CN113812215A

CN113812215A - Protection system for extreme ultraviolet light source

Info

Publication number: CN113812215A
Application number: CN202080034591.8A
Authority: CN
Inventors: S·德德亚; H·G·泰格波什; R·W·J·M·范登布蒙
Original assignee: ASML Holding NV
Current assignee: ASML Holding NV; ASML Netherlands BV
Priority date: 2019-05-08
Filing date: 2020-05-07
Publication date: 2021-12-17
Also published as: WO2020225347A1; TWI853024B; NL2025434A; JP2022532840A; TW202105040A; JP7536784B2; KR20220005464A

Abstract

A target delivery system for an Extreme Ultraviolet (EUV) source comprising: a conduit comprising an outer, inner conduit region and an end defining an aperture. The inner conduit region is configured to receive a target material that emits EUV light when in a plasma state, and the aperture is configured to provide the target material to an interior of the vacuum chamber. The target delivery system also includes a protection system configured to flow a shielding gas away from the end defining the aperture and toward an interior of the vacuum chamber. The flowing shielding gas is configured to direct the one or more contaminant species away from the end defining the aperture.

Description

Protection system for extreme ultraviolet light source

CorrelationCross reference to applications

This application claims priority from U.S. application No. 62/845,007 entitled "PROTECTION SYSTEM FOR extrem ULTRAVIOLET LIGHT SOURCE" filed on 8/5 in 2019, which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to a protection system for an Extreme Ultraviolet (EUV) light source.

Background

Extreme ultraviolet ("EUV") light, e.g., electromagnetic radiation having a wavelength of 100 nanometers (nm) or less (sometimes also referred to as soft x-rays), and including light having a wavelength of, for example, 20nm or less, between 5 and 20nm, or between 13 and 14nm, may be used in a lithographic process to produce extremely small features in a substrate (e.g., a silicon wafer) by inducing polymerization in a resist layer.

Methods of producing EUV light include, but are not necessarily limited to, converting materials comprising elements such as xenon, lithium, or tin, which materials when in a plasma state have emission lines in the EUV range. In one such method, commonly referred to as laser produced plasma ("LPP"), the required plasma can be produced by: the target material, for example in the form of droplets, plates, ribbons, streams or clusters of material, is irradiated with an amplified beam which may be referred to as a drive laser. For this process, plasma is typically generated in a sealed container (e.g., a vacuum chamber) and monitored using various types of metrology equipment.

Disclosure of Invention

In one aspect, a target delivery system for an Extreme Ultraviolet (EUV) source comprises: a conduit comprising an outer, inner conduit region and an end defining an aperture. The inner conduit region is configured to receive a target material that emits EUV light when in a plasma state, and the aperture is configured to provide the target material to an interior of the vacuum chamber. The target delivery system also includes a protection system configured to flow a shielding gas away from the end defining the aperture and toward an interior of the vacuum chamber. The flowing shielding gas is configured to direct the one or more contaminant species away from the end defining the aperture.

Implementations may include one or more of the following features. The shielding gas may include an inert gas or a reactive gas.

The shielding gas may include molecular hydrogen (H)₂)。

The shielding system may be configured to flow shielding gas along an exterior of the conduit. The protective system can include a body including a sidewall surrounding at least a portion of an exterior of the conduit, the body defining an open end region aligned with the aperture of the conduit. The shielding gas may flow in an open space between an exterior of the conduit and an inner wall of the sidewall, and the shielding gas may flow through the open end region to exit the body. The sidewall can include at least one port in fluid communication with the open space, the at least one port configured to be fluidly coupled to a gas supply containing a shielding gas.

The protection system includes at least one gas source.

The target delivery system may further include a temperature control block at least partially surrounding an exterior of the conduit, and the protection system may include a body surrounding at least a portion of the temperature control block, the body defining an open end region aligned with the aperture of the conduit. The shielding gas may flow in an open space between the temperature control block and an inner wall of the body, and the shielding gas may exit the body through the open end region.

The one or more pollutants may include mobile substances, and the flowing fluid may be configured to reduce interaction between the one or more mobile pollutants and the end of the conduit by changing a direction of motion of the one or more mobile pollutants away from the end of the conduit.

The one or more pollutants may include mobile substances, and the flowing fluid may be configured to prevent interaction between the one or more mobile pollutants and the end of the conduit by changing a direction of movement of the one or more mobile pollutants away from the end of the conduit.

The one or more pollutants may include one or more of a gas, a liquid, a vapor, and particles.

The one or more contaminating species may include silicon (Si) or silicon dioxide (SiO)₂)。

The one or more pollutants may include oxygen, water, or carbon dioxide (CO)₂)。

The conduit may comprise a capillary tube.

The shielding system may include a diffuser arrangement including a plurality of openings, each of which may be configured to direct shielding gas away from an end defining an aperture. The plurality of openings may surround the exterior of the conduit and may be evenly distributed with respect to the exterior of the conduit.

In another aspect, a method of protecting an orifice of a target material delivery system includes: passing target material through an aperture to provide a target stream to the interior of the vacuum chamber, each target in the stream comprising target material that emits EUV light when in a plasma state; and flowing a shielding gas in the target material delivery system and into the interior of the vacuum chamber away from the orifice, the shielding gas directing the one or more contaminating substances away from the orifice.

Implementations may include one or more of the following features. In some implementations, the flowing shielding gas does not alter the trajectory of the targeted stream. The flowing shielding gas may have a component of motion along the direction of travel of the stream of the target.

Flowing the shielding gas may include flowing the shielding gas in an open space between a conduit defining the aperture and a body surrounding the conduit. The shielding gas may flow into the open space at a port in the body and may flow out of the space through an open end region defined by the body and aligned with the aperture.

The shielding gas may have a uniform volumetric flow rate at the aperture between the orifice and the interior of the vacuum chamber.

The method may further include determining a status of an extreme ultraviolet light source comprising the target material delivery system; and determining which of a plurality of shielding gases is to be used as the shielding gas based on the determined state.

Implementations of any of the above techniques may include an EUV light source, a target supply system, a method, a process, an apparatus, or a device. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

Drawings

Fig. 1 is a block diagram of an example of an EUV light source.

Fig. 2A is a side cross-sectional view of an example of a supply system.

FIG. 2B is a bottom view of the supply system of FIG. 2A along line 2A-2A' of FIG. 2A.

Fig. 2C is a side cross-sectional view of another example of a supply system.

FIG. 2D is a bottom view of the supply system of FIG. 2C along line 2C-2C' of FIG. 2C.

Fig. 3A is a side cross-sectional view of another example of a supply system.

Fig. 3B is a bottom view of the supply system of fig. 3A.

Fig. 4A is a side cross-sectional view of another example of a supply system.

Fig. 4B is a bottom view of the supply system of fig. 5A.

Fig. 5A and 5B are flow diagrams of example processes associated with flowing a shielding gas.

Fig. 6 and 7 are block diagrams of examples of a lithographic apparatus.

Fig. 8 is a block diagram of an example of an EUV light source.

Detailed Description

Referring to FIG. 1, a block diagram of an EUV light source 100 including a supply system 110 is shown. The supply system 110 includes a protection system 130, the protection system 130 protecting the supply system 110 by directing a shielding gas 131 (shown in dotted and dashed form in fig. 1, 3A, and 4A) away from the supply system 110. The shielding gas 131 carries the contaminant 150 (shown as a shaded circle in fig. 1) away from the supply system 110 and/or prevents the contaminant 150 from reaching the supply system 110.

