Hybrid vacuum electrostatic chuck in dedicated chamber for highly warped wafers

Abstract

To provide a method and system for supporting, planarizing, and processing a sample including a highly warped substrate or wafer.SOLUTION: The method transfers the substrate into the main volume of the processing chamber and onto the upper surface of the substrate holder while the main volume is under vacuum pressure. The substrate holder comprises one or more vacuum channels disposed in the upper surface and one or more electrodes disposed within the substrate holder proximate to the upper surface. The method also includes moving the substrate holder with the substrate from the main space to the auxiliary space, sealing the auxiliary space from the main space, increasing the pressure in the auxiliary space, clamping and planarizing the substrate to the substrate holder by applying a vacuum while the substrate is in the auxiliary space, applying a voltage to the electrode while the substrate is in the auxiliary space and clamped to the substrate holder by the vacuum channel to clamp the substrate by an electrostatic force, and moving the substrate back into the main space while the substrate is clamped to the substrate holder by the electrostatic force; The substrate is processed under vacuum pressure in the main space.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. patent application Ser. No. 18 / 749,495, entitled "HYBRID VACUUM ELECTROSTATIC CHUCK IN DEDICATED CHAMBER FOR HIGH WARPAGE WAFERS," filed Jun. 20, 2024, the entire contents of which are incorporated herein by reference.

[0002]

[0002] Commonly assigned U.S. patent application Ser. No. 18 / 749,474, filed Jun. 20, 2024, entitled "Hybrid Vacuum Electrostatic Chuck Carrier for High Warpage Wafers," is incorporated herein by reference in its entirety.

[0003]

[0003] Commonly assigned U.S. patent application Ser. No. 18 / 749,484, filed Jun. 20, 2024, entitled "Hybrid Vacuum Electrostatic Chuck in Vacuum Chamber for High Warpage Wafers," is incorporated herein by reference in its entirety. [Background technology]

[0004]

[0004] In the study of electronic materials and the processes for fabricating such materials into electronic structures, samples such as semiconductor wafers can be analyzed with a scanning electron microscope (SEM) to examine specific features within the wafer. Such features can include fabricated circuits or defects formed during the fabrication process. Electron microscopes are one of the most useful instruments for analyzing the microstructure of semiconductor devices.

[0005]

[0005] In such inspection processes, it is common to inspect multiple locations on the sample. When doing so, it can be important that the sample is perfectly flat or planar so that measurements and other analyses performed are accurate. While many samples, such as semiconductor substrates or "wafers," appear flat on initial inspection, such samples can have a relatively large amount of warpage.

[0006]

[0006] In the semiconductor industry, several different types of sample support structures are commonly used to secure and planarize wafers to the support structure during processing. One such support structure is an electrostatic chuck, which includes one or more electrodes beneath the surface supporting the sample. If the sample is conductive, a voltage can be applied to the electrodes to clamp (secure) and planarize the sample to the chuck. Electrostatic chucks can be very effective at planarizing wafers with slight or moderate bowing, but may be less effective or unable to planarize wafers with significant bowing.

[0007]

[0007] Another type of support structure is a vacuum chuck, which applies a vacuum to the backside of the sample to clamp and flatten the sample. Vacuum chucks can be very effective for clamping and flattening wafers, including highly warped wafers that cannot be flattened by electrostatic chucks, but cannot be used to clamp or flatten wafers in sample processing chambers where substrates are processed at vacuum pressure.

[0008]

[0008] Although various electrostatic and vacuum chucks have been designed over the years, as discussed above, some previously designed chucks have been limited in their ability to support and adequately planarize wafers with significant bowing within sample processing chambers that are maintained at vacuum pressure during substrate processing operations. Therefore, new and improved systems for planarizing bowed samples and supporting such samples within substrate processing tools are desirable. Summary of the Invention

[0009]

[0009] Embodiments described herein provide methods and systems for supporting, planarizing, and then processing samples including highly warped substrates or wafers. While embodiments of the present disclosure can be used to support and planarize many different types of samples, which can have varying degrees of warping, prior to performing processing operations in a vacuum chamber, some embodiments are particularly useful for supporting and planarizing large, thin wafers, such as semiconductor wafers, which may be highly warped and therefore cannot be planarized by some conventional electrostatic chucks.

[0010] As described herein, for certain processing operations performed on a sample, it may be important that the sample be perfectly flat. For example, when using a scanning electron microscope (SEM) tool to image various locations on a wafer, it may be important to accurately know the working distance between the tip of the column and the sample. Accordingly, to this end, the methods and systems described herein flatten the sample before performing a processing operation (e.g., an SEM imaging operation) on the sample in a vacuum chamber. In some embodiments, the sample is flattened in a load lock or similar chamber before being transferred into a substrate processing chamber. In other embodiments, the sample is transferred into a main processing chamber and subsequently flattened in the main processing chamber before performing a substrate processing operation. In yet other embodiments, the processing chamber includes a main chamber region where the sample is processed and a separate, smaller chamber region (sometimes referred to herein as an "auxiliary space") sealed off from the main chamber. The sample can be moved into the auxiliary space and first flattened therein, and then returned to the main processing region before performing a substrate processing operation. Details of each of these embodiments are provided below.

[0011] Although some embodiments of the methods and systems disclosed herein are particularly useful for planarizing a warped wafer before performing an imaging operation in the vacuum chamber of an SEM tool, the embodiments are not limited to a particular type of substrate processing operation or substrate processing tool. The embodiments described herein can be used to clamp and planarize a sample before processing the sample in other types of sample processing tools that process samples in high vacuum, very high vacuum, or ultra-high vacuum environments.

[0012] According to some embodiments, a method for processing a substrate in a processing chamber including a main space and an auxiliary space that is environmentally sealable from the main space is disclosed. The method may include transporting a substrate into a main space of a processing chamber and to an upper surface of a substrate holder while the main space is under vacuum pressure, the substrate holder having one or more vacuum channels disposed on the upper surface and one or more electrodes disposed in the substrate holder proximate to the upper surface; moving the substrate holder within the processing chamber so that the substrate moves from the main space to an auxiliary space; sealing the auxiliary space from the main space and increasing the pressure in the auxiliary space; clamping and flattening the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels while the substrate is in the auxiliary space; applying a voltage to the one or more electrodes while the substrate is in the auxiliary space and clamped to the substrate holder by the one or more vacuum channels to further clamp the substrate to the substrate holder by electrostatic forces; and returning the substrate from the auxiliary space into the main space while the substrate is clamped to the substrate holder by electrostatic forces and processing the substrate under vacuum pressure in the main space.

[0013] In various implementations, embodiments may include one or more of the following: The auxiliary space may be directly attached to a lid of the substrate processing chamber; Increasing the pressure in the auxiliary space may include venting the auxiliary space to atmosphere; After electrostatically clamping the substrate to the substrate holder in the auxiliary space, the auxiliary space may be evacuated to a vacuum pressure while continuing to electrostatically clamp the substrate to the substrate holder before returning the substrate from the auxiliary space to the main space; After processing the substrate under vacuum in the main space, the application of voltage may be terminated so that the substrate is no longer electrostatically clamped to the substrate holder, and the substrate may be removed from the processing chamber; The processing chamber may include a scanning electron microscope, and processing the substrate in the processing chamber may include imaging the substrate with the scanning electron microscope; The substrate may have a bow of at least 1.0 millimeter between the lowest point and the highest point on the substrate; The vacuum pressure at which the substrate is processed in the processing chamber may be equal to or less than high vacuum pressure; The one or more electrodes may include at least two electrodes arranged in an interleaved pattern with respect to one another. The substrate may be a semiconductor wafer.

[0014]

[0014] In some embodiments, a system for processing a substrate is provided, the system comprising: a substrate processing chamber having a main processing region and an auxiliary space that is environmentally sealable from the main processing region; a substrate support disposed within the substrate processing chamber, the substrate support having one or more vacuum channels disposed on an upper surface and one or more electrodes disposed within the substrate support proximate to the upper surface; a stage operably coupled to move the substrate support between the main processing region and the auxiliary space within the substrate processing chamber; a transport unit configured to transport substrates into and out of the substrate processing chamber; a processor; and a memory coupled to the processor. The memory can include a plurality of computer readable instructions that, when executed by the processor, cause the system to: transfer a substrate into a main processing region of a substrate processing chamber and to an upper surface of a substrate holder while the main processing region is under vacuum pressure, the substrate holder comprising one or more vacuum channels disposed in the upper surface and one or more electrodes disposed in the substrate holder proximate to the upper surface; moving the substrate holder within the substrate processing chamber such that the substrate moves from the main processing region to an auxiliary space; sealing the auxiliary space from the main processing region and venting the auxiliary space to atmosphere; and, while the substrate is in the auxiliary space, performing one or more clamping and planarizing the substrate to the substrate holder by applying a vacuum to the vacuum channels; while the substrate is in the auxiliary space and clamped to the substrate holder by the one or more vacuum channels, applying a voltage to one or more electrodes to further clamp the substrate to the substrate holder by electrostatic forces; evacuating the auxiliary space to a vacuum pressure while the substrate continues to be clamped to the substrate holder by electrostatic forces; returning the substrate together with the substrate holder from the auxiliary space into the main processing region while the main processing region is under vacuum pressure; and processing the substrate under vacuum pressure in the main processing region while the substrate is clamped to the substrate holder by electrostatic forces.

