The embodiments provided herein generally relate to charged particle apparatuses and methods for projecting a multi-beam of charged particles toward a sample.
When manufacturing semiconductor integrated circuit (IC) chips, undesired pattern defects, as a consequence of, for example, optical effects and incidental particles, inevitably occur on a substrate (i.e. wafer) or a mask during the fabrication processes, thereby reducing the yield. Monitoring the extent of the undesired pattern defects is therefore an important process in the manufacture of IC chips. More generally, the inspection and/or measurement of a surface of a substrate, or other object/material, is an important process during and/or after its manufacture.
Pattern inspection tools with a charged particle beam have been used to inspect objects, for example to detect pattern defects. These tools typically use electron microscopy techniques, such as a scanning electron microscope (SEM). In a SEM, a primary electron beam of electrons at a relatively high energy is targeted with a final deceleration step in order to land on a sample at a relatively low landing energy. The beam of electrons is focused as a probing spot on the sample. The interactions between the material structure at the probing spot and the landing electrons from the beam of electrons cause electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons. The generated secondary electrons may be emitted from the material structure of the sample. By scanning the primary electron beam as the probing spot over the sample surface, secondary electrons can be emitted across the surface of the sample. By collecting these emitted secondary electrons from the sample surface, a pattern inspection tool may obtain an image representing characteristics of the material structure of the surface of the sample. The intensity of the electron beams comprising the backscattered electrons and the secondary electrons may vary based on the properties of the internal and external structures of the sample, and thereby may indicate whether the sample has defects.
The relatively high energy beam of electrons may be emitted from a source cathode. The final deceleration step may be achieved by biasing the sample to a high voltage close to that of the source cathode. The sample holder may be maintained at high voltage so as to bias the sample. This can make the design of any moving stage complicated. There is also a risk of damage to the sample and components of the tool through electric discharge, for which the risk may be greater between relatively moving components such as the holder and a stage which moves the sample and the holder.
It is an object of the present disclosure to provide embodiments that support beams of charged particles landing on a sample at low landing energy while reducing the complexity of any moving stage and reducing the risk of damaging the sample.
According to some embodiments of the present disclosure, there is provided a charged particle apparatus configured to project a multi-beam of charged particle along a multi-beam path toward a sample, the charged particle apparatus comprising: a charged particle source configured to emit a charged particle beam toward a sample; a charged particle-optical device configured to project sub-beams of a multi-beam of charged particles along the multi-beam path toward the sample, the sub-beams of the multi-beam of charged particles derived from the charged particle beam; a tube surrounding the multi-beam path configured to operate at a first potential difference from a ground potential; and a support configured to support the sample at a second potential difference from the ground potential, the first potential difference and the second potential difference having a difference so as to accelerate the multi-beam of charged particles towards the sample; wherein the first potential difference is greater than the second potential difference.
According to some embodiments of the present disclosure, there is provided a method for projecting a multi-beam of charged particles toward a sample, the method comprising: emitting a charged particle beam; projecting along a multi-beam path toward a sample sub-beams of a multi-beam of charged particles derived from the charged particle beam using a charged particle-optical device; accelerating the charged particle beam toward the sample using a tube surrounding the multi-beam path, wherein the tube operates at a first potential difference from a ground potential; and holding the sample at a second potential difference from the ground potential; wherein the first potential difference is greater than the second potential difference.
The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, taken in conjunction with the accompanying drawings.
The schematic diagrams and views show the components described below. However, the components depicted in the figures are not to scale.
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the invention. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the invention as recited in the appended claims.
The enhanced computing power of electronic devices, which reduces the physical size of the devices, can be accomplished by significantly increasing the packing density of circuit components such as transistors, capacitors, diodes, etc. on an IC chip. This has been enabled by increased resolution enabling yet smaller structures to be made. For example, an IC chip of a smart phone, which is the size of a thumbnail and available in, or earlier than, 2019, may include over 2 billion transistors, the size of each transistor being less than 1/1000th of a human hair. Thus, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process, with hundreds of individual steps. Errors in even one step have the potential to dramatically affect the functioning of the final product. Just one “killer defect” can cause device failure. The goal of the manufacturing process is to improve the overall yield of the process. For example, to obtain a 75% yield for a 50-step process (where a step can indicate the number of layers formed on a wafer), each individual step must have a yield greater than 99.4%. If each individual step had a yield of 95%, the overall process yield would be as low as 7%.
While high process yield is desirable in an IC chip manufacturing facility, maintaining a high substrate (i.e. wafer) throughput, defined as the number of substrates processed per hour, is also essential. High process yield and high substrate throughput can be impacted by the presence of a defect. This is especially true if operator intervention is required for reviewing the defects. Thus, high throughput detection and identification of micro and nano-scale defects by inspection tools (such as a Scanning Electron Microscope (‘SEM’)) is essential for maintaining high yield and low cost.
A SEM comprises a scanning device and a detector apparatus. The scanning device comprises an illumination apparatus that comprises an electron source, for generating primary electrons, and a projection apparatus for scanning a sample, such as a substrate, with one or more focused beams of primary electrons. Together at least the illumination apparatus, or illumination system, and the projection apparatus, or projection system, may be referred to together as the electron-optical system or apparatus. The primary electrons interact with the sample and generate signal electrons such as secondary electrons. The detection apparatus captures the signal electrons from the sample as the sample is scanned so that the SEM can create an image of the scanned area of the sample. For high throughput inspection, some of the inspection apparatuses use multiple focused beams, i.e. a multi-beam, of primary electrons. The component beams of the multi-beam may be referred to as sub-beams or beamlets. A multi-beam can scan different parts of a sample simultaneously. A multi-beam inspection apparatus can therefore inspect a sample at a much higher speed than a single-beam inspection apparatus.
An implementation of a known multi-beam inspection apparatus is described below.
Within the following description of drawings the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments are described. While the description and drawings are directed to an electron-optical system, it is appreciated that the embodiments are not used to limit the present disclosure to specific charged particles. References to electrons throughout the present document may therefore be more generally considered to be references to charged particles, with the charged particles not necessarily being electrons. For example, reference to an electron apparatus may be more generally considered to be reference to a charged particle apparatus.
Reference is now made to
The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include additional loading port(s). The first loading port 30a and the second loading port 30b may for example, receive substrate front opening unified pods (FOUPs) that contain substrates (e.g., semiconductor substrates or substrates made of other material(s)) or samples to be inspected (substrates, wafers and samples are collectively referred to as “samples” hereafter). One or more robot arms (not shown) in the EFEM 30 transport the samples to the load lock chamber 20.
The load lock chamber 20 is used to remove the gas around a sample. This creates a vacuum that is a local gas pressure lower than the pressure in the surrounding environment. The load lock chamber 20 maybe connected to a load lock vacuum pump system (not shown), which removes gas particles in the load lock chamber 20. The operation of the load lock vacuum pump system enables the load lock chamber to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robot arms (not shown) transport the sample from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles in the main chamber 10 so that the pressure in around the sample reaches a second pressure lower than the first pressure. After reaching the second pressure, the sample is transported to the electron apparatus 40 by which it may be inspected. The electron apparatus 40 comprises an electron-optical device 41. The electron-optical device 41 maybe an electron-optical column configured to project at least one electron beam towards the sample 208, and/or an objective lens module configured to focus at least one electron beam onto the sample 208. The electron-optical device may also comprise a detector module configured to detect electrons emitted from the sample 208, and/or a control lens module configured to adjust an electron-optical parameter of at least one electron beam. In some embodiments, the electron-optical column may comprise the objective lens module and the detector module and optionally the control lens module. In some embodiments, the electron-optical device comprises an objective lens assembly which may be comprised in the electron-optical column. The objective lens assembly comprises an objective lens array associated with (e.g. integrated with) one or more other electron-optical components such as a detector array and optionally a control lens array. The electron-optical device 41 maybe a multi-beam electron-optical device 41 for a multi-beam projected towards the sample 208.
The controller 50 is electronically connected to electron-optical components of the electron-optical device 41 of the electron apparatus 40. The controller 50 maybe a processor (such as a computer) configured to control the electron beam inspection apparatus 100. The controller 50 may also include a processing circuitry configured to execute various signal and image processing functions. While the controller 50 is shown in
Reference is now made to
The electron source 201 may comprise a cathode 121 (not shown in
The projection apparatus 230 is configured to convert the primary electron beam 202 into a plurality of sub-beams 211, 212, 213 and to direct each sub-beam onto the sample 208. Although three sub-beams are illustrated for simplicity, there may be many tens, many hundreds, or many thousands of sub-beams. The sub-beams may be referred to as beamlets.
The controller 50 maybe connected to various parts of the electron beam inspection apparatus 100 of
The projection apparatus 230 may be configured to focus sub-beams 211, 212, and 213 onto a sample 208 for inspection and may form three probe spots 221, 222, and 223 on the surface of sample 208. The projection apparatus 230 may be configured to deflect the primary sub-beams 211, 212, and 213 to scan the probe spots 221, 222, and 223 across individual scanning areas in a section of the surface of the sample 208. In response to incidence of the primary sub-beams 211, 212, and 213 on the probe spots 221, 222, and 223 on the sample 208, electrons are generated from the sample 208 which include secondary electrons and backscattered electrons, i.e. examples of signal electrons. The secondary electrons typically have electron energy ≤50 eV. Actual secondary electrons can have an energy of less than 5 eV, but anything beneath 50 eV is generally treated at a secondary electron. Backscattered electrons typically have electron energy between 0 eV and the landing energy of the primary sub-beams 211, 212, and 213. As electrons detected with an energy of less than 50 eV is generally treated as a secondary electron, a proportion of the actual backscatter electrons will be counted as secondary electrons.
