JP2002068712A - High concentration ozone gas supply method and apparatus - Google Patents

Abstract

(57) [Problem] To provide a high-concentration ozone gas supply method and apparatus capable of stably supplying a high-concentration ozone gas even to a small-scale ozone consuming facility. SOLUTION: An adsorption step of saturating an ozone gas generated by an ozone generator (6) with an adsorbent (1) cooled by a refrigerator (20) under an atmospheric pressure state, and containing the adsorbent (1). A purification step of depressurizing and exhausting the inside of the adsorption column (2) to the partial pressure of the supplied ozone gas, and an ozone consuming facility maintaining a vacuum state while maintaining a cooled state and a depressurized state in the adsorption column (2). And a desorption step of supplying high-concentration ozone at a predetermined flow rate according to a pressure difference by communicating with a pressure difference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for supplying a certain concentration of ozone gas to an ozone consuming facility.
In particular, the present invention relates to a method and an apparatus for purifying ozone gas generated by an ozone generator (ozonizer) and supplying it as high-concentration ozone gas.

[0002]

2. Description of the Related Art Generally, ozone gas is generated by supplying oxygen gas from an oxygen gas cylinder or oxygen gas separated from the atmosphere to an ozone generator. However, ozone gas can also be generated by using oxygen gas from an oxygen gas cylinder. Ozone gas has a concentration of only about 5 to 10 vol% in oxygen gas. In addition, since the ozone gas has a strong self-decomposition property, the ozone gas is self-decomposed in the ozone supply path, and when supplied to the ozone consuming equipment, has a lower concentration, and the supply concentration is not stable today. 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 has been increasing. In this case, in order to obtain an oxide film having an appropriate thickness in a short time, a high concentration of ozone gas is required, and the ozone gas generated by the ozone generator is concentrated and purified.

[0003] In view of the above, the present applicant first selectively adsorbs ozone gas generated by an ozone generator onto a cooled adsorbent and controls the cooling temperature of the adsorbent,
It has been proposed that ozone gas is desorbed from an adsorbent and high-concentration ozone gas is supplied to an ozone consuming facility (Japanese Patent Application Laid-Open No. HEI 1-1990).
No. 1-335102). In this device, three adsorption cylinders are arranged in parallel, and in each adsorption cylinder, an adsorption step, a stabilization and pressure increasing step,
The ozone desorption step and the cooling step are repeated, and each operation time in the adsorption step and the desorption step is set to twice the operation time in the stabilization / pressurization step and the cooling step. In this case, the operation is carried out by shifting by / 3 cycles, and the high-concentration ozone gas desorbed from each adsorption column is once received in the intermediate storage container and supplied to the ozone consuming equipment from the intermediate storage container.

[0004]

By the way, it is well known that in the case where ozone is desorbed by adjusting the temperature, the gas concentration and the flow rate of the desorbed ozone change every moment depending on the temperature. For this reason, in the conventional device, the ozone gas desorbed from the adsorption column is once received in the intermediate storage container, the ozone gas concentration is averaged, and then the ozone gas is supplied to the ozone consuming equipment. The concentration was about 30 vol%.

Further, in order to obtain the above-mentioned ozone gas having a stable gas concentration, three adsorption cylinders and an intermediate storage container are required, and the equipment becomes large-scale. There has been a problem that it is difficult to adopt it for small-scale ozone consuming equipment for which stable supply is desired.

The present invention has been made in view of such a point, and an object of the present invention is to provide a high-concentration ozone gas supply method and apparatus capable of stably supplying a high-concentration ozone gas even to a small-scale ozone consuming facility. And

[0007]

According to the first aspect of the present invention, an ozone gas generated by an ozone generator is supplied to an adsorbent cooled by a refrigerator under atmospheric pressure. An adsorption step of performing saturated adsorption, a purification step of depressurizing and exhausting the inside of the adsorption cylinder containing the adsorbent to a partial pressure of the supplied ozone gas, and maintaining a vacuum state while maintaining a cooled state and a depressurized state in the adsorption cylinder And a desorption step of supplying high-concentration ozone at a predetermined flow rate by a pressure difference in communication with the ozone consuming equipment.

According to a second aspect of the present invention, a plurality of adsorption cylinders arranged in parallel are cooled by one refrigerator, and one of the adsorption cylinders is desorbed. During the process, the other adsorption column is made to complete the adsorption process or the purification process, and when the gas extraction amount from each adsorption column reaches the preset integrated extraction amount, the adsorption column to be used is switched. 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.

