Distortion reduction in multibeam imaging systems

Abstract

The system may include a controller coupleable to an imaging subsystem that uses multiple particle beams. The imaging subsystem includes one or more control elements for manipulating the two or more particle beams, the control elements being adjustable by two or more control parameters. The controller may select values ​​for the two or more control parameters by iteratively performing steps until one or more completion conditions are met. For example, the controller may receive measurements of changes in distortion of the particle beam resulting from individual adjustments of the control parameters. The controller may further calculate values ​​of the control parameters that reduce distortion of the particle beam based on the changes in distortion resulting from the individual adjustments. The controller may also direct adjustments of the values ​​of the control parameters toward the calculated values.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to multiple particle beam imaging, and more particularly to reducing distortion in multiple particle beam imaging. [Background technology]

[0002] Typically, particle beam imaging systems generate images by illuminating a sample with one or more particle beams, such as, but not limited to, an electron beam. Multi-beam systems can generate parallel images of different regions of a sample by using simultaneous illumination of the sample with multiple particle beams. However, controlling distortions of multiple particle beams is difficult due to the number of beams and because the effects of modulation are typically coupled across multiple beams. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Application Publication No. 2019 / 0214222 [Patent Document 2] U.S. Patent No. 10,224,172 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, there is a need to develop systems and methods that address the above-mentioned shortcomings. [Means for solving the problem]

[0005] In accordance with one or more exemplary embodiments of the present disclosure, a system is disclosed. In one exemplary embodiment, the system includes a controller coupleable to an imaging subsystem using multiple particle beams, the imaging subsystem including one or more control elements for manipulating two or more particle beams, the one or more control elements being adjustable by two or more control parameters. In another exemplary embodiment, the controller iteratively receives measurements of changes in distortion of the two or more particle beams resulting from individual adjustments of the two or more control parameters, calculates values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments, and selects values ​​of the two or more control parameters by directing the adjustments of the values ​​of the two or more control parameters toward the calculated values.

[0006] In accordance with one or more exemplary embodiments of the present disclosure, a system is disclosed. In one exemplary embodiment, the system includes an imaging subsystem using multiple particle beams, the imaging subsystem including one or more control elements for manipulating two or more particle beams, the one or more control elements being adjustable by two or more control parameters. In another exemplary embodiment, the system includes a controller. In another exemplary embodiment, the controller iteratively receives measurements of changes in distortion of the two or more particle beams resulting from individual adjustments of the two or more control parameters, calculates values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments, and selects values ​​of the two or more control parameters by directing the adjustments of the values ​​of the two or more control parameters toward the calculated values.

[0007] According to one or more exemplary embodiments of the present disclosure, a method is disclosed. In one exemplary embodiment, the method includes directing two or more particle beams at a sample plane by an imaging system including at least one control element for manipulating the two or more particle beams, the one or more control elements being settable by two or more control parameters. In another exemplary embodiment, the method includes iteratively adjusting the two or more control parameters individually, measuring changes in distortion of the two or more particle beams resulting from the individual adjustments, calculating values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in distortion resulting from the individual adjustments, and adjusting the two or more control elements to the calculated values ​​to select values ​​of the two or more control parameters.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and do not necessarily restrict the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the general description, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0009] Many advantages of the present disclosure may be better understood by those skilled in the art by reference to the following drawings.

[0010] [Figure 1A] FIG. 1 is a block diagram of a multi-beam imaging system in accordance with one or more embodiments of the present disclosure. [Figure 1B] FIG. 1 is a conceptual diagram of an imaging subsystem in accordance with one or more embodiments of the present disclosure. [Figure 2] FIG. 1 is a top view of a sample plane showing a square distribution of a particle beam in accordance with one or more embodiments of the present disclosure. [Figure 3A] FIG. 1 is a flow diagram illustrating steps performed in a method for controlling distortion of multiple particle beams in accordance with one or more embodiments of the present disclosure. [Figure 3B] FIG. 1 is a flow diagram illustrating a series of steps for selecting values ​​for two or more control parameters in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Reference will now be made in detail to the subject matter of the present disclosure, as illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with reference to certain embodiments and certain features thereof. The embodiments shown are to be understood as illustrative and not restrictive. It will be apparent to those skilled in the art that various changes and modifications in form and detail can be made therein without departing from the spirit and scope of the present disclosure.

