TW202509665A - Optical component array substitution for metrology - Google Patents

Abstract

An optical component array substitution that simplifies a metrology system used for imaging a substrate is described. An array of cheaper and relatively optically simple optical components replaces a typical optical wedge for imaging and/or other metrology operations. In some embodiments, two of the optical components in the array are configured to create two oppositely defocused 0th order images in two different imaging locations on a radiation sensor, which facilitates determination of a focus position, without the need for a separate focus branch in the metrology system. In some embodiments, two of the optical components in the array comprise microlens arrays, with each microlens in a microlens array configured to form a focal spot on the radiation sensor whose position is useable to determine radiation wavefront aberrations, without a need for traditional wavefront aberration sensor.

Description

Optical component array replacement for metrology

This specification relates to an optical component array replacement for metrology.

Lithographic projection apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A patterned device (e.g., a photomask) may include or provide patterns corresponding to individual layers of the IC ("design layout"), and this pattern may be transferred to a target portion (e.g., comprising one or more dies) on a substrate (e.g., a silicon wafer) coated with a layer of radiation-sensitive material ("resist") by irradiating the target portion through the pattern on the patterned device. Typically, a single substrate includes a plurality of adjacent target portions, to which the pattern is transferred successively, one at a time, by the lithographic projection apparatus. In one type of lithographic projection apparatus, the entire pattern on the patterning device is transferred to a target portion in one operation. Such an apparatus is often referred to as a stepper. In an alternative apparatus, often referred to as a stepper-scan apparatus, the projection beam is scanned across the patterning device in a given reference direction (the "scanning" direction) while the substrate is synchronously moved parallel or antiparallel to this reference direction. Different portions of the pattern on the patterning device are progressively transferred to a target portion.

Before the pattern is transferred from the patterned 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 serves as the basis for manufacturing individual layers of a device (e.g., an 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 the individual layers of the device. If several layers are required in the device, the entire process or a variation thereof is repeated for each layer. Ultimately, there will be a device in each target portion on the substrate. These devices are then separated from one another by techniques such as cutting or sawing so that the individual devices can be mounted on a carrier, connected to pins, etc. This device manufacturing process can be considered a patterning process.

Lithography is a central step in the manufacture of devices such as integrated circuits, where patterns formed on a substrate define the functional components of the device, such as microprocessors, memory chips, etc. Similar lithography techniques are also used to form flat panel displays, microelectromechanical systems (MEMS), and other devices.

As semiconductor manufacturing processes continue to advance, the size of functional elements has been decreasing steadily over the decades, while the number of functional elements, such as transistors, per device has been increasing steadily, following a trend often referred to as "Moore's Law." In the current state of the art, the layers of a device are manufactured using lithography projection equipment that projects the 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).

This process for printing features smaller than the classical resolution limit of the lithographic projection equipment is usually referred to as low- _k1 lithography, according to the resolution formula CD = _k1 × λ/NA, where λ is the wavelength of the radiation employed (currently 248 nm or 193 nm in most cases), NA is the numerical aperture of the projection optics in the lithographic projection equipment, CD is the "critical dimension" (usually the smallest feature size printed), and _k1 is an empirical resolution factor. In general, the smaller _k1 is, 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, customized illumination schemes, use of phase-shift patterning devices, optical proximity correction (OPC, sometimes also called "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement technology" (RET).

The present invention describes a simplified optical component array replacement for a metrology system used to image a substrate. An array of inexpensive and relatively optically simple optical components replaces a typical optical wedge used for imaging and/or other metrology operations. In some embodiments, two of the optical components in the array are configured to produce two oppositely defocused 0-order images in two different imaging locations on a radiation sensor, which helps determine a focus position without the need to use a separate focus branch in the metrology system. In some embodiments, two of the optical components in the array include microlens arrays, wherein each microlens in a microlens array is configured to form a focal point on the radiation sensor, the position of the focal point being used to determine radiation wavefront aberrations without the need for a conventional wavefront aberration sensor.

According to an embodiment, a metrology system includes a radiation sensor configured to generate a metrology signal based on radiation received at different imaging locations on the radiation sensor. The metrology system includes an array of optical components configured to receive radiation of different diffraction orders from a substrate, change the angle of the radiation of the different diffraction orders, and direct the radiation of the different diffraction orders toward different imaging locations on the radiation sensor.

In some embodiments, the array of optical components includes four optical components, wherein two of the four optical components are associated with 0th diffraction order radiation and two of the four optical components are associated with 1st diffraction order radiation.

In some embodiments, the array of optical components includes an array of lenses. In some embodiments, each lens has a circular or square cross-sectional shape.

In some embodiments, the array of optical components includes a spatial light modulator (SLM). In some embodiments, the SLM is transmissive or reflective, or has transmissive or reflective portions. In some embodiments, the SLM includes a liquid crystal, a digital micromirror device (DMD), and/or a pattern configured to change the angle of radiation of different diffraction orders and direct the radiation of different diffraction orders toward different imaging locations on a radiation sensor.

In some embodiments, the array of optical components includes an array of super-lenses.

In some embodiments, the system includes one or more processors operatively connected to the radiation sensor and configured to determine metrology measurements based on the metrology signal. In some embodiments, the metrology measurements include alignment values, overlay values, focus values, and/or critical dimension values associated with a semiconductor manufacturing process performed on the substrate.

In some embodiments, two of the optical components in the array of optical components are configured to generate two oppositely defocused 0-order images in two different imaging locations on the radiation sensor. In some embodiments, the one or more processors are operatively connected to the radiation sensor and configured to determine a focus position for imaging a substrate using a metrology system based on the oppositely defocused 0-order images in the two different imaging locations on the radiation sensor. In some embodiments, the one or more processors are further configured to automatically adjust a position of a stage of a metrology system holding the substrate based on the focus position so that subsequent images of the substrate are in focus.

In some embodiments, two of the optical components in the array of optical components include microlens arrays, wherein each microlens in one of the microlens arrays is configured to form a focal point on the radiation sensor, and the position of the focal point can be used to determine radiation wavefront aberrations. In some embodiments, the one or more processors are operatively connected to the radiation sensor and configured to detect radiation wavefront aberrations based on the position of the focal point relative to a reference position.

In some embodiments, the radiation sensor includes a subsection configured to sense a focus, wherein the system further comprises a segmented mirror configured to direct radiation from the microlens array to the subsection of the radiation sensor. In some embodiments, the microlens array is positioned in a different plane of the metrology system than other optical components in the array of optical components, such that the radiation sensor is at a focal plane of the microlens array and other optical components in the array of optical components.

In some embodiments, the system includes a radiation source and one or more lenses. The radiation source and one or more lenses are configured to generate radiation and direct the radiation toward the substrate.

In some embodiments, the substrate includes a semiconductor wafer having one or more stacked targets configured to reflect radiation toward an array of optical components, and the sensor includes microdiffraction-based stacking associated with stacking measurements.

In some embodiments, the radiation sensor includes a camera, a charge coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS), and/or a photodiode array.

According to another embodiment, a metrology method is provided that includes one or more of the operations described above.

In semiconductor device manufacturing, metrology operations often include the measurement of a metrology mark (or marks) and/or other targets in the semiconductor device structure layer. The measurement is usually performed by irradiating the metrology mark with radiation and comparing the characteristics of radiation of different diffraction orders reflected from the metrology mark. These techniques are used to measure overlay, alignment and/or other parameters.

Many metrology systems include an optical wedge configured to direct radiation of different diffraction orders to specific locations on a radiation sensor, a separate focusing branch (e.g., part of a metrology system that includes a radiation source, several lenses, and many other optical components) to determine the focal position for imaging a substrate, a wavefront aberration sensor, and/or other components. Such systems are large, complex, and expensive. For example, the cost of the optical wedge and the physical system space required to implement the wedge is high compared to the other optical components. Such systems require additional components such as an additional beam splitter to combine the focusing branch with the remainder of the metrology system, which reduces the radiation flux to the central sensor. Focus determination in this system is not continuous because the radiation used to determine focus travels along at least a portion of the same optical path as the radiation ultimately used for metrological measurement. This means that the metrology system switches back and forth between a focus determination mode in which the radiation source and optics in the focusing branch are "on," and a metrology image acquisition mode in which the radiation source and optics in the focusing branch are "off." The focus gap between these modes can cause overlay errors due to defocus and/or other problems. In addition, different orders of diffracted light from a metrology target on a substrate have different focus positions based on the objective wavefront error, which is not taken into account by current metrology systems.

Optical component array replacements for simplifying metrology systems for metrology operations including imaging substrates are described. Advantageously, an array of inexpensive and optically relatively simple optical components replaces a typical optical wedge for imaging and/or other metrology operations. In some embodiments, two of the optical components in the array are configured to produce two oppositely defocused 0-order images in two different imaging locations on a radiation sensor, which aids in determining a focus position without requiring the use of a separate focus branch in the metrology system. In some embodiments, two of the optical components in the array include microlens arrays, wherein each microlens in a microlens array is configured to form a focal point on the radiation sensor, the position of the focal point being used to determine radiation wavefront aberrations without the need for a conventional wavefront aberration sensor.

