KR20200096777A - Method for regeneration of debris flux measurement system in vacuum vessel - Google Patents

Abstract

The device is a container; A target delivery system for directing a target including a target material that emits extreme ultraviolet rays when in a plasma state toward an interaction area within the container; And a measuring device. The metrology device includes a measurement system having a measurement surface configured to measure a flux of a target material; And a regeneration tool configured to regenerate this measurement system. Regeneration involves preventing the measuring surface from being saturated and/or desaturating the measuring surface if it is saturated.

Description

Method for regeneration of debris flux measurement system in vacuum vessel

Cross-reference of related applications

This application claims priority to U.S. Application No. 62/599,139, filed December 15, 2017, which application is incorporated herein by reference in its entirety.

The disclosed subject matter relates to a system and method for reproducing a measurement system that measures the flux or the amount of debris produced within the chamber of an extreme ultraviolet light source.

Extreme ultraviolet (EUV) light, for example, electromagnetic radiation having a wavelength of about 50 nm or less (also sometimes referred to as soft X-ray), and including light of a wavelength of about 13 nm, can be applied to a substrate, for example silicon It can be used in photolithography processes to create extremely small features on a wafer.

The method of generating EUV light includes, but is not limited to, converting a material having an element having a bright line in the EUV range, such as xenon, lithium, or tin, in a plasma state. In one of these methods, often referred to as laser-generated plasma ("LPP"), the required plasma is irradiated with an amplified light beam, for example a target material in the form of droplets, plates, tapes, streams, or clusters of material. It can be created by irradiating). In this process, plasma is typically generated in a closed vessel, for example a vacuum chamber, and monitored using various types of metrology equipment.

In some general aspects, the device comprises a container; A target delivery system for directing a target including a target material that emits extreme ultraviolet rays when in a plasma state toward an interaction area within the container; And a measuring device. The metrology device includes a measurement system having a measurement surface configured to measure a flux of a target material; And a regeneration tool configured to regenerate this measurement system. Regeneration involves preventing the measuring surface from being saturated and/or desaturating the measuring surface if it is saturated.

Implementations may include one or more of the following features. For example, the metrology device may include a removal device that communicates with the measurement system and regeneration tool. The control device may be configured to activate the regeneration tool based on the output from the measurement system.

The measuring surface can be configured to interact with the target material. The interaction between the target material and the measurement surface generates a measurement signal. The measurement system may also include a measurement controller configured to receive the measurement signal and calculate the flux of the target material across the measurement surface.

The measurement device may include a crystal microbalance. The crystal microbalance may be a quartz crystal microbalance.

A cavity may be formed in the container, and the container cavity may be maintained at a pressure below atmospheric pressure.

The interaction region may receive the amplified light beam, and when the target interacts with the amplified light beam, the target may be converted into a plasma that emits extreme ultraviolet rays.

The device may also include an optical element comprising an optical element surface within the container. The metrology device can be positioned relative to the optical element surface. The optical element may be an optical collector, wherein the optical element surface reacts with at least a portion of the extreme ultraviolet rays emitted when the target is converted to plasma.

The regeneration tool may be configured to regenerate the measurement system without removing the measurement device from the container. The regeneration tool may include a cleaning tool positioned to interact with the measurement system and configured to remove target material deposited on the measurement surface in response to a command by the measurement controller. The cleaning tool may include a free radical generation unit configured to generate free radicals adjacent to the measurement surface. Free radicals can chemically react with the deposited target material to form new chemicals that are released from the measurement surface. The free radical generating unit may include a wire filament adjacent to the measurement surface and a power supply for supplying current to the wire filament. The wire filament may have a shape matching the shape of the measuring surface. The free radical generation unit may include a plasma generator that generates a plasma material in a plasma state adjacent to the measurement surface, and the plasma material contains free radicals. Free radicals may be free radicals of hydrogen generated from hydrogen molecules originating in the vessel. The target material on the measurement surface may contain tin so that the chemical substance released from the measurement surface contains tin hydride.

The device may further comprise a removal device configured to remove fresh chemicals released from the container. The removal device may include a gas port in fluid communication with the interior of the container, and new chemicals released from the interior of the container are conveyed through the gas port.

The regeneration tool can be configured to remove the target material from the measuring surface in the presence of hydrogen in the vessel and without involving a reaction requiring oxygen.

In another general aspect, a method includes supplying a target into the interior of a container cavity; Measuring the flux of the target material on the measuring surface in the vessel cavity; And regenerating this measurement surface. The target includes a material that emits extreme ultraviolet rays upon conversion to plasma. Regeneration includes at least one of preventing the measuring surface from being saturated and/or desaturating the measuring surface if it is saturated.

Implementations may include one or more of the following features. For example, the method may include activating regeneration of the measuring surface based on the measured flux of the target material on the measuring surface.

The flux of the target material can be measured by interacting the target material with the measurement surface such that the target material is deposited on the measurement surface.

The target can be supplied into the interior of the container cavity by directing a plurality of targets toward the interaction area within the vacuum container. The interaction region receives the amplified light beam and causes the target to be converted into a plasma that emits extreme ultraviolet rays by the interaction between the target and the amplified light beam within this interaction region.

The measuring surface can be regenerated by removing the deposited target material from the measuring surface without removing the measuring surface from the container. The deposited target material can be removed from the measurement surface by generating free radicals of elements adjacent to the measurement surface, and the generated free radicals chemically react with the deposited target material to form a new chemical substance released from the measurement surface. The deposited target material may include tin, the element may be hydrogen, the free radical may be a hydrogen radical, and the new chemical may be tin hydride. Elements adjacent to the measurement surface may be derived from the vessel cavity. The deposited target material can be removed by removing the deposited target material in the absence of oxygen. The method may further include removing fresh chemicals released from the vessel cavity.

The flux of the target material can be measured by measuring the flux of the target material during a time when the deposited target material is not being removed from the measurement surface.

The deposited target material can be removed from the measuring surface to prevent it from reaching its saturation limit.

The method may further include maintaining the cavity formed in the container at a pressure below atmospheric pressure. The method may further include estimating an amount of extreme ultraviolet rays emitted when the target material is converted to plasma based on the measured flux. The method may further include estimating the amount of target material deposited on the surface within the vessel cavity based on the measured flux.

In another general aspect, the extreme ultraviolet light source includes a light source configured to generate an amplified light beam; A container having a cavity formed therein and configured to receive a light beam amplified in an interactive region within the cavity; A target delivery system configured to create a target that moves along the target path towards the interaction area; And a measuring device. The cavity is configured to remain at a pressure below atmospheric pressure. The target includes a target material that emits extreme ultraviolet rays in a plasma state. The metrology device includes a measurement system having a measurement surface configured to measure a flux of a target material; And a regeneration tool configured to regenerate the measurement system. Regeneration prevents the measurement surface from being saturated; And/or if the measuring surface is saturated, desaturating the measuring surface.

Implementations may include one or more of the following features. For example, the measurement surface may be configured to interact with a target material, and the interaction between the target material and the measurement surface generates a measurement signal; The measurement system may also include a measurement controller that receives the measurement signal and calculates the flux of the target material over the entire measurement surface. The regeneration tool may include a cleaning tool positioned to interact with the measurement system. The cleaning tool may be configured to regenerate the measurement system by removing target material deposited on the measurement surface.

The extreme ultraviolet light source may comprise an optical collector that collects at least a portion of the emitted extreme ultraviolet light used by an external lithographic apparatus.

In another general aspect, the metrology system is used in an extreme ultraviolet light source. The metrology system includes a metrology device configured to measure a flux of a target material across a measurement surface within the container; And a reproduction tool connected to the measuring device. The metrology device comprises a measurement system having a measurement surface configured to interact with a target material, the interaction between the target material and the measurement surface generating a measurement signal; And a measurement controller configured to receive the measurement signal and calculate a flux of the target material over the entire measurement surface based on the received measurement signal. The regeneration tool is configured to regenerate the measurement system. Regeneration involves preventing the measuring surface from being saturated and/or desaturating the measuring surface if it is saturated. The regeneration tool may include a cleaning tool positioned to interact with the measurement surface and to remove target material deposited on the measurement surface in accordance with commands from the measurement controller.