The supply system 110 emits a target stream 121 such that a target 121p is transported to a plasma formation location 123 in the vacuum chamber 109. The target 121p includes a target material that is of a material having a characteristic of when in a plasma stateAny material having an emission line in the Extreme Ultraviolet (EUV) range. The target material may be, for example, tin, lithium or xenon. Other materials may be used as the target material. For example, tin element may be used as pure tin (Sn); tin compounds, e.g. SnBr₄、SnBr₂、SnH₄(ii) a Tin alloys, such as tin-gallium alloys, tin-indium-gallium alloys, or any combination of these alloys.

The plasma formation location 123 receives the light beam 106. A light beam 106 is generated by a light source 105 and is transported to a vacuum chamber 109 via an optical path 107. The interaction between the beam 106 and the target material in the target 121p produces a plasma 196 that emits EUV light 197. The optical element 198 directs EUV light 197 towards a lithography tool 199.

Supply system 110 includes a conduit 112. The conduit 112 is a three-dimensional object, such as a tube or cylinder, defined by sidewalls 114. The sidewall 114 extends from a first end 115 to a second end 116. The second end 116 includes an aperture 117 that passes through the sidewall 114 into the interior of the conduit 112 and is fluidly coupled to the reservoir 140. The reservoir 140 holds a target mixture 141, which target mixture 141 comprises the target material and may also comprise impurities. In operational use, the target mixture 141 flows in the conduit 112 and is emitted from the orifice 117 as stream 121.

In the example of fig. 1, the supply system 110 also includes an actuator 135 mechanically coupled to the sidewall 114. The actuator 135 may be, for example, a piezoceramic material, such as lead zirconate titanate (PZT), that changes shape in response to application of a voltage. The sidewall 114 is deformed by the actuator 135. The sidewall 114 is deformed, thereby adjusting the pressure of the target mixture in the conduit 112 and breaking up the target material of the stream 121 flowing through the orifice into the target. The size and spacing of the targets in stream 121 may be controlled by controlling the frequency and/or amplitude of the deformation applied by actuator 135. Stream 121 includes a plurality of different spherical targets having diameters of, for example, 30 micrometers (μm). The supply system 110 may deliver the target material to the vacuum chamber 109 in another manner. For example, the supply system 110 may produce a jet of target material that does not break into individual targets.

The provisioning system 110 also includes a protection system 130. The shielding system 130 includes a gas directing system 132, the gas directing system 132 directing shielding gas 131 away from the second end 116. Gas directing system 132 includes a gas management system 167, and gas management system 167 includes devices, components, and/or systems configured to direct shielding gas 131. For example, the gas directing system 132 may include a pump, a flow control device (such as a valve and/or a fluid switch), an opening through which the shielding gas 131 flows, and/or a nozzle.

The gas directing system 132 is fluidly coupled to a gas supply 133 via a fluid connection 134. The gas supply 133 includes a chamber 137, and the chamber 137 contains a gas used as the shielding gas 131. For example, the chamber 137 of the gas supply device 133 may contain an inert gas or a reactive gas. The inert gas is a gas that does not react with anything in the vacuum chamber 109. The reactive gas is a gas capable of reacting with one or more articles within the vacuum chamber 109. The shielding gas 131 may be, for example, molecular hydrogen (H)₂) Or argon (Ar). The shielding gas 131 may include a non-gaseous phase. For example, the shielding gas 131 may include solid nanoclusters carried by the shielding gas 131.

In some implementations, the chamber 137 contains more than one different gas. For example, chamber 137 may include multiple chambers that are not fluidly coupled to each other, but each chamber is configured to be fluidly coupled to fluid connection 134. In these implementations, one chamber may include, for example, molecular hydrogen (H)₂) The other chamber may include argon (Ar) gas. In implementations including more than one chamber 137, the gas management system 167 includes a fluid switching mechanism that allows selection of one of the chambers 137.

In the example of FIG. 1, the flow 121 generally travels along the-X direction, and the shielding gas 131 also flows along the sidewall 114 and into the vacuum chamber 109 in the-X direction. The second end 116 extends generally in the Y-Z plane. Thus, the shielding gas 131 flows away from the second end 116 and the aperture 117. By directing the shielding gas 131 away from the second end 116, the shielding system 130 protects the supply system 110 from the contaminated material 150. In various implementations, the shielding gas 131 is parallel or substantially parallel to the direction of motion of the targets in the stream 121.

The contaminant 150 is any substance capable of blocking the orifice 117 and/or adhering to the second end 116 in a manner that blocks the orifice 117. For example, the contaminant 150 may be capable of forming a layer on the second end 116 that completely or partially blocks the orifice 117. The contaminant 150 moves within the vacuum chamber 109. For example, without the shielding gas 131, the contaminant 150 may move toward the second end 116 and/or the orifice 117. In response to interaction with the shielding gas 131, the contaminant 150 moves away from the second end 116 and the orifice 117.

The contaminant material 150 may include solid, liquid, and/or gaseous materials. The contaminant 150 may include more than one type of contaminant and/or more than one substance. For example, the contaminant 150 may include silicon dioxide, siloxane, silicon dioxide (SiO)₂) Tin oxide (SnO)₂) Particles of a gas (such as oxygen) and/or a vapor (such as tin vapor). The contaminant 150 may include, for example, silicon (Si), silicon dioxide (SiO) that can be deposited on the second end 216 from a vapor phase₂) And/or tin oxide (SnO)₂) Of (2) is added. The contaminant 150 may come from components within the vacuum chamber 109, and/or from items in the vacuum chamber 109 with oxygen, water, and/or carbon dioxide (CO) when the vacuum chamber 109 is depressurized₂) The interaction of (a).

By directing the contaminant 150 away from the second end 116, the shielding gas 131 prevents or reduces the likelihood of a layer of the contaminant 150 forming on the second end 116. A layer of contaminant material 150 on second end 116 may interfere with the formation of stream 121. For example, such a layer may completely or partially block the orifice 117, thereby blocking the flow 121 and/or altering the properties of the flow 121. Because stream 121 includes a target for producing EUV light 197, unexpected and/or undesired changes in stream 121 may result in reduced production of EUV light 197. Thus, by directing the contaminant 150 away from the end 116 and the aperture 117, the protection system 130 improves the overall performance of the supply system 110 and the EUV light source 100. In addition to improving the overall performance of the EUV light source 100 during operation, the protection system 130 also reduces the downtime of the EUV light source 100. For example, to remove a layer of contaminant 150 from the second end 116, the supply system 110 is removed from the EUV light source 100. Thus, by preventing or reducing the accumulation of contaminant 150 on the second end 116, the protection system 130 also reduces the amount of maintenance performed on the supply system 110 and reduces the downtime of the EUV light source 100.

The EUV light source 100 also includes a control system 160 that controls operation of the protection system 130. Control system 160 can be coupled to gas supply 133, gas management system 167, and/or gas direction system 132. For example, the control system 160 may control the flow of the shielding gas 131 by controlling valves and/or pumps within the gas directing system 132 or the gas supply 133. In another example, in implementations where gas supply 133 includes multiple chambers 137, control system 160 may be used to control switches in gas management system 167. This allows the control system 160 to switch between chambers such that the shielding gas 131 is formed by the gas in one of the chambers at a particular time. The control system 160 may also be coupled to other systems and components of the EUV light source 100, such as the actuator 135 and/or the light source 105.

