KR20190100460A - Apparatus of plural charged-particle beams - Google Patents

Abstract

A multibeam apparatus for observing a sample with high resolution and high throughput is presented. In such an apparatus, the source conversion unit transforms a single electron source into a virtual multi-source array, the primary projection imaging system projects this array to form a plurality of probe spots on the sample, and the focusing lens is configured to Adjust the flow In the source conversion unit, the image forming means is located upstream of the beam limiting means, producing less scattered electrons. The image forming means not only forms a virtual multi-source array, but also compensates for off-axis aberration of the plurality of probe spots.

Description

Apparatus using a plurality of charged particle beams {APPARATUS OF PLURAL CHARGED-PARTICLE BEAMS}

This application claims priority to US Provisional Application No. 62 / 130,819, filed March 10, 2015 by Ren et al., Entitled "Appratus of Plural Charged-Particle Beams," which is incorporated by reference in its entirety. Incorporated herein by reference.

The present invention relates to a charged particle device using a plurality of charged particle beams. More specifically, the present invention relates to an apparatus employing a plurality of charged particle beams to simultaneously obtain images of a plurality of scan areas of a viewing area on a sample surface. Thus, such devices can be used in the semiconductor manufacturing industry to inspect and / or examine defects on wafers / masks with high resolution and high throughput.

In manufacturing semiconductor IC chips, pattern defects and / or unwanted particles (residues) inevitably occur on the surface of the wafer / mask during the manufacturing process, which greatly reduces the yield. In order to meet even more advanced requirements for the performance of IC chips, patterns with even smaller critical feature dimensions are employed. Accordingly, existing yield management tools using optical beams have become increasingly inadequate due to diffraction effects, and more and more yield management tools using electron beams are being employed. Compared to the photon beam, the electron beam has a shorter wavelength, thereby providing excellent spatial resolution. Yield management tools using electron beams now employ the principle of scanning electron microscopy (SEM) using single electron beams, which can provide higher resolution but not adequate throughput for mass production. Increasingly larger beam flows can be used to increase throughput, but due to the Coulomb effect, good spatial resolution will fundamentally degrade.

To alleviate the limitation on throughput, it is a promising solution to use a plurality of electron beams each with a small flow instead of using a single electron beam with a large flow. Such a plurality of electron beams will form a plurality of probe spots on one surface under inspection or observation of the sample. For the sample surface, the plurality of probe spots can scan each and simultaneously a plurality of small scan areas within a wide viewing area on the sample surface. The electrons in each probe spot generate secondary electrons from the sample surface they reach. These secondary electrons include slow secondary electrons (energy is 50 eV or less) and backscattered electrons (energy is close to the reaching energy of the electrons). Secondary electrons from the plurality of small scan areas can be collected respectively and simultaneously by the plurality of electron detectors. As a result, it is much faster to obtain an image for a large viewing area that includes all of the smaller scan areas than when scanning a large viewing area using a single beam.

The plurality of electron beams may be from each of the plurality of electron sources or from a single electron source. In the case of electrons, a plurality of electron beams are typically focused on a plurality of small scan regions by a plurality of columns and scan them, and secondary electrons from each scan region are directed to one electron detector inside the corresponding column. Is detected. Thus, such a device is generally called a multi-column device. The plurality of columns may be independent or share a multi-axis magnetic or electromagnetic composite objective lens (eg US 8,294,095). The beam spacing between two adjacent beams on the sample surface typically amounts to 30-50 mm.

In the latter case a source conversion unit is used to virtually transform a single electron source into a plurality of sub sources. The source conversion unit comprises one beamlet forming means and one image forming means. The beamlet forming means basically comprises a plurality of beam limiting openings, which split each primary electron beam generated by a single electron source into a plurality of sub beams or beamlets. The image forming means basically comprises a plurality of electro-optical elements, which focus or deflect the plurality of beamlets to each form a plurality of parallel images of the electron source. Each of the plurality of parallel images may be treated as one sub source emitting one corresponding beamlet. The beamlet spacing, ie the beam limiting aperture spacing, is at the micrometer level to make more beamlets available, so the source conversion unit can be made by a semiconductor manufacturing process or a MEMS (microelectromechanical system) process. Naturally, one primary projection imaging system and one deflection scanning unit are used within one single column to project and scan a plurality of parallel images to each of a plurality of small scan areas, from which a plurality of secondary electrons The beams are each detected by a plurality of detection elements of one electronic detection device inside such a single column. The plurality of detection elements can be a plurality of electron detectors arranged side by side or a plurality of pixels of one electron detector. The device is therefore generally called a multibeam device.

In the source conversion unit 20-1 of FIG. 1A, the image forming means 22-1 is composed of a plurality of lenses 22_1L to 22_3L. The substantially parallel primary electron beam 2 from one single electron source is divided into a plurality of beamlets 2_1 to 2_3 by a plurality of beam limiting openings 21_1 to 21_3 of the beamlet forming means 21, The plurality of lenses each focus a plurality of beamlets to form a plurality of parallel images 2_1r to 2_3r of a single electron source. The plurality of parallel images is typically a real image, but may be a virtual image under certain conditions when each of the plurality of lenses is an aperture lens. US 7,244,949 and US 7,880,143 each propose a multibeam apparatus with one image forming means of this type. In the source conversion unit 20-2 of FIG. 1B, the image forming means 22-2 is composed of a plurality of deflectors 22_2D and 22_3D. A branched primary electron beam 2 from one single electron source is divided into a plurality of beamlets 2_2 and 2_3 by a plurality of beam limiting openings 21_2 and 21_3 of the beamlet forming means 21, and a plurality of The deflector deflects the plurality of beamlets, respectively, to form a plurality of parallel virtual images 2_2v and 2_3v of a single electron source.

The concept of using a deflector to form a virtual image of an electron source was used in a two-slit electromagnetic interference experiment, which was already popular in the 1950s, and used to form two virtual images as shown in FIG. (FIG. 1 of Rodolfo Rosa's article “The Merli-Missiroli-Pozzi Two-Slit Electron-Interference Experiment”, published in Physics in Perspective, 14 (2012) 178-195). The electron biprism basically comprises two parallel plates at ground potential and a very thin wire F therebetween. When a potential that is not equal to the ground potential is applied to the wire F, the electron biprism becomes two deflectors in which the deflection directions are opposite to each other. The primary electron beam from the electron source S passes through these two deflectors and becomes two deflected beamlets forming the virtual images S1 and S2 of the electron source S. If the potential is positive, the two beamlets overlap each other and an interference fringe occurs in the overlapped area.

Since then, the aforementioned concepts have been employed in a variety of ways in multibeam devices. JP-A-10-339711 and US Pat. No. 8,378,299 directly use one traditional electron biprism to form two prop spots on the sample surface. US 6,943,349 uses one annular deflector (FIG. 5 of the literature) or one corresponding deflector array (FIG. 12 of the literature) to form three or more probe spots on the sample surface, thus providing higher throughput. can do. The annular deflector includes an inner annular electrode and an outer annular electrode. If the potentials of the two annular electrodes are not equal to each other, there will be one electric field in the local radial direction within the annular gap between them, as a result of which the annular deflector can deflect three or more beamlets together in different directions. Further, the deflection function of the annular deflector may be performed by one corresponding deflector array having a plurality of multipole type deflectors arranged along the annular gap.