According to a fourth aspect of the present invention, an adsorption cylinder filled with an adsorbent is configured to be able to be cooled by a refrigerator, and the adsorption cylinder and an ozone generator are connected and connected by an ozone supply path.
The purified ozone extraction passage derived from the adsorption cylinder is connected to a first extraction passage that is open to the atmosphere via a flow passage opening / closing valve and an ozone decomposer, and to a vacuum pump via a flow passage opening / closing control valve and an ozone decomposition device. A second extraction path, and a third extraction path that communicates with the ozone consuming equipment via a flow path opening / closing valve, a flow meter and a flow controller, and is configured to selectively open these three extraction paths. When only the first extraction path is open, ozone is adsorbed by the adsorbent in the adsorption cylinder, and when only the second extraction path is open, the interior of the adsorption cylinder is depressurized and exhausted to the partial pressure of the supplied ozone gas. It is characterized in that the ozone gas is desorbed from the adsorbent in the adsorption cylinder when the take-out path and the second take-out path are open.

Further, the invention described in claim 5 is:
A plurality of adsorption cylinders filled with an adsorbent are arranged in parallel, the plurality of adsorption cylinders can be cooled by one refrigerator, and the plurality of adsorption cylinders can be selectively communicated with the ozone consuming equipment. The invention described in claim 6 is characterized in that, in the invention described in claim 4 or claim 5, the refrigerator is configured by a pulse tube refrigerator.

[0011]

According to the present invention, the ozone gas is selectively adsorbed to the cooled adsorbent under the atmospheric pressure, and the ozone gas is adsorbed. And then purify the ozone gas and connect the inside of the adsorption cylinder with the ozone consuming equipment after the purification, so that the ozone consuming equipment maintained in a high vacuum state and the inside of the adsorption cylinder maintained at the ozone partial pressure are separated. Due to the pressure difference, the ozone gas adsorbed and held by the adsorbent is transferred to the ozone consuming equipment.

[0012]

FIG. 1 is a system diagram showing an example of an embodiment of the present invention. This ozone gas purification apparatus comprises an adsorption cylinder (2) filled with an adsorbent (1) such as silica gel for selectively adsorbing ozone, an oxygen gas storage container (3) and an adsorption cylinder (2).
And a gas introduction path (4) for communicating the same and a purified ozone extraction path (5) led out from the adsorption column (2).

An ozone generator (6) and a mass flow controller (7) are arranged in the gas introduction path (4) in this order from the upstream side, and the ozone-oxygen mixture generated by the ozone generator (6) is maintained at a constant rate. The liquid is supplied to the adsorption column (2) at a flow rate. On the other hand, the refined ozone extraction passage (5) is branched into three systems. A flow opening / closing valve (9) and an ozone decomposer (10) are arranged in 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 path (11), a flow path opening / closing control valve (12), an ozone decomposer (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 an atmosphere. It is open to the public. The third extraction path (15) has a flow path opening / closing valve (16), a mass flow meter (17) and a mass flow controller (18).
Is connected to an ozone consuming facility that maintains a high vacuum state, such as a vacuum chamber in a semiconductor manufacturing apparatus (not shown), via a through-hole.

The adsorption cylinder (2) is thermally connected to a cold head (21) of the pulse tube refrigerator (20) via a heat storage (19), and the adsorption cylinder (2) and the heat storage ( 19), cold head
(21) is housed in a 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 controller for adjusting the output of the refrigerator. , (26) a third extraction path which branches out from the gas introduction path (4) upstream of the ozone generator (6) and
A bypass path connected downstream of the mass flow controller (18) of (15), and a mass flow controller (27) interposed in the bypass path (26). The heat storage element (19) is composed of a copper block or a liquid tank storing liquid florinate, and the adsorption tube (2) is disposed so as to be buried in the heat storage element (19).

