Secondary Charged Particle Imaging System

Abstract

A secondary charged particle imaging system comprises: a backscattered electron detector module, wherein the backscattered electron detector module can rotate around an axis between a first angular position (5452) and a second angular position (5454).

Description

[0001] Various aspects of the present disclosure relate to scanning charged particle beam apparatus, in particular for producing images on a sample. Various aspects relate in particular to secondary charged particle imaging systems. Another aspect relates to a scanning electron microscope including a backscattered electron detector module. Another aspect relates to a method of operating a secondary charged particle imaging system. Technical Background

[0002] Charged particle beam equipment has many functions in many industrial fields, including but not limited to, inspection of semiconductor devices during manufacturing, exposure systems for lithography, inspection devices and test systems. Therefore, there is a great demand for structuring and inspection of samples in micrometer and nanometer scales.

[0003] Process control, inspection or structuring at the micron and nanometer scale is usually performed using a charged particle beam (e.g., an electron beam) that is generated and focused in a charged particle beam device such as an electron microscope or an electron beam pattern generator. Compared to, for example, a photon beam, a charged particle beam provides superior spatial resolution due to the short wavelength of the photon beam.

[0004] Charged particle beam devices typically utilize charged particle imaging systems. Charged particle imaging systems can be configured for single beam or multi-beam imaging. A charged particle imaging system with improved performance is described below. Summary of the invention

[0005] As described above, a secondary charged particle imaging system, a charged particle beam apparatus, and a method of operating a secondary charged particle imaging system are provided.

[0006] According to one aspect, a secondary charged particle imaging system includes a backscattered electron detector module and wherein the backscattered electron detector module is rotatable about an axis between a first angular position and a second angular position.

[0007] According to one aspect, a charged particle beam apparatus includes a secondary charged particle imaging system.

[0008] According to one aspect, a method of operating a secondary charged particle imaging system includes rotating a backscattered electron detector about an axis between a first angular position and a second angular position.

[0009] Further advantages, features, aspects and details, which can be combined with the embodiments described herein, are apparent from the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The details will be described below with reference to the accompanying drawings, in which:

[0011] Figure 1is a simplified side view schematic diagram of a secondary charged particle imaging system according to an embodiment described herein,

[0012] Figure 2 is a simplified top view schematic diagram of a secondary charged particle imaging system according to an embodiment described herein,

[0013] Figure 3 is a simplified side view schematic diagram of a backscattered electron detector module and a backscattered electron detector actuator module according to an embodiment described herein,

[0014] Figure 4A and Figure 4B is a simplified pseudo 3D representation of an arm with a mechanical hinge joint as a backscattered electron detector module according to an embodiment described herein,

[0015] Figure 5A and Figure 5B is a simplified schematic side view of a backscattered electron detector module in a first angular position and a second angular position according to an embodiment described herein,

[0016] Fig. 6A and Figure 6B is a simplified schematic side view of a close-up of an aperture and a backscattered electron detector element of a backscattered electron detector module at a first angular position and a second angular position according to embodiments described herein,

[0017] Figure 7 is a simplified side view schematic diagram of a charged particle beam apparatus according to embodiments described herein, and

[0018] Figure 8 is a diagram of a method for operating a secondary charged particle imaging system according to an embodiment described herein. DETAILED DESCRIPTION

[0019] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in each of the accompanying drawings. Each example is provided by way of explanation and is not meant to be limiting. For example, features illustrated or described as part of one embodiment may be used in any other embodiment or combined with any other embodiment to produce further embodiments. The present disclosure is intended to include such modifications and variations.

[0020] In the following description of the accompanying drawings, the same reference numerals refer to the same or similar components. Generally speaking, only the differences with respect to the various embodiments are described. Unless otherwise specified, the description of a part or aspect in one embodiment also applies to the corresponding part or aspect in another embodiment.

[0021] The reference numerals used in the drawings are for illustration only. The aspects described herein are not limited to any particular embodiment. Conversely, unless otherwise stated, any aspect described herein may be combined with any other aspect or embodiment described herein.

[0022] Figure 1 A simplified side view schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, a secondary charged particle imaging system includes a backscattered electron detector module.

[0023] The backscattered electron detector module 1400 may be configured to collect and / or detect backscattered electrons (e.g., axial backscattered electrons) in the electron beam column. For example, the backscattered electrons may be backscattered electrons of the signal charged particle beam 1102. The backscattered electron detector module 1400 may be configured to allow the signal charged particle beam 1102 to pass through. According to an embodiment, the backscattered electron detector module 1400 may be configured to be movable and / or rotatable (such as between the first position 5452 and the second position 5454). The first position 5452 and the second position 5454 may be angular positions. In an example, the backscattered electron module 1400 may be configured to allow the signal charged particle beam 1102 to pass through the backscattered electron module in the first position 5452. The backscattered electron module 1400 may be configured to collect and / or detect backscattered electrons and / or signals in the signal charged particle beam 1102 in the second position 5454.

[0024] Thus, the backscattered electron detector module 1400 may include an aperture 1460. The backscattered electron detector module 1400 may include a backscattered electron detector element 1470. The aperture 1460 and the backscattered electron detector element 1470 may be arranged on the backscattered electron detector holder 1450. The aperture 1460 and the backscattered electron detector element 1470 may be arranged in a plane, or in a plurality of planes parallel to each other. For example, the backscattered electron detector element 1470 is supported on the backscattered electron detector holder 1450, and the aperture 1460 is formed in the backscattered electron detector holder 1450. In another example, the aperture 1460 may be fixed in a position on the optical axis 1103, and the backscattered electron detector holder 1450 may be movable between a first position 5452 and a second position 5454. The optical axis 1103 is the optical axis of the signal charged particle beam 1102. In a preferred embodiment, when the backscattered electron detector module 1400 is in the first position 5452, the aperture 1460 is arranged on the optical axis 1103, and the backscattered electron detector element 1470 is arranged offset from the optical axis 1103. In a preferred embodiment, when the backscattered electron detector module 1400 is in the second position 5454, the backscattered electron detector element 1470 is arranged on the optical axis 1103, and the aperture 1460 is arranged offset from the optical axis 1103. The phrase "on the optical axis" may be understood as a position that at least partially, preferably substantially overlaps or coincides with the position of the signal charged particle beam 1102. The phrase "off the optical axis" may be understood as a position that is at least partially, preferably substantially, and even more preferably completely different from or does not overlap with the position of the signal charged particle beam 1102.

[0025] According to one embodiment, the backscattered electron detector module 1400 includes a backscattered electron detector element 1470 and an aperture 1460. Alternatively, the aperture 1460 may be replaced by a recess, or the backscattered electron detector module 1400 may be moved at a sufficiently large angle so that the signal electrons or signal charged particle beam 1102 may pass by the backscattered electron detector module 1400.

[0026] In an embodiment, there may be a secondary charged particle optics module and / or a beam bender. The backscattered electron detector module 1400 may be arranged before the secondary charged particle optics module 1600 and / or after the beam bender 1392. For example, the backscattered electron detector module 1400 may be arranged between the secondary charged particle optics module 1600 and the beam bender 1392. The backscattered electron detector module 1400, the aperture 1460, and / or the backscattered electron detector element 1470 may be arranged after the beam bender 1392 or downstream of the beam bender 1392. The backscattered electron detector module may be arranged immediately or directly after the beam bender or downstream of the beam bender. The backscattered electron detector element 1470 and / or the aperture 1460 may be arranged before the secondary charged particle optics module 1600 or upstream of the secondary charged particle optics module 1600. The backscattered electron detector module may be arranged immediately before or directly before the secondary charged particle optics module 1600 or upstream of the secondary charged particle optics module 1600. "After / before" and / or "downstream / upstream" may be understood relative to the propagation of the signal charged particle beam 1102. For example, "downstream" may be understood to be similar to "after", and vice versa, "upstream" may be similar to "before".

