Apparatus and method for detecting one or more scanning charged particle beams

Abstract

The invention relates to an apparatus for inspecting a sample. The apparatus comprises a sample holder (10) for holding a sample (5), a charged particle column (7, 8) for generating one or more charged particle beams and focusing the one or more charged particle beams at one or more charged particle beam spots on the sample, a scanning deflector for moving the one or more charged particle beam spots over the sample, a photon detector (4) configured to detect generated photons when the one or more focused charged particle beams impinge on the sample or when the one or more charged particle beams impinge on a luminescent material layer (6) after transmission through the sample, an optical assembly (2) for projecting or imaging at least a portion of the photons from the one or more charged particle beam spots along a beam path onto the photon detector, and a displacement unit (3) for displacing the beam path and / or the photon detector relative to each other.

Description

Technical Field

[0001] The present invention relates to apparatus and methods for examining samples by scanning one or more beams of charged particles (such as scanning electron microscopes or multi-beam scanning electron microscopes). Background Technology

[0002] Such an apparatus or method is disclosed, for example, in US 2017 / 0133198 A1. That patent application describes an apparatus comprising: a charged particle array for focusing and scanning one or more beams of charged particles onto a sample; and a photon detector, particularly a multi-pixel photon detector, arranged to detect photons generated by the one or more focused charged particle beams when the one or more charged particle beams strike the sample or after the one or more charged particle beams have passed through the sample. The apparatus also includes optical components for conveying the photons generated by the one or more focused charged particle beams to the photon detector, preferably a multi-pixel photon detector.

[0003] As described in US 2017 / 0133198 A1, the optical components may be arranged on one side of the sample holder facing the electromagnetic lens system of the charged particle column, or on the opposite side of the sample holder away from the charged particle column.

[0004] The phenomenon of photon emission caused by the impact of charged particles on a material (particularly a luminescent material) is called cathodoluminescence. It should be noted that when a sample contains one or more cathodoluminescent components, photons are generated by the focused beam of charged particles when the primary charged particle beam impacts the sample, particularly its cathodoluminescent component. Alternatively, a layer of cathodoluminescent or scintillating material can be used to generate photons by impacting charged particles (such as electrons, protons, or ions).

[0005] US 2017 / 0133198 describes a device including a cathodic luminescent or scintillating material layer, wherein the device is configured to position a sample between an electromagnetic lens system and the cathodic luminescent or scintillating material layer such that charged particles strike the cathodic luminescent or scintillating material layer after passing through the sample. The device also includes optical components arranged to project or image the location of the generated photons onto a photon detector. Summary of the Invention

[0006] When one or more beams of charged particles are used to scan over a portion of the sample surface, the position of photons generated in the sample or in the cathodic luminescent or scintillating material layer moves during the scan. Therefore, when the sample or the cathodic luminescent or scintillating material layer is projected or imaged onto the photon detector, the spot of light originating from the impact position of the charged particles also moves on the photon detector.

[0007] On the one hand, when the light spot remains within the detector's area during its movement, the movement of the light spot on the detector does not cause a problem. However, detectors with relatively large detector areas typically have relatively slow responses, resulting in relatively slow image acquisition. Furthermore, in multi-beam systems, the scanning paths of two adjacent beams are arranged very close to each other or even overlap at a certain distance, making it very difficult or even impossible to arrange adjacent detectors to detect only one specific light spot among adjacent light spots.

[0008] On the other hand, a multi-pixel detector can be used to detect light spots, where, during the movement of the light spot, it is projected onto different pixels of the multi-pixel detector and measured by those different pixels. However, tracking and measuring the intensity of the light spot using a multi-pixel detector is a relatively slow process, which significantly hinders rapid image acquisition.

[0009] The object of the present invention is to provide an apparatus and method that at least partially solves one or more of the above-mentioned disadvantages.

[0010] According to a first aspect, the present invention provides an apparatus for examining a sample, wherein the apparatus comprises:

[0011] Sample holders used to hold samples;

[0012] A charged particle array for generating one or more charged particle beams and directing the one or more charged particle beams toward the sample holder, wherein the charged particle array is configured to focus the one or more charged particle beams onto the sample at one or more charged particle beam points.

[0013] A scanning unit, used to scan one or more charged particle beams on a sample along the scanning direction;

[0014] A photon detector for detecting photons generated by one or more focused charged particle beams when the one or more focused charged particle beams strike a sample or when the one or more focused charged particle beams strike a luminescent material layer after the one or more focused charged particle beams have passed through the sample.

[0015] Optical components for projecting or imaging at least a portion of the photons from the one or more charged particle beams along a beam path onto one or more light spots on the photon detector; and

[0016] A shifting unit for shifting the one or more light spots and / or the photon detector relative to each other, wherein the shifting unit is configured to at least partially compensate for the movement of one or more charged particle beams on the sample or on the luminescent material layer caused by the scanning unit scanning one or more charged particle beam spots.

[0017] The device of the present invention is provided with a shifting unit configured to move the beam path relative to the photon detector and / or to shift the photon detector relative to the beam path. The shifting unit is configured to at least partially compensate for the displacement of photon positions on the sample or on the luminescent or scintillating material layer caused by scanning one or more charged particle beams. Therefore, the shifting unit is configured to shift the optical path suitable for the photons and / or the position of the detector relative to each other, particularly such that, during scanning of one or more charged particle beam points by the scanning deflector, the degree of displacement of one or more positions on the detector by which photons are projected or imaged is minimal or even nonexistent.

