JP5453844B2 - High concentration ozone supply method and liquid ozone storage vessel - Google Patents

Description

  The present invention relates to a vessel portion that accumulates ozone in an apparatus that supplies high-concentration ozone gas concentrated by liquefying ozone gas.

In recent years, the use of ozone (element symbol: O ₃ ) has been developed in various fields including water and sewage treatment using its strong oxidizing power. In particular, in the field of manufacturing semiconductor devices, application to Si wafer cleaning and TEOS-CVD (Tetra Ethyl Ortho Silicon-Chemical Vapor Deposition) is being studied. In Si wafer cleaning, ozone water in which ozone gas is dissolved in pure water is used as a cleaning liquid, and it has been announced that heavy metals and organic substances on Si wafer can be removed by using together with dilute hydrofluoric acid aqueous solution (electronic material 1999). March issue PP. 13-18). TEOS-CVD is used to form an interlayer insulating film when a semiconductor element is formed into a multilayer wiring, and is characterized in that the unevenness of the wafer surface caused by the electrodes can be planarized by the insulating film. It has been reported that the planarization performance is improved by adding ozone to the TEOS-CVD (Jpn. J. Appl. Phys. Vol. 32 (1993) PP. L110-L112).

  These are examples using ozone gas with a relatively low concentration of about 10%, but by using ozone gas with a relatively high concentration of 80% or more, there is a possibility of a new application that could not be considered by conventional ozone gas usage. Has begun to be pointed out. As an example, there is an oxide film formation of a Si semiconductor disclosed in JP-A-8-335576. According to this publication, it is possible to form an oxide film at a relatively low temperature, which is impossible with the conventional thermal oxidation method, and to form a high-quality oxide film with less suboxide layer and defect structure. Has been.

  By the way, a silent discharge system is generally used to generate ozone gas. This generates a mixed gas of ozone and oxygen from oxygen gas by electric discharge. Due to the limit of generation efficiency and danger of explosion, it is difficult to generate ozone gas of about 10% by volume or more under normal temperature and pressure. It was.

  Therefore, Patent Document 1 introduces a method of generating high-concentration ozone gas of 80% or more by temporarily liquefying and storing the generated ozone gas and then vaporizing it. This method will be described with reference to the liquid ozone production apparatus shown in FIG.

  This apparatus for producing liquid ozone is composed of an ozone gas generator and an exhaust device 1 and a liquid ozone generator 2 for liquefying ozone. Oxygen gas is sent from the oxygen cylinder 3 to the ozonizer 5 through the pressure adjustment valve 4. In the ozonizer 5, the oxygen gas becomes an ozone-containing oxygen gas in which ozone gas is mixed with oxygen by silent discharge, and passes through a mass flow controller 6 for controlling the flow rate and a particulate removal filter 7 for removing particulates in the ozone-containing gas. It is introduced into a liquid ozone generator 2 that liquefies ozone gas.

  In the liquid ozone generator 2, as shown in detail in FIG. 5, the ozone-containing oxygen gas obtained by mixing the ozone gas with the oxygen gas introduced from the ozone gas generator 1 is converted into the flow rate adjusting valve 8 and the ozone-containing oxygen gas introduction pipe. 25 is introduced into the ozone chamber 9. The ozone chamber 9 is thermally coupled to a cold head 19 that has been cooled by a refrigerator 20 that is driven in advance by a compressor 21, and is within 0.1 K by a temperature sensor 24, a heater 23, and a temperature control device 22. The temperature can be precisely controlled with temperature accuracy, and is kept at a low temperature of 80K to 100K.

  The principle of liquefaction of ozone gas is to liquefy only ozone gas by the difference in vapor pressure between ozone and oxygen. For example, at 1 atmosphere, ozone has a boiling point of 161K, while oxygen has a boiling point of 90K. Therefore, if it is cooled to a temperature of 90K or more and less than 161K, most of ozone is in a liquid state and most of oxygen is in a gaseous state, so that only ozone can be separated as a liquid.

