WO2025165785A1

WO2025165785A1 - End effector for wafer transfer

Info

Publication number: WO2025165785A1
Application number: PCT/US2025/013452
Authority: WO
Inventors: Michael Thomas MYERS; Damon Tyrone Genetti; Namrata KARMAKAR
Original assignee: Lam Research Corp
Current assignee: Lam Research Corp
Priority date: 2024-02-02
Filing date: 2025-01-28
Publication date: 2025-08-07
Anticipated expiration: 2026-08-02

Abstract

An apparatus including an end effector is provided for a wafer handling system. The end effector includes a ring frame having a first inner diameter surface with a first inner diameter and coaxial with a center axis. The end effector further includes multiple support tabs extending radially inward from the first inner diameter surface of the ring frame towards the center axis and into a circular region centered on the center axis. The first inner diameter of the first inner diameter surface of the ring frame is larger than the outer diameter of the circular region.

Description

END EFFECTOR FOR WAFER TRANSFER

INCORPORATION BY REFERENCE

[0001] A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in their entireties and for all purposes.

FIELD

[0002] The present disclosure relates to wafer handling systems, and more specifically to an end effector configured to transfer a wafer and provide increased thermal uniformity within the wafer.

BACKGROUND

[0003] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] Different types of tools are used to perform hundreds of processing operations during semiconductor device fabrication. Most of these operations are performed in a medium vacuum within process chambers (i.e., within a range between 0.1 Pa and 100Pa as defined by ISO standard 3529, such as about 17Pa or lower). Such process chambers may be arranged about a central hub, and the hub and process chambers may be kept at substantially the same very low pressure. Wafers may be introduced to the process chambers by wafer handling systems that are mechanically coupled to the processing chambers. The wafer handling systems transfer wafers from the factory floor to the processing chamber. The wafer handling systems may include load locks to bring the wafers from atmospheric conditions to low-pressure conditions and back, and the wafer handling systems may further include robotic arms equipped with end effectors configured to support the wafers during wafer transport.

[0005] End effectors may be broadly differentiated from one another based on how the end effectors support the wafers that they transport. The most common type of end effector is a bottom-grip end effector that contacts only the bottom surface of the wafer being transported (at locations offset radially inward from the outer edge of the wafer). Such end effectors include a support structure (e.g., a fork-shaped part, a plateshaped part, or a spatula-shaped part) attached to a robotic arm and configured to engage a bottom surface of the wafers. These end effectors are simple in construction, relatively inexpensive to make, and can be quite compact, making them ideal for use in many contexts.

SUMMARY

[0006] Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims.

[0007] The present disclosure relates to an apparatus is provided for a robot (e.g., an atmospheric transfer module robot (ATM robot), etc.). The end effector is configured to thermally interact with a wafer in a manner that decreases a temperature differential across the wafer (e.g., a maximum temperature difference of 10 degrees Celsius across the wafer at 16 seconds after the end effector picking up the wafer, a maximum temperature difference of 8 degrees Celsius across the wafer at 40 seconds after the end effector picking up the wafer) thereby decreasing the associated thermal stresses within the wafer. The end effector is further configured to support the wafer, provide clearance for carrying the wafer through port openings of a wafer processing chamber, provide clearance for sensor beams used to determine a position of the wafer on the end effector, and provide clearance for lift pins in the wafer processing chamber when the end effector is moved underneath the wafer supported by the lift pins.

[0008] The apparatus may include an end effector having a ring frame. The ring frame may include a first inner diameter surface defining a first inner diameter and coaxial with a center axis. The end effector may further have a plurality of support tabs extending radially inward from the first inner diameter surface of the ring frame towards the center axis and into a circular region centered on the center axis. The first inner diameter of the first inner diameter surface of the ring frame may be larger than an outer diameter of the circular region.

[0009] In other implementations, no portion of the ring frame may overlap the circular region when the end effector is viewed along the center axis of the ring frame.

[0010] In other implementations, the ring frame may be C-shaped. [0011] In other implementations, the support tabs may be positioned at a plurality of locations on the ring frame that are angularly spaced apart.

[0012] In other implementations, the support tabs may consist of three support tabs positioned 120 degrees apart relative to one another.

[0013] In other implementations, the support tabs may consist of three support tabs, a first support tab may be positioned 115 degrees apart from a second support tab and from a third support tab, and the second support tab and the third support tab may be positioned 130 degrees apart from each other.

[0014] In other implementations, the support tabs may consist of three support tabs, a first support tab may be positioned at an angle ranging from about 100 degrees to about 140 degrees a second support tab and from a third support tab, and the second support tab and the third support tab may be positioned at the same angle apart from each other.

[0015] In other implementations, the first support tab may be closest to a proximal portion of the end effector than the second support tab and the third support tab

[0016] In other implementations, the first inner diameter surface may be spaced a first radius from the center axis. The ring frame may further include one or more recesses in the first inner diameter surface, and each recess in the one or more recesses may include a second inner diameter surface spaced a second radius from the center axis. The second radius may be greater than the first radius such that the one or more recesses define one or more clearance cutouts.

[0017] In other implementations, the ring frame may include two or more recesses and be bilaterally symmetric about a symmetry axis but with the recesses being asymmetrically positioned relative to the symmetry axis.

