Multiwavelength micro-optical patterning process metrology systems and methods

Abstract

Compact semiconductor patterning metrology is described. To reduce patterning errors, more metrology targets are measured in parallel across a wafer. Parallel measurements using multiple parallel metrology sensors requires smaller and smaller sensors. Photonic integrated circuits are small enough to be used to make these parallel measurements. The photonic integrated circuits described herein comprise an emitter that directs radiation toward a metrology target; receiving micromirrors that receive diffracted orders of radiation from the metrology target; and output waveguides configured to receive the diffracted orders of radiation from the receiving micromirrors, and cause interference of the diffracted orders of radiation in the photonic integrated circuit. A radiation detector is configured to generate a metrology signal based on the interfered diffracted orders of radiation. The photonic integrated circuit facilitates parallel sensing of diffracted radiation from multiple metrology targets, a dense arrangement to form a significantly more compact sensor, and has other advantages.

Description

MULTIWAVELENGTH MICRO-OPTICAL PATTERNING PROCESS METROLOGY SYSTEMS AND METHODSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 639,147 which was filed on April 26, 2024 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] This description relates to patterning process metrology systems and methods.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.

[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. This device manufacturing process may be considered a patterning process.

[0005] Lithography is a central step in the manufacturing of devices 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.

[0006] 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 illumination source, creating individual functional elements having dimensions well below 100 nm.

[0007] 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 = kjxk / NA, where I 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).

[0008] Metrology systems are key to these fine tuning steps.SUMMARY

[0009] Compact semiconductor patterning metrology is described. To reduce patterning errors, more metrology targets may be measured in parallel across a substrate such as a semiconductor wafer using multiple parallel metrology sensors. Parallel measurements using multiple parallel metrology sensors requires small sensors. The photonic integrated circuits described herein are small enough to be used to make these parallel measurements. Advantageously, the photonic integrated circuits described herein comprise an emitter that directs radiation toward a metrology target; receiving mirrors that receive diffracted orders of radiation from the metrology target; and output waveguides configured to receive the diffracted orders of radiation from the receiving micromirrors, and cause interference of the diffracted orders of radiation in the photonic integrated circuit. A radiation detector is configured to generate a metrology signal based on the interfered diffracted orders ofradiation. The photonic integrated circuit facilitates parallel sensing of diffracted radiation from multiple metrology targets, a dense arrangement to form a significantly more compact sensor, and has other advantages compared to prior systems.

[0010] According to an embodiment, a metrology system is provided. The system comprises a radiation source configured to generate radiation for irradiating a metrology target in a patterned substrate. The system comprises a photonic integrated circuit operatively coupled to the radiation source. The photonic integrated circuit comprises an emitter configured to direct the radiation from the radiation source toward the metrology target; two or more receiving micromirrors configured to receive two or more diffracted orders of radiation from the metrology target; and one or more output waveguides configured to receive the two or more diffracted orders of radiation from the two or more receiving micromirrors, and cause interference of the two or more diffracted orders of radiation in the photonic integrated circuit. The system comprises a radiation detector operatively coupled to the one or more output waveguides and configured to generate a metrology signal based on the interfered two or more diffracted orders of radiation from the photonic integrated circuit. The metrology signal comprises measurement information pertaining to the metrology target.

[0011] In some embodiments, there is an angular difference between the two or more diffracted orders of radiation. In some embodiments, the two or more diffracted orders of radiation comprise at least a positive and a negative diffracted order of radiation. In some embodiments, the two or more diffracted orders of radiation comprise +1 and -1, +2 and -2, +3 and -3, +1 and +2, -1 and -2, 0 (zeroorder reflection) and + or - 1 or 2 or 3, -1 and +3, etc. (these are just a small number of representative example combinations) diffracted orders of radiation.

[0012] In some embodiments, the metrology target comprises an alignment mark. In some embodiments, the metrology target comprises a grating (that may form all or a portion of an alignment mark), for example.

[0013] In some embodiments, the photonic integrated circuit has a generally planar arrangement. In some embodiments, the photonic integrated circuit is arranged in a parallel orientation, in a plane substantially parallel to, a substrate with the metrology target. In some embodiments, a position of the photonic integrated circuit relative to the metrology target in the patterned substrate is adjustable. The position of the photonic integrated circuit relative to the metrology target in the patterned substrate may be adjustable in an x, y, z, and / or rotational directions.

[0014] In some embodiments, the photonic integrated circuit is sized based on a distance between the metrology target and the photonic integrated circuit, a wavelength of the radiation from the radiation source, a period of the metrology target, and / or other factors. In some embodiments, the photonic integrated circuit comprises a 15mm x 15mm or smaller chip, as one possible representative example. In some embodiments, the photonic integrated circuit comprises multiple circuits, with each circuit configured in terms of pitch, wavelength, orientation, and / or location for measuring a different metrology target. In some embodiments, a size of the photonic integrated circuit is similar to a size ofa semiconductor wafer (e.g., an array of photonic integrated circuit sensors covering a wafer configured to maintain parallel functionality as described herein).

[0015] In some embodiments, the photonic integrated circuit comprises two or more photonic integrated circuits. The two or more photonic integrated circuits may comprise a first photonic integrated circuit arranged in an x-direction relative to the metrology target, and a second photonic integrated circuit arranged in a y-direction relative to the metrology target, for example. The two or more photonic integrated circuits may be formed in the same single chip, or in two different separate chips. In some embodiments, the two or more photonic integrated circuits comprise a plurality of photonic integrated circuits arranged to correspond to a plurality of metrology targets in the patterned substrate. In some embodiments, the plurality of photonic integrated circuits are arranged to correspond to a plurality of metrology targets in the patterned substrate, and are configured for parallel performance of metrology on each of the plurality of metrology targets at the same time.

[0016] In some embodiments, the radiation from the radiation source directed toward the metrology target is broadband, comprising a plurality of wavelengths. In some embodiments, the radiation source comprises a laser, for example. The radiation source may be configured to be integrated close to an input waveguide in the photonic integrated circuit such that a mode of the radiation couples to the input waveguide. The radiation source may be configured to be integrated on a support structure proximate to the photonic integrated circuit where the radiation source abuts an input waveguide. The radiation source may be configured to be located remotely from the photonic integrated circuit, and the system may comprise a fiber configured to conduct the radiation from the radiation source to the photonic integrated circuit. Other configurations are possible.

[0017] In some embodiments, the photonic integrated circuit comprises an input waveguide configured to propagate the radiation in the photonic integrated circuit toward the emitter, which focuses, shapes, and / or directs the radiation toward the metrology target.

[0018] In some embodiments, the emitter comprises a mirror or micromirror. In some embodiments, the two or more receiving micromirrors comprise two or more portions of a single larger receiving mirror. In some embodiments, each of the two or more receiving micromirrors comprises an elliptical micromirror. In some embodiments, the two or more receiving micromirrors are positioned at locations on the photonic integrated circuit wherein the two or more diffracted orders of radiation are expected to impinge on the photonic integrated circuit. In some embodiments, the system comprises multiple emitting mirrors or micromirrors configured to generate structured illumination by interference.

[0019] In some embodiments, the one or more output waveguides comprise waveguides that correspond to each elliptical micromirror, and are configured to collect the diffracted radiation and direct collected diffracted radiation toward the radiation detector. A path length of the waveguides that correspond to each elliptical micromirror may be the same prior to interfering the two or more diffracted orders of radiation in the photonic integrated circuit. In some embodiments, the one ormore output waveguides form, form part of, or conduct the two or more diffracted orders of radiation to, a multimode interference device to cause the interference.

[0020] In some embodiments, the system comprises a fiber edge coupled to the photonic integrated circuit configured to guide received interfered two or more diffracted orders of radiation to the radiation detector. In some embodiments, the radiation detector comprises a photodiode, and / or a charge coupled device (CCD). In some embodiments, the system comprises one or more processors operatively coupled to the radiation detector. The one or more processors are configured to determine a phase difference between the interfered orders of diffracted radiation based on the metrology signal.