[0015] In yet an additional embodiment, a non-transitory computer readable memory is provided that includes a step of: transferring a substrate into a main processing region of a processing chamber and to an upper surface of a substrate holder while the main processing region is under vacuum pressure, the substrate holder comprising one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder proximate the upper surface; moving the substrate holder within the processing chamber such that the substrate moves from the main processing region to an auxiliary space; sealing the auxiliary space from the main processing region and venting the auxiliary space to atmosphere; and clamping and flattening the substrate on the substrate holder by applying a vacuum to the one or more vacuum channels while the substrate is in the auxiliary space. The storage medium can store instructions for processing the substrate by: flattening the substrate; while the substrate is in the auxiliary space and is clamped to the substrate holder by one or more vacuum channels, applying a voltage to one or more electrodes to further clamp the substrate to the substrate holder by electrostatic forces; evacuating the auxiliary space to a vacuum pressure while the substrate continues to be clamped to the substrate holder by electrostatic forces; returning the substrate together with the substrate holder from the auxiliary space into the main processing region while the main processing region is under vacuum pressure; and processing the substrate under vacuum pressure in the main processing region while the substrate is clamped to the substrate holder by electrostatic forces.

[0016]

[0016] To better understand the nature and advantages of the present disclosure, reference should be made to the following description and the accompanying drawings. It should be understood, however, that the figures are for illustrative purposes only and are not intended to define limitations on the scope of the present disclosure. Furthermore, as a general rule, and unless otherwise clear from the description, when elements in different figures use the same reference numerals, those elements are typically identical or at least similar in function or purpose. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a simplified diagram of a sample evaluation system including a scanning electron microscope (SEM) column. [Figure 2]2A-2C are simplified block diagrams of a sample evaluation system including a substrate processing column and a load lock chamber. [Figure 3] 3A and 3B are simplified cross-sectional views of a conventional electrostatic chuck with the lift pins in the up and down positions, respectively. [Figure 4A] FIG. 3C is a simplified cross-sectional view of the electrostatic chuck shown in FIGS. 3A and 3B supporting a highly warped sample. [Figure 4B] FIG. 4B is an enlarged view of a portion of the electrostatic chuck and sample shown in FIG. 4A. [Figure 5A] FIG. 1 is a simplified cross-sectional view of a hybrid vacuum electrostatic chuck carrier according to some embodiments. [Figure 5B] FIG. 5B is an enlarged view of a portion of the hybrid vacuum electrostatic chuck carrier shown in FIG. 5A. [Figure 6] 1 is a flowchart illustrating steps associated with a method for planarizing and processing a warped substrate according to some embodiments. [Figure 7A] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7B] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7C] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7D] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7E]7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7F] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7G] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7H] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 7I] 7A-7I are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 8A] FIG. 1 illustrates a simplified cross-sectional view of a hybrid vacuum electrostatic chuck according to some embodiments. [Figure 8B] FIG. 8B is an enlarged view of a portion of the hybrid vacuum electrostatic chuck shown in FIG. 8A. [Figure 9] 1 is a flowchart illustrating steps associated with a method for planarizing and processing a warped substrate according to some embodiments. [Figure 10A] 10A-10D are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 10B] 10A-10D are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 10C]10A-10D are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 10D] 10A-10D are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 11] 1 is a flowchart illustrating steps associated with a method for planarizing and processing a warped substrate according to some embodiments. [Figure 12A] 12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 12B] 12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 12C] 12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 12D] 12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 12E] 12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 12F] 12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. [Figure 12G]12A-12G are simplified cross-sectional views of a substrate processing system according to some embodiments depicted at various stages of planarizing and processing a warped substrate according to the method described in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018]

[0032]

[0006] Embodiments described herein provide methods and systems for supporting, planarizing, and then processing samples that include highly warped substrates or wafers. While embodiments of the present disclosure can be used to support and planarize many different types of samples, which may have varying degrees of warping, prior to performing processing operations in a vacuum chamber, some embodiments are particularly useful for supporting and planarizing large, thin wafers, such as semiconductor wafers, which may be highly warped and therefore cannot be planarized by some conventional electrostatic chucks.

[0019]

[0033] As mentioned above, for certain processing operations performed on samples, such as semiconductor wafers, it can be important that the sample be perfectly flat. The embodiments described herein provide methods and systems for supporting, flattening, and then processing a sample, including a highly warped substrate or wafer, prior to performing a processing operation on the sample (e.g., prior to performing SEM imaging operations in a vacuum chamber on various regions of interest at different locations on the sample). In some embodiments, the sample is flattened in a load lock or similar chamber before being transferred into a substrate processing chamber. In other embodiments, the sample is transferred into a main processing chamber and subsequently flattened in the main processing chamber prior to performing a substrate processing operation. In still other embodiments, the processing chamber includes a main chamber region where the sample is processed and a separate, smaller chamber region (sometimes referred to herein as an “auxiliary space”) sealed off from the main chamber. The sample can be moved into the auxiliary space and first flattened therein, and then returned to the main processing region before performing the substrate processing operation. Details of each of these embodiments are provided below.

[0020]

[0034] While embodiments of the present disclosure can be used to support and planarize many different types of samples, which can have varying degrees of bowing, before performing processing operations in a vacuum chamber, some embodiments are particularly useful for supporting and planarizing large, thin wafers, such as semiconductor wafers, which may be significantly bowed and therefore cannot be planarized with some conventional electrostatic chucks. Additionally, while some embodiments of the methods and systems disclosed herein are particularly useful for planarizing warped semiconductor or dielectric wafers before performing imaging operations in the vacuum chamber of an SEM tool, the embodiments are not limited to any particular type of substrate processing operation or substrate processing tool. The embodiments described herein can be used to secure and planarize wafers (and other types of samples) before processing large wafers (or samples) in other types of sample processing tools that require high-vacuum, very-high-vacuum, or ultra-high-vacuum environments for processing operations.

[0021] Sample assessment tool example

[0035] To better understand and appreciate the present disclosure, reference is first made to Figure 1, which is a simplified schematic diagram of a conventionally known sample evaluation system 100. The sample evaluation system 100 can be used for operations such as defect review and analysis of structures formed on a sample, such as a semiconductor or dielectric wafer.

[0022]

[0036] The system 100 can include a vacuum chamber 110 along with 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 exposed to a charged particle beam 126 from the SEM column.

[0023]

[0037] The SEM column 120 is connected to the vacuum chamber 110 such that a charged particle beam generated by the column passes through a vacuum environment formed within the vacuum chamber 110 before striking the sample 150. The SEM column 120 can generate an image of a portion of the sample 150 by irradiating the sample with the charged particle beam 125, detecting particles emitted by the irradiation, and generating a charged particle image 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 that defines a drift space for the electron beam, a condenser lens arrangement 124, one or more deflection lenses such as lenses 130, 132, one or more focusing lenses 134, and a column cap 136.

[0024]

[0038] During the imaging process, the electron beam source 122 generates an electron beam 125, which passes through a condenser lens 124 and is first collected by the condenser lens 124, and then focused by lens 134 before striking the sample 150. The condenser lens 124 defines the numerical aperture and current of the electron beam (together with the final aperture), which directly relates to the resolution, while the focusing lens 134 focuses the beam onto the sample. A column cap 136, positioned between the bottom end of the anode tube 126 (first electrode) and the sample 150 (second electrode), can be a third electrode in the system that controls the electric field generated in the vicinity of the wafer.

[0025]

[0039] 1 shows an SEM column 120 that generates a charged particle beam 125 that is generally perpendicular to the sample 150 when the beam strikes the sample 150. In various embodiments, the SEM column 120 can be operated in a tilted mode, where the charged particle beam 125 strikes the sample 150 at a non-perpendicular angle, for example, a 45 degree angle.

[0026]

[0040] In both normal and tilt modes, the particle imaging process typically involves scanning a charged particle beam back and forth (e.g., in a raster or other scan pattern) over a specific area of ​​the sample being imaged. The deflection lenses 130, 132 can be magnetic, electrostatic, or a combination of both electric and magnetic lenses to achieve the scan pattern, as known to those skilled in the art. The scanned area is typically a small portion of the total area of ​​the sample. For example, the sample may be a semiconductor wafer with a diameter of 200 or 300 mm, but each scanned area on the wafer may be a rectangular region with a width and / or length of a few microns or tens of microns.

