TW202409553A - Source selection module and associated metrology and lithographic apparatuses - Google Patents

Abstract

Disclosed is a source selection module for selecting spectral characteristics of a broadband illumination beam to obtain a modulated illumination beam. The source selection module comprises a first beam dispersing element for dispersing the beam along a first direction, a second beam dispersing element for dispersing the beam along a second direction perpendicular to said first direction, a controllable diffractive element being operable to controllably spatially modulate the broadband illumination beam subsequent to being dispersed by said first beam dispersing element and said second beam dispersing element; and an aperture stop being operable to maximize transmission of one of specularly reflected radiation and diffracted radiation from said controllable diffractive element and minimize transmission of the other of said specularly reflected radiation and diffracted radiation.

Description

Source selection module and its related metrology and lithography equipment

The present invention relates to methods and apparatus that can be used, for example, for manufacturing devices by lithography, and to methods of manufacturing devices using lithography. More particularly, the present invention relates to metrology sensors and lithography apparatus having such metrology sensors, and more particularly, to illumination arrangements for such metrology sensors.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, typically onto a target portion of the substrate. Lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In that case, a patterning device (which is alternatively referred to as a mask or reticle) may be used to generate a circuit pattern to be formed on individual layers of the IC. This pattern may be transferred to a target portion (e.g., a portion including a die, a die, or several dies) on a substrate (e.g., a silicon wafer). The pattern is typically transferred by imaging onto a layer of radiation-sensitive material (resist) disposed on the substrate. In general, a single substrate will contain a network of sequentially patterned adjacent target portions. These target portions are typically referred to as "fields."

In the fabrication of complex devices, many lithographic patterning steps are often performed to form functional features in successive layers on a substrate. Therefore, a key aspect of the performance of the lithography equipment is the ability to properly and accurately place the coated pattern relative to features placed in previous layers (either by the same equipment or a different lithography equipment). For this purpose, the substrate is provided with one or more sets of alignment marks. Each mark is a structure whose position can later be measured using a position sensor (usually an optical position sensor). The lithography equipment includes one or more alignment sensors by which the position of the mark on the substrate can be accurately measured. Different types of markers and different types of alignment sensors are known from different manufacturers and different products from the same manufacturer.

In other applications, metrology sensors are used to measure exposed structures on substrates (in resist and/or after etching). A rapid and non-invasive form of specialized detection tool is a scatterometer, in which a radiation beam is directed to a target on the surface of a substrate and the properties of the scattered or reflected beam are measured. Examples of known scatterometers include angle-resolved scatterometers of the type described in US2006033921A1 and US2010201963A1. In addition to measuring feature shapes through reconstruction, such equipment can also be used to measure diffraction-based overlays, as described in published patent application US2006066855A1. Diffraction-based overlay alignment metrology using diffraction-order dark field imaging enables overlay measurement of smaller targets. Examples of dark field imaging metrology can be found in International Patent Applications WO 2009/078708 and WO 2009/106279, which patent applications are hereby incorporated by reference in their entirety. Further developments of this technology have been described in published patent publications US20110027704A, US20110043791A, US2011102753A1, US20120044470A, US20120123581A, US20130258310A, US20130271740A and WO2013178422A1 . These targets can be smaller than the illumination spot and can be surrounded by product structures on the wafer. Composite grating targets can be used to measure multiple gratings in one image. The contents of all such applications are also incorporated herein by reference.

In some metrology applications, such as in some scatterometers or alignment sensors, defects in the metrology target can cause wavelength/polarization-dependent changes in the measurement values of the target. Thus, correction and/or mitigation of this variation is sometimes achieved by performing the same measurement using multiple different wavelengths and/or polarizations (more generally, multiple different lighting conditions). Improvements in switching and selection of spectral components of illumination for these metrology applications will be required.

In a first aspect, the present invention provides a source selection module for selecting the spectral characteristics of a broadband illumination beam to obtain a modulated illumination beam, the source selection module comprising: a first beam dispersing element for dispersing the broadband illumination beam, the first beam dispersing element being operable to disperse the broadband illumination beam along a first direction; a second beam dispersing element for dispersing the broadband illumination beam, the second beam dispersing element being operable to disperse the broadband illumination beam along a second direction perpendicular to the first direction; a controllable A diffraction element having a controllable element arranged along the first direction so that a periodic direction of the controllable diffraction element includes the first direction; the controllable diffraction element is operable to controllably spatially modulate the broadband illumination beam after the broadband illumination beam is dispersed by the first beam dispersion element and the second beam dispersion element; and an aperture diaphragm is operable to maximize the transmission of one of the mirror-reflected radiation and the diffracted radiation from the controllable diffraction element and minimize the transmission of the other of the mirror-reflected radiation and the diffracted radiation.

In a second aspect, the present invention provides a source selection module for selecting the spectral characteristics of a broadband illumination beam to obtain a modulated illumination beam. The source selection module includes: at least one beam dispersion element for Dispersing the broadband illumination beam, the at least one beam dispersion element is operable to disperse the broadband illumination beam along a first direction; a controllable diffraction element having controllable elements disposed along the first direction such that the A periodic direction of the controllable diffraction element includes the first direction; the controllable diffraction element is operable to controllably spatially modulate the broadband illumination beam after the broadband illumination beam is dispersed by the first beam dispersing element; and an aperture stop operable to maximize the transmission of one of the specularly reflected radiation and the diffracted radiation from the controllable diffractive element and to minimize the other of the specularly reflected radiation and the diffracted radiation. transmission; and a plurality of lens elements comprising at least one lens or lens system operable to image the broadband illumination beam after being dispersed by the first beam spreading element onto the controllable diffraction element, and collecting the modulated illumination beam from the controllable diffraction element; wherein the first beam dispersing element is also configured to recombine the modulated illumination beam from the controllable diffraction element on a return path.

Also disclosed are a metrology apparatus and a lithography apparatus comprising a metrology device operable to perform the method of the first aspect or the second aspect.

The above and other aspects of the present invention will be understood based on consideration of the examples described below.

Before describing embodiments of the invention in detail, it is instructive to present example environments in which embodiments of the invention may be practiced.

In this document, the terms "radiation" and "beam" are used to cover all types of electromagnetic radiation, including ultraviolet radiation (for example, having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm or 126 nm) and EUV ( Extreme ultraviolet radiation, for example having a wavelength in the range of about 5 nm to 100 nm).

As used herein, the terms "reticle," "mask," or "patterning device" may be interpreted broadly to refer to general patterning devices that can be used to impart a patterned cross-section to an incident radiation beam. The patterned cross-section corresponds to the pattern to be produced in the target portion of the substrate. In this context, the term "light valve" may also be used. In addition to classic masks (transmissive or reflective, binary, phase-shifted, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

FIG1 schematically depicts a lithography apparatus LA. The lithography apparatus LA comprises an illumination system (also referred to as an illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask stage) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to certain parameters; a substrate support (e.g., a wafer stage) WT constructed to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS is configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (eg, comprising one or more dies).

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

The term "projection system" PS as used herein should be interpreted broadly to cover various types of projection systems appropriate to the exposure radiation used and/or to other factors such as the use of an immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, synthetic, magnetic, electromagnetic and/or electro-optical systems or any combination thereof. Any use of the term "projection lens" herein should be considered synonymous with the more general term "projection system" PS.

