Device and method for producing gas solution and cleaning device

A gas solution producing device having a simple structure to reduce a start-up time, and capable of reducing an amount of gas or solution for use, and a method therefor, as well as a cleaning device employing them. An ozone water solution producing device of the present invention includes a gas dissolving module for bringing ozone gas and deionized water in contact with each other for production of ozone solution, a gas introducing pipe for introducing ozone gas from an ozone gas producing device to the gas dissolving module, a buffer, connected on the gas introducing pipe, for temporarily storing ozone gas and thereafter discharging the gas stored to the gas introducing pipe, a first valve for opening or closing the gas introducing pipe to switch introduction and suspension of gas flow to the gas dissolving module, and backflow prevention valve for preventing a backflow of the gas discharged from the buffer.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a device and method for producing gas
 solution, such as hydrogen solution, ozone solution, or the like, for
 preferable use in cleaning of substrates or the like used in production of
 electronic components and other such devices, and also to a cleaning
 device employing the gas solution producing device.
 2. Description of the Related Art
 In the field of electronic devices (semiconductor devices, LCD panels, and
 so on), a step of cleaning substrates (semiconductor or glass substrates,
 and so on) is included in all production process. During cleaning, foreign
 objects, including organic material (e.g., particles, photoresists, and so
 on) in the atmosphere in a clean room, which have become attached to the
 substrates must be removed. There is therefore great interest in cleaning
 solutions superior in cleaning performance and preferable for use in such
 cleaning. Some candidates of such solution are ozone solution and hydrogen
 solution, and so on, which can be obtained by dissolving gas (ozone,
 hydrogen, and so on) in deionized water. As a method for dissolving these
 gases into deionized water, a method for bringing gas into contact with
 deionized water via hollow fiber membrane is well known conventionally.
 FIG. 13 is a diagram showing a conventional ozone solution producing device
 90. The ozone solution producing device 90 mainly comprises an ozone
 producing device 91 and a gas dissolving module 92. The gas dissolving
 module 92 is, for example, a cylinder vessel accommodating a number of
 hollow fiber membranes, and supplied with ozone gas produced in the ozone
 producing device 91, as well as deionized water. When ozone gas and
 deionized water are introduced into the gas dissolving module 92, the
 ozone gas flows into each hollow fiber membrane, while the deionized water
 fills interior space of the vessel. Then, when the ozone gas and deionized
 water come into contact with each other via the hollow fiber membranes,
 the ozone gas is dissolved into the deionized water and an ozone solution
 consisting of ozone dissolved in deionized water is produced. The
 resultant ozone solution is supplied to, for example, a nozzle 93 of a
 cleaning device, for use in cleaning.
 The above-mentioned conventional ozone solution producing device, however,
 has the following shortcomings. The conventional electrolytic ozone
 producing device for general use is constructed, for protection of the
 electrodes, such that ozone production cannot be suspended. Moreover, as
 the starting up of a gas dissolving module requires a relatively longer
 period of time, ozone production must be continued to ensure stable ozone
 concentration. Thus, there is no choice but to discard unused ozone
 solution. In addition, as the ozone producing device and the gas
 dissolving module are directly connected to each other via a pipe, ozone
 gas is always supplied to the gas dissolving module whether or not ozone
 solution is used. In other words, while ozone solution is not used, ozone
 gas is wastefully thrown away. This results in a very inefficient device.
 In order to improve the efficiency of such equipment, there has been
 proposed a structure in which a valve is provided in a pipe connecting the
 ozone producing device and the gas dissolving module. With this structure,
 the valve is closed while ozone solution is not used, to thereby stop
 supply of ozone gas. As a result, waste of ozone gas can be prevented.
 However, generally, as the total capacity of the hollow fiber membranes in
 an ozone solution producing equipment is relatively large compared to the
 amount of ozone gas produced, a relatively long time is required before
 the ozone gas concentration in the hollow fiber membranes becomes
 stabilized in a normal condition after supply of ozone gas is resumed.
 This results in a long time before ozone concentration of the ozone
 solution reaches a predetermined value, or a long start-up time, and thus
 an equipment of a reduced operation rate.
 On the other hand, where ozone solution may be needed quickly for cleaning,
 a constant supply of ozone gas to the gas dissolving module must be
 maintained. Not only may this result in a waste of ozone gas, provision of
 the valve becomes meaningless.
 In addition, components of the above-mentioned equipment, including pipes,
 must be highly pressure resistive as pressure increases on the ozone
 producing device side when the valve is closed, particularly, for a long
 time.
 SUMMARY OF THE INVENTION
 The present invention has been conceived to remedy the aforementioned
 shortcomings and aims to provide a device for producing gas solution,
 having a simple structure to reduce start-up time, and capable of reducing
 the amount of gas or solvent in use, and a method therefor, as well as a
 cleaning device employing the device and method.
 In order to achieve the above object, according to the present invention,
 there is provided a gas solution producing device. The device comprises
 gas dissolving means for receiving gas and solvent as material of gas
 solution and bringing the gas and the solvent to contact to each other to
 thereby dissolve the gas into the solvent; a gas introducing path for
 introducing the gas from a gas supply source to the gas dissolving means;
 gas storing means, provided on the gas introducing path, for temporarily
 storing the gas, and, after having stored a predetermined amount of gas,
 for discharging the gas stored to the gas introducing path; switching
 means, provided at a connection between the gas introducing path and the
 gas storing means or a position on the gas introducing path closer to the
 gas dissolving means than the connection, for switching introduction and
 suspension of the gas flowing into the gas dissolving means by opening or
 closing the gas introducing path; and stored gas backflow prevention
 means, provided at the connection between the gas introducing path and the
 gas storing means or a position on the gas introducing path closer to the
 gas supply source, for preventing the gas discharged from the gas storing
 means from backflowing to the gas supply source side.
