3D mapping of samples in charged particle microscopes

Abstract

3D mapping of a sample in a charged particle microscope. A sample can be positioned on the optical axis of a charged particle microscope based on a 3D map of the sample. The 3D map is generated using back illumination and telecentric imaging of the sample to produce profile images. The profile images are combined to form the 3D map. The 3D map is used to couple a processor to a sample stage to position a selected sample or sample portion for imaging in the charged particle microscope. In some examples, the processor responds to a selection of a sample using a graphical interface so that the sample stage is controlled to safely position the selected sample without further operator intervention.

Description

Technical Field

[0001] This disclosure relates to methods and systems for use in microscopes, and more specifically, to the positioning of samples in a charged particle microscope. Background Technology

[0002] Positioning samples for an electron microscope can be time-consuming and requires diligent operator work. Samples of varying sizes on the sample holder must be carefully positioned to avoid contact with microscope components, the electrodes used for magnetic lenses, the electron detector, or other components. In some cases, the sample holder holds multiple samples at different heights, and the operator must carefully move each sample into the microscope's field of view. After positioning in the field of view, additional operator time is required to focus the sample. Therefore, sample positioning and focusing are both time-consuming and error-prone, and the required operator skill may necessitate supervising new users who may experience sample / electrode contact, introduce astigmatism, misalignment, or damage to components or samples. For at least these reasons, alternative methods are needed. Summary of the Invention

[0003] The method includes illuminating a sample located within a vacuum chamber of a charged particle microscope from a first side and detecting at least one 2D projection of the sample on a second side opposite the first side. A 3D map is generated based on the at least one 2D projection, and the sample is positioned at an imaging location within the vacuum chamber based on the 3D map. In some instances, the first side is opposite the second side, and multiple 2D projections of the sample on the second side are detected and a 3D map is generated based on the multiple projections. Typically, the multiple 2D projections of the sample on the second side are detected by rotating the sample. In some instances, a set of 3D maps is generated, each 3D map based on a set of rotation angles, wherein the 3D map is based on a combination of each of the set of 3D maps. In one instance, the sample is moved to the imaging location after the 2D projection is detected. In other instances, the sample is loaded into the vacuum chamber of the charged particle microscope and illuminated with light. Based on the 3D map generated from the 2D projection, the sample is moved to the imaging location within the vacuum chamber. The sample can be processed or imaged at the imaging location using a charged particle beam. In some instances, illuminating the sample includes guiding a collimated beam to the sample and the collimated beam is guided along an axis perpendicular to the optical axis of the charged particles. Irradiating the sample can be performed using a light source located inside or outside the vacuum chamber. In some alternatives, irradiating the sample includes irradiating it with a beam of patterned intensity, and further includes marking the reflective surface of the sample based on said patterned intensity. In some instances, a telecentric optical system is used to perform the detection of at least one 2D projection of the sample on a second side opposite to the first side. The telecentric optical system may include an objective lens located inside or outside the vacuum chamber. The telecentric optical system is one or both object-side telecentric and image-side telecentric. In some instances, the central axis of the detector used to acquire the 2D projection is parallel to the sample platform used to hold the sample.

[0004] The charged particle microscope includes an illumination system positioned to illuminate a sample from a first side and an imaging system positioned to generate a 2D profile of the illuminated sample based on the illumination from the first side. A processor is coupled to receive the 2D profile and generate a 3D map based on the 2D profile. The imaging system includes an image sensor positioned to generate an image of the 2D profile of the illuminated sample based on the illumination from the first side; and the processor is coupled to a sample stage and configured to rotate the illuminated sample to generate the 2D profile. The imaging system may include a telecentric optical system to guide the 2D profile to the image sensor. The illumination system may be positioned to guide a diffuse beam or a collimated beam to the sample. The sample stage can be used to move the sample platform to the charged particle optical axis.

[0005] The foregoing and other features and advantages of the disclosed technology will become more apparent from the following detailed description with reference to the accompanying drawings. Attached Figure Description

[0006] Figure 1 A representative charged particle microscope incorporating an optical system for surface profile analysis is shown.

[0007] Figure 2 A representative graphical user interface is shown for focusing a charged particle microscope at the selected location.

[0008] Figure 3A It represents the sample located on the sample platform.

[0009] Figure 3B It corresponds to Figure 3A 3D mapping.

[0010] Figures 4A-4B A representative 3D mapping of the sample is shown, such as Figure 3B The 3D mapping shown.

[0011] Figure 4C This demonstrates a representative method for creating “safer” 3D mappings.

[0012] Figure 5 A representative optical system for surface profile analysis using collimated illumination is shown.

[0013] Figure 5A yes Figure 5 A cross-sectional view of the optical system.

[0014] Figure 6 A representative optical system is shown for surface profile analysis using a telecentric optical system.

[0015] Figure 6A yes Figure 6 A cross-sectional view of the optical system.

[0016] Figure 7 A representative optical system is shown for surface profile analysis using a telecentric optical system.

[0017] Figure 8 A representative optical system is shown for surface profile analysis using a telecentric optical system.

[0018] Figure 9A-10 An additional representative telecentric optical system fixed to the wall of the vacuum chamber is shown.

[0019] Figure 11 The image shown is a representative telecentric optical system where the object and image sides are telecentric.

[0020] Figure 12 This shows a portion of a charged particle microscope.

[0021] Figure 12A yes Figure 12 The image shows a cross-sectional view of a charged particle microscope.

[0022] Figure 12B Showing available as Figure 12-12A The optical system shown in the figure represents a typical 2D profile.

[0023] Figure 13 This shows a portion of a charged particle microscope with a tiltable sample platform.

[0024] Figures 14A-14B The sample with a reflective profile is shown.

[0025] Figure 15 A representative gradient intensity illuminator is shown.

[0026] Figure 16 A representative method for generating 3D mappings is shown.

[0027] Figure 17 A representative method is shown for generating a 3D map and moving the sample platform to the microscope axis for imaging based on the 3D map.

