Metrology tools and components thereof

Abstract

A metrology tool for determining one or more parameters of interest (e.g., overlay) of a structure on an object (e.g., wafer). The metrology tool includes a module for at least partially defining an aperture, a projection optic, a detection optic, and a detector. The module for at least partially defining an aperture is positionable to receive a beam of radiation and transmit a modified beam of radiation. The projection optic is arranged to project the modified radiation output by the module to a beam spot area in which the structure is positionable. The detection optic is arranged to receive at least a portion of the radiation scattered by the structure. The detector is operable to determine the one or more parameters from the received scattered radiation. The module is configured such that a size and / or shape of the aperture defined by the module is dependent on a wavelength of the received radiation.

Description

Cross-references to related applications

[0001] This application claims priority to US application 63 / 562,831, filed March 8, 2024, and EP application 24173430.0, filed April 30, 2024, which are incorporated herein by reference in their entirety. Technical Field

[0002] This invention relates to a novel measuring device or measuring tool. The invention also relates to a novel module for use in a measuring tool and for at least partially defining a hole in the measuring tool. Background Technology

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

[0004] To project a pattern 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, extreme ultraviolet (EUV) radiation in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0005] Low-k1 lithography can be used to process features smaller than the classical resolution limit of lithography equipment. In such a process, the resolution formula can be expressed as CD = k1 × λ / NA, where λ is the wavelength of radiation used, NA is the numerical aperture of the projection optics in the lithography equipment, CD is the "critical size" (typically the smallest feature size printed, but in this case, half a pitch), and k1 is an empirical resolution factor. Generally, the smaller k1 is, the more difficult it is to reproduce patterns on the substrate that are similar in shape and size to those planned by the circuit designer for specific electrical functions and performance. To overcome these difficulties, 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 apparatus, various optimizations of the design layout (such as optical proximity correction (OPC, sometimes also called "optical process correction")), 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.

[0006] It may be desirable to provide new metrological devices and components thereof for determining one or more parameters of a periodic target (e.g., a periodic target on a wafer), which at least partially solve one or more problems associated with a known arrangement, whether these problems are recognized herein or otherwise. Summary of the Invention

[0007] According to a first aspect of this disclosure, a measurement tool is provided for determining one or more parameters of interest of a structure on an object, the measurement tool comprising: a module for at least partially defining an aperture, the module being locating to receive and transmit a modified radiation beam; a projection optics arranged to project the modified radiation output by the module onto a beamspot region, the structure being locating in the beamspot region; a detection optics arranged to receive at least a portion of the radiation scattered by the structure; and a detector operable to determine one or more parameters based on the received scattered radiation; wherein the module is configured such that the size and / or shape of the aperture defined by the module depends on the wavelength of the received radiation.

[0008] A radiation beam can be received from a radiation source. Within the plane of the module, the radiation beam can be generally circular. The modified radiation beam can be altered by blocking radiation in certain portions of the module's plane. The modified radiation beam can also be modified by altering the transmission characteristics of certain portions of the module's plane.

[0009] Now we will discuss the advantages of the measurement tools based on the first aspect.

[0010] For example, the measurement tool may include a scatterer for measuring a target on an object (e.g., a photolithographic wafer). For example, a dark-field scatterer may be included. This module may be referred to as an orifice plate. Within such a scatterer, the target (e.g., a periodic structure or grating) can be illuminated with a radiation beam. The radiation will be scattered from the target, thus forming multiple diffraction beams. At least a portion of the scattered radiation (including at least some of the diffraction beams) may be collected by collecting optics.

[0011] The response of measurements performed in a scatterometer (e.g., overlap measurements) is typically sensitive to the wavelength of the radiation used by the scatterometer. Furthermore, due to this wavelength dependence, it is desirable to isolate any background signals. For this reason, these scattering measurement instruments typically perform multiple separate, sequential measurements on each measurement mark or target at different radiation wavelengths, and then combine these measurements. Specific wavelengths (and bandwidths) are often dependent on a particular lithography process or option and are typically optimized for a given process to maximize the response to overlap errors.

[0012] Furthermore, for a given target, it may be desirable to use different apertures for illumination at different wavelengths. Existing metrology tools can provide multiple different aperture plates, each adapted for use with different combinations of target pitch and wavelength. To define different apertures, the aperture plate can be swapped for another when a new wavelength is selected (e.g., multiple aperture plates can be mounted on a wheel so that each plate can be placed one at a time in the beam path). However, it has been found that this results in a loss of yield because it requires a non-zero amount of time to swap the aperture plates. An alternative could be to use the same aperture for all wavelengths; however, this means using suboptimal apertures for at least some wavelengths, which also leads to a loss of yield.

[0013] Advantageously, the measuring tool according to the first aspect allows for the selection of different apertures when using different irradiation wavelengths. That is, once the irradiation wavelength has been selected, the appropriate aperture is automatically selected by means of the module's transmission characteristics.

[0014] The module can be located in the pupil plane of the measurement tool.

[0015] It should be understood that the pupil plane of the measurement tool is intended to represent the Fourier transform plane or field plane of the beam-spot region. That is, the intensity distribution of radiation in the beam-spot region is the Fourier transform of the intensity distribution of radiation in the pupil plane. It should be understood that all rays from any given point in the pupil plane are mapped onto substantially the entire beam-spot region. In other words, rays from any given point in the pupil plane illuminate the entire field of view (FOV) of the measurement tool. Similarly, a single point in the beam-spot region is mapped onto substantially the entire pupil plane. The intensity distribution of radiation in the pupil plane characterizes the angular distribution of radiation in the field plane (i.e., the beam-spot region). In some embodiments, the module may be positioned in a plane close to the pupil plane of the measurement tool (and may be referred to as the "pupil plane").

[0016] The measurement tool may also include a beam modification module arranged to control one or more properties of the radiation beam. In some embodiments, the beam modification module may be arranged to control the spectrum of the radiation beam. Additionally or alternatively, in some embodiments, the beam modification module may include beam-shaping optics, such as, for example, a collimator and / or an aperture stop.

[0017] In other words, the beam modification module is optically located upstream of the module and is arranged to control one or more properties of the radiation beam (such as, for example, the spectrum of the radiation beam) before the radiation beam is received by the module. As used herein, control of the spectrum of the radiation beam may include control of the center wavelength, bandwidth, and / or shape of the spectrum of the radiation beam. For example, the beam modification module may include a color wheel, etc. It should be understood that other embodiments of the beam modification module may include other devices for controlling the spectrum of radiation, such as, for example, an acousto-optic tunable filter or similar devices.

[0018] The module can be configured such that it can define at least two different apertures, the defined apertures depending on the wavelength of the received radiation.

[0019] For example, irradiating the module with a radiation beam having a first wavelength (e.g., from a first wavelength range) can produce a first aperture, while irradiating the module with a radiation beam having a second wavelength (e.g., from a second wavelength range) can produce a second aperture, and so on.

[0020] It should be understood that the module can be configured to define any number of different apertures. Typically, the module can be configured such that the number of different apertures that can be defined by the module is equal to (or greater than) the number of different wavelengths that will be used with each target in use.

[0021] As explained above, scattering measurement tools can be used to perform multiple separate, sequential measurements on each measurement mark or target at different radiation wavelengths, and then combine these measurements. In principle, the greater the number of different wavelengths, the better the measurement accuracy; however, the slower the target measurement will be. Therefore, a balance needs to be found. In practice, each mark can be measured using two, three, or four different wavelengths.

[0022] The module can be configured such that a finite number of different holes can be defined by the module.

[0023] For example, different apertures may each be at least partially defined by multiple discrete wavelengths of the minimum wavelength transmitted by the module in one or more directions.

[0024] Alternatively, the module can be configured such that a continuum of different apertures can be defined by the module. For example, the different apertures can each be defined at least partially by a gradient of the minimum wavelength transmitted by the module in one or more directions.

[0025] The module can be configured such that at least two distinct holes that can be defined by the module at least partially overlap.

[0026] For example, in some embodiments, one of the (smaller) holes may completely overlap with another of the (larger) holes. That is, the smaller hole may include a first region of the module, and the larger hole may include the first region plus an additional second region of the module.

[0027] In some embodiments, the module is configured to define a plurality of different nested holes. In some embodiments, the module is configured to define a plurality of different holes, including (in ascending order) a first hole, a second hole, etc., and wherein each hole, starting from the second hole, includes the same area of ​​the module as the next smallest hole plus an additional area.

[0028] The module can be configured such that the size of the aperture defined by the module increases with increasing wavelength.

[0029] This is advantageous because, as discussed below, in some measurement instruments, it is generally desirable to use a larger (smaller) aperture at larger (smaller) wavelengths.

[0030] A module can include a generally planar main body.

[0031] It should be understood that the general planar subject is intended to represent a subject having two larger dimensions and one smaller dimension. These two larger dimensions define the planar aspect of the subject. The first and second parts can be portions of the planar aspect of the subject.

[0032] A module may include a generally opaque first part.

[0033] This is advantageous when the module is positioned in the first (illumination) pupil plane of the measuring tool, and it is desirable to separate one or more higher-order diffraction beams from the zero-order diffraction beam in the second (measuring) pupil plane of the measuring tool (which is optically downstream of the target). Since the first portion is substantially opaque, there will be a corresponding portion of the second pupil plane that is not illuminated by the zero-order diffraction beam.

[0034] It should be understood that the first part is generally opaque, which may be intended to indicate that it does not transmit a range of radiation wavelengths or a range of radiation wavelengths used in the measuring instrument in use.

[0035] The module may further include a second portion adjacent to the first portion and offset from the first portion in a first direction. The transmittance of the second portion in the first direction may depend on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the first portion in the first direction.

[0036] Advantageously, with this arrangement, the second part will transmit only a small range of smaller wavelengths in the first direction (i.e., will have a smaller aperture), while the second part will transmit a larger range of larger wavelengths in the first direction (i.e., will have a larger aperture). Therefore, as further explained below, if the first direction is aligned with the dual (Fourier transform) direction of the shear direction of the target, the transmittance properties of the second part will mean that a suitable aperture can be provided to avoid overlap between the zero-order and first-order beams for a range of illumination wavelengths or a range of illumination wavelengths. As used herein, the dual direction of the first direction is intended to represent the direction in the dual space (sometimes also called the Fourier space) to which the first direction is mapped by the Fourier transform. For example, in the field plane (e.g., the plane of a mark on a wafer), the position can be specified by two directions that can be referred to as the x-direction and the y-direction. In the pupil plane (e.g., the plane in which a module can be set), the position can be specified by two directions that can be referred to as the k-direction. x Direction and k y The two directions are specified. k x The direction is the dual (Fourier transform) direction of the x-direction, k y The direction is the dual direction of the y-direction (Fourier transform).

[0037] The module may also include a third portion adjacent to the first portion and offset from the first portion in a second direction. The transmittance of the third portion in the second direction may depend on the wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction.

[0038] Advantageously, this allows the module to simultaneously measure overlap in two directions (a first direction and a second direction). The second direction can be substantially perpendicular to the first direction.

[0039] The module may also include a generally opaque fourth part.

[0040] The fourth part may be adjacent to the second part and offset from the second part in the second direction. The transmittance of the second part in the second direction may depend on the wavelength, such that for at least a portion of the second part, the minimum wavelength transmitted by the second part increases with the distance from the fourth part in the second direction.

[0041] The fourth part may be adjacent to the third part and offset from the third part in the first direction. The transmittance of the third part in the first direction may depend on the wavelength, such that for at least a portion of the third part, the minimum wavelength transmitted by the third part increases with the distance from the fourth part in the first direction.

[0042] The module may include multiple adjacent filters provided as a separate layer and stacked in the direction of the optical axis of the measuring instrument. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the multiple filters may have a different threshold. The filters may partially overlap in a plane substantially perpendicular to the optical axis of the measuring instrument.

[0043] Alternatively, the module may include multiple filters arranged substantially in the same plane in a direction generally perpendicular to the optical axis of the measuring tool. The multiple filters may be disposed on a common support layer. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the multiple filters may have a different threshold.

[0044] The measurement tool may include multiple modules for at least partially defining an aperture, the modules being oriented to receive and transmit a modified radiation beam, and each of the multiple modules being configured such that the size and / or shape of the aperture defined by the module depends on the wavelength of the received radiation.

[0045] For example, the measuring tool may include multiple such modules mounted on a common support (e.g., a wheel). By moving the support (e.g., rotating the wheel), one of the multiple modules can be positioned in the path of the radiation beam. Advantageously, this arrangement can allow for the provision of multiple (automatically selected) apertures to provide a range of different pitches for the target.

[0046] For example, multiple modules can each define different sets of apertures. Additionally or alternatively, for different modules, the dependence of the size and / or shape of the apertures defined by the modules on the wavelength of the received radiation can be different.

[0047] The measuring tool may also include a radiation source operable to generate a radiation beam received by the module.

[0048] The radiation source can be a broadband radiation source. For example, the radiation source can be operated to produce radiation with a spectrum of about 400-900 nm. In some embodiments, the radiation source can be operated to produce radiation with a spectrum of about 400-1600 nm.

[0049] The measuring tool may also include a support for supporting the object, making the object positionable so that it can receive modified radiation from the module.

[0050] Supports for supporting objects may include substrate holders operable to hold substrates in place. For example, a support may include a clamp for holding a substrate to the support. A support may include a stage, such as a wafer stage.

[0051] The measuring instrument may also include a movement mechanism operable to cause relative movement between the support and the modified radiation beam.

[0052] This allows an object or substrate to be stepped or scanned by radiation. As used herein, scanning of an object is intended to represent continuous movement of the object. As used herein, stepping of an object is intended to represent movement of the object in multiple consecutive (temporally separated) steps.

