Patterning process assessment systems and methods

Abstract

Compact semiconductor manufacturing patterning process assessment (e.g., inspection, metrology, and / or other) systems and methods are described. For example, compact metrology systems for sensing multiple wavelengths and / or polarizations of diffracted radiation in parallel are described. These metrology systems may be configured for determining alignment and / or other semiconductor patterning process metrics. As another example, compact assessment systems configured to output multiple wavelengths of radiation in combination with charged particle beams (e.g., electron beams) are also described. These assessment systems may be used in voltage contrast defect inspection operations and / or other assessments. The assessment and / or metrology systems include a compact optical component comprising one or more planar photonic integrated circuits configured to emit (assessment systems) or receive (metrology systems) radiation. This optical component is used to form a significantly more compact assessment and / or metrology system, and / or has other advantages compared to prior systems.

Description

PATTERNING PROCESS ASSESSMENT SYSTEMS AND METHODSTECHNICAL FIELD

[0001] This description relates to patterning process assessment (e.g., metrology, inspection, and / or other related) systems and methods.BACKGROUND

[0002] 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.

[0003] 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.

[0004] Lithography is a central step in the manufacturing of device such as ICs, where patternsformed 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.

[0005] 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.

[0006] This process in which features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed, is commonly known as low-ki lithography, according to the resolution formula CD = ki / Z / NA. where Z 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).

[0007] Assessment (e.g., defect inspection, metrology, and / or other) systems are key to these fine tuning steps.SUMMARY

[0008] Compact semiconductor manufacturing patterning process assessment (e.g., inspection, metrology, and / or other) systems and methods are described. For example, compact metrology systems for sensing multiple wavelengths and / or polarizations of diffracted radiation in parallel are described. These metrology systems may be configured for determining alignment and / or other semiconductor patterning process metrics. As another example, other compact assessment systems configured to output multiple wavelengths of radiation in combination with charged particle beams (e.g., electron beams) are also described. These assessment systems may be used in voltage contrastdefect inspection operations, for example, and / or other assessments.

[0009] In some embodiments, an optical component of a metrology system comprises layers of collectors (or collector layers) each configured to collect diffracted radiation having a different wavelength (or wavelength range) from a metrology target. Wavelength or wavelength range, in practice, can refer to a certain bandwidth of wavelengths.

[0010] In some embodiments, the optical component comprises one or more planar photonic integrated circuits configured to receive diffracted radiation from the metrology target. The one or more planar photonic integrated circuits may be arranged in a perpendicular orientation relative to the metrology target, for example. The layers of collectors and / or the perpendicular orientation of the planar photonic integrated circuit facilitate parallel sensing of multiple different wavelengths and / or polarizations of diffracted radiation, dense stacking to form a significantly more compact patterning process sensor (e.g., an alignment sensor), and / or has other advantages compared to prior systems.

[0011] According to an embodiment, a metrology system is provided. The metrology system comprises a radiation source configured to irradiate a metrology target in a patterned substrate with radiation. The metrology system comprises an optical component comprising layers of collectors (or collector layers). The layers of collectors are each configured to collect diffracted radiation having a different wavelength range from the metrology target. The metrology system comprises a radiation detector configured to generate a metrology signal based on the diffracted radiation having the different wavelength ranges captured by the layers of collectors, and polarizations of the diffracted radiation. The metrology signal comprises measurement information pertaining to the metrology target.

[0012] In some embodiments, the collectors comprise dielectric grating couplers.

[0013] In some embodiments, the optical component comprises a photonic integrated circuit. The photonic integrated circuit comprises waveguides coupled to the grating couplers configured to conduct collected diffracted radiation toward the radiation detector.

[0014] In some embodiments, the optical component comprises a substrate, and at least two layers of dielectric grating couplers and waveguides. In some embodiments, the at least two layers of dielectric grating couplers and waveguides are stacked vertically in at least two different layers, substantially parallel to each other on the substrate, and each dielectric grating coupler and waveguide is optimized for a different wavelength range and / or polarization.

[0015] In some embodiments, the at least two layers of dielectric grating couplers and waveguides, and the substrate, are clad with silicon dioxide and / or a low index dielectric material.

[0016] In some embodiments, each of the layers of collectors is configured to collect diffracted radiation of different wavelength ranges and / or different polarizations.

[0017] In some embodiments, each of the layers of collectors is configured to collect diffracted radiation with specific polarizations, and / or orientations. An orientation of the diffracted radiation may comprise an X or Y orientation, and is dependent on a corresponding X or Y orientation of the metrology target.

[0018] In some embodiments, the collectors in each of the layers extend different distances, and / or are located at different distances, from an axis of the radiation from the radiation source in a given layer.

[0019] In some embodiments, the layers of collectors are each configured to collect diffracted radiation having a different wavelength range by adjusting a thickness of a layer of collectors; adjusting a stack for each layer; adjusting pitch and / or duty cycle of periodic structures in a layer of collectors; adjusting a curvature of the periodic structures; adjusting a separation between layers; determining and / or adjusting a material for each layer; forming one or more sub-layers of collectors in a given layer; and / or adjusting a distance of the optical component and / or a given layer to the metrology target in the patterned substrate.

[0020] In some embodiments, the system comprises an out-coupler coupled to one or more edges of the optical component and configured to conduct each of the different wavelength ranges of the collected diffracted radiation from the optical component to the radiation detector. In some embodiments, the out-coupler is configured to out-couple light from different facets of the optical component for each layer. In some embodiments, the out-coupler comprises one or more couplers for out-coupling one or more different wavelength ranges into a fiber. The one or more couplers may be grating couplers, for example, and need not be located at an edge of the optical component. In some embodiments, the out-coupler comprises a single fiber array configured to couple to an edge of the optical component. The edge of the optical component may be tapered to reduce a spacing between layers near the edge, for example.

[0021] In some embodiments, the different wavelength ranges overlap, and the layers of collectors are each optimized for a center of a given wavelength range. In some embodiments, each different wavelength range is associated with a different color and has a wavelength bandwidth for the associated color.

[0022] In some embodiments, the layers of collectors comprise 2-24 layers of collectors, and the layers of collectors are each configured to collect diffracted radiation having 2-24 different corresponding wavelength ranges. In some embodiments, there are 12 layers of collectors configured to collect diffracted radiation having 12 different corresponding wavelength ranges, for example.

[0023] In some embodiments, the system comprises one or more processors operatively coupled to the radiation detector. In some embodiments, the metrology target comprises an alignment mark.The one or more processors are configured to determine an alignment of a layer of the patterned substrate based on the metrology signal. In some embodiments, the radiation source, the optical component, and the radiation detector, form a portion of an alignment metrology system. In some embodiments, the alignment metrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor manufacturing process.

[0024] According to another embodiment, the metrology system again comprises the radiation source, the optical component, and the radiation detector. The radiation source is configured to irradiate the metrology target in the patterned substrate with radiation. In this embodiment, the optical component comprises one or more planar photonic integrated circuits configured to receive diffracted radiation from the metrology target. The one or more planar photonic integrated circuits are arranged in a perpendicular orientation relative to the metrology target. The radiation detector is configured to generate a metrology signal based on the diffracted radiation received by the one or more planar photonic integrated circuits. The metrology signal comprises measurement information pertaining to the metrology target.

[0025] In some embodiments, the radiation detector comprises an interferometer configured to interfere diffraction orders of received diffracted radiation, a photodiode, and / or a charge coupled device (CCD). In some embodiments, the radiation detector comprises multiple sensing devices operating in parallel.

[0026] In some embodiments, the one or more planar photonic integrated circuits comprise two or more planar photonic integrated circuits. The two or more planar photonic integrated circuits are arranged in the perpendicular orientation at two or more grid aligned positions relative to the metrology target. The perpendicular orientation at the two or more grid aligned positions is configured to facilitate dense stacking of the planar photonic integrated circuits.

[0027] In some embodiments, the radiation source comprises a fiber array edge coupled to an illumination source chip, a micro mirror or micro lens, and off axis parabolic mirrors. The fiber array is configured to conduct the radiation to the illumination source chip. The illumination source chip comprises a waveguide configured to propagate the radiation on the chip toward the micro mirror or micro lens and the off axis parabolic mirrors, which focus, shape, and / or direct the radiation toward the metrology target. In some embodiments, the illumination source chip is arranged in the perpendicular orientation relative to the metrology target, which is parallel to the two or more planar photonic integrated circuits.

[0028] In some embodiments, each of the planar photonic integrated circuits comprises one or more parabolic collector micro mirrors and one or more corresponding collector waveguides configured to collect the diffracted radiation and direct collected diffracted radiation toward theradiation detector. In some embodiments, the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise one parabolic collector micro mirror and one corresponding collector waveguide.

[0029] In some embodiments, each of the planar photonic integrated circuits further comprise an arrayed waveguide grating configured to demultiplex received diffracted radiation.

[0030] In some embodiments, the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise an array of parabolic collector micro mirrors and corresponding collector waveguides.

[0031] In some embodiments, the system comprises fibers edge coupled to each of the planar photonic integrated circuits configured to guide received diffracted radiation to the radiation detector.

[0032] In some embodiments, the one or more planar photonic integrated circuits comprise one planar photonic integrated circuit.

[0033] In some embodiments, the system comprises a fiber array edge coupled to the one planar photonic integrated circuit configured to receive and conduct the radiation from the radiation source to the one planar photonic integrated circuit. In some embodiments, the one planar photonic integrated circuit comprises a source waveguide or photonic crystal waveguide configured to conduct the radiation from the edge coupled fiber array through the one planar photonic integrated circuit and direct the radiation toward the metrology target.

[0034] In some embodiments, the one planar photonic integrated circuit comprises two elliptical mirrors and a beam combiner. The two elliptical mirrors are configured to reflect received diffracted radiation toward the beam combiner. The beam combiner is configured to combine received reflected diffracted radiation from the two elliptical mirrors such that the combined received reflected diffracted radiation is configured to be separated by a demultiplexer and signal processed.

[0035] In some embodiments, the one planar photonic integrated circuit comprises additional mirrors configured to fold a reflection path from the two elliptical mirrors to different angles relative to the beam combiner.

[0036] In some embodiments, the one planar photonic integrated circuit comprises a dispersion device configured to separate wavelengths of the received reflected diffracted radiation within the one planar photonic integrated circuit. In some embodiments, the dispersion device comprises a prism or an arrayed waveguide grating (AWG).

[0037] In some embodiments, the metrology target and the beam combiner are located at different foci of an ellipse associated with the two elliptical mirrors.

[0038] In some embodiments, the beam combiner comprises two beam combiners, and positive and negative orders of the received reflected diffracted radiation are each directed to a beam combiner fora corresponding diffraction order.

[0039] In some embodiments, the one planar photonic integrated circuit has a target thickness configured to facilitate propagation of the radiation within the one planar photonic integrated circuit.

[0040] In some embodiments, the system comprises an adjuster configured to adjust a distance between any two of the planar photonic integrated circuits. In some embodiments, the adjuster comprises an actuator between each two of the planar photonic integrated circuits. Each actuator is configured to independently adjust distances between each two of the planar photonic integrated circuits.

[0041] In some embodiments, the adjuster is configured to enable simultaneous measurement of a number of different metrology targets in a single field, without restriction on where the different metrology targets are located. A metrology target may comprise a grating, for example.

[0042] According to other embodiments, one or more metrology methods are provided. The one or more metrology methods comprise one or more of the operations described above performed by a metrology system.

[0043] According to another embodiment, an optical component for a charged particle optical system configured to direct a charged particle beam toward a sample location is provided. The optical component is configured to emit multiple optical beams of different wavelengths towards the sample location (though in some embodiments, the wavelengths may be the same or substantially overlapping, as described herein). The optical component comprises an optical stack having a plurality of emitter layers for emission of the multiple optical beams of different wavelengths towards the sample location. A first beam aperture is defined in the optical component for passage of the charged particle beam. Each of the plurality of emitter layers is configured to emit a respective optical beam of a respective wavelength towards the sample location.

[0044] In some embodiments, the optical stack having the plurality of emitter layers is configured to minimize beam distortion of the respective optical beams at the sample location.

[0045] In some embodiments, the plurality of emitter layers are configured to emit the respective optical beams such that the respective optical beams are substantially coincident at the sample location.

[0046] In some embodiments, each of the plurality of emitter layers comprises a respective emitter arrangement. The respective emitter arrangement is configured to emit the respective optical beam. In some embodiments, the respective emitter arrangement comprises a semi-periodic or periodic arrangement of emitter structures. The periodic or semi-periodic arrangement is configured to diffract optical radiation coupled into the respective emitter arrangement for emission of the respective optical beam. In some embodiments, each emitter arrangement is configured to minimize a furtherdiffraction of one or more diffraction orders associated with other emitter arrangements. In some embodiments, each emitter arrangement is configured to minimize diffraction of higher diffraction orders associated with the other emitter arrangements.

[0047] In some embodiments, a periodicity of the emitter structures in the emitter arrangement and / or a separation between each of the plurality of emitter layers is configured to minimize emission of higher orders of diffraction associated with the multiple optical beams, from one emitter layer to another emitter layer. The higher orders may comprise second, third, fourth, fifth, or higher diffraction orders. In some embodiments, each of the plurality of emitter layers is configured to minimize emission of a first order of diffracted radiation.

[0048] In some embodiments, the optical component comprises a photonic integrated circuit.

[0049] In some embodiments, the optical component is coupled to one or more optical sources for providing respective input optical radiation input into each of the plurality of emitter layers.

[0050] In some embodiments, the optical component comprises one or more waveguides configured to couple input optical radiation into each of the plurality of emitter layers.

[0051] In some embodiments, the respective optical beam emitted by each of the plurality of emitter layers has a component in a direction opposite to a direction of the respective optical radiation input.

[0052] In some embodiments, the emitter arrangements comprise grating couplers.

[0053] In some embodiments, the optical component comprises a silicon substrate, and at least two silicon nitride, aluminum oxide, lithium niobate, or quartz grating couplers and waveguides.

[0054] In some embodiments, at least two grating couplers and waveguides are stacked vertically in two or more different layers, substantially parallel to each other on the silicon substrate, and each grating coupler and waveguide is optimized for a different wavelength. In some embodiments, the at least two grating couplers and waveguides, and the silicon substrate, are clad with silicon dioxide.

[0055] In some embodiments, emitters in each of the plurality of emitter layers extend different distances, and / or are located at different distances, from an axis of a charged particle beam.

[0056] In some embodiments, the different wavelengths overlap, and the plurality of emitter layers are each optimized for a given wavelength. In some embodiments, the wavelengths are substantially the same.

[0057] In some embodiments, each different wavelength is associated with a different color and has a wavelength bandwidth for the associated color.

[0058] In some embodiments, a charged particle optical system configured to project a charged particle optical beam towards a sample location is provided. The charged particle optical system comprises the optical component, with the optical stack configured such that the multiple opticalbeams are substantially coincident with the charged particle beam at the sample location.

[0059] In some embodiments, the charged particle optical system is configured to project a plurality of charged particle optical beams towards the sample location. The optical component may comprise a plurality of first beam apertures for passage of the respective charged particle beams towards the sample location, and a plurality of optical stacks associated with each first beam aperture, for example. Each of the plurality of optical stacks is configured such that the multiple optical beams are substantially coincident with the charged particle beam at the sample location.

[0060] In some embodiments, an assessment system is provided. The assessment system comprises a charged particle optical source for generating one or more charged particle beams and the charged particle optical system. In some embodiments, the assessment system is a semiconductor assessment system that comprises at least a portion of scanning electron microscope. In some embodiments, the scanning electron microscope is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor defect inspection process.

[0061] According to other embodiments, one or more assessment related methods are provided. The one or more assessment related methods comprise one or more of the operations described above performed by an assessment system, a charged particle optical source, a charged particle optical system, an optical component, and / or other components.BRIEF DESCRIPTION OF THE DRAWINGS

[0062] 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.

[0063] Fig. 1 schematically depicts a lithography apparatus, according to an embodiment.

[0064] Fig. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.

[0065] Fig. 3 schematically depicts an example metrology system, according to an embodiment.

[0066] Fig. 4 schematically depicts an example metrology technique, according to an embodiment.

[0067] Fig. 5 illustrates the relationship between a radiation illumination spot of a metrology system and a metrology target, according to an embodiment.

[0068] Fig. 6 illustrates two representative views of diffracted radiation with overlapping wavelength ranges, according to an embodiment.

[0069] Fig. 7 illustrates an embodiment of an optical component configured to facilitate parallel sensing of multiple wavelengths and / or polarizations of incident diffracted radiation.

[0070] Fig. 8 illustrates a frequency response of the embodiment of the optical component shownin Fig. 7 as a function of working distance, according to an embodiment.

[0071] Fig. 9 graphically illustrates the Bragg condition for collectors of the optical component, according to an embodiment.

[0072] Fig. 10 illustrates a metrology method, according to an embodiment.

[0073] Fig. 11 illustrates another embodiment of the optical component.

[0074] Fig. 12 illustrates different possible embodiments of a one planar photonic integrated circuit (PIC) based optical component, according to an embodiment.

[0075] Fig. 13 illustrates side views of a two dimensional (2D) planar edge-coupled PIC, according to an embodiment.

[0076] Fig. 14 illustrates an embodiment of the optical component that comprises one or more adjusters configured to adjust a distance between any two planar PICs (photonic integrated circuits), according to an embodiment.

[0077] Fig. 15 illustrates another metrology method, according to an embodiment.

[0078] Fig. 16 is a schematic diagram of an exemplary assessment system, according to an embodiment.

[0079] Fig. 17 schematically depicts a multi-beam charged particle optical system, for example of the assessment system of Fig. 16, according to an embodiment.

[0080] Fig. 18 schematically depicts another potential embodiment of a multi-beam charged particle optical system, for example of the assessment system of Fig. 16, according to an embodiment.

[0081] Fig. 19 schematically depicts an alternative multi-beam charged particle optical system, for example of the assessment system of Fig. 16, according to an embodiment.

[0082] Fig. 20 is a schematic cross-sectional view of a planar optical component incorporated in a charged particle optical system (such as one of those shown as part of a multi-beam charged particle optical system shown in Fig. 16-19), according to an embodiment.

[0083] Fig. 21 is a schematic cross-sectional view of another planar optical component incorporated in a charged particle optical system, according to an embodiment.

[0084] Fig. 22 is a schematic cross-sectional view of another planar optical component incorporated in a charged particle optical system, according to an embodiment.

