Broadband light source assembly

Abstract

A broadband light source assembly, a metrology device, and a method of generating broadband radiation are disclosed. The broadband light source comprises a femtosecond pump laser arranged to emit a radiation pulse, wherein the radiation pulse has an energy per pump pulse greater than 50 nJ; and comprising a fully positive dispersive optical fiber arranged to receive the radiation pulse.

Description

Broadband light source components Cross-references to related applications

[0001] This application claims priority to European Patent Application No. 23201262.5, filed on 2 October 2023, and European Patent Application No. 23202487.7, filed on 9 October 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a broadband light source assembly. In particular, the broadband light source assembly includes a femtosecond pumped laser and a fully positive dispersive fiber. Background Technology

[0003] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. For example, a lithography apparatus can be used in the manufacture of integrated circuits (ICs). For example, a lithography apparatus can project a pattern (also often referred to as a “design layout” or “design”) at a patterning device (e.g., a mask) onto a radiation-sensitive material layer (resist) provided on a substrate (e.g., a wafer).

[0004] 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. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Compared to photolithography equipment using radiation with a wavelength of, for example, 193 nm, photolithography equipment using extreme ultraviolet (EUV) radiation in the wavelength range of 4–20 nm (e.g., 6.7 nm or 13.5 nm) can form smaller features on the substrate.

[0005] Low-k1 lithography can be used to fabricate features smaller than the classical resolution limit of lithography equipment. In such a process, the resolution formula can be expressed as CD = k1 × λ / NA, where λ is the wavelength of the radiation used, NA is the numerical aperture of the projection optics in the lithography equipment, CD is the “critical dimension” (typically the smallest feature size printed, but in this example, half a pitch), and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it is to replicate on the substrate a pattern with a shape and size similar to what the circuit designer has planned to achieve specific electrical functionality and performance. To overcome these difficulties, complex fine-tuning steps can be applied to the lithography projection equipment and / or the design layout. These steps include, but are not limited to: optimizing NA, customizing the illumination scheme, using phase-shifting patterning devices, various optimizations to the design layout (such as optical proximity correction (OPC, sometimes also called “optical and process correction”), or other methods generally defined as “resolution enhancement techniques” (RET). Alternatively, tight control loops used to control the stability of the lithography equipment can be used to improve pattern reproducibility at low k1.

[0006] Numerous measurement systems can be used in the field of photolithography, both within and outside the lithography apparatus. Typically, such measurement systems use a radiation source to irradiate a target and employ an operable detection system to measure at least one property of a portion of the incident radiation scattered from the target. Examples of measurement systems external to the lithography apparatus are inspection or metrological devices that can be used to determine the properties of patterns previously projected onto a substrate by the lithography apparatus. For example, such external inspection devices may include a scatterometer. Examples of measurement systems available within the lithography apparatus include: topography measurement systems (also known as leveling sensors); position measurement systems (e.g., interferometric devices) for determining the position of a mask or wafer stage; and alignment sensors for determining the position of alignment marks. These measurement devices can perform measurements using electromagnetic radiation.

[0007] Different types of radiation can be used to probe different properties of a pattern. Some measurement systems can use broadband light source components. Such broadband light source components can be supercontinuum light source components and can include an optical fiber through which a pulsed pump radiation beam propagates to broaden the radiation spectrum. The spectral broadening of the input radiation may be primarily dominated by modulation instabilities, self-phase modulation, or soliton dynamics. Summary of the Invention

[0008] The inventors have discovered that known broadband light source components are affected by the relative intensity noise (RIN) level of the generated white light, making them unsuitable for certain applications. For example, for known broadband light source components that use modulation instability (MI)-based white light generation processes to generate white light, the RIN of the white light may be too high to achieve the required on-product overlay (OPO), for example, an OPO of 1 nm or lower.

[0009] According to one aspect of the present invention, a broadband light source assembly is provided, comprising: a femtosecond pumped laser arranged to emit radiation pulses, wherein the radiation pulses have an energy greater than 50 nJ per pump pulse; and a fully positive dispersive fiber arranged to receive the radiation pulses, wherein the broadband radiation has a power spectral density of at least 3 mW / nm in a wavelength band of 500-900 nm.

[0010] This broadband light source component advantageously converts radiation pulses completely into broadband radiation, resulting in an output spectrum free of residual spectral spikes from the pump.

[0011] Furthermore, the relative intensity noise (RIN) level of the radiation generated by the broadband light source assembly (i.e., the output of the optical fiber) is lower than that of known light source assemblies based on soliton and modulation instability (MI) seeding processes. In particular, this broadband light source assembly can generate radiation with… Radiation.

[0012] The optical fiber may include: a core region; and a cladding region surrounding the core region; wherein both the core region and the cladding region include a material having a first refractive index, and the cladding region also includes a plurality of microstructures extending along the longitudinal axis of the optical fiber from the input end to the output end of the optical fiber, the plurality of microstructures (i) being arranged in a cross-sectional pattern including at least one microstructure ring surrounding the core region, and (ii) having a second refractive index less than the first refractive index.

[0013] Multiple microstructures can be hollow. Multiple microstructures can be air-filled. This broadband light source assembly advantageously eliminates the need to encase the optical fiber in a gas-containing reservoir (also referred to as a housing, container, or gas chamber). Because it contains no gas-related components, the size and complexity of the assembly can be reduced. This reduction in size means it is easier to integrate into suitable devices, such as sensors.

[0014] The ratio between the diameter of each microstructure and the pitch of the microstructure can be in the range of 0.33-0.45, and optionally in the range of 0.36-0.42.

[0015] The cross-sectional pattern may include multiple microstructure rings surrounding the fiber core region.

[0016] The cross-sectional pattern may include at least three microstructure rings surrounding the core region, optionally at least four microstructure rings surrounding the core region, and optionally at least five microstructure rings surrounding the core region.

[0017] The microstructure ring adjacent to the fiber core region can have six microstructures.

[0018] Each microstructure ring in at least one microstructure ring may have a hexagonal shape.

[0019] The core region can have a diameter of less than or equal to 3 µm.

[0020] The fiber length can be less than 10 cm, optionally less than 5 cm. This effectively reduces loss in the fiber and reduces fiber-related problems caused by bending or stretching. The shorter fiber length also advantageously allows for high integration of broadband light source components into suitable devices (which can be positioned vertically or horizontally according to sensor requirements).

[0021] The radiation pulse may have a pump pulse energy of at least 75 nJ, and optionally at least 100 nJ per pump pulse.

[0022] The radiation pulse can have a center pump wavelength in the range of 700-1800 nm.

[0023] The radiated pulse may have a peak power of at least 200 kW, optionally at least 300 kW, optionally at least 400 kW, optionally at least 500 kW, optionally at least 600 kW.

[0024] Optical fibers can generate broadband radiation in the wavelength range of 500-900 nm, optionally in the wavelength range of 500-1200 nm, optionally in the wavelength range of 500-1500 nm, optionally in the wavelength range of 500-1800 nm, and optionally in the wavelength range of 485-1800 nm.

