Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
  • G01B11/27—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes
  • G01B11/272—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes for testing the alignment of axes using photoelectric detection means
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
  • G03F7/70605—Workpiece metrology
  • G03F7/70616—Monitoring the printed patterns
  • G03F7/70633—Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
  • G03F7/70605—Workpiece metrology
  • G03F7/70681—Metrology strategies
  • G03F7/70683—Mark designs

Definitions

• the present disclosure is related generally to overlay metrology and, more particularly, for on-the-fly scatterometry overlay metrology.
• Overlay metrology targets are typically designed to provide diagnostic information regarding the alignment of multiple layers of a sample by characterizing an overlay target having target features located on sample layers of interest. Further, the overlay alignment of the multiple layers is typically determined by aggregating overlay measurements of multiple overlay targets at various locations across the sample.
• Some overlay metrology targets e.g., scatterometry overlay (SCOL) metrology targets
• SCOL scatterometry overlay
• Typical SCOL metrology targets include periodic structures contained within a plurality of cells, where the periodic structures are configured for illumination along at least two measurement directions.
• typical SCOL metrology targets containing a plurality of cells occupy a larger surface area of a sample, and metrology measurements using such targets require more time when compared to SCOL metrology targets having cells configured for metrology measurement along a single measurement direction.
• the metrology target includes a first cell.
• the first cell includes a first portion of a first set of pattern elements formed along a first measurement direction, wherein the first set of pattern elements comprises segmented pattern elements having a first pitch.
• the metrology target includes a first portion of a second set of pattern elements formed along the first measurement direction, wherein the second set of pattern elements comprises segmented pattern elements having a second pitch.
• the metrology target includes a first portion of a third set of pattern elements formed along the first measurement direction, wherein the third set of pattern elements comprises segmented pattern elements having a third pitch.
• the system includes one or more controllers having one or more processors communicatively coupled to one or more metrology subsystems, wherein the one or more processors are configured to execute a set of program instructions maintained in memory, wherein the set of program instructions is configured to cause the one or more processors to: receive, from the one or more metrology subsystems, one or more signals indicative of illumination emanating from a first set of pattern elements, a second set of pattern elements, and a third set of pattern elements of one or more metrology targets of a sample, wherein the one or more metrology targets of the sample comprise: a first cell, the first cell comprising a first portion of a first set of pattern elements formed along a first measurement direction, wherein the first set of pattern elements comprises segmented pattern elements having a first pitch; a first portion of a second set of pattern elements formed along the first measurement direction, wherein the second set of pattern elements comprises segmented pattern elements having
• the method includes illuminating a sample having one or more metrology targets.
• the method includes detecting one or more signals indicative of illumination emanating from a first set of pattern elements, a second set of pattern elements, and a third set of pattern elements of the one or more metrology targets of the sample, wherein the one or more metrology targets of the sample comprise a first cell, the first cell comprising a first portion of a first set of pattern elements formed along a first measurement direction, wherein the first set of pattern elements comprises segmented pattern elements having a first pitch; a first portion of a second set of pattern elements formed along the first measurement direction, wherein the second set of pattern elements comprises segmented pattern elements having a second pitch; and a first portion of a third set of pattern elements formed along the first measurement direction, wherein the third set of pattern elements comprises segmented pattern elements having a third pitch.
• the method includes acquiring a first overlay measurement based on the one or more signals indicative of illumination emanating from the first set of pattern elements. In another embodiment, the method includes acquiring a second overlay measurement based on the one or more signals indicative of illumination emanating from the second set of pattern elements. In another embodiment, the method includes acquiring a third overlay measurement based on the one or more signals indicative of illumination emanating from the third set of pattern elements. In another embodiment, the method includes determining an overlay error based on at least one of the first overlay measurement, the second overlay measurement, or the third overlay measurement.
• the method includes forming a first cell, the first cell comprising a first portion of a first set of pattern elements formed along a first measurement direction, wherein the first set of pattern elements comprises segmented pattern elements having a first pitch; a first portion of a second set of pattern elements formed along the first measurement direction, wherein the second set of pattern elements comprises segmented pattern elements having a second pitch; and a first portion of a third set of pattern elements formed along the first measurement direction, wherein the third set of pattern elements comprises segmented pattern elements having a third pitch.
• FIG. 1 A is a top view of a metrology target, in accordance with one or more embodiments of the present disclosure.
• FIG. 1 B is a top view of a metrology target, in accordance with one or more embodiments of the present disclosure.
• FIG. 1 C is a top view of a metrology target, in accordance with one or more embodiments of the present disclosure.
• FIG. 1 D is a side view of a metrology target, in accordance with one or more embodiments of the present disclosure.
• FIG. 2 is a conceptual view of a metrology system, in accordance with one or more embodiments of the present disclosure.
• FIG. 3 illustrates a conceptual view of a metrology sub-system, in accordance with one or more embodiments of the present disclosure.
