Undercut electrode for a gas discharge laser chamber

Abstract

A light source apparatus and an electrode design for use in a discharge chamber of the light source apparatus are provided. The discharge chamber is configured to hold a gas discharge medium configured to output a light beam. The light source apparatus includes a pair of opposing electrodes configured to excite the gas medium to form a discharge plasma. At least one electrode of the pair of opposing electrodes can include a recessed portion or a hollow portion at each end of the electrode or at other suitable locations. The disclosed electrode structure improves the uniformity of the erosion profile of the electrode as the local discharge particle flux is reduced at the recessed portion, significantly extending the lifetime of the discharge chamber by redistributing the discharge particle flux through the electrode with an optimized design of the electrode geometry.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 62 / 955,542, entitled “UNDERCUT ELECTRODES FOR A LIGHTSOURCE,” filed December 31, 2019, and U.S. Application No. 63 / 029,099, entitled “UNDERCUT ELECTRODES FOR A GASDISCHARGE LASER CHAMBER,” filed May 22, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to laser systems such as excimer lasers that generate light, and more specifically to optimized electrode designs for discharge plasmas in gas discharge lasers. Background Technology

[0004] A photolithography apparatus is a machine configured to apply a desired pattern onto a substrate. Photolithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A photolithography apparatus can project a pattern from a patterning apparatus (e.g., a mask, a photomask) onto a layer of radiation-sensitive material (photoresist, or simply "resist") provided on a substrate.

[0005] To project patterns onto a substrate, photolithography equipment can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Photolithography equipment using deep ultraviolet (DUV) radiation with wavelengths in the range of 20 nm to 400 nm, such as 193 nm or 248 nm, can be used to form features on a substrate.

[0006] A master oscillator power amplifier (MOPA) or master oscillator power ring amplifier (MOPRA) is a two-stage laser system that generates a highly coherent amplified beam. The performance of a MOPA or MOPRA is critically related to the master oscillator (MO), power amplifier (PA), and / or power ring amplifier (PRA). The electrodes of the MO, PA, and / or PRA surround a gaseous medium excited into a discharge plasma. Due to the corrosive nature of the gas and plasma, the electrodes may corrode over time. The discharge intensity may be non-uniform along the length of the electrode. Typically, the discharge intensity is highest at the ends of the electrode, and it can also be higher at the center compared to the rest of the length. This relatively elevated localized discharge intensity at the ends or middle of the discharge can lead to increased corrosion at the corresponding locations on the electrode. Non-uniform corrosion of the electrodes can result in poor discharge quality due to gas breakdown between the electrodes generating the discharge plasma, and therefore necessitates premature replacement of the discharge chamber. Summary of the Invention

[0007] Therefore, it is necessary to control the corrosion uniformity of the electrode to increase its lifespan.

[0008] In some embodiments, the light source device includes a chamber configured to hold a gaseous medium. The discharge chamber may be configured to output a light beam. The light source device may also include a pair of opposing electrodes configured to excite the gas into plasma (by means of a so-called breakdown process). In some embodiments, at least one electrode in the pair of opposing electrodes includes a recessed portion formed at each end of the at least one electrode.

[0009] In some embodiments, each electrode in the electrode pair includes a first surface facing inward toward the gas medium and toward the plasma after the gas medium is excited, and a second surface opposite to the first surface, and a recessed portion of at least one electrode is formed in or from each end of the second surface within the second surface.

[0010] In some embodiments, at least one electrode includes a body thickness and a flat first surface facing inward toward the plasma, and the recessed portion includes an undercut portion, wherein the end of at least one electrode has a thickness less than the body thickness.

[0011] In some embodiments, at least one electrode in the electrode pair includes an anode.

[0012] In some embodiments, at least one electrode in the electrode pair includes a cathode.

[0013] In some embodiments, each electrode in the electrode pair includes a recessed portion formed at each end.

[0014] In some embodiments, each electrode in the electrode pair includes a first surface facing inward toward the gaseous medium and toward the discharge plasma after excitation, and a second surface opposite to the first surface, and a recessed portion of at least one electrode is formed between the first and second surfaces.

[0015] Note that, for the sake of brevity, gaseous media and discharge plasma formed by gaseous media may be collectively referred to as gaseous discharge media in the following text.

[0016] In some embodiments, the gas discharge medium includes halogen gas and rare gas to form excimers and / or excitation complexes.

[0017] In some embodiments, the light source further includes an assembly of optical elements configured to form an optical resonator around the chamber.

[0018] In some embodiments, the undercut electrode includes a first surface facing inward toward the gas discharge medium, a second surface opposite to the first surface, and a partially recessed or undercut portion formed by undercutting into the second surface or between the first and second surfaces (i.e., “hollow”).

[0019] In some embodiments, the undercut electrode includes a body thickness and a flat first surface facing inward toward the gas discharge medium, and a recessed portion includes an undercut portion within a second surface, wherein the end of the undercut electrode has a thickness less than the body thickness.

[0020] In some embodiments, a recessed portion is formed between the first and second surfaces.

[0021] In some embodiments, the recessed portion includes a rectangular recess.

[0022] In some embodiments, the recessed portion includes a curved recess.

[0023] In some embodiments, the undercut electrode includes an anode.

[0024] In some embodiments, the undercut electrode includes a cathode.

[0025] In some embodiments, the opposing electrode pair is configured to decompose a gas into plasma. Each electrode in the electrode pair includes a first surface facing inward toward the plasma and a second surface opposite to the first surface. In some embodiments, at least one electrode in the opposing electrode pair includes a recessed portion formed at each end of the at least one electrode.

[0026] In some embodiments, at least one electrode includes a body thickness, and a first surface includes a flat surface facing inward toward a gas discharge medium, and wherein the recessed portion includes an undercut portion, and wherein the end of at least one electrode has a thickness less than the body thickness.

[0027] In some embodiments, the recessed portion includes a rectangular recess.

[0028] In some embodiments, the recessed portion includes a curved recess.

[0029] In some embodiments, each electrode in the electrode pair includes a recessed portion formed at each end.

[0030] In some embodiments, the light source device includes a chamber configured to hold a gas discharge medium and a pair of opposing electrodes configured to excite the gas discharge medium to generate plasma, the plasma generating an output light beam. In some embodiments, at least one electrode in the pair of opposing electrodes includes at least one of a recessed portion or a hollow portion.

[0031] In some embodiments, each electrode in the electrode pair includes a first surface facing inward toward the gas discharge medium and a second surface opposite to the first surface. At least one electrode may include a recessed portion formed within the second surface.

[0032] In some embodiments, the recessed portion may be positioned along the centerline of at least one electrode.

[0033] In some embodiments, the recessed portion may be located at the end of at least one electrode.

[0034] In some embodiments, the recessed portion may be offset from the centerline of at least one electrode.

[0035] In some embodiments, the recessed portion includes a plurality of recessed portions.

[0036] In some embodiments, a plurality of recessed portions may be located at each end of at least one electrode.