A description will be given of a case where the ozone gas purification apparatus having the above-described configuration is used to supply ozone gas having a high concentration to ozone consuming equipment. The supply of high-concentration ozone gas in this ozone gas purification device includes an adsorption step,
It consists of a purification step and a desorption step, and the adsorption column (2) is maintained at a predetermined cooling temperature (for example, 173K) throughout all the steps. In the adsorption step, the first extraction path (8) is opened,
Ozone is generated using the oxygen gas from the oxygen gas storage container (3) as a raw material with the gas introduction path (4) opened while the second extraction path (11) and the third extraction path (15) are closed. The ozone-oxygen mixed gas generated in the vessel (6) is supplied to the adsorption column (2), and the ozone gas in the mixed gas is adsorbed to the adsorbent (1) under atmospheric pressure by saturated adsorption. At this time, the ozone gas which has not passed through the adsorption column (2) together with the oxygen gas without being adsorbed by the adsorbent (1) is decomposed by the ozone decomposer (10) when passing through the first extraction passage (8), and (Atmosphere).

When the ozone gas is saturated and adsorbed on the adsorbent (2), the process is switched to the purification step. In the refining process, the second extraction path (1
1) is opened, the first extraction path (8) and the third extraction path (15) are closed, and the gas introduction path (4) is closed.
By actuating (14), the pressure atmosphere of the adsorption cylinder (2) is reduced up to the partial pressure of ozone in the ozone-oxygen mixed gas supplied from the ozone generator (6). And the ozone gas is included in the gas flowing out at the time of this decompression operation,
The ozone gas is decomposed by an ozone decomposer (13) interposed in the second extraction path (11), and is discharged from a vacuum pump (14) to the outside. The pressure atmosphere of the adsorption cylinder (2) in this purification step is maintained at about 5.3 kPa (40 torr) when the concentration of ozone generated by the ozone generator (6) is 5 vol%.

When the pressure in the adsorption cylinder (2) drops to a predetermined pressure, the operation is switched to a desorption step. In this desorption step, 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 channel opening / closing control valve (12) is opened / closed so as to maintain the atmospheric pressure in the purification step. Since the third extraction path (15) is connected to an ozone consuming facility which is maintained in a vacuum state or a state close to a vacuum, adsorption is performed by a pressure difference between the internal pressure of the adsorption cylinder (2) and the internal pressure of the ozone consuming facility. The gas component in the cylinder (2) moves to the ozone consuming equipment, and the internal pressure of the adsorption cylinder (2) decreases, so that the ozone adsorbed and held by the adsorbent (1) desorbs and moves to the ozone consuming equipment sequentially. Will do. During the desorption step, the second extraction path (11) operates the flow path opening / closing control valve (12) so that the pressure inside the adsorption cylinder (2) is maintained at the pressure set in the purification step. .

By supplying oxygen from the bypass passage (26), the concentration of ozone gas supplied to the ozone consuming equipment can be adjusted. Then, when the mass flow meter (17) interposed in the third extraction path (15) reaches the preset integrated flow rate, the desorption step is completed.

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 (2) and (2) are mounted on a common heat storage body (19). Then, while one adsorption column (2) is in the desorption step, the other adsorption column (2) is in a standby state after completing the adsorption step and the purification step. Therefore, the third exit route (15)
When the mass flow meter (17) interposed in the apparatus has reached a preset integrated flow rate, continuous removal can be performed by switching the adsorption cylinder (2) to be used.

Incidentally, an adsorption cylinder (2) having an inner volume of 0.25 liter is filled with 175 g of silica gel (adsorbent), and an ozone-oxygen mixed gas having an ozone concentration of 5 vol% is supplied at 1.2 liter / min. In this case, the adsorbent (1) was in a state of saturated adsorption in about 90 minutes. It took about 5 minutes to reduce the pressure from that state to 5.3 kPa. When ozone was extracted at a flow rate of 10 SCCM while maintaining the internal pressure of the adsorption cylinder (2) at 5.3 kPa, ozone gas having an ozone concentration of 80 vol% or more could be continuously extracted for 3 hours.

In each of the above embodiments, the pulse tube refrigerator (20) is used as the refrigerator for cooling the adsorption tube (2), but the refrigerator may be of any type. But,
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 released from the adsorption tube (2) is not limited to oxygen gas, but may be nitrogen gas or another gas.

[0022]

According to the present invention, since the ozone gas adsorbed by the adsorbent in the cooled state is desorbed by controlling the pressure in the adsorption cylinder, the ozone gas having a stable concentration can be extracted during the gas extraction period. Can be. Does not require a buffer tank to average the concentration of desorbed gas,
The entire device can be reduced in size accordingly.