 Further, according to the present invention, there is provided a method for
 producing gas solution using the above described gas solution producing
 device. The method comprises the steps of temporarily storing a
 predetermined amount of gas in the gas storing means while introduction of
 the gas from the gas supply source to the gas dissolving means is
 suspended by the switching means closing the gas introducing
 path;discharging, thereafter, the gas stored in the gas storing means to
 the gas dissolving means by the switching means opening the gas
 introducing path; and dissolving the gas into the solvent in the gas
 dissolving means by bringing the gas and the solvent into contact with
 each other.
 A gas solution producing device of the present invention as described above
 comprises gas storing means, provided on the way of a gas introducing path
 connecting the gas supply source and the gas dissolving means, switching
 means, provided on a position on the gas introducing path closer to the
 gas dissolving means than a connection between the gas introducing path
 and the gas storing means, and stored gas black-flow preventing means,
 provide on a position on the gas introducing path closer to the gas supply
 source than the connection between the gas introducing path and the gas
 storing means.
 With this arrangement, gas from the gas supply source is introduced into
 the gas storing means for temporal storage therein while gas introduction
 to the gas dissolving means is suspended by the switching means closing
 the gas introducing path. Thereafter, the gas introducing path is opened,
 whereby the gas temporarily stored in the gas storing means is discharged
 toward the gas dissolving means. During discharge, because stored gas
 backflow prevention means is provided to the gas solution producing
 device, the discharged gas does not flow back to the gas supply source,
 and is reliably introduced to the gas dissolving means side. When the gas
 and the solvent contact each other in the gas dissolving means, gas
 solution, containing gas dissolved in the solvent, is produced. It should
 be noted that the switching means and the stored gas black-flow prevention
 means are not necessarily separate entities, and may be a single component
 having both functions of these means.
 A conventional gas solution producing device, in which a gas producing
 device is directly connected to a gas dissolving module, is very
 inefficient because produced gas is wasted when gas solution is not used.
 In contrast, in a gas solution producing device of the present invention,
 gas may be supplied to and stored in a gas storing means while gas
 introduction to the gas dissolving means is suspended, and, when a
 predetermined amount of gas has been stored, the stored gas can be quickly
 introduced to the gas dissolving means. With this arrangement, gas
 concentration in the dissolution membrane in the gas dissolving means can
 be increased rapidly, and the time necessary for ozone concentration to
 reach a predetermined value can be reduced. As a result, there can be
 provided a highly efficient gas solution producing device with a shot
 start-up time. in addition, gas is not wasted, and a pressure increase in
 a pipe constituting a gas introducing path can be suppressed.
 In the above described gas solution producing device, a plurality of gas
 storing means, instead of only one, are provided on the way of the gas
 introducing path. The device may comprise switching control means for
 controlling such that, when gas stored in at least one of the plurality of
 gas storing means is discharged to the gas introducing path, gas to be
 supplied by the gas supply source to other gas storing means is
 temporarily stored, and the stored gas is not discharged to the gas
 introducing path.
 In this case, a preferred gas solution producing method is a method
 comprising the steps of temporarily storing a predetermined amount of gas
 in at least one of the plurality of gas storing means while introduction
 of the gas from the gas supply source to the gas dissolving means is
 suspended by the switching means closing the gas introducing path; opening
 the gas introducing path by the switching means; repeating, under control
 of the switching control means and while desirably selecting gas storing
 means, the operation of discharging the gas stored in at least one of the
 plurality of gas storing means to the gas dissolving means, while storing
 a predetermined amount of gas in at least one of other gas storing means;
 and dissolving the gas into the solvent in the gas dissolving means by
 bringing the gas and the solvent into contact with each other.
 In a gas solution producing device of the present invention, gas
 concentration of the produced gas solution can be controlled by
 controlling an amount of gas to be introduced to the gas dissolving means
 in a certain time period, i.e., a gas introducing speed. That is, when the
 gas introducing speed is high, gas concentration of the gas solution will
 be high. Then, when a plurality of gas storing means are provided so that
 gas is discharged alternately from the plurality of gas storing means to
 the gas dissolving means at different gas introducing speeds, gas
 solutions of different gas concentrations can be produced. This structure
 is effective when ozone solution with different concentrations must be
 prepared, one for use intact in cleaning and the other for mixture with
 hydrofluoric acid so that the resultant solution is used in cleaning.
 The gas dissolving means may be a type in which a gas and solvent are
 brought into contact with each other via a dissolution membrane whereby
 the gas is dissolved into solvent. For example, as described in the
 section of related art, use of a gas dissolving module consisting of
 bundles of hollow fiber membranes in a vessel, can ensure a sufficiently
 large contact area between the gas and the solvent, and efficient
 dissolution can be attained. Also, preferably, the capacity of the gas
 storing means for storing gas is larger than the sum of the amount of gas
 allowed to remain in the gas dissolving means and the amount of gas
 allowed to remain in a part of the gas introducing path, the part between
 the gas dissolving means and the connection between the gas introducing
 path and the gas storing means. With this arrangement, the gas in the gas
 dissolving means can be exchanged at a high speed.
 The gas storing means may include a gas storing section for storing the gas
 by enlarging a capacity thereof and for discharging the gas by reducing
 the capacity, and a driving mechanism for causing the gas storing section
 to change the capacity as desired. For example, a gas storing section may
 be a cylinder and a piston, or a vessel of an extendable bellows type. A
 driving mechanism may be provided in association with the gas storing
 section for driving the piston or the bellows-type vessel. A gas storing
 section may be made of stainless steel (preferably covered by passivated
 film at parts thereof directly contacting gas), fluororesin in, glass, and
 so on.
 Also, preferably, the gas storing means has speed changing means for
 changing a speed at which to discharge gas stored to the gas introducing
 path.
 A preferable gas solution producing method according to the present
 invention is a method in which discharge of the gas stored in the gas
 storing means is carried out following two steps, including a first
 discharge of the gas stored to the gas dissolving means at a predetermined
 speed, and a second discharge of the gas stored to the gas dissolving
 means at a speed slower than the speed in the first discharge.
 As described above, when two-step discharge, including first and second
 discharges, is carried out, gas concentration is rapidly increased to a
 predetermined value by supplying the gas stored, into the gas dissolving
 means at a relatively high speed in first discharge operation, and the gas
 concentration can thereafter be maintained constant at a predetermined
 value by supplying the gas stored into the gas dissolving means at a speed
 slower than that in the first discharge operation.
