Hybrid vacuum electrostatic chuck carrier for high warpage wafers

Abstract

The invention relates to a hybrid vacuum electrostatic chuck carrier for high warpage wafers. A method of processing a substrate according to the present invention comprises: positioning a substrate on an upper surface of a substrate holder of a first chamber, 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; adsorbing and flattening the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels while the substrate holder is located within the first chamber; applying a voltage to the one or more electrodes as the substrate is adsorbed to the substrate holder through the one or more vacuum channels to further adsorb the substrate to the substrate holder using an electrostatic force; the first chamber is vacuumized to a vacuum pressure when the electrostatic force is continuously utilized to adsorb the substrate to the substrate holder; transferring the substrate holder from the first chamber to the second chamber under a vacuum condition when the substrate is adsorbed to the substrate holder through electrostatic force; and maintaining the electrostatic force to adsorb the substrate to the substrate holder while the substrate holder is located in the second chamber and processing the substrate with vacuum pressure in the second chamber.

Description

TECHNICAL FIELD

[0001] This application claims the benefit of and priority to U.S. Patent Application No. 18 / 749,474, filed June 20, 2024, entitled “Hybrid Vacuum Electrostatic Chuck for Highly Warped Wafers,” and is hereby incorporated by reference in its entirety.

[0002] Commonly assigned U.S. Patent Application No. 18 / 749,484, entitled “In-Cavity Hybrid Vacuum Electrostatic Chuck for Highly Warped Wafers,” and is hereby incorporated by reference in its entirety.

[0003] Commonly assigned U.S. Patent Application No. 18 / 749,495, entitled “Specialized In-Cavity Hybrid Vacuum Electrostatic Chuck for Highly Warped Wafers,” and is hereby incorporated by reference in its entirety. BACKGROUND

[0004] In the study of electronic materials and the processes by which these materials are fabricated into electronic structures, a sample, such as a semiconductor wafer, can be analyzed in a scanning electron microscope (SEM) to study particular features in the wafer. Such features can include fabricated circuitry and any defects formed during the fabrication process. Electron microscopes are one of the most useful devices for analyzing the microstructure of semiconductor components.

[0005] In such an inspection process, multiple locations on the sample are typically inspected. In order to perform such an inspection, the sample must be completely flat or planar to ensure that the measurements or other analyses performed are accurate. While many samples, such as semiconductor substrates or “wafers,” appear flat at initial observation, these samples can actually have a relatively high degree of warpage.

[0006] In the semiconductor industry, several different types of sample support structures are commonly used to secure and flatten wafers to the support structure during processing. One such support structure is an electrostatic chuck, which includes one or more electrodes located beneath the surface of the support sample. If the sample is electrically conductive, a voltage can be applied to the electrodes to attract and flatten the sample to the chuck. Electrostatic chucks are very effective at flattening slightly or moderately warped wafers, but can be ineffective or even unable to flatten highly warped wafers.

[0007] Another support structure is a vacuum chuck, which applies a vacuum to the back of the sample to attract and flatten the sample to the chuck. Vacuum chucks are very effective at securing and flattening wafers, including some highly warped wafers that cannot be flattened by electrostatic chucks, but vacuum chucks cannot be used to secure or flatten substrates in sample processing chambers, as these chambers are processed under vacuum pressure.

[0008] While many designs of electrostatic and vacuum chucks have evolved over the years, some prior designs of chucks have limited ability to support and fully planarize highly warped wafers under vacuum pressure during substrate processing operations in a sample processing chamber. Accordingly, there is a need for novel and improved systems that flatten warped samples and support such samples in substrate processing tools. SUMMARY

[0009] Embodiments described herein provide methods and systems for supporting, flattening, and processing samples, including highly warped substrates or wafers. While embodiments of the present disclosure can be used to support and flatten many different types of samples that can have varying degrees of warpage prior to processing operations within a vacuum chamber, certain embodiments are particularly useful for supporting and flattening large thin wafers, such as semiconductor wafers, that can be highly warped and thus unable to be flattened by some conventional electrostatic chucks.

[0010] As described herein, for certain processing operations performed on a sample, the sample must be fully planarized. For example, when using a scanning electron microscope (SEM) tool to image various locations on a wafer, it is important to ensure that the working distance between the tip and the sample is accurate and known. Accordingly, to achieve this, the methods and systems described herein first flatten the sample prior to performing processing operations, such as SEM imaging operations, on the sample. In certain embodiments, the sample is flattened in a load lock or similar chamber prior to being transferred to a substrate processing chamber. In other embodiments, the sample is transferred to a main processing chamber and then flattened within the main processing chamber prior to performing substrate processing operations. In still other embodiments, the processing chamber includes a main chamber region in which the sample is processed and a separate, smaller chamber region (sometimes referred to herein as an "auxiliary space") that is isolated from the main chamber. The sample can be moved and initially flattened in the auxiliary space and then moved back to the main processing region prior to performing substrate processing operations. Details of each of these embodiments are described below.

[0011] While certain methods and systems of the present disclosure are particularly useful for flattening warped wafers prior to performing imaging operations in a vacuum chamber of an SEM tool, embodiments are not limited to any particular type of substrate processing operation or substrate processing tool. Embodiments described herein can be used to secure and flatten samples prior to processing the samples in other types of sample processing tools that process samples in high, very high, or ultra-high vacuum environments.

[0012] According to certain embodiments, a method of processing a substrate is disclosed, the method comprising: positioning a substrate on an upper surface of a substrate holder in a first chamber, wherein the upper surface of the substrate holder has one or more vacuum channels disposed on the upper surface and one or more electrodes disposed inside the substrate holder proximate to the upper surface; while the substrate holder is in the first chamber, adsorbing and flattening the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels; while the substrate is adsorbed to the substrate holder by the one or more vacuum channels, further adsorbing the substrate to the substrate holder using electrostatic forces by applying a voltage to the one or more electrodes; while the substrate continues to be adsorbed to the substrate holder using electrostatic forces, evacuating the first chamber to a vacuum pressure; while the substrate is adsorbed to the substrate holder by electrostatic forces, transferring the substrate holder from the first chamber to a second chamber under vacuum conditions; and while the substrate holder is in the second chamber, maintaining the substrate adsorbed to the substrate holder using electrostatic forces and processing the substrate at the vacuum pressure in the second chamber.

[0013] In various embodiments, the method according to embodiments of the disclosure can include one or more of the following. The first chamber can be a load lock chamber. The substrate can be adsorbed and flattened to the substrate holder by applying a vacuum to the one or more vacuum channels while the load lock chamber is maintained at atmospheric pressure. The second chamber can be a processing chamber containing a scanning electron microscope. Processing the substrate in the second chamber can include imaging the substrate using the scanning electron microscope. After processing the substrate in the processing chamber under vacuum conditions, the method can further include transferring the substrate holder with the substrate back to the load lock chamber. The substrate can have a bow between a lowest point and a highest point on the substrate of at least 1.0 millimeter. The vacuum pressure while processing the sample in the second chamber can be a high vacuum pressure or lower. The one or more electrodes can include at least two electrodes arranged in a staggered pattern. The substrate can be a semiconductor wafer.

[0014] In certain embodiments, a system for processing a substrate is disclosed. The system can include a main substrate processing chamber, a load lock chamber, a first external transport unit configured to transfer a substrate between the load lock chamber and a front opening unified pod (FOUP), a second internal transport unit configured to transfer a substrate between the load lock chamber and the main substrate processing chamber, a processor, and a memory coupled with the processor. The memory can include a plurality of computer readable instructions that, when executed by the processor, cause the system to: transfer the substrate to the load lock chamber using the first external transport unit and position the substrate on an upper surface of a substrate holder within the load lock chamber, wherein the substrate holder includes 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; while the substrate holder is positioned within the load lock chamber, adsorb and flatten the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels; while the substrate is adsorbed to the substrate holder by the one or more vacuum channels, further adsorb the substrate to the substrate holder using electrostatic forces by applying a voltage to the one or more electrodes; while the substrate continues to be adsorbed to the substrate holder using the electrostatic forces, evacuate the load lock chamber to a vacuum pressure; while under vacuum conditions, transfer the substrate and the substrate holder from the load lock chamber to the main processing chamber using the second internal transport unit; and while the substrate is adsorbed to the substrate holder using the electrostatic forces, process the substrate at the vacuum pressure within the main processing chamber.

