Wafer chuck assembly

Abstract

The present disclosure generally relates to chuck techniques for supporting semiconductor wafers during processing. In one example, a wafer chuck assembly includes a chuck hub and a centering hub disposed within the chuck hub. The engagement device is operable between an engaged position and a disengaged position, respectively, to engage the chuck hub with the centering hub to prevent relative movement therebetween in at least a first direction, or to allow relative movement therebetween. A chuck motor is provided to selectively rotate the chuck hub and / or the centering hub during a wafer processing operation and a wafer centering operation based on an engaged or disengaged position of the engagement device. A plurality of chuck arms are mounted on the chuck hub, each chuck arm extending radially between a proximal end adjacent the chuck hub and a distal end away from the chuck hub. Each of the plurality of centering cams is mounted at or near the distal end of the chuck arm and is movable to engage or release the wafer edge in response to rotational movement of the centering hub relative to the chuck hub.

Description

This application is a divisional application of the application with application number 201980043789.X, application date May 3, 2019, and invention name “Wafer chuck assembly”. Priority Declaration

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 667,190, filed May 4, 2018, and U.S. Patent Application No. 16 / 215,608, filed December 10, 2018, the entire disclosures of both of which are incorporated herein by reference. Technical Field

[0002] The present disclosure generally relates to chuck technology for supporting semiconductor wafers during processing. In one embodiment, a vacuum wafer chuck for edge bevel removal (EBR) is provided. In a more specific aspect, the present disclosure relates to a post-electrofill module (PEM) chuck for removing unwanted metal (e.g., plating film or seed layer) from the outer edge of a wafer during EBR. Background Art

[0003] The background description provided here is for the purpose of generally presenting the context of the present disclosure. No admission is made, either explicitly or implicitly, that the work of the presently designated inventors is prior art to the present disclosure to the extent that it is described in this background section and in aspects of the specification that were not determined to be prior art at the time the application was filed.

[0004] EBR is typically performed by applying chemicals through a nozzle pointed near the edge of the wafer as the wafer rotates. The wafer should be well centered or concentric on the chuck to produce uniform EBR results. Existing chucks that use friction pads or passive centering devices may not actively center the wafer before the EBR process. This can lead to poor EBR results. Poor EBR results with further errors can occur when, for example, the robot transfer that delivers the wafer to the PEM is inaccurate.

[0005] Additional challenges arise when the etchant used in the EBR process rebounds from the surrounding wafer support devices, such as the vertical alignment pin (VAP) surface. The rebounding liquid may interfere with the EBR process and lead to poor EBR results. This effect may be more pronounced as the edge exclusion (EE) zone is reduced. EE generally refers to the amount of material to be removed from the edge of the wafer.

[0006] In other examples, wafers can sometimes slip on conventional chuck supports during rotation, again leading to poor centering and poor EBR results. Wafer presence detection using external sensors may not always be reliable and can be affected by, for example, splashback from water droplets. Splashback can occur during wafer rinsing in the aforementioned or other ways. A slipping wafer can cut damaging grooves in the cams of chucks with centrifugal centering cams. This can reduce chuck life and even cause the grooved cams to bind on the wafer edge. Summary of the Invention

[0007] In some examples, a wafer chuck assembly for supporting a wafer includes: a chuck hub; a centering hub disposed within the chuck hub; an engagement device operable between an engaged position and a disengaged position, respectively, to engage the chuck hub with the centering hub, thereby preventing relative movement between the chuck hub and the centering hub in one of a clockwise rotational direction and a counterclockwise rotational direction, or allowing relative movement between the chuck hub and the centering hub in either rotational direction; and a chuck motor for engaging or disengaging the engagement device based on the engagement or disengagement of the engagement device. a plurality of chuck arms mounted on the chuck hub, each chuck arm extending radially between a proximal end adjacent the chuck hub and a distal end distal to the chuck hub; and a plurality of centering cams, each mounted at or near the distal end of a chuck arm and movable radially inwardly or outwardly relative to the centering hub to engage or release an edge of a supported wafer in response to rotational movement of the centering hub relative to the chuck hub.

[0008] In some examples, the chuck motor is configured to provide relative rotational motion between the centering hub and the chuck hub during the wafer centering operation. In some examples, the centering hub is fixed relative to the chuck motor during the wafer centering operation, and the chuck motor is configured to rotate the chuck hub in a first rotational direction during the wafer centering operation.

[0009] In some examples, the chuck motor is configured to rotate the centering hub and the chuck hub together in the same rotational direction during the wafer processing operation. In some examples, the same rotational direction of the centering hub and the chuck hub during the wafer processing operation is opposite to the first rotational direction of the chuck hub during the wafer centering operation.

[0010] In some examples, the centering hub includes at least one cam surface on its outer surface. In some examples, each chuck arm includes a corresponding elongated actuating rod that is operatively disposed between the at least one cam surface of the centering hub and a centering cam disposed at the distal end of each chuck arm. Each elongated actuating rod may include a bearing surface at its proximal end for engaging with the at least one cam surface of the centering hub. In some examples, each elongated actuating rod includes a connector at its distal end to the corresponding centering cam of the corresponding chuck arm. In some examples, rotational movement of the centering hub causes the corresponding cam surface of the centering hub to push the corresponding elongated actuating rod radially outward, thereby operating the corresponding centering cam via the connector.

[0011] In some examples, the wafer chuck assembly further includes at least one vacuum pad for supporting the wafer during the wafer centering and / or wafer handling operations. In some examples, the at least one vacuum pad is configured to maintain the wafer in a centered position in the wafer chuck assembly, at least during the wafer handling operations, when the wafer is released by the plurality of centering cams. In some examples, the at least one vacuum pad is disposed on at least one of the plurality of chuck arms. In some examples, each of the plurality of chuck arms may include a vacuum line for supplying vacuum pressure to the at least one vacuum pad. In some examples, the presence or absence of vacuum pressure at the at least one vacuum pad is detected and correlated with the presence or absence of a wafer in the wafer chuck assembly, or with the presence of a defective wafer.

[0012] In some examples, the plurality of centering cams are biased toward an open, wafer-releasing configuration. In some examples, each of the plurality of centering cams is movable between a first wafer-centering position and a second, retracted position disposed below an upper surface of a wafer supported in the wafer chuck assembly.

