Optical arrangement for metrology system

Abstract

An optical arrangement that eliminates the use of a four-quadrant non-polarizing beam splitter (QNPBS) and the need for image stitching. As QNPBS, the optical arrangement provides enhanced transmission gain to optimize system throughput. A metrology system (600) includes an illumination mode selector (IMS) including a porous pattern having a transmissive portion and a reflective portion. The IMS (650) is positioned in a pupil plane (655) of the system (600) and is configured to: transmit a transmissive portion (671) of the radiation (604) toward the diffraction grating target (610); and reflecting diffracted radiation from the target (610) along the second optical path (631) towards the detector (662). Regional decoupling of the transmissive and reflective portions on the IMS (650) optimizes the illumination light intensity and the detection light intensity at the same time. Positive and negative first diffraction order diffracted radiation from the target (610) may be reflected by two reflection quadrants of the porous pattern, which are located on a back side of the IMS (650) or a side (651) not facing the radiation source.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. application No. 63 / 341,220 filed on May 12, 2022, and the entire contents of that U.S. application are incorporated herein by reference. Technical Field

[0003] This specification relates to optical configurations for use in metrology systems. Background Art

[0004] Lithographic projection apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A patterning device (e.g., a mask) may include or provide a pattern (a "design layout") corresponding to a single layer of an IC, and such pattern may be transferred to a target portion (e.g., including one or more dies) by methods such as irradiating a target portion (e.g., including one or more dies) on a substrate (e.g., a silicon wafer) coated with a layer of radiation-sensitive material ("resist") via a pattern on the patterning device. Typically, a single substrate comprises a plurality of adjacent target portions to which the pattern is transferred successively, one at a time, by the lithographic projection apparatus. In this type of lithographic projection apparatus, the pattern on the entire patterning device is transferred to one target portion in one operation. Such an apparatus is often referred to as a stepper. In an alternative apparatus, often referred to as a step-and-scan apparatus, the projection beam is scanned across the patterning device in a given reference direction (the "scanning" direction) while synchronously moving the substrate parallel or antiparallel to such reference direction. Different portions of the pattern on the patterning device are gradually transferred to one target portion. Typically, since the lithographic projection apparatus will have a reduction ratio M (e.g. 4), the speed F at which the substrate is moved will be 1 / M times the speed at which the projection beam scans the patterning device. Further information on lithographic apparatus as described herein can be gleaned, for example, from US 6,046,792, which is incorporated herein by reference.

[0005] Before the pattern is transferred from the pattern forming device to the substrate, the substrate may undergo various processes, such as priming, resist coating, and soft baking. After exposure, the substrate may undergo other processes ("post-exposure processes"), such as post-exposure baking (PEB), development, hard baking, and measurement / inspection of the transferred pattern. This array of processes is used as the basis for making a single layer of a device (e.g., IC). The substrate may then undergo various processes, such as etching, ion implantation (doping), metallization, oxidation, deposition, chemical mechanical polishing, etc., all of which are intended to complete a single layer of the device. If several layers are required in the device, the entire process or its variants are repeated for each layer. Ultimately, there will be a device in each target portion on the substrate. These devices are then separated from each other by techniques such as cutting or sawing, so that individual devices can be mounted on a carrier, connected to pins, etc.

[0006] Therefore, manufacturing devices (such as semiconductor devices) generally involves using a certain number of manufacturing processes to process substrates (e.g., semiconductor wafers) to form various features and multiple layers of the device. These layers and features are generally manufactured and processed using, for example, deposition, photolithography, etching, deposition, chemical mechanical grinding, and ion implantation. Multiple devices can be manufactured on multiple dies on a substrate, and then the devices are separated into separate devices. This device manufacturing process can be considered a patterning process. The patterning process involves using a pattern forming device in a lithographic device to perform a patterning step, such as optical and / or nanoimprint lithography, to transfer the pattern on the pattern forming device to the substrate, and the patterning process generally but optionally involves one or more related pattern processing steps, such as resist development by a developing device, baking the substrate using a baking tool, etching using an etching device, deposition, etc.

[0007] Photolithography is a central step in the fabrication of devices such as ICs, where patterns formed on a substrate define the functional elements of the device, such as microprocessors, memory chips, etc. Similar photolithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS), and other devices.

[0008] As semiconductor manufacturing processes continue to advance, the size of functional elements has continued to decrease over the decades, while the number of functional elements, such as transistors, per device has steadily increased, following a trend often referred to as "Moore's Law." In the current state of the art, the layers of a device are fabricated using a lithographic projection apparatus that projects a design layout onto a substrate using illumination from a deep ultraviolet illumination source, thereby producing individual functional elements with dimensions well below 100 nm (i.e., less than half the wavelength of the radiation from the illumination source (e.g., a 193 nm illumination source)).

[0009] This process for printing features smaller than the classical resolution limit of a lithographic projection apparatus is based on the resolution formula CD = k 1 ×λ / NA and is often referred to as low-k 1 photolithography, where λ is the wavelength of the radiation used (currently 248 nm or 193 nm in most cases), NA is the numerical aperture of the projection optics in the photolithographic projection apparatus, CD is the “critical dimension” (usually the smallest feature size printed), and k 1 is the empirical resolution factor. Usually, k 1 The smaller it gets, the more difficult it becomes to reproduce a pattern on a substrate that resembles the shape and size planned by the designer in order to achieve specific electrical functionality and performance. To overcome these difficulties, complex fine-tuning steps are applied to the lithographic projection equipment, the design layout, or the patterning device. These steps include, for example, but are not limited to, optimization of NA and optical coherence settings, custom illumination schemes, use of phase-shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement technology" (RET). Summary of the invention

[0010] The measurement system optical arrangement eliminates the use of a four-quadrant non-polarizing beam splitter and thus eliminates the need for image stitching. As with the four-quadrant non-polarizing beam splitter, the optical arrangement provides enhanced transmission gain to optimize system throughput. The system includes an illumination mode selector, the illumination mode selector including a porous pattern having a transmission portion and a reflection portion. The illumination mode selector is positioned in a pupil plane of the system and is configured to: transmit a portion of the radiation toward a diffraction grating target; and reflect the diffracted radiation from the diffraction grating target toward a detector along a second optical path. The decoupling of the areas of the transmission portion and the reflection portion on the illumination mode selector facilitates simultaneous optimization of the illumination light intensity and the detection light intensity. About 50% of the radiation is transmitted through two transmission quadrants of the porous pattern. Positive first diffraction order diffracted radiation and negative first diffraction order diffracted radiation from the diffraction grating target are reflected by two reflection quadrants on at least one porous pattern, the two reflection quadrants being located on the back side of the optical element or on the side not facing the radiation source.

[0011] According to an embodiment, a metrology system is provided. The system includes an optical element, the optical element including at least one porous pattern having a transmissive and a reflective portion. The optical element is positioned in a pupil plane of the system. The optical element is configured to receive radiation from a radiation source along a first optical path and transmit a portion of the radiation through the transmissive portion of the at least one porous pattern toward a diffraction grating target. The optical element is configured to reflect diffracted radiation from the diffraction grating target along a second optical path toward a detector using the reflective portion of the at least one porous pattern.

[0012] In some embodiments, about 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern. The two transmission quadrants form a transmission portion of the at least one porous pattern.

[0013] In some embodiments, the positive and negative first diffraction order diffracted radiation from the diffraction grating target is reflected by two reflective quadrants on at least one porous pattern. The two reflective quadrants are located on the back side of the optical element or on the side not facing the radiation source. The two reflective quadrants form the reflective portion of the at least one porous pattern.

[0014] In some embodiments, the optical element is an illumination mode selector. In some embodiments, the illumination mode selector is movable to facilitate selecting the at least one porous pattern from other different possible porous patterns. In some embodiments, the illumination mode selector is a rotatable wheel having the at least one porous pattern and other different possible porous patterns formed therein.

[0015] In some embodiments, the at least one porous pattern comprises four quadrants, wherein opposing first and third quadrants comprise two opposing holes forming the transmissive portion, and opposing second and fourth quadrants comprise the reflective portion of the at least one porous pattern.

[0016] In some embodiments, the two opposing apertures are configured to split the radiation into a first beamlet and a second beamlet, direct the first beamlet through a first optical branch of the system to form a first spot, and direct the second beamlet through a second optical branch of the system to form a second spot.

[0017] In some embodiments, the reflective portion is configured to reflect the diffracted positive first order radiation and negative first order radiation along a second optical path through a detector branch of the system and to a detector. The detector is configured to receive the diffracted first order radiation and generate a detection signal.

[0018] In some embodiments, the system includes an alignment branch beam splitter configured to transmit transmission radiation from a transmission portion of at least one of the porous patterns. The alignment branch beam splitter and the detector branch are not located in a common path. In some embodiments, the alignment branch beam splitter is a transmission type optical cube. In some embodiments, the alignment branch beam splitter is positioned between the optical element and the diffraction grating target, and the optical element is not coupled to an alignment branch of the metrology system.

[0019] In some embodiments, at least one of the porous patterns comprises two opposing holes forming the transmissive portion, each opposing hole comprising an aperture shaped as a sector of a circle.

[0020] In some embodiments, the optical element is configured to replace a four-quadrant non-polarizing beam splitter in a metrology system.

[0021] In some embodiments, the reflective portion is formed by applying a reflective coating to selected portions of the body of the optical element.

[0022] In some embodiments, the system includes a radiation source. The radiation source is configured to generate the radiation along a first optical path.

[0023] In some embodiments, the system includes a detector configured to receive diffracted and reflected first order radiation from the first illumination spot and the second illumination spot on the diffraction grating target and generate a detection signal.

[0024] In some embodiments, the optical element forms part of the overlay detection sensor and / or the alignment sensor.

[0025] In some embodiments, the alignment sensor and / or overlay detection sensor is configured for use with a semiconductor wafer and used in a semiconductor manufacturing process.

[0026] According to another embodiment, another measurement system is provided. The measurement system includes a first optical element formed by a rotatable disk including at least one porous pattern. The first optical element is positioned in a pupil plane of the system. The first optical element is configured to receive radiation from a radiation source and transmit part of the radiation through a transmission part of at least one porous pattern toward a diffraction grating target and through a relay lens pair. The measurement system includes a second optical element, which includes a quad beam splitter having a transmission part and a reflection part. The transmission part of the quad beam splitter is configured to transmit a first part of the radiation received from the first optical element toward the diffraction grating target along a first optical path and transmit a second part of the radiation toward the diffraction grating target along a second optical path, and focus a corresponding spot of the radiation on the diffraction grating target. The reflection part of the quad beam splitter is configured to reflect the diffracted radiation from the diffraction grating target toward a detector along a third optical path.