[0037] In some embodiments, each electrode in the electrode pair includes a first surface facing inward toward the gas discharge medium and a second surface opposite to the first surface. In some embodiments, at least one electrode includes a hollow portion formed between the first and second surfaces.

[0038] In some embodiments, the hollow portion is positioned along the centerline of at least one electrode.

[0039] In some embodiments, the hollow portion is offset from the centerline of at least one electrode.

[0040] In some embodiments, the hollow portion includes a plurality of hollow portions.

[0041] In some embodiments, at least one electrode may include both a recessed portion and a hollow portion.

[0042] In some embodiments, at least one of the recessed portion or the hollow portion may be filled with a non-conductive material.

[0043] Implementations of any of the above technologies may include DUV light sources, systems, methods, processes, apparatuses, and / or devices. Details of one or more implementations are set forth in the accompanying drawings and the following description. Other features will be apparent from the specification, drawings, and claims.

[0044] Other features and exemplary aspects of the embodiments, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings. Note that the embodiments are not limited to the specific embodiments described herein. The embodiments presented herein are for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0045] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments and, together with the specification, further serve to explain the principles of the embodiments and enable those skilled in the art to make and use these embodiments.

[0046] Figure 1A This is a schematic diagram of a reflective lithography apparatus according to an exemplary embodiment.

[0047] Figure 1B This is a schematic diagram of a transmission lithography apparatus according to an exemplary embodiment.

[0048] Figure 2 This is a schematic diagram of a light source device according to an exemplary embodiment.

[0049] Figures 3-13 An example undercut electrode according to an exemplary embodiment is illustrated.

[0050] Figure 14 The illustration shows a graph demonstrating the corrosion rate of an electrode according to an exemplary embodiment.

[0051] The features and exemplary aspects of the embodiments will become more apparent from the specific embodiments described below, taken in conjunction with the accompanying drawings, in which the same reference numerals consistently identify corresponding elements. In the drawings, the same reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost numeral of the reference numerals identifies the drawing in which the reference numeral first appears. Unless otherwise stated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0052] This specification discloses one or more embodiments incorporating the features of the invention. The disclosed embodiments(s) are merely illustrative of the invention. The scope of the invention is not limited to the disclosed embodiments(s). The invention is defined by the appended claims.

[0053] The described embodiments and references to "an embodiment," "embodiment," "example embodiment," "exemplary embodiment," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include specific features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be understood that, whether explicitly described or not, implementing such a feature, structure, or characteristic in conjunction with other embodiments is within the knowledge of those skilled in the art.

[0054] This document may use spatially relative terms such as “below,” “lower,” “lower,” “above,” “upper,” “higher,” etc., to describe the relationship between one element or feature and another, as shown in the figure. In addition to the orientations shown in the figure, the spatially relative terms are intended to cover different orientations of the device in use or operation. The device may be oriented in other ways (rotated 90 degrees or otherwise) and the spatially relative descriptors used herein will be interpreted accordingly.

[0055] As used herein, the terms “approximately,” “substantially,” or “approximately” indicate a value of a given quantity that may vary based on a particular technique. Based on a particular technique, the terms “approximately,” “substantially,” or “approximately” may indicate a value of a given quantity that varies, for example, within 1-15% of the value (e.g., ±1%, ±2%, ±5%, ±10%, or ±15% of the value).

[0056] Embodiments of the present invention can be implemented in hardware, firmware, software, or any combination thereof. Embodiments of this disclosure can also be implemented as instructions stored on a machine-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 machine-readable (e.g., computing device) form. For example, a machine-readable medium can include read-only memory (ROM); random access memory (RAM); disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.). Furthermore, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and such actions are actually generated by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc.

[0057] However, it is beneficial to provide an example environment in which embodiments of the present disclosure can be implemented before describing these embodiments in more detail.

[0058] Example lithography system

[0059] Figure 1A and Figure 1BThese are schematic diagrams of lithography apparatus 100 and 100', respectively, which implement embodiments of the present invention. Lithography apparatus 100 and 100' each include: an irradiation system (irradiator) IL configured to modulate a radiation beam B (e.g., deep ultraviolet (DUV) radiation); a support structure (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask, stencil, or dynamic patterning apparatus) MA and connected to a first positioner PM configured to precisely position the patterning apparatus MA; and a substrate stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with photoresist) W and connected to a second positioner PW configured to precisely position the substrate W. Lithography apparatuses 100 and 100' also have a projection system PS configured to project a pattern imparted by the radiation beam B by the patterning apparatus MA onto a target portion (e.g., comprising one or more dies) C of the substrate W. In the lithography apparatus 100, the pattern forming apparatus MA and the projection system PS are reflective. In the lithography apparatus 100', the pattern forming apparatus MA and the projection system PS are transmissive.

[0060] The irradiation system IL may include various types of optical components for guiding, shaping, or controlling the radiation beam B, such as refractive, reflective, anti-refractive, magnetic, electromagnetic, electrostatic, or other types of optical components or any combination thereof.

[0061] The support structure MT holds the patterning apparatus MA in a manner related to the orientation of the patterning apparatus MA relative to the reference frame, the design of at least one of the lithography apparatuses 100 and 100', and other conditions (e.g., whether the patterning apparatus MA is held in a vacuum environment). The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning apparatus MA. The support structure MT can be, for example, a frame or a stage, which may be fixed or movable as needed. By using sensors, the support structure MT can ensure that the patterning apparatus MA is, for example, in a desired position relative to the projection system PS.

[0062] The term "patterning apparatus" MA should be interpreted broadly to refer to any apparatus that can be used to impart a pattern to a radiation beam B on its cross-section to create a pattern in a target portion C of a substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in the apparatus created in the target portion C to form an integrated circuit.

[0063] The pattern forming apparatus MA can be transmissive (e.g., in...). Figure 1B In the lithography equipment 100') or reflective type (such as in Figure 1A(In the photolithography apparatus 100). Examples of pattern forming apparatus MA include photomasks, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in photolithography and include mask types such as binary, alternating phase-shift, or attenuation phase-shift masks, 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 to reflect the incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by the matrix of small mirrors.

[0064] The term "projection system" PS can encompass any type of projection system suitable for the exposure radiation used or for other factors (such as the use of an immersion liquid on a substrate W or the use of a vacuum), including refractive, reflective, antirefractive, magnetic, electromagnetic, and electrostatic optical systems or any combination thereof. A vacuum environment can be used for DUV or electron beam radiation because other gases can absorb excessive radiation or electrons. A vacuum environment can therefore be provided throughout the beam path by means of vacuum walls and a vacuum pump.

[0065] The lithography apparatus 100 and / or lithography apparatus 100' can be of the type having two (dual-stage) or more substrate stages WT (and / or two or more mask stages). In such a "multi-stage" machine, the additional substrate stages WT can be used in parallel, or preparation steps can be performed on one or more stages while one or more other substrate stages WT are used for exposure. In some cases, the additional stages may not be substrate stages WT.