[0027]

[0041] The SEM column 120 can also include one or more detectors for detecting 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 irradiation of the sample by the charged particle beam 126. The in-lens detector 128 can include a central hole that allows the charged particle beam 126 to pass through the detector and that allows both secondary electrons and backscattered electrons entering the charged particle column 120 to pass through the detector 128 and reach the top detector 138. In some embodiments, the sample characterization system 120 can also include an external detector, which can also be configured to detect secondary electrons and backscattered electrons, or which can be configured to detect X-rays, such as an X-ray spectroscopy (EDX) detector.

[0028]

[0042] During operation of system 100, support element 140 can move the sample so that different portions (e.g., different regions of interest or "ROIs") are located directly under the field of view of SEM column 120. Support element 140 can move sample 150 side-to-side and front-to-back (i.e., along both the X and Y axes) within chamber 110 at relatively high speeds, and can also move sample 150 along the Z axis by raising and lowering it.

[0029]

[0043] Because many features formed on the sample 150 have submicron dimensions, it is important to accurately know the position of the sample relative to the focal point of the SEM column 120. To accurately determine the position of the sample 150, some embodiments can use a high-precision navigation interferometer system (not shown). The interferometer system is attached to the lid 112 of the chamber 110 and can direct collimated light (e.g., a laser beam) through a window (not shown) formed in the lid to target areas on the support element 140 that are encoded with various linear or other marks. The system can detect (e.g., using an array of photodetectors) the light from the collimated light pulse after it reflects off the encoded target areas on the support element 140 and returns to the interferometer system. A processor (e.g., a digital signal processor) within the interferometer system can then analyze the detected light signals to determine a very precise position of the sample along the X and Y axes.

[0030]

[0044] Additionally, system 100 may include a voltage supply 160 and one or more controllers 170, such as a processor or other hardware unit. Operating voltage supply 160 provides a desired effective voltage for the column, thereby improving image resolution. This can be achieved by appropriately distributing the voltage supply between the first and second electrodes (i.e., between the anode tube and the sample). Controller 170 may control the operation of the system, including the voltage supply, by executing computer instructions stored in one or more computer-readable memories 180, as known to those skilled in the art. By way of example, computer-readable memory may include solid-state memory (such as random access memory (RAM) and / or read-only memory (ROM) (which may be programmable, flash-updateable, etc.)), a disk drive, an optical storage device, or a similar non-transitory computer-readable storage medium.

[0031]

[0045] The system 100 may further include a user interface 190 that allows one or more users to interact with the system. For example, the user interface 190 may allow a user to set parameters for an SEM column or detector that may be used when analyzing a sample. The user interface 190 may include any known device(s) that allows a user to input information and interact with a computer system, such as a keyboard, mouse, monitor, touch screen, touch pad, voice-activated input controller, etc.

[0032] Transporting the sample into the processing chamber 110

[0046] To process a sample 150 in the chamber 110, the sample must first be transferred into the chamber. Although not shown in the figures of this application, some substrate processing systems include a factory interface that allows a cassette of wafers to be processed to be loaded into a docking station. The docking station can include one or more industry-standard front-opening unified pods (FOUPs) for temporarily holding wafers awaiting processing. A first external transport unit (ETU), which is part of the processing system and operates between the docking station and the load lock chamber, can pick up individual wafers from the FOUP and transfer the wafers to the load lock chamber. The docking station and FOUP are typically at atmospheric pressure.

[0033]

[0047] The processing chamber 110 operates at high, very high, or even ultra-high vacuum. Load lock chambers typically have a much smaller volume than processing chambers and can be pumped up and down between atmospheric and high vacuum levels as needed, much faster than processing chambers. For example, a wafer can be transferred from a FOUP into the load lock chamber at atmospheric pressure. The load lock chamber is then evacuated (pumped down) to vacuum, and a second internal transfer unit (ITU), part of the processing system and operating between the load lock chamber and the processing chamber, can pick up the wafer from the load lock chamber and transfer it to the processing chamber without breaking vacuum (i.e., while the load lock chamber and processing chamber are maintained at vacuum pressure). Each of the first and second transfer units can be, for example, a robotic arm with an end effector specifically designed to pick up and transfer semiconductor wafers or similar samples from one location to another within a processing tool or station.

[0034]

[0048] The samples enter the processing chamber, are processed, and then can be returned to the load lock chamber without breaking vacuum. The load lock chamber can then be vented to atmosphere, allowing the processed samples to be picked up by the ITU and transported to the next stage of the manufacturing or evaluation process. Using the load lock chamber in this way, hundreds or thousands of substrates can be processed sequentially without venting the processing chamber to atmosphere, while the main processing chamber is maintained at high or ultra-high vacuum.

[0035]

[0049] 2A-2C are simplified block diagrams of a conventionally known substrate processing system 200, including a substrate processing chamber 210 and a load lock chamber 220. The substrate processing chamber 210 may represent the substrate processing chamber 110, but for ease of illustration, the SEM column 120 and other components that are part of the processing chamber 110 are not shown in either FIG. 2A or 2B. The substrate processing system 200 may also include additional components, such as a docking station, one or more FOUPs, and various transfer units (e.g., ETU, ITU, other robots), as previously discussed, which are also not shown for ease of illustration.

[0036]

[0050] 2A-2C, the substrate processing chamber 210 may include a sample support element 240 capable of supporting a sample 250 (e.g., a semiconductor wafer) within the chamber 210 during processing operations in which the sample 250 is exposed to a charged particle beam from an SEM column (not shown). The support element 240 and the sample 250 may represent the support element 140 and the sample 150 described above with respect to FIG.

[0037]

[0051] The load lock chamber 220 can also include a sample support element 260 capable of supporting a sample 250 disposed within the load lock chamber. Each sample support element 240 and 260 can include an upper support surface 242, 262, respectively, and lift pins (not shown) that can lift the sample above the upper support surface so that a transport unit can slide under the sample to move the sample onto or off the support element, as known to those skilled in the art.

[0038]

[0052] To process sample 250 in processing chamber 210, the sample may first be transferred into load lock chamber 220 (indicated by the dashed arrow) and placed on sample support 260 as shown in Figure 2. This operation may be performed, for example, by a first transfer unit that removes sample 250 from the FOUP and transfers it into load lock chamber 220 while the load lock chamber is at atmospheric pressure. The chamber may then be evacuated to a suitable vacuum pressure, and a second transfer unit may transfer sample 250 from load lock chamber 220 into processing chamber 210 (indicated by the dashed arrow in Figure 2B), while both chambers are held at vacuum.

[0039]

[0053] After processing is complete, the sample 250 can be moved out of the processing chamber 210 and back into the load lock chamber 220 (as indicated by the dashed arrow in FIG. 2C), while both chambers are still held under vacuum.

[0040]

[0054] In some known systems, support element 240 may be an electrostatic chuck that applies a voltage to one or more electrodes disposed below surface 242 to clamp and planarize sample 250 to support element 240. Figures 3A and 3B are simplified diagrams of a known electrostatic chuck 300 that may be representative of support element 240 and that is used by some known sample evaluation systems to support a conductive sample, such as a semiconductor wafer, within a vacuum chamber during a sample evaluation process.

[0041]

[0055] 3A, an electrostatic chuck 300 includes a movable stage 310 coupled to a support plate 320. The support plate 320 has a planar support surface 322 upon which a sample 350 (e.g., a wafer such as a semiconductor wafer) can be placed during evaluation or other types of analytical operations.

[0042]

[0056] The stage 310 can move the support plate 320 (and thus the sample 350) in the X, Y, and Z directions within the vacuum chamber 110 to position a region of interest on the sample directly beneath the field of view of a charged particle column, such as the charged particle column 120. The plate 320 can be made of a dielectric material, such as a ceramic material, and one or more electrodes 324, 326 can be positioned below the surface 322. If the sample 350 is a semiconductor wafer or other conductive sample, voltages can be applied to the electrodes 324, 326 to clamp the sample to the planar support surface 322, securing the sample to the support plate 320, as shown in FIG. 3A , so that the sample does not shift or move as the stage 310 moves the sample support within the vacuum chamber 110. As long as the sample 350 has a certain limit of curvature, clamping the sample 350 in this manner also has the advantage of flattening the sample and ensuring a precise working distance across all regions of the sample.