• FIG. 4 is a process flow diagram depicting the steps of a method of measuring overlay of a sample, in accordance with one or more embodiments of the present disclosure.
• FIG. 5 is a process flow diagram depicting the steps of a method of forming a metrology target, in accordance with one or more embodiments of the present disclosure.
• a semiconductor device may be formed as multiple printed layers of patterned material on a substrate. Each printed layer may be fabricated through a series of process steps such as, but not limited to, one or more material deposition steps, one or more lithography steps, or one or more etching steps. In some fabrication processes, the printed layers may be formed using one or more photo resist materials. For example, a photo resist material may be deposited onto the substrate. The photo resist material may then be exposed to illumination, wherein the illumination produces a latent target pattern on the photo resist material.
• the latent target pattern (or a developed target pattern formed from the latent target pattern) may then be used as a pattern for one or more lithography and/or one or more etching steps configured to form a final target pattern on the substrate for use in overlay and/or metrology applications.
• the photo resist material is exposed to illumination to produce a latent target pattern on the photo resist material, and the latent target pattern (or a developed target pattern formed from the latent target pattern) is used in overlay and/or metrology applications.
• each printed layer must typically be fabricated within selected tolerances to properly construct the final device.
• the relative placement of printed elements in each layer e.g., the overlay or the overlay parameters
• metrology targets may be fabricated on one or more printed layers to enable efficient characterization of the overlay of the layers. Deviations of overlay target features on a printed layer may thus be representative of deviations of printed characteristics of printed device features on that layer.
• overlay measured at one fabrication step may be used to generate correctables for precisely aligning a process tool (e.g., a lithography tool, or the like) for the fabrication of an additional sample layer in a subsequent fabrication step.
• a process tool e.g., a lithography tool, or the like
• Metrology targets may typically include well-defined printed elements designed to provide an accurate representation of one or more printing characteristics.
• measured characteristics of printed elements of a metrology target e.g., by a metrology tool
• metrology targets are typically characterized as having one or more measurement cells, where each cell includes printed elements in one or more layers on the sample. A metrology measurement may then be based on any combination of measurements of the size, orientation, or location (e.g., pattern placement) of printed elements in a single cell or between multiple cells.
• one or more cells of an overlay metrology target may include printed elements on two or more sample layers arranged such that the relative positions of elements of each layer may be indicative of offset errors (e.g., pattern placement errors (PRE)) in a particular layer or overlay errors associated with registration errors between sample layers.
• process-sensitive metrology targets may include printed elements on a single sample layer, where one or more characteristics of the printed elements (e.g., width or critical dimension (CD), sidewall angle, position, or the like) are indicative of one or more process metrics including, without limitation, the dose of illumination during a lithography step or a focal position of the sample in a lithography tool during a lithography step.
• Overlay metrology is typically performed by fabricating one or more overlay targets across a sample, where each overlay target includes features in sample layers of interest, which are fabricated at the same time as features associated with a device or component being fabricated.
• overlay errors measured at a location of an overlay target may be representative of overlay errors of device features.
• overlay measurements may be used to monitor and/or control any number of fabrication tools to maintain production of devices according to specified tolerances.
• overlay measurements of a current layer with respect to a previous layer on one sample may be utilized as feed-back data to monitor and/or mitigate deviations of the fabrication of the current layer on additional samples within a lot.
• overlay measurements of a current layer with respect to a previous layer on one sample may be utilized as feed-forward data to fabricate a subsequent layer on the same sample in a way that takes into account the existing layer alignments.
• Overlay targets typically include features specifically designed to be sensitive to overlay errors between sample layers of interest.
• An overlay measurement may then be carried out by characterizing the overlay target using an overlay metrology tool and applying an algorithm to determine overlay errors on the sample based on the output of the metrology tool.
• an overlay metrology tool is typically configurable according to a recipe including a set of measurement parameters utilized to generate an overlay signal.
• a recipe of an overlay metrology tool may include, but is not limited to, an illumination wavelength, a detected wavelength of radiation emanating from the sample, a spot size of illumination on the sample, an angle of incident illumination, a polarization of incident illumination, a position of a beam of incident illumination on an overlay target, a position of an overlay target in the focal volume of the overlay metrology tool, or the like.
• an overlay recipe may include a set of measurement parameters for generating an overlay signal suitable for determining overlay of two or more sample layers.
• Overlay metrology tools may utilize a variety of techniques to determine the overlay of sample layers.
• image-based overlay metrology tools may illuminate an overlay target (e.g., an advanced imaging metrology (AIM) target, a box-inbox metrology target, or the like) and capture an overlay signal including an image of overlay target features located on different sample layers.
• overlay may be determined by measuring the relative positions of the overlay target features.
• scatterometry-based overlay metrology tools may illuminate an overlay target (e.g., a grating-over-grating metrology target, or the like) and capture an overlay signal including an angular distribution of radiation emanating from the overlay target associated with diffraction, scattering, and/or reflection of the illumination beam. Accordingly, overlay may be determined based on models of the interaction of an illumination beam with the overlay target.
