Classifications

• • 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
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
  • G01N21/274—Calibration, base line adjustment, drift correction
• • 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
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/8806—Specially adapted optical and illumination features
• • 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
  • G01N21/21—Polarisation-affecting properties
• • 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
  • 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
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
• • 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
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
• • 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
  • G01N2021/4704—Angular selective
  • G01N2021/4728—Optical definition of scattering volume
• • 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
  • G01N2021/4792—Polarisation of scatter light
• • 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
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/8806—Specially adapted optical and illumination features
  • G01N2021/8822—Dark field detection
• • 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
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
  • G01N21/274—Calibration, base line adjustment, drift correction
  • G01N21/278—Constitution of standards

Definitions

• the present invention generally relates to optical Instruments and tools, and more particularly, to a standard for light scattering.
• the inspection system includes one or more illumination sources configured to generate a beam of illumination.
• the inspection system includes one or more illumination optics configured to focus the beam of illumination into a volume of air contained within a chamber of an inspection chamber.
• the inspection system includes one or more collection optics configured to collect a portion of illumination scattered from the volume of air.
• the inspection system include a detector configured to receive the collected portion of illumination from the one or more collection optics.
• the inspection system includes a controller that includes one or more processors communicatively coupled to the detector.
• the one or more processors are configured to execute a set of program instructions stored in memory.
• the set of program instructions are configured to cause the one or more processors to receive one or more signals from the detector indicative of an intensity of the illumination scattered from the volume of air.
• the set of progra instructions are configured to cause the one or more processors to determine a state of the beam of illumination at one or more times based on a comparison between the intensity of the illumination scattered from the volume of air and a predetermined intensity standard.
• the method includes generating a beam of illumination in another embodiment, the method includes focusing the beam of illumination into a volume of air contained within a chamber of an inspection chamber. In another embodiment, the method includes collecting a portion of illumination scatered from the volume of air. In another embodiment, the method includes detecting, with a detector, the collected portion of illumination from the one or more collection optics in another embodiment, the method includes determining a state of the beam of illumination, such as beam intensity and/or polarization, at one or more times based on a comparison between the intensity of the illumination scatered from the volume of air and a predetermined intensity standard.
• a state of the beam of illumination such as beam intensity and/or polarization
• FIG. 1 illustrates a block diagram of an inspection system, In accordance with one or more embodiments of the present disclosure.
• FIG. 2 illustrates a diagram of air scattering intensity, in accordance with one or more embodiments of the present disclosure.
• FIG. 3A illustrates root mean square noise of a sensor, in accordance with one or more embodiments of the present disclosure
• FIG. 3B illustrates air scattering with incident P-polarized light, in accordance with one or more embodiments of the present disclosure.
• FIG. 3C illustrates air scattering with incident S-poSarized light, in accordance with one or more embodiments of the present disclosure.
• FIG. 4A illustrates an example of air scattering to measure polarization. In accordance with one or more embodiments of the present disclosure.
• FIG. 4B illustrates an example of air scattering to measure polarizations, in accordance with one or more embodiments of the present disclosure.
• FIG. 5 is a flow diagram illustrating steps performed in a method for determining a state of a beam of illumination in an inspection system, in accordance with one embodiment of the present disclosure.
• FIG. 6 is a flow diagram illustrating steps performed in a method for determining intensity of a beam of illumination in an inspection system, in accordance with one embodiment of the present disclosure.
• FIG. 7 is a flow diagram illustrating steps performed in a method for determining polarization of a beam of illumination in an inspection system, in accordance with one embodiment of the present disclosure.
• FIGS, 1 through 5 a system and method utilizing an air scattering standard to monitor and measure scattering, in accordance with the present disclosure.
• Embodiments of the present disclosure utilize air scattering as a scatering standard for optical systems and tools.
• Embodiments of the present disclosure are directed to measuring intensity and/or polarization of a beam of illumination based on scatering of the beam fro a volume of air.
