Inspection system and method

Abstract

To solve the problem in which: a current scatter standard brings about a possible source of contamination, requires an additional alignment step, increases cost, and deteriorates over time due to exposure to electromagnetic radiation and environment.SOLUTION: An inspection system 100 using an air scatter standard includes: one or more illumination sources 102 to generate a beam of illumination 104; illumination optics 106 configured to focus the beam of illumination 104 into a volume portion 108 of air contained within a chamber of an inspection chamber 110; collection optics 118 configured to collect a portion of illumination scattered from the volume portion 108 of air; a detector 120 configured to receive the collected portion of illumination from the collection optics 118; and a controller 122 determining a state of the beam of illumination 104.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates generally to optical instruments and devices, and more particularly to a reference for light scattering. [Background technology]

[0002] System calibration and alignment are necessary for optical systems to function properly. Optical systems often utilize scattering standards to calibrate the instrument, monitor the instrument's stability and health, and assist with optical alignment. Current scattering standards, such as spectralon tiles and silicon wafer standards, introduce possible sources of contamination, require additional alignment steps, increase cost, and degrade over time due to exposure to electromagnetic radiation and the environment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 6,326,608 Summary of the Invention [Problem to be solved by the invention]

[0004] It would therefore be advantageous to provide a system and method that provides improved system calibration that addresses the above-identified deficiencies. [Means for solving the problem]

[0005] An inspection system for use with an air scattering standard is disclosed according to one or more exemplary embodiments of the present disclosure. In one embodiment, the inspection system includes one or more illumination sources configured to generate a beam of illumination. In another embodiment, the inspection system includes one or more illumination optics configured to focus the beam of illumination into a volume of air contained within an inspection chamber. In another embodiment, the inspection system includes one or more collection optics configured to collect a portion of the illumination scattered from the volume of air. In another embodiment, the inspection system includes a detector configured to receive a collected portion of the illumination from the one or more collection optics. In another embodiment, the inspection system includes a controller including one or more processors communicatively coupled to the detector. In another embodiment, the one or more processors are configured to execute a set of program instructions stored in a memory. In another embodiment, 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. In another embodiment, the set of program instructions is configured to cause the one or more processors to determine a state of the beam of illumination based on a comparison between an intensity of illumination scattered from the volume of air at one or more times and a predetermined intensity criterion.

[0006] A method utilizing an air scattering criterion is disclosed according to one or more exemplary embodiments of the present disclosure. In one embodiment, 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 the examination chamber. In another embodiment, the method includes collecting a portion of the illumination scattered from the volume of air. In another embodiment, the method includes detecting the collected portion of the illumination from one or more collection optics by a detector. In another embodiment, the method includes determining a condition 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 scattered from the volume of air and a predetermined intensity criterion.

[0007] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and explanatory of the invention as claimed and are not necessarily restrictive. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description, serve to explain the principles of the invention.

[0008] The numerous advantages of the present disclosure may be better understood by those skilled in the art by reference to the accompanying drawings. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 illustrates a block diagram of an inspection system in accordance with one or more embodiments of the present disclosure. [Diagram 2] FIG. 1 illustrates a diagram of air scattering intensity in accordance with one or more embodiments of the present disclosure. [Figure 3A] FIG. 13 illustrates the root mean square noise of a sensor in accordance with one or more embodiments of the present disclosure. [Figure 3B] FIG. 2 illustrates air scattering by incident P-polarized light in accordance with one or more embodiments of the present disclosure. [Figure 3C]FIG. 2 illustrates air scattering by incident S-polarized light in accordance with one or more embodiments of the present disclosure. [Figure 4A] FIG. 1 illustrates an example of air scattering for measuring polarized light, in accordance with one or more embodiments of the present disclosure. [Figure 4B] FIG. 1 illustrates an example of air scattering for measuring polarized light, in accordance with one or more embodiments of the present disclosure. [Diagram 5] 1 is a flow diagram illustrating steps performed in a method for determining a state of a beam of illumination in an inspection system according to one embodiment of the present disclosure. [Figure 6] 1 is a flow diagram illustrating steps performed in a method for determining the intensity of a beam of illumination in an inspection system according to one embodiment of the present disclosure. [Figure 7] 1 is a flow diagram illustrating steps performed in a method for determining polarization of a beam of illumination in an inspection system according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Reference will now be made in detail to the disclosed subject matter, which is illustrated in the accompanying drawings.

[0011] Reference is now made generally to Figures 1-5, which illustrate a system and method for monitoring and measuring scattering utilizing an air scattering metric, in accordance with the present disclosure.

