Liquid supply device

Abstract

A liquid supply device increases the amount of liquid circulating in a liquid supply path equipped with a filter, thereby reducing the amount of foreign matter contained in the liquid. The liquid supply device (10) includes: a first pump (21) and a second pump (22), respectively provided in a liquid supply path (12) for supplying liquid collected in a liquid receiving section (11) to an application tool (13); a filter (15) for filtering the liquid flowing to the application tool (13); and a return channel (27) for returning the liquid that has passed through the filter to the liquid receiving section (11). In a circulation mode in which liquid is supplied to the return channel (27) and the supply of liquid to the application tool (13) is stopped, either the first pump (21) or the second pump (22) continuously supplies liquid to the return channel (27).

Description

Technical Field

[0001] The present invention relates to a liquid supply device for applying liquid such as a medical solution to an object to be applied. Background Art

[0002] In the manufacturing process of semiconductor devices or liquid crystal substrates, liquid chemicals such as photoresist liquid are used. For example, in the manufacturing process of semiconductor devices, in order to apply the photoresist liquid on the surface of the semiconductor wafer, the photoresist liquid is dripped onto the surface of the semiconductor wafer while the semiconductor wafer is rotated in a horizontal plane. The pumps used in the liquid supply device for applying the photoresist liquid include tubular diaphragm pumps and bellows pumps. The tubular diaphragm pump has a flexible tube, i.e., a tubular diaphragm, which can expand and contract freely in the radial direction, and the bellows pump has a flexible bellows that can expand and contract freely in the axial direction. These pumps are positive displacement pumps with an intake process and a discharge process.

[0003] As described in Patent Document 1, a tubular diaphragm pump has a tubular diaphragm, i.e., a flexible tube, disposed between a joint component on the inflow side and a joint component on the outflow side. A pump chamber that expands or contracts is formed on the inner side of the tube, and a drive chamber filled with an incompressible liquid medium is formed on the outer side of the tube. There are container storage types and bellows storage types. The container storage type has a container that stores the tube inside and a drive chamber formed between the container and the tube; the bellows storage type has the tube stored inside a bellows that connects two bellows of different diameters, and a drive chamber is formed between the bellows and the tube.

[0004] In the container-housed type, the pumping action is performed by supplying or discharging a liquid medium from the outside of the container, causing the pump chamber to expand or contract via the liquid medium in the drive chamber, while in the bellows-housed type, the pumping action is performed by reciprocating the connecting portion in the axial direction, causing the pump chamber to expand or contract via the liquid medium in the drive chamber formed inside the large and small bellows.

[0005] As described in Patent Document 2, a bellows pump has a pump body as a pump housing and a bellows disposed inside the pump body, and a pump chamber is formed between the bellows and the pump housing. The bellows includes a bellows portion that is freely expandable and contracted in the axial direction, a front end portion disposed at the front end of the bellows portion, and an annular base end portion disposed at the base end of the bellows portion. A drive shaft disposed inside the bellows is connected to the front end portion of the bellows portion, and the bellows portion is expanded and contracted in the axial direction by the drive shaft, so that the pump chamber expands or contracts to perform a pumping action. Patent Document 2 describes a bellows pump that uses two bellows to cause two pump chambers to alternately expand or contract, thereby continuously discharging liquid.

[0006] Patent document 3 describes a liquid medicine supply device having a bellows-type tube diaphragm pump. The liquid medicine supply device has a liquid supply path for supplying a liquid medicine such as a photoresist solution or a polyimide solution stored in a bottle to a nozzle, i.e., a coating tool, and the nozzle is used to coat a coating object such as a wafer. A pump and a filter are provided on the liquid supply path. The liquid discharged from the pump is supplied to the coating tool, and a return channel is provided for returning the liquid to the upstream portion of the liquid supply path or to the bottle.

