Movable support for securing conductive and non-conductive samples in vacuum chamber

Abstract

A chuck for supporting a sample in a processing chamber, comprising: a support plate formed of a dielectric material, the support plate comprising an upper planar support surface sized and shaped to hold a substrate disposed on the support plate; one or more electrodes disposed within the support plate in proximity to the upper planar support surface; a plurality of lifting rod holes, wherein the plurality of lifting rod holes are completely formed by penetrating through the supporting plate; a plurality of short column cavities, the plurality of short column cavities are formed in the support plate, and each short column cavity is provided with an opening at the upper plane support surface; a plurality of retractable stub posts, the plurality of retractable stub posts corresponding in number to the plurality of stub post cavities, with each retractable stub post disposed in a unique one of the stub post cavities; and a stub lift mechanism operable to move each retractable stub of the plurality of stubs between a downward position in which a distal end of the retractable stub is disposed within its respective stub cavity and recessed below the upper planar support surface, and an upward position in which a distal end of the retractable stub is disposed within its respective stub cavity and recessed below the upper planar support surface. And in the upward position, the distal end of the retractable stub protrudes above the upper planar support surface through the stub cavity opening.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to U.S. patent application Ser. No. 18 / 115,689, filed on February 28, 2023, entitled “MOVEABLE SUPPORT TO SECUREELECTRICALLY CONDUCTIVE AND NONCONDUCTIVE SAMPLES IN A VACUUM CHAMBER,” which is hereby incorporated by reference in its entirety. Background Art

[0003] When studying electronic materials and the processes used to fabricate electronic structures from such materials, samples of the electronic structures can be examined microscopically for the purposes of failure analysis and device verification. For example, samples of electronic structures (such as silicon wafers) can be analyzed in a scanning electron microscope (SEM) to study specific characteristic features within the wafer. Such characteristic features can include the fabricated circuits as well as any defects formed during the fabrication process. Electron microscopes are one of the most useful instruments for analyzing the microstructure of semiconductor devices.

[0004] An SEM instrument can capture images of an area on a sample by positioning the sample in a vacuum chamber, generating a charged particle beam, and illuminating the sample with the beam while the sample is positioned on a sample support structure within the vacuum chamber. Particles emitted as a result of the irradiation can then be detected to produce an SEM image of the area illuminated by the charged particle beam.

[0005] During failure analysis and / or device verification processes, SEM images are often taken at multiple locations on a sample. The charged particle column in an SEM instrument is typically located in a fixed position within a vacuum chamber. Therefore, to image multiple locations on a sample, a sample support can move the sample along the X and Y axes to position the area of ​​the sample being imaged directly below the charged particle column's field of view.

[0006] When obtaining SEM images, it is important that the sample be secured to a sample support in the vacuum chamber so that the sample does not shift or otherwise move as the sample support moves the sample to image the next location on the sample. Currently, some known SEM instruments include different types of sample support structures (referred to herein as "chucks") depending on the electrical properties of the sample to be imaged. For example, when imaging electrically conductive samples (e.g., semiconductor wafers), the sample support structure can be an electrostatic chuck (sometimes referred to herein as an "eChuck"). When imaging non-conductive samples (e.g., dielectric wafers such as glass or sapphire wafers), the sample support structure can be a short column chuck (sometimes referred to herein as an "sChuck") that supports the sample on a plurality of rods or "stubs." Thus, certain SEM instruments can only be reliably used to image certain types of samples depending on the sample support structure installed within the vacuum chamber of the instrument.

[0007] Thus, there is a need for new and improved methods and systems for supporting samples in a substrate processing chamber such as a SEM instrument. SUMMARY

[0008] The embodiments described herein provide methods and systems for securely supporting both electrically conductive and non-conductive samples on the same sample support (sometimes referred to herein as a "chuck") within a vacuum chamber of an instrument such as a scanning electron microscope. While embodiments of the present disclosure can be used to support many different types of electrically conductive and non-conductive samples within a vacuum chamber, some embodiments are particularly useful for supporting both samples that are dielectric wafers and samples that are semiconductor wafers on the same sample support in a vacuum chamber of a sample analysis tool that includes one or more charged particle columns.

[0009] In some embodiments, a chuck to support a sample in a process chamber is provided. The chuck can include a support plate formed of a dielectric material, a plurality of lift pin holes formed completely through the support plate, and a plurality of stub cavity formed within the support plate. The support plate can include an upper planar support surface sized and shaped to hold a substrate disposed on the support plate, and each stub cavity can have an opening at the upper planar support surface. The chuck can also include one or more electrodes disposed within the support plate proximate the upper planar support surface, a plurality of retractable stubs corresponding in number to the plurality of stub cavities, wherein each retractable stub is disposed in a unique one of the stub cavities, and a stub lift mechanism operable to move each retractable stub of the plurality of stubs between a down position and an up position, wherein in the down position, a distal end of the retractable stub is disposed within its respective stub cavity and recessed below the upper planar support surface, and in the up position, the distal end of the retractable stub protrudes above the upper planar support surface through the stub cavity opening.

[0010] In some embodiments, a system for evaluating a sample is provided. The system can include a vacuum chamber, a sample support disposed within the vacuum chamber and operable to hold a sample during a sample evaluation process, a charged particle column configured to direct a beam of charged particles into the vacuum chamber toward the sample positioned on the sample support, and a moveable stage configured to move the sample support within the vacuum chamber in X, Y, and Z directions. The sample support can include a support plate formed of a dielectric material, a plurality of lift pin holes formed completely through the support plate, and a plurality of stub cavity formed within the support plate. The support plate can include an upper planar support surface sized and shaped to hold a substrate disposed on the support plate, and each stub cavity can have an opening at the upper planar support surface. The sample support can further include one or more electrodes disposed within the support plate proximate the upper planar support surface, a plurality of retractable stubs corresponding in number to the plurality of stub cavities, wherein each retractable stub is disposed in a unique one of the stub cavities, and a stub lift mechanism operable to move each retractable stub of the plurality of stubs between a down position and an up position, wherein in the down position, a distal end of the retractable stub is disposed within its respective stub cavity and recessed below the upper planar support surface, and in the up position, the distal end of the retractable stub protrudes above the upper planar support surface through the stub cavity opening.

