Time-division multiplexing wafer z tilt-height sensor for charged particle beam focusing

Abstract

A method of measuring a tilt characteristic and a height characteristic in a charged particle system is disclosed. Time-division multiplexing may be employed to temporally separate measurements of a tilt characteristic and a height characteristic of a sample using one module. A first light beam may be reflected off a sample to measure a tilt characteristic and a second light beam may be reflected off a sample to measure a height characteristic. The first light beam may be triggered by an electrical signal associated with a falling edge of a clock signal and the second light beam may be triggered by an electrical signal associated with a rising edge of a clock signal.

Description

TIME-DIVISION MULTIPLEXING WAFER Z TILT-HEIGHT SENSOR FOR CHARGED PARTICLE BEAM FOCUSINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 625,774 which was filed on January 26, 2024 and which is incorporated herein in its entirety by reference.FIELD

[0002] The description herein relates to the field of charged particle systems, and more particularly to measuring a tilt characteristic and a height characteristic of a sample in a charged particle system.BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. The lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). An IC chip in a smart phone can be as small as a person’s thumbnail and may include over 2 billion transistors. Making an IC is a complex and time-consuming process, with circuit components in different layers and including hundreds of individual steps. Errors in even one step may potentially result in problems with the final IC and may cause device failure. Therefore, in manufacturing processes of ICs, unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as a scanning electron microscope (SEM) can be employed. As the physical sizes of IC components continue to shrink, accuracy and yield in IC inspection become increasingly important. High process yield and high wafer throughput can be impacted by the presence of defects, especially if physical testing is required for reviewing the defects. Therefore, accurate inspection and metrology to ensure defect-free ICs are properly manufactured is desired.SUMMARY

[0004] The embodiments provided herein disclose a method of monitoring and evaluating a wafer fabrication process variation using a characteristic of extracted two-dimensional measurement data of a fabricated feature on a wafer.

[0005] Some embodiments of the present disclosure provide a charged particle beam system. The charged particle beam system comprises a charged particle beam tool having circuitry configured to emit and focus a charged particle beam at a first location on a surface of a sample, an emitter module having circuitry configured to emit a first light beam and a second light beam to reflect off a second location on the surface of the sample, wherein the emitter module emits the first light beam after receiving a first signal and emits the second light beam after receiving a second signal, a detectormodule having circuitry configured to collect the first light beam to measure a first characteristic of the sample and to collect the second light beam to measure a second characteristic of the sample, and a controller communicatively connected to the emitter module and the detector module, wherein the controller is configured to determine the first signal and the second signal from an input signal and supply the first signal and the second signal to the emitter module.

[0006] In some embodiments, a non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for measuring a characteristic of a sample in a charged particle beam apparatus. The operations comprise emitting a light beam from a light source for delivering the light beam to a surface of the sample using a first lens, wherein the light beam is reflected off the surface of the sample, focusing the light beam reflected off the surface of the sample onto a surface of a detector using a second lens to generate a first measurement, and determining the characteristic of the sample using the first measurement.

[0007] Other advantages of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present disclosure.BRIEF DESCRIPTION OF FIGURES

[0008] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, taken in conjunction with the accompanying drawings.

[0009] FIG. 1 is a schematic diagram illustrating an example lithographic projection assembly to fabricate an IC, consistent with embodiments of the present disclosure.

[0010] FIG. 2 is a schematic diagram illustrating an example electron beam inspection (EBI) system, consistent with embodiments of the present disclosure.

[0011] FIG. 3 is a schematic diagram of an example multi-beam tool, consistent with embodiments of the present disclosure.

[0012] FIGs. 4A, 4B, and 4C are example illustrations of effects of uncorrected tilt characteristics in conventional charged particle beam systems.

[0013] FIG. 5A is an example charged particle beam system consistent with embodiments of the present disclosure.

[0014] FIG. 5B is an example charged particle beam system consistent with embodiments of the present disclosure.

[0015] FIG. 5C is an example charged particle beam system consistent with embodiments of the present disclosure.

[0016] FIG. 5D and 5E are illustrations of an example first lens and second lens configured to deliver a light beam to a detector, consistent with embodiments of the present disclosure.

[0017] FIG. 6 is an example illustration of a detector that can be used to monitor a light beam reflected from a sample, consistent with embodiments of the present disclosure.

[0018] FIGs. 7A, 7B, and 7C are illustrations of an example input signal for a controller to calculate a first signal and a second signal, consistent with embodiments of the present disclosure.

[0019] FIGs. 8A and 8B are illustrations of example charged particle beam systems consistent with embodiments of the present disclosure.

[0020] FIG. 9A is an illustration of measuring a characteristic of a sample using a light beam, consistent with embodiments of the present disclosure.

[0021] FIGs. 9B, 9C, 9D, 9E, 9F, 9G, 9H, 91, and 9J illustrate measuring a first characteristic and a second characteristic of a sample, consistent with embodiments of the present disclosure.

[0022] FIG. 10 is a flowchart illustrating an exemplary process, consistent with embodiments of the present disclosure.

[0023] FIG. 11 is a flowchart illustrating an exemplary process, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0024] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the invention. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the invention as recited in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the disclosure is not so limited. Other types of charged particle beams may be similarly applied. Furthermore, other imaging systems may be used, such as optical imaging, photo detection, x-ray detection, etc.

[0025] The enhanced computing power of electronic devices, while reducing the physical size of the devices, can be accomplished by significantly increasing the packing density of circuit components such as transistors, capacitors, diodes, etc. on an IC chip. For example, an IC chip of a smart phone, which is the size of a thumbnail, may include over 2 billion transistors, the size of each transistor being less than l / 1000th of a human hair. Thus, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process, with hundreds of individual steps. Errors in even one step have the potential to dramatically affect the functioning of the final product. Even one “killer defect” can cause device failure. The goal of the manufacturing process is to improve the overall yield of the process. For example, for a 50-step process to get to a 75% yield, each individual step must have a yield greater than 99.4%, and if the individual step yield is 95%, the overall process yield drops to 7%.

[0026] While high process yield is desirable in an IC chip manufacturing facility, maintaining a high wafer throughput, defined as the number of wafers processed per hour, is also essential. High process yields and high wafer throughput can be impacted by the presence of defects, especially if operator intervention is required for reviewing the defects. Moreover, the number of transistors fabricated onto an IC chip is forecasted to grow from billions up to one trillion by 2030. Thus, high throughput detection and identification of micro and nano-sized defects by inspection tools (such as a charged particle beam inspection tool) is essential for maintaining high yields and low cost. Inspection of a wafer using an electron beam inspection tool may generate images of the wafer to measure IC structure dimensions. The measured dimensions may be compared to a reference structure absent any defects to determine the presence of defects in the imaged structure. However, inspection of ICs for defect detection is often a time-consuming process. It may be desirable to prevent defects from occurring during the fabrication stages instead of further refining IC inspection methods. Therefore, it is desired to monitor and evaluate lithographic fabrication conditions that may induce defects in a fabricated IC structure.

[0027] ICs may be manufactured using lithography, which is a fabrication process involving creating complex circuit patterns drawn on a mask deposited onto a substrate. Lithography may be performed by a lithographic apparatus, which is a machine that applies a source of radiation (e.g., light or X-ray) onto a target portion of the substrate to form a desired pattern. The target portion of the substrate may be covered with a pattern device (e.g., mask) that may be either eliminated or developed after exposure to the radiation source. This process of transferring the desired pattern to the substrate is called a patterning process. The patterning process may include a patterning step to transfer a pattern from a pattern device (e.g., a mask) to the substrate. There can also be one or more related pattern processing steps, such as mask development by a development apparatus, baking of the substrate using a bake tool, etching the pattern onto the substrate using an etch apparatus, or other chemical and physical processing steps involved in fabricating a pattern onto the substrate. Variations in experimental parameters (e.g., stochastic variations, errors, or noise due to an inspection tool or pattern processing tool) can potentially limit lithography implementation for high volume manufacturing (HVM), or process yield, of ICs and introduce defects into IC structures.

[0028] In the manufacture of ICs using a lithographic apparatus, typically many lithographic patterning steps are performed, thereby forming functional features in successive layers on the substrate. A critical aspect of performance of the lithographic apparatus is therefore the ability to place the applied pattern correctly and accurately in relation to features laid down in previous layers. For this purpose, the substrate is provided with one or more sets of alignment marks. Each mark is a structure whose position can be measured later using, for example, an electron beam inspection tool. Defects may occur in which an applied pattern structure or pattern layer is incorrectly placed in relation to a reference mark, or when the fabrication conditions are suboptimal. A reference mark or layout define the desired structure, structure dimensions, and the distance between IC structures (suchas gates, capacitors, etc.) or interconnect lines. This may ensure that the IC devices or lines do not interact with one another in an undesirable way. The structure limitations provided by the reference layouts are typically referred to as critical dimensions. A critical dimension of a circuit can be defined as the smallest width of a line or hole or the smallest space between two lines or two holes. Thus, the critical dimension determines the overall size and packing density of the designed IC. A goal in IC fabrication is to faithfully reproduce the original IC design on the substrate. If an error occurs during fabrication where the created IC design pattern does not match the reference design, this may result in a defect in the IC structure and render the IC inoperable.

[0029] As mentioned above, high throughput of IC fabrication with low amounts of structural defects is desired. Additionally, the number of transistors fabricated onto a wafer is projected to reach one trillion by 2030. As the fabrication process for such transistors becomes more complex and includes a larger number of steps, this may increase fabrication process variation and introduce more defects. Additionally, scaling up production of semiconductors may introduce stochastic variation in the lithographic fabrication process. Stochasticity and process variation may introduce structural defects in a manufactured wafer such as dopant concentration fluctuation, pattern line edge roughness, edge placement error, and variation between structures intended to be identical, which may ultimately render the wafer inoperable. Therefore, the ability to accurately inspect manufactured IC structures and collect metrology measurements to compared to a desired design and fabrication conditions in lithography is desired. Current systems and methods rely on a height sensor to monitor in real-time the height of a sample to be inspected and maintain focus of a charged particle beam on the sample. A correct measurement of the height is important so the charged particle beam can be correctly focused onto the surface of the sample. However, the tilt of a sample, or local variation of sample height, cannot be monitored using a conventional height sensor because conventional height sensors only measure the relative distance between a sample and a top of a charged particle beam chamber. Furthermore, uncorrected tilt of a sample may block the path of the charged particle beam and degrade image quality and hinder efficient sample inspection and metrology. Additionally, variations in sample temperature during sample stage movement may induce sample deformation that can further exacerbate sample tilting. Conventional systems currently rely on adjusting the trajectory of the charged particle beam to compensate for sample tilt, but this may induce incontrollable aberrations or distortions to image quality and further decrease inspection and metrology throughput. Thus, using current methods and charged particle beam systems to compensate for sample tilt may result in inaccurate measurements, undesired degradation of sample and image quality, and decreased wafer yields during high volume manufacturing (HVM).