[0025] The broadband radiation exhibits a power spectral density of at least 3 mW / nm within the wavelength band of 500–900 nm. Therefore, this broadband light source component possesses a higher power spectral density compared to known light source components based on soliton self-compression.

[0026] Optical fibers can exhibit a dispersion at the minimum wavelength of -1 ps / (nm) km) and -100 ps / (nm) Dispersion values ​​between km).

[0027] Materials having a first refractive index may include silicon dioxide.

[0028] Radiation pulses can have pulse durations ranging from 10 to 500 fs.

[0029] According to another aspect of the present invention, a photolithography apparatus is provided, including a broadband light source assembly according to any embodiment described herein.

[0030] According to another aspect of the present invention, a measuring device is provided, including a broadband light source assembly according to any embodiment described herein.

[0031] According to another aspect of the present invention, a holographic measurement device is provided, comprising a photonic crystal fiber according to any embodiment described herein.

[0032] According to another aspect of the invention, a method for generating broadband radiation is provided, the method comprising: providing a radiation pulse emitted from a femtosecond pump laser to a fully positive dispersive optical fiber, wherein the radiation pulse has an energy greater than 50 nJ per pump pulse, the optical fiber outputting broadband radiation. Attached Figure Description

[0033] The embodiments of the invention are described by way of example only with reference to the accompanying schematic diagrams, in which: - Figure 1 depicts a schematic diagram of a photolithography apparatus; - Figure 2 depicts a schematic diagram of a photolithography unit; - Figure 3 illustrates a schematic representation of overall photolithography, showing collaboration among three key technologies to optimize semiconductor manufacturing; - Figure 4 depicts a schematic diagram of a scattering measurement tool used as a measurement device; - Figure 5 depicts a schematic diagram of a leveling sensor measurement tool; - Figure 6 depicts a schematic diagram of an alignment sensor measurement tool; - Figure 7 depicts a schematic diagram of a broadband light source assembly; - Figure 8 depicts a cross-sectional view of an optical fiber used in the broadband light source assembly to illustrate the dimensions of the optical fiber; - Figures 9a-9c illustrate how the diameter of the fiber core region can be measured; - Figure 10 depicts an example of a total positive dispersion profile of an optical fiber; - Figure 11 depicts spectral broadening plots of white light generated at cross-sections of different fiber lengths, highlighting the evolution mechanism of the white light generated by the optical fiber; and - Figure 12 depicts a power spectral density plot of the radiation generated by the broadband light source assembly. Detailed Implementation

[0034] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., radiation with wavelengths of 365, 248, 193, 157, or 126 nm) and extreme ultraviolet radiation (e.g., radiation with wavelengths in the range of 5–100 nm).

[0035] As used herein, the terms “mask,” “mask,” or “patterning device” can be broadly interpreted to refer to a general patterning device that can be used to impart a patterned cross-section to a radiation beam, corresponding to a pattern to be created in a target area of ​​a substrate. The term “light valve” can also be used in this context. Examples of other such patterning devices, besides classic masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), include programmable mirror arrays and programmable LCD arrays.

[0036] Figure 1 schematically depicts a lithography apparatus LA. The lithography apparatus LA includes: an irradiation system (also referred to as an irradiator) IL configured to modulate a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask stage) MT configured to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to specific parameters; a substrate support (e.g., a wafer stage) WT configured to carry a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW configured to accurately position the substrate support according to specific parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project the pattern imparted by the patterning device MA to the radiation beam B onto a target portion C (e.g., including one or more dies) of the substrate W.

[0037] In operation, the irradiation system IL receives a radiation beam from the radiation source SO, for example, via a beam delivery system BD. The irradiation system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for guiding, shaping, and / or controlling the radiation. The irradiator IL can be used to modulate the radiation beam B to have a desired spatial and angular intensity distribution in the planar cross-section of the patterning device MA.

[0038] The term “projection system” PS as used herein should be interpreted broadly to encompass all types of projection systems, including refractive, reflective, catadioptric, morphological, magnetic, electromagnetic, and / or electrostatic optical systems, or any combination thereof, depending on the exposure radiation used and / or other factors such as the use of immersion fluids or vacuum environments. Any use of the term “projection lens” herein is to be considered synonymous with the more general term “projection system” PS.

[0039] A lithography apparatus LA can be of a type in which at least a portion of the substrate is covered by a liquid (e.g., water) with a relatively high refractive index, thereby filling the space between the projection system PS and the substrate W—this is also known as immersion lithography. More information on immersion technology is given in U.S. Patent US6952253, the entire contents of which are incorporated herein by reference.

[0040] Photolithography equipment (LA) can also be of the type with two or more substrate supports (WT) (also known as "dual-stage"). In such "multi-stage" machines, the substrate supports (WT) can be used in parallel, and / or a preparation step for subsequent exposure of a substrate W located on one of the substrate supports (WT) can be performed on that substrate W, while another substrate W on another substrate support (WT) is used to expose a pattern on that other substrate W.

[0041] In addition to the substrate support WT, the lithography apparatus LA may also include a measurement stage. The measurement stage is arranged to carry sensors and / or cleaning devices. Sensors may be arranged to measure properties of the projection system PS or the radiation beam B. The measurement stage may carry multiple sensors. The cleaning devices may be arranged to clean part of the lithography apparatus, for example, part of the projection system PS or part of a system providing immersion fluid. When the substrate support WT is moved away from the projection system PS, the measurement stage may be moved below the projection system PS.

[0042] In operation, a radiation beam B is incident on a patterning device (e.g., a mask MA) carried on a mask support MT and patterned by a pattern (design layout) present on the patterning device MA. After traversing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The substrate support WT can be accurately moved using a second locator PW and a position measurement system IF, for example, to position different target portions C along the path of the radiation beam B to a focused and aligned position. Similarly, a first locator PM and possibly another position sensor (not explicitly depicted in Figure 1) can be used to accurately position the patterning device MA along the path of the radiation beam B. The patterning device MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although substrate alignment marks P1, P2 occupy dedicated target portions as shown, they can also be located in the space between target portions. When substrate alignment marks P1, P2 are located between target portions C, they are referred to as scribe alignment marks.

[0043] As shown in Figure 2, the lithography apparatus LA can form part of a lithography unit LC, sometimes referred to as a lithocell or (litho) cluster. The LC typically also includes equipment for performing pre- and post-exposure processing on the substrate W. Traditionally, this equipment includes a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH, and a baking plate BK (e.g., for regulating the temperature of the substrate W), for example, to regulate the solvent in the resist layer. A substrate processor (or robot) RO picks up the substrate W from input / output ports I / O1, I / O2, moves it between different process devices, and delivers the substrate W to the loading slot LB of the lithography apparatus LA. The devices in the lithography unit (often collectively referred to as lithography tracks) are typically controlled by a lithography track control unit TCU, which in turn can be controlled by a monitoring system SCS, which can also control the lithography apparatus LA, for example, via a lithography control unit LACU.