[0011] Various embodiments of a chuck and / or system for evaluating a sample can include one or more of the following features. Each retractable stub can be coupled to a biasing mechanism disposed within its respective stub cavity and configured to bias the retractable stub in a downward position. The biasing mechanism can include a coil spring. The stub lift mechanism can move all of the retractable stubs together between the upward position and the downward position. The stub lift mechanism can include a rotatable annular body and a plurality of ball bearings. Each ball bearing of the plurality of ball bearings can be positioned below a unique one of the retractable stubs. The stub lift mechanism can be operable to apply a force to the ball bearings to move their respective retractable stubs to the upward position. The stub lift mechanism can further include a plurality of recessed tracks formed in the annular ring. Each recessed track can have a deep end and a shallow end and a ramped surface extending between the deep end and the shallow end. Each ball bearing of the plurality of ball bearings can be seated within a unique one of the recessed tracks of the plurality of tracks. The stub actuator system can further include an actuator operably coupled to rotate the annular body in opposite first and second directions such that the ball bearing in each recessed track moves up and down in response to the ramped surface. Each retractable stub can further include a bearing seat including one or more walls that enclose the bearing positioned below the retractable stub such that the one or more walls prevent the bearing from rotating with the annular body. The stub lift mechanism can include a plurality of stub actuators including a separate stub actuator for each retractable stub. The stub lift mechanism can be operable to raise and lower each retractable stub of the plurality of retractable stubs between the upward position and the downward position independently of the other retractable stubs. The one or more electrodes can include at least two electrodes.

[0012] For a better understanding of the nature and advantages of the present disclosure, reference should be made to the following description and drawings. It is to be understood, however, that the figures are provided for purposes of illustration only and are not intended to limit the scope of the present disclosure. Also, as a general rule, and unless clearly indicated otherwise, where elements are shown in different figures, those elements generally are the same or at least similar in function or purpose. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a simplified diagram of a sample evaluation system including a scanning electron microscope (SEM) column;

[0014] Figure 2A and Figure 2B are simplified cross-sectional views of electrostatic chucks having lift pins in a downward position and an upward position, respectively;

[0015] Figure 3A and Figure 3Bis a simplified cross-sectional view of a short post chuck with lift pins in a down position and an up position, respectively;

[0016] Figure 4A and Figure 4B is a simplified cross-sectional view of a bridge chuck according to embodiments disclosed herein;

[0017] Figure 4C is a simplified cross-sectional view of a portion of a bridge chuck according to some embodiments disclosed herein; Figure 4B is a simplified cross-sectional view of a portion of a bridge chuck shown with a sample resting on a retractable short post;

[0018] Figure 5 is a simplified cross-sectional view of a bridge chuck according to some embodiments; Figure 4A and Figure 4B is a simplified top view of a bridge chuck depicted;

[0019] Figure 6 is a top view of a sample support according to some embodiments disclosed herein;

[0020] Figure 7 is a simplified diagram depicting a short post actuator system according to some embodiments;

[0021] Figure 8A is a simplified cross-sectional view of a bearing track taken along a first plane according to some embodiments; Figure 7 is a simplified cross-sectional view of a bearing track shown;

[0022] Figure 8B and Figure 8C is a simplified cross-sectional view of a bearing track taken along a second plane perpendicular to the first plane; Figure 8A is a simplified cross-sectional view of a bearing track shown;

[0023] Figure 9A and Figure 9B is a simplified cross-sectional view of a retractable short post in a down position and an up position, respectively, according to some embodiments; and

[0024] Figure 10 is a simplified cross-sectional view of a retractable short post according to additional embodiments. DETAILED DESCRIPTION

[0025] Embodiments described herein provide methods and systems for securely supporting both conductive and non-conductive samples on the same sample support within a vacuum chamber of an instrument, such as a scanning electron microscope. While embodiments of the present disclosure can be used to support many different types of conductive and non-conductive samples within a vacuum chamber, some embodiments are particularly useful for supporting samples that are dielectric wafers and samples that are semiconductor wafers in a vacuum chamber of a sample analysis tool that includes one or more charged particle columns.

[0026] Example sample evaluation tool

[0027] For better understanding and appreciation of the present disclosure, reference is first made to Figure 1 which is a simplified schematic diagram of a previously known sample evaluation system 100. Among other operations, the sample evaluation system 100 can be used for defect inspection and analysis of structures formed on a sample (e.g., a semiconductor or dielectric wafer).

[0028] The system 100 can include a vacuum chamber 110 and a scanning electron microscope (SEM) column 120. A support element 140 can support a sample 150 (e.g., a semiconductor wafer) within the chamber 110 during processing operations in which the sample 150 (sometimes referred to herein as an “object” or “specimen”) is subjected to a beam of charged particles 126 from the SEM column.

[0029] The SEM column 120 is connected to the vacuum chamber 110 such that a beam of charged particles generated by the column propagates through a vacuum environment formed within the vacuum chamber 110 before impinging on the sample 150. The SEM column 120 can generate an image of a portion of the sample 150 by illuminating the sample with a beam of charged particles 125, detecting particles emitted as a result of the illumination, and generating an image of the charged particles based on the detected particles. To this end, the SEM column 120 can include an electron beam source 122 (i.e., an “electron gun”), an anode tube 126 defining an electron beam drift space, a condenser lens arrangement 124, one or more deflection lenses (e.g., lenses 130, 132), one or more focusing lenses 134, and a column cap 136.