In another general aspect, the device comprises a container; A target delivery system for directing a target including a target material that emits extreme ultraviolet rays when in a plasma state toward an interaction area within the container; And a measuring device. The measuring device comprises means for measuring the flux of the target substance over the entire measuring surface in the container; And means for regenerating the measuring surface. The means for regenerating includes means for preventing the measurement surface from being saturated; And/or if the measuring surface is saturated, means for desaturating the measuring surface.

1 is a block diagram of an apparatus including a self-renewal metering device within a cavity formed in a container;
Fig. 2 is a cross-sectional side view and an enlarged view of part A of an implementation of the measurement device of Fig. 1;
Figure 3a is a perspective view of an implementation of the measuring device of Figures 1 and 2, the measuring system comprising a crystal microbalance having a measuring surface and a free radical regeneration tool comprising a wire filament adjacent to the measuring surface. Designed;
3B is a block diagram of the metrology device of FIG. 3A;
3C is a perspective view of a wire filament adjacent to the measuring surface of the crystal microbalance of FIGS. 3A and 3B;
3D is a side cross-sectional view of a wire filament adjacent to the measurement surface of the crystal microbalance of FIGS. 3A to 3C;
4 is an implementation form of an extreme ultraviolet (EUV) light source in which a self-reproducing measuring device such as the device of FIGS. 1 to 3D can be implemented in an EUV light source;
5A is a rear perspective view of an optical element in which the self-reproducing metrology device of FIGS. 1-4 is an optical collector that may be adjacent to the optical collector;
Fig. 5b is a front perspective view of the optical element of Fig. 5a;
5C is a cross-sectional side view of the optical element of FIG. 5A;
5D is a plan view of the optical element of FIG. 5A;
6 is a block diagram of a procedure for regenerating a measuring surface;
Fig. 7 is a schematic diagram showing a cross-sectional side view of the measuring surface during the procedure of Fig. 6;
Fig. 8 is a graph of the deposition thickness of the coating on the measuring surface versus time, showing the procedure of Fig. 6 and the application of the metrology device of Figs. 3A to 3D;
9 is a graph of the removal rate in arbitrary units versus the distance between the wire filaments of FIGS. 3A-3D and the measuring surface of FIGS. 3A-3D for different values of standard liters/minute;
Fig. 10 is a block diagram of a lithographic apparatus receiving the output of the EUV light source of Fig. 4;
11 is a block diagram of a lithographic apparatus receiving the output of the EUV light source of FIG. 4.

Referring to FIG. 1, the device 100 includes a self-regeneration metering device 105 within a cavity 118 formed by a container 120. The metrology device 105 includes a measurement system 110 having a measurement surface 112 configured to measure the flux of the target material 125. The flux of the target material 125 is the mass of the target material 125 passing through a predetermined area over a specific time. Moreover, since the density of the target material 125 is known, it is possible to determine or estimate the flux of the target material 125 by determining the thickness of the target material 125 deposited on the measurement surface 112.

Over time, the target material 125 is deposited as a coating 127 on the measurement surface 112, thereby saturating the measurement surface 112. The measuring surface 112 is saturated when it can no longer generate useful information about the flux of the target material 125. The saturation limit of the measuring surface 112 is related to the saturation thickness of the coating 127 of the target material 125, which saturation thickness can be relatively small compared to the saturation thickness of the nearby material in the vessel 120 ) Approaches its saturation limit before the nearby material in the container 120 needs cleaning, repair or replacement due to the coating by the target material 125. Therefore, it is inefficient to replace the measurement system 110 each time the measurement surface 112 becomes saturated. To this end, the measurement device 105 includes a regeneration tool 115 configured to regenerate the measurement system 110. In some cases, regeneration of the measurement system 110 may include preventing the measurement surface 112 from being saturated. In other cases, such as when the measurement surface 112 is already saturated, regeneration of the measurement system 110 involves desaturating the measurement surface 112.

The regeneration tool 115 operates even when the regeneration tool 115 is exposed to molecular hydrogen that may be present in the cavity 118 (i.e., to remove the target material 125 coating the measurement surface 112). Can be configured. Moreover, the regeneration tool 115 may be configured to operate with or without the use of oxygen, ie oxygen is not required or required for the regeneration tool 115 to operate or perform any function.

The target material 125 is created within the container 120 as follows. The device 100 includes a target delivery system 140 that directs the flow 142 of the target 145 within the container 120 toward the interaction area 150. This target 145 includes a target material 125 (also referred to as luminescent plasma material 160) that emits extreme ultraviolet (EUV) light 155 upon conversion to plasma material 160. However, a portion of the target material 125 is not completely converted to the plasma material 160 within the interaction region 150, or a portion of the plasma material 160 returns to the target material 125. Due to this, the remaining target material 125 (which has not changed or returned to the plasma material 160) moves through the cavity 118 of the container 120 and moves through the cavity 118 of the container 120. ) Can be coated with various objects such as walls or optical elements. The measurement system 110 is provided at a suitable location or multiple locations within the vessel 120 to measure the flux of the target material 125 moving through a portion of the interior of the vessel 120 in which the measurement system 110 is disposed. Decide. Although only one measurement system 110 is shown in FIG. 1, as discussed below, the cavity 118 of the vessel 120 contains specific information that needs to be obtained regarding the flux of the target material 125. Accordingly, a plurality of measurement systems 110 may be mounted at various locations. Moreover, one or more of these measurement systems 110 may be incorporated into metrology device 105 including regeneration tool 115.

The presence of the remaining or residual target material 125 in the vessel 120 is particles, vapor residues, or debris in the form of pieces of material present in the target 145. These debris may deposit on the surface of the object within the container 120. For example, if the target 145 comprises a molten metal of tin, the tin particles may be deposited (or coated) on one or more optical surfaces or walls within the vessel 120. The debris formed on the surface and also the coating 127 formed on the measuring surface 112 may include vapor residues, ions, particles, and/or clusters of substances formed from the target material 125. have. The presence of debris from target material 125 in vessel 120 can degrade the performance of surfaces in vessel 120 and can also reduce the overall efficiency of measurement system 110.

The target delivery system 140 delivers, controls, and directs the target 145 within the stream 142 in the form of droplets, liquid streams, solid particles, or clusters, solid particles contained within the droplet or solid particles contained within the liquid stream. Let it. The target 145 can be any material that emits EUV light when in a plasma state. For example, the target 145 may include water, tin, lithium, and/or xenon. The target 145 may be a target mixture including the target material 125 and impurities (eg, non-target particles).

When the target material 125 is in a plasma state (plasma material 160), the target material 125 is a material having a bright line in the EUV range. The target material 125 may be, for example, a droplet of liquid or molten metal, a portion of a liquid stream, a solid particle or cluster, a solid particle contained within a droplet, a foam of a target material, or a solid particle contained within a portion of the liquid stream. Can be The target material 125 may be, for example, water, tin, lithium, xenon, or any material having a bright line in the EUV range when converted to a plasma state. For example, the target material can be used as pure tin (Sn); For example, it can be used as a tin chemical such as SnBr ₄ , SnBr ₂ , SnH ₄ ; For example, it may be elemental tin that can be used as a tin alloy such as a tin-gallium alloy, a tin-indium alloy, a tin-indium-gallium alloy, or any combination of these alloys. Moreover, in the absence of impurities, the target 145 contains only the target material.

The cavity 118 within the vessel 120 may be maintained in a vacuum, ie at a pressure below atmospheric pressure. For example, the cavity 118 may be maintained at a low pressure between about 0.5 Torr(T) and about 1.5 T (eg, 1 T), which is the pressure chosen to generate EUV light 155. Thus, the metering device 105 is configured to operate under a vacuum environment within the cavity 118 of the vessel 120, which means that it is designed to operate under vacuum (eg, 1 T). Moreover, the metering device 105 is designed to enable its use without the need to change the design or operation of the container 120. Thus, the measurement device 105 is configured to operate in an environment in which EUV light 155 is most efficiently generated.