 A cleaning device of the resent invention is characterized by possession of
 a gas solution producing device of the present invention.
 A cleaning device of the present invention enables to construct a gas
 solution producing device with a short start-up time and an efficient rate
 of gas usage, and makes it possible to have an available cleaning device
 with a high operation rate. Such cleaning device is desirable for use in
 manufacturing of various electronic devices, such as semiconductor
 devices, LCD panels, and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 Embodiment 1
 In the following, a first preferred embodiment of the present invention
 will be described with reference to FIGS. 1 to 5.
 FIG. 1 is a diagram showing a schematic structure of an ozone solution
 producing device (a gas dissolved solution producing device) according to
 a first preferred embodiment of the present invention. This is an example
 of a device for producing ozone solution for use in cleaning of substrates
 of semiconductor devices, LCD panels, and so on, in a production line
 thereof.
 An ozone solution producing device 1 in this embodiment comprises an ozone
 producing device 2 (a gas supply source), a gas dissolving module 3 (a gas
 dissolving means), and a gas introducing pipe 4 (a gas introducing path)
 for introducing ozone gas from the ozone producing device 2 to the gas
 dissolving module 3, as shown in FIG. 1. In the path of the gas
 introducing pipe 4, a buffer 5 (a gas storage means) having a sufficient
 capacity for storing a predetermined amount of ozone gas, e.g., on the
 order of a few hundreds cc, is provided. The capacity of the buffer 5 is
 larger than the sum of the capacity of a part of the gas introducing pipe
 4 between the gas dissolving module 3 and the connection between the gas
 introducing pipe 4 and the buffer 5, and the capacity of the inside of the
 gas dissolving module 3. In the gas introducing pipe 4, at a position
 closer to the gas dissolving module 3 than the connection between the gas
 introducing pipe 4 and the buffer 5, a first valve 6 (a switching means)
 is provided for controlling the flow of ozone gas inside the gas
 introducing pipe 4. Also, in the gas introducing pipe 4, at a position
 closer to the ozone producing device 2 than the connection between the gas
 introducing pipe 4 and the buffer 5, a check valve 7 (a stored gas
 backflow prevention means) is provided for preventing the ozone gas
 discharged from the buffer 5 from flowing back into the ozone producing
 device 2.
 In addition, the gas dissolving module 3 is further connected to a
 deionized water introducing pipe 8 for introducing deionized water
 thereto, a redundant gas discharge pipe 9 for discharging redundant ozone
 gas, or gas remaining as being unable to be dissolved in the deionized
 water, and an ozone solution draining pipe 10 for draining produced ozone
 solution. In the path of the deionized water introducing pipe 8, a second
 valve 11 is provided for passing/blocking the flow of deionized water in
 the pipe. The end of the ozone solution draining pipe 10 is connected to a
 place where the produced ozone solution is used, such as a nozzle 12 of a
 cleaning device in this embodiment. It should be noted that the gas
 dissolving module 3 is identical to a conventional one, which accommodates
 a number of hollow fiber membranes (dissolution membranes).
 The buffer 5 is a syringe, constituting of a cylinder 13 and a piston 14,
 as shown in FIG. 2(A). With the piston 14 pulled out of the cylinder 13,
 ozone gas of an amount corresponding to the inner capacity of the cylinder
 13 is stored inside the cylinder 13. With the piston 14 being pressed into
 the cylinder 13, as shown in FIG. 2(B), the ozone gas, stored inside, is
 discharged from the cylinder 13. The piston 14 is driven by a driving
 mechanism 15, shown in FIG. 1, such as an air cylinder. The driving
 mechanism 15, the first valve 6, and the second valve 11 of the ozone
 solution producing device 1 operate interlockingly under control by the
 controlling device 16. The driving mechanism 15 is constructed such that
 it can drive the piston 14 at either a constant speed or at a speed
 varying depending on a command from the control device 16 (a speed
 changing means).
 Next, operation (sequence) of the above structured ozone solution producing
 device 1 will be described referring to FIG. 3.
 In the device of this embodiment, a constant flow (e.g., 0.5 liter/hr) of
 ozone gas is produced in the ozone gas producing device 2, as shown in
 FIG. 3. Note that, in actuality, the ozone producing device 2 produces
 mixture gas of O.sub.2 and O.sub.3, about 10% thereof being O.sub.3 gas.
 Thus, the total amount of gas produced by the ozone producing device 2 is
 about 5 liters/hr. During a period from time 0 to time t1, where the first
 valve 6 remains closed, ozone gas is stored in the buffer 5 (see FIG. 3,
 the rightward rising line for "gas amount in buffer"). The second valve 11
 also then remains closed, so that no deionized water is introduced to the
 gas dissolving module 3.
 At time t1, the first valve 6 is opened, and the piston 14 of the buffer 5
 is pressed into the cylinder 13 by the driving mechanism 15, whereby ozone
 gas of about 100 to 200 cc, stored in the buffer 5, is introduced to the
 gas dissolving module 3. Simultaneously, the second valve 11 is opened,
 whereby deionized water is introduced into the gas dissolving module 3 and
 thus brought into contact to the ozone gas via the hollow fiber membranes
 in the inside of the module, so that production of ozone solution is
 started.
 For discharging the ozone gas stored in the buffer 5 to the gas dissolving
 module 3, a two-step discharge operation is carried out. In FIG. 3, the
 line for "gas amount in buffer" in a discharging area (a rightward
 declining part) consists of a sharply declining line and a moderately
 declining line. The sharply declining line represents first discharge
 operation for supplying ozone gas into the gas dissolving module 3 at a
 relatively high speed, while the moderately declining line represents
 second discharge operation for supplying ozone gas into the gas dissolving
 module 3 at a relatively slow speed. As time passes time t1, the ozone
 concentration in the ozone solution begins to rise. That is, as ozone gas
 is rapidly supplied to the gas dissolving module 3 through the first
 discharge operation, ozone concentration in the ozone solution rapidly
 increases from 0, and thereafter continuously increases through the second
 discharge operation to predetermined concentration. During the period from
 time t1 to t2, the first valve 6 and the second valve 11 both remain open.
