Membranes and Related Methods and Apparatus

Abstract

A pellicle film including three or more layers, wherein the three or more layers include at least one inner layer and at least one outer layer on at least one surface of any of the at least one inner layer, and the at least one inner layer includes one or more of boron, zirconium, beryllium, niobium, yttrium, molybdenum, carbon, and / or one or more compounds of each of these materials, and / or consists of them, a pellicle film is disclosed. Also disclosed is a metrology apparatus using such a pellicle film as a beam splitter and / or a filter.

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims priority to European Patent Application No. 22176381.6 filed on May 31, 2022 and European Patent Application No. 22182745.4 filed on July 4, 2022, which are incorporated herein by reference in their entirety.

[0002]

[0002] The present invention relates to metrology applications in the manufacture of integrated circuits.

Background Art

[0003]

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

[0004]

[0004] A lithographic apparatus can use electromagnetic radiation to project a pattern onto a substrate. The minimum size of the features that can be formed on the substrate is determined by the wavelength of this radiation. Typical wavelengths currently in use are 365 nm (i - line), 248 nm, 193 nm, and 13.5 nm. For a lithographic apparatus that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 4 - 100 nm, e.g., 6.7 nm or 13.5 nm, it is possible to form smaller features on the substrate than, for example, a lithographic apparatus that uses radiation with a wavelength of 193 nm.

[0005]

[0005] To process features having dimensions smaller than the classical resolution limit of a lithographic apparatus, low - k 1 lithography can be used. In such a process, the resolution formula is CD = k 1It can be expressed as ×λ / NA, where λ is the wavelength of the radiation used, NA is the numerical aperture of the projection optical system of the lithographic apparatus, CD is the "Critical Dimension" (generally the smallest feature size to be printed, but in this case the half-pitch), and k 1 is an empirical resolution factor. Generally, the smaller k 1 is, the more difficult it becomes to reproduce on the substrate a pattern that resembles the shape and dimensions planned by the circuit designer to achieve a specific electrical functionality and performance. To overcome such difficulties, advanced fine-tuning steps can be applied to the lithographic projection apparatus and / or the design layout. Such steps include, for example, optimization of NA, customization of the illumination mode, use of a phase-shifting patterning device, various optimizations of the design layout, such as optical proximity correction (OPC, sometimes also called "optical and process correction") in the design layout or other methods generally defined as "resolution enhancement techniques" (RET), but are not limited thereto. Instead, a strict control loop for managing the stability of the lithographic apparatus can be used to improve pattern reproduction at low k 1 .

[0006]

[0006] In a lithography process or other manufacturing process, it is desirable to frequently measure the fabricated structures (e.g., for process control and verification). Various tools for performing such measurements are known, such as a scanning electron microscope often used for measuring the critical dimension (CD), and dedicated tools for measuring the overlay, which is the accuracy of the alignment of two layers within a device. Recently, various forms of scatterometers used in the field of lithography have been developed. The manufacturing process is, for example, lithography, etching, deposition, chemical mechanical planarization, oxidation, ion implantation, diffusion, or a combination of two or more of them.

[0007] [

[0007] ] Examples of known scatterometers often rely on the provision of dedicated metrology targets. For example, the method may require a target in the form of a simple grid large enough for the measurement beam to produce a spot smaller than the grid (i.e., the grid is in an underfilled state). In so-called reconstruction methods, the characteristics of the grid can be calculated by simulating the interaction between a mathematical model of the target structure and the scattered radiation. The parameters of the model are adjusted until a diffraction pattern similar to that observed from the actual target is generated by the simulated interaction.

[0008] [

[0008] ] In addition to measuring feature shapes by reconstruction, diffraction-based overlays can be measured using an apparatus as described in U.S. Patent Application Publication No. 2006066855A1. Diffraction-based overlay metrology using dark-field imaging of diffraction orders enables overlay measurements of smaller targets. These targets may be smaller than the illumination spot and may be surrounded by product structures on the wafer. Examples of dark-field imaging metrology can be found in many published patent applications, such as U.S. Patent Application Publication Nos. 2011102753A1 and 20120044470A. Multiple grids can be measured in one image using a composite grid target. Known scatterometers tend to use light in the visible or near-infrared (IR) wavelength range, so the pitch of the grid needs to be much coarser than the actual product structures whose characteristics are actually of interest. Such product features can be defined using deep ultraviolet (DUV), extreme ultraviolet (EUV), or X-ray radiation with much shorter wavelengths. Unfortunately, such wavelengths are usually not available or usable for metrology.

[0009]

[0009] On the one hand, due to the very small dimensions of recent product structures, they cannot be imaged by optical metrology techniques. Small features include, for example, features formed by multiple patterning processes and / or pitch increases. Therefore, in targets used for mass production metrology, features that are much larger than the product whose overlay error or critical dimension is the characteristic of interest are often used. The measurement results are only indirectly related to the dimensions of the actual product structure, and are inaccurate because the metrology target does not undergo the same distortion under different processes in optical projection in the lithography apparatus and / or other steps of the manufacturing process. A scanning electron microscope (SEM) can directly resolve such recent product structures, but SEM is much more time-consuming than optical measurement. Furthermore, electrons cannot penetrate thick process layers, so it is not suitable for metrology applications. Other techniques are also known, such as measurement of electrical characteristics using contact pads, but they only provide indirect evidence of the true product structure.

[0010]

[0010] By shortening the wavelength of the radiation used during metrology (e.g., moving towards the "soft X-ray (SXR)" wavelength spectrum), it becomes possible to resolve smaller structures, increase sensitivity to structural variations, and / or penetrate deeper into the product structure. One such method of generating suitable high-frequency radiation (e.g., hard X-rays, soft X-rays, and / or EUV radiation) is to excite a generation medium using pump radiation (e.g., infrared IR radiation), thereby causing the generation of emitted radiation and, optionally, harmonic generation including high-frequency radiation.

[0011]

[0011] In a metrology tool, it is desirable to split the source radiation into a main illumination branch and a reference sub-branch. The reference sub-branch can be used to monitor the radiation source spectrum or to obtain information regarding the radiation source spectrum that can be used to infer the value of a parameter of interest when using a measurement tool to measure a structure. When SXR or EUV radiation is used as the measurement radiation, this splitting can be difficult. A grating can also be used, but in that case, it becomes difficult to keep the transmittance of the measurement radiation high and to suppress scattering. Further, including a grating in the illumination path adds additional constraints to the optical design and makes it even more difficult to optimize this design for other system requirements.

[0012]

[0012] An improvement in splitting the source illumination into a main illumination branch and a reference sub-branch is desired.

Summary of the Invention

[0013]

[0013] In a first aspect of the present invention, an illumination branch including an illumination optical system for guiding a measurement radiation beam onto a structure, a pellicle beam splitter within the illumination branch, the pellicle beam splitter including a pellicle film operable to split a source radiation beam from an illumination source into a reference radiation beam and a measurement radiation beam, a measurement detector for detecting the measurement radiation beam after being scattered by the structure, and a reference detector for detecting the reference radiation beam, is provided.

[0014]

[0014] In a second aspect of the present invention, a pellicle film including three or more layers is provided, the three or more layers including at least one inner layer and at least one outer layer on at least one surface of any of the at least one inner layer, the at least one inner layer including boron, zirconium, beryllium, niobium, yttrium, molybdenum, carbon, and / or one or more compounds of each of these materials and / or consisting of them.

[0015]

[0015] In a third aspect of the present invention, there is provided a pellicle film including three or more layers, the three or more layers including at least one inner layer and at least one outer layer on at least one surface of any of the at least one inner layer, the at least one inner layer including one or more of silicon, boron, zirconium, beryllium, niobium, yttrium, molybdenum, carbon, and / or one or more compounds of each of these materials, and / or consisting of them, and the thickness of at least one outer layer on each surface of the at least one inner layer being 1 nm to 3 nm.

[0016]

[0016] In a fourth aspect of the present invention, there is provided a filter film including at least two materials, wherein at least a first material of the at least two materials includes or consists of germanium or selenium.

[0017]

[0017] In a fifth aspect of the present invention, there is provided a method for detecting damage and / or contamination in an irradiation region caused by radiation.

[0018]

[0018] The above and other aspects of the present invention will be understood by considering the embodiments described below.

[0019]

[0019] Hereinafter, embodiments will be described by way of example with reference to the accompanying schematic drawings.

Brief Description of the Drawings

[0020]

Figure 1

[0019] Schematically shows a general overview of a lithography apparatus.

Figure 2

[0019] Schematically shows a general overview of a lithography cell.

Figure 3

[0019] Shows a schematic diagram of holistic lithography, representing the cooperation between three important technologies for optimizing semiconductor manufacturing.

Figure 4

[0019] Schematically shows a scatterometry apparatus.

Figure 5

[0019] Shows a schematic representation of a metrology apparatus in which EUV and / or SXR radiation is used.

Figure 6

[0019] Shows a simplified schematic diagram of a light source that can be a light source for harmonic generation of a metrology apparatus as shown in FIG. 5.

Figure 7a

[0019] Schematic diagram of a dark field scatterometer for use in measuring a target using a first pair of illumination apertures according to an embodiment of the present invention.

Figure 7b

[0019] Detailed diagram of the diffraction spectrum of a target grating for a given illumination direction.

Figure 7c

[0019] Shows a second pair of illumination apertures that provide an additional illumination mode when using a scatterometer for diffraction-based overlay measurements.

Figure 7d

[0019] Shows a third pair of illumination apertures that combines the first pair of apertures and the second pair of apertures.

Figure 8

[0019] Schematic diagram of a metrology apparatus of a known configuration.

Figure 9

[0019] Schematic diagram of a metrology apparatus according to an embodiment.

Figure 10a

[0019] Plot of the transmittance Trn of a zirconium filter against the wavelength λ.

Figure 10b

[0019] Plot of the transmittance Trn of a germanium filter against the wavelength λ.

Figure 10c

[0019] Plot of the transmittance Trn of a selenium filter against the wavelength λ.

Figure 11

[0019] Plots of the transmittance Trn of germanium and zirconium filters, selenium and copper filters, boron, germanium and zirconium filters against their respective wavelengths λ.

Mode for Carrying Out the Invention

[0021]

[0011] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation and particle radiation, including ultraviolet radiation (e.g., having a wavelength of 365, 248, 193, 157, or 126 nm), EUV (e.g., extreme ultraviolet radiation having a wavelength in the range of about 5 - 100 nm), X-ray radiation, electron beam radiation, and other particle radiation.

[0022]

[0012] The terms "reticle", "mask", or "patterning device" as used in this specification can be broadly construed to mean a general patterning device that can be used to provide a patterned cross-section corresponding to the pattern to be created on a target portion of a substrate to an incident radiation beam. The term "light valve" may also be used in this context. In addition to classical masks (transmission or reflection masks, binary masks, phase shift masks, hybrid masks, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0023]

[0013] FIG. 1 schematically shows a lithographic apparatus LA. The lithographic apparatus LA includes an illumination system IL (also called an illuminator) configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, EUV radiation, or X-ray radiation), a mask support (e.g., a mask table) T connected to a first positioner PM constructed to support a patterning device (e.g., a mask) MA and configured to accurately position the patterning device MA according to certain parameters, a substrate support (e.g., a wafer table) WT connected to a second positioner PW constructed to hold a substrate (e.g., a resist-coated wafer) W and configured to accurately position the substrate support according to certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., including one or more dies) of the substrate W.

[0024]

[0014] During operation, the illumination system IL receives a radiation beam from the radiation source SO (e.g., via the beam delivery system BD). The illumination system IL may include various types of optical components for guiding, shaping, and / or controlling the radiation, and may include, for example, refractive, reflective, diffractive, magnetic, electromagnetic, electrostatic, and / or other types of optical components or any combination thereof. The illuminator IL can be used to adjust the radiation beam B such that the radiation beam B has a desired spatial intensity distribution and angular intensity distribution in the cross-section on the surface of the patterning device MA.

[0025]

[0015] The term "projection system" PS as used herein is to be construed broadly as encompassing various types of projection systems. Such systems can include refractive, reflective, diffractive, catadioptric, anamorphic, magnetic, electromagnetic, and / or electro-optical systems or any combination thereof, depending on the requirements of the exposure radiation being used and / or other factors (e.g., the use of an immersion liquid or the use of a vacuum). When the term "projection lens" is used herein, they can all be considered synonymous with the more general term "projection system" PS.

[0026]

[0016] The lithographic apparatus LA can be of a type in which at least a portion of the substrate is covered with a liquid having a relatively high refractive index (e.g., water) so as to fill the space between the projection system PS and the substrate W, which is also referred to as immersion lithography. Details of immersion techniques are shown in U.S. Patent No. 6,952,253, which is hereby incorporated by reference in its entirety.

[0027]

[0017] The lithographic apparatus LA may be of a type having two or more substrate support parts WT (also referred to as a "dual stage"). In such a "multi-stage" machine, those substrate support parts WT may be used in parallel, and / or while a substrate W placed on one of those substrate support parts WT is being used to expose a pattern onto that substrate W, preparatory steps for a subsequent exposure of another substrate W placed on the other substrate support part WT may be carried out with respect to that other substrate W.

[0028]

[0018] In addition to the substrate support part WT, the lithographic apparatus LA may include a measurement stage. The measurement stage is configured to hold a sensor and / or a cleaning device. The sensor may be configured to measure a characteristic of the projection system PS or a characteristic of the radiation beam B. The measurement stage may hold a plurality of sensors. The cleaning device may be configured to clean a part of the lithographic apparatus, for example, a part of the projection system PS or a part of the system for supplying the immersion liquid. The measurement stage may move under the projection system PS when the substrate support part WT is away from the projection system PS.

[0029]

[0019] During operation, the radiation beam B is incident on the patterning device (for example, the mask MA held on the mask support T) and is patterned by the pattern (design layout) on the patterning device MA. After passing through the mask MA, the radiation beam B passes through the projection system PS, and the projection system PS focuses the beam on the target portion C of the substrate W. With the assistance of the second positioner PW and the position measurement system IF, the substrate support WT can move accurately. For example, various target portions C can move accurately so as to be positioned at the focused and aligned positions in the path of the radiation beam B. Similarly, the first positioner PM and optionally another position sensor (not explicitly shown in FIG. 1) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B. The patterning device MA and the substrate W may be aligned using the mask alignment marks M1, M2 and the substrate alignment marks P1, P2. The substrate alignment marks P1, P2 occupy dedicated target portions as shown, but may be arranged in the space between the target portions. When the substrate alignment marks P1, P2 are arranged between the target portions C, they are called scribe line alignment marks.

[0030] As shown in FIG. 2, the lithography apparatus LA may form part of a lithography cell LC (which may also be referred to as a litho cell or a (litho) cluster), which often also includes apparatus for performing pre-exposure and post-exposure processes on a substrate W. Conventionally, such apparatus includes a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH and a bake plate BK (which, for example, regulate the temperature of the substrate W, which is done, for example, to regulate the solvent in the resist layer). A substrate handler (i.e. a robot) RO picks up the substrate W from the input / output ports I / O1, I / O2, moves those substrates W between the various process apparatuses, and delivers those substrates W to the loading bay LB of the lithography apparatus LA. The devices within the litho cell are often collectively referred to as a track and may be under the management of a track control unit TCU, which itself may be controlled by a monitoring control system SCS, which may also control the lithography apparatus LA (e.g. via a lithography control unit LACU).

