Phase mask for polarization and optical signal control in optical inspection systems

Abstract

The disclosed implementations describe, among other things, a sample inspection system that includes an illumination subsystem for generating light incident on a sample. The sample inspection system includes a collection subsystem having an optical element for collecting light generated when incident light interacts with a sample. The sample inspection system further includes a light detection subsystem configured to detect the collected light and generate one or more signals representative of a characteristic of the sample. The sample inspection system deploys a phase mask that interacts with incident light and / or collected light and includes a first region and a second region that impart different phases to light incident on the phase mask.

Description

Technical Field

[0001] The present disclosure relates generally to quality control of materials manufactured in substrate processing systems. More particularly, the present disclosure relates to optical inspection methods and apparatus for quality control of substrates, wafers, masks, and other products during various stages of manufacturing. Background Art

[0002] The manufacture of modern materials generally involves various deposition techniques, such as chemical vapor deposition, physical vapor deposition technology, atomic layer deposition technology, etching technology, polishing technology, photomask technology and / or various other manufacturing technologies. The materials and devices manufactured in the described manner may include single crystals, semiconductor films, fine coatings, patterns, transistor arrays, die, chips and numerous other structures used in practical applications (such as electronic device manufacturing). Many applications in these applications rely on the purity of the material and / or the accuracy of the structure prepared in the manufacturing system. Various detection and sensing systems are used to monitor whether the processing operation meets the manufacturing specifications, maintain the optimal chemical composition and physical conditions of the processing environment, etc. The quality of intermediate products and final products is monitored by an inspection system, including optical inspection. Optical inspection may include reflection technology, spectral technology, elliptical polarization technology, etc. Specular reflection light, diffuse reflection (scattering) light, transmitted light or its various combinations can be used to perform optical inspection. Summary of the Invention

[0003] Some of the embodiments described herein relate to a sample inspection system comprising an illumination subsystem for generating light incident on a sample. The sample inspection system further comprises a collection subsystem having one or more optical elements for collecting light generated when the incident light interacts with the sample. The sample inspection system further comprises a light detection subsystem configured to detect the collected light and generate one or more signals representing one or more characteristics of the sample. The sample inspection system comprises a phase mask positioned to interact with at least one of the incident light or the collected light. The phase mask may comprise at least a first region for engaging a first portion of the light that interacts with the phase mask; and a second region for (i) engaging a second portion of the light that interacts with the phase mask, and (ii) phase shifting the second portion relative to the first portion.

[0004] Another embodiment described relates to a method for performing an inspection of a sample. The method includes generating source light and directing the source light toward a phase mask. The phase mask includes a first region configured to interact with a first portion of the source light and a second region configured to (i) interact with a second portion of the source light and (ii) phase-shift the second portion of the source light relative to the first portion of the source light. The method further includes illuminating the sample with the source light, collecting light generated when the source light interacts with the sample, directing the collected light toward a light detection sensor to generate one or more of signals, and determining one or more characteristics of the sample using the one or more signals.

[0005] Yet another embodiment described relates to a method for performing an inspection of a sample. The method includes generating source light, illuminating a sample using the source light, and collecting light generated when the source light interacts with the sample. The method further includes directing at least a portion of the collected light to a phase mask. The phase mask includes a first region for interacting with a first portion of the collected light, and a second region for (i) interacting with a second portion of the collected light and (ii) phase-shifting the second portion of the collected light relative to the first portion of the collected light. The method further includes directing the collected light to a light detection sensor to generate one or more signals, and using the one or more signals to determine one or more characteristics of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 An example optical inspection system capable of deploying phase masks for optical inspection performed in the context of manufacturing operations in accordance with at least one embodiment is illustrated.

[0007] Figure 2 An example optical inspection tool capable of deploying a phase mask to improve an optical inspection signal in accordance with at least one embodiment is illustrated.

[0008] Figures 3A to 3C Illustrated is a deployment according to at least one embodiment Figure 2 An example two-segmented phase mask deployment as part of the illumination subsystem of an optical inspection tool.

[0009] Figures 4A to 4G Illustrated is a diagram for amplifying Figure 2 Out-of-plane dipole and quadrupole resonances in the detection channel of an optical inspection tool Figure 3C Example of a two-segment phase mask deployment.

[0010] 5A to 5D Illustrated is a diagram for using a Figure 2 The detection channel of the optical inspection tool is used to amplify the multipolar resonance Figure 3C Example of a four-segment phase mask deployment.

[0011] 6A to 6D Illustrated is an example use of birefringent material for constructing a phase mask in accordance with at least one embodiment.

[0012] 7A to 7D Illustrated is another use of an example two-segment phase mask for amplifying detection of magnetic dipole resonance in accordance with at least one embodiment.

[0013] Figures 8A to 8E An example embodiment of a phase mask deploying an acousto-optic modulator according to some aspects of the present disclosure is illustrated.

[0014] Figures 9A to 9B is a flow chart of an example method for deploying a phase mask for improving an optical inspection signal in accordance with at least one embodiment. DETAILED DESCRIPTION

[0015] Semiconductor device manufacturing typically involves dozens or even hundreds of complex operations to achieve raw wafer (substrate) preparation, polishing, material deposition, etching, etc. Since even a small amount of impurities or other defects introduced into the processing environment during such operations can render the manufactured products (masks, wafers, chips, etc.) unusable for their intended purpose, the various manufacturing operations are typically interspersed with quality control inspections to verify that the intermediate and final products meet the specifications of the technical process being performed. Inspections can determine the cleanliness of the product (also referred to herein as a sample), the presence of defects in the sample, the size of the sample, the physical and chemical composition of the sample, the surface morphology of the sample, etc.

[0016] Optical (including UV) inspection systems are capable of effectively detecting impurities, lattice / morphological defects, surface roughness, thickness non-uniformity and / or other product defects. The optical inspection system can implement bright field inspection techniques (the techniques use specular reflection of the probe light from the sample), dark field inspection techniques (the techniques use non-specular scattering of the probe light from the sample) and / or a combination thereof. The sample can be temporarily removed from the processing line and scanned position by position using an optical inspection system (including an illumination subsystem, a light collection subsystem, various additional optical elements, polarizers, field stops, light detection subsystems, data processing subsystems, etc.). The sample should be understood to be any patterned wafer or unpatterned wafer. Unpatterned wafers may include: bare wafers; wafers covered with any number of films, layers; polished, ground, annealed wafers; and / or any wafer that has undergone one or more processing operations to maintain or establish wafer uniformity. A patterned wafer may include any wafer having spatially non-uniform features deposited, grown, etched, cut, or otherwise formed, which may include one or more devices such as logic / memory transistors, interconnect circuitry, and / or combinations of such devices grouped into dies, chips, blocks, etc.

[0017] Various flaws and defects in a sample may often have resonant properties, where a certain mode (e.g., a dipole mode, a quadrupole mode, or a higher multipole mode (or some combination thereof)) is responsible for the majority of the scattered (or reflected) radiation from the site of the flaw / defect. This resonant radiation often has different angular patterns. For example, an electric dipole oriented perpendicular to the surface of the sample (along the z-axis) produces radiation with a radial pattern of in-plane electric fields at the pupil plane of the collection system (e.g., as shown in FIG. 2 ). Figures 4A to 4B ), while multipolar in-plane combinations can lead to other radial symmetries (such as Figures 6A to 6B ). Using a conventional uniform polarizer to collect such a pattern of radiation can result in an optical signal with a low signal-to-noise ratio (SNR), which reduces the likelihood of successful defect / flaw detection.

[0018] Aspects and embodiments of the present disclosure address these and other challenges of the prior art by providing techniques and systems for deploying phase masks that impart spatially non-uniform phase variations to transmitted light. In one example embodiment, the phase mask includes a first region and a second region that impart different phases (e.g., by π (half the wavelength of the light)) to light incident on the mask. Accordingly, when a first portion of the beam (e.g., a reflected or scattered beam) is transmitted through (or reflected from) the first region, and a second portion of the beam is transmitted through (or reflected from) the second region, the relative directions of the electric fields in the two portions are reversed. For example, if the first and second portions initially have antiparallel electric fields, the corresponding portions of the transmitted (or reflected) beam will have parallel electric fields. Such a phase mask—appropriately oriented in the pupil plane—can be used to increase the optical signal noise ratio (SNR) by replacing destructive interference of reflected / scattered radiation incident on a photodetector with constructive interference.

