A device for extreme ultraviolet generation

Abstract

Herein disclosed is a device operable to generate extreme ultraviolet light, the device comprising: a first cladding region; a second cladding region; and a central region configured between the first cladding region and the second cladding region, wherein the first cladding region, the second cladding region, and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated; and wherein the waveguide is configured to receive free electrons so as to generate extreme ultraviolet light in the presence of free-electron excitation. Also disclosed is a device operable to generate extreme ultraviolet light, the device comprising: a first cladding region; and a central region configured adjacent to the first cladding region, wherein the first cladding region and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated, and wherein the waveguide is configured to receive free electrons so as to generate extreme ultraviolet light in the presence of free-electron excitation.

Description

A DEVICE FOR EXTREME ULTRAVIOLET GENERATIONCross-Reference to Related Application

[0001] This application claims the benefit of priority of Singapore Patent Application No. 10202303516X, filed 14 December 2023, the content of it being hereby incorporated by reference in its entirety for all purposes.Technical Field

[0002] The present disclosure relates to a device operable to generate extreme ultraviolet light.Background

[0003] Traditional extreme-ultraviolet lithography (EUVL) at 13.5 nm tends to be internationally accepted as a successor to optical lithography for high-volume manufacturing (HVM) in the semiconductor chip industry. Traditionally, discharge- produced plasma (DPP) and laser-produced plasma (LPP) may be the leading technologies for generating EUV radiation at 13.5 nm. In the case of a DPP source, an electrical discharge may be struck on a target material, producing a plasma that emits radiation at the EUV wavelength, whereas in the case of LPP, the target material may be evaporated, heated, and ionized by the high-power laser pulse to emit the EUV wavelength radiation in plasma. To meet the requirements of EUVL, one criteria for selecting a working material is a reasonable conversion efficiency (CE) and low produced debris. Tin (Sn) may be a favored material but the problem of optics protection against debris may still remain a major challenge, along with issues related to the long-term operation, stable droplet generation, and longer collector lifetime for achieving high power. Moreover, such systems tend to be large and costly, c.g., about 150 million USD each.

[0004] EUV imaging experiments using synchrotron radiation (SR) may have been studied for a long time. However, the SR facility may not be suitable for HVM due to its complex structure, enormous size and high cost. Free-electron lasers may have also been explored for the generation of EUV sources but until now a 13.5 nm EUVL source may not have been realized or difficult to realize. A table-top EUV source based on theprinciple of a X-ray tube may have been demonstrated for “at-wavelength” metrology and small-scale lithographic manufacturing. However, the power demonstrated tends to quite low (about 30 pW) at 13.5 nm for practical applications.

[0005] There is thus a need to provide for a solution that addresses one or more of the limitations mentioned above. The solution should at least provide for a chip-scale EUV source that may be compact, low-cost, user-friendly, and / or debris-free with long-term stability.Summary

[0006] In a first aspect, there is provided for a device operable to generate extreme ultraviolet light, the device comprising: a first cladding region; a second cladding region; and a central region configured between the first cladding region and the second cladding region, wherein the first cladding region, the second cladding region, and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated, and wherein the waveguide is configured to receive free electrons so as to generate extreme ultraviolet light in the presence of free-electron excitation.

[0007] In a second aspect, there is provided for a device operable to generate extreme ultraviolet light, the device comprising: a first cladding region; and a central region configured adjacent to the first cladding region, wherein the first cladding region and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated, and wherein the waveguide is configured to receive free electrons so as to generate extreme ultraviolet light in the presence of free-electron excitation.Brief Description of the Drawings

[0008] The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the present disclosure. In the following description, various embodiments of the present disclosure are described with reference to the following drawings, in which:

[0009] FIG. 1 is a table comparing traditional technologies and the present device.

[0010] FIG. 2 shows a chip-scale device of the present disclosure. FIG. 2 shows generation of EUV light from the present device involving a combination of characteristic radiation, “Bremsstrahlung”, and coherent EUV / X-ray generation processes under continuous electron excitation in the device. FIG. 2 also shows the present device renders enhancement of the EUV radiation through a Purcell effect. FIG. 2 further shows a non-limiting example of the chip-scale device, and its applications, room FIG. 3A shows a schematic of the present chip-scale device (EUV-generating), in which EUV-emitting multi-layered films are used to guide and shape the EUV radiation emitted as a result of the field emission interacting with the structure.

[0012] FIG. 3B shows a plot of the computational results of the spectral power at wavelength 13.5 nm as a function of the emission angle for a tri-multi-lay ered structure (line denoted (1): 40 nm Mo - 20 nm Si - 40 nm Mo - Si Substrate, line denoted (2): 80 x [4 nm Si - 2.5 nm Mo] - 20 nm Si - 80 x [4 nm Si - 2.5 nm Mo] - Si Substrate, line denoted (3): 20 nm Si). For the structure associated with the line denoted (1), the 40 nm Mo constitutes the first and second cladding regions, and the 20 nm Si constitutes the central region. For the structure associated with the line denoted (2), the first and second cladding regions are formed of 80 layers (i.e., 80 x) of 4 nm Si and 2.5 nm Mo, and 20 nm Si constitutes the central region.

[0013] FIG. 4A shows various examples of the present device, wherein the central region is configured to have a multi-layer structure. The solid rectangle is a general abstract illustration of all layers, i.e., non-central layers (forming the first and second cladding regions), which are not part of the central region, and may be constructed in any arbitrary fashion as described in the present disclosure and in the examples and further illustrated FIG. 5 A and FIG. 5B. The layers depicted with “dots” denote one type of material while the layers depicted with diagonal strips denote a different type of material from the layers with dots.

[0014] FIG. 4B shows various examples of the present device, wherein the central region is configured as a collection of nanospheres. The solid rectangle is a general abstract illustration of all layers, i.e., non-central layers (forming the cladding region), which are not pail of the central region, and may be constructed in any arbitrary fashion as described in the present disclosure and in the examples and further illustrated FIG. 5A and FIG. 5B. FIG. 4B depicts absence of the top non-central layers (a cladding region) as another example of the present device.

[0015] FIG. 5A shows a variation of the non-central layers (e.g., the cladding regions) in various examples of the present device, as a positively chirped structure with increasing periodicity (as depicted by the arrows) away from the central region. The solid rectangle is a general abstract illustration of all layers in the central region, which arc not part of the non-central layers (cladding regions), and may be constructed in any arbitrary fashion as described in the present disclosure and in the examples and further illustrated in preceding FIG. 4A and FIG. 4B. The layers depicted with dots denote one type of material while the layers depicted with diagonal strips denote a different type of material from the layers with dots.

