Laser beam aperture

Abstract

A light source for a lithography system includes an optical component and an aperture. The optical component includes a first side with first and second surfaces. The aperture is positioned on or adjacent to and parallel to the first surface of the first side of the prism. The aperture includes a first part and a second part. The first part of the aperture blocks light from entering the optical component, and can reflect a portion of an incoming beam towards a beam dump. The second part of the aperture allows a portion of a beam to enter and exit the first side of the optical component.

Description

LASER BEAM APERTURECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 615,991, filed December 29, 2023, titled LASER BEAM APERTURE, which is incorporated herein by reference in its entirety.FIELD

[0002] The present disclosure relates to laser light sources, such as deep ultraviolet (DUV), extreme ultraviolet (EUV) and X-ray radiation. The laser light sources can be used as, for example, exposure radiation in lithographic apparatuses and systems.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 radiationsensitive 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 deep ultraviolet (DUV) light can be used to produce extremely small features on a substrate. DUV light generally refers to radiation having wavelengths ranging from 126 nm to 428 nm. A pulsed- discharge light source, such as a gas discharge laser, can be used to generate DUV light.

[0005] Alternatively, 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.

[0006] 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.

[0007] Throughput of a lithographic apparatus can be affected by power of light generated by a radiation source in an illumination system. As a radiation source generates higher power light, optical components of the radiation source become more susceptible to damage. When damage reaches a certain threshold, shut down and replacement of the optical components is required.SUMMARY

[0008] Accordingly, elements of a laser light source can be designed that can withstand high power light generation. For example, an aperture for an optical component, such as a beam reverser module of a laser light source can be designed and positioned based on aspects described herein.

[0009] In some aspects, a system comprises an optical component and an aperture. In some aspects the optical component comprises a first side. The first side includes a first surface and a second surface. In some aspects, the aperture can be positioned on or adjacent to and substantially parallel to the first surface of the first side of the optical component. In some aspects, the aperture can comprise a first part and a second part. In some aspects, the first part of the aperture is configured to block light from entering the prism. In some aspects, the second part of the aperture is configured to allow a first portion of a beam to enter and exit the first side of the prism. In some aspects, the first part of the aperture reflects a second portion of the beam towards the beam dump.

[0010] In some aspects, a lithography system comprises a light source. In some aspects the light source comprises a chamber, an optical component comprising a first surface, and an aperture on or adjacent to and parallel to the first surface of the optical component. In some aspects, the optical component is configured to reverse a direction of a beam exiting a chamber. In some aspects, the aperture is configured to block a portion of a beam from reaching the optical component. In some aspects, the aperture reduces damage to the optical component and chamber by reducing fluence of the beam.

[0011] 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 the specific 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

[0012] 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.

[0013] FIG. 1A and IB show a lithographic apparatus, according to some aspects.

[0014] FIG. 1C shows a lithographic cell, according to some aspects.

[0015] FIGS. 2A and 2B show another lithographic apparatus, according to some aspects.

[0016] FIG. 3 shows a radiation source, according to some aspects.

[0017] FIG. 4 shows a radiation subsystem, according to some aspects.

[0018] FIG. 5 shows a radiation apparatus, according some aspects.

[0019] FIGS. 6A and 6B show exemplary embodiments of a beam reversing optical component and an aperture.

[0020] FIG. 7 shows an aperture, according to some aspects.

[0021] 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 leftmost 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

[0022] 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 to effect such feature, structure, or characteristic in connection with other aspects whether or not explicitly described.

[0023] 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.

[0024] The terms “about,” “approximately,” or the like can be used herein to indicate 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).

[0025] Enumerative adjectives (e.g., “first,” “second,” “third,” or the like) can be used to distinguish like elements without establishing an order, hierarchy, quantity, or permanent numeric assignment(unless otherwise noted). For example, the terms “first target” and “second target” can be used in a manner analogous to “ithtarget” and “jthtarget” so as to facilitate the distinguishing of two targets without specifying a particular order, hierarchy, quantity, or immutable numeric correspondence.

[0026] 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 include 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.