[0019] In another example embodiment, the phase mask may include more than two distinct regions, for example, a first set of n regions that impart a π phase change relative to a second set of regions, the second set of regions being spaced apart from the first set of regions. Such a phase mask may be used to improve the SNR of the reflected / scattered optical signal where the electric field in the reflected / scattered optical signal undergoes 2n sign changes within the pupil plane. According to the disclosed techniques, polarized light may be manipulated in the coherent pupil plane of an optical system's illumination subsystem, an optical system's collection subsystem, or both. The phase masks disclosed herein may be passive or active. A passive (static) phase mask may include any optical element or combination of optical elements having properties that are fixed for the duration of the optical inspection, such as one or more films deposited on glass. Active (dynamic) phase masks may include any optical element or combination of optical elements in which at least one characteristic can be controlled during optical inspection (or in preparation for optical inspection), for example, an acousto-optic modulator in which a property (such as refractive index) can be controlled by controlling the amplitude and phase of an acoustic wave passing therethrough, an electro-optic modulator in which a property can be controlled by adjusting an electric field (voltage) applied thereto, etc. Advantages of the disclosed systems and techniques include improved efficiency and accuracy in defect and flaw detection for inspection of various products of semiconductor manufacturing.

[0020] The disclosed embodiments relate to optical inspection performed in the context of various manufacturing techniques, such as bare wafer fabrication, chemical mechanical polishing (CMP), physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced PVD and / or CVD, atomic layer CVD, combustion CVD, catalytic CVD, evaporative deposition, molecular beam epitaxy, wafer patterning, photomask application, etching, and / or other techniques. The disclosed embodiments may also be advantageously used to improve manufacturing techniques using vacuum deposition chambers (e.g., ultra-high vacuum CVD or PVD, low-pressure CVD, etc.) and / or atmospheric pressure deposition chambers.

[0021] Figure 1 An example optical inspection system 100 is illustrated that is capable of deploying a phase mask for optical inspection performed in the context of a manufacturing operation in accordance with at least one embodiment. In some embodiments, the optical inspection system 100 can be used to perform inline inspection, where product is transferred between processing chambers, between a processing chamber and a transfer chamber, between a transfer chamber and a load lock chamber, between a load lock chamber and a product carrier, and the like. In some embodiments, the optical inspection system 100 can be used as a stand-alone inspection system. In some embodiments, optical inspection is performed on a sample 112 (e.g., a wafer, a mask, a film, a patterned product, or any combination thereof) carried by a movable stage 110 (e.g., a robotic blade) that supports and moves the sample 112. In some embodiments, an optical inspection tool 114 equipped with a phase mask (PME) can be used to facilitate optical inspection of the sample 112, such as in conjunction with a Figure 2 9 is described in more detail.

[0022] The PME optical inspection tool 114 scans the sample 112 with one or more light beams 102 and collects light reflected from the sample 112, such as specularly reflected light 104 (as part of brightfield inspection) and / or non-specularly (diffusely) scattered light 106 (as part of darkfield inspection). Figure 1 An oblique incidence of beam 102 is depicted, but in other embodiments, beam 102 may be perpendicularly incident on the surface of sample 112. PME optical inspection tool 114 may be configured to inspect sample 112 using visible light, UV light, and / or other electromagnetic radiation.

[0023] The electronics module 130 can control the operation of the PME optical inspection tool 114 and can further control at least some processing of the optical inspection data collected by the PME optical inspection tool 114. The electronics module 130 can include a microcontroller and a memory device (e.g., a buffer) coupled to the microcontroller. The memory device can be used to store instructions for controlling the operation of the PME optical inspection tool 114 and the optical inspection data before transmitting the optical inspection data to the computing device 118. The computing device 118 can include an optical inspection control module 120 that selects (e.g., in response to instructions stored on the computing device 118 or received from a human operator of the optical inspection system 100) an inspection mode, an inspection resolution, a wavelength used by the PME optical inspection tool 114, an inspection frequency (e.g., a scanning frequency or a pulsed light source repetition rate), an inspection wavelength, objective lens zoom, the type and spatial orientation of the phase mask, etc. The computing device 118 can further include a stage control module 122 that controls the speed and timing of the rotational and / or translational motion of the sample 112 relative to the PME optical inspection tool 114. The computing device 118 can operate a sample quality control module 124 that processes the optical inspection data collected by the PME optical inspection tool 114 and determines the physical / chemical composition of the sample 112, such as the quality and quantity of impurities, surface flaws, pattern defects, thickness variations, etc. The sample quality control module 124 can compare the obtained morphological, physical, chemical, etc. properties of the sample 112 with the specifications of the manufacturing process being performed and determine whether the sample 112 meets these specifications. The sample quality control module 124 can then determine whether to continue or stop the manufacturing process, whether to remove the sample 112 from the processing line, return it to the processing line for further processing (e.g., additional polishing, deposition, cleaning, etc.), whether to output a warning or alarm signal to the operator, or can take any number of other programmed actions.

[0024] Figure 2 An example optical inspection tool 200 capable of deploying a phase mask to improve an optical inspection signal in accordance with at least one embodiment is illustrated. The optical inspection tool 200 can be used to inspect a sample 112 supported by a movable stage 202 (e.g., a robotic blade or some other similar movable stage). The optical inspection tool 200 may include an illumination subsystem configured to generate light at normal incidence and / or oblique incidence on the sample 112. In some embodiments, the illumination subsystem is configured to illuminate the sample 112 at any range of angles (e.g., through any fraction of the numerical aperture (NA) or full NA of the illumination subsystem). Figure 2 As depicted in FIG. 1 , the illumination subsystem may include a light source 204 configured to generate light for vertically illuminating the sample 112 (e.g., Figure 2) or obliquely illuminated incident light 206. Although Figure 2 In some embodiments, a single light source 204 is used to illuminate the sample 112 for both brightfield and darkfield inspection, but in other embodiments, multiple light sources may be used, such as separate light sources for brightfield and / or darkfield inspection. In some embodiments, the incident light 206 may be a flood beam. In some embodiments, the incident light 206 may be a spot beam focused on a specific point on the sample 112. The movable stage 202 may be used to reposition the spot relative to the sample 112. In some embodiments, the size of the illuminated spot may be less than 1 mm. The illumination intensity of the spot may be controlled by controlling the size of the spot and / or by controlling the intensity of the light generated by the light source 204 (and / or other light sources, if deployed).

[0025] In some embodiments, light source 204 may include a broadband lamp, a narrowband laser, a light emitting diode, a semiconductor laser, a gas laser, a pulsed laser, a continuous wave laser, or some other type of light source.

[0026] Incident light 206 may pass through one or more polarizers 208, which should be understood as any optical element / device or combination of optical elements / devices configured to control the polarization of light incident on sample 112. Polarizer 208 may cause incident light 206 to be linearly polarized, s-polarized (perpendicular to the plane of incidence on sample 112), p-polarized (parallel to the plane of incidence on sample 112), circularly polarized (e.g., right-handed or left-handed circular polarization), elliptically polarized, partially polarized, etc., along any direction (e.g., x-direction, y-direction, and / or some other direction). Polarizer 208 (and / or other polarizers that may be deployed by optical inspection tool 200) may be an absorptive polarizer, a reflective polarizer, a beam-splitting polarizer, a birefringent polarizer (e.g., a quarter-wave plate, a half-wave plate), a thin-film polarizer, a nanoparticle-based polarizer, an S-wave plate converter (which may convert linear polarization to radial or azimuthal polarization and may convert circular polarization to an optical vortex), and / or any other suitable polarizer. In some embodiments, polarizer 208 may include a segmented linear polarizer including two or more linear polarizer segments having axes of polarization having different orientations.