Control system 160 includes an electronic processing module 161, an electronic storage device 162, and an I/O interface 163. The electronic processing module 161 comprises one or more processors suitable for the execution of a computer program, such as a general or special purpose microprocessor, and any one or more processors of any kind of digital computer. Generally, an electronic processor receives instructions and data from a read-only memory, a Random Access Memory (RAM), or both. The electronic processing module 161 may be any type of suitable electronic processor.

Electronic storage 162 may be volatile memory, such as RAM, or non-volatile memory. In some implementations, electronic storage 162 includes non-volatile and volatile portions or components. Electronic storage 162 may store data and information used in the operation of control system 160. For example, the electronic storage 162 may store information regarding the operation of the supply system 110 and/or the protection system 130. For example, in some implementations, the electronic storage 162 stores a flow rate at which the shielding gas 131 should flow from the gas directing system 132 during typical operation of the EUV light source 100.

The electronic storage 162 also stores instructions, such as one or more computer programs, that, when executed, cause the electronic processing module 161 to communicate with components in the provisioning system 110 and/or the protection system 130. For example, the electronic storage 162 may store instructions that cause the electronic processing module 161 to provide a modulated signal sufficient to cause the actuator 135 to vibrate the catheter.

I/O interface 163 is any type of interface that allows control system 160 to receive or transmit information or data. For example, the I/O interface 163 may be a keyboard, mouse, or other computer peripheral that enables an operator to operate and/or program the control system 160. The I/O interface 163 may include a device that produces a perceptible alarm, such as a light or a speaker. Further, the I/O interface 163 may include a communication interface, such as a universal serial port (USB), a network connection, or any other interface that allows communication with the control system 160.

Fig. 2A is a side cross-sectional view of supply system 210 in the X-Z plane, supply system 210 including conduit 212 and gas directing system 232. Fig. 2B is a bottom view of conduit 212 and gas direction system 232 in the Y-Z plane, as seen from line 2A-2A' of fig. 2A. In fig. 2B, the X direction is a direction into the page. The conduit 212 may be used for the EUV light source 100 (fig. 1). The conduit includes a sidewall 214 extending along the X-direction from a first end 215 to a second end 216. The sidewall 214 forms a conduit 212, the conduit 212 being a three-dimensional object that is generally cylindrical and has a generally conical nozzle 250 at the end 216. The conduit 212 may be, for example, a capillary tube.

The sidewall 214 includes an inner surface 253 and an outer wall 254. The inner surface 253 defines an interior region 258 (fig. 2A and 2B) in fluid communication with the nozzle 250. Nozzle 250 narrows in the-X direction to define orifice 217. In the example of fig. 2A and 2B, the nozzle 250 is generally conical and the orifice 217 is at the apex of the cone. The interior region 258 is fluidly coupled to a reservoir (such as reservoir 140 of fig. 1) containing a target mixture (such as target mixture 141 of fig. 1), and the target mixture flows in the interior region 258 of the conduit 212 and through the orifice 217 in the-X direction.

The gas directing system 232 is a three-dimensional body that encloses a space 238. The space 238 is fluidly coupled to the gas supply 133. Gas introduction system 232 includes a plurality of openings 236 through a bottom 239 of gas introduction system 232. For simplicity, only one of the openings 236 is labeled in fig. 2A and 2B. The shielding gas 131 flows from the gas supply 133 into the space 238 and out of the opening 236 in the-X direction. The flow and direction of the shielding gas 131 exiting each opening 236 is substantially the same.

In the example of fig. 2B, the openings 236 are arranged in a rectilinear grid in the bottom 239. However, other implementations are possible. For example, the openings 236 may be arranged in a random pattern. Further, the opening 236 may have any shape. In the example of fig. 2B, each opening 236 is circular in the Y-Z plane. In other implementations, the openings 236 may be oval shaped, or the openings may form concentric circles centered on the aperture 217.

Furthermore, the gas direction system 232 may have any shape. In the example of fig. 2B, gas direction system 232 is a cylinder having a circular cross-section in the Y-Z plane. In other implementations, the gas direction system 232 may have a square or rectangular cross-section in the Y-Z plane, for example.

In the example of fig. 2A and 2B, the gas directing system 232 is a single element that includes a plurality of openings 236, each opening 236 directing the shielding gas 131 in a direction away from the nozzle 250. However, other implementations are possible. For example, the gas directing system 232 may be a collection of discrete gas collection systems, each individually fluidly coupled to the gas supply 133 or a separate gas supply. In these implementations, each gas directing system is individually controllable (e.g., with control system 160 of fig. 1) to provide a flow of shielding gas 131.

Furthermore, the provisioning system 210 may include additional components not shown in fig. 2A and 2B. For example, the supply system 210 may include an actuator (such as the actuator 135 of fig. 1) external to the conduit 212.

Fig. 2C and 2D illustrate a supply system 210C that is identical to the actuator 210, except that the supply system 210C includes an actuator 235 mounted to and surrounding a portion of the outer wall 254. The actuator 235 is shown in cross-hatched shading in fig. 2C and 2D. Fig. 2C is a cross-sectional view of supply system 210C in the X-Z plane. FIG. 2D is a bottom view of the supply system 210C from the perspective of line 2C-2C' of FIG. 2C. Provisioning system 210C is another example of an implementation of provisioning system 110 of fig. 1. Actuator 235 is an example of an implementation of actuator 135 (fig. 1).

The actuator 235 is a three-dimensional cylinder including an inner surface 259 and an outer surface 257. An inner surface 257 of actuator 235 is mechanically coupled to a portion of outer wall 254 of conduit 212 by, for example, an adhesive material. The actuator 235 surrounds a portion of the outer wall 254. As shown in fig. 2D, the actuator 235 has a circular cross-section in the Y-Z plane.

The actuator 235 may be made of a solid material (such as PZT) that is impermeable to the shielding gas 131. The adhesive coupling the actuator 235 may be, for example, an epoxy that is also generally impermeable to the shielding gas 131. Thus, under normal operation, when the actuator 235 is properly coupled to the outer wall 254, the shielding gas 131 flows around the actuator 235. In implementations such as shown in fig. 2C and 2D in which the actuator 235 is located between the gas directing system 232 and the orifice 217, the shielding gas 131 also flows along the outer wall 254 except at the portion where the actuator 235 is attached to the conduit 212. At the portion of the actuator 235 attached to the conduit 212, the shielding gas 131 still flows along the conduit 212, but the shielding gas 131 flows around the outer surface 357 of the actuator 235. In other words, the shielding gas 131 flowing along the exterior of the conduit 212 includes situations where the shielding gas 131 flows around an item (such as the actuator 235) attached to the outer wall 245 of the conduit 212 that is not permeable to the shielding gas 131.

Referring to fig. 3A and 3B, a supply system 310 is shown. Provisioning system 310 is another example of provisioning system 110. The supply system 310 may be used in the EUV light source 100 of fig. 1. For example, the supply system 310 may be mounted to the vacuum chamber 109 and used to generate the target stream 121. Fig. 3A is a cross-sectional view of delivery system 310 in the X-Z plane. Fig. 3B is a view of the end 379 of the delivery system 310 in the Y-Z plane. In fig. 3B, the X direction is a direction into the page.

Supply system 310 includes conduit 212 (discussed above with respect to fig. 2A and 2B) and housing 370. The housing 370 is a three-dimensional body that encloses the conduit 212. The housing 370 includes a sidewall 371. The sidewall 371 defines a fluid port 372 coupled to the gas supply 133. The fluid port 372 may be connected to a fluid connection (such as fluid connection 134 of fig. 1), or the fluid port 372 may be directly coupled to the gas supply 133. The sidewall 371 also defines an open area 378 at the end 379.