By way of brief introduction, the following description is about semiconductor device manufacturing and patterning processes. The following paragraphs also describe several components of systems and/or methods for semiconductor device metrology. Such systems and methods can be used, for example, to measure overlay, alignment, etc., or for other operations in semiconductor device manufacturing processes.

Although specific reference may be made herein to the measurement of overlay, alignment or other parameters and the fabrication of integrated circuits (ICs) for semiconductor devices, it should be understood that the description herein has many other possible applications. For example, such applications may be used in the fabrication of integrated optical systems, guide and detection patterns for magnetic resonance memory, liquid crystal display panels, thin film heads, etc. Those skilled in the art should understand that any use of the terms "mask", "wafer" or "die" herein should be considered interchangeable with the more general terms "mask", "substrate" and "target portion", respectively, in the context of such alternative applications.

As used herein, the term "projection optics" 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 components that operate according to any of these design types for collectively or singly directing, shaping, or controlling a projected radiation beam. The term "projection optics" may include any optical component in a lithography projection apparatus, regardless of where the optical component is positioned on the optical path of the lithography projection apparatus. Projection optics may include optical components for shaping, conditioning, and/or projecting radiation from a source before it passes through a patterning device, and/or optical components for shaping, conditioning, and/or projecting radiation after it passes through a patterning device. Projection optics typically exclude the light source and patterning device.

FIG1 schematically depicts an embodiment of a lithography apparatus LA. 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 stage) 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 stage (e.g., wafer stage) WT (e.g., WTa, WTb, or both) configured to hold a substrate (e.g., a resist-coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS is configured to project the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (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 transmissive type (e.g. using a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. using a programmable mirror array, or using a reflective mask).

The illuminator IL receives a radiation beam from a radiation source SO. When the radiation source is, for example, an excimer laser, the radiation source and the lithography apparatus may be separate entities. In such cases, the source is not considered to form part of the lithography 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 steering mirrors and/or a beam expander. In other cases, when the source is, for example, 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.

The illuminator IL may modify the intensity distribution of the beam. The illuminator may be configured to limit the radial extent of the radiated beam so that the intensity distribution is non-zero within an annular region in a pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operated to limit the distribution of the beam in the pupil plane so that the intensity distribution is non-zero in a plurality of equally spaced segments in the pupil plane. The intensity distribution of the radiated beam in the pupil plane of the illuminator IL may be referred to as an illumination mode.

The illuminator IL may comprise an adjuster AD configured to adjust the (angular/spatial) intensity distribution of the light beam. In general, at least the outer radial extent and/or the inner radial extent (usually referred to as σ outer and σ inner, respectively) of the intensity distribution in the pupil plane of the illuminator may be adjusted. The illuminator IL may be operated to change the angular distribution of the light beam. For example, the illuminator may be operated to change the number and the angular extent of the segments in the pupil plane where the intensity distribution is non-zero. By adjusting the intensity distribution of the light beam in the pupil plane of the illuminator, different illumination modes may be achieved. For example, by limiting the radial extent and the angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multipole distribution, such as a dipole, quadrupole or hexapole distribution. The illumination pattern may be obtained, for example, by inserting optics providing the desired illumination pattern into the illuminator IL or using a spatial light modulator.

The illuminator IL is operable to change the polarization of the light beam and is operable to adjust the polarization using an adjuster AD. The polarization state of the radiation beam that crosses the pupil plane of the illuminator IL can be referred to as a polarization mode. The use of different polarization modes allows a greater contrast to be achieved in the image formed on the substrate W. The radiation beam may be unpolarized. Alternatively, the illuminator may be configured so that the radiation beam is linearly polarized. The polarization direction of the radiation beam may change across the pupil plane of the illuminator IL. The polarization direction of the radiation may be different in different regions in the pupil plane of the illuminator IL. The polarization state of the radiation may be selected depending on the illumination mode. For multi-pole illumination modes, the polarization of each pole of the radiation beam may be substantially perpendicular to the position vector of the other pole in the pupil plane of the illuminator IL. For example, for a dipole illumination mode, the radiation may be linearly polarized in a direction substantially perpendicular to a line bisecting two opposing segments of the dipole. The radiation beam may be polarized in one of two different orthogonal directions that may be referred to as the X polarization state and the Y polarization state. For a quadrupole illumination mode, the radiation in a segment of each pole may be linearly polarized in a direction substantially perpendicular to a line bisecting that segment. This polarization mode may be referred to as XY polarization. Similarly, for a hexapole illumination mode, the radiation in a segment of each pole may be linearly polarized in a direction substantially perpendicular to a line bisecting that segment. This polarization mode may be referred to as TE polarization.

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

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

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 one embodiment, the patterning device is any device that can be used to impart a pattern to a radiation beam in a cross-section of the radiation beam 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 auxiliary features, the pattern may not exactly correspond to the desired pattern in the target portion of the substrate. In general, 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.

Patterned devices may be transmissive or reflective. Examples of patterned devices include photomasks, programmable mirror arrays, and programmable LCD panels. Photomasks 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. Examples of programmable mirror arrays use a matrix arrangement of mirror facets, each of which can be individually tilted so as to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam that is reflected by the mirror array.

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

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 so as to correct for aberrations (phase variations in the pupil plane across the field). To achieve this correction, the adjustment mechanism may be 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 whose optical axis extends in the z-direction. The adjustment mechanism may be operable to perform any combination of the following: displacing one or more optical elements; tilting one or more optical elements; and/or deforming one or more optical elements. The displacement of the optical elements may be in any direction (x, y, z, or a combination thereof). The tilt of the optical element is usually performed out of a plane perpendicular to the optical axis by rotation about an axis in the x and/or y direction, but for non-rotationally symmetric aspheric optical elements a rotation about the z-axis may be used. Deformations of the optical element may include low-frequency shape (e.g., astigmatism) and/or high-frequency shape (e.g., free-form asphericity). Deformations of the optical element may be performed, for example, by using one or more actuators to apply forces to one or more sides of the optical element and/or by using one or more heating elements to heat one or more selected areas of the optical element. In general, it is not possible to adjust the projection system PS to correct for apodization (transmission variations across the pupil plane). A transmission image of the projection system PS may be used in the design of a patterning device (e.g., a mask) MA for the lithography apparatus LA. Using computational lithography techniques, the patterning device MA can be designed to at least partially correct apodization.

The lithography apparatus may be of a type having two (dual stage) or more stages, for example two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb below the projection system in the absence of a dedicated substrate for example to facilitate metrology and/or cleaning etc. In such "multi-stage" machines the additional stages may be used in parallel or preparation steps may be performed on one or more stages while one or more other stages are being used for exposure. For example, alignment metrology using an alignment sensor AS and/or level (height, tilt etc.) measurement using a level sensor LS may be performed.

The lithography 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 (e.g., water) to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithography 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 projection systems. The term "liquid immersion" as used herein does not mean that structures such as the substrate must be immersed in the liquid, but only that the liquid is located between the projection system and the substrate during exposure.

In operation of the lithography 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. After 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. By means of a second positioner PW and a position sensor IF (e.g. an interferometric measurement device, a linear encoder, a 2D encoder or a capacitive sensor), the substrate table WT can be accurately moved, for example, so that different target portions C are positioned in the path of the radiation beam B. Similarly, a first positioner PM and a further position sensor (which is not explicitly depicted in FIG. 1 ) may be used to accurately position the patterning device MA relative to the path of the radiation beam B, for example after mechanical retrieval from a mask library or during scanning. In general, movement of the support structure MT may be achieved by means of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning) forming 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 forming part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected to a short-stroke actuator only, or may be fixed. The patterning device alignment marks M1, M2 and the substrate alignment marks P1, P2 may be used to align the patterning device MA with the substrate W. Although the substrate alignment marks are illustrated as occupying dedicated target portions, they may be located in spaces between target portions (these are referred to as scribe line alignment marks). Similarly, in the case where more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

The depicted apparatus may be used in at least one of the following modes. In step mode, the support structure MT and the substrate table WT are held essentially 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). The substrate table WT is then 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 the target portion C (i.e. a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure MT can be determined by the reduction factor and image inversion characteristics of the projection system PS. In the scanning 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 motion determines the height of the target portion (in the scanning direction). In another mode, the support structure MT, holding the programmable patterning device, is held substantially stationary, and the substrate table WT is moved or scanned while the pattern imparted to the radiation beam is projected onto the target portion C. In this mode, a pulsed radiation source is typically used, and the programmable patterning device is updated as necessary after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography using programmable patterning devices (e.g., programmable mirror arrays of the type mentioned above).

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

The substrate may be processed before or after exposure in, for example, a coating development system (a tool that typically applies a resist layer to a substrate and develops the exposed resist) or a metrology or inspection tool. The disclosures herein may be applied to these and other substrate processing tools, where applicable. Furthermore, a substrate may be processed more than once, for example to produce a multi-layer IC, so that the term substrate used herein may also refer to a substrate that has included multiple processed layers.

The terms "radiation" and "beam" used herein with respect to lithography cover 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.