[0030] Embodiments of the present disclosure provide a method to monitor and measure a tilt characteristic of a sample using a light beam. Some embodiments of the present disclosure may provide a method of measuring a tilt characteristic separately from a height characteristic using different light beams. The light beams may be visible light, and may each have different wavelengths.The present disclosure also provides a charged particle beam system configuration capable of timedivision multiplexing to efficiently and accurately measure a local tilt characteristic and height characteristic of a sample. In some embodiments, the present disclosure provides a charged particle beam system to integrate a tilt sensor and a height sensor into one module. Real-time and point-of- interest measurements of both local sample tilt and sample height may be achieved. Moreover, some embodiments of the present disclosure may increase throughput of IC manufacturing and confidence in inspection and metrology.

[0031] Relative dimensions of components in drawings may be exaggerated for clarity. Within the following description of drawings the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments are described. As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a database can include A or B, then, unless specifically stated otherwise or infeasible, the database can include A, or B, or A and B. As a second example, if it is stated that a database can include A, B, or C, then, unless specifically stated otherwise or infeasible, the database can include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0032] Reference is now made to FIG. 1, which is a schematic diagram illustrating an exemplary lithographic projection apparatus 100. Lithographic projection apparatus 100 may include an emission source 101, which may be a charged-particle emission source, deep-ultraviolet excimer laser source or other type of source including an extreme ultraviolet (EUV) source and emits a beam 108.Illumination optics which may include illumination optics components 102 and 103 that shape radiation from the radiation source 101; a patterning device 104; and transmission optics 105 that project an image of the patterning device pattern onto a substrate 106. An adjustable filter or aperture 107 at the pupil plane of the projection optics may restrict the range of beam angles that impinge on substrate 106, where the largest possible angle defines the numerical aperture of the projection optics NA=sin(0maxon substrate 106 where beam 108 impacts is called a target portion 109, in which the beam impacts the top layer or mask (not shown).

[0033] Illumination optics components 102 and 103 may direct and shape beam 108 via patterning device 104 onto substrate 106 and may include any optical component that may alter the wavefront of beam 108. A resist layer on substrate 106 may be exposed and a radiation intensity distribution at substrate 106 (i.e., an aerial image) may be transferred to the resist layer. Optical properties of the lithographic projection apparatus (e.g., properties of the source, the patterning device, and the projection optics) dictate this process. The resist layer may be removed and the applied pattern from beam 108 may then be applied to the substrate as discussed above.

[0034] Although reference may be made in the present disclosure to ICs, it is appreciated that the present disclosure may be applicable to other possible applications or designs. For example, the present disclosure may be applied to integrated optical systems, magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, and other nanoscale structures. It is further appreciated that the terms “reticle”, “wafer”, or “die” may be used interchangeably with the terms “mask”, “substrate” or “sample”, and “target portion”, respectively.

[0035] FIG. 2 illustrates an example electron beam inspection (EBI) system 200 consistent with embodiments of the present disclosure. EBI system 200 may be used for imaging. As shown in FIG. 2, EBI system 200 includes a main chamber 201, a load / lock chamber 202, a beam tool 204, and an equipment front end module (EFEM) 206. Beam tool 204 is located within main chamber 201. EFEM 206 includes a first loading port 206a and a second loading port 206b. EFEM 206 may include additional loading port(s). First loading port 206a and second loading port 206b receive wafer front opening unified pods (FOUPs) that contain wafers (e.g., semiconductor wafers or wafers made of other material(s)) or samples to be inspected (wafers and samples may be used interchangeably). A “lot” is a plurality of wafers that may be loaded for wafer processing as a batch.

[0036] One or more robotic arms (not shown) in EFEM 206 may transport the wafers to load / lock chamber 202. Load / lock chamber 202 is connected to a load / lock vacuum pump system (not shown) which removes gas molecules in load / lock chamber 202 to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) may transport the wafer from load / lock chamber 202 to main chamber 201. Main chamber 201 is connected to a main chamber vacuum pump system (not shown) which removes gas molecules in main chamber 201 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is subject to inspection by beam tool 204. Beam tool 204 may be a single-beam system or a multi-beam system.

[0037] A controller 209 is electronically connected to beam tool 204. Controller 209 may be a computer configured to execute various controls of EBI system 200. While controller 209 is shown in FIG. 2 as being outside of the structure that includes main chamber 201, load / lock chamber 202, and EFEM 206, it is appreciated that controller 209 may be a part of the structure.

[0038] In some embodiments, controller 209 may include one or more processors (not shown). A processor may be a generic or specific electronic device capable of manipulating or processing information. For example, the processor may include any combination of any number of a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, a programmable logic controller, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a Programmable Logic Array (PLA), a Programmable Array Logic (PAL), a Generic Array Logic (GAL), a Complex Programmable Logic Device (CPLD), a Field- Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), a neural processing unit (NPU), and any type of circuit capable of data processing. The processor may also be a virtual processor that includes one or more processors distributed across multiple machines or devices coupled via a network.

[0039] In some embodiments, controller 209 may further include one or more memories (not shown). A memory may be a generic or specific electronic device capable of storing codes and data accessible by the processor (e.g., via a bus). For example, the memory may include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or any type of storage device. The codes and data may include an operating system (OS) and one or more application programs (or “apps”) for specific tasks. The memory may also be a virtual memory that includes one or more memories distributed across multiple machines or devices coupled via a network.

[0040] FIG. 3 illustrates a schematic diagram of an example multi-beam tool 204 (also referred to herein as apparatus 204) and an image processing system 390 that may be configured for use in EBI system 200 (FIG. 2), consistent with embodiments of the present disclosure.

[0041] Beam tool 204 comprises a charged-particle source 302, a gun aperture 304, a condenser lens 306, a primary charged-particle beam 310 emitted from charged-particle source 302, a source conversion unit 312, a plurality of beamlets 314, 316, and 318 of primary charged-particle beam 310, a primary projection optical system 320, a motorized wafer stage 380, a wafer holder 382, multiple secondary charged-particle beams 336, 338, and 340, a secondary optical system 342, and a charged- particle detection device 344. Primary projection optical system 320 can comprise a beam separator 322, a deflection scanning unit 326, and an objective lens 328. Charged-particle detection device 344 can comprise detection sub-regions 346, 348, and 350.

[0042] Charged-particle source 302, gun aperture 304, condenser lens 306, source conversion unit 312, beam separator 322, deflection scanning unit 326, and objective lens 328 can be aligned with a primary optical axis 360 of apparatus 204. Secondary optical system 342 and charged-particle detection device 344 can be aligned with a secondary optical axis 352 of apparatus 204.

[0043] Charged-particle source 302 can emit one or more charged particles, such as electrons, protons, ions, muons, or any other particle carrying electric charges. In some embodiments, charged- particle source 302 may be an electron source. For example, charged-particle source 302 may include a cathode, an extractor, or an anode, wherein primary electrons can be emitted from the cathode and extracted or accelerated to form primary charged-particle beam 310 (in this case, a primary electron beam) with a crossover (virtual or real) 308. For ease of explanation without causing ambiguity, electrons are used as examples in some of the descriptions herein. However, it should be noted that any charged particle may be used in any embodiment of this disclosure, not limited to electrons. Primary charged-particle beam 310 can be visualized as being emitted from crossover 308. Gun aperture 304 can block off peripheral charged particles of primary charged-particle beam 310 to reduce Coulomb effect. The Coulomb effect may cause an increase in size of probe spots.

[0044] Source conversion unit 312 can comprise an array of image-forming elements and an array of beam-limit apertures. The array of image-forming elements can comprise an array of micro-deflectorsor micro-lenses. The array of image-forming elements can form a plurality of parallel images (virtual or real) of crossover 308 with a plurality of beamlets 314, 316, and 318 of primary charged-particle beam 310. The array of beam-limit apertures can limit the plurality of beamlets 314, 316, and 318. While three beamlets 314, 316, and 318 are shown in FIG. 3, embodiments of the present disclosure are not so limited. For example, in some embodiments, the apparatus 204 may be configured to generate a first number of beamlets. In some embodiments, the first number of beamlets may be in a range from 1 to 1000. In some embodiments, the first number of beamlets may be in a range from 200-500. In an exemplary embodiment, the apparatus 204 may generate 400 beamlets.

[0045] Condenser lens 306 can focus primary charged-particle beam 310. The electric currents of beamlets 314, 316, and 318 downstream of source conversion unit 312 can be varied by adjusting the focusing power of condenser lens 306 or by changing the radial sizes of the corresponding beam-limit apertures within the array of beam-limit apertures. Objective lens 328 can focus beamlets 314, 316, and 318 onto a wafer 330 for imaging, and can form a plurality of probe spots 370, 372, and 374 on a surface of wafer 330.

[0046] Beam separator 322 can be a beam separator of Wien filter type generating an electrostatic dipole field and a magnetic dipole field. In some embodiments, if they are applied, the force exerted by the electrostatic dipole field on a charged particle (e.g., an electron) of beamlets 314, 316, and 318 can be substantially equal in magnitude and opposite in a direction to the force exerted on the charged particle by magnetic dipole field. Beamlets 314, 316, and 318 can, therefore, pass straight through beam separator 322 with zero deflection angle. However, the total dispersion of beamlets 314, 316, and 318 generated by beam separator 322 can also be non-zero. Beam separator 322 can separate secondary charged-particle beams 336, 338, and 340 from beamlets 314, 316, and 318 and direct secondary charged-particle beams 336, 338, and 340 towards secondary optical system 342.