[0044] To ensure correct and consistent exposure of the substrate W by the lithography unit LA, it is desirable to inspect the substrate to measure properties of the patterned structure, such as overlay error between subsequent layers, line thickness, critical dimension (CD), etc. For this purpose, the lithography unit LC may include inspection tools (not shown). If errors are detected, especially if the inspection is completed before other substrates W in the same batch are still to be exposed or processed, adjustments can be made, for example, to the exposure of subsequent substrates or to other processing steps to be performed on the substrate W.

[0045] Inspection equipment (which may also be referred to as measurement equipment) is used to determine the properties of a substrate W, and in particular, to determine how the properties of different substrates W vary or how the properties associated with different layers of the same substrate W vary layer by layer. This inspection equipment may alternatively be configured to identify defects on the substrate W, and may, for example, be part of a lithography unit LC, or may be integrated into a lithography apparatus LA, or may even be an isolated device. This inspection equipment can measure properties on latent images (images in the resist layer after exposure), half-latent images (images in the resist layer after the post-exposure baking step PEB), developed resist images (where the exposed or unexposed portions of the resist have been removed), and even etched images (after pattern transfer steps such as etching).

[0046] Typically, patterning in a lithography apparatus (LA) is one of the most critical steps in fabrication, requiring the precise determination of the dimensions and locations of structures on a substrate (W). To ensure such high accuracy, three systems can be combined in a so-called “holistic” control environment, as schematically depicted in Figure 3. One of these systems is the lithography apparatus (LA), which is (virtually) connected to a metrology tool (MT) (the second system) and a computer system (CL) (the third system). The key to such a “holistic” environment is optimizing the collaboration between these three systems to expand the overall process window and provide a tight control loop, thereby ensuring that the patterning performed by the lithography apparatus (LA) remains within the process window. The process window defines a range of process parameters (e.g., dose, focal plane, overlay) within which a specific manufacturing process produces a defined result (e.g., a functional semiconductor device)—typically allowing variations in process parameters during either the lithography or patterning process within this range.

[0047] The computer system CL can use a portion of the design layout to be patterned to predict which resolution enhancement techniques to use, and perform computational lithography simulations and calculations to determine which mask layout and lithography equipment setup achieves the maximum overall process window for the patterning process (as depicted by the double arrows in the first scale bar SC1 in Figure 3). Typically, resolution enhancement techniques are arranged to match the patterning possibilities of the lithography equipment LA. The computer system CL can also be used to detect where the lithography equipment LA is currently operating within the process window (e.g., using input from the metrology tool MT) to predict the presence of defects, such as those due to suboptimal processing (as depicted by the arrows pointing to "0" in the second scale bar SC2 in Figure 3).

[0048] The measurement tool MT can provide input to the computer system CL to enable accurate simulation and prediction, and can provide feedback to the lithography equipment LA, for example, in the calibration state of the lithography equipment LA, to identify possible drift (as depicted by the multiple arrows in the third scale bar SC3 in Figure 3).

[0049] In photolithography, it is desirable to frequently measure the created structure, for example, for process control and verification. The tools used to perform these measurements are generally referred to as metrology tools (MTs). A wide variety of metrology tools are known for this purpose, including scanning electron microscopes and various forms of scatterometer metrology tools (MTs). A scatterometer is a versatile instrument that allows for the measurement of photolithography parameters in two ways: one is by placing the sensor in the pupil of the scatterometer objective or in a plane conjugate to that pupil; this method is often referred to as pupil-based measurement. The other method is by placing the sensor in the image plane or in a plane conjugate to that image plane; in this case, the measurement is often referred to as image-based or field-based measurement. Such a scattering instrument and the associated measurement techniques are further described in patent applications US20100328655, US2011102753A1, US20120044470A, US20110249244, US20110026032, or EP1,628,164A, the entire contents of which are incorporated herein by reference. The aforementioned scattering instrument can measure gratings using light in the wavelength range from soft X-rays to visible light to near-infrared (IR).

[0050] In the first embodiment, the scatterer MT is an angle-resolved scatterer. In such a scatterer, reconstruction methods can be applied to the measured signal to reconstruct or calculate the properties of the grating. For example, such reconstruction can be achieved by simulating the interaction between scattered radiation and a mathematical model of the target structure, and comparing the simulation results with the measurement results. The parameters of the mathematical model are adjusted until the simulated interaction produces a diffraction pattern similar to that observed from a real target.

[0051] In the second embodiment, the scatterer MT is a spectroscopic scatterer MT. In such a spectroscopic scatterer MT, radiation emitted by a radiation source is directed onto a target, and the reflected or scattered radiation from the target is directed to a spectroscopic detector, which measures the spectrum of the specularly reflected radiation (i.e., a measurement of intensity as a function of wavelength). From these data, for example, through rigorous coupled-wave analysis and nonlinear regression or by comparison with a simulated spectral library, the structure or distribution curve of the target that produced the detected spectrum can be reconstructed.

[0052] In the third embodiment, the scatterer MT is an elliptic scatterer. An elliptic scatterer allows for the determination of lithography process parameters by measuring the scattered radiation for each polarization state. Such a metrology device emits polarized light (such as linearly polarized, circularly polarized, or elliptically polarized light) by, for example, using a suitable polarizing filter in the illumination portion of the metrology device. The light source suitable for this metrology device can also provide polarized radiation. Various embodiments of existing elliptic scatterers are described in U.S. Patent Applications 11 / 451,599, 11 / 708,678, 12 / 256,780, 12 / 486,449, 12 / 920,968, 12 / 922,587, 13 / 000,229, 13 / 033,135, 13 / 533,110, and 13 / 891,410, the entire contents of which are incorporated herein by reference.

[0053] In one embodiment of a scattering instrument (MT), the MT is adapted to measure the overlay error between two misaligned gratings or periodic structures by measuring the reflectance spectrum and / or detecting an asymmetry in the configuration, the asymmetry being related to the magnitude of the overlay error. These two (typically overlapping) grating structures can be applied in two different layers (not necessarily consecutive layers) and can be formed substantially at the same location on the wafer. The scattering instrument can have a symmetrical detection configuration, such as described, for example, in the co-owned patent application EP1,628,164A, such that any asymmetry is readily discernible. This provides a simple method for measuring grating misalignment. For further examples of measuring the overlay error between two layers containing a periodic structure by means of an asymmetry in the periodic structure, see PCT patent application publication WO2011 / 012624 or U.S. patent application US20160161863, the entire contents of which are incorporated herein by reference.

[0054] Other parameters of interest may be focal plane and dose. As described in U.S. Patent Application US2011-0249244 (the entire contents of which are incorporated herein by reference), focal plane and dose can be determined simultaneously by scattering measurements (or alternatively by scanning electron microscopes). A single structure can be used that has a unique combination of critical dimensions and sidewall angle measurements for each point in the focal plane energy matrix (FEM—also known as the focal plane exposure matrix). If these unique combinations of critical dimensions and sidewall angles are available, the focal plane and dose values ​​can be uniquely determined from these measurements.