[0018] Therefore, a detector with a relatively small detector area can be used, which can have a grating response time compared to a detector with a relatively large detector area. Furthermore, overlap of the scan paths of two adjacent beams at the detector can be largely prevented, even if the scan paths of the charged particle beams on the sample partially overlap.

[0019] Furthermore, when a multi-pixel detector is used to measure a light spot, the shifting unit can at least partially compensate for or even invalidate the movement of the light spot on the detector, even when scanning a charged particle beam on the sample. Therefore, due to the shifting unit, light spot tracking can be avoided at least to a large extent.

[0020] Therefore, compared with existing devices, the device of the present invention allows for faster image acquisition.

[0021] Furthermore, due to compensation from the shifting unit, one or more charged particle beams can be moved a greater distance over the sample. This allows for the recording of a larger scan field or several adjacent scan fields before the sample holder must be moved to bring another portion of the sample into the scan field. Therefore, less sample movement is required and / or the stage stabilization time after moving the sample holder is reduced.

[0022] However, in one embodiment, the detector can be physically moved as the light spot moves.

[0023] Preferably, in one embodiment, the shifting unit is configured to provide a component of the optical assembly with the ability to shift the trajectory of the light beam between the sample and the detector. By configuring the optical assembly to include the shifting unit, which is configured to move the one or more photon beam points on the photon detector, the movement of one or more charged particle beam points on the sample can be at least partially compensated, and the movement of one or more photon beam points on the photon detector can be at least reduced and preferably eliminated.

[0024] In one embodiment, the optical assembly includes an objective lens for collecting at least a portion of the photons from the one or more charged particle beam points, wherein the shifting unit includes an objective lens actuator for moving the objective lens relative to the sample holder, and the objective lens actuator is configured to move the objective lens in a direction substantially parallel to the scanning direction. In one embodiment, the objective lens includes an optical axis, wherein the objective lens actuator is configured to move the objective lens in a direction substantially perpendicular to the optical axis of the objective lens. When the objective lens is moved relative to the sample holder, the image projected by the objective lens and other parts of the optical assembly will shift on the detector. In this embodiment, the image shift caused by the movement of the objective lens is used to at least partially compensate for the scanning of the charged particle beam on the sample.

[0025] In one embodiment, the optical assembly includes a projection lens for projecting at least a portion of the photons onto a photon detector, wherein the shifting unit includes a projection lens actuator for moving the projection lens relative to the photon detector. In one embodiment, the projection lens includes an optical axis, wherein the projection lens actuator is configured to move the projection lens in a direction substantially perpendicular to the optical axis of the projection lens. Just as with an objective lens, when the optical assembly includes a projection lens, the image projected by the optical assembly will move on the detector as the projection lens moves. In this embodiment, the image movement caused by the movement of the projection lens is used to at least partially compensate for the scanning of the charged particle beam on the sample.

[0026] In one embodiment, the optical assembly includes a mirror disposed in the beam path between the sample holder and the photon detector, wherein the mirror is configured to reflect the beam path at a deflection angle between 0 degrees and 180 degrees, and wherein the shifting unit includes a mirror actuator configured to tilt the mirror. In one embodiment, the mirror actuator is configured to tilt the mirror about a rotation axis, wherein the rotation axis is arranged substantially perpendicular to the scanning direction. The mirror is disposed in the beam path of the optical assembly to deflect the beam path at the deflection angle. Therefore, the beam path bends at the deflection angle along its path from the sample holder to the photon detector. By tilting the mirror at a tilt angle about the deflection angle, the beam path is scanned on the detector. In this embodiment, the tilting of the mirror is used to at least partially compensate for the scanning of the charged particle beam on the sample.

[0027] The tilt of the mirror can be a small tilt angle about a deflection angle, which only needs to be large enough to compensate for the scanning of the charged particle beam. In one embodiment, the tilted mirror is arranged to tilt at the tilt angle in both clockwise and counterclockwise directions about its axis of rotation, preferably reciprocating about the deflection angle. Alternatively, a rotating mirror can be used, which rotates in the same direction, either clockwise or counterclockwise, about its axis of rotation.

[0028] In one embodiment, the optical assembly includes a polyhedral mirror disposed in a beam path between a sample holder and a photon detector, wherein the mirror is configured to reflect the beam path at a deflection angle between 0 degrees and 180 degrees, and wherein the shifting unit includes a rotary actuator configured to rotate the polyhedral mirror. In one embodiment, the polyhedral mirror is configured to rotate about a rotation axis, wherein the rotation axis is arranged substantially perpendicular to the scanning direction. The polyhedral mirror includes a prism with a cross-section of a regular polygonal shape. Each side region of the prism with the polygonal cross-section includes a substantially flat mirror surface. In one embodiment, the cross-section is a square, pentagonal, hexagonal, octagonal, or similar shape. By rotating the polyhedral mirror about its central axis, adjacent flat mirror surfaces subsequently move into the beam path, and rotating the flat mirror surfaces provides a shift in the beam path and scans the beam path on the detector. In this embodiment, the rotation of the polyhedral mirror is used to at least partially compensate for the scanning of the charged particle beam on the sample.