  Actually, since it is handled under reduced pressure conditions for safety against explosive properties of high-concentration ozone, the separation conditions are determined by the difference between the vapor pressures of ozone and oxygen under the temperature and pressure conditions. For example, when considering a case where the temperature is 90K and the pressure is 10 mmHg (= 13.3 hPa), the vapor pressure of ozone is almost 0 mmHg (= 0 Pa) at 90K, but oxygen is about 690 mmHg (= 918 hPa), and only ozone is under this condition. Liquefied.

  Thus, in the ozone chamber 9, only ozone gas is liquefied by the difference in vapor pressure between ozone and oxygen at the cooled temperature. When the ozone gas is liquefied, the valve 15 between the oxidation treatment container 16 is closed and the valve 10 connected to the ozone killer 11 is opened. Oxygen gas that is not liquefied through the ozone discharge pipe 26 and the valve 10 connected to the ozone chamber 9 is introduced into the ozone killer 11 that is heated and converted into oxygen so that the remaining ozone gas is not discharged to the outside. A gas cooler 12 for cooling the heated oxygen gas and a liquid nitrogen trap 13 for preventing the ozone chamber 9 from being contaminated or mixed with carbides from the vacuum pump 14 are discharged to the outside by the vacuum pump 14. The

  When the liquefied liquid ozone 27 is used for the purpose of oxidation or the like in the oxidation treatment container 16, the flow rate adjusting valve 8 and the valve 10 are closed and the valve 15 is opened. By raising the temperature of the ozone chamber 9 thermally coupled to the cold head 19 by the temperature sensor 24, the heater 23 and the temperature control device 22, liquid ozone is vaporized as ozone gas through the ozone discharge pipe 26 and the valve 15. It is introduced into the oxidation treatment container 16. In addition, the safety valve 18 is for expelling liquid ozone or high-concentration ozone gas.

  In Patent Document 2, a plurality of ozone chambers are connected in parallel to enable continuous supply of high-concentration ozone gas.

  In an ozone generator using liquid ozone, the purity of liquid ozone is high, and the concentration of ozone gas generated therefrom is close to 100%. In general, high-concentration ozone gas causes a rapid self-decomposition reaction and may cause an explosion.

  Therefore, in the present ozone generator, in order to suppress the occurrence of ozone explosion, the temperature of the ozone chamber is controlled so that the pressure of the vaporized ozone gas is 10000 Pa or less.

Japanese Patent Publication No. 5-17164 JP 2003-20209 A

  However, in such an ozone generator, the pressure when supplying ozone gas to the process device is limited. Therefore, when supplying a large amount of ozone gas, there arises a problem that a sufficient supply amount cannot be obtained due to a pressure loss in the supply piping section.

  In addition, depending on the process to be performed, ozone gas having a concentration of nearly 100% is too reactive, so the ozone gas may be diluted before use. As a method of diluting the high-concentration ozone gas, there is a method of mixing in the mixing chamber 51 with a dilution gas whose flow rate is controlled by the mass flow controller 44 as shown in FIG.

  However, when a pipe portion having conductance characteristics such as a valve 47 and a filter 48 is inserted between the ozone chamber 9 and the mixing chamber 51, the conductance between the ozone chamber 9 and the mixing chamber 51 is changed when the amount of dilution gas changes. The characteristics will change. In this case, the flow rate of the high-concentration ozone gas varies, and it becomes difficult to supply the high-concentration ozone gas with a correct dilution amount.

  Therefore, an object of the present invention is to provide a high-concentration ozone supply method and an ozone storage vessel that can supply high-concentration ozone gas with an accurate concentration even if the amount of supply gas changes.

  The high-concentration ozone supply method of the present invention that achieves the above object provides the ozone concentration necessary for the reaction accurately regardless of the amount of ozone supply by providing a space for diluting ozone in the vessel that accumulates high-concentration ozone. It can be supplied.

