Color selection module

Abstract

A color selection module for outputting radiation with a desired spectral bandwidth and center wavelength includes: a radiation input for receiving an input radiation beam; a first dispersion device for receiving the input radiation beam from the radiation input and outputting the first dispersive radiation beam; a second dispersion device for receiving at least a portion of the first dispersive radiation beam and outputting the second dispersive radiation beam; and a radiation output device for receiving the second dispersive radiation beam and outputting the second dispersive radiation beam from the color selection module, wherein rotation of the second dispersion device changes a second direction of travel and a second spatial distribution of the second dispersive radiation beam, and thus changes the spectral bandwidth and center wavelength of the second dispersive radiation beam received and output by the radiation output device.

Description

Cross-reference to related applications

[0001] This application claims priority to EP application 24150650.0, filed on January 8, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a color selection module. The color selection module can be integrated into a measurement tool. The color selection module and / or the measurement tool can be integrated into a photolithography apparatus. This invention also relates to related methods. Background Technology

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

[0004] Measurement tools such as scatterometers, topography measurement systems, or position measurement systems are used to measure the properties of a substrate. Measurements can be performed after substrate exposure. These measurements can be used to adjust the operation of the photolithography equipment used for substrate exposure to improve pattern reproduction. Adjustments may include modifying the illumination scheme and / or adjusting the projection optics.

[0005] The radiation characteristics used by a measurement tool can affect the type and quality of measurements that can be performed. For some applications, it may be advantageous to use multiple radiation frequencies to measure a substrate, for example, broadband radiation. Multiple different frequencies can propagate, illuminate, and scatter away from the measurement target with little or no interference to other frequencies. Therefore, different frequencies can be used, for example, to obtain more measurement data. Different frequencies can be provided, for example, as a sequence of different frequencies (i.e., a series of frequencies). Different radiation frequencies can also interrogate and discover different characteristics of the measurement target. Broadband radiation can be used in measurement systems such as level sensors, alignment mark measurement systems, scattering measurement tools, or inspection tools. Broadband radiation sources can be hypercontinuum sources.

[0006] The controllable color selection module can be used to select a desired narrowband radiation from broadband radiation, use this narrowband radiation to illuminate the substrate for measurement, and then select another desired narrowband radiation to illuminate the substrate for subsequent measurements. The color selection module can be used to select the center wavelength and spectral bandwidth of the desired narrowband radiation.

[0007] Existing color selection modules may include a pair of color wheels through which broadband radiation is guided to produce desired narrowband radiation. Each color wheel can be considered as a multilayer (spectral) filter whose characteristics vary with its angular position around the color wheel. By controlling the angular position of each color wheel, the characteristics of the portion of the broadband radiation passing through each color wheel are controlled, and thus the characteristics of the narrowband radiation produced by the color wheels and therefore the color selection module can be controlled.

[0008] The drawback of existing color selection modules that include a color wheel is that changing the position of the color wheel and thus the desired narrowband radiation is difficult and / or slow. This has the effect of reducing the speed / throughput of the metrology tool, and therefore reducing the speed / throughput of the lithography equipment to which the metrology tool is part.

[0009] This invention provides a color selection module that overcomes the shortcomings of existing color selection modules, both those discussed above and others. This invention also provides an alternative color selection module. Summary of the Invention

[0010] According to a first aspect of the present invention, a color selection module is provided for outputting radiation having a desired spectral bandwidth and center wavelength, comprising: a radiation input for receiving an input radiation beam; A first dispersion device is configured to receive an input radiation beam from a radiation input and output a first dispersive radiation beam; a second dispersion device is configured to receive at least a portion of the first dispersive radiation beam and output a second dispersive radiation beam; a radiation output device is configured to receive at least a portion of the second dispersive radiation beam and output at least a portion of the second dispersive radiation beam from a color selection module; wherein a portion of the first dispersion device is coupled to a first actuator for rotating the portion of the first dispersion device; and a portion of the second dispersion device is coupled to a second actuator for rotating the portion of the second dispersion device, whereby the rotation of the portion of the second dispersion device changes a second direction of travel and a second spatial distribution of the second dispersive radiation beam, and thus changes the spectral bandwidth and center wavelength of the at least portion of the second dispersive radiation beam received and output by the radiation output device.

[0011] In use, a portion of the first dispersive device can be rotated to a first angular position by a first actuator, and a portion of the second dispersive device can be rotated to a second angular position by a second actuator, such that the spectral bandwidth and center wavelength of at least a portion of the second dispersive radiation beam received and output by the radiation output device correspond to the desired spectral bandwidth and center wavelength.

[0012] The spectral bandwidth and center wavelength of at least a portion of the second dispersive radiation beam can define the wavelength band of at least a portion of the second dispersive radiation beam.

[0013] In the case where a portion of the first dispersive device is coupled to the first actuator, and a portion of the second dispersive device is coupled to the second actuator, the respective actuator can be mechanically linked to the respective portion via a linkage through this coupling. Alternatively, the respective actuator can be indirectly connected to the respective portion, for example, via a magnet.

[0014] Rotation of the portion of the first dispersive apparatus can change the first incident angle of the input radiation beam on the portion of the first dispersive apparatus.

[0015] Rotation of the portion of the first dispersive device can change the first direction of travel and the first spatial distribution of the first dispersive radiation beam.

[0016] Rotation of the portion of the second dispersive apparatus can change the second angle of incidence of the first dispersive radiation beam on the portion of the second dispersive apparatus.

[0017] The first dispersive device may include a prism, and the portion of the first dispersive device may be the prism.

[0018] The first dispersion device may include a reflection grating, and the portion of the first dispersion device may be the reflection grating.

[0019] The first dispersion device may include a transmission grating, and the portion of the first dispersion device may be the transmission grating.

[0020] The first dispersion device may include a transmission grating that receives an input radiation beam and outputs a first intermediate dispersion beam incident on a first dispersion reflector, the first dispersion reflector outputting the first dispersion radiation beam; and wherein the portion of the first dispersion device may be the first dispersion reflector.

[0021] The second dispersion device may include a second prism, and the portion of the second dispersion device may be the second prism.

[0022] The second dispersion device may include a second reflection grating, and the portion of the second dispersion device may be the second reflection grating.

[0023] The second dispersion device may include a second transmission grating, and the portion of the second dispersion device may be the second transmission grating.

[0024] The second dispersion device may include a second transmission grating that receives at least a portion of the first dispersive radiation beam and outputs a second intermediate dispersive beam incident on a second dispersive reflector, the second dispersive reflector outputting the second dispersive radiation beam; and wherein the portion of the second dispersion device may be the second dispersive reflector.

[0025] The radiation output device may include a spatial filter through which at least a portion of the second dispersive radiation beam passes.

[0026] Spatial filters can be apertures.

[0027] The radiation output device may further include an output reflector for receiving at least a portion of the second dispersive radiation beam traveling in a third direction of travel, and for outputting the received at least a portion of the second dispersive radiation beam in a fourth direction of travel, different from the third direction of travel, once the at least a portion of the second dispersive radiation beam has passed through the aperture.

[0028] The output reflector can be coupled to a third actuator for rotating the output reflector, thereby changing the third angle of incidence of at least a portion of the second dispersive radiation beam on the output reflector, and thus changing the fourth direction of travel of the radiation output from the output reflector.

[0029] The third actuator can be mechanically linked to the output reflector via a linkage. Alternatively, the third actuator can be indirectly linked to the output reflector, for example, via a magnet.

[0030] The radiation output device may further include a retroreflector for receiving at least a portion of the second dispersive radiation beam traveling in a third direction of travel, and for outputting the received at least a portion of the second dispersive radiation beam in a fourth direction of travel opposite to the third direction of travel once the at least a portion of the second dispersive radiation beam has passed through the aperture.

[0031] The radiation output device may further include a second reflector for receiving, after at least a portion of the second dispersive radiation beam output from the retroreflector has interacted with the second dispersive device and the first dispersive device, the at least portion of the second dispersive radiation beam output from the retroreflector, and thereby outputting a recombined beam having a beam path different from that of the input radiation beam. In this document, "different from" can mean not parallel to.

[0032] At least one of the first actuator and the second actuator, or both the first actuator and the second actuator, may include a galvanometer mechanism.

[0033] According to a second aspect of the present invention, a measuring tool is provided that includes a color selection module as described in the foregoing aspects of the present invention.

[0034] A color selection module for outputting radiation with a desired spectral bandwidth and center wavelength, and a measurement tool operable to use the radiation as an illumination source for measuring structures or patterns on a substrate.

[0035] According to a third aspect of the present invention, a photolithography apparatus is provided, comprising a color selection module according to a first aspect of the present invention or a measurement tool according to a second aspect of the present invention.