[0007] [Prior art literature]

[0008] [Patent Literature]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2005-83337

[0010] [Patent Document 2] Japanese Patent Application Laid-Open No. 10-54368

[0011] [Patent Document 3] Japanese Patent Application Publication No. 2000-120530 Summary of the invention

[0012] The liquid supply device is provided with a return channel in the liquid supply path, and when the liquid is not applied from the coating tool, the liquid can be returned to the upstream part through the return channel. Therefore, since the liquid is filtered through the filter multiple times, foreign matter such as tiny particles, particles or bubbles contained in the liquid can be removed by the filter, which can reduce the foreign matter contained in the liquid applied to the coated object.

[0013] In recent years, in the field of semiconductor manufacturing technology, in order to improve the manufacturing yield rate, it is desired to further improve the reduction rate or reduction amount of foreign matter contained in the liquid. It is conceivable that by increasing the flow rate of the liquid returned to the bottle side through the return channel, the number of circulations of the liquid passing through the filter is increased, thereby increasing the reduction amount of foreign matter contained in the coating object.

[0014] To increase the number of liquid circulations, it is necessary to increase the flow rate of the liquid within a limited time. However, pumps using a tubular diaphragm or bellows made of flexible resin materials as pump components have a structure optimized for the amount of coating or coating operation of the coating object, and there are limitations in increasing the flow rate of this type of pump.

[0015] An object of the present invention is to increase the amount of liquid circulating in a liquid supply path provided with a filter and to improve the amount of reduction of foreign matter contained in the liquid.

[0016] The liquid supply device of the present invention supplies liquid stored in a liquid storage portion to a coating tool for applying the liquid to a coated object, and the liquid supply device includes: a first pump and a second pump, which are respectively arranged in a liquid supply path for supplying the liquid stored in the liquid storage portion to the coating tool; a filter, which is arranged in the liquid supply path and filters the liquid flowing to the coating tool; a return channel, which returns the liquid that has passed through the filter to the liquid storage portion, and a control unit, which controls the first pump and the second pump to a coating mode or a circulation mode, wherein the coating mode supplies liquid to the coating tool and stops supplying liquid to the return channel, and the circulation mode supplies liquid to the return channel and stops supplying liquid to the coating tool, in which one of the first pump and the second pump discharges a coating amount of liquid to the coated object, and in which the other of the first pump and the second pump causes the return flow rate of liquid to flow continuously to the return channel.

[0017] In the circulation mode, the liquid circulates continuously in the return channel, and the liquid returned to the liquid storage container through the return channel is supplied to the liquid supply path, so that the liquid can pass through the filter multiple times to reduce foreign matter contained in the liquid. Since the first pump and the second pump are provided, the liquid can be always circulated in the circulation mode, and the discharge amount can be controlled with high precision in the coating mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram showing a liquid supply device according to one embodiment.

[0019] Figure 2 This is a block diagram showing a control circuit of the liquid supply device.

[0020] Figure 3 This is a cross-sectional view showing an example of a tubular diaphragm pump.

[0021] Figure 4 It is a cross-sectional view showing a tubular diaphragm pump as a modified example.

[0022] Figure 5 This is a front view showing the appearance of the bellows pump.

[0023] Figure 6 yes Figure 5 AA line cross-section diagram.

[0024] Figure 7 yes Figure 5 BB line cross section.

[0025] Figure 8 1 is a timing chart showing an example of pump driving for performing a liquid application operation from an application tool. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 The liquid supply device 10 shown is used to apply a liquid L such as a photoresist liquid contained in a liquid storage portion 11 to a coating object W such as a semiconductor wafer. The liquid supply device 10 has a liquid supply path 12 composed of a pipe or a hose, etc., a coating tool 13 such as a nozzle is provided at the front end of the liquid supply path 12, and a liquid storage portion 11 is provided at the base end of the liquid supply path 12.

[0027] Two pumps 21 and 22 are arranged in series on the liquid supply path 12. The pump 21 arranged on the downstream side of the liquid supply path 12 is the first pump, and the pump 22 arranged on the upstream side is the second pump. The liquid in the liquid storage section 11 is supplied to the coating tool 13 by the two pumps 21 and 22. The liquid storage section 11 includes a tank 11a and a buffer tank 11b. When the remaining liquid in the tank 11a becomes empty below a predetermined value, a new tank is replaced. Even during replacement, in order to supply liquid to the coating tool 13, a buffer tank 11b is provided in the liquid supply path 12 located on the upstream side of the pump 22. The buffer tank 11b is used to replace the tank 11a before the liquid in the buffer tank 11b becomes empty during the replacement of the empty tank 11a with the new tank 11a filled with liquid.