[0047] Deflection scanning unit 326 can deflect beamlets 314, 316, and 318 to scan probe spots 370, 372, and 374 over a surface area of wafer 330. In response to the incidence of beamlets 314, 316, and 318 at probe spots 370, 372, and 374, secondary charged-particle beams 336, 338, and 340 may be emitted from wafer 330. Secondary charged-particle beams 336, 338, and 340 may comprise charged particles (e.g., electrons) with a distribution of energies. For example, secondary charged-particle beams 336, 338, and 340 may be secondary electron beams including secondary electrons (energies < 50 eV) and backscattered electrons (energies between 50 eV and landing energies of beamlets 314, 316, and 318). Secondary optical system 342 can focus secondary charged-particle beams 336, 338, and 340 onto detection sub-regions 346, 348, and 350 of charged-particle detection device 344. Detection sub-regions 346, 348, and 350 may be configured to detect corresponding secondary charged-particle beams 336, 338, and 340 and generate corresponding signals (e.g., voltage, current, or the like) used to reconstruct an SCPM image of structures on or underneath the surface area of wafer 330.

[0048] The generated signals may represent intensities of secondary charged-particle beams 336, 338, and 340 and may be provided to image processing system 390 that is in communication with charged-particle detection device 344, primary projection optical system 320, and motorized wafer stage 380. The movement speed of motorized wafer stage 380 may be synchronized and coordinated with the beam deflections controlled by deflection scanning unit 326, such that the movement of the scan probe spots (e.g., scan probe spots 370, 372, and 374) may orderly cover regions of interests on the wafer 330. The parameters of such synchronization and coordination may be adjusted to adapt to different materials of wafer 330. For example, different materials of wafer 330 may have different resistance-capacitance characteristics that may cause different signal sensitivities to the movement of the scan probe spots.

[0049] The intensity of secondary charged-particle beams 336, 338, and 340 may vary according to the external or internal structure of wafer 330, and thus may indicate whether wafer 330 includes defects. Moreover, as discussed above, beamlets 314, 316, and 318 may be projected onto different locations of the top surface of wafer 330, or different sides of local structures of wafer 330, to generate secondary charged-particle beams 336, 338, and 340 that may have different intensities. Therefore, by mapping the intensity of secondary charged-particle beams 336, 338, and 340 with the areas of wafer 330, image processing system 390 may reconstruct an image that reflects the characteristics of internal or external structures of wafer 330.

[0050] In some embodiments, image processing system 390 (which may be part of controller 209) may include an image acquirer 392, a storage 394, and a controller 396. Image acquirer 392 may comprise one or more processors. For example, image acquirer 392 may comprise a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, or the like, or a combination thereof. Image acquirer 392 may be communicatively coupled to charged-particle detection device 344 of beam tool 204 through a medium such as an electric conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, wireless radio, or a combination thereof. In some embodiments, image acquirer 392 may receive a signal from charged- particle detection device 344 and may construct an image. Image acquirer 392 may thus acquire SCPM images of wafer 330. Image acquirer 392 may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, or the like. Image acquirer 392 may be configured to perform adjustments of brightness and contrast of acquired images. In some embodiments, storage 394 may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer-readable memory, or the like.Storage 394 may be coupled with image acquirer 392 and may be used for saving scanned raw image data as original images, and post-processed images. Image acquirer 392 and storage 394 may be connected to controller 396. In some embodiments, image acquirer 392, storage 394, and controller 396 may be integrated together as one control unit.

[0051] In some embodiments, image acquirer 392 may acquire one or more SCPM images of a wafer based on an imaging signal received from charged-particle detection device 344. An imaging signal may correspond to a scanning operation for conducting charged particle imaging. An acquired image may be a single image comprising a plurality of imaging areas. The single image may be stored in storage 394. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may comprise one imaging area containing a feature of wafer 330. The acquired images may comprise multiple images of a single imaging area of wafer 330 sampled multiple times over a time sequence. The multiple images may be stored in storage 394. In some embodiments, image processing system 390 may be configured to perform image processing steps with the multiple images of the same location of wafer 330.

[0052] In some embodiments, image processing system 390 may include measurement circuits (e.g., analog-to-digital converters) to obtain a distribution of the detected secondary charged particles (e.g., secondary electrons). The charged-particle distribution data collected during a detection time window, in combination with corresponding scan path data of beamlets 314, 316, and 318 incident on the wafer surface, can be used to reconstruct images of the wafer structures under inspection. The reconstructed images can be used to reveal various features of the internal or external structures of wafer 330, and thereby can be used to reveal any defects that may exist in the wafer.

[0053] In some embodiments, the charged particles may be electrons. When electrons of primary charged-particle beam 310 are projected onto a surface of wafer 330 (e.g., probe spots 370, 372, and 374), the electrons of primary charged-particle beam 310 may penetrate the surface of wafer 330 for a certain depth, interacting with particles of wafer 330. Some electrons of primary charged-particle beam 310 may elastically interact with (e.g., in the form of elastic scattering or collision) the materials of wafer 330 and may be reflected or recoiled out of the surface of wafer 330. An elastic interaction conserves the total kinetic energies of the bodies (e.g., electrons of primary charged-particle beam 310) of the interaction, in which the kinetic energy of the interacting bodies does not convert to other forms of energy (e.g., heat, electromagnetic energy, or the like). Such reflected electrons generated from elastic interaction may be referred to as backscattered electrons (BSEs). Some electrons of primary charged-particle beam 310 may inelastically interact with (e.g., in the form of inelastic scattering or collision) the materials of wafer 330. An inelastic interaction does not conserve the total kinetic energies of the bodies of the interaction, in which some or all of the kinetic energy of the interacting bodies convert to other forms of energy. For example, through the inelastic interaction, the kinetic energy of some electrons of primary charged-particle beam 310 may cause electron excitation and transition of atoms of the materials. Such inelastic interaction may also generate electrons exiting the surface of wafer 330, which may be referred to as secondary electrons (SEs). Yield or emission rates of BSEs and SEs depend on, e.g., the material under inspection and the landing energy of the electrons of primary charged-particle beam 310 landing on the surface of the material, among others. The energy of the electrons of primary charged-particle beam 310 may be imparted in part by itsacceleration voltage (e.g., the acceleration voltage between the anode and cathode of charged-particle source 302 in FIG. 3). The quantity of BSEs and SEs may be more or fewer (or even the same) than the injected electrons of primary charged-particle beam 310.

[0054] The images generated by SCPM may be used for defect inspection. For example, a generated image capturing a test device region of a wafer may be compared with a reference image capturing the same test device region. The reference image may be predetermined (e.g., by simulation) and include no known defect. If a difference between the generated image and the reference image exceeds a tolerance level, a potential defect may be identified. For another example, the SCPM may scan multiple regions of the wafer, each region including a test device region designed as the same, and generate multiple images capturing those test device regions as manufactured. The multiple images may be compared with each other. If a difference between the multiple images exceeds a tolerance level, a potential defect may be identified.

[0055] Although reference may be made in the present disclosure to ICs, it is appreciated that the present disclosure may be applicable to other possible applications or designs. For example, the present disclosure may be applied to integrated optical systems, magnetic domain memories, liquidcrystal display panels, thin-film magnetic heads, and other nanoscale structures. It is further appreciated that the terms “die”, “structure”, and “IC structure” are used interchangeably in this disclosure.

[0056] Conventional charged particle beam systems do not provide a configuration capable of measuring a tilt characteristic of a sample or a method to measure a tilt characteristic. Monitoring and obtaining real-time tilt information of a sample may be important to ensure accurate inspection and metrology of a sample (e.g., fabricated ICs). Reference is now made to FIGs. 4A-4C, which illustrate challenges in conventional charged particle beam systems related to an inaccurate tilt measurement of a sample. FIG. 4A illustrates a sample 401 on a sample holder 402. Sample 401 may exhibit a change in flatness, or local height, across the surface of sample 401. For example, area 403 on sample 401 may illustrate a local area (e.g., 2 mm by 2 mm area) to be inspected in a charged particle beam apparatus. A charged particle beam may be focused on a location within area 403. However, the relative height of the sample may exceed an acceptable threshold and therefore skew any inspection or metrology results obtained. Conventional systems do not have a configuration or method to monitor a tilt characteristic of sample 401 and may not be able to adjust the tilt of sample 401 in real-time such that area 403 has a same relative height. Therefore, it may be difficult to obtain an accurate inspection or metrology measurement of sample 401 within area 403. FIG. 4B illustrates a charged particle beam 404 being focused onto a feature 405 on a first layer 406 of a sample. The sample includes a second layer 407, which is buried beneath first layer 406, and second layer 407 contains a feature 408. During fabrication of the sample, feature 405 and feature 408 were targeted to be fabricated at the same location on first layer 406 and second layer 407 (e.g., aligned vertically). Collecting an image 409 of the sample using charged particle beam 404 may be used to obtain a metrology overlay measurement410. However, FIG. 4B assumes there is no tilt of the sample during image collection. FIG. 4C illustrates the same sample, but with a non- zero tilt characteristic that is not accounted for or monitored using conventional systems. As illustrated in FIG. 4C, charged particle beam 404 does not tunnel into the sample enough to “capture” an image 411 of feature 408 in second layer 407. Therefore, image 411 would present no metrology overlay measurement, may indicate a false positive of a defect free structure, and allow for the possibility of missing defective wafers during wafer fabrication.

[0057] Reference is now made to FIG. 5A, which illustrates a charged particle beam system 500 consistent with embodiments of the present disclosure. As shown in FIG. 5A, charged particle beam system 500 may include a charged particle beam apparatus 501 (e.g., lithographic projection apparatus 100 of FIG. 1, beam tool 204 of FIG. 2, multi-beam tool 204 of FIG. 3), a sample 502 to be inspected, an emitter module 503a, a detector module 503b and a controller 504 (e.g., controller 209 of FIG. 2, controller 396 of FIG. 3). Charged particle beam apparatus 501 may emit and focus a charged particle beam 505 to a first location (not illustrated) on sample 502. Emitter module 503a may include circuitry configured to emit a light beam 506 to reflect off sample 502 and detector module 503b may include circuitry configured to collect light beam 506 and measure a characteristic of sample 502. In some embodiments, light beam 506 may be a visible light beam, an ultraviolet light beam, or an infrared light beam. In some embodiments, light beam 506 is a visible light beam. In some embodiments, light beam 506 may reflect off sample 502 at the first location. In some embodiments, light beam 506 may reflect off sample 502 at a second location, where the second location is within a local area surrounding the first location. It is appreciated that the phrase “within a local area” may be understood to mean within a 2-mm by 2-mm area surrounding the first location on sample 502. In some embodiments, the second location may be within a 2-mm distance from the first location. Emitter module 503a may emit light beam 506 at an angle of incidence 0 on sample 502. Light beam 506 may be collected by detector module 503b and used to calculate a characteristic of sample 502. In some embodiments, the characteristic is a tilt characteristic. In some embodiments, the characteristic is a height characteristic. Controller 504 may be communicatively connected to emitter module 503a and provide a signal to emitter module 503a to emit light beam 506. In some embodiments, controller 504 may be communicatively connected to detector module 503b. In some embodiments, controller 504 may receive a signal from detector module 503b to calculate the characteristic of sample 502. While not illustrated in FIG. 5A, controller 504 may be communicatively connected to charged particle beam apparatus 501.

