Method of operating charged particle beam device and charged particle beam device

Abstract

A method of operating a charged particle beam apparatus is described. The method includes directing a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam onto the sample by using an objective lens; in a first mode of operation, excitation of the intermediate lens is provided to electronically collimate a high energy signal comprising backscattered electrons to the opening of the on-axis detector; in a first mode of operation, low energy signal electrons including secondary electrons are detected with an on-axis detector; and in the first mode of operation, detecting backscattered electrons with a second electron detector upstream of the on-axis detector. A corresponding charged particle beam apparatus is also described.

Description

Technical Field

[0001] Embodiments described herein relate to one or more lenses for a charged particle beam in a charged particle beam device, such as in an electron microscope, particularly a scanning electron microscope (SEM). In addition, embodiments of the present disclosure relate to an intermediate lens and an objective lens, and a method of operating a charged particle beam device, particularly including performing energy filtering. Specifically, embodiments relate to a method of operating a charged particle beam device and a charged particle beam device. Background Art

[0002] Modern semiconductor technology has created a high demand for structuring and probing samples at the nanometer or even sub-nanometer level. Micrometer and nanometer process control, inspection or structuring are usually accomplished with charged particle beams (e.g., electron beams), which are generated, shaped, deflected and focused in charged particle beam devices (such as electron microscopes or electron beam pattern generators). For inspection purposes, charged particle beams provide a better spatial resolution than, for example, photon beams.

[0003] Devices using charged particle beams, such as scanning electron microscopes (SEMs), have many functions in multiple industrial fields, including but not limited to inspection of electronic circuits, exposure systems for photolithography, detection systems, defect inspection tools, and test systems for integrated circuits. In such particle beam systems, a fine beam probe with a high current density can be used. For example, in the case of a SEM, a primary electron beam generates signal particles, such as secondary electrons (SE) and / or backscattered electrons (BSE), that can be used to image and / or inspect a sample.

[0004] However, it is challenging to reliably inspect and / or image samples with good resolution using charged particle beam devices. In addition, particularly in the semiconductor industry, it is advantageous, for example, to have a high throughput for image generation. The throughput can be increased by increasing the signal-to-noise ratio of the signal electrons. For example, the collection efficiency of the signal electrons can be increased.

[0005] Additionally, the measurements may be improved by additional detection modes to increase the amount of information that can be determined based on the measurement of, for example, a semiconductor wafer or another sample.

[0006] In view of the above, it would be beneficial to provide an improved method of operating a charged particle beam apparatus and an improved charged particle beam apparatus. Summary of the invention

[0007] In view of the above, a method of operating a charged particle beam device and a charged particle beam device are provided according to the independent claims.Further advantages, features, aspects and details, which may be combined with the embodiments described herein, are apparent from the dependent claims, the description and the drawings.

[0008] According to an embodiment, a method for operating a charged particle beam device is provided. The method includes: guiding a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens, and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam onto the sample with the objective lens; in a first operating mode, providing an excitation to the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector; in the first operating mode, detecting low energy signal electrons including secondary electrons with the on-axis detector; and in the first operating mode, detecting backscattered electrons with a second electron detector upstream of the on-axis detector.

[0009] According to an embodiment, a charged particle beam device is provided. The charged particle beam device includes: a charged particle beam source, the charged particle beam source is configured to generate a primary charged particle beam; a beam guiding optical device, the beam guiding optical device is configured to guide the primary charged particle beam toward a sample stage; an on-axis detector, the on-axis detector has an opening configured for intrusion of the primary charged particle beam; a second detector, the second detector is upstream of the on-axis detector; an intermediate lens, the intermediate lens is arranged between the on-axis detector and the sample stage and is configured to collimate high energy signal electrons onto the opening of the on-axis detector; an objective lens, the objective lens is arranged between the intermediate lens and the sample stage; and an energy filter, the energy filter is along the signal beam path between the opening of the on-axis detector and the second detector.

[0010] According to an embodiment, a charged particle beam device is provided. The charged particle beam device comprises: a charged particle beam source, the charged particle beam source being configured to generate a primary charged particle beam; a beam guiding optical device, the beam guiding optical device being configured to guide the primary charged particle beam toward a sample stage; an on-axis detector, the on-axis detector having an opening configured for intrusion of the primary charged particle beam; a second detector, the second detector being upstream of the on-axis detector; an intermediate lens, the intermediate lens being disposed between the on-axis detector and the sample stage and being configured to collimate high energy signal electrons onto the opening of the on-axis detector; an objective lens, the objective lens being disposed between the intermediate lens and the sample stage; and a controller, the controller having a processor and a memory storing instructions, the instructions, when executed by the processor, causing the charged particle beam device to perform a method as described in any one of the embodiments herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order that the above features of the present disclosure can be understood in detail, a more particular description of the above brief summary may be provided by reference to embodiments. The accompanying drawings relate to one or more embodiments and are described below.

[0012] Figure 1 A schematic diagram of a charged particle device according to embodiments described herein is shown.

[0013] Figure 2 A portion of a charged particle beam device, in particular an intermediate lens, an objective lens and an on-axis detector are shown to describe an embodiment according to the present disclosure.

[0014] Figure 3 A flow chart showing a method of operating a charged particle beam apparatus according to embodiments described herein is shown.

[0015] Figure 4 Comparison of graphs in a case where the intermediate lens is not operated and in a case where the intermediate lens is operated according to an embodiment of the present disclosure is shown.