[0013] In some examples, the wafer chuck assembly further includes a control device for detecting a chuck motor torque and correlating the detected chuck motor torque with at least a first wafer centering position of the plurality of centering cams. In some examples, the wafer chuck assembly further includes a control device for detecting a chuck motor torque and correlating the detected chuck motor torque with a centering position of a wafer held in the wafer chuck assembly. In some examples, the wafer chuck assembly further includes a control device for detecting a chuck motor torque and correlating the detected chuck motor torque with a diameter of a wafer held in the wafer chuck assembly.

[0014] In other embodiments, a vacuum wafer chuck assembly is provided. An exemplary vacuum wafer chuck assembly includes: a chuck hub; a centering hub disposed within the chuck hub; a plurality of chuck arms mounted to the chuck hub, each chuck arm extending radially between a proximal end adjacent the chuck hub and a distal end distal from the chuck hub; a plurality of centering cams, each mounted at or near the distal end of the chuck arm and movable radially inwardly or outwardly relative to the centering hub to engage or release an edge of a supported wafer in response to rotational movement of the centering hub; and at least one vacuum pad for supporting the wafer during wafer centering or wafer handling operations.

[0015] In some examples, the wafer chuck assembly further includes: an engagement device operable between an engaged position and a disengaged position, respectively, to engage the chuck hub with the centering hub, thereby preventing relative movement between the chuck hub and the centering hub in one of a clockwise rotational direction or a counterclockwise rotational direction, or allowing relative movement between the chuck hub and the centering hub in either rotational direction; and a chuck motor for selectively rotating the chuck hub and / or the centering hub during wafer processing operations and wafer centering operations based on the engaged or disengaged position of the engagement device.

[0016] In some examples, the chuck motor is configured to provide relative rotational motion between the centering hub and the chuck hub during the wafer centering operation. In some examples, the centering hub is fixed relative to the chuck motor during the wafer centering operation, and the chuck motor is configured to rotate the chuck hub in a first rotational direction during the wafer centering operation.

[0017] In some examples, the chuck motor is configured to rotate the centering hub and the chuck hub together in the same rotational direction during the wafer processing operation. In some examples, the same rotational direction of the centering hub and the chuck hub during the wafer processing operation is opposite to the first rotational direction of the chuck hub during the wafer centering operation.

[0018] In some examples, the centering hub includes at least one cam surface on its outer surface. In some examples, each chuck arm includes a corresponding elongated actuator rod operatively disposed between the at least one cam surface of the centering hub and a centering cam of the plurality of centering cams disposed at the distal end of each chuck arm. In some examples, each elongated actuator rod includes a bearing surface at its proximal end for engaging the at least one cam surface of the centering hub. In some examples, each elongated actuator rod includes a connector at its distal end for the corresponding centering cam of the corresponding chuck arm.

[0019] In some examples, rotational movement of the centering hub causes corresponding cam surfaces of the centering hub to push corresponding elongated actuating rods radially outward, thereby operating corresponding centering cams via the connector.

[0020] In some examples, the at least one vacuum pad is configured to maintain the wafer in a centered position within the wafer chuck assembly, at least during the wafer handling operation, when the wafer is released by the plurality of centering cams. In some examples, the at least one vacuum pad is disposed on at least one of the plurality of chuck arms. In some examples, each of the plurality of chuck arms includes a vacuum line for supplying vacuum pressure to the at least one vacuum pad. In some examples, the presence of vacuum pressure at the at least one vacuum pad is detected and correlated with the presence of the wafer within the wafer chuck assembly or the presence of a defective wafer.

[0021] In some examples, the plurality of centering cams are biased toward an open wafer release configuration. In some examples, each of the plurality of centering cams is movable between a first wafer centering position and a second, retracted position disposed below an upper surface of a wafer supported in the wafer chuck assembly.

[0022] In some examples, the wafer chuck assembly further includes a control device for detecting a chuck motor torque and correlating the detected chuck motor torque with at least a first wafer centering position of the plurality of centering cams. In some examples, the wafer chuck assembly further includes a control device for detecting a chuck motor torque and correlating the detected chuck motor torque with a centering position of a wafer held in the wafer chuck assembly. In some examples, the wafer chuck assembly further includes a control device for detecting a chuck motor torque and correlating the detected chuck motor torque with a diameter of a wafer held in the wafer chuck assembly.

[0023] In other embodiments, a wafer chuck assembly for supporting a wafer is provided. An exemplary wafer chuck assembly includes: a chuck hub; a centering hub disposed within the chuck hub; a chuck motor for selectively rotating the chuck hub or the centering hub during a wafer handling operation or a wafer centering operation; a plurality of chuck arms mounted to the chuck hub, each chuck arm extending radially between a proximal end adjacent the chuck hub and a distal end distal from the chuck hub; a plurality of centering cams, each mounted at or near a distal end of the chuck arm and movable radially inwardly or outwardly relative to the centering hub to engage or release an edge of a supported wafer in response to rotational movement of the centering hub relative to the chuck hub; and a control device for detecting torque of the chuck motor and correlating the detected chuck motor torque with at least a first wafer centering position of the plurality of centering cams.

[0024] In some examples, the wafer chuck assembly further includes: an engagement device operable between an engaged position and a disengaged position, respectively, to engage the chuck hub with the centering hub, thereby preventing relative movement between the chuck hub and the centering hub in one of a clockwise rotational direction or a counterclockwise rotational direction, or allowing relative movement between the chuck hub and the centering hub in either rotational direction; and wherein the chuck motor selectively rotates the chuck hub or the centering hub during wafer processing operations and wafer centering operations based on the engaged or disengaged position of the engagement device.

[0025] In some examples, the control device detects a chuck motor torque and correlates the detected chuck motor torque to a centered position of a wafer held in a wafer chuck assembly. In some examples, the control device detects a chuck motor torque and correlates the detected chuck motor torque to a diameter of a wafer held in the wafer chuck assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Some embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings:

[0027] Figures 1A-1B Contains schematic cross-sectional views of aspects of a chuck assembly according to exemplary embodiments.

[0028] Figure 2 Contains a schematic diagram of a centering hub according to an exemplary embodiment.

