Title:
Cleaning equipment and cleaning method
Kind Code:
A1


Abstract:
The present invention provides a cleaning equipment provided with a cleaning solution tank, a cleaning solution supply route for supplying the cleaning solution stored in the cleaning solution tank to a cleaning bath, a cleaning solution return route for returning the cleaning solution that has been supplied to the cleaning bath to the cleaning solution tank, a gas supply route for supplying a purge gas into the cleaning solution tank, and a gas discharge route for discharging the purge gas from the cleaning solution tank. Moreover, a cleaning solution discharge opening of the cleaning solution return route is immersed in the cleaning solution stored in the cleaning solution tank.



Inventors:
Nagai, Toshihiko (Hyogo, JP)
Kanno, Itaru (Tokyo, JP)
Yokoi, Naoki (Tokyo, JP)
Asaoka, Yasuhiro (Tokyo, JP)
Higashi, Masahiko (Tokyo, JP)
Application Number:
10/351361
Publication Date:
01/29/2004
Filing Date:
01/27/2003
Assignee:
Matsushita Electrical Industrial Co., Ltd. (Osaka, JP)
Mitsubishi Denki Kabushiki Kaisha (Tokyo, JP)
Primary Class:
Other Classes:
134/42, 134/157, 134/184, 134/201
International Classes:
B08B3/02; B08B3/00; B08B3/04; B08B3/10; C03C23/00; H01L21/00; H01L21/304; (IPC1-7): C23G1/36
View Patent Images:
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Primary Examiner:
KORNAKOV, MIKHAIL
Attorney, Agent or Firm:
McDERMOTT, WILL & EMERY (WASHINGTON, DC, US)
Claims:

What is claimed is:



1. A cleaning equipment comprising: a cleaning solution tank for storing a cleaning solution; a cleaning bath in which cleaning of an object to be cleaned is carried out using the cleaning solution; a cleaning solution supply route for supplying the cleaning solution stored in the cleaning solution tank to the cleaning bath; a cleaning solution return route for returning the cleaning solution that has been supplied to the cleaning bath to the cleaning solution tank; a gas supply route for supplying a purge gas into the cleaning solution tank; and a gas discharge route for discharging the purge gas from the cleaning solution tank; wherein a cleaning solution discharge opening of the cleaning solution return route is immersed in the cleaning solution that is stored in the cleaning solution tank.

2. The cleaning equipment according to claim 1, wherein the gas supply route has a first valve for restricting a frequency at which the purge gas is supplied.

3. The cleaning equipment according to claim 2, wherein the first valve is an electromagnetic valve.

4. The cleaning equipment according to claim 1, wherein the gas discharge route has a second valve for restricting the volume of discharged purge gas.

5. The cleaning equipment according to claim 4, wherein the second valve is a pressure regulating valve.

6. The cleaning equipment according to claim 1, wherein the cleaning solution supply route has a pressure pump for pressurizing and supplying the cleaning solution.

7. The cleaning equipment according to claim 1, wherein the cleaning solution stored in the cleaning solution tank is a volatile cleaning solution.

8. The cleaning equipment according to claim 7, wherein the volatile cleaning solution contains an organic solvent.

9. The cleaning equipment according to claim 1, wherein the purge gas is an inert gas.

10. The cleaning equipment according to claim 1, wherein the object to be cleaned is a semiconductor substrate or a glass substrate.

11. The cleaning equipment according to claim 10, wherein the cleaning bath is a cleaning bath of a batch-type or a single-wafer-type spin cleaning equipment.

12. A cleaning method comprising: a first step of supplying a cleaning solution that is stored in a cleaning solution tank into a cleaning bath in which cleaning of an object to be cleaned is carried out; a second step of returning the cleaning solution that has been supplied into the cleaning bath to the cleaning solution tank; a third step of supplying a purge gas to the cleaning solution tank; and a fourth step of discharging the purge gas from the cleaning solution tank; wherein the second step is performed using a cleaning solution return route having a cleaning solution discharge opening immersed in the cleaning solution that is stored in the cleaning solution tank.

13. The cleaning method according to claim 12, wherein the third step includes a step of reducing a frequency at which the purge gas is supplied.

14. The cleaning method according to claim 13, wherein the fourth step includes a step of reducing the volume of discharged purge gas.

15. The cleaning method according to claim 12, wherein the cleaning solution that is stored in the cleaning solution tank is a volatile cleaning solution.

16. The cleaning method according to claim 15, wherein the volatile cleaning solution contains an organic solvent.

17. The cleaning method according to claim 12, wherein the purge gas is an inert gas.

18. The cleaning method according to claim 12, wherein the object to be cleaned is a semiconductor substrate or a glass substrate.