[0028] Figure 18 A representative processing environment for the disclosed methods and apparatus is shown.

[0029] Figure 19 This is a cross-sectional view of a representative electron microscope.

[0030] Figure 20 The 2D projection is shown.

[0031] Figure 21A A 2D projection with a reflective area is shown.

[0032] Figure 21B Show Figure 21A The portion that contains the reflective area.

[0033] Figures 22A-22B It is a partial 2D projection.

[0034] Figure 22C Through combination Figures 22A-22B The full 2D projection is obtained by 2D projection.

[0035] Figure 23 This shows a series of 2D projections at various rotation angles.

[0036] Figures 24A-24F This demonstrates a method for generating 3D mappings from 2D projections. Detailed Implementation

[0037] Representative examples of CPB systems, such as CPB microscopes and related components, sub-components, and methods, are disclosed below. In many practical examples, the electron beam is of interest, and for ease of illustration, these examples are described with reference to the electron beam. The disclosed methods can also be used in optical microscopy. In most examples, additional CPB components, such as lenses, deflectors, pillars, and additional apertures, are used, but are not shown for ease of illustration. The disclosed methods and apparatus can be used in both transmission and scanning microscopy. As discussed below, in some examples, a vacuum chamber can be evacuated while one or more samples are profiled at sample profile analysis locations to produce a 3D map. The sample can be located on a stage at the charged particle (CP) optical axis, or can be tilted relative to or displaced from the CP optical axis. The sample can be moved onto the CP optical axis for imaging or processing after profile analysis. As used herein, an image can refer to the presentation of image data on a display for operator visual inspection or the presentation of data associated with a visual image, for example, stored in a JPG, TIFF, or other data file. As used in this article, X and Y refer to axes orthogonal to the CP optical axis (Z-axis). These axes do not need to be mutually orthogonal, but orthogonal axes are convenient.

[0038] As used herein, illumination generally refers to directing electromagnetic radiation toward an object or to the electromagnetic radiation itself. This type of electromagnetic radiation is typically visible light with wavelengths between approximately 400 nm and 700 nm, which is convenient for use with readily available image sensors and allows for operator observation as well as use with cameras. Other wavelengths may also be used, but the range from 300 nm to approximately 2 μm is convenient. In this example, back illumination is typically used. Contour images produced by front illumination generally depend on the sample's reflectivity and detail. In contrast, contour images produced by back illumination have contrast between bright and dark areas (unshaded and shaded areas), which generally depends on the sample shape rather than surface features. Back illumination can be provided by placing a light source behind the object of interest or by placing a reflector behind the object and reflecting light back onto it.

[0039] For example, terms such as contour, projection, contour image, and projected image are used to refer to the sample contour produced using an optical system as a shadow or image. In some cases, these terms refer to the illumination distribution guided to an image sensor or the associated detected illumination distribution.

[0040] The lens is shown as a single lens in the examples, but multiple lenses can also be used. Optical systems are typically shown along a linear axis, but such axes can be bent or folded as needed using prisms or mirrors.

[0041] Example 1

[0042] Now for reference Figure 1 In a representative embodiment, the charged particle beam (CPB) system 100 includes a CPB microscope 102, such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and includes one or more CPB lenses, such as a condenser lens 104, positioned to guide the CPB from a CPB source 106 toward an objective lens 108. The CPB source 106 may be, for example, a field emitter that generates an electron beam, but other sources may also be used. In some embodiments, one or more additional CPB lenses may be provided, and may be magnetic lenses and / or electrostatic lenses. The main axis 110 may be determined during the manufacture of the microscope system. In use, the CPB propagates along the main axis 110 toward a sample stage 114, and a beam deflector 122 may be used to scan the beam relative to a sample S located on the sample stage 114. The sample stage 114 typically provides translation and / or rotation for positioning the sample S. Typically, the sample S is fixed to a sample platform, which is then fixed to the sample stage 114.

[0043] The CPB system 100 includes a vacuum chamber housing 112, which can be evacuated using a vacuum pump (not shown), and typically defines a first volume 112A and a second volume 112B. The first volume contains the CPB source 106 and selected other CPB optical components, and the second volume is positioned to receive a sample S and a sample stage 114. A column isolation valve (CIV) 120 is positioned to separate the first volume 112A and the second volume 112B. Typically, the CIV 120 is used to hermetically isolate the first volume 112A from the second volume 112B during sample exchange. The sample stage 114 is movable in the XY plane as shown relative to coordinate system 150, where the Y-axis is perpendicular to the plane of the diagram. The sample stage 114 can be further moved vertically (along the Z-axis) to compensate for height variations of the sample S and to help focus the beam onto the sample S. The sample stage 114 can also be rotated about an axis parallel to the Z-axis and to tilt the sample S. In some cases, sample profilometry is performed with the sample stage tilted, such as... Figure 13 As shown below, and further discussed in some embodiments, the CPB microscope 102 may be vertically positioned above the sample S and may be used to image the sample. In some embodiments, the CPB microscope 102 may be vertically positioned above the sample S and may be used to image the sample S while it is being processed by an ion beam machine or otherwise.

[0044] Light source 152 is positioned to deliver illumination beam 154 through window 156 in vacuum chamber housing 112. Illumination beam 154 is shown as a collimated beam, but may also be diffuse or collimated. An optical system including one or more lenses, such as lens 158, is positioned to receive the portion of illumination beam 154 not obstructed by sample S and to generate one or more contour images (or 2D projections) of sample S at or near image sensor 160. As shown, lens 158 and portions of the optical system extend into vacuum chamber 112. However, any one or both of the optical system, light source 152, or both may be inside, outside, or partially inside and outside vacuum chamber housing 112. Typically, sample stage 114 rotates about axis 110 (or a parallel axis) and contour images are acquired during rotation. For example, sample stage 114 may rotate 360 ​​degrees and contour images are acquired at 1-degree intervals.

