Illumination module for metrology device

Abstract

Disclosed is an illumination configuration module comprising: an active region comprising alternating first and second reflective regions, the first and second reflective regions comprising a configurable displacement between the first and second reflective regions in a direction perpendicular to the active region, a diffraction grating structure for selectively diffracting the dispersed radiation incident on the active region is selectively formed; wherein the active region includes an adapted reflectance ratio describing a reflectance of the first reflective region relative to a reflectance of the second reflective region, the adapted reflectance ratio minimizing a reflectance difference between the first reflective region and the second reflective region.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to EP application 23161366.2, filed on March 13, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to an irradiation configuration module for configuring an irradiation beam, particularly such an irradiation configuration module related to measurement applications in integrated circuit manufacturing. Background Technology

[0004] A lithography apparatus is a machine configured to apply a desired pattern onto a substrate. For example, a lithography apparatus can be used in the manufacture of integrated circuits (ICs). For example, a lithography apparatus can project a pattern (also known as a “design layout” or “design”) at a patterning device (e.g., a mask) onto a radiation-sensitive material (resist) layer provided on a substrate (e.g., a wafer).

[0005] To project patterns onto a substrate, photolithography apparatuses can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Compared to radiation with a wavelength of, for example, 193 nm, photolithography apparatuses using extreme ultraviolet (EUV) radiation in the 4-20 nm range (e.g., 6.7 nm or 13.5 nm) can be used to form even smaller features on the substrate.

[0006] Low-k1 lithography can be used to process features smaller than the classical resolution limits of lithography apparatuses. In this process, the resolution formula can be expressed as CD = k1 × λ / NA, where λ is the wavelength of radiation used, NA is the numerical aperture of the projection optics in the lithography apparatus, CD is the “critical size” (typically the smallest feature size to be printed, but in this case, half the pitch), and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it is to reproduce patterns on the substrate that are similar in shape and size to those planned by the circuit designer for specific electrical functions and performance. To overcome these difficulties, sophisticated fine-tuning steps can be applied to the lithography projection apparatus and / or design layout. These include, for example, but not limited to, optimization of NA, customized illumination schemes, the use of phase-shifting patterning devices, 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). Alternatively, tight control loops used to control the stability of the lithography apparatus can be used to improve pattern reproduction at low k1.

[0007] Metrological tools are used in many aspects of IC manufacturing processes, such as alignment tools for properly positioning substrates before exposure, leveling tools for measuring substrate surface topology, and focus control and scattering-based measurement tools for inspecting / measuring exposed and / or etched products in process control. In each case, a radiation source is required. For various reasons, including measurement robustness and accuracy, broadband or white light radiation sources are increasingly used in such metrological applications. In many cases, not all spectral and / or polarization components of white light are suitable for a specific measurement. For example, for a particular measurement, it is often desirable to change the spectral and / or polarization characteristics of the radiation. This can be achieved through filtering and polarization switching. However, this results in a loss of system yield because switching radiation characteristics using existing methods incurs significant switching time losses.

[0008] The goal is to improve the configurability of measuring radiation characteristics. Summary of the Invention

[0009] According to a first aspect of the invention, a radiation modulation apparatus is provided, the illumination configuration module comprising: an active region including alternating first and second reflective regions, wherein the first and second reflective regions include a configurable displacement in a direction perpendicular to the active region, thereby selectively forming a diffraction grating structure for selectively diffracting dispersed radiation incident on the active region; wherein the active region includes an adaptive reflectivity ratio describing the reflectivity of the first reflective region relative to the reflectivity of the second reflective region, the adaptive reflectivity ratio minimizing the reflectivity difference between the first and second reflective regions.

[0010] Other aspects of the invention include a measuring device comprising an irradiation arrangement according to a first, second, or third aspect. Attached Figure Description

[0011] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

[0012] Figure 1 A schematic diagram of the photolithography apparatus is depicted;

[0013] Figure 2 A schematic diagram of the photolithography unit is shown;

[0014] Figure 3 A schematic diagram of overall photolithography is depicted, illustrating the collaboration between three key technologies used to optimize semiconductor manufacturing;

[0015] Figure 4 A schematic diagram of a scattering measurement device used as a measurement device is depicted, which may include a radiation source according to an embodiment of the present invention;

[0016] Figure 5 (a) Figure 5 (b) Figure 5 (c) and Figure 5 (d) includes (a) a schematic diagram of a dark field scatterometer for measuring a target using a first pair of illumination apertures according to an embodiment of the invention, (b) details of the diffraction spectrum of a target grating given an illumination direction, (c) a second pair of illumination apertures providing other illumination modes when performing diffraction-based overlay measurements using the scatterometer, and (d) a third pair of illumination apertures combining the first pair of apertures and the second pair of apertures.

[0017] Figure 6 A schematic diagram of a horizontal sensor device according to an embodiment of the present invention is depicted, the horizontal sensor device may include a radiation source;

[0018] Figure 7 A schematic diagram of an alignment sensor device according to an embodiment of the present invention is depicted, the alignment sensor device may include a radiation source;

[0019] Figure 8 (a) Figure 8 (b) and Figure 8 (c) A grating light valve (GLV) is schematically depicted, with (a) a top view, (b) a cross-sectional view of the first configuration, and (c) a cross-sectional view of the second configuration illustrating its basic operation;

[0020] Figure 9 (a) and Figure 9 (b) A first view (along the Y-axis) and a second view (along the X-axis) of the GLV-based illumination configuration module are schematically depicted, respectively;

[0021] Figure 10 (a) A portion of the active region of the GLV is schematically depicted in cross-section, illustrating the problems of using GLV devices in first-order mode; Figure 10 (b) A portion of the GLV active region according to an embodiment is schematically depicted in cross-section;

[0022] Figure 11 A schematic view of the GLV-based illumination configuration module according to the first embodiment along the Y-axis is depicted.

[0023] Figure 12 A schematic depiction of a GLV-based illumination configuration module according to a second embodiment along the Y-axis is shown.

[0024] Figure 13 A top view of a GLV-based illumination configuration module according to a third embodiment is schematically depicted;

[0025] Figure 14A top view schematically depicting a GLV-based illumination configuration module according to a fourth embodiment; and

[0026] Figure 15 The edge diffraction problem in a GLV device is schematically depicted in cross-section. Detailed Implementation

[0027] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including one, some, or all of the following: visible light (e.g., 400 nm to 700 nm), (near)infrared radiation (700 nm to 1000 nm), ultraviolet radiation (e.g., wavelengths of 365, 248, 193, 157, or 126 nm), and EUV (extreme ultraviolet radiation, e.g., wavelengths in the range of about 5–100 nm).

[0028] As used herein, the terms “mask,” “mask,” or “patterning device” can be broadly interpreted to refer to a general patterning device that can be used to impart a patterned cross-section to an incident radiation beam corresponding to a pattern to be created in a target portion of a substrate. The term “optical valve” may also be used in this context. Examples of other such patterning devices, besides classic masks (transmission or reflection, binary, phase-shifting, hybrid, etc.), include programmable mirror arrays and programmable LCD arrays.

[0029] Figure 1 A lithography apparatus LA is schematically depicted. The lithography apparatus LA includes: an irradiation system (also called an irradiator) IL configured to modulate a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask stage) MT configured to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to precisely position the patterning device MA according to certain parameters; a substrate support (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW configured to precisely position the substrate support according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted by the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0030] In operation, the irradiation system IL receives a radiation beam from the radiation source SO, for example, via a beam delivery system BD. The irradiation system IL may include various types of optical elements, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical elements, or any combination thereof, used for directing, shaping, and / or controlling the radiation. The irradiator IL can be used to adjust the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0031] As used herein, the term "projection system" PS should be interpreted broadly to include all types of projection systems, including refractive, reflective, catadioptric, distorting, magnetic, electromagnetic, and / or electrostatic optical systems, or any combination thereof, depending on the exposure radiation and / or other factors used, such as the use of immersion liquids or vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0032] A lithography apparatus (LA) can be a device in which at least a portion of a substrate can be covered by a liquid (e.g., water) having a relatively high refractive index to fill the space between the projection system (PS) and the substrate (W), also known as immersion lithography. More information on immersion techniques is given in US6952253, which is incorporated herein by reference.

[0033] The lithography apparatus LA can also be of the type having two or more substrate supports WT (also known as "dual-stage"). In such a "multi-stage" machine, the substrate supports WT can be used in parallel, and / or preparation steps for subsequent exposure of substrate W can be performed on substrate W located on one substrate support WT, while another substrate W on another substrate support WT is used to expose patterns on another substrate W.

[0034] In addition to the substrate support WT, the lithography apparatus LA may also include a measurement stage. The measurement stage is arranged to house sensors and / or cleaning equipment. The sensors may be arranged to measure characteristics of the projection system PS or the radiation beam B. The measurement stage may hold multiple sensors. The cleaning equipment may be arranged as part of the cleaning lithography apparatus, such as part of the projection system PS or part of a system providing immersion liquid. The measurement stage may be movable below the projection system PS as the substrate support WT moves away from the projection system PS.