[0029] In one embodiment, the optical component includes an optical window disposed in a beam path between a sample holder and a photon detector, wherein the optical window is arranged such that the beam path traverses the optical window, and the shifting unit includes a tilt actuator configured to tilt the optical window. In one embodiment, the tilt actuator is configured to tilt the optical window about a rotation axis, wherein the rotation axis is arranged substantially perpendicular to the scanning direction. Preferably, the optical window includes a transparent front surface and a rear surface, wherein the rear surface is parallel to the front surface. When the optical window is disposed in the beam path such that the optical axis of the beam path is arranged perpendicular to the front and rear surfaces, the beam path traverses the optical window in a straight line. However, when the optical window is tilted such that the front or rear surface and the optical axis of the beam path comprise an angle between 0 degrees and 90 degrees, the beam path is shifted parallel to the original beam path, wherein the distance between the shifted beam path and the original beam path depends on the angle between the front surface and the optical axis of the beam path, and depends on the thickness of the optical window. By tilting the optical window about the rotation axis at a tilt angle, the beam path is shifted a distance in a direction perpendicular to the rotation axis, and the beam path is scanned on the detector. In this embodiment, the tilt of the optical window is used to at least partially compensate for the scanning of the charged particle beam on the sample.

[0030] The tilt of the optical window can be a small tilt angle around a predetermined angle between the front surface of the optical window and the optical axis of the beam path, which only needs to be large enough to compensate for the scanning of the charged particle beam. In one embodiment, the optical window is arranged to tilt at tilt angles in both clockwise and counterclockwise directions about its axis of rotation, preferably reciprocating around a predetermined angle. Alternatively, an optical window that rotates in the same direction (clockwise or counterclockwise) about its axis of rotation can be used.

[0031] In one embodiment, the optical assembly includes an optically transparent polyhedron disposed in a beam path between a sample holder and a photon detector, wherein the optically transparent polyhedron is arranged such that the beam path traverses the optically transparent polyhedron, and a shifting unit includes a rotary actuator configured to rotate the optically transparent polyhedron. In one embodiment, the rotary actuator is configured to rotate the optically transparent polyhedron about a rotation axis, wherein the rotation axis is arranged substantially perpendicular to the scanning direction. The optically transparent polyhedron comprises a prism having a cross-section of a regular polygon with an even number of sides. Each side of the prism with the polygonal cross-section provides an optically transparent surface. In one embodiment, the cross-section is a square, hexagonal, octagonal, or similar shape. Two optically transparent surfaces located on opposite sides relative to the optical axis serve as optical windows as described above. The beam traverses the optically transparent polyhedron, just as with the optical windows. By rotating the optically transparent polyhedron about its central axis, adjacent transparent surfaces are subsequently moved into the beam path, and the angle between the transparent surfaces and the optical axis of the beam path is changed, which provides a shift of the beam path and scans the beam path on the detector. In this embodiment, the rotation of the optically transparent polyhedron is used to at least partially compensate for the scanning of the charged particle beam on the sample.

[0032] In one embodiment, the device further includes a first control unit for controlling a scanning unit and a second control unit for controlling a shifting unit, wherein the first control unit is configured to send a scanning information signal to the second control unit, and wherein the second control unit is configured to control the shifting unit based on the scanning information signal. By providing the scanning information signal from the first control unit to the second control unit, the shifting unit can be controlled to accurately compensate for the scanning of the charged particle beam. In one embodiment, the first control unit and the second control unit are combined in a single control unit.

[0033] In one embodiment, the shifting unit is a first shifting unit, and the device further includes a second shifting unit configured to shift one or more light spots and / or photon detectors relative to each other along a shifting direction substantially perpendicular to the shifting direction of the first shifting unit. The combined first and second shifting units allow for compensation of scanning of one or more charged particle beams in orthogonal directions, which is typically used to scan regions on a sample.

[0034] In one embodiment, the charged particle array is configured to generate a plurality of charged particle beams and to guide and focus the plurality of charged particle beams onto an array of spaced-apart spots at a sample holder. In one embodiment, the detector includes a multi-pixel photon detector, preferably wherein the multi-pixel photon detector is configured to have one or more distinct pixels for detecting photons from each of the spaced-apart spots at the sample. In one embodiment, the device is configured to project photons originating from each of the plurality of charged particle beams onto a corresponding pixel of the multi-pixel photon detector. In one embodiment, the multi-pixel photon detector includes one pixel for each of the plurality of charged particle beams. In one embodiment, the detector includes a multi-pixel photon counting detector.

[0035] According to a second aspect, the present invention provides a method for examining a sample, wherein the method includes the following steps:

[0036] Arrange the samples in the sample holder;

[0037] One or more charged particle beams are generated using a charged particle array and directed toward a sample, wherein the charged particle array focuses the one or more charged particle beams onto one or more charged particle beam points on the sample.

[0038] Photons are generated by the one or more focused charged particle beams when they strike the sample or when they strike the luminescent material layer after passing through the sample.