• optical metrology tools e.g., light-based metrology tools using electromagnetic radiation for illumination and/or detection
• optical metrology tools For the purposes of the present disclosure, the term “optical metrology tools,” “optical metrology techniques,” and the like indicate metrology tools and techniques using electromagnetic radiation of any wavelength such as, but not limited to, x-ray wavelengths, extreme ultraviolet (EUV) wavelengths, vacuum ultraviolet (VUV) wavelengths, deep ultraviolet (DUV) wavelengths, ultraviolet (UV) wavelengths, visible wavelengths, or infrared (IR) wavelengths.
• EUV extreme ultraviolet
• VUV vacuum ultraviolet
• DUV deep ultraviolet
• UV ultraviolet
• IR infrared
• sample generally refers to a substrate formed of a semiconductor or non-semiconductor material (e.g., a wafer, or the like).
• a semiconductor or non-semiconductor material may include, but is not limited to, monocrystalline silicon, gallium arsenide, and indium phosphide.
• a sample may include one or more layers.
• such layers may include, but are not limited to, a resist (including a photoresist), a dielectric material, a conductive material, and a semiconductive material.
• resist including a photoresist
• One or more layers formed on a sample may be patterned or unpattemed.
• a sample may include a plurality of dies, each having repeatable patterned features. Formation and processing of such layers of material may ultimately result in completed devices.
• Many different types of devices may be formed on a sample, and the term sample as used herein is intended to encompass a sample on which any type of device known in the art is being fabricated.
• the term sample and wafer should be interpreted as interchangeable.
• the terms patterning device, mask and reticle should be interpreted as interchangeable.
• FIG. 1A is a top view of a metrology target 100, in accordance with one or more embodiments of the present disclosure.
• the metrology target 100 may include a first cell
• the first cell 101 may include a first portion 102a of a first set of pattern elements
• the first set of pattern elements 102 may be compatible with any metrology mode known in the art, including, without limitation, any scatterometry-based overlay (SCOL) metrology mode.
• the first set of pattern elements 102 may be configured to include periodic and/or segmented structures for metrology using SCOL-based metrology methods (e.g., grating-over-grating structures, or any structure known in the art to be suitable for diffracting, scattering, and/or reflecting an illumination beam).
• the first set of pattern elements 102 may have a first pitch (e.g., a periodic distance between repeated reference features of the first set of pattern elements 102).
• the first set of pattern elements 102 may be compatible with any image-based overlay metrology mode, including, without limitation, an advanced imaging metrology (AIM) mode, a box-in-box metrology mode, or any other metrology mode known in the art to be suitable for capturing an overlay signal (e.g., an image of overlay target features located on different sample layers).
• AIM advanced imaging metrology
• the first portion 102a of the first set of pattern elements 102 may be configured for metrology along a first measurement direction.
• the first portion 102a of the first set of pattern elements 102 may be configured for measurement along a y-direction.
• the first cell 101 may include a first portion 104a of a second set of pattern elements 104.
• the second set of pattern elements 104 may be compatible, along the first measurement direction, with any metrology mode known in the art, including, without limitation, any scatterometry-based overlay (SCOL) metrology mode.
• the second set of pattern elements 104 may be configured to include periodic and/or segmented structures for metrology using SCOL-based metrology methods (e.g., grating- over-grating structures, or any structure known in the art to be suitable for diffracting, scattering, and/or reflecting an illumination beam).
• the second set of pattern elements 104 may have a second pitch (e.g., a periodic distance between repeated reference features of the second set of pattern elements 104).
• the second set of pattern elements 104 may be compatible with any image-based overlay metrology mode, including, without limitation, an advanced imaging metrology (AIM) mode, a box-in-box metrology mode, or any other metrology mode known in the art to be suitable for capturing an overlay signal (e.g., an image of overlay target features located on different sample layers).
• AIM advanced imaging metrology
• box-in-box metrology mode or any other metrology mode known in the art to be suitable for capturing an overlay signal (e.g., an image of overlay target features located on different sample layers).
• the second pitch may not be equivalent to the first pitch.
• the first cell 101 may include a first portion 106a of a third set of pattern elements 106.
• the third set of pattern elements 106 may be compatible, along the first measurement direction, with any metrology mode known in the art, including, without limitation, any scatterometry-based overlay (SCOL) metrology mode.
• the third set of pattern elements 106 may be configured to include periodic and/or segmented structures for metrology using SCOL-based metrology methods (e.g., grating-over- grating structures, or any structure known in the art to be suitable for diffracting, scattering, and/or reflecting an illumination beam).
• the third set of pattern elements 106 may have a third pitch (e.g., a periodic distance between repeated reference features of the third set of pattern elements 106).
• the third set of pattern elements 106 may be compatible with any image-based overlay metrology mode, including, without limitation, an advanced imaging metrology (AIM) mode, a box-in-box metrology mode, or any other metrology mode known in the art to be suitable for capturing an overlay signal (e.g., an image of overlay target features located on different sample layers).