[0045] The CPB system 100 may further include a computer processing device 144, such as a control computer and a CPB system controller 140, for controlling the beam deflector, CPB lenses 104, 108 and other CPB lenses, as well as other components such as detectors and sample stage 114, including the rotation and translation of the sample stage 114. The computer processing device 144 may also control the display on a display unit of information collected from one or more CPB detectors. In some cases, the computer processing device 144 (e.g., the control computer) establishes various stimuli, records image data, and generally controls the operation of the CPB microscope 102, including controlling the acquisition of contour images. A so-called "navigation camera" 137 is positioned to provide a top-down image of the sample and sample stage, typically for operator observation. A camera 141 may also be provided to obtain a side view of the sample. The camera 141 is typically shifted along the Y-axis (into...) Figure 1 (within the plane) and positioned as follows Figure 1 Out-of-plane observation.

[0046] The sample stage 114 can be translated along the Z-axis to control focusing based on a contour image generated by the image sensor 160, controlled by one or both of the computer processing unit 144 and the CPB system controller 140. In some instances, the sample stage 114 can be positioned appropriately along the Z-axis for imaging a specific sample, with or without operator adjustment of the Z-axis position. Sample imaging can be based on transmitted, reflected, or scattered charged particles, X-rays, or other electromagnetic radiation, or by means of... Figure 1 Secondary transmissions received by one or more detectors not shown in the diagram.

[0047] Example 2

[0048] Figure 2 It shows that it can be set with, for example Figure 1 This is part of the graphical user interface 200 on the display device associated with the CPB system shown. In this example, display area 202 contains an image of the substrate surface, and display area 204 is a side view 205 of an electron microscope column containing an electrode 206 and a sample 208, which is fixed to a sample platform 209 and has a surface 210, an image of which is shown in display area 202. For example, [the following can be used] Figure 1A side view 205 is obtained using an optical system and image sensor, such as lens 158 and image sensor 160 or any of the optical systems described below. Display area 212 shows the top surface 214 of sample platform 209, indicating the location 216 for selecting the beam focus. Display area 220 contains a top view of sample platform 209 on which various samples 222-224 can be seen. Display area 230 includes display areas for stage X, Y, Z, rotation, and tilt coordinates 232, area 234 (shown as radio buttons) for indicating with a computer pointing device that CPB will be turned on, area 236 for indicating with a computer pointing device that autofocus will be activated for the area indicated by 216, and area 238 that may contain other controls and data. Through this user interface, using the computer pointing device to indicate that position 216 will be imaged causes the sample stage to be properly positioned relative to the electron microscope optical column based on contour data that allows for safe movement (i.e., collision-free movement).

[0049] Example 3

[0050] Figure 3A A representative plan view of the sample platform on which samples 301-303 are fixed is shown. Figure 3A For example Figure 1 The images were captured by a navigation camera such as the 137. For convenience, a 3D coordinate axis is provided. Based on multiple contour images (contours) obtained as discussed, in... Figure 3B A 3D mapping 350 is generated. The 3D mapping contains corresponding to Figure 3A The mapped regions 401-403 of sample 301-303 are shown in the illustration. From, for example... Figure 1 Images from cameras such as the 137 and 141 can be combined with 3D mapping for visualization, but 3D mapping does not require images from such cameras.

[0051] Example 4

[0052] Typically, multiple 2D projections or profiles of the sample platform and sample are obtained by rotating the sample platform approximately 1 degree multiple times within a 360-degree range. In some cases (e.g., where reflections from the sample surface exist in the profile), a first 3D map is obtained using a series of rotations within a 360-degree range, starting with a first angle in a first increment (e.g., 6 degrees). The first angle is then increased in a second increment, and the 360-degree range is traversed by additional profiles in the first increment. Thus, multiple series of 2D profiles can be obtained, for example, generating first 3D maps at 0, 6, 12, ..., 360 degrees, and then generating second 3D maps at 1, 7, 13, ..., etc. This can produce six 3D maps, each associated with 60 rotation angles. Each of these maps can show reflections not shown on the other maps. These maps can be combined, preferably using an OR operation, such that any reflective surfaces of the sample are included in the map. This often produces "safe" 3D maps for focus adjustment and allows the stage support to be moved without the sample contacting other components. As used in this article, secure 3D mapping refers to 3D mapping obtained by taking reflection into account. Figure 4A This illustrates a 3D mapping generated using 360 rotations that increase by 1 degree. Figure 4B The diagram illustrates a 3D mapping generated by combining six 3D maps produced using 60 incremental rotations. A 1-degree incremental mapping is better suited for visualizing the sample, but the combined 6-degree incremental mapping is safer for sample movement because reflective surfaces are included as potential obstacles.

[0053] One method for providing secure 3D mapping is to combine 3D mappings obtained from different angles, such as different initial angles with fixed angle increments. For example... Figure 4C As shown, representative method 450 includes selecting a set of initial angles and angle increments at 452. At 454, 2D projections associated with each initial angle at a multiple of the angle increment are combined to produce multiple 3D maps. For example, for a set of... n Initial angles θ1, ..., θ2 n The initial angle θ i And the angle increment Δθ, corresponding to θ for each initial angle combination. i + j 2D projection of Δθ to produce n A 3D mapping, in which jThis provides all integer values ​​for the angle within the full rotation. In 456, a 3D map can be processed using a logical OR operation within the angular range corresponding to the angle increment Δθ to obtain a safe 3D map. For example, five 3D maps made with an angle increment Δθ = 5 degrees can be obtained using 2D projections made in 1-degree increments. The first 3D map may contain values ​​of 62, 67, 72, and 77 degrees (and other angles within the full 360 degrees), the second 3D may contain values ​​of 63, 68, 73, and 78 degrees (and other angles within the full 360 degrees), and so on. These 3D maps can be combined, i.e., the map values ​​within the angle increment Δθ are processed to retain the values ​​corresponding to obstacles (the unilluminated areas of the sensor). In a typical 3D map with backlighting, the 3D map values ​​are 0 or 1 (obstacle-free or obstructed, respectively), and the 3D maps are combined using a logical OR operation. Some 3D maps show obstacles not in other maps, and such combinations of 3D maps provide a safe 3D map where reflections do not cause real obstacles to be missed. The resulting secure 3D mapping can be at a lower resolution, but it is usually not visually significantly different from a higher resolution 3D mapping, such as... Figures 4A-4B As shown in the diagram. Multiple sets of different angles can be used to obtain multiple 3D maps, and the disclosed example is selected for ease of explanation. The choice of angle for combining the map values ​​does not need to be the same as the angle increment. Typically, a 2D projection is obtained at a predetermined angular resolution, and then the 2D projections are combined to create multiple 3D maps for use in creating a safe 3D map. At 458, the 3D safe map is output for use in an electron microscope.