Lithography apparatus LA may be of the type in which at least a portion of the substrate may be covered by a liquid with a relatively high refractive index (e.g., water) in order to fill the space between the projection system PS and the substrate W, which is also referred to as an immersion micro. film. More information on infiltration techniques is given in US6952253, which is incorporated herein by reference.

The lithography apparatus LA may also be of the type having two or more substrate supports WT (also called "double stages"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and/or the step of preparing the substrate W for subsequent exposure may be performed on a 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 the other substrate W.

In addition to the substrate support WT, the lithography apparatus LA may also comprise a measurement stage. The measurement stage is configured to hold sensors and/or cleaning devices. The sensors may be configured to measure properties of the projection system PS or properties of the radiation beam B. The measurement stage may hold a plurality of sensors. The cleaning device may be configured to clean parts of the lithography apparatus, such as a part of the projection system PS or a part of a system for providing an immersion liquid. The measurement stage may be moved under the projection system PS when the substrate support WT is away from the projection system PS.

In operation, a radiation beam B is incident on a patterning device (e.g., a mask) MA held on a mask support MT and is patterned by a pattern (design layout) present on the patterning device MA. After traversing the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam on 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 accurately moved, for example, in order to position different target portions C in the path of the radiation beam B at focusing and alignment positions. Similarly, a first positioner PM and possibly a further position sensor (which is not explicitly depicted in FIG. 1 ) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. The mask alignment marks M1, M2 and the substrate alignment marks P1, P2 may be used to align the patterning device MA with the substrate W. Although the substrate alignment marks P1, P2 are shown occupying dedicated target portions, the substrate alignment marks may be located in spaces between target portions. When the substrate alignment marks P1, P2 are located between target portions C, the substrate alignment marks are referred to as scribe line alignment marks.

As shown in FIG. 2 , the lithography apparatus LA may form part of a lithography cell LC (sometimes also referred to as a lithography cell or (lithography) cluster), which typically also includes equipment for performing pre-exposure and post-exposure processes on a substrate W. As is known, such equipment includes a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a cooling plate CH and a baking plate BK (e.g. for regulating the temperature of the substrate W, e.g. for regulating the solvent in the resist layer). A substrate handler or robot RO picks up a substrate W from an input/output port I/O1, I/O2, moves the substrate W between the different process equipment, and delivers the substrate W to a loading box LB of the lithography apparatus LA. The devices in the lithography unit, which are generally also collectively referred to as the coating and developing system, are usually under the control of the coating and developing system control unit TCU. The coating and developing system control unit itself can be controlled by the supervisory control system SCS, and the supervisory control system can also control the lithography equipment LA, for example, via the lithography control unit LACU.

In order to correctly and consistently expose a substrate W exposed by the lithography apparatus LA, the substrate needs to be inspected to measure properties of the patterned structure, such as overlay errors between subsequent layers, line thickness, critical dimensions (CD), etc. For this purpose, an inspection tool (not shown) may be included in the lithography unit LC. If an error is detected, adjustments may 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 of the same batch or lot are still to be exposed or processed.

Inspection equipment, which may also be referred to as metrological equipment, is used to determine properties of a substrate W, and in particular, how properties of different substrates W change or how properties associated with different layers of the same substrate W change from layer to layer. The inspection device may alternatively be constructed to identify defects on the substrate W, and may for example be part of the lithography unit LC, or may be integrated into the lithography apparatus LA, or may even be a stand-alone device. Inspection equipment can measure properties on the latent image (the image in the resist layer after exposure), or the semi-latent image (the image in the resist layer after the post-exposure bake step PEB), Or properties on a developed resist image (where exposed or unexposed portions of resist have been removed), or even on an etched image (after a pattern transfer step such as etching).

Typically, the patterning process in a lithography apparatus LA is one of the most critical steps in a process that requires high accuracy in sizing and placement of structures on a substrate W. To ensure this high accuracy, the three systems can be combined in a so-called "holistic" control environment, as schematically depicted in Figure 3. One of these systems is the lithography apparatus LA, which is (actually) connected to the metrology tool MT (second system) and to the computer system CL (third system). The key to this "holistic" environment is to optimize the cooperation between these three systems to enhance the overall process window and provide a tight control loop to ensure that the patterning performed by the lithography equipment LA remains within the process window. A process window defines the 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 for either a lithography process or a patterning process. Program parameters vary within this range.

The computer system CL can use (part of) the design layout to be patterned to predict which resolution enhancement techniques to use and perform computational lithography simulations and calculations to determine which mask layouts and lithography equipment settings achieve the greatest totality of the patterning process Program window (depicted in Figure 3 by the double arrow in the first scale SC1). Typically, the resolution enhancement technology is configured to match the patterning possibilities of the lithography apparatus LA. The computer system CL may also be used to detect where within the program window the lithography apparatus LA is currently operating (e.g., using input from the metrology tool MT) to predict whether there may be defects due to, for example, suboptimal processing (in Figure 3 by Depicted by the arrow pointing to "0" in the second scale SC2).

The metrology tool MT may provide input to the computer system CL to enable accurate simulation and prediction, and may provide feedback to the lithography apparatus LA to identify, for example, possible drifts in the calibration state of the lithography apparatus LA (depicted in FIG. 3 by a plurality of arrows in the third scale SC3).

In lithography processes it is frequently necessary to carry out measurements of the produced structures, e.g. for process control and verification. The tool used to carry out such measurements is usually called a metrology tool MT. Different types of metrology tools MT for carrying out such measurements are known, including scanning electron microscopes or various forms of scatterometer metrology tools MT. Scatterometers are versatile instruments which allow to measure parameters of the lithography process either by having sensors in the pupil or in a plane conjugated to the pupil of the objective of the scatterometer, the measurements usually being called pupil-based measurements, or by having sensors in the image plane or in a plane conjugated to the image plane, in which case the measurements are usually called image- or field-based measurements. Such scatterometers and associated measurement techniques are further described in patent applications US20100328655, US2011102753A1, US20120044470A, US20110249244, US20110026032, or EP1,628,164A, which are incorporated herein by reference in their entirety. The aforementioned scatterometers can measure gratings using light from soft x-rays and visible to the near IR wavelength range.

In a first embodiment, the scatterometer MT is an angle-resolved scatterometer. In this scatterometer, reconstruction methods can be applied to the measured signals to reconstruct or calculate the properties of the grating. This reconstruction may be generated, for example, by simulating the interaction of the scattered radiation with a mathematical model of the target structure and comparing the simulation results with the measured results. The parameters of the mathematical model are adjusted until the simulated interactions produce a diffraction pattern similar to that observed from a real target.

In a second embodiment, the scatterometer MT is a spectral scatterometer MT. In this spectroscopic scatterometer MT, radiation emitted by a radiation source is directed onto a target, and reflected or scattered radiation from the target is directed to a spectrometer detector that measures specularly reflected radiation. Spectrum (that is, a measurement of intensity as a function of wavelength). From this data, the structure or profile of the target that gave rise to the detected spectrum can be reconstructed, for example, by rigorous coupled wave analysis and nonlinear regression or by comparison with a library of simulated spectra.