[0027] According to another embodiment, a metrology method is provided. The metrology method includes: receiving radiation from a radiation source along a first optical path; transmitting part of the radiation through a transmission portion of at least one porous pattern toward a diffraction grating target, the at least one porous pattern being formed in an optical element, the at least one porous pattern including a transmission portion and a reflection portion, the optical element being positioned in a pupil plane of a metrology system; and reflecting diffracted radiation from the diffraction grating target toward a detector along a second optical path using the reflection portion of the at least one porous pattern.

[0028] According to another embodiment, another metrology method is provided, comprising: receiving radiation from a radiation source with a first optical element formed of a rotatable disk including at least one porous pattern, the first optical element being positioned in a pupil plane of the system; and transmitting a portion of the radiation through a transmission portion of the at least one porous pattern and through a relay lens pair toward a diffraction grating target; and transmitting a first portion of the radiation received from the first optical element along a first optical path toward the diffraction grating target and transmitting a second portion of the radiation along a second optical path toward the diffraction grating target with a second optical element including a four-quadrant beam splitter having a transmission portion and a reflection portion; and focusing a corresponding spot of the radiation on the diffraction grating target, the reflection portion of the four-quadrant beam splitter being configured to reflect diffracted radiation from the diffraction grating target along a third optical path toward a detector. In some embodiments, this can be extended to a dual objective sensor and detection branch.

[0029] According to another embodiment, a system for generating a radiation spot is provided, the radiation spot being configured to be directed or directed at a diffraction grating target for an overlay detection sensor used in a semiconductor manufacturing process. The system is configured to generate a plurality of radiation spots. The system is configured to eliminate the need for a four-quadrant non-polarizing beam splitter and thus eliminate the need for alignment image stitching. The system includes a radiation source. The system includes an illumination mode selector, the illumination mode selector including at least one porous pattern having a transmission portion and a reflection portion. The illumination mode selector is positioned in a pupil plane of the system. The illumination mode selector is configured to: receive radiation from the radiation source along a first optical path, and transmit part of the radiation through the transmission portion of the at least one porous pattern toward the diffraction grating target; and reflect the diffracted radiation from the diffraction grating target toward the detector along a second optical path with the reflection portion of the at least one porous pattern. About 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern. The two transmission quadrants form the transmission portion of the at least one porous pattern. The positive first diffraction order diffracted radiation and the negative first diffraction order diffracted radiation from the diffraction grating target are reflected by two reflection quadrants on the at least one porous pattern. The two reflection quadrants are located on the back side of the optical element or on the side not facing the radiation source. The two reflection quadrants form a reflection portion of the at least one porous pattern. The system includes a detection sensor. The detection sensor is configured to receive the diffracted and reflected positive first order radiation and negative first order radiation from the diffraction grating target, and generate overlapping detection signals based on the diffracted and reflected positive first order radiation and negative first order radiation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above aspects as well as other aspects and features will become apparent to those of ordinary skill in the art after reviewing the following description of specific embodiments in conjunction with the accompanying drawings.

[0031] Figure 1 A lithographic apparatus according to an embodiment is schematically depicted.

[0032] Figure 2 Embodiments of a lithography cell or lithography cluster according to embodiments are schematically depicted.

[0033] Figure 3 An exemplary inspection system according to an embodiment is schematically depicted.

[0034] Figure 4 An exemplary metrology technique according to an embodiment is schematically depicted.

[0035] Figure 5 FIG. 2 illustrates the relationship between a radiation irradiation spot and a measurement target of an inspection system according to an embodiment.

[0036] Figure 6 A system configured to generate one or more illumination spots configured to be directed toward one or more metrology targets, such as one or more diffraction grating targets, is illustrated in accordance with an embodiment.

[0037] Figure 7 Optical elements comprising an illumination mode selector of the present system are illustrated according to an embodiment.

[0038] Figure 8 A four-quadrant porous pattern including two transmissive and two reflective is illustrated according to an embodiment.

[0039] Fig. 9 An alternative form of the present system according to an embodiment is illustrated.

[0040] Fig.10 FIG. 1 illustrates a measurement method according to an embodiment.

[0041] Fig.11 is a block diagram of an exemplary computer system according to an embodiment. DETAILED DESCRIPTION

[0042] In semiconductor device manufacturing, metrology operations typically include determining the position of a metrology mark (or marks) and / or other targets in a layer of a semiconductor device structure. Such positions are typically determined by irradiating the metrology mark with radiation and comparing the characteristics of different diffraction orders of radiation reflected from the metrology mark. These techniques are used to measure overlay, alignment, and / or other parameters.

[0043] Previous metrology systems used a four-quadrant non-polarizing beam splitter (NPBS) to transmit radiation to a target such as a metrology mark and reflect diffracted radiation from the metrology mark to a detector. However, this design includes limitations in that it does not provide a full field of view and therefore requires image stitching. Image stitching introduces (e.g., alignment) errors that are undesirable and adversely affect the ability of these previous metrology systems to meet future specifications.

[0044] Advantageously, the present system and method provide a new optical design architecture for a metrology system that eliminates the use of a four-quadrant non-polarizing beam splitter and thus eliminates the need for (e.g., alignment) image stitching. Instead of a four-quadrant non-polarizing beam splitter, a shaped aperture and a corresponding reflective portion are provided on an illumination mode selector (e.g., wheel) positioned in the pupil plane of the metrology system. This combines the functionality of the illumination mode selector aperture patterning and the four-quadrant non-polarizing beam splitter at the pupil plane by using a highly reflective coating on one or more portions of the illumination mode selector. In this way, the diffracted first-order radiation can be reflected to the detector branch of the system. Since the illumination mode selector with the shaped aperture and the reflective portion is conjugate to the pupil plane and is not located in a common path with the alignment branch of the metrology system, the present metrology system does not suffer from image stitching and error problems observed in previous metrology systems. In addition, to meet future requirements, for example, the reflected radiation from the illumination mode selector can be directed to a second objective and a low-cost high-photon efficiency dual objective sensor can be realized. Due to the functionality of the illumination mode selector, the diffracted first order radiation from both objective sensors can be measured synchronously with a single detection branch by means of the first order radiation diffracted from the transmitted / reflected radiation, respectively.

[0045] As a brief introduction, the following description relates to semiconductor device manufacturing and patterning processes. The following paragraphs also describe several elements of systems and / or methods for semiconductor device measurement. These systems and methods can be used, for example, to measure overlay, alignment, etc. during semiconductor device manufacturing, or for other operations.

[0046] Although specific reference may be made herein to the measurement of overlay, alignment or other parameters and integrated circuit (IC) manufacturing for semiconductor devices, it should be understood that the description herein has many other possible applications. For example, it can be used to manufacture integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal display panels, thin film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms "reticle", "wafer" or "die" herein should be considered to be interchangeable with the more general terms "mask", "substrate" and "target portion", respectively.

[0047] The term "projection optics" as used herein should be broadly interpreted to cover various types of optical systems, including, for example, refractive optics, reflective optics, apertures, and reflective-refractive optics. The term "projection optics" may also include elements that operate according to any of these design types for collectively or individually directing, shaping, or controlling a projection beam of radiation. The term "projection optics" may include any optical element in a lithographic projection apparatus, regardless of where the optical element is located in the optical path of the lithographic projection apparatus. Projection optics may include optical elements for shaping, adjusting, and / or projecting radiation before radiation from a source passes through a patterning device, and / or optical elements for shaping, adjusting, and / or projecting radiation after radiation passes through a patterning device. Projection optics typically do not include a source and a patterning device.

[0048] Figure 1 An embodiment of a lithographic apparatus LA is schematically depicted. The apparatus comprises an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation or EUV radiation); a support structure (e.g. mask table) MT constructed to support a patterning device (e.g. mask) MA and connected to a first positioner PM configured to accurately position the patterning device according to certain parameters; a substrate table (e.g. wafer stage) WT (e.g. WTa, WTb or both) configured to hold a substrate (e.g. a wafer coated with resist) W and coupled to a second positioner PW configured to accurately position the substrate according to certain parameters; and a projection system (e.g. refractive projection lens system) PS configured to project a pattern imparted by the patterning device MA to the radiation beam B onto a target portion C (e.g. comprising one or more dies and often referred to as a field) of the substrate W. The projection system is supported on a reference frame RF. As depicted, the apparatus is of a transmission type (e.g. using a transmission mask). Alternatively, the device may be of the reflective type (eg using a programmable mirror array or using a reflective mask).

[0049] The illuminator IL receives a radiation beam from a radiation source SO. For example, when the source is an excimer laser, the source and the lithographic apparatus may be separate entities. In these cases, the source is not considered to form part of the lithographic apparatus, and the radiation beam is delivered from the source SO to the illuminator IL by means of a beam delivery system BD comprising, for example, suitable directional mirrors and / or a beam expander. In other cases, for example, when the source is a mercury lamp, the source may be an integral part of the apparatus. The source SO and the illuminator IL together with the beam delivery system BD may be referred to as a radiation system when necessary.

[0050] The illuminator IL may modify the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam so that the intensity distribution within an annular region in a pupil plane of the illuminator IL is non-zero. Additionally or alternatively, the illuminator IL is operable to limit the distribution of the beam in the pupil plane so that the intensity distribution in a plurality of equally spaced sectors in the pupil plane is non-zero. The intensity distribution of the radiation beam in the pupil plane of the illuminator IL may be referred to as an illumination pattern.

[0051] The illuminator IL may comprise an adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. Typically, at least the outer radial extent and / or the inner radial extent (typically referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator may be adjusted. The illuminator IL may be operable to vary the angular distribution of the beam. For example, the illuminator may be operable to change the number and angular extent of sectors in the pupil plane in which the intensity distribution is non-zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination modes may be achieved. For example, by limiting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multipolar distribution, such as a dipole, quadrupole or hexapole distribution. The illumination mode may be obtained, for example, by inserting an optical device providing the desired illumination mode into the illuminator IL or by using a spatial light modulator.

[0052] The illuminator IL is operable to change the polarization of the beam and is operable to adjust the polarization using the adjuster AD. The polarization state of the radiation beam on the pupil plane of the illuminator IL can be referred to as a polarization mode. Using different polarization modes can allow a greater contrast to be achieved in the image formed on the substrate W. The radiation beam can be unpolarized. Alternatively, the illuminator can be arranged to polarize the radiation beam linearly. The polarization direction of the radiation beam can change on the pupil plane of the illuminator IL. The polarization direction of the radiation can be different in different zones in the pupil plane of the illuminator IL. The polarization state of the radiation can be selected depending on the illumination mode. For a multipolar illumination mode, the polarization of each pole of the radiation beam can be approximately perpendicular to the position vector of the pole in the pupil plane of the illuminator IL. For example, for a dipole illumination mode, the radiation can be linearly polarized in a direction approximately perpendicular to a line that bisects two opposite sectors of the dipole. The radiation beam can be polarized in one of two different orthogonal directions that can be referred to as an X polarization state and a Y polarization state. For a quadrupole illumination mode, the radiation in the sector of each pole can be linearly polarized in a direction approximately perpendicular to a line that bisects the sector. This polarization mode can be referred to as XY polarization. Similarly, for a hexapole illumination mode, the radiation in a sector of each pole may be linearly polarized in a direction approximately perpendicular to a line bisecting the sector. This polarization mode may be referred to as TE polarization.