[0085] Fig. 23 illustrates another embodiment of an assessment system, which has similar and / or the same components as those described above for the assessment systems shown in Fig. 16-22, comprising a compact optical component configured to emit radiation such as optical beams, according to an embodiment.

[0086] Fig. 24 provides a Fourier optics description of diffraction between emitter layers, according to an embodiment.

[0087] Fig. 25 illustrates an assessment method, according to an embodiment.

[0088] Fig. 26 is a block diagram of an example computer system, according to an embodiment.DETAILED DESCRIPTION

[0089] As described above, compact semiconductor manufacturing patterning process assessment (e.g., inspection, metrology, and / or other) systems and methods are described. These systems include a compact optical component comprising one or more planar photonic integrated circuits configured to emit (e.g., in inspection systems) or receive (e.g., in metrology systems) radiation. This optical component is used to form a significantly more compact system, and / or has other advantages compared to prior systems.

[0090] 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.

[0091] 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 PIC, it is possible to achieve a reduction in sensor size compared to sensor sizes in prior systems because the PIC can replace the high-numerical aperture objectives typically used to collect diffracted radiation. Grating couplers are often used for receiving diffracted radiation from a metrology mark into a PIC. However, a grating coupler can only be configured to receive a small range of wavelengths of the diffracted radiation, and typically has a very narrow capturing angle range (e.g., radiation has to be coming from a certain angle to be received by the grating coupler). Generally speaking, grating couplers are designed for one color, and one polarization.

[0092] 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 PIC / grating coupler based metrology systems are only configured to process a small number of wavelengths, often with only one polarization. Scaling a PIC / grating coupler 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. As another example, current sensor technologies do not allow stacking 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. In addition, a significant fraction of diffracted radiation for certain wavelength ranges overlaps. This hinders efficient capturing of all wavelength ranges (e.g., the twelve different color wavelength ranges) with a PIC / grating coupler based metrology system.

[0093] Advantageously, in the present systems and methods, a newly designed compact optical component for a metrology system is used to extend the functionality of typical PICs to facilitate parallel sensing of multiple wavelengths and / or polarizations.

[0094] In some embodiments, different grating couplers (or collectors as described below) are located in different layers of the optical component (e.g., designed to capture diffracted radiation associated with a specific numerical aperture of the metrology system and wavelength of the diffracted radiation) to divide a pupil space of the metrology system, and overcome difficulties caused by overlapping diffraction order wavelength ranges. The mark pitch defines the diffraction angle: sin(0) = A / P and NA is also defined as sin(0). If the pitch is large (NA is small) different colors start to overlap with each other in the pupil plane (where the photonic chips are located). If grating couplers for different colors are located in different layers, the pupil is divided, and overlap is avoided.

[0095] In some embodiments, the optical component comprises one or more planar PICs arranged in a perpendicular orientation relative to the metrology target, configured to receive diffracted radiation in that perpendicular orientation. The perpendicularly stacked vertical PIC based system facilitates densely stacked multiple sensors, allowing for parallel grid aligned metrology mark measurements, and / or has other advantages.

[0096] 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 and assessment. These systems and methods may be used for defect inspection; measuring alignment, overlay, etc.; in a semiconductor device manufacturing process, for example, or for other operations.

[0097] Although specific reference may be made in this text to the measurement of alignment or other parameters, defect inspection, and / or other operations, 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.

[0098] The term “projection optics” should be broadly interpreted as encompassing various types of optical systems, including refractive optics, reflective optics, apertures and catadioptric optics, for example. The term “projection optics” may also include components operating according to any of these design types for directing, shaping or controlling the projection beam of radiation, collectively or singularly. The term “projection optics” may include any optical component in the lithographic projection apparatus, no matter where the optical component is located on an optical path of the lithographic projection apparatus. Projection optics may include optical components for shaping, adjusting and / or projecting radiation from the source before the radiation passes the patterning device, and / or optical components for shaping, adjusting and / or projecting the radiation after the radiation passes the patterning device. The projection optics generally exclude the source and the patterning device.

[0099] 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).

[0100] 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.

[0101] The illuminator IL may alter the intensity distribution of the beam. The illuminator may bearranged to limit the radial extent of the radiation beam such that the intensity distribution is non-zero within an annular region in a pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in a pupil plane of the illuminator IL may be referred to as an illumination mode.

[0102] 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.

[0103] 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 modemay 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.

[0104] In addition, the illuminator IL generally comprises various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation. Thus, the illuminator provides a conditioned beam of radiation B, having a desired uniformity and intensity distribution in its cross section.

[0105] 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.”

[0106] 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.

[0107] 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.

[0108] The term “projection system” should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic andelectrostatic 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.”

[0109] The projection system PS may comprise a plurality of optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations across the pupil plane throughout the field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a coordinate system 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.

[0110] 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.

[0111] 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 aspace 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.

[0112] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Fig. 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0113] 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 isprojected 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.

[0114] Combinations and / or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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 / O 1 , 1 / 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.

[0119] In order that a substrate that is exposed by the lithographic apparatus is exposed correctly and consistently and / or in order to monitor a part of the patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties such as alignment, overlay (which can be, for example, between structures in overlying layers or between structures in a same layer that have been provided separately to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, a material property, etc. Accordingly, a manufacturing facility in which lithocell LC is located also typically includes a metrology system that measures some or all of the substrates W (Fig. 1) that have been processed in the lithocell or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example it may be part of the lithographic apparatus LA (such as alignment sensor AS (Fig. 1)).

[0120] 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.

[0121] 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 propertiesof 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).

[0122] Thus, in a device fabrication process (e.g., a patterning process or a lithography process), a substrate or other objects may be subjected to various types of measurement during or after the process. The measurement may determine whether a particular substrate is defective, may establish adjustments to the process and apparatuses used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and the apparatuses, or may be for other purposes. Examples of measurement include optical imaging (e.g., optical microscope), non-imaging optical measurement (e.g., measurement based on diffraction such as the ASML YieldStar metrology tool, the ASML SMASH metrology system), mechanical measurement (e.g., profiling using a stylus, atomic force microscopy (AFM)), and / or non- optical imaging (e.g., scanning electron microscopy (SEM)).

[0123] Metrology results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, an adjustment may be made to exposure of a subsequent substrate (especially if the inspection can be done soon and fast enough that one or more other substrates of the batch are still to be exposed) and / or to subsequent exposure of the exposed substrate. Also, an already exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding performing further processing on a substrate known to be faulty. In a case where only some target portions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications. Other manufacturing process adjustments are contemplated.

[0124] 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.

[0125] 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 moreperiodic 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).

[0126] 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, radiation 6 comprises one or more optical (e g., visible and / or non- visible light radiation) bearns having one or more wavelengths. 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 optical components 8 may be used to direct radiation to and / or receive diffracted radiation 12 from a metrology target 30 on substrate W.

[0127] 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.

[0128] 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.

[0129] 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).

[0130] 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.

[0131] 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.

[0132] For example, the measured data from metrology target 30 may indicate alignment for a layer of a semiconductor device. The measured data from target 30 may be used (e.g., by the one or more processors 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 positionadjustment, 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.

[0133] 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.

[0134] As described above, in diffracted radiation from a metrology target (such as target 30 shown in Fig. 3 and Fig. 5), a significant fraction of diffracted radiation for certain wavelength ranges overlaps. This hinders efficient capturing and / or detection of all wavelength ranges (e.g., twelve different color wavelength ranges) with prior metrology systems. Advantageously, in the present systems and methods, a newly designed compact optical component is used to extend the functionality of typical systems to facilitate parallel sensing of multiple wavelengths and / or polarizations, as described below.

[0135] For example, Fig. 6 illustrates two representative views 600 and 602 of diffracted radiation with overlapping wavelength ranges 604. Overlapping wavelength ranges 604 are shown in an X - Y dimensional plane. Views 600 and 602 comprise top views of diffracted radiation from a metrology target (e.g., target 30 shown in Fig. 3) propagating upward away from the X-Y dimensional plane. View 600 illustrates an area associated with a grating coupler for each wavelength incident on a photonic integrated circuit (PIC), as described below. The circles 610 represent illumination beams, and the ellipses on the right and left represent +1 and -1 diffracted radiation beams, respectively. In this example, 12 ellipses representing different colors are illustrated. As shown in view 600, a significant fraction of diffracted radiation for at least two or three colors overlap with each other. This hinders efficient capturing of all 12 colors with atypical single layer PIC / grating coupler based sensor. View 602 illustrates diffracted radiation from an obliquely illuminated (e.g., circles 610 are shifted 612 relative to an axis of the various ellipses) metrology target. Again here, a mode overlap of twelve colors is shown. Oblique illumination enables separation of orders by giving each wavelengtha different angle. For the example illustrated in Fig.6, there may not be a large difference between on- and off-axis illumination in functionality. However, in some embodiments, there may be multiple off- axis illumination spots, the different wavelengths divided across these illumination spots to reduce the overlap.

[0136] Fig. 7 illustrates an embodiment 700 of optical component 8 (also see Fig. 3) configured to facilitate parallel sensing of multiple wavelengths (Ai, A2, and A3 in this example) and / or polarizations of incident diffracted radiation 702. In this example, incident diffracted radiation 702 has been diffracted by a metrology target such as target 30 shown in Fig. 3. In Fig. 7, additional detail is illustrated for optical component 8 compared to the illustration of optical component 8 in system 10 shown in Fig. 3. In some embodiments, optical component 8 forms a portion of an alignment sensor that is used in a semiconductor manufacturing process, for example.

[0137] Embodiment 700 of optical component 8 comprises layers of collectors 704, 706, and 708 (or collector layers). Three layers of collectors are shown in this example, but other quantities of layers of collectors are contemplated. The layers of collectors 704, 706, and 708 are each configured to collect diffracted radiation having a different wavelength or wavelength range from a metrology target (e.g., target 30 shown in Fig. 3 - note that optical component 8 is shown upside down in Fig. 7 relative to how optical component 8 is shown in Fig. 3). As described above, a radiation source (such as source 2 shown in Fig. 3) irradiates a metrology target (such as target 30 shown in Fig. 3) in a patterned substrate (such as substrate W shown in Fig. 3) with radiation (such as radiation 6 shown in Fig. 3) such that the metrology target diffracts and / or otherwise directs diffracted radiation toward optical component 8. The radiation may comprise illumination such as light and / or other radiation.

[0138] Fig. 7 schematically illustrates a side view of the layers of collectors 704, 706, and 708. For simplicity, Fig. 7 only illustrates how diffracted radiation 702 is coupled into collectors 704, 706, and 708. The routing, interfering, and out-coupling for each layer may be the same as or similar to the routing, interfering, and out-coupling in other PICs. Optical component 8 and layers of collectors 704, 706, and 708 address several potential issues with collecting radiation in this way, including: (1) distortion of a collector mode by a layer above it (note that “above”, “top”, “bottom”, “below”, etc., are relative terms used here for clarity, but Fig. 7 could easily have been drawn in an alternate orientation); (2) cross-talk, or the coupling of a specific wavelength to the top or the bottom layer or the light coupling into an undesired collector in a different layer; (3) out-coupling of collected radiation from different layers; (4) distortion of a collector mode because of the top collectors positioned above that collector in the layers; and / or other issues.

[0139] Each layer of collectors of embodiment 700 of optical component 8 collects diffractedradiation 702 having a different wavelength range from the metrology target. In some embodiments, each different wavelength range is associated with a different color and has a wavelength bandwidth for the associated color. As described above, the different wavelength ranges overlap. The layers of collectors 704, 706, 708 are each optimized for a center of a given wavelength range and / or may have other configurations. Each of the layers of collectors 704, 706, 708 is configured to collect diffracted radiation of different wavelength ranges and / or different polarizations, configured to collect diffracted radiation with specific polarizations, and / or configured to collect diffracted radiation with different orientations. For example, an orientation of the diffracted radiation may comprise an X or Y orientation, and may be dependent on a corresponding X or Y orientation of the metrology target.

[0140] In some embodiments, the collectors 704, 706, 708 in each of the layers extend different distances, and / or are located at different distances (di, d2, and ds, in the example in Fig. 7), from an axis 750 of the radiation from the radiation source in a given layer. These distances correspond to the locations of the different wavelengths or wavelength ranges of diffracted radiation on the X-Y dimensional planes shown in Fig. 6, for example. This ensures that a certain collector is located to collect a specific wavelength or wavelength range of diffracted radiation. This arrangement enhances the ability of a given collector to collect a specific wavelength or wavelength range of diffracted radiation, and / or has other advantageous effects. For example, if three wavelengths overlap with each other, it may be preferred to put the collector for the longer wavelength at the bottom of the structure to reduce the distortion of the mode by the top layers. Also, different layers can be used to capture the same wavelength but different polarizations. Another advantage is that layer stacks can be optimized for those specific wavelengths and polarizations. Further, the layers of collectors may be configured to collect diffracted radiation having a different wavelength or wavelength range by adjusting a thickness of a layer of collectors (one example thickness t is shown in Fig. 7); adjusting a stack for each layer (e.g., the thickness of layers, the etch depth, single versus double layer: these things can be optimized depending on what wavelength range or polarization is associated with each layer); adjusting pitch and / or duty cycle of periodic structures in a layer of collectors (one example pitch or duty cycle p is shown in Fig. 7); adjusting a curvature of the periodic structures; adjusting a separation between layers; determining and / or adjusting a material for each layer; forming one or more sublayers of collectors in a given layer; adjusting a distance of the optical component and / or a given layer to the metrology target in the patterned substrate; and / or using other operations.

[0141] Embodiment 700 of optical component 8 may comprise a PIC. Collectors 704, 706, 708 may comprise dielectric grating couplers and / or other collectors, for example. The PIC may comprise waveguides 724, 726, 728 coupled to the grating couplers and / or other components configured to conduct (as indicated by the arrows pointing to the left in Fig. 7) collected diffracted radiation 702toward a radiation detector (such as detector 4 shown in Fig. 3, so that a corresponding signal can be processed by processor PRO). In some embodiments, embodiment 700 of optical component 8 comprises a substrate 780, and at least two layers of dielectric grating couplers and waveguides (though three layers of dielectric grating couplers and waveguides are shown in Fig. 7). The at least two layers of dielectric grating couplers and waveguides may be stacked vertically in at least two different layers, substantially parallel to each other on substrate 780 (e.g., as shown in Fig. 7). Each dielectric grating coupler and waveguide may be optimized for a different wavelength range and / or polarization (as described above). In some embodiments, the at least two layers of dielectric grating couplers and waveguides, and substrate 780, are clad (e.g., as shown in Fig. 7) with silicon dioxide (SiO2), a low index dielectric material, and / or other materials. In some embodiments, substrate 780 may be silicon or silicon based, and / or other materials. In some embodiments, waveguides 724, 726, and / or 728 are formed from silicon nitride (SiN) and / or other materials.

[0142] In some embodiments, the structures and / or the materials used in optical component 8 may be configured such that an index contrast between the waveguides (e.g., SiN) and the surrounding (SiO2) is low and the coupler thickness is much shorter than the operating wavelength. Cross talk between layers can be reduced significantly by using layers with different parameters (e.g., different materials, different thicknesses, etc., as described herein), increasing the spacing between the two layers, and / or using other techniques.

[0143] In some embodiments, the layers of collectors 704, 706, 708 comprise 2-24 layers of collectors, for example. The layers of collectors 704, 706, 708 are each configured to collect diffracted radiation having 2-24 different corresponding wavelength ranges and / or polarizations. In one representative embodiment, there may be 12 layers of collectors configured to collect diffracted radiation having 12 different corresponding wavelength ranges, for example.

[0144] In some embodiments, an out-coupler 790 is coupled to one or more edges of optical component 8 and configured to conduct each of the different wavelength ranges (Ai, A2, and A3 in this example) and / or polarizations of the collected diffracted radiation 702 from optical component 8 to the radiation detector (e.g., detector 4 shown in Fig. 3). Out-coupler 790 is configured to out-couple light from different facets of optical component 8 for each layer. In some embodiments, out-coupler 790 comprises one or more grating couplers for out-coupling one or more different wavelength ranges into a fiber, out-couplers for butt-coupling from the waveguides into fibers, and / or other components. Note that the one or more grating couplers need not be located at an edge of optical component 8. In some embodiments, out-coupler 790 comprises a single fiber array configured to couple to an edge of optical component 8. The edge of optical component 8 may be tapered and / or have other shapes configured to reduce a spacing between layers near the edge, for example.

[0145] If collectors 704, 706, and / or 708 have different thicknesses (t) or heights, the edge out- coupling may be challenging, because the height of an fiber groove can be optimized only for one layer. To avoid this, optical component 8 can be configured to out-couple light from different facets of the PIC for each layer. Grating couplers can also be used for out-coupling radiation into a fiber. Also, because the waveguides 724, 726, and / or 728 can be separated to avoid overlap near an edge, the spacing between the layers near the edge can be tapered, which reduces the separation between the layers near the edge, so that one fiber array can be used to out-couple radiation for multiple and / or all layers.

[0146] As described above, the radiation detector (e.g., detector 4 shown in Fig. 3) generates a metrology signal based on the diffracted radiation 702 having the different wavelength ranges (Ai, A2, and A3) captured by the layers of collectors 704, 706, 708, polarizations of diffracted radiation 702, and / or other information. The metrology signal comprises measurement information pertaining to the metrology target (e.g., target 30 described above). In some embodiments, the radiation detector comprises an interferometer configured to interfere diffraction orders of received diffracted radiation, 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, 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.

[0147] Fig. 8 illustrates a frequency response 800 of embodiment 700 of optical component 8 as a function of the working distance (h) - the distance between metrology target 30 and optical component 8 (e.g., as show in Fig. 3). Frequency response 800 is shown on a coupling efficiency 802 versus wavelength 804 (nm) scale. One or more collectors (e.g., collectors 704, 706, and / or 708 shown in Fig. 7) behave as a band-pass filter. By engineering the mode of the collector or changing the working distance, the coupling of neighboring colors (a wavelength or wavelength range as described above) can be reduced without needing extra filtering or demultiplexing. Collectors 704, 706, and / or 708 (e.g., grating couplers) shown in Fig. 7 are frequency selective by nature. Each collector is designed to capture a specific wavelength 810, and the capturing efficiency drops 820 exponentially as the operating wavelength is shifted from the designed wavelength of the collector.