[0029] Figure 3 Included is a schematic diagram of a chuck assembly mounted on a spindle assembly according to an exemplary embodiment.

[0030] Figures 4A-4BIncluded is a schematic diagram of a chuck spindle assembly and a vacuum supply assembly according to an exemplary embodiment.

[0031] Figure 5 Contains a schematic diagram of the top side of a chuck assembly according to an exemplary embodiment.

[0032] Figure 6 A schematic diagram of the underside of a chuck assembly including holding a wafer according to an exemplary embodiment.

[0033] Figure 7 Contains illustrations of a centering hub and related components of a chuck assembly according to an exemplary embodiment.

[0034] Figure 8 A cross-sectional view of a chuck assembly mounted to a head portion of a chuck spindle assembly is included according to an exemplary embodiment.

[0035] Figure 9 Contains schematic diagrams of engagement fin and locking pin configurations according to exemplary embodiments.

[0036] Figure 10 Included is a cross-sectional view of a chuck assembly according to an exemplary embodiment with the retaining pin retracted and the cam in a lowered position.

[0037] Figure 11 Containing according to exemplary embodiments Figure 10 A cross-sectional view of an exemplary chuck assembly with the retaining pin raised and the cam in a raised or wafer-centering position.

[0038] 12A-12B contain schematic illustrations of a conventional chuck assembly according to an exemplary embodiment.

[0039] Figure 12C Contains schematic diagrams of a chuck assembly and related components according to an exemplary embodiment.

[0040] Figure 13 Contains tabular and graphical results of exemplary EBR measurements according to exemplary embodiments.

[0041] Figure 14 Contains torque profile of a chuck motor during a centering operation according to an exemplary embodiment.

[0042] Figure 15 A block diagram is provided to illustrate an example of a machine on which one or more exemplary embodiments may be implemented or by which one or more exemplary embodiments may be controlled.

[0043] Figure 16 A flowchart illustrating operations in a method according to an illustrative embodiment is provided. DETAILED DESCRIPTION

[0044] The following description includes systems, methods, techniques, instruction sequences, and computer program products that implement exemplary embodiments of the present disclosure. In the following description, for the purpose of explanation, many specific details are provided to provide a thorough understanding of the exemplary embodiments. However, it will be apparent to those skilled in the art that the subject matter of the present invention may be practiced without these specific details.

[0045] A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. The following notice applies to any data described below and shown in the accompanying drawings that form a part of this document: Copyright Lam Research Corporation, 2018-19. All rights reserved.

[0046] In one example, a centering chuck assembly is provided. The chuck assembly includes a retractable gripping cam (or clamp) for centering a wafer held by the chuck assembly, as described more fully below. Some exemplary wafer chuck assemblies include a vacuum pad for improving wafer gripping and engagement adaptability in the chuck. The chuck assembly can actively center the wafer after the wafer is placed therein. In, for example, EBR processing, a wafer is placed in the chuck assembly by a robot prior to processing. In other applications, it is possible to center the wafer.

[0047] As described above, accurate and secure wafer centering in the chuck assembly (also referred to herein as a chuck, where applicable) can be important for achieving high EBR quality. In some examples of the present disclosure, the chuck assembly includes a vacuum pad to which a vacuum can be applied to secure an assembly (e.g., a substrate or wafer) thereto. In some examples, the chuck assembly further includes a centering cam that retracts horizontally below the upper surface of a wafer placed in the chuck assembly when a vacuum is applied to the vacuum pad to hold the wafer in position. The absence of surrounding structure due to the downwardly retracted cam allows the removal of splashback surfaces that could otherwise cause EBR chemicals or water to rebound onto the wafer surface. Thus, this configuration substantially eliminates an important contributing factor to poor EBR results and the above-mentioned shortcomings.

[0048] In some examples of the chuck assembly of the present invention, a high wafer gripping force can be generated. In some examples, a wafer can be vacuum-gripped in place with a gripping force that is more than six times greater than the gripping force of a conventional friction pad of the same diameter. In some examples, the presence or position of a wafer in the chuck assembly is detected or measured in conjunction with vacuum clamping. For example, the underside of a placed wafer can seal against a vacuum pad in the chuck, allowing a vacuum to be generated or applied to the wafer in a gradual or step-by-step manner. The simple fact that a vacuum can be applied can indicate the presence of a wafer in the chuck. In other examples, a low vacuum pressure can indicate that the wafer is not present in the chuck or is misplaced in some manner. A high vacuum pressure can indicate good wafer placement.

[0049] Now refer to Figures 1A-1B These figures contain schematic cross-sectional views of an exemplary chuck assembly 100. A centering hub 102 is disposed within a chuck hub 104. The centering hub 102 is rotatable independently of the chuck hub 104, but rotates in the same direction as the chuck hub 104 under normal rotational operation, such as during wafer processing. For example, normal rotational operation may be clockwise. A diagram of an exemplary centering hub 102 is shown in FIG. Figure 2 As shown, the centering hub 102 includes a series of cam surfaces 114 that abut the end of an actuating push rod 116, as described more fully below.

[0050] During the wafer centering operation, the centering hub 102 is locked to the chuck shaft 106 by means of the locking pin 108, which can be pushed upwardly into the recess 109 in the centering hub 102. Thus, the centering hub 102 becomes a fixed part to a certain extent. The chuck assembly 100 can then be rotated in another direction (e.g., counterclockwise) so that there is relative rotational movement between the centering hub 102 and the chuck hub 104. The relative rotational movement between the slowly rotating centering hub 102 and the chuck hub 104 causes the cam surface 114 (e.g., Figure 1B 1 ) pushes the actuator push rods 116 outward to rotate the cams 110, as shown. In some examples, the actuator push rods 116 are movably positioned within the hollow chuck arms 118. In some examples, the cams 110 are kinematically coupled to accommodate wafers 112 of varying diameters. Three cams 110 are shown. Other numbers and configurations of cams are possible.