[0053] In addition, the illuminator IL typically includes various other elements, such as an integrator IN and a condenser CO. The illumination system may include various types of optical elements for directing, shaping or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical elements, or any combination thereof. Thus, the illuminator provides a conditioned radiation beam B having a desired uniformity and intensity distribution in its cross-section.

[0054] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions (such as whether the patterning device is maintained in a vacuum environment). The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure can be, for example, a frame or a table, which can be fixed or movable as required. The support structure can ensure that the patterning device is in a desired position, for example relative to a projection system. Any use of the term "reticle" or "mask" herein can be considered synonymous with the more general term "patterning device".

[0055] The term "patterning device" as used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of a substrate. In an embodiment, the patterning device is any device that can be used to impart a pattern to a radiation beam in its cross-section to produce a pattern in a target portion of a substrate. It should be noted that if, for example, the pattern imparted to the radiation beam includes phase-shifting features or so-called assist features, the pattern may not exactly correspond to the desired pattern in the target portion of the substrate. Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device (such as an integrated circuit) produced in the target portion of the device.

[0056] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array uses a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam reflected by the matrix of mirrors.

[0057] The term "projection system" should be broadly interpreted as covering any type of projection system suitable for the exposure radiation used or for other factors such as the use of immersion liquid or the use of a vacuum, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

[0058] The projection system PS may include a plurality of optical (e.g., lens) elements, and may further include an adjustment mechanism configured to adjust one or more of the optical elements in order to correct aberrations (phase changes in the pupil plane throughout the field). To achieve such correction, the adjustment mechanism is operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system in which its optical axis extends in the z direction. The adjustment mechanism is operable to perform any combination of the following: shifting one or more optical elements; tilting one or more optical elements; and / or deforming one or more optical elements. The displacement of the optical element may be performed in any direction (x, y, z, or a combination thereof). The tilting of the optical element is typically performed outside a plane perpendicular to the optical axis by rotating around an axis in the x and / or y direction, but rotation around the z axis may be used for non-rotationally symmetric aspheric optical elements. The deformation of the optical element may include a low-frequency shape (e.g., astigmatism) and / or a high-frequency shape (e.g., a free-form aspheric surface). Deformation of the optical element may be performed, for example, by applying a force to one or more sides of the optical element using one or more actuators and / or heating one or more selected regions of the optical element using one or more heating elements. Typically, it is not possible to adjust the projection system PS to correct for apodization (transmission variations in the pupil plane). When designing a patterning device (e.g., mask) MA for the lithographic apparatus LA, a transmission map of the projection system PS may be used. Using computational lithography techniques, the patterning device MA may be designed to at least partially correct for apodization.

[0059] The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g. two or more substrate tables WTa, WTb, two or more patterning device tables, substrate table WTa and table WTb below the projection system without a dedicated substrate for, e.g., facilitating measurement and / or cleaning, etc.). In these "multi-stage" machines, the extra tables may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements using alignment sensor AS and / or level (height, inclination, etc.) measurements using level sensor LS may be performed.

[0060] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, so as to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, such as the space between the patterning device and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of a projection system. The term "immersion" as used herein does not mean that structures such as the substrate are necessarily immersed in the liquid, but only means that the liquid is located between the projection system and the substrate during exposure.

[0061] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by an illumination system IL. The radiation beam B is incident on a patterning device (e.g. a mask) MA held on a support structure (e.g. a mask table) MT and is patterned by the patterning device. Having traversed the patterning device 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 sensor IF (e.g. an interferometric measurement device, a linear encoder, a 2-D encoder or a capacitive sensor), the substrate table WT can be accurately moved, for example for positioning different target portions C in the path of the radiation beam B. Similarly, a first positioner PM and a further position sensor (which is not explicitly depicted in the figure) may be used, for example after mechanical retrieval from a mask library or during scanning. Figure 1 The support structure MT may be used to accurately position the pattern forming device MA relative to the path of the radiation beam B. Typically, movement of the support structure MT may be achieved with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) which form part of the first positioner PM. Similarly, movement of the substrate table WT may be achieved using a long-stroke module and a short-stroke module which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected only to the short-stroke actuator, or may be fixed. The pattern forming device MA and the substrate W may be aligned using pattern forming device alignment marks M1, M2 and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks occupy dedicated target portions, the marks may be located in the spaces between target portions (these marks are referred to as scribe alignment marks). Similarly, in the case where more than one die is arranged on the pattern forming device MA, the pattern forming device alignment marks may be located between the dies.

[0062] The depicted apparatus can be used in at least one of the following modes. In step mode, the support structure MT and the substrate table WT are held substantially stationary while a pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). Subsequently, the substrate table WT is shifted in the X and / or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure MT may be determined by the (or less) magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width of the target portion in a single dynamic exposure (in the non-scanning direction), while the length of the scanning movement determines the height of the target portion (in the scanning direction). In another mode, the support structure MT is held substantially stationary, thereby holding the programmable patterning device, and the substrate table WT is moved or scanned, while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, a pulsed radiation source is typically used, and the programmable patterning device is updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applied to maskless lithography utilizing a programmable patterning device, such as a programmable mirror array of the type mentioned above.

[0063] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be used.

[0064] The substrate may be processed before or after exposure in, for example, a coating and developing system (a tool that typically applies a resist layer to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to these and other substrate processing tools. In addition, a substrate may be processed more than once, for example to produce a multi-layer IC, so the term substrate as used herein may also refer to a substrate that already includes multiple processed layers.

[0065] The terms “radiation” and “beam” as used herein with respect to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g., having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm) and extreme ultraviolet (EUV) radiation (e.g., having a wavelength in the range of 5 nm to 20 nm), as well as particle beams, such as ion beams or electron beams.

[0066] Various patterns on or provided by a pattern forming device may have different process windows, i.e., the space of process variables according to which patterns will be produced within specifications. Examples of pattern specifications for potential systematic defects include checking for necking, line pullback, line thinning, CD, edge placement, overlay, resist top loss, resist undercut, and / or bridging. The process window of a pattern on a pattern forming device or a region thereof may be obtained by merging (e.g., overlapping) the process windows of each individual pattern. The boundaries of the process window of a pattern group include the boundaries of the process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the pattern group.

[0067] like Figure 2 As shown, the lithography equipment LA can form part of a lithography unit LC (sometimes also referred to as a lithography cell or cluster), which also includes equipment for performing pre-exposure processes and post-exposure processes on a substrate. Conventionally, these equipment include one or more spin coaters SC for depositing one or more resist layers, one or more developers for developing the exposed resist, one or more chill plates CH and / or one or more baking plates BK. The substrate conveyor or robot RO picks up one or more substrates from the input / output ports I / O1, I / O2, moves them between different process equipment and transfers them to the feed station LB of the lithography equipment. These equipment, which are often collectively referred to as coating and developing systems, are controlled by a coating and developing system control unit TCU, which itself is controlled by a management control system SCS, which also controls the lithography equipment via a lithography control unit LACU. Therefore, different equipment can be operated to maximize production volume and processing efficiency.

[0068] In order to correctly and consistently expose a substrate exposed by a lithographic apparatus and / or to monitor a portion of a patterning process (e.g. a device manufacturing process) comprising at least one pattern transfer step (e.g. an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties, such as alignment, overlay (which may be, for example, between structures in superimposed layers or between structures in the same layer that have been provided to that layer separately by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, material properties, etc. Therefore, a manufacturing facility in which a lithocell LC is located typically also comprises a metrology system that measures the properties of a substrate W ( Figure 1 ) or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example, it may be part of the lithographic apparatus LA (such as an alignment sensor AS ( Figure 1 )).

[0069] One or more measured parameters may include, for example, alignment between successive layers formed in or on a patterned substrate, overlay, critical dimensions (CD) of features formed in or on a patterned substrate (e.g., critical line width), focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberrations of an optical lithography step, etc. Such measurements are often performed on one or more dedicated metrology targets disposed on the substrate. Measurements may be performed after resist development but before etching, after etching, after deposition, and / or at other times.

[0070] There are various techniques for measuring structures formed during the patterning process, including the use of scanning electron microscopes, image-based measurement tools, and / or various specialized tools. A fast and non-invasive form of a specialized measurement tool is one in which a radiation beam is directed onto a target on the surface of a substrate and the properties of the scattered (diffraction / reflection) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Traditionally, this can be referred to as diffraction-based measurement. Applications of such diffraction-based measurement include measurements of overlay, alignment, and the like. For example, overlay and / or alignment can be measured by comparing portions of the diffraction spectrum (e.g., comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0071] Thus, in a device fabrication process (e.g., a patterning process or a lithography process), a substrate or other object may be subjected to various types of measurements during or after the process. The measurements may determine whether a particular substrate is defective, may establish adjustments to the process and adjustments to the equipment used in the process (e.g., aligning two layers on a substrate or aligning a pattern forming device to a substrate), may measure the performance of the process and equipment, or may be used for other purposes. Examples of measurements include optical imaging (e.g., optical microscopy), non-imaging optical measurements (e.g., diffraction-based measurements, such as ASML YieldStar metrology tools, ASML SMASH metrology systems), mechanical measurements (e.g., profile detection using a stylus, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)). The Smart Alignment Sensor Hybrid (SMASH) system described in U.S. Patent No. 6,961,116, which is incorporated herein by reference in its entirety, employs a self-referencing interferometer that produces two superimposed and relatively rotated images of an alignment marker, detects intensity in a pupil plane that interferes the Fourier transforms of the images, and extracts position information from the phase difference between the diffraction orders of the two images, which manifests itself as intensity variations in the interference orders.

[0072] The measurement results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, the exposure of subsequent substrates (especially where the inspection can be completed quickly and quickly enough that one or more other substrates of the batch remain to be exposed) and / or the subsequent exposure of the exposed substrate may be adjusted. In addition, the exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding further processing of substrates known to be defective. In the event that only some target portions of the substrate are defective, further exposure may be performed only on those portions that meet the specifications. Other manufacturing process adjustments are contemplated.

[0073] The metrology system may be used to determine one or more properties of a substrate structure, and in particular to determine how one or more properties of different substrate structures vary, or how different layers of the same substrate structure vary from layer to layer. The metrology system may be integrated into the lithographic apparatus LA or the lithocell LC, or may be a separate device.

[0074] In order to achieve the measurement, one or more targets are often specifically provided on the substrate. Typically, the target is specially designed and may include a periodic structure. For example, the target on the substrate may include one or more one-dimensional periodic structures (e.g., geometric features such as gratings), which are printed so that after development, the periodic structural features are formed by solid resist lines. As another example, the target may include one or more two-dimensional periodic structures (e.g., gratings), which are printed so that after development, one or more periodic structures are formed by solid resist guide posts or through holes in the resist. Alternatively, the bars, guide posts or through holes may be etched into the substrate (e.g., etched into one or more layers on the substrate).