[0030] During an imaging process, the electron beam source 122 generates an electron beam 125 that passes through the condenser lens 124 and is initially converged by the condenser lens 124, and then focused by the lens 134 before hitting the sample 150. The condenser lens 124 defines the numerical aperture and current of the electron beam (along with the final aperture) that is directly related to resolution, while the focusing lens 134 focuses the electron beam onto the sample. The column cap 136, which is located between the lower end of the anode tube 126 (a first electrode) and the sample 150 (a second electrode), can be a third electrode in the system that adjusts the electric field generated near the wafer.

[0031] Figure 1 The SEM column 120 is depicted with the beam of charged particles 125 generally orthogonal to the sample 150 when the beam of charged particles 125 impinges on the sample. In various embodiments, the SEM column 120 can operate in a tilt mode in which the beam of charged particles 125 impinges on the sample 150 at a non-perpendicular angle (e.g., a 45-degree angle).

[0032] In the rule mode and the tilt mode, the particle imaging process generally includes scanning the charged particle beam back and forth over a particular area of the sample being imaged (e.g., in a raster or other scan pattern). The deflection lenses 130, 132, which can be magnetic lenses, electrostatic lenses, or a combination of both electric and magnetic lenses, can implement scan patterns known to those skilled in the art. The area scanned generally occupies only a small fraction of the total area of the sample. For example, the sample can be a semiconductor wafer that is 200 or 300 mm in diameter, while each area scanned on the wafer can be a rectangular area having a width and / or length measured in microns or tens of microns.

[0033] The SEM column 120 can also include one or more detectors to detect charged particles generated from the sample during the imaging process. For example, the SEM column 120 can include an in-lens detector 128 and a top detector 138, which can be configured to detect secondary electrons and backscattered electrons emitted as a result of the charged particle beam 126 illuminating the sample. The in-lens detector 128 can include a central aperture that allows the charged particle beam 126 to pass through the detector and allows both secondary electrons and backscattered electrons entering the charged particle column 120 to pass through the detector 128 to the top detector 138. In some embodiments, the sample evaluation system 120 can also include an external detector, which can also be configured to detect secondary electrons and backscattered electrons or can be configured to detect X-rays, such as an X-ray spectrum (EDX) detector.

[0034] During operation of the system 100, the sample support 140 (sometimes referred to herein as a “stage”) can move the sample so that different portions (e.g., different regions of interest or “ROIs”) are positioned directly beneath the field of view of the SEM column 120. The sample support 140 can move the sample 150 relatively quickly back and forth and side to side (i.e., along the X and Y axes) within the chamber 110, and can also raise and lower the sample 150, moving the sample along the Z axis.

[0035] Because many of the features formed on the sample 150 have a size that is on the order of microns or less, it is important to know precisely the position of the sample relative to the focal point of the SEM column 120. To determine the position of the sample 150 precisely, a stage-precise navigation, interferometry system 160 can be used in some embodiments. The system 160 can be mounted on the lid 112 of the chamber 110 and direct a collimated light (e.g., a laser beam) through a window 114 formed in the lid to a target area on the sample support 140 that is encoded with various linear or other markings. After reflecting back to the system 160 from the encoded target area of the sample support 140, the system can detect the light from the collimated light pulse (e.g., with a photodetector array). A processor (e.g., a digital signal processor) within the system 160 can then analyze the detected light signal to determine the high-precision position of the sample along the X and Y axes.

[0036] Additionally, the system 100 can include a voltage source 165 and one or more controllers 170, such as a processor or other hardware unit. The voltage source 165 can be operated to provide a desired effective voltage of the column, thereby improving image resolution. This can be achieved by an appropriate distribution of voltage supply between the first and second electrodes (i.e., between the anode tube and the sample). The controller 170 can control operation of the system, including the voltage source, by executing computer instructions stored in one or more computer-readable memories 180, as known to those of ordinary skill in the art. For example, the computer-readable memories can include solid-state memory (such as random access memory (RAM) and / or read-only memory (ROM), which can be programmable, flash-updateable, and / or the like), disk drives, optical storage elements, or similar non-transitory computer-readable storage media.

[0037] The system 100 can also include a user interface 190, which can enable one or more users to interact with the system. For example, the user interface 190 can allow a user to set parameters of the SEM column or detector that can be used when analyzing a sample. The user interface 190 can include any known elements that enable a user to input information to interact with a computer system, such as a keyboard, mouse, monitor, touch screen, touch pad, voice-activated input controller, and the like.

[0038] When imaging or otherwise evaluating a sample using an SEM instrument such as the system 100, it can be important to know precisely the working distance between the column tip and the sample. As used herein, the "working distance" between a charged-particle column and a sample is the distance between the electrode of the lens device closest to the sample plane (i.e., the cap electrode in some examples below) and the sample plane.

[0039] Example sample support

[0040] As mentioned in the Background section, in some known SEM instruments, the sample support 140 is an electrostatic chuck or a short-column chuck, depending on whether the evaluation system 100 is optimized to evaluate a conductive sample or a non-conductive (dielectric) sample.

[0041] 1. Electrostatic chuck

[0042] Figure 2A and 2B is a simplified diagram of an electrostatic chuck 200 that some previously known sample evaluation systems use to support a conductive sample, such as a semiconductor wafer, in a vacuum chamber during a sample evaluation process. Referring first to Figure 2AAs shown, electrostatic chuck 200 includes a movable stage 210 coupled to a support plate 220. Support plate 220 has a planar support surface 222 upon which a sample 250 (e.g., a wafer such as a semiconductor wafer) may be positioned during evaluation or other types of analytical operations.