The detector 240 is configured to detect signal particles such as secondary electrons and/or backscattered electrons and to generate corresponding signals which are sent to a signal processing system 280, e.g. to construct images of the corresponding scanned areas of sample 208. The detector 240 may be incorporated into the projection apparatus 230.
The signal processing system 280 may comprise a circuit (not shown) configured to process signals from the detector 240 so as to form an image. The signal processing system 280 could otherwise be referred to as an image processing system. The signal processing system may be incorporated into a component of the multi-beam electron apparatus 40 such as the detector 240 (as shown in
The signal processing system 280 may include measurement circuitry (e.g., analog-to-digital converters) to obtain a distribution of the detected signal particles. The electron distribution data, collected during a detection time window, can be used in combination with corresponding scan path data of each of primary sub-beams 211, 212, and 213 incident on the sample surface, to reconstruct images of the sample structures under inspection. The reconstructed images can be used to reveal various features of the internal or external structures of the sample 208. The reconstructed images can thereby be used to reveal any defects that may exist in the sample.
The controller 50 may control the motorized stage 209 to move sample 208 during inspection of the sample 208. The controller 50 may enable the motorized stage 209 to move the sample 208 in a direction, preferably continuously, for example at a constant speed, at least during sample inspection. The controller 50 may control movement of the motorized stage 209 so that it changes the speed of the movement of the sample 208 dependent on various parameters. For example, the controller 50 may control the stage speed (including its direction) depending on the characteristics of the inspection steps of scanning process.
Known multi-beam systems, such as the electron apparatus 40 and electron beam inspection apparatus 100 described above, are disclosed in US2020118784,US 20200203116, US 2019/0259570 and US2019/0259564 which are hereby incorporated by reference.
As shown in
Components of an electron apparatus 40 which may be used are described below in relation to
The electron source 201 directs electrons toward an array of condenser lenses 231 (otherwise referred to as a condenser lens array). The electron source 201 is desirably a high brightness thermal field emitter with a good compromise between brightness and total emission current. There may be many tens, many hundreds, or many thousands of condenser lenses 231. The condenser lenses 231 may comprise multi-electrode lenses and have a construction based on EP1602121A1, which document is hereby incorporated by reference in particular to the disclosure of a lens array to split an electron beam, for example from the source, into a plurality of sub-beams, with the array providing a lens for each sub-beam. Each condenser lens in the condenser lens array may be for operating on a sub-beam. The array of condenser lenses 231 may take the form of at least two plates, acting as electrodes, with an aperture in each plate aligned with each other and corresponding to the location of a sub-beam. At least two of the plates are maintained during operation at different potentials to achieve the desired lensing effect.
In an arrangement the array of condenser lenses 231 is formed of three plate arrays in which charged particles have the same energy as they enter and leave each lens, which arrangement may be referred to as an Einzel lens. Thus, dispersion only occurs within the Einzel lens itself (between entry and exit electrodes of the lens), thereby limiting off-axis chromatic aberrations. When the thickness of the condenser lenses is low, e.g. a few mm, such aberrations have a small or negligible effect.
Each condenser lens 231 in the array directs electrons into a respective sub-beam 211, 212, 213 which is focused at a respective intermediate focus down beam of the condenser lens array. The sub-beams diverge with respect to each other. In some embodiments, deflectors 235 are provided at the intermediate focuses. The deflectors 235 are positioned in the sub-beam paths at, or at least around, the position of the corresponding intermediate points of focus. The deflectors 235 are positioned in or close to the sub-beam paths at the intermediate image plane of the associated sub-beam. The deflectors 235 are configured to operate on the respective sub-beams 211, 212, 213. The deflectors 235 are configured to bend a respective sub-beam 211, 212, 213 by an amount effective to ensure that the principal ray (which may also be referred to as the beam axis) is incident on the sample 208 substantially normally (i.e. at substantially 90° to the nominal surface of the sample). The deflectors 235 may be referred to as collimators or collimator deflectors. The deflectors 235 in effect collimate the paths of the sub-beams so that before the deflectors, the sub-beam paths with respect to each other are diverging. Down beam of the deflectors the sub-beam paths are substantially parallel with respect to each other, i.e. substantially collimated. Suitable collimators are deflectors disclosed in EP application Ser. No. 20156,253.5 filed on 7 Feb. 2020 which is hereby incorporated by reference with respect to the application of the deflectors to a multi-beam array. The collimator may comprise a macro collimator 270 (e.g. as shown in
Below (i.e. down beam or further from electron source 201) the deflectors 235 there is a control lens array 250. The sub-beams 211, 212, 213 having passed through the deflectors 235 are substantially parallel on entry to the control lens array 250. The control lenses pre-focus the sub-beams (e.g. apply a focusing action to the sub-beams prior to the sub-beams reaching the objective lens array 241). The pre-focusing may reduce divergence of the sub-beams or increase a rate of convergence of the sub-beams. The control lens array 250 and the objective lens array 241 operate together to provide a combined focal length. Combined operation without an intermediate focus may reduce the risk of aberrations.
In further detail, it is desirable to use the control lens array 250 to determine the landing energy. However, it is possible to use in addition the objective lens array 241 to control the landing energy. In such a case, a potential difference over the objective lens is changed when a different landing energy is selected. One example of a situation where it is desirable to partly change the landing energy by changing the potential difference over the objective lens is to prevent the focus of the sub-beams getting too close to the objective lenses. In such a situation there is a risk of components of the objective lens array 241 having to be too thin to be manufacturable. The same may be said about a detector at this location. This situation can for example occur in case the landing energy is lowered. This is because the focal length of the objective lens roughly scales with the landing energy used. By lowering the potential difference over the objective lens, and thereby lowering the electric field inside the objective lens, the focal length of the objective lens is made larger again, resulting in a focus position further below the objective lens. Note that use of just an objective lens would limit control of magnification. Such an arrangement could not control demagnification and/or opening angle. Further, using the objective lens to control the landing energy could mean that the objective lens would be operating away from its optimal field strength. That is unless mechanical parameters of the objective lens (such as the spacing between its electrodes) could be adjusted, for example by exchanging the objective lens.
The control lens array 250 comprises a plurality of control lenses. Each control lens comprises at least one electrode, preferably two electrodes (e.g. two or three electrodes) connected to respective potential sources. The control lens array 250 may comprise one or more (e.g. three) plate electrode arrays connected to respective potential sources. The control lens array 250 is associated with the objective lens array 241 (e.g. the two arrays are positioned close to each other and/or mechanically connected to each other and/or controlled together as a unit). Each control lens may be associated with a respective objective lens. The control lens array 250 is positioned up-beam of the objective lens array 241.
The control lens array 250 may be considered as one or more electrodes additional to the electrodes of the objective lens array 241. The control lens array 250 provides extra degrees of freedom for controlling the sub-beams. A greater number of electrodes comprised in the control lens array 250 provides a greater number of degrees of freedom. For example, these extra electrodes may permit landing energy and/or magnification control independent of the field strength of the objective lens array 241. In some designs the control lens may thus be part of the objective lens. Reference to such electrodes may thus be as part of the objective lens rather than a separate lens such as a control lens. Reference to a control lens in such an arrangement may be reference to functionally equivalent electrodes of the objective lens.
The control lens array 250 comprises a control lens for each sub-beam 211, 212, 213. A function of the control lens array 250 is to optimize the beam opening angle with respect to the demagnification of the beam and/or to control the beam energy delivered to the objective lens array 241 which directs the sub-beams 211, 212, 213 onto the sample 208. The opening angle (or demagnification) and beam energy delivered by the control lens to the objective lens may be considered two degrees of freedom of the sub-beams which the control lens may be used to control. The objective lens array 241 may be positioned at or near the base of the electron-optical system 41. The control lens array 250 is optional, but is preferred for optimizing a sub-beam up-beam of the objective lens array 241.
For ease of illustration, lens arrays are depicted schematically herein by arrays of oval shapes (as shown in
Optionally, an array of scan deflectors 260 is provided between the control lens array 250 and the array of objective lenses 234. The array of scan deflectors 260 comprises a scan deflector for each sub-beam 211, 212, 213. Each scan deflector is configured to deflect a respective sub-beam 211, 212, 213 in one or two directions so as to scan the sub beam across the sample 208 in one or two directions.
Sub-beams may be derived from the beam, for example, using a sub-beam forming array 252 (also known as a beam limiting aperture array) defining an array of beam-limiting apertures. The beam may separate into the sub-beams on meeting the control lens array 250, described below. The sub-beams are substantially parallel on entry to the control lens array 250.
The macro collimator 270 acts on the beam from the source 201 before the beam has been split into a multi-beam. The macro collimator 270 bends respective portions of the beam by an amount effective to ensure that a beam axis of each of the sub-beams derived from the beam is incident on the sample 208 substantially normally (i.e. at substantially 90° to the nominal surface of the sample 208). Thus the path of each sub-beam is at least intended to be orthogonal to the surface of the sample 208. The macro collimator 270 applies a macroscopic collimation to the beam. The macro collimator 270 may thus act on all of the beam rather than comprising an array of collimator elements that are each configured to act on a different individual portion of the beam. The macro collimator 270 may comprise a magnetic lens or magnetic lens arrangement comprising a plurality of magnetic lens sub-units (e.g. a plurality of electromagnets forming a multi-pole arrangement). Alternatively or additionally, the macro collimator may be at least partially implemented electrostatically. The macro collimator may comprise an electrostatic lens or electrostatic lens arrangement comprising a plurality of electrostatic lens sub-units. The macro collimator 270 may use a combination of magnetic and electrostatic lenses.
In another arrangement (not shown), the macro collimator 270 may be partially or wholly replaced by a collimator element array provided down-beam of the sub-beam forming array. Each collimator element collimates a respective sub-beam. The collimator element array may be formed using MEMS manufacturing techniques so as to be spatially compact. The collimator element array may be the first deflecting or focusing electron-optical array element in the beam path down-beam of the source 201. The collimator element array may be up beam of the control lens array 250. The collimator element array may be in the same module as the control lens array 250.