[0028] A filter 15 for filtering the liquid discharged from the pump 21 is provided on the downstream side of the pump 21. A ventilation passage 16 for discharging the gas in the filter 15 to the outside is connected to the filter 15. In addition, a ventilation passage 17 for discharging the gas in the buffer tank 11b to the outside is connected to the buffer tank 11b. On-off valves 18 and 19 are provided on the ventilation passages 16 and 17, respectively.

[0029] In order to discharge the gas in the buffer tank 11b to the outside, the pressurizing passage 23 is connected to the tank 11a, and nitrogen as an inert gas is supplied from the outside through the pressurizing passage 23. When the inert gas is supplied to the tank 11a from the pressurizing passage 23 through the switch valve 24 provided on the pressurizing passage 23 while the ventilation passage 17 is open by the switch valve 19, the gas in the buffer tank 11b is discharged to the outside through the ventilation passage 17. When the inert gas is supplied to the tank 11a while the ventilation passage 16 is open by the switch valve 18, the gas in the filter 15 is discharged to the outside. However, in the state where the ventilation passage 16 is open by the switch valve 18, the gas in the filter 15 can also be discharged by discharging liquid from the pump 21. In order to recover the liquid and the like discharged simultaneously with the gas when the ventilation passages 16 and 17 discharge the gas respectively, the discharge ends of the ventilation passages 16 and 17 are provided in the recovery container 25.

[0030] In order to apply the liquid filtered from the filter 15 from the coating tool 13 to the coating object W, a coating valve 26 is provided in the liquid supply path 12. A return channel 27 for returning the liquid that has passed through the filter 15 to the liquid storage section 11 is connected to the liquid supply path 12. The upstream end of the return channel 27 is connected to the liquid supply path 12 through a connection portion 29 between the filter 15 and the coating valve 26, and the downstream end of the return channel 27 is connected to the liquid storage section 11. A circulation valve 28 is provided in the return channel 27. The downstream end of the return channel 27 can be connected to the tank 11a, the buffer tank 11b, or between the buffer tank 11b and the pump 22.

[0031] Figure 2 2 is a block diagram showing a control circuit of the liquid supply device. The operation of the first pump 21, the second pump 22, the coating valve 26 and the circulation valve 28 is controlled by the control unit 30. The control unit 30 is connected to the operation panel 20, and the operation of the liquid supply device 10 is started by the command key (not shown) provided on the operation panel 20. The control unit 30 has a microprocessor for calculating control signals, a memory for storing control programs, and the like.

[0032] The operations of the pumps 21 and 22 and the valves 26 and 28 are controlled by the control unit 30 , so that the liquid supply device 10 is set to the coating mode and the circulation mode. Figure 1 The other components shown are also controlled by signals from the control unit 30, but in Figure 2 , only the components set to the coating mode and the circulation mode are shown.

[0033] Figure 3 is a cross-sectional view showing a tubular diaphragm pump 31, which is a positive displacement type and can be used as Figure 1 Pumps 21, 22 are shown.

[0034] like Figure 3 As shown, the tubular diaphragm pump 31 has a cylindrical storage container 32 as a storage component, a joint component 33 provided on the inflow side at one end thereof, and a joint component 34 provided on the outflow side at the other end. The inflow side portion 12a of the liquid supply path 12 is connected to the joint component 33 on the inflow side, and the outflow side portion 12b is connected to the joint component 34 on the outflow side. A flexible tube, i.e., a tubular diaphragm 35 is provided in the storage container 32, and the tubular diaphragm 35 has a fixed end portion 36 on the inflow side fixed to the joint component 33 on the inflow side, a fixed end portion 37 on the outflow side fixed to the joint component 34 on the outflow side, and an elastic deformation portion 38 between the two fixed ends 36 and 37. The joint components 33, 34 and the tubular diaphragm 35 are respectively formed of a synthetic resin such as a fluororesin.