[0015] In other additional embodiments, a non-transitory computer readable memory is disclosed. The computer readable memory can store instructions for processing a substrate, including: positioning a substrate on an upper surface of a substrate holder in a first chamber, wherein the substrate holder includes 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; while the substrate holder is positioned within the first chamber, adsorb and flatten the substrate to the substrate holder by applying a vacuum to the one or more vacuum channels; while the substrate is adsorbed to the substrate holder by the one or more vacuum channels, further adsorb the substrate to the substrate holder using electrostatic forces by applying a voltage to the one or more electrodes; while the substrate continues to be adsorbed to the substrate holder using the electrostatic forces, evacuate the first chamber to a vacuum pressure; transfer the substrate and the substrate holder from the first chamber to a second chamber under vacuum conditions; and process the substrate at the vacuum pressure within the second chamber while the substrate is adsorbed to the substrate holder using the electrostatic forces.

[0016] To better understand the nature and advantages of this disclosure, reference should be made to the following description and accompanying illustrations. However, it should be understood that each illustration is for illustrative purposes only and is not intended to define or limit the scope of this disclosure. Furthermore, according to general rules, unless it is obvious from the description to the contrary, elements using the same component symbols in different illustrations are generally either identical or at least similar in function or purpose. Attached Figure Description

[0017] Figure 1 This is a simplified schematic diagram of a sample evaluation system, which includes a scanning electron microscope (SEM) column;

[0018] Figures 2A-2C This is a simplified block diagram of a sample evaluation system, which includes a substrate processing pillar and a load locking chamber.

[0019] Figure 3A and 3B This is a simplified cross-sectional view of a previously known electrostatic chuck, showing the lifting pins in the upper and lower positions, respectively;

[0020] Figure 4A yes Figure 3A and 3B The simplified cross-section of the electrostatic chuck shown supports a highly warped sample;

[0021] Figure 4B yes Figure 4A An enlarged view of the electrostatic chuck and a portion of the sample shown in the image;

[0022] Figure 5A This is a simplified cross-sectional view of a hybrid vacuum electrostatic adsorption carrier according to certain embodiments;

[0023] Figure 5B yes Figure 5A An enlarged view of a portion of the hybrid vacuum electrostatic adsorption carrier shown in the image;

[0024] Figure 6 This is a flowchart showing the steps related to the method of flattening and processing warped substrates in some embodiments;

[0025] Figures 7A-7I This is a simplified cross-sectional view of a substrate processing system according to certain embodiments, showing that... Figure 6 The method involves different stages of flattening and treating warped substrates;

[0026] Figure 8A This is a simplified cross-sectional view of a hybrid vacuum electrostatic chuck according to certain embodiments;

[0027] Figure 8B yes Figure 8A An enlarged view of a portion of the hybrid vacuum electrostatic chuck shown in the image;

[0028] Figure 9 is a flow chart showing steps associated with a method of flattening and processing a warped substrate in accordance with certain embodiments;

[0029] Figures 10A-10D is a simplified cross-sectional view of a substrate processing system in accordance with certain embodiments, showing different stages of flattening and processing a warped substrate in accordance with the method described in Figure 9

[0030] Figure 11 is a flow chart showing steps associated with a method of flattening and processing a warped substrate in accordance with certain embodiments; and

[0031] Figures 12A-12G is a simplified cross-sectional view of a substrate processing system in accordance with certain embodiments, showing different stages of flattening and processing a warped substrate in accordance with the method described in Figure 11 DETAILED DESCRIPTION

[0032] The embodiments described herein provide methods and systems for supporting, flattening, and subsequent processing of samples, including highly warped substrates or wafers. While embodiments of the present disclosure can be used to support and flatten many different types of samples that can have varying degrees of warpage prior to being processed within a vacuum chamber, certain embodiments are particularly useful for supporting and flattening large, thin wafers, such as semiconductor wafers, that can be highly warped and thus unable to be flattened by certain conventional electrostatic chucks.

[0033] As described above, for certain processing operations performed on a sample, such as a semiconductor wafer, the sample must be completely flat. The embodiments described herein provide methods and systems for supporting, flattening, and subsequent processing of samples, including highly warped substrates or wafers, prior to performing processing operations on the sample (e.g., prior to performing SEM imaging operations on individual regions of different locations on the sample within a vacuum chamber). In certain embodiments, the sample is flattened in a load lock or similar chamber prior to being transferred to a substrate processing chamber. In other embodiments, the sample is transferred to a main processing chamber and then subsequently flattened within the main processing chamber prior to performing substrate processing operations. In still other embodiments, the processing chamber includes a main chamber region in which the sample is processed, and a separate, smaller chamber region (sometimes referred to herein as an "auxiliary space") that is isolated from the main chamber. The sample can be moved and initially flattened within the auxiliary space, and then moved back to the main processing region, where substrate processing operations are performed. Details of each of these embodiments are described below.

[0034] ​​While embodiments of the present disclosure can be used to support and flatten many different types of samples that can have varying degrees of warpage prior to performing processing operations within a vacuum chamber, certain embodiments are particularly useful for supporting and flattening large thin wafers, such as semiconductor wafers, that can be highly warped and thus unable to be flattened by certain conventional electrostatic chucks. Moreover, while certain methods and systems disclosed herein are particularly suitable for use in flattening warped semiconductor or dielectric wafers for performing imaging operations in a vacuum chamber of a SEM tool, embodiments are not limited to any particular type of substrate processing operation or substrate processing tool. Embodiments described herein can be used to process wafers (or samples) in other types of sample processing tools that require high, very high, or ultra-high vacuum environments to secure and flatten large wafers (and other types of samples) prior to performing processing operations.

[0035] Example sample evaluation tool

[0036] 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. The sample evaluation system 100 can be used to perform defect inspection and analysis of structures formed on a sample, such as a semiconductor or dielectric wafer.

[0037] The system 100 can include a vacuum chamber 110 and a scanning electron microscope (SEM) column 120. During processing operations, a support assembly 140 can support a sample 150, such as a semiconductor wafer, for irradiation by a charged particle beam 126 from the SEM column.

[0038] The SEM column 120 is coupled to the vacuum chamber 110 such that a charged particle beam generated by the column propagates through a vacuum environment formed within the vacuum chamber 110 prior to impinging on the sample 150. The SEM column 120 can generate partial images of the sample 150 by irradiating the sample with a charged particle beam 125, detecting particles emitted as a result of 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 defining an electron beam drift space, a condenser lens assembly 124, one or more deflection lenses, such as lenses 130, 132, and one or more focusing lenses 134, as well as a column cap 136.

[0039] During a process imaging procedure, electron beam source 122 generates electron beam 125, which passes through and is initially focused by condenser lens 124, and then is further focused by lens 134 before impinging on sample 150. Condenser lens 124 defines the numerical aperture and current of the electron beam (along with the final aperture), which is directly related to resolution, while focusing lens 134 focuses the beam onto the sample. Post 136, which is located between the lower end of anode tube 126 (the first electrode) and sample 150 (the second electrode), can be a third electrode in the system for adjusting the electric field generated near the wafer.

[0040] Figure 1 SEM column 120 is shown with charged particle beam 125 impinging on sample 150 at a generally normal angle to sample 150. In various embodiments, SEM column 120 can operate in a tilt mode, in which charged particle beam 125 impinges on sample 150 at a non-normal angle (e.g., a 45 degree angle).

[0041] In both the normal and tilt modes, the particle imaging procedure typically includes scanning the charged particle beam back and forth over a particular region of the sample being imaged (e.g., in a raster or other scan pattern). Deflection lenses 130, 132, which can be magnetic lenses, electrostatic lenses, or a combination of the two, enable the scan pattern, which is known to those skilled in the art. The scanned region is typically a small fraction of the overall area of the sample. For example, the sample can be a semiconductor wafer that is 200 or 300 mm in diameter, and each region scanned on the wafer can be a rectangular region that is a few or tens of microns in width and / or length.

[0042] SEM column 120 can also include one or more detectors for detecting charged particles generated from the sample during the process imaging procedure. For example, SEM column 120 can include in-lens detector 128 and top detector 138, both of which can detect secondary electrons and backscattered electrons generated by irradiating the sample with charged particle beam 126. In-lens detector 128 can include a central aperture that allows charged particle beam 126 to pass through the detector, and that allows secondary electrons and backscattered electrons entering charged particle column 120 to pass through detector 128 to top detector 138. In certain embodiments, sample evaluation 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 spectrometer (EDX) detector.

