum pressure loads of the buffer volume 80. Returning to the cycle illustrated in FIG. 2, the maximum pressure load of the buffer volume 80 occurs at 0 and 300 seconds. The minimum pressure load on the buffer volume 80 occurs in 180 seconds. The pressure in the buffer volume 80 at the minimum load is P _min . If the temperature in the buffer volume 80 is known, the density of carbon dioxide is determined.

Preferably, the buffer volume is maintained at isothermal conditions during special operating cycles. Therefore, the temperature of the buffer volume at the maximum and minimum load pressure is approximately the same. As mentioned above, the minimum pressure load (P _min ) must exceed the line pressure (P) required by the application tool 100. In a preferred embodiment, the maximum load pressure is selected to be 90% or less of the maximum allowable operating pressure of the buffer volume 80. Manipulating the buffer volume under these conditions takes into account safety issues, so the safety relief device built into the system does not need to be activated and rescues an unforeseeable emergency scene.

  By selecting the maximum load pressure, the carbon dioxide density at this particular pressure and the carbon dioxide density at the minimum load pressure can be measured. This allows the buffer volume to be calculated by dividing the buffer volume capacity by the density difference at the maximum and minimum load pressures. Once the buffer volume is configured, the amount of carbon dioxide that can be delivered instantaneously can be adjusted by changing the temperature of the buffer volume.

For example, if the application tool 100 requires an instantaneous 1.35 pounds at a pressure of 2,850 psig, the system calculator suggests that a 5 minute processing cycle is desirable. Since the 1.35 pound carbon dioxide demand is instantaneous, the high pressure carbon dioxide stream 75 is continuously delivered to the buffer volume 80 when it is drawn. However, the amount delivered is very small compared to the amount captured by the application tool. An analysis similar to that shown and described in FIG. 2 was performed at different temperature points. Assuming that there is a 50 psi pressure drop in the line leading from the buffer volume to the application tool, the minimum load pressure is 2,900 psig. The maximum load pressure for the buffer volume is selected to be 3,100 psig at a temperature of 110 ° F. The density of carbon dioxide at 3,100 psig and 110 ° F. is 52.238 pounds / ft ³ . The density of carbon dioxide at 2,900 psig and 110 ° F. is 51.418 pounds / ft ³ . Thus, 1.35 density difference buffer volume capacity needed (i.e., 52.238-51.418) by dividing in pounds / ft ^3, the buffer volume is 1.65ft ^3. This change in temperature changes the amount of carbon dioxide delivered to the application tool.

As described in the table below, the temperature associated with the buffer volume 80 was changed to a temperature other than 110 ° F. and calculated using the method described above.

  As shown in the table, as the buffer volume temperature rises, the density of carbon dioxide decreases and the total amount of carbon dioxide stored in the buffer volume 80 becomes smaller. The density difference between the maximum and minimum load pressure is given as the buffer volume temperature increases. As the temperature of the buffer volume increases, the required size of the buffer volume 80 decreases. Similarly, as the temperature increases, for a given buffer volume, the amount of carbon dioxide that is used to pump out to the application tool increases, while at the maximum pressure, the amount of carbon dioxide that is stored in the buffer volume increases. Less. This is unexpected, because usually the buffer volume temperature is lowered at a given pressure in order to increase the amount of carbon dioxide stored therein. It is useful for the present invention because it increases the volume of carbon dioxide that can be stored and delivered to the application tool 100.

  Increasing the buffer volume temperature will increase the ability of the buffer volume to momentarily deliver large amounts of carbon dioxide. Thus, the buffer volume temperature is selected on an individual basis and must be balanced against other factors that imply a lower temperature. These factors include the following items: (a) The buffer volume / container requires thicker walls because the strength of the wall material decreases with increasing buffer volume temperature; (b) additional Heat dissipates into the environment and the cost to maintain the buffer volume temperature increases with temperature; (c) to increase the temperature of carbon dioxide in the buffer volume 80 to the desired temperature, more May need energy.