[0035] The tubular diaphragm 35 is used to separate the pump chamber 39 inside and the liquid storage chamber 41 outside, and the liquid storage chamber 41 is formed between the tubular diaphragm 35 and the storage container 32. In this way, the tubular diaphragm 35 is set in the storage container 32, and the tubular diaphragm pump 31 is a container storage type.

[0036] Incompressible liquid is filled into the liquid storage chamber 41 as a liquid medium M, and the liquid medium M is supplied to the liquid storage chamber 41 from the outside via a supply and discharge port 42 formed on the storage container 32. A supply and discharge pump 43 is connected to the supply and discharge port 42. The supply and discharge pump 43 has a bellows 45 installed on a rod 44 that reciprocates in a straight line, and the rod 44 is driven axially by a driving component such as an electric motor or a pneumatic cylinder. The liquid storage chamber 46 outside the bellows 45 is also filled with a liquid medium, and the liquid storage chamber 46 is connected to the liquid storage chamber 41 of the tubular diaphragm pump 31 through the liquid medium M.

[0037] When the liquid medium M is supplied from the liquid storage chamber 46 to the liquid storage chamber 41 by driving the supply and discharge pump 43, the elastic deformation portion 38 of the tubular diaphragm 35 contracts radially through the liquid medium in the liquid storage chamber 41, thereby contracting the pump chamber 39. On the other hand, when the liquid medium is discharged from the liquid storage chamber 41, the elastic deformation portion 38 expands radially, thereby expanding the pump chamber 39. A check valve 47 is provided on the inflow side portion 12a of the liquid supply path 12, and a check valve 48 is provided on the outflow side portion 12b. When the pump chamber 39 expands, the liquid L flows into the pump chamber 39 from the inflow side portion 12a. At this time, the backflow of the liquid from the outflow side portion 12b is prevented. On the other hand, when the pump chamber 39 contracts, the liquid L flows out from the pump chamber 39 to the outflow side portion 12b. At this time, the liquid is prevented from flowing back to the inflow side portion 12a. The check valve 47 can be assembled into the joint component 33, and the check valve 48 can be assembled into the joint component 34. In addition, the supply and discharge pump 43 may not be provided with the bellows 45 , but the liquid medium M may be supplied to or discharged from the liquid storage chamber 41 by the rod 44 .

[0038] Figure 4 is a cross-sectional view showing a tube diaphragm pump 51 as a modified example. The tube diaphragm pump 51 can also be used as Figure 1 Pumps 21, 22 are shown.

[0039] The tubular diaphragm pump 51 is a bellows storage type, in which the tubular diaphragm 35 is stored inside a bellows container 52 as a storage component. The bellows container 52 has a fixing ring 53 mounted on the joint component 33 on the inflow side and a fixing ring 54 mounted on the joint component 34 on the outflow side. A large bellows 55 is provided on the fixing ring 53, a small bellows 56 is provided on the fixing ring 54, and an operating ring 57 is provided between the two bellows 55 and 56. The average effective diameter of the large bellows 55 is larger than the average effective diameter of the small bellows 56. The bellows container 52 is formed by integrally molding the two fixing rings 53 and 54 and the portion therebetween with a rigid resin such as fluororesin.

[0040] and Figure 3 The same tubular diaphragm 35 as shown is installed inside the bellows container 52, and a liquid receiving chamber 41 is formed between the tubular diaphragm 35 and the bellows container 52. A pump drive unit 61 is attached to the bellows container 52, and is used to deform the two bellows 55 and 56 in the axial direction, so that the pump chamber 39 is expanded or contracted in the radial direction via the liquid medium M in the liquid receiving chamber 41. The pump drive unit 61 has a ball screw 64 driven by a motor 62 via a power transmission mechanism 63, and a ball nut 65 threadedly connected to the ball screw 64, and an operating member 66 engaged with the operating ring 57 is provided on the ball nut 65.