• AIM advanced imaging metrology
• box-in-box metrology mode e.g., an image of overlay target features located on different sample layers.
• the third set of pattern elements 106 may have a third pitch. It is specifically noted that, in some embodiments, the third pitch may not be equivalent to either the first pitch or the second pitch.
• FIG. 1B is a top view of a metrology target 100, in accordance with one or more embodiments of the present disclosure.
• the metrology target 100 may include a second cell 103.
• the second cell 103 may include a second portion 102b of the first set of pattern elements 102.
• the second portion 102b of the first set of pattern elements 102 may be configured for metrology along a second measurement direction.
• the second portion 102b of the first set of pattern elements 102 may be configured for measurement along an x-direction.
• the second cell 103 may include a second portion 104b of the second set of pattern elements 104.
• the second portion 104b of the second set of pattern elements 104 may be configured for metrology along the second measurement direction.
• the second cell 103 may include a second portion 106b of the third set of pattern elements 106.
• the second portion 106b of the third set of pattern elements 106 may be configured for metrology along the second measurement direction.
• the first cell 101 and the second cell 103 may be formed such that the first cell 101 and the second cell 103 are adjacent to each other.
• the second cell 103 may be formed to a side of the first cell 101.
• each of the first cell 101 and the second cell 103 may be configured such that each of the first measurement direction and the second measurement direction are perpendicular to each other.
• the first cell 101 and the second cell 103 may be four-fold rotationally symmetric.
• the first cell 101 and the second cell 103 may be two-fold rotationally symmetric.
• the size of the first cell 101 and/or the second cell 103 may permit the metrology target 100 to be used in small areas of a sample.
• the metrology target 100 may be configured to include only the first cell 101 in order to comply with space considerations with respect to the sample. In other embodiments, the metrology target 100 may be configured to include only the second cell 103 in order to comply with space considerations with respect to the sample. In other embodiments, the metrology target 100 may be configured to include both the first cell 101 and the second cell 103 in order to comply with space considerations with respect to the sample. [0023] In some embodiments, as shown in FIGS. 1C and 1D, the metrology target 100 may be configured to occupy a smaller amount of surface area on a sample.
• the metrology target 100 may be configured such that the first cell 101 and the second cell 103 form a “grating-over-grating” structure.
• the first cell 101 may be formed in a first layer of the metrology target 100
• the second cell 103 may be formed in a second layer of the metrology target 100.
• the second cell 103 may be formed on top (e.g., along a z-direction) of the first cell 101 such that each of the first portion of the first set of pattern elements 102a, the first portion of the second set of pattern elements 104a, and the first portion of the third set of pattern elements 106a, may form a “grating-over-grating” structure that occupies a smaller surface area on the sample.
• the pattern elements of the metrology target 100 may be configured such that incident radiation directed to one or more portions of the first cell pattern elements 108 and/or the second cell pattern elements 112 may be diffracted by the one or more portions of the first set of pattern elements 102, the second set of pattern elements 104, and/or the third set of pattern elements 106, and the diffracted radiation may be detected and analyzed (e.g., by one or more metrology sub-systems) to determine one or more overlay measurements based on the diffracted radiation and/or one or more signals indicative of the diffracted radiation.
• the embodiments of the present disclosure including, without limitation, the components of the metrology target 100 (e.g., the first cell 101, the second cell 103, the first set of pattern elements 102, the second set of pattern elements 104, and/or the third set of pattern elements 106) may be configured to reduce an amount of time required to perform an overlay measurement.
• the configuration of the first cell 101 in that each of the first portion of the first set of pattern elements 102a, the first portion of the second set of pattern elements 104a, and the first portion of the third set of pattern elements 106a is configured for measurement along the first measurement direction, may reduce the time required for one or more portions of a metrology subsystem to capture a signal from each of the pattern elements of the first cell 101.
• a metrology sub-system may capture signals from such pattern elements without adjusting one or more measurement parameters related to the measurement direction (i.e., the metrology sub-system may receive a signal from the metrology target 100 along only one measurement direction with respect to a given cell).
• FIG. 2 illustrates a simplified block diagram of a metrology system 200, in accordance with one or more embodiments of the present disclosure.
• the metrology system 200 includes one or more metrology sub-systems 202
• the one or more metrology sub-systems 202 may be configured to operate in either an imaging more or a non-imaging mode.
• individual overlay target elements may be resolvable within the illuminated spot on the sample (e.g., as part of a bright-field image, a dark-field image, a phase-contrast image, or the like).
• the one or more metrology sub-systems 202 may operate as a scatterometry-based overlay (SOOL) metrology tool in which radiation from the sample is analyzed at a pupil plane to characterize the angular distribution of radiation from the sample (e.g., associated with scattering and/or diffraction of radiation by the sample).
• SOOL scatterometry-based overlay
• the one or more metrology sub-systems 202 may direct illumination to a sample and may further collect radiation emanating from the sample to generate an overlay signal suitable for the determination of overlay of two or more sample layers.