[0012] The embodiments of the present disclosure utilize air scattering as a scattering criterion for optical systems and instruments. The embodiments of the present disclosure are directed to measuring the intensity and / or polarization of a beam of illumination based on the scattering of the beam from a volume of air. The embodiments of the present disclosure may be used to align, calibrate, and / or monitor an optical system. For example, the illumination scattered from a volume of air contained within an examination chamber may be collected. Furthermore, the collected scattered illumination may be compared to an air scattering criterion (e.g., scattering data obtained with known beam characteristics). Furthermore, based on this comparison, one or more conditions of the beam (e.g., intensity or polarization) may be determined in a time step or monitored over a time zone. It is noted herein that the air criterion does not require that an insertable physical object be installed in the system.

[0013] 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.

[0014] Inspection system 100 may be configured in any inspection configuration known in the art of specimen inspection. For example, inspection system 100 may be configured as a darkfield inspection tool, although it is not required to be so configured.

[0015] The one or more illumination sources 102 may include any illumination source known in the art of specimen inspection. In one embodiment, the one or more illumination sources 102 are configured to generate one or more beams of illumination 104. For example, the one or more illumination sources 102 may be configured to generate infrared, visible, and / or ultraviolet radiation. In one embodiment, the one or more illumination sources 102 include a narrowband light source. For example, the one or more illumination sources 102 may include, but are not limited to, a laser source. In another embodiment, the one or more illumination sources 102 include a broadband light source. For example, the one or more illumination sources 102 include, but are not limited to, a discharge lamp or a laser sustained plasma (LSP) light source.

[0016] The one or more illumination optics 106 may include any optical element known in the art of specimen inspection used to focus, direct, filter, or otherwise condition light from the one or more illumination sources 102. For example, the one or more illumination optics 106 may include, but are not limited to, any combination of the following: one or more lenses, 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.

[0017] In another embodiment, the one or more illumination sources 102 and illumination optics 106 are configured to produce P-polarized and / or S-polarized illumination. In another embodiment, the illumination 104 is directed into a volume of air 108. The volume of air 108 may be contained within a chamber of the examination chamber 110.

[0018] In another embodiment, the inspection system 100 includes a sample stage 112 configured to support and secure one or more samples 114. In another embodiment, the inspection system 100 may be configured such that the sample stage 112 is arranged such that the detector 120 collects illumination scattered from the volume of air 108 located above the sample stage 112.

[0019] 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. For example, 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. Illustratively, the collection optics 118 may include an objective lens. In one embodiment, the one or more collection optics 118 are configured to collect air-scattered illumination 116. For example, 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 directs the illumination to a detector 120. For example, an objective lens may direct the illumination to the detector 120.

[0020] Detector 120 may include any detector known in the art of illumination detection used to detect, sense, record, or amplify illumination. For example, the detector may include, but is not limited to, a charge-coupled device (CCD) detector, a photomultiplier tube (PMT) detector, and the like.

[0021] The inspection system 100 may include a controller 122 including one or more processors 126 and a memory 128. In one embodiment, the controller 122 includes the one or more processors 126 communicatively coupled to the detector 120 and the memory 128. The one or more processors 126 may be configured to execute a set of program instructions 130 retained in the memory 128.

[0022] The one or more processors 126 of the controller 122 may be programmed to implement one or more steps of an alignment or calibration procedure as described below. The embodiment of the inspection system 100 illustrated in FIG. 1 may be further configured as described herein. In addition, the inspection system 100 may be configured to perform any other steps of any of the method embodiments described herein.

[0023] The one or more processors 126 may receive one or more signals from the detector 120 indicative of a state of the illumination beam 104 scattered from the volume of air 108. For example, the one or more processors 126 may receive one or more signals indicative of the intensity and / or polarization of the illumination scattered from the volume of air 108. The one or more processors 126 may further compare the intensity and / or polarization of the scattered illumination 116 to a predetermined intensity and / or polarization criterion. In one embodiment, the scattered illumination 116 data may be stored in the memory 128 and utilized as the scattering criterion. In another embodiment, the one or more processors 126 determine the state of the illumination 104 beam based on a comparison between the intensity and / or polarization of the illumination scattered from the volume of air 108 at one or more times and the predetermined intensity and / or polarization criterion.

[0024] The memory 128 may include a set of program instructions 130 for performing an analysis of the data received by the controller 122 from the detector 120. For example, the memory 128 may include a set of program instructions 130 for comparing data generated by the detector to a scatter criterion.

[0025] A set of program instructions 130 may cause the one or more processors 126 to determine the intensity and / or polarization of the beam of illumination at one or more selected times. For example, a set of program instructions 130 may cause the one or more processors 126 to monitor the intensity and / or polarization of the beam of illumination 104 at one or more times.

