CN118285157A - Valve system, liquid target material supply apparatus, fuel emitter, radiation source, lithographic apparatus and flow regulating method - Google Patents

Abstract

The present invention relates to a valve system of an apparatus for supplying a target material to a radiation source, the target material having a melting temperature above room temperature and being under a pressure of at least 200 bar, wherein the valve system comprises: a chamber having a circular cross-section; a circular valve body arranged in the chamber and matching the circular cross-section of the chamber, wherein the chamber comprises a first port and a second port, wherein the valve body is rotatable about a rotation axis in a plane parallel to the plane of the circular cross-section between an open position and a closed position; in the open position, a channel in the valve body provides a flow path between the first port and the second port; in the closed position, the channel in the valve body is disconnected from at least the first port.

Description

Valve system, liquid target material supply device, fuel emitter, radiation source, photolithography device and flow rate regulation method

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European application No. 21209686.1 filed on November 22, 2021, and the entire contents of this European application are incorporated herein by reference.

Technical Field

The invention relates to a valve system for an apparatus for supplying a target material to a lithographic apparatus. The invention also relates to an apparatus for supplying a target material to a lithographic apparatus comprising such a valve system, a fuel emitter comprising such an apparatus, a radiation source comprising such a fuel emitter, and a lithographic apparatus comprising such a radiation source. The invention further relates to a method for regulating the flow of a solid or liquid target material using the valve system.

Background technique

A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. A lithographic apparatus can be used, for example, to manufacture integrated circuits (ICs). For example, a lithographic apparatus can project a pattern at a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of the radiation determines the minimum size of features that can be formed on the substrate. A lithographic apparatus using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4 to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on a substrate, compared to a lithographic apparatus using radiation with a wavelength of, for example, 193 nm.

EUV radiation is used in lithography processes to produce extremely small features in substrates or silicon wafers. Methods for generating EUV radiation include, but are not limited to, converting materials having elements such as xenon, lithium, or tin in a plasma state using emission lines in the EUV range. In one such method, often referred to as laser produced plasma ("LPP"), the desired plasma can be generated by irradiating a target material, such as in the form of droplets, slabs, ribbons, streams, or clusters of the material, with an amplified beam of light. For this process, the plasma is typically generated in a sealed container, such as a vacuum chamber, and various types of metrology equipment are used to monitor the plasma.

In current technology equipment for supplying tin target material in the form of droplets, a reservoir containing liquid tin is pressurized using argon gas pressurized to a pressure of about 200 to 700 bar. The pressurized liquid tin is then delivered to a nozzle configured to provide a stream of droplets of liquid tin to be irradiated by a radiation source to form a plasma.

In order to regulate the flow of liquid tin, a so-called freezing valve is used. The freezing valve can be implemented in a pipe section, wherein the temperature can be controlled to be above the melting temperature of the tin to allow the liquid to flow, or below the melting temperature to solidify the liquid tin in the pipe section and prevent any further flow of the tin. A disadvantage of the freezing valve is that it takes a considerable time to cool or heat the pipe section including the target material in the pipe section. Another disadvantage may be that the liquefaction and solidification may cause volume changes of the target material due to expansion or contraction of the target material during liquefaction and solidification. These volume changes may cause undesirable pressure changes. Yet another disadvantage may be that at relatively high pressures, solid tin may be undesirably squeezed out via the freezing valve.

Summary of the invention

In view of the above, an object of the present invention is to use a valve to quickly and accurately regulate the flow rate of a liquid target material.

According to an embodiment of the present invention, there is provided a valve system of an apparatus for supplying a target material to a radiation source, the target material having a melting temperature above room temperature and under a pressure of at least 200 bar, wherein the valve system comprises:

- a chamber having a circular cross section,

a circular valve body arranged in the chamber and matching the circular cross-section of the chamber,

wherein the chamber comprises a first port and a second port, wherein the valve body is rotatable about a rotation axis in a plane parallel to the plane of the circular cross-section between an open position and a closed position; in the open position, a channel in the valve body provides a flow path between the first port and the second port; and in the closed position, the channel in the valve body is disconnected from at least the first port.

According to another embodiment of the present invention, there is provided an apparatus for supplying a target material to a radiation source, the apparatus comprising: a reservoir system comprising a reservoir configured to be connected to a nozzle supply system; and a pressurizing system, the pressurizing system pressurizing the target material in the reservoir, wherein the target material has a melting temperature higher than room temperature, wherein the pressurizing system is configured to provide a pressure of at least 200 bar to the target material, and wherein the apparatus further comprises a valve system according to the present invention for regulating a flow of the target material from or to the reservoir.