[0043] During operation of the system 100, the support assembly 140 can move the sample so that different regions (e.g., different regions of interest or "ROIs") are directly under the field of view of the SEM column 120. The support assembly 140 can move the sample 150 relatively quickly within the chamber 110 to the left and right (i.e., along the X-axis) and forward and backward (i.e., along the Y-axis), while also being able to raise and lower the sample 150, thereby moving the sample along the Z-axis.

[0044] Because many of the features formed on the sample 150 are on the order of microns or smaller, it is important to know the position of the sample relative to the focal point of the SEM column 120 with accuracy. To precisely determine the position of the sample 150, a high-precision navigation interferometry system (not shown) can be used in certain embodiments. The interferometry system can be mounted on the lid 112 of the chamber 110 and direct a collimated light (e.g., a laser beam) through a window (not shown) formed in the lid to a target area on the support assembly 140 that is encoded with various linear or other markings. The system can detect the light that returns to the interferometry system from the encoded target area on the support assembly 140 after reflecting off of the collimated light pulse (e.g., using an array of photodetectors). A processor (e.g., a digital signal processor) within the interferometry system can then analyze the detected light signal to determine the precise position of the sample along the X- and Y-axes.

[0045] In addition, the system 100 can include a voltage supply 160 and one or more controllers 170, such as processors or other hardware units. The voltage supply 160 can operate to provide the required column potential to improve image resolution. This can be accomplished by appropriately distributing the voltage supply to the first and second electrodes (i.e., between the anode tube and the sample). The controllers 170 can control the operation of the system, including the voltage supply, by executing computer instructions stored in one or more computer-readable memories 180, as is known to those of ordinary skill in the art. For example, these 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, etc.), disk drives, optical storage, or similar non-transitory computer-readable storage media.

[0046] The system 100 can also include a user interface 190, which can allow one or more users to interact with the system. For example, the user interface 190 can allow a user to set parameters for the SEM column or the detector that can be used when analyzing a sample. The user interface 190 can include any known devices that allow a user to input information to interact with a computer system, such as a keyboard, a mouse, a monitor, a touch screen, a touch pad, a voice-activated input controller, etc.

[0047] Transferring a sample to a processing chamber 110

[0048] To process a sample 150 within the chamber 110, the sample first needs to be transferred into the chamber. Although not shown in the drawings of the present application, some substrate processing systems include a factory interface that allows a cassette of wafers to be loaded into a docking station. The docking station can include one or more industry standard front opening unified pods (FOUPs) for temporarily storing wafers so that each wafer is kept in place while waiting for processing. A first external transfer unit (ETU), as part of the processing system, operates between the docking station and a load lock chamber, can extract individual wafers from the FOUPs and transfer the wafers to the load lock chamber. The docking station and FOUPs are typically at atmospheric pressure.

[0049] The processing chamber 110 operates at high, very high, or even ultra-high vacuum pressures. The load lock chamber is typically much smaller in volume than the processing chamber and can be rapidly raised and lowered between atmospheric pressure and high vacuum levels as needed, much faster than the processing chamber. For example, a wafer can be transferred from a FOUP at atmospheric pressure to the load lock chamber. The load lock chamber can then be pumped down to vacuum and a second internal transfer unit (ITU), as part of the processing system, can extract the wafer from the load lock chamber and transfer the wafer to the processing chamber without breaking vacuum (i.e., the load lock chamber and processing chamber are maintained at vacuum pressure). The first and second transfer units can be, for example, robotic arms with end effectors specifically designed for extracting and transferring semiconductor wafers or similar samples from one location to another within a processing tool or station.

[0050] Once in the processing chamber, the sample can be processed and then transferred back to the load lock chamber without breaking vacuum. The load lock chamber can then be vented to atmospheric pressure and the processed sample removed by the ITU for transfer to a subsequent stage of the manufacturing or evaluation process. Using the load lock chamber in this way can allow the main processing chamber to be maintained at high or ultra-high vacuum pressure while continuously processing hundreds or thousands of substrates without having to vent the processing chamber to atmospheric pressure.

[0051] Figures 2A-2C is a simplified block diagram of a previously known substrate processing system 200 that includes a substrate processing chamber 210 and a load lock chamber 220. The substrate processing chamber 210 can represent the substrate processing chamber 110, but for simplicity of illustration, Figure 2A or the SEM column 120 and other components of the processing chamber 110 are not shown in FIG. 2B. The substrate processing system 200 can also include additional components such as a docking station, one or more FOUPs, and various transfer units (e.g., ETUs, ITUs, and other robots) that are also not shown in the above discussion for simplicity of the drawings.

[0052] As Figures 2A-2CAs shown in FIG. 1, substrate processing chamber 210 can include a sample support assembly 240 that can support a sample 250 (e.g., a semiconductor wafer) within chamber 210 so that sample 250 is irradiated by a charged particle beam from an SEM column (not shown) during processing operations. Support assembly 240 and sample 250 can represent support assembly 140 and sample 150 discussed above in Figure 1

[0053] Load lock chamber 220 can also include a sample support assembly 260 that can support a sample when sample 250 is located within the load lock chamber. Each sample support assembly 240 and 260 can include an upper support surface 242, 262, respectively, and a lift pin (not shown) that allows the sample to be lifted above the upper support surface so that a transfer unit can slide under the sample and transfer the sample onto or off of the support assembly, as known to those skilled in the art.

[0054] To process sample 250 within processing chamber 210, the sample can first be transferred to load lock chamber 220 (as shown by the dashed arrow) and positioned on sample support 260, as shown in FIG. 2. This operation can be performed by a first transfer unit that removes sample 250 from a FOUP and transfers the sample to load lock chamber 220 while the load lock chamber is maintained at atmospheric pressure. The chamber can then be pumped down to an appropriate vacuum pressure, and a second transfer unit can transfer sample 250 from load lock chamber 220 to processing chamber 210 (as shown by the dashed arrow in FIG. 1), while both chambers are maintained at vacuum. Figure 2B

[0055] After processing is complete, sample 250 can be transferred from processing chamber 210 back to load lock chamber 220 (as shown by the dashed arrow in FIG. 1), while both chambers are still maintained at vacuum. Figure 2C

[0056] In some known systems, support assembly 240 can be an electrostatic chuck that applies a voltage to one or more electrodes located beneath surface 242 to attract and flatten sample 250 to support assembly 240. Figure 3A 3B FIGS. 3 and 4 are simplified schematic diagrams that represent a previously known electrostatic chuck 300 that can represent support assembly 240 and that is used by some previously known sample evaluation systems to support an electrically conductive sample, such as a semiconductor wafer, within a vacuum chamber during sample evaluation.

[0057] Referring first to FIG. 3 Figure 3A ​​​​The electrostatic chuck 300 includes a movable platform 310 connected to a support plate 320. The support plate 320 has a planar support surface 322 on which a sample 350 (e.g., a wafer such as a semiconductor wafer) can be placed for evaluation or other types of analytical operations.

[0058] Platform 310 can move support plate 320 (and thus sample 350) within vacuum chamber 110 in the X, Y, and Z directions to directly position the region of interest on the sample within the field of view of a charged particle column, such as charged particle column 120. Plate 320 can be made of a dielectric material, such as ceramic, and one or more electrodes 324, 326 can be disposed below surface 322. When sample 350 is a semiconductor wafer or other electrically conductive sample, voltage can be applied to electrodes 324, 326 to attract the sample to the flat support surface 322, such as... Figure 3A As shown, the sample is fixed to the support plate 320 so that the sample will not shift or move when the platform 310 moves the sample support within the vacuum chamber 110. Adsorbing the sample 350 in this manner, provided any warping of the sample 350 is within certain limits, can also advantageously flatten the sample to ensure accurate working distances in different areas of the sample.

[0059] The support plate 320 may also include multiple lifting pin holes 328 and a corresponding number of lifting pins 330 to facilitate the entry and exit of the sample 350 from the sample evaluation system. For example... Figure 3A and 3B As shown, each lifting pin hole 328 can completely penetrate the support plate 320. Moreover, although in Figure 3A As not shown in 3B, the lifting pin 330 can be fixed to a portion of the platform 310, allowing it to move with the support plate 320 in the X and Y directions, while simultaneously allowing the platform 310 to raise and lower the support plate 320 in the Z direction without moving the lifting pin 330. This allows the support plate 320 to be lowered, with the distal end of each lifting pin 330 protruding through its respective lifting pin hole 328, suspending the sample 350 above the upper surface 322 of the support plate 320, thus creating a gap 340 between the upper surface 322 of the support plate 320 and the bottom surface of the sample 350. Figure 3A As shown. When the suction cup is subsequently fully lifted (e.g., lifted to...), Figure 3B (as shown in the figure), each lifting pin 330 will retract into its respective lifting pin hole 328 in the support plate 320, and the sample 350 will rest on the upper surface 322.