[0036] According to a fourth aspect of the present invention, a method is provided for operating a color selection module to output radiation having a desired spectral bandwidth and center wavelength, the color selection module comprising: receiving an input radiation beam; a first dispersion device receiving the input radiation beam from the radiation input and outputting a first dispersive radiation beam; a second dispersion device receiving at least a portion of the first dispersive radiation beam and outputting a second dispersive radiation beam; a radiation output device receiving at least a portion of the second dispersive radiation beam and outputting the at least a portion of the second dispersive radiation beam from the color selection module; rotating a portion of the first dispersion device to a first angular position; rotating a portion of the second dispersion device to a second angular position; and setting the first angular position of the portion of the first dispersion device and the second angular position of the portion of the second dispersion device based on the desired spectral bandwidth and center wavelength.

[0037] Rotation of the portion of the first dispersive apparatus can change the first incident angle of the input radiation beam on the portion of the first dispersive apparatus.

[0038] Rotation of the portion of the second dispersive apparatus can change the second angle of incidence of the first dispersive radiation beam on the portion of the second dispersive apparatus.

[0039] The desired spectral bandwidth and center wavelength can define the desired radiation wavelength band.

[0040] The color selection module may include a radiation input that receives the input radiation beam.

[0041] The portion of the first dispersion device can be coupled to a first actuator, which rotates the portion of the first dispersion device to a first angular position.

[0042] The portion of the second dispersion device can be coupled to a second actuator, which rotates the portion of the second dispersion device to a second angular position.

[0043] Rotation of the portion of the first dispersive device can change the first direction of travel and the first spatial distribution of the first dispersive radiation beam.

[0044] Rotation of the portion of the second dispersive device can change the second direction of travel and the second spatial distribution of the second dispersive radiation beam, thereby changing the spectral bandwidth and center wavelength of at least a portion of the second dispersive radiation beam received and output by the radiation output device.

[0045] The different aspects of this invention can be combined together. Attached Figure Description

[0046] Embodiments of the invention will now be described by way of example only, with reference to the accompanying schematic diagrams, wherein: Figure 1 A schematic diagram of a photolithography device is depicted; Figure 2 A schematic diagram of the photolithography unit is shown; Figure 3 A schematic diagram of overall photolithography is depicted, illustrating the collaboration between three key technologies for optimizing semiconductor manufacturing; Figure 4 A schematic diagram of the scatterer is shown; Figure 5 A schematic diagram of a level sensor is depicted. Figure 6 The alignment sensor is described; Figure 7 A schematic diagram depicting a known type of color selection module is provided. Figure 8 A schematic diagram depicting a first embodiment of the color selection module according to the present invention is shown; Figure 9 A schematic diagram of a second embodiment of the color selection module according to the present invention, viewed from above, is depicted. Figure 9a It depicts a view from the side. Figure 9 An example of a color selection module is shown; Figure 10 Depicting what can be used for Figure 8 and 9 An illustrative model for modeling the performance parameters of the embodiments shown; Figures 11 to 16 Depicting the use Figure 10 The schematic model depicted in the figure shows the spectral bandwidth versus center wavelength curves for several arrangements. Figure 17 A schematic diagram illustrating a third embodiment of the color selection module according to the present invention is shown; Figure 18A schematic diagram depicting a fourth embodiment of the color selection module according to the present invention; and Figure 19 A schematic diagram of a fifth embodiment of the color selection module according to the present invention is depicted. Detailed Implementation

[0047] To project patterns onto a substrate, photolithography equipment can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Typical wavelengths currently used are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Compared to photolithography equipment using radiation with a wavelength of, for example, 193 nm, photolithography equipment using extreme ultraviolet (EUV) radiation in the 4-20 nm range, such as 6.7 nm or 13.5 nm, can be used to form smaller features on the substrate.

[0048] Low-k1 lithography can be used to process features smaller than the traditional resolution limits of lithography equipment. In this process, the resolution formula can be expressed as CD = k1 × λ / NA, where λ is the radiation wavelength used, NA is the numerical aperture of the projection optics in the lithography equipment, 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 resemble the shape and size designed by the circuit designer in order to achieve specific electrical functions and performance. To overcome these difficulties, complex fine-tuning steps can be applied to the lithography projection equipment 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, a tight control loop used to control the stability of the lithography equipment can be used to improve pattern reproduction at low k1.

[0049] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., with wavelengths of 365, 248, 193, 157, or 126 nm) and EUV (extreme ultraviolet radiation, e.g., with wavelengths in the range of about 5–100 nm).

[0050] 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 an incident radiation beam with a patterned cross-section corresponding to a pattern to be created in a target portion of a substrate. The term "optical valve" may also be used herein. Examples of such patterning devices, besides classic masks (transmission or reflection, binary, phase-shifting, hybrid, etc.), include programmable mirror arrays and programmable LCD arrays.

[0051] 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 resist-coated wafer) 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., including one or more dies) of the substrate W.

[0052] In operation, the irradiation system IL receives a radiation beam from the radiation source SO, for example, via a beam delivery system BD. The irradiation system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for guiding, shaping, and / or controlling the radiation. The irradiator IL can be used to adjust the radiation beam B to have a desired spatial and angular intensity distribution in a cross-section at the plane of the patterning device MA.

[0053] The term "projection system" PS as used herein should be interpreted broadly to include all types of projection systems, including refractive, reflective, anti-refractive, distorting, magnetic, electromagnetic, and / or electrostatic optical systems, or any combination thereof, suitable for the exposure radiation used, and / or suitable for other factors 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.

[0054] A lithography apparatus LA can be of the type in which at least a portion of the substrate can be covered by a liquid (e.g., water) with a relatively high refractive index to fill the space between the projection system PS and the substrate W; this is also known as immersion lithography. More information on immersion techniques is given in US6952253, which is incorporated herein by reference.

[0055] The lithography equipment LA can also be of the type with 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 subsequent exposure steps for preparing the substrate W can be performed on the substrate W located on one of the substrate supports WT, while another substrate W on another substrate support WT is used to expose a pattern on another substrate W.

[0056] In addition to the substrate support WT, the lithography apparatus LA may include a measurement stage. The measurement stage is arranged to hold sensors and / or cleaning devices. The sensors may be arranged to measure characteristics of the projection system PS or the radiation beam B. The measurement stage may accommodate multiple sensors. The cleaning devices may be arranged to clean part of the lithography apparatus, such as part of the projection system PS or part of a system providing immersion liquid. The measurement stage may move below the projection system PS as the substrate support WT leaves the projection system PS.

[0057] In operation, a radiation beam B is incident on a patterning device (e.g., a mask) MA held on a mask support MT, and a pattern is formed by the pattern (design layout) present on the patterning device MA. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be moved precisely, 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 occupy dedicated target portions, they can be located in the space between the target portions. When the substrate alignment marks P1, P2 are located between the target portions C, they are referred to as scribe-lane alignment marks.

[0058] like Figure 2As shown, a lithography apparatus LA can form part of a lithography unit LC, sometimes also called a lithocell or (lithography) cluster. The lithography unit LC typically also includes equipment for performing pre- and post-exposure processes on a substrate W. Conventionally, these include a spin coater SC to deposit a resist layer, a developer DE to develop the exposed resist, a cooling plate CH, and a baking plate BK, for example, to regulate the temperature of the substrate W, and for example, to regulate the solvent in the resist layer. A substrate processor or robot RO picks up the substrate W from input / output ports I / O1, I / O2, moves the substrate W between different processing devices, and delivers the substrate W to the loading chamber LB of the lithography apparatus LA. Devices in the lithography unit, often collectively referred to as a track, are typically under the control of 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 a lithography control unit LACU.

[0059] To ensure that the substrate W exposed by the lithography equipment LA is exposed correctly and consistently, it is desirable 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, inspection tools (not shown) may be included in the lithography unit LC. If an error is detected, adjustments can be made, for example, to the exposure of subsequent substrates or to other processing steps to be performed on the substrate W, especially if the inspection is performed before other substrates W in the same batch or lot are still to be exposed or processed.

[0060] Inspection equipment, also known as a measurement tool, 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. Alternatively, the inspection equipment can be configured to identify defects on the substrate W and can be, for example, part of a photolithography unit LC, integrated into a photolithography apparatus LA, or even a stand-alone device. The inspection equipment can measure characteristics on latent images (images in the resist layer after exposure), or semi-latent images (images in the resist layer after the post-exposure baking (PEB) step), or 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).

[0061] Typically, the patterning process in photolithography (LA) equipment is one of the most critical steps in the process, requiring high precision in the size and arrangement of structures on the substrate W. To ensure this high precision, three systems can be combined in a single assembly, such as... Figure 3The diagram illustrates a so-called "holistic" control environment. 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 entire 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 range of process parameters (e.g., dose, focus, overlay) within which a particular manufacturing process produces a defined result (e.g., a functional semiconductor device)—typically allowing process parameters in the lithography or patterning process to vary within this range.

[0062] The computer system CL can use (partially) the design layout to be patterned to predict which resolution enhancement techniques to use and perform computational lithography simulations and calculations to determine which mask layouts and lithography equipment settings will achieve the maximum overall process window (within) the patterning process. Figure 3 (Depicted by double arrows in the first scale SC1). Typically, resolution enhancement techniques are configured to match the patterning possibilities of the lithography equipment LA. The computer system CL can also be used to detect where within the process window the lithography equipment LA is currently operating (e.g., using input from the metrology tool MT) is, for example, due to suboptimal processing (in... Figure 3 (The arrow pointing to "0" in the second scale SC2) may be defective.

