CN111480071A - Regeneration of debris flux measurement system in vacuum vessel - Google Patents
Regeneration of debris flux measurement system in vacuum vessel Download PDFInfo
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- CN111480071A CN111480071A CN201880080455.5A CN201880080455A CN111480071A CN 111480071 A CN111480071 A CN 111480071A CN 201880080455 A CN201880080455 A CN 201880080455A CN 111480071 A CN111480071 A CN 111480071A
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- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
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- G—PHYSICS
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- G—PHYSICS
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Abstract
An apparatus comprising: a container; a target delivery system for directing a target to an interaction zone in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state; and a measuring device. The metrology apparatus includes a measurement system having a measurement surface configured to measure a flux of a target substance and a regeneration tool configured to regenerate the measurement system. The regeneration comprises the following steps: preventing the measurement surface from becoming saturated and/or desaturating the measurement surface if the measurement surface has become saturated.
Description
Cross Reference to Related Applications
This application claims priority to U.S. application 62/599,139 filed on 12/15/2017, the entire contents of which are incorporated herein by reference.
Technical Field
The disclosed subject matter relates to a system and method for regeneration of a measurement system that measures an amount or flux (flux) of debris generated within a chamber of an extreme ultraviolet light source.
Background
Extreme Ultraviolet (EUV) light, e.g., electromagnetic radiation having a wavelength of about 50nm or less (sometimes also referred to as soft X-rays), and including light having a wavelength of about 13nm, may be used in a lithographic process to produce extremely small features in a substrate, e.g., a silicon wafer.
In one such method, the desired plasma (commonly referred to as laser-generated plasma ("L PP")) may be generated by irradiating the target material with an amplified light beam in the form of droplets, plates, ribbons, streams, or clusters of materials.
Disclosure of Invention
In some general aspects, an apparatus includes: a container; a target delivery system for directing a target to an interaction zone in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state; and a measuring device. The metrology apparatus includes a measurement system having a measurement surface configured to measure a flux of a target substance and a regeneration tool configured to regenerate the measurement system. The regeneration comprises the following steps: preventing the measurement surface from becoming saturated and/or desaturating the measurement surface if the measurement surface has become saturated.
Implementations may include one or more of the following features. For example, the metrology device may include a control device in communication with the measurement system and the recycling tool. The control device may be configured to activate the regeneration means based on an output from the measurement system.
The measurement surface may be configured to interact with a target substance. The interaction between the target substance and the measurement surface generates a measurement signal. The measurement system may further comprise a measurement controller configured to receive the measurement signal and to calculate a flux of the target substance across the measurement surface.
The measuring device may comprise a crystal microbalance. The crystal microbalance may be a quartz crystal microbalance.
The container may define a cavity, and the container cavity may be maintained at a pressure less than atmospheric pressure.
The interaction region may receive the amplified light beam, and the target may be converted to a plasma that emits ultraviolet light as the target interacts with the amplified light beam.
The device may also include an optical element including an optical element surface within the container. The measuring device may be positioned relative to the surface of the optical element. The optical element may be a light collector in which the optical element surface interacts with at least some of the emitted extreme ultraviolet light as the target is converted into plasma.
The regeneration tool may be configured to: the measurement system is regenerated without removing the measuring device from the vessel. The regeneration tool may include a cleaning tool positioned to interact with the measurement system and configured to: the target substance that has been deposited on the measurement surface is removed according to the instructions of the measurement controller. The cleaning tool may include a radical generation unit configured to generate radicals in the vicinity of the measurement surface. The radicals may chemically react with the deposited target species to form new chemical species released from the measurement surface. The free radical generating unit may comprise a filament adjacent the measurement surface and a power source to provide current to the filament. The wire may have a shape matching the shape of the measurement surface. The radical generating unit may include a plasma generator that generates a plasma material in a plasma state, the plasma material including radicals, in the vicinity of the measurement surface. The free radicals may be hydrogen free radicals generated from natural hydrogen molecules within the vessel. The target substance on the measurement surface may comprise tin, such that the chemical substance released from the measurement surface comprises tin hydride.
The apparatus may further include a removal device configured to remove the released new chemical from the container. The removal device may include a gas port in fluid communication with the interior of the container, and the released new chemical is transferred from the interior of the container through the gas port.
The regeneration tool may be configured to: the target substance is removed from the measurement surface in the presence of hydrogen in the container and in the absence of a reaction requiring oxygen.
In other general aspects, a method includes: providing a target within a cavity of a container; measuring the flux of the target substance on a measurement surface within the vessel cavity; and regenerating the measurement surface. The target includes a substance that emits ultraviolet light when converted to plasma. The regeneration includes at least one of: preventing the measurement surface from becoming saturated; and/or desaturate the measurement surface if it has become saturated.
Implementations may include one or more of the following features. For example, the method may further comprise activating regeneration of the measurement surface based on the flux of the target substance measured on the measurement surface.
The flux of the target substance may be measured by interacting the target substance with the measurement surface so as to deposit the target substance on the measurement surface.
By directing multiple targets to an interaction zone in a vacuum vessel, targets may be provided within the vessel cavity. The interaction region also receives the amplified light beam such that interaction between the target and the amplified light beam in the interaction region converts the target into a plasma of emitter ultraviolet light.
The measurement surface may be regenerated by removing the deposited target substance from the measurement surface without removing the measurement surface from the container. The deposited target species may be removed from the measurement surface by generating elemental free radicals in the vicinity of the measurement surface, the generated free radicals chemically reacting with the deposited target species to form new chemical species released from the measurement surface. The target species deposited may include tin, the element may be hydrogen, the radical may be a hydrogen radical, and the new chemical species may be tin hydride. The elements adjacent to the measurement surface may be intrinsic to the vessel cavity. The deposited target substance may be removed by removing the deposited target substance in the absence of oxygen. The method may include removing the released new chemical from the container cavity.
The flux of the target substance may be measured by measuring the flux of the target substance at a time when the deposited target substance is not removed from the measurement surface.
The deposited target substance can be removed from the measurement surface, thereby preventing the measurement surface from reaching its saturation limit.
The method may further include maintaining a cavity defined by the container at a pressure below atmospheric pressure. The method may further include estimating an amount of extreme ultraviolet light emitted when the target species is converted into the plasma based on the measured flux. The method may further include estimating an amount of the target substance deposited on the surface within the vessel cavity based on the measured flux.
In other general aspects, an extreme ultraviolet light source includes: a light source configured to produce an amplified light beam; a container defining a cavity and configured to receive the amplified light beam at an interaction region in the cavity; a target delivery system configured to generate a target traveling along a target path toward the interaction zone; and a measuring device. The cavity is configured to be maintained at a pressure below atmospheric pressure. The target includes a target substance emitting ultraviolet light in a plasma state. The metrology apparatus includes a measurement system having a measurement surface configured to measure a flux of a target substance and a regeneration tool configured to regenerate the measurement system. The regeneration comprises the following steps: preventing the measurement surface from becoming saturated; and/or desaturate the measurement surface if it becomes saturated.
Implementations may include one or more of the following features. For example, the measurement surface may be configured to interact with a target substance, wherein the interaction between the target substance and the measurement surface generates a measurement signal; the measurement system may further comprise a measurement controller that receives the measurement signal and calculates a flux of the target substance across the 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 substances that have been deposited on the measurement surface.
The extreme ultraviolet light source may also include a light collector that collects at least some of the emitted extreme ultraviolet light for use by an external lithographic apparatus.
