JP3837280B2 - High concentration ozone gas supply method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for supplying ozone gas at a constant concentration to an ozone consuming facility, and more particularly to a method and apparatus for purifying ozone gas generated by an ozone generator (ozonizer) and supplying it as high-concentration ozone gas.
[0002]
[Prior art]
Generally, ozone gas is generated by supplying oxygen gas from an oxygen gas cylinder or oxygen gas separated into the atmosphere to an ozone generator. However, even if ozone is generated with oxygen gas from an oxygen gas cylinder, ozone gas is oxygen gas. The concentration is only about 5-10 vol%. Moreover, since ozone gas has a strong self-decomposition property, it has a property that when it is self-decomposed in the ozone supply path and supplied to the ozone consuming equipment, the concentration becomes lower and the supply concentration is not stable. In recent years, in the field of semiconductor manufacturing, the use of the oxidizing power of ozone gas for forming an oxide film on a substrate or the like is increasing. In this case, in order to obtain an oxide film with an appropriate thickness within a short time, high-concentration ozone gas is required, and the ozone gas generated by the ozone generator is concentrated and purified.
[0003]
Therefore, the present applicant first desorbs ozone gas from the adsorbent by selectively adsorbing the ozone gas generated by the ozone generator to the adsorbent that has been cooled and controlling the cooling temperature of the adsorbent. Have been proposed to supply high-concentration ozone gas to ozone consuming equipment (Japanese Patent Laid-Open No. 11-335102). In this, three adsorption cylinders are arranged in parallel, and each adsorption cylinder repeats the adsorption process, the stabilization / pressurization process, the ozone desorption process, and the cooling process, and each operation time in the adsorption process and the desorption process. Is set to twice the operating time of the stabilization and pressure-increasing step and the cooling step, and the three adsorbing cylinders are operated with a shift of 1/3 cycle to temporarily remove the high-concentration ozone gas desorbed from each adsorbing cylinder. It was configured to be received by an intermediate storage container and supplied from this intermediate storage container to the ozone consuming equipment.
[0004]
[Problems to be solved by the invention]
By the way, in the case where ozone is desorbed by adjusting the temperature, it is well known that the gas concentration and flow rate of the desorbed ozone change according to the temperature. For this reason, the ozone gas that has been desorbed from the adsorption cylinder is once received in the intermediate storage container and the ozone gas concentration is averaged and then supplied to the ozone consuming equipment. The concentration was about 30 vol%.
[0005]
Moreover, in order to obtain ozone gas with the above-mentioned stable gas concentration, three adsorption cylinders and intermediate storage containers are required, and since the facility is large-scale, high concentration ozone gas is stably supplied at a small flow rate. However, there is a problem that it is difficult to adopt for small-scale ozone consuming equipment.
[0006]
This invention pays attention to such a point, and it aims at providing the high concentration ozone gas supply method and apparatus which can supply high concentration ozone gas stably also to a small-scale ozone consumption installation.
[0007]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, in the invention described in claim 1, an adsorption process for adsorbing ozone gas generated by an ozone generator to an adsorbent cooled by a refrigerator in an atmospheric pressure state, and an adsorbent The purification cylinder is evacuated to the partial pressure of the supply ozone gas, and the adsorption cylinder is stored in a vacuum state while maintaining the cooled state and the reduced pressure state. And a desorption step of supplying high-concentration ozone at a predetermined flow rate by a pressure difference.
[0008]
The invention described in claim 2 is configured such that a plurality of adsorption cylinders arranged in parallel are cooled by a single refrigerator, and one of the adsorption cylinders is in the desorption process. The adsorption process or purification process is completed for other adsorption cylinders in the meantime, and the adsorption cylinder to be used is switched when the gas extraction amount from each adsorption cylinder reaches the preset integrated extraction amount. The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, the refrigerator is constituted by a pulse tube refrigerator.
[0009]
Further, in the invention described in claim 4, the adsorption cylinder filled with the adsorbent is configured to be cooled by a refrigerator, and the adsorption cylinder and the ozone generator are connected to each other through an ozone supply path and are led out from the adsorption cylinder. A first extraction passage that opens the purified ozone extraction passage to the atmosphere via a flow passage opening / closing valve and an ozone decomposer, and a second extraction passage that communicates with a vacuum pump via the flow passage opening / closing control valve and the ozone decomposition device And a third take-out passage communicating with the ozone consuming equipment through the flow passage opening / closing valve, the flow meter and the flow controller, and the three take-out passages are selectively opened. In the state where only the extraction path is opened, ozone is adsorbed by the adsorbent in the adsorption cylinder. In the state where only the second extraction path is opened, the adsorption cylinder is evacuated to the partial pressure of the supplied ozone gas, and the third extraction path and the second extraction path are exhausted. In the state where the two extraction paths are open, the ozone It is characterized by being configured to so as to desorption.