[0031]

[0021] In a lithography process, it is desirable to frequently measure the created structures (e.g., for process control and verification). A tool for performing such measurements can be called a metrology tool MT. Various types are known as metrology tools MT for performing such measurements, such as a scanning electron microscope or various forms of scatterometer metrology tools MT. A scatterometer is a multi-purpose instrument that enables measurement of parameters of a lithography process, and the measurement is performed by having a sensor at or near the pupil of the objective lens of the scatterometer or at a conjugate plane with respect to the pupil (a measurement commonly called pupil-based measurement), or by having a sensor at or near the image plane or at a conjugate plane with respect to the image plane (in this case, a measurement commonly called image-based or field-based measurement). Such scatterometers and related measurement techniques are detailed in U.S. Patent Application Publication Nos. 20100328655, 2011102753A1, 20120044470A, 20110249244, 20110026032, or European Patent Application Publication No. 1,628,164A, which are hereby incorporated by reference in their entirety. The aforementioned scatterometers can measure gratings using light from hard X-rays (HXR), soft X-rays (SXR), extreme ultraviolet (EUV), visible light to near-IR, and IR wavelength ranges. When the radiation is hard X-rays or soft X-rays, the aforementioned scatterometer can optionally be a small-angle X-ray scattering metrology tool.

[0032]

[0022] It is desirable to inspect the substrate so that the substrate W is accurately and consistently exposed by the lithography apparatus LA, and to measure characteristics of the patterned structures such as overlay errors, line widths, critical dimensions (CDs), and shapes of structures between successive layers. Therefore, an inspection tool and / or a metrology tool (not shown) can be included in the litho cell LC. If an error is detected, for example, adjustments can be made to subsequent substrate exposures or other processing steps to be performed on the substrate W, which can be done particularly when the inspection is performed before other substrates W in the same batch or lot are subsequently exposed or processed.

[0033]

[0023] An inspection apparatus, sometimes called a metrology apparatus, is used to determine the characteristics of a substrate W, and in particular, to determine how the characteristics of different substrates W vary, or how the characteristics associated with different layers of the same substrate W vary from layer to layer. Alternatively, the inspection apparatus can be configured to identify defects on the substrate W and can, for example, be part of a litho cell LC, incorporated into a lithography apparatus LA, or even be a stand-alone apparatus. The inspection apparatus can measure characteristics related to a latent image (the image in the resist layer after exposure), a semi-latent image (the image in the resist layer after the post-exposure bake step PEB), a developed resist image (where the exposed or unexposed portions of the resist have been removed), or even an etched image (the image after a pattern transfer step such as etching).

[0034]

[0024] In a first embodiment, the scatterometer MT is an angularly resolved scatterometer. In such a scatterometer, a reconstruction method for reconstructing or calculating the characteristics of a grating can be applied to the measurement signal. Such a reconstruction can be, for example, the result of simulating the interaction between the 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 by the simulation of the interaction until a diffraction pattern similar to the diffraction pattern observed from the actual target is generated.

[0035]

[0025] In the second embodiment, the scatterometer MT is a spectroscopic scatterometer MT. In such a spectroscopic scatterometer MT, the radiation emitted from the radiation source travels towards the target, and the radiation reflected, transmitted, or scattered from the target travels towards the spectrometer detector, and the spectrometer detector measures the spectrum of the specularly reflected radiation (i.e., measures the intensity as a function of wavelength). From this data, it is possible to reconstruct the structure or profile of the target that caused the detected spectrum, and this reconstruction can be done, for example, by rigorous coupled wave theory and non-linear regression, or by comparison with a library of simulated spectra.

[0036]

[0026] In the third embodiment, the scatterometer MT is an ellipsometer. An ellipsometer makes it possible to determine the parameters of a lithography process by measuring the radiation that can be scattered, diffracted, reflected, or transmitted for each polarization state. Such a metrology device emits polarized light (e.g., linearly polarized light, circularly polarized light, or elliptically polarized light) using, for example, a suitable polarization filter in the illumination section of the metrology device. Suitable sources for the metrology device can also provide polarized radiation. Various embodiments of existing ellipsometers are incorporated herein by reference in their entirety from U.S. Patent Application Publication Nos. 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.

[0037]

[0027] In one embodiment of the scatterometer MT, the scatterometer MT is adapted to measure an overlay of two misaligned gratings or periodic structures by measuring the reflection spectrum and / or the asymmetry of the detection configuration, and the asymmetry is related to the degree of overlay. The two (possibly overlapping) grating structures can be applied in two different layers (not necessarily consecutive layers) and can be formed at substantially the same position on the wafer. The scatterometer can have a symmetric detection configuration, as described, for example, in co-owned European Patent Application Publication No. 1628164A, so that any asymmetry can be clearly distinguished. This provides a straightforward method for measuring grating misalignment. Further examples of overlay errors between two layers including a periodic structure when the target is measured through the asymmetry of the periodic structure can be obtained from PCT Patent Application Publication International Publication No. 2011 / 012624 or US Patent Application No. 20160161863, which are hereby incorporated by reference in their entirety.

[0038]

[0028] Other target parameters can be focus and dose. Focus and dose can be determined simultaneously by scatterometry (or alternatively by a scanning electron microscope), as described in US Patent Application No. 2011-0249244, which is hereby incorporated by reference in its entirety. A single structure having a unique combination of critical dimension and sidewall angle measurements for each point of a focus energy matrix (FEM, also called a focus exposure matrix) can be used. When these unique combinations of critical dimension and sidewall angle are available, the focus and dose values can be uniquely determined from these measurements.

[0039]

[0029] A metrology target can be an assembly of composite gratings, most of which are formed by a lithography process in a resist, but can also be formed after other manufacturing processes, such as an etching process. The pitch and linewidth of the grating structure can strongly depend on the measurement optical system (specifically, the NA of the optical system) so as to be able to capture the diffraction orders obtained from the metrology target. As previously shown, the diffraction signal can be used to determine the shift (also called "overlay") between two layers and can also be used to reconstruct at least a part of the original grating such as generated by a lithography process. This reconstruction can be used to provide guidance on the quality of the lithography process and can be used to control at least a part of the lithography process. The target can have smaller sub-segmentations configured to mimic the dimensions of the functional part of the design layout in the target. This sub-segmentation causes the target to behave more similarly to the functional part of the design layout such that all process parameter measurements closely resemble the functional part of the design layout. The target can be measured in underfill mode or overfill mode. 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 an overfill mode, it may be possible to measure different targets simultaneously and thus it may also be possible to determine different process parameters at the same time.

[0040]

[0030] The quality of the overall measurement of lithography parameters using a specific target is, at least in part, determined by the measurement recipe used for the measurement of this lithography parameter. The term "substrate measurement recipe" may 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 recipe is a diffraction-based optical measurement, one or more of the parameters of this measurement may include the wavelength of the radiation, the polarization of the radiation, the angle of incidence of the radiation on the substrate, the orientation of the radiation with respect to the pattern on the substrate, and the like. One criterion in selecting a measurement recipe may be, for example, the sensitivity of one of the measurement parameters to process variations. Further examples are described in U.S. Patent Application No. 2016-0161863 and Published U.S. Patent Application No. 2016 / 0370717A1, which are hereby incorporated by reference in their entirety.

[0041]

[0031] The patterning process in the lithography apparatus LA can be one of the most critical steps in a process that requires high accuracy in determining the dimensions and placement of structures on the substrate W. To ensure this high accuracy, as schematically shown in FIG. 3, three systems can be combined in a so-called "holistic" control environment. One of these systems is the lithography apparatus LA, which is (virtually) connected to the metrology tool MT (the second system) and the computer system CL (the third system). The key to such a "holistic" environment is to optimize the cooperation between these three systems to enhance the overall process window and provide a strict control loop, so that the patterning performed by the lithography apparatus LA is reliably kept within the process window. The process window defines a range of process parameters (e.g., dose, focus, overlay), within which a particular manufacturing process produces a defined result (e.g., a functioning semiconductor device), and within which the process parameters of the lithography process or patterning process can vary.

[0042]

[0032] The computer system CL can predict which resolution improvement technique should be used using a (part of) the design layout to be patterned, and can execute simulation and calculation of computational lithography to determine a mask layout and a lithography apparatus setting that achieve maximization of the entire process window of the patterning process (shown by the double-headed arrow of the first scale SC1 in FIG. 3). The resolution improvement technique can be configured to conform to the patterning capability of the lithography apparatus LA. Also, using the computer system CL, it is possible to detect where in the process window the lithography apparatus LA is currently operating (e.g., using the input from the metrology tool MET), and for example, to predict whether there may be defects due to sub-optimal processing (shown by the arrow pointing to "0" of the second scale SC2 in FIG. 3).

[0043]

[0033] The metrology tool MT can provide the computer system CL with inputs for enabling accurate simulation and prediction, and for example, in the calibration status of the lithography apparatus LA, can provide the lithography apparatus LA with feedback for identifying possible drifts (shown by the plurality of arrows of the third scale SC3 in FIG. 3).

[0044]

[0034] Many different forms of the metrology tool MT can be provided for measuring the structures generated using the lithography patterning apparatus. The metrology tool MT can use electromagnetic radiation to examine the structure. The characteristics of the radiation (e.g., wavelength, bandwidth, power) can affect the different measurement characteristics of the tool, and generally, the shorter the wavelength, the greater the resolution that can be increased. The radiation wavelength affects the resolution that the metrology tool can achieve. Therefore, a metrology tool MT equipped with a short-wavelength radiation source is preferred in order to be able to measure structures having features with small dimensions.

[0045]

[0035] Another way in which the radiation wavelength can affect the measurement characteristics is the penetration depth and transparency / opacity of the material scheduled for inspection at the radiation wavelength. Depending on the opacity and / or penetration depth, radiation can be used for measurements in transmission or reflection. The type of measurement can affect whether information about the surface and / or the bulk inside of the structure / substrate can be obtained. Thus, the penetration depth and opacity are additional factors to be considered when selecting the radiation wavelength for the metrology tool.

[0046]

[0036] For measurements of structures patterned by lithography techniques, a metrology tool MT with a short wavelength is preferred to achieve higher resolution. This can include wavelengths shorter than the visible wavelength, such as, for example, the UV, EUV, and X-ray parts of the electromagnetic spectrum. Hard X-ray methods such as transmission small-angle X-ray scattering (TSAXS) utilize the high resolution and high penetration depth of hard X-rays and can thus operate in transmission mode. On the other hand, soft X-rays and EUV do not penetrate deep into the target but can induce a rich optical response in the material scheduled for probing. This can be a legitimate optical property of many semiconductor materials and can be due to structures of a size comparable to the probe wavelength. As a result, EUV and / or soft X-ray metrology tools MT can operate in reflection mode, for example, by imaging structures patterned by lithography techniques or analyzing diffraction patterns from such structures.

[0047]

[0037] In the case of hard X-rays, soft X-rays, and EUV radiation, the applicability in high-volume manufacturing (HVM) applications can be limited due to the lack of high-brightness radiation sources available at the required wavelengths. In the case of hard X-rays, the radiation sources commonly used in industrial applications include X-ray tubes. X-ray tubes (including advanced X-ray tubes based on, for example, liquid metal anodes or rotating anodes) are relatively readily available and compact, but may lack the brightness required for HVM applications. High-brightness X-ray sources such as synchrotron light sources (SLS) and X-ray free electron lasers (XFEL) currently exist, but due to their size (>100 m) and high cost (hundreds of millions of euros), they are prohibitively large and expensive for metrology applications. Similarly, there is a lack of availability of sufficiently bright EUV and soft X-ray radiation sources.

[0048]

[0038] In a lithography process, it is desirable to frequently measure the fabricated structures (e.g., for process control and verification). Various tools for performing such measurements are known and include various forms of metrology apparatuses such as scanning electron microscopes or scatterometers. Examples of known scatterometers often rely on the provision of dedicated metrology targets, such as underfill targets (targets in the form of a simple grating or gratings overlapping in different layers, of a size sufficient to generate a spot smaller than the grating for the measurement beam) or overfill targets (whereby the illumination spot partially or fully encompasses the target). Furthermore, for example, by using a metrology tool such as an angular-resolved scatterometer that illuminates an underfill target such as a grating, a so-called reconstruction method can be used, in which the interaction between the scattered radiation and a mathematical model of the target structure is simulated, and the characteristics of the grating can be calculated by comparing the simulation results with the measurement results. The parameters of the model are adjusted by the simulation of the interaction until a diffraction pattern similar to the diffraction pattern observed from the actual target is generated.

[0049]

[0039] A scatterometer is a multi-purpose instrument that enables the measurement of parameters in a lithography process. The measurement is performed by having a sensor at the pupil of the objective lens of the scatterometer or at a conjugate plane with respect to the pupil (a measurement commonly referred to as pupil-based measurement), or by having a sensor at the image plane or at a conjugate plane with respect to the image plane (in this case, a measurement commonly referred to as image-based or field-based measurement). Such scatterometers and related measurement techniques are further described in U.S. Patent Application Publication Nos. 20100328655, 2011102753A1, 20120044470A, 20110249244, 20110026032, or European Patent Application Publication No. 1,628,164A, which are hereby incorporated by reference in their entirety. The aforementioned scatterometer can measure multiple targets from multiple gratings in one image using light from the soft X-ray, extreme ultraviolet, visible to near-infrared IR wavelength ranges.

[0050]

[0040] An example of a metrology apparatus such as a scatterometer is shown in FIG. 4. It may include a broadband (e.g., white light) radiation projector 2 that projects radiation 5 onto a substrate W. The reflected or scattered radiation 10 is sent to a spectrometer detector 4, which measures the spectrum 6 of the specularly reflected radiation (i.e., the measurement of the intensity I as a function of the wavelength λ). From this data, the structure or profile 8 that gives rise to the detected spectrum can be reconstructed by a processing unit (PU), for example, by rigorous coupled-wave analysis and non-linear regression, or by comparison with a library of simulation spectra as shown at the bottom of FIG. 4. Generally, for reconstruction, the general form of the structure is known, and some parameters are assumed from the knowledge of the process in which the structure was made, thereby leaving only a few parameters of the structure to be determined from the scatterometry data. Such a scatterometer may be configured as a normal incidence scatterometer or an oblique incidence scatterometer.

[0051]

[0041] An example of a transmission version of a metrology apparatus (such as the scatterometer shown in FIG. 4) is shown. The transmitted radiation is passed to the spectrometer detector 4, which measures the spectrum as discussed with respect to FIG. 4. Such a scatterometer can be configured as a normal incidence scatterometer or an oblique incidence scatterometer. Optionally, a transmission version using hard X-ray radiation having a wavelength of <1 nm, optionally <0.1 nm, optionally <0.01 nm.