[0053] According to a second aspect of this disclosure, a module is provided for use in a measurement tool according to the first aspect of this disclosure.

[0054] According to a third aspect of this disclosure, a module is provided for at least partially defining a hole in a measuring tool, wherein the module is configured such that the size and / or shape of the hole defined by the module depends on the wavelength of the received radiation.

[0055] This module is advantageous for use with measuring tools because it allows for the automatic selection of different apertures when irradiated with radiation of different wavelengths. In other words, once the irradiation wavelength is selected, the appropriate aperture is automatically chosen based on the module's transmission characteristics.

[0056] The module can be configured such that it can define at least two different apertures, the defined apertures depending on the wavelength of the received radiation.

[0057] It should be understood that the module can be configured to define any number of different apertures. Typically, the module can be configured such that the number of different apertures that can be defined by the module is equal to (or greater than) the number of different wavelengths that will be used with each target within the measurement tool in which the module is used.

[0058] The module can be configured such that it can define a finite number of different holes.

[0059] For example, different apertures may each be at least partially defined by multiple discrete wavelengths of the minimum wavelength transmitted by the module in one or more directions.

[0060] Alternatively, the module can be configured such that it defines a series of different apertures. For example, each aperture can be defined at least partially by a gradient of the minimum wavelength transmitted by the module in one or more directions.

[0061] The module can be configured such that at least two distinct holes that can be defined by the module at least partially overlap.

[0062] For example, in some embodiments, one of the (smaller) holes may completely overlap with another of the (larger) holes. That is, the smaller hole may include a first region of the module, and the larger hole may include the first region plus an additional second region of the module.

[0063] In some embodiments, the module is configured to define a plurality of different nested holes. In some embodiments, the module is configured to define a plurality of different holes, including (in ascending order) a first hole, a second hole, etc., and wherein each hole, starting from the second hole, includes the same area of ​​the module as the next smallest hole plus an additional area.

[0064] The module can be configured such that the size of the aperture defined by the module increases with increasing wavelength.

[0065] This is advantageous because, as discussed below, in some measurement instruments, it is generally desirable to use a larger (smaller) aperture at larger (smaller) wavelengths.

[0066] A module can include a generally planar main body.

[0067] It should be understood that the general planar subject is intended to represent a subject having two larger dimensions and one smaller dimension. These two larger dimensions define the planar aspect of the subject. The first and second parts can be portions of the planar aspect of the subject.

[0068] A module may include a generally opaque first part.

[0069] This is advantageous when the module is positioned in the first (illumination) pupil plane of the measuring tool, and it is desirable to separate one or more higher-order diffraction beams from the zero-order diffraction beam in the second (measuring) pupil plane of the measuring tool (which is optically downstream of the target). Since the first portion is substantially opaque, there will be a corresponding portion of the second pupil plane that is not illuminated by the zero-order diffraction beam.

[0070] It should be understood that the first part is generally opaque, which may be intended to indicate that it does not transmit a range of radiation wavelengths or a range of radiation wavelengths used in the measuring instrument in use.

[0071] The module may further include a second portion adjacent to the first portion and offset from the first portion in a first direction. The transmittance of the second portion in the first direction may depend on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the first portion in the first direction.

[0072] Advantageously, with this arrangement, the second part will transmit only a small range of smaller wavelengths in the first direction (i.e., will have a smaller aperture), while the second part will transmit a larger range of larger wavelengths in the first direction (i.e., will have a larger aperture). Therefore, as further explained below, if the first direction is aligned with the dual (Fourier transform) direction of the target's shear direction, the transmittance properties of the second part will mean that a suitable aperture can be provided to avoid overlap between the zero-order and first-order beams for a series of irradiation wavelengths or a range of irradiation wavelengths.

[0073] The module may also include a third portion adjacent to the first portion and offset from the first portion in a second direction. The transmittance of the third portion in the second direction may depend on the wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction.

[0074] Advantageously, this allows the module to simultaneously measure overlap in two directions (a first direction and a second direction). The second direction can be substantially perpendicular to the first direction.

[0075] The module may also include a generally opaque fourth part.

[0076] The fourth part may be adjacent to the second part and offset from the second part in the second direction. The transmittance of the second part in the second direction may depend on the wavelength, such that for at least a portion of the second part, the minimum wavelength transmitted by the second part increases with the distance from the fourth part in the second direction.

[0077] The fourth part may be adjacent to the third part and offset from the third part in the first direction. The transmittance of the third part in the first direction may depend on the wavelength, such that for at least a portion of the third part, the minimum wavelength transmitted by the third part increases with the distance from the fourth part in the first direction.

[0078] The module may include multiple adjacent filters provided as a separate layer and stacked in a direction generally perpendicular to the plane of the module. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the multiple filters may have a different threshold. The filters may partially overlap in the plane of the module.

[0079] Alternatively, the module may include multiple filters arranged substantially in the same plane. The multiple filters may be disposed on a common support layer. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the multiple filters may have a different threshold.

[0080] According to a fourth aspect of this disclosure, a module is provided for at least partially defining an aperture in a measuring tool, the module comprising: a first portion; and a second portion adjacent to the first portion and offset from the first portion in a first direction; wherein the first portion is substantially opaque; wherein the transmittance of the second portion in the first direction depends on wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with distance from the first portion in the first direction.

[0081] As is now being discussed, it is advantageous to follow the module of the fourth aspect.

[0082] In use, the module can be incorporated into a measurement tool. For example, such a measurement tool may include a scatterer for measuring targets on an object (e.g., a photolithographic wafer). For instance, it may include a dark-field scatterer. The module can be used to define the shape and extent of the radiation beam within the illumination pupil plane of the measurement tool. That is, the module can be optically positioned upstream of the object under study and located in the Fourier transform plane of the object (the plane of the object may be referred to as the field plane). The module may be referred to as an orifice plate.

[0083] It should be understood that the pupil plane of a measurement instrument is intended to be represented as the Fourier transform plane of the beam-spot region or the field plane of the measurement instrument. That is, the intensity distribution of radiation in the beam-spot region is a Fourier transform of the intensity distribution of radiation illuminating the pupil plane. It should be understood that all rays from any given point in the pupil plane are mapped onto substantially the entire beam-spot region. In other words, rays from any given point in the pupil plane illuminate the entire field of view (FOV) of the measurement instrument. Similarly, a single point in the beam-spot region is mapped onto substantially the entire pupil plane. The intensity distribution of radiation in the pupil plane characterizes the angular distribution of radiation in the field plane (i.e., the beam-spot region).

[0084] Within such a scatterer, a target (e.g., a periodic structure or grating) can be illuminated with a radiation beam. The radiation will be scattered from the target, thus forming multiple diffraction beams. At least a portion of the scattered radiation (including at least some of the diffraction beams) can be collected by collecting optics. As described above, the measuring tool according to the fourth aspect can be used in the illumination pupil of the tool to define an aperture or illumination pattern for illuminating the target. Optically downstream of the target and conjugate to the plane of the module, a contribution from a zero-order diffraction beam will exist in the second pupil plane, which will illuminate a portion of the second pupil plane that is optically conjugate to the second part of the pupil. This zero-order diffraction beam will generally not illuminate the portion of the second pupil plane that is optically conjugate to the first part of the module.

[0085] In addition to the contribution to the second pupil plane from the zeroth-order diffraction beam, there will typically be contributions from each of the higher-order diffraction beams (or at least each of the higher-order diffraction beams received by the numerical aperture of the collecting optics). The contribution from the higher-order diffraction beams to the second pupil plane will generally be a copy of the contribution from the zeroth-order diffraction beam, which has been (a) shifted in the shear direction of the target; and (b) weighted by the diffraction efficiency of the target's diffraction order. This diffraction efficiency typically depends on the topology of the target, particularly the shape of the unit cell.

[0086] The amount by which the contribution from the higher-order diffraction beam to the second pupil plane shifts relative to the contribution from the zeroth-order diffraction beam depends on the target pitch and the wavelength of the irradiation. For example, for a target with a pitch p and irradiation with a wavelength λ, the angular separation between the zeroth-order and first-order diffraction beams is sin -1 (λ⁄p). Therefore, for a fixed pitch p, the larger the wavelength, the larger the angular spacing Δθ between the zeroth-order diffraction beam and the first-order diffraction beam.

[0087] It may be desirable to separate the higher-order diffraction beam from the zero-order diffraction beam within the measurement instrument. This can be achieved using appropriately selected optics positioned in or near the second pupil plane 1, provided that the higher-order diffraction beam does not overlap with the zero-order diffraction beam in the second pupil plane. Therefore, it may be desirable to have sufficient separation between the higher-order and zero-order diffraction beams in the second pupil plane such that the higher-order diffraction beam overlaps with the optically conjugate portion of the second pupil plane that is optically conjugate with the first part of the module.

[0088] The response to measurements (e.g., overlap measurements) performed in a scatterometer is typically sensitive to the wavelength of the radiation used by the scatterometer. Furthermore, due to this wavelength dependence, it is desirable to isolate any background signals. For this reason, these scattering measurement instruments typically perform multiple separate, sequential measurements on each measurement mark or target using different radiation wavelengths, and then combine these measurements. Specific wavelengths (and bandwidths) are often dependent on a particular lithography process or configuration and are typically optimized for a given process to maximize the response to overlap errors.

[0089] In existing measurement tools, multiple different aperture plates are available, each adapted for use with different combinations of target pitch and wavelength. For a given target, the pitch is fixed, and therefore the displacement of the first-order diffracted beam (relative to the zero-order diffracted beam) in the second pupil plane will vary when different wavelengths are used for measurement. Therefore, using existing arrangements, to avoid overlap between the zero-order and first-order beams, (a) the same aperture plate (i.e., the same pupil) is used for all wavelengths, and the aperture is small enough to avoid overlap between the zero-order and first-order beams; or (b) the aperture plate can be interchanged with another aperture plate (e.g., multiple aperture plates can be arranged on a wheel such that each aperture plate can be placed one at a time in the beam path). Disadvantageously, solution (a) implies the use of apertures smaller than optimal for some wavelengths, resulting in yield losses. Similarly, solution (b) results in yield losses due to the need for a non-zero amount of time to interchange aperture plates.

[0090] Advantageously, the module according to the fourth aspect includes a second portion having wavelength-dependent transmittance in the first direction, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with distance from the first portion in the first direction. Therefore, the second portion will transmit only a small range of smaller wavelengths in the first direction (i.e., will have a smaller aperture), while the second portion will transmit a larger range of larger wavelengths in the first direction (i.e., will have a larger aperture). Thus, if the first direction is aligned with the dual (Fourier transform) direction of the target's shear direction, the transmittance property of the second portion will mean that a suitable aperture can be provided to avoid overlap between the zero-order and first-order beams for a range of irradiation wavelengths or a range of irradiation wavelengths.

[0091] It should be understood that the first part is generally opaque, which can be intended to indicate that it does not transmit the range of radiation wavelengths used by the measuring instruments in use.

[0092] The module may also include a third portion adjacent to the first portion and offset from the first portion in a second direction. The transmittance of the third portion in the second direction may depend on the wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction.

[0093] Advantageously, this allows the module to simultaneously measure overlap in two directions (a first direction and a second direction). The second direction can be substantially perpendicular to the first direction.

[0094] The module may also include a generally opaque fourth part.

[0095] The fourth part may be adjacent to the second part and offset from the second part in the second direction. The transmittance of the second part in the second direction may depend on the wavelength, such that for at least a portion of the second part, the minimum wavelength transmitted by the second part increases with the distance from the fourth part in the second direction.

[0096] The fourth part may be adjacent to the third part and offset from the third part in the first direction. The transmittance of the third part in the first direction may depend on the wavelength, such that for at least a portion of the third part, the minimum wavelength transmitted by the third part increases with the distance from the fourth part in the first direction.

[0097] A module may include a generally planar body. It should be understood that a generally planar body is intended to represent a body having two larger dimensions and one smaller dimension. The two larger dimensions may define the plane of the body. A first part, a second part, a third part, and a fourth part may be portions of the plane of the body.

[0098] Alternatively, in some embodiments, the module may include multiple bodies. In use, each such body may be disposed in a different plane, all of which are optically conjugate (e.g., these planes may all be the pupil plane of the measuring tool). For example, a first portion may be defined on a first body, and a second portion may be defined on a second body.