In a third embodiment, the scatterometer MT is an elliptical metrology scatterometer. An elliptical metrology scatterometer allows to determine parameters of a lithography process by measuring the scattered radiation for each polarization state. This metrology device emits polarized light (such as linear, circular or elliptical) by using, for example, appropriate polarization filters in the illumination section of the metrology device. A source suitable for the metrology device may also provide polarized radiation. Various embodiments of prior art elliptical measurement scatterometers are described in U.S. Patent Applications 11/451,599, 11/708,678, 12/256,780, 12/486,449, 12/920,968, 12/922,587, 13/000,229, 13/033,135, 13/533,110, and 13/891,410, which are incorporated herein by reference in their entirety.

In Fig. 4 a metrological device, such as a scatterometer, is depicted. The metrological device comprises a broadband (white light) radiation projector 2 which projects radiation onto a substrate W (optionally spectrally filtered to narrowband before the substrate W). The reflected or scattered radiation is passed to a spectrometer detector 4 which measures the spectrum 6 of the radiation reflected by the mirror (i.e. a measurement of the intensity as a function of wavelength). From this data, the structure or profile 8 resulting from the detected spectrum can be reconstructed by a processing unit PU, for example by rigorous coupled wave analysis and nonlinear regression, or by comparison with a library of simulated spectra as shown at the bottom of Fig. 4 . In general, for the reconstruction, the general form of the structure is known, and some parameters are assumed from knowledge of the procedure used to make the structure, leaving only a few parameters of the structure to be determined from the scattering measurement data. The scatterometer can be configured as either a normal-incidence scatterometer or an oblique-incidence scatterometer.

The overall quality of the lithography parameter measured by measuring the target is determined at least in part by the measurement recipe used to measure the lithography parameter. The term "substrate measurement recipe" may include measuring one or more parameters of itself, measuring one or more parameters of one or more patterns, or both. For example, if the measurement used in the substrate measurement recipe is a diffraction-based optical measurement, one or more of the measured parameters may include the wavelength of the radiation, the polarization of the radiation, the relative angle of the radiation to The angle of incidence of the substrate, the orientation of the radiation relative to the pattern on the substrate, etc. One of the criteria used to select a measurement recipe may, for example, be the sensitivity of one of the measurement parameters to process changes. Further examples are described in US Patent Application US2016-0161863 and Published US Patent Application US2016/0370717A1, which are incorporated herein by reference in their entirety.

Another type of weight and measurement equipment is shown in Figure 5(a). A target T and the diffracted rays of the measurement radiation used to illuminate the target are shown in greater detail in Figure 5(b). The illustrated metrology equipment is of a type known as a dark field metrology equipment. The weights and measures equipment depicted here is illustrative only to provide an explanation of dark field weights and measures. The metrology equipment may be a stand-alone device, or may be incorporated in, for example, the lithography apparatus LA or the lithography unit LC at the measurement station. The optical axis, one of several branches throughout the device, is represented by a dashed line O. In this apparatus, light emitted by a source 11 (eg, a xenon lamp) is directed onto the substrate W via a beam splitter 15 by an optical system including lenses 12, 14 and an objective 16. These lenses are arranged in a double sequence in a 4F configuration. A different lens configuration can be used with the constraint that it still provides a substrate image to a detector while allowing access to an intermediate pupil plane for spatial frequency filtering. Thus, the angular range of radiation incident on the substrate can be selected by defining a spatial intensity distribution in one of the planes representing the spatial spectrum of the substrate plane (referred to here as a (conjugate) pupil plane). In particular, this selection can be made by inserting a suitable form of aperture plate 13 between lenses 12 and 14 in a plane of the back-projected image which is the objective pupil plane. In the example shown, the aperture plate 13 has different forms (labeled 13N and 13S), allowing different lighting modes to be selected. The lighting system in the current example forms an off-axis lighting pattern. In the first illumination mode, aperture plate 13N is provided off-axis from a direction designated "north" for purposes of description only. In the second illumination mode, aperture plate 13S is used to provide similar illumination, but from the opposite direction labeled "South". By using different apertures, other lighting patterns are possible. The remainder of the pupil plane is ideally dark because any unwanted light outside the desired illumination pattern will interfere with the desired measurement signal.

As shown in FIG5(b), a target T is placed with the substrate W perpendicular to the optical axis O of the objective lens 16. The substrate W may be supported by a support (not shown). A metrological radiation ray I impinging on the target T at an angle to the axis O produces a zeroth order ray (solid line 0) and two first order rays (dot chain line +1 and double dot chain line -1). It should be remembered that in the case of using a small overfilled target, these rays are only one of many parallel rays that cover the substrate area including the metrology target T and other features. Since the aperture in plate 13 has a finite width (necessary to admit a useful amount of light), the incident ray I may actually occupy a range of angles, and the diffracted rays 0 and +1/-1 will be slightly spread out. Rather than a single ideal ray as shown, the orders +1 and -1 will be further spread out over a range of angles, according to the point spread function of a small target. It should be noted that the grating pitch and illumination angle of the target may be designed or adjusted so that the first order rays entering the objective are closely aligned with the central optical axis. The rays shown in Figures 5(a) and 3(b) are shown slightly off-axis, simply to enable them to be more easily distinguished in the figures.

At least 0 and +1 orders diffracted by the target T on the substrate W are collected by the objective lens 16 and directed back through the beam splitter 15. Returning to FIG. 5( a ), both the first illumination mode and the second illumination mode are illustrated by indicating the diametrically opposite apertures marked as north (N) and south (S). When the incident ray I of the measurement radiation comes from the north side of the optical axis, that is, when the first illumination mode is applied using the aperture plate 13N, the +1 diffracted ray marked as +1 (N) enters the objective lens 16. Conversely, when the second illumination mode is applied using the aperture plate 13S, the -1 diffracted ray (marked as 1 (S)) is the diffracted ray that enters the lens 16.

The second beam splitter 17 divides the diffracted beam into two measurement branches. In the first measurement branch, the optical system 18 uses the zeroth-order diffraction beam and the first-order diffraction beam to form the diffraction spectrum of the target on the first sensor 19 (eg, CCD or CMOS sensor). (pupil plane image). Each diffraction order hits the sensor at a different point, allowing image processing to compare and contrast several orders. The pupil plane image captured by sensor 19 may be used to focus metrology equipment and/or to normalize intensity measurements of the first order beam. Pupil plane images can also be used for various measurement purposes such as reconstruction.

In the second measurement branch, the optical system 20, 22 forms an image of the target T on a sensor 23 (e.g., a CCD or CMOS sensor). In the second measurement branch, an aperture diaphragm 21 is provided in a plane concentric with the pupil plane. The aperture diaphragm 21 serves to block the zeroth order diffracted beams so that the image of the target formed on the sensor 23 is formed only by -1 or +1 first order beams. The image captured by the sensors 19 and 23 is output to a processor PU for processing the image, the functionality of which will depend on the specific type of measurement being performed. It should be noted that the term "image" is used in a broad sense. Thus, if only one of the -1 and +1 orders is present, no image of the grating lines will be formed.

