VACUUM SYSTEM FOR IMMERSION PHOTOLITHOGRAPHY

Abstract

A vacuum system for extracting a stream of a multi-phase fluid from a photo-lithography tool comprises a pumping arrangement for drawing the fluid from the tool, and an extraction tank located upstream from the pumping arrangement for separating the fluid drawn from the tool into gas and liquid phases. The pumping arrangement comprises a first pump for extracting gas from the tank, and a second pump for extracting liquid from the tank. In order to minimize any pressure fluctuations transmitted from the vacuum system back to the fluid within the tool, a pressure control system maintains a substantially constant pressure in the tank by regulating the amounts of liquid and gas within the tank.

Claims

1.-20. (canceled)

21. A lithographic apparatus, comprising: a projection device configured to project a radiation beam onto a substrate; an inlet configured to provide a liquid to a space between the projection device and the substrate; an outlet configured to remove at least part of the liquid as a multi-phase fluid; a separator configured to receive the multi-phase fluid from the outlet, the separator configured to separate the fluid into gas and liquid phases; a first opening at a first side of the separator, the first opening configured to allow the multi-phase fluid into a part of the separator; and a second opening at a second side of the separator opposite to the first side, the second opening configured to exhaust separated gas from the separator.

22. The apparatus of claim 21, further comprising a pump arrangement configured to draw the multi-phase fluid into the separator.

23. The apparatus of claim 21, further comprising a pump arrangement configured to extract separated liquid, via a third opening, from the separator.

24. The apparatus of claim 21, further comprising a control system configured to control a pressure within the separator by regulating the gas and/or liquid therein.

25. The apparatus of claim 21, further comprising a control system configured to control flow of gas from the separator.

26. The apparatus of claim 21, further comprising a control system configured to control an amount of liquid within the separator.

27. The apparatus of claim 21, further comprising a flow restriction in a fluid path from the separator to a pump fluidly connected to the separator.

28. The apparatus of claim 21, wherein the separator comprises a chamber having the first and second openings therein.

29. The apparatus of claim 21, wherein the first opening is located at a different height than a third opening configured to exhaust separated liquid from the separator.

30. The apparatus of claim 29, wherein the first opening is higher than the third opening.

31. The apparatus of claim 21, further comprising a control system configured to control a level of liquid within the separator.

32. A lithographic apparatus, comprising: a projection device configured to project a radiation beam onto a substrate; an inlet configured to provide a liquid to a space between the projection device and the substrate; an outlet configured to remove at least part of the liquid as a multi-phase fluid; a separator configured to receive the multi-phase fluid from the outlet, the separator configured to separate the fluid into gas and liquid phases; a first opening configured to allow the multi-phase fluid into a part of the separator; and a second opening configured to exhaust separated liquid from the separator, the first opening being located at a different height than the second opening.

33. The apparatus of claim 32, further comprising a pump arrangement configured to draw the multi-phase fluid into the separator.

34. The apparatus of claim 32, further comprising a pump arrangement configured to extract separated liquid, via the second opening, from the separator.

35. The apparatus of claim 32, further comprising a control system configured to control a pressure within the separator by regulating the gas and/or liquid therein.

36. The apparatus of claim 32, further comprising a control system configured to control flow of gas from the separator.

37. The apparatus of claim 32, further comprising a control system configured to control an amount of liquid within the separator.

38. The apparatus of claim 32, further comprising a flow restriction in a fluid path from the separator to a pump fluidly connected to the separator.

39. The apparatus of claim 32, wherein the separator comprises a chamber having the first and second openings therein.

40. A lithographic apparatus, comprising: a projection device configured to project a radiation beam onto a radiation-sensitive substrate; an inlet opening located above the stage, the inlet configured to provide a liquid to a space between the projection device and the substrate; an outlet opening located above the stage, the outlet configured to remove at least part of the liquid as a multi-phase fluid; a stage configured to support the substrate and moveable relative to the inlet and outlet; a separator configured to receive the multi-phase fluid from the outlet, the separator configured to separate the fluid into gas and liquid phases; a first opening at a first side of a chamber of the separator, the first opening configured to allow the multi-phase fluid into a part of the separator; a second opening at a second side of the chamber opposite to the first side, the second opening configured to exhaust separated gas from the separator; and a third opening configured to exhaust separated gas from the chamber, the second opening located at a different height than the second opening.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 schematically illustrates a known system for immersion photolithography; and

[0021] FIG. 2 schematically illustrates the present invention vacuum system for extracting a multi-phase fluid from an immersion photolithography tool.