[0012] SUMMARY Embodiments of the present disclosure relate to systems and methods for controlling distortions of multiple particle beams in a multi-beam imaging system, where the distortions may be related to the positions and / or aberrations of two or more particle beams.

[0013] The particle beam may include any type of particle, including, but not limited to, electrons (e.g., e-beam, e-beam, etc.), ions, neutral particles, etc. Multi-beam imaging systems can simultaneously direct multiple particle beams at a sample plane, thereby facilitating parallel imaging of multiple locations of the sample at the sample plane. Such systems may further include various control elements for manipulating the particle beam, such as, but not limited to, lenses, rotators, magnifiers, or stigmators (e.g., astigmatism correctors). For example, the control elements can be used to form a desired distribution of the particle beam in the sample plane and / or control various characteristics of the particle beam (e.g., focal spot size, beam shape, etc.). The control elements may have one or more control parameters that can be used to configure the operation of the element and thus the properties of the particle beam. By way of example, the control parameters of a control element may include, but are not limited to, the position of the control element, the orientation of the control element (e.g., rotation, etc.), or the focusing power.

[0014] Typically, it is desirable to reduce, minimize, eliminate, or otherwise control distortions of particle beams, particularly at the sample plane. Such distortions may thus be related to aberrations of individual particle beams and / or deviations of particle beam positions from their designed positions at the sample plane.

[0015] However, reducing distortions of multiple particle beams simultaneously can present various challenges. For example, adjusting a control parameter (e.g., of a control element) can have a non-uniform effect on the particle beam. As one example, particle beams near the center of the distribution can have a different effect than particle beams near the edge of the distribution due to off-axis aberrations or other effects. As another example, a multi-beam imaging system can have multiple control parameters associated with one or more control elements, and the effects of at least some of the control parameter adjustments can be coupled. Additionally, as the number of particle beams in a system increases, the complexity and computational requirements of the system also increase. In a general sense, a multi-beam imaging system can include any number of beams, including, but not limited to, tens or hundreds of beams.

[0016] Furthermore, it is believed that simultaneous reduction of distortion in multiple particle beams can be effectively achieved through linear predictive modeling of the effects of individual control parameter adjustments. For example, distortion control can be achieved by individually adjusting two or more control parameters affecting a particle beam, measuring changes in distortion in the two or more particle beams resulting from the individual adjustments, and calculating values ​​of the two or more control parameters that reduce distortion in the two or more particle beams based on the changes in distortion resulting from the individual adjustments. These steps may be repeated (e.g., iterated) until one or more completion conditions (e.g., an absolute distortion threshold, a minimum change between calculated values ​​in successive iterations, a maximum number of iterations, etc.) are met.

[0017] Various techniques can be used to calculate the control parameters that reduce distortion in any iteration. In embodiments, the distortion of each particle beam is considered to change linearly with each control parameter adjustment, and thus the measured change in distortion in response to a control parameter adjustment corresponds to a proportionality constant in the linear preview model. A minimization technique can then be applied to the linear preview model to determine values ​​of the control parameters that can reduce distortion across the set of particle beams. In this manner, the minimization technique can identify a local or absolute minimum of the linear preview model, which may correspond to a control parameter value that provides reduced distortion relative to its current value. Iterations of this process result in convergence on control parameter values ​​that satisfy completion conditions for a particular application.