[0055] The measurement target can be an assembly of composite gratings, typically formed with resist via photolithography, but may also be formed via etching, for example. Generally, the pitch and linewidth of the structures within the grating are largely dependent on the measurement optics (particularly the numerical aperture of the optics) to capture the diffraction order from the measurement target. As previously indicated, the diffraction signal can be used to determine the offset between two layers (also known as "overlay"), or it can be used to reconstruct at least a portion of the original grating produced by the photolithography process. This reconstruction can be used to provide guidance on the quality of the photolithography process and can be used to control at least a portion of the photolithography process. The target can have small subdivisions configured to simulate the dimensions of functional portions of the design layout within the target. Due to this subdivision, the target's behavior will more closely resemble the functional portions of the design layout, making the overall process parameter measurements better analogous to the functional portions of the design layout. The target can be measured in underfill or overfill modes. In underfill mode, the measurement beam generates a spot smaller than the entire target. In overfill mode, the measurement beam generates a spot larger than the entire target. In such overfill modes, different targets can also be measured simultaneously, thereby simultaneously determining different process parameters.

[0056] Figure 4 depicts a measurement device such as a scatterometer. It includes a broadband (white light) radiation projector 2 that projects radiation onto a substrate W. The reflected or scattered radiation is passed to a spectrometer detector 4, which measures the spectrum 6 of the specularly reflected radiation (i.e., a measurement of intensity as a function of wavelength). From these data, a processing unit PU can reconstruct the structure or distribution curve 8 that produced the detected spectrum, for example, through rigorous coupled-wave analysis and nonlinear regression, or by comparison with a simulated spectral library (as shown at the bottom of Figure 3). Typically, for reconstruction, the overall shape of the structure is known, and some parameters are assumed from knowledge of the structure's fabrication process; therefore, only a few parameters of the structure need to be determined from the scattering measurement data. Such a scatterometer can be configured as a normal-incident scatterometer or an oblique-incident scatterometer.

[0057] The overall measurement quality of a lithographic parameter measured via a measurement target is determined at least in part by the measurement formulation used to measure that lithographic parameter. The term "substrate measurement method" can include one or more parameters of the measurement itself, one or more parameters of one or more patterns being measured, or both. For example, if the measurement used in the substrate measurement formulation is a diffraction-based optical measurement, one or more of the measurement parameters might include radiation wavelength, radiation polarization, the angle of incidence of radiation relative to the substrate, the orientation of radiation relative to the pattern on the substrate, etc. For example, one criterion for selecting a measurement formulation could be the sensitivity of one of the measurement parameters to process variations. Further examples are described in U.S. Patent Application US2016-0161863 and published U.S. Patent Application US2016 / 0370717A1 (which are incorporated herein by reference in their entirety).

[0058] Another type of metrology tool used in IC manufacturing is a topography measurement system, leveling sensor, or height sensor. Such tools can be integrated into photolithography equipment to measure the topography of the top surface of a substrate (or wafer). These measurements can generate a topography map of the substrate (also known as a height map), which indicates how the substrate height varies with position on the substrate. This height map can then be used to correct the substrate's position during pattern transfer on the substrate, providing an aerial image of the patterning device at the exact focal point on the substrate. It's important to understand that "height" in this context refers to the dimension extending beyond the plane of the substrate (also known as the Z-axis). Typically, the leveling or height sensor performs measurements at a fixed location (relative to its own optical system), while relative movement between the substrate and the leveling or height sensor's optical system results in height measurements being taken at different locations on the substrate.

[0059] Figure 5 schematically illustrates an example of a leveling or height sensor LS known in the art, illustrating only the principle of operation. In this example, the leveling sensor includes an optical system comprising a projection unit LSP and a detection unit LSD. The projection unit LSP includes a radiation source LSO that provides a radiation beam LSB, which is imparted by a projection grating PGR of the projection unit LSP. For example, the radiation source LSO can be a narrowband or broadband light source, such as a supercontinuum light source, and can be polarized or unpolarized, pulsed or continuous, such as a polarized or unpolarized laser beam. The radiation source LSO can include multiple radiation sources with different colors or wavelength ranges, such as multiple LEDs. The radiation source LSO of the leveling sensor LS is not limited to visible radiation, but may additionally or alternatively include UV and / or IR radiation and any wavelength range suitable for reflection from the substrate surface.

[0060] The projection grating (PGR) is a periodic grating comprising a periodic structure that generates a radiation beam BE1 with periodically varying intensity. The periodically varying intensity radiation beam BE1 is guided to a measurement location MLO on a substrate W, with an incident angle ANG between 0° and 90°, typically between 70° and 80°, relative to an axis perpendicular to the incident substrate surface (Z-axis). At the measurement location MLO, the patterned radiation beam BE1 is reflected by the substrate W (indicated by arrow BE2) and guided to the detection unit LSD.

[0061] To determine the height level at the measurement location MLO, the leveling sensor also includes a detection system comprising a detection grating DGR, a detector DET, and a processing unit (not shown) for processing the output signal of the detector DET. The detection grating DGR can be the same as the projection grating PGR. The detector DET generates a detector output signal indicating the received light, for example, indicating the intensity of the received light (such as a photodetector), or representing the spatial distribution of the received intensity (such as a camera). The detector DET can include any combination of one or more detector types.

[0062] The height level at the measurement location MLO can be determined using triangulation techniques. The detected height level is typically related to the signal strength measured by the detector DET, which exhibits periodicity depending on the design of the projection grating PGR, the (tilted) incident angle ANG, etc.

[0063] The projection unit LSP and / or detection unit LSD may include more optical elements (such as lenses and / or mirrors) arranged along the path of the patterned radiation beam between the projection grating PGR and the detection grating DGR (not shown).

[0064] In this embodiment, the detection grating DGR can be omitted, and the detector DET can be placed at the location of the detection grating DGR. This configuration provides more direct detection of the image of the projection grating PGR.

[0065] In order to effectively cover the surface of the substrate W, the leveling sensor LS can be configured to project an array of measurement beams BE1 onto the surface of the substrate W, thereby generating a measurement area MLO or an array of light spots that covers a larger measurement range.

[0066] For example, various general-purpose height sensors are disclosed in US7265364 and US7646471, both of which are incorporated herein by reference. A height sensor using UV radiation instead of visible or infrared radiation is disclosed in US2010233600A1, which is also incorporated by reference. A compact height sensor described in WO2016102127A1, which is incorporated by reference, uses a multi-element detector to detect and identify the position of a grating image without needing to detect the grating itself.

[0067] Another type of metrology tool used in IC manufacturing is the alignment sensor. Therefore, a key aspect of lithography equipment performance lies in its ability to correctly and accurately place the applied pattern relative to features deposited in previous layers (by the same or different lithography equipment). For this purpose, the substrate is provided with one or more sets of markers or targets. Each marker is a structure whose position can be measured later using a position sensor (typically an optical position sensor). The position sensor can be called an "alignment sensor," and the markers can be called "alignment marks."

