Charged particle beam device

Abstract

A charged particle beam apparatus for examining a sample with an array of primary charged particle beamlets is described. The charged particle beam apparatus comprises: a charged particle beam source for generating a primary charged particle beam; a multi-aperture plate having at least two openings for generating the array of charged particle beamlets, the array of charged particle beamlets having at least a first beamlet having a first resolution on the sample and a second beamlet having a second resolution on the sample; an aberration correction element for correcting at least one of a spherical aberration and a chromatic aberration of a rotationally symmetric charged particle lens; and an objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate position on the sample.

Description

[0001] This application is a divisional application of Chinese patent application 201810724460.7, entitled “Charged particle beam device and method for imaging or illuminating a sample”, filed on July 4, 2018. Technical Field

[0002] The present invention relates to a charged particle beam device, for example, for use in inspection system applications, test system applications, defect inspection or critical dimension marking applications, and the like, and also relates to a charged particle beam device operating method. More specifically, it relates to a charged particle beam device for a multi-beam system for general purposes (such as imaging biometric structures) and / or for high throughput EBI (electron beam inspection). In particular, it relates to a scanning charged particle beam device and a method for performing electron beam inspection using the scanning charged particle beam device. Background Art

[0003] Modern semiconductor technology is highly dependent on accurate control of the various processes used during the production of integrated circuits. Therefore, wafers are repeatedly inspected to locate problems as early as possible. In addition, masks or reticles are inspected prior to actual use during wafer processing to ensure that the mask accurately defines the corresponding pattern. Inspecting the wafer or mask for defects includes inspecting the entire wafer or mask area. In particular, inspection of the wafer during manufacturing includes inspecting the entire wafer area in such a short time that the production output is not limited by the inspection process.

[0004] Scanning electron microscopes (SEMs) have been used to inspect wafers. The wafer surface is scanned using, for example, a single finely focused electron beam. When the electron beam strikes the wafer, secondary electrons and / or backscattered electrons, i.e., signal electrons, are generated and measured. Pattern defects at the same position on the wafer are detected by comparing the intensity signal of the secondary electrons with, for example, a reference signal corresponding to the same position on the pattern. However, due to the increasing demand for higher resolution, it takes a long time to scan the entire surface of the wafer. Therefore, it is difficult to inspect wafers using a conventional (single beam) scanning electron microscope (SEM) because this method does not provide a corresponding yield.

[0005] Wafer and mask defect inspection in semiconductor technology requires high-resolution and fast inspection tools that cover the entire wafer / mask application or hotspot inspection. Due to the limited resolution of optical tools and their inability to cope with the size of shrinking defects, electron beam inspection is gaining in importance. In particular, from the 20nm node and beyond, the high-resolution potential of electron beam-based imaging tools is needed to detect all defects of interest.

[0006] Current multi-particle beam systems can include aperture lens arrays. The focal length of the aperture lens is inversely proportional to the difference of the electric field components (along the mean axis) before and after the aperture. By shaping the field distribution along the aperture lens array, the focal length of the individual apertures can be varied so that the field curvature of the beamlets can be controlled (or corrected). In this configuration, other off-axis aberrations (field astigmatism, off-axis coma and distortion) still exist. In order to mitigate these residual aberrations, the middle beamlet focus is usually a strongly amplified image of the source. The image of the source is strongly reduced with the downstream objective lens. This compromise between reduction and residual off-axis aberrations limits the performance of such devices. Another mode often adopted is to limit the total emission angle (that is, the total beamlet number) from the source so that the off-axis aberration can be reduced. Summary of the invention

[0007] In view of the foregoing, a charged particle beam apparatus and a method of imaging a sample using an array of primary charged particle beamlets are provided that overcome at least some of the problems in the art.

[0008] In view of the above, a charged particle beam apparatus for examining a sample with an array of primary charged particle beamlets and a method of imaging or illuminating a sample with an array of primary charged particle beamlets are provided.

[0009] According to one embodiment, a charged particle beam device for inspecting a sample with an array of primary charged particle beamlets is provided. The charged particle beam device includes: a charged particle beam source for generating a primary charged particle beam; a multi-aperture plate having at least two openings to generate an array of charged particle beamlets, the array of charged particle beamlets having at least a first beamlet having a first resolution on the sample and a second beamlet having a second resolution on the sample; an aberration correction element for correcting at least one of a spherical aberration and a chromatic aberration of a rotationally symmetric charged particle lens; and an objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate position on the sample.

[0010] According to one embodiment, a charged particle beam device for inspecting a sample with an array of primary charged particle beamlets is provided. The charged particle beam device includes a charged particle beam source for generating a primary charged particle beam; a multi-aperture plate having at least two openings to generate an array of charged particle beamlets, the array of charged particle beamlets having at least a first beamlet having a first resolution on the sample and a second beamlet having a second resolution on the sample; an aberration correction element provided between the charged particle beam source and the multi-aperture plate to correct the difference between the first resolution on the sample and the second resolution on the sample, the aberration correction element including at least two multipole elements having 6 or more poles; and an objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate position on the sample.