[0039] At least a portion of the photons are projected or imaged from the one or more charged particle beams along the beam path onto one or more light spots on a photon detector using optical components;

[0040] Detecting photons using a photon detector; and

[0041] A scanning unit is used to scan one or more charged particle beams on the sample along the scanning direction, and a shifting unit is used to shift the one or more light spots and / or the photon detector relative to each other, wherein the shifting unit at least partially compensates for the movement of one or more charged particle beams on the sample or the luminescent material layer caused by the scanning of one or more charged particle beams by the scanning unit.

[0042] Therefore, this method of operating the inspection device (preferably the inspection device described in one or more of the above embodiments) causes the displacement of the position of the photon generated by the charged particle beam in the luminescent material to result only in a limited displacement of the photon on the detector, thereby limiting crosstalk to a defined limit.

[0043] In one embodiment, the shifting unit compensates for the movement of one or more charged particle beams such that during scanning of the one or more charged particle beams by the scanning unit, the one or more light spots remain substantially in the same position on the photon detector. Therefore, displacement of the position of photons generated by scanning the one or more charged particle beams does not cause displacement of the photons projected onto the photon detector.

[0044] In one embodiment, one or more charged particle beams are scanned over a first basic rectangular region on the sample, then the one or more charged particle beams and the sample are moved relative to each other at a distance substantially equal to the width of the basic rectangular region, and then the one or more charged particle beams are scanned over a second basic rectangular region on the sample.

[0045] According to a third aspect, the present invention provides a computer-readable medium having computer-executable instructions adapted to cause a device according to the first aspect of the present invention, as described above, to perform a method according to the second aspect of the present invention, as described above.

[0046] The aspects and features described and illustrated in the specification may be applied individually in any possible circumstances. These individual aspects, in particular the aspects and features described in the appended dependent claims, may become the subject of a divisional patent application. Attached Figure Description

[0047] The invention will be illustrated based on exemplary embodiments shown in the accompanying drawings, wherein:

[0048] Figure 1 A first exemplary embodiment of the device with typical improvements according to the present invention is shown schematically;

[0049] Figure 2 A second exemplary embodiment of the device with typical improvements according to the present invention is illustrated schematically;

[0050] Figure 3An example of a third embodiment of a portion of the improved optical component of the present invention is shown schematically;

[0051] Figure 4 An example of a fourth embodiment of a portion of the improved optical components of the present invention is shown schematically;

[0052] Figure 5 An example of a fifth embodiment of a portion of the improved optical components of the present invention is shown schematically;

[0053] Figure 6A and Figure 6B An example of a sixth embodiment of a portion of the improved optical component of the present invention is schematically shown; and

[0054] Figure 7 An example of a seventh embodiment of a portion of the improved optical components of the present invention is shown schematically. Detailed Implementation

[0055] Figure 1 A first exemplary embodiment of a device with a typical improvement to the present invention is illustrated schematically. The device includes at least a combination of charged particle microscopes 7 and 8 (such as ion microscopes or electron microscopes), optical components, and detector 3.

[0056] Charged particle microscopes 7 and 8 include a source 7 for emitting one or more primary charged particle beams 9 and guiding said primary charged particle beams to a sample 5 supported by a substrate included in a sample holder 10. The device includes a detector 8 for detecting secondary charged particles 11 that are backscattered from or emitted from the sample 10 and generated by the one or more primary charged particle beams 9. Charged particle microscopes 7 and 8 are substantially arranged within a vacuum chamber 13.

[0057] like Figure 1 As schematically shown, a charged particle microscope is configured to scan one or more primary charged particle beams 9 on sample 5. Electrostatic and / or magnetic deflectors may be used to scan one or more charged particle beams on sample 5. Such electrostatic and magnetic deflectors are known in the prior art and will not be described in detail in this application.

[0058] The optical assembly includes a light-collecting device 2, commonly referred to as an objective lens, for receiving light 12 from the sample or scintillating material sheet 6 during use. This light 12 is generated by one or more primary charged particle beams 9 in the sample, or after one or more primary charged particle beams 9 have transmitted through the sample 5. The optical assembly is configured to focus the light 12 onto a photon detector 4, such as a CCD camera known per se. In this example, the optical assembly and detector are housed within the vacuum chamber 13 of the charged particle microscopes 7 and 8.

[0059] The inspection device 1 includes a sample holder 10 for holding the sample 5. The sample holder 10 includes a stage 16 configured for positioning and moving the sample 5.

[0060] Additionally, the sample holder 10 may include a scintillation material sheet 6, such as yttrium aluminum garnet (YAG, Y3Al5O3). 12 The sample holder 10 is configured to position the sample 5 between the source 7 of the charged particle microscopes 7 and 8 and the scintillation material sheet 6. The optical components microscopes 2, 3, and 4 are arranged on the side of the scintillation material sheet 6 opposite to the sample 5.

[0061] A closed dashed line 14 surrounds a portion of the inspection apparatus 1 of the present invention, all or some of which may be mounted on the (replaceable) door of the vacuum chamber 13. Specifically, the sample holder 10, the light collecting device 2, and the photon detector 4 for the sample are preferably mounted on the door of the vacuum chamber 13. This particular configuration makes it possible to easily retrofit or complete existing charged particle microscopes to convert them into an integrated type of inspection apparatus according to the present invention.

[0062] exist Figure 1 In this embodiment, a processing unit 15 (alternately designated as a controller) is provided and can be used as an automation unit, for example in the form of a computer, which includes a personal computer configured with dedicated software to implement one or more methods using inspection equipment.