[0054] Example 5

[0055] Figure 5 It is a floor plan, and Figure 5A This is a cross-sectional view along AA of a representative contour measurement system 500 including a light source 502 configured to generate a collimated beam 504 guided to a sample platform 506 where representative samples 508 and 509 are located. A portion 510 of the transmitted beam is guided to an image sensor 512 to generate a 2D contour image. As shown, a portion of the collimated beam 504 is blocked by the sample 508, creating a corresponding dark or shadowed area 514 at the image sensor 512. The sample platform rotates about axis 520, causing changes in the bright and dark areas on the image sensor and obtaining different contour images. Samples 508 and 509 move into and out of the beam 504 during rotation.

[0056] Example 6

[0057] Figure 6 It is a floor plan, and Figure 6AThis is a cross-sectional view of a representative contour measurement system 600 including a light source 602 configured to generate a beam 604 guided to a sample platform 606 where representative samples 608 and 609 are located. A portion 610 of the transmitted beam is guided to an image sensor 612 via a telecentric optics system 611 (shown as a single lens for illustrative purposes) to generate a 2D contour image. As shown, a portion of the beam 604 is blocked by the sample 608, creating a corresponding dark or shadowed area 614 at the image sensor 612. The sample platform rotates about an axis 620, causing changes in the bright and dark areas on the image sensor and movement of samples 608 and 609 relative to the image sensor 612. In this example, the light source 602 is shown generating a collimated beam, but a diffuse or divergent beam could be used. Collimation is not required because the telecentric optics system 611 eliminates or reduces perspective errors, as discussed in detail below. While divergent or diffuse beams could be used, such beams could produce reflections from the sample surface that could be ignored and improperly considered as unobstructed areas.

[0058] Example 7

[0059] Figure 7 A portion of a representative profilometry system is shown, comprising a telecentric optical system 700 positioned to generate an image of a sample, which can be located at various positions along the optical system axis 701, such as 702A, 702B. The sample is fixed to a rotatable sample platform 704, allowing its position to vary along both the X and Y axes of a representative coordinate system 750. For convenience, the optical system axis 701 is shown parallel to the X-axis, and the electron microscope axis is parallel to the Z-axis. The telecentric optical system includes an objective lens 710 mounted within a vacuum chamber. The objective lens 710 is fixed to a lens tube 712, which is fixed to the vacuum chamber wall 714 at an optical window 716. An imaging lens 718 and an aperture stop 720 are located at the focal length F of the objective lens 710 to achieve telecentricity. As shown, the imaging lens 718 and aperture stop 720 are included in a camera 722, which also includes an image sensor 724 and associated electronics for acquiring, processing, storing, and transmitting images. In this example, the optical system can be described as object-centric because the principal ray is parallel on the object side of the optical system.

[0060] With this telecentric arrangement, the apparent size of the sample does not change with distance from the optical system, and the magnification is the same for all object distances. Defocused samples will have a blurred image, but the size of the blurred image corresponds to the size of the focused image of the sample. Sample edges may appear blurry, but are easily located. Parallax errors are avoided. In some instances, all samples are in focus due to the available depth of field. Placing the aperture stop at the focal point of the lens is a representative method for achieving telecentricity. Figure 7 As shown, with the sample located at 702A or 702B, the associated principal rays 730A and 730B pass through the center of the aperture stop 720, respectively. For clarity, the image formation performed by the imaging lens 718 is not shown to make the principal rays more easily visible. As discussed above, some or all of the telecentric optical system 700 may be located inside or outside the vacuum chamber, if convenient.

[0061] exist Figure 7 In this arrangement, the sample can be illuminated from either the front or the back. In a typical example, back illumination is used so that the sample blocks the illumination, and the image of the sample is shown as a dark area with edges. Front or back illumination can be provided using a light source located on the front or back of the sample, using mirrors or other reflectors. Side illumination can also be used, but it usually requires processing to properly identify the reflective areas for secure 3D mapping.

[0062] Example 8

[0063] Figure 8 A portion of a representative profilometry system is shown, comprising a telecentric optical system 800 positioned to generate an image of a sample, which can be located at various positions along the optical system axis 801, such as at 802A, 802B. The sample is fixed to a rotatable sample platform 804, allowing its position to vary along both the X and Y axes of a representative coordinate system 850. For convenience, the optical system axis 801 is shown parallel to the X-axis, and the electron microscope axis is parallel to the Z-axis. The telecentric optical system includes an objective lens 810 and an imaging lens 818, positioned around aperture stops 820 at their respective focal lengths F1, F2, to achieve telecentricity and generate an image at an image sensor 824. Associated electronics for acquiring, processing, storing, and transmitting the images are not shown. In this example, the optical system may be referred to as object-side telecentric and image-side telecentric because the principal rays are parallel on the object and image sides of the optical system.

[0064] With this telecentric arrangement, the apparent size of the sample does not change with distance from the optical system, and due to object-side telecentricity, the magnification is the same for all object distances. In the case of image-side telecentricity, the position of the principal ray at the image sensor does not depend on the object distance, and the magnification is constant. Figure 8 As shown, with the sample located at 802A or 802B, the associated principal rays 830A and 830B pass through the center of the aperture stop 820 and are parallel to the image side of the imaging lens 818. As described above, for clarity, the image formation performed by the imaging lens 818 is not shown to make the principal rays more easily visible. If convenient, some or all of the telecentric optical system 800 may be located inside or outside the vacuum chamber. Furthermore, the sample may be illuminated from the front or back. In a typical example, back illumination is used so that the sample blocks the illumination, and the image of the sample is shown as a dark area with edges.