• the one or more metrology sub-systems may include any type of overlay metrology tool known in the art suitable for generating overlay signals suitable for determining overlay associated with overlay targets on a sample, including, without limitation, any optical metrology tool (e.g., an advanced imaging metrology (AIM) tool, an advanced imaging metrology in-die (AIMid) tool, a triple advanced imaging metrology (Triple AIM) tool, and the like), any particlebased metrology tool (e.g., an electron-beam metrology tool), or a scatterometry-based overlay (SCOL) metrology tool.
• AIM advanced imaging metrology
• AIMid advanced imaging metrology in-die
• Triple AIM triple advanced imaging metrology
• SCOL scatterometry-based overlay
• the embodiments of the present disclosure are not limited to a metrology system 200 having only one metrology sub-system 202, and that the metrology system 200 may include at least two metrology sub-systems.
• the metrology system 200 may include an optical metrology tool and a scatterometry-based overlay (SCOL) metrology tool.
• SCOL scatterometry-based overlay
• the one or more metrology sub-systems 202 may be configurable to generate overlay signals based on any number of recipes defining measurement parameters for the acquiring an overlay signal suitable for determining overlay of an overlay target.
• a recipe the one or more metrology sub-systems 202 may include, but are not limited to, an illumination wavelength, a detected wavelength of radiation emanating from the sample, a spot size of illumination on the sample, an angle of incident illumination, a polarization of incident illumination, wave plan of the incident beam, a position of a beam of incident illumination on an overlay target, a position of an overlay target in the focal volume of the overlay metrology tool, or the like.
• the overlay metrology system 200 includes a controller 204 communicatively coupled to the one or more metrology sub-systems 202.
• the controller 204 may be configured to direct the one or more metrology sub-systems 202 to generate overlay signals based on one or more selected recipes.
• the controller 204 may be further configured to receive data including, but not limited to, overlay signals from the one or more metrology sub-systems 202. Additionally, the controller 204 may be configured to determine overlay associated with an overlay target based on the acquired overlay signals.
• the controller 204 includes one or more processors 206.
• the one or more processors 206 may be configured to execute a set of program instructions maintained in a memory device 208, or memory.
• the one or more processors 206 of a controller 204 may include any processing element known in the art. In this sense, the one or more processors 206 may include any microprocessor-type device configured to execute algorithms and/or instructions.
• the memory device 208 may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 206.
• the memory device 208 may include a non-transitory memory medium.
• the memory device 208 may include, but is not limited to, a read-only memory, a random-access memory, a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid-state drive and the like. It is further noted that memory device 208 may be housed in a common controller housing with the one or more processors 206.
• the metrology sub-system 202 may direct illumination to a sample and may further collect radiation emanating from the sample to generate an overlay signal suitable for the determination of overlay of two or more sample layers.
• the metrology sub-system 202 may be configurable to generate overlay signals based on any number of recipes defining measurement parameters for the acquiring an overlay signal suitable for determining overlay of an overlay target.
• a recipe the metrology sub-system 202 may include, but is not limited to, an illumination wavelength, a detected wavelength of radiation emanating from the sample, a spot size of illumination on the sample, an angle of incident illumination, a polarization of incident illumination, a position of a beam of incident illumination on an overlay target, a position of an overlay target in the focal volume of the overlay metrology tool, or the like.
• the one or more metrology sub-systems 202 may include an optical metrology sub-system 202, such as a metrology sub-system including an optical metrology tool.
• the optical metrology sub-system 202 may include any type of optical metrology tool known in the art suitable for generating metrology data of a sample, including, without limitation, an optical metrology tool configured to generate and/or detect an optical illumination beam having x-ray, ultraviolet (UV), infrared (IR), or visible light wavelengths.
• the one or more metrology subsystems 202 may include an advanced imaging metrology (AIM) tool, an advanced imaging metrology in-die (AIMid) tool, or a triple advanced imaging metrology (Triple AIM) tool.
• AIM advanced imaging metrology
• AIMid advanced imaging metrology in-die
• Triple AIM triple advanced imaging metrology
• the one or more metrology sub-systems 202 may include an optical illumination source 324 configured to generate an optical illumination beam 326.
• the optical illumination beam 326 may include one or more selected wavelengths of radiation including, but not limited to, x-ray, ultraviolet (UV) light, visible light, or infrared (IR) light.
• the optical illumination source 324 may include any type of illumination source suitable for providing an optical illumination beam 326.
• the optical illumination source 324 is a laser source.
• the optical illumination source 324 may include, but is not limited to, one or more narrowband laser sources, a broadband laser source, a supercontinuum laser source, a white light laser source, or the like.
• the optical illumination source 324 may provide an optical illumination beam 326 having high coherence (e.g., high spatial coherence and/or temporal coherence).
• the optical illumination source 324 includes a laser- sustained plasma (LSP) source.