[0035] In operation, the radiation beam B is incident on a patterning device (e.g., mask MA) held on a mask support MT and patterned by a pattern (design layout) on the patterning device MA. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be precisely moved, for example, to position different target portions C in the path of the radiation beam B at focused and aligned positions. Similarly, a first positioner PM and possibly another position sensor ( Figure 1 (Not explicitly shown) can be used to precisely position the patterning device MA relative to the path of the radiation beam B. The patterning device MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2, as shown, occupy dedicated target portions, they can be located in the space between target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are called scribing alignment marks.

[0036] like Figure 2 As shown, a lithography apparatus LA can form part of a lithography unit LC, sometimes referred to as a lithography unit or (lithography) cluster, which typically also includes devices for performing pre- and post-exposure processing on a substrate W. Traditionally, these devices include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH, and a baking plate BK, for example, to regulate the temperature of the substrate W, or to regulate the solvent in the resist. A substrate processor or robot RO picks up the substrate W from input / output ports I / O1, I / O2, moves the substrate between different processing devices, and transports the substrate W to the feed stage LB of the lithography apparatus LA. The equipment in the lithography unit (often collectively referred to as tracks) is typically controlled by a track control unit TCU, which itself can be controlled by a monitoring system SCS, which can also control the lithography apparatus LA, for example, via the lithography control unit LACU.

[0037] To ensure correct and consistent exposure of the substrate W by the lithography unit LA, it is necessary to inspect the substrate to measure characteristics of the patterned structure, such as overlay error between subsequent layers, line thickness, critical dimension (CD), etc. For this purpose, the lithography unit LC may include inspection tools (not shown). If errors are detected, adjustments can be made to the exposure of subsequent substrates or other processing steps to be performed on the substrate W, especially when the inspection is performed before other substrates W in the same batch or batch still require exposure or processing.

[0038] An inspection apparatus (also called a measurement device) is used to determine the characteristics of a substrate W, particularly how the characteristics of different substrates W vary, or how the characteristics associated with different layers of the same substrate W vary layer by layer. The inspection apparatus may alternatively be configured to identify defects on the substrate W, and may be, for example, part of a photolithography unit LC, integrated into a photolithography apparatus LA, or even a stand-alone device. The inspection apparatus can measure characteristics on latent images (images in a resist layer after exposure), semi-latent images (images in a resist layer after a post-exposure baking (PEB) step), developed resist images (where exposed or unexposed portions of the resist have been removed), or even etched images (after pattern transfer steps such as etching).

[0039] Typically, the patterning process in a photolithography (LA) apparatus is one of the most critical steps in the process, requiring high-precision dimensional determination and placement of the structure on the substrate W. To ensure this high precision, three systems can be combined in a so-called "monolithic" control environment, such as... Figure 3 As shown. One of these systems is the lithography apparatus LA, which is (virtually) connected to the metrology tool MT (second system) and the computer system CL (third system). The key to this “holistic” environment is optimizing the collaboration between these three systems to enhance the overall process window and provide a tight control loop to ensure that the patterning performed by the lithography apparatus LA remains within the process window. The process window defines a set of process parameters (e.g., dose, focus, overlay) within which a particular manufacturing process will produce a defined result (e.g., a functional semiconductor device). Typically, the process parameters in the lithography or patterning process are allowed to vary within these parameter ranges.

[0040] The computer system CL can use a portion of the design layout to be patterned to predict which resolution enhancement technique to use, and perform computational lithography simulations and calculations to determine which mask layout and lithography setup will achieve the maximum overall process window for the patterning process (e.g., ...). Figure 3 (As indicated by the double arrows on the first scale SC1). Typically, resolution enhancement techniques are arranged to match the patterning possibilities of the lithography apparatus LA. The computer system CL can also be used to detect the current operating position of the lithography apparatus LA within the process window (e.g., using input from the metrology tool MT) to predict whether defects (such as those caused by suboptimal processes) will occur. Figure 3 (As shown by the arrow pointing to "0" on the second scale SC2).

[0041] The measurement tool MT can provide input to the computer system CL for accurate simulation and prediction, and can also provide feedback to the lithography apparatus LA to identify possible drifts, for example, in the calibrated state of the lithography apparatus LA (e.g., ...). Figure 3 (As shown by the multiple arrows on the third scale SC3).

[0042] In photolithography, the created structure requires frequent measurements, for example, for process control and verification. The tools used to perform such measurements are generally called metrology tools (MTs). Different types of metrology tools (MTs) for such measurements are known, including scanning electron microscopes or various forms of scatterometric metrology tools (MTs). A scatterometer is a versatile instrument capable of measuring parameters of the photolithography process by mounting a sensor in the pupil of the scatterometer's objective lens or in a plane conjugate to the pupil; this is generally referred to as pupil-based measurement. Alternatively, it can measure parameters of the photolithography process by mounting a sensor in the image plane or a plane conjugate to the image plane; in this case, the measurement is generally referred to as image- or field-based measurement. Such scatterometers and related measurement techniques are further described in patent applications US20100328655, US2011102753A1, US20120044470A, US20110249244, US20110026032, or EP1,628,164A, the entire contents of which are incorporated herein by reference. The aforementioned scatterometer can use light from soft X-rays and the visible to near-infrared wavelength range to measure gratings.

[0043] In the first embodiment, the scatterometer MT is an angle-resolved scatterometer. In this scatterometer, reconstruction methods can be applied to the measurement signal to reconstruct or calculate the characteristics of the grating. For example, this reconstruction can be achieved by 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 until the simulated interaction produces a diffraction pattern similar to that observed from a real target.

[0044] In the second embodiment, the scatterometer MT is a spectroradiometer MT. In this spectroradiometer MT, radiation emitted by a radiation source is directed onto a target, and reflected or scattered radiation from the target is directed to a spectroradiometer detector, which measures the spectrum of the specularly reflected radiation (i.e., a measurement of intensity as a function of wavelength). Based on these data, the structure or profile of the target that produces the detected spectrum can be reconstructed, for example, through rigorous coupled-wave analysis and nonlinear regression, or by comparison with a simulated spectral library.

[0045] In the third embodiment, the scatterometer MT is an elliptic scatterometer. An elliptic scatterometer allows for the determination of parameters of a photolithography process by measuring the scattered radiation in each polarization state. This metrology device emits polarized light (such as linear, circular, or elliptical) using a suitable polarizing filter in the illumination section of the metrology device. A source suitable for the metrology device can also provide polarized radiation. Various embodiments of existing elliptic scatterometers are described in U.S. Patent Applications 11 / 451,599, 11 / 708,678, 12 / 256,780, 12 / 486,449, 12 / 920,968, 12 / 922,587, 13 / 000,229, 13 / 033,135, 13 / 533,110, and 13 / 891,410, the entire contents of which are incorporated herein by reference.

[0046] In one embodiment of a scatterometer MT, the scatterometer MT is adapted to measure the overlay of two misaligned gratings or periodic structures by measuring the reflectance spectrum and / or detecting asymmetry in the configuration, the asymmetry being related to the degree of overlay. These two (typically overlapping) grating structures can be applied to two different layers (not necessarily consecutive layers) and can be formed substantially at the same location on the wafer. The scatterometer can have a symmetrical detection configuration, such as described in the co-owned patent application EP1,628,164A, such that any asymmetry can be clearly distinguished. This provides a method for directly measuring grating misalignment. Other examples of measuring overlay errors between two layers containing a periodic structure as a target by means of asymmetry in the periodic structure can be found in PCT patent application publication WO 2011 / 012624 or U.S. patent application US20160161863, the entire contents of which are incorporated herein by reference.

[0047] Other parameters of interest may be focus and dose. Focus and dose can be determined simultaneously by scattering measurements (or alternatively by scanning electron microscopy), as described in U.S. Patent Application US2011-0249244, the entire contents of which are incorporated herein by reference. A single structure can be used, having a unique combination of critical dimensions and sidewall angle measurements at each point in the focal length energy matrix (FEM, also known as the focal length exposure matrix). If these unique combinations of critical dimensions and sidewall angles are available, the focus and dose values ​​can be uniquely determined from these measurements.

[0048] The measurement target can be an assembly of composite gratings formed by photolithography, primarily in a resist, but also after an etching process. Typically, the spacing and linewidth of the structures within the grating are strongly dependent on the measurement optics (particularly the NA of the optics) to capture the diffraction order from the measurement target. As previously mentioned, the diffraction signal can be used to determine the shift between two layers (also known as "overlap"), or to reconstruct at least a portion of the original grating produced by the photolithography process. This reconstruction can provide guidance on the quality of the photolithography process and can be used to control at least a portion of the photolithography process. The target can have smaller subdivisions configured to mimic the dimensions of functional portions of the design layout within the target. Due to this subdivision, the target's behavior will be more similar to the functional portions of the design layout, making the overall process parameter measurements better analogous to the functional portions of the design layout. The target can be measured in either an unfilled or overfilled mode. In the unfilled mode, the spot generated by the measurement beam is smaller than the overall target. In the overfilled mode, the spot generated by the measurement beam is larger than the overall target. In this overfilled mode, different targets can also be measured simultaneously, thereby simultaneously determining different processing parameters.