[0043]

[0057] The support plate 320 may also be provided with a plurality of lift pin holes 328 and a corresponding number of lift pins 330 to facilitate the insertion and removal of the sample 350 into and from the sample evaluation system. As shown in FIGS. 3A and 3B , each lift pin hole 328 may extend completely through the support plate 320. Additionally, although not shown in FIGS. 3A or 3B , the lift pins 330 may be mounted in a fixed position relative to a portion of the stage 310 such that the lift pins can move with the support plate 320 in the X and Y directions while the stage 310 can simultaneously raise and lower the support plate 320 in the Z direction without moving the lift pins 330. In this manner, the support plate 320 may be lowered so that the distal end of each lift pin 330 protrudes from a respective lift pin hole 328, holding the sample 350 above the top surface 322 of the support plate 320 and creating a gap 340 between the top surface 322 of the support plate 320 and the bottom surface of the sample 350, as shown in FIG. 3A . Thereafter, when the chuck is raised sufficiently (eg, to the position shown in FIG. 3B), each lift pin 330 retracts into a respective lift pin hole 328 in support plate 320 and sample 350 rests on top surface 322 .

[0044]

[0058] 3A, with the lift pins 330 in the raised position, an ITU or similar substrate transport device (not shown) can transport a sample 350 into the vacuum chamber, drop the sample onto the lift pins 330, and retract out of the vacuum chamber. The support plate 320 can then be raised to position the sample 350 on the upper surface 322, and one or more regions on the sample can be evaluated or analyzed as described above. Once the evaluation process for a given sample 350 is complete, the support plate can be lowered, thereby raising the sample 350 onto the lift pins 330, and a gap 340 created between the sample and the support surface 322 can allow an ITU (not shown) to pick up the sample 350 from the lift pins and transfer it out of the chamber.

[0045]

[0059] 3A and 3B show two lift pin holes 328 and two corresponding lift pins 330, a typical electrostatic chuck 300 includes at least three lift pin holes 328 and three lift pins 330 spaced around the periphery of the support plate 320. For example, in some embodiments, the electrostatic chuck 300 may include three lift pin holes 328 and three lift pins 330 spaced at 120 degree angles from one another.

[0046] Challenges in handling highly warped samples

[0060] As shown in Figures 1, 2 and 3A, 3B, the samples 150, 250, 350 processed in the systems 100, 200 are thin, flat wafers, such as semiconductor or dielectric wafers. All such samples have some degree of bow (i.e., the sample has some degree of convex or concave shape), where bow is defined as the difference between the lowest and highest points on the sample when the sample is placed on a flat surface without being secured to the surface by clamps or the like.

[0047]

[0061] Due to the use of non-silicon wafers and new manufacturing techniques, as well as the fact that semiconductor and other wafers have become larger over the years, the amount of bow has generally increased to the point where some wafers have bows of at least several hundred microns and others have bows of up to several millimeters. Some existing electrostatic chucks, such as the chuck 300 described above, are unable to completely flatten a wafer once the bow exceeds a certain threshold. For illustrative purposes, refer to FIGS. 4A and 4B. FIG. 4A is a simplified cross-sectional view of the aforementioned electrostatic chuck 300 supporting a highly bowed sample 450, and FIG. 4B is an enlarged view of a portion of the chuck 300 and sample 450.

[0048]

[0062] 4A and 4B, the sample 450 has a convex bow such that, when the sample is placed on the chuck's upper surface 322, the outer edge of the sample 450 is spaced a distance D from the surface 322. When a high voltage is applied to the electrodes 324, 326, the electrostatic chuck 300 can flatten a portion of the sample 450; however, if the bowing, which creates the distance D, is too great, the electrostatic chuck 300 cannot completely flatten the sample. In such a case, when the sample 450 is imaged or otherwise evaluated using an SEM instrument such as the system 100, the working distance between the tip of the column and the sample will be different at different locations across the sample 450, adversely affecting the accuracy of the images obtained.

[0049]

[0063] The actual distance D at which a given wafer is no longer fully planarized by a particular electrostatic chuck depends on several factors, including the wafer material, the wafer size, the type / model of electrostatic chuck, the voltage level applied to the electrodes, etc. With some known electrostatic chucks, when a particular wafer's bow exceeds several hundred microns, it becomes impossible for the electrostatic chuck to fully planarize the wafer using acceptable voltage levels.

[0050]

[0064] As noted above, certain processing operations performed on wafers or other samples may require that the sample be perfectly flat. For example, as noted above, when using a scanning electron microscope (SEM) tool to image various locations on a wafer, it may be important to precisely know the working distance between the tip of the column and the sample. Accordingly, to this end, the methods and systems described herein flatten a sample in a vacuum chamber before performing a processing operation on the sample (e.g., an SEM imaging operation). As described in detail below, embodiments disclosed herein can secure and flatten a sample to be processed in a chamber under high or ultra-high vacuum conditions in several different ways. In some embodiments, the sample is flattened in a load lock or similar chamber before being transferred into the processing chamber. In other embodiments, the sample is transferred into a main processing chamber and subsequently flattened in the main processing chamber before performing a substrate processing operation (e.g., an SEM imaging operation). In still other embodiments, the processing chamber includes a main chamber region where the sample is processed and a separate chamber region sealed off from the main chamber region where the sample is first flattened. Details of each of these embodiments are described below.

[0051] Hybrid Vacuum Electrostatic Chuck Carrier

[0065] In some embodiments, instead of placing the sample directly on a sample support (such as support elements 240 and 260) in the processing chamber and load lock chamber, the sample is first placed on a chuck carrier in the load lock chamber, and the chuck carrier itself is placed on a support structure. The chuck carrier, which can clamp and planarize the sample using both vacuum and electrostatic chucking techniques, is referred to herein as a hybrid vacuum-electrostatic chuck carrier. In operation, the hybrid chuck carrier can first clamp and planarize the sample in the load lock chamber using the vacuum chucking function while the load lock chamber is at atmospheric pressure. The hybrid chuck carrier can then activate the electrostatic chucking function to apply an electrostatic force to further clamp the sample, and the load lock chamber can be evacuated to leave the sample flattened and clamped to the hybrid chuck carrier using electrostatic force alone. With the sample clamped and planarized, both the hybrid vacuum-electrostatic chuck carrier and the sample are transferred under vacuum from the load lock chamber to the main processing chamber using an ITU, and the sample can be processed in the main chamber at vacuum pressure while on the hybrid chuck carrier.

[0052]

[0066] 5A is a simplified cross-sectional view of a sample support system 500 including a hybrid vacuum-electrostatic chuck carrier 520 (also referred to herein as "chuck carrier 520") and a platform 510 according to some embodiments. As shown, the chuck carrier 520 has a sample 550 disposed on its upper surface 502, and the chuck carrier is disposed on an upper surface 512 of the platform 510, which may be located either in a load lock chamber or in the main processing chamber in place of support elements 260 or 240, respectively. Each of the surfaces 502, 512 may be substantially planar and of a shape similar to, but at least slightly larger than, the sample 550.

[0053]

[0067] 5A also shows two sets of lift pins 504, 506, a vacuum system 525, and a high voltage system 530. The lift pins 504 enable the sample to be elevated above the upper support surface 502 so that a transfer unit can slide under the sample to load or unload the sample onto or from the chuck carrier 520. Similarly, the lift pins 506 enable the chuck carrier 520 to be elevated above the platform 510 so that a transfer unit can slide under the chuck carrier to load or unload the chuck carrier and sample onto or from the platform 510.

[0054]

[0068] As shown more clearly in Figure 5B, which shows a close-up of a portion of chuck carrier 520, sample 550, and platform 510, each lift pin 504, 506 is positioned within a respective lift pin hole 505, 507. Lift pin hole 507 extends completely through platform 510, and lift pin hole 505 extends completely through both platform 510 and chuck carrier 520.

[0055]

[0069] The chuck carrier 520 includes a plurality of vacuum channels 522 on its upper surface that can be operatively coupled to a vacuum system 525 when the chuck carrier is disposed on the platform 510. For example, a first vacuum line 524 extending from the vacuum system 525 through the platform 510 can be fluidly coupled by a coupling 528 to a second vacuum line 526 that passes through the chuck carrier 520. Thus, each vacuum channel 522 is fluidly coupled to the vacuum system 525 and is operable to apply a vacuum to the backside of the sample 550 when the vacuum system 525 is activated.

[0056]

[0070] The chuck carrier 520 also includes a series of electrodes 532, 534 that are operatively coupled to a high-voltage source 530 when the chuck carrier is positioned on the platform 510. The electrodes 532, 534 may be arranged in an interleaved or other pattern beneath the upper surface 502, as known to those skilled in the art, and may be driven with opposite charges (i.e., positive and negative) to generate an electrostatic field at the upper surface to securely clamp the sample 550 to the chuck carrier. As shown, high-voltage lines 536, 538 extend from the high-voltage source 530 through the platform 510. The lines 536, 538 may be electrically coupled by couplings 546, 548 to high-voltage lines 542, 544, respectively, that run through the chuck carrier 520. Thus, each series of electrodes 532, 534 is electrically coupled to the high-voltage system 530 and is operable to generate an electrostatic force that clamps the sample 550 to the chuck carrier 520 when the high-voltage source 530 is activated.