[0052] As an alternative to the optical metrology method, for example, the use of radiation having at least one wavelength range of <0.01 nm, <0.1 nm, <1 nm, 0.01 nm to 100 nm, 0.01 nm to 50 nm, 1 nm to 50 nm, 1 nm to 20 nm, 5 nm to 20 nm, and 10 nm to 20 nm, such as hard X-rays, soft X-rays, or EUV radiation, is also considered. An example of a metrology tool that functions in one of the wavelength ranges presented above is transmission small-angle X-ray scattering (T-SAXS), such as that described in U.S. Patent Application Publication No. 2007 / 224518A, the contents of which are incorporated herein by reference in their entirety. Profile (CD) measurements using T-SAXS are discussed by Lemaillet et al, “Intercomparison between optical and X-ray scatterometry measurements of FinFET structures”, Proc. of SPIE, 2013, 8681. Note that the use of a laser-produced plasma (LPP) X-ray source is described in U.S. Patent Application Publication No. 2019 / 003988A1 and U.S. Patent Application Publication No. 2019 / 215940A1, the contents of which are incorporated herein by reference in their entirety. Reflectivity measurement techniques using grazing-incidence X-rays (GI-XRS) and extreme ultraviolet (EUV) radiation can be used to measure the characteristics of stacks of films and layers on a substrate. Within the general field of reflectivity measurement methods, angular measurement and / or spectroscopic techniques can be applied. In the angular measurement method, the variation of the reflected beam at different incident angles can be measured. On the other hand, spectroscopic reflectivity measurement measures the spectrum of wavelengths reflected at a given angle (using broadband radiation). For example, EUV reflectivity measurement is used for the inspection of mask blanks prior to the manufacture of reticles (patterning devices) for use in EUV lithography.

[0053]

[0043] Depending on the application range, for example, the use of wavelengths in the hard X-ray, soft X-ray, or EUV regions may be insufficient. U.S. Patent Application Publication Nos. 20130304424A1 and 2014019097A1 (Bakeman et al / KLA) describe a hybrid metrology technique that combines measurements performed using X-rays with wavelengths in the range of 120 nm to 2000 nm and optical measurements to obtain measured values of parameters such as CD. The CD measurement values are obtained by combining through one or more common and by means of an X-ray mathematical model and an optical mathematical model. The content of the cited U.S. patent applications is incorporated herein by reference in its entirety.

[0054]

[0044] FIG. 5 shows a schematic representation of a metrology apparatus 302 that can use the aforementioned radiation to measure parameters of a structure on a substrate. The metrology apparatus 302 shown in FIG. 5 may be suitable for the hard X-ray, soft X-ray, and / or EUV regions.

[0055]

[0045] FIG. 5 shows, purely by way of example, a schematic physical arrangement of a metrology apparatus 302 that includes a spectroscopic scatterometer that optionally uses grazing incidence and hard X-ray, EUV, and / or SXR radiation. An alternative form of the inspection apparatus can be provided in the form of an angularly resolved scatterometer that can use radiation with normal incidence or near-normal incidence similar to a conventional scatterometer operating at longer wavelengths, and can also use radiation in a direction more than 1° or 2° from a direction parallel to the substrate. An alternative form of the inspection apparatus can be provided in the form of a transmission scatterometer.

[0056]

[0046] The inspection apparatus 302 includes what is referred to as a radiation source or illumination source 310, an illumination system 312, a substrate support 316, detection systems 318, 398, and a metrology processing unit (MPU) 320.

[0057]

[0047] The illumination source 310 in this example is for generating EUV, hard X-ray, or soft X-ray radiation. As shown in FIG. 6, the illumination source 310 may be based on the high harmonic generation (HHG) technique, and also, for example, other types of illumination sources such as a liquid metal jet source, an inverse Compton scattering (ICS) source, a plasma channel source, a magnetic undulator source, a free electron laser (FEL) source, a compact storage ring source, a discharge-generated plasma source, a soft X-ray laser source, a rotating anode source, a solid anode source, a particle acceleration source, a microfocus source, or a laser-generated plasma source may be used.

[0058]

[0048] The HHG source may be a gas jet / nozzle source, a capillary / fiber source, or a gas cell source.

[0059]

[0049] As shown in FIG. 6, in the case of an example of an HHG source, the main components of the radiation source are a pump radiation source 330 operable to emit pump radiation and a gas delivery system 332. Optionally, the pump radiation source 330 is a laser, and optionally, the pump radiation source 330 is a pulsed high-power infrared laser or an optical laser. The pump radiation source 330 may be, for example, a fiber-based laser equipped with an optical amplifier, and may generate pulses of infrared radiation that, if necessary, can last less than 1 ns (1 nanosecond) per pulse at a pulse repetition rate of up to several megahertz. The wavelength of the infrared radiation is in the range of 200 nm to 10 μm, for example, in the region of 1 μm (1 micron). Optionally, the laser pulse is delivered as the first pump radiation 340 to the gas delivery system 332, and a portion of the radiation gas is converted to a higher frequency than the first radiation and becomes the emitted radiation 342. The gas supply device 334 supplies an appropriate gas to the gas delivery system 332, and the gas is optionally ionized by the power source 336. The gas delivery system 332 may be a cut-off tube.

[0060]

[0050] The gas supplied by the gas delivery system 332 defines a gas target that is a gas flow or a static volume. The gas is, for example, air, neon (Ne), helium (He), nitrogen (N2 ) Oxygen (O 2 ), argon (Ar), krypton (Kr), xenon (Xe), carbon dioxide, and combinations thereof. These can be selectable within the same apparatus. The emitted radiation can include multiple wavelengths. If the emitted radiation were hypothetically monochromatic, measurement calculations (e.g., reconstruction) could be simplified, but it is easier to generate radiation having several wavelengths. The emission divergence angle of the emitted radiation can depend on the wavelength. If the wavelengths are different, for example, different levels of contrast are provided when imaging the structures of different materials. For example, in the inspection of metal or silicon structures, a wavelength different from that used to image features of a resist (carbon-based) or to detect contamination of such different materials can be selected. One or more filtering devices 344 can be provided. For example, a filter such as a thin film of aluminum (Al) or zirconium (Zr) serves to prevent further entry of the basic IR radiation into the inspection apparatus. A grating (not shown) can be provided to select one or more specific wavelengths from among the generated wavelengths. Optionally, the illumination source includes a space configured to be evacuated, and the gas delivery system is configured to supply a gas target into that space. Optionally, in view of the fact that SXR and / or EUV radiation is absorbed when traveling in air, part or all of the beam path can be included within a vacuum environment. The various components of the radiation source 310 and the illumination optics 312 can be adjustable to implement different metrology “recipes” within the same apparatus. For example, different wavelengths and / or polarizations can be made selectable.

[0061]

[0051] Depending on the material of the structure being inspected, different wavelengths may allow for the desired level of penetration into deeper layers. Then, for resolving the smallest device features and defects between the smallest device features, shorter wavelengths are considered preferable. For example, one or more wavelengths in the range of 0.01 to 20 nm, optionally in the range of 1 to 10 nm, or optionally in the range of 10 to 20 nm may be selected. Wavelengths shorter than 5 nm have the problem that the critical angle can become very low when reflecting off the materials of interest in semiconductor manufacturing. Therefore, by selecting a wavelength longer than 5 nm, a stronger signal can be obtained at a higher incident angle. On the other hand, if the inspection task is for detecting the presence of a particular material, e.g., for detecting contamination, wavelengths up to 50 nm may be useful.

[0062]

[0052] From the radiation source 310, a filtered beam 342 enters the inspection chamber 350, where a substrate W containing the structure of interest is held at the measurement position by the substrate support 316 for inspection. The structure of interest is labeled as T. Optionally, the atmosphere inside the inspection chamber 350 is maintained near vacuum by the vacuum pump 352, so that EUV radiation can pass through the atmosphere without excessive attenuation. The illumination system 312 has the function of focusing the radiation into a focused beam 356 and may include, for example, one two-dimensional curved mirror or a series of one-dimensional curved mirrors as described in U.S. Patent Application Publication No. 2017 / 0184981A1, the content of which is incorporated herein by reference in its entirety. The focusing is performed to achieve a circular or elliptical spot S with a diameter of less than 10 μm when projected onto the structure of interest. The substrate support 316 includes, for example, an X-Y translation stage and a rotation stage, whereby any part of the substrate W can be brought close to the focus of the beam in the desired orientation. Thus, the radiation spot S is formed on the structure of interest. As an alternative or in addition thereto, the substrate support 316 includes, for example, a tilt stage, and the substrate W can be tilted at an angle to control the incident angle of the focused beam with respect to the structure of interest T.

[0063]

[0053] Optionally, the illumination system 312 can provide a reference beam of radiation to the reference detector 314, and the reference detector 314 can be configured to measure the spectrum and / or intensity of different wavelengths of the filtered beam 342. The reference detector 314 can be configured to generate a signal 315 that is provided to the processor 320, and the filter can include information regarding the spectrum of the filtered beam 342 and / or the intensity of different wavelengths of the filtered beam.

[0064]

[0054] The reflected radiation 360 is captured by the detector 318, and the spectrum is provided to the processor 320 for use in calculating the characteristics of the target structure T. The illumination system 312 and the detection system 318 thus form an inspection apparatus. This inspection apparatus can include a hard X-ray, soft X-ray, and / or EUV spectroscopic reflectometer of the type described in U.S. Patent Application Publication No. 2016 / 282282A1, the contents of which are incorporated herein by reference in their entirety.

[0065]

[0055] When the target Ta has a certain periodicity, the radiation of the focused beam 356 may be partially diffracted. The diffracted radiation 397 follows a different path at an angle that is well-defined with respect to the incident angle and then the reflected radiation 360. In FIG. 5, the diffracted radiation 397 shown is shown schematically, and the diffracted radiation 397 may follow many paths other than the path shown. Also, the inspection device 302 may include a further detection system 398 that detects and / or images at least a portion of the diffracted radiation 397. In FIG. 5, a single further detection system 398 is shown, but embodiments of the inspection device 302 may also include a plurality of further detection systems 398 arranged at different positions for detecting and / or imaging the diffracted radiation 397 in a plurality of diffraction directions. In other words, the focused radiation beam of a (higher) diffraction order that impinges on the target Ta is detected and / or imaged by one or more further detection systems 398. One or more detection systems 398 generate a signal 399 that is provided to the metrology processor 320. The signal 399 can include information about the diffracted light 397 and / or an image obtained from the diffracted light 397.

[0066]

[0056] To assist in the alignment and focus of the spot S with the desired product structure, the inspection device 302 can also provide an auxiliary optical system that uses auxiliary radiation under the control of the metrology processor 320. The metrology processor 320 can also communicate with a position controller 372 that operates a translation stage, a rotation stage, and / or a tilt stage. The processor 320 receives high-precision feedback regarding the position and orientation of the substrate via a sensor. The sensor 374 can include, for example, an interferometer that can provide accuracy in the picometer range. During operation of the inspection device 302, the spectral data 382 captured by the detection system 318 is sent to the metrology processing unit 320.

[0067] As mentioned, in an alternative form of the inspection apparatus, optionally, hard X-rays, soft X-rays and / or EUV radiation are used in normal incidence or in a state close to normal incidence, for example, to perform diffraction-based asymmetry measurements. In another alternative form of the inspection apparatus, hard X-rays, soft X-rays and / or EUV radiation are used in a direction exceeding 1° or 2° from a direction parallel to the substrate. Both types of inspection apparatuses can be provided in a hybrid metrology system. The performance parameters to be measured include overlay (OVL), critical dimension (CD), the focus of the lithography apparatus during printing of the target structure by the lithography apparatus, coherent diffraction imaging (CDI) and at-resolution overlay (ARO) metrology. The hard X-rays, soft X-rays and / or EUV radiation can have a wavelength of less than 100 nm, for example, radiation in the range of 5 - 30 nm, optionally in the range of 10 nm - 20 nm can be used. The radiation can have a narrow-band or wide-band nature. The radiation can have discrete peaks in a specific wavelength band or more continuous characteristics.

[0068]

[0058] Similar to the optical scatterometers used in today's production equipment, the inspection apparatus 302 can be used to measure the structures in the resist material processed in the litho cell (post-development inspection or ADI) and / or to measure the structures after forming in a harder material (post-etch inspection or AEI). For example, the substrate can be inspected using the inspection apparatus 302 after being processed by a developing apparatus, an etching apparatus, an annealing apparatus and / or other apparatuses.

[0069] The metrology tool MT, including but not limited to the scatterometer mentioned above, can use radiation from a radiation source to perform measurements. The radiation used by the metrology tool MT can be electromagnetic radiation. The radiation can be, for example, optical radiation such as radiation in the infrared, visible, and / or ultraviolet portions of the electromagnetic spectrum. The metrology tool MT can use radiation to measure or inspect the characteristics and profiles of a substrate, such as a lithographic exposure pattern on a semiconductor substrate. The type and quality of the measurement can depend on some characteristics of the radiation used by the metrology tool MT. For example, the resolution of an electromagnetic measurement can depend on the radiation wavelength, and the smaller the wavelength, the smaller the features that can be measured, for example due to the diffraction limit. To measure features of small dimensions, it may be preferable to perform the measurement using radiation of short wavelengths, such as EUV, hard X-ray, and / or soft X-ray (SXR) radiation. To perform metrology at a specific wavelength or wavelength range, the metrology tool MT requires access to a radiation source that provides radiation of that / those wavelength(s). To provide radiation of various wavelengths, there are various types of radiation sources. Depending on the wavelength provided by the radiation source, different types of radiation generation methods can be used. In the case of extreme ultraviolet (EUV) radiation (e.g., 1 nm to 100 nm) and / or soft X-ray (SXR) radiation (e.g., 0.1 nm to 10 nm), the radiation source can use high harmonic generation (HHG) or any other type of illumination source mentioned above to obtain radiation of the desired wavelength. One of the challenges faced in the development of such radiation sources is how to efficiently separate the emitted radiation from the generation setup and separate the emitted radiation from the radiation used to drive the process.

[0070]

[0060] Figure 6 shows a simplified schematic diagram of an embodiment 600 of a light source 310 that can be a harmonic generation light source. One or more of the features of the light source in the metrology tool described with respect to FIG. 5 may also be present in the light source 600 as appropriate. The light source 600 includes a chamber 601. The light source 600 is configured to receive pump radiation 611 having a propagation direction indicated by the arrow. The pump radiation 611 shown here is an example of the pump radiation 340 from the pump radiation source 330 as shown in FIG. 5. The pump radiation 611 can be induced into the chamber 601 through a radiation input 605 that can be a viewport made of fused silica or equivalent material. The pump radiation 611 can have a Gaussian or hollow (e.g., annular) cross-sectional profile and can be incident on a gas flow 615 having a flow direction indicated by the second arrow in the chamber 601 and optionally focused. The gas flow 615 includes a so-called gas volume or gas target of a small volume (e.g., a few cubic mm) of a specific gas (e.g., air, neon (Ne), helium (He), nitrogen (N 2 ), oxygen (O 2 ), argon (Ar), krypton (Kr), xenon (Xe), carbon dioxide, and combinations thereof) at a gas pressure above a certain value. The gas flow 615 can be a steady flow. Other media such as a metal plasma (e.g., an aluminum plasma) can also be used.