According to another embodiment of the present invention, there is provided a fuel emitter comprising the apparatus according to the present invention and a nozzle supply system.

According to yet another embodiment of the present invention, there is provided a radiation source for a lithography tool comprising a fuel emitter according to the present invention.

According to another embodiment of the present invention, there is provided a lithographic apparatus comprising a radiation source according to the present invention.

According to another embodiment of the present invention, there is provided a method for regulating the flow of a solid or liquid target material using a valve system according to the present invention, the target material having a melting temperature above room temperature and under a pressure of at least 200 bar, the method comprising the following steps:

a) moving the valve body from the open position to the closed position, and

b) moving the valve body from the closed position to the open position.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

- FIG. 1 depicts a lithographic system comprising a lithographic apparatus and a radiation source;

- Fig. 2 schematically depicts a radiation source according to an embodiment of the invention;

- FIG. 3 a schematically depicts a cross-sectional top view of a valve system according to an embodiment of the invention in an open position;

- FIG. 3 b schematically depicts a cross-sectional top view of the valve system of FIG. 3 a in a closed position;

- FIG. 4 a schematically depicts a cross-sectional side view of the valve system of FIG. 3 a in an open position;

- FIG. 4 b schematically depicts a cross-sectional side view of the valve system of FIG. 3 b in a closed position;

- Fig. 5a schematically depicts a cross-sectional side view of a valve system according to another embodiment of the invention in an open position;

- FIG. 5 b schematically depicts a cross-sectional side view of the valve system of FIG. 6 a in a closed position;

- Fig. 6a schematically depicts a cross-sectional top view of a valve system according to another embodiment of the invention in an open position;

- FIG. 6 b schematically depicts a cross-sectional top view of the valve system of FIG. 6 a in a closed position;

- Figure 7a schematically depicts a cross-sectional side view of the valve system of Figure 6a in an open position; and

- Fig. 7b schematically depicts a cross-sectional side view of the valve system of Fig. 6b in a closed position.

Detailed ways

1 shows a lithographic system comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. In addition, the illumination system IL may include a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide an EUV radiation beam B having a desired cross-sectional shape and a desired intensity distribution. In addition to or instead of the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11, the illumination system IL may include other mirrors or arrangements.

After being so conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. For this purpose, the projection system PS may include a plurality of mirrors 13, 14, which are configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image having features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is shown as having only two mirrors 13, 14 in Figure 1, the projection system PS may include a different number of mirrors (for example, six or eight mirrors).

The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns an image formed by the patterned EUV radiation beam B' with a pattern previously formed on the substrate W.

A relative vacuum, ie a small amount of gas (eg hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL and/or in the projection system PS.

The radiation source SO shown in FIG1 is of a type that may be referred to as a laser produced plasma (LPP) source, for example. A laser system 1, which may, for example, include a CO ₂ laser, is arranged to deposit energy via a laser beam 2 into a fuel, which is alternatively referred to as a target material, such as tin (Sn) provided from, for example, a fuel emitter 3. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel may, for example, be in liquid form and may, for example, be a metal or an alloy. The fuel emitter 3 may include a nozzle supply system configured to guide tin, for example in the form of droplets, along a trajectory toward a plasma formation region 4. The laser beam 2 is incident on the tin at the plasma formation region 4. The deposition of laser energy into the tin generates a tin plasma 7 at the plasma formation region 4. During the de-excitation of electrons and the recombination of electrons with ions of the plasma, radiation including EUV radiation is emitted from the plasma 7.

EUV radiation from the plasma is collected and focused by a collector 5. The collector 5 includes, for example, a near normal incidence radiation collector 5 (sometimes more generally referred to as a normal incidence radiation collector). The collector 5 may have a multilayer mirror structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as 13.5 nm). The collector 5 may have an ellipsoidal configuration having two focal points. As described below, a first of the focal points may be at the plasma formation region 4, and a second of the focal points may be at the intermediate focus 6.

The laser system 1 may be spatially separated from the radiation source SO. In this case, the laser beam 2 may be delivered from the laser system 1 to the radiation source SO by means of a beam delivery system (not shown) comprising, for example, suitable guiding mirrors and/or a beam expander and/or other optical devices. The laser system 1, the radiation source SO and the beam delivery system may together be considered a radiation system.