[0148] Fig. 9 graphically illustrates the Bragg condition for two collectors 900 and 902 (which may be similar to and / or the same as collectors 704, 706, and / or 708 shown in Fig. 7). It is seen that the mode emitting in the desired direction is transmitted without a change in the spatial Fourier domain, and it only adds an extra phase to the main beam because of the Oth order transmission through the top layer but the beam profile is not impacted. However, a secondary beam is generated toward the mainbeam. If the period of the two gratings are the same, they propagate in the same direction, but if the period of the two gratings are different, their illumination angle is slightly different. For apodized grating couplers (grating couplers with varying periodicity and duty cycle), the overlap of the secondary beam with the main beam is reduced as the working distance increases. In Fig. 9, A is the periodicity or the unit cell size of each grating; neff is the effective index of the guided mode in each layer and ft is the propagation constant; and m is an integer (and the equations are showing the Bragg condition).

[0149] If two layers of collectors are used (e.g., as shown in Fig. 9) to capture two different polarizations, the overlapping between the main beam and secondary beam can be significant because the wavelength and the capturing angle is the same for both collectors. However, if the layers of collectors are configured such that that there is a large difference between the effective index of the two collectors, the pitch for the two layers of collectors can be large enough to avoid the overlap of the main and the secondary beam at the substrate (e.g., semiconductor wafer) location.

[0150] Secondary beams can be suppressed completely, if subwavelength gratings are used, so only the beam with a wave vector of / ? - 4TT / A can leak, so it cannot be diffracted by the top collectors.

[0151] The collector structure (grating structure in this example) adds wave-vectors to the propagation constant of the waveguide mode. Only one or two of these modes which have a wavevector less than the wave number in vacuum (ft < ko) can leak, and the rest are evanescent fields and stay inside the waveguide. The top collector 900 also adds extra wave-vectors, and two extra beams are generated. If the pitch of the two collectors 900 and 902 are the same, the two beams copropagate, but if the pitch is different, secondary beams are generated.

[0152] Fig. 10 illustrates a metrology method 1000. In some embodiments, method 1000 is performed as part of an alignment sensing operation in a semiconductor device manufacturing process, for example. In some embodiments, one or more operations of method 1000 may be implemented in or by system 10 illustrated in Fig. 3, optical component 8 illustrated in Fig. 3 and Fig.7, a computer system (e.g., as illustrated in Fig. 26 and described below), and / or in or by other systems, for example. In some embodiments, method 1000 comprises irradiating (operation 1002) a metrology target in a patterned substrate with radiation; collecting (operation 1004) diffracted radiation from the metrology target (with an optical component comprising layers of collectors); generating (operation 1006) a metrology signal; and determining (operation 1008) alignment of a layer of the patterned substrate based on the metrology signal.

[0153] The operations of method 1000 are intended to be illustrative. In some embodiments,method 1000 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 1000 may include an additional operation comprising determining an adjustment for a semiconductor device manufacturing process. Additionally, the order in which the operations of method 1000 are illustrated in Fig. 10 and described herein is not intended to be limiting.

[0154] In some embodiments, one or more portions of method 1000 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 1000 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 1000 (e.g., see discussion related to Fig. 26 below).

[0155] At operation 1002, a radiation source irradiates a metrology target in a patterned substrate with radiation. The radiation comprises light and / or other radiation. The radiation may be generated by the radiation source (e.g., source 2 shown in Fig. 3). In some embodiments, the radiation may be directed by the radiation source onto multiple targets, a single target, sub-portions (e.g., something less than the whole) of a target, and / or onto a substrate in other ways. In some embodiments, the radiation may be directed by the radiation source 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 (e.g., in other layers), and / or other analysis. In some embodiments, operation 1002 is performed by a radiation source similar to and / or the same as radiation source 2 shown in Fig. 3 and described above.

[0156] At operation 1004, each layer of collectors of an optical component collects diffracted radiation having a different wavelength range from the metrology target. Each different wavelength range is associated with a different color and has a wavelength bandwidth for the associated color. As described above, the different wavelength ranges overlap. The layers of collectors are each optimized for a center of a given wavelength range. Each of the layers of collectors is configured to collect diffracted radiation of different wavelength ranges and / or different polarizations, configured to collectdiffracted radiation with specific polarizations, and / or configured to collect diffracted radiation with different orientations. For example, an orientation of the diffracted radiation may comprise an X or Y orientation, and may be dependent on a corresponding X or Y orientation of the metrology target.

[0157] In some embodiments, the collectors in each of the layers extend different distances, and / or are located at different distances, from an axis of the radiation from the radiation source in a given layer. The layers of collectors may be configured to collect diffracted radiation having a different wavelength range by adjusting a thickness of a layer of collectors; adjusting a stack for each layer; adjusting pitch and / or duty cycle of periodic structures in a layer of collectors; adjusting a curvature of the periodic structures; adjusting a separation between layers; determining and / or adjusting a material for each layer; forming one or more sub-layers of collectors in a given layer; adjusting a distance of the optical component and / or a given layer to the metrology target in the patterned substrate; and / or using other operations.

[0158] The optical component may comprise a PIC. The collectors may comprise dielectric grating couplers and / or other collectors, for example. The PIC may comprise waveguides coupled to the grating couplers and / or other components configured to conduct collected diffracted radiation toward a radiation detector.

[0159] In some embodiments, the optical component comprises a substrate, and at least two layers of dielectric grating couplers and waveguides. The at least two layers of dielectric grating couplers and waveguides may be stacked vertically in at least two different layers, substantially parallel to each other on the substrate. Each dielectric grating coupler and waveguide may be optimized for a different wavelength range and / or polarization. In some embodiments, the at least two layers of dielectric grating couplers and waveguides, and the substrate, are clad with silicon dioxide, a low index dielectric material, and / or other materials.

[0160] In some embodiments, the layers of collectors comprise 2-24 layers of collectors, for example. The layers of collectors are each configured to collect diffracted radiation having 2-24 different corresponding wavelength ranges. In one representative embodiment, there may be 12 layers of collectors configured to collect diffracted radiation having 12 different corresponding wavelength ranges, for example.

[0161] In some embodiments, an out-coupler is coupled to one or more edges of the optical component and configured to conduct each of the different wavelength ranges of the collected diffracted radiation from the optical component to the radiation detector. The out-coupler is configured to out-couple light from different facets of the optical component for each layer. In some embodiments, the out-coupler comprises one or more grating couplers for out-coupling one or more different wavelength ranges into a fiber. Note that the one or more grating couplers need not belocated at an edge of the optical component. In some embodiments, the out-coupler comprises a single fiber array configured to couple to an edge of the optical component. The edge of the optical component may be tapered and / or have other shapes configured to reduce a spacing between layers near the edge, for example. In some embodiments, operation 1004 is performed by an optical component similar to and / or the same as optical component 8 shown in Fig. 3 and Fig. 7, and described above.

[0162] At operation 1006, the radiation detector generates a metrology signal based on the diffracted radiation having the different wavelength ranges captured by the layers of collectors, polarizations of the diffracted radiation, and / or other information. 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, a photodiode, a charge coupled device (CCD), and / or other components. The radiation detector may comprise multiple sensing devices operating in parallel, for example.

[0163] In some embodiments, operation 1006 comprises detecting diffracted radiation (with the radiation detector described above) from one or more diffraction grating targets. Detecting reflected 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.

[0164] 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.

[0165] In some embodiments, operation 1006 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 onradiation 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.

[0166] 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 1006 may be performed by a radiation detector similar to and / or the same as detector 4 shown in Fig. 3, and described herein.

[0167] At operation 1008, 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 optical component, 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 1008 may be performed by one or more processors similar to and / or the same as processors PRO shown in Fig. 3 and Fig. 26, and described herein.

[0168] In some embodiments, operation 1008 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 focus position so that a subsequent image of the substrate is in focus. In some embodiments, operation 1008 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 valueindicated 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.

[0169] 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. 26 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.

[0170] 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 1008), for example. In some embodiments, operation 1008 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.

[0171] Fig. 11 illustrates another embodiment 1100 of optical component 8 (also see Fig. 3). In embodiment 1100, optical component 8 comprises one or more planar and perpendicularly oriented PICs 1112 configured to receive diffracted radiation 1102 from metrology target 30. The one or moreplanar PICs 1112 are arranged in a perpendicular orientation relative to metrology target 30. Embodiment 1100 of optical component 8 facilitates stacking of multiple sensor elements (sensor elements 1101, 1103, 1105, and 1107 in this example) in a dense configuration (compared to prior metrology systems) for parallel measurement of diffracted radiation of (e.g., twelve) different colors at long (e.g., about 3mm) working distances. Embodiment 1100 is configured to facilitate parallel sensing of multiple wavelengths and / or polarizations of diffracted radiation 1102. In this example, diffracted radiation 1102 is diffracted by a metrology target such as target 30. In Fig. 11, additional detail is illustrated for optical component 8 compared to the illustration of optical component 8 in system 10 shown in Fig. 3. In some embodiments, embodiment 1100 of optical component 8 forms a portion of an alignment sensorthat is used in a semiconductor manufacturing process, for example.

[0172] In some embodiments, a radiation source (e.g., source 2 shown in Fig. 3) irradiates metrology target 30 in a patterned substrate (e.g., such as substrate W shown in Fig. 3) with radiation 1110. Radiation 1110 comprises light and / or other radiation. Radiation 1110 may be generated by the radiation source (e.g., source 2 shown in Fig. 3). In some embodiments, the radiation source in combination with one or more lenses, mirrors, waveguides, and / or other components may generate radiation 1110 and direct radiation 1110 toward optical component 8. In some embodiments, one or more portions of the radiation source may be formed by optical component 8 itself, in optical component 8, and / or on optical component 8. For example, in some embodiments, the radiation source and / or optical component 8 comprises a fiber array 1120 edge coupled to an illumination source chip 1122, a micro mirror or micro lens, a waveguide 1124, one or more (e.g., off axis) parabolic and / or other shaped mirrors 1126, and / or other components. Fiber array 1120 is configured to conduct radiation 1110 to illumination source chip 1122. Illumination source chip 1122 comprises (broadband) waveguide 1124 configured to propagate radiation 1110 on chip 1122 toward the micro mirror or micro lens and the off axis parabolic mirrors 1126, which focus, shape, and / or direct radiation 1110 toward metrology target 30. Illumination source chip 1122 may also be arranged in the perpendicular orientation relative to the metrology target, which is parallel to the planar PICs (e.g., as shown in Fig. 11). Oblique illumination (radiation 1110) goes through diffraction to be detected via the adjacent PIC(s) 1112 that is / are parallel to illumination source chip 1122.

[0173] In some embodiments, the one or more planar PICs 1112 comprise two or more PICs 1112 (see Fig. 11). The two or more planar PICs 1112 may be arranged in the perpendicular orientation at two or more grid aligned positions relative to metrology target 30. The perpendicular orientation at the two or more grid aligned positions is configured to facilitate dense stacking of planar PICs 1112, and / or have other advantages.

[0174] Each of the planar PICs 1112 may comprise one or more collector mirrors 1150 and / or other components (e.g., a sort of refractive element such as a lens could be used as well, although they have chromatic aberration). The one or more collector mirrors 1150 may comprise parabolic collector micro mirrors, for example, and / or other mirrors. Each planar PIC 1112 may comprise one or more corresponding collector waveguides 1152, and / or other components configured to collect diffracted radiation 1102 and direct collected diffracted radiation 1102 toward the radiation detector (e.g., toward detector 4 shown in Fig. 3). The one or more collector mirrors 1150 are configured to collect diffracted radiation 1102 into a collector waveguide 1152, for example.

[0175] In one representative embodiment, the one or more parabolic collector micro mirrors 1150 and the one or more corresponding collector waveguides 1152 may comprise one parabolic collector micro mirror 1150 and one corresponding collector waveguide 1152, for example. In some embodiments, the one or more parabolic collector micro mirrors 1150 and the one or more corresponding collector waveguides 1152 comprise an array of parabolic collector micro mirrors 1150 and corresponding collector waveguides 1152. In some embodiments, each of the planar PICs 1112 comprises an arrayed waveguide grating 1160 (AWG) configured to demultiplex received diffracted radiation. In some embodiments, fibers are edge coupled with an out-coupler 1170 to each of the planar PICs 1112, and configured to guide received diffracted radiation 1102 to the radiation detector.

[0176] In some embodiments, the one or more planar PICs 1112 of optical component 8 comprise one planar PIC. For example, Fig. 12 illustrates different possible embodiments 1200, 1202, and 1206 of a one planar PIC 1250 based optical component 8. In these embodiments, a fiber array 1210 and / or other structures may be edge coupled (and / or coupled in other ways) to the one planar PIC 1250 and configured to receive and conduct radiation 1260 (which is similar to and / or the same as radiation 1110 described above) from the radiation source (e.g., source 2 shown in Fig. 3) to the one planar PIC 1250, for example. Note that in the example shown in Fig. 6, fiber array 1210 sends the light (radiation) to the metrology target, rather than to the PIC 1250. Though it is indeed possible that fiber array 1210 conducts light from the source to the PIC and another element on the PIC guides the radiation towards the metrology target. In some embodiments, the one planar PIC 1250 comprises a source waveguide, photonic crystal waveguide, and / or other components configured to conduct radiation 1260 from the edge coupled fiber array through the one planar PIC 1250 and direct radiation 1260 toward metrology target 30. The one planar PIC 1250 may have a target thickness and / or other characteristics configured to facilitate propagation of the radiation within the one planar PIC 1250, for example.

[0177] In embodiments such as embodiment 1200, the one planar PIC 1250 comprises two elliptical mirrors 1270, a beam combiner 1272, and / or other components. Metrology target 30 andbeam combiner 1272 may be located at different foci of an ellipse 1274 (note that ellipse 1274 is drawn in each planar PIC 1250 in Fig. 12 for ease of understanding, but is not present in the physical system) associated with the two elliptical mirrors 1270. The two elliptical mirrors 1270 are configured to reflect received diffracted radiation 1280 toward beam combiner 1272. Plus and minus first order diffracted radiation 1280 may be received and reflected by each elliptical mirror 1270, respectively (e.g., as shown by the +1 and -1 in Fig. 12). Beam combiner 1272 is configured to combine received reflected diffracted radiation 1280 from the two elliptical mirrors 1270 such that the combined received reflected diffracted radiation 1280 is configured to be separated by a demultiplexer and signal processed, for example. In some embodiments, beam combiner 1272 comprises two beam combiners, and positive and negative orders of the received reflected diffracted radiation 1280 are each directed to a beam combiner for a corresponding diffraction order. In embodiments such as embodiments 1202 and / or 1204, the one planar PIC 1250 may also comprise one or more additional mirrors 1290, prisms 1292, wedges, and / or other components. Mirrors 1290 may be configured to fold a reflection path from the two elliptical mirrors 1270 to different angles relative to the beam combiner. Prisms 1292, wedges, and / or other components may be configured to facilitate on chip separation of wavelengths of diffracted radiation 1280, for example.

[0178] In some embodiments, the one planar PIC 1250 comprises a dispersion device configured to separate wavelengths of the received reflected diffracted radiation within the one planar photonic integrated circuit. The dispersion device may comprise a prism or an arrayed waveguide grating (AWG), for example. The dispersion device may be similar to and / or the same as arrayed waveguide grating 1160 shown in Fig. 11, for example.

[0179] Phrased another way, Fig. 12 illustrates possible embodiments of a two dimensional (2D) planar sensing device (e.g., optical component 8 comprising one planar PIC 1250) with a broadband waveguide or photonic crystal fiber (e.g., fiber array 1210) illuminating an alignment mark (e.g., metrology target 30) with different wavelengths of radiation (e.g., radiation 1260). As shown in Fig. 12, mirrors reflect and receive radiation out of the plane of the PIC. The diffraction orders for these wavelengths he in the plane of the sensing device, reflect off two elliptical mirrors (e.g., mirrors 1270), and recombine at a beam combiner (e.g., beam combiner 1272) to be further separated by a demultiplexer and signal processed. If the angle of incidence on the beam combiner is too big or takes up too much space, extra mirrors 1290 can be used to fold the reflection path to different angles on the beam combiner. Wavelengths can also be separated on-chip by way of a dispersion device like a prism 1292 or an arrayed waveguide grating (AWG), and lead the positive and negative orders of diffracted radiation 1280 to a beam combiner for each wavelength. Fabricating in-plane mirrors like mirrors 1270 and / or 1290 shown in Fig. 12 may be accomplished with focused ion beams, dedicatedetching, and / or other techniques. One additional example fabrication technique is through two-photon polymerization by a strongly focused beam followed by metal coating, with a writing device such as a NanoScribe. PIC 1250 uses the large bandwidth of out-couplers and combines the large bandwidth with reflecting modules to process multiple wavelengths in a very compact space, among other advantages.

[0180] As described above, the radiation detector (e.g., detector 4 shown in Fig. 3) generates a metrology signal based on diffracted radiation received by one or more planar PICs. In some embodiments, the radiation detector comprises an interferometer configured to interfere diffraction orders of received diffracted radiation, a photodiode, a charge coupled device (CCD), and / or other components. The radiation detector may comprise one or more components on, in, and / or otherwise coupled to a PIC 1112 (Fig. 11), PIC 1250 (Fig. 12), and / or other PICs described herein. The radiation detector may comprise one or more components separate from a PIC. The radiation detector 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.

[0181] Fig. 13 illustrates side view 1300 and side view 1302 of a 2D planar edge-coupled PIC 1350. PIC 1350 may be similar to and / or the same as PIC 1250 and / or another PIC described above. Side view 1300 shows diverging diffraction orders in diffracted radiation 1310 from a metrology target 30 that are captured by PIC 1350. As shown in side view 1302, if the distance D between PIC 1350 and metrology target 30 is larger, a cylindrical lens 1320 on the edge of PIC 1350 and / or other components may be used to couple radiation 1310 into PIC 1350.

[0182] As shown in Fig. 14, in some embodiments, optical component 8 comprises one or more adjusters 1400 (only labeled on one side in Fig. 14 to ease understanding of Fig. 14) configured to adjust a distance between any two planar PICs 1402. Planar PICs 1402 may be similar to and / or the same as PIC 1350 (Fig. 13), 1250 (Fig. 12), 1112 (Fig. 11), and / or other planar PICs. Fig. 14 illustrates a top (or bottom or end) view of planar PICs 1402. Planar PICs 1402 and adjusters 1400 are shown coupled to a fixed outer structure 1420. The left side of Fig. 14 illustrates an on axis radiation embodiment 1430 of optical component 8, and the right side of Fig. 14 illustrates an oblique or otherwise off-axis radiation embodiment 1440.

