Method and device for tuning flow velocity profile

Abstract

A radiation source includes a matter delivery system, an illumination source, and a jet flow generator. The matter delivery system directs target material to a target region. The illumination source irradiates the target material at the target region to generate radiation as an output of the radiation source. The jet flow generator directs a jet flow of a gas to the target region. The jet flow generator includes a flow injector and a diffuser. The flow injector adjusts a velocity profile of the jet flow. The diffuser adjusts a spread of the jet flow.

Description

METHOD AND DEVICE FOR TUNING FLOW VELOCITY PROFILECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 621,936, filed January 17, 2024, titled METHOD AND DEVICE FOR TLNIXG FLOW VELOCITY PROFILE, which is incorporated herein by reference in its entirety.FIELD

[0002] The present application relates to extreme ultraviolet (“EUV”) radiation sources and methods thereof. EUV radiation can be used as, for example, exposure radiation in a lithographic process to fabricate semiconductor devices.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which can be a mask or a reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (photoresist or simply “resist”) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatuses include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the target portions parallel or anti-parallel to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] A lithographic apparatus typically includes an illumination system that conditions radiation generated by a radiation source before the radiation is incident upon a patterning device. A patterned beam of EUV light can be used to produce extremely small features on a substrate. EUV light (also sometimes referred to as soft x-rays) is generally defined as electromagnetic radiation having wavelengths in the range of about 5-100 nm. One particular wavelength of interest for photolithography occurs at 13.5 nm.

[0005] Methods to produce EUV light include, but are not necessarily limited to, converting a source material into a plasma state that has a chemical element with an emission line in the EUV range. These elements can include, but are not necessarily limited to, xenon, lithium and tin.

[0006] In one such method, often termed laser-produced plasma (“LPP”), the desired plasma can be produced by irradiating a source material, for example, in the form of a droplet, stream or wire, with a laser beam. In another method, often termed discharge produced plasma (“DPP”), the plasma can be generated by positioning source material having an appropriate emission line between a pair of electrodes and causing an electrical discharge to occur between the electrodes.

[0007] A buffer gas can be used in an EUV source to mitigate deposition of contaminants on surfaces of the EUV source When the buffer gas is generated having a suitable flow velocity and directionality, the viscosity of the buffer gas can be used to steer the spent plasma material toward a suitable outflow (e.g., an exhaust). Control of the flow of the buffer gas can vastly reduce the contaminant deposition rate on surfaces of chamber. The flow of the buffer gas can be affected by one or more optical elements in the EUV source that are disposed in the path of the gas flow. While a given design for a gas flow system can be made to fit a given architecture of optical elements, a problem can arise when the architecture of the optical elements undergoes an update or redesign. In such a scenario, the former design of the gas flow system may be rendered unsuitable, which can increase cost and complexity by triggering a redesign of the gas flow system.SUMMARY

[0008] Accordingly, it is desirable to improve gas flow system so as to achieve performance goals that are unaffected by structural changes in the vicinity of the gas flow system.

[0009] In some aspects, a radiation source comprises a matter delivery system, an illumination source, and a jet flow generator. The matter delivery system is configured to direct target material to a target region. The illumination source is configured to irradiate the target material at the target region to generate radiation as an output of the radiation source. The jet flow generator is configured to direct a jet flow of a gas to the target region. The jet flow generator comprises a flow injector and a diffuser. The flow injector is configured to adjust a velocity profile of the jet flow. The diffuser is configured to adjust a spread of the jet flow.

[0010] In some aspects, a jet flow generator comprises a flow injector and a diffuser. The flow injector is configured to adjust a velocity profile of a jet flow of a gas. The diffuser is configured to adjust a spread of the jet flow. The jet flow generator is configured to direct the jet flow with the velocity profile toward a target region.

[0011] In some aspects, a method comprises adjusting a velocity profile of a jet flow of a gas using a flow injector comprising a cavity to generate a pressure gradient for a flow of the gas in the flow injector. The method also comprises adjusting a spread of the jet flow using a diffuser comprising spray holes to generate a diffuse gas flow to combine with the jet flow at an output structure of the flow injector.

[0012] Further features of various aspects of the present disclosure are described in detail below with reference to the accompanying drawings. It is noted that the present disclosure is not limited to thespecific aspects described herein. Such aspects are presented herein for illustrative purposes only. Additional aspects will be apparent to those skilled in the relevant art(s) based on the teachings contained herein.BRIEF DESCRIPTION OF THE DRAWINGS / FIGURES

[0013] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the present disclosure and to enable those skilled in the relevant art(s) to make and use aspects described herein.

[0014] FIG. 1 shows a reflective lithographic apparatus, according to some aspects.

[0015] FIG. 2 shows a lithographic cell, according to some aspects.

[0016] FIGS. 3 A, 3B, and 4 show more details of a radiation source that can be used in a reflective lithographic apparatus, according to some aspects.

[0017] FIG. 5 shows a portion of a radiation source, according to some aspects.

[0018] FIG. 6 shows a portion of a radiation source, according to some aspects.

[0019] FIG. 7 shows a jet flow generator, according to some aspects.

[0020] FIG. 8 shows graphs of a velocity profile of a jet flow for different settings of a jet flow generator, according to some aspects.

[0021] FIG. 9 shows an intensity map of a velocity profile of a jet flow, according to some aspects.

[0022] FIG. 10 shows a radiation system, according to some aspects.

[0023] FIG. 11 shows a flowchart of a method for adjusting a velocity profile of a jet flow, according to some aspects.

[0024] The features of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.DETAILED DESCRIPTION

[0025] The aspects described herein, and references in the specification to “one aspect,” “an aspect,” “an exemplary aspect,” “an example aspect,” etc., indicate that the aspects described can include a particular feature, structure, or characteristic, but every aspect may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same aspect. Further, when a particular feature, structure, or characteristic is described in connection with an aspect, it is understood that it is within the knowledge of those skilled in the art toeffect such feature, structure, or characteristic in connection with other aspects whether or not explicitly described.

[0026] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, can be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein can likewise be interpreted accordingly.