• LSP laser- sustained plasma
• the optical illumination source 324 may include, but is not limited to, a LSP lamp, a LSP bulb, or a LSP chamber suitable for containing one or more elements that, when excited by a laser source into a plasma state, may emit broadband illumination.
• the optical illumination source 324 includes a lamp source.
• the optical illumination source 324 may include, but is not limited to, an arc lamp, a discharge lamp, an electrode-less lamp, or the like.
• the optical illumination source 324 may provide an optical illumination beam 326 having low coherence (e.g., low spatial coherence and/or temporal coherence).
• the optical illumination source 324 directs the optical illumination beam 326 to the sample 316 via an illumination pathway 328.
• the illumination pathway 328 may include one or more illumination pathway lenses 334 or additional optical components 332 suitable for modifying and/or conditioning the optical illumination beam 326.
• the one or more optical components 332 may include, but are not limited to, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, or one or more beam shapers.
• the illumination pathway 326 may further include an objective lens 338 configured to direct the optical illumination beam 326 to the sample 316.
• the sample 316 is disposed on a sample stage 318.
• the sample stage 318 may include any device suitable for positioning and/or scanning the sample 318 within the one or more metrology sub-systems 202b.
• the sample stage 316 may include any combination of linear translation stages, rotational stages, tip/tilt stages, or the like.
• the one or more metrology sub-systems 202 include one or more detectors 322 configured to capture light emanating from the sample 316 through a collection pathway 330.
• the collection pathway 330 may include, but is not limited to, one or more collection pathway lenses 326, 340 for collecting light from the sample 316.
• the one or more detectors 322 may receive light reflected or scattered (e.g., via specular reflection, diffuse reflection, and the like) from the sample 316 via one or more collection pathway lenses 326, 340.
• the one or more detectors 322 may receive light generated by the sample 316 (e.g., luminescence associated with absorption of the optical illumination beam 326, or the like).
• the one or more detectors 322 may receive one or more diffracted orders of light from the sample 316 (e.g., 0-order diffraction, ⁇ 1 order diffraction, ⁇ 2 order diffraction, and the like).
• the one or more detectors 322 may be configured to simultaneously capture light emanating from a plurality of portions of the sample 316, such as the first set of pattern elements 102, the second set of pattern elements 104, and/or the third set of pattern elements 106.
• the metrology system 200 may be configured such that the amount of time required to determine an overlay error is reduced in that operation of the metrology system 200 may be performed “on-the-fly” and the operation need not be discontinued between each individual overlay measurement.
• the one or more detectors 322 may include any type of detector known in the art suitable for measuring illumination received from the sample 316.
• a detector 322 may include, but is not limited to, a CCD detector, a TDI detector, a photomultiplier tube (PMT), an avalanche photodiode (ARD), a complementary metal- oxide-semiconductor (CMOS) sensor, or the like.
• a detector 322 may include a spectroscopic detector suitable for identifying wavelengths of light emanating from the sample 316.
• the one or more detectors 322 are positioned approximately normal to the surface of the sample 316.
• the one or more metrology sub-systems 202 includes a beamsplitter oriented such that the objective lens 338 may simultaneously direct the optical illumination beam 326 to the sample 316 and collect light emanating from the sample 316. Further, the illumination pathway 326 and the collection pathway 330 may share one or more additional elements (e.g., objective lens 338, apertures, filters, or the like).
• the one or more metrology sub-systems 202 may include a controller 204 communicatively coupled to the one or more metrology sub- systems 202.
• the controller 204 may be configured to direct the one or more metrology sub-systems 204 to generate overlay signals based on one or more selected recipes.
• the controller 204 may be further configured to receive data including, but not limited to, overlay signals from the one or more metrology sub-systems 202. Additionally, the controller 204 may be configured to determine overlay associated with an overlay target based on the acquired overlay signals.
• the controller 204 may be configured to determine an overlay value of the sample 316 based on one or more overlay measurements of the sample. For example, the controller 204 may be configured to generate one or more overlay measurements of the sample 316 based on one or more signals indicative of illumination emanating from one or more portions of the sample 316 (e.g., the first set of pattern elements 102, the second set of pattern elements 104, and/or the third set of pattern elements 106). The one or more overlay measurements of the sample 202 may correspond to an overlay position of one or more layers of the sample 316.
• the one or more overlay measurements of the sample 316 may include one or more measurements of intensity of illumination emanating from the first set of pattern elements 102, the second set of pattern elements 104, and/or the third set of pattern elements 106.
• the controller 204 may be configured to determine an intensity of illumination collected by the one or more detectors 322 (and/or the particle detector 320).
• the controller 204 may be configured to determine the intensity of illumination emanating from the first set of pattern elements 102 (having a pitch Pi), the second set of pattern elements 104 (having a pitch P 2 ), and/or the third set of pattern elements 106 (having a pitch P3), as the sample 316 is moved at a velocity v (e.g., such as through translation of the stage 318), according to Equation 1.