• Embodiments of the present disclosure may be used to align, calibrate, and/or monitor an optical system. For example, illumination scattered from a volume of air contained in an inspection chamber may be collected. Further, the scattered illumination that is collected may be compared to an air scattering standard (e.g., scattering data obtained with known beam characteristics).
• an air scattering standard e.g., scattering data obtained with known beam characteristics.
• one or more states e.g., intensity or polarization
• one or more states e.g., intensity or polarization
• St is noted herein that an ai standard does not require an insertabfe physical object be mounted in the system.
• FIG. 1 illustrates a conceptual block diagram view of an inspection system 100, in accordance with one or more embodiments of the present disclosure.
• the inspection system 100 may include one or more illumination sources 102, one or more illumination optics 106, one or more collection optics 118, and a detector 120.
• the inspection system 100 may be configured in any inspection configuration known in the art of sample inspection.
• the inspection system 100 may be, but is not required to be, configured as a darkfieid inspection too!.
• the one or more illumination sources 102 may include any illumination source known in the art of sample inspection.
• the one or more illumination sources 102 are configured to generate one or more beams of illumination 104.
• the one or more illumination sources 102 may be configured to generate infrared, visible, and/or ultraviolet radiation.
• the one or more illumination sources 102 include a narrow band light source.
• the one or more illumination sources 102 may include, but are not limited to, a laser source.
• the one or more illumination sources 102 include a broadband Sight source.
• the one or more illumination sources 102 include, but are not limited to, a discharge lamp or a laser-sustained plasma (LSP) light source.
• LSP laser-sustained plasma
• the one or more illumination optics 106 may include any optical element known in the art of sample inspection used to focus, direct, filter, or otherwise condition light from the one or more illumination sources 102.
• the one or more illumination optics 106 may include, but are not limited to, any combination of the following; one or Senses, one or more mirrors, one or more filters, one or more polarizers, one or more prisms, one or more diffractive elements, one or more beam splitters, and the like.
• the one or more illumination sources 102 and illumination optics 106 are configured to produce P-potarized illumination and/or S-poiarized illumination.
• illumination 104 is directed to a volume of air 108.
• the volume of air 108 may be contained within a chamber of the inspection chamber 110.
• the inspection system 100 includes a stage 112 configured to support an secure one or more samples 114.
• the Inspection system 100 may be configured such that the sample stage 112 is arranged such that detector 120 collects illumination scattered from a volume of air 108 located above the sample stage 112. fool? ⁇
• the one or more collection optics 118 may include any optical element known in the art of illumination collection used to collect, focus, and direct illumination.
• the one or more collection optics 118 may include, but are not limited to, any combination of the following: one or more lenses, or one or more mirrors, and the like.
• the collection optics 112 may include an objective.
• the one or more collection optics 118 are configured to collect air scattered illumination 116.
• the collection optics 118 may be configured to collect air scattered illumination 116 of infrared, visible, and/or ultraviolet radiation. In another embodiment, the collection optics 118 direct illumination to the detector 120.
• an objective may direct illumination to the detector 120. fooisj
• the detector 120 may include any detector known in the art of illumination detection used to detect, sense, record, or amplify illumination.
• the detector may include, but is not limited to, a charge coupled device (CCD) detector, a photomultiplier tube (P T) detector, and the like.
• CCD charge coupled device
• P T photomultiplier tube
• the inspection syste 100 may include a controller 122 that includes one or more processors 126, and memory 128.
• the controller 122 includes one or more processors 126 communicatively coupled to the detector 120 and memory 128.
• the one or more processors 126 may be configured to execute a set of program instructions 130 maintained in memory 128.
• the one or more processors 126 of controller 122 may be programmed to carry out one or more steps of an alignment or calibration procedure as described below.
• the embodiments of inspection system 100 illustrated in FIG. 1 may be further configured as described herein.