[0057]

[0071] In operation, the chuck carrier 520 can first clamp and planarize the sample 550 onto its upper surface by activating the vacuum system 525. Then, once the sample 550 is planarized onto the chuck carrier 520, the high voltage source 530 can activate the electrodes 532, 534 to electrostatically clamp the sample to the chuck carrier, and the vacuum applied by the vacuum system 525 can be released. In this manner, the chuck carrier can vacuum-chuck a highly warped sample that cannot be completely planarized by electrostatic chucking alone. Then, after the sample has been electrostatically chucked, the chuck carrier can be transported into the main processing chamber.

[0058]

[0072] For a better understanding and appreciation of the method of planarizing a sample, such as a highly warped substrate, for processing in a substrate processing chamber evacuated to or below a high vacuum pressure level using a hybrid vacuum-electrostatic chuck 520, please refer to Figures 6 and 7A-7I. Figure 6 is a flowchart illustrating steps associated with a method 600 of planarizing and processing a warped substrate, according to some embodiments. Figures 7A-7I are simplified cross-sectional views of a substrate processing system 700, according to some embodiments, depicted at various stages of planarizing and processing a warped substrate according to the method described in Figure 6.

[0059]

[0073] As shown, the substrate processing system 700 includes a main processing chamber 710 and a load lock chamber 720, and uses a hybrid vacuum-electrostatic chuck carrier 765 to secure the sample 750 during transfer between the load lock chamber and the main processing chamber. The main processing chamber 710 may be similar to the chambers 110 and 210 of FIGS. 1 and 2A-2B, except that a stage 740 adapted to receive the chuck carrier 765 replaces the support elements 140 and 240. The load lock chamber 720 may be similar to the load lock chamber 220, except that a platform 760 replaces the substrate support 260. The chuck carrier 520 may be representative of the chuck carrier 765.

[0060]

[0074] 6 and 7A, method 600 begins by transferring sample 750 into load lock chamber 720 and placing the sample on the upper support surface of hybrid vacuum-electrostatic chuck carrier 765 (FIG. 6, step 610). Chuck carrier 765 can be, for example, chuck carrier 520 described above, and thus can secure the sample to its upper surface using either or both vacuum and electrostatic chucking. The chuck carrier can be placed on and mechanically clamped to platform 760 using any suitable clamping technique or mechanism (e.g., a releasable latch). Platform 760 can be, for example, platform 510 described above.

[0061]

[0075] Platform 760 can both position and align the chuck carrier and sample by rotating the sample and carrier by a specific angle so that when the transfer unit picks up the carrier and places it on the main chamber stage, the current sample being processed is in the same known position as the previously processed sample and the sample that will be processed after the current sample. Platform 760 includes vacuum connections 762 and high-voltage connections 764, which can respectively couple a vacuum system (not shown in FIG. 7A ) and a high-voltage source (also not shown) to corresponding connections on chuck carrier 765 when chuck carrier 765 is secured to platform 760. For example, vacuum connection 762 can represent vacuum line 524 and vacuum coupling 528, which couple vacuum system 525 to vacuum line 526 in the chuck carrier. Similarly, high-voltage connection 764 can represent high-voltage lines 536 and 538 and high-voltage couplings 546 and 548, which couple high-voltage source 530 to voltage lines 542 and 544 in the chuck carrier, respectively.

[0062]

[0076] Although not shown in FIG. 7A, the transfer can be performed by the ETU picking up the sample 750 from a docking station (e.g., a FOUP in the holding area of ​​the system 700) and placing the sample on lift pins (e.g., lift pins 504) that protrude above the top surface of the chuck carrier 765 in the load lock chamber. The lift pins can then be lowered so that the sample is supported by the top surface of the chuck carrier 765, as shown in FIG. 7A. This initial transfer step can be performed while the load lock chamber 720 is at atmospheric pressure, as indicated by the dotted background in the load lock chamber 720.

[0063]

[0077] The vacuum system can then be activated, as indicated by arrow 770, to generate a vacuum suction force on the bottom of sample 750 (FIG. 6, step 620). Applying a vacuum to the backside of sample 750 while the load lock chamber is above vacuum pressure clamps the sample to the top surface of chuck carrier 765, flattening the sample as shown in FIG. 7B. While the vacuum is applied to the backside of sample 765 (and while the load lock chamber is still at atmospheric pressure), a high voltage source can be activated, as indicated by arrow 772 in FIG. 7C, to apply an electrostatic force to further secure sample 750 to chuck carrier 765 (FIG. 6, step 630).

[0064]

[0078] The load lock chamber 720 can then be evacuated to a pressure equal to or between high and ultra-high vacuum pressures within the main processing chamber 710, and the vacuum system clamping the sample 750 to the chuck carrier 765 can be turned off, as indicated by the absence of arrow 770 in FIG. 7D. During this time, the high voltage applied to the electrode is maintained (arrow 772), so that the only force clamping the sample 750 to the chuck carrier is electrostatic force (FIG. 6, step 640).

[0065]

[0079] As mentioned above, a vacuum chuck may be able to flatten a highly warped wafer that a conventional electrostatic chuck cannot completely flatten. However, once the sample is chucked to the chuck carrier 765 by vacuum, the electrostatic chuck portion of the chuck carrier 765 can maintain the sample in a flat state. Therefore, by first chucking the sample 750 with a vacuum chuck and then switching the clamping force to electrostatic force, a highly warped sample that cannot be flattened by electrostatic force alone can remain flat.

[0066]

[0080] Next, as shown in FIG. 7E ( FIG. 6 , step 650), a transfer unit 780 picks up the chuck carrier 765 along with the sample 750 clamped to the chuck carrier by electrostatic forces and transfers the chuck carrier to a stage 740 within the main processing chamber 710 (which may be at high vacuum or lower pressure, as described above) as shown in FIG. 7F ( FIG. 6 , step 660). Although not shown in FIG. 7E , in order for the transfer unit 780 to transfer the chuck carrier from the load lock chamber 720, the chuck carrier is first lifted above the surface of the platform 760 by lift pins (e.g., lift pins 506). Similarly, in order for the transfer unit to transfer the chuck carrier onto the stage 740, the chuck carrier is placed on lift pins extending above the surface of the stage 740, the transfer unit is retracted, and the lift pins are slowly lowered into the body of the stage 740, so that the chuck carrier 765 (and sample 750) is placed on the stage 740 as shown in FIG. 7G.

[0067]

[0081] In the process of transferring the chuck carrier 765 to the stage 740, the chuck carrier is disconnected from the voltage source 772, moved into the processing chamber 710, and aligned with the stage 740, and two high voltage lines (represented by a single dashed line 742) are electrically coupled to corresponding lines in the chuck carrier (e.g., lines 536, 538). A high voltage connection (indicated by arrow 774) is then established to the voltage line 742, maintaining an electrostatic force that clamps the sample 750 to the chuck carrier and keeps the sample 750 flat.

[0068]

[0082] The sample 750 may then be processed in the main chamber 710 at high vacuum (or higher vacuum) pressure ( FIG. 6 , block 670) with a high voltage applied to the electrodes to maintain the sample in a flat state. In the illustrated embodiment, processing of the sample 750 may include imaging multiple locations on the sample using a scanning electron microscope, although as mentioned above, in other embodiments, the main chamber 710 may be a different type of processing chamber and the substrate processing operation may be other than an imaging operation.

[0069]

[0083] After processing is complete, as shown in FIG. 7H, the transfer unit picks up the chuck carrier 765 (with the sample 750 on top) and places the chuck carrier back into the load lock chamber 720 (FIG. 6, step 680) while both the main processing chamber 710 and the load lock chamber 720 are under vacuum. The load lock chamber 720 can then be vented to atmosphere (FIG. 6, step 690) to prepare the sample for transfer from the load lock chamber to the next processing step. The voltage to maintain the electrostatic clamping force during step 680 is no longer required, and the sample 750 may then return to its initial bowed state, as shown in FIG. 7I.

[0070]

[0084] The method 600 can then be repeated for the next sample.

