Fib and sem resolution enhancement using asymmetric probe deconvolution

Abstract

To solve problems with the prior art.SOLUTION: Elongated or other non-circular charged-particle beams (CPBs) are used to produce substrate images that can be processed, e.g., by deconvolution, to produce a final image. In some cases, first and second images associated with an asymmetric CPB beam aligned along parallel axes are deconvolved and then combined to produce the final image, or combined and then deconvolved to produce the final image. Milling or other processing can be performed by aligning an asymmetric CPB with respect to a CPB scan or processing direction.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present disclosure relates to the use of asymmetric beams in charged particle beam systems. [Background technology]

[0002] Resolution is an important performance metric for Charged-Particle Beam (CPB) optical systems, such as electron microscopes and Focused Ion Beam (FIB) milling systems. Conventional approaches require reducing CPB optical column lens aberrations or adding aberration correction elements. These approaches can be difficult to implement and require technical personnel. Even if successfully implemented, further improvements in resolution are still desirable. Therefore, improved CPB methods and apparatus that can improve CPB instrument resolution are desired. Summary of the Invention

[0003] Disclosed herein are methods, apparatus, and systems that can produce high resolution images and improve cutting placement in CPB imaging when used in combination with asymmetric beam CPB milling processes. In contrast to conventional methods that focus on providing aberration correction and symmetric CPB, the present disclosure relates to the use of one or more asymmetric CPB shapes, compensating the image obtained with the asymmetric beam shape to improve resolution, and processing a substrate using the asymmetric CPB shape.

[0004] The foregoing and other features and advantages of the disclosed technology will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0005] [Figure 1A] 1 illustrates an exemplary imaging or method using an asymmetric charged particle beam (CPB) geometry. [Figure 1A1]Images obtained using a circular CPB geometry and an elongated CPB geometry, respectively. [Figure 1A2] Images obtained using a circular CPB geometry and an elongated CPB geometry, respectively. [Figure 1A3] Images obtained with an asymmetric CPB configuration. [Figure 1A4] This is an image obtained by Wiener deconvolution of the image in Figure 1A3. [Figure 1A5] Images were obtained with an asymmetric CPB geometry using an ion beam current of 2.3 nA Ga and a horizontal field of view of 20 μm. [Figure 1A6] This is the image obtained by Richardson-Lucy deconvolution of the image in Figure 1A5. [Figure 1B] 1 shows a representative imaging method using asymmetric charged particle beams with different orientations, where the images are combined before deconvolution. [Figure 1C] 1 shows a representative imaging method using asymmetric charged particle beams with different orientations, where the images are combined after deconvolution. [Figure 2A] 1 illustrates a typical asymmetric beam shape: 1. An elongated shape, such as an oval or ellipse, with minimum and maximum beam dimensions along orthogonal axes. [Figure 2B] 1A-1C show representative asymmetric beam shapes, in which the minimum and maximum beam dimensions are along non-orthogonal axes. [Diagram 3] A representative dual beam CPB system is shown that provides asymmetric CPB and can deconvolve images obtained using such a CPB. [Figure 4] An exemplary processor-based control system is presented for use in controlling the acquisition and deconvolving of images obtained using the asymmetric CPB geometry, and the processing of a workpiece using the asymmetric CPB geometry. [Diagram 5]1 illustrates the orientation of an asymmetric CPB relative to a workpiece for substrate processing such as focused ion beam (FIB) milling. [Figure 6] 1 shows a workpiece provided with a predetermined pattern area that can be used for deconvolution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Disclosed herein are methods and systems that use an asymmetric charged particle beam (CPB) spot in combination with deconvolution to improve image resolution, typically producing higher resolution than would be achieved with a circular beam using the same optics. In some applications, asymmetric CPB can provide increased sharpness for FIB milling processes. Extending such improvements to imaging is possible through the combination of probe deconvolution and imaging processing.