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

As shown in FIG2 , the lithography apparatus LA may form part of a lithography cell LC (sometimes also referred to as a lithography fabrication cell or cluster) which also includes apparatus for performing pre-exposure and post-exposure processes on substrates. Typically, such apparatus 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 cooling plates CH and/or one or more baking plates BK. A substrate handler or robot RO picks up one or more substrates from input/output ports I/O1, I/O2, moves them between different process apparatuses and delivers them to a loading box LB of the lithography apparatus. These devices, often collectively referred to as the coating and developing system, are controlled by a coating and developing system control unit TCU, which itself is controlled by a supervisory control system SCS, which also controls the lithography equipment via a lithography control unit LACU. Thus, the different devices can be operated to maximize throughput and process efficiency.

For correct and consistent exposure of substrates exposed by lithography equipment, and/or for monitoring 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 necessary to inspect the substrate or other objects to measure or determine one or more properties, such as alignment, overlay (which may be, for example, between structures in an overlying layer or between structures in the same layer that have been separately provided to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, material properties, etc. Therefore, a manufacturing facility in which a lithography fabrication cell LC is located usually also includes a metrology system that measures some or all of the substrates W ( FIG. 1 ) that have been processed in the lithography fabrication cell or other objects in the lithography fabrication cell. The metrology system may be part of a lithography cell LC, for example, it may be part of a lithography apparatus LA (such as an alignment sensor AS ( FIG. 1 )).

For example, one or more measured parameters may include: alignment between consecutive layers formed in or on the patterned substrate, overlay, critical dimensions (CD) of features formed in or on the patterned substrate (e.g., critical line width), focus or focus error of a photolithography step, dose or dose error of a photolithography step, optical aberration of a photolithography step, etc. Such measurements are often performed on one or more dedicated metrology targets provided on the substrate. Measurements may be performed after resist development but before etching, after etching, after deposition, and/or at other times.

There are various techniques for measuring structures formed in the patterning process, including the use of scanning electron microscopes, image-based metrology tools, and/or various specialized tools. A rapid and non-invasive form of specialized metrology tools is one that directs a beam of radiation onto a target on the surface of a substrate and measures the properties of the scattered (diffracted/reflected) beam. 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 metrology. Applications of this diffraction-based metrology include measurement of overlay, alignment, etc. For example, overlay and/or alignment may be measured by comparing portions of the diffraction spectrum (eg, comparing different diffraction orders in the diffraction spectrum of a periodic grating).

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 metrology during or after the process. The metrology may determine whether a particular substrate is defective, may establish adjustments to the process and equipment used in the process (e.g., aligning two layers on a substrate or aligning a patterned device to a substrate), may measure the performance of the process and equipment, or may be used for other purposes. Examples of metrology include optical imaging (e.g., optical microscopes), non-imaging optical metrology (e.g., diffraction-based metrology, such as ASML YieldStar metrology tools, ASML SMASH metrology systems), mechanical metrology (e.g., profiling using an electric pencil, atomic force microscopy (AFM)), and/or non-optical imaging (e.g., scanning electron microscopy (SEM)).

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

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 vary between different substrate structures, or how different layers of the same substrate structure vary from layer to layer. The metrology system may be integrated into the lithography apparatus LA or the lithography cell LC, or may be a stand-alone device.

To achieve metrology, one or more targets are often specifically provided on a substrate. Typically, the target is specially designed and may include periodic structures. For example, a target on a substrate may include one or more 1-D periodic structures (e.g., geometric features such as a grating) that are printed so that after development, the periodic structure features are formed by solid resist lines. As another example, a target may include one or more 2-D periodic structures (e.g., a grating) that are printed so that after development, the one or more periodic structures are formed by solid resist guide posts or vias in the resist. The rods, guide posts or vias may alternatively be etched into the substrate (eg, etched into one or more layers on the substrate).

FIG3 depicts an example metrology (inspection) system 10 that can be used to detect overlay, alignment, and/or perform other metrology operations. It includes a radiation or illumination source 2 that projects or otherwise irradiates radiation onto a substrate W (e.g., which may typically include metrology markings). The redirected radiation is transmitted to a sensor such as a spectrometer detector 4 and/or other sensors that measure the spectrum (intensity as a function of wavelength) of the specularly reflected and/or diffracted radiation, such as shown in the graph on the left of FIG4. The sensor can generate a metrology signal that conveys metrology data indicative of the properties of the reflected radiation. From this data, the structure or profile that yields the detected spectrum may be reconstructed by one or more processors PRO (a general example of which is shown in FIG. 4 ), or by other operations.

As in the lithography apparatus LA in FIG. 1 , one or more substrate tables (not shown in FIG. 4 ) may be provided to hold the substrate W during the measurement operation. The one or more substrate tables may be similar or identical in form to the substrate table WT (WTa or WTb) of FIG. 1 . In an example in which the detection system 10 is integrated with the lithography 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 measurement optical system. Various sensors and actuators are provided, for example, to obtain the position of a target portion of a structure of interest (e.g., a metrology mark) and to bring the target portion of interest into position under the objective lens. Typically, many measurements will be performed 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 obtain 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, while it is practical for the optical system to remain substantially stationary (typically in the X and Y directions, but possibly also in the Z direction) and the substrate to be moved, it is convenient to consider and describe the operation as if the objective 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 one part of the optical system moving (e.g. in the Z direction and/or the tilt direction) and the rest of the optical system being stationary and the substrate moving (e.g. in the X and Y directions, but also in the Z direction and/or the tilt direction as appropriate).

For typical metrology measurements, the target 30 on the substrate W may be a 1-D grating that is printed such that after development, the rods are formed of solid resist lines (which may be covered by a deposited layer, for example) and/or other materials. Or the target 30 may be a 2-D grating that is printed such that after development, the grating is formed of solid resist guide posts and/or other features in resist.

The rods, guide posts, vias, and/or other features may be etched into or onto the substrate (e.g., 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., of the rods, guide posts, vias, etc.) is sensitive to changes in processing in the patterning process (e.g., optical aberrations, focus changes, dose changes, etc. in a lithographic projection apparatus such as a projection system), so that process changes manifest as changes in the target 30. Thus, measured data from the target 30 may be used to determine adjustments to one or more of the manufacturing processes and/or used as a basis for making actual adjustments.

For example, the measured data from the target 30 may indicate an overlay 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 overlay, and to determine adjustments to the semiconductor device manufacturing apparatus based on the 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 a mask design, a metrology target design, a semiconductor device design, the intensity of radiation, the angle of incidence of radiation, the wavelength of radiation, pupil size and/or shape, resist material, and/or other process parameters.

FIG. 5 illustrates a plan view of a typical target (e.g., a metrology mark) 30, and the extent of a typical radiated illumination spot S in the system of FIG. 4. Typically, in order to obtain a diffraction spectrum that is free from interference from surrounding structures, in some embodiments, the target 30 is 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 may 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 and the like external to the target itself. For example, the illumination arrangement may be configured to provide illumination of uniform intensity at the rear focal plane of the objective. Alternatively, illumination may be limited to an on-axis or off-axis direction, for example by including apertures in the illumination path.

FIG6 illustrates a metrology system 600. Metrology operations performed by system 600 may include imaging one or more metrology targets 30. For example, target 30 may include one or more metrology marks, such as diffraction grating targets, collectively referred to as targets 30, formed in a substrate 602, such as a semiconductor wafer. Target 30 may include one or more structures in a patterned substrate capable of providing diffraction signals. 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 1D or 2D features and/or other geometric features. As a few non-limiting examples, features may include gratings, lines, edges, a series of fine-pitch lines and/or edges, and/or other features.

System 600 includes a radiation sensor 604 configured to receive radiation from target 30 and generate a metrology signal. The radiation can be used to obtain an image of the metrology target 30, and/or for other purposes. The radiation can include illumination such as light and/or other radiation. System 600 includes an optical element 606 configured to receive radiation reflected from target 30 and substrate 602, change the angle of the radiation, and direct the radiation toward sensor 604. Optical element 606 includes an array of optical components 605, as described below. The system 600 includes one or more processors PRO operatively connected to the radiation sensor 604 and configured to: determine a metrology measurement value based on the metrology signal; determine a focus position for imaging a substrate; detect wavefront aberrations; and/or perform other operations.

System 600 may be similar to and/or identical to system 10 shown in FIG3 . In FIG6 , additional details are described for system 600 compared to system 10. In some embodiments, system 600 may form a portion of system 10 described above with respect to FIG3 . For example, system 600 may be a subsystem of system 10. In some embodiments, one or more components of system 600 may be similar to and/or identical to one or more components of system 10. In some embodiments, one or more components of system 600 may replace, be used with, and/or otherwise augment one or more components of system 10.

System 600 includes radiation source 612; optical element 606; stacked detection branch 660 with sensor 604; beam splitter 670; alignment branch 680; various lenses, reflectors, and other optical components (with example objective lens 690 labeled in FIG. 6); and/or other components. In some embodiments, the components of system 600 form part of a stacked and/or aligned sensor used in a semiconductor manufacturing process. Radiation source 612 is configured to generate radiation reflected from target 30 along an optical path such as optical path 621. The radiation may have a target wavelength and/or wavelength range, a target intensity, and/or other characteristics. Target wavelengths and/or wavelength ranges, target intensities, etc. may be entered and/or selected by a user, determined by a system (e.g., system 10 shown in FIG. 3 ) based on previous measurements and/or otherwise. In some embodiments, radiation includes light and/or other radiation. In some embodiments, light includes visible light, infrared light, and/or other light. In some embodiments, radiation may be any radiation suitable for interferometry.