[0043] The stage 210 can move the support plate 220 (and therefore the sample 250) within the vacuum chamber 110 in the X, Y, and Z directions so as to position a region of interest on the sample directly below the field of view of a charged particle column, such as the charged particle column 120. The plate 220 can be made of a dielectric material, such as a ceramic material, and one or more electrodes 224, 226 can be disposed below the surface 222. When the sample 250 is a semiconductor wafer or other conductive sample, a voltage can be applied to the electrodes 224, 226 to clamp the sample to the planar support surface 222, such as Figure 2A As shown, the sample is secured to support plate 220 so that the sample does not shift or otherwise move when stage 210 moves the sample support within vacuum chamber 110. Clamping sample 250 in this manner also advantageously flattens the sample to ensure accurate working distance across all areas of the sample.

[0044] The support plate 220 may also include a plurality of lift pin holes 228 and a corresponding number of lift pins 230 to facilitate transferring the sample 250 into and out of the sample evaluation system. Figure 2A and 2B As shown, each lifting rod hole 228 can extend completely through the support plate 220. Figure 2A 2B , the lift pins 230 can be attached in a fixed position relative to a portion of the workbench 210 such that the lift pins can move along with the support plate 220 in the X and Y directions while allowing the workbench 210 to raise and lower the support plate 220 in the Z direction without moving the lift pins 230. In this manner, the support plate 220 can be lowered such that the distal end of each lift pin 230 protrudes through its corresponding lift pin hole 228 while holding the sample 250 on the upper surface 222 of the support plate 220, thereby creating a gap 240 between the upper surface 222 of the support plate 220 and the bottom surface of the sample 250, as shown. Figure 2B Then, when the suction cup is sufficiently raised (e.g., to Figure 2A ), each lift pin 230 retracts into its corresponding lift pin hole 228 of the support plate 220 , and the sample 250 rests on the upper surface 222 .

[0045] Make the lifting rod 230 be in the following position Figure 2BThe raised position shown allows a robot arm or similar substrate transfer device (not shown) to transfer the sample 250 into the vacuum chamber, drop the sample onto the lift rod 230, and retract from the vacuum chamber. The support plate 220 can then be raised to position the sample 250 on the upper surface 222, and one or more regions on the sample can be evaluated or otherwise analyzed as described above. Once the evaluation process is complete for a given sample 250, the support plate can be lowered so that the sample 250 is lifted onto the lift rod 230, and the gap 240 created between the sample and the support surface 222 can cause the robot arm (not shown) to be activated to pick up the sample 250 from the lift rod and transfer the sample out of the chamber.

[0046] While the above discussion has been presented in the context of a single lift rod hole 228 and a single corresponding lift rod 230, a typical electrostatic chuck 200 will include at least three lift rod holes 228 and three lift rods 230 spaced around the perimeter of the support plate 220. For example, in some embodiments, the electrostatic chuck 200 can include three lift rod holes 228 and three lift rods 230 spaced 120 degrees apart from one another. Figure 2A 2B While the above discussion has been presented in the context of a single lift rod hole 228 and a single corresponding lift rod 230, a typical electrostatic chuck 200 will include at least three lift rod holes 228 and three lift rods 230 spaced around the perimeter of the support plate 220. For example, in some embodiments, the electrostatic chuck 200 can include three lift rod holes 228 and three lift rods 230 spaced 120 degrees apart from one another.

[0047] 2. Short-stem chuck

[0048] As described above in connection with the discussion of Figure 2A Figure 2B When the sample is electrically conductive, the electrostatic chuck 200 can use the electrodes 224, 226 to clamp the sample to the chuck, allowing the stage 210 to quickly move the sample within the vacuum chamber to a particular location so that the desired region of interest of the sample is directly under the field of view of the charged particle column. However, when the sample is a dielectric (non-conductive) sample, it cannot be electrostatically clamped by the electrodes 224, 226. Therefore, to prevent the dielectric sample from moving or otherwise undesirably moving on the sample support as it is quickly moved within the processing chamber, a short-stem chuck can be employed.

[0049] Figure 3A 3B is a simplified diagram of a short-stem chuck 300 that some previously known sample evaluation systems use to support dielectric (non-conductive) samples, such as sapphire wafers, within a vacuum chamber during a sample evaluation process. The short-stem chuck 300 can include some components similar to those described above with respect to the electrostatic chuck 200. Therefore, for the sake of brevity, these similar components are given the same element designations as shown in Figure 3A 3B Figure 2A 2B are not described in detail below.

[0050] ​​​​​​However, one difference between the short-stem chuck 300 and the electrostatic chuck 200 is that the short-stem chuck 300 includes a plurality of short-stems 324 (which hold the sample slightly above (e.g., a millimeter or less) the upper surface 322 of the sample support plate 320) rather than including electrodes 224, 226 to hold the sample as it is moved within the chamber by the worktable 210. Each short-stem 324 can include a hard rubber or similar surface that provides a relatively high degree of friction between the sample 350 and the short-stem, such that the sample does not move relative to the support plate 320 or otherwise move when the sample is rapidly moved within the processing chamber by the worktable 210.

[0051] As shown in Figure 3A and Figure 3B , the short-stem chuck 300 also includes a lift pin hole 228 and a lift pin 230, which operate as described above with reference to Figure 2A and Figure 2B .

[0052] Bridge chuck with retractable short-stem

[0053] As mentioned in the Background section and discussed above with respect to Figures 2A-3B , in some SEM instruments and other sample evaluation systems, the sample support 140 is either an electrostatic chuck or a short-stem chuck, depending on whether the evaluation system 100 is optimized to evaluate electrically conductive samples or non-conductive samples. Thus, evaluation systems having such sample supports can only reliably analyze the particular type of sample for which the support was intended to be fixed: systems with chucks evaluate electrically conductive samples, while systems with short-stem chucks evaluate non-conductive samples. The embodiments disclosed herein remedy the deficiencies provided by each of the above chuck types, and relate to a sample support or chuck (sometimes referred to herein as a “bridge chuck”) that is capable of safely and reliably supporting both electrically conductive samples and non-conductive samples in a sample evaluation system, such as the sample evaluation system 100.