[0027] The terms “about,” “approximately,” or the like can be used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the terms “about,” “approximately,” or the like can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0028] Aspects of the present disclosure can be implemented in hardware, firmware, software, or any combination thereof. Aspects of the disclosure can also be implemented as instructions stored on a computer-readable medium, which can be read and executed by one or more processors. A machine- readable medium can include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium can comprise read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc ), and others. Furthermore, firmware, software, routines, and / or instructions can be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. The term “machine -readable medium” can be interchangeable with similar terms, for example, “computer program product,” “computer-readable medium,” “non-transitory computer-readable medium,” or the like. The term “non -transitory” can be used herein to characterize one or more forms of computer readable media except for a transitory, propagating signal.

[0029] Before describing such aspects in more detail, however, it is instructive to present an example environment in which aspects of the present disclosure can be implemented.

[0030] Example Lithographic Systems

[0031] FIG. 1 shows a lithographic apparatus 100 in which aspects of the present disclosure can be implemented. In some aspects, lithographic apparatus 100 can comprise the following: an illumination system (illuminator) IL configured to condition a radiation beam B (for example, deep ultra violet or extreme ultra violet radiation); a support structure (for example, a mask table) MT configured to support a patterning device (for example, a mask, a reticle, or a dynamic patterning device) MA andconnected to a first positioner PM configured to accurately position patterning device MA; and, a substrate table (for example, a wafer table) WT configured to hold a substrate (for example, a resist coated wafer) W and connected to a second positioner PW configured to accurately position substrate W. Lithographic apparatus 100 also comprises a projection system PS configured to project a pattern imparted to radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of substrate W. In lithographic apparatus 100, patterning device MA and the projection system PS are reflective.

[0032] Illumination system IL can comprise various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B . Illumination system IL can also comprise a sensor ES that provides a measurement of, for example, one or more of energy per pulse, photon energy, intensity, average power, and the like. Illumination system IL can comprise a measurement sensor MS for measuring a movement of radiation beam B and a uniformity compensator UC that allow an illumination slit uniformity to be controlled. Measurement sensor MS can also be disposed at other locations. For example, measurement sensor MS can be on or near substrate table WT.

[0033] In some aspects, support structure MT can support patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, the design of lithographic apparatus 100, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. Support structure MT can implement mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. Support structure MT can be a frame or a table. Support structure MT can be fixed or movable. By using sensors, support structure MT can ensure that patterning device MA is at a desired position (e.g., a given position with respect to the projection system PS).

[0034] The term “patterning device” can be used herein to refer to any device that can be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in target portion C of substrate W. The pattern imparted to radiation beam B can correspond to a particular functional layer in a device being created in target portion C to form an integrated circuit.

[0035] Patterning device MA can be reflective. Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks can include different mask types, such as binary, alternating phase shift, or attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors can impart a pattern in radiation beam B, which is reflected by a matrix of small mirrors.

[0036] In some aspects, the term “projection system” can be used herein to refer to any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic andelectrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. Atmospheric gas can absorb EUV or electrons used for exposing a substrate. Therefore, a vacuum environment can be used for EUV or electron beam radiation. A vacuum environment can be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0037] Lithographic apparatus 100 can be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such “multiple stage” machines, additional substrate tables WT can be used in parallel, or preparatory steps can be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may be different from substrate table WT.

[0038] In some aspects, lithographic apparatus 100 can be of a type in which at least a portion of the substrate can be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system and the substrate. An immersion liquid can also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques can increase the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid. For example, a liquid can be located between the projection system and the substrate during exposure.

[0039] Illuminator IL can receive a radiation beam from a radiation source SO. Source SO and lithographic apparatus 100 can be separate physical entities. In such cases, source SO is not considered to be part of lithographic apparatus 100 and radiation beam B can pass from source SO to illuminator IL with the aid of a beam delivery system (not shown), which can include, for example, suitable directing mirrors and / or a beam expander. In other cases, source SO can be an integral part of the lithographic apparatus 100. A radiation system can comprise source SO, illuminator IL, and / or beam delivery system BD.

[0040] In some aspects, illuminator IL can be used to condition radiation beam B to have a desired uniformity and intensity distribution in its cross section. The desired uniformity of radiation beam B can be maintained by using uniformity compensator UC. Uniformity compensator UC can comprise a plurality of protrusions (e.g., fingers) that can be adjusted in the path of radiation beam B to control the uniformity of radiation beam B. Measurement sensor MS can be used to monitor the uniformity of radiation beam B.

[0041] Radiation beam B can be incident on patterning device MA, which is held on the support structure MT, and In this manner, radiation beam B can be patterned by the patterning device MA. In lithographic apparatus 100, radiation beam B can be reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device MA, radiation beam B can pass through projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF2 (for example, aninterferometric device, linear encoder, or capacitive sensor), substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (for example, mask) MA with respect to the path of the radiation beam B. Patterning device MA and substrate W can be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.

[0042] In some aspects, lithographic apparatus 100 can be used in at least one of the following modes:

[0043] 1 In step mode, support stmcture MT and substrate table WT can be kept essentially stationary, while an entire pattern imparted to radiation beam B is projected onto a target portion C at one time (e.g., a single static exposure). Substrate table WT can then be shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0044] 2 In scan mode, support structure MT and substrate table WT can be scanned synchronously while a pattern imparted to radiation beam B is projected onto a target portion C (e.g., a single dynamic exposure). The velocity and direction of substrate table WT relative to support structure MT can be determined by (de-)magnification and image reversal characteristics of projection system PS.

[0045] 3 In another mode, support structure MT can be kept substantially stationary holding a programmable patterning device, and substrate table WT can be moved or scanned while a pattern imparted to radiation beam B is projected onto a target portion C. A pulsed radiation source SO can be employed and the programmable patterning device is updated after each movement of 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 a programmable patterning device, such as a programmable mirror array.

[0046] Combinations and / or variations on the described modes of use or entirely different modes of use can also be employed.

[0047] In some aspects, lithographic apparatus 100 can comprise an EUV radiation source configured to generate a beam of EUV radiation for EUV lithography. The EUV radiation source can be configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0048] Example Lithographic Cell

[0049] FIG. 2 shows a lithographic cell 200, also sometimes referred to a lithocell or cluster, according to some aspects. Lithographic apparatus 100 (FIGS. 1, 3 A, 3B, and 4) can form part of lithographic cell 200. Lithographic cell 200 can also comprise one or more apparatuses to perform pre-exposure and post-exposure processes on a substrate. These can include spin coaters SC to deposit resist layers, developers DE to develop exposed resist, chill plates CH, and bake plates BK. A substrate handler, or robot, RO picks up substrates from input / output ports I / O I, I / O2, moves thembetween the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus 100. These devices, which are often collectively referred to as the track, are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0050] Example Illumination Sources and Illumination Optics

[0051] FIG. 3A shows different view of source SO (e.g., source collector apparatus), illumination system IL, and projection system PS that can be used in lithographic apparatus 100, according to some aspects. Source SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 320 of source SO. An EUV radiation emitting plasma 310 can be formed by a discharge-generated plasma source. In some aspects, a plasma of excited tin (Sn) (e.g., excited via a laser) is used to produce EUV radiation.