[0016] FIG. 5B shows a variation of the non-central layers (e.g., the cladding regions) in various examples of the present device, as a negatively chirped structure with decreasing periodicity (as depicted by the arrows) away from the central region. The solid rectangle is a general abstract illustration of all layers in the central region, which are not part of the non-central layers (cladding regions), and may be constructed in any arbitrary fashion as described in the present disclosure and in the examples and further illustrated in preceding FIG. 4A and FIG. 4B. The layers depicted with dots denote one type of material while the layers depicted with diagonal strips denote a different type of material from the layers with dots.

[0017] FIG. 6A shows one of the setups for EUV generation and waveguiding experiments.

[0018] FIG. 6B shows a cross-sectional scanning electron microscopy (SEM) image of the fabricated multi-layered anode structure (17 nm Mo / 13.5 nm Si / 17 nm Mo) of the present device. Scale bar denotes 100 nm.

[0019] FIG. 6C depicts the relationship between EUV intensity and emission angle.

[0020] FIG. 6D shows the change in EUV intensity with increasing aperture size and therefore increasing current.

[0021] FIG. 6E shows a plot of counts versus energy for identifying EUV intensity enhancement of 2.5 times resulting from waveguiding within a multi-layer anode structure compared to a solitary Si film.

[0022] FIG. 6F depicts a multi-layered Mo / Si film used to show more than 100 times intensity enhancement achievable via waveguiding and more than 40% Purcell enhancement for an in-plane dipole.

[0023] FIG. 6G shows a plot of the intensity enhancement results obtained using a finite-difference-time-domain algorithm for solving Maxwell’s equations (MEEP). Particularly, the plot shows the intensity enhancement of a dipole emitting in the multilayered nanostructure depicted in FIG. 6F.

[0024] FIG. 6H shows a plot of the Purcell enhancement results obtained with a consideration of a dipole emitting in the multi-layered nanostructure depicted in FIG. 6F.

[0025] FIG. 7A shows one non-limiting example of the setups for EUV generation and waveguiding experiments.

[0026] FIG. 7B shows a cross-sectional transmission electron microscopy (TEM) image of the fabricated five pair Si-Mo multi-layered anode structure (17 nm Mo / 2nm SiC / 13.5 nm Si / 2 nm SiC / 17 nm Mo).

[0027] FIG. 7C show s a schematic of the chip-scale EUV source architecture based on the waveguiding EUV emitter used (a relatively straightforward structure).

[0028] FIG. 7D shows EUV intensity enhancement resulting from waveguiding and field localization within the multi-layer anode structure compared to a solitary Si film.

[0029] FIG. 7E shows the change in EUV intensity with increasing aperture size and therefore increasing current.

[0030] FIG. 7F shows the energy dispersive spectroscopy (EDS) mapping of the five pair Si-Mo multi-layered anode structure (17 nm Mo / 2nm SiC / 13.5 nm Si / 2 nm SiC / 17 nm Mo). The scale bar denotes 50 nm.

[0031] FIG. 8 shows a schematic of the present device positioned over a wafer to operate as a chip-scale EUV source for nanopatterning.Detailed Description

[0032] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the present disclosure may be practised.

[0033] Features that arc described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0034] The present disclosure relates to a device operable to generate and / or emit extreme-ultraviolet (EUV) light. Distinct from traditional light sources and devices, such as those described above, the present device may have an architecture that include one or more EUV emitters comprising an EUV waveguide housed in the present device. The present device, compared to traditional light sources, enhances the resulting EUV radiation that is propagated through the waveguide under continuous electron excitation in the device and the EUV generated exits from the device through one end of the waveguide. Extreme ultraviolet light refers to a region of the electromagnetic spectrum with wavelengths in the range of 10 nm to 121 nm, for example 13.5 nm.

[0035] Advantageously, the present device is operable as a chip-scale EUV light source that is low cost with controllable EUV light output while providing stable and debris- free operation. The size of the present device can be in the several tens of centimeters range in various examples, hence termed a “chip-scale” device in such examples. As the present device is operable as an EUV light source, the present device may be referred to as a chip-scale EUV light source.

[0036] FIG. 1 is a table summarizing the advantages of the present device over traditional devices and technology. In various traditional examples that may involve plasma, such as discharge -produced plasma and laser-produced plasma, the footprint of the devices and technologies tend to be considerably larger, e.g., in magnitude of metres. Such sizes meant the traditional devices and devices are not even suitable for on-chip usage. Also, these plasma-based devices and technologies may suffer fromdebris, poor life span, overly complex system, and / or not suitable for use in high volume manufacturing. In another traditional example relying on electron-beam-induced emission, like traditional plasma-based technologies, traditional devices based on electron-beam-induced emission may involve undesirably high footprint not suitable for on-chip applications and may not be suitable for high volume manufacturing. Moreover, traditional electron-beam-induced-emission devices may have a short life span. Conversely, compared to traditional plasma-based devices and traditional electron-beam-induced-emission devices, the present device can be configured as an on-chip device, does not suffer from debris issue, is based on a more straightforward architecture, relatively more economical, suitable for high volume manufacturing, and comparatively higher life span, etc. To better understand the present device and its advantages, details regarding various embodiments of the present device, uses of the present device, and advantages associated with the various embodiments are described below. Embodiments and advantages described for the present device of the first aspect and can be analogously valid for uses of the device described in the present disclosure, and vice versa. Where the various embodiments and advantages have already been described above and / or in the examples, they shall not be iterated for brevity.

[0037] In the present disclosure, there is provided a device operable to generate extreme ultraviolet light. The device may include a first cladding region, a second cladding region, and a central region configured between the first cladding region and the second cladding region. In various embodiments, the second cladding region may not be in contact with the first cladding region. In the device, the first cladding region, the second cladding region, and the central region may define a waveguide in which extreme ultraviolet light generated within the device is propagated. With such an architecture, the first cladding region and / or the second cladding region may help to confine the extreme ultraviolet light generated within the waveguide, enhancing the propagation of the extreme ultraviolet light through the waveguide, e.g., in the central region, with minimal loss. In various embodiments, the device may include a first cladding region and a central region configured adjacent to the first cladding region, wherein the first cladding region and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated. With such an architecture, the first cladding region and / or the central region may help to confine the extreme ultravioletlight generated within the waveguide, enhancing the propagation of the extreme ultraviolet light through the waveguide, e.g., in the central region, with minimal loss. The first cladding region, the second cladding region, and / or the central region, may include or may be formed of a layered structure. The layered structure may include or may be defined by one or more layers.10038] In the device, for example, in connection with various embodiments mentioned above (e.g., (i) wherein the central region is configured between the first cladding region and the second cladding region, or (ii) the central region is configured adjacent to the first cladding region), the waveguide may be configured to receive free electrons (e.g., from a source that provides such free electrons) so as to generate extreme ultraviolet light in the presence of free-electron excitation. The device may include or may be operably coupled to the source that provides the free electrons. The source may be, for example, an electron gun or a free-electron emission layer. In various examples, the device may include a free-electron emission layer. The free-electron emission layer may be configured to face the waveguide, wherein the waveguide may be configured to receive free electrons from the free-electron emission layer so as to generate extreme ultraviolet light in the presence of free-electron excitation. The architecture mentioned above does not hinder a stimulus (e.g., free-electrons or light) from reaching the waveguide to generate extreme ultraviolet light.