[0068] Photolithography apparatuses may include one or more (e.g., multiple) alignment sensors that can accurately measure the position of alignment marks provided on a substrate. Alignment (or position) sensors can obtain position information from alignment marks formed on the substrate using optical phenomena such as diffraction and interference. Examples of alignment sensors used in current photolithography apparatuses are based on a self-reference interferometer described in U.S. Patent US6,961,116. Various enhancements and improvements to position sensors have been developed, for example, as disclosed in U.S. Patent US20,152,610,97A1. The contents of all these publications are incorporated herein by reference.

[0069] Figure 6 is a schematic block diagram of a known alignment sensor AS (e.g., as described in U.S. Patent US6961116, which is incorporated herein by reference). A radiation source RSO provides a radiation beam RB of one or more wavelengths, which is directed by a steering optics onto a marker (such as a marker AM located on a substrate W) to form an illumination spot SP. In this example, the steering optics include a spot mirror SM and an objective lens OL. The diameter of the illumination spot SP used to illuminate the marker AM can be slightly smaller than the width of the marker itself.

[0070] Radiation diffracted by the alignment mark AM (in this example, via the objective lens OL) is collimated into an information-carrying beam IB. The term "diffraction" is intended to include zero-order diffraction from the mark (which may be referred to as reflection). A self-referenced interferometer SRI (e.g., of the type disclosed in US6961116 mentioned above) causes the beam IB to interfere with itself, after which the beam is received by a photodetector PD. If the radiation source RSO creates more than one wavelength, additional optics (not shown) may be included to provide a separate beam. The photodetector may be a single element, or it may include several pixels as needed. The photodetector may comprise a sensor array.

[0071] Steering optics (which in this example include a spot mirror SM) can also be used to block zero-order radiation reflected from the marker, so that the information-carrying beam IB consists only of higher-order diffraction radiation from the marker AM (which is not necessary for the measurement but can improve the signal-to-noise ratio).

[0072] The intensity signal SI is supplied to the processing unit PU. Through a combination of optical processing in the module SRI and computational processing in the unit PU, the values ​​of the X and Y positions on the substrate relative to the reference frame are output.

[0073] The illustrated single measurement can only determine the mark position of the target within a specific range corresponding to one pitch of the mark. This is combined with coarser measurement techniques to identify which period of the sine wave contains the marked position. Coarser and / or finer measurements can be repeated at different wavelengths to improve accuracy and / or ensure reliable detection of the mark (regardless of the material the mark is made of or whether it is presented above or below the material). Wavelengths can be optically multiplexed and demultiplexed for simultaneous processing; and / or they can be multiplexed via time-division multiplexing or frequency-division multiplexing.

[0074] In this example, the alignment sensor and spot SP remain stationary, while the substrate W moves. Therefore, the alignment sensor can be rigidly and accurately mounted to the reference frame while effectively scanning the mark AM in the direction opposite to the direction of substrate W's movement. This movement of the substrate W is controlled by its mounting on a substrate support and a substrate positioning system that controls the movement of the substrate support. A substrate support position sensor (e.g., an interferometer) measures the position of the substrate support (not shown). In this embodiment, one or more (alignment) marks are provided on the substrate support. Position measurement of the marks provided on the substrate support allows correction of the substrate support position determined by the position sensor (e.g., relative to a reference frame connected to the alignment system). Position measurement of the alignment marks provided on the substrate allows determination of the substrate's position relative to the substrate support.

[0075] Figure 7 illustrates a broadband light source assembly 100 according to an embodiment of the present disclosure. The broadband light source assembly 100 can be employed in any of the devices described above. As shown in Figure 7, the broadband light source assembly 100 includes a femtosecond pump laser 20 and a fully positive dispersive fiber 10. The femtosecond pump laser 20 is arranged to emit radiation pulses. The fiber 10 is coupled to the femtosecond pump laser 20 such that it is arranged to receive the radiation pulses emitted by the femtosecond pump laser 20 at its input end.

[0076] The femtosecond pumped laser 20 can be configured to emit radiation pulses with a pump pulse energy greater than 1 nJ. Preferably, the femtosecond pumped laser 20 is configured to emit radiation pulses with a pump pulse energy greater than 50 nJ. For example, the femtosecond pumped laser 20 can be configured to emit radiation pulses with a pump pulse energy greater than 50 nJ, greater than 60 nJ, greater than 70 nJ, greater than 75 nJ, greater than 80 nJ, greater than 90 nJ, or greater than 100 nJ. The femtosecond pumped laser 20 can also be configured to emit radiation pulses with a pump pulse energy up to 500 nJ.

[0077] The radiation pulse may have a peak power of at least 200 kW (i.e., the maximum optical power that the pulse can achieve), optionally at least 300 kW, optionally at least 400 kW, optionally at least 500 kW, optionally at least 600 kW, optionally at least 625 kW.

[0078] Given the known relationship—the peak power of a laser beam equals the energy of each pulse divided by the pulse duration (also known as the pulse width)—the radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse duration of at least 10 fs. The radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse duration of less than 500 fs. That is, the radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse duration in the range of 10–500 fs. The radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse duration of at least 100 fs. The radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse duration in the range of 125–175 fs, optionally in the range of 130–170 fs, and optionally in the range of 140–160 fs.

[0079] The radiation pulse emitted by the femtosecond-pumped laser 20 has a natural full width at half maximum (FWHM). For example, the FWHM can be in the range of 2 nm to 100 nm. The radiation pulse can have a center pump wavelength in the range of 700 nm to 1800 nm. In one example, the center pump wavelength of the radiation pulse is 800 nm; in another example, the center pump wavelength of the radiation pulse is 1027 nm; and in yet another example, the center pump wavelength of the radiation pulse is 1064 nm.

[0080] The radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse repetition rate in the range of 1 MHz to 10 GHz. The radiation pulses emitted by the femtosecond-pumped laser 20 can have a pulse repetition rate in the range of 1 to 100 MHz, optionally in the range of 10 to 90 MHz, optionally in the range of 20 to 80 MHz, and optionally in the range of 30 to 70 MHz. For example, the pulse repetition rate can be 40 MHz.

[0081] Optical fiber 10 is a fully positive dispersion fiber. That is, the fully positive dispersion fiber 10 has a flat, convex normal group velocity dispersion (GVD) distribution curve, which has a distinct point at the minimum dispersion wavelength (MDW) where the dispersion is closest to zero, but does not exhibit a zero dispersion wavelength (ZDW) in the region of interest. Preferably, the center pump wavelength of the radiation pulse is in the range of + / - 50 nm near the MDW to maximize the broadening of the radiation spectrum input into the fiber 10.

[0082] As shown in Figure 8, the optical fiber 10 may include a core region and a cladding region surrounding the core region. Both the core region and the cladding region include a region having a first refractive index (n). B Background material 12. Additionally, the cladding region includes multiple microstructures 14 (also referred to as inclusions) extending along the longitudinal axis (z-direction) of the fiber 10 from the input end to the output end of the fiber 10. These microstructures have a second refractive index (n). inc ), where n inc <n B .