In other general aspects, a 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 substance across a measurement surface within a vessel and a regeneration tool coupled to the metrology device. The measuring device comprises: a measurement system having a measurement surface configured to interact with a target substance, wherein the interaction between the target substance and the measurement surface produces a measurement signal; and a measurement controller configured to receive the measurement signal and to calculate a flux of the target substance across the measurement surface based on the received measurement signal. The regeneration tool is configured to regenerate the measurement system. The regeneration comprises the following steps: preventing the measurement surface from becoming saturated; and/or desaturate the measurement surface if it has become saturated. The regeneration tool includes a cleaning tool positioned to interact with the measurement surface and remove target species that have been deposited on the measurement surface according to instructions from the measurement controller.
In other general aspects, an apparatus includes: a container; means for delivering a target to an interaction region in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state; and a measuring device. The measuring device comprises: means for measuring a flux of the target substance across a measurement surface within the vessel; and means for regenerating the measuring surface. The means for regenerating comprises: means for preventing the measurement surface from becoming saturated; and means for desaturating the measurement surface in the event it has become saturated.
Drawings
FIG. 1 is a block diagram of an apparatus including a self-regeneration measurement device within a cavity defined by a container;
FIG. 2 is a side cross-sectional and enlarged view taken at A of an implementation of the metrology device of FIG. 1;
FIG. 3A is a perspective view of an implementation of the metrology device of FIGS. 1 and 2, wherein the metrology device is designed with a measurement system including a crystal microbalance having a measurement surface and a radical regeneration tool having a wire adjacent to the measurement surface;
FIG. 3B is a block diagram of the metrology device of FIG. 3A;
FIG. 3C is a perspective view of a wire adjacent to the measurement surface of the crystal microbalance of FIGS. 3A and 3B;
FIG. 3D is a side cross-sectional view of a wire adjacent to a measurement surface of the crystal microbalance of FIGS. 3A-3C;
FIG. 4 is an implementation of an Extreme Ultraviolet (EUV) light source, wherein a self-regeneration measurement device, such as the device of FIGS. 1-3D, may be implemented within the EUV light source;
FIG. 5A is a rear perspective view of an optical element that acts as a light collector, wherein the self-regeneration measurement device of FIGS. 1-4 may be adjacent to the light collector;
FIG. 5B is a front perspective view of the optical element of FIG. 5A;
FIG. 5C is a side cross-sectional view of the optical element of FIG. 5A;
FIG. 5D is a plan view of the optical element of FIG. 5A;
FIG. 6 is a block diagram of a process for regenerating a measurement surface;
FIG. 7 is a schematic diagram showing a side cross-sectional view of the measurement surface during the process of FIG. 6;
FIG. 8 is a graph of deposited thickness of a coating on a measurement surface versus time depicting the process of FIG. 6 and the application of the metrology device of FIGS. 3A-3D;
FIG. 9 is a graph of removal rate in arbitrary units versus distance between the filament of FIGS. 3A-3D and the measurement surface of FIGS. 3A-3D for various values of standard liters per minute;
FIG. 10 is a block diagram of a lithographic apparatus receiving the output of the EUV light source of FIG. 4; and
FIG. 11 is a block diagram of a lithographic apparatus receiving the output of the EUV light source of FIG. 4.
Detailed description of the invention
Referring to FIG. 1, the apparatus 100 includes a self-regenerating measurement device 105 within a cavity 118 defined by a vessel 120. The metrology device 105 includes a measurement system 110, the measurement system 110 having a measurement surface 112 configured to measure a flux of a target substance 125. The flux of the target substance 125 is the mass of the target substance 125 that passes through a region in a certain amount of time. Furthermore, because the density of the target substance 125 may be known, the flux of the target substance 125 may be determined or estimated by determining the thickness of the target substance 125 deposited on the measurement surface 112.
Over time, the target substance 125 builds up as a coating 127 on the measurement surface 112, which causes the measurement surface 112 to become saturated. The measurement surface 112 is saturated when the measurement surface 112 is no longer able to produce any useful information about the flux of the target substance 125. The saturation limit on the measurement surface 112 is related to the saturation thickness of the coating 127 of the target substance 125 and can be relatively small compared to the saturation thickness of the nearby material within the container 120, and thus the measurement surface 112 is already approaching its saturation limit before the nearby material within the container 120 needs to be cleaned, serviced, or replaced due to being coated with the target substance 125. Therefore, the measurement system 110 must be replaced each time the measurement surface 112 becomes saturated, making efficiency inefficient. To this end, the metrology device 105 includes a regeneration tool 115 configured to regenerate the measurement system 110. At some point, regeneration of the measurement system 110 may involve preventing the measurement surface 112 from becoming saturated. At other times, such as when the measurement surface 112 has become saturated, regeneration of the measurement system 110 involves desaturating the measurement surface 112.
The regeneration tool 115 may be configured to operate (i.e., remove the target species 125 covering the measurement surface 112) even if the regeneration tool 115 is exposed to molecular hydrogen, which may be present in the cavity 118. The regeneration tool 115 may be configured to operate without the use of oxygen or in the absence of oxygen; that is, oxygen is not required or necessary in order for the regeneration tool 115 to operate or perform any function.
The target substance 125 is generated within the container 120 as follows. The apparatus 100 includes a target delivery system 140, the target delivery system 140 directing a stream 142 of targets 145 to an interaction zone 150 in the container 120. The target 145 includes a target species 125, and the target species 125 Emits Ultraviolet (EUV) light 155 when the target species 125 is converted into a plasmonic material 160 (also referred to as a light emitting plasmonic material 160). However, some target species 125 are not completely converted to plasma material 160 in the interaction region 150, or some of the plasma species 160 revert back to the target species 125. Thus, the retained target species 125 (i.e., either not converted to the plasma material 160 or not recovered) may travel in the cavity 118 of the container 120 and coat various objects, such as walls or optical elements within the cavity 118 of the container 120. The measurement system 110 is disposed at a suitable location or locations within the vessel 120 to determine the flux of the target substance 125 traveling through the portion of the interior of the vessel 120 where the measurement system 110 is disposed. Although only one measurement system 110 is shown in fig. 1, the cavity 118 of the container 120 may be equipped with multiple measurement systems 110 at various locations, as described below, depending on the particular information that needs to be obtained about the flux of the target substance 125. Furthermore, one or more of the measurement systems 110 may be incorporated into the metrology device 105 including the regeneration tool 115.
The present state of the target material 125 remaining or remaining in the container 120 is debris in the form of particles, vapor residue, or material fragments present in the target 145. This debris can accumulate on the surface of the objects in the container 120. For example, if the target 145 comprises a molten metal of tin, tin particles may accumulate (or coat) on one or more optical surfaces or walls within the container 120. Debris (which forms on the surface that also forms on the coating 127 formed on the measurement surface 112) may include vapor residue, ions, particles, and/or clusters of species formed by the target species 125. The presence of debris from the target material 125 within the receptacle 120 can reduce the performance of the surfaces within the receptacle 120 and can also reduce the overall efficiency of the measurement system 110.
The target delivery system 140 delivers, controls and directs targets 145 in a stream 142, which stream 142 is delivered in the form of droplets, streams of liquid, solid particles or clusters, solid particles contained in droplets, or solid particles contained in streams of liquid. 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 125 and impurities such as non-target particles.
The target substance 125 is a substance having an emission line in the EUV range when in a plasma state (plasma material 160). The target substance 125 may be, for example, a droplet of a liquid or a droplet of molten metal, a portion of a liquid stream, a solid particle or cluster, a solid particle contained in a droplet, a foam of a target material, or a solid particle contained in a portion of a liquid stream. The target substance 125 may be, for example, water, tin, lithium, xenon, or any material having an emission line in the EUV range when converted into a plasma state. For example, the target substance may be elemental tin, which may be used as pure tin (Sn); as the tin compound, for example, SnBr4, SnBr2, SnH 4; as the tin alloy, for example, tin-gallium alloy, tin-indium-gallium alloy, or any combination of these alloys. Further, in the absence of impurities, the target 145 includes only the target substance.