[0039] hi various embodiments, the free-electron emission layer (or the electron gun) is operable to generate a stimulus, e.g., as free electrons, which excites the waveguide into generating the extreme ultraviolet light. Said differently, the free electrons may be a stimulus for the waveguide to generate extreme ultraviolet light. The term “free electrons” refer to electrons that are not bound to any atom or molecule. The free electrons may collide with atoms or molecules of the materials forming the central region, transferring energy to render excitation of the materials of the central region, which generates the extreme ultraviolet light from the excitation. The free electrons may also be affected by the presence of atoms or molecules, resulting in acceleration and / or deceleration of the free electrons, and subsequent energy loss from the free electrons may be in the form of extreme ultraviolet light, hence rendering EUV as well. In various examples, the free-electron emission layer may be applied a voltage to render the free electrons. The voltage may be in the range of 1 kV to 15 kV. Despite suchvoltage, the present device advantageously operates with a very low current (in magnitudes of pA) and consumes reasonably low electrical power to generate the extreme ultraviolet light, compared to traditional devices that may require higher voltage and / or more current.

[0040] In various embodiments, the frcc-clcctron emission layer may be configured to face the first cladding region of the waveguide, and the waveguide may receive the free electrons projected from the free-electron emission layer orthogonally with respect to the first cladding region.

[0041] In various embodiments, the waveguide may comprise one end which the extreme ultraviolet light exits from. The other end of the waveguide may include a reflective element (e.g., a minor) that reflects light to the one end for exiting the waveguide.

[0042] In various embodiments, the first cladding region, the second cladding region, and the central region, may be configured to confine propagation of the extreme ultraviolet light in the central region. In various examples, the first cladding region and the second cladding region, may be constructed to render an architecture wherein the first cladding region and the second cladding region sandwich the central region. In addition, the first cladding region and the second cladding region may be formed of one or more materials that has a lower refractive index than the one or more materials of the central region for light to be contained and transmitted through the central region by total internal reflection. In various examples, the first cladding region and the second cladding region may be in contact with the central region to avoid extreme ultraviolet light from being lost through gaps between (i) the first cladding region and the central region and / or (ii) the second cladding region and the central region. In various examples, the first cladding region, the second cladding region, and the central region may be configured in a manner for the free electrons to encounter the first cladding region before the central region or the second cladding region before the central region. In such examples, the material of the first cladding region and / or the second cladding region may be selected or configured to minimize energy loss of the free electrons to the first cladding region or the second cladding region (before encountering the central region). In various examples, the first cladding region, the second cladding region, and the central region may be configured in a manner for the free electrons to be directed toa side of (i) the first cladding region, (ii) the second cladding region, and (iii) the central region. In such examples, the free electrons may directly encounter or enter the central region, avoiding or minimizing unwanted excitations in the first cladding region and / or second cladding regions so as to minimize energy loss of the free electrons to the first cladding region and / or the second cladding region.

[0043] hi certain non-limiting embodiments, the first cladding region may be formed of one material and / or the second cladding region may be formed of one material. That is to say, the first cladding region and / or the second cladding region may have a structure formed solely of one layer of one material.

[0044] In certain non-limiting embodiments, the first cladding region and / or the second cladding region may comprise a multi-layered structure, wherein the multi-layered structure may comprise a first material and a second material configured in an alternating manner parallel to the central region, wherein the first material and the second material may be compositionally different. The term “compositionally different” herein means two materials are not formed of the same material, for example, the first material may be molybdenum while the second material may be silicon carbide.

[0045] In certain non-limiting embodiments, the first material and the second material may be configured to each have a thickness decreasing in a manner which the first material and the second material proximal to the central region maybe thicker than the first material and the second material distal from the central region.

[0046] In certain non-limiting embodiments, the first material and the second material may be configured to each have a thickness increasing in a manner which the first material and the second material proximal to the central region may be thinner than the first material and the second material distal from the central region.

[0047] In various embodiments, the thickness of the one material fonning the first cladding region and / or the second cladding region, and the thickness of the first material and the second material, may be in the range of 1 nm to 10 pm, 10 nm to 10 pm, 100 nm to 10 pm, 1 pm to 10 pm, 10 nm to 100 nm, 10 nm to 50 nm, etc.

[0048] In various embodiments, the one material of the cladding region and / or the second cladding region, and the first material and the second material, may comprise molybdenum, silicon, silicon carbide, tungsten, cadmium, iron, a van der Waals material (e.g., a material whose atomic or molecular layers may be held together by vander Waals forces), a crystalline material, a nanomaterial (a material having a size or a dimension in the nanoscale, e.g., in a range of from 1 nm to 100 nm), or a quantum material (e.g., a material capable of exhibiting any quantum effect). Such materials, besides the ar chitecture of how the materials are configured, may be excited by the free electrons or the stimulus to render the extreme ultraviolet light. In addition, as mentioned above, the EUV generation may be generated from the free electrons themselves. For example, the free electrons may excite a material to produce EUV and / or the free electrons may be affected by the presence of a material that renders the free electrons to decelerate or accelerate, which may in turn render the free electrons to lose energy in the form of EUV radiation.

[0049] In certain non-limiting embodiments, the central region may be formed of one material. In such non-limiting embodiments, the second cladding region may be optionally present.

[0050] In certain non-limiting embodiments, the central region may comprise a multilayered structure formed with at least two compositionally different materials configured in an alternating manner parallel to the first cladding region and / or the second cladding region.

[0051] hi various embodiments, the thickness of the one material forming the central region, and the thickness of each of the at least two compositionally different materials, may be in the range of 1 nm to 10 pm, 10 nm to 10 pm, 100 nm to 10 pm, 1 pm to 10 pm, 10 nm to 100 nm, 10 nm to 50 nm, etc.

[0052] In various embodiments, the one material of the central region, and the at least two compositionally different materials, may comprise molybdenum, silicon, silicon carbide, tungsten, cadmium, iron, a van der Waals material, a crystalline material, a nanomaterial, or a quantum material.