[0065] Example 9

[0066] refer to Figure 9A The representative profile system 900 includes an objective lens 910 and an imaging lens 912 located around an aperture stop 914 to form a sample profile image at an image sensor 924. The aperture stop 914 is located at the focal point of the objective lens 910, such that lenses 910 and 912 form an object-side telecentric optical system. The telecentric objective lens 910 is separated from the vacuum chamber 916 by a vacuum-sealed transparent window 913. The imaging lens 912, aperture stop 914, and objective lens 910 are fixed in a lens tube 918, which is secured to the vacuum chamber 916 by one or more bolts 920 or other fasteners. The lens tube is bent to save space outside the vacuum chamber 916. For this purpose, a mirror 911 redirects the light beam from the vacuum chamber 916 to the telecentric objective lens 910. A rotatable sample stage 904 holds samples 902 and 906, with sample 906 shown as being located in the imaging field of view of the objective lens 910. Representative principal rays 930 and 931 are shown, but the ray paths associated with image formation performed by the imaging lens 912 are not shown.

[0067] refer to Figure 9BThe representative profile system 950 includes an objective lens 960 and an imaging lens 962 located around an aperture stop 964. The aperture stop 964 is located at the focal point of the objective lens 960, such that lenses 960 and 962 form an object-side telecentric optical system. The objective lens 960 serves as a window in a vacuum chamber 966. The imaging lens 962 and the aperture stop 964 are fixed in a lens tube 968, which is secured to the vacuum chamber 966 by one or more bolts 970 or other fasteners. Sealing gaskets or other components required to ensure a vacuum seal are not shown. A rotatable sample stage 954 holds samples 952 and 956, with sample 956 shown as being located in the imaging field of view of the objective lens 960. Representative principal rays 980 and 981 are shown, but the ray paths associated with image formation performed by the imaging lens 962 are not shown.

[0068] Example 10

[0069] refer to Figure 10 The representative profile system 1000 includes an objective lens 1010 and an imaging lens 1012 located around an aperture stop 1014 to form a sample profile image at an image sensor 1024. The aperture stop 1014 is located at the focal point of the objective lens 1010 and the focal point of the imaging lens 1012, such that lenses 1010 and 1012 form an object-side and image-side telecentric optical system. The objective lens 1010 and aperture stop 1014 are located in a vacuum chamber and are held by a lens tube 1018 extending through a wall 1016 of the vacuum chamber. The lens tube 1018 is secured to the vacuum chamber wall 1016 by one or more bolts 1020 or other fasteners. Sealing gaskets or other components required to ensure a vacuum seal are not shown.

[0070] Example 11

[0071] refer to Figure 11 Another representative telecentric optical system 1100 includes an objective lens 1112, an intermediate lens 1004, and an imaging lens 1106 located on axis 1101. An aperture stop 1108 is located at the focal point of objective lens 1102 and positioned relative to lenses 1104 and 1106 to achieve object-side and image-side telecentricity. In this example, three lenses are used, one of which (intermediate lens 1004) has negative optical power. Principal rays 1112 and 1113 are shown.

[0072] Example 12

[0073] refer to Figure 12-12AA portion 1200 of the electron microscope includes a sample chamber 1202 defined by a vacuum chamber 1204. An electron optical system extends along a column 1206, but is not shown further. Sample profiling is obtained using an illuminator 1212 that directs an illumination beam 1214 toward the sample fixed to a rotatable sample platform 1220, which is translatable along the X and Y axes of a coordinate system 1201, respectively, having translation stages 1226 and 1224. The approximate center 1228 of the electron optical system is displaced from the illumination beam 1214. The sample can be profiled using the illumination beam 1214 and then translated to an imaging position, for example, the center 1228, for imaging or processing with the electron optical system. The illumination beam 1214 can be a collimated beam or a diffuse beam, and is shown as rectangular for illustration purposes.

[0074] Figure 12B Image 1280 shows the 2D outlines of three objects 1282 of the same size located on sample platform 1284 and at different distances from the telecentric optics system, obtained using a telecentric optics system. As shown, the three objects 1282 have outlines of the same size, making their outlines usable for guiding safe sample stage movement and focusing.

[0075] Example 13

[0076] refer to Figure 13 A portion 1300 of the electron microscope includes a sample chamber defined by a vacuum chamber 1320 evacuated via a channel 1322. The electron optical system includes objective pole pieces 1324, but is not shown further. A 2D sample profile is obtained using an illuminator 1306 that directs an illumination beam 1308 toward a sample 1312 fixed to a rotatable sample platform 1308, which is translatable along any of the axes of coordinate system 1301 and tiltable to a sample position 1313 for profile analysis. The sample platform 1311 is typically coupled to a sample stage 1309 for translating the sample to the axis 1340 of the electron optical system. The sample can be tilted, profiled during displacement and tilting, and then translated without tilting for imaging with the electron optical system. The illumination beam 1308 can be a collimated beam or a diffuse beam. An objective lens 1302 is located on the wall of the vacuum chamber 1320, and a camera 1305 is positioned to form a telecentric optical system and record the sample profile. The central axis of the profile system 1304 is parallel to the sample platform plane during profile analysis.

[0077] Example 14

[0078] Figure 14AAspects of the sample profile image are shown. In a typical example, samples such as 1406 and 1420 are fixed to sample platform 1402 and back-illuminated using illumination system 1410. Due to back illumination, the profile of the sample, for example, sample region 1407, typically appears darker, but some portions of sample region 1455 appear brighter due to sample reflectivity and surface tilt. This sample region 1455 reflects light from illumination system 1410. To safely position the sample (without collision with components in the electro-optical system or other components), the central region of sample region 1455 can be treated in the same way as the darker regions, such as 1407 and 1421. If an area such as sample region 1455 appears darker, the treatment is straightforward, but such areas can still be identified as potential obstacles to be avoided when moving the sample to the imaging position.