[0099] In the example, we disclose a module for defining an aperture in a measuring tool in an optical path at least partially defined between an optical input section and an optical output section. The module includes: an optical input section for receiving an incident light beam; an optical output section for outputting a shaped light beam; a first transmission region configured to transmit light within a first spectral range; and a second transmission region configured to transmit light within a second spectral range, wherein the first and second spectral ranges are selected such that a first effective aperture is formed to provide a shaped light beam if light in a first wavelength band of the incident light beam is received by the optical input section, and a second effective aperture is formed to provide a shaped light beam if light in a second wavelength band of the incident light beam is received by the optical input section. Attached Figure Description

[0100] The embodiments will now be described by way of example only, with reference to the accompanying schematic diagrams, in which: Figure 1 A schematic diagram of a photolithography apparatus is depicted; Figure 2 A schematic diagram of the photolithography unit is depicted; Figure 3 A schematic representation of overall photolithography is depicted, illustrating the collaboration between three key technologies used to optimize semiconductor manufacturing. Figure 4 It is a schematic diagram of a measurement setup (such as a scatterer) including a radiation projector and a spectrometer detector; Figure 5 (a), 5(b), 5(c), and 5(d) include (a) a schematic diagram of a dark-field scattering instrument for measuring a target according to an embodiment of the invention using a first pair of illumination apertures, (b) details of the diffraction spectrum of a target grating under a given illumination direction, (c) a second pair of illumination apertures providing other illumination modes when performing diffraction-based overlap measurements using the scattering instrument; and (d) a third pair of illumination apertures combining the first pair of apertures and the second pair of apertures. 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 novel measurement tool for determining one or more parameters of interest on a structure on an object (such as, for example, a wafer) is illustrated schematically according to embodiments of the present disclosure. Figure 9 schematically shown Figure 8 The layout (in the plane of the module) of an embodiment of the measuring tool for at least partially defining the hole. Figure 10A It shows Figure 9The transmission spectrum of the first region in the illustrated embodiment; Figure 10B It shows Figure 9 The transmission spectrum of the second region in the illustrated embodiment; Figure 10C It shows Figure 9 The transmission spectrum of the third region in the illustrated embodiment; Figure 10D It shows Figure 9 The transmission spectrum of the fourth region in the illustrated embodiment; Figure 11A It shows that it can be used Figure 9 The first hole is defined in the embodiment shown; Figure 11B It shows that it can be used Figure 9 The second hole is defined in the embodiment shown; Figure 11C It shows that it can be used Figure 9 The third hole defined in the illustrated embodiment; and Figure 11D It shows that it can be used Figure 9 The fourth hole is defined in the embodiment shown. Detailed Implementation

[0101] In this document, the terms “radiation” and “beam” are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., wavelengths of 365, 248, 193, 157, or 126 nm) and EUV (extreme ultraviolet radiation, e.g., wavelengths in the range of about 5–100 nm).

[0102] As used herein, the terms “mask,” “mask,” or “patterning apparatus” can be broadly interpreted to refer to a general-purpose patterning apparatus that can be used to impart a patterned cross-section to an incident radiation beam corresponding to a pattern to be produced in a target portion of a substrate. The term “optical valve” may also be used in this context. Examples of such patterning apparatuses, in addition to classic masks (transmission or reflection masks, binary masks, phase-shifting masks, hybrid masks, etc.), include programmable mirror arrays and programmable LCD arrays.

[0103] Figure 1A lithography apparatus LA is schematically depicted. The lithography apparatus LA includes: an irradiation system (also referred to as an irradiator) IL configured to modulate a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation); a mask support (e.g., a mask stage) MT configured to support a patterning apparatus (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning apparatus MA according to specific parameters; a substrate support (e.g., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioner PW configured to accurately position the substrate support according to specific 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 apparatus MA onto a target portion C (e.g., including one or more dies) of the substrate W.

[0104] In operation, the irradiation system IL receives a radiation beam from the radiation source SO, for example via the beam transmission system BD. The irradiation system IL may include various types of optical components for guiding, 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 irradiator IL can be used to adjust the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the pattern forming apparatus MA.

[0105] As used herein, the term "projection system" PS should be interpreted broadly to encompass various types of projection systems, including refractive, reflective, catadioptric, distorting, magnetic, electromagnetic, and / or electrostatic optical systems, or any combination thereof, applicable to the exposure radiation and / or other factors used (such as the use of immersion liquids or vacuum). Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0106] 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 technology is given in US6952253 (which, by reference and incorporation herein),

[0107] Photolithography equipment (LA) can also be of the type having two (also known as "dual-stage") or more substrate supports (WT). In such "multi-stage" machines, substrate supports (WT) can be used in parallel, and / or while subsequent exposure preparation steps for substrate W are performed on substrate W located on one of the substrate supports (WT), another substrate W on another substrate support (WT) can be used to expose a pattern on the other substrate W.

[0108] 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 the properties of the projection system PS or the properties of the radiation beam B. The measurement stage may hold 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 moves away from the projection system PS.

[0109] In operation, a radiation beam B is incident on a pattern forming apparatus (e.g., a mask) MA held on a mask support MT, and patterned by a pattern (design layout) presented on the pattern forming apparatus MA. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be moved precisely, for example, to position different target portions C at focused and aligned positions along the path of the radiation beam B. Similarly, a first positioner PM and possibly another position sensor (which is not in...) Figure 1 (As explicitly shown in the diagram) the pattern forming apparatus MA can be used to accurately position itself relative to the path of the radiation beam B. The pattern forming apparatus 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 scribing alignment marks.

[0110] like Figure 2 As shown, a lithography apparatus LA can form part of a lithography unit LC, sometimes referred to as a lithography unit or (lithography) cluster. The lithography unit LC typically also includes equipment for performing pre-exposure and post-exposure processes on a substrate W. These devices typically include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chiller CH, and a baking plate BK, for example, to adjust the temperature of the substrate W, or to adjust the solvent in the resist layer. A substrate transport device (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 transports the substrate W to the loading stage LB of the lithography apparatus LA. The devices in the lithography unit (often collectively referred to as tracks) are typically controlled by a track control unit TCU, which itself can be controlled by a management control system SCS, which can also control the lithography apparatus LA, for example, via the lithography control unit LACU.

[0111] To ensure accurate and consistent exposure of the substrate W exposed by the lithography apparatus LA, it is desirable to inspect the substrate to measure properties of the patterned structure, such as overlap error between subsequent layers, line thickness, critical dimension (CD), etc. For this purpose, the lithography unit LC may include inspection tools (not shown). If an error is detected, especially if the inspection is performed before exposing or processing other substrates W in the same batch or batch, adjustments can be made, for example, to the exposure of subsequent substrates and / or other processing steps to be performed on the substrate W.

[0112] Inspection equipment (also referred to as measurement equipment) is used to determine the properties of a substrate W, particularly how the properties of different substrates W vary or how the properties associated with different layers of the same substrate W vary between layers. 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, or integrated into a photolithography apparatus LA, or even a stand-alone device. The inspection equipment can measure properties on latent images (images in a resist layer after exposure), or semi-latent images (images in a resist layer after a post-exposure baking (PEB) step), or developed resist images (where the exposed or unexposed portions of the resist have been removed), or even etched images (after pattern transfer steps such as etching).

[0113] Typically, the patterning process in photolithography (LA) equipment is one of the most critical steps in the process of achieving high-precision sizing and placement of structures on a substrate (W). To ensure this high precision, three systems can be combined into a so-called "integrated" control environment, such as... Figure 3 The diagram illustrates this schematically. One of these systems is the lithography apparatus LA, which is (in fact) connected to the metrology tool MT (second system) and the computer system CL (third system). The key to this “holistic” environment is optimizing the collaboration between these three systems to enhance the overall process window and providing tight control loops 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, overlap) within which a particular manufacturing process will produce a defined result (e.g., a functional semiconductor device), typically allowing process parameters in the lithography or patterning process to vary within these ranges.

[0114] The computer system CL can use a portion of the design layout to be patterned to predict which resolution enhancement technique to use and perform computational lithography simulations and calculations to determine which mask layouts and lithography equipment settings enable the largest overall process window (within) the patterning process. Figure 3(Represented by the double arrows in the first scale SC1). Typically, resolution enhancement techniques are arranged to match the patterning possibilities of the lithography apparatus LA. The computer system CL can also be used to detect where the lithography apparatus LA is currently operating within the process window (e.g., by using input from the metrology tool MT) to predict whether defects might exist due to, for example, suboptimal processes (in...). Figure 3 (This is indicated by the arrow pointing to "0" in the second scale SC2).

[0115] 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 possible drifts in, for example, the calibration state of the lithography equipment LA. Figure 3 (represented by multiple arrows in the third scale SC3).

[0116] During photolithography, it is often desirable to measure the resulting structure, for example, for process control and verification. The tools used to perform these measurements are generally referred to as metrology tools (MTs). Different types of metrology tools (MTs) for performing such measurements are known, including scanning electron microscopes or various forms of scatterometer metrology tools (MTs). A scatterometer is a versatile instrument that allows the measurement of parameters of the photolithography process by placing a sensor in the pupil of the scatterometer objective or in a plane conjugate to that pupil; such measurements are generally referred to as pupil-based measurements. Alternatively, the measurement of parameters of the photolithography process can be performed by placing a sensor in an image plane or in a plane conjugate to that image plane; in this case, the measurements are generally 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, which are incorporated herein by reference in their entirety. The aforementioned scatterer can measure gratings using light from soft X-rays and visible light to near-IR wavelengths.

[0117] 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 properties of the grating. For example, this reconstruction can be obtained 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.

[0118] In the second embodiment, the scatterer MT is a spectroscopic scatterer MT. In such a spectroscopic scatterer MT, radiation emitted by a radiation source is directed to the target, and radiation reflected or scattered from the target is directed to a spectroscopic detector that measures the spectrum of the specularly reflected radiation (i.e., the intensity as a function of wavelength). Based on this data, the structure or profile of the target that generated the detected spectrum can be reconstructed, for example, through rigorous coupled-wave analysis and nonlinear regression or by comparison with a simulated spectral library.

[0119] In the third embodiment, the scatterer MT is an elliptically polarized scatterer. An elliptically polarized scatterer allows the determination of parameters of the photolithography process by measuring the scattered radiation for each polarization state. Such a measurement device emits polarized light (e.g., linear, circular, or elliptical) by, for example, using a suitable polarizing filter in the illumination portion of the measurement device. A source suitable for the measurement device can also provide polarized radiation. Various embodiments of existing elliptically polarized 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.

[0120] In one embodiment of a scattering instrument (MT), the scattering instrument MT is adapted to measure the overlap of two misaligned gratings or periodic structures by measuring the reflectance spectrum and / or detecting asymmetry in the configuration, the asymmetry being related to the degree of overlap. The 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 a wafer. The scattering instrument can have a symmetrical detection configuration, for example, described in common patent application EP1,628,164A, such that any asymmetry can be clearly distinguished. This provides a direct method for measuring grating misalignment. Other examples of measuring the overlap error between two layers comprising a periodic structure when measuring a target by means of asymmetry in a periodic structure 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.

[0121] Other parameters of interest may be focus and dose. Focus and dose can be determined simultaneously by a scatterometer (or alternatively by a scanning electron microscope), as described in U.S. Patent Application US2011-0249244, the entire contents of which are incorporated herein by reference. A single structure with a unique combination of critical dimensions and sidewall angle measurements for each point in the focus energy matrix (FEM – also known as the focus exposure matrix) can be used. If these unique combinations of critical dimensions and sidewall angles are available, the focus and dose values ​​can be uniquely determined based on these measurements.

[0122] The measurement target can be a set of composite gratings formed mostly in the resist during the photolithography process, but also, for example, after the etching process. Typically, the pitch and linewidth of the structures in the gratings are largely dependent on the measurement optics (especially 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 drift (also known as "overlap") between two layers, or it can be used to reconstruct at least a portion of the original grating produced by the photolithography process. This reconstruction can be used to provide guidance on the quality of the photolithography process and can be used to control at least a portion of the photolithography process. The target can have smaller sub-segments configured to mimic the dimensions of functional portions of the design layout in the target. Due to these sub-segments, the behavior of the target will be more similar to the functional portions of the design layout, thus making the overall process parameter measurements more similar to the functional portions of the design layout. The target can be measured in either an unfilled mode or an overfilled mode. In the unfilled mode, the spot produced by the measurement beam is smaller than the overall target. In the overfilled mode, the spot produced by the measurement beam is larger than the overall target. In this overfilled mode, different targets can also be measured simultaneously, thereby simultaneously determining different processing parameters.

[0123] The overall measurement quality of a lithography parameter used for a specific target is determined at least in part by the measurement configuration used to measure that lithography parameter. The term "substrate measurement configuration" can include one or more parameters of the measurement itself, one or more parameters of one or more measured patterns, or both. For example, if the measurement used in the substrate measurement configuration is a diffraction-based optical measurement, the one or more measured parameters 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 criterion for selecting a measurement configuration 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 U.S. Patent Application US2016 / 0370717A1, the entire contents of which are incorporated herein by reference.

[0124] Figure 4A measuring device, such as a scatterer SM1, is described. This measuring device includes a broadband (white light) radiation projector 2, which projects radiation onto a substrate 6. The reflected or scattered radiation is transmitted to a spectrometer 4, which measures the spectrum 10 of the specularly reflected radiation (i.e., a measurement of intensity as a function of wavelength λ, In1). Based on this data, for example, by means of... Figure 4 As shown at the bottom, through rigorous coupled-wave analysis and nonlinear regression, or by comparison with a simulated spectral library, the processing unit (PU) can reconstruct the structure or profile that produced the detected spectrum. Typically, for reconstruction, the general form of the structure is known, and some parameters are set based on knowledge of the process that forms the structure, leaving only a few parameters of the structure determined from the scattering measurements. This scatterometer can be configured as a normal-incident scatterometer or an oblique-incident scatterometer.

[0125] During photolithography, frequent measurements of the formed structure are desired for purposes such as process control and verification. Various tools are known for performing these measurements, including scanning electron microscopes or various forms of metrology equipment such as scatterometers. Examples of known scatterometers typically rely on providing a dedicated measurement target, such as an unfilled target (a target in different layers, in the form of a simple or overlapping grating, large enough that the measurement beam produces a spot smaller than the grating) or an overfilled target (where the irradiated spot partially or completely contains the target). Furthermore, the use of metrology tools (e.g., an angle-resolved scatterometer irradiating an unfilled target, such as a grating) allows for the use of so-called reconstruction methods, where the properties of the grating can be calculated by simulating the interaction between scattered radiation and a mathematical model of the target structure, and comparing the simulation results with the measurement results. The parameters of the model are adjusted until the simulated interaction produces a diffraction pattern similar to that observed from a real target.