[0060] like Figure 3AAs shown, the lift pins 330 are placed in the raised position to allow an ITU or similar substrate transfer device (not shown) to transfer a sample 350 into the vacuum chamber, place the sample on the lift pins 330, and then retrieve the sample from the vacuum chamber. Next, the support plate 320 can be raised to position the sample 350 on the upper surface 322, and one or more areas on the sample can then be evaluated or other analysis performed as described above. Once the evaluation process is complete for a given sample 350, the support plate can be lowered to raise the sample 350 on the lift pins 330, and the gap 340 formed between the sample and the support surface 322 enables the ITU (not shown) to lift and transfer the sample 350 off the lift pins and out of the chamber.

[0061] While Figure 3A and 3B two lift pin holes 328 and two corresponding lift pins 330 are shown, a typical electrostatic chuck 300 will include 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 can include three lift pin holes 328 and three lift pins 330 spaced at 120 degree angles from each other.

[0062] Challenges in processing highly warped samples

[0063] As Figure 1 , 2, and 3A, 3B show, the samples 150, 250, 350 processed in the systems 100, 200 are thin and flat wafers, such as semiconductor or dielectric wafers. All of these samples have some degree of warp (i.e., the sample has a convex or concave shape at some level), and warp is defined as the difference between the lowest point and the highest point on the sample when the sample is placed on a flat surface and not attached or otherwise secured to the surface.

[0064] As non-silicon wafers and new manufacturing techniques are used, and as semiconductor and other wafers have become larger over the years, the amount of warp has generally increased, with some wafers having at least a few hundred microns of warp and other wafers having as much as a few millimeters of warp. Some existing electrostatic chucks, such as the chuck 300 discussed above, are not able to completely flatten a wafer when the warp exceeds a certain threshold. To illustrate, reference is made to Figure 4A and Figure 4B where Figure 4A is a simplified cross-sectional view of the electrostatic chuck 300 discussed above supporting a highly warped sample 450, Figure 4B is an expanded view of a portion of the chuck 300 and the sample 450.

[0065] As Figure 4A and Figure 4BAs shown, the sample 450 is convexly warped, such that when the sample is positioned on the upper surface 322 of the chuck, the outer edge of the sample 450 is a distance D from the surface 322. When high voltage is applied to the electrodes 324, 326, the electrostatic chuck 300 can flatten portions of the sample 450, but when the warpage resulting in the distance D is too great, the electrostatic chuck 300 cannot completely flatten the sample. In this case, when the sample 450 is imaged or otherwise evaluated using a SEM instrument, such as the system 100, the working distance between the tip and the sample will vary at different locations on the sample 450, which will adversely affect the accuracy of the images obtained.

[0066] The actual distance D at which a given wafer cannot be completely flattened will depend on a variety of factors, including but not limited to the material of which the wafer is made, the size of the wafer, the model / type of the electrostatic chuck, and the voltage level applied to the electrodes. For some known electrostatic chucks, once the warpage of a particular wafer exceeds a few hundred microns, it can no longer be possible to completely flatten the wafer using acceptable voltage levels.

[0067] As noted above, it is important for certain processing operations performed on wafers or other samples that the sample be completely flat. For example, as noted above, when imaging various locations on a wafer using a scanning electron microscope (SEM) tool, it is critical that the working distance between the tip and the sample be accurate and known. Thus, to achieve this, the methods and systems described herein first flatten the sample before performing a processing operation, such as a SEM imaging operation, on the sample. As described in detail below, the embodiments disclosed herein can fix and flatten a sample to be processed under high or even ultra-high vacuum conditions using several different methods. In some embodiments, the sample is flattened in a load lock or similar chamber before being transferred to a processing chamber. In other embodiments, the sample is transferred to a main processing chamber and then flattened within the main processing chamber before performing a substrate processing operation, such as a SEM imaging operation. In still other embodiments, the processing chamber includes a main chamber region in which the sample is processed, and a separate chamber region isolated from the main chamber region in which the sample is initially flattened. Details of each of these embodiments are provided below.

[0068] Hybrid vacuum electrostatic chucking carrier

[0069] In some embodiments, rather than placing the sample directly on the sample supports in the process chamber and load lock chamber, such as support assemblies 240 and 260, the sample is first placed on an adsorption carrier in the load lock chamber, which is itself placed on a support structure. The adsorption carrier can use vacuum chucking and electrostatic chucking techniques to secure and flatten the sample, and is therefore referred to herein as a hybrid vacuum electrostatic adsorption carrier. In operation, the hybrid adsorption carrier can first secure and flatten the sample using its vacuum adsorption capabilities within the load lock chamber, which is at atmospheric pressure at this time. Then, the hybrid adsorption carrier can activate its electrostatic adsorption capabilities to increase the electrostatic forces to further secure the sample, and subsequently the load lock chamber can be pumped down to vacuum, leaving the sample secured and flattened on the hybrid adsorption carrier by electrostatic forces alone. With the sample secured and flattened, the hybrid vacuum electrostatic adsorption carrier and sample can be transferred from the load lock chamber to the main process chamber under vacuum via the ITU, and the sample can be processed in the main chamber on the hybrid adsorption carrier.

[0070] Figure 5A is a cross-sectional view of a simplified sample support system 500, which includes a hybrid vacuum electrostatic adsorption carrier 520 (sometimes referred to herein as "adsorption carrier 520") and a platform 510. As shown, a sample 550 is placed on an upper surface 502 of the adsorption carrier 520, which is placed on an upper surface 512 of the platform 510, which can be in a load lock chamber or a main process chamber, to replace support assemblies 260 or 240, respectively. Each surface 502 and 512 can be generally flat and shaped similarly to the sample 550, but at least slightly larger than the sample 550.

[0071] In Figure 5A Two sets of lift pins 504, 506, a vacuum system 525, and a high voltage system 530 are also shown. The lift pins 504 allow the sample to be raised above the upper support surface 502 so that the transport unit can slide underneath the sample and move the sample to or from the adsorption carrier 520. Likewise, the lift pins 506 allow the adsorption carrier 520 to be raised above the platform 510 so that the transport unit can slide underneath the adsorption carrier and move the adsorption carrier and sample to or from the platform 510.

[0072] As Figure 5B shown, this is a partial enlarged view of the adsorption carrier 520, sample 550, and platform 510, with each lift pin 504, 506 in its respective lift pin hole 505, 507. The lift pin hole 507 passes completely through the platform 510, while the lift pin hole 505 passes completely through the platform 510 and the adsorption carrier 520.

[0073] The adsorption carrier 520 includes a plurality of vacuum channels 522 in its upper surface that can be operatively connected to the vacuum system 525 when the adsorption carrier is positioned on the platform 510. For example, a first vacuum line 524 extending from the vacuum system 525 through the platform 510 can be fluidly connected to a second vacuum line 526 that passes through the adsorption carrier 520 via a coupler 528. Thus, each vacuum channel 522 is fluidly connected to the vacuum system 525 and is capable of applying a vacuum to the backside of the sample 550 when the vacuum system 525 is activated.

[0074] The adsorption carrier 520 also includes a series of electrodes 532, 534 that are operatively coupled to the high voltage source 530 when the adsorption carrier is positioned on the platform 510. The electrodes 532, 534 can be arranged in an interlaced or other pattern beneath the upper surface 502 as is well known to those skilled in the art and can be driven with opposite charges (i.e., positive and negative) to induce an electrostatic field at the upper surface that is capable of securing and adsorbing the sample 550 to the adsorption carrier. As shown, high voltage lines 536, 538 extend from the high voltage source 530 to the platform 510. The lines 536, 538 can be electrically coupled to high voltage lines 542, 544 that run within the adsorption carrier 520 via couplings 546, 548. Thus, each series of electrodes 532, 534 is electrically coupled to the high voltage system 530 and is capable of generating electrostatic forces to adsorb the sample 550 to the adsorption carrier 520 when the high voltage source 530 is activated.