[0027] Incident light 206 may also pass through a phase mask 210, a beam splitter 212, and an aperture 213 in a beam splitter 214, which separates the reflected brightfield light from the scattered darkfield light. Incident light 206 may be relayed by relay optics 216 toward telescope optics 218 and objective 220, each of which may include one or more optical elements (e.g., lenses, mirrors, etc.). At least some elements of telescope optics 218 may be movable relative to objective 220 (and / or relative to other elements of telescope optics 218) to support multiple spot sizes and / or zoom (magnification).

[0028] Incident light 206 striking the sample 112 may generate specularly reflected light 222 (bright field light) and scattered light 224 (dark field light). The scattered light 224 may propagate in a series of directions (with angle-dependent intensities), with two such directions being Figure 2 The collection subsystem of the optical inspection tool 200 can collect light reflected and / or scattered from the sample 112. In some embodiments, the collection subsystem can share one or more optical elements with the illumination subsystem, such as Figure 2 2. The objective lens 220, telescope optics 218, relay optics 216, etc. in the example embodiment of FIG. The number and type of lenses (mirrors, diffractive elements) in the objective lens 220 and / or telescope optics 218 may be selected using any known technique, for example, to reduce optical aberrations, including but not limited to chromatic aberration.

[0029] The brightfield reflection channel may use an objective lens 220 and telescope optics 218 to collect reflected light 222 (indicated by dashed lines) and relay the collected reflected light 222 to a beam splitter 212 via relay optics 216. The beam splitter 212 may direct the reflected light 222 toward a polarizer 226, a phase mask 230, and one or more optical elements (e.g., focusing optics, relay optics, etc.). Figure 2 ), the one or more optical elements direct the reflected light 222 to the bright field detector 232. In some embodiments, the polarizer 226 may transmit the same polarization as the polarization of the incident light 206 produced by the polarizer 208. For example, the polarizer 208 may impart s-polarization to the incident light 206, and the polarizer 226 may also transmit the s-polarization toward the bright field detector 232. In some embodiments, the polarizer 226 may transmit a different polarization than the polarization produced by the polarizer 208. For example, the polarizer 208 may impart s-polarization to the incident light 206, and the polarizer 226 may also transmit p-polarized (or vice versa) reflected light 222 toward the bright field detector 232. In some embodiments, the collection subsystem may include one or more directional filters ( Figure 2(not shown), the directional filter is configured to pass light collected from a specific reflection angle interval (corresponding to a target numerical aperture) from the sample 112. Such a directional filter can be implemented via a light absorbing plate, in which a suitable aperture is cut to allow the reflected light to pass.

[0030] The dark field reflection channel can, for example, use the same objective lens 220 and telescope optics 218 to collect scattered light 224. The collected scattered light 224 can be relayed to the beam splitter 214 via relay optics 216. The scattered light 224 incident on the beam splitter 214 outside the central aperture 213 is directed toward the polarizer 234, the phase mask 240, and one or more optical elements (e.g., focusing lens, relay lens, etc.). Figure 2 The scattered light 224 is reflected by the optical element (not shown), which directs the scattered light 224 to the dark field detector 238. The polarizer 234 can transmit the same polarization as or a different polarization than that produced by the polarizer 208. In some embodiments, the collection subsystem may include one or more directional filters ( Figure 2 (not shown in the figure), the directional filter is configured to pass light collected from a specific scattering angle interval from the sample 112.

[0031] In some embodiments, objective lens 220 may be (or include) a catadioptric optical device. A catadioptric optical device may include one or more semi-transparent mirrors, focusing mirrors, lenses, diffraction gratings, and / or other optical elements. A catadioptric objective lens that deploys (multiple) focusing mirrors (e.g., spherical, elliptical, parabolic, etc.) may provide a wide field of view, for example, where one or more focusing mirrors have a large numerical aperture (collecting scattered light 224 from a wide range of angles). A catadioptric objective lens may support different spectral distributions (e.g., wavelengths) of imaging light without introducing detrimental dispersion into the optical paths of the various reflected and scattered beams.

[0032] The brightfield detector 232 and / or the darkfield detector 238 may utilize a photodiode, a phototransistor, a complementary metal oxide semiconductor (CMOS) image sensor, a charge coupled device (CCD), a hybrid CMOS-CCD image sensor, a photomultiplier tube (e.g., a pixel array based on a photocathode), or any other suitable photon detector. Each detector (e.g., pixel) of the brightfield detector 232 and / or the darkfield detector 238 may image a separate point on the sample 112 illuminated by the incident light 206. The light intensity (e.g., reflectivity) data collected by the brightfield detector 232 and / or the darkfield detector 238 may be provided to the sample quality control module 124, which determines the size, type, concentration, and location of various defects and flaws in the sample 112. The sample quality control module 124 may communicate with the optical inspection control module 120, which may be configured to change the settings of the optical inspection system 100 (and the optical inspection tool 200) based on instructions from the sample quality control module 124. For example, an initial inspection may be performed at a set resolution. When the sample quality control module 124 identifies the presence of a defect, for example based on the light reflectance data collected by the light detector 232-1 (or 232-2, etc.), the sample quality control module 124 may send a notification to the optical inspection control module 120 (see Figure 1 ) outputs instructions to the optical inspection control module, which can change the resolution of the imaging by zooming the telescope optics 218 and / or the objective lens 220 to a specific area on the sample 112 where the detected defect is located. For example, the optical inspection control module 120 can change the focal length of the objective lens 220 (or the telescope optics 218, etc.), change the distance from the objective lens 220 (or the telescope optics 218, etc.) to the sample 112, and so on. The optical inspection control module 120 can also change the numerical aperture of various directional filters; polarizers 208, 226, and / or 234; and phase masks 210, 230, and / or 240 to facilitate changes in imaging resolution. Inspection of any given location(s) of the sample 112 can be completed after the brightfield detector 232 and / or the darkfield detector 238 have collected a target amount of light. Subsequently, the movable stage 202 can reposition the sample 112 relative to the incident light 206 to inspect a different location of the sample 112. The stage control module 122 may determine a distance and direction for repositioning the sample 112 such that previously uninspected points are exposed to the incident light 206 .

[0033] In some embodiments, the CMOS image sensor, CCD image sensor, and / or any other image sensing element of the brightfield detector 232 and / or darkfield detector 238 can be operated in time delay and integration (TDI) mode. For example, if the light source 204 is a pulsed light source (e.g., an excimer laser pulsed laser source), each pulse can correspond to a sensing frame. In TDI mode, each sensing pixel can aggregate the electrical signals (e.g., charge signals, voltage signals, etc.) generated during multiple sensing frames. Thus, multiple low-intensity pulses can be used to achieve high imaging sensitivity and resolution without exposing the sample 112 to high-intensity beams that can damage the wafer. In those instances where imaging is performed on a moving sample 112 (e.g., transported by the movable stage 202), signal aggregation in TDI mode can be performed for pixels that are sequentially exposed to light reflected or scattered from the same area of the moving sample 112.

[0034] In some embodiments, the CMOS image sensor used in the bright field detector 232 and / or the dark field detector 238 may be a high-speed sensor and a low-noise sensor. For example, in some embodiments, the CMOS image sensor may have a speed equal to or higher than 1 gigapixel per second and a noise of 10e or less (e.g., in the range of 2e to 5e or even less).

[0035] In some embodiments, the optical inspection tool 200 may include phase contrast functionality. For example, the vertically incident light 206 may be split (e.g., using a Wollaston prism) into two beams having different polarizations (e.g., an s-polarized incident beam and a p-polarized incident beam). The reflected polarized beam may then pass through a polarizer to obtain a combined beam having an interference pattern that is detected by a brightfield detector 232. In some embodiments, the optical inspection tool 200 may have differential interference contrast (DIC) functionality, wherein the vertically incident beam is split into two beams of different polarization that follow close but different optical paths and probe two closely spaced locations of the sample 112.