The radiation reflected by the collector 5 forms an EUV radiation beam B. The EUV radiation beam B is focused at an intermediate focus 6 to form an image at the intermediate focus 6 of a plasma present at the plasma formation region 4. The image at the intermediate focus 6 acts as a virtual radiation source for illuminating the system IL. The radiation source SO is arranged so that the intermediate focus 6 is located at or near an opening 8 in an enclosure 9 of the radiation source SO.

FIG2 schematically depicts a radiation source SO according to an embodiment of the present invention that can be implemented in the lithographic apparatus LA of FIG1 . The radiation source SO comprises a fuel emitter 1111 similar to the fuel emitter 3 in FIG1 . The fuel emitter 1111 emits a stream ST of a target T so that the target Tp is delivered to a plasma formation position PF under a low pressure hydrogen environment 1101. The target Tp comprises a target material. The target material is any material that emits EUV radiation when in a plasma state. For example, the target material may comprise water, tin, lithium and/or xenon.

During operation, a container 1107 of a radiation source SO is maintained under a low pressure hydrogen environment 1101 by means of a hydrogen supply system and a pump system (both not shown). The radiation source SO comprises an optical source OS configured to generate a beam LB, such as a laser beam, and to deliver the beam LB to the low pressure hydrogen environment 1101 along an optical path OP. The optical source OS may comprise a pulsed laser device, such as a pulsed gas discharge CO2 laser device operating at a relatively high power, such as 10 kW or more, and a high pulse repetition rate, such as 40 kHz or more, for example using RF excitation to generate radiation of about 9300 nm or about 10600 nm. The pulse repetition rate may be, for example, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz or more. The plasma formation position PF receives the beam LB. The interaction between the beam LB and the target material in the target Tp generates a plasma PL that emits EUV radiation.

The fuel launcher 1111 includes an injection system 1104, which may include a capillary 1104ct fluidly coupled to a reservoir system 1112. The capillary 1104ct defines an orifice 1104o. The reservoir system 1112 accommodates a target material under a high pressure Pn. A transfer assembly may be disposed between the reservoir system 1112 and the injection system 1104. The target material is in a molten state and is capable of flowing, and the pressure Pext in the low-pressure hydrogen environment 1101 is much lower than the pressure Pn. Thus, the target material flows through the orifice 1104o. The capillary may be surrounded by a piezoelectric element (not shown) that excites the target material in the tube so as to generate an acoustic standing wave. The target material 102 may exit the orifice 1104o as a jet or continuous stream 1104cs of the target material. The jet of the target material decomposes into individual targets T (which may be droplets). The breakup of the jet 1104cs can be controlled so that individual droplets coalesce into larger droplets that reach the plasma formation position PF at a desired rate (e.g., tens of kHz, e.g., 50 kHz or greater). The target T in the stream ST can be generally spherical, with a diameter in the range of about 15 microns to 40 microns, e.g., about 30 microns. The stream of target T can be ejected from the ejection system 1104 using a combination of pressure within the reservoir system 1112 and vibration applied to the ejection system 1104 by a piezoelectric element (not shown).

In operation, a beam LB, which may be laser energy, is delivered synchronously with the operation of the fuel emitter 1111 to deliver a radiation pulse to cause each droplet Tp to become a plasma PL. In practice, the laser energy LB may be delivered in at least two pulses: a pre-pulse with finite energy may be delivered to the droplet before the pre-pulse with finite energy reaches the plasma formation position PF to transform the target material droplet into a disc-like shape. Then, a main pulse of laser energy LB may be delivered to the transformed target material at the plasma formation position PF to produce the plasma PL. A hopper 1130 may be disposed opposite the injection system 1104 to capture any target material that has not been transformed into plasma.

The radiation source SO may include a collector mirror 1105 having an aperture 1140 allowing the light beam LB to pass through and reach the plasma formation position PF. The collector mirror 1105 may be, for example, an ellipsoidal mirror having a primary focus at the plasma formation position PF and a secondary focus (also referred to as intermediate focus or IF) at an intermediate position 1106, wherein EUV radiation may be output from the radiation source SO and input to, for example, a lithography tool, such as the lithography apparatus LA of FIG.

The radiation source SO may further include a monitoring system 1150 to measure one or more parameters. The monitoring system 1150 may, for example, include one or more target or droplet imagers that provide an output indicating the position of the droplet, for example relative to the plasma formation position PF, and provide the output to the main controller 1160. The main controller 1160 may then be configured to calculate the droplet position and/or trajectory, from which the droplet position error may be calculated on a droplet-by-droplet or average basis. The monitoring system 1150 may additionally or alternatively include one or more radiation source detectors that measure one or more EUV radiation parameters, including but not limited to pulse energy, energy distribution as a function of wavelength, energy within a specific wavelength band, energy outside a specific wavelength band, and angular distribution of EUV intensity and/or average power.