[0011] According to another embodiment, a method for imaging or illuminating a sample with an array of primary charged particle beamlets is provided. The method includes: generating an array of charged particle beamlets having at least a first beamlet and a second beamlet by illuminating a multi-aperture plate with a primary charged particle beam; focusing the array of charged particle beamlets on the sample with an objective lens assembly; and correcting the aberration difference between the first beamlet and the second beamlet with an aberration correction element. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to be able to understand in detail the manner in which the above-mentioned features of the embodiments described herein are used, reference may be made to the more specific description briefly summarized above of the embodiments. The accompanying drawings relate to the embodiments and are described as follows:

[0013] Figure 1 A schematic diagram of a multi-beam apparatus for sample inspection is shown;

[0014] Figure 2 A schematic diagram of a multi-beam device for sample inspection having an array of objective lenses according to embodiments described herein is shown;

[0015] Figure 3 shows a schematic diagram of a multi-beam device for sample inspection having a lens array and a common objective lens according to embodiments described herein;

[0016] Figure 4 shows a schematic diagram of a multi-beam device for sample inspection having a lens array, a deflector array and a common objective lens according to embodiments described herein;

[0017] Figure 5A shows a portion of a schematic ray path of a beam in an aberration correction element according to embodiments described herein;

[0018] Figure 5B Schematic diagram showing a bundle in an aberration correction element according to an embodiment described herein;

[0019] Figure 6 A schematic diagram showing a column array of a multi-beam device column according to embodiments described herein; and

[0020] Figure 7 A flow chart of a method for examining a sample using a charged particle beam apparatus according to embodiments described herein is shown. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to various embodiments, one or more examples of which are shown in the accompanying drawings. In the following description of the drawings, the same reference numerals refer to the same parts. Only the differences relative to the individual embodiments are described. Each example is provided by way of explanation and is not meant to be limiting. In addition, the features shown or described as part of one embodiment can be used in other embodiments or combined with other embodiments to produce yet another embodiment. The description is intended to include modifications and variations.

[0022] Without limiting the scope of protection of the present application, hereinafter, a charged particle beam device or a component thereof will be exemplarily referred to as a charged particle beam device, including detection of secondary or backscattered particles (such as electrons). The embodiments are still applicable to devices and components for detecting microparticles (such as secondary and / or backscattered charged particles in the form of electrons or ions, photons, X-rays or other signals) in order to obtain a sample image. When referring to microparticles, microparticles should be understood as: optical signals, where the microparticles are photons; and particles, where the microparticles are ions, atoms, electrons or other particles. As described herein, the discussion and description of primary charged particle beams and primary charged particle beamlets are exemplarily described with respect to electrons in a scanning electron microscope. Other types of charged particles (e.g., positive ions) can be used as primary charged particle beams or primary charged particle beamlets.

[0023] According to embodiments of the present invention that may be combined with other embodiments, the signal (charged particle) beam or signal (charged particle) beamlet is referred to as a secondary particle beam, i.e., secondary and / or backscattered particles. Typically, the signal beam or auxiliary beam is generated by incidenting a primary beam or primary beamlet on a sample or by backscattering a primary beam from a sample. The primary charged particle beam or primary charged particle beamlet is generated by a particle beam source and is guided and deflected onto a sample to be inspected or imaged.

[0024] As referred to herein, "samples" or "specimens" include, but are not limited to, semiconductor wafers, semiconductor workpieces, photolithography masks, and other workpieces, such as storage disks, etc. Embodiments may be applied to any workpiece on which a material is deposited or structured. Samples include surfaces, edges, and typically bevels to be structured or on which layers are deposited. According to some embodiments, which may be combined with other embodiments described herein, the apparatus and method are constructed for or applied to electron beam inspection, critical dimensioning applications, and defect review applications.

[0025] Figure 1Schematically shown in FIG. 1 is a charged particle beam device 100. The charged particle beam device 100 comprises a charged particle beam source 110, which comprises a particle beam emitter 111 that emits a primary charged particle beam 14. According to the embodiments described herein, the charged particle beam source 110 is suitable for generating an array of primary charged particle beamlets 15. The charged particle beam source 110 may comprise a charged particle beam emitter 111 and a multi-aperture plate 113 having at least two openings. The primary charged particle beam 14 may be accelerated by an accelerating voltage supplied to an accelerating electrode 199. The charged particle beam device may comprise electrodes 112-1 and 112-2.

[0026] The electrode 112 of the charged particle beam device may be adapted and driven to generate an electric field on the surface of the multi-aperture lens plate.The surface of the multi-aperture plate 113 may be the surface of the multi-aperture plate facing the electrode 112-2.

[0027] The charged particle beam source 110 including a beam emitter, a multi-aperture plate and an electrode 112 can be indicated as the upper part of the charged particle beam device. The charged particle beam device 100 further exemplarily includes a lens 120, an objective lens 130 and a sample stage 141, on which the sample 140 can be placed. The lens 120, the objective lens 130 and the sample stage 141 can be described as a part of the lower part of the charged particle beam device. The reduction of the emitter tip of the charged particle device is given by the source position and the focal length of the objective lens array.

[0028] The electric field having a z component is generated by the voltage difference between the electrode 112-2 and the multi-aperture plate 113. The electric field may have a z component extending in the z direction of the charged particle beam device (i.e., along the optical axis 4). The component of the electric field provided by the electrode 112 in the z direction may vary across the plane of the surface of the multi-aperture lens plate.

[0029] For example, the rotationally symmetric z component of the electric field on the surface of the multi-aperture plate can be used for field curvature (or image field curvature) correction by the electrodes. In addition, for example, a non-rotationally symmetric configuration of the z component of the electric field can be achieved by a segmented arrangement of at least one of the electrodes 112 to correct image field tilt.

[0030] The varying field of the first electrode on the surface of a multi-aperture plate in a charged particle beam device can be used to correct the field curvature of the charged particle beam device, in particular the field curvature introduced by the imaging lens of the charged particle beam device. More than one electrode can be used to compensate or correct the field curvature.

[0031] Segmented electrodes can be used to generate rotationally non-symmetric field configurations on the surface of the multi-aperture, which can be used to correct for image field tilt that may originate from rotationally non-symmetric optical elements or from tilted samples.