[0027] Thus, in an example, the secondary charged particle optics module 1600 and / or the aperture 1460 are in a functional position in the first position 5452. In another example, the signal charged particle beam 1102 passes through the backscattered electron detector module 1400 in the first position 5452. Similarly, in a further example, the backscattered electron detector module 1400 and / or the backscattered electron detector element 1470 are in a functional position in the second position 5454. In yet another example, the signal charged particle beam 1102 is intercepted and / or detected by the backscattered electron detector module 1400 and / or the backscattered electron detector element 1470 in the second position 5454. Thus, in an example, the secondary charged particle optics module 1600, the aperture 1460, and the beam bender 1392, particularly in this order, are arranged on the optical axis 1102 in the first position 5452. In another example, the secondary charged particle optics module 1600, the backscattered electron detector element 1460 and the beam bender 1392, in particular in this order, are arranged on the optical axis 1102 in the second position 5454. In embodiments that can be combined with other embodiments described herein, the backscattered electron detector module 1400 and / or the backscattered electron detector element 1470 can be arranged at or adjacent to a point of minimum cross-section of the signal charged particle beam 1102. The point of minimum cross-section of the signal charged particle beam 1102 can be located after or downstream of the beam bender 1392, in particular immediately after the beam bender 1392. In embodiments, it is considered beneficial to arrange the backscattered electron detector module 1400 and / or the second lens 1616 as close to the beam bender 1392 as possible.

[0028] As described above, the arrangement of the backscattered electron detector module 1400 (such as the backscattered electron detector element 1470) can provide good performance of backscattered electron efficiency. For example, compared to arranging the backscattered electron detector module 1400 (such as the backscattered electron detector element 1470) after or downstream of the secondary charged particle optical device module 1600, the detection efficiency can be improved by up to 30%.

[0029] Figure 1 A simplified side schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, the secondary charged particle imaging system includes a beam bender.

[0030] The beam bender 1392 can be used to bend the signal charged particle beam 1102. The beam bender 1392 can have a fan-shaped (particularly hemispherical fan-shaped) shape or cross-section. The beam bender 1392 can be configured to change the direction of the signal charged particle beam 1102 so that the direction of travel of the signal charged particle beam 1102 entering the beam bender 1392 is different from the direction of travel of the signal charged particle beam 1102 leaving the beam bender 1392. The beam bender 1392 can be arranged to guide the signal charged particle beam 1102 further away from the primary charged particle beam 7101. For example, the beam bender 1392 can (particularly by electrostatic means) deflect the signal charged particle beam 1102. The beam bender 1392 can be arranged downstream of a beam separation component. Beam separation can be understood as a component that separates the primary charged particle beam from the secondary charged particle beam. The secondary charged particle beam 1102 may be understood as a charged particle beam originating from the sample 7350. The primary charged particle beam 7101 may be understood as a charged particle beam that strikes the sample 7350. The beam bender may be a spherical or fan-shaped beam bender. The beam bender 1392 may deflect and / or stigmatically focus the charged particle beam.

[0031] In an embodiment, the beam bender 1392 acting on the signal charged particle beam 1102 is arranged upstream of the second lens 1616 relative to the signal charged particle beam 1102. Figure 1 In the drawing plane of FIG. 1 , the beam bender 1392 is arranged to the right of the second lens 1616. As shown in the figure, the signal charged particle beam 1102 enters the beam bender 1392 from below and travels through the beam bender 1392. The signal charged particle beam 1102 leaving the beam bender travels in a substantially horizontal direction. The signal charged particle beam 1102 can travel from the beam bender 1392 to the second lens 1616 of the lens system 1610. Figure 1 As shown, the second lens 1616 can be arranged downstream of the beam bender 1392 and / or the backscattered electron detector module 1400 relative to the signal charged particle beam 1102. In a preferred embodiment, the second lens 1616 can be the next element acting on the signal charged particle beam 1102 leaving the backscattered electron detector module. The opening angle of the secondary charged particle beam as described herein can be the opening angle of the signal charged particle beam leaving the beam bender 1392.

[0032] Figure 1 A simplified side view schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, a secondary charged particle imaging system includes a secondary charged particle optics module.

[0033] In an embodiment, the secondary charged particle optics module 1600 includes a lens system 1610. The lens system 1610 may include a first lens 1612 and a second lens 1616. The first lens 1612 may be spaced apart from the second lens 1616. For example, the distance between the first lens 1612 and the second lens 1616 may be in the range of 40 mm to 200 mm.

[0034] At once Figure 1 With respect to the drawing plane of FIG. 16 , the first lens 1612 and / or the second lens 1616 extend in a vertical (“up and down”) direction. The first lens 1612 may be disposed between the aperture plate 1650 and the second lens 1616.

[0035] exist Figure 1 In the drawing plane of FIG. 1 , the signal charged particle beam 1102 travels from the right side to the left side. The signal charged particle beam 1102 enters the second lens 1616 of the lens system 1610 from the right hand side of the second lens 1616. Figure 1 As shown, the signal charged particle beam 1102 travels through the second lens 1616 and then through the first lens 1612 of the lens system 1610. As shown, the signal charged particle beam 1102 traveling through the lens system 1610 travels substantially along the optical axis 1103.

[0036] The first lens 1612 and / or the second lens 1616 can be suitable for shaping, focusing, and / or defocusing the signal charged particle beam 1102. The first lens 1612 and / or the second lens 1616 can be suitable for adjusting the opening angle of the signal charged particle beam 1102. The signal charged particle beam 1102 can be diverged or converged as required. Therefore, the collection efficiency of the signal charged particles by the detector arrangement 1900 can be improved. The opening angle of the signal charged particle beam 1102 can be the opening angle of the signal charged particle beam 1102 leaving the beam bender arranged upstream (relative to the propagation of the signal charged particle beam 1102) of the lens system 1610.

[0037] The lens system 1610 may be adapted to provide one or two intersection points of the signal charged particle beam 1102. Alternatively, the lens system 1610 may be adapted to allow the signal charged particle beam to pass through the lens system 1610 without an intersection point.

[0038] The first lens 1612 may include an electrostatic lens portion and / or a magnetic lens portion. The first lens 1612 may be a composite lens including both an electrostatic lens portion and a magnetic lens portion. Similarly, the second lens 1616 may include an electrostatic lens portion and / or a magnetic lens portion. The electrostatic lens portion of the first lens 1612 and / or the electrostatic lens portion of the second lens 1616 may be suitable for shaping, focusing, and / or defocusing the signal charged particle beam. The magnetic lens portion of the first lens 1612 and / or the second lens 1616 may be suitable for compensating for the Larmor rotation of the objective lens.

[0039] It is considered beneficial to arrange the second lens 1616 as close as possible to the backscattered electron detector module 1400 and / or the beam bender 1392. It is also considered beneficial to arrange the first lens 1612 sufficiently far away from the beam bender 1392. According to an embodiment that can be combined with other embodiments described herein, the distance between the backscattered electron detector module 1400 and the second lens 1616 is 60 mm or less, in particular 45 mm or less, more in particular 35 mm or less. According to an embodiment that can be combined with other embodiments described herein, the distance between the beam bender 1392 and the first lens 1612 is 50 mm or more, more in particular 100 mm or more, for example 115 mm or more.

[0040] The first lens 1612 may include a first magnetic lens portion 1614 adapted to generate a magnetic field. The first magnetic lens portion 1614 may include a coil for generating a magnetic field. The first magnetic lens portion 1614 may have an iron coating. Similarly, the second lens 1616 may include a second magnetic lens portion 1618. The second magnetic lens portion 1618 may include similar components as compared to the first magnetic lens portion 1614. The first magnetic lens portion 1614 and / or the second magnetic lens portion 1618 may be adapted to compensate for the Larmor rotation of the signal charged particle beam 1102. Due to the magnetic field (e.g., magnetic field) generated by the objective lens of the charged particle beam device Figure 11614 and / or the second magnetic lens portion 1618 may be adapted to rotate the signal charged particle beam 1102. The rotation of the signal charged particle beam 1102 may be a rotation around the optical axis 1103 defined by the aperture plate 1650, and may be a clockwise or counterclockwise rotation. The first magnetic lens portion 1614 may be adapted to rotate the signal charged particle beam 1102 by a first angle A1. The first angle A1 may be in the range of -45 degrees to 45 degrees. Therefore, the Larmor rotation of -45 degrees to 45 degrees may be compensated by the first magnetic lens portion. The second magnetic lens portion 1618 may be adapted to rotate the signal charged particle beam 1102 by a second angle A2. The second angle A2 may be in the range of -45 degrees to 45 degrees. Therefore, the Larmor rotation of -45 degrees to 45 degrees may be compensated by the second magnetic lens portion. A lens system (such as, for example, Figure 1 The lens system 1610 shown can be adapted to rotate the signal charged particle beam by a total angle in the range of -|A1|-|A2| to |A1|+|A2|, where |A1| and |A2| represent the absolute values ​​of A1 and A2, respectively. Therefore, Larmor rotation in the range of -|A1|-|A2| to |A1|+|A2| can be compensated by the lens system. For example, Larmor rotation between -90 degrees and 90 degrees can be compensated.