[0021] In some embodiments, the radiation source, the photonic integrated circuit, and the radiation detector, form a portion of an alignment metrology system. The alignment metrology system may be configured for a patterned substrate comprising a semiconductor wafer, and may be used in a semiconductor manufacturing process.

[0022] According to other embodiments, one or more metrology methods are provided. The one or more methods comprise one or more of the operations described above performed by a metrology system.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Fig. 1 schematically depicts a lithography apparatus, according to an embodiment.

[0025] Fig. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.

[0026] Fig. 3 schematically depicts an example metrology system, according to an embodiment.

[0027] Fig. 4 schematically depicts an example metrology technique, according to an embodiment.

[0028] Fig. 5 illustrates the relationship between a radiation illumination spot of a metrology system and a metrology target, according to an embodiment.

[0029] Fig. 6 illustrates a more detailed view of a portion of a photonic integrated circuit from the metrology system shown in Fig. 3, according to an embodiment.

[0030] Fig. 7 illustrates a perspective view of a chip, a receiving micromirror, and an output waveguide of the photonic integrated circuit, according to an embodiment.

[0031] Fig. 8 illustrates a perspective view of the receiving micromirror alone, according to an embodiment.

[0032] Fig. 9 illustrates a wider (top) view of the photonic integrated circuit, including an input waveguide, an emitter, multiple receiving micromirrors, multiple output waveguides, and / or other components, according to an embodiment.

[0033] Fig. 10 illustrates the view of the photonic integrated circuit from Fig. 9, along with a cross-sectional view of a portion of the photonic integrated circuit that includes the emitter, a receiving micromirror, and an output waveguide, according to an embodiment.

[0034] Fig. 11 illustrates a metrology method, according to an embodiment.

[0035] Fig. 12 is a block diagram of an example computer system, according to an embodiment.DETAILED DESCRIPTION

[0036] In semiconductor device manufacturing, metrology operations typically include determining the position of a metrology mark (or marks) and / or other target in a layer of a semiconductor device structure. This position is typically determined by irradiating a metrology mark with radiation, and comparing characteristics of different diffraction orders of radiation received from the metrology mark. Such techniques are used to measure alignment, overlay, and / or other parameters.

[0037] A photonic integrated circuit (PIC) is a versatile platform that can be configured for various processing operations (e.g. interferometry, demultiplexing, filtering, etc.) on diffracted radiation. Moving detection and diffraction order interference functionality to a photonic integrated circuit, it is possible to achieve a reduction in sensor size compared to sensor sizes in prior systems because the photonic integrated circuit can replace the high-numerical aperture objectives typically used to collect diffracted radiation. Typical metrology sensors need to be able to receive and process a wide range of diffracted radiation wavelengths (e.g., twelve different color wavelength ranges with two different polarizations), from a wide variety of angles. Past photonic integrated circuit based metrology systems are only configured to process a small number of wavelengths, often with only one polarization. Scaling a photonic integrated circuit based system to process a wide range of radiation wavelengths and multiple polarizations (in parallel) was thought to require a larger, bulky arrangement of components, or not be possible at all. Current sensor technologies do not allow arrangement of multiple sensors in a dense configuration for parallel measurement of diffracted radiation of (e.g., twelve) different colors at long (e.g., about 3mm) working distances.

[0038] Advantageously, in the present systems and methods, a newly designed compact photonic integrated circuit for a metrology system is used to extend the functionality of typical photonic integrated circuits to facilitate parallel sensing of multiple wavelengths and / or polarizations. The photonic integrated circuits described herein comprise an emitter that directs radiation toward a metrology target; receiving mirrors that receive diffracted orders of radiation from the metrology target; and output waveguides configured to receive the diffracted orders of radiation from the receiving micromirrors, and cause interference of the diffracted orders of radiation in the photonic integrated circuit. A radiation detector is configured to generate a metrology signal based on the interfered diffracted orders of radiation. The photonic integrated circuit facilitates parallel sensing of diffracted radiation from multiple metrology targets, a dense arrangement to form a significantly more compact sensor, and has other advantages compared to prior systems.

[0039] By way of a brief introduction, the description below relates to semiconductor device manufacturing and patterning processes. The following paragraphs also describe several components of systems and / or methods for semiconductor device metrology. These systems and methods may be used for measuring alignment, overlay, etc., in a semiconductor device manufacturing process, for example, or for other operations.

[0040] Although specific reference may be made in this text to the measurement of alignment or other parameters, and the manufacture of integrated circuits (ICs) for semiconductor devices, it should be understood that the description herein has many other possible applications. For example, 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.

[0041] 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).

[0042] 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.

[0043] 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, theilluminator 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.

[0044] 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 wherein 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.

[0045] 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.

[0046] 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 opticalcomponents, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation. Thus, the illuminator provides a conditioned beam of radiation B, having a desired uniformity and intensity distribution in its cross section.

[0047] The support structure MT supports the patterning device MA 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” herein may be considered synonymous with the more general term “patterning device.”

[0048] The term “patterning device” used herein 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 crosssection 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.

[0049] 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.

[0050] 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” herein may be considered as synonymous with the more general term “projection system.”

[0051] 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) elementswithin the projection system PS in one or more different ways. The projection system may have a coordinate system wherein 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.

[0052] 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 conducted 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.

[0053] The lithographic apparatus LA may also be of a type wherein 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” as used herein 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.

[0054] 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 aidof 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.

[0055] 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.

[0056] Combinations and / or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0057] 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 herein 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 used herein may also refer to a substrate that already includes multiple processed layers.

[0058] The terms “radiation” and “beam” used herein with respect to lithography encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g. having a wavelength of 365, 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.

[0059] 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.

[0060] As shown in Fig. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to as 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.

[0061] 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, forexample, 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)).

[0062] 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 one or more dedicated metrology targets provided on the substrate. The measurement can be performed afterdevelopment of a resist but before etching, after-etching, after deposition, and / or at other times.

[0063] 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. 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. Applications of this diffraction-based metrology include the measurement of alignment, overlay, etc. For example, alignment and / or overlay can be measured by comparing parts of the diffraction spectrum (for example, comparing different diffraction orders in the diffraction spectrum of a periodic grating).

[0064] 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), mechanical measurement (e.g., profiling using a stylus, atomic force microscopy (AFM)), and / or non-optical imaging (e.g., scanning electron microscopy (SEM)).

[0065] 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 avoidingperforming 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.

[0066] 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.

[0067] To enable the metrology, often one or more metrology targets are specifically provided on the substrate. 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).

[0068] Fig. 3 depicts an example metrology system 10 that may be used to detect alignment and / or perform other metrology operations. It comprises an illumination or radiation source 2 which projects or otherwise irradiates radiation 6 onto a substrate W (e.g., which may typically include a metrology target 30). Radiation 6 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 system 10 based on previous measurements, and / or determined in other ways. In some embodiments, radiation 6 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. One or more photonic integrated circuits 8 (a photonic integrated circuit) may be used to direct radiation to and / or receive diffracted radiation 12 from a metrology target 30 on substrate W.

[0069] Target 30 may comprise one or more metrology marks, such as diffraction grating targets, formed in a substrate (such as patterned substrate W shown in Fig. 3) such as a semiconductor wafer, collectively referred to as target 30, for example. Target 30 may comprise one or more structures in the patterned substrate capable of providing a diffraction signal. One or more targets 30 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 grating, a line, an edge, a fine-pitched series of lines and / or edges, and / or other features.

[0070] Redirected or diffracted radiation 12 is passed to a sensor such as a radiation 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.Detector 4 generates a metrology signal conveying metrology 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 (Fig. 3), a generalized example of which is shown in Fig. 4, or by other operations.

[0071] As in the lithographic apparatus LA in Fig. 1 , one or more substrate tables (not shown in Fig. 3) 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 metrology 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., a metrology mark), and to bring it into position under optical component 8 and / or other components such as a 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 optical components are 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).

[0072] For typical metrology measurements, a metrology target 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.

[0073] 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. Metrology target 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.

[0074] For example, the measured data from metrology target 30 may indicate alignment for alayer of a semiconductor device. The measured data from target 30 may be used (e.g., by the one or more processors PRO and / or other processors) for determining one or more semiconductor device manufacturing process parameters based the alignment, and / or 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 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.