[0053] In certain non-limiting embodiments, the central region may comprise nanospheres. In such non-limiting embodiments, the second cladding region may be optionally absent. The nanospheres each may comprise silicon and molybdenum, or a silicon core coated with a shell comprising molybdenum. The nanospheres are advantageous in molding the flow of EUV light on a nanoscale. Configuration of the nanospheres may lead to the formation of structures that can affect the emission of EUV light via the Purcell effect, and also shape and / or guide the EUV light after it has beenemitted. The diameter of the nanospheres may vary from 100 pm down to a subnanometer scale (e.g., 10 nm to 100 nm).

[0054] In various embodiments, the device may further comprise a cathode configured on a first substrate and proximal to the first cladding region. In various embodiments, the cathode may comprise the frcc-clcctron emission layer, wherein the frcc-clcctron emission layer may be configured on the first substrate.

[0055] In various embodiments, the free-electron emission layer may comprise nanowires or nanocones, wherein the nanowires or nanocones may comprise zinc oxide, silicon, or molybdenum. Nanocones may include cone-shape structures having a size or dimension in the nanoscale (e.g., in a range of from 1 nm to 100 nm). In various embodiments, the free-electron emission layer may comprise zinc oxide, silicon, molybdenum nanowircs, nanoconcs, or carbon nanotubes, and / or the cathode may comprise a metal contact configured on the first substrate. The metal contact (i.e., cathode metal contact) may be configured distal to the free-electron emission layer. The cathode metal contact may be any suitable metal that aids in the application of a voltage to the present device.

[0056] In various embodiments, the first substrate may comprise silicon and / or glass.

[0057] hr various embodiments, the waveguide may be configured as an anode, and wherein the waveguide may be configured on a second substrate. The anode and the cathode may be externally coupled for application of a voltage to the free-electron emission layer. A metal contact (i.e., anode metal contact) may be configured on the second substrate and / or distal to the waveguide. The anode metal contact may be any suitable metal that aids in the application of a voltage to the present device.

[0058] In various embodiments, the second substrate may comprise silicon and / or glass.

[0059] In various embodiments, the device may further comprise a cavity configured between the free-electron emission layer and the first cladding region, wherein the cavity may comprise vacuum. Advantageously, the cavity allows the free electrons generated from the cathode to accelerate and gain energy in an electric field so that the free electrons can reach a desirable energy level before contacting the anode. In other words, the cavity sets out a space for the free electrons to accelerate in an electric field to gain sufficient energy for later generation of EUV light.

[0060] In a second aspect of the present disclosure, there is provided a device operable to generate extreme ultraviolet light. The device has been described above in various embodiments of the first aspect of the present disclosure. The device may comprise a first cladding region, and a central region configured adjacent to the first cladding region, wherein the first cladding region and the central region define a waveguide in which extreme ultraviolet light generated within the device may be propagated, and wherein the waveguide may be configured to receive free electrons so as to generate extreme ultraiovlet light in the presence of free-electron excitation. Embodiments, features, and advantages described for the device in the first aspect of the present disclosure can be analogously valid for the device described in the second aspect of the present disclosure, and vice versa. For example, in various embodiments, the central region may comprise nanosphcrcs. In such non-limiting embodiments, the second cladding region may be optionally absent. The nanospheres each may comprise silicon and molybdenum, or a silicon core coated with a shell comprising molybdenum. The nanospheres are advantageous in molding the flow of EUV light on a nanoscale. Configuration of the nanospheres may lead to the formation of structures that can affect the emission of EUV light via the Purcell effect, and also shape and / or guide the EUV light after it has been emitted. The diameter of the nanospheres may vary from 100 pm down to a sub-nanometer scale (e.g., 10 nm to 100 nm). As another example, the embodiments, features, and advantages regarding the first cladding region described in various embodiments of the device in the first aspect are applicable to various embodiments of the device in the second aspect. Tn any case, as the various embodiments, features, and advantages, have already been described above and in the examples section further hereinbelow, they shall not be iterated for brevity.

[0061] The word “substantially” does not exclude “completely” e.g. a composition which is “substantially free” from Y may be completely free from Y. Where necessary, the word “substantially” may be omitted from the definition of the present disclosure.

[0062] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0063] Tn the context of various embodiments, the tilde symbolas well as the terms “about” and “approximately”, as applied to a numeric value encompasses the exactvalue and a reasonable variance. The variance may be ±20%, ±10%, ±5%, ±1%, ±0.5%, ±0.1%, etc.

[0064] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0065] Unless specified otherwise, the terms "comprising" and "comprise", and grammatical variants thereof, are intended to represent "open" or "inclusive" language such that they include recited elements but also permit inclusion of additional, unrecited elements.Examples

[0066] The present disclosure relates to a chip-scale device operable to produce extreme ultraviolet (EUV) light. The chip-scale device includes free electron-driven nanomaterial(s), which generate EUV light. The free electron-driven nanomaterials may form or may include an EUV-waveguiding structure (interchangeably referred to as a “waveguide”) in the device and utilize on the combination of characteristic radiation, “Bremsstrahlung”, and coherent EUV / X-ray generation processes inside this waveguide under continuous electron excitation wtihin the device (see FIG. 2). In FIG. 2, it can be seen that the chip-scale device can be configured, for example, as an on- chip EUV source, which includes an anode, the waveguide (comprising the free electron-driven nanomaterials) from which EUV outputs, wherein the waveguide is arranged proximal to the anode, a cavity, and a cathode. The anode may be termed a “nanophotonic anode”, as it may include or may be configured with the waveguide that generates EUV light.

[0067] FIG. 2 shows generation of EUV light from free electron-driven nanomaterials characteristically comprising the EUV-waveguiding structure in the device and involving a combination of characteristic radiation, “Bremsstrahlung”, and coherent EUV / X-ray generation processes inside the waveguide (i.e., waveguiding structure) under continuous electron excitation in the device. Characteristic radiation, Bremsstrahlung and coherent radiative can happen even with a single layer structure. As for a multi-layer structure, the multi-layer structure may (i) enhance the emission rate and intensity of the processes, and (ii) shape and control the EUV light after it is emitted. The term “Bremsstrahlung” refers to braking radiation, which is radiationproduced when charged particles, such as electrons, are decelerated or deflected by other charged particles, such as an atomic nuclei. In other words, the radiation may come from a charged particle that is being decelerated or deflected. FIG. 2 shows the present device renders enhancement of the EUV radiation through a Purcell effect. The resulting EUV light, which is generated, enhanced and propagated all along the same waveguide under constant electron excitation inside the device, is then finally allowed to exit the device from its side through the end of the waveguide, avoiding the need for using an additional transparent optical window to outcouple the EUV light.