[0126] A scatterometer is a versatile instrument that allows for the measurement of parameters of a photolithography process by placing a sensor in the pupil of the scatterometer's objective lens or in a plane conjugate to the pupil (the measurement is typically referred to as a pupil-based measurement), or by placing a sensor in the image plane or a plane conjugate to the image plane (in which case the measurement is typically referred to as an image- or field-based measurement). 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 scatterometer can measure multiple targets from multiple gratings in a single image using light from soft X-rays and the visible to near-IR wavelength range.

[0127] Figure 5(a) An embodiment of the measurement apparatus (more specifically, a dark-field scatterometer) is presented. Figure 5 (b) illustrates the target T and the diffracted rays of the measurement radiation used to illuminate the target in more detail. The illustrated measurement device belongs to the type known as a dark-field measurement device. The measurement device can be a stand-alone device or can be incorporated into a lithography apparatus LA (e.g., at a measurement station) or a lithography unit LC. The optical axis with multiple branches throughout the device is indicated by the dashed line O. In this device, light emitted by source 11 (e.g., a xenon lamp) is guided onto the substrate W via a beam splitter 15 through an optical system including lenses 12, 14 and objective lens 16. These lenses are arranged in a double sequence of 4F. Different lens arrangements can be used, as long as the lens arrangement still provides an image of the substrate to the detector and allows simultaneous access to the intermediate pupil plane for spatial frequency filtering. Thus, the range of angles at which radiation is incident on the substrate can be selected by defining the spatial intensity distribution in the plane that defines the spatial spectrum of the substrate plane (referred to herein as the (conjugate) pupil plane). Specifically, this can be achieved by inserting a suitably shaped aperture plate 13 between lenses 12 and 14 in the plane of the back-projected image, which serves as the objective pupil plane. In the illustrated example, the aperture plate 13 has different shapes (labeled 13N and 13S), allowing for the selection of different illumination modes. The illumination system in this example forms an off-axis illumination mode. In the first illumination mode, aperture plate 13N provides off-axis illumination from a direction designated "north" for description purposes only. In the second illumination mode, aperture plate 13S is used to provide similar illumination, but from the opposite direction, labeled "south." Other illumination modes are possible by using different apertures. The remainder of the pupil plane is desiccated because any unwanted light outside the desired illumination mode will interfere with the desired measurement signal.

[0128] like Figure 5 As shown in (b), the 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). The measuring radiation ray I striking the target T at an angle off-axis O produces a zero-order ray (solid line 0) and two first-order rays (dotted line +1 and double-dotted line -1). It should be remembered that in the case of an overfilled small target, these rays are only one of many parallel rays covering the substrate area including the measuring target T and other features. Due to the limited width of the aperture in plate 13 (necessary to allow a useful amount of light), the incident ray I will actually occupy an angular range, and the diffracted rays 0 and +1 / -1 will spread out slightly. According to the dot spread function of the small target, each order +1 and -1 will further spread across the angular range, rather than a single ideal ray as shown. It should be noted that the grating pitch and illumination angle of the target can be designed or adjusted so that the first-order rays entering the objective lens are closely aligned with the central optical axis. Figure 5 (a) and Figure 3 The rays illustrated in (b) are shown slightly off-axis, only for easier distinction in the accompanying figures. Figure 5 (a) and Figure 3 The ray shown in (b).

[0129] At least the 0th and +1st orders of diffraction from the target T on the substrate W are collected by objective lens 16 and guided back by beam splitter 15. Figure 5 (a) The first and second illumination modes are illustrated by specifying completely opposite apertures labeled North (N) and South (S). When the incident ray I for measuring radiation comes from the north side of the optical axis, i.e., when the first illumination mode is applied using aperture plate 13N, the +1 diffraction ray, labeled +1 (N), enters the objective lens 16. Conversely, when the second illumination mode is applied using aperture plate 13S, the -1 diffraction ray (labeled 1 (S)) is the ray entering the lens 16.

[0130] The second beam splitter 17 divides the diffracted beam into two measurement branches. In the first measurement branch, the optical system 18 uses the zeroth-order and first-order diffracted beams to form the diffraction spectrum (pupil plane image) of the target on the first sensor 19 (e.g., a CCD or CMOS sensor). Each diffraction order hits a different point on the sensor, so image processing can compare and contrast multiple orders. The pupil plane image captured by the sensor 19 can be used for focusing measurement devices and / or to normalize the intensity measurements of the first-order beam. The pupil plane image can also be used for many measurement purposes, such as reconstruction.

[0131] In the second measurement branch, optical systems 20 and 22 form an image of the target T on sensor 23 (e.g., a CCD or CMOS sensor). In this second measurement branch, an aperture stop 21 is positioned in a plane conjugate to the pupil plane. Aperture stop 21 blocks the zero-order diffraction beam, ensuring that only a first-order beam (either -1 or +1) forms the image of the target on sensor 23. The images captured by sensors 19 and 23 are output to a processor PU that processes the images; the functionality of the processor PU will depend on the specific type of measurement being performed. Note that the term "image" as used herein is broad. If only one of the -1 or +1 orders is present, such a grid-like image will not be formed.

[0132] Figure 5 The specific forms of the aperture plate 13 and field stop 21 shown are merely examples. In another embodiment of the invention, on-axis illumination of the target is used, and an aperture stop with an off-axis aperture is used to transmit essentially only a first-order diffracted beam to the sensor. In other embodiments, instead of a first-order beam or an adjoining first-order beam, second-order, third-order, and higher-order beams can be used in the measurement. Figure 5 (Not shown in the image).

[0133] To make the measured radiation suitable for these different types of measurements, the orifice plate 13 may include multiple aperture patterns formed around a disk that rotates to position the desired pattern. Note that the orifice plates 13N or 13S can be used only to measure gratings oriented in one direction (X or Y, depending on the setup). For measurements of orthogonal gratings, the target can be rotated 90° and 270°. Figure 5 (c) and Figure 5 Different orifice plates are shown in (d). These uses and many other variations and applications of the device are described in the previously published application mentioned above.

[0134] Figure 6 This is a schematic block diagram of an embodiment of a known alignment sensor AS (such as the alignment sensor described, for example, in US6961116, which is incorporated by reference). A radiation source RSO provides a radiation beam RB of one or more wavelengths, which is directed by a steering optics onto a marker (such as a marker AM located on a substrate W) as an illumination spot SP. In this example, the steering optics include a spot reflector SM and an objective lens OL. The diameter of the illumination spot SP used to illuminate the marker AM may be slightly smaller than the width of the marker itself.

[0135] The radiation diffracted by the marker AM is collimated (in this example via the objective lens OL) into an information-carrying beam IB. The term "diffraction" is intended to include zero-order diffraction 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. In cases where more than one wavelength is generated by the radiation source RSO, additional optics (not shown) may be included to provide a separate beam. If desired, the photodetector may be a single element, or it may include multiple pixels. The photodetector may include a sensor array.

[0136] In this example, the steering optics that include the spot reflector SM can also be used to block the zero-order radiation reflected from the marker, so that the information-carrying beam IB only includes higher-order diffraction radiation from the marker AM (this is not necessary for the measurement, but it improves the signal-to-noise ratio).

[0137] The intensity signal SI is provided to the processing unit PU. Through a combination of optical processing in the block SRI and computational processing in the unit PU, the values ​​of the X and Y positions on the substrate relative to the reference frame are output.

[0138] A single measurement of this type fixes the mark's position within a specific range corresponding to one pitch of the mark. This is combined with coarse measurement techniques to identify which period of the sine wave includes the mark's position. The same process can be repeated at coarser or finer levels at different wavelengths to improve accuracy and / or robustly detect the mark, regardless of its material or the materials placed on or under it. Wavelengths can be optically multiplexed and demultiplexed for simultaneous processing, and / or multiplexed via time-division or frequency-division multiplexing.

[0139] In this example, the alignment sensor and the light spot SP remain stationary, while the substrate W moves. Therefore, the alignment sensor can be fixed and accurately mounted to the reference frame while effectively scanning the marker AM in the direction opposite to the movement direction of the substrate W. The substrate W is controlled during this movement by mounting it on a substrate support and by 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) markers are provided on the substrate support. Measuring the position of the markers provided on the substrate support allows for calibration of the substrate support position determined by the position sensor (e.g., calibration relative to the frame to which the alignment system is attached). Measuring the position of the alignment markers provided on the substrate allows for determination of the substrate's position relative to the substrate support.

[0140] 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 nature of the measurement. One distinguishing property of radiation is the wavelength(s)(s) used to obtain the measurement results, as different wavelengths may provide different information about the target being measured. Some measuring instruments can use broadband radiation (e.g., supercontinuum radiation) to perform measurements using broadband radiation, or use tunable broadband radiation and select(s)(s) of the measurement wavelength(s) to be used. Depending on the range of output wavelengths and the nature of the broadband source, different methods can be used to obtain broadband radiation. 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 constraining the pump radiation to achieve the high intensity required to experience significant nonlinear effects.

[0141] To provide a radiation source capable of switching between desired wavelengths, the radiation source may include a color selection module. Figure 7A known example of such a color selection module CM is schematically depicted. The color selection module CM is provided with an input section 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 with different transmission spectra. 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 said portion. One or more properties of the multilayer structure (e.g., the thickness of each layer of the multilayer structure) vary as a function of the angular position about the wheel. Therefore, the total transmission spectrum of each color wheel varies as a function of the angular position about the wheel. Each of the wheels 14a, 14b can rotate about its respective rotation axis 16a, 16b. Thus, the total transmission spectrum of each color wheel 14a, 14b varies with the angular orientation about 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 of the color wheels 14a and 14b, the portion through which the broadband radiation beam 12 of each of the color wheels 14a and 14b passes can be controlled. This provides control over the overall transmission spectrum of the multilayer structure of the portion through which the radiation beam 12 of each color wheel 14a and 14b passes. Therefore, this provides control over the properties of the narrowband radiation beam 18 output from the color wheels 14a and 14b. For example, one of the color wheels 14a can be used as a low-pass filter, and the other of the color wheels 14b can be used as a high-pass filter. By controlling the angular position of each of the color wheels 14a and 14b about its respective axes 16a and 16b, the cutoff frequency 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, both the center wavelength and the spectral bandwidth of the narrowband radiation 18 output from the color wheels 14a and 14b can be controlled. Narrowband radiation 18 exits at the output section 20 of the color selection module CM.

[0142] The color selection module CM may also include a reflector 22 that creates a secondary beam path 24. A portion of the radiation 18 along this secondary beam path 24 can be used during operation of the color selection module CM to measure the properties of the narrowband radiation 18, which can be used to calibrate the color selection module CM. For example, the portion of the radiation 18 along the secondary beam path 24 can be used to ensure that the desired center wavelength and spectral bandwidth of the narrowband radiation 18 are output by the color selection module CM when the color wheels 14a, 14b are in a specific position.

[0143] Color wheels 14a and 14b can be relatively large (because their size can be partly determined by the nature of the multilayer structure that forms a portion of each color wheel and may need to have specific dimensions to achieve a desired degree of spatial resolution based on the angular position of the color wheels). The switching speed of the color selection module CM can depend on: (a) the quality of color wheels 14a and 14b; and (b) the typical distance by which each color wheel is moved to change the center wavelength and spectral bandwidth of the narrowband radiation 18 output by the color selection module CM. As used herein, the switching speed of the color selection module CM is intended to represent the time spent switching between (i) a first desired center wavelength and spectral bandwidth of the narrowband radiation 18 and (ii) a second desired center wavelength and spectral bandwidth of the narrowband radiation 18.

[0144] Some embodiments of this disclosure relate to a novel measurement tool for determining one or more parameters of interest for a structure on an object (such as, for example, a wafer W). Figure 8 An example of this new measurement tool 100 is schematically shown and described herein.

[0145] The measurement tool 100 includes: a module 110 for at least partially defining an aperture; a projection optics 120; a detection optics 130; and a detector 140. In some embodiments, the measurement tool 100 may, for example, be generally... Figure 5 (a) shows the form of the dark field scatterer.

[0146] Module 110, which at least partially defines the aperture, is positionable to receive radiation beam 150 and transmit modified radiation beam 152. This module will be described in further detail below. In some embodiments, module 110 may be placed instead of... Figure 5 (a) shows the perforated plate 13.

[0147] Projection optics 120 are arranged to project modified radiation 152 output from module 110 onto a beam spot region 122 in which the structure (e.g., a target on wafer W) is locatable. In some embodiments, projection optics 120 may be placed instead of Figure 5 Objective lens 16 is shown in (a). In this embodiment, beam splitter 124 is provided to direct a portion of the modified radiation 152 output by module 110 to projection optics 120.

[0148] The detection optics 130 are arranged to receive at least a portion of the radiation 154 scattered by the structure. In some embodiments, the detection optics 130 may be placed instead of Figure 5 The optical device shown in (a) is disposed between the wafer W and the sensor 23. Specifically, the detection optics 130 may include a device similar to... Figure 5(a) shows one or more components of the aperture stop 21. Specifically, in some embodiments, the detection optics 130 includes a component 132 disposed in the measurement pupil plane 134. The component 132 disposed in the measurement pupil plane 134 may be similar to... Figure 5 (a) shows the aperture stop 21.

[0149] As used herein, detector 140 is intended to represent both sensor 142 (e.g., sensor array or camera) and processor 144.

[0150] The detection optics 130 may include optics 136 arranged to form an image of the beamspot region 122 on the sensor 142 of the detector 140. That is, the sensor 142 of the detector 140 may be positioned in the conjugate plane of the beamspot region 122. As described above, it is desirable that the zero-order diffraction beam from the target does not contribute to or act on the "image" formed by the optics 136. Therefore, as described above, the component 132 disposed in the measurement pupil plane 134 may be arranged to ensure that zero-order radiation from the target does not contribute to or act on the image formed on the sensor 142 of the detector 140. For example, zero-order radiation may be blocked.