[0016] Figure 5A and Figure 5B A comparison of a first operating mode and a second operating mode according to an embodiment of the present disclosure is shown.

[0017] Figure 6 A method of operating a charged particle beam apparatus according to a second mode of operation is shown. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the accompanying drawings. In the following description of the drawings, the same reference numerals denote the same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation and is not intended to be limiting. In addition, features illustrated or described as part of one embodiment may be used on other embodiments or used in conjunction with other embodiments to produce yet further embodiments. This specification is intended to include such modifications and changes.

[0019] Embodiments of the present disclosure provide an intermediate lens, in particular a composite electrostatic-magnetic objective lens, between the on-axis detector and the objective lens, for example to improve the detection efficiency of backscattered electrons (BSE) (i.e., high-energy signal electrons). Additionally or alternatively, different operating modes may be provided for energy filtering of signal electrons.

[0020] According to an embodiment, a method for operating a charged particle beam device is provided. The method includes guiding a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens, and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens. The method includes focusing the charged particle beam onto the sample with the objective lens. In a first operating mode, the intermediate lens is excited to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector. In addition, in the first operating mode, low energy signal electrons including secondary electrons are detected with the on-axis detector, and backscattered electrons are detected with a second electron detector upstream of the on-axis detector.

[0021] Figure 1 1 is a schematic diagram of a charged particle beam apparatus 100 for inspecting and / or imaging a sample 10 or a portion of a sample according to embodiments described herein. The charged particle beam apparatus 100 includes a column 102. The column 102 may provide a vacuum enclosure such that a charged particle beam travels under a vacuum. The beam optical components of the charged particle beam apparatus 100 may be placed in a vacuum chamber of the column 102, which may be evacuated. The vacuum may facilitate propagation of the charged particle beam, for example, along an optical axis 12 from a charged particle beam source 104 toward a sample stage 130. The charged particle beam may be at a sub-atmospheric pressure (e.g., less than 10 -3 mbar pressure or less than 10 -5 The sample is impacted at a pressure of 100 mbar.

[0022] The charged particle beam device 100 includes a charged particle beam source 104. The charged particle beam source may be configured to emit a charged particle beam. The charged particle beam may be an electron beam. The charged particle beam may propagate along an optical axis 12. The charged particle beam device 100 further includes a sample stage 130. The objective lens 110 focuses the charged particle beam (i.e., the primary charged particle beam) onto the sample 10. The sample may be placed on the sample stage 130.

[0023] A condenser lens 106 or a condenser lens system including one or more condenser lenses may be arranged downstream of the charged particle beam source 104. The condenser lens system may collimate the charged particle beam propagating toward the objective lens 110. In addition, an electrode or tube 107 configured to accelerate the beam may be provided. The electrode or tube may be provided at a high potential. The high potential may be, for example, a high positive potential relative to the charged particle beam source to accelerate the electron beam.

[0024] According to some embodiments, which can be combined with other embodiments described herein, the charged particle beam device may include a condenser lens or a condenser lens system, in particular between the charged particle beam source 104 and the detector (downstream of the condenser lens).

[0025] Electrode or tube 107 can provide for electron beam acceleration to the acceleration section of electron energy of 5keV or higher, for example.Electron can be first accelerated by the extraction electrode that is arranged on positive potential with respect to the emission tip of charged particle beam source 104.Electrode or tube can provide further beam acceleration.In certain embodiments, charged particle (for example, electron) is accelerated to 10keV or higher, 30keV or higher, or even 50keV or higher electron energy.High electron energy in column can reduce the negative influence of electron and electron interaction.High beam energy in charged particle beam device can improve imaging resolution.

[0026] The charged particle beam device 100 further includes two or more charged particle detectors, in particular two or more electron detectors. According to the embodiments described herein, an on-axis detector 122 is provided. In addition, a second electron detector is provided. For example, the second electron detector can be an off-axis detector 123. The on-axis detector and the second electron detector can detect signal particles emitted or released from the sample 10. When the primary charged particle beam is incident on the sample, signal electrons are emitted or released from the sample. According to different operating modes, the charged particle detectors can each detect high-energy signal electrons or low-energy signal electrons. For example, high-energy signal electrons can be backscattered electrons, and low-energy signal electrons can be secondary electrons. According to different operating modes, filtering of the signal electrons can be provided depending on the energy of the signal electrons.

[0027] Figure 1 An energy filter 140 is shown. An embodiment of the present disclosure includes an intermediate lens. The intermediate lens is configured to guide the signal electrons toward the opening of the on-axis detector or toward the second electron detector upstream of the on-axis detector. Signal loss can be reduced. In particular, for high-energy signal electrons (e.g., backscattered signal electrons), signal loss may occur, for example, depending on the starting angle. As described herein, the backscattered electrons may have an energy of 1 keV or more and even 10 keV or more. The increased detection efficiency for high-energy signal electrons improves the utilization of energy filters, especially for high-energy signal electrons. Therefore, an embodiment of the present disclosure that can be combined with other embodiments described herein may include an energy filter 140. The energy filter 140 may be provided along the signal beam path between the opening of the on-axis detector and the second electron detector upstream of the on-axis detector. According to some embodiments that can be combined with other embodiments described herein, the energy filter 140 may be configured to provide a bandpass filter. The energy filter may be a bandpass filter.