System 600 does not include a separate focus branch 650 (illustrated as removed in FIG. 6 ), or a separate wavefront aberration sensor. System 600 provides a new optical design architecture. System 600 uses the position of a field of view image obtained from a target 30 in a substrate in a metrological measurement process using the sensing components of the system (e.g., sensor 604, optical element 606, array of optical components 605, etc.) to determine the focus position, rather than using focus branch 650 and the principles of focus measurement described above. System 600 can also be configured so that two of the optical components in the array of optical components 605 include microlens arrays, wherein each microlens in the microlens array is configured to form a focus on sensor 604, the position of which can be used to determine radiation wavefront aberrations.

The new architecture reduces cost and size compared to previous systems because no wedge (and associated lens), components of the focusing branch 650, and/or a separate wavefront aberration sensor are required. The new architecture increases the radiation flux to the sensor 604 because no additional beam splitter is required to combine the focusing branch 650 with the rest of the system 600. The new architecture does not require chromatic focus calibration because there is no change in radiation wavelength between the sensor 604 and the focusing branch 650 (e.g., because the focusing branch 650 is no longer present). The new architecture provides continuous focus determination because switching back and forth between focus mode and measurement mode is no longer required. The new architecture takes objective wavefront errors into account, and/or has other advantages.

Radiation reflected from a target 30 in a substrate 602, such as a semiconductor wafer, is received using an optical element 606 (including an array of optical components 605), which changes the angle of the radiation and directs the radiation toward a radiation sensor 604. Radiation from the array of optical components 605 is received using sensor 604, and a signal is generated indicating the position of a field of view image of the radiation. Radiation sensor 604 may be similar and/or identical to detector 4 and/or processor PRO and/or other components shown in FIG. 3. In some embodiments, sensor 604 includes a camera, a charge coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS), a photodiode array, and/or other sensors. In some embodiments, the sensor 604 includes a micro-diffraction based overlay camera associated with overlay measurement. In previous systems, the overlay detection branch 660 includes a wedge and/or other optical components, such as a micro-diffraction based overlay wedge.

For example, FIG7 illustrates a stacked detection branch 660 including a wedge 700, lenses 702 (e.g., which are similar and/or identical to objective lens 690 in FIG6), 704, 706, and 708, sensor 604, illumination pupil 711, detection pupil 712, and an example field image 714 (the array of optical components 605 from FIG6 is not included here). Wedge 700 includes four segments that are placed in the plane of detection pupil 712 and that redirect the +1 and -1 diffraction orders (in the upper right and lower left quadrants) and the 0 order (in the upper left and lower right quadrants) of radiation 720 from substrate 602 to four spaced-apart locations in field image 714. However, these components are large, complex, and expensive. For example, the cost of the optical wedge and the physical system space required to implement the optical wedge is high compared to other optical components.

FIG8 illustrates an optical component array (array of optical components 605) alternative to simplified system 600. Compared to optical wedge 700 (FIG. 7), array of optical components 605 is less expensive and relatively simple optically. Wedge 700 and lens 708 are replaced with array of optical components 605, which reduces the number of components in system 600 (FIG. 6). For example, array of optical components 605 replaces wedge 700 and one or more lenses (e.g., lens 708) shown in FIG7. The array of optical components 605 is configured to receive radiation 710 of different diffraction orders from the substrate 602, change the angle of the radiation 710 of different diffraction orders, and direct the radiation 710 of different diffraction orders toward different imaging locations on the radiation sensor 604 to produce a field of view image 714.

In some embodiments, the array of optical components 605 includes four optical components (e.g., divided into quadrants Q1 to Q4), wherein two of the four optical components are associated with 0th diffraction order radiation 710, and two of the four optical components are associated with 1st diffraction order radiation 710. Each quadrant is configured to direct a portion of the radiation (e.g., 0th order radiation, and/or +/-1st order radiation) to a different region of interest of the sensor 604 to form a spot of radiation on the sensor 604 (see corresponding field of view image 714). In some embodiments, the array of optical components 605 includes an array of lenses and/or other components. For example, each lens may have a circular shape 800, a square shape 802, and/or other cross-sectional shapes.

In some embodiments, an array of four circular lenses may be used. Although circular lenses may not capture a small portion of the illumination at or near the center region of the pupil, they may be convenient to implement, and/or have other advantages. In some embodiments, an array of four square shaped lenses may be used, which will capture the entire pupil. In some embodiments, for the 0th order quadrants Q1 and Q3, cylindrical lenses may be used, which may be less expensive than square lenses. Other configurations are contemplated.

The lens optical capabilities of these lenses can be configured to maintain the edge ray angle at the sensor 604, the target magnification at the sensor 604, and/or have other effects. This can reduce the cost and size of the detection branch 660 of the system 600 (Figure 6), and/or have other advantages. The optical axis position of the lenses can also be optimized. The angle of the ray leaving each lens can be linearly modulated by changing the optical axis on each lens in the y dimension in this example. In addition, each lens has its own optical axis and can be independently selected to produce the desired tilt of the ray leaving the lens. This can change the x-y position of each of the quadrant images from the sensor 604.

In some embodiments, the array of optical components 605 includes a spatial light modulator (SLM). The SLM can be transmissive or reflective, or have transmissive or reflective portions. The SLM can include liquid crystals, digital micromirror devices (DMDs), patterns configured to change the angle of radiation of different diffraction orders, and/or other features configured to direct radiation of different diffraction orders toward different imaging locations on the radiation sensor. In some embodiments, the array of optical components 605 includes an array of superlenses. One or more processors PRO (such as shown in Figures 3, 6, and 15 described below) are operatively connected to the radiation sensor 604 and are configured to determine metrological measurement values based on the metrological signal. For example, the metrology measurements may include alignment values, overlay values, focus values, critical dimension values, and/or other metrology measurements associated with a semiconductor manufacturing process performed on the substrate 602.

In some embodiments, as shown in FIG. 9 , two of the optical components in the array of optical components 605 (in quadrants Q1 and Q3 in this example) are configured to produce two oppositely defocused (900, 902) 0-order images in two different imaging locations on the radiation sensor 604 (see corresponding defocused images 904, 906 in field of view image 910). This configuration may include, for example, changing the curvature of the two optical components so that positive and negative defocus are produced at the image planes of these two quadrants. A differential defocus signal may be measured from these two 0-order images and thus enable real-time focus detection and/or other operations.

For example, the displacement of the field image position images 904 and/or 906 from the expected field image position is determined by one or more processors PRO. Defocused radiation incident on the detection pupil 712 causes the displacement. The signal generated by the sensor 604 indicates the four individual field image positions of the light point of the radiation. In addition, the blurring of the images 904 and/or 906 can also be used in the same way. For example, when the images 904 and 906 are displaced by the same distance and blurred at the same level, the ideal focus can be achieved. One or more processors PRO (e.g., and/or the PRO shown in FIGS. 3 , 6 , and/or the processor described below with respect to FIG. 15 ) operatively connected to the radiation sensor 604 may be configured to determine a focal position for imaging the substrate 602 using the system 600 ( FIG. 6 ) based on oppositely defocused 0-order images 904, 906, blur and/or other information at two different imaging positions on the radiation sensor 604.

In some embodiments, the focus position is determined based on the relationship between the shift and the defocus of the objective of the metrology system 600. This relationship can be linear and/or have other corresponding relationships. For example, one or more processors (such as the PRO shown in Figure 3 and/or the processor described below with respect to Figure 15) are configured to determine the shift of the 0th and 1st order light spots, and determine the focus position based on the shift of the 0th and 1st order light spots. The linear relationship between the shift and the defocus of the objective means that as the defocus increases, the light spots are further away from their expected positions. This shift and this relationship can be used to determine the (optimal) focus position for optical components such as the objective 690 to image the target 30. In some embodiments, one or more processors PRO may determine the shift of the field of view image position of field of view images 904, 906 based on, for example, the centroid of the radiated light spot in image 910 and/or by other methods. In some embodiments, the shift of the field of view image position of field of view images 904, 906 is determined based on intensity detection of field of view images 904, 906. In some embodiments, for example, the intensity detection is determined at one or more halves of one or more annuli of the radiated light spot in field of view images 904, 906. In addition, as described above, the blurring of images 904 and/or 906 may also be used in a similar manner. For example, ideal focus may be achieved when images 904 and 906 are shifted the same distance and blurred at the same level.

In some embodiments, one or more processors are configured to automatically adjust the position of a stage (e.g., similar and/or identical to WTa and/or WTb shown in FIG. 1 and described above) of the system 600 holding the substrate 602 based on the focus position so that subsequent images of the substrate 602 are in focus. It should be noted that FIG. 9 illustrates an array of optical components 605 including an array of square 802 cross-sectional shaped lenses from FIG. 8 as one possible example. However, these lenses may have any shape that allows them to function as described herein.