As shown in
Below (i.e. down beam or further from the electron source 201) the macro collimator 270 there is a control lens array 250. The control lens array 250 is configured to apply a focusing action to the sub-beams prior to the sub-beams reaching the objective lens array. The pre-focusing may reduce divergence of the sub-beams or increase a rate of convergence of the sub-beams. The control lens array 250 and the objective lens array 241 operate together to provide a combined focal length. Combined operation without an intermediate focus may reduce the risk of aberrations. Additionally or alternatively, the control lenses in the control lens array 250 are configured to control the opening angle of the sub-beams and/or to control demagnification (i.e. magnification) of the sub-beams and/or to control landing energy.
The control lens array 250 may be as described above in relation to
In the example of
In another arrangement (not shown), the macro scan deflector 265 may be partially or wholly replaced by a scan deflector array. The scan deflector array comprises a plurality of scan deflectors. The scan deflector array may be formed using MEMS manufacturing techniques. Each scan deflector scans a respective sub-beam over the sample 208. The scan-deflector array may thus comprise a scan deflector for each sub-beam. Each scan deflector may deflect the sub-beam in one direction (e.g. parallel to a single axis, such as an X axis) or in two directions (e.g. relative to two non-parallel axes, such as X and Y axes). The deflection is such as to cause the sub-beam to be scanned across the sample 208 in the one or two directions (i.e. one dimensionally or two dimensionally). The scan deflector array may be up beam of an objective lens array 241. The scan deflector array may be down beam of a control lens array 250. Although reference is made to a single sub-beam associated with a scan deflector, groups of sub-beams may be associated with a scan deflector. In some embodiments, the scanning deflectors described in EP2425444, which document is hereby incorporated by reference in its entirety specifically in relation to scan deflectors, may be used to implement the scan-deflector array. A scan-deflector array (e.g. formed using MEMS manufacturing techniques as mentioned above) may be more spatially compact than a macro scan deflector. The scan deflector array may be in the same module as the objective lens array 241.
In other embodiments both a macro scan deflector 265 and the scan-deflector array are provided. In such an arrangement, the scanning of the sub-beams over the sample surface may be achieved by controlling the macro scan deflector and the scan-deflector array together, preferably in synchronization.
In some embodiments, the electron-optical device 41 further comprises a sub-beam forming array 252. The sub-beam forming array 252 defines an array of beam-limiting apertures. The sub-beam forming array 252 may be referred to as an upper beam-limiting aperture array or up-beam beam-limiting aperture array. The sub-beam forming array 252 may comprise a plate (which may be a plate-like body) having a plurality of apertures. The sub-beam forming array 252 forms sub-beams from a beam of electrons emitted by the source 201. Portions of the beam other than those contributing to forming the sub-beams may be blocked (e.g. absorbed) by the sub-beam forming array 252 so as not to interfere with the sub-beams down-beam. The sub-beam forming array 252 may be referred to as a sub-beam defining aperture array or an upper beam limiter. The apertures of the sub-beam forming array 252 may have a diameter of at least 10 μm, optionally at least 20 μm, optionally at least 50 μm, optionally at least 100 μm, and optionally 120 μm. The apertures have a pitch that may by equal to that of the apertures of the beam apertures 406.
In some embodiments, as exemplified in
In an arrangement, the beam shaping aperture array 262 is structurally integrated with an electrode of the objective lens array 241. Desirably, the beam shaping aperture array 262 is positioned in a region of low electrostatic field strength. Each of the beam-limiting apertures is aligned with a corresponding objective lens in the objective lens array 241. The alignment is such that a portion of a sub-beam from the corresponding objective lens can pass through the beam-limiting aperture and impinge onto the sample 208. Each beam-limiting aperture has a beam limiting effect, allowing only a selected portion of the sub-beam incident onto the beam shaping aperture array 262 to pass through the beam-limiting aperture. The selected portion may be such that only a portion of the respective sub-beam passing through a central portion of respective apertures in the objective lens array reaches the sample. The central portion may have a circular cross-section and/or be centered on a beam axis of the sub-beam.
Any of the electron apparatuses 40 described herein may further comprise a detector 240. The detector 240 detects electrons emitted from the sample 208. The detected electrons may include any of the electrons detected by an SEM, including secondary and/or backscattered electrons emitted from the sample 208, which may be types of signal electron. An exemplary construction of a detector 240 is shown in
In some embodiments, the electron apparatus 40 comprises an array of condenser lenses 231, or at least a beam limiting aperture array. (In an arrangement the macro-collimator may be located up-beam of the condenser lens array, or at least the beam limiting array.) The array of condenser lenses 231 (or at least the beam limiting aperture array) generates a plurality of sub-beams from the incidental beam from the source 201. (Note if item 231 is the beam limiting aperture array without any lensing function, the lensing function may be undertaken by the macro condenser 270). There may be many tens, many hundreds, or many thousands of condenser lenses 231. The condenser lenses 231 may comprise multi-electrode lenses and have a construction based on EP1602121A1, which document is hereby incorporated by reference in particular to the disclosure of a lens array to split an e-beam into a plurality of sub-beams, with the array providing a lens for each sub-beam. The array of condenser lenses 231 may take the form of at least two plates, acting as electrodes, with an aperture in each plate aligned with each other and corresponding to the location of a sub-beam. At least two of the plates are maintained during operation at different potentials to achieve the desired lensing effect.
In an arrangement the array of condenser lenses 231 is formed of three plate arrays in which electrons have the same energy as they enter and leave each lens, which arrangement may be referred to as an Einzel lens. Thus, dispersion only occurs within the Einzel lens itself (between entry and exit electrodes of the lens), thereby limiting off-axis chromatic aberrations. When the thickness of the condenser lenses is low, e.g. a few mm, such aberrations have a small or negligible effect. In some embodiments, the objective lens may have four or more plates which may function as electrodes.
As described above, in some embodiments, the detector 240 is between the objective lens array 241 and the sample 208. The detector 240 may face the sample 208. Alternatively, as shown in
In some embodiments, a deflector array 95 is between the detector 240 and the objective lens array 241. In some embodiments, the deflector array 95 comprises a Wien filter so that deflector array may be referred to as a beam separator. The deflector array 95 is configured to provide a magnetic field to disentangle the electrons projected to the sample 208 from the signal particles such as secondary electrons from the sample 208.
In some embodiments, the detector 240 is configured to detect signal particles by reference to the energy of the electron, i.e. dependent on a band gap. Such a detector 240 may be called an indirect current detector. The signal electrons emitted from the sample 208 gain energy from the fields between the electrodes. The signal electrons have sufficient energy once they reach the detector 240.
In some embodiments, the fluorescent strips 92 extend substantially in the horizontal direction (or orthogonal to the paths of the sub-beams). Alternatively, the electron to photon converter array 91 may comprise a plate of a fluorescent material with openings 93 for the projected electron beams.
The projected electron beams, indicated by dashed lines in
In some embodiments, the deflector array 95 comprises a magnetic deflector 96 and an electrostatic deflector 97. The electrostatic deflector 97 is configured to counteract the deflection of the magnetic deflector 96 for the projected electron beams transmitted towards the sample 208. Accordingly, the projected electron beams may be shifted to a small extent in the horizontal plane. The beams down-beam of the deflector array 95 are substantially parallel to the beams up-beam of the deflector array 95.
In some embodiments, the objective lens array 241 comprises a plurality of plates for guiding signal electrons created in the sample 208 towards the deflector array 95. For the signal electrons, which travel in opposite direction with respect to the projected electron beams, the electrostatic deflector 97 does not counteract the deflection of the magnetic deflector 96. Instead, the deflections of the signal electrons by the electrostatic deflector 97 and the magnetic deflector 96 add up. Accordingly, the signal electrons are deflected to travel at an angle with respect to the optical axis in order to transmit the secondary electrons onto the fluorescent strips 92 of the detector 240.
At the fluorescent strips 92, photons are created upon incidence of the signal electrons such as secondary electrons. In some embodiments, the photons are transported from the fluorescent strip 92 to a photo detector (not shown) via a photon transport unit. In some embodiments, the photon transport unit comprises an array of optical fibers 98. Each optical fiber 98 comprises an end which is arranged adjacent or attached to one of the fluorescent strips 92 for coupling photons from the fluorescent strip 92 into the optical fiber 98, and another end which is arranged to project photons from the optical fiber 98 onto the photo detector.
The objective lens array 241 of any example may comprise at least two electrodes in which are defined aperture arrays. In other words, the objective lens array comprises at least two electrodes with a plurality of holes or apertures.
The objective lens array 241 may comprise two electrodes, as shown in
Adjacent electrodes of the objective lens array 241 are spaced apart from each other along the sub-beam paths. The distance between adjacent electrodes, in which an insulating structure might be positioned as described below, is larger than the objective lens.
Preferably, each of the electrodes provided in the objective lens array 241 is a plate. The electrode may otherwise be described as a flat sheet. Preferably, each of the electrodes is planar. In other words, each of the electrodes will preferably be provided as a thin, flat plate, in the form of a plane. Of course, the electrodes are not required to be planar. For example, the electrode may bow due to the force due to the high electrostatic field. It is preferable to provide a planar electrode because this makes manufacturing of the electrodes easier as known fabrication methods can be used. Planar electrodes may also be preferable as they may provide more accurate alignment of apertures between different electrodes.
The objective lens array 241 can be configured to demagnify the electron beam by a factor greater than 10, desirably in the range of 50 to 100 or more.
A detector 240 is provided to detect signal electrons for example secondary and/or backscattered electrons emitted from the sample 208. The detector 240 is positioned between the objective lenses 234 and the sample 208. The detector 240 may otherwise be referred to as a detector array or a sensor array, and the terms “detector” and “sensor” are used interchangeably throughout the application.