[0058] Reference is now made to FIG. 5B, which illustrates a charged particle beam system 500 consistent with embodiments of the present disclosure. FIG. 5B illustrates emitter module 503a may include an emitter component 507 and a first lens 508, and detector module 503b may include a second lens 509 and a detector 510. Charged particle beam apparatus 501 may emit and focus charged particle beam 505 onto sample 502 as described above in FIG. 5A. Controller 504 may becommunicatively connected to emitter component 507 and to detector 510. In some embodiments, controller 504 may calculate a first signal and deliver the first signal to emitter component 507. Emitter component 507 may then emit a light beam 511 (e.g., light beam 506 of FIG. 5A), and first lens 508 may deliver light beam 511 to a surface of sample 502. Light beam 511 may be reflected off the surface of sample 502 and be collected by second lens 509. In some embodiments, second lens509 may focus light beam 511 to detector 510. The focused light beam 511 may impact a surface of detector 510, and detector 510 may measure and generate an output signal. Detector 510 may output the output signal to controller 504, and controller 504 may use the output signal to calculate a first characteristic of sample 502. In some embodiments, controller 504 may calculate a second signal, deliver the second signal to emitter component 507, and emitter component 507 may emit a second light beam (not shown). The second light beam may follow a same trajectory as light beam 511 and a second characteristic of sample 502 may be calculated as described above. In some embodiments, emitter component 507 may include a first emitter configured to emit light beam 511 (e.g., a first light beam) in response to receiving the first signal. In some embodiments, the first emitter may be a light source (e.g., a laser). In some embodiments, emitter component 507 may include a second emitter configured to emit the second light beam in response to receiving the second signal. In some embodiments, the second emitter may be a light source (e.g., a laser). In some embodiments, the first emitter and the second emitter may be a same emitter and may be configured to separately emit light beam 511 and the second light beam.

[0059] In some embodiments, the first emitter and the second emitter may be separate and may be positioned in separate emitter components. Reference is now made to FIG. 5C, which illustrates a charged particle beam system 512, consistent with embodiments of the present disclosure. FIG. 5C illustrates emitter module 503a may include a first emitter 513, a second emitter 514, a beam component 515, and first lens 508. Detector module 503b may include second lens 509 and detector 510. Charged particle beam apparatus 501 may emit and focus charged particle beam 505 onto sample 502 as described above. Controller 504 may be communicatively connected to first emitter 513, second emitter 514, and detector 510. In some embodiments, controller 504 may calculate a first signal and deliver the first signal to first emitter 513. First emitter 513 may then emit a first light beam 516, which may pass through beam component 515. First lens 508 may deliver first light beam 516 to a surface of sample 502. First light beam 516 may be reflected off the surface of sample 502 and be collected by second lens 509. In some embodiments, second lens 509 may focus first light beam 516 to detector 510. The focused first light beam 516 may impact a surface of detector 510, and detector510 may measure and generate an output signal. Detector 510 may output the output signal to controller 504, and controller 504 may use the output signal to calculate a first characteristic of sample 502. In some embodiments, controller 504 may calculate a second signal, deliver the second signal to second emitter 514, and second emitter 514 may emit a second light beam 517. Second light beam 517 may be reflected off beam component 515 and delivered to sample 502 via first lens 508. Insome embodiments, beam component 515 is a mirror. In some embodiments, beam component 515 is a dichroic mirror. A second characteristic of sample 502 may be calculated as described above. In some embodiments, first emitter 513 may be a light source (e.g., a laser). In some embodiments, second emitter 514 may be a light source (e.g., a laser). In some embodiments, first light beam 516 and second light beam 517 may exhibit different wavelengths. In some embodiments, the wavelength of second light beam 517 may be smaller than the wavelength of first light beam 516. In some embodiments, the first characteristic of sample 502 is a tilt characteristic. In some embodiments, the second characteristic of sample 502 is a height characteristic. It is appreciated that beam component515 may be excluded in some embodiments of the present disclosure and thus may be optionally included as illustrated in FIG. 5C. In some embodiments, first emitter 513 and second emitter 514 may be positioned such that first light beam 516 and second light beam 517 may be emitted with parallel trajectories. In some embodiments, first emitter 513 and second emitter 514 may be positioned such that first light beam 516 and second light beam 517 may be emitted with intersecting trajectories.

[0060] Reference is now made to FIGs. 5D and 5E, which are schematics of an example first lens and second lens configured to deliver a light beam to a detector, consistent with embodiments of the present disclosure. FIG. 5D illustrates first emitter 513 emitting first light beam 516 (after receiving a first signal from controller 504). First light beam 516 passes through beam component 515 and is delivered to sample 502 using first lens 508. In some embodiments, first lens 508 collimates first light beam 516 and first light beam remains collimated when reflecting off sample 502. Second lens 509 receives collimated first light beam 516 and focuses first light beam 516 to detector 510. FIG. 5E illustrates second emitter 514 emitting second light beam 517 (after receiving a second signal from controller 504). Second light beam 517 reflects off beam component 515 and is delivered to sample 502 using first lens 508. In some embodiments, first lens 508 focuses second light beam 517. Focused second light beam 517 is reflected off sample 502 and is received by second lens 509. Second lens 509 focuses second light beam 517 to detector 510. In some embodiments, first lens 508 and second lens 509 are configured to adjust the convergence, divergence, and parallel statuses of first light beam516 and second light beam 517. In some embodiments, first lens 508 and second lens 509 are designed to accommodate for a specific wavelength of a light beam. In some embodiments, first lens 508 and second lens 509 may be designed to optimize a focal power difference between first light beam 516 and second light beam 517. In some embodiments, first lens 508 may separately collimate first light beam 516 and focus second light beam 517 via applying a chromatic focal power difference. In some embodiments, second lens 509 may focus first light beam 516 and second light beam 517 via applying a chromatic focal power difference.

[0061] Reference is now made to FIG. 6 which shows a top-view of a surface of a detector that can be used monitor a light beam reflected from a sample, consistent with embodiments of the present disclosure. In some embodiments, detector 610 may include multiple detection segments that areconfigured to measure the intensity of a light beam impacting a detection segment. For example, detector 610 may comprise four quadrants 610-1, 610-2, 610-3, 610-4, as shown in FIG. 6. In some embodiments, detector 610 may be pixelated to measure parameter fluctuations of a light beam (e.g., first light beam 516 of FIG. 5C, 5D and second light beam 517 of FIG. 5C, 5E). In some embodiments, detector 610 may measure relative position shift of a light beam impacting detector 610 to ascertain a characteristic of a sample from which the light beam reflected off. For example, as shown in FIG. 6, light beam 620 may exhibit an off-axis shift when impacting detector 610. Detector 610 by itself or in conjunction with a controller (e.g., controller 209 of FIG. 2, controller 396 of FIG. 3, controller 504 of FIGs. 5A-5C) may calculate the amount of the off-axis shift by measuring the impact intensity of each portion of light beam 620 in each quadrant of detector 610 (620-1 in 610-1, 620-2 in 610-2, 620-3 in 610-3, and 620-4 in 610-4). For example, as shown in FIG. 6, quadrant 610- 1 is impacted by the largest portion 620-1 of light beam 620, and accordingly produces the largest impact intensity output. In contrast, quadrant 610-3 is impacted by the smallest portion 620-3 of light beam 620, and accordingly produces the lowest impact intensity output. The measured intensity signals ( / g20-i, ^20-2 ^620-3 , and ^620-4) from quadrants 610-1, 610-2, 610-3, and 610-4 may be delivered to a controller where a displacement in an X-plane 630 and a displacement in a Y-plane 640 of light beam 620 may be calculated. It is appreciated that X-plane displacement 630 and Y-plane displacement 640 may be attributed as parameters of a sample. As an example, displacement of sample in an X-plane 630 may be calculated by determining the ratio of light beam 620 intensity on a positive X-axis of detector 610 to the total detected light beam 620 intensity. Thus, characteristics of a sample may be calculated as630, A 640, ADetector 610 may collect and deliver the measured parameters or characteristics from light beam 620 to a controller (e.g., controller 209 of FIG. 2, controller 396 of FIG. 3, controller 504 of FIGs. 5A- 5C).

[0062] Reference is now made to FIGs. 7A-7C, which are schematics of an example input signal for a controller to calculate a first signal and a second signal, consistent with embodiments of the present disclosure. FIG. 7A illustrates an input signal for a controller (e.g., controller 209 of FIG. 2, controller 396 of FIG. 3, controller 504 of FIGs. 5A-5C) that may have input value 702 and a time 701 components. In some embodiments, the input signal is a clock signal. FIG. 7A illustrates a clock signal varying from a lower value 704 and a higher value 705. In some embodiments, the clock signal may comprise a rising edge 706 where lower value 704 switches to higher value 705. In some embodiments, the clock signal may comprise a falling edge 707 where higher value 705 switches to lower value 704. In some embodiments, a controller may detect rising edge 706 and falling edge 707and separate rising edge 706 from falling edge 707. FIG. 7B illustrates a rising edge detection 708 over time 701, where a controller may be configured to identify if a rising edge event 709 occurs in the clock signal (e.g., a rising edge detection value of 1). FIG. 7C illustrates a falling edge detection710 over time 701, where a controller may be configured to identify if a falling edge event 711 occurs in the clock signal (e.g., a falling edge detection value of 1). If rising edge event 709 occurs, a controller may calculate a first signal associated with rising edge event 709. In some embodiments, the first signal may be a value of an electrical signal (e.g., a voltage or current). If a falling edge event711 occurs, a controller may calculate a second signal associated with falling edge event 711. In some embodiments, the second signal may be a value of an electrical signal (e.g., a voltage or current). In some embodiments, the first signal may be associated with a rising edge (e.g., rising edge event 709) and the second signal may be associated with a falling edge (e.g., falling edge event 711). In some embodiments, the first signal may be associated with a falling edge and the second signal may be associated with a rising edge. It is appreciated that more than one clock signal may be used as an input signal for a controller. It is appreciated that any time between a rising edge (e.g., rising edge 706) and a falling edge (e.g., falling edge 707) may be set in a clock signal as input to a controller.Embodiments of the present disclosure are not so limited as illustrated in FIGs. 7A-7C, and may include any number of clock signals, rising edge events, and falling edge events.