[0068] In the present device, characteristic radiation may arise when high energy free electrons collide with a material, the material may eject inner-shell electrons from atoms. As outer-shell electrons fall into these vacancies, the material may emit radiation at specific energies (characteristic of the element of the material). For generation of extreme ultraviolet light, the material is selected to emit a radiation in the EUV range (e.g., 10 nm to 121 nm). In the present device, “Bremsstrahlung” may arise when electrons are decelerated as the electrons pass near the nuclei of atoms in a material, resulting in the emission of radiation across a continuous spectrum. For EUV generation, the “Bremsstrahlung” may produce radiation in the EUV range, especially when the incident electrons have high energy (e.g., free electrons) and the material selected emits EUV radiation when bombarded with such electrons. The continuous spectrum may include a range of wavelengths that includes EUV light or just radiation in the EUV range, contributing to the overall EUV output. In the present device, coherent EUV generation processes may be involved. Coherent EUV generation processes, in the context of the present disclosure, may include parametric X-ray radiation (PXR), coherent Bremsstrahlung, and / or other high-order emission processes that result when free electrons interact with a periodic array of atoms, ions, or molecules (e.g., in a crystalline material). Parametric X-ray radiation is generated when a free electron at constant velocity traverses a periodic array of atoms (or ions or molecules) - this excites dipoles in each atom (or ion or molecule), and the radiation of the resulting periodic array of excited dipoles constructively interferes to generate intense coherent radiation peaks at selected photon energies (in the present context, EUV photon energies). Coherent Bremsstrahlung occurs when the free electron is wiggled by the periodic atomic potential as it traverses the periodic atomic structure. The wiggling ofthe free electron trajectory causes the free electron to lose energy in the form of EUV light, like how electrons radiate in a wiggler or an undulator. Higher-order coherent EUV radiation processes may also occur through the excitation of atomic dipoles by the wiggling part of the electron trajectory. In summary, the present device may involve any combination of these processes to generate EUV light.

[0069] The present device, due to its architecture of the claddings regions (e.g., layers) and the central region as mentioned above, in combination with the materials used for the cladding and central regions, is able to render a Purcell effect to enhance generation of extreme ultraviolet light. The enhancement of the EUV radiation in the present device involves a Purcell effect at the nanoscale along the waveguide while also collecting and propagating the EUV light (see FIG. 2). The Purcell effect involves the enhancement of spontaneous emission of a light (in this instance extreme ultraviolet light) from an excited atom or molecule when it is placed in a cavity or a structured environment that supports such enhancement. The resulting EUV light is generated, enhanced and propagated all along the same waveguide under constant electron excitation inside the device. The resulting EUV light is then directed to finally exit from the device from its side through an end of the waveguide, avoiding the need for any additional transparent optical window to outcouple the EUV light. The term “outcouple”, in the context of the present disclosure, refers to directing light (e.g., EUV light) out from the source that generates the light.

[0070] The waveguide of the present device, to render EUV generation and / or emission, can include a variety of semiconductor-based and composite-based materials, that may range in the form of powder to thin film to Van der Waals stacked two dimensional (2D) materials, wherein such materials can be made into an EUV waveguide.

[0071] As mentioned above, the present device includes a material that can be frcc- electron driven, that is, the material can be driven by free electrons, wherein the free electrons (e.g., high energy electrons) are utilized to generate or manipulate electromagnetic waves so as to direct or control the electrons to render EUV. For the “free-electron driving” in the present device, it may involve a cold field emission process that generates an electron beam in the device when biased under high voltages of 1 kV to 15 kV. Advantageously, the present device operates with a very low current(in magnitudes of pA) and thus consumes reasonably low electrical power (in magnitudes of mW) despite the high bias (kV).

[0072] Advantageously, compared to traditional EUV generation systems and devices, which tend to be undesirably large (several orders of magnitude larger in size compared to the present device), the size of the present EUV device arc in the several tens of centimeters range, hence termed “chip-scale”, and can be stacked in arrays if desired.

[0073] The present device, its uses and applications, are described in further details, by way of non-limiting examples, as set forth below.

[0074] Example 1: Non-Limiting Examples of Architectures of the Present Device

[0075] The present example describes a non-limiting demonstration of the chip-scale device of the present disclosure, showing EUV light generation, as depicted in FIG. 3A. The device contains frcc-clcctron emitters on a first substrate (substrate 1). In the present disclosure, the terms “free-emission emitters” and “free-electron emission layer” are used exchangeably to refer to a component in the device that renders free electrons. Such free-electron emission layer may undergo a cold field emission process as mentioned above. In a cold field emission process (denoted as “field emission” in FIG. 3 A), free electrons may be generated and emitted from a material’s surface due to an electric field and in the absence of any thermal excitation. The electric field may be rendered by applying a voltage to the free-electron emission layer. One non-limiting example of such free-electron emission layer may include zinc oxide nanowires or a layer of zinc oxide nanowires. The device also houses a multi-layer structure capable of radiating EUV under free-electron excitation (via any of the combinations of characteristic radiation, Bremsstrahlung, and coherent EUV / X-ray generation processes) with enhanced field localization (Purcell effect) and to guide this EUV light, wherein the multi-layer structure may be proximal to (e.g„ placed on) a second substrate (substrate 2). The multi-layer structure may be referred to as the waveguiding structure, as it includes materials constructed with an architecture that serves as a waveguide for propagation of extreme ultraviolet light that is generated therein. Both the substrates (1 and 2) can be made from a variety of wafer, such as but not limited to, wafer formed of silicon and / or glass. It may be possible to bond these substrates, for this reason, the substrates can be of the same material, which makes the thermal expansion coefficientsidentical. In other words, the first and second substrates can be of any suitable materials having the same thermal coefficients.