• inspection system 100 may be configured to perform any other step(s) of any of the method embodiments) described herein.
• the one or more processors 126 may receive from the detector 120 one or more signals indicative of a state of the illumination beam 104 scatered from the volume of s air 108.
• the one or more processors 126 may receive one or more signals indicative of an intensity and/or polarization of the illumination scattered from the volume of air 108.
• the one or more processors 126 may aiso compare the intensity and/or polarization of scattered illumination 116 to a predetermined intensity and/or polarization standard in one embodiment, data of scattered illumination 116 may be stored in memory 126 and utilized as a scattering standard.
• the one or more processors 126 determine a state of a beam of iifumination 104 at one or more times based on a comparison between the intensity and/or polarization of the ii!umination scattered from the volume of air 108 and a predetermined intensity and/or polarization standard.
• the memory 128 may Include a set of program instructions 130 to perform analysis of data received by the controller 122 from the detector 120.
• memory 128 may include a set of program instructions 130 to compare data generated by the detector to a scattering standard.
• the set of program instructions 130 may cause the one or more processors 126 to determine an intensity and/or polarization of the beam of illumination at one or more selected times. For example, the set of program instructions 130 may cause the one or more processors 126 to monitor an intensity and/or polarization of the beam of illumination 104 at one or more times.
• an air scatering standard includes data obtained from ii!umination scattered from a bea of illumination having known characteristics.
• a scattering standard may include data of detected scattered illumination from a beam of illumination 104 having known intensity characteristics.
• a scatering standard may include data of detected scattered illumination from a beam of illumination 104 having known polarization characteristics.
• the one or more illumination sources 102, the one or more illumination optics 106, and/or the one or more of the Collection optics 108 are adjusted.
• a user may adjust the power of the one or more illumination sources 102 based on the determined state of the beam of illumination 104.
• the one or more processors 126 may adjust the power of the one or more illumination sources 102 based on the determined state of the beam of illumination.
• the one or more illumination sources 102, the one or more illumination optics 106, and/or the one or more collection optics 108 may be aligned by a user or the one or more processors 126 based on the determined state of the beam of illumination 104.
• one or more of the one or more illumination sources 102, the one or more illumination optics 106, or the collection optics 118 are adjusted until a difference between the collected scattered illumination to a scattering standard i within a selected threshold.
• the one or more processors 126 may adjust iteratively or simultaneously the power and/or alignment of the one or more illumination sources 102, and/or the alignment of the one or more illumination optics 106, and/or collection optics 108 until of the difference between collected scattered illumination to a scattering standard is within a selected threshold.
• the controller 122 may be configured to receive and/or acquire data or information from other systems (e.g., intensity from a detector, optical element orientation from illumination and/or collection optics) by a transmission medium that may include wireline and/or wireless portions.
• the controller 122 may be configured to transmit data or information (e.g , the output of one or more processes disclosed herein) to one or more systems or sub-systems (e.g., illumination optics or collection optics) by a transmission medium that may include wireline and/or wireless portions.
• the transmission medium may serve as a data link between the controller 122 and other subsystems of inspection system 100.
• the controller 122 may send data to external systems via a transmission medium (e.g , network connection).
• the detector 120 and controller 122 may be communicatively coupled in any suitable manner (e.g., by one or more wireline or wireless transmission media indicated by the Sine shown in FIG. 1 ) such that the controller 122 receives information from the detector 120.
• the detector 120 transmits one or more images 124 or intensity data to the controller 122.
• one or more images 124 are stored in memory 123.
• the one or more processors 126 of controller 122 may include any one or more processing elements known in the art. In this sense, the one or more processors 126 may include any microprocessor device configured to execute algorithms and/or instructions. In one embodiment, the one or more processors 126 consist of a desktop computer, mainframe computer system, workstation, image computer, parallel processor, or other computer system (e.g , networked computer) configured to execute a program configure to operate ail or part of the inspection system 100, as described throughout the present disclosure. It should be recognized that the steps described throughout the present disclosure may be carried out by a single computer system or, alternatively, multiple computer systems.
