Minimization of energy spread and coulomb interactions in focused ion beam (FIB) systems

Abstract

SOLUTION: Charged-particle beam (CPB) optical systems can include a beam acceptance aperture plate defining a first acceptance aperture and at least one second acceptance aperture, situated with respect to a CPB source so that a first CPB is transmitted by the first acceptance aperture and a second CPB is transmitted by a second acceptance aperture. A CPB lens is situated to receive the first and second CPBs from the beam acceptance aperture plate and direct the first and second CPBs towards a filter aperture plate to transmit a selected spectral portion of the second CPB.EFFECT: The selected spectral component of the first CPB can be selectively directed to a workpiece by a beam steering deflector along the same axis. In some examples, the first and second CPBs have different beam currents, and only one is directed to a workpiece.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present disclosure relates to ion beam systems and ion beam processing. [Background technology]

[0002] Focused ion beam devices (FIBs) are important tools in semiconductor, material science, and life science workflows. FIBs can be used for sputtering of bulk materials or for nanometer-scale micromachining. The brightness and energy spread of the FIB are important considerations in determining the FIB spot size. Coulomb interactions are another important limiting factor in determining the FIB spot size. Coulomb interactions can be suppressed by limiting the beam current, but many FIB applications require huge beam currents that are not practical to limit. Prior art approaches described in U.S. Pat. No. 7,034,315, incorporated herein by reference, use beam-limiting diaphragms in combination with energy dispersion created by chromatic aberration to produce high current central beams and low current off-center beams. However, improved approaches are needed to deliver charged particle beams (CPBs) with variable beam current and energy spread. Summary of the Invention

[0003] The CPB system and method allows for delivery of the CPB based on a selected portion of the emitted CPB and a selected energy width. In an exemplary embodiment, the axial CPB and the off-axis CPB are created with an extractor aperture plate that defines a corresponding aperture. The off-axis CPB is chromatically dispersed, and a filtering aperture is used to select a portion of the chromatically dispersed off-axis CPB to generate a CPB with a selected spectrum or energy width. Typically, the spectrum of the CPB is selected by limiting the chromatic spread of the CPB at the aperture edge. A beam steering deflector is disposed optically downstream of the filtering aperture and is operable to direct the spectrally selected off-axis CPB portion to the workpiece along an axis associated with the propagation of the axial CPB. In most cases, the axial CPB is a relatively high current CPB that does not substantially limit the energy width. In general, the beam current of the off-axis CPB is relatively low and the energy width is limited. The filtering deflector is operable to select which portion of the off-axis chromatic spread is transmitted by the filtering aperture, thereby selecting the off-axis CPB energy width. Either or both of the on-axis and off-axis beams can have a circular, elliptical, or other shape. An elliptical or linear shape in which the CPB is spread over a larger area can reduce the current density, thereby reducing sputtering or other damage to the aperture edge.

[0004] The foregoing features and advantages of the disclosed techniques 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] FIG. 1 illustrates an exemplary charged particle beam (CPB) system capable of delivering CPB with various current and energy ranges, showing an off-axis CPB being directed towards a workpiece. [Figure 1B]FIG. 1B illustrates the CPB system of FIG. 1A showing an axial CPB directed towards the workpiece. [Figure 1C] 1B is a cross-sectional view of FIG. 1A illustrating a CPB position at a filter aperture that transmits an axial CPB with a given spectrum and an off-axis CPB. [Figure 1D] 1A and 1B are cross-sectional views, respectively, illustrating CPB positions at a filter aperture that transmit off-axis CPB (FIG. 1A) and axial CPB (FIG. 1B) having a predetermined spectrum. [Figure 1E] 1A and 1B are cross-sectional views, respectively, illustrating CPB positions at a filtering aperture that transmit off-axis CPB (FIG. 1A) and axial CPB (FIG. 1B) having a predetermined spectrum. [Figure 1F] FIG. 2 is a cross-sectional view of a filtering aperture plate that can be used as an alternative to the filtering aperture plate of FIGS. 1A-1B. [Diagram 2] 1 illustrates an exemplary method for generating multiple CPBs and delivering a selected CPB having a selected spectral spread to a workpiece. [Diagram 3] FIG. 1 illustrates a CPB system operable to provide a CPB having a selectable beam current and energy spread. [Figure 4A] FIG. 2 illustrates a representative receiving aperture. [Figure 4B] FIG. 2 illustrates a representative receiving aperture. [Figure 5A] FIG. 1 illustrates a CPB system that generates axial and off-axis CPBs, either of which can be delivered to a workpiece along a common axis. [Figure 5B] FIG. 1 illustrates a CPB system that generates axial and off-axis CPBs, either of which can be delivered to a workpiece along a common axis. [Figure 6]FIG. 1 illustrates a CPB system that generates axial and off-axis CPBs, either of which can be delivered to a workpiece along an axis. [Figure 7] FIG. 7 illustrates a portion of a CPB system such as that of FIG. 6 having a beam-receiving aperture plate defining a plurality of beam-receiving apertures. [Figure 8] 1 illustrates an exemplary method for generating multiple CPBs and delivering selected CPBs to a workpiece, e.g., selecting a CPB current. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Systems, methods, and devices are disclosed that allow for selective delivery of charged particle beams (CPBs) having various currents and energy ranges. In this embodiment, two or more CPBs are provided, typically a first CPB with a relatively high beam current and a wide energy range, and a second CPB with a lower beam current and a narrower energy range. The disclosed approach allows for the provision of one or more CPBs with different selected beam currents and energy ranges.