[0079] Figure 14B Show Figure 14A The sample arrangement is the same, but uses an illuminator 1450 that provides variable illumination in the Z-axis direction 1454. As shown, the illuminator 1450 includes a relatively bright area (higher intensity) 1451 and a relatively dark area (lower intensity) 1452, the relatively dark area producing a relatively darker area 1456—if compared with... Figure 14A When used in conjunction with illumination system 1410, region 1456 will appear brighter and more difficult to identify as a potential obstacle in the 2D profile. Reflection from region 1456 is related to the reflectivity of the sample surface and the tilt of the sample surface. By varying the illumination intensity in the z-direction, the top of the sample can be imaged with higher contrast and thus identified with greater accuracy in the 3D mapping. Other stepped or gradual increases or decreases in illumination intensity along the z-axis can be used and achieved through appropriate numbers of light emitters, variations in light scattering, or light attenuation, or other methods. Because obstacles should appear dark, reflective obstacles, such as the sides of the sample, can appear relatively bright compared to obstacles that completely block illumination. These relatively bright areas (e.g., region 1456) should be identified as obstacles.

[0080] Example 15

[0081] Figure 15A representative illuminator 1500 is shown, comprising one or more light emitters, such as LED 1502, that couple light into the edge of a transparent sheet 1504 serving as a light guide. Coordinate axis 1550 indicates the Z-axis associated with the optical axis of the charged particle beam and the Y-axis associated with the axis of the optical system used to obtain the 2D profile. The main surface of sheet 1504 is optically roughened by grinding, sandblasting, or other processes to scatter light for illumination. As light introduced at edge 1506 propagates toward the opposite edge 1507, the light is attenuated by scattering. To allow for uniform illumination, regions 1510-1514 of the surface of sheet 1504 may have increased roughness to increase scattering, thereby compensating for the light intensity loss as light propagates from LED 1502 to edge 1507. The roughness or other scattering characteristics may vary smoothly or gradually (as shown), or both. The intensity of the output light can be further customized through top-to-bottom (gradual or continuous) illumination gradients, such that, for example, the top and bottom edges of the illuminator surface are associated with different intensities. Variable factors (stepped or gradient attenuators) can also be used to achieve higher light density near edge 1506 and lower light density near edge 1507. Other illumination patterns besides stepped or continuous gradients can be used.

[0082] Example 16

[0083] refer to Figure 16A representative method 1600 for generating a 3D mapping includes selecting multiple sample views (rotation angles) at 1602 and selecting an initial view height and view width at 1604. In some cases, the field of view of the optical system is not large enough to obtain the complete profile, and the sample platform or optical system is adjusted to capture the full sample height. At 1606, a rotation angle is selected, and at 1608, the sample platform is set at the initial height and rotation angle. At 1610, a 2D profile is obtained. In some instances, the 2D profile or 2D projection is an image with binary contrast. The binary 2D profile can be transformed by thresholding the image detected by the detector. For example, the 2D profile presents a first intensity corresponding to light received directly from the light source without being blocked by the sample and / or sample platform. The binary 2D profile may also present a second intensity, less than the first intensity, in areas corresponding to shadows generated by the light-obstructing sample. At 1612, it is determined whether to use an additional angle to obtain an additional profile. If so, method 1600 returns to 1606 to select a rotation angle and repeats the necessary steps. At 1614, determine whether to adjust the view height. If so, adjust the view height at 1618 and return to 1606. The view width can be changed at 1620 as determined at 1616, and the process can return to 1606. Once all contours are available, they can be combined at 1630 to produce a 3D map. The 3D map can be produced as shown below with reference to Figure 24. If desired, the 3D map can optionally be combined with a camera image, for example, with an image acquired using a navigation camera, at 1632. Method 1600 can be performed after the sample is loaded into the vacuum chamber and before imaging or processing with a charged particle beam. In one example, method 1600 can be performed while the vacuum chamber is evacuated for charged particle beam imaging or processing. A 3D sample contour can be generated when the sample or sample platform is in the contour analysis position. The sample platform is then moved from the contour analysis position to the sample imaging position for imaging or processing of one or more samples held by the sample platform. The sample platform is moved from the contour analysis position to the imaging position based on the 3D sample contour to avoid collision between the sample and the internal structure of the CPM.

[0084] Example 17

[0085] like Figure 17Representative method 1700 includes determining at 1702 whether to obtain a 3D map adapted to reflectivity. Such a 3D map is referred to herein as a “safe” 3D map. A safe 3D map can be generated for a sample with a highly reflective surface oriented in a manner that may cause light reflection. As discussed above, the 3D map defines an area around an electrode or other component within a vacuum chamber in which the sample can travel to a position for imaging or other evaluation without contacting other components. If the reflective surface has sufficient reflectivity to appear similar to direct illumination from a light source, the reflective surface may be omitted in the map. The reflectivity of the sample may need to be taken into account when generating a map for a reflective sample. If a safe map is to be generated, mutually shifted 3D maps are obtained at 1712 and the 3D maps are combined using “OR” logic at 1714 to generate a safe 3D map. The shifted 3D maps are typically based on multiple angles spanning a full rotation, but each map covers a different set of angles, such as 0, 5, 10, ..., 360 degrees and 1, 6, 11, ... degrees, etc. Otherwise, a 2D projection within the desired range and resolution (i.e., angular increment) is obtained at 1706, and said 2D projection is combined at 1708 to produce a 3D map. For non-reflective samples, the 3D map allows safe movement without considering reflection. However, at 1710, the resulting 3D map (i.e., whether or not a safe 3D map) can optionally be combined with a camera image. At 1722, a sample position can be selected, and at 1724, the selected position can be positioned for focusing using the 3D map. For example, the sample platform or other mechanical or electro-optical components can be moved without operator intervention by moving within an unoccupied area in the 3D map, such that the selected focal position is in the imaging position, aligned with the CP beam under the electrode of the CPM, for imaging or processing. Thus, the 3D map allows for the determination of a safe path that avoids collisions between the sample and the optical components.