[0018] As used herein, the terms “minimize,” “minimization,” “optimize,” and “optimize” refer to determining an acceptable value from a set of alternatives. It is not necessary that such minimization or optimization produce a single “best” result. Instead, any acceptable result within selected performance criteria (e.g., tolerances) is within the spirit and scope of the present disclosure. For example, a linear preview model described herein may relate adjustments to various control parameters of a multi-beam imaging system to distortions of a set of particle beams. Thus, application of a minimization technique to such a model may identify control parameter values ​​that at least reduce distortions, and in some cases may identify local or absolute minima. In a general sense, any type of minimization or optimization technique may be used, including, but not limited to, iterative or heuristic techniques.

[0019] It is believed that the linear preview modeling-based distortion control disclosed herein can facilitate simultaneous and efficient minimization of distortions in a set of particle beams in a multi-beam imaging system, providing improved accuracy over techniques in which each control parameter is optimized (e.g., minimized) in turn. In particular, methods that find the minimum of a multidimensional function by iteratively minimizing each parameter in turn are generally inefficient. As an example, in the case of a long, narrow minimum whose major axes do not coincide with the parameter axes, each parameter minimization may proceed across the valley rather than along the valley. Thus, the disclosed technique can enable better distortion control with greater accuracy for a given time or number of iterations compared to alternative techniques.

[0020] Additional efficiency improvements can be achieved by first performing distortion correction on a subset of particle beams (e.g., coarse distortion correction) and then performing distortion control on the entire set of particle beams (e.g., fine distortion correction). In this case, the coarse distortion correction can reduce the complexity of the linear preview model, reducing the required computational time and resources. The fine distortion correction can then effectively provide fine correction for all beams.

[0021] 1A-3B, systems and methods for distortion correction of multiple particle beams will be described in more detail, in accordance with one or more embodiments of the present disclosure.

[0022] FIG. 1A is a block diagram of a multi-beam imaging system 100 in accordance with one or more embodiments of the present disclosure.

[0023] In an embodiment, the multi-beam imaging system 100 includes an imaging subsystem 102 that illuminates a sample 104 (or, more generally, a sample plane 106) with two or more particle beams 108, and at least one detector 110 that collects sample radiation 112 from the sample 104 in response to the illumination.

[0024] In an embodiment, the imaging subsystem 102 includes one or more control elements 114 suitable for manipulating the particle beam 108. For example, the control elements 114 may control or otherwise influence parameters of the particle beam 108, such as, but not limited to, the beam profile, spot size, or aberrations. As another example, the control elements 114 may control or otherwise influence the distribution of the particle beam 108 at the sample plane 106 (e.g., the relative position of the particle beam 108, the orientation of the pattern of the particle beam 108, etc.).

[0025] The imaging subsystem 102 may shape any distribution of the particle beam 108 at the sample plane 106. As a non-limiting illustrative example, Figure 2 is a top view of the sample plane 106 showing a square distribution of the particle beam 108, in accordance with one or more embodiments of the present disclosure.

[0026] In an embodiment, the imaging subsystem 102 further includes a stage 116 for securing and / or positioning the sample 104 in the sample plane 106 .

[0027] In embodiments, the multi-beam imaging system 100 further includes a controller communicatively coupled to any of the components. In some embodiments, the controller 118 includes one or more processors 120. For example, the one or more processors 120 may be configured to execute a series of program instructions held in the memory 122 or a memory device. The one or more processors 120 of the controller 118 may include any processing element known in the art. In this sense, the one or more processors 120 may include any microprocessor-based device configured to execute algorithms and / or instructions.

[0028] The one or more processors 120 of the controller 118 may include any processor or processing element known in the art. For purposes of this disclosure, the term “processor” or “processing element” may be broadly defined to include any device having one or more processing or logic elements (e.g., one or more microprocessor devices, one or more application specific integrated circuit (ASIC) devices, one or more field programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, the one or more processors 120 may include any device configured to execute algorithms and / or instructions (e.g., program instructions stored in a memory). In some embodiments, the one or more processors 120 may be embodied as a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, a networked computer, or any other computer system configured to execute programs configured to operate or operate with the multi-beam imaging system 100 described in this disclosure. Also, different subsystems of the multi-beam imaging system 100 may include processors or logic elements suitable for performing at least some of the steps described in this disclosure. Accordingly, the above description should not be construed as a limitation on the embodiments of the present disclosure, but merely as examples. Furthermore, the steps described in this disclosure may be performed by a single controller, or alternatively, by multiple controllers. The controller 118 may also include one or more controllers housed in a common housing or one or more controllers housed in multiple housings. This allows a controller or combination of controllers to be packaged separately as a module suitable for integration into the multi-beam imaging system 100.