[0032] The charged particle beam device may include electrodes 112-1 and 112-2 (two electrodes are shown exemplarily). According to some embodiments, the first electrode may be used to provide an electric field to generate an aperture lens, and the second electrode may be used as a field curvature correction electrode. In addition, the charged particle beam device 100 may include a scanning deflector 150. The scanning deflector 150 may be provided between the lens 120 and the sample stage 141. In particular, the scanning deflector may be surrounded by a pole piece assembly of the objective lens 130 and / or at the position of an electrode of the electrostatic lens.

[0033] The field across the multi-aperture plate can be varied so that the field curvature or field tilt of the beamlets can be controlled (or corrected). However, other off-axis aberrations (eg, field astigmatism, off-axis coma, and distortion) still exist.

[0034] According to embodiments described herein, there is provided an inspection of a sample using an array of primary charged particle beamlets. A multi-aperture plate is provided to generate an array of primary charged particle beamlets from a primary charged particle beam. The multi-aperture plate may have two or more openings. The multi-aperture plate may divide a large beam of a primary charged particle beam into separate beamlets, i.e., an array of primary charged particle beamlets. An aberration correction element is provided to specifically correct the aberration difference between different beamlets of the array of primary charged particle beamlets. According to some embodiments that may be combined with other embodiments described herein, the aberration correction element may correct Cs (i.e., spherical aberration), or both Cc and Cs (i.e., chromatic aberration and spherical aberration).

[0035] Figure 2 A charged particle beam apparatus 200 is shown, for example, for examining a sample with an array of primary charged particle beamlets. The charged particle beam source 110 comprises a particle beam emitter 111 emitting a primary charged particle beam 14 .

[0036] A collimator device (such as a condenser lens assembly 220) can be provided in a charged particle beam device (e.g., a multi-particle beam system). The charged particle beam device can be used for particle beam inspection or particle beamlet lithography applications. According to some embodiments that can be combined with other embodiments described herein, the condenser lens assembly can include one or more circular lenses, for example, an electrostatic lens, a magnetostatic lens, or a combined magnetic electrostatic lens acting on the primary charged particle beam emitted by the charged particle beam source 110. One or more electrostatic or magnetostatic lenses can be included by a collimator device (such as a condenser lens assembly 220), and one or more electrostatic or magnetostatic lenses are used to produce a beam divergence that is less than a few millirads of parallel (or nearly parallel) particle beams.

[0037] Due to the spherical and chromatic aberrations (i.e., Cs and Cc) of such a collimator, high-angle trajectories and trajectories of particles that differ slightly from the nominal energy are not parallel to the system axis, even for paraxial trajectories with nominal energy. This is due to second, third, and higher order path deviations, which are unavoidable with conventional circular lens systems according to Scherzer's theorem.

[0038] The second-order path deviations and third-order path deviations of the circular lens system, i.e., the second-order aberrations and third-order aberrations, have chromatic and spherical aberrations that increase, in particular, with the half-angle Q of the central trajectory of the individual beamlets and the angle β of the off-axis trajectory within a beamlet. These aberrations can increase linearly or quadratically with the half-angle Q and the angle α. In addition, the chromatic aberrations can increase with the chromatic parameter k related to the energy width of the source. The resulting aberrations correspond to radial color distortion and chromatic aberration, radial geometric distortion, radial field astigmatism, field curvature, radial off-axis coma and spherical aberration. All of the above-mentioned aberrations (except chromatic aberration and spherical aberration) depend on the beamlet angle Q and thus lead to non-uniformity from beamlet to beamlet, and therefore to non-uniform resolution on the sample.

[0039] According to the embodiments described herein, an aberration correction element 210 is provided. The aberration correction element is used to correct the spherical aberration and / or chromatic aberration coefficients Cs and Cc of the collimator lens, and optionally as a supplement to the objective lens. The above-mentioned second-order aberrations and third-order aberrations of the primary charged particle beam can be considered to be the cause of the field curvature aberrations between the primary charged particle beamlets. Therefore, the field curvature of the beamlet array can be corrected by controlling the corresponding chromatic aberrations and spherical aberrations of the primary charged particle beam (i.e., the composition of the beamlets). For example, the aberration correction element can generate an electro-magnetic quadrupole field. Figure 2 A first magnetic quadrupole 212, a first electromagnetic quadrupole 214, a second electromagnetic quadrupole 216, and a second magnetic quadrupole 218 are shown. The resulting correction is shown by the beam path 14' in the YZ plane and the beam path 14" in the XZ plane. As can be seen, beam trajectories with different energies (see different lines) leave the aberration correction element 210 parallel or substantially parallel to the optical axis, thereby correcting chromatic aberration. In addition, spherical aberration can be corrected using superimposed octopole fields. The corresponding octopole is, for example, Figure 2 . The first octopole 215 may be stacked with the first electromagnetic quadrupole 214. The third octopole 219 may be stacked with the second electromagnetic quadrupole 216. The second octopole 217 may be provided between the first octopole and the third octopole, for example, in the middle of the two octopoles. According to some embodiments that may be combined with other embodiments described herein, it may be beneficial if the aberration correction element 210 is symmetrical, i.e., the quadrupole and the octopole are symmetrical with respect to a symmetry plane perpendicular to the optical axis.

[0040] According to another embodiment, the aberration correction element 210 described above may be modified by having four or more octopoles. For example, four octopoles may be stacked with corresponding ones of the quadrupoles represented by reference numerals 212, 214, 216, and 218.

[0041] According to further embodiments, further modifications of the aberration correction element 210 may include quadrupoles 212 and 218, which may also be electrostatic or a combined magnetic-electrostatic.