The main controller 1160 may be configured to control the light source OS to adjust or set, for example, the beam position, direction, shaping and/or timing so as to adjust or set the position and/or focal length of the beam focus within the low-pressure hydrogen environment 1101. The main controller 1160 may additionally or alternatively be configured to control the injection system 1104 and/or the reservoir system 1112 of the fuel emitter 1111 to adjust or set, for example, the pressure Pn in the reservoir system 1112 and/or the release point of the target T as released using the injection system 1104 to allow the correct amount of target material to be delivered to the plasma formation position PF at the desired moment.

Figures 3a, 3b, 4a and 4b schematically depict a valve system 400 according to an embodiment of the present invention. The valve system 400 is suitable, for example, as a regulating device in an apparatus for supplying a target material to a lithographic radiation apparatus, such as the apparatus 1112 of the fuel emitter 1111 in Figure 2. Typical conditions for such an apparatus are that the target material has a melting temperature (i.e., a melting point) above room temperature and that the target material is under a pressure of at least 200 bar.

The valve system 400 includes a chamber 410 having a circular cross-section, and a circular valve body 420 disposed in the chamber 410 and matching the circular cross-section of the chamber 410 .

The chamber 410 includes a first port 411 and a second port 412. The valve body 420 includes a channel 421 and is capable of rotating in a plane parallel to the plane of the circular cross section around an axis of rotation 422. The plane parallel to the plane of the circular cross section is also parallel to the plane of the diagram in Figures 3a and 3b. The valve body 420 can rotate between an open position as shown in Figures 3a and 4a and a closed position as shown in Figures 3b and 4b. In the open position, the channel 421 provides a flow path between the first port 411 and the second port 412. In other words, the first port 411 is in fluid communication with the second port 412. In the closed position, the channel 421 rotates away from both the first port 411 and the second port 412, so that the channel 421 in the valve body 420 is disconnected from both the first port 411 and the second port 412.

An advantage of the valve system 400 is that switching requires only rotation of the valve body 420 in the chamber 410, which can be performed relatively quickly and does not require temperature changes. Therefore, switching can be performed without causing volume changes. Another advantage may be that in the closed position of the valve body, the valve system 400 can withstand relatively high pressures, even pressures high enough to push/force/squeeze solid target material through the channel 421 in the open position of the valve body.

In an embodiment, in the case of using a valve system for a liquid target material, the valve system itself may also act as a freezing valve. For example, the valve system may be configured to cool the target material to below the melting point in the closed position. The benefit may be that the solidified target material acts as a seal between the valve body 420 and the first port 411 and the second port 412. Although solidification may occur after rotation to the closed position, it may also occur before rotation to the closed position. Therefore, the valve body may include a temperature control system 420b for heating the target material in the valve body to a temperature above the melting temperature of the target material or cooling the target material in the valve body to a temperature below the melting temperature of the target material, respectively.

The valve body 420 is connected to the actuator 424 via a shaft 423, thereby allowing the actuator 424 to rotate the valve body between an open position and a closed position. However, other connections between the actuator 424 and the valve body 420 are also envisioned, for example, a gear can be connected to the valve body 420 having the same axis of rotation 422, and the gear can be driven by a sprocket, which has the benefit of introducing a gear ratio to reduce the required actuator force and improve position accuracy.

5a and 5b schematically depict cross-sectional side views of a valve system 400 according to another embodiment of the present invention. The valve system 400 is suitable, for example, as a regulating device in an apparatus for supplying a target material to a lithographic radiation apparatus, such as the apparatus 1112 of the fuel emitter 1111 in FIG. 2 . Typical conditions for such an apparatus are that the target material has a melting temperature (i.e., a melting point) above room temperature and that the target material is under a pressure of at least 200 bar.

The valve system 400 includes a chamber 410 having a circular cross-section, and a circular valve body 420 disposed in the chamber 410 and matching the circular cross-section of the chamber 410 .

The valve body 420 is rotatable about a rotation axis 422 in a plane parallel to the plane of the circular cross section between an open position as shown in FIG. 5 a and a closed position as shown in FIG. 5 b . The valve body 420 is a piston or plunger (or a part of the piston or plunger) that is movable in a direction parallel to the rotation axis 422 in the chamber 410.

The chamber 410 includes a first port 411, a second port 412, and a third port 413. The valve body 420 includes a first passage 421a that provides a flow path between the first port 411 and the second port 412 in an open position of the valve body. The valve body 420 further includes a second passage 421b that provides a flow path between the third port 413 and the second port 412 in an open position of the valve body.