[0051] In some examples, the motor torque of the chuck shaft 106 is monitored, and a peak in the motor torque indicates that the cam 110 is fully closed with the edge of the wafer 112, indicating that the wafer 112 is centered. The centering hub 102 can be radially spring-loaded as shown to release the cam 110 and release the wafer 112 when rotation stops or when the chuck assembly 100 slows down. In some examples, the chuck hub 104 is configured so that it remains stationary during wafer centering while the centering hub 102 rotates within it to operate the cam 110. In other examples, neither the centering hub 102 nor the chuck hub 104 is stationary during centering, but counter-rotational motion between these components is still provided so that the cam 110 remains operational and can be closed and opened. In some examples, one or more sensors monitor the position of the locking pin 108. The motor of the chuck shaft 106 can be used for both rotation and centering operations.

[0052] Some examples of the chuck assembly 100 include a vacuum supply line 120. Figure 1A , vacuum supply line 120 provides vacuum (or negative pressure) to vacuum pads 122, which support wafer 112. In some examples, hollow chuck arm 118 is radially aligned with vacuum supply line 120 to minimize profile and reduce potential splashback of rinse agent during EBR.

[0053] Figure 3 A schematic diagram of the chuck assembly 100 is included, with some internal components shown in dashed outline. Components corresponding to components described above are labeled with the same numbers. The chuck assembly 100, the chuck spindle 106, the spindle motor 126, and the connection to the rotary joint (at Figure 4A ) of the vacuum supply accessory 124.

[0054] Figures 4A-4B Other views of the chuck shaft 106 assembly and vacuum supply are shown. A rotary joint 128 is shown transferring vacuum up to the chuck's vacuum line, somewhat similar to how slip rings in an electric motor transfer current to a coil, and an appropriately sized O-ring 130 seals the vacuum circuit to the chuck assembly 100. Figure 4A The view in FIG also shows the locking pin 108 in a raised or locked position to engage the centering hub 102 with the chuck shaft 106. The pneumatic air supply 107 for the drive cylinder 132 that drives the locking pin 108 can be seen in FIG. Figure 4B middle.

[0055] In some examples, the chuck spindle motor 126 has an encoder or indexing capability so that the precise rotational position of the motor or the component mounted thereon can be determined. In some examples, the motor or chuck has a 20-bit encoder mounted thereon, which has 1.04 million detectable positions per revolution. The coded information, combined with the motor torque information, can be used to perform self-diagnostic tests, as discussed more fully below. For example, if a motor torque peak occurs at an unexpected rotational position, this may indicate that a centering error has occurred. Alternatively, the diameter of the wafer 112 can be known based on the occurrence or position of the torque peak of the spindle motor 126, because the cam 110 stops moving and provides resistance when it contacts the circumference of the wafer 112. A range of acceptable torque peaks can be established.

[0056] In some examples, the extent to which the cam 110 at the outer end of the chuck arm 118 rotates to grip the edge of the wafer 112 is proportional to the extent to which the centering hub 102 rotates, causing the cam 110 to rotate. The rotational position of the centering hub 102 can be derived and measured based on the indexed rotational position of the corresponding spindle motor 126. The cam 110 and centering hub 102 are directly interconnected via the actuating push rod 116. In some examples, the rotational position of the centering hub 102 is correlated to the radial or clamping position of the cam 110. The rotational position (or change in motor position) is detected by an encoder and determined accordingly. This is then mapped to the radial position of the centering fixture.

[0057] In some examples, the diameter of a wafer 112 positioned in the chuck cams 110 is determined based on the encoded rotational position of the spindle motor 126, since a peak in motor torque can be expected at the instant the cams 110 engage the edge of a wafer 112 positioned therebetween. The rotational position of the centering hub 102 at which the peak in motor torque is detected is correlated with the radial position of the cams 110 (or all three of them), and the diameter of the wafer 112 gripped therebetween is derived, since the radial position corresponds to the outer edge of the wafer 112. In some examples of the present chucks, the calculated or measured correlations between various aspects such as motor torque, encoder position, wafer presence, wafer diameter, and vacuum pressure (or absence) are used in certain method embodiments discussed further below.

[0058] Figure 5A schematic diagram of the top side of the chuck assembly 100 is included according to some exemplary embodiments. Components corresponding to those described above are labeled with corresponding numbers. When activated, the vacuum pad 122 can be used in conjunction with the cam 110 to grip a wafer disposed in the chuck assembly 100, or the wafer can be gripped without the cam 110. The cam 110 can center the wafer as described above. The tubular chuck arm 118 houses the push rod 116 for operating the cam 110. A vacuum supply line 120 transmits vacuum from a rotary joint (such as described above) to the vacuum pad 122.

[0059] Figure 6 Include Figure 5 , which is a diagram illustrating the underside of an exemplary chuck assembly 100. In this view, centering hub supports or fins 134 are visible. In the example shown, fins 134 are integrally formed with centering hub 102. Other configurations are possible. Fins 134 can be selectively engaged by locking pin 108 to initiate wafer centering operations, as further described above.

[0060] Initial relative rotational movement in one direction between the chuck hub 104 (e.g., stationary in this example) and the centering hub 102 is shown to cause the cam 110 to approach the center and grip the wafer 112 therebetween. Once the cam 110 is closed, no further relative rotational movement between the centering hub 102 and the chuck hub 104 is possible, and a torque spike from the spindle motor 126 indicates that the wafer 112 is centered and secured. The chuck spindle 106 is then driven, accelerating both the hub and the chuck in a direction opposite to their operating rotational speeds. At high processing speeds, and given the high centripetal forces generated and the precision typically required, it is important to securely and concentrically hold the wafer 112 within the chuck assembly 100.

[0061] Figure 7 Further details of the exemplary chuck assembly 100 are shown. Here, the centering hub 102 is again shown. As the centering hub 102 rotates, the cam surface 114 of the centering hub 102 acts on a spring-loaded ball plunger 136 disposed at the lower end of each push rod 116. The upper end of each push rod 116 actuates the rotatable cam 110, which rotates accordingly to grip the wafer 112 disposed therebetween. A vacuum pad 122 is shown adjacent to the cam 110 in the illustration. When pushed radially outward by the movement of the cam surface 114 of the rotating centering hub 102 (e.g., clockwise in the illustration), the push rods 116 move radially outward. The push rods 116 can be retracted by rotating the centering hub 102 in the other direction, thereby retracting the cam 110.