[0028] For example, a dispersive element such as an electrostatic sector or a magnetic sector (or a magnetic prism) may be provided, such as a hemispherical energy analyzer. According to some embodiments that may be combined with other embodiments described herein, the energy filter may include a spherical electrode or a curved electrode, in particular a pair of spherical electrodes or curved electrodes. The dispersive element deflects the signal electrons depending on their energy, which can typically select an energy range by, for example, a slit opening or a hole with an opening. According to some embodiments that may be combined with other embodiments described herein, the dispersive element may also include a Wien filter element having a magnetic field and an electrostatic field that are perpendicular to each other. More complex energy filters, such as Omega filters, may also be used.

[0029] According to some embodiments, which can be combined with other embodiments described herein, a beam splitter 124 may be provided. In particular for a charged particle beam device comprising an off-axis detector, the signal charged particle beam 22 may be separated from the primary charged particle beam travelling along the optical axis 12. The beam splitter 124 may comprise a magnetic deflector, wherein a beam deflection of the signal charged particle beam 22 is caused by the signal charged particle beam travelling in a direction opposite to the primary charged particle beam.

[0030] An image generation unit (not shown) may be provided. The image generation unit may be configured to generate one or more images of the sample 10. The image generation unit may generate one or more images based on the signals received from the detector. The image generation unit may forward one or more images of the sample to a processing unit (not shown).

[0031] The sample stage 130 can be a movable stage. In particular, the sample stage 130 can be moved in the Z direction (i.e., in the direction of the optical axis 12) so that the distance between the objective lens 110 and the sample stage 130 can be adjusted. By moving the sample stage 130 in the Z direction, the sample 10 can be moved to different "working distances". In addition, the sample stage 130 can also be moved in a plane perpendicular to the optical axis 12 (also referred to as the XY plane in this article). By moving the sample stage 130 in the XY plane, a specific surface area of ​​the sample 10 can be moved to an area below the objective lens 110, such as a field of view (FOV), so that a specific surface area can be imaged by focusing a charged particle beam onto the surface area of ​​the sample.

[0032] For example, the charged particle beam device 100 can be an electron microscope, in particular a scanning electron microscope. According to some embodiments, which can be combined with other embodiments described herein, a scanning deflector (not shown) can be provided to scan the charged particle beam, in particular on the surface of the sample 10, along a predetermined scanning pattern (e.g., in the X direction and / or the Y direction).

[0033] The charged particle beam device 100 can be used to inspect and / or image one or more surface areas of the sample 10. The term "sample" as used herein may also be referred to as a "specimen" and may relate to, for example, a substrate having one or more layers or features formed thereon, a semiconductor wafer, a glass substrate, a flexible substrate (such as a web substrate), or another sample to be inspected. The sample can be inspected for one or more of the following: (1) imaging the surface of the sample; (2) measuring the dimensions of one or more features of the sample, for example in a lateral direction (i.e., in an XY plane); (3) performing critical dimension measurements and / or metrology; (4) detecting defects; and / or (5) investigating the quality of the sample.

[0034] According to an embodiment of the present disclosure, the charged particle beam device 100 includes an intermediate lens 150. Figure 2 The intermediate lens 150, on-axis detector 122 and objective lens 110, and the operation of the components are described in more detail. Backscattered electrons (BSEs), such as high energy backscattered electrons with high polar angles, have difficulty entering the column where signal electrons can be detected and / or filtered. Due to spherical aberrations of the objective lens 110, for example, high polar angle BSEs are strongly focused and may hit the funnel 230 before the signal electrons reach the detector. Therefore, the detection efficiency is reduced due to the loss of signal electrons. According to an embodiment of the present disclosure, an intermediate lens 150 is provided. An intermediate lens (IML) or an intermediate magnetic lens reduces the divergence of the BSE beam. Therefore, the BSE can be collimated to the opening of the on-axis detector 122 and can be detected by, for example, a second electron detector (such as an off-axis detector 123). The improved collection efficiency increases the processing volume. This is caused by Figure 2 The BSE beam 201 shown in FIG. According to embodiments of the present disclosure, as described below, an intermediate lens may control the BSE and / or may be used for energy filtering.

[0035] Figure 2 The intermediate lens 150 and the objective lens 110 are depicted. The objective lens 110 may be a magnetic lens or in particular a composite electrostatic-magnetic lens. The objective lens 110, when having magnetic components, comprises a coil 215, a lower pole piece 212 and an upper pole piece 214. In addition, an electrode 217 may be provided to communicate with another element (e.g. Figure 1 The tube 107 shown in FIG. 1 forms a lens together. Therefore, the deceleration electrostatic lens component can be arranged in the objective lens 110. The intermediate lens 150 can be a magnetic lens. When the intermediate lens 150 has a magnetic component, it includes a coil 255 and an upper pole piece 254. The intermediate lens and the objective lens can share a common pole piece, so that the upper pole piece 214 of the objective lens can provide a part of the lower pole piece of the intermediate lens 150.

[0036] The funnel 230 may be disposed in the gap of the objective lens. Figure 1The high potential tube 107 shown in FIG. 1 can be arranged in the gap of the intermediate lens.

[0037] like Figure 2 As shown, the on-axis detector 122 has a first distance Dd from the sample stage, and the intermediate lens 150 has a second distance Di from the intermediate stage. Typically, the distance of the intermediate lens can be measured from the center of the gap between the pole pieces, or in the case of an electrostatic lens, from the intermediate electrode. The second distance is equal to or less than 50% of the first distance. In addition, the second distance is 1 / 3 or more relative to the first distance.