[0007] General Terms As used herein, an "optical column" refers to a system of one or more CPB optical elements, such as electrostatic lenses, magnetic lenses, apertures, stigmators, deflectors, scanners, CPB sources such as electron emitters, or ion emitters. For ease of explanation, an aperture is referred to as being defined in an aperture plate, and as used herein, an "aperture plate" refers to any material used to define an aperture, whether shaped as a plate, some other shape, or part of one or more CPB optical elements. A spectral component, or CPB spectral component, refers to a CPB having a selected energy range. The CPB beam cross section may be symmetric or asymmetric, and in the embodiments described herein, an elliptical or other elongated beam shape may be used. The apertures used to control and shape the CPBs may be symmetrical or asymmetrical, such as elliptical or elongated in nature, and in some cases the apertures are defined by a single edge, which may be straight or curved, and the CPBs are arranged so that they only or primarily interact with this single edge. In some embodiments, with or without spectral limiting or energy filtering, the higher current CPBs may propagate along the optical axis to the workpiece without deflection, and the lower current CPBs may propagate off-axis and reach the workpiece after one or more deflections. However, the optical column may be arranged such that either or both of these CPBs require deflection to be directed to the workpiece. For convenience, a substrate onto which one or more CPBs are directed for processing, imaging, or other purposes is referred to as a workpiece, even in situations where one or more CPBs are used only for imaging. For convenience of explanation, the embodiments generally illustrate a CPB that is typically incident on the workpiece, but any angle of incidence may be used. In some embodiments, the aperture plate may be referred to as a blanking aperture plate and may be associated with blocking or attenuating one or more CPBs.

[0008] As used herein, energy width, energy range, and spectral width refer to the range of charged particle energies associated with a CPB. Filtering refers to reducing or essentially limiting the energy width or energy range of a CPB and / or selecting a particular energy width or spectral content.

[0009] In this embodiment, the propagation direction of the CPB is illustrated as being varied using a beam deflector that generally does not provide focusing or defocusing of the CPB, and a CPB lens that can change the beam propagation direction to provide focusing or defocusing of the CPB. As used herein, a beam selector or beam selector system includes one or more CPB lenses or beam deflectors. Additionally, in this embodiment, a CPB lens is used to provide spectral dispersion of the CPB beam based on chromatic aberration, although other CPB optical elements can be used. As used herein, a CPB spectral disperser includes one or more CPB lenses and / or other spectrally dispersive CPB optical components.

[0010] Typically, the CPB is defined using a CPB source and one or more apertures, generally referred to herein as beam receiving apertures. In typical embodiments based on a focused ion beam (FIB), such beam receiving apertures and associated beam receiving aperture plates function to extract the CPB and may alternatively be referred to as extractor apertures and extractor aperture plates.

[0011] 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.

[0012] 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.

[0013] 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. Furthermore, 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.

[0014] In some instances, 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.

[0015] Example 1 1A, a portion of a charged particle beam (CPB) optical system 100 includes a CPB emitter 102 positioned to direct a CPB 104 to a beam-receiving aperture plate 106. The beam-receiving aperture plate 106 defines a first aperture 108 (typically along an axis 101 of the CPB optical system 100) and a second aperture 110 (typically an off-axis aperture) to define an axial CPB 111A and an off-axis CPB 111B, respectively, as well as to block or otherwise attenuate a portion of the CPB from the CPB emitter 102. The CPB 111A may be referred to as an axial CPB because it propagates from the CPB source 102 through the first aperture 108 along the axis 101. The CPB 111B may be referred to as an off-axis CPB because it propagates from the CPB source 102 through the second aperture 110 at an angle relative to the axis 101.

[0016] The axial CPB 111A is directed along the axis 101 to a lens 112 operable to focus the axial CPB 111A along the axis 101 to a crossover 113 through a filtering aperture 120 of a filtering aperture plate 118. Typically, the CPB 111A is associated with a substantially higher beam current than the CPB 111B. The apertures 120 are bounded by respective edges 118A, 118B, and typically, the spectral components to be selected or blocked are incident on the filtering aperture plate 118 or filtering aperture 120 at or near the edges 118A or 118B.

[0017] CPB 111B is directed to lens 112, which produces a chromatically dispersed and focused CPB 116 in which beam portions with various beam spectral content are directed to different locations on filtering aperture plate 118. In this illustration, three spectral beam portions 151-153 are shown, but typically there will be a continuous distribution of spectral content on filtering aperture plate 118. Spectral beam portion 151 is typically associated with lower beam energies than spectral beam portion 153, since chromatic aberration of lens 112 tends to produce greater beam deflection at lower beam energies.

[0018] The CPB optical system 100 further includes a first deflector 122 (in some embodiments referred to as a beam-filtering deflector) that functions to provide a spectrally filtered beam and is located between the CPB lens 112 and the filtering aperture plate 106. A second deflector 124 (in some embodiments referred to as a beam-steering deflector) is located optically downstream of the filtering aperture plate 118, along the axis 101, at or near a plane 127 proximate to an axial location where the axial CPB 111A and the spectrally spread CPB 116 (i.e., the portion transmitted through the aperture 120) form a crossover 113. The beam-filtering deflector 122 is operable to selectively deflect the spectral components of the CPB 116 such that the beam focal point is located on or proximate to the axis 101. As seen in FIG. 1A, the spectral distribution is provided by the lens 112 without deflection by the beam-filtering deflector 122. However, the spectrally distributed beam portion can be deflected to allow for the selection of spectral components that would otherwise be attenuated or blocked by the filtering aperture plate 118. In other embodiments, the filtering aperture plate 118 can be moved or positioned using an actuator 119 shown in FIG. 1A as allowing translation in the XY plane of a coordinate system 150 with the Y axis extending out of the plane to allow for the transmission of selected spectral components.

[0019] In the exemplary configuration shown in FIG. 1A, the CPB spectral beam portion 151 is directed to have a focus on the axis 101, and the spectral beam portions 152, 153 are blocked by the filtering aperture plate 118. Without being deflected by the beam-steering deflector 124, the first CPB 114 propagates through a blanking aperture 128 defined in the blanking aperture plate 126 for delivery to a workpiece, sample, or other target. As shown, the beam-steering deflector 124 is energized to deflect the axial CPB 111A so that it is blocked by the blanking aperture plate 126, and the spectral beam portion 151 is directed through the aperture 128 along the axis 101 for delivery to a workpiece, sample, or other target. With the appropriate deflection applied by the beam filtering deflector 122 (or positioning of the filtering aperture 120), the selected spectral CPB portion is coupled through the filtering aperture 120. The beam steering deflector 124 can be energized to deflect a selected spectral portion along the axis 101 toward the target (as shown in FIG. 1A), while without any deflection, the axial CPB 111A propagates toward the target, as shown in FIG. 1B.