[0071]

[0061] The gas delivery system of the illumination source 600 is configured to supply a gas flow 615. The illumination source 600 is configured to supply pump radiation 611 into the gas flow 615 in order to drive the generation of emitted radiation 613. The region where at least the majority of the emitted radiation 613 is generated is called the interaction region. The interaction region can vary from tens of micrometers (for strongly focused pump radiation) to several millimeters or centimeters (for moderately focused pump radiation) or up to several meters (for very weakly focused pump radiation). The gas delivery system is configured to provide a gas target to generate the emitted radiation in the interaction region of the gas target. Optionally, the illumination source is configured to receive the pump radiation and provide the pump radiation in the interaction region. Optionally, the gas flow 615 is supplied by the gas delivery system into a space that has been evacuated or is nearly evacuated. The gas delivery system includes a gas nozzle 609, as shown in FIG. 6, and this gas nozzle 609 can include an opening 617 in the exit surface of the gas nozzle 609. The gas flow 615 is supplied from the opening 617. The gas catcher is for confining the gas flow 615 to a constant volume by extracting the residual gas flow and maintaining the inside of the chamber 601 in a vacuum or near-vacuum atmosphere. Optionally, the gas nozzle 609 can be made of a thick-walled tube and / or a high thermal conductivity material to avoid thermal deformation by the high-power pump radiation 611.

[0072]

[0062] The dimensions of the gas nozzle 609 can be considered for use in scaled-up or scaled-down versions ranging from micrometer-sized nozzles to meter-sized nozzles. This wide range of dimensions stems from the fact that the setup can be scaled such that the intensity of the pump radiation in the gas flow is within a specific range that can be beneficial for the emitted radiation, and it is necessary to determine different dimensions for different pump radiation energies, which can be a pulsed laser, and the pulse energy can vary from tens of microjoules to tens of joules. Optionally, the gas nozzle 609 has a thick wall to reduce nozzle deformation caused by, for example, the thermal expansion effect that can be detected by a camera. A gas nozzle with a thick wall can generate a stable gas volume with reduced fluctuations. Optionally, the illumination source includes a gas catcher proximate to the gas nozzle to maintain the pressure in the chamber 601.

[0073]

[0063] Due to the interaction between the pump radiation 611 and the gas atoms in the gas flow 615, the gas flow 615 converts a portion of the pump radiation 611 into emitted radiation 613, which can be an example of the emitted radiation 342 shown in FIG. 5. The central axis of the emitted radiation 613 can be parallel to the central axis of the incident pump radiation 611. The emitted radiation 613 can have a wavelength in the X-ray or EUV range, and its wavelength can be in the range of 0.01 nm to 100 nm, optionally 0.1 nm to 100 nm, optionally 1 nm to 100 nm, optionally 1 nm to 50 nm, or optionally 10 nm to 20 nm.

[0074]

[0064] During operation, the emitted radiation 613 beam passes through the radiation output 607 (e.g., an aperture or window) and is then manipulated by an illumination system 603, which can be an example of the illumination system 312 in FIG. 5, and can be directed to the substrate scheduled for inspection for metrology measurements. The emitted radiation 613 is directed to the structures on the substrate and can optionally be focused.

[0075]

[0065] Since air (and in fact any gas) strongly absorbs SXR or EUV radiation, the volume between the gas stream 615 and the wafer to be inspected can be evacuated or nearly evacuated. Since the central axis of the emitted radiation 613 can be parallel to the central axis of the incident pump radiation 611, it may be necessary to shield the pump radiation 611 so that the pump radiation 611 does not enter the illumination system 603 through the radiation output 607. This can be done by incorporating the filtering device 344 shown in FIG. 6 into the radiation output 607. This filtering device 344 is arranged in the radiation beam path and does not pass or hardly passes the pump radiation (e.g., does not pass or hardly passes infrared or visible light), but at least partially passes the emitted radiation beam. The filter can be manufactured using zirconium or a plurality of materials combined in multiple layers. The filter can be a hollow block, optionally an annular block, when the pump radiation 611 has a hollow cross-sectional profile, optionally an annular cross-sectional profile. Optionally, the filter is neither perpendicular nor parallel to the propagation direction of the emitted radiation beam so that pump radiation filtering is efficient. Optionally, the filtering device 344 includes a hollow block and a thin film filter such as an aluminum (Al) or zirconium (Zr) membrane filter. Optionally, the filtering device 344 can include a mirror that efficiently reflects the emitted radiation but hardly reflects the pump radiation, or a wire mesh that efficiently transmits the emitted radiation but hardly transmits the pump radiation.

[0076]

[0066] In this specification, methods, apparatuses, and assemblies for optionally obtaining emitted radiation at the harmonic frequency of pump radiation are described. The radiation generated through the process, optionally using HHG that utilizes non-linear effects to optionally generate radiation at the harmonic frequency of the provided pump radiation, can be provided as radiation in a metrology tool MT for inspection and / or measurement of a substrate. When the pump radiation includes short pulses (i.e., a few cycles), the generated radiation does not necessarily exactly match the harmonics of the pump radiation frequency. The substrate can be a substrate patterned by lithography techniques. The radiation obtained through the process can also be provided to a lithography apparatus LA and / or a lithography cell LC. The pump radiation can be pulsed radiation and can provide a high peak intensity in a short time.

[0077]

[0067] The pump radiation 611 can include radiation having one or more wavelengths higher than one or more wavelengths of the emitted radiation. The pump radiation can include infrared radiation. The pump radiation can include radiation having wavelengths in the range of 500 nm to 1500 nm. The pump radiation can include radiation having wavelengths in the range of 800 nm to 1300 nm. The pump radiation can include radiation having wavelengths in the range of 900 nm to 1300 nm. The pump radiation can be pulsed radiation. The pulsed pump radiation can include pulses having a duration in the femtosecond range.

[0078]

[0068] In some embodiments, the emitted radiation, optionally harmonic radiation, can include one or more harmonics of the pump radiation wavelength. The emitted radiation can include wavelengths in the extreme ultraviolet, soft X-ray, and / or hard X-ray portions of the electromagnetic spectrum. The emitted radiation 613 can include one or more wavelengths in the ranges of less than 1 nm, less than 0.1 nm, less than 0.01 nm, 0.01 nm to 100 nm, 0.1 nm to 100 nm, 0.1 nm to 50 nm, 1 nm to 50 nm, and 10 nm to 20 nm.

[0079]

[0069] The radiation such as the above-mentioned harmonic radiation can be provided as the source radiation in the metrology tool MT. The metrology tool MT can use the source radiation to perform measurements on a substrate that is exposed by a lithographic apparatus. The measurements can be for determining one or more parameters of a structure on the substrate. By using radiation with a shorter wavelength (e.g., radiation with wavelengths of EUV, SXR, and / or HXR as included in the above-mentioned wavelength range), the metrology tool can resolve smaller features of the structure as compared to the case of using radiation with a longer wavelength (e.g., visible radiation, infrared radiation). Radiation with a short wavelength such as EUV, SXR, and / or HXR radiation can also penetrate deeper into materials such as a patterned substrate, which means that metrology of deeper layers on the substrate is possible. Such deeper layers may not be accessible with radiation having a long wavelength.

[0080]

[0070] In the metrology tool MT, the source radiation can be emitted from a radiation source and induced onto a target structure (or other structure) on the substrate. The source radiation can include EUV, SXR, and / or HXR radiation. The target structure can reflect, transmit, and / or diffract the source radiation incident on the target structure. The metrology tool MT can include one or more sensors for detecting the diffracted radiation. For example, the metrology tool MT can include a detector for detecting positive first-order (+1) diffraction and negative first-order (-1) diffraction. Also, the metrology tool MT can measure specularly reflected or transmitted radiation (zero-order diffracted radiation). In the metrology tool MT, there can be additional sensors for metrology, for example, for measuring further diffraction orders (e.g., higher diffraction orders).

[0081]

[0071] In an exemplary lithography metrology application, the HHG generated radiation can be focused onto a target on a substrate using an optical column, which can be referred to as an illuminator, for transmitting the radiation from the HHG source to the target. The HHG radiation is then reflected from the target and detected and processed such that, for example, the characteristics of the target are measured and / or inferred.

[0082]

[0072] The gas target HHG configurations can be broadly classified into three distinct categories: gas jets, gas cells, and gas capillaries. FIG. 7 shows an example of a gas jet configuration where the gas volume is introduced into the driving radiation laser beam. In the gas jet configuration, the interaction between the driving radiation and the solid part is minimized. The gas volume can include, for example, a gas stream perpendicular to the driving radiation beam, and the gas volume is enclosed within a gas cell. In a gas capillary setup, the dimensions of the capillary structure that holds the gas are small in the lateral direction such that they significantly affect the propagation of the driving radiation laser beam. The capillary structure can be, for example, a hollow core fiber, and the hollow core is configured to hold the gas.

[0083]

[0073] The gas jet HHG configuration can provide a relative degree of freedom for forming the spatial profile of the driving radiation beam in the far field since it is not subject to the constraints imposed by the gas capillary structure. Also, the gas jet configuration can have less stringent alignment tolerances. On the other hand, the gas capillary can expand the interaction zone between the driving radiation and the gaseous medium, thereby optimizing the HHG process.

[0084]

[0074] For example, for using HHG radiation in metrology applications, the HHG radiation is separated from the drive radiation downstream of the gas target. The separation of the HHG radiation and the drive radiation can be different in the gas jet configuration and the gas capillary configuration. In either case, the drive radiation removal scheme can include a metal transmissive filter for filtering the residual drive radiation from the short wavelength radiation. However, before using such a filter, it is necessary to significantly reduce the intensity of the drive radiation from the intensity at the gas target in order to avoid damage to the filter. The methods that can be used for this intensity reduction are different in the gas jet configuration and the gas capillary configuration. In the case of gas jet HHG, due to the relative freedom of the shape and spatial profile (which may also be called spatial distribution and / or spatial frequency) of the drive radiation beam focused on the gas target, in the far field, it can be designed to have a low intensity along the direction in which the short wavelength radiation propagates. This spatial separation in the far field means that an aperture can be used to shield the drive radiation and reduce its intensity.

[0085]

[0075] In contrast, in the gas capillary structure, the spatial profile of the beam when passing through the gaseous medium can be greatly influenced by the capillary. The spatial profile of the drive radiation can be determined by the shape and material of the capillary structure. For example, when using a hollow core fiber as the capillary structure, the mode of the drive radiation supported for propagation in the fiber is determined by the shape and material of the fiber structure. In the case of most standard fibers, the supported propagation mode leads to a spatial profile where the high-intensity drive radiation overlaps with the high-intensity HHG radiation. For example, the drive radiation intensity can be concentrated in the center with a Gaussian profile or a profile close to a Gaussian profile in the far field.

[0086]

[0076] A further metrology apparatus suitable for use in an embodiment of the present invention is shown in Fig. 7(a). It should be noted that this is only an example of a suitable metrology apparatus. Alternative suitable metrology apparatuses can use EUV radiation, for example, as disclosed in WO 2017 / 186483 A1. Fig. 7(b) shows in detail the target structure T and the diffracted rays of the measurement radiation used to illuminate the target structure. The metrology apparatus shown is of a type known as a dark-field metrology apparatus. The metrology apparatus may be a stand-alone device, incorporated into a lithography apparatus LA (e.g., at a measurement station), or incorporated into a lithography cell LC. The optical axis having several branches throughout the apparatus is represented by a dotted line O. In this apparatus, light emitted by a radiation source 11 (e.g., a xenon lamp) is directed onto a substrate W via a beam splitter 15 by an optical system including lenses 12, 14, and an objective lens 16. These lenses are in a double array in a 4F configuration. Different lens arrangements can also be used if they provide a substrate image on the detector and at the same time allow access to the intermediate pupil plane for spatial frequency filtering. Thus, the angular range at which the radiation is incident on the substrate can be selected by defining the spatial intensity distribution in a plane that shows the spatial spectrum of the substrate plane, here called the (conjugate) pupil plane. In particular, this can be done by inserting an aperture plate 13 in a suitable form into the plane that is the inverse projection image of the pupil plane of the objective lens between lenses 12 and 14. In the example shown, the aperture plate 13 has different forms labeled 13N and 13S, whereby different illumination modes can be selected. The illumination system of this embodiment forms an off-axis illumination mode. In the first illumination mode, the aperture plate 13N provides an off-axis from the direction designated "north" for illustrative purposes only. In the second illumination mode, the aperture plate 13S is used to provide similar illumination, but from the opposite direction labeled "south". Other illumination modes are also possible by using different apertures.Since unnecessary light other than the desired illumination mode interferes with the desired measurement signal, it is desirable to darken the remaining portion of the pupil plane.

[0087]

[0077] As shown in FIG. 7(b), the target structure T is arranged such that the substrate W is perpendicular to the optical axis O of the objective lens 16. The substrate W can be supported by a support portion (not shown). The measurement radiation ray I (for example, including the SXR wavelength) that impinges on the target structure T from an angle outside the axis O generates a zero-order ray (solid line 0) and two first-order rays (one-dot chain line +1 and two-dot chain line -1). It should be remembered that in a small target structure in an overfilled state, these rays are just one of many parallel rays that cover the region of the substrate including the metrology target structure T and other features. The width of the aperture of the plate 13 is finite (necessary to accept a useful amount of light, so the incident ray I will actually occupy a wide range of angles, and the diffracted rays 0 and +1 / -1 will be somewhat diffused. According to the point spread function of a small target, each of the orders +1 and -1 will further spread over a wide range of angles rather than being an ideal single ray as shown. Note that the grating pitch and illumination angle of the target structure can be designed or adjusted such that the first-order rays incident on the objective lens are closely aligned with the central optical axis. The rays shown in FIGS. 7(a) and 7(b) are shown somewhat off-axis purely for easier distinction in the figure.

[0088]

[0078] The at least 0th and +1st order diffractions by the target structure T on the substrate W are collected by the objective lens 16 and returned through the beam splitter 15. Returning to Fig. 7(a), both the first illumination mode and the second illumination mode are shown by designating the opposite apertures labeled North (N) and South (S). When the incident light ray I of the measurement radiation is from the north side of the optical axis, i.e., when the first illumination mode is applied using the aperture plate 13N, the +1 diffracted ray labeled +1(N) is incident on the objective lens 16. In contrast, when the second illumination mode is applied using the aperture plate 13S, the -1 diffracted ray (labeled 1(S)) is incident on the lens 16.

[0089]

[0079] The second beam splitter 17 splits the diffracted beam into two measurement branches. In the first measurement branch, the optical system 18 uses the 0th and 1st order diffracted beams to form the diffraction spectrum (pupil plane image) of the target structure on the first sensor 19 (e.g., a CCD or CMOS sensor). Since each diffraction order hits a different point on the sensor, the orders can be compared and contrasted by image processing. The pupil plane image captured by the sensor 19 can be used for the focus of the metrology device and / or the normalization of the intensity measurement of the 1st order beam. Also, the pupil plane image can be used for many measurement purposes such as reconstruction.