[0038] According to an embodiment, a charged particle beam device is provided. The charged particle beam device includes a charged particle beam source, which is configured to generate a primary charged particle beam. The charged particle beam device further includes: a beam guiding object, which is configured to guide the primary charged particle beam toward the sample stage; and an on-axis detector, which has an opening configured for the intrusion of the primary charged particle beam. A second detector is arranged upstream of the on-axis detector. An intermediate lens is arranged between the on-axis detector and the sample stage and is configured to collimate high energy signal electrons onto the opening of the on-axis detector. The charged particle beam device further includes an objective lens, which is arranged between the intermediate lens and the sample stage, wherein the on-axis detector has a first distance from the sample stage, and the intermediate lens has a second distance from the sample stage. The second distance is 1 / 3 to 1 / 2 of the first distance.

[0039] The relative arrangement between the on-axis detector, the intermediate lens and the objective lens allows a cross-over of the BSE to be generated between the objective lens and the intermediate lens. Thus, the BSE can be collimated onto the opening of the on-axis detector 122 to improve the overall detection efficiency.

[0040] like Figure 2 As shown, the charged particle beam device may further include a first power supply 264. The first power supply 264 is connected to the coil 255 and can provide current to the coil to excite the intermediate lens 150. The charged particle beam device may further include a second power supply 266. The second power supply 266 is connected to the coil 215 and can provide current to the coil to excite the objective lens 110. The first power supply 264 and the second power supply 266 may be connected to a controller 260. The controller controls the current and voltage used to operate the objective lens 110 and the intermediate lens and allows various operating modes, in particular switching between operating modes as described in more detail below.

[0041] According to an embodiment, a method for operating a charged particle beam device is provided. The method includes guiding a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens, and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens. The method includes focusing the charged particle beam onto the sample with the objective lens. In a first operating mode, the intermediate lens is excited to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector. In addition, in the first operating mode, low energy signal electrons including secondary electrons are detected with the on-axis detector, and backscattered electrons are detected with a second electron detector upstream of the on-axis detector.

[0042] According to an embodiment of the present disclosure, high energy signal electrons are signal electrons that are (at or) above an energy threshold, and low energy signal electrons are signal electrons that are below an energy threshold. According to some embodiments that can be combined with other embodiments described herein, high energy signal electrons may be at or above 20% of the landing energy of the primary charged particle beam, and low energy signal electrons may be below 20% of the landing energy of the primary charged particle beam. According to some embodiments that can be combined with other embodiments described herein, high energy signal electrons may be at or above 30% of the landing energy of the primary charged particle beam, and low energy signal electrons may be below 30% of the landing energy of the primary charged particle beam. According to some embodiments that can be combined with other embodiments described herein, high energy signal electrons may be at or above 50% of the landing energy of the primary charged particle beam, and low energy signal electrons may be below 50% of the landing energy of the primary charged particle beam.

[0043] According to some embodiments, the energy threshold may be different for the first operation mode and the second operation mode.

[0044] about Figure 3 , a method of operating a charged particle beam apparatus includes directing and focusing a primary charged particle beam onto a sample. Figure 3 The flowchart shown in FIG. 1 shows a first mode of operation. In operation 302, high energy electrons are collimated to the opening of the on-axis detector. As shown in operation 304, low energy signal electrons are detected with the on-axis detector. In operation 306, a second electron detector (e.g., Figure 1 An off-axis detector (shown in FIG. 1 ) is used to detect backscattered electrons.

[0045] According to some embodiments, which can be combined with other embodiments described herein, the intermediate lens is excited to generate a crossover of high energy signal electrons between the objective lens and the intermediate lens. Figure 2 For example, the collimated high energy signal electrons allow the high energy signal electrons having a starting angle of 30° or more to pass through the opening of the on-axis detector. Figure 4A comparison between a case where the middle lens is closed shown on the left and a case where the middle lens is opened according to the first operation mode is shown. Figure 4 The angular distribution of the signal electrons as a function of energy is shown. Figure 4 The signal electrons in the upper part of the figure shown in FIG (i.e., the signal electrons with a large starting angle (further away from the optical axis)) are collected by the on-axis detector or the impacting part of the charged particle beam device or the wafer and lost without being detected. The white area below the dotted line shows the signal electrons that pass through the opening of the on-axis detector and are detected by the second electron detector. Figure 4 As can be seen from the comparison of , a significant increase in the signal electrons transmitted toward the second electron detector can be achieved.

[0046] In a first operating mode, in which high energy electrons (ie, mainly backscattered electrons) are focused onto an opening of the on-axis detector for detection on a second electron detector, Figure 4 The increase shown in results in an increased collection efficiency of backscattered electrons. Embodiments of the present disclosure improve signal-to-noise ratio by increasing collection efficiency to improve electron detection. This increases throughput. Reducing BSE losses increases throughput for detecting medium and high landing energies.

[0047] The energy of the backscattered electrons depends on the energy of the landing energy of the primary electron beam. For smaller landing energies, such as 2 keV or lower or even 1 keV or lower, the energy of the BSE is such that the collection of signal electrons may be sufficient without an intermediate lens. However, in this case, the intermediate lens may also further improve the collection efficiency. According to some embodiments that may be combined with other embodiments described herein, for landing energies of 2 keV or higher, in particular for landing energies of 2 keV to 5 keV, excitation of the intermediate lens may be provided. In addition, for landing energies of 5 keV or higher, excitation of the intermediate lens may be provided. For such medium landing energies or high landing energies, the use of an intermediate lens may be particularly useful.