Referring to FIG. 2, in some implementations, the metrology device 205 includes, as a regeneration tool 115, a free radical regeneration tool 215 adjacent to the measurement surface 212 of the measurement system 210. . Free radical regeneration tool 215 is a cleaning tool positioned to interact with measurement system 210. The free radical regeneration tool 215 is configured to remove target material 125 deposited as a coating 227 on the measurement surface 212 of the measurement system 210. The free radical regeneration tool 215 comprises a free radical generation unit configured to generate free radicals 216 adjacent to the measuring surface 212, which free radicals 216 are deposited target material ( 125) to form a new chemical substance 228 that is released from the measurement surface 212. For example, new chemicals 228 may be in a gaseous state and thus are released from the measurement surface 212. This gaseous new chemical 228 can then be pumped out of the container 120.

Free radicals 216 are atoms, molecules, or ions whose unpaired valences have electrons or open electron shells and thus can be viewed as having dangling covalent bonds. These dangling bonds can make free radicals highly chemically reactive, i.e. free radicals can easily react with other substances. Free radicals 216 can be used to remove certain substances (eg, deposited target substances 125) from an object such as the measuring surface 212 due to its reactive nature. The free radicals 216 can remove the deposited target material 125 by, for example, etching the target material 125, reacting with it, and/or burning it.

Free radicals 216 can be generated in any suitable manner. For example, free radicals 216 decompose larger molecules 230 present in (or derived from) vessel 120 near measurement system 210 or free radical regeneration tool 215. It can be formed by doing. Larger molecules 230 present in vessel 120 near measurement system 210, for example, inject sufficient energy to the larger molecules, such as ionizing radiation, heat, discharge, electrolysis, and chemical reactions. It can be decomposed by any process. Thus, the formation of free radicals involves supplying sufficient energy to the larger molecule 230 to break the bonds (generally covalent bonds) between the atoms of the larger molecule.

As another example, free radicals 216 may be formed at a location away from measurement system 210 and then delivered to measurement surface 212. Thus, free radicals 216 can be formed outside of the container 120 and then transported into the container 120.

In another implementation, the free radical regeneration tool 215 may be a capacitively coupled plasma (CCP) device. In a CCP device, the two metal electrodes are separated by a small distance and are driven by a power source (eg, a high frequency (RF) power source). When an electric field is created between the electrodes, the atoms of the larger molecule 230 ionize and emit electrons. The electrons in the gas are accelerated by the RF field, and directly or indirectly ionize the gas by collision to generate secondary electrons. Ultimately, plasma is created when the electric field is strong enough.

In some implementations, as discussed above, target 145 includes tin (Sn), and in these implementations, target material 125 deposited on measurement surface 212 includes tin particles. . As discussed above, the vessel 120 is a controlled environment, and the larger molecules 230 that may exist and be tolerated within the vessel 120 are molecular hydrogen (H ₂ ). In this case, the free radical regeneration tool 215 generates free radicals 216 from molecular hydrogen originating from or present in the vessel 120. The free radical of hydrogen 216 is a single element of hydrogen (H*). This chemical process can be represented by the formula:

H ₂ (g) ↔ 2 H ^*( g), where (g) indicates that the chemical is in a gaseous state.

Specifically, the generated free radicals of hydrogen H ^* combine with the tin particles (Sn) on the measurement surface 212 to form a new chemical substance 228 called tin hydride (SnH ₄ ), which is the measurement surface 212 ). This chemical process is represented by the formula:

4 H ^*( g) + Sn(s) ↔ SnH ₄ (g), where (s) indicates that the chemical is in a solid state.

In this way, the coating 227 (formed from the target material 125) can be etched or removed from the measurement surface 212 at a rate of 1 nanometer/min or more over the entire measurement surface 212, and free radical regeneration. It is not removed in the area closest to the tool 215. This is because the free radicals 216 are generated at a position adjacent to the measurement surface 212 as opposed to being transferred to the measurement surface 212 after being generated apart from the measurement surface 212. This is important because the hydrogen radical H ^** has a short lifetime and tends to recombine to reform molecular hydrogen. The design of the free radical regeneration tool 215 allows the formation of hydrogen radicals H ^* as close as possible to the measuring surface 212, so that more hydrogen radicals ^* can recombine with each other to form a molecular hydrogen before they have a chance to form molecular hydrogen. This allows the measurement system 210 to be regenerated without the need to remove the measurement device 205 from the container 120.

3A and 3B an embodiment of a measurement device 305 is shown. The measuring device 305 is a free radical regeneration tool 315 including a wire filament 365 adjacent to the measuring surface 312 of the measuring system 310 and a power supply 370 supplying current to the wire filament 365. It is designed to have. Wire filaments 365 should be made of a material having a high enough melting point to withstand temperatures high enough to provide sufficient heat to break the bonds of nearby larger molecules. For example, in some implementations, the current flowing through the wire filament 365 can raise the temperature of the wire filament 365 to a temperature in excess of 1000°C. Moreover, the wire filaments 365 must be chemically non-reactive with larger molecules or other components within the container 120. In addition, the wire filament 365 may be made of a material that is a catalyst for the above-described chemical reaction H ₂ (g) ↔ 2 H ^* (g), where (g) indicates that the chemical substance is in a gaseous state. In this way, the wire filament 365 can be any material that accelerates this chemical reaction but is not consumed by this chemical reaction. For example, the material of the wire filament 365 may be tungsten (W), rhenium (Re), or an alloy of at least one of W and Re. Finally, the wire filament 365 must be robust and have a high tensile strength capable of withstanding temperature fluctuations during use. For example, the wire filament 365 may be made of tungsten or rhenium.

Also, referring to FIGS. 3C and 3D, the wire filament 365 obtains energy by the current from the power source 370 to obtain any unique hydrogen molecules 330 in the container 120 and adjacent to the wire filament 365. Is heated to a temperature high enough to apply energy to the point where the atoms in the molecule 330 decompose into free radicals. Since the wire filament 365 has a shape that is suitable for or complementary to the shape of the measurement surface 312, it enables interaction between the free radicals 216 and the coating 327 on the measurement surface 312 more effectively.

In some implementations, the measurement system 310 includes a crystal microbalance, such as a quartz crystal microbalance. The crystal microbalance is shown in Figure 3A. The crystal microbalance is a device that outputs a measurement signal that can be used to determine the flux of the target material 125 impinging on the measurement surface 312. The amount of agglomerate deposited on the measuring surface 312 is related to a change in one or more resonant frequencies associated with the measuring surface 312. Thus, by measuring the change in one or more resonant frequencies, it is possible to determine the amount of lumps deposited on the measurement surface 312. A crystal microbalance includes a crystal, such as a quartz crystal, and a set of electrodes, the electrodes providing an alternating potential to the crystal plane, thereby providing an alternating potential to the crystal plane such that the crystal vibrates at one or more resonant frequencies. The measurement surface 312 may correspond to one of the crystal planes.

The measuring surface 312 is mounted on an adapter or flange 375 made of a non-reactive material, and the flange 375 is mounted on a housing 377 that can be water cooled. The measurement surface 312 may include a coating (not shown) of a thin layer of a free radical resistant material such as zirconium nitride (ZrN). In this embodiment, the generated free radicals 216 react with the deposited target material 125 as a coating 327 on the measurement surface 312, but not with the ZrN coating, so that ZrN is free radical regeneration tool 315. It remains the same even though it is in motion.

When the target material 125 is tin and the crystal microbalance is a quartz crystal microbalance, the saturation limit of the measurement surface 312 is about 8 micrometers (μm). The saturation limit is the maximum thickness of the coating 327 formed from the deposited target material 125, and if this saturation limit is exceeded, the measurement system 110 cannot accurately measure the flux of the target material 125. In contrast, other elements in the vessel 120 can withstand a deposited coating of target material 125 having a thickness of several thousand times on the order of 8 μm. The free radical regeneration tool 315 can remove the coating 327 without the need to open the container 120 and without the need to stop operation of other components within the container 120.