[0036] although Figure 2 The optical inspection tool 200 in FIG. 1 is shown as including a phase mask 210 in the illumination subsystem, a phase mask 230 in the brightfield collection channel, and a phase mask 240 in the darkfield collection channel, but in other embodiments, one or more of the phase masks may not be present. In one example embodiment, the phase mask 210 in the illumination subsystem may be deployed without the phase masks 230 and 240. In another example embodiment, the phase mask 210 in the illumination subsystem may not be present, while the phase mask 230 and / or the phase mask 240 may be deployed.

[0037] In some embodiments, any, some, or all of the phase masks 210, 230, 240 may operate by altering the phase of light reflected from (rather than transmitted through) the corresponding mask. For example, any, some, or all of the phase masks 210, 230, 240 may include a reflective surface partially coated with a film having a thickness selected to impart a phase difference to light reflected from the coated portion(s) compared to light reflected from the uncoated portion(s) of the reflective surface.

[0038] In some embodiments, any, some, or all of the phase masks 210, 230, 240 may be combined with a corresponding polarizer 208, 226, 234. For example, a portion of the corresponding polarizer may be coated with a phase-inverting coating deposited on a portion of the polarizer.

[0039] Figures 3A to 3C Illustrated is a deployment according to at least one embodiment Figure 2 An example two-segmented phase mask deployment is shown as part of the illumination subsystem of the optical inspection tool 200. Figure 3A The diagram illustrates coherent linearly polarized incident light 206 focused by focusing optics 300 onto a point on the surface of sample 112. Although for the sake of brevity and simplicity, the Figure 3A and Figure 3B The focusing optics 300 are illustrated in FIG. 3 via a single lens, but the focusing optics 300 may include any number of optical elements, such as the objective 220, the telescope optics 218, the relay optics 216, and / or any other suitable elements. Figure 3A The middle figure shows parallel (in-phase) electric fields. The focusing optics 300 changes the direction of the rays and rotates the electric field so that the two electric fields are different from each other (non-collinear), At the surface of the sample 112, the two electric fields add up to a total electric field, The total electric field is parallel to the surface of the sample 112: Such fields are efficient at coupling to and exciting resonant electric dipole modes of various defects and imperfections, where the electric dipoles are parallel to the surface of the sample 112 (eg, parallel to the x-axis).

[0040] like Figure 3B As shown, when the two-segment phase mask 210 is placed in the optical path of the incident light 206, and the phase of the ray 206-2 is delayed (or advanced) by π relative to the phase of the ray 206-1, the electric field of the ray 206-2 is reversed. When the focusing optics 300 changes the direction of the rays, the directions of the electric fields in the two rays change accordingly. like Figure 3BAt the surface of the sample 112, the two electric fields now add up to equal the total field, The total field is normal to the surface: This field is efficient at coupling to and exciting various defects and flaws where the electric dipole is perpendicular to the surface of the sample 112 (parallel to the z-axis). Accordingly, to detect such z-dipole resonances, a coherent incident beam may be transmitted through Figure 3C The illustrated phase mask 210 includes a first region 210-1 (indicated by a phase of 0) and a second region 210-2 (indicated by a phase of π), wherein rays traveling through the second region 210-2 acquire a phase difference of π (half the wavelength) relative to rays traveling through the first region 210-1.

[0041] Figures 4A to 4G Illustrated is a diagram for amplifying Figure 2 Out-of-plane dipole and quadrupole resonances in the detection channel of the optical inspection tool 200 Figure 3C Example of a two-segment phase mask deployment. Figure 4A The diagram shows the z-polarized dipole Two rays 224 - 1 and 224 - 2 of scattered light are emitted. Figure 4B A top view 401 of the electric field of emitted radiation in a plane above the focusing optics (e.g., the coherence pupil plane) is shown. Figure 4B As shown, the electric field in the scattered light is radially symmetric. Figure 4C The diagram illustrates the modification of the electric field of the emitted radiation after it passes through the x-polarizer 234, which filters out the y-component of the electric field. The top view 402 depicts the electric field in the left half of the pupil plane. and the opposite electric field in the right half of the pupil plane When the focusing lens ( Figure 4A When the scattered light is focused onto the detector pixels (not shown), the electric fields largely cancel (destructive interference), resulting in a low SNR for the signal detected by the pixels. The polarizer 234 can be placed before or after the phase mask 240.

[0042] Figure 4D is a diagram showing the scattered light passing through the Figure 3C FIG4 is a top view 404 of an additional modification of the emitted radiation achieved by using the same or similar two-segment phase mask 240 as the phase mask 210. As illustrated, the direction of the electric field is reversed in the right half of the pupil plane: When the focusing lens then focuses the scattered light onto the detector pixels, the electric field increases (constructive interference), resulting in a significantly enhanced SNR of the signal detected by the pixels. Detection of radiation emitted by resonant dipoles (and resonant quadrupoles) with a z-symmetry axis is improved by a phase mask. In some embodiments, for maximum enhancement, a two-segmented π mask can be deployed in both the illumination subsystem (to enhance the z-component of the electric field at the surface of the sample 112 for better coupling to the dipole / quadrupole resonance) and the collection channel (to convert destructive interference into constructive interference for improved detection SNR).

[0043] Figure 4E An example optical signal 406 is shown collected using the x-polarizer 234, which forms Figure 4C A picture of the electric field is shown. Figure 4F An example optical signal 408 is shown collected using the x-polarizer 234 and the phase mask 240, which form Figure 4D 4. A graph of the electric field is shown. The maxima (bright fringes) and minima (dark fringes) of optical signal 408 are inverted compared to the maxima and minima of optical signal 406. Because the dominant maximum in optical signal 408 has a stronger signal-to-noise ratio (SNR) than the two weaker maxima in optical signal 406, the use of optical signal 408 facilitates better defect / flaw detection and higher resolution. In particular, the improved resolution enables more accurate optical inspection of patterned wafers, masks, films, and / or any other samples with small-scale features and / or structures.

[0044] Figure 4G An example deployment of a segmented phase mask is illustrated in which a central portion of the phase mask is rendered impenetrable to light, e.g., blocked by a directional filter 410. More specifically, a central portion of the phase mask 240 (or any other phase mask, such as the phase mask 210 and / or the phase mask 243) includes a region where the imparted phase φ gradually changes from φ=0 to φ=π. Such a region may be less efficient in facilitating constructive interference of light transmitted by the remaining regions of the phase mask 240. The directional filter 410 may be used to block light transmitted through the central region from reaching the light detector. This increases the SNR of the detected optical signal (by reducing the portion of light that does not substantially improve the optical signal but contributes to the overall noise). Although Figure 4G A segmented phase mask is illustrated having regions that block light, but in some implementations, the phase mask may have one or more regions that attenuate any targeted portion of light, including region(s) where the attenuation function of the phase mask varies continuously with position.

[0045] 5A to 5D Illustrated is a diagram for using a Figure 2The detection channel of the optical inspection tool 200 is used to amplify the sample multipolar resonance Figure 3C Example of a four-segment phase mask deployment. Figure 5A is a schematic top view 500 of the charge (or current) distribution within the plane of the sample 112 . Figure 5B A top view 501 of the electric field of the multipolar emission radiation in the plane above the focusing optics (the coherence pupil plane) is schematically illustrated. Even though the application of a linear y-polarizer may result in an electric field E in both the upper and lower parts of the pupil plane y components of the same sign, but the electric field E y The resulting small component (and low signal-to-noise optical signal) allows the application of an x-polarizer to filter out the electric field E y This results in Figure 5C The electric field E shown in the top view 502 is x In such an embodiment, the four-segmented phase mask 240 may be used to align the electric field directions in all four quadrants of the pupil plane, such as Figure 5D 504 in FIG. The four segments of phase mask 240 may include two segments (e.g., occupying the first and second quadrants of the pupil plane, as shown) that add a π phase to the transmitted light relative to the light transmitted through the other two "0" segments (e.g., occupying the second and fourth quadrants of the pupil plane, as shown). Polarizer 234 may be placed before or after phase mask 240.