[0048] Figure 4Such signal electrons in the upper part of the figure shown in (e.g., detected by the on-axis detector 122) have a large starting angle. Signal electrons with a large starting angle provide information about the morphology of the sample (e.g., a wafer). In other words, signal electrons with a large starting angle have more morphological information than signal electrons with a small starting angle (e.g., signal electrons emitted along the optical axis). Therefore, according to some embodiments that can be combined with other embodiments described herein, the on-axis detector can be a segmented detector. For example, 4 segments of a circle (each covering, for example, 90°) can be provided as segments of the on-axis detector. The on-axis detector can be a quad detector, in which the directions of the starting angles (x-direction and y-direction in the sample plane) can be detected independently.

[0049] Embodiments of the present disclosure provide a method for operating a charged particle beam, wherein a backscattered electron beam (BSE) in a scanning electron microscope is controlled. The method uses an intermediate lens (IML) near a magnetic objective lens, such as an intermediate magnetic lens, which gathers the BSE so as to increase the total collection to collimate the BSE to the opening of an on-axis detector. Off-axis BSE (high polar angle) at higher landing energies is difficult to bring to the detector within the SEM column because the BSE hits other parts within the column and is therefore lost. According to some implementations, the IML can provide different functionality in controlling the BSE beam. Backscattered electrons arriving at the IML region are focused by the IML and collimated to the opening of the on-axis detector, where the BSE beam continues to a second electron detector.

[0050] The method of operating a charged particle beam device according to an embodiment of the present disclosure may further include adjusting the excitation of the intermediate lens to a second operating mode. The second operating mode includes: detecting high energy signal electrons with an on-axis detector; and aligning low energy signal electrons to the opening of the on-axis detector. Energy filtering can be provided to improve the signal-to-noise ratio. In the second operating mode, the intermediate lens forms a crossover of the primary charged particle beam. In the second operating mode, the objective lens focuses on the crossover (compared with the focusing source and the first operating mode). Therefore, the excitation of the objective lens is stronger in the second operating mode.

[0051] According to some embodiments that can be combined with other embodiments described herein and the second operating mode, the excitation of the intermediate lens is higher compared to the excitation in the first operating mode. Additionally or alternatively, the excitation of the intermediate lens in the second operating mode generates a crossing of the primary charged particle beam between the intermediate lens and the objective lens. Thus, the excitation of the objective lens and the second operating mode is higher compared to the excitation in the first operating mode.

[0052] The detection of signal electrons may be described by detecting high energy signal electrons and low energy signal electrons. Additionally or alternatively, reference may be made to the detection of secondary electrons or backscattered electrons, wherein secondary electrons have energies up to about 50 eV and backscattered electrons have energies of about 50 eV or more. High energy signal electrons include BSEs, and low energy signal electrons include secondary electrons.

[0053] The energy threshold between high energy signal electrons and low energy signal electrons can be determined by an absolute energy value, for example, the threshold can be 50eV, 200eV, 500eV, 1keV, 2keV or even 5keV. The threshold between high energy signal electrons and low energy signal electrons can be determined relative to the landing energy of the primary charged particle beam, for example, the threshold can be 20%, 30%, 50% or 60% of the landing energy of the primary charged particle beam. High energy signal electrons are (at or) above the threshold, and low energy signal electrons are below the threshold.

[0054] The energy threshold may vary depending on the application and the measurement to be performed, for example, based on the sample structure. According to some embodiments that can be combined with other embodiments described herein, the first operating mode may have a first energy threshold as described above, and the second operating mode may have a second threshold as described above. The first threshold and / or the second threshold may be adapted. The landing energy of the primary charged particle beam may be, for example, 1 keV or more, 3 keV or more, 5 keV or more, or even 10 keV or more.

[0055] According to an embodiment of the present disclosure, an on-axis detector is provided. For example, the on-axis detector may be segmented, for example to improve the detection of topographic information. The on-axis detector may generally not include an energy filter for energy filtering beyond the different operating modes according to an embodiment of the present disclosure. According to an embodiment of the present disclosure, a second electronic detector is provided, for example, Figure 1 The off-axis electron detector shown. The second electron detector may include an additional energy filter. According to some embodiments, the second electron detector may not provide topographic information. Embodiments of the present disclosure that provide an intermediate lens may separate low energy signal electrons (e.g., secondary electrons) from high energy signal electrons (e.g., backscattered electrons). In a first operating mode, the high energy signal electrons may be collimated onto the opening of the on-axis detector to be detected by the second electron detector. In a second operating mode, the high energy signal electrons may be filtered to be detected by the on-axis detector.

[0056] According to some embodiments that can be combined with other embodiments described herein, high energy signal electrons (such as backscattered electrons) can be energy filtered and detected by a segmented detector. Therefore, the topographic information (i.e., angular information) of the backscattered electrons can be detected by the on-axis detector. In the second operating mode, the on-axis detector detects high energy signal electrons, such as backscattered electrons at or above an energy threshold. Therefore, according to some embodiments that can be combined with other embodiments described herein, a high pass filter can be provided.