[0007] (General terms and considerations) As used herein, optical column generally refers to CPB lenses, deflectors, stigmators, and other CPB optical elements used for imaging or beam shaping. In dual beam CPB instruments, such as ion beam / electron beam systems, some or all of the optical column elements may be used with both beams, or some or all of the optical column elements may be different. Exemplary CPB systems that include the disclosed approach include dual beam systems, including an ion beam system for ion beam milling and a SEM (Scanning Electron Microscope) system for evaluating samples, standalone SEM or ion beam systems, and STEMs (Scanning Transmission Electron Microscopes).

[0008] As used herein, an image refers to imaging data stored in various formats, such as JPG, TIFF, BMP, or other formats, or a display view of a specimen as presented on a display device or other visual display. For ease of explanation in the following examples, representation as a one-dimensional array or a two-dimensional array is generally used.

[0009] A probe beam typically refers to a CPB directed at a specimen for either or both of imaging and processing, such as CPB milling. As used herein, a CPB shape at a workpiece corresponds to the beam intensity as a function of position at the workpiece or other substrate, i.e., I(x,y), where x, y are coordinates substantially orthogonal to the CPB propagation direction. Beam intensity typically refers to beam current / area, but in the applications disclosed herein, beam intensity may refer to dose / area. In the embodiments described herein, the CPB spot is generally asymmetric. As used herein, a CPB shape is referred to as asymmetric if it is not substantially circular, such that the ratio of the maximum CPB size along a first axis to the minimum CPB size along a second axis different from the first axis is 1.25, 1.5, 1.75, 2.0, 2.5, 3.0, 4, 5, or more. In an exemplary embodiment, two asymmetric CPB shapes (elongated shapes) are used, with maximum and minimum sizes along orthogonal directions. Although the embodiments are generally presented with reference to one or more elongated CPB shapes, such as elliptical shapes, the disclosed approach may be applied to any CPB shape. It will be understood that the asymmetric CPBs used herein may exhibit various rotational symmetries.

[0010] As used in this application and the claims, the singular forms "a," "an," and "the" include the plural forms unless the content clearly dictates otherwise. Furthermore, the term "includes" means "comprises." Furthermore, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0011] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with each other. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require that any one or more particular advantages exist or problems be solved. Any theory of operation is provided for ease of explanation, but the disclosed systems, methods, and devices are not limited to such theory of operation.

[0012] Although some operations of the disclosed methods are described in a particular sequential order for convenient presentation, it should be understood that this style of description encompasses reordering unless a particular ordering is required by specific language set forth below. For example, operations described in sequence may in some cases be reordered or performed simultaneously. Moreover, for the sake of simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and apparatuses may be used in conjunction with other systems, methods, and apparatuses. Furthermore, the description may use terms such as "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular implementation and are readily discernible by those of ordinary skill in the art.

[0013] In some examples, values, procedures, or devices are referred to as "lowest," "best," "minimum," etc. Such descriptions are intended to indicate that a selection may be made from among many functional alternatives used, but it will be understood that such a selection is not necessarily better than, less than, or otherwise preferred to other selections.

[0014] The examples are described with reference to orientations indicated as "above," "below," "upper," "lower," etc. These terms are used for convenient description only and do not imply a particular spatial orientation.

[0015] Various techniques for deconvolution are available, including, for example, Wiener deconvolution, Richardson-Lucy deconvolution, maximum likelihood deconvolution, deep learning deconvolution, or other computer vision approaches. Deconvolution may be blind or use known CPB shapes. As described below, imaging processing may be used to correct or compensate for the CPB shape to produce higher resolution imaging. A single imaging or multiple imaging with different CPB orientations may be used for this correction.

[0016] (Example 1. Asymmetric Beam Imaging) Referring to FIG. 1A, an exemplary method 100 includes selecting a beam shaping method at 102. Exemplary examples of beam shaping include beam shaping with an asymmetric aperture, anisotropic beam expansion, introduction of aberrations based on tuning of the optical column, and disabling aberration compensation to provide an asymmetric CPB. At 104, a CPB having an asymmetric shape is generated using the selected method, and the asymmetric CPB is directed to a sample or workpiece. Based on the illumination with the asymmetric beam spot, an image of the workpiece is acquired at 105, for example, by SEM or STEM (in the case of electron beams), or by similar imaging approaches using other CPBs, such as ion beams. At 106, a deconvolution method is selected for the imaging process. At 108, it is determined whether the CPB shape should be measured or otherwise estimated for use in the deconvolution. In some cases, the CPB shape is known or can be derived, for example, from characteristics of the CPB optical column and / or characteristics of the voltages and currents applied to the optical column. In this case, the CPB shape may be retrieved from memory or calculated at 110. Alternatively, the CPB shape may be measured at 112. Using the CPB shape, the acquired image is deconvolved at 114 and a reconstructed image is obtained at 116. In some embodiments, the workpiece is processed at 118. Processing may be accomplished with the asymmetric CPB appropriately aligned based on its different extents in different directions.

[0017] 1A1-1A2 show images obtained using a symmetric CPB (circular beam shape) (FIG. 1A1) and an elongated asymmetric CPB (FIG. 1A2). The image in FIG. 1A2 is clearer than the image in FIG. 1A1 with comparable currents. The image in FIG. 1A2 can be further enhanced by deconvolution. These images are graphite images, obtained with a horizontal field of view of 5 μm and a beam current of 2.5 nA generated by a Liquid Metal Ion Source (LMIS) in the FIB instrument.

[0018] The original (elongated beam) images are shown in Figures 1A3 and 1A5, and the corresponding deconvolved images are shown in Figures 1A4 and 1A6, respectively, where the Wiener deconvolution method (Figure 1A4) and the Richardson-Lucy deconvolution method (Figure 1A6) are used.

[0019] Example 2. Asymmetric beams and two-dimensional deconvolution 1B, an exemplary method 130 includes acquiring a first image having a first asymmetric CPB shape at 132 and acquiring a second image having a second asymmetric CPB shape at 134. In this example, the first asymmetric CPB shape and the second asymmetric CPB shape are selected to be orthogonal. The first image and the second image are combined at 136. A deconvolution method is selected at 138 and a two-dimensional deconvolution is applied at 140. The combined image can be deconvolved in a single two-dimensional deconvolution using orthogonal CPB shapes, where the one-dimensional deconvolution is selected to be appropriate for the first image and the second image independently. The reconstructed image produced by the two-dimensional deconvolution is stored at 142.

[0020] (Example 3. Asymmetric beam imaging with multiple CPB shapes) 1C , an imaging method 150 includes acquiring a first image having a first asymmetric CPB shape 151 at 152 and acquiring a second image having a second asymmetric CPB shape 153 at 154. The first and second images are deconvolved at 156, 158 based on the first and second asymmetric CPB shapes, respectively, to generate a first deconvolved image at 160 and a second deconvolved image at 162. The deconvolved images are combined at 164 to generate a reconstructed image at 164.

[0021] Although FIG. 1C shows the use of two CPB shapes 151, 153 elongated along orthogonal axes, multiple CPB shapes may be used in any orientation. Typically, deconvolution is applied to enhance imaging based on the longer dimension of the asymmetric beam shape, but deconvolution may be applied to enhance imaging in two directions as well. With asymmetric CPB, workpiece processing typically requires alignment of the beam asymmetry to the workpiece. For example, when milling a groove, the longer dimension of the asymmetric CPB can be aligned to the groove direction to obtain a groove width based on the CPB shape in the shorter dimension.

[0022] Method 100 uses a measurement of the asymmetric beam shape in the deconvolution, while methods 130, 150 of Figures 1B-1C do not show the use of this beam shape. In any of the above examples, the deconvolution can be based on a beam shape corresponding to a known or estimated Point Spread Function (PSF), or based on so-called "blind" deconvolution that uses limited or no data on the PSF associated with the asymmetric beam. These blind methods can be iterative (e.g., maximum a posteriori probability or expectation maximization approaches) or non-iterative. In some of these approaches, an estimate of the PSF is useful, but not required. When using two-dimensional deconvolution based on the sum of images obtained with orthogonal elongated beams, it is assumed that the PSFs are separable, i.e., operated independently along the relevant elongated beam axes.

[0023] (Example 4. Representative beam shapes) Referring to Figure 2, a representative beam shape 200 at the workpiece is shown with respect to an XY coordinate system aligned with the longest and shortest dimensions of the beam shape 200. Ellipses 203-205 correspond to beam intensities (current / area) of 75%, 50%, and 25% of the maximum intensity at the beam center. For convenience, the beam width is defined as the full width to 25% of the maximum, shown as Dx and Dy in Figure 2. Other values ​​such as 50%, full width to 33%, or half width may be selected. 1 / e, 1e 2 where e is Euler's number. Beam shapes associated with the elongated beams shown in Figure 2 are referred to herein as asymmetric if the ratio of the longest dimension to the narrowest dimension (Dy / Dx) is greater than 1.25, 1.5, 1.75, 2.0, 2.5, 3.0, 4, 5. More complex asymmetric CPB shapes may also be used, such as shapes in which the longest and shortest dimensions are not orthogonal, such as beam shape 250 of Figure 2B, in which the longest and shortest dimensions are along non-orthogonal axes 252, 254.

[0024] Example 5. Dual beam system with asymmetric beam(s) 3, the dual beam system 300 includes a system controller 302 coupled to an ion beam source 304 and an electron beam source 306 that generate an ion beam and an electron beam, respectively, that can be shaped by one or more apertures 373 selectable by the system controller 302. In some implementations, separate actuators and apertures are provided to independently shape the ion beam and the electron beam. An optical column 312 is positioned to receive the ion beam and the electron beam and direct the beams toward a workpiece or specimen 320. Typically, the optical column 312 includes an objective lens that focuses one or both of the ion beam and the electron beam onto the workpiece 320. It should be noted that the optical column 312 may include one or more scanners that direct one or both of the beams across the workpiece 320. In dual beam implementations, such as an ion beam / electron beam system, separate optical columns and objective lenses are provided. In some applications, imaging is based on a scanned electron beam, while a scanned ion beam is used for specimen modification, such as ion beam milling. However, imaging can be achieved with either a scanned ion beam, a scanned electron beam, or both. In some cases, the imaging system includes only one of an electron beam source and an ion beam source. For many biochemical specimens, only the electron beam is required, and no ion beam components are used. The scanning beam can be asymmetrically shaped by control of the optical column 312, for example, by control of one or more CPB lenses, astigmatism correctors, deflectors, and other CPB optical elements.

[0025] The specimen 320 is fixed to a stage 322 that is coupled to a stage controller 324, which is coupled to the system controller 302. The stage 322 may typically provide one or more of translation, rotation, or tilt as directed by the system controller 302. A beam 316 in response to the scanning beam 315 (such as an ion or electron beam) is directed to an electron or ion detector 328 that is coupled to system electronics 330, which may include one or more analog-to-digital converters (ADCs), digital-to-analog converters (DACs), amplifiers, and buffers, for control of the detector 328 and processing (amplification, digitization, buffering) of signals associated with the detector 328. Although the scanning beam 315 is shown as being normally incident on the specimen 320, in many cases such beams may be directed at angles of incidence of 60 degrees or more. In other embodiments, photon detectors are used that generate electrical signals that are further processed by the system electronics. In most practical applications, at least one ADC is used to generate digitized detector signals that can be stored in one or more tangible computer-readable media, such as an image, shown as image storage 332. In other embodiments, the image storage is remote, such as via a communication connection, such as a wired or wireless network connection. The beam 316 can be a scanned ion beam, a scanned electron beam, secondary electrons, ions, or scattered portions of neutral atoms. An optical imaging element 351, such as a camera, is coupled to generate an image of the specimen 320, for example, to provide visual feedback to a technician.

[0026] The system controller 302 is coupled to a memory 335 that stores processor executable instructions for imaging processing and acquisition, such as beam shaping 336, to generate an asymmetric CPB by suitable control of the optical column 312, deconvolution 338, imaging combination 340 (which may be provided before or after deconvolution), and to provide a Graphical User Interface (GUI) 342 for various functions, including parameters associated with selection of an asymmetric beam shape. Additionally, the system controller 302 is coupled to an actuator 372 operable to select one or more apertures 373 in the beam path for beam shaping. Imaging (both CPB and optical) may be stored in the memory portion 332. Stage coordinates (including rotation) may be stored in the memory portion 332 as well. The system controller 302 sets the imaging acquisition parameters and is in communication with the stage controller 324. Specimen images, such as deconvolved images, may be presented on a display 352, and system control and imaging parameters may be specified using internally stored values ​​from memory 335 or may be provided by a user using one or more user input devices 350.

[0027] It will be understood that the layout of Figure 3 is for convenience of illustration and that the actual arrangement of the various beam sources, optical column 312, and other components need not be the same as shown. Components used to establish a suitable vacuum environment have been omitted as well. Although a dual beam (ion beam / electron beam) system is shown, either or both beams may be used, and in many applications such as electron microscopes, only the electron beam is used.

[0028] Example 6. Representative Computing Environment for System Control FIG. 4 and the following discussion are intended to provide a brief, general description of an exemplary computing environment in which the disclosed technology may be implemented. In particular, some or all of this computing environment may be used in conjunction with the methods and apparatus described above to, for example, control beam shapes, obtain imaging with multiple beam shapes, and select deconvolution approaches. Although not required, the disclosed technology is described in the general context of computer-executable instructions, such as program modules, executed by a personal computer (PC). Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The disclosed technology may also be implemented with other computer system configurations, including handheld devices, tablets, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, etc. The disclosed technology may also be practiced in distributed computing environments, where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. As used herein, the term "processor" means a central processing unit (CPU). The term "controller" refers to a processor, a processor module, a processor array, a processor array controller, a processor array controller (CPU), ...

[0029] With reference to FIG. 4, an exemplary system for implementing the disclosed technology includes a general-purpose computing device in the form of an exemplary conventional PC 400 including one or more processors 402, a system memory 404, and a system bus 406 coupling the one or more processors 402 to various system components including the system memory 404. The system bus 406 may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The exemplary system memory 404 includes a Read Only Memory (ROM) 408 and a Random-Access Memory (RRAM) 409. The PC 400 includes a basic input / output system (BIOS) 412, which contains the basic routines that help transfer information between elements within the PC 400.

[0030] The exemplary PC 400 further includes one or more storage devices 430, such as a hard disk drive for reading from and writing to a hard disk, a magnetic disk drive for reading from and writing to a removable magnetic disk, a memory device such as a thumb drive, and an optical disk drive for reading from and writing to a removable optical disk (such as a CD-ROM or other optical media). Such storage devices may be connected to the system bus 406 by a hard disk drive interface, a magnetic disk drive interface, and an optical drive interface, respectively. The drives and associated computer-readable media provide non-volatile storage of computer-readable instructions, data structures, program modules, and other data for the PC 400. Other types of computer-readable media may store data accessible by a PC, such as magnetic cassettes, flash memory cards, digital video disks, CDs, DVDs, RAM, ROM, and the like, and may be used in the exemplary operating environment. As used herein, memory, storage devices, and the like refer to non-transitory storage, i.e., storage that does not carry signals.

[0031] Several program modules may be stored in the storage device 430, including an operating system, one or more application programs, other program modules, and program data. A user may input commands and information to the PC 400 through one or more input devices 440, such as a keyboard and a pointing device such as a mouse. For example, a user may input commands to select a CPB shape and a deconvolution approach. Other input devices may include a digital camera, a microphone, a joystick, a game pad, a satellite receiver, or a scanner. These and other input devices are often connected to the one or more processing units 402 through a serial port interface coupled to the system bus 406, but may also be connected by other interfaces such as a parallel port, a game port, a Universal Serial Bus (USB), or a wired or wireless network connection. A monitor 446 or other type of display device may also be connected to the system bus 406 through an interface such as a video adapter and may display, for example, an image or ROI image obtained with the asymmetric CPB shape, or a processed image obtained by deconvolution. A monitor 446 may also be used to assist in CPB equipment control, to confirm successful beam shape control, image acquisition, and selection of deconvolution approaches, and other functions. Other peripheral output devices, such as speakers and a printer (not shown), may also be included.

[0032] The PC 400 may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer 460. In some embodiments, one or more network or communication connections 450 are included. The remote computer 460 may be another PC, a server, a router, a network PC, a peer device, or other common network node, and typically includes many or all of the elements described above in relation to the PC 400, although only a memory storage device 462 is illustrated in FIG. 4. The personal computer 400 and / or the remote computer 460 may be connected to a logical Local Area Network (LAN) and a Wide Area Network (WLAN). A remote computer 460 may be connected to a local area network (WAN), such as a local area network (WAN), or a local area network (WAN). Some or all of the functionality provided by the PC 400 may be provided by a remote computer 460.

[0033] 4, memory 490 (or a portion of this or other memory) stores processor-executable instructions for deconvolution, beam combining, and beam shaping. Additionally, memory 490 may store a menu of beam shape settings that allow easy setting of beam characteristics for use in imaging, deconvolution, and CPB shapes to control CPB instrument 492.

[0034] (Example 7. FIB processing using elongated asymmetric beam shape) When using asymmetric CPB, the beam orientation is adjusted to match the processing feature, such as a feature being milled. 5 illustrates the processing of a workpiece 500 with an ion beam to form grooves 502, 512 that use a common beam shape but are aligned in different directions. Groove 502 is milled with a beam shape 504 aligned with the longest dimension along groove 502. Groove 512 is milled with a beam shape 514 aligned with the shortest dimension along groove 512. In milling grooves 502, 512, the differently aligned beams are scanned along parallel axes 506, 516.

[0035] Example 8. Imaging Combination As mentioned above, the images obtained with different beam shapes and / or orientations may be combined before or after deconvolution. The images may be combined by adding the image values ​​pixel by pixel. In some cases, the different images are scaled to have pixel values ​​within a common range. For example, the pixel values ​​in each image may be scaled based on the maximum pixel value so that both images have pixel values ​​between 0 and 1. Different weighting factors may be applied to the images to select the contribution of the individual images to the combined image.

[0036] Example 9. Deconvolution using a predetermined pattern In the embodiment shown in FIG. 6, a region of interest 600 that is subject to imaging and / or CPB processing is provided with a predefined patterned region 602. The patterned region 602 includes at least one feature, such as feature 604. An image of the ROI 600 acquired using asymmetric CPB includes a corresponding imaged portion that can be used in deconvolution, since suitable image reproductions tend to reproduce the associated pattern. Thus, the patterned region 602 can be used to guide and evaluate the deconvolution. In some cases, a reference pattern defined on the workpiece is available and can serve to guide the deconvolution.

[0037] (Disclosure paragraph) Paragraph 1 includes a charged particle beam (CPB) imaging method comprising steps of acquiring an image of a sample, the image being acquired using a first asymmetric CPB shape, and processing the image based on the first asymmetric CPB shape to generate a final image of the sample.

[0038] Paragraph 2 includes the subject matter of paragraph 1 and further specifies that the first asymmetric CPB shape is an elongated shape, and that the imaging is processed based on the first asymmetric CPB shape by deconvolution.

[0039] Paragraph 3 includes the subject matter of any of paragraphs 1-2, and further includes operating the CPB optical column to select a first asymmetric CPB shape.

[0040] Paragraph 4 includes the subject matter of any of paragraphs 1-3 and further specifies that the first asymmetric CPB shape is selected by one or more of directing the CPB beam into an asymmetric aperture, providing different CPB magnifications along different axes, and tuning the CPB optical column to provide different chromatic aberrations along different axes.

[0041] Paragraph 5 includes the subject matter of any of paragraphs 1 to 4 and further specifies that obtaining the image includes obtaining a first image and a second image of the sample, the first image and the second image being obtained using a first asymmetric CPB shape and a second asymmetric CPB shape, respectively, the first asymmetric CPB shape being different from the second asymmetric CPB shape, and the final image being obtained by processing the first image and the second image.

[0042] Paragraph 6 includes the subject matter of any of paragraphs 1 to 5 and further includes: Deconvolving a first image based on a first asymmetric CPB shape and deconvolving a second image based on a second asymmetric CPB shape, wherein a final image is generated based on the deconvolved first image and the deconvolved second image.

[0043] Paragraph 7 includes the subject matter of any of paragraphs 1 to 6 and further includes: Combining the first image and the second image, and deconvolving the combined image to generate a final image.

[0044] Paragraph 8 includes the subject matter of any of paragraphs 1 to 7 and further provides that the first asymmetric CPB shape is aligned along a first axis and the second asymmetric CPB shape is aligned along a second axis that is different from the first axis.

[0045] Paragraph 9 includes the subject matter of any of paragraphs 1 to 8, and further specifies that the first axis and the second axis are perpendicular to each other.

[0046] Paragraph 10 includes the subject matter of any of paragraphs 1-9 and further specifies that the first axis is at an angle of between 45 degrees and 90 degrees to the second axis.

[0047] Paragraph 11 includes the subject matter of any of paragraphs 1-10, and further includes adjusting the CPB optical column to generate the first asymmetric CPB shape and the second asymmetric CPB shape.

[0048] Paragraph 12 includes the subject matter of any of paragraphs 1-11, and further includes acquiring a third image of the sample, where the third image is acquired using a third beam shape that is different from the first asymmetric CPB shape and the second asymmetric CPB beam shape, and deconvolving the first image, the second image, and the third image to generate a final image based on the deconvolved first image, the second image, and the third image.

[0049] Paragraph 13 is a CPB imaging system including a CPB optical column operable to generate a first asymmetric CPB positionable along a first axis, a CPB detector positioned to generate first images in response to the first asymmetric CPB, and a processor coupled to generate a final image based on the first images.

[0050] Paragraph 14 includes the subject matter of paragraph 13 and further specifies that the processor is configured to generate a final image from the first image and the shape of the first asymmetric CPB.

[0051] Paragraph 15 includes the subject matter of any of paragraphs 13-14 and further specifies that the processor is operable to generate a final image by deconvolution.

[0052] Paragraph 16 includes the subject matter of any of paragraphs 13-16 and further specifies that the CPB optical column is operable to generate a first asymmetric CPB and a second asymmetric CPB that are positionable along a first axis and a second axis, respectively, the first axis being different from the second axis, a CPB detector is positioned to generate a first image and a second image of the substrate in response to the first asymmetric CPB and the second asymmetric CPB, respectively, and a processor generates a final image based on the first image and the second image.

[0053] Paragraph 17 includes the subject matter of any of paragraphs 13-16 and further specifies that the processor is configured to generate a final image based on the deconvolution.

[0054] Paragraph 18 includes the subject matter of any of paragraphs 13-17 and further provides that the deconvolution is based on the respective shapes of the first asymmetric CPB and the second asymmetric CPB.

[0055] Paragraph 19 includes the subject matter of any of paragraphs 13-18 and further specifies that the processor is operable to combine the deconvolved first image and the deconvolved second image to generate a final image.

[0056] Paragraph 20 includes the subject matter of any of paragraphs 13-19 and further specifies that the first asymmetric CPB beam is an elongated beam, and the processor is further configured to scan the first CPB across the substrate along a direction parallel to the elongated direction of the first asymmetric CPB.

[0057] Considering the many possible embodiments to which the principles of the disclosed technology may be applied, it should be understood that the illustrated embodiments are merely preferred examples, and we claim all that comes within the scope and spirit of the appended claims.

Claims

1. 1. A charged particle beam (CPB) imaging method comprising: acquiring an image of a sample, the image being acquired using a first asymmetric CPB geometry; and processing the image based on the first asymmetric CPB shape to generate a final image of the sample. CPB imaging method.

2. The CPB imaging method of claim 1 , wherein the first asymmetric CPB shape is an elongated shape, and the imaging is processed based on the first asymmetric CPB shape by deconvolution.

3. The CPB imaging method of claim 1 , further comprising operating a CPB optical column to select the first asymmetric CPB shape.

4. 4. The CPB imaging method of claim 3, wherein the first asymmetric CPB shape is selected by one or more of: directing a CPB beam into an asymmetric aperture, providing different CPB magnifications along different axes, and tuning the CPB optical column to provide different chromatic aberrations along different axes.

5. 5. The CPB imaging method of claim 4, wherein acquiring the image comprises acquiring a first image and a second image of a sample, the first image and the second image being acquired using the first asymmetric CPB shape and a second asymmetric CPB shape, respectively, the first asymmetric CPB shape being different from the second asymmetric CPB shape, and the final image being acquired by processing the first image and the second image.

6. deconvolving the first image based on the first asymmetric CPB shape; and deconvolving the second image based on the second asymmetric CPB shape, wherein the final image is generated based on the deconvolved first image and the deconvolved second image. The CPB imaging method of claim 5.

7. combining the first image and the second image; and deconvolving the combined image to generate the final image. The CPB imaging method of claim 5.

8. 7. The CPB imaging method of claim 6, wherein the first asymmetric CPB shape is aligned along a first axis and the second asymmetric CPB shape is aligned along a second axis different from the first axis.

9. The CPB imaging method of claim 8 , wherein the first axis and the second axis are orthogonal.

10. 9. The CPB imaging method of claim 8, wherein the first axis is at an angle of between 45 degrees and 90 degrees to the second axis.

11. The CPB imaging method of claim 5 , further comprising adjusting a CPB optical column to generate the first asymmetric CPB shape and the second asymmetric CPB shape.

12. acquiring a third image of the sample, the third image being acquired using a third beam shape that is different from the first asymmetric CPB shape and the second asymmetric CPB shape; and deconvolving the first image, the second image, and the third image to generate the final image based on the deconvolved first image, the second image, and the third image. The CPB imaging method of claim 11.

13. 1. A charged particle beam (CPB) imaging system comprising: a CPB optical column operable to generate a first asymmetric CPB that is positionable along a first axis; a CPB detector positioned to generate a first image in response to the first asymmetric CPB; a processor coupled to generate a final image based on the first image. CPB imaging system.

14. The CPB imaging system of claim 13 , wherein the processor is configured to generate the final image from the first image and a shape of the first asymmetric CPB.

15. The CPB imaging system of claim 13 , wherein the processor is operable to generate the final image by deconvolution.

16. the CPB optical column is operable to generate the first asymmetric CPB and the second asymmetric CPB that are alignable along the first axis and the second axis, respectively, the first axis being different from the second axis; the CPB detector is positioned to generate the first and second images of a substrate in response to the first and second asymmetric CPBs, respectively; the processor generating a final image based on the first image and the second image.

14. The CPB imaging system of claim 13.

17. The CPB imaging system of claim 16 , wherein the processor is configured to generate the final image based on deconvolution.

18. The CPB imaging system of claim 17 , wherein the deconvolution is based on the respective shapes of the first asymmetric CPB and the second asymmetric CPB.

19. 20. The CPB imaging system of claim 17, wherein the processor is operable to combine the deconvolved first image and the deconvolved second image to generate a final image.

20. 20. The CPB imaging system of claim 17, wherein the first asymmetric CPB beam is an elongated beam, and the processor is further configured to scan the first asymmetric CPB across the substrate along a direction parallel to an elongated direction of the first asymmetric CPB.

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