In the conventional source conversion unit 20-2 of FIG. 1B, the plurality of beamlets pass through the plurality of beam limiting apertures at different incidence angles due to the branching of the primary electron beam 2, thereby causing strong and different electron scattering. do. Scattered electrons in each beamlet will expand the prop spot and / or will be background noise, so the image resolution of the corresponding scan area will be degraded.

In US Pat. No. 6,943,349, the flow of a plurality of beamlets can be changed only by changing the emission of a single electron source or by changing the size of the beam limiting aperture. A single electron source needs a long time to be stable when its emission is changed. The beam forming means must have at least two opening groups and the size of the openings of one group is different from the other groups. Changing the group in use can be time consuming. In addition, the secondary electron beam can be focused onto multiple detection elements of the in-lens detector only under some specific operating conditions of the objective lens. Therefore, available applications are limited.

Therefore, there is a need to provide a multibeam apparatus capable of simultaneously acquiring images of a plurality of small scan areas in a large viewing area on a sample surface with high image resolution and high throughput. In particular, there is a need for a multibeam device capable of inspecting and / or examining defects on a wafer / mask with high resolution and high throughput to meet the roadmap of the semiconductor manufacturing industry.

It is an object of the present invention to provide a new multibeam device capable of providing high resolution and high throughput for observing samples and in particular functioning as a yield management tool in the semiconductor manufacturing industry to inspect and / or examine defects on wafers / masks. To provide. Such a multibeam device comprises first a new source conversion unit for forming a plurality of parallel virtual images of a single electron source and secondly limiting the flow of the corresponding plurality of beamlets, a focusing lens for adjusting the flow of the plurality of beamlets, A primary projection imaging system for projecting a plurality of parallel virtual images to form a plurality of probe spots on the viewing surface of the sample, a beam separator for deflecting the plurality of secondary electron beams from a path of the plurality of beamlets, and electrons A secondary projection imaging system is employed to focus the plurality of secondary electron beams to be detected by the plurality of detection elements of the detection device, respectively.

The present invention thus comprises an image forming means comprising an upper layer having a plurality of upper quadrupole structures and a lower layer having a plurality of lower quadrupole structures, and comprising a plurality of beam limiting openings underneath such image forming means. It provides a source conversion unit comprising a beamlet limiting means. Each upper quadrupole structure is aligned with it on one corresponding lower quadrupole structure, both of which have a 45 ° difference in azimuth to form a pair of four-pole structures. Therefore, the plurality of upper quadrupole structures and the plurality of lower quadrupole structures form a plurality of pairs of four-pole structures. The plurality of beam limiting openings are each aligned with a plurality of pairs of four-pole structures. The pair of four-pole structures function as a micro deflector to deflect one beamlet of the electron beam generated by the electron source to form a virtual image and as a microlens to focus one beamlet to the required extent. And / or act as a micro stigmatizer to add the required amount of astigmatism to one beamlet.

The present invention also provides a multibeam device for observing the surface of a sample, which device comprises an electron source, a focusing lens below the electron source, a source conversion unit below the focusing lens, a source conversion unit and an object A primary projection imaging system including a lens, a deflection scanning unit inside the primary projection imaging system, a sample stage below the primary projection imaging system, a beam separator above the objective lens, a secondary projection imaging system above the beam separator, and An electronic detection device having a plurality of detection elements. The source conversion unit comprises image forming means having a plurality of micro deflectors and beamlet limiting means having a plurality of beam limiting openings, wherein the image forming means is above the beamlet limiting means. The electron source, focusing lens, source conversion unit, primary projection imaging system, deflection scanning unit and beam splitter are aligned with the primary optical axis of such a device. The sample stage holds the sample so that the surface faces the objective lens. The secondary projection imaging system and the electronic detection device are aligned with the secondary optical axis of the apparatus and the secondary optical axis is not parallel to the primary optical axis. The electron source produces a primary electron beam along the primary optical axis, and the plurality of micro deflectors deflect the primary electron beam to form a plurality of parallel virtual images of the electron source. Thus, the virtual multi-source array is converted from the electron source, and a plurality of beamlets including the virtual multi-source array pass through the plurality of beam limiting openings, respectively. Therefore, the flow of each beamlet is limited by one corresponding beam limiting opening, and the flow of the plurality of beamlets can be changed by adjusting the focusing lens. The primary projection imaging system images a virtual multi-source array onto a surface such that a plurality of probe spots are formed thereon. The deflection scanning unit deflects the plurality of beamlets to respectively scan the plurality of probe spots over the plurality of scan areas within the viewing area on the surface. A plurality of secondary electron beams are each generated from the plurality of scan regions by the plurality of probe spots and are focused by the objective lens upon passing. The beam splitter then deflects the plurality of secondary electron beams into the secondary projection imaging system and the secondary projection imaging system focuses and maintains the plurality of secondary electron beams so that they are each detected by the plurality of detection elements. Each detection element thus provides an image signal of one corresponding scan area.

Such a multibeam device may further comprise a main aperture plate underneath the electron source, the main aperture plate having a main opening aligned with the primary optical axis and functioning as a beam limiting aperture for the primary electron beam. . The primary projection imaging system may further comprise a transfer lens over the objective lens, which focuses the plurality of beamlets to reach vertically on the surface. Each of the plurality of micro deflectors has a four-pole structure capable of generating a deflection field in any radial direction. The multibeam device may further comprise a single beam electron detector that is above the beam splitter and can be used in a single beam mode. The multibeam device can further include an in-lens electron detector having a beamlet through hole aligned with the primary optical axis, which is under the beam splitter and can be used in single beam mode.