When the valve body 420 is rotated from the open position shown in FIG. 5a to the closed position shown in FIG. 5b , for example by rotation of the valve body 420 as indicated by arrow A in FIG. 5a , the first channel 421a is disconnected from the first port 411 and the second channel 421b is disconnected from the third port 413, while the first channel 421a and the second channel 421b remain connected to the second port 412.

According to an embodiment, in the open position of the valve body, the target material and the pressure medium (e.g., argon, a mixture of argon and hydrogen, or helium) will be supplied via the first port and the second port. The valve system is configured to move the piston or plunger downward after the valve body has moved to the closed position. This will increase the pressure, for example to more than 200 bar, 500 bar, 700 bar, 1400 bar or 2000 bar, to move the tin to the droplet generator.

Alternatively or additionally, a variable reservoir volume is provided between the valve body 420 and the second port 412 due to the movability of the valve body 420 in a direction parallel to the rotation axis 422. Thus, when the valve body is in an open position, it is possible to fill the reservoir volume with a target material using the first port and/or the third port, and then rotate the valve body to a closed position and push the target material out of the second port 412.

The embodiments of Figures 3a to 5b can be configured to function when channels 421 and/or 421a and/or 421b contain liquid target materials, respectively. Additionally or alternatively, the embodiments of Figures 3a to 5b can be configured to function when channels 421 and/or 421a and/or 421b contain solid target materials, respectively.

The chamber 410 and the valve body 420 of the above-described embodiments may include one or more of the following materials: polyimide, polytetrafluoroethylene, tungsten, tantalum, molybdenum, or suitable alloys thereof.

The described valve system 400 may further include a freezing valve connected to the first port 411 or the second port 412, the freezing valve including a temperature control system, which is used to heat the target material in the freezing valve to a temperature higher than the melting temperature of the target material or cool the target material in the freezing valve to a temperature lower than the melting temperature of the target material, respectively.

Although in the embodiments of Figures 5a and 5b, the second port 412 is connected to both the first channel 421a and the second channel 421b, it is also possible that the chamber includes a fourth port, wherein the first channel provides a flow path between the first port and the second port, and the second channel provides a flow path between the third port and the fourth port.

In the embodiments of Figures 5a and 5b, the first channel 421a and the second channel 421b may be used for different materials. The first channel 421a may be configured to supply the target material, and the second channel 421b may be configured to supply the pressure fluid, for example.

Figures 6a, 6b, 7a and 7b schematically depict a valve system 400 according to yet another embodiment of the present invention. The valve system 400 is suitable, for example, as a regulating device in an apparatus for supplying a target material to a lithographic radiation apparatus, such as the apparatus 1112 of the fuel emitter 1111 in Figure 2. Typical conditions for such an apparatus are that the target material has a melting temperature (i.e., a melting point) above room temperature and that the target material is under a pressure of at least 200 bar.

The valve system 400 includes a spherical chamber 410 having a circular cross-section and a spherical valve body 420 disposed in the chamber 410 and matching the circular cross-section of the chamber 410 .

The chamber 410 includes a first port 411 and a second port 412. The valve body 420 includes a channel 421 and is capable of rotating in a plane parallel to the plane of the circular cross section around an axis of rotation 422. The plane parallel to the plane of the circular cross section is also parallel to the plane of the diagram in Figures 6a and 6b. The valve body 420 can rotate between an open position as shown in Figures 6a and 7a and a closed position as shown in Figures 6b and 7b. In the open position, the channel 421 provides a flow path between the first port 411 and the second port 412. In other words, the first port 411 is in fluid communication with the second port 412. In the closed position, the channel 421 rotates away from both the first port 411 and the second port 412, so that the channel 421 in the valve body 420 is disconnected from both the first port 411 and the second port 412.

An advantage of the valve system 400 is that switching requires only rotation of the valve body 420 in the chamber 410, which can be performed relatively quickly and does not require temperature changes. Therefore, switching can be performed without causing volume changes. Another advantage may be that in the closed position of the valve body, the valve system 400 can withstand relatively high pressures, even pressures high enough to push/force/squeeze solid target material through the channel 421 in the open position of the valve body.