[0071]

[0085] 7A-7I, the electrodes within the chuck carrier 765 are temporarily disconnected from the high voltage source when the chuck carrier 765 is transferred from the platform 760 to the stage 740. For example, when the transfer unit picks up the chuck carrier 765 from the platform 760 in step 650, the high voltage connection 772 is temporarily disconnected and is not restored until the transfer unit places the chuck carrier on the stage 740 in step 660 and establishes the high voltage connection 774. However, the electrodes within the chuck carrier 765 (e.g., the set of electrodes 532, 534) can be designed to be of sufficient magnitude such that a sufficient charge is accumulated on the electrodes to ensure that the sample 750 remains chucked to the chuck carrier during the transfer process.

[0072]

[0086] In other embodiments, the transfer unit may include a high voltage connection that mates with a high voltage line in the chuck carrier to provide a continuous high voltage level to the electrode in the chuck carrier during the transfer process.

[0073] Hybrid vacuum electrostatic chuck in the main chamber

[0087] In some embodiments, the main processing chamber can include a sample support that can function as both a vacuum chuck and an electrostatic chuck to secure and planarize the sample. Such a sample support is referred to herein as a hybrid vacuum-electrostatic chuck (or simply abbreviated as a "hybrid chuck"). The hybrid chuck can first use its vacuum chucking function to secure and planarize the sample while the main chamber is at atmospheric pressure. The hybrid chuck can then activate its electrostatic chucking function to apply an electrostatic force to further secure the sample. The main chamber can then be evacuated, leaving the electrostatic force as the only technique for flattening and clamping the sample to the hybrid chuck, allowing the sample to be processed at the desired vacuum pressure in the main chamber.

[0074]

[0088] FIG. 8A is a simplified cross-sectional view of a sample support system 800 including a hybrid vacuum-electrostatic chuck 820 (also referred to herein as a “hybrid chuck 820”) and a stage 810 according to some embodiments. The hybrid chuck 820 may be similar to the hybrid chuck carrier 520 described above with respect to FIGS. 5A and 5B , except that the hybrid chuck 820 remains directly coupled to the stage 810 within the processing chamber and is not transported by a transport unit between the processing chamber and the load lock chamber. Thus, the hybrid chuck 820 includes a single set of lift pins 804 that can raise and lower a sample relative to an upper support surface 802 of the chuck, rather than the two separate sets of lift pins 504, 506 described with respect to the hybrid chuck carrier 520. As shown, the hybrid chuck 820 positions a sample 850 on its upper surface 802 and is positioned on a stage 810 that can move the hybrid chuck along the X, Y, and Z axes within the sample processing chamber.

[0075]

[0089] Also shown in Figure 8A are a set of lift pins 804, a vacuum system 825, and a high voltage system 830. The lift pins 804 allow the sample to be elevated above the upper support surface 802 so that a transfer unit can slide under the sample to load or unload it from the hybrid chuck 820. Referring to both Figure 8A and Figure 8B, which shows a close-up of a portion of the hybrid chuck 820, sample 850, and platform 810, each lift pin 804 is positioned within a respective lift pin hole 805 that extends completely through the platform and hybrid chuck 820.

[0076]

[0090] The hybrid chuck 820 includes a plurality of vacuum channels 822 on its upper surface, which can be operatively coupled to a vacuum system 825 when the hybrid chuck is disposed on the platform 810. For example, a first vacuum line 824 extending from the vacuum system 825 through the platform 810 can be fluidly coupled by a coupling 828 to a second vacuum line 826 passing through the hybrid chuck 820. Thus, each vacuum channel 822 is fluidly coupled to the vacuum system 825 and is operable to apply a vacuum to the backside of the sample 850 when the vacuum system 825 is activated.

[0077]

[0091] The hybrid chuck 820 also includes a series of electrodes 832, 834 that are operatively coupled to a high-voltage source 830 when the chuck is disposed on the platform 810. The electrodes 832, 834 may be arranged in an alternating or other pattern beneath the upper surface 802, as described above with respect to electrodes 532, 534. As shown, high-voltage lines 836, 838 extend from the high-voltage source 830 through the platform 810. The lines 836, 838 may be electrically coupled by couplings 846, 848 to high-voltage lines 842, 844, respectively, that run through the hybrid chuck 820. Thus, each series of electrodes 832, 834 is electrically coupled to the high-voltage system 830 and is operable to generate an electrostatic force that clamps the sample 850 to the hybrid chuck when the high-voltage source 830 is activated.

[0078]

[0092] For a better understanding and appreciation of this embodiment, reference is made to Figures 9 and 10A-10D. Figure 9 is a flowchart illustrating steps associated with a method 900 for planarizing and processing a warped substrate, according to some embodiments, and Figures 10A-10D are simplified cross-sectional views of a substrate processing system 1000, according to some embodiments, shown at various stages of planarizing and processing a warped substrate 1050 according to the method described in Figure 9.

[0079]

[0093] As shown, the substrate processing system 1000 includes a main processing chamber 1010, which is capable of performing the same substrate processing operations as the chambers 110 and 210 described above and, therefore, includes many of the same components. However, instead of the sample support 140 or 240, the substrate processing system 1000 includes a hybrid vacuum-electrostatic chuck 1020 operable to secure a sample 1050 within the processing chamber during substrate processing operations. The hybrid chuck can be positioned on a stage 1040 within the processing chamber 1010, which can move both the hybrid chuck and the sample 1050 within the processing chamber 1010 so that various portions of the sample are positioned directly below the field of view of the SEM column. To this end, the stage 1040 can move the hybrid chuck and sample 1050 left and right and back and forth (i.e., along both the X-axis and the Y-axis) within the chamber 1010, and can also move the hybrid chuck and sample up and down along the Z-axis.

[0080]

[0094] The stage 1040 also includes a vacuum connection 1062 and a high voltage connection 1064, which can respectively couple a vacuum system (not shown in FIG. 10A ) and a high voltage source (also not shown) to corresponding connections on the hybrid chuck 1020 when the hybrid chuck 1020 is secured to the stage 1040. For example, the vacuum connection 1062 can represent the vacuum line 824 and vacuum coupling 828 that couple the vacuum system 825 to the vacuum line 826 within the hybrid chuck. Similarly, the high voltage connection 1064 can represent the high voltage lines 836, 838 and high voltage couplings 846, 848 that couple the high voltage source 830 to the voltage lines 842, 844, respectively, within the hybrid chuck.

[0081]

[0095] 9 and 10A, the method 900 begins by transferring a sample 1050 into a substrate processing chamber 1010 and placing the sample on an upper support surface of a hybrid chuck 1020 (FIG. 9, step 910). The hybrid chuck 1020 may be, for example, the hybrid chuck 820 described above, and may therefore secure the sample to its upper surface using either or both vacuum and electrostatic chucking. The sample 1050 may be, for example, a thin semiconductor wafer. The system 1000 may continuously process hundreds or thousands of samples 1050, some of which may be significantly warped, as shown in FIG. 10A.

[0082]

[0096] 10A, the transfer can be performed by the ETU picking up the sample 1050 from the load lock chamber and placing the sample on lift pins (e.g., lift pins 804) that protrude above the top surface of the hybrid chuck 1020 in the processing chamber 1010. The lift pins can then be lowered (or the stage 1040 can be raised) so that the sample is supported by the top surface of the chuck 1020, as shown in FIG. 10A. This initial transfer step can be performed while the processing chamber 1010 is at atmospheric pressure (as indicated by the dotted background of the processing chamber 1010).

[0083]

[0097] Next, the vacuum system can be activated, as shown by arrow 1070 in FIG. 10B, to generate a vacuum suction force on the bottom of the sample 1050 (FIG. 9, step 920). Applying a vacuum to the backside of the sample 1050 clamps the sample to the top surface of the hybrid chuck 1020, flattening the sample as shown in FIG. 10B. While the vacuum is applied to the backside of the sample 1050 (and while the load lock chamber is still at atmospheric pressure), the high voltage source can be activated, as shown by arrow 1072 in FIG. 10C, to apply an electrostatic force to further secure the sample 1050 to the chuck carrier 1020 (FIG. 9, step 930).

[0084]

[0098] The processing chamber 1010 can then be evacuated (indicated by the absence of a dotted background in FIG. 10C) to a desired substrate processing pressure (e.g., a pressure between a high vacuum level and an ultra-high vacuum level), and the vacuum system clamping the sample 1050 to the chuck carrier 1020 can be turned off, as indicated by the absence of arrow 1070 in FIG. 10C. During this time, the high voltage applied to the electrodes is maintained (arrow 1072), so that the only force clamping the sample 1050 to the hybrid chuck is electrostatic force ( FIG. 9 , step 940).

[0085]

[0099] At this stage, the sample 1050 can be processed in the processing chamber 1010 (FIG. 9, block 950) while a high voltage remains applied to the electrodes to keep the sample flat. In the method 900, the sample 1050 is first chucked with a vacuum chuck and then the clamping force is switched to electrostatic force, allowing highly warped samples that cannot be flattened by electrostatic force alone to remain flat.