[0041] An advantage of compensating the Larmor rotation of the signal charged particle beam using the first magnetic lens portion comprised by the first lens and / or the second magnetic lens portion comprised by the second lens is that the aperture plate and / or the detector arrangement do not need to be mechanically rotated to compensate for the Larmor rotation.

[0042] The first lens 1612 can be a composite lens including an electrostatic lens portion (not shown) and a first magnetic lens portion 1614. Compared to a first lens including an electrostatic lens portion but not including a first magnetic lens portion, the composite lens provides additional degrees of freedom for affecting the secondary charged particle beam. In particular, two such additional degrees of freedom provided by the first magnetic lens portion 1614 can include the magnitude and direction of the current flowing through the coil included in the first magnetic lens portion 1614. Similar considerations also apply to embodiments in which the second lens is a composite lens.

[0043] The magnetic field generated by the first magnetic lens part 1614 can affect the focusing of the signal charged particle beam 1102 on the aperture plate 1650. This focusing effect can be compensated or further amplified by setting the excitation of the electrostatic lens part of the first lens 1612 to an appropriate value. For example, the focusing effect can be affected by reducing or increasing the refractive power of the electrostatic lens part. Therefore, the signal charged particle beam 1102 can be shaped, focused, and / or defocused in a desired manner. Therefore, via the combined effect of the first magnetic lens part 1614 and the electrostatic lens part, the first lens 1612 can be configured to compensate for the Larmor rotation of the objective lens, and / or shape, focus, and / or defocus the signal charged particle beam 1102. Similar considerations also apply to the embodiment in which the second lens is a composite lens.

[0044] Instead of the first lens 1612 and the second lens 1616 including a magnetic lens portion Figure 1 According to other embodiments described herein, only one of the first lens 1612 and the second lens 1616 may include a magnetic lens portion for compensating for Larmor rotation. According to an embodiment, at least one of the first lens and the second lens includes a magnetic lens portion for compensating for Larmor rotation of the objective lens.

[0045] According to further embodiments, which can be combined with other embodiments described herein, the first lens and the second lens comprise or consist of an electrostatic lens portion. For example, the first lens and the second lens do not comprise a magnetic lens portion. As an optional modification (particularly for such embodiments), the Larmor gyration can be provided or compensated by a coil (e.g., a Larmor gyration coil). For example, the Larmor gyration coil can be downstream of the first lens and / or the second lens.

[0046] According to an embodiment, the secondary charged particle optics module 1600 may include a controller 1630 . Figure 1 The controller 1630 shown can be configured to control the excitation of the first lens 1612 and the excitation of the second lens 1616. Controlling the excitation of the first lens 1612 can include controlling the excitation of the electrostatic lens portion of the first lens 1612 and / or controlling the excitation of the magnetic lens portion of the first lens 1612. Similar considerations also apply to the case where the second lens 1616 includes electrostatic and / or magnetic lens portions.

[0047] The electrostatic lens portion of the first lens 1612 may include one or more electrodes for generating an electric field. A potential may be applied to the electrodes to generate an electric field. The electric field may be generated under the control of the controller 1630. In particular, the intensity of the electric field may be controlled by the controller 1630, the intensity of the electric field may be determined by the controller 1630, and / or the intensity of the electric field may be adjusted under the control of the controller 1630. The magnetic lens portions 1612 of the first lens may each include one or more coils for generating a magnetic field. A current may flow through the coils to generate a magnetic field. The magnetic field may be generated under the control of the controller 1630. In particular, the intensity of the magnetic field and the field direction determined by the direction of the current flowing through the coil may be controlled by the controller 1630, the intensity of the magnetic field and the field direction determined by the direction of the current flowing through the coil may be determined by the controller 1630, and / or the intensity of the magnetic field and the field direction determined by the direction of the current flowing through the coil may be adjusted under the control of the controller 1630. Similar considerations also apply to the electrostatic lens portion and / or magnetic lens portion included in the second lens 1616. According to embodiments described herein, the first lens may include an electrostatic lens portion, a magnetic lens portion, or both an electrostatic lens portion and a magnetic lens portion. According to embodiments described herein, the second lens may include an electrostatic lens portion, a magnetic lens portion, or both an electrostatic lens portion and a magnetic lens portion. Providing a combined electrostatic magnetic lens (i.e., having an electrostatic lens portion and a magnetic lens portion) for the first lens and / or the second lens may allow for increased degrees of freedom for adjusting the signal charged particle beam (particularly with respect to Larmor gyrations).

[0048] The controller 1630 may be configured to independently control the excitation of the first lens 1612 and the excitation of the second lens 1616. Thus, the controller 1630 may allow the focusing, defocusing, and / or shaping of the signal charged particle beam 1102 to be controlled by the first lens 1612 independently of the focusing, defocusing, and / or shaping of the signal charged particle beam 1102 controlled by the second lens 1616. In the profile detection mode of the secondary charged particle imaging system, the independent control of the excitation of the first lens 1612 and the excitation of the second lens 1616 provides that the first beamlet of the signal charged particle beam 1102 passes through the first opening 1653 and is detected by the first detection element 1970, the central beamlet of the signal charged particle beam 1102 passes through the central opening 1655 and is detected by the central detection element 1950, and the second beamlet of the signal charged particle beam 1102 passes through the second opening 1657 and is detected by the second detection element 1930.

[0049] According to an embodiment that can be combined with other embodiments described herein, the controller 240 can be configured to switch between the topography detection mode and the bright field detection mode by adapting the excitation of the first lens 1612 and the excitation of the second lens 1616. At a first time point, the excitation of the first lens 1612 and the excitation of the second lens 1616 can be set to a first configuration under the control of the controller 1630 to image the signal charged particle beam 1102 in the topography detection mode. At a second time point (e.g., later), the excitation of the first lens 1612 and the excitation of the second lens 1616 can be set to a second configuration under the control of the controller 1630 to image the signal charged particle beam 1102 in the bright field detection mode. Therefore, the flexibility of the system is enhanced.

[0050] According to embodiments that can be combined with other embodiments described herein, the secondary charged particle imaging system can be configured to switch between the secondary charged particle detection mode and the backscattered electron detection mode, respectively, by rotating the backscattered electron detector module 1400 between the first position 5452 and the second position 5454. Thus, the flexibility of the system is further enhanced.

[0051] An advantage of having a controller configured to switch between a topography detection mode and a brightfield detection mode, as compared to a system configured to operate in either a topography detection mode or a brightfield detection mode, is that multiple aspects of a sample (e.g., relating to topography information, defects on the sample, chemical composition of the sample, etc.) can be analyzed by a single system.

[0052] Figure 1 A simplified side schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, a secondary charged particle imaging system includes an aperture plate.

[0053] The aperture plate 1650 may include a first opening 1653, a central opening 1655, and / or a second opening 1657. The first opening 1653 may be spaced apart from the second opening 1657. The aperture plate 1650 may be arranged parallel to the first lens 1612 and / or the second lens 1616, and / or spaced apart from the first lens 1612 and / or the second lens 1616. The first opening 1653 may be formed at an upper portion 1650 of the aperture plate relative to a vertical direction. The central opening 1655 may be formed at a central portion of the aperture plate 1650. The second opening 1657 may be formed at a lower portion of the aperture plate 1650. The aperture plate 1650 may define the optical axis 1103. In an example, a distance between the center of the aperture plate 1650 and the center of the first lens 1612 may be in a range of 40 mm to 200 mm.

[0054] Aperture plate 1650 , first lens 1612 , and / or second lens 1616 may be parallel to a plane defined by detector arrangement 1900 .

[0055] In addition to the first opening 1653, the central opening 1655, and the second opening 1657, the aperture plate 1650 may include other openings. For example, the aperture plate 1650 may include five openings. The first opening 1653, the second opening 1657, and any other openings may be positioned around the optical axis 1103 so that the aperture plate 1650 has a four-fold rotational symmetry relative to the optical axis 1103. The first opening 1653, the second opening 1657, and any other openings may be openings radially outward relative to the optical axis 1103. In an example, the diameter or corresponding size of the central opening 1655 may be 1 mm to 4 mm. In another example, the first opening 1653, the second opening 1657, and / or the other openings may have a diameter or corresponding size in the range of 3 mm to 15 mm. In yet another example, the distance between the center of the first opening and the center of the second opening may be in the range of 4 mm to 15 mm.