[0027] 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.Example Lithographic Systems

[0028] FIGS. 1A and IB show schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100’, respectively, in which embodiments of the present disclosure may be implemented. Lithographic apparatus 100 and lithographic apparatus 100’ each include 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 and connected to a first positioner PM configured to accurately position the 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 the substrate W. Lithographic apparatus 100 and 100’ also have a projection system PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of the substrate W. In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100’, the patterning device MA and the projection system PS are transmissive.

[0029] The illumination system IL may include 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.

[0030] The support structure MT holds the 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 at least one of the lithographic apparatus 100 and 100’, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT may be a frame or a table, for example, which may be fixed or movable, as required. By using sensors, the support structure MT may ensure that the patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0031] The term “patterning device” MA should be broadly interpreted as referring to any device that may be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in the target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0032] The terms “inspection apparatus,” “metrology system,” or the like may be used herein to refer to, e.g., a device or system used for measuring a property of a structure (e.g., overlay error, critical dimension parameters) or used in a lithographic apparatus to inspect an alignment of a wafer (e.g., alignment apparatus).

[0033] The patterning device MA may be transmissive (as in lithographic apparatus 100’ ofFIG. IB) or reflective (as in lithographic apparatus 100 of FIG. 1A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography, and include 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 may be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by a matrix of small mirrors.

[0034] The term “projection system” PS may encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic 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. A vacuum environment may be used for EUV or electron beam radiation since other gases may absorb too much radiation or electrons. A vacuum environment may therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0035] Lithographic apparatus 100 and / or lithographic apparatus 100’ may 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, the additional substrate tables WT may be used in parallel, or preparatory steps may 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 not be a substrate table WT.

[0036] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fdl a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing 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, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0037] Referring to FIGS. 1A and IB, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 100’ may be separate physical entities, for example, when the source SO is an excimer laser. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100’, and the radiation beam B passes from the source SO to the illuminator IL with the aid of a beam delivery system BD (in FIG. IB) including, for example, suitable directing mirrors and / or a beam expander. In other cases, the source SO may be an integral part of the lithographic apparatus 100, 100’, for example, when the source SO is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD, if required, may be referred to as a radiation system.

[0038] The illuminator IL may include an adjuster AD (in FIG. IB) for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as “n-outer” and “n-inner,” respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. In addition, the illuminator IL may comprise various other components (in FIG. IB), such as an integrator IN and a condenser CO. The illuminator IL may be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0039] Referring to FIG. 1A, the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device (for example, mask) MA, the radiation beam B passes through the 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, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT may be moved accurately (for example, 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 IF1 may be used to accurately position the patterning device (for example, mask) MA withrespect to the path of the radiation beam B. Patterning device (for example, mask) MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.

[0040] Referring to FIG. IB, the radiation beam B is incident on the patterning device (for example, mask MA), which is held on the support structure (for example, mask table MT), and is patterned by the patterning device. Having traversed the 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. The projection system has a pupil conjugate PPU to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse a mask pattern without being affected by diffraction at the mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0041] The projection system PS projects an image of the mask pattern MP, where the image is formed by diffracted beams produced from the mark pattern MP by radiation from the intensity distribution, onto a photoresist layer coated on the substrate W. For example, the mask pattern MP may include an array of lines and spaces. A diffraction of radiation at the array and different from zeroth order diffraction generates diverted diffracted beams with a change of direction in a direction perpendicular to the lines. Undiffracted beams (i.e., so-called zeroth order diffracted beams) traverse the pattern without any change in propagation direction. The zeroth order diffracted beams traverse an upper lens or upper lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zeroth order diffracted beams is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IU. The aperture device PD, for example, is disposed at or substantially at a plane that includes the pupil conjugate PPU of the projection system PS.

[0042] The projection system PS is arranged to capture, by means of a lens or lens group U, not only the zeroth order diffracted beams, but also first-order or first- and higher-order diffracted beams (not shown). In some embodiments, dipole illumination for imaging line patterns extending in a direction perpendicular to a line may be used to utilize the resolution enhancement effect of dipole illumination. For example, first-order diffracted beams interfere with corresponding zeroth-order diffracted beams at the level of the wafer W to create an image of the line pattern MP at highest possible resolution and process window (i.e., usable depth of focus in combination with tolerable exposure dose deviations). In some embodiments, astigmatism aberration may be reduced by providing radiation poles (not shown) in opposite quadrants of the illumination system pupil IPU. Further, in some embodiments, astigmatism aberration may be reduced by blocking the zeroth order beams in the pupil conjugate PPU of the projection system associated with radiation poles in opposite quadrants. This is described in more detail in US 7,511,799 B2, issued Mar. 31, 2009, which is incorporated by reference herein in its entirety.