Referring to FIG. 4, a self-reproducing metrology device 405, such as devices 105, 205, 305, may be implemented within an EUV light source 400, wherein the container 120 is, as discussed below, EUV. It is a vacuum chamber 420. The EUV light source 400 includes a target delivery system 440 that directs the flow 442 of the target 445 towards the interaction region 480 in the EUV chamber 420. The interaction region 480 receives the amplified light beam 481. As discussed above, target 445 includes a material that emits EUV light when in a plasma state. The interaction between the material in the target 445 and the amplified light beam 481 within the interaction region 480 converts some of the material in the target 445 into a plasma material 460. This plasma material 460 emits EUV light 455. The plasma material 460 has an element having a bright line in the EUV wavelength range. The generated plasma material 460 has specific properties that depend on the composition of the target 445. These properties include the wavelength of EUV light 455 produced by plasma material 460.

Plasma material 460 can be considered a highly ionized plasma with an electron temperature of several tens of electron volts (eV). Higher energy EUV light 455 can be generated using other fuel materials (different types of targets 445), such as terbium (Tb) and gadolinium (Gd). The energetic radiation generated during the de-excitation and recombination of these ions is emitted from the plasma material 460 and is then collected by the optical element 482.

5A-5D, optical element 482 can be an optical collector that interacts with at least a portion of EUV light 455 from which surface 483 is emitted. Surface 483 of optical collector 482 receives at least a portion of EUV light 455 and directs this collected EUV light 454 for use outside of EUV light source 400 (shown in FIG. 4). It may be a reflective surface positioned to allow. Reflective surface 483 directs the collected EUV light 484 to a secondary focal plane, where the EUV light 484 is external to the EUV light source 400 (e.g., a lithographic apparatus). The exemplary lithographic apparatus 1000 and 1100 that are captured for use by are described with reference to FIGS. 10 and 11 respectively.

The reflective surface 483 may be configured to reflect light in the EUV wavelength range, but to absorb, diffuse, or block light outside the EUV wavelength range. The optical collector 482 also includes an opening 590 that allows the amplified light beam 481 to pass through the optical collector 482 and directed towards the interaction region 480. The optical collector 482 may be, for example, an elliptical mirror having a primary focus on the interaction area 480 and a secondary focus on the secondary focal plane. This means that the planar section (eg, planar section C-C) is oval or circular. Thus, the planar section C-C cuts the reflective surface 483, which is formed from a part of the ellipse. The plan view of the optical collector 482 shows that the edge of the reflective surface 483 forms a circular shape.

The optical collector 482 shown is a single curved mirror, but it may take other forms. For example, the optical collector 482 may be a Schwarzschild collector having two radiation collecting surfaces. In one implementation, optical collector 482 is a grazing incident collector comprising a plurality of substantially cylindrical reflectors superimposed on each other.

Referring again to FIG. 4, the EUV light source 400 includes an optical system 486 that generates an amplified light beam 481 due to a gain medium or density reversal in the media. The optical system 486 may include a light source that generates a light beam, and a beam delivery system that modulates and modifies the light beam and also focuses the light beam into the interaction region 480. The light source in the optical system 486 may have one or more main pulses forming an amplified light beam 481 and optionally one or more pre-pulses forming a precursor amplified light beam (not shown). One or more optical amplifiers, lasers, and/or lamps for providing. 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 forming a laser cavity. Thus, the optical system 486 produces an amplified light beam 481 due to the density inversion of the gain medium of the amplifier even in the absence of a laser cavity. Moreover, the optical system 486 can generate an amplified light beam 481 that is a coherent laser beam when there is a laser cavity that provides sufficient feedback to the optical system 486. Thus, the term “amplified light beam” refers to one or more of the light from the optical system 486, which is amplified but not necessarily coherent laser oscillations, and the amplified, coherent laser oscillation. Include.

The optical amplifier used in the optical system 486 contains carbon dioxide (CO ₂ ) as a gain medium and transmits light at a wavelength of about 9100 to 11000 nanometers (nm), for example, about 10600 nm with a gain of 100 or more. It may contain a gas that can be amplified. Amplifiers and lasers suitable for use in the optical system 486 operate with relatively high powers of 10 kW or more, for example, using DC or RF excitation, and with A high pulse repetition rate, for example, 40 kHz or more. Pulsed laser devices that produce radiation of about 9300 nm or about 10600 nm, such as pulsed gas discharge CO ₂ laser devices.

EUV light source 400 also includes a control device 487 in communication with one or more controllable components or systems of EUV light source 400. This control device 487 communicates with the optical system 486 and the target delivery system 440. The target delivery system 440 may operate in response to signals from one or more modules in the control device 487. For example, the control device 487 transmits a signal to the target delivery system 440 to modify the release point of the target 445 to reach the desired interaction area 480. Try to correct the error. Optical system 486 may operate in response to signals from one or more modules in control device 487. The various modules of the control device 487 may be standalone modules in which data between modules is not transferred from the module to the module. Alternatively, one or more of the modules in the control device 487 may communicate with each other. The modules in the control device 487 may be physically co-located or separated from each other.

For example, a module that controls the target delivery system 440 may be disposed at the same location as the target delivery system 440, and the module that controls the optical system 486 is disposed at the same location as the optical system 486. Can be.

The measuring device 405 includes a measuring system 310 and a control device 488 that communicates with the regeneration tool 415 of the measuring device 405. This control device 488 performs an action, such as to receive the output from the measurement system 310, and analyze this output as necessary, and transmit data to the control device 488, or based on the analysis. To activate the playback tool 415. Thus, the control device 488 communicates with the measurement system 410 and receives a measurement signal from the measurement system 410 to calculate the flux of the target material 425 over the entire measurement surface of the measurement system 410. It may include a measurement controller configured to. The control device 488 may provide a signal to activate or activate the regeneration tool 415. For example, the control device 488 may provide a signal to the power source 370 of the measurement device 305 to supply current to the wire filament 365.

EUV system 400 also includes a removal or evacuation device 489 configured to remove chemicals 428 released from EUV chamber 420 as well as other gaseous by-products that may form within EUV chamber 420. . As discussed above, the released chemicals 428 are free radicals 416 (which are generated from larger molecules 430 by the regeneration tool 415) and are deposited on the measurement surface of the measurement system 410. It is formed from interaction with the target material 425. Removal device 489 may be a pump that removes chemicals 428 released from EUV chamber 420. The removal device 489 includes a gas port in fluid communication with the cavity 418 or the interior of the EUV chamber 420 so that the released new chemicals 428 from the cavity 418 through this gas port through the EUV chamber 420 ) Can be transferred to the outside. For example, when chemical 428 is formed, it is released, and since chemical 428 may be volatile, the control device 488 to remove chemical 428 released from EUV chamber 420 Is aspirated.

Other components of EUV light 455, not shown, include, for example, a detector for measuring parameters associated with the generated EUV light 455. The detector can be used to measure the energy or energy distribution of the amplified light beam 481. The detector may be used to measure the angular distribution of the intensity of the EUV light 455. The detector may measure a pulse timing or focus error of the amplified light beam 481. The output from this detector may be provided to a control device 487, which analyzes the output and determines aspects of other components of the EUV light source 400, such as the optical system 486 and target delivery system 440. It may include a module that adjusts.

In summary, the amplified light beam 481 is generated by the optical system 486, is redirected along the beam path and irradiated to the target 445 in the interaction region 480 to transfer the material in the target 445 to the EUV wavelength range. Converts it into a plasma that emits light. The amplified light beam 481 operates at a specific wavelength (source wavelength) determined based on the design and characteristics of the optical system 486.

Although only one measuring device 405 is shown in the EUV chamber 420 of FIG. 4, a plurality of measuring devices 405 may be configured over the entire EUV chamber 420. Another possible location for the metrology device 405 is indicated by the crosshair icon 495 shown in FIG. 4. For example, the metrology device 405 may be positioned next to any optical element, including a surface that is likely to interact with the target material 125 and thus may be coated with debris during operation of the EUV light source 400. I can. Thus, one or more metrology devices 405 may be adjacent to the optical collector 482, such as in the vicinity of the rim of the optical collector 482; The side of a cone disposed between the wall of the EUV chamber 420 and the optical collector 482; And/or near the target delivery system 440, near the exhaust unit (eg, control device 488).