[0054] To illustrate, reference is first made to Figure 4A and Figure 4B , which are simplified cross-sectional views of a bridge chuck 400 according to some embodiments. The bridge chuck 400 includes a movable worktable 410 that is connected to a support plate 420. The movable worktable 410 can move the support plate 420 (and thus a sample 450 supported on the plate) within a processing chamber (e.g., the vacuum chamber 110) in X, Y, and Z directions in order to position a region of interest on the sample 450 directly beneath a field of view of a charged particle column (e.g., the charged particle column 120). The support plate 420 can be made of a dielectric material, such as a ceramic material, and in some embodiments can be coated with titanium or a similar material. The support plate 420 includes a planar support surface 422 on which the sample 450 can be positioned during processing operations.

[0055] As shown in Figure 4A and 4B , the bridge chuck 400 can include one or more electrodes (e.g., electrodes 424, 426) disposed below the surface 422. The bridge chuck 400 also includes a set of retractable stubs 440 positioned within the support plate 420. As described in greater detail below, the set of retractable stubs 440 are controllably switchable between an up position and a down position. In the down position, the retractable stubs 440 are fully recessed within the support plate 420 such that the entirety of each retractable stub 440 is at a level lower than the upper surface 422. When the retractable stubs 440 are in the up position, the retractable stubs 440 protrude a short distance above the upper surface 422 such that the sample 450 rests on the stubs 440 rather than on the upper surface 422 of the support plate.

[0056] In operation, when the sample 450 is a semiconductor wafer or other electrically conductive sample, the retractable stubs 440 are set to the down position and a voltage can be applied to the one or more electrodes 424, 426 to clamp the sample to the planar support surface 422 as shown in Figure 4A and secure the sample to the support plate 420. The clamping force can be sufficient such that the sample does not move or otherwise shift when the worktable 410 moves the sample support within the vacuum chamber 110. Clamping the sample 450 in this manner can also advantageously level the sample to ensure accurate working distances across all areas of the sample.

[0057] When the sample 450 is a dielectric wafer or other non-conductive sample, the retractable stubs 440 can be set to the up position such that the sample 450 rests slightly above the upper surface 422 of the support plate 420 as shown in Figure 4B and Figure 4C , which is an enlarged view of a portion of the bridge chuck 400 shown in Figure 4B As a non-limiting example, during a sample evaluation process, in some embodiments, the retractable stubs 440 can secure the sample at a distance D of one millimeter or less above the upper surface 422 of the sample support plate 420, and in some embodiments, the retractable stubs can secure the sample 450 between 20-200 microns above the surface 422. Details of different embodiments of the retractable stubs 440 will be discussed below with reference to Figures 7-10 .

[0058] The bridge chuck 400 can also include a plurality of lift pin holes 428 extending through the support plate 420 and a corresponding number of lift pins 430. The lift pins 430 facilitate transfer of the sample 450 into and out of the sample evaluation system and thus serve a different purpose than the retractable stubs 440. As shown in Figures 4A-4CAs shown, each lift rod hole 428 can extend completely through the support plate 420, i.e., from an opening in the lower surface to an opening in the upper planar support surface 422. Also, although not shown in the figures, the lift rods 430 can be attached in a fixed position relative to a portion of the workbench 410 such that the lift rods 430 can be moved with the support plate 420 in the X and Y directions by the workbench, while allowing the workbench 410 to raise and lower the support plate 420 in the Z direction without raising or lowering the lift rods 430, as discussed above with respect to the lift rods 230. In this manner, the support plate 420 can be lowered such that the distal end of each lift rod 430 protrudes through its corresponding lift rod hole 428, holding the sample 450 against the upper surface 422 of the support plate 420, thereby creating a gap 432 between the upper surface 422 of the support plate 420 and the bottom surface of the sample 450, as discussed above with respect to the lift rods 230. Figure 5 shown.

[0059] As shown, the gap 432 is greater than the distance D created by the retractable stud 440 between the sample and the surface 422. The increased height of the gap 432 allows the robotic arm to slide under the sample 450 to transfer the sample into and out of the processing chamber. For example, the robotic arm can transfer the sample into the processing chamber and position the sample on the lifting rod. Once the robotic arm is withdrawn from the processing chamber, the suction cup can be fully raised (e.g., to Figure 4A and 4B , so that each lift pin 430 retracts into its corresponding lift pin hole 428 of the support plate 420, thereby allowing the sample 450 to rest on the upper surface 422 or the retractable stud 440, depending on whether the retractable stud is in the up or down position.

[0060] Although Figure 4A 、 Figure 4B and Figure 5 420. The cross-sectional view of FIG. 400 shows two lifter holes 428 and two corresponding lifter rods 430, but a bridge suction cup according to embodiments disclosed herein may include any reasonable number of lifter holes and lifter rods. Some embodiments generally include at least three lifter holes 428 and three lifter rods 430 equally spaced around the perimeter of the support plate 420. As a non-limiting example, in some embodiments, the bridge suction cup 400 may include three lifter holes 428 and three lifter rods 430 spaced at 120 degrees from one another. In other embodiments, the bridge suction cup 400 may include four lifter holes 428 and four lifter rods 430 spaced at 90 degrees from one another.