[0029] The memory 122 may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 120. For example, the memory 122 may include a non-transitory memory medium. As other examples, the memory 122 may include, but is not limited to, read-only memory (ROM), random access memory (RAM), magnetic or optical memory devices (e.g., disks), magnetic tape, solid-state drives, etc. Furthermore, it should be noted that the memory 122 may be housed in a common controller housing with one or more processors 120. In some embodiments, the memory 122 may be located in a remote location relative to the physical location of one or more processors 120 and the controller 118. For example, one or more processors 120 of the controller 118 may access a remote memory (e.g., a server) accessible over a network (e.g., the Internet, an intranet, etc.).

[0030] Controller 118 may send data (e.g., via control signals) to and / or receive data from any of the components or subsystems of multi-beam imaging system 100, such as, but not limited to, detector 110 or control element 114. Controller 118 may also be configured to perform any of the various processing steps described in this disclosure.

[0031] In an embodiment, the multi-beam imaging system 100 includes a user interface 124 communicatively coupled to the controller 118. In one embodiment, the user interface 124 may include, but is not limited to, one or more desktops, laptops, tablets, etc. In another embodiment, the user interface 124 includes a display device used to display data from the multi-beam imaging system 100 to a user. The display device of the user interface 124 may include any display device known in the art. For example, the display device may include, but is not limited to, a liquid crystal display (LED), an organic light-emitting diode (OLED)-based display, or a CRT display. One skilled in the art will recognize that any display device that can be integrated with the user interface 124 is suitable for practicing the present disclosure. In another embodiment, a user can use a user input device of the user interface 124 to input selections and / or commands in response to data displayed to the user.

[0032] FIG. 1B is a conceptual diagram of an imaging subsystem 102 in accordance with one or more embodiments of the present disclosure.

[0033] The imaging subsystem 102 may include any combination of elements suitable for generating two or more particle beams 108, which may include any type of particle, such as, but not limited to, electrons, ions, or neutral particles.

[0034] In an embodiment, the imaging subsystem 102 includes a particle source 126 that generates particle radiation 128 and a gun lens 130 that collects, collimates, and / or focuses the particle radiation 128. The particle source 126 may include any type of gun or emitter known in the art, including, but not limited to, a thermal field emission (TFE) source. The imaging subsystem 102 may further include one or more components that separate the particle radiation 128 into multiple particle beams 108, such as, but not limited to, a microaperture array 132 or a microlens array 134. The imaging subsystem 102 may also include a beam-limiting aperture 136 to control the spatial extent of the particle radiation 128 and contribute to generating the particle beams 108.

[0035] 1B also conceptually illustrates various control elements 114 for manipulating the particle beam 108 and / or directing the particle beam 108 to the sample plane 106 for interaction with the sample 104. For example, the control elements 114 may include one or more beam shape correctors 138, such as, but not limited to, stigmators or other aberration control elements. As an example, the beam shape corrector 138 may include one or more multipole correctors (e.g., multipole aberration correctors), such as, but not limited to, a quadrupole corrector or a hexapole corrector. As another example, the beam shape corrector 138 may include a corrector array (e.g., a stigmator array). As another example, the control elements 114 may include one or more lenses 140, such as, but not limited to, one or more transfer lenses or objective lenses. Lens 140 may include any type of element suitable for manipulating the focus of at least one particle beam 108, such as, but not limited to, an electrostatic lens, a magnetic lens, a mono-power lens, or a bi-power lens. Thus, lens 140 may control the focal spot size of each of particle beams 108 and may also control the magnification of the pattern of particle beams 108 (e.g., the spacing between particle beams 108) provided by microaperture array 132 and / or microlens array 134. Additionally, although not explicitly shown, control element 114 may include one or more rotators that control the orientation (e.g., rotation angle) of the pattern of particle beams 108 at sample plane 106.