[0076] In various examples of the device (having the architecture shown in FIG. 3A), a multi-layered structure comprising of 40 nm thick Mo, 20 nm thick Si and 40 nm thick Mo films on a Si substrate (substrate 2 in FIG. 3A) was constructed. Si denotes silicon and Mo denotes molybdenum. In addition, it was found that the global Purcell enhancement Fp, for the present device, demonstrated that an emission rate enhancement of over 100% is possible (FIG. ,3B). A Purcell factor greater than one indicates an enhancement of the emission rate, and a larger Fpindicates greater enhancement. In FIG. 3B, the spectral power refers to the power per unit wavelength per unit solid angle emitted by a dipole located between the multi-layer films. Each case is labelled with Fp, which denotes the Purcell enhancement. The Purcell enhancement represents the enhancement in intrinsic decay rate of an emitter (e.g., free-electron emitter). Fpis obtained by integrating the spectral power curve shown in FIG. 3B over all emission angles and dividing it by the total radiated power of a dipole in free space, i.e., it is the total rate / power enhancement compared to free space. It can be seen that the profile of the spectral power in both space and frequency, as well as the value of Fp, appears to heavily depend on and can be controlled by its nanophotonic environment. It can be seen that even with a one-dimensional (ID) structure, values of Fpachieved in excess of 100% is possible. In FIG. 3B, the multi-layer structures denoted (1) and (2) are non-limiting examples of the present device having unique architectures of materials that confer the ability to harness the Purcell effect for EUV enhancement. As mentioned above, multi-layer structure (1) is constructed based on 40 nm Mo - 20 nm Si - 40 nm Mo - Si substrate, this rendered a Fpof 2.34. Multi-layer structure (2) is constructed based on 80 x [4nm Si - 2.5 nm Mo] - 20 nm Si - 80 x [4nm Si - 2.5 nm Mo] - Si Substrate, this rendered a Fpof 2.75. Structure (3) is just 20 nm of silicon, which indicates a Fpof 1.21. In general, the Purcell effect at a certain selected photon energy may increase with number of layers, but there may be many other factors to consider, such as the material and the thicknesses of each individual material or layer. Therefore, a multi-layer architecture X with N layers may perform better than another multi-layer architecture Y with M layers (wherein M is greater than N, and both M and N are whole numbers) just because the multi-layer architecture Y may include a poorermaterial and / or other parameters (e.g., thinner). In any case, FIG. 3B demonstrates the possibility of achieving Purcell factor enhancement using multi-layer structures, instead of rigorously analyzing how the Purcell mechanism scales with various parameters.

[0077] The choice of materials is not limited to Mo and Si as demonstrated for FIG. 3B, but can include any materials that include single clement materials, such as W, Cd, Fe, etc., as well as quantum materials such as van der Waals materials and / or having heterostructures. W denotes tungsten, Cd denotes cadmium, and Fe denotes iron. The choice of material may depend on (a) the nature of the EUV emission mechanism being used (e.g., characteristic lines vs. parametric X-ray radiation in the EUV regime), and / or (b) the desired emission wavelength, because different elements have different bound electron energies, and the desired emission wavelength may have to match an existing difference in bound electron energies in the material if, for example, characteristic lines are used. The thickness is optionally unique, and may depend on the wavelength(s) to enhance or control, the properties of the output radiation desired, and the quality factor and other properties of the nanophotonic structure to be constructed. However, the thickness for each material layer may be in the range of 1 nm to 10 micrometers. Although a one-dimensional periodic structure may be considered, the nanophotonics- enhanced EUV generation of the present device subsumes all periodic and non-periodic structures with variations in two and / or three spatial dimensions, for the purposes of enhancing and / or controlling the output spectra of free-electron driven EUV emission.

[0078] In various non-limiting examples, a device operable to generate extreme ultraviolet (EUV) light is demonstrated. The device may include a waveguide having a first cladding region, a second cladding region, and a central region (which serves as a light guiding layer) between the first cladding region and the second cladding region. The device may include a free-electron emission layer arranged to face the first cladding region of the waveguide and configured to provide light (or free electrons) emission (as a stimulus) to the waveguide so as to excite the waveguide to emit EUV light.

[0079] In various non-limiting examples, the waveguide may be configured to receive the light emission from the free-electron emission layer in a direction perpendicular to the first cladding region, provide Purcell enhancement to the received light emission, and guide the light emission along the light guiding layer and to emit the light at the end of the waveguide in a direction parallel to the first cladding region.

[0080] In various non-limiting examples, each of the first cladding region and the second cladding region may be a multi-layered structure comprising alternating layers of a first material and a second material. The first material is composed of a different material from the second material. For example, in a tri-layer structure of Mo-Si-Mo, the EUV light is propagated in the central Si rcgion / laycr. In a multi-layer structure formed of alternating layers of Mo and Si, the light may propagate in one or more of the Si layers, and hence multiple layers of guided EUV light, which may be one way of scaling up an EUV generation process, e.g., by including a multi-layer structure instead of just relying on one layer.

[0081] In various non-limiting examples, the central region (e.g., the central layer, which serves as a light guiding layer) may be or may include nanospheres or configured to have a multi-layer central region configuration, sec FIG. 4B and FIG. 4A, respectively. As mentioned above, FIG. 4A depicts examples of the present device, wherein the central region is configured as a multi-layer structure. Such multi-layer structure may be composed of two compositionally different materials arranged in an alternating manner. FIG. 4B, as mentioned above, depicts examples of the present device, wherein the central region includes nanospheres. An example of a nanosphere is a Si core coated with a Mo shell around the Si core. In such examples where nanospheres are used, the top non-central layers (top cladding region) may be optionally absent, i.e., only one cladding region / layer may be used. In examples where only one cladding region is used (or where nanospheres are used), the EUV generation and propagation are affected not by confining layers, but by the presence and configuration of the nanospheres. The nanospheres are not only for generating the EUV light, but also serve to confine and guide the EUV light, depending on how the nanospheres are distributed. An example illustration of only “one cladding region” is already in FIG. 4B (showing nanosphcrcs). Another example illustration of only “one cladding region” is in FIG. 3A, where the nanophotonic “multilayer films” is completely replaced by an archiecture having only “one cladding region”.

[0082] Advantageously, the present device is versatile in that it may be constructed to have structures to generate and / or guide and / or enhance EUV of one or more wavelengths, wherein the structures may be configured to have different parameters from other wavelength ranges. For instance, the thickness of each layer and material foreach layer can be different. As another instance, different geometries may be desirable for different wavelengths. Hence, in a device for generating EUV with multiple wavelengths, it may be advantageous to accommodate all the different geometries while ensuring that the geometries cater to one wavelength without suppressing another wavelength. Advantageously, the present device is further versatile in that it can be configured for one EUV wavelength output or for an output with multiple EUV wavelengths. Furthermore, in certain non-limiting examples, the present device may involve layered structures where the thickness of each layer is not constant (i.e., nonperiodic), see FIG. 5 A and FIG. 5B. FIG. 5 A depicts examples of the present device, wherein the two non-central layers (each of the non-central layers constitute a cladding layer of a cladding region) has a positively chirped structure, with increasing periodicity away from the central region. That is to say, the materials forming the non-central layers (i.e., cladding regions) decreases in thickness with increasing distance from central region, e.g., the layer of material closest to the central region is the thickest while the layer of material furthest from the central region is the thinnest. FIG. 5B depicts examples of the present device, wherein the two non-central layers (each of the non- central layers constitute a cladding layer of a cladding region) has a negatively chirped structure, with decreasing periodicity away from the central region. That is to say, the materials forming the non-central layers (i.e., cladding regions) increases in thickness with increasing distance from central region, e.g., the layer of material closest to the central region is the thinnest while the layer of material furthest from the central region is the thickest. The chirped structures in FIG. 5 A and 5B may help to manage how different frequency components of radiation travel through a medium, which in turn helps minimize distortion and enhance EUV propagation. The term “chirped structure” in the present disclosure refers to a structure having materials of different thicknesses, such that the periodic arrangcmcnt / thickncss of the materials is not constant, e.g., thickness of the materials vary with vertical distance within a cladding region. By containing multiple periodicities, chirped structures may offer the potential for a stronger interaction with free electrons in a manner that enhances a broader range of EUV wavelengths generated.