[0062] As they move outward, the push rods 116 cause their corresponding cams 110, located at the upper ends of each push rod 116, to rotate, thereby gripping and centering the wafer 112 held in the chuck. If the vacuum source is activated, the vacuum pads 122 grip the underside of the wafer 112, and the cams 110 can be retracted accordingly, as the wafer 112 is still securely held in place by the vacuum pads 122. With the vacuum pads 122 holding the wafer 112 in place, the cams 110 can be fully retracted below the upper surface of the wafer 112, allowing a clean, unobstructed upper surface of the wafer 112 to be presented during the EBR procedure or other processing. The ability to fully retract the cams 110 can provide at least some of the benefits described further above.

[0063] In the example shown, push rods 116 are biased inwardly by springs 138, and thus cams 110 are biased in an open manner until they are closed by outward movement of push rods 116. The biased-open spring load of the illustrated chuck assembly 100 enables cams 110 to retract and release wafer 112 when centering hub 102 is rotated counterclockwise relative to chuck hub 104. This configuration is the default wafer release configuration.

[0064] Figure 8 A cross-sectional view of the chuck assembly 100 including the head mounted on the chuck spindle 106 assembly. In this view, the locking pin 108 is viewed in the raised or locked position. When the locking pin 108 is raised, the centering hub abutment or fin 134 engages the sidewall of the locking pin 108, and the chuck hub 104 rotates counterclockwise when viewed from above. Rotational movement of the centering hub 102 is prevented by the locking pin 108, and relative rotational movement between the chuck hub 104 (carrying the push rod 116) and the locked centering hub 102 is permitted. The camming motion caused by the relative rotational movement between the chuck hub 104 and the centering hub 102 moves the push rod 116 outward, causing the cam 110 to close as described above.

[0065] exist Figure 9, a schematic diagram of an exemplary centering hub fin 134 is shown, which is disposed on the underside of the exemplary centering hub 102. When the locking pin 108 is extended (upward), the locking pin 108 engages the fin 134. When the locking pin 108 is retracted (lowered), the centering hub 102 can rotate freely in either direction, but generally rotates most commonly in the direction used when rotating at very high speeds during wafer processing. The locking pin 108 is actuated by the locking drive cylinder 132, as mentioned above. The locking pin 108 and the drive cylinder 132 do not rotate and are fixed. When the locking pin 108 is extended (upward), it engages the centering hub fin 134 and locks the centering hub 102 against rotational movement in the locking direction. The centering hub 102 is thus fixed relative to the ground to prevent rotational movement, at least in the direction blocked by the locking pin 108. As the chuck hub 104 is slowly rotated in the opposite direction above the stationary centering hub 102 located below it by the spindle motor 126, the actuating push rods 116 carried by the chuck hub 104 are pushed outward by the cam surfaces 114, causing the cams 110 to operate in the manner described above and center the wafer 112 held therebetween. Vacuum is applied to the vacuum pads 122, which grip the underside of the wafer 112 in the centered position. The locking pins 108 can then be retracted, allowing the chuck hub 104 to be rotated in the direction opposite to the locking direction to the processing speed (operating speed) by the spindle motor 126.

[0066] Figure 10 A cross-sectional view of the chuck assembly 100 is included, rotating at operating speed. The chuck assembly configuration shown is referred to as "at home". In this mode, the cam 110 of the chuck assembly 100 is in a retracted or lowered position, as shown. The wafer 112 is held in place by (negative) vacuum pressure, which is applied by the vacuum pad 122. The locking pin 108 is in a retracted or lowered position, as shown. A bearing contact 140 is provided at the lower end of each actuating push rod 116. In the mode shown, the bearing contact 140 is positioned at the "deepest" (most inward) position on the cam surface 114 of the centering hub 102, the position at which the bearing contact 140 acts during use. Figure 11 A similar cross-sectional view of the chuck assembly 100 is included, but in this case the cams 110 are extended or in a raised position to center a wafer 112 held therebetween. In the illustrated embodiment, the bearing contact 140 is positioned on the cam surface 114 of the centering hub 102 at its "shallowest" (most outward) position, which is the position at which the bearing contact 140 acts during use.

[0067] The series of views in Figures 12A-12C attempt to provide Figure 12CA convenient visual comparison of certain aspects of the chuck assembly 100 of the present invention is shown with those of a conventional chuck assembly 1200 shown in Figures 12A-12B. The chuck assembly 1200 shown in Figure 12A includes centrifugal cams 200 of the centrifugal or passive type, as opposed to the active or positive cam type of the present disclosure. Figure 12B includes a larger view of the VAPs 202 of the centrifugal cams 200. As described more fully in the Background section above, the presence of such VAPs 202 may not be beneficial, for example, during EBR or when rinsing the wafer 112. Friction (rather than vacuum) pads 204 can be seen near each cam 200.

[0068] In contrast, Figure 12C The diagram depicts an exemplary chuck assembly 100 according to an exemplary embodiment of the present disclosure. In the example shown, three cam-carrying arms 119 are radially spaced equidistantly around the central chuck hub 104. Each arm 119 carries a corresponding cam 110. Three non-cam-carrying arms 121 are disposed between these cam-carrying arms 119, as shown. Each cam-carrying arm 119 and each non-cam-carrying arm 121 includes a vacuum pad 122 disposed toward the outer end of the arm. In some examples, the vacuum pad 122 is formed from or includes a vacuum cup. Vacuum pressure can be applied to the vacuum pad 122 to draw or secure the wafer thereto under the negative pressure of the applied vacuum. In the example shown, six vacuum pads 122 are provided. Each cam-carrying arm 119 includes a vacuum supply line 120 and a hollow chuck arm 118 that accommodates the push rod 116 in the manner described above. Other arm configurations or constructions are possible.

[0069] After the wafer is transferred from the robot to the chuck assembly 100, Figure 12C An exemplary chuck assembly 100 of the type shown in FIG can actively center the wafer. The ability to center the wafer after placement can eliminate, or at least significantly reduce, the need for a robot to precisely position the wafer in the chuck assembly. Different centering configurations can be employed for a range of wafer diameters. Concentricity maintenance can be achieved through robust centering and the removal of VAPs from the wafer edge. The chuck assembly 100 shown can also minimize streaking and taper width by allowing the use of higher rpm EBR processes, and can provide supplemental wafer detection, for example, by utilizing a degree of vacuum grip.