[0043] With the aid of the second positioner PW and position sensor IFD (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT may be moved accurately (for example, 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 (not shown in FIG. IB) may be used to accurately position the mask MA with respect to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during a scan).

[0044] In general, movement of the mask table MT may be realized with the aid of a long- stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected to a short-stroke actuator only or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks Ml, M2, and substrate alignment marks Pl , P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they may be located in spaces between target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0045] Mask table MT and patterning device MA may be in a vacuum chamber V, where an in-vacuum robot IVR may be used to move patterning devices such as a mask in and out of vacuum chamber. Alternatively, when mask table MT and patterning device MA are outside of the vacuum chamber, an out-of-vacuum robot may be used for various transportation operations, similar to the invacuum robot IVR. Both the in-vacuum and out-of-vacuum robots need to be calibrated for a smooth transfer of any payload (e.g., mask) to a fixed kinematic mount of a transfer station.

[0046] The lithographic apparatus 100 and 100’ may be used in at least one of the following modes:

[0047] 1. In step mode, the support structure (for example, mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B 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 may be exposed.

[0048] 2. In scan mode, the support structure (for example, mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B 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 (for example, mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0049] 3. In another mode, the support structure (for example, mask table) MT is kept substantially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO may be employed and the programmable patterning device is updated asrequired after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation may be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0050] Combinations and / or variations on the described modes of use or entirely different modes of use may also be employed.

[0051] In some aspects, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. In general, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0052] In some aspects, lithographic apparatus 100’ can comprise a deep ultraviolet (DUV) source, which is configured to generate a beam of DUV radiation for DUV lithography. In general, the DUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the DUV radiation beam of the DUV source.

[0053] FIG. 1C shows a lithographic cell 110, also sometimes referred to a lithocell or cluster, according to some aspects. Lithographic apparatus 100 or 100’can form part of lithographic cell 110. Lithographic cell 110 can also include one or more apparatuses to perform pre- and post-exposure processes on a substrate. Examples of such apparatuses 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 can pick up substrates from input / output ports I / Ol, I / O2, move them between the different process apparatuses and deliver the substrates to a loading bay LB of lithographic apparatus 100 or 100’ . The different apparatuses, which are often collectively referred to as the track, can be under the control of a track control unit TCU, which can itself be controlled by a supervisory control system SCS. Supervisory control system can also control lithographic apparatus 100 or 100’ via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0054] FIG. 2A shows a lithographic apparatus 200, including source SO (e.g., source collector apparatus), illumination system IL, and projection system PS, according to some aspects. Source SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 220 of source SO. An EUV radiation emitting plasma 210 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.

[0055] The radiation emitted by the EUV radiation emitting plasma 210 can be passed from a source chamber 211 into a collector chamber 212 via an optional gas barrier or contaminant trap 230 (in some cases also referred to as contaminant barrier or foil trap), which is positioned in or behind an opening in source chamber 211. Contaminant trap 230 can comprise a channel structure. Contamination trap 230 can also comprise a gas barrier and / or a channel structure.

[0056] In some aspects, collector chamber 212 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 251 and a downstream radiation collector side 252. Radiation that traverses radiation collector CO can be reflected off a grating spectral filter 240 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 219 of enclosing structure 220. The virtual source point INTF can be an image of the EUV radiation emitting plasma 210. Grating spectral filter 240 can be used for suppressing infrared (IR) radiation.

[0057] Subsequently, the radiation traverses the illumination system IL. Illumination system IL can include a faceted field mirror device 222 and a faceted pupil mirror device 224 arranged to provide a desired angular distribution of radiation beam 221, at patterning device MA, as well as a desired uniformity of radiation intensity at patterning device MA. Upon reflection of beam of radiation 221 at patterning device MA, held by support structure MT, a patterned beam 226 is formed and the patterned beam 226 is imaged by projection system PS via reflective elements 228, 229 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 221 to patterning device MA.