[0066] Photolithography apparatuses can also be of the type in which at least a portion of the substrate can be covered by a liquid (e.g., water) with a relatively high refractive index to fill the space between the projection system and the substrate. Immersion liquids can also be applied to other spaces within the photolithography apparatus, such as the space between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term “immersion” as used herein does not imply that structures such as the substrate must be submerged in the liquid, but simply that the liquid is located between the projection system and the substrate during exposure.

[0067] refer to Figure 1A and Figure 1B The irradiator IL receives the radiation beam from the radiation source SO. For example, when the source SO is an excimer laser (e.g., a master oscillator power amplifier (MOPA) or a master oscillator power ring amplifier (MOPRA)), the source SO and the lithography apparatus 100, 100' can be separate physical entities. In this case, the source SO is not considered to form part of the lithography apparatus 100 or 100', and the radiation beam B is transmitted by means of a beam transmission system BD including, for example, suitable directional mirrors and / or beam expanders (in... Figure 1B(In the middle) the light is transmitted from the source SO to the irradiator IL. In other cases, such as when the source SO is a mercury lamp, the source SO can be an integral part of the lithography apparatus 100, 100'. If desired, the source SO, the irradiator IL, and the beam transmission system BD can be referred to as the radiation system.

[0068] The irradiator IL may include an adjuster AD for adjusting the angular intensity distribution of the radiation beam (in Figure 1B (In the middle). Typically, at least the outer and / or inner radial ranges (usually referred to as "-outer" and "-inner") of the intensity distribution in the pupil plane of the irradiator can be adjusted. Additionally, the irradiator IL may include various other components (in... Figure 1B In the middle, such as integrator IN and concentrator CO. Irradiator IL can be used to adjust the radiation beam B to have the desired uniformity and intensity distribution in its cross section.

[0069] refer to Figure 1A A radiation beam B is incident on a patterning apparatus (e.g., a mask) MA held on a support structure (e.g., a mask stage) MT and patterned by the patterning apparatus MA. In the lithography apparatus 100, the radiation beam B is reflected from the patterning apparatus (e.g., the mask) MA. After reflection from the patterning apparatus (e.g., the mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. The substrate stage WT can be precisely moved (e.g., to position different target portions C in the path of the radiation beam B) using a second positioner PW and a position sensor IF2 (e.g., an interferometer, a linear encoder, or a capacitive sensor). Similarly, a first positioner PM and another position sensor IF1 can be used to precisely position the patterning apparatus (e.g., the mask) MA relative to the path of the radiation beam B. The patterning apparatus (e.g., the mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0070] refer to Figure 1B A radiation beam B is incident on a patterning apparatus (e.g., a mask MA) held on a support structure (e.g., a mask stage MT) and patterned by the patterning apparatus. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam onto a target portion C of the substrate W. The projection system has a pupil PPU conjugate with the illumination system pupil IPU. Part of the radiation is emitted from the intensity distribution at the illumination system pupil IPU and passes through the mask pattern unaffected by diffraction at the mask pattern, creating an intensity distribution image at the illumination system pupil IPU.

[0071] The projection system PS projects an image MP' of a mask pattern MP onto a photoresist layer coated on a substrate W, wherein the image MP' is formed by a diffracted beam generated from radiation from the marked pattern MP through an intensity distribution. For example, the mask pattern MP may comprise an array of lines and spacings. Radiation diffraction at the array, distinct from zero-order diffraction, generates a diffracted beam with a directional change in a direction perpendicular to the lines. The undiffracted beam (i.e., the so-called zero-order diffracted beam) passes through the pattern without any change in its propagation direction. The zero-order diffracted beam passes upstream of the pupil conjugate PPU of the projection system PS through the upper lens or upper lens group of the projection system PS, reaching the pupil conjugate PPU. The intensity distribution portion in the plane of the pupil conjugate PPU and associated with the zero-order diffracted beam is the intensity distribution image in the illumination system pupil IPU of the illumination system IL. An aperture device PD is, for example, positioned or substantially positioned at the plane comprising the pupil conjugate PPU of the projection system PS.

[0072] The projection system PS is arranged to capture not only the zeroth-order diffracted beam but also first-order or higher-order diffracted beams (not shown) via an upper lens or upper lens group L1 and a lower lens or lower lens group L2. In some embodiments, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to utilize the resolution enhancement effect of dipole illumination. For example, a first-order diffracted beam interferes with the corresponding zeroth-order diffracted beam at the level of the wafer W, thereby creating an image MP' of the line pattern MP at the highest possible resolution and process window (i.e., the available depth of focus combined with tolerable exposure dose deviation). In some embodiments, astigmatism can be reduced by providing a radiating pole (not shown) in the opposing quadrant of the illumination system pupil IPU. For example, illumination at the illumination system pupil IPU can use only two opposing illumination quadrants, sometimes referred to as BMW illumination, such that the remaining two quadrants are not used for illumination but are configured to capture the first-order diffracted beam. Furthermore, in some embodiments, astigmatism can be reduced by blocking the zeroth-order beam associated with the radiating pole in the opposing quadrant of the projection system pupil conjugate PPU.

[0073] With the aid of a second positioner PW and a position sensor IF (e.g., an interferometer, linear encoder, or capacitive sensor), the substrate stage WT can be precisely moved (e.g., to position different target portions C within the path of the radiation beam B). Similarly, the first positioner PM and another position sensor ( Figure 1B (Not shown) can be used to precisely position the path of the mask MA relative to the radiation beam B (e.g., after mechanical acquisition from the mask library or during scanning).

[0074] Typically, the movement of the mask stage MT can be achieved using long-stroke modules (coarse positioning) and short-stroke modules (precise positioning), which form part of the first positioner PM. Similarly, the movement of the substrate stage WT can be achieved using long-stroke modules and short-stroke modules, which form part of the second positioner PW. In the case of a stepper (opposite to a scanner), the mask stage MT can be connected only to the short-stroke actuator or can be fixed. The mask MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as shown) occupy dedicated target portions, they can be located in the space between the target portions (referred to as scribing alignment marks). Similarly, when more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0075] The mask stage MT and pattern forming apparatus MA can be located within a vacuum chamber V, where an IVR (Indoor Vacuum Robot) can be used to move the pattern forming apparatus, such as the mask, into and out of the vacuum chamber. Alternatively, when the mask stage MT and pattern forming apparatus MA are outside the vacuum chamber, an external vacuum robot, similar to an internal vacuum robot IVR, can be used for various transport operations. Both the internal and external vacuum robots need to be calibrated to smoothly transfer any payload (e.g., the mask) to a fixed motion support at the transport station.

[0076] Photolithography equipment 100 and 100' can be used in at least one of the following modes:

[0077] 1. In step mode, the support structure (e.g., mask stage) MT and substrate stage WT remain substantially stationary, while the entire pattern imparting the radiation beam B is projected onto the target portion C in one pass (i.e., single static exposure). The substrate stage WT then moves in the X and / or Y directions so that different target portions C can be exposed.