19. The cleaning method according to claim 18, wherein the cleaning bath is a cleaning bath of a batch-type or a single-wafer-type spin cleaning equipment.

Description:

BACKGROUND OF THE INVENTION

[0001] The present invention relates to cleaning equipments having a system for circulating cleaning solution and cleaning methods using the same, and in particular relates to cleaning equipments and cleaning methods in which a volatile cleaning solution including an organic solvent or the like is used to perform cleaning of a semiconductor substrate or a glass substrate, for example.

[0002] In the cleaning step of manufacturing processes for semiconductor devices, for example, a substrate cleaning equipment having a system for circulating cleaning solution may be used. As for the schematic configuration of a batch-type spin cleaner for wafer, for example, such cleaners include a cleaning solution tank for storing cleaning solution and adjusting the temperature of the cleaning solution, and a chamber (cleaning bath) in which cleaning of a semiconductor substrate or the like is carried out.

[0003] If a volatile cleaning solution containing an organic solvent, for example, is used, then the component that is volatilized from the cleaning solution is present in the space above the liquid surface of the cleaning solution that is stored in the cleaning solution tank. Accordingly, an inert gas such as nitrogen is constantly supplied into the cleaning solution tank as a purge gas in order to prevent accidents such as the volatilized component igniting and exploding. More specifically, 5 to 25 L (liter) of an inert gas such as helium, argon, or nitrogen is supplied per minute to a cleaning solution tank having a 10 to 40 L capacity.

[0004] FIG. 5 shows the pipe structure of an ordinary batch-type spin cleaner for wafer.

[0005] As shown in FIG. 5, a cleaning solution 2 that is supplied into a cleaning bath 1 in which the cleaning of an object to be cleaned, such as a semiconductor substrate (not shown), is carried out is stored in a cleaning solution tank 3. To the cleaning tank 3 are attached a thermometer 4 for measuring the temperature of the cleaning solution 2 and a heat source 5 for heating the cleaning solution 2. That is, the cleaning solution 2 is maintained at a predetermined temperature by a feedback control using the thermometer 4 and the heat source 5, and thus the temperature of the cleaning solution 2 is controlled. If the cleaning solution 2 is volatile and the volatilized component from the cleaning solution 2 is ignitable, then an inert gas, as a purge gas, is flowed into a space 6 of the cleaning tank 3 from a gas supply pipe 7 in order to prevent the ignition and explosion of the volatilized component that is present in the space 6 above the liquid surface of the cleaning solution 2 that is stored in the cleaning solution tank 3. The inert gas and the volatilized component are discharged from the space 6 of the cleaning solution tank 3 via a gas discharge pipe 8. Thus, the volatilized component of the cleaning solution 2 is purged from the cleaning solution tank 3.

[0006] Also, as shown in FIG. 5, the cleaning solution 2 is first pressurized and pumped by a pump 9 on the cleaning solution 2 supply route from the cleaning solution tank 3 to the cleaning bath 1. The cleaning solution 2 subsequently passes through a filter 10 for removing foreign matters such as particles, a flow meter 11 for controlling the flow of the cleaning solution 2, and a valve 12 for switching the route of the cleaning solution 2, after which the cleaning solution 2 is expelled toward the object to be cleaned, such as a semiconductor substrate (not shown), arranged inside the cleaning bath 1 from a nozzle (not shown) attached to an upper portion the cleaning bath 1. Then, after the cleaning solution 2 has been applied to the object to be cleaned inside the cleaning bath 1, the cleaning solution 2 is discharged from the cleaning bath 1 through a drain (not shown) provided at a bottom portion the cleaning bath 1, and is returned to cleaning solution tank 3. That is, substrate cleaning is performed using a cleaning solution 2 that is circulated in the substrate cleaning equipment shown in FIG. 5.

[0007] It should be noted that during substrate cleaning (that is, when the equipment is in operation) the valve 12 opens a route over which the cleaning solution 2 is supplied to the cleaning bath 1, shown by the solid line, whereas when the device is in standby, the valve 12 opens a flow route for the cleaning solution 2, shown by the dashed line, over which the cleaning solution 2 is returned to the cleaning solution tank 3 without passing through the cleaning bath 1.