[0058] More elements than shown can generally be present in illumination system IL and projection system PS. Grating spectral filter 240 can optionally be present, depending upon the type of lithographic 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.

[0059] 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.

[0060] Collector CO, as illustrated in FIG. 2A, is depicted as an example of a nested collector with grazing incidence reflectors 253, 254, and 255 (or collector mirror). Grazing incidence reflectors 253, 254, and 255 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.

[0061] FIG. 2B shows lithographic apparatus 200, but with alternative collection optics in source SO, according to some aspects. It should be appreciated that structures shown in FIG. 2A that do not appear in FIG. 2B (for drawing clarity) can still be included in aspects referring to FIG. 2B. Elements in FIG. 2B having the same reference numbers as those in FIG. 2A have the same or substantially similar structures and functions as described in reference to FIG. 2A. In some aspects, the lithographic apparatus 200 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. 2B, illumination system IL and projection system PS are represented combined as an exposure device 256 (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 proximitymask, etc.) that uses EUV light from source SO. Lithographic apparatus 200 can also comprise collector 258 that reflects EUV light from the EUV radiation emitting plasma 210 along a path into the exposure device 256 to irradiate substrate W. Collector 258 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.Example Radiation Source

[0062] There are many applications of pulsed-discharge radiation sources. In some aspects, a pulsed-discharge laser can be used for lithographic processes, medical procedures, machining via laser ablation, laser imprinting, and more. A lithographic apparatus is one example in which a stable radiation source is desirable.

[0063] FIG. 3 shows a radiation source 300, according to some aspects. In some aspects, radiation source 300 is a pulsed-discharge radiation source. A gas discharge laser is an example of a pulsed-discharge radiation source. Source SO of lithographic apparatuses can use implement radiation source 300. Radiation source 300 can comprise a gas chamber 302, a window 304, conduit system 306, and one or more electrodes 310 (also “electrical connection”). Conduit system 306 can comprise a network of valves, conduits, and contaminant fdters (not shown).

[0064] In some aspects, gas chamber 302 can confine a gas 308. Gas 308 includes at least one of nitrogen, halogens, and noble gases, such as fluorine, neon, krypton, argon, xenon and the like. Gas 308 can be rarified via a pressure control system (e.g., vacuum system) that controls a pressure within gas chamber 302. Conduit system 306 is connected to gas chamber 302. Conduit system 306 can allow management of gas 308 in gas chamber 302. For example, conduit system 306 can direct a flow (e.g., circulation) of gas 308 to a filter within conduit system 306 to purify gas 308. A voltage / current can be supplied to gas 308 (e.g., via one or more electrodes 310) to generate radiation 312. The voltage / current can be in the form of pulse with sufficient power to strike a plasma of gas 308. The plasma can generate radiation with a set of wavelengths that depend on energy states of the plasma. The type of gas 308 (e.g., fluorine) can determine the wavelengths that are produced (e.g., DUV wavelengths). Window 304 can allow radiation 312 to exit gas chamber 302.

[0065] FIG. 4 shows a radiation subsystem 400, according to some aspects.In some aspects, radiation subsystem 400 can comprise discharge chamber 402, one or more electrodes 410, and a gas circulator 414. Gas circulator 414 can be blower or an external pressure system that is connected to discharge chamber 402 via ducting. Discharge chamber 402 can confine a gas. Gas 408 includes at least one of nitrogen, halogens, and noble gases, such as fluorine, neon, krypton, argon, xenon or other similar species. To generate radiation, an electrical pulse can be supplied to gas 408 viaelectrodes 410, thereby igniting a plasma of gas 408 at plasma region 416 of gas chamber 402. The generated plasma can release radiation, thereby operating as a radiation source.

[0066] In some aspects, in the process of generating radiation, gas 408 and electrodes 410 can interact chemically. For example, a material of electrodes 410 (e.g., copper) can chemically interact with a chemical content of gas 408 (e.g., fluoride) to create a dust-like byproduct (e.g., metal -fluoride by product). The airborne byproduct can become a contaminant that absorbs radiation in subsequent radiation pulses. Therefore, a gas flow 418 (indicated by arrows) can be implemented in order to optimize the production of radiation by circulating the spent portion of gas 408 and contaminants out of the plasma-generation zone while supplying unspent gas for the next plasma ignition. Gas circulator 414 can generate gas flow 418. Heat exchangers 422 can remove heat from gas 408. In some aspects, chamber 402 can include one or more filters 420 (e.g., screens, traps, etc.) configured to collect particles (e.g., metal fluoride dust) generated by electrodes 410.