The present invention also provides a multibeam device for observing the surface of a sample, which device comprises an electron source, a focusing lens below the electron source, a source conversion unit below the focusing lens, a source conversion unit and an object A primary projection imaging system including a lens, a deflection scanning unit inside the primary projection imaging system, a sample stage below the primary projection imaging system, a beam separator above the objective lens, a secondary projection imaging system above the beam separator, and An electronic detection device having a plurality of detection elements. The source conversion unit comprises image forming means with a plurality of micro deflector-compensator elements and beamlet limiting means with a plurality of beam limiting apertures, each micro deflector-compensator element comprising one microlens and one One micro compensator and one micro deflector with a micro stigator. The image forming means is above the beamlet limiting means. The electron source, focusing lens, source conversion unit, primary projection imaging system, deflection scanning unit and beam splitter are aligned with the primary optical axis of the device. The sample stage holds the sample so that the surface faces the objective lens. The secondary projection imaging system and the electronic detection device are aligned with the secondary optical axis of the apparatus and the secondary optical axis is not parallel to the primary optical axis. The electron source produces a primary electron beam along the primary optical axis, and the plurality of micro deflectors deflect the primary electron beam to form a plurality of parallel virtual images of the electron source. Thus, a virtual multi-source array is converted from the electron source. A plurality of beamlets comprising an imaginary multi-source array pass through each of the plurality of beam limiting apertures so that the flow of each beamlet is limited by one corresponding beam limiting aperture. The flow of the plurality of beamlets can be changed by adjusting the focusing lens. The primary projection imaging system images a virtual multi-source array onto a surface such that a plurality of probe spots are formed thereon. One micro lens and one micro stigator of one micro compensator each compensate for the topographic curvature and astigmatism of one corresponding probe spot, and the deflection scanning unit has a plurality of probe spots within the viewing area on the surface. A plurality of beamlets are deflected to scan respectively over the scan area of. A plurality of secondary electron beams are each generated from the plurality of scan areas by the plurality of probe spots and are focused by the objective lens upon passing, and the beam splitter deflects the plurality of secondary electron beams into the secondary projection imaging system. Let's do it. The secondary projection imaging system focuses and maintains the plurality of secondary electron beams so that they are each detected by the plurality of detection elements, so that each detection element provides an image signal of one corresponding scan area.

The multibeam device may further comprise a main aperture plate underneath the electron source, the main aperture plate having a main opening aligned with the primary optical axis and functioning as a beam limiting aperture for the primary electron beam. Each of the plurality of micro deflector-compensator elements functions as one micro deflector by generating the required deflection field and one micro by generating the required quadrupole field and the required round-lens field. It has an eight-pole structure that functions as a compensator. Each of the plurality of micro deflector-compensator elements includes an upper quadrupole structure and a lower quadrupole structure in the upper layer and the lower layer, respectively, and the upper layer is above the lower layer, and the upper quadrupole structure and the lower quadrupole structure Are aligned with each other and have a 45 ° difference in azimuth. The upper quadrupole structure and the lower quadrupole structure can function as one micro deflector by creating the required deflection field and as one micro compensator by creating the required quadrupole field and the required round lens field. The primary projection imaging system may further include a transfer lens over the objective lens, which focuses the plurality of beamlets to reach vertically on the surface. The multibeam device may also further comprise a single beam electron detector that is above the beam splitter and can be used in a single beam mode. The multibeam device can further include an in-lens electron detector having a beamlet through hole aligned with the primary optical axis, which is under the beam splitter and can be used in single beam mode.

The invention also provides a method for configuring a source conversion unit to form a virtual multi-source array from an electron source, which method comprises a top layer having a plurality of top quadrupole structures and a plurality of bottom quadrupole structures. Providing an image forming means comprising an underlayer having, and providing beamlet limiting means below the image forming means and comprising a plurality of beam limiting openings. Each upper quadrupole structure is aligned with one corresponding lower quadrupole structure above one corresponding lower quadrupole structure, both of which form a pair of four-pole structures with a 45 ° difference in azimuth. Therefore, the plurality of upper four-pole structures and the plurality of lower four-pole structures form a plurality of pairs of four-pole structures. The plurality of beam limiting openings are each aligned with a plurality of pairs of four-pole structures. The pair of four-pole structures function as a micro deflector to deflect one beamlet of the electron beam generated by the electron source to form a virtual image and as a microlens to focus one beamlet to the required extent. And / or act as a micro stigmatizer to add the required amount of astigmatism to one beamlet.

The source conversion unit may comprise an upper electrically conducting plate having a plurality of upper through holes, each aligned with a plurality of pairs of four-pole structures. The source conversion unit may further comprise a bottom electrically conductive plate having a plurality of bottom through holes, each aligned with a plurality of pairs of four-pole structures.

The present invention also provides a method for forming a virtual multi-source array from an electron source, which method uses an upper layer having a plurality of upper quadrupole structures and a lower layer having a plurality of lower quadrupole structures. Deflecting electron beams from the plurality of electron sources into the plurality of beamlets, and limiting the plurality of beamlets by using the plurality of openings. Each upper quadrupole structure is aligned with one corresponding lower quadrupole structure above one corresponding lower quadrupole structure, both of which form a pair of four-pole structures with a 45 ° difference in azimuth.

The present invention also provides a charged particle beam apparatus, comprising: a single charged particle source for providing a primary beam, means for converting the primary beam into a plurality of beamlets, and images from a plurality of beamlets. A first projection system for forming a plurality of probe spots in the apparatus, a deflection scanning unit for scanning the plurality of probe spots on the specimen, means for separating the plurality of signal electron beams from the plurality of beamlets, and receiving the plurality of signal electron beams And a second projection system for forming a plurality of signal spots from the plurality of signal electron beams, respectively, on the plurality of electron detection elements of the detection device. The conversion means comprises a plurality of deflectors for deflecting the plurality of beamlets and a plurality of beam limiting openings under the plurality of deflectors. A plurality of signal electron beams are each generated due to the collision of the plurality of beamlets on the specimen.

The charged particle beam device may further include a focusing lens for adjusting the flow of the plurality of probe spots. The conversion means may comprise a plurality of compensators for respectively compensating for aberrations of the plurality of probe spots.

Other advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which specific embodiments of the invention will be presented for purposes of illustration.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be readily understood from the following detailed description taken in conjunction with the accompanying drawings, wherein like reference numerals designate like elements.
1A and 1B show schematic diagrams of existing source conversion units, respectively.
2 schematically illustrates an electromagnetic interference experiment using an electron abdominal prism.
3A is a schematic diagram showing one configuration of a new multibeam device according to an embodiment of the present invention.
3B-3D schematically illustrate the modes of operation of the new multibeam device of FIG. 3A, respectively.
4 is a schematic diagram showing another configuration of a new multi-beam apparatus according to another embodiment of the present invention.
5a-5c show schematic views, respectively, of one configuration of the image forming means of FIG. 3a according to another embodiment of the invention.
6A-6D show schematic views, respectively, of one configuration of the image forming means of FIG. 3A according to another embodiment of the invention.
FIG. 7 shows a schematic view of one configuration of the improved image forming means of FIG. 4 in accordance with another embodiment of the present invention.
8A-8D schematically illustrate one configuration of the improved image forming means of FIG. 4 in accordance with another embodiment of the present invention.
9A is a schematic diagram showing another configuration of a novel multibeam device according to another embodiment of the present invention.
9B and 9C show schematic views of the operation modes of the new multibeam device of FIG. 9A, respectively.
10 is a schematic diagram of one mode of operation of the new multibeam device of FIG.
11A is a schematic diagram showing another configuration and one operation mode of a new multibeam device according to another embodiment of the present invention.
11B is a schematic diagram showing another configuration and one operation mode of a new multibeam device according to another embodiment of the present invention.

DETAILED DESCRIPTION Various exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which several exemplary embodiments of the invention are shown. Without limiting the scope of protection of the present invention, all descriptions and drawings for this embodiment will refer to, for example, electron beams. However, these examples are not intended to limit the invention to particular charged particles.