[0046] 6A to 6D An example use of a birefringent material for constructing a phase mask, according to at least one embodiment, is illustrated. Light propagates through the birefringent material at different speeds for light polarized along the ordinary axis and light polarized along the extraordinary axis. This property enables the introduction of a controlled phase shift between the two polarizations. 6A to 6D Illustration of the deployment of a half-wave plate for improving the optical signal. Figure 6A An example distribution of the electric field in a pupil plane of an optical inspection system (e.g., a pupil plane of an illumination subsystem or a pupil plane of a collection subsystem) is illustrated, where the electric field in the left half of the pupil is antiparallel to the electric field in the right half of the pupil. The light then passes through a two-segmented phase mask 600 having a left half-wave plate ("λ / 2"), in which the fast axis (f) of the birefringent material is oriented at 45 degrees (or -45 degrees) to the direction of the electric field, and a right half-wave plate, in which the fast axis is oriented perpendicular to the fast axis of the left half-wave plate. In one illustrative example, the thickness of the half-wave plate can be selected in such a way that light propagating along the slow axis is delayed by half a wavelength λ / 2 relative to the fast axis. Thus, as Figure 6BAs shown, the electric field of light passing through the left half-wave plate is rotated 90 degrees in one direction, while the electric field of light passing through the right half-wave plate is rotated 90 degrees in the opposite direction, so that the electric field has the same direction everywhere in the pupil plane.

[0047] Figure 6C Another example distribution of the electric field in the pupil plane is shown, where the electric field is Figure 6A The distribution of is tilted 45 degrees. Then, the light passes through a four-segment phase mask 602 made of a uniform material, in which two half-wave plate segments have two fast axes tilted 45 degrees (or -45 degrees) relative to the other two half-wave plate segments, resulting in an electric field distribution in the pupil plane, such as Figure 6D shown.

[0048] 7A to 7D Illustrated is another use of an example two-segment phase mask for amplifying detection of magnetic dipole resonance in accordance with at least one embodiment. Figure 7A is the radiating magnetic dipole polarized along the z axis Schematic diagram 700. Figure 7B A top view 701 of the circulating electric field (in the coherence pupil plane) of radiation emitted by a magnetic dipole is shown. Figure 7C A top view 702 of the electric field after the scattered light passes through the x-polarizer 234 is shown. Application of the two-segment phase mask 240 then aligns the direction of the electric field in the entire pupil plane, as Figure 7D This is shown in the top view 704 in FIG.

[0049] The phase masks illustrated in conjunction with Figures 3 to 7 (e.g., two 180-degree segmented masks and four 90-degree segmented masks) should be understood as illustrative, non-limiting examples. In some embodiments, the number of segments may be greater than four, for example, 2n segments with n π phase segments and n 0 phase segments, where n can be any integer. Such phase masks can be used to detect radiation from higher-order multipolar resonances (e.g., octupole modes, etc.) and / or combinations of two or more multipolar modes (e.g., dipole and quadrupole modes, dipole and octupole modes, etc.). Although phase masks with 0 and π phase shifts have been illustrated above, in some embodiments, the relative offset between two (or more) segments of the phase mask may differ from ππ, e.g., greater than π or less than π. In some embodiments, the phase mask can also be used as an amplitude mask, e.g., different segments of the phase mask have different transmission coefficients. For example, the 0 phase shift region may have a first transmission coefficient T1, and the π phase shift region may have a second transmission coefficient T2 that is different from (e.g., less than or greater than) the first transmission coefficient T1. Although the phase mask illustrated above has a circular shape, in other embodiments, the phase mask may have a non-circular shape, such as an elliptical shape, a square shape, a rectangular shape, or the like.

[0050] Although the lighting subsystem has been integrated ( Figures 3A to 3C ) and dark-field scattering channels (FIGS. 4-7) to illustrate the above examples, but the phase mask may be deployed in the bright-field reflectance channel using substantially the same or similar techniques.

[0051] The disclosed techniques can be used with any optical inspection configuration, for example, with point illumination (such as scanning point illumination), line scan illumination, area (flood beam) illumination, and the like. In point illumination, coherent light can be focused onto a point (small area) of sample 112. The light collected from the point can be associated with a single imaging pixel (or a small number of such pixels). Once a target amount of scattered and / or reflected light has been collected from a given point of sample 112, a value characterizing the amount of light collected (and its polarization, etc.) can be stored in association with the location of the point, and the focused beam can be moved to a different (e.g., adjacent) point of sample 112. In scanned line illumination, incident light can be focused (e.g., using a cylindrical lens) onto a linear area of sample 112. In area illumination, incoherent (or partially coherent) light can be used to illuminate a larger area of sample 112, such as a 2×2 mm area (or some other sized area). Collection optics can then coherently collect the scattered light to form an image on a sensor (e.g., a camera sensor). In all instances of point illumination, line scan illumination, and area illumination, optical inspection may include brightfield (eg, using brightfield detector 232 ) and / or darkfield (eg, using darkfield detector 238 ) inspection of sample 112 simultaneously or sequentially.

[0052] In some embodiments, a phase mask can be fabricated using a static combination of mechanical and optical elements. For example, the 0 phase region(s) of the phase mask can be made of one material, and the π phase region(s) can be made of a different material. In some embodiments, the 0 phase region(s) and the π phase region(s) can be made of the same material, while the π phase region(s) (or alternatively, the 0 phase region(s)) can be additionally coated with a film of a suitably selected material and a thickness selected to achieve a half-wavelength shift in transmitted light. In some embodiments, the phase mask can be implemented using acousto-optic and / or electro-optical elements.

[0053] For example, in the case of an electro-optic modulator (EOM) (e.g., a piezoelectric modulator (such as a lithium niobate-based modulator)), the same voltage (or electric field) can be applied to two (or more) portions of the EOM having different thicknesses, such that the combination of the applied voltage and the different thicknesses causes a π phase difference caused by light passing through the two portions. Alternatively, different voltages (or electric fields) can be applied to two (or more) portions of the EOM having the same thickness (to produce the same π phase difference). In some embodiments, a combination of these techniques can be used, where the two (or more) portions have different thicknesses and receive different voltages. The control voltage can also be used to cause the two lights to have a phase difference different from π, such as π / 2, 3π / 2, or a phase difference between π / 2 and 3π / 2, or within other limits.

[0054] Figures 8A to 8B An example embodiment of a phase mask deploying an acousto-optic modulator (AOM) according to some aspects of the present disclosure is illustrated. The AOM 800 may include a transparent portion 801 that receives an incident electromagnetic wave, wherein Figure 8A The two regions 206-1 and 206-2 are schematically depicted in FIG. The AOM 800 may be subjected to a Figure 8A The induced acoustic wave 802 is generated by a frequency modulated acoustic wave 802 (not shown in FIG. 1 ), such as a piezoelectric transducer capable of inducing an acoustic wave with controlled amplitude, phase, and frequency f within the AOM 800. In some embodiments, the induced acoustic wave 802 can be a propagating wave (e.g., the other end of the AOM 800 is coupled to a second transducer that induces a matching oscillation of the AOM material to prevent the formation of a reflected acoustic wave). The propagating light waves can experience modulated Bragg reflection from the elastic deformation of the AOM material. Bragg reflection occurs when the wave vector is conserved. So that the diffraction wave vector From the incident wave vector Changing the wave vector of the acoustic wave q (or an integer number of wave vectors ); n represents the refractive index of the AOM material. The scattering of light waves occurs at an angle θ determined by the Bragg condition,

[0055]

[0056] Where λ is the wavelength of light in a vacuum (k = 2π / λ), f is the frequency of sound, and s is the speed of the sound wave 802 in the AOM material.