[0061] Each retractable stud 440 may include a hard rubber or similar surface at its distal end that provides a relatively high degree of friction between the sample 450 and the stud. Figure 4A and 4BA cross-sectional view of the bridge chuck 400 is depicted as depicting four short posts, can include any suitable number of short posts, and a typical bridge chuck will include a sufficient number of retractable short posts 440 such that the plurality of retractable short posts 440 combine to provide a sufficient amount of friction to the sample 450 such that the sample does not move relative to the support plate 420 or otherwise move when the sample is moved by the worktable 410 within the processing chamber. By way of non-limiting example, Figure 6 is a simplified top view of the support plate 420 including eight retractable short posts 440 and four lift pins 430. It should be understood that, Figure 6 The embodiments disclosed herein are not limited to any particular number of retractable short posts 440 or any particular number of lift pins 430 for illustrative purposes only. The embodiments are also not limited to any particular arrangement of retractable short posts or lift pins.

[0062] In some embodiments, this set of retractable short posts is biased to be set in a downward position such that the retractable short posts 440 are recessed below the support plate surface 422 Figures 4A-4C or Figure 5 (not shown in FIG. 4) and the short post lift mechanism can lift the short posts to an upward position. Figure 7 is a simplified diagram of one such short post lift mechanism 700 that can be switched to lift the short posts 440 above the support plate surface 422 and allow the retractable short posts 440 to lower below the support surface.

[0063] Short-stem lift mechanism

[0064] As shown, the short post lift mechanism 700 includes a rotatable ring body 710 and a plurality of ball bearings 720. Each ball bearing 720 is located within a recessed track 730 having a deep end 732 and a shallow end 734. Each ball bearing 720 and recessed track 730 can be paired with a unique one of the retractable short posts 440 such that each ball bearing 720 is positioned directly below and abutting the lower surface of its respective retractable short post 440.

[0065] The actuator 740 can rotate the ring body 710 (and thus the recessed tracks 730) a fixed distance in opposite directions, as shown by arrows 742, 744. As the ring body 710 rotates, each ball bearing can remain in place by a portion (e.g., a bearing seat) of its respective retractable pin (not shown in FIG. 7) such that the ball bearing moves within its respective track between the deep end and the shallow end. Figure 7

[0066] To illustrate, reference is made to Figures 8A-8C . Figure 8A is a simplified cross-sectional view of the bearing track 710 along Figure 7 the first plane shown in FIG. 7, Figure 8B ​and Figure 8C is a simplified cross-sectional view of the bearing track 710 along Figure 7 a second plane perpendicular to the first plane. As shown, the bearing track 710 can include a curved surface 736 that slopes upward from a deep end 732 to a shallow end 734. The ball bearing 720 can be operably connected to its respective retractable stub 440 Figures 8A-8C , Figure 8A , 8B not shown in any of the foregoing figures), such that the ball bearing 720 can rotate and / or spin while remaining in a generally fixed position directly below its retractable stub 440. Thus, as the annular body 710 is rotated by the actuator 740, the ball bearing 720 can move between the deep end 732 and the shallow end 734 of the track 730. For example, when the actuator 740 moves the annular ring in the direction 742, the ball bearing 720 can move to the shallow end 734 (as shown) essentially lifting the retractable stub 440 paired with the ball bearing 720. Figure 8B

[0067] Similarly, when the actuator 740 rotates the annular body 710 in the opposite direction shown by arrow 744, the ball bearing 720 can move (as shown) toward the deep end 732, thereby allowing the retractable stub 440 to be pushed down by the biasing mechanism below the surface 422, as discussed below with respect to Figure 8C and Figure 9A . 9B Returning to

[0068] As shown, the actuator 740 can be any suitable device that applies a force to rotate the annular ring 710 in the directions 742, 744. For example, in various embodiments, the actuator 740 can be a motor and linear screw, a linear bearing, a servo actuator, a piezoelectric actuator, an electromagnetic device, or other type of actuator. Figure 7

[0069] Retractable short-stem

[0070] Figure 9A and Figure 9B are simplified cross-sectional views of a retractable stub 900 according to some embodiments. The retractable stub 900 can represent each retractable stub 440 discussed above. For ease and ease of illustration, the retractable stub 900 is depicted with respect to the support plate 420 and the sample 450 shown in Figures 4A-5 However, it should be understood that while Figure 9A and Figure 9B depict specific details of a particular embodiment of the support plate 420, the bridge chuck disclosed herein can include support plates that differ in various ways and implementations from the details depicted in Figure 9A and Figure 9B . ​​

[0071] As shown, retractable stub 900 includes a body portion 910 and a head portion 920 coupled to the body. Body portion 910 can be made of a rigid material such as hard rubber, metal, or plastic. Head portion 920 can be formed of hard rubber or similar material that provides sufficient friction between the wafer and the head of the retractable pin set when wafer 450 is positioned on head portion 920 so that wafer 450 does not move or otherwise shift relative to support plate 420 even when the sample is rapidly moved by stage 410 within the processing chamber to position different areas of interest on the sample under the field of view of the charged particle column (e.g., SEM column 120).

[0072] Support plate 420 can include a plurality of cavities 930, the number of which corresponds to the number of retractable stubs 440. Each cavity includes an opening 935 at the upper surface 422 of the support plate and is sized and shaped to receive one of the retractable stubs 440. Figure 9A and Figure 9B A single retractable stub 900 is depicted positioned within its corresponding cavity 930. Retractable stub 900 is connected to support plate 920 and thus moves with support plate 920 in the X, Y, and Z directions when the support plate is moved by stage 410. Retractable stub 900 is also movable within cavity 930 independently of support plate 420 between a stub down position, in which head portion 920 is below support surface 422 (as shown in Figure 9A ), and a stub up position, in which head portion 920 protrudes through opening 935 to a position slightly above support surface 422 (depicted in Figure 9B ) by the interaction of two independent mechanisms: a biasing mechanism 940 and a stub lift mechanism, in Figure 9A and Figure 9B In the embodiment shown, this mechanism is stub lift mechanism 700, which includes ball bearing 720 and rotatable ring 710 discussed above in Figure 7 .