[0078] 2. In the scanning mode, while the pattern imparted to the radiation beam B is projected onto the target portion C, the support structure (e.g., mask stage) MT and the substrate stage WT are scanned simultaneously (i.e., single dynamic exposure). The velocity and direction of the substrate stage WT relative to the support structure (e.g., mask stage) MT can be determined by the (reduced) magnification and image inversion characteristics of the projection system PS.

[0079] 3. In another mode, the support structure (e.g., mask stage) MT of the programmable patterning apparatus remains substantially stationary, and the substrate stage WT is moved or scanned while the pattern imparted by the radiation beam B is projected onto the target portion C. A pulsed radiation source SO can be used, and the programmable patterning apparatus is updated as needed after each movement of the substrate stage WT or between successive radiation pulses during scanning. This operating mode can be readily applied to maskless lithography utilizing programmable patterning apparatuses such as programmable mirror arrays.

[0080] Alternatively, the described usage pattern or a combination and / or variation of completely different usage patterns may be adopted.

[0081] In another embodiment, the lithography apparatus 100 includes an extreme ultraviolet (EUV) radiation source configured to generate an EUV radiation beam for EUV lithography.

[0082] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure much lower than atmospheric pressure, can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS. The radiation source SO can be a laser-generated plasma (LPP) source, a discharge-generated plasma (DPP) source, a free-electron laser (FEL), an excimer laser, a master oscillator power amplifier (MOPA), a master oscillator power ring amplifier (MOPRA), or any other radiation source capable of generating DUV radiation.

[0083] Exemplary light source device

[0084] Inhomogeneous corrosion of the electrodes in gas discharge lasers limits the lifetime of the discharge chamber. This inhomogeneous corrosion can be significantly improved by redistributing the discharge intensity across the entire electrode through optimized electrode geometry design. The undercut and / or hollow electrodes disclosed herein reduce the localized discharge intensity at the locations of the undercut or hollow sections of the electrode, thus resulting in a more uniform corrosion profile and increased discharge chamber lifetime. In some embodiments, the undercut electrodes disclosed herein reduce the localized plasma discharge intensity at both ends of the electrode to achieve a more uniform corrosion profile and increased discharge chamber lifetime.

[0085] As described above, a master oscillator power amplifier (MOPA) or master oscillator power ring amplifier (MOPRA) is a two-stage laser arrangement. The master oscillator (MO) (e.g., a first optical resonator stage) generates a highly coherent beam. The power amplifier (PA) or power ring amplifier (PRA) (e.g., a second optical resonator stage) amplifies the beam power while preserving the beam properties. The MO may include a gas discharge chamber, an optical coupler (OC), and a linewidth narrowing module (LNM). The OC and LNM form an optical resonator around the gas discharge chamber. The PA or PRA may include a second gas discharge chamber, a wavefront engineering box (WEB), and a beam inverter (BR). The WEB and BR may form a second optical resonator around the second gas discharge chamber. For example, certain MOPAs and MOPRAs have been previously described in U.S. Patent No. 7,643,528, issued January 5, 2010, and U.S. Patent No. 7,822,092, issued October 26, 2010, the entire contents of which are incorporated herein by reference.

[0086] As an example of a MOPA / MOPRA system or a MO-only system, an excimer laser utilizes excimers (e.g., stimulated dimers) or excitation complexes (e.g., stimulated complexes) to output deep ultraviolet (DUV) radiation. Excimers are short-lived homodimers formed from two substances (e.g., Ar2, Kr2, F2, Xe2). Excitation complexes are heterodimers formed from more than two species (e.g., ArF, KrCl, KrF, XeBr, CeCl, XeF). Electrodes of the MO, PA, and / or PRA surrounding a plasma generated by a breakdown gas (e.g., F2, ArF, KrF, and / or XeF) may corrode over time, generating metal fluoride dust (e.g., with an average diameter of approximately 2.0 μm). This metal fluoride dust may undesirably deposit on the optical windows of the MO, PA, and / or PRA and can cause optical damage (e.g., localized thermal adsorption and / or heating). Furthermore, the cycling of metal fluoride dust in MO can also lead to a decrease in discharge voltage from the electrodes and poor laser performance.

[0087] In some embodiments, a metal fluoride trap (MFT) may be coupled to the chamber of the MO and the chambers of the PA and / or PRA to reduce contamination in the gas discharge medium.

[0088] The embodiments of the light source devices and systems disclosed herein can improve the uniformity of gas discharge intensity along the entire length of the electrode, prevent non-uniform degradation of the electrode, improve control of flow distribution through the window housing device, provide effective purification without increasing the clean gas return rate from the metal fluoride trap, reduce metal fluoride dust accumulation on the optical window, and increase the service life of the metal fluoride trap and the master oscillator, power amplifier and / or power ring amplifier, thereby providing, for example, an excimer laser beam (e.g., DUV radiation) to a DUV lithography device.

[0089] Figure 2 The illustration shows a light source device 200 according to various exemplary embodiments. The light source device 200 can provide, for example, a DUV lithography apparatus (e.g., lithography apparatus 100') with a highly coherent and aligned laser beam (e.g., laser beam 202). While the light source device 200 in… Figure 2 While illustrated as a standalone device and / or system, embodiments of this disclosure can be used with other optical systems, such as, but not limited to, radiation source SO, lithography apparatus 100, 100', and / or other optical systems. In some embodiments, light source device 200 may be radiation source SO in lithography apparatus 100, 100'. For example, the DUV radiation beam B may be laser beam 202. In some embodiments, light source device 200 may be a MOPA or MOPRA formed from a gas discharge stage 210 (e.g., MO) and a second gas discharge stage (e.g., a PA and / or PRA similar to gas discharge stage 210) (not shown). As described above, for example, certain MOPAs and MOPRAs have previously been described in U.S. Patent No. 7,643,528, issued January 5, 2010, and U.S. Patent No. 7,822,092, issued October 26, 2010, the entire contents of which are incorporated herein by reference.

[0090] like Figure 2 As shown, the light source device 200 may include a gas discharge stage 210, a voltage control system 230, and a pressure control system 240. In some embodiments, all the components listed above may be housed in a three-dimensional (3D) frame 201. For example, the 3D frame 201 may include metal (e.g., aluminum, steel, etc.), ceramic, and / or any other suitable rigid material.