[0020] 1A-1B, the beam receiving aperture plate 106 defines two apertures that can be used to generate a central, or axial, beam, and an off-axis, or eccentric, beam, although additional apertures of different diameters and located at different distances from the optical axis 101 may be provided. The beam receiving aperture plate 106 is shown to be located proximate to the CPB source 102 and may function as an extractor aperture in conjunction with the generation of CPB from the CPB source 102. In general, operating currents and voltages, including those used for the CPB lenses, beam deflectors, and optical columns, may be supplied from one or more sources 117 and applied as controlled by a processor system 121, such as a personal computer, or other hardware.

[0021] FIG. 1C is a schematic cross-sectional view of the filter aperture plate 118, illustrating the CPB position. As seen in FIG. 1C, the axial CPB 111A and the cross-sections of the spectral beam portions 151 to 153 are shown as being directed towards the filter aperture plate 118. The axial CPB 111A and the spectral beam portion 151 are directed towards the filter aperture 120, and the spectral beam portions 152 to 153 are incident on the filter aperture plate 118 and blocked. By adjusting the position of the spectral beam portion, a specific spectral beam component can be selected. The axial CPB 111A and the spectral beam portion 151 can overlap at the filter aperture 118, but in the embodiment of FIG. 1A, the beam overlap is slightly downstream at the plane 127.

[0022] FIGS. 1D to 1E are schematic cross-sectional views of the blanking aperture plate 126, illustrating the CPB position. As seen in FIG. 1D, corresponding to FIG. 1A, the cross-sections of the axial CPB 111A and the spectral beam portion 151 are shown as being incident in the direction of the blanking aperture plate 126. The spectral beam portion 151 is incident on and transmitted through the blanking aperture 128. The axial CPB 111A is directed towards the blanking aperture plate 126 and blocked. As seen in FIG. 1E, corresponding to FIG. 1B, the cross-sections of the axial CPB 111A and the spectral beam portion 151 are shown as being directed towards the blanking aperture plate 126. The spectral beam portion 151 is incident on the blanking aperture plate 126 and blocked. The axial CPB 111A is directed towards the blanking aperture 128 and transmitted. Therefore, by using the beam steering deflector 124, either the axial CPB 111A or the spectral beam portion 151 can be transmitted to the workpiece.

[0023] Embodiment 2 FIG. 1F is a cross-sectional view of a filter aperture plate 178, which can be used in place of the filter aperture plate 118, illustrating an alternative filtering arrangement for use with the CPB system 100 of FIGS. 1A-1B. The filter aperture plate 178 defines a first aperture 170 and a second aperture 174 separated by a CPB blocking region 176. In this embodiment, the spectral beam portions 151, 153 are blocked, the spectral beam portion 152 is transmitted by the second aperture 174, and the axial CPB 111A is transmitted by the first aperture 170. A selected one of the spectral beam components 151-153 can be transmitted to the work piece by adjusting the position of the beam filter aperture plate 168 with the actuator 119 or by adjusting the beam position with the beam filtering deflector 122. In other embodiments, the filter aperture plate can have multiple apertures to select one or more selected spectral beam components.

[0024] Example 3 Referring to FIG. 2, an exemplary method 200 includes selecting a CPB type at 202, such as a CPB with a higher beam current without spectral filtering or a CPB with a lower beam current with selected spectral components. In this embodiment, the CPB with the higher beam current without spectral filtering is referred to as having a standard spectrum, or energy width (STD). As described above in FIGS. 1A-1B, the lower current CPB is generally produced by spectral filtering and is therefore referred to as having a limited energy width (LTD). If the standard energy width is selected at 204, a first CPB without spectral filtering is transmitted and at 206, an additional beam with limited spectral components is blocked with a filter aperture and / or a blanking aperture. At 210, the CPB with the STD energy width is directed toward the workpiece. In the embodiment of FIGS. 1A-1B, beam portions with some spectral components are blocked by the filter aperture and at least one beam with selected spectral components is blocked by the blanking aperture. If an LTD energy range is selected at 224, then a particular energy range and beam current can be selected at 225, unselected spectral components and CPBs having the STD energy range are blocked or attenuated at 226, and a CPB having the LTD energy range is directed to the workpiece at 228.

[0025] Specific low current beam and spectral components (LTD CPB) can be selected using one or more filter apertures, blanking apertures, and / or beam deflectors, such as beam steering deflectors and beam filtering deflectors. A filter aperture can be selected by adjusting the beam position with a beam deflector or by moving an associated aperture plate with an actuator to block unselected beam portions.

[0026] Example 4 Referring to FIG. 3, a CPB system 300 includes a system controller 302 coupled to a CPB source 304 that generates an axial CPB 306 and an off-axis CPB 308 defined by respective apertures 307, 309 of a beam receiving aperture plate 310. A lens 312 directs the axial CPB 306 along an axis 314 and spectrally spreads the off-axis CPB 308 over an area 311. For convenience, the spectral spreading is associated with the chromatic aberration of the lens 312, but can be provided by other CPB optical elements. For purposes of this description, FIG. 3 illustrates representative first and second spectral components CPB 308A, 308B oriented along respective axes, such as axis 315 associated with the first spectral component CPB 308A. In a typical embodiment, the spectral component CPB 308A has a lower beam energy than the spectral beam component 308B, since the CPB lens 312 tends to provide a larger deflection for the lower energy CPB.