[0073] Biasing mechanism 940 can be a coil spring or similar device that biases retractable stub 900 in the down (recessed) position so that head portion 920 is below support surface 422 in the absence of a stronger opposing force exerted by the lift mechanism. For example, support plate 420 can include an annular ledge 932 that extends into cavity 930. Biasing mechanism 940 (shown as a coil spring in Figure 9A and Figure 9B ) is disposed within cavity 930 between the lower surface of annular ledge 932 and foot portion 912 of retractable stub 900. In this way, biasing mechanism 940 provides a downward force (indicated by the downward arrow in Figure 9Athe right (indicated by the dashed arrow) forces the retractable stub 900 down until the arm portion 914 of the retractable stub 900 contacts the upper surface of the annular shelf 932 or the ball bearing 720. As a result Figure 9A The ball bearing 720 is depicted in the deep end 732 of the recessed track 730, thus Figure 9A The retractable stub 900 is shown in the middle with the arm portion 914 stopped by the shelf 932.

[0074] In Figure 9B The ball bearing 720 is in the raised position (i.e., moved to the shallow end 934 of the recessed track 930), in which an upward force F2 is exerted on the retractable stub body 910. When the force F2 is greater than the force Fl, the coil spring 940 is compressed and the retractable stub 900 is raised until the arm portion 914 of the retractable stub contacts the annular shelf 934 defining the opening 935, as shown in Figure 9B ("up" or "raised" position). In the up position, the head portion 920 protrudes through the opening 935 above the upper surface 422 of the support plate by a distance D, such that the sample 450 rests on the retractable stub 900 instead of the planar surface 422 of the support plate.

[0075] Figure 9A And Figure 9B The wall or retainer 952 is also shown in FIGS. 7B and 7C as part of the ball bearing seat 950. As the stub actuator system 700 moves the ball bearing 720 within the groove 730, the wall 952 can surround the ball bearing 720, thereby keeping the ball bearing 720 centered beneath the retractable stub 900.

[0076] In Figure 9A And Figure 9B In the depicted embodiment, the retractable stub 900 has a generally cylindrical shape (not visible in the cross-sectional view) with a cutout between the arm portion 914 and the foot 912 that defines an area in which the coil spring 940 can fit. The cavity 930 and the opening 935 can have complementary shapes with their inner surfaces parallel and spaced apart proximate the outer surface of the retractable stub 900. However, embodiments are not limited to any particular shape of the retractable stub 900 and its related parts. In other embodiments, the retractable stub can have other suitable shapes, including a generally cuboid shape or other suitable shapes.

[0077] While Figure 9A And Figure 9B The depicted embodiments can include the stub lift mechanism 700 as a lift mechanism, embodiments are not limited to any particular lift mechanism or any particular design of retractable stub, and those skilled in the art will be able to design other suitable lift mechanisms and other retractable stubs based on the present disclosure. As one example, Figure 10is a simplified cross-sectional view of a retractable stub 1000, which can represent retractable stubs 440 and a lifting mechanism 1050, which can be a piezoelectric actuator for raising and lowering retractable stub 1000 instead of stub lifting mechanism 700. In some embodiments, each individual retractable stub 1000 has an individually controllable lifting mechanism 1050 directly underneath it. In this way, the height of each individual retractable stub in support plate 420 can be controlled independently of the other retractable stubs, enabling the stubs to be used to counteract potential warping within sample 450.

[0078] Additional embodiments

[0079] For purposes of explanation, specific nomenclature was used in the foregoing description to provide a thorough understanding of the embodiments described. However, it will be apparent to one skilled in the art that the described embodiments can be practiced without the specific details. For example, while the examples set forth above discuss embodiments with two concentric electrodes disposed below a sample support 422, embodiments are not limited to any particular number of electrodes or any particular arrangement of electrodes. In some embodiments, a single electrode can be included, while in other embodiments, two or more electrodes can be disposed in an arrangement in which the electrodes are not concentric. For example, some embodiments can include four pie slice-shaped electrodes, each of which is disposed in a different sector of the support plate. As another example, while lift rods 430 are discussed above as being coupled to a portion of worktable 410 such that the worktable raises and lowers support plate 420 in the Z direction relative to the lift rods, in other embodiments, a worktable or another device can raise and lower the lift rods in the Z direction instead of or in addition to the support plate.

[0080] As yet another example, while the systems described above include a scanning electron microscope as the charged particle column, in other embodiments, the charged particle column can be a focused ion beam column, and in still other embodiments, the system can include both a SEM and FIB column as part of a SEM / FIB tool.

[0081] While various embodiments of the present disclosure have been disclosed above, specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of embodiments of the present disclosure. Further, it will be apparent to one of ordinary skill in the art that, in view of the above disclosure, many modifications and variations are possible. Thus, it is intended that the appended claims encompass all such modifications and variations as fall within the true spirit and scope of embodiments of the present disclosure.

[0082] Insofar as the exemplary embodiments of the present disclosure can be implemented, at least in part, using electronic components and circuits known to those skilled in the art, details of such components and circuits will not be explained in any greater detail for the sake of brevity and to avoid obscuring the basic concepts of the present disclosure.

[0083] Additionally, any reference to method in the above description is to be interpreted also as an attempt to claim a computer program for performing the method, when the computer program is stored in a computer readable storage medium. Similarly, any reference to system in the above description is to be interpreted also as an attempt to claim a computer program for performing the method, when the computer program is stored in a computer readable storage medium; and any reference in the above description to computer program is to be interpreted also as a reference to a system configured to perform the computer program.