[0083] Background material 12 may include silicon dioxide. As shown in Figure 8, optical fiber 10 may be a solid optical fiber (where background material 12 fills the core region).

[0084] In some embodiments, the plurality of microstructures 14 are hollow. In some embodiments, the hollow microstructures 14 comprise air. In other embodiments, the plurality of microstructures 14 comprise a vacuum. In still other embodiments, the plurality of microstructures 14 comprise a second refractive index (n). incThe medium can be a solid material such as doped silicon dioxide. For example, the doping material can be fluorine (F), germanium (Ge), and / or phosphorus (P). In embodiments where doped silicon dioxide includes fluorine-doped silicon dioxide, the molar percentage of fluorine can be, for example, in the range of 1-10%, such as in the range of 3-8%.

[0085] As shown in Figure 8, a plurality of microstructures 14 in the cladding region are arranged in a cross-sectional pattern, the cross-sectional pattern including at least one loop of microstructures surrounding the core region. In the context of this application, a "microstructure loop" refers to a cladding microstructure that is generally substantially equidistant from the core and aligned in a ring-like configuration surrounding the core. The microstructure loop does not necessarily have to be perfectly circular. As shown in Figure 8, the microstructure loop can be arranged in a hexagonal shape (or other shapes with several gentle angles). It should be understood that this is merely an example, and the microstructure loop can also be arranged in a circular or elliptical shape.

[0086] In some embodiments, all microstructures 14 of the microstructure ring are substantially the same in size and shape (as shown in Figure 8), but it should be understood that the size and / or cross-sectional shape of one or more of the microstructures 14 may differ from the remaining microstructures.

[0087] Although Figure 8 shows an optical fiber 10 with five microstructure rings 14, it should be understood that this is merely an example. In some embodiments, there is only one microstructure ring. In other embodiments, there are multiple microstructure rings, for example, at least two microstructure rings, at least three microstructure rings, at least four microstructure rings, or at least five microstructure rings 14.

[0088] As shown in Figure 8, each microstructure has a diameter (d), and the pitch Λ of the microstructure is defined as the center distance between adjacent microstructures.

[0089] The factor contributing to the optical properties of fiber 10 is the normalized inclusion diameter (d / Λ), which corresponds to the ratio of the diameter (d) of each microstructure in the microstructure to the pitch Λ of the microstructure. The normalized inclusion diameter (d / Λ) can range from 0.33 to 0.45, and optionally from 0.36 to 0.42. For example, the normalized inclusion diameter (d / Λ) can be 0.39.

[0090] As shown in Figure 8, the microstructure ring closest to (i.e., adjacent to) the core region can have six microstructures. In Figure 8, the diameter of the core region is shown as D. core .

[0091] The microstructure ring with six microstructures closest to (i.e., adjacent to) the core region is merely an example, and embodiments of this disclosure can be extended to optical fibers with different numbers of microstructures in the microstructure ring closest to (i.e., adjacent to) the core region.

[0092] In another example, the microstructure ring closest to (i.e., adjacent to) the core region has twelve microstructures. In some embodiments (such as the example where the microstructure ring closest to the core region has twelve microstructures), the core region has a maximum span (illustrated in Figure 9a) and a minimum span (illustrated in Figure 9b), and the diameter D of the core region... core It is defined as the average of the maximum and minimum spans of the fiber core region.

[0093] Figure 9a illustrates how to apply the diameter D of the maximum span of the fiber core region. core-max Measurement of the diameter (D) of the maximum span of the fiber core region. core-max This corresponds to the distance between microstructures at the opposite vertices of the closest (i.e., adjacent) core regions on the hexagonal microstructure ring. Figure 9a illustrates this distance, shown as a crosshair pattern, and can be used to calculate D. core-max The microstructure at the vertices of the hexagonal microstructure ring. The diameter D of the maximum span in the core region. core-max It is given by the following formula: Λ – d

[0094] Figure 9b illustrates how to perform the minimum span diameter D for the fiber core region. core-min Measurement of the diameter (D) of the minimum span of the fiber core region. core-min This corresponds to the distance between the microstructures on opposite sides of the closest (i.e., adjacent) core region on the hexagonal microstructure ring. Figure 9b shows a crosshair pattern illustrating the distance that can be used to calculate D. core-min The microstructure of the hexagonal microstructure ring side surface. Minimum diameter D of the core region. core-min It is given by the following formula:

[0095] Figure 9c illustrates how to perform adjustments to the core region diameter D when the core region has maximum and minimum spans. core The measurement, as illustrated in Figure 9c, is used to calculate D. core The microstructures at the vertices and sides of the hexagonal microstructure ring are represented by crosshair patterns. The core region diameter D... core It is given by the following formula:

[0096] Core region diameter D core It can be less than or equal to 3 µm. Core region diameter D core It can be in the range of 2-3 µm, and optionally in the range of 2.1-2.6 µm.

[0097] The geometry and dimensions of the optical fiber (such as pitch Λ, microstructure diameter d, and core diameter D) coreIt plays an important role in achieving the all-positive dispersion distribution curve of fiber 10.

[0098] Optical fiber 10 can be polarization-maintaining fiber (PM fiber) or non-PM fiber. Polarization-maintaining fiber is an fiber in which linearly polarized light can be injected into the fiber and maintain linear polarization. Advantageously, the injected polarized light maintains linear polarization as it propagates along the PM delivery fiber and leaves the fiber in a linear polarization state.

[0099] In embodiments of the invention, the PM PCF 10 can be implemented by incorporating stress elements (e.g., stress bars) into the optical fiber. The stress elements are included within the cladding region and are covered by a background material 12 within the cladding region. The stress elements extend along the longitudinal axis (z-direction) of the optical fiber from the fiber input end to the fiber output end. The stress elements induce stress within the fiber core region (thus providing birefringence). The stress elements can have any suitable cross-sectional shape, such as circular, triangular, square, polygonal (e.g., hexagonal), elliptical, etc.

[0100] Figure 10 illustrates the all-positive dispersion profile of example fiber 10. The all-positive dispersion profile illustrated in Figure 10 corresponds to fiber 10 designed for 1027 nm MDW, with a core diameter D. core The fiber has a diameter of 2.3 µm, five air hole rings, an air hole pitch of 1.44 µm, a normalized inclusion diameter (d / Λ) of 0.39, and each air hole has a diameter of 0.5616 µm. It should be understood that the specific parameters of fiber 10 specified above are merely examples. In this example, fiber 10 has a median wavelength (MDW) of 1027 nm, at which point it exhibits a dispersion of -17 ps / (nm). (km). Fiber 10 can have a value between -1 ps / (nm) in MDW. km) and -100 ps / (nm) Dispersion values ​​between (km) and optionally between -1 ps / (nm) km) and -50 ps / (nm) Between km).