[0075] Figure 3 An exemplary metrology (inspection) system 10 that can be used to detect overlay, alignment, and / or perform other metrology operations is depicted. The system includes a radiation or illumination source 2 that projects or otherwise irradiates radiation onto a substrate W (which may typically include metrology marks, for example). The redirected radiation is passed to a sensor such as a spectrometer detector 4 and / or other sensor that measures the spectrum (intensity as a function of wavelength) of the specularly reflected and / or diffracted radiation, for example, at Figure 4 The sensor may generate a measurement signal expressing measurement data indicative of the nature of the reflected radiation. From this data, the structure or profile resulting from the detected spectrum may be reconstructed by one or more processors PRO, a general example of which is shown in Figure 4 as shown in , or reconstructed through other operations.

[0076] As in Figure 1In the lithographic apparatus LA, one or more substrate tables ( Figure 4 The substrate table may be a substrate table (not shown) for holding the substrate W during the measurement operation. Figure 1 The substrate tables WT (WTa or WTb or both) of the inspection system 10 are similar or identical. In an example where the inspection system 10 is integrated with a lithographic apparatus, the one or more substrate tables may even be the same substrate table. Coarse and fine positioners may be provided and configured to accurately position the substrate relative to the measuring optical system. Various sensors and actuators are provided, for example, for acquiring the position of a target portion of interest (e.g., a measurement mark) of a structure, and bringing the target portion of interest into a position below the objective lens. Typically, many measurements will be made on the target portion of the structure at different locations on the substrate W. The substrate support may be moved in the X and Y directions to acquire different targets, and in the Z direction to obtain the desired position of the target portion relative to the focus of the optical system. For example, when in practice the optical system can remain substantially stationary (usually in the X and Y directions, but possibly also in the Z direction) and the substrate moves, it is convenient to consider and describe the operation as if the objective lens is brought into different positions relative to the substrate. Provided that the relative position of substrate and optical system is correct, it is in principle unimportant which of the substrate and the optical system is moving, or whether both the substrate and the optical system are moving, or a combination of a part of the optical system moving (e.g. in the Z direction and / or in the tilt direction) and a part of the optical system being stationary and the substrate moving (e.g. in the X direction and Y direction, but optionally also in the Z direction and / or in the tilt direction).

[0077] For typical metrology measurements, the target (portion) 30 on the substrate W may be a one-dimensional grating, which is printed so that after development, the grating bars are formed by solid resist lines (which may be covered by a deposited layer, for example) and / or other materials. Or the target 30 may be a two-dimensional grating, which is printed so that after development, the grating is formed by solid resist guide posts and / or other features in the resist.

[0078] The bars, guide posts, vias, and / or other features may be etched into or onto the substrate (e.g., etched into one or more layers on the substrate), deposited on the substrate, covered by a deposited layer, and / or have other properties. The target (portion) 30 (e.g., bars, guide posts, vias, etc.) is sensitive to changes in processing during the patterning process (e.g., optical aberrations in a lithographic projection device (such as a projection system), focus changes, dose changes, etc.), so that process changes appear as changes in the target 30. Therefore, the measured data from the target 30 can be used to determine adjustments to one or more manufacturing processes, and / or used as a basis for making actual adjustments.

[0079] For example, the measured data from the target 30 may indicate an overlap of layers of a semiconductor device. The measured data from the target 30 may be used (e.g., by one or more processors PRO and / or other processors) to determine one or more semiconductor device manufacturing process parameters based on the overlap, and to determine adjustments to semiconductor device manufacturing equipment based on one or more determined semiconductor device manufacturing process parameters. In some embodiments, this may include, for example, stage position adjustments, or this may include determining adjustments to mask design, measurement target design, semiconductor device design, intensity of radiation, incident angle of radiation, wavelength of radiation, pupil size and / or shape, resist material, and / or other process parameters.

[0080] Figure 5 A plan view showing a typical target (eg, measurement mark) 30, and Figure 4 The range of a typical radiation illumination spot S in a system of. In general, in order to obtain a diffraction spectrum that is not affected by interference from surrounding structures, in some embodiments, the target 30 can be a periodic structure (e.g., a grating) that is larger than the width (e.g., diameter) of the illumination spot S. The width of the spot S can be smaller than the width and length of the target. In other words, the target is "underfilled" by the illumination, and the diffraction signal is substantially free of any signal from product features, etc., external to the target itself. For example, the illumination device can be configured to provide illumination of uniform intensity at the back focal plane of the objective. Alternatively, the illumination can be limited to an on-axis direction or an off-axis direction by, for example, including an aperture in the illumination path.

[0081] Figure 6 The system 600 is shown as being configured to generate one or more spots 602 of radiation 604 that is configured to be directed toward one or more metrology targets 30, such as one or more diffraction grating targets. The radiation shown can be used to obtain an image of the metrology target, and / or for other purposes. The radiation 604 can include illumination such as light and / or other radiation. For example, the target 30 can include one or more metrology marks, such as a diffraction grating target, formed in a substrate such as a semiconductor wafer 610. The system 600 can form the image as described above with respect to Figure 3 System 600 may be a subsystem of system 10. In some embodiments, one or more elements of system 600 may be similar to and / or identical to one or more elements of system 10. In some embodiments, one or more elements of system 600 may replace one or more elements of system 10, be used together with one or more elements of system 10, and / or otherwise augment one or more elements of system 10. System 600 is configured to generate a plurality of radiation spots (e.g., Figure 3 Source 2 shown in (similar and / or identical to source 2).

[0082] As described above, among other advantages, system 600 is configured to eliminate the need for a four-quadrant non-polarizing beam splitter and, therefore, eliminate the need for (e.g., overlapping or alignment) image stitching. Previous metrology systems used a four-quadrant non-polarizing beam splitter to enhance the intensity of radiation transmitted to a target such as a metrology mark (e.g., increase the number of photons), for example, to facilitate faster image acquisition. However, if a four-quadrant non-polarizing beam splitter is used, image stitching is required because the four-quadrant non-polarizing beam splitter is in a common path with the alignment branch and is not located at the pupil plane of the system. The non-pupil plane location causes defocus and / or radiation intensity non-uniformity issues and results in the acquisition of something that is less than the full field of view of the metrology target for, for example, alignment purposes. Image stitching introduces (e.g., alignment) errors that are undesirable and adversely affects the ability of these previous metrology systems to meet future (e.g., alignment and / or various critical dimensions (CD)) specifications.

[0083] In more detail, previous four-quadrant non-polarizing beam splitters were designed to optimize zero-order reflection and first-order transmission in order to achieve >3x radiation transmission gain for metrology sensors. The concept is implemented with a patterned coating that provides both transmission and reflection parts. However, the four-quadrant non-polarizing beam splitter is in a common path with the alignment branch and is not located at the pupil plane in these systems, which has a critical impact on the intensity uniformity of the sensed image. Therefore, only a partial field of view in the image can be used. In order to obtain the full field of view, multiple images and stitching are required. Stitching errors from intensity non-uniformities have been shown to cause chip position errors of up to 20μm.

[0084] Additionally, if previous metrology systems used wedges or other similar optical elements to separate radiation reflected from the target, a four-quadrant non-polarizing beam splitter (not located in the pupil plane) causes this radiation to spread into a "safety zone" of overlap between the portion of radiation intended to prevent diffraction and the portion of radiation reflected. To overcome this problem, in previous metrology systems, the safety zone size is typically increased, and / or the transmission aperture size and / or shape is adjusted, which further reduces the corresponding field of view for alignment purposes and increases the likelihood of stitching-related errors.

[0085] For radiation detection in previous metrology systems, due to the fact that the wedge and the four-quadrant non-polarizing beam splitter are not optically conjugated in previous systems, there is a transmission safety zone around the boundary of the reflective and transmissive parts of the coating in the four-quadrant non-polarizing beam splitter. Therefore, if the first-order diffracted radiation overlaps the transmission safety zone, the first-order diffracted radiation may affect the accuracy of, for example, the overlay measurement. In order to prevent this accuracy impact, a smaller illumination mode selector aperture is used to try to avoid the overlap, but this costs illumination light intensity and / or system throughput (which the four-quadrant non-polarizing beam splitter was originally intended to improve).

[0086] System 600 provides a new optical design architecture. Instead of a four-quadrant non-polarizing beam splitter, a shaped aperture and corresponding reflective portion are provided on an optical element 650 (illumination mode selector) positioned in the pupil plane of system 600. This architecture still enhances the intensity of radiation transmitted to a target such as a metrology mark (e.g., increases the number of photons), for example, to facilitate faster image acquisition, but without the need for image stitching. System 600 can reduce costs compared to previous systems because the four-quadrant non-polarizing beam splitter and / or other additional optical elements are removed compared to previous designs. With system 600, alignment position errors are reduced or eliminated because a full field of view can be obtained without image stitching that often causes (e.g., alignment) errors. System 600 enhances throughput compared to previous systems because the illumination mode selector and wedge-shaped safety zone can be minimized while still being able to apply a relatively large illumination mode selector aperture and optimize the illumination mode selector aperture for illumination intensity. In addition, system 600 still allows different illumination patterns for various metrology applications. Other advantages are contemplated.

[0087] System 600 includes: radiation source 612; optical element 650; detection branch 660 with detector 662; beam splitter 670; alignment branch 680; various lenses, reflectors and other optical elements (with Figure 6 ); and / or other elements. In some embodiments, elements of system 600 form part of an overlay and / or alignment sensor used in a semiconductor manufacturing process. In some embodiments, system 600 may have other uses, including use in any metrology system where multiple radiation spots need to be generated from a single radiation beam on a target, for example.

[0088] The radiation source 612 is configured to generate radiation along the first optical path 621. The radiation can have a target wavelength and / or wavelength range, a target intensity, and / or other characteristics. The target wavelength and / or wavelength range, target intensity, etc. can be entered and / or selected by a user, determined by the system (e.g., based on previous measurements, Figure 3In some embodiments, the radiation includes light and / or other radiation. In some embodiments, the light includes visible light, infrared light, near infrared light, and / or other light. In some embodiments, the radiation can be any radiation suitable for interferometry.

[0089] The optical element 650 is configured to replace a four-quadrant non-polarizing beam splitter in a previous metrology system. The optical element 650 is configured to be positioned in a pupil plane 655 of the system 100 (e.g., to mitigate the problems with the previous metrology system described above). The optical element 650 is configured to receive radiation from a radiation source 612 along a first optical path 621, and transmit a portion of the radiation through a transmission portion of at least one porous pattern toward a target 30. The target 30 may be one or more metrology marks, such as a diffraction grating target on a semiconductor wafer as described herein, for example, collectively referred to as a target 30. The target 30 may include one or more structures in a patterned substrate capable of providing a diffraction signal. For example, one or more targets 30 may be included in a substrate layer in a semiconductor device structure. In some embodiments, the features include geometric features, such as one-dimensional or two-dimensional features, and / or other geometric features. As several non-limiting examples, the features may include gratings, lines, edges, a series of fine pitch lines and / or edges, and / or other features.