• processor may be broadly defined to encompass any device having one or more processing elements, which execute program instructions from a non-transstory memory medium (e.g., memory 128). Therefore, the above description should not be interpreted as a limitation on the present invention but merely an illustration.
• the memory media of memory 128 may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 126.
• memory 128 may include a nan-transitory memory medium.
• memory 128 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 in another embodiment, it is noted herein that memory 123 is configured to store one or more resuits from inspection system 100 and/or the output of the various steps described herein. It is further noted that memory 128 may be housed in a common controller housing with the one or more processors 126.
• the memory 126 may be located remotely with respect to the physical location of the processors 126 and controller 122.
• the one or more processors 126 of controller 122 may access a remote memory (e.g., server), accessible through a network (e.g., internet, intranet and the like).
• the memory 128 stores the program instructions 130 for causin the one or more processors 128 to carry out the various steps described through the present disclosure.
• the inspection system 100 has been depicted in a simplified block diagram. This depiction, including the components and geometrical configuration, Is not limiting and is provided for illustrative purposes only it is recognized herein that the inspection system 100 may include any number of optical elements (e.g., lenses, mirrors, filers beam splitter and the like), energy sources (e.g, , illumination source) and detectors (e.g., illumination detector) to carry out the comparison of an illumination beam state to an air scatter standard.
• optical elements e.g., lenses, mirrors, filers beam splitter and the like
• energy sources e.g, illumination source
• detectors e.g., illumination detector
• FIG- 2 illustrates a diagram of air scattering intensity 200, in accordance with one or more embodiments of the present disclosure. More specifically, air scattering intensity 200 illustrates a diagram of air scattering intensity of a single scafterer by a single wavelength of polarized electromagnetic radiation. St is noted herein that FIG. 2 illustrates air scattering intensity 200 of radiation polarized in the E direction that is traveling in the Z direction in one embodiment, air scattering by a single wavelength and polarization of radiation is described by: where air scattering intensity is calculated as a function of r, the distance from the scattered and the angle Q, the azimuthal angle starting from the E axis.
• FIG. 3 ⁇ illustrates root mean square (RMS) noise 310 of a SurfSoan® sensor, in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 3A illustrates RMS noise 310 for air scattering as measured on a SurfS can® inspection fool for P and S incident polarizations.
• RMS noise 310 for air scattering as measured on a SurfS can® inspection fool for P and S incident polarizations.
• the portion of illumination that includes an electric field parallel to the plane of incidence is P-polarized illumination.
• the portion of illumination that includes an electric field perpendicular to the plane of incident Is S-poSahzed illumination.
• FIG. 3B illustrates air scattering 320 with incident P-pofarized light, in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 3B illustrates P-incident air scattered 320 as measured on a SurfScan® inspection tool from P and S incident polarizations.
• FIG. 3C illustrates air scatering 330 with Incident S-polarized illumination, in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 3C illustrates S-polarized incident air scattered 330 as measured on a SurfScan® inspection tool from P and $ incident polarizations.
• air scattering 320 and 330 is measured above the RMS noise 310 of the SurfScan® sensor. It is further noted that the air scattering 320 and 330 measured is incident polarization sensitive. It is further noted herein that air scatering can be utilized as a scattering standard in optical systems and tools.
• FIG. 4A illustrates an example of air scattering to measure polarization, in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 4A illustrates an example of P-polarized illumination air scattering 410 and S-po!arized illumination air scattering 420 to measure a polarization of illumination where in oblique mode the numerical aperture (NA) of an objective is 75°.
