WO2024184017A1

WO2024184017A1 - Broad spectrum metrology systems and methods for various metrology mark types

Info

Publication number: WO2024184017A1
Application number: PCT/EP2024/053395
Authority: WO
Inventors: Yuxiang LIN
Original assignee: ASML Netherlands BV
Current assignee: ASML Netherlands BV
Priority date: 2023-03-06
Filing date: 2024-02-09
Publication date: 2024-09-12
Anticipated expiration: 2025-09-06
Also published as: CN120826646A

Abstract

Broad spectrum metrology for various metrology mark types are described. The systems and methods utilize a modulator such as a spatial light modulator (SLM). An alignment mark is projected onto to an SLM by an imaging lens. With a sequence of patterns on the SLM modulating the incoming images and all reflected energy collected by a collection lens, a time varying signal can be generated from a single detector or a detector array. A color demultiplexer can be added to separate the signals of different wavelengths and direct them to respective detectors to allow simultaneous multicolor measurements. An alignment mark can be irradiated in a static or scanning mode. A combination of the varying mark position and SLM patterns allows generation of a variety of signals for alignment position measurements. Also, a region of interest and the sizes of the marks can be easily accommodated with the SLM.

Description

BROAD SPECTRUM METROLOGY SYSTEMS AND METHODS FOR VARIOUS METROLOGY MARK TYPES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority of US application 63/450,273 which was filed on 6 March 2023 and which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

[0002] This description relates generally to broad spectrum metrology systems and methods for various metrology mark types.

BACKGROUND

[0003] A lithographic projection apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A patterning device (e.g., a mask) may include or provide a pattern corresponding to an individual layer of the IC (“design layout”), and this pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate includes a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatus, the pattern on the entire patterning device is transferred onto one target portion in one operation. Such an apparatus is commonly referred to as a stepper. In an alternative apparatus, commonly referred to as a step-and- scan apparatus, a projection beam scans over the patterning device in a given reference direction (the “scanning” direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively. Since, in general, the lithographic projection apparatus will have a reduction ratio M (e.g., 4), the speed F at which the substrate is moved will be 1/M times that at which the projection beam scans the patterning device. More information with regard to lithographic devices can be gleaned, for example, from US 6,046,792, incorporated herein by reference.

[0004] Prior to transferring the pattern from the patterning device to the substrate, the substrate may undergo various procedures, such as priming, resist coating, and a soft bake. After exposure, the substrate may be subjected to other procedures (“post-exposure procedures”), such as a post-exposure bake (PEB), development, a hard bake and measurement/inspection of the transferred pattern. This array of procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, deposition, chemo-mechanical polishing, etc., all intended to finish the individual layer of the device. If several layers are required in the device, then the whole procedure, or a variant thereof, is repeated for each layer. Eventually, a device will be present in each target portion on the substrate. These devices are then separated from one another by a technique such as dicing or sawing, such that the individual devices can be mounted on a carrier, connected to pins, etc. [0005] Thus, manufacturing devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, lithography, etch, deposition, chemical-mechanical polishing, and ion implantation. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. This device manufacturing process may be considered a patterning process. A patterning process involves a patterning step, such as optical and/or nanoimprint lithography using a patterning device in a lithographic apparatus, to transfer a pattern on the patterning device to a substrate and typically, but optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a bake tool, etching using the pattern using an etch apparatus, deposition, etc.

[0006] Lithography is a central step in the manufacturing of device such as ICs, where patterns formed on substrates define functional elements of the devices, such as microprocessors, memory chips, etc. Similar lithographic techniques are also used in the formation of flat panel displays, microelectro mechanical systems (MEMS) and other devices.

[0007] As semiconductor manufacturing processes continue to advance, the dimensions of functional elements have continually been reduced while the number of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as “Moore’s law”. At the current state of technology, layers of devices are manufactured using lithographic projection apparatuses that project a design layout onto a substrate using illumination from a deep-ultraviolet or extreme ultraviolet illumination source, creating individual functional elements having 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).

[0008] This process in which features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed, is commonly known as low-ki lithography, according to the resolution formula CD = ki xz./NA, where X is the wavelength of radiation employed (currently in most cases 248nm or 193nm), NA is the numerical aperture of projection optics in the lithographic projection apparatus, CD is the “critical dimension”-generally the smallest feature size printed-and ki is an empirical resolution factor. In general, the smaller ki the more difficult it becomes to reproduce a pattern on the substrate that resembles the shape and dimensions planned by a designer in order to achieve particular electrical functionality and performance. To overcome these difficulties, sophisticated fine-tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These include, for example, but are not limited to, optimization of NA and optical coherence settings, customized illumination schemes, use of phase shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as “optical and process correction”) in the design layout, or other methods generally defined as “resolution enhancement techniques” (RET).

SUMMARY

[0009] The systems and methods described here facilitate broad spectrum metrology for various metrology mark types. As one metrology example, generating an alignment signal for alignment of features in a layer of a substrate (e.g., a semiconductor wafer) as part of a semiconductor manufacturing process is described. The systems and methods utilize a modulator such as a spatial light modulator (SLM). An alignment mark is projected onto to an SLM by an imaging lens. With a sequence of patterns on the SLM modulating the incoming radiation and reflected energy collected by a collection lens, a time varying signal can be generated from a single detector or a detector array. A color demultiplexer can be added to separate the signals of different wavelengths and direct them to respective detectors to allow simultaneous multicolor measurements. An alignment mark can be irradiated in a static or scanning mode. A combination of the varying mark position and SLM patterns allows generation of a variety of signals for alignment position measurements. Also, a region of interest and the sizes of the marks can be easily accommodated with the SLM.

[0010] According to an embodiment, a metrology system is provided. The system comprises a radiation source configured to irradiate a feature in a patterned substrate with radiation. The system comprises a modulator configured to modulate received radiation from the feature to generate time varying radiation. The system comprises a radiation sensor configured to receive the time varying radiation and generate a metrology signal. The metrology signal comprises measurement information pertaining to the feature.

[0011] In some embodiments, the feature comprises a metrology mark. The metrology mark may comprise a diffraction grating, for example. The radiation is diffracted by the diffraction grating. In some embodiments, the metrology mark is associated with an alignment and/or overlay measurement for the patterned substrate.

[0012] In some embodiments, the modulator is a spatial light modulator (SLM). In some embodiments, the SLM is a digital micromirror device (DMD). In some embodiments, the SLM comprises a sequence of binary or grayscale patterns configured to modulate incoming radiation. In some embodiments, the SLM is transmissive or reflective.

[0013] In some embodiments, modulation comprises successively transmitting one or more subportions of the received radiation over time.

[0014] In some embodiments, the time varying radiation conveys location information related to different portions of the feature.