[0018] In other implementations, a first clearance cutout in the one or more clearance cutouts may be located in the ring frame at a first distance from the symmetry axis and spaced along a first direction orthogonally from the symmetry axis. A second clearance cutout in the one or more clearance cutouts may be located in the ring frame at a second distance from the symmetry axis and spaced along a second direction orthogonally from the symmetry axis opposite to the first direction.

[0019] In other implementations, the first distance may be less than the second distance. [0020] In other implementations, the ring frame may further include an outer surface. The ring frame may further include a set of one or more flats in the outer surface. A first width between two flats in the set of one or more flats may be less than a second width of a port opening of a wafer process chamber to provide clearance for the ring frame when the ring frame translates along the symmetry axis and is inserted through the port opening of the wafer process chamber.

[0021] In other implementations, the ring frame may include a pair of diametrically opposite sides. The set of one or more flats may include a first flat and a second flat located in a corresponding one of the diametrically opposite sides of the ring frame.

[0022] In other implementations, the first flat in set of one or more flats and the second flat in the set of one or more flats may be arranged parallel to the symmetry axis.

[0023] In other implementations, the ring frame may have a stepped thickness including a first step portion having a first thickness and a second step portion having a second thickness greater than the first thickness. The second step portion may be located radially outward from the first step portion.

[0024] In other implementations, the first step portion may include the first inner diameter surface spaced the first radius from the center axis. The second step portion may include a third inner diameter surface spaced a third radius from the center axis, with the third radius being greater than the first radius.

[0025] In other implementations, the first radius may be within a range between 151 and 155 millimeters, and the third radius may be within a range between 155 and 165 millimeters.

[0026] In other implementations, the second step portion may extend an angle about the center axis, with the angle being in a range between 165 degrees and 195 degrees.

[0027] In other implementations, the first step portion may extend at least 180 degrees about the center axis.

[0028] In other implementations, the ring frame and the support tabs may be made of a ceramic material.

[0029] In other implementations, the apparatus may further include a plurality of wafer pads attached to a corresponding one of the support tabs. [0030] In other implementations, each one of the wafer pads may include a convex cone portion located on a first side of the corresponding support tab. Each one of the wafer pads may further include a shank portion configured to extend through an opening in that support tab. Each one of the wafer pads may further include a flange portion located on a second side of that support tab.

[0031] In other implementations, each one of the wafer pads may include a concave cone portion located on a first side of the corresponding support tab. Each one of the wafer pads may further include a shank portion configured to extend through an opening in that support tab. Each one of the wafer pads may further include a flange portion located on a second side of that support tab.

[0032] In other implementations, each one of the wafer pads may be made of an elastomer.

[0033] In other implementations, each one of the wafer pads may be located on the corresponding support tab at a location spaced radially inward from the ring frame by an offset distance in a range between 5 millimeters and 15 millimeters.

[0034] In other implementations, each one of the support tabs may extend up to 20 millimeters from the first inner diameter surface towards the center axis.

[0035] In other implementations, each support tab may have a counterbore and each wafer pad may be positioned at least partially inside the counterbore of the respective support tab.

[0036] Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0038] FIG. 1 depicts a perspective view of an example end effector having a ring frame and a plurality of support tabs extending radially inward from the ring frame.

[0039] FIG. 2 depicts a perspective view of the end effector of FIG. 1 , with the support tabs supporting an outer edge region of a wafer. [0040] FIG. 3 depicts a top plan view of the end effector of FIG. 2, illustrating the entire ring frame located radially outward from an outer diameter of the wafer.

[0041] FIG. 4 depicts an enlarged view of Region A in FIG. 3.

[0042] FIG. 5 depicts a cross-sectional view of the end effector as taken along line

B-B in FIG. 4, illustrating the support tab including a wafer pad configured to support the wafer in a position such that the wafer has an outer peripheral edge spaced radially inward from the ring frame and the wafer is at least partially located below a top surface of the ring frame.

[0043] FIG. 6 depicts a cross-sectional view of the wafer pad in FIG. 5.

[0044] FIG. 7 depicts a cross-sectional view of another example wafer pad.

[0045] FIG. 8 depicts a first heat map for a first wafer supported on the end effector of FIG. 1 and a second heat map for a second wafer supported on a fork-shaped end effector after a first elapsed amount of time.

[0046] FIG. 9 depicts third and fourth heat maps for a corresponding one of the first and second wafers in FIG. 8 after a second elapsed amount of time.

[0047] FIG. 10 depicts a schematic representation of a robot having an example arm assembly terminating at an end upon which the end effector of FIGS. 1-5 may be mounted.

[0048] FIG. 11 depicts a top plan view of another implementation of an end effector similar to that of FIGS. 2 and 3.

[0049] FIG. 12 depicts a cross-sectional side view of the wafer pad of FIG. 6 and a portion of an end effector.

[0050] FIG. 13 depicts a cross-sectional side view of the wafer pad of FIG. 7 and a portion of an end effector.