[0183] In Fig. 14, the small squares in the middle represent an illumination mirror / lens viewed from the bottom, and the longer rectangles to the top and bottom comprise capturing mirrors. In the device shown on the left of Fig. 14 (e.g., 1430), light is captured by the mirrors from the same PIC. The off-axis configuration, shown on the right side in Fig. 14 may be designed either to illuminate andcapture with elements on the same PIC (elements on front and back side of the PIC in this drawing) or it may be designed to illuminate with an illuminator on one PIC and the capture elements on the neighboring PIC. The drawing in Fig. 14 allows the most flexibility in positioning of the metrology targets to be measured in parallel when each illuminator / capture element reside on the same fixed block and can be moved with respect to the other blocks of illuminator / capture elements. For maximum flexibility of positioning the metrology targets, the drawing may be interpreted drawing as illuminator / capture elements being on the front / back side of the same PIC. There can be different implementations possible where the illuminator / collector are on two different PICs, but these two PICs are fixed to each other (this is similar to skipping every 2nd illuminator in the drawing). If the illuminator / capture elements are on separate movable blocks, and use of all illuminator / capture elements is desired, flexibility of the positioning of the metrology targets to be measured in parallel may be reduced (since in this case, the location of the illuminator of a subsequent illuminator-capture group is fixed to the capture element of the previous illuminator-capture group).

[0184] An adjuster 1400 may comprise an actuator and / or other components located between each two of the planar PICs 1402, between a planar PIC 1402 and fixed outer structure 1420, and / or in other locations. The actuator may be a piezoelectric actuator and / or other actuators, for example. Each actuator may be configured to independently adjust distances (illustrated by the double sided arrows in Fig. 14) between each two of the planar PICs 1402, between a planar PIC 1402 and fixed outer structure 1420, and / or other distances. In some embodiments, an adjuster 1400 is configured to enable simultaneous measurement of a number of different metrology targets in a single field, without restriction on where the different metrology targets are located.

[0185] The configuration shown in Fig. 14 enables measuring an alignment mark, for example, with a single orientation (horizontal lines). A 90 degree oriented construct can be added for measuring marks with vertical lines and / or other orientations. Alternatively, a PIC / mirror embodiment configured to measure lines under a diagonal orientation, where diffracted light can be captured by mirrors under 45 degrees, can be implemented. The mirrors in such an embodiment would extend further in the 45 degree direction from the PIC substrate and may require larger and more complex implementation of the mirrors on the PIC.

[0186] Fig. 15 illustrates another metrology method 1500. Method 1500 may also be performed as part of an alignment sensing operation in a semiconductor device manufacturing process, for example. In some embodiments, one or more operations of method 1500 may be implemented in or by system 10 illustrated in Fig. 3, optical component 8 illustrated in Fig. 3 and Fig. 11, 12, 13, and / or 14, a computer system (e.g., as illustrated in Fig. 26 and described below), and / or in or by other systems, for example. In some embodiments, method 1500 comprises irradiating (operation 1502) a metrologytarget (e.g., an alignment mark) in a patterned substrate with radiation; receiving (operation 1504) diffracted radiation from the metrology target (now with an optical component comprising one or more planar perpendicularly oriented PICs); generating (operation 1506) a metrology signal; and determining (operation 1508) alignment of a layer of the patterned substrate based on the metrology signal.

[0187] As with method 1000, the operations of method 1500 are intended to be illustrative. In some embodiments, method 1500 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 1500 may include an additional operation comprising determining an adjustment for a semiconductor device manufacturing process. Additionally, the order in which the operations of method 1500 are illustrated in Fig. 15 and described herein is not intended to be limiting.

[0188] In some embodiments, one or more portions of method 1500 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 1500 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 1500 (e.g., see discussion related to Fig. 26 below).

[0189] At operation 1502, a radiation source irradiates a metrology target in a patterned substrate with radiation. The radiation comprises light and / or other radiation. The radiation may be generated by the radiation source (e.g., source 2 shown in Fig. 3). In some embodiments, the radiation may be directed by the radiation source onto multiple targets, a single target, sub-portions (e.g., something less than the whole) of a target, and / or onto a substrate in other ways. In some embodiments, the radiation may be directed by the radiation source 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 (e.g., in other layers), and / or other analysis.

[0190] In some embodiments, operation 1502 may include generating, with the radiation source,one or more lenses, and / or other components incident radiation and directing the radiation toward the optical component. In some embodiments, one or more portions of the radiation source may be formed by the optical component itself, in the optical component, and / or on the optical component (e.g., as described above). For example, in some embodiments, the radiation source comprises a fiber array edge coupled to an illumination source chip, a micro mirror or micro lens, off axis parabolic mirrors, and / or other components. The fiber array is configured to conduct the radiation to the illumination source chip. The illumination source chip comprises a waveguide configured to propagate the radiation on the chip toward the micro mirror or micro lens and the off axis parabolic mirrors, which focus, shape, and / or direct the radiation toward the metrology target. The illumination source chip may also be arranged in the perpendicular orientation relative to the metrology target, which is parallel to the planar PICs (e.g., see Fig. 11). In some embodiments, operation 1502 is performed by a radiation source similar to and / or the same as radiation source 2 shown in Fig. 3 and described above.

[0191] At operation 1504, the optical component comprising the one or more planar and perpendicularly oriented PICs receives diffracted radiation from the metrology target. As described above, the one or more planar PICs are arranged in a perpendicular orientation relative to the metrology target.

[0192] In some embodiments, the one or more planar PICs comprise two or more PICs (see Fig. 11). The two or more planar PICs may be arranged in the perpendicular orientation at two or more grid aligned positions relative to the metrology target. The perpendicular orientation at the two or more grid aligned positions is configured to facilitate dense stacking of the planar PICs, and / or have other advantages.

[0193] Each of the planar PICs may comprise one or more parabolic collector micro mirrors, one or more corresponding collector waveguides, and / or other components configured to collect the diffracted radiation and direct collected diffracted radiation toward the radiation detector. In one representative embodiment, the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides may comprise one parabolic collector micro mirror and one corresponding collector waveguide, for example. In some embodiments, the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise an array of parabolic collector micro mirrors and corresponding collector waveguides.

[0194] In some embodiments, each of the planar PICs comprises an arrayed waveguide grating configured to demultiplex received diffracted radiation. In some embodiments, fibers are edge coupled to each of the planar PICs and configured to guide received diffracted radiation to the radiation detector.

[0195] In some embodiments, the one or more planar PICs comprise one planar PIC (see Fig. 12). A fiber array may be edge coupled to the one planar PIC and configured to receive and conduct the radiation from the radiation source to the one planar PIC, for example. In some embodiments, the one planar PIC comprises a source waveguide or photonic crystal waveguide configured to conduct the radiation from the edge coupled fiber array through the one planar PIC and direct the radiation toward the metrology target. The one planar PIC may have a target thickness and / or other characteristics configured to facilitate propagation of the radiation within the one planar PIC.

[0196] In some embodiments, the one planar PIC comprises two elliptical mirrors and a beam combiner, and / or other components. The metrology target and the beam combiner may be located at different foci of an ellipse associated with the two elliptical mirrors. The two elliptical mirrors are configured to reflect received diffracted radiation toward the beam combiner. The beam combiner is configured to combine received reflected diffracted radiation from the two elliptical mirrors such that the combined received reflected diffracted radiation is configured to be separated by a demultiplexer and signal processed. In some embodiments, the beam combiner comprises two beam combiners, and positive and negative orders of the received reflected diffracted radiation are each directed to a beam combiner for a corresponding diffraction order. The one planar PIC may also comprise one or more additional mirrors configured to fold a reflection path from the two elliptical mirrors to different angles relative to the beam combiner and / or other components.

[0197] In some embodiments, the one planar PIC comprises a dispersion device configured to separate wavelengths of the received reflected diffracted radiation within the one planar photonic integrated circuit. The dispersion device may comprise a prism or an arrayed waveguide grating (AWG), for example.

[0198] In some embodiments, an adjuster is configured to adjust a distance between any two of the planar PICs. The adjuster may comprise an actuator and / or other components located between each two of the planar PICs. The actuator may be a piezoelectric actuator and / or other actuators. Each actuator may be configured to independently adjust distances between each two of the planar PICs. In some embodiments, the adjuster is configured to enable simultaneous measurement of a number of different metrology targets in a single field, without restriction on where the different metrology targets are located. In some embodiments, operation 1504 is performed by an optical component similar to and / or the same as optical component 8 shown in Fig. 3 and Fig. 11, 12, 13, and / or 14, and described above; one or more adjusters similar to and / or the same as adjuster(s) 1400 shown in Fig. 14 and described above; and / or other components.

[0199] At operation 1506, the radiation detector generates a metrology signal based on the diffracted radiation received by the one or more planar photonic integrated circuits, and / or otherinformation. 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, a photodiode, a charge coupled device (CCD), and / or other components. The radiation detector may comprise multiple sensing devices operating in parallel, for example.

[0200] As in operation 1006 in method 1000 shown in Fig. 10 and described above, in some embodiments, operation 1506 comprises detecting diffracted radiation (with the radiation detector described above) from one or more diffraction grating targets. Detecting reflected 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.

[0201] 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 interference of diffracted radiation orders while scanning a specific area of a target may comprise a sinusoidal waveform having a certain phase and / or amplitude. The interference of diffracted radiation orders while scanning 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.

[0202] In some embodiments, operation 1506 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 detectors) 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.

[0203] The metrology signal comprises an electronic signal that represents and / or otherwisecorresponds 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 1506 may be performed by a radiation detector similar to and / or the same as detector 4 shown in Fig. 3, and described herein.

[0204] Similar to and / or the same as operation 1008 of method 1000 shown in Fig. 10 and described above, at operation 1508, 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 optical component, 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 1508 may be performed by one or more processors similar to and / or the same as processors PRO shown in Fig. 3 and Fig. 26, and described herein.

[0205] In some embodiments, operation 1508 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 focus position so that a subsequent image of the substrate is in focus. In some embodiments, operation 1508 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 targetdesign, 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.

[0206] In some embodiments, operation 1508 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. 26 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.

[0207] 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 1508), for example. In some embodiments, operation 1508 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.

[0208] For some assessment operations, such as for defect inspection with a multi-beam scanning electron microscope (SEM), it is desirable to illuminate a sample with optical beams (light radiation in this example) in proximity to (one or more) electron beams from the SEM, to control charge on the sample and enhance contrast during defect inspection. A sample may be any object of interest. For example, a sample may be a substrate such as a semiconductor wafer, an individual die, a mask, and / or other samples. Illuminating a sample with optical beams (light radiation in this example) in proximity to (one or more) electron beams from the SEM, to control charge on the sample and enhance contrast during defect inspection is known as voltage contrast inspection using advancedcharge control (ACC). Typical systems have a macroscopic objective lens. Such a lens has sufficient clearance from a substrate (the working distance, usually > 1 mm) to direct a light beam under a shallow angle onto the substrate, with a field of view of less than about 10 - 50 microns. However, in micro electro mechanical based systems (MEMS based systems), the working distance is only on the order of tens of microns, and the field of view can be as large as 15 mm. Therefore, present ACC methods cannot be used in MEMS based systems (e.g., because of the very small working distance, among other possible reasons).

[0209] One of the challenges in an application like this is to couple optical beams out of an optical component in a very narrow physical space with sufficient power such that a power threshold for ACC is met. Sufficient available physical space for routing the optical beams is also required. In some MEMS based systems, the routing and / or outcoupling is accomplished using a one layer grating coupler. Grating couplers like this are typically designed for one wavelength (and one polarization) of radiation. However, this restricts the design of the system in terms of the amount of wavelengths than can be output, and the associated power. It is infeasible to output multiple wavelengths of radiation from the same layer in such systems. This single layer grating coupler system is unable to output multiple wavelengths of radiation, with the power and uniformity required for assessment operations such as SEM voltage contrast inspection using ACC.

[0210] Advantageously, the assessment systems and methods described herein include a compact optical component (e.g., similar to optical component 8 described above, comprising one or more planar photonic integrated circuits in some embodiments) configured to emit radiation. This optical component is used to form a significantly more compact assessment system, and / or has other advantages compared to prior systems. The optical component comprises a plurality of emitter layers. For a voltage contract ACC defect inspection system example, the optical component is configured to output multiple optical beams of different wavelengths (though these wavelengths may also be substantially overlapping or the same) of radiation in combination with charged particle beams (e.g., electron beams) within the working distance required for MEMS based systems. Each of the plurality of emitter layers is configured to emit an optical beam having a respective wavelength, and to reduce or avoid emission of at least one evanescent order (e.g., configured to minimize a further diffraction of one or more diffraction orders associated with other emitter arrangements, minimize diffraction of higher diffraction orders associated with the other emitter arrangements, etc.). This optical component with the plurality of emitter layers enables output of multiple optical beams with different wavelengths of radiation within available physical space, with the power and uniformity required for assessment operations such as SEM voltage contrast inspection using ACC.

[0211] By way of a brief introduction, during the manufacturing of, for example, semiconductorintegrated circuit (IC) chips or displays, undesired defects may occur on a substrate (e.g., a substrate such as wafer or a mask, or other substrate). Such defects may reduce yield. Defects may occur as a consequence of all kinds of processing necessary to produce an integrated circuit or display, for example, lithography, etching, deposition or chemical mechanical polishing (etc., as described above). Defects may include patterning defects, in which the created pattern lies outside the pattern tolerance for the process, and particles. Monitoring the extent of defects during the manufacturing processes is therefore important. Such monitoring (or more generally assessment) includes the determination of the existence of a defect, but also the classification of the types of defects found.

[0212] For the assessment of a sample such as a substrate, different types of inspection or metrology systems have been used, including charged particle optical systems such as electron microscopes. Such assessment for inspection may relates to defects, for example the existence and classification of such defects. Electron microscopes typically generate a probe beam (also often referred to as primary beam) which may, for example, be scanned across a part of the substrate (such as in a scanning electron microscopes (SEM)). Collecting interaction products that result from the interaction of the primary beam with the part of the substrate, allows the electron microscope to collect data representing the probed part of the substrate. The data may be processed / rendered for example by the electron microscope to generate an image representation of the part of the substrate. The collected data for example as a generated image representation allows for measuring structures on the part of the substrate, or allows for identifying defective structures by comparing the image representation with a reference. Such measurement may be referred to as metrology; the identification of defective structures may be referred to as (defect) inspection. The interaction products may contain charged particles which may be referred to as signal particles (e.g. signal electrons), such as secondary electrons and backscattered electrons, and may contain other interaction products, such as X-ray radiation and even light.

[0213] Fig. 16 is a schematic diagram illustrating an exemplary assessment system 1600, e.g. a metrology system or an inspection system. Assessment system 1600 may be configured to scan a sample with one or more beams of electrons. The sample may be a semiconductor substrate, a substrate made of other material, a mask, or other samples, for example. The electrons interact with the sample and generate interaction products. The interaction products comprise signal electrons, e.g. secondary electrons and / or backscattered electrons, and possibly X-ray radiation. Assessment system 1600 may be configured to detect the interaction products from the sample so that a data set may be generated which may be processable into an image or any other data representation of the scanned area of the sample. For clarity, the description below focuses on embodiments in which the interaction products that are detected are signal electrons. Assessment system 1600 may comprise,for example during operation, a single beam or a plurality of beams, i.e. a multi-beam. The component beams of a multi -beam may be referred to as sub-beams or beamlets. A multi -beam may be used to scan different parts of a sample simultaneously. When assessment system 1600 uses a multi -beam, assessment system 1600 may assess a sample more quickly than when assessment system 1600 uses a single-beam. For example, a higher throughput of a sample such as a substrate assessment may be achieved using a multi -beam assessment system 1600 compared to a single beam assessment system 1600.

[0214] Assessment system 1600 comprises a vacuum chamber 1610, a load lock chamber 1620, an electron optical apparatus 1640, an equipment front end module (EFEM) 1630 and a controller 1650 (e.g., comprising one or more processors). The electron optical apparatus 1640 (also known as a charged particle beam apparatus, an electron beam apparatus, or an electron apparatus) may be within the vacuum chamber 1610. The electron optical apparatus 1640 may comprise a charged particle, or electron, optical system (described in more detail below) and an actuatable stage. It should be appreciated that reference in the description to the electron optical elements of the electron optical apparatus 1640 can be considered to be a reference to the charged particle optical system.

[0215] The EFEM 1630 includes a first loading port 1630a and a second loading port 1630b. The EFEM 1630 may include additional loading port(s). The first loading port 1630a and the second loading port 1630b may, for example, receive sample front opening unified pods that contain samples. One or more robot arms (not shown) in the EFEM 1630 transport the samples to the load lock chamber 1620.

[0216] The load lock chamber 1620 is used to remove the gas around a sample. The load lock chamber 1620 may be connected to a load lock vacuum pump system (not shown), which removes gas particles in the load lock chamber 1620. The operation of the load lock vacuum pump system enables the load lock chamber to reach a first pressure below the atmospheric pressure. The vacuum chamber 1610, which may be a main chamber of assessment system 1600, is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas molecules from the vacuum chamber 1610 so that the pressure around the sample reaches a second pressure equal to or lower than the first pressure. Different parts of the electron optical apparatus 1640 may have different levels of pressure below the atmospheric pressure. After reaching the required pressure, the sample leaves the load lock chamber 1620 and is transported to the electron optical apparatus 1640 by which it may be assessed. The electron optical apparatus 1640 may use either a single beam or a multi-beam for the assessment. Alternatively, a charged particle optical system array comprising a plurality of charged particle optical systems may be used, further also referred to as a multi-column electron-array, in which each charged particle optical system (or each column in the multi-columnarray) comprises, for example during operation, either a single beam or a multi -beam.

[0217] The controller 1650 is electronically connected to the electron-optical apparatus 1640. The controller 1650 may be a processor (such as a computer) configured to control assessment system 1600. The controller 1650 may also include processing circuitry configured to execute data, signal and image processing functions for example on the data set e.g. embodied as signals such as detection signals. The controller 1650 may thus include processing circuitry configured to execute processing functions on signal, image and other data produced in the assessment system 1600. While the controller 1650 is shown in Fig. 16 as being outside of the structure that includes the vacuum chamber 1610, the load lock chamber 1620, and the EFEM 1630, it is appreciated that the controller 1650 may be part of the structure. The controller 1650 may be located in one of the components of assessment system 1600 or it may be distributed over at least two of the components.