[0042] According to some embodiments, which may be combined with other embodiments described herein, the aberration correction element 210 may correct or compensate for Cc, Cs, or both Cc and Cs.

[0043] According to further embodiments, where the energy width of the source is small enough, simpler Cs correctors (e.g., sextupole fields and transfer doublets) may be used, as long as color effects can be ignored. Thus, the aberration correction element 210 may optionally include a first electric or magnetic sextupole and a second electric or magnetic sextupole. A transfer lens system consisting of at least one lens may be provided to provide a symmetrical ray path through the field arrangement. The symmetrical arrangement allows correction of spherical aberrations while preventing the introduction of second-order geometric aberrations, such as triple astigmatism. By utilizing an aberration correction element according to an embodiment described herein, the parallelism of the individual beamlets may be limited only by fourth-order or higher-order path deviations and aberration correction element imperfections.

[0044] According to embodiments described herein, the aberration correction element may be a non-rotationally symmetric multipole corrector. For example, a quadrupole-octupole corrector for simultaneous correction of Cs and Cc or a double hexapole corrector for Cs correction may be provided. Embodiments include at least two multipole elements with 6 or more poles, for example, hexapole elements, octupole elements, or even higher order multipole elements. According to yet another embodiment that may be combined with other embodiments described herein, the aberration correction element is constructed to operate with fixed excitation at any time and / or for various operating modes.

[0045] According to yet another embodiment that can be combined with other embodiments described herein, the aberration correction element can be configured to correct at least one of spherical aberration and chromatic aberration of the rotationally symmetric charged particle lens. For example, the aberration correction element is configured to correct the difference between a first resolution on the sample and a second resolution on the sample, and includes at least two multipole elements, each multipole element consisting of 6 or more poles. According to yet another example or modification that can be combined with other embodiments described herein, the aberration correction element can be selected from the group consisting of: a foil lens, a film corrector (in which primary electrons invade a film of varying thickness), a space charge lens, a high-frequency lens, and a mirror corrector.

[0046] Due to the increasing demand for high throughput particle beam inspection devices, charged particle beam devices with arrays of primary charged particle beamlets, i.e., multi-beam systems, have been proposed. At least two beams are scanned across the same column or sample within the device. Charged particle beam devices may include, for example, Figure 1 The scanning deflector 150 is described. The primary charged particle beamlet array is provided by generating a relatively large collimated particle beam, which is then divided into a plurality of parallel beamlets by a porous array 113, such as for example Figure 2 The primary charged particle beamlet 15 is focused on the sample 140 by the objective lens assembly 230. Figure 2 As shown, the objective lens assembly can be an objective lens array. The objective lens array can include a plurality of individual lenses for focusing the beamlets onto the sample (eg, onto individual locations on the sample). The sample can be supported on a sample stage 141.

[0047] Radial geometric and chromatic distortions (outer beamlets are not parallel to the center beamlet), radial field astigmatism (outer beamlets are astigmatic), field curvature (outer beamlets are more or less converging or diverging within themselves compared to the inner beamlets), and radial off-axis coma (outer beamlets exhibit coma) may result in varying resolution on the sample, depending on the off-axis distance of the beamlets. Therefore, embodiments described herein provide an aberration correction element 210 to correct the varying resolution of the beamlets. The beamlets may have extinctions Cc and Cs before entering the objective lens assembly. Using such an arrangement it is possible to produce beamlets that are parallel to each other and within themselves (up to third order). A multi-beam system according to embodiments described herein can therefore improve resolution uniformity on the sample.

[0048] Figure 3 Another embodiment of a charged particle beam device 200 having an array of primary charged particle beamlets is shown. The primary charged particle beam is generated by a charged particle beam source 110. An aberration correction element 210 is provided, wherein aspects, details and optional modifications may be as described with respect to Figure 2 The primary charged particle beam 15 is used as described. A relatively wide primary charged particle beam (e.g., can be parallel) illuminates the multi-aperture plate 113. An array of primary charged particle beamlets 15 is generated. The lens array 320 generates individual bridges 315. For example, the lens array that generates the intermediate bridges can, for example, include Einzel lenses or aperture lenses. The common objective lens 130 focuses the beamlets on different or separate locations on the sample 140.

[0049] exist Figure 3 , an objective lens 130 is schematically shown. The objective lens 130 may be provided for use in the embodiments described herein, such as Figure 1The objective lens may include a coil and upper and lower pole pieces, wherein magnetic lens components for the primary charged particle beamlet array are provided. In addition, the upper and lower electrodes may provide an electrostatic lens assembly of the objective lens 130. The reduction of the emitter tip of the charged particle device is given by the source position and the focal length of the objective lens array.

[0050] According to some optional modifications that lead to yet another embodiment, the possible fifth-order spherical aberration coefficient C5 can be adjusted by an appropriate distance between the condenser lens array and the aberration correction element.

[0051] In particular, the objective lens may be a combined magnetic electrostatic lens. According to some embodiments, the electrostatic lens component may provide a deceleration lens, wherein the landing energy of the beamlet on the sample may be reduced compared to the energy of the beamlet in the column. For example, the landing energy may be between about 100 eV and 8 keV, more typically 2 keV or lower, for example 1 keV or lower, such as 500 eV or even 100 eV. The beam energy of the beamlet in the column may be 5 keV or higher, for example 20 keV or higher, or even 50 keV or higher.