DETAILED DESCRIPTION

[0051] An end effector is provided for a robotic arm of a wafer handling system. In one implementation, the wafer handling system may use the end effector to transfer a wafer from a wafer processing chamber that maintains the wafer under one or more predetermined conditions (e.g., under a predetermined pressure, at a predetermined elevated temperature, such as 300 degrees Celsius, etc.) to a vacuum transfer module (VTM) (which may also be maintained at a similar low pressure). The end effector may have a temperature substantially lower than that of the wafer, thus causing heat to transfer from the wafer to the end effector. For instance, the end effector may have a temperature of ~30 degrees Celsius when the end effector picks up a wafer that may, as noted above, be at a temperature of 300 degrees Celsius. As discussed in detail with reference to FIGS. 1 -9 below, the end effectors disclosed herein are configured to thermally interact with the wafer in a manner that decreases a temperature differential across the wafer (e.g., a maximum temperature difference of 10 degrees Celsius across the wafer at 16 seconds after the end effector picking up the wafer, a maximum temperature difference of 8 degrees Celsius across the wafer at 40 seconds after the end effector picking up the wafer) thereby decreasing the associated thermal stresses within the wafer. The end effector is further configured to support the wafer, provide clearance for carrying the wafer through port openings of a wafer processing chamber, provide clearance for sensor beams used to determine a position of the wafer on the end effector, and provide clearance for lift pins in the wafer processing chamber when the end effector is moved underneath the wafer supported by the lift pins.

[0052] In the following example figures and discussion, some implementations of an end effector that improves thermal uniformity across wafers are presented. Any one or more of the structural parameters of the end effector may collectively or independently characterize an apparatus for supporting and transferring a wafer in a manner that thermally interacts with the wafer (e.g., uniformly insulates the wafer) so as to decrease heat transfer from the wafer to the end effector, decrease a temperature differential across the wafer, and decrease the associated thermal stresses. Stated another way, while the figures and associated discussion present a combination of structural features allowing less heat transfer from the wafer to the end effector, the disclosure embodies many other combinations, some of which do not include one or more of the disclosed features.

[0053] Referring to FIGS. 1 and 2, an end effector 100 includes a ring frame 102 configured to thermally interact with a wafer 104 (FIG. 2) so as to cause the wafer 104 to have enhanced thermal uniformity (for example, a first maximum temperature differential up to 10 degrees Celsius across the wafer 104 after a first amount of elapsed time after the end effector 100 picks up the wafer 104, e.g., 16 seconds; a second maximum temperature differential up to 8 degrees Celsius across the wafer after a second amount of elapsed time after the end effector 100 picks up the wafer 104, e.g., 40 seconds). In this implementation, the ring frame 102 has a first inner diameter surface 106 broken up by various features, e.g., recesses 130 and support tabs 114, and defining a first inner diameter ID1 (e.g., within a range between 300 and 310 millimeters, such as 304 millimeters). The first inner diameter surface 106 is disposed about a center axis 108 and spaced a first radius R1 from the center axis 108 (e.g., within a range between 150 and 155 millimeters from the center axis 108, such as 152 millimeters). The first inner diameter ID1 of the first inner diameter surface 106 is larger than an outer diameter OD1 of an outer peripheral edge 110 of the wafer 104 (e.g., about 300 millimeters +/- 0.2 millimeters). When that wafer 104 is positioned on the end effector 100 such that the wafer 104 and the ring frame 102 are coaxial with one another, the outer peripheral edge 110 of the wafer 104 may be offset radially inward from the first inner diameter surface 106 of the ring frame 102 (e.g., by an offset distance within a range between 0 to 5 millimeters, such as 2 millimeters). In this implementation, the ring frame 102 is C-shaped and configured to reduce pathways of heat transfer from the wafer 104 to the ring frame 102 (e.g., via radiative heat transfer).

[0054] The end effector 100 further includes a plurality of support tabs 114 configured to support the outer edge region 112 of the wafer 104. The support tabs 114 extend radially inward from the first inner diameter surface 106 of the ring frame 102 towards the center axis 108 (e.g., up to 20 millimeters from the first inner diameter surface 106) and into a circular region centered on the center axis 108. In this implementation, the support tabs 114 are configured to support the wafer 104 such that no portion of the ring frame 102 overlaps the circular region and the wafer 104 therein (when the end effector 100 is viewed along the center axis 108) when a center of the wafer 104 is positioned on the center axis 108 of the ring frame 102 or when the center of the wafer 104 is offset up to a maximum lateral distance from the center axis 108 (e.g., offset up to 2 millimeters from the center axis 108). The support tabs 114 may be positioned at locations on the ring frame 102 that are angularly spaced apart. In one implementation, the support tabs 114 may consist of three support tabs positioned 120 degrees apart relative to one another.

[0055] In some implementations, the support tabs 114 may consist of three support tabs, with two support tabs each positioned between about 100 degrees and about 140 degrees relative to the third support tab. For example, the angular offset between the third support tab and each of the two other support tabs may be about 110 degrees, about 115 degrees, about 120 degrees, about 125 degrees, or about 130 degrees. The two support tabs are thereby positioned about 130 degrees relative to each other. FIG. 11 depicts a top plan view of another implementation of an end effector similar to that of FIGS. 2 and 3. End effector 1100 in FIG. 11 may be the same as end effector 100 except for noted differences. Here, the end effector 1100 consists of three support tabs 114A-114C. Support tab 114A is closest to a wrist 128 of the end effector 1100, or to the proximal portion of the end effector 1100 that would otherwise connect with a robot arm. The two other support tabs 114B and 114C are each positioned at an angular position from the support tab 114A and the angular position may range from about 100 degrees and about 140 degrees, including about 110 degrees, about 115 degrees, about 120 degrees, or about 125 degrees, for example. In this example of FIG. 11 , the end effector 1100 has a first support tab 114A closest to the proximal portion, or wrist 128, of the end effector 1100, a second support tab 114B positioned 115 degrees from the first support tab 114A, and a third support tab 114C positioned 115 degrees from the first support tab 114A. The second support tab 114B and the third support tab 114C are thereby positioned 130 degrees from each other.