[0027] The spectral components CPB308A, 308B, and the axial beam 306 are directed toward a filter aperture 316 having first and second edges 316A, 316B defined within a filter aperture plate 318. As shown, the first spectral component CPB308A and the axial CPB306 are transmitted by the filter aperture 316, while the second spectral component CPB308B is directed toward and blocked by the filter aperture plate 318. A beam filtering deflector 319 can be arranged to deflect the selected spectral component CPB to be transmitted by the filter aperture 316. For example, the second spectral component CPB308B can be deflected to be transmitted, and unselected spectral beam portions, such as the spectral component CPB308A, are blocked elsewhere. Alternatively, the filter aperture plate 318 can define one or more additional apertures used to select spectral components. Unselected components can be blocked by the filter aperture plate 318 or elsewhere. In some cases, the selection of a particular spectral component is used to select the CPB current, and further, the CPB spectrum is mostly or entirely irrelevant.

[0028] The beam steering deflector 320 is positioned to direct either the first component CPB 308A or the axial CPB 306 along axis 314 or otherwise towards the workpiece. As shown, the axial CPB 306 is deflected to be incident on the blanking aperture plate 322 and the first spectral component CPB 308A is directed through a blanking aperture 323 defined within the blanking aperture plate 322. The beam steering deflector 320 can be further activated to direct the axial beam 306 through the blanking aperture 323 such that the first spectral component beam 308A continues to be incident on the blanking aperture plate 322 along axis 315 and is blocked. Blocking the axial CPB 306 with the blanking aperture plate 322 can be advantageous since this beam is typically a high current CPB and can be blocked by the blanking aperture plate 322 without degrading the blanking aperture 320.

[0029] The selected CPBs are delivered to a workpiece 324 disposed on a stage 326 that provides translational motion along one, two, or three axes, such as X, Y, and Z axes of a right-handed Cartesian coordinate system 350, with the Y axis extending outside the drawing plane, and one or more angular rotations, such as specified by polar and azimuthal angles. The stage 326 is responsive to a stage controller 328 that couples to the system controller 302. An optical imaging device 352 may be positioned to provide an optical image of the workpiece 324.

[0030] As discussed above, the beam filtering deflector and filter aperture plate 318 can be used to select CPB spectral components. In the example of FIG. 3, if a spectral component is selected at a lower energy than that of the spectral component CPB 308A, the spectral component CPB 308B and the higher energy components can be directed to and blocked by the filter aperture plate 318. If a higher energy component, such as the spectral component CPB 308B, is selected (transmitted), the lower energy components, such as the spectral component CPB 308A, are blocked by the aperture edge 316A. One or both of the beam-accepting aperture plate 306 and the filter aperture plate 318 can include multiple apertures to aid in the selection of the spectral components and / or the CPB current. An actuator 330 can be coupled to the filter aperture plate 318 to adjust the positioning of the filter aperture edges 316A, 316B to select the spectral components or the CPB current or to compensate for beam-induced degradation.

[0031] The system controller 302 couples to a memory 335 that stores processor-executable instructions for image processing and provides a GUI 342 for various functions, such as CPB current selection 336, spectral content selection 338, deflector control 340, and aperture selection and positioning 344. System control parameters may be specified using internally stored values ​​from the memory 335 or may be provided by a user using one or more user input devices 350. In most embodiments, interface circuitry 346, such as one or more ADCs, DACs, amplifiers, or buffer amplifiers, is included to control the CPB source 304, the actuator 330, and other parts of the system 302.

[0032] It will be understood that the layout of Figure 3 is for convenience of illustration and that the actual arrangement is not shown. Additionally, although only a single CPB source and associated optical column is shown, in some embodiments, two or more CPB sources and optical columns are provided, such as an ion beam optical column used in workpiece processing and an electron beam optical column used in workpiece imaging.

[0033] Example 5 4A, a receiving aperture plate 400 defines beam receiving apertures 404-407, each having a different diameter and area and positioned at different distances from a central aperture 402. The receiving aperture plate 400 may be positioned to generate CPBs with various beam currents and thus different levels of Coulomb interaction. The apertures defined within the beam receiving aperture plate 400 may be distributed radially, azimuthally, or in any direction to provide a CPB current and CPB incident on one or more CPB optical elements, such as a CPB lens, allowing for selection of spectral content.

[0034] With the central aperture 402 aligned with respect to the optical column, the apertures 404-407 define additional CPBs with different beam currents due to their different areas and different locations with respect to the axis of the CPB emitter or the axis of the optical column. As shown in FIG. 1A, different locations may result in different positions of the spectral components focused by the downstream CPB lens. The apertures need not be circular, but may have any shape, which may be the same or different. Furthermore, multi-aperture plates may also be used to define filter apertures, and the CPB associated with a particular aperture in the multi-aperture plate may be selected by appropriate positioning of the aperture plate with linear and / or rotary actuators, by use of CPB deflectors, or by both positioning the aperture plate with actuators and positioning the CPB with CPB deflectors.

[0035] 4B, receiving aperture plate 450 defines beam receiving apertures 454-457, each having a different diameter and area and positioned at different distances from central aperture 452. In this embodiment, central receiving aperture 452 has a smaller diameter than at least one other receiving aperture, and furthermore has a lower beam current than that produced by an off-axis receiving aperture, such as receiving aperture 456, and thus can be used to provide an on-axis beam with a different level of Coulomb interaction. Although the apertures defined by beam receiving aperture plates 400, 450 are shown as circular, other shapes such as rectangular or other polygonal shapes, as well as oval, elliptical, etc., may also be used. Additionally, the receiving aperture plates need not be circular.