 At time t2, the first valve 6 is closed, and the piston 14 is pulled out of
 the buffer 5 by the driving mechanism 15, whereby operation for storing
 ozone gas in the buffer 5 is resumed. Simultaneously, the deionized valve
 11 is also closed, whereby introduction of deionized water to the gas
 dissolving module 3 is suspended, so that production of ozone solution is
 discontinued. The above operation will thereafter be repeated.
 According to the ozone solution producing device 1 in this embodiment, it
 is possible to retain ozone gas in the buffer 5 while introduction of the
 ozone gas to the gas dissolving module 3 is suspended, and, after a
 predetermined amount of ozone gas has been stored, the stored ozone gas
 can be rapidly introduced to the gas dissolving module 3. With this
 arrangement, ozone concentration in the hollow fiber membranes in the gas
 dissolving module 3 can be rapidly increased so that the time required for
 the ozone concentration in the ozone solution to reach a predetermined
 value can be reduced. In particular, as discharge operation of the gas
 from the buffer 5 to the gas dissolving module 3 is carried out at
 two-step sequence in this embodiment, in which the ozone gas is introduced
 into the gas dissolving module 3 initially at a high speed, start-up of
 ozone concentration in the ozone solution can be accelerated. As a result,
 as is obvious from the above description on the operation, a highly
 efficient ozone solution producing device can be realized through
 reduction of a short start-up time of ozone concentration when ozone
 solution is used, and elimination of wasted ozone gas when ozone solution
 is not used as ozone gas is not introduced into the gas dissolving module
 3. Similarly, according to an ozone solution producing device 1 of the
 present invention, the amount of deionized water to be used can be
 reduced. Further, a pressure increase in the gas introducing pipe 4 can be
 suppressed as ozone gas flows into the buffer 5 even when the first valve
 6 is closed.
 It should be noted that the buffer 5, which is a syringe in the above, may
 be a buffer 17 comprising a vessel 18 of a bellows type, as shown in FIG.
 4(A). As for the buffer 17, a convex 18a may be formed on the inside
 bottom of the vessel 18 so that as much gas as possible can be discharged,
 leaving little, if any, gas inside, when the vessel 18 is contracted to
 the extreme, as shown in FIG. 4(B).
 In addition, instead of using two separate valves of the first valve 6 for
 switching between supplies of ozone gas from the ozone producing device 2
 to the gas dissolving module 3 side and to the buffer 5 side, and the
 check valve 7 for preventing backflow of the ozone gas to the ozone
 producing device 2 side when the stored ozone gas is discharged, as shown
 in FIG. 1, a three-way valve having two functions, namely, a switching
 function and a backflow preventing function, may be used, as shown in
 FIGS. 5(A) to 5(C). FIG. 5(A) shows a state in which a gas path connects
 the ozone producing device 2 and the buffer 5 with the gas dissolving
 module 3 being cut off, so that the gas is stored in the buffer 5. FIG.
 5(B) shows a state in which a gas path connects between the buffer 5 and
 the gas dissolving module 3 with the ozone producing device 2 being cut
 off, so that the gas stored in the buffer 5 is discharged to the gas
 dissolving module 3. FIG. 5(C) shows a state in which a gas path connects
 the ozone producing device 2 and the gas dissolving module 3 with the
 buffer 5 being cut off, so that the gas from the ozone producing device 2
 is directly introduced to the gas dissolving module 3 for production of
 ozone solution. That is, the example in FIG. 1, which does not have a
 sequence for introducing gas from the ozone producing device 2 directly to
 the gas dissolving module 3 for ozone solution production, may be
 reconstructed into the structure shown in FIGS. 5(A) to 5(C) so that ozone
 solution can be produced through direct introduction of gas from the ozone
 producing device 2 to the gas dissolving module 3.
 Embodiment 2
 In the following, a second preferred embodiment of the present invention
 will be described with reference to FIGS. 6 to 8.
 FIG. 6 is a diagram showing a schematic structure of an ozone solution
 producing device in this embodiment. This structure is almost identical to
 that of the device in the first embodiment, with the only difference being
 that a plurality of buffers (specifically, two) are provided. Components
 of the device in FIG. 6 corresponding to those in FIG. 1 are given
 identical reference numerals and their detailed explanation is not
 repeated here.
 In the ozone solution producing device 21 in this embodiment, two buffers,
 namely a first buffer 22a and a second buffer 22b, are provided in the gas
 introducing pipe 4, which connects the ozone producing device 2 and the
 gas dissolving module 3. The first and second buffers 22a, 22b are
 connected to driving mechanisms 23a, 23b, respectively, and the respective
 pistons of the buffers 22a, 22b are independently driven by the
 controlling device 16.
 Next, operation (sequence) of the ozone solution producing device 21 in
 this embodiment will be described with reference to FIG. 7.
 As shown in FIG. 7, a constant flow (e.g., 0.5 liter/hr) of ozone gas is
 produced by the ozone producing device 2. During a period from time 0 to
 time t1, the first valve 6 remains closed and the piston of the first
 buffer 22a remains pulled out, so that ozone gas can be stored in the
 first buffer 22a, while the piston of second buffer 22b remains pressed
 therein, so that no ozone gas is stored in the second buffer 22b. As a
 result, ozone gas is being stored in the first buffer 22a during the
 period from 0 to t1. During this period, the second valve 11 also remains
 closed, so that no deionized water is introduced to the gas dissolving
 module 3.
 At time t1, the first valve 6 is opened, and the piston of the first buffer
 22a is pressed into the first buffer 22a by the driving mechanism 23a,
 whereby a predetermined amount of ozone gas, stored in the first buffer
 22a, is introduced to the gas dissolving module 3. Simultaneously, the
 second valve 11 is opened, whereby deionized water is introduced into the
 gas dissolving module 3 and brought into contact with the ozone gas via
 the hollow fiber membranes in the inside of the module, so that first
 ozone solution production is started (see FIG. 7, indicated by reference
 I).