[0056] These angles may be measured around a referential center axis CA1 of the end effector 1100. A referential circular plane 1115 may be centered on, and perpendicular to, the center axis CA1 and its circumference may extend through all of the support tabs 114A-114C. The support tabs 114A-114C may be considered positioned along the circumference of the referential circular plane 1115. As illustrated in FIG. 11 , the first support tab 114A is 115 degrees from both the second support tab 114B and third support tab 114C along the referential circular plane 1115 and around the referential center axis CA1 . The second support tab 114B is 115 degrees from the first support tab 114A and 130 degrees from the third support tab 114C along the referential circular plane 1115 and around the referential center axis CA1 . Similarly, the third support tab 114C is 115 degrees from the first support tab 114A and 130 degrees from the second support tab 114B. In some instances, the second support tab 114B may be considered 115 degrees in a first direction around the center axis CA1 from the first support tab 114A, and the third support tab 114C may be considered 115 degrees in a second direction opposite, the first direction, around the center axis CA1 from the first support tab 114A.

[0057] As provided herein, the second support tab 114B may be considered about 100 degrees and about 140 degrees in a first direction around the center axis CA1 from the first support tab 114A, and the third support tab 114C may be considered about 100 degrees and about 140 degrees in a second direction opposite, the first direction, around the center axis CA1 from the first support tab 114A. These angles may be about 110 degrees, about 115 degrees, about 120 degrees, about 125 degrees, or about 130 degrees.

[0058] Positioning the three support tabs 114 in these angles has numerous benefits. In some instances, having support tabs positioned 120 degrees apart, or two support tabs 115 degrees from the third support tab, provides placement stability when the end effector is in motion while minimizing contacts to the bottom surface of the wafer. Further, in some instances, positioning the two support tabs 115 degrees from the third support tab may provide additional clearance for the end effector 100 when moving within the system.

[0059] In other implementations, the end effector 100 may include more than three support tabs angularly spaced about the center axis by a common angle or a plurality of different angles. In the above implementations, the outer edge region 112 of the wafer 104 includes a bottom surface 116 (FIG. 5) terminating at the outer peripheral edge 110 defining the outer diameter OD1 , and the support tabs 114 are configured to support the bottom surface 116 in the outer edge region 112 of the wafer 104.

[0060] Referring to FIGS. 5 and 6, the end effector 100 further includes a plurality of wafer pads 118 configured to support the bottom surface 116 (FIG. 6) of the outer edge region 112 of the wafer 104 and friction between the wafer pads 118 and the wafer 104 hold the wafer 104 in place on the wafer pads 118 laterally, absent vibration and/or acceleration that may overcome the friction forces and cause the wafer 104 to move relative to the end effector 100. The wafer pads 118 may further space the bottom surface 116 apart from the corresponding support tabs 114 by a height H1 (i.e., to decrease or prevent conductive heat transfer from the wafer 104 directly to the support tabs 114). In some instances, the height H1 may range from about 0.0075 inches to about 0.025 inches, such as 0.01 inches, 0.0125 inches, 0.015 inches, 0.0175 inches, and about 0.02 inches. These height ranges may position the substrate in known, desired locations which are configured to be engaged by other robots in the semiconductor processing tool, thereby providing compatible heights with such other robots. This can advantageously provide for integration to existing tools or systems with minimal to no reconfiguration of the robot or tool. In this implementation, each wafer pad 118 includes a concave cone portion 120 located on a first side of the corresponding support tab 114. The concave cone portion 120 includes a concave lateral surface and a tip configured to support the bottom surface 116 of the outer edge region 112 of the wafer 104 and provide for minimal contact at the tip, much like a conical feature would, but maintains a smaller cross- sectional area when compressed as compared to a conical portion, thereby reducing potential physical contact area between the wafer and wafer pad.

[0061] Each wafer pad 118 further includes a flange portion 122 located on a second side of that support tab 114 and a shank portion 124 configured to extend through an opening in that support tab 114 and interposed between the concave cone portion 120 and the flange portion 122. At least one of the wafer pads 118 is made of an elastomer (e.g., a perfluoroelastomer), and includes a center axis located on the corresponding support tab 114 at a location spaced radially inward from the ring frame 102 by an offset distance in a range between 5 millimeters and 15 millimeters (e.g., 7 millimeters radially inward from a circular region defined by the first inner diameter surface 106 of the ring frame 102 (towards the center axis 108) when the outer peripheral edge 110 of the wafer 104 is offset 2 millimeters radially inward from the first inner diameter surface 106 of the ring frame 102 towards the center axis 108 and the wafer pad 118 engages a location on the bottom surface 116 of the wafer 104 spaced 5 millimeters radially inward from the outer peripheral edge 110 of the wafer 104 towards the center axis 108).

[0062] FIG. 7 depicts another implementation of a wafer pad 218 according to certain embodiments. To avoid undue repetition, elements in the implementation of FIG.