[0091] Gas discharge stage 210 can be configured to output a highly coherent beam (e.g., laser beam 202). Gas discharge stage 210 may include discharge chamber 206, a first optical module 250 (e.g., optical coupler (OC), wavefront engineering box (WEB)) and a second optical module 260 (e.g., linewidth narrowing module (LNM), beam reverser (BR)). In some embodiments, the first optical module 250 may include a first optical resonator element 252, and the second optical module 260 may include a second optical resonator element 262. Optical resonator 270 may be defined by the first optical module 250 (e.g., via the first optical resonator element 252) and the second optical module 260 (e.g., via the second optical resonator element 262). The first optical resonator element 252 may be partially reflective (e.g., a partial mirror), and the second optical resonator element 262 may be reflective (e.g., a mirror, grating, etc.) to form optical resonator 270. Optical resonator 270 can guide the light generated by discharge chamber 206 to form a associated laser beam 202. In some embodiments, gas discharge stage 210 can output the laser beam 202 to a PA stage (not shown) as part of an MOPA arrangement, or a PRA stage (not shown) as part of an MOPRA arrangement. In some embodiments, gas discharge stage 210 can be, for example, an MO stage having OC and LNM. In some embodiments, gas discharge stage 210 can be, for example, a PA stage having WEB and BR. In some embodiments, gas discharge stage 210 can be, for example, a PRA stage having WEB and BR.

[0092] like Figure 2 As shown, the discharge chamber 206 may include a chamber body 211, a first window housing device 218, and a second window housing device 220. The chamber body 211 may be configured to hold a gas discharge medium 213 within the first and second window housing devices 218, 220. As described above, the gas discharge medium 213 may represent a gas or gaseous medium prior to gas breakdown or excitation, and / or a plasma or discharge plasma formed upon gas breakdown or excitation, and the arrows indicate the gas flow of the gas discharge medium 213. When the gas is broken down and / or excited, the resulting plasma or discharge plasma forms between electrodes 204a, 204b in the plasma region 215. The chamber body 211 may include electrodes 204a, 204b (collectively referred to as electrode 204), a blower 212, the gas discharge medium 213, the first window housing device 218, and the second window housing device 220. In some embodiments, as will be understood by those skilled in the art, electrode 204a may be a cathode, and electrode 204b may be an anode.

[0093] The discharge chamber 206 can be optically coupled to an optical resonator 270 defined by a first optical module 250 and a second optical module 260. The discharge chamber 206 can be configured to convert the gaseous discharge medium 213 between electrodes 204 in the chamber body 211 into a plasma discharge, thereby outputting amplified spontaneous emission (ASE) and / or a laser beam 202. The gaseous discharge medium 213 can be circulated between the electrodes 204 in the chamber body 211 by a blower 212. In some embodiments, the blower 212 can be a tangential blower that generates an airflow 217.

[0094] The gas discharge medium 213 can be configured to output an ASE and / or laser beam 202 (e.g., 193 nm). In some embodiments, the gas discharge medium 213 may include a gas for excimer laser emission (e.g., Ar2, Kr2, F2, Xe2, ArF, KrCl, KrF, XeBr, XeCl, XeF, etc.). For example, the gas discharge medium 213 may form ArF upon excitation (e.g., voltage application) from the surrounding electrode 204 in the chamber body 211 and output an ASE and / or laser beam 202 (e.g., 193 nm) via the first and second window housing devices 218, 220. In some embodiments, the gas discharge medium 213 may include halogen gases and rare gases to form excimer and / or excitation complexes. For example, the gas discharge medium 213 may include F2, Ar, Kr, and / or Xe to form ArF, KrF, and / or XeF under discharge plasma.

[0095] In some embodiments, the first optical module 250 may be configured to partially reflect the light beam and form part of the optical resonator 270. For example, the first optical module (e.g., OC, WEB) has previously been described in U.S. Patent No. 7,885,309, issued February 8, 2011, and U.S. Patent No. 7,643,528, issued January 5, 2010, which are incorporated herein by reference in their entirety. Figure 2 As shown, the first optical module 250 may include a first optical resonator element 252 for guiding light (e.g., ASE and / or laser beam 202) from the discharge chamber 206 back into the discharge chamber 206 and / or outputting the laser beam 202. In some embodiments, the first optical resonator element 252 may be adjusted (e.g., tilted).

[0096] In some embodiments, the second optical module 260 may be configured to provide spectral narrowing to the light beam and form part of the optical resonator 270. For example... Figure 2As shown, the second optical module 260 may include a second optical resonator element 262 for directing light (e.g., ASE and / or laser beam 202) from the discharge chamber 206 back into the discharge chamber 206 towards the first optical module 250. In some embodiments, the second optical resonator element 262 may be adjusted (e.g., tilted, angled).

[0097] The voltage control system 230 can be configured to apply high-voltage electrical pulses across electrodes 204 in the chamber body 211 to discharge and excite the gas medium 213, thereby outputting an ASE and / or a laser beam 202 (e.g., 193 nm). The voltage control system 230 may include a voltage supply line 232. In some embodiments, the voltage control system 230 may include a high-voltage power supply (not shown), a voltage compression amplifier (not shown), a pulse energy monitor (not shown), and / or a controller (not shown) for providing high-voltage electrical pulses across electrodes 204.

[0098] Pressure control system 240 can be configured to control the fluorine concentration in chamber body 211 and supply gas discharge medium 213 to chamber body 211. Pressure control system 240 may include gas discharge line 242 and vacuum line 244. Gas discharge line 242 may be configured to supply one or more gas components (e.g., Ar, Kr, F2, Xe, etc.) of gas discharge medium 213 to chamber body 211. Vacuum line 244 may be configured to provide a negative pressure (e.g., extraction) on a portion of gas discharge medium 213 in chamber body 211, for example, during the injection of one or more gas components into gas discharge medium 213 via gas discharge line 242. In some embodiments, gas discharge line 242 and vacuum line 244 are combined into a single gas line. In some embodiments, pressure control system 240 may include one or more gas sources (not shown), one or more pressure regulators (not shown), a vacuum pump (not shown), a fluorine (F2) trap, and / or a controller (not shown) for controlling the fluorine concentration in chamber body 211 and refilling gas charging medium 213 into chamber body 211.

[0099] Figures 3-13 Each figure illustrates an electrode pair according to various aspects of this disclosure. That is, Figures 3-13 The diagram illustrates a side view of the electrodes and the gas discharge medium 213 between electrodes 204a and 204b. For example, as... Figures 3-6As shown, each of the electrodes 204 (i.e., electrodes 204a and 204b) may each include a first surface 305a, 305b (collectively referred to as first surface 305), wherein the first surface 305 faces inward toward the gas discharge medium 213, which is a plasma when excited by electrodes 204a and 204b. Additionally, each electrode may each include a second surface 310a, 310b (collectively referred to as second surface 310), wherein the second surface 310 faces away from the gas discharge medium 213.

[0100] In some embodiments, one or more of the electrodes 204 may include a recessed portion at each end of the electrode 204. An electrode with a recessed portion may be referred to as an undercut electrode. For example, as... Figure 3 As shown, electrode 204b may include a recessed portion 315 at each end of electrode 204b. In some embodiments, electrode 204b may include a recessed portion 315 at only one end of electrode 204b. As described above, in some embodiments, electrode 204a may be a cathode and electrode 204b may be an anode, but other arrangements are used in other embodiments. In some embodiments, electrode 204b may have a body thickness X and a flat first surface facing inward toward the discharge plasma, and the recessed portion 315 includes an undercut portion such that the end of electrode 204b has a thickness Y less than the body thickness X.