 For discharging the ozone gas stored in the buffer 22a to the gas
 dissolving module 3, two-step discharge operation is carried out at high
 and low flow speeds, which is similar to the first embodiment, so that
 ozone concentration of the ozone solution can increase rapidly to a steady
 state. On the other hand, at time t1, the piston of the first buffer 22a
 is pressed in the first buffer 22a, and, simultaneously, the piston of the
 second buffer 22b is pulled out, so that storage of ozone gas from the
 ozone producing device 2 in the second buffer 22b is started. It should be
 noted that the speed at which the piston of the second buffer 22b is
 pulled out is less than half of the speed at which the piston of the first
 buffer 22a is pressed into the first buffer 22a, as is obvious from the
 change in the amount of gas stored in the first and second buffers 22a,
 22b during a period from t1, t2, to t3 in FIG. 7. Thus, most of the ozone
 gas pushed out from the first buffer 22a is introduced to the gas
 dissolving module 3, with only a negligible amount of gas moving to the
 second buffer 22b side.
 At time t2, by which point discharge of ozone gas from the first buffer 22a
 to the gas dissolving module 3 has been completed, the first valve 6 and
 the second valve 11 are both closed, so that the first ozone solution
 production is halted. At this point, ozone gas is still stored in the
 second buffer 22b.
 At time t3, the first valve 6 is opened, and the piston of the second
 buffer 22b is pressed into the second buffer 22b by the driving mechanism
 23b, whereby a predetermined amount of ozone gas, stored in the second
 buffer 22b, is introduced into the gas dissolving module 3. At the same
 time, the second valve 11 comes to be in an open state, and deionized
 water is supplied to the gas dissolving module 3 to be brought into
 contact with ozone gas via the hollow fiber membranes in the module, so
 that second ozone solution production is started (indicated by reference
 numeral II in FIG. 7). Then, when, in response to a command from the
 controlling device 16, an amount of ozone gas to be stored in the second
 buffer 22b or the speed at which ozone gas is to be supplied to the gas
 dissolving module 3 or the like, is changed from the values for the first
 buffer 22a, ozone concentration of the produced ozone solution can be
 changed from that of the first ozone solution production. Also, at time
 t3, the piston of the second buffer 22b is pressed in the second buffer
 22b, and the piston of the first buffer 22a is pulled out, so that ozone
 gas storing operation is resumed on the first buffer 22a side.
 At time t4, by which point discharge of the ozone gas from the second
 buffer 22b to the gas dissolving module 3 has been completed, the first
 valve 6 and the second valve 11 are both in a closed state, so that the
 second ozone solution production is halted. At this time, ozone gas is
 still stored in the first buffer 22a. The above operation will thereafter
 be repeated. That is, under control by the controlling device 16 (a switch
 control means), gas storing operation and gas discharge operation are
 carried out alternately, not simultaneously, with respect to the first
 buffer 22a and the second buffer 22b.
 As described above, the ozone solution producing device 21 of this
 embodiment can attain the same advantage as that which would be obtained
 in the first preferred embodiment, specifically, realization of a highly
 efficient ozone solution producing device with a short start-up time and
 less waste of ozone gas or deionized water. Further, a device configured
 according to this embodiment can produce an additional advantage, such
 that ozone solution with two different concentrations can be produced due
 to provision of two buffers 22a, 22b by changing an amount of gas allowed
 to be stored or a speed at which to discharge the gas, and so on, for the
 respective buffers 22a, 22b. Thus, this embodiment is particularly
 effective in a case where ozone solution with different concentrations
 must be prepared, one for use intact in cleaning and the other for mixture
 with hydrofluoric acid so that the resultant solution is used in cleaning.
 Note that, although, as shown in FIG. 6, the first valve 6 for switching
 between supplies of ozone gas from the ozone producing device 2 to the gas
 dissolving module 3 side and to the buffers 22a and 23b, and the check
 valve 7 for preventing backflow of the ozone gas to the ozone producing
 device 2 side when the stored ozone gas is discharged are shown as
 separate components in this embodiment, as in the case of the first
 embodiment, these valves may be substituted by a single three-way valve
 24, which has both switching function and backflow prevention function, as
 shown in FIG. 8(A) to 8(C). FIG. 8(A) shows a gas path connecting the
 ozone producing device 2 and the first buffer 22a, and another gas path
 connecting the second buffer 22b and the gas dissolving module 3, so that
 gas is stored on the first buffer 22a side and gas is discharged from the
 second buffer 22b side. FIG. 8(B) shows a gas path connecting the ozone
 producing device 2 and the second buffer 22b, and another gas path
 connecting the first buffer 22a and the gas dissolving module 3, so that
 gas is stored on the second buffer 22b side, and gas is discharged from
 the first buffer 22a side. FIG. 8(C) shows a gas path connecting the ozone
 producing device 2 and the gas dissolving module 3 with the first buffer
 22a and the second buffer 22b being both blocked, so that gas from the
 ozone producing device 2 is directly introduced to the gas dissolving
 module 3 for use in ozone solution production. That is, the example in
 FIG. 6, which does not have a sequence for producing ozone solution
 through direct introduction of gas from the ozone producing device 2 to
 the gas dissolving module 3, may be reconstructed into a structure shown
 in FIGS. 8(A) to 8(C), to allow direct introduction of gas from the ozone
 producing device 2 to the gas dissolving module 3 for gas solution
 production.
 Embodiment 3
 In the following, a third preferred embodiment of the present invention
 will be described with reference to FIG. 9.
 FIG. 9 is a diagram showing a schematic structure of an ozone solution
 producing device in this embodiment. This embodiment is preferable
 particularly in a case, e.g., where a plurality of ozone solution
 producing devices are connected to a single ozone producing device in an
 electronic device manufacturing line including a plurality of cleaning
 devices.