[0218] Fig. 17 is a schematic diagram illustrating an exemplary electron-optical apparatus 1640. The electron-optical apparatus 1640 may be provided as part of assessment system 1600 of Fig. 16. The electron-optical apparatus 1640 includes a source 1701 and a charged particle optical system 1730 (which may also be referred to as an electron-optical column). The source 1701 may comprise a cathode (not shown) and an extractor and / or anode (not shown). During operation, the source 1701 is configured to emit electrons from the cathode. The electrons may be extracted or accelerated by the extractor and / or the anode to form the source beam 1702 (e.g., a charged particle beam).

[0219] The charged particle optical system 1730 may be configured to convert the source beam 1702 into a plurality of primary beams 1711, 1712, 1713 (charged particle beams), which may be referred to as sub-beams or beamlets. The charged particle optical system 1730 may be configured to direct the primary beams 1711, 1712, 1713 along respective beam paths toward a sample location for a sample such as a substrate 1708 (e.g., similar to and / or the same as the other substrates described herein). Although three beams are illustrated, the number of beams may be of the order of 100s or 1,000s, for example up to 20,000 per electron-optical apparatus 1640. The plurality of beams may be referred to collectively as a multi-beam or a beam grid. The different beams may be arranged relative to each other across the beam grid in a pattern. The pattern of the beam grid may be referred to array. The charged particle optical system 1730 has a field of view which may be defined as the area of the surface of the substrate 1708 (or a portion thereof) within which the primary beams 1711, 1712, 1713 can scan while the aberrations of charged particle optical system 1730 remain within a defined value. Alternatively, the field of view may be defined by the maximum scan range of charged particle optical system 1730. The field of view may be of the order of millimeters, for example up to 20mm at the substrate 1708.

[0220] The charged particle optical system 1730 comprises a plurality of electron-optical elementspositioned along the beam paths. The electron-optical elements are configured to manipulate the beams. For example, the electron-optical elements may be configured to lens, focus, deflect or correct the beams. The electron-optical elements may be arranged in at least one stack of electron-optical elements. Such an electron-optical element may be positioned upbeam or downbeam with respect to another of the electron-optical elements. The terms upbeam and downbeam relate to the direction of the beams from the source 1701 to the sample (e.g., substrate 1708) during use of charged particle optical system 1730, which may be expressed as a direction along one or more of the beam paths. In an embodiment, some of the different electron-optical elements may take a planar form, such as a plate 1761. An electric field that manipulates the beams may be generated between two plates 1761, e.g. by applying, in use, different potentials to neighboring / adjoining plates 1761 such as along the beam path. An electric field that manipulates the beams may be generated between surfaces of plates 1761 across the beam path for example between the neighboring plates 1761. One or more beam apertures 1766 may be defined in the plates 1761 for the passage of one or more beams. The beam apertures 1766 may be arranged in a pattern such as a regular grid e.g. hexagonal or square. Such a pattern of the beam apertures 1766 may be referred to as an aperture array (i.e. a two-dimensional array over the surface of the plate). The pattern of the beam apertures 1766 may correspond to the pattern of beams within the beam grid. Beam apertures 1766 in different plates operating on the same beam(s) are typically aligned.

[0221] The electron-optical elements may comprise one or more corrector arrays. For example, a corrector array may be integrated into the shape, position and / or size of the beam apertures 1766 of the plates 1761. One or more corrector arrays may comprise multipole deflectors with a specific superposition of potentials applied across the individually controllable electrodes. One or more of the electron-optical elements may comprise an aperture for the path of a plurality of the beams. For example, the aperture may be a macro aperture for all of the beams. One or more electron-optical elements may comprise one or more plate electrodes that are curved across the path of the beam grid for use as a lens array, a corrector array and / or a collimator array.

[0222] In the example embodiment shown in Fig. 17, charged particle optical system 1730 may form three probe spots 1781, 1782, 1783 on the surface of a sample such as substrate 1708. The charged particle optical system 1730 may be configured to deflect the primary beams 1711, 1712, 1713 so as to scan the probe spots 1781, 1782, 1783 across individual scanning areas of substrate 1708. In response to incidence of the primary beams 1711, 1712, 1713 on substrate 1708, signal electrons are generated from substrate 1708, which may include secondary electrons and backscattered electrons. Secondary electrons typically have electron energy of at most 50 eV. Backscattered electrons typically have electron energy of more than 50 eV and less than the landingenergy of the primary beams 1711, 1712, 1713.

[0223] The electron-optical apparatus 1640 comprises a holder 1707 that supports the sample (e.g., substrate 1708). The holder 1707 supports the sample (substrate 1708 in Fig. 17) for assessment. The holder 1707 is supported by an actuatable stage 1709. The electron-optical apparatus 1640 further comprises a detector array 1740 (or more generally a detector). The detector array 1740 may be part of charged particle optical system 1730. The detector array 1740 e.g. detects signal electrons from substrate 1708. The detector array 1740 generates detection signals based on detection of the signal electrons.

[0224] In an embodiment, the detector array 1740 may define the surface of the electron-optical apparatus 1640 facing a sample (e.g., substrate 1708), e.g., the bottom surface of charged particle optical system 1730. There may be more than one detector array at different positions along the paths of the primary beams 1711, 1712, 1713.

[0225] The detector array 1740 may comprise a plurality of detector elements, with at least one detector element per beam. The detector elements may, for example, be charge capture electrodes, for example metal plates, which may be configured to detect at least some of the signal electrons. Alternatively or additionally, the detector elements may comprise detection diodes configured to detect at least some of the signal electrons. Alternatively or additionally, the detector elements may comprise a scintillator material (such as YAG) configured to convert signal electrons into photons that may be subsequently detected. The detector elements may be arranged around beam apertures 1766 in the bottom surface of charged particle optical system 1730 to allow the primary beams 1711, 1712, 1713 to pass towards the sample (e.g., substrate 1708). Each detector element may comprise a plurality of detection segments or may constitute a single sensitive surface for each beam. The detection signal generated by a detector element may be transmitted to a processor for generation of an image. For example, the detection signal may represent a grey value or an intensity value of a pixel of an image.

[0226] The detector array 1740 may send the detection signals, for example as an imaging signal or a detection signal, to the controller 1650 or to a signal processing system (not shown) which may be part of the controller 1650. The controller 1650 or the signal processing system may be configured to generate images of the corresponding scanned areas of a sample. The detector array 1740 may be incorporated at least partly into charged particle optical system 1730. Alternatively, the detector array 1740 may be separate from charged particle optical system 1730. For example, the electron-optical apparatus 1640 may comprise a secondary electron-optical device configured to direct secondary electrons to the detector array 1740. In such an embodiment, the secondary electron-optical device comprises a beam separator (such as a Wien filter, not shown). The beam separator may separate thepaths of the primary electrons towards substrate 1708 from the paths of the signal electrons away from the sample (e.g., substrate 1708). Note, such a beam separator may be present in a different embodiment with a detector array within charged particle optical system 1730 for directing the primary electrons towards the sample and the signal particles to detector elements of the detector array.

[0227] The controller 1650 (for example a control system comprising distributed controllers) may be connected to various parts (e.g. components) of the electron-optical apparatus 1640 of Fig. 17, such as the source 1701, the detector array 1740, charged particle optical system 1730, and the actuatable stage 1709. The controller 1650 may perform various image processing functions and signal processing functions. The controller 1650 may also generate various control signals to govern operations of the assessment system 1600 (Fig. 16).

[0228] Fig. 18 schematically depicts another potential embodiment of an electron-optical apparatus 1640 of an assessment system, e.g. assessment system 1600 of Fig. 16. The electron-optical apparatus 1640 of Fig. 18 may be the electron-optical apparatus 1640 of Fig. 17 in which the electron-optical elements of charged particle optical system 1730 comprise a beam limiting aperture array 1752, a condenser lens array 1731, a collimator array 1771 desirably at an intermediate focus plane 1773, a scan deflector array 1760, an objective lens array 1741 and the detector array 1740.

[0229] The source 1701 generates a diverging source beam 1702 (a charged particle beam). The beam limiting aperture array 1752 defines a plurality of primary beams 1711, 1712, 1713 (charged particle beams) from the source beam 1702. The condenser lens array 1731 focuses the primary beams 1711, 1712, 1713 at the intermediate focus plane 1773. The condenser lens array 1731 may comprise the beam limiting aperture array 1752. Alternatively, the condenser lens array 1731 may be downbeam of the beam limiting aperture array 1752. The condenser lens array 1731 may be electrostatic. In an alternative embodiment the condenser lens array 1731 comprises a magnetic element for example as a plurality of magnetic elements / one or more magnetic elements.

[0230] The collimator array 1771 is configured to collimate the primary beams 1711, 1712, 1713 along respective beam paths towards and substantially orthogonal to a surface of the sample (e.g., substrate 1708). The collimator array 1771 may be located at or near the intermediate focus plane 1773. The collimator array 1771 may comprise a plurality of deflectors configured to deflect respective primary beams 1711, 1712, 1713. Additionally or alternatively the collimator array 1771 may comprise a lens array that operates on the different beams to deflect the relative paths of the beams. The collimator array 1771 may be electrostatic. The collimator array 1771 may comprise a single plate 1761 (Fig. 17) comprising electrodes around the beam apertures 1766, such as on the surface around the beam apertures 1766 and / or on the inside of the beam apertures 1766. Theelectrodes may cooperate as a deflector per beam aperture 1766. Alternatively, the collimator array 1771 may comprise a stack of plates 1761. In use a potential difference is applied between the plates 1761 so as to generate a lensing effect at the beam apertures 1766. The plates 1761 may have a curvature across the beam path. Alternatively, the collimator array 1771 may comprise a plurality of layers of strip electrode deflectors. A layer of strip electrode deflectors may comprise a plate. Although not shown in Fig. 18, in an alternative embodiment, the collimator array 1771 is replaced by a macro collimator configured to collimate the primary beams 1711, 1712, 1713. The macro collimator may be a magnetic lens, or an electrostatic lens, or a combination of magnetic and electrostatic lens. In a further alternative embodiment, charged particle optical system 1730 comprises a macro collimator in addition to the collimator array 1771.

[0231] The deflectors of the scan deflector array 1760 may be formed at apertures of the scan deflector array 1760. The deflectors may comprise respective sets of individually controllable electrodes. Such a deflector may be referred to as a multipole deflector. The individually controllable electrodes extend partially along the beam path of the respective beam. The individually controllable electrodes may be controlled to generate, in use, a scan movement of the respective beam across a sample (e.g., substrate 1708). Typically, the sets of individually controllable electrodes operate to scan all of the primary beams 1711, 1712, 1713 simultaneously in parallel across the individual fields of view of the respective objective lenses of the objective lens array 1741. Alternatively, the scan deflector array 1760 may comprise strip deflectors configured to deflect a row of beams along the individual fields of view of the respective objective lenses of the objective lens array 1741.

[0232] The objective lens array 1741 is configured to focus the primary beams 1711, 1712, 1713 onto the sample (e.g., substrate 1708 in this example). The objective lens array 1741 may comprise a stack of plates 1761 (Fig. 17). Different potentials are applied to respective plates 1761 so as to generate electrostatic fields between adjacent plates 1761. The electrostatic fields generate electrostatic lenses that may be configured to focus the primary beams 1711, 1712, 1713. The objective lens array 1741 may be proximate substrate 1708.

[0233] The stack of plates 1761 (Fig. 17) of the objective lens array 1741 may be referred to as, or as part of, an objective lens assembly. The objective lens assembly may comprise one or more of the scan deflector array 1760, a corrector array (not shown) and the detector array 1740 in addition to the objective lens array 1741. The objective lens assembly may comprise additional plates having lens functionality providing additional degrees of electron-optical freedom. A control lens array may be comprised by such an additional plate.

[0234] In an embodiment the detector array 1740 may be integrated into the objective lens array 1741. Alternatively (or additionally) the detector array 1740 may be upbeam of the bottom surface ofcharged particle optical system 1730. For example, the detector array 1740 may be within the objective lens assembly or even upbeam of the objective lens assembly. For example, the detector array 1740 may be in or upbeam of the objective lens array 1741.

[0235] The charged particle optical system 1730 may comprise one or more corrector arrays configured to at least partly correct one or more types of aberration of the beams. Such corrector arrays may be associated with or integrated into the condenser lens array 1731, the collimator array 1771 and / or the objective lens array 1741, or between two of these arrays, e.g. between the condenser lens array and the collimator array.

[0236] Fig. 19 illustrates another potential embodiment of an electron-optical apparatus 1640 of an assessment apparatus, e.g. the assessment system 1600 of Fig. 16. The electron-optical apparatus 1640 of Fig. 19 may be the electron-optical apparatus 1640 of Fig. 17 in which charged particle optical system 1730 comprises a macro condenser lens 1774, a macro scan deflector 1775, a beam limiting aperture array 1752 (which may be referred to as an upper beam limiter), a control lens array 1750, a collimator array 1771, an objective lens array 1741, a beam shaper array 1742 (which may be referred to as a lower beam limiter) and the detector array 1740.

[0237] The source 1701 generates a diverging source beam 1702 (a charged particle beam). The macro condenser lens 1774 is located between the source 1701 and the objective lens array 1741. The macro condenser lens 1774 is configured to at least partly collimate the source beam 1702. The macro scan deflector 1775 is located between the macro condenser lens 1774 and the objective lens array 1741. The macro scan deflector 1775 is configured to operate on the source beam 1702 so that the primary beams 1711, 1712, 1713 (charged particle beams) scan the surface of substrate 1708.Additionally or alternatively charged particle optical system 1730 may comprise a scan deflector array (not shown) downbeam of the control lens array 1750. The macro condenser lens 1774 and / or the macro scan deflector 1775 may at least in part be magnetic.

[0238] The beam limiting aperture array 1752 defines a plurality of primary beams 1711, 1712, 1713 from the source beam 1702. The beam shaper array 1742 and the beam limiting aperture array 1752 are plates 1761 (Fig. 17) in which the beam apertures 1766 are smaller in dimension than other plates of charged particle optical system 1730. The beam apertures 1766 of the beam limiting aperture array 1752 define the primary beams 1711, 1712, 1713. The beam apertures 1766 of the beam shaper array 1742 shape the primary beams 1711, 1712, 1713 to at least partially correct for types of aberration in the beams.

[0239] The collimator array 1771 is configured to collimate the primary beams 1711, 1712, 1713 along respective beam paths towards and substantially orthogonal to a surface of a sample (e.g., substrate 1708). The collimator array 1771 may be located between the beam limiting aperture array1752 and the objective lens array 1741. The collimator array 1771 may be omitted. Alternatively, when the collimator array 1771 is provided, then the macro condenser lens 1774 may be omitted. The collimator array 1771 may comprise a plurality of deflectors configured to deflect respective primary beams 1711, 1712, 1713. The collimator array 1771 may be electrostatic. The collimator array 1771 may comprise a single plate 1761 comprising the deflectors around the beam apertures 1766, for example on the surface around the beam apertures 1766 and / or on the inside of the beam apertures 1766. Alternatively, the collimator array 1771 may comprise a stack of plates 1761. In use a potential difference is applied between the plates 1761 so as to generate a lensing effect at the beam apertures 1766. One or more of the plates may be curved across the path of the beam grid. Alternatively or additionally, the collimator array 1771 may comprise a plurality of layers of strip electrode deflectors. A layer of strip electrode deflectors may be a plate.

[0240] The objective lens array 1741 is configured to focus the primary beams 1711, 1712, 1713 onto a sample (e.g., substrate 1708). The objective lens array 1741 may comprise a stack of plates 1761. In use, different potentials may be applied to respective plates 1761 so as to generate electrostatic fields between adjacent plates 1761. The electrostatic fields generate electrostatic lenses that may be configured to focus the primary beams 1711, 1712, 1713. The objective lens array 1741 may be proximate a sample (substrate 1708).

[0241] The control lens array 1750 may be upbeam of the objective lens array 1741. The control lens array 1750 may comprise a stack of plates 1761, for example at least three plates 1761. The control lens array 1750 may be configured to control electron-optical parameters of the primary beams 1711, 1712, 1713. In an embodiment, the most downbeam plate of the control lens array 1750 is the most upbeam plate of the objective lens array 1741. Alternatively, the control lens array 1750 may be considered to be part of the objective lens array 1741. The control lens array may provide one or more additional degrees in electron-optical freedom such as in pre-focusing, magnification and beam current setting.

[0242] The stack of plates 1761 of the objective lens array 1741 may be referred to as an objective lens assembly. The objective lens assembly may comprise one or more of the beam limiting aperture array 1752, the control lens array 1750, a corrector array (not shown), the collimator array 1771, the beam shaper array 1742 and the detector array 1740 in addition to the objective lens array 1741. The objective lens assembly may comprise additional plates having lens functionality providing additional degrees of electron-optical freedom. A control lens array may be comprised by such an additional plate.

[0243] In an embodiment, the detector array 1740 may be integrated into the objective lens array 1741. Alternatively (or additionally) the detector array 1740 may be upbeam of the bottom surface ofcharged particle optical system 1730. For example, the detector array 1740 may be within the objective lens assembly or even upbeam of the objective lens assembly. For example, the detector array 1740 may be in or upbeam of the objective lens array 1741.

[0244] The charged particle optical system 1730 may comprise one or more corrector arrays (not shown) configured to at least partly correct one or more types of aberration of the beams. Such corrector arrays may be associated with or integrated into the control lens array 1750, the collimator array 1771 and / or the objective lens array 1741, for example as part of the objective lens assembly.

[0245] In charged particle systems comprising an objective lens array (such as shown in and described with reference to Fig. 16-19), which may be referred to as a MEMS based system) the working distance may be less than 500 microns, such as less than 100 microns, for example in the range of 10 to 70 microns, such as only 50 microns or less. The field of view can be as large as 3 mm, 5 mm, 10 mm or as much as 20 mm. Optical beams (e.g., light beams) directed into such a gap (e.g., for ACC applications) would have difficulty reaching a portion of the sample on which a charged particle beam grid is incident. The angle of illumination of an optical beam into the gap may exceed the angular threshold, for example with respect to the normal of the sample surface, at or below which the illuminating light may be absorbed by the material of the sample, so at such an angle that exceeds the angular threshold where most if not all of an optical beam is reflected. Alternatively expressed, the threshold may correspond to a small angle with respect to the sample surface below which most if not all of an optical beam is reflected (i.e. not absorbed). This method cannot be used in such a charged particle system with an objective lens array.