[0026] In one embodiment, the air scattering criterion includes data obtained from illumination scattered from a beam of illumination having known characteristics. For example, the scattering criterion may include detected scattered illumination data from a beam of illumination 104 having known intensity characteristics. As another example, the scattering criterion may include detected scattered illumination data from a beam of illumination 104 having known polarization characteristics.

[0027] In one embodiment, one or more of the one or more illumination sources 102, one or more illumination optics 106, and / or one or more collection optics 118 are adjusted in response to determining at least one of the intensity or polarization of the illumination beam 104. For example, a user may adjust the power of one or more illumination sources 102 based on the determined state of the illumination 104 beam. As another example, one or more processors 126 may adjust the power of one or more illumination sources 102 based on the determined state of the illumination beam. As another example, one or more illumination sources 102, one or more illumination optics 106, and / or one or more collection optics 118 may be aligned by a user or one or more processors 126 based on the determined state of the illumination 104 beam.

[0028] In one embodiment, one or more of the one or more illumination sources 102, one or more illumination optics 106, or collection optics 118 are adjusted until the difference between the collected scattered illumination and the scatter criterion is within a selected threshold. Illustratively, the one or more processors 126 may iteratively or simultaneously adjust 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 118 until the difference between the collected scattered illumination and the scatter criterion is within a selected threshold.

[0029] The controller 122 may be configured to receive and / or acquire data or information (e.g., intensity from a detector, optical element orientation from illumination and / or collection optics) from other systems via a transmission medium that may include wired and / or wireless portions. In another embodiment, the controller 122 may be configured to transmit data or information (e.g., output of one or more processes disclosed herein) to one or more systems or subsystems (e.g., illumination optics or collection optics) via a transmission medium that may include wired and / or wireless portions. In this manner, the transmission medium may serve as a data link between the controller 122 and other subsystems of the inspection system 100. Additionally, the controller 122 may send data to an external system via a transmission medium (e.g., a network connection).

[0030] The detector 120 and controller 122 may be communicatively coupled in any suitable manner (e.g., by one or more wired or wireless transmission media as indicated by the lines shown in FIG. 1 ) such that the controller 122 receives information from the detector 120. In one embodiment, the detector 120 transmits one or more images 124 or intensity data to the controller 122. In another embodiment, the one or more images 124 are stored in the memory 128.

[0031] The one or more processors 126 of the 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 comprise a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, or other computer system (e.g., a networked computer) configured to execute a program configured to operate all or a portion of the inspection system 100 as described throughout this disclosure. It should be appreciated that the steps described throughout this disclosure may be performed by a single computer system, or alternatively, by multiple computer systems. In general, the term "processor" may be broadly defined to encompass any device having one or more processing elements that executes program instructions from a non-transitory memory medium (e.g., memory 128). Therefore, the above description should be taken as merely illustrative and not limiting on the present invention.

[0032] The memory medium of the 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. For example, the memory 128 may include a non-transitory memory medium. By way of illustration, the 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 the memory 128 is configured to store one or more results from the inspection system 100 and / or outputs of various steps described herein. It is further noted that the memory 128 may be housed in a common controller housing with the one or more processors 126. In an alternative embodiment, the memory 128 may be located remotely with respect to the physical location of the processor 126 and the controller 122. As an example, the one or more processors 126 of the controller 122 may access a remote memory (e.g., a server) accessible over a network (e.g., the Internet, an intranet, and the like). In another embodiment, the memory 128 stores program instructions 130 that cause the one or more processors 126 to perform various steps described by this disclosure.

[0033] It is noted that for purposes of brevity, inspection system 100 is depicted in a simplified block diagram. This depiction, including components and geometric configurations, is not limiting and is provided for illustrative purposes only. It is recognized herein that inspection system 100 may include any number of optical elements (e.g., lenses, mirrors, filters beam splitters, and the like), energy sources (e.g., illumination sources), and detectors (e.g., illumination detectors) for implementing a comparison of illumination beam conditions to an air scattering reference.

[0034] 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 scatterer due to polarized electromagnetic radiation of a single wavelength. It is noted herein that FIG. 2 illustrates air scattering intensity 200 of radiation polarized in the E direction traveling in the Z direction. In one embodiment, air scattering due to radiation of a single wavelength and polarization is described by the following equation:

number

[0035] FIG. 3A illustrates the root mean square (RMS) noise 310 of a SurfScan® sensor in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 3A illustrates the RMS noise 310 for air scattering as measured on a SurfScan® inspection instrument for P and S incident polarizations. It is noted in the figure that a portion of the illumination that includes an electric field parallel to the plane of incidence is P-polarized illumination. It is further noted herein that a portion of the illumination that includes an electric field perpendicular to the plane of incidence is S-polarized illumination.