The cavity 118 within the container 120 may be maintained under vacuum, i.e., at a pressure less than atmospheric pressure. For example, the cavity 118 may be maintained at a low pressure (e.g., at 1T) between about 0.5 Torr (T) and about 1.5T, which is a pressure selected for generating EUV light 155. Thus, the metrology device 105 is configured to operate in a vacuum environment within the cavity 118 of the container 120, which means that the metrology device 105 is designed to operate in a vacuum (such as at 1T). Furthermore, the metrology device 105 is designed such that it can be used without having to change the design or operation of the container 120. Thus, the metrology device 105 is configured to operate in an environment in which EUV light 155 is most efficiently generated.
Referring also to FIG. 2, in some implementations, the metrology device 205 includes a radical regeneration tool 215 proximate to the measurement surface 212 of the measurement system 210 as the regeneration tool 115. The radical regeneration tool 215 is a cleaning tool positioned to interact with the measurement system 210. The radical regeneration tool 215 is configured to remove the target species 125 that accumulates as a coating 227 on the measurement surface 212 of the measurement system 210. The radical regeneration tool 215 comprises a radical generation unit configured to generate radicals 216 in the vicinity of the measurement surface 212 and these radicals 216 chemically react with the deposited target species 125 of the coating 227 to form new chemical species 228 released from the measurement surface 212. For example, the new chemical 228 may be in a gaseous state and thus released from the measurement surface 212. The new chemical 228 in the gaseous state may then be pumped out of the container 120.
The free radical 216 is an atom, molecule or ion having an unpaired valence electron or open electron shell, and thus can be considered to have a dangling (dangling) covalent bond. The dangling bonds may render the radicals highly chemically reactive, that is, the radicals may readily react with other substances. Due to its reactivity, the radicals 216 may be used to remove a substance (such as the deposited target substance 125) from an object, such as the measurement surface 212. The radicals 216 may remove the deposited target species 125 by, for example, etching the target species 125, reacting with the target species 125, and/or burning the target species 125.
The free radicals 216 may be generated in any suitable manner. For example, the radicals 216 may be formed by decomposing larger molecules 230 present (or inherent) in the vessel 120 near the measurement system 210 or the radical regeneration tool 215. The larger molecules 230 present in the container 120 and near the measurement system 210 may be decomposed by any process that injects sufficient energy into these larger molecules, such as ionizing radiation, heat, electrical discharge, electrolysis, and chemical reactions. Thus, the formation of free radicals involves providing the larger molecule 230 with sufficient energy to break bonds (typically covalent bonds) between atoms of the larger molecule.
As another example, the radicals 216 may be formed at a location remote from the measurement system 210 and may then be transferred to the measurement surface 212. Thus, the radicals 216 may form outside of the container 120 and then be transported into the container 120.
In other implementations, the radical regeneration tool 215 may be a Capacitively Coupled Plasma (CCP) device. In CCP devices, two metal electrodes are separated by a small distance and are driven by a power source, such as a Radio Frequency (RF) power source. When an electric field is generated between the electrodes, the atoms of the larger molecules 230 are ionized and release electrons. Electrons in the gas are accelerated by the RF field and, through collisions, ionize the gas directly or indirectly, thereby generating secondary electrons. Eventually, when the electric field is strong enough, a plasma is generated.
In some implementations, as described above, the target 145 includes tin (Sn), and in these implementations, the target substance 125 deposited on the measurement surface 212 includes tin particles. As described above, the container 120 is a controlled environment, and one of the larger molecules 230 that may be present and allowed within the container 120 is molecular hydrogen (H)2). In this case, the radical regeneration means 215 generates radicals 216 from molecular hydrogen, either natural or present in the vessel 120. The hydrogen radicals 216 are the single hydrogen element (H). This chemistry can be represented by the following formula:
wherein g represents that the chemical substance is in a gaseous state.
In particular, the hydrogen radicals H generated combine with the tin particles (Sn) on the measurement surface 212 and form new chemical species 228, called tin hydride (SnH)4) The new chemical 228 is released from the measurement surface 212. The chemistry is represented by the following formula:
wherein s represents that the chemical substance is in a solid state.
In this way, the coating 227 (formed by the target substance 125) may be etched or removed from the measurement surface 212 at a rate of at least 1 nanometer/minute over the entire measurement surface 212, not just over the region closest to the radical regeneration tool 215. This is because the radicals 216 are generated at a position close to the measurement surface 212, rather than being generated far from the measurement surface 212 and then being transported to the measurement surface 212. This is important because the hydrogen radicals H have a short lifetime and are easily recombined to reform molecular hydrogen. The design of the radical regeneration tool 215 is such that the formation of hydrogen radicals H is as close as possible to the measurement surface 212, so that more hydrogen radicals H are bound to the tin particles, which then have the opportunity to recombine with each other to reform molecular hydrogen, and this enables the measurement system 210 to be regenerated without having to remove the measurement device 205 from the vessel 120.
Referring to fig. 3A and 3B, an example of a metrology device 305 is shown. The metrology apparatus 305 is designed with a radical regeneration tool 315, the radical regeneration tool 315 including a wire 365 proximate to the measurement surface 312 of the measurement system 310 and a power source 370 that provides current to the wire 365. The filaments 365 should be made of a material that has a high melting point, at least high enough that it can withstand a high enough temperature to provide enough heat to break bonds of nearby larger molecules. For example, in some implementations, the current flowing through the filament 365 may raise the temperature of the filament 365 to over 1000 ℃. In addition, the threads 365 should not chemically react with larger molecules or other components within the container 120. Alternatively, the thread 365 may be formed by a chemical reaction as described above
Wherein g represents that the chemical substance is in a gaseous state. In this manner, the thread 365 may be any substance that accelerates the chemical reaction but is not consumed by the chemical reaction. For example, the material of wire 365 may be tungsten (W), rhenium (Re), or an alloy of one or more of W and Re. Finally, the filaments 365 should be strong and have a high tensile strength to withstand temperature fluctuations during use. For example, silkWire 365 may be made of tungsten or rhenium.
Referring also to fig. 3C and 3D, the filament 365 may be energized by current from the power source 370 to heat to a sufficiently high temperature to excite any native hydrogen molecules 330 within the container 120 adjacent the filament 365 to the point where atoms within the molecules 330 break down into free radicals. The threads 365 have a shape that conforms or complements the shape of the measurement surface 312 to more effectively allow interaction between the radicals 216 and the coating 327 on the measurement surface 312.
In some implementations, the measurement system 310 includes a crystal microbalance, such as a quartz crystal microbalance. The crystal microbalance is shown in fig. 3A. A crystal microbalance is a device that outputs a measurement signal that can be used to determine the flux of target substance 125 impinging on the measurement surface 312. The amount of mass deposited on the measurement surface 312 is related to the change in the one or more resonant frequencies associated with the measurement surface 312. Thus, by measuring the change in one or more resonant frequencies, it is possible to determine how much mass has been deposited on the measurement surface 312. A crystal microbalance includes a crystal, such as a quartz crystal, and a set of electrodes that provide an alternating current to a surface of the crystal to cause the crystal to oscillate at one or more resonant frequencies. The measurement surface 312 may correspond to one of the faces of the crystal.