[0063] like Figure 1 As schematically shown, the sample holder includes a stage 16 for moving the sample 5 relative to the optical components and / or charged particle microscopes 7, 8. Preferably, the stage is configured to provide six degrees of freedom for moving the sample 5; thus providing translational motion along the X, Y, and Z axes and rotational motion about the X, Y, and Z axes.

[0064] Furthermore, the examination apparatus includes an objective lens actuator 3 for moving the objective lens 2 and / or a detector actuator 3' for moving the detector. The objective lens actuator 3 and / or the detector actuator provide shifting units for shifting the optical path of the light 12 and / or the photon detector 4 relative to each other. Specifically, the first shifting unit 3 and / or the second shifting unit 3' are configured to at least partially compensate for the movement of one or more charged particle beams 9 on the sample 5 or on the luminescent material layer 6 caused by the scanning unit of the charged particle microscope scanning one or more charged particle beam points. Figure 1As schematically shown, objective lens 2 includes an optical axis OA, wherein objective lens actuator 3 is configured to move objective lens 2 in a direction substantially perpendicular to the optical axis OA, and particularly substantially parallel to the scanning direction of one or more charged particle beams 9. Objective lens actuator 3 preferably includes a voice coil.

[0065] Figure 2 A second exemplary embodiment of the device, which is a typical improvement of the present invention, is illustrated schematically. Figure 2 The apparatus 20 includes a scanning electron microscope (SEM) 27, which includes a vacuum chamber 23 connected to a vacuum pump via a connector 35. Inside the vacuum chamber 23, a sample 40 is arranged, which can be irradiated with one or more primary electron beams 29. The apparatus 20 includes a detector 28 for detecting secondary charged particles 31 that are backscattered from or emitted from the sample 40 due to impacts of one or more primary electron beams 29 onto the sample 40.

[0066] As schematically shown, sample 40 is arranged on top of sheet of scintillating material 30, which serves as a holder for sample 40. Sheet of scintillating material 30 may include, for example, yttrium aluminum garnet (YAG, Y3Al5O4). 12 ) thin slices.

[0067] The sample holder includes a stage 41 configured for positioning and moving a sheet of sample 40 and scintillating material 30. The sample holder includes a stage for moving sample 40 to provide six degrees of freedom for the sample 40; thus, translational motion along the X, Y, and Z axes and rotational motion about the X, Y, and Z axes are provided. The sample holder is configured to position sample 40 between SEM 27 and the sheet of scintillating material 30.

[0068] Beneath the sheet of scintillating material 30, a microscope objective 22 is arranged inside the vacuum chamber 23, and is part of an optical assembly for detecting the emission from the scintillating material 30. In this particular example, the other main parts of the optical assembly are arranged outside the vacuum chamber 23 in an illumination and detection chamber 24.

[0069] The illumination and detection chamber 24 may include a light source 21, such as an LED of a laser. Emitted light 36 from the light source 21 is guided out of the illumination and detection chamber 24 via a semi-transparent mirror or dichroic mirror 25 and into the vacuum chamber 23 via a window 32. This light 37, 38 is coupled to the microscope objective lens 22 via a mirror 26 to illuminate the sample 40. Although the illumination arrangement can be used to illuminate and study a sample under light, it is not necessary to obtain an image using electrons transmitted through the sample 40 (which are converted into light by the sheet of scintillating material 30).

[0070] Light 37, 38 from the sheet of sample 40 and / or scintillation material 30 is collected by microscope objective 22 and guided to illumination and detection chamber 24 via mirror 26 and window 32, and imaged 39 onto camera 33 (e.g., CCD detector).

[0071] like Figure 2 As shown, the light beam used to irradiate and / or image the sample 40 enters and passes through the vacuum chamber 23 via window 32, which in this example is arranged within the door 34 of the vacuum chamber 23. The irradiation and detection chamber 24 of the optical microscope system is arranged outside the vacuum chamber 23 and may be attached to the outside of the door 34. However, the irradiation and detection portion of the optical components may also be entirely contained within the vacuum chamber 23, for example, attached to the bottom portion of the vacuum chamber 23.

[0072] In this exemplary embodiment, it is advantageous to select a sheet of scintillating material 30 that is at least substantially transparent, preferably wherein the sheet of scintillating material is substantially transparent to light in the wavelength range of the visible spectrum. Therefore, the sample 40 can be observed through the sheet of scintillating material 30 using an optical microscope.

[0073] like Figure 2 As schematically shown, the mirror 26 is provided with an actuator 42 for moving the mirror 26 by reciprocating linear movement in directions toward and away from the microscope objective 22. Thus, the mirror 26 and the microscope objective 22 provide a shifting unit for displacing the beam path relative to the camera 33. Furthermore, the inspection apparatus includes a first control unit 44 for controlling the SEM, particularly the scanning unit within the SEM, and a second control unit 43 for controlling the actuator 42 of the shifting unit. The first control unit 44 is configured to send a scanning information signal to the second control unit 43, and the second control unit 43 is configured to control the actuator based on the scanning information signal so as to synchronize the shifting of the beam path by the shifting unit using the scanning of one or more electron beams by the SEM 27, particularly for at least partially compensating for the movement of one or more electron beams 29 on the sample 40 or the luminescent material layer 30 caused by the scanning of one or more electron beam points by the scanning unit within the SEM 27. Preferably, the actuator 42 includes a voice coil.