In an embodiment, in the case of using a valve system for a liquid target material, the valve system itself may also act as a freezing valve. For example, the valve system may be configured to cool the target material to below the melting point in the closed position. The benefit may be that the solidified target material acts as a seal between the valve body 420 and the first port 411 and the second port 412. Although solidification may occur after rotation to the closed position, it may also occur before rotation to the closed position. Therefore, the valve body may include a temperature control system for heating the target material in the valve body to a temperature above the melting temperature of the target material or cooling the target material in the valve body to a temperature below the melting temperature of the target material, respectively.

The valve body 420 is connected to the actuator 424 via a shaft 423, thereby allowing the actuator 424 to rotate the valve body between an open position and a closed position. However, other connections between the actuator 424 and the valve body 420 are also envisioned, for example, a gear can be connected to the valve body 420 having the same axis of rotation 422, and the gear can be driven by a sprocket, which has the benefit of introducing a gear ratio to reduce the required actuator force and improve position accuracy.

The advantage of the valve body having a spherical shape rather than a disc shape as in the embodiments of Figures 3a, 3b, 4a and 4b is that the valve seal is less sensitive to deflection of a spherical valve body than a disc-shaped valve body. In the closed position, the spherical valve body will automatically push over the entire circumference of the low-pressure side port, thereby creating a seal that is insensitive to deflection. The area at the high-pressure side is also automatically larger than the area at the low-pressure side, and therefore a net force will be generated in the closing direction, thereby maintaining the seal.

Although in the above embodiments the pressure has been specified as at least 200 bar, the pressure may be higher than 300 bar, preferably higher than 500 bar, more preferably higher than 700 bar, even more preferably at least 900 bar, even more preferably at least 1100 bar, and most preferably at least 1300 bar, for example 1400 bar.

Although specific reference may be made herein to the use of lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include: manufacturing integrated optical systems, guidance and detection patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

Although embodiments of the invention may be specifically referenced herein in the context of lithographic equipment, embodiments of the invention may be used for other equipment. Embodiments of the invention may form part of mask inspection equipment, metrology equipment, or any equipment for measuring or processing objects such as wafers (or other substrates) or masks (or other pattern forming devices). These equipment may be collectively referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

Although the above may have made specific reference to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention is not limited to optical lithography and may be used in other applications such as imprint lithography where the context permits.

Where the context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form that can be read by a machine (e.g., a computing device). For example, a machine-readable medium may include: a read-only memory (ROM); a random access memory (RAM); a magnetic storage medium; an optical storage medium; a flash memory device; an electrical, optical, acoustic, or other form of a propagating signal (e.g., a carrier wave, an infrared signal, a digital signal, etc.), etc. In addition, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that these descriptions are merely for convenience, and that these actions are in fact caused by a computing device, a processor, a controller, or other device that executes firmware, software, routines, instructions, etc., and that doing so may cause an actuator or other device to interact with the physical world.

Although specific embodiments of the present invention have been described above, it will be appreciated that the present invention may be practiced in other ways than those described. The above description is intended to be illustrative, not restrictive. Therefore, it will be apparent to those skilled in the art that the described invention may be modified without departing from the scope of the aspects set forth below.

aspect

1. A valve system for an apparatus for supplying a target material to a radiation source, the target material having a melting temperature above room temperature and under a pressure of at least 200 bar, wherein the valve system comprises:

- a chamber having a circular cross section,

a circular valve body arranged in the chamber and matching the circular cross-section of the chamber,

wherein the chamber comprises a first port and a second port, wherein the valve body is rotatable about a rotation axis in a plane parallel to the plane of the circular cross-section between an open position and a closed position; in the open position, a channel in the valve body provides a flow path between the first port and the second port; and in the closed position, the channel in the valve body is disconnected from at least the first port.

2. A valve system according to aspect 1, wherein the valve body is a plunger or piston, or a part of a plunger or piston, and the plunger or piston is capable of moving in the chamber in a direction parallel to the rotation axis, thereby providing a variable reservoir volume between the valve body and the second port.

3. The valve system of aspect 1, wherein the chamber and the valve body are configured such that in the closed position of the valve body, the passage in the valve body is disconnected from the second port.

4. The valve system of any one of aspects 1 to 3, the valve system being configured to rotate the valve body when the channel contains a liquid target material.

5. The valve system of any one of aspects 1 to 3, the valve system being configured to rotate the valve body when the channel contains a solid target material.

6. The valve system of any one of aspects 1 to 5, wherein the target material is tin.

7. The valve system according to any one of aspects 1 to 6, wherein the chamber and the valve body include one or more of the following materials: polyimide, polytetrafluoroethylene, tungsten, tantalum, molybdenum.