[0056] Aperture plate 1650 may include an integer number N of further openings, wherein first opening 1653 , second opening 1657 and N further openings are positioned around optical axis 1103 of aperture plate 1650 , such that aperture plate 1650 has N+2-fold rotational symmetry relative to optical axis 1103 of aperture plate 1650 .

[0057] In yet another example, the aperture plate can have a thickness of 5 mm or more, more particularly, the thickness can be 10 mm to 20 mm. The thickness of the aperture plate can be a thickness in the axial direction of the aperture plate and / or in a direction parallel to the optical axis defined by the aperture plate. Having a thickness of 10 mm to 20 mm can provide an increased spacing of the sub-beams of the signal charged particle beam. The increased spacing allows the use of a detector arrangement in which the detection element (e.g., a first detection element, a second detection element, and / or a central detection element) can be a standard pin diode with a diameter of 5 mm. Therefore, a feasible design of a detector arrangement can be provided. In addition, in view of the fact that the penetration of the acceleration field generated between the aperture plate and the detector arrangement is affected by the thickness of the aperture plate, the reduced operating voltage is a beneficial side effect of the minimum thickness of the aperture plate with at least 5 mm. Therefore, better high voltage immunity, reliability and stability can be provided.

[0058] The aperture plate is arranged upstream of the detector arrangement with respect to the propagation of the secondary charged particle beam.

[0059] Figure 1 A simplified side schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, the secondary charged particle imaging system includes one or more deflection elements.

[0060] One or more deflection elements may be configured to affect the signal charged particle beam 1102. By providing one or more deflection elements, the information carried by the signal charged particles is more easily preserved as the signal charged particle beam 1102 is transferred from the sample to the detector arrangement 1900. As shown, the first deflection element 1720 and the second deflection element 1710 may be arranged between the beam bender 1392 and the detector arrangement 1900. According to alternative embodiments, the secondary charged particle imaging system may include the first deflection element 1720 without the second deflection element 1710, or vice versa, or may include an additional deflection element arranged between the beam bender 1392 and the detector arrangement 1900. A third deflection element (not shown) may be disposed between the beam bender 1392 and the second lens 1616. Alternatively, the third deflection element may be disposed upstream of the beam bender 1392 relative to the signal charged particle beam 1102. For example, a third deflection element may be disposed between a beam splitter and a beam bender as described herein. The third deflection element improves alignment and / or imaging of the signal charged particle beam on the detector arrangement. Thus, signal generation may be improved, and thus contrast may be improved. Improved signal generation results in better yield (particularly for EBI applications). The third deflection element may be the next deflection element through which the signal charged particle beam 1102 leaving the beam bender 1392 passes. The third deflection element may be disposed directly downstream of the beam bender 1392 or the backscattered electron detector module 1400 relative to the signal charged particle beam 1102. Alternatively, the third deflection element may be disposed between the first lens 1612 and the detector arrangement 1900. As described above, the advantage of providing a third deflection element between the beam bender and the second lens or between the first lens and the detector arrangement is that the potential spatial limitations of the third deflection element are not as strict, compared to, for example, a third deflection element positioned between the beam splitter and the beam bender (insufficient separation between the signal charged particle beam and the primary charged particle beam). Arranging the third deflection element between the beam splitter and the beam bender may provide an improved back scanning of the signal charged particle beam. In particular, deviations of the signal charged particle beam emitted from off-axis positions of its axis from the center of the field of view may be more easily compensated.

[0061] like Figure 1As shown, the second deflection element 1710 can be arranged between the first lens 1612 and the second lens 1616. The second deflection element 1710 can affect the signal charged particle beam 1102 traveling from the second lens 1616 to the first lens 1612. The first deflection element 1720 can be arranged between the aperture plate 1650 and the first lens 1612. The first deflection element 1720 can affect the signal charged particle beam 1102 traveling from the first lens 1612 to the aperture plate 11650. Figure 1 As shown, the first deflection element 1720 and / or the second deflection element 1710 may be aligned with the optical axis 1103. The optical axis 1103 may extend longitudinally through the first deflection element 1720 and / or the second deflection element 1710.

[0062] Deflection elements for influencing the signal charged particle beam (such as, for example, Figure 1 The first deflection element 1720 and / or the second deflection element 1710 shown may include an electrostatic deflection portion and / or a magnetic deflection portion. The electrostatic deflection portion may include an electrostatic dipole, quadrupole, or higher-order multipole element. The magnetic deflection portion may include a magnetic dipole, quadrupole, or higher-order multipole element. The deflection element may include two deflection plates, which are arranged on opposite sides of the optical axis defined by the aperture plate and / or on opposite sides of the signal charged particle beam. In order to deflect in two directions, two perpendicular dipole fields may be provided, or two deflectors may be provided, which are operable to allow a dipole field to rotate depending on the operation of the two deflectors. For example, the separate fields of the two deflectors may respectively enclose an angle of 70° to 110° (such as 90°). As Figure 1 As shown, the first deflection element 1720 and / or the second deflection element 1710 may each include two deflection plates for deflecting the signal charged particle beam in the first direction.

[0063] The deflection element for influencing the signal charged particle beam may be adapted to align the signal charged particle beam with the optical axis of the aperture plate (e.g. in bright field detection mode). Additionally or alternatively, the deflection element (e.g. the third deflection element described herein) may be adapted to backscan the signal charged particle beam. The signal charged particle beam may be backscanned in a charged particle beam device (in which the primary charged particle beam is scanned over the sample). Scanning the primary charged particle beam over the sample may provide an unwanted deflection of the signal charged particle beam, wherein the position at which the signal charged particle beam impinges on the detector arrangement and / or the position of the signal charged particle beam relative to the aperture plate may depend on the position of the primary charged particle beam scanned over the sample. This dependency may result in poor detection quality with blurred images. (e.g. by Figure 1The back scanning of the signal charged particle beam (performed by the first deflection element 1720 and / or the second deflection element 1710 shown) can compensate for the deflection of the signal charged particle beam caused by scanning the primary charged particle beam, and / or can align the signal charged particle beam with the target axis (for example, the optical axis defined by the aperture plate) regardless of the position of the primary charged particle beam scanned above the sample. Therefore, off-axis aberrations of the signal charged particle beam can be avoided. The back scanning of the signal charged particle beam may be particularly advantageous for a charged particle beam device with a large field of view. According to embodiments that can be combined with other embodiments described herein, the field of view of the charged particle beam device may be 500 μm or more.

[0064] In order to provide reverse scanning of the signal charged particle beam using the deflection element, a deflection voltage may be applied to the deflection element. The deflection voltage may be synchronized with the scanning of the primary charged particle beam to compensate for the deflection of the signal charged particle beam caused by the scanning of the primary charged particle beam.

[0065] The deflection element configured to backscan the signal charged particle beam can be arranged upstream of the aperture plate, upstream of the first lens, and / or between the first lens and the second lens relative to the signal charged particle beam. Compared with backscanning the signal charged particle beam downstream of the aperture plate, the advantage of backscanning the upstream of the aperture plate is that the signal charged particle beam can be more easily aligned with the target axis. In addition, because the energy filter has a higher sensitivity to the position of the signal charged particle beam relative to the optical axis 1103, backscanning upstream of the aperture plate may be advantageous for a system in which an energy filter is arranged at the aperture plate.

[0066] Figure 1 A simplified side schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, a secondary charged particle imaging system comprises a detector arrangement.

[0067] The detector arrangement 1900 may include a first detection element 1970, a central detection element 1950, and / or a second detection element 1930. The second detection element 1930 may be spaced apart from the first detection element 1970. The first detection element 1970, the central detection element 1950, and / or the second detection element 1930 may be supported by a holder of the detector arrangement 1900. The holder may include a holder plate to which the first detection element 1970, the central detection element 1950, and / or the second detection element 1930 may be attached. Figure 1As shown, the first detection element 1970, the central detection element 1950, and / or the second detection element 1930 can be arranged at the upper part, the central part, and / or the lower part of the detector arrangement 1900, respectively, relative to the vertical direction. The first detection element 1970 and the first opening 1653 can be arranged on a first side of a reference plane containing the optical axis 1102. The second detection element 1930 and the second opening 1657 can be arranged on a second side of the reference plane, wherein the second side is opposite to the first side.