[0074] Figure 3A third exemplary embodiment of an optical component 50 for use in an inspection apparatus, a typical improvement of the present invention, is illustrated schematically. The optical component 50 includes an objective lens 51, a folding mirror 52, and a projection lens 53 for projecting at least a portion of the photons onto a photon detector 54. The projection lens 53 is connected to a projection lens actuator 55 for moving the projection lens 53 relative to the photon detector 54. The projection lens 53 having the projection lens actuator 55 provides a shifting unit. The projection lens 53 includes an optical axis OA, and the projection lens actuator 55 is configured to move the projection lens 53 in a direction 56 substantially perpendicular to the optical axis OA of the projection lens 53. When the projection lens actuator 55 moves the projection lens 53 in direction 56, the light projected by the projection lens 53 is moved on the detector 54 in direction 57. When applied in the inspection apparatus of the present invention, this movement serves to at least partially compensate for scanning movement of one or more charged particle beams. Preferably, the projection lens actuator 55 includes a voice coil.

[0075] Figure 4 A fourth exemplary embodiment of an optical assembly 60 for use in an inspection apparatus, a typical improvement of the present invention, is illustrated schematically. The optical assembly 60 includes an objective lens 61, a folding mirror 62, and a projection lens 63 for projecting at least a portion of the photons onto a photon detector 64. The mirror 62 is configured to reflect the beam path at a deflection angle between 0 and 180 degrees (in this example, a substantially 90-degree deflection angle). The mirror 62 is connected to a mirror actuator 65 for tilting the mirror 62 relative to the photon detector 64. The mirror 62 with the mirror actuator 65 provides a shifting unit. The mirror actuator 65 is configured to tilt the mirror 62 about a rotation axis 68, wherein the rotation axis 68 is substantially perpendicular to the planar arrangement of the figures. When the mirror actuator 65 moves the mirror 62 in direction 66, the light projected onto the detector moves along direction 67 on the detector 64. When applied in the inspection apparatus of the present invention, this movement is used to at least partially compensate for scanning movement of one or more charged particle beams. Preferably, the mirror actuator 65 includes a galvanometer or a piezoelectric motor.

[0076] Figure 5A fifth exemplary embodiment of an optical assembly 70 for use in an inspection apparatus, a typical improvement of the present invention, is schematically illustrated. The optical assembly 70 includes an objective lens 71, a polyhedral mirror 72, and a projection lens 73 for projecting at least a portion of the photons onto a photon detector 74. The polyhedral mirror 72 is configured to reflect the beam path toward the detector 74 by a deflection angle. The polyhedral mirror 72 is connected to a rotation actuator (not shown) for rotating the polyhedral mirror 72 about a rotation axis 78, wherein the rotation axis 78 is substantially perpendicular to the planar arrangement of the figures. The outwardly facing mirror surfaces 75, 75', 75”… of the polyhedral mirror each include a mirror surface for reflecting light from the objective lens 71. As the rotation actuator rotates the polyhedral mirror 72, the mirror surfaces 75, 75', 75”… are sequentially arranged in the beam and continuously reflect light from the objective lens 71 toward the detector 74. The polyhedral mirror 72 with the rotation actuator provides a shifting unit. Due to the rotation, the angle of the mirror surface 75 relative to the optical axis OA changes continuously. When the rotary actuator rotates the polyhedral mirror 72 along direction 76, the light projected onto the detector moves along direction 77 on the detector 74. When applied in the inspection apparatus of the present invention, this movement is used to at least partially compensate for the scanning movement of one or more charged particle beams.

[0077] Figure 6A A sixth exemplary embodiment of an optical assembly 80 for use in an inspection apparatus, a typical improvement of the present invention, is schematically illustrated. The optical assembly 80 includes an objective lens 81, a folding mirror 82, and a projection lens 83 for projecting at least a portion of the photons onto a photon detector 84. The optical assembly 80 also includes an optical window 85 disposed in a beam path between a sample holder and the photon detector 84. In this particular example, the optical window 85 is disposed between the projection lens 83 and the detector 84. The optical assembly also includes a tilt actuator 86 configured to tilt the optical window 85 in a tilt direction 87, such as... Figure 6A and Figure 6B As illustrated schematically, the optical window 85, with its tilt actuator 86, provides a shifting unit. When the optical window 85 is arranged as shown... Figure 6B In the tilted position shown, the beam path between the optical window 85 and the detector 84 is shifted along direction 87' in the plane of the drawing. Figure 6B In the specific position shown, the focal point of the light shifts from a first position 88 when the optical window is not tilted to a second position 89 when the optical window is tilted, as illustrated. When applied to the inspection device of the present invention, this shift serves to at least partially compensate for the scanning movement of one or more charged particle beams.