[0052] The radiation emitted by the EUV radiation emitting plasma 310 can be passed from a source chamber 311 into a collector chamber 312 via an optional gas barrier or contaminant trap 330 (in some cases also referred to as contaminant barrier or foil trap), which is positioned in or behind an opening in source chamber 311. Contaminant trap 330 can comprise a channel structure. Contamination trap 330 can also comprise a gas barrier and / or a channel structure.

[0053] In some aspects, collector chamber 312 can comprise a radiation collector CO. Radiation collector CO can be a so-called grazing incidence collector. Radiation collector CO can comprise an upstream radiation collector side 351 and a downstream radiation collector side 352. Radiation that traverses radiation collector CO can be reflected off a grating spectral filter 340 to be focused in a virtual source point INTF. Virtual source point INTF can be referred to as the intermediate focus. Source collector apparatus can be arranged such that the intermediate focus INTF is located at or near an opening 319 of enclosing structure 320. The virtual source point INTF can be an image of the EUV radiation emitting plasma 310. Grating spectral filter 340 can be used for suppressing infrared (IR) radiation.

[0054] Subsequently, the radiation traverses the illumination system IL. Illumination system IL can include a faceted field mirror device 322 and a faceted pupil mirror device 324 arranged to provide a desired angular distribution of radiation beam 321, at patterning device MA, as well as a desired uniformity of radiation intensity at patterning device MA. Upon reflection of beam of radiation 321 at patterning device MA, held by support structure MT, a patterned beam 326 is formed and the patterned beam 326 is imaged by projection system PS via reflective elements 328, 329 onto substrate W held by the wafer stage or substrate table WT. In some aspects, other configurations of mirrors and / or optical devices can be used to direct radiation beam 321 to patterning device MA.

[0055] More elements than shown can generally be present in illumination system IL and projection system PS. Grating spectral filter 340 can optionally be present, depending upon the type oflithographic apparatus. Further, there can be more mirrors present than those shown in the FIG. 2A, for example there can be one to six additional reflective elements present in the projection system PS than shown in FIG. 2A.

[0056] In some aspects, uniformity compensator UC, sensor ES, and / or measurement sensor MS shown in FIGS. 2A and 2B can be as described above in reference to FIG. 1.

[0057] Collector CO, as illustrated in FIG. 2A, is depicted as an example of a nested collector with grazing incidence reflectors 353, 354, and 355 (or collector mirror). Grazing incidence reflectors 353, 354, and 355 can be disposed axially symmetric around an optical axis O. A collector optic of this type can be used in combination with a discharge-generated plasma source, often called a DPP source.

[0058] FIG. 3B shows different view of source SO with alternative collection optics that can be used in lithographic apparatus 100, according to some aspects. It should be appreciated that structures shown in FIG. 3 A that do not appear in FIG. 3B (for drawing clarity) can still be included in aspects referring to FIG. 3B. Elements in FIG. 3B having the same reference numbers as those in FIG. 3 A have the same or substantially similar structures and functions as described in reference to FIG. 3A.

[0059] In some aspects, the lithographic apparatus 100 can be used, for example, to expose a substrate W such as a resist-coated wafer with a patterned beam of EUV illumination. In FIG. 3B, illumination system IL and projection system PS are represented combined as an exposure device 356 (e.g., an integrated circuit lithography tool such as a stepper, scanner, step and scan system, direct write system, device using a contact and / or proximity mask, etc.) that uses EUV light from source SO. Lithographic apparatus 100 can also comprise collector 358 that reflects EUV light from the EUV radiation emitting plasma 310 along a path into the exposure device 356 to irradiate substrate W. Collector 358 can comprise a near-normal incidence collector mirror having a reflective surface in the form of a prolate spheroid (e.g., an ellipse rotated about its major axis). The prolate spheroid structure can have a graded multi-layer coating with alternating layers of Molybdenum and Silicon, and in some cases, one or more high temperature diffusion barrier layers, smoothing layers, capping layers and / or etch stop layers.

[0060] FIG. 4 shows a detailed view of source SO and associated elements that can be used in lithographic apparatus 100, according to some aspects. Elements in FIG. 4 having the same reference numbers as those in FIGS. 1, 3 A. and 3B have the same or substantially similar structures and functions as described in reference to FIGS. 1, 3A, and 3B. In some aspects, source SO can be a LPP EUV source. Source SO can comprise a laser system 402 (or a suitable illumination system) for generating illumination to be used in the production of EUV -producing plasma, source SO can generate a train of light pulses and deliver the light pulses into a light source chamber 312. For the lithographic apparatus 100, the light pulses can travel along one or more beam paths from the laser system 402 and into the chamber 312 to illuminate a source material (or target material) at an irradiation region 404 (or target region, or primary focus) to generate a plasma. For example, EUVradiation emitting plasma 310 (FIGS. 3B) is generated at irradiation region 404. EUV light is produced by the plasma. The EUV light is used for substrate exposure in the exposure device 356.

[0061] In some aspects, laser system 402 can comprise a pulsed laser device, e.g., a pulsed gas discharge CO2 laser device producing radiation at 9.3 pm or 10.6 pm, e.g., with DC or RF excitation, operating at relatively high power, e.g., 10 kW or higher and high pulse repetition rate, e.g., 50 kHz or more. In some aspects, the laser can be an axial -flow RF -pumped CO2 laser having an oscillator amplifier configuration (e.g., master oscillator / power amplifier (MOPA) or power oscillator / power amplifier (POPA)) with multiple stages of amplification and having a seed pulse that is initiated by a Q-switched oscillator with relatively low energy and high repetition rate, e.g., capable of 100 kHz operation. From the oscillator, the laser pulse can then be amplified, shaped and / or focused before reaching the irradiation region 404. Continuously pumped CO2 amplifiers can be used for the laser system 402. Alternatively, the laser can be configured as a so-called “self-targeting” laser system in which the droplet serves as one mirror of the optical cavity of the laser.