The high-concentration ozone supply method of the present invention includes a ozone chamber for accumulating liquefied ozone, and a liquid ozone accumulating vessel that generates high-concentration ozone gas by vaporizing liquid ozone accumulated in the ozone chamber. The filter for removing particulates contained in the gas discharged from the chamber is cylindrical, the upper end of the filter is connected to the ceiling surface of the chamber, and the lower end of the filter is connected to the bottom surface of the chamber , is communicated hollow part and the communicating of the filter pipe for discharging the high-concentration ozone gas is generated by introducing a diluent gas into the hollow portion of the front Symbol filter, it diluted the ozone gas, the diluted gas in the vessel It supplies to the apparatus provided outside.

  In the high-concentration ozone supply method, when a second filter for removing particulates in the gas introduced into the ozone chamber is integrally provided on the lid of the chamber, a vessel for accumulating liquid ozone from the outside is provided. It is possible to prevent fine particles from penetrating into the body.

  Furthermore, in the high-concentration ozone supply method, when the liquid ozone permeation preventing member for preventing the liquefied ozone permeation is provided at the lower end of the cylindrical filter, the liquid ozone permeates the gas to the dilution part. Can be prevented.

Liquid ozone storage vessel of the present invention has an ozone chamber for storing liquefied ozone, the ozone stored liquid a vaporized high-concentration liquid ozone storage vessel to the ozone gas generating in the ozone chamber In the ozone chamber, a cylindrical filter is prepared so that the upper end of the filter is connected to the ceiling surface of the chamber and the lower end of the filter is connected to the bottom surface of the chamber, and diluted in the hollow portion of the filter. A dilution gas supply means for introducing a gas is provided at the bottom of the chamber.

  According to the high concentration ozone supply method and the liquid ozone storage vessel described above, the high concentration gas can be diluted in the liquid ozone storage vessel.

  Therefore, according to the above invention, it is possible to supply high-concentration ozone gas having an accurate concentration even if the supply gas amount changes.

(A) Apparatus sectional drawing which shows the structure of the vessel for liquid ozone storage which concerns on 1st Embodiment of this invention, (b) Apparatus sectional drawing which shows the ozone dilution method by the ozone storage apparatus which concerns on 1st Embodiment of this invention. Schematic which shows the ozone dilution control method which concerns on 1st Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an apparatus cross-sectional view showing the configuration of an accumulation vessel obtained by improving the liquid ozone accumulation vessel according to the first embodiment of the present invention. The schematic sectional drawing of the liquid ozone manufacturing apparatus which concerns on a prior art. The detailed schematic sectional drawing of the liquid ozone manufacturing apparatus which concerns on a prior art. Schematic which shows the high concentration ozone gas dilution control method which concerns on a prior art.

  A high-concentration ozone supply method according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  FIG. 1A is a cross-sectional view showing a configuration of a liquid ozone storage vessel according to the first embodiment of the present invention, and FIG. 1B is an ozone storage device according to the first embodiment of the present invention. FIG. 2 is an apparatus cross-sectional view showing an ozone dilution method, and FIG. 2 is a schematic view showing an ozone dilution control method according to the first embodiment of the present invention.

  As shown in FIG. 1A, a liquid ozone storage vessel 30 according to the first embodiment includes an ozone chamber 31 that stores liquid ozone, a gas introduction pipe 32 that is supplied with a gas containing ozone gas, and an ozone-containing gas. Are provided with a gas discharge pipe 33 through which other gas (for example, oxygen) and high-concentration ozone gas are discharged, and a dilution gas introduction pipe 43.

  In the ozone chamber, a filter 35 for removing fine particles in the gas supplied to the outside is provided. The accumulated ozone is supplied to an external device (not shown) through the filter 35.

  The filter 35 has, for example, a cylindrical shape, and the upper end of the filter 35 is connected to the ceiling surface of the ozone chamber 31, and the lower end of the filter 35 is connected to the bottom surface of the ozone chamber 31. An outer peripheral portion 41 of the filter 35 and an ozone exhaust portion 42 (a hollow portion of the filter 35) are formed. The liquid ozone storage unit 41 communicates with the gas introduction pipe 32, and the ozone exhaust unit 42 communicates with the gas discharge pipe 33.

  At this time, a fluororesin seal 36 is provided at the upper end of the filter 35 and a liquid ozone permeation preventing member 40 is provided at the lower end of the filter 35.