• the intensity determined by the controller 204 using Eqn. 1 is shown in the context of illumination having a +1 -diffraction order. It is expressly contemplated that the embodiments of the present disclosure are not limited to such context, and that the controller 204 may be configured to determine intensity of illumination emanating from the sample 316 having various diffraction orders (e.g., a -1- diffraction order).
• the controller 204 may be configured to further determine a relative variation in intensity of illumination emanating from various portions of the sample 316 (e.g., a difference in intensity between illumination emanating from the first set of pattern elements 102, and second set of pattern elements 104, and/or the third set of pattern elements 106). For example, the controller 204 may determine an intensity variation between illumination emanating from the first set of pattern elements 102, and second set of pattern elements 104, and/or the third set of pattern elements 106 according to Equation 2.
• the intensity determined by the controller 204 using Eqn. 2 is shown in the context of illumination having a +1 -diffraction order. It is expressly contemplated that the embodiments of the present disclosure are not limited to such context, and that the controller 104 may be configured to determine intensity of illumination emanating from the sample 316 having various diffraction orders (e.g., a -1- diffraction order). [0049] The controller 204 may be further configured to determine a phase difference with respect to illumination emanating from the first set of pattern elements 102, and second set of pattern elements 104, and/or the third set of pattern elements 106).
• the controller 104 may determine an phase difference between illumination emanating from the first set of pattern elements 102 and second set of pattern elements 104 (such phase difference denoted by ⁇ 12 ), the second set of pattern elements 104 and the third set of pattern elements 106 (such phase difference denoted by ⁇ 23 ), and/or the first set of pattern elements 102 and the third set of pattern elements 106 such phase difference denoted by ⁇ 13 ) according to Equation 3.
• the controller 104 may be further configured to determine an overlay value (e.g., an overlay error) between two layers of the sample 316 based on the phase differences computed according to Equation 3.
• the controller 204 may be configured to determine an overlay error between a first layer of the sample 316 and a second layer of the sample 316 (e.g., OVL1-2), according to Equation 4.
• the one or more processors 206 of the controller 204 may include any processor or processing element known in the art.
• the term “processor” or “processing element” may be broadly defined to encompass any device having one or more processing or logic elements (e.g., one or more microprocessor devices, one or more application specific integrated circuit (ASIC) devices, one or more field programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)).
• the one or more processors 206 may include any device configured to execute algorithms and/or instructions (e.g., program instructions stored in memory).
• the one or more processors 206 may be embodied as a desktop computer, mainframe computer system, workstation, image computer, parallel processor, networked computer, or any other computer system configured to execute a program configured to operate or operate in conjunction with the metrology system 200, as described throughout the present disclosure. Further, the steps described throughout the present disclosure may be carried out by a single controller 204 or, alternatively, multiple controllers. Additionally, the controller 204 may include one or more controllers housed in a common housing or within multiple housings. In this way, any controller or combination of controllers may be separately packaged as a module suitable for integration into metrology system 200. Further, the controller 204 may analyze data received from the one or more metrology sub-systems 202 and feed the data to additional components within the metrology system 200 or external to the metrology system 200.
• the memory medium 208 may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 204.
• the memory medium 208 may include a non-transitory memory medium.
• the memory medium 208 may include, but is not limited to, a read-only memory (ROM), a random-access memory (RAM), a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid-state drive and the like. It is further noted that memory medium 208 may be housed in a common controller housing with the one or more processors 206. In one embodiment, the memory medium 208 may be located remotely with respect to the physical location of the one or more processors 206 and controller 204.
• a user interface (not shown) is communicatively coupled to the controller 204.
• the user interface may include, but is not limited to, one or more desktops, laptops, tablets, and the like.
• the user interface includes a display used to display data of the metrology system 200 to a user.
• the display of the user interface may include any display known in the art.
• the display may include, but is not limited to, a liquid crystal display (LCD), an organic light-emitting diode (OLED) based display, or a CRT display.
• LCD liquid crystal display
• OLED organic light-emitting diode
• CRT display Those skilled in the art should recognize that any display device capable of integration with a user interface is suitable for implementation in the present disclosure.
• a user may input selections and/or instructions responsive to data displayed to the user via a user input device of the user interlace.
• the controller 204 is communicatively coupled to one or more elements of the metrology system 200.
• the controller 204 may transmit and/or receive data from any component of the metrology system 200.
• the controller 204 may be communicatively coupled to the detector 320, 322 to receive one or more images from the detector 320, 322. Further, the controller 204 may direct or otherwise control any component of the metrology system 200 by generating one or more control signals for the associated components.
• FIG. 4 illustrates a process flow diagram depicting the steps of a method 400 of measuring overlay of a sample, in accordance with one or more embodiments of the present disclosure.
• Step 402 a sample including one or more metrology targets 100 is illuminated.
• the metrology system 200 may direct an illumination beam onto the sample 316.
• illumination beam may refer to any radiant beam, including, without limitation, the optical illumination beam 326.