[0052] In some embodiments that may be combined with other embodiments described herein, the objective lens 130 can be a field compound lens. For example, the objective lens can be a combination of a magnetic lens component and an electrostatic lens component. Thus, the objective lens can be a composite magnetic-electrostatic lens. Typically, the electrostatic portion of the composite magnetic-electrostatic lens is an electrostatic hysteresis field lens. In the case of a scanning electron microscope (SEM), the use of a composite magnetic-electrostatic lens produces excellent resolution at low landing energies, such as several hundred electron volts. Low landing energies are beneficial (especially in the modern semiconductor industry) to avoid charging and / or damage to radiation sensitive samples.

[0053] In addition, the charged particle beam device 200 may include a scanning deflector 150. The scanning deflector 150 may be provided between the lens and the sample stage 141. In particular, the scanning deflector may be surrounded by a pole piece assembly of the objective lens 130 and / or at the location of an electrode of an electrostatic lens component.

[0054] According to some embodiments that can be combined with other embodiments described herein, it is also possible to operate the correction element (i.e., a Cc-Cs corrector having two or more multipole elements) as a lens. The aberration correction element can focus the primary charged particle beam to reduce the divergence between the first beamlet and the second beamlet, for example, to produce parallel beamlets. Therefore, a condenser lens or condenser lens assembly that collimates the primary charged particle beam before incident on the multi-aperture plate is optional for some configurations.

[0055] In addition, for the embodiment using a shared objective lens (see, for example Figure 3and Figure 4 ), the aberration correction element (i.e., Cc-Cs corrector) is operable to imperfectly correct the aberrations of the lens array, and a condenser lens assembly is optionally present. The aberration correction element 210 in combination with the lens array 320 can provide an array of intermediate beamlet bridges having off-axis aberrations (field curvature, field astigmatism, radial chromatic distortion, etc.) that are opposite to the common objective lens. For embodiments having a common objective lens and a condenser lens assembly, the aberration correction element is operable to imperfectly correct the aberrations of the condenser lens. This operation will produce an array of intermediate beamlet bridges having off-axis aberrations (field curvature, field astigmatism, radial chromatic distortion, etc.) that are opposite to the common objective lens. Therefore, according to some embodiments, the Cc-Cs corrector within the collimator can be used to produce defined field curvature, field astigmatism, and radial chromatic aberration, which eliminates the inherent off-axis aberrations of the common objective lens.

[0056] exist Figure 3 In the collimator, the beamlets pass through the objective without passing through the common bridge. The Cc-Cs corrector in the collimator can be adjusted so that the off-axis coma of the objective is corrected. By avoiding the common bridge, Coulomb or electron-electron interactions that may lead to a reduction in resolution on the sample can be reduced.

[0057] In addition, the charged particle beam device 200 may include a scanning deflector 150. The scanning deflector 150 may be provided within the objective lens or between the lens and the sample stage 141. In particular, the scanning deflector may be surrounded by a pole piece assembly of the objective lens and / or at the location of an electrode of an electrostatic lens component.

[0058] Figure 4 Another embodiment of the charged particle beam device 200 is shown. An additional deflection element 450 having a deflector 454 and optionally another lens 452 near the intermediate bridging plane can be used to adjust the off-axis coma of the beamlet. The beamlet can be deflected on a "coma-free" path. Alternatively, the deflection element 450 that guides the beamlet through the coma-free point of the objective lens can include another lens 452, and the deflector array with deflector 454 can be optional. Therefore, the deflection element 450 can include an additional lens 452, a deflector array with deflector 454, or both.

[0059] According to some embodiments, the deflector array may be arranged in or near the further lens. According to some embodiments, the deflector array being arranged "in or near the further lens" or "in the further lens" may be understood as the deflector array being placed within the focal length of the further lens. For example, the further lens may include three electrodes, and the deflector array may be placed within the three electrodes. According to some embodiments, the deflector array may be placed approximately at the height of the middle electrode of the three electrodes of the further lens.

[0060] According to some embodiments, an additional lens can be used to achieve the main effect of guiding the primary charged particle beamlets, for example for guiding the primary charged particle beamlets to the coma-free point of the objective lens. In some embodiments, a deflector array can be used to fine-tune individual primary charged particle beamlets, in particular to fine-tune the primary charged particle beamlets to be guided into or through the coma-free point of the objective lens.

[0061] As used throughout this disclosure, the term "coma-free plane" or "coma-free point" refers to a plane or point of an objective lens (or provided by it) that introduces minimal or even no coma in a primary charged particle beamlet when the primary charged particle beamlet passes through the coma-free point or coma-free plane. The coma-free point or coma-free plane of an objective lens is a point or plane of the objective lens that satisfies the Fraunhofer condition (the condition for zero coma). The coma-free point or coma-free plane of an objective lens is located on the z-axis of the optical system of the charged particle beam device, wherein the z-axis is along the optical axis 4 of the objective lens (see Figure 1 ) is extended. The coma-free point or coma-free plane can be positioned within the objective lens. For example, the coma-free point or coma-free plane can be surrounded by the objective lens.

[0062] According to embodiments described herein, a charged particle beam apparatus and method for examining a sample with an array of primary charged particle beamlets as described herein allows correction of off-axis aberrations to compensate for differences in resolution between different beamlets of the array of primary charged particle beamlets. Embodiments described herein thus allow a system in which off-axis aberrations will be caused only or primarily by, for example, 4th or higher order aberrations of a condenser-corrector system.

[0063] like Figure 2 , Figure 3 , Figure 4 and Figure 6 The embodiment of the charged particle beam device 200 shown exemplarily may include another optional modification to produce another embodiment. The charged particle beam emitter 111 of the charged particle beam source 110 may be a cold field emitter (CFE), a Schottky emitter, a TFE, or another high current high brightness charged particle beam source (such as an electron beam source). The high current is considered to be 5μA at 100 millirads or above, for example up to 5mA, for example, 30mA at 100 millirads to 1mA at 100 millirads, such as about 300μA at 100 millirads. According to some implementations, the current is substantially uniformly distributed, for example, with a deviation of ±10%, particularly in the case of a linear or rectangular array.