[0015] In some embodiments, the patterned substrate is configured to be scanned by the radiation source, and the modulator is configured such that received reflected or transmitted radiation from the different portions is transmitted to the radiation sensor as the substrate moves relative to the radiation source to form the time varying radiation. In some embodiments, the patterned substrate is configured to be held stationary relative to the radiation source, and the modulator is configured to generate the time varying radiation by successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor.

[0016] In some embodiments, the system comprise an imaging lens configured to receive radiation from the feature and direct the received radiation toward the modulator.

[0017] In some embodiments, the system comprises a collection lens configured to receive the time varying radiation from the modulator and direct the time varying radiation toward the radiation sensor.

[0018] In some embodiments, the system comprises a color demultiplexer configured to receive the time varying radiation from the modulator, and separate the time varying radiation into different signals for different colors of radiation. In some embodiments, the radiation sensor comprises different detectors for the different colors of radiation.

[0019] In some embodiments, the system comprises a polarization splitter configured to facilitate detection of radiation with various polarizations.

[0020] In some embodiments, the system comprises one or more processors configured to determine, based on the metrology signal, an alignment inspection location or an overlay inspection location of the feature.

[0021] In some embodiments, the one or more processors are configured to adjust a semiconductor device manufacturing process based on the metrology signal.

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

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above aspects and other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

[0023] Fig. 1 schematically depicts a lithography apparatus, according to an embodiment.

[0024] Fig. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.

[0025] Fig. 3 schematically depicts an example inspection system, according to an embodiment.

[0026] Fig. 4 schematically depicts an example metrology technique, according to an embodiment.

[0027] Fig. 5 illustrates the relationship between a radiation illumination spot of an inspection system and a metrology target, according to an embodiment.

[0028] Fig. 6 illustrates a metrology method, according to an embodiment.

[0029] Fig. 7 illustrates a metrology system comprising a modulator, according to an embodiment.

[0030] Fig. 8 is a block diagram of an example computer system, according to an embodiment. DETAILED DESCRIPTION

[0031] In semiconductor device manufacturing, determining alignment typically includes determining the position of an alignment mark (or marks) in a layer of a semiconductor device structure. Alignment is typically determined by irradiating an alignment mark with radiation, and comparing characteristics of different diffraction orders of radiation reflected from the alignment mark. Similar techniques are used to measure overlay and/or other parameters. In order to meet smaller and smaller node sizes, measurements of smaller and smaller metrology (e.g., alignment, overlay, etc.) marks with higher accuracy and robustness are needed. Smaller marks facilitate placement of multiple marks in a field with a limited area, placement of marks closer to the edges of a substrate, and/or other locations.

[0032] A difficulty in measuring features in a patterned substrate is that the spot size of the radiation used for inspection usually covers other, uncontrolled structures, for example other alignment marks, overlay targets, and/or other product features. This creates noise or other unwanted portions of a measured signal that can overwhelm a desired portion of the signal (e.g., the portion of the signal corresponding to the desired metrology target). The present systems and methods overcome this and other difficulties by modulating radiation received from a target metrology mark - which facilitates obtaining measurement information from desired structures, while excluding unwanted information from surrounding structures.

[0033] Advantageously, as mentioned above, the systems and methods described here facilitate broad spectrum metrology for various metrology mark types, including these smaller and smaller alignment marks. The systems and methods descried here are robust and can be used for one and two dimensional (ID and 2D) marks with a range of pitches, can facilitate mark region selection and/or defect exclusion/analysis, can be used for analysis of multi-color radiation, and/or have other applications.

[0034] The systems and methods described here utilize a modulator such as a spatial light modulator (SLM). An alignment mark (as one example of a metrology mark) may be projected onto to an SLM by an imaging lens. With a sequence of patterns on the SLM modulating the incoming radiation and reflected energy collected by a collection lens, a time varying signal can be generated from a single detector or a detector array. A color demultiplexer can be added to separate the signals of different wavelengths and direct them to respective detectors to allow simultaneous multicolor measurements. An alignment mark can be irradiated in a static or scanning mode. A combination of the varying mark position and SLM patterns allows generation of a variety of signals for alignment position measurements. Also, a region of interest and the sizes of the marks can be easily accommodated with the SLM.

[0035] By way of a brief introduction, the following description relates generally to semiconductor device manufacturing and patterning processes. More particularly, the following paragraphs describe several components of a system and/or related systems. As described above these systems and methods may be used for measuring alignment in a semiconductor device manufacturing process, for example, or for other operations.

[0036] Although specific reference may be made in this text to the measurement of alignment and the manufacture of integrated circuits (ICs) for semiconductor devices, it should be understood that the description has many other possible applications. For example, it may be employed in the measurement of overlay and/or other parameters. It may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle”, “wafer” or “die” in this text should be considered as interchangeable with the more general terms “mask”, “substrate” and “target portion”, respectively.

[0037] The term “projection optics” should be broadly interpreted as encompassing various types of optical systems, including refractive optics, reflective optics, apertures and catadioptric optics, for example. The term “projection optics” may also include components operating according to any of these design types for directing, shaping or controlling the projection beam of radiation, collectively or singularly. The term “projection optics” may include any optical component in the lithographic projection apparatus, no matter where the optical component is located on an optical path of the lithographic projection apparatus. Projection optics may include optical components for shaping, adjusting and/or projecting radiation from the source before the radiation passes the patterning device, and/or optical components for shaping, adjusting and/or projecting the radiation after the radiation passes the patterning device. The projection optics generally exclude the source and the patterning device.

[0038] Fig. 1 schematically depicts an embodiment of a lithographic 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. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters; a substrate table (e.g. a wafer table) 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 in accordance with certain parameters; and a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies and often referred to as fields) 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. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array, or employing a reflective mask).

[0039] The illuminator IL receives a beam of radiation from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising for example suitable directing mirrors and/or a beam expander. In other cases, the source may be an integral part of the apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0040] The illuminator IL may alter the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam such 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 operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in a pupil plane of the illuminator IL may be referred to as an illumination mode.

[0041] The illuminator IL may comprise adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. Generally, at least the outer and/or inner radial extent (commonly referred to as o-outer and o-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. The illuminator IL may be operable to vary the angular distribution of the beam. For example, the illuminator may be operable to alter the number, and angular extent, of sectors in the pupil plane where the intensity distribution is non-zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination modes may be achieved. For example, by limiting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multi-pole distribution such as, for example, a dipole, quadrupole or hexapole distribution. A desired illumination mode may be obtained, e.g., by inserting an optic which provides that illumination mode into the illuminator IL or using a spatial light modulator.