In some embodiments, the electron-optical device 41 is configured to project a beam of electrons towards the sample 208. The electron-optical device 41 may comprise the objective lens array 241. The electron-optical device 41 may comprise the detector 240. The array of objective lenses (i.e. the objective lens array 241) may correspond with the array of detectors (i.e. the detector 240) and/or any of the beams (i.e. the sub-beams). As will be described with respect to
As shown in
As shown in
As shown in
In the arrangement shown in
In some embodiments, the controller 50 is configured to control the voltage applied to the middle electrode 254 and the down-beam electrode 255 of the control lens array 250 in order to adjust the focus of the incoming sub-beams.
In some embodiments, the controller 50 is configured to control the objective lenses of the objective lens array 241 to operate as decelerating lenses. The controller 50 may control the voltages applied to the electrodes 242, 243 of the objective lens array 241 such that the objective lenses decelerate the electrons of the sub-beams that are projected toward the sample 208. The controller 50 is configured to adjust the voltages applied to the electrodes 242, 243 during use of the electron-optical device 41.
As shown in
In the arrangement shown in
As shown in
As shown in
As shown in
In some embodiments, the controller 50 is configured to control the electron apparatus 40 to operate to detect signal particles emitted by the sample 208. As shown in
An exemplary detector 240 is described below. However, any reference to the detector 240 could be a single detector (i.e. at least one detector) or multiple detectors, for example positioned along the multi-beam path (or example a path of the multibeam), as appropriate. The detector 240 may comprise detector elements 405 (e.g. sensor elements such as capture electrodes). The detector 240 may comprise any appropriate type of detector. For example, capture electrodes for example to detect directly electron charge, scintillators or PIN elements can be used. The detector 240 may be a direct current detector or an indirect current detector. The detector 240 may be a detector as described below in relation to
The detector 240 may be positioned between the objective lens array 241 and the sample 208. The detector 240 is configured to be proximate the sample 208. The detector 240 may be very close to the sample 208. Alternatively, there may be a larger gap between, the detector 240 and the sample 208. The detector 240 may be positioned in the device so as to face the sample 208. Alternatively, the detector 240 may be positioned elsewhere in the electron-optical device 41 such that part of the electron-optical device that faces the sample 208 is other than, and thus is not, a detector. For example the detector 240 may have a part at least associated with an electrode of the objective lens array 241.
For a multi-beam system of the type shown in
In some embodiments, the beam apertures 406 have a pitch P of at least 20 μm, optionally at least 50 μm, optionally at least 100 μm, optionally at least 200 μm and optionally 210 μm. A greater pitch allows for the diameter d of the beam apertures 406 to be greater. In some embodiments, the beam apertures 406 have a pitch P of at most 1000 μm, optionally at most 500 μm, and optionally at most 250 μm. The pitch of the beam apertures 406 defines the pitch of the sub-beams of the multi-beam of sub-beams (or multi-beam of electrons) that is projected toward the sample 208. In some embodiments, the sub-beams of the multi-beam of electrons have a pitch of at least 50 μm, optionally at least 100 μm, optionally at least 200 μm and optionally 210 μm. In some embodiments, the beam apertures 406 have a diameter d that is less than the pitch P. In some embodiments, the beam apertures 406 have a diameter d that is at least 10 μm, and optionally at least 20 μm. In some embodiments, the beam apertures 406 have a diameter d that is at most 100 μm, optionally at most 50 μm, and optionally at most 30 μm. A smaller diameter d improves the resolution such that smaller defects can be detected.
A wiring layer 408 is provided on the backside of, or within, the substrate 404 and connected to the logic layer 407 by through-substrate vias 409. The number of through-substrate vias 409 need not be the same as the number of beam apertures 406. In particular if the electrode signals are digitized in the logic layer 407 only a small number of through-silicon vias may be required to provide a data bus. The wiring layer 408 can include control lines, data lines and power lines. It will be noted that in spite of the beam apertures 406 there is ample space for all necessary connections. The detection module 402 can also be fabricated using bipolar or other manufacturing techniques. A printed circuit board and/or other semiconductor chips may be provided on the backside of detector 240.
The integrated detector array described above is particularly advantageous when used with a tool having tunable landing energy as signal electron, e.g. secondary electron, capture can be optimized for a range of landing energies.
The detector 240 may be implemented by integrating a CMOS chip detector into a bottom electrode of the objective lens array 241. Integration of a detector 240 into the objective lens array 241 or other component of the electron-optical device 41 allows for the detection of electrons emitted in relation to multiple respective sub-beams. The CMOS chip is preferably orientated to face the sample (because of the small distance (e.g. 50 μm or less) between the sample and a bottom of the electron-optical column). In some embodiments, detector elements 405 to capture the signal electrons are formed in the surface metal layer of the CMOS device. The detector elements 405 can be formed in other layers. Power and control signals of the CMOS may be connected to the CMOS by through-silicon vias. For robustness, preferably a passive silicon substrate with holes shields the CMOS chip from high E-fields.
In order to maximize the detection efficiency it is desirable to make the surface of the detector elements 405 as large as possible, so that substantially all the area of the objective lens array 241 (excepting the apertures) is occupied by detector elements 405. Additionally or alternatively, each detector element 405 has a diameter substantially equal to the array pitch (i.e. the aperture array pitch described above in relation to the electrodes of the objective lens assembly 241); preferably with electrically isolating material separating the detector elements. Therefore, the diameter of each detector element may be less than approximately 600 μm, and preferably between approximately 50 μm and 500 μm. As described above, the pitch may be selected depending on the intended distance between the sample 208 and the detector 240. In some embodiments, the outer shape of the detector element 405 is a circle, but this can be made a square to maximize the detection area. Also the diameter of the through-substrate via 409 can be minimized. A typical size of the electron beam is in the order of 5 to 15 micron.
In some embodiments, a single detector element 405 surrounds each beam aperture 406. In some embodiments, a plurality of detector elements 405 are provided around each beam aperture 406. The electrons captured by the detector elements 405 surrounding one beam aperture 406 may be combined into a single signal or used to generate independent signals. The detector elements 405 may be divided radially. The detector elements 405 may form a plurality of concentric annuluses or rings. The detector elements 405 may be divided angularly. The detector elements 405 may form a plurality of sector-like pieces or segments. The segments may be of similar angular size and/or similar area. The electrode elements may be separated both radially and angularly or in any other convenient manner.
However a larger surface for the detector elements 405 leads to a larger parasitic capacitance, so a lower bandwidth. For this reason it may be desirable to limit the outer diameter of the detector elements 405. Especially in case a larger detector element 405 gives only a slightly larger detection efficiency, but a significantly larger capacitance. A circular (annular) detector element 405 may provide a good compromise between collection efficiency and parasitic capacitance.
A larger outer diameter of the detector element 405 may also lead to a larger crosstalk (sensitivity to the signal of a neighboring hole). This can also be a reason to make the outer diameter of the detector element 405 smaller. Especially in case a larger detector element 405 gives only a slightly larger detection efficiency, but a significantly larger crosstalk.
The electron current collected by detector element 405 is amplified, for example by an amplifier such as a TIA.
The detector may be provided with multiple portions and more specifically, multiple detecting portions . The detector comprising multiple portions may be associated with one of the sub-beams 211, 212, 213. Thus, the multiple portions of one detector 240 may be configured to detect signal particles emitted from the sample 208 in relation to one of the primary beams (which may otherwise be referred to as sub-beams 211, 212, 213). In other words, the detector comprising multiple portions may be associated with one of the apertures in at least one of the electrodes of the objective lens assembly. More specifically, the detector 405 comprising multiple portions may be arranged around a single aperture 406 as shown in
As shown in
In some embodiments, the objective lens array 241 is an exchangeable module, either on its own or in combination with other elements such as the control lens array 250 and/or the detector 240 and/or the beam shaping aperture array 262 and/or the sub-beam forming array 252. In an arrangement the whole electron-optical device 41 maybe exchangeable. The exchangeable module may be field replaceable, i.e. the module can be swapped for a new module by a field engineer. In some embodiments, multiple exchangeable modules are contained within the tool and can be swapped between operable and non-operable positions without opening the electron apparatus 40.
In some embodiments, the exchangeable module comprises an electron-optical component, and specifically may be the electron-optical device, which is on a stage permitting actuation for positioning of the component. In some embodiments, the exchangeable module comprises a stage. In an arrangement the stage and the exchangeable module may be an integral part of the tool 40. In an arrangement the exchangeable module is limited to the stage and the device, such as the electron-optical device, it supports. In an arrangement the stage is removable. In an alternative design the exchangeable module comprising the stage is removable. The part of the electron apparatus 40 for the exchangeable module is isolatable, that is the part of the electron apparatus 40 is defined by a valve up-beam and a valve down-beam of the exchangeable module. The valves can be operated to isolate the environment between the valves from the vacuum up-beam and down-beam of the valves respectively enabling the exchangeable module to be removed from the electron apparatus 40 whilst maintaining the vacuum up-beam and down-beam of the part of the electron apparatus 40 associated with the exchangeable module. In some embodiments, the exchangeable module comprises a stage. The stage is configured to support a device, such as the electron-optical device, relative to the beam path. In some embodiments, the module comprises one or more actuators. The actuators are associated with the stage. The actuators are configured to move the device relative to the beam path. Such actuation may be used to align the device and the beam path with respect to each other.
In some embodiments, one or more aberration correctors are provided that reduce one or more aberrations in the sub-beams. The one or more aberration correctors may be provided in any of the embodiments, e.g. as part of the electron-optical device, and/or as part of an optical lens array assembly, and/or as part of an assessment system. In some embodiments, each of at least a subset of the aberration correctors is positioned in, or directly adjacent to, a respective one of the intermediate foci (e.g. in or adjacent to the intermediate image plane). The sub-beams have a smallest cross-sectional area in or near a focal plane such as the intermediate plane. This provides more space for aberration correctors than is available elsewhere, i.e. up-beam or down-beam of the intermediate plane (or than would be available in alternative arrangements that do not have an intermediate image plane).