[0151] Detector 140 is operable to determine one or more parameters based on the received scattered radiation 154. Specifically, processor 144 of detector 140 is operable to determine one or more parameters based on the received scattered radiation 154. Specifically, processor 144 of detector 140 is operable to determine one or more parameters (e.g., overlap measurement) based on an image formed by detection optics 130 on sensor 142 of detector 140. In some embodiments, detector 140 may be placed instead of... Figure 5 The sensor 23 shown in (a) can be replaced, for example, by placing sensor 142 of detector 140. Figure 5 Sensor 23 is shown in (a). It will be understood that the invention can also be applied to other inspection devices or scatterers as described above, such as devices in which the detector or sensor is in the pupil plane or conjugate pupil plane, in which case the measurement is based on the pupil.

[0152] Optionally, the measurement tool 100 may further include a radiation source 160 operable to generate a radiation beam 150 received by module 110. The radiation source 160 may be a broadband radiation source. For example, the radiation source 160 may be operable to generate radiation with a spectrum of approximately 400-900 nm. In some embodiments, the radiation source 160 may be operable to generate radiation with a spectrum of approximately 400-1600 nm.

[0153] Optionally, the measurement tool 100 may also include a support 170 for supporting an object (such as a wafer W) such that the object is positionable to receive modified radiation 152 from module 110. That is, the object may be positionable such that a portion of it is positioned within the beam spot region 122.

[0154] The support 170 for supporting the object may include a substrate holder operable to fix the substrate W. For example, the support 170 may include a clamp for holding the substrate W to the support 170. The support may include a stage, such as a wafer stage (e.g., having...). Figure 1 The substrate support shown is in the form of WT.

[0155] The measurement tool 100 may also include a movement mechanism 180 operable to cause relative movement between the support 170 and the modified radiation beam 152. This relative movement is schematically indicated by arrows 182, 184. This allows an object or substrate W to step or scan through the radiation 152. As used herein, a scan of the object W is intended to represent continuous movement of the object W. As used herein, a step of the object W is intended to represent movement of the object W in multiple consecutive (temporally separated) steps.

[0156] Optionally, the measurement tool 100 may also include a beam modification module 190, which is arranged to control one or more properties of the radiation beam 150, such as, for example, the spectrum of the radiation beam 150.

[0157] In other words, the beam modification module 190 is optically located upstream of module 110 and is arranged to control one or more properties of the radiation beam 150 (such as, for example, the spectrum of the radiation beam 150) before the radiation beam 150 is received by module 110. As used herein, control of the spectrum of the radiation beam 150 may include control of the center wavelength, bandwidth, and / or shape of the spectrum of the radiation beam 150. For example, the beam modification module may include a color wheel, etc. The beam modification module 190 may include... Figure 7 The color selection module CM is schematically shown and described above as being of the same type. It should be understood that other embodiments of the beam modification module 190 may include other devices for controlling the spectrum of radiation 150, such as an acousto-optic tunable filter or similar devices.

[0158] Additionally or alternatively, in some embodiments, the beam modification module 190 may include beam-shaping optics, such as, for example, collimators and / or aperture stops.

[0159] Module 110 is configured such that the size and / or shape of the aperture defined by the module depends on the wavelength of the received radiation 150.

[0160] The radiation beam 150 can be received (directly or indirectly) from the radiation source 160. The radiation beam 150 can be approximately circular in the plane of module 110. As discussed further below, the modified radiation beam 152 can be modified by blocking radiation in portions of the plane of module 110. As discussed further below, the modified radiation beam 152 can be modified by the transmission characteristics of portions of the plane of module 110.

[0161] Now let's discuss Figure 8 The advantages of the new measurement tool 100 shown are illustrated.

[0162] For example, measurement tool 100 may include a scatterer for measuring a target on an object (e.g., a photolithographic wafer W). For example, it may include a dark-field scatterer. Module 110 may be referred to as an aperture plate or apodizer. Within such a scatterer, a target (e.g., a periodic structure or grating) may be illuminated with a radiation beam 152. The radiation will be scattered from the target, thus forming multiple diffraction beams. At least a portion of the scattered radiation 154 (including at least some of the diffraction beams) may be collected by collecting optics 120.

[0163] The response of measurements performed in a scatterometer (such as overlap measurements) is typically sensitive to the wavelength of the radiation used by the scatterometer. Furthermore, due to this wavelength dependence, it is desirable to isolate any background signals. For this reason, these scattering measurement instruments typically perform multiple separate, sequential measurements on each measurement mark or target at different radiation wavelengths, and then combine these measurements. Specific wavelengths (and bandwidths) are often dependent on a particular lithography process or configuration and are typically optimized for a given process to maximize the response to overlap errors.

[0164] Furthermore, for a given target, it may be desirable to use different apertures for illumination at different wavelengths. Existing metrology tools can provide multiple different aperture plates, each adapted for use with different combinations of target pitch and wavelength. To define different apertures, the aperture plate can be swapped for another when a new wavelength is selected (e.g., multiple aperture plates can be mounted on a wheel so that each plate can be placed one at a time in the beam path). However, it has been found that this results in a loss of yield because it requires a non-zero amount of time to swap the aperture plates. An alternative could be to use the same aperture for all wavelengths; however, this means using suboptimal apertures for at least some wavelengths, which also leads to a loss of yield.

[0165] Advantageously, Figure 8 The measurement tool 100 shown allows for the selection of different apertures when using different illumination wavelengths. That is, once the illumination wavelength has been selected (e.g., via beam modification module 190), the appropriate aperture is automatically selected by means of the transmission characteristics of module 110.

[0166] In some embodiments, module 110 may be locatable in the pupil plane 112 of the measuring tool 100.

[0167] It should be understood that the pupil plane of the measurement tool 100 is intended to represent the Fourier transform plane or field plane of the beamspot region 122. That is, the intensity distribution of radiation in the beamspot region 122 is a Fourier transform of the intensity distribution of radiation in the pupil plane 112. It should be understood that all rays from any given point in the pupil plane 112 are mapped onto substantially the entire beamspot region 122. In other words, rays from any given point in the pupil plane 112 illuminate the entire field of view (FOV) of the measurement tool 100. Similarly, a single point in the beamspot region 122 is mapped onto substantially the entire pupil plane 112. The intensity distribution of radiation in the pupil plane 112 characterizes the angular distribution of radiation in the field plane (i.e., the beamspot region 122). In some embodiments, the module 110 may be positioned in a plane close to the pupil plane of the measurement tool (and may be referred to as the "pupil plane").

[0168] In some embodiments, the measuring tool 100 includes a plurality of modules 110. For example, the measuring tool 100 may include a plurality of such modules 110 disposed on a common support (e.g., a wheel). By moving the support (e.g., rotating the wheel), one of the plurality of modules 110 may be able to be positioned in the path of the radiation beam 150. Advantageously, this arrangement may allow for the provision of a plurality of (automatically selected) apertures to provide a range of different pitches for the target.

[0169] For example, multiple modules 110 may each define different groups of apertures. Additionally or alternatively, for different modules 110, the dependence of the size and / or shape of the apertures defined by module 110 on the wavelength of the received radiation may be different.

[0170] As described above, the module 110 for at least partially defining the aperture is configured such that the size and / or shape of the aperture defined by the module 110 depends on the wavelength of the received radiation 150. Referring now to... Figures 9 to 11D An embodiment of such module 110 is discussed.

[0171] Typically, module 110 may include a generally planar body. It should be understood that a generally planar body is intended to represent a body having two larger dimensions and one smaller dimension. The two larger dimensions may define the plane of the body.

[0172] Figure 9 schematically shown Figure 8The layout of embodiment 200 within the measuring tool 100 for at least partially defining the hole in module 110 (in the plane of module 110). It should be understood that, in use, this embodiment is configured such that the optical axis of radiation 150 is substantially perpendicular to... Figure 9 The plane.

[0173] Embodiment 200 includes a generally circular portion 210, which, in use, is concentric with the optical axis of radiation 150 and corresponds to the numerical aperture of the projection optics 120. This generally circular portion 210 can be considered to comprise four parts: a first part 212, a second part 214, a third part 216, and a fourth part 218. Each of the four parts 210 corresponds to one-quarter of the circular portion 210. The first part 212 and the fourth part 218 are diametrically opposed to each other, and the second part 214 and the third part 216 are also diametrically opposed to each other. The first part 212 and the fourth part 218 are opaque, and therefore, in use, the first part 212 and the fourth part 218 block the radiation beam 150.

[0174] Each of the second portion 214 and the third portion 216 of Embodiment 200 includes multiple regions with different transmissive properties. Specifically, each of the second portion 214 and the third portion 216 of Embodiment 200 includes a first region 220, a second region 222, a third region 224, and fourth regions 226a and 226b. Except for the first region 220, the second region 222, the third region 224, and the fourth regions 226a and 226b, all other regions of Embodiment 200 are generally opaque. In this embodiment, each of the second portion 214 and the third portion 216 of Embodiment 200 includes a generally L-shaped opaque portion 228, except for the first region 220, the second region 222, the third region 224, and the fourth regions 226a and 226b. In other embodiments, the first region 220, the second region 222, the third region 224, and the fourth regions 226a and 226b of each group may substantially occupy the entirety of one-quarter of the circular portion 210.

[0175] The first area 220 is typically square, but it is conceivable that it can take any shape, such as, for example, rectangle, triangle, circle, ellipse, rhombus, or any other shape derived from or combined from these shapes.

[0176] The second region 222 is approximately L-shaped and is configured such that each first region 220 and the corresponding second region 222 together define an approximately square region.

[0177] The third region 224 is defined by a portion of a generally L-shaped region intersecting the circular region 210 (corresponding to the numerical aperture of the projection optics 120). Specifically, the third region 224 is defined by a portion of a generally L-shaped region located within the circular region 210 (corresponding to the numerical aperture of the projection optics 120). The third region 224 is configured such that the respective first region 220, second region, and third region 224 of each group together define a generally square region partially truncated by the circular region 210 (corresponding to the numerical aperture of the projection optics 120).

[0178] The fourth regions 226a and 226b are defined by a portion of a generally L-shaped region intersecting the circular region 210 (corresponding to the numerical aperture of the projection optics 120). Specifically, the fourth regions 226a and 226b are defined by a portion of a generally L-shaped region located within the circular region 210 (corresponding to the numerical aperture of the projection optics 120). In this embodiment, the fourth regions 226a and 226b comprise two separate regions. The fourth regions 226a and 226b are configured such that the corresponding first region 220, second region, third region 224, and fourth region 226a and 226b of each group together define a generally square region partially truncated by the circular region 210 (corresponding to the numerical aperture of the projection optics 120). It is contemplated that the described regions can take any shape, such as, for example, rectangles, squares, triangles, circles, ellipses, rhombuses, or any other shape derived from or combined from these shapes.

[0179] The transmission spectra 230, 232, 234, and 236 of regions 220, 222, 224, 226a, and 226b of regions 226a and 226b are respectively located at... Figure 10A-10DThe following is illustrated. For simplicity, transmission spectra 230, 232, 234, and 236 are shown as typically binary (blocking radiation or transmitting radiation); however, note that in actual embodiments, smooth transitions may exist. Typically, when a region is described as being transmissive for a wavelength (or wavelength range), this can mean 95% or greater transmittance. In some embodiments, a region described as being transmissive for a wavelength (or wavelength range) can mean 50% or greater transmittance. In some embodiments, a region described as being transmissive for a wavelength (or wavelength range) can mean 60% or greater transmittance. In some embodiments, a region described as being transmissive for a wavelength (or wavelength range) can mean 70% or greater transmittance. In some embodiments, a region described as being transmissive for a wavelength (or wavelength range) can mean 80% or greater transmittance. In some embodiments, a region described as being transmissive for a wavelength (or wavelength range) can mean 90% or greater, preferably 95% or greater transmittance. Furthermore, typically, when a region is described as being transmissive for a wavelength (or wavelength range), the variation in transmittance can be less than 2% of the absolute transmittance.

[0180] Each of the first region 220, the second region 222, the third region 224, and the fourth regions 226a, 226b includes a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Alternatively, the passband filter may transmit radiation with wavelengths below a threshold and block radiation with wavelengths above a threshold. The passband filter may also have multiple thresholds, wherein radiation above a first threshold is transmitted and radiation below the first threshold is blocked, and wherein radiation above a second threshold is blocked and radiation below the second threshold is transmitted, ultimately serving as a bandpass filter. Each of the multiple filters may have a different threshold. The first region 220 may transmit substantially all wavelengths (i.e., may not have a non-zero threshold). For example, the first region 220 may transmit substantially all wavelengths (e.g., the first region 220 may include an aperture). Alternatively, the first region 220 may transmit substantially all wavelengths that will be received when the embodiment 200 of module 110 is used. For example, the first region 220 may have a threshold value that is substantially equal to or less than the lower value of the spectral output of the radiation source 160 of the measuring instrument 100. For example, as described above, the radiation source 160 is operable to generate radiation with a spectrum of about 400-900 nm (or 400-1600 nm), and the first region 220 may have a threshold value of about 400 nm or lower. The threshold value of the second region 222... Less than the threshold of 224 in the third region The threshold of region 224 in the third region. Less than the threshold of 226 in the fourth region .

[0181] This arrangement 200 of module 110 is configured such that the size and shape of the aperture defined by module 110 depend on the wavelength of the received radiation 150, as now referenced. Figures 11A to 11D The subject of discussion.