[0075] Fig. 5 illustrates a plan view of a typical metrology target 30, and the extent of a typical radiation illumination spot S in the system of Fig. 3. Typically, to obtain a diffraction spectrum that is free of interference from surrounding structures, 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.

[0076] Advantageously, in the present systems and methods, a newly designed compact photonic integrated circuit based metrology system is used to extend the functionality of typical systems to facilitate parallel sensing of multiple wavelengths and / or polarizations. For example, Fig. 6 illustrates a more detailed view of a portion of photonic integrated circuit 8 from system 10 shown in Fig. 3 (though oriented upside down relative to what is shown in Fig. 3). This portion of photonic integrated circuit 8 comprises base structures of the new system (e.g., system 10 shown in Fig. 3), including a receiving micromirror 602, an output waveguide 604, and / or other components. These base structures may be repeated across photonic integrated circuit 8 to provide the functionality described herein. Compared to other structures such as gratings, mirrors (or micromirrors) can accommodate larger bandwidth radiation. For example, radiation wavelengths from deep ultraviolet (DUV) to far-infrared (FIR) can be reflected by micromirrors, while gratings are typically designed for one specific wavelength. Designing multiwavelength grating couplers is very difficult. In addition, the coupling efficiency of micromirrors is better than grating couplers over a larger range of wavelengths and coupling angles.

[0077] Fig. 6 illustrates a side view of receiving micromirror 602 receiving a diffracted order of radiation 12 from metrology target 30 (or a portion thereof). In some embodiments, metrology target 30 comprises an alignment mark. In some embodiments, metrology target 30 comprises a grating (that may form all or a portion of an alignment mark), for example. In some embodiments, photonicintegrated circuit 8 forms a portion of an alignment sensor that is used in a semiconductor manufacturing process, for example. In Fig. 6, additional detail is illustrated for photonic integrated circuit 8 compared to the illustration in system 10 shown in Fig. 3. In this example, incident diffracted radiation 12 has been diffracted by metrology target such as target 30.

[0078] Receiving micromirror 602 reflects the order of diffracted radiation 12 into output waveguide 604. Receiving micromirror 602 may comprise an angled surface 603 configured according to the position of output waveguide 604. For example, angled surface 603 may be angled at approximately 15 - 45 degrees, and face output waveguide 604. For example, this may be equal to the diffraction angle from an alignment marker. In an example embodiment, this may be associated with 500-900nm radiation diffracted from a 1.6 micron marker (e.g., an angle of about 18-35 degrees). Angled surface 603 may have a concave shape or other shapes configured to focus or otherwise collect the order of diffracted radiation 12 into output waveguide 604. In some embodiments, receiving micromirror 602 comprises an elliptical micromirror, and / or a micromirror with other shapes. In some embodiments, receiving micromirror 602 is about 100 - 500 microns in size, and / or has another size that allows it to function as described herein.

[0079] A micromirror may be made by three dimensional microprinting using a tool such as a NanoScribe, for example, by two-photon polymerization with a focused laser beam and / or other processes. Their size may be limited by the range of the sample stage in such a process, which is about 500 x 500 x 500 microns. However, one can make larger structures using stitching and / or other processes, for example (though step-like irregularities should be avoided). Complete optical systems with lens arrays may be fabricated using a NanoScribe tool. This distinguishes these devices from microlenses or microlens arrays which are usually fabricated by a chemical process and / or imprint lithography, for example.

[0080] Output waveguide 604 receives the order of diffracted order of radiation 12 from receiving micromirror 602. Output waveguide 604 is configured to conduct received diffracted radiation toward a radiation sensor (e.g., radiation sensor 4 shown in Fig. 3). The conduction may occur due to internal reflection of the diffracted radiation off of interior surfaces of output waveguide 604, for example, and / or by other mechanisms. Output waveguide 604 is configured to cause interference of the diffracted order of radiation 12 with other orders of diffracted radiation in photonic integrated circuit 8 (as described below).

[0081] In some embodiments, receiving micromirror 602 and output waveguide 604 may be formed in or on a chip 610 and / or other structures. Chip 610 may be made from silicon, for example. In some embodiments, micromirror 602 may comprise a photoresist body 612 with an aluminum coating 614 and / or other structures. The photoresist has a combination of mechanical and optical properties which are well suited for micromirrors. Waveguide 604 may be formed from SiN, surrounded by an exterior structure 620 made of SiO2. These materials are provided as examples. Other material compositions are contemplated. In some embodiments, the structures and / or thematerials used in photonic integrated circuit 8 may be configured such that an index contrast between the waveguides (e.g., SiN) and the surrounding (SiO2) is low and a coupler thickness is much shorter than the operating wavelength.

[0082] In some embodiments, receiving micromirror 602, output waveguide 604, and / or chip 610 may be formed by additive manufacturing processes such as three dimensional printing (or three dimensional microprinting), lithography-like patterning processes, etching processes, evaporation (e.g., for coating purposes), optical or e-beam lithography and subsequent SiN or CMOS processing, imprint lithography, and / or using other techniques. In some embodiments, receiving micromirrors 602 may be fabricated using a Nanoscribe machine using a focused spot and two-photon polymerization, after which body 612 is coated with aluminum, for example. Since receiving micromirror 602 (and output waveguide 604) and / or other components of photonic integrated circuit 8 are fabricated on-chip, system 10 (Fig. 3) and photonic integrated circuit 8 provide a fully on-chip metrology (e.g., alignment) sensor that irradiates metrology target 30 at multiple wavelengths, among other advantages.

[0083] Fig. 7 illustrates a perspective view of chip 610, receiving micromirror 602, and output waveguide 604. Fig. 8 illustrates a perspective view of receiving micromirror 602 alone. In Fig. 7 and Fig. 8, micromirror 602 comprises an angled surface 603 configured according to the position of output waveguide 604 (Fig. 7, Fig., 6). For example, angled surface 603 may is angled at approximately 45 degrees in these examples, and faces output waveguide 604. Angled surface 603 also has a concave shape configured to focus or otherwise collect the order of diffracted radiation 12 (Fig. 6) into output waveguide 604 (Fig. 7 and Fig. 6).

[0084] As a reminder, before diffracting from metrology target 30 (as shown in Fig. 6), the radiation is generated by radiation source 2 (Fig. 3), and directed, with an emitter of photonic integrated circuit 8 that is operatively coupled to radiation source 2, toward metrology target 30. After passing through output waveguide 604, interfered diffracted orders of radiation from photonic integrated circuit 8 impinge on radiation detector 4 (Fig. 3), which is operatively coupled to output waveguide 604. Radiation detector 4 is configured to generate a metrology signal comprising measurement information pertaining to metrology target 30.

[0085] Fig. 9 illustrates a wider (top) view 901 of photonic integrated circuit 8, including an input waveguide 902, an emitter 904, multiple receiving micromirrors 602, multiple output waveguides 604, and / or other components. Fig. 9 also illustrates radiation source 2 and radiation detector 4, along with structures 950 configured to block stray light from an input coupling between radiation source 2 and input waveguide 902.

[0086] Input waveguide 902 is configured to conduct radiation 6 in photonic integrated circuit 8 toward the emitter 904, which focuses, shapes, and / or directs radiation 6 toward the metrology target (e.g., metrology target 30 shown in Fig. 6, Fig. 3, etc. - which would be located above photonic integrated circuit 8 and out of the page in this example). Input waveguide 902 and / or outputwaveguides 604 may have any length and / or orientation that allows photonic integrated circuit 8 and / or system 10 to function as described herein. For example, input waveguide 902 may comprise an undulation around structures 950. Structures 950 may comprise blocks of radiation absorbing material, for example, and / or other structures. This arrangement may block or otherwise reduce stray light in photonic integrated circuit 8. As another example, output waveguides 604 may have a minimum spacing (e.g., 50 pm in this example) to prevent cross-talk and / or for other purposes (e.g., before or after diffraction orders of radiation are interfered with each other as described herein). Cross-talk comprises the coupling of wavelengths of radiation into an undesired waveguide in photonic integrated circuit 8. Cross-talk can be reduced significantly by using different materials, different thicknesses, increasing the spacing between waveguides, and / or using other techniques. In some embodiments, photonic integrated circuit 8 may be configured such that the positive and negative order modes are recombined, and the interference signal is out coupled through a grating to a fiber. Other configurations are contemplated.