[0062] In some aspects, depending on the application, other types of lasers can also be suitable, e.g., an excimer or molecular fluorine laser operating at high power and high pulse repetition rate. Some examples include, a solid state laser, e.g., having a fiber, rod, slab, or disk-shaped active media, other laser architectures having one or more chambers, e.g., an oscillator chamber and one or more amplifying chambers (with the amplifying chambers in parallel or in series), a master oscillator / power oscillator (MOPO) arrangement, a master oscillator / power ring amplifier (MOPRA) arrangement, or a solid state laser that seeds one or more excimer, molecular fluorine or CO2 amplifier or oscillator chambers, can be suitable. Other suitable designs are envisaged.

[0063] In some aspects, a source material can first be irradiated by a pre-pulse and thereafter irradiated by a main pulse. Pre-pulse and main pulse seeds can be generated by a single oscillator or two separate oscillators. One or more common amplifiers can be used to amplify both the pre-pulse seed and main pulse seed. In some aspects, separate amplifiers can be used to amplify the pre-pulse and main pulse seeds.

[0064] In some aspects, source SO can also comprise a beam conditioning unit 406 having one or more optics for beam conditioning, such as expanding, steering, and / or focusing the beam between the laser system 402 and irradiation region 404. For example, a steering system, which can comprise one or more mirrors, prisms, lenses, etc., can be provided and arranged to steer the laser focal spot to different locations in the chamber 312. For example, the steering system can comprise a first flat mirror mounted on a tip-tilt actuator, which can move the first mirror independently in two dimensions, and a second flat mirror mounted on a tip-tilt actuator, which can move the second mirror independently in two dimensions. With the described arrangement(s), the steering system can controllably move the focal spot in directions substantially orthogonal to the direction of beam propagation (beam axis or optical axis).

[0065] Beam conditioning unit 406 can comprise a focusing assembly to focus the beam to irradiation region 404 and adjust the position of the focal spot along the beam axis. For the focusing assembly, an optic can be used, such as a focusing lens or mirror. The optic can be coupled to an actuator to allow for movement in a direction along the beam axis to move the focal spot along the beam axis.

[0066] In some aspects, the source SO can also comprise a source material delivery system 408 for delivering source material, such as tin droplets, to irradiation region 404, where the droplets can interact with light pulses from the laser system 402 to produce plasma and generate EUV emission. Source material delivery system 408 can also be referred to as a matter delivery system or target material delivery system. The EUV emission is used to expose a substrate such as a resist-coated wafer at exposure device 36. More details regarding various droplet dispenser configurations can be found in, e.g., U.S. Pat. No. 7,872,245, issued on January 18, 2011, titled “Systems and Methods for Target Material Delivery in a Laser Produced Plasma EUV Light Source”, U.S. Pat. No. 7,405,416, issued on July 29, 2008, titled “Method and Apparatus For EUV Plasma Source Target Delivery”, U.S. Pat. No. 7,372,056, issued on May 13, 2008, titled “LPP EUV Plasma Source Material Target Delivery System”, and International Appl. No. WO 2019 / 137846, titled “Apparatus for and Method of Controlling Coalescence of Droplets In a Droplet Stream”, published on July 18, 2019, the contents of each of which are incorporated by reference herein in their entirety.

[0067] In some aspects, the source material for producing an EUV light output for substrate exposure can include, but is not necessarily limited to, a material that includes tin, lithium, xenon or combinations thereof. The source material can be in the form of liquid droplets and / or solid particles contained within liquid droplets. For example, the element tin can be used as pure tin, as a tin compound, e.g., SnBr4, SnBr2, SnH4. as a tin alloy, e.g., tin-gallium alloys, tin-indium alloys, tin- indium-gallium alloys, or a combination thereof. Depending on the material used, the source material, when sent to irradiation region 404, can be at various temperatures, for example, room temperature or near room temperature (e g., tin alloys, SnBr4), at an elevated temperature (e.g., pure tin), or at temperatures below room temperature (e.g., SnH4).

[0068] In some aspects, the source SO can also comprise a controller 410 and / or a drive laser control system 412 for controlling devices in laser system 402 to generate light pulses for delivery into the chamber 312 and / or for controlling movement of optics in beam conditioning unit 306. Source SO can also comprise a droplet position detection system which can comprise one or more droplet imagers 414 that provide an output signal indicative of the position of one or more droplets (e.g., to ensure that droplets arrive on target at irradiation region 404). The droplet imager(s) 414 can provide measurement output to a droplet position detection feedback system 416. Droplet position detection feedback system 416 can compute a droplet position and trajectory, from which a droplet error can be computed (e.g., on a droplet-by-droplet basis, or on average). The droplet error can then be provided as an input to controller 410, which can, for example, provide a position, direction and / or timingcorrection signal to laser system 402 to control laser trigger timing and / or to control movement of optics in beam conditioning unit 406, e.g., to change the location and / or focal power of the light pulses being delivered to irradiation region 404 in chamber 312. Furthermore, source material delivery system 408 can comprise a control system operable in response to a signal from controller 410 (which in some implementations can include the droplet error described above, or some quantity derived therefrom) to modify the release point, initial droplet stream direction, droplet release timing and / or droplet modulation to correct for errors in the droplets arriving at irradiation region 404

[0069] In some aspects, source SO can also comprise collector 358 and a gas dispenser device 420. Gas dispenser device 420 can dispense gas in the path of the source material from source material delivery system 408 (e.g., irradiation region 404). Gas dispenser device 420 can comprise a nozzle through which dispensed gas can exit. Gas dispenser device 420 can be structured (e.g., having an aperture) such that, when placed near the optical path of laser system 402, light from laser system 402 is not blocked by gas dispenser device 420 and is allowed to reach irradiation region 404. A buffer gas such as hydrogen, helium, argon or combinations thereof, can be introduced into chamber 312. The buffer gas can be present in the chamber 312 during plasma discharge and can act to slow plasma- created ions, reduce degradation of optics, and / or increase plasma efficiency. Alternatively, a magnetic field and / or electric field (not shown) can be used alone, or in combination with a buffer gas, to reduce damage caused by fast-moving ions.