In some embodiments, two of the optical components in the array of optical components 605 include microlens arrays, wherein each microlens in one microlens array is configured to form a focal point on the radiation sensor 604, the position of which can be used to determine radiation wavefront aberrations. Individual microlenses in the microlens array can collect light that fills its aperture and form a focal point on the sensor 604, which is located at the focal plane of the microlens array. A wavefront without aberrations (e.g., zero slope) can produce a light spot centered behind the individual microlens, which can be used as a reference position. In a wavefront with aberrations (e.g., non-zero slope), the position of the light spot is displaced relative to its corresponding reference position. Measuring the displacement facilitates wavefront aberration determination (e.g., slope of the wavefront). For example, one or more processors PRO (FIGS. 3, 6, 15) operatively connected to the radiation sensor 604 may be configured to detect radiation wavefront aberrations based on the (displaced) position of the focus relative to a reference position. Additionally, a minimum slope detectable by the one or more processors corresponds to a minimum value measurable by the defocus sensor 604 and/or the one or more processors PRO.

10 illustrates a microlens 1000 (e.g., a microlens) in a microlens array 1001 configured to form a focal point 1002 on a radiation sensor 604 whose position can be used to determine aberrations of a radiation wavefront 1004, 1006. An individual microlens 1000 in the microlens array 1001 can collect light filling its aperture and form a focal point 1002 on the sensor 604. A wavefront 1004 with no aberrations (e.g., zero slope) can produce a light spot 1002 centered right behind an individual microlens as shown in view 1020, which can be used as a reference position 1003. In a wavefront 1006 having an aberration (e.g. a non-zero slope), the position 1008 of the spot is displaced relative to its corresponding reference position 1003 (as shown in view 1021). Measuring the displacement facilitates wavefront aberration determination (e.g. the slope of the wavefront). For example, one or more processors PRO (FIGS. 3, 6, 15) operatively connected to the radiation sensor 604 may be configured to detect radiation wavefront aberrations based on the (displaced) position of the focus relative to a reference position. In the example shown in FIG. 10, several displaced spots 1012 are illustrated together with missing spots 1014.

11 also illustrates microlenses 1000 (e.g., microlenses) in a microlens array 1001 (in this example, in Q1 and Q4) configured to form a focal point 1002 (also see the corresponding image 1100 of the focal point 1002 in the image 1102) on the radiation sensor 604 whose position can be used to determine the radiation wavefront aberration, but the situation in the array of optical components 605 is similar to that shown in FIGS. 8 and 9. As shown in FIG. 11, two of the optical components in the array of optical components 605 include a microlens array 1001, wherein each microlens 1000 (microlens) in the microlens array 1001 is configured to form a focal point 1002 on the radiation sensor 604. In this example, the microlens array 1001 in Q1 and Q4 and the 0th order radiation 710 can be used for aberration detection.

Individual microlenses 1000 (microlenses) in the microlens array 1001 can collect light filling its aperture and form a focus 1002 located at a focal plane 1110 of the microlens array 1001. As shown in Figure 12, the focal plane 1110 of the microlens array 1001 can be different from the focal plane 1202 of the light point 1200 of the radiation 710 from other optical components in the array of optical components 605, such as the lenses in Q2 and Q3 in this example. As a result, in some embodiments, microlens array 1001 can be positioned in a different plane of system 600 ( FIG. 6 ) than the optical components in the array of optical components 605, such that radiation sensor 604 is located at focal plane 1110 of microlens array 1001 and the other optical components in the array of optical components 605 (lenses in Q2 and Q3 in this example). For example, microlens array 1001 can be positioned so that the example focal planes 1110 and 1202 shown in FIG. 12 coincide (e.g., at or near sensor 604).

FIG. 13 illustrates another embodiment in which the radiation sensor 604 includes one or more sub-portions 1300 configured to sense the focal point 1002 from FIG. 10 to FIG. 12. In this example, the stack detection branch 660 of the system 600 (FIG. 6) includes a segmented mirror 1302 (and/or similar functional components) configured to direct radiation from the microlens array 1001 (in quadrants Q1 and Q4 in this example) to the sub-portions 1300 of the radiation sensor 604. The sub-portions 1300 may also be independent sensors with different operating specifications that are separately mounted from the radiation sensor 604 (and thus are not actually sub-portions at all, but rather separate sensors). For example, if high defocus monitoring speed is required, portion 1300 may have a higher detection speed than sensor 604. If high spatial resolution is not required (or less required) for defocus monitoring, portion 1300 may have fewer pixels than sensor 604 (e.g., it is faster and cheaper). Mirror 1302 may be, for example, an edge mounted segmented mirror, and/or other components configured for similar functionality. FIG. 13 illustrates a side view 1305, a front view 1310, and a top view 1320 of mirror 1302. Radiation from optical component 605 in quadrants Q2 and Q3 may be directed toward sensor 604 as described above. Mirror 1302 may be positioned and/or otherwise configured so that spot 1002 of radiation 710 is formed at a focal plane corresponding to subsection 1300. In this example, the focal length of microlens array 1001 in quadrants Q1 and Q4 may be approximately 10-20 nm, while the focal length of optical assembly 605 in quadrants Q2 and Q3 may be approximately 190 nm. Other configurations are contemplated.

Returning to FIG6 , various lenses (example objective lens 690 is labeled in FIG6 ), reflectors, and other optical components are configured to receive, transmit, reflect, focus, and/or perform other operations on illumination generated by source 612, split by beam splitter 670, transmitted or reflected by various optical elements, received by detection branch 660, received by alignment branch 680, and/or used by other portions of system 600. These various lenses, reflectors, and/or other optical components may include any type of lenses, reflectors, and/or other optical components configured to allow system 600 to function as described. For example, objective lens 690 may be formed of any transparent material and have curved surfaces that are configured to concentrate or otherwise focus one or more radiated spots onto target 30. The various lenses, reflectors, optical elements, beam splitters, and other optical elements may be positioned at any position and/or at any angle relative to each other, thereby allowing the system 600 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, the various lenses, reflectors, optical elements, beam splitters, and other optical components are positioned relative to each other in the system 600 via structural members, clips, fixtures, screws, nuts, bolts, adhesives, and/or other mechanical devices. In some embodiments, more than one of the lenses, reflectors, optical elements, beam splitters, and other optical elements may be moved relative to each other. The movement may be configured to adjust, for example, the position of a corresponding illumination spot on one or more targets 30. In some embodiments, movement includes tilting, translating, or otherwise changing the distances between various lenses, reflectors, and other optical components. Other examples of movement are encompassed.

In some embodiments, movement may be controlled electronically by a processor, such as processor PRO (and also discussed below in FIG. 3 and FIG. 15 ). Processor PRO may be included in computing system CS ( FIG. 15 ) and may operate based on computer or machine readable instructions (e.g., as described below with respect to FIG. 15 ). Electronic communication may occur by transmitting electronic signals between individual components, transmitting data between individual components of system 600, transmitting values between individual components, and/or other communications. The components of system 600 may communicate wirelessly via wired communications or 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 intranet, and/or other networks).

In some embodiments, one or more actuators (not shown in FIG. 6 ) may be coupled to and configured to move one or more components of the system 600. The actuators may be coupled to one or more components of the system 600 by adhesives, clips, clamps, screws, collars, and/or other mechanisms. The actuators may be configured to be electronically controlled. Individual actuators may be configured to convert electrical signals into mechanical displacements. Mechanical displacements are configured to move components of the system 600. As an example, one or more of the actuators may be piezoelectric. One or more processors PRO may be configured to control the actuators. One or more processors PRO may be configured to individually control each of the one or more actuators.

The number of various lenses, reflectors and/or other optical components shown in Fig. 6 is not intended to be limiting. The principles described herein can be expanded so that in some embodiments, system 600 includes additional or fewer lenses, reflectors and/or other optical components.

FIG. 14 illustrates a metrology method 1400. In some embodiments, the method 1400 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 1400 may be implemented in or by, for example, the system 600 illustrated in FIG. 6 , the system 10 illustrated in FIG. 3 , a computer system (e.g., as illustrated in FIG. 15 and described below), and/or other systems. In some embodiments, method 1400 includes receiving (operation 1402) radiation reflected from a substrate using an array of optical components, changing the angle of the radiation of different diffraction orders, and directing the radiation of different diffraction orders toward different imaging locations on a radiation sensor; determining (operation 1404) a focus position for imaging the substrate; detecting (operation 1406) wavefront aberrations; generating (operation 1408) metrology signals based on the radiation received at different imaging locations; determining (operation 1410) metrology measurement values based on the metrology signals, focus position, wavefront aberrations, and/or other information; and/or performing other operations.

The operations of method 1400 are intended to be illustrative. In some embodiments, method 1400 may be implemented with one or more additional operations not described and/or without one or more of the operations discussed. For example, in some embodiments, method 1400 may include additional operations that include determining adjustments to a semiconductor device manufacturing process. Additionally, the order in which the operations of method 1400 are illustrated in FIG. 14 and described herein is not intended to be limiting.