[0057] Figure 5A and Figure 5B A comparison of different operating modes is shown. Figure 5A A first mode of operation according to an embodiment of the present disclosure is shown. An intermediate lens pre-focuses the primary charged particle beam, and the objective lens can operate at a reduced excitation level. The intermediate lens collimates high energy signal electrons (e.g., backscattered electrons) onto an opening of an on-axis detector. The high energy signal electrons can be detected by a second electron detector upstream of the on-axis detector. Low energy signal electrons are detected by the on-axis detector. Figure 5A A simulation of signal counts as a function of the energy of the signal electrons is shown. The curve with hollow circles shows the signal counts on the on-axis detector. The curve with hollow squares shows the signal counts on the second electron detector. The remaining curves show simulated signal counts on various other components whose signal electrons are lost and cannot generate an image of the sample.

[0058] According to some embodiments, which can be combined with other embodiments described herein, in particular in the second operating mode, the energy threshold for filtering can be adjusted by varying the excitation of the intermediate lens.

[0059] about Figure 6 , a method of operating a charged particle beam apparatus includes directing and focusing a primary charged particle beam onto a sample. Figure 6 The illustrated flow chart shows a second mode of operation. In operation 602, the excitation of the intermediate lens is adjusted to operate the charged particle beam device in the second mode of operation. In operation 604, high energy electrons are detected with an on-axis detector. As shown in operation 606, low energy signal electrons are collimated to the opening of the on-axis detector. According to some embodiments that can be combined with other embodiments described herein, low energy signal electrons (e.g., secondary electrons) can be detected by a second electron detector upstream of the on-axis detector.

[0060] According to various embodiments of the present disclosure, a method of operating a charged particle beam apparatus may include: Figure 3 The method shown in Figure 6The method of switching between the methods illustrated in FIG. 1 and 2 may be switched between the methods illustrated in FIG. Switching between different operating modes may be provided one or more times. In addition, in particular for the second operating mode, it is possible to adjust the energy threshold of the energy filtering. According to some embodiments, the threshold may also be adjusted for the first operating mode, in particular for separating SE from BSE. For example, the threshold in the first operating mode may be set to 10 eV to 100 eV.

[0061] As about Figure 1 As described, a beam splitter 124 for separating the primary charged particle beam from the signal electrons may be provided. The beam splitter may be provided upstream of the on-axis detector. According to some embodiments that may be combined with other embodiments described herein, the method for operating a charged particle beam device may further include separating the primary charged particle beam from the signal electrons upstream of the on-axis detector, particularly when the second electron detector is an off-axis detector. According to some embodiments that may be combined with other embodiments described herein, the method may further include energy filtering the signal electrons between the opening of the on-axis detector and the second electron detector. In particular, the filtering may include bandpass filtering. The detection of high-energy signal electrons may be improved by a combination of improving the detection efficiency and energy filtering the signal. For example, this may be particularly advantageous for BSE energies of 1 keV or above, such as 10 keV or above.

[0062] According to an embodiment, a charged particle beam device is provided. The charged particle beam device includes a charged particle beam source, which is configured to generate a primary charged particle beam. The charged particle beam device further includes: a beam guiding object, which is configured to guide the primary charged particle beam toward the sample stage; and an on-axis detector, which has an opening configured for the intrusion of the primary charged particle beam. A second detector is provided upstream of the on-axis detector. An intermediate lens is arranged between the on-axis detector and the sample stage and is configured to collimate high energy signal electrons onto the opening of the on-axis detector. The charged particle beam device further includes an objective lens, which is arranged between the intermediate lens and the sample stage, wherein the on-axis detector has a first distance from the sample stage, and the intermediate lens has a second distance from the sample stage. The second distance is 1 / 3 to 1 / 2 of the first distance.

[0063] According to some embodiments, which can be combined with other embodiments described herein, the first distance of the on-axis detector may be about 100 mm to 300 mm, and the second distance of the intermediate lens may be about 33.3 mm to 150 mm.

[0064] Embodiments of charged particle beam devices that can be combined with other embodiments described herein can be found in Figure 1 and Figure 2 To describe. Figure 1As shown exemplarily, the objective lens may be a composite electrostatic-magnetic objective lens. In addition, the intermediate lens may be a magnetic lens. In particular, the intermediate lens may be an axial gap lens. According to some optional implementations, the objective lens and the intermediate lens may have a common pole piece.

[0065] like Figure 2 It is shown that according to some embodiments, which can be combined with other embodiments described herein, a first distance D1 of one or more of the pole pieces of the intermediate lens from the optical axis can be greater than a second distance D2 of one or more of the pole pieces of the objective lens.

[0066] According to some embodiments, which can be combined with other embodiments described herein, a charged particle beam device may include a controller having a processor and a memory storing instructions which, when executed by the processor, cause the device to perform a method as described in any of the embodiments described herein.

[0067] Figure 2 The controller 260 shown exemplarily controls the operation of the objective lens 110 and the operation of the intermediate lens 150. The controller 260 includes a central processing unit (CPU), a memory and, for example, a support circuit. In order to facilitate the control of the charged particle beam device, and in particular to control the intermediate lens 150 to operate in different operating modes, the CPU can be one of any form of general-purpose computer processors that can be used in industrial environments to control various chambers and subprocessors. The memory is coupled to the CPU. The memory or computer-readable medium can be one or more readily available memory devices, such as random access memory, read-only memory, hard disk or any other form of local or remote digital storage device. The support circuit can be coupled to the CPU to support the processor in a conventional manner. The circuit includes a cache, a power supply, a clock circuit, an input / output circuit system and related subsystems, etc. The inspection process instructions are generally stored in the memory as a software routine typically referred to as a recipe. The software routine can also be stored and / or executed by a second CPU (not shown) located away from the hardware controlled by the CPU. The software routines, when executed by the CPU, transform a general purpose computer into a special purpose computer (controller) that controls the operation of the device, such as a special purpose computer (controller) that can provide control of backscattered electron detection and / or electronic filtering of signals. Although the methods and / or processes of the present disclosure are discussed as being implemented as software routines, some of the method steps disclosed in the present disclosure may be implemented in hardware and by a software controller. Thus, the present invention may be implemented in software such as executed on a computer system and in hardware as an application specific integrated circuit or other type of hardware implementation, or in a combination of software and hardware.