[0070] In some aspects, collector 358 can be a near-normal incidence collector mirror having a reflective surface in the form of a prolate spheroid as descnbed above. Collector 358 can be formed with an aperture to allow the light pulses generated by laser system 402 to pass through and reach irradiation region 404. The same, or another aperture, can be used to allow gas from the gas dispenser device 420 to flow into chamber 312. As shown, the collector 358 can be, e.g., a prolate spheroid mirror that has a first focus within or near the irradiation region 404 and a second focus at an intermediate region 318, where the EUV light can be transmitted to exposure device 356. It is to be appreciated that other optics can be used in place of the prolate spheroid mirror for collecting and directing light to an intermediate location for subsequent delivery to a device utilizing EUV light. It is also envisaged that structures and functions described in reference to FIG. 3 can be used with collectors other than collector 358 (e.g., collector CO (FIG. 2A)).

[0071] Example Jet / Cone Flow Generator

[0072] The buffer gas provided by gas dispenser device 420 provides functions other than those described above. For example, spent plasma material (e.g., liquid tin) can be a contaminant to the environment in chamber 312. When the buffer gas is generated having a suitable flow velocity and directionality, the viscosity of the buffer gas can be used to steer the spent plasma material toward a suitable outflow (e.g., an exhaust). Control of the flow of the buffer gas can vastly reduce the contaminant deposition rate on surfaces of chamber 312.

[0073] Protection of collector 358 is also a function provided by the buffer gas. The protection of collector 358 may be achieved by a combination of buffer gas flows, including an umbrella flow, a perimeter flow, and a cone flow. The cone flow can be the most dominant in protecting collector 358, as it can be the fastest moving of the flows and it directly exerts a pressure on the droplet material, as described above.

[0074] FIG. 5 shows a jet flow generator 516 for use with a radiation source 500, according to some aspects Radiation source 500 includes a collector 502, an optical system 504 with one or more optical elements 508, a beam of illumination 510 for irradiating target droplet materials to produce a plasma, an aperture 512 to allow through a gas flow and beam of radiation 510, and a flow adjustment structure 513.

[0075] In some aspects, a buffer gas can be provided to a plasma region of radiation source 500. A number of configurations are envisaged for delivering a buffer gas (e.g., hydrogen) to the irradiation region. Depending on the arrangement of the buffer gas source, one or more optical elements 508 can affect gas flow paths and interfere with delivery of the buffer gas to the irradiation (e.g., turbulence due to physical obstructions in the path of the gas). The turbulence can be accounted for if the configuration of one or more optical elements 508 is static and by carefully arranging the paths of gas flow. However, as optical sources change and evolve, it is envisaged that newer and different optical configurations of one or more optical elements 508 can be implemented. Changing a configuration of one or more optical elements 508 can alter gas flow and adversely impact flow performance of the buffer gas. Therefore, it is desirable to provide a gas flow system that is capable of adapting to changes of the hardware structure in a radiation source.

[0076] In some aspects, jet flow generator 516 can comprise a flow injector 518 and a diffuser 520. Flow injector 518 and diffuser 520 can have a ring shaped structure (see description and illustration of FIG. 7). Flow injector 518 and diffuser 520 can output a buffer gas, such as hydrogen, helium, argon and nitrogen used for addressing issues with EUV plasma material as described herein. The directionality of the initial output from jet flow generator 516 can be as shown by arrows of high velocity output 522 and diffuse output 524. High velocity output 522 can be directed radially inward toward an axis 526. Axis 526 can be aligned with an irradiation region or a primary focus of radiation source 500. Beam of radiation 510 can be directed substantially parallel to axis 526 that is aligned with the irradiation region at which beam of radiation 510 meets droplets in order to produce a plasma. A pressure differential 523 can be setup (e.g., using a vacuum) such that high velocity output 522 can be further tilted according to pressure differential 523 (e.g., having a more vertically upward component), in addition to the radially inward component. In this manner, a jet flow 528 can be generated that is output through aperture 512 and toward the irradiation region.

[0077] In some aspects, diffuser 520 can generate diffuse output 524 along a direction that is, initially, substantially anti-parallel to jet flow 528 (e.g., downward toward optical system 504, away from collector 502). The pressure differential that gives jet flow 528 its directionality can also be usedfor drawing diffuse output 524 toward axis 526 — radially inward. As will be described further below with respect to other figures, diffuse output 524 can be combined with high velocity output 522 in order to control a spread of jet flow 528. Jet flow generator 516 can also comprise a flow distributor to distribute an input gas load to flow injector 518 and diffuser 520. The flow distributor can be implemented as feeds 530 and 532 (e.g., first and second feeds) and a flow control 534. The gas load through each of feeds 530 and 532 can be independently controlled using flow control 534. Flow control 534 can adjust a ratio — the ratio of a portion of an input gas supplied to flow injector 518 to a portion of the input gas supplied to diffuser 520 — so as to control the velocity profile of jet flow 528.

[0078] It is to be appreciated that velocity profile and flow rates are interrelated, but also distinct — as evidenced by their distinct units. Velocity is measured as distance over unit time (e.g., meters per second or m / s). A velocity profile of a flow can be considered as the distribution of velocities across a cross-section of flow. In an example, a velocity at a center of a flow (e g., in a duct) can be higher compared to velocities at an edge of the flow (e.g., closer to a wall of the duct). In contrast, flow rates are measured in volume over unit time (e.g., cubic feet per minutes (cfm) or standard liters per minute (slm)). A high flow rate (e.g., high slm) can be an indication of a high velocity flow. However, a high flow rate can also be an indication of a high volume flow at slower velocity (e.g., slow but high volume flow through a wide duct). While achieving a high flow rate can be straightforward (e.g., either enlarge a cross-section of flow or increase pressure), controlling a velocity profile of a jet flow can be challenging.

[0079] Aspects disclosed herein can achieve control of a velocity profile of a jet flow via a jet flow generator. Example velocity profiles are described in more detail in reference to FIG. 8, which is covered further below.

[0080] In some aspects, flow injector 518 can shape jet flow 528 as a cone flow. The cone flow can be achieved by adjusting the velocity profile of jet flow 528. Flow injector 518 can be used to adjust a symmetry of the cone flow (or the symmetry of any shape of jet flow 528, not just cone flows). Diffuser 520 can adjust a width of the cone flow. Flow adjustment structure 513 can be designed to be symmetric about axis 526. Flow adjustment structure 513 can adjust a shape (e.g., symmetry) and / or intensity of jet flow 528. In some aspects, adjustment structure 513 can be asymmetric about axis 526. The asymmetry can be used to a tilt jet structure, a feature that is described further below with reference to FIG. 10.