[0078] Figure 7A seventh exemplary embodiment of an optical assembly 90 for use in an inspection apparatus, a typical improvement of the present invention, is illustrated schematically. The optical assembly 90 includes an objective lens 91, a folding mirror 92, and a projection lens 93 for projecting at least a portion of the photons onto a photon detector 94. The optical assembly 90 also includes an optically transparent polyhedron 95 arranged in the beam path toward the photon detector. In this example, the optically transparent polyhedron 95 is arranged between the projection lens 93 and the detector 94. The optically transparent polyhedron 95 is arranged such that the beam path passes through the optically transparent polyhedron 95 via two opposing side mirrors 96, 96'. The optically transparent polyhedron 95 preferably includes an even number of sides 96, 96', preferably 4, 6, or 8 side mirrors. The optically transparent polyhedron 95 is coupled to a rotary actuator (not shown) configured to rotate the optically transparent polyhedron 95 about a rotation axis 97. The optically transparent polyhedron 95 and the rotary actuator provide a displacement unit. When the optically transparent polyhedron 95 rotates in direction 98, the two opposing side mirrors 96 and 96' interact with... Figure 6B The optical window shown is moved to the tilted position in the same manner. Therefore, the beam path between the optically transparent polyhedron 95 and the detector 94 is shifted along direction 98' in the plane of the drawing. As rotation continues, the two opposing side mirrors 96, 96' tilt further and further, and the beam path shifts further and further until the next adjacent opposing side mirrors 99, 99' are arranged in the beam path and a new shift of the beam path begins. When applied to the inspection apparatus of the present invention, this movement serves to at least partially compensate for scanning movement of one or more charged particle beams.

[0079] It should be noted that, in the above exemplary embodiments, the movement of the described shifting unit is a translation or rotation in the plane of the drawing. However, the movement of the shifting unit in various examples may also be a translation or rotation in another direction (particularly in a direction perpendicular to the plane of the drawing) to compensate for the scanning direction of one or more charged particle beams in a direction perpendicular to the plane of the drawing.

[0080] Additionally, when the scanning deflector is arranged to move one or more charged particle beams in more than one direction (particularly two orthogonal directions), the inspection device may include a first shifting unit and a second shifting unit. The second shifting unit is preferably configured to shift one or more spot detectors and / or photon detectors relative to each other in a shifting direction substantially perpendicular to the shifting direction of the first shifting unit. Each of the above embodiments may be used in one or both of the first and second shifting units.

[0081] In summary, the present invention relates to an apparatus for examining samples. The apparatus includes:

[0082] Sample holder for holding samples

[0083] A charged particle array, used to generate one or more beams of charged particles and focus the one or more beams of charged particles onto one or more charged particle beam points on a sample.

[0084] A scanning deflector, used to move the charged particle beam point over the sample;

[0085] A photon detector configured to detect photons generated when the one or more beams of charged particles strike a sample or when the one or more beams of charged particles strike a layer of luminescent material after being transmitted through the sample.

[0086] Optical components for projecting or imaging at least a portion of the photons from the charged particle beam point along the beam path onto the photon detector; and

[0087] A shifting unit is used to shift the beam path relative to the photon detector, or vice versa.

[0088] In a particular embodiment, a transmission detector for multi-beam SEM is provided, wherein an electron beam array strikes a light-emitting plate after passing through a thin sample. An optical microscope images the bottom of the light-emitting plate onto a photodetector. Furthermore, a unit is arranged in the optical path between the light-emitting plate and the photodetector, which can independently move the light spot on the photodetector. Without this unit, the light spot generated in the light-emitting plate moves as the electron beam scans the sample. Therefore, the light spot imaged on the photodetector also moves on the surface of the photodetector. However, it is preferable to keep the signal from a particular electron beam substantially at the same point on the photodetector. Thus, the unit arranged in the optical path can compensate for the movement of the light spot on the light-emitting plate, so that the light spot on the photodetector does not move. Furthermore, the detector of the present invention also allows the electron beam array to be moved over a greater distance, which allows several (e.g., 3×3) scan fields to be recorded before moving the sample stage. This saves time associated with stage stabilization.

[0089] It should be understood that the above description is intended to illustrate the operation of preferred embodiments and is not intended to limit the scope of the invention. Many variations will be apparent to those skilled in the art from the above discussion, and these variations will also be covered by the scope of the invention.

Claims

1. A device for examining samples, characterized in that, The device includes: Sample holders used to hold samples; A charged particle array for generating one or more charged particle beams and guiding one or more charged particle beams toward a sample holder, wherein the charged particle array is configured to focus the one or more charged particle beams onto one or more charged particle beam points on the sample. A scanning unit, used to scan one or more charged particle beams on a sample along the scanning direction; A photon detector for detecting photons generated by the one or more focused charged particle beams when the one or more charged particle beams strike a sample or when the one or more charged particle beams strike a luminescent material layer after the one or more charged particle beams have passed through the sample. An optical assembly for projecting or imaging at least a portion of photons from the one or more charged particle beam points onto one or more light spots on the photon detector along a beam path, wherein the optical assembly includes a folded mirror or a polyhedral mirror disposed in the beam path between a sample holder and the photon detector, wherein the folded mirror or the polyhedral mirror is configured to reflect the beam path at a deflection angle between 0 degrees and 180 degrees; and A shifting unit for shifting one or more light spots and / or photon detectors relative to each other, wherein the shifting unit includes a mirror actuator or a first rotation actuator, the mirror actuator being configured to adjust the tilt angle of a folding mirror, the first rotation actuator being configured to rotate a polyhedral mirror, wherein the shifting unit is configured to at least partially compensate for the movement of one or more charged particle beams on the sample or on the luminescent material layer caused by the scanning unit scanning one or more charged particle beam points.