[0063] The measurement tool (MT) can provide input to the computer system (CL) for accurate simulation and prediction, and can provide feedback to the lithography equipment (LA) to identify potential drift, for example, in the calibration state of the lithography equipment (LA). Figure 3 (Depicted by multiple arrows in the third scale SC3).

[0064] In photolithography, the created structure requires frequent measurements, for example, for process control and verification. The tools used to perform such measurements are commonly referred to as metrology tools (MTs). Different types of metrology tools (MTs) for such measurements are known, including scanning electron microscopes or various forms of scattering metrology tools (MTs). A scatterometer is a versatile instrument that can measure parameters of the photolithography process by mounting a sensor in the pupil of the scatterometer objective or in a plane conjugate to the pupil (commonly referred to as pupil-based measurement) or by mounting a sensor in the image plane or a plane conjugate to the image plane (in which case the measurement is commonly 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 scatterer can use light from soft X-rays and the visible to near-infrared wavelength range to measure gratings.

[0065] In the first embodiment, the scatterer MT is an angle-resolved scatterer. In such a scatterer, 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.

[0066] In the second embodiment, the scatterer MT is a spectroscopic scatterer MT. In this spectroscopic scatterer MT, radiation emitted by a radiation source is directed onto the target, and reflected or scattered radiation from the target is directed to a spectroscopic detector that measures the spectrum of specularly reflected radiation (i.e., the intensity as a function of wavelength). Based on this 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.

[0067] In the third embodiment, the scatterer MT is an elliptic scatterer. An elliptic scatterer allows the determination of lithography process parameters by measuring the scattered radiation for each polarization state. This metrology device emits polarized light (such as linear, circular, or elliptical) by using an appropriate polarization 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 scatterers are described in U.S. Patent Applications 11 / 451,599, 11 / 708,678, 12 / 256,780, 12 / 486,449, 12 / 920,968, 12 / 922,587, 13 / 000,229, 13 / 033,135, 13 / 533,110, and 13 / 891,410, the entire contents of which are incorporated herein by reference.

[0068] In one embodiment of a scattering instrument (MT), the MT is adapted to measure the overlay error between two misaligned gratings or periodic structures by measuring the reflectance spectrum and / or detecting 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 scattering instrument 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 error between two layers targeting a periodic structure by means of asymmetry can be found in PCT patent application publication WO 2011 / 012624 or U.S. patent application US 20160161863 (the entire contents of which are incorporated herein by reference).

[0069] Other parameters of interest may be focus and dose. Focus and dose can be determined simultaneously by scattering measurements (or 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 size and sidewall angle measurements at each point in the focusing energy matrix (FEM, also known as the focusing exposure matrix). If these unique combinations of critical size and sidewall angles are available, the focus and dose values ​​can be uniquely determined from these measurements.

[0070] The measurement target can be an assembly of composite gratings formed by photolithography, primarily in a resist, but also after etching. 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 offset 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 process. The target can have small sub-segments configured to mimic the dimensions of functional portions of the design layout within the target. Due to these sub-segments, the target's behavior will be more similar to the functional portions of the design layout, thus allowing for a better approximation of the overall process parameter measurements to the functional portions of the design layout. The target can be measured in underfill or overfill modes. In underfill mode, the spot generated by the measurement beam is smaller than the overall target. In overfill mode, the spot generated by the measurement beam is larger than the entire target. In this overfill mode, different targets can also be measured simultaneously, allowing for the simultaneous determination of different processing parameters.

[0071] 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 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 for selecting 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.

[0072] Figure 4 A measurement device such as a scatterer SM1 is described. 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 specularly reflected radiation (i.e., the intensity In1 as a function of wavelength λ). Based on this data, it can be processed by a processing unit PU, for example through rigorous coupled-wave analysis and nonlinear regression, or through... Figure 4The simulated spectral library shown at the bottom is compared to reconstruct the structure or profile of the detected spectrum. Typically, for reconstruction, the general form of the structure is known, and some parameters are assumed based on knowledge of the structure manufacturing process, leaving only a few parameters of the structure determined from the scattering measurement data. This scatterometer can be configured as a vertically incident scatterometer or an obliquely incident scatterometer.

[0073] In photolithography, it is desirable to frequently measure the resulting structure, for example, for process control and verification. Various tools are known for performing such measurements, including scanning electron microscopes or various forms of metrology equipment, such as scatterometers. Examples of known scatterometers typically depend on providing a specific measurement target, such as an underfilled target (a target in the form of a simple grating or overlapping gratings in different layers, large enough that the measurement beam generates a spot smaller than the grating) or an overfilled target (whereby the spot partially or completely encloses the target). Furthermore, the use of metrology tools, such as angle-resolved scatterometers illuminating underfilled targets like gratings, allows for the use of so-called reconstruction methods, where the characteristics of the grating can be calculated by simulating the interaction of scattered radiation using a mathematical model of the target structure and comparing the simulation results with the measurement results. The parameters of the model are adjusted until the simulated interaction produces a diffraction pattern similar to that observed from a real target.

[0074] A scatterometer is a general-purpose instrument that allows for the measurement of parameters of a photolithography process by means of a sensor located in the pupil or in a plane conjugate to the pupil of the scatterometer's objective lens; such measurements are typically referred to as pupil-based measurements. Alternatively, parameters can be measured by means of a sensor located in the image plane or in a plane conjugate to the image plane; in this case, the measurements are typically referred to as image- or field-based measurements. Such scatterometers and related measurement techniques are further described in patent applications US20100328655, US2011102753A1, US20120044470A, US20110249244, US20110026032, or EP1,628,164A, all of which are incorporated herein by reference. The aforementioned scatterometers can measure multiple targets from multiple gratings in a single image using light from soft X-rays and visible near-IR wavelengths.

[0075] A topography measurement system, which can be integrated into a photolithography apparatus, is configured with a horizontal or height sensor to measure the topography of the top surface of a substrate (or wafer). A topography map of the substrate (also known as a height map) can be generated from these measurements, which represent the substrate height as a function of position on the substrate. This height map can then be used to correct the substrate position during pattern transfer on the substrate to provide a spatial image of the patterning apparatus at the appropriate focus position on the substrate. It should be understood that “height” as used herein refers to a generalized dimension from the plane to the substrate (also known as the Z-axis). Typically, the horizontal 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 horizontal or height sensor results in a height measurement at a position on the substrate.

[0076] exist Figure 5 The image schematically depicts an example of a horizontal or vertical sensor LS known in the art. Figure 5 Only the operating principle is described. In this example, the horizontal sensor includes an optical system comprising a projection unit LSP and a detection unit LSD. The projection unit LSP includes a radiation source LSO that provides a radiation beam LSB, which is provided by a projection grating PGR of the projection unit LSP. The radiation source LSO can be, for example, a narrowband or broadband radiation source, such as a supercontinuum light source, polarized or unpolarized, pulsed or continuous, such as a polarized or unpolarized laser beam. The radiation source LSO can include multiple radiation sources with different colors or wavelength ranges, such as multiple LEDs. The radiation source LSO of the horizontal 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.

[0077] The projection grating (PGR) is a periodic grating comprising a periodic structure that results in a periodically varying intensity of the radiation beam BE1. The radiation beam BE1 with its periodically varying intensity is guided to a measurement position MLO on a substrate W, the substrate W having an incident angle ANG between 0 and 90 degrees, typically between 70 and 80 degrees, relative to an axis perpendicular to the incident substrate surface (Z-axis). At the measurement position MLO, the patterned radiation beam BE1 is reflected by the substrate W (indicated by arrow BE2) and directed to the detection unit LSD.

[0078] 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 a projection grating PGR. The detector DET generates a detector output signal representing the received light, such as representing 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.

[0079] 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 has a periodicity that is particularly dependent on the design of the projection grating PGR and the (tilted) incident angle ANG.

[0080] The projection unit LSP and / or the detection unit LSD may include additional 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.

[0081] 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.

[0082] To effectively cover the surface of substrate W, a horizontal sensor LS can be configured to project an array of measurement beams BE1 onto the surface of substrate W, thereby generating an array of measurement regions MLO or spots that cover a larger measurement range.

[0083] For example, US7265364 and US7646471 disclose various height sensors of general types, both of which are incorporated herein by reference. US2010233600A1 discloses a height sensor that uses UV radiation instead of visible or infrared radiation, which is also incorporated herein by reference. WO2016102127A1, incorporated by reference, describes a compact height sensor that uses a multi-element detector to detect and identify the position of a grating image without requiring the detection of the grating itself.

[0084] A position measurement system (PMS) can include any type of sensor suitable for determining the position of a substrate stage WT. A position measurement system (PMS) can include any type of sensor suitable for determining the position of a mask support MT. The sensor can be an optical sensor, such as an interferometer or encoder. A position measurement system (PMS) can include a combined system of interferometers and encoders. The sensor can be another type of sensor, such as a magnetic sensor, a capacitive sensor, or an inductive sensor. The position measurement system (PMS) can determine the position relative to a reference (e.g., a measurement frame MF or a projection system PS). The position measurement system (PMS) can determine the position of the substrate stage WT and / or the mask support MT by measuring the position or by measuring the time derivative of the position (e.g., velocity or acceleration).