[0081] FIG. 6 shows a jet flow generator 616 for use with a radiation source 600, according to some aspects. Radiation source 600 includes a collector 602, an optical system 604, one or more optical elements 608, a beam of illumination 610, an aperture 612, a flow adjustment structure 613, a jet flow generator 616, a flow injector 618, a diffuser 620, a high velocity output 622, a pressure differential 623, a diffuse output 624, an axis 626, a jet flow 628, and a feed 630.

[0082] Jet flow 616 implements a single feed 630 and includes a flow splitter 636 disposed on the body or frame of flow injector 618 and / or diffuser 620. Flow splitter 636 can receive a single gasinput load from feed 630 and then split the gas input load. Flow splitter 636 can adjust a ratio — the ratio of a portion of an input gas supplied to flow injector 618 to a portion of the input gas supplied to diffuser 620 — so as to control the velocity profile of jet flow 628.

[0083] FIG. 7 shows a layout view (left) and a perspective cross-section (right) of a jet flow generator 716, according to some aspects. In some aspects, jet flow generator 716 is illustrated so as to have correspondence with elements of FIG. 6 (e.g., a flow splitter 736 is shown). However, it is to be appreciated that descriptions of FIG. 7 can also apply to jet flow FIG. 5 by replacing the splitter / single-feed setup with a two-feed setup. Therefore, unless otherwise noted, descriptions of elements of FIGS. 5 and 6 can also apply to elements of FIG. 7. Elements appearing in FIG. 7 that correspond to elements in FIGS. 5 and 6 can have like reference numbers (e.g., reference numbers sharing the two right-most numeric digits). Such elements in FIG. 7 can include, for example, jet flow generator 716, a flow injector 718, a diffuser 720, a high velocity output 722, a diffuse output 724, an axis 726, a feed 730, and a flow splitter 736.

[0084] In some aspects, jet flow generator 716 can comprise a support 738. Support 738 can provide a frame structure for supporting flow injector 718 and diffuser 720. Jet flow generator 716 can also comprise an aperture 740. In a radiation source, jet flow generator 716 can be disposed such that aperture 740 is coincident with aperture 512 / 612 (FIGS. 5 and 6) (e.g., at least partially overlapping). The apertures can allow beam of radiation 510 / 610 and jet flow 528 / 628 (FIGS. 5 and 6) to pass through unobstructed.

[0085] In some aspects, flow injector 718 can comprise a cavity 742 and / or a cavity 744 (e.g., first and second cavities of the flow injector). Cavity 742 and / or cavity 744 can be ring-shaped cavities. The ring shape of the cavities can be contiguous (e.g., uninterrupted cavity structure) or can be implemented comprising two or more segments of the ring. Cavity 742 and cavity 744 can be concentric ring-shaped cavities. Cavity 742 can be have a larger ring diameter than cavity 744 (e.g., outer cavity is farther from the central axis than the inner cavity while the inner cavity is closer to the central axis than the outer cavity). Cavity 742 can provide a pressure gradient for a flow of gas in flow injector 716. Cavity 744 can receive the flow of gas from cavity 742 and diffuse the flow of gas so as to avoid overly narrowing jet flow 528 / 628 (FIGS. 5 and 6).

[0086] In some aspects, flow injector can also comprise an output 746 and / or an output 748. The pressure gradient in flow injector 718 (e.g., generated by cavity 744) can cause an input gas load to flow toward outputs 746 and 748 at a high velocity. The working pressure can be in the range of about 150 to 20000 Pa (e.g., at the input). The working flow rate can be in the range of about 80 to 200 slm. If the flow rate is smaller than 80 slm, a jet flow is not sufficient to inhibit tin contamination, in some instances. If the flow rate is greater than 200 slm, a jet flow easily overshoots and misaligns with a dynamic gas lock flow, in some instances. The peak flow velocity at the center of the jet flow can be in the range of about 200 to 400 m / s. The high velocity gas flowing through cavities 742 and / or 744 can be ejected at outputs 746 and 748 to generate jet flow 528 / 628 (FIGS. 5 and 6). Output 746 can bea slit opening along the ring-shaped inner perimeter of flow injector 718. The structure of output 746 can be a contiguous slit or two or more segments of slits (the segmented example is illustrated in FIG. 7). High velocity output 722 ejected via output 746 can be directed radially inward toward axis 726. Output 748 can be another slit opening along the ring-shaped inner perimeter of flow injector 718. Output 748 can be disposed above (e.g., up as in the direction of jet flow 528 / 628 (FIGS. 5 and 6)) with respect to output 746. The role of output 748 can be to impart additional directionality to the ejected gas. Whereas the ejected gas from output 746 can be primarily radially inward, the ejected gas from output 748 can be both radially inward and upward in the direction of jet flow 528 / 628 (FIGS. 5 and 6) (e.g., at an angle with respect to the gas ejected from output 748).

[0087] In some aspects, diffuser 720 can comprise a cavity 750 and / or a cavity 752 (e.g., first and second cavities of the diffuser). Cavity 750 and / or cavity 752 can be ring-shaped cavities. The ring shape of the cavities can be contiguous (e.g., uninterrupted cavity structure) or can be implemented comprising two or more segments of the ring. Cavity 750 and cavity 752 can be concentric ringshaped cavities. Cavity 750 can have a larger ring diameter and be outside of cavity 752 (e.g., outer cavity is farther from the central axis than the inner cavity while the inner cavity is closer to the central axis than the outer cavity). Diffuser 720 can receive an input gas load to generate a gas flow through cavity 752 to cavity 750. Cavity 752 can generate a pressure differential to guide and spread the gas into cavity 750.

[0088] In some aspects, diffuser 720 can comprise spray holes 754 at a face of diffuser 720 that is facing opposite of the direction of propagation of jet flow jet flow 528 / 628 and / or beam of radiation 510 / 610 (FIGS. 5 and 6) (e.g., down-facing). Gas from diffuser 720 can be ejected via spray holes 754 to produce diffuse output 724. The diffuse gas from spray holes 754 is biased by a pressure differential so as to drift toward high velocity output 722, where the diffuse gas and the high velocity gas are combined to form jet flow 528 / 628 with a controllable velocity profile.

[0089] FIG. 8 shows graphs 802, 804, and 806 of the velocity profile of jet flow for different settings of a jet flow generator, according to some aspects. In some aspects, the vertical axes of the graphs represent a velocity in normalized velocity units. The horizontal axes of the graphs represent a radial distance from a center of a jet flow in normalized length units. In some aspects, an approximate width of the “bell curves” of the velocity profiles can be about the width of apertures.