The fluid port 372 is open to the interior 373 of the housing 370. The conduit 212 is within the interior 373. The conduit 212 and the housing 370 are positioned relative to each other such that the aperture 217 of the conduit 212 is aligned with the open area 378 along the X-direction. The alignment of the aperture 217 and the open area 378 allows target material emitted from the aperture 217 to exit the housing 370 in the-X direction.

The side wall 371 includes an inner wall 375, the inner wall 375 being spaced apart from the outer wall 254 of the conduit 212 to form an open space 376. The open space 376 is the portion of the interior 373 (within the housing 370) located between the outer wall 254 and the inner wall 375 of the conduit 212. Open space 376 is fluidly coupled to fluid port 372. The shielding gas 131 in the supply device 133 is maintained at a pressure higher than the pressure in the vacuum chamber 109, so the shielding gas 131 flows from the gas supply device 133 into the fluid port 372 and into the open space 376. The pressure in the vacuum chamber 109 is lower than the pressure in the interior 373. The shielding gas 131 flows generally in the-X direction along the outer wall 254 of the conduit 212 and exits the enclosure 370 through the open area 378. Both the shielding gas 131 and the target material flow through the open area 378 in substantially the same direction. In the example of fig. 3A and 3B, the target material and the shielding gas 131 move generally in the-X direction through the open area 378.

The shielding gas 131 may have a uniform flow rate at the open area 378 at all points in the Y-Z plane and not substantially interfere with the trajectory of the target material through the open area 378. The flow of the shielding gas 131 in the X-Y plane at the open area 378 is referred to as a gas flow field. Although the airflow field may affect the trajectory of the individual targets emitted from the apertures 317, the characteristics of the airflow field (e.g., flow and direction) are such that the trajectory of the individual targets does not substantially change. For example, the gas flow field does not cause the target trajectory to deviate so much that the target in stream 121 is not transported to the plasma formation location 123 (FIG. 1). In addition, the mass and density of the target emitted from the orifice 317 is much higher than the mass and density of the shielding gas 131. The ratio of the mass and/or density of the target compared to the shielding gas 131 also minimizes the effect of the shielding gas 131 on the target trajectory.

The flow of the shielding gas 131 is sufficient to move the contaminant 150 (fig. 1) away from the open area 378 and/or to prevent the contaminant 150 from moving through the open area 378 and into the open space 376. The flow rate of the shielding gas 131 is higher than the diffusion rate of the contaminant 150. Diffusion is the net movement of material (e.g., molecules or atoms in the contaminant 150) from a region of higher concentration (or high chemical potential) to a region of lower concentration (or low chemical potential). Diffusion is driven by a gradient in the chemical potential of the diffusing species. The shielding gas 131 may be considered to mitigate the movement of the contaminant 150 into the orifice 317 by the belief (Peclet) effect, which is quantified by the Peclet number (Pe). The Peclet number is the ratio of advection transport rate to diffusion transport rate. The advection transfer rate is the transfer rate of the shielding gas 131. The diffusion transport rate is the diffusion rate of the contaminant 150. As the Peclet number increases, the shielding gas 131 is more likely to dominate the interaction between the gas 131 and the contaminant 150, and the shielding gas 131 is more likely to push the contaminant 150 away from the open area 378. The Peclet number may be increased by increasing the flow rate of the shielding gas 131 and/or increasing the characteristic length (e.g., the length of the shielding gas 131 flowing in the supply system 310 along the X-direction). Thus, the Perclet number and the mitigating contaminant 150 are controllable by the design of the enclosure 371 and/or the control of the flow of the shielding gas 131.

In some implementations, the flow rate of the shielding gas 131 may be between 1 and 50 standard liters per minute (slm). The flow rate of the shielding gas 131 at the open area 378 depends on the extent of the open space 376 in the X-direction, the flow rate of the shielding gas 131 entering the fluid port 372 from the gas supply 133, the physical properties of the inner wall 375, and the size of the open area 378 in the Y-Z plane.

The example of fig. 3A and 3B includes one gas port 372. However, in other implementations, more gas ports may be used. For example, a plurality of air ports 372 may be included. The plurality of gas ports 372 may be circumferentially spaced and equidistant from each other in the Y-Z plane. Further, in some implementations, the delivery system 310 includes an actuator, such as the actuator 237 (fig. 2C and 2D), attached to and enclosing a portion of the outer wall 254. When the actuator is positioned between the gas port 372 and the orifice 217, the shielding gas 131 flows along the outer wall 254 and/or the outer surface of the actuator. When the actuator is attached to the outer wall 254, the shielding gas 131 does not flow between the actuator and the outer wall 254.

Fig. 4A and 4B illustrate a supply system 410. Provisioning system 410 is another example of an implementation of provisioning system 110. The supply system 410 may be used in the EUV light source 100 of fig. 1. For example, the supply system 410 may be mounted to the vacuum chamber 109 and used to generate the target stream 121. Fig. 4A is a cross-sectional view of delivery system 410 in the X-Z plane. Fig. 4B is a view of end 479 of delivery system 410 in the Y-Z plane. In fig. 4B, the X direction is a direction into the page. The supply system 410 is similar to the supply system 310 (fig. 3A and 3B), except that the supply system 410 includes a temperature control block 480, the temperature control block 480 controlling the temperature of the conduit 212 and/or the nozzle 250.

The supply system 410 includes a housing 470. The housing 470 includes a sidewall 471 defining an interior 473. The conduit 212 (fig. 2A and 2B) is in the interior 473. The conduit 212 and the housing 470 are positioned relative to each other such that the aperture 217 is aligned with the open area 478 at the end 479 of the housing. The stream 121 emitted from the orifice 217 exits the housing 470 in the-X direction.

Supply system 410 includes a temperature control block 480. Temperature control block 480 is within interior 473. The temperature control block 480 surrounds at least a portion of the outer wall 254 of the conduit 212. In the example of fig. 4A and 4B, temperature control block 480 is a cylinder having a longitudinal axis along the X-direction that is concentric with the longitudinal axis of conduit 212 along the X-direction.

Temperature control block 480 is made of a material that can be heated or cooled. Temperature control block 480 is made of any thermally conductive material. Temperature control block 480 is thermally coupled to a controllable heater and/or cooler such that the temperature of control block 480 is controllable. Temperature control block 480 may be a solid block material, for example, having corrosion resistance to the target material. In implementations where the target material includes tin, the temperature control block 480 may be, for example, molybdenum (Mo).

The temperature control block 480 is sufficiently close to the outer wall 254 to affect the temperature of the outer wall 254 (and thus the conduit 212), but the temperature control block 480 does not contact the outer wall 254. If temperature control block 480 is hotter than conduit 212, temperature control block 480 heats conduit 212. Heating the conduit 212 may, for example, cause the target material in the conduit 212 to flow more efficiently. When temperature control block 480 is cooler than conduit 212, temperature control block 480 reduces the temperature of conduit 212.

The temperature control block 480 is not in direct physical contact with the outer wall 254 and there is an open space 481 between the temperature control block 480 and the outer wall 254. A fluid (such as shielding gas 131) can flow in the open space 481 between the temperature control block 480 and the wall 254. The temperature control block 480 may be mounted to the inner wall 475 of the housing 470 or the reservoir 140. Accordingly, temperature control block 480 does not necessarily contact inner wall 475, and fluid (such as shielding gas 131) may flow between temperature control block 480 and inner wall 475. In the implementation of fig. 4A and 4B, open space 482 is between temperature control block 480 and inner wall 475, and open space 481 is between temperature control block 480 and outer wall 254 of conduit 212. Shield fluid 131 flows in open space 481 and open space 482.