[0085] A position measurement system (PMS) may include an encoder system. For example, an encoder system is known from U.S. Patent Application US2007 / 0058173A1, filed September 7, 2006, which is incorporated herein by reference. The encoder system includes an encoder head, a grating, and a sensor. The encoder system can receive a primary radiation beam and a secondary radiation beam. The primary and secondary radiation beams originate from the same radiation beam, i.e., the original radiation beam. At least one of the primary and secondary radiation beams is created by diffracting the original radiation beam using a grating. If the primary and secondary radiation beams are created by diffracting the original radiation beam using a grating, the primary radiation beam needs to have a different diffraction order than the secondary radiation beam. Different diffraction orders are, for example, +1, -1, +2, and -2 orders. The encoder system optically combines the primary and secondary radiation beams into a combined radiation beam. A sensor in the encoder head determines the phase or phase difference of the combined radiation beam. The sensor generates a signal based on the phase or phase difference. This signal represents the position of the encoder head relative to the grating. One of the encoder head and the grating can be disposed on the substrate structure WT. The other of the encoder head and the grating can be disposed on the measurement frame MF or the base frame BF. For example, multiple encoder heads are disposed on the measurement frame MF, and the grating is disposed on the top surface of the substrate support WT. In another example, the grating is disposed on the bottom surface of the substrate support WT, and the encoder head is disposed below the substrate support WT.

[0086] A position measurement system (PMS) may include an interferometer system. Interferometer systems are known, for example, from U.S. Patent 6,020,964, filed July 13, 1998, which is incorporated herein by reference. An interferometer system may include a beam splitter, a mirror, a reference mirror, and a sensor. A radiation beam is split into a reference beam and a measurement beam by the beam splitter. The measurement beam propagates to the mirror and is reflected back to the beam splitter. The reference beam propagates to the reference mirror and is reflected back to the beam splitter. At the beam splitter, the measurement beam and the reference beam are combined into a combined radiation beam. The combined radiation beam is incident on the sensor. The sensor determines the phase or frequency of the combined radiation beam. The sensor generates a signal based on the phase or frequency. This signal represents the displacement of the mirror. In one embodiment, the mirror is connected to a substrate support WT. The reference mirror may be connected to a measurement frame MF. In one embodiment, the measurement beam and the reference beam are combined into a combined radiation beam by additional optical components instead of a beam splitter.

[0087] In the fabrication of complex devices, numerous photolithographic patterning steps are typically performed to form functional features in successive layers on a substrate. Therefore, a key aspect of the performance of a photolithography apparatus is its ability to correctly and accurately align the applied pattern relative to features arranged in previous layers (using the same or different photolithography apparatuses). For this purpose, the substrate has one or more sets of markers. Each marker is a structure whose position can be measured at a later time using a position sensor (typically an optical position sensor). The position sensor may be called an "alignment sensor," and the marker may be called an "alignment marker." The marker can also be referred to as a measurement target.

[0088] Photolithography apparatuses may include one or more alignment sensors that can precisely measure the position of alignment marks formed on a substrate. Alignment (or position) sensors can use optical phenomena such as diffraction and interference to obtain position information from alignment marks formed on the substrate. Examples of alignment sensors used in current photolithography apparatuses are based on self-reference interferometers as described in US6961116. Various enhancements and modifications of position sensors have been developed, for example, as disclosed in US2015261097A1. The contents of all these publications are incorporated herein by reference.

[0089] Markings or alignment marks may comprise a series of bars formed on or therein of a layer provided on a substrate, or (directly) formed in the substrate. These bars may be regularly spaced and function as grating lines, such that the mark can be considered a diffraction grating with a well-known spatial period (spacing). Depending on the orientation of these grating lines, the mark can be designed to allow measurement of position along the X-axis or along the Y-axis (with its orientation substantially perpendicular to the X-axis). Markings comprising bars arranged at +45 degrees and / or -45 degrees relative to the X- and Y-axis allow for combined X- and Y-measurements using techniques as described in US2009 / 195768A, which is incorporated herein by reference.

[0090] The alignment sensor uses a radiating point optical scan to obtain a periodically changing signal, such as a sine wave. The phase of this signal is analyzed to determine the position of the mark, and thus the position of the substrate relative to the alignment sensor, which is fixed relative to a reference frame of the photolithography apparatus. So-called coarse and fine marks, associated with different (coarse and fine) mark sizes, can be provided, allowing the alignment sensor to distinguish different periods of the periodic signal, and the precise position (phase) within each period. Marks with different pitches can also be used for this purpose.

[0091] The location of the measurement marks can also provide information about the deformation of the substrate on which the marks are set, for example, in the form of a wafer grating. The deformation of the substrate can occur, for example, by electrostatically clamping the substrate to a substrate stage and / or by heating the substrate when it is exposed to radiation.

[0092] Figure 6 This is a schematic block diagram of an embodiment of a known alignment sensor AS, such as that described in US6961116, which is incorporated herein by reference. A radiation source RS0 provides a radiation beam RB of one or more wavelengths, which is directed by a steering optics onto a mark, such as a mark AM located on a substrate W, as an illumination spot SP. In this example, the steering optics include a spot mirror SM and an objective lens OL. The diameter of the illumination spot SP illuminating the mark AM may be slightly smaller than the width of the mark itself.

[0093] The radiation diffracted by the marker AM is collimated (in this case, by the objective lens OL) into an information-carrying beam IB. The term "diffraction" is intended to include zero-order diffraction from the marker (which may be referred to as reflection). A self-referenced interferometer SRI, such as the type disclosed in US6961116 mentioned above, causes the beam IB to interfere with itself, after which the beam is received by a photodetector PD. Additional optics (not shown) may be included to provide a separated beam if the radiation source RSO creates more than one wavelength. The photodetector may be a single element, or it may include multiple pixels if desired. The photodetector may include a sensor array.

[0094] Steering optics (in this example, a spot mirror SM) can also be used to block zero-order radiation reflected from the markers, so that the information-carrying bundle IB includes only higher-order diffraction radiation from the marker AM (which is not necessary for measurement but improves the signal-to-noise ratio).

[0095] The intensity signal SI is provided to the processing unit PU. Through optical processing in the combined 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.

[0096] A single measurement of the type shown fixes the mark's position within a specific range corresponding to one pitch of the mark. Coarser measurement techniques are used in conjunction with this to identify which period of the sine wave contains the mark's position. The same coarser and / or finer-level process can be repeated at different wavelengths to improve the mark's accuracy and / or robustly detect it, regardless of the material on which the mark is made and the material on and / or beneath it. Wavelengths can be optically multiplexed and demultiplexed for simultaneous processing, and / or they can be multiplexed via time-division or frequency-division multiplexing.

[0097] In this example, the alignment sensor and spot 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 the direction opposite to the direction of movement of the substrate W. The movement of the substrate W is controlled by mounting the substrate W 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 on the substrate support allows calibration of the substrate support position determined by the position sensor (e.g., relative to the frame to which the alignment system is attached). Measuring the position of the alignment marks on the substrate allows determination of the substrate position relative to the substrate support.

[0098] Measurement and / or inspection tools (also known as measuring instruments), such as those described above, typically use radiation to obtain measurement data. Different types of radiation can be used depending on the target being measured and the characteristics to be measured. One distinct characteristic of radiation is the wavelength used to obtain the measurement, as different wavelengths can provide different information about the target being measured. Some measuring instruments can use broadband radiation, such as supercontinuum radiation, to perform measurements using broadband radiation, or can tune and select one or more measurement wavelengths(s) to be used. Broadband radiation can be obtained using different methods depending on the range of output wavelengths and the characteristics of the broadband source. In some implementations for generating broadband radiation, nonlinear effects can be used to broaden the narrow wavelength range of the input radiation (also known as pump radiation). Different known setups and methods exist for achieving nonlinear broadening. Typically, these methods rely on limiting the pump radiation to achieve the desired high intensity that undergoes significant nonlinear effects.

[0099] Embodiments of the present invention can advantageously provide a radiation source capable of rapidly switching between a desired wavelength (i.e., a desired center wavelength) and a desired spectral bandwidth (e.g., by using a color selection module that includes an automatically movable dispersion device provided at the output of the radiation source).