[0063] In some embodiments, the present disclosure provides a charged particle beam system configured to facilitate separate measurements of a tilt characteristic and a height characteristic of a sample. Reference is now made to FIGs. 8A and 8B, which illustrate a charged particle beam system capable of separating a first measurement from a second measurement of a sample, consistent with embodiments of the present disclosure. FIG. 8A illustrates a charged particle beam system 800 including an emitter module 803a, a detector module 803b, a controller 804, a sample 802, and a charged particle beam apparatus (not shown). Emitter module 803a includes a first emitter 813, a second emitter 814, a beam component 815, and a first lens 808. Detector module 803b includes a second lens 809 and a detector 810. In some embodiments, controller 804 may be configured to calculate a first signal from an input signal (e.g., as described in FIGs. 7A-7C above) and provide the first signal to first emitter 813 and to detector 810. After receiving the first signal, first emitter 813 may emit a first light beam 816 to measure a first characteristic of sample 802. In some embodiments, the input signal may be a clock signal. In some embodiments, the first signal may be associated with a falling edge of the clock signal or associated with a rising edge of the clock signal. In some embodiments, the first signal is associated with a falling edge of the clock signal. The first light beam 816 is collimated by first lens 808 and reflected off sample 802. Second lens 809 may receive first light beam 816 and focus first light beam 816 to detector 810, where a measurement for a first characteristic of sample 802 may be collected. In some embodiments, the measurement may be a ratio, wherein the ratio is a ratio of intensity values of first light beam 816 across one or more sections of detector 810. In some embodiments, detector 810 may output the measurement (e.g., output signal)to controller 804 to calculate a first characteristic of sample 802. In some embodiments, the first characteristic is a tilt characteristic of sample 802.

[0064] FIG. 8B illustrates charged particle beam 800 configured to emit a second light beam 817 to measure a second characteristic of a sample, consistent with embodiments of the present disclosure. In some embodiments, second light beam 817 may be emitted after or before the measurement for the first characteristic is collected as described in FIG. 8A. In some embodiments, controller 804 may be configured to calculate a second signal from an input signal (e.g., as described in FIGs. 7A-7C above) and provide the second signal to second emitter 814 and to detector 810. After receiving the second signal, second emitter 814 may emit second light beam 817 to measure a second characteristic of sample 802. In some embodiments, the input signal may be a clock signal. In some embodiments, the second signal may be associated with a falling edge of the clock signal or associated with a rising edge of the clock signal. In some embodiments, the second signal is associated with a rising edge of the clock signal. Second light beam 817 is focused by first lens 808 and reflected off sample 802. Second lens 809 may receive second light beam 817 and focus second light beam 817 to detector 810, where a measurement for a second characteristic of sample 802 may be collected. In some embodiments, the measurement may be a ratio, wherein the ratio is a ratio of intensity values of second light beam 817 across one or more sections of detector 810. In some embodiments, detector 810 may output the measurement (e.g., output signal) to controller 804 to calculate a second characteristic of sample 802. In some embodiments, the second characteristic is a height characteristic of sample 802.

[0065] FIGs. 8A and 8B illustrate that temporal separation of a first measurement and a second measurement of a sample may be achieved according to embodiments of the present disclosure.

[0066] Reference is now made to FIG. 9A, which illustrates measuring a characteristic of a sample using a light beam, consistent with embodiments of the present disclosure. FIG. 9A illustrates an emitter 901 configured to emit an emitted beam 902 (e.g., first light beam 816 or second light beam 817 of FIGs. 8A and 8B) to reflect off a sample 903 and be measured by a detector 904. Detector 904 may comprise one or more sections configured to measure the reflected emitted beam 902 to measure a characteristic of sample 903 as described above.

[0067] Reference is now made to FIGs. 9B-9J, which illustrate how emitted beam 902 may reflect off sample 903 and be measured according to different characteristics of sample 903, consistent with embodiments of the present disclosure. FIGs. 9B-9D are relevant to a tilt characteristic of sample 903, wherein sample 903 may tilt (e.g., rotate) about an X-axis, and illustrate a top-view of emitted beam 902 impacting detector 904. As illustrated in FIG. 9B, sample 903 does not exhibit any tilt about the X-axis. Reflected emitted beam 902 may impact at the center of detector 904-B. As illustrated in FIG. 9C, sample 903 exhibits a clockwise tilt about the X-axis. The reflected emitted beam 902 may impact at a right-hand side of detector 904-C. FIG. 9D illustrates a counterclockwise tilt of sample 903 about the X-axis. Reflected emitted beam 902 may thus impact at a left-hand side ofdetector 904-D. FIGs. 9B-9D illustrate tilt about an X-axis only, so an impacted reflected beam may be illustrated as located on the horizontal axis on detectors 904-B, 904-C, and 904-D. It is appreciated that the dotted arrows illustrated in FIGs. 9B-9D are understood to mean “in the plane of the page” and the bold arrows are “coming out of the page.” FIGs. 9E-9G are relevant to a tilt characteristic of sample 903, wherein sample 903 may tilt (e.g., rotate) about a Y-axis, and illustrate a top-view of emitted beam 902 impacting detector 904. As illustrated in FIG. 9E, sample 903 does not exhibit any tilt about the Y-axis. Reflected emitted beam 902 may impact at the center of detector 904-E. As illustrated in FIG. 9F, sample 903 exhibits a clockwise tilt about the Y-axis. The reflected emitted beam 902 may impact at a lower half of detector 904-F. FIG. 9G illustrates a counterclockwise tilt of sample 903 about the Y-axis. Reflected emitted beam 902 may thus impact at an upper-half of detector 904-G. FIGs. 9E-9G illustrate tilt of sample 903 about a Y-axis only, so the impacted reflected beam may be illustrated as located on the vertical axis on detectors 904-E, 904-F, and 904- G. It is appreciated that sample 903 may exhibit a tilt about both the X-axis and the Y-axis. In some embodiments, reflected emitted beam 902 may impact detector 904 within one of the quadrants (e.g., not on the horizontal or vertical axis illustrated in detectors 904-B through 904-G).

[0068] FIGs. 9H-9J are relevant to a height characteristic of sample 903, where sample 903 may shift up or down a Z-axis. FIGs. 9H-9J are relevant to a height characteristic of sample 903 and illustrate a top-view of emitted beam 902 impacting detector 904 depending on if a height characteristic of sample 903 changes. FIG. 9H illustrates sample 903 does not exhibit any change in height. Reflected emitted beam 902 may impact at the center of detector 904-H. FIG. 91 illustrates sample 903 has a height below an expected height value. The dotted outline of sample 903 illustrates an expected height of sample 903, and the bold outline of sample 903-1 illustrates the actual height of sample 903. Reflected emitted beam 902 may impact at a lower half of detector 904-1 on the vertical axis. FIG. 9 J illustrates sample 903-J has a height higher than an expected height value. Emitted beam 902 is reflected off sample 903-J at the actual height and may impact at an upper half of detector 904-J on the vertical axis. It is appreciated that embodiments of the present disclosure may provide for no cross-talking between measurements of a first characteristic and second characteristic of sample. For example, a measurement of a tilt characteristic (e.g., tilt about a Y-axis) may be separate from a measurement of a height characteristic of a sample. Therefore, embodiments of the present disclosure avoid confusion of measurement and provide a system to clearly measure a tilt characteristic in addition to a height characteristic of a sample in a charged particle beam apparatus.

[0069] Reference is now made to FIG. 10, which is an example flow diagram illustrating a method 1000 of measuring a characteristic of a sample in a charged particle beam apparatus, consistent with embodiments of the present disclosure. The steps of method 1000 may be performed by a computing device that includes, e.g., controller 209 of FIG. 2, controller 504 of FIGs. 5A-5D, controller 804 of FIGs. 8A, 8B, or image processing system 390 of FIG. 3. It is appreciated that the illustrated method 1000 may be altered to modify the order of steps and to include the additional steps.

[0070] In step 1001, a light beam from a light source is emitted for delivering the light beam to a surface of the sample using a first lens and the light beam is reflected off the surface of the sample. The light beam may be a visible light beam. The light source may be a laser. In some embodiments, the light source may receive a signal from a controller to emit the light beam. The signal from the controller may be an electrical signal associated with a clock signal. In some embodiments, the clock signal comprises a rising edge and a falling edge. In some embodiments, the first lens may focus the light beam such that the light beam is focused when delivered to the surface of the sample. In some embodiments, the first lens may collimate the light beam. In some embodiments, the collimated light beam may remain collimated after reflecting off the surface of the sample.

[0071] In step 1002, the reflected light beam is focused onto a surface of a detector, using a second lens, to generate a first measurement. In some embodiments, the second lens focuses the reflected light beam via applying a chromatic focal power difference. In some embodiments, the second lens is configured to optimize a focal power of the reflected light beam. The surface of the detector comprises one or more sections to monitor a characteristic of the reflected light beam. In some embodiments, the detector comprises quadrants. In some embodiments, the first measurement is a ratio. In some embodiments, the ratio is a ratio of intensity values from the light beam impacting different sections of the detector. In some embodiments, the first measurement is an electrical signal.

[0072] In step 1003, a characteristic of the sample is determined using the first measurement. In some embodiments, the first measurement is supplied to a controller, which performs the determination. In some embodiments, the characteristic of the sample is a tilt characteristic. In some embodiments, the characteristic of the sample is a height characteristic.