In some embodiments, aberration correctors positioned in, or directly adjacent to, the intermediate foci (or intermediate image plane) comprise deflectors to correct for the source 201 appearing to be at different positions for different beams. Correctors can be used to correct macroscopic aberrations resulting from the source that prevent a good alignment between each sub-beam and a corresponding objective lens.
The aberration correctors may correct aberrations that prevent a proper column alignment. Such aberrations may also lead to a misalignment between the sub-beams and the correctors. For this reason, it may be desirable to additionally or alternatively position aberration correctors at or near the condenser lenses 231 (e.g. with each such aberration corrector being integrated with, or directly adjacent to, one or more of the condenser lenses 231). This is desirable because at or near the condenser lenses 231 aberrations will not yet have led to a shift of corresponding sub-beams because the condenser lenses are vertically close or coincident with the beam apertures. A challenge with positioning correctors at or near the condenser lenses, however, is that the sub-beams each have relatively large sectional areas and relatively small pitch at this location, relative to locations further down-beam. The aberration correctors may be CMOS based individual programmable deflectors as disclosed in EP2702595A1 or an array of multipole deflectors as disclosed EP2715768A2, of which the descriptions of the beamlet manipulators in both documents are hereby incorporated by reference.
In some embodiments, each of at least a subset of the aberration correctors is integrated with, or directly adjacent to, the objective lens array 241. In some embodiments, these aberration correctors reduce one or more of the following: field curvature; focus error; and astigmatism. Additionally or alternatively, one or more scanning deflectors (not shown) may be integrated with, or directly adjacent to, the objective lens array 241 for scanning the sub-beams 211, 212, 213 relative to, for example over, the sample 208. In some embodiments, the scanning deflectors described in US 2010/0276606, which document is hereby incorporated by reference in its entirety, may be used.
Features of the electron apparatus 40 that are described above are not described again below, so as to avoid repetition. In some embodiments, the electron apparatus 40 comprises a source 201, a macro collimator 270, a macro deflector 265, a sub-beam forming array 252, a control lens array 250, an objective lens array 241 and a beam shaping aperture array 262 as described above with reference to
As shown in
In some embodiments, the tube 70 is configured to operate at a first potential difference from ground (or liner potential difference). The tube 70 maybe connected to a potential source to set the tube 70 at the first potential difference. The tube 70 maybe electrically connected to the controller 50. In some embodiments, the tube 70 is configured to accelerate the electron beam toward the sample 208. In some embodiments, the controller 50 is configured to control the first potential difference. The first potential difference may be controlled so as to control the acceleration of the electron beam toward the sample 208. In embodiments the electric potential of various elements of the electron apparatus 40 are controlled. Each of these controlled elements is connected, or connectable, to a potential source. The controller 50 (or another controller) is configured to control the potential applied to the respective element.
The tube 70 maybe at high voltage. For example, the first potential difference may be greater than 100V, optionally at least 200V, optionally at least 500V, optionally at least 1 kV, optionally at least 2 kV, optionally at least 5 kV, optionally at least 10 kV, optionally at least 20 kV, optionally at least 30 kV, and optionally at least 60 kV. When the charged particles are negatively charged e.g. electrons, the tube 70 maybe at a high positive voltage. Alternatively, when the charged particles are positively charged, the tube 70 maybe at a high negative voltage. The tube 70 is configured to cause the electrons of the electron beam to travel through the electron apparatus 40 (i.e. from the source 201 to the sample 208) at high energy.
In some embodiments, the electron apparatus 40 comprises a support 207, for example as described above with reference to
In some embodiments, the first potential difference is greater than the second potential difference. That is the difference of the linear potential from ground is greater than the sample potential difference from ground. The second potential difference may be less than half of the first potential difference. In some embodiments, the second potential difference is substantially zero. The sample 208 may be held at ground potential. Alternatively, the sample 208 may be at a low voltage, for example proximate to the ground potential (which may be referred to as a proximate potential) Note with reference to the potential of the sample, ground potential may be considered to refer to sample being at proximate potential. For example, the second potential difference may be at most 100V, optionally at most 50 V, optionally at most 20V, optionally at most 10 V and optionally at most 5V.
Some embodiments of the present disclosure are expected to reduce the risk of damaging the sample 208 and features of the electron apparatus 40 such as of the electron-optical device 41 which may include the detector 240 positioned very close to the sample 208. The lower voltage of the sample 208 reduces the possibility of electrical breakdown with or in the immediate environment of the sample 208. This can reduce the possibility of the sample 208 being damaged. The risk of damage to components of the electron-optical device 41 such as the detector 240 (which may feature delicate electronic elements) may be reduced.
In some embodiments, the electron apparatus 40 comprises a motorized stage 209, for example as described above with reference to
Some embodiments of the present disclosure are expected to simplify the design of the motorized stage 209. By providing the sample 208 at a lower voltage, the motorized stage 209 may similarly be at a low voltage, e.g. ground. The design of electrical connection to and within the motorized stage 209 may be simplified. In particular the possibility of electrical breakdown between the motorized stage and components at ground is reduced because the motorized stage 209 is at a lower voltage. Thus the risk of damage to the sample 208 supported by the stage 209, the stage 209, and elements of the electron-optical device 41 close to the stage 209 is desirably reduced. This reduces the need for connections to be designed specifically for high voltage environments.
As described above and shown in
In some embodiments, the electron beam is extracted to high energy. In particular, the electron beam from the cathode 121 may be accelerated in the source (e.g. by the anode 122), and thus extracted from the electron source 201 as a high energy electron beam for example along the charged particle path. The electron apparatus 40 is configured such that the electrons of the electron beam travel through the electron apparatus 40 at high energy. Some embodiments of the present disclosure are expected to maintain the resolution of the inspection of the sample 208. The alternative possibility of extracting the electron beam only to low energy is known. This means that the electron beam is at low energy along the multi-beam path (or charged particle path) through the electron apparatus 40 towards the sample 208. This can increase the impact of chromatic aberration and electron-electron interaction, which can lower resolution. Some embodiments of the present disclosure are expected to achieve lower chromatic aberration and/or higher resolution compared to such an alternative configuration.
In some embodiments, the cathode 121 is configured to operate at a lower voltage than the tube 70. Thus, the cathode 121 is configured to operate at a lower voltage than a cathode potential difference. For example, the cathode 121 may be at a potential difference of at most 15 kV, optionally at most 10 kV, optionally at most 5 kV, optionally at most 2 kV and optionally at most 1 kV from ground. The cathode 121 may be configured to operate at a negative voltage.
In some embodiments, the potential difference between the sample 208 and the cathode 121 is less than the potential difference between the sample 208 and the tube 70. The potentials of the cathode 121, the tube 70 and the sample 208 (e.g. the sample potential difference, the cathode potential difference and the liner potential difference) are controlled such that the electrons of the electron beam decelerate before reaching the sample 208. The electron apparatus 40 is configured such that the electrons land on the sample 208 (i.e. are incident with the sample 208) with a low landing energy, for example of the order of about 1 keV.
In some embodiments, the potential difference between the tube 70 and the cathode 121 is at least 1 kV, optionally at least 2 kV, optionally at least 5 kV, optionally at least 10 kV optionally at least 20 kV, optionally at least 30 kV, and optionally at least 60 kV. The tube 70 is thus configured such that the electrons of the electron beam travel through the electron apparatus 40, i.e. at high energy. This helps to reduce chromatic aberration and electron-electron interaction, thereby improving resolution.
In some embodiments, the tube 70 is at the same electric potential as the anode 122. Alternatively, there may be a non-zero potential difference between the anode 122 and the tube 70. The potential difference between the tube 70 and the anode 122 may be at most 100V, optionally at most 50V, optionally at most 20V, optionally at most 10V and optionally at most 5V. The most up-beam end of the tube 70 is the part of the tube 70 that is located closest to the anode 122. The most up-beam end of the tube 70 may be referred to as a termination 71 of the tube 70. The tube 70 may terminate at its most up-beam end, or termination 71, in a region where there is a small electric field or no electric field. This can help to reduce, or even prevent, any lensing effect on the electron beam which may otherwise be caused by such an electric field.
As shown in
Alternatively, the tube 70 maybe separated from the source 201. The tube 70 maybe distanced along the axial direction from the anode 122. When the anode 122 and the tube 70 are at the same potential, no electric field is formed between the tube 70 and the anode 122. Alternatively, when there is a potential difference between the tube 70 and the anode 122, there may be an electric field formed between the tube 70 and the anode 122. In some embodiments, the gap in the axial direction between the anode 122 and the tube 70 is at most 1 mm. By providing that the gap is small, any electric field formed between the tube 70 and the anode 122 is particularly confined to a small region. Preferably the small region is remote from, i.e. removed from, the multi-beam path (charged particle path) of the multi-beam of electrons; that is the small region is remote from the path of the multibeam (i.e. the paths of the sub-beams). This may help to reduce any undesirable effect of the electric field on the electron beam.
As shown in
In some embodiments, the potential difference between the ending 72 (i.e. the most down-beam end of the tube 70) and the most up-beam electrostatic component of the down-beam device 42 is less than the liner potential difference (e.g. the first potential difference). For example, in the arrangement shown in
In some embodiments, the potential difference between the ending 72 of the tube 70 and the up-beam plate of the down-beam device 42 is less than the liner potential difference (i.e. the first potential difference). The potential difference between the ending 72 of the tube 70 and the most up-beam electrostatic component of the down-beam device 42 maybe at most 100V, optionally at most 50V. optionally at most 20V, optionally at most 10V, optionally at most 5V and optionally substantially zero. In some embodiments, the most up-beam electrostatic component of the down-beam device 42 is at the same electric potential as the ending 72 of the tube 70.