[0036] 3B illustrates air scattering 320 from incident P polarized light in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 3B illustrates air scattered P incident 320 from P and S incident polarizations, as measured on a SurfScan® inspection instrument.

[0037] 3C illustrates air scattering 330 with incident S-polarized illumination in accordance with one or more embodiments of the present disclosure. More specifically, FIG. 3C illustrates air scattered S-polarized incident 330 as measured on a SurfScan® inspection instrument from P and S incident polarizations.

[0038] It is noted herein that the air scattering 320 and 330 are measured above the RMS noise 310 of the SurfScan® sensor. It is further noted that the measured air scattering 320 and 330 is sensitive to the incident polarization. It is further noted herein that the air scattering can be utilized as a scattering criterion in optical systems and instruments.

[0039] FIG. 4A illustrates an example of air scattering for measuring polarization, according to one or more embodiments of the present disclosure. More specifically, FIG. 4A illustrates an example of air scattering 410 for P-polarized illumination and 420 for S-polarized illumination for measuring the polarization of illumination when the numerical aperture (NA) of the objective lens is 75° in an oblique mode. In one embodiment, the percentage of total air scattering collected for P-polarized and S-polarized incident light can be calculated by integrating over the area collected by the objective lens. For example, the following formula can be utilized to calculate the percentage of total air scattering collected for P-polarized and S-polarized incident light.

number

[0040] FIG. 4B illustrates an example of air scattering for measuring polarization according to one or more embodiments of the present disclosure. More specifically, FIG. 4B illustrates the normalized air scattering power collected by a Surfscan® SP7 objective lens as the beam polarization rotates around the axis of travel. It is pointed out herein that in FIG. 4B, 0 degrees is P-polarized incident light and 90 degrees is S-polarized incident light. It is further pointed out herein that the air scattering patterns shown in FIG. 4B are different for P-polarized and S-polarized incident illumination, indicating that air scattering is sensitive to incident beam polarization. It is additionally pointed out herein that when the quantity of P-polarized and S-polarized incident illumination intensities captured by the objective lens is different, the intensity ratio of P and S incident illumination can be informative about the quality of the polarization of the incident beam.

[0041] In one embodiment, the inspection system 100 utilizes the signal from the scattered illumination 116 to monitor the intensity of the incident beam of illumination 104. For example, the signal from the scattered illumination 116 may be utilized as a scattering reference to monitor the incident beam of illumination 104 of the inspection system 100 over time. In another embodiment, the signal from the scattered illumination 116 is utilized for standardization calibration of air scattering intensity across multiple instruments. It is noted herein that a stable and uniform signal from the scattered illumination 116 is believed to improve system monitoring and calibration.

[0042] In one embodiment, the inspection system 100 utilizes signals from the scattered illumination 116 to measure the polarization of the incident beam of illumination 104. In another embodiment, the inspection system 100 utilizes signals from the scattered illumination 116 to monitor the polarization of the incident beam of illumination 104. For example, one or more signals from the scattered illumination 116 may be utilized to measure and monitor the polarization of the illumination 104 over time.

[0043] In one embodiment, the inspection system 100 utilizes signals from the scattered illumination 116 to align polarization sensitive optics and masks in the collection path. In another embodiment, the scattered illumination 116 can be utilized to qualify and monitor optical masks and polarizers. It is pointed out herein that air scattering provides polarized uniform scattering. It is further pointed out herein that any process in an optical system that requires a scattering reference can be performed with air scattering, provided that air is in the system's working environment and the system is sensitive enough to measure air scattering intensity. It is additionally pointed out herein that it is conceivable that systems that rely on an inserted physical scattering reference would benefit from a scattering reference that does not introduce potential contamination and eliminates space constraints due to an insertable physical scattering reference. It is still further pointed out herein that systems that require optical calibration and / or alignment that are not feasible due to constraints created by an insertable physical reference can now be realized utilizing an air scattering reference for alignment and / or calibration.

[0044] 5 is a flow diagram illustrating steps performed in a method 500 for determining a state of a beam of illumination in an inspection system 100, according to one embodiment of the present disclosure. It is noted herein that the steps of method 500 may be implemented in whole or in part by inspection system 100. However, it is further recognized that method 500 is not limited to inspection system 100 in that additional or alternative system level embodiments may implement all or a portion of the steps of method 500.