[0073] Reference is now made to FIG. 11, which is an example flow diagram illustrating a method 1100 of measuring a first characteristic of a sample and a second characteristic of a sample in a charged particle beam apparatus, consistent with embodiments of the present disclosure. The steps of method 1100 may be performed by a computing device that includes, e.g., controller 209 of FIG. 2, controller 504 of FIGs. 5A-5D, controller 804 of FIGs. 8A, 8B, or image processing system 390 of FIG. 3. It is appreciated that the illustrated method 1100 may be altered to modify the order of steps and to include the additional steps.

[0074] In step 1101, a first emitter is caused to emit a first light beam. The first light beam may be a visible light beam. In some embodiments, the first emitter is light source. In some embodiments, the light source is a laser. The first emitter may receive a signal from a controller to emit the first light beam. The signal from the controller may be an electrical signal associated with a clock signal. In some embodiments, the clock signal comprises a rising edge and a falling edge. In some embodiments, the signal from the controller may be a value of an electrical signal associated with a falling edge of the clock signal.

[0075] In step 1102, the first light beam is delivered to a surface of a sample using a first lens and the first light beam is reflected off the surface of the sample. In some embodiments, the first lenscollimates the first light beam such that the first light beam is collimated when reflecting off the surface of the sample.

[0076] In step 1103, the first light beam is focused onto a surface of a detector, using a second lens, to generate a first measurement. In some embodiments, the second lens focuses the first light beam via applying a chromatic focal power difference. In some embodiments, the second lens is configured to optimize a focal power of the first light beam. The surface of the detector comprises one or more sections to monitor a characteristic of the first light beam. In some embodiments, the detector comprises quadrants. In some embodiments, the first measurement is a ratio. In some embodiments, the ratio is a ratio of intensity values from the first light beam impacting different sections of the detector. In some embodiments, the first measurement is an electrical signal.

[0077] In step 1104, a second emitter is caused to emit a second light beam. The second light beam may be a visible light beam. In some embodiments, the second emitter is a light source. In some embodiments, the light source is a laser. The second emitter may receive a signal from a controller to emit the second light beam. The signal from the controller may be an electrical signal associated with a clock signal. In some embodiments, the clock signal comprises a rising edge and a falling edge. In some embodiments, the signal from the controller may be a value of an electrical signal associated with a rising edge of the clock signal. In some embodiments, the second light beam has a smaller wavelength than the first light beam.

[0078] In step 1105, the second light beam is delivered to the surface of the sample using the first lens and the second light beam is reflected off the surface of the sample. In some embodiments, the first lens may focus the second light beam such that the second light beam is focused when delivered to the surface of the sample.

[0079] In step 1106, the second light beam is focused onto the surface of the detector, using the second lens, to generate a second measurement. In some embodiments, the second lens focuses the second light beam via applying a chromatic focal power difference. In some embodiments, the second lens is configured to optimize a focal power of the second light beam. The surface of the detector comprises one or more sections to monitor a characteristic of the second light beam. In some embodiments, the detector comprises quadrants. In some embodiments, the second measurement is a ratio. In some embodiments, the ratio is a ratio of intensity values from the second light beam impacting different sections of the detector. In some embodiments, the second measurement is an electrical signal.

[0080] In step 1107, the first measurement is used to determine a first characteristic of the sample and the second measurement is used to determine a second measurement of the sample. In some embodiments, a controller determines the first characteristic and the second characteristic. In some embodiments, the first characteristic is a tilt characteristic of the sample, and the second characteristic is a height characteristic of the sample.

[0081] A benefit provided by embodiments of the present disclosure may be a method to measure a tilt characteristic of a sample in a charged particle beam system. In some embodiments, more accurate information regarding local tilt characteristics of a sample can be measured and used to avoid degradation in inspection image quality and metrology measurement accuracy. In some embodiments, a method of measuring a tilt characteristic separately from a height characteristic using different light beams is disclosed. The light beams may be visible light and may each have different wavelengths. The present disclosure also provides a charged particle beam system configuration capable of timedivision multiplexing to measure a local tilt characteristic and height characteristic of a sample efficiently and accurately. In some embodiments, the present disclosure provides a charged particle beam system to integrate a tilt sensor and a height sensor into one module. Real-time and point-of- interest measurements of both local sample tilt and sample height may be achieved. Moreover, some embodiments of the present disclosure may increase throughput of IC manufacturing and confidence in inspection and metrology.

[0082] A non-transitory computer readable medium may be provided that may store instructions for a processor of a lithographic projection apparatus (e.g., lithographic projection apparatus 100 of FIG. 1), a processor of an inspection tool (e.g., EBI system 200 of FIG. 2 or multi-beam inspection tool 204 of FIG. 3) to collect images of a sample, method 1000 of FIG. 10, method 1100 of FIG. 11, and other executable functions relating to measuring a characteristic of a sample, separately measuring a first characteristic and a second characteristic of a sample, or measuring a tilt characteristic of a sample using a light beam. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM), a FLASH- EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same.