[0041] When the motor 62 Figure 4 When the operating ring 57 is driven upward in the middle, the large bellows 55 stretches in the axial direction and the small bellows 56 contracts in the axial direction, so that the average effective diameter of the bellows as a whole becomes larger. As a result, the tubular diaphragm 35 expands in the radial direction, and the liquid L flows into the pump chamber 39 from the inflow side portion 12a. On the other hand, when the operating ring 57 is driven in the opposite direction, the large bellows 55 contracts in the axial direction and the small bellows 56 stretches in the axial direction, so that the average effective diameter of the bellows as a whole becomes smaller. As a result, the tubular diaphragm 35 contracts in the radial direction, and the liquid L in the pump chamber 39 flows out from the outflow side portion 12b.

[0042] Therefore, the ball nut 65 is reciprocated in a straight line by the motor 62, and the elastic deformation portion 38 of the tubular diaphragm 35 expands or contracts, thereby Figure 3 Similarly, in the illustrated tube diaphragm pump 31 , the liquid L flows out from the pump chamber 39 toward the outflow side portion 12 b , and the pump operation is performed.

[0043] Figure 3 and Figure 4The tubular diaphragm pumps 31 and 51 shown are intermittent discharge pumps that alternately discharge liquid from the pump chamber 39 and suck liquid. The intermittent discharge pump can control the discharge amount with high precision. At least two tubular diaphragm pumps are combined into a unit as a pump having at least two pump chambers, and it is set so that when one pump chamber contracts to perform a discharge operation, the other pump chamber expands to perform a suction operation, thereby becoming a continuous discharge pump capable of continuously discharging liquid.

[0044] Figures 5 to 7 A bellows pump 71 is shown as a modified example of a positive displacement pump. The bellows pump 71 has a pump housing 72 and a drive unit 73, and the pump housing 72 includes a pump body 74 made of a synthetic resin such as a fluororesin. Two pump chambers 39a and 39b are formed in the pump body 74, and the pump chamber 39a has a bellows 75a, and the pump chamber 39b has a bellows 75b. The bellows 75a and 75b respectively have annular bases 76a and 76b fixed to the pump body 74, closed ends 77a and 77b, and bellows portions 78a and 78b that can be freely extended and retracted therebetween, and are formed of synthetic resin.

[0045] In order to drive each bellows portion 78a, 78b to expand and contract axially, a drive shaft 79a, 79b is arranged inside the bellows 75a, 75b, and the front end of each drive shaft 79a, 79b is mounted on the closed end 77a, 77b. Nuts 81a, 81b are mounted on the large-diameter base end of the drive shaft 79a, 79b, and ball screws 82a, 82b are threadedly connected to the nuts 81a, 81b. The ball screws 82a, 82b are supported by bearings 83a, 83b provided in the drive unit 73 so as to be freely rotatable. The ball screw 82a is connected to the shaft of the motor 84a through the joint 85a, and the ball screw 82b is connected to the shaft of the motor 84b through the joint 85b.

[0046] like Figure 7 As shown, the inflow side block 86 is installed on the lower surface of the pump body 74, and the outflow side block 87 is installed on the upper surface. Inflow channels 88a and 88b are formed in the inflow side block 86, which are connected to the inflow side portion 12a of the liquid supply path 12. The inflow channel 88a is connected to the pump chamber 39a, and the inflow channel 88b is connected to the pump chamber 39b. Outflow channels 89a and 89b are formed in the outflow side block 87, which are connected to the outflow side portion 12b. The outflow channel 89a is connected to the pump chamber 39a, and the outflow channel 89b is connected to the pump chamber 39b. Check valves 47a and 47b are respectively provided in the inflow channels 88a and 88b, and check valves 48a and 48b are respectively provided in the outflow channels 89a and 89b.

[0047] By driving the motors 84a and 84b, the bellows 75a and 75b are extended, the pump chambers 39a and 39b are contracted, and the liquid L is discharged to the outflow side portion 12b through the check valves 48a and 48b. On the other hand, when the bellows 75a and 75b are contracted, the pump chambers 39a and 39b are expanded, and the liquid flows in from the inflow side portion 12a through the check valves 47a and 47b. Figure 6 The state in which the bellows 75b is extended and the bellows 75a is contracted is shown.