[0049] The overall measurement quality of lithography parameters for a specific target is determined at least in part by the measurement formulation used to measure those parameters. The term "substrate measurement formulation" can include one or more parameters of the measurement itself, one or more parameters of one or more patterns being measured, or both. For example, if the measurement used in the substrate measurement formulation is a diffraction-based optical measurement, the one or more parameters measured can include the wavelength of the radiation, the polarization of the radiation, the angle of incidence of the radiation relative to the substrate, the orientation of the radiation relative to the pattern on the substrate, etc. For example, one of the criteria used to select the measurement formulation could be the sensitivity of one of the measurement parameters to processing variations. Further examples are described in U.S. Patent Application US2016-0161863 and published U.S. Patent Application US2016 / 0370717A1, the entire contents of which are incorporated herein by reference.

[0050] Measurement devices such as scatterometers Figure 4 As shown, it includes a broadband (white light) radiation projector 2 that projects radiation onto a substrate 6. The reflected or scattered radiation is passed to a spectrometer detector 4, which measures the spectrum 10 of the specular reflected radiation (i.e., a measurement of intensity as a function of wavelength). Based on these data, the processing unit PU can reconstruct the structure or profile that produces the detected spectrum, for example, through rigorous coupled-wave analysis and nonlinear regression, or through... Figure 3The simulated spectral library shown at the bottom is compared. Typically, for reconstruction, the general form of the structure is known, and some parameters are assumed based on knowledge of the process used to manufacture the structure, leaving only a few parameters of the structure that need to be determined from scattering measurement data. This scatterometer can be configured as a normal incidence scatterometer or an oblique incidence scatterometer.

[0051] The overall measurement quality of lithographic parameters obtained through measurement of a measurement target is determined at least in part by the measurement formulation used to measure that lithographic parameter. The term "substrate measurement formulation" can include one or more parameters of the measurement itself, one or more parameters of one or more patterns being measured, or both. For example, if the measurement used in the substrate measurement formulation is a diffraction-based optical measurement, the one or more parameters being measured can include the wavelength of the radiation, the polarization of the radiation, the angle of incidence of the radiation relative to the substrate, the orientation of the radiation relative to the pattern on the substrate, etc. For example, one of the criteria used to select the measurement formulation could be the sensitivity of one of the measurement parameters to processing variations. Further examples are described in U.S. Patent Application US2016 / 0161863 and published U.S. Patent Application US2016 / 0370717A1, the entire contents of which are incorporated herein by reference.

[0052] Figure 5 (a) represents one embodiment of the measuring device, and more specifically, a dark field scatterometer. Figure 5(b) describes the target T and the diffracted rays of the measurement radiation used to illuminate the target in more detail. The measurement device shown is a type called a dark-field measurement device. The measurement device can be a stand-alone device or can be included in a lithography apparatus LA, for example at a measurement station, or included in a lithography unit LC. The optical axis having several branches throughout the device is indicated by the dashed line O. In this device, the light emitted by the light source 11 (e.g., a xenon lamp) is guided onto the substrate W by an optical system including lenses 12, 14 and objective lens 16 via a beam splitter 15. These lenses are arranged in a double order of 4F. Different lens arrangements can be used, provided that it still provides a substrate image on the detector and simultaneously allows access to the intermediate pupil plane for spatial frequency filtering. Thus, the range of angles at which radiation is incident on the substrate can be selected by defining the spatial intensity distribution in the plane that presents the spatial spectrum of the substrate plane (here referred to as the (conjugate) pupil plane). In particular, this can be achieved by inserting a suitable aperture plate 13 between lenses 12 and 14 in the plane of the back-projected image, which serves as the objective pupil plane. In the example shown, the orifice plate 13 has different forms, labeled 13N and 13S, to allow for the selection of different illumination modes. The illumination system in this example forms an off-axis illumination mode. In the first illumination mode, orifice plate 13N provides off-axis illumination in a direction designated 'north' for illustrative purposes only. In the second illumination mode, orifice plate 13S is used to provide similar illumination, but in the opposite direction, labeled 'south'. Other illumination modes are also possible by using different orifices. The remainder of the pupil plane is ideally dark, as any unwanted light outside the desired illumination mode would interfere with the desired measurement signal.

[0053] like Figure 5 As shown in (b), the target T is positioned such that the substrate W is perpendicular to the optical axis O of the objective lens 16. The substrate W may be supported by a support (not shown). The ray of measurement radiation I incident on the target T from an angle offset from axis O produces a zero-order ray (solid line 0) and two first-order rays (dotted line +1 and double-dotted line -1). It should be remembered that for a small, dense target, these rays are just one of many parallel rays covering the substrate area (including the measurement target T and other features). Due to the finite width of the aperture in plate 13 (to allow for a useful amount of light), the incident ray I will actually occupy a certain range of angles, and the diffracted rays 0 and +1 / -1 will spread slightly. According to the point spread function of the small target, each order of +1 and -1 will spread further over the angular range, rather than a single ideal ray as shown. It should be noted that the grating spacing and illumination angle of the target can be designed or adjusted so that the first-order rays entering the objective lens are closely aligned with the central optical axis. Figure 5 (a) and Figure 3 The light rays shown in (b) are slightly off-axis, purely to make them easier to distinguish in the diagram.

[0054] At least the 0th and +1st orders of the target T diffraction on the substrate W are collected by objective lens 16 and guided back by beam splitter 15. Back Figure 5 (a) The first and second illumination modes are shown through apertures with opposite diameters, labeled North (N) and South (S). When the incident ray I for measuring radiation comes from the north side of the optical axis, i.e., when the first illumination mode is applied using aperture plate 13N, the +1 diffracted ray, labeled +1 (N), enters the objective lens 16. Conversely, when the second illumination mode is applied using aperture plate 13S, the -1 diffracted ray (labeled 1 (S)) is the ray entering the lens 16.

[0055] The second beam splitter 17 divides the diffracted beam into two measurement branches. In the first measurement branch, the optical system 18 uses the zeroth-order and first-order diffracted beams to form the diffraction spectrum (pupil plane image) of the target on the first sensor 19 (e.g., a CCD or CMOS sensor). Each diffraction order hits a different point on the sensor, allowing image processing to compare and contrast the orders. The pupil plane image captured by the sensor 19 can be used for focusing measurement devices and / or intensity measurements of the normalized first-order beam. The pupil plane image can also be used for many measurement purposes, such as reconstruction.

[0056] In the second measurement branch, optical systems 20 and 22 form an image of the target T on sensor 23 (e.g., a CCD or CMOS sensor). In this branch, aperture stop 21 is positioned in a plane conjugate to the pupil plane. Aperture stop 21 blocks the zero-order diffraction beam, ensuring that the target image formed on sensor 23 is formed only by the -1 or +1 order beam. The images captured by sensors 19 and 23 are output to processor PU, which processes the images, the function of which will depend on the specific type of measurement being performed. Note that the term "image" used here is broad. If only one of the -1 or +1 orders is present, no image of the grating lines will be formed.

[0057] Figure 5 The specific forms of the aperture plate 13 and field stop 21 shown are purely illustrative. In another embodiment of the invention, coaxial illumination of the target is used, and an aperture stop with an off-axis aperture is used to deliver essentially only a first-order diffracted beam to the sensor. In other embodiments, second-, third-, and higher-order beams can be used in the measurement. Figure 5 (not shown in the image) to replace or supplement a first-order bundle.

[0058] To accommodate these different types of measurements, the orifice plate 13 can include multiple aperture patterns formed around a disk that rotates to position the desired pattern. Note that orifice plates 13N or 13S can only be used to measure gratings oriented in one direction (X or Y, depending on the setup). For measurements of orthogonal gratings, the target can be rotated 90° and 270°. Different orifice plates, such as... Figure 5 (c) and Figure 5 As shown in (d). The use of these devices, as well as many other variations and applications of the devices, are described in the aforementioned previously disclosed applications.

[0059] Another measurement tool used in IC manufacturing is a topography measurement system, a level sensor, or a height sensor. This tool can be integrated into a photolithography apparatus to measure the topography of the top surface of a substrate (or wafer). A topography map of the substrate (also called a height map) can be generated from these measurements to indicate the height of the substrate as a function of its position on the substrate. This height map can then be used to correct the substrate's position during the transfer of patterns onto the substrate, providing a spatial image of the patterning apparatus at the appropriate focal position on the substrate. It is understood that in this context, "height" refers to a dimension approximately extending beyond the plane of the substrate (also known as the Z-axis). Typically, the level or height sensor performs measurements in a fixed position (relative to its own optical system), and the relative motion between the substrate and the optical system of the level or height sensor yields height measurements at different locations on the substrate.

[0060] Figure 6 The figure schematically illustrates an example of a level or height sensor LS known in the art; the figure only shows the operating principle. In this example, the level sensor includes an optical system comprising a projection unit LSP and a detection unit LSD. The projection unit LSP includes a radiation source LSO that provides a radiation beam LSB applied by a projection grating PGR of the projection unit LSP. The radiation source LSO can be, for example, a narrowband or broadband light source, such as a supercontinuum light source, which is polarized or unpolarized, pulsed or continuous, such as a polarized or unpolarized beam. The radiation source LSO can include multiple radiation sources with different colors or wavelength ranges, such as multiple LEDs. The radiation source LSO of the level sensor LS is not limited to visible radiation, but may additionally or alternatively include UV and / or IR radiation and any wavelength range suitable for reflection from the substrate surface.