[0090]

[0080] In the second measurement branch, the optical systems 20, 22 form an image of the target structure T on the sensor 23 (e.g., a CCD or CMOS sensor). In the second measurement branch, the aperture stop 21 is provided in a plane conjugate to the pupil plane. The aperture stop 21 functions to shield the zero-order diffraction beam so that the image of the target formed on the sensor 23 is formed only from the -1 or +1 first-order beam. The images captured by the sensors 19, 23 are output to a processor PU that processes the images, and its function depends on the specific type of measurement being performed. Note that in this specification, the term "image" is used in a broad sense. Therefore, if only one of the -1st order and +1st order exists, the image of the grating lines is not formed.

[0091]

[0081] The specific forms of the aperture plate 13 and the field stop 21 shown in FIG. 5 are merely pure examples. In another embodiment of the present invention, on-axis illumination of the target is used and an aperture stop with an off-axis aperture is used to pass only substantially one first-order diffracted light to the sensor. In yet other embodiments, second-order, third-order, and higher-order beams (not shown in FIG. 5) can be used for measurement instead of or in addition to the first-order beam.

[0092]

[0082] To adapt the measurement radiation to these different types of measurements, the aperture plate 13 can include many aperture patterns formed around a disk that rotates to provide the desired pattern at a predetermined position. Note that the aperture plate 13N or 13S can only be used for the measurement of a grating oriented in one direction (X or Y depending on the setup). In the case of measuring an orthogonal grating, 90° and 270° rotations of the target can be performed. FIGS. 7(c) and (d) show different aperture plates. The use of these and many other variations and applications of this apparatus are described in the previously mentioned published application.

[0093]

[0083] An illumination source such as the radiation source 310 of FIG. 5 or the radiation source 600 of FIG. 6 may include a high harmonic generation (HHG) source. Typically, when performing measurements, while radiation is used to illuminate a structure (or called a target) on a substrate, optionally on a semiconductor wafer or a patterning device, it is necessary to continuously or periodically measure the characteristics of the radiation generated by the HHG source in the illumination branch. In particular, it is necessary to measure real-time information regarding the spectral components of the source radiation. Then, an interference algorithm for inferring the parameters of the target from the source radiation scattered by the target can be input into the diagnosis of the radiation source.

[0094]

[0084] The method for achieving this is to provide a reference sub-branch within the illumination branch and induce a part of the source radiation into the reference sub-branch by a grating within the illumination branch. This grating can reflect a part of the source radiation back to the main illumination branch and diffract a part of the light into the reference sub-branch, forming spatially separated spectra on the reference detector. This grating can be a stand-alone grating or a grating manufactured on the focusing mirror (one of the illumination optics) of the illumination branch.

[0095]

[0085] FIG. 8 is a schematic diagram of such a configuration. The pump radiation 800 (for example, infrared radiation) is focused on the HHG generation point 805 (for example, the gas jet outlet) and used to generate the HHG radiation (source radiation) 810. The aperture or spatial filter 815 shields the pump radiation while accepting the source radiation 810. The focusing mirror 820 includes a grating 822 that operates to split the source radiation 810 into measurement radiation 825 (for example, the specularly reflected radiation or the 0th order radiation of the scattered radiation scattered by the grating 822) and (dispersed) reference radiation 855 (for example, one or both of the 1st order diffractions of the scattered radiation scattered by the grating 822).

[0096]

[0086] In one embodiment, the line source radiation 810 includes radiation having a wavelength in the range of 10 nm to 20 nm. In one embodiment, the line source radiation 810 includes radiation having a wavelength in the range of 8 nm to 18 nm.

[0097]

[0087] The measurement radiation 825 is used to measure the target 830 (e.g., in certain optional measurement methods, the target may be in an underfill state, i.e., the measurement spot is smaller than the target). The first scattered radiation 870 (e.g., higher order or first order scattered radiation) can be detected by one or more measurement detectors 875 (e.g., via an optical system not shown). In addition, the second scattered radiation 835 from the target (e.g., more specifically, zero order or specularly reflected radiation) can be captured (e.g., via an optical system not shown). This scattered radiation 835 can then be dispersed by a dispersive element 840 (e.g., a grating) and then detected at another measurement detector 850.

[0098]

[0088] The dispersed reference radiation 855 can be detected by a reference detector 860 via a beam steering optical system such as a mirror 865, for example. A processor (not shown) can be used to determine the value of a parameter of the object from the first scattered radiation 870 and / or the dispersed scattered radiation 845 with reference to the dispersed reference radiation 855 (as captured at the reference detector 860) (e.g., knowledge regarding the spectral characteristics of the illumination before being scattered by the target may be required when determining the parameter of the object from the pattern detected on the detector 875 and / or detector 850). Also, the dispersed reference radiation 855 can be used to monitor the illumination source, for example, to monitor the stability of the illumination and / or to monitor the spectral characteristics of the illumination.

[0099] Optionally, there is one or more automatic feedback control loops for controlling the operation of the radiation source configuration based at least in part on signals detected by reference detector 860 and / or one or more measurement detectors 850, 875. Optionally, a compensation optical device is disposed in front of the HHG generation point 805 for wavefront correction of the pump radiation 800. The compensation optical device can be a programmable spatial light modulator (SLM) and / or a deformable mirror.

[0100]

[0090] The configuration shown in FIG. 8 has many problems. Using grating 822 as a beam splitter causes further scattering within the specular reflection beam. This makes it even more difficult to underfill small targets. Also, within the wavelength range typically emitted by such illumination sources (e.g., 10 - 20 nm), gratings typically generate higher orders than first order, resulting in energy loss. Consequently, the transmittance to the wafer decreases, thereby reducing throughput. When designing the illumination optics, there are certain conditions regarding specific limits to be met due to the use of the aforementioned short wavelengths. These conditions regarding limits can include, for example, minimizing the number of reflective surfaces as much as possible, keeping the grazing incidence angle as far from the normal as possible, providing a very smooth surface, placing the reflective surface as close as possible to the target, minimizing the distance between the source generation point and the target, and not making the local radius of curvature of the surface too small. Including a grating in the design makes this even more complex, resulting in compromises in focusing to the target, the transmittance of the illuminator, the size of the optical path, and the reduction ratio of the illuminator. In addition, manufacturing such a grating mirror is very difficult. Placing a high - end grating on a high - end mirror is high - risk and complex in terms of procurement.

[0101]

[0091] In this specification, a metrology apparatus for measuring a structure on a substrate is disclosed, the structure being optionally patterned on the substrate in a lithography process, the metrology apparatus comprising an illumination branch for directing measurement radiation onto the structure on the substrate, a measurement detector for detecting the measurement radiation after being scattered by the structure, a pellicle beam splitter in the illumination branch, the pellicle beam splitter including a pellicle film operable to split the source radiation from an illumination source into measurement radiation for measuring the structure and reference radiation, and a reference detector for detecting the reference radiation.

[0102]

[0092] This concept can also be used for EUV pellicle membranes by keeping such particles out of the focus of the lithography tool so as not to image them in order to protect the EUV reticle from contaminating particles. These pellicles are designed to have a low reflectivity / high transmittance (among other requirements).

[0103]

[0093] In one embodiment, it is proposed that the pellicle film used in the concept disclosed herein is specially designed for beam splitting applications. Thus, the pellicle film can be specially designed to separate a very small portion of the measurement radiation beam (e.g., SXR). In one embodiment, the transmittance can be maximized with a separation ratio to the reference branch that is less than 3%, less than 2%, less than 1.5%, less than 1.2% of the total energy of the incident beam. In combination with any of these upper percentage limits, the separation ratio to the reference branch can include more than 0.1%, more than 0.5%, more than 0.6%, more than 0.7%, more than 0.8% or more than 0.9%. Thus, in a particular embodiment, the separation ratio to the reference branch can be 0.5% - 1.5% or 0.2% - 1.2% (e.g., about 1%).

[0104]

[0094] Preferably, the spectral signature should be as low as possible (e.g., there should be a flat response over the relevant wavelength range). For example, the transmittance and / or reflectivity of the pellicle film can vary by less than 35%, less than 30%, less than 25%, less than 20%, less than 15% or less than 10% over a wavelength range of 10 nm to 20 nm or over a wavelength range of 5 nm to 30 nm.

[0105]

[0095] The pellicle beam splitter can be used in combination with a dispersive element (e.g., a reference grating) for spectrally dispersing the split beam before detection by a reference detector.

[0106]

[0096] In one embodiment, the pellicle film can include three or more layers. For example, it can include at least one outer layer on each side of at least one inner layer, and the at least one outer layer can be the same or different, and / or optionally, the at least one outer layer can have the same or different thicknesses, and / or optionally, the at least one outer layer can include the same or different materials. In one embodiment, the pellicle film can include two layers, and the two layers can be the same or different, and / or optionally the two layers can have the same or different thicknesses, and / or optionally the two layers can include the same or different materials.

[0107]

[0097] In one embodiment, one or more outer layers on each side of the inner layer can include and / or can consist of one or more oxides. Such oxides can be, for example, silicon oxide (e.g., SiO 2 ), aluminum oxide (e.g., Al 2 O 3 ), zirconium oxide (e.g., ZrO 2 ), or yttrium oxide (e.g., YO 2 or Y 2 O 3It may include one or more of (). The oxide layer can function as a protective layer for the inner layer, for example, to provide mechanical, thermal, and chemical stability. Further, this layer can function within the film to obtain desired reflection characteristics as a function of wavelength.

[0108]

[0098] In one embodiment, the outer layer can be made as thin as possible while ensuring a closed layer. Optionally, the thickness of at least one outer layer on one side (or each side) of at least one inner layer can be less than 4 nm or less than 3 nm, for example, with a thickness of 1 nm to 3 nm, 1.5 nm to 2.5 nm, 1.7 nm to 2.3 nm, 1.8 nm to 2.2 nm, or 1.9 nm to 2.1 nm (e.g., about 2 nm).

[0109]

[0099] The reason the outer layer should not be made too thick is that the transmittance of the oxide decreases, especially at long wavelengths. Further, the (thickness of the) outer layer affects the reflectivity. When the oxide layer is thick, the variation in reflectivity over the wavelength increases. Its core function is a capping layer for chemical stability, so the layer needs to be completely closed. If the layer becomes too thin, islands are formed and the layer cannot be closed. This limit is about 1 to 1.5 nm depending on the material.

[0110]

[0100] At least one inner layer can include a silicon or silicon compound layer (e.g., pure silicon Si, silicon carbide SiC, silicon dicarbide SiC 2 , silicon nitride SiN, zirconium silicide ZrSi), and / or a boron layer (e.g., pure boron B) or a boron compound layer (e.g., boron carbide B 4 C, zirconium diboride ZrB 2 , boron nitride BN), and / or one or more of zirconium, beryllium, niobium, yttrium, molybdenum, carbon, and / or their respective compounds or mixtures of these materials. B 4 Both BC and BN have high mechanical strength and relatively good transmittance over the entire spectrum of 8 nm to 18 nm. B 4C is preferred over BN because it has high strength and high transmittance.

[0111]

[0101] When manufacturing a metal into a thin film, internal stress may occur, and its use for a pellicle film is not preferred. This solution is, for example, doping a metal material such as zirconium, beryllium, niobium, yttrium, molybdenum, etc. to reduce internal stress. In one embodiment, at least one inner layer may include a metal doped with one or more of the elements Si, B, C, and / or N.

[0112]

[0102] In addition to the silicon and / or boron-based materials mentioned above, at least one inner layer may include one or more zirconium-based materials, optionally including zirconium and / or zirconium compounds. Zirconium-based materials may have excellent optical performance.

[0113]

[0103] In one embodiment, the pellicle beam splitter is based on one or more silicon-based materials, optionally silicon or silicon compounds. Silicon-based materials are easy to manufacture and have a high transmittance for radiation with a wavelength of 13.5. However, for the source radiation 810 that optionally includes radiation with a wavelength in the range of 8 nm to 18 nm, the transmittance of the silicon-based material for radiation with a wavelength below 13 nm is sufficient. One solution is to manufacture the pellicle film thin, but this is not preferred because it makes the film fragile. The second solution is to reduce the silicon content in the silicon-based material to improve the transmittance. In one embodiment, at least one inner layer includes silicon nitride instead of silicon. In another embodiment, at least one inner layer includes silicon carbide instead of silicon (note that the elements Si and C can have any chemical ratio formulated as Si x C y ). Both silicon nitride and silicon carbide have a higher transmittance than silicon for broadband radiation (e.g., radiation with a wavelength of 8 nm to 18 nm) optionally generated by HHG.

[0114]

[0104] In one embodiment, one or more outer layers are optional.

[0115]

[0105] In one embodiment, one or more outer layers contain ruthenium because ruthenium has better damage resistance. In one embodiment, the front surface side (the side facing the incident radiation) of the inner layer is capped with ruthenium, and the back surface side of the inner layer is capped with one or more outer layers as mentioned above.

[0116]

[0106] In one embodiment, the front surface side of the inner layer is capped with an outer layer different from the back surface side of the inner layer. In one embodiment, only the front surface side of the inner layer is capped with an outer layer, and the back surface side of the inner layer is not capped. In one embodiment, only the back surface side of the inner layer is capped with an outer layer, and the front surface side of the inner layer is not capped.

[0117]

[0107] The inner layer can be made as thin as possible from the viewpoints of manufacturability and tensile stress. In one embodiment, the total inner layer thickness can be less than 20 nm, less than 15 nm, less than 10 nm, or less than 6 nm. In combination with any of these lower thickness limits, the total inner layer thickness can be greater than 1 nm, greater than 2 nm, greater than 4 nm, greater than 6 nm, greater than 8 nm, greater than 10 nm, or greater than 11 nm.

[0118]

[0108] The minimum inner layer thickness depends on the size of the pellicle film. For a large pellicle, for example, in the case of a pellicle used in a lithography apparatus using EUV radiation, since the beam size is large, for example, larger than 100 cm 2 or larger than 120 cm 2 and the reticle used is large, the pellicle film and the inner layer must be, for example, thicker than 10 nm. However, in the SXR metrology apparatus mentioned above, the beam size of the source radiation 810 is much smaller than 100 cm 2 and is, for example, less than 10 mm 2 or less than 1 mm 2It can be at this level. Therefore, together with a thinner pellicle film and / or a thinner inner layer, a smaller pellicle (e.g., less than 10 mm 2 or 1 mm 2 in size) can be used. In one embodiment, the total inner layer thickness can be less than 6 nm. In one embodiment, the total inner layer thickness can be from 1 nm to 6 nm.

[0119]

[0109] Since the thickness of the inner layer is optimized for transmittance, it is empirically better to be thinner. In addition, for mechanical stability, the overall stack should not be too thin so that the limit becomes low. Therefore, the more layers there are, the thinner each individual layer will be, but to prevent island formation, the minimum layer thickness should still be about 1 - 2 nm.

[0120]

[0110] To make the device compact, there is a volume limitation due to the narrow space inside the device. Therefore, the beam splitter can be arranged at an oblique incident angle with respect to the source radiation. Furthermore, since the reflectivity of the beam splitter is also affected by the incident angle, it is necessary to carefully select the incident angle of the source radiation to the beam splitter. In one embodiment, the incident angle of the source radiation beam to the beam splitter (pellicle film) can be 30 - 70 degrees, 30 - 60 degrees, 30 - 50 degrees, 40 - 50 degrees, or more specifically about 45 degrees.