[0008] However, when the above-described conventional substrate cleaning equipment is used, the cleaning solution performance, that is, its cleaning ability, drops sooner than anticipated, and as a result, foreign matters such as particles adhered to the substrate are not removed and remain where they are, and this causes the problem of an increased defect density and thus diminished yield of the semiconductor devices, for example. On the other hand, frequently exchanging the cleaning solution so as to maintain the performance of the cleaning solution results in the problem of increased running costs for the cleaning solution. Also, in this case, it is necessary to stop the cleaning equipment when the cleaning solution is changed, which results in the problem of a drop in the productivity of the cleaning equipment.

SUMMARY OF THE INVENTION

[0009] In light of the foregoing, if a cleaning equipment having a system in which cleaning solution is circulated is used, it is an object of the present invention to obtain an excellent cleaning ability while keeping down costs related to the cleaning solution and increasing the productivity of the cleaning equipment by reducing the frequency at which the cleaning solution is exchanged and preventing deterioration of cleaning solution performance.

[0010] To achieve the foregoing objects, the inventors of the present application examined the cause of the premature drop in cleaning solution performance that occurs when conventional substrate cleaning equipments are used, and arrived at the following findings.

[0011] FIG. 6 illustrates the problematic aspects of conventional substrate cleaning equipments, and more particularly illustrates the problematic aspects of conventional cleaning solution tanks.

[0012] As shown in FIG. 6, a cleaning solution 52 that is stored inside a cleaning solution tank 51 is supplied from an outlet 53 provided in the bottom portion of the cleaning solution tank 51 to a cleaning bath (not shown) via a cleaning solution supply pipe 54. At this time, the cleaning solution 52 is pressurized and pumped by a pressure pump 55 that is provided in the cleaning solution supply pipe 54. On the other hand, the cleaning solution 52 that has been supplied into the cleaning bath is returned into the cleaning solution tank 51 from a cleaning solution discharge opening 57 that is provided in the ceiling portion of the cleaning solution tank 51 via a cleaning solution return pipe 56. Thus, cleaning is carried out by circulating the cleaning solution 52. A thermometer 58 and a heat source 59 are provided on the cleaning solution tank 51, and through a feedback control using the thermometer 58 and the heat source 59, the temperature of the cleaning solution 52 is adjusted.

[0013] Also, as shown in FIG. 6, there is a space 60 above the liquid surface of the cleaning solution 52 that is stored in the cleaning solution tank 51, or put differently, between the liquid surface of the cleaning solution 52 that is stored in the cleaning solution tank 51 and the ceiling portion of the cleaning solution tank 51. If the cleaning solution 52 is volatile and the component volatilized from the cleaning solution 52 is ignitable, then an inert gas serving as a purge gas is flowed from a gas supply opening 62 that is provided in the ceiling portion of the cleaning solution tank 51 into the space 60 via a gas supply pipe 61 in order to prevent the volatilized component that is present in the space 60 inside the cleaning solution tank 51 from igniting and exploding. On the other hand, the inert gas that is introduced into the space 60 and the volatilized component are discharged from a gas discharge opening 63 provided in the ceiling portion of the cleaning solution tank 51 via a gas discharge pipe 64. At this time, the volatilization of components included in the cleaning solution 52 (hereinafter, referred to as “specific components”) is promoted by the introduction of the inert gas into the cleaning solution tank 51. The reason for this is that the concentration of specific components in the cleaning solution 52 that is stored in the cleaning solution tank 51 and the concentration of specific components volatilized from the cleaning solution 52 in the space 60 are maintained at a constant equilibrium. Consequently, the greater the area of contact between the cleaning solution 52 and the inert gas inside the cleaning solution tank 51, the more the volatilization of specific components included in the cleaning solution 52 is facilitated.

[0014] Incidentally, in conventional substrate cleaning equipments, the cleaning solution 52 (dotted region of FIG. 6) that has been discharged from the cleaning solution discharge opening 57 via the cleaning solution return pipe 56 flows through the space 60 in a stream or a cylindrical fashion. For that reason, the contact area between the cleaning solution 52 and the inert gas inside the cleaning solution tank 51 becomes the total of the contact area between the cleaning solution 52 that is stored in the cleaning solution tank 51 and the inert gas and the contact area between the inert gas and the cleaning solution 52 that flows through the space 60 in a stream or cylindrical fashion. As a result there is noticeable volatilization of specific components from the cleaning solution 52, and as a result there is a danger that the performance of the cleaning solution 52 will drop. This danger becomes increasingly conspicuous if the usage temperature of the cleaning solution 52 is set at or above room temperature, and particularly if the cleaning solution 52 is used at an elevated temperature of about 50 to 100° C.