[0067] FIG. 5 shows a radiation system 500, according to some aspects.In some aspects, radiation apparatus 500 can include a radiation generation system 520 and an amplification system 522. In some aspects, radiation generation system 520 generates a beam 524 comprising a desired wavelength. In some aspects amplification system 522 receives beam 524 from radiation generation system 520. In some aspects, amplification system 522 amplifies the power of beam 524.

[0068] In some aspects, radiation generation system 520 comprises a gas chamber 502, a wavelength selector 526, and an output coupler 528.

[0069] In some aspects, an electrical pulse is applied to gas 508 to ignite a plasma and generate radiation 512. Molecules of gas 508 can have multiple energy levels capable of decaying with the release of photons (photon wavelengths correspond to the multiple energy levels). Subsequently, a beam of radiation 524 is output from radiation generation system 520.

[0070] A narrow and stable wavelength is desirable for lithographic processes because wavelength instabilities can adversely impact the accuracy of patterns that get printed on a substrate. As a nonlimiting example, beam of radiation 524 can have a DUV wavelength of approximately 193 nm or approximately 248 nm, which can be used for a lithographic process. Therefore, it is desirable to select a narrowband wavelength from the plurality of wavelengths that are generated in the plasma of gas 508.

[0071] In some aspects, wavelength selector 526 can be used to perform wavelength selection. The wavelength selection process can rely on lasing to further amplify the radiation at the desired wavelength in comparison to the unselected wavelengths (e.g., higher signal -to-noise (SNR)). The process can begin by allowing radiation 512 to propagate toward wavelength selector 526 (e.g., can be achieved via implementation of window(s)). Wavelength -dependent reflector 530 can reflect a portion of radiation 512 (the portion that has the selected wavelength) along a “gain path” while rejecting other portions of radiation 512 that have undesirable wavelengths (e.g., diverting unselected wavelengths toward a beam dump). Hence, the wavelength of radiation 512 can be narrowed to a narrowband havinga peak central wavelength and a small full -width-half-maximum. In some aspects, wavelengthdependent reflector 530 can comprise a refractive element (e.g., one or more prisms) and / or a diffractive element (e.g., a grating). Wavelength selector 526 can be referred to as a wavelength narrowing device, narrowing module, line narrowing module (LNM), or the like.

[0072] In some aspects, adjusting the wavelength (e.g., selecting another wavelength) can be achieved by adjusting a position of wavelength-dependent reflector 530 (e.g., rotating a diffractive or refractive element). Diffractive and refractive elements have wavelength -dependent scattering directions. As the position of the diffractive (or refractive) element is changed, a different wavelength can be aligned along the gain path while other wavelengths are directed away from the gain path. The lasing process can then amplify radiation 512 for the adjusted wavelength.

[0073] Additional details about wavelength-selection are described in U.S. Patent No. 8,254,420, issued on August 28, 2012, which is incorporated by reference herein in its entirety.

[0074] In some aspects, the “gain path” can be defined between wavelength-dependent reflector 530 and output coupler 528, with the plasma of gas 508 being the gain medium. Lasing can be achieved as radiation 512 (at the selected wavelength) bounces back and forth between wavelength-dependent reflector 530 and output coupler 528 (output coupler 528 can have a reflective property). Output coupler 528 can comprise a partial reflector that allows a fraction of the, now amplified, radiation 512 (at the selected wavelength) to be output as beam of radiation 524.

[0075] In some aspects, gas chamber 502 can be referred to as a master oscillator (MO) chamber since radiation 512 is generated at gas chamber 502 and oscillates back and forth through gas chamber 502 to achieve intensity gains.

[0076] In some aspects, line center analysis module 532 receives beam 524 from output coupler 528. In some aspects, a beam modification optical system 534 can modify the size and / or shape of beam 524.