[0068] In addition to the first detection element 1970, the central detection element 1950 and the second detection element 1930, the detector arrangement 1900 may include further detection elements. For example, the detector arrangement 1900 may include five detection elements, and / or the same number of detection elements as the number of openings provided in the aperture plate 1650. Each of the detection elements may be associated with a corresponding opening in the aperture plate 1650. According to embodiments, which may be combined with other embodiments described herein, the detector arrangement 1900 includes an integer number N of further detection elements, the integer N being zero or greater than zero.

[0069] The detection elements of the detector arrangement 1900 (such as, for example, the first detection element 1970, the central detection element 1950, and / or the second detection element 1930) can be, for example, pin diode detectors or scintillator detectors. In particular for EBI applications, high throughput is desired, which leads to the need for very fast sensors. Therefore, pin diode detectors can be used. The achievable bandwidth may depend on the size of the pin diode detector. A 1 mm 2 or below the sensor area.

[0070] The first detection element 1970, the center detection element 1950, the second detection element 1930, and / or other detection elements of the detector arrangement 1900 can be separate detectors that can be spatially separated from each other. The separate signals obtained by the detection elements of the detector arrangement can be combined (e.g., subtracted) to enhance contrast. Compared to, for example, detection elements arranged adjacent to each other (e.g., segmented pin diodes), the advantage provided by having spatially separated detection elements is that problems associated with pin diode areas with divided active segments (e.g., charging, signal loss, crosstalk) can be more easily overcome. In addition, spatially separated detection elements are cheaper, have a shorter development cycle, improved sensor design flexibility, and / or faster time to market.

[0071] The distance between the first detection element and the second detection element may be in the range of 1 mm to 20 mm. The distance between the first detection element and the central detection element may be in the range of 1 mm to 14 mm.

[0072] A detector arrangement 1900 including multiple detection elements as described herein provides enhanced sensitivity to changes in sample topography (e.g., caused by physical defects) compared to, for example, a bright field detector. The multiple detection elements may collect secondary charged particles only within a specific range of departure angles at the sample. Thus, enhanced contrast of inspected features and / or defects may be provided (e.g., for use in defect inspection tools and review tools or critical dimension determination tools).

[0073] The detector arrangement 1900 can be an integrated detector arrangement. The first detection element 1970, the central detection element 1950, and / or the second detection element 1930 can be integrated into the detector arrangement. The detection elements of the detector arrangement 1900 can be separated from each other in the integrated detector arrangement. The detection elements of the detector arrangement 1900 can be fixedly positioned in the detector arrangement 1900 or at the detector arrangement 1900. The detection elements of the detector arrangement 1900 can be fixed to a holder or holder plate of the detector arrangement 1900.

[0074] Figure 1 A simplified side view schematic diagram of a secondary charged particle imaging system is shown. According to embodiments described herein, the secondary charged particle imaging system includes a signal charged particle beam 1102 and / or an optical axis 1103 .

[0075] The optical axis 1103 may extend through the center of the aperture plate 230. Figure 1 With respect to the drawing plane of FIG. 1 , the optical axis 1103 extends along a horizontal (“left-right”) direction perpendicular to the vertical direction. As shown, the signal charged particle beam 1102 can travel along the optical axis 1103. Alternatively or additionally, the optical axis 1103 can be the optical axis of the signal charged particle beam 1102, the optical axis of the secondary charged particle optical device module 1600, the optical axis of the aperture plate 1650, and / or the optical axis of the detector arrangement 1900.

[0076] The optical axis 1103 may extend through the central detection element 1950. The optical axis 1103 may be perpendicular or substantially perpendicular to the plane defined by the aperture plate 1650, the plane defined by the first lens 1612, and / or the plane defined by the second lens 1616. The term "substantially perpendicular" may refer to an angle between 90 and 110 degrees. The optical axis 1103 may be an axis of symmetry of the aperture plate 1650, an axis of symmetry of the first lens 1612, and / or an axis of symmetry of the second lens 1616. The optical axis 1103 may be an axis of symmetry of the aperture plate 1650, an axis of symmetry of the first lens 1612, and / or an axis of symmetry of the second lens 1616.

[0077] Figure 2 1 shows a simplified top view schematic diagram of a secondary charged particle imaging system according to embodiments described herein. Figure 2 As shown, a housing 2220 may be provided. The housing 2220 may provide vacuum containment and / or a vacuum state for the signal charged particle beam 1102. In a preferred embodiment, the housing 2220 may house at least some elements of the secondary charged particle imaging system (such as the beam bender 1392, the backscattered electron detector module 1400, and the secondary charged particle optical device module 1600). Therefore, the beam bender 1392, the backscattered electron detector holder 1450, the backscattered electron detector element 1470, the aperture 1460, and / or the secondary charged particle optical device module 1600 may be arranged in the housing 2220. In a preferred embodiment, the beam bender 1392 is arranged upstream of the backscattered electron detector module 1400, and the backscattered electron detector module 1400 is arranged upstream of the secondary charged particle optical device module 1600.

[0078] According to an embodiment, an arm 2420 (e.g., a rigid arm) may be provided. The arm 2420 may connect and / or support the backscattered electron detector holder 1450, the backscattered electron detector element 1470, and / or the aperture 1460. The arm may be included in the backscattered electron detector module 1400. In an example, the arm 2420 extends into the housing 2220, extends to the outside of the housing 2220, and / or extends through the side of the housing 2220. The arm 2420 may be rotatable. The arm 2420 may rotate around an axis. The axis may be arranged inside the housing 2220. The axis may be closer to the side of the housing 2220 rather than near the center of the housing 2220. Therefore, the backscattered electron detector module 1400, the backscattered electron detector holder 1450, the aperture 1460, and / or the backscattered electron detector element 1470 may rotate around the axis.

[0079] Figure 3 A simplified side view schematic diagram of a backscattered electron detector module and a backscattered electron detector actuator module according to embodiments described herein is shown. According to embodiments, a backscattered electron detector actuator module 3440, a bearing module 3260, a hinge joint slot 3424, a hinge joint pin 3422, and / or a flexible housing 3430 may be provided.

[0080] According to an embodiment, the backscattered electron detector actuator module 3440 is configured to actuate, in particular move, preferably rotate or tilt the backscattered electron detector module 1400 (e.g., by actuating the arm 2420). The backscattered electron detector actuator module 3440 may include a pneumatic actuator and / or a mechanical actuator. In another example, the backscattered electron detector actuator module 3440 includes a first limiting block and an optional second limiting block. The first limiting block may correspond to a first angular position 5452. The second limiting block may correspond to a second angular position 5454. In an example, the backscattered electron detector actuator module 3440 is operated by a switch (such as a mechanical switch, a pneumatic switch, or an electronic switch). The backscattered electron detector actuator module 3440 may be configured to rotate the backscattered electron detector module 1400 and / or the arm 2420 between the first angular position 5452 and the second angular position 5454. The backscattered electron detector actuator module 3440 may be coupled to, integrated into, or included in the housing 2220, the bearing module 3260, the arm 2420, and / or the backscattered electron detector module 1400. The backscattered electron detector actuator module 3440 may be disposed on the outside and / or outside surface of the housing 2220 and / or the bearing module 3260; disposed as a part of the housing 2220, the bearing module 3260, and / or the arm 2420; and / or disposed on an end portion of the arm 2420.

[0081] According to an embodiment, the arm 2420 includes a hinge joint pin 3422. The hinge joint pin 3422 may be configured to rotate within and / or be a part of a hinge joint slot 3424. The hinge joint slot 3434 may be connected to and / or be a part of a bearing module 3260. The hinge joint pin 3433 and the hinge joint slot 3434 may serve as a hinge joint and / or axis for rotation and / or tilting of the arm 2420 and / or the backscattered electron detector module 1400.