[0045] In step 502, one or more illumination sources 102 provide illumination to generate a beam of illumination 104. In one embodiment, the beam of illumination 104 is unpolarized. In another embodiment, the beam of illumination 104 is polarized. For example, the beam of illumination 104 can be one or more of linearly polarized, elliptically polarized, circularly polarized, or randomly polarized. In another embodiment, the illumination 104 includes P-polarized illumination and S-polarized illumination.

[0046] At step 504, a beam of illumination is focused into a volume of air contained within the inspection chamber. In one embodiment, illumination optics 106 focus the illumination 104 into the volume of air 108. For example, the illumination optics 106 may be aligned and configured such that the illumination 104 is directed toward and focused into the volume of air 108. As another example, the illumination optics 106 may be aligned and configured such that the illumination 104 is focused into the volume of air 108 contained within the inspection chamber 110 of the darkfield inspection instrument.

[0047] At step 506, a portion of the illumination scattered from the volume of air is collected. In one embodiment, the scattered illumination 116 is collected by collection optics 118. For example, the scattered illumination 116 is collected by an objective lens. In another embodiment, the collection optics 118 is configured to direct the scattered illumination towards a detector 120. For example, an objective lens may be configured to direct, collected, scattered illumination 116 towards the detector 120.

[0048] The collected portion of the illumination from the one or more collection optics is detected, step 508. In one embodiment, the collected portion of the scattered illumination 116 from the volume of air 108 is detected by a detector 120. For example, the detector 120 may detect the scattered illumination 116 that is collected by the objective lens and directed towards the detector 120.

[0049] At step 510, a state of the beam of illumination 104 is determined based on a comparison between a state of illumination scattered from the volume of air 108 at one or more times and a predetermined scattering criterion. 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 the predetermined scattering criterion by the one or more processors 126. In one embodiment, the one or more images 124 are stored in the memory 128 and used for later analysis. In another embodiment, one or more results from the comparison between a state of illumination scattered from the volume of air 108 and a predetermined scattering criterion are stored in the memory 128 for later use.

[0050] At step 512, one or more of the illumination sources 102, the illumination optics 106, or the collection optics 118 are adjusted based on the determined state of the beam of illumination. For example, the one or more processors 126 may adjust one or more of the illumination sources 102, the illumination optics 106, or the collection optics 118 based on the determined state of the beam of illumination. As another example, the one or more processors 126 may adjust at least one of the power of one or more illumination sources or the alignment of one or more illumination sources based on the determined state of the beam of illumination.

[0051] 6 is a flow diagram illustrating steps performed in a method 600 for determining the intensity of a beam of illumination in an inspection system 100, according to one embodiment of the present disclosure. It is noted herein that the steps of method 600 may be implemented in whole or in part by inspection system 100. However, it is further recognized that method 600 is not limited to inspection system 100 in that additional or alternative system level embodiments may implement all or a portion of the steps of method 600.

[0052] In step 602, one or more illumination sources 102 provide illumination to generate a beam of illumination 104. In one embodiment, the beam of illumination 104 is unpolarized. In another embodiment, the beam of illumination 104 is polarized. For example, the beam of illumination 104 can be one or more of linearly polarized, elliptically polarized, circularly polarized, or randomly polarized. In another embodiment, the illumination 104 includes P-polarized illumination and S-polarized illumination.

[0053] In step 604, a beam of illumination is focused into a volume of air contained within the inspection chamber. In one embodiment, illumination optics 106 focus the illumination 104 into the volume of air 108. For example, the illumination optics 106 may be aligned and configured such that the illumination 104 is directed toward and focused into the volume of air 108. As another example, the illumination optics 106 may be aligned and configured such that the illumination 104 is focused into the volume of air 108 contained within the inspection chamber 110 of the darkfield inspection instrument.

[0054] At step 606, a portion of the illumination scattered from the volume of air is collected. In one embodiment, the scattered illumination 116 is collected by collection optics 118. For example, the scattered illumination 116 is collected by an objective lens. In another embodiment, the collection optics 118 is configured to direct the scattered illumination towards a detector 120. For example, an objective lens may be configured to direct, collected, scattered illumination 116 towards the detector 120.

[0055] In step 608, the intensity of the collected portion of the illumination from the one or more collection optics is detected. In one embodiment, the intensity of the collected portion of the scattered illumination 116 from the volume of air 108 is detected by a detector 120. For example, the detector 120 may detect the intensity of the scattered illumination 116 that is collected by the objective lens and directed towards the detector 120.