The specific forms of aperture plate 13 and field diaphragm 21 shown in FIG. 5 are examples only. In another embodiment of the invention, coaxial illumination of the target is used, and an aperture diaphragm with an off-axis aperture is used to pass substantially only one first-order diffracted light to the sensor. In other examples, two quadrant apertures may be used. This may enable detection of positive and negative orders simultaneously, as described in US2010201963A1 mentioned above. As described in US2011102753A1 mentioned above, an embodiment with a wedge (segmented prism or other suitable element) in the detection branch may be used to separate several orders used in imaging space in a single image. In yet other embodiments, instead of or in addition to the first order beam, 2nd, 3rd and higher order beams (not shown in FIG. 5 ) may also be used in the measurement. In other embodiments, a segmented prism may be used instead of the aperture diaphragm 21 so that the +1 and -1 orders can be captured simultaneously at spatially separated locations on the image sensor 23.

In order to adapt the measurement radiation to these different types of measurements, the aperture plate 13 may contain several aperture patterns formed around a disk that is rotated to bring the desired pattern into position. It should be noted that aperture plate 13N or 13S can only be used to measure gratings oriented in one direction (depending on the X or Y setting). For measuring orthogonal gratings, target rotations of up to 90° and 270° can be implemented.

Light sources that can be used for metrological applications of the concepts disclosed herein can include any broadband source and a color selection configuration for selecting one or more colors from the broadband output. As an example, the radiation source can be based on a hollow fiber or a solid fiber, such as a hollow core photonic crystal fiber (HC-PCF) or a solid core photonic crystal fiber (SC-PCF). For example, in the case of an HC-PCF, the hollow fiber can be filled with a gas that acts as a widening medium for widening the input radiation. This fiber and gas configuration can be used to produce a supercontinuum radiation source. The radiation input to the fiber can be electromagnetic radiation, such as radiation in one or more of the infrared, visible, UV, and extreme UV spectra. The output radiation may consist of or include broadband radiation, which may be referred to herein as white light. This is only one example of a broadband light source technology that may be used in the methods and apparatus disclosed herein, and other suitable technologies may be used instead.

When using metrology sensors including those described above and/or other types of metrology sensors (e.g., alignment sensors, level sensors), it is often necessary to control the illumination spectrum, e.g., to Switch illumination between different wavelengths (colors) and/or wavefront profiles.

To perform color selection, color selection modules have been proposed that use grating light valve (GLV) technology such as that sold by Silicon Light Machines (SLM), for example, as described in US6947613B, which is incorporated herein by reference. GLV is an electrically programmable diffraction grating based on microelectromechanical systems (MEMS) technology. Figure 6 illustrates the principle. Figure 6 is a schematic illustration of a GLV pixel or component 500 from (a) above and (b) and (c) ends. The GLV assembly contains two types of alternating GLV reflective strips: a static or biased strip 510 that is typically grounded along with a common electrode and a driven or active strip 520 that is driven by an electronic driver channel. A GLV module may include any number of these GLV components 500 configured in an array. The active and bias bands can be essentially the same except for how they are driven. When no voltage is applied to active strip 520, it is coplanar with the bias strip, the configuration shown in Figure 6(b). In this configuration, the GLV essentially acts as a mirror, where incident light is specularly reflected (ie, specularly reflected radiation or zeroth diffraction order radiation is formed). When a voltage is applied to active strip 520, as shown in Figure 6(c), it deflects relative to bias strip 510, thereby establishing a square well diffraction grating. In this state, the incident light is diffracted to a fixed diffraction angle. The ratio of reflected light to diffracted light can be continuously varied by controlling the voltage on the active band 520, which controls the magnitude of its deflection. Therefore, the amount of light diffracted by the GLV can be controlled by analogy from zero (full specular reflection) to all incident light (zero specular reflection). Within the context of this disclosure, this control of the amount of reflected radiation relative to the amount of radiation diffracted into non-zero diffraction orders may be referred to as modulated illumination.

The GLV module can be used in zeroth order mode such that diffraction radiation is blocked/dumped and specularly reflected (zeroth order diffraction) radiation is provided to the metrology tool. This has the advantage of maintaining etendue. Thus, an aperture stop may be provided in the pupil plane with the purpose of maximizing transmission of the zeroth order and maximizing blocking (minimizing transmission) of the first order (and other diffraction orders). However, the diffraction angle depends on the wavelength. In addition, the spot size in the pupil plane can also be wavelength-dependent, so that each color has a different spot size in the pupil plane. For example, sources currently used in some metrology applications may contain different etendues for different colors of light, such that the respective beam widths for the different colors are different.

Because of this, it is difficult to configure an aperture diaphragm to maximize transmission of the first order with zeroth-order blockage for all wavelengths of interest (e.g., the wavelength band covered by the source selection module). Any particular shape or configuration of a hard aperture diaphragm may be suboptimal for certain wavelength ranges (e.g., may result in too much zeroth-order blockage and/or too much first-order leakage in the transmission window). The problem becomes greater as the wavelength range used increases.

This problem is exacerbated when using beams with high etendue. High etendue beams make it difficult to minimize the spot size on the GLV (per wavelength), and difficult to have a low numerical aperture (NA) per order. A small spot on the GLV is highly desirable in order to operate over a flat region of the activated band and thus not lose contrast. Low NA orders are beneficial in separating the zeroth and first orders over several wavelengths.

Known color selection module configurations based on controllable diffraction elements such as GLV can include: beam spreading elements for spreading the broadband illumination beam; controllable diffraction elements or GLV modules for spreading the broadband illumination beam through The broadband illumination beam is spatially modulated after dispersion; an aperture stop is located in the far field (the pupil plane of the GLV, or its conjugate) to remove all but the desired order (e.g., to remove all but the desired order) all orders except the zeroth order; however, this can be inverted so that the zeroth order is blocked and the first order is transmitted); and a light combining element for recombining the spatially modulated broadband illumination beam to obtain an output source beam. The beam dispersing element can disperse the color of the white light source above the GLV in a first direction (eg, where the GLV is included in the image plane or field plane of the system). The combined elements and discrete elements can be different elements or a single element.

FIG7 illustrates a first color selection module configuration based on GLV. At the top of FIG7 is a side view of the configuration and at the bottom of the figure is a top view of the same configuration. A broadband source SO emits broadband radiation. A lens system represented by a plurality of lens elements (e.g., lenses L1 and L2) provides access to a pupil plane where a beam dispersing element DE (e.g., a grating or prism) is located. The beam dispersing element DE disperses the broadband illumination beam onto the GLV via an intermediate image at a first spectrally dispersive image plane SDIP (or field plane) between lenses L2 and L3, as the case may be (as shown here). Lens L4 focuses the spectrally dispersive radiation onto the GLV module GLV at a second spectrally dispersive image plane. Reflected (zeroth-order) radiation from the GLV is captured by lens L4 (e.g., in this embodiment, i.e., where incident radiation is focused onto the GLV, and spatially modulated reflected radiation is captured from the GLV using the same lens configuration). An aperture aperture _ST0 is located in pupil plane P2 provided by lens L4 to block any unwanted diffraction orders from the GLV module; e.g., passing the zeroth-order substantially unattenuated while blocking the first-order. In the configuration shown, the modulated illumination beam is reconstructed on the return path using the same dispersive element DE as used to disperse the beam on the outward path. The lens L1 then focuses the output beam into the metrology device MET (for example, into a suitable optical fiber, such as a single-mode optical fiber for transmitting radiation to the metrology device MET).