[0075] In operation, the adsorption carrier 520 can initially adsorb and flatten the sample 550 to its upper surface by activating the vacuum system 525. Then, once the sample 550 is flattened to the adsorption carrier 520, the high voltage source 530 can activate the electrodes 532, 534 to electrostatically adsorb the sample to the adsorption carrier and the vacuum applied by the vacuum system 525 can be released. In this manner, the adsorption carrier can utilize its vacuum chuck to flatten certain highly warped samples that cannot be completely flattened using an electrostatic chuck alone. Then, after the sample is adsorbed by the electrostatic forces, the adsorption carrier can be transferred to a main processing chamber.

[0076] To better understand and appreciate how the hybrid vacuum electrostatic chuck 520 can be used to flatten a sample (e.g., a highly warped substrate) for processing in a substrate processing chamber that is pumped down to a high vacuum pressure level or lower, please refer to Figure 6 and Figures 7A-7I . Figure 6 is a flow diagram depicting steps of a method 600 of flattening and processing a warped substrate in accordance with certain embodiments. Figures 7A-7I is a simplified cross-sectional view of a substrate processing system 700 in accordance with certain embodiments showing a substrate 650 being processed in accordance with Figure 6The methods described in the middle stages of the process of flattening and processing a warped substrate.

[0077] As shown, the substrate processing system 700 includes a main processing chamber 710 and a load lock chamber 720, and relies on a hybrid vacuum electrostatic chuck 765 to secure the sample 750 when being transferred between the load lock and the main processing chamber. The main processing chamber 710 can be similar to the main processing chamber 210, except that a platform 740 adapted to receive the chuck 765 replaces the support assembly 140, 240. The load lock chamber 720 can be similar to the load lock chamber 220, except that a platform 760 replaces the substrate support 260. The chuck 520 can represent the chuck 765. Figure 1 and 2A The chuck 765 can be a hybrid vacuum electrostatic chuck, such as the chuck 520 described above. The chuck 765 can be secured to the platform 760 using any suitable chucking technique or mechanism, such as a releaseable latch. The platform 760 can be similar to the platform 510 described above.

[0078] Referring first to Figure 6 and Figure 7A The method 600 begins by transferring a sample 750 to the load lock chamber 720 and placing the sample on an upper support surface of a hybrid vacuum electrostatic chuck 765 (step 610). The chuck 765 can be the chuck 520 described above, and can use vacuum chucking or electrostatic chucking, or both, to secure the sample to its upper surface. The chuck can be positioned on the platform 760 and mechanically chucked using any suitable chucking technique or mechanism, such as a releaseable latch. The platform 760 can be similar to the platform 510 described above. Figure 6 The chuck 765 can be a hybrid vacuum electrostatic chuck, such as the chuck 520 described above. The chuck 765 can be secured to the platform 760 using any suitable chucking technique or mechanism, such as a releaseable latch. The platform 760 can be similar to the platform 510 described above.

[0079] The platform 760 can position and align the chuck and sample by rotating the sample and chuck to a particular angle, so that the sample currently being processed is in the same, known position as the sample previously processed and the sample to be subsequently processed when the transfer unit lifts and places the chuck on the platform of the main chamber. The platform 760 includes a vacuum connection 762 and a high voltage connection 764, which can connect a vacuum system (not shown in Figure 7A ) and a high voltage source (also not shown) to respective connection points of the chuck 765 secured to the platform 760, respectively. For example, the vacuum connection 762 can represent the vacuum line 524 and vacuum coupling 528 connecting the vacuum system 525 to the vacuum line 526 within the chuck. Likewise, the high voltage connection 764 can represent the high voltage lines 536, 538 and high voltage couplings 546, 548 connecting the high voltage source 530 to the voltage lines 542, 544 within the chuck.

[0080] Although in Figure 7ANot shown, the transfer can be performed by an ETU that retrieves sample 750 from a docking station (e.g., a FOUP within the storage area of ​​system 700) and places the sample on lifting pins (e.g., lifting pins 504) that protrude above the upper surface of the adsorption carrier 765 within the load-locking chamber. The lifting pins can then be lowered so that the sample is supported by the upper surface of the adsorption carrier 765, as... Figure 7A As shown. This initial transfer step can be performed with the load lock chamber 720 at atmospheric pressure, as shown by the dashed background inside chamber 720.

[0081] Next, the vacuum system can be activated as indicated by arrow 770 to generate a vacuum suction at the bottom of sample 750. Figure 6 (Step 620). While maintaining the load lock chamber above the vacuum pressure, a vacuum is applied to the back of the sample 750, causing the sample to adhere to the upper surface of the adsorption carrier 765 and flatten the sample, as shown. Figure 7B As shown. While a vacuum is applied to the back of sample 765 (and the load lock chamber remains at atmospheric pressure), it is possible to... Figure 7C The high-voltage source is activated as indicated by the middle arrow 772 to increase the electrostatic force and further fix the sample 750 to the adsorbent carrier 765. Figure 6 (Step 630).

[0082] Then, the load lock chamber 720 can be evacuated to match the pressure in the main processing chamber 710 (e.g., a pressure equal to or between high vacuum and ultra-high vacuum), and the vacuum system applied to the adsorption carrier 765 for the sample 750 can be shut off, as... Figure 7D The missing arrow 770 indicates this. During this period, the high voltage applied to the electrode is maintained (arrow 772), making electrostatic force the only force that adsorbs sample 750 onto the adsorption carrier. Figure 6 (Step 640).

[0083] As described above, vacuum chucks can sometimes flatten highly warped wafers that conventional electrostatic chucks cannot completely flatten. However, once the sample is adsorbed onto the adsorption carrier 765 via vacuum, the electrostatic adsorption portion of the adsorption carrier 765 can maintain the flattened state of the sample. Therefore, by initially using a vacuum chuck to adsorb the sample 750, and then switching the adsorption force to electrostatic force, it is possible to keep some highly warped samples in a flattened state, samples that cannot be flattened by electrostatic force alone.

[0084] Next, the transfer unit 780 picks up the adsorption carrier 765, and the sample 750 is adsorbed onto the adsorption carrier by electrostatic force, such as... Figure 7E As shown ( Figure 6(Step 650), and transfer the adsorbent carrier to platform 740 in the main processing chamber 710, which can be under high vacuum or lower pressure, such as Figure 7F As shown ( Figure 6 (Step 660). Although in Figure 7E Not shown, in order for the transfer unit 780 to transfer the adsorbent carrier from the load lock chamber 720, the adsorbent carrier must first be lifted onto the surface of the platform 760 by the lifting pin (e.g., lifting pin 506). Similarly, in order for the transfer unit to transfer the adsorbent carrier onto the platform 740, the adsorbent carrier needs to be placed on the lifting pin extending above the surface of the platform 740. The transfer unit will retract, and the lifting pin will slowly descend onto the main body of the platform 740, placing the adsorbent carrier 765 (and sample 750) onto the platform 740, as... Figure 7G As shown.

[0085] During the transfer of the adsorbent carrier 765 to the platform 740, the adsorbent carrier is disconnected from the power supply 772 and then moved into the processing chamber 710, aligned with the platform 740 so that two high-voltage lines (indicated by a single dashed line 742) can be electrically connected to corresponding lines (e.g., lines 536, 538) in the adsorbent carrier. Then, high-voltage connection is established with the high-voltage line 742 (indicated by arrow 774) to maintain electrostatic adsorption of the sample 750 to the adsorbent carrier, thereby keeping the sample 750 in its flattened state.

[0086] Next, sample 750 can be processed within the main chamber 710 at a high vacuum (or even higher) pressure, while still applying a high voltage to the electrodes to keep the sample in a flattened state. Figure 6 (Step 670). In the depicted embodiment, processing the sample 750 may include imaging multiple locations on the sample using a scanning electron microscope, but as previously described, in other embodiments, the main chamber 710 may be a different type of processing chamber, and the substrate processing operation may be other types of processing operation.

[0087] After processing, the transfer unit picks up the adsorbent carrier 765 (with sample 750 on its upper surface) and transfers the adsorbent carrier back to the load lock chamber 720, as follows. Figure 7H As shown, at this time, both the main processing chamber 710 and the load lock chamber 720 are in a vacuum. Figure 6 (Step 680). Then, the load lock chamber 720 can be vented to the atmosphere. Figure 6 (Step 690) prepares the sample for transfer from the load lock chamber to subsequent processing steps. In step 680, it is no longer necessary to apply voltage to maintain the electrostatic attraction, at which point the sample 750 may return to its initial warped state, such as... Figure 7I As shown.