[0182] When module 110 receives wavelength Less than the threshold of the second region 222 When radiation occurs, this radiation is transmitted only through the first region 220. Utilizing this arrangement ( < ), defining only the first hole 240 including the first region 220 (see Figure 11A ).

[0183] When module 110 receives wavelength Greater than the threshold of the second region 222 And less than the threshold of 224 in the third region. When radiation occurs, this radiation is transmitted only through the first region 220 and the second region 222. Utilizing this arrangement ( < < ), defining a second hole 242 including a first region 220 and a second region 222 (see Figure 11B ).

[0184] When module 110 receives wavelength The threshold of 224 in the third region is greater than And less than the threshold values ​​of regions 226a and 226b in the fourth region. When radiation occurs, this radiation is transmitted only through the first region 220, the second region 222, and the third region 224. Utilizing this arrangement ( < < ), defining a third hole 244 comprising a first region 220, a second region 222, and a third region 224 (see Figure 11C ).

[0185] When module 110 receives wavelength Greater than the thresholds of regions 226a and 226b in the fourth region When radiation occurs, this radiation is transmitted through the first region 220, the second region 222, the third region 224, and the fourth regions 226a and 226b. Utilizing this arrangement ( > ), defining a fourth hole 246 including a first region 220, a second region 222, a third region 224, and fourth regions 226a, 226b (see Figure 11D ).

[0186] therefore, Figure 9 The illustrated embodiment 200 is configured such that four different holes can be defined by module 110 (see Figures 11A to 11D The size of the aperture depends on the wavelength of the received radiation (150 nm). It should be understood that this is merely a single exemplary embodiment, and other embodiments may allow defining different numbers of different holes. Typically, module 110 is configured such that at least two different holes can be defined by module 110 (the defined holes depend on the wavelength of the received radiation 150). For example, irradiating module 110 with a radiation beam having a first wavelength (e.g., from a first wavelength range) can produce a first aperture, while irradiating the module with a radiation beam having a second wavelength (e.g., from a second wavelength range) can produce a second aperture, and so on.

[0187] It should be understood that module 110 can be configured such that module 110 can define any number of different apertures. Typically, module 110 can be configured such that the number of different apertures that can be defined by module 110 is equal to (or greater than) the number of different wavelengths that will be used with each target in use.

[0188] As explained above, scattering measurement tools can be used to perform multiple separate, sequential measurements on each measurement mark or target at different radiation wavelengths, and then combine these measurements. In principle, the greater the number of different wavelengths, the better the measurement accuracy; however, the slower the target measurement will be. Therefore, a balance needs to be found. In practice, each mark can be measured using, for example, two, three, or four different wavelengths.

[0189] Figure 9 The illustrated embodiment 200 is configured such that a finite number (four) of different holes can be defined by module 110. (Refer to the above...) Figures 10A to 11D As explained, each of the different apertures 240, 242, 244, and 246 is at least partially defined by multiple discrete wavelengths of the minimum wavelength transmitted by module 110 in one or more directions.

[0190] Alternatively, in other embodiments, module 110 may be configured such that a continuum of different apertures can be defined by module 110. For example, the different apertures may each be defined at least partially by a gradient of the minimum wavelength transmitted by the module in one or more directions.

[0191] Figure 9 The illustrated embodiment 200 is configured such that four different holes 240, 242, 244, 246, which can be defined by module 110, at least partially overlap each other. Typically, module 110 can be configured such that at least two different holes, which can be defined by module 110, at least partially overlap.

[0192] For example, in some embodiments, one of the (smaller) holes 240, 242, 244 may completely overlap with another of the (larger) holes 242, 244, 246. That is, the smaller hole (e.g., hole 240) may include a first region of module 110 (e.g., first region 220), and the larger hole (e.g., hole 242) may include the first region (e.g., first region 220) plus an additional second region of the module (e.g., second region 222).

[0193] In some embodiments (such as, for example, Figure 9 As shown in embodiment 200), module 110 can be configured to define a plurality of different nested holes 240, 242, 244, 246. In some embodiments, module 110 is configured to define a plurality of different holes, including (in ascending order) a first hole 240, a second hole 242, etc., and wherein each hole starting from the second hole includes the same area of ​​module 110 as the next smallest hole plus an additional area.

[0194] Figure 9 The illustrated embodiment 200 is configured such that the dimensions of the apertures 240, 242, 244, 246 defined by module 110 vary with the wavelength of the received radiation 150. The size increases with the increase of wavelength. This is advantageous because, as discussed below, in some measuring instruments 100, it is generally desirable to use a larger (smaller) aperture for larger (smaller) wavelengths.

[0195] Figure 9 The illustrated embodiment 200 includes a generally opaque first portion 212. This is advantageous when the module 110 is positioned in the first (illumination) pupil plane 112 of the measuring tool 100, and it is desirable to be able to separate one or more higher-order diffraction beams from the zero-order diffraction beam in the second (measuring) pupil plane 134 of the measuring tool 100 (which is optically downstream of the target). Because the first portion 212 is generally opaque, there will be a corresponding portion of the second pupil plane 134 that is not illuminated by the zero-order diffraction beam.

[0196] It should be understood that the first part 212 is generally opaque and can be intended to represent that it does not transmit radiation within the wavelength range used by the measuring instrument 100 in use. Generally, as used herein, opacity can mean a transmittance of less than 1% for a wavelength range of 400–1600 nm. For example, generally, as used herein, opacity can mean a transmittance of less than 0.1% for a wavelength range of 400–1600 nm. For example, generally, as used herein, opacity can mean a transmittance of less than 0.1% for a wavelength range of 400–900 nm. For example, generally, as used herein, opacity can mean a transmittance of less than 0.01% for a wavelength range of 400–1600 nm. For example, generally, as used herein, opacity can mean a transmittance of less than 0.01% for a wavelength range of 400–900 nm.

[0197] The module 110 described above may include a generally transmissive carrier layer (e.g., formed of a glass material). The opaque portions of the module 110 may be achieved by applying a black coating (or similar material) to portions of this generally transmissive carrier layer to block radiation incident on these portions.

[0198] Figure 9 The illustrated embodiment 200 also includes a second portion 214, which is adjacent to the first portion 212 and in the first direction ( Figure 9 The second portion 214 is offset from the first portion 214 in the x' direction. Furthermore, the transmittance of the second portion 214 in the first direction (x' direction) depends on the wavelength, such that for at least a portion of the second portion 214, the minimum wavelength transmitted by the second portion 214 increases with the distance from the first portion 212 in the first direction (x' direction).

[0199] Advantageously, with this arrangement, the second portion 214 will transmit only a small range of smaller wavelengths in the first direction (i.e., will have a smaller aperture), while the second portion 214 will transmit a larger range of larger wavelengths in the first direction (i.e., will have a larger aperture). Therefore, as explained further below, if the first direction is aligned with the dual (Fourier transform) direction of the target's shear direction, the transmittance properties of the second portion 214 will mean that a suitable aperture can be provided to avoid overlap between the zero-order and first-order beams for a range of irradiation wavelengths or a range of irradiation wavelengths.

[0200] Figure 9 The illustrated embodiment 200 also includes a third portion 216, which is adjacent to the first portion 212 and in the second direction ( Figure 9The third portion deviates from the first portion 212 in the second direction (y' direction). The transmittance of the third portion in the second direction (y' direction) depends on the wavelength, such that for at least a portion of the third portion 216, the minimum wavelength transmitted by the third portion 216 increases with the distance from the first portion 212 in the second direction (y' direction).

[0201] Advantageously, this allows module 110 to simultaneously measure the overlap in two directions (the first direction and the second direction) (by simultaneously illuminating markers having shear directions corresponding to the Fourier transform coordinates of the first and second directions). The second direction (y' direction) can be substantially perpendicular to the first direction (x' direction).

[0202] Figure 9 The illustrated embodiment 200 also includes a generally opaque fourth portion 218.

[0203] The fourth portion 218 is adjacent to the second portion 214 and offset from the second portion 214 in the second direction (y' direction). Furthermore, the transmittance of the second portion 214 in the second direction (y' direction) depends on the wavelength, such that for at least a portion of the second portion 214, the minimum wavelength transmitted by the second portion 214 increases with the distance from the fourth portion 218 in the second direction (y' direction).

[0204] The fourth portion 218 is adjacent to the third portion 216 and offset from the third portion 216 in the first direction (x' direction). The transmittance of the third portion 216 in the first direction (x' direction) depends on the wavelength, such that for at least a portion of the third portion 216, the minimum wavelength transmitted by the third portion 216 increases with the distance from the fourth portion 218 in the first direction (x' direction).

[0205] In some embodiments, module 110 may include a plurality of adjacent filters provided as a separate layer and stacked in the direction of the optical axis of the measuring tool 100. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the plurality of filters may have a different threshold. The filters may be in a plane substantially perpendicular to the optical axis of the measuring tool 100 (i.e., Figure 9 The two planes (i.e., the planes) partially overlap. The advantage of this arrangement is that the two planes (i.e., the planes) are generally perpendicular to the optical axis of the measuring tool 100. Figure 9In the plane of the measuring tool 100, the transition between each of adjacent regions 220, 222, 224, 226a, and 226b can potentially be sharper than in the case where there is no such partial overlap in a plane substantially perpendicular to the optical axis of the measuring tool 100. This is because multiple filters can partially overlap in a plane substantially perpendicular to the optical axis of the measuring tool 100 (since the filters are positioned at different locations in the direction of the optical axis of the measuring tool 100).

[0206] For example, a first filter layer having the transmission characteristics of a first region 220 can be provided (e.g., see...). Figure 10A Such a layer can be positioned at least above the region of module 110 corresponding to the first hole 240 (see...). Figure 11D ), that is, in the first region 220 (see Figure 9 Above. In some embodiments, the first filter layer is disposed only above the region of module 110 corresponding to the first region 220 (see above). Figure 9 In some other embodiments, since the threshold of the first region 220 is lower than the thresholds of the second region 222, the third region 224, and the fourth regions 226a, 226b, a first filter layer can be disposed over the entire region of module 110 corresponding to the fourth aperture 246 (see [link]). Figure 11D For example, the first filter layer can be applied to the supporting substrate.

[0207] A second filter layer with the transmission characteristics of the second region 222 can be provided (e.g., see...). Figure 10B Such a layer can be set in at least the second region 222 (see...). Figure 9 Above. In some embodiments, the second filter layer is disposed only on module 110 corresponding to the second region 222 (see above). Figure 9 Above the region 222. In some other embodiments, due to the threshold of the second region 222 The threshold values ​​are lower than those of the third region 224 and the fourth regions 226a, 226b, so a second filter layer can be disposed over the entire region of module 110 corresponding to the second region 222, the third region 224, and the fourth regions 226a, 226b. For example, the second filter layer can be applied onto a first filter layer, which can be supported by a support substrate.

[0208] A third filter layer with the transmission characteristics of the third region 224 can be provided (e.g., see...). Figure 10C Such a layer can be set at least in the third region 224 (see...). Figure 9 Above. In some embodiments, the third filter layer is disposed only in the module 110 corresponding to the third region 224 (see above). Figure 9Above the region 224. In some other embodiments, due to the threshold of the third region 224 The threshold values ​​are below those of the fourth regions 226a and 226b, therefore a third filter layer can be disposed over the entire region of module 110 corresponding to the third region 224 and the fourth regions 226a and 226b. For example, the third filter layer can be applied onto a second filter layer, which can be supported by a first filter layer and a support substrate.

[0209] A fourth filter layer with transmission characteristics of fourth regions 226a, 226b can be provided (e.g., see...). Figure 10D Such layers can be set only in the fourth region 226a, 226b (see...) Figure 9 Above. Such a layer can be disposed above the entire area of ​​module 110 corresponding to the fourth regions 226a, 226b. For example, the fourth filter layer can be applied on the third filter layer, which can be supported by the second filter layer, the first filter layer and the support substrate.

[0210] Advantageously, by overlapping multiple filter layers in a plane substantially perpendicular to the optical axis of the measuring tool 100, the plane substantially perpendicular to the optical axis of the measuring tool 100 (i.e., Figure 9 The transition between each of the adjacent regions 220, 222, 224, 226a, 226b in the plane can be clearer than the transition in a plane that is generally perpendicular to the optical axis of the measuring tool 100 where multiple filter layers do not overlap at all.

[0211] In some embodiments, the module 110 for at least partially defining the aperture of the measuring tool 100 may include a plurality of filters arranged substantially in the same plane in a direction substantially perpendicular to the optical axis of the measuring tool. That is, each filter may (in a plane substantially perpendicular to the optical axis of the measuring tool 100) have a... Figure 9 The four different regions 220, 222, 224, 226a, and 226b shown have the same shape. The advantage of this arrangement is that all the multiple filters can be positioned within the pupil plane of the measuring instrument, and therefore, even with a relatively small depth of focus in the optical system, the edges of the apertures can be sharp or well-defined. All the multiple filters can be positioned on a common support layer. Each filter can include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the multiple filters can have a different threshold value.

[0212] Some embodiments of this disclosure relate to... Figure 8 Module 110 is shown and described above in the new measurement tool 100. Typically, module 110 can have any of the features discussed above.

[0213] Some embodiments of this disclosure relate to a novel module 110 for at least partially defining a hole in a measuring tool 100.

[0214] According to some embodiments, the new module 110 is configured such that the size and / or shape of the aperture defined by module 110 depends on the wavelength of the received radiation. This module 110 is advantageous for the measuring tool 100 because it allows for the automatic selection of different apertures when irradiated with radiation of different wavelengths. That is, once the irradiation wavelength is selected, the appropriate aperture is automatically selected based on the transmission characteristics of the module.