[0100] To provide a radiation source capable of switching between desired wavelengths, the radiation source may include a color selection module (CM). Figure 7The diagram schematically depicts a known example of a color selection module CM. The color selection module CM has an input 11 for a broadband radiation beam 12. The radiation beam 12 passes through a pair of rotatable color wheels 14a, 14b. Color wheels 14a, 14b can each be considered as multilayer (spectral) filters. That is, each color wheel has a multilayer structure—each layer is formed of different materials, each with a different transmission spectrum. The total transmission spectrum of a particular portion of each color wheel depends on the thickness and material of each layer of the multilayer structure at that portion. One or more characteristics of the multilayer structure (e.g., the thickness of each layer of the multilayer structure) vary according to the angular position around the wheel. Thus, the total transmission spectrum of each color wheel varies according to the angular position around that wheel. Each of the wheels 14a, 14b is rotatable about a corresponding rotation axis 16a, 16b. Consequently, the total transmission spectrum of each of the color wheels 14a, 14b varies with the angular position around the rotation axis 16a, 16b. By rotating each of the color wheels 14a and 14b about its respective axes 16a and 16b and controlling the angular position of each color wheel, this controls the portion of each color wheel through which the broadband radiation beam 12 passes, and thus controls the total transmission spectrum of the multilayer structure of said portion of each color wheel through which the radiation beam 12 passes. Therefore, this controls the characteristics of the narrowband radiation beam 18 output from the color wheels 14a and 14b. For example, one color wheel in color wheel 14a can be used as a low-pass filter, while the other color wheel in color wheel 14b can be used as a high-pass filter. By controlling the angular position of each color wheel in color wheels 14a and 14b about their respective axes 16a and 16b, the cutoff frequencies provided by the low-pass filter of one color wheel and the high-pass filter of the other color wheel can be changed. In this way, the center wavelength and spectral bandwidth of the narrowband radiation 18 output from the color wheels 14a and 14b can be controlled. The narrowband radiation 18 is emitted at the output 20 of the color selection module CM.

[0101] The color selection module CM may also include a reflector 22, which creates a secondary beam path 24. The secondary beam path 24 can be used to calibrate the color selection module CM (i.e., to ensure that the correct center wavelength and spectral bandwidth of the narrowband radiation output by the color selection module are when the color wheels 14a and 14b are in a specific position), and to measure the characteristics of the narrowband radiation during operation of the color selection module CM.

[0102] Color wheels 14a and 14b are relatively large (because their size is partly determined by the characteristics of the multilayer structure forming a part of each color wheel, and must have specific dimensions to achieve a desired level of spatial resolution based on the angular position of the color wheels). It has been found that the mass of the color wheels, combined with the momentum of each color wheel during movement, and the desired distance required to move each color wheel to change the center wavelength and spectral bandwidth of the narrowband radiation output by the color selection module, limits the switching speed of the color selection module. That is, when switching is desired between i) a first desired center wavelength and spectral bandwidth of the narrowband radiation and ii) a second desired center wavelength and spectral bandwidth of the narrowband radiation, the speed at which this is done is undesirably slow. This results in an undesirable reduction in the speed / throughput of the metrology tool (and thus the lithography apparatus to which the metrology tool forms part).

[0103] Figure 8 A first embodiment of the color selection module CM according to the present invention is described. The color selection module CM is adapted to output narrowband radiation having a desired spectral bandwidth and a desired center wavelength. That is, the color selection module CM is capable of controlling the spectral bandwidth and center wavelength of the output narrowband radiation.

[0104] The color selection module CM includes a radiation input 30, which is configured to receive an input radiation beam 32 during use.

[0105] The color selection module CM also includes a first dispersion device 34 and a second dispersion device 36. The first dispersion device 34 is configured to receive an input radiation beam 32 from the radiation input 30 and output a first dispersive radiation beam 38 during use.

[0106] The second dispersive device 36 is configured to receive at least a portion of the first dispersive radiation beam 38 and output the second dispersive radiation beam 40 during use.

[0107] The color selection module CM also includes a radiation output device 42, which is configured to receive at least a portion of the second dispersive radiation beam 40 in use and output the second dispersive radiation beam 40 from the color selection module CM.

[0108] In this embodiment, the first dispersion device 34 is in the form of a prism 34a, and the second dispersion device 36 is in the form of a second prism 36a.

[0109] A portion of the first dispersive device 34 is mechanically linked to a first actuator (not shown). The first actuator is configured to rotate said portion of the first dispersive device during use, thereby changing the first angle of incidence of the input radiation beam 32 on said portion of the first dispersive device, and thus changing the first direction of travel and the first spatial distribution of the first dispersive radiation beam. In the present case, a first prism 34a of the first dispersive device 34 is mechanically linked to the first actuator, which rotates the first prism 34a about a first rotation axis A.

[0110] A portion of the second dispersive device 36 is mechanically linked to a second actuator (not shown). The second actuator is configured to rotate said portion of the second dispersive device 36 during use, thereby changing the second angle of incidence of the first dispersive radiation beam 38 on said portion of the second dispersive device 36, and thus changing the second direction of travel and the second spatial distribution of the second dispersive radiation beam 40. In the present case, the second prism 36a of the second dispersive device 36 is mechanically linked to the second actuator such that the second actuator can rotate the second prism 36a about a second rotation axis B.

[0111] It should be understood that, in addition to mechanical linkage, any actuator in this or other embodiments may be coupled by other tools such as magnets, or may use any other suitable actuator or coupling tool.

[0112] By changing the second direction of travel and the second spatial distribution of the second dispersive radiation beam 40, rotating the second prism 36a alters the wavelength band of at least a portion of the second dispersive radiation beam received and output by the radiation output device 42. Specifically, in the present case, the radiation output device 42 includes an aperture 44 through which at least a portion of the second dispersive radiation beam 40 passes. The size and position of the aperture 44 are used to spatially filter a portion of the second dispersive radiation beam 40, thereby determining the wavelength band of that portion of the second dispersive radiation beam 40 output by the radiation output device 42.

[0113] In this embodiment, assuming the aperture 44 of the output device 42 has a fixed size and position, rotating the prisms 34a and 34b to allow the desired radiation wavelength band to pass through the aperture 44 will result in a change in the travel direction of the portion of the second scattered radiation beam 40 that passes through the aperture. To manage this change in the direction of the portion of the second dispersive radiation beam passing through the aperture of the output device, the output reflector 46 is configured to receive the at least portion of the second dispersive radiation beam (which travels in a third travel direction through the aperture) once the at least portion of the second dispersive radiation beam has passed through the aperture, and to output the received portion of the second dispersive radiation beam in a fourth travel direction different from the third travel direction. The output reflector is mounted to rotate about axis C and is driven by a third actuator (not shown). Rotating the output reflector changes the third angle of incidence of the at least portion of the second distributed radiation beam on the output reflector, and thus changes the fourth travel direction of the radiation output from the output reflector.

[0114] In this way, the output reflector can be used to ensure that the second dispersive radiation beam passing through the aperture of the output device can be guided regardless of the direction of the selected wavelength band, so that it leaves the color selection module CM in the correct direction / position, so that the radiation output by the color selection module CM can be used by the measurement system and / or lithography equipment, wherein the color selection module CM forms part of the measurement system and / or lithography equipment.

[0115] It should be understood that when an embodiment is mentioned to include an aperture, this can also be understood to include a spatial filter. Such a spatial filter can be, for example, an aperture, an apodizer, or any other suitable device for spatial filtering of a portion of the beam.

[0116] By replacing the relatively large and heavy color wheel of a known type of color selection module with a relatively small (and therefore lighter) rotatable dispersive element (a prism in this case, but other dispersive elements are also possible, as discussed in further detail below), the speed at which the color selection module can select the desired wavelength band of the narrowband radiation output by the color selection module is increased, thereby increasing the potential throughput of the metrology tool / lithography equipment to which the color selection module is a part.

[0117] Furthermore, the angular movement required for the prism to induce the desired change in the spectral properties of the radiation output by the color selection module can be significantly smaller than that required for the color wheel to produce the same change. Similarly, for this reason, the actuator can drive the prism much faster than the color wheel to achieve the desired change in the spectral properties of the radiation output by the color selection module. Therefore, the desired change in the spectral properties of the radiation output by the color selection module can be achieved much faster, reducing the time spent by related metrology tools and / or lithography equipment switching between different radiation wavelengths, thus increasing throughput.

[0118] It should be understood that, according to the invention (whether relating to this embodiment or the embodiments described later), the axis of rotation of each rotatable portion of the first and second dispersive devices is generally not parallel to the direction of travel of the incident radiation beam (in the case of the first dispersive device: the input radiation beam; and in the case of the second dispersive device: the portion of the first dispersive radiation beam). In this particular example, the axis of rotation of the relevant portions of the first and second dispersive devices may be substantially perpendicular to the direction of travel of the incident radiation beam. In other embodiments, the axis of rotation of the relevant portions of the first and second dispersive devices need not be substantially perpendicular to the direction of travel of the incident radiation beam.

[0119] The first and second dispersive devices, in part, rotate about an axis containing the centroid of the respective rotatable portion. This helps ensure that the actuator driving the rotation of the respective portion drives something balanced for rotation, thereby minimizing stress on the system. In other embodiments, the rotating portions of the first and second dispersive devices do not need to rotate about an axis containing the centroid of the respective rotatable portion.

[0120] As mentioned earlier, in Figure 8 In the illustrated embodiment, the wavelength band selected for output from the color selection module will affect the angle at which a portion of the second dispersive radiation beam passes through the aperture 44 of the output device 42. As previously described, the output reflector 46 can be used to correct for this change in the direction of travel of the selected portion of the second dispersive radiation beam. Figure 9 A second embodiment of the invention is described, in which the need for a movable output reflector is avoided.