  The choice of buffer volume temperature must also take into account the carbon dioxide temperature desired in the application 100. In a preferred embodiment, the buffer volume temperature must be maintained at about 110 to 120 ° F., somewhat above ambient.

Returning to FIG. 1, the entire carbon dioxide supply system according to one embodiment will be described in detail. The carbon dioxide (CO ₂ ) source for this system is the CO ₂ bulk tank 10. This tank is the size range of a tank that holds 300 tons of CO ₂ from 200 L dewar. Typically, the capacity of the bulk tank is in the range of 6 to 100 tons. For example, the CO ₂ bulk tank 10 can be replenished from a CO ₂ delivery trailer without interrupting the operation of the CO ₂ supply system.

The CO ₂ bulk tank 10 typically contains liquid CO ₂ with a vapor headspace maintained at a pressure of 250 to 350 psig and a temperature of −9 to 10 ° F. The saturated liquid carbon dioxide is extracted from the lower part of the bulk tank 10 and sent to the CO ₂ booster pump 15. The pump tends to increase the CO ₂ pressure by about 50 to 120 psi and increase the temperature. A part of the supercooled liquid present in the booster pump 15 is carried to the pressurizing means 20. The pressurizing means may be a pump selected from a diaphragm pump, a metal diaphragm pump, a piston pump, or other pump means.

In the CO ₂ pressurizing means 20, the CO ₂ is pressurized to such a high pressure that the maximum load pressure in the buffer volume 80 + line pressure drops between the CO ₂ pressurizing means 20 and the buffer volume 80. The Typically, CO ₂ will be at a temperature in the range of about 10 to 30 ° F. with a temperature increase of about 20 ° F. across CO ₂ .

Exits the booster pump 15, and exceeds the maximum capacity of the CO ₂ pressure means 20, a portion of subcooled CO ₂ is circulated through the back pressure regulator 16, returned to the CO ₂ bulk tank 10 It is. A small portion of this supercooled liquid CO ₂ evaporates momentarily as it passes through the back pressure regulator 16. Over the specified time, this steam will increase the pressure in the CO ₂ bulk tank 10. In order to prevent this phenomenon, the refrigeration system 12 carries the refrigerant to the CO ₂ bulk tank 10 through the cooling coil 11 and condenses the CO ₂ vapor generated from the instantaneous evaporation over the back pressure regulator 16. This cooling also condenses the CO ₂ vapor that is generated due to heat leaks entering the CO ₂ bulk tank 10 from the surroundings.

Pressurized CO ₂ flowing out from the pressurizing means 20 is conveyed through the heat exchangers 29 and 30, and performs indirect heat exchange with a part or all of the CO ₂ returned from the CO ₂ purification apparatus 40 there. The heat exchangers 29 and 30 allow the heat recovery of the CO ₂ purification device 40 to occur at a temperature higher than the temperature of CO ₂ flowing out of the CO ₂ pressurizing means 20. CO ₂ is to flow through the heater 35, the heater raises the temperature to the temperature of CO ₂ required CO ₂ purification device 40. The heater 35 is essential because heat recovery in the heat exchangers 29 and 30 is not efficient overall.

The CO ₂ purification apparatus 40 can be selected from any purification apparatus that can be operated at a temperature higher than the temperature of CO ₂ flowing out from the pressurizing means 20. Preferably, the device operates at a temperature between 100 ° F and 1,000 ° F, and most preferably at a temperature between 200 ° F and 700 ° F. Typical purification equipment includes adsorption, absorption, chemical reaction, catalytic oxidation, and filtration.

Filtration at elevated temperatures, can be part of the function of CO ₂ purification apparatus. Filters such as sintered metal filters commonly used in the electronics industry are known and perform better in gas phase applications than in liquid phase applications. This is largely due to the increase in particle diffusivity and Brownian motion in the gas phase. The characteristics of filters in supercritical conditions (ie pressures above 1,060 psig and temperatures above 88 ° F.) have not been well studied. However, it is known that as the temperature of the supercritical fluid increases, the characteristics of the gas, including its diffusivity, become similar.