It should be understood that, although this configuration is shown as illustrating problems of prior art configurations that are solved by the concepts disclosed herein, the actual configuration shown is not prior art. Source selection module configurations that use the same optical components for the outgoing path to the GLV and the return path from the GLV are not known from the prior art. This includes, for example, using a single element DE (e.g., a fluorophore) as a dispersing element in the outward path and a combined element in the return path, and sharing all lenses including imaging lens L4 to image the dispersed radiation onto the GLV And the modulated radiation is collected from the GLV. This is achieved by having a first off-axis beam path (outward path) to the GLV (black in the top image, note that this aspect is only visible in the top image) and a second off-axis beam path (return) from the GLV path) (gray in the top image) to achieve. Prior art configurations typically use individual optical branches to and from the GLV, with each branch having dedicated optics, and such configurations are within the scope of the present disclosure.

A schematic representation of the light distribution at lens L2 (plane P1) is also shown in Figure 7. The top of the representation corresponds to the outward path and shows scattered source radiation; the bottom of the representation corresponds to the return path and shows GLV modulated radiation (illustrative color selections shown only). Shades of gray represent different colors/wavelengths. Also shown is an image representation at the spatially dispersed image plane SDIP, which shows the dispersed light beam in the image plane.

Also shown is a first pupil plane representation _P20 associated with pupil plane P2 of the lens system including lenses L3 and L4. This includes the position of the (first order) aperture _ST0 , defining an aperture _AP0 configured for zeroth order mode operation; that is, blocking the first diffraction orders +1, -1 (shown as dotted lines in the bottom figure, these are not visible in the top figure), and transmitting the zeroth order 0 and the source beam SB. Note the different positions in the pupil plane (that is, diffraction angles) and the spot sizes/diameters for each wavelength of the first diffraction orders +1, -1 (in this case, different colors will also have different diameters in the source beam SB). It is not necessary for different colors to have different spot sizes, and the concepts disclosed herein can be used with sources whose spot sizes are not wavelength dependent.

FIG8 shows a second color selection module configuration based on GLV. FIG8(a) is a side view of the configuration and FIG8(b) is a top view. In this example, the GLV is configured for first-order mode operation; that is, transmitting the first diffraction order (for clarity, only two colors +1 _λ1 , +1 _λ2 , -1 _λ1 , -1 _λ2 are shown, both of which are selected by the GLV; of course there may be more and/or continuous spectra) and the source beam SB; and blocking the zeroth order 0 _λ1 , 0 _λ2 . More specifically, in the depicted example, two wavelengths are shown to be transmitted through configuration λ ₁ , λ ₂ (ie, both selected by the GLV), with the resulting diffraction orders +1 _{λ 1 ,} −1 _{λ 1} , +1 _{λ 2} , −1 _{λ 2} being captured by lens L ₃ .

Many components are as described with respect to Figure 7 and will not be described again. Figure 8(c) is a second pupil plane representation _P21 corresponding to the first pupil plane representation _P20 shown in Figure 7. In this configuration, aperture _ST1 acts as a zeroth order aperture, which is positioned to block only the zeroth order (specular radiation), thereby defining an aperture _AP1 that transmits the first order (and/or other higher orders).

As explained, the aperture diaphragm should maximize the transmission of the zeroth order beam (for all selected wavelengths) and minimize the transmission of the first order beam for all wavelengths, or vice versa. Maximizing the transmission (e.g., of the zeroth order beam or of the diffracted, e.g., first order beam for all wavelengths) should be understood to mean increasing the transmission as much as possible given the constraints of the configuration and tradeoffs required to minimize the transmission of the blocked radiation. Similarly, minimizing the transmission (e.g., of the 1st order or zeroth order for all wavelengths) should be understood to mean blocking these orders as much as possible given these same constraints and tradeoffs. In particular, the fact that the spots have spatially overlapping tails (if one considers a plot of intensity or amplitude versus pupil position for each spot) necessitates either passing some unwanted light (resulting in poor out-of-band contrast) or blocking the tail of the desired zeroth order, resulting in less signal and therefore less throughput. This problem increases the larger the spots are compared to the separation of the orders (i.e., the larger the NA of the beam).

In embodiments, maximizing transmission may include transmitting 90% or more, transmitting 95% or more, transmitting 98% or more, transmitting 99% or more, transmitting 99.9% or more, or transmitting 99.99% or more. More transmitted radiation. In embodiments, minimizing transmission may include blocking 90% or more, blocking 95% or more, blocking 98% or more, blocking 99% or more, blocking 99.9% or more, or blocking 99.99% or more. More warps block radiation.

FIG9 illustrates the problem with a pupil representation shown with aperture aperture ST ₀ (e.g., corresponding to a zeroth order mode configuration). It shows a source beam SB, where for clarity only two wavelengths (indicated by shading as before) and the corresponding zeroth order beam 0 and diffraction orders +1, -1 are shown. When the source beam SB is diffracted by the GLV, each of the first diffraction orders +1, -1 is scattered in a first direction labeled X here, and when reflected, the source beam is reflected by a mirror into the zeroth order 0 (the ratio of diffraction into the first diffraction orders +1, -1 and reflection into the zeroth order can be controlled via the GLV, as already described). Below the pupil representation is a plot of intensity versus pupil position in one dimension through the zeroth order beam 0 and diffraction orders +1, -1 and spatially aligned with the pupil representation. As can be seen from these intensity plots, the overlapping tails of the zeroth and first order mean that optimal blocking of the first order is not possible in this case; it must be the case that either some zeroth order radiation is blocked or first order radiation is transmitted. This is particularly the case when first order radiation is blocked for short wavelengths and zeroth order is transmitted for longer wavelengths.

The same principle applies when the GLV is configured for first order mode operation. For example, if aperture diaphragm ST ₁ is used instead of aperture diaphragm ST ₀ in FIG. 9 , it is not possible to completely block the zeroth order and completely transmit the desired first order.

To solve this problem, in addition to dispersing a first beam of a broadband illumination beam (e.g., source beam radiation) in a first direction in a (conjugate) image plane of a controllable (e.g., electrically programmable) diffractive element or GLV In addition to the dispersing element (e.g., a beam or a grating), it is proposed to provide at least one second beam dispersing element (e.g., a beam dispersing element) that disperses the broadband illumination beam in a second direction in the pupil plane of the controllable diffractive element or GLV. or raster). The first and second directions may be orthogonal, with the first direction being the periodic direction of the GLV and the second direction being the direction in which each GLV strip extends. Thus, at least one second beam spreading element may be located at the (conjugate) image plane of the GLV. This enables better optimization of the aperture stop shape for better blocking of undesired radiation (eg, non-zeroth or first diffraction orders from GLV).