[0042] The illuminator IL may be operable to alter the polarization of the beam and may be operable to adjust the polarization using adjuster AD. The polarization state of the radiation beam across a pupil plane of the illuminator IL may be referred to as a polarization mode. The use of different polarization modes may allow greater contrast to be achieved in the image formed on the substrate W. The radiation beam may be unpolarized. Alternatively, the illuminator may be arranged to linearly polarize the radiation beam. The polarization direction of the radiation beam may vary across a pupil plane of the illuminator IL. The polarization direction of radiation may be different in different regions in the pupil plane of the illuminator IL. The polarization state of the radiation may be chosen in dependence on the illumination mode. For multi-pole illumination modes, the polarization of each pole of the radiation beam may be generally perpendicular to the position vector of that 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 that is substantially perpendicular to a line that bisects the two opposing sectors of the dipole. The radiation beam may be polarized in one of two different orthogonal directions, which may be referred to as X-polarized and Y-polarized states. For a quadrupole illumination mode, the radiation in the sector of each pole may be linearly polarized in a direction that is substantially perpendicular to a line that bisects that sector. This polarization mode may be referred to as XY polarization. Similarly, for a hexapole illumination mode the radiation in the sector of each pole may be linearly polarized in a direction that is substantially perpendicular to a line that bisects that sector. This polarization mode may be referred to as TE polarization.

[0043] In addition, the illuminator IL generally comprises various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.

[0044] Thus, the illuminator provides a conditioned beam of radiation B, having a desired uniformity and intensity distribution in its cross section.

[0045] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not 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 a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” may be considered synonymous with the more general term “patterning device.”

[0046] The term “patterning device” should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of the substrate. In an embodiment, a patterning device is any device that can be used to impart a radiation beam with a pattern in its cross-section to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in a target portion of the device, such as an integrated circuit.

[0047] A patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phaseshift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam, which is reflected by the mirror matrix. [0048] The term “projection system” should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” may be considered as synonymous with the more general term “projection system”.

[0049] The projection system PS may comprise a plurality of optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations across the pupil plane throughout the field). To achieve this, 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 where its optical axis extends in the z direction. The adjustment mechanism may be operable to do any combination of the following: displace one or more optical elements; tilt one or more optical elements; and/or deform one or more optical elements. Displacement of an optical element may be in any direction (x, y, z, or a combination thereof). Tilting of an optical element is typically out of a plane perpendicular to the optical axis, by rotating about an axis in the x and/or y directions although a rotation about the z axis may be used for a non-rotationally symmetric aspherical optical element. Deformation of an optical element may include a low frequency shape (e.g. astigmatic) and/or a high frequency shape (e.g. free form aspheres). Deformation of an optical element may be performed for example by using one or more actuators to exert force on one or more sides of the optical element and/or by using one or more heating elements to heat one or more selected regions of the optical element. In general, it may not be possible to adjust the projection system PS to correct for apodization (transmission variation across the pupil plane). The transmission map of a projection system PS may be used when designing a patterning device (e.g., mask) MA for the lithography apparatus LA. Using a computational lithography technique, the patterning device MA may be designed to at least partially correct for apodization.

[0050] The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb below the projection system without a substrate that is dedicated to, for example, facilitating measurement, and/or cleaning, etc.). In such “multiple stage” machines, the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements using an alignment sensor AS and/or level (height, tilt, etc.) measurements using a level sensor LS may be made.

[0051] The lithographic apparatus may also be of a type where at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, 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 “immersion” does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0052] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Fig. 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0053] 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 kept 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 a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure MT may be determined by the (de-) magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above. [0054] Combinations and/or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0055] The substrate may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate may also refer to a substrate that already includes multiple processed layers.

[0056] The terms “radiation” and “beam” used with respect to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g. having a wavelength of 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0057] Various patterns on or provided by a patterning device may have different process windows, i.e., a space of processing variables under which a pattern will be produced within specification. Examples of pattern specifications that relate to potential systematic defects include checks for necking, line pull back, line thinning, CD, edge placement, overlapping, resist top loss, resist undercut and/or bridging. The process window of the patterns on a patterning device or an area thereof may be obtained by merging (e.g., overlapping) process windows of each individual pattern. The boundary of the process window of a group of patterns comprises boundaries of process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the group of patterns.

[0058] As shown in Fig. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to a lithocell or cluster, which also includes apparatuses to perform pre- and post-exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit one or more resist layers, one or more developers to develop exposed resist, one or more chill plates CH and/or one or more bake plates BK. A substrate handler, or robot, RO picks up one or more substrates from input/output port I/Ol, I/O2, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus. These apparatuses, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0059] In order that a substrate that is exposed by the lithographic apparatus is exposed correctly and consistently and/or in order to monitor a part of the patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties such as alignment, overlay (which can be, for example, between structures in overlying layers or between structures in a same layer that have been provided separately to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, a material property, etc. Accordingly, a manufacturing facility in which lithocell LC is located also typically includes a metrology system that measures some or all of the substrates W (Fig. 1) that have been processed in the lithocell or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example it may be part of the lithographic apparatus LA (such as alignment sensor AS (Fig. 1)).

[0060] The one or more measured parameters may include, for example, alignment, overlay between successive layers formed in or on the patterned substrate, critical dimension (CD) (e.g., critical linewidth) of, for example, features formed in or on the patterned substrate, focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberrations of an optical lithography step, etc. This measurement is often performed on a dedicated metrology target provided on the substrate. The measurement can be performed after-development of a resist but before etching, after-etching, after deposition, and/or at other times.

[0061] There are various techniques for making measurements of the structures formed in the patterning process, including the use of a scanning electron microscope, an image-based measurement tool and/or various specialized tools. As discussed above, a fast and non-invasive form of specialized metrology tool is one in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered (diffracted/reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. Traditionally, this may be termed diffraction-based metrology. One such application of this diffraction-based metrology is in the measurement of alignment. For example, alignment can be measured by comparing parts of the diffraction spectrum (for example, comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0062] Thus, in a device fabrication process (e.g., a patterning process or a lithography process), a substrate or other objects may be subjected to various types of measurement during or after the process. The measurement may determine whether a particular substrate is defective, may establish adjustments to the process and apparatuses used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and the apparatuses, or may be for other purposes. Examples of measurement include optical imaging (e.g., optical microscope), non-imaging optical measurement (e.g., measurement based on diffraction such as the ASML YieldStar metrology tool, the ASML SMASH metrology system), mechanical measurement (e.g., profiling using a stylus, atomic force microscopy (AFM)), and/or non- optical imaging (e.g., scanning electron microscopy (SEM)).

[0063] Metrology results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, an adjustment may be made to exposure of a subsequent substrate (especially if the inspection can be done soon and fast enough that one or more other substrates of the batch are still to be exposed) and/or to subsequent exposure of the exposed substrate. Also, an already exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding performing further processing on a substrate known to be faulty. In a case where only some target portions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications. Other manufacturing process adjustments are contemplated.