[0057] The acoustic wave propagating within the AOM 800 may be amplitude A(t) and / or phase modulated φ(t). The modulation of the acoustic wave may cause the AOM 800 to operate as a generator of a traveling lens, wherein the output beams 806-1 and 806-2 are focused on a particular point 803 of the sample (for the sake of simplicity, no intermediate optical elements are shown), and the point 803 moves across the surface of the sample in response to the propagation of the acoustic wave 802 across the AOM 800. In one example, non-limiting embodiment, the frequency of the acoustic wave 802 may have a linear frequency modulation, for example, from a low value f1 to a high value f2 (and then reset back to frequency f1), as shown. Figure 8B As shown in the figure,

[0058]

[0059] Where T c is the frequency modulation period. If the frequency modulation period matches the propagation time of the sound wave over the length L of the AOM 800, L≈s·T c , then each frequency modulation cycle causes a motion cycle of the illumination point 803. For example, for an AOM 800 with L = 2 mm and s = 5 × 10 3 The speed of sound is m / s, and the frequency modulation period can be T c =2mm÷(5×10 3 m / s)=4×10 -7 s. Figures 8C to 8E This movement is schematically illustrated, where Figure 8C indicates the diffraction of light from an acoustic wave with the initial frequency, Figure 8D depicts the diffraction of light at the middle period of the frequency modulation, and Figure 8E Figure 2 shows the diffraction of light near the end of the frequency modulation period. Figure 8A As further illustrated in Figure 8E In the same picture at the end of the FM cycle, the diffraction angle (for linear FM) is the vertical coordinate z

[0060] A linear function of (0≤z≤L),

[0061]

[0062] Such that all output beams 806-1, 806-2, 806-3, etc. intersect at the same point 803 located at a horizontal distance d and a vertical distance z0 from the top of the AOM 800:

[0063]

[0064] Phase and amplitude modulation of the acoustic wave can be used to configure the output beam to have a phase difference of π (or some other desired phase difference). For example, during the first half of the FM duration, t∈(0, T c / 2), the amplitude of the acoustic wave may have a first value and be equal to φ(t)=2π(f1t+(f2-f1)t 2 / 2T c ) phase. During the second half of the FM duration, t∈(T c / 2, T c ), the amplitude of the acoustic wave may have a second sign opposite to the first sign, and the phase π is added to the phase, φ(t) → φ(t) + π, flipping the sign of the converter: signal(t) = amplitude(t)·sinφ(t). This also flips the phase of the beam propagating within the interval bounded by beams 806-2 and 806-3 compared to the beam propagating within the interval bounded by beams 806-1 and 806-3.

[0065] Various other implementations of phase masks are within the scope of the present disclosure. In some embodiments, the phase mask can be implemented using a spatial light modulator (SLM) (e.g., a liquid crystal based SLM) that changes the refractive index of the SLM, causing the light to undergo a (e.g., voltage controlled) phase change. Different segments of the phase mask can experience different voltages, resulting in the desired phase difference being imparted to different parts of the light in the pupil plane. In some embodiments, the phase mask can be implemented using a deformable mirror (e.g., a microelectromechanical (MEM) deformable mirror or a piezoelectric deformable mirror). A deformable mirror changes the optical wavefront in reflection by deforming the shape of the surface. For example, a MEM deformable mirror uses multiple electrostatic actuators to change the shape of the surface of a membrane coated with a reflective film. When placed in a reflective pupil plane, the surface deformation results in a phase difference between rays reflected at different angles. The phase difference can be designed to have the form of a phase mask, for example, as combined with Figures 4A to 4G and 5A to 5D As shown in the picture.

[0066] Figures 9A to 9B is a flow chart of example methods 900 and 901 for deploying phase masks for improving optical inspection signals according to at least one embodiment. Method 900 may deploy a phase mask for configuring source light used in optical inspection. Method 901 may deploy a phase mask for configuring light collected (e.g., reflected, scattered) during optical inspection. Operations in boxes indicated with dashed lines may be optional during execution of the corresponding method. For example, during execution of method 900, configuring the collected light using a phase mask (box 950) may be optional, while during execution of method 901, configuring the source light using a phase mask (box 920) may be optional. In some embodiments, method 900 may be combined with method 901, such as using both source light and scattered light configured with corresponding phase masks. Figure 18 or a combination thereof to perform method 900 and / or method 901. In some embodiments, method 900 and / or method 901 may be performed in conjunction with the operation of a semiconductor manufacturing system. Figure 1 The computing device 118 and / or the electronic module 130 may execute some or all of the blocks of method 900 and / or method 901 using instructions from the computing device 118 and / or the electronic module 130. The computing device 118 and / or the electronic module 130 may include one or more processing devices, such as a central processing unit (CPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), a network processor, and the like. The processing device(s) may be communicatively coupled to one or more memory devices, such as read-only memory (ROM), flash memory, static memory, dynamic random access memory (DRAM), and the like. In some embodiments, the computing device 118 and / or the electronic module 130 may be connected to a larger network of computing devices. In some embodiments, method 900 and / or method 901 may be performed while the sample is still positioned within the processing chamber. In some embodiments, method 900 and / or method 901 may be performed once the sample has been removed from the processing chamber. The testing process may occur at low temperatures, or at temperatures below or significantly below room temperature. Alternatively, the testing process may occur at room temperature, above room temperature, or significantly above room temperature. In some embodiments, during the inspection process, the sample may experience pressures less than atmospheric pressure, including low vacuum or high vacuum conditions.

[0067] In some embodiments, the inspection system performing method 900 and / or method 901 may be a PME optical inspection tool 114, which may include an illumination subsystem, a collection subsystem, and / or a detection subsystem. The PME optical inspection tool performing method 900 and / or method 901 may further include a polarization filter stage, a directional filter stage, and the like.

[0068] The directional filter stage of a PME optical inspection tool performing methods 900 and / or 901 may include one or more directional filters configured to pass light collected from a specific range of reflection (or scattering) angles from the sample. The directional filters may be implemented using a light-absorbing plate with appropriate apertures cut into the plate to allow light to pass. Some apertures may allow perpendicularly reflected light to pass, while other apertures may allow scattered light to pass. In some embodiments, the directional filters may be positioned at the Fourier plane of the objective lens of the collection subsystem.

[0069] In some embodiments, the detection subsystem may include relay optics having one or more optical elements (e.g., lenses, mirrors, waveguides, waveguide arrays, etc.) for delivering (e.g., focusing) reflected and scattered light onto one or more photodetectors. The photodetectors may use complementary metal oxide semiconductor (CMOS) image sensors, charge coupled devices (CCDs), hybrid CMOS-CCD image sensors, photomultiplier tubes (e.g., photocathode-based pixel arrays), photodiodes, phototransistors, or any other suitable photon detectors. Each photodetector of the detection subsystem may image a separate point (pixel) of the sample illuminated by the illumination subsystem.

[0070] Light intensity (e.g., reflectivity) data collected by the light detectors can be provided to the sample quality control module 124, which determines the size, type, concentration, and / or location of various defects and flaws in the sample 112. The sample quality control module 124 can communicate with the optical inspection control module 120, which can change the settings of the illumination subsystem, collection subsystem, detection subsystem, polarization filter stage, directional filter stage, and / or other systems and stages. For example, the sample can be initially inspected at a certain set resolution. When the sample quality control module 124 identifies the presence of a defect, for example, based on light reflectivity data collected by the detection subsystem, the sample quality control module 124 can output instructions to the optical inspection control module 120 to change the resolution of the imaging by zooming the illumination subsystem and / or collection subsystem to a specific area on the sample where the defect is located. More specifically, the optical inspection control module 120 can change the focal length of the collection subsystem's objective lens, the distance from the objective lens to the sample, and the like. The optical inspection control module 120 can additionally change the numerical aperture of the directional filter of the directional filter stage to facilitate changes in imaging resolution. The stage control module 122 can determine the distance and direction of repositioning the sample so that previously uninspected points are exposed to the light pulses. The stage control module 122 can further ensure coordination between the movement of the movable stage 110 and the collection of inspection data.