DETAILED DESCRIPTION

[0022] With reference to FIG. 2, a system 30 for extracting a multi-phase fluid from an immersion photolithography tool comprises a separating means depicted for purposes of illustration as an extraction tank 32 for receiving the multi-stream fluid drawn from the tool by a pumping arrangement located downstream from the tank 32. The tank 32 is connected to the tool by flexible tubing 34 so as to minimize the amount of mechanical coupling between the system 30 and the tool, and thereby minimize the transmission of vibrations generated during use of the system 30 back to the tool.

[0023] The tank 32 is configured to separate the liquid and gas phases within the fluid received from the tool. In this example, the fluid received from the tool comprises a mixture of clean dry air (CDA) and ultra-pure water, and so the tank 32 contains any suitable material and/or structure for affecting the separation of the CDA from the water. However, the tank 32 may be configured to separate a different liquid-gas mixture received from the tool. For example, the liquid may comprise an aqueous or non-aqueous solution, and the gas may be other than CDA.

[0024] The pumping arrangement comprises a first pumping unit 36 for extracting gas from the tank 32, and a second pumping unit 38 for extracting liquid from the tank 32.

[0025] The first pumping unit 36 may comprise any suitable pump for extracting the gas from the tank 32, and is preferably chosen for compatibility with the gas extracted from the tank 32, which is likely to be saturated with liquid vapor, for minimum transmission of pressure fluctuations back to the gas contained in the tank 32, and for relatively long maintenance periods. In this embodiment, the first pumping unit 36 may conveniently comprise an air-powered ejector pump or a water-based liquid ring pump for extracting CDA from the tank 32. In order to inhibit the transfer of vibrations to the tank 32 during use, the first pumping unit 36 is connected to the tank using flexible tubing 40. As the gas exhaust from the first pumping unit 36 may be saturated or supersaturated with liquid vapor, in this embodiment water vapor, a separator vessel 42 may be connected to the exhaust of the first pumping unit 36, the vessel 42 containing any suitable material and/or structure for affecting the separation of water vapor from the CDA. The water extracted from the CDA is exhaust to a drain, and the CDA is vented to the atmosphere.

[0026] The second pumping unit 38 may comprise any suitable pump for extracting the liquid from the tank 32, and is preferably chosen for compatibility with the liquid extracted from the tank 32 and for relatively long maintenance periods. In this embodiment where the liquid is water, the second pumping unit 38 may conveniently comprise a water-powered ejector pump or a diaphragm pump for extracting water from the tank 32. In order to inhibit the transfer of vibrations to the tank 32 during use, the second pumping unit 38 is connected to the tank using flexible tubing 44. The internal diameter of the flexible tubing 44 may be chosen to restrict the flow rate of liquid from the tank 32 to the second pumping unit 38. Alternatively, or in addition, a fixed or variable flow restrictor may be located between the tank 32 and the second pumping unit 38.

[0027] In order to minimize any pressure fluctuations transmitted from the system 30 back to the fluid within the tool, the system 30 includes a pressure control system for maintaining a substantially constant pressure in the tank 32. In this embodiment, this is achieved by regulating the amounts of liquid and gas within the tank 32.

[0028] The amount of liquid contained in the tank 32 is maintained at a substantially constant level by a controller 46, thereby maintaining a substantially constant volume of gas in the tank 32. The controller 46 is connected to a sensor 48 for detecting the amount of liquid within the tank 32. The sensor 48 may comprise, for example, a level meter, float meter or other form of suitable sensor. The sensor 48 outputs a signal to the controller 46 indicative of the level of the liquid within the tank 32. In response to this signal, the controller 46 outputs to a variable flow control device 50 located between the tank 32 and a pressurized external liquid source 52 connected to the tank 32 a signal which causes the device 50 to vary the flow of liquid, in this embodiment water, to the tank 32. For example, the device 50 may be a butterfly or other control valve having a conductance that can be varied in dependence on, preferably in proportion to, the signal received from the controller 46. By varying the flow rate of the water to the tank from the external source 52, the controller 46 can compensate for any variation in the flow rate of fluid to the tank 32 from the tool and/or any variation in the rate of extraction of liquid from the tank 32 by the second pumping unit 38, and thus maintain the liquid in the tank 32 at a substantially constant level. The controller 46 may be arranged to process the signal received from the sensor 48 to compensate for any ripples generated in the surface of the liquid during use.

[0029] With the gas occupying a substantially constant volume within the tank 32, any variations in the amount of gas contained in the multi-phase fluid received from the tank, and/or any in the rate of extraction of gas from the tank 32 by the first pumping unit 36, and any temperature fluctuations within the tank 32, could vary the pressure of the gas within the tank 32, and impart pressure and flow fluctuations to the fluid in the tool. The pressure control system is therefore configured to maintain a substantially constant pressure within the tank 32 by also regulating the amount of gas within the tank 32.