[0010]
Furthermore, the invention described in claim 5 is configured such that a plurality of adsorption cylinders filled with an adsorbent are arranged in parallel, and the plurality of adsorption cylinders are configured to be cooled by a single refrigerator. Of these, the adsorption cylinder ( 2 ) that has finished the purification step is configured to communicate with an ozone consuming facility as an alternative, and the invention described in claim 6 is characterized in that in claim 4 or claim 5. In the described invention, the refrigerator is constituted by a pulse tube refrigerator.
[0011]
[Effects of the Invention]
In the present invention, ozone gas is selectively adsorbed to the cooled adsorbent under atmospheric pressure, and after adsorbing ozone gas, the inside of the adsorption cylinder containing the adsorbent is reduced to the ozone partial pressure in the supply gas, By refining ozone gas and making the inside of the adsorption cylinder communicate with the ozone consuming equipment after purification, adsorption is performed by the pressure difference between the ozone consuming equipment maintained in a high vacuum state and the adsorption cylinder maintained at the ozone partial pressure. The ozone gas adsorbed and held by the agent is transferred to the ozone consuming equipment.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram showing an example of an embodiment of the present invention. This ozone gas refining device is a gas that connects an adsorption cylinder (2) filled with an adsorbent (1) such as silica gel that selectively adsorbs ozone, and an oxygen gas storage container (3) and an adsorption cylinder (2). It has an introduction path (4) and a purified ozone extraction path (5) led out from the adsorption cylinder (2).
[0013]
In the gas introduction path (4), an ozone generator (6) and a mass flow controller (7) are arranged in order from the upstream side, and adsorb the ozone-oxygen mixture generated by the ozone generator (6) at a constant flow rate. The cylinder (2) is supplied. On the other hand, the purified ozone extraction path (5) is branched into three systems. A flow path opening / closing valve (9) and an ozonolysis device (10) are arranged in this order from the upstream side in the first extraction path (8), and the first extraction path (8) is open to the atmosphere. In the second extraction passage (11), a flow control valve (12), an ozonolysis device (13), and a vacuum pump (14) are arranged in this order from the upstream side, and the discharge port of the vacuum pump (14) is the atmosphere. It is open to. In addition, the third extraction path (15) is maintained in a high vacuum state such as a vacuum chamber in a semiconductor manufacturing apparatus (not shown) via a channel opening / closing valve (16), a mass flow meter (17), and a mass flow controller (18). It is connected to the ozone consuming equipment connected.
[0014]
The adsorption cylinder (2) is thermally connected to the cold head (21) of the pulse tube refrigerator (20) via the heat storage body (19). These are the adsorption cylinder (2), the heat storage body (19), The cold head (21) is accommodated in the vacuum chamber (22). In the figure, reference numeral (23) is a compressor unit of the pulse tube refrigerator (20), (24) is a valve unit of the pulse tube refrigerator (20), and (25) is a temperature control device for adjusting the output of the refrigerator. , (26) is a bypass route that branches from the upstream side of the ozone generator (6) of the gas introduction channel (4) and is connected to the downstream side of the mass flow controller (18) of the third extraction channel (15), (27) is a mass flow controller interposed in the bypass (26). In addition, as the heat storage body (19), it is comprised by the liquid tank which stored the copper block and liquid florinate, and the adsorption cylinder (2) is arrange | positioned in the state buried in this heat storage body (19).
[0015]
The case where the ozone gas refinement | purification apparatus which consists of the above-mentioned structure is used and ozone gas concentrated at high concentration is supplied to ozone consumption equipment is explained. The supply of high-concentration ozone gas in this ozone gas purification apparatus consists of an adsorption process, a purification process, and a desorption process, and the adsorption cylinder (2) is maintained at a predetermined cooling temperature (for example, 173 K) throughout the entire process. Yes.
In the adsorption step, the first extraction path (8) is opened, the second extraction path (11) and the third extraction path (15) are closed, and the gas introduction path (4) is opened, The ozone-oxygen mixed gas generated by the ozone generator (6) using oxygen gas from the gas storage container (3) as a raw material is supplied to the adsorption cylinder (2), and the ozone gas in the mixed gas is adsorbed (1). And saturated adsorption at atmospheric pressure. At this time, the ozone gas that has not been adsorbed by the adsorbent (1) and has passed through the adsorption cylinder (2) together with the oxygen gas is decomposed by the ozone decomposer (10) when passing through the first extraction passage (8), To the atmosphere.