[0036] The operation of the control elements 114, singly or in combination, can be adjusted through one or more control parameters, which can be considered settings of the imaging subsystem 102. A control parameter may include any type of setting that is adjustable (e.g., by a user). For example, a control parameter may include the position of the control element 114 in any direction, such as along the illumination axis 142 or in a plane perpendicular to the illumination axis 142. As another example, a control parameter may include the focusing power of the control element 114 (e.g., any of the lenses 140). As another example, a control parameter may include the current applied to and / or voltage applied to the control element 114, which affect the magnitude of the effect on the particle beam. As one example, adjusting the current and / or voltage may affect the focusing power of the lens 140, the amount of aberration correction by the stigmator, etc.

[0037] In an embodiment, the imaging subsystem 102 is configured to simultaneously and independently scan each of the particle beams 108 across the sample plane 106 using any suitable element, such as, but not limited to, a microlens array 134 or other element in the path of the individual particle beams 108.

[0038] In an embodiment, the imaging subsystem 102 includes at least one detector 110, which can be used for a variety of purposes. For example, the detector 110 can be used to capture sample radiation 112 in response to illumination by the particle beams 108. Signals provided by the detector 110 can then be used (e.g., by the controller 118) to generate an image. The detector 110 can then generate independent signals associated with the sample radiation 112 from locations illuminated by each of the particle beams 108. As another example, the detector 110 can be used to measure distortion of the particle beams 108 or to measure changes in distortion in response to adjustments to control parameters.

[0039] The detector 110 may include any type of sensor known in the art. For example, the detector 110 may include a particle sensor (e.g., a secondary electron sensor, a backscattered electron sensor, etc.). As another example, the detector 110 may include a photon sensor (e.g., a light detector, an X-ray detector, a scintillation element coupled to a photomultiplier tube (PMT) detector, etc.) for detecting photons from the sample surface. By way of example, FIG. 1B illustrates the detector 110 configured to capture secondary electrons emitted from the sample 104. Note that for purposes of illustration, FIG. 1B depicts the sample radiation 112 as a straight, dotted line. However, it should be understood that the sample radiation 112 may reach the detector 110 via any path. For example, the sample radiation 112 may be collected by a lens 140 and directed to the detector 110.

[0040] 3A is a flow diagram illustrating steps performed in a method 300 for controlling distortion of multiple particle beams 108, in accordance with one or more embodiments of the present disclosure. The embodiments and implementation techniques described above with respect to the multi-beam imaging system 100 should be construed as extending to the method 300. However, it should also be noted that the method 300 is not limited to the structure of the multi-beam imaging system 100.

[0041] In an embodiment, the method 300 includes directing 302 two or more particle beams 108 to the sample plane 106 by an imaging system including at least one or more control elements 114, where the one or more control elements 114 are configurable by two or more control parameters. As described with respect to the multi-beam imaging system 100, and without limiting the method 300, the control parameters may include any type of adjustable setting, such as, but not limited to, the position of the control element 114 in any direction, the focusing power of the control element 114, or the current and / or voltage applied to the control element 114.

[0042] In an embodiment, the method 300 includes a step 304 of selecting values ​​for two or more control parameters. Figure 3B is a flow diagram illustrating a series of steps 306 to 310 (e.g., substeps) for selecting values ​​for two or more control parameters in accordance with one or more embodiments of the present disclosure. For example, the steps of Figure 3B may be performed iteratively until the values ​​of the two or more control parameters converge.

[0043] In an embodiment, step 304 of method 300 includes step 306 of individually adjusting two or more control parameters. In an embodiment, method 300 includes step 308 of measuring changes in distortion of two or more particle beams 108 resulting from the individual adjustments. In an embodiment, method 300 includes step 310 of calculating values ​​of two or more control parameters that reduce distortion of two or more particle beams 108 based on the changes in distortion resulting from the individual adjustments. In an embodiment, method 300 includes step 312 of adjusting two or more parameters to the calculated values.