[0077] In some aspects, beam 524 can be amplified by amplification system 522. In some aspects, amplification system 522 comprises a beam modification optical system 536, a chamber 538, a beam turning optical element 540. In some aspects, beam turning optical element 540 includes at least one of a prism, a mirror and a combination thereof.

[0078] In some aspects, beam modification optical system 536 directs beam 524 towards chamber 538, and then towards beam turning optical element 540. In some aspects, beam 524 can propagate from chamber 538 towards beam turning optical element 540 through a window. In some aspects, beam turning optical element 540 modifies the direction of beam 524 so that beam 524 travels back into chamber 538. In some aspects, beam 524 can be amplified through repeated passes through amplification system 522.

[0079] In some aspects, chamber 538 comprises one or more electrodes, a gain medium, such as a gas, and a fan for circulating the gas. In some aspects, a second “gain path” can be defined between beam modification optical system 536 and beam turning optical element 540, with agas in chamber 538 being the gain medium. Lasing can be achieved as radiation 524 bounces back and forth between beammodification optical system 536 and beam turning optical element 540. In some aspects, beam modification optical system 536 comprises an optical coupler 542, for example, a partially reflecting mirror, which can in-couple beam 524 and out-couple a portion of amplified radiation from chamber 538 to form output beam 544.

[0080] In some aspects, output laser beam 544 can be directed through a bandwidth analysis module 546 and then through a pulse stretcher 548. In some aspects, pulse stretcher 548 can stretch each of the pulses of beam 544, for example, in an optical delay unit, to adjust for performance properties of the laser beam. In the context of lithographic processes, beam of radiation 544 can be a radiation beam in a lithographic equipment.Example Beam Turning Optical Element

[0081] In some aspects, as a beam is amplified in an amplification system, optical components in the amplification system are irradiated with a higher fluence, or optical energy per unit area, of radiation. In some aspects, the higher fluence can cause damage to the optical components.

[0082] FIGS. 6A illustrates a beam turning optical element 640, according to some aspects. Beam turning optical element 640 may reverse the direction of a beam as the beam travels through a power amplification chamber. In some aspects, FIG. 6A can represent a more detailed view of a portion of a radiation apparatus.

[0083] A cross-sectional view of beam turning optical element 640 can have a triangle, a tetragon, a pentagon, or a hexagon shape, for example. In some aspects, beam turning optical element 640 can comprise an aperture 650, a prism 652, and a beam dump 654. Aperture 650 includes a first surface facing an incoming beam 624 and a second surface opposite to the first face. The first surface of aperture 650 is configured to reflect incoming beam 624. In some embodiments, the first surface of aperture 650 is a reflective coating, a metallic material, or a multi-layer mirror, or the like. Aperture 650 can comprise one or more openings 651. In some aspects, beam turning optical element 640 reverses the direction of incoming beam 624. In some aspects, beam turning optical element 640 can be designed to withstand a high power beam, for example, a beam with a laser pulse energy of at least 20 milliJoules (mJ).

[0084] In some aspects, prism 652 comprises at least a first side 656, a second side 658, a third side 659 and a fourth side 660. In some aspects, first side 656 comprises a first surface 662 and a second surface 664 opposite to first surface 662. In some aspects, incoming beam 624 is incident on a first facet 661 of beam turning optical element 640 and outgoing beam 624’ exits from a second facet 663 of beam turning optical element 640. In some aspects, first facet 661 and second facet 663 share a same plane. In some aspects, first facet 661 and second facet 663 extend along different planes. In some aspects, at least one of first side 656, second side 658, third side 659 and fourth side 660 comprise a reflective surface.

[0085] In some aspects, aperture 650 is attached to first surface 662 of first side 656. In some aspects, aperture 650 is separated from first surface 662 of first side 656 by a distance up to about 40 cm. Aseparation greater than 40 cm increases spatial accessibility for other component, in some instances. In some embodiments, when first facet 661 and second facet 663 share the same plane, aperture 650 is flat and substantially parallel to the same plane. In another embodiment, when first facet 661 extends along a different plane from that of second facet 663, aperture 650 is bending to be substantially parallel to both facets. In some embodiments, aperture 650 is substantially vertical to at least one of incoming 624 and outgoing beam 624’.