[0015] In the above-described conventional substrate cleaning equipment, the cleaning solution performance, that is, its cleaning ability, drops in a shorter period than expected because a large volume of specific components included in the cleaning solution is volatilized, and as a result, foreign matters such as particles adhered to the substrate are not removed and remain on the substrate, and this causes increased defect density and thus a diminished yield of semiconductor devices. On the other hand, if the cleaning solution is frequently exchanged in order to maintain the performance of the cleaning solution, then this conversely results in an increase in running costs for the cleaning solution and diminished productivity of the cleaning equipment.

[0016] From these circumstances, the inventors of the present application concluded that to achieve the objects of the present invention it is imperative that fluctuations in the cleaning solution composition are inhibited so as to stabilize the cleaning solution composition by inhibiting the volatilization of cleaning solution components in the cleaning solution tank of a cleaning equipment that has a system for circulating cleaning solution, or in other words, by inhibiting volatilization of cleaning solution components caused by contact between the purge gas that is introduced into the cleaning solution tank and the cleaning solution. Accordingly, the inventors of the present application arrived at the following cleaning equipments and cleaning methods.

[0017] More specifically, a cleaning equipment according to the present invention is provided with a cleaning solution tank for storing a cleaning solution, a cleaning bath in which cleaning of an object to be cleaned is carried out using the cleaning solution, a cleaning solution supply route for supplying the cleaning solution stored in the cleaning solution tank to the cleaning bath, a cleaning solution return route for returning the cleaning solution supplied to the cleaning bath to the cleaning solution tank, a gas supply route for supplying a purge gas into the cleaning solution tank, and a gas discharge route for discharging the purge gas from the cleaning solution tank, and a cleaning solution discharge opening of the cleaning solution return route is immersed in the cleaning solution that is stored in the cleaning solution tank.

[0018] According to the cleaning equipment of the present invention, the cleaning solution discharge opening of the cleaning solution return route for returning the cleaning solution to the cleaning solution tank is immersed in the cleaning solution that is stored in the cleaning solution tank. Put differently, the cleaning solution discharge opening is positioned below the liquid surface of the cleaning solution that is stored in the cleaning solution tank, and thus the problem, seen with conventional cleaning equipments in which the cleaning solution discharge opening is provided in the ceiling portion of the cleaning solution tank, of the cleaning solution that is discharged from the cleaning solution discharge opening dropping in a stream or a cylindrical manner through the space above the liquid surface of the cleaning solution that is stored in the cleaning solution tank is avoided. Put differently, the cleaning solution that is released from the cleaning solution discharge opening can be kept from coming into contact with the purge gas that is introduced into the cleaning solution tank. As a result, the area of contact between the cleaning solution and the inert gas within the cleaning solution tank can be reduced, and thus volatilization of cleaning solution components can be inhibited. Consequently, fluctuations in the cleaning solution composition are inhibited so that the cleaning solution composition can be stabilized, and thus cleaning solution performance, that is, its cleaning ability, can be kept from deteriorating. In addition, the frequency at which the cleaning solution is changed can be reduced because inhibiting volatilization of cleaning solution components allows the cleaning solution to be used for longer periods. Therefore, costs related to the cleaning solution can be kept down and the operation ratio of the cleaning equipment in production line can be increased, so that production costs can be significantly reduced.

[0019] In the cleaning equipment of the present invention, it is preferable that the gas supply route has a first valve for restricting a frequency at which the purge gas is supplied.

[0020] Thus, by using the first valve to lower the frequency at which the purge gas is supplied, the frequency at which the purge gas and the cleaning solution come into contact inside the cleaning solution tank can be reduced. Thus, volatilization of cleaning solution components, that is, fluctuations in the cleaning solution composition, can be inhibited even further, and thus the cleaning solution composition can be further stabilized.

[0021] In addition, in this case, the first valve can be an electromagnetic valve.

[0022] In the cleaning equipment of the present invention, it is preferable that the gas discharge route has a second valve for restricting the volume of discharged purge gas.

[0023] Thus, by using the second valve to lower the volume of purge gas that is discharged, the purge gas inside the cleaning solution tank is pressurized and thus the volume of volatilized (vaporized) cleaning solution components can be reduced even further. Consequently, fluctuations in the cleaning solution composition can be reduced even further and the cleaning solution composition can be further stabilized, so that deterioration of the cleaning ability can be more reliably prevented. Also, by further inhibiting the volatilization of cleaning solution components, the usage period of the cleaning solution can be extended even longer, and thus the frequency at which the cleaning solution must be exchanged can be reduced even more and therefore costs related to the cleaning solution can be further reduced.

[0024] In addition, in this case, the second valve can be a pressure regulating valve.