2. The device according to claim 1, characterized in that, The optical assembly includes an objective lens for collecting at least a portion of the photons from the one or more charged particle beams, wherein the shifting unit includes an objective lens actuator for moving the objective lens relative to the sample holder, and wherein the objective lens actuator is configured to move the objective lens in a direction substantially parallel to the scanning direction.

3. The device according to claim 2, characterized in that, The objective lens includes an optical axis, wherein an objective lens actuator is configured to move the objective lens in a direction substantially perpendicular to the optical axis of the objective lens.

4. The device according to claim 1, characterized in that, The optical assembly includes a projection lens for projecting at least a portion of the photons onto a photon detector, wherein the shifting unit includes a projection lens actuator for moving the projection lens relative to the photon detector.

5. The device according to claim 4, characterized in that, The projection lens includes an optical axis, wherein the projection lens actuator is configured to move the projection lens in a direction substantially perpendicular to the optical axis of the projection lens.

6. The device according to claim 1, characterized in that, The mirror actuator is configured to tilt the folding mirror about a rotation axis, which is arranged substantially perpendicular to the scanning direction.

7. The device according to claim 1, characterized in that, The first rotary actuator is configured to cause the polyhedral mirror to rotate about a rotation axis, wherein the rotation axis is arranged substantially perpendicular to the scanning direction.

8. The device according to claim 1, characterized in that, The optical assembly includes an optical window arranged in a beam path between a sample holder and a photon detector, wherein the optical window is arranged such that the beam path traverses the optical window, and wherein the shifting unit includes a tilt actuator configured to tilt the optical window.

9. The device according to claim 8, characterized in that, The tilt actuator is configured to tilt the optical window about a rotation axis, which is arranged substantially perpendicular to the scanning direction.

10. The device according to claim 1, characterized in that, The optical assembly includes an optically transparent polyhedron disposed in a beam path between a sample holder and a photon detector, wherein the optically transparent polyhedron is arranged such that the beam path traverses the optically transparent polyhedron, and wherein the shifting unit includes a second rotation actuator configured to rotate the optically transparent polyhedron.

11. The device according to claim 10, characterized in that, The second rotary actuator is configured to rotate the optically transparent polyhedron about a rotation axis, wherein the rotation axis is arranged substantially perpendicular to the scanning direction.

12. The device according to any one of claims 1-11, characterized in that, The device further includes a first control unit for controlling the scanning unit and a second control unit for controlling the shifting unit, wherein the first control unit is configured to send a scanning information signal to the second control unit, and wherein the second control unit is configured to control the shifting unit based on the scanning information signal.

13. The device according to any one of claims 1-11, characterized in that, The shifting unit is a first shifting unit, wherein the device further includes a second shifting unit, wherein the second shifting unit is configured to shift one or more light spots and / or photon detectors relative to each other in a shifting direction substantially perpendicular to the shifting direction of the first shifting unit.

14. The device according to claim 12, characterized in that, The shifting unit is a first shifting unit, and the device further includes a second shifting unit, wherein the second shifting unit is configured to shift one or more light spots and / or photon detectors relative to each other in a shifting direction substantially perpendicular to the shifting direction of the first shifting unit.

15. A method for examining a sample, characterized in that, The method includes the following steps: Arrange the samples in the sample holder; One or more charged particle beams are generated using a charged particle array and directed toward a sample, wherein the charged particle array focuses the one or more charged particle beams onto one or more charged particle beam points on the sample. Photons are generated by the one or more focused charged particle beams when they strike the sample, or when they strike the luminescent material layer after the one or more charged particle beams have passed through the sample. At least a portion of the photons from the one or more charged particle beams are projected or imaged along a beam path onto one or more light spots on a photon detector using an optical assembly, wherein the optical assembly includes a folded mirror or a polyhedral mirror arranged in the beam path between the sample holder and the photon detector, wherein the folded mirror or the polyhedral mirror is configured to reflect the beam path with a deflection angle between 0 degrees and 180 degrees. Detecting photons using a photon detector; and A scanning unit scans one or more charged particle beams on the sample along a scanning direction, and a shifting unit shifts one or more light spots and / or photon detectors relative to each other, wherein the shifting unit includes a mirror actuator or a first rotation actuator, the mirror actuator being configured to adjust the tilt angle of a folding mirror, and the first rotation actuator being configured to rotate a polyhedral mirror, wherein the shifting unit at least partially compensates for the movement of one or more charged particle beams on the sample or on the luminescent material layer caused by the scanning unit scanning one or more charged particle beams.

16. The method according to claim 15, characterized in that, The shifting unit compensates for the movement of one or more charged particle beams, such that during the scanning of one or more charged particle beams by the scanning unit, one or more light spots remain substantially in the same position on the photon detector.

17. The method according to claim 15 or 16, characterized in that, One or more charged particle beams are scanned over a first basic rectangular region on the sample, and then the one or more charged particle beams and the sample are moved relative to each other over a distance substantially equal to the width of the basic rectangular region, and then one or more charged particle beams are scanned over a second basic rectangular region on the sample.

18. A computer-readable medium having computer-executable instructions, characterized in that, The computer-executable instructions are adapted to cause the device according to claim 1 to perform the method according to claim 15.

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