The measuring surface 312 is held in an adapter or flange 375 made of a non-reactive material, and the flange 375 is mounted to a housing 377, which can be water cooled. The measurement surface 312 may include a coating (not visible) of a thin layer of a radical resistant material, such as zirconium nitride (ZrN). In this implementation, the generated radicals 216 will react with the target species 125 deposited on the measurement surface 312 as a coating 327, but will not react with the ZrN coating, so that ZrN remains intact even if the radical regeneration tool 315 is running.
If the target substance 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 by the deposited target species 125; above this saturation limit, the measurement system 110 will not be able to accurately measure the flux of the target substance 125. In contrast, other components within the container 120 may withstand a deposited coating of the target substance 125 having a thickness on the order of thousands of times the thickness of 8 μm. The free radical regeneration tool 315 is capable of removing the coating 327 without opening the vessel 120 and without stopping operation of other components within the vessel 120.
Referring to FIG. 4, a self-regeneration metrology device 405, such as the apparatus 105, 205, 305, may be implemented within an EUV light source 400 where the container 120 is an EUV vacuum chamber 420, as described below. The EUV light source 400 includes a target delivery system 440 that directs a stream 442 of a target 445 to an interaction region 480 in the EUV chamber 420. Interaction region 480 receives amplified light beam 481. As described above, the target 445 includes a substance that emits EUV light when in a plasma state. The interaction between the species within the target 445 and the amplified light beam 481 at the interaction region 480 converts some of the species in the target 445 into plasma material 460. The plasma material 460 emits EUV light 455. The plasma material 460 has an element whose emission line is in the EUV wavelength range. Certain characteristics of the plasma material 460 produced depend on the composition of the target 445. These characteristics include the wavelength of EUV light 455 generated by plasma material 460.
The plasma material 460 may be considered to be a highly ionized plasma with electron temperatures of tens of electron volts (eV). Higher energy EUV light 455 may be generated with other fuel materials (other 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 then collected by the optical element 482.
Referring also to fig. 5A-5D, optical element 482 can be a light collector, where surface 483 interacts with at least some of the emitted EUV light 455. Surface 483 of light collector 482 can be a reflective surface positioned to receive at least a portion of EUV light 455 and direct used collected EUV light 484 out of EUV light source 400 (shown in fig. 4). Reflective surface 483 directs the collected EUV light 484 to a second focal plane where the EUV light 484 is then captured for use by a tool 485 (e.g., a lithographic device) external to EUV light source 400. Exemplary lithographic apparatus 1000, 1100 are discussed with reference to FIGS. 10 and 11, respectively.
The reflective surface 483 may be configured to reflect light in the EUV wavelength range, but absorb or scatter or block light outside the EUV wavelength range. The optical collector 482 further comprises an aperture 590, the aperture 590 allowing the amplified light beam 481 to pass through the optical collector 482 towards the interaction region 480. The optical collector 482 may be, for example, an elliptical mirror having a primary focus at the interaction region 480 and a secondary focus at a secondary focal plane. This means that the shape of the planar cross-section, such as the planar cross-section C-C, is elliptical or circular. Thus, the planar cross-section C-C cuts through the reflective surface 483 and is formed by a portion of an ellipse. The plan view of optical collector 482 shows that the edges of reflective surface 483 form a circle.
Although the optical collector 482 shown herein is a single curved mirror, it may take other forms. For example, the optical collector 482 can be a schwarzschild collector with two radiation collection surfaces. In one implementation, optical collector 482 is a grazing incidence collector that includes a plurality of substantially cylindrical reflectors nested within one another.
Referring again to FIG. 4, the EUV light source 400 includes an optical system 486 that produces an amplified light beam 481 due to population inversion in one or more gain media. The optical system 486 may include a light source that generates a light beam, and a beam delivery system that manipulates and modifies the light beam and also focuses the light beam onto the interaction region 480 for delivery. The light source within the optical system 486 includes one or more optical amplifiers, lasers, and/or lamps for providing one or more main pulses that form the amplified light beam 481 and, in some cases, one or more pre-pulses that form a precursor amplified light beam (not shown). 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 a laser cavity. Thus, even without a laser cavity, optical system 486 produces amplified light beam 481 due to population inversion in the gain medium of the amplifier. Furthermore, if a laser cavity is present to provide sufficient feedback to the optical system 486, the optical system 486 may produce the amplified light beam 481 as a coherent laser beam. Thus, the term "amplifying the light beam" encompasses one or more of the following: the light from the optical system 486 is only amplified and not necessarily coherent laser oscillation, and the light from the optical system 486 is amplified and also coherent laser oscillation.
The optical amplifier used in the optical system 486 may include a gas including carbon dioxide (CO) as a gain medium2) And light having a wavelength between about 9100 and 11000 nanometers (nm), e.g., about 10600nm, may be amplified with a gain greater than or equal to 100. Amplifiers and lasers suitable for use in the optical system 486 include pulsed laser devices, e.g., pulsed gas discharge CO that produce radiation at about 9300nm or about 10600nm (e.g., excited by DC or RF)2A laser apparatus that operates at a relatively high power (e.g., 10kW or more) and a high pulse repetition rate (e.g., 40kHz or more).
The EUV light source 400 also includes a control 487 that communicates with one or more controllable components or systems of the EUV light source 400. Control 487 is in communication with optical system 486 and target delivery system 440. Target delivery system 440 may operate in response to signals from one or more modules within control device 487. For example, the control device 487 may send a signal to the target delivery system 440 to modify the release point of the target 445 to correct for errors of the target 445 reaching the target interaction region 480. The optical system 486 may operate in response to signals from one or more modules within the control device 487. Each module of control 487 may be a stand-alone module because data between modules is not transferred between modules. Alternatively, one or more modules within control 487 may communicate with each other. The modules within control 487 may be physically located at the same location or separate from each other.
For example, the module controlling the target delivery system 440 may be co-located with the target delivery system 440, while the module controlling the optical system 486 may be co-located with the optical system 486.
The metrology device 405 includes a control device 488 in communication with the measurement system 410 and the regeneration tool 415 of the metrology device 405. The control 488 is configured to receive the output from the measurement system 410, analyze the output as needed, and perform actions such as sending data to the control 487 or activating the regeneration tool 415 based on the analysis. Accordingly, the control device 488 may include a measurement controller in communication with the measurement system 410, the measurement controller configured to receive measurement signals from the measurement system 410 and calculate the flux of the target substance 425 across the measurement surface of the measurement system 410. The control 488 may provide a signal to activate or actuate the regeneration tool 415. For example, control device 488 can provide a signal to power source 370 of measurement device 305 to provide current to wire 365.
The EUV system 400 also includes a removal or exhaust 489 configured to remove released chemicals 428 and other gaseous byproducts that may form within the EUV chamber 420 from the EUV chamber 420. As described above, the released chemical species 428 are formed as a result of the interaction of the radicals 416 (which are generated from the larger molecules 430 by the regeneration tool 415) with the target species 425 deposited on the measurement surface of the measurement system 410. The removal device 489 may be a pump that removes the released chemical 428 from the EUV chamber 420. The removal device 489 may include a gas port in fluid communication with the interior of the EUV chamber 420 or the cavity 418 such that the released new chemistry 428 is carried out of the EUV chamber 420 through the gas port from the cavity 418. For example, once the chemical 428 is formed, it is released and, as the chemical 428 may be volatile, it is drawn to the removal device 489, which removes the released chemical 428 from the EUV chamber 420.