[0025] In the cleaning equipment of the present invention, it is preferable that the cleaning solution supply route has a pressure pump for pressurizing and supplying the cleaning solution.

[0026] Thus, the cleaning solution that is stored in the cleaning solution tank can be reliably supplied to the cleaning bath.

[0027] In the cleaning equipment of the present invention, if the cleaning solution that is stored in the cleaning solution tank is a volatile cleaning solution containing an organic solvent or the like, then the above effects become readily apparent.

[0028] In the cleaning equipment of the present invention, it is preferable that an inert gas such as helium, argon, or nitrogen is used as the purge gas.

[0029] In the cleaning equipment of the present invention, if the object to be cleaned is for example a semiconductor substrate or a glass substrate, that is, if the cleaning equipment of the present invention is a substrate cleaning equipment, then the above effects become particularly apparent. In this case, it is preferable that the substrate cleaning equipment is a batch-type or a single-wafer-type spin cleaning equipment.

[0030] A cleaning method according to the present invention includes a first step of supplying a cleaning solution that is stored in a cleaning solution tank into a cleaning bath in which cleaning of an object to be cleaned is carried out, a second step of returning the cleaning solution that has been supplied into the cleaning bath to the cleaning solution tank, a third step of supplying a purge gas to the cleaning solution tank, and a fourth step of discharging the purge gas from the cleaning solution tank, wherein the second step is performed using a cleaning solution return route having a cleaning solution discharge opening immersed in the cleaning solution that is stored in the cleaning solution tank.

[0031] According to the cleaning method of the present invention, the same effects as the cleaning equipment of the present invention are obtained because the method is a cleaning method in which the cleaning equipment of the present invention is used.

[0032] In the cleaning method of the present invention, it is preferable that the third step includes a step of reducing a frequency at which the purge gas is supplied.

[0033] Thus, volatilization of cleaning solution components, that is, fluctuations in the cleaning solution composition, can be inhibited even further because the frequency at which the purge gas and the cleaning solution come into contact inside the cleaning solution tank can be reduced, and thus the cleaning solution composition can be further stabilized.

[0034] In the cleaning method of the present invention, it is preferable that the fourth step includes a step of reducing the volume of discharged purge gas.

[0035] Thus, volatilization of cleaning solution components, that is, fluctuations in the cleaning solution composition, can be inhibited even further because the purge gas inside the cleaning solution tank can be pressurized, and thus the cleaning solution composition can be further stabilized so that deterioration of the cleaning ability can be more reliably prevented. Also, by further inhibiting volatilization of the cleaning solution components, the usage period of the cleaning solution can be maintained even longer, so that the frequency at which the cleaning solution must be changed can be even further reduced and therefore costs pertaining to the cleaning solution can be reduced further.

[0036] In the cleaning method of the present invention, if the cleaning solution that is stored in the cleaning solution tank is a volatile cleaning solution that contains an organic solvent or the like, then the above effects become more apparent.

[0037] In the cleaning method of the present invention, it is preferable that an inert gas such as helium, argon, or nitrogen is used as the purge gas.

[0038] In the method device of the present invention, if the object to be cleaned is for example a semiconductor substrate or a glass substrate, that is, if the cleaning method of the present invention is a substrate cleaning method, then the above effects become particularly apparent. In this case, it is preferable that the substrate cleaning equipment is a batch-type or a single-wafer-type spin cleaning equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is shows the configuration of the cleaning equipment according to Embodiment 1 of the present invention.

[0040] FIG. 2 is shows the configuration of the cleaning equipment according to Embodiment 2 of the present invention.

[0041] FIG. 3 is shows the configuration of the cleaning equipment according to Embodiment 3 of the present invention.

[0042] FIG. 4 shows the total cleaning solution exchange frequency for the cleaning equipments according to Embodiments 1 to 3 of the present invention in a case where a representative volatile cleaning solution is used at a temperature of 70° C.

[0043] FIG. 5 shows the pipe structure of a general spin-type batch semiconductor cleaning equipment.

[0044] FIG. 6 shows the problematic aspects of a conventional semiconductor cleaning equipment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Embodiment 1

[0046] Hereinafter, the cleaning equipment and the cleaning method according to Embodiment 1 of the present invention are described with reference to the drawings. It should be noted that the cleaning equipment according to Embodiment 1 is a cleaning equipment having a system for circulating cleaning solution like that shown in FIG. 5, for example.

[0047] FIG. 1 shows the configuration of a cleaning equipment according to Embodiment 1, and more specifically shows the configuration of the cleaning solution tank and surrounding elements of a cleaning equipment according to Embodiment 1.