[0064] A metrology system may be used to determine one or more properties of the substrate structure, and in particular, how one or more properties of different substrate structures vary, or different layers of the same substrate structure vary from layer to layer. The metrology system may be integrated into the lithographic apparatus LA or the lithocell LC, or may be a stand-alone device. [0065] To enable the metrology, often one or more targets are specifically provided on the substrate. A target may include an alignment mark, for example, and/or other targets. Typically, the target is specially designed and may comprise a periodic structure. For example, the target on a substrate may comprise one or more 1-D periodic structures (e.g., geometric features such as gratings), which are printed such that after development, the periodic structural features are formed of solid resist lines. As another example, the target may comprise one or more 2-D periodic structures (e.g., gratings), which are printed such that after development, the one or more periodic structures are formed of solid resist pillars or vias in the resist. The bars, pillars, or vias may alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0066] Fig. 3 depicts an example inspection system 10 that may be used to detect alignment and/or perform other metrology operations. It comprises a radiation source 2 which projects or otherwise irradiates radiation onto a substrate W (e.g., which may typically include an alignment mark). The redirected radiation is passed to a radiation sensor such as a spectrometer detector 4 and/or other sensors, which measures a spectrum (intensity as a function of wavelength) of the specular reflected and/or diffracted radiation, as shown, e.g., in the graph on the left of Fig. 4. The sensor may generate an alignment signal conveying alignment data indicative of properties of the reflected radiation. From this data, the structure or profile giving rise to the detected spectrum may be reconstructed by one or more processors PRO, a generalized example of which is shown in Fig. 4, or by other operations. Note that these are generalized examples. Often, illumination of a target such as an alignment mark is done orthogonal to the target and/or mark, and not at an angle as shown in these figures. [0067] As in the lithographic apparatus LA in Fig. 1, one or more substrate tables (not shown in Fig.

4) may be provided to hold the substrate W during measurement operations. The one or more substrate tables may be similar or identical in form to the substrate table WT (WTa or WTb or both) of Fig. 1. In an example where inspection system 10 is integrated with the lithographic apparatus, they may even be the same substrate table. Coarse and fine positioners may be provided and configured to accurately position the substrate in relation to a measurement optical system. Various sensors and actuators are provided, for example, to acquire the position of a target portion of interest of a structure (e.g., an alignment mark), and to bring it into position under an objective lens. Typically, many measurements will be made on target portions of a structure at different locations across the substrate W. The substrate support can be moved in X and Y directions to acquire different targets, and in the Z direction to obtain a desired location of the target portion relative to the focus of the optical system. It is convenient to think and describe operations as if the objective lens is being brought to different locations relative to the substrate, when, for example, in practice the optical system may remain substantially stationary (typically in the X and Y directions, but perhaps also in the Z direction) and the substrate moves. Provided the relative position of the substrate and the optical system is correct, it does not matter in principle which one of those is moving, or if both are moving, or a combination of a part of the optical system is moving (e.g., in the Z and/or tilt direction) with the remainder of the optical system being stationary and the substrate is moving (e.g., in the X and Y directions, but also optionally in the Z and/or tilt direction).

[0068] For typical alignment measurements, a target (portion) 30 on substrate W may be a 1-D grating, which is printed such that after development, the bars are formed of solid resist lines (e.g., which may be covered by a deposition layer), and/or other materials. Or the target 30 may be a 2-D grating, which is printed such that after development, the grating is formed of solid resist pillars, and/or other features in the resist.

[0069] The bars, pillars, vias, and/or other features may be etched into or on the substrate (e.g., into one or more layers on the substrate), deposited on a substrate, covered by a deposition layer, and/or have other properties. Target (portion) 30 (e.g., of bars, pillars, vias, etc.) is sensitive to changes in processing in the patterning process (e.g., optical aberration in the lithographic projection apparatus such as in the projection system, focus change, dose change, etc.) such that process variation manifests in variation in target 30. Accordingly, the measured data from target 30 may be used to determine an adjustment for one or more of the manufacturing processes, and/or used as a basis for making the actual adjustment.

[0070] For example, the measured data from target 30 may indicate alignment for a layer of a semiconductor device. The measured data from target 30 may be used (e.g., by the one or more processors) for determining one or more semiconductor device manufacturing process parameters based the alignment, and determining an adjustment for a semiconductor device manufacturing apparatus based on the one or more determined semiconductor device manufacturing process parameters. In some embodiments, this may comprise a stage position adjustment, for example, or this may include determining an adjustment for a mask design, a metrology target (e.g., an alignment mark) design, a semiconductor device design, an intensity of the radiation, an incident angle of the radiation, a wavelength of the radiation, a pupil size and/or shape, a resist material, and/or other process parameters.

[0071] Angle resolved scatterometry is useful in the measurement of asymmetry of features in product and/or resist patterns. A particular application of asymmetry measurement is for the measurement of alignment. The base concepts of asymmetry measurement using system 10 of Fig. 3 are described, for example, in U.S. patent application publication US2006-066855, which is incorporated herein in its entirety. In brief, for an alignment measurement, the positions of the diffraction orders in the diffraction spectrum of the target are determined by the periodicity of the target (e.g., alignment mark). Asymmetry in the diffraction spectrum is indicative of asymmetry in the individual features which make up the target. For example, any regions, from a significant fraction of an exposure field, to a whole exposure field, are useful regions for more accurate intrafield alignment fitting.

[0072] Fig. 5 illustrates a plan view of a typical target (e.g., alignment mark) 30, and the extent of a radiation illumination spot S in the system of Fig. 4. Typically, to obtain a diffraction spectrum that is free of interference from surrounding structures, the target 30, in an embodiment, is a periodic structure (e.g., grating) larger than the width (e.g., diameter) of the illumination spot S. The width of spot S may be smaller than the width and length of the target. The target, in other words, is ‘underfilled’ by the illumination, and the diffraction signal is essentially free from any signals from product features and the like outside the target itself. The illumination arrangement may be configured to provide illumination of a uniform intensity across a back focal plane of an objective, for example. Alternatively, by, for example, including an aperture in the illumination path, illumination may be restricted to on axis or off axis directions.

[0073] Fig. 6 illustrates a metrology method 600. In some embodiments, method 600 is performed as part of a semiconductor device manufacturing process. In some embodiments, one or more operations of method 600 may be implemented in or by system 10 illustrated in Fig. 3 and 4 (and Fig. 7 described below), a computer system (e.g., as illustrated in Fig. 8 and described below), and/or in or by other systems, for example. In some embodiments, method 600 comprises irradiating (operation 602) a feature in a patterned substrate with radiation, modulating (operation 604) radiation received from the feature to generate time varying radiation, generating (operation 606) a metrology signal based on the received time varying radiation, and/or other operations. Method 600 is described below in the context of alignment, but this is not intended to be limiting. Method 600 may be generally applied to a number of different processes.