6 that are similar to elements shown in FIG. 7 are called out with numbers that share the same last two digits as those similar elements in FIG. 7. Thus, the discussion provided above with respect to the elements of the implementation of FIG. 6 will be understood to be equally applicable to the similar elements in FIG. 7 unless indicated otherwise. In the interest of conciseness, discussion of these elements that would be redundant of earlier discussion herein of similar elements is not provided, with the understanding that the earlier discussion of such elements is applicable to these similar elements in FIG. 7. While the wafer pad 118 of FIG. 6 has a concave cone portion 120, the wafer pad 218 of FIG.

7 has a convex cone portion 220 configured to support the bottom surface 116 of the outer edge region 112 of the wafer 104.

[0063] Both the concave cone portion 120 of FIG. 6 and the convex cone portion 220 of FIG. 7 may be shaped such that they have the same or a substantially similar point-sized contact area touching the wafer 104 but not compressed by the wafer weight. However, when the concave cone portion 120 and the convex cone portion 220 are compressed slightly, the conical contact area of the concave cone portion 120 may be smaller than that associated with the conical contact area of the convex cone portion 220, such that the conical contact area of the concave cone portion 120 provides a comparatively smaller conductive heat transfer interface and thermally interacts with the wafer 104 to a lesser degree.

[0064] In some implementations, each support tab 114 has a counterbore where the respective wafer pad 118 or 218 is positioned. FIG. 12 depicts a cross-sectional side view of the wafer pad of FIG. 6 and a portion of a support tab of an end effector. FIG. 13 13 depicts a cross-sectional side view of the wafer pad of FIG. 7 and a portion of a support tab of another end effector. Here in FIGS. 12 and 13, portions of support tabs 114 of end effectors 100 with counterbores CB1A and CB2A, respectively, are shown. The counterbores CB1A and CB2A are configured to receive the wafer pads 118 and 218, respectively, such that these wafer pads are configured to be inserted into the counterbores CB1A and CB2A. In some implementations, like in FIGS. 12 and 13, the wafer pads 118 and 218 are positioned at least partially inside the counterbores CB1A and CB2A, respectively. In some implementations, the support tabs 114 may have additional counterbores, or double counterbores, for the other end each wafer pad. FIGS. 12 and 13 illustrate these additional counterbores, with the support tab 114 of FIG. 12 having a second counterbore CB1 B opposite the counterbore CB1A and of FIG. 13 having a second counterbore CB2B opposite the counterbore CB2A. These second counterbores receive the non-wafer supporting end of the wafer pad to prevent the wafer pads from striking or contacting other components in the system.

[0065] This results in some of the wafer pads 118 and 218 extending upwards from the end effector and creating and offset distance from a tip 121 and 221 , respectively, of the wafer pads 118 and 218 and the end effector which is the same as the offset height H1 in these Figures. As further illustrated, these counterbores result in an offset height H1 between the bottom surface 116 of the wafer and the support tabs 114 that is smaller than without such a counterbore. In some instances, the height H1 may range from about 0.0075 inches to about 0.025 inches, such as 0.01 inches, 0.0125 inches, 0.015 inches, 0.0175 inches, and about 0.02 inches. These heights may be the same as with other end effectors, such as those with vacuum transfer module robots, to thereby position and hold the wafer in a similar position as other robots. In some embodiments, the ring frame 102 is configured to provide clearance for sensor beams used to determine a position of the wafer 104 relative to the end effector 100. More specifically, the ring frame 102 is bilaterally symmetric about a symmetry axis 126 but with one or more recesses 130 being asymmetrically positioned relative to the symmetry axis 126. The end effector 100 may be caused to translate along the symmetry axis 126 and between a first position and a second position during insertion of the end effector 100 (and wafer 104) into a wafer processing chamber, a load lock, or other chamber attached to the Vacuum Transfer Module (VTM). The symmetry axis 126 may be orthogonal to the center axis 108 of the ring frame 102, and the end effector 100 may include a wrist portion 128 configured to attach to a robotic arm (not shown) of the wafer handling system that may be controlled to move the end effector 100 along the symmetry axis 126.

[0066] The wafer handling system may further include an automatic wafer centering (AWC), which may also be referred to herein as a dynamic alignment system, having a pair of optical beam-break sensors (e.g., LEDs coupled with opposing photodetectors). The optical beam-break sensors may be configured to detect when an optical beam that is emitted by that sensor and that is parallel to the center axis 108 is either broken (due to being blocked by the wafer 104) or unbroken (due to no longer being blocked by the wafer 104). The optical beam-break sensors may be further configured to transmit a signal to a controller of the AWC system each time the corresponding sensor experiences a beam break or beam unbreak event, e.g., each time the outer peripheral edge 110 of the wafer 104 breaks or unblocks the sensor optical beam. While a gap between the outer peripheral edge 110 of the wafer 104 and the first inner diameter surface 106 of the ring frame 102 may allow such optical sensors to detect a beam unbreak event caused by the wafer 104 being moved out of the beam path and thus permit the dynamic alignment system to determine the edges of the wafer 104 (and thus the location of the center of the wafer 104), the outer edge region 112 of an out-of-position wafer 104 (i.e. , with the center of the wafer 104 being offset from the center axis 108 by some distance) may cause the outer edge region 112 to overlap the ring frame 102 (when viewed along the center axis 108) and eliminate the gap between the outer peripheral edge 110 of the wafer 104 and the first inner diameter surface 106 of ring frame 102, thereby preventing the optical beam from being unbroken and preventing the sensor from being able to detect the corresponding wafer edge as the ring frame 102 translates along the symmetry axis 126.