[0070] Comparative results supporting the efficacy of the above features were obtained. For example, Figure 13An exemplary graphical result of EBR measurements performed at 360 measurement points on a test wafer, observed within a specified edge exclusion (EE) wafer range (here, 1.7 and 2.3 mm), is provided. The EBR results for a conventional point-of-reference (POR) chuck show obvious deformations representing striations or notches, as shown by the sharp downward peaks at three different locations 1301, 1303, and 1305 around the test wafer. These locations correspond to the presence of VAPs.

[0071] By comparison, and for example Figure 13 As shown by the top line 1307 of the graph for the inventive vacuum (VAC) chuck (2.3 mm), wafers supported by the inventive chuck exhibit very little, if any, of this deformation. Similar smooth results are seen for the inventive VAC chuck (1.7 mm). It can be noted that for the conventional POR chuck, the smaller the EE (y-axis), the more extreme the downward peak in the graph. This is believed to represent the increasing effect of the VAP at the corresponding location. The 1.7 mm location is closer to the outer edge of the wafer than the 2.3 mm location and is more likely to suffer from negative peripheral effects. A comparative range of the measured deformation values ​​can be seen in the columns marked by rectangles in the table at the bottom right of the diagram.

[0072] Certain embodiments of the present disclosure include method embodiments or processes. In some examples, a method includes processes for wafer centering, wafer gripping, and fluid obstruction mitigation to achieve high-quality EBR. An exemplary method may include at least the following operations or aspects, as described below. The method may, for example, be combined with one or more of the chuck assemblies of the present invention described herein (e.g., chuck assembly 100 having cam 110 and vacuum pad 122 (e.g., Figure 12C as shown) to execute.

[0073] refer to Figure 16 , method 1600 may include, at 1602, placing a wafer in the chuck assembly 100. At 1604, the wafer is centered by the centering cams 110, as described above. At 1606, once the wafer is centered (e.g., detected by increasing spindle motor torque), the wafer is vacuum-clamped at 1608 by the vacuum pads 122, on which the wafer is positioned. At 1610, vacuum is continuously applied while the centering cams 110 are retracted so that the wafer remains correctly and concentrically clamped in place.

[0074] Sometimes, when the action of the centering cams deforms the wafer, the vacuum pads may leak. If the wafer fails to be vacuum clamped, the method 1600 is aborted because failure to properly vacuum clamp the wafer may indicate that the wafer is broken, cracked, missing, or misplaced and not seated on all vacuum pads 122.

[0075] Assuming vacuum is maintained, the centering cam 110 is maintained in a retracted position below the top surface of the wafer during wafer processing steps (e.g., EBR, rinsing, or drying steps). Because the centering cam 110 is below the wafer surface, the EBR chemical that is centrifuged off the edge of the wafer does not encounter any obstacles to reflect it.

[0076] In another example, a method for vacuum gripping a wafer in a wet processing chamber is provided. The method may include at least the following operations or address some of the following aspects.

[0077] In some cases, gripping the underside of a wafer in a wet processing chamber can be challenging. For example, when the pressure differential across the surface or lip of the vacuum pad is large, some fluid leakage may occur, causing liquid to be drawn into the vacuum circuit. Liquid that enters the vacuum circuit may later exit the vacuum circuit, resulting in centrifugal deposition on the underside of the wafer at the end of the EBR process. Therefore, for successful wafer processing, it is crucial that no liquid leaks past the edge or lip of the vacuum pad 122.

[0078] Therefore, in some examples, a geometry of a vacuum pad or cup is selected that does not leave a wet water ring or cause leaks. Different rubber compounds and durometers are possible to seal properly without leaving contaminants on the underside of the wafer.

[0079] In some examples, a method is provided for determining wafer centering independently of wafer diameter by utilizing monitored motor torque. The method may include at least the following operations or address some of the following aspects.

[0080] As described above, the motor torque and encoder position may be interdependent and may be measured together to verify wafer centering or concentricity in a wafer chuck. Figure 3 ), when the centering cam 110 is clamped against the edge of the wafer, the spindle motor torque suddenly increases, and the high torque is recognized as an indication of the wafer clamping position. In some examples, the associated motor encoder position falls within a known range, verifying that the chuck is clamped against a 300 mm wafer (for example) when the torque suddenly increases.

[0081] In another example, a method for preventing EBR excursion using chuck self-diagnostics is provided. The method may include at least the following operations or address some of the following aspects. Here, the measurement of motor torque and encoder readback enables the detection of inherent errors in centering verification. For example, if the motor torque suddenly increases while the encoder position is outside the allowable limits, this indicates that there is a centering error. Some exemplary situations that may cause centering errors include cam damage, wafer damage, component damage or freezing, or motor or encoder failure. The use of aspects such as motor torque and encoder correlation enables centering errors to be detected on the first or early wafers in a series of wafers, rather than on subsequent wafers. Early corrective measures can be taken to avoid EBR excursions on subsequent wafers, which can avoid a lot of waste and avoid significant financial losses as well as wasted time.

[0082] In another example, a method for measuring wafer diameter during a centering operation and providing automatic EBR adjustment is described. The method may include at least the following operations or address some of the following aspects. The wafer diameter may be inferred from an encoder readback of the spindle motor torque peak during the wafer centering operation procedure. The wafer diameter may vary, and this may affect the parameters of the edge exclusion zone. Other variations may include measuring the edge exclusion zone from the wafer edge to the copper etched by the EBR process, regardless of the actual wafer diameter. Therefore, small variations in wafer diameter allowed by a given specification may result in variations in the measured edge exclusion zone.

[0083] Despite this variability, if a wafer is measured to be abnormally small or large, the wafer diameter can be forwarded to the EBR system. In some examples, the EBR system can be configured to automatically adjust the position of the EBR nozzle based on applicable EBR parameters to maintain a desired edge exclusion zone.

[0084] In another example, a method for center reference of edge detection is provided. The method may include at least the following operations or address some of the following aspects. In some examples, it may be desirable to verify that the diameter of the copper plating film on a wafer is the same between wafers in a batch, regardless of the edge exclusion zone. In some examples, the chuck measures the wafer diameter during a centering operation procedure. EBR metrology measures the edge exclusion zone after EBR. If EBR metrology detects an offset in the edge exclusion zone, the wafer diameter can be determined by the chuck to see if the offset is due to a process problem or a change in wafer diameter. If the edge exclusion zone offset is caused by a change in wafer diameter, it can be determined that the center reference of edge detection has not changed. Based on this determination, it is concluded that the copper plating diameter has not changed.