[0086]

[0100] After processing is complete, the high voltage supply 1072 is turned off and the processing chamber is vented to atmosphere (FIG. 9, step 960), as shown in FIG. 10D. The sample is then raised above the top surface of the hybrid chuck 1020 by the lift pins, allowing the ITU (not shown) to pick up the sample 1050 and place it back into the load lock chamber (not shown) while both the main processing chamber 1010 and the load lock chamber 1020 are at atmospheric pressure (FIG. 9, step 970).

[0087]

[0101] The method 900 can then be repeated for the next sample.

[0088] Processing chamber with main chamber and separate auxiliary space

[0102] In yet other embodiments, the main processing chamber can include a separate auxiliary space or chamber that can be sealed from the main chamber. The system can include a substrate support that functions as both a vacuum chuck and an electrostatic chuck, capable of clamping and planarizing a sample, similar to that described above with respect to the hybrid vacuum-electrostatic chuck. However, when processing a series of samples, instead of repeatedly venting the main chamber and then pumping it down to the desired vacuum pressure for the processing operation, the substrate support (stage) can move the hybrid chuck and sample between the main processing chamber and the auxiliary space. The auxiliary space, which can have a much smaller volume than the main processing chamber, can then be sealed from the main processing chamber and vented to atmosphere.

[0089]

[0103] Once positioned within the auxiliary space, the hybrid chuck can use its vacuum chucking function to clamp and planarize a sample while the auxiliary chamber is at atmospheric pressure. The hybrid chuck can then activate its electrostatic chucking function to apply an electrostatic force to clamp the sample. The auxiliary space can then be evacuated to a vacuum, leaving the electrostatic force as the only force to flatten and clamp the sample to the hybrid chuck. Because the auxiliary space has a much smaller volume than the main processing chamber, it can be evacuated to the required vacuum pressure much faster, improving throughput for processing multiple wafers. The hybrid chuck can then be returned to its processing position within the main chamber and processed at the required vacuum pressure. For illustrative purposes, refer to FIGS. 11 and 12A-12G. FIG. 11 is a flowchart illustrating steps associated with a method 1100 for planarizing and processing a warped substrate according to some embodiments, and FIGS. 12A-12G are simplified cross-sectional views of a substrate processing system 1200 according to some embodiments, shown at various stages of planarizing and processing a warped substrate 1250 according to the method described in FIG. 11.

[0090]

[0104] As shown, the substrate processing system 1200 includes a main processing chamber 1210 that contains many of the same components and is capable of performing the same general substrate processing operations as the above-described chambers 110 or 210. The substrate processing system 1200 also includes a hybrid vacuum-electrostatic chuck 1220 and a separate auxiliary chamber or space that can be environmentally sealed from the main processing chamber 1210.

[0091]

[0105] The hybrid vacuum-electrostatic chuck 1220 can be positioned within the chamber 1210 on a stage 1240 that can secure the sample 1250 within the processing chamber during substrate processing operations and that can move both the hybrid chuck and the sample 1250 within the processing chamber. The hybrid chuck 1220 and stage 1240 can be similar to the hybrid chuck 1020 and stage 1040 described above. However, in this embodiment, the stage 1040 can move the hybrid chuck to various locations within the processing chamber 1210 so that different portions of the sample are directly under the field of view of the SEM column, and can also move the hybrid chuck in and out of the auxiliary space 1030.

[0092]

[0106] As shown, stage 1240 includes vacuum connections 1262 and high voltage connections 1264 that can respectively couple a vacuum system (not shown in FIG. 12A ) and a high voltage source (also not shown) to corresponding connections on hybrid chuck 1220 when hybrid chuck 1220 is secured to stage 1040. For example, vacuum connection 1262 can represent vacuum line 824 and vacuum coupling 828 that couple vacuum system 825 to vacuum line 826 within the hybrid chuck. Similarly, high voltage connection 1264 can represent high voltage lines 836, 838 and high voltage couplings 846, 848 that couple high voltage source 830 to voltage lines 842, 844, respectively, within the hybrid chuck.

[0093]

[0107] 11 and 12A, method 1100 begins by transferring a sample 1250 into a substrate processing chamber 1210 and placing the sample on an upper support surface of a hybrid chuck 1220 (FIG. 11, step 1110). The hybrid chuck 1220 may be, for example, the hybrid chuck 820 described above, and may therefore secure the sample to its upper surface using either or both vacuum and electrostatic chucking. The sample 1250 may be, for example, a thin semiconductor wafer that may have varying degrees of bow.

[0094]

[0108] 12A, the transfer can be performed by the ETU picking up the sample 1250 from the load lock chamber and placing it on lift pins (e.g., lift pins 804) that protrude above the top surface of the hybrid chuck 1220 in the processing chamber 1210. The lift pins can then be lowered (or the stage 1240 can be raised) so that the sample is supported by the top surface of the chuck 1220, as shown in FIG. 12A. This initial transfer step can be performed while both the load lock chamber and the substrate processing chamber 1210 are at vacuum pressure.

[0095]

[0109] Next, stage 1240 moves the sample from main chamber 1210 to auxiliary space 1230 ( FIG. 11 , step 1120), as shown in FIG. 12B. Moving the stage in step 1120 may include moving the stage along one or both of the X and Y axes until the stage is properly positioned below auxiliary space 1230, and then raising the stage so that sample 1250 and at least a portion of hybrid chuck 1220 are within auxiliary space 1230 such that the auxiliary space is environmentally sealed from main processing chamber 1210. Sealing the auxiliary space from the main processing chamber may be accomplished using any suitable technique or mechanism known to those skilled in the art.

[0096]

[0110] Next, as shown in Figure 12C, the auxiliary space 1230 can be vented to the atmosphere (Figure 11, step 1130) while the main processing chamber remains under vacuum. Next, the vacuum chuck portion of the hybrid chuck 1220 can be actuated to generate a vacuum suction force on the bottom of the sample 1250 (Figure 11, step 1140), as indicated by arrow 1270 in Figure 12D. Applying a vacuum to the backside of the sample 1250 clamps the sample to the top surface of the hybrid chuck 1220, flattening the sample as shown in Figure 12D.

[0097]

[0111] While the vacuum is applied to the backside of the sample 1250 (and the auxiliary space 1030 is still at atmospheric pressure), the high voltage source can be activated as shown by arrow 1272 in FIG. 12E to apply an electrostatic force to further secure the sample 1250 to the hybrid chuck 1220 ( FIG. 11 , step 1150).

[0098]

[0112] The auxiliary space 1230 can then be evacuated (indicated by the absence of dotted background in FIG. 12F) to the same vacuum pressure as the substrate processing system 1210, and the vacuum system clamping the sample 1250 to the hybrid chuck 1220 can be turned off, as indicated by the absence of arrow 1270 in FIG. 12F. During this time, the high voltage applied to the electrodes is maintained (arrow 1272), so that the only force clamping the sample 1250 to the hybrid chuck 1220 is electrostatic force ( FIG. 11 , step 1160).

[0099]

[0113] 12G, the stage 1240 can be returned to the main processing region of the chamber 1210 (FIG. 11, step 1170), and the sample 1250 can be processed in the processing chamber 1210 (FIG. 11, step 1180) while continuing to apply a high voltage to the electrodes to keep the sample flat. As described above with respect to the previous embodiment, the method 1100 can first chuck the sample 1250 with a vacuum chuck and then switch the clamping force to electrostatic force to keep highly warped samples that cannot be flattened by electrostatic force alone flat.

[0100]

[0114] After processing is complete, the high voltage source 1172 is turned off, the sample is raised above the top surface of the hybrid chuck 1220 by the lift pins, and the ITU (not shown) can pick up the sample and place it back into the load lock chamber (not shown) while both the main processing chamber 1210 and the load lock chamber 1220 are under vacuum ( FIG. 11 , step 1190).

[0101]

[0115] The method 1100 can then be repeated for the next sample.

[0102] Additional Embodiments

[0116] In the above description, specific terminology is used for convenience of explanation to enable a thorough understanding of the described embodiments. However, it will be apparent to those skilled in the art that specific details are not necessary to practice the described embodiments. For example, while the examples described above sometimes refer to the sample processing chamber as a scanning electron microscope tool, those skilled in the art will understand that the embodiments disclosed herein can be used with many other types of sample processing chambers that require substrates or other types of samples to be fixed and / or planarized before processing under vacuum conditions. As another example, while all of the above described examples involve operating the vacuum chuck function to fix and planarize the sample while the sample is within a chamber or other sealed, enclosed area at atmospheric pressure (i.e., 760 torr), embodiments are not limited thereto, and in other embodiments, the sample may initially be fixed and planarized by the vacuum chuck at pressures less than 760 torr. In fact, those skilled in the art will understand that the difference between the pressure generated by the vacuum chuck at the underside of the sample and the pressure of the chamber / environment in which the sample is located is important. If the sample is in a high-vacuum environment, the vacuum chuck will not be able to completely fix and planarize the sample. However, such chucks can clamp and flatten some samples at pressure levels below 760 torr, e.g., in what is considered the "rough vacuum range" (e.g., pressures below 760 torr but above 25 torr). Those skilled in the art will further appreciate that a greater pressure differential between the vacuum pressure created by the vacuum chuck at the sample's lower surface and the chamber / ambient pressure at the sample's upper surface can clamp and flatten samples with greater degrees of bowing than can be clamped and flattened when a smaller pressure differential is created between the opposite surfaces of the sample.