[0090] In some aspects, graph 802 represents the velocity profile when the flow injector receives about 100% of the input gas load while a diffuser receives about 0% of the input gas load. With a severely diminished diffuser contribution, the velocity profile of the jet flow is as shown — a narrow cone profile. The narrow cone is narrower than those illustrated in graphs 804 and 806.

[0091] In some aspects, as the injector-to-diffuser gas load ratio is adjusted to about 80:20, the velocity profile can resemble that of graph 804. Comparing graph 804 to 802, the velocity profile of graph 804 is slightly broadened and has a dip at the center (e g., “donut-like profile”).

[0092] In some aspects, as the injector-to-diffuser gas load ratio is adjusted to about 60:40, the velocity profde can resemble that of graph 806. Comparing graph 806 to those of graphs 802 and 804, the velocity profde of graph 806 is again more broadened and is relatively flat (e.g., “top hat profde”). Further velocity profdes are envisaged based on other adjustments of the jet flow generators.

[0093] FIG. 9 shows a cross-section of a velocity intensity map of a jet flow 928, according to some aspects. In some aspects, FIG. 9 is illustrated so as to have correspondence with elements of FIGS. 5- 7. Therefore, unless otherwise noted, descriptions of elements of FIGS. 5-7 can also apply to elements of FIG. 9. Elements appearing in FIG. 9 that correspond to elements in FIGS. 5-7 can have like reference numbers (e g., reference numbers sharing the two right -most numeric digits). Such elements in FIG. 9 can include, for example, a high velocity output 922, a diffuse output 924, axis 926, and jet flow 928.

[0094] In some aspects, the velocity intensity map of jet flow 928 corresponds to the cross-section at line AA' of FIG. 7. The velocities are represented in grayscale, where darker is a higher velocity and lighter / brighter is a slower velocity (values are normalized so as to be unitless). To feed jet flow 928, high velocity output 922 is ejected at outputs 746 and 748 (FIG. 7). Diffuse output 924 can be supplied from diffuser 520 / 620 / 720 (FIGS. 5-7).

[0095] In some aspects, as the flows converge toward axis 926, a high-pressure region is formed. A pressure differential with an upward bias (e g., lower-pressure region is above) can establish the upward direction of jet flow 928. The intensity map of velocities in FIG. 9 shows a substantially same velocity magnitude for most of the cone flow, with some slowing of the flow toward the outer fringes of the flow. This configuration corresponds to the velocity profile of graph 806 (FIG. 8).

[0096] FIG. 10 shows a jet flow 1028 used in a radiation source 1000, according to some aspects. In some aspects, unless otherwise noted, descriptions of elements of FIGS. 5-7 can also apply to elements of FIG. 10. Elements appearing in FIG. 10 that correspond to elements in FIGS. 5-7 can have like reference numbers (e.g., reference numbers sharing the two right-most numeric digits). Such elements in FIG. 10 can include, for example, collector 1002 and jet flow 1028.

[0097] In some aspects, radiation source 1000 can generate a plasma at irradiation region 1056. As explained above, the plasma is generated by irradiating a target material (e.g., liquid tin droplets) with a high-energy light pulse. When the target material exits the plasma phase, the target material can be considered a spent waste material to be removed from the vicinity in order to make way for new target material in order to initiate a new plasma ignition (a process that can occur periodically at a high frequency rate). To protect collector 1002 from the waste material (it is a contaminant), jet flow 1028 can be used to guide the waste material toward an exhaust 1058.

[0098] It was explained above that aspects of jet flow generators and flow adjustment structures described herein can control velocity profiles, directionality, and symmetry of a jet flow. In some aspects, a jet flow generator and / or a flow adjustment structure can be used to cause an asymmetric velocity profile so as to deflect jet flow 1028 toward a desired direction. Jet flow 1028 can bedeflected toward exhaust 1058 (toward positive y) to minimize the travel distance of the waste material from irradiation region 1056. Jet flow 1028 can be deflected away from exhaust 1058 (toward negative y). Jet flow 1028 can be deflected towards a waste capture element or a shroud. Jet flow 1028 can be deflected in an arbitrary direction. Deflecting jet flow 1028 can reduce risk of downstream contamination of a lithographic apparatus. The inner wall of the plasma chamber of radiation source 1000 may be coated with a wall liner. By adjusting a deflection of jet flow 1028, a lifetime of the wall liner can be increased by reducing or spreading the waste material deposition

[0099] A pressure differential can also be used to further bias the plume of jet flow 1028. The tilt can be, for example, from about 10 degrees to about 30 degrees with respect to an axis extending along a direction of a beam radiation to direct jet flow 1028 toward exhaust 1058. The tilt can also be adjusted azimuthally with respect to the axis, for example toward exhaust 1058, away from exhaust, 1058, or any other direction within the 360 degrees range of the azimuth. The jet flow generator and / or the flow adjustment structure can tilt jet flow 1028 toward a desired direction by adjusting the velocity profile. For aiming the jet flow toward exhaust 1058, the injector-to-diffuser gas load ratio can be about from 60:40 to about 80:20.

[0100] Jet flow generator 516 / 616 / 716 (FIGS. 5-7) can be used to vastly reduce the deposition rate of waste material (e.g., by a factor of about 2) compared to a performance of other gas flow generators.

[0101] FIG. 11 shows a method 1100 for controlling a velocity profile of a jet flow, according to some aspects.

[0102] In some aspects, at operation 1102, a velocity profile of the jet flow of a gas is adjusted using a flow injector. The structure of the flow injector can be as described above (e.g., having one or more cavities to generate a pressure gradient).

[0103] In some aspects, at operations 1304, a spread of the jet flow is adjusted using a diffuser. The structure of the diffuser can be as described above (e.g., having spray holes to generate a diffuse gas output). Operation 1104 can be performed simultaneously with operation 1102.

[0104] In some aspects, at operation 1106, the jet flow is measured to determine whether the velocity profile is within a nominal or a pre-determined range (e.g., a top-hat profile). If not within the nominal range, operations 1102 and / or 1104 can be repeated to further fine tune the velocity profile and achieve nominal flow performance. If the velocity profile is within the nominal range, then the method can proceed to operation 1108 to terminate adjustment operations.