[0101] The broadband light source assembly 100 according to an embodiment of the present invention can be configured to generate broadband radiation (output by optical fiber 10) with a wavelength range of at least 500-900 nm. The lower limit of this broadband radiation wavelength range can be at least 100 nm, at least 200 nm, at least 300 nm, or at least 400 nm. The upper limit of this broadband radiation wavelength range can be 2000 nm or less, 1800 nm or less, 1500 nm or less, or 1200 nm or less. In one example, the broadband light source assembly 100 is configured to generate broadband radiation with a wavelength range of 485-1800 nm.

[0102] Broadband radiation can be radiation that spans a wavelength range much larger than narrowband or single-wavelength radiation. Broadband radiation includes continuous or substantially continuous wavelength ranges. The wavelength range can also be referred to as the spectral / spectral range. Continuous wavelength ranges can be at least in the range of 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 400 nm, or larger. Broadband radiation may have gaps within the wavelength range. These gaps can separate one or more continuous sub-ranges within the wavelength range. A substantially continuous range may lack discrete wavelength(s) and / or narrow wavelength(s) and can still be considered continuous. The power spectral density can be discontinuous, and the power may vary within the broadband wavelength range.

[0103] Broadband radiation can include supercontinuum radiation. For example, supercontinuum radiation can include electromagnetic radiation with wavelengths ranging from 500 to 900 nm. The lower limit of the wavelength range of supercontinuum radiation can be at least 100 nm, at least 200 nm, at least 300 nm, or at least 400 nm. The upper limit of the wavelength range of supercontinuum radiation can be 2000 nm or less, 1800 nm or less, 1500 nm or less, or 1200 nm or less. In one example, a broadband light source component 100 is configured to generate supercontinuum radiation with wavelengths ranging from 485 to 1800 nm. Supercontinuum radiation can include white light.

[0104] Those skilled in the art will understand that, according to this disclosure, "supercontinuum" generally refers to a continuous spectral power distribution exhibiting substantially flatness. In some embodiments, a supercontinuum includes a continuous spectral power distribution with a wavelength range of at least 100 nm. In some embodiments, the flatness of the supercontinuum corresponds to a peak-to-valley spectral power ratio of less than 100:1, i.e., 20 dB. In some embodiments, the flatness of the supercontinuum corresponds to a peak-to-valley spectral power ratio of less than 10:1, or 10 dB.

[0105] The dispersion profile of fiber 10 and the nonlinearity of the background material 12 (e.g., glass) of fiber 10 determine the physical mechanism of white light generation. The inherent mechanism for generating white light in the broadband light source assembly 100 is self-phase modulation leading to wave-breaking. Figure 11 shows spectral broadening of white light generated at different fiber lengths, illustrating the evolution of the white light spectrum, culminating in the broadest white light. In Figure 11, these mechanisms can be identified by characteristic self-phase modulation fringes near the pump wavelength (1027 nm in this example), followed by smooth wave-breaking (for the broadest spectrum shown). Waveform 1102 is a radiation pattern generated at a distance of 0.5 cm from the input end of fiber 10, into which radiation pulses emitted by the femtosecond pump laser 20 are supplied. Waveform 1104 is a radiation pattern generated at a distance of 1.5 cm from the input end of fiber 10. Waveform 1106 is a radiation pattern generated at a distance of 3.75 cm from the input end of fiber 10. Waveform 1108 is a radiation waveform generated at a distance of 12.75 cm from the input end of fiber 10. As shown in Figure 11, the radiation spectrum generated along the fiber broadens with increasing distance from the input end of fiber 10.

[0106] The broadband radiation output from fiber 10 can have a power spectral density of at least 3 mW / nm in the wavelength band of 500-900 nm. Figure 12 depicts a power spectral density diagram of radiation that can be generated by the broadband light source assembly according to an embodiment of the present invention. The power spectral density diagram in Figure 12 was obtained using a femtosecond pumped laser 20, which is configured to emit a radiation pulse with a center wavelength of 1027 nm, a pulse duration of 150 fs, and a pump energy of 100 nJ. The power spectral density diagram in Figure 12 was obtained using fiber 10 specifically designed for 1027 nm MDW, the fiber having a core diameter D. core The fiber has a diameter of 2.3 µm and five air-hole rings with a pitch of 1.44 µm. A normalization of 0.39 includes the diameter (d / Λ), and each air-hole has a diameter of 0.5616 µm. It should be understood that the specific parameters specified above for the femtosecond pump laser 20 and fiber 10 are merely examples. It can be observed that in the long wavelength range (e.g., 800–900 nm), the spectral intensity may be below 3 mW / nm, as illustrated in Figure 12. However, by slightly altering the input energy of the radiation pulse emitted by the femtosecond pump laser 20, the intensity in the long wavelength range can be easily increased to above 3 mW / nm.

[0107] As mentioned above, the relative intensity noise (RIN) of the radiation generated by fiber 10 is lower than that of known light source components based on soliton and modulation instability (MI) seeding processes. It is important to note that RIN is different from dose noise. RIN is the inter-pulse power fluctuation and is caused by the physical characteristics of white light generation. It is independent of the laser's repetition rate. On the other hand, dose noise (i.e., the power fluctuation of the dose per exposure) is related to the sensor's acquisition time and the laser's repetition rate. Closely related. The formula is: Furthermore, the signal-to-noise ratio was determined, and the performance of the OPO was ultimately established.

[0108] While the above describes a specific structure of a typical fully positive dispersion fiber, it should be understood that these embodiments are also applicable to other implementations of fully positive dispersion fibers.

[0109] Other embodiments are described in the following numbered clauses: 1. A broadband light source assembly comprising: a femtosecond pumped laser arranged to emit radiation pulses, wherein the radiation pulses have an energy greater than 50 nJ per pump pulse; and

[0110] A fully positive dispersion fiber is arranged to receive the radiation pulse.

[0111] 2. The broadband light source assembly according to Clause 1, wherein the optical fiber comprises: a core region; and a cladding region surrounding the core region;

[0112] The core region and the cladding region comprise a material having a first refractive index, the cladding region further comprising a plurality of microstructures extending along the longitudinal axis of the optical fiber from the input end to the output end of the optical fiber, the plurality of microstructures (i) being arranged in a cross-sectional pattern comprising at least one microstructure ring surrounding the core region, and (ii) having a second refractive index less than the first refractive index.

[0113] 3. The broadband light source assembly according to Clause 2, wherein the plurality of microstructures are hollow.

[0114] 4. The broadband light source assembly according to Clause 3, wherein the plurality of microstructures are air-filled.

[0115] 5. A broadband light source assembly according to any one of clauses 2 to 4, wherein the ratio between the diameter of each microstructure and the pitch of the microstructure is in the range of 0.33 to 0.45, and optionally in the range of 0.36 to 0.42.

[0116] 6. A broadband light source assembly according to any one of Clauses 2 to 5, wherein the cross-sectional pattern comprises a plurality of microstructure rings surrounding the core region.

[0117] 7. The broadband light source assembly according to Clause 6, wherein the cross-sectional pattern includes at least three microstructure rings surrounding the core region, optionally at least four microstructure rings surrounding the core region, and optionally at least five microstructure rings surrounding the core region.