• Step 404 illumination emanating from the first set of pattern elements 102, the second set of pattern elements 104, and the third set of pattern elements 106 of the metrology target 100 is detected.
• the optical illumination beam 326 may be detected.
• Step 406 one or more first overlay measurements are generated.
• the controller 204 may be configured to generate one or more first overlay measurements of the sample 316 based on one or more signals indicative of illumination emanating from one or more portions of the first set of pattern elements 102.
• the one or more first overlay measurements of the sample 316 may include one or more intensity measurements (e.g., the controller 204 may determine one or more intensities and/or phase differences according to Eqns. 1-3).
• one or more second overlay measurements are generated.
• the controller 204 may be configured to generate one or more second overlay measurements of the sample 316 based on one or more signals indicative of illumination emanating from one or more portions of the second set of pattern elements 104.
• the one or more second overlay measurements of the sample 316 may include one or more intensity measurements (e.g., the controller 204 may determine one or more intensities and/or phase differences according to Eqns. 1-3).
• one or more third overlay measurements are generated.
• the controller 204 may be configured to generate one or more third overlay measurements of the sample 316 based on one or more signals indicative of illumination emanating from one or more portions of the third set of pattern elements106.
• the one or more third overlay measurements of the sample 316 may include one or more intensity measurements (e.g., the controller 204 may determine one or more intensities and/or phase differences according to Eqns. 1-3).
• an overlay error is determined based on the one or more first overlay measurements, the one or more second overlay measurements, and/or the one or more third overlay measurements.
• the controller 204 may be configured to generate an overlay error between a first layer of the sample 316 and a second layer of the sample 316 using Eqn. 4.
• the method 400 may include one or more additional steps (e.g., optional Step 414) wherein one or more overlay correctables are provided based on the one or more overlay values determined in at least Step 412.
• the one or more additional steps may include the controller 204 generating one or more control signals (or corrections to the control signals) for adjusting one or more parameters (e.g., fabrication settings, configuration, and the like) of one or more process tools (e.g., lithographic tools).
• the control signals (or corrections to the control signals) may be provided by the controller 204 as part of a feedback and/or feedforward control loop.
• the controller 204 may cause the one or more process tools to execute one or more adjustments to the one or more parameters of the one or more process tools based on the one or more control signals (or corrections to the control signals). In some embodiments, the controller 204 may alert a user to make the one or more adjustments. In this sense, the one or more control signals may compensate for errors of one or more fabrication processes of the one or more process tools, and thus may enable the one or more process tools to maintain overlay within selected tolerances across multiple exposures on subsequent samples in the same or different lots.
• FIG. 5 illustrates a process flow diagram illustrating the steps of a method 500 of forming a metrology target 100, in accordance with one or more embodiments of the present disclosure.
• a first set of pattern elements 102 is formed within a first cell 101 and a second cell 103 of a sample.
• the first portion of the first set of pattern elements 102 may be formed within the first cell 101
• the second portion of the first set of pattern elements 102 may be formed within the second cell 103.
• the first set of pattern elements 102 may be fabricated through one or more process steps such as, but not limited to, one or more deposition, lithographic, or etching steps.
• the first set of pattern elements 102 may be formed using one or more process tools (e.g., lithographic tools).
• a second set of pattern elements 104 is formed within a first cell 101 and a second cell 103 of a sample.
• the first portion of the second set of pattern elements 104 may be formed within the first cell 101
• the second portion of the second set of pattern elements 104 may be formed within the second cell 103.
• the second set of pattern elements 104 may be fabricated through one or more process steps such as, but not limited to, one or more deposition, lithographic, or etching steps.
• the second set of pattern elements 104 may be formed using one or more process tools (e.g., lithographic tools).
• a third set of pattern elements 106 is formed within a first cell 101 and a second cell 103 of a sample.
• the first portion of the third set of pattern elements 106 may be formed within the first cell 101
• the second portion of the third set of pattern elements 106 may be formed within the second cell 103.
• the third set of pattern elements 106 may be fabricated through one or more process steps such as, but not limited to, one or more deposition, lithographic, or etching steps.
• the third set of pattern elements 106 may be formed using one or more process tools (e.g., lithographic tools).
• All of the methods described herein may include storing results of one or more steps of the method embodiments in memory.
• the results may include any of the results described herein and may be stored in any manner known in the art.
• the memory may include any memory described herein or any other suitable storage medium known in the art.
• the results can be accessed in the memory and used by any of the method or system embodiments described herein, formatted for display to a user, used by another software module, method, or system, and the like.
• the results may be stored “permanently,” “semi-permanently,” temporarily,” or for some period of time.
• the memory may be random access memory (RAM), and the results may not necessarily persist indefinitely in the memory.
• each of the embodiments of the method described above may include any other step(s) of any other method(s) described herein.
• each of the embodiments of the method described above may be performed by any of the systems described herein.
• any two components so associated can also be viewed as being “connected,” or “coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “couplable,” to each other to achieve the desired functionality.
• Specific examples of couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

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