The measurement system 310 can measure the properties of the coating 327 formed on the measurement surface 312, and then to determine the thickness of this coating 327 and thus the flux of the target material 125. It is any device that enables analysis. In another implementation, the measurement system 310 may include a refractometer, an elliptic spectrometer; And/or designed as a four-point probe.

As discussed above, in the implementation of FIGS. 3A-3D, the metrology device 305 is designed to have a free radical regeneration tool 315 comprising a wire filament 365 adjacent to the measurement surface 312. There are other ways to design the free radical regeneration tool 315. In other implementations, the free radical regeneration tool 315 is close to the measuring surface 312 from a material already present in the vessel 120 and originating within the vessel 120 (a native material such as a larger molecule 330). Or a plasma generator that enables the generation of a material in a plasma state (plasma material) in an adjacent location. The material (e.g., larger molecules 330) is derived from the container 120 or when present in the container 120 without having to be transferred into the container 120 from the outside of the container 120 Exists within The plasma material includes free radicals 216 that chemically react with the deposited target material 125 as a coating 327 on the measurement surface 312, as discussed above. In addition to free radicals, the plasma material may contain a unique material, electrons generated from this intrinsic material, and other components that do not react with the target material 125 such as chemically neutral items. The free radical regeneration tool 315 can remove more target material 125 (deposited as coating 327) as the number of free radicals present in the plasma material increases. In other words, the higher the density of free radicals in the plasma material, the higher the rate of debris removal.

In some implementations, the free radical regeneration tool 315 is designed as an inductively coupled plasma (ICP) tool that includes a conductor disposed adjacent to the measurement surface 312 as a plasma generator. The conductor is connected to the power supply of the measuring device 305 and is housed inside a dielectric tube such as porcelain, ceramic, mica, polyethylene, glass, or quartz. In the ICP process, a time-varying current flows through a conductor (from a power source), and the flow of time-varying current creates a time-varying magnetic field adjacent to this conductor. In addition, the generated time-varying magnetic field induces an electric field or current in a place adjacent to the measurement surface 312. The induced current is large enough to generate a plasma material at a location adjacent to the measurement surface 312 from the material originating in the vessel 120.

In another implementation, the free radical regeneration tool 315 is designed as a heated capillary tube. The free radical regeneration tool 315 is not limited to the specific design mentioned herein, and may be any tool that generates free radicals.

Referring back to FIG. 2, since the size of the measuring surface 312 is relatively small, the free radicals 216 generated by the free radical regeneration tool 215 or 315 are formed by the tool 21° 5 and then diffused. It flows over the entire measurement surface 212 by the action of. However, since the pressure in the vessel 120 can be relatively high (although this can be a low vacuum, even if it is a vacuum), in some implementations where the measuring surface 212 is larger or other factors reduce the amount of diffusion, additional It can be difficult to disperse free radicals over the entire measurement surface 212 without the aid of. Thus, metrology device 205 may include a gas flow mechanism configured to push or disperse free radicals 216 over the entire surface of measurement surface 312.

Referring to FIG. 6, a procedure 600 is performed by the device 100. A target 145 is supplied 605 into the cavity 118 of the container 120. This target 145 includes a target material 125 that emits EUV light 155 upon conversion to plasma material 160. The flux of the target material 125 is measured (610) on the measuring surface 112 in the vessel 120 (eg, using the measuring system 110). The measuring surface 112 is reproduced (615). Reproduction 112 and 615 of the measurement surface may include preventing the measurement surface 112 from being saturated (615A). The regeneration 112 and 615 of the measurement surface may include desaturating the measurement surface 112 when it is saturated (615B). Alternatively, the regeneration 112 and 615 of the measurement surface may be performed by both preventing the measurement surface 112 from being saturated (615A) and desaturating (615B) when the measurement surface 112 is saturated. Can include.

4, the target 445 is within the cavity 418 by directing the flow 442 of the plurality of targets 445 or the target 445 toward the interaction region 480 in the EUV chamber 420. Can be supplied (605). The interaction region 480 also receives the amplified light beam 481 to direct the target 445 to the EUV light 455 by interaction between the target 445 and the amplified light beam 481 in the interaction region 480. ) To emit plasma material 460.

The flux of the target material 125 may be measured by interacting the target material 125 with the measurement surface 112 so that the target material 125 is deposited on the measurement surface 112 (610).

The regeneration 112 and 615 of the measurement surface may be activated based on the flux measured on the measurement surface 112. Moreover, regeneration 615 can be performed and completed without removing the measuring surface 112 from the container 120.

Also referring to FIG. 7, a measurement surface 312 is shown to explain how the reproduction 615 of the measurement surface is affected. The measuring surface 312 is regenerated (615) by removing the deposited target material 125 from the measuring surface 312. The target material 125 forms a coating 327 on the measurement surface 312 (716). The deposited target material 125 (which forms the coating 327) is removed 717 from the measurement surface 312 by generating free radicals 216. Free radicals 216 may be generated from elements or materials such as larger molecules 230 that are already present in the vessel 120 and are adjacent to the measurement surface 312. In addition, after the free radicals 216 are generated, these free radicals 216 chemically react with the deposited target material 125 (this forms the coating 327) on the measurement surface 312 to form a new chemical substance. Form 228, which is emitted 718 from the measuring surface 312. The deposited target material 125 may be removed from the measurement surface 312 without using oxygen as an element of a catalyst or reaction.

Procedure 600 may include removing chemicals 228 released from vessel 120 using, for example, evacuation devices 489.

The flux of the target material 125 may be measured by measuring the flux of the target material 125 during a time period when the deposited target material 125 is not being removed from the measurement surface 112 (610). Accordingly, the measurement of the flux of the target material 125 may occur at a time distinct from the time when the measurement surface 112 is regenerated (615 ). Removal of the deposited target material 125 from the measurement surface 112 (which is part of the regeneration 615) can prevent the measurement surface 112 from reaching its saturation limit. Moreover, if the target material 125 is removed too quickly, the measurement system 110 may not be able to determine the flux of the target material 125 so that the removal of the deposited target material 125 will result in the target material 125 being removed soon. Should be performed after the flux of is measured by the measurement system 110.

The measured flux 610 can also be used by the control device 487 to estimate the amount of EUV light 455 emitted from the plasma material 460. For example, the production stability of EUV light 455 is generally related to the production of target material 125 (this is, for example, a fragment of tin). Therefore, a large fluctuation in the measured flux 610 of the target material 125 indicates that the operation of the EUV light source 400 is unstable. Moreover, the measured flux 610 can be used to further estimate the amount of target material 125 deposited on a surface within the vessel 120, eg, a surface adjacent to the metrology device 405.

The measuring device 105 can be placed at a specific location throughout the container 120 according to the desired information. For example, the measured flux 610 can be used to determine malfunction of equipment adjacent to a particular metrology device 105. As another example, the measured flux 610 can be used to measure the cleaning rate of the surface when the metrology device 105 is placed next to the surface being cleaned.

The measured flux 610 can be used to determine whether the flow field of the transferred target material 125 is changed. In particular, the target material 125 may be incorporated into the molecular hydrogen present in the vessel 120, and this molecular hydrogen is transported through the vessel 120 along a specific flow path, and the measurement device 105 If placed in the vicinity, this can be used to determine whether the flow field is altered by measuring the flux 610 of the target material 125.

Referring to FIG. 8, a graph 800 is shown showing the use of the procedure 600 and the measurement device 305 of FIGS. 3A-3D. This graph 800 shows the deposition thickness 805 of the coating 327 over time 810 (or pulse accumulation equivalent). The saturation limit 815 of the measurement surface 312 is also shown in dotted line in this graph 800. As discussed above, in embodiments where the measurement system 310 is a quartz crystal microbalance, the target material 125 is tin, and the saturation limit 815 may be in the range of 5-15 μm. Initially, metrology device 305 functions in measurement mode 820, in which mode 820 the measurement system 310 measures the flux of the target material 125 across the measurement surface 312. It works. In this measurement mode 820, since the free radical regeneration tool 315 does not operate, current is not supplied from the power source 370 to the wire filament 365. During this measurement mode 820, the thickness 805 of the coating 327 is generally increasing. In this measurement mode 820, the slope of the graph 800 may be stored in the memory of the measurement system 310 or a control device that receives the output from the measurement system 310, and the system performance monitor and process excursion ) Can be used as protection. Moreover, the measurement system 310 operates to determine the deposition rate, flux, or other property of the target material 125. As the thickness 805 of the coating 327 reaches the saturation limit 815, the metrology device 305 switches to operate in the regeneration mode 825. In the regeneration mode 825, the measurement system 310 may or may not perform a function, but the wire filament 365 may receive energy by the current from the power source 370, so the coating on the measurement surface 312 Acts actively to remove the deposited target material 125 as 327. The cycles of the measurement mode 820 and the regeneration mode 825 are repeated as necessary while the device 100 is operating. Moreover, the timing or frequency of the cycle may be selected according to the desired data collection frequency of the measurement system 310.