[0090] Figure 7 An example of an optical element 650 is shown. The optical element 650 includes a body 701, at least one porous pattern 703 having a transmissive portion 705 and a reflective portion 707 (e.g., on the bottom side of the body 701), and / or other elements. In some embodiments, the optical element 650 is an illumination mode selector. The illumination mode selector is movable 653 to facilitate selecting at least one porous pattern 703 from among other different possible porous patterns 720. In some embodiments, as Figure 7 As shown, the irradiation mode selector is a rotatable wheel in which at least one porous pattern 703 and other different possible porous patterns 720 are formed.

[0091] Figure 8 The at least one porous pattern 703 is shown to include four quadrants 800, 802, 804, and 806. Opposing first and third quadrants 800 and 804 include two opposing holes forming a transmissive portion 705, and opposing second and fourth quadrants 802 and 806 include a reflective portion 707 of the at least one porous pattern 703. In some embodiments, the at least one porous pattern 703 includes opposing holes (in quadrants 800 and 804) forming the transmissive portion 705, wherein each opposing hole includes an aperture shaped as a sector of a circle (e.g., Figure 8 ). For example, this exemplary shape can be configured based on other optical elements in the metrology sensor (such as an objective lens and / or a wedge). In such a case, relative transmission quadrants are desired, but a specific sector shape is not absolutely required. For example, other shapes such as squares (such as Figure 7 is to be expected.

[0092] The two transmissive holes in the quadrants 800 and 804 form the transmissive portion 705 of the at least one porous pattern 703. The transmissive holes in the two opposite quadrants 800 and 804 are configured to split the radiation 604 into a first sub-beam and a second sub-beam, and direct the first sub-beam and the second sub-beam toward the target 30 ( Figure 6 ). In some embodiments, about 50% of the radiation 604 is transmitted through two transmissive holes in quadrants 800 and 804 of the at least one porous pattern 703. In some embodiments, about 30%, 40%, 60%, 70%, 80%, or 90% of the radiation 604 is transmitted.

[0093] The optical element 650 reflects the diffracted radiation 850 from the diffraction grating target 30 along the optical path 631 toward the detector 662 using the reflective portion 707 (quadrants 802 and 806) of the at least one porous pattern 703 ( Figure 6 ). In some embodiments, the reflective portion 707 is formed by applying a reflective coating (e.g., gold, silver, etc.) to selected portions of the body of the optical element 650. For example, multiple layers of dielectric coatings may also be used. These layers may be patterned and added by photolithography techniques (with sputtering, thermal evaporation coating, and / or other techniques).

[0094] Back to Figure 6 In some embodiments, the reflective portion 707 ( Figure 7 and Figure 8 ) is configured to reflect the diffracted positive and negative first order radiation along the optical path 631 through the detector branch 660 of the system 600 and to the detector 662. The detector 662 is configured to receive the diffracted first order radiation and generate a detection signal (e.g., as described above with respect to Figures 3 to 5 This may include generating and / or analyzing one or more images of the target 30 using the radiation described herein. The positive and negative first diffraction order diffracted radiation from the diffraction grating target 30 is reflected by the at least one porous pattern 703 ( Figure 7 ) on the two reflection quadrants 802 and 806 ( Figure 8 ) reflection. The two reflecting quadrants 802 and 806 are located on the back side of the optical element 650 or the side 651 that does not face the radiation source. The two reflecting quadrants 802 and 806 form the reflecting portion 707 ( Figure 7 and Figure 8 ).

[0095] The alignment branch 680 is configured to receive the reflected radiation and generate an alignment signal (eg, as described above with respect to Figures 3 to 5 ). This may include generating and / or analyzing one or more images of the target 30 using the radiation described herein. The beam splitter 670 is an alignment branch 680 beam splitter configured to transmit transmission radiation 671 from the transmission portion of the at least one porous pattern. In some embodiments, the alignment branch 680 beam splitter 670 is, for example, a transmission type optical cube. Figure 6 As shown, the alignment branch 680 beam splitter 670 is positioned between the optical element 650 and the diffraction grating target 30. This ensures that the optical element 650 is not coupled to the alignment branch 680, and that the alignment branch 680 beam splitter 670 is not in a common path with the detector branch 660. This is at least advantageous because, since the optical element 650 is conjugate with the pupil plane and is not in a common path with the alignment branch 680, the system 600 does not suffer from image stitching and error problems observed in previous metrology systems (e.g., as described above).

[0096] System 600 may take alternative forms. One such alternative is Fig. 9 900. System 900 is configured such that radiation from radiation source 612 is received by optical element 902 (e.g., similar to optical element 650 described above) formed of a rotatable disk including at least one porous pattern 904. Optical element 902 is positioned in a pupil plane of system 900. Optical element 902 transmits a portion of radiation 604 through a transmitted portion of at least one porous pattern 904 and relay lens pair 910 toward diffraction grating target 30 (or target 30). Compared to Figure 6 , the system 600 is configured to transmit a first portion 952 of radiation received from the optical element 902 along a first optical path 953 toward the diffraction grating target 30 and a second portion 954 of the radiation along a second optical path 955 toward the diffraction grating target 30 using a second optical element 950 including a quad beam splitter having a transmissive portion and a reflective portion. The system 900 is configured to focus a corresponding spot 602 of radiation onto the diffraction grating target 30. The reflective portion of the quad beam splitter is configured to reflect diffracted radiation from the diffraction grating target along a third optical path 960 toward the detector 662.

[0097] refer to Figure 6 and Fig. 9 , various lenses (exemplary objective lens 690 in Figure 6are marked in; and 990 and 991 are in Fig. 9 ), reflectors and other optical elements (e.g., wedge 697) are configured to receive, transmit, reflect, focus, and generate light from the illumination source 612 and the beam splitter 670 ( Figure 6 ) is split and composed of optical element 650 ( Figure 6 ) and / or 902, 950 ( Fig. 9 ) transmitted or reflected, received by detection branch 660, received by alignment branch 680, and / or used by other parts of system 600 and / or 900 and / or perform other operations on it. These various lenses, reflectors, and / or other optical elements may include any type of lens, reflector, and / or other optical element configured to allow system 600 and / or 900 to function as described. For example, objective lens 690, 990, and / or 991 can be formed of any transparent material and have a curved surface that is configured to concentrate or otherwise focus one or more spots 602 of radiation on target 30. The various lenses, reflectors, optical elements 650, 902, and / or 950, beam splitter 670, and other optical elements can be positioned in any position and / or at any angle relative to each other that allows system 600 and / or system 900 to function as described herein. This may include positioning at a specific relative distance between elements, a specific angle between elements, etc. In some embodiments, various lenses, reflectors, optical elements, beam splitters, and other optical elements are positioned relative to each other in system 600 and / or system 900 via structural members, clips, fixtures, screws, nuts, bolts, adhesives, and / or other mechanical devices. In some embodiments, each of the lenses, reflectors, optical elements, beam splitters, and other optical elements is movable relative to each other. Movement can be configured to adjust, for example, the location of a corresponding illumination spot on one or more targets 30. In some embodiments, movement includes tilting, translating, or otherwise changing the distance between various lenses, reflectors, and other optical elements. Other examples of movement are contemplated.

[0098] In some embodiments, movement can be performed by a processor, such as in Figure 3 (Also discussed below) Fig.11 ) is electronically controlled by a processor PRO shown in FIG. The processor PRO may be included in a computing system CS ( Fig.11 ) and can be operated based on computer or machine readable instructions MRI (for example, as described below with respect to Fig.11Electronic communication may occur by transmitting electronic signals between separate elements, transmitting data between separate elements of system 600 and / or system 900, transmitting values ​​between separate elements, and / or other communications. The elements of system 600 and / or system 900 may communicate by wire or wirelessly via a network (such as the Internet, or the Internet in combination with various other networks, such as a local area network, a cellular network or a personal area network, an intra-organizational network, and / or other networks).

[0099] In some embodiments, one or more actuators (in Figure 6 or Fig. 9 The actuator (not shown) can be connected to one or more elements of system 600 and / or system 900 and configured to move the one or more elements. The actuator can be connected to one or more elements of system 600 and / or system 900 by adhesive, clip, clamp, screw, collar and / or other mechanism. The actuator can be configured to be controlled electronically. A separate actuator can be configured to convert an electrical signal into a mechanical displacement. The mechanical displacement is configured to move elements of system 600 and / or system 900. As an example, one or more of the actuators can be piezoelectric. One or more processors PRO can be configured to control the actuator. One or more processors PRO can be configured to control each actuator of the one or more actuators individually.

[0100] exist Figure 6 and / or Fig. 9 The number of various lenses, reflectors, and / or other optical elements shown in is not intended to be limiting. The principles described herein can be extended so that in some embodiments, system 600 and / or system 900 include additional or fewer lenses, reflectors, and / or other optical elements.

[0101] Fig.10 A measurement method 1001 for generating an illumination spot configured to be pointed or directed at a target is shown. In some embodiments, the method 1001 is performed as part of an overlay and / or alignment sensing operation, such as in a semiconductor device manufacturing process. In some embodiments, one or more operations of the method 1001 may be implemented, for example, in or by: Figure 6 The system 600 shown in FIG. Fig. 9 The system 900 shown in Figure 3 The system 10 shown in FIG. 1 , a computer system (e.g., Fig.11In some embodiments, the method 1001 includes: receiving (operation 1002) illumination from an illumination source with a first optical element; reflecting diffracted radiation from a diffraction grating target (operation 1004); determining (operation 1006) overlap and / or alignment based on the reflected diffracted radiation from the diffraction grating target; and / or other operations.

[0102] The operations of method 1001 are intended to be illustrative. In some embodiments, the method 1001 may be implemented with one or more additional operations not described and / or without one or more operations discussed. For example, in some embodiments, the method 1001 may include additional operations including determining adjustments to a semiconductor device manufacturing process. Additionally, the operations of method 1001 may be implemented with one or more additional operations not described and / or without one or more operations discussed. Fig.10 The order illustrated and described herein is not intended to be limiting.

[0103] In some embodiments, one or more portions of the method 1001 may be implemented in and / or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices that perform some or all of the operations of the method 1001 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured via one or more hardware, firmware, and / or software specifically designed to perform the operations of the method 1001 (e.g., see below regarding Fig.11 of the discussion).