[0071] In some embodiments, a PME optical inspection tool may be deployed with a default phase mask having a fixed orientation, for example, relative to the scanning direction of the sample (e.g., a phase mask with a given number of 0-phase and π-phase segments, e.g., Figure 3CIn one embodiment, the PME optical inspection tool may be programmed to use a two-segment phase mask 210 to detect the presence of a defect at a particular location on the sample using the default phase mask. In such an embodiment, the electronic module 130 may cause the PME optical inspection tool to collect additional optical signals using one or more of the following: a different orientation of the default phase mask (e.g., by rotating the default mask 90 degrees and / or other angles), another phase mask used in place of the default phase mask (e.g., a four-segment phase mask), a different polarizer (or polarizer orientation), etc., or some combination thereof. In some embodiments, the default phase mask may be of a type and orientation that facilitates detection of the types of defects / blemishes most likely to be encountered (e.g., defects having a dipole resonance perpendicular to the surface polarization of the sample). In some embodiments, the PME optical inspection tool may be programmed to use multiple phase masks (and / or phase mask / polarizer combinations) to collect optical signals for each location on the sample.

[0072] At block 910, method 900 and / or method 901 may include generating source light (eg, Figure 2 In some embodiments, the source light may be generated using a gas laser, a semiconductor laser, a laser diode, an excimer laser (e.g., a laser with an excimer gain medium), and / or other light source(s). The source light may include continuous light, pulsed light, or some combination thereof.

[0073] At block 920, method 900 and / or method 901 may include directing source light to a first phase mask (e.g., phase mask 210). In some embodiments, the first phase mask (and other phase masks, if deployed) may include: a first region (e.g., Figure 3C) of the phase mask 210, wherein the first region is configured to interact with the first portion of the source light; and a second region (e.g., the "π" segment of the phase mask 210) is configured to interact with the second portion of the source light. The first (or second, etc.) phase mask can cause the second portion to phase shift relative to the first portion by half (or approximately half) the wavelength λ of the source light (π phase shift). In some implementations, the second region of the phase mask is configured to phase shift the second portion of the light relative to the first portion by a phase shift between 0.45λ and 0.55λ. In some implementations, the second region of the phase mask is configured to phase shift the second portion of the light relative to the first portion by a phase shift between λ / 4 and 3λ / 4. In some embodiments, the first region can include air or a first material (e.g., glass), and the second region can include a second material different from the first material. In some embodiments, the second region can include the first material having a different thickness than the thickness of the first region. In some embodiments, the second material can be a coating disposed on the first material (or a different third material). In some embodiments, the first region and / or the second region can include one or more birefringent materials, such as one or more half-wave plates and / or quarter-wave plates. In some embodiments, the phase mask can be combined with the polarizer into a single device. For example, the first material can be the polarizer material, and the second material can be a phase-reversing coating deposited on a portion of the polarizer material.

[0074] In some embodiments, a first region and a similar second region may include multiple spatially separated portions (e.g., 6A to 6D The first region of the phase mask 240 illustrated in includes two "0" segments positioned diagonally, and further includes two "π" segments similarly positioned relative to each other).

[0075] In some embodiments, the first (second, etc.) phase mask can be a transmissive mask (the transmissive mask modifies the phase of light transmitted through the mask). In some embodiments, the first (second, etc.) phase mask can be a reflective mask (the reflective mask modifies the phase of light reflected from the mask).

[0076] In some embodiments, the first phase mask may include an acoustic wave supporting a temporally modulated frequency (e.g., Figure 8B As shown) of an acousto-optic modulator (e.g., Figure 8A 800 in FIG. 1 ). The AOM may be configured to diffract a first portion of the source light (e.g., first incident ray 206-1) in a first direction (e.g., first diffracted ray 806-1) and a second portion of the source light (e.g., second incident ray 206-1) in a second direction (e.g., second diffracted ray 806-2).

[0077] In some embodiments, the first (second, third, etc.) phase mask may be mechanically engaged by an actuator configured to: reposition the first (second, third, etc.) phase mask, e.g., rotate or flip the phase mask; or replace the phase mask with a different phase mask (e.g., with Figure 3C The phase mask 210 is replaced 6A to 6D phase mask 240, or vice versa); removing the first (second, third, etc.) phase mask from the optical path of the corresponding (e.g., incident, reflected, or scattered) beam, etc.

[0078] In some embodiments, the first (second, etc.) phase mask may be positioned at the pupil plane of the illumination subsystem or the pupil plane of the collection (eg, brightfield reflectance and / or darkfield scattering) subsystem.

[0079] At block 922, method 900 and / or method 901 may include directing the source light to a first polarizer. In some embodiments, the first polarizer (and / or other polarizers, if deployed) may be positioned to polarize the source light before it interacts with the phase mask. In some embodiments, the first (second, etc.) polarizer may be positioned to polarize the source light after it interacts with the phase mask.

[0080] At block 930, method 900 and / or method 901 may include illuminating the sample using source light. In some embodiments, the sample may be illuminated using s-polarized source light, p-polarized source light, right-handed circularly (or elliptically) polarized source light, left-handed circularly (or elliptically) polarized source light, partially polarized source light, or any combination (e.g., superposition) thereof.

[0081] At block 940, method 900 and / or method 901 may include collecting light (e.g., a portion of the light) generated when the source light interacts with the sample. The generated portion of the light may be collected by a collection subsystem. Generated light should be understood to include specularly reflected light and / or diffusely reflected (scattered) light. The collection subsystem may include an objective (having one or more lenses and / or one or more curved mirrors), one or more polarizing elements, one or more directional filters, a beam splitter, elements of relay optics, and the like. Some of the components of the collection subsystem(s), such as the objective, beam splitter, polarizer, and the like, may be shared with the illumination subsystem(s). The collection subsystem may be configured in one of a plurality of configurations. In some embodiments, in each of the plurality of configurations, the collection subsystem may be characterized by a different size of the region of the sample from which a portion of the light is collected. In some embodiments, the collected light may be varied by moving the side aperture of the directional filter to a different position relative to the optical axis of the collection subsystem (or replacing the directional filter with another filter having a differently positioned side aperture).

[0082] At block 950, method 900 and / or method 901 may include directing the collected light to a second (third, etc.) phase mask. For example, reflected (bright field) light may be directed to phase mask 230 (at Figure 2 ), and the scattered (dark field) light may be directed to the phase mask 240. At block 952, method 900 and / or method 901 may include directing the collected light to a second polarizer. The operations of blocks 950 and 952 performed in conjunction with the collection of reflected / scattered light may be similar to the operations of blocks 920 and 922 performed in conjunction with illumination of the sample.

[0083] At block 960, method 900 and / or method 901 may include directing the collected light to a light detection sensor to generate one or more signals. The one or more signals (e.g., electrical signals) may represent a state (e.g., quality) of the sample. In some embodiments, the light detection sensor may include a CMOS image sensor. In some embodiments, the light detector array may include a CCD camera. In some embodiments, the light detector array may include a photomultiplier tube array.

[0084] At block 970, method 900 and / or method 901 may include repositioning the sample relative to the source light using a movable stage. In some embodiments, repositioning the sample may include imparting a combination of translational and rotational motion to the sample. As indicated by the dashed arrows in FIG. 9 , after repositioning the sample, the operations of blocks 910 through 960 may be repeated for a new area of the sample exposed to the source light.

[0085] At block 980, method 900 and / or method 901 may include determining one or more characteristics of the sample using one or more generated signals. For example, a processing device may process the generated signals and determine the location, type, amount, etc. of various defects and flaws present on the surface of the sample or in the bulk of the sample. The processing device may then determine whether the detected defects and / or flaws place the sample outside of specifications for the technical process being performed or determine whether the sample meets specifications.