[0088] Method 600 can be repeated on the next sample.

[0089] exist Figures 7A-7I In the illustrated embodiment, when the adsorbent carrier 765 is transferred from platform 760 to platform 740, the connection between the electrodes within the adsorbent carrier and the high-voltage source is temporarily interrupted. For example, when the transfer unit picks up the adsorbent carrier 765 from platform 760 in step 650, the high-voltage connection 772 is temporarily interrupted until step 660, when the transfer unit places the adsorbent carrier onto platform 740, forming the high-voltage connection 774. However, the electrodes designed within the adsorbent carrier 765 (e.g., a series of electrodes 532, 534) can have sufficient mass to accumulate enough charge on the electrodes during transfer, keeping the sample 750 still attached to the adsorbent carrier.

[0090] In other embodiments, the transfer unit may include a high-voltage connection that cooperates with a high-voltage line in the adsorbent carrier to provide a continuous high voltage level to the electrodes in the adsorbent carrier during transfer.

[0091] Hybrid vacuum electrostatic chuck in main chamber

[0092] In some embodiments, the primary processing chamber may include a sample support that can simultaneously function as a vacuum chuck and an electrostatic chuck to secure and flatten the sample. Such a sample support is referred to herein as a hybrid vacuum-electrostatic chuck (sometimes simply called a "hybrid chuck"). The hybrid chuck may initially use its vacuum adsorption properties to secure and flatten the sample while the primary chamber remains at atmospheric pressure. Next, the hybrid chuck may activate its electrostatic adsorption function to increase electrostatic force for further sample fixation. The primary chamber can then be evacuated, leaving electrostatic force as the sole technique for securing and adsorbing the sample to the hybrid chuck, allowing the sample to be processed within the primary chamber at the desired vacuum pressure.

[0093] Figure 8A This is a simplified cross-sectional view of a sample support system 800, which includes a hybrid vacuum electrostatic chuck 820 (sometimes referred to herein as "hybrid chuck 820") according to certain embodiments and a platform 810. The hybrid chuck 820 can be used with the aforementioned Figure 5A and 5BThe hybrid chuck 820 is similar to the hybrid chuck 520 discussed above, but differs in that the hybrid chuck 820 remains coupled directly to the stage 810 in the process chamber, and is not transferred between the process chamber and the load lock chamber by a transfer unit. Thus, the hybrid chuck 820 includes a single set of lift pins 804 that can raise or lower the sample 850 relative to the upper support surface 802 of the chuck, rather than two separate sets of lift pins 504, 506 as discussed above with respect to the hybrid chuck 520. As shown, a sample 850 is placed on the upper surface 802 of the hybrid chuck 820, which is positioned on the stage 810 that can be moved along the X, Y, and Z axes within the sample processing chamber.

[0094] Figure 8A A set of lift pins 804, a vacuum system 825, and a high voltage system 830 are also shown in FIG. 8. The lift pins 804 can raise the sample 850 above the upper support surface 802 so that a transfer unit can slide underneath the sample and transfer the sample onto or off of the hybrid chuck 820. Referring to Figure 8A and Figure 8B (the latter being an enlarged view of a portion of the hybrid chuck 820), the sample 850, and the stage 810, each of the lift pins 804 is disposed within a respective lift pin hole 805 that extends completely through the stage and the hybrid chuck 820.

[0095] The upper surface of the hybrid chuck 820 includes a plurality of vacuum channels 822 that can be operatively coupled with the vacuum system 825 when the hybrid chuck is positioned on the stage 810. For example, a first vacuum line 824 extending from the vacuum system 825 through the stage 810 can be fluidly coupled with a second vacuum line 826 extending through the hybrid chuck 820 via a coupler 828. Thus, each of the vacuum channels 822 is fluidly coupled with the vacuum system 825 and is capable of applying a vacuum to the backside of the sample 850 when the vacuum system 825 is activated.

[0096] The hybrid chuck 820 also includes a series of electrodes 832, 834 that are operatively coupled with the high voltage source 830 when the chuck is positioned on the stage 810. The electrodes 832, 834 can be arranged in an alternating or other pattern just below the upper surface 802 as described above with respect to the electrodes 532, 534. As shown, high voltage lines 836, 838 extend from the high voltage source 830 through the stage 810. The lines 836, 838 can be electrically coupled to high voltage lines 842, 844 extending through the hybrid chuck 820 via couplings 846, 848, respectively. Thus, each series of electrodes 832, 834 is electrically coupled with the high voltage system 830 and is capable of generating electrostatic forces to attract the sample 850 to the hybrid chuck when the high voltage source 830 is activated.

[0097] For a better understanding and appreciation of this embodiment, reference is made to Figure 9 and Figures 10A-10D,in Figure 9 This is a flowchart showing a method 900 for planarizing and treating a warped substrate according to certain embodiments, and Figures 10A-10D It is based on Figure 9 A simplified cross-sectional view of the substrate processing system 1000 that planarizes and processes the warped substrate 1050 at different stages according to the method.

[0098] As shown in the figure, the substrate processing system 1000 includes a main processing chamber 1010, which performs the same substrate processing operations as chambers 110 and 210 described above, and therefore contains many of the same components. However, at the sample support 140 or 240, the substrate processing system 1000 includes a hybrid vacuum electrostatic chuck 1020, which holds the sample 1050 within the processing chamber during substrate processing operations. The hybrid chuck can be placed on a platform 1040 within the chamber 1010, which can simultaneously move the hybrid chuck and the sample 1050 so that different portions of the sample are directly within the field of view of the SEM column. To this end, the platform 1040 can move left and right, and forward and backward (i.e., along the X and Y axes) within the chamber 1010, and can also raise and lower the hybrid chuck and the sample along the Z axis.

[0099] Platform 1040 also includes a vacuum connection 1062 and a high-pressure connection 1064, which can respectively connect the vacuum system (not in) Figure 10A The corresponding connections (shown in the image) and high-voltage sources (not shown) are coupled to the mixing chuck 1020 when it is secured to the platform 1040. For example, vacuum connection 1062 could represent vacuum line 824 and vacuum coupler 828 connecting vacuum system 825 to vacuum line 826 within the mixing chuck. Similarly, high-voltage connection 1064 could represent high-voltage lines 836, 838 and high-voltage couplers 846, 848 connecting high-voltage sources 830 to voltage lines 842, 844 within the mixing chuck.

[0100] refer to Figure 9 and Figure 10A Method 900 begins by transferring sample 1050 to substrate processing chamber 1010 and placing the sample on the upper support surface of mixing chuck 1020. Figure 9 (Step 910). The hybrid chuck 1020 can be, for example, the hybrid chuck 820 discussed above, so that either or both of vacuum and electrostatic adsorption can be used to fix the sample to its upper surface. The sample 1050 can be a thin semiconductor wafer. For example, the system 1000 can process hundreds or thousands of samples 1050 sequentially, some of which may be like... Figure 10A It is highly warped as shown.

[0101] Although Figure 10AAs shown, the transfer can be performed by an ETU that picks up the sample 1050 from the load lock chamber and places the sample on a lift pin (e.g., lift pin 804) within the process chamber 1010 above the upper surface of the hybrid chuck 1020. The lift pin (or lift platform 1040) can then be lowered, causing the sample to be supported by the upper surface of the chuck 1020, as shown. Figure 10A This preliminary transfer step can be performed with the process chamber 1010 at atmospheric pressure (as indicated by the dashed background of the chamber 1010).

[0102] Next, the vacuum system can be activated, as indicated by arrows 1070, to create a vacuum suction force at the bottom of the sample 1050 Figure 10B , step 920. Applying a vacuum to the back of the sample 1050 causes the sample to be attracted to the upper surface of the hybrid chuck 1020 and to be flattened, as shown. Figure 9 Figure 10B While the vacuum is applied to the back of the sample 1050 (and the load lock chamber remains at atmospheric pressure), a high voltage source can be activated, as indicated by arrows 1072 in Figure 10C , to increase the electrostatic force that holds the sample 1050 to the chuck 1020 Figure 9 , step 930.

[0103] The process chamber 1010 can then be pumped down to vacuum (as indicated by the absence of the dashed background in Figure 10C to a desired substrate processing pressure (e.g., a pressure between high vacuum and ultra-high vacuum levels), and the function of the vacuum system to attract the sample 1050 to the chuck 1020 can be turned off, as indicated by the absence of arrows 1070 in Figure 10C . The high voltage applied to the electrodes remains in place during this time (arrows 1072), so the electrostatic force becomes the only force holding the sample 1050 to the hybrid chuck Figure 9 , step 940.