[0048] The bellows pump 71 is provided with two bellows 75a, 75b, and is therefore a continuous discharge pump. When one of the bellows 75a, 75b is extended to discharge liquid from one of the pump chambers 39a, 39b, the other of the bellows 75a, 75b is contracted to suck liquid into the other of the pump chambers 39a, 39b, thereby being able to continuously discharge the liquid L to the outflow side portion 12b. Encoders 90a, 90b are provided in the motors 84a, 84b, respectively, for detecting the rotation speed and rotation direction of the motors 84a, 84b, respectively.

[0049] like Figure 1 As shown, two pumps 21 and 22 are provided in the liquid supply path 12. When the coating valve 26 is opened and the circulation valve 28 is closed, any one of the first pump 21 and the second pump 22 supplies the liquid to the coating tool 13 and discharges the coating amount of the liquid to the coating object W. On the other hand, when the coating valve 26 is closed and the circulation valve 28 is opened, the other of the first pump 21 and the second pump 22 supplies the liquid of the return flow rate to the return channel 27. Since all the liquid discharged from the two pumps 21 and 22 is supplied to the return channel 27 and the coating tool 13 through the filter 15, the liquid passes through the filter 15 multiple times, thereby improving the cleanliness of the liquid.

[0050] Figure 8 The timing chart shows an application mode in which the liquid L is applied from the application tool 13 and a circulation mode in which the circulation operation is performed when the first pump 21 provided downstream is an intermittent discharge pump and the second pump provided upstream is a continuous discharge pump. Figure 8 The coating flow rate in φ represents the flow rate of the liquid flowing through the coating tool 13 , and the circulation flow rate represents the flow rate of the liquid flowing through the return channel 27 .

[0051] In the coating mode, the coating valve 26 is opened and the circulation valve 28 is closed, so that the liquid is discharged to the coating object W, and the supply of the liquid to the return channel 27 is stopped. On the other hand, in the circulation mode, the coating valve 26 is closed and the circulation valve 28 is opened, so that the discharge of the liquid to the coating object W is stopped, and the liquid is supplied to the return channel 27. Instead of the coating valve 26 and the circulation valve 28, a three-way valve as a switching device may be provided in the connection portion 29 to switch between the coating mode and the circulation mode.

[0052] Since only the continuous discharge pump, i.e., the second pump 22, is driven in the circulation mode, the liquid can always circulate in the return channel 27. Therefore, in the circulation mode, the amount of liquid circulated can be increased, thereby increasing the amount of foreign matter contained in the liquid. In addition, in the coating mode, since only the intermittent discharge pump, i.e., the first pump 21, is driven, the discharge amount can be controlled with high precision. The suction operation of the first pump can be performed in the circulation mode or in the coating mode.

[0053] When the tubular diaphragm pumps 31, 51 or the bellows pump 71 are used as the two pumps 21, 22, unlike the piston type pump, since there is no sliding part, the possibility of foreign matter such as abrasion powder being contained in the liquid can be reduced. In addition, when the two pumps 21, 22 are arranged in series, the liquid always passes through the two pumps 21, 22, so the generation of particles can be suppressed and the cleanliness of the liquid can be improved. Furthermore, when the first pump 21 is an intermittent discharge pump and the second pump 22 is a continuous discharge pump, the liquid discharge accuracy can be further improved.

[0054] The present invention is not limited to the above-mentioned embodiments, and various changes can be made without departing from the scope of the present invention. For example, the first pump can be a continuous discharge pump, and the second pump can be an intermittent discharge pump. The second pump 22 can be driven to stop the first pump 21 in the coating mode, and the first pump 21 can be stopped to drive the second pump 22 in the circulation mode.