In the drawings, the relative dimensions of each component and the dimensions between each component may be exaggerated for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or objects, and only individual differences will be described with respect to individual embodiments. Although only three beamlets are shown in the figure for clarity, the number of beamlets may be any number.

Accordingly, exemplary embodiments of the invention may be variously modified and alternative forms, the drawings of which are shown for illustrative purposes in the drawings and will be described in detail herein. However, it is not intended to limit the exemplary embodiments of the present invention to the specific forms disclosed, on the contrary, the exemplary embodiments of the present invention are intended to cover all modifications, equivalents, and alternatives falling within the scope of the present invention. .

In the present invention, "axial direction" means "lens (round or multipole), optical axis direction of an imaging system or apparatus", and "radial direction" means "direction perpendicular to the optical axis", and "on" -axial) "means" on or aligned with the optical axis "and" off-axis "means" not on or aligned with the optical axis ".

The expression "imaging system is aligned with the optical axis" in the present invention means that "all electro-optical elements (round lenses and multipole lenses) are aligned with the optical axis".

In the present invention, the X, Y, and Z axes form a rectangular coordinate system. The optical axis of the primary projection imaging system is on the Z axis and the primary electron beam travels along the Z axis.

In the present invention, "primary electron" means "electrons emitted from an electron source and incident on a surface under observation or inspection of a sample", and "secondary electrons" means "electrons generated from a surface by primary electrons." "Means.

By "signal electrons" is meant herein "electrons generated from the surface under observation or inspection of a sample by a primary charged particle beam."

In the present invention, "single beam mode" means that only one beamlet is in use.

All terms relating to through holes, openings and orifices in the present invention mean openings or holes penetrating through one plate.

The present invention will next provide some embodiments of a novel multibeam device. The multibeam apparatus comprises first a new source conversion unit for forming a plurality of parallel virtual images of a single electron source and secondly limiting the flow of the corresponding plurality of beamlets, a focusing lens for adjusting the flow of the plurality of beamlets, a sample A primary projection imaging system for projecting a plurality of parallel virtual images to form a plurality of probe spots on the observing surface of a beam splitter for deflecting the plurality of secondary electron beams from a path of the plurality of beamlets, and electron detection A secondary projection imaging system is employed to focus the plurality of secondary electron beams to be detected by the plurality of detection elements of the device, respectively.

The new source conversion unit comprises image forming means having a plurality of micro deflectors and beamlet limiting means having a plurality of beam limiting openings, the image forming means being located upstream of the beamlet limiting means. The primary electron beam from a single electron source is first deflected by a plurality of micro deflectors to form a plurality of parallel virtual images of a single electron source, and the plurality of beamlets forming the plurality of parallel virtual images are arranged in a plurality of beam limiting apertures. Is penetrated vertically or substantially vertically. In this way, the plurality of beam limiting openings not only produce fewer scattered electrons as compared to the prior art, but also block scattered electrons generated upstream, eliminating image resolution degradation due to electron scattering. The image forming means may further comprise a plurality of micro-compensators for respectively compensating the off-axis aberration (top curvature and astigmatism) of the plurality of probe spots, thereby further improving the image resolution of the surface under observation.

One embodiment 100A of a new multibeam device is shown in FIG. 3A. The single electron source 101 is on the primary optical axis 100_1. The common focusing lens 110, the main aperture plate 171, the new source conversion unit 120, the primary projection imaging system 130, the deflection scanning unit 132 and the beam splitter 160 have a primary optical axis ( 100_1) and aligned with the primary optical axis. Secondary projection imaging system 150 and electronic detection device 140 are disposed along secondary optical axis 150_1 and aligned with the secondary optical axis.

The main aperture plate 171 may be disposed on the common focusing lens 110 or just above the new source conversion unit 120 as shown. The new source conversion unit 120 includes a micro deflector array 122 having two micro deflectors 122_2 and 122_3 and a beamlet limiting plate 121 having three beam limiting openings 121_1, 121_2 and 121_3. The beam limiting opening 121_1 is aligned with the primary optical axis 100_1. If the beam limiting opening 121_1 is not aligned with the primary optical axis 100_1, there will be one more micro deflector 122_1 (as shown in FIG. 5C). The primary projection imaging system 130 includes a transfer lens 133 and an objective lens 131. The deflection scanning unit 132 includes at least one deflector. The beam splitter 160 includes one Wien filter. Secondary projection imaging system 150 includes an anti-scanning deflector 151, a zoom lens 152 (including at least two lenses 152_1 and 152_2) and an anti-rotation magnetic lens 154. The electronic detection device 140 includes three detection elements 140_1, 140_2 and 140_3. Each lens mentioned above may be an electrostatic lens, a magnetic lens or an electromagnetic composite lens.

3B-3D illustrate three modes of operation of the new multibeam device 100A. The single electron source 101 comprises a cathode, an extractor and / or an anode, wherein primary electrons are emitted from the cathode and extracted and / or accelerated so that high energy (eg 8-20 keV), high angular intensity (eg 0.5-5 mA / sr) and here the primary electron beam 102 having a crossover 101s (virtual or real) represented by an axial oval mark. Therefore, it is convenient to think that the primary electron beam 102 is emitted from the crossover 101s and the single electron source 101 is simplified to the crossover 101s.

In FIG. 3B, the focusing lens 110 is in an off state. The primary electron beam 102 passes through the focusing lens 110 without affecting focusing and the outer electrons are blocked by the main opening of the main aperture plate 171. Micro deflectors 122_2 and 122_3 deflect beamlets 102_2 and 102_3 of primary electron beam 102, respectively. The deflected beamlets 102_2 and 102_3 form off-axis virtual images 102_2v and 102_3v of the crossover 101s of the single electron source 101, respectively. The deflected beamlets 102_2 and 102_3 are parallel or substantially parallel to the primary optical axis 100_1, and thus are incident vertically on the beamlet limiting plate 121. Beam limiting openings 121_1, 121_2 and 121_3 restrict their flow by blocking outward electrons in deflected beamlets 102_2 and 102_3 and central portion 102_1 of primary electron beam 102, respectively. As a result, one virtual multi-source array 101v is formed, which includes a crossover 101s and its two parallel off-axis virtual images 102_2v and 102_3v. One virtual image can avoid the Coulomb effect in one real image in FIG. 1A. In order to further reduce the Coulomb effect, the main aperture plate 171 may be disposed on the focusing lens 110 to block the outer electrons as early as possible.

The crossover 101s and its two parallel off-axis virtual images 102_2v and 102_3v are then imaged onto the surface 7 being viewed by the transfer lens 133 and the objective lens 131, the images of which are Three probe spots 102_1s, 102_2s, 102_3s are formed thereon. In order for the two off-axis beamlets 102_2 and 102_3 to reach vertically on the surface 7 being viewed, the transfer lens 133 focuses them to pass through the front focal point of the objective lens 131. When the objective lens 131 includes one magnetic lens, the two off-axis beamlets 102_2 and 102_3 may not pass exactly the forward focus due to the effects of magnetic rotation, which means that the beamlet crossover ( This is a great help in reducing the Coulomb effect in CS. The deflection scanning unit 132 deflects the three beamlets 102_1-102_3 and consequently scans three separate areas on the surface 7 on which the three probe spots 102_1s-102_3s are being observed.