[0121]

[0111] One drawback of using an incident angle of 45 degrees is that it may not function when polarization switching of the source radiation is required (e.g., at 45 degrees, p-polarization does not actually reflect. In one embodiment, the incident angle of the source radiation beam to the beam splitter (pellicle film) can be 20 degrees to 44 degrees, 30 degrees to 44 degrees, 35 degrees to 44 degrees, or 40 degrees to 44 degrees. In one embodiment, the incident angle of the source radiation beam to the beam splitter (pellicle film) can be 46 degrees to 70 degrees, 46 degrees to 60 degrees, 46 degrees to 55 degrees, or 46 degrees to 50 degrees. In one embodiment, the incident angle of the source radiation beam to the beam splitter (pellicle film) can be 50 degrees to 70 degrees, 55 degrees to 65 degrees, 57 degrees to 63 degrees, 59 degrees to 61 degrees, or about 60 degrees. Such incident angles can result in optimal reflection / transmission. In essentially all materials, total external reflection causes a dramatic increase in reflection at angles exceeding 70 degrees. At the same time, at angles close to normal incidence, the reflection becomes very small (orders of magnitude). The optimizer balances reflection and transmission. If the angle is too small (e.g., less than 30 degrees), the reflected light (e.g., the reference radiation 910 in FIG. 9) does not have sufficient intensity, and a material with a higher reflectivity may be required.

[0122]

[0112] FIG. 9 is a schematic diagram of a metrology apparatus according to an embodiment. Components and elements of the metrology apparatus that are common to the metrology apparatus shown in FIG. 8 will not be described again. Here, a pellicle beam splitter 900 is used instead of a grating, and this beam splitter 900 splits the source radiation 810 into measurement radiation 825 and reference radiation 910. The reference radiation 910 is dispersed using a dispersive element 915, and spectrally dispersed reference radiation 920 is obtained. Then, this spectrally dispersed reference radiation 920 can be detected using a reference detector 860. The dispersive element 915 can be a grating. The dispersive element 915 can be, for example, a reflective dispersive element such as a reflective grating. The dispersive element 915 can be, for example, a transmissive dispersive element such as a transmissive grating. Advantages of the transmissive dispersive element include not being troubled by contamination deposition such as carbon deposition optionally, not requiring extremely smooth polishing that is difficult to manufacture, being relatively easy to manufacture, typically being less expensive than a reflective dispersive element, and being easy to calibrate.

[0123]

[0113] In one embodiment, as shown in FIG. 9, the pellicle beam splitter 900 can be disposed upstream of the focusing mirror 820. When the dispersive element 915 is a transmissive dispersive element (for example, a transmissive grating), the reference radiation 910 is not focused. Therefore, in one embodiment, the pellicle beam splitter 900 can be disposed downstream of the focusing mirror 820, which is preferable because the reference radiation 910 is focused. In one embodiment, the pellicle beam splitter 900 can be disposed immediately before the target 830 without an optical element therebetween and the target 830. Further advantages of disposing the pellicle beam splitter 900 downstream of the focusing mirror 820 include calibrating the reference branch with the radiation after the focusing mirror 820 and providing more information about the measurement radiation 825 at the wafer level, and the design tolerances being more relaxed, for example, the pellicle beam splitter 900 can be designed to be switchable (i.e., the pellicle beam splitter 900 can be optionally detached during operation) without strongly affecting the measurement radiation 825.

[0124]

[0114] Also, a pellicle beam splitter including a pellicle film, wherein the pellicle film includes three or more layers, the three or more layers include at least one inner layer and at least one outer layer on any surface of the at least one inner layer, and the at least one inner layer includes a silicon or silicon compound layer, and / or a boron layer (e.g., pure boron B) or a boron compound layer (e.g., B 4 C, ZrB 2 , BN), and / or one or more of zirconium, beryllium, niobium, yttrium, molybdenum and / or carbon layers, and / or one or more compounds of each of these materials are also disclosed. The outer layer may include one or more oxides and / or may be composed of one or more oxides. Such oxides may include, for example, silicon oxide (e.g., SiO 2 ), aluminum oxide (e.g., Al 2 O 3 ), zirconium oxide (e.g., ZrO 2 ), or yttrium oxide (e.g., YO 2 or Y 2 O 3 ). The pellicle film may include any of the thicknesses / dimensions disclosed above. For example, the advantages of boron or boron compounds, yttrium or yttrium compounds, and / or carbon or carbon compounds, among others, are that they have good transmittance in the full wavelength range of 10 to 20 nm (Si has a silicon edge).

[0125]

[0115] Also, a pellicle beam splitter including a pellicle film, wherein the pellicle film includes three or more layers, the three or more layers include at least one inner layer and at least one outer layer on any surface of the at least one inner layer, and the at least one inner layer includes a boron layer (e.g., pure boron B), a boron compound layer (e.g., B 4 C, ZrB 2, BN), a silicon layer, zirconium, beryllium, niobium, yttrium, molybdenum and / or carbon, and / or one or more compounds of each of these materials, and the total thickness of at least one outer layer on one side (or each side) of at least one inner layer is 1 nm to 3 nm (for example, 1.5 nm to 2.5 nm, 1.7 nm to 2.3 nm, 1.8 nm to 2.2 nm or 1.9 nm to 2.1 nm), and the total thickness of the inner layer is less than 20 nm (for example, less than 15 nm, less than 13 nm, or 12 nm or less, and optionally more than 6 nm, more than 8 nm, more than 10 nm or more than 11 nm), a pellicle beam splitter is also disclosed.

[0126]

[0116] The above-described pellicle film design has a transmittance of 70% to 80% and a reflectance of 1% to 2%, and can provide a film having a very flat response over a target wavelength range (for example, 10 nm to 20 nm). In contrast, commercially available EUV beam splitters typically have very poor (not flat) spectral behavior and low transmittance. On the other hand, when using a grating beam splitter as shown in FIG. 8, the transmittance (and thus the throughput) is expected to be 5 times larger and the manufacturing cost is substantially reduced.

[0127]

[0117] In all cases and / or embodiments, the total thickness of the pellicle film can be less than 20 nm or less than 15 nm.

[0128]

[0118] In the above description, a pellicle film for use as a beam splitter has been described, but the disclosed concepts and films can also be used for other applications such as attenuation (for example, to attenuate a high-intensity full beam on a camera during source beam profile monitoring), filtering (for example, to filter infrared-driven radiation such as the filtering device 344 in FIG. 5 or the spatial filter 815 in FIG. 9). When used as an attenuation filter, for example, the pellicle film may be thicker than the thickness described in the context of beam splitting, for example, thicker than 15 nm, thicker than 20 nm (for example, up to 1.5 μm).

[0129]

[0119] Here, additional embodiments will be described mainly in the context of attenuation filtering or drive radiation / infrared filtering (e.g., as the filtering device 344 in FIG. 5 or the spatial filter 815 in FIG. 9). However, the pellicle films of these additional embodiments can also be used within the context of beam splitting (e.g., as the beam splitter 900 in FIG. 9). The films of all embodiments disclosed herein can be used in any situation where it is desirable to have a flat spectral transmission and / or reflection profile for the wavelength range of interest (e.g., SXR wavelengths).

[0130]

[0120] The drive laser filter is currently being implemented using materials with the highest ratio of SXR transmittance to IR rejection rate. These filters rely on the transmission characteristics of the materials. Currently, these filters can include, for example, thin films of zirconium or aluminum.

[0131]

[0121] Typically, the structures being measured have low diffraction efficiency. In addition to measuring the diffraction signals from such structures (in one or more diffraction signal detectors), the source beam profile can be periodically monitored, for example, in a dedicated detector. Optionally, the dedicated detector is configured to receive the SXR illumination beam for source calibration before the beam is used to measure the structure (i.e., upstream of the wafer stage). Since this beam is measured just before a structure with low diffraction efficiency, the intensity can be very high.

[0132]

[0122] Currently, an attenuation filter can be used to attenuate this high intensity and prevent the integration time at the detector from becoming very short. Currently, this attenuation can be achieved using a thick (e.g., having a thickness of 2 μm or more) zirconium filter. Zirconium has the advantage of having optimal transmission characteristics at large thicknesses. When using other materials, filters with optimal transmittance may be too thin to be difficult to manufacture / handle.

[0133]

[0123] As an example, the calibration of the metrology tool may include performing an alignment of the optical system. This optical alignment can be performed by placing one or more detectors (e.g., cameras) at the focus of the main beam (SXR beam). In such cases, the measurement intensity can be very high. When performing the alignment of the SXR optical system in this way, currently, typically, attenuation is performed using a zirconium filter.

[0134]

[0124] Neutral density filters with wavelengths down to 120 nm are commercially available, but there are no suitable commercially available examples at the SXR wavelength. Attenuation at the SXR wavelength using a thick zirconium filter changes the SXR spectrum (i.e., does not function as a neutral filter over the target wavelength range). This is a problem because what is required by the measurement is the "true" source profile. Therefore, when using a zirconium filter, monitoring of the source beam profile will be based on incorrect spectral components. The beam profile is known to be wavelength-dependent. This also applies to the focused SXR beam.

[0135]

[0125] Without attenuating the SXR beam, the integration time at the detector can be a few milliseconds, or even less than 1 millisecond. This is shorter than the minimum time the shutter can be opened and faster than most high-speed detectors. In addition, the radiation source output may increase significantly in the future, and without attenuation, it can result in an impossibly long integration time.

[0136]

[0126] FIG. 10(a) is a plot 1000 of the transmittance Trn versus the wavelength λ of a zirconium filter (e.g., 1.2 μm in this example). At this thickness, the long-wavelength side of the SXR range is strongly attenuated. In the case of higher radiation source output and / or in-focus beam measurement, a thicker filter is naturally required, so this situation is further aggravated.

[0137]

[0127] As the output of the radiation source increases, a thicker filter is required to achieve the necessary attenuation, and the spectrum changes even more strongly. For example, when using a thick zirconium filter, only the short-wavelength side of the SXR spectrum remains. Another commonly used material, aluminum, attenuates the short-wavelength side and only passes through the long-wavelength side.

[0138]

[0128] To address this, a specific combination of filter materials having a substantially or approximately spectrally flat response over a target wavelength range (e.g., 10 - 20 nm) will be described. In the embodiments described herein, a filter film or pellicle film including two or more different materials is used, and at least one of the materials is germanium (Ge) or selenium (Se).

[0139]

[0129] Most materials, like the zirconium example shown in FIG. 10(a), have a higher transmittance on the short-wavelength side in the region of 10 - 20 nm. There are very few materials that exhibit qualitatively different behavior. Germanium and selenium are two examples where the transmittance increases with increasing wavelength. Aluminum has an absorption edge that can approximate this behavior, but as a result, the spectral variation becomes large and it is not ideal.

[0140]

[0130] FIG. 10(b) shows a plot equivalent to the spectral response plot of FIG. 10(a) for germanium, and FIG. 10(c) shows an equivalent spectral response for selenium, both of which exhibit this desirable behavior.

[0141]

[0131] Therefore, it is proposed to construct a filter including a layer of one (or both) of germanium and selenium and one or more additional layers of one or more other materials to obtain a filter film having a substantially flat spectral profile over the target spectral range. By using Ge or Se in combination with other materials, many combinations with the required spectral characteristics can be made.

[0142]

[0132] Further, these layers can be partially or fully mixed or combined. This would require a more specialized manufacturing setup, but presumably the same performance could be achieved. In such an approach, a filter having only a single layer is completed.

[0143]

[0133] Specific examples can include, for example, germanium and zirconium, boron and germanium and zirconium, carbon and germanium and zirconium, or selenium and copper.

[0144]

[0134] FIG. 11 is a plot of the spectral response (transmittance Trn versus wavelength λ) of each of these specific examples over a wavelength range of 10 - 20 nm. Specifically, the plot relates to germanium and zirconium filter 1110, selenium and copper filter 1120, and boron, germanium and zirconium filter 1130. For comparison, the spectral response 1100 of a zirconium and aluminum filter is also shown, which has a variation of ±50% over most of its bandwidth and a transmittance that drops to zero at 20 nm. In contrast, the other three filters have a much flatter response over the range shown. As can be seen from the figure, for example, the combination 1130 of the three materials boron, germanium and zirconium has a flat transmittance within ±5% over the range of 10 - 20 nm.

[0145]

[0135] The use of two separate filters (e.g., one Zr filter and one Al filter) also functions as an alternative, but the single composite filter as disclosed herein has the following advantages. The composite filter is thicker, mechanically stronger, and can be produced at a lower cost because the manufacturing procedure is simpler. For example, the release process of transferring the film on the substrate to a free-standing film only needs to be done once.

[0146]

[0136] The combination of materials can also be implemented as a continuous discrete filter. However, a thicker filter is mechanically stronger and can withstand a higher thermal load.

[0147]

[0137] The proposed filter film may include a transmittance characteristic such that the transmittance variation is less than 50%, less than 40%, less than 30%, less than 20%, less than 10% or less than 5% over a wavelength range of 10 nm to 20 nm.

[0148]

[0138] In each combination of filters containing germanium, the germanium layer can be, for example, 30 nm to 450 nm, 50 nm to 450 nm, 50 nm to 300 nm, 100 nm to 300 nm, 120 nm to 270 nm or 135 nm to 150 nm, and the total thickness can be, for example, 100 nm to 700 nm, 100 nm to 500 nm, 100 nm to 400 nm, 150 nm to 400 nm, 200 nm to 400 nm, 300 nm to 400 nm, 230 nm to 270 nm.

[0149]

[0139] In each combination of filters containing selenium, the selenium layer can be, for example, 30 nm to 600 nm, 30 nm to 500 nm, 30 nm to 400 nm, 30 nm to 300 nm, 30 nm to 200 nm, 30 nm to 100 nm, 30 nm to 70 nm or 40 nm to 60 nm, and the total thickness can be, for example, 50 nm to 1.5 μm, 50 nm to 1 μm, 50 nm to 800 nm, 50 nm to 500 nm, 50 nm to 300 nm, 50 nm to 200 nm or 50 nm to 150 nm.

[0150]

[0140] It should be understood that references to the first layer, second layer, etc. or the first material, second material, etc. in the following clauses and claims are for the sole purpose of distinction and do not imply any particular order of the layers or materials in any way.

[0151]

[0141] In the embodiments of the filter film mentioned above, for beam splitting, instead of a thick layer, a thin layer of the same material can also be used. The thickness of the thin layer may be the same as the thickness of the layer of the pellicle film mentioned above.

[0152]

[0142] In the embodiment of the pellicle film mentioned above, for filtering, instead of a thin layer, a thick layer can also be used. The thickness of the thick layer may also be the same as the thickness of the layer of the filter film mentioned above.

[0153]

[0143] The embodiments mentioned above can also be used, for example, as the filtering device 344 of FIG. 5 as an IR blocker and an SXR transmitter, and as the spatial filter 815 of FIG. 9 having a pinhole.

[0154]

[0144] The films mentioned above may be damaged during operation. Such damage can be mitigated by periodically moving the film to find a new undamaged area or by replacing the film. In the following embodiments, the filtering device 344 of FIG. 5 is taken as an example, but the embodiments can be implemented not only for all the films, filters, and films mentioned above, but also for mirrors and lenses.