Some embodiments of the present disclosure are intended such that the electron beam passes through the electron apparatus 40 without unduly introducing undesirable lensing effects on the electron beam. The ending 72 of the tube 70 maybe in a region that has a small electric field or no electric field. This can help reduce or avoid any lensing effect on the electron beam that could be caused by an electric field between the tube 70, e.g. the ending 72, and the down-beam device 42, for example between the ending 72 and the up-beam plate. (Note the down-beam device 42 is located between the tube 70 and the sample 208).
As shown in
As shown in
In some embodiments, the tube 70 is electrically connected to the electron-optical device 41 that is down-beam of the tube 70, e.g. the ending 72. For example, the tube 70 maybe structurally connected to the associated plate, for example the sub-beam forming array 252. The tube 70 maybe integral with the associated plate.
As shown in
In some embodiments, the macro collimator 270 comprises an electrostatic component. Such an electrostatic component may be affected by the tube 70, for example its shielding of electrostatic fields external to the tube 70 relative to the path of the multi-beam of electrons. In some embodiments, the electrostatic component of the macro collimator 270 is located within the tube 70. The macro collimator 270 is configured to act on the electron beam without being hindered, for example the electrostatic fields generated by the macro collimator 270 being shielded by the tube 70.
It is noted that some embodiments exists in which an electrostatic collimator array is provided integrated into the electron-optical device 41. The collimator array (not depicted) may be associated with the beam forming array 252 and/or the control lens array 250. In an arrangement an electrostatic collimator of the array is associated with the path of a sub-beam of the multi-beam.
In some embodiments, the tube 70 comprises at least one section, each section extending along different positions along the multi-beam path and surrounding the multi-beam path. That is, each section may extend along different positions along the charged particle path and surrounding the charged particle path, such as at least part of one of the primary beam path and the path of the multibeam. In some embodiments, the macro collimator 270 adjoins at least one section of the tube 70. For example the macro collimator 270 may be located between a section of the tube 70 and an adjoining component of the electron-optical device 41. In some embodiments, the macro collimator 270 is between adjoining sections of the tube 70. The adjoining sections of the tube 70 may extend in a similar or even common direction, for example between the source and the sample. The different sections may extend substantially along and around the path of the charged particles from the source to the sample and/or a geometrical axis of the charged particle path from the source to the sample.
In some embodiments, the electron apparatus 40 comprises a macro scan deflector 265. The macro scan deflector 265 is configured to deflect respective portions of the electron beam for example along the charged particle path. The different portions of the beam correspond to different sub-beams further down-beam for example down beam along the charged particle path. Deflection of the portions by the macro scan deflector 265 thus causes deflection of the respective sub-beams of electrons, in the multi-beam, to be scanned relative to, for example over, the sample 208. As shown in
As shown in
In some embodiments, a scan deflector comprising an array of deflectors may be provided instead of a macro scan deflector. Such an array of deflectors is provided within the electron-optical device 41 as an array of scan deflectors 260 as depicted in
In some embodiments, the potential difference between the most down-beam component of the electron-optical device 41 and ground is less than the first potential difference (i.e. the linear potential difference) for example with respect to the ground potential. The components of the electron-optical device 41 down-beam of the tube 70 are configured to decelerate the electron beam. The most down-beam component of the electron-optical device 41, or in other words the component that in use faces a sample 208, may have a potential close to that of the sample 208 and/or close to ground. In some embodiments, the most down-beam component is a plate of the down-beam device 42. For example, the most down-beam component may comprise at least part of the detector 240.
As described above, the electron-optical device 41 comprises an objective lens array 241 comprising a plurality of objective lenses configured to focus respective sub-beams of the multi-beam of electrons on the sample 208. The objective lens array 241 is down-beam of the tube 70. The down-beam device 42 comprises the objective lens array 241. The down-beam device 42 maybe referred to as an objective lens assembly.
The ending 72 of the tube 70 is in a region with small or no electric fields. Preferably any generated electrically field is remote, for example radially distant, from the path of the electrons in the beam from the source. The objective lenses focus the sub-beams onto the sample 208. It is not necessary, indeed it is even preferable to avoid introduction of aberrations to the sub-beams, for the tube 70 to be used to form electric fields that focus the sub-beams onto the sample 208.
In some embodiments, the macro scan deflector 265 comprises an electrostatic component, desirably a macro electrostatic component. In the present arrangement, at the position of the beam path, the beam is a single beam of electrons suited for operation on by a macro scan deflector 265. Performance of such an electrostatic component may be affected by the tube 70 because, for example, the tube 70 is likely to shield some or all of the electric field generated by the electrostatic component. In some embodiments, the tube 70 comprises at least one section, each section extending along different positions along the charged particle path surrounding the primary beam path and/or the path of the multibeam (or multi-beam path and surrounding the multi-beam path). As shown in
For example, in the arrangement shown in
As shown in
The electrostatic component that is located between adjacent sections 70a, 70b of the tube 70 can act on the electron beam without being hindered by the tube 70; that is without the tube shielding or at least interfering with the electrostatic field generated by the component. In some embodiments, the electrostatic component is at the same electric potential as at least one of the sections 70a, 70b of the tube 70 between which the electrostatic component is located. In some embodiments, the electrostatic component is at the same electric potential as both of the sections 70a, 70b of the tube 70 between which the electrostatic component is located, for example as depicted in
In some embodiments, the electrostatic component is distanced from each of the sections 70a, 70b in the axial direction by no more than 1 mm. Any unwanted electric fields may be confined to small axial distances, which are preferably radially remote from the path of the beam of electrons, so as to reduce if not prevent effect of any generated electric fields on the electron beam.
In some embodiments, the electrostatic component of the macro scan deflector 265 is located within the tube 70. The macro scan deflector 265 is configured to act on the electron beam without being hindered by the tube 70; that is the field generated by the electrostatic macro scan deflector 265 may operate on the beam of electrons without being shielded and thus hindered by the tube 70. However, this example may be less preferred because it requires electrical connections within the shielding of the tube 70.
In a variation, the macro scan deflector 265 may have magnetic and electrostatic components. In some embodiments, the arrangement may take the form as described with reference to and as depicted in
In this arrangement, the control lens array 250, the array of scan deflectors 260, the objective lens array 241 and the detector array 240 may be comprised in the electron-optical device 41. The control lens array 250, the array of scan deflectors 260 and the objective lens array 241 and optionally the array of deflectors 235 may be integrated together.
As shown in
As described above with reference to
In some embodiments, the sub-beams of electrons in the multi-beam are formed up-beam of the most down-beam end of the tube 70. For example, the sub-beams may be generated at the array of condenser lenses 231, preferably a sub-beam forming array which may either be separate from the plates of the condenser lens array or an up-beam most plate of the condenser lens array 231, i.e. integral to the condenser lens array.
In some embodiments, at least one of the electrodes of the array of condenser lenses 231 is at substantially the same potential as at least one of the sections 70a, 70c of the tube 70 between which the array of condenser lenses 231 is located. That is an electrode or plate of the condenser lens array that is an up-beam most or down-beam most electrode of the condenser lens array may be the same potential as the adjacent section 70a, 70c of the tube 70. As described above, in some embodiments, the array of condenser lenses 231 is formed of three plate arrays 231a, 231b, 231c in which the potential differences are controlled such that the electrons in the sub-beams have the same energy on entering a respective condenser lens as on leaving the respective condenser lens. This lens arrangement may be referred to as an Einzel lens. In some embodiments, the most up-beam plate array 231a is at substantially the same potential as the ending 72 of the up-beam section 70a of the tube 70. In a variation there may be a small (e.g. no more than 100V) potential difference between the most up-beam plate array 231a and the up-beam section 70a of the tube 70. In some embodiments, the most down-beam plate array 231c is at substantially the same potential as the intermediate section 70c of the tube 70. In a variation there may be a small (e.g. no more than 100V) potential difference between the most down-beam plate array 231c and the intermediate section 70c of the tube 70. Some embodiments of the present disclosure are expected to minimize any unwanted electric fields at the terminations 71 and endings 72 of the sections 70a, 70b, 70c of the tube 70, for example specifically operating or acting on the paths of the beam and sub-beams of electrons.
As shown in
In some embodiments, the array of deflectors 235 is at substantially the same potential as at least one of, optionally both of, the adjacent sections 70b, 70c of the tube 70 between which the array of deflectors 235 is located. In some embodiments, the array of deflectors 235 is at substantially the same potential as the intermediate section 70c of the tube 70. In a variation, there may be a small (e.g. no more than 100V) potential difference between the array of deflectors 235 and the intermediate section 70c of the tube 70. In some embodiments, the array of deflectors 235 is at substantially the same potential as the most down-beam section 70b of the tube 70. In a variation, there may be a small (e.g. no more than 100V) potential difference between the array of deflectors 235 and the most down-beam section 70b of the tube 70. Some embodiments of the present disclosure are expected to minimize any unwanted electric fields at the terminations 71 and endings 72 of the sections 70a, 70b, 70c of the tube 70, for example specifically operating or acting on the paths of the beam and sub-beams of electrons.
In some embodiments, the array of deflectors 235 comprises an electrostatic component. By providing the array of deflectors 235 between sections 70b, 70c of the tube 70, the operation of the array of deflectors 235 is unhindered by the tube 70. The deflector array 235 is positioned with respect to the tube 70 such that the tube 70 does not shield the electrostatic fields generated by the array of deflectors 235 so that the deflectors may operate on the sub-beams of electrons, in the multi-beam.