[0016]
When the ozone gas is saturated and adsorbed on the adsorbent (2), the process is switched to the purification process. In the refining process, the second extraction path (11) is opened, the first extraction path (8) and the third extraction path (15) are closed, and the gas introduction path (4) is closed, and the vacuum pump (14) depressurizing the ozone partial pressure of oxygen in the gas mixture as a limit - ozone pressure atmosphere is supplied from the ozone generator (6) of the suction tube (2) by activating the. The gas that flows out during this decompression operation also contains ozone gas, which is decomposed by the ozone decomposer (13) interposed in the second extraction passage (11) and released to the outside from the vacuum pump (14). Is done. The pressure atmosphere in the adsorption cylinder (2) in this purification step is maintained at about 5.3 kPa (40 torr) when the ozone concentration generated in the ozone generator (6) is 5 vol%.
[0017]
When the pressure in the adsorption cylinder (2) drops to a predetermined pressure, the process switches to the desorption process. In this desorption process, the third extraction path (15) is opened, the first extraction path (8) and the gas introduction path (4) are closed, and the second extraction path (11) reduces the internal pressure of the adsorption cylinder (2). The flow path opening / closing control valve (12) is opened / closed so as to maintain the atmospheric pressure in the purification step. The third extraction path (15) is connected to the ozone consuming equipment that is maintained in a vacuum state or a state close to vacuum, so that the adsorption is performed by the pressure difference between the internal pressure of the adsorption cylinder (2) and the internal pressure of the ozone consuming equipment. The gas component in the cylinder (2) moves to the ozone consuming equipment, and the internal pressure of the adsorption cylinder (2) decreases, so the ozone adsorbed and held by the adsorbent (1) desorbs and moves to the ozone consuming equipment in sequence. Will do. During the desorption process, the second take-out path (11) operates the flow path opening / closing control valve (12) so that the inside of the adsorption cylinder (2) maintains the set pressure in the purification process. .
[0018]
Note that the concentration of ozone gas supplied to the ozone consuming equipment can be adjusted by supplying oxygen from the bypass path (26).
Then, when the mass flow meter (17) interposed in the third take-out path (15) reaches a preset integrated flow rate, the desorption process is completed.
[0019]
FIG. 2 is a system diagram showing a different embodiment of the present invention. In this embodiment, two adsorption cylinders (2) and (2) are cooled by the same pulse tube refrigerator (20), and two adsorption cylinders (19) are connected to a common heat storage body (19). 2) ・ (2) is installed. And while one adsorption cylinder (2) is in a desorption process, the other adsorption cylinder (2) is in a standby state after completing the adsorption process and the purification process. Therefore, when the mass flow meter (17) interposed in the third extraction path (15) reaches a preset integrated flow rate, continuous extraction can be performed by switching the suction cylinder (2) to be used.
[0020]
By the way, when 175 g of silica gel (adsorbent) is filled in an adsorption cylinder (2) having an internal volume of 0.25 liter and an ozone - oxygen mixed gas having an ozone concentration of 5 vol% is supplied at 1.2 liter / min, In about 90 minutes, the adsorbent (1) was in a saturated adsorption state. From this state, it took about 5 minutes to reduce the pressure to 5.3 kPa. When ozone was extracted at a flow rate of 10 SCCM while the internal pressure in the adsorption cylinder (2) was maintained at 5.3 kPa, ozone gas having an ozone concentration of 80 vol% or more could be continuously extracted for 3 hours.
[0021]
In each of the above embodiments, the pulse tube refrigerator (20) is used as a refrigerator for cooling the adsorption cylinder (2), but the refrigerator may be of any type. However, since the adsorbent (1) may be shaken by vibration and ozone may be partially decomposed, it is desirable to use a pulse tube refrigerator (20) with less vibration as the refrigerator. Further, the gas for diluting the ozone gas separated from the adsorption cylinder (2) is not limited to oxygen gas, and nitrogen gas or other gas may be used.
[0022]
【The invention's effect】
In the present invention, since ozone gas adsorbed by the adsorbent in the cooled state is desorbed by pressure control in the adsorption cylinder, ozone gas having a stable concentration can be extracted during the gas extraction period. A buffer tank for averaging the concentration of desorbed gas is not required, and the entire apparatus can be reduced in size accordingly.
[0023]
In addition, the ozone gas is desorbed from the adsorbent and the ozone gas is transferred by the pressure difference between the pressure in the adsorption cylinder and the internal pressure of the ozone consuming equipment. Can be supplied.