[0086] Such system controllers, such as control computers, can be used to automatically check and control sample positioning using full 3D mapping, or to guide manual operation by issuing alarms or preventing samples from moving into areas where collisions may occur.

[0087] It should be understood that the generation of 3D maps can be performed outside the electron microscope chamber or during or after the microscope is evacuated. For example, [examples of methods can be used]. Figure 2 The visual interface shown indicates the sample's location. In some cases, the 3D map can be processed to remove areas that would otherwise appear to be occupied by the sample.

[0088] Example 18

[0089] refer to Figure 18An exemplary system for implementing the disclosed technology includes a general-purpose computing device in the form of an exemplary conventional PC 1800, the general-purpose computing device including one or more processing units 1802, system memory 1804, and a system bus 1806 coupling various system components including the system memory 1804 to the one or more processing units 1802. The system bus 1806 may be any of several types of bus structures using any of a variety of bus architectures, including a memory bus or memory controller, a peripheral bus, and a local bus. The exemplary system memory 1804 includes read-only memory (ROM) 1808 and random access memory (RAM) 1810. A basic input / output system (BIOS) 1812 is stored in the ROM 1808, the BIOS containing basic routines that facilitate the transfer of information between components within the PC 1800. The memory 1804 also contains portions 1871-1875, which contain computer-executable instructions and data for acquiring 2D profiles (including sample stage control), determining 3D profiles based on the acquired 2D profiles, determining safe sample paths, a graphical user interface for operator input and output, and overall instrument control.

[0090] The exemplary PC 1800 further includes one or more storage devices 1830, such as hard disk drives or memory devices like thumb drives. Such storage devices can be connected to the system bus 1806 via a suitable interface. This type of computer-readable medium provides the PC 1800 with non-volatile storage of computer-readable instructions, data structures, program modules, and other data. Other types of computer-readable media that can store data accessible by the PC, such as magnetic tape cartridges, flash memory cards, digital video optical discs, CDs, DVDs, RAM, ROM, etc., may also be used in the exemplary operating environment.

[0091] Numerous program modules may be stored in storage device 1830, which includes an operating system, one or more application programs, other program modules, and program data. Users can input commands and information into PC 1800 via one or more input devices 1840, such as a keyboard, and pointing devices such as a mouse, touchpad, digital camera, microphone, joystick, or gamepad. These and other input devices are typically connected to one or more processing units 1802 via a serial port interface coupled to system bus 1806, but may be connected via other interfaces such as a parallel port, game port, or Universal Serial Bus (USB). Monitor 1846 or other types of display devices are also connected to system bus 1806 via an interface such as a video adapter. Other peripheral output devices, such as speakers and printers (not shown), may be included.

[0092] PC 1800 can operate in a networked environment using logical connections to one or more remote computers, such as remote computer 1860. In some instances, one or more network or communication connections 1850 are included. Remote computer 1860 may be another PC, server, router, network PC, or peer device or other public network node, and typically includes many or all of the elements described above with respect to PC 1800, although only memory storage device 1862 is present. Figure 18 As shown in the diagram, the personal computer 1800 and / or the remote computer 1860 can be connected to a logical local area network (LAN) and a wide area network (WAN). Such network environments are common in offices, enterprise-wide computer networks, intranets, and the Internet.

[0093] When used in a LAN networking environment, PC 1800 connects to the LAN via a network interface. When used in a WAN networking environment, PC 1800 typically includes a modem or other devices for establishing communication over a WAN, such as the Internet. In a networked environment, program modules or portions thereof depicted relative to PC 1800 may be stored in remote storage devices or other locations on the LAN or WAN. The network connections shown are exemplary, and other devices for establishing communication links between computers may be used.

[0094] Example 19

[0095] refer to Figure 19 The representative electron microscope 1900 includes pole pieces 1902 that guide a light beam to a sample platform 1904 coupled to translation stages 1906, 1908 and a translation / rotation stage 1910. An electron optics column 1901 includes lenses, deflectors, and other electron optics components (not shown). Representative samples 1912-1914 are fixed to the sample platform 1904. An illuminator 1920 directs a light beam 1922 to samples 1912-1914 and a transparent window 1924 in a vacuum chamber housing 1925. A telecentric optical system 1926 is positioned to form a contour image on an image sensor 1928 based on back illumination of samples 1912-1914 for various rotation angles provided by the translation / rotation stage 1910.

[0096] Example 20

[0097] Figure 20 The diagram shows a sequence 2000 of contour images, obtained during sample rotation to generate 3D mappings, such as... Figure 3B 3D mapping 350. Representative samples 2001-2003 are shown. Each contour image corresponds to a different rotation angle.

[0098] Figures 21A-21B An example 2D projection 2100 shows samples 2102 and 2104 fixed to sample platform 2106. Figure 21B The reflective region 2107 associated with the edge of the sample platform 2106 is shown. For safe movement within the vacuum chamber, the reflective region 2107 should be marked as an obstacle, although it is not as dark as the rest of the 2D projection of the sample platform 2106. For example, the reflective region 2107 is typically presented with the chosen rotation angle and associated 2D projection.

[0099] Figures 22A-22B 2D projections 2200 and 2202 are shown, which depict sample 2201 and are obtained using a telecentric optical system with a field of view smaller than that of the sample platform. 2D projections 2202 and 2204 can be combined to produce... Figure 22C The complete 2D outline in 2206.

[0100] Figure 23 A series of 2D projections obtained at different rotation angles are shown. Representative samples 2302 and 2304 are shown. At rotation angles of 68, 69, 70, and 71 degrees, sample 2302 has a reflective region 2308, which can be identified as an obstacle in the 3D mapping. The intensity of the reflective region 2308 is similar to that of the unobstructed region. Such regions can be properly identified as obstacles if the 2D projection values ​​are thresholded with appropriate values ​​to distinguish between reflective and unobstructed regions. Reflection can be reduced by collimating illumination or increasing the distance between the light source and the sample. Alternatively, patterned illumination can be used to simplify the identification of reflective regions, or the above references can be used. Figures 4A-4B The methods discussed.