The side wall 471 defines a fluid port 472, the fluid port 472 fluidly coupled to the gas supply 133 and the interior 473. The shielding gas 131 flows from the gas supply device 133 into the interior 473. The pressure in the vacuum chamber 109 is lower than the pressure in the interior 473, and the shielding gas 131 is drawn through the open space 481 and the open space 482.

The shielding gas 131 flows through the open area 478 and into the vacuum chamber 109 generally in the-X direction. The shielding gas 131 and the flow 121 flow through the open area 478 in substantially the same direction (-X direction). Thus, the shielding gas 131 flows through the open area 478 and into the vacuum chamber 109 in a direction away from the aperture 217 and away from the end 479. The flow direction of the shielding gas 131 inhibits or prevents the contaminant 150 from entering the housing 470 through the open area 478 and reduces the likelihood that the apertures 217 will become blocked by the contaminant 150.

The shielding gas 131 has a uniform flow at all points in the Y-Z plane at the open area 478 and, therefore, does not interfere with the trajectory of the target material through the open area 478. The flow of the shielding gas 131 is sufficient to move the contaminating material 150 away from the open area 478 and/or to prevent the contaminating material 150 from moving through the open area 478 into the interior 473. For example, the flow rate of the shielding gas 131 may be 1 to 50 standard liters per minute (slm). The flow rate of the shielding gas 131 at the open area 478 depends on the extent of the

open spaces

481 and 482 in the X-direction, the size and placement of the temperature control block 480, the flow rate of the shielding gas 131 entering the fluid port 472 from the gas supply 133, the pressure differential between the interior 473 and the vacuum chamber 109, the physical characteristics of the interior wall 475, and the size of the open area 478 in the Y-Z plane.

Other implementations are also possible. For example, the temperature control block 480 may be mounted to the inner wall 475 such that fluid does not flow between the inner wall 475 and the temperature control block 480. In these implementations, the protection fluid 131 flows only in the open space 481.

Further, supply system 410 may include a gas directing system, such as gas directing system 232 of fig. 2A and 2B. The gas directing system 232 may be mounted on a temperature control block 480 and in the x-direction relative to the open area 378. For example, the gas introduction system 232 may be mounted at the end of the temperature control block 480 closest to the open area 378. In implementations that include the gas direction system 232, the diameter of the gas direction system 232 in the Y-Z plane is slightly larger than the diameter of the open area 378 in the Y-Z plane.

Further, in some implementations, the delivery system 410 includes a three-dimensional actuator, such as the actuator 237 (fig. 2C and 2D), attached to and enclosing a portion of the outer wall 254. When the actuator is positioned between the gas port 472 and the aperture 217, the shielding gas 131 flows along the outer wall 254 and/or the outer surface of the actuator. Temperature control block 480 is not connected to an actuator. Thus, in these implementations, all or part of space 481 may be located between temperature control block 480 and the actuator. When the actuator is attached to the outer wall 254, the shielding gas 131 does not flow between the actuator and the outer wall 254.

Referring to fig. 5, a flow chart of a process 500 is shown. Process 500 is an example of a process for protecting an orifice of a supply system, such as orifice 217 of conduit 212 (fig. 2). Fig. 5 is discussed with respect to port 217. However, the process 500 may be used to protect other orifices, such as the orifice 117 of fig. 1.

The target material passes through the orifice 217 to form a stream 121 (510). Stream 121 moves along a trajectory away from orifice 217. The trajectory may be, for example, in the-X direction, as shown in fig. 1, 3A, and 4A. The shielding gas 131 flows in a direction away from the orifice 217 (520). By flowing away from the orifice 217, the shielding gas 131 blocks or prevents the contaminant 150 from reaching the orifice 217 and/or forming a layer of the contaminant 150 on the exterior of the nozzle 250 (fig. 2A). In this manner, shielding gas 131 protects orifice 217 and ensures that flow 121 is produced in the intended manner. In addition, as the vacuum chamber 109 is vented and oxygen enters the chamber 109, the flowing shielding gas 131 shields the orifice 217. When oxygen enters the chamber 109, the metallic material (such as tin) oxidizes and may plug or block the orifice 217. The shielding gas 131 is used to keep oxygen away from the aperture 217.

The shielding gas 131 may flow along the outer wall 254. For example, and still referring to FIG. 2A, the shielding gas 131 may flow from the gas directing system 232 and along the outer wall 254 in the-X direction. The shielding gas 131 continues to flow along the nozzle 250 and into the vacuum chamber 109 in the-X direction. Thus, the shielding gas 131 flows along the outer wall 254 and away from the aperture 217.

The shielding gas 131 may flow in the open space between the conduit 212 and the inner wall of the housing surrounding the conduit. For example, as shown in fig. 3A, the shielding gas 131 may flow in an open space 376, the open space 376 being located between the outer wall 254 of the conduit 212 and the inner wall 375 of the enclosure 370.

As discussed with respect to fig. 1, in some implementations, the gas supply 133 includes more than one chamber 137, and each chamber may include a different gas to serve as the shielding gas 131. In these implementations, the control system 160 may select a particular one of the chambers 137 to supply the shielding gas 131. Fig. 5B illustrates a process 515 that may be performed in conjunction with process 500 or independently of process 500. For example, process 515 may be performed after execution (510) and before execution (520). In other examples, process 515 is performed independently of process 500. Process 500 may be performed by one or more electronic processors in electronic processing module 161.

The state of the EUV light source 100 is determined (516). The state of the EUV light source 100 may be an operation mode, for example. The state may be, for example, a typical operating or venting state. In typical operation, stream 121 is generated as expected, and vacuum chamber 109 is sealed. In the vented state, the vacuum chamber 109 is open and oxygen is present in the chamber. The state of the EUV light source 100 may be determined by, for example, an oxygen sensor in the vacuum chamber 109 or by input made by an operator at the I/O interface 163.

The protective gas 131 to be used is determined based on the determined status (518). For example, the instructions 162 may store a database or look-up table that stores relationships between a particular chamber 137 and possible states of the EUV light source 100. For example, the database may define a relationship between a first chamber 137 and typical operating conditions and a relationship between a different second chamber 137 and ventilation conditions. When the EUV light source 100 is manufactured or programmed by an operator, a database may be generated and stored.

Control system 160 determines which chamber is to be coupled to fluid connection 134. For example, the control system 160 may operate a fluid switch that connects the fluid connection 134 to the first chamber 137 during typical operation and connects the fluid connection 134 to the second chamber 137 during a venting state. In this example, the first chamber 137 may contain molecular hydrogen (H)₂) The gas, and the second chamber 137 may contain argon (Ar). H₂The mass of the gas is lower than that of the Ar gas. Thus, in this example, the shielding gas 131 has a relatively low mass during typical operation such that the flow 121 is substantially undisturbed, while in a vent stateWith a relatively high mass during, so that oxygen is pushed away from the supply system, thereby preventing or reducing oxidation of components of the supply system.

Figures 6 and 7 are examples of EUV lithographic apparatus that may use the control system and/or supply system described above. FIG. 8 is an example of an EUV light source that may use the control system and/or supply system described above.

FIG. 6 is a block diagram of a lithographic apparatus 700 including a source collector module SO. The lithographic apparatus 700 includes:

an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. EUV radiation).