 The ozone solution producing device 31 in this embodiment has a plurality
 of (three in this embodiment) gas introducing pipes 4a, 4b, 4c connected
 in parallel to a single ozone producing device 2, as shown in FIG. 9, and
 each gas introducing pipe also connected to two buffers 33a/33b, 33c/33d,
 or 33e/33f and one gas dissolving module 3a, 3b, or 3c, in much the same
 manner as the second embodiment. The structures of the first valve 6 and
 the backflow prevention valve 7 are identical to those in the first and
 second preferred embodiments.
 Supposing that three gas dissolving modules 3a, 3b, 3c connected to a
 single ozone producing device 2, as described above, and without a buffer
 are used, problems may result if production of ozone solution is halted in
 one of the three modules. Specifically, in such a situation, the remaining
 two modules may be supplied with an increased amount of gas corresponding
 to the amount which would otherwise be supplied to the suspended module,
 with a result that the ozone concentration of the ozone solution produced
 by the two modules may vary. In this embodiment, by contrast, as two
 buffers 33a/33b, 33c/33d, or 33e/33f are provided to each of the gas
 introducing pipes 4a, 4b, and 4c so that gas can be stored in the buffers
 33a to 33f when ozone solution is not used in any pipe system, an amount
 of gas to be supplied to other systems will not vary significantly. Thus,
 ozone concentration of the produced ozone solution can be stabilized.
 Embodiment 4
 A fourth preferred embodiment of the present invention will next be
 described with reference to FIG. 10.
 FIG. 10 is a diagram showing a schematic structure of a gas solution
 producing device in this embodiment. This embodiment is preferable
 particularly as associated equipment of a cleaning device, e.g., which
 employs two or more different cleaning solutions containing such gasses as
 ozone, hydrogen, and the like.
 A gas solution producing device 41 of this embodiment comprises three pipe
 systems, connected to a single gas dissolving module 3, including a
 nitrogen gas introducing pipe 45 connected to a nitrogen gas supply source
 42, an ozone gas introducing pipe 46 connected to an zone gas supply
 source 43, and a hydrogen gas introducing pipe 47 connected to a hydrogen
 gas supply source 44. The nitrogen gas introducing pipe 45 is provided, in
 the middle thereof, with a valve 48 and a check valve 49, while the ozone
 gas introducing pipe 46 and the hydrogen gas introducing pipe 47 are
 additionally provided, between a valve 48 and a check valve 49, with
 buffers 50a and 50b, respectively.
 The gas solution producing device 41 in this embodiment can produce two
 types of cleaning gas solution, i.e., ozone solution and hydrogen
 solution, and uses nitrogen gas as a substitutional gas when switching
 between ozone solution production and hydrogen solution production. That
 is, ozone gas discharge from the buffer 50a to the gas dissolving module 3
 and hydrogen gas discharge from the buffer 50b to the gas dissolving
 module 3 are carried out alternately in the same manner as the sequence of
 a device having two buffers in the second embodiment, so that ozone
 solution and hydrogen solution can be produced alternately using a single
 gas dissolving module 3. When switching between ozone gas discharge and
 hydrogen gas discharge, the valve 48 on the nitrogen gas introducing pipe
 45 remains open while valves 48 on the ozone gas introducing pipe 46 and
 the hydrogen gas introducing pipe 47 remain closed so that nitrogen gas is
 supplied to the gas dissolving module 3 for substitution of the residual
 gas therein.
 With the gas solution producing device 41 in this embodiment, two types of
 cleaning gas solution can be produced using a single gas dissolving module
 3, and an efficient device can thus be realized. In particular, ozone gas
 and hydrogen gas, which would otherwise react with each other, can be
 rapidly dissolved in deionized water without mixing. Also, as nitrogen gas
 is always supplied while switching between ozone gas discharge and
 hydrogen gas discharge, constant conditions can be ensured in the gas
 dissolving module at the time to start dissolution of ozone or hydrogen.
 Thus, constant dissolution condition of the effective components (gasses)
 can be ensured, which can improve consistency in gas concentration.
 Embodiment 5
 A fifth preferred embodiment of the present invention will be described
 with reference to FIG. 11.
 This embodiment is an example of a cleaning device equipped with a gas
 solution producing device. FIG. 11 is a diagram showing a schematic
 structure of a cleaning device 51 in this embodiment, which may be, e.g.,
 a device for sheet cleaning of large glass substrates (hereinafter simply
 referred to as a substrate), each being on the order of a few hundred
 square mm.
 The drawing shows a cleaning section 52, a stage 53, cleaning nozzles 54,
 55, 56, a substrate carrying robot 57, a loader cassette 58, an unloader
 cassette 59, a hydrogen water solution/ozone water solution producing
 section 60, a cleaning solution rejuvenation section 61, and a substrate
 W.
 As shown in FIG. 11, the middle of the upper surface of the device
 constitutes a cleaning section 52, where a stage 53 is formed for holding
 a substrate W. A concave in a rectangular shape corresponding to the shape
 of a substrate W is formed on the stage 53 so that the substrate W can be
 fit into the concave and supported on the stage 53 such that the surface
 of the substrate W and the surface of the stage 53 come into close contact
 with each other. Also, space is formed in the lower part of the concave,
 into which a substrate elevation shaft protrudes from the lower part of
 the stage 53. At the lower end of the substrate elevation shaft, a shaft
 driving source, such as a cylinder, is provided, so that the substrate
 elevation shaft and accordingly the substrate W also are moved vertically
 due to the operation of the cylinder when a substrate W is positioned on a
 substrate carrying robot 57 (described later). Note that a nozzle
 protrudes through an opening on the middle part of the stage, for cleaning
 the rear surface of the substrate W. With this arrangement, the rear
 surface of a substrate can be roughly cleaned while the front surface
 thereof is mainly cleaned in this device.
 A pair of rack bases 62 are provided opposing each other with the stage 53
 intervening, and cleaning nozzles 54, 55, 56 are formed bridging between
 the rack bases 62. Cleaning nozzles comprise three nozzles arranged in
 parallel, each for cleaning in different manners. In this embodiment,
 these three nozzles are a hydrogen water supersonic cleaning nozzle 54 for
 cleaning with hydrogen water solution while applying supersonic vibration
 by a supersonic element 63, an ozone supersonic cleaning nozzle 55 for
 cleaning with ozone water solution while applying supersonic vibration by
 a supersonic element 63, and a deionized water rinsing nozzle 56 for
 rinsing with deionized water. These three nozzles sequentially move along
 the rack bases 62 above the substrate W while keeping a constant distance
 from the substrate W, so that the entire area of the substrate W is
 cleaned in three different cleaning agents.