[0082] According to an embodiment, the flexible housing 3430 is configured to provide vacuum containment and / or vacuum conditions of the backscattered electron detector element 1470. The flexible housing 3430 may be configured to maintain the hinge joint pin 3422, the hinge joint slot 3424, and / or the bearing module 3260 at atmospheric pressure, conditions, environments, and / or conditions. The flexible housing 3430 may be coupled, attached, and / or connected to the housing 2220 and / or the bearing module 3260 in an airtight or sealed manner at a first end portion. The flexible housing 3430 may similarly be coupled, attached, and / or connected to the arm 2420 in an airtight or sealed manner at a second end portion, preferably between the axis and / or the hinge joint pin 3422 and the backscattered electron detector element 1470, the aperture 1460, and / or the backscattered electron detector holder 1450. In an example, the flexible housing 3430 is a hose, a bellows, and the flexible housing 3430 is flexible and / or suitable for vacuum use. In yet another example, the flexible housing 3430 is a flexible bellows that provides a seal between air and vacuum to maintain the moving parts of the hinge joint pin 3422 and the hinge joint slot 3424 or certain rotating joints, and / or the moving parts of the bearing module 3260 on the air side or atmosphere side, and / or maintain the backscattered electron detector element 1470 on the vacuum side and / or inside the housing 2220. The flexible housing 3430 can be pre-stretched, preferably pre-stretched in an assembled state, and preferably pre-stretched in an axial direction. The pre-stretched flexible housing 3430 can apply force to the arm 2420 and / or pull the arm 2420 to abut against the bearing module 3260 and / or the housing 2220. The flexible housing 3430 can be suitable for surrounding at least a portion of the rotation axis of the arm 2420, the hinge joint pin 3422, the hinge joint slot 3424, and / or the backscattered electron detector module 1400.

[0083] According to an embodiment, the bearing module 3260 is an axial bearing. The bearing module 3260 can be configured to support the arm 2420 and / or the backscattered electron detector module 1400. The bearing module 3260 and / or the housing 2220 can provide a reaction force to the arm 2420. The reaction force can be less than the pre-tensioning force of the flexible housing 3430, wherein the balance is provided by the vacuum force in the operating state and / or the assembled state. In an example, the reaction force can be 40N or between 0N and 100N. In another example, the pre-stretched flexible housing 3430 can have a pre-stretching force greater than the reaction force 60N or more.

[0084] Depending on the embodiment, the backscattered electron detector elements 1470 may have a circular, square, or polygonal cross-section and / or shape. The apertures 1460 may similarly have a circular, square, triangular, or polygonal cross-section.

[0085] Figure 4Aand Figure 4B is a simplified pseudo 3D representation of an arm and hinge joint according to an embodiment described herein.

[0086] According to an embodiment, the hinge joint pin 3422 and / or the hinge joint slot 3424 can form a hinge joint. The hinge joint slot 3424 can be in a U-shaped slot. The hinge joint slot 3424 can be suitable for providing a reaction force to the hinge joint pin 3422. The hinge joint slot can be arranged on the bearing module 3260. The hinge joint pin 3422 can be arranged on the arm 2420. The hinge joint pin 3422 can be a plurality of pins (e.g., two pins), and / or arranged on the diametrically opposite sides of the arm 2420. Similarly, the hinge joint slot 3424 can be a plurality of slots (e.g., two slots), and / or separated by a distance at least equal to the diameter or critical dimension or cross-sectional side of the arm 2420. The hinge joint pin 3422 can include a connecting angle or polygonal ring on the arm 2420. The angle or polygonal ring can be suitably used as a guide, an assembly guide, and / or a complementary surface for the hinge joint slot 3424.

[0087] Figure 5A and Figure 5B 14 is a simplified side view schematic diagram of a backscattered electron detector module in a first angular position and a second angular position according to embodiments described herein. According to embodiments, the backscattered electron detector module 1400 and / or the arm 2420 can be switchable, rotatable, tiltable, and / or movable between a first angular position 5452 and a second angular position 5454. In the first angular position 5452, the aperture 1460 can be configured to be operable, and / or the backscattered electron detector element 1470 can be configured to be inoperable. In the second angular position 5454, the backscattered electron detector element 1470 can be configured to be operable, and / or the aperture 1460 can be configured to be inoperable. The first angular position 5452 can correspond to the arm 2420 and / or the backscattered electron detector actuator module 3440 being in a first limiting blocker and / or an upward rotation position / upward tilt position. Similarly, the second angular position 5454 can correspond to the arm 2420 and / or the backscattered electron detector actuator module 3440 being at a second limit stop and / or downward rotation position / downward tilt position. The angular distance and / or spacing between the first angular position 5452 and the second angular position 5454 can be at least 0 degrees and / or less than 10 degrees, preferably in the range of 2 degrees to 5 degrees. The rotation can be around the axis. The rotation can be around the hinge joint pin 3422.

[0088] Fig. 6A and Figure 6BSchematic diagram of a close-up simplified side view of an aperture and a backscattered electron detector element of a backscattered electron detector module at a first angular position and a second angular position according to an embodiment described herein. According to an embodiment, a beam bender shield may be present. In an example, the beam bender shield 6394 is a high voltage shield. The beam bender shield 6394 may include a shield aperture 6396. The shield aperture 6396 may have a circular, square, triangular, or polygonal cross-section or shape. The shield aperture 6396 may have a similar or identical cross-section to the aperture 1460 or the backscattered electron detector element 1470. In an example, as Fig. 6A and Figure 6B As shown, shield aperture 6396 and / or aperture 1460 have a triangular shape. In an example, shield aperture 6396 and aperture 1460 can have the same size. In another example, at least one of shield aperture 6396 and / or aperture 1460 has a circular shape and the other has a triangular shape.

[0089] Aberrations may occur in a beam bender 1392 (e.g., a fan beam bender) used to deflect the signal charged particle beam 1102. For example, a sextupole component of the electric field may introduce a triple aberration in the signal charged particle beam (e.g., a secondary electron beam) passing through the fan beam bender 1392. As the width of the signal charged particle beam 1102 inside the fan beam bender 1392 increases, the increase in the amount of the sextupole component deforms the signal charged particle beam 1102. An aperture (such as the shield aperture 6396 or the aperture 1460) for the passage area of ​​the signal charged particle beam 1102 having a substantially triangular shape (such as an isosceles triangle shape) may reduce the sextupole component of the edge field or reduce the sextupole aberration on the signal charged particle beam 1102. An aperture (such as shield aperture 6396 or aperture 1460) having a substantially circular shape (such as a circular shape) for the passage area of ​​the signal charged particle beam 1102 can reduce or minimize the effects of unwanted deflection fields (e.g., deflection fields from the fan beam bender 1392).

[0090] In a preferred embodiment, which may be combined with other embodiments described herein, the shield aperture 6396 may be upstream of the aperture 1460. The shield aperture 6396 may be triangular in shape. The aperture 1460 may be circular in shape. Alternatively, at least one of the shield aperture 6396 and / or the aperture 1460 positioned on the downstream side of the beam bender 1392 may have two sides, a first side facing the beam bender 1392 having a substantially circular shape and a second side facing away from the beam bender 1392 having a substantially triangular shape.

[0091] In some embodiments, the shield aperture 6396 may be upstream of the aperture 1460. The shield aperture 6396 may have a substantially triangular-shaped passage area for the signal charged particle beam. Therefore, the triangular shape of the shield aperture 6396 may minimize the hexapole component of the fringe electric field. The aperture 1460 may be downstream of the shield aperture 6396. The aperture 1460 may have a substantially circular-shaped passage area for the signal charged particle beam 1102. The circular shape of the aperture 1460 may minimize the influence of the fringe electric field on the signal charged particle beam 1102. Alternatively, the aperture 1460 may have a substantially triangular-shaped passage area to minimize the influence of the hexapole component of the fringe electric field on the signal charged particle beam 1102. Alternatively or additionally, the shield aperture 6396 may have a substantially circular-shaped passage area for the signal charged particle beam 1102. The circular shape of the shield aperture 6396 may minimize the influence of the fringe electric field on the signal charged particle beam 1102. In a preferred embodiment, which may be combined with other embodiments described herein, the aperture 1460 has a substantially triangular shape, the shield aperture 6396 has a substantially triangular shape, and the backscattered electron detector element 1470 has a substantially circular shape.

[0092] In another example, the backscattered electron detector element 1470 has a circular shape with a diameter that is the same as, smaller than, or larger than the size or height of the aperture 1460 or the shield aperture 6396. The first angular position 5452 can correspond to the operation of the aperture 1460, or to the secondary electron detection mode. The second position 5454 can correspond to the operation of the backscattered electron detector element 1470, or to the backscattered electron detection mode. The first angular position 5452 and the second angular position 5454 are understood as one of two possible sequences of angular positions, and the reverse sequence is also possible, with a corresponding reversal of related elements, components, operations, and effects.

[0093] Figure 7 A simplified side view schematic diagram of a charged particle beam device according to embodiments described herein is shown. In an example, the charged particle beam device can be a scanning electron microscope. In a further example, the charged particle beam device can be a multi-beam device. The charged particle beam device can include a charged particle beam emitter, a beam splitter, and / or an objective lens.