A support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask or reticle) MA and connected to a first positioner PM configured to accurately position the patterning device;

a substrate table (e.g. a wafer table) WT constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate; and

a projection system (e.g. a reflective projection system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.

The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.

The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be, for example, a frame or table, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system.

The term "patterning device" should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. The pattern imparted to the radiation beam may correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam which is reflected by the mirror matrix.

As with the illumination system IL, the projection system PS can include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, depending on the exposure radiation being used, or depending on other factors, such as the use of a vacuum. It may be desirable to use vacuum for EUV radiation, as other gases may absorb too much radiation. A vacuum environment can thus be provided for the entire beam path with the aid of the vacuum wall and the vacuum pump.

In the examples of fig. 6 and 7, the apparatus is of a reflective type (e.g. employing a reflective mask). The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more patterning tables). In such "multiple stage" machines the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure.

Referring to fig. 6, the illuminator IL receives an euv radiation beam from a source collector module SO. Methods for generating EUV light include, but are not necessarily limited to, converting a material into a plasma state, the material having at least one element, such as xenon, lithium, or tin, with one or more elements in the EUV rangeAn emission line. In one such method, commonly referred to as laser produced plasma ("LPP"), the desired plasma is produced by irradiating a fuel, such as a droplet, stream or cluster of material having the desired line emitting element, with a laser beam. The source collector module SO may be part of an EUV radiation system comprising a laser, not shown in fig. 6, which provides a laser beam for exciting the fuel. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector disposed in the source collector module. The laser and the source collector module may be separate entities, for example when carbon dioxide (CO)₂) A laser is used to provide a laser beam for fuel excitation.

In such cases, it is considered that the laser does not form part of the lithographic apparatus and the radiation beam is passed from the laser to the source collector module with the aid of a beam delivery system comprising, for example, suitable directing mirrors and/or a beam expander. In other cases, the source may be an integral part of the source collector module, for example when the source is a discharge produced plasma EUV generator (commonly referred to as a DPP source).

The illuminator IL may comprise an adjuster for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as outer σ and inner σ, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as a facet field and a pupil mirror device. The illuminator IL may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. After reflection from the patterning device (e.g. mask) MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor PS2 (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor PS1 can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam B. Patterning device (e.g. mask) MA and substrate W may be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2.

The depicted apparatus can be used in at least one of the following modes:

1. in step mode, the support structure (e.g. mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed.

2. In scan mode, the support structure (e.g. mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (e.g. mask table) MT may be determined by the (de-) magnification and image reversal characteristics of the projection system PS.

3. In another mode, the support structure (e.g., mask table) MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, a pulsed radiation source is typically employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

FIG. 7 shows an implementation of the lithographic apparatus 700 in more detail, including the source collector module SO, the illumination system IL and the projection system PS. The source collector module SO is constructed and arranged such that a vacuum environment can be maintained in the enclosure 720 of the source collector module SO. The systems IL and PS are also housed in their own vacuum environment. The EUV radiation emitting plasma 2 may be formed by a laser produced LPP plasma source. The function of the source collector module SO is to deliver a beam 20 of EUV radiation from the plasma 2 such that it is focused in a virtual source point. The virtual source point is often referred to as an Intermediate Focus (IF), and the source collector module is arranged such that the intermediate focus IF is located at or near the aperture 721 in the enclosure 720. The virtual source point IF is an image of the radiation emitting plasma 2.

From the aperture 721 at the intermediate focus IF, the radiation passes through an illumination system IL, which in this example comprises a faceted field mirror device 22 and a faceted pupil mirror device 24. These devices form a so-called "fly's eye" illuminator that is arranged to provide a desired angular distribution of the radiation beam 21 at patterning device MA, and a desired uniformity of radiation intensity at patterning device MA (as indicated by reference numeral 760). When beam 21 is reflected at patterning device MA, which is held by support structure (mask table) MT, patterned beam 26 is formed and patterned beam 26 is imaged by projection system PS via

reflective elements

28, 30 onto substrate W held by substrate table WT. To expose a target portion C on the substrate W, pulses of radiation are generated while the substrate table WT and patterning table MT perform synchronized movements to scan a pattern on the patterning device MA through an illumination slit.

Each system IL and PS is disposed in its own vacuum or near-vacuum environment defined by an enclosure similar to enclosure 720. There may generally be more elements in the illumination system IL and the projection system PS than shown. Further, there may be more mirrors than shown. For example, in addition to those shown in FIG. 7, there may be one to six additional reflective elements in the illumination system IL and/or the projection system PS.

Considering the source collector module SO in more detail, a laser energy source comprising a laser 723 is arranged to deposit laser energy 724 into the fuel comprising the target material. The target material may be any material that emits EUV radiation when in a plasma state, such as xenon (Xe), tin (Sn), or lithium (Li). The plasma 2 is a highly ionized plasma, the electron temperature of which is several tens of electron volts (eV). With other fuel materials, such as terbium (Tb) and gadolinium (Gd), higher energy EUV radiation may be generated. High energy radiation generated during de-excitation and recombination of these ions is emitted from the plasma, collected by the near normal incidence collector 3, and focused on the aperture 721. The plasma 2 and the apertures 721 are located at a first focus and a second focus of the collector CO, respectively.

Although the collector 3 shown in fig. 7 is a single curved mirror, the collector may take other forms. For example, the collector may be a Schwarzschild collector having two radiation collecting surfaces. In one embodiment, the collector may be a grazing incidence collector comprising a plurality of substantially cylindrical reflectors nested within one another.

For delivering a fuel, for example liquid tin, a droplet generator 726 is arranged within the structure 720, arranged to emit a high frequency stream 728 of droplets towards a desired location of the plasma 2. The drop generator 726 may be, for example, the

supply system

110, 210, 310, or 410. In operation, laser energy 724 is delivered in synchronization with the operation of drop generator 726 to deliver pulses of radiation to turn each fuel drop into plasma 2. The delivery frequency of the droplets may be a few kilohertz, for example 50 kHz. In practice, laser energy 724 is delivered in at least two pulses: before the droplets reach the plasma location, a pre-pulse of limited energy is delivered to the droplets to vaporize the fuel material into a small cloud, and then a main pulse of laser energy 724 is delivered to the cloud at the desired location to generate the plasma 2. A trap 730 is provided on the opposite side of the enclosing structure 720 to trap fuel that for any reason has not become plasma.

The droplet generator 726 includes a reservoir 701 containing a fuel liquid (e.g., molten tin), as well as a filter 769 and a nozzle 702. The nozzle 702 is configured to inject droplets of the fuel liquid toward the plasma 2 formation position. Droplets of fuel liquid may be ejected from nozzle 702 by a combination of pressure within reservoir 701 and vibration applied to the nozzle by a piezoelectric actuator (not shown).

Those skilled in the art will appreciate that reference axes X, Y and Z may be defined for measuring and describing the geometry and behavior of the device, its various components, and the radiation beams 20, 21, 26. At each part of the device, X, Y local frames of reference for the Z-axis may be defined. In the example of fig. 7, the Z-axis is substantially coincident with the directional optical axis O at a given point in the system, and is substantially perpendicular to the plane of the patterning device (reticle) MA and to the plane of the substrate W. In the source collector module, the X-axis is generally coincident with the direction of fuel flow 728, while the Y-axis is orthogonal thereto, pointing out of the page as shown in FIG. 7. On the other hand, in the vicinity of the support structure MT holding the reticle MA, the X-axis is substantially transverse to the scan direction aligned with the Y-axis. For convenience, in this region of the schematic diagram of FIG. 7, the X axis points out of the page, again labeled. These names are conventional in the art and will be used herein for convenience. In principle, any frame of reference may be chosen to describe the device and its behavior.