[0085] In another example, tool diagnostics and safety measures are provided. Some examples use multi-position vacuum grip sensors distributed across the underside of a wafer to detect broken or misplaced wafers. The method may include the following operations or aspects.

[0086] As background, the wafers selected for processing may be defective. For example, one wafer may be cracked (e.g., in the shape of a pizza slice). The remaining wafer contains open space and may not be gripped in the chuck assembly, which, for example, has only three vacuum cups spaced 120° apart around the chuck perimeter. In this unstable state, the wafer may violently and completely break apart or fly apart at high speeds. By increasing the number of vacuum pads or cups, the detection of smaller missing fragments is improved.

[0087] refer to Figure 14 , the motor torque sensing procedure of the exemplary chuck assembly 100 is now described with reference to graphic 1400. During centering, the chuck hub of the chuck assembly 100 is moved in a reverse direction (e.g., counterclockwise when viewed from above) on an internal, temporarily stationary centering hub by the spindle motor to actuate the centering cam, as described above. The reverse rotation direction of the spindle motor can be contrasted with the positive rotation direction (e.g., clockwise) used during processing such as EBR processing. When moving in the reverse direction, the spindle motor displays a negative torque value. Negative values ​​are displayed on the y-axis of graphic 1400. A "higher" negative torque has a larger negative value and will be seen at a lower position on graphic 1400.

[0088] Figure 14 Graph 1400 of FIG. 1 contains an exemplary torque profile for the spindle motor during the centering step described above. Referring to graph 1400 , in stage 1402, the chuck assembly is rotating before the centering hub fins 134 (described above) strike the locking pin 108, and the torque is very low (approximately -5% of rated torque). At point 1404, the locking pin 108 engages the fins 134, and the (negative) torque increases. The results shown show an overshoot and undershoot torque profile at and just after point 1406. Next, as the centering hub 102 moves relative to the chuck hub 104 to actuate and close the centering cam 110, the spindle motor torque stabilizes and maintains a nearly constant value until point 1408. Cam 110 begins to engage with wafer 112 and moves it to the desired center position until point 1408. Next, the motor torque suddenly increases, meaning that the wafer 112 is no longer moving, has reached its slightly squeezed, centered position, and is now beginning to provide resistance to the centering cam 110. An exemplary motor torque peak is shown at point 1410.

[0089] The magnitude of the centering torque can vary between chucks due to component variations, tolerance differences, spring strain rates, and the like. Calibrating the chuck to determine the torque required to center a 300 mm wafer can account for these variations. For example, the cutoff torque in the stage between points 1410 and 1412 can be appropriately set to ensure that a given wafer is not overly compressed or damaged during centering. In stage 1414, the chuck arm spring extends as the cam 110 retracts. The undershoot and overshoot peak 1416 following stage 1414 occurs when the centering hub fin 134 breaks contact with the locking pin 108.

[0090] Figure 15 1500. In an exemplary block diagram, one or more exemplary method embodiments described herein may be implemented on or controlled by machine 1500. In alternative embodiments, machine 1500 may operate as a standalone device or may be connected (e.g., networked) to other machines. In a networked deployment, machine 1500 may operate as a server machine, a client machine, or both a server machine and a client machine in a server-client network environment. In one example, machine 1500 may function as a peer machine in a peer-to-peer (P2P) (or other distributed) network environment. Furthermore, while a single machine 1500 is illustrated, the term "machine" shall also be construed to include any collection of machines that individually or collectively execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein, such as via cloud computing, software as a service (SaaS), or other computer cluster configurations.

[0091] Examples as described herein may include, or may be operated by, logic, multiple components, or mechanisms. A circuit system is a collection of circuits implemented in a tangible entity, including hardware (e.g., simple circuits, gates, logic, etc.). Circuit system qualifications can be flexible over time and with potential hardware variability. A circuit system includes components that can perform specified operations individually or in combination during operation. In one example, the hardware of the circuit system can be designed to perform specific operations (e.g., hardwired). In one example, the hardware of the circuit system may include variably connected physical components (e.g., execution units, transistors, simple circuits, etc.), which include computer-readable media modified by physical properties (e.g., magnetic, electrical, movable placement of unchanged clustered particles, etc.) to encode instructions for specific operations. In connecting the physical components, the potential electrical properties of the hardware components are changed (e.g., from an insulator to a conductor, or vice versa). The instructions enable embedded hardware (e.g., an execution unit or a loading mechanism) to establish components of the circuit system in the hardware via variable connections to perform a portion of a specific operation during operation. Thus, when the device is operating, the computer-readable medium is communicatively coupled to other components of the circuit system. In one example, any of the physical components can be used in more than one component of more than one circuit system. For example, in an operational state, an execution unit can be used in a first circuit in a first circuit system at one point in time and reused at a different time by a second circuit in the first circuit system or by a third circuit in the second circuit system.

[0092] Machine (e.g., computer system) 1500 may include a hardware processor 1502 (e.g., a central processing unit (CPU), a hardware processor core, or any combination thereof), a graphics processing unit (GPU) 1503, main memory 1504, and static memory 1506, some or all of which may communicate with each other via an interconnection link (e.g., a bus) 1508. Machine 1500 may also include a display device 1510, an alphanumeric input device 1512 (e.g., a keyboard), and a user interface (UI) navigation device 1514 (e.g., a mouse). In one example, display device 1510, alphanumeric input device 1512, and UI navigation device 1514 may be a touch screen display. Machine 1500 may also include a mass storage device (e.g., a drive unit) 1516, a signal generating device 1518 (e.g., a speaker), a network interface device 1520, and one or more sensors 1521 (such as a global positioning system (GPS) sensor, a compass, an accelerometer, or another sensor). The machine 1500 may include an output controller 1528, such as a serial (e.g., universal serial bus (USB)), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection, to communicate with or control one or more peripheral devices (e.g., a printer, a card reader, etc.).