[0121] exist Figure 9 In the illustrated embodiment, with Figure 8 The same features in the illustrated embodiments are indicated by the same reference numerals. For the sake of brevity, only [the following is discussed]. Figure 8 and 9 Differences between the illustrated embodiments.

[0122] Figure 8In the embodiment, the output reflector is replaced by a retroreflector 48, such that the aperture 44 of the output device 42 is positioned relative to the radiation path through the system between the first and second dispersive devices 34, 36 and the retroreflector 48. The retroreflector 48 is configured to receive at least a portion of the second dispersive radiation beam 40 traveling in a third direction of travel, once it has passed through the aperture 44. The retroreflector 48 is also configured to output the received at least a portion of the second scattered radiation beam in a fourth direction of travel opposite to the third direction of travel. Figure 9a As best seen in the side view shown, the retroreflector 48 outputs at least a portion of the received second dispersive radiation beam in the fourth direction of travel, which is not only opposite to but also spaced from the third direction of travel (in the present case, in a direction parallel to axes A and B, i.e.) Figure 9a (Vertical direction in the system). As previously mentioned, in the current case, the third and fourth directions of travel are antiparallel (i.e., parallel but opposite in direction). Thus, the retroreflector 48 causes a portion of the second dispersive radiation beam incident on it to be reflected, so that it travels along a substantially the same path as the second dispersive radiation beam before being incident on the retroreflector, although the radiation beam reflected by the retroreflector 48 is spaced apart from the radiation beam incident on the retroreflector 48 in a direction parallel to axes A and B. That is, the radiation incident on the retroreflector essentially backscans its path through the system before being incident on the retroreflector, i.e., it returns through the second prism 36a of the second dispersive device 36 and then through the first prism 34a of the first dispersive device 34.

[0123] The output device 42 also includes a second reflector 50. The second reflector 50 may be in the same direction as the beam path of the input radiation beam 32 and spaced apart from the beam path of the input radiation beam 32 by the same distance between the radiation beam reflected by the retroreflector 48 and the radiation beam incident on the retroreflector 48. As previously stated, the retroreflector 48 is assumed to reflect a portion of the second dispersive radiation beam passing through the aperture 44 substantially along the radiation beam path through the system before it is incident on the retroreflector 48 (i.e., such that the radiation beam reflected by the retroreflector 48 is antiparallel to, but spaced apart from, the radiation beam incident on the retroreflector 48). And assuming the second reflector is positioned such that it is in the same direction as the beam path of the input radiation beam 32 and spaced apart from the beam path of the input radiation beam 32 by the same distance as the interval between the radiation beam reflected by the retroreflector 48 and the radiation beam incident on the retroreflector 48, the second reflector is configured to receive a portion of the dispersive radiation beam output by the retroreflector after the second dispersive radiation beam output by the retroreflector has interacted with the second dispersive device 36 and the first dispersive device 34 (i.e., in the current case, after the relevant radiation has passed through prisms 34a and 34b for the second time). The second reflector 50 then outputs a recombined beam 52 having a beam path different from that of the input radiation beam 32. The recombined beam 52 can then be output from the color selection module CM and subsequently used by measurement tools and / or lithography equipment.

[0124] It should be noted that when it is mentioned that the recombined beam 52 has a beam path different from that of the input radiation beam 32, "different" does not mean "opposite" or "antiparallel." The recombined beam 52 has a beam path that is not parallel to that of the input radiation beam 32.

[0125] As previously described, a portion of the first dispersive device 34 is mechanically linked to the first actuator, a portion of the second dispersive device is mechanically linked to the second actuator, and the output reflector 46 is mechanically linked to the third actuator. In each case, in addition to the mechanical link, the actuator can be coupled by other means such as a magnet, or any other suitable actuator or coupling tool can be used. A suitable actuator is one that includes a galvanometer mechanism. A galvanometer mechanism is a mechanism in which current flows through a coil located in a constant magnetic field to cause deflection of the coil and any deflection of the object to which the coil is mounted. The coil can be biased to a rest position by means of an elastic biasing member (e.g., a spring). Under the action of a permanent magnetic field, an increase in current within the coil will cause an increase in the deflection of the coil. Therefore, by changing the current supplied to the coil, the amount of deflection of the coil can be changed, and thus the amount of deflection (and thus its angular position) of the object to which the coil is mechanically linked can be changed.

[0126] In one example, each prism of the first and second dispersive devices can have three sides, a length of 10 mm, a height of 10 mm, and be made of F2 glass. The mass of such a prism is approximately 1.8 grams. This is a sufficiently small mass to be compatible with actuators that include galvanometers. Such actuators have been found to have a response time of less than 1 millisecond.

[0127] It should be understood that although the use of a galvanometer mechanism as part of at least one of the first, second, or third actuators has been discussed with respect to the embodiments previously discussed in this invention, the galvanometer mechanism can also form part of one of the actuators that forms part of an embodiment of the color selection module according to the invention, which will be discussed in further detail below.

[0128] In order to simulate Figure 8 Or the performance of the color selection module shown in Figure 9, create and evaluate such as Figure 10 The model shown. Figure 10 The model shown and Figure 8 and 9 Equivalent features in the embodiments shown are denoted by the same reference numerals. Prism 34a of the first dispersive device is also denoted as P1, and prism 36a of the second dispersive device is also denoted as P2.

[0129] Apart from Figure 8 and 9 In addition to the features shown, Figure 10 The following features were also described. AOI P1 It is the angle of incidence formed by the prism 34a of the first dispersive device around the input radiation beam 32. TA P1 It is the prism apex angle of prism 34a, TA P2 It is the apex angle of prism 36a. P1_P2 It is the angle between the rear surface of prism 34a and the front surface of prism 36a. The rear surface of the first prism can also be called the exit surface of the first prism, and the front surface of the second prism can also be called the incident surface or entry surface of prism 36a. IN_OUT It is the angle between the beam path of the input radiation 32 and the beam path of the second dispersive radiation beam 40. HA SlitWidth It is a half-angle defined by the width of slit 44. The half-angle (HA) defined by the width of slit 44. SlitWidth The angle is defined as half the angle between i) the first ray extending between the point on prism 36a from which the second dispersive radiation beam exits and the first edge 44a of slit 44, and ii) the second ray extending between the point on prism 36a from which the second dispersive radiation beam exits and the second edge 44b of aperture 44.

[0130] Figure 11 , 12 Figures 13, 14, 15, and 16 each depict a graph of the bandwidth of a portion of the second dispersive radiation beam passing through aperture 44 relative to the center wavelength of said portion of the second dispersive radiation beam passing through aperture 44.

[0131] exist Figure 11 In the middle, the apex angle TA of prism 34a P1 The apex angle TA of prism 36a is 20°. P2 It is 40°. Angle IN_OUT -120°, aperture width HA SlitWidth The half-angle is 0.1°. To obtain this curve, the incident angle AOI on prism 34a is... P1 The angle varies from 60° to 0° in 1° increments. For each incident angle of the incident radiation beam on prism 34a, the angle Angle between prism 34a and prism 36a is... P1_P2 The range is changed from -40° to 40° in 1° increments. The variables under discussion are varied, and the results for all possible scenarios are plotted.

[0132] Apart from Figure 12 The aperture width HA in SlitWidth The half angle is 0.05°. Figure 11 Apart from the half used, the same process and variables are used to create... Figure 12 The curve in the graph.

[0133] By comparison Figure 11 and Figure 12 As can be seen from the graph, by reducing the width of aperture 44, although a similar center wavelength is possible for a portion of the second dispersive radiation beam passing through the aperture, the achievable bandwidth of that portion of the second dispersive radiation beam is generally reduced.

[0134] Figure 13 and 14 Describes the use and Figure 11 The same methods and variables in the graphs, except in Figure 13 The apex angle TA of prism 34a P1 It is 15° and the apex angle TA of the prism is 36a. P2 It is outside 45 degrees; in Figure 14 In the middle, the apex angle TA of prism 34a P1 The apex angle TA of prism 36a is 25°. P2 It is 35°. From Figure 11 , 13As can be seen from Figure 1, slightly changing the apex angle of the prism has no significant effect on the achievable center wavelength of the portion of the second dispersive radiation beam passing through aperture 44, and has a minor effect on the bandwidth of said portion of the second dispersive radiation beam. Figure 14 Maximum achievable bandwidth ratio Figure 13 The bandwidth is slightly higher. Figure 13 bandwidth ratio Figure 11 The bandwidth is slightly higher.

[0135] Figure 15 Depicting and Figure 11 , 13 Similar to the case shown in 14, except for the apex angles TA of prisms 34a and 36a. P1 and TA P2 They are the same—both are 30°. Similarly, it can be seen that while this setup results in a similar achievable center wavelength for a portion of the second dispersive radiation beam, the achievable bandwidth of the resulting radiation is slightly different.