[0083] The embodiments may further be described using the following clauses:1. A charged particle beam system, comprising: a charged particle beam tool having circuitry configured to emit and focus a charged particle beam at a first location on a surface of a sample; an emitter module having circuitry configured to emit a first light beam and a second light beam to reflect off a second location on the surface of the sample, wherein the emitter module emits the first light beam after receiving a first signal and emits the second light beam after receiving a second signal; a detector module having circuitry configured to collect the first light beam to measure a first characteristic of the sample and to collect the second light beam to measure a second characteristic of the sample; anda controller communicatively connected to the emitter module and the detector module, wherein the controller is configured to determine the first signal and the second signal from an input signal and supply the first signal and the second signal to the emitter module.2. The charged particle beam system of clause 1, wherein the first location on the surface of the sample is different from the second location.3. The charged particle beam system of clause 1 or 2, wherein the second location on the surface of the sample is within a local area surrounding the first location.4. The charged particle beam system of clause 3, wherein the second location on the surface of the sample is less than or equal to 2 mm from the first location.5. The charged particle beam system of any one of clauses 1 to 4, wherein the first light beam has a wavelength different from a wavelength of the second light beam.6. The charged particle beam system of any one of clauses 1 to 5, wherein the first light beam is a visible light beam.7. The charged particle beam system of any one of clauses 1 to 6, wherein the second light beam is a visible light beam.8. The charged particle beam system of any one of clauses 1 to 7, wherein the first characteristic of the sample is a tilt characteristic, and the second characteristic is a height characteristic.9. The charged particle beam system of any one of clauses 5 to 8, wherein the second light beam has a wavelength smaller than the wavelength of the first light beam.10. The charged particle beam system of any one of clauses 1 to 9, wherein the first light beam is collimated at the second location on the surface of the sample and the second light beam is focused at the second location on the surface of the sample.11. The charged particle beam system of any one of clauses 1 to 10, wherein the emitter module is configured to separate emission of the first light beam and the second light beam.12. The charged particle beam system of any one of clauses 1 to 11, wherein the input signal is an electrical signal.13. The charged particle beam system of clause 12, wherein the electrical signal comprises a clock signal; the first signal comprises an electrical signal associated with a first edge of the clock signal; and the second signal comprises an electrical signal associated with a second edge of the clock signal.14. The charged particle beam system of any one of clauses 1 to 13, wherein the emitter module comprises: a first emitter configured to emit the first light beam in response to receiving the first signal;a second emitter configured to emit the second light beam in response to receiving the second signal; and a first lens configured to deliver the first light beam and the second light beam to the second location on the sample.15. The charged particle beam system of clause 14, wherein the first emitter is a light source.16. The charged particle beam system of clause 15, wherein the first emitter is a laser.17. The charged particle beam system of clause 14 or 15, wherein the second emitter is a light source.18. The charged particle beam system of clause 17, wherein the second emitter is a laser.19. The charged particle beam system of any one of clauses 14 to 18, wherein the first lens is configured to collimate the first light beam and to focus the second light beam.20. The charged particle beam system of any one of clauses 1 to 19, wherein the detector module comprises: a detector; and a second lens configured to collect the first light beam and the second light beam reflected from the sample and deliver the first light beam and the second light beam to the detector.21. The charged particle beam system of clause 20, wherein the second lens is configured to focus the first light beam and the second light beam to a surface of the detector.22. The charged particle beam system of clause 20 or 21, wherein the second lens is configured to apply a chromatic focal power difference to the first light beam and the second light beam to focus the first light beam and the second light beam to the detector.23. The charged particle beam system of any one of clauses 20 to 22, wherein the detector comprises one or more sections to monitor a change in intensity from the first light beam or the second light beam impacting the detector.24. The charged particle beam system of clause 23, wherein the detector comprises quadrants.25. The charged particle beam system of any one of clauses 20 to 24, wherein the detector outputs a third signal.26. The charged particle beam system of clause 25, wherein the third signal provides information representing a position of the first light beam or the second light beam impacting the detector.27. The charged particle beam system of clause 26, wherein the third signal provides information representing a ratio.28. The charged particle beam system of clause 27, wherein the ratio is a ratio of intensity values.29. The charged particle beam system of any one of the clauses 26 to 28, wherein the third signal is used to calculate the first characteristic of the sample or the second characteristic of the sample.30. The charged particle beam system of any one of clauses 1 to 29, wherein the emitter module further comprises a beam component.31. The charged particle beam system of clause 30, wherein the beam component is configured to combine the first light beam and the second light beam before the first light beam and the second light beam are delivered to the second location on the surface of the sample.32. The charged particle beam system of clause 30 or 31, wherein the beam component is a mirror.33. The charged particle beam system of clause 32, wherein the first light beam passes through the mirror and the second light beam reflects off the mirror.34. A charged particle beam system, comprising: a charged particle beam tool having circuitry configured to emit and focus a charged particle beam at a first location on a surface of a sample; a first emitter configured to emit a first light beam onto a second location of the surface of the sample in response to the first emitter receiving a first signal; a second emitter configured to emit a second light beam onto the second location on the surface of the sample in response to the second emitter receiving a second signal; a detector configured to receive the first light beam and the second light beam reflected from the second location on the surface of the sample, wherein the detector measures a first characteristic of the sample from the first light beam and a second characteristic of the sample from the second light beam; and a controller having circuitry configured to determine the first signal and the second signal from an input signal, wherein the controller is configured to toggle supplying the first signal to the first emitter and the second signal to the second emitter.35. The charged particle beam system of clause 34, wherein the first location on the surface of the sample is different from the second location.36. The charged particle beam system of clause 34 or 35, wherein the second location on the surface of the sample is within a local area surrounding the first location.37. The charged particle beam system of clause 36, wherein the second location on the surface of the sample is less than or equal to 2 mm from the first location.38. The charged particle beam system of any one of clauses 34 to 37, wherein the first light beam has a wavelength different from a wavelength of the second light beam.39. The charged particle beam system of any one of clauses 34 to 38, wherein the first light beam is a visible light beam.40. The charged particle beam system of any one of clauses 34 to 39, wherein the second light beam is a visible light beam.41. The charged particle beam system of any one of clauses 34 to 40, wherein the first characteristic of the sample is a tilt characteristic, and the second characteristic of the sample is a height characteristic.42. The charged particle beam system of any one of clauses 38 to 41, wherein the second light beam has a wavelength smaller than the wavelength of the first light beam.43. The charged particle beam system of any one of clauses 34 to 42, wherein the first light beam is collimated when the first light beam reflects off the second location on the surface of the sample and the second light beam is focused when the second light beam reflects off the second location on the surface of the sample.44. The charged particle beam system of any one of clauses 34 to 43, wherein the first emitter is a light source.45. The charged particle beam system of any one of clauses 34 to 44, wherein the second emitter is a light source.46. The charged particle beam system of clause 44, wherein the first emitter is a laser.47. The charged particle beam system of clause 45, wherein the second emitter is a laser.48. The charged particle beam system of any one of clauses 34 to 47, wherein the input signal comprises an electrical signal.49. The charged particle beam system of clause 48, wherein the electrical signal comprises a clock signal; the first signal comprises an electrical signal associated with a first edge of the clock signal; and the second signal comprises an electrical signal associated with a second edge of the clock signal.50. The charged particle beam system of any one of clauses 24 to 49, wherein the detector comprises one or more sections to monitor a change in intensity measured from the first light beam or the second light beam impacting the detector.51. The charged particle beam system of clause 50, wherein the detector comprises quadrants.52. The charged particle beam system of any one of clauses 34 to 51, wherein the detector outputs a third signal.53. The charged particle beam system of clause 52, wherein the third signal provides information representing a position of the first light beam or the second light beam impacting the detector.54. The charged particle beam system of clause 52 or 53, wherein the third signal provides information representing a ratio.55. The charged particle beam system of clause 54, wherein the ratio is a ratio of intensity values.56. The charged particle beam system of any one of clauses 52 to 55, wherein the third signal is used to calculate the first characteristic of the sample or the second characteristic of the sample.57. The charged particle beam system of any one of clauses 34 to 56, further comprising: a first lens configured to deliver the first light beam and the second light beam to the second location on the sample; and a second lens configured to collect the first light beam and the second light beam reflected from the second location on the sample and deliver the first light beam and the second light beam to the detector.58. The charged particle beam system of clause 57, wherein the first lens is configured to collimate the first light beam and to focus the second light beam.59. The charged particle beam system of clause 57 or 58, wherein the second lens is configured to focus the first light beam and the second light beam to a surface of the detector.60. The charged particle beam system of any one of clauses 57 to 59, wherein the second lens is configured to apply a chromatic focal power difference to the first light beam and the second light beam to focus the first light beam and the second light beam to the detector.61. The charged particle beam system of any one of clauses 34 to 60 wherein the system further comprises a beam component.62. The charged particle beam system of clause 61, wherein the beam component is configured to combine the first light beam and the second light beam before the first light beam and the second light beam are reflected from the second location on the surface of the sample.63. The charged particle beam system of clause 61 or 62, wherein the beam component is a mirror.64. The charged particle beam system of clause 63, wherein the first light beam passes through the mirror and the second light beam reflects off the mirror.65. A method of measuring a characteristic of a sample in a charged particle beam apparatus, the method comprising: emitting a light beam from a light source for delivering the light beam to a surface of the sample using a first lens, wherein the light beam is reflected off the surface of the sample; focusing the light beam reflected off the surface of the sample onto a surface of a detector, using a second lens, to generate a first measurement; and determining the characteristic of the sample using the first measurement.66. The method of clause 65, wherein the light beam is a visible light beam.67. The method of clause 65 or 66, wherein the light source is a laser.68. The method of any one of clauses 65 to 67, wherein delivering the light beam to the surface of the sample comprises collimating light beam using the first lens.69. The method of any one of clauses 65 to 68, wherein the light beam is collimated when reflecting off the surface of the sample.70. The method of any one of clauses 65 to 69, wherein the detector monitors a change in intensity measured from the light beam impacting the surface of the detector.71. The method of any one of clauses 65 to 70, wherein the first measurement provides information representing a position of the light beam impacting the detector.72. The method of any one of clauses 65 to 71, wherein the first measurement provides information representing a ratio.73. The method of clause 72, wherein the ratio is a ratio of intensity values.74. The method of any one of clauses 65 to 73, wherein the characteristic of the sample comprises a tilt characteristic.75. The method of any one of clauses 65 to 74, wherein emitting the light beam from the light source further comprises: determining a first signal from an input signal using a controller; and supplying the first signal to the light source for triggering emission of the light beam from the light source.76. The method of clause 75, wherein the input signal comprises an electrical signal.77. The method of clause 76, wherein the electrical signal comprises a clock signal.78. The method of clause 77, wherein the first signal comprises an electrical signal associated with a first edge of the clock signal.79. The method of clause 77, wherein the first signal comprises an electrical signal associated with a second edge of the clock signal.80. The method of any one of clauses 75 to 79, wherein the controller supplies the first signal to the light source and the detector.81. The method of any one of clauses 65 to 80, wherein the characteristic of the sample represents a characteristic of a first location on the sample.82. The method of clause 81, wherein the first location on the sample is within a local area surrounding a second location, wherein the second location is where a charged particle beam is focused on the surface of the sample.83. The method of clause 82, wherein the first location is less than or equal to 2 mm from the second location.84. The method of any one of clauses 65 to 83, wherein the charged particle beam apparatus is a scanning electron microscope.85. The method of any one of clauses 65 to 83, wherein the charged particle beam apparatus is a lithography apparatus.86. A method of measuring a first characteristic and a second characteristic of a sample in a charged particle beam apparatus, the method comprising: causing a first emitter to emit a first light beam; delivering the first light beam to a surface of the sample using a first lens, wherein the first light beam is reflected off the surface of the sample; focusing the first light beam onto a surface of a detector, using a second lens, to generate a first measurement; causing a second emitter to emit a second light beam; delivering the second light beam to the surface of the sample using the first lens, wherein the second light beam is reflected off the surface of the sample; focusing the second light beam onto the surface of the detector, using the second lens, to generate a second measurement; and using the first measurement to determine the first characteristic of the sample and the second measurement to determine the second characteristic of the sample.87. The method of clause 86, wherein the first light beam has a wavelength different from a wavelength of the second light beam.88. The method of clause 86 or 87, wherein first light beam is a visible light beam.89. The method of any one of clauses 86 to 88, wherein the second light beam is a visible light beam.90. The method of any one of clauses 86 to 89, wherein the first characteristic of the sample is a tilt characteristic, and the second characteristic of the sample is a height characteristic.91. The method of any one of clauses 87 to 90, wherein the second light beam has a wavelength smaller than the wavelength of the first light beam.92. The method of any one of clauses 86 to 91, wherein delivering the first light beam to the surface of the sample using the first lens comprises collimating the first light beam.93. The method of any one of clauses 86 to 92, wherein delivering the second light beam to the surface of the sample using the first lens comprises focusing the second light beam.94. The method of any one of clauses 86 to 93, wherein the first emitter is a light source.95. The method of clause 94, wherein the first emitter is a laser.96. The method of any one of clauses 86 to 95, wherein the second emitter is a light source.97. The method of clause 96, wherein the second emitter is a laser.98. The method of any one of clauses 86 to 97, wherein the detector monitors a change in intensity measured from the first light beam or the second light beam impacting the surface of the detector.99. The method of any one of clauses 86 to 98, wherein the first measurement provides information representing a position of the first light beam impacting the detector and the secondmeasurement provides information representing a position of the second light beam impacting the detector.100. The method of clause 99, wherein the first measurement provides information representing a first ratio and the second measurement provides information representing a second ratio.101. The method of clause 100, wherein the first ratio is a first ratio of intensity values, and the second ratio is a second ratio of intensity values.102. The method of any one of clauses 86 to 101, wherein causing the first emitter to emit the first light beam comprises: determining a first signal from an input signal using a controller; and supplying the first signal to the first emitter for triggering emission of the first light beam.103. The method of any one of clauses 86 to 102, wherein causing the second emitter to emit the second light beam comprises: determining a second signal from an input signal using a controller; and supplying the second signal to the second emitter for triggering emission of the second light beam.104. The method of clause 102 or 103, wherein the input signal comprises an electrical signal.105. The method of clause 104, wherein the input signal comprises a clock signal; the first signal comprises an electrical signal associated with a first edge of the clock signal; and the second signal comprises an electrical signal associated with a second edge of the clock signal.106. The method of any one of clauses 86 to 105, wherein the first characteristic of the sample represents a characteristic of a first location on the sample.107. The method of any one of clauses 86 to 106, wherein the second characteristic of the sample represents a characteristic of a first location on the sample.108. The method of clause 106 or 107, wherein the first location on the sample is within a local area surrounding a second location, wherein the second location is where a charged particle beam is focused on the surface of the sample.109. The method of clause 108, wherein the first location is less than or equal to 2 mm from the second location.110. The method of any one of clauses 86 to 109, wherein the charged particle beam apparatus is a scanning electron microscope.111. The method of any one of clauses 86 to 109, wherein the charged particle beam apparatus is a lithography apparatus.112. A non- transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for measuring a characteristic of a sample in a charged particle beam apparatus, the operations comprising: emitting a light beam from a light source for delivering the light beam to a surface of the sample using a first lens, wherein the light beam is reflected off the surface of the sample; focusing the light beam reflected off the surface of the sample onto a surface of a detector using a second lens to generate a first measurement; and determining the characteristic of the sample using the first measurement.113. The non-transitory computer readable medium of clause 112, wherein the light beam is a visible light beam.114. The non-transitory computer readable medium of clause 112 or 113, wherein the light source is a laser.115. The non-transitory computer readable medium of any one of clauses 112 to 114, wherein delivering the light beam to the surface of the sample comprises collimating light beam using the first lens.116. The non-transitory computer readable medium of any one of clauses 112 to 115, wherein the light beam is collimated when reflecting off the surface of the sample.117. The non-transitory computer readable medium of any one of clauses 112 to 116, wherein the detector monitors a change in intensity measured from the light beam impacting the surface of the detector.118. The non-transitory computer readable medium of any one of clauses 112 to 117, wherein the first measurement provides information representing a position of the light beam impacting the detector.119. The non-transitory computer readable medium of any one of clauses 112 to 118, wherein the first measurement provides information representing a ratio.120. The non-transitory computer readable medium of clause 119, wherein the ratio is a ratio of intensity values.121. The non-transitory computer readable medium of any one of clauses 112 to 120, wherein the characteristic of the sample comprises a tilt characteristic.122. The non-transitory computer readable medium of any one of clauses 112 to 121, wherein emitting the light beam from the light source further comprises: determining a first signal from an input signal using a controller; and supplying the first signal to the light source for triggering emission of the light beam from the light source.123. The non-transitory computer readable medium of clause 122, wherein the input signal comprises an electrical signal.124. The non-transitory computer readable medium of clause 123, wherein the electrical signal comprises a clock signal.125. The non-transitory computer readable medium of clause 124, wherein the first signal comprises an electrical signal associated with a first edge of the clock signal.126. The non-transitory computer readable medium of clause 124, wherein the first signal comprises an electrical signal associated with a second edge of the clock signal.127. The non-transitory computer readable medium of any one of clauses 122 to 126, wherein the controller supplies the first signal to the light source and the detector.128. The non-transitory computer readable medium of any one of clauses 112 to 127, wherein the characteristic of the sample represents a characteristic of a first location on the sample.129. The non-transitory computer readable medium of clause 128, wherein the first location on the sample is within a local area surrounding a second location, wherein the second location is where a charged particle beam is focused on the surface of the sample.130. The non-transitory computer readable medium of clause 129, wherein the first location is less than or equal to 2 mm from the second location.131. The non-transitory computer readable medium of any one of clauses 112 to 130, wherein the charged particle beam apparatus is a scanning electron microscope.132. The non-transitory computer readable medium of any one of clauses 112 to 130, wherein the charged particle beam apparatus is a lithography apparatus.133. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for measuring a first characteristic and a second characteristic of a sample in a charged particle beam apparatus, the operations comprising: causing a first emitter to emit a first light beam; delivering the first light beam to a surface of the sample using a first lens, wherein the first light beam is reflected off the surface of the sample; focusing the first light beam onto a surface of a detector using a second lens to generate a first measurement; causing a second emitter to emit a second light beam; delivering the second light beam to the surface of the sample using the first lens, wherein the second light beam is reflected off the surface of the sample; focusing the second light beam onto the surface of the detector using the second lens to generate a second measurement; and using the first measurement to determine the first characteristic and the second measurement to determine the second characteristic.134. The non-transitory computer readable medium of clause 133, wherein the first light beam has a wavelength different from a wavelength of the second light beam.135. The non-transitory computer readable medium of clause 133 or 134, wherein first light beam is a visible light beam.136. The non-transitory computer readable medium of any one of clauses 133 to 135, wherein the second light beam is a visible light beam.137. The non-transitory computer readable medium of any one of clauses 133 to 136, wherein the first characteristic of the sample comprises a tilt characteristic, and the second characteristic of the sample comprises a height characteristic.138. The non-transitory computer readable medium of any one of clauses 134 to 137, wherein the second light beam has a wavelength smaller than the wavelength of the first light beam.139. The non-transitory computer readable medium of any one of clauses 133 to 138, wherein delivering the first light beam to the surface of the sample using the first lens comprises collimating the first light beam.140. The non-transitory computer readable medium of any one of clauses 133 to 139, wherein delivering the second light beam to the surface of the sample using the first lens comprises focusing the second light beam.141. The non-transitory computer readable medium of any one of clauses 133 to 140, wherein the first emitter is a light source.142. The non-transitory computer readable medium of clause 141, wherein the first emitter is a laser.143. The non-transitory computer readable medium of any one of clauses 133 to 142, wherein the second emitter is a light source.144. The non-transitory computer readable medium of clause 143, wherein the second emitter is a laser.145. The non-transitory computer readable medium of any one of clauses 133 to 144, wherein the detector monitors a change in intensity measured from the first light beam or the second light beam impacting the surface of the detector.146. The non-transitory computer readable medium of any one of clauses 133 to 145, wherein the first measurement provides information representing a position of the first light beam impacting the detector and the second measurement provides information representing a position of the second light beam impacting the detector.147. The non-transitory computer readable medium of clause 146, wherein the first measurement provides information representing a first ratio and the second measurement provides information representing a second ratio.148. The non-transitory computer readable medium of clause 147, wherein the first ratio is a first ratio of intensity values, and the second ratio is a second ratio of intensity values.149. The non-transitory computer readable medium of any one of clauses 133 to 148, wherein causing the first emitter to emit the first light beam comprises:determining a first signal from an input signal using a controller; and supplying the first signal to the first emitter for triggering emission of the first light beam.150. The non-transitory computer readable medium of any one of clauses 113 to 149, wherein causing the second emitter to emit the second light beam comprises: determining a second signal from an input signal using a controller; and supplying the second signal to the second emitter for triggering emission of the second light beam.151. The non-transitory computer readable medium of clause 149 or 150, wherein the input signal comprises an electrical signal.152. The non-transitory computer readable medium of clause 151, wherein the input signal comprises a clock signal; the first signal comprises an electrical signal associated with a first edge of the clock signal; and the second signal comprises an electrical signal associated with a second edge of the clock signal.153. The non-transitory computer readable medium of any one of clauses 133 to 152, wherein the first characteristic of the sample represents a first characteristic of a first location on the sample and wherein the second characteristic of the sample represents a second characteristic of a first location on the sample.154. The non-transitory computer readable medium of clause 153, wherein the first location on the sample is within a local area surrounding a second location, and wherein the second location is where a charged particle beam is focused on the surface of the sample.155. The non-transitory computer readable medium of clause 154, wherein the first location is less than or equal to 2 mm from the second location.156. The non-transitory computer readable medium of any one of clauses 133 to 155, wherein the charged particle beam apparatus is a scanning electron microscope.157. The non-transitory computer readable medium of any one of clauses 133 to 155, wherein the charged particle beam apparatus is a lithography apparatus.158. The charged particle beam system of any one of clauses 1 to 32, wherein the charged particle beam tool is a scanning electron microscope.159. The charged particle beam system of any one of clauses 1 to 32, wherein the charged particle beam tool is a lithography apparatus.160. The charged particle beam system of any one of clauses 33 to 64, wherein the charged particle beam tool is a scanning electron microscope.161. The charged particle beam system of any one of clauses 33 to 64, wherein the charged particle beam tool is a lithography apparatus.