[0055] [Description of Reference Numerals]

[0056] 10 Liquid supply device

[0057] 11 Liquid storage area

[0058] 12 Liquid supply path

[0059] 13 Coating tools

[0060] 15 Filters

[0061] 21 First Pump

[0062] 22 Second Pump

[0063] 26 Coating valve

[0064] 27 Return Channel

[0065] 28 Circulation valve

[0066] 29 Connection

[0067] 31 Tube Diaphragm Pump

[0068] 32 Storage Containers

[0069] 35 Tubular diaphragm

[0070] 38 Elastic deformation part

[0071] 39 Pump Room

[0072] 41, 46 Liquid Storage Room

[0073] 51 Tube Diaphragm Pump

[0074] 52 Bellows Container

[0075] 55, 56 bellows

[0076] 57 Operation ring

[0077] 61 Pump drive unit

[0078] 71 Bellows Pump

[0079] 75a, 75b bellows

[0080] 79a Drive shaft

[0081] 84a, 84b Electric motor

Claims

1. A liquid supply device for supplying liquid contained in a liquid container to a coating tool for coating the liquid on a coating object, the liquid supply device comprising: A first pump and a second pump are respectively arranged in a liquid supply path for supplying the liquid contained in the liquid containing portion to the coating tool; a filter, disposed in the liquid supply path, for filtering the liquid flowing toward the coating tool; a return channel for returning the liquid having passed through the filter to the liquid receiving portion, and a control unit, controlling the first pump and the second pump to a coating mode and a circulation mode, wherein the coating mode supplies liquid to the coating tool and stops supplying liquid to the return channel, and the circulation mode supplies liquid to the return channel and stops supplying liquid to the coating tool, In the coating mode, one of the first pump and the second pump discharges a coating amount of liquid to the coating object by alternately performing an operation of discharging liquid and an operation of sucking liquid. In the circulation mode, the other of the first pump and the second pump continuously discharges liquid so that the return flow of liquid continuously flows to the return channel; The first pump and the second pump are connected in series, and the filter is provided between the downstream pump and the coating tool.

2. The liquid supply device according to claim 1, wherein: A connection portion for connecting the return passage and the liquid supply path is provided between the application tool and the filter.

3. The liquid supply device according to claim 2, wherein: The liquid supply device comprises: an application valve provided between the connection portion and the application tool, and a circulation valve provided in the return passage. In the circulation mode, the coating valve is closed and the circulation valve is opened, In the coating mode, the coating valve is opened and the circulation valve is closed.

4. The liquid supply device according to claim 2, wherein: A switching device for switching between the coating mode and the circulation mode is provided at the connection portion.

5. The liquid supply device according to claim 1, wherein: The second pump has at least two pump chambers, and in a circulation mode, when one pump chamber contracts, the other pump chamber expands.

6. The liquid supply device according to claim 2, wherein: The second pump has at least two pump chambers, and in a circulation mode, when one pump chamber contracts, the other pump chamber expands.

7. The liquid supply device according to claim 3, wherein: The second pump has at least two pump chambers, and in a circulation mode, when one pump chamber contracts, the other pump chamber expands.

8. The liquid supply device according to claim 4, wherein: The second pump has at least two pump chambers, and in a circulation mode, when one pump chamber contracts, the other pump chamber expands.

9. The liquid supply device according to any one of claims 2 to 8, wherein: The second pump is arranged upstream of the first pump, In the coating mode, the coating amount of liquid is applied to the coating object only by the first pump, and in the circulation mode, the return flow rate of liquid is made to flow to the return channel only by the second pump.

10. The liquid supply device according to claim 9, wherein: The first pump is a tubular diaphragm pump, comprising: a tubular diaphragm that expands or contracts in a radial direction and forms a pump chamber inside; a storage component that stores the tubular diaphragm and forms a liquid storage chamber between the storage component and the tubular diaphragm; and a liquid medium filled in the liquid storage chamber. The tubular diaphragm is expanded or contracted by a liquid medium, thereby performing pump operation.

11. The liquid supply device according to claim 9, wherein: The first pump is a bellows pump, comprising: a bellows that expands and contracts in the axial direction; a receiving component that receives the bellows and forms a liquid receiving chamber with the bellows; and a liquid medium filled in the liquid receiving chamber. The bellows is driven in the axial direction to expand and contract, thereby performing pump operation.

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