[0048] As shown in FIG. 1, an end of a cleaning solution supply pipe 104 for supplying cleaning solution 102 into a cleaning bath (not shown) in which cleaning of an object to be cleaned is carried out is attached to an outlet 103 provided in the bottom portion of a cleaning solution tank 101 for storing the cleaning solution 102. The other end of the cleaning solution supply pipe 104 is connected to the cleaning bath and also provided with a pressure pump 105 proximate to the outlet 103 of the cleaning solution supply pipe 104.

[0049] In addition, a cleaning solution return pipe 106 for returning the cleaning solution 102 that has been supplied into the cleaning bath back into the cleaning solution tank 101 is connected to the cleaning solution tank 101. Here, the cleaning solution return pipe 106 passes through the ceiling portion of the cleaning solution tank 101, and a cleaning solution discharge opening 107, which is one end of the cleaning solution return pipe 106, is immersed in the cleaning solution 102 that is stored in the cleaning solution tank 101. It should be noted that in this embodiment there are no particular limitations to where the cleaning solution return pipe 106 penetrates into the cleaning solution tank 101.

[0050] Furthermore, a thermometer 108 for measuring the temperature of the cleaning solution 102 and a heat source 109 for heating the cleaning solution 102 are attached to the cleaning solution tank 101. A space 110 is provided above the liquid surface of the cleaning solution 102 that is stored in the cleaning solution tank 101, that is, between the liquid surface of the cleaning solution 102 that is stored in the cleaning solution tank 101 and the ceiling portion of the cleaning solution tank 101. In addition, an end of a gas supply pipe 111 for supplying inert gas as a purge gas into the space 110 of the cleaning solution tank 101 is attached to a gas supply opening 112 provided in the ceiling portion of the cleaning solution tank 101. Moreover, an end of a gas discharge pipe 114 for discharging the inert gas from the space 110 of the cleaning solution tank 101 is attached to a gas discharge opening 113 provided in the ceiling portion of the cleaning solution tank 101. It should be noted that in the present embodiment, helium, argon, or nitrogen, for example, can be used as the inert gas that is introduced into the cleaning solution tank 101.

[0051] A description of the operation of the cleaning equipment according to Embodiment 1 and shown in FIG. 1 follows.

[0052] First, the cleaning solution 102 stored inside the cleaning solution tank 101 is supplied from the outlet 103 in the bottom portion of the cleaning solution tank 101 to the cleaning bath (not shown) via the cleaning solution supply pipe 104. At this time, the cleaning solution is pressurized and pumped by the pressure pump 105. On the other hand, the cleaning solution 102 that has been supplied into the cleaning bath is passed through the cleaning solution return pipe 106 and returned into the cleaning solution tank 101 from the cleaning solution discharge opening 107. In the present embodiment, cleaning of the object to be cleaned is carried out by circulating the cleaning solution 102 in this way. In addition, the temperature of the cleaning solution 102 is adjusted through a feedback control in which the thermometer 108 and the heat source 109 that are attached to the cleaning solution tank 101 are used. If the cleaning solution 102 is volatile and the component volatilized from the cleaning solution 102 is ignitable, then an inert gas is delivered from the gas supply opening 112 into the space 110 via the gas supply pipe 111 in order to prevent the volatilized component in the space 110 inside the cleaning solution tank 101 from igniting and exploding. On the other hand, the inert gas that is introduced into the space 110 and the volatilized component are discharged from the gas discharge pipe 114 via the gas discharge opening 113.

[0053] As explained above, according to Embodiment 1, the cleaning solution discharge opening 107 of the cleaning solution return pipe 106 for returning the cleaning solution 102 to the cleaning solution tank 101 is immersed in the cleaning solution 102 stored in the cleaning solution tank 101. That is, the cleaning solution discharge opening 107 is located below the liquid surface of the cleaning solution 102 stored in the cleaning solution tank 101, and thus the cleaning solution 102 that is discharged from the cleaning solution discharge opening 107 can be kept from falling in a stream or a cylindrical fashion through the space 110 inside the cleaning solution tank 101. In other words, the cleaning solution 102 that is released through the cleaning solution discharge opening 107 can be kept from coming into contact with the purge gas that is introduced into the cleaning solution tank 101. As a result, the area of contact between the cleaning solution 102 and the inert gas inside the cleaning solution tank 101 can be reduced, so that volatilization of cleaning solution components can be inhibited. Consequently, fluctuations in the cleaning solution composition are inhibited so that the cleaning solution composition can be stabilized, and thus deterioration of cleaning solution 102 performance, that is, its cleaning ability, can be prevented. In addition, by inhibiting volatilization of cleaning solution components, the period of time that the cleaning solution 102 can be used is extended, and thus the frequency at which the cleaning solution 102 must be changed can be reduced. Therefore, costs associated with the cleaning solution 102 can be kept down and the operation ratio of the cleaning equipment in production line can be increased, so that production costs can be significantly reduced.