As shown in
In an arrangement the macro scan deflector 236 is configured to deflect sub-beams so as to cause the sub-beams to be scanned relative to the surface of the sample 208, for example over the sample 208. The macro scan deflector 236 may be down-beam of the tube 70. Alternatively, the macro scan deflector 236 may be up-beam of the most down-beam end of the tube 70.
As shown in
In some embodiments, the most up-beam electrostatic component of the down-beam device 42 is at a different electric potential from the ending 72 of the tube 70 or down-beam section 70b. For example, in the arrangement shown in
As shown in
In the arrangement shown in
In some embodiments, at least one of the electrodes of the array of condenser lenses 231 is at substantially the same potential as at least one of the sections 70a, 70b of the tube 70 between which the array of condenser lenses 231 is located. As described above, in some embodiments, the array of condenser lenses 231 is formed of three plate arrays 231a, 231b, 231c in which electrons have the same energy as they enter and leave each lens, which arrangement may be referred to as an Einzel lens. In some embodiments, the up-beam plate array 231a is at substantially the same potential as the up-beam section 70a of the tube 70. In a variation, there may be a small (e.g. no more than 100V) potential difference between the up-beam plate array 231a and the up-beam section 70a of the tube 70. In some embodiments, the down-beam plate array 231c is at substantially the same potential as the down-beam section 70b of the tube 70. In a variation, there may be a small (e.g. no more than 100V) potential difference between the down-beam plate array 231c and the down-beam section 70b of the tube 70. Some embodiments of the present disclosure are expected to minimize any unwanted electric fields at the ending 72 of the up-beam section 70a adjacent the condenser lens array 231 and at the termination 71 of the down-beam section 70b of the tube 70. The ending 72 of the down-beam section 70b of the tube 70, for example with respect to down-beam device 42 down-beam of the ending of the down-beam section 70b, is controlled to provide an electric field adjacent to the ending 72 so as to form the half lens 237.
In some embodiments, the electrostatic component of the electron-optical device 41 immediately down-beam of the tube 70 may have a similar (or the same) potential as the anode 122 and/or the up-beam section 70a of the tube 70. As explained above a potential difference may be controlled between the down-beam section 70b of the tube 70 and the electrostatic component of the electron-optical device 41 immediately down-beam of the tube 70. There may be a potential difference between the up-beam section 70a of the tube 70 and the down-beam section 70b of the tube 70. The potential difference may be at least 1 kV, optionally at least 2 kV and optionally at least 5 kV. The potential difference may be at most 10 kV and optionally at most 5 kV. There may be a potential difference between the up-beam plate array 231a and the down-beam plate array 231c. The potential difference may be at least 1 kV, optionally at least 2 kV and optionally at least 5 kV. The potential difference may be at most 10 kV and optionally at most 5 kV. Electrons may have a slightly different energy as they enter and leave each lens of the array of condenser lenses 231. The array of condenser lenses 231 functions substantially as an array of Einzel lenses.
As shown in
As shown in
In the arrangement shown in
As mentioned above, in some embodiments, one or more aberration correctors are provided that reduce one or more aberrations in the sub-beams for example generated by fields associated with an ending 72 or termination 71 of the tube 70 or a section 70a, 70b, 70c of the tube 70. In some embodiments, the down-beam device 42 comprises one or more aberration correctors. Additionally or alternatively, one or more aberration correctors may be provided up-beam of the most down-beam end of the tube 70. For example, one or more aberration correctors may be associated with the condenser lens array 231 shown in
The embodiments of the present disclosure can be applied to various different tool architectures. For example, the electron apparatus 40 may comprise a plurality of electron-optical columns of multi-beams. The electron-optical columns may comprise the electron-optical device 41 described in any of the above embodiments or aspects. As a plurality of electron-optical columns (or a multi-column tool), the devices may be arranged in an array which may number two to one hundred electron-optical columns or more. The electron apparatus 40 may take the form of an example as described with respect to and depicted in
In some embodiments, the electron apparatus 40 comprises a plurality of electron-optical devices as depicted in the figures, for example at least
In some embodiments, there is provided a method for projecting a multi-beam of electrons toward a sample 208.
In some embodiments, the method comprises emitting an electron beam. In some embodiments, the method comprises projecting toward the sample 208 sub-beams of a multi-beam of electrons derived from the electron beam using an electron-optical device 41. The multi-beam of electrons may be for detecting defects of the sample 208.
In some embodiments,, the method comprises accelerating the electron beam toward the sample 208 using a tube 70 surrounding the multi-beam path, may be referred to as at least part of the charged particle path and may be the primary beam path and/or the path of the multibeam. The tube operates at the first potential difference from ground.
In some embodiments, the method comprises holding the sample 208 at a second potential difference from ground. The first potential difference is greater than the second potential difference. The second potential difference may be substantially zero.
Reference to a component or system of components or elements being controllable to manipulate an electron beam in a certain manner includes configuring a controller or control system or control unit to control the component to manipulate the electron beam in the manner described, as well optionally using other controllers or devices (e.g. voltage supplies and or current supplies) to control the component to manipulate the electron beam in this manner. For example, a voltage supply may be electrically connected to one or more components to apply potentials to the components, such as in a non-limited list the control lens array 250, the objective lens array 241, the condenser lenses 231, correctors, a collimator element array and deflector arrays 235, 265, under the control of the controller or control system or control unit. An actuatable component, such as a stage, may be controllable to actuate and thus move relative to another components such as the beam path using one or more controllers, control systems, or control units to control the actuation of the component.
The embodiments herein described may take the form of a series of aperture arrays or electron-optical elements arranged in arrays along a beam or a multi-beam path; that is along the charged particle path between the source and the sample, for example along the path of a primary beam and/or a multibeam such as a plurality of sub-beams . Such electron-optical elements may be electrostatic. In some embodiments, all the electron-optical elements, for example from a sub-beam forming array to a last electron-optical element in a sub-beam path before a sample, may be electrostatic and/or may be in the form of an aperture array or a plate array.
In some arrangements one or more of the electron-optical elements are manufactured as a microelectromechanical system (MEMS) (i.e. using MEMS manufacturing techniques). MEMS are miniaturized mechanical and electromechanical elements that are made using microfabrication techniques. For example, in some embodiments, the exchangeable module is a MEMS module.
In some embodiments, the exchangeable module is configured to be replaceable within the electron apparatus 40. In some embodiments, the exchangeable module is configured to be field replaceable. Field replaceable is intended to mean that the module may be removed and replaced with the same or different module while maintaining the vacuum in which the electron-optical tool 40 is located. Only a section of the electron apparatus 40 is vented corresponding to the module is vented for the module to be removed and returned or replaced. The control lens array 250 may be in the same module as an objective lens array 241, i.e. forming an objective lens array assembly or objective lens arrangement, or it may be in a separate module.
References to upper and lower, up and down, above and below should be understood as referring to directions parallel to the (typically but not always vertical) up-beam and down-beam directions of the beam or multi-beam of electrons impinging on the sample 208. Thus, references to up beam and down beam are intended to refer to directions in respect of the beam path independently of any present gravitational field.
An electron apparatus according to some embodiments of the disclosure may be a tool which makes a qualitative assessment of a sample (e.g. pass/fail), one which makes a quantitative measurement (e.g. the size of a feature) of a sample or one which generates an image of map of a sample. Examples of assessment systems are inspection tools (e.g. for identifying defects), review tools (e.g. for classifying defects) and metrology tools, or tools capable of performing any combination of assessment functionalities associated with inspection tools, review tools, or metrology tools (e.g. metro-inspection tools). The electron-optical column may be a component of an assessment system; such as an inspection tool or a metro-inspection tool, or part of an e-beam lithography tool. Any reference to a tool herein is intended to encompass a device, apparatus or system, the tool comprising various components which may or may not be collocated, and which may even be located in separate rooms, especially for example for data processing elements.
The terms “sub-beam” and “beamlet” are used interchangeably herein and are both understood to encompass any radiation beam derived from a parent radiation beam by dividing or splitting the parent radiation beam. The term “manipulator” is used to encompass any element which affects the path of a sub-beam or beamlet, such as a lens or deflector.
References to elements being aligned along a beam path or sub-beam path are understood to mean that the respective elements are positioned along the beam path or sub-beam path.
While the present invention has been described in connection with various embodiments, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the technology disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and clauses.
Clause 1: A charged particle apparatus configured to project a multi-beam of charged particles along a multi-beam path toward a sample, the charged particle apparatus comprising: a charged particle source configured to emit a charged particle beam (or primary beam path) toward a sample (desirably the primary beam path comprising part of a path of charged particles from the source toward the sample); a charged particle-optical device configured to project sub-beams of a multi-beam of charged particles along the multi-beam path toward the sample (desirably comprising part of the path of the charged particles towards the sample), the sub-beams of the multi-beam of charged particles derived from the charged particle beam (desirably the path of the charged particle beam comprising part of the path of the charged particles towards the sample); a tube surrounding the multi-beam path configured to operate at a first potential difference from a ground potential (or at least a proximate potential desirably proximate to a ground potential); and a support configured to support the sample at a second potential difference from the ground potential (desirably greater than the proximate potential), the first potential difference and the second potential difference having a difference so as to accelerate the multi-beam of charged particles towards the sample; wherein the first potential difference is greater than the second potential difference. The path of the charged particles towards the sample may comprise the path of the multibeam. The path of the charged particles towards the sample may comprise a path of a primary beam (or the charged particle beam), desirably the primary beam is upbeam of the path of the multi-beam. The tube may extend along and surround a part of the path of the charged particles towards the sample. The tube may extend along and surround the path of the single beam and/or the multibeam path. The different parts of the path of the charged particle beam (for example the path of the multibeam and the path of the primary beam) may be related to different or separate sections of the tube.