When the CO ₂ purification device 40 is operated at a temperature higher than the buffer volume 80, the CO ₂ becomes more gaseous. Therefore, filtration will be more effective. If a filter is included as part of the CO ₂ purification unit 40, it must be placed downstream of any particle generation means for purification such as adsorption and catalytic oxidation.

CO ₂ was removed from the CO ₂ purification apparatus 40 is again sent through the heat exchanger 30, where CO ₂ is CO ₂ to CO ₂ and indirect towards the heat exchanger from the pressurizing means 20 for heat exchange. The CO ₂ required by the buffer volume 80 flows into the high pressure carbon dioxide feed stream heating or cooling means 74. Based on the pressure sensed in the buffer volume 80, CO ₂ exceeding a predetermined level is recirculated to the bulk tank 10 at the valve 60. Unnecessary CO ₂ in the buffer volume 80 is sent through the heat exchanger 29 where additional heat is recovered. The CO ₂ leaving the heat exchanger 29 flows through the valve 60 as a recirculation stream 59. This valve releases the CO ₂ pressure and approaches the CO ₂ bulk tank 10 pressure. A portion of the CO ₂ evaporates instantaneously across the valve 60, but this vapor is recondensed in the CO ₂ bulk tank 10 by the refrigerant supplied to the cooling coil 11 by the refrigeration system 12.

Since it may be desirable to have a flow rate that exceeds the average demand of the application 100, S _avg, and through the CO ₂ pressurizing means 20 and the CO ₂ purifier 40, the CO ₂ to the bulk tank 10 may be desirable. Recirculation of is optional. For example, for reasons of average flow, if the application 100 to interrupt the removal of carbon dioxide, to continue the operation of the carbon dioxide supply system, the CO ₂ pressure means 20 to the CO ₂ purification apparatus 40 Energy / It is desirable to maintain heat recovery.

In this embodiment, heat recovery from the CO ₂ purification unit 40 is performed using two heat exchangers 29 and 30 rather than a single heat exchanger. Otherwise, all the CO ₂ from the purifier 40, if replacing the CO ₂ and energy / heat from the pressing means 20, the CO _2, the temperature below the desired temperature of the buffer volume 80 Will be cooled to. The use of two heat exchangers 29 and 30 means that when CO ₂ exits the heat exchanger 30, the CO ₂ is at a temperature close to the desired temperature in the buffer volume 80 and the CO ₂ is at a high pressure carbon dioxide feed stream heating or cooling means 74. To be sent to. Accordingly, the recirculation stream 59 is further cooled in the heat exchanger 29 before returning this stream to the bulk tank 10.

The temperature of CO ₂ sent through the high pressure carbon dioxide feed stream heating or cooling means 74 is adjusted to the desired temperature in the buffer volume 80 depending on the temperature of the incoming CO ₂ . Exemplary devices that can be used as the heating or cooling means 74 include air cooling coils, water-cooled or refrigerant-cooled heat exchangers, and heaters. The high pressure carbon dioxide feed stream 75 exits the high pressure carbon dioxide feed stream heating or cooling means 74 and is sent to the buffer volume 80.

The CO ₂ in the buffer volume 80 can be heated or cooled by the buffer volume temperature adjusting means 81. The high pressure carbon dioxide feed stream heating or cooling means 74 adjusts the temperature of the high pressure carbon dioxide feed stream 75 to match the desired temperature in the buffer volume 80, so that the work required of the buffer volume temperature adjustment means 81 is Is minimal. Typically, it is designed to compensate for heat loss or heat acquisition between the buffer volume 80 and ambient temperature. Devices that can be used for the buffer volume temperature control means 81 include heat traces, internal heaters, external band or cable heaters, external cooling coils and internal cooling coils. Usually, the buffer volume 80 is insulated and reduces the amount of heat exchange with the outside environment. Alternatively, it may be advantageous to operate the buffer volume so that the buffer volume / tank temperature is lower at the bottom than at the top. The temperature of the fluid contained in the upper part of the buffer volume is such that the fluid is recovered from the lower part (not shown) of the buffer volume, the fluid is heated using temperature adjusting means, and this flow is returned to the upper part of the buffer volume 80. Can be controlled.