[0246] Transporting optical beams, especially optical beams having different wavelengths (noting that wavelength or wavelength range, in practice, can refer to a certain bandwidth of wavelengths, as described above) while reducing or avoiding emission of at least one evanescent order, on to an inspected substrate with a stack of planar elements comprising electron-optical arrays is not a straightforward task due to the working distance being so small, among other factors.

[0247] The present assessment systems include an optical component configured to transport and emit multiple optical beams of different wavelengths (or the same wavelength in some embodiments), such as stimulation light (e.g., for controlling contrast during defect inspection). The optical component is configured to transport the multiple optical beams through total internal reflection inside the optical component, in integrated waveguides in the optical component, or using other techniques (as further described below). Emission is accomplished with emitter layers, as described herein. Three generalized embodiments of such an arrangement are described below and illustrated schematically in Fig. 20-22. It should be noted that the features may be used as alternatives, or may be combinable as may be desired.

[0248] Fig. 20 illustrates a sample (e.g., substrate) facing optical component 2001. Optical component 2001 is illustrated as planar and part of a stack 2002. In some embodiments, optical component 2001 includes some or all of stack 2002. Optical component 2001 guides optical beams 2071 (e.g., stimulation light) of different wavelengths and couples them to free space, towards the sample (e.g., substrate 1708 in this example), using layers of emitters (generally illustrated as out- coupling features comprising recesses 2003 in a surface of optical component 2001 in this figure, and further described below). The layers of emitters can be configured to direct optical beams 2071 to be coincident (i.e. incident at the same place and / or time, and / or otherwise proximate to) on the sample (substrate 1708) with the charged particle beams. As optical component 2001 is part of the stack 2002, a plurality of apertures 2004 may be defined in optical component 2001 for passage of the charged particle beams of a beam grid and optionally signal particles from a sample such as substrate 1708. The position of the apertures 2004 in optical component 2001 may correspond to apertures in other elements of the stack 2002.

[0249] For stimulation of substrate 1708 (e.g., in this example for ACC), optical beams 2071 are coincidently incident on a portion of the substrate surface with an incidental charged particle, that is at the same or nearly the same time. In some embodiments, illumination with optical beams 2071 shortly before the incidence of the charged particle beams can be effective. Optical beams 2071 are incident at the same location (or nearly the same location) as respective charged particle beams. Optical beams 2071 (e.g. of stimulation light) extend over a portion of the substrate surface over which the charged particle beam is scanned. Illumination of the portion of the substrate surface with optical beams 2071 may start before the charged particle beam is scanned over the portion. The illumination may continue after the portion is scanned by the charged particle beam (although it may be desirable to stop illumination as soon as the portion has been scanned by the charged particle beam). Desirably, the charged particle beam is scanned over the portion of the substrate surface during optical stimulation / photonic illumination of the portion.

[0250] The field of view of a charged particle beam may be less than 50 nm, for example less than 20 nm such as smaller than 10 nm. However the charged particle beam is continually scanned relative to the substrate 1708 surface. For example the charged particle beam may be scanned electrostatically, using a scan deflector, across a range of less than 10 microns, for example less than 5 microns, for example less than 1 micron in a scan direction. The sample (e.g., substrate 1708) may be continually scanned in a different direction from the scan direction electrostatically and / or by mechanically scanning the stage 1709 and thus the substrate 1708. Such mechanical scanning may comprise continuously scanning the sample (substrate 1708) relative to the path of the beam grid or scanning the substrate relative to the path of the beam grid between sequential steps of the sample relative tothe path, for example in a direction different to the scanning direction of the stage.

[0251] Optical component 2001 may be configured with in-couplers (not shown), waveguides, power splitters, out-couplers, and / or other components. The in-couplers couple the optical beams into the waveguides, e.g. from fibers or another source. The in-couplers may be edge couplers, for example. The waveguides transmit the optical signal. Power splitters may guide distribute the optical beams signal to multiple out-couplers such as grating couplers. The out-couplers couple light out from the waveguides to free space and direct it towards the substrate 1708 being assessed (e.g., inspected). Edge couplers, grating couplers (as in-couplers or out-couplers), and / or other components can support multiple wavelengths.

[0252] Coupling optical beams from fibers and / or other sources into waveguides can be done in different ways, for example: edge coupling, grating coupling, and micromirrors as three examples. In edge coupling the fiber is brought in-line with the waveguide at close proximity. In a grating coupler the light is coupled from the fiber into the waveguide. A micro-mirror redirects the light from the fiber and focuses it into the waveguide. Other in-coupling cases also apply if instead of having an optical fiber, a free-space beam focused onto the facet of a chip (for example) is used. Various arrangements for splitting of integrated optical waveguides are known, for example: Y-splitters; multi-mode interferometers (MMI); and directional couplers. Optical component 2001 can be mounted to (or otherwise incorporated into) a support substrate which is positioned within and / or otherwise adjacent to stack 2002.

[0253] In the example shown in Fig. 21, optical beams 2071 are out-coupled at the bottom of the stack 2002. In this example, out-couplers 2007 may comprise grating couplers and / or other components. In the example shown in Fig. 22, optical beams 2071 (e.g., stimulation light) is out- coupled from optical component 2001 and then passes through apertures for the charged particle beams in a bottom-most element of the stack 2002. In this example, optical component 2001 is a separate element 2006 that is separate from an electron-optical element of the stack 2002; such that optical component 2001 is itself an element of the stack 2002. Optionally, optical component 2001 may be apart from other elements, such as other planar elements, of the stack 2002.

[0254] Optical component 2001 may occupy different positions in stack 2002. In an embodiment such as that of Fig. 22, where optical component 2001 is not the bottommost element of the stack 2002, additional optical elements may be provided to assist the propagation of optical beams 2071 through apertures in elements of the stack 2002 that are below (i.e. closer to the sample - e.g., substrate 1708) than optical component 2001. For example, the sides of the apertures may be treated or coated to reduce absorption of light. Alternatively or in addition, one or more light guiding structures (which may be a type of waveguide such as hollow-core optical fibers) may be provided ina respective aperture and / or proximate to a respective aperture, desirably without adversely influencing the electric field around the path of a sub-beam through the aperture. The light guiding structures guide the light from optical component 2001, towards the portion of the substrate surface, e.g. the region of interest on the substrate under assessment, e.g. inspection. The light guiding structure may comprise an end facet. The end facet may be in the respective aperture, for example to provide at least part of a surface of the aperture through an element of the stack. An optical element may be provided at the entrance and exit of the aperture and / or the end facet of the light guiding structure in the down-beam elements of the stack to guide stimulation light into and out of the apertures for example towards the sample. It is desirable that any optical elements provided in apertures of the stack not hinder or alter the passage of electron beams through such apertures.

[0255] Fig. 23 illustrates another embodiment of an assessment system (assessment system 2300 in this figure, which has similar and / or the same components as those described above for the assessment systems shown in Fig. 16-22) comprising a compact optical component 2302 (e.g., similar to optical component 8 and / or 2001 described above) configured to emit radiation such as optical beams 2071. In some embodiments, optical component 2302 is a photonic integrated circuit (PIC) and / or other structures. In some embodiments, optical component 2302 comprises grating couplers and / or other integrated optical components, as described herein. Optical component 2302 is used to form a significantly more compact assessment system 2300, compared to prior assessment systems, and / or has other advantages compared to prior systems. While Fig. 23 illustrates one embodiment where the optical component 2302 is positioned at or adjacent a detector in the assessment system, other embodiments are also possible where the optical component can be positioned elsewhere within the assessment system (for example, between a lens array, preferably the objective lens array and the detector).

[0256] Optical component 2302 comprises a plurality of emitter layers 2310. Three emitter layers are shown in this example, but other quantities of emitter layers (e.g., two or more, three or more, four or more, five or more, etc.) are contemplated. For a voltage contract ACC defect inspection system example, optical component 2302 is configured to output multiple optical beams 2071 of different wavelengths (e.g., red (R), green (G), and blue (B), or Ai, A2, and A3 in this example) of radiation in combination with charged particle beams 1711, 1712, 1713 (e.g., electron beams) within the working distance required for MEMS based systems. These may be incident on a sample location (e.g., a location on the surface of a substrate 1708, for example, as described above). Each of the plurality of emitter layers 2310 is configured to emit an optical beam 2071 having a respective wavelength, and to minimize beam distortion of the respective optical beams at the sample location. This optical component 2302 with the plurality of emitter layers 2310 enables output of multiple optical beams2071 with different wavelengths of radiation within available physical space, with the power and uniformity required for assessment operations such as SEM voltage contrast inspection using ACC.

[0257] System 2300 includes a charged particle optical source, such as an electron source (e.g., source 1701 shown in Fig. 17-19), configured to project one or more charged particle beams 1711, 1712, 1713 (e.g., electron beams) towards a sample location (e.g., on substrate 1708). In this example, incident optical radiation has been emitted toward substrate 1708. Optical component 2302 (like optical component 2001 shown in Fig. 20-22) is configured to emit multiple optical beams 2071 of different wavelengths towards a sample location (e.g., on substrate 1708), though note that in some embodiments, these wavelengths may be substantially the same.

[0258] Each of the plurality of emitter layers 2310 is configured to emit an optical beam 2071 having a respective wavelength (R, G, or B in Fig. 23), and to reduce or avoid emission of at least one evanescent order. Each of the plurality of emitter layers 2310 comprises a respective emitter arrangement 2320. The respective emitter arrangement 2320 is configured to emit an optical beam 2071. The respective emitter arrangement 2320 comprises a semi-periodic or periodic arrangement of emitter structures 2322 (shown as periodic grating structures in this example). In other embodiments, the plurality of emitter layers 2310 can comprise other periodic or semi-periodic structures. The periodic or semi-periodic arrangement is configured to diffract optical radiation coupled into the respective emitter arrangement for emission of the respective optical beam. In some embodiments, each emitter arrangement is configured to minimize a further diffraction of one or more diffraction orders associated with other emitter arrangements. In some embodiments, each emitter arrangement is configured to minimize diffraction of higher diffraction orders associated with the other emitter arrangements.

[0259] For example, a periodicity (e.g., the pitch or duty cycle p also shown in Fig. 7) and / or separation (s) between each of the plurality of emitter layers 2310 may be configured to reduce or avoid first and / or higher orders of diffraction of the multiple optical beams 2071 of different wavelengths from one emitter layer 2310 by another emitter layer 2310. The higher orders comprise second, third, fourth, fifth, or higher diffraction orders.

[0260] In some embodiments, emitters in each of the plurality of emitter layers 2310 extend different distances, and / or are located at different distances, from an axis 2527 of a charged particle beam 1711, 1712, 1713 (d4, ds, and de, in the example in Fig. 7). These distances are set to ensure that emitted radiation from each emitter impinges on a sample such as substrate 1708 in a target (e.g., sample) location.

[0261] Fig. 23 schematically illustrates a side view of emitter layers 2310. For simplicity, Fig. 23 only illustrates how radiation is emitted toward a sample such as substrate 1708. The routing, in-coupling, and / or out-coupling for each layer may be the same as or similar to the routing, in-coupling, and out-coupling in other PICs (e.g., as described related to Fig. 20-22 above). For example, in some embodiments, the emitter layers 2310 comprise waveguides 2515 coupled to grating couplers (formed by emitter structures 2322) configured to direct the optical beams 2071 of different wavelengths toward the grating couplers.

[0262] In some embodiments, each emitter layer 2310 emits radiation having a different wavelength (or wavelength range). In some embodiments, each different wavelength (range) is associated with a different color and has a wavelength bandwidth for the associated color. As described above, the different wavelength ranges may overlap. The emitter layers 2310 are each optimized for a center of a given wavelength (range) and / or may have other configurations. Each emitter layer 2310 is configured to emit radiation of different wavelength ranges and / or different polarizations, configured to emit radiation with specific polarizations, and / or is configured in other ways.

[0263] In some embodiments, optical component 2302 comprises an optical component substrate 2330, and at least two emitter layers 2310 (though three layers are shown in Fig. 23). The at least two emitter layers 2310 may be stacked vertically in at least two different layers, substantially parallel to each other on substrate 2330 (e.g., as shown in Fig. 23). In some embodiments, the at least two emitter layers 2310 (e.g., comprising grating couplers), waveguides 2315, and substrate 2330, are clad with silicon dioxide (SiO2), a low index dielectric material, and / or other materials. In some embodiments, the at least two emitter layers 2310 (e.g., comprising grating couplers), waveguides 2315, and substrate 2330 comprise silicon nitride, aluminum oxide, lithium niobate, quartz, and / or other materials. In some embodiments, substrate 2530 may be silicon or silicon based, any suitable non-optical / semiconductor substrate, and / or other materials.

[0264] In some embodiments, an edge coupler (see discussion above related to Fig. 20-22) is coupled to one or more edges of optical component 2302 and configured to conduct the optical radiation (e.g., of each of the different wavelengths and / or polarizations of the radiation toward emitter layers 2310. An edge-coupler may be configured to edge-couple radiation from one or more sources for each emitter layer. Note that the one or more edge couplers need not be located at an edge of optical component 2302. In some embodiments, an incident radiation beam (based on a fiber-to- PIC coupling) can be incident into one layer of the emitter structure with a propagating order being coupled to other emitter layers (for example, by vertical directional coupling) or each layer may have its own incident light beam (from a respective fiber array).

[0265] In some embodiments, system 2300 comprises a detector (detector array 1740 shown in Fig. 17-19) configured to detect reflected and / or diffracted charged particle beams 1711, 1712, 1713 froma sample such as substrate 1708 and generate an assessment signal (e.g., as described above in the discussion of detector array 1740). The assessment signal may be useable to generate charged particle beam voltage contrast defect inspection images, for example, and / or other assessment information.

[0266] Comparing ACC operations and optical component 2302 to alignment operations and optical component 8 (see the discussion related to Fig. 1-15 above), grating couplers for alignment may emit (if configured for emission) light into two directions. If an additional layer is added, light is diffracted by the other layer, which can interfere with a primary optical beam (see the Fourier optics description in Fig. 9). Thus, for two layer grating couplers, four emission beams are observed if they are configured for different wavelengths.

[0267] Beam distortion at a sample location can be caused by overlap of beam spots of the respective emitter layers with unintended beam spots. A multilayer arrangement of emitters (as shown in Fig. 23) can result in secondary beams (distinguished from the main beam for which the emitter layer is designed to emit). If the PIC is placed below the detector (i.e. a close proximity to the sample location), then this secondary beam can cause beam distortion as a result of a beam spot from the main beam interfering with the undesired beam spot from the secondary beam. This is undesirable as it is not power efficient (causes power dissipation). However, the periodicity of the emitter arrangement and / or the spacing between emitter layers can be configured to minimize beam distortion, as described above.

[0268] For example, secondary beams may form when a grating coupler like the ones used in optical component 8 described above, having multiple layers (two in this example), emits radiation. For alignment applications, the secondary beams are relatively far from a main beam, such that they do not interfere with the main beam(s) during alignment measurement. Hence, secondary beams do not pose a problem for alignment measurement. However, secondary beams do cause beam distortion for ACC applications, because the working distance in assessment systems like those described above is only a few tens of microns (e.g., see discussion above). To overcome this issue, in the emitter arrangement 2320 (Fig. 23) for each of the plurality of emitter layers 2310, the periodicity of the semi-periodic or periodic arrangement of emitter structures 2322 is reduced compared to that in optical component 8, and the separation between layers is increased compared to that of the grating couplers used for alignment (in optical component 8).

[0269] In general, the emission from a grating coupler at wavelength x should not be diffracted by grating couplers emitting at wavelengths (y x). With reference to Fig. 24, which illustrates a second Fourier optics description, if the periodicity of the emitter structures Ai and A2is reduced, the first diffraction order from a first emitter layer will be evanescent because P , , > k0. If there are twolayers, the second layer diffracts each order twice, so there will be four diffraction orders, but only two of them are propagating [32,4 and [F ? , which have a wave-vector smaller than the wave-vector in a vacuum, ko. Note that the second layer converts the evanescent field into a propagating field. However, if the separation between the two layers is increased, the evanescent field from the bottom layer will decay and the intensity will be too weak to be diffracted by the top layer. Hence, only one beam will reach the sample (e.g., substrate) and the second layer will not distort the main beam. Note that, for ease of illustration, Fig. 4 is shown upside down from how layers may actually be typically arranged in an assessment system.

[0270] Fig. 25 illustrates an assessment method 2500. In some embodiments, method 2500 is performed as part of an defect inspection operation in a semiconductor device manufacturing process, for example. In some embodiments, one or more operations of method 2500 may be implemented in or by assessment system 2300 illustrated in Fig. 23, optical component 2302 illustrated in Fig. 23, a computer system (e.g., a computer system as illustrated in Fig. 26 and described below, etc.) or a controller described herein, and / or in or by other systems, for example. In some embodiments, method 2500 comprises projecting (operation 2502) one or more charged particle beams towards a sample (e.g., substrate) location; emitting (operation 2504) multiple optical beams of one or more wavelengths towards the sample location; detecting (operation 2506) charged particle beams from the sample; and / or other operations.

[0271] The operations of method 2500 are intended to be illustrative. In some embodiments, method 2500 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 2500 may include an additional operation comprising determining an adjustment for a semiconductor device manufacturing process. Additionally, the order in which the operations of method 2500 are illustrated in Fig. 25 and described herein is not intended to be limiting.

[0272] In some embodiments, one or more portions of method 2500 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 2500 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 2500 (e.g., see discussion related to Fig. 26 below).

[0273] At operation 2502, one or more charged particle beams are projected towards a samplelocation (e.g., on a sample such as a substrate) with a charged particle optical source, which forms a portion of a charged particle optical system (e.g., as described above). In some embodiments, the charged particle optical source is an electron source. The charged particle optical system and the optical component (see next paragraph) may form a semiconductor assessment system that comprises at least a portion of scanning electron microscope, for example. In some embodiments, the scanning electron microscope is configured for a sample such as a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor defect inspection process. In some embodiments, the charged particle optical system is configured to project multiple charged particle beams comprising electron beams toward a sample location (e.g., on a sample such as a substrate) for an assessment (e.g., a defect inspection). In some embodiments, operation 2502 is performed by a charged particle optical system similar to and / or the same as system 1730 shown in Fig. 17-19, and / or other components as described above.