[0101] exist Figure 4 In another example shown, electrode 204a may include a recessed portion 415 at each end of electrode 204a.

[0102] exist Figure 5 In another example shown, both electrodes 204 may include a recessed portion 515 at each end of the electrode 204. In some embodiments, one or both electrodes 204 may include a recessed portion 515 at only one end of the electrode 204.

[0103] exist Figure 6 In another example shown, electrode 204 may include a recessed portion 615 at each end of electrode 204, wherein the recessed portion is formed between the first surface 305 and the second surface 310 of each electrode 204. Although Figure 6 The example shown illustrates two electrodes with recessed portions 615, but those skilled in the art will understand that either or both of the electrodes 204 may have recessed portions 615.

[0104] Although Figures 3-6The examples shown depict electrode 204 with rectangular or square recesses, but those skilled in the art will understand that these are for illustrative purposes only, and other shapes of recesses are further contemplated according to various aspects of the invention. For example, as Figure 7 As shown, the recessed portion 715 of electrode 204b may have a rounded edge. Those skilled in the art will understand that electrode 204a may also have a similar shape. Figure 7 The circle shown.

[0105] exist Figure 8 In one example shown, electrode 204b may include a recessed portion 815 formed within the second surface 310b. In some embodiments, the recessed portion 815 may be centrally located along the length of electrode 204b, i.e., the recessed portion 815 may be positioned along the centerline of electrode 204b. In some embodiments, the recessed portion 815 may be partially undercut to achieve a uniform local corrosion rate to match the remainder of electrode 204b. Although Figure 8 Electrode 204b is shown as having a recessed portion 815; however, those skilled in the art will understand that, according to various aspects of this disclosure, electrode 204a may also have a recessed portion 815 formed in the second surface 310a. That is, in some embodiments, either or both of electrodes 204a and 204b may include a recessed portion 815.

[0106] exist Figure 9 In one example shown, electrode 204b may include a plurality of recessed portions 915 formed within the second surface 310b. In some embodiments, the plurality of recessed portions 915 may be offset from the centerline of electrode 204b. In some embodiments, the plurality of recessed portions 915 may be partially undercut to achieve a uniform local corrosion rate to match the remainder of electrode 204b. Although Figure 9 The electrode 204b is shown to have a plurality of recessed portions 915; however, those skilled in the art will understand that the electrode 204a may also have a plurality of recessed portions 915 according to various aspects of this disclosure. That is, in some embodiments, either or both of electrodes 204a and 204b may include a plurality of recessed portions 915.

[0107] exist Figure 10In one example shown, electrode 204b may include a recessed portion 1015a formed within the second surface 310b, and a combination of recessed portions 1015b formed at one or both ends of electrode 204b. In some embodiments, the recessed portion 1015a may be formed along the centerline of electrode 204b, or the recessed portion 1015a may be offset from the centerline. In some embodiments, the recessed portion 1015a may be partially undercut to achieve a uniform local corrosion rate to match the remainder of electrode 204b. Although Figure 10 Electrode 204b is shown as having recessed portions 1015a and 1015b; however, those skilled in the art will understand that, according to various aspects of this disclosure, electrode 204a may also have recessed portions 1015a and 1015b. That is, in some embodiments, either or both of electrodes 204a and 204b may include recessed portions 1015a and 1015b.

[0108] exist Figure 11 In one example shown, electrode 204b may include a hollow portion 1115 formed within the body of electrode 204b. In some embodiments, the hollow portion 1115 may be formed along the centerline of electrode 204b. In some embodiments, the hollow portion 1115 may be partially undercut to allow for a uniform local corrosion rate to match the rest of electrode 204b. Although Figure 11 Electrode 204b is shown as having a hollow portion 1115; however, those skilled in the art will understand that electrode 204a may also have a hollow portion 1115 according to various aspects of this disclosure. That is, in some embodiments, either or both of electrodes 204a and 204b may include a hollow portion 1115.

[0109] exist Figure 12 In one example shown, electrode 204b may include a plurality of hollow portions 1215 formed within the body of electrode 204b. In some embodiments, the plurality of hollow portions 1215 may be offset from the centerline of electrode 204b. In some embodiments, the plurality of hollow portions 1215 may be partially undercut to achieve a uniform local corrosion rate to match the remainder of electrode 204b. Although Figure 12 Electrode 204b is shown as having a plurality of hollow portions 1215; however, those skilled in the art will understand that electrode 204a may also have a plurality of hollow portions 1215 according to various aspects of this disclosure. That is, in some embodiments, either or both of electrodes 204a and 204b may include a plurality of hollow portions 1215.

[0110] In some embodiments, Figures 3-12In the example shown, the recessed and / or hollow portions of electrode 204 can be filled with a non-conductive material. For example, as... Figure 13 As shown, the undercut portion of electrode 204b can be filled with a non-conductive material 1315. In some embodiments, the non-conductive material 1315 may be, for example, ceramic, plastic, polymer, etc. Those skilled in the art will understand that these are merely examples of non-conductive materials, and other non-conductive materials are conceivable based on various aspects of this disclosure.

[0111] In some embodiments, the recessed and hollow portions described herein can be combined in any combination and at different locations to achieve optimal uniform electrode corrosion.

[0112] In some embodiments, the depth and height of the recessed portion of electrode 204 can be determined based on the intensity of the partial discharge plasma near electrode 204.

[0113] In some embodiments, the depth of the recessed portion can be from about 0.1 cm to about 10 cm, and the height of the recessed portion can be from about 0.05 cm to about 5 cm. Those skilled in the art will understand that these are merely example dimensions of the depth and height of the recessed portion of the electrode 204, and other dimensions are considered according to various aspects of this disclosure. For example, different sizes of recesses may be required for different electrode materials or different electrode thicknesses.

[0114] Figure 14 This diagram illustrates the corrosion performance of the undercut electrode of this disclosure compared to that of a conventional electrode. The performance diagram shows the corrosion rate relative to the position on the electrode, expressed in arbitrary units, where the corrosion rate is defined as the change in electrode height per certain number of laser pulses. Figure 14 The first corrosion rate of conventional electrode 1405 is shown. Figure 3 The corrosion rate of the illustrated embodiment. Figure 14 For example, it is shown that, compared to the inner portion of the electrode, the first corrosion rate 1405 exhibits increased corrosion at each end of the conventional electrode and at the center of the conventional electrode. In some embodiments, as shown by the first corrosion rate 1405, the corrosion rate exhibited at each end of the conventional electrode is 2-2.5 times greater than the corrosion rate at the center portion of the same electrode.