[0054] The above effects are particularly conspicuous if, in Embodiment 1, substrate cleaning of a semiconductor substrate or a glass substrate, for example, is carried out using a volatile cleaning solution that contains an organic solvent or the like. In this case, it is preferable that the substrate cleaning equipment is a batch-type or a single-wafer-type spin cleaning equipment.

[0055] Embodiment 2

[0056] Hereinafter, the cleaning equipment and the cleaning method according to Embodiment 2 of the present invention are described with reference to the drawings. It should be noted that the cleaning equipment according to Embodiment 2 is a cleaning equipment having a system for circulating cleaning solution like that shown in FIG. 5, for example.

[0057] FIG. 2 schematically shows the configuration of a cleaning equipment according to Embodiment 2, and more specifically schematically shows the configuration of the cleaning solution tank and surrounding elements of a cleaning equipment according to Embodiment 2. It should be noted that in FIG. 2, elements that are identical to those of the cleaning equipment according to Embodiment 1 shown in FIG. 1 have been assigned identical reference numerals and a description thereof has been omitted.

[0058] As shown in FIG. 2, the cleaning equipment according to Embodiment 2 differs from that according to Embodiment 1 in that the gas supply pipe 111 for supplying inert gas as a purge gas to the cleaning solution tank 101 has a first valve 120 for restricting the frequency at which inert gas is supplied. An electromagnetic valve or the like can be employed as the first valve 120. Also, the first valve 120 is for example provided proximate to the gas supply opening 112 in the gas supply pipe 111. As an example of a specific opening/closing method for the first valve 120, the first valve 120 can be closed when the equipment is in operation (during cleaning operation: if a cleaning equipment like that shown in FIG. 5 with a system for circulating cleaning solution, the time during which the route for supplying cleaning solution to the cleaning bath 1, shown by the solid line, is open), whereas the first valve 120 can be open during equipment standby (if the cleaning equipment shown the FIG. 5, then this is the time during which the route shown by the dashed line is open so that the cleaning solution 2 is circulated without passing through the cleaning bath 1).

[0059] According to Embodiment 2, the following effect can be obtained in addition to the effects of Embodiment 1. That is, by using the first valve 120 to lower the frequency at which inert gas is supplied to the cleaning solution tank 101, the frequency at which the inert gas and the cleaning solution 102 come into contact inside the cleaning solution tank 101 can be reduced. Thus, volatilization of cleaning solution components, that is, fluctuations in the cleaning solution composition, can be even further inhibited, so that the cleaning solution composition can be further stabilized, and therefore deterioration of its cleaning ability can be more reliably prevented.

[0060] The above effects are particularly conspicuous if, in Embodiment 2, substrate cleaning of a semiconductor substrate or a glass substrate, for example, is carried out using a volatile cleaning solution that contains an organic solvent or the like. In this case, it is preferable that the substrate cleaning equipment is a batch-type or a single-wafer-type spin cleaning equipment.

[0061] Embodiment 3

[0062] Hereinafter, the cleaning equipment and the cleaning method according to Embodiment 3 of the present invention are described with reference to the drawings. It should be noted that the cleaning equipment according to Embodiment 3 is a cleaning equipment having a system for circulating cleaning solution like that shown in FIG. 5, for example.

[0063] FIG. 3 schematically shows the configuration of a cleaning equipment according to Embodiment 3, and more specifically schematically shows the configuration of the cleaning solution tank and surrounding elements of a cleaning equipment according to Embodiment 3. It should be noted that in FIG. 3, elements that are identical to those of the cleaning equipment according to Embodiment 1 shown in FIG. 1 have been assigned identical reference numerals and a description thereof has been omitted.

[0064] As shown in FIG. 3, the first aspect in which the cleaning equipment according to Embodiment 3 differs from that according to Embodiment 1 is that the gas supply pipe 111 for supplying inert gas as a purge gas to the cleaning solution tank 101 has a first valve 120 for restricting the frequency at which inert gas is supplied. An electromagnetic valve or the like can be employed as the first valve 120. Also, the first valve 120 is for example provided proximate to the gas supply opening 112 in the gas supply pipe 111. As an example of a specific opening/closing method for the first valve 120, the first valve 120 can be closed when the equipment is in operation, whereas the first valve 120 can be open when the equipment is in standby.