When the application tool 100 requires CO ₂ , the fluid exits the buffer volume 80 and becomes a high pressure carbon dioxide feed stream 85. The high pressure carbon dioxide feed stream 85 can then be heated or cooled using heating or cooling means 86 to produce the temperature required by the application tool 100. It passes through the filter 88 and across the valve 90. The use of the filter 88 facilitates the supply of particle free CO ₂ even when the buffer volume 80 does not have an electropolished internal surface. The valve 90 controls the flow rate of the high pressure carbon dioxide feed stream 85 to ensure that the pressure downstream of the valve 90 is the pressure desired by the application tool 100. The CO ₂ is then sent through the filter 92 along the way to the application tool 100 where it is used for semiconductor wafer processing.

Next, referring to the embodiment shown in FIG. 3, it is possible to incorporate a heat exchanger into one heat exchanger core 31. This arrangement can reduce the space CO ₂ feed stream is required, the cost can be reduced also, compared to those with two heat exchangers. One type of heat exchanger suitable for this task would be a microchannel heat exchanger such as a Printed Circuit Heat Exchanger (PCHE, Printed Circuit Heat Exchanger) supplied by the Heath division of Meggett (UK).

FIG. 4 shows another embodiment of the supply system. The CO ₂ booster pump 15 and the back pressure regulator 16 shown in FIG. 1 were replaced with a cooling system 13 and a subcooler heat exchanger 14. This modified system provides an alternative supply of supercooled liquid to the CO ₂ pressurizing means 20. CO ₂ sent from the CO ₂ bulk pump 10, after being only supercooled 20 ° F or more subcooler heat exchanger 14, is sent to the CO ₂ pressure means 20.

The refrigeration system 13 is used to supply refrigerant to the condenser heat exchanger 65. Instead of recondensing the vapor directed to the bulk tank by use of the cooling coil 11, the CO ₂ vapor resulting from the pressure drop across the valve 60 is recondensed in the condenser heat exchanger 65 and then the CO ₂ bulk tank 10. Returned to

Alternatively, although not shown, a supply device including the CO ₂ booster pump 15 and the back pressure regulator 16 can be arranged to be connected to the condenser heat exchanger 65 and the refrigeration system 13. Further, the system can house both the refrigeration system 12 and the cooling coil 11 along with the refrigeration system 13 and the subcooler heat exchanger 14 and / or the condenser heat exchanger 65.

  Referring now to FIG. 5, an embodiment employing an alternative heat exchanger arrangement system is shown. The heat exchangers 29 and 30, the subcooler heat exchanger 14, and the condenser heat exchanger 65 shown in FIG. 4 can be replaced with one heat exchanger core such as the heat exchanger 21. The heat exchanger 21 will include high and low pressure side plates. The advantage of employing heat exchanger 21 would be to reduce space and potentially reduce the cost to the system. One type of heat exchanger suitable for this task would be a microchannel heat exchanger such as a Printed Circuit Heat Exchanger (PCHE, Printed Circuit Heat Exchanger) supplied by the Heath division of Meggett (UK).

FIG. 6 illustrates an alternative embodiment in which a recycle stream 59 is received after the high pressure carbon dioxide feed heating or cooling means 86 and filter 88. Those skilled in the art will recognize that recirculation stream 59 can be incorporated at other points in the system. Another position is downstream of the valve 90, moreover upstream of high-pressure carbon dioxide feed stream heating or cooling means 86, during the high-pressure carbon dioxide feed stream heating or cooling means 74 and the buffer volume 80, and CO ₂ pressure means and heat exchange Including between chambers 33.