[0105] The method steps of FIG. 11 can be performed in any conceivable order and it is not required that all steps be performed. Moreover, the method steps of FIG. 11 described above merely reflect an example of steps and are not limiting. That is, further method steps and functions are envisaged based aspects described in reference to FIGS. 1-10.

[0106] The terms “radiation,” “beam,” “light,” “illumination,” or the like can be used herein to refer to one or more types of electromagnetic radiation, for example, ultraviolet (UV) radiation (forexample, having a wavelength Z of 365, 248, 193, 157 or 126 nm), extreme ultraviolet (EUV or soft X-ray) radiation (for example, having a wavelength in the range of 5-100 nm such as, for example, 13.5 nm), or hard X-ray working at less than 5 nm, as well as particle beams, such as ion beams or electron beams. Generally, radiation having wavelengths between about 400 to about 700 nm is considered visible radiation; radiation having wavelengths between about 780-3000 nm (or larger) is considered IR radiation. UV refers to radiation with wavelengths of approximately 100-400 nm. Within lithography, the term “UV” also applies to the wavelengths that can be produced by a mercury discharge lamp: G-line 436 nm; H-line 405 nm; and / or, I-line 365 nm. Vacuum UV, or VUV (i.e., UV absorbed by gas), refers to radiation having a wavelength of approximately 100-200 nm. It should be appreciated that radiation having a wavelength in the range of, for example, 5-20 nm relates to radiation with a certain wavelength band, of which at least part is in the range of 5-20 nm.

[0107] Although some aspects of the present disclosure are described in the context of lithographic apparatuses in the manufacture of ICs, it should be understood that lithographic apparatuses described herein can be used in other applications, for example, in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, ECDs, thin-film magnetic heads, etc. Those skilled in the art will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein can be considered as specific examples of the more general terms “substrate” or “target portion”, respectively. A substrate can be processed before or after exposure in, for example, a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) and / or a metrology unit. Where applicable, aspects disclosed herein can be applied to such and other substrate processing tools. Furthermore, a substrate can be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein can also refer to a substrate that already contains multiple processed layers.

[0108] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0109] The present disclosure has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. The foregoing description of specific aspects will so fully reveal the general nature of the present disclosure that others can, by applying knowledge within the skill of the art, readily modify and / or adapt for various applications such specific aspects, without undue experimentation and without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed aspects, based on the teaching and guidance presented herein.

[0110] It is to be understood that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections can set forth one or more, but not necessarily all, aspects of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way. The breadth and scope of the protected subject matter should not be limited by any of the abovedescribed aspects, but should be defined in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A radiation source comprising: a matter delivery system configured to direct target material to a target region; an illumination source configured to irradiate the target material at the target region to generate radiation as an output of the radiation source; and a jet flow generator configured to direct a jet flow of a gas to the target region, the jet flow generator comprising: a flow injector configured to adjust a velocity profile of the jet flow; and a diffuser configured to adjust a spread of the jet flow.

2. The radiation source of claim 1, wherein the jet flow is a cone flow and the flow injector is further configured to adjust a symmetry of the cone flow.

3. The radiation source of claim 2, wherein the diffuser is further configured to adjust a dimension of the cone flow.

4. The radiation source of claim 1, wherein the flow injector comprises a cavity configured to generate a pressure gradient for a flow of the gas in the flow injector.

5. The radiation source of claim 4, wherein the cavity is a ring-shaped cavity.

6. The radiation source of claim 4, wherein: the flow injector further comprises another cavity coupled to the cavity by a duct; the cavity is further configured to inject the flow of the gas into the other cavity; and the other cavity is configured to reduce a velocity of the injected flow.

7. The radiation source of claim 1, wherein the diffuser comprises spray holes configured to generate a diffuse gas flow to combine with the jet flow at an output structure of the flow injector.

8. The radiation source of claim 1, wherein the jet flow generator further comprises a flow splitter configured to adjust a ratio of a portion of an input gas supplied to the flow injector to a portion of the input gas supplied to the diffuser so as to control the velocity profile.

9. The radiation source of claim 1, further comprising a flow adjustment structure configured to tilt the j et flow to direct the j et flow to an exhaust port of the radiation source .

10. A jet flow generator comprising: a flow injector configured to adjust a velocity profile of a jet flow of a gas; and a diffuser configured to adjust a spread of the jet flow, wherein the jet flow generator is configured to direct the jet flow with a velocity profile toward a target region.

11. The jet flow generator of claim 10, wherein the flow injector is further configured to adjust the velocity profile so as to shape the jet flow as a cone flow and to adjust a symmetry of the cone flow, and the diffuser is further configured to adjust a dimension of the cone flow.

12. The jet flow generator of claim 11, wherein a flow rate of the jet flow is approximately 80 to 200 liters per minute.

13. The j et flow generator of claim 10, wherein the flow inj ector comprises a ring-shaped cavity configured to generate a pressure gradient for a flow of the gas in the flow injector.

14. The jet flow generator of claim 13, wherein: the flow injector further comprises another cavity coupled to the cavity by a duct; the cavity is further configured to inject the flow of the gas into the other cavity; and the other cavity is configured to reduce a velocity of the injected flow.

15. The j et flow generator of claim 10, wherein the difluser is further configured to output a diffuse gas flow in a direction that is substantially anti -parallel to the jet flow.

16. The jet flow generator of claim 10, wherein the jet flow generator is configured to adjust a ratio of a portion of an input gas supplied to the flow injector to a portion of the input gas supplied to the diffuser so as to control the velocity profile, wherein the velocity profile is shaped a narrow cone profile, a donut-like profile, or a top-hat profile based on the ratio.

17. The jet flow generator of claim 10, wherein the jet flow generator is further configured to tilt the jet flow to direct the jet flow to an exhaust port of the radiation source.

18. A method comprising : adjusting a velocity profile of a jet flow of a gas using a flow injector comprising a cavity to generate a pressure gradient for a flow of the gas in the flow injector; and adjusting a spread of the jet flow using a diffuser comprising spray holes to generate a diffuse gas flow to combine with the jet flow at an output structure of the flow injector.

19. The method of claim 18, further comprising adjusting a ratio using a flow splitter to control the velocity profile, the ratio being a ratio of a portion of an input gas supplied to the flow injector to a portion of the input gas supplied to the diffuser.

20. The method of claim 18, further comprising measuring the velocity profile of the jet flow; and deciding whether the velocity profile is within a pre-determined range

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