[0115] In some embodiments, Figure 3 The second corrosion rate 1410 of the undercut electrode illustrates a more uniform corrosion rate along the entire electrode length. In some embodiments, each end of the conventional electrode is etched at a rate 1405, which is... Figure 3The second corrosion rate 1410 at the edge portion of the electrode shown is 2-2.5 times that of the electrode shown. Each end of the undercut electrode can have a corrosion rate comparable to that of the center portion of the undercut electrode. In some respects, the lifespan of electrode 204 can be increased due to the uniform corrosion of the electrode. For example, compared to conventional designs, Figure 14 The improved corrosion rate and uniform corrosion profile at the electrode tip may be a result of the reduced discharge plasma intensity at the undercut electrode tip, or the reduced discharge plasma intensity at the tip may be due to the hollow portion at the electrode tip, or due to... Figures 3-13 The undercut portion or hollow portion shown is filled with a non-conductive material.

[0116] In some embodiments, for example Figure 8 , Figure 9 , Figure 11 and Figure 12 In the embodiment shown, at the location of the undercut portion, the reduced corrosion rate due to the decreased discharge plasma intensity at that location will also result in a similar smoothing corrosion profile, such as the corrosion profile shown at the second corrosion rate 1410.

[0117] Although the embodiments have been specifically referenced above in the context of optical lithography, it should be understood that the embodiments can be used in other applications, such as imprint lithography, and are not limited to optical lithography where the context permits.

[0118] It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes, and that the terminology or terminology used herein should be interpreted by those skilled in the art based on the teachings herein.

[0119] As used herein, the term "substrate" describes the material on which a layer of material is added. In some embodiments, the substrate itself may be patterned, and the material added on top of it may also be patterned, or may remain unpatterned.

[0120] The following examples illustrate, but are not limited, embodiments of this disclosure. Other suitable modifications and adaptations to various conditions and parameters commonly encountered in the art (which will be apparent to those skilled in the art) are within the spirit and scope of this invention.

[0121] While specific embodiments have been described above, it should be understood that embodiments may be practiced in ways other than those described. This specification is not intended to limit the scope of the claims.

[0122] It should be understood that the Detailed Description section, rather than the Summary and Abstract section, is intended to be used to interpret the claims. The Summary and Abstract section may set forth one or more, but not all, exemplary embodiments contemplated by the inventors, and is therefore not intended to limit the embodiments and the appended claims in any way.

[0123] The embodiments described above use functional building blocks to illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly executed.

[0124] The above description of the specific embodiments will fully reveal the general nature of the embodiments, enabling others to easily modify and / or adapt various applications of such specific embodiments by applying knowledge of the art without extensive experimentation or departing from the general concept of the embodiments. Therefore, based on the teachings and guidance given herein, such adaptations and modifications are intended to fall within the meaning and scope of equivalents of the disclosed embodiments.

[0125] The breadth and scope of the embodiments should not be limited by any of the exemplary embodiments described above, but should be defined only by the appended claims and their equivalents.

[0126] Other aspects of the invention are set forth in the following numbered clauses.

[0127] 1. A light source device, comprising:

[0128] The chamber is configured to maintain the gas discharge medium; and

[0129] The opposing electrode pair is configured to excite the gas discharge medium to generate plasma, which produces an output beam.

[0130] At least one electrode in the opposing electrode pair includes a recessed portion formed at each end of the at least one electrode.

[0131] 2. The light source device according to Clause 1, wherein each electrode in the electrode pair comprises:

[0132] A first surface, facing inward toward the gas discharge medium; and

[0133] A second surface, opposite to the first surface, wherein the recessed portion of the at least one electrode is formed within the second surface at each end of the second surface.

[0134] 3. The light source device according to Clause 1, wherein the at least one electrode includes a body thickness and a flat first surface facing inward toward the gas discharge medium, and wherein each of the recessed portions includes an undercut portion, wherein the end of the at least one electrode has a thickness less than the body thickness.

[0135] 4. The light source device according to Clause 1, wherein the at least one electrode in the electrode pair comprises an anode.

[0136] 5. The light source device according to Clause 1, wherein the at least one electrode in the electrode pair comprises a cathode.

[0137] 6. The light source device according to Clause 1, wherein each electrode in the electrode pair includes a recessed portion formed at each end.

[0138] 7. The light source device according to Clause 1, wherein each electrode in the electrode pair comprises:

[0139] A first surface, facing inward toward the gas discharge medium; and

[0140] The second surface is opposite to the first surface, and the recessed portion of the at least one electrode is a hollow portion formed between the first surface and the second surface.

[0141] 8. The light source device according to Clause 1, wherein the gas discharge medium comprises halogen gas and rare gas to form excimer and / or excitation complex.

[0142] 9. The light source device according to Clause 1, wherein the gas discharge medium includes F2, ArF, KrF and / or XeF.

[0143] 10. The light source apparatus according to Clause 1, further comprising:

[0144] An assembly of optical elements is configured to form an optical resonator around the chamber.

[0145] 11. An undercut electrode, comprising:

[0146] The first surface faces inward toward the gas discharge medium;

[0147] A second surface, opposite to the first surface; and

[0148] The recessed portion is formed at each end of the undercut electrode.

[0149] 12. The undercut electrode according to Clause 11, wherein the undercut electrode includes a body thickness, and wherein each of the recessed portions includes an undercut portion within the second surface, wherein the end of the undercut electrode has a thickness less than the body thickness.

[0150] 13. The undercut electrode according to Clause 11, wherein the recessed portion is a hollow portion formed between the first surface and the second surface.

[0151] 14. The undercut electrode as described in Clause 13, wherein the hollow portion is filled with a non-conductive material.

[0152] 15. The undercut electrode as described in Clause 11, wherein the recessed portion comprises a rectangular recess.

[0153] 16. The undercut electrode as described in Clause 11, wherein the recessed portion includes a curved recess.

[0154] 17. The undercut electrode as described in Clause 11, wherein the undercut electrode includes an anode.

[0155] 18. The undercut electrode as described in Clause 11, wherein the undercut electrode includes a cathode.

[0156] 19. A pair of opposing electrodes configured to excite a gaseous medium to form a plasma, each electrode in the pair comprising:

[0157] A first surface, facing inward toward the gaseous medium; and

[0158] The second surface is opposite to the first surface.

[0159] At least one electrode in the opposing electrode pair includes a recessed portion formed at each end of the at least one electrode.

[0160] 20. The opposing electrode pair according to Clause 19, wherein the at least one electrode includes a body thickness, and the first surface includes a flat surface facing inward toward the gas discharge medium, and wherein each of the recessed portions includes an undercut portion, wherein the end of the at least one electrode has a thickness less than the body thickness.

[0161] 21. The opposing electrode pair according to Clause 19, wherein the recessed portion includes a rectangular recess.

[0162] 22. The opposing electrode pair as described in Clause 19, wherein the recessed portion includes a curved recess.

[0163] 23. The opposing electrode pair as described in Clause 19, wherein each electrode in the electrode pair includes a recessed portion formed at each end.

[0164] 24. A light source device, comprising:

[0165] The chamber is configured to maintain the gas discharge medium; and

[0166] The opposing electrode pair is configured to excite the gas discharge medium to generate plasma, which produces an output beam.