Other components of the EUV light source 400 that are not shown include a detector, for example, for measuring a parameter associated with the generated EUV light 455. The detector may be used to measure the energy or energy distribution of amplified light beam 481. A detector may be used to measure the angular distribution of the intensity of the EUV light 455. The detector may measure the error in the timing or focus of the pulses of amplified light beam 481. The outputs of these detectors may be provided to a control device 487, which may include modules that analyze the outputs and adjust aspects of other components of the EUV light source 400, such as the optical system 486 and the target delivery system 440.
In summary, an amplified light beam 481 is generated by an optical system 486 and directed along a beam path to illuminate the target 445 at the interaction region 480, thereby converting material within the target 445 into a plasma that emits light in the EUV wavelength range. Amplified light beam 481 operates at a particular wavelength (source wavelength) determined based on the design and characteristics of optical system 486.
Although only one metrology device 405 is shown in the EUV chamber 420 of fig. 4, multiple metrology devices 405 may be configured throughout the EUV chamber 420. Other possible locations for the metrology device 405 are marked with the cross icon 495 shown in FIG. 4. For example, the metrology device 405 may be placed near any optical element that includes a surface that may interact with the target species 125 and thus may be covered by debris during operation of the EUV light source 400. Accordingly, one or more metrology devices 405 may be placed near the optical collector 482, such as near an edge of the optical collector 482; near the taper between the walls of the EUV chamber 420 and the optical collector 482; and/or near target delivery system 440, near an exhaust unit (such as removal device 489).
The measurement system 310 is any device that can measure the properties of the coating 327 formed on the measurement surface 312 and then analyze to determine the thickness of the coating 327 and the flux of the target species 125. In other implementations, the measurement system 310 is designed as a refractometer, ellipsometer, and/or 4-point probe.
As described above, in the implementation of fig. 3A-3D, the metrology device 305 is designed with a radical regeneration tool 315 that includes a wire 365 adjacent to the measurement surface 312. There are other ways to design the radical regeneration tool 315. In other implementations, the radical regeneration tool 315 can include a plasma generator that can generate or generate material in a plasma state (plasma material) at a location local to or proximate to the measurement surface 312 from material already present and native within the vessel 120 (native material, such as larger molecules 330). A material, such as larger molecules 330, is native or present in the container 120 if it is present within the container 120 without being transported into the container 120 from outside the container 120. The plasma material includes radicals 216, which radicals 216 chemically react with the target species 125 deposited as a coating 327 on the measurement surface 312, as described above. In addition to the radicals, the plasma material may include other components that do not react with the target species 125, such as ions formed from natural materials, electrons generated from natural materials, and chemically neutral species. As the number of radicals present in the plasma material increases, the radical regeneration tool 315 is able to remove more of the target species 125 (deposited as the coating 327). In other words, the higher the density of radicals in the plasma material, the higher the debris removal rate.
In some implementations, the radical regeneration tool 315 is designed as an Inductively Coupled Plasma (ICP) tool that includes an electrical conductor that is positioned adjacent to the measurement surface 312 and that acts as a plasma generator. The electrical conductors are connected to the power source of the measuring device 305 and are contained within a dielectric tube such as porcelain, ceramic, mica, polyethylene, glass or quartz. In the ICP process, a time-varying current flows (from a power supply) through an electrical conductor, and the flow of the time-varying current generates a time-varying magnetic field in the vicinity of the electrical conductor. Also, the generated time-varying magnetic field induces an electric field or current at a location adjacent to the measurement surface 312. The induced current is large enough to generate a plasma material from the native material within the vessel 120 at a location adjacent the measurement surface 312.
In other implementations, the radical regeneration tool 315 is designed as a heated capillary tube. The free radical regeneration tool 315 is not limited to the specific design described herein, but may be any tool that generates free radicals.
Referring again to fig. 2, since the measurement surface 212 is relatively small in size, radicals 216 generated by the radical regeneration tool 215 (or 315) flow on the measurement surface 212 by a diffusion action after being formed by the tool 215. However, since the pressure in the vessel 120 may be relatively high (even a vacuum, which may be a low vacuum), in certain implementations where the measurement surface 212 is large or other factors may reduce the amount of diffusion, it may be a challenge to disperse the free radicals across the measurement surface 212 without additional assistance. Accordingly, the metrology device 205 may also include a gas flow mechanism configured to push or disperse the radicals 216 over the entire surface of the measurement surface 212.
Referring to fig. 6, a process 100 is performed by the apparatus 100. Targets 145(605) are provided within cavity 118 of container 120. The target 145 includes a target species 125 that emits EUV light 155 when converted into a plasma material 160. The flux of the target substance 125 is measured (e.g., using the measurement system 110) over the measurement surface 112 within the receptacle 120 (610). The measurement surface 112(615) is regenerated. Regenerating (615) the measurement surface 112 may include preventing (615A) the measurement surface 112 from becoming saturated. Regenerating 615 the measurement surface 112 may include desaturating 615B the measurement surface 112 if the measurement surface 112 becomes saturated. Alternatively, regenerating 615 the measurement surface 112 may include preventing the measurement surface 112 from becoming saturated 615A and desaturating the measurement surface 112 if it has become saturated 615B.
Referring also to fig. 4, a target 445(605) may be provided within the cavity 418 by directing a plurality of targets 445 or streams 442 of targets 445 to an interaction region 480 in the EUV chamber 420. Interaction region 480 also receives amplified light beam 481 such that interaction between target 445 and amplified light beam 481 in interaction region 480 converts target 445 into plasma material 460 that emits EUV light 455.
The flux of the target substance 125 may be measured by interacting the target substance 125 with the measurement surface 112, thereby depositing the target substance 125 on the measurement surface 112 (610).
Regeneration of the measurement surface 112 may be activated based on the flux measured on the measurement surface 112 (615). Further, regeneration may be performed and completed without removing the measurement surface 112 from the container 120 (615).
Referring also to fig. 7, the measurement surface 312 is shown to illustrate how regeneration of the measurement surface is affected (615). The measurement surface 312 is regenerated (615) by removing the deposited target substance 125 from the measurement surface 312. The target substance 125 forms a coating 327(716) on the measurement surface 312. By generating the radicals 216, the deposited target species 125 (which forms the coating 327) is removed from the measurement surface 312. The radicals 216 may be generated by elements or materials such as larger molecules 230 already present in the container 120 and adjacent to the measurement surface 312. In addition, after the generation of the radicals 216, these radicals 216 then chemically react with the target species 125 (which forms the coating 327) deposited on the measurement surface 312 to form new chemical species 228(718) released from the measurement surface 312. The deposited target substance 125 may be removed from the measurement surface 312 without using oxygen as a catalyst or element for the reaction.
The process 600 may also include the step of removing the released chemical 228 from the container 120, for example, using a vent 489.
The flux of the target substance 125 may be measured 610 by measuring the flux of the target substance 125 at a time when the deposited target substance 125 is not removed from the measurement surface 112. Thus, the flux of the measurement target substance 125 may occur at a different time than the time of regenerating the measurement surface 112 (615). Removing the deposited target species 125 (which is part of the regeneration 615) from the measurement surface 112 may prevent the measurement surface 112 from reaching its saturation limit. Furthermore, the removal of the deposited target species 125 should occur after the measurement system 110 has measured the flux of the target species 125 to be removed, because if the target species 125 is removed too quickly, it makes it impossible for the measurement system 110 to determine the flux of the target species 125.
The measured flux 610 may additionally be used by the control 487 to estimate the amount of EUV light 455 emitted from the plasma material 460. For example, the stability of the production of EUV light 455 is generally related or related to the production of target species 125 (e.g., tin debris). Thus, large fluctuations in the measured flux 610 of the target substance 125 may indicate unstable operation of the EUV light source 400. In addition, the measured flux 610 may be used to further estimate the amount of target substance 125 deposited on a surface within the vessel 120 (e.g., a surface proximate the metrology device 105).