Claims

1. A sample support for supporting a sample in a processing chamber, the sample support comprising: a support plate formed of a dielectric material, the support plate including an upper planar support surface sized and shaped to retain a substrate disposed thereon; one or more electrodes, the one or more electrodes disposed within the support plate proximate the upper planar support surface; a plurality of lift rod holes formed completely through the support plate; a plurality of stub cavities formed in the support plate, each stub cavity having an opening at the upper planar support surface; a plurality of retractable studs corresponding in number to the plurality of stud cavities, wherein each retractable stud is disposed in only one of the stud cavities; as well as a stud lift mechanism operable to move each retractable stud of the plurality of studs between a downward position in which a distal end of the retractable stud is disposed within its respective stud cavity and recessed below the upper planar support surface, and an upward position in which the distal end of the retractable stud protrudes through the stud cavity opening and above the upper planar support surface.

2. The sample support of claim 1, wherein the stub lift mechanism moves all of the plurality of retractable stubs together between the upward and downward positions.

3. The sample support of claim 2, wherein: The short column lifting mechanism includes a rotatable annular body and a plurality of ball bearings; Each ball bearing of the plurality of ball bearings is positioned below only one of the retractable studs; and The stub lift mechanism is operable to apply a force to the ball bearings to move their respective retractable stubs to the upward position.

4. The sample support of claim 3, wherein: The stub lifting mechanism further includes a plurality of recessed tracks formed in the annular ring, each recessed track having a deep end and a shallow end and a ramp surface extending between the deep end and the shallow end; each ball bearing of the plurality of ball bearings is seated within only one of the recessed tracks of the plurality of tracks; and The stub lift mechanism further includes an actuator operably coupled to rotate the annular body in opposite first and second directions such that the ball bearing in each recessed track moves up and down in response to the ramp surface.

5. The sample support of claim 4 , wherein each retractable stud further comprises a bearing seat comprising one or more walls surrounding the bearing positioned below the retractable stud, such that the one or more walls prevent the bearing from rotating with the annular body.

6. The sample support of claim 1, wherein the stub lift mechanism comprises a plurality of stub actuators including a separate stub actuator for each retractable stub.

7. The sample support of claim 6, wherein the stub lift mechanism is operable to raise and lower each of the plurality of retractable stubs between the upward position and the downward position independently of the other retractable stubs.

8. The sample support of any one of claims 1 to 7, wherein each retractable stud is coupled to a biasing mechanism disposed within its respective stud cavity and configured to bias the retractable stud in the downward position.

9. The sample support of claim 8, wherein the biasing mechanism comprises a coil spring.

10. The sample support of claim 8, wherein the one or more electrodes comprises at least two electrodes.

11. A system for evaluating a sample, the system comprising: vacuum chamber; a sample support disposed within the vacuum chamber and operable to hold a sample during a sample evaluation process; a charged particle column configured to direct a charged particle beam into the vacuum chamber toward a sample positioned on the sample support; and a movable stage configured to move the sample support within the vacuum chamber along X, Y, and Z directions; The sample support comprises: a support plate formed of a dielectric material, the support plate including an upper planar support surface sized and shaped to retain a substrate disposed thereon; one or more electrodes, the one or more electrodes disposed within the support plate proximate the upper planar support surface; a plurality of lift rod holes formed completely through the support plate; a plurality of stub cavities formed in the support plate, each stub cavity having an opening at the upper planar support surface; a plurality of retractable studs corresponding in number to the plurality of stud cavities, wherein each retractable stud is disposed in only one of the stud cavities; and a stud lift mechanism operable to move each retractable stud of the plurality of studs between a downward position in which a distal end of the retractable stud is disposed within its respective stud cavity and recessed below the upper planar support surface, and an upward position in which the distal end of the retractable stud protrudes through the stud cavity opening and above the upper planar support surface.

12. The system for evaluating a sample of claim 11, wherein the stud lift mechanism moves all of the plurality of retractable studs together between the upward and downward positions.

13. The system for evaluating a sample of claim 12, wherein: The short column lifting mechanism includes a rotatable annular body and a plurality of ball bearings; Each ball bearing of the plurality of ball bearings is positioned below only one of the retractable studs; and The stub lift mechanism is operable to apply a force to the ball bearings to move their respective retractable stubs to the upward position.

14. The system for evaluating a sample of claim 13, wherein: The stub lifting mechanism further includes a plurality of recessed tracks formed in the annular ring, each recessed track having a deep end and a shallow end and a ramp surface extending between the deep end and the shallow end; each ball bearing of the plurality of ball bearings is seated within only one of the recessed tracks of the plurality of tracks; and The stub actuator system further includes an actuator operably coupled to rotate the annular body in opposite first and second directions such that the ball bearing in each recessed track moves up and down in response to the ramped surface.

15. A system for evaluating a sample as described in claim 14, wherein each retractable short column further includes a bearing seat, the bearing seat including one or more walls surrounding the bearing positioned below the retractable short column, such that the one or more walls prevent the bearing from rotating with the annular body.

16. The system for evaluating a sample of claim 11, wherein the stub lifting mechanism comprises a plurality of stub actuators, the plurality of stub actuators comprising a separate stub actuator for each retractable stub.

17. The system for evaluating a sample of claim 16, wherein the stub lift mechanism is operable to raise and lower each of the plurality of retractable stubs between the upward position and the downward position independently of the other retractable stubs.

18. The system for evaluating a sample of claim 11, wherein the one or more electrodes include at least two electrodes.

19. The system for evaluating a sample of any one of claims 11 to 18, wherein each retractable stud is coupled to a biasing mechanism disposed within its respective stud cavity and configured to bias the retractable stud in the downward position.

20. The system for evaluating a sample of claim 19, wherein the biasing mechanism comprises a coil spring.

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