[0087] Fig. 10 illustrates view 901 of photonic integrated circuit 8 from Fig. 9, along with a cross- sectional view 1050 of a portion of photonic integrated circuit 8 that includes emitter 904, a receiving micromirror 602, and an output waveguide 604 on chip 610. As shown in Figs. 10 and 9, radiation source 2 is configured to generate radiation 6 for irradiating metrology target 30 in a patterned substrate (e.g., substrate W shown in Fig. 3). Photonic integrated circuit 8 is operatively coupled to radiation source 2. Photonic integrated circuit 8 comprises emitter 904 configured to direct radiation 6 from radiation source 2 toward metrology target 30. Two or more receiving micromirrors 602 are configured to receive two or more diffracted orders of radiation 12 from metrology target 30. The different receiving micromirrors are each configured to receive different orders of diffracted radiation 12 from metrology target 30. One or more output waveguides 604 are configured to receive the two or more diffracted orders of radiation 12 from the two or more receiving micromirrors 602, and cause interference of the two or more diffracted orders of radiation 12 in photonic integrated circuit 8.

[0088] Radiation detector 4 (also see Fig. 3) is operatively coupled to the one or more output waveguides 604 and configured to generate a metrology signal based on the interfered two or more diffracted orders of radiation 12 from photonic integrated circuit 8. The metrology signal comprises measurement information pertaining to metrology target 30.

[0089] In some embodiments, there is an angular difference between the two or more diffracted orders of radiation 12. In some embodiments, the two or more diffracted orders of radiation comprise at least a positive and a negative diffracted order of radiation 12. In some embodiments, the two or more diffracted orders of radiation 12 comprise +1 and -1, +2 and -2, +3 and -3, +1 and +2, -1 and -2, 0 (zero-order reflection) and + or - 1 or 2 or 3, -1 and +3, etc. (these are just a small number of representative example combinations) diffracted orders of radiation. In some embodiments, receiving micromirrors 602 on either side of emitter 904 may be configured to receive such pairs of diffracted orders of radiation 12. For example, the orders of diffracted radiation 12 are captured by receivingmicromirrors 602 and coupled into waveguides 604, from where a phase difference between positive and negative (or other) orders of diffracted radiation 12 can be determined on-chip. In this example, positive and negative diffraction orders may be captured by receiving micromirrors 602 above and below (in the two dimensional plane shown in Fig. 9 and Fig. 10) emitter 904. In some embodiments, receiving micromirrors 602 are configured to capture the first order (positive and negative) diffracted radiation for 532 and 780 nm from a 3.2pm alignment metrology mark, for example. The waveguide modes from receiving micromirrors 602 are made to interfere to measure their phase difference as a function of metrology mark 30 position. In this configuration, both modes are made to interfere in the far field (for simplicity), but any on-chip interferometer device is suited to measure the phase difference. “On-chip” refers to recombining diffracted orders on-chip in a multimode interference device. That can give the sum of both signals, the intensity of which varies sinusoidally with marker position. This signal can be coupled out through a grating or edge coupler, for example, to a fiber to be detected somewhere else. Detection can also be on-chip, with a diode on-chip and detection of the electrical signal outside. Thermal heat load considerations, for example, and / or other information may be a basis for using a certain configuration.

[0090] In some embodiments, photonic integrated circuit 8 has a generally planar arrangement. In some embodiments, photonic integrated circuit 8 is arranged in a parallel orientation, in a plane substantially parallel to, a substrate (e.g., substrate W shown in Fig. 3) with metrology target 30 (e.g., as shown in Fig. 3 and in Fig. 10). In some embodiments, a position of photonic integrated circuit 8 relative to metrology target 30 in the patterned substrate is adjustable. The position of photonic integrated circuit 8 relative to metrology target 30 in the patterned substrate may be adjustable in an x, y, z, and / or rotational (r) directions (see Fig. 10).

[0091] For example, in some embodiments, system 10 may comprise one or more adjusters configured to adjust distance d between photonic integrated circuit 8 and metrology target 30. An adjuster may comprise an actuator and / or other components coupled to photonic integrated circuit 8 and / or metrology target 30, fixed to a frame structure of system 10, and / or other adjusters. System 10 may include multiple actuators. An actuator may be a piezoelectric actuator and / or other actuators, for example. Each actuator may be configured to independently adjust distances between different photonic integrated circuits 8 and metrology targets 30, between a photonic integrated circuit and a fixed outer structure of system 10, and / or other distances. In some embodiments, an adjuster is configured to enable simultaneous measurement of a number of different metrology targets 30 in a single field, without restriction on where the different metrology targets are located.

[0092] In some embodiments, photonic integrated circuit 8 is sized based on distance d (Fig. 10) between metrology target 30 and photonic integrated circuit 8 (e.g., chip 610), a wavelength of the radiation 6 from radiation source 2, a period of metrology target 30, and / or other factors. In some embodiments, photonic integrated circuit 8 comprises a 15mm x 15mm or smaller chip 610, as one possible representative example. In some embodiments, photonic integrated circuit 8 comprisesmultiple circuits, with each circuit configured in terms of pitch, wavelength, orientation, and / or location for measuring a different metrology target 30. In some embodiments, a size of photonic integrated circuit 8 is similar to a size of a semiconductor wafer.

[0093] In some embodiments, photonic integrated circuit 8 comprises two or more photonic integrated circuits. The two or more photonic integrated circuits may comprise a first photonic integrated circuit arranged in an x-direction relative to metrology target 30, and a second photonic integrated circuit arranged in a y-direction relative to the metrology target, for example. The two or more photonic integrated circuits may be formed in a same single chip 610, or in two different separate chips 610. In some embodiments, the two or more photonic integrated circuits comprise a plurality of photonic integrated circuits arranged to correspond to a plurality of metrology targets 30 in the patterned substrate (e.g., patterned substrate W shown in Fig. 3). In some embodiments, the plurality of photonic integrated circuits are arranged to correspond to a plurality of metrology targets 30 in the patterned substrate, and are configured for parallel performance of metrology on each of the plurality of metrology targets 30 at the same time.

[0094] In some embodiments, radiation 6 from radiation source 2 (Fig. 3, Fig. 9) directed toward metrology target 30 is broadband, comprising a plurality of wavelengths. In some embodiments, radiation source 2 comprises a laser, and / or other sources as described above, for example. Radiation source 2 may be configured to be integrated close to an input waveguide 902 in photonic integrated circuit 8 such that a mode of radiation 6 couples to input waveguide 902. In some embodiments, radiation source 2 may be configured to be integrated on a support structure proximate to photonic integrated circuit 8, where radiation source 2 abuts an input waveguide 902. In some embodiments, radiation source 2 may be configured to be located remotely from photonic integrated circuit 8, and system 10 may comprise a fiber 960 (Fig. 9) configured to conduct radiation 6 from radiation source 2 to photonic integrated circuit 8. Other configurations are possible. The routing, in-coupling, and out- coupling of radiation 6 and / or diffracted radiation 12 may be the same as or similar to the routing, incoupling, and out-coupling in other photonic integrated circuits.

[0095] In some embodiments, emitter 904 comprises a mirror or micromirror. In some embodiments, system 10 comprises multiple emitting mirrors or micromirrors configured to generate structured illumination by interference. In this embodiment, there is only one emitting mirror 904. However, two emitting mirrors can be used. For example, if two capturing mirrors are instead used as emitting devices, they would give an interference pattern right above 904. This is structured illumination that could be used in optically integrated level sensing.