[0061] The projection grating PGR is a periodic grating comprising a periodic structure that generates a radiation beam BE1 with periodically varying intensity. The radiation beam BE1 with periodically varying intensity is guided to a measurement position MLO on a substrate W, the substrate having an incident angle ANG between 0 and 90 degrees, typically between 70 and 80 degrees, relative to an axis perpendicular to the surface of the incident substrate (Z-axis). At the measurement position MLO, the patterned radiation beam BE1 is reflected by the substrate W (indicated by arrow BE2) and directed towards the detection unit LSD.

[0062] To determine the height level at the measurement location MLO, the level sensor also includes a detection system comprising a detection grating DGR, a detector DET, and a processing unit (not shown) for processing the output signal of the detector DET. The detection grating DGR can be the same as the projection grating PGR. The detector DET generates a detector output signal indicating the received light, such as indicating the intensity of the received light, like a photodetector, or representing the spatial distribution of the received intensity, like a camera. The detector DET can include any combination of one or more detector types.

[0063] The height level at the measurement location MLO can be determined using triangulation techniques. The detected height level is typically related to the signal strength measured by the detector DET, which exhibits periodicity. This periodicity depends on the design of the projection grating PGR, the (tilted) incident angle ANG, and other factors.

[0064] The projection unit LSP and / or the detection unit LSD may include other optical elements, such as lenses and / or mirrors (not shown), along the path of the patterned radiation beam between the projection grating PGR and the detection grating DGR.

[0065] In one embodiment, the detection grating DGR can be omitted, and the detector DET can be placed where the detection grating DGR is located. This configuration provides more direct detection of the image of the projection grating PGR.

[0066] In order to effectively cover the surface of the substrate W, the horizontal sensor LS can be configured to project an array of measurement beams BE1 onto the surface area of ​​the substrate W, thereby generating a measurement area MLO or spot array that covers a larger measurement range.

[0067] Various general types of height sensors are disclosed, for example, in US7265364 and US7646471, both of which are incorporated herein by reference. A height sensor that uses UV radiation instead of visible or infrared radiation is disclosed in US2010233600A1, which is also incorporated herein by reference. In WO2016102127A1, which is incorporated by reference, a compact height sensor is described that uses a multi-element detector to detect and identify the position of a grating image without requiring the detection of the grating itself.

[0068] Another measurement tool used in IC manufacturing is the alignment sensor. Therefore, a key aspect of the performance of a lithography apparatus is its ability to correctly and accurately align the applied pattern relative to features set in previous layers (by the same or different lithography apparatuses). For this purpose, one or more sets of marks or targets are provided on the substrate. Each mark is a structure whose position can be measured later using a position sensor (typically an optical position sensor). The position sensor can be called an "alignment sensor," and the marks can be called "alignment marks."

[0069] Photolithography apparatuses may include one or more (e.g., multiple) alignment sensors that allow for the precise measurement of the position of alignment marks formed on a substrate. Alignment (or position) sensors can acquire positional information from alignment marks formed on the substrate using optical phenomena such as diffraction and interference. An example of an alignment sensor used in current photolithography apparatuses is based on a self-reference interferometer described in US6961116. Various enhancements and modifications of position sensors have been developed, such as those disclosed in US2015261097A1. The contents of all these publications are incorporated herein by reference.

[0070] Figure 7 This is a schematic block diagram of one embodiment of a known alignment sensor AS, such as that described in US6961116, which is incorporated herein by reference. A radiation source RSO provides a radiation beam RB of one or more wavelengths, which can be directed as an illumination point SP by optics directed onto a mark (such as a mark AM located on a substrate W). In this example, the directing optics include a point mirror SM and an objective lens OL. The diameter of the illumination point SP illuminating the mark AM can be slightly smaller than the width of the mark itself.

[0071] The radiation diffracted by the aligned marker AM is collimated (in this example via the objective lens OL) into an information-carrying beam IB. The term "diffraction" is intended to include zero-order diffraction (which may be referred to as reflection) from the marker. For example, a self-reference interferometer SRI of the type disclosed in US6961116 above causes the beam IB to interfere with itself, after which the beam is received by a photodetector PD. Additional optics (not shown) may be included to provide a separate beam if the radiation source RSO generates more than one wavelength. The photodetector may be a single element or may include multiple pixels, if desired. The photodetector may include a sensor array.

[0072] In this example, the steering optics that include the point reflector SM can also be used to block the zero-order radiation reflected from the marker, so that the information-carrying beam IB only includes higher-order diffraction radiation from the marker AM (this is not necessary for the measurement, but can improve the signal-to-noise ratio).

[0073] The intensity signal SI is provided to the processing unit PU. Through a combination of optical processing in the block SRI and computational processing in the unit PU, the values ​​of the X and Y positions on the substrate relative to the reference frame are output.

[0074] A single measurement of this type fixes the position of the marker within a specific range corresponding to a spacing between the markers. Coarser measurement techniques are used in conjunction with this to identify which period of the sine wave contains the marker position. The same process can be repeated at coarser and / or finer levels at different wavelengths to improve accuracy and / or achieve robust marker detection, regardless of the material the marker is made of or the material on which and / or under it are placed. Wavelengths can be optically multiplexed and demultiplexed for simultaneous processing, and / or they can be multiplexed via time-division or frequency-division multiplexing.

[0075] In this example, the alignment sensor and point SP remain stationary while the substrate W moves. Therefore, the alignment sensor can be rigidly and precisely mounted to the reference frame while effectively scanning the mark AM in a direction opposite to the direction of movement of the substrate W. The movement of the substrate W is controlled by a substrate mounting on a substrate support and a substrate positioning system that controls the movement of the substrate support. A substrate support position sensor (e.g., an interferometer) measures the position of the substrate support (not shown). In one embodiment, one or more (alignment) marks are provided on the substrate support. Measuring the position of the marks provided on the substrate support allows calibration of the position of the substrate support determined by the position sensor (e.g., relative to the frame connected to the alignment system). Measuring the position of the alignment marks provided on the substrate allows determination of the position of the substrate relative to the substrate support.

[0076] Measurement tools (MTs) such as the aforementioned scatterometers, topography measurement systems, or position measurement systems can perform measurements using radiation derived from a radiation source. The characteristics of the radiation used by the measurement tool can affect the type and quality of measurements that can be performed. For some applications, it can be advantageous to use multiple radiation frequencies and / or polarization states to measure the substrate, for example, using broadband radiation. Multiple different frequencies can propagate, illuminate, and scatter the measurement target without interfering with or minimizing interference with other frequencies. Therefore, for example, different frequencies can be used to acquire more measurement data simultaneously. Different radiation frequencies can also be used to query and discover different characteristics of the measurement target. Broadband radiation can be used in measurement systems (MTs) such as, for example, level sensors, alignment mark measurement systems, scattering measurement tools, or inspection tools. The broadband radiation source can be a supercontinuum source.

[0077] In many metrology applications, such as those based on scattering or interferometry, for example, to perform pre-exposure measurements (e.g., alignment) or post-exposure measurements (e.g., overlay, CD, focusing, or other parameters of interest), different information can be obtained from measurements of the same structure depending on the wavelength and polarization state of the measurement illumination used. For instance, some existing metrology systems offer configurable measurement illumination in multiple colors and three polarization settings (horizontal, vertical, and both). However, the illumination configuration modules (color switching modules) currently used in such systems are often based on bulky, slow mechanical modules. Furthermore, such modules only offer three options when selecting the polarization of the incident beam: all wavelengths in a first polarization state (e.g., horizontal H), all wavelengths in a second polarization state (e.g., vertical V), or all wavelengths in both polarizations. At some wavelengths, any polarization choice is likely to be suboptimal. Measuring each wavelength at the optimal polarization requires twice as many measurements as a single-polarization measurement, with slow polarization switching in between. Moreover, it is currently impossible to arbitrarily combine different polarization states.

[0078] A rapid illumination configuration module or color switching module based on the grating light valve (GLV) concept has been described. The GLV device disperses light (already dispersed onto the GLV), allowing the module to selectively remove or modulate one or more specific wavelengths of light. The resulting spectrum can be configured to include any desired shape and can vary at very high frequencies, potentially up to the MHz range. This spectral design offers a fast (microsecond-switchable) method for extracting large amounts of information from a target. However, known literature on GLV-based illumination configurations only describes color selection, without any polarization selection functionality. Wavelength is only one degree of freedom. Measuring the polarization of the illumination is another useful degree of freedom that can be utilized in the measurement.