[0056] At step 610, the intensity of the beam of illumination 104 is determined based on a comparison between the intensity of illumination scattered from the volume of air 108 at one or more times and a predetermined intensity criterion. 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 the predetermined intensity criterion 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 the comparison between the intensity of illumination scattered from the volume of air 108 and the predetermined intensity are stored in memory 128 for later use.

[0057] At step 612, one or more of the illumination sources 102, the illumination optics 106, or the collection optics 118 are adjusted based on the determined intensity of the beam of illumination. For example, the one or more processors 126 may adjust one or more of the illumination sources 102, the illumination optics 106, or the collection optics 118 based on the determined intensity of the beam of illumination. As another example, the one or more processors 126 may adjust at least one of the power of one or more illumination sources or the alignment of one or more illumination sources based on the determined intensity of the beam of illumination.

[0058] 7 is a flow diagram illustrating steps performed in a method 700 for determining the polarization of a beam of illumination in an inspection system 100, according to one embodiment of the present disclosure. It is noted herein that the steps of method 700 may be implemented in whole or in part by inspection system 100. However, it is further recognized that method 700 is not limited to inspection system 100 in that additional or alternative system level embodiments may implement all or a portion of the steps of method 700.

[0059] In step 702, one or more illumination sources 102 provide illumination to generate a beam of illumination 104. In one embodiment, the beam of illumination 104 is unpolarized. In another embodiment, the beam of illumination 104 is polarized. For example, the beam of illumination 104 can be one or more of linearly polarized, elliptically polarized, circularly polarized, or randomly polarized. In another embodiment, the illumination 104 includes P-polarized illumination and S-polarized illumination.

[0060] At step 704, a beam of illumination is focused into a volume of air contained within the inspection chamber. In one embodiment, illumination optics 106 focus the illumination 104 into the volume of air 108. For example, the illumination optics 106 may be aligned and configured such that the illumination 104 is directed toward and focused into the volume of air 108. As another example, the illumination optics 106 may be aligned and configured such that the illumination 104 is focused into the volume of air 108 contained within the inspection chamber 110 of the darkfield inspection instrument.

[0061] At step 706, a portion of the illumination scattered from the volume of air is collected. In one embodiment, the scattered illumination 116 is collected by collection optics 118. For example, the scattered illumination 116 is collected by an objective lens. In another embodiment, the collection optics 118 is configured to direct the scattered illumination towards a detector 120. For example, an objective lens may be configured to direct and collect the scattered illumination 116 towards the detector 120.

[0062] In step 708, the polarization of the collected portion of the illumination from the one or more collection optics is detected. In one embodiment, the polarization of the collected portion of the scattered illumination 116 from the volume of air 108 is detected by a detector 120. For example, the detector 120 may detect the polarization of the scattered illumination 116 that is collected by the objective lens and directed towards the detector 120.

[0063] At step 710, the polarization of the beam of illumination 104 is determined based on a comparison between the polarization of the illumination scattered from the volume of air 108 at one or more times 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. The one or more images 124 generated by the detector 120 and transmitted to the controller 122 are compared to the predetermined polarization standard by the one or more processors 126. In one embodiment, the one or more images 124 are stored in the memory 128 and used for later analysis. In another embodiment, one or more results from the comparison between the polarization of the illumination scattered from the volume of air 108 and the predetermined polarization are stored in the memory 128 for later use.

[0064] At step 712, one or more of the illumination sources 102, the illumination optics 106, or the collection optics 118 are adjusted based on the determined polarization of the beam of illumination. For example, the one or more processors 126 may adjust one or more of the illumination sources 102, the illumination optics 106, or the collection optics 118 based on the determined polarization of the beam of illumination. As another example, the one or more processors 126 may adjust at least one of the power of one or more illumination sources or the alignment of one or more illumination sources based on the determined polarization of the beam of illumination.

[0065] All of the methods described herein may include storing the results of one or more steps of the method embodiments in a storage medium. The results may include any of the 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. After the results are stored, they may be accessed in the storage medium 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, etc. Furthermore, the results may be stored "permanently," "semi-permanently," temporarily, or for some period of time. For example, the storage medium may be a random access memory (RAM), and the results may not necessarily persist indefinitely in the storage medium.