[0083] Possible architectures of the waveguide can include, but not limited to, a combination of the central region of FIG. 4A and non-central layers (cladding regions)of FIG. 5A, a combination of the central region of FIG. 4A and non-central layers (cladding regions) of FIG. 5B, a combination of the central region of FIG. 4B and at least one non-central layer (cladding region) of FIG. 5A, and a combination of the central region of FIG. 4B and at least one non-central layer (cladding region) of FIG. 5B.

[0084] Example 2A: Characterisation and Results for a Non-limiting Example of the Present Device

[0085] Experimental and preliminary theoretical results demonstrating EUV waveguiding and enhancement are demonstrated in FIG. 6A to 6H.

[0086] FIG. 6A to 6E present an experimental demonstration of EUV waveguiding and enhancement, including scaling up the EUV power by increasing incident current. With micro- Ampcrc-lcvcl currents, EUV powers in excess of 10 pW can already be accessed. FIG. 6F to 6H show preliminary theoretical results predicting the enhancement of output power by over 100 times with a multilayer one-dimensional waveguide design. For FIG. 6A to 6H, where applicable or suitable, preliminary theoretical results were obtained using classical Maxwell’s equations.

[0087] FIG. 6A shows the experimental setup used to demonstrate EUV generation from the present device. The experimental setup is also used to demonstrate the waveguiding and enhancement of EUV generation and propagation in the present device. A sample of the multi-layer structure used in various examples of the present device is placed on a sample holder. The multi-layer structure is composed of 17 nm Mo / 13.5 nm Si / 17 nm Mo as shown in FIG. 6B. An electron gun is configured to provide free electrons (in place of a free-electron emission layer) to the sample. An EUV detector is placed proximal to the sample holder to detect EUV generated and emitted from the multi-layer structure. It can be seen in FIG. 6A that the sample may be positioned in a manner to project the EUV from the multi-layer at a desired direction (demonstrating capability of the multi-layer structure to serve as a waveguide). The angle a and the angle of 61° may be arbitrary. FIG. 6B shows the EUV generated and propagated within the multi-layer structure, wherein the materials (e.g., Mo and Si are constructed as shown in the architecture) are continuously excited by the free electrons to generate the EUV therein. FIG. 6C depicts the relationship between EUV intensity and emission angle. From FIG. 6C, it can be seen that the analytical expression and theexperimental results are a fit, taking into account the distribution of generated EUV photons inside the silicon layer, and their “re-absorption” when propagating out of the target, demonstrating successful waveguiding and scaling of the layers. The term “reabsorption” herein refers to a material absorbing the photons (which excite bound electrons in the material or become phonons). FIG. 6D shows the change in EUV intensity with increasing aperture size (size of the aperture of the electron gun from which free electrons are emitted) and therefore increasing current. The aperture of the electron gun may be used to block some part of the current from reaching the sample. FIG. 6E demonstrates that the EUV intensity is enhanced 2.5 times due to waveguiding within the multi-layer structure (configured as the anode) compared to a solitary Si film.

[0088] FIG. 6F shows a multi-layered structure formed from alternating layers of Mo and Si, wherein examples of present device including such architecture arc capable of demonstrating more than 100 times intensity enhancement achievable via waveguiding and more than 40% Purcell enhancement for an in-plane dipole (see FIG. 6G and 6H, which substantiates such results). The results in FIG. 6G were obtained using a finite- difference-time-domain algorithm for solving Maxwell’s equations (MEEP). More specifically, the results in FIG. 6G show the EUV intensity enhancements possible using the type of structure shown in FIG. 6F. The horizontal axis in FIG. 6G identified as “transverse dimension” refers to the length of the multilayer structure depicted in FIG. 6F, and in this instance, the “length” refers to the distance between the leftmost and rightmost ends of the multilayer structure. The intensity enhancement varies as the multilayer structure developed becomes longer, with a desirable “length” in the range of about 500 nm to 1000 nm in this instance. The colormap denotes the side emission power enhancement of the multilayer structure compared to just using any traditional bulk material. The maximum enhancement was at around 1000 nm transverse dimension and the minimum enhancement was at around 3000 nm transverse dimension. For the results in FIG. 6H, a dipole emitting in a nanostructure (e.g., the spontaneous emission of a dopant ion) was considered. Using ab initio electrodynamic calculations, the Purcell factors computed are plotted in FIG. 6H, where an in-plane dipole was considered - demonstrating intensity enhancements exceeding 100 times, and Purcell enhancements exceeding 40%. The findings also revealed that out-of-plane dipoles experience intensity enhancements exceeding 10 times, and Purcellenhancements exceeding 20%, just by using, for example, a 7-layer waveguide construction. It is to note that such Purcell enhancements - which correspond to decay rate enhancements of the emitters - can lead to significant speed-ups in the throughput of any EUV application by reducing the emitter response time, in addition to their modest contribution to output power enhancement. In FIG. 6H, the transverse dimension is 200 nm, and the colormap denotes the Purcell enhancement compared to just usign any traditional bulk material.

[0089] Example 2B; Characterisation and Results for another Non-limiting Example of the Present Device

[0090] Experiments were further conducted for the present device having other architectures in addition to the investigation conducted for the multi-layered structure shown in FIG. 6F. FIG. 7A to 7F demonstrate for the results of the further experiments, achieving up to a 20-fold enhancement of the EUV emission using Si-Mo multi-layers (with SiC layers) in such examples of the present device so as to be operable as a waveguiding EUV emitter. FIG. 7A shows the same apparatus used in FIG. 6A, except that the sample loaded on the holder in FIG. 7A is a multi-layered structure comprising the alternating layers of Mo and Si (with SiC layers) with a platinum layer formed on the multi-layered structure as an additional layer for imaging purposes, i.e., to avoid charging issues during imaging and not integral to the multi-layered structure (see FIG. 7B). There may be an aluminum used as an anode contact (not shown). The angle of 61° may be arbitrary. The sample holder is a silicon substrate (same as that used in FIG. 6A). FIG. 7D is a plot demonstrating EUV intensity enhancement resulting from waveguiding and field localization within the multi-layer structure compared to a solitary Si film and a multi-layer structure consisting of one layer of Si-Mo. In general, more layers may lead to higher EUV enhancement (e.g., intensity), and more layers may better confine the EUV to the Si layers. That said, other factors, such as geometrical configurations as mentioned above and material choice, may affect the EUV intensity. FIG. 7E shows the change in EUV intensity with increasing aperture size (size of the aperture of the electron gun from which free electrons are emitted) and therefore increasing current. In general, an increase in aperture size may render more free electrons bombarding the multi-layer structure and hence a higher EUV intensity.