[0094] According to an embodiment, the beam emitter 7310 is used to emit a primary charged particle beam 7101. The beam emitter 7310 may be, for example, an electron gun. The charged particle beam device may include an objective lens 7370 for focusing the primary charged particle beam 7101 onto the sample 7350. The charged particle beam device may include a beam splitter 7330 for separating the primary charged particle beam 7101 from the signal charged particle beam 1102 emitted from the sample 7350. The charged particle beam device may include a secondary charged particle imaging system according to an embodiment described herein. The secondary charged particle imaging system may be arranged downstream of the beam splitter 7330 relative to the propagation of the signal charged particle beam 1102.

[0095] like Figure 7 As shown, the primary charged particle beam 7101 emitted from the beam emitter 7310 can travel from the beam emitter 7310 to the beam splitter 7330. As further shown, the primary charged particle beam 7101 can be deflected in the beam splitter 7330. As further shown, the primary charged particle beam 7101 can travel from the beam splitter 7330 to the objective lens 7370, which is suitable for focusing the primary charged particle beam 7101 onto the sample 7350. Figure 7 In the exemplary embodiment shown, the primary charged particle beam 7101 travels along the optical axis defined by the objective lens 7370 when traveling from the beam splitter 7330 to the sample 7350 via the objective lens 7370. After the primary charged particle beam 7101 hits the sample 7350, a signal charged particle beam 1102 is generated. Figure 7 As shown, the signal charged particle beam 1102 can travel from the sample 7350 to the beam splitter 7330, wherein the signal charged particle beam 1102 can travel in the opposite direction to the primary charged particle beam 7101. The beam splitter 7330 acts on the primary charged particle beam 7101, as well as on the signal charged particle beam 1102, and is suitable for separating the primary charged particle beam 7101 from the signal charged particle beam 1102. As shown, the signal charged particle beam 1102 can be deflected in the beam splitter 7330. The deflection can cause the signal charged particle beam leaving the beam splitter to be directed away from the primary charged particle beam 7101. The signal charged particle beam 1102 travels from the beam splitter 7330 to the secondary charged particle imaging system.

[0096] The beam splitter 7330 may include a magnetic beam splitting portion (e.g., including one or more coils) adapted to generate a magnetic field. Additionally or alternatively, the beam splitter 7330 may include an electrostatic beam splitting portion (e.g., including one or more electrodes) adapted to generate an electric field. The electric field and / or the magnetic field may act on the primary charged particle beam 7101 and / or on the signal charged particle beam 1102 passing through the beam splitter 7330. Under the influence of the magnetic field and / or the electric field, the primary charged particle beam 7101 and the signal charged particle beam 1102 may be deflected in the beam splitter 7330.

[0097] The charged particle beam device may further include at least one of the following: a platform, wherein the platform may be movable relative to the objective lens 7370 for changing the working distance; a sampling voltage source, adapted to change the landing energy of the primary charged particle beam 7101; one or more adjacent electrodes, adapted to change the strength of the extraction field acting on the signal charged particle beam 1102; a magnetic objective lens portion included in the objective lens 7370, adapted to generate a magnetic field. As further described above, under the action of the controller 1630, (e.g., in a topographic detection mode or a bright field detection mode) the signal charged particle beam 1102 may be mapped onto the aperture plate 1650, independently of changes in at least one first operating parameter and / or independently of changes in at least one second operating parameter.

[0098] Figure 7 The charged particle beam apparatus shown includes a secondary charged particle imaging system according to the embodiments described herein. As described above, Figure 7 The secondary charged particle imaging system shown includes a beam bender 1392. As discussed further above, the signal charged particle beam 1102 is directed away from the primary charged particle beam 7101 by a beam splitter 7330. Figure 7 As shown, the beam bender 1392 can direct the signal charged particle beam 1102 away from the primary charged particle beam 7101 .

[0099] Figure 8802 is a diagram of a method for operating a secondary charged particle imaging system according to an embodiment described herein. According to one embodiment, a method for operating a secondary charged particle imaging system is provided. The method includes rotating a backscattered electron detector module around an axis between a first angular position 5452 and a second angular position 5454, for example as shown in operation 802. In an embodiment, a first operating mode and a second operating mode may be provided by rotating the backscattered electron detector module 1400. In the first operating mode, a signal electron or a signal charged particle beam 1102 may pass through the backscattered electron detector module 1400. In the second operating mode, the signal electron or the signal charged particle beam 1102 may impact a backscattered electron detector element 1470 of the backscattered electron detector module 1400.

[0100] At least one of the following advantages may be achieved by the embodiments described herein. The backscattered electron detector may be moved into and out of the optical axis. When the backscattered electron detector is moved out of the optical axis, a conventional secondary electron detector with a secondary electron optical device may be used. By placing the backscattered electron detector before the secondary electron optical device, the efficiency (particularly the detection efficiency) is improved, for example, by up to 30%, depending on the landing energy involved.

[0101] The efficiency of backscattered electron detection is comparable to that of a single beam system without secondary electron optics. Another advantage is that a multi-beam system can be combined with backscattered electron detection capabilities. Axial backscattered electron detection can be provided for single beam mode, for multi-beam systems with secondary electron optics or for single beam systems. Secondary electron optics are particularly advantageous for multi-beam systems. Axial secondary electrons and backscattered electrons can be detected in one column using simple mechanical switching. Multi-beam columns can be used to detect detection defects using backscattered electrons. A specific advantage is that multi-beam columns can be used in a simple manner in single beam mode, secondary electron detection mode and backscattered electron detection mode. Another specific advantage is that the tilting or rotational motion concept allows for minimal space requirements on the inside of the column, and especially on the outside of the column. Minimized space is required on the outside of the column and on the inside of the housing. Much less space is required in the tilting or rotational concept compared to linear actuation motion. A further advantage is that both detection efficiency and accessibility can be optimized by positioning the detector after the beam bender. The space near the primary beam may be particularly narrow. Yet another advantage is that the electron beam can have a minimum cross section at the point after the beam bender. The small cross section allows for good detection efficiency. Furthermore, the moving parts are outside the vacuum containment and contamination is avoided. This concept may be advantageous for electron beam inspection and electron beam mask inspection.

[0102] Further embodiments are described below.

[0103] According to a first embodiment, there is a secondary charged particle imaging system comprising a backscattered electron detector module, wherein the backscattered electron detector module is rotatable about an axis between a first angular position 5452 and a second angular position 5454.

[0104] According to a second embodiment, there is a secondary charged particle imaging system according to the first embodiment, wherein the backscattered electron detector module comprises a backscattered electron detector element 1470 .

[0105] According to a third embodiment, there is a secondary charged particle imaging system according to the second embodiment, wherein the backscattered electron detector module comprises an aperture 1460 .

[0106] According to a fourth embodiment, there is a secondary charged particle imaging system according to the second embodiment or the third embodiment, further comprising a beam bender 1392 .

[0107] According to a fifth embodiment, there is a secondary charged particle imaging system according to any one of the second to fourth embodiments, wherein in a first angular position 5452 the aperture 1460 is arranged on the optical axis 1103 of the signal charged particle beam 1102 .

[0108] According to a sixth embodiment, there is a secondary charged particle imaging system according to the fourth or fifth embodiment, wherein in a first angular position 5452 , the aperture 1460 is arranged between the beam bender 1392 and the lens system 1610 .

[0109] According to a seventh embodiment, there is a secondary charged particle imaging system according to any one of the third to sixth embodiments, wherein in a first angular position 5452 , the aperture 1460 is configured to allow the signal charged particle beam 1102 to pass through the aperture 1460 .

[0110] According to an eighth embodiment, there is a secondary charged particle imaging system according to any one of the first to seventh embodiments, wherein in a first angular position 5452, the secondary charged particle imaging system is configured to detect secondary electrons.

[0111] According to a ninth embodiment, there is a secondary charged particle imaging system according to any one of the second to eighth embodiments, wherein in a second angular position 5454 the backscattered electron detector element 1470 is arranged on the optical axis 1103 of the signal charged particle beam 1102 .

[0112] According to a tenth embodiment, there is a secondary charged particle imaging system according to any one of the third to ninth embodiments, wherein in the second angular position 5454 the backscattered electron detector element 1470 is arranged between the beam bender 1392 and the lens system 1610 .

[0113] According to an eleventh embodiment, there is a secondary charged particle imaging system according to any one of the second to tenth embodiments, wherein in a second angular position 5454 , the backscattered electron detector element 1460 is configured to collect backscattered electrons of the signal charged particle beam 1102 .