• NA numerical aperture
• integrating over the region collected by the objective the percentage of total air scatter coiiected in P-polarized and S-polarized incident light can be calculated. For example, the following equation may be utilized to calculate the percentage of total air scatter collected in P-polarized and S-polarized incident light:
• FiG. 4B illustrates an example of air scattering to measure polarization, in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 4B illustrates the normalized air scattering power collected by a Surfscan® SP7 objective as beam polarization rotates about the axis of travel It is noted herein that in FIG. 4B 0 degrees is P-poiarized incident light and 90 degrees is S-polarized incident light. It is further note herein the air scattering pattern shown in FIG.
• inspection system 100 utilizes a signal from scattered illumination 116 to monitor intensity of an incident beam of illumination 104.
• a signal from scattered illumination 116 may be utilized as a scattering standard to monitor an incident beam of illumination 104 of inspection system 100 over time.
• a signal from scattered illumination 116 is utilized for normalization calibration of air scattering intensity across multiple tools. It is noted herein a signal from scattered illumination 116 being stable and uniform is thought to improve system monitoring and calibration.
• inspectio system 100 utilizes a signal from scattered illumination 116 to measure polarization of an incident bea of illumination 104.
• inspection system 100 utilizes a signal from scattered illumination 116 to monitor polarization of an incident beam of illumination 104
• one or more signals from scattered illumination 116 may be utilized to measure polarization of illumination 104 and monitor polarization of illumination 104 over time.
• inspection system 100 utilizes a signal from scattered illumination 116 to align polarization sensitive optics and masks in the collection path in another embodiment, scattered illumination 116 can be utilized to qualify and monitor optical masks and polarizers. St is noted herein that air scattering provides uniform scattering that is polarized.
• any process in an optical system that requires a scattering standard can be performed with air scattering provided air is in the working environment of the system and the system is sufficiently sensitive to measure air scattering intensity. It is additionally noted herein that it is thought systems that rely on an inserted physical scattering standard will benefit from a scattering standard that does not introduce potential contamination and eliminates space constraints due to an insertable physical scattering standard. It is still further noted herein that systems requiring optical calibration and/or alignment that are not feasible due to the constraints created by an insertable physical standard are now realizable utilizing an air scatter standard for alignment and/or calibration.
• FIG. 5 is a flow diagram illustrating step performed in a method 500 for determining a state of a beam of illumination in an inspection system 100, in accordance with one embodiment of the present disclosure. It is noted herein that the steps of method 500 may be implemented ail or in part by inspection system 100. It is further recognized, however, that method 500 is not limited to inspection system 100 in that additional or alternative system-level embodiments may carry out all or part of the steps of method 500,
• one or more illumination sources 102 provide illumination to generate a bea of illumination 104.
• the beam of illumination 104 in unpoSarized.
• the beam of illumination 104 is polarized.
• the beam of illumination 104 may be one or more of linearly polarized, eiliptical!y polarized, circularly polarizer, or randomly polarized.
• illumination 104 includes P-polartzed illumination and S ⁇ poiarized illumination.
• illumination optics 106 focus illumination 104 to the volume of air 108.
• illumination optics 108 may be aligned and configured such that illumination 104 is directed toward and focused into a volume of air 108.
• the illumination optics 106 may be aligned and configured such that illumination 104 is focused into a volume of air 108 contained within an inspection chamber 110 of a darkfie!d inspection tool,
• step 506 a portion of illumination scattered from the volume of air is collected in one embodiment, scattered illumination 116 Is collected by the collection optics 118.
• scattered illumination 116 Is collected by the collection optics 118.
• the collection optics 118 are configured to direct scattered illumination toward a detector 120
• an objective may be configured to direction scattered illumination 116 collected toward the detector 120,
• a collected portion of illumination tom the one or more collection optics is detected.
• a collected portion of scattered illumination 118 from the volume of air 108 is detected by detector 120.
• the detector 120 may detector scattered illumination 118 collected by the objective and directed toward the detector 120.
• Step 510 a state of a beam of illumination 104 is determined at one or more times based on a comparison between the state of the illumination scattered from the volume of air 108 and a predetermined scatter standard.