[0067] To avoid this scenario, the ring frame 102 further includes one or more recesses 130 in the first inner diameter surface 106 in some embodiments. Each recess 130 in the one or more recesses includes a second inner diameter surface 132 spaced a second radius R2 from the center axis 108. The second radius R2 is greater than the first radius R1 , e.g., the difference between them may be greater than or equal to a maximum anticipated potential wafer off-centeredness such that the one or more recesses 130 define one or more corresponding clearance cutouts. Such clearance cutouts provide sufficient clearance that even when wafer 104 is off-center by the maximum permissible amount, there still is a gap that allows the beam detect event to occur, i.e. , there is no overlap between second diameter surface and wafer at the clearance cutout when viewed along the center axis.

[0068] In one implementation, the optical beam-break sensors may be further configured to transmit signals via a single channel to a controller of the AWC system thus requiring the sensors and the corresponding recesses to be asymmetrically positioned relative to a symmetry axis 126 as discussed with reference to FIG. 3. In other implementations where the sensors transmit signals via two separate corresponding channels to the controller of the AWC system, the sensors and the corresponding recesses may be symmetrically positioned relative to the symmetry axis 126.

[0069] As can be seen in FIG. 3, in implementations where the dynamic alignment system includes two or more sensors transmitting signals via a single channel to the controller of the AWC system, the end effector 100 is shaped such that two parallel lines that represent the optical beam paths as the end effector 100 and the wafer 104 pass under the sensors cross the wafer edge and lead ing/trai I ing edges of the end effector 100 all at different locations staggered along the symmetry axis 126. In this implementation, the sensors and the corresponding recesses 130 are asymmetrically positioned relative to the symmetry axis 126. A first clearance cutout 134 in the one or more clearance cutouts is located in the ring frame 102 at a first distance D1 (e.g., 3.25 inches) from the symmetry axis 126 and spaced along a first direction orthogonally from the symmetry axis 126. A second clearance cutout 136 in the one or more clearance cutouts is located in the ring frame 102 at a second distance D2 (e.g., 4.75 inches) from the symmetry axis 126 and spaced along a second direction orthogonally from the symmetry axis 126 opposite to the first direction, with the first distance being less than the second distance. In one implementation, the first clearance cutout 134 has a first cutout portion 138 located the first distance D1 from the symmetry axis 126 to provide clearance for the corresponding optical beam, and the second clearance cutout has a second cutout portion 140 located the second distance D2 from the symmetry axis 126 to provide clearance for the corresponding optical beam. In another implementation, the first clearance cutout 134 and the second clearance cutout 136 extend a predetermined length from the corresponding first cutout portion 138 and the second cutout portion 140 to provide clearance for an associated nearby lift pin L1 , L2 supporting the wafer 104 in the wafer processing chamber. The predetermined length of each of the clearance cutouts further provide clearance for part assembly tolerances, robot station teaching tolerances, robot trajectory following error (i.e., overshoot), and the offset needed to center the wafer 104 as the wafer 104 is transferred to the lift pins. In one implementation, the first clearance cutout 134 and the second clearance cutout 136 are configured to provide clearance (e.g., of at least 8 millimeters) of all sides of the end effector 100 from the wafer processing chamber.

[0070] In this implementation, the ring frame 102 is further configured to provide clearance for moving through a port opening connecting the processing chamber with the VTM without increasing the size of the port opening. More specifically, the ring frame 102 further includes an outer surface 142 with a pair of diametrically opposite sides. The ring frame 102 further includes a set of one or more flats in the outer surface 142 configured to provide clearance for the ring frame 102 when the ring frame 102 translates along the symmetry axis 126 and is inserted through the port opening of the VTM. For instance, the ring frame 102 may include a first flat 144 and a second flat 146 located in a corresponding one of the diametrically opposite sides of the ring frame 102. The first flat 144 and the second flat 146 may be arranged parallel to the symmetry axis 126.