FIG10( a) is an equivalent of the pupil representation of FIG9 , in which the concepts disclosed herein are implemented. Here, due to the second beam spreading element, the source beam SB is now spread in a second direction (here labeled Y) within this pupil plane. Although only two wavelengths are shown for clarity, it should be understood that the source beam may actually include more wavelengths, for example, a continuous wavelength band, and thus, the spread source beam may actually include a continuously spread spectrum (or multiple discrete wavelengths) in the second direction. Thus, the position of the source radiation toward the GLV in this second direction is wavelength dependent (in the example shown, the short WL has a larger angle of incidence onto the GLV; this is a design choice and can be reversed). The resulting zeroth-order radiation O is similarly spread in the second direction. Due to diffraction by the GLV, the first order +1, -1 will also be scattered in this second direction, and also in the first direction (the scatter in the first direction will be the same as that of FIG. 9 ).

This two-dimensional dispersion of the first order enables better optimization of the aperture diaphragm ST ₀ 'configuration/shape, and specifically, enables different effective aperture sizes (e.g., in a first direction) for each wavelength. As can be seen in the illustrated example of FIG. 10( a), the diffracted radiation of a first (e.g., short) wavelength is constrained by the effective aperture size b, and the diffracted radiation of a second (e.g., long) wavelength is constrained by the effective aperture size a. The dotted line represents a compromise fixed aperture size in the example of FIG. 9 . Thus, the aperture diaphragm ST ₀ 'can be configured to include an aperture size in a first direction (e.g., at least for a portion (e.g., approximately half) of the pupil used for the optical return path downstream of the GLV) that varies in size (increases or decreases) along a second direction. The smaller apertures of this continuously increasing aperture width (or stepwise increasing aperture width) may be located in a pupil region corresponding to the positions to which the diffraction steps in the second direction (in that second direction) will be diverted, the diffraction steps also divert to smaller angles in the first direction, and/or the spot sizes for the diffraction steps in the pupil are smaller. Similarly, larger apertures or larger ends of continuously increasing aperture widths may be located in a pupil region in a second direction that corresponds to locations to which diffraction steps (in that second direction) will be diverted, which also divert to larger angles in the first direction, and/or have larger spot sizes in the pupil for those diffraction steps.

FIG10( b ) shows an equivalent configuration, but in which the aperture ST ₁ ′ is configured for first-order mode operation; that is, blocking the zeroth order and transmitting at least one higher diffraction order (e.g., one or two first orders). Thus, this configuration includes a continuously decreasing (zeroth) aperture ST ₁ ′ width, rather than a continuously increasing aperture width.

It will be appreciated that the shape of the continuously increasing aperture or the continuously decreasing (zeroth) aperture may differ from that shown, for example, the aperture/aperture edges need not be straight lines as shown here; It may eg be curved from bottom to top (from the perspective of the drawing) or may gradually increase/decrease. Alternatively or additionally, the aperture stop may contain "soft" edges that transmit/block in a non-binary manner (eg, the blocking portion of the aperture at the edge may partially transmit radiation).

It will be appreciated that the GLV may be used in the opposite configuration (high order mode) where the desired radiation is diffracted radiation (e.g., first order radiation) and the undesired radiation is specularly reflected (zeroth order) radiation. In this configuration, the aperture may be reversed from that shown in the pupil region corresponding to the return path downstream of the GLV (but not blocking the source beam in the outward path). For example, in FIG. 10 , the diaphragm may block the central region between the diaphragm/blocking portions shown to block zeroth order 0, and transmit first order +1, -1.

FIG. 11 is a schematic illustration of an exemplary color selection module according to the first embodiment. The configuration is the same as the configuration shown in FIG. 7 , except that a second beam dispersing element DE2 is added in addition to the first beam dispersing element DE1. In the configuration shown, the second beam dispersing element DE2 is provided in the outward path for dispersing source radiation in a pupil plane (e.g., P2) in the second direction. In contrast, the first beam dispersing element disperses source radiation in an image plane in the first direction. In the return path, a second beam combining element CE2 is provided for recombining illumination in the second direction. It should be noted that in this embodiment, the first beam dispersing element DE1 also serves as a first beam combining element for recombining illumination in the first direction; this may be optional as appropriate, and a separate first beam combining element may alternatively be provided for recombining illumination in the first direction.

The second beam dispersing element DE2 and the second beam combining element CE2 may be located at a conjugate image plane of the GLV. In addition to these elements DE2, CE2, a wedge WG (e.g. made of a low dispersion material) may be provided at plane P2 (e.g. the pupil plane defined by lens system L3, L4) for splitting the illumination in the outward path at the first spectrally dispersive image plane SDIP (e.g. at the approximate location of elements DE2, CE2). The second beam dispersing element DE2 and the second beam combining element CE2 may comprise a pair of (e.g. similar but oppositely oriented) dispersing elements or prisms.

Figure 12(a) is a schematic illustration of an exemplary color selection module according to the second embodiment. This configuration is the same as that shown in Figure 8, except that in addition to the first beam spreading element DE1 (which doubles as the first beam combining element as mentioned above), a second beam spreading element DE2 and a second beam combining element CE2 are added . In the arrangement shown, a second beam spreading element DE2 is provided in the outward path for spreading the source radiation in a pupil plane in a second direction. In contrast, the first beam spreading element disperses the source radiation in an image plane in a first direction. In the return path, a second beam combining element CE2 is provided for recombining the illumination in this second direction.

Figure 12(b) shows the resulting pupil plane representation P2 ₁ '' of the plane containing the zeroth-order stop ST ₁ ''. The zeroth-order stop ST ₁ ″ has a varying (eg, continuously decreasing) width defining a first-order or diffraction aperture AP ₁ ″ configured to transmit the first diffractive order.

As an alternative to the illustrated position of the second beam spreading element DE2 / combination element CE2 (in either embodiment), it could be located directly in front of the GLV (e.g. at one of the input windows of the GLV or Replace the input window of GLV). The second beam spreading element DE2/combination element CE2 (in either embodiment) optionally contains a compound prism, such as Amici prism.

Therefore, as can be seen from the respective exemplary pupil representations P2 ₀ '', P2 ₁ '' of the two embodiments, the source beam SB and all the diffracted/reflected beams spectrally dispersed in the second direction can be used more optimally. Optimal aperture shapes AP ₀ '', AP ₁ '', as already described.

For the sake of simplicity, the beam path after the second beam spreading element DE2/combining element CE2 is not drawn as tilted; in fact it may have to be tilted.

GLV-based source selection modules enable the ability to control the degree of transmission of each output beam color or frequency band, rather than just turning colors/bands on and off.

Advantages of the proposed configuration include: providing the option of using larger etendue sources; achieving higher achievable throughput (signal) for a given out-of-band (OoB) signal; or conversely, achieving better achievable OoB suppression for a given throughput (signal); and achieving smaller minimum bandwidth (by achieving a smaller spot on the GLV for a given throughput and OoB performance).