[0079] As an example, and for reference Figure 8 and Figure 9 A GLV-based illumination configuration module will now be described, configured to selectively transmit or block (diffract or reflect) at least a portion of incident broadband illumination. A GLV is an electrically programmable diffraction grating based on microelectromechanical systems (MEMS) technology. A GLV device may include a configurable diffraction structure for selectively reflecting or diffracting incident broadband illumination into an output radiation beam. Therefore, the output radiation illumination from such a module may include a spectrally configured beam modulated by the GLV device. The GLV devices used in the embodiments disclosed herein may be GLV devices sold by Silicon Light Machines (SLM) and / or based on the GLV concept described in US6947613B, which is incorporated herein by reference.

[0080] Figure 8 (a)- Figure 8 (c) Explains how GLV works. Figure 8 (a)- Figure 8 (c) are schematic diagrams of the GLV pixels or component 500 from the top and bottom, respectively. Note that... Figure 8 (a)- Figure 8 (c) The GLV component shown is only an example design, and other different GLV designs (e.g., the “real GLV” design used in the G1088 and G8192 modules sold by SLM) can also be used in any illumination configuration module disclosed herein. In the real GLV design, the bias band is replaced by a metallized region on the substrate (the bottom of the GLV device).

[0081] GLV components include two types of alternating GLV reflective strips: a static or bias strip 510 (more generally referred to as a bias region) typically grounded with a common electrode, and a drive or active strip 520 (more generally referred to as an active region) driven by an electronic driver channel. A GLV device may include an active region comprising or defined by a plurality of alternating first reflective regions (e.g., first reflective strips or bias strips) and second reflective regions (e.g., second reflective strips or active strips). The active region may include a plurality of GLV components 500 arranged in an array (e.g., a 1D or 2D array), or a single array of alternating first and second reflective regions.

[0082] Aside from the driving method, the active band and the bias band can be essentially the same. In one embodiment, when no voltage is applied to the active band 520, they are coplanar with the bias band, such as... Figure 8 The configuration shown in (b) is as follows. In this configuration, the GLV essentially acts as a mirror, where incident light is reflected by the mirror (i.e., forming specular reflection radiation or zero diffraction order radiation). When a voltage is applied to the active band 520, as... Figure 8As shown in (c), they are deflected relative to the bias band 510 to establish a square-well diffraction grating. In this state, the incident light is diffracted to a fixed diffraction angle. By controlling the voltage on the active band 520 (which controls the deflection amplitude of the active band), the ratio of reflected light to diffracted light can be continuously changed. Therefore, the amount of light diffracted by the GLV can be controlled in a simulated manner from zero (total specular reflection) to all incident light (zero specular reflection). In the context of this disclosure, such control of the amount of reflected radiation relative to the amount of radiation diffracted to a non-zero diffraction order can be referred to as modulation of the illumination.

[0083] Figure 9 (a) and Figure 9 (b) A known illumination configuration module is schematically illustrated from two different perspectives. A broadband input beam emitted from a broadband light source LS is dispersed in the X direction by a beam-dispersing element DE, which may include, for example, a prism or a grating. The dispersion of the broadband input beam is based on the principle that the direction of light emitted from the beam-dispersing element DE is related to its wavelength. Before being dispersed by the beam-dispersing element DE, the broadband input beam may optionally be collimated by a first optical lens L1. The dispersed broadband input beam can then be (e.g., by a second optical lens L2) focused onto a band of the GLV device, which is substantially located at the focal plane of the second lens L2. Different shadings represent different wavelengths of the dispersed radiation.

[0084] In some embodiments, the GLV device can operate in a wavelength selection mode to fully select one or more selected wavelengths (e.g., without significant attenuation) and completely block unselected wavelengths. That is, the bands of the GLV device corresponding to the selected wavelength can be set to equal height so that they act as standard mirrors at the selected wavelength, while other bands are actuated in such a way that they form gratings that will diffract the undesired wavelengths to higher diffraction orders (e.g., -1 and +1 diffraction orders). These higher diffraction orders are then blocked or cut off by beam blocks BL1, BL2, respectively. The GLV device can also operate in an intermediate mode or a spectral shaping mode, for example, to form gratings that partially reflect and diffract incident radiation of one or more wavelengths to attenuate but not completely block those wavelengths. The degree of attenuation can be controlled via band configuration (offset of the active bands relative to the static bands). In this way, the spectral shape / composition of the output radiation can be dynamically controlled.

[0085] Spatially modulated reflected (zero-order) radiation from the GLV device can be captured by a second optical lens L2. The spatially modulated beam is recombined on the return path, for example, using the same dispersive element DE used for the dispersed beam on the outward path (alternatively, separate dispersive elements can be used for dispersion and combination). The return path within the dispersive element DE can be substantially parallel to the outward path and displaced in the Y direction relative to the outward path. The recombined output beam can then be guided by a directional mirror SM toward, for example, a third optical lens L3. This third optical lens L3 can be used as an output lens to focus the output beam into a measurement device, for example, via a suitable optical fiber, such as a single-mode photonic crystal fiber.

[0086] Figure 9 A GLV device is shown configured in a "zero-order mode," which applies spatial modulation to a focused broadband input beam to selectively reflect desired wavelengths and diffract unwanted wavelengths. Therefore, in this configuration, diffracted radiation is blocked / cut off, and specular reflection (zero diffraction order) radiation is selected (e.g., transmitted into the output illumination beam). Figure 9 In this process, an aperture stop can be provided in the pupil plane to maximize the zero-order transmission and maximize the blocking of the first order (and other diffraction orders) (to minimize their transmission).

[0087] This zero-order operating mode has the advantage of maintaining the light collection rate because specular reflection radiation will have no wavelength-dependent output (reflection) angle. Therefore, it is fairly straightforward to combine the selected wavelengths into a common path and maintain the small light collection rate required to couple the light into (e.g., single-mode) fiber.

[0088] Figure 9 Another advantage of the arrangement shown is that the optical path has fewer elements due to the use of lenses L2 and prisms in both the outward and return directions. This offers cost and size advantages.

[0089] A significant drawback of operating GLV devices in the aforementioned zero-order mode configuration is that the out-of-band rejection of GLV devices is insufficient for many applications, including... Figures 4 to 7 The measurement tool shown is used as a radiation source. With this zero-order mode configuration, there will always be a small but noticeable amount of unwanted color leakage into the output illumination beam. For example, when configured in zero-order mode, it is difficult (if not impossible) to reduce the leakage to significantly less than 0.1% (i.e., typically at least 0.1% of the incident radiation is reflected from the GLV region, which is configured to diffract / block all incident radiation on these regions). For measurement applications, this leakage should be at least an order of magnitude smaller than this, i.e., suppression at least four orders of magnitude smaller than the full signal (at least 0.01%).

[0090] It is difficult or impossible to configure GLV strips to form a grating with sufficiently high diffraction efficiency to achieve leakage of 0.01% or better, because there are always gaps between the strips, which cause light to be reflected through these gaps.

[0091] To address this limited diffraction efficiency and thus the out-of-band suppression problem, an inverted configuration is proposed, enabling the use of diffracted radiation (e.g., first-order, although other non-zero-order radiation can also be used) and rejecting specular zero-order radiation; that is, configuring the GLV device in "first-order mode." In this configuration, diffraction efficiency becomes less critical; while some low diffraction efficiency may indicate some (desired) radiation loss, it does not affect out-of-band suppression. The little or no radiation incident on the GLV region configured to reflect radiation will diffract in the same (multiple) directions as the desired first-order radiation, thus resulting in excellent out-of-band suppression.

[0092] The disadvantage of using the first-order operating mode is that the light-gathering power is no longer preserved. The emitted radiation will now (in the first-order mode) include the wavelength-dependent diffraction angle (output radiation direction). Therefore, to properly overlap all wavelengths in a single common path using conventional GLV equipment in first-order mode, an optical solution is needed for just one diffraction order (there will certainly be two complementary first orders, often referred to as +1 and -1). This solution would require dispersive elements (e.g., prisms or gratings) before and after the collimating lens. Such a large number of additional optics is undesirable in terms of cost and size. Even with additional optics, the recombination of different wavelengths is not as good as in the zero-order configuration, making it difficult to couple the light back into the (single-mode) fiber. Therefore, while out-of-band suppression requirements can be met with a first-order selection scheme, it is difficult to collect the diffracted light and couple it into the fiber for, for example, measurements.

[0093] To address the difficulty of collecting first-order radiation (or at least half of it) into small light-gathering rates, it has also been proposed to introduce variable spacing or period (e.g., chirping) into GLV devices. Figure 10 This explains the principle. Figure 10(a) A graphical representation of two portions of the active region of a conventional GLV device illustrates the problems of using a conventional GLV device in first-order mode. The active region of a conventional GLV device has a fixed spacing P, where the active region (and GLV grating) spacing (or local spacing) can be defined herein as the combined width of two adjacent reflective regions or bands in the grating direction (X direction as shown); for example, a first reflective region or bias band 510 and an adjacent second reflective region or active band 520. A first incident radiation of a first wavelength λ1 is incident on the first portion of the GLV device and diffracts at a first diffraction angle β1, and a second incident radiation of a second wavelength λ2 is incident on the second portion of the GLV device and diffracts at a second diffraction angle β2. Thus, the diffracted radiation diffracts in various directions according to the wavelength.