[0101] Example 21

[0102] Figure 24A-2 4E illustrates the processing of 2D contours to produce 3D mappings. Figure 24A A representative 2D projection 2402 at the selected angle is shown, and Figure 24B The cylindrical volume 2404 is shown as indicating the initial, fully occupied sample space; that is, space that can potentially be moved but may contain portions occupied by the sample and therefore unsafe for movement. Figure 24B As shown, the initial size of the cylindrical volume 2404 is based on the size of the sample holder and the microscope configuration, and indicates the maximum volume of the sample that can be positioned. Using 2D projection 2402, a portion of the cylindrical volume 2404 is removed, as... Figure 24D and Figure 24FAs shown in Figure 24C, the unoccupied space 2406 in the 2D projection 2402 is used to define the corresponding feature 2416 indicating the area that is allowed to move. The unoccupied space 2406 extends through the cylindrical volume 24D to remove a portion of the cylindrical volume 2404, such that feature 2416 extends through the cylindrical volume 2404. Other unoccupied spaces indicated by the 2D projection 2402 define corresponding features and extend through the cylindrical volume 2404. The resulting volume 2405 ( Figure 24D The upper boundary of the 2D projection 2402 is used to indicate the safe area for movement. In this example, the upper boundary of the 2D projection 2402 is used, and this method can be referred to as the "envelope" method. Then, additional 2D projections at other rotation angles are used to define the features in the cylindrical volume 2404 to produce a 3D mapping. Alternatively, complete 2D projection data can be used, as shown in Figures 24E-24F. In this case, the lower unoccupied space 2408 in the 2D projection 2402 is used to define the corresponding feature 2418 in the volume 2404. Then, additional 2D projections at other angles are used to define the features in the volume 2404 to produce a 3D mapping. This method may be computationally more intensive than the envelope method.

[0103] Given the many possible embodiments to which the disclosed technical principles can be applied, it should be recognized that the illustrated embodiments are merely preferred examples and should not be considered as limiting the scope. Therefore, I claim that all are within the scope and spirit of the appended claims.

Claims

1. A method for positioning a sample, comprising: The sample located in the vacuum chamber of the charged particle microscope is illuminated from the first side with light; Detect at least one 2D projection of the sample; Generate a 3D map based on the at least one 2D projection; and Based on the 3D mapping, the sample is positioned at an imaging location within the vacuum chamber, where the sample is imaged or processed using a charged particle beam. The 2D projection of the sample is detected on a second side opposite to the first side, and the 2D projection is generated by receiving light that is not blocked by the sample.

2. The method of claim 1, wherein the sample is illuminated from the first side by a light source, and the sample is imaged or processed at the imaging position by a beam of charged particles.

3. The method of claim 1 or claim 2, further comprising detecting a plurality of 2D projections of the sample on the second side by rotating the sample, wherein the 3D mapping is generated based on the plurality of 2D projections.

4. The method of claim 3, further comprising determining a set of initial 3D maps, wherein each of the initial 3D maps is based on a different set of rotation angles and the 3D maps are based on a combination of the initial 3D maps such that the 3D maps are safe 3D maps that take into account reflections from the sample surface.

5. The method of claim 1 or claim 2, wherein the sample is illuminated at the contour analysis position, and the sample is moved from the contour analysis position to the imaging position based on the 3D mapping.

6. The method of claim 1, wherein irradiating the sample comprises guiding a collimated beam onto the sample.

7. The method of claim 1 or claim 6, wherein the irradiation of the sample is performed using an illumination source located within the vacuum chamber.

8. The method of claim 1, wherein irradiating the sample comprises irradiating the sample with a light beam having a patterned intensity.

9. The method of claim 1 or claim 2, wherein a telecentric optical system is used to perform the detection of at least one 2D projection of the sample on a second side opposite to the first side.

10. The method of claim 9, wherein when the sample is irradiated, the central axis of the telecentric optical system is parallel to the sample platform holding the sample.

11. The method of claim 10, wherein the telecentric optical system comprises an objective lens located within a vacuum chamber or in the wall of the vacuum chamber.

12. The method according to claim 11, wherein the telecentric optical system is object-side telecentric.

13. The method according to claim 11, wherein the telecentric optical system is object-side telecentric and image-side telecentric.

14. A charged particle microscope, comprising: An illumination system, which is positioned to illuminate the sample from a first side; An imaging system is positioned to generate a 2D projection of an illuminated sample based on illumination from the first side; as well as The processor is configured to: Receive the 2D projection; and A 3D map of the sample is generated, which is used to move the sample to an imaging position within the vacuum chamber based on the 3D map. The sample is imaged or processed using a charged particle beam at the imaging location. The 2D projection is generated by receiving light that is not blocked by the sample.

15. The charged particle microscope of claim 14, wherein the imaging system includes an image sensor located on a second side opposite to the first side to generate a 2D contour image of the irradiated sample, and the processor is coupled to the sample platform and configured to rotate the sample to generate the 2D projection.

16. The charged particle microscope of claim 15, wherein the illumination system is positioned to direct a diffuse beam of light onto the sample, and the imaging system comprises a telecentric optical system that directs a 2D projection onto the image sensor.

17. The charged particle microscope of claim 14, wherein the illumination system is positioned to guide a collimated beam onto the sample.

18. The charged particle microscope according to any one of claims 14 to 17, further comprising a sample stage, the sample stage being configured to move a sample platform holding the sample to the charged particle optical axis.

19. The charged particle microscope according to any one of claims 14 to 17, wherein the processor is coupled to initiate evacuation of the charged particle microscope vacuum chamber during the acquisition of the 2D projection.

20. A computer-readable medium storing processor-executable instructions, which, when executed by a processor, cause the processor to perform the method according to any one of claims 1-13.

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