[0068] According to the embodiments of the present disclosure and as Figures 3 to 6 As exemplarily described and explained, the controller may execute or perform a method of operating a charged particle beam apparatus.

[0069] In the present disclosure, multiple embodiments are described, which include, among other things, the following embodiments.

[0070] Embodiment 1. A method for operating a charged particle beam device, the method comprising: guiding a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam onto the sample with the objective lens; in a first operating mode, providing excitation to the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector; in the first operating mode, detecting low energy signal electrons including secondary electrons with the on-axis detector; and in the first operating mode, detecting backscattered electrons with a second electron detector upstream of the on-axis detector.

[0071] Embodiment 2. The method of embodiment 1, wherein the high energy signal electrons are collimated so that the high energy signal electrons having a starting angle of 30° or greater pass through an opening of the on-axis detector.

[0072] Embodiment 3. The method as described in any one of Embodiments 1 to 2 further comprises: adjusting the excitation of the intermediate lens to a second operating mode, wherein the second operating mode comprises: detecting high energy signal electrons with an on-axis detector; and collimating low energy signal electrons to an opening of the on-axis detector.

[0073] Embodiment 4. The method of embodiment 3, wherein the excitation of the intermediate lens is higher in the second operating mode compared to the excitation in the first operating mode.

[0074] Embodiment 5. The method of any one of embodiments 1 to 4, further comprising: separating the primary charged particle beam from the signal electrons upstream of the on-axis detector, wherein the second electron detector is an off-axis detector.

[0075] Embodiment 6. The method as described in any one of embodiments 1 to 5 further comprises: energy filtering the signal electrons between the opening of the on-axis detector and the second electron detector.

[0076] Embodiment 7. A charged particle beam device, comprising: a charged particle beam source, which is configured to generate a primary charged particle beam; a beam guiding optical device, which is configured to guide the primary charged particle beam toward a sample stage; an on-axis detector, which has an opening configured for intrusion of the primary charged particle beam; a second detector, which is upstream of the on-axis detector; an intermediate lens, which is arranged between the on-axis detector and the sample stage and is configured to collimate high-energy signal electrons onto the opening of the on-axis detector; an objective lens, which is arranged between the intermediate lens and the sample stage; and an energy filter, which is along the signal beam path between the opening of the on-axis detector and the second detector.

[0077] Embodiment 8. The charged particle beam device as described in Embodiment 7 further comprises: a controller having a processor and a memory storing instructions, wherein the instructions, when executed by the processor, cause the charged particle beam device to execute the method as described in any one of Embodiments 1 to 6.

[0078] Embodiment 9. A charged particle beam device as described in any one of embodiments 7 to 8, wherein the objective lens is a composite magnetic-electrostatic objective lens.

[0079] Embodiment 10. A charged particle beam device as described in any one of embodiments 7 to 9, wherein the intermediate lens is a magnetic lens.

[0080] Embodiment 11. A charged particle beam device as described in Embodiment 10, wherein the intermediate lens is an axial gap lens.

[0081] Embodiment 12. A charged particle beam device as described in any of embodiments 7 to 11, wherein the first distance of the on-axis detector is about 100 mm to 300 mm, and the second distance of the intermediate lens is about 33.3 mm to 150 mm.

[0082] Embodiment 13. The charged particle beam device as described in any one of embodiments 7 to 12 further comprises: a beam splitter, wherein the beam splitter is upstream of the on-axis detector.

[0083] Embodiment 14. A charged particle beam device as described in any one of embodiments 7 to 13, wherein the objective lens and the intermediate lens have a common pole piece.

[0084] Embodiment 15. A charged particle beam device as described in any one of Embodiments 7 to 14, wherein a first distance between one or more first pole pieces of the intermediate lens and the optical axis is greater than a second distance between one or more second pole pieces of the objective lens and the optical axis.

[0085] Embodiment 16. A charged particle beam device, comprising: a charged particle beam source, configured to generate a primary charged particle beam; a beam guiding optical device, configured to guide the primary charged particle beam toward a sample stage; an on-axis detector, the on-axis detector having an opening configured for intrusion of the primary charged particle beam; a second detector, the second detector being upstream of the on-axis detector; an intermediate lens, the intermediate lens being arranged between the on-axis detector and the sample stage and being configured to collimate high-energy signal electrons onto the opening of the on-axis detector; an objective lens, the objective lens being arranged between the intermediate lens and the sample stage; and a controller, the controller having a processor and a memory storing instructions, the instructions, when executed by the processor, causing the charged particle beam device to perform a method as described in any one of Embodiments 1 to 6.