[0094] exist Figure 10 In (b), again, incident radiation of the first wavelength λ1 is incident on a first portion of the active region of the GLV device, and second incident radiation of the second wavelength λ2 is incident on a second portion of the active region of the GLV device. However, the first portion of the active region, including the first reflection region / bias band 1010 and the second reflection region / active band 1020, has a first local spacing P1, and the second portion of the active region, including the first reflection region / bias band 1010' and the second reflection region / active band 1020', has a second local spacing P2. Spacings P1 and P2 make the diffraction angle β of the first wavelength λ1 and the second wavelength λ2 the same. For example, when the first wavelength λ1 is half of the second wavelength λ2, spacing P1 can be half of spacing P2.

[0095] For all wavelengths, appropriate local matching of the spacing / spacing of the GLV devices to the local wavelengths can be achieved to ensure that the diffraction angles of all wavelengths of interest are substantially consistent or constant. For example, within the active region, the local spacing can be substantially locally dependent on the intended receiving location for each corresponding local wavelength of the broadband radiation with spectral dispersion (i.e., the intended receiving location includes the corresponding location for each color of the dispersed radiation that is intended to be received in operation). Thus, a first intended receiving location can be arranged to receive radiation of a first wavelength, and therefore the local spacing of the first intended receiving location can be configured for that first wavelength, and a second intended receiving location can be arranged to receive radiation of a second wavelength, and therefore the local spacing of the second intended receiving location can be configured for that second wavelength, such that each order of diffraction radiation is identical for each of these first and second wavelengths.

[0096] For example, a GLV device can have a spacing that decreases continuously (or more generally monotonically varies) along its length, corresponding to the incident wavelength on the GLV. For instance, in such an embodiment, no two pairs of bias bands and adjacent active bands have the same combined width; instead, the spacing decreases with each successive pair of the aforementioned bands (in the grating direction). Alternatively, in cases where the GLV device comprises an array of pixels or GLV components (e.g., 1D), the spacing can decrease or vary monotonically with each successive pixel / GLV component (in the grating direction). Other less continuous spacing variations are possible, although this correspondingly reduces the light-gathering efficiency.

[0097] In this way, all wavelengths of each diffraction order will propagate in (at least substantially) the same direction after the GLV device and can be collected using a single collimating lens and prism (for each diffraction order), thus creating a common path that allows for efficient external coupling.

[0098] Therefore, both limiting factors of the prior art arrangement are mitigated: although the gap between the aforementioned bands will introduce some diffraction in mirror mode (suppression mode), when configured in non-mirror mode, the spacing of the diffraction grating caused by such gaps will be twice as large as the expected grating, and thus this unwanted diffraction radiation will not propagate in the same direction as any desired diffraction order, nor will it be collected by the collecting optics. Furthermore, imperfect diffraction due to the local bending of the flexible bands does not limit out-of-band suppression. For the selected wavelength, it introduces only a very small (typically <1%) loss.

[0099] Therefore, a radiation modulation device (e.g., a GLV device) is disclosed herein, comprising: an active region including alternating first reflection regions (e.g., a first set of strips) and second reflection regions (e.g., a second set of strips), wherein the first reflection regions and the second reflection regions include a configurable displacement in a direction perpendicular to the active region, thereby selectively forming a diffraction grating structure for selectively diffracting dispersed radiation incident on the active region; wherein the local spacing of the active regions varies within the active region, and the local spacing is defined by a combined width of one of the first reflection regions and an adjacent second reflection region in the second reflection regions. The first reflection regions may be fixed (e.g., as shown in the image). Figure 8 The first and second reflection regions can be either the offset band in a "classic GLV" or the offset region in a "real GLV" arrangement, and the second reflection region is displaceable (e.g., an active band), or vice versa. The first and second reflection regions can also both be displaceable.

[0100] An illumination configuration module is also disclosed, comprising: a beam dispersive element operable to receive and spectrally dispersive broadband radiation to obtain spectrally dispersive broadband radiation; and the radiation modulation device operable to receive spectrally dispersive broadband radiation on the active region and selectively spectrally modulate the dispersive broadband radiation; wherein the local spacing of the active region is substantially dependent on the local expected wavelength of the spectrally dispersive broadband radiation incident on the active region.

[0101] The illumination configuration module is operable to form an output beam solely based on diffracted radiation from the active region, while blocking specular reflection radiation from the active region. The illumination configuration module can form the output beam based on a single diffraction order, or based on each of a pair of complementary diffraction orders (e.g., two orders of the same order; typically +1 and -1). The illumination configuration module may include combined optics (e.g., a half-wave plate and a polarizing beam splitter for first order) for combining each of the pair of complementary diffraction orders into a single output beam. The illumination configuration module may include a corresponding beam-passing arrangement operable to cause the pair of complementary diffraction orders to overlap at the output of the illumination configuration module.

[0102] The spacing of the aforementioned active regions can be varied such that the aforementioned diffraction radiation includes substantially the same diffraction angle for each diffraction order for all wavelengths of interest included in the aforementioned broadband radiation with spectral dispersion.

[0103] The biggest drawback of this proposed method for a single measurement device is that the output light includes only a single diffraction order and is therefore effectively halved. However, embodiments for addressing this problem will be disclosed herein. One approach is to use a single illumination configuration module to provide illumination for a pair of measurement devices (or a pair of other devices), i.e., such that one measurement device receives +1 diffraction radiation and the other receives -1 diffraction radiation. Other embodiments may include providing additional optics to combine the +1 and -1 diffraction radiation for coupling into a single measurement device (or other device). If polarized radiation is assumed, the radiation can overlap back to a concentration equal to the incident concentration, thus allowing the radiation to couple back into a single-mode fiber. If unpolarized radiation is used, the fact that all wavelengths diffract in the same direction can be used to combine the radiation into a single multimode fiber. This will now be combined with... Figures 11 to 14 There are many such configurations described.

[0104] Figure 11An embodiment is illustrated in which diffracted radiation is collected into a single small collection rate for each diffraction order (or a diffraction order). A broadband input beam (broadband radiation) 1105 emitted from a broadband light source 1100 is optionally collimated by a first optical lens or an input lens 1103. The (e.g., collimated) broadband input beam is then dispersed (e.g., in the X direction shown) by a beam dispersive element 1110 (e.g., a prism). The dispersed broadband radiation 1115 can then be focused (e.g., by a second optical lens 1120) onto the band of a GLV device 1125, which is substantially located at the focal plane of the second optical lens 1120. The GLV device 1125 (in...) Figures 11 to 14 As described above, each of the embodiments shown includes, for example, a variable spacing configured such that two or more wavelengths of interest incident on the GLV device 1125 diffract substantially in a common direction (e.g., at a common diffraction angle) for each diffraction order.

[0105] In one embodiment, the term "substantially in the common direction" may allow the light collection rate of the output illumination beam (or each output illumination beam) to not exceed 20%, 15%, 10%, or 5% of the light collection rate of the broadband input beam.

[0106] For example, the light-gathering rate can have a negligible increase, allowing virtually all or at least most of the light to be coupled into a single-mode fiber (e.g., which may include photonic crystal fiber (PCF)). Maintaining single-mode also preserves the coherence of the supercontinuum source beam; this is a requirement, for example, in digital holographic measurements. Therefore, maintaining the light-gathering rate allows coherence to be preserved, and the output beam to be suitable for applications that rely on coherent beams.

[0107] Light-gathering efficiency can be defined as the product of the source area and the solid angle seen from the source towards the system's incident pupil. Light-gathering efficiency corresponds to the beam parameter product (BPP) in Gaussian beam optics. However, the precise definition of light-gathering efficiency is not important, as these concepts pertain to systems where the light-gathering efficiency will not increase (or at least not by more than a small fraction), regardless of its specific definition.

[0108] At least one of the first diffraction orders (e.g., +1 diffraction radiation 1130) is collected by a corresponding collecting lens 1135 and recombined into an output illumination beam 1140 using a second dispersive element 1145. This output illumination beam 1140 can be focused by an output lens 1150 into, for example, a first fiber input 1155, for transmission to a first measurement device or other device. For clarity, the optical path of blocked radiation (e.g., specular reflection radiation from a GLV device 1125) is not shown. Such radiation can be blocked using a radiation emission field (not shown). In the illustrated embodiment, another first diffraction order (e.g., -1 diffraction radiation 1160) is collected by a corresponding collecting lens 1165 and recombined into an output illumination beam 1170 using a second dispersive element 1175. This output illumination beam 1170 can be focused by an output lens 1180 into a second fiber input 1185, for transmission to a second measurement device or other device.

[0109] As Figure 11 An alternative arrangement shown could be to collect and use only one of the first diffraction orders 1130 and 1160, while blocking / cutting off the other of the first diffraction orders 1130 and 1160.