[0136] at last, Figure 16 The diagram depicts the angle between the input radiation beam and the second dispersive radiation beam when the apex angle of each of prisms 34a and 36a is 25°. IN_OUT It is approximately -141° and the half-angle HA of the aperture width. SlitWidth This is the result of the model at 0.02°. It can be seen that using... Figure 16 The model results for the variables in the model depict similar achievable center wavelengths and bandwidths. However, it appears that there are achievable results with a greater density that spread more uniformly across the center wavelength to bandwidth domain. This could be beneficial, as it could mean a greater resolution of the achievable center wavelength and bandwidth of the resulting radiation for a specific achievable resolution of the angular positioning of the first and second prisms 34a and 36a.

[0137] It should be noted that, due to the nonlinear dispersion characteristics of any prism material, as shown in the figures discussed earlier, the scanning range (i.e., how the center wavelength and bandwidth of the second dispersive radiation beam vary with the angular position of the prism) is not linear. In fact, for the relatively short center wavelength of the second dispersive radiation beam, a smaller bandwidth will be easier to achieve, while for the relatively long center wavelength of the second dispersive radiation beam, a larger bandwidth will be easier to achieve.

[0138] In the embodiments described above, such as Figure 8 and 9 As shown, the first and second dispersive devices each utilize a prism as a corresponding dispersive element within the dispersive device. In other embodiments, the dispersive devices may utilize different dispersive elements.

[0139] For example, such as Figure 17 As shown (where with) Figure 8 and 9 (Equivalent features in the illustrated embodiments are given the same reference numerals). The first dispersion device 34 of the color selection module CM includes a reflective grating 34b, and the portion of the first dispersion device mechanically linked to the first actuator is the reflective grating 34b. Similarly, the second dispersion device 36 of the color selection module CM includes a second reflective grating 36b, and the portion of the second dispersion device 36 mechanically linked to the second actuator for rotation is the second reflective grating 36b.

[0140] exist Figure 18 In the optional embodiment shown, the first dispersion device 34 of the color selection module CM includes a transmission grating 34c that receives the input radiation beam 32 and outputs a first intermediate dispersion beam 34f incident on the first dispersion reflector 34d. The first dispersion reflector 34d outputs a first dispersive radiation beam 38. The portion of the first dispersion device 34 mechanically linked to the actuator to rotate about axis A is the first dispersion reflector 34d.

[0141] As an optional feature, Figure 18 The illustrated embodiment also includes a first beam block 34e forming part of the first dispersive device 34. The beam block 34e is positioned to absorb the portion of radiation output from the first transmission grating 34c that is not guided onto the first dispersive reflector 34d.

[0142] The second dispersive device 36 includes a second transmission grating 36c that receives at least a portion of the first dispersive radiation beam 38 and outputs a second intermediate dispersive beam 36f incident on the second dispersive reflector 36d. The second dispersive reflector 36d outputs the second dispersive radiation beam 40. The portion of the second dispersive device 36 mechanically linked to the second actuator to rotate about axis B is the second dispersive reflector 36d.

[0143] Similarly, as an optional feature, the second dispersion device 36 includes a second beam block 36e for absorbing the portion of radiation output by the second transmission grating 36c that is not directed to the second dispersion reflector 36d.

[0144] exist Figure 19 In the optional embodiments shown, with Figure 18 As in the illustrated embodiment, the first dispersion device 34 of the color selection module CM includes a transmission grating 34c that receives the input radiation beam 32. The transmission grating 34c outputs the first dispersive radiation beam 38. The portion of the first dispersion device 34 mechanically linked to the actuator to rotate about axis A is the transmission grating 34c.

[0145] The second dispersive device 36 includes a second transmission grating 36c, which receives at least a portion 38a of the first dispersive radiation beam 38 and outputs a second dispersive radiation beam 40. The portion of the second dispersive device 36 mechanically linked to the second actuator for rotation about axis B is the second transmission grating 36c.

[0146] The radiation output device 42 receives and outputs a portion 40a of the second dispersive radiation beam 40. Specifically, the portion 40a is received by the aperture 44 of the output device 42 and by the output reflector 46 in relation to... Figure 8 The redirection is similar to the method discussed in the illustrated embodiments.

[0147] As an optional feature, Figure 19 The illustrated embodiment also includes a first beam block 34e forming part of the first dispersion device 34. The beam block 34e is positioned to absorb the portion of radiation output from the first transmission grating 34c that is not directed to incident on the second transmission grating 36c.

[0148] Similarly, as an optional feature, the second dispersion device 36 includes a second beam block 36e for absorbing a portion of the aperture 44 of the non-pointing output device 44 of the radiation output by the second transmission grating 36c.

[0149] and Figure 8 and 9 The embodiments of the present invention shown are the same. Figure 17 , 18 The embodiment shown in 19 operates in a similar manner, wherein rotating the relevant portions of the first and second dispersive devices changes the direction of travel and spatial distribution of the first and second dispersive radiation beams, and thus changes the wavelength band of at least a portion of the second dispersive radiation beam received and output by the radiation output device 44.

[0150] also, Figure 17 , 18 Each embodiment shown in 19 includes a radiation output device 42, which includes an output reflector 46 that is aligned with a reference. Figure 8 Operate in the same manner as described in the embodiments. Of course, in Figure 17 , 18 The output device of the embodiment shown in 19 may alternatively include a component for communication with respect to... Figure 9 The embodiments shown in the diagram discuss those retroreflectors and second reflectors that operate in the same manner.

[0151] In some embodiments, using a grating (transmitting or reflecting) as the dispersive element may be undesirable compared to a prism. This is especially true when it is desired that the entire spectrum of radiation emitted by the color selection module spans more than one octave (i.e., the lowest desired center wavelength emitted by the color selection module is less than half the highest desired center wavelength emitted by the color selection module). Furthermore, a prism may be a more desirable choice than a grating when selecting a suitable dispersive element because a prism has a much lower spectral resolution than a grating when used to control the spectral bandwidth of the radiation output by the color selection module. That is, a relatively small annular adjustment to the prism's angular position can result in a relatively large change in the spatial distribution of the wavelengths of the radiation output by the prism. This means that using the prism's angular position as the dispersive element to control the spectral characteristics of the radiation output by the color selection module may be easier than using other types of dispersive elements.

[0152] The variables in the embodiments of the color selection module discussed herein can be modified to further maximize the ability of the color selection module to select output radiation with desired spectral characteristics. For example, the color selection module may use an additional dispersive device between its input and output. Alternatively, an output device including an aperture having a variable diameter may be used, or the aperture may be movable so that its position can be changed, for example, by movement within or outside the aperture plane.

[0153] In the embodiments discussed above, in each respective embodiment, the dispersive element of each of the first and second dispersive devices is of the same type. However, this is not necessary. For example, in some embodiments, the dispersive element of one dispersive device may be a prism, and the dispersive element of the other dispersive device may be a grating.