[0167] At least one electrode in the said pair of opposing electrodes includes at least one of a recessed portion or a hollow portion.

[0168] 25. The light source device according to Clause 24, wherein each electrode in the electrode pair comprises:

[0169] A first surface, facing inward toward the gas discharge medium; and

[0170] A second surface, opposite to the first surface, wherein the at least one electrode includes the recessed portion formed within the second surface.

[0171] 26. The light source device according to Clause 24, wherein the recessed portion comprises a plurality of recessed portions.

[0172] 27. The light source device according to Clause 26, wherein the plurality of recessed portions are located at each end of the at least one electrode.

[0173] 28. The light source device according to Clause 24, wherein each electrode in the electrode pair comprises:

[0174] A first surface, facing inward toward the gas discharge medium; and

[0175] A second surface, opposite to the first surface, wherein at least one electrode includes the hollow portion formed between the first surface and the second surface.

[0176] 29. The light source device according to Clause 28, wherein the hollow portion comprises a plurality of hollow portions.

[0177] 30. The light source according to Clause 29, wherein each of the plurality of hollow portions is filled with a non-conductive material.

[0178] 31. The light source device according to Clause 24, wherein the recessed portion or the hollow portion is positioned along the centerline of the at least one electrode.

[0179] 32. The light source device according to Clause 24, wherein the recessed portion or the hollow portion is located at the end of the at least one electrode.

[0180] 33. The light source device according to Clause 24, wherein the recessed portion or the hollow portion is offset from the centerline of the at least one electrode.

[0181] 34. The light source device according to Clause 24, wherein the at least one electrode includes the recessed portion and the hollow portion.

[0182] 35. The light source device according to Clause 24, wherein at least one of the recessed portion or the hollow portion is filled with a non-conductive material.

[0183] The breadth and scope of the embodiments should not be limited by any of the exemplary embodiments described above, but should be defined only by the appended claims and their equivalents.

Claims

1. A light source device, comprising: The chamber is configured to maintain the gas discharge medium; as well as Optical electrode pairs are positioned within the chamber and configured to excite the gaseous discharge medium to generate plasma, which produces an output beam. At least one electrode in the opposing electrode pair includes a recessed portion formed at each end of the at least one electrode. Each electrode in the electrode pair includes: The first surface faces inward toward the gas discharge medium; as well as A second surface, opposite to the first surface, wherein the recessed portion of the at least one electrode is formed within the second surface at each end of the second surface.

2. The light source device according to claim 1, wherein the at least one electrode includes a body thickness and a flat first surface facing inward toward the gas discharge medium, and wherein each of the recessed portions includes an undercut portion, wherein the end of the at least one electrode has a thickness less than the body thickness.

3. The light source device according to claim 1, wherein the at least one electrode in the electrode pair comprises an anode.

4. The light source device according to claim 1, wherein at least one electrode in the electrode pair comprises a cathode.

5. The light source device according to claim 1, wherein each electrode in the electrode pair includes a recessed portion formed at each end.

6. The light source device according to claim 1, wherein the at least one electrode further comprises a hollow portion formed between the first surface and the second surface.

7. The light source device according to claim 1, wherein the gas discharge medium comprises halogen gas and rare gas to form excimer and / or excitation complex.

8. The light source device according to claim 1, wherein the gas discharge medium includes F2, ArF, KrF and / or XeF.

9. The light source device according to claim 1, further comprising: An assembly of optical elements is configured to form an optical resonator around the chamber.

10. An undercut electrode, comprising: The first surface faces inward toward the gas discharge medium and is in physical contact with it; The second surface is opposite to the first surface; as well as The recessed portion is formed within the second surface at each end of the undercut electrode.

11. The undercut electrode of claim 10, wherein the undercut electrode includes a body thickness, and wherein each of the recessed portions includes an undercut portion within the second surface, wherein the end of the undercut electrode has a thickness less than the body thickness.

12. The undercut electrode of claim 10, wherein the undercut electrode further comprises a hollow portion formed between the first surface and the second surface.

13. The undercut electrode of claim 12, wherein the hollow portion is filled with a non-conductive material.

14. The undercut electrode of claim 10, wherein the recessed portion comprises a rectangular recess.

15. The undercut electrode of claim 10, wherein the recessed portion includes a curved recess.

16. The undercut electrode of claim 10, wherein the undercut electrode comprises an anode.

17. The undercut electrode of claim 10, wherein the undercut electrode comprises a cathode.

18. A pair of opposing electrodes configured to physically contact a gaseous medium to excite a plasma, each electrode in the pair comprising: The first surface faces inward toward the gaseous medium; as well as The second surface is opposite to the first surface. At least one electrode in the opposing electrode pair includes a recessed portion formed in the second surface at each end of the at least one electrode.

19. The opposing electrode pair of claim 18, wherein the at least one electrode includes a body thickness, and the first surface includes a flat surface facing inward toward the gas discharge medium, and wherein each of the recessed portions includes an undercut portion, wherein the end of the at least one electrode has a thickness less than the body thickness.

20. The opposing electrode pair according to claim 18, wherein the recessed portion comprises a rectangular recess.

21. The opposing electrode pair according to claim 18, wherein the recessed portion includes a curved recess.

22. The opposing electrode pair according to claim 18, wherein each electrode in the electrode pair includes a recessed portion formed at each end.

23. A light source device, comprising: The chamber is configured to maintain the gas discharge medium; as well as Optical electrode pairs are positioned within the chamber and configured to excite the gaseous discharge medium to generate plasma, which produces an output beam. At least one electrode in the opposing electrode pair includes at least one of a recessed portion or a hollow portion, and each electrode in the electrode pair includes: The first surface faces inward toward the gas discharge medium; as well as A second surface, opposite to the first surface, wherein the at least one electrode includes the recessed portion formed within the second surface.

24. The light source device according to claim 23, wherein the recessed portion comprises a plurality of recessed portions.

25. The light source device of claim 24, wherein the plurality of recessed portions are located at each end of the at least one electrode.

26. The light source device of claim 23, wherein the at least one electrode includes the hollow portion formed between the first surface and the second surface.

27. The light source device according to claim 26, wherein the hollow portion comprises a plurality of hollow portions.

28. The light source device of claim 27, wherein each of the plurality of hollow portions is filled with a non-conductive material.

29. The light source device of claim 23, wherein the recessed portion or the hollow portion is positioned along the centerline of the at least one electrode.

30. The light source device according to claim 23, wherein the recessed portion or the hollow portion is located at the end of the at least one electrode.

31. The light source device of claim 23, wherein the recessed portion or the hollow portion is offset from the centerline of the at least one electrode.

32. The light source device according to claim 23, wherein the at least one electrode comprises the recessed portion and the hollow portion.

33. The light source device according to claim 23, wherein at least one of the recessed portion or the hollow portion is filled with a non-conductive material.

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