[0215] In some embodiments, the new module 110 is configured such that it can define at least two distinct apertures, the defined apertures depending on the wavelength of the received radiation. It should be understood that the module 110 can be configured such that it can define any number of distinct apertures. Typically, the module 110 can be configured such that the number of distinct apertures that can be defined by the module 110 is equal to (or greater than) the number of distinct wavelengths that will be used in conjunction with each target within the measurement tool 100 to which the module 110 is applied.

[0216] In some embodiments, module 110 is configured such that module 110 can define a finite number of different apertures. For example, each of the different apertures may be defined at least in part by multiple discrete wavelengths of the minimum wavelength transmitted by the module in one or more directions.

[0217] Alternatively, module 110 can be configured such that it can define a series of different apertures. For example, each aperture can be defined at least partially by a gradient of the minimum wavelength transmitted by the module in one or more directions.

[0218] In some embodiments, module 110 is configured such that at least two different holes that can be defined by module 110 at least partially overlap.

[0219] For example, in some embodiments, one of the (smaller) holes may completely overlap with another of the (larger) holes. That is, the smaller hole may include a first region of module 110, and the larger hole may include the first region plus an additional second region of module 110.

[0220] In some embodiments, module 110 is configured to define a plurality of different nested holes. In some embodiments, the module is configured to define a plurality of different holes, including (in ascending order) a first hole, a second hole, etc., and wherein each hole, starting from the second hole, includes the same area of ​​the module as the next smallest hole plus an additional area.

[0221] In some embodiments, module 110 may be configured such that the size of the aperture defined by module 110 increases with increasing wavelength.

[0222] This is advantageous because, as discussed below, in some measurement instruments, it is generally desirable to use a larger (smaller) aperture at larger (smaller) wavelengths.

[0223] In some embodiments, module 110 may include a generally planar body. It should be understood that a generally planar body is intended to represent a body having two larger dimensions and one smaller dimension. These two larger dimensions may define the plane of the body.

[0224] In some embodiments, module 110 includes a generally opaque first portion 212. This is advantageous when module 110 is positioned in the first (illumination) pupil plane 112 of the measuring tool 100, and it is desirable to separate one or more higher-order diffraction beams from the zero-order diffraction beam in the second (measuring) pupil plane 134 of the measuring tool 100 (which is optically downstream of the target). Because the first portion 212 is generally opaque, there will be a corresponding portion of the second pupil plane 134 that is not illuminated by the zero-order diffraction beam.

[0225] It should be understood that the first part is generally opaque, which may be intended to indicate that it does not transmit radiation wavelengths or a range of radiation wavelengths used by the measuring instrument 100 in use.

[0226] In some embodiments, module 110 further includes a second portion 214 adjacent to the first portion 212 and offset from the first portion 214 in a first direction (e.g., the x' direction). The transmittance of the second portion 214 in the first direction may depend on the wavelength, such that for at least a portion of the second portion 214, the minimum wavelength transmitted by the second portion 214 increases with the distance from the first portion 212 in the first direction.

[0227] Advantageously, with this arrangement, the second portion 214 will transmit only a small range of smaller wavelengths in the first direction (i.e., will have a smaller aperture), while the second portion 214 will transmit a larger range of larger wavelengths in the first direction (i.e., will have a larger aperture). Therefore, as explained further below, if the first direction is aligned with the dual (Fourier transform) direction of the target's shear direction, the transmittance properties of the second portion 214 will mean that a suitable aperture can be provided to avoid overlap between the zero-order and first-order beams for a range of irradiation wavelengths or a range of irradiation wavelengths.

[0228] In some embodiments, module 110 further includes a third portion 216 adjacent to the first portion 212 and offset from the first portion 212 in a second direction (e.g., the y' direction). The transmittance of the third portion 216 in the second direction may depend on the wavelength, such that for at least a portion of the third portion 216, the minimum wavelength transmitted by the third portion 216 increases with the distance from the first portion 212 in the second direction.

[0229] Advantageously, this allows the module to simultaneously measure overlap in two directions (a first direction and a second direction). The second direction can be substantially perpendicular to the first direction.

[0230] In some embodiments, module 110 further includes a generally opaque fourth portion 218.

[0231] The fourth portion 218 may be adjacent to the second portion 214 and offset from the second portion 214 in a second direction (e.g., the y' direction). The transmittance of the second portion 214 in the second direction depends on the wavelength, such that for at least a portion of the second portion 214, the minimum wavelength transmitted by the second portion 214 increases with the distance from the fourth portion 218 in the second direction.

[0232] The fourth portion 218 may be adjacent to the third portion 216 and offset from the third portion 216 in a first direction (e.g., the x' direction). The transmittance of the third portion 216 in the first direction may depend on the wavelength, such that for at least a portion of the third portion 216, the minimum wavelength transmitted by the third portion 216 increases with the distance from the fourth portion 218 in the first direction.

[0233] In some embodiments, module 110 may include a plurality of adjacent filters stacked as a separate layer in a direction generally perpendicular to the plane of module 110. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the plurality of filters may have a different threshold. The filters may partially overlap in the plane of module 110.

[0234] Alternatively, module 110 may include a plurality of filters substantially arranged in the same plane. The plurality of filters may be disposed on a common support layer. Each filter may include a passband filter that transmits radiation with wavelengths above a threshold and blocks radiation with wavelengths below a threshold. Each of the plurality of filters may have a different threshold.

[0235] Some embodiments of this disclosure relate to a novel module 110 for at least partially defining an aperture in a measuring tool 100, the novel module 110 comprising at least a first portion 212 and a second portion 214, the second portion 214 being adjacent to the first portion 212 and offset from the first portion 212 in a first direction. The first portion 212 may be substantially opaque, and the transmittance of the second portion 214 in the first direction may depend on wavelength, such that for at least a portion of the second portion 214, the minimum wavelength transmitted by the second portion 214 increases with distance from the first portion 212 in the first direction. As now discussed, such a module is advantageous.

[0236] In use, module 110 can be incorporated into measurement tool 100. For example, such measurement tool 100 may include a scatterer for measuring a target on an object (e.g., a photolithography wafer W). For example, it may include a dark-field scatterer. Module 110 can be used to define the shape and extent of the radiation beam in the illumination pupil plane of measurement tool 100. That is, the module can be optically positioned upstream of the object W under study and located in the Fourier transform plane of the object (the plane of the object may be referred to as the field plane). Module 110 may be referred to as an orifice plate.

[0237] It should be understood that the pupil plane of a measurement instrument is intended to be represented as the Fourier transform plane of the beam-spot region or the field plane of the measurement instrument. That is, the intensity distribution of radiation in the beam-spot region is a Fourier transform of the intensity distribution of radiation illuminating the pupil plane. It should be understood that all rays from any given point in the pupil plane are mapped onto substantially the entire beam-spot region. In other words, rays from any given point in the pupil plane illuminate the entire field of view (FOV) of the measurement instrument. Similarly, a single point in the beam-spot region is mapped onto substantially the entire pupil plane. The intensity distribution of radiation in the pupil plane characterizes the angular distribution of radiation in the field plane (i.e., the beam-spot region).

[0238] Within this scatterer, a target (e.g., a periodic structure or grating) can be illuminated with a radiation beam 152. The radiation will be scattered from the target, forming multiple diffraction beams 154. At least a portion of the scattered radiation (including at least some of the diffraction beams) can be collected by collecting optics 120, 130. As described above, module 110 can be used in the illumination pupil 112 of tool 100 to define an aperture or illumination pattern for illuminating the target. In a second pupil plane 134, optically downstream of the target and conjugate to the plane 112 of module 110, there will be a contribution from a zero-order diffraction beam that will illuminate a portion of the second pupil plane 134 optically conjugate to the second portion 214 of pupil 112. This zero-order diffraction beam will generally not illuminate the portion of the second pupil plane 134 optically conjugate to the first portion 212 of module 110.

[0239] In addition to the contribution to the second pupil plane 134 from the zeroth-order diffraction beam, there will typically be contributions from each of the higher-order diffraction beams (or at least each of the higher-order diffraction beams received by the numerical apertures of the collecting optics 120, 130). The contribution to the second pupil plane 134 from the higher-order diffraction beams will typically be a copy of the contribution from the zeroth-order diffraction beam, which has been (a) shifted in the shear direction of the target; and (b) weighted by the diffraction efficiency of the target's diffraction order. This diffraction efficiency typically depends on the topology of the target, particularly the shape of the unit cell.

[0240] The amount by which the contribution from the higher-order diffraction beam to the second pupil plane 134 is shifted relative to the contribution from the zeroth-order diffraction beam depends on the target pitch and the wavelength of the illumination radiation 152. For example, for a target with a pitch p and illumination radiation 152 with a wavelength λ, the angular separation between the zeroth-order and first-order diffraction beams is... (And the shift in the pupil plane 134 will be related to...) (Proportional). Therefore, for a fixed pitch p, the larger the wavelength, the greater the angular spacing between the zeroth-order diffraction beam and the first-order diffraction beam. The larger.

[0241] It may be desirable to separate the higher-order diffraction beam from the zero-order diffraction beam within the measurement tool 100. This can be achieved by a suitably chosen optics 132 disposed in or near the second pupil plane 134, provided that the higher-order diffraction beam does not overlap with the zero-order diffraction beam in the second pupil plane 134. Therefore, it may be desirable to have sufficient separation or spacing between the higher-order diffraction beam and the zero-order diffraction beam in the second pupil plane such that the higher-order diffraction beam and the portion of the second pupil plane 134 optically conjugate with the first portion 212 of module 110 overlap.

[0242] The response of measurements performed in a scatterometer (e.g., overlap measurements) is typically sensitive to the wavelength of the radiation used by the scatterometer. Furthermore, due to this wavelength dependence, it is desirable to isolate any background signals. For this reason, these scattering measurement instruments typically perform multiple separate, sequential measurements on each measurement mark or target at different radiation wavelengths, and then combine these measurements. Specific wavelengths (and bandwidths) are often dependent on a particular lithography process or configuration and are typically optimized for a given process to maximize the response to overlap errors.

[0243] In existing measurement tools, multiple different aperture plates are available, each adapted for use with different combinations of target pitch and wavelength. For a given target, the pitch is fixed, and therefore the displacement of the first-order diffraction beam (relative to the zero-order diffraction beam) in the second pupil plane 134 will vary when different wavelengths are used for measurement. Therefore, using existing arrangements, to avoid overlap between the zero-order and first-order beams, (a) the same aperture plate (i.e., the same pupil) is used for all wavelengths, and the aperture is small enough to avoid overlap between the zero-order and first-order beams; or (b) the aperture plate can be interchanged with another aperture plate (e.g., multiple aperture plates can be arranged on a wheel such that each aperture plate can be placed one at a time in the beam path). Disadvantageously, solution (a) implies the use of apertures smaller than optimal for some wavelengths, resulting in yield loss. Similarly, solution (b) results in yield loss due to the need for a non-zero amount of time to interchange the aperture plates.

[0244] Advantageously, in some embodiments, module 110 includes a second portion 214 having wavelength-dependent transmittance in a first direction, such that for at least a portion of the second portion 214, the minimum wavelength transmitted by the second portion 214 increases with distance from the first portion 212 in the first direction. Therefore, the second portion 214 will transmit only a small range of smaller wavelengths in the first direction (i.e., will have a smaller aperture), while the second portion 214 will transmit a larger range of larger wavelengths in the first direction (i.e., will have a larger aperture). Thus, if the first direction is aligned with the dual (Fourier transform) direction of the target's shear direction, the transmittance property of the second portion 214 will mean that a suitable aperture can be provided to avoid overlap between the zero-order and first-order beams for a range of illumination radiation wavelengths or a range of illumination radiation wavelengths.

[0245] Such embodiments may also include the third portion 216 and the fourth portion 218 of the module 110 described above. However, it should be understood that the third portion 216 and the fourth portion 218 are optional (and may allow overlapping measurements to be performed simultaneously in two different directions).

[0246] In some embodiments, module 110 includes a generally planar body. It should be understood that a generally planar body is intended to represent a body having two larger dimensions and one smaller dimension. The two larger dimensions may define the plane of the body. First portion 212, second portion 214, third portion 216, and fourth portion 218 may be portions of the plane of the body.

[0247] Alternatively, in some embodiments, module 110 may include multiple bodies. In use, each such body may be disposed in a different plane, all of which are optically conjugate (e.g., these planes may all be the pupil plane of the measuring tool). For example, a first portion 212 may be defined on a first body, and a second portion 214 may be defined on a second body.

[0248] In Figures 9 to 1 In a related example, we disclose a module for defining an aperture in a measuring tool in an optical path at least partially defined between an optical input section and an optical output section. The module includes: an optical input section for receiving an incident light beam; an optical output section for outputting a shaped light beam; a first transmission region configured to transmit light within a first spectral range; and a second transmission region configured to transmit light within a second spectral range, wherein the first and second spectral ranges are selected such that a first effective aperture is formed to provide a shaped light beam if light in a first wavelength band of the incident light beam is received by the optical input section, and a second effective aperture is formed to provide a shaped light beam if light in a second wavelength band of the incident light beam is received by the optical input section.

[0249] The optical input section is used to receive the incident light beam. The incident light beam can be a broadband light source. The broadband light source can have wavelengths in, for example, within the ranges of 400-1600 nm, 600-1600 nm, 800-1600 nm, 450-900 nm, 600-900 nm, or 800-900 nm. The optical output section is used to output a shaped light beam, wherein the shaped light beam is shaped by the described module. The optical input section and the optical output section are located on different sides of the module perpendicular to the optical path. The incident light beam can also be referred to as a radiation beam from a radiation source. As mentioned above, the radiation beam can be generally circular. As mentioned above, the shaped light beam can also be referred to as a modified radiation beam modified by blocking radiation in some portions of the plane of the module. For example, in a cross-sectional view along the optical path, the modified or shaped beam can have two square regions after modification.