Based on the desired information, the metrology devices 105 may be placed at specific locations throughout the container 120. For example, the measured flux 610 may be used to determine a failure of equipment proximate to a particular metrology device 105. As another example, if the metrology device 105 is placed near a surface being cleaned, the measured flux 610 may be used to measure the cleaning rate of the surface.
The measured flux 610 may be used to determine whether the flow field of the delivered target substance 125 has changed. In particular, the target substance 125 may be entrained in molecular hydrogen present in the vessel 120, and the molecular hydrogen is transferred through the vessel 120 according to a particular flow path, and if the metrology device 105 is placed in proximity to a particular flow field, it may be used to determine whether the flow field is altered by measuring the flux 610 of the target substance 125.
Referring to FIG. 8, a graph 800 depicting the process 600 of FIGS. 3A-3D and an application of the metrology device 305 is shown. The graph 800 shows the deposited thickness 805 of the coating 327 as a function of time 810 (or pulse cumulative equivalent). The saturation limit 815 of the measurement surface 312 is also depicted in the graph 800 as a dashed line. As described above, in examples where the measurement system 310 is a quartz microbalance and the target substance 125 is tin, the saturation limit 815 may be in the range of 5-15 μm. Initially, the metrology device 305 operates in a measurement mode 820, and in this mode 820, the measurement system 310 is used to measure the flux of the target substance 125 across the measurement surface 312. In the measurement mode 820, the radical regeneration tool 315 is not operating, and thus the wire 365 is not supplied with current from the power source 370. During this measurement mode 820, the thickness 805 of the coating 327 is generally increasing. The slope of the graph 800 in this measurement mode 820 may be stored in the measurement system 310, or in a memory of a control device receiving an output from the measurement system 310, and used as a system performance monitor and process offset protection. In addition, the measurement system 310 operates to determine the deposition rate, flux, or other property of the target substance 125. When the thickness 805 of the coating 327 reaches the saturation limit 815, the measurement apparatus 305 switches to operate in a regeneration mode 825. In the regeneration mode 825, the measurement system 310 may or may not perform a function, but the filament 365 is energized by current from the power source 370 and thus actively acts to remove the target species 125 that has been deposited on the measurement surface 312 as a coating 327. During operation of the apparatus 100, the cycle of the measurement mode 820 and the regeneration mode 825 is repeated as needed. Further, the timing or frequency of the cycle may be selected according to the desired data acquisition frequency of the measurement system 310.
For the measurement system 310, which is a quartz crystal microbalance and has a ZrN surface coating, and depending on the distance between the wire 365 and the measurement surface 312, the rate of tin removal from the measurement surface 312 may be up to 4 nanometers (nm) per minute at a radial distance of about 20 millimeters (mm) from the circumference of the wire 365. The dimensions of the quartz crystal microbalance are small and the measuring surface 312 is well within 20mm, so the rate of removal of tin from the quartz crystal microbalance is greater than 4nm/min in these cases. Such a removal rate is higher (e.g., tens of times) than the deposition rate on nearby critical surfaces (about 450 nm/gps), thereby improving the temporal profile of the regeneration of the measurement surface 112.
For example, fig. 9 shows a graph 900 of removal rate 905 expressed in arbitrary units versus distance between the thread 365 and the measurement surface 312 for different values of standard liters per minute (slm).
Referring to FIG. 10, in some implementations, the metrology device 105 (or 205, 305, 405) is implemented within an EUV light source 1000 that provides EUV light 1084 to a lithographic device 1085. the lithographic device 1085 includes an illumination system (illuminator) I L configured to condition a radiation beam B (e.g., EUV light 1084), 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 B by the patterning device MA onto a target portion C (e.g., including one or more dies) of the substrate W.
The illumination system I L 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 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.
Like the illumination system I L, the projection system PS may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, suitable for the exposure radiation being used or other factors, such as the use of a vacuum.
As depicted herein, 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.
Illuminator I L receives an extreme ultraviolet radiation beam (EUV light 1175) from EUV light source 1000. methods of generating EUV light include, but are not limited to, converting a material into a plasma state having at least one element (e.g., xenon, lithium, or tin), with one or more emission lines in the EUV range in one such method, a desired plasma (which is commonly referred to as a laser generated plasma ("L PP")) may be generated by irradiating a fuel (such as a droplet, stream, or cluster of material having the desired line emitting element) with a laser beam.
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 being reflected 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 interferometer, 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, generally a pulsed radiation source is 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. 11 shows an implementation of lithographic device 1185 in more detail, including EUV light source 1100, illumination system I L, and projection system ps. EUV light source 1100 constructed and arranged as described above in the description of EUV light source 400.
Systems I L and PS are also contained in their own vacuum environment the Intermediate Focus (IF) of EUV light source 1100 is arranged such that it is located at or near an aperture in an enclosed structure.
The radiation beam passes through illumination system I L from an aperture at intermediate focus IF, in this example illumination system I L comprises a multi-faceted field mirror apparatus 1122 and a multi-faceted pupil mirror apparatus 1124. these apparatus form a so-called "fly's eye" illuminator arranged to provide a desired angular distribution of the radiation beam 1121 at patterning device MA and a desired uniformity of intensity of radiation at patterning device MA (as indicated by reference numeral 1160). when beam 1121 reflects at patterning device MA, which is held by a support structure (mask table) MT, a patterned beam 1126 is formed and patterned beam 1126 is imaged by projection system PS via reflective elements 1128, 1130 onto a substrate W held by WT. to expose a target portion C on substrate W, pulses of radiation are generated whilst the substrate table WT and patterning device MT perform synchronised movement to scan the pattern on patterning device MA through an illumination aperture.
Each system I L and PS is disposed in its own vacuum or near-vacuum environment, defined by an enclosed structure similar to the EUV chamber 420.
Referring again to fig. 4, the target delivery system 440 may include a droplet generator disposed within the EUV chamber 420 and arranged to emit a high frequency stream 442 of droplets toward an interaction region 480. In operation, amplified light beam 481 is delivered in synchronization with the operation of the droplet generator to deliver pulses of radiation to transform each droplet (each target 445) into a light-emitting plasma 460. The delivery frequency of the droplets may be a few kilohertz, for example 50 kHz.
In some implementations, energy from amplified light beam 481 is delivered in at least two pulses: that is, a pre-pulse with limited energy is delivered to the droplets before they reach the interaction region 480 to vaporize the fuel material into a small cloud, and then a main energy pulse is delivered into the cloud at the interaction region 480 to generate the light-emitting plasma 460. A trap (which may be a container, for example) is provided on the other side of the EUV chamber 420 to trap fuel (i.e., the target 445) which does not become plasma for any reason.
The droplet generator in the target delivery system 440 includes a container containing a fuel liquid (e.g., molten tin) and a filter and nozzle. The nozzle is configured to eject droplets of fuel liquid toward interaction region 480. Droplets of fuel liquid may be injected from the nozzle by a combination of pressure within the vessel and vibration applied to the nozzle by a piezoelectric actuator (not shown).
Other aspects of the invention are set forth in the following numbered clauses.
1. An apparatus, comprising:
a container;
a target delivery system to direct a target at an interaction region in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state; and
a measurement device, comprising:
a measurement system comprising a measurement surface configured to measure a flux of a target substance;
and
a regeneration tool configured to regenerate the measurement system, wherein regenerating comprises:
preventing the measuring surface from becoming saturated, and/or
Desaturating the measurement surface if the measurement surface has become saturated.