8. The valve system according to any one of Aspects 1 to 7 further includes a freezing valve connected to the first port or the second port, the freezing valve including a temperature control system, which is used to heat the target material in the freezing valve to a temperature higher than the melting temperature of the target material or cool the target material in the freezing valve to a temperature lower than the melting temperature of the target material, respectively.

9. The valve system of any one of aspects 1 to 8, wherein the chamber comprises a third port, and wherein the valve body has an open position in which the third port is connected to the passage in the valve body.

10. The valve system of aspect 9, wherein the chamber and the valve body are configured such that in the closed position of the valve body, the passage in the valve body is disconnected from the third port.

11. A valve system according to any one of aspects 1 to 8, wherein the chamber includes a third port and a fourth port, and wherein the valve body has a second channel to provide a flow path between the third port and the fourth port in an open position, and wherein, in a closed position, the second channel is disconnected from at least the third port.

12. The valve system of aspect 1, wherein the passage in the valve body is configured for the target material, and wherein the second passage in the valve body is configured for a pressure fluid.

13. A valve system according to any one of aspects 1 to 12, wherein the valve system is configured for use with a target material at a pressure of at least 300 bar, preferably above 700 bar, more preferably at least 900 bar, even more preferably at least 1100 bar, and most preferably at least 1300 bar.

14. A device for supplying a target material to a radiation source, the device comprising: a reservoir system, the reservoir system comprising a reservoir configured to be connected to a nozzle supply system; and a pressurizing system, the pressurizing system pressurizing the target material in the reservoir, wherein the target material has a melting temperature higher than room temperature, wherein the pressurizing system is configured to provide a pressure of at least 200 bar to the target material, and wherein the device also includes a valve system according to any one of Aspects 1 to 13 for regulating the flow of the target material from or to the reservoir.

15. The apparatus according to aspect 14, wherein the valve system is the valve system according to aspect 5, and wherein the valve system is arranged at a position where the temperature is below the melting temperature of the target material.

16. An apparatus according to aspect 15, wherein the pressurizing system is configured to pressurize the solid target material in the reservoir, wherein the apparatus further comprises a heating system arranged between the reservoir and the nozzle supply system to liquefy the solid target material after the solid target material is pressurized in the reservoir, and wherein the valve system is arranged between the reservoir and the heating system.

17. The apparatus according to aspect 14, wherein the valve system is the valve system according to aspect 4, and wherein the valve system is arranged at a position where the temperature is higher than the melting temperature of the target material.

18. An apparatus according to aspect 14 or 17, wherein the pressurizing system is configured to pressurize the liquid target material in the reservoir, wherein the valve system is the valve system according to aspect 4, wherein the apparatus further comprises: a filling system configured to receive a solid substance including the target material; and a conveying system extending from the filling system to the reservoir system, wherein the conveying system is configured to provide a flow path between the filling system and the reservoir system, and wherein the valve system is arranged in the flow path provided by the conveying system to control the flow of the target material from the filling system.

19. The apparatus of any one of aspects 14 to 18, wherein the target material is tin.

20. A fuel launcher comprising an apparatus according to any one of aspects 14 to 19 and a nozzle supply system.

21. The fuel emitter of aspect 20, wherein the nozzle supply system is configured to eject a stream of droplets into a plasma formation location.

22. The fuel emitter of aspect 21 further comprising a droplet monitoring device for monitoring the droplet stream.

23. The fuel launcher of aspect 22, further comprising a control unit for adjusting the pressure applied by the pressurizing system to the solid target material in the reservoir based on the output of the droplet monitoring device.

24. The fuel emitter of aspect 22, further comprising a control unit for adjusting operation of the nozzle supply system based on the output of the droplet monitoring device.

25. A radiation source for a lithography tool, the radiation source comprising a fuel emitter according to any one of clauses 20 to 24.

26. The radiation source of clause 25, wherein the radiation source is configured to output EUV radiation.

27. The radiation source of aspect 25 or 26, wherein the radiation source is a laser produced plasma source.

28. A lithographic apparatus comprising a radiation source according to any of clauses 25 to 27.

29. A method for regulating the flow of a solid or liquid target material using a valve system according to any one of aspects 1 to 13, the target material having a melting temperature above room temperature and under a pressure of at least 200 bar, the method comprising the steps of:

a. moving the valve body from the open position to the closed position, and

b. Moving the valve body from the closed position to the open position.

30. A method according to aspect 29, wherein the target material is at a pressure of at least 300 bar, preferably above 700 bar, more preferably at least 900 bar, even more preferably at least 1100 bar, and most preferably at least 1300 bar.