The secondary electron beams 102_1se, 102_2se and 102_3se emitted from the three scan regions are focused by the objective lens 131 and deflected by the beam splitter 160 along the secondary optical axis 150_1. Enter 150. Lenses 152 and 153 focus the secondary electron beam onto three detection elements 140_1 to 140_3, respectively. Each detection element will therefore provide an image signal of one corresponding scan area. If some secondary electrons of the secondary electron beam go from one scan area to a neighboring detection element, the image signal of the neighboring detection element will also contain foreign information from this scan area, The foreign information for neighboring detection elements becomes crosstalk from this scan area. To avoid crosstalk between the detection elements, the zoom lens 152 makes the spot size of each secondary electron beam smaller than the corresponding detection element, while the deflection scanning unit 132 deflects the beamlets 102_1-102_3. The anti-scanning deflector 151 simultaneously deflects the secondary electron beams 102_1se-102_3se to maintain it in the corresponding detection element.

Different samples typically require different viewing conditions such as the arrival energy and flow of the beamlet. This is especially true for the inspection and / or review of defects on wafers / masks in the semiconductor manufacturing industry. The focusing force of the objective lens 131 will depend on the energy reached, which will affect the position of the secondary electron beam on the electron detection device 140 causing crosstalk. In this case, the zoom lens 152 will be adjusted to eliminate the radial displacement of the secondary electron beam. If the objective lens 131 includes one magnetic lens, the anti-rotation magnetic lens 154 will be adjusted to eliminate rotation of the secondary electron beam.

Each of the two off-axis probe spots 102_2s and 102_3s includes an off-axis aberration generated by the objective lens 131, the transfer lens 133, and the focusing lens when turned on. The off-axis aberration of each off-axis probe spot can be reduced by individually optimizing the trajectory of the corresponding beamlet. The static part of the off-axis aberration can be reduced by adjusting the biasing force of the corresponding micro deflector. The dynamic portion of the off-axis aberration can be reduced by optimizing the performance of the deflection scanning unit 132, which can therefore include more than one deflector.

Unlike FIG. 3B, the focusing lens 110 is turned on in FIG. 3C, which focuses the primary electron beam 102 to form an axial virtual image 101sv of the crossover 101s of the single electron source 101. do. Micro deflectors 122_2 and 122_3 respectively deflect beamlets 102_2 and 102_3 of the focused primary electron beam 102 and form two off-axis virtual images 102_2v and 102_3v of crossover 101s. The deflected beamlets 102_2 and 102_3 are parallel or substantially parallel to the primary optical axis 100_1, and thus are incident vertically on the beamlet limiting plate 121. The beam limiting openings 121_1, 121_2, 121_3 block the electrons outside the central portion 102_1 of the deflected beamlets 102_2 and 102_3 and the focused primary electron beam 102, respectively, thereby restricting their flow. The focusing function of the focusing lens 110 increases the flow density of the focused primary electron beam 102, thereby increasing the flow of the beamlets 102_1-102_3 to be higher than in the case of FIG. 3B. Thus, the flow of all beamlets can be continuously adjusted by the focusing lens 110.

As with conventional SEM, the size of each probe spot is minimized by balancing geometric and diffraction aberrations, Gaussian image size, and Coulomb effect. The focusing function of the focusing lens 110 changes the imaging magnification from the crossover 101s to the surface 7 under observation, whereby the balance can be affected and the size of each probe spot can be increased. In the case where the flow of the beamlet changes greatly, the size of the beam limiting openings 121_1 to 121 to 3 may be changed accordingly to avoid a large increase in the size of the probe spot. As a result, the beamlet limiting plate 121 having a plurality of groups of beam limiting openings is preferred. The size of the beam limiting openings in one group is different from the size of the beam limiting openings in the other group. Alternatively, the focusing force of the transfer lens 133 can be changed to reduce the change in imaging magnification. The trajectories of the off-axis beamlets 102_2 and 102_3 will be affected by the change in the focal force of the transfer lens 133, so that the deflection forces of the micro deflectors 122_2 and 122_3 can be adjusted to maintain this trajectory. In this way, the beamlets 102_2 and 102_3 may not be slightly parallel to the primary optical axis 100_1 as shown in FIG. 3D.

Another embodiment 110A of a new multibeam device is shown in FIG. 4. Unlike embodiment 100A, new source conversion unit 120_1 includes one micro deflector-compensator array 122-1 with three micro deflector-compensator elements 122_1dc, 122_2dc, 122_3dc. Each micro deflector-compensator element includes one micro compensator and one micro deflector having one micro lens and one micro stigator. The micro deflector is used to form one virtual multi-source array in the same manner as the functions of the micro deflectors 122_2 and 122_3 shown in FIGS. 3B-3D. As is well known, the focusing lens 110, the transfer lens 133 and the objective lens 131 will produce off-axis aberration. As mentioned above, the effect of off-axis aberration on the size of the probe spot can be reduced by individually optimizing the trajectory of the beamlet. Thus, microlenses and microstigators will be used to compensate for the remaining topside curvature and astigmatism of the probe spot, respectively. Compared to the micro deflector array 122 of FIG. 3A, the micro deflector-compensator array 122-1 is an improved image forming means.

Each of the micro deflectors 122_2 and 122_3 in FIG. 3 may simply include two parallel electrodes perpendicular to the desired deflection direction of the corresponding beamlet, as shown in FIG. 5A. For example, the micro deflector 122_2 deflects the beamlet 102_2 in the X-axis direction by having two parallel electrodes 122_2_e1 and 122_2_e2 perpendicular to the X-axis. 5B illustrates one embodiment of a micro deflector array 122 for deflecting eight beamlets. Because each micro deflector has a specific orientation, it is difficult to make one micro deflector array 122 that includes multiple micro deflectors. From a manufacturing point of view, it is preferable that all micro deflectors have the same configuration and the same orientation geometrically. Therefore, a micro deflector having a quadrupole or quadrupole configuration can meet this requirement as shown in FIG. 5C. The four electrodes of each micro deflector can form two deflectors that can deflect one electron beamlet in any direction. The micro deflector 122_1 may be used when the corresponding beam limiting aperture 121-1 is not properly aligned with the primary optical axis 101.