[0096] In some embodiments, the two or more receiving micromirrors 602 comprise two or more portions of a single larger receiving mirror. In some embodiments, each of the two or more receiving micromirrors 602 comprises an elliptical micromirror. In some embodiments, the two or more receiving micromirrors 602 are positioned at locations on photonic integrated circuit 8 wherein the two or more diffracted orders of radiation 12 are expected to impinge on photonic integrated circuit 8.In Fig. 9 and Fig. 10, this is illustrated as multiple receiving micromirrors 602 spaced equidistantly on either side of emitter 904. In some embodiments, the receiving micromirrors 602 may be placed at the location where the diffraction orders intersect the chip. As one example, the diffraction angle for + / - 1 st orders is given by sin(diffraction angle) = + / - wavelength / period. The location on photonic integrated circuit 8 is given by: tan(diffraction angle) = + / - x_grating dimension / working distance.

[0097] In some embodiments, the one or more output waveguides 604 comprise waveguides that correspond to each (elliptical) receiving micromirror 602, and are configured to collect the diffracted radiation 12 and direct collected diffracted radiation toward radiation detector 4. A path length of the waveguides 604 that correspond to each elliptical receiving micromirror 602 may be the same prior to interfering the two or more diffracted orders of radiation 12 in photonic integrated circuit 8. In some embodiments, the one or more output waveguides 604 form, form part of, or conduct the two or more diffracted orders of radiation 12 to, a multimode interference device to cause the interference. In some embodiments, on-chip interference may be performed by merging waveguides - carefully configuring the waveguides so that there is constructive interference, and / or using other techniques. A multimode interference device can be though of as a structure that combines two inputs and gives two outputs, or one output, that is the sum or difference of the two inputs.

[0098] In some embodiments, an out coupler is coupled to an edge of photonic integrated circuit 8 and configured to conduct the interfered diffracted radiation from photonic integrated circuit 8 to the radiation detector (e.g., detector 4 shown in Fig. 3). The out coupler may be configured to out couple radiation from one or more waveguides 604. In some embodiments, the out coupler comprises one or more grating couplers for out coupling radiation into a fiber, out couplers for butt-coupling from the waveguide(s) into fibers, and / or other components. Note that the out coupler need not be located at an edge of photonic integrated circuit 8.

[0099] For example, in some embodiments, system 10 comprises a fiber edge coupled to photonic integrated circuit 8 configured to guide received interfered two or more diffracted orders of radiation 12 to radiation detector 4. In some embodiments, radiation detector 4 comprises a photodiode, a charge coupled device (CCD), and / or other sensors as described above. Radiation detector 4 may comprise multiple sensing devices operating in parallel, for example. In some embodiments, the metrology signal may be an alignment signal comprising alignment measurement information, and / or other metrology signals. The measurement information (e.g., an alignment value, and / or other information) may be determined using principles of interferometry and / or other principles. In some embodiments, system 10 comprises one or more processors (see processors PRO shown in Fig. 3 and Fig. 12) operatively coupled to radiation detector 4. The one or more processors are configured to determine a phase difference between the interfered orders of diffracted radiation 12 based on the metrology signal. This phase difference may be used to determine an alignment and / or other metrology values, for example.

[0100] Fig. 11 illustrates a metrology method 1000. In some embodiments, method 1100 isperformed as part of an alignment sensing operation in a semiconductor device manufacturing process, for example. In some embodiments, one or more operations of method 1100 may be implemented in or by system 10 illustrated in Fig. 3, one or more components of a photonic integrated circuit (e.g., as illustrated and described above), a computer system (e.g., as illustrated in Fig. 12 and described below), and / or in or by other systems, for example. In some embodiments, method 1100 comprises irradiating (operation 1102) a metrology target in a patterned substrate with radiation; collecting (operation 1104) diffracted radiation from the metrology target; generating (operation 1106) a metrology signal; and determining (operation 1108) alignment of a layer of the patterned substrate based on the metrology signal.

[0101] The operations of method 1100 are intended to be illustrative. In some embodiments, method 1100 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 1100 may include an additional operation comprising determining an adjustment for a semiconductor device manufacturing process. Additionally, the order in which the operations of method 1100 are illustrated in Fig. 11 and described herein is not intended to be limiting.

[0102] In some embodiments, one or more portions of method 1100 may be implemented in and / or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and / or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method 1100 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 1100 (e.g., see discussion related to Fig. 12 below).

[0103] At operation 1102, a radiation source (e.g., source 2 shown in Fig. 3)generates radiation for irradiating a metrology target in a patterned substrate. The radiation comprises light and / or other radiation. An emitter of a photonic integrated circuit (PIC) that is operatively coupled to the radiation source directs the radiation from the radiation source toward the metrology target. The emitter comprises a mirror, a micromirror, or other components. In some embodiments, there are multiple emitting mirrors or micromirrors configured to generate structured illumination by interference. In some embodiments, an input waveguide of the photonic integrated circuit propagates the radiation in the PIC toward the emitter, which focuses, shapes, and / or directs the radiation toward the metrology target.

[0104] In some embodiments, the radiation may be directed by the emitter onto a metrology target, sub-portions (e.g., something less than the whole) of a target, multiple metrology targets and / or onto a patterned substrate in other ways. In some embodiments, the radiation may be generated by the radiation source (so that the emitter directs the radiation onto the target) in a time varying manner.For example, the radiation may be rastered over a target (e.g., by moving the target under the radiation) such that different portions of the target are irradiated at different times. As another example, characteristics of the radiation (e.g., wavelength, intensity, etc.) may be varied. This may create time varying data envelopes, or windows, for analysis. The data envelopes may facilitate analysis of individual sub-portions of a target, comparison of one portion of a target to another and / or to other targets, and / or other analysis.

[0105] In some embodiments, the metrology target comprises an alignment mark. In some embodiments, the metrology target comprises a grating (that may form all or a portion of an alignment mark), for example.

[0106] In some embodiments, the radiation from the radiation source directed toward the metrology target is broadband, comprising a plurality of wavelengths. In some embodiments, the radiation source comprises a laser, for example. The radiation source may be configured to be integrated close to an input waveguide in the photonic integrated circuit such that a mode of the radiation couples to the input waveguide. The radiation source may be configured to be integrated on a support structure proximate to the photonic integrated circuit where the radiation source abuts an input waveguide. The radiation source may be configured to be located remotely from the photonic integrated circuit, and the system may comprise a fiber configured to conduct the radiation from the radiation source to the photonic integrated circuit. Other configurations are possible. In some embodiments, operation 1102 is performed by a radiation source similar to and / or the same as radiation source 2 shown in Fig. 3 and described above, an input waveguide similar to and / or the same as input waveguide 902 shown in Fig. 9 and Fig 10 and described above; and / or an emitter similar to and / or the same as emitter 904 shown in Fig. 9 and Fig 10 and described above.

[0107] At operation 1104, diffracted radiation is collected from the metrology target. Two or more receiving micromirrors of the photonic integrated circuit receive two or more diffracted orders of radiation from the metrology target. One or more output waveguides of the photonic integrated circuit receive the two or more diffracted orders of radiation from the two or more receiving micromirrors, and cause interference of the two or more diffracted orders of radiation in the photonic integrated circuit. In some embodiments, there is an angular difference between the two or more diffracted orders of radiation. In some embodiments, the two or more diffracted orders of radiation comprise at least a positive and a negative diffracted order of radiation. In some embodiments, the two or more diffracted orders of radiation comprise +1 and -1, +2 and -2, +3 and -3, +1 and +2, -1 and -2, 0 (zero-order reflection) and + or - 1 or 2 or 3, -1 and +3, etc. (these are just a small number of representative example combinations) diffracted orders of radiation.

[0108] In some embodiments, the two or more receiving micromirrors comprise two or more portions of a single larger receiving mirror. In some embodiments, each of the two or more receiving micromirrors comprises an elliptical micromirror. In some embodiments, the two or more receiving micromirrors are positioned at locations on the photonic integrated circuit wherein the two or morediffracted orders of radiation are expected to impinge on the photonic integrated circuit.