[0024]
Further, in the present invention, the cooling conditions and ozone adsorbent at atmospheric pressure - because it is so as to selectively adsorb ozone gas from oxygen gas mixture, after which it is possible to increase the adsorption amount throughout the entire process, the constant Since the cooling state is maintained, the amount of adsorption can be easily managed, and the operation can be controlled by detecting the remaining amount from the integrated flow rate.
[0025]
When a plurality of adsorption cylinders are cooled by a single refrigerator, the cooling state of each adsorption cylinder can be made uniform, so that all the adsorption cylinders can be controlled under the same conditions. Even when switched and used, the state of the ozone gas supplied to the ozone consuming equipment can be made uniform without any control.
[0026]
In addition, when a pulse tube refrigerator is used as a cooling source for the adsorbent, since there is no vibration associated with the operation of the refrigerator, partial decomposition of ozone gas can be suppressed, and safety can be further improved. .
[Brief description of the drawings]
FIG. 1 is a system diagram showing an example of an embodiment of the present invention.
FIG. 2 is a system diagram showing a different embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Adsorbent, 2 ... Adsorption cylinder, 4 ... Gas introduction path, 5 ... Purified ozone extraction path, 6 ... Ozone generator, 8 ... First extraction path, 9 ... Flow path opening / closing valve, 10 ... Ozone decomposer, 11 ... 2nd extraction path, 12 ... Flow path opening / closing control valve, 13 ... Ozone decomposer, 14 ... Vacuum pump, 15 ... 3rd extraction path, 16 ... Flow path opening / closing valve, 17 ... Mass flow meter, 18 ... Mass flow controller, 20 …refrigerator.

Claims (6)

  An adsorption process in which the ozone gas generated by the ozone generator (6) is saturated and adsorbed at the atmospheric pressure to the adsorbent (1) cooled by the refrigerator (20), and an adsorption containing the adsorbent (1) Refining process to evacuate cylinder (2) to partial pressure of supply ozone gas A high-concentration ozone gas supply method comprising a desorption step of supplying high-concentration ozone at a predetermined flow rate by a pressure difference A plurality of adsorption cylinders (2) arranged in parallel are configured to be cooled by a single refrigerator (20), and one adsorption cylinder (2) of the plurality of adsorption cylinders (2) is used in the desorption process. In the meantime, the other adsorption cylinder (2) is made to finish the adsorption process or the purification process, and when the amount of gas extracted from each adsorption cylinder (2) reaches a preset integrated extraction amount, the adsorption cylinder (2 2) The high-concentration ozone gas supply method according to claim 1.   The high-concentration ozone gas supply method according to claim 1 or 2, wherein the refrigerator (20) for cooling the adsorbent (2) is a pulse tube refrigerator. The adsorption cylinder (2) filled with the adsorbent (1) is configured to be cooled by the refrigerator (20), and the adsorption cylinder (2) and the ozone generator (6) are connected by the gas introduction path (4). The first extraction passage (8) which is connected to the exhaust pipe and is open to the atmosphere through the flow opening / closing valve (9) and the ozone decomposer (10) through the purified ozone extraction passage (5) led out from the adsorption cylinder (2). ), A second take-out passage (11) communicating with the vacuum pump (14) via the passage opening / closing control valve (12) and the ozonolysis device (13), the passage opening / closing valve (16) and the mass flow meter (17 ) And a third extraction path (15) communicating with the ozone consuming equipment via the mass flow controller (18), and configured to selectively open these three extraction paths, the first extraction path (8 ) Is opened, ozone is adsorbed by the adsorbent (1) in the adsorption cylinder (2), and in the state where only the second extraction path (11) is opened, the partial pressure of the supply ozone gas in the adsorption cylinder (2) Evacuate to 3rd removal Road (15) and a second extraction path (11) is high-concentration ozone gas supply apparatus configured to desorb ozone from the adsorbent (1) in the suction tube (2) is in a state of opening. A plurality of adsorption cylinders (2) filled with the adsorbent (1) are arranged in parallel, and the plurality of adsorption cylinders (2) can be cooled by one refrigerator (20). The high-concentration ozone gas supply device according to claim 4, wherein the adsorption cylinder ( 2 ) that has completed the purification step of ( 2 ) is configured to communicate with an ozone consuming facility alternatively.   The high-concentration ozone gas supply device according to claim 4 or 5, wherein the refrigerator (20) for cooling the adsorption cylinder (2) is a pulse tube refrigerator.

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