[0074] The operations of method 600 presented below are intended to be illustrative. In some embodiments, method 600 may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. For example, in some embodiments, method 600 may include an additional operation comprising determining an adjustment for a semiconductor device manufacturing process. Additionally, the order in which the operations of method 600 are illustrated in Fig. 6 and described below is not intended to be limiting.

[0075] In some embodiments, one or more portions of method 600 may be implemented in and/or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information - see the description of processors PRO). The one or more processing devices may include one or more devices executing some or all of the operations of method 600 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of method 600 (e.g., see discussion related to Fig. 8 below).

[0076] Operation 602 comprises irradiating a feature in a patterned substrate with radiation. The feature may comprise a metrology mark on patterned substrate and/or other features. In some embodiments, the metrology mark is associated with an alignment and/or overlay measurement for the patterned substrate. For example, the metrology mark may be or include a dedicated alignment mark such as a diffraction grating. The radiation may be diffracted by the diffraction grating. In some embodiments, the feature comprises one or more structures in the patterned substrate capable of providing a diffraction signal. In some embodiments, the feature can be any structure in a pattern design layout capable of generating a wide angle diffraction signal.

[0077] The feature may be included in a layer of a substrate in a semiconductor device structure, for example. In some embodiments, the feature comprises a geometric feature such as a ID or 2D feature, and/or other geometric features. By way of several non-limiting examples, the feature may comprise a line, an edge, a fine -pitched series of lines and/or edges, and/or other features. In some embodiments, a fine-pitch has a pitch dimension of less than one micrometer, for example. In some embodiments, the feature (e.g., the line, edge, series, etc.) has a length spanning a region of measurement interest (e.g., a region larger than a normal target, such as the width/length of a die, but can be as long as a full wafer diameter).

[0078] The radiation may have a target wavelength and/or wavelength range, a target intensity, and/or other characteristics. The target wavelength and/or wavelength range, the target intensity, etc., may be entered and/or selected by a user, determined by the system based on previous alignment measurements, and/or determined in other ways. In some embodiments, the radiation comprises light and/or other radiation. In some embodiments, the light comprises visible light, infrared light, near infrared light, and/or other light. In some embodiments, the radiation may be any radiation appropriate for interferometry.

[0079] The radiation may be generated by a radiation source (e.g., source 2 shown in Fig. 3 and 4 and described above). In some embodiments, the radiation may be directed by the radiation source (e.g., by way of one or more lenses, a modulator, and/or other components) onto a feature, subportions (e.g., something less than the whole) of a feature, multiple features, and/or onto the substrate in other ways.

[0080] Operation 604 comprises modulating radiation received from the feature to generate time varying radiation. The modulating may be performed by a modulator and/or other components. In some embodiments, the modulator is a spatial light modulator (SLM) and/or other modulators. In general, an SLM is any device configured to cause some form of spatially varying change in a beam of radiation. The SLM may control whether radiation is transmitted (e.g., radiation on or off), which portions of the radiation are transmitted, an intensity of the radiation (e.g., intensity levels between on and off), and/or perform other modulation. In some embodiments, the SLM may be controlled, or have portions which are controlled, electronically by a processor (see processors PRO described herein), mechanically by an actuator and/or other mechanical components, may be static, or may have portions which are static, and/or have other configurations. In some embodiments, the SLM may be and/or have portions that are transmissive or reflective. For example, in some embodiments, the SLM comprises a sequence of binary or grayscale patterns configured to modulate incoming radiation.

[0081] By way of a non-limiting example, the SLM may be a digital micromirror device (DMD). A DMD has a plurality of microscopic mirrors arranged in an array, for example. The mirrors can be individually moved (e.g., electronically controlled by a processor PRO via electrodes, hinges, springs, and/or other components associated with each individual mirror) such that selected radiation from certain mirrors can be reflected toward the radiation sensor. Each mirror on the DMD can be independently modulated in a time sequence to provide grayscale modulation of the incoming radiation. The mirrors can have a very high refresh rate (multi-tens of kilohertz), for example, which allows generation of fast modulated signals.

[0082] In some embodiments, modulation comprises successively transmitting one or more subportions of the received radiation over time. The time varying radiation conveys location information related to different portions of the feature. The different portions of the feature may be different regions of interest and/or other portions. For example, in some embodiments, the patterned substrate is configured to be scanned by the radiation source, and the modulator is configured such that received reflected or transmitted radiation from the different portions is transmitted (e.g., sub-portions of the received radiation that correspond to the different portions of the feature) to the radiation sensor as the substrate moves relative to the radiation source to form the time varying radiation.

[0083] Scanning may comprise rastering the radiation over a feature such that different portions of the feature are irradiated at different times. In some embodiments, the scanning is performed at a predefined scan speed for a given sampling rate. The predefined scan speed and/or given sampling rate are determined based on a size of the feature and/or other information. In some embodiments, the predefined scan speed and/or given sampling rate are adjustable based on the size and/or other characteristics of the feature. In some embodiments, conversely, sizes of features that can be scanned are determined based on a ratio of the predefined scan speed to the given sampling rate.

[0084] In some embodiments, the modulator may be configured such that all or only certain subportions of radiation are transmitted for a scan. For example, at a given moment in time during a scan, the modulator may be configured to transmit all of the radiation for the whole of the portion of the metrology mark in view at that time, or some sub-portion of the radiation for a specific region of interest in view at that time (e.g., using radiation from certain mirrors of a DMD). The sub-portion of radiation may be configured such that it corresponds to a smaller area of the metrology mark, certain wavelengths of radiation, certain diffraction orders of radiation, a certain polarization of radiation, or other sub-portions, for example.

[0085] As another example, in some embodiments, the patterned substrate is configured to be held stationary relative to the radiation source, and the modulator is configured to generate the time varying radiation by successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor (e.g., with different mirrors of a DMD, mirrors moved to different positions, etc.). Successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor may mimic a scan, for example. The modulator may be configured to successively transmit sub-portions of radiation that correspond to smaller areas of the metrology mark (e.g., the portions as described above), certain wavelengths of radiation, certain diffraction orders of radiation, a certain polarization of radiation, or other sub-portions, for example. [0086] In some embodiments, characteristics of the transmitted radiation (e.g., wavelength, intensity, etc.) may be varied by the modulator over time (whether in a scanning or stationary mode). This may create and/or supplement the time varying radiation for analysis. This may also facilitate analysis of individual portions of a feature, comparison of one portion of a feature to another and/or to other features, and/or other analysis.