In the case of the measurement system 310 which is a quartz crystal microbalance and has a ZrN surface coating, depending on the distance between the wire filament 365 and the measurement surface 312, the rate of removal of tin from the measurement surface 312 is the wire filament ( 365) at a radial distance of about 20 millimeters (mm) from the periphery of 4 nm/min. Since the quartz crystal microbalance is small in size and the measuring surface 312 is within 20 mm, the removal rate of tin from the quartz crystal microbalance exceeds 4 nm/min in this situation. This removal rate is much higher than the deposition rate on a nearby critical surface, which is about 450 nm/gps (e.g., several tens of times higher), thus improving the time distribution of the regeneration of the measuring surface 112.

For example, FIG. 9 shows a graph 900 of the removal rate 905 in arbitrary units versus the distance between the wire filament 365 and the measuring surface 312 for various values of standard liters/minute (slm). do.

Referring to FIG. 10, in some implementations, metrology device 105 (or 205, 305, 405) is implemented within EUV light source 1000 that supplies EUV light 1084 to lithographic apparatus 1085. The lithographic apparatus 1085 includes an illumination system (illuminator) IL configured to condition a radiation beam B (eg, EUV light 1084); A support structure (e.g., a mask table) MT configured 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 configured 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 configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (e.g., comprising one or more dies) (e.g. , Reflective projection system) (PS).

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 to direct, shape or control radiation. have. 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 the patterning device is held in a vacuum environment. . The support structure MT may use mechanical clamping, vacuum clamping, electrostatic clamping, or other clamping techniques to hold the patterning device. The support structure MT may be, for example, a frame or a table that is fixed or movable as needed. The support structure MT can ensure that the patterning device is in a desired position with respect to the projection system, for example.

The term “patterning device” should be broadly interpreted as referring to any device that can be used to impart a radiation beam having a pattern in its cross-section, for example, to create a pattern in a target portion of a substrate. The pattern imparted to the radiation beam may correspond to a specific functional layer of a device being created in the target portion, such as an integrated circuit. The patterning device can 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 attenuating phase shift, as well as various hybrid mask types. One embodiment of the programmable mirror array uses a matrix arrangement of small mirrors, each mirror can be individually tilted to reflect the incident radiation beam in a different direction. The tilted mirror imparts a pattern to the radiation beam reflected by the mirror matrix.

Like the illumination system (IL), the projection system (PS) is a refractive, reflective, magnetic, electromagnetic, electrostatic or other type of optical component, or any of these, depending on the exposure radiation used or other factors such as the use of vacuum. It can include various types of optical components, such as combinations. For EUV radiation, it may be desirable to use a vacuum as other gases may absorb too much of the radiation. Thus, vacuum walls and vacuum pumps can be used to provide a vacuum environment for the entire beam path.

As shown herein, the device is of a reflective type (eg, using a reflective mask).

This lithographic apparatus may be of a type with two (dual stage) or more substrate tables (and/or more than two patterning device tables). In such "multi-stage" machines, additional tables may be used in parallel, or preliminary steps may be performed on one or more tables while one or more other tables are being used for exposure.

The illuminator IL receives an extreme ultraviolet radiation beam (EUV light 1175) from the EUV light source 1000. Methods of generating EUV light include, but are not limited to, converting a material with at least one element, such as xenon, lithium or tin, to a plasma state with one or more bright lines in the EUV range. In one of these methods, often referred to as laser generated plasma (“LPP”), the required plasma can be created by irradiating with a laser beam a fuel, such as droplets, streams, or clusters of material having the required prior emission elements. The EUV light source 1000 may be designed similar to the EUV light source 400. As discussed above, the generated plasma emits output radiation, for example EUV radiation, which is collected using optical element 482 (or radiation collector).

The radiation beam B is incident on a patterning device (eg, a mask) MA held on a support structure (eg, a mask table) MT, and is patterned by the patterning device. After being reflected from the patterning device (e.g. mask) MA, the radiation beam passes through a projection system PS that focuses this beam onto a target portion C of the substrate W. Using a second positioner PW and a position sensor PS2 (e.g., an interfering device, a linear encoder or a capacitive sensor), the substrate table WT is, for example, a different target in the path of the radiation beam B. It can be accurately moved to position part C. Similarly, a patterning device (e.g., a mask) with respect to the path of the radiation beam B using a first positioner PM and another position sensor PS1 )(MA) can be accurately positioned. The patterning device (e.g., mask) (MA) and the substrate (W) use patterning device alignment marks (M1, M2) and substrate alignment marks (P1, P2). Can be aligned.

The illustrated device can be used in at least one of the following modes:

One. In step mode, the support structure (e.g., mask table) MT and substrate table WT remain essentially stationary, and the entire pattern imparted to the radiation beam is at once (i.e., with a single static exposure). It is projected onto the target portion C. Next, the substrate table WT is moved in the X direction and/or the Y direction so that different target portions C can be exposed.

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

3. In another mode, the support structure (e.g., mask table) MT is held essentially stationary by holding a programmable patterning device, and the substrate table WT is provided with the pattern imparted to the radiation beam at the target portion C. ) Is moved or scanned while being projected on. In this mode, generally a pulsed radiation source is used, and the programmable patterning device is updated as needed after each movement of the substrate table WT or between successive radiation pulses during scanning. This mode of operation can be easily applied to maskless lithography using a programmable patterning device such as a programmable mirror array of the type mentioned above.

Combinations and/or variations of the above-described modes of use or completely different modes of use may also be used.

11 shows in more detail an implementation of a lithographic apparatus 1185 comprising an EUV light source 1100, an illumination system IL, and a projection system PS. The EUV light source 1100 is configured and arranged as discussed when describing the EUV light source 400 above.

The systems (IL, PS) are likewise maintained in their own vacuum environment. The intermediate focal point IF of the EUV light source 1000 is disposed to be located at or near the opening of the surrounding structure. The virtual source point (IF) is an image of a radiation emitting plasma (eg, EUV light 484).

The radiation beam from the opening of the intermediate focal point IF traverses the illumination system IL comprising, in this embodiment, a multi-faceted field mirror device 1122 and a multi-faceted pupil mirror device 1124. These devices form a so-called "fly-eye" illuminator, which is shown by reference number 1160 as well as the desired angular distribution of the radiation beam 1121 in the patterning device MA as well as the radiation intensity of the patterning device MA. ) Are arranged to provide. When the radiation beam 1121 is reflected in the patterning device MA held by the support structure (mask table) MT, a patterned beam 1126 is formed, and the patterned beam 1126 is converted to the substrate table WT. It is imaged by the projection system PS via reflective elements 1128 and 1130 on the substrate W held by ). In order to expose the target portion C on the substrate W, the substrate table WT and the patterning device table MT perform synchronized movement while scanning the pattern on the patterning device MA through the slit of illumination. A pulse of radiation is produced.

Each of the systems IL and PS is placed in its own vacuum or near-vacuum environment formed by surrounding structures similar to EUV chamber 420. More elements than shown may generally be present in the illumination system IL and the projection system PS. Also, there may be more mirrors than shown. For example, there may be 1 to 6 additional reflective elements in the illumination system IL and/or projection system PS in addition to those shown in FIG. 11.