[0030] To achieve this, the pressure control system comprises a controller 54 connected to a sensor 56 for detecting the gas pressure with the tank 32. The sensor 56 may comprise, for example, a pressure sensor, a capacitance manometer or other form of sensor of sufficient sensitivity to achieve the required level of pressure control. The sensor 56 outputs a signal to the controller 54 indicative of the gas pressure within the tank 32. In response to this signal, the controller 54 outputs to a variable flow control device 58 located between the tank 32 and a pressurized external gas source 60 connected to the tank 32 a signal which causes the device 58 to vary the flow of gas, in this embodiment CDA, to the tank 32. A further variable flow control device 62 may be located between the tank 32 and the first pumping unit 36 and configured to receive a signal from the controller 54 to vary the flow of gas from the tank 32. For example, the devices 58, 62 may also be butterfly or other control valves having a conductance that can be varied in dependence on, preferably in proportion to, the signal received from the controller. 54. By controlling the flow of gas into and out from the tank 32, the controller 54 can maintain a substantially constant gas pressure within the tank 32.

[0031] System 30 provides the capability of extracting a multi-phase fluid from the immersion lithography tool while minimizing any pressure fluctuations imparted thereby to the fluid within the tool.

[0032] In an embodiment, there is provided a system for extracting a stream of multi-phase fluid from a photo-lithography tool comprising: a pumping arrangement for drawing the fluid from the tool; separating means located upstream from the pumping arrangement for separating the fluid drawn from the tool into gas and liquid phases, the pumping arrangement further comprising a first pumping unit for extracting gas from the separating means and a second pumping unit for extracting liquid from the separating means; and a pressure control system for controlling the pressure within the separating means by regulating the amounts of gas and liquid therein.

[0033] In an embodiment, the pressure control system comprises gas supply means for supplying gas to the separating means from a source thereof, and control means for controlling the flow of gas to the separating means. In an embodiment, the gas supply means comprises a variable flow control device for gas supply to the separating means, the control means configured to vary the conductance of the variable flow control device to control the pressure within the separating means. In an embodiment, the control means comprises a controller configured to receive a signal indicative of the pressure within the separating means and to control the conductance of the variable flow control device. In an embodiment, the controller is further configured to control the flow of gas from the separating means in response to the received signal. In an embodiment, the pressure control system comprises a further variable flow control device through which gas is extracted from the separating means by the first pumping unit, the controller being configured to control the conductance of the further variable flow control device in response to the received signal. In an embodiment, the pressure control system comprises control means for controlling the flow of gas from the separating means. In an embodiment, the pressure control system comprises a variable flow control device through which gas is extracted from the separating means by the first pumping unit, the control means configured to control the conductance of the variable flow control device to control the pressure within the separating means. In an embodiment, the control means comprises a controller configured to receive a signal indicative of the pressure within the separating means, and to control the conductance of the variable flow control device. In an embodiment, the pressure control system comprises liquid supply means for supplying liquid to the separating means, and control means for controlling the flow of liquid to the separating means. In an embodiment, the control means is configured to control the amount of liquid within the separating means. In an embodiment, the liquid supply means comprises a variable flow control device through which liquid is supplied to the separating means, the control means configured to vary the conductance of the variable flow control device to control the amount of liquid within the separating means. In an embodiment, the control means comprises a controller configured to receive a signal indicative of the amount of liquid within the separating means, and to control the conductance of the variable flow control device in response to the received signal. In an embodiment, the pressure control system comprises liquid supply means for supplying liquid to the separating means from a source thereof, and liquid supply control means for controlling the flow of liquid to the separating means. In an embodiment, the liquid supply control means is configured to control the amount of liquid within the separating means. In an embodiment, the liquid supply means comprises a variable flow control device through which liquid is supplied to the separating means, the liquid supply control means being configured to vary the conductance of the variable flow control device to control the amount of liquid within the separating means. In an embodiment, the liquid supply control means comprises a controller configured to receive a signal indicative of the level of liquid within the separating means, and to control the conductance of the variable flow control device in response to the received signal. In an embodiment, the separation means comprises an extraction tank. In an embodiment, the system comprises a flexible tube for conveying gas from the separating means to the first pumping unit. In an embodiment, the system comprises a flexible tube for conveying liquid from the separating means to the second pumping unit. In an embodiment, the system comprises a flexible tube for conveying liquid from the photolithography tool to the separating means.

[0034] In an embodiment, there is provided a method of extracting a stream of multi-phase fluid from a photo-lithography tool, the method comprising the steps of: connecting a pumping arrangement to the tool via an extraction tank; operating the pumping arrangement to draw the fluid from the tool; separating the fluid drawn from the tool into gas and liquid phases within the extraction tank, the pumping arrangement extracting separately gas and liquid from the extraction tank; and controlling the pressure within the extraction tank by regulating the amounts of gas and liquid therewithin.

[0035] While the foregoing description and drawings represent the preferred embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the true spirit and scope of the present invention.