2. The apparatus of clause 1, wherein the metrology device comprises a control device in communication with the measurement system and the regeneration tool, wherein the control device is configured to activate the regeneration tool based on an output from the measurement system.
3. The apparatus of clause 1, wherein:
the measurement surface is configured to interact with the target substance, wherein the interaction between the target substance and the measurement surface produces a measurement signal; and
the measurement system further comprises a measurement controller configured to receive the measurement signal and to calculate a flux of the target substance across the measurement surface.
4. The device of clause 1, wherein the measurement device comprises a crystal microbalance.
5. The apparatus of clause 4, wherein the crystal microbalance is a quartz crystal microbalance.
6. The apparatus of clause 1, wherein the container defines a cavity, and the container cavity is maintained at a pressure less than atmospheric pressure.
7. The apparatus of clause 1, wherein the interaction region receives an amplified light beam, and the target is converted to a plasma of emitter ultraviolet light when the target interacts with the amplified light beam.
8. The device of clause 1, further comprising an optical element surface within the container, wherein the metrology device is positioned relative to the optical element surface.
9. The apparatus of clause 8, wherein the optical element is a light collector in which the optical element surface interacts with at least some of the emitted extreme ultraviolet light as the target is converted into the plasma.
10. The apparatus of clause 1, wherein the regeneration tool is configured to: regenerating the measurement system without removing the metrology device from the vessel.
11. The apparatus of clause 1, wherein the regeneration tool comprises a cleaning tool positioned to interact with the measurement system and configured to: removing the target substance that has been deposited on the measurement surface under the direction of the measurement controller.
12. The apparatus of clause 11, wherein the cleaning tool comprises a radical generation unit configured to generate radicals in proximity to the measurement surface, wherein the radicals chemically react with the deposited target species to form new chemical species released from the measurement surface.
13. The apparatus of clause 12, wherein the free radical generating unit comprises a filament adjacent to the measurement surface and a power source providing current to the filament.
14. The device of clause 13, wherein the shape of the wire matches the shape of the measurement surface.
15. The apparatus according to clause 12, wherein the radical generation unit comprises a plasma generator that generates a plasma material in a plasma state near the measurement surface, the plasma material including the radicals.
16. The device of clause 12, wherein the free radicals are free radicals of hydrogen produced from natural hydrogen molecules within the container.
17. The apparatus of clause 16, wherein the target substance on the measurement surface comprises tin, such that the chemical species released from the measurement surface comprises tin hydride.
18. The apparatus of clause 12, further comprising a removal device configured to remove the released new chemical substance from the container.
19. The apparatus of clause 18, wherein the removal device comprises a gas port in fluid communication with the interior of the container, wherein the released new chemical is transferred from the interior of the container through the gas port.
20. The apparatus of clause 1, wherein the regeneration tool is configured to: removing the target substance from the measurement surface in the presence of hydrogen in the container and in the absence of a reaction requiring oxygen.
21. A method, comprising:
providing a target within a cavity of a vessel, wherein the target comprises a substance that emits ultraviolet light when converted to a plasma;
measuring the flux of the target substance on a measurement surface within the vessel cavity; and
regenerating the measurement surface, wherein regenerating comprises at least one of:
preventing the measuring surface from becoming saturated, and/or
Desaturating the measurement surface if the measurement surface has become saturated.
22. The method of clause 21, further comprising activating regeneration of the measurement surface based on the flux of the target substance measured on the measurement surface.
23. The method of clause 21, wherein measuring the flux of the target substance comprises interacting the target substance with the measurement surface such that the target substance is deposited on the measurement surface.
24. The method of clause 21, wherein providing the targets within the container cavity comprises directing a plurality of targets at an interaction region in the vacuum container, the interaction region further receiving an amplified light beam such that interaction between the targets and the amplified light beam in the interaction region converts the targets into a plasma of emitter ultraviolet light.
25. The method of clause 21, wherein regenerating the measurement surface comprises: removing deposited target species from the measurement surface without removing the measurement surface from the container.
26. The method of clause 25, wherein removing the deposited target species from the measurement surface comprises generating elemental radicals in the vicinity of the measurement surface, the generated radicals chemically reacting with the deposited target species to form a new chemical species, the new chemical species being released from the measurement surface.
27. The method of clause 26, wherein the deposited target species comprises tin, the element is hydrogen, the radical is a hydrogen radical, and the new chemical species is tin hydride.
28. The method of clause 26, wherein the element adjacent the measurement surface is intrinsic to the container cavity.
29. The method of clause 26, wherein removing the deposited target species comprises removing the deposited target species in the absence of oxygen.
30. The method of clause 26, further comprising removing the released new chemical from the container cavity.
31. The method of clause 25, wherein measuring the flux of the target substance comprises measuring the flux of the target substance at a time when the deposited target substance is not removed from the measurement surface.
32. The method of clause 25, wherein the deposited target species is removed from the measurement surface, thereby preventing the measurement surface from reaching a saturation limit of the measurement surface.
33. The method of clause 21, further comprising maintaining the cavity defined by the container at a pressure below atmospheric pressure.
34. The method of clause 21, further comprising estimating an amount of extreme ultraviolet light emitted when the target species is converted to plasma based on the measured flux.
35. The method of clause 21, further comprising estimating an amount of a target substance deposited on a surface within the container cavity based on the measured flux.
36. An extreme ultraviolet light source comprising:
a light source configured to generate an amplified light beam;
a container defining a cavity, the container configured to receive the amplified light beam at an interaction region in the cavity, and the cavity configured to be maintained at a pressure that is I below atmospheric pressure;
a target delivery system configured to generate a target traveling along a target path toward the interaction region, the target comprising a target substance that emits ultraviolet light in a plasma state; and
a measurement device, comprising:
a measurement system comprising a measurement surface configured to measure a flux of a target substance; and
a regeneration tool configured to regenerate the measurement system, wherein regenerating comprises:
preventing the measurement surface from becoming saturated; and/or
Desaturating the measurement surface if the measurement surface becomes saturated.
37. The euv light source of clause 36, wherein the measurement surface is configured to interact with a target substance, wherein the interaction between the target substance and the measurement surface produces a measurement signal; and the measurement system further comprises a measurement controller that receives the measurement signal and calculates a flux of a target substance across the measurement surface.
38. The euv light source according to clause 37, wherein the regeneration tool comprises a cleaning tool positioned to interact with the measurement system, wherein the cleaning tool is configured to regenerate the measurement system by removing target substances that have been deposited on the measurement surface.
39. The euv light source of clause 36, further comprising a light collector that collects at least some of the emitted euv light for use by an external lithographic apparatus.
40. A metrology system for use in an extreme ultraviolet light source, the metrology system comprising:
a metrology device configured to measure a flux of a target substance across a measurement surface within a vessel, the metrology device comprising:
a measurement system comprising the measurement surface configured to interact with the target substance, wherein the interaction between the target substance and the measurement surface generates a measurement signal; and
a measurement controller configured to receive the measurement signal and to calculate a flux of the target substance across the measurement surface based on the received measurement signal; and
a regeneration tool coupled to the metrology device and configured to regenerate the measurement system,
wherein the regeneration comprises:
preventing the measurement surface from becoming saturated; and/or
Desaturating the measurement surface if the measurement surface has become saturated,
wherein the regeneration tool comprises a cleaning tool positioned to interact with the measurement surface and remove target species that have deposited on the measurement surface according to instructions from the measurement controller.
41. An apparatus, comprising:
a container;
means for delivering a target to an interaction region in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state;
a measurement device, comprising:
means for measuring a flux of a target substance across a measurement surface within the vessel; and
means for regenerating the measurement surface, wherein the means for regenerating comprises:
means for preventing the measurement surface from becoming saturated; and/or
Means for desaturating the measurement surface if the measurement surface has become saturated.