In some embodiments, one or more portions of method 1400 may be implemented in and/or controlled by one or more processing devices (e.g., digital processors, analog processors, digital circuits designed to process information, analog circuits designed to process information, state machines, 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 method 1400 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 hardware, firmware, and/or software specifically designed to perform one or more of the operations of method 1400 (eg, see discussion below with respect to FIG. 15 ).

At operation 1402, radiation reflected from the substrate is received using an array of optical components. The array of optical components is configured to change the angle of radiation of different diffraction orders and direct the radiation of different diffraction orders toward different imaging locations on a radiation sensor. The radiation sensor may be similar and/or identical to the detector 4, sensor 604, and/or processor PRO (operably coupled to the radiation sensor) and/or other components shown in Figures 3 and 6. In some embodiments, the array of optical components is similar and/or identical to one or more of the arrays of optical components 605 shown in Figures 8 to 13 described above. Such arrays of optical components may include four optical components (e.g., divided into quadrants Q1 to Q4), wherein two of the four optical components are associated with 0th order radiation and two of the four optical components are associated with 1st order radiation. Each quadrant is configured to direct a portion of the radiation (e.g., 0th order radiation, and/or +/-1st order radiation) to a different region of interest of the sensor to form a spot of radiation on the sensor.

In some embodiments, the array of optical components includes an array of lenses. For example, each lens may have a circular or square cross-sectional shape. In some embodiments, the array of optical components includes a spatial light modulator (SLM). The SLM may be transmissive or reflective, or have transmissive or reflective portions. The SLM may include liquid crystals, digital micromirror devices (DMDs), patterns configured to change the angle of radiation of different diffraction orders, and/or other features configured to direct radiation of different diffraction orders toward different imaging locations on a radiation sensor. In some embodiments, the array of optical components includes an array of super-lenses.

In some embodiments, operation 1402 includes generating radiation using a radiation source (such as source 2 shown in FIG. 3 and/or 612 shown in FIG. 6 ), and directing the radiation toward a substrate. In some embodiments, the substrate includes a semiconductor wafer having one or more targets configured to reflect the radiation toward an array of optical components. In some embodiments, the sensor includes a camera, a charge coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS), a photodiode array, and/or other sensors. In some embodiments, the sensor includes a micro-diffraction based overlay camera associated with overlay measurement.

In some embodiments, operation 1402 includes illuminating (and/or otherwise irradiating) one or more targets in the patterned substrate (e.g., target 30 shown in FIG. 3 ) with radiation. The radiation includes light and/or other radiation. In some embodiments, the radiation may be otherwise directed by a radiation source onto multiple targets, a single target, a sub-portion of a target (e.g., something less than the entire coating), and/or onto the substrate. In some embodiments, the radiation may be directed by a radiation source onto the target in a time-varying manner. For example, the radiation may be rastered over the target (e.g., by moving the target under the radiation) so that different portions of the target are irradiated at different times. As another example, a characteristic of the radiation (e.g., wavelength, intensity, etc.) may vary. This can generate a time-varying data envelope or window for analysis. The data envelope can facilitate analysis of individual sub-portions of the target, comparison of one portion of the target with another portion and/or other targets (e.g., in other layers), and/or other analysis.

In some embodiments, operation 1402 includes detecting reflected radiation from one or more diffraction grating targets (using the radiation sensors described above). Detecting reflected radiation includes detecting one or more phase and/or amplitude (intensity) shifts in 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 reflected radiation from one side of the target is different relative to the phase and/or amplitude of reflected radiation from another side of the target.

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 particular 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. Detecting reflected radiation also includes measuring phase and/or amplitude differences in reflected radiation of different diffraction orders. Detecting one or more local phase and/or amplitude shifts can be performed using, for example, a Hilbert transform and/or other techniques. Interferometry techniques and/or other operations may be used to measure phase and/or amplitude differences in reflected radiation of different diffraction orders.

At operation 1404, a focus position for imaging the substrate is determined. In some embodiments, two of the optical components in the array of optical components are configured to produce two oppositely defocused 0-order images in two different imaging positions on the radiation sensor (see FIG. 9 ). One or more processors, such as processor PRO, are configured to determine a focus position for imaging the substrate using the metrology system based on the oppositely defocused 0-order images in the two different imaging positions on the radiation sensor. In some embodiments, the one or more processors are configured to automatically adjust the position of a stage of the metrology system holding the substrate based on the focus position so that subsequent images of the substrate are in focus.

At operation 1406, wavefront aberrations are detected. In some embodiments, two of the optical components in the optical component array include a microlens array and/or other components. Each microlens in the microlens array is configured to form a focal point on the radiation sensor, and the position of the focal point can be used to determine the radiation wavefront aberration (see Figures 10-11 and corresponding descriptions above). The one or more processors PRO can be configured to detect wavefront aberrations based on the position of the focal point relative to a reference position and/or other information. In some embodiments, the microlens array is positioned in a different plane of the metrology system than other optical components in the array of optical components, such that the radiation sensor is located at a focal plane of the microlens array and other optical components in the array of optical components. In some embodiments, the radiation sensor includes a sub-portion (positioned in a different plane) configured for sensing focus (see FIG. 12 described above). Operation 1406 may include directing radiation from the microlens array to the sub-portion of the radiation sensor using a segmented mirror (e.g., as shown in FIG. 13 and described above).

At operation 1408, a metrology signal is generated based on the radiation and/or other information received at different imaging locations. The metrology signal is generated by a radiation sensor (e.g., detector 4 in FIG. 3 and/or other sensors). The metrology signal includes an electronic signal that represents and/or otherwise corresponds to radiation reflected from a target. The metrology signal may indicate a metrology value and/or other information associated with, for example, a diffraction grating target. Generating the metrology signal includes sensing the reflected radiation and converting the sensed reflected radiation into an electronic signal. In some embodiments, generating the metrology signal includes sensing different portions of reflected radiation from different regions of the target and/or different geometric shapes and/or multiple targets, and combining the different portions of the reflected radiation to form the metrology signal. This may include generating and/or analyzing one or more images of the target using the radiation described herein. This sensing and conversion may be performed by components similar and/or the same as the detector 4, sensor 604 and/or processor PRO shown in Figures 3 and 6 and/or other components.

At operation 1410, metrological measurement values are determined based on metrology signals, focal position, wavefront aberrations, and/or other information. The metrological measurement values may be determined by one or more processors (e.g., processor PRO described herein) and/or other components. In some embodiments, the metrological measurement values include alignment values, overlay values, focus values, key dimension values, and/or other metrological values associated with a semiconductor manufacturing process performed on a substrate. The measurement information (e.g., overlay values, alignment values, and/or other information) may be determined using the principles of interferometry and/or other principles. In some embodiments, for example, operation 1410 includes determining overlay and/or alignment. Overlay and/or alignment may be determined based on diffracted radiation reflected from a diffracted grating target on the substrate, focal position, wavefront aberrations, and/or other information.

In some embodiments, method 1400 includes determining adjustments to a semiconductor device manufacturing process. For example, this may include using one or more processors PRO to automatically adjust the position of a stage of a metrology system holding a substrate based on the determined focus position so that subsequent images of the substrate are in focus (as described above). In some embodiments, method 1400 includes determining one or more semiconductor device manufacturing process parameters. The one or more semiconductor device manufacturing process parameters may be determined based on one or more detected phase and/or amplitude changes, overlay and/or alignment values indicated by the metrology signal, and/or other information. The one or more parameters may include parameters of radiation (radiation for metrology), metrology detection locations on layers of semiconductor device structures, radiation beam trajectories on targets, and/or other parameters. In some embodiments, process parameters may be broadly interpreted to include stage position, mask design, metrology target design, semiconductor device design, intensity of radiation (for exposing resist, etc.), angle of incidence of radiation (for exposing resist, etc.), wavelength of radiation (for exposing resist, etc.), pupil size and/or shape, resist material, and/or other parameters.

In some embodiments, method 1400 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. This may be performed by one or more processors, such as the PRO shown in Figures 3 and 6, a processor described as part of the computer system illustrated in Figure 15 and described below, and/or other processors. For example, if it is determined that a metric measurement is not within a process tolerance, the out-of-tolerance measurement may be caused by one or more manufacturing processes whose process parameters have drifted and/or otherwise changed such that the process no longer produces acceptable devices (e.g., the measurement may exceed an acceptable threshold value). One or more new or adjusted process parameters may be determined based on the measurement determination. The new or adjusted process parameters can be configured so that the manufacturing process again produces acceptable devices.

For example, new or adjusted process parameters may cause previously unacceptable measurements to be adjusted back into an acceptable range. The new or adjusted process parameters may be compared to existing parameters for a given process. For example, if there is a difference, the difference may be used to determine an adjustment to a device used to produce the apparatus (e.g., parameter "x" should be increased/decreased/changed so that it matches a new or adjusted version of parameter "x" determined to be part of method 1400). In some embodiments, method 1400 may include electronically adjusting the device (e.g., based on the determined process parameters). Electronically adjusting the device may include sending an electronic signal and/or other communication to the device that, for example, causes a change in the device. Electronic adjustments may include, for example, changing settings on the device, and/or other adjustments.