[0091] FIG. 7C is a schematic showing an example architecture of the present device based on a multi-layer structure comprising 17 nm Mo / 2 nm SiC / 13.5 nm Si / 2 nm SiC / 17 nm Mo. FIG. 7F is an EDS mapping of the multi-layer structure based on 17 nm Mo / 2 nm SiC / 13.5 nm Si / 2 nm SiC / 17 nm Mo. Examples of present device involving such multi-layer structure shown in FIG. 7C and FIG. 7F also demonstrated EUV enhancement. In these examples, EUV is generated from the characteristic peak of silicon, which is the characteristic X-ray radiation generated in and enhanced by the waveguide structure.

[0092] Example 3: Applications of the Present Device

[0093] Using the chip-scale device of the present disclosure as an EUV source, nanopatterning / nanolithography can be carried out, with the option of using a single chip or integration of multiple chips into an array to meet industrial requirements for EUV applications. The nanopatterning process can be accomplished through an optical setup integrating EUV-emitting chip-scale devices, alongside essential components including an EUV mask, robust mounting and alignment systems, as depicted in FIG. 8. The fabrication of masks proceeds with precision, beginning with the deposition of a SisN4 membrane on a Si substrate, followed by controlled etching to form the desired membrane structure. Subsequent steps, such as spin-coating of resist and direct electron beam lithography, enable the creation of nanopatterns with specific dimensions (~10 nm). Integrating these masks onto stainless steel mounts helps ensure stability and precise alignment within the optical system. The fine-tuning and alignment of EUV- emitting chip-scale devices and masks play pivotal roles in improving the overall performance of the system.

[0094] In summary, commercial applications of the present device, which is a debris- free chip-scale EUV source, can include EUV nanolithography, EUV microscopy, and EUV characterization tools (sec FIG. 2).

[0095] While the present disclosure has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims. The scope of the present disclosure is thus indicated by the appended claims and all changeswhich come within the meaning and range of equivalency of the claims are therefore intended to be embraced.

Claims

CLAIMS1. A device operable to generate extreme ultraviolet light, the device comprising: a first cladding region; a second cladding region; and a central region configured between the first cladding region and the second cladding region, wherein the first cladding region, the second cladding region, and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated, and wherein the waveguide is configured to receive free electrons so as to generate extreme ultraviolet light in the presence of free-electron excitation.

2. The device of claim 1 , further comprising a free-electron emission layer, wherein the free-electron emission layer is configured to face the first cladding region of the waveguide, and the waveguide receives the free electrons projected from the free- electron emission layer orthogonally with respect to the first cladding region.

3. The device of claim 1 or 2, wherein the waveguide comprises one end which the extreme ultraviolet light exits from.

4. The device of any one of claims 1 to 3, wherein the first cladding region, the second cladding region, and the central region are configured to confine propagation of the extreme ultraviolet light in the central region.

5. The device of any one of claims 1 to 4, wherein the first cladding region and / or the second cladding region are formed of one material.

6. The device of any one of claims 1 to 4, wherein the first cladding region and / or the second cladding region comprise a multi-layered structure, wherein the multilayered structure comprises a first material and a second material configured in analternating manner parallel to the central region, wherein the first material and the second material are compositionally different.

7. The device of claim 6, wherein the first material and the second material are configured to each have a thickness decreasing in a manner which the first material and the second material proximal to the central region are thicker than the first material and the second material distal from the central region.

8. The device of claim 6, wherein the first material and the second material are configured to each have a thickness increasing in a manner which the first material and the second material proximal to the central region axe thinner than the first material and the second material distal from the central region.

9. The device of any one of claims 5 to 8, wherein the one material of the first cladding region and / or the second cladding region, and the first material and the second material, comprise molybdenum, silicon, silicon carbide, tungsten, cadmium, iron, a Van der Waals material, a crystalline material, a nanomaterial, or a quantum material.

10. The device of any one of claims 1 to 9, wherein the central region is formed of one material.1 1 . The device of any one of claims 1 to 9, wherein the central region comprises a multi-layered structure formed with at least two compositionally different materials configured in an alternating manner parallel to the first cladding region and / or the second cladding region.

12. The device of claim 10 or 11, wherein the one material of the central region, and the at least two compositionally different materials, comprise molybdenum, silicon, silicon carbide, tungsten, cadmium, iron, a van der Waals material, a crystalline material, a nanomaterial, or a quantum material.

13. The device of any one of claims 1 to 9, wherein the central region comprises nanospheres, and wherein the nanospheres each comprises silicon and molybdenum, or a silicon core coated with a shell comprising molybdenum.

14. The device of any one of claims 1 to 13, further comprising a cathode configured on a first substrate and proximal to the first cladding region.

15. The device of claim 14, wherein the cathode comprises the free-electron emission layer, wherein the free-electron emission layer is configured on the first substrate.

16. The device of any one of claims 1 to 15, wherein the frcc-clcctron emission layer comprises zinc oxide, silicon, molybdenum nanowires, nanocones, or carbon nanotubes, and / or the cathode comprises a metal contact configured on the first substrate.

17. The device of any one of claims 14 to 16, wherein the first substrate comprises silicon and / or glass.

18. The device of any one of claims 1 to 17, wherein the waveguide is configured as an anode, and wherein the waveguide is configured on a second substrate.

19. The device of claim 18, wherein the second substrate comprises silicon and / or glass.

20. The device of any one of claims 1 to 19, further comprising a cavity configured between the free-electron emission layer and the first cladding region, wherein the cavity comprises vacuum.

21. A device operable to generate extreme ultraviolet light, the device comprising: a first cladding region; and a central region configured adjacent to the first cladding region,wherein the first cladding region and the central region define a waveguide in which extreme ultraviolet light generated within the device is propagated, and wherein the waveguide is configured to receive free electrons so as to generate extreme ultraviolet light in the presence of frcc-clcctron excitation.

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