[0066] Those skilled in the art will recognize that the state of the art has progressed to a point where there is little remaining difference between hardware and software implementations of aspects of a system, and that the use of hardware or software is generally (though not always, in that in certain contexts the choice between hardware and software may be meaningful) a design choice that represents a cost-efficiency tradeoff. Those skilled in the art will recognize that there are a variety of representations (e.g., hardware, software, and / or firmware) by which the processes and / or systems and / or other techniques described herein may be accomplished, and that the preferred representation will vary depending on the context in which the processes and / or systems and / or other techniques are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may choose a primarily hardware and / or firmware representation; alternatively, if flexibility is paramount, the implementer may choose a primarily software implementation, or, again alternatively, the implementer may choose some combination of hardware, software, and / or firmware. Thus, there are several possible representations by which the processes and / or devices and / or other techniques described herein may be accomplished, and any representations that will be utilized are a choice dependent upon the context in which the representations will be deployed and the particular concerns of the implementer (e.g., speed, flexibility, or predictability), and none of the possible representations is inherently better than another, in that any of those contexts and concerns may vary.Those skilled in the art will recognize that the optical aspects of the implementations will typically employ optically oriented hardware, software, and / or firmware.

[0067] While particular aspects of the inventive subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based on the teachings herein, changes and modifications can be made without departing from the subject matter described herein and its broader aspects, and therefore, the appended claims will cover within their scope all such changes and modifications that are within the true spirit and scope of the subject matter described herein.

[0068] Furthermore, it should be understood that the present invention is defined by the appended claims. It will be understood by those skilled in the art that, in general, the terms used herein, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "comprises (present participle)" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "comprises (third person singular present tense)" should be interpreted as "including but not limited to," etc.). If a specific number of claim recitations to be introduced is intended, such intent will be explicitly stated in the claims, and it will be further understood by those skilled in the art that, in the absence of such recitation, no such intent exists. For example, as an aid to understanding, the appended claims which follow may include the use of the introductory phrases "at least one" and "one or more" to introduce the claim recitations. However, the use of such phrases should not be construed to suggest that the introduction of a claim recitation by the indefinite article "a" or "an" limits any individual claim that incorporates such an introduced claim recitation to an invention that incorporates only one such recitation, even when the same claim includes the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should typically be interpreted to mean "at least one" or "one or more"), and the same applies to the use of definite articles used to introduce claim recitations. In addition, those skilled in the art will recognize that even when a particular number of introduced claim recitations is explicitly recited, such a recitation should typically be interpreted to mean at least the recited number (e.g., the mere recitation of "two recitations" without other modifiers typically means at least two recitations, or more than two recitations).Furthermore, in instances where idiomatic expressions similar to "at least one of A, B, and C, etc." are used, such syntax is generally intended in the sense that one of ordinary skill in the art would understand the idiomatic expressions (e.g., "a system having at least one of A, B, and C" would include, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In instances where idiomatic expressions similar to "at least one of A, B, or C, etc." are used, such syntax is generally intended in the sense that one of ordinary skill in the art would understand the idiomatic expressions (e.g., "a system having at least one of A, B, or C" would include, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). It will be further understood by those skilled in the art that virtually any disjunctive word and / or phrase, whether in the description, claims, or drawings, presenting two or more alternative terms, should be understood to contemplate the possibility of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0069] It will be believed that the present disclosure and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes can be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or sacrificing all of its essential advantages. The forms described are merely illustrative, and it is the intent of the following claims to embrace and include such modifications.

Claims

1. one or more illumination sources configured to generate a beam of illumination; one or more illumination optics configured to focus the beam of illumination into a volume of air contained within the examination chamber; one or more collection optics configured to collect a portion of the illumination scattered from the volume of air; a detector configured to receive the collected portion of the illumination from the one or more collection optics; a controller including one or more processors communicatively coupled to the detector, the one or more processors configured to execute a set of program instructions stored in a memory, the set of program instructions configuring the one or more processors to: receiving one or more signals from the detector indicative of an intensity of the illumination scattered from the volume of air; determining a condition of the beam of illumination based on a comparison between the intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion; a controller configured to cause the Including, The controller calculates a ratio of total air scattering of P-polarized light and S-polarized light based on the one or more signals from the detector, and determines a polarization state of the beam of illumination based on the ratio of total air scattering.

1. An inspection system comprising:

2. 2. The system of claim 1, wherein determining a state of the beam of illumination based on a comparison between the intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion comprises: determining an intensity of said beam of illumination at a selected time; A system comprising:

3. 2. The system of claim 1, wherein determining a state of the beam of illumination based on a comparison between the intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion comprises: monitoring the intensity of said beam of illumination at multiple times; A system comprising:

4. 2. The system of claim 1, wherein determining a state of the beam of illumination based on a comparison between the intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion comprises: monitoring the polarization of said beam of illumination at multiple times; A system comprising:

5. 10. The system of claim 1, wherein the one or more collection optics comprises an objective lens.

6. 2. The system of claim 1, wherein the volume of air is contained within an inspection chamber of a darkfield inspection instrument.