[0086] In some aspects, a first portion 666 of incoming beam 624 enters and exits prism 652 through aperture 650, while a second portion 668 of incoming beam 624 is reflected from aperture 650 towards beam dump 654.

[0087] In some aspects, prism 652 is configured to reverse the direction of beam 624 through internal reflections. First portion 666 of incoming beam 624 can take several different internal reflection paths. For example, in some aspects, first portion 666 reflects from second side 658 to third side 659 before first portion 666 exits prism 652 through aperture opening 651. In some embodiments, the second surface of aperture 650 reflects a third portion 680 of incoming beam 624 and directs third portion 680 toward the fourth side 660 of prism 652. In some embodiments, the second surface of aperture 650 has an anti -reflecting material or a diffusive material.

[0088] In some aspects, first side 656 of prism 652 and / or aperture 650 is tilted at an angle 670 with respect to beam 624 to increase surface area of first side 656 and / or aperture 650 that interacts with beam 624. In some aspects, the surface area can be increased by 30%. In some aspects, the increased surface area can reduce the fluence, or energy delivered per unit area, experienced by aperture 650 from beam 624.

[0089] FIG. 6B illustrates a beam turning optical element 640’, according to some aspects. In some aspects, FIG. 6B can represent a more detailed view of a portion of a radiation apparatus. Elements in FIG. 6B sharing the same numbering as elements in FIG. 6A may have substantially the same function.

[0090] Beam turning optical element 640’ includes an aperture 650’ Aperture 650’ includes a first portion 650’A and a second portion 650’B. The first portion 650’A can include a reflective coating on the first surface 662 of first side 656. First portion 650A’ may reflect light incident on aperture 650’ towards beam dump 654. The second portion 650’B can include a transparent material and / or an area free of any materials. In some aspects, a first region of second portion 65 OB’ may comprise a transparent coating and second region of second portion 650’B may be free of any materials. Second portion 650’B allows a beam of radiation 624 to enter and exit prism 652.

[0091] Aperture 650 or aperture 650’ can be applied to any optical component in a lithography system. For example, the aperture 650 or the aperture 650’ may be applied to an optical component in a light source, an exposure apparatus or an inspection system. Another example of the application is to have the aperture on a chamber window or one or more lenses in a semiconductor manufacturing equipment.

[0092] FIG. 7 illustrates a front view of an aperture 750 according to some aspects. For example, aperture 750 can be an embodiment of aperture 650 or 650’, as described above. Aperture 750 mayreduce the amount of radiation incident on an optical component in a lithography system by reflecting a portion of an incoming beam away from the optical component.

[0093] In some aspects, aperture 750 can comprise a first part 772 and a second part 774. In some aspects, first part 772 can be configured to block, reflect and / or diffuse a beam of radiation, for example towards a beam dump (e.g., beam dump 654 in FIG. 6). In some aspects, second part 774 can be configured to allow a beam of radiation to enter and exit a prism (e.g., prism 652 in FIG. 6).

[0094] Second part 774 can comprise one or more regions (e.g., opening) of aperture 750. In some aspects, second part 774 can comprise a first region 774a and a second region 774b. In some aspects, first region 774a and second region 744b can be configured to allow a beam to enter and exit a prism, respectively. In some embodiments, a dimension D of first region 774a and second region 774b ranges from about 3 nanometer (nm) to about 6 nm. The selected range is mainly determined by factors, such as a material of the optical component, a beam wavelength, and a Brewster angle. A dimension smaller than 3 nm reduces an efficiency, in some instances. A dimension greater than 6 nm, a peak influence increases, in some instances.

[0095] In some aspects, aperture 750 may be an independent element attached to or adjacent to a surface of an optical component, as described in FIG. 6A. First part 772 of aperture 750 may comprise a metal, and second part 774 may comprise one or more openings in the metal. In some aspects, the metal may be polished. First part 772 may additionally comprise a highly reflective or diffusive coating on top of the metal.