Many additional components used in the operation of the source collector module and the lithographic apparatus 700 as a whole are present in a typical apparatus, although not shown here. These include arrangements for reducing or mitigating the effects of contamination within the enclosed vacuum, for example to prevent deposits of fuel material from damaging or impairing the performance of the trap 3 and other optics. Other features that are present but not described in detail are all sensors, controllers and actuators that participate in controlling the various components and subsystems of the lithographic apparatus 700.

Referring to fig. 8, an implementation of an LPP EUV light source 800 is shown. The light source 800 may be used as a source collector module SO in the lithographic apparatus 700. Further, the drive laser 815 of fig. 1 may be part of the drive laser 815. The drive laser 815 may be used as the laser 723 (fig. 7).

The LPP EUV light source 800 is formed by irradiating a target mixture 814 at a plasma formation location 805 with an amplified light beam 810, the amplified light beam 810 traveling along a beam path toward the target mixture 814. The target material discussed with respect to fig. 1 and the target in the target stream 121 discussed with respect to fig. 1 may be or include a target mixture 814. The plasma formation location 805 is within the interior 807 of vacuum chamber 830. When the amplified light beam 810 impinges on the target mixture 814, the target material within the target mixture 814 is converted to a plasma state having elements with emission lines in the EUV range. The generated plasma has certain characteristics that depend on the composition of the target material within the target mixture 814. These characteristics may include the wavelength of EUV light generated by the plasma and the type and amount of debris released from the plasma.

Light source 800 includes a driven laser system 815 that generates an amplified light beam 810 due to population inversion within one or more gain media of laser system 815. Light source 800 includes a beam delivery system between laser system 815 and plasma formation location 805, which includes a beam delivery system 820 and a focusing assembly 822. The beam delivery system 820 receives the amplified light beam 810 from the laser system 815, and manipulates and modifies the amplified light beam 810 as desired and outputs the amplified light beam 810 to the focusing assembly 822. The focusing assembly 822 receives the amplified light beam 810 and focuses the light beam 810 to the plasma formation location 805.

In some implementations, the laser system 815 may include one or more optical amplifiers, lasers, and/or lamps to provide one or more main pulses and, in some cases, one or more pre-pulses. Each optical amplifier includes a gain medium capable of optically amplifying a desired wavelength with high gain, an excitation source, and internal optics. The optical amplifier may or may not have a laser mirror or other feedback device that forms the laser cavity. Thus, even without a laser cavity, laser system 815 produces an amplified light beam 810 due to population inversion in the gain medium of the laser amplifier. In addition, laser system 815 can produce amplified light beam 810 as a coherent laser beam if a laser cavity is present to provide sufficient feedback to laser system 815. The term "amplified light beam" includes one or more of the following: light from the laser system 815 that is only amplified but not necessarily coherent laser oscillation, and light from the laser system 815 that is amplified and is also coherent laser oscillation.

The optical amplifier in laser system 815 may include a fill as a gain mediumA gas, the fill gas comprising CO₂And light having a wavelength between about 9100 and about 11000nm, and particularly about 10600nm, may be amplified with a gain of greater than or equal to 800 times. Suitable amplifiers and lasers for the laser system 815 may include pulsed laser devices, e.g., pulsed gas discharge CO that produces radiation at about 9300nm or about 10600nm₂Laser devices, for example using DC or RF excitation, operate at relatively high power (e.g., 10kW or more) and high pulse repetition rates (e.g., 40kHz or more). The pulse repetition rate may be, for example, 50 kHz. The optical amplifier in laser system 815 may also include a cooling system, such as water, which may be used when operating laser system 815 at a higher power.

The light source 800 includes a collector mirror 835, the collector mirror 835 having an aperture 840 to allow the amplified light beam 810 to pass through and reach the plasma formation location 805. Collector mirror 835 can be, for example, an elliptical mirror having a primary focus at plasma formation location 805 and a secondary focus (also referred to as an intermediate focus) at intermediate location 845, where EUV light can be output from light source 800 and can be input to, for example, an integrated circuit lithography tool (not shown). The light source 800 can also include an open-ended hollow cone-shaped shroud 850 (e.g., a gas cone), the shroud 850 tapering from the collector mirror 835 toward the plasma formation location 805 to reduce the amount of plasma-generated debris entering the focusing assembly 822 and/or the beam delivery system 820, while allowing the amplified light beam 810 to reach the plasma formation location 805. To this end, a gas flow may be provided in the shield, which is directed towards the plasma formation location 805.

Light source 800 may also include a main controller 855 connected to drop position detection feedback system 856, laser control system 857, and beam control system 858. Light source 800 can include one or more target or drop imagers 860, imagers 860 providing outputs indicative of drop position, e.g., relative to plasma formation location 805, and providing the outputs to drop position detection feedback system 856, system 856 can, e.g., calculate drop position and trajectory from which drop position errors can be calculated on a drop-by-drop or average basis. Thus, droplet position detection feedback system 856 provides the droplet position error as an input to master controller 855. Thus, master controller 855 may provide laser position, direction, and time correction signals to, for example, laser control system 857 and/or beam control system 858, laser control system 857 may be used to control laser timing circuitry, for example, and beam control system 858 may be used to control the amplified beam position and shape of beam delivery system 820 to change the position and/or focus power of the beam focus within chamber 830, for example.

The supply system 825 includes a target material delivery control system 826, the system 826 being operable in response to signals from the main controller 855 to, for example, modify the release point of droplets released by the target material supply apparatus 827 to correct for errors in droplets reaching the desired plasma formation location 805.

Further, the light source 800 may include

light source detectors

865 and 870, the

light source detectors

865 and 870 measuring one or more EUV light parameters including, but not limited to, pulse energy, energy distribution as a function of wavelength, energy within a particular wavelength band, energy outside a particular wavelength band, and angular distribution of EUV intensity and/or average power. Light source detector 865 generates a feedback signal for use by master controller 855. For example, the feedback signal may indicate errors in parameters such as timing and focusing of the laser pulses to properly intercept the droplet at the correct location and time for effective and efficient EUV light production.

Light source 800 can also include a directing laser 875 that can be used to align various portions of light source 800 or to help steer amplified light beam 810 to plasma formation location 705. In conjunction with the guiding laser 875, the light source 800 includes a metrology system 824, the metrology system 824 being placed within the focusing assembly 822 to sample a portion of the light from the guiding laser 875 and the amplified light beam 810. In other implementations, the metrology system 824 is placed within the beam delivery system 820. Metrology system 824 can include optical elements that sample or redirect a subset of the light, such optical elements being made of any material that can withstand the power of the directed laser beam and the amplified light beam 810. The beam analysis system is formed by metrology system 824 and master controller 855 because master controller 855 analyzes the sampled light from guide laser 875 and uses that information to adjust the components within focusing assembly 822 through beam control system 858.

Thus, in summary, the light source 800 produces an amplified light beam 810 directed along a beam path to irradiate the target mixture 814 at the plasma formation location 805 to convert target material within the mixture 814 into a plasma that emits light in the EUV range. The amplified light beam 810 operates at a particular wavelength (also referred to as the drive laser wavelength) determined based on the design and characteristics of the laser system 815. In addition, the amplified light beam 810 may be a laser beam when the target material provides sufficient feedback back to the laser system 815 to generate a coherent laser or if the drive laser system 815 includes suitable optical feedback to form a laser cavity.