[0104] At this stage, the sample 1050 can be processed within the process chamber 1010 while the high voltage remains applied to the electrodes to maintain the flattened state of the sample Figure 9 , step 950. Using a vacuum chuck to initially attract the sample 1050, and then switching the attraction force to an electrostatic force in the method 900, can keep some highly warped samples flattened that would not be able to be flattened if relying only on electrostatic force.

[0105] After processing is complete, the high voltage source 1072 is turned off, and the process chamber is vented to atmospheric pressure Figure 9 , step 960, as indicated by Figure 10D ​The sample 1050 can then be lifted from the upper surface of the hybrid chuck 1020 by the lift pins, and then an internal transport unit (ITU, not shown) can retrieve the sample 1050 and transfer it back to the load lock chamber (not shown) while both the main process chamber 1010 and the load lock chamber 1020 are at atmospheric pressure. Figure 9

[0106] The method 900 can then repeat for the next sample.

[0107] Processing chamber with main chamber and separate auxiliary space

[0108] In other embodiments, the main process chamber can include a separate auxiliary space or chamber that is isolated from the main chamber. The system can include a substrate support device that can secure and flatten the sample as a combination of a vacuum chuck and an electrostatic chuck, similar to the description above regarding the hybrid vacuum electrostatic chuck. But instead of repeatedly evacuating the main chamber and then pulling the main chamber to the desired vacuum pressure for processing operations when processing a series of samples, the substrate support (platform) can move the hybrid chuck and sample between the main process chamber and the auxiliary space. The auxiliary space can have a much smaller volume than the main process chamber, and thus can be isolated from the main process chamber and pulled to atmospheric pressure.

[0109] Once positioned within the auxiliary space, the hybrid chuck can secure and flatten the sample using its vacuum suction functionality while the auxiliary chamber is at atmospheric pressure. Next, the hybrid chuck can activate its electrostatic suction capability, increasing the electrostatic force to secure the sample. The auxiliary space can then be pulled to vacuum, making the electrostatic force the only force to flatten and suction the sample onto the hybrid chuck. Because the auxiliary space has a much smaller volume than the main process chamber, it can be pulled to the desired vacuum pressure much faster, thereby improving the efficiency of processing multiple wafers. The hybrid chuck can then be moved back to the processing position in the main chamber and processed at the desired vacuum pressure. To illustrate, refer to Figure 11 and 12A through 12G, where Figure 11 is a flowchart depicting steps of a method 1100 for flattening and processing a warped substrate according to certain embodiments, and Figures 12A-12G is a simplified cross-sectional view of a substrate processing system 1200 as depicted according to certain embodiments, showing different stages of a warped substrate 1250 being flattened and processed according to the method described in Figure 11

[0110] ​​As shown in the figure, the substrate processing system 1200 includes a main processing chamber 1210, which may contain many of the same components as the chambers 110 or 210 described above, and perform the same general substrate processing operations. The substrate processing system 1200 also includes a hybrid vacuum electrostatic chuck 1220 and separate auxiliary chambers or spaces that can be isolated from the environment of the main processing chamber 1210.

[0111] The hybrid vacuum electrostatic chuck 1220 can hold the sample 1250 within the processing chamber during substrate processing operations and can be positioned on a platform 1240 within the chamber 1210, which can move the hybrid chuck and sample 1250 within the processing chamber. The hybrid chuck 1220 and platform 1240 can be similar to the hybrid chuck 1020 and platform 1040 described above. However, in this embodiment, the platform 1040 can move the hybrid chuck to different positions within the processing chamber 1210, placing different portions of the sample directly within the field of view of the SEM rod, and can also move the hybrid chuck into and out of the auxiliary space 1030.

[0112] As shown in the figure, platform 1240 includes a vacuum connection 1262 and a high-pressure connection 1264. These connections can be used to connect the vacuum system (not included) when the mixing suction cup 1220 is fixed to platform 1240. Figure 12A The connections shown in the diagram (and not shown) to the high-voltage source (also not shown) are connected to the corresponding connections on the mixing chuck 1220. For example, vacuum connection 1262 could represent vacuum line 824 and vacuum coupler 828 connecting vacuum system 825 to vacuum line 826 within the mixing chuck. Similarly, high-voltage connection 1264 could represent high-voltage lines 836 and 838 and high-voltage couplers 846 and 848 connecting high-voltage source 830 to voltage lines 842 and 844 within the mixing chuck.

[0113] refer to Figure 11 and Figure 12A Method 1100 begins by transferring sample 1250 into substrate processing chamber 1210 and placing the sample on the upper support surface of mixing chuck 1220. Figure 11 (Step 1110). The hybrid chuck 1220 can be the hybrid chuck 820 discussed above, thus enabling the sample to be fixed to its upper surface using one or both vacuum and electrostatic adsorption. The sample 1250 can be a thin semiconductor wafer, which may have varying degrees of warping.

[0114] Although Figure 12ANot shown, but the transfer can be performed by an ETU that picks up sample 1250 from the load lock chamber and places it on a lifting pin (e.g., lifting pin 804) protruding above the upper surface of the mixing suction cup 1220 within the processing chamber 1210. The lifting pin can then be lowered (or the platform 1240 raised) so that the sample is supported by the upper surface of the suction cup 1220, as... Figure 12A As shown. This initial transfer step can be performed while both the load lock chamber and the substrate processing chamber 1210 are under vacuum pressure.

[0115] Next, platform 1240, as Figure 12B The sample is moved from the main chamber 1210 to the auxiliary space 1230 as shown. Figure 11 (Step 1120). In step 1120, the moving platform may include one or two moving platforms along the X and Y axes until the platform is properly positioned below the auxiliary space 1230, and then the platform is raised such that at least a portion of the sample 1250 and the mixing suction cup 1220 are located within the auxiliary space 1230, thereby isolating the auxiliary space from the environment of the main processing chamber 1210. Sealing the auxiliary space from the main processing chamber can be accomplished using any suitable technique or mechanism, as is well known to those skilled in the art.

[0116] Auxiliary space 1230 can then be opened to the atmosphere ( Figure 11 (Step 1130), while the main processing chamber is kept under vacuum, such as Figure 12C As shown. The vacuum adsorption section of the mixing suction cup 1220 can then be based on... Figure 12D The indicator at the middle arrow 1270 is activated, generating a vacuum suction at the bottom of sample 1250. Figure 11 (Step 1140). A vacuum is applied to the back of sample 1250 to cause the sample to adhere to the upper surface of the mixing suction cup 1220 and flatten the sample, as shown. Figure 12D As shown.

[0117] While applying a vacuum to the back of sample 1250 (and while maintaining atmospheric pressure in auxiliary space 1030), it is possible to... Figure 12E The middle arrow 1272 indicates the activation of the high-voltage source to increase electrostatic force, further securing sample 1250 onto mixing chuck 1220. Figure 11 (Step 1150).

[0118] The auxiliary space 1230 can then be evacuated to a vacuum (as in...). Figure 12F (The dotted background is no longer shown in the image), reaching the same vacuum pressure as the substrate processing system 1210, while the vacuum system for adsorbing the sample 1250 to the mixing suction cup 1220 can be shut off, as shown in the image. Figure 12FThe high voltage applied to the electrodes is maintained (arrow 1272) during this time, so the electrostatic force is the only force holding the sample 1250 to the hybrid chuck 1220. Figure 11

[0119] Next, the platform 1240 can be moved back into the main processing region of the chamber 1210 (step 1170), as shown. Figure 11 The sample 1250 can be processed in the processing chamber 1210 while the high voltage is still applied to the electrodes to maintain the flat state of the sample (step 1180), as shown. Figure 12G As described in previous embodiments, the ability to initially use a vacuum chuck to hold the sample 1250 and then switch to an electrostatic force in the method 1100 can allow certain highly warped samples to be flattened that could not be flattened using electrostatic force alone. Figure 11 After processing is complete, the high voltage source 1172 can be turned off, the sample can be lifted up above the upper surface of the hybrid chuck 1220 using the lift pins, and the ITU (not shown) can remove the sample and transfer it back to a load lock chamber (not shown) while both the main processing chamber 1210 and the load lock chamber 1220 remain under vacuum (step 1190).

[0120] Figure 11 The method 1100 can then be repeated for the next sample.