7. 2. The system of claim 1, wherein the volume of air is located above a sample stage.

8. 10. The system of claim 1, wherein the detector comprises a charge-coupled device (CCD) detector.

9. 2. The system of claim 1, adjusting a condition of at least one of the one or more illumination sources, the one or more illumination optics, or the one or more collection optics based on the determined condition of the beam of illumination. The system further comprising:

10. 2. The system of claim 1, adjusting 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 condition of the beam of illumination. The system further comprising:

11. generating a beam of illumination; focusing the beam of illumination into a volume of air contained within an examination chamber; collecting a portion of the illumination scattered from said volume of air; detecting, with a detector, the collected portion of illumination from one or more collection optics; determining a state of the beam of illumination based on a comparison between an intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion, calculating a ratio of total air scattering of P-polarized light and S-polarized light based on one or more signals detected by the detector, and determining a polarization state of the beam of illumination based on the ratio of total air scattering; The method according to claim 1, further comprising:

12. 12. The method of claim 11, wherein the step of determining a state of the beam of illumination based on a comparison between an intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion comprises: determining an intensity of said beam of illumination at a selected time; The method according to claim 1, further comprising:

13. 12. The method of claim 11, wherein the step of determining a state of the beam of illumination based on a comparison between an intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion comprises: monitoring the intensity of said beam of illumination at a plurality of times; The method according to claim 1, further comprising:

14. 12. The method of claim 11, wherein the step of determining a state of the beam of illumination based on a comparison between an intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion comprises: monitoring the polarization of the beam of illumination at a plurality of times; The method according to claim 1, further comprising:

15. 12. The method of claim 11, wherein the step of collecting a portion of the illumination scattered from the volume of air comprises: collecting a portion of the illumination scattered from said volume of air, comprising utilizing an objective lens. The method according to claim 1, further comprising:

16. 12. The method of claim 11, wherein the step of focusing the beam of illumination into a volume of air contained within an examination chamber comprises: focusing said beam of illumination into a volume of air contained within an inspection chamber of a dark field inspection instrument. The method according to claim 1, further comprising:

17. 12. The method of claim 11, wherein the step of focusing the beam of illumination into a volume of air contained within an examination chamber comprises: Focusing the beam of illumination into a volume of air contained within an examination chamber, the volume of air being located above a sample stage. The method according to claim 1, further comprising:

18. 12. The method of claim 11, wherein the step of detecting the collected portion of illumination from the one or more collection optics by a detector comprises: detecting the collected portion of illumination from the one or more collection optics with a charge-coupled device (CCD) detector. The method according to claim 1, further comprising:

19. 12. The method of claim 11, adjusting a condition of at least one of one or more illumination sources, one or more illumination optics, or the one or more collection optics based on the determined condition of the beam of illumination. The method further comprising:

20. 12. The method of claim 11, adjusting at least one of a power of 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. The method further comprising:

21. one or more illumination sources configured to generate a beam of illumination; one or more illumination optics configured to focus the beam of illumination into a volume of air contained within the examination chamber; one or more collection optics configured to collect a portion of the illumination scattered from the volume of air; a detector configured to receive the collected portion of the illumination from the one or more collection optics; a controller including one or more processors communicatively coupled to the detector, the one or more processors configured to execute a set of program instructions stored in a memory, the set of program instructions configuring the one or more processors to: receiving one or more signals from the detector indicative of an intensity of the illumination scattered from the volume of air; determining an intensity of the beam of illumination based on a comparison between the intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion; a controller configured to cause the Including, The controller calculates a ratio of total air scattering of P-polarized light and S-polarized light based on the one or more signals from the detector, and determines a polarization state of the beam of illumination based on the ratio of total air scattering.

1. An inspection system comprising:

22. one or more illumination sources configured to generate a beam of illumination; one or more illumination optics configured to focus the beam of illumination into a volume of air contained within the examination chamber; one or more collection optics configured to collect a portion of the illumination scattered from the volume of air; a detector configured to receive the collected portion of the illumination from the one or more collection optics; a controller including one or more processors communicatively coupled to the detector, the one or more processors configured to execute a set of program instructions stored in a memory, the set of program instructions configuring the one or more processors to: receiving one or more signals from the detector indicative of an intensity of the illumination scattered from the volume of air; determining a polarization of the beam of illumination based on a comparison between the intensity of the illumination scattered from the volume of air at one or more times and a predetermined intensity criterion; a controller configured to cause the wherein the controller calculates a ratio of total air scattering of P polarization and S polarization based on the one or more signals from the detector, and determines a polarization state of the beam of illumination based on the ratio of total air scattering.

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