[0104] At operation 1002, radiation is received from a radiation source along a first optical path, and a portion of the radiation is transmitted through a transmission portion of at least one porous pattern toward a diffraction grating target. The at least one porous pattern is formed in an optical element. The at least one porous pattern includes a transmission portion and a reflection portion. The optical element is positioned in a pupil plane of a measurement system. About 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern. The two transmission quadrants form the transmission portion of the at least one porous pattern. In some embodiments, the at least one porous pattern includes four quadrants, wherein the opposing first and third quadrants include two opposing holes forming the transmission portion, and the opposing second and fourth quadrants include the reflection portion of the at least one porous pattern. The opposing two (transmission) holes are configured to split the radiation into a first sub-beam and a second sub-beam, direct the first sub-beam through a first optical branch of the system to form a first spot, and direct the second sub-beam through a second optical branch of the system to form a second spot. In some embodiments, each opposing transmission hole includes an aperture shaped as a sector of a circle. Other shapes that facilitate the execution of the described method 1001 are contemplated.

[0105] In some embodiments, the optical element is an illumination mode selector. The illumination mode selector is movable to facilitate selecting at least one porous pattern from other different possible porous patterns. For example, the illumination mode selector can be a rotatable wheel in which at least one porous pattern and other different possible porous patterns are formed. As described above, the illumination mode selector is configured to replace a four-quadrant non-polarizing beam splitter in a previous measurement system.

[0106] In some embodiments, the optical element is Figure 6 650 is the same or similar to the element 650 shown in FIG. 1 and described above. In some embodiments, operation 1002 includes providing an illumination source (e.g., Figure 3 2). The illumination source comprises a single source configured to produce illumination along a first axis.

[0107] At operation 1004, diffracted radiation from the diffraction grating target is reflected along a second optical path toward a detector using a reflective portion of at least one porous pattern. Positive and negative first diffraction order diffracted radiation from the diffraction grating target is reflected by two reflective quadrants of at least one porous pattern. The two reflective quadrants are located on the back side of the optical element or on the side that does not face the radiation source. The two reflective quadrants form the reflective portion of at least one porous pattern. The reflective portion may be formed by applying a reflective coating (e.g., gold, silver, etc.) to selected portions of the body of the optical element (e.g., two opposing reflective quadrants as described above).

[0108] The reflective portion is configured to reflect the diffracted positive first order radiation and negative first order radiation along an optical path through a detector branch of the system and to a detector. The detector is configured to receive the diffracted first order radiation and generate a detection signal. For example, this may be an overlap (or in some embodiments, an alignment) signal. In some embodiments, by Figure 6 An optical element that is the same as or similar to optical element 650 described above is shown performing operation 1004 .

[0109] In some embodiments, the method 1001 includes transmitting the transmitted radiation from the transmission portion of at least one porous pattern with an alignment branch beam splitter. The alignment branch beam splitter is not located in a common path with a detector branch of the system. For example, the alignment branch beam splitter can be a transmission type optical cube. The alignment branch beam splitter is positioned between the optical element and the diffraction grating target so that the optical element is not coupled to the alignment branch.

[0110] In some embodiments, operations 1002 and 1004 alternatively include: (operation 1002) receiving radiation from a radiation source with a first optical element formed by a rotatable disk including at least one porous pattern, wherein the first optical element is positioned in a pupil plane of the system; and transmitting a portion of the radiation toward a diffraction grating target through a transmission portion of the at least one porous pattern and a relay lens pair; (operation 1004) transmitting a first portion of the radiation received from the first optical element along a first optical path toward the diffraction grating target and transmitting a second portion of the radiation along a second optical path toward the diffraction grating target with a second optical element including a four-quadrant beam splitter having a transmission portion and a reflection portion; and focusing a corresponding spot of the radiation on the diffraction grating target, wherein the reflection portion of the four-quadrant beam splitter is configured to reflect the diffracted radiation from the diffraction grating target toward a detector along a third optical path (see Fig. 9 and the corresponding description above).

[0111] At operation 1006, overlap and / or alignment is determined. Overlap and / or alignment is determined based on reflected diffracted radiation from the diffraction grating target and / or other information. In some embodiments, the overlap and / or alignment is determined based on the reflected diffracted radiation from the diffraction grating target and / or other information. Figure 3 The detector 4 and the processor PRO shown in FIG. 1 and described above are the same or similar detectors and / or the above description of the detector 4 and the processor PRO Figure 6 and / or Fig. 9 The described detector and / or alignment branch performs operation 1006 .

[0112] In some embodiments, the method 1001 includes illuminating (and / or otherwise irradiating) one or more targets (eg, Figure 3 , Figure 6 and Fig. 9Target 30 shown in FIG. 1 ). The radiation includes light and / or other radiation separated into illumination spots, as described above.

[0113] Radiation can be emitted by a radiation source (e.g. Figure 3 Source 2 shown in and / or in Figure 6 and Fig. 9 In some embodiments, radiation may be directed by a radiation source onto multiple targets, a single target, a sub-portion of a target (e.g., a portion that is less than the entire target), and / or onto a substrate in other ways. In some embodiments, radiation may be directed by a radiation source onto a target in a time-varying manner. For example, the radiation may be rastered across the target (e.g., by moving the target under the radiation) such that different portions of the target are irradiated at different times. As another example, the characteristics of the radiation (e.g., wavelength, intensity, etc.) may vary. This may produce a time-varying data envelope or window for analysis. The data envelope may facilitate analysis of separate sub-portions of a target, comparison of one portion of a target with another portion and / or other targets (e.g., in other layers), and / or other analysis.

[0114] In some embodiments, the method 1001 includes detecting reflected radiation from one or more diffraction grating targets. Detecting the reflected radiation includes detecting one or more phase and / or amplitude (intensity) shifts of the reflected radiation from one or more geometric features of the target. The one or more phase and / or amplitude shifts correspond to one or more dimensions of the target. For example, the phase and / or amplitude of the reflected radiation from one side of the target is different relative to the phase and / or amplitude of the reflected radiation from another side of the target.

[0115] Detecting one or more phase and / or amplitude (intensity) shifts of reflected radiation from a target includes measuring local phase shifts (e.g., local phase increments) and / or amplitude changes corresponding to different parts of the target. For example, reflected radiation from a specific area of ​​the target may include a sinusoidal waveform with a certain phase and / or amplitude. Reflected radiation from different areas of the target (or targets in different layers) may also include sinusoidal waveforms, but with different phases and / or amplitudes. The detected reflected radiation also includes measuring phase differences and / or amplitude differences of reflected radiation of different diffraction orders. Detection of one or more local phase and / or amplitude shifts may be performed using, for example, Hilbert transforms and / or other techniques. Interferometric measurement techniques and / or other operations may be used to measure phase differences and / or amplitude differences of reflected radiation of different diffraction orders.

[0116] In some embodiments, as described above, the method 1001 includes generating a measurement signal based on the detected reflected radiation from the diffraction grating target. Figure 3 The detector 4, camera and / or other sensor in the embodiment of the present invention generates a measurement signal based on the radiation received by the sensor. The measurement signal includes measurement information about the target. For example, the measurement signal can be an overlap and / or alignment signal and / or other measurement signal including overlap and / or alignment measurement information. The measurement information (e.g., overlap value, alignment value and / or other information) can be determined using interferometry principles and / or other principles.

[0117] The measurement signal includes an electronic signal representing and / or otherwise corresponding to radiation reflected from the target. The measurement signal may indicate, for example, a measurement value associated with a diffraction grating target, and / or other information. Generating the measurement signal includes sensing the reflected radiation and converting the sensed reflected radiation into the electronic signal. In some embodiments, generating the measurement signal includes sensing different portions of reflected radiation from different areas of the target and / or different geometries and / or multiple targets, and combining the different portions of the reflected radiation to form the measurement signal. This may include generating and / or analyzing one or more images of the target using the radiation described herein. The measurement signal may be generated by communicating with the target in a manner similar to that described in the embodiment of the present invention. Figure 3 Such sensing and conversion may be performed by similar and / or identical elements to the detector 4 and / or processor PRO shown in FIG.

[0118] In some embodiments, the method 1001 includes determining adjustments to a semiconductor device manufacturing process. In some embodiments, the method 1001 includes determining one or more semiconductor device manufacturing process parameters. One or more semiconductor device manufacturing process parameters can be determined based on one or more detected phase changes and / or amplitude changes, overlap and / or alignment values ​​indicated by the measurement signal, and / or other similar systems and / or other information. One or more parameters may include parameters of radiation (radiation for measurement), overlap values, alignment values, measurement inspection locations on the layers of the semiconductor device structure, radiation beam trajectories across targets, and / or other parameters. In some embodiments, process parameters can be broadly interpreted as including platform position, mask design, measurement target design, semiconductor device design, radiation (for exposure resist, etc.) intensity, radiation (for exposure resist, etc.) incident angle, radiation (for exposure resist, etc.) wavelength, pupil size and / or shape, resist material, and / or other parameters.

[0119] In some embodiments, the method 1001 includes determining a process adjustment based on one or more determined semiconductor device manufacturing process parameters, adjusting semiconductor device manufacturing equipment based on the determined adjustment, and / or other operations. For example, if the determined metrology measurement is not within process tolerance, the out-of-tolerance measurement may be caused by one or more manufacturing processes, and the process parameters of the one or more manufacturing processes have drifted and / or changed in other ways so that the process no longer produces acceptable devices (e.g., the measurement may exceed an acceptable threshold). One or more new or adjusted process parameters may be determined based on the measurement determination. The new or adjusted process parameters may be configured so that the manufacturing process again produces acceptable devices.

[0120] For example, a new or adjusted process parameter can cause a previously unacceptable measurement to be adjusted back into an acceptable range. The new or adjusted process parameter can be compared to the existing parameters for a given process. For example, if there is a difference, the difference can be used to determine an adjustment to the equipment used to produce the device (e.g., the parameter "x" should be increased / decreased / changed so that it matches the new or adjusted version of the parameter "x" determined as part of method 1001). In some embodiments, the method 1001 may include (e.g., based on the determined process parameter) electronically adjusting the equipment. Electronically adjusting the equipment may include sending an electronic signal and / or other communication to the equipment that causes, for example, a change in the equipment. Electronic adjustments may include, for example, changing settings on the equipment and / or other adjustments.

[0121] Fig.11 1 is a diagram of one or more exemplary computer systems CS that may be used in the operations described herein. The computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or processors) coupled to the bus BS for processing information. Figure 3 The computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage, coupled to the bus BS for storing information and instructions to be executed by the processor PRO. The main memory MM can also be used to store temporary variables or other intermediate information during the execution of instructions by the processor PRO. The computer system CS also includes a read-only memory (ROM) ROM or other static storage device coupled to the bus BS for storing static information and instructions for the processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to the bus BS for storing information and instructions.

[0122] The computer system CS can be connected by a bus BS to a display DS for displaying information to a computer user, such as a flat-panel or touch panel display or a cathode ray tube (CRT). An input device ID including alphanumeric and other keys is connected to the bus BS for communicating information and command selections to the processor PRO. Another type of user input device is a cursor control CC, such as a mouse, trackball or cursor direction keys, for communicating direction information and command selections to the processor PRO and for controlling cursor movement on the display DS. This input device typically has two degrees of freedom on two axes, a first axis (e.g., x) and a second axis (e.g., y), allowing the device to specify a position in a plane. A touch panel (screen) display can also be used as an input device.