In order to operate one micro deflector, a drive circuit needs to be connected with its respective electrode. In order to prevent the drive circuit from being damaged by the primary electron beam 102, it is more preferable to place one electrically conducting plate over the electrodes of all micro deflectors in FIGS. 5A-5C. In FIG. 6A, taking FIG. 5C as an example, the micro deflectors 122_1 to 122_3 include the upper electrically conductive plate 122-CL1 having a plurality of upper through holes and the upper insulating plate 122-IL1 having a plurality of upper orifices. Is placed on the electrode. Electrodes of the micro deflectors 122_1 to 122_3 may be attached to the upper insulating plate 122-IL1. The upper through hole and the upper orifice are respectively aligned with the optical axis of the micro deflector, for example, the upper through hole CL1_2 and the upper orifice IL1_2 are on the optical axis 122_2_1 of the micro deflector 122_2. The radial size of each upper through hole is less than or equal to the inner radial dimension of the electrode of the corresponding micro deflector to protect the drive circuit, and the radial size of each upper orifice prevents charge buildup on the inner sidewalls. In order to be larger than the radial size of the corresponding upper through hole. In this way, the deflection field of all micro deflectors will have a short fringe range on the top side, which will reduce deflection aberrations.

Based on FIG. 6A, the micro deflector array 122 of FIG. 6B further includes a bottom electrically conductive plate 122-CL2 having a plurality of bottom through holes. Each lower through hole is aligned with the optical axis of one micro deflector, for example, the lower through hole CL2_2 is on the optical axis 122_2_1 of the micro deflector 122_2. In this way, the deflection field of all micro deflectors will have a short pattern range on both the upper and lower sides, thereby reducing the deflection aberration. Unlike FIG. 6B, the micro deflector array 122 of FIG. 6C employs a lower insulating plate 122-IL2 having a plurality of lower orifices to support the electrodes of the micro deflectors 122_1 to 122_3. Each lower orifice is aligned with the optical axis of one micro deflector, for example the lower orifice IL2_2 is on the optical axis 122_2_1 of the micro deflector 122_2. The radial size of each lower orifice is larger than the inner radial dimension of the electrode of the corresponding micro deflector. The micro deflector array 122 of FIG. 6D is a combination of FIGS. 6B and 6C, which is more stable in construction.

FIG. 7 illustrates one embodiment of the micro deflector-compensator element 122_2dc of the micro deflector-compensator array 122-1 of FIG. 4, having an 8-pole structure. Eight electrodes 122_2dc_e1 to 122_2dc_e8 are driven to generate a dipole field (deflection field) in any direction, with a base amount for generating a virtual image of the electron source 1 and an additional amount to compensate for distortion. A quadrupole field (astigmatism field) can be generated in any direction to compensate for astigmatism, and a round lens field can be generated to compensate for image curvature.

FIG. 8A shows another embodiment of the micro deflector-compensator array 122-1 of FIG. 4. Each micro deflector-compensator element comprises a pair of four-pole lenses arranged in two layers that are aligned with each other and have a 45 ° difference in azimuth or orientation. The micro deflector-compensator elements 122_1dc, 122_2dc and 122_3dc are each a pair of upper and lower quadrupole lenses 122_1dc-1 and 122_1dc-2, and a pair of upper and lower quadrupole lenses 122_2dc-1 and 122_2dc-2, respectively. ) And pairs of upper and lower quadrupole lenses 122_3dc-1 and 122_3dc-2. The upper four-pole lenses 122_1dc-1, 122_2dc-1 and 122_3dc-1 are disposed in the upper layer 122-1-1, and the lower four-pole lenses 122_1dc-2, 122_2dc-2 and 122_3dc-2 are lower Layers 122-1-2 and are aligned with the upper quadrupole lenses 122_1dc-1, 122_2dc-1, and 122_3dc-1, respectively. As an example, with respect to the X axis, the azimuth angles of the upper quadrupole lenses 122_1dc-1, 122_2dc-1, and 122_3dc-1 are 0 ° as shown in FIG. 8B, and the lower quadrupole lenses 122_1dc-2, 122_2dc- 2 and 122_3dc-2) is 45 ° as shown in FIG. 8C. In FIG. 8D the upper and lower layers are shielded by upper and lower electrically conductive plates 122-CL1 and 122-CL2, as in FIG. 6D, and the upper and lower insulating plates 122-IL1 and 122-IL2 and a plurality of intermediates. Supported by an intermediate insulation plate 122-IL3 having an orifice. For each micro deflector-compensator element, a deflection field and round lens field in any desired direction can be produced by one or both of the upper and lower quadrupole lenses, and both the upper and lower quadrupole lenses By all the quadrupole fields in any direction can be generated.

Another embodiment 200A of a new multibeam device is shown in FIG. 9A. Compared to the embodiment 110A of FIG. 4, the transfer lens 133 is removed from the primary projection imaging system. FIG. 9B shows one mode of operation in which the off-axis beamlets 102_2 and 102_3 are deflected parallel to the primary optical axis 200_1 by the micro deflector-compensator elements 122_2dc and 122_3dc, respectively, and the viewing surface 7 Reach obliquely to the phase. This mode can be used in observation applications where there are no stringent requirements on the incident conditions of the beamlets and require stereo imaging. The micro deflector-compensator elements 122_2dc and 122_3dc can compensate for the large off-axis aberrations of the two off-axis beamlets 102_2 and 102_3 due to passing through the objective lens 131 with a large radial shift. 9C shows another mode of operation, in which the off-axis beamlets 102_2 and 102_3 are further deflected towards the primary optical axis 200_1 by the micro deflector-compensator elements 102_2dc and 102_3dc, respectively, and viewing the surface 7. Less obliquely reaches the phase. When the micro deflector-compensator elements 122_2dc and 122_3dc deflect the off-axis beamlets 102_2 and 102_3, respectively, to pass through the forward focus of the objective lens 131, the off-axis beamlets 102_2 and 102_3 may be viewed from the surface under observation 7. Will be perpendicular to the image. In order to prevent the off-axis beamlets 102_2 and 102_3 from passing through the beam limiting aperture at a large angle of incidence, it is desirable to maintain a distant distance between the front focus of the objective lens 131 and the micro deflector-compensator array 122-1. Do.

As is well known, the more beamlets scan the surface 7 being viewed, the more charge can accumulate thereon. Thus, some of the beamlets may not be needed for certain observation applications. In this case, such beamlets may be directed to be blanked by the beamlet limiting plate. FIG. 10 illustrates this mode of operation of the embodiment 110A of FIG. 4, where the micro deflector-compensator 122_2dc is off and the beamlet 102_2 is blocked by the beamlet limiting plate 121. The micro deflector-compensator 122_2dc may need to be turned on to direct the beamlet 102_2 to be blocked by the beamlet limiting plate 121, which depends on the detailed structure of the source conversion unit 120-1.