[0274] At operation 2504, multiple optical beams of different wavelengths (though in some embodiments the wavelengths overlap or are substantially the same) are emitted towards the sample location with an optical component. In some embodiments, the optical component comprises a photonic integrated circuit. The optical component comprises a plurality of emitter layers (or layers of emitters). In some embodiments, the optical component comprises an optical stack having the plurality of emitter layers for emission of the multiple optical beams of different wavelengths towards the sample location. One or more beam apertures are defined in the optical component for passage of the charged particle beam(s). Each of the plurality of emitter layers may be configured to emit a respective optical beam of a respective wavelength towards the sample location.

[0275] The optical stack having the plurality of emitter layers is configured to minimize beam distortion of the respective optical beams at the sample location. The plurality of emitter layers are configured to emit the respective optical beams such that the respective optical beams are substantially coincident at the sample location.

[0276] In some embodiments, each of the plurality of emitter layers comprises a respective emitter arrangement. The respective emitter arrangement is configured to emit the respective optical beam. In some embodiments, the respective emitter arrangement comprises a semi-periodic or periodic arrangement of emitter structures. The periodic or semi-periodic arrangement is configured to diffract optical radiation coupled into the respective emitter arrangement for emission of the respective optical beam. Each emitter arrangement may be configured to minimize a further diffraction of one or more diffraction orders associated with other emitter arrangements. For example, each emitter arrangement may be configured to minimize the first order, or diffraction of higher diffraction orders associated with the other emitter arrangements. A periodicity of the emitter structures in the emitter arrangementand / or a separation between each of the plurality of emitter layers is configured to minimize emission of higher orders of diffraction associated with the multiple optical beams, from one emitter layer to another emitter layer.

[0277] In some embodiments, the assessment system comprises an edge coupler coupled to one or more edges of the optical component and configured to conduct the optical beams of different wavelengths toward the plurality of emitter layers.

[0278] In some embodiments, the different wavelengths overlap, and the plurality of emitter layers are each optimized for a given wavelength. In some embodiments, each different wavelength is associated with a different color and has a wavelength bandwidth for the associated color. In some embodiments, the wavelengths are the same.

[0279] In some embodiments, the plurality of emitter layers comprise grating couplers. In some embodiments, the emitter layers comprise waveguides coupled to the grating couplers configured to direct the optical beams of different wavelengths toward the grating couplers.

[0280] The optical component may be configured to direct the multiple optical beams of different wavelengths toward the sample location such that the multiple optical beams impinge the sample location coincident with and / or in proximity to the electron beams to control charge on the sample to enhance the assessment. In some embodiments, enhancing the assessment comprises increasing contrast to increase defect visibility (on a sample such as a substrate). Directing the multiple optical beams of different wavelengths toward the sample such that the multiple optical beams impinge the sample coincident with or in proximity to the electron beams to control charge on the sample comprises advanced charge control (ACC).

[0281] In some embodiments, the optical component comprises a silicon substrate, and at least two silicon nitride, aluminum oxide, lithium niobate or quartz grating couplers and waveguides. The at least two grating couplers and waveguides may be stacked vertically in two or more different layers, substantially parallel to each other on the silicon substrate. Each grating coupler and waveguide may be optimized for a different wavelength. In some embodiments, the at least two grating couplers and waveguides, and the silicon substrate, are clad with silicon dioxide. In some embodiments, emitters in each of the plurality of emitter layers extend different distances, and / or are located at different distances, from an axis of a charged particle beam. In some embodiments, operation 2504 is performed by an optical component similar to and / or the same as optical component 2302 shown in Fig. 23, and described above.

[0282] At operation 2506, charged particle beams from the sample (e.g., substrate) are detected with a detector. In some embodiments, the detector is configured to detect reflected and / or diffracted charged particle beams from the sample, and generate an assessment signal. The assessment signalmay be useable to generate charged particle beam voltage contrast defect inspection images, for example. Operation 2506 may be performed by a detector similar to and / or the same as detector array 1740 shown in Fig. 17-19, and described herein.

[0283] In some embodiments, operation 2506 comprises determining an adjustment for a semiconductor device manufacturing process. For example, this may include automatically adjusting, with one or more processors, one or more lithography patterning process parameters. In some embodiments, operation 2506 includes determining one or more semiconductor device manufacturing process 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.

[0284] In some embodiments, operation 2506 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 a processor described as part of the computer system illustrated in Fig. 26 and described below, and / or other processors. For example, if a defect inspection indicates that at lithography process is producing an excessive amount of defects, the defects 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., inspection results may breach a threshold for acceptability). One or more new or adjusted process parameters may be determined. The new or adjusted process parameters may be configured to cause a manufacturing process to again produce acceptable devices.

[0285] Fig. 26 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 one or more of the processors described herein) 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 storinginformation and instructions.

[0286] 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. An input device ID, including alphanumeric and other keys, is coupled to bus BS for communicating information and command selections to processor PRO. Another type of user input device is cursor control CC, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor PRO and for controlling cursor movement on display DS. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

[0287] 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 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.

[0288] The term “computer-readable medium” or “machine-readable medium” refers to any medium that participates in providing instructions to processor PRO for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device SD. Volatile media include dynamic memory, such as main memory MM. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus BS. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Computer-readable media can be non-transitory, for example, a 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 electromagneticsignal, for example.

[0289] 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 / or instructions 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.

[0290] 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.

[0291] 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.

[0292] 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 codein the form of a carrier wave.