[0123] In some embodiments, the computer system CS can be responsive to the processor PRO to execute one or more sequences of one or more instructions included in the main memory MM to perform all or some of the one or more operations described herein. These instructions can be read from another computer readable medium (such as, storage device SD) into the main memory MM. The execution of the instruction sequence included in the main memory MM causes the processor PRO to perform the process steps (operations) described herein. One or more processors in a multi-processing arrangement can also be used to execute the instruction sequence included in the main memory MM. In some embodiments, hard-wired circuit systems can be used instead of or in combination with software instructions. Therefore, the description herein is not limited to any specific combination of hardware circuit systems and software.

[0124] As used herein, the term "computer-readable medium" or "machine-readable medium" refers to any medium that participates in providing instructions to the processor PRO for execution. This medium can take many forms, including but not limited to non-volatile media, volatile media and transmission media. Non-volatile media include, for example, optical disks or disks, such as storage devices SD. Volatile media include volatile memories, such as main memory MM. Transmission media include coaxial cables, copper wires and optical fibers, including wires containing bus BS. Transmission media can also take the form of sound waves or light waves, such as sound waves or light waves generated during radio frequency (RF) and infrared (IR) data communication. Computer-readable media can be non-temporary, such as floppy disks, floppy disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punch cards, paper tapes, any other physical media with hole patterns, RAMs, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or cassettes. Non-temporary computer-readable media can have instructions recorded thereon. The instructions can implement any of the operations described herein when executed by a computer. Transitory computer readable media may include, for example, carrier waves or other propagated electromagnetic signals.

[0125] Various forms of computer-readable media can be involved when one or more sequences of one or more instructions are loaded into the processor PRO for execution. For example, the instructions can be initially carried on the disk of the remote computer. The remote computer can load the instructions into its volatile memory and send the instructions via the telephone line using a modem. The modem local to the computer system CS can receive the data on the telephone line and use an infrared transmitter to convert the data into an infrared signal. The infrared detector connected to the bus BS can receive the data carried in the infrared signal and place the data on the bus BS. The bus BS loads the data into the main memory MM, from which the processor PRO obtains and executes the instructions. The instructions received by the main memory MM can be optionally stored on the storage device SD before or after being executed by the processor PRO.

[0126] The computer system CS may also include a communication interface CI connected to the bus BS. The communication interface CI provides a bidirectional data communication connection with a network link NDL, which is connected to a local area network LAN. For example, the communication interface CI may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection with a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card that provides a data communication connection with a compatible LAN. A wireless link may also be implemented. In any such embodiment, the communication interface CI sends and receives electrical signals, electromagnetic signals, or optical signals that carry digital data streams representing various types of information.

[0127] The network link NDL typically provides data communications to other data devices via one or more networks. For example, the network link NDL may be provided by a local area network LAN for connection to a host computer HC. This may include data communications services provided via the global packet data communications network (now commonly referred to as the "Internet" INT). The local area network LAN (Internet) may use electrical, electromagnetic or optical signals that carry digital data streams. Signals via various networks and signals on the network data link NDL and via the communication interface CI are carrier waves that convey information in an exemplary form, which load digital data into and transmit digital data from the computer system CS.

[0128] The computer system CS can send messages and receive data (including program code) through the network, the network data link NDL and the communication interface CI. In the Internet example, the host computer HC can transmit the requested code for the application program through the Internet INT, the network data link NDL, the local area network LAN and the communication interface CI. For example, such a downloaded application program can provide all or part of the method described herein. The received code can be executed by the processor PRO when it is received, and / or stored in the storage device SD or other non-volatile storage for later execution. In this way, the computer system CS can obtain the application code in the form of a carrier wave.

[0129] Various embodiments of the present system and method are disclosed in the subsequent list of numbered aspects. In the following, other features, characteristics and exemplary technical solutions of the present disclosure will be described according to aspects that can be optionally claimed in any combination:

[0130] 1. A metrology system, comprising: an optical element, the optical element comprising at least one porous pattern having a transmissive portion and a reflective portion, the optical element being positioned in a pupil plane of the metrology system, the optical element being configured to: receive radiation from a radiation source along a first optical path, and transmit part of the radiation through the transmissive portion of the at least one porous pattern toward a diffraction grating target; and reflect diffracted radiation from the diffraction grating target along a second optical path toward a detector using the reflective portion of the at least one porous pattern.

[0131] 2. The system of aspect 1, wherein about 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern, the two transmission quadrants forming a transmission portion of the at least one porous pattern.

[0132] 3. A system according to any one of the preceding aspects, wherein positive first diffraction order diffraction radiation and negative first diffraction order diffraction radiation from the diffraction grating target are reflected by two reflection quadrants on the at least one porous pattern, and the two reflection quadrants are located on the back side of the optical element or on the side not facing the radiation source, and the two reflection quadrants form a reflection portion of the at least one porous pattern.

[0133] 4. A system according to any of the preceding aspects, wherein the optical element is an illumination mode selector.

[0134] 5. The system according to any of the preceding aspects, wherein the illumination mode selector is movable to facilitate selection of the at least one porous pattern from among other different possible porous patterns.

[0135] 6. The system according to any of the preceding aspects, wherein the illumination mode selector is a rotatable wheel in which the at least one porous pattern and the other different possible porous patterns are formed.

[0136] 7. A system according to any one of the preceding aspects, wherein the at least one porous pattern includes four quadrants, wherein the relative first and third quadrants include two relative holes forming the transmissive portion, and the relative second and fourth quadrants include the reflective portion of the at least one porous pattern.

[0137] 8. A system according to any of the preceding aspects, wherein the two opposing holes are configured to: split the radiation into a first sub-beam and a second sub-beam, guide the first sub-beam through a first optical branch of the system to form a first spot, and guide the second sub-beam through a second optical branch of the system to form a second spot.

[0138] 9. A system according to any of the preceding aspects, wherein the reflective portion is configured to cause the diffracted positive first-order radiation and negative first-order radiation to be reflected along a second optical path through a detector branch of the system and reflected to a detector; wherein the detector is configured to receive the diffracted first-order radiation and generate a detection signal.

[0139] 10. The system according to any of the preceding aspects, further comprising an alignment branch beam splitter configured to transmit transmission radiation from the transmission portion of the at least one porous pattern, wherein the alignment branch beam splitter is not located in a common path with the detector branch.

[0140] 11. The system of any of the preceding aspects, wherein the alignment branch beam splitter is a transmissive optical cube.

[0141] 12. The system of any of the preceding aspects, wherein an alignment branch beam splitter is positioned between the optical element and a diffraction grating target, and wherein the optical element is not coupled to an alignment branch of a metrology system.

[0142] 13. The system according to any of the preceding aspects, wherein the at least one porous pattern comprises two opposing holes forming the transmissive portion, each opposing hole comprising an aperture shaped as a sector of a circle.

[0143] 14. The system according to any of the preceding aspects, wherein the optical element is configured to replace a four-quadrant non-polarizing beam splitter in a metrology system.

[0144] 15. A system according to any of the preceding aspects, wherein the reflective portion is formed by applying a reflective coating to selected portions of the body of the optical element.

[0145] 16. The system according to any of the preceding aspects, further comprising a radiation source configured to generate radiation along the first optical path.

[0146] 17. The system according to any one of the preceding aspects, further comprising a detector configured to receive diffracted and reflected first-order radiation from the first illumination spot and the second illumination spot on the diffraction grating target and generate a detection signal.

[0147] 18. A system according to any of the preceding aspects, wherein the optical element forms part of an overlap detection sensor and / or an alignment sensor.

[0148] 19. The system according to any of the preceding aspects, wherein the alignment sensor and / or the overlap detection sensor is configured for a semiconductor wafer and is used in a semiconductor manufacturing process.

[0149] 20. A measurement system, comprising: a first optical element, which is formed by a rotatable disk including at least one porous pattern, and the first optical element is positioned in a pupil plane of the system, and the first optical element is configured to receive radiation from a radiation source and transmit part of the radiation toward a diffraction grating target through a transmission part of the at least one porous pattern and through a relay lens pair; and a second optical element, which includes a four-quadrant beam splitter having a transmission part and a reflection part, and the transmission part of the four-quadrant beam splitter is configured to transmit a first part of the radiation received from the first optical element toward the diffraction grating target along a first optical path and transmit a second part of the radiation toward the diffraction grating target along a second optical path; and focus corresponding spots of the radiation on the diffraction grating target, and the reflection part of the four-quadrant beam splitter is configured to reflect the diffracted radiation from the diffraction grating target toward a detector along a third optical path.

[0150] 21. A measurement method, comprising: receiving radiation from a radiation source along a first optical path; and transmitting part of the radiation toward a diffraction grating target through a transmission part of at least one porous pattern, wherein the at least one porous pattern is formed in an optical element, wherein the at least one porous pattern includes a transmission part and a reflection part, and the optical element is positioned in a pupil plane of a measurement system; and reflecting the diffracted radiation from the diffraction grating target toward a detector along a second optical path using the reflection part of the at least one porous pattern.

[0151] 22. The method according to any of the preceding aspects, wherein about 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern, the two transmission quadrants forming the transmission portion of the at least one porous pattern.

[0152] 23. A method according to any one of the preceding aspects, wherein positive first diffraction order diffraction radiation and negative first diffraction order diffraction radiation from a diffraction grating target are reflected by two reflection quadrants on the at least one porous pattern, and the two reflection quadrants are located on the back side of the optical element or on the side not facing the radiation source, and the two reflection quadrants form the reflection portion of the at least one porous pattern.

[0153] 24. The method according to any of the preceding aspects, wherein the optical element is an illumination mode selector.

[0154] 25. The method according to any of the preceding aspects, wherein an illumination mode selector is movable to facilitate selection of the at least one porous pattern from among different other possible porous patterns.

[0155] 26. The method according to any of the preceding aspects, wherein the illumination mode selector is a rotatable wheel in which the at least one porous pattern and the other different possible porous patterns are formed.

[0156] 27. A method according to any one of the preceding aspects, wherein the at least one porous pattern includes four quadrants, having a relative first quadrant and a third quadrant and a relative second quadrant and a fourth quadrant, the first quadrant and the third quadrant include two relative holes forming the transmissive part, and the second quadrant and the fourth quadrant include the reflective part of the at least one porous pattern.

[0157] 28. A method according to any one of the preceding aspects, wherein the two opposing holes are configured to: split the radiation into a first sub-beam and a second sub-beam, guide the first sub-beam through a first optical branch of the system to form a first spot, and guide the second sub-beam through a second optical branch of the system to form a second spot.