FIG. 15 is a diagram of an example computer system CS that can be used for one or more of the operations described herein. The computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processors similar to and/or identical to the processor PRO shown in FIG. 3 and FIG. 6 ) coupled to the bus BS for processing information. The computer system CS also includes a main memory MM coupled to the bus BS for storing information and instructions to be executed by the processor PRO, such as a random access memory (RAM) or other dynamic storage device. 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 further comprises 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.

The computer system CS can be coupled via 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 coupled 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 directional information and command selections to the processor PRO and for controlling the movement of a cursor 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.

In some embodiments, all or some of the one or more operations described herein may be executed by the computer system CS in response to the processor PRO executing one or more sequences of one or more instructions contained in the main memory MM. These instructions may be read from another computer-readable medium (such as a 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 execute the program steps (operations) described herein. One or more processors in a multi-processing configuration may also be used to execute the instruction sequence contained in the main memory MM. In some embodiments, a hard-wired circuit system may be used instead of or in conjunction with software instructions. Therefore, the description herein is not limited to any specific combination of hardware circuit systems and software.

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 implementation. 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 discs or magnetic disks, such as storage devices SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wires and optical fibers, including wires that include bus bars BS. Transmission media can also take the form of sound waves or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer readable media may be non-transitory, such as floppy disks, flexible 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, RAM, PROMs and EPROMs, FLASH-EPROMs, any other memory chips or cartridges. Non-transitory computer readable media may have instructions recorded thereon. Such instructions, when executed by a computer, may implement any of the operations described herein. For example, a transient computer readable medium may include a carrier wave or other propagated electromagnetic signal.

Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to the processor PRO for execution. For example, the instructions may initially be carried on a disk of a remote computer. The remote computer may load the instructions into its dynamic memory and send the instructions via a telephone line using a modem. The modem at the local end of the computer system CS may receive the data on the telephone line and convert the data into an infrared signal using an infrared transmitter. An infrared detector coupled to the bus BS may receive the data carried in the infrared signal and place the data on the bus BS. The bus BS carries the data to the main memory MM, from which the processor PRO retrieves and executes the instructions. The commands received by the main memory MM may be stored in the storage device SD before or after their execution by the processor PRO, as the case may be.

The computer system CS may also include a communication interface CI coupled to the bus BS. The communication interface CI provides a two-way data communication coupling 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 to a corresponding type of telephone line. As another example, the communication interface CI may be a local area network (LAN) card to provide a data communication connection with a compatible LAN. A wireless link may also be implemented. In any such implementation, the communication interface CI sends and receives electrical signals, electromagnetic signals, or optical signals carrying digital data streams representing various types of information.

The network link NDL typically provides data communications with other data devices via one or more networks. For example, the network link NDL may provide a connection to a host computer HC via a local area network LAN. This may include providing data communications services via a 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 through various networks and signals on the network data link NDL and through the communication interface CI are exemplary carrier forms for transmitting information, which carry digital data to and from the computer system CS.

The computer system CS can send messages and receive data (including program codes) via the network, the network data link NDL and the communication interface CI. In the Internet example, the host computer HC can transmit the requested program code for the application via the Internet INT, the network data link NDL, the local area network LAN and the communication interface CI. For example, one such downloaded application can provide all or part of the method described herein. The received program code can be executed by the processor PRO at the time of reception, 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.

Various embodiments of the system and method of the present invention are disclosed in the subsequent list of numbered clauses. In the following, further features, characteristics and exemplary technical solutions of the present invention will be described according to the clauses, which can be claimed in any combination as appropriate: 1. A metrology system, comprising: a radiation sensor configured to generate a metrology signal based on radiation received at different imaging positions on the radiation sensor; and an optical component array configured to receive radiation of different diffraction orders from a substrate, change the angles of the radiation of the different diffraction orders, and direct the radiation of the different diffraction orders toward the different imaging positions on the radiation sensor. 2. The system of clause 1, wherein the array of optical components comprises four optical components, wherein two of the four optical components are associated with 0th diffraction order radiation, and two of the four optical components are associated with 1st diffraction order radiation. 3. The system of any of the preceding clauses, wherein the array of optical components comprises a lens array. 4. The system of any of the preceding clauses, wherein each lens has a circular or square cross-sectional shape. 5. The system of any of the preceding clauses, wherein the array of optical components comprises a spatial light modulator (SLM). 6. The system of any of the preceding clauses, wherein the SLM is transmissive or reflective, or has transmissive or reflective portions. 7.  The system of any of the preceding clauses, wherein the SLM comprises liquid crystal, a digital micromirror device (DMD), and/or a pattern configured to change the angles of the radiation of the different diffraction orders and direct the radiation of the different diffraction orders toward the different imaging locations on the radiation sensor. 8.  The system of any of the preceding clauses, wherein the array of optical components comprises an array of super-smooth lenses. 9.  The system of any of the preceding clauses, further comprising one or more processors operatively connected to the radiation sensor and configured to determine a metrological measurement value based on the metrological signal. 10. The system of any of the preceding clauses, wherein the metrology measurement comprises an alignment value, an overlay value, a focus value, and/or a critical dimension value associated with a semiconductor manufacturing process performed on the substrate. 11. The system of any of the preceding clauses, wherein two of the optical components in the array of optical components are configured to produce two oppositely defocused 0-order images in two different imaging positions on the radiation sensor. 12. The system of any of the preceding clauses, further comprising one or more processors operatively connected to the radiation sensor and configured to determine a focus position for imaging the substrate using the metrology system based on the oppositely defocused 0-order images in the two different imaging positions on the radiation sensor. 13.  The system of any of the preceding clauses, wherein the one or more processors are further configured to automatically adjust a position of a stage of the metrology system holding the substrate based on the focal position so that a subsequent image of the substrate is in focus. 14.  The system of any of the preceding clauses, wherein two of the optical components in the optical component array include microlens arrays, wherein each microlens in a microlens array is configured to form a focal point on the radiation sensor, the position of the focal point being used to determine radiation wavefront aberrations. 15.  The system of any of the preceding clauses, further comprising one or more processors operatively connected to the radiation sensor and configured to detect wavefront aberrations of the radiation based on the positions of the focal points relative to a reference position. 16.  The system of any of the preceding clauses, wherein the radiation sensor includes a subsection configured to sense the focal points, the system further comprising a segmented mirror configured to direct radiation from the microlens array to the subsection of the radiation sensor. 17.  The system of any of the preceding clauses, wherein the array of microlenses is positioned in a different plane of the metrology system than other optical components in the array of optical components, such that the radiation sensor is located at the focal plane of the array of microlenses and other optical components in the array of optical components. 18.  The system of any of the preceding clauses, further comprising a radiation source and one or more lenses configured to generate the radiation and direct the radiation toward the substrate. 19.  The system of any of the preceding clauses, wherein the substrate comprises a semiconductor wafer having one or more stacked targets configured to reflect the radiation toward the array of optical components, and wherein the sensor comprises a micro-diffraction based stacking camera associated with stacking measurements. 20.  The system of any of the preceding clauses, wherein the radiation sensor comprises a camera, a charge coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS) and/or a photodiode array. 21. A metrology method comprising: using an optical component array to receive radiation of different diffraction orders from a substrate; changing the angle of the radiation of the different diffraction orders; and directing the radiation of the different diffraction orders toward different imaging locations on a radiation sensor; and using the radiation sensor to generate a metrology signal based on the radiation received at different imaging locations on the radiation sensor. 22. The method of clause 21, wherein the optical component array comprises four optical components, wherein two of the four optical components are associated with 0th diffraction order radiation, and two of the four optical components are associated with 1st diffraction order radiation. 23.  A method as in any of the preceding clauses, wherein the array of optical components comprises an array of lenses. 24.  A method as in any of the preceding clauses, wherein each lens has a circular or square cross-sectional shape. 25.  A method as in any of the preceding clauses, wherein the array of optical components comprises a spatial light modulator (SLM). 26.  A method as in any of the preceding clauses, wherein the SLM is transmissive or reflective, or has transmissive or reflective portions. 27. The method of any of the preceding clauses, wherein the SLM comprises liquid crystal, a digital micromirror device (DMD), and/or a pattern configured to change the angles of the radiation of the different diffraction orders and direct the radiation of the different diffraction orders toward the different imaging locations on the radiation sensor. 28. The method of any of the preceding clauses, wherein the array of optical components comprises an array of super-lenses. 29. The method of any of the preceding clauses, further comprising determining a metrological measurement value based on the metrological signal using one or more processors operatively connected to the radiation sensor. 30. The method of any of the preceding clauses, wherein the metrological measurement comprises an alignment value, an overlay value, a focus value, and/or a critical dimension value associated with a semiconductor manufacturing process performed on the substrate. 31. The method of any of the preceding clauses, wherein two of the optical components in the array of optical components are configured to produce two oppositely defocused 0-order images in two different imaging positions on the radiation sensor. 32. The method of any of the preceding clauses, further comprising determining a focus position for imaging the substrate based on the oppositely defocused 0-order images in the two different imaging positions on the radiation sensor using one or more processors operatively connected to the radiation sensor. 33.  The method of any of the preceding clauses, wherein the one or more processors are further configured to automatically adjust a position of a stage of the metrology system holding the substrate based on the focal position so that a subsequent image of the substrate is in focus. 34.  The method of any of the preceding clauses, wherein two of the optical components in the optical component array include microlens arrays, wherein each microlens in a microlens array is configured to form a focal point on the radiation sensor, the position of the focal point being usable to determine radiation wavefront aberrations. 35.  The method of any of the preceding clauses, further comprising using one or more processors operatively connected to the radiation sensor to detect the radiation wavefront aberrations based on the positions of the focal points relative to a reference position. 36.  The method of any of the preceding clauses, wherein the radiation sensor includes a sub-portion configured to sense the focal points, the method further comprising using a segmented mirror to direct radiation from the microlens array to the sub-portion of the radiation sensor. 37.  The method of any of the preceding clauses, wherein the array of microlenses is positioned in a different plane than other optical components in the array of optical components such that the radiation sensor is located at a focal plane of the array of microlenses and other optical components in the array of optical components. 38.  The method of any of the preceding clauses, further comprising generating the radiation using a radiation source and directing the radiation toward the substrate. 39.  The method of any of the preceding clauses, wherein the substrate comprises a semiconductor wafer having one or more stacked targets configured to reflect the radiation toward the array of optical components, and wherein the sensor comprises a microdiffraction based stacking camera associated with stacking measurement. 40.  A method as in any of the preceding clauses, wherein the radiation sensor comprises a camera, a charge coupled device (CCD) array, a complementary metal oxide semiconductor (CMOS) and/or a photodiode array.