• Step 510 includes the detector 120 acquiring one or more images 124 and transmitting the one or more images 124 to the controller 122.
• the one or more images 124 generated by the detector 120 and transmitted to the controller 122 are compared to a predetermined scatter standard by the one or more processors 126 in one embodiment, the one or more images 124 are stored in memory 128 and used for later analysis in another embodiment, one or more results from comparison between the state of the illumination scattered from the volume of air 108 and a predetermined scatter standard are stored in memory 128 for later use.
• step 512 adjust one or more of the illumination source 102, one or more of the illumination optics 106, or one or more of the collection optics 108 based on the determined state of the beam of illumination.
• the one or more processors 126 may adjust one or more of tile one or more Illumination sources 102, illumination optics 106, or collection optics 108 based on the determined state of the beam of illumination.
• the one or more processors 126 may adjust at least one of a power of the one or more illumination sources or an alignment of the one or more illumination sources based on the determined state of the beam of illumination.
• FIG. 6 is a flow diagram illustrating steps performed in a method 606 for determining intensity of a beam of illumination in an inspection system 100, in accordance with one embodiment of the present disclosure it is noted herein that the steps of method 600 may be implemented all or in part by inspection system 100. St is further recognized, however, that method 600 is not limited to inspection system 100 in that additional or alternative system-level embodiments may carry out all or part of the steps of method 800.
• one or more illumination sources 102 provide illumination to generate a bea of illumination 104.
• the beam of illumination 104 in unpolarized.
• the beam of illumination 104 is polarized.
• the beam of illumination 104 may be one or more of linearly polarized, ellipticaiiy polarized, circularly polarizer, or randomly polarized in another embodiment, illumination 104 includes P-poiarized illumination and S ⁇ po!arized illumination.
• the beam of illumination is focused into a volume of air contained within a chamber of an inspection chamber.
• illumination optics 106 focus illumination 104 to the volume of air 108.
• illumination optics 106 may be aligned and configured such that illumination 104 is directed toward and focused into a volume of air 108.
• the illumination optics 106 may be aligned and configure such that illumination 104 is focused into a volume of air 108 contained within an inspection chamber 110 of a darkfield inspection tool.
• step 606 a portion of illumination scattered from the volume of air is collected.
• scattere illumination 116 is collected by the collection optios 118
• scattered Illumination 116 is collected by an objective
• the collection optics 118 are configured to direct scattered illumination
• an objective may be configured to direction scattered illumination 116 collected toward the detector 120
• step 60S intensity of a collected portion of illumination from the one or more collection optics is detected.
• an intensity of a collected portion of scattered illumination 116 from the volume of air 108 is detected by detector 120
• the defector 120 may detector an intensity of scattered illumination 116 collected by the objective and directed toward the detector 120.
• step 610 an intensity of a beam of illumination 104 is determined at one or more times based on a comparison between the intensity of the illumination scattered from the volume of air 108 and a predetermined intensity standard.
• Step 610 includes the detector 120 acquiring one or more images 124 and transmitting the one or more images 124 to the controller 122.
• the one or more images 124 generated by the detector 120 and transmitted to the controller 122 are compared to a predetermined intensity standard by the one or more processors 126.
• the one or more images 124 are stored in memory 128 and used for later analysis.
• one or more results from comparison between the intensity of the illumination scattered from the volume of air 108 and a predetermined intensity are stored in memory 128 for later use
• step 612 adjust one or more of the illumination source 102, one or more of the illumination optics 106, or one or more of the collection optics 108 based on the determined intensity of the beam of illumination.
• the one or more processors 126 may adjust one or more of the one or more illumination sources 102, illumination optics 106, or collection optics 108 based on the determined intensity of the beam of illumination.
• the one or more processors 126 may adjust at least one of a power of the one or more illumination sources or an alignment of the one or more illumination sources based on the determined intensity of the beam of illumination.