[0065] Moreover, as shown in FIG. 3, a second aspect in which the cleaning equipment according to Embodiment 3 differs from that according to Embodiment 1 is that the gas discharge pipe 114 for discharging inert gas from the cleaning solution tank 101 has a second valve 130 for restricting the discharged volume of inert gas, that is, purge gas. A pressure regulating valve or the like can be employed as the second valve 130. Also, the second valve 130 is for example provided proximate to the gas discharge opening 113 in the gas discharge pipe 114. Moreover, in this embodiment, a pressure sensor 131 is provided between the gas supply opening 112 and the first valve 120 in the gas supply pipe 111 in order to measure the pressure of the inert gas inside the cleaning solution tank 101. Thus, in this embodiment, the pressure of the inert gas inside the cleaning solution tank 101 can be set higher than atmospheric pressure and maintained using the second valve 130 and the pressure sensor 131.

[0066] As explained above, according to Embodiment 3, the following two effects can be obtained in addition to the effects of Embodiment 1.

[0067] First, like Embodiment 2, by using the first valve 120 to lower the frequency at which inert gas is supplied to the cleaning solution tank 101, the frequency at which the inert gas and the cleaning solution 102 come into contact inside the cleaning solution tank 101 can be reduced. Thus, volatilization of cleaning solution components, that is, fluctuations in the cleaning solution composition, can be even further inhibited, so that the cleaning solution composition can be further stabilized and therefore deterioration of its cleaning ability can be more reliably prevented.

[0068] In addition, by using the second valve 130 to reduce the volume of discharged inert gas, the inert gas inside the cleaning solution tank 101 can be pressurized and therefore the volume of volatilized (vaporized) cleaning solution components can be further inhibited. Consequently, fluctuations in the cleaning solution composition can be inhibited even further so that the cleaning solution composition can be further stabilized, and thus deterioration of the cleaning ability can be more reliably reduced. Also, by further inhibiting volatilization of cleaning solution components, the usage period of the cleaning solution 102 can be maintained longer, and thus the frequency at which the cleaning solution 102 must be changed can be reduced even more, so that costs associated with the cleaning solution 102 can be further reduced.

[0069] The above effects are particularly conspicuous if, in Embodiment 3, substrate cleaning of a semiconductor substrate or a glass substrate, for example, is carried out using a volatile cleaning solution that contains an organic solvent or the like. In this case, it is preferable that the substrate cleaning equipment is a batch-type or a single-wafer-type spin cleaning equipment.

[0070] It should be noted that in Embodiment 3, the pressure of the inert gas in the cleaning solution tank 101 is preferably set to a pressurized state of about 105 to 120 kPa, in contrast to atmospheric pressure at 101.3 kPa. Also, the period during which this pressurized state is maintained can be the period of device standby, which is when the first valve 120 is open. Alternatively, the opening and closing of the first valve 120 can be controlled so that the above pressurized state is maintained without regard to whether the equipment is in operation or standby.

[0071] FIG. 4 shows the frequency (hereinafter, referred to as the total cleaning solution exchange frequency) at which the cleaning solution (all cleaning solution in the circulation system) must be exchanged per day in order to sustain the cleaning ability in a case where a representative volatile cleaning solution is used at a temperature of 70° C. in the cleaning equipments according to Embodiments 1 to 3. It should be noted that FIG. 4 also shows the total cleaning solution exchange frequency of the conventional cleaning equipment shown in FIG. 6 as a conventional example in a case where the same volatile cleaning solution is used at the same temperature.

[0072] As shown in FIG. 4, the usage period (period from when the cleaning solution is exchanged once to when it is exchanged next) of the cleaning solution in each embodiment is longer than that for the comparative example, and more particularly, the usage period of the cleaning solution in Embodiment 3 is longest. This is due to combined effect of the cleaning solution component volatilization prevention effect of Embodiment 1 due to the reduction of contact area between the inert gas and the cleaning solution 102 in the cleaning solution tank 101 because the cleaning solution 102 is kept from flowing from the cleaning solution discharge opening 107 into the space 110 in a stream, for example, the cleaning solution component volatilization prevention effect of Embodiment 2 due to the reduction of the frequency of contact between the inert gas and the cleaning solution 102 in the cleaning solution tank 101 because the frequency at which the inert gas is supplied into the cleaning solution tank 101 is reduced, and the cleaning solution component volatilization prevention effect of Embodiment 3 due to the reduction of the volume of discharged inert gas so as to keep the inert gas inside the cleaning solution tank 101 in a pressurized state.

[0073] The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.