Referring back to FIG. 4, the target delivery system 440 includes a droplet generator disposed within the EUV chamber 420 and configured to fire a high frequency droplet flow 442 towards the interaction region 480. I can. During operation, the amplified light beam 481 is transmitted in synchronization with the operation of the droplet generator, and a pulse of radiation is transmitted to change each droplet (each target 445 to a luminescent plasma 460. The delivery frequency of droplets) May be several kilohertz, for example 50 kHz.

In some implementations, the energy from the amplified light beam 481 is delivered in two or more pulses. That is, a pre pulse with limited energy is sent to the droplet before reaching the interaction region 480 to vaporize the fuel material into a small cloud, and then the main pulse of energy is It is delivered to this cloud in the interaction region 480 to create a luminescent plasma 460. On the opposite side of the EUV chamber 420 is provided a trap (which may be, for example, a receptacle) for trapping fuel that has not been converted to plasma (i.e., target 445) for any reason.

The droplet generator of the target delivery system 440 includes a filter and nozzle and a reservoir for receiving a fuel liquid (eg, molten tin). The nozzle is configured to eject droplets of fuel liquid towards the interaction zone 480. Droplets of fuel liquid can be discharged from the nozzle by a combination of pressure in the reservoir and vibration applied to the nozzle by a piezoelectric actuator (not shown).

Other aspects of the invention are described in the numbered sections below.

1. As a device,

Vessel;

A target delivery system for directing a target toward an interactive area within the vessel, the target comprising a target material that emits extreme ultraviolet radiation when in a plasma state; And

A measurement device comprising:

A measurement system comprising a measurement surface configured to measure the flux of the target material; And

And a regeneration tool configured to regenerate the measurement system, the regeneration:

Preventing the measurement surface from being saturated, and/or

And desaturating the measuring surface when the measuring surface is saturated.

2. The apparatus of clause 1, wherein the measurement device comprises a removal device in communication with the measurement system and a regeneration tool, the removal device being configured to activate a regeneration tool based on an output from the measurement system.

3. In Section 1,

The measurement surface is configured to interact with a target material, and the interaction between the target material and the measurement surface generates a measurement signal;

And the measurement system further comprises a measurement controller configured to receive the measurement signal and calculate a flux of the target material across the measurement surface.

4. The device of clause 1, wherein the metrology device comprises a crystal microbalance.

5. The apparatus according to section 4, wherein the crystal microbalance is a quartz crystal microbalance.

6. The apparatus of clause 1, wherein the vessel is formed with a cavity and the vessel cavity is maintained at a pressure below atmospheric pressure.

7. The apparatus of clause 1, wherein the interaction region receives an amplified light beam, and when the target interacts with the amplified light beam, the target is converted into a plasma that emits extreme ultraviolet rays.

8. The device of clause 1, wherein the device further comprises an optical element comprising an optical element surface within the container, the metrology device being positioned relative to the optical element surface.

9. The apparatus of clause 8, wherein the optical element is an optical collector in which the optical element surface interacts with at least a portion of the extreme ultraviolet rays emitted when the target is converted to plasma.

10. The apparatus of clause 1, wherein the regeneration tool is configured to regenerate the measurement system without removing the measurement device from the container.

11. The apparatus of clause 1, wherein the regeneration tool is positioned to interact with the measurement system and is configured to remove target material deposited on the measurement surface in accordance with a command by the measurement controller.

12. The method of Section 11, wherein the cleaning tool includes a free radical generation unit configured to generate free radicals adjacent to the measurement surface, and the free radicals are chemically reacted with the deposited target material to be released from the measurement surface. Devices that form new chemicals that become.

13. The apparatus of clause 12, wherein the free radical generating unit comprises a wire filament adjacent to the measuring surface and a power supply for supplying electric current to the wire filament.

14. The apparatus of clause 13, wherein the wire filament is of a shape matching the shape of the measuring surface.

15. The apparatus according to clause 12, wherein the free radical generating unit comprises a plasma generator for generating a plasma material in a plasma state adjacent to the measurement surface, and the plasma material includes free radicals.

16. The apparatus of clause 12, wherein the free radicals are free radicals of hydrogen generated from hydrogen molecules originating in the vessel.

17. The apparatus of clause 16, wherein the target material on the measurement surface includes tin, and the chemical substance released from the measurement surface includes tin hydride.

18. The apparatus of clause 12, wherein the apparatus further comprises a removal apparatus configured to remove fresh chemicals released from the vessel.

19. The apparatus of clause 18, wherein the removal device comprises a gas port in fluid communication with the interior of the container, and the new chemical being released is conveyed through the gas port from the interior of the container.

20. The apparatus of clause 1, wherein the regeneration tool is configured to remove the target material from the measuring surface in the presence of hydrogen within the vessel and without involving a reaction requiring oxygen.

21. As a method,

Supplying a target into the cavity of the container, the target comprising a material that emits extreme ultraviolet rays when converted to plasma;

Measuring the flux of the target material across the measuring surface within the vessel cavity; And

And regenerating the measuring surface, wherein the regenerating step includes:

Preventing the measurement surface from being saturated and/or

At least one of desaturating the measuring surface when the measuring surface is saturated.

22. The method of clause 21, wherein the method further comprises activating regeneration of the measuring surface based on the measured flux of the target material across the measuring surface.

23. The method of clause 21, wherein measuring the flux of the target material comprises interacting the target material with the measurement surface such that the target material is deposited on the measurement surface.

24. The method of clause 21, wherein the step of supplying a target into the cavity of the vessel comprises directing a plurality of targets toward an interaction region within the vacuum vessel, wherein the interaction region also receives an amplified light beam. So that the target is converted into a plasma that emits extreme ultraviolet rays by an interaction between the target and the light beam amplified within the interaction region.

25. The method of clause 21, wherein regenerating the surface comprises removing the deposited target material from the measuring surface without removing the measuring surface from the container.

26. The method of Section 25, wherein removing the deposited target material from the measurement surface comprises generating free radicals of a predetermined element adjacent to the measurement surface, and the generated free radical is chemically separated from the deposited target material. Reacting to form new chemicals released from the measuring surface.

27. The method of clause 26, wherein the deposited target material comprises tin, the element is hydrogen, the free radical is a hydrogen radical, and the new chemical is tin hydride.

28. The method of clause 26, wherein the element adjacent to the measuring surface is derived from a vessel cavity.

29. The method of clause 26, wherein removing the deposited target material comprises removing the deposited target material in the absence of oxygen.

30. The method of clause 26, wherein the method further comprises removing fresh chemicals released from the vessel cavity.

31. The method of clause 25, wherein measuring the flux of the target material comprises measuring the flux of the target material during a time period when the deposited target material is not being removed from the measurement surface.

32. The method of clause 25, wherein the measuring surface is prevented from reaching the saturation limit by removing the deposited target material from the measuring surface.

33. The method of clause 21, wherein the method further comprises maintaining the cavity formed in the vessel at a pressure below atmospheric pressure.

34. The method of clause 21, wherein the method further comprises estimating an amount of extreme ultraviolet rays emitted when the target material is converted to plasma based on the measured flux.

35. The method of clause 21, wherein the method further comprises estimating an amount of target material deposited on a surface within the vessel cavity based on the measured flux.

36. As an extreme ultraviolet light source,

A light source configured to generate an amplified light beam;

A cavity formed vessel, wherein the vessel is configured to receive the amplified light beam in an interactive region within the cavity, the cavity being configured to be maintained at a pressure below atmospheric pressure;

A target delivery system configured to create a target that moves along a target path towards the interaction area, the target comprising a target material that emits extreme ultraviolet rays in a plasma state; And

A measurement device comprising:

A measurement system comprising a measurement surface configured to measure the flux of the target material; And

And a regeneration tool configured to regenerate the measurement system, the regeneration:

Preventing the measurement surface from being saturated; And/or

The extreme ultraviolet light source comprising desaturating the measurement surface when the measurement surface is saturated.

37. In section 36,

The measurement surface is configured to interact with a target material, and the interaction between the target material and the measurement surface generates a measurement signal; The measurement system further comprises a measurement controller for receiving the measurement signal and calculating a flux of the target material over the entire measurement surface.

38. The regeneration tool of clause 37, wherein the regeneration tool comprises a cleaning tool here positioned to interact with the measurement system, the cleaning tool regenerating the measurement system by removing target material deposited on the measurement surface. Configured to let, an extreme ultraviolet light source.