[0158] 29. A method according to any one of the preceding aspects, wherein the reflecting portion is configured to cause the diffracted positive first-order radiation and negative first-order radiation to be reflected along a second optical path through a detector branch of the system and reflected to a detector; wherein the detector is configured to receive the diffracted first-order radiation and generate a detection signal.

[0159] 30. The method according to any of the preceding aspects, further comprising transmitting the transmitted radiation from the transmitted portion of the at least one porous pattern with an alignment branch beam splitter, wherein the alignment branch beam splitter and the detector branch are not located in a common path.

[0160] 31. The method according to any of the preceding aspects, wherein the alignment branch beam splitter is a transmissive optical cube.

[0161] 32. A method according to any of the preceding aspects, wherein an alignment branch beam splitter is positioned between the optical element and a diffraction grating target, and wherein the optical element is not coupled to an alignment branch of a metrology system.

[0162] 33. The method according to any of the preceding aspects, wherein the at least one porous pattern comprises two opposing holes forming the transmissive portion, each opposing hole comprising an aperture shaped as a sector of a circle.

[0163] 34. The method according to any of the preceding aspects, further comprising replacing a four-quadrant non-polarizing beam splitter in a measurement system with the optical element.

[0164] 35. A method according to any one of the preceding aspects, wherein the reflective portion is formed by applying a reflective coating to selected portions of the body of the optical element.

[0165] 36. The method of any of the preceding aspects, further comprising generating radiation along the first optical path with a radiation source.

[0166] 37. The method according to any of the preceding aspects, further comprising: receiving diffracted and reflected first-order radiation from the first illumination spot and the second illumination spot on the diffraction grating target with a detector, and generating a detection signal with the detector.

[0167] 38. A method according to any of the preceding aspects, wherein the optical element forms part of an overlap detection sensor and / or an alignment sensor.

[0168] 39. The method according to any of the preceding aspects, wherein the alignment sensor and / or the overlap detection sensor is configured for a semiconductor wafer and is used in a semiconductor manufacturing process.

[0169] 40. A measurement method, comprising: receiving radiation from a radiation source using a first optical element formed by a rotatable disk including at least one porous pattern, the first optical element being positioned in a pupil plane of the system; transmitting a portion of the radiation toward a diffraction grating target through a transmission portion of the at least one porous pattern and through a relay lens pair; and transmitting a first portion of the radiation received from the first optical element toward the diffraction grating target along a first optical path and transmitting a second portion of the radiation toward the diffraction grating target along a second optical path using a second optical element including a four-quadrant beam splitter having a transmission portion and a reflection portion; and focusing a corresponding spot of the radiation on the diffraction grating target, the reflection portion of the four-quadrant beam splitter being configured to reflect the diffracted radiation from the diffraction grating target toward a detector along a third optical path.

[0170] 41. A system for generating a radiation spot, the radiation spot being configured to be pointed or directed toward a diffraction grating target for an overlay detection sensor used in a semiconductor manufacturing process, the system being configured to generate a plurality of radiation spots, the system being configured to eliminate the need for a four-quadrant non-polarizing beam splitter and thereby eliminate the need for alignment image stitching, the system comprising: a radiation source; an illumination mode selector, the illumination mode selector comprising at least one porous pattern having a transmissive portion and a reflective portion, the illumination mode selector being positioned in a pupil plane of the system, the illumination mode selector being configured to: receive radiation from the radiation source along a first optical path, and transmit a portion of the radiation through the transmissive portion of the at least one porous pattern toward the diffraction grating target; and transmit the radiation with the reflective portion of the at least one porous pattern. reflecting diffracted radiation from the diffraction grating target along a second optical path toward a detector; wherein about 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern, the two transmission quadrants forming the transmission portion of the at least one porous pattern; and wherein positive first diffraction order diffraction radiation and negative first diffraction order diffraction radiation from the diffraction grating target are reflected by two reflection quadrants on the at least one porous pattern, the two reflection quadrants being located on the back side of the optical element or on the side not facing the radiation source, the two reflection quadrants forming the reflection portion of the at least one porous pattern; and a detection sensor configured to receive diffracted and reflected positive first order radiation and negative first order radiation from the diffraction grating target, and to generate overlapping detection signals based on the diffracted and reflected positive first order radiation and negative first order radiation.

[0171] 42. A system according to any of the preceding aspects, wherein the irradiation mode selector is a rotatable wheel, in which the at least one porous pattern and other different possible porous patterns are formed, so that the irradiation mode selector is configured to facilitate the selection of the at least one porous pattern from the other different possible porous patterns.

[0172] 43. A system according to any of the preceding aspects, wherein the at least one porous pattern comprises four quadrants, wherein relative first and third quadrants comprise two relative holes forming the transmissive portion, each relative hole comprising an orifice shaped as a sector of a circle, and relative second and fourth quadrants comprise the reflective portion.

[0173] 44. A system according to any of the preceding aspects, wherein the two opposing holes are configured to split the illumination into a first sub-beam and a second sub-beam, guide the first sub-beam through a first optical branch of the system to form a first spot, and guide the second sub-beam through a second optical branch of the system to form a second spot.

[0174] 45. A system according to any of the preceding aspects, wherein the reflective portion is configured to cause the diffracted positive first-order radiation and negative first-order radiation to be reflected along a second optical path through a detector branch of the system and reflected to a detection sensor; wherein the detection sensor is configured to receive the diffracted and reflected first-order radiation and generate a detection signal.

[0175] The concepts disclosed herein can be associated with any general imaging system for imaging sub-wavelength features, and can be particularly useful for emerging imaging technologies that can produce shorter and shorter wavelengths. Emerging technologies already in use include extreme ultraviolet (EUV), DUV lithography, which can produce wavelengths of 193 nm by using ArF lasers, and can even produce wavelengths of 157 nm by using fluorine lasers. In addition, EUV lithography can produce wavelengths in the range of 20 nm to 5 nm by using a synchrotron or by firing high-energy electrons at a material (either solid or plasma) to produce photons in this range.

[0176] Although the concepts disclosed herein can be used for imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts can be used with any type of lithography imaging system, for example, a lithography imaging system for imaging on substrates other than silicon wafers. In addition, combinations and subcombinations of the disclosed elements can include separate embodiments.

[0177] The above description is intended to be illustrative rather than limiting. Accordingly, it will be appreciated by those skilled in the art that modifications may be made as described without departing from the scope of the claims set forth hereinafter.

Claims

1. A measurement system, comprising: an optical element, the optical element comprising at least one porous pattern having transmissive and reflective parts, the optical element being positioned in a pupil plane of the metrology system, the optical element being configured to: receiving radiation from a radiation source along a first optical path and transmitting a portion of said radiation through said transmitted portion of said at least one porous pattern toward a diffraction grating target; and Diffracted radiation from the diffraction grating target is reflected by the reflective portion of the at least one porous pattern along a second optical path toward a detector.

2. The measurement system according to claim 1, wherein: About 50% of the radiation is transmitted through two transmission quadrants of the at least one porous pattern, the two transmission quadrants forming the transmission portion of the at least one porous pattern.

3. The measurement system according to claim 1 or 2, wherein: The positive first diffraction order diffraction radiation and the negative first diffraction order diffraction radiation from the diffraction grating target are reflected by two reflection quadrants on the at least porous pattern, and the two reflection quadrants are located on the back side of the optical element or the side not facing the radiation source, and the two reflection quadrants form the reflection part of the at least one porous pattern.

4. The measurement system according to any one of claims 1 to 3, wherein: The optical element is an illumination mode selector.

5. The measurement system according to claim 4, wherein: The illumination mode selector is movable to facilitate selecting the at least one porous pattern from among different other possible porous patterns.

6. The measurement system according to claim 5, wherein: The illumination mode selector is a rotatable wheel in which the at least one porous pattern and the other different possible porous patterns are formed.

7. The measurement system according to any one of claims 1 to 6, wherein: The at least one porous pattern includes four quadrants, wherein opposing first and third quadrants include two opposing holes forming the transmissive portion, and opposing second and fourth quadrants include the reflective portion of the at least one porous pattern.

8. The measurement system according to claim 7, wherein: The two opposing apertures are configured to split the radiation into a first beamlet and a second beamlet, direct the first beamlet through a first optical branch of the metrology system to form a first spot, and direct the second beamlet through a second optical branch of the metrology system to form a second spot.

9. The measurement system according to claim 8, wherein: The reflecting portion is configured to reflect the diffracted positive first order radiation and negative first order radiation along the second optical path through a detector branch of the metrology system and to the detector; The detector is configured to receive the diffracted first order radiation and generate a detection signal.

10. The metrology system of claim 9, further comprising an alignment branch beam splitter configured to transmit transmission radiation from the transmission portion of the at least one porous pattern, wherein The alignment branch beam splitter and the detector branch are not located in a common path.

11. The measurement system according to claim 10, wherein: The alignment branch beam splitter is a transmissive optical cube.

12. The measurement system according to claim 10 or 11, wherein: The alignment branch beam splitter is positioned between the optical element and the diffraction grating target, and wherein the optical element is not coupled to an alignment branch of the metrology system.

13. The measurement system according to any one of claims 1 to 12, wherein: The at least one porous pattern comprises two opposing holes forming the transmissive portion, each opposing hole comprising an aperture shaped as a sector of a circle.

14. The measurement system according to any one of claims 1 to 13, wherein: The optical element is configured to replace a four-quadrant non-polarizing beam splitter in the metrology system.

15. The measurement system according to any one of claims 1 to 14, wherein: The reflective portion is formed by applying a reflective coating on selected portions of the body of the optical element.

16. The metrology system of any one of claims 1 to 15, further comprising the radiation source configured to generate the radiation along the first optical path.

17. The metrology system according to any one of claims 1 to 16, further comprising the detector configured to receive diffracted and reflected first-order radiation from the first illumination spot and the second illumination spot on the diffraction grating target and generate a detection signal.

18. The measurement system according to any one of claims 1 to 17, wherein: The optical element forms part of an alignment sensor and / or an overlay detection sensor.

19. The measurement system according to claim 18, wherein: The alignment sensor and / or the overlap detection sensor is configured for a semiconductor wafer and used in a semiconductor manufacturing process.

20. A measurement system comprising: a first optical element formed by a rotatable disk comprising at least one porous pattern, the first optical element being positioned in a pupil plane of the metrology system, the first optical element being configured to receive radiation from a radiation source and to transmit a portion of the radiation through a transmission portion of the at least one porous pattern and a relay lens pair towards a diffraction grating target; and a second optical element, the second optical element comprising a four-quadrant beam splitter having a transmissive portion and a reflective portion, the transmissive portion of the four-quadrant beam splitter being configured to transmit a first portion of radiation received from the first optical element along a first optical path toward the diffraction grating target and to transmit a second portion of the radiation along a second optical path toward the diffraction grating target, and to focus a corresponding spot of radiation on the diffraction grating target, the reflective portion of the four-quadrant beam splitter being configured to reflect diffracted radiation from the diffraction grating target along a third optical path toward a detector.

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