Claims (17)

1. A valve system for an apparatus for supplying a target material to a radiation source, the target material being under a pressure of at least 200 bar, wherein the valve system comprises: - a chamber having a circular cross section, - a valve body arranged in the chamber and having a circular cross section matching the circular cross section of the chamber, wherein the chamber comprises a first port and a second port, wherein the valve body is rotatable between an open position and a closed position about a rotation axis in a plane parallel to the plane of the circular cross-section; in the open position, a channel in the valve body provides a flow path between the first port and the second port; and in the closed position, the channel in the valve body is disconnected from at least the first port. 2. A valve system according to claim 1, wherein the valve body is a plunger or piston capable of moving in the chamber in a direction parallel to the rotation axis to provide a variable reservoir volume between the valve body and the second port, or a part of the plunger or piston. 3 . The valve system of claim 1 , wherein the chamber and the valve body are configured such that in the closed position of the valve body, the passage in the valve body is disconnected from the second port. 4. The valve system according to any one of claims 1 to 3, wherein the chamber and the valve body comprise one or more of the following materials: polyimide, polytetrafluoroethylene, tungsten, tantalum, molybdenum. 5. The valve system according to any one of claims 1 to 4, further comprising a freezing valve connected to the first port or the second port, the freezing valve comprising a temperature control system, which is used to heat the target material in the freezing valve to a temperature higher than the melting temperature of the target material or cool the target material in the freezing valve to a temperature lower than the melting temperature of the target material, respectively. 6. The valve system according to any one of claims 1 to 5, wherein the chamber comprises a third port, and wherein the valve body has an open position wherein the third port is connected to the passage in the valve body. 7. The valve system of claim 6, wherein the chamber and the valve body are configured such that in the closed position of the valve body, the passage in the valve body is disconnected from the third port. 8. The valve system according to any one of claims 1 to 7, wherein the valve system is configured for a target material at a pressure of at least 300 bar, preferably above 700 bar, more preferably at least 900 bar, even more preferably at least 1100 bar, and most preferably at least 1300 bar. 9. An apparatus for supplying a target material to a radiation source, the apparatus comprising: a reservoir system, the reservoir system comprising a reservoir configured to be connected to a nozzle supply system; and a pressurizing system, the pressurizing system pressurizing the target material in the reservoir, wherein the target material has a melting temperature higher than room temperature, wherein the pressurizing system is configured to provide a pressure of at least 200 bar to the target material, and wherein the apparatus further comprises a valve system according to any one of claims 1 to 8 for regulating the flow of the target material from or to the reservoir. 10. The apparatus of claim 9, wherein the valve system is a valve system according to any one of claims 1 to 3, and is further configured to rotate the valve body when the channel contains a solid target material, and wherein the valve system is arranged at a position where the temperature is lower than the melting temperature of the target material. 11. The apparatus of claim 10, wherein the pressurizing system is configured to pressurize the solid target material in the reservoir, wherein the apparatus further comprises a heating system arranged between the reservoir and the nozzle supply system to liquefy the solid target material after the solid target material is pressurized in the reservoir, and wherein the valve system is arranged between the reservoir and the heating system. 12. The apparatus of claim 9, wherein the apparatus comprises a valve according to any one of claims 1 to 3, the valve further being configured to rotate the valve body when the channel contains a liquid target material, wherein the valve system is arranged at a position where the temperature is higher than the melting temperature of the target material. 13. An apparatus according to claim 9 or 12, wherein the pressurizing system is configured to pressurize the liquid target material in the reservoir, wherein the valve system is a valve system according to any one of claims 1 to 3, and the valve system is further configured to rotate the valve body when the channel contains the liquid target material, wherein the apparatus further comprises: a filling system, the filling system being configured to receive a solid substance including the target material; and a conveying system, the conveying system extending from the filling system to the reservoir system, wherein the conveying system is configured to provide a flow path between the filling system and the reservoir system, and wherein the valve system is arranged in the flow path provided by the conveying system to control the flow of the target material from the filling system. 14. A fuel launcher comprising an apparatus as claimed in any one of claims 9 to 13, the fuel launcher further comprising a nozzle supply system. 15. A radiation source for a lithography tool, the radiation source comprising a fuel emitter according to claim 14. 16. A lithographic apparatus comprising a radiation source according to claim 15. 17. A method for regulating the flow of a solid or liquid target material having a melting temperature above room temperature and under a pressure of at least 200 bar using a valve system according to any one of claims 1 to 8, the method comprising the steps of: a. moving the valve body from the open position to the closed position, and b. Moving the valve body from the closed position to the open position.