[0036] Example 6 5A-5B, a CPB system 500 operable to provide a CPB having various CPB currents includes a CPB source 502 directing a CPB 504 to a receiving aperture plate 506. The receiving aperture plate 506 defines a first aperture 506A and a second aperture 506B that transmit a first CPB 514 and a second CPB 512. In this example, the first CPB 514 and aperture 506A are disposed on an axis 501 and are referred to as an axial, or on-axis, CPB, and an axial, or on-axis aperture, respectively. The second CPB 512 and aperture 506B are not disposed on an axis 501 and are referred to as an off-axis CPB and an off-axis aperture, respectively. However, as discussed below, such CPBs can be manipulated to propagate as on-axis or off-axis CPBs at various locations within the optical column depending on the applied deflection. Typically (but not necessarily), the first CPB 514 will have a substantially higher beam current and will tend to have greater Coulomb interactions than the second CPB 512, which may, for example, limit beam focus. A CPB lens 508 is positioned on axis 501 to focus or shape the CPB, although focusing is not shown in Figures 5A-5B.

[0037] The first CPB 514 and the second CPB 512 are directed along the beam selection deflector 516 shown in FIG. 5A such that the first CPB 514 is directed towards the blanking aperture plate 520 and further a deflection is added to direct the second CPB 512 towards the aperture 522 of the blanking aperture plate 520. The added deflection is shown to occur in the deflection plane 518, but the deflection may be dispersed along the axis 501. The second deflector 524 (beam steering deflector) deflects the selected CPB (i.e., the second CPB 512) and directs the selected CPB to propagate along the axis 501. As a result, the second CPB 512 is directed towards the workpiece while the first CPB 514 is blocked.

[0038] Referring to FIG. 5B, the beam selection deflector 516 is shown without adding a deflection such that the first CPB 514 propagates along the axis 501 without being deflected by the second deflector 524. The second CPB 512 is directed towards the blanking aperture plate 520 and blocked. In this configuration, the second CPB 512 is blocked and the first CPB 514 is directed towards the workpiece along the axis 501. Thus, in the arrangements of FIGS. 5A - 5B, either an axially different CPB or an off-axis CPB with different currents can be selected and delivered to the workpiece along the common axis (axis 501).

[0039] Example 7 6, a CPB system 600 includes a system controller 602 coupled to a CPB source 604 that generates an axial CPB 606 and an off-axis CPB 608 defined by respective apertures 610, 611 in a beam-receiving aperture plate 614, which may include additional apertures 609, 612 that can also be used to define the CPB. In some cases, the apertures are sized to provide a desired beam current, and in some embodiments, the off-axis CPB 608 has a higher beam current than the axial CPB 606. As shown, the axial CPB 606 propagates along an optical axis 601, and the off-axis CPB propagates along an axis 629 established based on the location of the CPB source 604 and the beam-receiving aperture plate 614.

[0040] The first beam deflector 616 is operable to deflect the off-axis CPB 608 towards the optical axis 601 as a deflected off-axis CPB 628 and to further deflect the axial CPB 606 away from the axis 601 as a deflected axial CPB 626. Alternatively, the first beam deflector 616 can be operated such that the axial CPB 606 propagates undeflected along the optical axis 601 and the off-axis beam 608 continues to propagate away from the optical axis 601 along the axis 629. The second deflector 618 is operable to deflect the deflected off-axis CPB 628 to form an actuation beam 638 that propagates along the optical axis 601 through a blanking aperture 622 defined in a blanking aperture plate 620 towards a workpiece 644. The deflected axial beam 626 is similarly deflected by the second deflector 618 towards the optical axis 601 but is blocked by the blanking aperture plate 620. The axial beam 606 and the off-axis beam 608 can have different beam currents. For example, the off-axis beam 608 can have a greater beam current than the axial beam current 606 and vice versa. The system controller 602 couples the first deflector 616 and the second deflector 618 to selectively direct one of the axial CPB 606 and the off-axis CPB 608 towards the workpiece 644. In FIG. 6, with the first deflector 616 and the second deflector 618 operating to not provide beam deflection, the axial CPB 606 is delivered to the workpiece 644 such that the off-axis beam 608 propagates along the axis 629 and is blocked by the blanking aperture plate 620. In other embodiments, the deflectors 616, 618 generate a deflection that deflects the axial CPB 606 away from the optical axis 601 and through a blanking aperture 622, delivering the axial CPB 606 to the workpiece 644. The off-axis CPB 606 can be deflected to propagate along the optical axis 601 and then deflected again to enter the blanking aperture plate 620.

[0041] As shown, the beam-receiving aperture plate 614 can define multiple apertures, and a CPB based on any of these apertures can be selectively directed to the workpiece 644 while the other CPBs are blocked. In this example, aperture 610 is used to generate an axial CPB and aperture 611 is used to generate an off-axis CPB, although in other examples, both CPBs can be off-axis CPBs. Selection of a particular CPB as the active CPB can be accomplished by blocking the CPBs associated with all but one aperture of the beam-receiving aperture plate 614 with a first deflector 616 and a second deflector 618. In some cases, the beam-receiving aperture plate 614 can be rotated and / or translated with one or more actuators to position the selected receiving aperture relative to the CPB source 604 to provide an off-axis beam at a particular angle and CPB current.

[0042] The system controller 602 is coupled to a memory 635 that stores processor executable instructions for image processing and provides a GUI 642 for various functions, such as CPB current selection 636, deflector control 640, and beam receiving aperture selection and positioning 644. System control parameters may be specified using internally stored values ​​from the memory 635 or may be provided by a user using one or more user input devices 650. In most embodiments, interface circuitry 646, such as one or more ADCs, DACs, amplifiers, or buffer amplifiers, is included to control the CPB source 604, actuators, and other parts of the system 600. Although a beam deflector is shown in FIG. 6, in other embodiments, a CPB lens, or a combination of lenses and beam deflectors, may be used to direct the selected CPB to the workpiece 644. The workpiece 644 may be positioned on a stage 645 that couples to a stage controller 647 for positioning the workpiece in response to the system controller 602.

[0043] It will be understood that the layout of Figure 6 is for convenience of illustration and that the actual arrangement is not shown. Additionally, although only a single CPB source and associated optical column is shown, in some embodiments, two or more CPB sources and optical columns are provided, such as an ion beam optical column used in workpiece processing and an electron beam optical column used in workpiece imaging.