[0044] The first iteration of steps 306 to 312 may begin with initial values ​​for two or more control parameters, while subsequent iterations may begin with values ​​calculated in step 310 and set in step 306 of the previous iteration.

[0045] In each iteration, steps 306 and 308 may be repeated for different control parameters. For example, a first control parameter may be adjusted (step 306) and the associated change in distortion of particle beam 108 may be measured (step 308). The first control parameter may then be returned to its pre-adjustment value. This process may then be repeated for a second control parameter, a third control parameter, and so on.

[0046] The distortion measured in step 308 may include any type of variation in either the particle beam 108 from design or ideal conditions. For example, the distortion may be related to any aberration of the particle beam 108 (e.g., defocus, astigmatism, beam shape error, etc.).

[0047] As another example, distortion may relate to a misalignment of any of the particle beams 108 within the sample plane 106, which may be measured in absolute terms (e.g., relative to a fixed reference) or relative terms (e.g., relative positions of two or more particle beams 108 relative to one another). In one example considering the particle beam 108 pattern of FIG. 2, distortion may include an absolute measurement of the position error of a particular particle beam 108a. As another example, distortion may include a relative measurement of the position error of a particular particle beam 108a relative to one or more neighboring particle beams 108. For example, such relative position error may be determined by comparing multiple distances 202 between the particle beam 108a and multiple surrounding particle beams 108.

[0048] As another example, the distortion may be related to the magnification and / or rotation error of the pattern of particle beam 108 (e.g., as defined by microaperture array 132 and / or microlens array 134 shown in FIG. 1B). As another example, the distortion may include the magnification and / or rotation error of the pattern shown throughout FIG.

[0049] It is believed that measurements of such individual adjustments of the control parameters can provide a predictive model of distortion responsive to adjustments of the control parameters (e.g., a multivariate predictive model of distortion). Furthermore, such a predictive model may be linear (or may be considered linear) if the adjustments to the control parameters are sufficiently small. In this approach, the measurements generated in step 308 may be related to a proportionality constant in a linear model.

[0050] In an embodiment, calculating 310 values ​​of two or more control parameters that reduce distortion for two or more particle beams 108 based on changes in distortion resulting from their individual adjustments is performed by generating a predictive model of the distortion responsive to the control parameter adjustments and applying a minimization technique to calculate values ​​of the control parameters that reduce the distortion. Any suitable minimization technique (or more generally, optimization technique) may be used. For example, iterative techniques such as, but not limited to, interpolation, pattern search, direct search, descent, random search, gradient evaluation, perturbation, or Hessian-based techniques may be used. As another example, heuristic techniques may be used that are not guaranteed to converge.

[0051] Step 312 of adjusting the two or more parameters to the calculated values ​​can be performed using any suitable technique. In embodiments, step 312 may include generating a control signal (e.g., via controller 118) that directly adjusts control element 114, if necessary. In this manner, distortion control may be automated. In embodiments, step 312 may include prompting a user (e.g., via user interface 124 or any suitable technique) to adjust control element 114, if necessary.

[0052] The initial values ​​of the two or more control parameters associated with the first iteration of steps 306 through 312 may be selected using any suitable technique. For example, the initial values ​​of the control parameters may be arbitrary values. As another example, the initial values ​​of the control parameters may be selected by performing initial adjustments that reduce distortion of the particle beam 108. This initial adjustment may be performed by a user, but is not limited to this. Providing initial adjustments to the control parameters to provide at least an initial alignment may reduce the number of iterations of steps 306 through 312 required to reach a converged value and / or prevent runaway conditions in which the values ​​of the control parameters do not converge through the iterations of steps 306 through 312.