Based on the embodiment 110A of FIG. 4, another embodiment 111A of the new multibeam device is shown in FIG. 11A, where a single beam electron detector 141 is added. For some reason, the device will operate in single beam mode if only one beamlet is needed, for example for finding the optimal imaging conditions (reaching energy and probe flow) for a given observation application. In this case, beam splitter 160 can deflect the corresponding secondary electron beam to single beam electron detector 141. Here, the beamlet 102_1 is treated as a beamlet in use. The secondary electron beam 102_1se generated by the beamlet 102_1 is deflected to be detected by the single beam electron detector 141. The use of a single beam electron detector 141 avoids the process of adjusting the secondary projection imaging system 150 to changes in focal force of the objective lens 131. As mentioned above, the focal force of the objective lens 131 will change as the energy and / or flow of arrival of the beamlet in use changes. Furthermore, FIG. 11B shows another embodiment 112A of the new multibeam device, with an in-lens electron detector 142 having beamlet through holes disposed below the beam separator 160. When the device is operating in single beam mode, within the secondary electron beam associated with the beamlet in use, secondary electrons having a large emission angle can be detected by the in-lens electron detector 142 and having a small emission angle Secondary electrons will be detected by the corresponding detection element of the electron detection device 140 through the beamlet through hole. The beamlet 102_1 is treated here as a beamlet in use. Within the secondary electron beam 102_1se generated by the beamlet 102_1, secondary electrons 102_1se_2 having a large emission angle impinge on the in-lens electron detector 142 and secondary electrons 102_1se_1 having a small emission angle. ) Is biased to be detected by the electronic detection device 140. The single beam electron detector 141 and the in-lens electron detector 142 may be used in combination. In this case, secondary electrons 102_1se_2 having a large emission angle can be detected by the in-lens electron detector 142, and secondary electrons 102_1se_1 having a small emission angle are detected by the single beam electron detector 141. It may be deflected by beam splitter 160 to be detected. Although not shown here, the in-lens electron detector 142 may also be disposed above the beam splitter 160. In this case, the in-lens electron detector 142 may detect the outer portion of the secondary electron beam 102_1se when the beam splitter is in the off state.

In summary, the present invention proposes a new multibeam apparatus for observing samples with high resolution and high throughput. This new multibeam device can serve as a yield management tool for inspecting and / or examining defects on wafers / masks in the semiconductor manufacturing industry. Such a multibeam device includes a new source conversion unit for forming a plurality of parallel virtual images of a single electron source, a focusing lens for adjusting the flow of the plurality of beamlets, and a plurality of probe spots on the viewing surface of the sample. A primary projection imaging system for projecting a plurality of parallel virtual images to form, a beam splitter for deflecting the plurality of secondary electron beams from a path of the plurality of beamlets, and a plurality of detection elements of the electronic detection device, respectively. A secondary projection imaging system is employed to focus the plurality of secondary electron beams as much as possible. In the new source conversion unit, the image forming means is located upstream of the beamlet limiting means, thereby mitigating image resolution degradation due to electron scattering. The image forming means comprises a plurality of micro deflectors for forming a plurality of parallel virtual images, or a plurality of micro deflector-compensator elements for forming a plurality of parallel virtual images and compensating for off-axis aberration of the plurality of probe spots. .

While the invention has been described in terms of its preferred embodiments, it will be understood that other modifications and variations can be made without departing from the scope and spirit of the invention as hereinafter claimed.

Claims (24)