[0064] According to further embodiments that may be combined with other embodiments described herein, the TFE or another high brightness reduced source (e.g., an electron beam source capable of providing a large beam current) is a source whose brightness does not drop by more than 20% of the maximum value when the emission angle is increased to provide a maximum of 10 μA to 100 μA (e.g., 30 μA). According to some embodiments that may be combined with other embodiments described herein, the objective lens array may include a separate electrostatic lens (in particular, a delayed field lens). In some embodiments, the objective lens array may be used in the embodiments described herein, including, in particular, a separate magnetic lens lens with a common excitation coil. According to some embodiments, the objective lens array for a charged particle beam device according to the embodiments described herein may include a combination of a separate electrostatic lens and a separate magnetic lens. Alternatively, it may be as described with respect to Figure 3 and Figure 4 A common objective lens is used as described.

[0065] In About Figure 2 , Figure 3 , Figure 4 and Figure 6 In the illustrated embodiment, the primary charged particle beam 14 can pass through a multi-aperture plate 113 after leaving the charged particle beam emitter 111 (i.e., the emitter tip). The primary charged particle beam 14 passes through a multi-aperture plate 113 having a plurality of aperture openings. The aperture openings can be located in any array configuration on the multi-aperture plate 113, such as a line, rectangle, square, ring, or any suitable one-dimensional or two-dimensional array. According to the embodiments described herein, the charged particle beam device as described herein allows the aperture openings of the multi-aperture plate to be arranged in any configuration without defects caused by field curvature or aberrations. For example, it is known that different small beams are arranged in an annular shape so as to provide the same conditions for each beam passing through the lens like a parabola. When the small beams are arranged in an annular shape, the aberration effects of the corresponding lenses can be minimized. However, the annular arrangement provides limitations on high throughput. With a charged particle beam apparatus according to embodiments described herein, the arrangement of the beamlet array can be accomplished in any arrangement (e.g., an arrangement suitable for rapid inspection, an arrangement suitable for the sample structure to be inspected, an arrangement allowing a large number of beams, an arrangement suitable for beam intensity, etc.) For example, the beam array can be arranged in a line, rectangle, hexagon, or square.

[0066] In some embodiments, the primary charged particle beamlet array can be arranged in a one-dimensional (line) array or a two-dimensional array (e.g., 4×4, 3×3, 5×5) or an asymmetric array (e.g., 2×5). The embodiments described herein are not limited to array examples and can include any suitable array configuration of the primary charged particle beamlets.

[0067] By illuminating the multi-aperture plate 113 with the primary charged particle beam 14, several primary charged particle beamlets 15 are generated. In the focusing plane of the primary charged particle beamlets 15, a lens 120 may be arranged.

[0068] In the drawings, some of the primary charged particle beamlets in the array of primary charged particle beamlets are shown behind a lens, whereas other primary charged particle beamlets are omitted from the drawings for better overview.

[0069] According to some embodiments, which may be combined with other embodiments described herein, the aberration correction element may be an electrostatic corrector, i.e., an electrostatic multipole is included in the aberration correction element. The electrostatic corrector may be, for example, purely electrostatic, i.e., not including magnetic multipoles. This is useful for arranging as follows with respect to Figure 6 The plurality of columns described may be beneficial. For example, the aberration correction element may include an electrostatic lens field and an electrostatic quadrupole field for chromatic aberration correction. Additionally, an electrostatic octopole magnetic field may be superimposed for spherical aberration correction. The electrostatic lens field may be superimposed with the quadrupole field. Figure 5A In , the resulting correction is shown by the beam path 14' in the YZ plane and the beam path 14" in the XZ plane. Electrostatic correctors can be beneficial for achieving reduced space when having an array of two or more columns, each of which can provide a multi-beam charged particle device. A further benefit can be that hysteresis is avoided and the field accuracy is limited primarily by machining tolerances. This is described, for example, in "Electrostatic correction of the colours and of the spherical aberration of charged-particle lenses" by Christoph WeiBbacker, Harald Rose, J Electron Microsc (Tokyo) (2001) 50(5): 383-390.

[0070] The combined magnetic-electrostatic aberration correction element may benefit from decoupling focus properties and Cc correction, moderate higher order aberrations, moderate sensitivity to alignment errors and damping of noise in the magnetic circuits to the low kHz range.

[0071] Figure 5BAn exemplary embodiment of the electrostatic aberration correction element 210 is shown in FIG. The corrector includes a plurality of electrostatic multipoles and lenses, which are, for example, advantageously arranged symmetrically. That is, there is a symmetry plane in which the aberration correction element is orthogonal to the optical axis. For example, element 512 can be an electrostatic quadrupole, and element 514 can be a combination of an electrostatic lens and an electrostatic quadrupole superimposed. Elements 512 and 514 can correct Cc. Elements 513 and 515 can be electrostatic octopoles for correcting Cs. The aberration correction element 210 can include elements for correcting Cc, Cs, or both Cc and Cs.

[0072] As described above, the charged particle beam device according to the embodiments described herein allows for providing an array of primary charged particle beamlets. According to some embodiments, the array of primary charged particle beamlets may typically include three or more primary charged particle beamlets per column, and more typically include ten or more primary charged particle beamlets. According to some embodiments described herein, the charged particle beam device and the method for examining a sample with the charged particle beam device according to the embodiments described herein may provide an array of primary charged particle beamlets with a small distance between each other at the sample surface within one column of the charged particle beam device. For example, the distance between two primary charged particle beamlets within one column may typically be less than 150 μm, more typically less than 100 μm, or even less than 50 μm.