[0110] Figure 12 An embodiment is schematically shown in which both +1 diffraction radiation 1130 and -1 diffraction radiation 1160 are collected and combined into a single output irradiation beam 1240. If the elements are... Figure 11 If the same applies, it will not be described further. This arrangement includes beam-directing elements 1203 and 1206 for +1 diffraction radiation 1130 and -1 diffraction radiation 1160, respectively. The input radiation 1105 may include a single linear polarization. A half-wave plate 1209 may be positioned in one of the diffraction order paths (in the example shown, the -1 order path, although the choice of diffraction order is arbitrary) to rotate the polarization of that diffraction order by 90 degrees. A polarization beam splitter 1213 may be used to combine the radiation into a (unpolarized) output illumination beam 1240. The half-wave plate and polarization beam splitter may be substantially achromatic.

[0111] Figure 13 Explained with Figure 12 A similar embodiment exists, but in which the input radiation 1105 is unpolarized (or non-linearly polarized). In this embodiment, the collected orders 1140, 1170 are simply directed to the output lens 1150 and overlap at the fiber facet or input 1155. This arrangement is only compatible with multimode outputs.

[0112] Therefore, even without utilizing linear input polarization, it is still possible to recombine two orders into a single multimode output fiber. This is possible because, due to the band spacing variation of the GLV device 1125, the output concentration (at least substantially) is the same as the concentration of the input bundle. In a specific example, the maximum concentration bundle at the GLV input of the GLV device could be a 900nm bundle. It has a bundle waist (radius) w0 = 12μm and a divergence (half-angle) α = 0.024 (both of which are in the range of 1 / e 2 (Definition). A suitable multimode fiber has a core diameter d. core =50 μm and numerical aperture NA = 0.22. For the shown combination, the spots formed by each diffraction order can overlap at the 1150 facet of the fiber. This does not increase the required size. In the far field, the beam is separated. However, the NA of the beam is almost 10 times the beam divergence, so this is also easily matched. Note that a larger size is required because the waist and divergence are in the range of 1 / e. 2 This means that approximately 13% of the light energy exceeds this beam definition.

[0113] Figure 14 An embodiment is described, with Figure 9 The zero-order mode configuration is similar; this embodiment uses the same beam-dispersing element 1110 and lens 1120 in the outward and return paths to and from the GLV device 1425. Figures 10 to 13 In this embodiment, the incident angle on the GLV device 1425 is kept zero (perpendicular to the GLV strip plane). In this embodiment, a non-zero incident angle is proposed for the GLV device 1425. Changing the incident angle α also changes the diffraction angle β. If the incident angle α = -β, then the diffraction order (i.e., a first diffraction order) propagates precisely backward relative to the incident beam (this is a grating configuration also used, for example, in Littrow external cavity diode lasers). This condition can be satisfied if the following condition is met:

[0114]

[0115] Where λ is the wavelength, p is the GLV (local) spacing, and n is the diffraction order (i.e., n = 1).

[0116] In the variable-pitch GLV device 1425, the local pitch can be matched with the local wavelength of the incident radiation 1115 along the direction of the GLV grating to achieve the condition that all wavelengths are incident on the GLV device 1425.

[0117] The backpropagation of the diffracted beam allows the same optics (e.g., beam dispersive element 1110 and lens 1120) to disperse and focus the illumination onto the GLV device 1425, and to collect and recombine the modulated illumination. Figure 9The configuration is similar; by using lens 1120 off-center and / or tilting GLV device 1425 around its local X-axis, the outgoing and returning beams can be spatially separated. Furthermore, as previously described, the output beam 1140 can be guided toward output lens 1150 and fiber input 1155 on the return path using directional mirror 1427.

[0118] The angle of incidence α should be kept small to avoid large field-of-view defocusing on the GLV. A smaller focal length (NA) helps accommodate a larger depth of focus. If necessary, the depth of focus can be further increased by adjusting the magnification. For example, the angle of incidence α can be less than 10 degrees.

[0119] The advantage of this embodiment is that, compared with the current configuration (e.g., as...), it is more efficient than the current configuration. Figure 9 Compared to the previous embodiment, the illumination path remains relatively unchanged, and a simpler, more compact configuration can be achieved. However, capturing two diffraction steps is not as straightforward as other embodiments, especially in terms of combining them for use in a single (e.g., measurement) device. Figure 14 In this process, the other diffraction order 1160 and the zeroth order 1416 are blocked; for example, using corresponding beam collectors 1421 and 1424. Alternatively, the other first-order radiation 1160 can be captured in a second outward path to form a second output beam for use with a second (e.g., measurement) device, in a manner similar to... Figure 10 The method shown is similar. It is also conceivable that a more complex optical arrangement would combine the +1 and -1 diffraction orders into a single output beam or a pair of overlapping beams at the output, similar to... Figure 12 and Figure 13 The layout shown.

[0120] In all the above embodiments, the GLV device can operate in wavelength selection mode and / or intermediate (spectral shaping) mode, as previously described.

[0121] Another embodiment relating to the use of a GLV device in zero-order mode will now be described (e.g., as...). Figure 9 (Part of the illumination arrangement shown). This method applies to any GLV, but is more suitable for "true GLVs". This is because the layout of a "classic GLV" makes the effective reflectivity of the actuated and unactuated bands the same, while the other leakage contributions of a classic GLV (e.g., reflectivity mainly through the gaps between the bands) are much larger.

[0122] In this arrangement, edge diffraction at the active band will result in reduced energy reflected from the bias band, or, in the case of a "true GLV," reduced energy reflected from the bias region on the underlying layer. Therefore, it is impossible to drive a GLV device to zero reflectivity of the zeroth order. This results in a leakage of 0.2%, which is too high (as previously stated). Figure 15As shown, this figure illustrates illumination III incident on and reflected from a real GLV comprising the bias region BR and the active region (or active band) AR. The edge diffraction component ED, which causes a reduction in energy reflected from the bias region BR, is also shown. Edge diffraction depends on both the wavelength and the actual distance from the band to the bottom (bias region).

[0123] To address this issue, an adaptive effective reflectivity ratio r was proposed. bias :r active This ratio describes the bias region r bias The reflectivity relative to the active region r active The reflectivity of the bias region is adjusted. Specifically, a method has been proposed to adapt this ratio closer to 1:1 (e.g., in a reflected electric field). One proposed approach to achieve this is to adjust the width of the active region relative to the bias region (e.g., not a 50% duty cycle); that is, to reduce the ratio of the active region width to the bias region width. As a concrete example, for an incident wavelength of 900 nm, the ratio of the active region to the half-spacing (e.g., locally) could be 0.94. As explained below, this ratio can be wavelength-dependent. Another proposed approach is to adjust the reflectivity of the bias region relative to the reflectivity of the active region (e.g., for an incident wavelength of 900 nm, the bias region has approximately 83% reflectivity relative to the active region).

[0124] It is understandable that the amount of edge diffraction depends on the wavelength (the longer the wavelength, the more edge diffraction). The proposed correction can be implemented at several different levels:

[0125] 1) Fixed adaptation across locations on GLV. This can be a compromise based on the center wavelength of the wavelength range of interest and can reduce leakage to about 0.1% (e.g., spectral splitting between the maximum and minimum wavelengths).

[0126] 2) Gradual changes in reflectivity correction on the GLV correspond to the desired color at a given GLV location. This can reduce leakage to ~1e-5.

[0127] 3) Correction and wavelength precise matching. It's understandable that the actual distance from the active band to the bias band / bottom is not a constant factor depending on the wavelength. This will result in a jagged pattern in the height, and therefore also a jagged profile in the correction of the GLV device.

[0128] Other embodiments are disclosed in the following list of numbered chapters:

[0129] 1. A radiation modulation device, comprising:

[0130] The active region includes alternating first and second reflective regions, with a configurable displacement between the first and second reflective regions in a direction perpendicular to the active region, thereby selectively forming a diffraction grating structure for selectively diffracting dispersed radiation incident on the active region.

[0131] The local spacing of the active regions varies within the active regions, and the local spacing is defined by the combined width of a first reflective region in the first reflective region and an adjacent second reflective region in the second reflective region.

[0132] 2. The radiation modulation apparatus according to Clause 1, comprising a grating light valve apparatus having a plurality of reflective bands, wherein each of the first reflective region and the second reflective region comprises a corresponding reflective band among the plurality of reflective bands.

[0133] 3. The radiation modulation apparatus according to clause 1 or 2, wherein the first reflective region is fixed and only the second reflective region is displaceable; or the second reflective region is fixed and only the first reflective region is displaceable.

[0134] 4. The radiation modulation apparatus according to any one of the preceding clauses, wherein the local spacing varies monotonically with each pair of consecutive first reflective regions and adjacent second reflective regions.

[0135] 5. The radiation modulation apparatus according to any one of clauses 1 to 3, wherein the active region comprises a pixel array, and the local spacing varies monotonically with each consecutive pixel within the active region.

[0136] 6. An irradiation configuration module, comprising:

[0137] A beam dispersive element, which can be operated to receive and spectrally dispersed broadband radiation to obtain spectrally dispersed broadband radiation;

[0138] The radiation modulation apparatus according to any one of the foregoing clauses is operable to receive spectrally dispersed broadband radiation over the active region and selectively spectrally modulate the dispersed broadband radiation to obtain output radiation.

[0139] Within the active region, the local spacing is substantially locally dependent on the expected receiving location for each corresponding local wavelength of the spectrally dispersed broadband radiation.