[0053] Steps 306 through 312 may be repeated any number of times as part of step 304. In an embodiment, steps 306 through 312 are repeated until one or more completion conditions are met. For example, the completion condition may include a distortion threshold (e.g., an absolute threshold). In this manner, if the measured distortion of particle beam 108 is within an acceptable distortion threshold after an iteration, no further iterations are necessary. As another example, the completion condition may include a minimum difference between calculated values ​​for two consecutive iterations. As another example, the completion condition may include a maximum number of iterations.

[0054] Referring generally to Figures 3A-3B, method 300 may be performed multiple times under different conditions.

[0055] In embodiments, method 300 may be performed with a first set of conditions to provide coarse distortion correction, followed by a second set of conditions to provide fine distortion correction. As one example, the first set of conditions may include adjustment of a subset of control parameters of interest and associated measurements (e.g., steps 306 and 308), whereas the second set of conditions may include the complete set of control parameters of interest. As another example, the first set of conditions may include a more lenient completion condition (e.g., with respect to step 304) than the second set of conditions. It should be understood that such techniques may go beyond coarse and fine distortion correction and generally include operating method 300 any number of times under any conditions.

[0056] In embodiments, the selection of control parameters in different iterations of step 304 may have different conditions. For example, one or more iterations may include adjustment and associated measurements of a subset of control parameters of interest (e.g., steps 306 and 308), while one or more additional iterations may include the complete set of control parameters of interest.

[0057] The subject matter disclosed herein may at times depict different components contained within or connected to other components. It should be understood that such depicted structures are for illustrative purposes only, and that other structures may be embodied that achieve the same functionality. In a conceptual sense, any arrangement of components that achieve the same functionality is substantially "associated" to achieve the desired functionality. Thus, if two components combine to achieve a particular function, these components can be viewed as "associated" with each other to achieve the desired functionality, regardless of structure or intermediate components. Similarly, any two associated components can be viewed as "connected" or "coupled" to each other to achieve the desired functionality, and any two components that can be associated can be viewed as "couplable" to each other to achieve the desired functionality. Specific examples of "couplable" include, but are not limited to, physically interactable and / or physically interacting components, wirelessly interactable and / or wirelessly interacting components, and / or logically interactable and / or logically interacting components.

[0058] The present disclosure and many of its attendant advantages will be understood from the foregoing description. It will also be apparent that various changes can be made in the form, construction, and arrangement of the elements without departing from the disclosed subject matter or sacrificing its material advantages. The forms set forth in this disclosure are exemplary only, and it is intended that the following claims encompass and include all such modifications. It will further be understood that the invention is defined by the appended claims.

Claims

1. 1. A system comprising: a controller configured to be coupled to an imaging subsystem that uses multiple particle beams, the imaging subsystem including one or more control elements for manipulating two or more particle beams, the one or more control elements being adjustable by two or more control parameters; The controller includes one or more processors configured to execute program instructions that, when executed, perform at least the following steps: receiving measurements of changes in distortion of the two or more particle beams resulting from individual adjustment of the two or more control parameters, the distortions being related to at least one of positions or aberrations of the two or more particle beams; calculating values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments; adjusting the values ​​of the two or more control parameters toward the calculated values; repeatedly executing the method until one or more completion conditions are met to select values ​​for the two or more control parameters.

2. 10. The system of claim 1, The system, wherein at least one control element of the one or more control elements includes at least one of a lens, a stigmator, a rotator, or a magnifier.

3. 10. The system of claim 1, The system wherein at least one control element of the one or more control elements includes a multipole corrector.

4. 4. The system of claim 3, The system, wherein the multipole corrector comprises at least one of a quadrupole corrector or a hexapole corrector.

5. 10. The system of claim 1, The system, wherein the two or more control parameters include at least one of a voltage applied to any of the one or more control elements or a current passed through any of the one or more control elements.

6. 10. The system of claim 1, The system wherein the two or more control parameters include a position of any of the one or more control elements.

7. 10. The system of claim 1, calculating the values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments; calculating, using at least one of a minimization technique or an optimization technique, values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments.