• FIG. 7 Is a flow diagram illustrating steps performed in a method 700 for determining polarization of a beam of illumination in an inspection system TOO, in accordance with one embodiment of the present disclosure it is noted herein that the steps of method 700 may be implemented all or in part by inspection system 100. It is further recognized, however, that method 700 is not limited to inspection system 100 in that additional or alternative system-level embodiments may carry out alt or part of the steps of method 700.
• one or more illumination sources 102 provide illumination to generate a beam of illumination 104.
• the beam of illumination 104 in unpoiarized.
• the beam of illumination 104 is polarized.
• the beam of illumination 104 ma be one or more of linearly polarized, eiliptica!ly polarized, circularly polarizer, or randomly polarized.
• illumination 104 includes P-polarized illumination and S -polarized illumination.
• the beam of illumination is focused into a volume of air contained within a chamber of an inspection chamber.
• Illumination optics 108 focus illumination 104 to the volume of air 108.
• illumination optics 106 may be aligned and configured such that illumination 104 is directed toward and focused into a volume of air 108.
• the illumination optics 106 may be aligned and configured such that illumination 104 is focused into a volume of air 108 contained within an inspection chamber 110 of a darkfietd inspection tool,
• a portion of iiumination scattered from the volume of air is collected.
• scattered Illumination 116 is collected by the collection optics 118.
• scatered illumination 118 is collected by an objective.
• the collection optics 118 are configured to direct scattered illumination toward a detector 120.
• an objective may be configured to direction scattered illumination 116 collected toward the detector 120.
• polarization of a collected portion of illumination from the one or more collection optics is detected.
• a polarization of a collected portion of scattered illumination 118 from the volume of air 108 is detected by detector 120.
• the detecto 120 may detector a polarization of scattered illumination 116 collected by the objective and directed toward the detector 120.
• a polarization of a beam of illumination 104 is determined at one or more times based on a comparison between the polarization of the illumination scattered from trie volume of air 108 and a predetermined polarization standard.
• Step 710 includes the detector 120 acquiring one or more images 124 and transmitting the one or more images 124 to the controller 122.
• Trie one or more images 124 generated by the detector 120 and transmitted to the controller 122 are compared to a predetermined polarization standard by the one or more processors 128.
• the one or more images 124 are stored in memory 128 and used for later analysis.
• one or more results from comparison between the polarization of the illumination scattered from the volume of air 108 and a predetermined polarization are stored in memory 128 for later use.
• step 712 adjust one or more of the Illumination source 102, one or more of trie illumination optics 106, or one or more of the collection optics 108 based on the determined polarization of trie beam of illumination.
• trie one or more processors 126 may adjust one or more of trie one or more illumination sources 102, illumination optics 106, or collection optics 108 based on trie determined polarization of trie beam of illumination.
• the one or more processors 126 may adjust at least one of a power of the one or more illumination sources or an alignment of trie one or more illumination sources based on the determined polarization of the beam of illumination.
• Trie results may include any of trie results described herein and may be stored in any manner known in the art.
• the storage medium may include any storage medium described herein or any other suitable storage medium known in the art.
• the results can be accessed in the storage medium and used by any of trie method or system embodiments described herein, formatted for display to a user, used by another software module, method, or system, etc.
• the results may be stored “permanently,” “semi-permanently,” temporarily, or for some period of time.
• the storage medium may be random access memory (RAM), and the resuits may not necessarily persist indefinitely in the storage medium.
• the imp!ementer may opt for a mainly hardware and/or firmware vehicle; alternatively, if flexibility is paramount, the implementer may opt for a mainly software implementation; or, yet again alternatively, the implementer may opt for some combination of hardware, software, and/or firmware.
• any vehicle to be utilized is a choice dependent upon the context in which the vehicle will be deployed and the specific concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary.
• Those skilled in the art will recognize that optical aspects of implementations will typically employ optically-oriented hardware, software, and or firmware.

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