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

Claims

1. A method of operating a charged particle beam apparatus, the method comprising: directing a primary charged particle beam through an opening of an on-axis detector, through an intermediate lens, through an objective lens, and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam onto the sample using the objective lens; in a first mode of operation, providing excitation to the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector; in the first operating mode, detecting low energy signal electrons including secondary electrons with the on-axis detector; as well as In the first operating mode, the backscattered electrons are detected with a second electron detector upstream of the on-axis detector. 2 . The method of claim 1 , wherein the high energy signal electrons are collimated so that the high energy signal electrons having a starting angle of 30° or more pass through the opening of the on-axis detector.

3. The method of claim 1, further comprising: adjusting the excitation of the intermediate lens to a second operating mode, the second operating mode comprising: detecting high energy signal electrons with the on-axis detector; and A low energy signal is electronically collimated to the opening of the on-axis detector.

4. The method of claim 3, wherein the excitation of the intermediate lens in the second operating mode is higher than the excitation in the first operating mode.

5. The method according to any one of claims 1 to 4, further comprising: The primary charged particle beam is separated from signal electrons upstream of the on-axis detector, wherein the second electron detector is an off-axis detector.

6. The method according to any one of claims 1 to 4, further comprising: Signal electrons between the opening of the on-axis detector and the second electron detector are energy filtered.

7. A charged particle beam device, comprising: a charged particle beam source configured to generate a primary charged particle beam; beam directing optics configured to direct the primary charged particle beam toward a sample stage; an on-axis detector having an opening configured for intrusion of the primary charged particle beam; a second detector upstream of the on-axis detector; an intermediate lens disposed between the on-axis detector and the sample stage and configured to electronically collimate a high energy signal onto the opening of the on-axis detector; an objective lens, the objective lens being arranged between the intermediate lens and the sample stage; as well as An energy filter is along a signal beam path between the opening of the on-axis detector and the second detector.

8. The charged particle beam device according to claim 7, further comprising: A controller having a processor and a memory storing instructions, the instructions, when executed by the processor, causing the charged particle beam device to perform a method of operating the charged particle beam device, the method comprising: directing the primary charged particle beam through the opening of the on-axis detector, through the intermediate lens, through the objective lens, and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam onto the sample using the objective lens; in a first mode of operation, providing excitation to the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector; in the first operating mode, detecting low energy signal electrons including secondary electrons with the on-axis detector; and In the first operating mode, the backscattered electrons are detected with a second electron detector upstream of the on-axis detector.

9. The charged particle beam device as claimed in claim 8, wherein the high energy signal electrons are collimated to have a 30° High energy signal electrons with a starting angle of or greater pass through the opening of the on-axis detector.

10. The charged particle beam apparatus of claim 8, further comprising: adjusting the excitation of the intermediate lens to a second operating mode, the second operating mode comprising: detecting high energy signal electrons with the on-axis detector; and A low energy signal is electronically collimated to the opening of the on-axis detector.

11. The charged particle beam device according to any one of claims 7 to 10, wherein the objective lens is a composite magnetic-electrostatic objective lens.

12. The charged particle beam device according to any one of claims 7 to 10, wherein the intermediate lens is a magnetic lens.

13. The charged particle beam apparatus of claim 12, wherein the intermediate lens is an axial gap lens.

14. A charged particle beam apparatus as claimed in any one of claims 7 to 10, wherein the first distance of the on-axis detector is about 100 mm to 300 mm, and the second distance of the intermediate lens is about 33.3 mm to 150 mm.

15. The charged particle beam device according to any one of claims 7 to 10, further comprising: A beam splitter is provided upstream of the on-axis detector.

16. A charged particle beam apparatus as claimed in any one of claims 7 to 10, wherein the objective lens and the intermediate lens have a common pole piece.

17. A charged particle beam device as claimed in any one of claims 7 to 10, wherein a first distance between one or more first pole pieces of the intermediate lens and the optical axis is greater than a second distance between one or more second pole pieces of the objective lens and the optical axis.

18. A charged particle beam device, comprising: a charged particle beam source configured to generate a primary charged particle beam; beam directing optics configured to direct the primary charged particle beam toward a sample stage; an on-axis detector having an opening configured for intrusion of the primary charged particle beam; a second detector upstream of the on-axis detector; an intermediate lens disposed between the on-axis detector and the sample stage and configured to electronically collimate a high energy signal onto the opening of the on-axis detector; an objective lens disposed between the intermediate lens and the sample stage, and A controller having a processor and a memory storing instructions, the instructions, when executed by the processor, causing the charged particle beam device to perform a method of operating the charged particle beam device, the method comprising: directing the primary charged particle beam through the opening of the on-axis detector, through the intermediate lens, through the objective lens, and onto a sample, wherein the intermediate lens is disposed between the on-axis detector and the objective lens; focusing the primary charged particle beam onto the sample using the objective lens; in a first mode of operation, providing excitation to the intermediate lens to collimate high energy signal electrons including backscattered electrons to the opening of the on-axis detector; in the first operating mode, detecting low energy signal electrons including secondary electrons with the on-axis detector; and In the first operating mode, the backscattered electrons are detected with a second electron detector upstream of the on-axis detector.

19. The charged particle beam device of claim 18, wherein the high energy signal electrons are collimated to have a 30° High energy signal electrons with a starting angle of or greater pass through the opening of the on-axis detector.

20. The charged particle beam apparatus according to any one of claims 18 to 19, further comprising: adjusting the excitation of the intermediate lens to a second operating mode, the second operating mode comprising: detecting high energy signal electrons with the on-axis detector; and A low energy signal is electronically collimated to the opening of the on-axis detector.

Images