[0096] In some aspects, aperture 750 may be a coating on an outer and / or inner surface of an optical component, as described in FIG. 6B. Fist part 772 may comprise a highly reflective coating. Second part 774 may comprise an anti -reflective coating. In some aspects, the highly reflective coating may be applied to an outer surface of the optical component and the anti-reflective coating may be applied to an inner surface of the optical component. In some aspects, when a beam of radiation is incident on the optical component at the Brewster angle, an anti-reflective coating may not be applied. The highly reflective and anti -reflective coatings may be wavelength dependent (i.e., the coatings are only highly / anti -reflective at certain wavelengths).

[0097] It may be understood by one of ordinary skill in the art that an aperture, such as aperture 750, may be applied to a surface of any optical component in a lithography system. For example, an aperture may be applied to an optical component in a power amplifier of an EUV or DUV light source. An aperture may also be applied to a chamber window or one or more lenses in a lithography apparatus.

[0098] 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 (for example, having a wavelength X 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 visibleradiation; 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. Deep UV (DUV) generally refers to radiation having wavelengths ranging from 126 nm to 428 nm, and in some aspects, an excimer laser can generate DUV radiation used within a lithographic apparatus. It should be appreciated that radiation having a wavelength in the range of, for example, 180-200 nm relates to radiation with a certain wavelength band, of which at least part is in the range of 180-200 nm.

[0099] 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, UCDs, 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.

[0100] Furthermore, although some aspects of the present disclosure are described in the context of optical lithography, it should be understood that aspects of the present disclosure are not limited to optical lithography. For example, in imprint lithography, a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device can be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[0101] 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.

[0102] 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, readilymodify 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.

[0103] 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 above -described aspects, but should be defined in accordance with the following claims and their equivalents.

Claims

CLAIMS1. A system comprising: an optical component comprising a first side having a first surface and a second surface; and an aperture comprising a first part and a second part, wherein the first part is configured to block light from entering the optical component, wherein the second part is configured to allow a first portion of a beam to enter and exit the first side of the optical component; wherein the first part of the aperture reflects a second portion of the beam, and wherein the aperture is positioned substantially parallel to the first surface of the first side of the optical component.

2. The system of claim 1, wherein the aperture separate from the optical component.

3. The system of claim 2, wherein the separation from the optical component is shorter than 40 cm.

4. The system of claim 1, wherein the first part of the aperture comprises a coating on the first side of the optical component.

5. The system of claim 3, wherein the first part of the aperture comprises a reflective coating.

6. The system of claim 1, wherein the first part of the aperture comprises a diffusive material.

7. The system of claim 1 , wherein one or more regions of the second part of the optical component includes an antireflective coating.

8. The system of claim 7, wherein the second part of the aperture comprises one or more uncoated regions on the first side of the optical component.

9. The system of claim 1, wherein the first part of the aperture includes at least one of a metallic material, a multilayer mirror, or reflective coating.

10. The system of claim 1, wherein the aperture is configured to withstand a laser pulse energy of at least 20 mJ.

11. A lithography system comprising:a light source comprising: a chamber; an optical component comprising a first side and configured to reverse a direction of an incoming beam exiting the chamber; and an aperture substantially parallel to a first surface on the first side of the optical component and configured to block a portion of the incoming beam entering the optical component.

12. The lithography system of claim 11, wherein the aperture is configured to tolerate a laser pulse energy of at least 20 mJ.

13. The lithography system of claim 11, wherein an angle of tilt of the aperture relative to the incoming beam is configured to increase a surface area of the aperture that interacts with the incoming beam.

14. The lithography system of claim 11, wherein the aperture comprises a first part configured to block light from reaching the optical component and a second part configured to allow a portion of the beam to reach the optical component.

15. The lithography system of claim 14, wherein the first part of the aperture comprises a first side facing the incoming beam and a second side facing the optical component, the first side having a reflective material and the second side having a diffusive material.

16. The lithography system of claim 14, wherein the first part of the aperture comprises a first side facing the incoming beam and a second side facing the optical component, the first side having a first reflective material and the second side having a second reflective material.

17. The lithography system of claim 14, wherein the first part of the aperture comprises a metal plate.

18. The lithography system of claim 17, wherein the second part of the aperture comprises one or more openings in the metal plate.

19. The lithography system of claim 15, wherein the second part of the aperture comprises one or more regions on the first side of the optical component comprising an antireflective coating.

20. The lithography system of claim 15, wherein the second part of the aperture comprises only one uncoated region on the first side of the optical component.

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