[0121] The method 1100 can then be repeated for the next sample.

[0122] Other embodiments

[0123] ​​The foregoing description for purposes of explanation has been presented to illustrate specific nomenclature used to describe the present embodiments. However, it will be apparent to those skilled in the art that the specific details are not required in order to practice the described embodiments. For example, although the above examples sometimes refer to a sample processing chamber as a scanning electron microscope tool, embodiments of the present disclosure can be used in many other types of sample processing chambers in which a substrate or other type of sample needs to be secured and / or flattened prior to being processed under vacuum conditions, as will be apparent to those skilled in the art. Also for example, although the exemplary examples above enable a vacuum chuck function to secure and flatten the sample while the sample is at atmospheric pressure (i.e., 760 torr) within the chamber or other enclosed area, these embodiments are not limited thereto, and in other embodiments, the sample can be initially secured and flattened by the vacuum chuck at a pressure lower than 760 torr. In fact, those skilled in the art will recognize that the key is the difference between the pressure exerted by the vacuum chuck on the lower surface of the sample and the pressure of the chamber / environment in which the sample is located. In a high vacuum environment, the vacuum chuck cannot fully secure and flatten the sample. However, the chuck can secure and flatten certain samples at a pressure level lower than 760 torr, such as in what can be considered a "rough vacuum range" (e.g., a pressure lower than 760 torr but higher than 25 torr). Those skilled in the art will further recognize that a greater pressure difference between the vacuum pressure exerted by the vacuum chuck on the lower surface of the sample and the chamber / environment pressure on the upper surface of the sample can secure and flatten samples having a higher degree of warpage than if the pressure difference between these opposing surfaces is smaller.

[0124] Moreover, although the foregoing disclosure has been described in terms of different embodiments, the contents of a specific embodiment can be combined in any suitable manner in the absence of departing from the spirit and scope of the embodiments of the present disclosure. Additionally, many modifications and alterations will occur to others upon reading and understanding the above teaching. Therefore, it is understood that all additional modifications and alterations are intended to be included within the scope of the present disclosure.

[0125] While the exemplary embodiments of the present disclosure can be implemented in part using electronic components and circuits known to those skilled in the art, such details have not been shown in order not to obscure aspects of the present disclosure with unnecessary detail and in order to more clearly understand and appreciate the basic concepts of the present disclosure.

[0126] Furthermore, any reference to method in the above description is to be interpreted as any one, combination or subset of the method steps described in the specification. Furthermore, any reference to system in the above description is to be interpreted as any one, combination or subset of the system elements described in the specification. Furthermore, any reference to computer program product in the above description is to be interpreted as any one, combination or subset of the computer program elements described in the specification.

Claims

1. A method for processing a substrate, the method comprising: The substrate is positioned on the upper surface of a substrate holder in a first chamber, wherein the substrate holder includes one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder near the upper surface. When the substrate holder is located in the first cavity, the substrate is adsorbed and flattened to the substrate holder by applying a vacuum to the one or more vacuum channels; While the substrate is adsorbed onto the substrate holder through the one or more vacuum channels, a voltage is applied to the one or more electrodes to further adsorb the substrate onto the substrate holder using electrostatic force. While continuously using electrostatic force to attract the substrate to the substrate holder, the first chamber is evacuated to a vacuum pressure; When the substrate is attracted to the substrate holder by electrostatic force, the substrate holder is transferred from the first chamber to the second chamber under vacuum conditions; as well as When the substrate holder is located in the second chamber, the electrostatic force is maintained to attract the substrate to the substrate holder, and the substrate is processed with vacuum pressure in the second chamber.

2. The method for processing a substrate according to claim 1, wherein the first chamber is a load-locking chamber, and the second chamber is a substrate processing chamber.

3. The method for processing a substrate according to claim 2, wherein when the load lock chamber is at atmospheric pressure, the substrate is adsorbed and flattened to the substrate holder by applying a vacuum to the one or more vacuum channels.

4. The method for processing a substrate according to claim 3, further comprising, after processing the substrate in the second chamber under vacuum conditions, transferring the substrate holder with the substrate attached back to the load lock chamber.

5. The method of processing a substrate according to claim 4, further comprising, after turning the substrate holder on which the substrate is attached back into the load lock chamber, opening the load lock chamber to the atmosphere and turning the substrate out of the load lock chamber.

6. The method of processing a substrate according to claim 2, wherein the substrate processing chamber includes a scanning electron microscope, and processing the substrate includes imaging the substrate using the scanning electron microscope.

7. The method for processing a substrate according to claim 1, wherein the vacuum pressure during sample processing in the second chamber is a high vacuum pressure or lower.

8. The method of processing a substrate according to claim 1, wherein the one or more electrodes comprise at least two electrodes arranged in an interlaced pattern.

9. The method for processing a substrate according to claim 1, wherein the substrate is a semiconductor wafer.

10. The method of processing a substrate according to any one of claims 1 to 9, wherein the warpage of the substrate between the lowest point and the highest point of the substrate is at least 1.0 mm.

11. A system for processing a substrate, the system comprising: Main substrate processing chamber; Load-locking chamber; An internal transfer unit is configured to transfer the substrate between the load lock chamber and the main substrate processing chamber; At least one processor and at least one memory coupled to said at least one processor, said at least one memory including a plurality of computer-readable instructions, which, when executed by said at least one processor, cause the system to perform: The substrate is transferred to the load locking chamber and positioned on the upper surface of the substrate holder in the load locking chamber, wherein the substrate holder includes one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder near the upper surface. When the substrate holder is located in the load locking chamber, the substrate is adsorbed and flattened to the substrate holder by applying a vacuum to the one or more vacuum channels; While the substrate is adsorbed onto the substrate holder through the one or more vacuum channels, a voltage is applied to the one or more electrodes to further adsorb the substrate onto the substrate holder using electrostatic force. While continuously using electrostatic force to attract the substrate to the substrate holder, the load locking chamber is evacuated to a vacuum pressure; Under vacuum conditions, the internal transport unit is used to transfer the substrate and substrate holder from the load lock chamber to the main processing chamber; as well as While the substrate is electrostatically attracted to the substrate holder, the substrate is processed under vacuum pressure in the main processing chamber.

12. The system for processing a substrate according to claim 11, wherein when the load lock chamber is at atmospheric pressure, the substrate is adsorbed and flattened onto the substrate holder by applying a vacuum to the one or more vacuum channels.

13. The system for processing a substrate according to claim 11, wherein the main processing chamber includes a scanning electron microscope, and processing the substrate in the processing chamber includes imaging the substrate using the scanning electron microscope.

14. The system for processing a substrate according to claim 11, wherein the vacuum pressure during processing of the sample in the main processing chamber is a high vacuum pressure or lower.

15. The system for processing a substrate according to claim 11, wherein the one or more electrodes comprise at least two electrodes arranged in an interlaced pattern with each other.

16. The system for processing a substrate according to any one of claims 11 to 15, wherein the warpage of the substrate between the lowest and highest points of the substrate is at least 1.0 mm.

17. A non-transient computer-readable storage memory storing instructions for processing a substrate, comprising: The substrate is positioned on the upper surface of a substrate holder in a first chamber, wherein the substrate holder includes one or more vacuum channels disposed on the upper surface and one or more electrodes disposed within the substrate holder near the upper surface. When the substrate holder is located in the first cavity, the substrate is adsorbed and flattened to the substrate holder by applying a vacuum to the one or more vacuum channels; While the substrate is adsorbed onto the substrate holder through the one or more vacuum channels, a voltage is applied to the one or more electrodes to further adsorb the substrate onto the substrate holder using electrostatic force. While continuously using electrostatic force to attract the substrate to the substrate holder, the first chamber is evacuated to a vacuum pressure; The substrate and substrate holder are transferred from the first chamber to the second chamber under vacuum conditions; as well as While the substrate is electrostatically attracted to the substrate holder, the substrate is subjected to vacuum pressure in the second chamber.

18. The non-transient computer-readable memory of claim 17, wherein when the first chamber is at atmospheric pressure, the substrate is adsorbed and flattened to the substrate holder by applying a vacuum to the one or more vacuum channels.

19. The non-transient computer-readable storage device of claim 17, wherein the vacuum pressure during sample processing in the second chamber is a high vacuum pressure or lower.

20. The non-transient computer-readable memory according to any one of claims 17 to 19, wherein processing the substrate in the processing chamber includes imaging the substrate using a scanning electron microscope.

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