Other embodiments are disclosed in subsequent numbered clauses: 1. A source selection module for selecting the spectral characteristics of a broadband illumination beam to obtain a modulated illumination beam, the source selection module comprising: A first beam dispersion element for dispersing the broadband illumination beam, the first beam dispersion element being operable to disperse the broadband illumination beam along a first direction; A second beam dispersion element for dispersing the broadband illumination beam, the second beam dispersion element being operable to disperse the broadband illumination beam along a second direction perpendicular to the first direction; A controllable diffraction element having a controllable element arranged along the first direction such that the periodic direction of the controllable diffraction element includes the first direction; the controllable diffraction element being operable to controllably spatially modulate the broadband illumination beam after the broadband illumination beam is dispersed by the first beam dispersion element and the second beam dispersion element; and An aperture diaphragm operable to maximize transmission of one of the mirror-reflected radiation and the diffracted radiation from the controllable diffraction element and minimize transmission of the other of the mirror-reflected radiation and the diffracted radiation. 2. A source selection module as in clause 1, wherein the controllable diffraction element comprises a grating diaphragm module. 3. A source selection module as in clause 1 or 2, wherein the first beam dispersion element is located in a pupil plane of the controllable diffraction element or a conjugate thereof so as to disperse the broadband illumination beam in an image plane of the controllable diffraction element or a conjugate thereof. 4.  A source selection module as in any of the preceding clauses, wherein the second beam dispersion element is located in the image plane of the controllable diffraction element or its conjugate, so as to disperse the broadband illumination beam in the pupil plane of the controllable diffraction element or its conjugate. 5.  A source selection module as in any of the preceding clauses, further comprising at least a first beam combination element, the first beam combination element being used to recombine the modulated illumination beam in the first direction to obtain an output source beam. 6.  A source selection module as in any of clauses 1 to 4, wherein the first beam dispersion element is also configured to recombine the modulated illumination beam from the controllable diffraction element on a return path. 7.  The source selection module of clause 6, wherein at least one lens element is shared between an outward path of the broadband illumination beam to the controllable diffraction element and the return path, the outward path includes a first off-axis path, and the return path includes a second off-axis path through the at least one lens element and the first beam dispersion element. 8.  The source selection module of clause 7, wherein the at least one lens element includes at least one lens or lens system, the lens or lens system being operable to image the broadband illumination beam after being dispersed by the first beam dispersion element and the second beam dispersion element onto the controllable diffraction element, and to collect the modulated illumination beam from the controllable diffraction element. 9.  A source selection module as in any of the preceding clauses, further comprising at least a second beam combination element for recombining the modulated illumination beam in the second direction to obtain an output source beam. 10.    A source selection module as in any of the preceding clauses, wherein the aperture diaphragm is located in a pupil plane of the controllable diffraction element or a conjugate thereof. 11.    A source selection module as in clause 10, wherein the aperture diaphragm is operable to maximize transmission of the mirror-reflected radiation from the controllable diffraction element and minimize transmission of diffracted radiation from the controllable diffraction element. 12.    The source selection module of clause 10, wherein the aperture diaphragm is operable to minimize transmission of the mirror-reflected radiation from the controllable diffraction element and maximize transmission of the diffracted radiation from the controllable diffraction element. 13.    The source selection module of any preceding clause, wherein the aperture diaphragm defines an aperture having an aperture size in the first dimension, the aperture size varying along the second dimension for at least a portion of the return path of the pupil plane corresponding to the modulated illumination beam. 14.    The source selection module of clause 13, wherein the aperture size in the first dimension and/or the aperture diaphragm size increases or decreases continuously or stepwise along the second dimension. 15.    A source selection module as in any of the preceding clauses, wherein the first beam dispersion element and the second beam dispersion element each comprise a prism. 16.    A source selection module for selecting the spectral characteristics of a broadband illumination beam to obtain a modulated illumination beam, the source selection module comprising: At least one beam dispersion element for dispersing the broadband illumination beam, the at least one beam dispersion element being operable to disperse the broadband illumination beam along a first direction; A controllable diffraction element having a controllable element arranged along the first direction such that the periodic direction of the controllable diffraction element includes the first direction; the controllable diffraction element being operable to controllably spatially modulate the broadband illumination beam after the broadband illumination beam is dispersed by the first beam dispersion element; an aperture diaphragm operable to maximize transmission of one of the mirror-reflected radiation and the diffracted radiation from the controllable diffraction element and minimize transmission of the other of the mirror-reflected radiation and the diffracted radiation; and a plurality of lens elements, comprising at least one lens or lens system operable to image the broadband illumination beam after being dispersed by the first beam dispersing element onto the controllable diffraction element, and to collect the modulated illumination beam from the controllable diffraction element; wherein the at least one first beam dispersing element is also configured to recombine the modulated illumination beam from the controllable diffraction element on a return path. 17.    The source selection module of clause 16, wherein each of the plurality of lens elements is shared between an outward path of the broadband illumination beam to the controllable diffraction element and the return path, the outward path comprising a first off-axis path, and the return path comprising a second off-axis path through the plurality of lens elements and at least one beam spreading element. 18.    The source selection module of clause 16 or 17, wherein the controllable diffraction element comprises a grating light valve module. 19.    The source selection module of any of the preceding clauses, comprising an illumination source for providing the input illumination. 20.    A source selection module as in claim 19, wherein the illumination source comprises a hollow fiber for confining a widening medium and an excitation radiation source operable to provide excitation radiation for exciting the widening medium. 21.    A metrology device comprising a source selection module as in any of the preceding claims to provide measurement illumination. 22.    A metrology device as in claim 21, wherein the metrology device comprises a scatterometer. 23.    A metrology device as in claim 22, comprising: a support for a substrate; an optical system for directing the measurement illumination to a structure on the substrate; and a detector for detecting measurement radiation scattered by a structure on the substrate. 24.    The metrology device of clause 21, wherein the metrology device comprises an alignment sensor. 25.    A lithography apparatus comprising: a patterning device support for supporting a patterning device; a substrate support for supporting a substrate; and the metrology device of clause 24, operable to perform alignment of the patterning device and/or the substrate support.

It should be understood that the term color is used throughout this document synonymously with wavelength or spectral component, and that color can include colors outside the visible band (e.g., infrared or ultraviolet wavelengths).

Although specific embodiments of the invention have been described above, it should be understood that the invention may be practiced otherwise than as described.

Although specific reference may be made above to the use of embodiments of the invention in the context of optical lithography, it will be understood that the invention may be used in other applications (eg, imprint lithography) and, where the context permits, is not limited to Optical lithography. In imprint lithography, topography in the patterning device defines the pattern produced on the substrate. The patterned device's configuration can be pressed into a resist layer supplied to the substrate, whereupon the resist is cured by application of electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist, leaving a pattern therein.

The terms "radiation" and "beam" as used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having a wavelength at or about 365 nm, 355 nm, 248 nm, 193 nm, 157 nm, or 126 nm). nm) and extreme ultraviolet (EUV) radiation (e.g., having wavelengths in the range of 1 nm to 100 nm), and particle beams, such as ion beams or electron beams.

The term "lens", where the context permits, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components. Reflective components may be used in equipment operating in the UV and/or EUV range.