Ozone gas is desorbed from the adsorbent by a pressure difference between the pressure in the adsorption cylinder and the internal pressure of the ozone consuming equipment,
Since the ozone gas is transferred, the ozone gas can be supplied at a stable flow rate even at a small flow rate.

Further, in the present invention, since the ozone gas is selectively adsorbed from the ozone-oxygen mixed gas to the adsorbent in the cooled state and the atmospheric pressure, the adsorbed amount can be increased, and the adsorbent can be used throughout. , Because it is maintained in a constant cooling state, it is easy to control the amount of adsorption,
The operation can be controlled by detecting the remaining amount from the integrated discharge flow rate.

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 must be controlled under the same conditions. Therefore, even when the apparatus is switched and used, the state of the ozone gas supplied to the ozone consuming equipment can be made uniform without any control.

Further, 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. be able to.

[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 on-off valve, 10… Ozone decomposer, 11… Second extraction path, 12…
Channel opening / closing control valve, 13… Ozone decomposer, 14… Vacuum pump,
15 ... third extraction path, 16 ... flow path on-off valve, 17 ... mass flow meter, 18 ... mass flow controller, 20 ... refrigerator.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Kunihiko Koike 4-5-1, Katsube, Moriyama City, Shiga Prefecture Inside Shiga Technology Center, Iwatani Corporation (72) Shoichiro Kenya 4-5, Katsube, Moriyama City, Shiga Prefecture No. 1 In Iwatani Gas Co., Ltd. (72) Inventor Eiichi Sugaya 4-5-1 Katsube, Moriyama-shi, Shiga F-term in Iwatani Gas Development Laboratory Co., Ltd. 4G042 AA07 CA05

Claims (6)

[Claims] An adsorbing step in which an ozone gas generated by an ozone generator (6) is saturatedly adsorbed at atmospheric pressure to an adsorbent (1) cooled by a refrigerator (20); A purification step of depressurizing and exhausting the inside of the adsorption column (2) to a partial pressure of the supplied ozone gas, and ozone consumption maintaining a vacuum state while maintaining the cooled and depressurized state of the adsorption column (2) 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 in communication with the equipment. 2. A plurality of adsorption cylinders (2) arranged in parallel are cooled by a single refrigerator (20), and one of the adsorption cylinders (2) is cooled by one of the adsorption cylinders (2). During the desorption step, the other adsorption column (2) is allowed to complete the adsorption step or the purification step, and is used when the gas extraction amount from each adsorption column (2) reaches a preset integrated extraction amount. 2. The method for supplying high-concentration ozone gas according to claim 1, wherein the adsorption cylinder is switched. 3. The high-concentration ozone gas supply method according to claim 1, wherein the refrigerator (20) for cooling the adsorbent (2) is constituted by a pulse tube refrigerator. 4. An adsorption cylinder (2) filled with an adsorbent (1) is configured to be able to be cooled by a refrigerator (20), and the adsorption cylinder (2) and an ozone generator (6) are introduced with gas. Connected by road (4)
The purified ozone extraction passage (5) derived from (2) is connected to a flow passage opening / closing valve.
(9) and a first extraction path (8) open to the atmosphere via an ozone decomposer (10), and a vacuum pump (14) via a flow path opening / closing control valve (12) and an ozone decomposer (13). (2)
1), and a third outlet path (15) that communicates with the ozone consuming equipment via the flow path on-off valve (16), the mass flow meter (17), and the mass flow controller (18). In a state where only the first extraction passage (8) is opened, ozone is adsorbed to the adsorbent (1) in the adsorption tube (2), and only the second extraction passage (11) is opened. In the open state, the interior of the adsorption cylinder (2) is evacuated to the partial pressure of the supplied ozone gas under reduced pressure, and when the third extraction path (15) and the second extraction path (11) are open, the adsorbent is adsorbed in the adsorption cylinder (2). A high-concentration ozone gas supply device configured to desorb ozone gas from (1). 5. A plurality of adsorption cylinders (2) filled with an adsorbent (1) are arranged in parallel, and the plurality of adsorption cylinders (2) can be cooled by one refrigerator (20). 5. The high-concentration ozone gas supply device according to claim 4, wherein the plurality of adsorption cylinders (2) are selectively connected to the ozone consuming equipment. 6. The high-concentration ozone gas supply device according to claim 4, wherein the refrigerator (20) for cooling the adsorption cylinder (2) is a pulse tube refrigerator.