Clause 2: A charged particle apparatus configured to project a multi-beam of charged particles along a multi-beam path toward a sample, the charged particle apparatus comprising: a charged particle source configured to emit a charged particle beam (or a primary beam) along a charged particle path towards a sample the charged particle path comprising a primary beam path (or a path of the charged particle beam); a charged particle-optical device configured to project sub-beams of a multi-beam of charged particles along a multi-beam path toward the sample, the charged particle path comprising the multi-beam path, the sub-beams of the multi-beam of charged particles derived from the charged particle beam, desirably the multi-beam of charged particles being along a part of the multi-beam path down beam of the primary beam path; a tube surrounding at least part of the charged particle path, for example the primary beam path, configured to operate at a first potential difference from a ground potential; and a support configured to support the sample at a second potential difference from the ground potential, the first potential difference and the second potential difference having a difference so as to accelerate the multi-beam of charged particles towards the sample; wherein the first potential difference is greater than the second potential difference.
Clause 3: The charged particle apparatus of clause 1 or 2, wherein the tube comprises at least one section, each section extending along different positions along the charged particle path for example the multi-beam path and surrounding at least part of the charged particle path for example the multi-beam path, desirably the tube comprising at least one section extending along the path of the charged particle beam, desirably the different sections extending a common direction, desirably the common direction substantially the path of the charged particles from the source to the sample and/or a geometrical axis of the charged particle path from the source to the sample.
Clause 4: The charged particle apparatus of clause 3, wherein at least part of the charged particle-optical device is down-beam of a most down-beam end of the tube or at least a section of the tube, the charged particle-optical device that is down-beam of the most down-beam end of the tube or at least a section of the tube being a down-beam device, desirably the multibeam path is down beam of the a most down-beam end of the tube or at least a section of the tube, desirably down beam of the at least part of the charged particle-optical device, desirably a part of the down beam device, desirably a most up beam part of the down beam device.
Clause 5: The charged particle apparatus of clause 4, wherein the potential difference between the most down-beam end of the tube and a most up-beam electrostatic component of the down-beam device is less than the first potential difference desirably with respect to the ground potential.
Clause 6: The charged particle apparatus of clause 4 or 5, wherein the most up-beam electrostatic component of the down-beam device is at the same electric potential as the most down-beam end of the tube, desirably which is less than the first potential difference.
Clause 7: The charged particle apparatus of clause 5, wherein the most up-beam electrostatic component of the down-beam device is at a different electric potential from the most down-beam end of the tube such that an electric field between the most up-beam electrostatic component of the down-beam device and the down-beam end of the tube collimates respective sub-beams of the multi-beam of charged particles.
Clause 8: The charged particle apparatus of any of clauses 4 to 7, wherein the down-beam device comprises an up-beam plate (i.e. being the most up-beam electrostatic component of the device) in which is defined an array of apertures for the paths of the sub-beams of the multi-beam of charged particles.
Clause 9: The charged particle apparatus of clause 8, wherein the down-beam device comprises a plurality of plates in each of which are defined an array of apertures for the paths of the sub-beams of the multi-beam of charged particles, the plurality of plates comprising the up-beam plate.
Clause 10: The charged particle apparatus of clause 9, wherein the up-beam plate is a sub-beam forming array, the apertures configured to form the sub-beams of the multi-beam of charged particles from the charged particle beam from the charged particle source.
Clause 11: The charged particle apparatus of clause 10, wherein the plurality of plates comprises a beam shaping aperture array in which is defined an array of beam shaping apertures for shaping the sub-beams of the multi-beam of charged particles, the beam shaping aperture array being down-beam of the up-beam plate.
Clause 12: The charged particle apparatus of any of clauses 4 to 11, wherein the down-beam device comprises an objective lens array comprising a plurality of objective lenses configured to focus respective sub-beams of the multi-beam of charged particles on the sample.
Clause 13: The charged particle apparatus of any of clauses 4 to 12, wherein the down-beam device comprises a detector.
Clause 14: The charged particle apparatus of clause 13, wherein the detector comprises a detector array comprised in one or more of the plates of the down-beam device.
Clause 15: The charged particle apparatus of clause 14, wherein the detector array comprises a detector element associated with a respective sub-beam of the multi-beam of charged particles.
Clause 16: The charged particle apparatus of clause 14 or 15, wherein at least part of the detector array is proximate the sample.
Clause 17: The charged particle apparatus of any of clauses 13 to 16, wherein at least part of the detector array is comprised in a most down-beam plate of the down-beam device.
Clause 18: The charged particle apparatus of any of clauses 13 to 17, wherein at least part of the detector array faces the sample.
Clause 19: The charged particle apparatus of any of clauses 3 to 18, wherein the charged particle-optical device comprises a scan deflector configured to deflect respective portions of the charged particle beam to cause the sub-beams of the multi-beam of charged particles to be scanned over the sample.
Clause 20: The charged particle apparatus of clause 19, wherein the scan deflector comprises a macro scan deflector.
Clause 21: The charged particle apparatus of clause 20, wherein the macro scan deflector comprises a magnetic deflector.
Clause 22: The charged particle apparatus of clause 21, wherein the magnetic deflector is outside of the tube.
Clause 23: The charged particle apparatus of any of clauses 19 to 22, wherein the scan deflector comprises an electrostatic deflector.
Clause 24: The charged particle apparatus of any of clauses 19 to 23, wherein the scan deflector comprises an array of deflectors configured to deflect respective sub-beams of the multi-beam of charged particles to cause the sub-beams to be scanned over the sample.
Clause 25: The charged particle apparatus of clause 24, wherein the deflectors are further configured to collimate respective sub-beams of the multi-beam of charged particles.
Clause 26: The charged particle apparatus of any of clauses 19 to 25, wherein at least part of the scan deflector is inside the tube.
Clause 27: The charged particle apparatus of any of clauses 19 to 26, wherein at least part of the scan deflector is between adjacent sections of the tube.
Clause 28: The charged particle apparatus of any of clauses 3 to 27, wherein the charged particle-optical device comprises at least one electrostatic component located between adjacent sections of the tube.
Clause 29: The charged particle apparatus of clause 28, wherein the electrostatic component is at substantially the same electric potential as at least one of the sections of the tube between which the electrostatic component is located.
Clause 30: The charged particle apparatus of clause 29, wherein the electrostatic component comprises a plurality of plates along the path of the multi-beam, in each plate are defined an array of apertures for the paths of the sub-beams of the multi-beam of charged particles, at least one of an up-beam plate and a down-beam plate being at the same electric potential as its adjoining section of the tube.
Clause 31: The charged particle apparatus of clause 30, wherein the up-beam plate is a sub-beam forming array, the apertures configured to form the sub-beams of the multi-beam of charged particles from the charged particle beam from the charged particle source.
Clause 32: The charged particle apparatus of any of clauses 28 to 31, wherein the at least one electrostatic component located between adjacent sections of the tube comprises an array of condenser lenses configured to direct charged particles of respective sub-beams of the multi-beam of charged particles to respective intermediate foci.
Clause 33: The charged particle apparatus of clause 32, further comprising a collimator configured to collimate the sub-beams.
Clause 34: The charged particle apparatus of clause 33, wherein the collimator is located at or around a plane of the intermediate foci.
Clause 35: The charged particle apparatus of clause 33 or 34, wherein the at least one electrostatic component being located between adjacent sections of the tube comprises at least part of the collimator.
Clause 36: The charged particle apparatus of any of clauses 33 to 35,wherein the collimator comprises a macro collimator configured to collimate respective sub-beams of the multi-beam of charged particles.
Clause 37: The charged particle apparatus of clause 36, wherein the macro collimator comprises a magnetic component.
Clause 38: The charged particle apparatus of clause 36 or 37, wherein the macro collimator is located outside of the tube.
Clause 39: The charged particle apparatus of any of clauses 36 to 38, wherein the macro collimator comprises an electrostatic component.
Clause 40: The charged particle apparatus of any of clauses 36 to 39, wherein the macro collimator is located at or near an intermediate focal plane comprising the intermediate foci.
Clause 41: The charged particle apparatus of any preceding clause, wherein a potential difference between a most down-beam component of the charged particle-optical device and the ground potential is less than the first potential difference.
Clause 42: The charged particle apparatus of clause 41, wherein the most down-beam component has a potential proximate to the second potential difference.
Clause 43: The charged particle apparatus of any preceding clause, wherein the charged particle source comprises a cathode and an anode configured to operate with a potential difference between the cathode and the anode so as to emit the charged particle beam, wherein the tube is at the same electric potential as the anode.
Clause 44: The charged particle apparatus of clause 43, wherein the tube is electrically connected to the anode.
Clause 45: The charged particle apparatus of any preceding clause, wherein the second potential difference is substantially zero.
Clause 46: The charged particle apparatus of any preceding clause, wherein the sample is at the ground potential.
Clause 47: A method for projecting a multi-beam of charged particles toward a sample, the method comprising: emitting a charged particle beam; projecting along a multi-beam path toward a sample sub-beams of a multi-beam of charged particles derived from the charged particle beam using a charged particle-optical device; accelerating the charged particle beam toward the sample using a tube surrounding the multi-beam path, wherein the tube operates at a first potential difference from a ground potential; and holding the sample at a second potential difference from the ground potential; wherein the first potential difference is greater than the second potential difference, , desirably the method comprising generating sub-beams of the multibeam from a primary beam, a path of charged particles comprising the charged particle beam and the multibeam path, desirably the primary beam path is upbeam of generation of the sub-beams desirably from the charged particle beam.
The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.
Number | Date | Country | Kind |
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21199203.7 | Sep 2021 | EP | regional |
This application claims priority of International application PCT/EP2022/074525, filed on 2 Sep. 2022, which claims priority of EP application Ser. No. 21/199,203.7, filed on 27 Sep. 2021. These applications are incorporated herein by reference in their entireties.
Number | Date | Country | |
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Parent | PCT/EP2022/074525 | Sep 2022 | WO |
Child | 18618957 | US |