[0087] Operation 606 comprises generating a metrology signal based on the received time varying radiation and/or other information. The metrology signal may be generated by a radiation sensor (e.g., such as sensor detector 4 shown in 3) and/or other components. Operation 606 includes detecting reflected and/or transmitted radiation from the feature. Detecting such radiation comprises detecting one or more phase and/or amplitude (intensity) shifts in radiation received from one or more geometric features. The one or more phase and/or amplitude shifts correspond to one or more dimensions of a feature. For example, the phase and/or amplitude of reflected radiation from one side of a feature is different relative to the phase and/or amplitude of reflected radiation from another side of the feature.

[0088] Detecting the one or more phase and/or amplitude (intensity) shifts in the radiation from the feature comprises measuring local phase shifts (e.g., local phase deltas) and/or amplitude variations that correspond to different portions of a feature. For example, the radiation from a specific area of a feature may comprise a sinusoidal waveform having a certain phase and/or amplitude. The radiation from a different area of the feature may also comprise a sinusoidal waveform, but one with a different phase and/or amplitude. Detecting radiation also comprises measuring a phase and/or amplitude difference in radiation of different diffraction orders. Detecting the one or more local phase and/or amplitude shifts may be performed using Hilbert transformations, for example, 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.

[0089] By way of a non-limiting example, Fig. 7 illustrates an example metrology system 700 comprising a modulator 702 and/or other components. System 700 is the same as or similar to system 10 described above with respect to Fig. 3, with one or more components of system 700 being similar to and/or the same as one or more components of system 10 (and Fig. 7 illustrating additional possible components of the system). In some embodiments, one or more components of system 700 may replace, be used with, and/or otherwise augment one or more components of system 10. For example, Fig. 7 illustrates modulator 702, an imaging lens 704, a collection lens 706, a color demultiplexer 708, a sensor (detector 4), and/or other components. In Fig. 7, radiation may be generated and directed to a feature (e.g., target 30) by a radiation source such as source 2 shown in Fig. 3 (but not repeated in Fig. 7).

[0090] Imaging lens 704 is configured to receive radiation 701 from the feature (e.g., target 30, which in this example is a diffraction grating) and direct the received radiation 701 toward modulator 702. Collection lens 706 is configured to receive time varying radiation 703 from modulator 702 and direct time varying radiation 703 toward radiation sensor (detector 4). Color demultiplexer 708 is configured to receive time varying radiation 703 from modulator 702, and separate time varying radiation 703 into different signals 707, 709, 711 for different colors of radiation. Sensor (detector 4) comprises different detectors 4a, 4b, 4c, for the different colors of radiation 703. In some embodiments, system 700 includes a polarization splitter configured to facilitate detection of radiation with various polarizations. The polarization splitter may be located anywhere between reference numerals 703 and 708, 30 and 704, or 708 and 4a/4b/4c in Fig. 7, for example.

[0091] In some embodiments, system 700 comprises one or more processors (not shown in Fig. 7, but see PRO in Fig. 3 and Fig. 8 described below). In some embodiments, the one or more processors are configured to control modulator 702 to modulate received radiation (e.g., e.g., by moving modulator 702 and/or actuatable parts of modulator 702). In some embodiments, the one or more processors are configured to determine, based on the metrology signal, an alignment inspection location or an overlay inspection location of the feature. In some embodiments, the one or more processors are configured to adjust a semiconductor device manufacturing process based on the metrology signal.

[0092] As described above, modulation by modulator 702 comprises successively transmitting one or more sub-portions of the received radiation over time. In Fig. 7, time varying radiation 703 includes sub-portion 705 (e.g., at the instant in time depicted in Fig. 7). Sub-portion 705 is generated because the pattern (e.g., the black and white squares in this example) of modulator 702 reflects or transmits only radiation from certain overlapping areas of target 30 (e.g., see the overlay of target 30 on modulator 702 in Fig. 7). Modulator 702 is configured such that this process is successively repeated for different portions of target 30 (and/or other surrounding structures) at later instances in time to form time varying radiation 703. Sub-portion 705 may change for each successive instant in time, for example. The successive repetition may be caused by modulator 702 when modulator 702 is configured such that received reflected or transmitted radiation from the different portions of target 30 is transmitted (e.g., sub-portions of the received radiation that correspond to the different portions of the feature) to the radiation sensor (detector 4) as the substrate moves relative to the radiation source to form the time varying radiation; when the patterned substrate (and target 30 in this example) is configured to be held stationary relative to the radiation source, and modulator 702 is configured to generate the time varying radiation by successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor (e.g., from different parts of the black and white pattern in this example); and/or some combination of both of these techniques. Modulator 702 may be configured to successively transmit sub-portions of radiation that correspond to smaller areas of target 30 (e.g., the portions as described above), certain wavelengths of radiation, certain diffraction orders of radiation, certain polarizations of radiation, or other sub-portions, for example. This flexibility (static or scanning modes, different selectable portions of an metrology mark, different selectable portions of a wavelength spectrum, etc.) may facilitate broad spectrum metrology for various metrology mark types and/or have other advantages.

[0093] Returning to Fig. 6, and as described above, operation 606 comprises generating a metrology signal based on the detected modulated radiation from the feature. The metrology signal comprises measurement information pertaining to the feature. For example, the metrology signal may be an alignment signal comprising alignment measurement information, an overlay signal comprising overlay measurement information, and/or other metrology signals. In some embodiments, operation 606 includes determining, based on the metrology signal, an alignment inspection location of the feature. The measurement information (e.g., the alignment inspection location of the feature) may be determined using principles of interferometry and/or other principles.

[0094] The metrology signal comprises an electronic signal that represents and/or otherwise corresponds to the modulated radiation from a feature. The metrology signal may indicate an alignment value for the feature, for example, and/or other information. Generating the metrology signal comprises sensing the modulated radiation and converting the sensed modulated radiation into the electronic signal. In some embodiments, generating the metrology signal comprises sensing different portions of the modulated radiation from different portions and/or different geometries of the feature, and combining the different portions of the sensed modulated radiation to form the metrology signal. This sensing and converting may be performed by components similar to and/or the same as radiation sensor detector 4 and/or processors PRO shown in Fig. 3, Fig. 4, and Fig. 7, and/or other components.

[0095] In some embodiments, generating the metrology signal may comprise directly measuring the dimensions of a feature. For example, direct dimensional measurements of a feature may be made with a scatterometer and/or other systems. In some embodiments, direct dimensional measurements may be used in combination with, and/or instead of the local phase and/or amplitude shifts described here, to determine the alignment of a feature. For example, output dimensional measurements from the scatterometer system may be provided to processor PRO (Fig. 3) and/or other system components, which may generate the metrology signal based at least in part on the output dimensional measurements from the scatterometer system.