Other implementations are within the scope of the following claims.
Claims (25)
1. An apparatus, comprising:
a container;
a target delivery system that directs a target to an interaction region in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state; and
a measurement device, comprising:
a measurement system comprising a measurement surface configured to measure a flux of a target substance; and
a regeneration tool configured to regenerate the measurement system, wherein regenerating comprises:
preventing the measuring surface from becoming saturated, and/or
Desaturating the measurement surface if the measurement surface has become saturated.
2. The apparatus of claim 1, wherein:
the measurement surface is configured to interact with the target substance, wherein the interaction between the target substance and the measurement surface produces a measurement signal; and
the measurement system further comprises a measurement controller configured to receive the measurement signal and to calculate a flux of the target substance across the measurement surface.
3. The apparatus of claim 1, wherein the measurement device comprises a quartz crystal microbalance.
4. The apparatus of claim 1, wherein the interaction region receives an amplified light beam and the target is converted to a plasma of emitter ultraviolet light when the target interacts with the amplified light beam.
5. The device of claim 1, further comprising an optical element surface within the vessel, wherein the metrology device is positioned relative to the optical element surface, and the optical element is a light collector in which the optical element surface interacts with at least some of the emitted extreme ultraviolet light as the target is converted into the plasma.
6. The apparatus of claim 1, wherein the regeneration means is configured to: regenerating the measurement system without removing the metrology device from the vessel.
7. The apparatus of claim 1, wherein the regeneration tool comprises a cleaning tool positioned to interact with the measurement system and configured to: removing the target substance that has been deposited on the measurement surface under the direction of the measurement controller.
8. The apparatus of claim 7, wherein the cleaning tool comprises a radical generation unit configured to generate radicals in proximity to the measurement surface, wherein the radicals chemically react with the deposited target species to form new chemical species that are released from the measurement surface.
9. The apparatus of claim 8, wherein the radical generation unit comprises one of:
a wire adjacent the measurement surface, and a power source providing a current to the wire; and
a plasma generator that generates a plasma material in a plasma state near the measurement surface, the plasma material including the radicals.
10. The apparatus of claim 8, wherein the radicals are radicals of hydrogen generated from natural hydrogen molecules within the container and the target species on the measurement surface comprises tin, such that the new chemical species released from the measurement surface comprises tin hydride.
11. The apparatus of claim 8, further comprising a removal device configured to remove the released new chemical from the container, the removal device comprising a gas port in fluid communication with an interior of the container, and wherein the released new chemical is transferred from the interior of the container through the gas port.
12. The apparatus of claim 1, wherein the regeneration means is configured to: removing the target substance from the measurement surface in the presence of hydrogen in the container and in the absence of a reaction requiring oxygen.
13. A method, comprising:
providing a target within a cavity of a vessel, wherein the target comprises a substance that emits ultraviolet light when converted to a plasma;
measuring the flux of the target substance on a measurement surface within the cavity; and
regenerating the measurement surface, wherein the regenerating comprises at least one of:
preventing the measuring surface from becoming saturated, an
Desaturating the measurement surface if the measurement surface has become saturated.
14. The method of claim 13, further comprising: activating regeneration of the measurement surface based on the flux of the target substance measured on the measurement surface.
15. The method of claim 13, wherein providing the target within the container cavity comprises: directing a plurality of targets to an interaction region in a vacuum vessel, the interaction region also receiving an amplified light beam such that interaction between the targets and the amplified light beam in the interaction region converts the targets to a plasma of emitter ultraviolet light.
16. The method of claim 13, wherein regenerating the measurement surface comprises: removing the deposited target substance from the measurement surface without removing the measurement surface from the container and in the absence of oxygen.
17. The method of claim 13, wherein regenerating the measurement surface comprises: removing the deposited target substance from the measurement surface without removing the measurement surface from the container, and removing the deposited target substance from the measurement surface comprises: generating elemental radicals in the vicinity of the measurement surface, the generated radicals chemically reacting with the deposited target species to form new chemical species released from the measurement surface.
18. The method of claim 17, wherein the deposited target species comprises tin, the element is hydrogen, the radical is a hydrogen radical, and the new chemical species is tin hydride.
19. The method of claim 13, wherein regenerating the measurement surface comprises: removing the deposited target substance from the measurement surface without removing the measurement surface from the container, and removing the deposited target substance from the measurement surface thereby preventing the measurement surface from reaching a saturation limit of the measurement surface.
20. The method of claim 13, further comprising: estimating an amount of extreme ultraviolet light emitted when the target species is converted into a plasma based on the measured flux.
21. The method of claim 13, further comprising: estimating an amount of a target substance deposited on a surface within the vessel cavity based on the measured flux.
22. An extreme ultraviolet light source comprising:
a light source configured to generate an amplified light beam;
a container defining a cavity, the container configured to receive the amplified light beam at an interaction region in the cavity, and the cavity configured to be maintained at a pressure below atmospheric pressure;
a target delivery system configured to generate a target traveling along a target path toward the interaction region, the target comprising a target substance that emits ultraviolet light in a plasma state; and
a measurement device, comprising:
a measurement system comprising a measurement surface configured to measure a flux of a target substance; and
a regeneration tool configured to regenerate the measurement system, wherein regenerating comprises:
preventing the measurement surface from becoming saturated; and/or
Desaturating the measurement surface if the measurement surface becomes saturated.
23. The euv light source of claim 22, wherein the regeneration tool comprises a cleaning tool positioned to interact with the measurement system, the cleaning tool configured to regenerate the measurement system by removing target species that have been deposited on the measurement surface.
24. A metrology system for use in an extreme ultraviolet light source, the metrology system comprising:
a metrology device configured to measure a flux of a target substance across a measurement surface within a vessel, the metrology device comprising:
a measurement system comprising the measurement surface configured to interact with the target substance, wherein the interaction between the target substance and the measurement surface generates a measurement signal; and
a measurement controller configured to receive the measurement signal and to calculate a flux of the target substance across the measurement surface based on the received measurement signal; and
a regeneration tool coupled to the metrology device and configured to regenerate the measurement system,
wherein the regeneration comprises:
preventing the measurement surface from becoming saturated; and/or
Desaturating the measurement surface if the measurement surface has become saturated,
wherein the regeneration tool comprises a cleaning tool positioned to interact with the measurement surface and remove target species that have been deposited on the measurement surface according to instructions from the measurement controller.
25. An apparatus, comprising:
a container;
means for delivering a target to an interaction region in the vessel, the target comprising a target substance that emits ultraviolet light when in a plasma state;
a measurement device, comprising:
means for measuring a flux of a target substance across a measurement surface within the vessel; and
means for regenerating the measurement surface, wherein the means for regenerating comprises:
means for preventing the measurement surface from becoming saturated; and/or
Means for desaturating the measurement surface if the measurement surface has become saturated.
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| PCT/EP2018/081498 WO2019115144A1 (en) | 2017-12-15 | 2018-11-16 | Regeneration of a debris flux measurement system in a vacuum vessel |
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| CN111480071A true CN111480071A (en) | 2020-07-31 |
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| US20230375506A1 (en) * | 2022-05-18 | 2023-11-23 | Applied Materials, Inc. | Sensor for measurement of radicals |
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| KR102697196B1 (en) | 2024-08-20 |
| JP2021507204A (en) | 2021-02-22 |
| NL2022007A (en) | 2019-06-21 |
| WO2019115144A1 (en) | 2019-06-20 |
| KR20200096777A (en) | 2020-08-13 |
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