[0073] In some embodiments, Figure 6 As exemplarily shown, charged particle beam devices according to embodiments described herein allow for arrangement in a multi-column microscope (MCM). Multiple columns, each with an array of primary charged particle beamlets for examining a sample, increase processing speed and throughput.

[0074] Figure 6 A multi-column microscope configuration 600 is shown. The multi-column microscope configuration 600 is exemplarily shown as having three charged particle beam devices 200. According to the embodiments described herein, the number of charged particle beam devices may deviate from the example shown in the multi-column microscope configuration. For example, the multi-column microscope configuration according to the embodiments described herein may have two or more charged particle beam devices, such as two, three, four, five or even more than five charged particle beam devices. The charged particle beam devices may be arranged in a 1-dimensional or 2-dimensional array. Each of the charged particle beam devices of the multi-column microscope configuration may be a charged particle beam device having an array of primary charged particle beamlets as described in any one of the embodiments described herein.

[0075] exist Figure 6 In the exemplary view of FIG. 1 , the multi-column microscope includes Figure 2The charged particle beam device shown and described. The multi-column microscope configuration 600 includes a sample stage 141 on which the sample 140 to be examined is placed. In some embodiments, the charged particle beam device of the multi-column microscope configuration 600 can examine one sample. Alternatively, more than one sample 140 can be placed on the sample stage 141.

[0076] like Figure 6 As shown, each charged particle beam device 200 includes a condenser lens assembly having, for example, one or more condenser lenses, an aberration correction element 210, a multi-aperture plate 113, and a lens array (e.g., an objective lens assembly 230). According to some embodiments described herein, the charged particle beam device 200 of the multi-column microscope configuration 600 can have a common objective lens assembly.

[0077] In addition, a control electrode (e.g., a proximity electrode for extracting signal particles, such as secondary electrons (SE) or backscattered electrons) can be provided for the charged particle beam device and / or multi-column microscope configuration 600 of the embodiments described herein. The control electrode can be a common electrode for more than one column or can be a control electrode for one column. For example, with an objective lens as described in embodiments of the present disclosure, very low landing energies (e.g., 100 eV) and low extraction fields can be provided without compromising the overall performance of the charged particle beam imaging system.

[0078] According to some embodiments, the charged particle beam devices 200 of the multi-column microscope configuration can have a distance between each other typically between about 10mm to about 60mm, more typically between about 10mm to about 50mm. In some embodiments, the distance between the individual charged particle beam devices of the multi-column microscope configuration can be measured as the distance between the corresponding optical axes of the charged particle beam devices.

[0079] By using multiple charged particle beam devices in a multi-column microscope configuration, e.g. Figure 6 As exemplarily shown, a sufficient number of primary charged particle beamlets can be provided with a sufficient resolution and with sufficiently small crosstalk between the signal beamlets.

[0080] Figure 7A flow chart of a method 700 for imaging a sample with an array of primary charged particle beamlets is shown. In block 701, an array of charged particle beamlets is generated by illuminating a multi-aperture plate with a primary charged particle beam. The charged particle beamlet region may have at least a first beamlet and a second beamlet. The primary charged particle beam may be generated with a charged particle beam source including a beam emitter. The beam emitter may be, for example, a CFE, a Schottky emitter, a TFE, or another high current-high brightness charged particle beam source (such as an electron beam source), as mentioned above, for example. According to some embodiments, the beam emitter may emit a primary charged particle beam, and the primary charged particle beam may be processed (e.g., by being divided by a multi-aperture plate) so as to generate a plurality of primary charged particle beamlets. For example, the aperture openings in the multi-aperture plate may be arranged into a 1-dimensional beamlet array or a 2-dimensional beamlet array, such as a hexagonal, rectangular, or secondary beamlet array.

[0081] As indicated in block 702, the array of charged particle beamlets is focused on the sample, for example, using an objective lens assembly. The objective lens assembly can be an objective lens array or a shared objective lens assembly. For example, the objective lens array can include two or more electrostatic lenses and / or two or more magnetic lenses. The shared objective lens assembly can include a magnetic lens component and an electrostatic lens component, particularly an electrostatic lens component operating in a deceleration mode.

[0082] As indicated in box 703, an aberration correction element can be used to correct the aberration difference within the primary charged particle beamlet array, such as the difference in aberration and / or resolution between the first beamlet and the second beamlet. The aberration correction element can correct Cs (i.e., spherical aberration), or both Cc and Cs (i.e., chromatic aberration and spherical aberration). According to the embodiments described herein, the aberration correction element can be a non-rotationally symmetric multipole corrector. For example, a quadrupole-octopole corrector for simultaneous correction of Cs and Cc or a double hexapole corrector for Cs correction can be provided.

[0083] According to some embodiments, the aberration correction element can act on the primary charged particle beam or can act on the primary charged particle beamlets. In addition, additionally or optionally, for a common objective lens assembly, the aberration correction element can correct the off-axis aberration of the objective lens assembly. For an objective lens array, the beamlets can enter the lens of the objective lens array along the optical axis. Therefore, correction of the condenser lens assembly (and optionally another lens) can be provided by the aberration correction element. According to another embodiment that can be combined with other embodiments described herein, the aberration correction element can act as a collimating lens, wherein the condenser lens assembly can be omitted.