[0044] Example 8 In some embodiments, a CPB can be selected from a plurality of beam receiving apertures. Referring to FIG. 7, a beam receiving aperture plate 714 defines a plurality of beam receiving apertures that generate corresponding CPBs, such as representative first CPB 706 and second CPB 708. These CPBs propagate toward the workpiece relative to the optical axis 701. A first deflector 716 and a second deflector 718 are positioned to select one or more CPBs associated with the corresponding beam receiving apertures for delivery to the workpiece through a blanking aperture 722 in the blanking aperture plate 720. Representative CPB paths 770-773 are illustrated for the second CPB 708. The beam path 770 is deflected by the first deflector to the optical axis 701, and then deflected along the axis 701 by the second deflector 718 for transmission by the blanking aperture 722. Beam path 771 is associated with a deflection toward (but not to) the optical axis 701 and then through blanking aperture 722, but not parallel to the optical axis 701. Beam path 772 corresponds to a beam path without deflection by either the first deflector 716 or the second deflector 718. Beam path 773 is the result of another CPB, such as the first CPB 706, being deflected toward the optical axis 701. Any of the CPBs generated at the beam-receiving aperture plate 722 can be directed to the workpiece, while some or all of the other CPBs can be blanked.

[0045] Example 8 8, an exemplary method 800 includes fabricating a plurality of CPBs with corresponding apertures in an extractor aperture plate, at 802. A particular CPB is selected, for example, based on a desired beam current, at 804. A deflection system is activated, at 806, to direct the selected CPB through the blanking aperture to the workpiece and block the other CPBs.

[0046] Disclosure Provisions Item 1 is a charged particle beam (CPB) optical system including: a beam receiving aperture plate defining a first receiving aperture and at least one second receiving aperture and positioned relative to a CPB source such that the first CPB is transmitted by the first receiving aperture and the second CPB is transmitted by the at least one second receiving aperture; a CPB lens positioned to receive the first CPB and the second CPB from the beam receiving aperture plate; the filter aperture plate defining a filter aperture, the CPB lens operable to direct selected portions of the first CPB and the second CPB through the filter aperture such that at least the second CPB has an associated spectral spread proximate the filter aperture plate; and a beam steering deflector operable to deflect the first CPB or the selected portion of the second CPB transmitted by the filter aperture to a workpiece.

[0047] Item 2 includes the subject matter described in item 1 and further specifies that the first receiving aperture of the beam receiving aperture plate is positioned on an optical axis defined by the CPB lens.

[0048] Item 3 includes the subject matter described in any one of items 1 to 2, and further includes a CPB emitter, and the first receiving aperture of the beam receiving aperture plate, the CPB lens, and the CPB emitter are arranged on the optical axis.

[0049] Item 4 includes the subject matter described in any of items 1-3, and further includes a blanking aperture plate defining a blanking aperture, the blanking aperture being positioned to transmit the first CPB and attenuate a selected portion of the second CPB received from the beam filtering deflector, or alternatively to transmit a selected portion of the second CPB and attenuate the first CPB received from the beam filtering deflector.

[0050] Item 5 includes the subject matter described in any of items 1-4, further including a beam selection deflector operable to selectively direct either the first CPB, or a selected portion of the second CPB, through the blanking aperture.

[0051] Item 6 includes the subject matter described in any of items 1 to 5, and further provides that the beam selective deflector is operable to selectively direct either the first CPB or a selected portion of the second CPB along the optical axis.

[0052] Item 7 includes the subject matter described in any of items 1-6, and further includes an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned to pass through a selected portion of the second CPB.

[0053] Clause 8 includes the subject matter of any of clauses 1-7, and further includes an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned such that the unselected portion of the second CPB is blocked by the filtering aperture plate.

[0054] Clause 9 includes the subject matter of any of clauses 1-8, and further includes an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned such that the unselected portion of the second CPB is blocked by the filtering aperture plate.

[0055] Item 10 includes the subject matter described in any of items 1-9, and further includes a control system coupled to the actuator and operable to move the filter aperture plate so that a selected portion of the second CPB passes through the filter aperture.

[0056] Clause 11 includes the subject matter described in any of clauses 1-10, and further specifies that the at least one second receiving aperture includes a plurality of secondary receiving apertures arranged to define respective second CPBs that are directed toward the filtering aperture plate such that the filtering aperture transmits at least one of the second CPBs, and further includes a beam selection deflector arranged to direct either the first CPB or a selected one of the second CPBs along the optical axis.

[0057] Item 12 is a method that includes generating at least a first CPB and a second CPB propagating along a first axis and a second axis, respectively, the first axis being different from the second axis; directing the second CPB toward the first axis and toward a filter aperture using a charged particle beam lens such that spectral components of the second CPB are dispersed at the filter aperture; selectively transmitting at least selected spectral components of the second CPB at the filter aperture; and directing either the first CPB or the selected spectral components of the second CPB along the first axis.

[0058] Item 13 includes the subject matter of item 12, further including using a beam-selecting deflector to direct selected spectral components of the second CPB along the first axis.

[0059] Item 14 includes the subject matter described in any of items 12-13, and further specifies that the distribution of the spectral components of the second CPB at the filtering aperture is based on the chromatic aberration of the CPB lens.

[0060] Paragraph 15 includes the subject matter described in any of paragraphs 12 to 14, and further includes selectively attenuating either the spectral components of the first CPB or the second CPB in the blanking aperture plate, and transmitting either the spectral components of the second CPB or the first CPB through a blanking aperture defined in the blanking aperture plate.

[0061] Item 16 includes the subject matter of any of items 12-15, and further includes positioning an edge of the blanking aperture such that selected spectral components of the second CPB are transmitted through the blanking aperture and unselected spectral components are attenuated.

[0062] Item 17 includes the subject matter described in any one of items 12 to 16, and further specifies that the first axis is an optical axis.

[0063] Paragraph 18 includes the subject matter described in any of paragraphs 12 to 17, and further specifies that the first CPB and the second CPB are generated by directing at least one CPB to a beam-receiving aperture plate that defines a first aperture and a second aperture, the first aperture being positioned on the optical axis.