[0118] 8. A broadband light source assembly according to any one of clauses 2 to 7, wherein the microstructure ring adjacent to the fiber core region has six microstructures.

[0119] 9. A broadband light source assembly according to any one of clauses 2 to 8, wherein each of the at least one microstructure ring has a hexagonal shape.

[0120] 10. A broadband light source assembly according to any one of clauses 2 to 9, wherein the core region has a diameter of less than or equal to 3 µm.

[0121] 11. The broadband light source assembly according to any one of clauses 2 to 10, wherein the material having the first refractive index comprises silicon dioxide.

[0122] 12. The broadband light source assembly according to any one of the foregoing clauses, wherein the length of the optical fiber is less than 10 cm, optionally less than 5 cm.

[0123] 13. The broadband light source assembly according to any one of the preceding clauses, wherein the radiation pulse has a pump pulse energy of at least 75 nJ, optionally at least 100 nJ.

[0124] 14. The broadband light source assembly according to any one of the preceding clauses, wherein the radiation pulse comprises radiation with a center pump wavelength in the range of 700-1800 nm.

[0125] 15. The broadband light source assembly according to any one of the preceding clauses, wherein the radiation pulse has a peak power of at least 200 kW, optionally at least 300 kW, optionally at least 400 kW, optionally at least 500 kW, optionally at least 600 kW.

[0126] 16. A broadband light source assembly according to any one of the preceding clauses, wherein the optical fiber generates broadband radiation in the wavelength range of 500-900 nm, optionally in the wavelength range of 500-1200 nm, optionally in the wavelength range of 500-1500 nm, optionally in the wavelength range of 500-1800 nm, or optionally in the wavelength range of 485-1800 nm.

[0127] 17. The broadband light source assembly according to Clause 16, wherein the broadband radiation has a power spectral density of at least 3 mW / nm in a wavelength band of 500-900 nm.

[0128] 18. A broadband light source assembly according to any one of the preceding clauses, wherein the optical fiber has a dispersion value between -1 ps / (nm) at the minimum dispersion wavelength. km) and -100 ps / (nm) Between km).

[0129] 19. The broadband light source assembly according to any one of the preceding clauses, wherein the pulse duration of the radiation pulse is in the range of 10-500 fs.

[0130] 20. A photolithography apparatus comprising a broadband light source assembly according to any one of the preceding clauses.

[0131] 21. A measuring device comprising a broadband light source assembly as described in any one of clauses 1 to 19.

[0132] 22. A method for generating broadband radiation, the method comprising: providing a radiation pulse emitted from a femtosecond pump laser to a fully positive dispersive optical fiber, wherein the radiation pulse has an energy greater than 50 nJ per pump pulse, and the optical fiber outputs the broadband radiation.

[0133] The broadband light source assembly according to any embodiment described herein can be used in a photolithography apparatus (LA) such as the apparatus depicted in FIG1. ​​Although photolithography apparatus used in IC manufacturing may be specifically mentioned in this text, it should be understood that the photolithography apparatus described herein may also have other applications. Other possible applications include fabricating integrated optical systems, guiding and detecting patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc.

[0134] While embodiments of the invention in the context of a lithography apparatus may be specifically referred to herein, embodiments of the invention may also be used in other apparatuses. For example, a broadband light source assembly may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses are commonly referred to as lithography tools. Such lithography tools may operate under vacuum or ambient (non-vacuum) conditions. That is, according to any embodiment described herein, the broadband light source assembly may be used in a metrology apparatus (such as the apparatus depicted in FIG. 4). The broadband light source assembly according to any embodiment described herein may be used in a leveling sensor LS (such as the apparatus depicted in FIG. 5). The broadband light source assembly according to any embodiment described herein may be used in an alignment sensor (such as the apparatus depicted in FIG. 6).

[0135] While the application of the embodiments of the present invention in the context of optical lithography may have been specifically mentioned above, it should be understood that, where the context permits, the present invention is not limited to optical lithography, and broadband light source components can also be used in other applications (e.g., imprint lithography).

[0136] While specific embodiments of the invention have been described above, it should be understood that the invention can be practiced in ways different from those described above. The above description is intended to illustrate, not limit, the invention. Therefore, it will be apparent to those skilled in the art that modifications can be made to the invention without departing from the scope of the following claims.

Claims

1. A broadband light source component, comprising: A femtosecond pumped laser is arranged to emit radiation pulses, wherein the radiation pulses have an energy greater than 50 nJ per pump pulse. And a fully positive dispersion fiber is arranged to receive the radiation pulse, wherein the broadband radiation is configured to provide a power spectral density of at least 3 mW / nm in the wavelength band of 500-900 nm during use.

2. The broadband light source assembly according to claim 1, wherein the optical fiber comprises: The fiber core region; and the cladding region surrounding the fiber core region; wherein the fiber core region and the cladding region comprise a material having a first refractive index, the cladding region further comprising a plurality of microstructures extending along the longitudinal axis of the optical fiber from the input end to the output end of the optical fiber, the plurality of microstructures (i) being arranged in a cross-sectional pattern comprising at least one microstructure ring surrounding the fiber core region, and (ii) having a second refractive index less than the first refractive index.

3. The broadband light source assembly according to claim 2, wherein the plurality of microstructures are hollow.

4. The broadband light source assembly according to claim 3, wherein the plurality of microstructures are air-filled.

5. The broadband light source assembly according to any one of claims 2 to 4, wherein the ratio between the diameter of each microstructure and the pitch of the microstructure is in the range of 0.33-0.45, and optionally in the range of 0.36-0.

42.

6. The broadband light source assembly according to any one of claims 2 to 5, wherein the cross-sectional pattern comprises a plurality of microstructure rings surrounding the core region.

7. The broadband light source assembly according to any one of claims 2 to 6, wherein the microstructure ring adjacent to the fiber core region has six microstructures.

8. The broadband light source assembly according to any one of claims 2 to 7, wherein the fiber core region has a diameter of less than or equal to 3 µm.

9. The broadband light source assembly according to any one of claims 2 to 8, wherein the material having the first refractive index comprises silicon dioxide.

10. The broadband light source assembly according to any one of the preceding claims, wherein the length of the optical fiber is less than 10 cm, optionally less than 5 cm.

11. The broadband light source assembly according to any one of the preceding claims, wherein the radiation pulse has a peak power of at least 200 kW.

12. The broadband light source assembly according to any one of the preceding claims, wherein the optical fiber has a dispersion value between -1 ps / (nm) at the minimum dispersion wavelength. km) and -100 ps / (nm) Between km).

13. The broadband light source assembly according to any one of the preceding claims, wherein the radiation pulse has a pulse duration in the range of 10-500 fs.

14. A measuring device comprising a broadband light source assembly according to any one of claims 1 to 13.

15. A method for generating broadband radiation, the method comprising providing a radiation pulse emitted from a femtosecond pump laser to a fully positive dispersive optical fiber, wherein the radiation pulse has an energy greater than 50 nJ per pump pulse, and the optical fiber outputs the broadband radiation.

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