[0109] In some embodiments, the one or more output waveguides comprise waveguides that correspond to each elliptical micromirror, and are configured to collect the diffracted radiation and direct collected diffracted radiation toward a radiation detector. A path length of the waveguides that correspond to each elliptical micromirror may be the same prior to interfering the two or more diffracted orders of radiation in the photonic integrated circuit. In some embodiments, the one or more output waveguides form, form part of, or conduct the two or more diffracted orders of radiation to, a multimode interference device to cause the interference. In some embodiments, operation 1104 is performed by receiving micromirrors of the photonic integrated circuit that are similar to and / or the same as receiving micromirrors 602 shown in Figs. 6-10 and described above, and / or output waveguides similar to and / or the same as output waveguides 604 shown in Figs 6, 7, 9 and 10, and described above.

[0110] In some embodiments, the photonic integrated circuit may be similar to and / or the same as photonic integrated circuit 8 illustrated in Figs. 3 and 6-10. The photonic integrated circuit has a generally planar arrangement. In some embodiments, the photonic integrated circuit is arranged in a parallel orientation, in a plane substantially parallel to, a patterned substrate with the metrology target (e.g., as shown in Fig. 3). In some embodiments, a position of the photonic integrated circuit relative to the metrology target in the patterned substrate is adjustable. The position of the photonic integrated circuit relative to the metrology target in the patterned substrate may be adjustable in an x, y, z, and / or rotational directions.

[0111] In some embodiments, the photonic integrated circuit is sized based on a distance between the metrology target and the photonic integrated circuit, a wavelength of the radiation from the radiation source, a period of the metrology target, and / or other factors. In some embodiments, the photonic integrated circuit comprises a 15mm x 15mm or smaller chip, as one possible representative example. In some embodiments, the photonic integrated circuit comprises multiple circuits, with each circuit configured in terms of pitch, wavelength, orientation, and / or location for measuring a different metrology target. In some embodiments, a size of the photonic integrated circuit is similar to a size of a semiconductor wafer.

[0112] In some embodiments, the photonic integrated circuit comprises two or more photonic integrated circuits. The two or more photonic integrated circuits may comprise a first photonic integrated circuit arranged in an x-direction relative to the metrology target, and a second photonic integrated circuit arranged in a y-direction relative to the metrology target, for example. The two or more photonic integrated circuits may be formed in a same single chip, or in two different separate chips. In some embodiments, the two or more photonic integrated circuits comprise a plurality of photonic integrated circuits arranged to correspond to a plurality of metrology targets in the patterned substrate. In some embodiments, the plurality of photonic integrated circuits are arranged to correspond to a plurality of metrology targets in the patterned substrate, and are configured forparallel performance of metrology on each of the plurality of metrology targets at the same time.

[0113] At operation 1106, the radiation detector (which is operatively coupled to the one or more output waveguides) generates a metrology signal based on the interfered two or more diffracted orders of radiation from the photonic integrated circuit. The metrology signal comprises measurement information pertaining to the metrology target. In some embodiments, the radiation detector comprises an interferometer configured to interfere diffraction orders of received diffracted radiation (if not already interfered in the one or more output waveguides), a photodiode, a charge coupled device (CCD), and / or other components. The radiation detector may comprise multiple sensing devices operating in parallel, for example. In some embodiments, a fiber edge coupled to the photonic integrated circuit is configured to guide received interfered two or more diffracted orders of radiation to the radiation detector.

[0114] In some embodiments, operation 1106 comprises detecting diffracted radiation (with the radiation detector described above) from one or more diffraction grating targets. Detecting diffracted radiation comprises detecting one or more phase and / or amplitude (intensity) shifts in diffracted radiation from one or more geometric features of the target(s). The one or more phase and / or amplitude shifts correspond to one or more dimensions of a target. For example, the phase and / or amplitude of reflected radiation from one side of a target is different relative to the phase and / or amplitude of reflected radiation from another side of the target.

[0115] Detecting the one or more phase and / or amplitude (intensity) shifts in the diffracted radiation from the target comprises measuring local phase shifts (e.g., local phase deltas) and / or amplitude variations that correspond to different portions of a target. For example, the diffracted radiation from a specific area of a target may comprise a sinusoidal waveform having a certain phase and / or amplitude. The diffracted radiation from a different area of the target (or a target in a different layer) may also comprise a sinusoidal waveform, but one with a different phase and / or amplitude. Detecting diffracted radiation also comprises measuring a phase and / or amplitude difference in reflected 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.

[0116] In some embodiments, operation 1106 comprises generating a metrology signal based on the detected reflected radiation from diffraction grating target(s), as described above. The metrology signal is generated by a radiation detector (such as detector 4 in Fig. 3, and / or other sensors) based on radiation received by the detector. The metrology signal comprises measurement information pertaining to the target(s) on a substrate. For example, the metrology signal may be an alignment signal comprising alignment measurement information, and / or other metrology signals. The measurement information (e.g., an alignment value, and / or other information) may be determined using principles of interferometry and / or other principles.

[0117] The metrology signal comprises an electronic signal that represents and / or otherwise corresponds to radiation reflected from the target(s). The metrology signal may indicate a metrology value associated with a diffraction grating target, for example, and / or other information. Generating the metrology signal comprises sensing the diffracted radiation and converting the sensed diffracted radiation into the electronic signal. In some embodiments, generating the metrology signal comprises sensing different portions of the diffracted radiation from different areas and / or different geometries of the target, and / or multiple targets, and combining the different portions of the diffracted radiation to form the metrology signal. This sensing and converting may be performed by components similar to and / or the same as detector 4 and / or processors PRO shown in Fig. 3, and / or other components. Operation 1106 may be performed by a radiation detector similar to and / or the same as detector 4 shown in Fig. 3, and described herein.

[0118] At operation 1108, alignment of a layer of the patterned substrate is determined based on the metrology signal and / or other information. The alignment is determined based on information from the reflected diffracted radiation from the metrology target on the substrate in the metrology signal, and / or other information. Alignment may be determined by one or more processors operatively coupled to the radiation detector and / or other components. The radiation source, the photonic integrated circuit, and the radiation detector may form, or form a portion of, an alignment metrology system such as system 10 shown in Fig. 3. The alignment metrology system may be configured for a patterned substrate comprising a semiconductor wafer, and may be used in a semiconductor manufacturing process, as described herein, for example. Operation 1108 may be performed by one or more processors similar to and / or the same as processors PRO shown in Fig. 3 and Fig. 12, and described herein.

[0119] In some embodiments, operation 1108 comprises determining an adjustment for a semiconductor device manufacturing process. For example, this may include automatically adjusting, with the one or more processors, a location of a stage of a metrology system holding the substrate based on a determined alignment position. In some embodiments, operation 1108 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, 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 metrology), an alignment value, a metrology inspection location on a layer of a semiconductor device structure, a radiation beam trajectory across a target, 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.), a pupil size and / or shape, a resist material, and / or other parameters.

[0120] In some embodiments, operation 1008 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. This may be performed by one or more processors such as PRO shown in Fig. 3, a processor described as part of the computer system illustrated in Fig. 12 and described below, and / or other processors. For example, if a determined metrology measurement is not within process tolerances, the out of tolerance measurement 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., measurements may breach a threshold for acceptability). One or more new or adjusted process parameters may be determined based on the measurement determination. The new or adjusted process parameters may be configured to cause a manufacturing process to again produce acceptable devices.

[0121] For example, a new or adjusted process parameter may cause a previously unacceptable measurement value 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 1108), for example. In some embodiments, operation 1108 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, which causes a change in the apparatus. The electronic adjustment may include changing a setting on the apparatus, for example, and / or other adjustments.

[0122] Figure 12 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 similar to and / or the same as processor PRO shown in Fig. 3) 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.

[0123] Computer system CS may be coupled via bus BS to a display DS, such as a flat panel or touch panel display or a cathode ray tube (CRT) for displaying information to a computer user. Aninput 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.

[0124] In some embodiments, all or some of one or more operations described herein 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) described herein. 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, the description herein is not limited to any specific combination of hardware circuitry and software.

[0125] The term “computer-readable medium” or “machine -readable medium” as used herein 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 herein. Transitory computer-readable media can include a carrier wave or other propagating electromagnetic signal, for example.

[0126] 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 network. Computer system CS can receive the data over the network convert the data to instructions, and place the data and / orinstructions on bus BS. Bus BS carries the data and / or instructions 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.