  The fluororesin seal 36 prevents gas movement between the ozone exhaust part 42 and the liquid ozone storage part 41 without passing through the filter 35.

  The material of the liquid ozone permeation prevention member 40 is a fluororesin or the like, and the shape of the permeation prevention member 40 may be, for example, a cylindrical shape. The height of the liquid ozone permeation preventing member 40 is set to be higher than the height of the accumulated liquid ozone.

  The dilution gas introduction pipe 43 is provided at the bottom of the ozone chamber 31. Then, a dilution gas for diluting the high-concentration ozone gas is introduced from the dilution gas introduction pipe 43 into the gas exhaust part 42.

  A cooling block 37 is provided on the outer periphery of the bottom of the ozone chamber 31. When accumulating liquid ozone, the cooling block 37 sets the ozone chamber 31 to a temperature at which only ozone gas is liquefied by means such as cooling the ozone chamber 31 with a helium refrigerator or the like. When ozone is supplied, the temperature of the ozone chamber 31 is controlled by the cooling block 37 to a temperature at which liquid ozone is vaporized.

  First, the case where the ozone storage vessel 30 according to the present invention stores liquid ozone will be described.

  An ozone-containing gas (ozone concentration of 10% or more) supplied from an ozone gas generator (not shown) is introduced into the ozone chamber 31 through a gas introduction pipe 32.

  The bottom of the ozone chamber 31 is cooled by a cooling block 37, and only ozone gas is liquefied in the ozone chamber 31, and liquid ozone is accumulated. The remaining gas (for example, oxygen gas) passes through the filter 35 and enters the gas exhaust part 42, and is discharged from the gas exhaust pipe 33 to the outside of the liquid ozone storage vessel 30. In this manner, liquid ozone is accumulated in the liquid ozone accumulation vessel 30.

  Next, a method for diluting the high-concentration ozone gas will be described with reference to FIG.

  As shown in FIG. 1 (b), the dilution gas is introduced from the dilution gas introduction pipe 43. The diluted gas is mixed with high-concentration ozone gas in the gas exhaust unit 42, and the diluted ozone gas is supplied from the storage vessel 30 to the process chamber (not shown). At this time, the cooling block 37 controls the temperature in the ozone chamber 31 so that the liquid ozone is vaporized, and the liquid ozone 39 is supplied as ozone gas.

  That is, the liquid ozone 39 is vaporized, and high-concentration ozone gas is accumulated in the liquid ozone reservoir 41. The high-concentration ozone gas in the liquid ozone reservoir 41 passes through the filter 35 by vacuum evacuation, enters the gas exhaust unit 42, is mixed with the dilution gas, and passes from the liquid ozone accumulation vessel 30 through the gas exhaust pipe 33 to the external device. (Not shown).

  Further, a method for controlling dilution of high-concentration ozone gas will be described in detail with reference to FIG.

  As shown in FIG. 2, the dilution gas introduction pipe 43 for introducing the dilution gas into the liquid ozone accumulation chamber 30 is provided with a mass flow controller 44 for adjusting the amount of oxygen gas for dilution. A process chamber 49 is connected to the liquid ozone storage chamber 30 via a gas filter 48 and a flow rate adjustment valve 47. An ozone chamber vacuum gauge 45 is provided between the ozone storage vessel 30 and the gas filter 48, and a supply line vacuum gauge 46 is provided between the gas filter 48 and the flow rate adjustment valve 47.

  A dilution gas having a flow rate necessary for the reaction in the process chamber 49 is caused to flow by the mass flow controller 44, and the ozone chamber pressure at that time is measured by the vacuum gauge 45. Then, the dilution gas is lowered to a flow rate corresponding to the concentration required for the reaction in the process chamber 49, and at the same time, the ozone chamber 30 is adjusted to change the amount of ozone vaporized from the liquid ozone. Adjust to the measured pressure.

  As described above, since the high-concentration ozone generation unit and the mixing unit of the dilution gas are connected in the shortest distance, the variation in conductance characteristics is small, and the high-concentration ozone gas can be accurately diluted to a concentration necessary for the reaction. Therefore, ozone gas with an accurate concentration can be supplied.