[0096] In some embodiments, operation 606 comprises determining an adjustment for a semiconductor device manufacturing process. In some embodiments, operation 606 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 variations, an alignment value indicated by the metrology signal, dimensions determined by a scatterometer system, and/or other similar systems, and/or other information. The one or more parameters may include a parameter of the radiation (the radiation used for determining alignment), an alignment inspection location within a feature, an alignment inspection location on a layer of a semiconductor device structure, and/or other parameters. In some embodiments, process parameters can be interpreted broadly to include a stage position, a mask design, a metrology target design, a semiconductor device design, an intensity of the radiation (used for exposing resist, etc.), an incident angle of the radiation (used for exposing resist, etc.), a wavelength of the radiation (used for exposing resist, etc.), the polarization of the radiation, a pupil size and/or shape, a resist material, and/or other parameters.

[0097] A parameter of the radiation used for determining alignment, for example, may include a wavelength, an intensity, an angle of incidence, and/or parameters of the radiation. These parameters may be adjusted to better measure features with specific shapes, enhance the intensity of reflected radiation, increase and/or otherwise enhance (e.g., maximize) the phase and/or amplitude shifts (if any) in reflected radiation from one area of a feature to the next, and/or for other purposes. This may enable and/or enhance detection of more subtle deviations, make the phase and/or amplitude shifts easier to detect, and/or have other advantages.

[0098] In some embodiments, operation 606 includes determining a process adjustment based on the one or more determined semiconductor device manufacturing process parameters, adjusting a semiconductor device manufacturing apparatus based on the determined adjustment, and/or other operations. For example, if a determined alignment is not within process tolerances, the misalignment may be caused by one or more manufacturing processes whose process parameters have drifted and/or otherwise changed so that the process is no longer producing acceptable devices (e.g., alignment measurements may breach a threshold for acceptability). One or more new or adjusted process parameters may be determined based on the alignment determination. The new or adjusted process parameters may be configured to cause a manufacturing process to again produce acceptable devices. For example, a new or adjusted process parameter may cause a previously unacceptable alignment (or misalignment) to be adjusted back into an acceptable range. The new or adjusted process parameters may be compared to existing parameters for a given process. If there is a difference, that difference may be used to determine an adjustment for an apparatus that is used to produce the devices (e.g., parameter “x” should be increased / decreased / changed so that it matches the new or adjusted version of parameter “x” determined as part of operation 606), for example. In some embodiments, operation 606 may include electronically adjusting an apparatus (e.g., based on the determined process parameters). Electronically adjusting an apparatus may include sending an electronic signal, and/or other communications to the apparatus, for example, that causes a change in the apparatus. The electronic adjustment may include changing a setting on the apparatus, for example, and/or other adjustments.

[0099] Figure 8 is a diagram of an example computer system CS that may be used for one or more of the operations described herein. Computer system CS includes a bus BS or other communication mechanism for communicating information, and a processor PRO (or multiple processors) coupled with bus BS for processing information. Computer system CS also includes a main memory MM, such as a random access memory (RAM) or other dynamic storage device, coupled to bus BS for storing information and instructions to be executed by processor PRO. Main memory MM also may be used for storing temporary variables or other intermediate information during execution of instructions by processor PRO. Computer system CS further includes a read only memory (ROM) ROM or other static storage device coupled to bus BS for storing static information and instructions for processor PRO. A storage device SD, such as a magnetic disk or optical disk, is provided and coupled to bus BS for storing information and instructions.

[00100] Computer system CS may be coupled via bus BS to a display DS, such as a cathode ray tube (CRT) or flat panel or touch panel display for displaying information to a computer user. An input device ID, including alphanumeric and other keys, is coupled to bus BS for communicating information and command selections to processor PRO. Another type of user input device is cursor control CC, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor PRO and for controlling cursor movement on display DS. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

[00101] In some embodiments, portions of one or more methods may be performed by computer system CS in response to processor PRO executing one or more sequences of one or more instructions contained in main memory MM. Such instructions may be read into main memory MM from another computer-readable medium, such as storage device SD. Execution of the sequences of instructions included in main memory MM causes processor PRO to perform the process steps (operations). One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory MM. In some embodiments, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, this description is not limited to any specific combination of hardware circuitry and software.

[00102] The term “computer-readable medium” or “machine-readable medium” refers to any medium that participates in providing instructions to processor PRO for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer -readable media can be non- transitory, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge. Non-transitory computer readable media can have instructions recorded thereon. The instructions, when executed by a computer, can implement any of the operations described. Transitory computer-readable media can include a carrier wave or other propagating electromagnetic signal, for example.

[00103] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor PRO for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system CS can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus BS can receive the data carried in the infrared signal and place the data on bus BS. Bus BS carries the data to main memory MM, from which processor PRO retrieves and executes the instructions. The instructions received by main memory MM may optionally be stored on storage device SD either before or after execution by processor PRO.

[00104] Computer system CS may also include a communication interface CI coupled to bus BS. Communication interface CI provides a two-way data communication coupling to a network link NDL that is connected to a local network LAN. For example, 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, communication interface CI may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface CI sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

[00105] Network link NDL typically provides data communication through one or more networks to other data devices. For example, network link NDL may provide a connection through local network LAN to a host computer HC. This can include data communication services provided through the worldwide packet data communication network, now commonly referred to as the “Internet” INT. Local network LAN (Internet) may use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network data link NDL and through communication interface CI, which carry the digital data to and from computer system CS, are exemplary forms of carrier waves transporting the information.

[00106] Computer system CS can send messages and receive data, including program code, through the network(s), network data link NDL, and communication interface CI. In the Internet example, host computer HC might transmit a requested code for an application program through Internet INT, network data link NDL, local network LAN, and communication interface CI. One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor PRO as it is received, and/or stored in storage device SD, or other nonvolatile storage for later execution. In this manner, computer system CS may obtain application code in the form of a carrier wave.

[00107] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses:

1. A metrology system, comprising: a radiation source configured to irradiate a feature in a patterned substrate with radiation; a modulator configured to modulate received radiation from the feature to generate time varying radiation; and a radiation sensor configured to receive the time varying radiation and generate a metrology signal, the metrology signal comprising measurement information pertaining to the feature.

2. The system of clause 1, wherein the feature comprises a metrology mark.

3. The system of any of the previous clauses, wherein the metrology mark comprises a diffraction grating.

4. The system of any of the previous clauses, wherein the radiation is diffracted by the diffraction grating.

5. The system of any of the previous clauses, wherein the metrology mark is associated with an alignment and/or overlay measurement for the patterned substrate.

6. The system of any of the previous clauses, wherein the modulator is a spatial light modulator (SLM).

7. The system of any of the previous clauses, wherein the SLM is a digital micromirror device (DMD).

8. The system of any of the previous clauses, wherein the SLM comprises a sequence of binary or grayscale patterns configured to modulate incoming radiation.

9. The system of any of the previous clauses, wherein the SLM is transmissive or reflective.

10. The system of any of the previous clauses, wherein modulation comprises successively transmitting one or more sub-portions of the received radiation over time.