[0103]

[0117] Furthermore, while various different embodiments of the present disclosure have been disclosed above, the specific details of particular embodiments can be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present disclosure. Moreover, it will be apparent to those skilled in the art that many modifications and variations are possible in light of the above teachings. It is therefore to be understood that the appended claims are intended to cover all modifications and variations that fall within the true spirit of the embodiments of the present disclosure.

[0104]

[0118] While the illustrated embodiments of the present disclosure can be implemented, for the most part, using electronic components and circuits known to those skilled in the art, details thereof have not been described beyond the extent deemed necessary, as explained above, for an understanding and appreciation of the concepts underlying the present disclosure and so as not to obscure or distract from the teachings of the present disclosure.

[0105]

[0119] Furthermore, references in the above specification to a method also apply mutatis mutandis to a system capable of performing the method, and also to a computer program product storing instructions that, when executed, result in the performance of the method. Similarly, references in the above specification to a system also apply mutatis mutandis to a method that may be performed by the system, and also to a computer program product storing instructions that may be executed by the system, and also references in the specification to a computer program product also apply mutatis mutandis to a method that may be performed when executing instructions stored in the computer program product, and also to a system configured to execute instructions stored in the computer program product.

Claims

1. 1. A method for processing a substrate in a processing chamber including a main volume and an auxiliary volume environmentally sealable from the main volume, comprising: transferring the substrate into the main volume of the processing chamber and onto an upper surface of a substrate holder while the main volume is under vacuum pressure, the substrate holder comprising one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder proximate to the upper surface; moving the substrate holder within the processing chamber such that the substrate moves from the main space to the auxiliary space; sealing the auxiliary space from the main space and increasing pressure in the auxiliary space; clamping and flattening the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels while the substrate is in the auxiliary space; applying a voltage to the one or more electrodes while the substrate is in the auxiliary space and clamped to the substrate holder by the one or more vacuum channels to further clamp the substrate to the substrate holder by electrostatic forces; returning the substrate from the auxiliary space into the main space while the substrate is clamped to the substrate holder by the electrostatic force, and processing the substrate in the main space under vacuum pressure; A method comprising:

2. The method for processing a substrate according to claim 1 , wherein the auxiliary space is directly attached to a lid of a substrate processing chamber.

3. 2. The method for processing a substrate according to claim 1, further comprising, after processing the substrate under vacuum conditions in the main space, stopping the application of the voltage so that the substrate is no longer clamped to the substrate holder by the electrostatic force, and removing the substrate from the processing chamber.

4. 10. The method of processing a substrate of claim 1, wherein the processing chamber comprises a scanning electron microscope, and processing the substrate in the processing chamber comprises imaging the substrate with the scanning electron microscope.

5. 10. The method of processing a substrate of claim 1, wherein the substrate has a bow that is at least 1.0 millimeter between the lowest point and the highest point on the substrate.

6. 10. The method of processing a substrate of claim 1, wherein the vacuum pressure at which the substrate is processed in the processing chamber is a high vacuum pressure or a lower pressure.

7. The method for processing a substrate according to claim 1 , wherein increasing the pressure in the auxiliary space comprises venting the auxiliary space to atmosphere.

8. 8. The method of processing a substrate of claim 7, further comprising, after clamping the substrate to the substrate holder by electrostatic forces in the auxiliary space and before returning the substrate from the auxiliary space into the main space, evacuating the auxiliary space to a vacuum pressure while continuing to clamp the substrate to the substrate holder by electrostatic forces.

9. 1. A system for processing a substrate, the system comprising: a substrate processing chamber having a main processing region and an auxiliary volume that is environmentally sealable from the main processing region; a substrate support disposed within the substrate processing chamber, the substrate support comprising one or more vacuum channels disposed on an upper surface thereof and one or more electrodes disposed within the substrate support proximate the upper surface; a stage operably coupled to move the substrate support between the main processing region and the auxiliary space within the substrate processing chamber; at least one processor; and at least one memory coupled to the at least one processor; wherein the at least one memory includes a plurality of computer-readable instructions that, when executed by the at least one processor, cause the system to: transferring the substrate into a main volume of the processing chamber and onto an upper surface of a substrate holder while the main volume of the processing chamber is under vacuum pressure, the substrate holder comprising one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder proximate to the upper surface; moving the substrate holder within the processing chamber such that the substrate moves from the main space to the auxiliary space; sealing the auxiliary space from the main space and increasing pressure in the auxiliary space; clamping and flattening the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels while the substrate is in the auxiliary space; applying a voltage to the one or more electrodes while the substrate is in the auxiliary space and clamped to the substrate holder by the one or more vacuum channels to further clamp the substrate to the substrate holder by electrostatic forces; returning the substrate from the auxiliary space into the main space while the substrate is clamped to the substrate holder by the electrostatic force, and processing the substrate in the main space under vacuum pressure; A system that executes the following.

10. 10. The system for processing a substrate of claim 9, wherein increasing the pressure in the auxiliary space comprises venting the auxiliary space to atmosphere.

11. 11. The system for processing a substrate of claim 10, wherein the computer readable instructions, when executed by the processor, further comprise instructions that cause the system to, after clamping the substrate to the substrate holder by electrostatic forces in the auxiliary space and before returning the substrate from the auxiliary space into the main space, evacuate the auxiliary space to a vacuum pressure while continuing to clamp the substrate to the substrate holder by electrostatic forces.

12. 10. The system for processing a substrate of claim 9, wherein the computer readable instructions, when executed by the processor, further comprise instructions that cause the system to, after processing the substrate under vacuum conditions in the main processing region, stop applying the voltage so that the substrate is no longer clamped to the substrate holder by the electrostatic force, and remove the substrate from the substrate processing chamber.

13. 10. The system for processing a substrate of claim 9, wherein the processing chamber comprises a scanning electron microscope, and processing the substrate in the substrate processing chamber comprises imaging the substrate with the scanning electron microscope.

14. 10. The system for processing a substrate of claim 9, wherein the vacuum pressure at which the substrate is processed in the substrate processing chamber is a high vacuum pressure or a lower pressure.

15. The system for processing a substrate according to claim 9 , wherein the auxiliary space is directly attached to a lid of the substrate processing chamber.

16. Instructions for processing a substrate in a processing chamber, comprising: transferring the substrate into a main volume of the processing chamber and onto an upper surface of a substrate holder while the main volume of the processing chamber is under vacuum pressure, the substrate holder comprising one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder proximate to the upper surface; moving the substrate holder within the processing chamber such that the substrate moves from the main space to an auxiliary space; sealing the auxiliary space from the main space and increasing pressure in the auxiliary space; clamping and flattening the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels while the substrate is in the auxiliary space; applying a voltage to the one or more electrodes while the substrate is in the auxiliary space and clamped to the substrate holder by the one or more vacuum channels to further clamp the substrate to the substrate holder by electrostatic forces; returning the substrate from the auxiliary space into the main space while the substrate is clamped to the substrate holder by the electrostatic force, and processing the substrate in the main space under vacuum pressure; a non-transitory computer-readable memory storing instructions for processing a substrate in a processing chamber by

17. 17. The non-transitory computer-readable memory of claim 16, wherein increasing the pressure in the auxiliary space comprises venting the auxiliary space to atmosphere.

18. 17. The non-transitory computer readable memory of claim 16, further comprising computer readable instructions that, when executed by a processor, cause a system to: after clamping the substrate to the substrate holder by electrostatic forces in the auxiliary space and before returning the substrate from the auxiliary space into the main space, evacuate the auxiliary space to a vacuum pressure while continuing to clamp the substrate to the substrate holder by electrostatic forces.

19. 17. The non-transitory computer-readable memory of claim 16, wherein the processing chamber comprises a scanning electron microscope, and wherein processing the substrate in the processing chamber comprises imaging the substrate with the scanning electron microscope.

20. 20. The non-transitory computer-readable memory of claim 16, wherein the substrate has a bow of at least 1.0 millimeter between the lowest point and the highest point on the substrate.

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