  As described above, the liquid ozone storage vessel 30 according to the first embodiment can dilute high concentration ozone in the storage vessel 30 and supply the diluted ozone gas.

  Therefore, even if the supply gas amount changes, it is possible to supply high-concentration ozone gas having an accurate concentration.

  In addition, since the dilution gas is not sprayed directly on the liquid ozone part, the gas can be diluted safely in the ozone chamber 31.

  Furthermore, since ozone gas can be diluted in the ozone accumulation chamber 31, it is not necessary to install a mixing chamber outside.

  Therefore, it is possible to improve the safety of the high-concentration ozone supply device, reduce the size of the high-concentration ozone supply device, and supply ozone with an accurate concentration.

  Next, an ozone storage vessel obtained by improving the ozone storage vessel according to the first embodiment of the present invention will be described with reference to FIG.

  FIG. 3 is an apparatus cross-sectional view showing a configuration of an ozone storage vessel 50 obtained by improving the ozone storage vessel according to the first embodiment of the present invention.

  As shown in FIG. 3, the ozone storage vessel 50 includes a filter 34 for removing fine particles in the introduced gas so as to be built in a gas introduction pipe portion in the lid portion 38 of the ozone chamber 31.

  With such a configuration, it is possible to prevent fine particles in the gas introduced into the storage vessel 50 from entering the chamber, so that the safety of the storage vessel 50 is improved.

  That is, by providing the gas introduction pipe 32 and the filter 34 integrally with the lid portion 38 of the storage vessel 50, it is not necessary to provide a filter in the external pipe (not shown), and a plurality of storage vessels 50 are connected in parallel. The connection piping can be simplified.

  Further, by simplifying the connecting pipe, the dead space in the pipe is reduced, and corrosion on the inner surface of the pipe is less likely to occur. That is, contamination of impurities into ozone gas is reduced.

  Therefore, it is possible to reduce the size of the high concentration ozone supply device and improve the safety of the high concentration ozone gas supply device.

30, 50 ... Vessel 31 for accumulating liquid ozone ... Ozone chamber 33 ... Gas outlet 34, 35 ... Filter 38 ... Lid 40 ... Liquid ozone permeation prevention member 43 ... Dilution gas introduction pipe (dilution gas supply means)
44 ... Mass flow controller 49 ... Process chamber

Claims (4)

It has an ozone chamber that accumulates liquefied ozone ,
In a liquid ozone storage vessel that generates high-concentration ozone gas by vaporizing liquid ozone stored in the ozone chamber ,
The filter for removing fine particles contained in the gas discharged from the ozone chamber is cylindrical,
The upper end of the filter is on the ceiling surface of the chamber,
Further, the lower end of the filter is connected to the bottom surface of the chamber,
Furthermore, in order to discharge the generated high-concentration ozone gas, the piping is communicated with the hollow portion of the filter ,
By introducing a diluent gas into the hollow portion of the front Symbol filter, it diluted the ozone gas,
A method for supplying high-concentration ozone, comprising supplying the diluted gas to an apparatus provided outside the vessel. The high-concentration ozone supply method according to claim 1, wherein a second filter for removing particulates in the gas introduced into the ozone chamber is integrally provided on the lid of the chamber. 3. The high-concentration ozone supply method according to claim 1, wherein a liquid ozone permeation preventing member for preventing the liquefied ozone permeation is provided at a lower end of the cylindrical filter. It has an ozone chamber that accumulates liquefied ozone ,
The ozone accumulated liquid into the ozone chamber and vaporized a high concentration ozone gas liquid ozone storage vessel for generating,
In the ozone chamber, a cylindrical filter is provided so that the upper end of the filter is connected to the ceiling surface of the chamber, and the lower end of the filter is connected to the bottom surface of the chamber,
A vessel for accumulating liquid ozone, characterized in that dilution gas supply means for introducing a dilution gas into the hollow portion of the filter is provided at the bottom of the chamber.

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