[0155]

[0145] The filtering device 344 of FIG. 5 may generally include a metal transmission film disposed normal to the beam path. Optionally, the metal transmission film may be a Zr filter with a thickness of 300 nm to 500 nm including a Zr film. The Zr filter may be required even though there are other filter elements upstream in the optical path, because due to scattering and imperfect alignment, some IR light always leaks (referred to as leaky IR). The irradiation area due to the leaky IR of the Zr filter may be damaged after continuous use for a long time, optionally by a high-temperature irradiation area and / or deposition of a material (e.g., carbon). Damage and / or contamination can be detected by measuring the same and / or different radiation reflected by the irradiation area. The leaky IR is mentioned as an example for illustrative purposes only, but it should be noted that in embodiments, it is applicable to any film, surface, and / or interface irradiated by any type of radiation. Here, optionally, a method for detecting damage and / or contamination on the irradiation area caused by a first radiation (e.g., leaky IR) is reported. This method includes irradiating the irradiation area of the film with the first radiation and simultaneously irradiating the irradiation area of the film with a second radiation (e.g., a probe beam). The second radiation is reflected by the irradiation area to generate reflected radiation, and this reflected radiation is detected to obtain a signal. Based on this signal, damage and / or contamination information regarding the irradiation area can be obtained.

[0156]

[0146] In one embodiment, a laser, which is an example of a second radiation, is used to monitor the integrity of the Zr filter. The laser can be a part of an IR-driven laser beam that passes through the mirror as a probe beam. Due to the imperfection of the mirror and / or the pinholes on the mirror, a very small part of the IR light can pass through the mirror. A very small part of the IR light as the probe beam can be reflected by the Zr filter in the same irradiation area as the area where the leaked IR hits the Zr filter. The intensity of the probe beam reflected by the Zr filter can be measured by a probe detector (optionally a photodiode). The intensity of the light measured by the photodiode is expected to be kept constant over time if the Zr filter does not deteriorate. When the Zr filter is damaged over time, the signal measured by the photodiode changes. It has also been observed that the deposition of materials (e.g., carbon) accumulated on the Zr filter surface affects the transmittance of the SXR. The accumulated carbon can also be monitored by this method. When the quality degradation of the Zr filter is detected, the Zr filter can be moved so that the SXR beam passes through a new area that is not damaged.

[0157]

[0147] Real-time temporal feedback on the Zr filter quality can be useful for maintaining the quality of the transmitted SXR beam and ensuring sufficient leakage IR suppression. Also, this method can prevent unnecessary replacement of the Zr filter. This method can reduce the number of Zr filters required over time. Also, this method can provide information about the contamination on the Zr filter. Hydrocarbon contaminants may deposit on the surface of the Zr filter irradiated with the laser pulse. This method can detect the presence of contaminants because the reflectivity of the probe beam changes. By changing the position of the Zr filter, there is a possibility that the SXR hits a new area without contaminants. Since the intensity of the probe beam is much weaker than the intensity of the leaked IR, it is expected that the probe beam will not affect the Zr filter.

[0158]

[0148] In practice, the photodiode may be saturated by IR light scattered from various optical components within the system. Therefore, accurate measurement of the probe beam signal may be difficult. Optionally, it has been proposed to monitor the polarization of the probe beam using a half-wave plate and to filter the scattered IR light using a polarizer in front of the photodiode.

[0159]

[0149] Optionally, instead of a single photodiode, a pair of balanced detectors is used as the probe detector. The probe beam is split into two beams by a beam splitter before being reflected by the Zr filter. One of the two beams is the reference probe beam and is measured by the first detector of the pair of balanced detectors. The second detector of the pair of balanced detectors measures the other of the two beams, which is the probe beam after reflection by the Zr filter. When the Zr filter is not damaged and / or contaminated, the signals on the two detectors are balanced and the difference signal is measured, which should be adjusted to zero. When the Zr filter is damaged or contaminated, the difference signal can change.

[0160]

[0150] Optionally, the probe beam referred to in the above embodiments can be transmitted from a separate laser. The advantage is that the wavelength of the laser can be selected so that it can be filtered using a color filter in the detector. Therefore, any scattered IR light is removed. The separate laser is inexpensive and the complexity is also reduced in this embodiment.

[0161] Optionally, the intensity of the probe beam can be measured in pulse units. The above embodiments may include, for example, a high-speed detector such as a high-speed photodiode. The intensity of each pulse after reflection from the Zr filter can be measured. Optionally, there is a delay between the leaked IR pulse and the probe beam pulse hitting the Zr filter. By carefully selecting the delay, the time response of the Zr filter from the leaked IR can be measured. Before the metal surface is damaged by the accumulation of laser pulses, a short-term change in the refractive index, which is a precursor to damage, can be observed. Also, various other phenomena caused by different mechanisms, such as long-term electron excitation and changes in phonon binding rates, can be observed. Time-resolved measurements can provide evidence of these phenomena. Time-resolved measurements function as an early indicator of damage to the Zr filter and can provide information about possible damage to the Zr filter even before it is damaged.

[0162] Optionally, the Zr filter is positioned at an oblique angle with respect to the SXR optical path, the reflected leaked IR is measured, and the quality of the Zr filter is directly monitored. The incident angle of the source radiation beam on the Zr filter can be 50 degrees to 70 degrees, 55 degrees to 65 degrees, 57 degrees to 63 degrees, 59 degrees to 61 degrees, or more specifically about 60 degrees. Such an incident angle can provide optimal reflection / transmission. The range of the incident angle balances reflection and transmission. One advantage of setting the Zr filter at an angle of 50 degrees to 70 degrees is that IR suppression is more excellent.

[0163] The above-mentioned embodiments provide a tool for monitoring the quality of the Zr filter, changing the position of the Zr filter when the Zr filter is damaged and / or contaminated / before the Zr filter is damaged and / or contaminated, detecting the presence of damage and / or contamination on the Zr filter, which is useful for maintaining a certain SXR transmittance and IR suppression, and reducing the amount of Zr filter required by monitoring the quality of the Zr filter in real time.

[0164] The above-mentioned embodiments for detecting damage and / or contamination of an irradiation area caused by radiation are also applicable to the film elements, surfaces and interfaces of a lithographic apparatus using extreme ultraviolet (EUV) radiation.

[0165]

[0155] The illumination source can be provided, for example, in a metrology apparatus MT, an inspection apparatus, a lithographic apparatus LA and / or a lithography cell LC.

[0166]

[0156] The characteristics of the emitted radiation used to perform the measurement can affect the quality of the resulting measurement. For example, the shape and size of the lateral beam profile (cross-section) of the radiation beam, the intensity of the radiation, the power spectral density of the radiation, etc. can affect the measurement performed by the radiation. Therefore, it is beneficial to have a radiation source that provides radiation with characteristics that result in high-quality measurements.

[0167]

[0157] Further embodiments are disclosed in the clauses (clause set 1) numbered subsequently. 1. An illumination branch including an illumination optical system for structurally guiding measurement radiation, A pellicle beam splitter within the illumination branch, the pellicle beam splitter including a pellicle film operable to split the source radiation beam from the illumination source into a reference radiation beam and measurement radiation, A measurement detector for detecting the measurement radiation after being scattered by the structure, A reference detector for detecting the reference radiation beam And a metrology apparatus comprising. 2. The metrology apparatus according to clause 1, wherein the reference radiation beam contains less than 3% of the total energy of the source radiation beam. 3. The metrology apparatus according to clause 1, wherein the reference radiation beam contains less than 1.5% of the total energy of the source radiation beam. 4. The metrology apparatus according to any one of clauses 1 to 3, wherein the reference radiation beam contains more than 0.1% of the total energy of the source radiation beam. 5. The metrology device according to any one of clauses 1 to 3, wherein the reference radiation beam includes more than 0.8% of the total energy of the source radiation beam. 6. The metrology device according to any one of the preceding clauses, wherein the transmittance and / or reflectance of the pellicle film changes by less than 25% over a wavelength range of 10 nm to 20 nm. 7. The metrology device according to any one of the preceding clauses, wherein the transmittance and / or reflectance of the pellicle film changes by less than 20% over a wavelength range of 10 nm to 20 nm. 8. The metrology device according to any one of the preceding clauses, comprising a dispersive element operable to spectrally disperse the reference radiation beam between the pellicle beam splitter and the reference detector. 9. The metrology device according to any one of the preceding clauses, wherein the pellicle film includes three or more layers, and the three or more layers include at least one outer layer on each side of at least one inner layer. 10. The metrology device according to clause 9, wherein at least one outer layer includes an oxide material. 11. The metrology device according to clause 10, wherein the oxide material includes one or more of silicon oxide, aluminum oxide, zirconium oxide, or yttrium oxide. 12. The metrology device according to any one of clauses 9 to 11, wherein the thickness of at least one outer layer on each side of at least one inner layer is less than 4 nm. 13. The metrology device according to any one of clauses 9 to 11, wherein the thickness of at least one outer layer on each side of at least one inner layer is less than 3 nm. 14. The metrology device according to any one of clauses 9 to 11, wherein the thickness of at least one outer layer on each side of at least one inner layer is less than 2.5 nm. 15. The metrology device according to any one of clauses 9 to 14, wherein the thickness of at least one outer layer on each side of at least one inner layer exceeds 1 nm. 16. The metrology device according to any one of clauses 9 to 14, wherein the thickness of at least one outer layer on each side of at least one inner layer exceeds 1.5 nm. 17. The metrology device according to any one of clauses 9 to 16, wherein at least one inner layer includes a silicon layer. 18. The metrology device according to any one of clauses 9 to 17, wherein at least one inner layer includes one or more of silicon, boron, zirconium, beryllium, niobium, yttrium, molybdenum, carbon, and / or one or more compounds of each of these materials, and / or consists of them. 19. The metrology device according to any one of clauses 9 to 18, wherein at least one inner layer has a thickness of less than 20 nm. 20. The metrology device according to any one of clauses 9 to 18, wherein at least one inner layer has a thickness of less than 15 nm. 21. The metrology device according to any one of clauses 9 to 18, wherein at least one inner layer has a thickness of less than 6 nm. 22. The metrology device according to any one of clauses 9 to 21, wherein at least one inner layer has a thickness greater than 1 nm. 23. The metrology device according to any one of clauses 9 to 21, wherein at least one inner layer has a thickness greater than 4 nm. 24. The metrology device according to any one of the preceding clauses, wherein the line source radiation beam includes wavelengths in the range of 5 nm to 30 nm. 25. The metrology device according to any one of clauses 1 to 23, wherein the line source radiation beam includes wavelengths in the range of 10 nm to 20 nm. 26. The metrology device according to any one of the preceding clauses, wherein the incident angle of the line source radiation beam on the pellicle film is 45 degrees to 70 degrees. 27. The metrology device according to any one of the preceding clauses, wherein the incident angle of the line source radiation beam on the pellicle film is 55 degrees to 65 degrees. 28. The metrology device according to any one of the preceding clauses, which is configured to measure a structure on a wafer, wherein the structure is exposed on the wafer in a lithography process. 29. The metrology device according to any one of the preceding clauses, wherein the total thickness of the pellicle film is less than 20 nm. 30. A metrology apparatus according to any one of the preceding clauses, wherein the total thickness of the pellicle film is less than 15 nm. 31. A pellicle film comprising three or more layers, the three or more layers including at least one inner layer and at least one outer layer on at least one surface of the at least one inner layer, the at least one inner layer including one or more of boron, zirconium, beryllium, niobium, yttrium, molybdenum, and / or carbon, and / or one or more compounds of each of these materials, and / or consisting of them. 32. The pellicle film according to clause 31, wherein at least one outer layer includes an oxide material. 33. The pellicle film according to clause 32, wherein the oxide material includes one or more of silicon oxide, aluminum oxide, zirconium oxide, or yttrium oxide. 34. The pellicle film according to any one of clauses 31 to 33, wherein the thickness of at least one outer layer on each surface of the at least one inner layer is less than 4 nm. 35. The pellicle film according to any one of clauses 31 to 33, wherein the thickness of at least one outer layer on each surface of the at least one inner layer is less than 3.5 nm. 36. The pellicle film according to any one of clauses 31 to 33, wherein the thickness of at least one outer layer on each surface of the at least one inner layer is less than 3 nm. 37. The pellicle film according to any one of clauses 31 to 33, wherein the thickness of at least one outer layer on each surface of the at least one inner layer is less than 2.5 nm. 38. The pellicle film according to any one of clauses 31 to 37, wherein the thickness of at least one outer layer on each surface of the at least one inner layer exceeds 1 nm. 39. The pellicle film according to any one of clauses 31 to 37, wherein the thickness of at least one outer layer on each surface of the at least one inner layer exceeds 1.5 nm. 40. The pellicle film according to any one of clauses 31 to 39, wherein at least one inner layer includes a silicon layer. 41. The pellicle film according to any one of clauses 31 to 40, wherein at least one inner layer includes one or more of a boron layer and a boron compound layer. 42. The pellicle film according to any one of clauses 31 to 41, wherein at least one inner layer has a thickness of less than 20 nm. 43. The pellicle film according to any one of clauses 31 to 41, wherein at least one inner layer has a thickness of less than 15 nm. 44. The pellicle film according to any one of clauses 31 to 41, wherein at least one inner layer has a thickness of less than 6 nm. 45. The pellicle film according to any one of clauses 31 to 44, wherein at least one inner layer has a thickness of more than 1 nm. 46. The pellicle film according to any one of clauses 31 to 44, wherein at least one inner layer has a thickness of more than 4 nm. 47. The pellicle film according to any one of clauses 31 to 46, wherein the transmittance and / or reflectance of the pellicle film changes by less than 25% over a wavelength range of 10 nm to 20 nm. 48. The pellicle film according to any one of clauses 31 to 47, wherein the transmittance and / or reflectance of the pellicle film changes by less than 20% over a wavelength range of 10 nm to 20 nm. 49. The pellicle film according to any one of clauses 27 to 48, wherein the total thickness of the pellicle film is less than 20 nm. 50. The pellicle film according to any one of clauses 27 to 48, wherein the total thickness of the pellicle film is less than 15 nm. 51. A pellicle film including three or more layers, the three or more layers including at least one inner layer and at least one outer layer on at least one surface of any of the at least one inner layer, the at least one inner layer including one or more of silicon, boron, zirconium, beryllium, niobium, yttrium, molybdenum, and / or carbon, and / or one or more compounds of each of these materials, and / or consisting of them, A pellicle film wherein the thickness of at least one outer layer on each surface of the at least one inner layer is 1 nm to 3 nm. 52. The pellicle film according to clause 51, wherein the thickness of at least one outer layer on each surface of the at least one inner layer is 1.5 nm to 2.5 nm. 53. The pellicle film according to clause 51, wherein at least one outer layer contains an oxide material. 54. The pellicle film according to clause 53, wherein the oxide material contains one or more of silicon oxide, aluminum oxide, zirconium oxide, or yttrium oxide. 55. The pellicle film according to any one of clauses 51 to 54, wherein the total thickness of the pellicle film is less than 20 nm. 56. The pellicle film according to any one of clauses 51 to 54, wherein the total thickness of the pellicle film is less than 15 nm. 57. The pellicle film according to any one of clauses 51 to 56, wherein at least one inner layer has a thickness of less than 20 nm. 58. The pellicle film according to any one of clauses 51 to 56, wherein at least one inner layer has a thickness of less than 15 nm. 59. The pellicle film according to any one of clauses 51 to 56, wherein at least one inner layer has a thickness of less than 6 nm. 60. The pellicle film according to any one of clauses 51 to 59, wherein at least one inner layer has a thickness greater than 1 nm. 61. The pellicle film according to any one of clauses 51 to 59, wherein at least one inner layer has a thickness greater than 4 nm. 62. The pellicle film according to any one of clauses 51 to 61, wherein the transmittance and / or reflectance of the pellicle film changes by less than 25% over a wavelength range of 10 nm to 20 nm. 63. The pellicle film according to any one of clauses 51 to 62, wherein the transmittance and / or reflectance of the pellicle film changes by less than 20% over a wavelength range of 10 nm to 20 nm. 64. A pellicle beam splitter including the pellicle film according to any one of clauses 31 to 63. 65. An attenuator and / or a drive radiation filter including the pellicle film according to any one of clauses 31 to 63. 66. A filter film including at least two materials, wherein at least a first material of the at least two materials contains or consists of germanium or selenium. 67. The filter film according to clause 66, including a transmittance characteristic such that the transmittance variation is less than 50% over a wavelength range of 10 nm to 20 nm. 68. The filter film according to clause 66, including a transmittance characteristic such that the transmittance variation is less than 30% over a wavelength range of 10 nm to 20 nm. 69. The filter film according to clause 66, including a transmittance characteristic such that the transmittance variation is less than 10% over a wavelength range of 10 nm to 20 nm. 70. The filter film according to any one of clauses 66 to 69, wherein at least two materials are mixed or combined in a single layer. 71. The filter film according to any one of clauses 66 to 69, wherein each of at least two materials is included in a separate layer. 72. The filter film according to any one of clauses 66 to 71, wherein the first material includes and / or consists of germanium, and further includes a second material including and / or consisting of zirconium for at least two materials. 73. The filter film according to clause 72, further including a third material including and / or consisting of boron or carbon for at least two materials. 74. The filter film according to any one of clauses 70 to 73, wherein the first layer of the film including the first material has a thickness of 30 nm to 450 nm. 75. The filter film according to any one of clauses 70 to 73, wherein the first layer of the film including the first material has a thickness of 50 nm to 300 nm. 76. The filter film according to any one of clauses 70 to 75, having an overall thickness of 100 nm to 700 nm. 77. The filter film according to any one of clauses 70 to 75, having an overall thickness of 100 nm to 500 nm. 78. The filter film according to any one of clauses 66 to 71, wherein the first material includes and / or consists of selenium, and further includes a second material including and / or consisting of copper for at least two materials. 79. The filter film according to clause 78, wherein the first layer of the film including the first material has a thickness of 30 nm to 600 nm. 80. The filter film according to clause 78, wherein the first layer of the film containing the first material has a thickness of 30 nm to 400 nm. 81. The filter film according to any one of clauses 78 to 80, wherein the total thickness is 50 nm to 1.5 μm. 82. The filter film according to any one of clauses 78 to 80, wherein the total thickness is 50 nm to 500 nm. 83. A beam splitter, an attenuator and / or a drive radiation filter comprising the filter film according to any one of clauses 66 to 82. 84. A metrology device comprising the beam splitter, the attenuator and / or the drive radiation filter according to clause 83. 85. A method for detecting damage and / or contamination of an irradiation area caused by a first radiation, comprising: irradiating the irradiation area with a second radiation, wherein the irradiation area is also irradiated by the first radiation, the second radiation is reflected by the irradiation area, and reflected radiation is generated; detecting the reflected radiation to obtain a signal; and obtaining damage and / or contamination information regarding the irradiation area based on the signal. 86. The method according to clause 85, wherein the irradiation area is an area of a film. 87. The method according to clause 85 or 86, wherein the first radiation is presumed. 88. The method according to any one of clauses 85 to 87, wherein the second radiation is from the same radiation source as the first radiation. 89. The method according to any one of clauses 85 to 87, wherein the second radiation is from a radiation source different from the first radiation. 90. The method according to any one of clauses 85 to 89, wherein both the first radiation and the second radiation contain pulses. 91. The method according to clause 90, wherein there is a delay between the first radiation and the second radiation. 92. The method according to any one of clauses 85 to 91, wherein the reflected radiation is detected by a pair of balanced detectors. ​93. The method according to any one of clauses 85 to 92, wherein the second radiation is polarized.