 As a nozzle moving means, horizontally movable sliders are provided along
 the linear guides on the respective rack bases 62. Pillars are formed on
 the upper surfaces of the respective sliders, to which both ends of the
 cleaning nozzles 54, 55, 56 are fixed. Driving sources, such as a motor,
 are provided on the respective sliders, so that the respective sliders
 automatically move on the rack bases 62. When the driving sources (motors)
 on the respective sliders operate in response to a control signal from the
 controlling device (not shown) of the device, the cleaning nozzles 54, 55,
 56 individually move horizontally. Also, a driving source, such as a
 cylinder (not shown), is provided to the pillar so that the height of the
 respective cleaning nozzles 54, 55, 56, i.e., the distances between the
 respective cleaning nozzles and the substrate W, can be adjusted by
 vertical movement of the pillars.
 The respective cleaning nozzles 54, 55, 56 are referred to as push/pull
 nozzles, in which each has an introducing path and a draining path. The
 introducing path has an introducing opening formed on one end thereof for
 introducing cleaning solution. The draining path has a draining opening
 formed on one end thereof for draining the cleaning waste solution. The
 introducing path and the draining path cross over to each other at the
 other ends thereof, thereby constituting a crossing section. An opening is
 formed on the crossing section, facing the substrate W. In this case, the
 opening is formed extending at least longer than the width of the
 substrate W in the direction perpendicular to the direction in which
 cleaning nozzles 54, 55, 56 are arranged in parallel (in this embodiment,
 three crossing sections and openings are formed for each cleaning nozzle,
 the three openings combined extending longer than the width of the
 substrate W). A pressure reducing pump is employed as a pressure control
 device provided on the discharge path side. The force for sucking the
 cleaning solution on the crossing section is controlled by using the
 pressure reducing pump so that the pressure of the cleaning solution in
 contact with the atmosphere via the opening section (including surface
 tension of the cleaning solution and that of the surface to be cleaned of
 the substrate W) is balanced with the atmosphere pressure. That is, when
 Pw.apprxeq.Pa is held for the relationship between the pressure Pw of the
 cleaning solution in contact with the atmosphere via the opening section
 (including surface tension of the cleaning solution and that of the
 surface to be cleaned of the substrate W) and the air pressure Pa, the
 cleaning solution supplied via the opening section to the substrate W and
 thus brought into contact therewith is directed to the draining path
 without leakage to the outside of the cleaning nozzle. That is, the
 cleaning solution supplied from the cleaning nozzle to the substrate W is
 removed from the substrate W, without contacting parts other than the part
 via which the cleaning solution was supplied, or the opening section.
 Further, a supersonic element 63 is provided above the crossing section,
 opposing the substrate W, so that supersonics are applied to the cleaning
 solution while the substrate W is being cleaned.
 On the flank side of the cleaning section 52, there are formed a hydrogen
 water solution/ozone water solution producing section 60 and a cleaning
 solution rejuvenation section 61. The hydrogen water solution/ozone water
 solution producing section 60 incorporates a hydrogen solution producing
 device 64 and an ozone solution producing device 65, as described in the
 preceding embodiment. These cleaning solutions can be produced by
 dissolving hydrogen gas or ozone gas into deionized water. Hydrogen
 solution, produced by the hydrogen solution producing device 64, is
 supplied to the hydrogen supersonic cleaning nozzle 54 via a liquid
 feeding pump 67, provided on the hydrogen solution supply pipe 66.
 Similarly, ozone solution, produced by the ozone solution producing device
 65, is supplied to the ozone supersonic cleaning nozzle 55 via the liquid
 feeding pump 69, provided on the ozone solution supply pipe 68. Note that
 the deionized water rinse cleaning nozzle 56 is supplied with deionized
 water from a deionized water supply pipe (not shown) in a manufacturing
 line.
 The cleaning solution rejuvenation section 61 is provided with filters 70,
 71 for removing particles and other foreign materials in the cleaning
 solution after cleaning. Specifically, the filter 70 for removing
 particles and other foreign materials in hydrogen solution and a filter 71
 for removing those in ozone solution are provided separately. That is,
 used hydrogen water, drained from the drain opening of the hydrogen water
 supersonic cleaning nozzle 54, is fed to a filter 70 by a liquid feeding
 pump 73, provided on the hydrogen water collecting pipe 72. Similarly,
 used ozone water, drained from the drain opening of the ozone supersonic
 cleaning nozzle 55, is fed to a filter 71 by a liquid feeding pump 75,
 provided on the ozone solution collecting pipe 74.
 Then, hydrogen water filtered via the filter 70 is supplied to the hydrogen
 supersonic cleaning nozzle 54 by a liquid feeding pump 77, provided on the
 rejuvenated hydrogen solution supply pipe 76. Similarly, ozone water
 filtered via the filter 71 is supplied to the ozone supersonic cleaning
 nozzle 55 by a liquid feeding pump 79, provide on the rejuvenated ozone
 solution supply pipe 78. Also, the hydrogen water supply pipe 66 and the
 rejuvenated hydrogen water supply pipe 76 are connected to each other
 prior to the cleaning nozzle 54, so that whether to supply fresh or
 rejuvenated hydrogen water to the cleaning nozzle 54 can be switched by
 means of a valve 80. Similarly, the ozone water supply pipe 68 and the
 rejuvenated ozone solution supply pipe 78 are connected prior to the
 cleaning nozzle 55, so that whether to supply fresh or rejuvenated ozone
 solution can be switched by means of a valve 81. Note that hydrogen water
 and ozone water having been filtered by the respective filters 70, 71 are
 returned to the hydrogen solution producing device 64 or the ozone
 solution producing device 65 for supplement of hydrogen gas or ozone gas
 as gas concentration of such rejuvenated hydrogen or ozone water is
 reduced, though it does not contain particles.