Other aspects of the invention are set forth in the following numbered clauses.

1. A target delivery system for an Extreme Ultraviolet (EUV) source, the system comprising:

a conduit comprising an outer, an inner conduit region and an end defining an aperture, wherein the inner conduit region is configured to receive a target material that emits EUV light when in a plasma state and the aperture is configured to provide the target material to an interior of a vacuum chamber; and

a shielding system configured to flow a shielding gas away from the end defining the aperture and toward the interior of the vacuum chamber, wherein the flowing shielding gas is configured to direct one or more contaminating substances away from the end defining the aperture.

2. The target delivery system of clause 1, wherein the shielding gas comprises an inert gas or a reactive gas.

3. The target delivery system of clause 1, wherein the shielding gas comprises molecular hydrogen (H)₂)。

4. The target delivery system of clause 1, wherein the protection system is configured to flow the shielding gas along the exterior of the conduit.

5. The target delivery system of clause 4, wherein the protection system comprises:

a body comprising a sidewall surrounding at least a portion of the exterior of the conduit, the body defining an open end region aligned with the aperture of the conduit, and wherein

The shielding gas flows in an open space between the exterior of the conduit and an inner wall of the sidewall, and the shielding gas flows through the open end region to exit the body.

6. The object delivery system of clause 5, wherein the sidewall includes at least one port in fluid communication with the open space, the at least one port configured to be fluidly coupled to a gas supply containing the shielding gas.

7. The target delivery system of clause 1, wherein the protection system comprises at least one gas source.

8. The target delivery system of clause 1, wherein the target delivery system further comprises a temperature control block at least partially surrounding the exterior of the conduit, and the protection system comprises a body surrounding at least a portion of the temperature control block, the body defining an open end region aligned with the aperture of the conduit, and wherein

The shielding gas flows in an open space between the temperature control block and an inner wall of the body, and the shielding gas exits the body through the open end region.

9. The target delivery system of clause 1, wherein the one or more contaminating substances include mobile substances, and the fluid flowing is configured to reduce interaction between the one or more mobile contaminating substances and the end of the conduit by changing a direction of motion of the one or more mobile contaminating substances away from the end of the conduit.

10. The target delivery system of clause 1, wherein the one or more contaminating substances include mobile substances, and the fluid flowing is configured to prevent interaction between the one or more mobile contaminating substances and the end of the conduit by changing a direction of movement of the one or more mobile contaminating substances away from the end of the conduit.

11. The target delivery system of clause 1, wherein the one or more contaminating substances comprise one or more of a gas, a liquid, a vapor, and a particle.

12. The target delivery system of clause 1, wherein the one or more contaminating substances comprise silicon (Si) or silicon dioxide (SiO)₂)。

13. The target delivery system of clause 1, wherein the one or more pollutants comprise oxygen, water, or carbon dioxide (CO)₂)。

14. The target delivery system of clause 1, wherein the conduit comprises a capillary tube.

15. The object delivery system of clause 1, wherein the protection system comprises a diffuser device comprising a plurality of openings, each opening configured to direct the shielding gas away from the end defining the orifice.

16. The target delivery system of clause 15, wherein the plurality of openings surround and are evenly distributed relative to the exterior of the conduit.

17. A method of protecting an orifice of a target material delivery system, the method comprising:

passing a target material through an aperture to provide a stream of targets to the interior of a vacuum chamber, each target in the stream comprising a target material that emits EUV light when in a plasma state; and

flowing a shielding gas in the target material delivery system and into the interior of the vacuum chamber away from the orifice, the shielding gas directing one or more contaminating substances away from the orifice.

18. The method of clause 17, wherein the flowing shielding gas does not alter the trajectory of the target stream.

19. The method of clause 18, wherein the flowing shielding gas has a component of motion along a direction of travel of the stream of the target.

20. The method of clause 17, wherein flowing the shielding gas comprises flowing the shielding gas in an open space between a conduit defining the aperture and a body surrounding the conduit.

21. The method of clause 20, wherein the shielding gas flows into the open space at a port in the sidewall and out of the space through an open end region defined by the body and aligned with the aperture.

22. The method of clause 17, wherein the shielding gas has a uniform volumetric flow rate at an aperture between the orifice and the interior of the vacuum chamber.

23. The method of clause 17, further comprising:

determining a state of an extreme ultraviolet light source comprising the target material delivery system; and

determining which of a plurality of shielding gases to use as the shielding gas based on the determined state.

Other implementations are within the scope of the following claims.

Claims

2. The target delivery system of claim 1, wherein the shielding gas comprises an inert gas or a reactive gas.

3. The target delivery system of claim 1, wherein the shielding gas comprises molecular hydrogen (H)₂)。

4. The target delivery system of claim 1, wherein the protection system is configured to flow the shielding gas along the exterior of the conduit.

5. The object delivery system of claim 4, wherein the protection system comprises:

6. The target delivery system of claim 5, wherein the sidewall includes at least one port in fluid communication with the open space, the port configured to be fluidly coupled to a gas supply containing the shielding gas.

7. The target delivery system of claim 1, wherein the protection system comprises at least one gas source.

8. The target delivery system of claim 1, wherein the target delivery system further comprises a temperature control block at least partially surrounding the exterior of the conduit, and the protection system comprises a body surrounding at least a portion of the temperature control block, the body defining an open end region aligned with the aperture of the conduit, and wherein

9. The target delivery system of claim 1, wherein the one or more contaminating substances include mobile substances, and the flowing fluid is configured to reduce interaction between the one or more mobile contaminating substances and the end of the conduit by changing a direction of motion of the one or more mobile contaminating substances away from the end of the conduit.

10. The target delivery system of claim 1, wherein the one or more contaminating substances include mobile substances and the flowing fluid is configured to prevent interaction between the one or more mobile contaminating substances and the end of the conduit by changing a direction of movement of the one or more mobile contaminating substances away from the end of the conduit.

11. The target delivery system of claim 1, wherein the one or more contaminating substances comprise one or more of a gas, a liquid, a vapor, and a particle.

12. The target delivery system of claim 1, wherein the one or more contaminant species comprise silicon (Si) or silicon dioxide (SiO)₂)。

13. The target delivery system of claim 1, wherein the one or more pollutants comprise oxygen, water, or carbon dioxide (CO)₂)。

14. The target delivery system of claim 1, wherein the conduit comprises a capillary tube.

15. The target delivery system of claim 1, wherein the protection system includes a diffuser device including a plurality of openings, each opening configured to direct the shielding gas away from the end defining the orifice.

16. The target delivery system of claim 15, wherein the plurality of openings surround and are evenly distributed relative to the exterior of the catheter.

18. The method of claim 17, wherein the flowing shielding gas does not alter a trajectory of the flow of the target.

19. The method of claim 18, wherein the flowing shielding gas has a component of motion along a direction of travel of the stream of the target.

20. The method of claim 17, wherein flowing the shielding gas comprises: flowing the shielding gas in an open space between a conduit defining the aperture and a body surrounding the conduit.

21. The method of claim 20, wherein the shielding gas flows into the open space at a port in the sidewall and out of the space through an open end region defined by the body and aligned with the aperture.

22. The method of claim 17, wherein the shielding gas has a uniform volumetric flow rate at an aperture between the orifice and the interior of the vacuum chamber.

23. The method of claim 17, further comprising: