FIB and SEM resolution enhancement using asymmetric probe deconvolution

Abstract

An elongated or other non-circular charged particle beam (CPB) is used to produce a substrate image, which may be processed, for example, by deconvolution to produce a final image. In some cases, first and second images associated with asymmetric CPB beams aligned along parallel axes are deconvolved and then combined to produce a final image, or combined and then deconvolved to produce a final image. Milling or other processing may be performed by aligning asymmetric CPBs with respect to a CPB scan or process direction.

Description

Technical Field

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

[0002] Resolution is a key performance metric for charged particle beam (CPB) optical systems such as electron microscopes and focused ion beam (FIB) milling systems. Conventional methods require reducing CPB optical cylindrical lens aberrations or adding aberration correction elements. These methods may be difficult to implement and may require a technician. Even if successfully implemented, additional improvements in resolution are still desired. Therefore, there is a need for improved CPB methods and equipment that can improve the resolution of CPB instruments. Summary of the invention

[0003] Disclosed herein are methods, apparatus, and systems capable of creating high resolution images and improving cut placement in CPB imaging when used in combination with asymmetric beam CPB milling. Compared to conventional methods that focus on providing aberration correction and symmetric CPB, the present disclosure involves using one or more asymmetric CPB shapes, compensating images obtained using asymmetric beam shapes to enhance resolution, and processing substrates using asymmetric CPB shapes.

[0004] The foregoing and other features and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1A Representative imaging or methods using asymmetric charged particle beam (CPB) shapes are illustrated.

[0006] Figure 1A1 to Figure 1A2 These are the images obtained using a circular CPB shape and an elongated CPB shape, respectively.

[0007] Figure 1A3 is the image obtained using an asymmetric CPB shape.

[0008] Figure 1A4 is through Figure 1A3 The image is obtained by Wiener deconvolution of the image.

[0009] Fig.1A5 is an image obtained with an asymmetric CPB shape using 2.3 nA Ga ion beam current and 20 μm horizontal field of view.

[0010] Figure 1A6 is through Fig.1A5 The image is obtained by Richardson-Lucy deconvolution of the image.

[0011] Figure 1BA representative imaging method using asymmetric charged particle beams with different orientations is illustrated, where the images are combined before deconvolution.

[0012] Figure 1C A representative imaging method using asymmetric charged particle beams with different orientations is illustrated, where the images are combined after deconvolution.

[0013] FIG. 2A to FIG. 2B Representative asymmetric bundle shapes are illustrated. Figure 2A An elongated shape such as an oval or ellipse is illustrated, wherein the minimum and maximum beam dimensions are along orthogonal axes. Figure 2B An asymmetric beam shape is illustrated, where the minimum and maximum beam dimensions are along non-orthogonal axes.

[0014] Figure 3 A representative dual-beam CPB system is illustrated that can provide asymmetric CPB and deconvolute images acquired with such CPB.

[0015] Figure 4 A representative processor-based control system for acquiring and deconvolving images obtained using an asymmetric CPB shape and controlling workpiece processing using the asymmetric CPB shape is illustrated.

[0016] Figure 5 The orientation of an asymmetric CPB relative to a workpiece for substrate processing such as focused ion beam (FIB) milling is illustrated.

[0017] Figure 6 A workpiece is illustrated with a predetermined pattern area that can be used for deconvolution. DETAILED DESCRIPTION

[0018] Disclosed herein are methods and systems for improving image resolution using an asymmetric charged particle beam (CPB) spot in combination with deconvolution, and typically produce higher resolution than that achieved with a circular beam using the same optical system. In some applications, an asymmetric CPB can provide increased sharpness for FIB milling. Extending such improvements to imaging is possible using a combination of probe deconvolution and image processing.

[0019] General terms and notes

[0020] As used herein, optical columns generally refer to CPB lenses, deflectors, stigmators, and other CPB optical elements used for imaging or beam forming. 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. Representative CPB systems that include the disclosed methods include dual-beam systems including an ion beam system for ion beam milling and a SEM system for evaluating samples, and STEMs.

[0021] As used herein, an image refers to image data stored in various formats (such as JPG, TIFF, BMP or other formats) or a display view of a sample (such as presented on a display device or other visual display). For ease of description in the following examples, a one-dimensional or two-dimensional array representation is generally used.

[0022] The probe beam is a CPB directed at a specimen, typically for one or both of imaging and processing (such as CPB milling). As used herein, the CPB shape at a workpiece corresponds to the beam intensity as a function of the 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 for the applications disclosed herein, beam intensity may refer to dose / area. In the examples described herein, the CPB spot is typically 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 greater than 1.25, 1.5, 1.75, 2.0, 2.5, 3.0, 4, 5 or more. In a typical example, two asymmetric CPB shapes (elongated shapes) having maximum and minimum sizes along orthogonal directions are used. Examples are generally presented with reference to one or more elongated CPB shapes (such as ellipses), but the disclosed method can be applied to any CPB shape. It should be understood that asymmetric CPBs as used herein may exhibit various rotational symmetries.

[0023] As used in this application and in the claims, the singular forms "a", "an", and "the" include plural forms unless the context clearly dictates otherwise. In addition, the term "comprising" means "including". Furthermore, the term "coupled" does not exclude the presence of intervening elements between the coupled items.

[0024] The systems, devices, and methods described herein should not be construed as limiting in any way. On the contrary, the present disclosure relates to all novel and non-obvious features and aspects of the various disclosed embodiments, either individually or in various combinations and sub-combinations formed with each other. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, nor do the disclosed systems, methods, and devices require the presence of any one or more specific advantages or solutions to problems. Any theory of operation is for ease of explanation, but the disclosed systems, methods, and devices are not limited to such theory of operation.

[0025] Although the operations of some of the disclosed methods are described in a particular sequential order for ease of presentation, it should be understood that this description includes rearrangement unless the specific language described below requires a specific order. For example, the operations described in sequence may be rearranged or performed simultaneously in some cases. In addition, for simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and devices can be used in conjunction with other systems, methods, and devices. In addition, the specification sometimes uses terms like "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of the actual operations performed. The actual operations corresponding to these terms will vary depending on the specific implementation and can be easily discerned by those skilled in the art.

[0026] In some examples, values, procedures, or devices are referred to as "lowest," "optimal," "minimum," etc. It should be understood that such descriptions are intended to indicate that choices can be made among a number of functional alternatives used, and that such choices are not necessarily better, lesser, or otherwise preferred over other choices.

[0027] Examples are described with reference to directions indicated as "above," "below," "upper," "lower," etc. These terms are used for convenience of description but do not imply any particular spatial orientation.

[0028] Various techniques can be used for deconvolution, including, for example, Wiener deconvolution, Richardson-Lucy deconvolution, maximum likelihood deconvolution, deep learning deconvolution or other computer vision methods. Deconvolution can be blind or use a known CPB shape. As described below, image processing can be used to correct or compensate for the CPB shape and produce a higher resolution image. A single image or multiple images with different CPB orientations can be used for this correction.

[0029] Example 1. Asymmetric beam imaging

[0030] refer to Figure 1A, a representative method 100 includes selecting a beam shaping method at 102. Typical examples of beam shaping include beam shaping with an asymmetric aperture, anisotropic beam magnification, introduction of aberrations based on adjustment of an optical column, and disabling aberration compensation to provide an asymmetric CPB. At 104, using the selected method, a CPB with an asymmetric shape is generated and the asymmetric CPB is directed to a sample or workpiece. Based on illumination with an asymmetric beam spot, an image of the workpiece is obtained at 105 by, for example, a SEM or STEM (for electron beams) or by similar imaging methods using other CPBs such as ion beams. At 106, a deconvolution method is selected for image processing. At 108, it is determined whether the CPB shape is to be measured or otherwise estimated for deconvolution. In some cases, the CPB shape is known or can be derived from, for example, properties of the CPB optical column and / or properties of the voltage and current applied to the optical column. In this case, the CPB shape can be retrieved from a memory or calculated at 110. Alternatively, the CPB shape can 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 examples, the workpiece is processed at 118. Processing can be accomplished with an asymmetric CPB based on its different degrees of proper alignment in different directions.

[0031] Figure 1A1 to Figure 1A2 The image obtained using symmetric CPB (circular beam shape) is shown ( Figure 1A1 ) and images obtained using an extended asymmetric CPB ( Figure 1A2 ). When the current is equal, Figure 1A2 Image ratio Figure 1A1 The image is clearer. Figure 1A2 The images can be further enhanced by deconvolution. These images are of graphite and were acquired in a 5 μm horizontal field of view with a 2.5 nA beam current generated by a liquid metal ion source (LMIS) in the FIB instrument.

[0032] exist Figure 1A3 and Fig.1A5 The original (stretched beam) image is shown in Figure 1A4 and Figure 1A6 The corresponding deconvolution images are shown in Figure 1, where Wiener deconvolution is used ( Figure 1A4 ) and Richardson-Lucy deconvolution ( Figure 1A6 ).

[0033] Example 2. Asymmetric bundles and 2D deconvolution

[0034] refer to Figure 1B, a representative 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. At 136, the first image and the second image are combined. A deconvolution method is selected at 138, and a two-dimensional deconvolution is applied at 140. By selecting orthogonal CPB shapes so that a one-dimensional deconvolution is independently appropriate for the first image and the second image, the combined image can be deconvolved in a single two-dimensional deconvolution. A reconstructed image resulting from the two-dimensional deconvolution is stored at 142.

[0035] Example 3. Asymmetric beam imaging with multiple CPB shapes

[0036] exist Figure 1C In another example illustrated in , the 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 image and the second image are deconvolved at 156, 158 based on the first asymmetric CPB shape and the second asymmetric CPB shape, respectively, to produce a first deconvolved image at 160 and a second deconvolved image at 162. The deconvolved images are combined at 164 to produce a reconstructed image at 164.

[0037] Although Figure 1C The use of two CPB shapes 151, 153 elongated along orthogonal axes is illustrated, but multiple CPB shapes may be used in any orientation. Although deconvolution is typically applied to enhance the image based on the longer dimension of the asymmetric beam shape, deconvolution may also be applied to enhance the image in both directions. For asymmetric CPBs, workpiece processing typically requires asymmetric alignment of the beam relative to the workpiece. For example, when milling a groove, the longer dimension of the asymmetric CPB may be aligned with the groove direction so that the groove width may be obtained based on the CPB shape in the shorter dimension.

[0038] Although method 100 uses a measure of asymmetric beam shape in deconvolution, Figure 1B to Figure 1CMethods 130, 150 do not show the use of such beam shapes. 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 a so-called "blind" deconvolution used with limited or no data about the PSF associated with the asymmetric beam. These blind methods can be iterative (e.g., maximum a posteriori or expectation-maximization methods) or non-iterative. In some of these methods, an estimate of the PSF is helpful, although not required. When using a two-dimensional deconvolution based on the sum of images obtained using orthogonal elongated beams, it is assumed that the PSFs are separable, i.e., operate independently along the associated elongated beam axes.

[0039] Example 4. Representative beam shapes

[0040] 2, a representative beam shape 200 at a workpiece is illustrated relative 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 center of the beam. For convenience, the beam width is defined as the full width to 25% of the maximum value and is indicated as Dx and Dy in FIG2. Other values ​​may be selected, such as the full width or half width to 50%, 33%, 1 / e, 1e 2 , where e is the Euler number. A beam shape associated with the elongated beam shown in FIG. 2 is 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 Figure 2B A beam shape 250 in which the longest and shortest dimensions are along non-orthogonal axes 252 , 254 .

[0041] Example 5. Dual-beam system with asymmetric beams

[0042] refer to Figure 3, the dual beam system 300 includes a system controller 302, which is coupled to an ion beam source 304 and an electron beam source 306 that respectively generate an ion beam and an electron beam, which can be shaped by one or more apertures 373 that can be selected by the system controller 302. In some specific implementations, separate actuators and apertures are provided for independently shaping the ion beam and the electron beam. The optical column 312 is positioned to receive the ion beam and the electron beam to direct the beam to a workpiece or a sample 320. Typically, the optical column 312 includes an objective lens that focuses one or both of the ion beam and the electron beam on the workpiece 320. In addition, the optical column 312 may include one or more scanners that guide one or both of the beams through the workpiece 320. In a dual beam implementation such as an ion beam / electron beam system, a separate optical column and objective lens are provided. In some applications, an image is obtained based on a scanned electron beam, and the scanned ion beam is used for sample modification such as ion beam milling. However, an image can be obtained using either or both of the scanned ion beam and the scanned electron beam. In some cases, the imaging system includes only one of an electron beam source and an ion beam source. For many biological samples, only an electron beam is required, and no ion beam assembly is used. The scanned beam can be shaped to be asymmetric by controlling the optical column 312, for example, by controlling one or more CPB lenses, stigmators, deflectors, and other CPB optical elements.

[0043] The specimen 320 is secured to a platform 322, which is coupled to a platform controller 324, which in turn is coupled to the system controller 302. The platform 322 can typically provide one or more translations, rotations, or tilts as directed by the system controller 302. A beam 316 responsive to a scanned beam 315 (such as an ion beam or electron beam) is directed to an electron or ion detector 328, which is coupled to system electronics 330, which may include one or more analog / digital converters (ADCs), digital / analog converters (DACs), amplifiers, and buffers for controlling the detector 328 and processing (amplifying, digitizing, buffering) signals associated with the detector 328. The scanned beam 315 is shown as perpendicularly incident to the specimen 320, but in many cases such beams may be directed at an angle of incidence of 60 degrees or more. In other examples, a photon detector is used that generates an electrical signal that is further processed by the system electronics. In most practical examples, at least one ADC is used to generate a digitized detector signal that can be stored as an image in one or more tangible computer-readable media (shown as image storage device 332). In other examples, the image storage is remote 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, a scattered portion of secondary electrons, ions, or neutral atoms. An optical imager 351 such as a camera is coupled to produce an image of the specimen 320, for example, to provide visual feedback to a technician.

[0044] The system controller 302 is coupled to a memory 335 that stores processor-executable instructions for image processing and acquisition, such as beam shaping 336 to produce an asymmetric CPB by appropriately controlling the optical column 312, deconvolution 338, image combination 340 (which may be provided before or after deconvolution), and provides a graphical user interface (GUI) 342 for various functions, including parameters associated with the selection of an asymmetric beam shape. In addition, the system controller 302 is coupled to an actuator 372 that is operable to select one or more apertures 373 in the beam path for beam shaping. Images (both CPB and optical) may be stored in the memory portion 332. Stage coordinates (including rotation) may also be stored in the memory portion 332. The system controller 302 establishes image acquisition parameters and communicates with the stage controller 324. The specimen image (such as a deconvolved image) may be presented on a display 352, and system control and imaging parameters may be specified using internally stored values ​​from the memory 335 or provided by a user using one or more user input devices 350.

[0045] It should be understood that Figure 3The layout is for convenience of illustration, and the actual alignment of the various beam sources, optical column 312 and other components need not be the same as shown. Components for establishing a suitable vacuum environment are also omitted. Although a dual beam (ion / electron beam) system is shown, one or two beams can be used, and in many practical examples such as electron microscopy, only electron beams are used.

[0046] Example 6. Representative computing environment for system control

[0047] Figure 4 The following discussion is intended to provide a brief summary description of an exemplary computing environment in which the disclosed technology can be implemented. In particular, some or all parts of the computing environment can be used with the above-mentioned methods and apparatuses to, for example, control beam shapes, acquire images with multiple beam shapes, and select deconvolution methods. Although not required, the disclosed technology is described in the general context of computer-executable instructions executed by a personal computer (PC) such as program modules. Typically, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In addition, the disclosed technology can be implemented with other computer system configurations including: handheld devices, tablet computers, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, microcomputers, mainframe computers, etc. The disclosed technology can also be practiced in a distributed computing environment where remote processing devices linked by a communication network perform tasks. In a distributed computing environment, program modules can be located in both local memory storage devices and remote memory storage devices. As used herein, the term "processor" refers to CPUs and other logic processing devices, such as FPGAs, ASICs, and CPLDs. A system controller or other controller generally includes at least one processor and additional components such as memory, communication buses, etc., as discussed below.

[0048] refer to Figure 4 , an exemplary system for implementing the disclosed technology includes a general purpose computing device in the form of an exemplary conventional PC 400, which includes one or more processors 402, a system memory 404, and a system bus 406 that couples various system components including the system memory 404 to the one or more processors 402. The system bus 406 can 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 (RAM) 410. A basic input / output system (BIOS) 412 containing the basic routines that help transfer information between elements within the PC 400 is stored in the ROM 408.

[0049] The exemplary PC 400 also includes one or more storage devices 430, such as a hard disk drive for reading from and writing to a hard disk, a disk drive for reading from or writing to a removable disk, a storage device such as a thumb drive, and an optical drive for reading from or writing to a removable optical disk (such as a CD-ROM or other optical media). Such storage devices can be connected to the system bus 406 via a hard disk drive interface, a disk drive interface, and an optical drive interface, respectively. The drives and their 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 capable of storing data accessible by the PC, such as magnetic tape cassettes, flash memory cards, digital video disks, CDs, DVDs, RAM, ROM, etc., can also be used in the exemplary operating environment. As used herein, memory, storage, etc. refer to non-transitory storage devices, i.e., do not propagate signals.

[0050] A plurality of program modules may be stored in a storage device 430 including the following items: 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 via 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 method. Other input devices may include a digital camera, a microphone, a joystick, a game pad, a satellite dish, a scanner, and the like. Although these and other input devices are often connected to one or more processing units 402 via a serial port interface coupled to the system bus 406, they may be connected via 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 is also connected to the system bus 406 via an interface such as a video adapter, and may display, for example, one or more ROI images obtained using an asymmetric CPB shape or a processed image obtained by deconvolution. The monitor 446 may also be used to assist in CPB instrument control, confirm successful beam shape control, image acquisition, and selection of a deconvolution method, as well as other functions. Other peripheral output devices may be included, such as a speaker and a printer (not shown).

[0051] PC 400 may operate in a networked environment using logical connections to one or more remote computers, such as remote computer 460. In some examples, one or more network or communication connections 450 are included. Remote computer 460 may be another PC, a server, a router, a network PC or peer device, or other common network node, and typically includes many or all of the elements described above with respect to PC 400, although in some embodiments, the remote computer 460 may be a PC, a server, a router, a network PC, or a peer device, or other common network node. Figure 4Only memory storage device 462 is shown. Personal computer 400 and / or remote computer 460 can be connected to logical local area networks (LAN) and wide area networks (WAN). Some or all functions provided by PC 400 can be provided by remote computer 460.

[0052] like Figure 4 As shown, the memory 490 (or a portion of the memory or other memory) stores processor executable instructions for deconvolution, beam combining and beam shaping. In addition, the memory 490 can store images, beam characteristics for deconvolution, and a beam shape setting menu that allows easy setting of the CPB shape to control the CPB instrument 492.

[0053] Example 7. FIB processing with elongated asymmetric beam shape

[0054] When using an asymmetric CPB, the beam orientation may be selected based on the processing feature, such as the feature to be milled. Figure 5 Illustrated is processing a workpiece 500 with an ion beam to form grooves 502, 512 using a common beam shape but aligned in different directions. The groove 502 is milled to have a beam shape 504 that is aligned with the longest dimension along the groove 502. The groove 512 is milled to have a beam shape 514 that is aligned with the shortest dimension along the groove 512. While milling the grooves 502, 512, the differently aligned beams are scanned along parallel axes 506, 516.

[0055] Example 8. Image combination

[0056] As described above, images obtained using different beam shapes and / or orientations can be combined before or after deconvolution. The images can 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 can be scaled based on the maximum pixel value so that both images have pixel values ​​between 0 and 1. Different weighting factors can be applied to the images to select the individual image contributions to the combined image.

[0057] Example 9. Deconvolution using a predetermined pattern

[0058] exist Figure 6 In the example shown, a region of interest 600 to be imaged and / or CPB treated is provided with a predetermined pattern region 602. The patterned region 602 includes at least one feature, such as feature 604. An image of the ROI 600 obtained using asymmetric CPB contains a corresponding image portion that can be used in deconvolution, because a suitable image reconstruction tends to reproduce the associated pattern. Therefore, the pattern region 602 can be used to guide and evaluate deconvolution. In some cases, a fiducial pattern defined on the workpiece is available and can be used to guide deconvolution.

[0059] Public paragraphs

[0060] Paragraph 1 is a charged particle beam (CPB) imaging method, comprising: obtaining an image of a sample, wherein the image is obtained using a first asymmetric CPB shape; and processing the image based on the first asymmetric CPB shape to produce a final image of the sample.

[0061] Paragraph 2 includes the subject matter of Paragraph 1, and further specifies that the first asymmetric CPB shape is an elongated shape, and the image is processed by deconvolution based on the first asymmetric CPB shape.

[0062] 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.

[0063] Paragraph 4 includes the subject matter of any of Paragraphs 1-3, and further provides that the first asymmetric CPB shape is selected by one or more of: directing the CPB beam to an asymmetric aperture, providing different CPB magnifications along different axes, and adjusting the CPB optical column to provide different chromatic aberrations along different axes.

[0064] Paragraph 5 includes the subject matter of any of paragraphs 1-4, and further provides that obtaining an image includes obtaining a first image and a second image of the sample, wherein the first image and the second image are obtained using a first asymmetric CPB shape and a second asymmetric CPB shape, respectively, wherein the first asymmetric CPB shape is different from the second asymmetric CPB shape, and wherein the final image is obtained by processing the first image and the second image.

[0065] Paragraph 6 includes the subject matter of any of Paragraphs 1-5, and also includes:

[0066] Deconvolving the first image based on a first asymmetric CPB shape; and deconvolving the 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.

[0067] Paragraph 7 includes the subject matter of any of Paragraphs 1-6, and also includes:

[0068] combining the first image and the second image; and deconvolving the combined image to produce a final image.

[0069] Paragraph 8 includes the subject matter of any of Paragraphs 1-7, and further specifies that 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.

[0070] Paragraph 9 includes the subject matter of any of Paragraphs 1-8, and further specifies that the first axis and the second axis are orthogonal.

[0071] Paragraph 10 includes the subject matter of any of Paragraphs 1-9 and further provides that the first axis is at an angle between 45 degrees and 90 degrees relative to the second axis.

[0072] Paragraph 11 includes the subject matter of any of Paragraphs 1-10, and further includes adjusting the CPB optical column to produce a first asymmetric CPB shape and a second asymmetric CPB shape.

[0073] Paragraph 12 includes the subject matter of any of paragraphs 1-11, and also includes: obtaining a third image of the sample, wherein the third image is obtained 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, and generating a final image based on the deconvolved first image, the second image, and the third image.

[0074] Paragraph 13 is a CPB imaging system comprising: a CPB optical column operable to produce a first asymmetric CPB alignable along a first axis; a CPB detector positioned to produce a first image in response to the first asymmetric CPB, respectively; and a processor coupled to produce a final image based on the first image.

[0075] Paragraph 14 includes the subject matter of Paragraph 13, and further specifies that the processor is configured to generate a final image based on the first image and the shape of the first asymmetric CPB.

[0076] Paragraph 15 includes the subject matter of any of Paragraphs 13-14, and further specifies that the processor is operable to produce the final image by deconvolution.

[0077] Paragraph 16 includes the subject matter of any of paragraphs 13-16 and further provides that: the CPB optical column is operable to generate a first asymmetric CPB and a second asymmetric CPB that can be aligned along a first axis and a second axis, respectively, wherein the first axis is different from the second axis; the 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 the processor generates a final image based on the first image and the second image.

[0078] Paragraph 17 includes the subject matter of any of paragraphs 13-16, and further specifies that the processor is configured to generate the final image based on deconvolution.

[0079] Paragraph 18 includes the subject matter of any of Paragraphs 13-17, and further specifies that the deconvolution is based on respective shapes of the first asymmetric CPB and the second asymmetric CPB.

[0080] 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 produce a final image.

[0081] Paragraph 20 includes the subject matter of any of paragraphs 13-19, further providing that the first asymmetric CPB beam is an elongated beam, and the processor is further configured to scan the first CPB at the substrate along a direction parallel to an elongated direction of the first asymmetric CPB.

[0082] In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only preferred examples. We claim all that is within the scope and spirit of the following claims.

Claims

1. A charged particle beam (CPB) imaging method, comprising: obtaining an image of the sample, wherein the image is obtained using a first asymmetric CPB shape; as well as The image is processed based on the first asymmetric CPB shape to produce a final image of the sample. 2 . The CPB imaging method according to claim 1 , wherein the first asymmetric CPB shape is an elongated shape, and the image is processed by deconvolution based on the first asymmetric CPB shape.

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

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

5. The CPB imaging method according to claim 4, wherein obtaining the image comprises obtaining a first image and a second image of the sample, wherein the first image and the second image are obtained using the first asymmetric CPB shape and the second asymmetric CPB shape, respectively, wherein the first asymmetric CPB shape is different from the second asymmetric CPB shape, and wherein the final image is obtained by processing the first image and the second image.

6. The CPB imaging method according to claim 5, further comprising: deconvolving the first image based on the first asymmetric CPB shape; as well as The second image is deconvolved based on the second asymmetric CPB shape, wherein the final image is generated based on the deconvolved first image and the deconvolved second image.

7. The CPB imaging method according to claim 5, further comprising: combining the first image and the second image; as well as The combined images are deconvolved to produce the final image.

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

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

12. The charged particle beam (CPB) imaging method according to claim 11, further comprising: obtaining a third image of the sample, wherein the third image is obtained using a third beam shape different from the first asymmetric CPB shape and the second asymmetric CPB beam shape; as well as The first image, the second image, and the third image are deconvolved, and the final image is generated based on the deconvolved first image, second image, and third image.

13. A CPB imaging system, comprising: a CPB optical column operable to produce a first asymmetric CPB alignable along a first axis; CPB detectors positioned to generate first images in response to the first asymmetric CPBs, respectively; and A processor is coupled to generate a final image based on the first image.

14. The CPB imaging system of claim 13, wherein the processor is configured to generate the final image based on the first image and the 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 imaging system of claim 13, wherein: The CPB optical column is operable to generate the first asymmetric CPB and the second asymmetric CPB respectively alignable along the first axis and the second axis, wherein the first axis is different from the second axis; The CPB detector is positioned to generate the first and second images of the substrate in response to the first asymmetric CPB and the second asymmetric CPB, respectively; and The processor generates a final image based on the first image and the second image.

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 respective shapes of the first asymmetric CPB and the second asymmetric CPB.

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

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 CPB at a substrate along a direction parallel to an elongated direction of the first asymmetric CPB.

Images