[0084] According to some embodiments described herein, the charged particle beam device may include additional beam optical elements, such as a condenser lens, a (scanning) deflector, a beam bender, a corrector, etc. In some embodiments, the condenser lens may be placed in front of the multi-aperture plate (i.e., upstream of the primary charged particle beam when viewed along the propagation direction of the primary charged particle beamlets). The charged particle beam device according to embodiments described herein may include a beam blanker, such as a separate beam blanker for each beamlet or a common beam blanker.

[0085] According to further embodiments that may be combined with other embodiments described herein, the condenser lens assembly may include one or more condenser lenses. Each of the condenser lenses may be electrostatic, magnetic, or a combination of magnetic and electrostatic. According to some embodiments, the multi-aperture plate (i.e., the aperture opening array) may be replaced with a different multi-aperture plate, for example, for changing the diameter of the aperture opening. This enables switching between different beamlet currents. In particular, in order to replace the multi-aperture plate, the condenser lens assembly may include two or more condenser lenses for adjusting the focal length. Adjusting the focal length may be beneficial for adjusting the total magnification of the source. As described above, the charged particle beam device as described herein may be used for particle beam inspection or particle beam lithography applications. In addition, the method of imaging a sample with a primary charged particle beamlet array may be similarly applied to a method of illuminating a sample with a primary charged particle beamlet array, for example, for particle beamlet lithography applications.

[0086] While the foregoing is directed to particular embodiments, other and further embodiments may be envisaged without departing from the basic scope of the invention, and the scope of the invention is determined by the appended claims.

[0087] Component Symbol List

[0088] 4 optical axes

[0089] 14 Primary charged particle beam

[0090] 15 Primary charged particle beam

[0091] 100 Charged particle beam device

[0092] 110 Particle beam source

[0093] 111 Particle Beam Emitter

[0094] 112 Electrode

[0095] 112-1 Electrode

[0096] 112-2 Electrode

[0097] 112-2 Electrode

[0098] 113 multi-aperture plate

[0099] 120 Lens

[0100] 130 Objective

[0101] 14' beam path

[0102] 14” beam path

[0103] 140 samples

[0104] 141 Sample table

[0105] 150 Scanning Deflector

[0106] 199 Accelerating Electrode

[0107] 200 Charged Particle Beam Device

[0108] 210 Aberration Correction Element

[0109] 212 Quadrupole

[0110] 214 Electromagnetic quadrupole

[0111] 215 Baji

[0112] 216 Electromagnetic quadrupole

[0113] 217 Baji

[0114] 218 Quadrupole

[0115] 219 Baji

[0116] 220 Condenser lens assembly

[0117] 230 Objective lens assembly

[0118] 315 Separate jumper

[0119] 320 lens array

[0120] 450 Deflection element

[0121] 452 Lens

[0122] 454 Deflector

[0123] 512 Components

[0124] 513 Components

[0125] 514 Components

[0126] 515 Components

[0127] 600 Multi-column microscope configuration

[0128] 700 Methods

[0129] 701 Box

[0130] 702 Box

[0131] 703 Box

Claims

1. A charged particle beam apparatus for examining a sample using an array of primary charged particle beamlets, comprising: a charged particle beam source, for generating a primary charged particle beam; a condenser lens assembly to collimate the primary charged particle beam; an aberration correction element for correcting at least one of spherical aberration and chromatic aberration of the condenser lens assembly; a multi-aperture plate having at least two openings for generating an array of primary charged particle beamlets from the primary charged particle beam, the array of primary charged particle beamlets having at least a first beamlet having a first resolution on the sample and a second beamlet having a second resolution on the sample; and An objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate location on the sample, wherein the objective lens assembly comprises an array of objective lenses to individually focus each beamlet of the array of primary charged particle beamlets. 2 . The charged particle beam apparatus according to claim 1 , wherein the aberration correction element is configured to correct a difference between the first resolution on the sample and the second resolution on the sample, and comprises at least two multipole elements.

3. A charged particle beam device according to claim 2, wherein the at least two multipole elements each consist of 6 or more poles.

4. A charged particle beam apparatus according to claim 2, wherein the at least two multipole elements generate at least two hexapole fields. 5 . The charged particle beam device according to claim 4 , wherein the aberration correction element further comprises at least one electrostatic lens. 6 . The charged particle beam device according to claim 2 , wherein the at least two multipole elements are two combined electric-magnetic quadrupole elements, and the aberration correction element further comprises two electric or magnetic quadrupole elements. 7 . The charged particle beam apparatus according to claim 6 , wherein the aberration correction element further comprises at least three electric or magnetic octupole elements.

8. The charged particle beam apparatus according to claim 1, wherein the aberration correction element further comprises at least three electric octupole elements.

9. A charged particle beam apparatus according to claim 1, wherein the objective lens assembly comprises a magnetic lens component acting on the array of primary charged particle beamlets.

10. The charged particle beam device according to claim 9, further comprising: A lens array is provided between the multi-aperture plate and the objective lens assembly.

11. A charged particle beam apparatus for examining a sample using an array of primary charged particle beamlets, comprising: a charged particle beam source, for generating a primary charged particle beam; a condenser lens assembly to collimate the primary charged particle beam; an aberration correction element for correcting at least one of spherical aberration and chromatic aberration of the condenser lens assembly; a multi-aperture plate having at least two openings for generating an array of primary charged particle beamlets from the primary charged particle beam, the array of primary charged particle beamlets having at least a first beamlet having a first resolution on the sample and a second beamlet having a second resolution on the sample; and an objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate location on the sample, wherein the objective lens assembly comprises an array of objective lenses for individually focusing each beamlet of the array of primary charged particle beamlets; The aberration correction element is along an optical axis extending from the charged particle beam source to the objective lens assembly.

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