 On the flank side of the cleaning section 52, the loader cassette 58 and
 the unloader cassette 59 are detachably provided. These two cassettes 58,
 59 have identical shapes allowing accommodation of a plurality of
 substrates W. The loader cassette 58 accommodates substrates W yet to be
 cleaned, while the unloader cassette 59 accommodates cleaned substrates W.
 A substrate carrying robot 57 is provided between the cleaning section 52
 and the loader cassette 58, the unloader cassette 59. The substrate
 carrying robot 57 has, at the upper part thereof, an arm 82 having an
 retractable link mechanism. The arm 82, which is provided rotatably and
 elevatably, supports and carries, by an end thereof, a substrate W.
 The thus structured cleaning device 51 operates automatically as operation
 of the respective components is controlled by a controlling device, except
 for determination of various cleaning conditions by an operator, such as
 distances between the cleaning nozzles 54, 55, 56 and a substrate W,
 moving speeds of the cleaning nozzles, the amount of cleaning solution to
 be supplied, and so on. Specifically, , when an operator using the
 cleaning device 51 operates a start switch after setting a substrate w yet
 to be cleaned on the loader cassette 58, the substrate carrying robot 57
 carries the substrate W from the loader cassette 58 to the stage 53, and
 hydrogen water supersonic cleaning, ozone water supersonic cleaning, rinse
 cleaning are sequentially, automatically applied using the respective
 cleaning nozzles 54, 55, 56, on the stage 53. After rinse cleaning, the
 substrate carrying robot 57 carries the cleaned substrate W to the
 unloader cassette 59 for accommodation.
 A cleaning device 51 of the present invention, which is constructed for
 cleaning in various cleaning methods, such as hydrogen water supersonic
 cleaning, ozone water supersonic cleaning, and rinse cleaning, by using
 three cleaning nozzles 54, 55, 56, allows application of various cleaning
 methods by using a single device. This enables thorough removal of various
 objects by removing objects on the surface of the substrate using hydrogen
 water supersonic cleaning and ozone water supersonic cleaning, and
 subsequently rinsing the surface of the substrate to wash out the cleaning
 solution attached thereon. Also, the device of this embodiment, in which
 hydrogen water solution/ozone water solution producing section 60 is
 provided and ozone solution producing device 65 is integrally incorporated
 thereinto, can use ozone water solution before the strength of ozone water
 is deteriorated, though the life of ozone is rather short. That is, ozone
 water supersonic cleaning can be applied effectively.
 In addition, as a cleaning device 51 of this embodiment comprises a
 hydrogen solution producing device 64 and an ozone solution producing
 device 65, which have a short start-up time and a high efficiency in use
 of gas and deionized water, there can be realized a cleaning device with a
 high operation rate and high productivity for preferable use in a
 manufacturing line of various electronic devices (such as semiconductor
 devices, LCD panels, and similar devices).
 It should be noted that the scope of the present invention is not limited
 to the above described embodiments, and can be applied to various
 amendments without departing from the gist of the present invention. For
 example, an ozone producing device, which is described above as one of the
 components of an ozone water solution producing device, may not be
 configured as a component of an ozone solution producing device, and ozone
 may be supplied from any external ozone gas supply source. Also, a
 structure of a gas dissolving module as a gas dissolving means and that of
 a buffer as a gas storing means, as well as a valve and a black-flow
 prevention valve, and so on, may be changed as necessary.
 Experiment
 The inventors of the present invention carried out an experiment to
 ascertain that the concentration of the effective components in a gas
 solution reliably increased rapidly when a gas storing means of the
 present invention was employed. This experiment will be described in the
 following.
 In a conventional ozone solution producing device without a buffer (a gas
 storing means) and an ozone solution producing device with a buffer
 according to the present invention, ozone gas was dissolved into deionized
 water using a gas dissolving module, so that change in ozone concentration
 of the resultant ozone water solution could be checked. In this
 experiment, the gas capacity of the gas dissolving module in use was 125
 cc, the amount of deionized water was 185 cc, the amount of ozone produced
 was 1 g/hour, ozone gas concentration was about 10% (volume ratio), and
 the flow rate of the deionized water was 2 liters/min. A syringe of 200 cc
 was used as a buffer. Ozone gas was driven for discharge by a cylinder
 pump. Discharge speed was 60 cc/min for the initial one second, and 2.5
 cc/min for subsequent 30 seconds. Produced ozone solution was introduced
 to an ozone concentration meter for measurement of ozone concentration, of
 which result is shown in FIG. 12. In FIG. 12, the ordinate represents time
 (seconds), and the abscissa represents ozone concentration (ppm). The
 broken line indicates the result obtained from a conventional ozone
 solution producing device, and the solid line indicates the result
 obtained from an ozone solution producing device of the present invention.
 As is obvious from FIG. 12, with the conventional device without a buffer,
 ozone concentration did not come to be in a normal state even after 60
 seconds after the start of supplying ozone. On the other hand, in the case
 of a device of the present invention, ozone concentration increased quite
 rapidly as ozone gas was supplied quickly at the start of supplying ozone,
 coming to be at the maximum value in about one second, and remaining so
 for about thirty seconds.
 As described above, the most significant feature of a device of the present
 invention is proved, i.e., the use of a buffer enables a quick increase of
 ozone concentration in a gas dissolving module immediately after the start
 of supplying gas, and, as a result, the ozone concentration in the
 resultant ozone solution can be increased quickly.
 As described in detail, according to the present invention, gas
 concentration in a gas dissolving means can be quickly increased, so that
 a time required until concentration of effective components in the gas
 solution comes to be at a predetermined value, can be reduced. As a
 result, a highly efficient gas dissolving producing device with a shorter
 start-up time and less waste of source gas and solvent can be realized.
 Also, employment of such a gas solution producing device make possible a
 cleaning device with a high operation ratio and high productivity, which
 is preferable for use in a manufacturing line for various electronic
 devices (LCD panels and so on).