[0127] 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 network. 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.

[0128] 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.

[0129] Computer system CS can send messages and receive data, including program code, through the network(s), network data link NDL, and communication interface CL 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 CL 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.

[0130] Various embodiments of the present systems and methods are disclosed in the subsequent list of numbered clauses. In the following, further features, characteristics, and exemplary technical solutions of the present disclosure will be described in terms of clauses that may be optionally claimed in any combination:1. A metrology system, comprising: a radiation source configured to generate radiation for irradiating a metrology target in a patterned substrate; a photonic integrated circuit operatively coupled to the radiation source, the photonic integrated circuit comprising: an emitter configured to direct the radiation from the radiation source toward the metrology target; two or more receiving micromirrorsconfigured to receive two or more diffracted orders of radiation from the metrology target; and one or more output waveguides configured to receive the two or more diffracted orders of radiation from the two or more receiving micromirrors, and cause interference of the two or more diffracted orders of radiation in the photonic integrated circuit; and a radiation detector operatively coupled to the one or more output waveguides and configured to generate a metrology signal based on the interfered two or more diffracted orders of radiation from the photonic integrated circuit, the metrology signal comprising measurement information pertaining to the metrology target.2. The system of clause 1 , wherein there is an angular difference between the two or more diffracted orders of radiation.3. The system of any of the previous clauses, where the two or more diffracted orders of radiation comprise at least a positive and a negative diffracted order of radiation.4. The system of any of the previous clauses, wherein the two or more diffracted orders of radiation comprise +1 and -1, +2 and -2, +3 and -3, +1 and +2, -1 and -2, 0 (zero-order reflection) and + or - 1 or 2 or 3, and / or -1 and +3 diffracted orders of radiation.5. The system of any of the previous clauses, wherein the metrology target comprises an alignment mark.6. The system of any of the previous clauses, wherein the photonic integrated circuit has a generally planar arrangement.7. The system of any of the previous clauses, wherein the one or more output waveguides form, form part of, or conduct the two or more diffracted orders of radiation to, a multimode interference device to cause the interference.8. The system of any of the previous clauses, wherein the two or more receiving micromirrors comprise two or more portions of a single larger receiving mirror.9. The system of any of the previous clauses, further comprising one or more processors operatively coupled to the radiation detector, the one or more processors configured to determine a phase difference between the interfered orders of diffracted radiation based on the metrology signal.10. The system of any of the previous clauses, wherein: the radiation source, the photonic integrated circuit, and the radiation detector, form a portion of an alignment metrology system; and the alignment metrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor manufacturing process.11. The system of any of the previous clauses, wherein the radiation detector comprises a photodiode, and / or a charge coupled device (CCD).12. The system of any of the previous clauses, wherein the photonic integrated circuit comprises two or more photonic integrated circuits.13. The system of any of the previous clauses, wherein the two or more photonic integrated circuits comprise a first photonic integrated circuit arranged in an x-direction relative to the metrology target, and a second photonic integrated circuit arranged in a y-direction relative to the metrology target; andwherein the two or more photonic integrated circuits are formed in a same single chip, or in two different separate chips.14. The system of any of the previous clauses, wherein the two or more photonic integrated circuits comprise a plurality of photonic integrated circuits arranged to correspond to a plurality of metrology targets in the patterned substrate.15. The system of any of the previous clauses, wherein the plurality of photonic integrated circuits arranged to correspond to the plurality of metrology targets in the patterned substrate are configured for parallel performance of metrology on each of the plurality of metrology targets at the same time.16. The system of any of the previous clauses, wherein a position of the photonic integrated circuit relative to the metrology target in the patterned substrate is adjustable.17. The system of any of the previous clauses, wherein the position of the photonic integrated circuit relative to the metrology target in the patterned substrate is adjustable in an x, y, z, and / or rotational direction.18. The system of any of the previous clauses, wherein the photonic integrated circuit is sized based on a distance between the metrology target and the photonic integrated circuit, a wavelength of the radiation from the radiation source, and / or a period of the metrology target.19. The system of any of the previous clauses, wherein the photonic integrated circuit comprises a 15mm x 15mm or smaller chip.20. The system of any of the previous clauses, wherein the photonic integrated circuit comprises multiple circuits, each circuit in configured in terms of pitch, wavelength, orientation, and / or location for measuring a different metrology target.21. The system of any of the previous clauses, wherein a size of the photonic integrated circuit is similar to a size of a semiconductor wafer.22. The system of any of the previous clauses, the photonic integrated circuit further comprising an input waveguide configured to propagate the radiation in the photonic integrated circuit toward the emitter, which focuses, shapes, and / or directs the radiation toward the metrology target.23. The system of any of the previous clauses, wherein each of the two or more receiving micromirrors comprises an elliptical micromirror, and the one or more output waveguides comprise waveguides that correspond to each elliptical micromirror, configured to collect the diffracted radiation and direct collected diffracted radiation toward the radiation detector.24. The system of any of the previous clauses, wherein a path length of the waveguides that correspond to each elliptical micromirror is the same prior to interfering the two or more diffracted orders of radiation in the photonic integrated circuit.25. The system of any of the previous clauses, wherein the two or more receiving micromirrors are positioned at locations on the photonic integrated circuit wherein the two or more diffracted orders of radiation are expected to impinge on the photonic integrated circuit.26. The system of any of the previous clauses, further comprising a fiber edge coupled to thephotonic integrated circuit configured to guide received interfered two or more diffracted orders of radiation to the radiation detector.27. The system of any of the previous clauses, wherein the metrology target comprises a grating.28. The system of any of the previous clauses, wherein the radiation source comprises a laser.29. The system of any of the previous clauses, wherein the radiation source is configured to be integrated close to an input waveguide in the photonic integrated circuit such that a mode of the radiation couples to the input waveguide.30. The system of any of the previous clauses, wherein the radiation source is configured to be integrated on a support structure proximate to the photonic integrated circuit where the radiation source abuts an input waveguide.31. The system of any of the previous clauses, wherein the radiation source is configured to be located remotely from the photonic integrated circuit, and the system comprises a fiber configured to conduct the radiation from the radiation source to the photonic integrated circuit.32. The system of any of the previous clauses, wherein the radiation from the radiation source directed toward the metrology target is broadband, comprising a plurality of wavelengths.33. The system of any of the previous clauses, wherein the photonic integrated circuit is arranged in a parallel orientation, in a plane substantially parallel to, a substrate with the metrology target.34. The system of any of the previous clauses, wherein the emitter comprises a mirror or micromirror.35. The system of any of the previous clauses, the emitter further comprising multiple emitting mirrors or micromirrors configured to generate structured illumination by interference.36. A metrology method, comprising: generating, with a radiation source, radiation for irradiating a metrology target in a patterned substrate; directing, with an emitter of a photonic integrated circuit that is operatively coupled to the radiation source, the radiation from the radiation source toward the metrology target; receiving, with two or more receiving micromirrors of the photonic integrated circuit, two or more diffracted orders of radiation from the metrology target; receiving, with one or more output waveguides of the photonic integrated circuit, the two or more diffracted orders of radiation from the two or more receiving micromirrors, and causing interference of the two or more diffracted orders of radiation in the photonic integrated circuit; and generating, with a radiation detector operatively coupled to the one or more output waveguides, a metrology signal based on the interfered two or more diffracted orders of radiation from the photonic integrated circuit, the metrology signal comprising measurement information pertaining to the metrology target.37. The method of clause 36, wherein there is an angular difference between the two or more diffracted orders of radiation.38. The method of any of the previous clauses, where the two or more diffracted orders of radiation comprise at least a positive and a negative diffracted order of radiation.39. The method of any of the previous clauses, wherein the two or more diffracted orders of radiationcomprise +1 and -1, +2 and -2, +3 and -3, +1 and +2, -1 and -2, 0 (zero-order reflection) and + or - 1 or 2 or 3, and / or -1 and +3 diffracted orders of radiation.40. The method of any of the previous clauses, wherein the metrology target comprises an alignment mark.41. The method of any of the previous clauses, wherein the photonic integrated circuit has a generally planar arrangement.42. The method of any of the previous clauses, wherein the one or more output waveguides form, form part of, or conduct the two or more diffracted orders of radiation to, a multimode interference device to cause the interference.43. The method of any of the previous clauses, wherein the two or more receiving micromirrors comprise two or more portions of a single larger receiving mirror.44. The method of any of the previous clauses, further comprising determining, with one or more processors operatively coupled to the radiation detector, a phase difference between the interfered orders of diffracted radiation based on the metrology signal.45. The method of any of the previous clauses, wherein: the radiation source, the photonic integrated circuit, and the radiation detector, form a portion of an alignment metrology system; and the alignment metrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor manufacturing process.46. The method of any of the previous clauses, wherein the radiation detector comprises a photodiode, and / or a charge coupled device (CCD).47. The method of any of the previous clauses, wherein the photonic integrated circuit comprises two or more photonic integrated circuits.48. The method of any of the previous clauses, wherein the two or more photonic integrated circuits comprise a first photonic integrated circuit arranged in an x-direction relative to the metrology target, and a second photonic integrated circuit arranged in a y-direction relative to the metrology target; and wherein the two or more photonic integrated circuits are formed in a same single chip, or in two different separate chips.49. The method of any of the previous clauses, wherein the two or more photonic integrated circuits comprise a plurality of photonic integrated circuits arranged to correspond to a plurality of metrology targets in the patterned substrate.50. The method of any of the previous clauses, wherein the plurality of photonic integrated circuits arranged to correspond to the plurality of metrology targets in the patterned substrate are configured for parallel performance of metrology on each of the plurality of metrology targets at the same time.51. The method of any of the previous clauses, further comprising adjusting a position of the photonic integrated circuit relative to the metrology target in the patterned substrate.52. The method of any of the previous clauses, wherein the position of the photonic integrated circuit relative to the metrology target in the patterned substrate is adjustable in an x, y, z, and / or rotationaldirection.53. The method of any of the previous clauses, wherein the photonic integrated circuit is sized based on a distance between the metrology target and the photonic integrated circuit, a wavelength of the radiation from the radiation source, and / or a period of the metrology target.54. The method of any of the previous clauses, wherein the photonic integrated circuit comprises a 15mm x 15mm or smaller chip.55. The method of any of the previous clauses, wherein the photonic integrated circuit comprises multiple circuits, each circuit in configured in terms of pitch, wavelength, orientation, and / or location for measuring a different metrology target.56. The method of any of the previous clauses, wherein a size of the photonic integrated circuit is similar to a size of a semiconductor wafer.57. The method of any of the previous clauses, further comprising propagating, with an input waveguide of the photonic integrated circuit, the radiation in the photonic integrated circuit toward the emitter, which focuses, shapes, and / or directs the radiation toward the metrology target.58. The method of any of the previous clauses, wherein each of the two or more receiving micromirrors comprises an elliptical micromirror, and the one or more output waveguides comprise waveguides that correspond to each elliptical micromirror, configured to collect the diffracted radiation and direct collected diffracted radiation toward the radiation detector.59. The method of any of the previous clauses, wherein a path length of the waveguides that correspond to each elliptical micromirror is the same prior to interfering the two or more diffracted orders of radiation in the photonic integrated circuit.60. The method of any of the previous clauses, wherein the two or more receiving micromirrors are positioned at locations on the photonic integrated circuit wherein the two or more diffracted orders of radiation are expected to impinge on the photonic integrated circuit.61. The method of any of the previous clauses, further comprising guiding, with a fiber edge coupled to the photonic integrated circuit, received interfered two or more diffracted orders of radiation to the radiation detector.62. The method of any of the previous clauses, wherein the metrology target comprises a grating.63. The method of any of the previous clauses, wherein the radiation source comprises a laser.64. The method of any of the previous clauses, wherein the radiation source is configured to be integrated close to an input waveguide in the photonic integrated circuit such that a mode of the radiation couples to the input waveguide.65. The method of any of the previous clauses, wherein the radiation source is configured to be integrated on a support structure proximate to the photonic integrated circuit where the radiation source abuts an input waveguide.66. The method of any of the previous clauses, wherein the radiation source is configured to be located remotely from the photonic integrated circuit, and a fiber is configured to conduct theradiation from the radiation source to the photonic integrated circuit.67. The method of any of the previous clauses, wherein the radiation from the radiation source directed toward the metrology target is broadband, comprising a plurality of wavelengths.68. The method of any of the previous clauses, wherein the photonic integrated circuit is arranged in a parallel orientation, in a plane substantially parallel to, a substrate with the metrology target.69. The method of any of the previous clauses, wherein the emitter comprises a mirror or micromirror.70. The method of any of the previous clauses, the emitter further comprising multiple emitting mirrors or micromirrors configured to generate structured illumination by interference.