39. The extreme ultraviolet light source of clause 36, wherein the extreme ultraviolet light source further comprises an optical collector for collecting at least a portion of the emitted extreme ultraviolet light used by an external lithographic apparatus.

40. As a measuring system for use in extreme ultraviolet light sources,

The metrology system:

A measuring device configured to measure the flux of a target substance across the entire measuring surface in the container, the measuring device

A measurement system comprising a measurement surface configured to interact with the target material, wherein a measurement signal is generated by the interaction between the target material and the measurement surface; And

A measurement controller configured to receive the measurement signal and calculate a flux of the target material over the entire measurement surface based on the received measurement signal; And

A regeneration tool coupled to the measurement device and configured to regenerate the measurement system,

The playback is:

Preventing the measurement surface from being saturated, and/or

Desaturating the measurement surface when the measurement surface is saturated,

Wherein the regeneration tool includes a cleaning tool positioned to interact with the measurement surface and remove target material deposited on the measurement surface in accordance with a command from the measurement controller.

41. As a device,

Vessel;

Means for delivering a target toward an interactive region within the vessel, the target comprising a target material that emits extreme ultraviolet rays when in a plasma state; And

A measurement device comprising:

Means for measuring the flux of the target material over the entire measuring surface in the container; And

And means for regenerating said measuring surface, said means for regenerating:

Means for preventing the measurement surface from being saturated; And/or

And means for desaturating the measurement surface when the measurement surface is saturated.

Other implementations are set forth in the following claims.

Claims (25)

Vessel;
A target delivery system for directing a target toward an interactive area within the vessel, the target comprising a target material that emits extreme ultraviolet radiation when in a plasma state; And
A measurement device comprising:
A measurement system comprising a measurement surface configured to measure the flux of the target material; And
And a regeneration tool configured to regenerate the measurement system, the regeneration:
Preventing the measurement surface from being saturated, and/or
And desaturating the measuring surface when the measuring surface is saturated. The method of claim 1,
The measurement surface is configured to interact with a target material, and the interaction between the target material and the measurement surface generates a measurement signal;
And the measurement system further comprises a measurement controller configured to receive the measurement signal and calculate a flux of the target material across the measurement surface. The method of claim 1,
Wherein the metrology device comprises a quartz crystal microbalance. The method of claim 1,
Wherein the interaction region receives an amplified light beam, and when the target interacts with the amplified light beam, the target is converted into a plasma that emits extreme ultraviolet rays. The method of claim 1,
The device further comprises an optical element comprising an optical element surface within the vessel, the metrology device positioned relative to the optical element surface, the optical element at least of the extreme ultraviolet rays emitted when the target is converted to plasma. The apparatus of claim 1, wherein a portion of the optical element surface is an optical collector through which the surface of the optical element will interact. The method of claim 1,
Wherein the regeneration tool is configured to regenerate the measurement system without removing the measurement device from the container. The method of claim 1,
Wherein the regeneration tool includes a cleaning tool positioned to interact with the measurement system, the cleaning tool configured to remove target material deposited on the measurement surface in response to an instruction by the measurement controller. The method of claim 7,
The cleaning tool comprises a free radical generation unit configured to generate free radicals adjacent to the measurement surface, the free radicals chemically reacting with the deposited target material to form new chemicals released from the measurement surface, Device. The method of claim 8,
The free radical generating unit is:
A wire filament adjacent to the measuring surface and a power supply for supplying current to the wire filament; And
A plasma generator for generating a plasma material in a plasma state adjacent to the measurement surface, the plasma material containing free radicals;
A device comprising one of. The method of claim 8,
The free radical is a free radical of hydrogen generated from hydrogen molecules derived from the container, the target material on the measurement surface contains tin, and the new chemical substance released from the measurement surface contains tin hydride, Device. The method of claim 8,
The device further comprises a removal device configured to remove new chemicals released from the container, the removal device comprising a gas port in fluid communication with the interior of the container, and the released new chemicals The apparatus, conveyed through the gas port from the inside. The method of claim 1,
Wherein the regeneration tool is configured to remove the target material from the measurement surface in the presence of hydrogen in the vessel and without involving a reaction requiring oxygen. Supplying a target into the cavity of the container, the target comprising a material that emits extreme ultraviolet rays when converted to plasma;
Measuring the flux of the target material across the measuring surface within the cavity; And
And regenerating the measuring surface, wherein the regenerating step includes:
Preventing the measurement surface from being saturated, and
At least one of desaturating the measuring surface when the measuring surface is saturated. The method of claim 13,
The method further comprises activating regeneration of the measuring surface based on the measured flux of the target material across the measuring surface. The method of claim 13,
The step of supplying a target into the cavity of the vessel comprises directing a plurality of targets toward an interaction region within the vacuum vessel, wherein the interaction region also receives an amplified light beam within the interaction region. Wherein the interaction between the target and the amplified light beam causes the target to be converted into a plasma that emits extreme ultraviolet rays. The method of claim 13,
The method, wherein regenerating the measuring surface comprises removing the deposited target material from the measuring surface without removing the measuring surface from the container and in the absence of oxygen. The method of claim 13,
Regenerating the measurement surface includes removing the target material deposited from the measurement surface without removing the measurement surface from the container, and removing the deposited target material from the measurement surface Generating free radicals of a predetermined element adjacent to, wherein the generated free radicals react with the deposited target material to form new chemicals released from the measuring surface. The method of claim 17,
Wherein the deposited target material comprises tin, the element is hydrogen, the free radical is a hydrogen radical, and the new chemical is tin hydride. The method of claim 13,
The step of regenerating the measurement surface includes removing the deposited target material from the measurement surface without removing the measurement surface from the container, thereby removing the deposited target material from the measurement surface The method of preventing the measuring surface from reaching its saturation limit. The method of claim 13,
The method further comprises estimating the amount of extreme ultraviolet rays emitted when the target material is converted to plasma based on the measured flux. The method of claim 13,
The method further comprises estimating an amount of target material deposited on a surface within the vessel cavity based on the measured flux. As an extreme ultraviolet light source,
A light source configured to generate an amplified light beam;
A cavity formed vessel, wherein the vessel is configured to receive the amplified light beam in an interactive region within the cavity, and the cavity is configured to be maintained at a pressure below atmospheric pressure;
A target delivery system configured to create a target that moves along a target path towards the interaction area, the target comprising a target material that emits extreme ultraviolet rays in a plasma state; And
A measurement device comprising:
A measurement system comprising a measurement surface configured to measure the flux of the target material; And
And a regeneration tool configured to regenerate the measurement system, the regeneration:
Preventing the measurement surface from being saturated; And/or
And desaturating the measurement surface when the measurement surface is saturated. The method of claim 22,
Wherein the regeneration tool includes a cleaning tool positioned to interact with the measurement system, the cleaning tool configured to regenerate the measurement system by removing target material deposited on the measurement surface. As a measurement system for use in extreme ultraviolet light sources,
The metrology system:
A measuring device configured to measure the flux of a target substance over the entire measuring surface in a container, the measuring system comprising a measuring surface configured to interact with the target substance-measured by interaction between the target substance and the measuring surface Signal is generated -; And a measurement controller configured to receive the measurement signal and calculate a flux of the target material over the entire measurement surface based on the received measurement signal; And
A regeneration tool coupled to the measurement device and configured to regenerate the measurement system,
The playback is:
Preventing the measurement surface from being saturated, and/or
Desaturating the measurement surface when the measurement surface is saturated,
Wherein the regeneration tool includes a cleaning tool positioned to interact with the measurement surface and remove target material deposited on the measurement surface in accordance with commands from the measurement controller. Vessel;
Means for delivering a target toward an interactive region within the vessel, the target comprising a target material that emits extreme ultraviolet rays when in a plasma state; And
A measurement device comprising:
Means for measuring the flux of the target material over the entire measuring surface in the container; And
And means for regenerating said measuring surface, said means for regenerating:
Means for preventing the measurement surface from being saturated; And/or
And means for desaturating the measurement surface when the measurement surface is saturated.

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