8. 10. The system of claim 1, directing the adjustment of the values ​​of the two or more control parameters toward the calculated values; generating control signals to adjust the values ​​of the two or more control parameters to the calculated values.

9. 10. The system of claim 1, directing the adjustment of the values ​​of the two or more control parameters toward the calculated values; prompting a user to adjust the values ​​of the two or more control parameters to the calculated values.

10. 10. The system of claim 1, further comprising: one or more detectors that measure radiation from the sample at the sample plane in response to the two or more particle beams; The one or more processors, when the program instructions are executed, receiving data relating to the sample at the sample plane after selecting the values ​​of the two or more control parameters; The system is configured to generate one or more images based on the received data.

11. 10. The system of claim 1, The system, wherein the one or more completion conditions include at least one of a distortion threshold, a minimum difference between values ​​calculated in two consecutive iterations, or a maximum number of iterations.

12. 1. A system comprising: an imaging subsystem using multiple particle beams, the imaging subsystem including one or more control elements for manipulating two or more particle beams, the one or more control elements being adjustable by two or more control parameters; a controller configured to be coupled to the imaging subsystem; The controller includes one or more processors configured to execute program instructions that, when executed, perform at least the following steps: individually adjusting the two or more control parameters and measuring a change in distortion of the two or more particle beams resulting from the individual adjustments, the distortion being related to at least one of a position or an aberration of the two or more particle beams; calculating values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments; adjusting the values ​​of the two or more control parameters toward the calculated values; repeatedly executing the method until one or more completion conditions are met, thereby selecting values ​​for the two or more control parameters.

13. 13. The system of claim 12, The system, wherein at least one control element of the one or more control elements includes at least one of a lens, a stigmator, a rotator, or a magnifier.

14. 13. The system of claim 12, The system wherein at least one control element of the one or more control elements includes a multipole corrector.

15. 15. The system of claim 14, The system, wherein the multipole corrector comprises at least one of a quadrupole corrector or a hexapole corrector.

16. 13. The system of claim 12, The system, wherein the two or more control parameters include at least one of a voltage applied to any of the one or more control elements or a current passed through any of the one or more control elements.

17. 13. The system of claim 12, The system wherein the two or more control parameters include a position of any of the one or more control elements.

18. 13. The system of claim 12, calculating the values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments; calculating, using at least one of a minimization technique or an optimization technique, values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments.

19. 13. The system of claim 12, directing the adjustment of the values ​​of the two or more control parameters toward the calculated values; generating control signals to adjust the values ​​of the two or more control parameters to the calculated values.

20. 13. The system of claim 12, directing the adjustment of the values ​​of the two or more control parameters toward the calculated values; prompting a user to adjust the values ​​of the two or more control parameters to the calculated values.

21. 13. The system of claim 12, the imaging subsystem further comprising: one or more detectors that measure radiation from the sample at the sample plane in response to the two or more particle beams; The one or more processors, when the program instructions are executed, receiving data relating to the sample at the sample plane after selecting the values ​​of the two or more control parameters; The system is configured to generate one or more images based on the received data.

22. 13. The system of claim 12, The system, wherein the one or more completion conditions include at least one of a distortion threshold, a minimum difference between values ​​calculated in two consecutive iterations, or a maximum number of iterations.

23. 1. A method comprising: directing two or more particle beams at a sample plane using an imaging system including one or more control elements for manipulating the two or more particle beams, the one or more control elements being configurable by two or more control parameters; selecting values ​​for said two or more control parameters, said selection comprising at least the following steps: individually adjusting the two or more control parameters and measuring a change in distortion of the two or more particle beams resulting from the individual adjustments, the distortion being related to at least one of a position or an aberration of the two or more particle beams; calculating values ​​of the two or more control parameters that reduce the distortion of the two or more particle beams based on the changes in the distortion resulting from the individual adjustments; adjusting the two or more control elements to the calculated values; repeatedly performing the above steps until one or more completion conditions are met to select values ​​for the two or more control parameters; A method comprising:

Images