[0140] 7. The irradiation configuration module according to Clause 6 is operable to form the at least one output radiation beam solely based on diffracted radiation diffracted from the active region, while blocking specular reflection radiation from the active region.

[0141] 8. The illumination configuration module according to Clause 7, wherein the illumination configuration module is operable to form the at least one output radiation beam according to a single diffraction order.

[0142] 9. The illumination configuration module according to Clause 7, wherein the illumination configuration module is operable to form the corresponding output radiation beam according to each of a pair of complementary diffraction orders.

[0143] 10. The irradiation configuration module according to Clause 9, wherein the irradiation configuration module includes a corresponding beam delivery arrangement operable to cause the output radiation beam to overlap with the output of the irradiation configuration module.

[0144] 11. The illumination configuration module according to Clause 7, wherein the illumination configuration module includes a combination optics device operable to combine each of a pair of complementary diffraction orders into a single output radiation beam.

[0145] 12. The illumination configuration module according to Clause 11, wherein the combined optics includes a half-wave plate located in the path of one of the pair of complementary diffraction orders, and a polarization beam splitter operable to combine the pair of complementary diffraction orders.

[0146] 13. The irradiation configuration module according to any one of clauses 8 to 12, wherein each of the diffraction orders includes a first diffraction order.

[0147] 14. The illumination configuration module according to any one of clauses 7 to 13, wherein the local spacing of the active region is such that the diffracted radiation includes substantially the same diffraction angle for each diffraction order for all wavelengths of interest included in the spectrally dispersed broadband radiation.

[0148] 15. The illumination configuration module according to any one of clauses 7 to 14, wherein the local spacing, the local wavelength, and the incident angle of the spectrally dispersed broadband radiation are configured such that for all wavelengths of interest, one diffraction order of the diffracted radiation propagates in the opposite direction as the incident spectrally dispersed broadband radiation.

[0149] 16. The irradiation configuration module according to Clause 15, wherein the beam dispersive element is also operable to recombine the back-propagating diffractive radiation.

[0150] 17. The illumination configuration module according to Clause 15 or 16, comprising a common lens arrangement for focusing the spectrally dispersed broadband radiation onto the active region and collecting the back-propagating diffracted radiation.

[0151] 18. The irradiation configuration module according to any one of clauses 6 to 14 is configured such that the spectrally dispersed broadband radiation has a substantially perpendicular incident incidence over the active region.

[0152] 19. The illumination configuration module according to any one of clauses 6 to 18, wherein the beam dispersive element comprises a prism or a grating.

[0153] 20. A radiation modulation device, comprising:

[0154] The active region includes alternating first and second reflective regions, with a configurable displacement between the first and second reflective regions in a direction perpendicular to the active region, thereby selectively forming a diffraction grating structure for selectively diffracting dispersed radiation incident on the active region.

[0155] The active region includes an adaptive reflectivity ratio, which describes the reflectivity of the first reflectivity region relative to the reflectivity of the second reflectivity region, and the adaptive reflectivity ratio minimizes the reflectivity difference between the first reflectivity region and the second reflectivity region.

[0156] 21. The radiation modulation apparatus according to clause 20, wherein the radiation modulation apparatus includes a grating light valve device; and

[0157] The first reflective region is a displaceable region, and the second reflective region is a fixed reflective region.

[0158] 22. The radiation modulation apparatus according to Clause 21, wherein the width of the first reflective region is different from the width of the second reflective region.

[0159] 23. The radiation modulation apparatus according to clause 21 or 22, wherein the width of the first reflective region is smaller than the width of the second reflective region.

[0160] 24. The radiation modulation apparatus according to Clause 21, wherein the reflectivity of the second reflective region is different from the reflectivity of the first reflective region.

[0161] 25. The radiation modulation apparatus according to clause 21 or 22, wherein the reflectivity of the second reflective region is less than that of the first reflective region.

[0162] 26. An illumination configuration module, comprising:

[0163] A beam dispersive element, which can be operated to receive and spectrally dispersed broadband radiation to obtain spectrally dispersed broadband radiation;

[0164] The radiation modulation apparatus according to any one of Clauses 20 to 25 is operable to receive spectrally dispersed broadband radiation over the active region and selectively spectrally modulate the dispersed broadband radiation to obtain output radiation.

[0165] 27. The illumination configuration module according to Clause 26, wherein the adaptive reflectivity ratio is constant across the active region.

[0166] 28. The illumination configuration module according to Clause 26 is configured such that the local adaptive reflectivity ratio is substantially dependent on the local wavelength of the spectrally dispersed broadband radiation incident on the active region.

[0167] 29. The illumination configuration module according to Clause 26, wherein the local adaptive reflectivity ratio varies substantially continuously over the active region.

[0168] 30. The illumination configuration module according to Clause 26, wherein the adaptive reflectivity ratio is locally configured for each wavelength of interest included in the broadband radiation with spectral dispersion.

[0169] 31. The irradiation configuration module according to any one of clauses 6 to 19 and 26 to 30 further includes a broadband radiation source operable to provide the broadband radiation.

[0170] 32. A measurement device comprising a radiation modulation device according to any one of clauses 1 to 5 and 20 to 25, or an irradiation configuration module according to any one of clauses 6 to 19 and 26 to 30, said measurement device being operable to use the output irradiation beam as a measurement irradiation.

[0171] 33. The measuring device according to Clause 32, wherein the measuring device includes a scatterometer, an interferometer, or a holographic microscope.

[0172] 34. The measuring device according to clause 32 or 33, wherein the measuring device includes an alignment sensor or a level sensor.

[0173] While this article can specifically mention the use of photolithography equipment in IC manufacturing, it should be understood that the photolithography equipment described herein can have other applications. Other potential applications include the fabrication of integrated optical systems, the guiding and detection of patterns in magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc.

[0174] Although embodiments of the invention may be specifically referred to herein in the context of a lithography apparatus, embodiments of the invention can also be used in other apparatuses. Embodiments of the invention may form part of a mask inspection apparatus, metrology equipment, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses are generally referred to as lithography tools. Such lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0175] Although the embodiments of the present invention may be specifically mentioned above in the context of optical lithography, it should be understood that, where the context permits, the present invention is not limited to optical lithography, but may also be used in other applications, such as imprint lithography.

[0176] While specific embodiments of the invention have been described above, it should be understood that the invention can be practiced in ways other than those described. The foregoing description is intended to illustrate and not limit. Therefore, those skilled in the art will understand that modifications can be made to the invention without departing from the scope of the following claims.

Claims

1. A radiation modulation device, comprising: The active region includes alternating first and second reflection regions, the first and second reflection regions including configurable displacements between the first and second reflection regions in a direction perpendicular to the active region, thereby selectively forming a diffraction grating structure for selectively diffracting dispersed radiation incident on the active region. The active region includes an adaptive reflectivity ratio, which describes the reflectivity of the first reflective region relative to the reflectivity of the second reflective region, and the adaptive reflectivity ratio minimizes the reflectivity difference between the first reflective region and the second reflective region.

2. The radiation modulation device according to claim 1, wherein the radiation modulation device includes a grating light valve device; and The first reflective region is a displaceable region, and the second reflective region is a fixed reflective region.

3. The radiation modulation device according to claim 2, wherein the width of the first reflective region is different from the width of the second reflective region.

4. The radiation modulation device according to claim 2 or 3, wherein the width of the first reflective region is smaller than the width of the second reflective region.

5. The radiation modulation device according to claim 2, wherein the reflectivity of the second reflective region is different from the reflectivity of the first reflective region.

6. The radiation modulation device according to claim 2 or 3, wherein the reflectivity of the second reflective region is less than the reflectivity of the first reflective region.

7. An irradiation configuration module, comprising: A beam dispersive element, which can be operated to receive and spectrally dispersed broadband radiation to obtain spectrally dispersed broadband radiation; The radiation modulation apparatus according to any one of claims 1 to 6 is operable to receive the spectrally dispersed broadband radiation over the active region and selectively spectrally modulate the dispersed broadband radiation to obtain output radiation.

8. The illumination configuration module according to claim 7, wherein the adaptive reflectivity ratio is constant across the active region.

9. The illumination configuration module of claim 7, configured such that the local adaptive reflectivity ratio is substantially dependent on the local wavelength of the spectrally dispersed broadband radiation incident on the active region.

10. The illumination configuration module according to claim 7, wherein the local adaptive reflectivity ratio varies substantially continuously over the active region.

11. The illumination configuration module of claim 7, wherein the adaptive reflectivity is locally configured for each wavelength of interest included in the spectrally dispersed broadband radiation.

12. The irradiation configuration module according to any one of claims 7 to 11, It also includes broadband radiation sources that can be operated to provide the broadband radiation.

13. A measurement device comprising a radiation modulation device according to any one of claims 1 to 6, or an irradiation configuration module according to any one of claims 7 to 12, the measurement device being operable to use the output irradiation beam as a measurement irradiation for measurement.

14. The measuring device according to claim 13, wherein the measuring device includes a scatterometer, an interferometer, or a holographic microscope.

15. The measuring device according to claim 13 or 14, wherein the measuring device includes an alignment sensor or a level sensor.

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