In addition to the use of pump, such as CO ₂ pressure means 20, it is possible to adopt a compressor. If a compressor is employed as the CO ₂ pressurizing means 20, the CO ₂ from the bulk tank 10 will need to be sent to the CO ₂ pressurizing means 20 after being transported through a vaporizer. Therefore, the CO ₂ booster pump 15 and the back pressure regulator 16 will not be utilized in such an assembly.

  High pressure carbon dioxide feed stream heating or cooling means 74 and high pressure carbon dioxide feed stream heating or cooling means 86 are optional, such as filters 88, 89 and 92.

The purification part of the feed system is also optional. In some cases, CO ₂ from the CO ₂ bulk tank 10 is sufficiently pure for use in the application tool 100. In such a case, the heat exchangers 29 and 30, the heater 35 and the CO ₂ purification device 40 are removed. CO ₂ is sent directly from the CO ₂ pressurizing means 20 to the high pressure carbon dioxide feed stream heating or cooling means 74.

  Although the invention has been described in detail with reference to specific embodiments, various changes and modifications can be made without departing from the scope of the appended claims, and equivalents may be used. It will be apparent to those skilled in the art that it can be used.

It is explanatory drawing which showed the whole system for sending a carbon dioxide to a semiconductor application tool. Example 1 It is explanatory drawing which showed the typical 5-minute operation cycle for sending out a carbon dioxide. It is explanatory drawing which showed the whole system with a single core heat exchanger. (Example 2) It is explanatory drawing which showed the whole system according to another improved embodiment. (Example 3) FIG. 3 is an illustration showing the overall system according to another embodiment with a single core heat exchanger. Example 4 FIG. 6 is an illustration showing the overall system according to another embodiment in which recirculation is redesigned. (Example 5)

Claims (10)

A method of supplying high-pressure carbon dioxide to application tools that require various carbon dioxide flow conditions,
Supplying the buffer volume with a high-pressure carbon dioxide feed stream;
The minimum pressure that exceeds the pressure required by the application tool and the average density of carbon dioxide stored in the buffer volume at the minimum pressure is the average density of carbon dioxide stored in the buffer volume at the maximum pressure. Maintaining between maximum pressures, different from
Adjust the average temperature of the buffer volume so that the flow conditions related to the application tool are met, the average density of carbon dioxide stored in the buffer volume at the minimum pressure and carbon dioxide stored in the buffer volume at the maximum pressure A method comprising correcting a difference between the average densities of the gas and delivering a high pressure carbon dioxide feed stream from the buffer volume at various flow rates as required by the application tool.   The method of claim 1, further comprising adjusting the buffer volume to a state required to deliver a predetermined amount of carbon dioxide to the application tool based on the temperature adjustment of the buffer volume.   The method of claim 1, wherein the required flow conditions for the application tool are discontinuous.   The method of claim 1, wherein the application tool is a semiconductor application tool.   The method of claim 1, wherein the carbon dioxide required for delivery to the application tool is predetermined.   The method of claim 1, wherein the buffer volume is at least one pressure vessel.   The method of claim 1, further comprising heating or cooling carbon dioxide contained in the buffer volume by a heating or cooling device. A system for supplying high pressure carbon dioxide to applications that require various carbon dioxide flow conditions,
A buffer volume that accepts a high pressure carbon dioxide feed stream, where the pressure in the buffer volume is the minimum pressure above the pressure required by the application tool, and the density of carbon dioxide at the minimum pressure is the density of carbon dioxide at the maximum pressure. A buffer volume, which is maintained between a maximum pressure, such as different from, and the temperature in the buffer volume is adjusted,
A carbon dioxide purifier located upstream of the buffer volume that delivers a high pressure carbon dioxide feed stream, and a downstream of the buffer volume that accepts carbon dioxide from the buffer volume at various flow rates as required by application tools A system that includes application tools.   9. The system of claim 8, further comprising an apparatus for heating or cooling the high pressure carbon dioxide feed stream disposed downstream of the carbon dioxide purification apparatus. 9. The system of claim 8, further comprising a carbon dioxide pressurizing device disposed upstream of the purifier to provide carbon dioxide supplied from the bulk storage tank.

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