[0071] In this implementation, the ring frame 102 is further configured to have a predetermined strength and stiffness to, for example, reduce vibration experienced by the end effector 100 and the wafer 104 on the end effector 100 and permit one or more portions of the ring frame 102 to pass between the bottom surface 116 of the wafer 104 supported by the lift pins L1 , L2 and a surface of the wafer processing chamber facing the bottom surface 116 of the wafer 104, i.e., prior to the end effector 100 picking up the wafer 104. More specifically, the ring frame 102 and the support tabs 114 may be made of a ceramic material (e.g., aluminum oxide, etc.) or stainless steel. The ring frame 102 may have a stepped thickness configured to provide the predetermined strength and stiffness. The stepped thickness includes a first step portion 148 having a first thickness T1 and a second step portion 150 having a second thickness T2 greater than the first thickness T1 , such that the first step portion 148 and the second step portion 150 individually and/or collectively increase the strength and stiffness of the end effector 100. The second step portion 150 with its second thickness T2 does not pass under the bottom surface 116 of the wafer 104 and thus does not require clearance (e.g., a minimum clearance greater than the second thickness T2) for the second step portion 150 to move between the bottom surface 116 of the wafer 104 and the surface of the wafer processing chamber facing the bottom surface 116 of the wafer 104. Stated another way, only sections S1 , S2, of the first step portion 148 pass under the bottom surface 116 of the wafer 104 and thus requires clearance (e.g., a minimum clearance greater than the first thickness T1 ) for only sections S1 , S2, of the first step portion 148 to move between the bottom surface 116 of the wafer 104 and the surface of the wafer processing chamber facing the bottom surface 116 of the wafer 104. Also, in this implementation, the second step portion 150 is located radially outward from the first step portion 148 along a lateral direction relative to the center axis 108, and the second step portion 150 may further extend by a height H2 along a longitudinal direction parallel to the center axis 108 and from a side of the first step portion 148 facing the wafer 104. As can be seen, the first step portion 148 includes the first inner diameter surface 106 spaced the first radius R1 from the center axis 108. The first step portion 148 extends at least 180 degrees about the center axis 108 and includes the sections S1 , S2 configured to move beneath the wafer 104 when the ring frame 102 translates along the symmetry axis 126 to position the support tabs 114 beneath the wafer 104 and lift the wafer 104 from the lift pins L1 , L2 in the wafer processing chamber. Each region of the corresponding support tabs 114 that is overlapped by the wafer 104 is shown with cross-hatch lines in FIG.3. As can be further seen, the second step portion 150 includes a third inner diameter surface 152 spaced a third radius R3 from the center axis 108, with the third radius R3 being greater than the first radius R1. The third radius R3 may be within a range between 155 and 165 millimeters, and the second step portion 150 may extend an angle about the center axis 108, with the angle being in a range between 165 degrees and 195 degrees.

[0072] FIG. 8 depicts a first heat map 154 for a first wafer supported on the end effector 100 of FIG. 1 and a second heat map 156 for a second wafer supported on a fork-shaped end effector 158, with each heat map showing regions of the corresponding wafer that are within common temperature ranges after a first elapsed amount of time (in this case, 16 seconds) from when the wafer was placed on the respective end effector while at a given elevated temperature, e.g., on the order of 250 degrees Celsius to 350 degrees Celsius. The fork-shaped end effector 158 is, for example, an end effector that is in the style of a conventional end effector, i.e., not implementing the end effector designs discussed above.

[0073] Both heat maps 154, 156 use the same temperature differential scale, which spans approximately 100 degrees Celsius — each of the thirteen greyscale colors in FIG. 8 thus represents a corresponding temperature band spanning about 7.7 degrees Celsius. Thus, the temperatures in the white/lightest region(s) will be at least ~85 degrees Celsius more than the temperatures in the black/darkest region(s).

[0074] As can readily be seen, there is a much larger range of temperatures — and thus a larger temperature differential — present in the second wafer as compared with the first wafer. For example, all thirteen temperature bands exist on the second wafer. Moreover, it is also clear that the cooler temperatures in the second wafer correspond to regions of the second wafer that overlap with the end effector 158 (even though the second wafer and the end effector 158 would only actually contact one another at three or four locations where pads for supporting the second wafer are positioned). In contrast, the first wafer exhibits regions with temperatures that occupy only three of the temperature bands (i.e., a first region at the center of the first wafer and having temperatures occupying a first temperature band, a second region surrounding the first region and having temperatures occupying a second temperature band, and three separate regions of a set of third regions proximal to a corresponding one of the three support tabs and each having temperatures occupying a third temperature band). The difference between the maximum and minimum temperatures in the first wafer is less than the total temperature range represented by those three temperature bands. The resulting temperature map in the first wafer is thus much more uniform than the temperature map of the second wafer.

[0075] FIG. 9 depicts third and fourth heat maps 160, 162 for a corresponding one of the first and second wafers in FIG. 8, with each heat map showing regions of the corresponding wafer that are within common temperature ranges after a second elapsed amount of time. Both heat maps 160, 162 similarly use the same temperature differential scale, but in this case, the scale spans approximately 65 degrees Celsius, so each of the thirteen greyscale colors in FIG. 9 represents a corresponding temperature band spanning about 5 degrees Celsius. As can be seen, the first wafer continues to exhibit a much more uniform temperature distribution at 40 seconds after the first wafer was placed on the end effector 100 as compared to the temperature distribution in the second wafer after the same amount of time has elapsed.

[0076] As can be seen, the end effector designs discussed herein may improve the in-transport thermal uniformity in wafers significantly, e.g., nearly six-fold, as compared with standard end effector designs, thereby reducing the potential for higher thermal stress fields within such wafers and the potential consequences of such higher thermal stress fields, e.g., cracking, bowing, etc.

[0077] In other implementations, similar end effectors can be designed for other wafer sizes, with the parameters discussed above being understood to apply to wafers having a diameter of 300 millimeters. For other wafer sizes, such parameters of the end effector may be scaled up or down in similar fashion as the wafers are scaled up or down.

[0078] FIG. 10 depicts a schematic representation of an atmospheric transfer module robot 300 (ATM robot) including an example arm assembly 302 terminating at an end upon which the end effector 100 of FIGS. 1 -5 may be mounted. It is contemplated that the end effector 100 may be mounted to any suitable arm assembly 302 of other robots or tools.

[0079] The term “between,” as used herein and when used with a range of values, is to be understood, unless otherwise indicated, as being inclusive of the start and end values of that range. For example, between 1 and 5 is to be understood to be inclusive of the numbers 1 , 2, 3, 4, and 5, not just the numbers 2, 3, and 4.

[0080] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure may be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A, B, or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.