[0154] Further embodiments are disclosed in the subsequent list of numbered clauses: 1. A color selection module for outputting radiation with a desired spectral bandwidth and center wavelength, comprising: Radiation input, used to receive the input radiation beam; A first dispersive device is used to receive the input radiation beam from the radiation input and output a first dispersive radiation beam. The second dispersive device is used to receive at least a portion of the first dispersive radiation beam and output the second dispersive radiation beam. A radiation output device is configured to receive at least a portion of the second dispersive radiation beam and output the at least a portion of the second dispersive radiation beam from the color selection module; wherein A portion of the first dispersion device is coupled to a first actuator for rotating said portion of the first dispersion device; and A portion of the second dispersive device is coupled to a second actuator for rotating the portion of the second dispersive device, thereby altering the second direction of travel and the second spatial distribution of the second dispersive radiation beam, and thus changing the spectral bandwidth and center wavelength of at least a portion of the second dispersive radiation beam received and output by the radiation output device. 2. The color selection module according to Clause 1, wherein the first dispersion device includes a prism, and the portion of the first dispersion device is the prism. 3. The color selection module according to Clause 1, wherein a) the first dispersion device includes a reflective grating and the portion of the first dispersion device is the reflective grating; or b) the first dispersion device includes a transmission grating and the portion of the first dispersion device is the transmission grating. 4. The color selection module according to Clause 1, wherein the first dispersion device includes a transmission grating that receives the input radiation beam and outputs a first intermediate dispersion beam incident on the first dispersion reflector, the first dispersion reflector outputting the first dispersion radiation beam; and wherein the portion of the first dispersion device is the first dispersion reflector. 5. The color selection module according to clauses 1, 2, 3 or 4, wherein the second dispersion device includes a second prism, and the portion of the second dispersion device is the second prism. 6. The color selection module according to clauses 1, 2, 3 or 4, wherein a) the second dispersion device includes a second reflective grating and the portion of the second dispersion device is the second reflective grating; or b) the second dispersion device includes a second transmission grating and the portion of the second dispersion device is the second transmission grating. 7. The color selection module according to clauses 1, 2, 3 or 4, wherein the second dispersion device includes a second transmission grating that receives at least a portion of the first dispersive radiation beam and outputs a second intermediate dispersive beam incident on a second dispersive reflector, the second dispersive reflector outputting the second dispersive radiation beam; and wherein the portion of the second dispersion device is the second dispersive reflector. 8. The color selection module according to any of the preceding clauses, wherein the radiation output device includes a spatial filter through which at least a portion of the second dispersive radiation beam passes. 9. The color selection module according to Clause 8, wherein the radiation output device further comprises an output reflector for receiving at least a portion of the second dispersive radiation beam traveling in a third direction of travel, and for outputting the received at least a portion of the second dispersive radiation beam in a fourth direction of travel, different from the third direction of travel, once the at least a portion of the second dispersive radiation beam has passed through the spatial filter. 10. The color selection module according to Clause 9, wherein the output reflector is coupled to a third actuator for rotating the output reflector, whereby the rotation of the output reflector changes the third angle of incidence of at least a portion of the second dispersive radiation beam on the output reflector, and thus changes the fourth direction of travel of the radiation output from the output reflector. 11. The color selection module according to Clause 8, wherein the radiation output device further comprises a retroreflector for receiving at least a portion of the second dispersive radiation beam traveling in a third direction of travel, and outputting the received at least a portion of the second dispersive radiation beam in a fourth direction of travel opposite to the third direction of travel once the at least a portion of the second dispersive radiation beam has passed through the spatial filter. 12. The color selection module according to Clause 11, wherein the radiation output device further comprises a second reflector for receiving, after at least a portion of the second dispersive radiation beam output by the retroreflector has interacted with the second dispersive device and the first dispersive device, the second reflector for outputting a recombined beam having a beam path different from that of the input radiation beam. 13. The color selection module according to any of the preceding clauses, wherein at least one of the first actuator and the second actuator, or both the first actuator and the second actuator, includes a galvanometer mechanism. 14. A measurement tool comprising a color selection module as described in any of the preceding clauses. 15. A photolithography apparatus comprising a color selection module according to any one of Clauses 1 to 13 or a measurement tool according to Clause 14. 16. A method for operating a color selection module to output radiation having a desired spectral bandwidth and center wavelength, the method comprising: Receive input radiation beam; The first dispersive device receives the input radiation beam from the radiation input and outputs the first dispersive radiation beam; The second dispersive device receives at least a portion of the first dispersive radiation beam and outputs the second dispersive radiation beam. The radiation output device receives at least a portion of the second dispersive radiation beam and outputs the at least a portion of the second dispersive radiation beam from the color selection module; Rotate a portion of the first dispersive device to a first angular position; Rotate a portion of the second dispersive device to a second angular position; and The first angular position of the portion of the first dispersive device and the second angular position of the portion of the second dispersive device are set based on the desired spectral bandwidth and center wavelength. 17. The method according to Clause 16, wherein The color selection module includes a radiation input, which receives the input radiation beam; The portion of the first dispersion device is coupled to a first actuator, which rotates the portion of the first dispersion device to the first angular position. The portion of the second dispersion device is coupled to a second actuator, which rotates the portion of the second dispersion device to the second angular position; Rotation of said portion of the first dispersive device alters the first direction of travel and the first spatial distribution of the first dispersive radiation beam; and The rotation of said portion of the second dispersive device changes the second direction of travel and the second spatial distribution of the second dispersive radiation beam, and thus changes the spectral bandwidth and center wavelength of said at least a portion of the second dispersive radiation beam received and output by said radiation output device.

[0155] While this article specifically refers to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein can have other applications. Possible other 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.

[0156] Although embodiments of the invention may be specifically referred to herein in the context of lithography equipment, these embodiments can be used in other equipment. Embodiments of the invention may form part of mask inspection equipment, metrology tools, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These devices are commonly referred to as lithography tools. Such lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0157] 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 above description is intended to illustrate and not limit. Therefore, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the scope of the following claims.

[0158] Although specific references are made to "measuring equipment / tools / systems" or "inspection equipment / tools / systems," these terms can refer to the same or similar types of tools, equipment, or systems. For example, inspection or measuring equipment including embodiments of the present invention can be used to determine the characteristics of structures on a substrate or wafer. For example, inspection or measuring equipment including embodiments of the present invention can be used to detect defects in a substrate or defects in structures on a substrate or wafer. In such embodiments, the characteristics of interest in the structure on the substrate may relate to defects in the structure, the absence of a specific portion of the structure, or the presence of unwanted structures on the substrate or wafer.

Claims

1. A color selection module for outputting radiation with a desired spectral bandwidth and center wavelength, comprising: Radiation input, used to receive the input radiation beam; A first dispersive device is configured to receive the input radiation beam from the radiation input and output a first dispersive radiation beam. The second dispersive device is used to receive at least a portion of the first dispersive radiation beam and output the second dispersive radiation beam. A radiation output device for receiving at least a portion of the second dispersive radiation beam and outputting the at least a portion of the second dispersive radiation beam from the color selection module; in A portion of the first dispersion device is coupled to a first actuator for rotating said portion of the first dispersion device; as well as A portion of the second dispersive device is coupled to a second actuator for rotating the portion of the second dispersive device, thereby changing the second direction of travel and the second spatial distribution of the second dispersive radiation beam, and thus changing the spectral bandwidth and center wavelength of at least a portion of the second dispersive radiation beam received and output by the radiation output device.

2. The color selection module according to claim 1, wherein the first dispersion device includes a prism, and the portion of the first dispersion device is the prism.

3. The color selection module according to claim 1, wherein a) the first dispersion device includes a reflective grating, and the portion of the first dispersion device is the reflective grating; or b) the first dispersion device includes a transmission grating, and the portion of the first dispersion device is the transmission grating.

4. The color selection module according to claim 1, wherein the first dispersion device includes a transmission grating that receives the input radiation beam and outputs a first intermediate dispersion beam incident on a first dispersion reflector, the first dispersion reflector outputting the first dispersion radiation beam; and wherein the portion of the first dispersion device is the first dispersion reflector.

5. The color selection module according to claim 1, 2, 3 or 4, wherein the second dispersion device includes a second prism, and the portion of the second dispersion device is the second prism.

6. The color selection module according to claim 1, 2, 3 or 4, wherein a) the second dispersion device includes a second reflective grating, and the portion of the second dispersion device is the second reflective grating; or b) the second dispersion device includes a second transmission grating, and the portion of the second dispersion device is the second transmission grating.

7. The color selection module according to claim 1, 2, 3 or 4, wherein the second dispersion device includes a second transmission grating, the second transmission grating receiving at least a portion of the first dispersive radiation beam and outputting a second intermediate dispersive beam incident on a second dispersive reflector, the second dispersive reflector outputting the second dispersive radiation beam; and wherein the portion of the second dispersion device is the second dispersive reflector.

8. The color selection module according to any one of the preceding claims, wherein the radiation output device includes a spatial filter, and the at least portion of the second dispersive radiation beam passes through the spatial filter.

9. The color selection module of claim 8, wherein the radiation output device further comprises an output reflector for receiving at least a portion of the second dispersive radiation beam traveling in a third direction of travel, and outputting the received at least a portion of the second dispersive radiation beam in a fourth direction of travel, different from the third direction of travel, once the at least a portion of the second dispersive radiation beam has passed through the spatial filter.

10. The color selection module of claim 9, wherein the output reflector is coupled to a third actuator for rotating the output reflector, whereby the rotation of the output reflector changes the third angle of incidence of at least a portion of the second dispersive radiation beam on the output reflector, and thus changes the fourth direction of travel of the radiation output from the output reflector.

11. The color selection module of claim 8, wherein the radiation output device further comprises a retroreflector for receiving at least a portion of the second dispersive radiation beam traveling in a third direction of travel, and outputting the received at least a portion of the second dispersive radiation beam in a fourth direction of travel opposite to the third direction of travel once the at least a portion of the second dispersive radiation beam has passed through the spatial filter.

12. The color selection module of claim 11, wherein the radiation output device further comprises a second reflector for receiving, after at least a portion of the second dispersive radiation beam output by the retroreflector has interacted with the second dispersive device and the first dispersive device, the second reflector for outputting a recombined beam having a beam path different from that of the input radiation beam.

13. The color selection module according to any one of the preceding claims, wherein at least one of the first actuator and the second actuator, or both the first actuator and the second actuator, comprises a galvanometer mechanism.

14. A measuring tool comprising the color selection module as described in any of the preceding claims.

15. A method for operating a color selection module to output radiation having a desired spectral bandwidth and center wavelength, the method comprising: Receive input radiation beam; The first dispersive device receives the input radiation beam from the radiation input and outputs the first dispersive radiation beam; The second dispersive device receives at least a portion of the first dispersive radiation beam and outputs the second dispersive radiation beam. The radiation output device receives at least a portion of the second dispersive radiation beam and outputs the at least a portion of the second dispersive radiation beam from the color selection module; Rotate a portion of the first dispersive device to a first angular position; Rotate a portion of the second dispersion device to a second angular position; as well as The first angular position of the portion of the first dispersion device and the second angular position of the portion of the second dispersion device are set based on the desired spectral bandwidth and center wavelength.

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