The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

0: Solid line/0th order 0 _λ1 : 0th order 0 _λ2 : 0th order 1(S):-1 diffraction ray+1: point chain line/diffraction order/1st order+1(N): +1 diffraction ray+1 _λ1 : color/resulting diffraction order +1 _λ2 : color/resulting diffraction order-1: double-point chain line/diffraction order/first order-1 _λ1 : color/resulting diffraction order -1 _λ2 : Color/Resulting Diffraction Order 2: Broadband Radiation Projector 4: Spectrometer Detector 6: Spectrum 8: Profile 11: Source 12: Lens 13: Aperture Plate 13N: Aperture Plate 13S: Aperture Plate 14: Lens 15 : Beam splitter 16: Objective lens 17: Second beam splitter 18: Optical system 19: First sensor 20: Optical system 21: Aperture diaphragm/field diaphragm 22: Optical system 23: Sensor 500: GLV Component 510: Bias Band 520: Active Band a: Effective Aperture Size AP ₀ : Aperture AP ₀ '': Aperture Shape AP ₁ : Aperture AP ₁ '': Aperture/Aperture Shape b: Effective Aperture Size B: Radiation Beam BD: Beam delivery system BK: Baking plate C: Target part CE2: Second beam combining element CH: Cooling plate CL: Computer system DE: Developer/beam dispersing element DE1: First beam dispersing element DE2: Second beam dispersing element GLV :GLV module I: Measure radiation ray I/O1: Input/output port I/O2: Input/output port IF: Position measurement system IL: Illumination system L1: Lens L2: Lens L3: Lens L4: Lens LA: Lithography equipment LACU: Lithography control unit LB: Loading area LC: Lithography unit M1: Mask alignment mark M2: Mask alignment mark MA: Patterning device MET: Metrology device MT: Metrology tool/scatterometer/mask Cover support O: point line/axis P1: substrate alignment mark/plane P2: substrate alignment mark/pupil plane P2 ₀ : first pupil plane representation P2 ₀ '': pupil representation P2 ₁ : second light Pupil plane representation P2 ₁ '': Pupil representation PEB: Post-exposure baking step PM: First positioner PS: Projection system PU: Processing unit/processor PW: Second positioner RO: Robot SB: Source beam SC: Spin coater SC1: First scale SC2: Second scale SC3: Third scale SCS: Supervisory control system SDIP: First spectral dispersion image plane SO: Radiation source/broadband source ST ₀ : Aperture diaphragm ST ₀ ' :Aperture stop ST ₁ :Aperture stop ST ₁ ':Aperture ST ₁ '':0th-order stop T:Target TCU:Coating and developing system control unit W:Substrate WG:Wedge WT:Substrate support λ ₁ , λ ₂ : configuration

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 depicts the lithography equipment; Figure 2 depicts a schematic overview of the lithography unit; Figure 3 depicts a schematic representation of a monolithic lithography illustrating the cooperation between three key technologies for optimizing semiconductor manufacturing; Figure 4 depicts a schematic overview of a scatterometry apparatus used as a metrology device, which may include a dark field digital holographic microscope, in accordance with an embodiment of the present invention; Figure 5 contains (a) a schematic diagram of a dark field scatterometer for measuring a target using a first pair of illumination apertures, (b) details of the diffraction spectrum of the target grating for a given illumination direction; Figure 6 is a schematic representation of a grating light valve illustrating basic operation in (a) top view, (b) end view in a first configuration, and (c) end view in a second configuration; Figure 7 is a schematic illustration of the operating principle of an illumination arrangement including a grating light valve in a first configuration; 8(a), 8(b) and 8(c) are schematic illustrations of the operating principle of an illumination arrangement including a grating light valve in a second configuration; Figure 9 is a pupil representation illustrating the difficulty of optimizing the aperture diaphragm configuration for the configuration of Figure 7; Figures 10(a) and 10(b) are pupil representations for lighting configurations according to embodiments of the present invention; Figure 11 is a schematic illustration of the operating principle of a lighting arrangement including a grating light valve according to a first embodiment of the present invention; and 12(a) and 12(b) are schematic illustrations of the operating principle of an illumination arrangement including a grating light valve according to a second embodiment of the present invention.

0:0th level

+1: First level

-1:First level

a: effective aperture size

b: Effective aperture size

SB: source beam

ST ₀ ': Aperture aperture

ST ₁ ': Optical

Claims (15)

A source selection module for selecting the spectral characteristics of a broadband illumination beam to obtain a modulated illumination beam, the source selection module comprising: a first beam dispersion element for dispersing the broadband illumination beam, the first beam dispersion element being operable to disperse the broadband illumination beam along a first direction; a second beam dispersion element for dispersing the broadband illumination beam, the second beam dispersion element being operable to disperse the broadband illumination beam along a second direction perpendicular to the first direction; a controllable diffraction element having a controllable element arranged along the first direction, so that a periodic direction of the controllable diffraction element includes the first direction; the controllable diffraction element being operable to controllably spatially modulate the broadband illumination beam after the broadband illumination beam is dispersed by the first beam dispersion element and the second beam dispersion element; and An aperture diaphragm operable to maximize transmission of one of the mirror-reflected radiation and the diffracted radiation from the controllable diffraction element and minimize transmission of the other of the mirror-reflected radiation and the diffracted radiation. The source selection module of claim 1, wherein the controllable diffraction element includes a grating light valve module. The source selection module of claim 1 or 2, wherein the first beam dispersion element is located in a pupil plane of the controllable diffraction element or its conjugate, so as to disperse the broadband illumination beam in the controllable diffraction element. in one of the image planes of the radiating element or its conjugate. A source selection module as claimed in claim 1 or 2, wherein the second beam dispersing element is located in an image plane of the controllable diffraction element or a conjugate thereof so as to disperse the broadband illumination beam in a pupil plane of the controllable diffraction element or a conjugate thereof. The source selection module of claim 1 or 2 further comprises at least one first beam combination element, which is used to recombine the modulated illumination beam in the first direction to obtain an output source beam. A source selection module as claimed in claim 1 or 2, wherein the first beam dispersing element is also configured to reconstitute the modulated illumination beam from the controllable diffraction element on a return path. The source selection module of claim 6, wherein at least one lens element is used between an outward path of the broadband illumination beam to the controllable diffraction element and the return path, the outward path including a first off-axis path , and the return path includes a second off-axis path through the at least one lens element and the first beam spreading element. The source selection module of claim 7, wherein the at least one lens element includes at least one lens or lens system operable to cause the broadband illumination beam to be dispersed by the first beam dispersing element and the second beam. The elements are dispersed onto the controllable diffraction element and then imaged, and the modulated illumination beam is collected from the controllable diffraction element. The source selection module of claim 1 or 2 further comprises at least one second beam combining element, which is used to recombine the modulated illumination beam in the second direction to obtain an output source beam. The source selection module of claim 1 or 2, wherein the aperture stop is located in one of the pupil planes of the controllable diffraction element or its conjugate, and is operable to maximize the light intensity from the controllable diffraction element. The specularly reflects the transmission of radiation and minimizes the transmission of the diffracted radiation from the controllable diffractive element. A source selection module as claimed in claim 1 or 2, wherein the first beam dispersing element and the second beam dispersing element each comprise a prism. A source selection module as in claim 1 or 2, wherein the aperture diaphragm defines an aperture having an aperture size in the first dimension, the aperture size varying along the second dimension for at least a portion of a return path of the modulated illumination beam corresponding to the pupil plane. A source selection module as claimed in claim 12, wherein the aperture size in the first dimension increases or decreases continuously or stepwise along the second dimension. The source selection module of claim 1 or 2 includes an illumination source for providing the input illumination. A weight and measurement device, which includes a source selection module according to any one of claims 1 to 14 to provide measurement illumination.