11. The system of any of the previous clauses, wherein the time varying radiation conveys location information related to different portions of the feature.

12. The system of any of the previous clauses, wherein the patterned substrate is configured to be scanned by the radiation source, and the modulator is configured such that received reflected or transmitted radiation from the different portions is transmitted to the radiation sensor as the substrate moves relative to the radiation source to form the time varying radiation.

13. The system of any of the previous clauses, wherein patterned substrate is configured to be held stationary relative to the radiation source, and the modulator is configured to generate the time varying radiation by successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor.

14. The system of any of the previous clauses, further comprising an imaging lens configured to receive radiation from the feature and direct the received radiation toward the modulator.

15. The system of any of the previous clauses, further comprising a collection lens configured to receive the time varying radiation from the modulator and direct the time varying radiation toward the radiation sensor.

16. The system of any of the previous clauses, further comprising a color demultiplexer configured to receive the time varying radiation from the modulator, and separate the time varying radiation into different signals for different colors of radiation.

17. The system of any of the previous clauses, wherein the radiation sensor comprises different detectors for the different colors of radiation.

18. The system of any of the previous clauses, further comprising a polarization splitter configured to facilitate detection of radiation with various polarizations.

19. The system of any of the previous clauses, further comprising one or more processors configured to determine, based on the metrology signal, an alignment inspection location or an overlay inspection location of the feature.

20. The system of any of the previous clauses, wherein the one or more processors are further configured to adjust a semiconductor device manufacturing process based on the metrology signal.

21. A metrology method, comprising: irradiating, with a radiation source, a feature in a patterned substrate with radiation; modulating, with a modulator, received radiation from the feature to generate time varying radiation; and receiving the time varying radiation with a radiation sensor, and generating a metrology signal, the metrology signal comprising measurement information pertaining to the feature.

22. The method of clause 21, wherein the feature comprises a metrology mark. 23. The method of any of the previous clauses, wherein the metrology mark comprises a diffraction grating.

24. The method of any of the previous clauses, wherein the radiation is diffracted by the diffraction grating.

25. The method of any of the previous clauses, wherein the metrology mark is associated with an alignment and/or overlay measurement for the patterned substrate.

26. The method of any of the previous clauses, wherein the modulator is a spatial light modulator (SLM).

27. The method of any of the previous clauses, wherein the SLM is a digital micromirror device (DMD).

28. The method of any of the previous clauses, wherein the SLM comprises a sequence of binary or grayscale patterns configured to modulate incoming radiation.

29. The method of any of the previous clauses, wherein the SLM is transmissive or reflective.

30. The method of any of the previous clauses, wherein modulation comprises successively transmitting one or more sub-portions of the received radiation over time.

31. The method of any of the previous clauses, wherein the time varying radiation conveys location information related to different portions of the feature.

32. The method of any of the previous clauses, wherein the patterned substrate is configured to be scanned by the radiation source, and the modulator is configured such that received reflected or transmitted radiation from the different portions is transmitted to the radiation sensor as the substrate moves relative to the radiation source to form the time varying radiation.

33. The method of any of the previous clauses, wherein patterned substrate is configured to be held stationary relative to the radiation source, and the modulator is configured to generate the time varying radiation by successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor.

34. The method of any of the previous clauses, further comprising receiving, with an imaging lens, radiation from the feature and directing the received radiation toward the modulator.

35. The method of any of the previous clauses, further comprising receiving, with a collection lens, the time varying radiation from the modulator and directing the time varying radiation toward the radiation sensor.

36. The method of any of the previous clauses, further comprising receiving, with a color demultiplexer, the time varying radiation from the modulator, and separating the time varying radiation into different signals for different colors of radiation.

37. The method of any of the previous clauses, wherein the radiation sensor comprises different detectors for the different colors of radiation.

38. The method of any of the previous clauses, further comprising facilitating detection, with a polarization splitter, of radiation with various polarizations. 39. The method of any of the previous clauses, further comprising determining, with one or more processors, based on the metrology signal, an alignment inspection location or an overlay inspection location of the feature.

40. The method of any of the previous clauses, further comprising adjusting, with the one or more processors, a semiconductor device manufacturing process based on the metrology signal.

[00108] The concepts disclosed herein may be associated with any generic imaging system for imaging sub wavelength features, and may be especially useful with emerging imaging technologies capable of producing increasingly shorter wavelengths. Emerging technologies already in use include EUV (extreme ultra violet), DUV lithography that is capable of producing a 193nm wavelength with the use of an ArF laser, and even a 157nm wavelength with the use of a Fluorine laser. Moreover, EUV lithography is capable of producing wavelengths within a range of 20-5nm by using a synchrotron or by hitting a material (either solid or a plasma) with high energy electrons in order to produce photons within this range.

[00109] While the concepts disclosed herein may be used for imaging on a substrate such as a silicon wafer, it shall be understood that the disclosed concepts may be used with any type of lithographic imaging systems, e.g., those used for imaging on substrates other than silicon wafers. In addition, the combination and sub-combinations of disclosed elements may comprise separate embodiments.

[00110] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.

Claims

2. The system of claim 1, wherein the feature comprises a metrology mark.

3. The system of claim 2, wherein the metrology mark comprises a diffraction grating.

4. The system of claim 3, wherein the radiation is diffracted by the diffraction grating.

5. The system of any of claims 2-4, wherein the metrology mark is associated with an alignment and/or overlay measurement for the patterned substrate.

6. The system of any of claims 1-5, wherein the modulator is a spatial light modulator (SLM).

7. The system of claim 6, wherein the SLM is a digital micromirror device (DMD).

8. The system of claims 6 or 7, wherein the SLM comprises a sequence of binary or grayscale patterns configured to modulate incoming radiation.

9. The system of any of claims 6-8, wherein the SLM is transmissive or reflective.

10. The system of any of claims 1-9, wherein modulation comprises successively transmitting one or more sub-portions of the received radiation over time.

11. The system of any of claims 1-10, wherein the time varying radiation conveys location information related to different portions of the feature.

12. The system of claim 11, wherein the patterned substrate is configured to be scanned by the radiation source, and the modulator is configured such that received reflected or transmitted radiation from the different portions is transmitted to the radiation sensor as the substrate moves relative to the radiation source to form the time varying radiation.

13. The system of claim 11, wherein patterned substrate is configured to be held stationary relative to the radiation source, and the modulator is configured to generate the time varying radiation by successively selecting and transmitting reflected or transmitted radiation from the different portions to the radiation sensor.

14. The system of any of claims 1-13, further comprising an imaging lens configured to receive radiation from the feature and direct the received radiation toward the modulator.

15. The system of any of claims 1-14, further comprising a collection lens configured to receive the time varying radiation from the modulator and direct the time varying radiation toward the radiation sensor.