[0250] The first transmission region is configured to transmit light within a first spectral range. This first region can take any shape, such as, for example, a rectangle, square, triangle, circle, ellipse, rhombus, or any other shape derived from or combined from these shapes. Similarly, the second transmission region is configured to transmit light within a second spectral range. As described with respect to the first region, this second region can also take any shape. After shaping, the dimensions of the transmission regions can also vary, wherein the dimensions are defined by the dimensions of a particular shape. Different regions can have substantially similar dimensions or substantially different dimensions. It should be understood that the described transmission regions can also be described as multiple regions with different transmission properties as described above.

[0251] For example, the transmission region can be configured such that the spectral range of the transmitted light can be limited to 400-1600 nm, 600-1600 nm, 800-1600 nm, 450-900 nm, 600-900 nm, or 800-900 nm. For instance, a first region can transmit light with a wavelength range of approximately 400-900 nm, and a second region can transmit light with a wavelength range of approximately 600-900 nm. In another example, the first region can transmit light with a wavelength range of approximately 400-405 nm, and the second region can transmit light with a wavelength range of approximately 400-410 nm. Alternatively, in another example, the first region can transmit light with a wavelength range of approximately 400-405 nm, and the second region can transmit light with a wavelength range of approximately 406-410 nm. It should be understood that the spectral range can also be described as a transmission spectrum, as further described above.

[0252] By transmitting light within a selected spectral range, an effective aperture is formed to shape the beam, thereby providing a shaped beam for output.

[0253] The above description describes two transmission regions; however, it is conceivable to provide more than two transmission regions, each with a spectral range selected such that an effective aperture is formed to provide a shaped beam.

[0254] Other embodiments are disclosed in the subsequent list of numbered entries: 1. A measurement tool for determining one or more parameters of interest of a structure on an object, the measurement tool comprising: A module for at least partially defining an aperture, the module being positionable to receive and transmit a modified radiation beam; A projection optics device arranged to project modified radiation output by the module onto a beam spot region, the structure being locatable in the beam spot region; A detection optics device, the detection optics device being arranged to receive at least a portion of the radiation scattered by the structure; and A detector capable of determining one or more parameters based on received scattered radiation; The module is configured such that the size and / or shape of the aperture defined by the module depends on the wavelength of the received radiation. 2. The measuring tool according to item 1, wherein the module is capable of being positioned in the pupil plane of the measuring tool. 3. The measurement tool according to item 1 or item 2, the measurement tool further comprising a beam modification module arranged to control one or more properties of the radiation beam. 4. The measuring tool according to any one of the preceding clauses, wherein the module is configured such that the module can define at least two different apertures, the defined apertures depending on the wavelength of the received radiation. 5. The measuring tool according to any one of the preceding clauses, wherein the module is configured such that the module can define a finite number of different holes. 6. The measuring tool according to any one of the preceding clauses, wherein the module is configured such that at least two different holes defined by the module at least partially overlap. 7. The measuring tool according to any one of the preceding clauses, wherein the module is configured such that the size of the aperture defined by the module increases with increasing wavelength. 8. The measuring tool according to any one of the preceding clauses, wherein the module comprises a generally planar body. 9. The measuring tool according to any one of the preceding clauses, wherein the module includes a generally opaque first portion. 10. The measuring tool according to item 9, wherein the module further comprises a second portion adjacent to the first portion and offset from the first portion in a first direction; wherein the transmittance of the second portion in the first direction depends on wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the first portion in the first direction. 11. The measuring tool according to item 9 or item 10, wherein the module further comprises a third portion adjacent to the first portion and offset from the first portion in a second direction, and wherein the transmittance of the third portion in the second direction depends on wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction. 12. The measuring tool according to any one of clauses 9 to 11, wherein the module further comprises a generally opaque fourth portion. 13. The measuring instrument according to clause 12 when it is subordinate to clause 11, wherein the fourth portion is adjacent to the second portion and offset from the second portion in the second direction, and wherein the transmittance of the second portion in the second direction depends on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the fourth portion in the second direction. 14. A measuring instrument according to clause 12 or clause 13 when subordinate to clause 11, wherein the fourth portion is adjacent to the third portion and offset from the third portion in the first direction, and wherein the transmittance of the third portion in the first direction depends on wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the fourth portion in the first direction. 15. The measuring tool according to any one of the preceding clauses, wherein the module comprises a plurality of adjacent filters provided as a separate layer and stacked in the direction of the optical axis of the measuring tool. 16. A measuring tool according to any one of clauses 1 to 14, wherein the module comprises a plurality of filters arranged substantially in the same plane in a direction generally perpendicular to the optical axis of the measuring tool. 17. The measuring tool according to any one of the preceding clauses, wherein the measuring tool comprises a plurality of modules according to any one of the preceding clauses. 18. The measuring tool according to any one of the preceding clauses, the measuring tool further comprising a radiation source operable to generate a radiation beam received by the module. 19. The measuring tool according to any one of the preceding clauses, the measuring tool further comprising a support for supporting an object so that the object can be positioned to receive modified radiation from the module. 20. The measuring tool according to item 19, further comprising a movement mechanism operable to cause relative movement between the support and the modified radiation beam. 21. A module for use in a measuring tool according to any one of the preceding clauses. 22. A module for at least partially defining a hole in a measuring tool, wherein the module is configured such that the size and / or shape of the hole defined by the module depends on the wavelength of the received radiation. 23. The module according to clause 22, wherein the module is configured such that the module can define at least two distinct apertures, the defined apertures depending on the wavelength of the received radiation. 24. The module according to clause 22 or clause 23, wherein the module is configured such that the module can define a finite number of different holes. 25. The module according to any one of clauses 22 to 24, wherein the module is configured such that at least two distinct holes defined by the module can at least partially overlap. 26. The module according to any one of the preceding clauses, wherein the module is configured such that the size of the aperture defined by the module increases with increasing wavelength. 27. The module according to any one of clauses 22 to 26, wherein the module comprises a generally planar body. 28. The module according to any one of clauses 22 to 27, wherein the module includes a generally opaque first portion. 29. The module according to clause 28 further includes a second portion adjacent to the first portion and offset from the first portion in a first direction; wherein the transmittance of the second portion in the first direction depends on wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the first portion in the first direction. 30. The module according to clause 28 or clause 29, wherein the module further comprises a third portion adjacent to the first portion and offset from the first portion in a second direction; and wherein the transmittance of the third portion in the second direction depends on wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction. 31. The module according to any one of clauses 28 to 30, wherein the module further comprises a generally opaque fourth portion. 32. The module according to clause 31 when subordinate to clause 30, wherein the fourth portion is adjacent to the second portion and offset from the second portion in the second direction, and wherein the transmittance of the second portion in the second direction depends on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the fourth portion in the second direction. 33. When a module is described in clause 30 or clause 31 when it is subordinate to clause 29, wherein the fourth portion is adjacent to the third portion and offset from the third portion in the first direction, and wherein the transmittance of the third portion in the first direction depends on the wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the fourth portion in the first direction. 34. The module according to any one of clauses 22 to 33, the module comprising a plurality of adjacent filters provided as a separate layer and stacked in a direction substantially perpendicular to the plane of the module. 35. The module according to any one of clauses 22 to 33, the module comprising a plurality of filters substantially arranged in the same plane. 36. A module for at least partially defining a hole in a measuring tool, the module comprising: Part One; and The second part is adjacent to the first part and is offset from the first part in a first direction; The first part is generally opaque; The transmittance of the second portion in the first direction depends on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the first portion in the first direction. 37. The module according to clause 36, the module further comprising a third portion adjacent to the first portion and offset from the first portion in a second direction; and wherein the transmittance of the third portion in the second direction depends on wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction. 38. The module according to any one of clauses 36 to 37, the module further comprising a generally opaque fourth portion. 39. The module according to clause 38 when subordinate to clause 37, wherein the fourth portion is adjacent to the second portion and offset from the second portion in the second direction, and wherein the transmittance of the second portion in the second direction depends on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the fourth portion in the second direction. 40. The module according to clause 38 or clause 39 when subordinate to clause 37, wherein the fourth portion is adjacent to the third portion and offset from the third portion in the first direction, and wherein the transmittance of the third portion in the first direction depends on wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the fourth portion in the first direction. 41. The module according to any one of clauses 36 to 40, wherein the module comprises a generally planar body. 42. A module for defining a hole in a measuring tool in an optical path at least partially between an optical input section and an optical output section, the module comprising: An optical input section is used to receive an incident light beam; A light output unit, wherein the light output unit is used to output a shaped light beam; A first transmission region, configured to transmit light within a first spectral range; A second transmission region, configured to transmit light within a second spectral range, wherein the first and second spectral ranges are selected such that... If the light of the first wavelength band of the incident beam is received by the light input section, a first effective aperture is formed to provide a shaped beam, and If the light of the second wavelength band of the incident beam is received by the light input section, a second effective aperture is formed to provide a shaped beam.

[0255] Although references are specifically made to "measuring equipment / tools / systems" or "inspection equipment / tools / systems," these terms can refer to tools, equipment, or systems of the same or similar type. 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 a structure on a substrate may relate to defects in the structure, the absence of specific portions of the structure, or the presence of unwanted structures on the substrate or wafer.

[0256] While specific references are made to the use of lithography equipment in IC manufacturing herein, it should be understood that the lithography equipment described herein may have other applications. Possible other applications include the fabrication of integrated optical systems, patterning for guiding and detecting magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and the like.

[0257] Although embodiments of the invention may be specifically referred to herein in the context of lithography equipment, embodiments of the invention can be used in other equipment. Embodiments of the invention can be part of mask inspection equipment, metrology equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning apparatus). These devices are generally referred to as lithography tools. Such lithography tools can use vacuum conditions or ambient (non-vacuum) conditions.

[0258] Although the use of embodiments of the invention may have been specifically referenced above in the context of optical lithography, it should be understood that the invention is not limited to optical lithography, and may be used in other applications, such as imprint lithography, where the context permits.

[0259] Although 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 description above is intended to be illustrative and not restrictive. 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 claims set forth below.

Claims

1. A module for at least partially defining a hole in a measuring tool, wherein the module is configured such that the size and / or shape of the hole defined by the module depends on the wavelength of the received radiation.

2. The module according to claim 1, wherein the module comprises: An optical input section is used to receive an incident light beam; A light output unit, wherein the light output unit is used to output a shaped light beam; The optical path between the optical input section and the optical output section; A first transmission region, configured to transmit light within a first spectral range; A second transmission region, configured to transmit light within a second spectral range, wherein the first and second spectral ranges are selected such that... If the light in the first wavelength band of the incident beam is received by the light input section, a first effective aperture is formed to provide a shaped beam. If the light of the second wavelength band of the incident beam is received by the light input section, a second effective aperture is formed to provide a shaped beam.

3. A measurement tool for determining one or more parameters of interest of a structure on an object, the measurement tool comprising: The module according to claim 1 or claim 2 is configured to be positioned to receive and transmit a modified radiation beam. A projection optics device arranged to project modified radiation output by the module onto a beam spot region, the structure being locatable in the beam spot region; A detection optics device, the detection optics device being arranged to receive at least a portion of the radiation scattered by the structure; and The detector is operable to determine one or more parameters based on the received scattered radiation.

4. The measuring tool according to claim 3, wherein the module is configured to be positionable in the pupil plane of the measuring tool.

5. The measurement tool according to claim 3 or claim 4, further comprising a beam modification module arranged to control one or more properties of the radiation beam.

6. The measuring tool according to any one of the preceding claims, wherein the module is configured such that the module can define at least two different holes.

7. The measuring tool according to any one of the preceding claims, wherein the module is configured such that the size of the aperture defined by the module increases with increasing wavelength.

8. The measuring tool according to any one of the preceding claims, wherein the module includes a generally opaque first portion.

9. The measuring tool of claim 8, wherein the module further comprises a second portion, the second portion comprising a first transmission region and / or a second transmission region, the second portion being adjacent to the first portion and offset from the first portion in a first direction; wherein the transmittance of the second portion in the first direction depends on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the first portion in the first direction.

10. The measuring tool according to claim 8 or claim 9, wherein the module further comprises a third portion adjacent to the first portion and offset from the first portion in a second direction, and wherein the transmittance of the third portion in the second direction depends on the wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the first portion in the second direction.

11. The measuring tool according to any one of claims 8 to 10, wherein the module further comprises a generally opaque fourth portion.

12. The measuring instrument according to claim 11 when dependent on claim 10, wherein the fourth portion is adjacent to the second portion and offset from the second portion in the second direction, and wherein the transmittance of the second portion in the second direction depends on the wavelength, such that for at least a portion of the second portion, the minimum wavelength transmitted by the second portion increases with the distance from the fourth portion in the second direction.

13. The measuring instrument according to claim 11 or claim 12 when dependent on claim 10, wherein the fourth portion is adjacent to the third portion and offset from the third portion in the first direction, and wherein the transmittance of the third portion in the first direction depends on the wavelength, such that for at least a portion of the third portion, the minimum wavelength transmitted by the third portion increases with the distance from the fourth portion in the first direction.

14. The measuring tool according to any one of the preceding claims, wherein the module comprises a plurality of adjacent filters provided as a separate layer and stacked in the direction of the optical axis of the measuring tool.

15. The measuring tool according to any one of claims 3 to 14, wherein the module includes a plurality of filters arranged substantially in the same plane in a direction generally perpendicular to the optical axis of the measuring tool.

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