[0131] 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.

[0132] While the concepts disclosed herein may be used for imaging and / or metrology 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 and / or metrology on substrates other than silicon wafers. In addition, the combination and sub-combinations of disclosed elements may comprise separate embodiments.

[0133] 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

CLAIMS1. A metrology system, comprising: a radiation source configured to generate radiation for irradiating a metrology target in a patterned substrate; a photonic integrated circuit operatively coupled to the radiation source, the photonic integrated circuit comprising: an emitter configured to direct the radiation from the radiation source toward the metrology target; two or more receiving micromirrors configured to receive two or more diffracted orders of radiation from the metrology target; and one or more output waveguides configured to receive the two or more diffracted orders of radiation from the two or more receiving micromirrors, and cause interference of the two or more diffracted orders of radiation in the photonic integrated circuit; and a radiation detector operatively coupled to the one or more output waveguides and configured to generate a metrology signal based on the interfered two or more diffracted orders of radiation from the photonic integrated circuit, the metrology signal comprising measurement information pertaining to the metrology target.

2. The system of claim 1 , wherein there is an angular difference between the two or more diffracted orders of radiation.

3. The system of claims 1 or 2, where the two or more diffracted orders of radiation comprise at least a positive and a negative diffracted order of radiation.

4. The system of any of claims 1-3, wherein the two or more diffracted orders of radiation comprise+1 and -1, +2 and -2, +3 and -3, +1 and +2, -1 and -2, 0 (zero-order reflection) and + or - 1 or 2 or 3, and / or -1 and +3 diffracted orders of radiation.

5. The system of any of claims 1-4, wherein the metrology target comprises an alignment mark.

6. The system of any of claims 1-5, wherein the photonic integrated circuit has a generally planar arrangement.

7. The system of any of claims 1-6, wherein the one or more output waveguides form, form part of, or conduct the two or more diffracted orders of radiation to, a multimode interference device to cause the interference.

8. The system of any of claims 1-7, wherein the two or more receiving micromirrors comprise two or more portions of a single larger receiving mirror.

9. The system of any of claims 1-8, further comprising one or more processors operatively coupled to the radiation detector, the one or more processors configured to determine a phase difference between the interfered orders of diffracted radiation based on the metrology signal.

10. The system of any of claims 1-9, wherein: the radiation source, the photonic integrated circuit, and the radiation detector, form a portion of an alignment metrology system; and the alignment metrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor manufacturing process.

11. The system of any of claims 1-10, wherein the radiation detector comprises a photodiode, and / or a charge coupled device (CCD).

12. The system of any of claims 1-11, wherein the photonic integrated circuit comprises two or more photonic integrated circuits.

13. The system of claim 12, wherein the two or more photonic integrated circuits comprise a first photonic integrated circuit arranged in an x-direction relative to the metrology target, and a second photonic integrated circuit arranged in a y-direction relative to the metrology target; and wherein the two or more photonic integrated circuits are formed in a same single chip, or in two different separate chips.

14. The system of claims 12 or 13, wherein the two or more photonic integrated circuits comprise a plurality of photonic integrated circuits arranged to correspond to a plurality of metrology targets in the patterned substrate.

15. The system of claim 14, wherein the plurality of photonic integrated circuits arranged to correspond to the plurality of metrology targets in the patterned substrate are configured for parallel performance of metrology on each of the plurality of metrology targets at the same time.

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