[0293] 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 irradiate a metrology target in a patterned substrate with radiation; an optical component comprising layers of collectors, the layers of collectors each configured to collect diffracted radiation having a different wavelength range from the metrology target; and a radiation detector configured to generate a metrology signal based on the diffracted radiation having the different wavelength ranges captured by the layers of collectors, and polarizations of the diffracted radiation, the metrology signal comprising measurement information pertaining to the metrology target.2. The system of clause 1, wherein the collectors comprise dielectric grating couplers.3. The system of any of the previous clauses, wherein the optical component further comprises a photonic integrated circuit.4. The system of any of the previous clauses, wherein the photonic integrated circuit comprises waveguides coupled to the grating couplers configured to conduct collected diffracted radiation toward the radiation detector.5. The system of any of the previous clauses, wherein the optical component comprises: a substrate, and at least two layers of dielectric grating couplers and waveguides.6. The system of any of the previous clauses, wherein the at least two layers of dielectric grating couplers and waveguides are stacked vertically in at least two different layers, substantially parallel to each other on the substrate, and each dielectric grating coupler and waveguide is optimized for a different wavelength range and / or polarization.7. The system of any of the previous clauses, wherein the at least two layers of dielectric grating couplers and waveguides, and the substrate, are clad with silicon dioxide and / or a low index dielectric material.8. The system of any of the previous clauses, wherein each of the layers of collectors is configured to collect diffracted radiation of different wavelength ranges and / or different polarizations, and further configured to collect diffracted radiation with specific polarizations, and / or orientations.9. The system of any of the previous clauses, wherein an orientation of the diffracted radiation comprises an X or Y orientation, and is dependent on a corresponding X or Y orientation of the metrology target.10. The system of any of the previous clauses, wherein the collectors in each of the layers extenddifferent distances, and / or are located at different distances, from an axis of the radiation from the radiation source in a given layer.11. The system of any of the previous clauses, wherein the layers of collectors are each further configured to collect diffracted radiation having a different wavelength range by: adjusting a thickness of a layer of collectors; adjusting a stack for each layer; adjusting pitch and / or duty cycle of periodic structures in a layer of collectors; adjusting a curvature of the periodic structures; adjusting a separation between layers; determining and / or adjusting a material for each layer; forming one or more sub-layers of collectors in a given layer; and / or adjusting a distance of the optical component and / or a given layer to the metrology target in the patterned substrate.12. The system of any of the previous clauses, further comprising an out-coupler coupled to one or more edges of the optical component and configured to conduct each of the different wavelength ranges of the collected diffracted radiation from the optical component to the radiation detector.13. The system of any of the previous clauses, wherein the out-coupler: is configured to out-couple light from different facets of the optical component for each layer; comprises one or more grating couplers for out-coupling one or more different wavelength ranges into a fiber, wherein the one or more grating couplers need not be located at an edge of the optical component; and / or comprises a single fiber array configured to couple to an edge of the optical component, the edge of the optical component being tapered to reduce a spacing between layers near the edge.14. The system of any of the previous clauses, wherein the different wavelength ranges overlap, and the layers of collectors are each optimized for a center of a given wavelength range.15. The system of any of the previous clauses, wherein each different wavelength range is associated with a different color and has a wavelength bandwidth for the associated color.16. The system of any of the previous clauses, wherein the layers of collectors comprise 2-24 layers of collectors, the layers of collectors each configured to collect diffracted radiation having 2-24 different corresponding wavelength ranges.17. The system of any of the previous clauses, wherein there are 12 layers of collectors configured to collect diffracted radiation having 12 different corresponding wavelength ranges.18. 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 an alignment of a layer of the patterned substrate based on the metrology signal.19. The system of any of the previous clauses, wherein the radiation source, the optical component, and the radiation detector, form a portion of an alignment metrology system.20. The system of any of the previous clauses, wherein the alignment metrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductormanufacturing process.21. A metrology method, comprising: irradiating, with a radiation source, a metrology target in a patterned substrate with radiation; collecting, with an optical component comprising layers of collectors, diffracted radiation having different wavelength ranges from the metrology target with each layer of collectors; and generating, with a radiation detector, a metrology signal based on the diffracted radiation having the different wavelength ranges captured by the layers of collectors, and polarizations of the diffracted radiation, the metrology signal comprising measurement information pertaining to the metrology target.22. The method of clause 21, wherein the collectors comprise dielectric grating couplers.23. The method of any of the previous clauses, wherein the optical component further comprises a photonic integrated circuit.24. The method of any of the previous clauses, wherein the photonic integrated circuit comprises waveguides coupled to the grating couplers configured to conduct collected diffracted radiation toward the radiation detector.25. The method of any of the previous clauses, wherein the optical component comprises: a substrate, and at least two layers of dielectric grating couplers and waveguides.26. The method of any of the previous clauses, wherein the at least two layers of dielectric grating couplers and waveguides are stacked vertically in at least two different layers, substantially parallel to each other on the substrate, and each dielectric grating coupler and waveguide is optimized for a different wavelength range and / or polarization.27. The method of any of the previous clauses, further comprising cladding the at least two layers of dielectric grating couplers and waveguides, and the substrate, with silicon dioxide and / or a low index dielectric material.28. The method of any of the previous clauses, wherein each of the layers of collectors is configured to collect diffracted radiation of different wavelength ranges and / or different polarizations, and further configured to collect diffracted radiation with specific polarizations, and / or orientations.29. The method of any of the previous clauses, wherein an orientation of the diffracted radiation comprises an X or Y orientation, and is dependent on a corresponding X or Y orientation of the metrology target.30. The method of any of the previous clauses, wherein the collectors in each of the layers extend different distances, and / or are located at different distances, from an axis of the radiation from the radiation source in a given layer.31. The method of any of the previous clauses, further comprising configuring each of the layers of collectors to collect diffracted radiation having a different wavelength range by: adjusting a thicknessof a layer of collectors; adjusting a stack for each layer; adjusting pitch and / or duty cycle of periodic structures in a layer of collectors; adjusting a curvature of the periodic structures; adjusting a separation between layers; determining and / or adjusting a material for each layer; forming one or more sub-layers of collectors in a given layer; and / or adjusting a distance of the optical component and / or a given layer to the metrology target in the patterned substrate.32. The method of any of the previous clauses, further comprising conducing, with an out-coupler coupled to one or more edges of the optical component, each of the different wavelength ranges of the collected diffracted radiation from the optical component to the radiation detector.33. The method of any of the previous clauses, wherein the out-coupler: is configured to out-couple light from different facets of the optical component for each layer; comprises one or more grating couplers for out-coupling one or more different wavelength ranges into a fiber, wherein the one or more grating couplers need not be located at an edge of the optical component; and / or comprises a single fiber array configured to couple to an edge of the optical component, the edge of the optical component being tapered to reduce a spacing between layers near the edge.34. The method of any of the previous clauses, wherein the different wavelength ranges overlap, and the layers of collectors are each optimized for a center of a given wavelength range.35. The method of any of the previous clauses, wherein each different wavelength range is associated with a different color and has a wavelength bandwidth for the associated color.36. The method of any of the previous clauses, wherein the layers of collectors comprise 2-24 layers of collectors, the layers of collectors each configured to collect diffracted radiation having 2-24 different corresponding wavelength ranges.37. The method of any of the previous clauses, wherein there are 12 layers of collectors configured to collect diffracted radiation having 12 different corresponding wavelength ranges.38. The method of any of the previous clauses, further comprising determining, with one or more processors operatively coupled to the radiation detector, an alignment of a layer of the patterned substrate based on the metrology signal.39. The method of any of the previous clauses, wherein the radiation source, the optical component, and the radiation detector, form a portion of an alignment metrology system.40. The method of any of the previous clauses, wherein the alignment metrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor manufacturing process.41. A metrology system, comprising: a radiation source configured to irradiate a metrology target in a patterned substrate with radiation; an optical component comprising one or more planar photonic integrated circuits configured to receive diffracted radiation from the metrology target, the one ormore planar photonic integrated circuits arranged in a perpendicular orientation relative to the metrology target; and a radiation detector configured to generate a metrology signal based on the diffracted radiation received by the one or more planar photonic integrated circuits, the metrology signal comprising measurement information pertaining to the metrology target.42. The system of any of the previous clauses, wherein the metrology target comprises an alignment mark.43. 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 an alignment of a layer of the patterned substrate based on the metrology signal.44. The system of any of the previous clauses, wherein: the radiation source, the optical component, 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.45. The system of any of the previous clauses, wherein the radiation detector comprises an interferometer configured to interfere diffraction orders of received diffracted radiation, a photodiode, and / or a charge coupled device (CCD).46. The system of any of the previous clauses, wherein the one or more planar photonic integrated circuits comprise two or more planar photonic integrated circuits.47. The system of any of the previous clauses, wherein the two or more planar photonic integrated circuits are arranged in the perpendicular orientation at two or more grid aligned positions relative to the metrology target, and wherein the perpendicular orientation at the two or more grid aligned positions is configured to facilitate dense stacking of the planar photonic integrated circuits.48. The system of any of the previous clauses, wherein the radiation detector comprises multiple sensing devices operating in parallel.49. The system of any of the previous clauses, wherein: the radiation source comprises a fiber array edge coupled to an illumination source chip, a micro mirror or micro lens, and off axis parabolic mirrors; the fiber array is configured to conduct the radiation to the illumination source chip; and the illumination source chip comprises a waveguide configured to propagate the radiation on the chip toward the micro mirror or micro lens and the off axis parabolic mirrors, which focus, shape, and / or direct the radiation toward the metrology target.50. The system of any of the previous clauses, wherein the illumination source chip is arranged in the perpendicular orientation relative to the metrology target, which is parallel to the two or more planar photonic integrated circuits.51. The system of any of the previous clauses, wherein each of the planar photonic integrated circuitscomprises one or more parabolic collector micro mirrors and one or more corresponding collector waveguides configured to collect the diffracted radiation and direct collected diffracted radiation toward the radiation detector.52. The system of any of the previous clauses, wherein the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise one parabolic collector micro mirror and one corresponding collector waveguide.53. The system of any of the previous clauses, each of the planar photonic integrated circuits further comprise an arrayed waveguide grating configured to demultiplex received diffracted radiation.54. The system of any of the previous clauses, wherein the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise an array of parabolic collector micro mirrors and corresponding collector waveguides.55. The system of any of the previous clauses, further comprising fibers edge coupled to each of the planar photonic integrated circuits configured to guide received diffracted radiation to the radiation detector.56. The system of any of the previous clauses, wherein the one or more planar photonic integrated circuits comprise one planar photonic integrated circuit.57. The system of any of the previous clauses, further comprising a fiber array edge coupled to the one planar photonic integrated circuit configured to receive and conduct the radiation from the radiation source to the one planar photonic integrated circuit.58. The system of any of the previous clauses, wherein the one planar photonic integrated circuit comprises a source waveguide or photonic crystal waveguide configured to conduct the radiation from the edge coupled fiber array through the one planar photonic integrated circuit and direct the radiation toward the metrology target.59. The system of any of the previous clauses, wherein the one planar photonic integrated circuit comprises two elliptical mirrors and a beam combiner, the two elliptical mirrors configured to reflect received diffracted radiation toward the beam combiner, the beam combiner configured to combine received reflected diffracted radiation from the two elliptical mirrors such that the combined received reflected diffracted radiation is configured to be separated by a demultiplexer and signal processed.60. The system of any of the previous clauses, wherein the one planar photonic integrated circuit comprises additional mirrors configured to fold a reflection path from the two elliptical mirrors to different angles relative to the beam combiner.61. The system of any of the previous clauses, wherein the one planar photonic integrated circuit comprises a dispersion device configured to separate wavelengths of the received reflected diffracted radiation within the one planar photonic integrated circuit.62. The system of any of the previous clauses, wherein the dispersion device comprises a prism or an arrayed waveguide grating (AWG).63. The system of any of the previous clauses, wherein the metrology target and the beam combiner are located at different foci of an ellipse associated with the two elliptical mirrors.64. The system of any of the previous clauses, wherein the beam combiner comprises two beam combiners, and wherein positive and negative orders of the received reflected diffracted radiation are each directed to a beam combiner for a corresponding diffraction order.65. The system of any of the previous clauses, wherein the one planar photonic integrated circuit has a target thickness configured to facilitate propagation of the radiation within the one planar photonic integrated circuit.66. The system of any of the previous clauses, further comprising an adjuster configured to adjust a distance between any two of the planar photonic integrated circuits.67. The system of claim 66, wherein the adjuster comprises an actuator between each two of the planar photonic integrated circuits.68. The system of any of the previous clauses, wherein each actuator is configured to independently adjust distances between each two of the planar photonic integrated circuits.69. The system of any of the previous clauses, wherein the adjuster is configured to enable simultaneous measurement of a number of different metrology targets in a single field, without restriction on where the different metrology targets are located.70. The system of any of the previous clauses, wherein the metrology target comprises a grating.71. A metrology method, comprising: irradiating, with a radiation source, a metrology target in a patterned substrate with radiation; receiving, with an optical component comprising one or more planar photonic integrated circuits, diffracted radiation from the metrology target, the one or more planar photonic integrated circuits arranged in a perpendicular orientation relative to the metrology target; and generating, with a radiation detector, a metrology signal based on the diffracted radiation received by the one or more planar photonic integrated circuits, the metrology signal comprising measurement information pertaining to the metrology target.72. The method of any of the previous clauses, wherein the metrology target comprises an alignment mark.73. The method of any of the previous clauses, further comprising determining, with one or more processors operatively coupled to the radiation detector, an alignment of a layer of the patterned substrate based on the metrology signal.74. The method of any of the previous clauses, wherein: the radiation source, the optical component, and the radiation detector, form a portion of an alignment metrology system; and the alignmentmetrology system is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor manufacturing process.75. The method of any of the previous clauses, wherein the radiation detector comprises an interferometer configured to interfere diffraction orders of received diffracted radiation, a photodiode, and / or a charge coupled device (CCD).76. The method of any of the previous clauses, wherein the one or more planar photonic integrated circuits comprise two or more planar photonic integrated circuits.77. The method of any of the previous clauses, wherein the two or more planar photonic integrated circuits are arranged in the perpendicular orientation at two or more grid aligned positions relative to the metrology target, and wherein the perpendicular orientation at the two or more grid aligned positions is configured to facilitate dense stacking of the planar photonic integrated circuits.78. The method of any of the previous clauses, wherein the radiation detector comprises multiple sensing devices operating in parallel.79. The method of any of the previous clauses, wherein: the radiation source comprises a fiber array edge coupled to an illumination source chip, a micro mirror or micro lens, and off axis parabolic mirrors; the fiber array is configured to conduct the radiation to the illumination source chip; and the illumination source chip comprises a waveguide configured to propagate the radiation on the chip toward the micro mirror or micro lens and the off axis parabolic mirrors, which focus, shape, and / or direct the radiation toward the metrology target.80. The method of any of the previous clauses, wherein the illumination source chip is arranged in the perpendicular orientation relative to the metrology target, which is parallel to the two or more planar photonic integrated circuits.81. The method of any of the previous clauses, wherein each of the planar photonic integrated circuits comprises one or more parabolic collector micro mirrors and one or more corresponding collector waveguides configured to collect the diffracted radiation and direct collected diffracted radiation toward the radiation detector.82. The method of any of the previous clauses, wherein the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise one parabolic collector micro mirror and one corresponding collector waveguide.83. The method of any of the previous clauses, each of the planar photonic integrated circuits further comprise an arrayed waveguide grating configured to demultiplex received diffracted radiation.84. The method of any of the previous clauses, wherein the one or more parabolic collector micro mirrors and the one or more corresponding collector waveguides comprise an array of parabolic collector micro mirrors and corresponding collector waveguides.85. The method of any of the previous clauses, further comprising guiding, with fibers edge coupled to each of the planar photonic integrated circuits, received diffracted radiation to the radiation detector.86. The method of any of the previous clauses, wherein the one or more planar photonic integrated circuits comprise one planar photonic integrated circuit.87. The method of any of the previous clauses, further comprising receiving and conducting, with a fiber array edge coupled to the one planar photonic integrated circuit, the radiation from the radiation source to the one planar photonic integrated circuit.88. The method of any of the previous clauses, wherein the one planar photonic integrated circuit comprises a source waveguide or photonic crystal waveguide configured to conduct the radiation from the edge coupled fiber array through the one planar photonic integrated circuit and direct the radiation toward the metrology target.89. The method of any of the previous clauses, wherein the one planar photonic integrated circuit comprises two elliptical mirrors and a beam combiner, the two elliptical mirrors configured to reflect received diffracted radiation toward the beam combiner, the beam combiner configured to combine received reflected diffracted radiation from the two elliptical mirrors such that the combined received reflected diffracted radiation is configured to be separated by a demultiplexer and signal processed.90. The method of any of the previous clauses, wherein the one planar photonic integrated circuit comprises additional mirrors configured to fold a reflection path from the two elliptical mirrors to different angles relative to the beam combiner.91. The method of any of the previous clauses, wherein the one planar photonic integrated circuit comprises a dispersion device configured to separate wavelengths of the received reflected diffracted radiation within the one planar photonic integrated circuit.92. The method of any of the previous clauses, wherein the dispersion device comprises a prism or an arrayed waveguide grating (AWG).93. The method of any of the previous clauses, wherein the metrology target and the beam combiner are located at different foci of an ellipse associated with the two elliptical mirrors.94. The method of any of the previous clauses, wherein the beam combiner comprises two beam combiners, and wherein positive and negative orders of the received reflected diffracted radiation are each directed to a beam combiner for a corresponding diffraction order.95. The method of any of the previous clauses, wherein the one planar photonic integrated circuit has a target thickness configured to facilitate propagation of the radiation within the one planar photonic integrated circuit.96. The method of any of the previous clauses, further comprising adjusting, with an adjuster, adistance between any two of the planar photonic integrated circuits.97. The method of any of the previous clauses, wherein the adjuster comprises an actuator between each two of the planar photonic integrated circuits.98. The method of any of the previous clauses, wherein each actuator is configured to independently adjust distances between each two of the planar photonic integrated circuits.99. The method of any of the previous clauses, wherein the adjuster is configured to enable simultaneous measurement of a number of different metrology targets in a single field, without restriction on where the different metrology targets are located.100. The method of any of the previous clauses, wherein the metrology target comprises a grating.101. An optical component for a charged particle optical system configured to direct a charged particle beam toward a sample location, the optical component being configured to emit multiple optical beams of different wavelengths towards the sample location, wherein the optical component comprises an optical stack having a plurality of emitter layers for emission of the multiple optical beams of different wavelengths towards the sample location, wherein a first beam aperture is defined in the optical component for passage of the charged particle beam, and wherein each of the plurality of emitter layers is configured to emit a respective optical beam of a respective wavelength towards the sample location.102. The optical component of clause 101, wherein the optical stack having the plurality of emitter layers is configured to minimize beam distortion of the respective optical beams at the sample location.103. The optical component of any of the clauses 101 or 102, wherein the plurality of emitter layers are configured to emit the respective optical beams such that the respective optical beams are substantially coincident at the sample location.104. The optical component of any of the clauses 101-103, wherein each of the plurality of emitter layers comprises a respective emitter arrangement, the respective emitter arrangement configured to emit the respective optical beam.105. The optical component of clause 104, wherein the respective emitter arrangement comprises a semi-periodic or periodic arrangement of emitter structures, the periodic or semi-periodic arrangement being configured to diffract optical radiation coupled into the respective emitter arrangement for emission of the respective optical beam.106. The optical component of any of the clauses 104 or 105, wherein each emitter arrangement is configured to minimize a further diffraction of one or more diffraction orders associated with other emitter arrangements.107. The optical component of any of the clauses 104-106, wherein each emitter arrangement is configured to minimize diffraction of higher diffraction orders associated with the other emitter arrangements.108. The optical component of any of the clauses 104-107, wherein a periodicity of the emitter structures in the emitter arrangement and / or a separation between each of the plurality of emitter layers is configured to minimize emission of higher orders of diffraction associated with the multiple optical beams, from one emitter layer to another emitter layer.109. The optical component of clause 108, wherein the higher orders comprise second, third, fourth, fifth, or higher diffraction orders.110. The optical component of any of the previous clauses, wherein the optical component comprises a photonic integrated circuit.111. The optical component of any of the previous clauses, wherein the optical component is coupled to one or more optical sources for providing respective input optical radiation into each of the plurality of emitter layers.112. The optical component of clause 111, further comprising one or more waveguides configured to couple input optical radiation into each of the plurality of emitter layers.113. The optical component of any of the previous clauses, wherein the respective optical beam emitted by each of the plurality of emitter layers has a component in a direction opposite to a direction of the respective optical radiation input.114. The optical component of any of the clauses 104-113, wherein the emitter arrangements comprise grating couplers.115. The optical component of clause 114, further comprising: a silicon substrate, and at least two silicon nitride, aluminum oxide, lithium niobate or quartz grating couplers and waveguides.116. The optical component of clause 115, wherein at least two grating couplers and waveguides are stacked vertically in two or more different layers, substantially parallel to each other on the silicon substrate, and each grating coupler and waveguide is optimized for a different wavelength.117. The optical component of clause 116, wherein the at least two grating couplers and waveguides, and the silicon substrate, are clad with silicon dioxide.118. The optical component of any of the previous clauses, wherein emitters in each of the plurality of emitter layers extend different distances, and / or are located at different distances, from an axis of a charged particle beam.119. The optical component of any of the previous clauses, wherein the different wavelengths overlap, and the plurality of emitter layers are each optimized for a given wavelength.120. The optical component of any of the previous clauses, wherein each different wavelength is associated with a different color and has a wavelength bandwidth for the associated color.121. A charged particle optical system configured to project a charged particle optical beam towards a sample location, the charged particle optical system comprising: an optical component according to any of the clauses 101-120, wherein the optical stack is further configured such that the multiple optical beams are substantially coincident with or substantially in the proximity of the charged particle beam at the sample location.122. A charged particle optical system configured to project a plurality of charged particle optical beams towards a sample location, the charged particle optical system comprising: an optical component according to any of the previous clauses, wherein the optical component comprises a plurality of first beam apertures for passage of the respective charged particle beams towards the sample location and a plurality of optical stacks associated with each first beam aperture, each of the plurality of optical stacks being configured such that the multiple optical beams are substantially coincident with or substantially in the proximity of the respective charged particle beam at the sample location.123. An assessment system comprising: a charged particle optical source for generating one or more charged particle beams; and a charged particle optical system according to any of clauses 121 or 122; and a detector for detecting charged particle beams emitted from the sample at the sample location and generate an assessment signal for assessing one or more characteristics of the sample based on an interaction of the one or more charged particle beams and the multiple optical beams with the sample.124. The assessment system of clause 123, wherein the assessment system is a semiconductor assessment system that comprises at least a portion of scanning electron microscope.125. The assessment system of any of the previous clauses, wherein the scanning electron microscope is configured for a sample or a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor defect inspection process.126. A method, comprising: emitting multiple optical beams of different wavelengths towards a sample location with an optical component for a charged particle optical system, the charged particle optical system configured to direct a charged particle beam toward the sample location; wherein the optical component comprises an optical stack having a plurality of emitter layers for emission of the multiple optical beams of different wavelengths towards the sample location, wherein a first beam aperture is defined in the optical component for passage of the charged particle beam, and wherein each of the plurality of emitter layers is configured to emit a respective optical beam of a respective wavelength towards the sample location.127. The method of clause 126, wherein the optical stack having the plurality of emitter layers is configured to minimize beam distortion of the respective optical beams at the sample location.128. The method of any of clauses 126 or 127, wherein the plurality of emitter layers are configured to emit the respective optical beams such that the respective optical beams are substantially coincident at the sample location.129. The method of any of clauses 126-128, wherein each of the plurality of emitter layers comprises a respective emitter arrangement, the respective emitter arrangement configured to emit the respective optical beam.130. The method of clause 129, wherein the respective emitter arrangement comprises a semiperiodic or periodic arrangement of emitter structures, the periodic or semi-periodic arrangement being configured to diffract optical radiation coupled into the respective emitter arrangement for emission of the respective optical beam.131. The method of any clauses 129-130, wherein each emitter arrangement is configured to minimize a further diffraction of one or more diffraction orders associated with other emitter arrangements.132. The method of any of clauses 129-131, wherein each emitter arrangement is configured to minimize diffraction of higher diffraction orders associated with the other emitter arrangements.133. The method of any of clauses 129-132, wherein a periodicity of the emitter structures in the emitter arrangement and / or a separation between each of the plurality of emitter layers is configured to minimize emission of higher orders of diffraction associated with the multiple optical beams, from one emitter layer to another emitter layer.134. The method of clause 133, wherein the higher orders comprise second, third, fourth, fifth, or higher diffraction orders.135. The method of any of the previous clauses 126-134, wherein the optical component comprises a photonic integrated circuit.136. The method of clause 135 , wherein the optical component is coupled to one or more optical sources for providing respective input optical radiation into each of the plurality of emitter layers.137. The method of clause 136, further comprising one or more waveguides configured to couple input optical radiation into each of the plurality of emitter layers.138. The method of any of clauses 126-137, wherein the respective optical beam emitted by each of the plurality of emitter layers has a component in a direction opposite to a direction of the respective optical radiation input.139. The method of any of clauses 129-138, wherein the emitter arrangements comprise grating couplers.140. The method of clause 139, wherein the optical component comprises: a silicon substrate, and at least two silicon nitride, aluminum oxide, lithium niobate or quartz grating couplers and waveguides.141. The method of any clause 140, wherein at least two grating couplers and waveguides are stacked vertically in two or more different layers, substantially parallel to each other on the silicon substrate, and each grating coupler and waveguide is optimized for a different wavelength.142. The method of clause 141, wherein the at least two grating couplers and waveguides, and the silicon substrate, are clad with silicon dioxide.143. The method of any of the previous clauses 126-142, wherein emitters in each of the plurality of emitter layers extend different distances, and / or are located at different distances, from an axis of a charged particle beam.144. The method of any of the previous clauses 126-143, wherein the different wavelengths overlap, and the plurality of emitter layers are each optimized for a given wavelength.145. The method of any of the previous clauses 126-144, wherein each different wavelength is associated with a different color and has a wavelength bandwidth for the associated color.146. A method comprising: projecting, using a charged particle optical system according to clause121, a charged particle optical beam towards a sample location, the method comprising: using the optical component of the said charged particle optical system such that the optical stack directs the multiple optical beams to be substantially coincident with the charged particle beam at the sample location.147. A method comprising: projecting, using a charged particle optical system according to clause 122, a plurality of charged particle optical beams towards a sample location, the method comprising: using the optical component of the said charged particle optical system such that a plurality of first beam apertures formed in the optical component pass the respective charged particle beams towards the sample location, a plurality of optical stacks are associated with each first beam aperture, and each of the plurality of optical stacks is configured such that the multiple optical beams are substantially coincident with the respective charged particle beam at the sample location.148. An assessment method comprising: generating, with a charged particle optical source, one or more charged particle beams; and using the charged particle optical system according to clause 121 or122, for directing the one or more charged particle beams towards a sample location and using the optical component for emitting the multiple optical beams of different wavelengths towards the sample location; and assessing one or more characteristics of the sample based on an interaction of the one or more charged particle beams and the multiple optical beams with the sample.149. The assessment method of any of the previous clauses, wherein the assessment system is a semiconductor assessment system that comprises at least a portion of scanning electron microscope.150. The assessment method of any of the previous clauses, wherein the scanning electron microscope is configured for a patterned substrate comprising a semiconductor wafer, and is used in a semiconductor defect inspection process.

[0294] 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.

[0295] While the concepts disclosed herein may be used for imaging on a substrate such as a silicon wafer, it shall be understood that the disclosed concepts may be used with any type of lithographic imaging systems, e.g., those used for imaging on substrates other than silicon wafers. In addition, the combination and sub-combinations of disclosed elements may comprise separate embodiments.

[0296] 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

WHAT IS CLAIMED IS:

1. A metrology system, comprising: a radiation source configured to irradiate a metrology target in a patterned substrate with radiation; an optical component comprising layers of collectors, the layers of collectors each configured to collect diffracted radiation having a different wavelength range from the metrology target; and a radiation detector configured to generate a metrology signal based on the diffracted radiation having the different wavelength ranges captured by the layers of collectors, and polarizations of the diffracted radiation, the metrology signal comprising measurement information pertaining to the metrology target.

2. The system of claim 1, wherein the collectors comprise dielectric grating couplers.

3. The system of claim 2, wherein the optical component further comprises a photonic integrated circuit.

4. The system of claim 3, wherein the photonic integrated circuit comprises waveguides coupled to the grating couplers configured to conduct collected diffracted radiation toward the radiation detector.

5. The system of claim 4, wherein the optical component comprises: a substrate, and at least two layers of dielectric grating couplers and waveguides.

6. The system of claim 5, wherein the at least two layers of dielectric grating couplers and waveguides are stacked vertically in at least two different layers, substantially parallel to each other on the substrate, and each dielectric grating coupler and waveguide is optimized for a different wavelength range and / or polarization.

7. The system of claim 6, wherein the at least two layers of dielectric grating couplers and waveguides, and the substrate, are clad with silicon dioxide and / or a low index dielectric material.

8. The system of any of claims 1-7, wherein each of the layers of collectors is configured to collect diffracted radiation of different wavelength ranges and / or different polarizations, and further configured to collect diffracted radiation with specific polarizations, and / or orientations.

9. The system of claim 8, wherein an orientation of the diffracted radiation comprises an X or Y orientation, and is dependent on a corresponding X or Y orientation of the metrology target.

10. The system of any of claims 1-9, wherein the collectors in each of the layers extend different distances, and / or are located at different distances, from an axis of the radiation from the radiation source in a given layer.

11. The system of claim 10, wherein the layers of collectors are each further configured to collect diffracted radiation having a different wavelength range by: adjusting a thickness of a layer of collectors; adjusting a stack for each layer; adjusting pitch and / or duty cycle of periodic structures in a layer of collectors; adjusting a curvature of the periodic structures; adjusting a separation between layers; determining and / or adjusting a material for each layer; forming one or more sub-layers of collectors in a given layer; and / or adjusting a distance of the optical component and / or a given layer to the metrology target in the patterned substrate.

12. The system of any of claims 1-11, further comprising an out-coupler coupled to one or more edges of the optical component and configured to conduct each of the different wavelength ranges of the collected diffracted radiation from the optical component to the radiation detector.

13. The system of claim 12, wherein the out-coupler: is configured to out-couple light from different facets of the optical component for each layer; comprises one or more grating couplers for out-coupling one or more different wavelength ranges into a fiber, wherein the one or more grating couplers need not be located at an edge of the optical component; and / orcomprises a single fiber array configured to couple to an edge of the optical component, the edge of the optical component being tapered to reduce a spacing between layers near the edge.

14. The system of any of claims 1-13, wherein the different wavelength ranges overlap, and the layers of collectors are each optimized for a center of a given wavelength range.

15. The system of any of claims 1-14, wherein each different wavelength range is associated with a different color and has a wavelength bandwidth for the associated color.

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