[0064] Item 19 is a method that includes generating at least a first CPB and a second CPB propagating along a first axis and a second axis, respectively, the first axis being different from the second axis; directing the second CPB toward the first axis and toward a filter aperture such that spectral components of the second CPB are dispersed at the filter aperture; selectively transmitting at least selected spectral components of the second CPB at the filter aperture; and directing either the first CPB or the selected spectral components of the second CPB toward a workpiece.

[0065] Paragraph 20 includes the subject matter of paragraph 19, further including directing either the first CPB or the selected spectral components of the second CPB toward the workpiece along a first axis.

[0066] Clause 21 includes the subject matter of any of clauses 19-20, and further includes attenuating unselected spectral components of the second CPB at an aperture plate arranged to transmit the selected spectral components, and selectively directing one of the selected spectral components of the first CPB and the second CPB through a blanking aperture to attenuate the selected spectral components of the second CPB or the first CPB, respectively, at the blanking aperture.

[0067] Item 22 is a charged particle beam (CPB) optical system including a beam receiving aperture plate defining a first receiving aperture and at least one second receiving aperture and positioned relative to a CPB source such that the first CPB is transmitted by the first receiving aperture and the second CPB is transmitted by the at least one second receiving aperture, a blanking aperture plate defining a blanking aperture, and a beam selector operable to selectively direct the first CPB or the second CPB through the blanking aperture to the workpiece.

[0068] Paragraph 23 includes the subject matter of any of paragraphs 22, further including an optical column arranged to receive the first CPB and the second CPB, and the first receiving aperture or the selected second receiving aperture is located on an optical axis of the optical column.

[0069] Paragraph 24 includes the subject matter described in any of paragraphs 22-23 and further specifies that the beam selector includes a first beam deflector and a second beam deflector, the first beam deflector operable to deflect the second CPB toward the optical axis, and the second beam deflector operable to direct the second CPB received from the first beam deflector through a blanking aperture to the workpiece.

[0070] Item 25 includes the subject matter of any of items 22-24, further specifying that the first receiving aperture and the second receiving aperture are off-axis apertures.

[0071] Item 26 includes the subject matter described in any one of items 22 to 25, wherein the first receiving aperture is an on-axis aperture and the second receiving aperture is an off-axis aperture.

[0072] Item 27 includes the subject matter of any of items 22-26, further specifying that the beam current associated with the second acceptance aperture is greater than the beam current associated with the first acceptance aperture.

[0073] Paragraph 28 includes the subject matter described in any of paragraphs 22-27, and further specifies that the beam receiving aperture plate defines a first receiving aperture, a second receiving aperture, and a third receiving aperture, the third receiving aperture transmitting a third CPB, and the beam selector is operable to selectively direct the second CPB and the third CPB through the blanking aperture to the workpiece.

[0074] Item 29 includes the subject matter of any of items 22-28, further specifying that the beam selector includes at least one beam deflector or at least one CPB lens.

[0075] Clause 30 includes the subject matter of any of clauses 22-29, and further includes a spectral disperser arranged to receive the first CPB and the second CPB from the beam receiving aperture plate and spectrally disperse at least one of the first CPB and the second CPB, and a filter aperture plate defining a filter aperture, the spectral disperser operable to direct selected portions of the first CPB and the second CPB through the filter aperture such that at least the second CPB has an associated spectral dispersion proximate the filter aperture plate, and the beam selector operable to deflect the first CPB or the selected portion of the second CPB transmitted by the filter aperture to the workpiece.

[0076] Item 31 includes the subject matter described in any of items 22 to 30, and further specifies that the spectral disperser includes a CPB lens operable to spectrally disperse at least one of the first CPB and the second CPB based on chromatic aberration.

[0077] Item 32 includes the subject matter described in any of items 22 to 31, further including a CPB emitter, and the first receiving aperture of the beam receiving aperture plate, the CPB lens, and the CPB emitter are disposed on the optical axis.

[0078] Clause 33 includes the subject matter described in any of clauses 22-32, further including an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned to pass through a selected portion of the second CPB.

[0079] Clause 34 includes the subject matter of any of clauses 22-33, further including an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned such that the unselected portion of the second CPB is blocked by the filtering aperture plate.

[0080] Paragraph 35 includes the subject matter described in any of paragraphs 22 to 34, and further includes a control system coupled to the actuator and operable to move the filter aperture plate so that a selected portion of the second CPB passes through the filter aperture.

[0081] Item 36 is a method that includes generating at least a first CPB and a second CPB propagating along a first axis and a second axis, respectively, the first axis being different from the second axis; directing the second CPB toward the first axis and toward a filter aperture using a charged particle beam lens such that spectral components of the second CPB are dispersed at the filter aperture; selectively transmitting at least selected spectral components of the second CPB at the filter aperture; and directing either the first CPB or the selected spectral components of the second CPB along the first axis.

[0082] Item 37 includes the subject matter of item 36, further including using a beam-selecting deflector to direct selected spectral components of the second CPB along the first axis.

[0083] Item 38 includes the subject matter of any of items 36-37, and further specifies that the distribution of the spectral components of the second CPB at the filtering aperture is based on the chromatic aberration of the CPB lens.

[0084] Paragraph 39 includes the subject matter of any of paragraphs 36 to 38, and further includes selectively attenuating either the spectral components of the first CPB or the second CPB in the blanking aperture plate, and transmitting either the spectral components of the second CPB or the first CPB through a blanking aperture defined in the blanking aperture plate.

[0085] Clause 40 includes the subject matter of any of clauses 36-39, and further includes positioning an edge of the blanking aperture such that selected spectral components of the second CPB are transmitted through the blanking aperture and unselected spectral components are attenuated.

[0086] Item 41 includes the subject matter described in any one of items 36 to 40, and further specifies that the first axis is an optical axis.