A multibeam device for observing the surface of a sample,
Electron source;
A focusing lens beneath the electron source;
A source conversion unit under the focusing lens;
A primary projection imaging system below the source conversion unit and including an objective lens;
A deflection scanning unit inside the primary projection imaging system;
A sample stage underneath the primary projection imaging system;
A beam splitter on the objective lens;
A secondary projection imaging system above the beam splitter; And
An electronic detection device having a plurality of detection elements,
The source conversion unit comprises image forming means having a plurality of micro deflectors and beamlet limiting means having a plurality of beam limiting openings, the image forming means being above the beamlet limiting means,
The electron source, the focusing lens, the source conversion unit, the primary projection imaging system, the deflection scanning unit and the beam splitter are aligned with the primary optical axis of the device, and the sample stage has the surface in contact with the objective lens. Supporting the sample to face, the secondary projection imaging system and the electronic detection device are aligned with a secondary optical axis of the apparatus, the secondary optical axis not being parallel to the primary optical axis,
The electron source generates a primary electron beam along the primary optical axis, and the plurality of micro deflectors deflect the primary electron beam to form a plurality of parallel virtual images of the electron source to produce a virtual beam from the electron source. A multi-source array is transformed, wherein a plurality of beamlets comprising the virtual multi-source array pass through the plurality of beam limiting openings, respectively, so that the flow of each beamlet is limited by one corresponding beam limiting opening, The flow of the plurality of beamlets can be changed by adjusting the focusing lens,
The primary projection imaging system images the virtual multi-source array onto the surface such that a plurality of probe spots are formed thereon, and the deflection scanning unit is configured to display the plurality of probe spots within a viewing area on the surface. Deflecting the plurality of beamlets to scan each over a scan area of;
A plurality of secondary electron beams are each generated from the plurality of scan areas by the plurality of probe spots and are focused by the objective lens upon passing through, and the beam splitter projects the plurality of secondary electron beams onto the secondary projection. Deflecting into an imaging system and the secondary projection imaging system focuses and maintains the plurality of secondary electron beams so that they are each detected by the plurality of detection elements, thereby allowing each detection element to capture an image signal of one corresponding scan area. A multibeam device for observing the surface of a sample provided. The method of claim 1,
The apparatus further comprises a main aperture plate under the electron source, the main aperture plate having a main aperture aligned with the primary optical axis and functioning as a beam limiting aperture for the primary electron beam. , A multibeam device for observing the surface of a sample. The method of claim 2,
The primary projection imaging system includes a transfer lens over the objective lens, the transfer lens focusing the plurality of beamlets to reach vertically on the surface. Beam device. The method of claim 3,
Wherein each of said plurality of micro deflectors has a four-pole structure capable of generating a deflection field in any radial direction. The method of claim 4, wherein
And a single beam electron detector that is above the beam splitter and that can be used in single beam mode. The method of claim 4, wherein
And an in-lens electron detector having a beamlet through hole aligned with the primary optical axis, the in-lens electron detector capable of being used in a single beam mode. The method of claim 5,
The apparatus further includes an in-lens electron detector having a beamlet through hole aligned with the primary optical axis, the in-lens electron detector being below the beam splitter and capable of being used in the single beam mode. Multibeam device for observation. A multibeam device for observing the surface of a sample,
Electron source;
A focusing lens beneath the electron source;
A source conversion unit under the focusing lens;
A primary projection imaging system below the source conversion unit and including an objective lens;
A deflection scanning unit inside the primary projection imaging system;
A sample stage underneath the primary projection imaging system;
A beam splitter on the objective lens;
A secondary projection imaging system above the beam splitter; And
An electronic detection device having a plurality of detection elements,
The source converting unit comprises image forming means with a plurality of micro deflector-compensator elements and beamlet limiting means with a plurality of beam limiting apertures, each micro deflector-compensator element comprising one microlens and one A micro compensator and a micro deflector having a micro stigator of said image forming means, said image forming means being above said beamlet limiting means,
The electron source, the focusing lens, the source conversion unit, the primary projection imaging system, the deflection scanning unit and the beam splitter are aligned with the primary optical axis of the device, and the sample stage has the surface in contact with the objective lens. Supporting the sample to face, the secondary projection imaging system and the electronic detection device are aligned with a secondary optical axis of the apparatus, the secondary optical axis not being parallel to the primary optical axis,
The electron source generates a primary electron beam along the primary optical axis, and the plurality of micro deflectors deflect the primary electron beam to form a plurality of parallel virtual images of the electron source to produce a virtual beam from the electron source. A multi-source array is transformed, wherein a plurality of beamlets comprising the virtual multi-source array pass through the plurality of beam limiting openings, respectively, so that the flow of each beamlet is limited by one corresponding beam limiting opening, The flow of the plurality of beamlets can be changed by adjusting the focusing lens,
The primary projection imaging system images the virtual multi-source array onto the surface such that a plurality of probe spots are formed thereon, the one micro lens and the one micro stigator of the one micro compensator. Respectively compensate for top surface curvature and astigmatism of one corresponding probe spot, and the deflection scanning unit scans the plurality of beamlets to respectively scan the plurality of probe spots over a plurality of scan areas within a viewing area on the surface. Deflect,
A plurality of secondary electron beams are each generated from the plurality of scan areas by the plurality of probe spots and are focused by the objective lens upon passing through, and the beam splitter projects the plurality of secondary electron beams onto the secondary projection. Deflecting to enter an imaging system and the secondary projection imaging system focuses and maintains the plurality of secondary electron beams to be respectively detected by the plurality of detection elements, such that each detection element is an image of one corresponding scan area. A multibeam device for viewing a surface of a sample that provides a signal. The method of claim 8,
The apparatus further comprises a main aperture plate under the electron source, the main aperture plate having a main aperture aligned with the primary optical axis and functioning as a beam limiting aperture for the primary electron beam. , A multibeam device for observing the surface of a sample. The method of claim 9,
Each of the plurality of micro deflector-compensator functions as the one micro deflector by generating the required deflection field and by generating the required quadrupole field and the required round-lens field. A multibeam apparatus for observing the surface of a sample having an eight-pole structure that functions as one micro compensator. The method of claim 9,
Each of the plurality of micro deflector-compensator elements includes an upper quadrupole structure and a lower quadrupole structure in an upper layer and a lower layer, respectively, wherein the upper layer is above the lower layer, the upper quadrupole structure and Wherein the lower quadrupole structure is aligned with each other and has a 45 ° difference in azimuth angle. The method of claim 11,
The upper quadrupole structure and the lower quadrupole structure function as the one micro deflector by generating the required deflection field and as the one micro compensator by generating the required quadrupole field and the required round lens field. The multi-beam apparatus for observing the surface of a sample. The method of claim 12,
And the primary projection imaging system includes a transfer lens over the objective lens, the transfer lens focusing the plurality of beamlets to reach vertically on the surface. The method of claim 13,
And a single beam electron detector that is above the beam splitter and that can be used in single beam mode. The method of claim 13,
And an in-lens electron detector having a beamlet through hole aligned with said primary optical axis, which may be used in single beam mode. The method of claim 14,
The apparatus further includes an in-lens electron detector having a beamlet through hole aligned with the primary optical axis, the in-lens electron detector being below the beam splitter and capable of being used in the single beam mode. Multibeam device for observation. A method for configuring a source conversion unit to form a virtual multi-source array from an electron source,
Providing an image forming means comprising an upper layer having a plurality of upper quadrupole structures and a lower layer having a plurality of lower quadrupole structures; And
Providing beamlet limiting means below said image forming means and comprising a plurality of beam limiting openings,
Each upper quadrupole structure is aligned with the one corresponding lower quadrupole structure above one corresponding lower quadrupole structure, both forming a pair of four pole structures with a 45 ° difference in azimuth angle, such that The plurality of upper quadrupole structures and the plurality of lower quadrupole structures form a plurality of pairs of four-pole structures,
The plurality of beam limiting apertures are each aligned with the plurality of pairs of four-pole structures,
The pair of quadrupole structures function as micro deflectors to deflect one beamlet of the electron beam generated by the electron source to form a virtual image, and micro to focus the one beamlet to the required degree. A method for configuring a source conversion unit to form a virtual multi-source array from an electron source, functioning as a lens and / or functioning as a microstigmator to add the desired astigmatism to the one beamlet . The method of claim 17,
Wherein the source conversion unit comprises an upper electrically conducting plate having a plurality of top through holes, each aligned with the plurality of pairs of four-pole structures, to configure a source conversion unit to form a virtual multi-source array from an electron source. Way. The method of claim 18,
Wherein the source conversion unit comprises a bottom electrically conducting plate having a plurality of bottom through-holes, each aligned with the plurality of pairs of four-pole structures, to configure a source conversion unit to form a virtual multi-source array from an electron source. Way. A method for forming a virtual multi-source array from an electron source,
Deflecting electron beams from the plurality of electron sources into a plurality of beamlets using an upper layer having a plurality of upper quadrupole structures and a lower layer having a plurality of lower quadrupole structures, each upper quadrupole structure being Deflecting over the one corresponding lower quadrupole structure, the one corresponding lower quadrupole structure, the two forming a pair of four-pole structures with a 45 ° difference in azimuth angle; And
Confining the plurality of beamlets by using a plurality of openings. As a charged particle beam device,
A single charged particle source for providing a primary beam;
Means for converting the primary beam into a plurality of beamlets, the converting means comprising a plurality of deflectors for deflecting the plurality of beamlets and a plurality of beam limiting openings below the plurality of deflectors;
A first projection system for forming a plurality of probe spots on a specimen from the plurality of beamlets;
A deflection scanning unit for scanning the plurality of probe spots on the specimen;
Means for separating from the plurality of beamlets a plurality of signal electron beams each generated due to the plurality of beamlets impinging on the specimen;
A detection device for receiving the plurality of signal electron beams; And
And a second projection system for forming a plurality of signal spots from the plurality of signal electron beams, respectively, on the plurality of electron detection elements of the detection device. The method of claim 21,
And a focusing lens for adjusting the flow of the plurality of probe spots. The method of claim 22,
And said converting means comprises a plurality of compensators for respectively compensating aberrations of said plurality of probe spots. As a source conversion unit,
Image forming means including an upper layer having a plurality of upper quadrupole structures and a lower layer having a plurality of lower quadrupole structures; And
Beamlet limiting means below said image forming means and comprising a plurality of beam limiting openings,
Each upper quadrupole structure is aligned with the one corresponding lower quadrupole structure above one corresponding lower quadrupole structure, both forming a pair of four pole structures with a 45 ° difference in azimuth angle, such that The plurality of upper quadrupole structures and the plurality of lower quadrupole structures form a plurality of pairs of four-pole structures,
The plurality of beam limiting apertures are each aligned with the plurality of pairs of four-pole structures,
The pair of four-pole structures function as a micro deflector to deflect one beamlet of the electron beam generated by the electron source to form a virtual image, and microlens to focus the one beamlet to the required degree. And as a micro stigmatizer to add a desired astigmatism to the one beamlet.

Images