Claims

CLAIMS What is claimed is:

1 . An apparatus comprising: an end effector comprising: a ring frame including a first inner diameter surface defining a first inner diameter and coaxial with a center axis; and a plurality of support tabs extending radially inward from the first inner diameter surface of the ring frame towards the center axis and into a circular region centered on the center axis, wherein the first inner diameter of the first inner diameter surface of the ring frame is larger than an outer diameter of the circular region.

2. The apparatus of claim 1 , wherein no portion of the ring frame overlaps the circular region when the end effector is viewed along the center axis of the ring frame.

3. The apparatus of any of claims 1 or 2, wherein the ring frame is C-shaped.

4. The apparatus of any of claims 1 through 3, wherein the support tabs are positioned at a plurality of locations on the ring frame that are angularly spaced apart.

5. The apparatus of claim 4, wherein the plurality of support tabs consists of three support tabs positioned 120 degrees apart relative to one another.

6. The apparatus of claim 4, wherein: the plurality of support tabs consists of three support tabs, a first support tab is positioned 115 degrees apart from a second support tab and from a third support tab, and the second support tab and the third support tab are positioned 130 degrees apart from each other.

7. The apparatus of claim 4, wherein: the plurality of support tabs consists of three support tabs, a first support tab is positioned at an angle ranging from about 100 degrees to about 140 degrees a second support tab and from a third support tab, and the second support tab and the third support tab are positioned at the same angle apart from each other.

8. The apparatus of claim 6 or 7, wherein the first support tab is closest to a proximal portion of the end effector than the second support tab and the third support tab.

9. The apparatus of any of claims 1 through 8, wherein: the first inner diameter surface is spaced a first radius from the center axis; the ring frame further includes one or more recesses in the first inner diameter surface, each of the one or more recesses including a second inner diameter surface spaced a second radius from the center axis; and the second radius is greater than the first radius such that the one or more recesses define one or more clearance cutouts.

10. The apparatus of claim 9, wherein there are two or more recesses and the ring frame is bilaterally symmetric about a symmetry axis but with the recesses being asymmetrically positioned relative to the symmetry axis.

11 . The apparatus of claim 10, wherein: a first clearance cutout in the one or more clearance cutouts is located in the ring frame at a first distance from the symmetry axis and spaced along a first direction orthogonally from the symmetry axis; and a second clearance cutout in the one or more clearance cutouts is located in the ring frame at a second distance from the symmetry axis and spaced along a second direction orthogonally from the symmetry axis opposite to the first direction.

12. The apparatus of claim 11 , wherein the first distance is less than the second distance.

13. The apparatus of claim 12, wherein: the ring frame further includes an outer surface; and the ring frame further includes a set of one or more flats in the outer surface, with a first width between two flats in the set of one or more flats being less than a second width of a port opening of a wafer process chamber to provide clearance for the ring frame when the ring frame translates along the symmetry axis and is inserted through the port opening of the wafer process chamber.

14. The apparatus of claim 13, wherein: the ring frame includes a pair of diametrically opposite sides; and the set of one or more flats includes a first flat and a second flat located in a corresponding one of the diametrically opposite sides of the ring frame.

15. The apparatus of claim 13, wherein a first flat in the set of one or more flats and a second flat in the set of one or more flats are arranged parallel to the symmetry axis.

16. The apparatus of claim 9, wherein: the ring frame has a stepped thickness including a first step portion having a first thickness and a second step portion having a second thickness greater than the first thickness; and the second step portion is located radially outward from the first step portion.

17. The apparatus of claim 16, wherein: the first step portion includes the first inner diameter surface spaced the first radius from the center axis; and the second step portion includes a third inner diameter surface spaced a third radius from the center axis, with the third radius being greater than the first radius.

18. The apparatus of claim 17, wherein: the first radius is within a range between 151 and 155 millimeters; and the third radius is within a range between 155 and 165 millimeters.

19. The apparatus of claim 16, wherein the second step portion extends an angle about the center axis, with the angle being in a range between 165 degrees and 195 degrees.

20. The apparatus of claim 16, wherein the first step portion extends at least 180 degrees about the center axis.

21 . The apparatus of claim 1 , wherein the ring frame and the plurality of support tabs are made of a ceramic material.

22. The apparatus of any of claims 1 through 21 , further comprising a plurality of wafer pads attached to a corresponding one of the plurality of support tabs.

23. The apparatus of claim 22, wherein the plurality of wafer pads each comprises: a convex cone portion located on a first side of the corresponding support tab; a shank portion configured to extend through an opening in that support tab; and a flange portion located on a second side of that support tab.

24. The apparatus of claim 22, wherein the plurality of wafer pads each comprises: a concave cone portion located on a first side of the corresponding support tab; a shank portion configured to extend through an opening in that support tab; and a flange portion located on a second side of that support tab.

25. The apparatus of claim 22, wherein the plurality of wafer pads each is made of an elastomer.

26. The apparatus of claim 22, wherein the plurality of wafer pads each is located on the corresponding support tab at a location spaced radially inward from the ring frame by an offset distance in a range between 5 millimeters and 15 millimeters.

27. The apparatus of claim 22, wherein the plurality of support tabs each extends up to 20 millimeters from the first inner diameter surface towards the center axis.

28. The apparatus of claim 22, wherein: each support tab comprises a counterbore, and each wafer pad is positioned at least partially inside the counterbore of the respective support tab.