[0093] The mass storage device 1516 may include a machine-readable medium 1522 on which is stored one or more sets of data structures or instructions 1524 (e.g., software) embodying or utilizing any one or more of the techniques or functionality described herein. The instructions 1524 may also reside, completely or at least partially, within the main memory 1504, within the static memory 1506, within the hardware processor 1502, or within the GPU 1503 during execution thereof by the machine 1500. In one example, one or any combination of the hardware processor 1502, the GPU 1503, the main memory 1504, the static memory 1506, or the mass storage device 1516 may constitute a machine-readable medium.

[0094] Although the machine-readable medium 1522 is illustrated as a single medium, the term "machine-readable medium" may include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) configured to store one or more instructions 1524.

[0095] The term "machine-readable medium" may include any medium capable of storing, encoding, or carrying instructions 1524 for execution by machine 1500, causing machine 1500 to perform any one or more of the techniques of this disclosure, or capable of storing, encoding, or carrying data structures used by or associated with instructions 1524. Non-limiting examples of machine-readable media include solid-state memory, and optical and magnetic media. In one example, a clustered machine-readable medium includes a machine-readable medium 1522 having a plurality of particles having a constant (e.g., stationary) mass. Thus, the clustered machine-readable medium is not a transient propagating signal. Specific examples of a clustered machine-readable medium include non-volatile memory, such as semiconductor memory devices (e.g., electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM)), and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Instructions 1524 may also be transmitted or received over a communication network 1526 via a network interface device 1520 using a transmission medium. .

[0096] Although the embodiments have been described with reference to specific exemplary embodiments, it is apparent that various modifications and variations may be made to these embodiments without departing from the broader scope of the subject matter of the present invention. Therefore, the description and drawings should be regarded as illustrative and not restrictive. The drawings forming a part of this document show specific embodiments in which the subject matter may be implemented by way of illustration and not limitation. The illustrated embodiments are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom so that structural and logical substitutions and changes may be made without departing from the scope of the present disclosure. Therefore, the foregoing description should not be regarded as having a limiting meaning, and the scope of the various embodiments is defined solely by the appended claims and the full scope of equivalents to which these claims are assigned.

[0097] Such embodiments of the subject matter of the present invention may be referred to herein individually and / or collectively by the term "invention" for convenience only, and if in fact more than one invention or inventive concept is disclosed, it is not intended to automatically limit the scope of the present application to any single invention or inventive concept. Thus, although specific embodiments have been illustrated and described herein, it should be understood that any configuration calculated to achieve the same purpose may replace the specific embodiments shown. This disclosure is intended to cover all adaptations or variations of the various embodiments. Upon reviewing the above description, combinations of the above embodiments with other embodiments not specifically described herein will be apparent to those skilled in the art.

Claims

1. A wafer chuck assembly for supporting a wafer, the chuck assembly comprising: chuck hub; a centering hub disposed within the chuck hub; an engagement device operable between an engaged position and a disengaged position to engage the chuck hub with the centering hub to prevent relative movement between the chuck hub and the centering hub in one of a clockwise rotational direction or a counterclockwise rotational direction, or to allow relative movement between the chuck hub and the centering hub in either rotational direction, respectively; a chuck motor for selectively rotating the chuck hub and / or the centering hub during wafer handling operations and during wafer centering operations based on the engaged position or the disengaged position of the engagement device; a plurality of chuck arms mounted on the chuck hub, each chuck arm extending radially between a proximal end adjacent the chuck hub and a distal end distal from the chuck hub; as well as A plurality of centering cams are each mounted at or near a distal end of the chuck arm and are movable radially inwardly or outwardly relative to the centering hub to engage or release an edge of a supported wafer in response to rotational movement of the centering hub relative to the chuck hub. 2 . The wafer chuck assembly of claim 1 , wherein the chuck motor is configured to provide relative rotational motion between the centering hub and the chuck hub during the wafer centering operation.

3. The wafer chuck assembly of claim 2 , wherein the centering hub is fixed relative to the chuck motor during the wafer centering operation, and the chuck motor is configured to rotate the chuck hub in a first rotational direction during the wafer centering operation.

4. The wafer chuck assembly of claim 3, wherein the chuck motor is configured to rotate the centering hub and the chuck hub together in the same rotational direction during the wafer handling operation.

5. The wafer chuck assembly of claim 4, wherein the same rotational direction of the centering hub and the chuck hub during the wafer handling operation is opposite to the first rotational direction of the chuck hub during the wafer centering operation.

6. The wafer chuck assembly of claim 1 wherein the centering hub includes at least one cam surface on an exterior surface thereof.

7. A wafer chuck assembly according to claim 6, wherein each chuck arm includes a corresponding slender actuator rod which is operatively disposed between the at least one cam surface of the centering hub and a centering cam disposed at the distal end of each chuck arm of the plurality of centering cams.

8. The wafer chuck assembly of claim 7, wherein each elongated actuator rod includes a bearing surface at a proximal end thereof for engaging the at least one cam surface of the centering hub.

9. The wafer chuck assembly of claim 7, wherein each elongated actuator rod includes a connection at a distal end thereof to a corresponding centering cam of a corresponding chuck arm.

10. The wafer chuck assembly of claim 9, wherein rotational movement of the centering hub causes corresponding cam surfaces of the centering hub to push corresponding elongated actuator rods radially outwardly, thereby operating corresponding centering cams through the connector.

11. The wafer chuck assembly of claim 1 further comprising at least one vacuum pad for supporting the wafer during the wafer centering operation and / or during the wafer handling operation.

12. The wafer chuck assembly of claim 11 , wherein the at least one vacuum pad is configured to maintain the wafer in a centered position in the wafer chuck assembly at least during the wafer handling operation when the wafer is released by the plurality of centering cams.

13. The wafer chuck assembly of claim 11, wherein the at least one vacuum pad is disposed on at least one of the plurality of chuck arms.

14. The wafer chuck assembly of claim 11, wherein each of the plurality of chuck arms comprises a vacuum line for supplying vacuum pressure to the at least one vacuum pad.

15. The wafer chuck assembly of claim 14, wherein: The presence or absence of vacuum pressure at the at least one vacuum pad is detected and correlated to the presence or absence of the wafer in the wafer chuck assembly or to the presence of a defective wafer.

Images