[0084] It will be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in connection with various embodiments, other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

CLAIMS1. A charged particle beam system, comprising: a charged particle beam tool having circuitry configured to emit and focus a charged particle beam at a first location on a surface of a sample; an emitter module having circuitry configured to emit a first light beam and a second light beam to reflect off a second location on the surface of the sample, wherein the emitter module emits the first light beam after receiving a first signal and emits the second light beam after receiving a second signal; a detector module having circuitry configured to collect the first light beam to measure a first characteristic of the sample and to collect the second light beam to measure a second characteristic of the sample; and a controller communicatively connected to the emitter module and the detector module, wherein the controller is configured to determine the first signal and the second signal from an input signal and supply the first signal and the second signal to the emitter module.

2. The charged particle beam system of claim 1, wherein the second location on the surface of the sample is within a local area surrounding the first location.

3. The charged particle beam system of claim 1, wherein the first light beam has a wavelength different from a wavelength of the second light beam.

4. The charged particle beam system of claim 1, wherein the first characteristic of the sample is a tilt characteristic, and the second characteristic is a height characteristic.

5. The charged particle beam system of claim 1, wherein the input signal comprises a clock signal; the first signal comprises an electrical signal associated with a first edge of the clock signal; and the second signal comprises an electrical signal associated with a second edge of the clock signal.

6. The charged particle beam system of claim 1, wherein the emitter module comprises: a first emitter configured to emit the first light beam in response to receiving the first signal; a second emitter configured to emit the second light beam in response to receiving the second signal; anda first lens configured to deliver the first light beam and the second light beam to the second location on the sample.

7. The charged particle beam system of claim 6, wherein the first lens is configured to collimate the first light beam and to focus the second light beam.

8. The charged particle beam system of claim 1, wherein the detector module comprises: a detector; and a second lens configured to collect the first light beam and the second light beam reflected from the sample and deliver the first light beam and the second light beam to the detector.

9. The charged particle beam system of claim 8, wherein the second lens is configured to focus the first light beam and the second light beam to a surface of the detector.

10. The charged particle beam system of claim 8, wherein the second lens is configured to apply a chromatic focal power difference to the first light beam and the second light beam to focus the first light beam and the second light beam to the detector.

11. The charged particle beam system of claim 8, wherein the detector comprises one or more sections to monitor a change in intensity from the first light beam or the second light beam impacting the detector.

12. The charged particle beam system of claim 8, wherein the detector outputs a third signal.

13. The charged particle beam system of claim 12, wherein the third signal provides information representing a position of the first light beam or the second light beam impacting the detector.

14. The charged particle beam system of claim 13, wherein the third signal is used to calculate the first characteristic of the sample or the second characteristic of the sample.

15. A non-transitory computer readable medium comprising a set of instructions that is executable by one or more processors of a computing device to cause the computing device to perform operations for measuring a characteristic of a sample in a charged particle beam apparatus, the operations comprising:emitting a light beam from a light source for delivering the light beam to a surface of the sample using a first lens, wherein the light beam is reflected off the surface of the sample; focusing the light beam reflected off the surface of the sample onto a surface of a detector using a second lens to generate a first measurement; and determining the characteristic of the sample using the first measurement.

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