[0087] Paragraph 42 includes the subject matter described in any of paragraphs 36 to 41, and further specifies that the first CPB and the second CPB are generated by directing at least one CPB to a beam-receiving aperture plate defining a first aperture and a second aperture, the first aperture being positioned on the optical axis.

[0088] Item 43 is a method that includes generating at least a first CPB and a second CPB propagating along a first axis and a second axis, respectively, the first axis being different from the second axis, selectively directing the second CPB toward the first axis, and transmitting the second CPB toward a workpiece and attenuating the first CPB at a blanking aperture plate.

[0089] Item 44 includes the subject matter described in item 43, and further specifies that the second CPB is selectively directed toward the first axis by the first beam selector and directed along the first axis by the second beam selector.

[0090] In view of the many contemplated 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 should not be taken as limiting the scope of the present disclosure.

Claims

1. 1. A charged particle beam (CPB) optical system comprising: a beam receiving aperture plate defining a first receiving aperture and at least one second receiving aperture and positioned relative to the CPB source such that a first CPB is transmitted by the first receiving aperture and a second CPB is transmitted by the at least one second receiving aperture; a blanking aperture plate defining a blanking aperture; a beam selector operable to selectively direct either the first CPB or the second CPB to a workpiece through the blanking aperture.

2. 2. The charged particle beam optical system of claim 1, further comprising an optical column positioned to receive the first CPB and the second CPB, wherein the first receiving aperture or a selected second receiving aperture is positioned on an optical axis of the optical column.

3. 2. The charged particle beam optical system of claim 1, wherein the beam selector includes a first beam deflector and a second beam deflector, the first beam deflector operable to deflect the second CPB toward an optical axis, and the second beam deflector operable to direct the second CPB received from the first beam deflector through the blanking aperture to a workpiece.

4. The charged particle beam optical system of claim 3 , wherein the first and second receiving apertures are off-axis apertures.

5. The charged particle beam optical system of claim 3 , wherein the first receiving aperture is an on-axis aperture and the second receiving aperture is an off-axis aperture.

6. The charged particle beam optical system of claim 5 , wherein a beam current associated with the second receiving aperture is greater than a beam current associated with the first receiving aperture.

7. 2. The charged particle beam optical system of claim 1, wherein the beam receiving aperture plate defines the first receiving aperture, the second receiving aperture, and a third receiving aperture, the third receiving aperture transmitting a third CPB, and the beam selector is operable to selectively direct the second CPB and the third CPB through the blanking aperture and onto the workpiece.

8. The charged particle beam optical system of claim 1 , wherein the beam selector comprises at least one beam deflector or at least one CPB lens.

9. a spectral disperser positioned to receive the first CPB and the second CPB from the beam-receiving aperture plate and to spectrally disperse at least one of the first CPB and the second CPB; 2. The charged particle beam optical system of claim 1, further comprising: a filtering aperture plate defining a filtering aperture, wherein the spectral disperser is operable to direct selected portions of the first CPB and the second CPB through the filtering aperture such that at least the second CPB has an associated spectral spread proximate the filtering aperture plate, and wherein the beam selector is operable to deflect the selected portions of the first CPB or the second CPB transmitted by the filtering aperture to a work piece.

10. 10. The charged particle beam optical system of claim 9, wherein the spectral disperser comprises a CPB lens operable to spectrally disperse at least one of the first CPB and the second CPB based on chromatic aberration.

11. 11. The charged particle beam optical system of claim 10, further comprising a CPB emitter, wherein the first receiving aperture of the beam receiving aperture plate, the CPB lens, and the CPB emitter are positioned on an optical axis.

12. 12. The charged particle beam optical system of claim 11, further comprising an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned to pass through the selected portion of the second CPB.

13. 12. The charged particle beam optical system of claim 11, further comprising an actuator coupled to the filtering aperture plate and operable to position the filtering aperture plate such that an edge of the filtering aperture plate is positioned such that an unselected portion of the second CPB is blocked by the filtering aperture plate.

14. 13. The charged particle beam optical system of claim 12, further comprising a control system coupled to the actuator and operable to move the filtering aperture plate so that the selected portion of the second CPB passes through the filtering aperture.

15. 1. A method comprising: generating at least a first CPB and a second CPB propagating along a first axis and a second axis, respectively, the first axis being different from the second axis; directing the second CPB toward the first axis and toward the filter aperture using a charged particle beam lens such that the spectral components of the second CPB are dispersed at the filter aperture; selectively transmitting at least selected spectral components of the second CPB at the filtering aperture; and directing either the first CPB or the selected spectral components of the second CPB along the first axis.

16. 16. The method of claim 15, further comprising directing the selected spectral components of the second CPB along the first axis using a beam-selecting deflector.

17. The method of claim 15 , wherein a distribution of the spectral components of the second CPB at the filtering aperture is based on chromatic aberration of a CPB lens.

18. 16. The method of claim 15, further comprising selectively attenuating either the spectral components of the first CPB or the second CPB in a blanking aperture plate, and transmitting either the spectral components of the second CPB or the first CPB through a blanking aperture defined in the blanking aperture plate.

19. 20. The method of claim 18, further comprising positioning an edge of the blanking aperture such that the selected spectral components of the second CPB are transmitted through the blanking aperture and unselected spectral components are attenuated.

20. The method of claim 15 , wherein the first axis is the optical axis.

21. 16. The method of claim 15, wherein the first CPB and the second CPB are generated by directing at least one CPB to a beam-receiving aperture plate defining a first aperture and a second aperture, the first aperture being located on an optical axis.

22. 1. A method comprising: generating at least a first CPB and a second CPB propagating along a first axis and a second axis, respectively, the first axis being different from the second axis; Selectively orienting the second CPB toward the first axis; transmitting the second CPB toward a workpiece and attenuating the first CPB at a blanking aperture plate.

23. 23. The method of claim 22, wherein the second CPB is selectively directed toward the first axis by a first beam selector and further directed along the first axis by a second beam selector.

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