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 techniques that can produce shorter and shorter wavelengths. Emerging techniques already in use include extreme ultraviolet (EUV), DUV lithography can produce wavelengths of 193 nm by using ArF lasers and even 157 nm by using fluorine lasers. In addition, EUV lithography can produce wavelengths in the range of 20 nm to 5 nm by using synchrotrons or by applying high energy electrons to hit materials (solid or plasma) in order to produce photons in this range.

Although the concepts disclosed herein may be used for imaging on substrates such as silicon wafers, it should be understood that the disclosed concepts may be used with any type of lithography imaging system, for example, lithography imaging systems for imaging on substrates other than silicon wafers. Furthermore, combinations and subcombinations of the disclosed elements may comprise separate embodiments.

The above description is intended to be illustrative rather than restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made as described without departing from the scope of the claims set forth below.

2: Illumination source 4: Detector 10: Detection system 30: Target 600: Metrology system 602: Substrate 604: Radiation sensor 605: Optical assembly 606: Optical element 612: Radiation source 621: Optical path 650: Focusing branch 660: Overlap detection branch 670: Beam splitter 680: Alignment branch 690: Example objective lens 700: Optical wedge 702: Lens 704: Lens 706: Lens 708: Lens 710: Radiation 711: Illumination pupil 712: Detection pupil 714: Example field image 800:circle 802:square 900:opposite defocus 902:opposite defocus 904:defocus image/field image/field image position image 906:defocus image/field image/field image position image 910:field image 1000:microlens 1001:microlens array 1002:focal point 1003:reference position 1004:radiation wavefront 1006:radiation wavefront 1008:position 1012:displaced light spot 1014:missing light spot 1020:view 1021:view 1100:corresponding image 1102:image 1110:focal plane 1200:light spot 1202: focal plane 1300: subsection 1302: segmented mirror/mirror 1305: side view 1310: front view 1320: top view 1400: metrology 1402: operation 1404: operation 1406: operation 1408: operation 1410: operation AD: adjuster AS: alignment sensor B: radiation beam BD: beam delivery system BK: bake plate BS: bus bar CC: cursor control CH: cooling plate CI: communication interface CO: condenser CS: computer system DS: display HC: host computer ID: input device IF: position sensor IL: illuminator IN: integrator INT: Internet I/O1: Input/Output Port I/O2: Input/Output Port LA: Lithography Equipment LACU: Lithography Control Unit LAN: Local Area Network LB: Loading Box LC: Lithography Fabrication Unit LS: Level Sensor MA: Patterning Device MM: Main Memory MT: Support Structure M1: Patterning Device Alignment Mark M2: Patterning Device Alignment Mark NDL: Network Data Link PM: Primary Positioner PRO: Processor PS: Projection System PW: Secondary Positioner P1: Substrate Alignment Mark P2: Substrate Alignment Mark Q1: Quadrant Q2: Quadrant Q3: Quadrant Q4: Quadrant RF: Reference Frame RO: Robot ROM: Read-Only Memory S: Illumination spot SC: Spin coater SCS: Supervisory control system SD: Storage device SO: Radiation source TCU: Coating and developing system control unit W: Substrate WTa: Substrate stage WTb: Substrate stage

The above aspects and 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.

FIG. 1 schematically illustrates a lithography apparatus according to an embodiment.

FIG. 2 schematically depicts an embodiment of a lithography fabrication unit or cluster according to an embodiment.

FIG3 schematically depicts an example detection system according to an embodiment.

FIG4 schematically depicts an example metrology technique according to an embodiment.

FIG. 5 illustrates the relationship between the radiation illumination spot and the metrology target of the detection system according to an embodiment.

FIG. 6 illustrates a metrology system according to an embodiment.

FIG. 7 illustrates an optical system including a wedge, a lens, a sensor, an illumination pupil, a detection pupil, and an example field of view image according to an embodiment.

FIG. 8 illustrates an optical component array alternative (for the wedge and one or more lenses shown in FIG. 7 ) to simplify the system shown in FIG. 6 , according to an embodiment.

9 illustrates two optical components in the optical component array from FIG. 8 (in quadrants Q1 and Q3 in this example) configured to produce two oppositely defocused 0-order images for focus determination in two different imaging locations on the radiation sensor, according to an embodiment.

FIG. 10 illustrates a microlens in a microlens array configured to form a focus on a radiation sensor whose position can be used to determine radiation wavefront aberrations according to an embodiment.

FIG. 11 also illustrates microlenses in a microlens array configured to form a focus on a radiation sensor whose position can be used to determine radiation wavefront aberrations according to an embodiment, but in an array of optical components similar to that shown in FIGS. 8 and 9 .

FIG. 12 illustrates how the focal plane from the microlens array of FIG. 11 may be different from the focal plane of radiation spots from other optical components in the optical component array (quadrants Q2 and Q3 in this example) according to an embodiment.

13 illustrates an embodiment of a metrology system according to an embodiment, wherein a radiation sensor includes a sub-portion configured for sensing a focus, and the optical elements of the metrology system include a segmented mirror (and/or similar functional components) configured to direct radiation from a microlens array to the sub-portion of the radiation sensor.

FIG. 14 illustrates a metrology method according to an embodiment.

Figure 15 is a block diagram of an example computer system according to an embodiment.

2: Lighting source

4: Detector

10: Detection system

30: Target

PRO: Processor

W: Substrate

Claims (15)

A metrology system comprising: a radiation sensor configured to generate a metrology signal based on radiation received at different imaging locations on the radiation sensor; and an array of optical components configured to receive radiation of different diffraction orders from a substrate, change the angles of the radiation of the different diffraction orders, and direct the radiation of the different diffraction orders toward the different imaging locations on the radiation sensor. The system of claim 1, wherein the array of optical components comprises four optical components, wherein two of the four optical components are associated with 0th diffraction order radiation and two of the four optical components are associated with 1st diffraction order radiation. A system as in claim 1 or 2, wherein the optical component array comprises a lens array. A system as in claim 3, wherein each lens has a circular or square cross-sectional shape. A system as in claim 1 or 2, wherein the optical component array comprises a spatial light modulator (SLM). A system as claimed in claim 5, wherein the SLM is transmissive or reflective, or has a transmissive or reflective portion. A system as in claim 5, wherein the SLM comprises liquid crystal, a digital micromirror device (DMD), and/or a pattern configured to change the angles of the radiation of the different diffraction orders and to direct the radiation of the different diffraction orders toward the different imaging locations on the radiation sensor. A system as in claim 1 or 2, wherein the optical component array comprises a super lens array. The system of claim 1 or 2, further comprising one or more processors operatively connected to the radiation sensor and configured to determine a metrology measurement value based on the metrology signal. A system as in claim 9, wherein the metrology measurement comprises an alignment value, an overlay value, a focus value, and/or a critical dimension value associated with a semiconductor manufacturing process performed on the substrate. A system as in claim 1 or 2, wherein two of the optical components in the optical component array are configured to produce two oppositely defocused 0-order images in two different imaging locations on the radiation sensor. The system of claim 11, further comprising one or more processors operatively connected to the radiation sensor and configured to determine a focal position for imaging the substrate using the metrology system based on the oppositely defocused 0-order images in the two different imaging positions on the radiation sensor. The system of claim 12, wherein the one or more processors are further configured to automatically adjust a position of a stage of the metrology system holding the substrate based on the focal position so that a subsequent image of the substrate is in focus. A system as in claim 1 or 2, wherein two of the optical components in the optical component array include microlens arrays, wherein each microlens in a microlens array is configured to form a focus on the radiation sensor, and the position of the focus can be used to determine radiation wavefront aberrations. The system of claim 14, further comprising one or more processors operatively connected to the radiation sensor and configured to detect the radiation wavefront aberrations based on the positions of the focal points relative to a reference position.