[0168]

[0158] Further embodiments are disclosed in the clauses numbered subsequently (Clause Set 2). 1. A pellicle film comprising three or more layers, wherein the three or more layers include at least one inner layer and at least one outer layer on at least one surface of any of the at least one inner layer, the at least one inner layer includes and / or consists of one or more of silicon carbide, silicon dicarbide, boron carbide, and boron nitride, and at least one of the at least one outer layer includes an oxide material. 2. The pellicle film according to clause 1, wherein the oxide material includes one or more of silicon oxide, aluminum oxide, zirconium oxide, or yttrium oxide. 3. The pellicle film according to clause 1 or 2, wherein the at least one inner layer has a thickness of less than 6 nm. 4. The pellicle film according to any one of the preceding clauses, wherein the at least one inner layer has a thickness of more than 1 nm. 5. The pellicle film according to any one of the preceding clauses, wherein at least one of the at least one outer layer includes ruthenium. 6. The pellicle film according to clause 5, wherein the front surface side of the at least one inner layer is capped with an outer layer including ruthenium, and the back surface side of the at least one inner layer is capped with an outer layer including an oxide material. 7. An illumination branch including an illumination optical system for structurally guiding measurement radiation, A pellicle splitter within the illumination branch, the pellicle splitter including a pellicle film operable to split a line source radiation beam from an illumination source into a reference radiation beam and measurement radiation, A measurement detector for detecting the measurement radiation after being scattered by the structure, A reference detector for detecting the reference radiation and a metrology device comprising The metrology device, wherein an incident angle of the line source radiation beam to the pellicle splitter is 45 to 70 degrees. 8. The metrology apparatus according to clause 7, wherein the incident angle of the source radiation beam to the pellicle splitter is between 46 degrees and 50 degrees. 9. The metrology apparatus according to clause 7, wherein the incident angle of the source radiation beam to the pellicle splitter is between 55 degrees and 65 degrees. 10. An illumination branch including an illumination optical system for guiding measurement radiation onto a structure, a pellicle splitter within the illumination branch, the pellicle splitter including a pellicle film operable to split a source radiation beam from an illumination source into a reference radiation beam and measurement radiation, a measurement detector for detecting the measurement radiation after being scattered by the structure, a reference detector for detecting the reference radiation beam and a metrology apparatus comprising: The metrology apparatus, wherein the incident angle of the source radiation beam to the pellicle splitter is between 40 and 44 degrees. 11. The metrology apparatus according to any one of clauses 7 to 10, comprising a dispersive element operable to spectrally disperse the reference radiation beam between the pellicle beam splitter and the reference detector. 12. The metrology apparatus according to clause 11, wherein the dispersive element is a transmissive dispersive element. 13. The metrology apparatus according to any one of clauses 7 to 12, comprising a focusing mirror. 14. The metrology apparatus according to clause 13, wherein the pellicle beam splitter is disposed upstream of the focusing mirror. 15. The metrology apparatus according to clause 13, wherein the pellicle beam splitter is disposed downstream of the focusing mirror. 16. A pellicle film including three or more layers, the three or more layers including at least one inner layer and at least one outer layer on at least one surface of any of the at least one inner layer, the at least one inner layer including one or more of boron, zirconium, beryllium, niobium, yttrium, molybdenum, and / or carbon, and / or one or more compounds of each of these materials, and / or consisting of them, the at least one inner layer having a thickness of less than 6 nm. 17. An illumination branch including an illumination optical system for structurally guiding measurement radiation, a pellicle splitter within the illumination branch, the pellicle splitter including a pellicle film operable to split a source radiation beam from an illumination source into a reference radiation beam and measurement radiation, a measurement detector for detecting the measurement radiation after being scattered by the structure, a reference detector for detecting the reference radiation beam, a dispersive element between the pellicle beam splitter and the reference detector operable to spectrally disperse the reference radiation beam, and a metrology apparatus comprising: the dispersive element being a transmissive dispersive element, the metrology apparatus.

[0169]

[0159] In the present text, although specific reference may be made to embodiments in the context of a reflective (or transmissive) film, the embodiments can also be used with a transmissive (or reflective) film. One or more layers forming different embodiments can be further combined to provide a higher level of functionality (e.g., less variation in transmissivity / reflectivity).

[0170]

[0160] Although the lithography apparatus is specifically referred to in this specification as being used in the manufacture of ICs, it should be understood that the lithography apparatus described in this specification can have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0171]

[0161] Although this specification may specifically refer to embodiments in the context of a lithographic apparatus, the embodiments can be used in other apparatuses. The embodiments can form part of an apparatus for measuring or processing an object such as a mask inspection apparatus, a metrology apparatus or a wafer (or other substrate) or a mask (or other patterning device). These apparatuses can collectively be referred to as lithography tools. Such lithography tools can use vacuum conditions or ambient (non-vacuum) conditions.

[0172]

[0162] Although this specification may make specific reference to embodiments in the context of an inspection or metrology apparatus, the embodiments can be used in other apparatuses. The embodiments can form part of an apparatus for measuring or processing an object such as a mask inspection apparatus, a lithographic apparatus, or a wafer (or other substrate) or a mask (or other patterning device). The term "metrology apparatus" (or "inspection apparatus") can also refer to an inspection apparatus or inspection system (or a metrology apparatus or metrology system). For example, an inspection apparatus including the embodiments can be used to detect defects on a substrate or defects in a structure on the substrate. In such embodiments, the target characteristics of the structure on the substrate can be related to defects in the structure, the absence of a particular part of the structure, or the presence of an unnecessary structure on the substrate.

[0173]

[0163] Although the above may make specific reference to the use of embodiments in the context of optical lithography, it is understood that the invention is not limited to optical lithography and can be used in other applications, such as imprint lithography, where permitted by the context.

[0174]

[0164] The above target or target structure (more generally, a structure on a substrate) is a metrology target structure specifically designed and formed for measurement purposes. However, in other embodiments, it is possible to measure the target characteristics in one or more structures that are functional parts of a device formed on a substrate. Many devices have regular, grid-like structures. The terms structure, target grid, and target structure, as used herein, do not require that the structure be specifically provided for the measurement being performed. Further, the pitch of the metrology target may be near or smaller than the resolution limit of the optical system of the scatterometer, but can be much larger than the dimensions of typical non-target structures (optionally, product structures) generated by a lithography process in target portion C. In practice, the lines and / or spaces of the overlay grid within the target structure can be generated to include smaller structures similar in dimension to those of the non-target structures.

[0175]

[0165] Although specific embodiments have been described above, it will be understood that the present invention can be practiced in other ways than those described. The above description is intended to be illustrative, not restrictive. Thus, it will be apparent to those skilled in the art that modifications can be made to the present invention as described without departing from the scope of the claims set forth below.

[0176]

[0166] Although specific reference has been made to "metrology apparatus / tool / system" or "inspection apparatus / tool / system", these terms can refer to the same or similar types of tools, apparatus, or systems. For example, an inspection or metrology apparatus including embodiments of the present invention can be used to determine the characteristics of structures on a substrate or wafer. For example, an inspection apparatus or metrology apparatus including embodiments of the present invention can be used to detect defects in a substrate or in structures on a substrate or wafer. In such embodiments, the target characteristics of the structures on the substrate can be related to defects in the structures, the absence of specific portions of the structures, or the presence of unwanted structures on the substrate or wafer.

[0177]

[0167] Although specific reference is made to HXR, SXR, and EUV electromagnetic radiation, it will be understood that the present invention can be practiced using all electromagnetic radiation, including radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays, where context permits.

[0178]

[0168] Although specific embodiments have been described above, it will be understood that one or more features of one embodiment may also be present in different embodiments, and that features of two or more different embodiments may be combined.

Claims

1. A pellicle film including three or more layers, wherein the three or more layers include at least one inner layer and at least one outer layer on at least one surface of the at least one inner layer, the at least one inner layer includes and / or consists of one or more of silicon carbide, silicon dicarbide, boron carbide, and boron nitride, and at least one of the at least one outer layer includes an oxide material.

2. The pellicle film according to claim 1, wherein the oxide material includes one or more of silicon oxide, aluminum oxide, zirconium oxide, or yttrium oxide.

3. The pellicle film according to claim 1 or 2, wherein the at least one inner layer has a thickness of less than 6 nm.

4. The pellicle film according to any one of claims 1 to 3, wherein the at least one inner layer has a thickness of more than 1 nm.

5. The pellicle film according to any one of claims 1 to 4, wherein at least one of the at least one outer layer includes ruthenium.

6. The pellicle film according to claim 5, wherein the front surface side of the at least one inner layer is capped with the outer layer including ruthenium, and the back surface side of the at least one inner layer is capped with the outer layer including the oxide material.

7. An illumination branch including an illumination optical system for guiding measurement radiation onto a structure, a pellicle splitter within the illumination branch, the splitter including a pellicle film operable to split a source radiation beam from an illumination source into a reference radiation beam and the measurement radiation, a measurement detector for detecting the measurement radiation after being scattered by the structure, and a reference detector for detecting the reference radiation A metrology apparatus comprising: The metrology apparatus, wherein an incident angle of the source radiation beam onto the pellicle splitter is 45 to 70 degrees.

8. The metrology apparatus according to claim 7, wherein the incident angle of the source radiation beam onto the pellicle splitter is 46 degrees to 50 degrees.

9. The metrology apparatus according to claim 7, wherein the incident angle of the source radiation beam onto the pellicle splitter is 55 degrees to 65 degrees.

10. An illumination branch including an illumination optical system for guiding measurement radiation onto a structure, A pellicle splitter within the illumination branch, the splitter including a pellicle film operable to split a line source radiation beam from an illumination source into a reference radiation beam and the measurement radiation; A measurement detector for detecting the measurement radiation after being scattered by the structure; A reference detector for detecting the reference radiation beam; A metrology apparatus comprising: The metrology apparatus, wherein an incident angle of the line source radiation beam on the pellicle splitter is 40 to 44 degrees. **Claim 11** The metrology apparatus according to any one of claims 7 to 10, further comprising a dispersive element operable to spectrally disperse the reference radiation beam between the pellicle beam splitter and the reference detector. **Claim 12** The metrology apparatus according to claim 11, wherein the dispersive element is a transmissive dispersive element. **Claim 13** The metrology apparatus according to any one of claims 7 to 12, further comprising a focusing mirror. **Claim 14** The metrology apparatus according to claim 13, wherein the pellicle beam splitter is disposed upstream of the focusing mirror. **Claim 15** The metrology apparatus according to claim 13, wherein the pellicle beam splitter is disposed downstream of the focusing mirror.

Images