[0086] In some embodiments, method 900 and / or method 901 may include configuring one or more processing operations of the manufacturing system in response to the detected defects and / or flaws. For example, configuring the processing operation(s) may include performing some remedial processing of the sample, such as performing additional polishing, etching, and / or deposition on the sample. In some cases, adjustments may be applied to subsequent samples processed by the manufacturing system. For example, such adjustments may include modifying the chemical composition, pressure, temperature, etc., of the environment of some portion of the manufacturing system (such as a processing chamber, a transfer chamber, a loading chamber, etc.).

[0087] It should be understood that the above description is intended to be illustrative, not restrictive. After reading and understanding the above description, many other embodiment examples will be apparent to those skilled in the art. Although the present disclosure describes specific examples, the systems and methods of the present disclosure are not limited to the examples described herein and may be modified to practice within the scope of the appended claims. Therefore, the description and drawings should be regarded as illustrative, not restrictive. Therefore, the scope of the present disclosure should be determined with reference to the appended claims and the full scope of equivalents to which these claims are entitled.

[0088] Embodiments of the above methods, hardware, software, firmware, or code may be implemented via instructions or code stored on a machine-accessible, machine-readable, computer-accessible, or computer-readable medium that is executable by a processing element. "Memory" includes any mechanism that provides (i.e., stores and / or transmits) information in a form readable by a machine (such as a computer or electronic system). For example, "memory" includes: random access memory (RAM), such as static RAM (SRAM) or dynamic RAM (DRAM); ROM; magnetic or optical storage media; flash memory storage devices; electrical storage devices; optical storage devices; acoustic storage devices; and any type of tangible machine-readable medium suitable for storing or transmitting electronic instructions or information in a form readable by a machine (e.g., a computer).

[0089] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0090] In the foregoing description, a detailed description has been given with reference to specific exemplary embodiments. However, it will be apparent that various modifications and changes may be made to the embodiments without departing from the broad spirit and scope of the present disclosure as set forth in the appended claims. Therefore, the description and drawings should be regarded as illustrative rather than restrictive. Furthermore, the foregoing use of the words "embodiment," "example," and / or other exemplary language does not necessarily refer to the same embodiment or the same example, but may refer to different and distinct embodiments and potentially to the same embodiment.

[0091] As used herein, the words "example" or "exemplary" serve as examples, instances, or illustrations. Any aspect or design described herein as an "example" or "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, the use of the words "example" or "exemplary" is intended to present concepts in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or clear from the context, "X includes A or B" is intended to mean any natural inclusive permutation. That is, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied in any of the foregoing cases. Furthermore, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more," unless otherwise specified or clear from the context to indicate the singular form. Furthermore, unless so described, the use of the terms "embodiment" or "one embodiment" or "an embodiment" or "an embodiment" is not intended to refer to the same embodiment or embodiments. Furthermore, the terms “first,” “second,” “third,” “fourth,” etc. as used herein are intended as labels for distinguishing different elements and may not necessarily have ordinal meanings according to their numerical designations.

Claims

1. A sample testing system comprising: an illumination subsystem for generating light incident on the sample; a collection subsystem comprising one or more optical elements for collecting light generated when incident light interacts with the sample; as well as a light detection subsystem configured to detect the collected light and generate one or more signals representative of one or more characteristics of the sample; and wherein the sample inspection system comprises a first phase mask positioned to interact with at least one of the incident light or the collected light, and wherein the first phase mask comprises at least: a first region for engaging a first portion of light that interacts with the first phase mask, and A second region is provided for (i) engaging a second portion of the light that interacts with the first phase mask and (ii) phase shifting the second portion relative to the first portion.

2. The sample inspection system of claim 1 , wherein the second region of the first phase mask is configured to phase shift the second portion of the light relative to the first portion by a phase shift between λ / 4 and 3λ / 4, where λ is the wavelength of the light incident on the first phase mask.

3. The sample testing system of claim 1, wherein the second region of the first phase mask is configured to phase shift the second portion of the light relative to the first portion by half a wavelength of the light incident on the first phase mask.

4. The sample inspection system of claim 1, wherein the first phase mask is positioned within an optical path of the incident light, and wherein the sample inspection system further comprises a second phase mask positioned within an optical path of the collected light.

5. The sample inspection system of claim 4, wherein the collected light includes light reflected from the sample and light scattered from the sample, wherein the first phase mask is positioned within the optical path of the reflected light and the second phase mask is positioned within the optical path of the scattered light.

6. The sample testing system of claim 1 , wherein the first region comprises air or a first material of a first thickness, and the second region comprises at least one of: Second material, or a second thickness of the first material.

7. The sample testing system of claim 1, wherein the first region comprises a first material and the second region comprises the first material and a second material, wherein the first material comprises a polarizing material.

8. The sample testing system of claim 1, wherein at least one of the first region or the second region comprises one or more birefringent materials.

9. The sample inspection system of claim 1 , wherein the first phase mask comprises at least one of: an acousto-optic modulator that supports an acoustic wave that causes the first portion of light and the second portion of light to form the incident light that dynamically scans the sample, One or more segments made of liquid crystal material, or Deformable mirror.

10. A sample inspection system as described in claim 1, wherein the first phase mask includes an electro-optical modulator; and wherein at least one of (i) a first thickness of the first region of the first phase mask or (ii) a first voltage applied to the first region of the first phase mask is different from a corresponding one of (i) a second thickness of the second region of the first phase mask or (ii) a second voltage applied to the second region of the first phase mask.

11. The sample testing system of claim 1 , further comprising a polarization optical element, wherein the polarization optical element is configured to: polarizing the light interacting with the first phase mask prior to interacting with the first phase mask, or After interacting with the first phase mask, at least one of the first portion of the light or the second portion of the light is polarized.

12. The sample testing system of claim 11, wherein the polarization optical element comprises at least one of: Linear polarizer, Segmented polarizers, Half-wave plate, a quarter-wave plate, or S-wave plate converter.

13. The sample inspection system of claim 1, wherein the first phase mask is positioned at a pupil plane of the illumination subsystem or a pupil plane of the collection subsystem.

14. The sample inspection system of claim 1, wherein the first phase mask attenuates at least a portion of: (i) the first portion of the light or (ii) the second portion of the light.

15. The sample testing system of claim 1, further comprising: An actuator configured to perform at least one of the following: repositioning the first phase mask, replacing the first phase mask with a second phase mask, or The first phase mask is removed from an optical path of the at least one of the incident light or the collected light.

16. The sample inspection system of claim 1, wherein each of the first region and the second region of the first phase mask comprises a plurality of spatially separated portions.

17. The sample testing system of claim 1, further comprising: A processing device is configured to determine the one or more characteristics of the sample using the one or more signals.

18. The sample testing system of claim 1, wherein the second region of the first phase mask is used to rotate the polarization of the second portion of the light relative to the first portion of the light.

19. A method for performing an optical inspection of a sample, the method comprising: Generate source light; directing the source light to a first phase mask, wherein the first phase mask comprises: a first region for interacting with a first portion of the source light, and a second region for (i) interacting with a second portion of the source light and (ii) phase shifting the second portion of the source light relative to the first portion of the source light; illuminating the sample using the source light; collecting light generated when the source light interacts with the sample; directing the collected light to a light detecting sensor to generate one or more of the signals; and One or more characteristics of the sample are determined using the one or more signals.

20. The method of claim 19, further comprising: The collected light is directed to a second phase mask.

21. A method for performing an optical inspection of a sample, comprising: Generate source light; illuminating the sample using the source light; collecting light generated when the source light interacts with the sample; directing at least a portion of the collected light to a first phase mask, wherein the first phase mask comprises: a first region for interacting with a first portion of the collected light, and a second region for (i) interacting with a second portion of the collected light and (ii) phase shifting the second portion of the collected light relative to the first portion of the collected light; directing the collected light to a light detecting sensor to generate one or more signals; and One or more characteristics of the sample are determined using the one or more signals.

22. The method of claim 21 , wherein the collected light comprises a first portion reflected from the sample and a second portion scattered from the sample, wherein the first phase mask is positioned within an optical path of the first portion of the collected light, the method further comprising: The second portion of the collected light is directed to a second phase mask.

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