[0114] According to a twelfth embodiment, there is a secondary charged particle imaging system according to any one of the first to eleventh embodiments, wherein in the second angular position 5454, the secondary charged particle imaging system is configured for detecting backscattered electrons.

[0115] According to a thirteenth embodiment, there is a secondary charged particle imaging system according to any one of the second to twelfth embodiments, wherein in a second angular position 5454, the backscattered electron detector element 1470 is arranged at a point of minimum cross-section of the signal charged particle beam 1102, or is arranged to be adjacent to the point of minimum cross-section of the signal charged particle beam 1102.

[0116] According to a fourteenth embodiment, there is a secondary charged particle imaging system according to any one of the first to thirteenth embodiments, further comprising a backscattered electron detector actuator module 3440 .

[0117] According to a fifteenth embodiment, there is a secondary charged particle imaging system according to the fourteenth embodiment, wherein the backscattered electron detector actuator module 3440 includes a first limiting blocker and a second limiting blocker.

[0118] According to a sixteenth embodiment, there is a secondary charged particle imaging system according to the fifteenth embodiment, wherein the backscattered electron module at the first limiting blocker is at a first angular position 5452, and wherein the backscattered electron module at the second limiting blocker is at a second angular position 5454.

[0119] According to a seventeenth embodiment, there is a secondary charged particle imaging system according to any one of the fourteenth to sixteenth embodiments, wherein the backscattered electron detector actuator module 3440 is configured to rotate the backscattered electron detector module between a first angular position 5452 and a second angular position 5454.

[0120] According to an eighteenth embodiment, there is a secondary charged particle imaging system according to any one of the first to seventeenth embodiments, wherein the backscattered electron module comprises an arm 2420, and wherein the arm 2420 comprises a hinge joint pin 3422 at an axis.

[0121] According to a nineteenth embodiment, there is a secondary charged particle imaging system according to any one of the first to eighteenth embodiments, further comprising a flexible housing 3430 .

[0122] According to a twentieth embodiment, there is a secondary charged particle imaging system according to the second embodiment, the eighteenth embodiment and the nineteenth embodiment, wherein the flexible housing 3430 is hermetically coupled to the arm 2420 at a first end portion between the hinge joint pin 3422 and the backscattered electron detector element 1470.

[0123] According to a twenty-first embodiment, there is the secondary charged particle imaging system according to the second embodiment, the eighteenth embodiment, and the nineteenth embodiment, wherein the flexible housing 3430 is hermetically coupled to the housing 2220 at the second end portion.

[0124] According to a twenty-second embodiment, there is a secondary charged particle imaging system according to any one of the nineteenth to twenty-first embodiments, wherein the flexible housing 3430 is a flexible hose or a bellows.

[0125] According to a twenty-third embodiment, there is a secondary charged particle imaging system according to any one of the nineteenth to twenty-second embodiments, wherein the flexible housing 3430 is configured to maintain the backscattered electron detector element 1470 under vacuum conditions and to maintain the hinge joints 3422, 3424 under atmospheric conditions.

[0126] According to a twenty-fourth embodiment, there is a secondary charged particle imaging system according to any one of the first to twenty-third embodiments, wherein an angular interval between the first angular position 5452 and the second angular position 5454 is less than 10 degrees.

[0127] According to a twenty-fifth embodiment, there is a charged particle beam apparatus including the secondary charged particle imaging system according to any one of the first to twenty-fourth embodiments.

[0128] According to a twenty-sixth embodiment, there is the charged particle beam device according to the twenty-fifth embodiment, wherein the charged particle beam device is a multi-beam charged particle beam device.

[0129] According to a twenty-seventh embodiment, there is a method of operating a secondary charged particle imaging system, comprising rotating 802 a backscattered electron detector module about an axis between a first angular position 5452 and a second angular position 5454 .

Claims

1. A secondary charged particle imaging system, comprising: a backscattered electron detector module configured to collect and / or detect backscattered electrons of the signal charged particle beam, the backscattered electron detector module comprising a backscattered electron detector element (1470); a secondary charged particle optics module (1600), the secondary charged particle optics module being configured to shape, focus, and / or defocus the signal charged particle beam; wherein the backscattered electron detector module is arranged upstream of the secondary charged particle optical device module (1600), wherein the backscattered electron detector module is rotatable between a first angular position (5452) in which the signal charged particle beam is able to pass through the backscattered electron detector module and a second angular position (5454) in which the optical axis of the backscattered electron detector element and the signal charged particle beam are aligned.

2. The secondary charged particle imaging system of claim 1, wherein the backscattered electron detector module comprises a backscattered electron detector element (1470), and wherein in the second angular position (5454) at least one of the following is satisfied: The backscattered electron detector element (1470) is arranged on the optical axis (1103) of the signal charged particle beam (1102), The backscattered electron detector element (1470) is between the beam bender (1392) and the lens system (1610), The backscattered electron detector element (1470) is configured to collect backscattered electrons of the signal charged particle beam (1102), The backscattered electron detector element (1470) is arranged at or adjacent to the point of minimum cross section of the signal charged particle beam (1102).

3. The secondary charged particle imaging system of claim 1, wherein the backscattered electron detector module comprises an aperture (1460), and wherein in the first angular position (5452) at least one of the following is satisfied: The aperture (1460) is arranged on the optical axis (1103) of the signal charged particle beam (1102), The aperture (1460) is arranged between the beam bender (1392) and the lens system (1610), The aperture (1460) is configured to allow the signal charged particle beam (1102) to pass through the aperture (1460).

4. The secondary charged particle imaging system of any one of claims 1 to 3, further comprising a beam bender (1392).

5. The secondary charged particle imaging system of any one of claims 1 to 3, wherein in the first angular position (5452), the secondary charged particle imaging system is configured for detecting secondary electrons.

6. The secondary charged particle imaging system of any one of claims 1 to 3, wherein in the second angular position (5454), the secondary charged particle imaging system is configured for detecting backscattered electrons.

7. The secondary charged particle imaging system of any one of claims 1 to 3, further comprising a backscattered electron detector actuator module (3440).

8. The secondary charged particle imaging system of claim 7, wherein the backscattered electron detector actuator module (3440) comprises a first limiting blocker and a second limiting blocker.

9. The secondary charged particle imaging system of claim 8, wherein the backscattered electron detector module at the first limiting blocker is at the first angular position (5452), and wherein the backscattered electron detector module at the second limiting blocker is at the second angular position (5454).

10. The secondary charged particle imaging system of claim 7, wherein the backscattered electron detector actuator module (3440) is configured to rotate the backscattered electron detector module between the first angular position (5452) and the second angular position (5454).

11. A secondary charged particle imaging system as described in any one of claims 1 to 3, wherein the backscattered electron detector module is capable of rotating about an axis between a first angular position and a second angular position, the backscattered electron detector module includes an arm (2420), and wherein the arm (2420) includes a hinge joint pin (3422) at the axis.

12. The secondary charged particle imaging system of claim 11, further comprising a flexible housing (3430).

13. The secondary charged particle imaging system of claim 12, wherein the flexible housing (3430) is hermetically coupled to the arm (2420) at a first end portion between the hinge joint pin (3422) and the backscattered electron detector element (1470) of the backscattered electron detector module.

14. The secondary charged particle imaging system of claim 12, wherein the flexible housing (3430) is hermetically coupled to the casing (2220) at the second end portion.

15. The secondary charged particle imaging system of claim 12, wherein the flexible housing (3430) is a flexible hose or a bellows.

16. The secondary charged particle imaging system of claim 12, wherein the flexible housing (3430) is configured to maintain the backscattered electron detector element (1470) of the backscattered electron detector module under vacuum conditions and to maintain the hinge joint pin (3422) under atmospheric conditions.

17. The secondary charged particle imaging system of any one of claims 1 to 3, wherein the angular separation between the first angular position (5452) and the second angular position (5454) is less than 10 degrees.

18. A charged particle beam apparatus comprising the secondary charged particle imaging system according to any one of claims 1 to 3.

19. A multi-beam charged particle beam apparatus comprising the secondary charged particle imaging system according to any one of claims 1 to 3.

20. A method of operating a secondary charged particle imaging system as described in any one of claims 1 to 3, comprising: rotating (802) a backscattered electron detector module about an axis between a first angular position (5452) and a second angular position (5454), wherein the backscattered electron detector module is arranged upstream of a secondary charged particle optical device module (1600).

Images